CONDENSED FINANCIAL INFORMATION OF PARENT COMPANY (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 29, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net earnings (loss)	$ 19,892	$ 16,088	$ 15,557	$ 5,264	$ 13,883	$ 13,304	$ 12,841	$ 10,676	$ 56,801	$ 50,704	$ (62,016)
Adjustments to reconcile net earnings (loss) to net cash provided by (used in) operating activities:
Change in other assets									18,754	18,053	27,205
Tax effect in stockholders' equity of restricted stock vesting									(283)	937	1,840
Earned stock compensation									5,999	7,896	8,496
Net cash provided by operating activities									117,980	170,273	234,298
Cash flows from investing activities:
Purchases of securities available-for-sale									(485,860)	(658,310)	(627,884)
Net cash provided by investing activities									170,921	99,065	226,567
Cash flows from financing activities:
Redemption of subordinated debentures									(18,558)
Net proceeds from issuance of common stock											26,587
Tax effect included in stockholders' equity of restricted stock vesting									283	(937)	(1,840)
Restricted stock surrendered									(1,475)	(1,465)	(1,831)
Cash dividends paid									(28,787)	(7,626)	(1,445)
Net cash used in financing activities									(420,114)	(82,273)	(563,361)
Net (decrease) increase in cash and cash equivalents									(131,213)	187,065	(102,496)
Cash and cash equivalents at beginning of year				295,617				108,552	295,617	108,552	211,048
Cash and cash equivalents at end of year	164,404				295,617				164,404	295,617	108,552
Parent company
Cash flows from operating activities:
Net earnings (loss)									56,801	50,704	(62,016)
Adjustments to reconcile net earnings (loss) to net cash provided by (used in) operating activities:
Change in other assets									711	(4,533)	(6,002)
Change in liabilities									(4,122)	6,262	(2,650)
Tax effect in stockholders' equity of restricted stock vesting									(102)	501	909
Earned stock compensation									715	3,551	4,174
Equity in undistributed (earnings) losses of subsidiaries									(11,213)	(32,554)	53,287
Net cash provided by operating activities									42,790	23,931	(12,298)
Cash flows from investing activities:
Purchases of securities available-for-sale									(1,500)	(2,580)
Net increase in investment in subsidiaries											(30,000)
Net cash provided by investing activities									(1,500)	(2,580)	(30,000)
Cash flows from financing activities:
Redemption of subordinated debentures									(18,558)
Net proceeds from issuance of common stock											26,587
Tax effect included in stockholders' equity of restricted stock vesting									102	(501)	(909)
Restricted stock surrendered									(1,475)	(1,465)	(1,831)
Cash dividends paid									(28,787)	(7,626)	(1,445)
Net cash used in financing activities									(48,718)	(9,592)	22,402
Net (decrease) increase in cash and cash equivalents									(7,428)	11,759	(19,896)
Cash and cash equivalents at beginning of year				35,900				24,141	35,900	24,141	44,037
Cash and cash equivalents at end of year	$ 28,472				$ 35,900				$ 28,472	$ 35,900	$ 24,141