Derivative Instruments (Narrative) (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Derivative [Line Items]
Maximum amount of future guarantee payments	$ 17,100,000,000
Insured derivatives ceded under reinsurance agreements	48,000,000
Cash collateral posted to derivative counterparties	115,000,000		160,000,000
Securities posted as collateral to derivative counterparties	65,000,000		42,000,000
Number of credit support annexes	1		1
Fair value of Credit Support Annex	4,000,000		4,000,000
Amount of counterparty netting	54,000,000		42,000,000
Derivative assets, after counterparty netting	14,000,000		13,000,000
Other assets and other assets of consolidated VIEs, after counterparty netting and embedded reclass	4,000,000		4,000,000
Counterparty netting	54,000,000		42,000,000
Derivative liabilities, after counterparty netting and posting of cash collateral	386,000,000		1,200,000,000
Derivative Liabilities [Member]
Derivative [Line Items]
Cash collateral posted to derivative counterparties	99,000,000		123,000,000
Total derivative liabilities	560,000,000	[1]	1,347,000,000	[1]
Other Liabilities [Member]
Derivative [Line Items]
Cash collateral posted to derivative counterparties	16,000,000		16,000,000
Other Assets [Member]
Derivative [Line Items]
Cash collateral posted to derivative counterparties			21,000,000
Medium Term Notes And Other Investments [Member]
Derivative [Line Items]
Embedded derivative assets	10,000,000		9,000,000
Medium Term Notes And Other Investments [Member] | Embedded [Member]
Derivative [Line Items]
Total derivative liabilities	$ 21,000,000		$ 19,000,000

[1] In accordance with the accounting guidance for derivative instruments and hedging activities, the balance sheet location of the Company’s embedded derivative instruments is determinedby the location of the related host contract.