CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net earnings	$ 90,954	$ 57,393	$ 57,917
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(2,462)	2,929	1,024
Pension and postretirement plans	(16)	(16)	(19)
Total other comprehensive income (loss), net of tax	(2,478)	2,913	1,005
Total comprehensive income	88,476	60,306	58,922
Comprehensive income (loss) attributable to noncontrolling interest, net of tax:
Net earnings	68	0	0
Foreign currency translation adjustments	15	0	0
Comprehensive income (loss) attributable to noncontrolling interest, net of tax	83	0	0
Comprehensive income attributable to SMP	$ 88,393	$ 60,306	$ 58,922