Commitments and Contingencies - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Long-term Purchase Commitment [Line Items]
Purchase commitment, amount to be paid in 2020	$ 9,000,000
Purchase commitment, amount to be paid in 2021	9,000,000
Estimate of possible losses	0
Inventories
Long-term Purchase Commitment [Line Items]
Purchase commitment	$ 208,000,000
Purchase commitment, period (in years)	5 years
Purchase commitment, purchases made	$ 9,000,000	$ 11,000,000
Purchase commitment, amount to be paid in 2018	3,000,000
Purchase commitment, amount to be paid in 2019	$ 187,000,000