Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2018
Accounting Policies [Abstract]
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents include cash on hand and cash invested in highly liquid short-term securities, which have remaining maturities at the date of purchase of less than 90 days. Cash and cash equivalents are carried at cost, which approximates fair value.
Revenue Recognition, Policy [Policy Text Block]	Revenues In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-09. ASU 2014-09 provides guidance for management to reassess revenue recognition as it relates to: (1) transfer of control, (2) variable consideration, (3) allocation of transaction price based on relative standalone selling price, (4) licenses, (5) time value of money, and (6) contract costs. We adopted ASU 2014-09 as of January 1, 2018 using the modified retrospective method for all of our customer contracts, whereby the cumulative effect of applying ASU 2014-09 is recognized at the date of initial application. At January 1, 2018, we recognized the cumulative effect of initially applying ASU 2014-09 as an adjustment to the opening balance of (distributions in excess of earnings) earnings in excess of distributions, resulting in a decrease of $30,233 to stockholders' equity. The reduction of (distribution in excess of earnings) earnings in excess of distributions represents the net effect of (i) the write-off of Free Move Costs, net (which were capitalized and amortized prior to the adoption of ASU 2014-09) based upon the net book value of the Free Move Costs as of December 31, 2017, (ii) the recognition of certain Contract Fulfillment Costs, specifically Intake Costs (each as defined below) and commission assets, (iii) the recognition of deferred revenue associated with Intake Costs billed to our customers (as discussed below), and (iv) the deferred income tax impact of the aforementioned items. As we adopted ASU 2014-09 on a modified retrospective basis, the comparative Condensed Consolidated Balance Sheet as of December 31, 2017, the Condensed Consolidated Statements of Operations and the Condensed Consolidated Statements of Comprehensive Income (Loss) for the three and nine months ended September 30, 2017 and the Condensed Consolidated Statement of Equity and the Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2017 have not been restated to reflect the adoption of ASU 2014-09 and reflect our revenue policies in place at that time, as disclosed in Note 2.l. to Notes to Consolidated Financial Statements included in our Annual Report. Storage rental and service revenues are recognized in the month the respective storage rental or service is provided, and customers are generally billed on a monthly basis on contractually agreed-upon terms. The performance obligation is a series of distinct services (as determined for purposes of ASU 2014-09, a “series”) that have the same pattern of transfer to the customer that is satisfied over time. For those contracts that qualify as a series, we have a right to consideration from the customer in an amount that corresponds directly with the value of the underlying performance obligation transferred to the customer to date. This concept is known as "right to invoice" and we are applying the "right to invoice" practical expedient to all revenues, with the exception of storage revenues in our data center business. For all of our businesses, with the exception of the storage component of our data center business, each purchasing decision is fully in the control of the customer and, therefore, consideration beyond the current reporting period is variable and allocated to the specific period, which is consistent with the practical expedient above. Our data center business features storage rental provided to the customer at contractually specified rates over a fixed contractual period. The storage rental revenue related to the storage component of our data center business is recognized on a straight-line basis over the contract term. The revenue related to the service component of our data center business is recognized in the period the data center access or related services are provided. Total data center revenues represent approximately 5% of our total consolidated revenues for the nine months ended September 30, 2018. The costs associated with the initial movement of customer records into physical storage and certain commissions are considered costs to obtain or fulfill customer contracts (“Contract Fulfillment Costs”). The following describes each of these Contract Fulfillment Costs recognized under ASU 2014-09: Intake Costs (and associated deferred revenue) Prior to the adoption of ASU 2014-09, intake costs incurred but not charged to a customer to transport records to our facilities (or Free Move Costs, as described in Note 2.b.), which include labor and transportation costs, were capitalized and amortized as a component of depreciation and amortization in our Consolidated Statements of Operations. The initial movement of customer records into physical storage must take place prior to initiation of the storage of records and is not considered a separate performance obligation and, therefore, the costs of the initial intake of customer records into physical storage (“Intake Costs”) represent a contract fulfillment cost for the storage of records as the earnings process does not commence until a customer’s records or other assets are in our possession. Accordingly, upon the adoption of ASU 2014-09, all Intake Costs, regardless of whether or not the services associated with such initial moves are billed to the customer or are provided to the customer at no charge, will be deferred and amortized as a component of depreciation and amortization in our Consolidated Statements of Operations over three years, consistent with the transfer of the performance obligation to the customer to which the asset relates. Similarly, in instances where such Intake Costs are billed to the customer, the associated revenue will be deferred and recognized over the same three year period. Commissions Prior to the adoption of ASU 2014-09, commissions we paid related to our long-term storage contracts were expensed as incurred. Upon the adoption of ASU 2014-09, certain commission payments that are directly associated with the fulfillment of long-term storage contracts are capitalized and amortized as a component of depreciation and amortization in our Consolidated Statements of Operations over three years, consistent with the transfer of the performance obligation to the customer to which the asset relates. Certain direct commission payments associated with contracts with a duration of one year or less are expensed as incurred under the practical expedient which allows an entity to expense as incurred an incremental cost of obtaining a contract if the amortization period of the asset that the entity otherwise would have recognized is one year or less.
