Investments Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $)
In Millions |
Sep. 30, 2011 |
Dec. 31, 2010 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
$ 1,565
|
$ 1,150
|
Fair Value, Inputs, Level 1 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
196
|
247
|
Fair Value, Inputs, Level 1 | Marketable securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
179
|
247
|
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 |
179
|
206
|
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 |
|
41
|
Fair Value, Inputs, Level 1 | Other Long-term Investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
17
|
|
Fair Value, Inputs, Level 2 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
1,141
|
498
|
Fair Value, Inputs, Level 2 | Marketable securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
1,141
|
498
|
Fair Value, Inputs, Level 2 | Marketable securities | Asset-backed Securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
229
|
222
|
Fair Value, Inputs, Level 2 | Marketable securities | Corporate debt securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
881
|
183
|
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
|
33
|
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 |
16
|
60
|
Fair Value, Inputs, Level 3 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
228
|
405
|
Fair Value, Inputs, Level 3 | Marketable securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
|
138
|
Fair Value, Inputs, Level 3 | Marketable securities | Asset-backed Securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
|
79
|
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 |
|
45
|
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 |
|
14
|
Fair Value, Inputs, Level 3 | Other Long-term Investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
228
|
267
|
Marketable securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
1,320
|
883
|
Marketable securities | U.S. government and agency debt securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
179
|
206
|
Marketable securities | Asset-backed Securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
229
|
301
|
Marketable securities | Corporate debt securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
881
|
183
|
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
|
78
|
Marketable securities | Other debt and equity securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
16
|
115
|
Other Long-term Investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
$ 245
|
$ 267
|