Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Held To Maturity Securities [Abstract]
Total Held-To-Maturity, amortized cost	$ 2,689	$ 2,757
Total Held-To-Maturity, fair value	2,401	$ 2,632
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	412
Due after one year through five years	1,577
Due after five years through ten years	859
Due after ten years	1,486
Mortgage-Backed and Asset-Backed	1,463
Total Available-For-Sale, amortized cost	5,797
Due in one year or less	412
Due after one year through five years	1,587
Due after five years through ten years	876
Due after ten years	1,458
Mortgage-Backed and Asset-Backed	1,423
Total Available-For-Sale, fair value	5,756
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	2,689
Mortgage-Backed and Asset-Backed	0
Total Held-To-Maturity, amortized cost	2,689
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	2,401
Mortgage-Backed and Asset-Backed	0
Total Held-To-Maturity, fair value	$ 2,401