Goodwill and Other Intangible Assets	Finite-lived intangible assets and liabilities i. Customer Relationship Intangible Assets Customer relationship intangible assets, which are acquired through either business combinations or acquisitions of customer relationships, are amortized over periods ranging from 10 to 30 years and are included in depreciation and amortization in the accompanying Condensed Consolidated Statements of Operations. The value of customer relationship intangible assets is calculated based upon estimates of their fair value. ii. Customer Inducements Prior to the adoption of ASU 2014-09, free intake costs to transport boxes to one of our facilities, which include labor and transportation costs ("Free Move Costs"), were capitalized and amortized over periods ranging from 10 to 30 years. The amortization of Free Move Costs is included in depreciation and amortization in the accompanying Condensed Consolidated Statements of Operations for the three and nine months ended September 30, 2017. Subsequent to the adoption of ASU 2014-09, Free Move Costs are considered a Contract Fulfillment Cost (as defined in Note 2.c.) and, therefore, are now deferred and amortized and included in amortization expense over three years, consistent with the transfer of the performance obligation to the customer to which the asset relates. See Note 2.c. for information regarding the accounting for Free Move Costs, which are now a component of Intake Costs (as defined in Note 2.c.), following the adoption of ASU 2014-09. Payments that are made to a customer's current records management vendor in order to terminate the customer's existing contract with that vendor, or direct payments to a customer ("Permanent Withdrawal Fees"), are amortized over periods ranging from 5 to 15 years and are included in storage and service revenue in the accompanying Condensed Consolidated Statements of Operations. Our accounting for Permanent Withdrawal Fees did not change as a result of the adoption of ASU 2014-09. Free Move Costs (prior to the adoption of ASU 2014-09) and Permanent Withdrawal Fees are collectively referred to as "Customer Inducements". If the customer terminates its relationship with us, the unamortized carrying value of the Customer Inducement intangible asset is charged to expense or revenue. However, in the event of such termination, we generally collect, and record as income, permanent removal fees that generally equal or exceed the amount of the unamortized Customer Inducement intangible asset. iii. Data Center Intangible Assets and Liabilities Finite-lived intangible assets associated with our data center business consist of the following: Data Center In-Place Lease Intangible Assets and Data Center Tenant Relationship Intangible Assets Data Center In-Place Lease Intangible Assets (“Data Center In-Place Leases”) and Data Center Tenant Relationship Intangible Assets (“Data Center Tenant Relationships") are acquired through either business combinations or asset acquisitions in our data center business. These intangible assets reflect the value associated with acquiring a data center operation with active tenants as of the date of acquisition. The value of Data Center In-Place Leases is determined based upon an estimate of the economic costs (such as lost revenues and unreimbursed operating expenses during the lease-up period, tenant improvement costs, commissions, legal expenses and other costs to acquire new data center leases) avoided by acquiring a data center operation with active tenants that would have otherwise been incurred if the data center operation was purchased vacant. Data Center In-Place Leases are amortized over the weighted average remaining term of the acquired data center leases and are included in depreciation and amortization in the accompanying Condensed Consolidated Statements of Operations. The value of Data Center Tenant Relationships is determined based upon an estimate of the economic costs avoided upon lease renewal of the acquired tenants, based upon expectations of lease renewal. Data Center Tenant Relationships are amortized over the weighted average remaining anticipated life of the relationship with the acquired tenant and are included in depreciation and amortization