Net Income Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Net income	$ 10,310	$ 11,236	$ 9,205	$ 14,371	$ 7,561	$ 6,742	$ 5,488	$ 5,461		$ 45,122	$ 25,252	$ 6,909
Gain on exchange of preferred stock for trust preferred debt												11,353
Loss on CPP unamortized discount						(1,401)					(1,401)	(1,301)
Loss on extinguishment of trust preferred securities						(10,857)			(10,857)		(10,857)
Preferred stock dividends and discount accretion	(1,135)	(1,134)	(1,135)	(1,135)	(1,135)	(868)	(990)	(988)		(4,539)	(3,981)	(5,239)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	9,175	10,102	8,070	13,236	6,426	(6,384)	4,498	4,473		40,583	9,013	11,722
Net income available to common stockholders										$ 40,583	$ 9,013	$ 11,722
Net income available to common stockholders (in shares)	28,673,802	28,649,996	28,624,609	28,582,616	28,540,469	26,367,067	25,656,826	25,605,571		28,632,915	26,550,043	24,519,033
Effect of dilutive stock options and warrants (in shares)										213,769	143,805	123,392
Net income available to common stockholders (in shares)	28,930,392	28,888,076	28,815,019	28,754,713	28,699,505	26,367,067	25,782,799	25,763,378		28,846,684	26,693,848	24,642,425
Basic net income (loss) per share:
Net income (loss) available to common stockholders (usd per share)	$ 0.32	$ 0.35	$ 0.29	$ 0.46	$ 0.24	$ (0.25)	$ 0.18	$ 0.17		$ 1.42	$ 0.34	$ 0.48
Diluted net income (loss) per share:
Net income (loss) available to common stockholders (usd per share)	$ 0.32	$ 0.35	$ 0.28	$ 0.46	$ 0.24	$ (0.25)	$ 0.18	$ 0.17		$ 1.41	$ 0.34	$ 0.48