Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2016	Sep. 30, 2015
Commitment And Contingencies [Line Items]
Reserves for legal, environmental and regulatory matters	$ 9.3
Long-term Debt	6,353.8	$ 6,439.1
Commitments and contingencies	147.8
Expiration of partial amount of unfunded, legally binding lending commitments	31.8
Loss Contingency Accrual, Provision	$ 9.2
Maximum [Member]
Commitment And Contingencies [Line Items]
Expiry date of partial amount of notional amount	1 year
Expiry date of remainder part of notional amount	5 years
Minimum [Member]
Commitment And Contingencies [Line Items]
Expiry date of remainder part of notional amount	1 year
Fidelity And Guaranty Life Holdings [Member]
Commitment And Contingencies [Line Items]
Accrued amount of guaranty fund assessments	$ 3.0
Estimated future premium tax deductions	3.0
Spectrum Brands [Member]
Commitment And Contingencies [Line Items]
Environmental costs recognized, capitalized	4.3
FGL [Member]
Commitment And Contingencies [Line Items]
Reserves for legal, environmental and regulatory matters	5.0
Salus Capital Partners L L C [Member]
Commitment And Contingencies [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	10.8	10.7
Haverhill Retirement vs HRG [Member]
Commitment And Contingencies [Line Items]
Litigation Settlement, Expense	0.2
Cressy Plaintiff [Member]
Commitment And Contingencies [Line Items]
Loss Contingency Accrual, Provision	1.3
Estimated Litigation Liability	1.4
Eddie L. Cressy v. Fidelity Guaranty [sic] Life Insurance Company, et. al. [Member]
Commitment And Contingencies [Line Items]
Legal Fees	4.6
Litigation Settlement, Expense	3.3
Dale R. Ludwick, on behalf of Herself and All Others Similarly Situated v. Harbinger Group Inc., Fidelity & Guaranty Life Insurance Company, Raven Reinsurance Company, and Front Street Re (Cayman) Ltd [Member]
Commitment And Contingencies [Line Items]
Estimated Litigation Liability	1.5
Radioshack [Member] | Salus Capital Partners L L C [Member]
Commitment And Contingencies [Line Items]
Long-term Debt	250.0	$ 250.0
Revolving Loan Facility	585.0
Proposed Settlement [Member] | Kahn v. Philip A. Falcone et al [Member]
Commitment And Contingencies [Line Items]
Litigation Settlement, Amount	3.8
Asset based loan receivables [Member]
Commitment And Contingencies [Line Items]
Commitments and contingencies	$ 39.1