Consolidating Financial Information - Schedule of Balance Sheet Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Mar. 31, 2014	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Condensed Balance Sheet [Line Items]
Document Period End Date	Mar. 31, 2014
Assets:
Investments	$ 18,312.8	$ 16,465.9
Cash and cash equivalents	1,319.8	1,899.7	1,475.0	1,470.7
Receivables, net	657.3	611.3
Inventories, net	725.9	632.9
Accrued investment income	182.0	161.2
Reinsurance recoverable	2,387.4	2,363.7
Deferred tax assets	227.1	293.4
Properties, including oil and natural gas properties, net	930.6	993.3
Goodwill	1,479.6	1,476.7
Intangibles, including deferred acquisition costs and value of business acquired, net	2,691.5	2,729.1
Other assets	408.5	281.6
Total assets	29,322.5	27,908.8
Liabilities and Equity:
Debt	5,277.0	4,793.2
Equity conversion feature of preferred stock	364.8	330.8
Employee benefit obligations	92.5	99.6
Deferred tax liabilities	493.0	492.8
Total liabilities	27,579.8	26,445.9
Temporary equity	319.3	329.4
Total stockholders' equity	693.5	724.7
Noncontrolling interests	729.9	408.8
Total permanent equity	1,423.4	1,133.5
Total liabilities and equity	29,322.5	27,908.8
Consumer Products Segment [Member]
Assets:
Investments
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	93.4	207.3
Receivables, net	591.9	546.9
Inventories, net	725.9	632.9
Accrued investment income
Reinsurance recoverable
Deferred tax assets	35.7	33.0
Properties, including oil and natural gas properties, net	444.2	412.5
Goodwill	1,479.6	1,476.7
Intangibles, including deferred acquisition costs and value of business acquired, net	2,154.9	2,163.2
Other assets	162.0	154.2
Total assets	5,687.6	5,626.7
Liabilities and Equity:
Insurance reserves
Debt	3,429.5	3,218.9
Accounts payable and other current liabilities	666.8	849.4
Equity conversion feature of preferred stock
Employee benefit obligations	89.8	96.6
Deferred tax liabilities	490.7	492.8
Other liabilities	28.0	28.9
Affiliated debt and payables
Total liabilities	4,704.8	4,686.6
Temporary equity
Total stockholders' equity	550.6	531.0
Noncontrolling interests	432.2	409.1
Total permanent equity	982.8	940.1
Total liabilities and equity	5,687.6	5,626.7
Insurance [Member]
Assets:
Investments	17,884.5	16,282.3
Investments in subsidiaries and affiliates	67.9	62.0
Affiliated loans and receivables	146.4	150.1
Cash and cash equivalents	761.8	1,248.3
Receivables, net	0.9
Inventories, net
Accrued investment income	178.7	159.3
Reinsurance recoverable	2,387.4	2,363.7
Deferred tax assets	190.5	260.4
Properties, including oil and natural gas properties, net	8.9	7.0
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net	536.6	565.9
Other assets	200.4	84.1
Total assets	22,364.0	21,183.1
Liabilities and Equity:
Insurance reserves	19,783.0	18,895.9
Debt	300.0	300.0
Accounts payable and other current liabilities	48.8	52.9
Equity conversion feature of preferred stock
Employee benefit obligations	0
Deferred tax liabilities
Other liabilities	542.1	640.2
Affiliated debt and payables	1.9	0.8
Total liabilities	20,675.8	19,889.8
Temporary equity
Total stockholders' equity	1,389.7	1,293.3
Noncontrolling interests	298.5
Total permanent equity	1,688.2	1,293.3
Total liabilities and equity	22,364.0	21,183.1
Energy Segment [Member]
Assets:
Investments
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	19.3	18.7
Receivables, net	17.2	22.2
Inventories, net
Accrued investment income
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net	476.1	572.6
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net
Other assets	2.9	4.1
Total assets	515.5	617.6
Liabilities and Equity:
Insurance reserves
Debt	250.6	271.2
Accounts payable and other current liabilities	33.0	32.8
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities
Other liabilities	26.3	25.4
Affiliated debt and payables	102.1	102.2
Total liabilities	412.0	431.6
Temporary equity		0.1
