Investments in Unconsolidated Affiliates (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Summarized financial information for significant equity investments
Equity in (loss) earnings from unconsolidated affiliates	$ (161,589)	$ 2,049	$ (158,581)	$ (19,788)
Distributions			17,961	16,999
Bighorn [Member]
Summarized financial information for significant equity investments
Operating revenue			20,436	23,793
Operating expenses			(7,089)	(8,904)
Depreciation and amortization			(3,874)	(3,887)
Interest income (expense) and other			62	77
Net income (loss)			9,535	11,079
Ownership Percentage	51.00%	51.00%	51.00%	51.00%
Copano's share, net income (loss)			4,863	5,650
Priority allocation of earnings and other			460	379
Copano's share of management fees charged			147	213
Amortization of difference between the carried investment and the underlying equity in net assets			(128,445)	(33,899)
Equity in (loss) earnings from unconsolidated affiliates			(122,975)	(27,657)
Distributions			7,415	8,423
Contributions			530	810
Current assets	5,304	6,188	5,304	6,188
Noncurrent assets	86,587	89,750	86,587	89,750
Current liabilities	(1,852)	(1,206)	(1,852)	(1,206)
Noncurrent liabilities	(289)	(257)	(289)	(257)
Net assets	89,570	94,475	89,570	94,475
Fort Union Gas Gathering [Member]
Summarized financial information for significant equity investments
Operating revenue			41,011	42,852
Operating expenses			(5,175)	(5,362)
Depreciation and amortization			(5,994)	(5,628)
Interest income (expense) and other			(1,705)	(3,520)
Net income (loss)			28,137	28,342
Ownership Percentage	37.04%	37.04%	37.04%	37.04%
Copano's share, net income (loss)			10,422	10,498
Copano's share of management fees charged			68	66
Amortization of difference between the carried investment and the underlying equity in net assets			(49,817)	(4,817)
Equity in (loss) earnings from unconsolidated affiliates			(39,327)	5,747
Distributions			9,927	8,704
Contributions				774
Current assets	12,447	14,424	12,447	14,424
Noncurrent assets	198,227	206,580	198,227	206,580
Current liabilities	(20,285)	(19,949)	(20,285)	(19,949)
Noncurrent liabilities	(63,046)	(78,190)	(63,046)	(78,190)
Net assets	127,343	122,865	127,343	122,865
Eagle Ford Gathering LLC ("Eagle Ford Gathering") [Member]
Summarized financial information for significant equity investments
Operating revenue			10,494
Operating expenses			(5,609)	(41)
Depreciation and amortization			(1,064)
Net income (loss)			3,821	(41)
Ownership Percentage	50.00%	50.00%	50.00%	50.00%
Copano's share, net income (loss)			1,911	(21)
Copano's share of management fees charged			74	20
Amortization of difference between the carried investment and the underlying equity in net assets			(7)
Equity in (loss) earnings from unconsolidated affiliates			1,978	(1)
Distributions			775
Contributions			73,514	9,492
Current assets	21,464	11,667	21,464	11,667
Noncurrent assets	211,859	22,763	211,859	22,763
Current liabilities	(23,886)	(15,486)	(23,886)	(15,486)
Noncurrent liabilities	(272)		(272)
Net assets	$ 209,165	$ 18,944	$ 209,165	$ 18,944

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