Financial Instruments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Interest rate cap, fair value	$ 1.0	$ 1.0
Unrealized gain (loss) on effective portion of interest rate cap agreement	0.6	11.3	$ 5.9
Interest Rate Cap
Derivative [Line Items]
Notional amount	1,400.0	2,800.0
Interest Rate Cap Agreement Effective December 31, 2020
Derivative [Line Items]
Notional amount	1,400.0
Interest Rate Contract
Derivative [Line Items]
Unrealized gain (loss) on effective portion of interest rate cap agreement	(0.6)	(11.3)	(5.9)
Amount expected to be reclassified from AOCL to interest expense	(3.0)
Derivative
Derivative [Line Items]
Interest income (expense) reclassified into earnings (less than)	(6.0)	$ (1.7)	$ (3.9)
Interest Rate Cap Agreement Effective December 31, 2022
Derivative [Line Items]
Notional amount	$ 1,400.0