Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income
Beginning balance (in shares) at Dec. 31, 2017		11,534
Beginning balance at Dec. 31, 2017	$ 449,108	$ 1,158	$ 103,864	$ (426)	$ 374,678	$ (30,166)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income	58,821				73,486	(14,665)
Stock-based compensation expense	2,450		2,450
Stock-based compensation transactions (in shares)		86
Stock-based compensation transactions	2,116	$ 8	2,108
Dividends paid	(5,124)				(5,124)
Ending balance (in shares) at Dec. 31, 2018		11,620
Ending balance at Dec. 31, 2018	507,371	$ 1,166	108,422	(426)	443,040	(44,831)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income	66,899				62,906	3,993
Stock-based compensation expense	3,269		3,269
Stock-based compensation transactions (in shares)		90
Stock-based compensation transactions	1,984	$ 9	1,975
Repurchased shares (in shares)		(40)
Repurchased shares	(4,140)			(4,140)
Dividends paid	(5,626)				(5,626)
Ending balance (in shares) at Dec. 31, 2019		11,670
Ending balance at Dec. 31, 2019	569,757	$ 1,175	113,666	(4,566)	500,320	(40,838)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income	57,142				56,630	512
Stock-based compensation expense	4,119		4,119
Stock-based compensation transactions (in shares)		57
Stock-based compensation transactions	749	$ 6	743
Dividends paid	(6,124)				(6,124)
Ending balance (in shares) at Dec. 31, 2020		11,727
Ending balance at Dec. 31, 2020	$ 625,643	$ 1,181	$ 118,528	$ (4,566)	$ 550,826	$ (40,326)