Stock-Based Compensation - Restricted Stock Unit Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares
Vested (in shares)	(381,916)	(351,938)
Restricted Stock
Shares
Balance at beginning of year (in shares)	1,204,883	977,069	772,016
Granted (in shares)	845,862	789,500	484,450
Forfeited (in shares)	(205,033)	(209,748)	(13,306)
Vested (in shares)	(381,916)	(351,938)	(266,091)
Balance at end of year (in shares)	1,463,796	1,204,883	977,069
Weighted Average Grant Date Fair Value
Balance at beginning of year (in dollars per share)	$ 4.21	$ 5.36	$ 5.35
Granted (in dollars per share)	1.88	3.33	5.63
Forfeited (in dollars per share)	4.25	4.62	5.27
Vested (in dollars per share)	4.36	5.17	5.84
Balance at end of year (in dollars per share)	$ 2.82	$ 4.21	$ 5.36