Consolidated Condensed Statements Of Changes In Stockholders' Equity (USD $) In Thousands	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Treasury Stock At Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2009	$ 96,483	$ 306,569	$ 423,872	$ (125,321)	$ 15,661
Net Income			61,522			61,522	61,522
Other comprehensive income (loss), net of tax:
Unrealized net holding gain (loss) on cash flow hedge, net of income taxes					(277)	(277)
Unrealized net holding gain (loss) on securities available-for-sale, net of income taxes					(3,030)	(3,030)
Total comprehensive income						58,215	58,200
Cash dividends on common stock at $2.82 per share			(42,668)
Cash payment for fractional shares in dividend reinvestment plan		(2)
Reissuance of common stock from treasury shares held for warrants issued		(852)	(9,495)	37,915
Accretion of discount on preferred stock	605		(605)
Preferred stock dividends			(3,750)
Balance at Sep. 30, 2010	97,088	305,715	428,876	(87,406)	12,354
Balance at Dec. 31, 2010	97,290	305,677	422,458	(77,733)	(1,868)		745,824
Net Income			60,004			60,004	60,004
Other comprehensive income (loss), net of tax:
Unrealized net holding gain (loss) on cash flow hedge, net of income taxes					348	348
Unrealized net holding gain (loss) on securities available-for-sale, net of income taxes					644	644
Total comprehensive income						60,996	61,000
Cash dividends on common stock at $2.82 per share			(43,425)
Cash payment for fractional shares in dividend reinvestment plan		(2)
Common stock warrants cancelled		(66)	66
Accretion of discount on preferred stock	642		(642)
Preferred stock dividends			(3,750)
Balance at Sep. 30, 2011	$ 97,932	$ 305,609	$ 434,711	$ (77,733)	$ (876)		$ 759,643