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 (Loss) Income [Member]	Total
Beginning balance at Dec. 31, 2017	$ 5,396	$ 107,176	$ 1,414,485	$ (525,422)	$ (149,334)
Beginning balance (in shares) at Dec. 31, 2017				10,759,291
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings			157,360			$ 157,360
Other comprehensive income (loss)					(14,832)
Cash dividends paid			(57,410)
Share-based compensation		503
Stock options exercised		(80)		$ 200
Stock options exercised (in shares)				(4,000)
Non-vested stock issued upon vesting		(5,454)		$ 5,454
Non-vested stock issued upon vesting (in shares)				(111,185)
Benefit plans		350		$ 769
Benefit plans (in shares)				(15,126)
Purchase of treasury stock				$ (76,734)
Purchase of treasury stock (in shares)				1,060,000
Other		(832)	1,808	$ (2,067)	(1,389)
Other (in shares)				42,243
Ending balance at Dec. 31, 2018	5,396	101,663	1,516,243	$ (597,800)	(165,555)
Ending balance (in shares) at Dec. 31, 2018				11,731,223
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings			82,047			82,047
Other comprehensive income (loss)					2,547
Cash dividends paid			(62,190)
Share-based compensation		(739)
Non-vested stock issued upon vesting		(2,343)		$ 2,343
Non-vested stock issued upon vesting (in shares)				(45,981)
Benefit plans		72		$ 948
Benefit plans (in shares)				(18,597)
Other		(228)		$ (815)
Other (in shares)				15,991
Ending balance at Dec. 31, 2019	5,396	98,425	1,536,100	$ (595,324)	(163,008)	$ 881,589
Ending balance (in shares) at Dec. 31, 2019				11,682,636		11,682,636
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings			109,472			$ 109,472
Other comprehensive income (loss)					3,917
Cash dividends paid			(66,057)
Share-based compensation		5,608
Non-vested stock issued upon vesting		(1,352)		$ 1,352
Non-vested stock issued upon vesting (in shares)				(26,515)
Benefit plans		241		$ 833
Benefit plans (in shares)				(16,344)
Other		(13)	(853)	$ (401)
Other (in shares)				7,850
Ending balance at Dec. 31, 2020	$ 5,396	$ 102,909	$ 1,578,662	$ (593,540)	$ (159,091)	$ 934,336
Ending balance (in shares) at Dec. 31, 2020				11,647,627		11,647,627