Consolidating Financial Information - Schedule of Balance Sheet Information (Detail) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Assets:
Investments	$ 19,252,500,000	$ 16,465,900,000
Cash and cash equivalents	1,319,200,000	1,899,700,000	1,470,700,000	1,137,400,000
Receivables, net (Note 10)	585,100,000	611,300,000
Inventories, net (Note 11)	635,200,000	632,900,000
Accrued investment income	184,900,000	161,200,000
Reinsurance recoverable (Note 19)	2,397,600,000	2,363,700,000
Deferred tax assets (Note 21)	186,700,000	293,400,000
Properties, including oil and natural gas properties, net (Note 12)	908,600,000	993,300,000
Goodwill (Note 13)	1,524,800,000	1,476,700,000	694,200,000
Intangibles, including DAC and VOBA, net (Note 13)	2,683,700,000	2,729,100,000	1,988,500,000
Other assets	421,900,000	281,600,000
Consolidated total assets	30,100,200,000	27,908,800,000
Liabilities and Equity:
Debt	5,061,100,000	4,793,200,000
Equity conversion feature of preferred stock (Note 6 and Note 16)		330,800,000
Employee benefit obligations (Note 18)	86,200,000	99,600,000
Deferred tax liabilities (Note 21)	533,300,000	492,800,000
Total liabilities	27,843,200,000	26,445,900,000
Carrying value of Preferred Stock		329,400,000
Total Harbinger Group Inc. stockholders' equity	1,441,600,000	724,700,000
Noncontrolling interests	815,400,000	408,800,000
Total permanent equity	2,257,000,000	1,133,500,000	1,598,900,000	1,373,000,000
Total liabilities and equity	30,100,200,000	27,908,800,000
Consumer Products Segment
Assets:
Investments
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	194,600,000	207,300,000
Receivables, net (Note 10)	515,300,000	546,900,000
Inventories, net (Note 11)	624,500,000	632,900,000
Accrued investment income
Reinsurance recoverable (Note 19)
Deferred tax assets (Note 21)	46,700,000	33,000,000
Properties, including oil and natural gas properties, net (Note 12)	428,900,000	412,500,000
Goodwill (Note 13)	1,469,600,000	1,476,700,000
Intangibles, including DAC and VOBA, net (Note 13)	2,091,500,000	2,163,200,000
Other assets	141,900,000	154,200,000
Consolidated total assets	5,513,000,000	5,626,700,000
Liabilities and Equity:
Insurance reserves
Debt	2,990,900,000	3,218,900,000
Accounts payable and other current liabilities	816,200,000	849,400,000
Equity conversion feature of preferred stock (Note 6 and Note 16)
Employee benefit obligations (Note 18)	81,900,000	96,600,000
Deferred tax liabilities (Note 21)	516,000,000	492,800,000
Other liabilities	21,200,000	28,900,000
Affiliated debt and payables
Total liabilities	4,426,200,000	4,686,600,000
Carrying value of Preferred Stock
Total Harbinger Group Inc. stockholders' equity	612,400,000	531,000,000
Noncontrolling interests	474,400,000	409,100,000
Total permanent equity	1,086,800,000	940,100,000
Total liabilities and equity	5,513,000,000	5,626,700,000
Insurance
Assets:
Investments	18,820,700,000	16,282,300,000
Investments in subsidiaries and affiliates	68,200,000	62,000,000
Affiliated loans and receivables	157,200,000	150,100,000
Cash and cash equivalents	633,800,000	1,248,300,000
Receivables, net (Note 10)	2,100,000
Inventories, net (Note 11)
Accrued investment income	181,800,000	159,300,000
Reinsurance recoverable (Note 19)	2,397,600,000	2,363,700,000
Deferred tax assets (Note 21)	139,000,000	260,400,000
Properties, including oil and natural gas properties, net (Note 12)	11,400,000	7,000,000
Goodwill (Note 13)
Intangibles, including DAC and VOBA, net (Note 13)	550,400,000	565,900,000
Other assets	233,600,000	84,100,000
Consolidated total assets	23,195,800,000	21,183,100,000
Liabilities and Equity:
Insurance reserves	20,215,100,000	18,895,900,000
