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Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net fair value of the interest rate lock commitments	$ 14		$ 14
Change in FV of IRLCs, due to 10% adverse changes in the assumed loan closing rates	2		2
Change in FV of IRLCs, due to 20% adverse changes in the assumed loan closing rates	3		3
Commercial aggregate borrower relationship subject to individual review for impairment	1		1
Operating lease equipment impairment			(1)	$ 2
OTTI	(1)	$ 0	(1)	0
Private equity, observable price change adjustment	6	16	11	51
Private equity, impairment	2	1	5	11
Private equity, cumulative impairment	17		17
Private equity, cumulative observable price change	59		59
Fair value changes included in earnings for instruments for which the fair value option was elected			36	18
Change in FV of IRLCs, due to 10% favorable changes in the assumed loan closing rates	2		2
Change in FV of IRLCs, due to 20% favorable changes in the assumed loan closing rates	3		3
Change In Fair Value of IRLC Due To Rate Increase 25 Bp	6		6
Change In Fair Value of IRLC Due To Rate Increase 50 Bp	13		13
Change In Fair Value of IRLC Due To Rate Decrease 25 Bp	6		6
Change In Fair Value of IRLC Due To Rate Decrease 50 Bp	11		11
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value adjustment	$ 1		2	2
Private Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
OTTI		4		10
Transfer \| Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value gains or losses		$ 1	1	$ 2
Residential Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FVO valuation adjustments related to instrument-specific credit risk			$ 1		$ 1