Investments (Distribution Of Securities By Contractual Maturity Of AFS And HTM) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Due in one year or less, Amortized Cost	$ 274
Due after one year through five years, Amortized Cost	898
Due after five years through ten years, Amortized Cost	794
Due after ten years through fifteen years, Amortized Cost	370
Due after fifteen years, Amortized Cost	991
Total available for sale, Amortized Cost	4,623
Due in one year or less, Fair Value	275
Due after one year through five years, Fair Value	921
Due after five years through ten years, Fair Value	831
Due after ten years through fifteen years, Fair Value	398
Due after fifteen years, Fair Value	1,043
Total available for sale, Fair Value	4,709
Fixed-Maturity Investments [Member] | Mortgage And Asset Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total available for sale, Amortized Cost	1,296
Total available for sale, Fair Value	1,241
Variable Interest Entity [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total held-to-maturity investments, Fair Value	2,759	2,674
Variable Interest Entity [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Due in one year or less, Amortized Cost	17
Due after one year through five years, Amortized Cost	107
Due after ten years through fifteen years, Amortized Cost	84
Total available for sale, Amortized Cost	408
Due in one year or less, Fair Value	18
Due after one year through five years, Fair Value	116
Due after ten years through fifteen years, Fair Value	82
Total available for sale, Fair Value	403
Due in one year or less, Amortized Cost
Due after one year through five years, Amortized Cost
Due after five years through ten years, Amortized Cost
Due after ten years through fifteen years, Amortized Cost
Due after fifteen years, Amortized Cost	2,826
Total held-to-maturity investments, Amortized Cost	2,826
Due in one year or less, Fair Value
Due after one year through five years, Fair Value
Due after five years through ten years, Fair Value
Due after ten years through fifteen years, Fair Value
Due after fifteen years, Fair Value	2,759
Total held-to-maturity investments, Fair Value	2,759
Variable Interest Entity [Member] | Fixed-Maturity Investments [Member] | Mortgage And Asset Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total available for sale, Amortized Cost	200
Total available for sale, Fair Value	187
Total held-to-maturity investments, Amortized Cost
Total held-to-maturity investments, Fair Value