Income Taxes Components of Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income before income taxes:
United States	$ 354.7	$ 349.5	$ 347.2
International	88.4	80.9	71.4
Income before income taxes	443.1	430.4	418.6
Provision for income taxes — current:
Federal	164.1	85.5	110.4
State	15.3	17.4	13.7
International	28.1	17.0	17.6
Total provision-current	207.5	119.9	141.7
Provision for income taxes — deferred:
Federal	(10.4)	13.5	(1.7)
State	(0.9)	1.3	0.4
International	(3.0)	(2.1)	(3.9)
Total provision — deferred	(14.3)	12.7	(5.2)
TOTAL PROVISION FOR INCOME TAXES	$ 193.2	$ 132.6	$ 136.5