Investments - Net Investment Gains (Losses) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Sep. 30, 2012	Sep. 30, 2011
Net Investment Gains (Losses)
Net realized gains on fixed maturity available-for-sale securities	$ 264,408	$ 16,912
Realized gains (losses) on equity securities	924	(10,977)
Net realized gains on securities	265,332	5,935
Realized losses on certain derivative instruments	(10,280)	(44,776)
Unrealized gains (losses) on certain derivative instruments	156,332	(125,976)
Change in fair value of derivatives	146,052	(170,752)
Realized losses on other invested assets	(1,384)	(2,074)
Net investment gains (losses)	$ 410,000	$ (166,891)

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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