Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of the beginning and ending balances of the total amounts of unrecognized tax benefits
Balance at the beginning of the year	$ 4.1	$ 5.2	$ 22.9
Increases in tax positions for prior years	0.4		0.4
Decreases in tax positions for prior years		(0.1)	(0.6)
Increases in tax positions for current year			0.1
Settlements		(0.2)	(17.6)
Lapse of statute of limitations	(2.1)	(0.8)
Balance at the end of the year	2.4	4.1	$ 5.2
Unrecognized tax benefits, if recognized, would affect the effective tax rate	2.4
Accrued interest and penalties on uncertain tax positions	$ 0.5	$ 0.5