Income Tax Uncertainties (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Income Tax Uncertainties
Unrecognized tax benefits, including penalties and interest that if recognized would impact effective tax rate	$ 12.3	$ 11.5
Unrecognized tax benefits, including penalties and interest, net of federal tax benefit that if recognized would affect effective tax rate	9.0	8.4
Accrued interest and penalties related to uncertain tax positions	4.2	3.8
Accrued interest and penalties related to uncertain tax positions, net of federal benefit	3.4	$ 3.1
Total expense of interest and penalties, net of federal benefit related to uncertain tax positions	$ 0.3