Owners' Equity (Changes in Owners' Equity) (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Balance, January 1, 2011			$ 1,469,571
Net income (loss)	102,999	102,452	193,064	166,986
Net gain on commodity hedges	4,613		4,613	(289)
Reclassification of net gain on interest rate cash flow hedges to interest expense	(41)	(41)	(82)	(82)
Amortization of prior service credit and actuarial loss	77	(36)	155	(21)
Total other comprehensive income (loss)	107,648	102,375	197,750	168,629
Distributions			(172,205)
Equity method portion of equity-based incentive compensation expense			6,004
Issuance of 255,222 common units in settlement of long-term incentive plan awards and board of director retainer fees			4,315
Settlement of tax withholdings on long-term incentive compensation			(7,410)	(3,371)
Acquisition of non-controlling owners' interests			(40,500)
Other			(75)
Balance, June 30, 2011	1,457,450		1,457,450
Issuance of common units	255,222		255,222
Limited Partners' Capital [Member]
Balance, January 1, 2011			1,466,404
Net income (loss)			193,127
Reclassification of net gain on interest rate cash flow hedges to interest expense
Amortization of prior service credit and actuarial loss
Total other comprehensive income (loss)			193,127
Distributions			(172,205)
Equity method portion of equity-based incentive compensation expense			6,004
Issuance of 255,222 common units in settlement of long-term incentive plan awards and board of director retainer fees			4,315
Settlement of tax withholdings on long-term incentive compensation			(7,410)
Acquisition of non-controlling owners' interests			(26,300)
Other			(75)
Balance, June 30, 2011	1,463,860		1,463,860
Limited Partners' Accumulated Other Comprehensive Loss [Member]
Balance, January 1, 2011			(11,096)
Net income (loss)
Net gain on commodity hedges			4,613
Reclassification of net gain on interest rate cash flow hedges to interest expense			(82)
Amortization of prior service credit and actuarial loss			155
Total other comprehensive income (loss)			4,686
Distributions
Equity method portion of equity-based incentive compensation expense
Issuance of 255,222 common units in settlement of long-term incentive plan awards and board of director retainer fees
Settlement of tax withholdings on long-term incentive compensation
Other
Balance, June 30, 2011	(6,410)		(6,410)
Non-controlling Owners' Interest [Member]
Balance, January 1, 2011			14,263
Net income (loss)			(63)
Reclassification of net gain on interest rate cash flow hedges to interest expense
Amortization of prior service credit and actuarial loss
Total other comprehensive income (loss)			(63)
Distributions
Equity method portion of equity-based incentive compensation expense
Issuance of 255,222 common units in settlement of long-term incentive plan awards and board of director retainer fees
Settlement of tax withholdings on long-term incentive compensation
Acquisition of non-controlling owners' interests			(14,200)
Other
Balance, June 30, 2011