Hedging Activities, Derivative Instruments and Fair Value Measurements - Comprehensive Income (Loss) (Details) - Interest Rate Swaps - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Gains and Losses on Derivatives Designated as Cash Flow Hedges [Abstract]
Loss recognized in AOCI on derivatives	$ 0.0	$ (0.6)	$ 0.0	$ (4.3)
Loss reclassified from AOCI into income (effective portion)	$ 0.0	$ (7.9)	$ 0.0	$ (13.2)