Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Lessee Lease Description [Line Items]
Cash paid for operating leases	$ 67
Right-of-use assets obtained in exchange for operating lease liabilities	$ 67	$ 0
Weighted average remaining lease term in years	4 years
Weighted average discount rate	3.50%
Operating lease, cost	$ 66
Variable lease costs not included in the lease liability	14
Total lease cost	$ 80
Branch Office Space [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, description	The Partnership leases branch office space under numerous operating leases from non-affiliates and financial advisors. Branch offices are generally leased for terms of five years and generally contain a renewal option.
Lessee, operating lease term of contract	5 years
Lessee Operating Lease Home Office Spaces [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, description	The Partnership also leases a few of its home office spaces from non-affiliates with terms ranging from 12 to 30 years.
Minimum [Member] | Lessee Operating Lease Home Office Spaces [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease term of contract	12 years
Maximum [Member] | Lessee Operating Lease Home Office Spaces [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease term of contract	30 years