Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Total held-to-maturity, amortized cost	$ 890	$ 890
Held-To-Maturity Securities Fair Value	894	$ 876
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	627
Due after one year through five years	1,060
Due after five years through ten years	666
Due after ten years	1,206
Mortgage-Backed and Asset-Backed	1,137
Total Available-For-Sale, amortized cost	4,696
Due in one year or less	613
Due after one year through five years	1,043
Due after five years through ten years	619
Due after ten years	1,267
Mortgage-Backed and Asset-Backed	1,125
Total Available-For-Sale, fair value	4,667
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	894
Mortgage-Backed and Asset-Backed	0
Held-To-Maturity Securities Fair Value	$ 894