CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $)	Preferred Stock [Member]	Common Stock [Member]	Common Stock Warrants [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total
Balances at Dec. 31, 2009	$ 89,462,633	$ 33,029,719	$ 3,348,402	$ 524,366,603	$ 43,372,743	$ 7,440,081	$ 701,020,181
Balances (in shares) at Dec. 31, 2009		33,029,719
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee common stock options, stock appreciation rights, common stock warrants and related tax benefits	0	601,023	0	2,884,789	0	0	3,485,812
Exercise of employee common stock options, stock appreciation rights, common stock warrants and related tax benefits (in shares)		601,023
Issuance of restricted common shares, net of forfeitures	0	252,053	0	(252,053)	0	0	0
Issuance of restricted common shares, net of forfeitures (in shares)		252,053
Restricted shares withheld for taxes	0	(12,415)	0	(151,333)	0	0	(163,748)
Restricted shares withheld for taxes (in shares)		(12,415)
Compensation expense for restricted shares	0	0	0	2,303,720	0	0	2,303,720
Compensation expense for stock options	0	0	0	1,677,293	0	0	1,677,293
Accretion on preferred stock discount	1,326,049	0	0	0	(1,326,049)	0	0
Preferred dividends paid	0	0	0	0	(4,750,000)	0	(4,750,000)
Net income (loss)	0	0	0	0	(24,300,492)	0	(24,300,492)
Other comprehensive income (loss)	0	0	0	0	0	(1,815,481)	(1,815,481)
Ending Balances at Dec. 31, 2010	90,788,682	33,870,380	3,348,402	530,829,019	12,996,202	5,624,600	677,457,285
Balances (in shares) at Dec. 31, 2010		33,870,380
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee common stock options, stock appreciation rights, common stock warrants and related tax benefits	0	163,829	0	1,014,653	0	0	1,178,482
Exercise of employee common stock options, stock appreciation rights, common stock warrants and related tax benefits (in shares)		163,829
Repurchase of preferred stock	(23,750,000)	0	0	0	0	0	(23,750,000)
Issuance of restricted common shares, net of forfeitures	0	299,715	0	(299,715)	0	0	0
Issuance of restricted common shares, net of forfeitures (in shares)		299,715
Issuance of salary stock units	0	54,526		722,292			776,818
Issuance of salary stock units (in shares)		54,526
Restricted shares withheld for taxes	0	(33,490)	0	(474,448)	0	0	(507,938)
Restricted shares withheld for taxes (in shares)		(33,490)
Compensation expense for restricted shares	0	0	0	3,239,677	0	0	3,239,677
Compensation expense for stock options	0	0	0	1,196,059	0	0	1,196,059
Accretion on preferred stock discount	2,058,146	0	0	0	(2,058,146)	0	0
Preferred dividends paid	0	0	0	0	(4,891,839)	0	(4,891,839)
Net income (loss)	0	0	0	0	43,737,367	0	43,737,367
Other comprehensive income (loss)	0	0	0	0	0	11,708,657	11,708,657
Ending Balances at Dec. 31, 2011	69,096,828	34,354,960	3,348,402	536,227,537	49,783,584	17,333,257	710,144,568
Balances (in shares) at Dec. 31, 2011		34,354,960
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee common stock options, stock appreciation rights, common stock warrants and related tax benefits	0	245,229	0	1,455,969	0	0	1,701,198
Exercise of employee common stock options, stock appreciation rights, common stock warrants and related tax benefits (in shares)		245,229
Repurchase of preferred stock	(71,250,000)	0	0	0	0	0	(71,250,000)
Issuance of restricted common shares, net of forfeitures	0	102,119	0	(102,119)	0	0	0
Issuance of restricted common shares, net of forfeitures (in shares)		102,119
Issuance of salary stock units	0	57,508	0	942,565	0	0	1,000,073
Issuance of salary stock units (in shares)		57,508
Restricted shares withheld for taxes	0	(63,219)	0	(1,021,409)	0	0	(1,084,628)
Restricted shares withheld for taxes (in shares)		(63,219)
Compensation expense for restricted shares	0	0	0	3,270,028	0	0	3,270,028
Compensation expense for stock options	0	0	0	394,466	0	0	394,466
Cancellation of outstanding warrants	0	0	(3,348,402)	2,593,402	0	0	(755,000)
Accretion on preferred stock discount	2,153,172	0	0	0	(2,153,172)	0	0
Preferred dividends paid	0	0	0	0	(2,127,604)	0	(2,127,604)
Net income (loss)	0	0	0	0	41,883,881	0	41,883,881
Other comprehensive income (loss)	0	0	0	0	0	(4,105,623)	(4,105,623)
Ending Balances at Dec. 31, 2012	$ 0	$ 34,696,597	$ 0	$ 543,760,439	$ 87,386,689	$ 13,227,634	$ 679,071,359
Balances (in shares) at Dec. 31, 2012		34,696,597