CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock and Paid in Capital [Member]	(Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income [Member]	Unearned Restricted ESOP Shares [Member]
Balance, beginning of the period at Dec. 31, 2011	$ 532,450	$ 120,702	$ 531,149	$ (119,465)	$ 2,051	$ (1,987)
Balance, beginning of the period (in shares) at Dec. 31, 2011		124,000	17,519,132
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	64,882			64,882
Change in valuation of securities - available-for-sale, net of income tax	42				42
Amortization of unrealized loss on tax exempt securities transferred from available-for-sale to held-to-maturity, net of income tax	8				8
Accretion of preferred stock discount	0	3,298		(3,298)
Accrual of dividends on preferred stock	(4,938)			(4,938)
Repurchase of preferred stock (in shares)		(124,000)
Repurchase of preferred stock	(124,000)	(124,000)
Gain on repurchase of preferred stock	2,471			2,471
Accrual of dividends on common stock	(754)			(754)
Proceeds from issuance of common stock for stockholder reinvestment program (in shares)			1,814,320
Proceeds from issuance of common stock for stockholder reinvestment program	36,317		36,317
Amortization of compensation related to restricted stock grant (in shares)			87,173
Amortization of compensation related to restricted stock grant	434		434
Amortization of compensation related to stock options	7		7
Balance, end of the period at Dec. 31, 2012	506,919	0	567,907	(61,102)	2,101	(1,987)
Balance, end of the period (in shares) at Dec. 31, 2012	19,420,625	0	19,420,625
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	35,001			35,001
Change in valuation of securities - available-for-sale, net of income tax	(4,956)				(4,956)
Accrual of dividends on preferred stock	0
Gain on repurchase of preferred stock	0
Accrual of dividends on common stock	(7,600)			(7,600)
Proceeds from issuance of common stock for stockholder reinvestment program (in shares)			1,379
Proceeds from issuance of common stock for stockholder reinvestment program	45		45
Amortization of compensation related to restricted stock grant (in shares)			86,706
Amortization of compensation related to restricted stock grant	583		583
Balance, end of the period at Sep. 30, 2013	$ 529,992		$ 568,535	$ (33,701)	$ (2,855)	$ (1,987)
Balance, end of the period (in shares) at Sep. 30, 2013	19,518,549		19,508,710