Fair Value, Option, Changes in Fair Value Included in Earnings (Details) - Fair value option election [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Mortgage banking noninterest income [Member] | Mortgage loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	$ 348	$ 214
Mortgage banking noninterest income [Member] | Loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	0	0
Mortgage banking noninterest income [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	0	0
Net gains (losses) from trading activities [Member] | Mortgage loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	0	0
Net gains (losses) from trading activities [Member] | Loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	(13)	14
Net gains (losses) from trading activities [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	0	0
Other noninterest income [Member] | Mortgage loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	0	0
Other noninterest income [Member] | Loans held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	0	1
Other noninterest income [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) on changes in fair value	$ 0	$ 0