Segment Information Schedule of Assets Related to Balance Sheet (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Total assets	$ 5,719,645	$ 5,567,856
Gathering And Processing [Member]
Segment Reporting Information [Line Items]
Total assets	1,978,072	1,959,697
Corporate Joint Venture [Member]
Segment Reporting Information [Line Items]
Total assets	2,007,414	1,924,705
Contract Compression [Member]
Segment Reporting Information [Line Items]
Total assets	1,395,797	1,405,600
Contract Treating [Member]
Segment Reporting Information [Line Items]
Total assets	211,593	215,172
Corporate and Others [Member]
Segment Reporting Information [Line Items]
Total assets	$ 126,769	$ 62,682