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		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Goodwill			$ 1,476.7
Beginning Balance, Indefinite Lived Intangible Assets			1,178.1
Beginning Balance, Finite Lived Intangible Assets			985.1
Beginning Balance, Intangible Assets, Excluding Goodwill			2,729.1
Goodwill, Acquired During Period			65.2
Acquisitions (Note 3), Indefinite Lived Intangible Assets			46.8
Acquisitions (Note 13)			68.8
Deferrals			172.5
Less: Components of amortization:
Amortization of intangibles	40.7	85.0	121.5	220.6
Adjustment for unrealized investment (gains), net, Goodwill			(191.2)
Effect of translation, Goodwill			(2.8)
Effect of translation, Indefinite Lived intangible assets			6.0
Effect of translation, Intangible Assets Excluding Goodwill			7.1
Ending Balance, Goodwill	1,539.1		1,539.1
Ending Balance, Indefinite Lived Intangible Assets	1,230.9		1,230.9
Ending Balance, Finite Lived Intangible Assets	947.0		947.0
Ending Balance, Intangible Assets, Excluding Goodwill	2,664.8		2,664.8
Unlocking [Member]
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of intangibles			(25.2)
Interest [Member]
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of intangibles			(21.1)
Periodic amortization [Member]
Less: Components of amortization:
Goodwill Amortization
Indefinite Lived Intangible Assets, Amortization
Amortization of intangibles			167.8
Definite Lived Intangible Assets [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets			985.1
Acquisitions (Note 3), Finite-Lived Intangible Assets			22.0
Deferrals
Less: Components of amortization:
Amortization of intangibles	20.5	20.3	61.2	57.5
Adjustment for unrealized investment (gains), net, Goodwill
Effect of translation, Finite Lived intangible assets			1.1
Ending Balance, Finite Lived Intangible Assets	947.0		947.0
Definite Lived Intangible Assets [Member] | Unlocking [Member]
Less: Components of amortization:
Amortization of intangibles
Definite Lived Intangible Assets [Member] | Interest [Member]
Less: Components of amortization:
Amortization of intangibles
Definite Lived Intangible Assets [Member] | Periodic amortization [Member]
Less: Components of amortization:
Amortization of intangibles			61.2
VOBA [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets			225.3
Acquisitions (Note 3), Finite-Lived Intangible Assets
Deferrals
Less: Components of amortization:
Amortization of intangibles	10.8	37.3	34.9	113.0
Adjustment for unrealized investment (gains), net, Goodwill			(108.2)
Effect of translation, Finite Lived intangible assets
Ending Balance, Finite Lived Intangible Assets	82.2		82.2
VOBA [Member] | Unlocking [Member]
Less: Components of amortization:
Amortization of intangibles			(21.8)
VOBA [Member] | Interest [Member]
Less: Components of amortization:
Amortization of intangibles			(11.0)
VOBA [Member] | Periodic amortization [Member]
Less: Components of amortization:
Amortization of intangibles			67.7
DAC [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Beginning Balance, Finite Lived Intangible Assets			340.6
Acquisitions (Note 3), Finite-Lived Intangible Assets
Deferrals			172.5
Less: Components of amortization:
Amortization of intangibles	9.4	27.4	25.4	50.1
Adjustment for unrealized investment (gains), net, Goodwill			(83.0)
Effect of translation, Finite Lived intangible assets
Ending Balance, Finite Lived Intangible Assets	404.7		404.7
DAC [Member] | Unlocking [Member]
Less: Components of amortization:
Amortization of intangibles			(3.4)
DAC [Member] | Interest [Member]
Less: Components of amortization:
Amortization of intangibles			(10.1)
DAC [Member] | Periodic amortization [Member]
Less: Components of amortization:
Amortization of intangibles			38.9
Goodwill [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Deferrals
Less: Components of amortization:
Adjustment for unrealized investment (gains), net, Goodwill
Indefinite Lived Intangible Assets [Member]
Intangible Assets, Including Goodwill [Roll Forward]
Deferrals
Less: Components of amortization:
Adjustment for unrealized investment (gains), net, Goodwill