Consolidating Financial Information - Schedule of Balance Sheet Information (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Assets:
Investments	$ 155.6	$ 278.9
Cash and cash equivalents	576.4	695.2	$ 755.9	$ 742.8
Funds Withheld Receivable	1,664.0	1,710.1
Receivables, net	636.9	632.9
Inventories, net	867.7	780.8
Properties, including oil and natural gas properties, net	664.3	798.4
Goodwill	2,478.1	2,487.4
Intangibles	2,445.3	2,480.3
Other assets	143.6	134.3
Disposal Group, Including Discontinued Operation, Assets, Current	25,097.5	24,984.5
Total assets	35,032.8	35,034.0
Liabilities and Equity:
Debt	6,239.7	6,265.4
Employee benefit obligations	84.7	92.9
Deferred tax liabilities	905.0	574.5
Disposal Group, Including Discontinued Operation, Liabilities, Current	23,630.8	23,420.9
Total liabilities	33,659.8	33,445.9
Total stockholders' equity	391.0	586.7
Noncontrolling interests	982.0	1,001.4
Total permanent equity	1,373.0	1,588.1
Total liabilities and equity	35,032.8	35,034.0
Consolidated Entities [Member]
Assets:
Investments	155.6	278.9
Cash and cash equivalents	576.4	695.2
Funds Withheld Receivable	1,664.0	1,710.1
Receivables, net	636.9	632.9
Inventories, net	867.7	780.8
Deferred tax assets	303.4	51.2
Properties, including oil and natural gas properties, net	664.3	798.4
Goodwill	2,478.1	2,487.4
Intangibles	2,445.3	2,480.3
Other assets	143.6	134.3
Disposal Group, Including Discontinued Operation, Assets, Current	25,097.5	24,984.5
Total assets	35,032.8	35,034.0
Liabilities and Equity:
Insurance reserves	1,827.1	1,856.0
Debt	6,285.4	6,310.5
Accounts payable and other current liabilities	854.1	1,095.6
Employee benefit obligations	84.7	92.9
Deferred tax liabilities	905.0	574.5
Other liabilities	72.7	95.5
Disposal Group, Including Discontinued Operation, Liabilities, Current	23,630.8	23,420.9
Total liabilities	33,659.8	33,445.9
Total stockholders' equity	391.0	586.7
Noncontrolling interests	982.0	1,001.4
Total permanent equity	1,373.0	1,588.1
Total liabilities and equity	35,032.8	35,034.0
Consolidation, Eliminations [Member]
Assets:
Investments	(1.5)	(1.5)
Investments in subsidiaries and affiliates	(1,975.4)	(2,025.3)
Affiliated loans and receivables	(23.9)	(32.3)
Funds Withheld Receivable	(39.4)	(33.7)
Receivables, net	0.1	0.1
Deferred tax assets	19.0	14.2
Other assets	16.4	17.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	(2,004.7)	(2,061.4)
Liabilities and Equity:
Insurance reserves	144.7	124.1
Debt	249.0	330.7
Accounts payable and other current liabilities	0.4	2.2
Employee benefit obligations	0.0
Deferred tax liabilities	1.3
Other liabilities	9.7	8.4
Affiliated debt and payables	(334.9)	(415.3)
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	70.2	50.1
Total stockholders' equity	(2,074.9)	(2,111.5)
Noncontrolling interests	0.0
Total permanent equity	(2,074.9)	(2,111.5)
Total liabilities and equity	(2,004.7)	(2,061.4)
Corporate and Other [Member]
Assets:
Investments		32.8
Investments in subsidiaries and affiliates	1,964.8	2,014.7
Affiliated loans and receivables	0.3	0.1
Cash and cash equivalents	297.4	300.4
Funds Withheld Receivable	0.0	0.0
Receivables, net	1.6	0.8
Deferred tax assets	251.6	3.9
Properties, including oil and natural gas properties, net	1.2	1.3
Other assets	2.2	1.5
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	2,519.1	2,355.5
Liabilities and Equity:
Debt	1,706.5	1,705.1
Accounts payable and other current liabilities	73.0	53.7
Employee benefit obligations	4.8	4.8
Deferred tax liabilities	340.6	1.9
Other liabilities	3.2	3.3
Affiliated debt and payables	0.0
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	2,128.1	1,768.8
Total stockholders' equity	391.0	586.7
Noncontrolling interests	0.0
Total permanent equity	391.0	586.7
Total liabilities and equity	2,519.1	2,355.5
Discontinued Operations, Held-for-sale [Member]
