Income Taxes - Consolidated Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 109.0	$ 103.4	$ 106.3
State	18.9	22.9	18.3
Foreign	54.1	50.0	37.6
Total current	182.0	176.3	162.2
Deferred:
Federal	(124.9)	62.3	103.8
State	10.4	10.0	14.8
Foreign	(9.1)	(13.0)	(17.4)
Total deferred	(123.6)	59.3	101.2
Provision for income taxes	$ 58.4	$ 235.6	$ 263.4