Compensation Plans Non Stock-based Compensation (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net Profits Plan [Member]
General and administrative expense	$ 3,443,000	$ 3,682,000	$ 7,229,000	$ 8,094,000
Exploration expense	323,000	493,000	697,000	1,018,000
Total	3,766,000	4,175,000	7,926,000	9,112,000
Cash Bonus Plan [Member]
Cash Paid in Current Period for Bonus Compensation			16,000,000	24,000,000
Accrued Cash Bonus Plan Expense	$ 5,300,000	$ 4,600,000	$ 10,900,000	$ 9,300,000