Compensation Plans Non Stock-based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cash Bonus Plan [Member]
Cash Paid in Current Period for Bonus Compensation			$ 16,000,000	$ 24,000,000
Accrued Cash Bonus Plan Expense	5,800,000	4,300,000	16,700,000	13,600,000
Net Profits Plan [Member]
Cash Payments Made or Accrued under Profit Sharing Plan Related to Divested Property		274,000	2,600,000	1,990,202
General and administrative expense	4,302,000	4,083,000	11,531,000	12,177,000
Exploration expense	329,000	403,000	1,026,000	1,421,000
Total	$ 4,631,000	$ 4,486,000	$ 12,557,000	$ 13,598,000