Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Commitments And Contingencies [Line Items]
Letters of credit outstanding	$ 26.4	$ 26.4
Letters of credit expiration date	Dec. 31, 2030
Manufacturing
Commitments And Contingencies [Line Items]
Purchase commitments for inventory, content licensing, advertising buys and other platform services	$ 52.4
Loss on purchase obligation for inventory	0.4	$ 0.1
Content Providers and Other Vendors
Commitments And Contingencies [Line Items]
Purchase commitments for inventory, content licensing, advertising buys and other platform services	$ 12.3