Fair Value of Financial Instruments - Assets and Liabilities Carrying at Fair Value on Non-Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013	Sep. 30, 2013		Dec. 31, 2012	Sep. 30, 2012
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 755.6		$ 419.0		$ 755.6		$ 419.0		$ 709.5	$ 523.5		$ 313.5	$ 206.0
Document Period End Date					Mar. 31, 2014
Assets
Cash and cash equivalents	1,319.8				1,319.8					1,899.7		1,475.0	1,470.7
Derivatives, Assets
Derivatives	273.0				273.0					221.8
Fixed maturity securities, available-for-sale:
Asset-backed loans	795.7				795.7					560.4
Derivatives, Liabilities
Equity conversion feature of preferred stock	364.8				364.8					330.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			(0.1)		0.6		(0.3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	11.3		3.3		4.6		1.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	41.7		154.2		234.3		288.4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales							(9.6)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(1.9)		(13.0)		(2.4)		(13.7)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	(5.0)	[1]	(38.9)	[2]	(5.0)	[1]	(53.0)	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	2,234.5		1,842.3		2,234.5		1,842.3		2,172.6	1,875.2		1,680.1	1,782.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	81.2		162.2		228.0		59.5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	0				150.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	19.3				19.3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net	0			[2]	0	[1]		[2]
Asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	10.7		5.3		10.7		5.3		9.8	5.0		5.3	15.9
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(0.1)				(0.3)		(0.1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0				5.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	1.0	[1]		[2]	1.0	[1]	(10.5)	[2]
Commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			6.2				6.2		6.0	5.7		6.1	5.0
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			0.1		0.3		0.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases							1.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	(6.0)	[1]		[2]	(6.0)	[1]		[2]
Corporates [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	657.0		356.5		657.0		356.5		607.1	461.1		256.1	135.3
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		(0.1)		0		(0.3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	10.1		3.2		4.0		1.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	41.7		144.2		194.3		277.4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0				0		(9.6)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(1.9)		(13.0)		(2.4)		(13.7)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net		[1]	(33.9)	[2]		[1]	(33.8)	[2]
Hybrids [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value												5.0	8.8
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)							(0.1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net			(5.0)	[2]			(8.7)	[2]
Municipals [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	35.6				35.6				34.3
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	1.3				0.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0				35.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net		[1]				[1]
Held for trading [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	10.8				10.8				10.8	10.7
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					0.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0	[1]			0	[1]
Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			10.0				10.0					0	0
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	484.9				484.9					352.5
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			10.0				10.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales			0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements			0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net			0	[1]			0	[1]
Recurring [Member] | Fair Value [Member]
Assets
Cash and cash equivalents	1,319.8	[3],[4]			1,319.8	[3],[4]				1,899.7	[3],[4]
Contingent purchase price reduction receivable	41.5	[3]			41.5	[3]				41.0	[3]
Fixed maturity securities, available-for-sale:
Asset-backed loans	795.7				795.7					560.4
Total financial assets	926.2				926.2					591.6
Liabilities
Total debt	5,488.1	[5]			5,488.1	[5]				4,773.2	[5]
Derivatives, Liabilities
Equity conversion feature of preferred stock	364.8	[3]			364.8	[3]				330.8	[3]
Redeemable preferred stock, excluding equity conversion feature	319.3				319.3					377.1
Investment contracts, included in contractholder funds	12,872.3				12,872.3					12,378.6
Financial Liabilities Fair Value Disclosure	18,679.7				18,679.7					17,528.9
