Schedule I (Summary Of Investments Other Than Investments In Related Parties) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 5,758
Fair Value	5,862
Amount at which shown in the balance sheet	5,862
Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5,309
Fair Value	5,034
Amount at which shown in the balance sheet	5,189
Other Aggregated Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	9
Fair Value	9
Amount at which shown in the balance sheet	9
Long Term Available-For-Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	4,582
Fair Value	4,685
Amount at which shown in the balance sheet	4,685
Long Term Available-For-Sale [Member] | U.S. Treasury And Government Agency [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	752
Fair Value	791
Amount at which shown in the balance sheet	791
Long Term Available-For-Sale [Member] | State And Municipal Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,417
Fair Value	1,502
Amount at which shown in the balance sheet	1,502
Long Term Available-For-Sale [Member] | State And Municipal Bonds [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	33
Fair Value	36
Amount at which shown in the balance sheet	36
Long Term Available-For-Sale [Member] | Foreign Governments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	151
Fair Value	164
Amount at which shown in the balance sheet	164
Long Term Available-For-Sale [Member] | Corporate Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	916
Fair Value	945
Amount at which shown in the balance sheet	945
Long Term Available-For-Sale [Member] | Corporate Obligations [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	175
Fair Value	178
Amount at which shown in the balance sheet	178
Short Term Available-For-Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	881
Fair Value	888
Amount at which shown in the balance sheet	888
Equity Available For Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	22
Fair Value	23
Amount at which shown in the balance sheet	23
AFS Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5,485
Fair Value	5,596
Amount at which shown in the balance sheet	5,596
AFS Investments [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	637
Fair Value	625
Amount at which shown in the balance sheet	625
Fair Value [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	264
Fair Value	257
Amount at which shown in the balance sheet	257
Fair Value [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,843
Fair Value	1,735
Amount at which shown in the balance sheet	1,735
HTM Investments [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,829
Fair Value	2,674
Amount at which shown in the balance sheet	2,829
HTM Investments [Member] | Corporate Obligations [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,829
Fair Value	2,674
Amount at which shown in the balance sheet	2,829
Mortgage-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Residential Mortgage-Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	928
Fair Value	946
Amount at which shown in the balance sheet	946
Mortgage-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Residential Mortgage-Backed Non-Agency [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	79
Fair Value	80
Amount at which shown in the balance sheet	80
Mortgage-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Residential Mortgage-Backed Non-Agency [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	92
Fair Value	82
Amount at which shown in the balance sheet	82
Mortgage-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Commercial Mortgage-Backed [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	46
Fair Value	42
Amount at which shown in the balance sheet	42
Mortgage-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Collateralized Debt Obligations [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	97
Fair Value	89
Amount at which shown in the balance sheet	89
Mortgage-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Other Asset-Backed [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	20
Fair Value	20
Amount at which shown in the balance sheet	20
Asset-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	417
Fair Value	405
Amount at which shown in the balance sheet	405
Asset-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Collateralized Debt Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	157
Fair Value	87
Amount at which shown in the balance sheet	87
Asset-Backed Securities [Member] | Long Term Available-For-Sale [Member] | Other Asset-Backed [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	136
Fair Value	128
Amount at which shown in the balance sheet	128
Asset-Backed Securities [Member] | Short Term Available-For-Sale [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	220
Fair Value	220
Amount at which shown in the balance sheet	$ 220