Stockholders' Equity - Change in AOCI Gain (Loss) by Component (Net of Tax) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	$ (430)	$ (872)	$ 739
Other comprehensive income (loss) before reclassifications	(124)	477	(1,632)
Net realized (gains) losses reclassified from AOCI into earnings	(62)	(35)	21
Other comprehensive income (loss), net of tax	(186)	442	(1,611)
AOCI ending balance	(616)	(430)	(872)
Accumulated Net Unrealized Investment Gain (Loss) \| Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	410	106	703
Other comprehensive income (loss) before reclassifications	(268)	302	(619)
Net realized (gains) losses reclassified from AOCI into earnings	20	2	22
Other comprehensive income (loss), net of tax	(248)	304	(597)
AOCI ending balance	162	410	106
Accumulated Net Unrealized Investment Gain (Loss) \| Securities Held to Maturity
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	(821)	(897)	0
Other comprehensive income (loss) before reclassifications	0	0	(915)
Net realized (gains) losses reclassified from AOCI into earnings	96	76	18
Other comprehensive income (loss), net of tax	96	76	(897)
AOCI ending balance	(725)	(821)	(897)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	10	(110)	45
Other comprehensive income (loss) before reclassifications	284	228	(124)
Net realized (gains) losses reclassified from AOCI into earnings	(174)	(108)	(31)
Other comprehensive income (loss), net of tax	110	120	(155)
AOCI ending balance	120	10	(110)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	(8)	40	32
Other comprehensive income (loss) before reclassifications	(135)	(48)	8
Net realized (gains) losses reclassified from AOCI into earnings	0	0	0
Other comprehensive income (loss), net of tax	(135)	(48)	8
AOCI ending balance	(143)	(8)	40
Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI beginning balance	(21)	(11)	(41)
Other comprehensive income (loss) before reclassifications	(5)	(5)	18
Net realized (gains) losses reclassified from AOCI into earnings	(4)	(5)	12
Other comprehensive income (loss), net of tax	(9)	(10)	30
AOCI ending balance	$ (30)	$ (21)	$ (11)

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

No definition available.

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- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 31
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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