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Summary of Significant Accounting Policies | 12 Months Ended
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Dec. 31, 2018
Summary of Significant Accounting Policies |
Summary of Significant Accounting Policies | 3. Summary of Significant Accounting Policies Principles of Consolidation The accompanying Consolidated Financial Statements include the accounts of WM, its wholly-owned and majority-owned subsidiaries and certain variable interest entities for which we have determined that we are the primary beneficiary. All material intercompany balances and transactions have been eliminated. Investments in unconsolidated entities are accounted for under the appropriate method of accounting. Estimates and Assumptions In preparing our financial statements, we make numerous estimates and assumptions that affect the accounting for and recognition and disclosure of assets, liabilities, equity, revenues and expenses. We must make these estimates and assumptions because certain information that we use is dependent on future events, cannot be calculated with precision from available data or simply cannot be calculated. In some cases, these estimates are difficult to determine, and we must exercise significant judgment. In preparing our financial statements, the most difficult, subjective and complex estimates and the assumptions that present the greatest amount of uncertainty relate to our accounting for landfills, environmental remediation liabilities, long-lived asset impairments and reserves associated with our insured and self-insured claims. Each of these items is discussed in additional detail below. Actual results could differ materially from the estimates and assumptions that we use in the preparation of our financial statements. Cash and Cash Equivalents Cash in excess of current operating requirements is invested in short-term interest-bearing instruments with maturities of three months or less at the date of purchase and is stated at cost, which approximates market value. Concentrations of Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash and cash equivalents, investments held within our restricted trust and escrow accounts, and accounts receivable. We make efforts to control our exposure to credit risk associated with these instruments by (i) placing our assets and other financial interests with a diverse group of credit-worthy financial institutions; (ii) holding high-quality financial instruments while limiting investments in any one instrument and (iii) maintaining strict policies over credit extension that include credit evaluations, credit limits and monitoring procedures, although generally we do not have collateral requirements for credit extensions. We also control our exposure associated with trade receivables by discontinuing service, to the extent allowable, to non-paying customers. However, our overall credit risk associated with trade receivables is limited due to the large number and diversity of customers we serve. As of December 31, 2018 and 2017, no single customer represented greater than 5% of total accounts receivable. Accounts and Other Receivables Our receivables, which are recorded when billed, when services are performed or when cash is advanced, are claims against third parties that will generally be settled in cash. The carrying value of our receivables, net of the allowance for doubtful accounts, represents the estimated net realizable value. We estimate our allowance for doubtful accounts based on historical collection trends; type of customer, such as municipal or commercial; the age of outstanding receivables and existing economic conditions. If events or changes in circumstances indicate that specific receivable balances may be impaired, further consideration is given to the collectability of those balances and the allowance is adjusted accordingly. The activity within our allowance for doubtful accounts was not material for the reported periods. Past-due receivable balances are written off when our internal collection efforts have been unsuccessful. Also, we recognize interest income on long-term interest-bearing notes receivable as the interest accrues under the terms of the notes. We no longer accrue interest once the notes are deemed uncollectible. Other receivables, as of December 31, 2018 and 2017, include receivables related to income tax payments in excess of our current income tax obligations of $284 million and $504 million, respectively. Parts and Supplies Parts and supplies consist primarily of spare parts, fuel, tires, lubricants and processed recycling materials. Our parts and supplies are stated at the lower of cost, using the average cost method, or market. Landfill Accounting Cost Basis of Landfill Assets — We capitalize various costs that we incur to make a landfill ready to accept waste. These costs generally include expenditures for land (including the landfill footprint and required landfill buffer property); permitting; excavation; liner material and installation; landfill leachate collection systems; landfill gas collection systems; environmental monitoring equipment for groundwater and landfill gas; and directly related engineering, capitalized interest, on-site road construction and other capital infrastructure costs. The cost basis of our landfill assets also includes asset retirement costs, which represent estimates of future costs associated with landfill final capping, closure and post-closure activities. These costs are discussed below. Final Capping, Closure and Post-Closure Costs — Following is a description of our asset retirement activities and our related accounting:
| · |  | Final Capping — Involves the installation of flexible membrane liners and geosynthetic clay liners, drainage and compacted soil layers and topsoil over areas of a landfill where total airspace capacity has been consumed. Final capping asset retirement obligations are recorded on a units-of-consumption basis as airspace is consumed related to the specific final capping event with a corresponding increase in the landfill asset. Each final capping event is accounted for as a discrete obligation and recorded as an asset and a liability based on estimates of the discounted cash flows and capacity associated with each final capping event.
