Consolidating Financial Information - Schedule of Balance Sheet Information (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014
Assets:
Investments	$ 139.3	$ 278.9
Cash and cash equivalents	465.6	695.2	$ 430.3	$ 742.8
Funds Withheld Receivable	1,679.4	1,710.1
Receivables, net	662.3	632.9
Inventories, net	924.4	780.8
Properties, including oil and natural gas properties, net	664.7	798.4
Goodwill	2,494.1	2,487.4
Intangibles	2,432.4	2,480.3
Other assets	149.1	134.3
Disposal Group, Including Discontinued Operation, Assets, Current	25,544.0	24,984.5
Total assets	35,455.1	35,034.0
Liabilities and Equity:
Debt	6,186.0	6,265.4
Employee benefit obligations	87.6	92.9
Deferred tax liabilities	895.6	574.5
Disposal Group, Including Discontinued Operation, Liabilities, Current	23,988.1	23,420.9
Total liabilities	33,947.2	33,445.9
Total stockholders' equity	465.1	586.7
Noncontrolling interests	1,042.8	1,001.4
Total permanent equity	1,507.9	1,588.1
Total liabilities and equity	35,455.1	35,034.0
Consolidated Entities [Member]
Assets:
Investments	139.3	278.9
Cash and cash equivalents	465.6	695.2
Funds Withheld Receivable	1,679.4	1,710.1
Receivables, net	662.3	632.9
Inventories, net	924.4	780.8
Deferred tax assets	299.8	51.2
Properties, including oil and natural gas properties, net	664.7	798.4
Goodwill	2,494.1	2,487.4
Intangibles	2,432.4	2,480.3
Other assets	149.1	134.3
Disposal Group, Including Discontinued Operation, Assets, Current	25,544.0	24,984.5
Total assets	35,455.1	35,034.0
Liabilities and Equity:
Insurance reserves	1,824.8	1,856.0
Debt	6,232.0	6,310.5
Accounts payable and other current liabilities	847.5	1,095.6
Employee benefit obligations	87.6	92.9
Deferred tax liabilities	895.6	574.5
Other liabilities	71.6	95.5
Disposal Group, Including Discontinued Operation, Liabilities, Current	23,988.1	23,420.9
Total liabilities	33,947.2	33,445.9
Total stockholders' equity	465.1	586.7
Noncontrolling interests	1,042.8	1,001.4
Total permanent equity	1,507.9	1,588.1
Total liabilities and equity	35,455.1	35,034.0
Consolidation, Eliminations [Member]
Assets:
Investments	(1.6)	(1.5)
Investments in subsidiaries and affiliates	(2,079.5)	(2,025.3)
Affiliated loans and receivables	(24.5)	(32.3)
Funds Withheld Receivable	(29.7)	(33.7)
Receivables, net		0.1
Deferred tax assets	17.9	14.2
Other assets	16.7	17.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	(2,100.7)	(2,061.4)
Liabilities and Equity:
Insurance reserves	138.3	124.1
Debt	217.6	330.7
Accounts payable and other current liabilities	2.0	2.2
Employee benefit obligations	0.0
Deferred tax liabilities	(8.8)
Other liabilities	9.3	8.4
Affiliated debt and payables	(305.2)	(415.3)
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	53.2	50.1
Total stockholders' equity	(2,153.9)	(2,111.5)
Noncontrolling interests	0.0
Total permanent equity	(2,153.9)	(2,111.5)
Total liabilities and equity	(2,100.7)	(2,061.4)
Corporate and Other [Member]
Assets:
Investments		32.8
Investments in subsidiaries and affiliates	2,067.5	2,014.7
Affiliated loans and receivables	0.3	0.1
Cash and cash equivalents	239.4	300.4
Funds Withheld Receivable	0.0	0.0
Receivables, net	0.3	0.8
Deferred tax assets	249.1	3.9
Properties, including oil and natural gas properties, net	1.2	1.3
Other assets	1.7	1.5
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	2,559.5	2,355.5
Liabilities and Equity:
Debt	1,708.0	1,705.1
Accounts payable and other current liabilities	37.7	53.7
Employee benefit obligations	4.8	4.8
Deferred tax liabilities	340.6	1.9
Other liabilities	3.3	3.3
Affiliated debt and payables	0.0
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	2,094.4	1,768.8
Total stockholders' equity	465.1	586.7
Noncontrolling interests	0.0
Total permanent equity	465.1	586.7
Total liabilities and equity	2,559.5	2,355.5
Discontinued Operations, Held-for-sale [Member]
Assets:
