CONDENSED HOLDING COMPANY ONLY FINANCIAL STATEMENTS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
ASSETS:
Cash and due from banks	$ 78,187				$ 45,777				$ 78,187		$ 45,777
Investment securities available-for-sale	3,806				18,649				3,806		18,649
Trading securities	8,559				6,822				8,559		6,822
MBS available-for-sale	26,409				31,543				26,409		31,543
Other assets	52,040				51,413				52,040		51,413
Total assets	4,497,107				4,028,190				4,497,107		4,028,190
LIABILITIES AND STOCKHOLDERS' EQUITY:
Trust Preferred securities payable	70,680				70,680				70,680		70,680
Other liabilities	41,264				35,454				41,264		35,454
Stockholders' equity	459,725				435,506				459,725		435,506		391,574
Total liabilities and stockholders' equity	4,497,107				4,028,190				4,497,107		4,028,190
CONDENSED STATEMENTS OF OPERATIONS [Abstract]
Net interest loss	31,728	31,959	30,594	30,255	30,767	31,653	33,752	32,314	124,536		128,487		109,842
Non-interest income	2,596	1,817	1,565	3,060	1,837	2,008	1,721	1,898	9,038		7,463		23,849
Non-interest expense	15,231	14,724	15,298	15,823	15,461	15,575	15,347	16,309	61,076		62,692		62,572
Income tax credit	7,628	7,788	7,531	7,177	6,891	7,215	8,059	7,176	30,124		29,341		26,890
Net income	11,987	11,765	10,460	10,034	10,308	10,631	12,039	10,570	44,246		43,548		40,308
CONDENSED STATEMENTS OF CASH FLOWS [Abstract]
Net income	11,987	11,765	10,460	10,034	10,308	10,631	12,039	10,570	44,246		43,548		40,308
Adjustments to reconcile net income to net cash provided by operating activities:
Net amortization									2,641		2,834		2,880
Decrease (Increase) in other assets									2,873		(8,168)		(6,009)
(Decrease) Increase in other liabilities									5,573		5,637		3,663
Net cash provided by operating activities									47,263		61,151		72,705
Cash flows from Investing Activities:
Proceeds from sale of investment securities available-for-sale									3,780		366		22,415
Proceeds from the sales of trading securities									7,115		131		171
Purchases of investment securities available-for-sale									3,884		458		80,153
Net purchases of trading securities									8,839		1,814		3,158
Principal collected on MBS available-for-sale									5,863		17,372		42,822
Net cash provided by investing activities									(433,935)		(168,403)		149,568
Cash flows from Financing Activities:
Release of stock for benefit plan awards									201		293		145
Net cash used in financing activities									419,332		73,953		(187,457)
Net increase (decrease) in cash and due from banks									32,660		(33,299)		34,816
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD				45,777				79,076	45,777		79,076		44,260
CASH AND CASH EQUIVALENTS, END OF PERIOD	78,437				45,777				78,437		45,777		79,076
Holding Company [Member]
ASSETS:
Cash and due from banks	58,112				61,665				58,112		61,665
Investment securities available-for-sale	3,736				3,558				3,736		3,558
Trading securities	8,559				6,822				8,559		6,822
MBS available-for-sale	496				573				496		573
ESOP loan to subsidiary	3,222				3,401				3,222		3,401
Investment in subsidiaries	454,095				427,083				454,095		427,083
Other assets	3,798				3,435				3,798		3,435
Total assets	532,018				506,537				532,018		506,537
LIABILITIES AND STOCKHOLDERS' EQUITY:
Trust Preferred securities payable	70,680				70,680				70,680		70,680
Other liabilities	1,613				351				1,613		351
Stockholders' equity	459,725				435,506				459,725		435,506
Total liabilities and stockholders' equity	532,018				506,537				532,018		506,537
CONDENSED STATEMENTS OF OPERATIONS [Abstract]
Net interest loss									(4,748)	[1]	(4,851)	[1]	(4,830)	[1]
Dividends received from Bank									18,050	[1]	54,500	[1]	20,000	[1]
Non-interest income									1,376	[1]	812	[1]	1,493	[1]
Non-interest expense									(643)	[1]	(636)	[1]	(635)	[1]
Income before income taxes and equity in undistributed earnings of direct subsidiaries									14,035	[1]	49,825	[1]	16,028	[1]
Income tax credit									1,803	[1]	2,183	[1]	1,823	[1]
Income before equity in undistributed earnings of direct subsidiaries									15,838	[1]	52,008	[1]	17,851	[1]
Equity in (overdistributed) undistributed earnings of subsidiaries									28,408	[1]	(8,460)	[1]	22,457	[1]
Net income									44,246	[1]	43,548	[1]	40,308	[1]
CONDENSED STATEMENTS OF CASH FLOWS [Abstract]
Net income									44,246	[1]	43,548	[1]	40,308	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in (undistributed) overdistributed earnings of direct subsidiaries									(28,408)		8,460		(22,457)
Net gain on the sale of investment securities available for sale									(997)		(110)		(941)
Net (gain) loss on trading securities									45		(265)		(103)
Decrease (Increase) in other assets									(489)		355		1,866
(Decrease) Increase in other liabilities									1,680		(595)		(149)
Net cash provided by operating activities									16,077		51,393		18,524
Cash flows from Investing Activities:
Proceeds from sale of investment securities available-for-sale									3,780		366		2,418
Proceeds from the sales of trading securities									7,056		131		0
Purchases of investment securities available-for-sale									(3,884)		(458)		(403)
Reimbursement from subsidiary for purchases of investment securities available-for-sale									1,620		642		2,917
Net purchases of trading securities									(8,839)		(202)		(2,997)
Principal collected on MBS available-for-sale									72		138		72
Principal repayments on ESOP loan									179		166		154
Net cash provided by investing activities									(16)		783		2,161
Cash flows from Financing Activities:
Common stock issued for exercise of stock options									278		11,228		5,608
Release of stock for benefit plan awards									202		293		145
Cash dividends paid to stockholders									(20,094)		(19,716)		(19,208)
Net cash used in financing activities									(19,614)		(8,195)		(13,455)
Net increase (decrease) in cash and due from banks									(3,553)		43,981		7,230
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD				61,665				17,684	61,665		17,684		10,454
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 58,112				$ 61,665				$ 58,112		$ 61,665		$ 17,684

[1] Other comprehensive income for the Holding Company approximated other comprehensive income for the consolidated Company during the years ended December 31, 2014, 2013 and 2012.