Consolidating Financial Information - Schedule of Balance Sheet Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2012
Condensed Balance Sheet [Line Items]
Document Period End Date	Jun. 30, 2014
Assets:
Investments	$ 18,751.1	$ 16,465.9
Cash and cash equivalents	1,455.9	1,899.7	1,243.7	1,470.7
Receivables, net	664.9	611.3
Inventories, net	746.7	632.9
Accrued investment income	159.9	161.2
Reinsurance recoverable	2,393.7	2,363.7
Deferred tax assets	145.9	293.4
Properties, including oil and natural gas properties, net	924.5	993.3
Goodwill	1,539.1	1,476.7
Intangibles, including deferred acquisition costs and value of business acquired, net	2,664.8	2,729.1
Other assets	438.7	281.6
Total assets	29,885.2	27,908.8
Liabilities and Equity:
Debt	5,181.9	4,793.2
Equity conversion feature of preferred stock		330.8
Employee benefit obligations	87.4	99.6
Deferred tax liabilities	522.2	492.8
Total liabilities	27,534.5	26,445.9
Temporary equity		329.4
Total stockholders' equity	1,534.3	724.7
Noncontrolling interests	816.4	408.8
Total permanent equity	2,350.7	1,133.5
Total liabilities and equity	29,885.2	27,908.8
Consolidated Entities [Member]
Assets:
Investments	18,751.1	16,465.9
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	1,455.9	1,899.7
Receivables, net	664.9	611.3
Inventories, net	746.7	632.9
Accrued investment income	159.9	161.2
Reinsurance recoverable	2,393.7	2,363.7
Deferred tax assets	145.9	293.4
Properties, including oil and natural gas properties, net	924.5	993.3
Goodwill	1,539.1	1,476.7
Intangibles, including deferred acquisition costs and value of business acquired, net	2,664.8	2,729.1
Other assets	438.7	281.6
Total assets	29,885.2	27,908.8
Liabilities and Equity:
Insurance reserves	19,988.0	18,895.9
Debt	5,303.4	4,896.1
Accounts payable and other current liabilities	899.9	1,012.7
Equity conversion feature of preferred stock		330.8
Employee benefit obligations	87.4	99.6
Deferred tax liabilities	522.2	492.8
Other liabilities	733.6	718.0
Affiliated debt and payables
Total liabilities	27,534.5	26,445.9
Temporary equity		329.4
Total stockholders' equity	1,534.3	724.7
Noncontrolling interests	816.4	408.8
Total permanent equity	2,350.7	1,133.5
Total liabilities and equity	29,885.2	27,908.8
Consolidation, Eliminations [Member]
Assets:
Investments	(246.8)	(248.0)
Investments in subsidiaries and affiliates	(2,320.2)	(2,074.9)
Affiliated loans and receivables	(186.5)	(151.0)
Cash and cash equivalents
Receivables, net
Inventories, net
Accrued investment income	(0.6)	(0.4)
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net
Other assets
Total assets	(2,754.1)	(2,474.3)
Liabilities and Equity:
Insurance reserves
Debt
Accounts payable and other current liabilities
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities	0.1
Other liabilities
Affiliated debt and payables	(433.5)	(396.3)
Total liabilities	(433.4)	(396.3)
Temporary equity
Total stockholders' equity	(2,320.7)	(2,078.0)
Noncontrolling interests
Total permanent equity	(2,320.7)	(2,078.0)
Total liabilities and equity	(2,754.1)	(2,474.3)
Corporate and Other [Member]
Assets:
Investments	88.2	42.3
Investments in subsidiaries and affiliates	2,247.8	2,012.9
Affiliated loans and receivables	0.3
Cash and cash equivalents	328.9	258.9
Receivables, net	42.2	41.0
Inventories, net	11.9
Accrued investment income
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net	2.0	0.5
Goodwill	43.9
Intangibles, including deferred acquisition costs and value of business acquired, net	41.7
Other assets	33.8	27.9
Total assets	2,840.7	2,383.5
Liabilities and Equity:
Insurance reserves
Debt	1,124.3	924.2
Accounts payable and other current liabilities	120.6	71.3
Equity conversion feature of preferred stock		330.8
Employee benefit obligations	2.6	3.0
Deferred tax liabilities	15.4
Other liabilities	1.2	0.2
Affiliated debt and payables	34.6
Total liabilities	1,298.7	1,329.5
Temporary equity		329.3
Total stockholders' equity	1,534.3	724.7
