Property and Equipment (Summary of Oil and Gas Properties Not Subject to Amortization) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	$ 3,109,143	$ 1,580,305
Utica
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	1,614,824
MidCon
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	1,491,144
Niobrara
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	2,173
Southern Louisiana
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	536
Bakken
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	98
Other
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	$ 368