CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Total
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 (loss) 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						29,264
Other comprehensive income (loss) net of tax					1,809	1,809
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
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 (loss) 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
Adjustments to beginning retained earnings for adoption of accounting standard			(198)			(198)
Adjusted Balances	$ 288	333,943	532,989	$ (104,578)	203	762,845
Balances at Dec. 31, 2019	$ 288	333,943	533,187	$ (104,578)	203	763,043
Balances (in shares) at Dec. 31, 2019	28,811			3,405
Increase (Decrease) in Stockholders' Equity
Net income			1,902			1,902
Other comprehensive income (loss) net of tax					(2,467)	(2,467)
Issuance of common stock under share-based compensation plans (in shares)	6
Tax effect of share-based compensation plans		(60)				(60)
Share-based compensation expense		2,181				2,181
Purchase of treasury stock				$ (3,162)		(3,162)
Purchase of treasury stock (in shares)				150
Dividends declared on common stock			(2,033)			(2,033)
Balances at Mar. 31, 2020	$ 288	336,064	532,858	$ (107,740)	(2,264)	759,206
Balances (in shares) at Mar. 31, 2020	28,817			3,555
Balances at Dec. 31, 2019	$ 288	333,943	533,187	$ (104,578)	203	763,043
Balances (in shares) at Dec. 31, 2019	28,811			3,405
Increase (Decrease) in Stockholders' Equity
Net income						17,782
Other comprehensive income (loss) net of tax					(2,293)	(2,293)
Balances at Jun. 30, 2020	$ 290	337,942	546,689	$ (107,740)	(2,090)	775,091
Balances (in shares) at Jun. 30, 2020	28,958			3,555
Balances at Mar. 31, 2020	$ 288	336,064	532,858	$ (107,740)	(2,264)	759,206
Balances (in shares) at Mar. 31, 2020	28,817			3,555
Increase (Decrease) in Stockholders' Equity
Net income			15,880			15,880
Other comprehensive income (loss) net of tax					174	174
Issuance of common stock under share-based compensation plans	$ 2	(2)
Issuance of common stock under share-based compensation plans (in shares)	141
Tax effect of share-based compensation plans		(1,010)				(1,010)
Share-based compensation expense		2,890				2,890
Dividends declared on common stock			(2,049)			(2,049)
Balances at Jun. 30, 2020	$ 290	$ 337,942	$ 546,689	$ (107,740)	$ (2,090)	$ 775,091
Balances (in shares) at Jun. 30, 2020	28,958			3,555