Income Taxes - Valuation Allowance and Carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes
Increase in valuation allowance	$ 24.7	$ 24.1	$ 6.7
Increase in valuation allowance in association with acquisition activity	1.7
Decrease in valuation allowance resulting from a tax rate change	3.3
Operating loss carryforwards	192.3
Uncertain tax position	0.0	0.0	$ 0.0	$ 2.3
Unrecognized tax benefit for income tax penalties and interest expense	0.7	0.6
Unrecognized Tax Benefits, Interest on Income Taxes Expense	$ 0.1	$ 0.1