Acquisitions - Schedule of Preliminary purchase price (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended						0 Months Ended	3 Months Ended				12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2014 HHI Business	Sep. 30, 2013 HHI Business	Dec. 17, 2012 HHI Business	Nov. 08, 2013 Shaser Biosciences, Inc.	Dec. 31, 2013 Shaser Biosciences, Inc.	Sep. 30, 2013 Shaser Biosciences, Inc.	Nov. 08, 2012 Shaser Biosciences, Inc.	Apr. 08, 2013 TLM Taiwan	Sep. 30, 2014 The Liquid Fence Company [Member]	Mar. 05, 2013 HGI Cotton-Valley Oil and Gas Properties	Feb. 14, 2013 HGI Compass	Mar. 05, 2013 Compass Cotton-Valley Oil and Gas Properties	Feb. 14, 2013 Compass	Sep. 30, 2013 Business Combination Measurement Period Adjustment Shaser Biosciences, Inc.	Sep. 30, 2014 Business Combination Measurement Period Adjustment Hardware Acquisition	Apr. 08, 2013 Business Combination Measurement Period Adjustment Hardware Acquisition
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value	$ 12.0
Payments to Acquire Businesses, Gross	1.5						50.0					24.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash					24.0	17.4			0.9	0.9	0.8		0	0.1	0	0.1	0		5.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles				489.1	489.1	470.0			29.3	35.5	17.1						(6.2)	2.0	2.0
Preliminary working capital and other adjustments														30.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Unproved Oil and Natural Gas Properties													7.2	65.1	5.4	48.5
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Proved Developed and Undeveloped Oil and Natural Gas Properties													130.9	632.2	97.5	471.0
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Oil And Natural Gas Properties													138.1	697.3	102.9	519.5
Other long-term assets					7.6	3.1			0.2	2.7	0.1		0	32.7	0	24.5	(2.5)		4.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities, Accrued Liabilities					42.8	37.6					0.2		0	10.8	0	(8.0)			5.0
Other long-term liabilities					19.7	11.2					8.1		(7.4)	(24.8)	(5.5)	(18.5)			0.4
Business combination, assets acquired					661.2	629.4			21.6	24.7	47.9		130.7	694.5	97.4	517.6	(3.1)		(16.1)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets					985.4	920.1			30.4	39.1	58.1						(8.7)		7.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities					324.2	290.7			8.8	14.4	10.2						(5.6)		23.3
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value					3.9	2.2			39.1	39.0	0						0.1		1.7
Goodwill (Note 13)	1,524.8	1,476.7	694.2		717.8	662.1			67.2	63.9	45.6						3.3		10.1
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest					1,375.1	1,289.3			49.7	49.6	93.5						0.1		(7.7)
Business Combination, Consideration Transferred, Liabilities Incurred												9.5
Business Combination, Consideration Transferred, Other							(0.4)	0.1				1.5
Business Combination, Consideration Transferred							49.7					35.8
Business Combination, Consideration Transferred, Including Equity Interest in Acquiree Held Prior to Combination	$ 13.5