Debt Obligations (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended																			0 Months Ended					1 Months Ended						9 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 17, 2012	Dec. 31, 2011	Aug. 31, 2011	Sep. 30, 2012 Fiscal Quarter Ending Before December 31 2013 [Member]	Sep. 30, 2012 Fiscal Quarter Ending on or After December 31, 2013, and Prior to December 31, 2014 [Member]	Sep. 30, 2012 Each Fiscal Quarter Ending December 31, 2014 and Beyond [Member]	Sep. 30, 2012 Fiscal Quarters Ending Prior to December 31, 2013 [Member]	Sep. 30, 2012 Fiscal Quarters Ending On Or After December 31, 2013 [Member]	Aug. 31, 2011 Secured Debt [Member]	Sep. 30, 2012 Term Loan [Member]	Dec. 31, 2011 Term Loan [Member]	Aug. 22, 2012 Incremental Facility Agreement [Member]	Dec. 31, 2011 Revolving [Member]	Sep. 30, 2012 Unsecured Debt [Member]	Sep. 17, 2012 Unsecured Debt [Member]	Sep. 30, 2012 Other [Member]	Dec. 31, 2011 Other [Member]	Aug. 22, 2012 Incremental Facility Agreement [Member]	Aug. 23, 2012 Incremental Facility Agreement [Member] Term Loan [Member]	Sep. 30, 2012 Incremental Facility Agreement [Member] Term Loan [Member]	Aug. 22, 2012 Incremental Facility Agreement [Member] Term Loan [Member]	Aug. 22, 2012 Incremental Facility Agreement [Member] Revolving [Member]	Sep. 30, 2012 Line of Credit [Member]	Sep. 30, 2011 Secured Debt [Member] Term Loan [Member]	Sep. 30, 2012 Secured Debt [Member] Term Loan [Member]	Aug. 31, 2011 Secured Debt [Member] Term Loan [Member]	Sep. 30, 2012 Secured Debt [Member] Revolving [Member]	Aug. 31, 2011 Secured Debt [Member] Revolving [Member]	Sep. 30, 2012 Base Rate [Member] Secured Debt [Member]	Sep. 30, 2012 Base Rate [Member] Minimum [Member] Secured Debt [Member]	Sep. 30, 2012 Base Rate [Member] Maximum [Member] Secured Debt [Member]	Sep. 30, 2012 Federal Funds Rate [Member] Secured Debt [Member]	Sep. 30, 2012 LIBOR [Member] Minimum [Member] Secured Debt [Member]	Sep. 30, 2012 LIBOR [Member] Maximum [Member] Secured Debt [Member]	Sep. 30, 2012 Twelve Month Period Commencing On July 15, 2017 [Member] Unsecured Debt [Member]	Sep. 30, 2012 Twelve Month Period Commencing On July 15, 2018 [Member] Unsecured Debt [Member]	Sep. 30, 2012 Twelve Month Period Commencing On July 15, 2019 [Member] Unsecured Debt [Member]	Sep. 30, 2012 Twelve Month Period Commencing On July 15, 2020 [Member] Unsecured Debt [Member]	Sep. 30, 2012 Prior To July 15, 2017 [Member] Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 1,462		$ 853								$ 850	$ 700		$ 140	$ 600	$ 600	$ 12	$ 13
Short-term borrowings	54		1
Long-term debt	1,408		852
Secured Credit Facility Maximum Borrowing Amount	1,700									1,400																	700		700
Additional Amount of Incremental Term Loan or Incremental Revolving Commitment																			300			150	150
Additional Amount of Incremental Term Loan or Incremental Revolving Commitment	200
Line of Credit Facility, Amount Outstanding																										850		0
Line of Credit Facility, Amount Outstanding, Short Term																										53
Line of Credit Facility, Amount Outstanding, Long Term																										797
Line of Credit Facility, Reduction in Borrowing Capacity From Usage of Letters of Credit																								19
Debt Instrument, Periodic Payment																				3.75					17.50
Debt Instrument, Amont Due at Maturity Date																					97.5					455.0
Debt Instrument, Basis Spread on Variable Rate																														1.00%			0.50%
Debt Instrument, Margin for Base Rate Loans																															0.25%	1.50%		1.25%	2.50%
Maximum Incremental Borrowing Per Secured Credit Facility	500
Deferred Finance Costs, Noncurrent, Net				29									3			10
Debt Instrument Covenant Consolidated Leverage Ratio					350.00%	325.00%	300.00%
Debt Instrument Covenant Interest Coverage Ratio								350.00%	400.00%
Interest Coverage Ratio Determination Period	four consecutive fiscal quarters
Debt Instrument, Interest Rate, Stated Percentage		5.00%
Percentage of Principle Amount Notes Were Sold At																100.00%
Debt Instrument Redemption Price As Percentage Of Principle Amount																																				102.50%	101.667%	100.833%	100.00%	100.00%
Debt Instrument, Fair Value Disclosure	$ 1,480		$ 855