Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Assets:
Fair Value	$ 78,398	$ 79,117
Loans held for sale	$ 1,200	$ 347
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Other assets:
Derivative assets, gross amount	$ 2,649	$ 2,675
Derivative Asset, netting adjustments	(1,050)	(1,005)
Derivative asset	1,599	1,670
Liabilities:
Derivative liabilities, gross amount	2,934	2,932
Derivative Liability, netting adjustments	(440)	(597)
Derivative liability	$ 2,494	$ 2,335
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other liabilities	Other liabilities
Net valuation allowance	$ 1	$ 2
Level 1
Assets:
Loans held for sale	0	0
Level 2
Assets:
Loans held for sale	431	515
Level 3
Assets:
Loans held for sale	0	0
Recurring
Assets:
Fair Value	78,398	79,117
Loans held for sale	1,212	347
Other assets:
Derivative asset	1,599	1,670
Other	687	627
Total	81,896	81,761
Liabilities:
Derivative liability	2,494	2,335
Recurring | Level 1
Assets:
Fair Value	5,898	5,408
Loans held for sale	0	0
Other assets:
Derivative assets, gross amount	733	788
Other	649	589
Total	7,280	6,785
Liabilities:
Derivative liabilities, gross amount	593	449
Deferred compensation plan assets	646	578
Recurring | Level 2
Assets:
Fair Value	72,062	73,431
Loans held for sale	1,212	347
Other assets:
Derivative assets, gross amount	942	1,001
Other	3	3
Total	74,219	74,782
Liabilities:
Derivative liabilities, gross amount	1,421	1,655
Recurring | Level 3
Assets:
Fair Value	438	278
Loans held for sale	0	0
Other assets:
Derivative assets, gross amount	974	886	$ 837
Other	35	35
Total	1,447	1,199
Liabilities:
Derivative liabilities, gross amount	920	828	$ 819
Retained interests in securitizations	35	35
Recurring | Fair Value Inputs Level 1 And Level 2
Liabilities:
Equity securities	6	14
Debt and equity securities, unrealized gain (loss)	1	5
U.S. Treasury securities
Assets:
Fair Value	5,728	5,282
U.S. Treasury securities | Recurring
Assets:
Fair Value	5,728	5,282
U.S. Treasury securities | Recurring | Level 1
Assets:
Fair Value	5,728	5,282
U.S. Treasury securities | Recurring | Level 2
Assets:
Fair Value	0	0
U.S. Treasury securities | Recurring | Level 3
Assets:
Fair Value	0	0
Total RMBS
Assets:
Fair Value	62,398	63,638
Total RMBS | Recurring
Assets:
Fair Value	62,398	63,638
Total RMBS | Recurring | Level 1
Assets:
Fair Value	0	0
Total RMBS | Recurring | Level 2
Assets:
Fair Value	62,089	63,492
Total RMBS | Recurring | Level 3
Assets:
Fair Value	309	146
CMBS | Recurring
Assets:
Fair Value	8,193	8,323
CMBS | Recurring | Level 1
Assets:
Fair Value	0	0
CMBS | Recurring | Level 2
Assets:
Fair Value	8,064	8,191
CMBS | Recurring | Level 3
Assets:
Fair Value	129	132
Other securities
Assets:
Fair Value	2,079	1,874
Other securities | Recurring
Assets:
Fair Value	2,079	1,874
Other securities | Recurring | Level 1
Assets:
Fair Value	170	126
Other securities | Recurring | Level 2
Assets:
Fair Value	1,909	1,748
Other securities | Recurring | Level 3
Assets:
Fair Value	$ 0	$ 0