Supplemental Disclosures of Cash Flow Information Supplemental Cash Flow Elements (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Interest, net of capitalized interest	$ 41,483	$ 39,470
Income taxes	261	(6,707)
Change in accounts payable related to purchases of properties and equipment	(57,696)	91,444
Change in asset retirement obligation, with a corresponding change to crude oil and natural gas properties, net of disposals	13,493	6,720
Other Nonoperating Expense	2,818		$ 0
Operating Lease, Payments	4,107	0
Operating Cash Flow from Financing Leases	193	0
Finance Lease, Principal Payments	1,492	873
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	1,428	0
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	2,323	0
Treasury Stock, Common [Member]
Other Nonoperating Expense	2,800	$ 0
Treasury Stock, Common [Member] | Accrued Liabilities [Member]
Other Nonoperating Expense	$ 2,818