Compensation Plans Non Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Bonus Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Accrued Cash Bonus Plan Expense	$ 37,800,000	$ 41,800,000	$ 16,300,000
Non-qualified Deferred Compensation Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Base Salary Minimum Deferral Percentage	0.00%
Base Salary Maximum Deferral Percentage	50.00%
Cash Bonus Minimum Deferral Percentage	0.00%
Cash Bonus Maximum Deferral Percentage	100.00%
Cash Retainer Minimum Deferral Percentage	0.00%
Cash Retainer Maximum Deferral Percentage	100.00%
Company Percentage Contribution of Employee Deferred Amount	100.00%
Company Percentage Contribution Limit of Employee Deferred Amount	6.00%
Employee Vesting Percentage in Company Contribution After Two Years	40.00%
Employee Vesting Percentage in Company Contribution Year Three and Each Year Thereafter	20.00%
Distribution Option Minimum Years	1
Distribution Option Maximum Years	10
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	8,326,000	13,734,000	15,565,000
Cash Payments Made or Accrued under Profit Sharing Plan Allocated to Oil and Gas Exploration Expense	690,000	1,310,000	1,751,000
Total Cash Payments, Made or Accrued under Profit Sharing Plan	9,016,000	15,044,000	17,316,000
Cash Payments Made or Accrued under Profit Sharing Plan Related to Divested Property	8,300,000	10,300,000	2,300,000
401-K 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, Employer Discretionary Contribution Amount	$ 6,400,000	$ 4,200,000	$ 3,500,000