Related Party Transaction (Details) (USD $)	3 Months Ended					9 Months Ended
	Sep. 30, 2011		Jun. 30, 2011	Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Summary of transactions between CPNO and affiliates
Natural gas sales	$ 120,815,000			$ 87,524,000		$ 348,538,000		$ 292,559,000
Compressor rental fees	11,169,000			13,272,000		37,299,000		41,204,000
Gathering and compression services	30,337,000			17,909,000		82,706,000		47,539,000
Natural gas purchases	281,858,000	[1]		174,461,000	[1]	779,986,000	[1]	551,939,000	[1]
Transportation	6,991,000	[1]		5,340,000	[1]	19,202,000	[1]	16,619,000	[1]
Related Party Transactions (Textual) [Abstract]
Purchase of vessel from Copano's Operations			102,000
Affiliates of Mr. Lawing [Member]
Summary of transactions between CPNO and affiliates
Natural gas sales				14,000		(1,000)		16,000
Gathering and compression services				2,000		3,000		7,000
Natural gas purchases				67,000		82,000		455,000
Reimbursable costs	57,000			57,000		171,000		207,000
Webb Duval [Member]
Summary of transactions between CPNO and affiliates
Natural gas sales				33,000		39,000		45,000
Natural gas purchases	459,000			(179,000)		90,000		(66,000)
Management fees	57,000			56,000		169,000		168,000
Reimbursable costs	184,000			503,000		521,000		642,000
Transportation	178,000			56,000		348,000		187,000
Payable to us as of September 30, 2011	81,000					81,000
Payable by us as of September 30, 2011	454,000					454,000
Eagle Ford Gathering [Member]
Summary of transactions between CPNO and affiliates
Natural gas sales	1,091,000					1,091,000
Gathering and compression services	739,000					739,000
Natural gas purchases	7,298,000					7,298,000
Management fees	67,000			41,000		149,000		41,000
Reimbursable costs	999,000			1,389,000		14,594,000
Capital project fees	181,000			189,000		729,000		189,000
Payable to us as of September 30, 2011	375,000					375,000
Payable by us as of September 30, 2011	3,677,000					3,677,000
Liberty Pipeline Group [Member]
Summary of transactions between CPNO and affiliates
Gathering and compression services	145,000					145,000
Management fees	38,000					38,000
Reimbursable costs	1,726,000					17,231,000
Capital project fees						94,000
Payable by us as of September 30, 2011	45,000					45,000
Southern Dome [Member]
Summary of transactions between CPNO and affiliates
Management fees	63,000			63,000		188,000		188,000
Reimbursable costs	98,000			96,000		299,000		253,000
Payable to us as of September 30, 2011	42,000					42,000
Bighorn [Member]
Summary of transactions between CPNO and affiliates
Compressor rental fees	299,000			417,000		1,114,000		1,250,000
Natural gas purchases								3,000
Management fees	96,000			139,000		289,000		417,000
Reimbursable costs	579,000			648,000		1,741,000		1,873,000
Transportation								16,000
Payable to us as of September 30, 2011	21,000					21,000
Other [Member]
Summary of transactions between CPNO and affiliates
Natural gas sales				50,000				175,000
Payable to us as of September 30, 2011	2,000					2,000
Affiliate of TPG [Member]
Related Party Transactions (Textual) [Abstract]
Amount paid for purchase and installation of compressor, compression services , repairs	15,000					70,000
Exterran Holdings [Member]
Related Party Transactions (Textual) [Abstract]
Amount paid for purchase and installation of compressor, compression services , repairs	4,286,000			2,984,000		6,317,000		7,104,000
Fort Union [Member]
Summary of transactions between CPNO and affiliates
Natural gas purchases						6,000		52,000
Management fees	62,000			60,000		185,000		180,000
Reimbursable costs	57,000			32,000		833,000		161,000
Transportation	1,610,000			1,288,000		4,269,000		3,926,000
Payable to us as of September 30, 2011	$ 6,000					$ 6,000

[1] Exclusive of operations and maintenance and depreciation, amortization and impairment shown separately below.