Recurring [Member] | Fair Value [Member] | U.S. Government securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	392.6	[3]			392.6	[3]				1,001.8	[3]
Recurring [Member] | Fair Value [Member] | Foreign exchange forward agreements [Member]
Derivatives, Assets
Derivatives	2.1	[3]			2.1	[3]				1.8	[3]
Derivatives, Liabilities
Derivative Liability	7.2	[3]			7.2	[3]				10.0	[3]
Recurring [Member] | Fair Value [Member] | Commodity Option [Member]
Derivatives, Assets
Derivatives	0.4	[3]			0.4	[3]				4.1	[3]
Derivatives, Liabilities
Derivative Liability	5.1	[3]			5.1	[3]				2.4	[3]
Recurring [Member] | Fair Value [Member] | Call options [Member]
Derivatives, Assets
Derivatives	273.0	[3]			273.0	[3]				221.8	[3]
Recurring [Member] | Fair Value [Member] | Available-for-sale embedded derivatives [Member]
Fixed maturity securities, available-for-sale:
Equity securities - available-for-sale	353.1	[3]			353.1	[3]				271.0	[4]
Recurring [Member] | Fair Value [Member] | FIA embedded derivatives, included in contractholder funds [Member]
Derivatives, Liabilities
Derivative Liability	1,718.7	[3]			1,718.7	[3]				1,544.4	[3]
Recurring [Member] | Fair Value [Member] | Future contracts [Member]
Derivatives, Liabilities
Derivative Liability										1.0	[3]
Recurring [Member] | Fair Value [Member] | Asset-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	1,587.2	[3]			1,587.2	[3]				1,523.1	[3]
Recurring [Member] | Fair Value [Member] | Commercial mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	486.6	[3]			486.6	[3]				454.4	[3]
Recurring [Member] | Fair Value [Member] | Corporates [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	10,522.1	[3]			10,522.1	[3]				9,418.3	[3]
Recurring [Member] | Fair Value [Member] | Hybrids [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	451.6	[3]			451.6	[3]				428.8	[3]
Recurring [Member] | Fair Value [Member] | Municipals [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	1,240.0	[3]			1,240.0	[3]				1,007.0	[3]
Recurring [Member] | Fair Value [Member] | Agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	99.4	[3]			99.4	[3]				98.6	[3]
Recurring [Member] | Fair Value [Member] | Non-agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	1,847.1	[3]			1,847.1	[3]				1,368.0	[3]
Recurring [Member] | Carrying Amount [Member]
Fixed maturity securities, available-for-sale:
Asset-backed loans	795.7				795.7					560.4
Total financial assets	926.2				926.2					591.6
Liabilities
Total debt	5,396.3	[5]			5,396.3	[5]				4,896.1	[5]
Derivatives, Liabilities
Redeemable preferred stock, excluding equity conversion feature	319.3				319.3					329.4
Investment contracts, included in contractholder funds	14,279.6				14,279.6					13,703.8
Financial Liabilities Fair Value Disclosure	19,995.2				19,995.2					18,929.3
Recurring [Member] | Equity [Member] | Fair Value [Member]
Fixed maturity securities, available-for-sale:
Equity securities - trading	131.8	[3]			131.8	[3]				81.5	[4]
Recurring [Member] | Policy loans [Member] | Fair Value [Member]
Fixed maturity securities, available-for-sale:
Policy loans and other invested assets	130.5				130.5					31.2
Recurring [Member] | Policy loans [Member] | Carrying Amount [Member]
Fixed maturity securities, available-for-sale:
Policy loans and other invested assets	130.5				130.5					31.2
Recurring [Member] | Level 1 [Member]
Assets
Cash and cash equivalents	1,319.8	[3],[4]			1,319.8	[3],[4]				1,899.7	[3],[4]
Contingent purchase price reduction receivable											[3]
Fixed maturity securities, available-for-sale:
Asset-backed loans
Total financial assets	0				0					0
Liabilities
Total debt		[5]				[5]				0	[5]
Derivatives, Liabilities
Equity conversion feature of preferred stock		[3]				[3]					[3]
Redeemable preferred stock, excluding equity conversion feature
Investment contracts, included in contractholder funds
Financial Liabilities Fair Value Disclosure	0				0					0
Recurring [Member] | Level 1 [Member] | U.S. Government securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	181.5	[3]			181.5	[3]				790.9	[3]
Recurring [Member] | Level 1 [Member] | Foreign exchange forward agreements [Member]
Derivatives, Assets
Derivatives		[3]				[3]					[3]
Derivatives, Liabilities
Derivative Liability		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Commodity Option [Member]
Derivatives, Assets
Derivatives		[3]				[3]					[3]
Derivatives, Liabilities
Derivative Liability		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Call options [Member]
Derivatives, Assets
Derivatives		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Available-for-sale embedded derivatives [Member]
Fixed maturity securities, available-for-sale:
Equity securities - available-for-sale		[3]				[3]					[4]
