Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Total Held-To-Maturity, amortized cost	$ 890	$ 2,689
Total Held-To-Maturity, fair value	876	$ 2,401
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	334
Due after one year through five years	1,206
Due after five years through ten years	784
Due after ten years	1,327
Mortgage-Backed and Asset-Backed	1,278
Total Available-For-Sale, amortized cost	4,929
Due in one year or less	334
Due after one year through five years	1,221
Due after five years through ten years	725
Due after ten years	1,366
Mortgage-Backed and Asset-Backed	1,263
Total Available-For-Sale, fair value	4,909
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	890
Mortgage-Backed and Asset-Backed	0
Total Held-To-Maturity, amortized cost	890
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	876
Mortgage-Backed and Asset-Backed	0
Total Held-To-Maturity, fair value	$ 876