Fair Value of Financial Instruments - Schedule of Unobservable Inputs Used for Level Three Fair Value Measurements of Financial Instruments on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended								3 Months Ended					3 Months Ended			3 Months Ended				3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2013 Equity Securities [Member]	Sep. 30, 2013 Equity Securities [Member]	Dec. 31, 2013 Broker Quoted [Member] Municipal Bonds [Member]	Dec. 31, 2013 Option Pricing [Member] Equity Securities [Member]	Dec. 31, 2013 Broker Quoted [Member] Asset-backed securities [Member]	Sep. 30, 2013 Broker Quoted [Member] Asset-backed securities [Member]	Dec. 31, 2013 Broker Quoted [Member] Commercial mortgage-backed securities [Member]	Sep. 30, 2013 Broker Quoted [Member] Commercial mortgage-backed securities [Member]	Dec. 31, 2013 Broker Quoted [Member] Corporates [Member]	Sep. 30, 2013 Broker Quoted [Member] Corporates [Member]	Dec. 31, 2013 Market pricing [Member] Corporates [Member]	Sep. 30, 2013 Market pricing [Member] Corporates [Member]	Dec. 31, 2013 Market pricing [Member] Municipal Bonds [Member]	Dec. 31, 2013 Contingent purchase price reduction receivable [Member]	Sep. 30, 2013 Contingent purchase price reduction receivable [Member]	Dec. 31, 2013 Contingent purchase price reduction receivable [Member] Discounted cash flow [Member]	Dec. 31, 2013 Fixed Index Annuity [Member]	Sep. 30, 2013 Fixed Index Annuity [Member]	Dec. 31, 2013 Fixed Index Annuity [Member] Discounted cash flow [Member]	Dec. 31, 2013 Front Street Future Policyholder Benefits Reserve [Member]	Dec. 31, 2013 Equity conversion feature of preferred stock [Member]	Sep. 30, 2013 Equity conversion feature of preferred stock [Member]	Dec. 31, 2013 Equity conversion feature of preferred stock [Member] Monte Carlo simulation / Option model [Member]	Dec. 31, 2013 Minimum [Member] Asset-backed securities [Member]	Dec. 31, 2012 Minimum [Member] Asset-backed securities [Member]	Dec. 31, 2013 Minimum [Member] Corporates [Member]	Dec. 31, 2012 Minimum [Member] Corporates [Member]	Dec. 31, 2012 Minimum [Member] Hybrids [Member]	Dec. 31, 2013 Minimum [Member] Equity Securities [Member]	Dec. 31, 2013 Minimum [Member] Contingent purchase price reduction receivable [Member]	Dec. 31, 2012 Minimum [Member] Contingent purchase price reduction receivable [Member]	Dec. 31, 2013 Minimum [Member] Fixed Index Annuity [Member]	Dec. 31, 2012 Minimum [Member] Fixed Index Annuity [Member]	Dec. 31, 2013 Minimum [Member] Equity conversion feature of preferred stock [Member]	Dec. 31, 2012 Minimum [Member] Equity conversion feature of preferred stock [Member]	Dec. 31, 2013 Maximum [Member] Asset-backed securities [Member]	Dec. 31, 2012 Maximum [Member] Asset-backed securities [Member]	Dec. 31, 2012 Maximum [Member] Commercial mortgage-backed securities [Member]	Dec. 31, 2013 Maximum [Member] Corporates [Member]	Dec. 31, 2012 Maximum [Member] Corporates [Member]	Dec. 31, 2012 Maximum [Member] Hybrids [Member]	Dec. 31, 2013 Maximum [Member] Equity Securities [Member]	Dec. 31, 2013 Maximum [Member] Contingent purchase price reduction receivable [Member]	Dec. 31, 2012 Maximum [Member] Contingent purchase price reduction receivable [Member]	Dec. 31, 2013 Maximum [Member] Fixed Index Annuity [Member]	Dec. 31, 2012 Maximum [Member] Fixed Index Annuity [Member]	Dec. 31, 2013 Maximum [Member] Equity conversion feature of preferred stock [Member]	Dec. 31, 2012 Maximum [Member] Equity conversion feature of preferred stock [Member]	Dec. 31, 2013 Weighted Average [Member]	Dec. 31, 2013 Weighted Average [Member] Asset-backed securities [Member]	Dec. 31, 2012 Weighted Average [Member] Asset-backed securities [Member]	Dec. 31, 2013 Weighted Average [Member] Commercial mortgage-backed securities [Member]	Dec. 31, 2013 Weighted Average [Member] Corporates [Member]	Dec. 31, 2012 Weighted Average [Member] Corporates [Member]	Dec. 31, 2013 Weighted Average [Member] Municipal Debt Securities [Member]	Dec. 31, 2013 Weighted