Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at beginning of year	$ 57.6	$ 60.3	$ 69.8
Additions based on tax positions related to the current year	3.0	3.5	9.0
Additions for tax positions of prior years	8.0	2.7	2.2
Reductions for tax positions of prior years	(5.3)	(7.7)	(19.5)
Settlements	(0.2)	(1.2)	(0.4)
Statute expirations	(10.7)	0.0	(0.8)
Balance at end of year	52.4	57.6	60.3
Net unrecognized tax benefit that would affect the effective tax rate	43.6	40.9	$ 42.0
Interest and penalties liability increase (decrease)	2.7	(1.1)
Unrecognized tax benefits, interest and penalties liability	13.1
Resolution of federal income tax refund claims of domestic manufacturing deduction		$ 11.9
Minimum | U.S. government
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Uncertain tax positions that may reverse in 2016	5.0
Maximum | U.S. government
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Uncertain tax positions that may reverse in 2016	$ 7.0