v3.26.3
Accumulated Other Comprehensive Income Attributable to SMP (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Jun. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Jun. 30, 2025
Mar. 31, 2025
Sep. 30, 2026
Sep. 30, 2025
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]                
Beginning balance $ 732,333   $ 698,262 $ 703,459   $ 630,082 $ 698,262 $ 630,082
Ending balance 740,999 $ 732,333   692,132 $ 703,459   740,999 692,132
Unrealized gain (loss) on cash flow hedge, pretax 4,000           6,000 (3,100)
Unrealized gain (loss) on cash flow hedge, net of tax 3,000           4,400 (2,300)
Cash settlement receipts (payments), pretax 300     (300)     600 (1,200)
Cash settlement receipts (payments), net of tax 200     (200)     500 (900)
Accumulated Other Comprehensive Income (Loss)                
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]                
Beginning balance 9,569 11,664 17,857 16,825 (13,655) (25,832) 17,857 (25,832)
Other comprehensive income (loss) before reclassifications 294 (1,842) (4,921) (2,602) 24,962 9,339    
Amounts reclassified from accumulated other comprehensive income (loss) 249 195 201 370 439 408    
Net other comprehensive income (loss) 543 (1,647) (4,720) (2,232) 25,401 9,747    
Tax amounts (1,316) (448) (1,473) (38) 5,079 2,430    
Ending balance 8,796 9,569 11,664 14,555 16,825 (13,655) 8,796 14,555
Foreign Currency Translation                
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]                
Beginning balance 6,197 8,394 15,931 15,198 (16,754) (29,769) 15,931 (29,769)
Other comprehensive income (loss) before reclassifications (3,460) (1,786) (6,535) (2,265) 27,390 10,881    
Amounts reclassified from accumulated other comprehensive income (loss) 0 0 0 0 0 0    
Net other comprehensive income (loss) (3,460) (1,786) (6,535) (2,265) 27,390 10,881    
Tax amounts (276) (411) (1,002) (30) 4,562 2,134    
Ending balance 2,461 6,197 8,394 12,903 15,198 (16,754) 2,461 12,903
Cash Flow Hedges                
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]                
Beginning balance 3,370 3,267 1,923 1,619 3,088 3,924 1,923 3,924
Other comprehensive income (loss) before reclassifications 3,754 (56) 1,614 (337) (2,428) (1,542)    
Amounts reclassified from accumulated other comprehensive income (loss) 251 196 202 374 443 412    
Net other comprehensive income (loss) 4,005 140 1,816 37 (1,985) (1,130)    
Tax amounts (1,041) (37) (472) (10) 516 294    
Ending balance 6,334 3,370 3,267 1,646 1,619 3,088 6,334 1,646
Postretirement Benefit Plans                
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]                
Beginning balance 2 3 3 8 11 13 3 13
Other comprehensive income (loss) before reclassifications 0 0 0 0 0 0    
Amounts reclassified from accumulated other comprehensive income (loss) (2) (1) (1) (4) (4) (4)    
Net other comprehensive income (loss) (2) (1) (1) (4) (4) (4)    
Tax amounts 1 0 1 2 1 2    
Ending balance $ 1 $ 2 $ 3 $ 6 $ 8 $ 11 $ 1 $ 6