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		29	(2,781)
Shares issued for employee stock purchase plan		13	1,550
Shares issued to directors		10	(10)
Equity compensation expense			13,147
Net income	$ 85,002			85,002
Other comprehensive income (loss)	(18,454)				(18,454)
Balance, end of period at Sep. 30, 2021	1,099,261	18,729	159,867	958,694	(38,029)
Balance, beginning of period at Jun. 30, 2021		18,722	154,330	933,565	(29,955)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		1	(69)
Shares issued for employee stock purchase plan		6	853
Shares issued to directors		0	0
Equity compensation expense			4,753
Net income	25,129			25,129
Other comprehensive income (loss)	(8,074)				(8,074)
Balance, end of period at Sep. 30, 2021	1,099,261	18,729	159,867	958,694	(38,029)
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		69	(10,820)
Shares issued for employee stock purchase plan		6	944
Shares issued to directors		7	(7)
Equity compensation expense			11,576
Net income	49,321			49,321
Other comprehensive income (loss)	(80,138)				(80,138)
Balance, end of period at Sep. 30, 2022	1,089,853	18,812	165,276	1,031,146	(125,381)
Balance, beginning of period at Jun. 30, 2022		18,811	161,885	1,016,308	(90,433)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		1	(129)
Shares issued for employee stock purchase plan		0	0
Shares issued to directors		0	0
Equity compensation expense			3,520
Net income	14,838			14,838
Other comprehensive income (loss)	(34,948)				(34,948)
Balance, end of period at Sep. 30, 2022	$ 1,089,853	$ 18,812	$ 165,276	$ 1,031,146	$ (125,381)