Debt (Narrative) (Details) (USD $)	1 Months Ended	9 Months Ended				3 Months Ended		3 Months Ended		0 Months Ended				0 Months Ended				9 Months Ended
	Feb. 28, 2011 interest_rate_swaps	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Jul. 15, 2011	Sep. 30, 2012 Senior Debt Obligations Due 2017 [Member]	Dec. 31, 2011 Senior Debt Obligations Due 2017 [Member]	Sep. 30, 2012 Senior Debt Obligations Due 2012 [Member]	Dec. 31, 2011 Senior Debt Obligations Due 2012 [Member]	Jul. 15, 2011 Senior Debt Obligations Due 2014 [Member]	Sep. 30, 2012 Senior Debt Obligations Due 2014 [Member]	Dec. 31, 2011 Senior Debt Obligations Due 2014 [Member]	Jun. 27, 2011 Senior Debt Obligations Due 2014 [Member]	Jul. 15, 2011 Senior Debt Obligations Due 2015 [Member]	Sep. 30, 2012 Senior Debt Obligations Due 2015 [Member]	Dec. 31, 2011 Senior Debt Obligations Due 2015 [Member]	Jun. 27, 2011 Senior Debt Obligations Due 2015 [Member]	Sep. 30, 2011 Senior Debt Obligations Due In Ten Years [Member]	Sep. 30, 2012 September 2011 Debt Obligation [Member]	Oct. 13, 2011 September 2011 Debt Obligation [Member]
Debt instrument, interest rate, stated percentage						2.30%		6.25%			5.375%		5.375%		5.75%		5.75%	4.80%
Extinguishment of Debt, Amount								$ 250,000,000		$ 330,000,000				$ 270,000,000
Line of Credit Facility Term																			5 years
Line of credit facility, current borrowing capacity																				1,000,000,000
Number of interest rate swaps (in interest rate swaps)	2
Interest rate swap for hedging	125,000,000
Interest rate swap maturity, in years	3.5
Floating rate three-month LIBOR plus fixed spread interest percentage	3.726%
Interest rate swaps, fair value adjustment	0
Swap agreements, effectiveness recognized during the period		0
5.375% senior notes due in 2014, hedged value											250,000,000
Revolving credit facility, amount outstanding		0
Proceeds from issuance of debt		248,000,000	496,000,000			250,000,000												500,000,000
Upper Limit For Tender Purchase Of Aggregate Principal Amount													500,000,000
Term of interest rate swap net settlement (in months)		6 months
Long-term debt and capital lease obligations		2,660,000,000		2,668,000,000		249,000,000	0	0	250,000,000		326,000,000	326,000,000	650,000,000		479,000,000	479,000,000	750,000,000
Long-term Debt, Current Maturities		$ 259,000,000		$ 260,000,000	$ 600,000,000