Long Term Debt (Indebtedness Table) (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Debt classified as long-term	$ 1,102,357,000	$ 1,036,305,000
Line of Credit [Member] | Twenty Sixteen [Member]
Debt Instrument [Line Items]
Long-term Debt	76,000,000	71,000,000
Interest rate during the period	3.60%	4.30%
CEI Credit Facility [Member] | Twenty Sixteen [Member]
Debt Instrument [Line Items]
Long-term Debt	47,275,000	0
Interest rate during the period	5.30%
Unsecured Debt [Member] | Twenty Eighteen [Member] | Eight Point Eight Seven Five Percent [Member]
Debt Instrument [Line Items]
Long-term Debt	716,728,000	715,305,000
Percentage bearing fixed interest rate	8.875%	8.875%
Unamortized discount (premium)	8,300,000	9,700,000
Unsecured Debt [Member] | Twenty Twentytwo [Member] | Seven Point One Two Five Percent [Member]
Debt Instrument [Line Items]
Long-term Debt	250,000,000	250,000,000
Percentage bearing fixed interest rate	7.125%	7.125%
Other Debt Obligations [Member] | Twenty Sixteen [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 12,354,000	$ 0