Asset Acquisitions (Clearfield PPA) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 02, 2012 Clearfield Energy	Dec. 31, 2013 Clearfield Energy
Business Acquisition [Line Items]
Midstream	$ 1,944,312	$ 1,791,288	$ 2,013,942		$ 108,000
Payments to Acquire Businesses, Gross		400		215,397
Assets acquired:
Current assets				17,622
Assets held for sale				19,358
Property, Plant, and Equipment				91,422
Goodwill	153,802	152,627		153,802
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				37,600
Liabilities assumed:
Current liabilities				(28,274)
Liabilities held for disposition				(1,400)
Deferred Taxes				(65,228)
Long term liabilities				(9,505)
Total purchase price				215,397
Cost of Purchased Oil and Gas	$ 1,546,987	$ 1,397,530	$ 1,638,777		$ 94,200