Summary of Significant Accounting Policies - Reconciliation of Net Income (Loss) and Weighted Average Shares used in Computing Basic and Diluted Net Income (Loss) Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic net income per share:
Net income applicable to common shares									$ 4,064	$ 34,708	$ 1,447
Weighted average common shares outstanding									11,131	10,813	11,180
Basic net income per share of common stock	$ 0.06	$ 0.09	$ 0.15	$ 0.06	$ 2.99	$ 0.17	$ 0.13	$ (0.08)	$ 0.37	$ 3.21	$ 0.13
Diluted net income per share:
Net income applicable to common shares									$ 4,064	$ 34,708	$ 1,447
Weighted average common shares outstanding									11,131	10,813	11,180
Dilutive effects of stock options and restricted stock awards									1,959	1,218	409
Weighted average common shares, assuming dilutive effect of stock options									13,090	12,031	11,589
Diluted net income per share of common stock	$ 0.05	$ 0.08	$ 0.13	$ 0.06	$ 2.55	$ 0.14	$ 0.12	$ (0.08)	$ 0.31	$ 2.88	$ 0.13