Long-Term Debt - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended				1 Months Ended	6 Months Ended		1 Months Ended	6 Months Ended		1 Months Ended	6 Months Ended		6 Months Ended							6 Months Ended								6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	May 13, 2013	Dec. 12, 2012	Jan. 11, 2012 6.125 Percent Senior Notes due July 2022	Jun. 30, 2013 6.125 Percent Senior Notes due July 2022	Dec. 31, 2012 6.125 Percent Senior Notes due July 2022	Apr. 19, 2011 5.875 Percent Senior Notes due April 2021	Jun. 30, 2013 5.875 Percent Senior Notes due April 2021	Dec. 31, 2012 5.875 Percent Senior Notes due April 2021	Dec. 19, 2012 4.875 Percent Senior Notes due May 2023	Jun. 30, 2013 4.875 Percent Senior Notes due May 2023	Dec. 31, 2012 4.875 Percent Senior Notes due May 2023	Jun. 30, 2013 Achieving Investment Grade Status	Jun. 30, 2013 Senior Notes	Jun. 30, 2013 Federal Funds Effective Rate Plus	Jun. 30, 2013 Libor Plus Rate	Jun. 30, 2013 Minimum Revolving Credit Facilities	Jun. 30, 2013 Minimum London Inter Bank Offered Rate Plus	Jun. 30, 2013 Minimum Eurodollar rate plus a margin	Jun. 30, 2013 Minimum Leverage Based Pricing Grid	Jun. 30, 2013 Minimum Ratings Based Pricing Grid	Dec. 12, 2012 Maximum	Jun. 30, 2013 Maximum 6.125 Percent Senior Notes due July 2022	Jun. 30, 2013 Maximum 5.875 Percent Senior Notes due April 2021	Jun. 30, 2013 Maximum 4.875 Percent Senior Notes due May 2023	Jun. 30, 2013 Maximum London Inter Bank Offered Rate Plus	Jun. 30, 2013 Maximum Eurodollar rate plus a margin	Jun. 30, 2013 Maximum Leverage Based Pricing Grid	Jun. 30, 2013 Maximum Ratings Based Pricing Grid	May 13, 2013 Amended Revolving Credit Facility	Dec. 12, 2012 Swing Line Loan	Dec. 12, 2012 Letter of Credit	Jun. 30, 2013 Guarantors
Line Of Credit Facility [Line Items]
Revolving credit facility																																	$ 1,750,000,000	$ 100,000,000	$ 200,000,000
Maturity date of revolving credit facility outstanding amount					2018-05	2016-06
Borrowing capacity description			The revolving credit facility is secured by all of the Partnership’s assets, and loans thereunder (other than swing line loans) bear interest at the Partnership’s option at either (i) the greater of (a) the reference rate of Wells Fargo Bank, NA, (b) the federal funds effective rate plus 0.50 percent or (c) the Eurodollar rate which is based on the London Interbank Offered Rate (LIBOR), plus 1.00 percent, each of which is subject to a margin that varies from 0.50 percent to 1.50 percent per annum, according to the Partnership’s leverage ratio (as defined in the agreement), or (ii) the Eurodollar rate plus a margin that varies from 1.50 percent to 2.50 percent per annum, according to the Partnership’s leverage ratio.
Commitment fee description			The unused portion of the credit facility is subject to commitment fees of (a) 0.25 percent to 0.375 percent per annum while the Partnership is subject to the leverage-based pricing grid, according to the Partnership’s leverage ratio and (b) 0.15 percent to 0.30 percent per annum while the Partnership is subject to the ratings-based pricing grid, according to its senior unsecured long-term debt ratings.
Debt instrument variable rate																		0.50%	1.00%		0.50%	1.50%							1.50%	2.50%
Unused credit facility commitment fees																							0.25%	0.15%							0.375%	0.30%
Outstanding principal amount																				15,000,000
Leverage ratio			5.5													5.0
Senior Notes issued through private placement							750,000,000						1,400,000,000
Debt, interest rate							6.125%	6.125%	6.125%	5.875%	5.875%	5.875%	4.875%	4.875%	4.875%
Debt issuance cost							13,800,000			8,200,000			25,800,000
Debt redemption percentage																										35.00%	35.00%	35.00%
Proceeds from issuance of private placement										350,000,000
Notes maturity date								Jul. 15, 2022			Apr. 15, 2021			May 15, 2023
Interest payable on Senior Notes								January 15 and July 15			April 15 and October 15			May 15 and November 15
Debt redemption date								Jan. 15, 2017			Apr. 15, 2015			Dec. 15, 2017
Debt redemption description								In addition, the Partnership may redeem up to 35 percent of the 2022 Notes prior to January 15, 2015 under certain circumstances with the net cash proceeds from certain equity offerings.			In addition, the Partnership may redeem up to 35 percent of the 2021 Notes prior to April 15, 2014 under certain circumstances with the net cash proceeds from certain equity offerings.			In addition, the Partnership may redeem up to 35 percent of the 2023 Notes prior to December 15, 2015 under certain circumstances with the net cash proceeds from certain equity offerings.
Senior notes covenants																	The 2023 Notes, 2022 Notes and the 2021 Notes indentures contain covenants that, among other things, limit the Partnership’s ability and the ability of certain of the Partnership’s subsidiaries to: (1) sell assets including equity interests in its subsidiaries; (2) pay distributions on, redeem or purchase the Partnership’s units, or redeem or purchase the Partnership’s subordinated debt; (3) make investments; (4) incur or guarantee additional indebtedness or issue preferred units; (5) create or incur certain liens; (6) enter into agreements that restrict distributions or other payments from certain subsidiaries to the Partnership; (7) consolidate, merge or transfer all or substantially all of the Partnership’s or certain of the Partnership’s subsidiaries’ assets; (8) engage in transactions with affiliates; and (9) create unrestricted subsidiaries. These covenants are subject to important exceptions and qualifications. If the 2023 Notes, 2022 Notes or the 2021 Notes achieve an investment grade rating from either of Moody’s Investors Service, Inc. or Standard & Poor’s Ratings Services and no default, as defined in the indentures, has occurred or is continuing, many of these covenants will terminate.
Percent of ownership interest																																				100.00%
Capitalized interest	10,200,000	3,500,000	19,900,000	5,700,000
Additional borrowing capacity																									$ 2,000,000,000