Consolidating Financial Information - Schedule of Balance Sheet Information (Detail) (USD $)	3 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Condensed Balance Sheet [Line Items]
Document Period End Date	Dec. 31, 2014
Assets:
Investments	$ 19,740,300,000us-gaap_Investments	$ 19,252,500,000us-gaap_Investments
Cash and cash equivalents	1,311,400,000	1,319,200,000	1,293,800,000	1,899,700,000
Receivables, net	660,100,000us-gaap_ReceivablesNetCurrent	585,100,000us-gaap_ReceivablesNetCurrent
Inventories, net	710,200,000us-gaap_InventoryNet	635,200,000us-gaap_InventoryNet
Accrued investment income	167,900,000	184,900,000
Reinsurance recoverable	2,416,700,000us-gaap_ReinsuranceRecoverables	2,397,600,000us-gaap_ReinsuranceRecoverables
Deferred tax assets	178,800,000us-gaap_DeferredTaxAssetsNet	186,700,000us-gaap_DeferredTaxAssetsNet
Properties, including oil and natural gas properties, net	1,054,800,000	908,600,000
Goodwill	1,491,900,000us-gaap_Goodwill	1,524,800,000us-gaap_Goodwill
Intangibles, including deferred acquisition costs and value of business acquired, net	2,712,300,000	2,683,700,000
Other assets	762,300,000us-gaap_OtherAssets	421,900,000us-gaap_OtherAssets
Total assets	31,206,700,000us-gaap_Assets	30,100,200,000us-gaap_Assets
Liabilities and Equity:
Debt	5,560,700,000us-gaap_LongTermDebtNoncurrent	5,061,100,000us-gaap_LongTermDebtNoncurrent
Employee benefit obligations	82,500,000	86,200,000
Deferred tax liabilities	518,000,000	533,300,000
Total liabilities	29,124,700,000us-gaap_Liabilities	27,843,200,000us-gaap_Liabilities
Total stockholders' equity	1,276,200,000us-gaap_StockholdersEquity	1,441,600,000us-gaap_StockholdersEquity
Noncontrolling interests	805,800,000us-gaap_MinorityInterest	815,400,000us-gaap_MinorityInterest
Total permanent equity	2,082,000,000	2,257,000,000
Total liabilities and equity	31,206,700,000	30,100,200,000
Consolidated Entities [Member]
Assets:
Investments	19,740,300,000	19,252,500,000
Cash and cash equivalents	1,311,400,000	1,319,200,000
Receivables, net	660,100,000	585,100,000
Inventories, net	710,200,000	635,200,000
Accrued investment income	167,900,000	184,900,000
Reinsurance recoverable	2,416,700,000	2,397,600,000
Deferred tax assets	178,800,000	186,700,000
Properties, including oil and natural gas properties, net	1,054,800,000	908,600,000
Goodwill	1,491,900,000	1,524,800,000
Intangibles, including deferred acquisition costs and value of business acquired, net	2,712,300,000	2,683,700,000
Other assets	762,300,000	421,900,000
Total assets	31,206,700,000	30,100,200,000
Liabilities and Equity:
Insurance reserves	21,246,600,000	20,215,100,000
Debt	5,666,000,000	5,157,800,000
Accounts payable and other current liabilities	899,600,000	1,033,000,000
Employee benefit obligations	82,500,000	86,200,000
Deferred tax liabilities	518,000,000	533,300,000
Other liabilities	712,000,000	817,800,000
Total liabilities	29,124,700,000	27,843,200,000
Total stockholders' equity	1,276,200,000	1,441,600,000
Noncontrolling interests	805,800,000	815,400,000
Total permanent equity	2,082,000,000	2,257,000,000
Total liabilities and equity	31,206,700,000	30,100,200,000
Consolidation, Eliminations [Member]
Assets:
Investments	(247,600,000)	(246,500,000)
Investments in subsidiaries and affiliates	(2,373,600,000)	(2,306,100,000)
Affiliated loans and receivables	(157,200,000)	(185,700,000)
Accrued investment income	(700,000)	(600,000)
Deferred tax assets	(100,000)	(100,000)
Other assets	100,000
Total assets	(2,779,100,000)	(2,739,000,000)
Liabilities and Equity:
Insurance reserves	0
Accounts payable and other current liabilities	500,000	500,000
Employee benefit obligations	0
Deferred tax liabilities	2,400,000	100,000
Other liabilities	0
Affiliated debt and payables	(403,500,000)	(431,400,000)
Total liabilities	(400,600,000)	(430,800,000)
Total stockholders' equity	(2,378,500,000)	(2,308,200,000)
Noncontrolling interests	0
Total permanent equity	(2,378,500,000)	(2,308,200,000)
Total liabilities and equity	(2,779,100,000)	(2,739,000,000)
Corporate and Other [Member]
Assets:
Investments	81,900,000	93,700,000
Investments in subsidiaries and affiliates	2,309,100,000	2,237,900,000
Affiliated loans and receivables	100,000
Cash and cash equivalents	211,700,000	423,100,000
Receivables, net	45,300,000	43,100,000
Inventories, net	8,300,000	10,700,000
Deferred tax assets	1,100,000	1,100,000
Properties, including oil and natural gas properties, net	2,000,000	2,500,000
Goodwill	16,200,000	44,500,000
Intangibles, including deferred acquisition costs and value of business acquired, net	9,900,000	41,800,000
Other assets	35,100,000	34,700,000
Total assets	2,720,700,000	2,933,100,000
Liabilities and Equity:
