Divestitures - Disposal Groups, Including Discontinued Operations, Disclosure (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	$ 758.8	$ 294.6	$ 758.8	$ 294.6	$ 270.1	$ 465.2
Other receivables, net	337.6		337.6		266.0
Deferred charges and other assets	60.8		60.8		43.7
Assets	8,240.3		8,240.3		35,849.7
Disposal Group, Including Discontinued Operation, Assets, Current	1,976.0		1,976.0		28,929.2
Long Term Debt Current And Non Current	5,318.7		5,318.7		5,705.1
Accounts Payable and Accrued Liabilities, Current	360.7		360.7		373.1
Selling, acquisition, operating and general expenses	242.4	216.5	458.5	415.4
Total operating costs and expenses	737.2	662.1	1,357.1	1,223.1
Operating income	28.9	95.3	55.5	136.6
Interest Expense	67.6	77.7	143.1	156.4
Less: Net income attributable to noncontrolling interest	0.5	30.7	72.0	79.3
Other income (expense), net	0.2	(1.4)	1.2	(0.4)
Net income	(36.6)	(51.4)	542.3	209.4
Net Income (Loss) Attributable to Parent	(37.1)	(82.1)	470.3	130.1
Other long-term liabilities	101.1		101.1		26.2
Liabilities	6,896.6		6,896.6		33,902.8
Disposal Group, Including Discontinued Operation, Liabilities, Current	558.6		558.6		26,851.3
Stockholders' Equity Attributable to Parent	691.6		691.6		758.0
Noncontrolling interest	652.1		652.1		1,188.9
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax	0.0	0.0	445.9	0.0
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0.7	(43.6)	501.5	259.2
Insurance Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Other Income		0.1		0.1
Disposal Group, Including Discontinued Operation, Revenue		418.4	378.6	741.7
Disposal Group, Including Discontinued Operation, Benefits and other changes in policy reserves		301.1	241.3	309.4
Disposal Group, Including Discontinued Operation, General and Administrative Expense		35.7	52.8	66.4
Disposal Group, Including Discontinued Operation, Depreciation and Amortization		36.5	35.8	156.5
Disposal Group, Including Discontinued Operation, Operating Expense		373.3	329.9	532.3
Disposal Group, Including Discontinued Operation, Operating Income (Loss)		45.1	48.7	209.4
Disposal Group, Including Discontinued Operation, Interest Expense		6.0	3.9	12.1
Disposal Group, Including Discontinued Operation, Other Expense			0.1
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax		72.8	14.2	(71.7)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		(33.6)	476.4	269.1
Discontinued Operation, Tax Effect of Discontinued Operation		29.1	16.5	81.4
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0.0	(62.7)	459.9	187.7
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest		6.4	5.4	27.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		(69.1)	454.5	160.2
Insurance Segment [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		3.1	6.8	14.3
Insurance Segment [Member] | Net Investment Income
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue		258.7	181.9	509.2
Insurance Segment [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		112.0	154.8	134.6
Insurance Segment [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		44.6	35.1	83.6
Consumer Products Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Other Income	0.1		0.4
Disposal Group, Including Discontinued Operation, Assets, Current	1,976.0		1,976.0		1,979.9
Disposal Group, Including Discontinued Operation, Revenue	427.8	413.5	1,031.1	1,023.0
Disposal Group, Including Discontinued Operation, Liabilities, Current	558.6		558.6		$ 656.7
Disposal Group, Including Discontinued Operation, General and Administrative Expense	134.4	109.2	266.1	230.5
Disposal Group, Including Discontinued Operation, Operating Expense	415.1	374.3	950.2	894.2
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	12.7	39.2	80.9	128.8
Disposal Group, Including Discontinued Operation, Other Expense		0.2		0.2
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	0.2	27.7	54.4	104.5
Discontinued Operation, Tax Effect of Discontinued Operation	(0.5)	8.6	12.8	33.0
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0.7	19.1	41.6	71.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	0.3	7.7	17.1	30.0
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 0.4	$ 11.4	$ 24.5	$ 41.5