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Financial Instruments - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Mar. 31, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Derivative [Line Items] |  |  |  |  |
Premium payments on interest rate cap agreements |  |  |  | $ 12.6 | $ 0.0
Unrealized gain (loss) on effective portion of interest rate cap agreements | $ 0.0 |  | $ 0.0 |  |
Interest income (expense) reclassified into earnings (less than) |  |  |  |  | 1.0
Cap agreement effective 12/31/18-12/31/20 |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional amount | 1,400.0 | $ 1,400.0 |  | 1,400.0 |
Premium payments on interest rate cap agreements |  | $ 13.0 |  |  |
Interest Rate Contract |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Unrealized gain (loss) on effective portion of interest rate cap agreements |  |  |  | 6.0 | $ (1.0)
Amount expected to be reclassified from AOCL to interest expense in next twelve months |  |  |  | (5.0) |
Derivative |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Interest income (expense) reclassified into earnings (less than) | $ (1.0) |  |  | $ (3.0) |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994 + Details
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- Definition The amount of net gains or losses on interest rate cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959 + Details
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- Definition Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=109978405&loc=d3e80720-113993 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580 + Details
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