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Long-Term Debt and Commercial Paper (Narrative) (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2017 | Dec. 31, 2016
Debt Instrument [Line Items] |  |  |
Letters of credit, amount outstanding |  | $ 49.0 |
Commercial paper, maximum aggregate amount outstanding permitted |  | 1,000.0 |
Commercial paper, amount outstanding |  | 790.0 | $ 942.0
6.75% Senior Notes Due 2018 [Member] | Senior Notes [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Senior notes |  | $ 400.0 | 400.0
Percentage interest on debt instrument (percent) |  | 6.75% |
Debt instrument, maturity date |  | Apr. 15, 2018 |
5.5% Senior Notes Due 2020 [Member] | Senior Notes [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Senior notes |  | $ 350.0 | 350.0
Percentage interest on debt instrument (percent) |  | 5.50% |
Debt instrument, maturity date |  | Feb. 01, 2020 |
3.35% Senior Notes due 2021 [Member] | Senior Notes [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Senior notes |  | $ 300.0 | 300.0
Percentage interest on debt instrument (percent) |  | 3.35% |
Debt instrument, maturity date |  | Jan. 15, 2021 |
4.5% Senior Notes due 2025 [Member] | Senior Notes [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Senior notes |  | $ 450.0 | 450.0
Percentage interest on debt instrument (percent) |  | 4.50% |
Debt instrument, maturity date |  | Oct. 01, 2025 |
Revolving Credit Facility Due 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Maximum borrowing capacity under revolving credit facility |  | $ 1,800.0 |
Additional borrowing capacity under accordion feature of revolving credit facility |  | 500.0 |
Revolving credit facility, amount outstanding |  | 0.0 | 0.0
Revolving credit facilities letter of credit sublimit |  | 200.0 |
Additional borrowing capacity under the revolving credit facility |  | 1,800.0 |
Borrowing capacity limited under the maximum consolidated leverage ratio |  | $ 1,000.0 |
Leverage ratio, minimum threshold, current credit spread |  | 2.0 |
Leverage ratio, maximum threshold, current credit spread |  | 3.25 |
Leverage ratio, minimum threshold, increase in credit spread |  | 3.25 |
Impact on credit spread from increase in leverage ratio |  | 0.125% |
Revolving Credit Facility Due 2019 [Member] | Line of Credit [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt instrument, maturity date |  | Dec. 03, 2019 |
Mortgage Facility [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Mortgage facility, amount outstanding | [1] | $ 148.2 | 153.2
Mortgage Facility [Member] | Secured Debt [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt instrument, maturity date |  | Nov. 30, 2017 |
Mortgage facility, fixed interest rate (percent) |  | 5.864% |
Number of years of mortgage loans |  | 10 years |
Monthly principal and interest payments on mortgage facility |  | $ 1.6 |
Balloon payment for mortgage |  | 143.9 |
Capital Leases and Other Debt [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Capital leases and other debt |  | $ 139.4 | $ 136.2
Minimum [Member] | Revolving Credit Facility Due 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Commitment fee on undrawn amounts (percent) |  | 0.175% |
Maximum [Member] | Revolving Credit Facility Due 2019 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Commitment fee on undrawn amounts (percent) |  | 0.25% |
Commercial Paper [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Weighted-average annual interest rate |  | 1.72% | 1.26%
Commercial Paper [Member] | Maximum [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Maturity period of debt |  | 397 days |
Commercial Paper [Member] | Weighted Average [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Maturity period of debt |  | 15 days | 24 days
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Revolving Credit Facility Due 2019 [Member] | Line of Credit [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Basis spread on variable interest rates (percent) |  | 1.25% |
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Revolving Credit Facility Due 2019 [Member] | Line of Credit [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Basis spread on variable interest rates (percent) |  | 1.625% |
Base Rate [Member] | Minimum [Member] | Revolving Credit Facility Due 2019 [Member] | Line of Credit [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Basis spread on variable interest rates (percent) |  | 0.25% |
Base Rate [Member] | Maximum [Member] | Revolving Credit Facility Due 2019 [Member] | Line of Credit [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Basis spread on variable interest rates (percent) |  | 0.625% |
[1] | The mortgage facility requires monthly principal and interest payments of $1.6 million based on a fixed amortization schedule with a balloon payment of $143.9 million due November 2017.

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- Definition The minimum, inclusive, leverage ratio, as defined in the credit agreement, in which the credit spread on the revolver would increase based on the pricing terms outlined in the agreement. + References No definition available. + Details
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- Definition Maximum amount of increase in the revolving credit facility allowed under the accordion feature of the credit agreement, subject to credit availability and certain other conditions. + References No definition available. + Details
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- Definition Term of mortgages on certain of our store properties that secure our mortgage facility. + References No definition available. + Details
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- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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