Loans, Lending Commitments and Related Allowance for Credit Losses - Past Due Loans Held for Investment Modified in the Last 12 Months (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	$ 219,116	$ 204,554
Total
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	109		$ 22
30-89 Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	42		21
90+ Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	67		1
Commercial real estate
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	8,688	8,678
Commercial real estate | Total
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	67		21
Commercial real estate | 30-89 Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	0		21
Commercial real estate | 90+ Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	67		0
Securities-based lending and Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	93,395	89,245
Securities-based lending and Other | Total
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	42
Securities-based lending and Other | 30-89 Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	42
Securities-based lending and Other | 90+ Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	0
Residential real estate
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans	$ 65,001	$ 60,375
Residential real estate | Total
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans			1
Residential real estate | 30-89 Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans			0
Residential real estate | 90+ Days Past Due
Financing Receivable, Modified, Subsequent Default [Line Items]
Total loans			$ 1