Stock-Based Compensation - Restricted Stock Award Activity (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock nonvested, beginning balance	834,225	556,194	450,223
Restricted stock, Shares, Granted	950,340	825,120	609,355
Restricted stock, Shares, Vested	(380,218)	(493,270)	(458,888)
Restricted stock, Shares, Forfeited	(220,594)	(53,819)	(44,496)
Restricted stock nonvested, ending balance	1,183,753	834,225	556,194
Restricted stock nonvested, Weighted Average Price beginning balance	$ 6.49	$ 5.76	$ 6.25
Restricted stock nonvested, Weighted Average Price, Granted	3.89	6.78	5.70
Restricted stock, Weighted Average Price, Vested	5.34	6.18	6.12
Restricted stock nonvested, Weighted Average Price, Forfeited	5.98	6.15	6.13
Restricted stock nonvested, Weighted Average Price ending balance	$ 4.87	$ 6.49	$ 5.76