Debt	300,000,000	300,000,000
Accounts payable and other current liabilities	71,900,000	52,900,000
Equity conversion feature of preferred stock (Note 6 and Note 16)
Employee benefit obligations (Note 18)	0
Deferred tax liabilities (Note 21)
Other liabilities	748,900,000	640,200,000
Affiliated debt and payables	7,800,000	800,000
Total liabilities	21,343,700,000	19,889,800,000
Carrying value of Preferred Stock
Total Harbinger Group Inc. stockholders' equity	1,526,900,000	1,293,300,000
Noncontrolling interests	325,200,000
Total permanent equity	1,852,100,000	1,293,300,000
Total liabilities and equity	23,195,800,000	21,183,100,000
Energy Segment
Assets:
Investments
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	14,200,000	18,700,000
Receivables, net (Note 10)	23,700,000	22,200,000
Inventories, net (Note 11)
Accrued investment income
Reinsurance recoverable (Note 19)
Deferred tax assets (Note 21)
Properties, including oil and natural gas properties, net (Note 12)	464,400,000	572,600,000
Goodwill (Note 13)
Intangibles, including DAC and VOBA, net (Note 13)
Other assets	2,500,000	4,100,000
Consolidated total assets	504,800,000	617,600,000
Liabilities and Equity:
Insurance reserves
Debt	243,200,000	271,200,000
Accounts payable and other current liabilities	31,300,000	32,800,000
Equity conversion feature of preferred stock (Note 6 and Note 16)
Employee benefit obligations (Note 18)
Deferred tax liabilities (Note 21)
Other liabilities	27,300,000	25,400,000
Affiliated debt and payables	102,300,000	102,200,000
Total liabilities	404,100,000	431,600,000
Carrying value of Preferred Stock		100,000
Total Harbinger Group Inc. stockholders' equity	100,700,000	185,900,000
Noncontrolling interests
Total permanent equity	100,700,000	185,900,000
Total liabilities and equity	504,800,000	617,600,000
Asset Management segment [Member]
Assets:
Investments	584,600,000	389,300,000
Investments in subsidiaries and affiliates
Affiliated loans and receivables	28,500,000	900,000
Cash and cash equivalents	53,500,000	166,500,000
Receivables, net (Note 10)	900,000	1,200,000
Inventories, net (Note 11)
Accrued investment income	3,700,000	2,300,000
Reinsurance recoverable (Note 19)
Deferred tax assets (Note 21)
Properties, including oil and natural gas properties, net (Note 12)	1,400,000	700,000
Goodwill (Note 13)	10,700,000
Intangibles, including DAC and VOBA, net (Note 13)
Other assets	9,200,000	11,300,000
Liabilities and Equity:
Insurance reserves
Debt	298,700,000	181,800,000
Accounts payable and other current liabilities	8,500,000	6,300,000
Equity conversion feature of preferred stock (Note 6 and Note 16)
Employee benefit obligations (Note 18)
Deferred tax liabilities (Note 21)
Other liabilities	19,300,000	23,300,000
Affiliated debt and payables	286,500,000	293,300,000
Carrying value of Preferred Stock
Total Harbinger Group Inc. stockholders' equity	68,200,000	67,800,000
Noncontrolling interests	11,300,000	(300,000)
Other Segments [Member]
Assets:
Consolidated total assets	692,500,000	572,200,000
Liabilities and Equity:
Total liabilities	613,000,000	504,700,000
Total permanent equity	79,500,000	67,500,000
Total liabilities and equity	692,500,000	572,200,000
Corporate and Other
Assets:
Investments	93,700,000	42,300,000
Investments in subsidiaries and affiliates	2,237,900,000	2,012,900,000
Affiliated loans and receivables
Cash and cash equivalents	423,100,000	258,900,000
Receivables, net (Note 10)	43,100,000	41,000,000
Inventories, net (Note 11)	10,700,000
Accrued investment income
Reinsurance recoverable (Note 19)
Deferred tax assets (Note 21)	1,100,000
Properties, including oil and natural gas properties, net (Note 12)	2,500,000	500,000