Average [Member] Hybrids [Member]	Dec. 31, 2012 Weighted Average [Member] Hybrids [Member]	Dec. 31, 2013 Weighted Average [Member] Equity Securities [Member]	Dec. 31, 2013 Weighted Average [Member] Contingent purchase price reduction receivable [Member]	Dec. 31, 2012 Weighted Average [Member] Contingent purchase price reduction receivable [Member]	Dec. 31, 2013 Weighted Average [Member] Fixed Index Annuity [Member]	Dec. 31, 2012 Weighted Average [Member] Fixed Index Annuity [Member]	Dec. 31, 2013 Weighted Average [Member] Equity conversion feature of preferred stock [Member]	Dec. 31, 2012 Weighted Average [Member] Equity conversion feature of preferred stock [Member]	Dec. 31, 2013 Front Street Future Policyholder Benefits Reserve [Member] Minimum [Member]	Dec. 31, 2013 Front Street Future Policyholder Benefits Reserve [Member] Maximum [Member]	Dec. 31, 2013 Front Street Future Policyholder Benefits Reserve [Member] Weighted Average [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Document Period End Date	Dec. 31, 2013
Valuation Technique					Broker-quoted	Option Pricing	Broker-quoted						Market Pricing					Discounted cash flow			Discounted cash flow				Monte Carlo simulation / Option model
Assets, Fair Value Disclosure	$ 709.5	$ 523.5	$ 10.8	$ 10.7			$ 9.8	$ 5.0	$ 6.0	$ 5.7	$ 540.9	$ 404.5	$ 66.2	$ 56.6	$ 34.3	$ 41.5	$ 41.0
Probability of collection																																88.00%	88.00%												96.00%	96.00%															92.00%	92.00%
Expected term																																													6 months	9 months
Discount rate																																													1.00%	1.00%
Credit insurance risk premium																																													11.00%	11.00%
Quoted prices																												0.00%	0.00%												132.00%	113.00%													92.00%	90.00%			0.00%
Fair Value Measurements Revenue Multiple																															0.3													0.4
Offered quotes																										98.00%	100.00%	91.00%	90.00%									107.00%	107.00%	96.00%	115.00%	131.00%										101.00%	101.00%	102.00%	99.00%	97.00%	98.00%	25.00%
Fair Value Measurements Probability of Transaction																																																												95.00%
Fair Value Inputs, Risk-free Discount Factor																																																			0.999
Fair Value Inputs, Risk-adjusted Discount Factor																																																			0.995
Fair Value Inputs, Upward Movement																																																			1.1
Fair Value Inputs, Downward Movement																																																			0.9
Fair Value Inputs, Probability of Upward Movement																																																			48.60%
Fair Value Inputs, Probability of Downward Movement																																																			51.40%
Liabilities
Liabilities, Fair Value Disclosure	$ 2,172.6	$ 1,875.2																	$ 1,644.7	$ 1,544.4		$ 149.9	$ 378.0	$ 330.8
Market value of option																																		0.00%	0.00%												43.00%	38.00%															5.00%	4.00%
SWAP rates																																		2.00%	2.00%												3.00%	3.00%															2.00%	2.00%
Mortality multiplier																																																															80.00%	80.00%
Surrender rates																																		0.50%	0.50%												75.00%	75.00%															7.00%	7.00%
Non-performance spread																																			0.25%													0.25%															0.25%	0.25%			0.65%	1.50%
Fair Value Measurements Liquidity Spread																																																																					0.50%
Annualized volatility of equity																																																																	40.00%	42.00%
Discount yield																																																																	11.00%	11.00%
Non-cash accretion rate																																																	0.00%	0.00%
Calibration adjustment																																				0.00%	0.00%												1.00%	1.00%															0.00%	0.30%