Income Taxes - Income taxes relating to continuing operations and deferred taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income from continuing operations before income taxes by geographic region
U.S.	$ 375.4	$ 316.7	$ 309.4
Non-U.S.	172.8	191.4	182.5
Income from continuing operations before income taxes	548.2	508.1	491.9
Current:
Federal	(3.5)	(47.2)	61.8
State and local	4.2	4.7	11.5
Foreign	43.2	41.0	40.1
Total current	43.9	(1.5)	113.4
Deferred:
Federal	(150.5)	140.6	40.1
State and local	47.2	22.3	8.4
Foreign	(5.4)	(0.7)	(3.9)
Total deferred	(108.7)	162.2	44.6
Income taxes	$ (64.8)	$ 160.7	$ 158.0
Reconciliation of income taxes from continuing operations at federal statutory rate
Federal statutory income tax rate (as a percent)	35.00%	35.00%	35.00%
Income taxes at federal statutory rate of 35%	$ 191.9	$ 177.8	$ 172.2
State and local income taxes, net of federal taxes	13.7	14.7	13.3
Non-U.S. income taxed at other rates	(25.2)	(26.8)	(27.4)
Revaluation of U.S. deferreds	(301.6)
Deemed mandatory repatriation	54.8
Other	1.6	(5.0)	(0.1)
Income taxes	(64.8)	160.7	158.0
Deferred Tax Assets
Accrued liabilities	53.6	71.4
Net operating loss and credit carryforwards	131.0	32.4
Other	24.0	18.7
Total deferred tax assets	208.6	122.5
Valuation allowance	(36.6)	(17.2)
Net deferred tax assets	172.0	105.3
Deferred Tax Liabilities
Depreciation and amortization	(178.1)	(210.9)
Partnership investments	(469.5)	(448.1)
Convertible notes	(1.5)	(5.0)
Other	(4.4)	(5.9)
Total deferred tax liabilities	(653.5)	(669.9)
Net deferred tax liabilities	(481.5)	(564.6)
Income from continuing operations before income taxes of non-U.S. subsidiaries	172.8	$ 191.4	$ 182.5
Amount of deemed repatriation of foreign earnings and profits	992.7
Amount of temporary difference related to the excess of financial reporting basis over tax basis in non-U.S. subsidiaries due to the position that the Company is permanently reinvested for this basis difference, on which U.S. federal income taxes are not provided	$ 138.7