Significant Customers and Geographic Information - Revenue by U.S. and International Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net revenue by geographic information
Revenue	$ 192.7	$ 181.8	$ 175.5	$ 175.4	$ 181.7	$ 173.3	$ 178.0	$ 169.4	$ 725.4	$ 702.4	$ 654.6
U.S.
Net revenue by geographic information
Revenue									521.9	499.4	456.8
International
Net revenue by geographic information
Revenue									$ 203.5	$ 203.0	$ 197.8