Long-Term Debt (Details)			12 Months Ended					12 Months Ended			12 Months Ended		12 Months Ended		12 Months Ended								12 Months Ended		12 Months Ended									12 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2011 Uncommitted Credit Facility [Member] USD ($)	Dec. 31, 2011 Commercial Paper [Member] USD ($)	Dec. 31, 2011 Revolving Credit Agreement 2005 [Member] USD ($)	Dec. 31, 2011 Revolving Credit Agreement 2010 [Member] USD ($)	Dec. 31, 2010 Subsidiary Revolving Credit Facility 2010 [Member] USD ($)	Dec. 31, 2011 Revolving Credit Agreement 2011 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2013 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2013 [Member] USD ($)	Dec. 31, 2010 Floating Rate Senior Notes Due 2014 [Member] USD ($)	Dec. 31, 2011 Floating Rate Senior Notes Due 2014 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2015 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2015 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2016 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2016 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2017 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2017 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2018 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2018 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2019 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2019 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2020 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2020 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2021 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2021 [Member] USD ($)	Dec. 31, 2011 Senior Notes Due 2028 [Member] USD ($)	Dec. 31, 2010 Senior Notes Due 2028 [Member] USD ($)	Dec. 31, 2011 Subsidiary Debt Due 2011 [Member] USD ($)	Dec. 31, 2010 Subsidiary Debt Due 2011 [Member] USD ($)	Dec. 31, 2011 Subsidiary Debt Due 2014 [Member] USD ($)	Dec. 31, 2010 Subsidiary Debt Due 2014 [Member] USD ($)	Dec. 31, 2010 Subsidiary Debt Due 2014 [Member] CAD	Dec. 31, 2010 Senior Notes 2.95% Due 2015 And Senior Notes 4.40% Due 2020 [Member] USD ($)	Dec. 31, 2010 Fixed Rate Notes And Floating Rate Notes [Member] USD ($)
Debt Instrument Table [Line Items]
Total Long-Term Debt	$ 5,040,000,000	$ 5,260,000,000							$ 400,000,000	$ 400,000,000	$ 350,000,000	$ 350,000,000	$ 500,000,000	$ 500,000,000	$ 400,000,000	$ 400,000,000	$ 600,000,000	$ 600,000,000	$ 350,000,000	$ 350,000,000	$ 900,000,000	$ 900,000,000	$ 500,000,000	$ 500,000,000	$ 750,000,000	$ 750,000,000	$ 140,000,000	$ 140,000,000	$ 0	$ 220,000,000	$ 150,000,000	$ 150,000,000
Current Portion of Long-Term Debt	0	220,000,000
Unamortized Debt Discount	30,834,000	36,659,000
Total Long-Term Debt, Net	5,009,166,000	5,003,341,000
Interest Rate (in hundredths)									61.25%				2.95%		2.50%		58.75%		68.75%		56.25%		4.40%		4.10%		6.65%		7.00%			4.75%	4.75%
Effective Interest Rate (in hundredths)													3.148%		2.698%								4.565%		4.276%
Variable Rate Basis											LIBOR
Basis Spread (in hundredths)											0.75%
Subsidiary Debt Due 2014 (Canadian)																																	201,300,000
Interest Rate - Canadian Subsidiary Note																																5.275%	5.275%
Interest Rate Swap Agreement (Fixed Rate) (in hundredths)											1.87%
Debt Instrument Issuance [Abstract]
Debt Instrument Issuance Date											November 23, 2010		May 20, 2010		November 23, 2010								May 20, 2010		November 23, 2010
Debt Instrument Issuance Face Value											350,000,000		500,000,000		400,000,000								500,000,000		750,000,000							150,000,000
Debt Instrument Frequency of Periodic Payment											quarterly		semi-annually		semiannually								semi-annually		semiannually
Net Proceeds From Issuance of Senior Notes																																		990,000,000	1,487,000,000
Long-Term Debt by Maturity [Abstract]
Aggregate annual maturity of long-term debt in 2012	0
Aggregate annual maturity of long-term debt in 2013	400,000,000
Aggregate annual maturity of long-term debt in 2014	500,000,000
Aggregate annual maturity of long-term debt in 2015	500,000,000
Aggregate annual maturity of long-term debt in 2016	400,000,000
Line of Credit Facility [Line Items]
Weighted average interest rate				0.34%
Average Borrowings Outstanding			0	3,000,000
Line of Credit Facility, Expiration Date					June 28, 2012	September 10, 2013		October 11, 2016
Maximum borrowing capacity					1,000,000,000	1,000,000,000	75,000,000	2,000,000,000
Outstanding balance					0	0	37,000,000
Eurodollar rate at period end (in hundredths)								1.17%
Weighted average Eurodollar rate for the outstanding amount during the year (in hundredths)							2.74%
Base rate at period end (in hundredths)								3.25%
Maximum total debt-to-total capitalization ratio allowed under financial covenant (in hundredths)	65.00%
Advances up to an aggregate principal amount								2,000,000,000
Increases in the aggregate commitments to an amount not to exceed								3,000,000,000
Fair Value of Debt	$ 5,657,000,000	$ 5,602,000,000