Income Taxes - Pretax Income, Provision for Income Taxes and Reconciliation of Effective Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pretax income (loss)
U.S.									$ 451.8	$ 248.2	$ 451.9
International									80.1	31.0	6.9
Income from continuing operations before income taxes and non-controlling interest	$ 99.2	$ 61.8	$ 108.7	$ 262.2	$ 81.4	$ 82.6	$ 56.6	$ 58.6	531.9	279.2	458.8
Current
Federal									93.7	57.7	147.4
State and local									4.0	11.4	10.2
International									13.7	15.0	7.1
Total current									111.4	84.1	164.7
Deferred
Federal									(34.2)	19.9	(13.5)
State and local									2.4	(1.9)	0.5
International									4.7	(1.0)	(2.5)
Total deferred									(27.1)	17.0	(15.5)
Income taxes	18.0	13.0	35.2	18.1	27.3	31.6	22.1	20.1	84.3	101.1	149.2
Differences between the Company's effective income tax rate and the U.S. federal income tax statutory rate
Provision for income taxes using the statutory rate in effect									186.2	97.7	160.6
Tax effect of:
State and local income taxes, net									4.5	5.9	4.3
International income taxes, net									(9.5)	2.5	(1.0)
Earnings of U.S. unconsolidated affiliates									(1.0)	(2.3)	(1.5)
Valuation allowance (reversal), net									(1.3)	(0.9)	1.2
Tax credits									(1.0)	(5.0)	(7.7)
Uncertain tax positions (reversal), net									(2.8)	1.7	(7.9)
Dividend received deduction									(0.1)	(0.8)	(1.2)
Domestic production activities deduction									(2.5)	(1.7)	(0.1)
Repatriation									1.0	1.0	1.9
Tax Cuts and Jobs Act impact									(13.7)	0.0	0.0
Tax impact of transactions									(71.4)	0.0	0.0
Other									(4.1)	3.0	0.6
Income taxes	$ 18.0	$ 13.0	$ 35.2	$ 18.1	$ 27.3	$ 31.6	$ 22.1	$ 20.1	$ 84.3	$ 101.1	$ 149.2
Effective tax rate (as a percent)									15.80%	36.20%	32.50%
Statutory federal tax rate (as a percent)									35.00%	35.00%	35.00%