Supplemental Disclosures of Cash Flow Information - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	$ 29,357	$ 29,168
Cash paid for income taxes	0	0
Cash paid for operating leases	1,555	970
Non-cash operating activities:
Operating leases	853	14,955
Non-cash investing and financing activities:
Accounts payable and accrued liabilities - oil and gas properties	5,907	44,970
Change in asset retirement obligations, net of disposals	(486)	(5,443)
Retirement of treasury stock	(668)	(1,725)
Properties exchanged in non-cash transactions	$ 4,753	$ 4,561