Summary of Significant Accounting Policies - Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment
Depreciation expense	$ 914,867	$ 972,465	$ 824,610
Oil and Gas Properties
Exploratory drilling costs initially capitalized, but subsequently charged to expense		0	0
Impairment of oil and gas properties	1,300,444	549,437	159,598
Impairment of oil and gas properties for leases expired or expected to expire	393,000	549,000	160,000
Impairment of proved properties	14,782	9,658	23,431
Depreciation, depletion, and amortization expense for oil and gas properties	884,000	832,000	694,000
Impairment of long-lived assets other than oil and gas properties	15,000	10,000	23,000
Deferred Financing Costs
Unamortized deferred financing costs included in other assets	7,000
Unamortized deferred financing costs included in long-term debt	19,000
Amounts amortized and the write-off of previously deferred debt issuance costs	11,000	13,000	13,000
Utica Shale
Oil and Gas Properties
Impairment of proved properties	$ 881,000
Gathering Systems and Facilities
Property and Equipment
Estimated useful life	50 years
Other property and equipment
Property and Equipment
Depreciation expense	$ 8,000	9,000	10,000
Other property and equipment | Minimum
Property and Equipment
Estimated useful life	2
Other property and equipment | Maximum
Property and Equipment
Estimated useful life	20 years
Gathering pipelines, compressor stations, and fresh water distribution systems
Property and Equipment
Depreciation expense	$ 22,000	$ 131,000	$ 120,000
Water handling and treatment | Minimum
Property and Equipment
Estimated useful life	5
Water handling and treatment | Maximum
Property and Equipment
Estimated useful life	20 years
Oil and gas property wells
Oil and Gas Properties
Impairment of oil and gas properties	$ 26,000