Equity-method investments Schedule of Investments in Equity-Method Investments (Details) (USD $)			12 Months Ended
	Sep. 30, 2014 HC2 Holdings Inc. [Member]	Jan. 03, 2014 HC2 Holdings Inc. [Member]	Sep. 30, 2014 HGI Energy Holdings, LLC EXCO/HGI Partnership and the General Partner	Sep. 30, 2013 HGI Energy Holdings, LLC EXCO/HGI Partnership and the General Partner
Schedule of Equity Method Investments [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	24.70%	40.50%
Equity Method Investment, Quoted Market Value	$ 26.5
Assets
Total current assets			50,100,000	54,400,000
Oil and natural gas properties, net			599,400,000	741,500,000
Other assets			29,000,000	32,700,000
Total assets			678,500,000	828,600,000
Liabilities and members' equity
Total current liabilities			42,900,000	44,900,000
Total long-term liabilities			362,900,000	397,300,000
Total members' equity			272,700,000	386,400,000
Total liabilities and members' equity			678,500,000	828,600,000
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Revenues			197,500,000	121,100,000
Costs and Expenses
Oil and natural gas direct operating costs			93,500,000	59,000,000
Selling, acquisition, operating and general expenses			67,200,000	49,500,000
Impairment of proved oil and natural gas properties			109,000,000	72,800,000
Total costs and expenses			269,700,000	181,300,000
Operating income			(72,200,000)	(60,200,000)
Other expense			(19,000,000)	(8,000,000)
Net loss			$ (91,200,000)	$ (68,200,000)