Compensation Plans Non Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Profits Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Minimum percentage of oil and gas wells, costs recovered for payment to employees from Net Profit Plan	100.00%
Percentage of future net cash flow received by participants from Net Profit Plan	10.00%
Percentage of future net cash flow received by participants from Net Profit Plan increased to	20.00%
Percentage of oil and gas wells costs recovered for additional payment employees from Net Profit Plan	200.00%
Cash payments made or accrued related to operations	$ 63	$ (54)	$ 6,608
Cash payments made or accrued related to divestitures	0	2,753	24,349
Total net settlements	$ 63	2,699	30,957
401K Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined Contribution Plan, maximum annual contributions per employee, percent	60.00%
Defined Contribution Plan, employer matching contribution, percent of employees' gross pay	6.00%
Defined Contribution Plan, matching contributions	$ 4,900	$ 4,500	$ 5,400
Prior to 2014 [Member] | 401K Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined Contribution Plan, employer matching contribution, percent of match	100.00%
After 2014 [Member] | 401K Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined Contribution Plan, employer matching contribution, percent of match	150.00%