| · |  | Closure — Includes the construction of the final portion of methane gas collection systems (when required), demobilization and routine maintenance costs. These are costs incurred after the site ceases to accept waste, but before the landfill is certified as closed by the applicable state regulatory agency. These costs are recorded as an asset retirement obligation as airspace is consumed over the life of the landfill with a corresponding increase in the landfill asset. Closure obligations are recorded over the life of the landfill based on estimates of the discounted cash flows associated with performing closure activities.
| · |  | Post-Closure — Involves the maintenance and monitoring of a landfill site that has been certified closed by the applicable regulatory agency. Generally, we are required to maintain and monitor landfill sites for a 30-year period. These maintenance and monitoring costs are recorded as an asset retirement obligation as airspace is consumed over the life of the landfill with a corresponding increase in the landfill asset. Post-closure obligations are recorded over the life of the landfill based on estimates of the discounted cash flows associated with performing post-closure activities.
We develop our estimates of these obligations using input from our operations personnel, engineers and accountants. Our estimates are based on our interpretation of current requirements and proposed regulatory changes and are intended to approximate fair value. Absent quoted market prices, the estimate of fair value is based on the best available information, including the results of present value techniques. In many cases, we contract with third parties to fulfill our obligations for final capping, closure and post-closure. We use historical experience, professional engineering judgment and quoted or actual prices paid for similar work to determine the fair value of these obligations. We are required to recognize these obligations at market prices whether we plan to contract with third parties or perform the work ourselves. In those instances where we perform the work with internal resources, the incremental profit margin realized is recognized as a component of operating income when the work is completed. Once we have determined final capping, closure and post-closure costs, we inflate those costs to the expected time of payment and discount those expected future costs back to present value. During the years ended December 31, 2018, 2017 and 2016, we inflated these costs in current dollars to the expected time of payment using an inflation rate of 2.5%. We discounted these costs to present value using the credit-adjusted, risk-free rate effective at the time an obligation is incurred, consistent with the expected cash flow approach. Any changes in expectations that result in an upward revision to the estimated cash flows are treated as a new liability and discounted at the current rate while downward revisions are discounted at the historical weighted average rate of the recorded obligation. As a result, the credit-adjusted, risk-free discount rate used to calculate the present value of an obligation is specific to each individual asset retirement obligation. The weighted average rate applicable to our long-term asset retirement obligations as of December 31, 2018 was approximately 5.50%. We record the estimated fair value of final capping, closure and post-closure liabilities for our landfills based on the capacity consumed through the current period. The fair value of final capping obligations is developed based on our estimates of the airspace consumed to date for each final capping event and the expected timing of each final capping event. The fair value of closure and post-closure obligations is developed based on our estimates of the airspace consumed to date for the entire landfill and the expected timing of each closure and post-closure activity. Because these obligations are measured at estimated fair value using present value techniques, changes in the estimated cost or timing of future final capping, closure and post-closure activities could result in a material change in these liabilities, related assets and results of operations. We assess the appropriateness of the estimates used to develop our recorded balances annually, or more often if significant facts change. Changes in inflation rates or the estimated costs, timing or extent of future final capping, closure and post-closure activities typically result in both (i) a current adjustment to the recorded liability and landfill asset and (ii) a change in liability and asset amounts to be recorded prospectively over either the remaining capacity of the related discrete final capping event or the remaining permitted and expansion airspace (as defined below) of the landfill. Any changes related to the capitalized and future cost of the landfill assets are then recognized in accordance with our amortization policy, which would generally result in amortization expense being recognized prospectively over the remaining capacity of the final capping event or the remaining permitted and expansion airspace of the landfill, as appropriate. Changes in such estimates associated with airspace that has been fully utilized result in an adjustment to the recorded liability and landfill assets with an immediate corresponding adjustment to landfill airspace amortization expense. Interest accretion on final capping, closure and post-closure liabilities is recorded using the effective interest method and is recorded as final capping, closure and post-closure expense, which is included in operating expenses within our Consolidated Statements of Operations. Amortization of Landfill Assets — The amortizable basis of a landfill includes (i) amounts previously expended and capitalized; (ii) capitalized landfill final capping, closure and post-closure costs; (iii) projections of future purchase and development costs required to develop the landfill site to its remaining permitted and expansion capacity and (iv) projected asset retirement costs related to landfill final capping, closure and post-closure activities. Amortization is recorded on a units-of-consumption basis, applying expense as a rate per ton. The rate per ton is calculated by dividing each component of the amortizable basis of a landfill by the number of tons needed to fill the corresponding asset’s airspace. For landfills that we do not own, but operate through lease or other contractual agreements, the rate per ton is calculated based on expected capacity to be utilized over the lesser of the contractual term of the underlying agreement or the life of the landfill. We apply the following guidelines in determining a landfill’s remaining permitted and expansion airspace:
| · |  | Remaining Permitted Airspace — Our engineers, in consultation with third-party engineering consultants and surveyors, are responsible for determining remaining permitted airspace at our landfills. The remaining permitted airspace is determined by an annual survey, which is used to compare the existing landfill topography to the expected final landfill topography.
