Derivative Financial Instruments - FGL's Exposure to Credit Loss on Call Options Held (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Derivatives, Fair Value [Line Items]
Notional Amount	$ 5,830,395	$ 5,604,269
Fair Value	200,667	52,335
Bank of America [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	1,884,047	1,692,142
Fair Value	64,101	14,637
Credit Rating (Moody's/S&P)	Baa2/A-
Deutsche Bank [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	1,816,532	1,463,596
Fair Value	61,704	11,402
Credit Rating (Moody's/S&P)	A2/A+
Morgan Stanley [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	1,634,686	1,629,247
Fair Value	51,630	15,373
Credit Rating (Moody's/S&P)	Baa1/A-
Royal Bank of Scotland [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	353,875
Fair Value	19,595
Credit Rating (Moody's/S&P)	Baa1/A-
Barclay's Bank [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	131,255	385,189
Fair Value	3,081	4,105
Credit Rating (Moody's/S&P)	A2/A+
Credit Suisse [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	10,000	327,095
Fair Value	556	2,785
Credit Rating (Moody's/S&P)	A2/A
Nomura [Member]
Derivatives, Fair Value [Line Items]
Notional Amount		107,000
Fair Value		$ 4,033
Credit Rating (Moody's/S&P)	Baa2/A