Summary of Significant Accounting Policies - Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of Significant Accounting Policies
Advertising costs	$ 0.4	$ 1.1	$ 1.1
Shipping and handling costs	8.2	7.0	4.5
Capitalized software	1.3	0.8
Amortized expense	$ 0.6	$ 0.2	$ 0.0