CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Capital Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance, beginning of period at Dec. 31, 2020		$ 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	(2,712)
Shares issued for employee stock purchase plan		7	697
Shares issued to directors		10	(10)
Equity compensation expense			8,394
Net income	$ 59,873			59,873
Other comprehensive income (loss)	(10,380)				(10,380)
Balance, end of period at Jun. 30, 2021	1,076,662	18,722	154,330	933,565	(29,955)
Balance, beginning of period at Mar. 31, 2021		18,712	150,004	904,910	(32,771)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		0	(52)
Shares issued for employee stock purchase plan		0	0
Shares issued to directors		10	(10)
Equity compensation expense			4,388
Net income	28,655			28,655
Other comprehensive income (loss)	2,816				2,816
Balance, end of period at Jun. 30, 2021	1,076,662	18,722	154,330	933,565	(29,955)
Balance, beginning of period at Dec. 31, 2021	1,118,895	18,730	163,583	981,825	(45,243)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		68	(10,691)
Shares issued for employee stock purchase plan		6	944
Shares issued to directors		7	(7)
Equity compensation expense			8,056
Net income	34,483			34,483
Other comprehensive income (loss)	(45,190)				(45,190)
Balance, end of period at Jun. 30, 2022	1,106,571	18,811	161,885	1,016,308	(90,433)
Balance, beginning of period at Mar. 31, 2022		18,803	157,164	998,425	(56,914)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		1	(126)
Shares issued for employee stock purchase plan		0	0
Shares issued to directors		7	(7)
Equity compensation expense			4,854
Net income	17,883			17,883
Other comprehensive income (loss)	(33,519)				(33,519)
Balance, end of period at Jun. 30, 2022	$ 1,106,571	$ 18,811	$ 161,885	$ 1,016,308	$ (90,433)