Assets:
Funds Withheld Receivable	0.0	0.0
Disposal Group, Including Discontinued Operation, Assets, Current	25,097.5	24,984.5
Total assets	25,097.5	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	23,630.8	23,420.9
Total liabilities	23,630.8	23,420.9
Total stockholders' equity	1,192.5	1,270.7
Noncontrolling interests	274.2	292.9
Total permanent equity	1,466.7	1,563.6
Total liabilities and equity	25,097.5	24,984.5
Asset Management segment [Member]
Assets:
Investments	151.0	223.9
Affiliated loans and receivables	1.0	1.1
Cash and cash equivalents	74.1	94.7
Funds Withheld Receivable	0.0	0.0
Receivables, net	1.9	0.7
Deferred tax assets	0.1	0.2
Properties, including oil and natural gas properties, net	1.0	1.1
Goodwill	10.7	10.7
Other assets	1.4	2.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	241.2	334.5
Liabilities and Equity:
Insurance reserves	0.0
Debt	43.2	42.9
Accounts payable and other current liabilities	4.7	7.7
Employee benefit obligations	0.0
Deferred tax liabilities	0.0
Other liabilities	9.4	10.3
Affiliated debt and payables	234.6	313.1
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	291.9	374.0
Total stockholders' equity	(53.5)	(41.8)
Noncontrolling interests	2.8	2.3
Total permanent equity	(50.7)	(39.5)
Total liabilities and equity	241.2	334.5
Energy Segment [Member]
Assets:
Cash and cash equivalents	10.1	34.2
Funds Withheld Receivable	0.0	0.0
Receivables, net	11.2	19.1
Properties, including oil and natural gas properties, net	157.7	288.9
Other assets	0.9	1.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	179.9	343.3
Liabilities and Equity:
Debt	159.0	325.9
Accounts payable and other current liabilities	14.1	33.6
Employee benefit obligations	0.0
Other liabilities	21.5	39.1
Affiliated debt and payables	100.0	102.2
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	294.6	500.8
Total stockholders' equity	(114.6)	(157.2)
Noncontrolling interests	(0.1)	(0.3)
Total permanent equity	(114.7)	(157.5)
Total liabilities and equity	179.9	343.3
Insurance Segment [Member]
Assets:
Investments	6.1	23.7
Investments in subsidiaries and affiliates	10.6	10.6
Affiliated loans and receivables	22.6	31.1
Cash and cash equivalents	32.8	18.0
Funds Withheld Receivable	1,703.4	1,743.8
Receivables, net	22.9	25.6
Deferred tax assets	23.4	23.6
Other assets	12.4	7.4
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	1,834.2	1,883.8
Liabilities and Equity:
Insurance reserves	1,682.4	1,731.9
Debt	0.0
Accounts payable and other current liabilities	4.2	5.4
Employee benefit obligations	0.0
Deferred tax liabilities	0.0
Other liabilities	6.5	7.1
Affiliated debt and payables	0.3
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	1,693.4	1,744.4
Total stockholders' equity	140.8	139.4
Noncontrolling interests	0.0
Total permanent equity	140.8	139.4
Total liabilities and equity	1,834.2	1,883.8
Consumer Products Segment [Member]
Assets:
Cash and cash equivalents	162.0	247.9
Funds Withheld Receivable	0.0	0.0
Receivables, net	599.2	586.6
Inventories, net	867.7	780.8
Deferred tax assets	9.3	9.3
Properties, including oil and natural gas properties, net	504.4	507.1
Goodwill	2,467.4	2,476.7
Intangibles	2,445.3	2,480.3
Other assets	110.3	105.1
Disposal Group, Including Discontinued Operation, Assets, Current	0.0	0.0
Total assets	7,165.6	7,193.8
Liabilities and Equity:
Debt	4,127.7	3,905.9
Accounts payable and other current liabilities	757.7	993.0
Employee benefit obligations	79.9	88.1
Deferred tax liabilities	563.1	572.6
Other liabilities	22.4	27.3
Disposal Group, Including Discontinued Operation, Liabilities, Current	0.0	0.0
Total liabilities	5,550.8	5,586.9
Total stockholders' equity	909.7	900.4
Noncontrolling interests	705.1	706.5
Total permanent equity	1,614.8	1,606.9
Total liabilities and equity	$ 7,165.6	$ 7,193.8