Fair Value of Financial Instruments - Liabilities, Recurring (Details) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Total Carrying Value in Consolidated Balance Sheet
Liabilities Recorded at Fair Value in the Financial Statements:
Interest Rate Swap Liabilities (included in other current and non-current liabilities)	$ 34	$ 56
Total Derivative Liabilities Recorded at Fair Value in the Financial Statements	34	56
Long-term Debt, including the current portion:
Term Loans	2,602	2,603
Senior Notes	5,186	5,185
Convertible Notes	675	846
Capital Leases and Other	73	98
Total Long-term Debt, including the current portion:	8,536	8,732
Unadjusted Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
Liabilities Recorded at Fair Value in the Financial Statements:
Interest Rate Swap Liabilities (included in other current and non-current liabilities)	0	0
Total Derivative Liabilities Recorded at Fair Value in the Financial Statements	0	0
Long-term Debt, including the current portion:
Term Loans	2,617	2,631
Senior Notes	5,504	5,712
Convertible Notes	274	286
Capital Leases and Other	0	0
Total Long-term Debt, including the current portion:	8,395	8,629
Significant Other Observable Inputs (Level 2)
Liabilities Recorded at Fair Value in the Financial Statements:
Interest Rate Swap Liabilities (included in other current and non-current liabilities)	34	56
Total Derivative Liabilities Recorded at Fair Value in the Financial Statements	34	56
Long-term Debt, including the current portion:
Term Loans	0	0
Senior Notes	0	0
Convertible Notes	558	748
Capital Leases and Other	73	98
Total Long-term Debt, including the current portion:	$ 631	$ 846