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, 2016	$ 5,396	$ 107,686	$ 1,378,923	$ (442,799)	$ (213,465)
Beginning balance (in shares) at Dec. 31, 2016				9,716,504
Net earnings			89,600			$ 89,600
Other comprehensive income (loss)					64,131
Cash dividends paid			(54,038)
Share-based compensation		5,855
Stock options exercised		(202)		$ 499
Stock options exercised (in shares)				(10,667)
Non-vested stock issued upon vesting		(5,478)		$ 5,478
Non-vested stock issued upon vesting (in shares)				(114,393)
Benefit plans		445		$ 596
Benefit plans (in shares)				(12,999)
Purchase of treasury stock				$ (87,217)
Purchase of treasury stock (in shares)				1,139,734
Other		(1,130)		$ (1,979)
Other (in shares)				41,112
Ending balance at Dec. 31, 2017	5,396	107,176	1,414,485	$ (525,422)	(149,334)
Ending balance (in shares) at Dec. 31, 2017				10,759,291
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)	$ 859,947
Ending balance (in shares) at Dec. 31, 2018				11,731,223		11,731,223
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