Redeemable Convertible Notes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Aug. 19, 2015
Debt Instrument [Line Items]
Conversion of convertible notes in to common stock, value		$ 117,647,000
Gain on extinguishment of redeemable convertible notes	$ 99,000	52,000
Convertible Notes
Debt Instrument [Line Items]
Convertible notes, total outstanding principal amount			$ 37,000,000
Redeemable convertible notes, conversion per share price	$ 137.85
Convertible notes, maturity date	Feb. 19, 2018
Convertible notes, maturity period	30 months
Redeemable convertible notes, threshold trading days	10 days
Redeemable convertible notes, conversion feature	$ 1,500,000
Redeemable convertible notes, estimated fair value	37,100,000
Redeemable convertible notes, debt discount	1,400,000
Redeemable convertible notes, interest expense	0	$ 1,400,000
Redeemable convertible notes, redeemed	17,300,000
Conversion of convertible notes in to common stock, value	$ 300,000
Convertible Notes | After Reverse Stock Split
Debt Instrument [Line Items]
Redeemable convertible notes, conversion per share price	$ 137.85