|
Investments Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $)
In Millions, unless otherwise specified
|
Sep. 30, 2012
|
Dec. 31, 2011
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
$ 782
|
$ 1,475
|
|
Marketable securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
586
|
1,241
|
|
Marketable securities | U.S. government and agency debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
245
|
187
|
|
Marketable securities | Mortgage and asset-backed debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
156
|
191
|
|
Marketable securities | Corporate debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
163
|
837
|
|
Marketable securities | U.S. state and local municipal debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
15
|
15
|
|
Marketable securities | Other debt and equity securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
7
|
11
|
|
Other Long-term Investments
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
196
|
234
|
|
Fair Value, Inputs, Level 1
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
264
|
204
|
|
Fair Value, Inputs, Level 1 | Marketable securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
245
|
187
|
|
Fair Value, Inputs, Level 1 | Marketable securities | U.S. government and agency debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
245
|
187
|
|
Fair Value, Inputs, Level 1 | Marketable securities | Mortgage and asset-backed debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 1 | Marketable securities | Corporate debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 1 | Marketable securities | U.S. state and local municipal debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 1 | Marketable securities | Other debt and equity securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 1 | Other Long-term Investments
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
19
|
17
|
|
Fair Value, Inputs, Level 2
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
341
|
1,054
|
|
Fair Value, Inputs, Level 2 | Marketable securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
341
|
1,054
|
|
Fair Value, Inputs, Level 2 | Marketable securities | U.S. government and agency debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 2 | Marketable securities | Mortgage and asset-backed debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
156
|
191
|
|
Fair Value, Inputs, Level 2 | Marketable securities | Corporate debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
163
|
837
|
|
Fair Value, Inputs, Level 2 | Marketable securities | U.S. state and local municipal debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
15
|
15
|
|
Fair Value, Inputs, Level 2 | Marketable securities | Other debt and equity securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
7
|
11
|
|
Fair Value, Inputs, Level 2 | Other Long-term Investments
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 3
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
177
|
217
|
|
Fair Value, Inputs, Level 3 | Marketable securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 3 | Marketable securities | U.S. government and agency debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 3 | Marketable securities | Mortgage and asset-backed debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 3 | Marketable securities | Corporate debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 3 | Marketable securities | U.S. state and local municipal debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 3 | Marketable securities | Other debt and equity securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
0
|
0
|
|
Fair Value, Inputs, Level 3 | Other Long-term Investments
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
$ 177
|
$ 217
|