Schedule I- Investments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 6,970
Fair Value	6,835
Amount at which shown in the balance sheet	6,835
Assets Of Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	3,820
Fair Value	3,374
Amount at which shown in the balance sheet	3,524
Other Aggregated Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5
Fair Value	5
Amount at which shown in the balance sheet	5
Long-Term Available-For-Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5,308
Fair Value	5,174
Amount at which shown in the balance sheet	5,174
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	472
Fair Value	479
Amount at which shown in the balance sheet	479
Long-Term Available-For-Sale [Member] | US States And Political Subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,812
Fair Value	1,761
Amount at which shown in the balance sheet	1,761
Long-Term Available-For-Sale [Member] | Foreign Governments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	114
Fair Value	120
Amount at which shown in the balance sheet	120
Long-Term Available-For-Sale [Member] | Corporate Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,290
Fair Value	1,275
Amount at which shown in the balance sheet	1,275
Short-Term Available-For-Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,370
Fair Value	1,371
Amount at which shown in the balance sheet	1,371
Short-Term Available-For-Sale [Member] | Assets Of Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	136
Fair Value	136
Amount at which shown in the balance sheet	136
Equity Available For Sale [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	10
Fair Value	11
Amount at which shown in the balance sheet	11
AFS Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	6,688
Fair Value	6,556
Amount at which shown in the balance sheet	6,556
Investments At Fair Value [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	277
Fair Value	274
Amount at which shown in the balance sheet	274
Investments At Fair Value [Member] | Assets Of Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	883
Fair Value	587
Amount at which shown in the balance sheet	587
Held-To-Maturity [Member] | Corporate Obligations [Member] | Assets Of Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,801
Fair Value	2,651
Amount at which shown in the balance sheet	2,801
Mortgage-backed [Member] | Long-Term Available-For-Sale [Member] | Residential Mortgage Backed Agency [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,155
Fair Value	1,134
Amount at which shown in the balance sheet	1,134
Mortgage-backed [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	70
Fair Value	77
Amount at which shown in the balance sheet	77
Mortgage-backed [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	33
Fair Value	33
Amount at which shown in the balance sheet	33
Asset-backed [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	205
Fair Value	151
Amount at which shown in the balance sheet	151
Asset-backed [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	157
Fair Value	144
Amount at which shown in the balance sheet	$ 144