Recurring [Member] | Level 1 [Member] | FIA embedded derivatives, included in contractholder funds [Member]
Derivatives, Liabilities
Derivative Liability		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Future contracts [Member]
Derivatives, Liabilities
Derivative Liability											[3]
Recurring [Member] | Level 1 [Member] | Asset-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Commercial mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Corporates [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Hybrids [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Municipals [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Non-agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 1 [Member] | Equity [Member]
Fixed maturity securities, available-for-sale:
Equity securities - trading	121.0	[3]			121.0	[3]				70.8	[4]
Recurring [Member] | Level 1 [Member] | Policy loans [Member]
Fixed maturity securities, available-for-sale:
Policy loans and other invested assets
Recurring [Member] | Level 2 [Member]
Assets
Cash and cash equivalents		[3],[4]				[3],[4]				0	[3],[4]
Contingent purchase price reduction receivable											[3]
Fixed maturity securities, available-for-sale:
Asset-backed loans
Total financial assets	0				0					0
Liabilities
Total debt	5,488.1	[5]			5,488.1	[5]				4,773.2	[5]
Derivatives, Liabilities
Equity conversion feature of preferred stock		[3]				[3]					[3]
Redeemable preferred stock, excluding equity conversion feature
Investment contracts, included in contractholder funds
Financial Liabilities Fair Value Disclosure	5,488.1				5,488.1					4,773.2
Recurring [Member] | Level 2 [Member] | U.S. Government securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	211.1	[3]			211.1	[3]				210.9	[3]
Recurring [Member] | Level 2 [Member] | Foreign exchange forward agreements [Member]
Derivatives, Assets
Derivatives	2.1	[3]			2.1	[3]				1.8	[3]
Derivatives, Liabilities
Derivative Liability	7.2	[3]			7.2	[3]				10.0	[3]
Recurring [Member] | Level 2 [Member] | Commodity Option [Member]
Derivatives, Assets
Derivatives	0.4	[3]			0.4	[3]				4.1	[3]
Derivatives, Liabilities
Derivative Liability	5.1	[3]			5.1	[3]				2.4	[3]
Recurring [Member] | Level 2 [Member] | Call options [Member]
Derivatives, Assets
Derivatives	273.0	[3]			273.0	[3]				221.8	[3]
Recurring [Member] | Level 2 [Member] | Available-for-sale embedded derivatives [Member]
Fixed maturity securities, available-for-sale:
Equity securities - available-for-sale	353.1	[3]			353.1	[3]				271.0	[4]
Recurring [Member] | Level 2 [Member] | FIA embedded derivatives, included in contractholder funds [Member]
Derivatives, Liabilities
Derivative Liability		[3]				[3]					[3]
Recurring [Member] | Level 2 [Member] | Future contracts [Member]
Derivatives, Liabilities
Derivative Liability										1.0	[3]
Recurring [Member] | Level 2 [Member] | Asset-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	1,576.5	[3]			1,576.5	[3]				1,518.1	[3]
Recurring [Member] | Level 2 [Member] | Commercial mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	486.6	[3]			486.6	[3]				448.7	[3]
Recurring [Member] | Level 2 [Member] | Corporates [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	9,865.1	[3]			9,865.1	[3]				8,957.2	[3]
Recurring [Member] | Level 2 [Member] | Hybrids [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	451.6	[3]			451.6	[3]				428.8	[3]
Recurring [Member] | Level 2 [Member] | Municipals [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	1,204.4	[3]			1,204.4	[3]				1,007.0	[3]
Recurring [Member] | Level 2 [Member] | Agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	99.4	[3]			99.4	[3]				98.6	[3]
Recurring [Member] | Level 2 [Member] | Non-agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	1,847.1	[3]			1,847.1	[3]				1,368.0	[3]
Recurring [Member] | Level 2 [Member] | Equity [Member]
Fixed maturity securities, available-for-sale:
Equity securities - trading		[3]				[3]					[4]
Recurring [Member] | Level 2 [Member] | Policy loans [Member]
Fixed maturity securities, available-for-sale:
Policy loans and other invested assets
Recurring [Member] | Level 3 [Member]
Assets
Cash and cash equivalents		[3],[4]				[3],[4]					[3],[4]
Contingent purchase price reduction receivable	41.5	[3]			41.5	[3]				41.0	[3]
Fixed maturity securities, available-for-sale:
Asset-backed loans	795.7				795.7					560.4
Total financial assets	926.2				926.2					591.6
Liabilities
Total debt		[5]				[5]					[5]
Derivatives, Liabilities
Equity conversion feature of preferred stock	364.8	[3]			364.8	[3]				330.8	[3]
Redeemable preferred stock, excluding equity conversion feature	319.3				319.3					377.1
Investment contracts, included in contractholder funds	12,872.3				12,872.3					12,378.6
