Debt (Cash Flow Hedges) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 300,000,000.0
(Losses) gains recognized in other comprehensive income	(8,200,000)	$ 3,100,000	$ 32,400,000
Accumulated and other comprehensive income (loss), net of tax	11,200,000	(11,800,000)
Effective portion of interest rate locks amortized as an adjustment to interest expense	300,000	2,700,000	9,800,000
Interest Rate Locks
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 725,000,000.0	$ 825,000,000.0
Floor interest rate	1.90%	1.90%
Cap interest rate	3.25%	2.418%
Amount of ineffectiveness on cash flow hedges	$ 0	$ 0	0
(Losses) gains recognized in other comprehensive income	(6,500,000)	(700,000)	$ 12,200,000
Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Effective portion of interest rate locks amortized as an adjustment to Interest expense expected over the next twelve months	700,000
Other Noncurrent Liabilities | Interest Rate Locks
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative liability	$ 10,300,000	$ 19,100,000