Income Taxes (Details) (USD $)	1 Months Ended		3 Months Ended			12 Months Ended
	Jun. 30, 2013	Apr. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2012
Income Taxes
Decrease in valuation allowance					$ 229,700,000
Amount of valuation allowance released					54,200,000
Operating loss carryforwards
Reduction in deferred tax assets related to net operating losses					229,700,000	229,700,000
Income tax expense paid for alternative minimum tax	550,000	475,000		270,000
Income tax expense recorded for alternative minimum tax			540,000	453,000		268,000
State | Colorado
Operating loss carryforwards
NOLs suspended in excess of amount	$ 250,000		$ 250,000