Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance at Dec. 31, 2008	$ 308,206	$ 75,386	$ 149,982	$ 81,943	$ 895
Balance (in shares) at Dec. 31, 2008	15,077,324
Increase (Decrease) in Stockholders' Equity [Roll forward]
Net income	25,059			25,059
Net change in unrealized gain/loss on securities available-for-sale, net of tax	3,318	0	0	0	3,318
Comprehensive income	28,377	0	0	0	0
Cash dividends declared	(18,162)	0	0	(18,162)	0
Issuance of common stock (in shares)	117,739
Issuance of common stock	2,292	589	1,703	0	0
Issuance of restricted stock (shares)	5,710
Issuance of restricted stock	0	29	(29)
Stock-based compensation and related excess tax benefits	947	0	947	0	0
Other adjustments	(203)	0	(203)	0	0
Balance at Dec. 31, 2009	321,457	76,004	152,400	88,840	4,213
Balance (in shares) at Dec. 31, 2009	15,200,773
Increase (Decrease) in Stockholders' Equity [Roll forward]
Net income	33,034			33,034
Net change in unrealized gain/loss on securities available-for-sale, net of tax	(302)	0	0	0	(302)
Comprehensive income	32,732	0	0	0	0
Cash dividends declared	(18,435)	0	0	(18,435)	0
Issuance of common stock (in shares)	93,115
Issuance of common stock	1,875	466	1,409	0	0
Issuance of restricted stock (shares)	44,996
Issuance of restricted stock	0	225	(225)
Forfeiture of restricted stock (shares)	(4,474)
Forfeiture of restricted stock	0	(22)	22	0	0
Stock-based compensation and related excess tax benefits	1,009	0	1,009	0	0
Balance at Dec. 31, 2010	338,638	76,673	154,615	103,439	3,911
Balance (in shares) at Dec. 31, 2010	15,334,410
Increase (Decrease) in Stockholders' Equity [Roll forward]
Net income	38,827			38,827
Net change in unrealized gain/loss on securities available-for-sale, net of tax	6,272	0	0	0	6,272
Comprehensive income	45,099	0	0	0	0
Cash dividends declared	(18,835)	0	0	(18,835)	0
Issuance of common stock (in shares)	50,256
Issuance of common stock	1,291	251	1,040	0	0
Issuance of restricted stock (shares)	45,542
Issuance of restricted stock		228	(228)
Forfeiture of restricted stock (shares)	(216)
Forfeiture of restricted stock	0	(1)	1	0	0
Stock-based compensation and related excess tax benefits	673	0	673	0	0
Balance at Dec. 31, 2011	$ 366,866	$ 77,151	$ 156,101	$ 123,431	$ 10,183
Balance (in shares) at Dec. 31, 2011	15,429,992