Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Unallocated ESOP Shares [Member]	Common Stock Acquired By Directors Deferred Fee Plan [Member]	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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	52,412			52,412
Other comprehensive income, net of tax	5,905				5,905
Cash dividends declared	(28,023)			(28,023)
Distributions from DDFP	0							69	(69)
Purchases of treasury stock	(4,401)					(4,401)
Treasury shares issued - Team Capital acquisition	83,517		(962)			84,479
Shares issued dividend reinvestment plan	1,019		0			1,019
Stock option exercises	144		(22)			166
Allocation of ESOP shares	2,190		46				2,144
Allocation of SAP shares	5,301		5,301
Allocation of treasury shares			(4,253)			4,253
Allocation of stock options	225		225
Balance at Sep. 30, 2014	1,129,042	832	1,026,479	452,152	1,054	(304,864)	(46,611)	(7,136)	7,136
Balance at Dec. 31, 2014	1,144,099	832	995,053	465,276	29	(271,779)	(45,312)	(7,113)	7,113
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	62,207			62,207
Other comprehensive income, net of tax	2,069				2,069
Cash dividends declared	(31,810)			(31,810)
Distributions from DDFP	49		49					405	(405)
Purchases of treasury stock	(1,946)					(1,946)
Shares issued dividend reinvestment plan	1,069		75			994
Stock option exercises	2,054		(175)			2,229
Allocation of ESOP shares	2,119		171				1,948
Allocation of SAP shares	3,863		3,863
Allocation of stock options	200		200
Balance at Sep. 30, 2015	$ 1,183,973	$ 832	$ 999,236	$ 495,673	$ 2,098	$ (270,502)	$ (43,364)	$ (6,708)	$ 6,708