Compensation Plans Non Stock-based Compensation (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Document Period End Date			Jun. 30, 2014
Cash Bonus Plan [Member]
Cash Paid in Current Period for Bonus Compensation			$ 41,700,000	$ 16,000,000
Accrued Cash Bonus Plan Expense	6,200,000	5,300,000	12,800,000	10,900,000
Net Profits Plan [Member]
General and administrative expense	1,986,000	3,443,000	4,964,000	7,229,000
Exploration expense	194,000	323,000	482,000	697,000
Total	2,180,000	3,766,000	5,446,000	7,926,000
Net Profits Plan [Member]
Cash Payments Made or Accrued under Profit Sharing Plan Related to Divested Property	$ 8,500,000	$ 2,600,000	$ 8,500,000