Consolidating Financial Information - Schedule of Balance Sheet Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Sep. 30, 2012	Jan. 01, 2012	Sep. 30, 2011
Assets:
Investments	$ 17,033.5	$ 16,918.4
Cash and cash equivalents	1,475.0	1,470.7	2,319.7	1,137.4
Receivables, net	593.4	414.4
Inventories, net	705.4	452.6
Accrued investment income	169.5	191.6
Reinsurance recoverable	2,330.4	2,363.1
Deferred tax assets	167.7	312.7
Properties, including oil and natural gas properties, net	965.6	221.6
Goodwill	1,434.0	694.2
Intangibles, including DAC and VOBA, net	2,467.5	1,988.5
Other assets	374.7	172.6
Total assets	27,716.7	25,200.4
Liabilities and Equity:
Debt	4,567.2	2,150.6
Accounts payable and other current liabilities	401.7	325.9
Equity conversion feature of preferred stock	202.7	232.0
Employee benefit obligations	104.5	95.1
Deferred tax liabilities	515.2	382.4
Other liabilities	488.9	600.6
Total liabilities	25,791.3	23,282.3
Temporary equity	326.8	319.2
Total stockholders' equity	1,171.9	1,177.6
Noncontrolling interests	426.7	421.3
Total permanent equity	1,598.6	1,598.9
Total liabilities and equity	27,716.7	25,200.4
Consumer Products [Member]
Assets:
Investments
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	77.5	158.0
Receivables, net	529.6	373.4
Inventories, net	705.4	452.6
Accrued investment income
Reinsurance recoverable
Deferred tax assets	23.0	28.2
Properties, including oil and natural gas properties, net	316.3	214.0
Goodwill	1,434.0	694.2
Intangibles, including DAC and VOBA, net	2,170.7	1,715.0
Other assets	264.2	116.2
Total assets	5,520.7	3,751.6
Liabilities and Equity:
Insurance reserves
Debt	3,258.9	1,669.3
Accounts payable and other current liabilities	678.7	594.2
Equity conversion feature of preferred stock
Employee benefit obligations	99.6	90.0
Deferred tax liabilities	509.0	377.5
Other liabilities	32.4	31.6
Affiliated debt and payables
Total liabilities	4,578.6	2,762.6
Temporary equity
Total stockholders' equity	515.9	567.7
Noncontrolling interests	426.2	421.3
Total permanent equity	942.1	989.0
Total liabilities and equity	5,520.7	3,751.6
Insurance [Member]
Assets:
Investments	16,734.0	16,556.7
Investments in subsidiaries and affiliates	48.2	32.0
Affiliated loans and receivables	267.2	150.1
Cash and cash equivalents	1,194.5	1,054.6
Receivables, net	41.0	41.0
Inventories, net
Accrued investment income	169.5	191.6
Reinsurance recoverable	2,330.4	2,363.1
Deferred tax assets	139.8	279.6
Properties, including oil and natural gas properties, net	7.4	6.9
Goodwill
Intangibles, including DAC and VOBA, net	296.8	273.5
Other assets	66.7	41.2
Total assets	21,295.5	20,990.3
Liabilities and Equity:
Insurance reserves	19,087.8	19,051.0
Debt	300.0
Accounts payable and other current liabilities	29.9	93.2
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities	1.3
Other liabilities	411.5	555.3
Affiliated debt and payables	1.4
Total liabilities	19,831.9	19,699.5
Temporary equity
Total stockholders' equity	1,463.6	1,290.8
Noncontrolling interests
Total permanent equity	1,463.6	1,290.8
Total liabilities and equity	21,295.5	20,990.3
Energy Segment [Member]
Assets:
Investments	0.2
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	11.1
Receivables, net	22.8
Inventories, net
Accrued investment income
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net	641.1
Goodwill
Intangibles, including DAC and VOBA, net
Other assets	4.9
Total assets	680.1
Liabilities and Equity:
Insurance reserves
Debt	278.6
Accounts payable and other current liabilities	30.0
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities
Other liabilities	32.6
Affiliated debt and payables	101.1
Total liabilities	442.3
Temporary equity
Total stockholders' equity	237.8
Noncontrolling interests
Total permanent equity	237.8
Total liabilities and equity	680.1
Other Financial Services [Member]
