Fair Value Measurement - Nonrecurring Basis (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities adjusted based on the measurement alternative	$ 2,620,000,000	$ 1,704,000,000	$ 2,620,000,000	$ 1,704,000,000	$ 2,400,000,000
Net losses as a result of measurement alternative	9,000,000	36,000,000	171,000,000	42,000,000
Net gains as a result of measurement alternative	4,000,000	52,000,000	$ 13,000,000	136,000,000
Residential mortgage | Broker price opinions | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, liquidation value discount			15.00%
Residential mortgage | Broker price opinions | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, liquidation value discount			46.00%
Residential mortgage | Broker price opinions | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, liquidation value discount			28.00%
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	3,012,000,000	2,583,000,000	$ 3,012,000,000	2,583,000,000
Total liabilities measured at fair value on a nonrecurring basis	95,000,000	0	95,000,000	0
Total nonrecurring fair value gains/(losses)	387,000,000	(66,000,000)	(604,000,000)	(10,000,000)
Nonrecurring | Accounts payable and other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value on a nonrecurring basis	95,000,000		95,000,000
Held-for-sale positions, including unfunded commitments in bridge financing portfolio	3,400,000,000		3,400,000,000
Total nonrecurring fair value gains/(losses)	465,000,000	0	(95,000,000)	0
Nonrecurring | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	2,616,000,000	1,857,000,000	2,616,000,000	1,857,000,000
Total nonrecurring fair value gains/(losses)	(39,000,000)	(79,000,000)	(303,000,000)	(100,000,000)
Nonrecurring | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	396,000,000	726,000,000	396,000,000	726,000,000
Total nonrecurring fair value gains/(losses)	(39,000,000)	13,000,000	(206,000,000)	90,000,000
Net losses as a result of measurement alternative	4,000,000		158,000,000
Net gains as a result of measurement alternative		16,000,000		95,000,000
Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	0	0	0	0
Total liabilities measured at fair value on a nonrecurring basis	0		0
Nonrecurring | Level 1 | Accounts payable and other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value on a nonrecurring basis	0		0
Nonrecurring | Level 1 | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	0	0	0	0
Nonrecurring | Level 1 | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	0	0	0	0
Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	1,797,000,000	1,729,000,000	1,797,000,000	1,729,000,000
Total liabilities measured at fair value on a nonrecurring basis	0		0
Nonrecurring | Level 2 | Accounts payable and other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value on a nonrecurring basis	0		0
Nonrecurring | Level 2 | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	1,793,000,000	1,716,000,000	1,793,000,000	1,716,000,000
Nonrecurring | Level 2 | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	4,000,000	13,000,000	4,000,000	13,000,000
Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	1,215,000,000	854,000,000	1,215,000,000	854,000,000
Total liabilities measured at fair value on a nonrecurring basis	95,000,000		95,000,000
Nonrecurring | Level 3 | Accounts payable and other liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value on a nonrecurring basis	95,000,000		95,000,000
Nonrecurring | Level 3 | Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	823,000,000	141,000,000	823,000,000	141,000,000
Nonrecurring | Level 3 | Residential mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	372,000,000		372,000,000
Nonrecurring | Level 3 | Other assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	392,000,000	$ 713,000,000	392,000,000	$ 713,000,000
Equity securities adjusted based on the measurement alternative	$ 209,000,000		$ 209,000,000