Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended			36 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Other Property and Equipment
Depreciation expense	$ 477,896,000	$ 233,876,000	$ 102,026,000
Oil and Gas Properties
Exploratory drilling costs are initially capitalized, but charged to expense				0
Impairment of unproved properties for leases expired or expected to expire	15,200,000	10,900,000	12,100,000
Impairment of proved properties	0	0	0
Period of deferment of significant costs, pending proved reserves	1 year
Depreciation, depletion, and amortization expense for oil and gas properties	418,700,000	219,800,000	181,700,000
Impairment of long-lived assets other than oil and gas properties	0
Deferred Financing Costs
Unamortized deferred financing costs included in other long-term assets	52,000,000			52,000,000
Amounts amortized and the write-off of previously deferred debt issuance costs	11,000,000	15,800,000	5,200,000
Gathering Systems and Facilities
Other Property and Equipment
Estimated useful life	P20Y
Other property and equipment
Other Property and Equipment
Depreciation expense	5,900,000	2,200,000	1,700,000
Other property and equipment | Minimum
Other Property and Equipment
Estimated useful life	P2Y
Other property and equipment | Maximum
Other Property and Equipment
Estimated useful life	P20Y
Gathering pipelines, compressor stations, and fresh water distribution systems
Other Property and Equipment
Depreciation expense	$ 53,200,000	$ 11,900,000	$ 7,400,000
Fresh Water Distribution | Minimum
Other Property and Equipment
Estimated useful life	P5Y
Fresh Water Distribution | Maximum
Other Property and Equipment
Estimated useful life	P20Y