Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended			6 Months Ended							0 Months Ended		0 Months Ended																0 Months Ended												0 Months Ended
	Mar. 31, 2013	Mar. 31, 2013	Apr. 01, 2012	Sep. 30, 2012	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 VOBA [Member]	Mar. 31, 2013 Technology assets [Member] Minimum [Member]	Mar. 31, 2013 Technology assets [Member] Maximum [Member]	Mar. 31, 2013 Customer relationships [Member] Minimum [Member]	Mar. 31, 2013 Customer relationships [Member] Maximum [Member]	Dec. 17, 2012 HHI Business [Member]	Mar. 31, 2013 HHI Business [Member]	Dec. 17, 2012 HHI Business [Member] Technology assets [Member]	Dec. 17, 2012 HHI Business [Member] Technology assets [Member] Minimum [Member]	Dec. 17, 2012 HHI Business [Member] Technology assets [Member] Maximum [Member]	Dec. 17, 2012 HHI Business [Member] Trade name license agreement [Member]	Dec. 17, 2012 HHI Business [Member] Trade name license agreement [Member] Minimum [Member]	Dec. 17, 2012 HHI Business [Member] Trade name license agreement [Member] Maximum [Member]	Dec. 17, 2012 HHI Business [Member] Trade name [Member]	Dec. 17, 2012 HHI Business [Member] Trade name [Member] Minimum [Member]	Dec. 17, 2012 HHI Business [Member] Trade name [Member] Maximum [Member]	Dec. 17, 2012 HHI Business [Member] Customer relationships [Member]	Dec. 17, 2012 HHI Business [Member] Trademarks and trade names [Member]	Dec. 17, 2012 HHI Business [Member] Trademarks and trade names [Member] Minimum [Member]	Dec. 17, 2012 HHI Business [Member] Trademarks and trade names [Member] Maximum [Member]	Dec. 17, 2012 HHI Business [Member] Business Combination Measurement Period Adjustment [Member]	Mar. 31, 2013 Shaser Biosciences, Inc. [Member]	Nov. 08, 2012 Shaser Biosciences, Inc. [Member]	Nov. 08, 2012 Shaser Biosciences, Inc. [Member] Non-controlling Interest [Member]	Nov. 08, 2012 Shaser Biosciences, Inc. [Member] Technology assets [Member]	Nov. 08, 2012 Shaser Biosciences, Inc. [Member] Call Option exercisable between January 1, 2017 and March 31, 2017 [Member]	Mar. 31, 2013 Shaser Biosciences, Inc. [Member] Business Combination Measurement Period Adjustment [Member]	Feb. 14, 2013 EXCO/HGI Partnership [Member] EXCO [Member]	Feb. 14, 2013 EXCO/HGI Partnership [Member] HGI [Member]	Feb. 14, 2013 EXCO/HGI Partnership [Member] HGI Energy Holdings, LLC [Member]	Feb. 14, 2013 EXCO/HGI Partnership [Member] EXCO/HGI General Partner [Member]	Feb. 14, 2013 EXCO/HGI Partnership [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 Partnership [Member]	Apr. 06, 2011 FGL [Member]	Mar. 31, 2013 FGL [Member]
Business Acquisition [Line Items]
Negotiated sales price paid												$ 100,000,000
Goodwill	1,434,000,000	1,434,000,000		694,200,000								662,200,000	682,300,000														20,100,000	65,600,000	63,900,000				1,700,000
Deferred tax liability - long-term												104,700,000	115,900,000														11,200,000
Property, plant and equipment												104,500,000	99,300,000														(5,200,000)
Inventory												207,100,000	204,700,000														(2,400,000)
Inventory adjustment to fair value												31,000,000
Property, plant and equipment, net adjustment to fair value												4,000,000
Intangible asset												470,000,000	470,000,000														0	32,800,000	35,500,000				(2,700,000)
Estimated sales growth rate															2.50%	31.00%		2.50%	5.00%		2.50%	5.00%	3.00%		2.50%	5.00%				3.00%	3.00%
Customer retention rate																							95.00%
Estimated Income tax rate	35.00%	35.00%												35.00%			35.00%			35.00%			35.00%	35.00%						35.00%	35.00%
Discounted rate														12.00%			12.00%			12.00%			12.00%	12.00%						12.00%	11.00%
Carrying value, intangible asset														51,000,000			12,000,000			3,000,000			74,000,000	330,000,000							32,800,000
Amortization period, intangible asset					1 year	20 years	5 years 2 months 0 days	4 years	17 years	15 years	20 years						5 years			8 years			20 years								13 years
Royalty rate															4.00%	5.00%	4.00%			3.50%					3.00%	5.00%					10.50%
Expected terminal year growth rate																								2.50%
Remaining legal life												10 years
Deferred tax liabilities, net												122,900,000
Business Acquisition Percentage Of Equity Interests Acquired																													56.00%			44.00%		24.50%	74.50%	73.50%	2.00%
Trailing revenues																																100.00%
Adjusted trailing EBITDA																																700.00%
Non-controlling interest																														39,000,000				119,100,000
Business Combination, Consideration Transferred																																		725,000,000	348,300,000			573,300,000
Preliminary working capital and other adjustments												(10,600,000)																	(400,000)						32,500,000
Purchase price												629,400,000	611,500,000														(17,900,000)	23,000,000	24,700,000				(1,700,000)		692,500,000			516,100,000	130,900,000	130,900,000	97,500,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Oil And Natural Gas Properties																																			697,300,000			519,500,000		138,400,000	103,100,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Gas Gathering Assets																																						21,500,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Asset Retirement Obligation																																						18,500,000			5,600,000
Cash consideration		1,903,500,000	185,100,000																																							350,000,000
Cash consideration re-characterized as expense																																										5,000,000
Reduction in purchase price																																										50,000,000
Insurance obligations under annuity contract																																										3,000,000,000
Maximum amount of asset securing reinsurance obligations																																										1,000,000,000
Maximum amount required to pay under Front Street Reinsurance Transaction																																										50,000,000
Fair value assigned to the contingent purchase price reduction																																										0
Estimated a fair value for reduction in purchase price																																											$ 41,000,000