Accumulated Other Comprehensive Income - Reclassifications Out of AOCI (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income — Loans	$ 1,025	$ 928	$ 2,965	$ 2,753
Interest expense — Long-term debt	(108)	(86)	(302)	(228)
Income (loss) from continuing operations before income taxes	576	511	1,652	1,520
Income taxes	87	134	252	386
Personnel expense	553	559	1,733	1,669
INCOME (LOSS) FROM CONTINUING OPERATIONS	482	363	1,377	1,095
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Unrealized Gains (Losses) on Derivative Financial Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before income taxes	(17)	0	(44)	18
Income taxes	(3)	0	(10)	7
INCOME (LOSS) FROM CONTINUING OPERATIONS	(14)	0	(34)	11
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Net Pension and Postretirement Benefit Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before income taxes	(4)	(4)	(12)	(12)
Income taxes	(2)	(1)	(4)	(4)
INCOME (LOSS) FROM CONTINUING OPERATIONS	(2)	(3)	(8)	(8)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Net Pension and Postretirement Benefit Costs [Member] \| Amortization of Losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Personnel expense	(4)	(4)	(12)	(12)
Interest Income [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Unrealized Gains (Losses) on Derivative Financial Instruments [Member] \| Interest Rate [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income — Loans	(15)	1	(42)	21
Interest Expense [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Unrealized Gains (Losses) on Derivative Financial Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense — Long-term debt	$ (2)	$ (1)	$ (2)	$ (3)

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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Amount after tax of income (loss) from continuing operations including portion attributable to the noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Interest and fee income generated by loans the Entity intends and has the ability to hold for the foreseeable future, or until maturity or payoff, including commercial and consumer loans, whether domestic or foreign, which may consist of: (1) industrial and agricultural; (2) real estate; and (3) real estate construction loans; (4) trade financing; (5) lease financing; (6) home equity lines-of-credit; (7) automobile and other vehicle loans; and (8) credit card and other revolving-type loans. Also includes interest income for leases held by the Entity.

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Aggregate amount of interest paid or due on all long-term debt.

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Amount of expense for salary, wage, profit sharing; incentive and equity-based compensation; and other employee benefit.

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