Debt	1,325,700,000	1,325,000,000
Accounts payable and other current liabilities	92,500,000	104,600,000
Employee benefit obligations	4,200,000	4,300,000
Deferred tax liabilities	5,400,000	17,200,000
Other liabilities	1,300,000	1,100,000
Affiliated debt and payables	30,900,000	34,800,000
Total liabilities	1,460,000,000	1,487,000,000
Total stockholders' equity	1,276,200,000	1,441,600,000
Noncontrolling interests	(15,500,000)	4,500,000
Total permanent equity	1,260,700,000	1,446,100,000
Total liabilities and equity	2,720,700,000	2,933,100,000
Asset Management segment [Member]
Assets:
Investments	546,300,000	584,600,000
Affiliated loans and receivables	18,300,000	28,500,000
Cash and cash equivalents	78,900,000	53,500,000
Receivables, net	800,000	900,000
Accrued investment income	4,800,000	3,700,000
Deferred tax assets	100,000
Properties, including oil and natural gas properties, net	1,300,000	1,400,000
Goodwill	10,700,000	10,700,000
Other assets	8,900,000	9,200,000
Total assets	670,100,000	692,500,000
Liabilities and Equity:
Insurance reserves	0
Debt	297,700,000	298,700,000
Accounts payable and other current liabilities	11,300,000	8,500,000
Employee benefit obligations	0
Deferred tax liabilities	0
Other liabilities	12,800,000	19,300,000
Affiliated debt and payables	271,400,000	286,500,000
Total liabilities	593,200,000	613,000,000
Total stockholders' equity	65,800,000	68,200,000
Noncontrolling interests	11,100,000	11,300,000
Total permanent equity	76,900,000	79,500,000
Total liabilities and equity	670,100,000	692,500,000
Energy Segment [Member]
Assets:
Cash and cash equivalents	12,900,000	14,200,000
Receivables, net	36,400,000	23,700,000
Properties, including oil and natural gas properties, net	620,000,000	464,400,000
Other assets	1,700,000	2,500,000
Total assets	671,000,000	504,800,000
Liabilities and Equity:
Debt	327,000,000	243,200,000
Accounts payable and other current liabilities	31,100,000	31,300,000
Employee benefit obligations	0
Other liabilities	37,400,000	27,300,000
Affiliated debt and payables	100,000,000	102,300,000
Total liabilities	495,500,000	404,100,000
Total stockholders' equity	175,100,000	100,700,000
Noncontrolling interests	400,000
Total permanent equity	175,500,000	100,700,000
Total liabilities and equity	671,000,000	504,800,000
Insurance Segment [Member]
Assets:
Investments	19,359,700,000	18,820,700,000
Investments in subsidiaries and affiliates	64,500,000	68,200,000
Affiliated loans and receivables	138,800,000	157,200,000
Cash and cash equivalents	599,500,000	633,800,000
Receivables, net	800,000	2,100,000
Accrued investment income	163,800,000	181,800,000
Reinsurance recoverable	2,416,700,000	2,397,600,000
Deferred tax assets	136,000,000	139,000,000
Properties, including oil and natural gas properties, net	11,700,000	11,400,000
Intangibles, including deferred acquisition costs and value of business acquired, net	635,700,000	550,400,000
Other assets	564,700,000	233,600,000
Total assets	24,091,900,000	23,195,800,000
Liabilities and Equity:
Insurance reserves	21,246,600,000	20,215,100,000
Debt	300,000,000	300,000,000
Accounts payable and other current liabilities	50,100,000	71,900,000
Employee benefit obligations	0
Deferred tax liabilities	0
Other liabilities	640,300,000	748,900,000
Affiliated debt and payables	1,200,000	7,800,000
Total liabilities	22,238,200,000	21,343,700,000
Total stockholders' equity	1,522,300,000	1,526,900,000
Noncontrolling interests	331,400,000	325,200,000
Total permanent equity	1,853,700,000	1,852,100,000
Total liabilities and equity	24,091,900,000	23,195,800,000
Consumer Products Segment [Member]
Assets:
Cash and cash equivalents	408,400,000	194,600,000
Receivables, net	576,800,000	515,300,000
Inventories, net	701,900,000	624,500,000
Deferred tax assets	41,700,000	46,700,000
Properties, including oil and natural gas properties, net	419,800,000	428,900,000
Goodwill	1,465,000,000	1,469,600,000
Intangibles, including deferred acquisition costs and value of business acquired, net	2,066,700,000	2,091,500,000
Other assets	151,800,000	141,900,000
Total assets	5,832,100,000	5,513,000,000
Liabilities and Equity:
Debt	3,415,600,000	2,990,900,000
Accounts payable and other current liabilities	714,100,000	816,200,000
Employee benefit obligations	78,300,000	81,900,000
Deferred tax liabilities	510,200,000	516,000,000
Other liabilities	20,200,000	21,200,000
Total liabilities	4,738,400,000	4,426,200,000
Total stockholders' equity	615,300,000	612,400,000
Noncontrolling interests	478,400,000	474,400,000
Total permanent equity	1,093,700,000	1,086,800,000
Total liabilities and equity	$ 5,832,100,000	$ 5,513,000,000

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