Consolidated Condensed Statements Of Changes In Stockholders' Equity - USD ($)	Total	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock At Cost [Member]	Accumulated Other Comprehensive Income (loss) [Member]
Balance at Dec. 31, 2018		$ 0	$ 358,598,000	$ 614,069,000		$ (90,373,000)	$ (49,788,000)
Balance (Accounting Standards Update 2016-02 [Member]) at Dec. 31, 2018				613,926,000	$ (143,000)
Net Income				25,455,000
Other comprehensive income (loss)							14,335,000
Dividends on common shares				(19,137,000)
Cash payment for fractional shares in dividend reinvestment plan			(1,000)
Stock issued during period, shares, withheld for tax, tax restricted stock	8,736
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures			(2,480,000)	(273,000)		(1,926,000)
Treasury Stock, Value, Acquired, Cost Method						8,502,000
Share-based Payment Arrangement, Expense			1,358,000
Balance at Mar. 31, 2019		0	357,475,000	619,971,000		(96,949,000)	(35,453,000)
Treasury Stock, Shares, Acquired	86,650
Common Stock, Dividends, Per Share, Cash Paid	$ 1.21
Stock Issued During Period, Shares, Restricted Stock Award, Gross	27,719
Balance at Dec. 31, 2018		0	358,598,000	614,069,000		(90,373,000)	(49,788,000)
Balance (Accounting Standards Update 2016-02 [Member]) at Dec. 31, 2018				613,926,000	$ (143,000)
Net Income	$ 78,764,000
Other comprehensive income (loss)	37,174,000
Share-based Payment Arrangement, Expense	$ 3,800,000
Balance at Sep. 30, 2019		0	$ 458,142,000	639,594,000		(128,982,000)	(12,614,000)
Treasury Stock, Shares, Acquired			421,253
Stock Issued During Period, Shares, Acquisitions	1,037,205
Balance at Mar. 31, 2019		0	$ 357,475,000	619,971,000		(96,949,000)	(35,453,000)
Net Income				22,163,000
Other comprehensive income (loss)							9,146,000
Dividends on common shares				(16,907,000)
Cash payment for fractional shares in dividend reinvestment plan			(1,000)
Treasury Stock, Value, Acquired, Cost Method						24,450,000
Share-based Payment Arrangement, Expense			1,162,000
Balance at Jun. 30, 2019		0	456,911,000	625,227,000		(121,399,000)	(26,307,000)
Proceeds from Issuance of Common Stock			98,275,000
Treasury Stock, Shares, Acquired	250,000
Common Stock, Dividends, Per Share, Cash Paid	$ 1.01
Stock Issued During Period, Shares, Acquisitions	1,037,205
Net Income	$ 31,146,000			31,146,000
Other comprehensive income (loss)	13,693,000						13,693,000
Dividends on common shares				(16,779,000)
Cash payment for fractional shares in dividend reinvestment plan			(1,000)
Treasury Stock, Value, Acquired, Cost Method						7,583,000
Share-based Payment Arrangement, Expense	$ 1,200,000		1,232,000
Balance at Sep. 30, 2019		0	$ 458,142,000	639,594,000		(128,982,000)	(12,614,000)
Treasury Stock, Shares, Acquired	84,603		84,603
Common Stock, Dividends, Per Share, Cash Paid	$ 1.01
Balance at Dec. 31, 2019	$ 969,014,000	0	$ 459,389,000	646,847,000		(127,633,000)	(9,589,000)
Net Income				22,372,000
Other comprehensive income (loss)							17,693,000
Dividends on common shares				(20,111,000)
Cash payment for fractional shares in dividend reinvestment plan			(1,000)
Stock issued during period, shares, withheld for tax, tax restricted stock	11,646
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures			(3,865,000)	(528,000)		(2,500,000)
Treasury Stock, Value, Acquired, Cost Method						7,507,000
Share-based Payment Arrangement, Expense			1,254,000
Balance at Mar. 31, 2020		0	456,777,000	649,636,000		(132,640,000)	8,104,000
Treasury Stock, Shares, Acquired	76,000
Common Stock, Dividends, Per Share, Cash Paid	$ 1.22
Stock Issued During Period, Shares, Restricted Stock Award, Gross	25,028
Balance at Dec. 31, 2019	$ 969,014,000	0	459,389,000	646,847,000		(127,633,000)	(9,589,000)
Net Income	82,723,000
Other comprehensive income (loss)	23,789,000
Share-based Payment Arrangement, Expense	3,700,000
Balance at Sep. 30, 2020	$ 1,016,996,000	0	$ 458,440,000	676,465,000		(132,109,000)	14,200,000
Treasury Stock, Shares, Acquired			76,000
Balance at Mar. 31, 2020		0	$ 456,777,000	649,636,000		(132,640,000)	8,104,000
Net Income				29,505,000
Other comprehensive income (loss)							5,757,000
Dividends on common shares				(16,837,000)
Stock issued during period, shares, withheld for tax, tax restricted stock	530
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures			(142,000)	(7,000)		(96,000)
Share-based Payment Arrangement, Expense			1,331,000
Balance at Jun. 30, 2020		0	457,966,000	662,311,000		(132,544,000)	13,861,000
Common Stock, Dividends, Per Share, Cash Paid	$ 1.02
Stock Issued During Period, Shares, Restricted Stock Award, Gross	970
Net Income	$ 30,846,000			30,846,000
Other comprehensive income (loss)	$ 339,000						339,000
Dividends on common shares				(16,821,000)
Stock issued during period, shares, withheld for tax, tax restricted stock	1,860
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures			(690,000)	(129,000)		(435,000)
Share-based Payment Arrangement, Expense	$ 1,200,000		1,164,000
Balance at Sep. 30, 2020	$ 1,016,996,000	$ 0	$ 458,440,000	$ 676,465,000		$ (132,109,000)	$ 14,200,000
Treasury Stock, Shares, Acquired			0
Common Stock, Dividends, Per Share, Cash Paid	$ 1.02
Stock Issued During Period, Shares, Restricted Stock Award, Gross	4,345