Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Dec. 31, 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	925	$ 916
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	820
Due after one year through five years	715
Due after five years through ten years	651
Due after ten years	1,030
Mortgage-Backed and Asset-Backed	601
Total Available-For-Sale, amortized cost	3,817
Due in one year or less	831
Due after one year through five years	741
Due after five years through ten years	568
Due after ten years	1,053
Mortgage-Backed and Asset-Backed	588
Total Available-For-Sale, fair value	3,781
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	925
Mortgage-Backed and Asset-Backed	0
Held-To-Maturity Securities Fair Value	$ 925