Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	$ 398	$ 364	$ 398	$ 364
Fair value adjustment	(79)	(30)	(178)	(140)
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	3	0	3	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	395	364	395	364
Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	47		47
Fair value adjustment	(1)		(1)
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	0		0
Commercial loans held for sale | Commercial | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	47		47
Commercial loans and leases | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	125	154	125	154
Fair value adjustment	(73)	(21)	(177)	(118)
Commercial loans and leases | Commercial | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial loans and leases | Commercial | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Commercial loans and leases | Commercial | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	125	154	125	154
Consumer and residential mortgage loans | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	208	188	208	188
Fair value adjustment	(7)	(2)	(10)	(10)
Consumer and residential mortgage loans | Consumer | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Consumer and residential mortgage loans | Consumer | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Consumer and residential mortgage loans | Consumer | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	208	188	208	188
OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	6	18	6	18
Fair value adjustment	0	(7)	(1)	(8)
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	6	18	6	18
Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	9	4	9	4
Fair value adjustment	0	0	0	(2)
Bank premises and equipment | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Bank premises and equipment | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0	0	0
Bank premises and equipment | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	9	4	9	4
Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	3	0	3	0
Fair value adjustment	2	0	11	(2)
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	3	0	3	0
Private equity investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	$ 0	$ 0	$ 0	$ 0