Accumulated Other Comprehensive Income (Changes In The Components Of AOCI) (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Beginning balance	$ (19)
Other comprehensive income (loss) before reclassification	(55)
Amounts reclassified from AOCI	0
Total other comprehensive income (loss)	(55)	$ 97
Ending balance	(241)
ASU 2018-02 [Member]
Cumulative effect of prospective application of new accounting principle	3
Unrealized gains (losses) on AFS, net [Member]
Beginning balance	(10)
Other comprehensive income (loss) before reclassification	(42)
Amounts reclassified from AOCI	0
Total other comprehensive income (loss)	(42)
Ending balance	(57)
Unrealized gains (losses) on AFS, net [Member] \| ASU 2016-01 [Member]
Cumulative effect of prospective application of new accounting principle	(2)
Unrealized gains (losses) on AFS, net [Member] \| ASU 2018-02 [Member]
Cumulative effect of prospective application of new accounting principle	(3)
Foreign currency translation, net [Member]
Beginning balance	(9)
Other comprehensive income (loss) before reclassification	1
Amounts reclassified from AOCI	0
Total other comprehensive income (loss)	1
Ending balance	(8)
Foreign currency translation, net [Member] \| ASU 2016-01 [Member]
Cumulative effect of prospective application of new accounting principle	0
Foreign currency translation, net [Member] \| ASU 2018-02 [Member]
Cumulative effect of prospective application of new accounting principle	0
Instrument-specific credit risk of liabilities measured at fair value, net [Member]
Beginning balance	0
Other comprehensive income (loss) before reclassification	(14)
Amounts reclassified from AOCI	0
Total other comprehensive income (loss)	(14)
Ending balance	(176)
Instrument-specific credit risk of liabilities measured at fair value, net [Member] \| ASU 2016-01 [Member]
Cumulative effect of prospective application of new accounting principle	(162)
Instrument-specific credit risk of liabilities measured at fair value, net [Member] \| ASU 2018-02 [Member]
Cumulative effect of prospective application of new accounting principle	0
Accumulated Other Comprehensive Income [Member]
Total other comprehensive income (loss)	(55)
Accumulated Other Comprehensive Income [Member] \| ASU 2016-01 [Member]
Cumulative effect of prospective application of new accounting principle	(164)
Accumulated Other Comprehensive Income [Member] \| ASU 2018-02 [Member]
Cumulative effect of prospective application of new accounting principle	$ (3)

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Amount after tax of other comprehensive income (loss) attributable to parent entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount after tax of reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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