Fair Value Measurements (Financial Instruments Measured At Fair Value Using Significant Unobservable Inputs) (Detail) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014		Dec. 31, 2014	Jun. 30, 2014
Schedule Of Fair Value Measurements [Line Items]
Document Period End Date					Sep. 30, 2015
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets							$ 0
Equity Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	$ 0		$ 0		$ 0		0
Balance- Beginning of Period, Assets	2		2		2		4
Transfers out of Level 3, Assets							(2)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	2		0		2		1
Purchases, Assets	1		0		2		1
Sales, Assets	0		0		0		(2)
Settlements, Assets	0		0		0
Balance-End of Period, Assets	4		2		4		2
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(1)		0		(2)
Equity Securities [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Assets	(1)		0		(2)		0
Short-term Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3							0
Balance- Beginning of Period, Assets							7
Transfers out of Level 3, Assets							(7)
Change in Net Unrealized Gains (Losses) included in OCI, Assets							0
Purchases, Assets							0
Sales, Assets							0
Balance-End of Period, Assets			0				0
Short-term Investments [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Assets							0
Other Long-term Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		0		0
Balance- Beginning of Period, Assets	214		203		204		196
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(7)		(1)		(7)		1
Purchases, Assets	5		6		21		15
Sales, Assets	0		0		0		0
Settlements, Assets	(3)		(3)		(9)		(7)
Balance-End of Period, Assets	209		205		209		205
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		0		0		0
Other Long-term Investments [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Assets	0		0		0		0
Other Derivative Instruments Fair Value [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance - Beginning of Period, Liabilities	3				4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0
Change in Net Unrealized Gains (Losses) included in OCI, Assets					0
Purchases, Assets					0
Sales, Assets					0
Settlements, Assets					0
Balance-End of Period, Assets	7				7
Balance - End of Period, Liabilities	7				7
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	4				3
Other Derivative Instruments Fair Value [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Liabilities	4				3
Available-for-sale Securities [Member] | Foreign [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	1		1		29		3
Balance- Beginning of Period, Assets	56		12		22		44
Transfers out of Level 3, Assets							(34)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	1		0		(1)		(1)
Purchases, Assets	0		0		9		2
Sales, Assets	0		(1)		(1)		(3)
Settlements, Assets	(4)		0		(4)		0
Balance-End of Period, Assets	53		12		53		12
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(1)		0		(1)
Available-for-sale Securities [Member] | Foreign [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Assets	(1)		0		(1)		1
Available-for-sale Securities [Member] | Corporate Debt Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	2		5		15		35
Balance- Beginning of Period, Assets	167		204		187		166
Transfers out of Level 3, Assets							(22)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	1		(1)		1		1
Purchases, Assets	22		20		38		65
Sales, Assets	(5)		(9)		(10)		(17)
Settlements, Assets	(3)		(13)		(44)		(22)
Balance-End of Period, Assets	183		208		183		208
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		0		(2)
Available-for-sale Securities [Member] | Corporate Debt Securities [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Assets	(1)		2		(4)		2
Available-for-sale Securities [Member] | Collateralized Mortgage Backed Securities [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0		0		0		0
Balance- Beginning of Period, Assets	55		7		15		8
Transfers out of Level 3, Assets							0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		0		0		0
Purchases, Assets	0		8		41		8
Sales, Assets	(1)		0		(1)		0
Settlements, Assets	0		0		(1)		(1)
Balance-End of Period, Assets	54		15		54		15
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		0		0
Available-for-sale Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Assets	0		0		0		0
Guaranteed Living Benefit [Member]
Schedule Of Fair Value Measurements [Line Items]
Balance - Beginning of Period, Liabilities	347	[1]	241	[2]	406	[3]	193	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0				0		0
Transfers out of Level 3, Assets							0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0				0		0
Purchases, Assets	0				0		0
Sales, Assets	0				0		0
Settlements, Assets	0				0		0
Balance - End of Period, Liabilities	744	[1],[3]	317	[2],[4]	744	[1],[3]	317	[2],[4]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	397		76	[2]	338	[3]	124	[4]
Reported liabilities	1,000		566		1,000		566		$ 663	$ 486
Guaranteed Living Benefit [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Net Realized Gains/Losses, Liabilities	$ 397		$ 76		$ 338		124
Fair Value, Inputs, Level 3 [Member]
Schedule Of Fair Value Measurements [Line Items]
Settlements, Assets							$ 0

[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 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 liability classified as Future policy benefits in the consolidated balance sheets. The liability for GLB reinsurance was $566 million at September 30, 2014, and $486 million at June 30, 2014, which includes a fair value derivative adjustment of $317 million and $241 million, respectively.

[3] 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 liability classified as Future policy benefits in the consolidated balance sheets. Refer to Note 5 for additional information.

[4] 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 liability classified as Future policy benefits in the consolidated balance sheets. The liability for GLB reinsurance was $566 million at September 30, 2014 and $427 million at December 31, 2013, which includes a fair value derivative adjustment of $317 million and $193 million, respectively.