Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
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	948	$ 925
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	846
Due after one year through five years	631
Due after five years through ten years	658
Due after ten years	987
Mortgage-Backed and Asset-Backed	612
Total Available-For-Sale, amortized cost	3,734
Due in one year or less	863
Due after one year through five years	669
Due after five years through ten years	623
Due after ten years	1,019
Mortgage-Backed and Asset-Backed	602
Total Available-For-Sale, fair value	3,776
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	948
Mortgage-Backed and Asset-Backed	0
Held-To-Maturity Securities Fair Value	$ 948