Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (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 [Member]	Treasury Stock [Member]	Unearned ESOP Shares [Member]
Beginning balance at Dec. 31, 2010	$ 749,777	$ 105,515	$ 366,488	$ 291,492	$ (2,458)	$ (7,660)	$ (3,600)
Beginning balance, shares at Dec. 31, 2010		104,846,194
Shareholders Equity [Line Items]
Net income	20,991			20,991
Other comprehensive income	6,371				6,371
Cash dividends declared	(9,418)			(9,418)
Net decrease in unearned ESOP shares	1,500						1,500
ESOP market value adjustment	(495)		(495)
Discount on dividend reinvestment plan purchases	(48)		(48)
Tax benefit of stock options exercised	6		6
Treasury stock acquired	(9)					(9)
Treasury stock acquired, shares		(1,336)
Treasury stock reissued	72			(83)		155
Treasury stock reissued, shares		13,760
Restricted stock	101	25	(2)	0		78
Restricted stock, shares		25,000
Common stock issuance	144	23	121			0
Common stock issuance, shares		23,376
Ending balance at Sep. 30, 2011	768,992	105,563	366,070	302,982	3,913	(7,436)	(2,100)
Ending balance, shares at Sep. 30, 2011		104,906,994
Beginning balance at Dec. 31, 2011	758,543	105,563	365,868	294,056	2,001	(7,345)	(1,600)
Beginning balance, shares at Dec. 31, 2011	104,916,994	104,916,994
Shareholders Equity [Line Items]
Net income	33,219			33,219
Other comprehensive income	2,966				2,966
Cash dividends declared	(13,633)			(13,633)
Net decrease in unearned ESOP shares	1,500						1,500
ESOP market value adjustment	(445)		(445)
Discount on dividend reinvestment plan purchases	(67)		(67)
Tax benefit of stock options exercised	1		1
Treasury stock acquired	(9,112)					(9,112)
Treasury stock acquired, shares		(1,342,517)
Treasury stock reissued	617		0	(329)		946
Treasury stock reissued, shares		95,552
Restricted stock	302		37	(1,264)		1,529
Restricted stock, shares		220,000
Ending balance at Sep. 30, 2012	$ 773,891	$ 105,563	$ 365,394	$ 312,049	$ 4,967	$ (13,982)	$ (100)
Ending balance, shares at Sep. 30, 2012	103,890,029	103,890,029