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, 2015	Jun. 30, 2014		Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Schedule Of Fair Value Measurements [Line Items]
Document Period End Date					Jun. 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		0	0		0	(2)
Change in Net Unrealized Gains (Losses) included in OCI, Assets		0	0		0	1
Purchases, Assets		1	0		1	1
Sales, Assets		0	0		0	(2)
Settlements, Assets		0	0		0
Balance-End of Period, Assets		2	2		2	2
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		(1)	0		(1)
Equity Securities [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(1)	0		(1)	0
Equity Securities [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			0		0	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]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings						0
Short-term Investments [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0				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		2,789	2,611		2,719	2,440
Transfers out of Level 3, Assets		0	0		0
Change in Net Unrealized Gains (Losses) included in OCI, Assets		6	7		(14)	48
Purchases, Assets		52	109		177	248
Sales, Assets		(25)	(2)		(25)	(3)
Settlements, Assets		(172)	(125)		(229)	(194)
Balance-End of Period, Assets		2,679	2,640		2,679	2,640
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		0	(3)		0	(3)
Other Long-term Investments [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		11	(3)		11	(3)
Other Long-term Investments [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		18	43		40	104
Other Derivative Instruments Fair Value [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value		3			3		$ 4	$ 4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0
Transfers out of Level 3, Assets		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		3			3
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		(1)
Other Derivative Instruments Fair Value [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(1)			(1)
Other Derivative Instruments Fair Value [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		0			0
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		28	2		28	2
Balance- Beginning of Period, Assets		22	26		22	44
Transfers out of Level 3, Assets		0	(16)		0	(34)
Change in Net Unrealized Gains (Losses) included in OCI, Assets		(2)	0		(2)	(1)
Purchases, Assets		8	0		9	2
Sales, Assets		0	(1)		(1)	(2)
Settlements, Assets		0	0		0	0
Balance-End of Period, Assets		56	12		56	12
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets		0	0		0
Available-for-sale Securities [Member] | Foreign [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	1		0	1
Available-for-sale Securities [Member] | Foreign [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	0		0	0
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		12	26		13	30
Balance- Beginning of Period, Assets		167	151		187	166
Transfers out of Level 3, Assets		0	0		0	(22)
Change in Net Unrealized Gains (Losses) included in OCI, Assets		(3)	2		0	2
Purchases, Assets		8	30		16	45
Sales, Assets		(2)	(2)		(5)	(8)
Settlements, Assets		(15)	(3)		(41)	(9)
Balance-End of Period, Assets		167	204		167	204
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]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	0		(3)	0
Available-for-sale Securities [Member] | Corporate Debt Securities [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	0		0	0
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		33	8		15	8
Transfers out of Level 3, Assets		0	0		0	0
Change in Net Unrealized Gains (Losses) included in OCI, Assets		0	0		0	0
Purchases, Assets		23	0		41	0
Sales, Assets		0	0		0	0
Settlements, Assets		(1)	(1)		(1)	(1)
Balance-End of Period, Assets		55	7		55	7
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]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	0		0	0
Available-for-sale Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	0		0	0
Guaranteed Living Benefit [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	[1]	347	241		347	241	$ 451	406	$ 243	$ 193
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0			0	0
Transfers out of Level 3, Assets		0			0	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
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities		(104)	(2)	[1]	(59)	48
Reported liabilities		615	486		615	486		$ 663	$ 483
Guaranteed Living Benefit [Member] | Gain (Loss) on Investments [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(104)	(2)		(59)	48
Guaranteed Living Benefit [Member] | Other Income (Expense) [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		$ 0	$ 0		$ 0	0
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.