Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - Fixed Maturities [Member] $ in Millions	Sep. 30, 2019 USD ($)
Available For Sale Securities [Abstract]
Due in one year or less	$ 598
Due after one year through five years	496
Due after five years through ten years	436
Due after ten years	729
Mortgage-Backed and Asset-Backed	749
Total Available-For-Sale, amortized cost	3,008
Due in one year or less	599
Due after one year through five years	503
Due after five years through ten years	423
Due after ten years	840
Mortgage-Backed and Asset-Backed	748
Total Available-For-Sale, fair value	3,113
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	977
Mortgage-Backed and Asset-Backed	0
Held-To-Maturity Securities Fair Value	$ 977