Fair Value, Option, Changes in Fair Value Included in Earnings (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
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	$ 379	$ 114	$ 593	$ 55
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	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	0	0
Mortgage banking noninterest income [Member] | Other interests held [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0	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	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	(4)	9	10	15
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	0	0
Net gains (losses) from trading activities [Member] | Other interests held [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	(1)	(1)	(2)	(2)
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	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	0	1	0
Other noninterest income [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	1	0	1	(1)
Other noninterest income [Member] | Other interests held [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	$ 0	$ 0	$ 0	$ 0