| · |  | Expansion Airspace — We also include currently unpermitted expansion airspace in our estimate of remaining permitted and expansion airspace in certain circumstances. First, to include airspace associated with an expansion effort, we must generally expect the initial expansion permit application to be submitted within one year and the final expansion permit to be received within five years. Second, we must believe that obtaining the expansion permit is likely, considering the following criteria:
| · |  | Personnel are actively working on the expansion of an existing landfill, including efforts to obtain land use and local, state or provincial approvals;
| · |  | We have a legal right to use or obtain land to be included in the expansion plan;
| · |  | There are no significant known technical, legal, community, business, or political restrictions or similar issues that could negatively affect the success of such expansion; and
| · |  | Financial analysis has been completed based on conceptual design, and the results demonstrate that the expansion meets Company criteria for investment.
For unpermitted airspace to be initially included in our estimate of remaining permitted and expansion airspace, the expansion effort must meet all the criteria listed above. These criteria are evaluated by our field-based engineers, accountants, managers and others to identify potential obstacles to obtaining the permits. Once the unpermitted airspace is included, our policy provides that airspace may continue to be included in remaining permitted and expansion airspace even if certain of these criteria are no longer met as long as we continue to believe we will ultimately obtain the permit, based on the facts and circumstances of a specific landfill. In these circumstances, continued inclusion must be approved through a landfill-specific review process that includes approval by our Chief Financial Officer and a review by the Audit Committee of our Board of Directors on a quarterly basis. Of the 15 landfill sites with expansions included as of December 31, 2018, two landfills required the Chief Financial Officer to approve the inclusion of the unpermitted airspace because the permit application process did not meet the one- or five-year requirements. When we include the expansion airspace in our calculations of remaining permitted and expansion airspace, we also include the projected costs for development, as well as the projected asset retirement costs related to final capping, closure and post-closure of the expansion in the amortization basis of the landfill. Once the remaining permitted and expansion airspace is determined in cubic yards, an airspace utilization factor (“AUF”) is established to calculate the remaining permitted and expansion capacity in tons. The AUF is established using the measured density obtained from previous annual surveys and is then adjusted to account for future settlement. The amount of settlement that is forecasted will take into account several site-specific factors including current and projected mix of waste type, initial and projected waste density, estimated number of years of life remaining, depth of underlying waste, anticipated access to moisture through precipitation or recirculation of landfill leachate and operating practices. In addition, the initial selection of the AUF is subject to a subsequent multi-level review by our engineering group and the AUF used is reviewed on a periodic basis and revised as necessary. Our historical experience generally indicates that the impact of settlement at a landfill is greater later in the life of the landfill when the waste placed at the landfill approaches its highest point under the permit requirements. After determining the costs and remaining permitted and expansion capacity at each of our landfills, we determine the per ton rates that will be expensed as waste is received and deposited at the landfill by dividing the costs by the corresponding number of tons. We calculate per ton amortization rates for each landfill for assets associated with each final capping event, for assets related to closure and post-closure activities and for all other costs capitalized or to be capitalized in the future. These rates per ton are updated annually, or more often, as significant facts change. It is possible that actual results, including the amount of costs incurred, the timing of final capping, closure and post-closure activities, our airspace utilization or the success of our expansion efforts could ultimately turn out to be significantly different from our estimates and assumptions. To the extent that such estimates, or related assumptions, prove to be significantly different than actual results, lower profitability may be experienced due to higher amortization rates or higher expenses; or higher profitability may result if the opposite occurs. Most significantly, if it is determined that expansion capacity should no longer be considered in calculating the recoverability of a landfill asset, we may be required to recognize an asset impairment or incur significantly higher amortization expense. If at any time management makes the decision to abandon the expansion effort, the capitalized costs related to the expansion effort are expensed immediately. Environmental Remediation Liabilities A significant portion of our operating costs and capital expenditures could be characterized as costs of environmental protection. The nature of our operations, particularly with respect to the construction, operation and maintenance of our landfills, subjects us to an array of laws and regulations relating to the protection of the environment. Under current laws and regulations, we may have liabilities for environmental damage caused by our operations, or for damage caused by conditions that existed before we acquired a site. In addition to remediation activity required by state or local authorities, such liabilities include potentially responsible party (“PRP”) investigations. The costs associated with these liabilities can include settlements, certain legal and consultant fees, as well as incremental internal and external costs directly associated with site investigation and clean up. Where it is probable that a liability has been incurred, we estimate costs required to remediate sites based on site-specific facts and circumstances. We routinely review and evaluate sites that require remediation, considering whether we were an owner, operator, transporter, or generator at the site, the amount and type of waste hauled to the site and the number of years we were associated with the site. Next, we review the same type of information with respect to other named and unnamed PRPs. Estimates of the costs for the likely remedy are then either developed using our internal resources or by third-party environmental engineers or other service providers. Internally developed estimates are based on:
| · |  | Management’s judgment and experience in remediating our own and unrelated parties’ sites;
| · |  | Information available from regulatory agencies as to costs of remediation;
| · |  | The number, financial resources and relative degree of responsibility of other PRPs who may be liable for remediation of a specific site; and
| · |  | The typical allocation of costs among PRPs, unless the actual allocation has been determined.
