Income Taxes - Unrecognized tax benefits narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Unrecognized tax benefits, including penalties and interest that if recognized would impact effective tax rate	$ 2.7	$ 10.9
Unrecognized tax benefits, including penalties and interest, net of federal tax benefit that if recognized would affect effective tax rate	2.4	8.9
Unrecognized Tax Benefits, Period Increase (Decrease)	9.3
Unrecognized tax benefits, net of federal benefit	7.6
Accrued interest and penalties related to uncertain tax positions	0.7	4.0
Accrued interest and penalties related to uncertain tax positions, net of federal benefit	0.6	$ 3.5
Total expense of interest and penalties, net of federal benefit related to uncertain tax positions	2.8
Unrecognized tax benefits, settlement	3.0
Uncertain tax positions, additional penalties and interest	$ 0.2