Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Available For Sale Securities [Abstract]
Total Available-For-Sale, Amortized Cost	$ 6,647	$ 6,122
Total Available-For-Sale, Fair Value	6,572	6,221
Held To Maturity Securities [Abstract]
Total Held-To-Maturity, Fair Value	2,690	2,674
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	933
Due after one year through five years	798
Due after five years through ten years	819
Due after ten years	1,349
Mortgage-Backed and Asset-Backed	1,357
Total Available-For-Sale, Amortized Cost	5,256	4,883
Due in one year or less	934
Due after one year through five years	812
Due after five years through ten years	818
Due after ten years	1,340
Mortgage-Backed and Asset-Backed	1,276
Total Available-For-Sale, Fair Value	5,180	4,993
Fixed Maturities [Member] | Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	2,818
Mortgage-Backed and Asset-Backed	0
Total Held-To-Maturity, Amortized Cost	2,818
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	2,690
Mortgage-Backed and Asset-Backed	0
Total Held-To-Maturity, Fair Value	$ 2,690