Leases (Summary of Lease Related Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Amortization of asset	$ 268	$ 210
Interest on lease liabilities	96	101
Sublease income	(306)	(217)
Net lease expense	110,024	88,197
Variable lease expense	6,300	7,200
Lease operating expense	209,148	131,696
Property, plant and equipment
Lessee, Lease, Description [Line Items]
Operating lease	24,556	23,447
Lease operating expense	15,400	20,100
Asset retirement obligations
Lessee, Lease, Description [Line Items]
Operating lease	0	3,024
Lease operating expense		3,000
Lease operating expenses
Lessee, Lease, Description [Line Items]
Operating lease	71,601	48,671
Lease operating expense	32,900	12,000
Transportation, gathering and processing
Lessee, Lease, Description [Line Items]
Operating lease	9,926	9,852
Lease operating expense	1,400
Selling and general expense
Lessee, Lease, Description [Line Items]
Operating lease	3,469	3,109
Lease operating expense	1,200	1,100
Other operating expense
Lessee, Lease, Description [Line Items]
Operating lease	$ 414	$ 0