Summary of Significant Accounting Policies - Changes in Accrued Sales Returns (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Changes in Accrued Sales Returns [Roll Forward]
Beginning balance	$ 32.3	$ 28.7
Amounts accrued	123.0	127.4
Returns charged to accrual	(126.8)	(123.8)
Ending balance	$ 28.5	$ 32.3