Immaterial Correction of Prior Period Financial Statements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Total revenues	$ 454,737	$ 394,402	$ 900,427	$ 820,361
Purchased gas, NGLs and crude oil	359,093	304,098	700,115	630,304
Total operating costs and expenses	448,859	376,021	880,419	779,907
Operating income	5,878	18,381	20,008	40,454
Scenario, Actual [Member]
Total revenues		394,402		820,361
Purchased gas, NGLs and crude oil		304,098		630,304
Total operating costs and expenses		376,021		779,907
Operating income		18,381		40,454
Classification of New Opportunity Processing [Member] | Scenario, Previously Reported [Member]
Total revenues		351,194		722,903
Purchased gas, NGLs and crude oil		260,890		532,846
Total operating costs and expenses		332,813		682,449
Operating income		18,381		40,454
Classification of New Opportunity Processing [Member] | Scenario, Adjustment [Member]
Purchased gas, NGLs and crude oil		$ 43,200		$ 97,500