Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common stock	Paid-in Capital	Accumulated Other Comprehensive Earnings (Loss)	Retained Earnings	Deferred Compensation	Treasury Stock at Cost	Total
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2017	$ 67,079	$ 233,077	$ 157,919	$ 788,522	$ 8,640	$ (401,639)	$ 853,598
Balance (in shares) at Dec. 31, 2017	44,148,355
Increase (Decrease) in Shareholders' Equity
Net earnings				12,216			12,216
Other comprehensive earnings (loss), net of tax			(26,398)				(26,398)
Deferred compensation under Rabbi trust plans					(584)	584
Share-based compensation	$ 104	2,617					2,721
Share-based compensation (in shares)	104,771
Dividends and dividend equivalents ($0.22 and $0.21 per share at 3/31/19 and 3/31/18, respectively)				(9,290)			(9,290)
Stockholders' Equity Attributable to Parent, Ending Balance at Mar. 31, 2018	$ 67,183	235,694	(6,973)	930,028	8,056	(401,055)	832,933
Balance (in shares) at Mar. 31, 2018	44,253,126
Increase (Decrease) in Shareholders' Equity
Cumulative-effect adjustment from ASU 2016-01 and 2018-02			(138,494)	138,580			86
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2018	$ 674	305,660	(14,572)	908,079	8,354	(401,353)	806,842
Balance (in shares) at Dec. 31, 2018	44,504,043
Increase (Decrease) in Shareholders' Equity
Net earnings				65,473			65,473
Other comprehensive earnings (loss), net of tax			29,301				29,301
Deferred compensation under Rabbi trust plans					(1,039)	1,039
Share-based compensation	$ 1	2,891					2,892
Share-based compensation (in shares)	50,213
Dividends and dividend equivalents ($0.22 and $0.21 per share at 3/31/19 and 3/31/18, respectively)				(9,803)			(9,803)
Stockholders' Equity Attributable to Parent, Ending Balance at Mar. 31, 2019	$ 675	$ 308,551	$ 14,729	$ 963,749	$ 7,315	$ (400,314)	$ 894,705
Balance (in shares) at Mar. 31, 2019	44,554,256