Investments (Distribution By Contractual Maturity Of Available-For-Sale and Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Total held-to-maturity, amortized cost	$ 890	$ 890
Total Held-To-Maturity, fair value	879	$ 876
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Due in one year or less	400
Due after one year through five years	1,209
Due after five years through ten years	773
Due after ten years	1,352
Mortgage-Backed and Asset-Backed	1,202
Total Available-For-Sale, amortized cost	4,936
Due in one year or less	399
Due after one year through five years	1,215
Due after five years through ten years	727
Due after ten years	1,386
Mortgage-Backed and Asset-Backed	1,187
Total Available-For-Sale, fair value	4,914
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	879
Mortgage-Backed and Asset-Backed	0
Total Held-To-Maturity, fair value	$ 879