Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	$ 330	$ 159
Marketable securities, Fair value	131	286
Derivative Assets	3	4
Derivative Liability Fair Value Gross Liability	(2)	(8)
Corporate debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	82	174
U.S. government and agency debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	16	32
Foreign Government Debt Securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	1	0
Asset-backed debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	6	18
Certificates of deposit [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	16	35
Municipal debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	10	27
Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	284	128
Derivative Assets	0	0
Derivative Liability Fair Value Gross Liability	0	0
Level 1 [Member] | Corporate debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 1 [Member] | U.S. government and agency debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 1 [Member] | Foreign Government Debt Securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 1 [Member] | Asset-backed debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 1 [Member] | Certificates of deposit [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 1 [Member] | Municipal debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	46	31
Derivative Assets	3	4
Derivative Liability Fair Value Gross Liability	(2)	(8)
Level 2 [Member] | Corporate debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	82	174
Level 2 [Member] | U.S. government and agency debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	16	32
Level 2 [Member] | Foreign Government Debt Securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	1	0
Level 2 [Member] | Asset-backed debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	6	18
Level 2 [Member] | Certificates of deposit [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	16	35
Level 2 [Member] | Municipal debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	10	27
Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	0	0
Derivative Assets	0	0
Derivative Liability Fair Value Gross Liability	0	0
Level 3 [Member] | Corporate debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 3 [Member] | U.S. government and agency debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 3 [Member] | Foreign Government Debt Securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 3 [Member] | Asset-backed debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 3 [Member] | Certificates of deposit [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	0	0
Level 3 [Member] | Municipal debt securities [Member]
Assets and liabilities measured at fair value on a recurring basis
Marketable securities, Fair value	$ 0	$ 0