Assumed Life Reinsurance Programs Involving Minimum Benefit Guarantees Under Annuity Contracts (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Guaranteed Minimum Death Benefit [Member]	Dec. 31, 2013 Guaranteed Minimum Death Benefit [Member]	Sep. 30, 2014 Guaranteed Minimum Income Benefit [Member]	Dec. 31, 2013 Guaranteed Minimum Income Benefit [Member]	Sep. 30, 2013 Guaranteed Minimum Income Benefit [Member]	Jun. 30, 2013 Guaranteed Minimum Income Benefit [Member]	Dec. 31, 2012 Guaranteed Minimum Income Benefit [Member]	Sep. 30, 2014 Guaranteed Minimum Deaths Benefits And Guaranteed Living Benefits [Member]	Dec. 31, 2013 Guaranteed Minimum Deaths Benefits And Guaranteed Living Benefits [Member]	Sep. 30, 2014 Guaranteed Living Benefits [Member]	Dec. 31, 2013 Guaranteed Living Benefits [Member]
Guaranteed Minimum Benefits [Line Items]
Reported liabilities		$ 108	$ 100	$ 566	$ 427	$ 746	$ 880	$ 1,400
Fair value derivative adjustment in liability				317	193
Net amount at risk		520	586								241	136
Mortality percentage according to Annuity 2000 mortality table											100.00%
Discounting assumption used in the calculation of the benefit reserve averaging - lower range		2.00%							3.50%		3.50%
Discounting assumption used in the calculation of the benefit reserve averaging - upper range		3.00%							4.50%		4.50%
Total claim amount payable, if all of the Company's cedants' policyholders covered were to die immediately		629							39
GMBD net amount of risk									75	73
GLB net amount of risk									$ 168	$ 141
Average attained age of all policyholders under all benefits reinsured, years	69 years