Fair Value Measurements (Fair Value Measurements - Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Net fair value of the interest rate lock commitments	$ 7
Change in the fair value of the interest rate lock commitments, due to decrease in current interest rates of 25 bp	3
Change in the fair value of the interest rate lock commitments, due to decrease in current interest rates of 50 bp	6
Change in the fair value of the interest rate lock commitments, due to increase in current interest rates of 25 bp	4
Change in the fair value of the interest rate lock commitments, due to increase in current interest rates of 50 bp	9
Change in fair value of interest rate lock commitments, due to 10% adverse changes in the assumed loan closing rates	1
Change in fair value of interest rate lock commitments, due to 20% adverse changes in the assumed loan closing rates	1
Change in fair value of interest rate lock commitments, due to 10% favorable changes in the assumed loan closing rates	1
Change in fair value of interest rate lock commitments, due to 20% favorable changes in the assumed loan closing rates	1
Larger commercial loans, subject to impairment review	1
Asset Impairment Charges	67	$ 266
OTTI	0	(54)	$ (15)
Residential Portfolio Segment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value gains or losses	20	14
FVO valuation adjustments related to instrument-specific credit risk	1	2
Affordable Housing Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Asset Impairment Charges		57
Other Real Estate Owned | Transfer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value adjustment	4	4
Other Real Estate Owned | Existing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value adjustment	3	6
Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
OTTI	10	1
Private equity, observable price change adjustment	64
Private equity, impairment	12
Private equity, cumulative impairment	12
Private equity, cumulative observable price change	48
Loans held for sale | Commercial Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value gains or losses		2
Loans held for sale | Transfer | Commercial Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Lower of cost or fair value adjustment	1	85
Fair value adjustment		$ 31
Loans held for sale | Existing | Commercial Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value adjustment	$ 3