|
Financial Assets Measured At Fair Value On Recurring Basis (Detail) (USD $)
In Millions, unless otherwise specified
|
Jun. 30, 2012
|
Dec. 31, 2011
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents, Fair Value |
$ 3,646 |
$ 1,205 |
| Total debt securities, Fair Value |
9,665 |
9,453 |
| Total invested assets |
13,311 |
10,658 |
|
Debt Securities | Tax-exempt municipal securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
2,886 |
2,856 |
|
Debt Securities | Residential Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
38 |
44 |
|
Debt Securities | Commercial Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
448 |
381 |
|
Debt Securities | Asset-backed securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
44 |
83 |
|
Debt Securities | Corporate Debt Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
3,741 |
3,580 |
|
Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | US Treasury And Agency Obligations
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
553 |
725 |
|
Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
1,955 |
1,784 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1)
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents, Fair Value |
3,646 |
1,205 |
| Total debt securities, Fair Value |
0 |
0 |
| Total invested assets |
3,646 |
1,205 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt Securities | Tax-exempt municipal securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt Securities | Residential Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt Securities | Commercial Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt Securities | Asset-backed securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt Securities | Corporate Debt Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | US Treasury And Agency Obligations
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Significant Other Observable Inputs (Level 2)
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents, Fair Value |
0 |
0 |
| Total debt securities, Fair Value |
9,625 |
9,412 |
| Total invested assets |
9,625 |
9,412 |
|
Significant Other Observable Inputs (Level 2) | Debt Securities | Tax-exempt municipal securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
2,871 |
2,840 |
|
Significant Other Observable Inputs (Level 2) | Debt Securities | Residential Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
38 |
44 |
|
Significant Other Observable Inputs (Level 2) | Debt Securities | Commercial Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
448 |
381 |
|
Significant Other Observable Inputs (Level 2) | Debt Securities | Asset-backed securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
43 |
82 |
|
Significant Other Observable Inputs (Level 2) | Debt Securities | Corporate Debt Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
3,717 |
3,556 |
|
Significant Other Observable Inputs (Level 2) | Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | US Treasury And Agency Obligations
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
553 |
725 |
|
Significant Other Observable Inputs (Level 2) | Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
1,955 |
1,784 |
|
Significant Unobservable Inputs (Level 3)
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Cash equivalents, Fair Value |
0 |
0 |
| Total debt securities, Fair Value |
40 |
41 |
| Total invested assets |
40 |
41 |
|
Significant Unobservable Inputs (Level 3) | Debt Securities | Tax-exempt municipal securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
15 |
16 |
|
Significant Unobservable Inputs (Level 3) | Debt Securities | Residential Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Significant Unobservable Inputs (Level 3) | Debt Securities | Commercial Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Significant Unobservable Inputs (Level 3) | Debt Securities | Asset-backed securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
1 |
1 |
|
Significant Unobservable Inputs (Level 3) | Debt Securities | Corporate Debt Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
24 |
24 |
|
Significant Unobservable Inputs (Level 3) | Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | US Treasury And Agency Obligations
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
0 |
0 |
|
Significant Unobservable Inputs (Level 3) | Debt Securities | U.S. Treasury And Other U.S. Government Corporations And Agencies | Mortgage-Backed Securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Total debt securities, Fair Value |
$ 0 |
$ 0 |