Funds Withheld Receivable	0.0	0.0
Disposal Group, Including Discontinued Operation, Assets, Current	25,544.0	24,984.5
Total assets	25,544.0	24,984.5
Liabilities and Equity:
Debt	0.0
Employee benefit obligations	0.0
Deferred tax liabilities	0.0
Other liabilities	0.0
Affiliated debt and payables	0.0
Disposal Group, Including Discontinued Operation, Liabilities, Current	23,988.1	23,420.9
Total liabilities	23,988.1	23,420.9
Total stockholders' equity	1,259.6	1,270.7
Noncontrolling interests	296.3	292.9
Total permanent equity	1,555.9	1,563.6
Total liabilities and equity	25,544.0	24,984.5
Asset Management segment [Member]
Assets:
Investments	134.8	223.9
Affiliated loans and receivables	1.0	1.1
Cash and cash equivalents	51.6	94.7
Funds Withheld Receivable	0.0	0.0
Receivables, net	0.8	0.7
Deferred tax assets	0.1	0.2
Properties, including oil and natural gas properties, net	0.9	1.1
Goodwill	10.7	10.7
Other assets	1.1	2.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	201.0	334.5
Liabilities and Equity:
Insurance reserves	0.0
Debt	43.5	42.9
Accounts payable and other current liabilities	3.7	7.7
Employee benefit obligations	0.0
Deferred tax liabilities	0.0
Other liabilities	8.7	10.3
Affiliated debt and payables	202.8	313.1
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	258.7	374.0
Total stockholders' equity	(60.1)	(41.8)
Noncontrolling interests	2.4	2.3
Total permanent equity	(57.7)	(39.5)
Total liabilities and equity	201.0	334.5
Energy Segment [Member]
Assets:
Cash and cash equivalents	8.3	34.2
Funds Withheld Receivable	0.0	0.0
Receivables, net	6.6	19.1
Properties, including oil and natural gas properties, net	133.7	288.9
Other assets	1.4	1.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	150.0	343.3
Liabilities and Equity:
Debt	159.1	325.9
Accounts payable and other current liabilities	11.3	33.6
Employee benefit obligations	0.0
Other liabilities	21.9	39.1
Affiliated debt and payables	102.2	102.2
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	294.5	500.8
Total stockholders' equity	(144.3)	(157.2)
Noncontrolling interests	(0.2)	(0.3)
Total permanent equity	(144.5)	(157.5)
Total liabilities and equity	150.0	343.3
Insurance Segment [Member]
Assets:
Investments	6.1	23.7
Investments in subsidiaries and affiliates	12.0	10.6
Affiliated loans and receivables	23.2	31.1
Cash and cash equivalents	33.0	18.0
Funds Withheld Receivable	1,709.1	1,743.8
Receivables, net	18.7	25.6
Deferred tax assets	23.4	23.6
Other assets	12.8	7.4
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	1,838.3	1,883.8
Liabilities and Equity:
Insurance reserves	1,686.5	1,731.9
Debt	0.0
Accounts payable and other current liabilities	6.6	5.4
Employee benefit obligations	0.0
Deferred tax liabilities	0.0
Other liabilities	5.5	7.1
Affiliated debt and payables	0.2
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	1,698.8	1,744.4
Total stockholders' equity	139.5	139.4
Noncontrolling interests	0.0
Total permanent equity	139.5	139.4
Total liabilities and equity	1,838.3	1,883.8
Consumer Products Segment [Member]
Assets:
Cash and cash equivalents	133.3	247.9
Funds Withheld Receivable	0.0	0.0
Receivables, net	635.9	586.6
Inventories, net	924.4	780.8
Deferred tax assets	9.3	9.3
Properties, including oil and natural gas properties, net	528.9	507.1
Goodwill	2,483.4	2,476.7
Intangibles	2,432.4	2,480.3
Other assets	115.4	105.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	7,263.0	7,193.8
Liabilities and Equity:
Debt	4,103.8	3,905.9
Accounts payable and other current liabilities	786.2	993.0
Employee benefit obligations	82.8	88.1
Deferred tax liabilities	563.8	572.6
Other liabilities	22.9	27.3
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	5,559.5	5,586.9
Total stockholders' equity	959.2	900.4
Noncontrolling interests	744.3	706.5
Total permanent equity	1,703.5	1,606.9
Total liabilities and equity	$ 7,263.0	$ 7,193.8