Reinsurance (Assumed Life Reinsurance Programs Involving Minimum Benefit Guarantees Under Annuity Contracts - Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Guaranteed Minimum Benefits [Line Items]
Document Period End Date	Dec. 31, 2015
Reinsurance recoveries on losses and loss expenses incurred	$ 3,100	$ 3,100	$ 3,100
Provision for uncollectible reinsurance	$ 328	357
Average attained age of all policyholders under all benefits reinsured, years	69 years
Guaranteed Minimum Death Benefit
Guaranteed Minimum Benefits [Line Items]
Net Amount at Risk	$ 364	418
Reported liabilities	$ 117	111
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	4.30%
GLB
Guaranteed Minimum Benefits [Line Items]
Net Amount at Risk	$ 733	440
Guaranteed Minimum Deaths Benefits And Guaranteed Living Benefits [Member]
Guaranteed Minimum Benefits [Line Items]
Mortality percentage according to Annuity 2000 mortality table	100.00%
Guaranteed Living Benefits [Member]
Guaranteed Minimum Benefits [Line Items]
Reported liabilities	$ 888	663	$ 427	$ 1,400
Fair value derivative adjustment in liability	$ 609	$ 406
Minimum | Guaranteed Minimum Death Benefit
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	3.80%
Minimum | GLB
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	4.50%
Minimum | Guaranteed Minimum Deaths Benefits And Guaranteed Living Benefits [Member]
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	4.50%
Maximum | Guaranteed Minimum Death Benefit
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	5.00%
Maximum | GLB
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	5.00%