Total stockholders' equity	103.5	185.9
Noncontrolling interests
Total permanent equity	103.5	185.9
Total liabilities and equity	515.5	617.6
Other Financial Services [Member]
Assets:
Investments	595.6	389.3
Investments in subsidiaries and affiliates
Affiliated loans and receivables	2.1	0.9
Cash and cash equivalents	73.0	166.5
Receivables, net	0.3	1.2
Inventories, net
Accrued investment income	3.9	2.3
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net	0.9	0.7
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net
Other assets	10.4	11.3
Total assets	686.2	572.2
Liabilities and Equity:
Insurance reserves
Debt	291.9	181.8
Accounts payable and other current liabilities	5.1	6.3
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities
Other liabilities	32.3	23.3
Affiliated debt and payables	289.8	293.3
Total liabilities	619.1	504.7
Temporary equity
Total stockholders' equity	67.9	67.8
Noncontrolling interests	(0.8)	(0.3)
Total permanent equity	67.1	67.5
Total liabilities and equity	686.2	572.2
Corporate and Other [Member]
Assets:
Investments	82.0	42.3
Investments in subsidiaries and affiliates	2,038.8	2,012.9
Affiliated loans and receivables
Cash and cash equivalents	372.3	258.9
Receivables, net	46.0	41.0
Inventories, net
Accrued investment income
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net	0.5	0.5
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net
Other assets	32.8	27.9
Total assets	2,572.4	2,383.5
Liabilities and Equity:
Insurance reserves
Debt	1,124.3	924.2
Accounts payable and other current liabilities	67.8	71.3
Equity conversion feature of preferred stock	364.8	330.8
Employee benefit obligations	2.7	3.0
Deferred tax liabilities
Other liabilities		0.2
Affiliated debt and payables
Total liabilities	1,559.6	1,329.5
Temporary equity	319.3	329.3
Total stockholders' equity	693.5	724.7
Noncontrolling interests
Total permanent equity	693.5	724.7
Total liabilities and equity	2,572.4	2,383.5
Consolidation, Eliminations [Member]
Assets:
Investments	(249.3)	(248.0)
Investments in subsidiaries and affiliates	(2,106.7)	(2,074.9)
Affiliated loans and receivables	(148.5)	(151.0)
Cash and cash equivalents
Receivables, net	1.0
Inventories, net
Accrued investment income	(0.6)	(0.4)
Reinsurance recoverable
Deferred tax assets	0.9
Properties, including oil and natural gas properties, net
Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net
Other assets
Total assets	(2,503.2)	(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	2.3
Other liabilities
Affiliated debt and payables	(393.8)	(396.3)
Total liabilities	(391.5)	(396.3)
Temporary equity
Total stockholders' equity	(2,111.7)	(2,078.0)
Noncontrolling interests
Total permanent equity	(2,111.7)	(2,078.0)
Total liabilities and equity	(2,503.2)	(2,474.3)
Consolidated Entities [Member]
Assets:
Investments	18,312.8	16,465.9
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	1,319.8	1,899.7
Receivables, net	657.3	611.3
Inventories, net	725.9	632.9
Accrued investment income	182.0	161.2
Reinsurance recoverable	2,387.4	2,363.7
Deferred tax assets	227.1	293.4
Properties, including oil and natural gas properties, net	930.6	993.3
Goodwill	1,479.6	1,476.7
Intangibles, including deferred acquisition costs and value of business acquired, net	2,691.5	2,729.1
Other assets	408.5	281.6
Total assets	29,322.5	27,908.8
Liabilities and Equity:
Insurance reserves	19,783.0	18,895.9
Debt	5,396.3	4,896.1
Accounts payable and other current liabilities	821.5	1,012.7
Equity conversion feature of preferred stock	364.8	330.8
Employee benefit obligations	92.5	99.6
Deferred tax liabilities	493.0	492.8
Other liabilities	628.7	718.0
Affiliated debt and payables
Total liabilities	27,579.8	26,445.9
Temporary equity	319.3	329.4
Total stockholders' equity	693.5	724.7
Noncontrolling interests	729.9	408.8
Total permanent equity	1,423.4	1,133.5
Total liabilities and equity	$ 29,322.5	$ 27,908.8