Noncontrolling interests	7.7
Total permanent equity	1,542.0	724.7
Total liabilities and equity	2,840.7	2,383.5
Asset Management segment [Member]
Assets:
Investments	544.7	389.3
Investments in subsidiaries and affiliates
Affiliated loans and receivables	28.8	0.9
Cash and cash equivalents	98.9	166.5
Receivables, net	0.5	1.2
Inventories, net
Accrued investment income	3.3	2.3
Reinsurance recoverable
Deferred tax assets	0.1
Properties, including oil and natural gas properties, net	1.2	0.7
Goodwill	10.7
Intangibles, including deferred acquisition costs and value of business acquired, net
Other assets	12.7	11.3
Total assets	700.9	572.2
Liabilities and Equity:
Insurance reserves
Debt	291.9	181.8
Accounts payable and other current liabilities	7.3	6.3
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities
Other liabilities	24.0	23.3
Affiliated debt and payables	293.4	293.3
Total liabilities	616.6	504.7
Temporary equity
Total stockholders' equity	72.4	67.8
Noncontrolling interests	11.9	(0.3)
Total permanent equity	84.3	67.5
Total liabilities and equity	700.9	572.2
Energy Segment [Member]
Assets:
Investments
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	22.5	18.7
Receivables, net	17.1	22.2
Inventories, net
Accrued investment income
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net	471.0	572.6
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net
Other assets	2.8	4.1
Total assets	513.4	617.6
Liabilities and Equity:
Insurance reserves
Debt	250.6	271.2
Accounts payable and other current liabilities	33.1	32.8
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities
Other liabilities	26.9	25.4
Affiliated debt and payables	99.9	102.2
Total liabilities	410.5	431.6
Temporary equity		0.1
Total stockholders' equity	102.9	185.9
Noncontrolling interests
Total permanent equity	102.9	185.9
Total liabilities and equity	513.4	617.6
Insurance [Member]
Assets:
Investments	18,365.0	16,282.3
Investments in subsidiaries and affiliates	72.4	62.0
Affiliated loans and receivables	157.4	150.1
Cash and cash equivalents	920.5	1,248.3
Receivables, net	0.5
Inventories, net
Accrued investment income	157.2	159.3
Reinsurance recoverable	2,393.7	2,363.7
Deferred tax assets	106.7	260.4
Properties, including oil and natural gas properties, net	9.9	7.0
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net	486.9	565.9
Other assets	217.0	84.1
Total assets	22,887.2	21,183.1
Liabilities and Equity:
Insurance reserves	19,988.0	18,895.9
Debt	300.0	300.0
Accounts payable and other current liabilities	58.2	52.9
Equity conversion feature of preferred stock
Employee benefit obligations	0
Deferred tax liabilities
Other liabilities	653.0	640.2
Affiliated debt and payables	5.6	0.8
Total liabilities	21,004.8	19,889.8
Temporary equity
Total stockholders' equity	1,548.7	1,293.3
Noncontrolling interests	333.7
Total permanent equity	1,882.4	1,293.3
Total liabilities and equity	22,887.2	21,183.1
Consumer Products Segment [Member]
Assets:
Investments
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	85.1	207.3
Receivables, net	604.6	546.9
Inventories, net	734.8	632.9
Accrued investment income
Reinsurance recoverable
Deferred tax assets	39.1	33.0
Properties, including oil and natural gas properties, net	440.4	412.5
Goodwill	1,484.5	1,476.7
Intangibles, including deferred acquisition costs and value of business acquired, net	2,136.2	2,163.2
Other assets	172.4	154.2
Total assets	5,697.1	5,626.7
Liabilities and Equity:
Insurance reserves
Debt	3,336.6	3,218.9
Accounts payable and other current liabilities	680.7	849.4
Equity conversion feature of preferred stock
Employee benefit obligations	84.8	96.6
Deferred tax liabilities	506.7	492.8
Other liabilities	28.5	28.9
Affiliated debt and payables
Total liabilities	4,637.3	4,686.6
Temporary equity
Total stockholders' equity	596.7	531.0
Noncontrolling interests	463.1	409.1
Total permanent equity	1,059.8	940.1
Total liabilities and equity	$ 5,697.1	$ 5,626.7