Derivative Instrument and Hedging Activities 2 (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	$ 9,665	$ 16,931
Derivative Fair Value Of Derivative Liability	78,166	91,177
Gathering And Processing [Member] | Derivative Instruments Liabilitiy [Member] | Designated As Hedging Instrument [Member] | Natural Gas Price Swaps [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	9,275	16,459
Derivative Fair Value Of Derivative Liability	0	0
Gathering And Processing [Member] | Derivative Instruments Liabilitiy [Member] | Designated As Hedging Instrument [Member] | NGL Price Swaps [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	0	0
Derivative Fair Value Of Derivative Liability	2,408	0
Gathering And Processing [Member] | Derivative Instruments Liabilitiy [Member] | Nondesignated [Member] | NGL Processing Spread Swaps [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	0	0
Derivative Fair Value Of Derivative Liability	26,716	29,057
Distribution [Member] | Derivative Instruments Liabilitiy [Member] | Nondesignated [Member] | Natural Gas Price Swaps [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	100	234
Derivative Fair Value Of Derivative Liability	13,098	34,968
Derivative Instruments Liabilitiy [Member] | Designated As Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	0	0
Derivative Fair Value Of Derivative Liability	23,353	19,694
Gathering And Processing [Member] | Prepayments And Other Assets [Member] | Nondesignated [Member] | Other Derivative Instruments [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	9	133
Derivative Fair Value Of Derivative Liability	0	0
Gathering And Processing [Member] | Deferred Credits [Member] | Designated As Hedging Instrument [Member] | Natural Gas Price Swaps [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	230	0
Derivative Fair Value Of Derivative Liability	0	0
Gathering And Processing [Member] | Deferred Credits [Member] | Designated As Hedging Instrument [Member] | NGL Price Swaps [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	0	0
Derivative Fair Value Of Derivative Liability	836	0
Distribution [Member] | Deferred Credits [Member] | Nondesignated [Member] | Natural Gas Price Swaps [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	51	105
Derivative Fair Value Of Derivative Liability	716	2,806
Deferred Credits [Member] | Designated As Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	0	0
Derivative Fair Value Of Derivative Liability	11,039	4,652
Designated As Hedging Instrument [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	9,505	16,459
Derivative Fair Value Of Derivative Liability	37,636	24,346
Nondesignated [Member]
Derivatives Fair Value Line Items
Derivative Fair Value Of Derivative Asset	160	472
Derivative Fair Value Of Derivative Liability	$ 40,530	$ 66,831