Loans - By Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Loan balances by portfolio segment:
Retained loans	$ 963,665	$ 965,448	$ 963,665	$ 965,448	$ 960,506
Held-for-sale	15,513		15,513		7,873
At fair value	61,776		61,776		44,474
Total	1,040,954		1,040,954		1,012,853
Accrued interest receivables	2,800		2,800		2,900
Accrued interest receivables written off	19	34	32	48
Consumer, excluding credit card
Loan balances by portfolio segment:
Retained loans	297,731	307,005	297,731	307,005	302,127
Held-for-sale	1,075		1,075		1,305
At fair value	30,879		30,879		15,147
Total	329,685		329,685		318,579
Credit card
Loan balances by portfolio segment:
Retained loans	141,079		141,079		143,432
Held-for-sale	723		723		784
At fair value	0		0		0
Total	141,802		141,802		144,216
Wholesale
Loan balances by portfolio segment:
Retained loans	524,855	$ 516,787	524,855	$ 516,787	514,947
Held-for-sale	13,715		13,715		5,784
At fair value	30,897		30,897		29,327
Total	$ 569,467		$ 569,467		$ 550,058