CONDENSED CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Capital Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance, beginning of period at Dec. 31, 2019		$ 18,577	$ 138,526	$ 823,702	$ (46,905)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		79	(5,076)
Shares issued for employee stock purchase plan		6	658
Equity compensation expense			3,127
Net income	$ 13,259			13,259
Other comprehensive income (loss)	(8,144)				(8,144)
Balance, end of period at Mar. 31, 2020	937,809	18,662	137,235	836,961	(55,049)
Balance, beginning of period at Dec. 31, 2020	1,020,755	18,677	147,961	873,692	(19,575)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		28	(2,660)
Shares issued for employee stock purchase plan		7	697
Equity compensation expense			4,006
Net income	31,218			31,218
Other comprehensive income (loss)	(13,196)				(13,196)
Balance, end of period at Mar. 31, 2021	$ 1,040,855	$ 18,712	$ 150,004	$ 904,910	$ (32,771)