Financing Receivables - Credit Quality Information - Financial Advisor Loans (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Financing receivables - credit quality information
Allowance for credit losses	$ 60,000,000	$ 59,000,000	$ 63,000,000	$ 59,000,000
Loan write-offs	2,000,000	1,000,000
Commercial Loans
Financing receivables - credit quality information
Allowance for credit losses	51,000,000	52,000,000	54,000,000	$ 54,000,000
Loan write-offs	1,000,000	$ 1,000,000
Commercial Loans | Loans to financial advisors
Financing receivables - credit quality information
Loan write-offs	0
Amortized cost basis by year of origination and loan-to-value ratio
Year 1	120,000,000		395,000,000
Year 2	386,000,000		312,000,000
Year 3	300,000,000		152,000,000
Year 4	145,000,000		108,000,000
Year 5	102,000,000		83,000,000
Prior	222,000,000		161,000,000
Total	1,275,000,000		1,211,000,000
Commercial Loans | Loans to financial advisors | Active
Amortized cost basis by year of origination and loan-to-value ratio
Year 1	120,000,000		395,000,000
Year 2	386,000,000		310,000,000
Year 3	299,000,000		151,000,000
Year 4	144,000,000		107,000,000
Year 5	99,000,000		79,000,000
Prior	215,000,000		157,000,000
Total	1,263,000,000		1,199,000,000
Commercial Loans | Loans to financial advisors | Terminated
Financing receivables - credit quality information
Allowance for credit losses	7,000,000		7,000,000
Amortized cost basis by year of origination and loan-to-value ratio
Year 1	0		0
Year 2	0		2,000,000
Year 3	1,000,000		1,000,000
Year 4	1,000,000		1,000,000
Year 5	3,000,000		4,000,000
Prior	7,000,000		4,000,000
Total	$ 12,000,000		$ 12,000,000