Fair Value Measurements - Gains (Losses) on Interest Rate Swaps (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments unrealized (loss) gain, net of tax	$ (0.1)	$ 4.2	$ 3.0
Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments unrealized (loss) gain, net of tax	0.1	(4.2)	(3.0)
Interest expense recorded related to interest rate swap contracts	$ 2.6	$ 7.0	$ 8.2