Equity-method investments (Details) (HGI Energy Holdings, LLC, EXCO/HGI Partnership and the General Partner, USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013
HGI Energy Holdings, LLC | EXCO/HGI Partnership and the General Partner
Assets
Total current assets	$ 54.4
Oil and natural gas properties, net	741.5
Other assets	32.7
Total assets	828.6
Liabilities and members' equity
Total current liabilities	44.9
Total long-term liabilities	397.3
Total members' equity	386.4
Total liabilities and members' equity	828.6
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Revenues	121.1
Costs and Expenses
Oil and natural gas direct operating costs	59.0
Selling, acquisition, operating and general expenses	49.5
Impairment of proved oil and natural gas properties	72.8
Total costs and expenses	181.3
Operating income	(60.2)
Other expense	(8.0)
Net loss	$ (68.2)