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, 2016		$ 0	$ 305,826	$ 535,631	$ (81,472)	$ (17,745)
Net Income	$ 20,267			20,267
Other comprehensive income, net of tax:
Unrealized net holding (loss) gain on securities available-for-sale, net of income taxes	1,022					1,022
Dividends on common shares at $0.94 per share				(14,460)
Cash payment for fractional shares in dividend reinvestment plan			(1)
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures			(795)	(197)	(645)
Allocated Share-based Compensation Expense	826		826
Treasury Stock, Value, Acquired, Cost Method					5,425
Balance at Mar. 31, 2017		0	305,856	541,241	(86,252)	(16,723)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				3,806		(3,806)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets | Accounting Standards Update 2016-01 [Member]						(995)
Balance at Dec. 31, 2017	756,101	0	307,726	561,908	(87,079)	(26,454)
Balance (Adjustments for New Accounting Pronouncement [Member]) at Dec. 31, 2017				563,825		(27,449)
Net Income	31,123			31,123
Other comprehensive income, net of tax:
Unrealized net holding (loss) gain on securities available-for-sale, net of income taxes	(23,410)					(21,386)
Dividends on common shares at $0.94 per share				(14,496)
Cash payment for fractional shares in dividend reinvestment plan			(1)
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures			(1,597)	(317)	(1,304)
Allocated Share-based Compensation Expense	1,121		1,121
Balance at Mar. 31, 2018	$ 752,774	$ 0	$ 307,249	583,941	$ (85,775)	$ (52,641)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets | Accounting Standards Update 2016-01 [Member]				$ 1,917