Divestitures Divestitures - Schedule of components of net income (loss) from discontinued operations (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Document Fiscal Year Focus		2017
Funds Withheld Receivable		$ 1,609.0		$ 1,650.4
Other assets		157.2		172.6
Disposal Group, Including Discontinued Operation, Assets, Current		26,801.6		26,738.7
Assets		35,662.7		35,792.8
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		258.8	$ (2.5)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent			(2.5)
Insurance reserves		1,721.9		1,751.3
Debt		5,459.0		5,430.9	[1],[2]
Accounts payable and other current liabilities		900.4		989.8
Other liabilities		26.7		32.0
Disposal Group, Including Discontinued Operation, Liabilities, Current		25,200.5		25,100.2
Total liabilities		33,993.3		33,975.6
Selling, acquisition, operating and general expenses		321.7	330.7
Total operating costs and expenses		1,071.9	1,109.6
Operating Income (Loss)		117.7	99.8
Interest Expense		(91.7)	(95.2)
Other income (expense), net		1.4	(0.7)
Net income from continuing operations		260.8	7.0
Income tax expense (benefit)		25.4	(5.6)
Less: Net income attributable to noncontrolling interest		48.6	40.9
Net income (loss) attributable to controlling interest		212.2	(33.9)
Compass Production Partners G.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue			16.8
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax			40.6
Oil and Gas Production Expense			17.1
Selling, acquisition, operating and general expenses			9.8
Asset Impairment Charges			54.4
Total operating costs and expenses			81.3
Operating Income (Loss)			(64.5)
Interest Expense			(2.3)
Gain (Loss) on Disposition of Oil and Gas Property			105.6
Other income (expense), net			1.8
Net income from continuing operations		0.0	33.1
Income tax expense (benefit)			7.5
FGL [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue		345.5	332.6
Disposal Group, Including Discontinued Operation, Benefits and other changes in policy reserves		19.9	180.9
Disposal Group, Including Discontinued Operation, General and Administrative Expense		28.3	28.2
Disposal Group, Including Discontinued Operation, Depreciation and Amortization		120.0	33.5
Disposal Group, Including Discontinued Operation, Operating Expense		168.2	242.6
Disposal Group, Including Discontinued Operation, Operating Income (Loss)		177.3	90.0
Disposal Group, Including Discontinued Operation, Interest Expense		(6.1)	(5.9)
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax		144.5	0.0
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		315.7	84.1
Discontinued Operation, Tax Effect of Discontinued Operation	[3]	56.9	119.7
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		258.8	(35.6)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest		21.1	9.4
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		237.7	(45.0)
FGL [Member] | Insurance Premiums [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue		11.1	15.4
FGL [Member] | Investment Income [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue		239.8	222.2
FGL [Member] | Gain (Loss) on Investments [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue		56.3	66.2
FGL [Member] | Insurance and investment product fees [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue		38.3	$ 28.8
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		939.5		978.8
Other assets		15.0		15.1
Disposal Group, Including Discontinued Operation, Assets, Current		1,349.0		1,375.5
Assets		2,303.5		2,369.4
Insurance reserves		1,087.5		1,119.5
Debt		58.8		63.0
Disposal Group, Including Discontinued Operation, Liabilities, Current		1,157.2		1,186.9
Total liabilities		$ 2,303.5		$ 2,369.4
HGI [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Document Fiscal Year Focus		2016

[1] The carrying value of cash and cash equivalents, trade receivables, accounts payable and accrued investment income approximate fair value due to their short duration and, accordingly, they are not presented in the tables above.

[2] The fair value of debt set forth above is generally based on quoted or observed market prices.

[3] (a) Included in the income tax expense for the three months ended December 31, 2015 was a $90.9 net income tax expense related to the establishment of a deferred tax liability of $338.6 at December 31, 2015, which was a result of classifying the Company’s ownership interest in FGL as held for sale, partially offset by a $247.7 reduction of valuation allowance on HRG’s net operating and capital loss carryforwards expected to offset the FGL taxable gain.