Fair Value Measurements (Financial Instruments Measured At Fair Value Using Significant Unobservable Inputs) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014		Dec. 31, 2013
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
Balance- Beginning of Period, Assets	2		4
Transfers out of Level 3, Assets	0		(2)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		1
Net Realized Gains/Losses, Assets	0		0
Purchases, Assets	0		1
Sales, Assets	0		(2)
Settlements, Assets	0		0
Balance-End of Period, Assets	2		2
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets			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
Net Realized Gains/Losses, Assets			0
Purchases, Assets			0
Sales, Assets			0
Settlements, Assets			0
Balance-End of Period, 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
Balance- Beginning of Period, Assets	2,719		2,440
Transfers out of Level 3, Assets	0		0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(20)		41
Net Realized Gains/Losses, Assets	0		0
Purchases, Assets	147		200
Sales, Assets	0		(1)
Settlements, Assets	(57)		(69)
Balance-End of Period, Assets	2,789		2,611
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		0
Other Derivative Instruments Fair Value [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	4
Transfers out of Level 3, Assets	0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0
Sales, Assets	0
Balance-End of Period, Assets	4
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	0		0
Balance- Beginning of Period, Assets	22		44
Transfers out of Level 3, Assets	0		(18)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		(1)
Net Realized Gains/Losses, Assets	0		0
Purchases, Assets	1		2
Sales, Assets	(1)		(1)
Settlements, Assets	0		0
Balance-End of Period, Assets	22		26
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	1		4
Balance- Beginning of Period, Assets	187		166
Transfers out of Level 3, Assets	0		(22)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	3		0
Net Realized Gains/Losses, Assets	(3)		0
Purchases, Assets	8		15
Sales, Assets	(3)		(6)
Settlements, Assets	(26)		(6)
Balance-End of Period, Assets	167		151
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(2)
Available-for-sale Securities [Member] | 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
Balance- Beginning of Period, Assets	15		8
Transfers out of Level 3, Assets	0		0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		0
Net Realized Gains/Losses, Assets	0		0
Purchases, Assets	18		0
Sales, Assets	0		0
Settlements, Assets	0		0
Balance-End of Period, Assets	33		8
Guaranteed Living Benefit [Member]
Schedule Of Fair Value Measurements [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	451	[1]	243	[1]	406	[1]	193	[1]
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
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	45	[1]	50	[1]
Purchases, Assets	0
Sales, Assets	0
Settlements, Assets	0
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	45		50	[1]
Reported liabilities	$ 716		$ 483		$ 663		$ 427

[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.