Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	$ 921	$ 225	$ 921	$ 225
Total (Losses) Gains	(130)	(23)	(225)	(64)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	37	17	37	17
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	884	208	884	208
Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	186		186
Total (Losses) Gains	2		3
Consumer | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0		0
Consumer | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0		0
Consumer | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	186		186
Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	54		54
Total (Losses) Gains	(1)		(4)
Commercial loans held for sale | Commercial | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0		0
Commercial loans held for sale | Commercial | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	37		37
Commercial loans held for sale | Commercial | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	17		17
Commercial and industrial loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	501	140	501	140
Total (Losses) Gains	(107)	(14)	(143)	(34)
Commercial and industrial loans | Commercial | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial and industrial loans | Commercial | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial and industrial loans | Commercial | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	501	140	501	140
Commercial mortgage loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	57	11	57	11
Total (Losses) Gains	(4)	1	(33)	1
Commercial mortgage loans | Commercial | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial mortgage loans | Commercial | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial mortgage loans | Commercial | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	57	11	57	11
Commercial leases | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	11	15	11	15
Total (Losses) Gains	(7)	(11)	(16)	(12)
Commercial leases | Commercial | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial leases | Commercial | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial leases | Commercial | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	11	15	11	15
OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	18	13	18	13
Total (Losses) Gains	(1)	(1)	(6)	(3)
OREO | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
OREO | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
OREO | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	18	13	18	13
Property and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	14	27	14	27
Total (Losses) Gains	(12)	(2)	(14)	(22)
Property and equipment | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Property and equipment | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Property and equipment | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	14	27	14	27
Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	10		10
Total (Losses) Gains	0		(3)
Operating lease equipment | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0		0
Operating lease equipment | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0		0
Operating lease equipment | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	10		10
Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	70	19	70	19
Total (Losses) Gains	0	4	(9)	6
Private equity investments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Private equity investments | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	17	0	17
Private equity investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	$ 70	$ 2	$ 70	$ 2