Fair Value, Option, Instrument Specific Credit Risk (Details) - Fair value option election [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) attributable to instrument-specific credit risk	$ 13	$ 7	$ 23	$ 14
Mortgage loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) attributable to instrument-specific credit risk	16	(2)	12	(1)
Loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) attributable to instrument-specific credit risk	$ (3)	$ 9	$ 11	$ 15