|
Investments Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $)
In Millions, unless otherwise specified
|
Mar. 31, 2013
|
Dec. 31, 2012
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
$ 1,045
|
$ 779
|
|
Marketable securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
876
|
597
|
|
Marketable securities | U.S. government and agency debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
241
|
238
|
|
Marketable securities | Mortgage and asset-backed debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
143
|
174
|
|
Marketable securities | Corporate debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
421
|
163
|
|
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 |
56
|
7
|
|
Other Long-term Investments
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
169
|
182
|
|
Fair Value, Inputs, Level 1
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
259
|
256
|
|
Fair Value, Inputs, Level 1 | Marketable securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
240
|
237
|
|
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 |
240
|
237
|
|
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
|
19
|
|
Fair Value, Inputs, Level 2
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
636
|
360
|
|
Fair Value, Inputs, Level 2 | Marketable securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
636
|
360
|
|
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 |
1
|
1
|
|
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 |
143
|
174
|
|
Fair Value, Inputs, Level 2 | Marketable securities | Corporate debt securities
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Investments |
421
|
163
|
|
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 |
56
|
7
|
|
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 |
150
|
163
|
|
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 |
$ 150
|
$ 163
|