Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	TREASURY STOCK	UNALLOCATED ESOP SHARES	COMMON STOCK ACQUIRED BY DDFP	Deferred Compensation DDFP [Member]
Balance at Dec. 31, 2013	$ 1,010,753	$ 832	$ 1,026,144	$ 427,763	$ (4,851)	$ (390,380)	$ (48,755)	$ (7,205)	$ 7,205
Net income	17,029			17,029
Other comprehensive income, net of tax	3,878				3,878
Cash dividends declared	(9,190)			(9,190)
Distributions from DDFP	0							23	(23)
Purchases of treasury stock	(3,881)					(3,881)
Shares issued dividend reinvestment plan	334		0			334
Allocation of ESOP shares	756		42				714
Allocation of SAP shares	1,583		1,583
Transfer of treasury shares to SAP	0		(4,253)			4,253
Allocation of stock options	79		79
Balance at Mar. 31, 2014	1,021,341	832	1,023,595	435,602	(973)	(389,674)	(48,041)	(7,182)	7,182
Balance at Dec. 31, 2014	1,144,099	832	995,053	465,276	29	(271,779)	(45,312)	7,113	(7,113)
Net income	19,802			19,802
Other comprehensive income, net of tax	3,706				3,706
Cash dividends declared	(10,798)			(10,798)
Distributions from DDFP	0							(23)	23
Purchases of treasury stock	(1,882)					(1,882)
Shares issued dividend reinvestment plan	377		23			354
Stock option exercises	395		(17)			412
Allocation of ESOP shares	687		38				649
Allocation of SAP shares	1,213		1,213
Allocation of stock options	72		72
Balance at Mar. 31, 2015	$ 1,157,671	$ 832	$ 996,382	$ 474,280	$ 3,735	$ (272,895)	$ (44,663)	$ 7,090	$ (7,090)