Segment Information - Financial Information for Partnership's Reportable Segments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 27, 2025	Jun. 28, 2024	Jun. 27, 2025	Jun. 28, 2024	Dec. 31, 2024
Revenues From External Customers And Long Lived Assets [Line Items]
Net revenue	$ 4,235	$ 3,903	$ 8,402	$ 7,697
FA compensation	1,692	1,512	3,345	2,991
Home office operating expenses	878	775	1,683	1,518
Branch office operating expense	606	555	1,191	1,110
Variable compensation	588	591	1,199	1,141
Total operating expenses	3,764	3,433	7,418	6,760
Income before allocations	$ 471	$ 470	$ 984	$ 937
Income before allocations margin	11.00%	11.80%	11.60%	12.00%
Net interest and dividends revenue	$ 216	$ 236	$ 435	$ 476
Depreciation and amortization	179	151	343	294
Assets	27,087	25,893	27,087	25,893	$ 28,964
United States [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Net revenue	4,129	3,793	8,176	7,481
FA compensation	1,646	1,469	3,251	2,906
Home office operating expenses	851	751	1,629	1,468
Branch office operating expense	588	538	1,156	1,076
Variable compensation	574	578	1,172	1,117
Total operating expenses	3,659	3,336	7,208	6,567
Income before allocations	$ 470	$ 457	$ 968	$ 914
Income before allocations margin	11.20%	11.80%	11.70%	12.00%
Net interest and dividends revenue	$ 207	$ 224	$ 413	$ 452
Depreciation and amortization	175	148	334	287
Assets	25,861	24,789	25,861	24,789
Canada [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Net revenue	106	110	226	216
FA compensation	46	43	94	85
Home office operating expenses	27	24	54	50
Branch office operating expense	18	17	35	34
Variable compensation	14	13	27	24
Total operating expenses	105	97	210	193
Income before allocations	$ 1	$ 13	$ 16	$ 23
Income before allocations margin	1.00%	11.70%	7.20%	10.60%
Net interest and dividends revenue	$ 9	$ 12	$ 22	$ 24
Depreciation and amortization	4	3	9	7
Assets	$ 1,226	$ 1,104	$ 1,226	$ 1,104