Asset Retirement Obligation (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Asset Retirement Obligation [Abstract]
Asset retirement obligations at beginning of period	$ 60,814,000	$ 42,052,000
Accretion expense	5,171,000	4,922,000
Liabilities incurred	7,730,000	13,638,000
Liabilities settled	(2,334,000)	(1,182,000)
Asset Retirement Obligation, Revision of Estimate	1,426,000	1,384,000
Asset retirement obligations at end of period	72,807,000	60,814,000
Less: current asset requirement obligations	(96,000)	(702,000)
Long-term asset retirement obligations	$ 72,711,000	$ 60,112,000