Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 85,928	$ 81,087
Other comprehensive (loss):
Foreign currency translation adjustments, before tax	(4,317)	(2,732)
Income tax benefit (expense)	30	(30)
Foreign currency translation adjustments, net of tax	(4,287)	(2,762)
Changes in employee benefit related items:
Amortization of prior service cost	2	(2)
Recognized actuarial gain (loss)	84	(274)
Changes in employee benefit related items	86	(276)
Income tax (expense) benefit	(3)	2
Employee benefit (expense) related items, net of tax	83	(274)
Other comprehensive (loss)	(4,204)	(3,036)
Comprehensive income	$ 81,724	$ 78,051