Estimating our degree of responsibility for remediation is inherently difficult. We recognize and accrue for an estimated remediation liability when we determine that such liability is both probable and reasonably estimable. Determining the method and ultimate cost of remediation requires that a number of assumptions be made. There can sometimes be a range of reasonable estimates of the costs associated with the likely site remediation alternatives identified in the environmental impact investigation. In these cases, we use the amount within the range that is our best estimate. If no amount within a range appears to be a better estimate than any other, we use the amount that is the low end of such range. If we used the high ends of such ranges, our aggregate potential liability would be approximately $140 million higher than the $237 million recorded in the Consolidated Balance Sheet as of December 31, 2018. Our ultimate responsibility may differ materially from current estimates. It is possible that technological, regulatory or enforcement developments, the results of environmental studies, the inability to identify other PRPs, the inability of other PRPs to contribute to the settlements of such liabilities, or other factors could require us to record additional liabilities. Our ongoing review of our remediation liabilities, in light of relevant internal and external facts and circumstances, could result in revisions to our accruals that could cause upward or downward adjustments to our balance sheet and income from operations. These adjustments could be material in any given period. Where we believe that both the amount of a particular environmental remediation liability and the timing of the payments are fixed or reliably determinable, we inflate the cost in current dollars (by 2.5% as of December 31, 2018 and 2017) until the expected time of payment and discount the cost to present value using a risk-free discount rate, which is based on the rate for U.S. Treasury bonds with a term approximating the weighted average period until settlement of the underlying obligation. We determine the risk-free discount rate and the inflation rate on an annual basis unless interim changes would materially impact our results of operations. For remedial liabilities that have been discounted, we include interest accretion, based on the effective interest method, in operating expenses in our Consolidated Statements of Operations. The following table summarizes the impacts of revisions in the risk-free discount rate applied to our environmental remediation liabilities and recovery assets for the years ended December 31 (in millions) and the risk-free discount rate applied as of December 31:
|  | 2018 |  | 2017 |  | 2016 |
Decrease in operating expenses |  | $ | (2) |  | $ | — |  | $ | (2) |
Risk-free discount rate applied to environmental remediation liabilities and recovery assets |  |  | 2.75 | % |  | 2.5 | % |  | 2.5 | %
The portion of our recorded environmental remediation liabilities that were not subject to inflation or discounting, as the amounts and timing of payments are not fixed or reliably determinable, was $35 million and $47 million as of December 31, 2018 and 2017, respectively. Had we not inflated and discounted any portion of our environmental remediation liability, the amount recorded would have increased $3 million as of December 31, 2018 and remained the same as of December 31, 2017. Property and Equipment (Exclusive of Landfills, Discussed Above) We record property and equipment at cost. Expenditures for major additions and improvements are capitalized and maintenance activities are expensed as incurred. We depreciate property and equipment over the estimated useful life of the asset using the straight-line method. We assume no salvage value for our depreciable property and equipment. When property and equipment are retired, sold or otherwise disposed of, the cost and accumulated depreciation are removed from our accounts and any resulting gain or loss is included in results of operations as an offset or increase to operating expense for the period. The estimated useful lives for significant property and equipment categories are as follows (in years):
|  | Useful Lives
Vehicles — excluding rail haul cars |  | 3 to 10
Vehicles — rail haul cars |  | 10 to 30
Machinery and equipment — including containers |  | 3 to 30
Buildings and improvements |  | 5 to 40
Furniture, fixtures and office equipment |  | 3 to 10
We include capitalized costs associated with developing or obtaining internal-use software within furniture, fixtures and office equipment. These costs include direct external costs of materials and services used in developing or obtaining the software and internal costs for employees directly associated with the software development project. Leases We lease property and equipment in the ordinary course of our business. Our most significant lease obligations are for property and equipment specific to our industry, including real property operated as a landfill or transfer station. Our leases have varying terms. Some may include renewal or purchase options, escalation clauses, restrictions, penalties or other obligations that we consider in determining minimum lease payments. The leases are classified as either operating leases or capital leases, as appropriate. See Note 2 for information related to the pending adoption of ASU 2016-02. Operating Leases (Excluding Landfill Leases Discussed Below) — The majority of our leases are operating leases. This classification generally can be attributed to either (i) relatively low fixed minimum lease payments as a result of real property lease obligations that vary based on the volume of waste we receive or process or (ii) minimum lease terms that are much shorter than the assets’ economic useful lives. Management expects that in the normal course of business our operating leases will be renewed, replaced by other leases, or replaced with fixed asset expenditures. Our rent expense during each of the last three years and our future minimum operating lease payments for each of the next five years for which we are contractually obligated as of December 31, 2018 are disclosed