Long Term Debt (Narrative) (Details) (USD $)	9 Months Ended				9 Months Ended			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 CEI Credit Facility [Member] Post Amendment [Member]	Sep. 30, 2013 CEI Credit Facility [Member] Pre Amendment [Member]	Sep. 30, 2013 CEI Credit Facility [Member]	Sep. 30, 2013 Other Debt Obligations [Member]	Sep. 30, 2013 Revolving Credit Facility [Member]	Dec. 31, 2012 Revolving Credit Facility [Member]	Sep. 30, 2013 Maximum [Member]	Sep. 30, 2013 Minimum [Member]	Sep. 30, 2013 September 30, 2013 And December 31, 2013 [Member] Minimum [Member]	Sep. 30, 2013 After December 31, 2014 [Member] Maximum [Member]	Sep. 30, 2013 After December 31, 2014 [Member] Minimum [Member]	Sep. 30, 2013 March 31, 2014, June 30, 2014 and September 30, 2014 [Member] Maximum [Member]	Sep. 30, 2013 Prior To December 31, 2013 [Member] Maximum [Member]	Sep. 30, 2013 March 31, 2014, June 30, 2014, September 30, 2014 and December 31, 2014 [Member] Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Initiation Date	Mar. 05, 2013				Sep. 04, 2013
Line of Credit Facility, Maximum Borrowing Capacity		$ 90,000,000	$ 75,000,000		$ 20,000,000	$ 635,000,000.0
Line of Credit Facility, Interest Rate at Period End					4.00%
Line of Credit Facility, Expiration Date	Mar. 05, 2016				Sep. 04, 2016
Line of Credit Facility, Amount Outstanding				47,300,000	11,800,000	76,000,000.0	71,000,000
Notes Payable, Noncurrent					600,000
Notes Payable, Maturity Date					Jul. 09, 2017
Notes Payable, Interest Rate, Stated Percentage Rate Range, Minimum					4.20%
Notes Payable, Interest Rate, Stated Percentage Rate Range, Maximum					7.00%
Line of Credit Facility, Remaining Borrowing Capacity				42,700,000	8,200,000	496,700,000
Line Of Credit Facility Collateral Units	10,700,000
Line Of Credit Facility Base Interest Rate	5.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.75%
Line Of Credit Facility Loan To Equity Value Percentage	47.00%								42.50%
Letters of Credit Outstanding, Amount						62,300,000
Debt Instrument, Covenant Compliance, Additional Borrowing Capacity						$ 271,400,000
Interest Coverge Ratio									2.50 to 1.0	2.25 to 1.0		2.50 to 1.0			2.25 to 1.0
Leverage ratios								5.25 to 1.0			5.25 to 1.0		5.50 to 1.0	5.50 to 1.0