Fair Value, Assets Recorded at Fair Value on Nonrecurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	$ 76,358	$ 79,850
Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	5,013	2,446
Loans held for sale	26	313
Loans	380	686
Other assets	153	155
Total assets recorded at fair value	6,467	4,531
Nonrecurring [Member] | Nonmarketable equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonmarketable equity securities	895	931
Nonrecurring [Member] | Total Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	215	339
Nonrecurring [Member] | Total Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	165	347
Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	0	0
Loans held for sale	0	0
Loans	0	0
Other assets	0	0
Total assets recorded at fair value	0	0
Nonrecurring [Member] | Level 1 [Member] | Nonmarketable equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonmarketable equity securities	0	0
Nonrecurring [Member] | Level 1 [Member] | Total Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Nonrecurring [Member] | Level 1 [Member] | Total Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	1,865	1,213
Loans held for sale	26	313
Loans	379	685
Other assets	153	149
Total assets recorded at fair value	3,235	3,134
Nonrecurring [Member] | Level 2 [Member] | Nonmarketable equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonmarketable equity securities	812	774
Nonrecurring [Member] | Level 2 [Member] | Total Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	215	339
Nonrecurring [Member] | Level 2 [Member] | Total Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	164	346
Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	3,148	1,233
Loans held for sale	0	0
Loans	1	1
Other assets	0	6
Total assets recorded at fair value	3,232	1,397
Nonrecurring [Member] | Level 3 [Member] | Nonmarketable equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonmarketable equity securities	83	157
Nonrecurring [Member] | Level 3 [Member] | Total Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Nonrecurring [Member] | Level 3 [Member] | Total Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 1	$ 1