Acquisition Acquisition (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Goodwill	$ 60,676	$ 9,884
Mid-America Midstream Gas Services, L.L.C. [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	123,316
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	169,244
Goodwill	23,587
Total assets acquired	$ 316,147