Stock-Based Compensation - Summary of Outstanding Stock Options and Related Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding Shares, beginning balance	373,000	411,000	534,000
Granted Shares	0	33,000	18,000
Exercised Shares			(2,000)
Cancelled Shares	(234,000)	(71,000)	(139,000)
Outstanding Shares, ending balance	139,000	373,000	411,000
Exercisable Shares	116,000	307,000	1,291,000	322,000
Vested and expected to vest Shares	123,000
Outstanding Weighted Ave. Exercise Price, beginning balance	$ 22.51	$ 21.56	$ 21.16
Granted, Weighted Ave. Exercise Price		2.36	5.08
Exercised, Weighted Ave. Exercise Price			4.76
Cancelled, Weighted Ave. Exercise Price	32.54	8.04	16.20
Outstanding Weighted Ave. Exercise Price, ending balance	5.69	22.51	21.56
Exercisable, Weighted Ave. Exercise Price	6.16	$ 26.48	$ 8.04	$ 32.16
Vested and expected to vest, Weighted Ave. Exercise Price	$ 4.48