Derivative Financial Instruments - FGL's Exposure to Credit Loss on Call Options Held (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013
Derivatives, Fair Value [Line Items]
Document Period End Date	Dec. 31, 2013
Derivative, Notional Amount	$ 6,606.8	$ 6,407.4
Derivative Asset, Fair Value, Gross Asset	294.5	221.8
Bank of America [Member]
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	NA/A
Derivative, Notional Amount	2,157.9	2,037.8
Deutsche Bank [Member]
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A3/A
Derivative, Notional Amount	2,379.0	1,620.4
Morgan Stanley [Member]
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A2/A
Derivative, Notional Amount	1,706.8	2,264.1
Royal Bank of Scotland [Member]
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A3/A
Derivative, Notional Amount	245.3	364.3
Barclay's Bank [Member]
Derivatives, Fair Value [Line Items]
Credit Rating (Moody's/S&P)	A2/A
Derivative, Notional Amount	117.8	120.8
Call options [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	174.3	149.8
Derivative Asset, Fair Value, Gross Asset	294.1	221.8
Derivative Asset, Collateral, Obligation to Return Cash, Offset	119.8	72.0
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	299.7	227.7
Derivatives For Trading And Investment [Member] | Not Designated as Hedging Instrument [Member] | Call options [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	294.1	221.8
Derivatives For Trading And Investment [Member] | Not Designated as Hedging Instrument [Member] | Call options [Member] | Bank of America [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	54.5	70.7
Derivative Asset, Fair Value, Gross Asset	99.6	70.7
Derivative Asset, Collateral, Obligation to Return Cash, Offset	45.1	0
Derivatives For Trading And Investment [Member] | Not Designated as Hedging Instrument [Member] | Call options [Member] | Deutsche Bank [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	70.4	28.7
Derivative Asset, Fair Value, Gross Asset	103.1	51.7
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	23.0
Derivatives For Trading And Investment [Member] | Not Designated as Hedging Instrument [Member] | Call options [Member] | Morgan Stanley [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	28.4	26.7
Derivative Asset, Fair Value, Gross Asset	70.4	75.7
Derivative Asset, Collateral, Obligation to Return Cash, Offset	74.7	49.0
Derivatives For Trading And Investment [Member] | Not Designated as Hedging Instrument [Member] | Call options [Member] | Royal Bank of Scotland [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	16.9	20.3
Derivative Asset, Fair Value, Gross Asset	16.9	20.3
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	0
Derivatives For Trading And Investment [Member] | Not Designated as Hedging Instrument [Member] | Call options [Member] | Barclay's Bank [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	4.1	3.4
Derivative Asset, Fair Value, Gross Asset	4.1	3.4
Derivative Asset, Collateral, Obligation to Return Cash, Offset	$ 0	$ 0