Stock-Based Compensation - Summary of Stock Option Activity for Company's Stock Option Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jul. 10, 2017	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, Beginning Balance, Number of Shares		2,641,000
Options granted, Number of Shares	543,650	2,105,000
Options exercised, Number of Shares		(8,000)
Options forfeited or expired, Number of Shares		(1,206,000)
Outstanding, Ending Balance, Number of Shares		3,532,000
Vested and expected to vest as of December 31, 2017, Number of Shares		3,532,000
Exercisable as of December 31, 2017, Number of Shares		1,327,000
Outstanding, Beginning Balance, Weighted Average Exercise Price Per Share		$ 13.50
Options granted, Weighted Average Exercise Price Per Share		3.19
Options exercised, Weighted Average Exercise Price Per Share		3.00
Options forfeited or expired, Weighted Average Exercise Price Per Share		17.00
Outstanding, Ending Balance, Weighted Average Exercise Price Per Share		6.18
Vested and expected to vest as of December 31, 2017, Weighted Average Exercise Price Per Share		6.18
Exercisable as of December 31, 2017, Weighted Average Exercise Price Per Share		$ 10.74
Outstanding, Weighted Average Remaining Contractual Term (Years)		7 years 2 months 8 days
Vested and expected to vest as of December 31, 2017, Weighted Average Remaining Contractual Term (Years)		7 years 2 months 8 days
Exercisable as of December 31, 2017, Weighted Average Remaining Contractual Term (Years)		4 years 1 month 17 days
Outstanding, Aggregated Intrinsic Value		$ 1,064
Vested and expected to vest as of December 31, 2017, Aggregate Intrinsic Value		1,064
Ending Balance, Exercisable, Aggregate Intrinsic Value		$ 246