in Note 10. Capital Leases (Excluding Landfill Leases Discussed Below) — Assets under capital leases are capitalized using interest rates determined at the inception of each lease and are amortized over either the useful life of the asset or the lease term, as appropriate, on a straight-line basis. The present value of the related lease payments is recorded as a debt obligation. Our future minimum annual capital lease payments are included in our future debt obligations as disclosed in Note 7. Landfill Leases — From an operating perspective, landfills that we lease are similar to landfills we own because generally we will operate the landfill for the life of the operating permit. The most significant portion of our rental obligations for landfill leases is contingent upon operating factors such as disposal volumes and often there are no contractual minimum rental obligations. Contingent rental obligations are expensed as incurred. For landfill capital leases that provide for minimum contractual rental obligations, we record the present value of the minimum obligation as part of the landfill asset, which is amortized on a units-of-consumption basis over the shorter of the lease term or the life of the landfill. Acquisitions We generally recognize assets acquired and liabilities assumed in business combinations, including contingent assets and liabilities, based on fair value estimates as of the date of acquisition. Contingent Consideration — In certain acquisitions, we agree to pay additional amounts to sellers contingent upon achievement by the acquired businesses of certain negotiated goals, such as targeted revenue levels, targeted disposal volumes or the issuance of permits for expanded landfill airspace. We have recognized liabilities for these contingent obligations based on their estimated fair value as of the date of acquisition with any differences between the acquisition-date fair value and the ultimate settlement of the obligations being recognized as an adjustment to income from operations. Acquired Assets and Assumed Liabilities — Assets and liabilities arising from contingencies such as pre-acquisition environmental matters and litigation are recognized at their acquisition-date fair value when their respective fair values can be determined. If the fair values of such contingencies cannot be determined, they are recognized as of the acquisition date if the contingencies are probable and an amount can be reasonably estimated. Acquisition-date fair value estimates are revised as necessary if, and when, additional information regarding these contingencies becomes available to further define and quantify assets acquired and liabilities assumed. Subsequent to finalization of purchase accounting, these revisions are accounted for as adjustments to income from operations. All acquisition-related transaction costs are expensed as incurred. Goodwill and Other Intangible Assets Goodwill is the excess of our purchase cost over the fair value of the net assets of acquired businesses. We do not amortize goodwill, but as discussed in the Long-Lived Asset Impairments section below, we assess our goodwill for impairment at least annually. Other intangible assets consist primarily of customer and supplier relationships, covenants not-to-compete, licenses, permits (other than landfill permits, as all landfill-related intangible assets are combined with landfill tangible assets and amortized using our landfill amortization policy), and other contracts. Other intangible assets are recorded at fair value on the acquisition date and are generally amortized using either a 150% declining balance approach or a straight-line basis as we determine appropriate. Customer and supplier relationships are typically amortized over a term of ten years. Covenants not-to-compete are amortized over the term of the non-compete covenant, which is generally two to five years. Licenses, permits and other contracts are amortized over the definitive terms of the related agreements. If the underlying agreement does not contain definitive terms and the useful life is determined to be indefinite, the asset is not amortized. Long-Lived Asset Impairments We assess our long-lived assets for impairment as required under the applicable accounting standards. If necessary, impairments are recorded in (gain) loss from divestitures, asset impairments and unusual items, net in our Consolidated Statement of Operations. Property and Equipment, Including Landfills and Definite-Lived Intangible Assets — We monitor the carrying value of our long-lived assets for potential impairment on an ongoing basis and test the recoverability of such assets generally using significant unobservable (“Level 3”) inputs whenever events or changes in circumstances indicate that their carrying amounts may not be recoverable. These events or changes in circumstances, including management decisions pertaining to such assets, are referred to as impairment indicators. If an impairment indicator occurs, we perform a test of recoverability by comparing the carrying value of the asset or asset group to its undiscounted expected future cash flows. If cash flows cannot be separately and independently identified for a single asset, we will determine whether an impairment has occurred for the group of assets for which we can identify the projected cash flows. If the carrying values are in excess of undiscounted expected future cash flows, we measure any impairment by comparing the fair value of the asset or asset group to its carrying value and the difference is recorded in the period that the impairment indicator occurs. Fair value is generally determined by considering (i) internally developed discounted projected cash flow analysis of the asset or asset group; (ii) actual third-party valuations and/or (iii) information available regarding the current market for similar assets. Estimating future cash flows requires significant judgment and projections may vary from the cash flows eventually realized, which could impact our ability to accurately assess whether an asset has been impaired. The assessment of impairment indicators and the recoverability of our capitalized costs associated with