Supplemental Disclosures of Cash Flow Information - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	$ 27,635	$ 26,689
Cash paid for income taxes	0	0
Cash paid for operating leases	873	595
Non-cash operating activities:
Operating leases	777	14,955
Non-cash investing and financing activities:
Accounts payable and accrued liabilities - oil and gas properties	11,746	87,109
Change in asset retirement obligations, net of disposals	(12)	(5,022)
Retirement of treasury stock	(654)	(1,506)
Properties exchanged in non-cash transactions	$ 4,753	$ 4,561