Nature of operations and summary of significant accounting policies and going concern (Cash and Cash Equivalents and Accounts Receivable) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Cash held	$ 12,698
Number of portfolio segments | segment	4
Components of accounts receivable
Accounts receivable, gross	$ 46,085	$ 50,744
Allowance for doubtful accounts	(2,768)	(1,097)
Accounts receivable, net	43,317	49,647
Joint interests
Components of accounts receivable
Accounts receivable, gross	16,362	16,664
Allowance for doubtful accounts	(2,570)	(1,097)
Commodity sales
Components of accounts receivable
Accounts receivable, gross	19,818	30,819
Allowance for doubtful accounts	(198)	0
Derivative settlements
Components of accounts receivable
Accounts receivable, gross	8,009	717
Allowance for doubtful accounts	0	0
Other
Components of accounts receivable
Accounts receivable, gross	1,896	2,544
Allowance for doubtful accounts	$ 0	$ 0
Customer Concentration Risk | Sales | Commodity sales
Segment Reporting Information [Line Items]
Concentration Risk, Percentage		75.00%
Credit evaluations | Sales | Commodity sales
Segment Reporting Information [Line Items]
Concentration Risk, Percentage		85.00%