Fair Value, Option, Changes in Fair Value Included in Earnings (Details) - Fair value option election [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 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	$ 214	$ (59)
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
Mortgage banking noninterest income [Member] | Nonmarketable equity securities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	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
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	14	6
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
Net gains (losses) from trading activities [Member] | Nonmarketable equity securities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	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)
Net gains (losses) from equity securities [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 equity securities [Member] | 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 equity securities [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0
Net gains (losses) from equity securities [Member] | Nonmarketable equity securities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	926	101
Net gains (losses) from equity securities [Member] | Other interests held [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	1	0
Other noninterest income [Member] | Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	(1)
Other noninterest income [Member] | Nonmarketable equity securities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	0	0
Other noninterest income [Member] | Other interests held [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) on changes in fair value	$ 0	$ 0