Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Decrease in Income Tax Expenses Unrecognized Tax Benefits if Recognized Net of Federal Tax		$ 2.8
Effective Income Tax Rate Reconciliation, Percent		30.00%	33.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	7.00%	5.25%
Deferred Tax Assets
Net deferred tax liabilities		$ 1,134.1		$ 1,089.4
Gross liability for unrecognized tax benefits
Beginning balance	$ 4.3
Ending balance		$ 4.3