Financial Liabilities Fair Value Disclosure	13,191.6				13,191.6					12,755.7
Recurring [Member] | Level 3 [Member] | U.S. Government securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 3 [Member] | Foreign exchange forward agreements [Member]
Derivatives, Assets
Derivatives		[3]				[3]					[3]
Derivatives, Liabilities
Derivative Liability		[3]				[3]					[3]
Recurring [Member] | Level 3 [Member] | Commodity Option [Member]
Derivatives, Assets
Derivatives		[3]				[3]					[3]
Derivatives, Liabilities
Derivative Liability		[3]				[3]					[3]
Recurring [Member] | Level 3 [Member] | Call options [Member]
Derivatives, Assets
Derivatives		[3]				[3]					[3]
Recurring [Member] | Level 3 [Member] | Available-for-sale embedded derivatives [Member]
Fixed maturity securities, available-for-sale:
Equity securities - available-for-sale		[3]				[3]					[4]
Recurring [Member] | Level 3 [Member] | FIA embedded derivatives, included in contractholder funds [Member]
Derivatives, Liabilities
Derivative Liability	1,718.7	[3]			1,718.7	[3]				1,544.4	[3]
Recurring [Member] | Level 3 [Member] | Future contracts [Member]
Derivatives, Liabilities
Derivative Liability											[3]
Recurring [Member] | Level 3 [Member] | Asset-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	10.7	[3]			10.7	[3]				5.0	[3]
Recurring [Member] | Level 3 [Member] | Commercial mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	0	[3]			0	[3]				5.7	[3]
Recurring [Member] | Level 3 [Member] | Corporates [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	657.0	[3]			657.0	[3]				461.1	[3]
Recurring [Member] | Level 3 [Member] | Hybrids [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	0	[3]			0	[3]					[3]
Recurring [Member] | Level 3 [Member] | Municipals [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities	35.6	[3]			35.6	[3]					[3]
Recurring [Member] | Level 3 [Member] | Agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 3 [Member] | Non-agency residential mortgage-backed securities [Member]
Fixed maturity securities, available-for-sale:
Available-for-sale Securities		[3]				[3]					[3]
Recurring [Member] | Level 3 [Member] | Equity [Member]
Fixed maturity securities, available-for-sale:
Equity securities - trading	10.8	[3]			10.8	[3]				10.7	[4]
Recurring [Member] | Level 3 [Member] | Policy loans [Member]
Fixed maturity securities, available-for-sale:
Policy loans and other invested assets	130.5				130.5					31.2
Contingent purchase price reduction receivable [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	41.5		41.0		41.5		41.0		41.5	41.0		41.0	41.0
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					0.5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net		[1]		[2]		[1]		[2]
FIA embedded derivatives, included in contractholder funds [Member]
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	1,718.7		1,639.6		1,718.7		1,639.6		1,644.7	1,544.4		1,517.0	1,550.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	74.0		122.6		174.3		88.8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net		[1]		[2]		[1]		[2]
Front Street Future Policyholder Benefits Reserve [Member]
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	151.0				151.0				149.9	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	3.7				3.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)					0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases					150.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales					0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	(2.6)				2.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net		[1]			0	[1]
Equity conversion feature of preferred stock [Member]
Derivatives, Liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	364.8		202.7		364.8		202.7		378.0	330.8		163.1	232.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	3.5		39.6		50.7		(29.3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	(16.7)				(16.7)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net		[1]		[2]		[1]		[2]

[1] This includes a $6.0 transfer to asset-backed securities from commercial mortgage-backed securities, the remaining transfers were from level 3 to level 2.

[2] (a)The net transfers in and out of Level 3 during the six months ended March 31, 2013 were exclusively to or from Level 2.

[3] The carrying amounts of trade receivables, accounts payable, accrued investment income and portions of other insurance liabilities approximate fair value due to their short duration and, accordingly, they are not presented in the tables above.

[4] The fair values of cash equivalents and equity investments set forth above are generally based on quoted or observed market prices.

[5] (a)