Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	$ 101,766	$ 100,445
Loans held for sale	371	596
Derivative assets, gross amount	3,716	3,415
Derivative asset, netting adjustments	(964)	(1,148)
Derivative asset	2,752	2,267
Liabilities:
Derivative liabilities, gross amount	2,410	1,518
Derivative liability, netting adjustments	(850)	(739)
Derivative liability	1,560	779
Net valuation allowance	23	31
Level 1
Assets:
Loans held for sale	0	0
Level 2
Assets:
Loans held for sale	6,385	2,214
Level 3
Assets:
Loans held for sale	0	0
Recurring
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	101,766	100,445
Loans held for sale	371	596
Derivative asset	2,752	2,267
Other assets	544	1,037
Total assets	105,433	104,345
Liabilities:
Derivative liability	1,560	779
Recurring | Level 1
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	9,402	9,460
Loans held for sale	0	0
Derivative assets, gross amount	602	268
Other assets	496	430
Total assets	10,500	10,158
Other assets:
Deferred compensation plan assets	472	414
Liabilities:
Derivative liabilities, gross amount	1,144	271
Recurring | Level 2
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	92,066	90,546
Loans held for sale	371	596
Derivative assets, gross amount	2,985	3,006
Other assets	2	552
Total assets	95,424	94,700
Liabilities:
Derivative liabilities, gross amount	1,156	1,137
Recurring | Level 3
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	298	439
Loans held for sale	0	0
Derivative assets, gross amount	129	141	$ 151
Other assets	46	55
Total assets	473	635
Other assets:
Retained interests in securitizations	46	55
Liabilities:
Derivative liabilities, gross amount	110	110	$ 117
Recurring | Fair Value Inputs Level 1 And Level 2 [Member]
Other assets:
Equity securities	26	568
Liabilities:
Debt and Equity Securities, Unrealized Gain (Loss)	24	535
U.S. Treasury securities
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	9,231	9,318
U.S. Treasury securities | Recurring
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	9,231	9,318
U.S. Treasury securities | Recurring | Level 1
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	9,231	9,318
U.S. Treasury securities | Recurring | Level 2
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	0	0
U.S. Treasury securities | Recurring | Level 3
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	0	0
RMBS
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	78,322	76,703
RMBS | Recurring
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	78,322	76,703
RMBS | Recurring | Level 1
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	0	0
RMBS | Recurring | Level 2
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	78,033	76,375
RMBS | Recurring | Level 3
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	289	328
CMBS | Recurring
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	11,087	11,735
CMBS | Recurring | Level 1
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	0	0
CMBS | Recurring | Level 2
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	11,078	11,624
CMBS | Recurring | Level 3
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	9	111
Other securities
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	3,126	2,689
Other securities | Recurring
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	3,126	2,689
Other securities | Recurring | Level 1
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	171	142
Other securities | Recurring | Level 2
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	2,955	2,547
Other securities | Recurring | Level 3
Assets:
Securities available for sale (amortized cost of $100.3 billion and $97.6 billion and allowance for credit losses of $1 million as of both June 30, 2021 and December 31, 2020)	$ 0	$ 0