CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net earnings	$ 19,438	$ 21,000
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(638)	(1,916)
Pension and postretirement plans	(5)	(5)
Total other comprehensive income (loss), net of tax	(643)	(1,921)
Total comprehensive income	18,795	19,079
Comprehensive income (loss) attributable to noncontrolling interest, net of tax:
Net earnings (loss)	(8)	0
Foreign currency translation adjustments	3	0
Comprehensive income (loss) attributable to noncontrolling interest, net of tax	(5)	0
Comprehensive income attributable to SMP	$ 18,800	$ 19,079