CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Capital Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative-effect adjustment for lease accounting	Accumulated Other Comprehensive Loss
Balance, beginning of period at Dec. 31, 2018		$ 18,395	$ 132,360	$ 776,403	$ (20)	$ (78,834)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for vested restricted stock units, net of shares withheld for taxes		144	(7,694)
Stock options exercised		11	333
Shares issued for employee stock purchase plan		15	1,234
Shares issued to directors		12	(12)
Equity compensation expense			12,305
Net income	$ 47,319			47,319
Other comprehensive income (loss)	31,929					31,929
Balance, end of period at Dec. 31, 2019	933,900	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		82	(5,439)
Shares issued for employee stock purchase plan		13	1,347
Shares issued to directors		5	(5)
Equity compensation expense			13,532
Net income	49,990			49,990
Other comprehensive income (loss)	27,330					27,330
Balance, end 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		29	(2,910)
Shares issued for employee stock purchase plan		14	1,548
Shares issued to directors		10	(10)
Equity compensation expense			16,994
Net income	108,133			108,133
Other comprehensive income (loss)	(25,668)					(25,668)
Balance, end of period at Dec. 31, 2021	$ 1,118,895	$ 18,730	$ 163,583	$ 981,825		$ (45,243)