Commitments (Details) (USD $)	12 Months Ended					9 Months Ended	12 Months Ended				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Drilling Rig Leasing Contracts	Dec. 31, 2013 Gas gathering through-put commitments	Sep. 30, 2013 Office Space Leases	Dec. 31, 2013 Office Space Leases	Dec. 31, 2013 Other miscellaneous contracts and leases	Dec. 31, 2013 Natural Gas [Member] MMcf	Dec. 31, 2013 Crude Oil [Member] MMBbls	Dec. 31, 2013 Shares Issued to the Board of Directors [Member]	Dec. 31, 2012 Shares Issued to the Board of Directors [Member]	Dec. 31, 2011 Shares Issued to the Board of Directors [Member]	Dec. 31, 2013 Pending Litigation [Member]
Commitments and Contingencies
Stock-based compensation expense	$ 32,347,000	$ 30,185,000	$ 26,824,000								$ 1,400,000	$ 1,300,000	$ 1,200,000
Long-term Purchase Commitment, Amount				65,700,000	1,100,000,000	12,900,000	69,400,000	7,600,000
Long-term Purchase Commitment, Time Period	12 years
Contractual Obligation, Due in Next Twelve Months	179,118,000
Contractual Obligation, Due in Second Year	147,119,000
Contractual Obligation, Due in Third Year	144,438,000
Contractual Obligation, Due in Fourth Year	132,559,000
Contractual Obligation, Due in Fifth Year	128,418,000
Contractual Obligation, Due after Fifth Year	481,947,000
Commitment amount	1,213,599,000
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume									1,807,000,000,000	53,000,000
Operating Leases, Rent Expense	5,700,000	5,400,000	3,700,000
Other Commitment	33,000,000
Estimated Litigation Liability	23,100,000
Accounts Payable and Other Accrued Liabilities														9,600,000
Amount paid (related to litigation)														$ 13,500,000