Other Comprehensive Income - Changes in AOCI, Net of Tax, by Component (Detail) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 4,409
Other comprehensive (loss) income before reclassifications	(21)
Amounts reclassified from AOCI	(2)
Net current period other comprehensive (loss) income	(23)
Balance at end of period	4,608
Unrealized Net Gains (Losses) on Debt Securities Available for Sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(29)
Other comprehensive (loss) income before reclassifications	(17)
Amounts reclassified from AOCI	0
Net current period other comprehensive (loss) income	(17)
Balance at end of period	(46)
Unrealized Net Gains (Losses) on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	5
Other comprehensive (loss) income before reclassifications	(2)
Amounts reclassified from AOCI	(2)
Net current period other comprehensive (loss) income	(4)
Balance at end of period	1
Unrecognized Pension and Postretirement Obligations
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(59)
Other comprehensive (loss) income before reclassifications	(2)
Amounts reclassified from AOCI	0
Net current period other comprehensive (loss) income	(2)
Balance at end of period	(61)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(83)
Balance at end of period	$ (106)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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