Income Taxes (Provision for Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal	$ 106.0	$ 101.0	$ 84.3
State	14.5	13.1	10.1
Foreign	9.7	3.6	9.6
Total current	130.2	117.7	104.0
Deferred:
Federal	(4.5)	(21.4)	2.3
State	(1.2)	(0.6)	1.0
Foreign	(0.4)	(0.3)	2.2
Total deferred	(6.1)	(22.3)	5.5
Total provision for income taxes	$ 124.1	$ 95.4	$ 109.5