Fair Value Measurements (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Level 1 inputs | Fair Value
Fair Value, by Balance Sheet Grouping
Investments	$ 153		$ 123
Level 1 inputs | Fair Value | Less than 1 year
Fair Value, by Balance Sheet Grouping
Investments	53		44
Level 1 inputs | Fair Value | 1 - 2 years
Fair Value, by Balance Sheet Grouping
Investments	27	[1]	45	[1]
Level 1 inputs | Fair Value | 1 - 2 years | Callable Bonds
Fair Value, by Balance Sheet Grouping
Investments	0		5
Level 1 inputs | Fair Value | 2 - 5 years
Fair Value, by Balance Sheet Grouping
Investments	73	[2]	31	[2]
Level 1 inputs | Fair Value | 2 - 5 years | Callable Bonds
Fair Value, by Balance Sheet Grouping
Investments	8		5
Level 1 inputs | Fair Value | Greater than 5 years
Fair Value, by Balance Sheet Grouping
Investments	0		3
Level 1 inputs | Carrying Value
Fair Value, by Balance Sheet Grouping
Investments	152		121
Level 2 inputs | Fair Value
Fair Value, by Balance Sheet Grouping
Long-term Debt Including Current Maturities	10,043		9,624
Level 2 inputs | Carrying Value
Fair Value, by Balance Sheet Grouping
Long-term Debt Including Current Maturities	$ 8,654		$ 8,664

[1] The 1-2 year category includes callable bonds of approximately $5 million as of year end 2010, which are classified as short-term investments on the consolidated balance sheet. There were no callable bonds in this category as of nine months ended 2011.

[2] The 2-5 year category includes callable bonds of approximately $8 million and $5 million as of nine months ended 2011 and year end 2010, respectively, which are classified as short-term investments on the consolidated balance sheet.