Goodwill and Intangibles, including DAC and VOBA, net - Summary of Changes in Carrying Amounts of Goodwill and Intangible Assets Including FGL's DAC and VOBA Balances (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Goodwill	$ 694.2	$ 610.3
Beginning Balance, Indefinite Lived Intangible Assets	841.1	826.8
Beginning Balance, Finite Lived Intangible Assets	873.9
Beginning Balance, Intangible Assets, Excluding Goodwill	1,988.5	2,141.1
Acquisitions (Note 3), Goodwill	786.6	85.9
Acquisitions (Note 3), Indefinite Lived Intangible Assets	331.0	22.0
Acquisitions (Note 13)	519.3	104.1
Deferrals	147.4	194.9
Less: Components of amortization:
Amortization of Intangible Assets	(260.1)	(224.3)	(46.6)
Adjustment for unrealized investment (gains), net, Goodwill	327.3	(217.9)
Effect of translation, Goodwill	(4.1)	(2.0)
Effect of translation, Indefinite Lived intangible assets	6.0	(4.2)
Effect of translation, Intangible Assets Excluding Goodwill	6.7	(9.3)
Ending Balance, Goodwill	1,476.7	694.2	610.3
Ending Balance, Indefinite Lived Intangible Assets	1,178.1	841.1	826.8
Ending Balance, Finite Lived Intangible Assets	985.1	873.9
Ending Balance, Intangible Assets, Excluding Goodwill	2,729.1	1,988.5	2,141.1
Periodic amortization
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of Intangible Assets	(334.5)	(255.8)
Interest
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of Intangible Assets	31.3	30.8
Unlocking
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of Intangible Assets	43.1	0.6
Reclassifications
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization		(3.5)
Amortization of Intangible Assets
Goodwill
Intangible Assets, Including Goodwill [Roll Forward]
Deferrals
Less: Components of amortization:
Adjustment for unrealized investment (gains), net, Goodwill
Definite Lived Intangible Assets
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets	873.9	857.1
Acquisitions (Note 3), Finite-Lived Intangible Assets	188.3	82.1
Deferrals
Less: Components of amortization:
Amortization of Intangible Assets	(77.8)	(63.7)	(57.7)
Adjustment for unrealized investment (gains), net, Goodwill
Effect of translation, Finite Lived intangible assets	0.7	(5.1)
Ending Balance, Finite Lived Intangible Assets	985.1	873.9	857.1
Definite Lived Intangible Assets | Periodic amortization
Less: Components of amortization:
Amortization of Intangible Assets	(77.8)	(63.7)
Definite Lived Intangible Assets | Interest
Less: Components of amortization:
Amortization of Intangible Assets
Definite Lived Intangible Assets | Unlocking
Less: Components of amortization:
Amortization of Intangible Assets
Definite Lived Intangible Assets | Reclassifications
Less: Components of amortization:
Amortization of Intangible Assets		3.5
VOBA
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets	104.3	419.1
Acquisitions (Note 3), Finite-Lived Intangible Assets
Deferrals
Less: Components of amortization:
Amortization of Intangible Assets	(137.0)	(145.5)	12.0
Adjustment for unrealized investment (gains), net, Goodwill	258.0	(169.3)
Effect of translation, Finite Lived intangible assets
Ending Balance, Finite Lived Intangible Assets	225.3	104.3	419.1
VOBA | Periodic amortization
Less: Components of amortization:
Amortization of Intangible Assets	(194.6)	(171.9)
VOBA | Interest
Less: Components of amortization:
Amortization of Intangible Assets	21.8	28.9
VOBA | Unlocking
Less: Components of amortization:
Amortization of Intangible Assets	35.8	(2.5)
VOBA | Reclassifications
Less: Components of amortization:
Amortization of Intangible Assets
DAC
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets	169.2	38.1
Acquisitions (Note 3), Finite-Lived Intangible Assets
Deferrals	147.4	194.9
Less: Components of amortization:
Amortization of Intangible Assets	(45.3)	(15.2)	(0.9)
Adjustment for unrealized investment (gains), net, Goodwill	69.3	(48.6)
Effect of translation, Finite Lived intangible assets
Ending Balance, Finite Lived Intangible Assets	340.6	169.2	38.1
DAC | Periodic amortization
Less: Components of amortization:
Amortization of Intangible Assets	(62.1)	(20.2)
DAC | Interest
Less: Components of amortization:
Amortization of Intangible Assets	9.5	1.9
DAC | Unlocking
Less: Components of amortization:
Amortization of Intangible Assets	7.3	3.1
DAC | Reclassifications
Less: Components of amortization:
Amortization of Intangible Assets
Indefinite Lived Intangible Assets
Intangible Assets, Including Goodwill [Roll Forward]
Deferrals
Less: Components of amortization:
Adjustment for unrealized investment (gains), net, Goodwill