CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance at beginning of period (shares) at Dec. 31, 2017		25,018
Balance at beginning of period at Dec. 31, 2017	$ 353,396	$ 250	$ 88,006	$ 374,783	$ (20,148)	$ (89,495)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	11,054			11,054
Other comprehensive income (loss), net of tax	2,845				2,845
Stock repurchased	(823)					(823)
Stock issued (canceled) under employee plans (shares)		50
Stock issued (canceled) under employee plans	667	$ 1	666
Stock-based compensation expense	1,096		1,096
Balance at end of period (shares) at Mar. 31, 2018		25,068
Balance at end of period at Mar. 31, 2018	369,833	$ 251	89,768	387,435	(17,303)	(90,318)
Balance at beginning of period (shares) at Dec. 31, 2017		25,018
Balance at beginning of period at Dec. 31, 2017	353,396	$ 250	88,006	374,783	(20,148)	(89,495)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	21,504
Balance at end of period (shares) at Jun. 30, 2018		25,070
Balance at end of period at Jun. 30, 2018	370,715	$ 251	91,177	397,885	(28,280)	(90,318)
Balance at beginning of period (shares) at Mar. 31, 2018		25,068
Balance at beginning of period at Mar. 31, 2018	369,833	$ 251	89,768	387,435	(17,303)	(90,318)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	10,450			10,450
Other comprehensive income (loss), net of tax	(10,977)				(10,977)
Stock issued (canceled) under employee plans (shares)		2
Stock issued (canceled) under employee plans	0
Stock-based compensation expense	1,275		1,275
Stock issued to directors	134		134
Balance at end of period (shares) at Jun. 30, 2018		25,070
Balance at end of period at Jun. 30, 2018	370,715	$ 251	91,177	397,885	(28,280)	(90,318)
Balance at beginning of period (shares) at Dec. 31, 2018		25,254
Balance at beginning of period at Dec. 31, 2018	369,275	$ 253	90,851	411,325	(42,685)	(90,469)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	3,890			3,890
Other comprehensive income (loss), net of tax	(587)				(587)
Stock repurchased	(42)					(42)
Stock issued (canceled) under employee plans (shares)		(26)
Stock issued (canceled) under employee plans	(1)	$ (1)
Stock-based compensation expense	862		862
Balance at end of period (shares) at Mar. 31, 2019		25,228
Balance at end of period at Mar. 31, 2019	373,214	$ 252	91,713	415,032	(43,272)	(90,511)
Balance at beginning of period (shares) at Dec. 31, 2018		25,254
Balance at beginning of period at Dec. 31, 2018	369,275	$ 253	90,851	411,325	(42,685)	(90,469)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(3,056)
Balance at end of period (shares) at Jun. 30, 2019		25,235
Balance at end of period at Jun. 30, 2019	387,105	$ 253	92,297	408,086	(23,007)	(90,524)
Balance at beginning of period (shares) at Mar. 31, 2019		25,228
Balance at beginning of period at Mar. 31, 2019	373,214	$ 252	91,713	415,032	(43,272)	(90,511)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(6,946)			(6,946)
Other comprehensive income (loss), net of tax	20,265				20,265
Stock repurchased	(13)					(13)
Stock issued (canceled) under employee plans (shares)		(3)
Stock issued (canceled) under employee plans	13	$ 1	12
Stock-based compensation expense	332		332
Stock issued to directors (shares)		10
Stock issued to directors	240		240
Balance at end of period (shares) at Jun. 30, 2019		25,235
Balance at end of period at Jun. 30, 2019	$ 387,105	$ 253	$ 92,297	$ 408,086	$ (23,007)	$ (90,524)