CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Company Shares Held by SERP [Member]	Retained Earnings [Member]	Non-Controlling Interest [Member]	Total
Balance at Dec. 31, 2014	$ 4,586	$ 135,887	$ (12,915)	$ (2,929)	$ 467,337	$ 4,186	$ 596,152
Balance (in shares) at Dec. 31, 2014	22,930
Net income					32,797	(831)	31,966
Quarterly dividends ($0.10 per share for 4 quarters)		8			(9,201)		(9,193)
Other comprehensive income (loss)			(10,649)			(772)	(11,421)
Change in ownership percentage of subsidiary						(663)	(663)
Stock-based compensation	$ 1	1,249					1,250
Stock-based compensation (in shares)	4
RSU vesting, including tax benefit	$ 11	406					417
RSU vesting, including tax benefit (in shares)	54
Withholding tax on vested RSUs		(600)					(600)
Sale of Company stock held by SERP, net		933		1,151			2,084
Other						(134)	(134)
Balance at Dec. 31, 2015	$ 4,598	137,883	(23,564)	(1,778)	490,933	1,786	609,858
Balance (in shares) at Dec. 31, 2015	22,988
Net income					55,159	(171)	54,988
Quarterly dividends ($0.10 per share for 4 quarters)		9			(9,226)		(9,217)
Other comprehensive income (loss)			(7,998)			34	(7,964)
Change in ownership percentage of subsidiary						(1,322)	(1,322)
Stock-based compensation	$ 1	2,935					2,936
Stock-based compensation (in shares)	5
RSU vesting	$ 10	(10)					0
RSU vesting, including tax benefit (in shares)	53
Withholding tax on vested RSUs		(1,024)					(1,024)
Sale of Company stock held by SERP, net		27		(180)			(153)
Other						684	684
Balance at Dec. 31, 2016	$ 4,609	139,970	(31,562)	(1,958)	536,771	1,011	$ 648,841
Balance (in shares) at Dec. 31, 2016	23,046						23,046
Cumulative effect of adopting ASU No. 2016-09		150			(95)		$ 55
Net income					37,795	(205)	37,590
Quarterly dividends ($0.10 per share for 4 quarters)		10			(9,236)		(9,226)
Other comprehensive income (loss)			7,319			(27)	7,292
Change in ownership percentage of subsidiary						(43)	(43)
Stock-based compensation		2,172					2,172
Stock-based compensation (in shares)	1
RSU vesting	$ 5	(5)					0
RSU vesting, including tax benefit (in shares)	23
Withholding tax on vested RSUs		(507)					(507)
Sale of Company stock held by SERP, net		291		(2)			289
Other						357	357
Balance at Dec. 31, 2017	$ 4,614	$ 141,931	$ (24,243)	$ (1,960)	$ 565,330	$ 1,093	$ 686,765
Balance (in shares) at Dec. 31, 2017	23,070						23,070