Fair Value - Changes in FV under the FV Option (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value gains (losses), net	$ (17)	$ (327)	$ 321	$ (1,621)
Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value gains (losses), net	28	107	48	248
Long-term debt
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value gains (losses), net	$ 62	$ (32)	$ 346	$ (344)