Divestitures - Schedule of Intercompany Assets and Liabilities of Business Held for Sale (Details) - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Funds Withheld Receivable	$ 1,650.4	$ 1,710.1
Other assets (Note 13)	172.6	412.0
Disposal Group, Including Discontinued Operation, Assets, Current	26,738.7	24,976.5
Assets	35,792.8	35,031.5
Insurance Reserves	1,751.3	1,856.0
Debt (Note 15)	5,430.9	5,984.6
Accounts payable and other current liabilities (Note 14)	989.8	1,062.0
Other liabilities	32.0	56.3
Disposal Group, Including Discontinued Operation, Liabilities, Current	25,100.2	23,418.5
Liabilities	33,975.6	33,443.4
Majority-Owned Subsidiary, Unconsolidated [Member] | FGL [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Funds Withheld Receivable	978.8	1,058.0
Other assets (Note 13)	15.1	15.9
Disposal Group, Including Discontinued Operation, Assets, Current	1,375.5	1,769.8
Assets	2,369.4	2,843.7
Insurance Reserves	1,119.5	1,226.8
Debt (Note 15)	63.0	330.7
Accounts payable and other current liabilities (Note 14)		1.6
Other liabilities		11.0
Disposal Group, Including Discontinued Operation, Liabilities, Current	1,186.9	1,273.6
Liabilities	$ 2,369.4	$ 2,843.7