Fair Value Measurement - Nonrecurring Basis (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities adjusted based on the measurement alternative	$ 2,302	$ 2,560	$ 2,400
Net gains as a result of measurement alternative	7	9
Net losses as a result of measurement alternative	$ (1)	(162)
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	13.00%
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	45.00%
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	26.00%
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 2,542	3,240
Total liabilities measured at fair value on a nonrecurring basis	14	775
Total nonrecurring fair value gains/(losses)	(34)	(1,211)
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	14	775
Total nonrecurring fair value gains/(losses)	(3)	(775)
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	2,160	2,895
Total nonrecurring fair value gains/(losses)	(33)	(267)
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	382	345
Total nonrecurring fair value gains/(losses)	2	(169)
Net gains as a result of measurement alternative	6
Net losses as a result of measurement alternative		(154)
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
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
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
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	1,869	2,347
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	1,857	2,336
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	12	11
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	673	893
Total liabilities measured at fair value on a nonrecurring basis	14	775
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	14	775
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	303	559
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	137
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	370	$ 334
Equity securities adjusted based on the measurement alternative	$ 316