landfills and related expansion projects require significant judgment due to the unique nature of the waste industry, the highly regulated permitting process and the sensitive estimates involved. During the review of a landfill expansion application, a regulator may initially deny the expansion application although the expansion permit is ultimately granted. In addition, management may periodically divert waste from one landfill to another to conserve remaining permitted landfill airspace, or a landfill may be required to cease accepting waste, prior to receipt of the expansion permit. However, such events occur in the ordinary course of business in the waste industry and do not necessarily result in impairment of our landfill assets because, after consideration of all facts, such events may not affect our belief that we will ultimately obtain the expansion permit. As a result, our tests of recoverability, which generally make use of a probability-weighted cash flow estimation approach, may indicate that no impairment loss should be recorded. Indefinite-Lived Intangible Assets, Including Goodwill — At least annually, and more frequently if warranted, we assess the indefinite-lived intangible assets including the goodwill of our reporting units for impairment using Level 3 inputs. Beginning in 2018, we first performed a qualitative assessment to determine if it was more likely than not that the fair value of a reporting unit was less than its carrying value. If the assessment indicated a possible impairment, we completed a quantitative review, comparing the estimated fair value of a reporting unit to its carrying amount, including goodwill. An impairment charge was recognized if the asset’s estimated fair value was less than its carrying amount. Fair value is typically estimated using an income approach. However, when appropriate, we may also use a market approach. The income approach is based on the long-term projected future cash flows of the reporting units. We discount the estimated cash flows to present value using a weighted average cost of capital that considers factors such as market assumptions, the timing of the cash flows and the risks inherent in those cash flows. We believe that this approach is appropriate because it provides a fair value estimate based upon the reporting units’ expected long-term performance considering the economic and market conditions that generally affect our business. The market approach estimates fair value by measuring the aggregate market value of publicly-traded companies with similar characteristics to our business as a multiple of their reported earnings. We then apply that multiple to the reporting units’ earnings to estimate their fair values. We believe that this approach may also be appropriate in certain circumstances because it provides a fair value estimate using valuation inputs from entities with operations and economic characteristics comparable to our reporting units. Fair value is computed using several factors, including projected future operating results, economic projections, anticipated future cash flows, comparable marketplace data and the cost of capital. There are inherent uncertainties related to these factors and to our judgment in applying them in our analysis. However, we believe our methodology for estimating the fair value of our reporting units is reasonable. Refer to Note 11 for information related to impairments recognized during the reported periods. Insured and Self-Insured Claims We have retained a significant portion of the risks related to our health and welfare, general liability, automobile liability and workers’ compensation claims programs. The exposure for unpaid claims and associated expenses, including incurred but not reported losses, generally is estimated with the assistance of external actuaries and by factoring in pending claims and historical trends and data. The gross estimated liability associated with settling unpaid claims is included in accrued liabilities in our Consolidated Balance Sheets if expected to be settled within one year; otherwise, it is included in other long-term liabilities. Estimated insurance recoveries related to recorded liabilities are reflected as other current receivables or other long-term assets in our Consolidated Balance Sheets when we believe that the receipt of such amounts is probable. In December 2017, we elected to use a wholly-owned insurance captive to insure the deductibles for our general liability, automobile liability and workers’ compensation claims programs. We continue to maintain conventional insurance policies with third-party insurers. In addition to certain business and operating benefits of having a wholly-owned insurance captive, we expect to receive certain cash flow benefits related to the timing of tax deductions related to these claims. WM will pay an annual premium to the insurance captive, typically in the first quarter of the year, for the estimated losses based on the external actuarial analysis. These premiums are held in a restricted escrow account to be used solely for paying insurance claims, resulting in a transfer of risk from WM to the insurance captive and are allocated between current and long-term assets depending on timing on the use of funds. Restricted Trust and Escrow Accounts Our restricted trust and escrow accounts consist principally of funds deposited for purposes of funding insurance claims and settling landfill final capping, closure, post-closure and environmental remediation obligations. These funds are allocated between cash, money market funds and available-for-sale securities depending on the estimated timing and purpose of the use of funds. In December 2017, we elected to use a wholly-owned insurance captive to insure the deductibles for certain claims programs, as discussed above in Insured and Self-Insured Claims, and the premiums paid were directly deposited into a restricted escrow account to be used solely for paying insurance claims. At several of our landfills, we provide financial assurance by depositing cash into restricted trust or escrow accounts for purposes of settling final capping, closure, post-closure and environmental remediation