Goodwill and Intangibles, including DAC and VOBA - 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	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Apr. 01, 2012	Mar. 31, 2013	Apr. 01, 2012
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Goodwill			$ 694.2
Beginning Balance, Indefinite Lived Intangible Assets			841.1
Beginning Balance, Finite Lived Intangible Assets			873.9
Beginning Balance, Intangible Assets, Excluding Goodwill			1,988.5
Acquisitions (Note 3), Goodwill			748.0
Acquisitions (Note 3), Indefinite Lived Intangible Assets			330.0
Acquisitions (Note 13)			502.8
Deferrals			71.5
Less: Components of amortization:
Amortization of intangibles	(49.0)	(58.8)	(135.6)	(115.5)
Adjustment for unrealized investment (gains), net, Goodwill			50.2
Effect of translation, Goodwill			(8.2)
Effect of translation, Indefinite Lived intangible assets			(6.5)
Effect of translation, Intangible Assets Excluding Goodwill			(9.9)
Ending Balance, Goodwill	1,434.0		1,434.0
Ending Balance, Indefinite Lived Intangible Assets	1,164.6		1,164.6
Ending Balance, Finite Lived Intangible Assets	1,006.1		1,006.1
Ending Balance, Intangible Assets, Excluding Goodwill	2,467.5		2,467.5
Indefinite Lived Intangible Assets [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Deferrals
Less: Components of amortization:
Adjustment for unrealized investment (gains), net, Goodwill
Periodic amortization [Member]
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of intangibles			(177.6)
Interest [Member]
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of intangibles			15.9
Unlocking [Member]
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of intangibles			26.1
Reclassifications [Member]
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of intangibles
Definite Lived Intangible Assets [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets			873.9
Acquisitions (Note 3), Finite-Lived Intangible Assets			172.8
Deferrals
Less: Components of amortization:
Amortization of intangibles	(20.1)	(15.8)	(37.2)	(30.4)
Adjustment for unrealized investment (gains), net, Goodwill
Effect of translation, Finite Lived intangible assets			(3.4)
Ending Balance, Finite Lived Intangible Assets	1,006.1		1,006.1
Definite Lived Intangible Assets [Member] | Periodic amortization [Member]
Less: Components of amortization:
Amortization of intangibles			(37.2)
Definite Lived Intangible Assets [Member] | Interest [Member]
Less: Components of amortization:
Amortization of intangibles
Definite Lived Intangible Assets [Member] | Unlocking [Member]
Less: Components of amortization:
Amortization of intangibles
Definite Lived Intangible Assets [Member] | Reclassifications [Member]
Less: Components of amortization:
Amortization of intangibles
VOBA [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets			104.3
Acquisitions (Note 3), Finite-Lived Intangible Assets
Deferrals
Less: Components of amortization:
Amortization of intangibles	(16.8)	(41.0)	(75.7)	(77.5)
Adjustment for unrealized investment (gains), net, Goodwill			61.8
Effect of translation, Finite Lived intangible assets
Ending Balance, Finite Lived Intangible Assets	90.4		90.4
VOBA [Member] | Periodic amortization [Member]
Less: Components of amortization:
Amortization of intangibles			(108.2)
VOBA [Member] | Interest [Member]
Less: Components of amortization:
Amortization of intangibles			10.6
VOBA [Member] | Unlocking [Member]
Less: Components of amortization:
Amortization of intangibles			21.9
VOBA [Member] | Reclassifications [Member]
Less: Components of amortization:
Amortization of intangibles
DAC [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets			169.2
Acquisitions (Note 3), Finite-Lived Intangible Assets
Deferrals			71.5
Less: Components of amortization:
Amortization of intangibles	(12.1)	(2.0)	(22.7)	(7.6)
Adjustment for unrealized investment (gains), net, Goodwill			(11.6)
Effect of translation, Finite Lived intangible assets
Ending Balance, Finite Lived Intangible Assets	206.4		206.4
DAC [Member] | Periodic amortization [Member]
Less: Components of amortization:
Amortization of intangibles			(32.2)
DAC [Member] | Interest [Member]
Less: Components of amortization:
Amortization of intangibles			5.3
DAC [Member] | Unlocking [Member]
Less: Components of amortization:
Amortization of intangibles			4.2
DAC [Member] | Reclassifications [Member]
Less: Components of amortization:
Amortization of intangibles
Goodwill [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Deferrals
Less: Components of amortization:
Adjustment for unrealized investment (gains), net, Goodwill