Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Commitments And Contingencies [Line Items]
Letters of credit outstanding	$ 2.2		$ 1.5
Letters of credit expiration date	Dec. 31, 2019
Office Space
Commitments And Contingencies [Line Items]
Rent expense	$ 2.2	$ 1.5
Operating lease latest expiration date	Nov. 30, 2024
Manufacturing
Commitments And Contingencies [Line Items]
Purchase commitments for inventory	$ 72.0
Manufacturing | Accrued Liabilities
Commitments And Contingencies [Line Items]
Loss on purchase obligation for inventory	0.9		$ 0.6
Content License
Commitments And Contingencies [Line Items]
Purchase obligation that do not yet Meet criteria for asset recognition	0.7
Content License | Accrued Liabilities
Commitments And Contingencies [Line Items]
Purchase commitments for inventory	$ 0.1