Fair Value Measurements (Financial Instruments Measured At Fair Value Using Significant Unobservable Inputs) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016		Jun. 30, 2015		Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Assets						$ (1)
Guaranteed Living Benefit [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance - Beginning of Period, Liabilities	[1]	$ 839	$ 451	$ 609		406
Transfers into level 3, liability		0	0	0		0
Transfers out of Level 3, Liabilities				0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities		0	0	0		0
Net Realized Gains/Losses, Liabilities		132	(104)	362		(59)
Sales, Liabilities		0	0	0		0
Settlements, Liabilities		0	0	0		0
Balance - End of Period, Liabilities	[1],[2]	971	347	971		347
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		132	(104)	362	[2]	(59)	[2]
Purchases, Liabilities		0	0	0		0
Reported liabilities		1,300	615	1,300		615		$ 888	$ 716	$ 663
Foreign [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance-End of Period, Assets			214			214
Equity Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Transfers Into Level 3, Asset		0	0	0		0
Balance- Beginning of Period, Assets		29	2	16		2
Transfers out of Level 3, Assets				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets		1	0	(1)		0
Net Realized Gains/Losses, Assets		1	(1)	1
Sales, Assets		(2)	0	(2)		0
Settlements, Assets		0	0	0		0
Balance-End of Period, Assets		37	2	37		2
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		0	(1)	0		(1)
Purchases, Assets		10	1	23		1
Short-term Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Transfers Into Level 3, Asset		0		0
Balance- Beginning of Period, Assets		0		0
Transfers out of Level 3, Assets				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets		0		0
Net Realized Gains/Losses, Assets		0		0
Sales, Assets		0		0
Settlements, Assets		0		0
Balance-End of Period, Assets		50		50
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		0		0
Purchases, Assets		50		50
Other Long-term Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Transfers Into Level 3, Asset		0	0	0		0
Balance- Beginning of Period, Assets		211	208	212		204
Transfers out of Level 3, Assets				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets		0	(2)	0		0
Net Realized Gains/Losses, Assets		0		0		0
Sales, Assets		0	0	0		0
Settlements, Assets		(3)	(3)	(10)		(6)
Balance-End of Period, Assets		216	214	216		214
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		0	0	0		0
Purchases, Assets		8	7	14		16
Other Derivative Instruments Fair Value [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance - Beginning of Period, Liabilities		10	4	6		4
Transfers into level 3, liability		0				0
Transfers out of Level 3, Liabilities				0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities		0				0
Net Realized Gains/Losses, Liabilities		0	(1)	2		(1)
Sales, Liabilities		0				0
Settlements, Liabilities		0				0
Balance - End of Period, Liabilities		10	3	10		3
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		0	1	(2)		(1)
Purchases, Liabilities		0		2		0
Available-for-sale Securities [Member] | Foreign [Member]
Schedule Of Fair Value Measurements [Line Items]
Transfers Into Level 3, Asset		3	28	9		28
Balance- Beginning of Period, Assets		62	22	57		22
Transfers out of Level 3, Assets				(2)
Change in Net Unrealized Gains (Losses) included in OCI, Assets		(3)	2	9		(2)
Net Realized Gains/Losses, Assets		(1)	0	(6)		0
Sales, Assets		(7)	0	(8)		(1)
Settlements, Assets		0	0	(4)		0
Balance-End of Period, Assets		87	56	87		56
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		(1)	0	(5)		0
Purchases, Assets		27	8	32		9
Available-for-sale Securities [Member] | Corporate [Member]
Schedule Of Fair Value Measurements [Line Items]
Transfers Into Level 3, Asset		2	12	18		13
Balance- Beginning of Period, Assets		261	167	174		187
Transfers out of Level 3, Assets				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets		(9)	3	11		0
Net Realized Gains/Losses, Assets		(2)	0	(8)		(3)
Sales, Assets		(16)	(2)	(30)		(5)
Settlements, Assets		(4)	(15)	(8)		(41)
Balance-End of Period, Assets		281	167	281		167
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		0	0	(7)		(2)
Purchases, Assets		31	8	124		16
Available-for-sale Securities [Member] | Collateralized Mortgage Backed Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Transfers Into Level 3, Asset		0	0	0		0
Balance- Beginning of Period, Assets		48	33	53		15
Transfers out of Level 3, Assets				0
Change in Net Unrealized Gains (Losses) included in OCI, Assets		0	0	0		0
Net Realized Gains/Losses, Assets		0	0	0		0
Sales, Assets		0	0	(5)		0
Settlements, Assets		0	(1)	0		(1)
Balance-End of Period, Assets		49	55	49		55
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		0	0	0		0
Purchases, Assets		$ 1	$ 23	$ 1		$ 41

[1] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the consolidated balance sheets. Refer to Note 5 for additional information.

[2] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the consolidated balance sheets. The liability for GLB reinsurance was $615 million at June 30, 2015, and $716 million at March 31, 2015, which includes a fair value derivative adjustment of $347 million and $451 million, respectively.