v3.26.1
Segment Information - Financial Information for Partnership's Reportable Segments (Detail) - USD ($)
$ in Millions
 3 Months Ended
Mar. 27, 2026
Mar. 28, 2025
Dec. 31, 2025
Revenues From External Customers And Long Lived Assets [Line Items]      
Net revenue $ 4,677 $ 4,167  
FA compensation and benefits 1,875 1,653  
Home office operating expense 888 805  
Branch office operating expense 625 585  
Variable compensation 748 611  
Operating expenses 4,136 3,654  
Income before allocations $ 541 $ 513  
Income before allocations margin 11.50% 12.20%  
Net interest and dividends revenue $ 188 $ 219  
Depreciation and amortization 194 164  
Total assets 29,011 27,980 $ 30,508
United States [Member]      
Revenues From External Customers And Long Lived Assets [Line Items]      
Net revenue 4,548 4,047  
FA compensation and benefits 1,821 1,605  
Home office operating expense 856 778  
Branch office operating expense 606 568  
Variable compensation 732 598  
Operating expenses 4,015 3,549  
Income before allocations $ 533 $ 498  
Income before allocations margin 11.60% 12.10%  
Net interest and dividends revenue $ 179 $ 206  
Depreciation and amortization 190 159  
Total assets 27,507 26,758  
Canada [Member]      
Revenues From External Customers And Long Lived Assets [Line Items]      
Net revenue 129 120  
FA compensation and benefits 54 48  
Home office operating expense 32 27  
Branch office operating expense 19 17  
Variable compensation 16 13  
Operating expenses 121 105  
Income before allocations $ 8 $ 15  
Income before allocations margin 6.20% 12.80%  
Net interest and dividends revenue $ 9 $ 13  
Depreciation and amortization 4 5  
Total assets $ 1,504 $ 1,222