CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss	Total
Increase (Decrease) in Stockholders' Equity
Adjustments to beginning retained earnings for adoption of accounting standards			$ 3,992		$ (3,576)	$ 416
Adjusted Balances	$ 285	$ 319,436	442,371	$ (86,064)	(24,150)	651,878
Balances at Dec. 31, 2017	$ 285	319,436	438,379	$ (86,064)	(20,574)	651,462
Balances (in shares) at Dec. 31, 2017	28,496			2,852
Increase (Decrease) in Stockholders' Equity
Net income			9,954			9,954
Other comprehensive income, net of tax					4,072	4,072
Issuance of common stock under share-based compensation plans (in shares)	3
Tax effect of share-based compensation plans		(41)				(41)
Share-based compensation expense		1,870				1,870
Purchase of treasury stock				$ (201)		(201)
Purchase of treasury stock (in shares)				5
Dividends declared on common stock			(2,058)			(2,058)
Balances at Mar. 31, 2018	$ 285	321,265	450,267	$ (86,265)	(20,078)	665,474
Balances (in shares) at Mar. 31, 2018	28,499			2,857
Balances at Dec. 31, 2017	$ 285	319,436	438,379	$ (86,064)	(20,574)	651,462
Balances (in shares) at Dec. 31, 2017	28,496			2,852
Increase (Decrease) in Stockholders' Equity
Net income						51,963
Other comprehensive income, net of tax					1,530	1,530
Balances at Sep. 30, 2018	$ 285	325,533	488,158	$ (86,265)	(22,620)	705,091
Balances (in shares) at Sep. 30, 2018	28,548			2,857
Balances at Mar. 31, 2018	$ 285	321,265	450,267	$ (86,265)	(20,078)	665,474
Balances (in shares) at Mar. 31, 2018	28,499			2,857
Increase (Decrease) in Stockholders' Equity
Net income			1,233			1,233
Other comprehensive income, net of tax					2,236	2,236
Issuance of common stock under share-based compensation plans (in shares)	43
Tax effect of share-based compensation plans		(44)				(44)
Share-based compensation expense		1,674				1,674
Dividends declared on common stock			(2,058)			(2,058)
Balances at Jun. 30, 2018	$ 285	322,895	449,442	$ (86,265)	(17,842)	668,515
Balances (in shares) at Jun. 30, 2018	28,542			2,857
Increase (Decrease) in Stockholders' Equity
Net income			40,776			40,776
Other comprehensive income, net of tax					(4,778)	(4,778)
Issuance of common stock under share-based compensation plans (in shares)	6
Tax effect of share-based compensation plans		(3)				(3)
Share-based compensation expense		2,641				2,641
Dividends declared on common stock			(2,060)			(2,060)
Balances at Sep. 30, 2018	$ 285	325,533	488,158	$ (86,265)	(22,620)	705,091
Balances (in shares) at Sep. 30, 2018	28,548			2,857
Balances at Dec. 31, 2018	$ 287	325,712	501,389	$ (95,468)	(14,238)	717,682
Balances (in shares) at Dec. 31, 2018	28,685			3,098
Increase (Decrease) in Stockholders' Equity
Net income			4,888			4,888
Other comprehensive income, net of tax					1,850	1,850
Tax effect of share-based compensation plans		(8)				(8)
Share-based compensation expense		2,058				2,058
Purchase of treasury stock				$ (2,663)		(2,663)
Purchase of treasury stock (in shares)				74
Dividends declared on common stock			(2,052)			(2,052)
Balances at Mar. 31, 2019	$ 287	327,762	504,225	$ (98,131)	(12,388)	721,755
Balances (in shares) at Mar. 31, 2019	28,685			3,172
Balances at Dec. 31, 2018	$ 287	325,712	501,389	$ (95,468)	(14,238)	717,682
Balances (in shares) at Dec. 31, 2018	28,685			3,098
Increase (Decrease) in Stockholders' Equity
Net income						45,534
Other comprehensive income, net of tax					6,608	6,608
Balances at Sep. 30, 2019	$ 288	331,773	540,778	$ (101,583)	(7,630)	763,626
Balances (in shares) at Sep. 30, 2019	28,801			3,300
Balances at Mar. 31, 2019	$ 287	327,762	504,225	$ (98,131)	(12,388)	721,755
Balances (in shares) at Mar. 31, 2019	28,685			3,172
Increase (Decrease) in Stockholders' Equity
Net income			24,376			24,376
Other comprehensive income, net of tax					(41)	(41)
Issuance of common stock under share-based compensation plans	$ 1	(1)
Issuance of common stock under share-based compensation plans (in shares)	101
Tax effect of share-based compensation plans		(1,174)				(1,174)
Share-based compensation expense		2,801				2,801
Purchase of treasury stock				$ (2,508)		(2,508)
Purchase of treasury stock (in shares)				94
Dividends declared on common stock			(2,050)			(2,050)
Balances at Jun. 30, 2019	$ 288	329,388	526,551	$ (100,639)	(12,429)	743,159
Balances (in shares) at Jun. 30, 2019	28,786			3,266
Increase (Decrease) in Stockholders' Equity
Net income			16,270			16,270
Other comprehensive income, net of tax					4,799	4,799
Issuance of common stock under share-based compensation plans (in shares)	15
Tax effect of share-based compensation plans		(24)				(24)
Share-based compensation expense		2,409				2,409
Purchase of treasury stock				$ (944)		(944)
Purchase of treasury stock (in shares)				34
Dividends declared on common stock			(2,043)			(2,043)
Balances at Sep. 30, 2019	$ 288	$ 331,773	$ 540,778	$ (101,583)	$ (7,630)	$ 763,626
Balances (in shares) at Sep. 30, 2019	28,801			3,300