obligations. Balances maintained in these restricted trust and escrow accounts will fluctuate based on (i) changes in statutory requirements; (ii) future deposits made to comply with contractual arrangements; (iii) the ongoing use of funds; (iv) acquisitions or divestitures and (v) changes in the fair value of the financial instruments held in the restricted trust or escrow accounts. See Note 18 for additional discussion related to restricted trust and escrow accounts for final capping, closure, post-closure or environmental remediation obligations. Investments in Unconsolidated Entities Investments in unconsolidated entities over which the Company has significant influence are accounted for under the equity method of accounting. Prior to 2018, investments in entities in which the Company does not have the ability to exert significant influence over the investees’ operating and financing activities were accounted for under the cost method of accounting. On January 1, 2018, we adopted ASU 2016-01, which resulted in certain equity investments previously accounted for under the cost method to be measured using a quantitative approach as we concluded these investments did not have readily determinable fair values. The quantitative approach, or measurement alternative, is equal to its cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. See Note 2 for additional information related to this amended guidance. The fair value of our redeemable preferred stock has been measured based on third-party investors’ recent or pending transactions in these securities, which are considered the best evidence of fair value. The following table summarizes our investments in unconsolidated entities as of December 31 (in millions):
|  | 2018 |  | 2017
Equity method investments |  | $ | 257 |  | $ | 127
Investments without readily determinable fair values |  |  | 83 |  |  | 87
Redeemable preferred stock |  |  | 66 |  |  | 55
Investments in unconsolidated entities |  | $ | 406 |  | $ | 269
We monitor and assess the carrying value of our investments throughout the year for potential impairment and write them down to their fair value when other-than-temporary declines exist. Fair value is generally based on (i) other third-party investors’ recent transactions in the securities; (ii) other information available regarding the current market for similar assets; (iii) a market or income approach, as deemed appropriate and/or (iv) a quantitative approach, or measurement alternative, as noted above. Impairments of our investments are recorded in equity in net losses of unconsolidated entities or other, net in the Consolidated Statements of Operations in accordance with appropriate accounting guidance. Refer to Notes 11 and 16 for information related to impairments and other adjustments recognized during the reported periods. Foreign Currency We have operations in Canada, as well as certain support functions in India. Local currencies generally are considered the functional currencies of our operations and investments outside the U.S. The assets and liabilities of our foreign operations are translated to U.S. dollars using the exchange rate as of the balance sheet date. Revenues and expenses are translated to U.S. dollars using the average exchange rate during the period. The resulting translation difference is reflected as a component of other comprehensive income (loss). Cross-Currency Swaps From time to time, we will use derivative financial instruments to manage our risk associated with fluctuations in foreign currency exchange rates. Through March 2016, we used cross-currency swaps to hedge our exposure to fluctuations in exchange rates for anticipated intercompany cash transactions between Waste Management Holdings, Inc., a wholly-owned subsidiary (“WM Holdings”), and its Canadian subsidiaries. Our cross-currency swaps had been designated as cash flow hedges for accounting purposes, which resulted in the unrealized changes in the fair value of the derivative instruments being recorded in accumulated other comprehensive income (loss) within our Consolidated Balance Sheets. The associated balance in accumulated other comprehensive income (loss) was reclassified to earnings as the hedged cash flows affected earnings. The financial statement impacts of our cross-currency swaps are discussed in Note 7. Revenue Recognition Our Solid Waste operating revenues are primarily generated from fees charged for our collection, transfer, disposal, and recycling and resource recovery services, and from sales of commodities by our recycling and landfill gas-to-energy operations. Revenues from our collection operations are influenced by factors such as collection frequency, type of collection equipment furnished, type and volume or weight of the waste collected, distance to the disposal facility or material recovery facility and our disposal costs. Revenues from our landfill operations consist of tipping fees, which are generally based on the type and weight or volume of waste being disposed of at our disposal facilities. Fees charged at transfer stations are generally based on the weight or volume of waste deposited, taking into account our cost of loading, transporting and disposing of the solid waste at a disposal site. Recycling revenues generally consist of tipping fees and the sale of recycling commodities to third parties. The fees we charge for our services generally include our environmental fee, fuel surcharge and regulatory recovery fee, which are intended to pass through to customers direct and indirect costs incurred. We also provide additional services that are not managed through our Solid Waste business, including operations managed by both our Strategic Business Solutions (“WMSBS”) and Energy and Environmental Services (“EES”) organizations, recycling brokerage services, landfill gas-to-energy services and certain other expanded service offerings and solutions. Our revenue from sources other than customer contracts primarily relates to lease revenue associated with compactors and balers. Revenue from these leasing arrangements was not material and represented approximately 1% of total revenue for each of the reported periods. We generally