Schedule of Pre-Tax Income (Loss) Effects of Cash Flow Hedges (Detail) (Cash Flow Hedges, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	$ 1,215		$ (866)		$ (115)
Gain (loss) reclassified into net income (loss) from OCI	57		45		35
Gain (loss) recognized in net income (loss)	15	[1]	(14)	[1]	(12)	[1]
Interest Rate Swaps Hedging Assets | Net Investment Income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	1,229		(892)		(74)
Gain (loss) reclassified into net income (loss) from OCI	63		47		40
Interest Rate Swaps Hedging Assets | Net Investment Gains (Losses)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	0		0		0
Gain (loss) reclassified into net income (loss) from OCI	2		1		2
Gain (loss) recognized in net income (loss)	15	[1]	(14)	[1]	(12)	[1]
Interest Rate Swaps Hedging Liabilities | Net Investment Gains (Losses)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in net income (loss)	0	[1]	0	[1]	0	[1]
Interest Rate Swaps Hedging Liabilities | Interest Expense
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	(69)		42		0
Gain (loss) reclassified into net income (loss) from OCI	1		2		2
Forward bond purchase commitments | Net Investment Income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	34		(60)		14
Gain (loss) reclassified into net income (loss) from OCI	0		0		0
Forward bond purchase commitments | Net Investment Gains (Losses)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in net income (loss)	0	[1]	0	[1]	0	[1]
Inflation indexed swaps | Net Investment Income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	17		45		(58)
Gain (loss) reclassified into net income (loss) from OCI	(9)		(5)		(9)
Inflation indexed swaps | Net Investment Gains (Losses)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in net income (loss)	0	[1]	0	[1]	0	[1]
Foreign currency swaps | Net Investment Gains (Losses)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in net income (loss)	0	[1]	0	[1]	0	[1]
Foreign currency swaps | Interest Expense
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	4		(1)		3
Gain (loss) reclassified into net income (loss) from OCI	0		0		0
Gain Or Loss Recognized In Net Income | Interest Rate Swaps Hedging Assets | Net Investment Gains (Losses)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in net income (loss)	$ 0	[1]	$ 0	[1]	$ 0	[1]

[1] Represents ineffective portion of cash flow hedges as there were no amounts excluded from the measurement of effectiveness.