Assets:
Investments	241.6	180.1
Investments in subsidiaries and affiliates
Affiliated loans and receivables	1.4
Cash and cash equivalents	41.1	12.4
Receivables, net
Inventories, net
Accrued investment income
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net	0.5	0.4
Goodwill
Intangibles, including DAC and VOBA, net
Other assets	11.1	2.2
Total assets	295.7	195.1
Liabilities and Equity:
Insurance reserves
Debt	63.5
Accounts payable and other current liabilities	0.2
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities
Other liabilities	12.2	13.3
Affiliated debt and payables	166.1	150.1
Total liabilities	242.0	163.4
Temporary equity
Total stockholders' equity	53.2	31.7
Noncontrolling interests	0.5
Total permanent equity	53.7	31.7
Total liabilities and equity	295.7	195.1
Corporate and Other [Member]
Assets:
Investments	57.7	181.6
Investments in subsidiaries and affiliates	2,222.3	1,858.2
Affiliated loans and receivables
Cash and cash equivalents	150.8	245.7
Receivables, net
Inventories, net
Accrued investment income
Reinsurance recoverable
Deferred tax assets	4.9	4.9
Properties, including oil and natural gas properties, net	0.3	0.3
Goodwill
Intangibles, including DAC and VOBA, net
Other assets	27.8	13.0
Total assets	2,463.8	2,303.7
Liabilities and Equity:
Insurance reserves
Debt	695.7	497.7
Accounts payable and other current liabilities	56.7	66.8
Equity conversion feature of preferred stock	202.7	232.0
Employee benefit obligations	4.9	5.1
Deferred tax liabilities	4.9	4.9
Other liabilities	0.2	0.4
Affiliated debt and payables
Total liabilities	965.1	806.9
Temporary equity	326.8	319.2
Total stockholders' equity	1,171.9	1,177.6
Noncontrolling interests
Total permanent equity	1,171.9	1,177.6
Total liabilities and equity	2,463.8	2,303.7
Consolidation, Eliminations [Member]
Assets:
Investments
Investments in subsidiaries and affiliates	(2,270.5)	(1,890.2)
Affiliated loans and receivables	(268.6)	(150.1)
Cash and cash equivalents
Receivables, net
Inventories, net
Accrued investment income
Reinsurance recoverable
Deferred tax assets
Properties, including oil and natural gas properties, net
Goodwill
Intangibles, including DAC and VOBA, net
Other assets
Total assets	(2,539.1)	(2,040.3)
Liabilities and Equity:
Insurance reserves
Debt
Accounts payable and other current liabilities
Equity conversion feature of preferred stock
Employee benefit obligations
Deferred tax liabilities
Other liabilities
Affiliated debt and payables	(268.6)	(150.1)
Total liabilities	(268.6)	(150.1)
Temporary equity
Total stockholders' equity	(2,270.5)	(1,890.2)
Noncontrolling interests
Total permanent equity	(2,270.5)	(1,890.2)
Total liabilities and equity	(2,539.1)	(2,040.3)
Consolidated Entities [Member]
Assets:
Investments	17,033.5	16,918.4
Investments in subsidiaries and affiliates
Affiliated loans and receivables
Cash and cash equivalents	1,475.0	1,470.7
Receivables, net	593.4	414.4
Inventories, net	705.4	452.6
Accrued investment income	169.5	191.6
Reinsurance recoverable	2,330.4	2,363.1
Deferred tax assets	167.7	312.7
Properties, including oil and natural gas properties, net	965.6	221.6
Goodwill	1,434.0	694.2
Intangibles, including DAC and VOBA, net	2,467.5	1,988.5
Other assets	374.7	172.6
Total assets	27,716.7	25,200.4
Liabilities and Equity:
Insurance reserves	19,087.8	19,051.0
Debt	4,596.7	2,167.0
Accounts payable and other current liabilities	795.5	754.2
Equity conversion feature of preferred stock	202.7	232.0
Employee benefit obligations	104.5	95.1
Deferred tax liabilities	515.2	382.4
Other liabilities	488.9	600.6
Affiliated debt and payables
Total liabilities	25,791.3	23,282.3
Temporary equity	326.8	319.2
Total stockholders' equity	1,171.9	1,177.6
Noncontrolling interests	426.7	421.3
Total permanent equity	1,598.6	1,598.9
Total liabilities and equity	$ 27,716.7	$ 25,200.4