Acquisitions - Summary of Amounts Recorded in Connection with Acquisition of Business (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		9 Months Ended
	Jun. 30, 2013	Sep. 30, 2012	Jun. 30, 2013 HGI [Member]	Feb. 14, 2013 EXCO/HGI General Partner [Member] EXCO [Member]	Feb. 14, 2013 EXCO/HGI JV [Member] EXCO [Member]	Feb. 14, 2013 EXCO/HGI JV [Member] HGI [Member]	Feb. 14, 2013 EXCO/HGI JV [Member]	Mar. 05, 2013 Cotton-Valley Oil and Gas Properties [Member]	Mar. 05, 2013 Cotton-Valley Oil and Gas Properties [Member] HGI [Member]	Mar. 05, 2013 Cotton-Valley Oil and Gas Properties [Member] EXCO/HGI JV [Member]	Jun. 30, 2013 HHI Business [Member]	Dec. 17, 2012 HHI Business [Member]	Apr. 08, 2013 TLM Taiwan [Member]	Dec. 17, 2012 Hardware Acquisition [Member] Business Combination Measurement Period Adjustment [Member]	Jun. 30, 2013 Shaser Biosciences, Inc. [Member]	Nov. 08, 2012 Shaser Biosciences, Inc. [Member]	Jun. 30, 2013 Shaser Biosciences, Inc. [Member] Business Combination Measurement Period Adjustment [Member]
Business Acquisition [Line Items]
Document Period End Date	Jun. 30, 2013		Jun. 30, 2013
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Cash						$ 0.1	$ 0.1		$ 0	$ 0	$ 24.0	$ 17.4	$ 0.8	$ 5.8	$ 0.9	$ 0.9	$ 0
Accounts receivable											109.0	104.6	0	4.4
Inventory											205.9	207.2	1.1	(2.4)
Prepaid expenses and other											11.2	13.3	2.1	(4.2)
Property, plant and equipment											136.2	104.5	36.8	(5.1)
Intangible asset											487.1	470.0	17.1	0	32.8	35.5	(2.7)
Other long-term assets						32.7	24.5		0	0	3.2	3.1	0.1	0	2.7	2.7	0
Total assets acquired											976.6	920.1	58.0	(1.5)	36.4	39.1	(2.7)
Oil and natural gas properties
Unproved oil and natural gas properties						65.1	48.5		7.2	5.4
Proved developed and undeveloped oil and natural gas properties						632.2	471.0		131.2	97.7
Total oil and natural gas properties						697.3	519.5		138.4	103.1
Accounts payable											138.1	130.1	0	8.0
Deferred tax liability - current											7.1	7.1	0	0
Accrued liabilities						(10.8)	(8.0)		0	0	(37.8)	(37.5)	(0.2)	(0.1)
Deferred tax liability - long-term											117.8	104.7	1.9	11.2
Other long-term liabilities						(24.8)	(18.5)		(7.5)	(5.6)	(17.1)	(11.2)	(8.1)	2.2
Total liabilities assumed											317.9	290.6	10.2	17.1	13.4	14.4	(1.0)
Total identifiable net assets						694.5	517.6	130.9	130.9	97.5	658.7	629.5	47.8	(18.6)	23.0	24.7	(1.7)
Non-controlling interests					(119.1)						(4.4)	(2.2)	0	(2.2)	(39.0)	(39.0)	0
Goodwill	1,470.2	694.2									720.8	662.1	45.6	13.1	65.6	63.9	1.7
Total net assets acquired											1,375.1	1,289.4	93.4	(7.7)	49.6	49.6	0
Business Acquisition Percentage Of Equity Interests Acquired				50.00%	24.50%	74.50%										56.00%
Business Combination Purchase Consideration Transferred					725.0	349.8	574.8
Preliminary working capital and other adjustments						$ 30.5					$ (7.7)	$ (10.7)	$ (6.5)			$ (0.4)