Investments (Distribution Of Held-To-Maturity Investments By Contractual Maturity) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Held-To-Maturity [Member]
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less, Fair Value
Due after one year through five years, Fair Value	1	[1]
Due after five years through ten years, Fair Value
Due after ten years through fifteen years, Fair Value
Due after fifteen years, Fair Value
Total held-to-maturity investments, Fair Value	1
Due in one year or less, Amortized Cost
Due after one year through five years, Amortized Cost	1	[1]
Due after five years through ten years, Amortized Cost
Due after ten years through fifteen years, Amortized Cost
Due after fifteen years, Amortized Cost
Total held-to-maturity investments, Amortized Cost	1
Variable Interest Entity [Member]
Schedule of Held-to-maturity Securities [Line Items]
Total held-to-maturity investments, Fair Value	2,867		3,489
Variable Interest Entity [Member] | Held-To-Maturity [Member]
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less, 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
Total held-to-maturity investments, Fair Value	2,867
Due in one year or less, 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
Total held-to-maturity investments, Amortized Cost	3,015
Variable Interest Entity [Member] | Asset-Backed Securities [Member] | Held-To-Maturity [Member]
Schedule of Held-to-maturity Securities [Line Items]
Total held-to-maturity investments, Fair Value	2,867
Total held-to-maturity investments, Amortized Cost	$ 3,015

[1] Relates to tax credit investments reported in "Other investments" on the Company's consolidated balance sheets.