recognize revenue as services are performed or products are delivered. For example, revenue typically is recognized as waste is collected, tons are received at our landfills or transfer stations, or recycling commodities are collected or delivered as product. We bill for certain services prior to performance. Such services include, among others, certain commercial and residential contracts and equipment rentals. These advance billings are included in deferred revenues and recognized as revenue in the period service is provided. See Note 19 for additional information related to revenue by reportable segment and major lines of business. Deferred Revenues We record deferred revenues when cash payments are received or due in advance of our performance and classify them as current since they are earned within a year and there are no significant financing components. Substantially all our deferred revenues during the reported periods are realized as revenues within one to three months, when the related services are performed. Contract Acquisition Costs Our incremental direct costs of obtaining a contract, which consist primarily of sales incentives, are generally deferred and amortized to selling, general and administrative expense over the estimated life of the relevant customer relationship, ranging from 5 to 13 years. Contract acquisition costs that are paid to the customer are deferred and amortized as a reduction in revenue over the contract life. Our contract acquisition costs are classified as current or noncurrent based on the timing of when we expect to recognize amortization and are included in other assets in our Consolidated Balance Sheet. As of December 31, 2018, we had $145 million of deferred contract costs, of which $109 million was related to deferred sales incentives. During the year ended December 31, 2018, we amortized $22 million of sales incentives to selling, general and administrative expense and $35 million of other contract acquisition costs as a reduction in revenue. Long-Term Contracts Approximately 25% of our total revenue is derived from contracts with a remaining term greater than one year. The consideration for these contracts is primarily variable in nature. The variable elements of these contracts primarily include the number of homes and businesses served and annual rate changes based on consumer price index, fuel prices or other operating costs. Such contracts are generally within our collection, recycling and other lines of business and have a weighted average remaining contract life of approximately four years. We do not disclose the value of unsatisfied performance obligations for these contracts as our right to consideration corresponds directly to the value provided to the customer for services completed to date and all future variable consideration is allocated to wholly unsatisfied performance obligations. Capitalized Interest We capitalize interest on certain projects under development, including landfill expansion projects, certain assets under construction, including operating landfills and landfill gas-to-energy projects and internal-use software. During 2018, 2017 and 2016, total interest costs were $400 million, $383 million and $394 million, respectively, of which $16 million, $15 million and $9 million was capitalized in 2018, 2017 and 2016, respectively. Income Taxes The Company is subject to income tax in the U.S. and Canada. Current tax obligations associated with our income tax expense are reflected in the accompanying Consolidated Balance Sheets as a component of accrued liabilities and our deferred tax obligations are reflected in deferred income taxes. Deferred income taxes are based on the difference between the financial reporting and tax basis of assets and liabilities. Deferred income tax expense represents the change during the reporting period in the deferred tax assets and liabilities, net of the effect of acquisitions and dispositions. Deferred tax assets include tax loss and credit carry-forwards and are reduced by a valuation allowance if, based on available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. We establish reserves for uncertain tax positions when, despite our belief that our tax return positions are fully supportable, we believe that certain positions may be challenged and potentially disallowed. When facts and circumstances change, we adjust these reserves through our income tax expense. Should interest and penalties be assessed by taxing authorities on any underpayment of income tax, such amounts would be accrued and classified as a component of our income tax expense in our Consolidated Statements of Operations. See Note 8 for discussion of the impacts of enactment of the Act which was signed into law on December 22, 2017 and is generally effective for tax years beginning January 1, 2018. Contingent Liabilities We estimate the amount of potential exposure we may have with respect to claims, assessments and litigation in accordance with authoritative guidance on accounting for contingencies. We are party to pending or threatened legal proceedings covering a wide range of matters in various jurisdictions. It is difficult to predict the outcome of litigation, as it is subject to many uncertainties. Additionally, it is not always possible for management to make a meaningful estimate of the potential loss or range of loss associated with such contingencies. See Note 10 for discussion of our commitments and contingencies. Supplemental Cash Flow Information The following table shows supplemental cash flow information for the years ended December 31 (in millions):
|  | 2018 |  | 2017 |  | 2016
Interest, net of capitalized interest |  | $ | 339 |  | $ | 380 |  | $ | 375
Income taxes |  |  | 349 |  |  | 562 |  |  | 442
During 2018, we had $250 million of non-cash financing activities from our recent federal low-income housing investment discussed in Note 8 and new capital leases. During 2017 and 2016, we did not have any significant non-cash investing and financing activities. Non-cash investing and financing activities are generally excluded from the Consolidated Statements of Cash Flows.

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