Compensation Plans Non Stock-Based Compensation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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 under Profit Sharing Plan Allocated to General and Administrative Expense	$ 3,239,000	$ 8,326,000	$ 13,734,000
Cash Payments Made or Accrued under Profit Sharing Plan Allocated to Oil and Gas Exploration Expense	259,000	690,000	1,310,000
Total Cash Payments, Made or Accrued under Profit Sharing Plan	3,498,000	9,016,000	15,044,000
Cash Payments Made or Accrued under Profit Sharing Plan Related to Divested Property	$ 3,800,000	8,300,000	10,300,000
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, Employees Hired December 31, 2014 and Prior	6.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay, Employees Hired After December 31, 2014	9.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Bonus, Employees Hired December 31, 2014 and Prior	6.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Bonus, Employees Hired After December 31, 2014	9.00%
Defined Contribution Plan, Cost Recognized	$ 5,600,000	6,400,000	4,200,000
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0	$ 0	$ 0