Goodwill (Note 13)	44,500,000
Intangibles, including DAC and VOBA, net (Note 13)	41,800,000
Other assets	34,700,000	27,900,000
Consolidated total assets	2,933,100,000	2,383,500,000
Liabilities and Equity:
Insurance reserves
Debt	1,325,000,000	924,200,000
Accounts payable and other current liabilities	104,600,000	71,300,000
Equity conversion feature of preferred stock (Note 6 and Note 16)		330,800,000
Employee benefit obligations (Note 18)	4,300,000	3,000,000
Deferred tax liabilities (Note 21)	17,200,000
Other liabilities	1,100,000	200,000
Affiliated debt and payables	34,800,000
Total liabilities	1,487,000,000	1,329,500,000
Carrying value of Preferred Stock		329,300,000
Total Harbinger Group Inc. stockholders' equity	1,441,600,000	724,700,000
Noncontrolling interests	4,500,000
Total permanent equity	1,446,100,000	724,700,000
Total liabilities and equity	2,933,100,000	2,383,500,000
Consolidation, Eliminations
Assets:
Investments	(246,500,000)	(248,000,000)
Investments in subsidiaries and affiliates	(2,306,100,000)	(2,074,900,000)
Affiliated loans and receivables	(185,700,000)	(151,000,000)
Cash and cash equivalents
Receivables, net (Note 10)
Inventories, net (Note 11)
Accrued investment income	(600,000)	(400,000)
Reinsurance recoverable (Note 19)
Deferred tax assets (Note 21)	(100,000)
Properties, including oil and natural gas properties, net (Note 12)
Goodwill (Note 13)
Intangibles, including DAC and VOBA, net (Note 13)
Other assets
Consolidated total assets	(2,739,000,000)	(2,474,300,000)
Liabilities and Equity:
Insurance reserves
Debt
Accounts payable and other current liabilities	500,000
Equity conversion feature of preferred stock (Note 6 and Note 16)
Employee benefit obligations (Note 18)
Deferred tax liabilities (Note 21)	100,000
Other liabilities
Affiliated debt and payables	(431,400,000)	(396,300,000)
Total liabilities	(430,800,000)	(396,300,000)
Carrying value of Preferred Stock
Total Harbinger Group Inc. stockholders' equity	(2,308,200,000)	(2,078,000,000)
Noncontrolling interests
Total permanent equity	(2,308,200,000)	(2,078,000,000)
Total liabilities and equity	(2,739,000,000)	(2,474,300,000)
Consolidated Entities
Assets:
Investments	19,252,500,000	16,465,900,000
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	1,319,200,000	1,899,700,000
Receivables, net (Note 10)	585,100,000	611,300,000
Inventories, net (Note 11)	635,200,000	632,900,000
Accrued investment income	184,900,000	161,200,000
Reinsurance recoverable (Note 19)	2,397,600,000	2,363,700,000
Deferred tax assets (Note 21)	186,700,000	293,400,000
Properties, including oil and natural gas properties, net (Note 12)	908,600,000	993,300,000
Goodwill (Note 13)	1,524,800,000	1,476,700,000
Intangibles, including DAC and VOBA, net (Note 13)	2,683,700,000	2,729,100,000
Other assets	421,900,000	281,600,000
Consolidated total assets	30,100,200,000	27,908,800,000
Liabilities and Equity:
Insurance reserves	20,215,100,000	18,895,900,000
Debt	5,157,800,000	4,896,100,000
Accounts payable and other current liabilities	1,033,000,000	1,012,700,000
Equity conversion feature of preferred stock (Note 6 and Note 16)		330,800,000
Employee benefit obligations (Note 18)	86,200,000	99,600,000
Deferred tax liabilities (Note 21)	533,300,000	492,800,000
Other liabilities	817,800,000	718,000,000
Affiliated debt and payables
Total liabilities	27,843,200,000	26,445,900,000
Carrying value of Preferred Stock		329,400,000
Total Harbinger Group Inc. stockholders' equity	1,441,600,000	724,700,000
Noncontrolling interests	815,400,000	408,800,000
Total permanent equity	2,257,000,000	1,133,500,000
Total liabilities and equity	$ 30,100,200,000	$ 27,908,800,000