Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
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	892	$ 916
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	648
Due after one year through five years	770
Due after five years through ten years	646
Due after ten years	1,123
Mortgage-Backed and Asset-Backed	666
Total Available-For-Sale, amortized cost	3,853
Due in one year or less	653
Due after one year through five years	774
Due after five years through ten years	570
Due after ten years	1,149
Mortgage-Backed and Asset-Backed	657
Total Available-For-Sale, fair value	3,803
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	892
Mortgage-Backed and Asset-Backed	0
Held-To-Maturity Securities Fair Value	$ 892