| 2007 |
Schedule of Available-for-sale Securities [Line Items] | Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract] | | Marketable Securities, Current | | US Government-sponsored Enterprises Debt Securities [Member] | 260,000,000 |
Asset-backed Securities [Member] | 186,000,000 |
Other Debt Securities [Member] | 133,000,000 |
Major Types of Debt and Equity Securities [Domain] | 579,000,000 |
Marketable Securities, Noncurrent | | US Government-sponsored Enterprises Debt Securities [Member] | 56,000,000 |
Asset-backed Securities [Member] | 267,000,000 |
Auction Rate Securities [Member] | 16,000,000 |
Other Debt Securities [Member] | 29,000,000 |
Corporate Medium-Term Notes Securities [Member] | 112,000,000 |
Major Types of Debt and Equity Securities [Domain] | 480,000,000 |
Marketable Securities | Major Types of Debt and Equity Securities [Domain] | 1,059,000,000 |