CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Earnings Reinvested in the Business [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-In Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Earnings Reinvested in the Business [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Treasury Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning balance at Dec. 31, 2019	$ 5,396	$ 98,425	$ 1,536,100	$ (595,324)	$ (163,008)	$ 881,589
Beginning balance (ASU 2016-13 [Member]) at Dec. 31, 2019							$ 0	$ 0	$ (853)	$ 0	$ 0	$ (853)
Beginning balance (in shares) at Dec. 31, 2019				11,682,636
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	20,773	$ 0	0	20,773
Other comprehensive loss	0	0	0	0	(44,353)	(44,353)
Cash dividends paid	0	0	(16,500)	0	0	(16,500)
Share-based compensation	0	1,177	0	0	0	1,177
Non-vested stock issued upon vesting	0	(724)	0	$ 724	0	0
Non-vested stock issued upon vesting (in shares)				(14,200)
Benefit plans	0	241	0	$ 833	0	1,074
Benefit plans (in shares)				(16,344)
Other	0	(39)	0	$ (210)	0	(249)
Other (in shares)				4,114
Ending balance at Mar. 31, 2020	5,396	99,080	1,539,520	$ (593,977)	(207,361)	842,658
Ending balance (in shares) at Mar. 31, 2020				11,656,206
Beginning balance at Dec. 31, 2020	5,396	102,909	1,578,662	$ (593,540)	(159,091)	934,336
Beginning balance (in shares) at Dec. 31, 2020				11,647,627
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	0	0	31,668	$ 0	0	31,668
Other comprehensive loss	0	0	0	0	(15,139)	(15,139)
Cash dividends paid	0	0	(16,535)	0	0	(16,535)
Share-based compensation	0	2,113	0	0	0	2,113
Non-vested stock issued upon vesting	0	(563)	0	$ 563	0	0
Non-vested stock issued upon vesting (in shares)				(11,045)
Benefit plans	0	338	0	$ 756	0	1,094
Benefit plans (in shares)				(14,791)
Purchase of treasury stock	0	0	0	$ (11,665)	0	(11,665)
Purchase of treasury stock (in shares)				151,843
Other	0	(72)	0	$ (154)	0	(226)
Other (in shares)				3,020
Ending balance at Mar. 31, 2021	$ 5,396	$ 104,725	$ 1,593,795	$ (604,040)	$ (174,230)	$ 925,646
Ending balance (in shares) at Mar. 31, 2021				11,776,654