in the accompanying Condensed Consolidated Statements of Operations. Data Center In-Place Leases and Data Center Tenant Relationships are included in Customer relationships, customer inducements and data center lease-based intangibles in the accompanying Condensed Consolidated Balance Sheets. Data Center Above-Market and Below-Market In-Place Lease Intangible Assets Data Center Above-Market In-Place Lease Intangible Assets (“Data Center Above-Market Leases”) and Data Center Below-Market In-Place Lease Intangible Assets (“Data Center Below-Market Leases”) are acquired through either business combinations or asset acquisitions in our data center business. We record Data Center Above-Market Leases and Data Center Below-Market Leases at the net present value of the difference between (i) the contractual amounts to be paid pursuant to each in-place lease and (ii) management’s estimate of the fair market lease rates for each corresponding in-place lease. Data Center Above-Market Leases and Data Center Below-Market Leases are amortized over the remaining non-cancellable term of the acquired in-place lease to storage revenue in the accompanying Condensed Consolidated Statements of Operations. Data Center Above-Market Leases are included in Customer relationships, customer inducements and data center lease-based intangibles in the accompanying Condensed Consolidated Balance Sheets. Data Center Below-Market Leases are included in Other long-term liabilities in the accompanying Condensed Consolidated Balance Sheets.
Stock-Based Compensation	Stock-Based Compensation We record stock-based compensation expense, utilizing the straight-line method, for the cost of stock options, restricted stock units ("RSUs"), performance units ("PUs") and shares of stock issued under our employee stock purchase plan ("ESPP") (together, "Employee Stock-Based Awards"). Under our various equity compensation plans, we may also make awards of PUs. For the majority of outstanding PUs, the number of PUs earned is determined based on our performance against predefined targets of revenue and return on invested capital ("ROIC") and, beginning with PUs granted in 2018, Adjusted EBITDA (as defined in Note 7). The number of PUs earned may range from 0% to 200% of the initial award. The number of PUs earned is determined based on our actual performance as compared to the targets at the end of a three-year performance period. Certain PUs that we grant will be earned based on a market condition associated with the total return on our common stock in relation to either (i) a subset of the Standard & Poor's 500 Index (for certain PUs granted prior to 2017), or (ii) the MSCI United States REIT Index (for certain PUs granted in 2017 and thereafter), rather than the revenue, ROIC and Adjusted EBITDA targets noted above. The number of PUs earned based on the applicable market condition may range from 0% to 200% of the initial award. We forecast the likelihood of achieving the predefined revenue, ROIC and Adjusted EBITDA targets for our PUs in order to calculate the expected PUs to be earned. We record a compensation charge based on either the forecasted PUs to be earned (during the performance period) or the actual PUs earned (at the three-year anniversary of the grant date) over the vesting period for each of the awards. The fair value of PUs based on our performance against revenue, ROIC and Adjusted EBITDA targets is the excess of the market price of our common stock at the date of grant over the purchase price (which is typically zero). For PUs earned based on a market condition, we utilize a Monte Carlo simulation to fair value these awards at the date of grant, and such fair value is expensed over the three-year performance period.
Income (Loss) Per Share-Basic and Diluted	Income (Loss) Per Share—Basic and Diluted Basic income (loss) per common share is calculated by dividing income (loss) by the weighted average number of common shares outstanding. The calculation of diluted income (loss) per share is consistent with that of basic income (loss) per share but gives effect to all potential common shares (that is, securities such as stock options, RSUs or PUs) that were outstanding during the period, unless the effect is antidilutive.
