Derivative Financial Instruments - FGL's Exposure to Credit Loss on Call Options Held (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Derivatives, Fair Value [Line Items]
Notional Amount	$ 6,407.4	$ 5,830.4
Fair Value	221.8	200.7
Bank of America
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	NA/A
Notional Amount	2,037.8	1,884.0
Deutsche Bank
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A2/A
Notional Amount	1,620.4	1,816.5
Morgan Stanley
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	Baa1/A
Notional Amount	2,264.1	1,634.7
Royal Bank of Scotland
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A3/A
Notional Amount	364.3	353.9
Barclay's Bank
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A2/A
Notional Amount	120.8	131.3
Credit Suisse
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A2/A-
Notional Amount	0	10.0
Call options
Derivatives, Fair Value [Line Items]
Fair Value	221.8	200.7
Collateral	72.0	0
Net Credit Risk	149.8	200.7
Derivatives not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Fair Value	227.7	203.9
Derivatives | Derivatives not designated as hedging instrument | Call options
Derivatives, Fair Value [Line Items]
Fair Value	221.8	200.7
Derivatives | Derivatives not designated as hedging instrument | Call options | Bank of America
Derivatives, Fair Value [Line Items]
Fair Value	70.7	64.1
Collateral	0	0
Net Credit Risk	70.7	64.1
Derivatives | Derivatives not designated as hedging instrument | Call options | Deutsche Bank
Derivatives, Fair Value [Line Items]
Fair Value	51.7	61.7
Collateral	23.0	0
Net Credit Risk	28.7	61.7
Derivatives | Derivatives not designated as hedging instrument | Call options | Morgan Stanley
Derivatives, Fair Value [Line Items]
Fair Value	75.7	51.6
Collateral	49.0	0
Net Credit Risk	26.7	51.6
Derivatives | Derivatives not designated as hedging instrument | Call options | Royal Bank of Scotland
Derivatives, Fair Value [Line Items]
Fair Value	20.3	19.6
Collateral	0	0
Net Credit Risk	20.3	19.6
Derivatives | Derivatives not designated as hedging instrument | Call options | Barclay's Bank
Derivatives, Fair Value [Line Items]
Fair Value	3.4	3.1
Collateral	0	0
Net Credit Risk	3.4	3.1
Derivatives | Derivatives not designated as hedging instrument | Call options | Credit Suisse
Derivatives, Fair Value [Line Items]
Fair Value	0	0.6
Collateral	0	0
Net Credit Risk	$ 0	$ 0.6