Summary of Significant Accounting Policies - Changes In Accrued Sales Returns (Details) - Sales Returns $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Changes in Accrued Sales Returns [Roll Forward]
Beginning balance	$ 44.9
Amounts accrued	105.2
Returns charged to accrual	(101.8)
Ending balance	$ 48.3