Summary of Significant Accounting Policies - Changes in Accrued Sales Returns (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018
Changes in Accrued Sales Returns [Roll Forward]
Beginning balance	$ 30.0	$ 34.3	$ 30.0
Amounts accrued		112.4	83.8
Returns charged to accrual		(107.4)	(81.2)
Reclassification and remeasurement of sales return asset under Topic 606	1.7
Ending balance	$ 31.7	$ 39.3	$ 34.3