Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	AOCI Attributable to Parent [Member] Cumulative Effect, Period of Adoption, Adjustment	AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2017		$ 0	$ 307,726	$ 561,908	$ 3,806	$ (87,079)	$ (26,454)	$ (3,806)
Beginning balance (Adjustments for New Accounting Pronouncement [Member]) at Dec. 31, 2017				563,825			(27,449)
Beginning balance (Accounting Standards Update 2016-01 [Member]) at Dec. 31, 2017				1,917					$ (995)
Beginning balance, shares at Dec. 31, 2017		0	15,288,194
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	$ 110,387			110,387
Other Comprehensive Income (Loss), Net of Tax	$ (18,533)						(18,533)
Dividends, Common Stock, Cash				63,555
Stock Issued During Period, Shares, Dividend Reinvestment Plan			44
Stock Issued During Period, Value, Dividend Reinvestment Plan			$ 4
Stock Issued During Period, Shares, Acquisitions	435,457		435,457
Stock Issued During Period, Value, Acquisitions			$ 48,519
Allocated Share-based Compensation Expense	$ 4,000		$ 3,954
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			12,921
Stock Granted, Value, Share-based Compensation, Net of Forfeitures			$ 1,597	317		1,304
Treasury Stock, Shares, Acquired			50,000
Treasury Stock, Value, Acquired, Cost Method						(5,784)
Treasury Stock Reissued Shares For Director Grants	11,650		11,650
Treasury shares reissued for director grants				77		1,186
Ending balance, shares at Dec. 31, 2018		0	15,698,178
Ending balance at Dec. 31, 2018		$ 0	$ 358,598	614,069		(90,373)	(49,788)
Ending balance (Adjustments for New Accounting Pronouncement [Member]) at Dec. 31, 2018				613,926
Ending balance (Accounting Standards Update 2016-02 [Member]) at Dec. 31, 2018				(143)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 4.07
Net Income (Loss) Attributable to Parent	$ 102,700			102,700
Other Comprehensive Income (Loss), Net of Tax	$ 40,199						40,199
Dividends, Common Stock, Cash				69,482
Stock Issued During Period, Shares, Dividend Reinvestment Plan			171
Stock Issued During Period, Value, Dividend Reinvestment Plan			$ 3
Stock Issued During Period, Shares, Acquisitions	1,037,205		1,037,205
Stock Issued During Period, Value, Acquisitions			$ 98,275
Allocated Share-based Compensation Expense	$ 5,000		$ 4,999
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			18,983
Stock Granted, Value, Share-based Compensation, Net of Forfeitures			$ 2,480	273		1,926
Treasury Stock, Shares, Acquired			421,253
Treasury Stock, Value, Acquired, Cost Method						(40,535)
Treasury Stock Reissued Shares For Director Grants	13,500		13,500
Treasury shares reissued for director grants				24		1,349
Ending balance, shares at Dec. 31, 2019		0	16,346,442
Ending balance at Dec. 31, 2019	$ 969,014	$ 0	$ 459,389	646,847		(127,633)	(9,589)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 4.24
Net Income (Loss) Attributable to Parent	$ 127,923			127,923
Other Comprehensive Income (Loss), Net of Tax	15,160						15,160
Dividends, Common Stock, Cash				70,601
Stock Issued During Period, Shares, Dividend Reinvestment Plan			36
Stock Issued During Period, Value, Dividend Reinvestment Plan			$ 3
Allocated Share-based Compensation Expense	$ 6,000		$ 5,998
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			30,341
Stock Granted, Value, Share-based Compensation, Net of Forfeitures			$ 4,697	664		3,031
Treasury Stock, Shares, Acquired			76,000
Treasury Stock, Value, Acquired, Cost Method						(7,507)
Treasury Stock Reissued Shares For Director Grants	13,450		13,450
Treasury shares reissued for director grants				69		1,343
Ending balance, shares at Dec. 31, 2020		0	16,314,197
Ending balance at Dec. 31, 2020	$ 1,040,256	$ 0	$ 460,687	$ 704,764		$ (130,766)	$ 5,571
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 4.28