Summary of Significant Accounting Policies - Changes in Accrued Sales Returns (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Changes in Accrued Sales Returns [Roll Forward]
Beginning balance	$ 28.5	$ 32.3
Amounts accrued	130.6	123.0
Returns charged to accrual	(128.8)	(126.8)
Ending balance	$ 30.3	$ 28.5