Income Taxes	We provide for income taxes during interim periods based on our estimate of the effective tax rate for the year. Our estimate of the effective tax rate for the year ending December 31, 2018 reflects the impact of the Tax Reform Legislation (as defined below). Discrete items and changes in our estimate of the annual effective tax rate are recorded in the period they occur. Our effective tax rate is subject to variability in the future due to, among other items: (1) changes in the mix of income between our qualified REIT subsidiaries ("QRSs") and our domestic taxable REIT subsidiaries ("TRSs"), as well as among the jurisdictions in which we operate; (2) tax law changes; (3) volatility in foreign exchange gains and losses; (4) the timing of the establishment and reversal of tax reserves; and (5) our ability to utilize net operating losses that we generate.
Fair Value Measurements	Fair Value Measurements Our financial assets or liabilities that are carried at fair value are required to be measured using inputs from the three levels of the fair value hierarchy. A financial asset or liability's classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. The three levels of the fair value hierarchy are as follows: Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities that we have the ability to access at the measurement date. Level 2—Inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs). Level 3—Unobservable inputs that reflect our assumptions about the assumptions that market participants would use in pricing the asset or liability.
New Accounting Pronouncements	New Accounting Pronouncements Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU 2014-09. We adopted ASU 2014-09 on January 1, 2018 using the modified retrospective method. See Note 2.c. for information regarding the impact of the adoption of ASU 2014-09 on our consolidated financial statements. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01"). ASU 2016-01 requires that most equity investments be measured at fair value, with subsequent changes in fair value recognized in net income, while eliminating the available-for-sale classification for equity securities with readily determinable fair values and the cost method for equity investments without readily determinable fair values. ASU 2016-01 also impacts financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. We adopted ASU 2016-01 on January 1, 2018. ASU 2016-01 did not have an impact on our consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities ("ASU 2017-12"). ASU 2017-12 amends the hedge accounting recognition and presentation requirements as outlined in Accounting Standards Codification Topic 815 with the objective of improving the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements and enhance the transparency and understandability of hedge transactions. In addition, ASU 2017-12 simplifies the application of the hedge accounting guidance. We adopted ASU 2017-12 on January 1, 2018. ASU 2017-12 did not have a material impact on our consolidated financial statements. Other As Yet Adopted Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) ("ASU 2016-02"). ASU 2016-02 will require lessees to recognize assets and liabilities on the balance sheet for the rights and obligations created by all leases with terms of more than 12 months. ASU 2016-02 also will require certain qualitative and quantitative disclosures designed to give financial statement users information on the amount, timing, and uncertainty of cash flows arising from leases. ASU 2016-02 will be effective for us on January 1, 2019. We have established a cross functional project team responsible for the assessment and implementation of ASU 2016-02. We have also entered into an agreement for the use of a lease accounting software solution that will support us in meeting the accounting and reporting requirements specific to ASU 2016-02, and are in the process of implementing this solution. In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases (“ASU 2018-10”) and ASU No. 2018-11, Leases (Topic 842) Targeted Improvements (“ASU 2018-11”). ASU 2018-10 amends certain aspects of the guidance issued in ASU 2016-02. ASU 2018-11 provides entities with relief from the costs of implementing certain aspects of the new leasing standard, ASU 2016-02; specifically, (1) entities may elect not to recast the comparative periods presented when transitioning to ASU 2016-02, and (2) lessors may elect not to separate lease and nonlease components when certain conditions are met. We are currently evaluating the impact ASU 2016-02, including ASU 2018-10 and ASU 2018-11, will have on our consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force) ("ASU 2018-15"). ASU 2018-15 aligns the accounting for costs incurred to implement a cloud computing arrangement that is a service arrangement with the guidance on capitalizing costs associated with developing or obtaining internal-use software. ASU 2018-15 is effective for us on January 1, 2020, with early adoption permitted. We do not expect ASU 2018-15 will have a material impact on our consolidated financial statements.

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.