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]
Balance at Dec. 31, 2015		$ 0	$ 303,966	$ 507,505	$ (82,473)	$ (15,643)
Net Income	$ 66,133			66,133
Other comprehensive income, net of tax:
Unrealized net holding (loss) gain on securities available-for-sale, net of income taxes	13,850					13,850
Dividends on common shares at $2.82 per share				(43,461)
Cash payment for fractional shares in dividend reinvestment plan			(3)
Allocated Share-based Compensation Expense	1,200		1,189
Balance at Sep. 30, 2016		0	305,152	530,177	(82,473)	(1,793)
Balance at Dec. 31, 2016	742,240	0	305,826	535,631	(81,472)	(17,745)
Net Income	61,411			61,411
Other comprehensive income, net of tax:
Unrealized net holding (loss) gain on securities available-for-sale, net of income taxes	4,740					4,740
Dividends on common shares at $2.82 per share				(43,411)
Cash payment for fractional shares in dividend reinvestment plan			(4)
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures			(795)	(197)	(645)
Allocated Share-based Compensation Expense	2,116		2,116
Treasury Stock, Value, Acquired, Cost Method	(7,378)
Balance at Sep. 30, 2017	$ 759,367	$ 0	$ 307,143	$ 553,434	$ (88,205)	$ (13,005)