Shareholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jul. 28, 2016
Stockholders Equity Note [Line Items]
Reclassification of Russia cumulative translation loss to Net Loss upon sale	$ 33,347,000	$ 0	$ 33,347,000	$ 0
ATM Program
Stockholders Equity Note [Line Items]
Proceeds from sale of common stock under ATM program			0	$ 45,564,000
ATM Program | Cowen and Company LLC
Stockholders Equity Note [Line Items]
Aggregate offering price authorized					$ 75,000,000
Proceeds from sale of common stock under ATM program gross			46,612,000
Proceeds from sale of common stock under ATM program			45,564,000
Commissions paid			$ 1,048,000
ATM Program | Common Stock | Cowen and Company LLC
Stockholders Equity Note [Line Items]
Shares sold under ATM program			3,405,709
Average price per share	$ 13.69		$ 13.69