Consolidated Condensed Statements Of Changes In Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Treasury Stock At Cost [Member]	Accumulated Other Comprehensive Income (loss) [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance				$ 484,484
Cumulative Effect of New Accounting Principle in Period of Adoption				(2,057)
Balance at Dec. 31, 2014		$ 0	$ 303,104	486,541	$ (77,439)	$ (13,608)
Net Income	$ 40,083			40,083
Other comprehensive income, net of tax:
Unrealized net holding (loss) gain on securities available-for-sale, net of income taxes	(372)					(372)
Dividends on common shares at $1.88 per share				(28,975)
Cash payment for fractional shares in dividend reinvestment plan			(1)
Allocated Share-based Compensation Expense	470		470
Treasury Stock, Value, Acquired, Cost Method					(1,783)
Balance at Jun. 30, 2015		0	303,573	495,592	(79,222)	(13,980)
Balance at Dec. 31, 2015	713,355	0	303,966	507,505	(82,473)	(15,643)
Net Income	38,684			38,684
Other comprehensive income, net of tax:
Unrealized net holding (loss) gain on securities available-for-sale, net of income taxes	16,032					16,032
Dividends on common shares at $1.88 per share				(28,974)
Cash payment for fractional shares in dividend reinvestment plan			(2)
Allocated Share-based Compensation Expense	792		792
Balance at Jun. 30, 2016	$ 739,887	$ 0	$ 304,756	$ 517,215	$ (82,473)	$ 389