Reconciliations of Changes in Level Three Assets Measured at Fair Value (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended																							3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014 Common Stock	Sep. 30, 2014 Debt Securities U.S. corporate bonds		Sep. 30, 2013 Debt Securities U.S. corporate bonds		Sep. 30, 2014 Debt Securities Foreign corporate bonds	Sep. 30, 2013 Debt Securities Foreign corporate bonds	Sep. 30, 2014 Debt Securities Mortgage and asset backed securities RMBS		Sep. 30, 2013 Debt Securities Mortgage and asset backed securities RMBS		Sep. 30, 2014 Debt Securities Mortgage and asset backed securities CMBS		Sep. 30, 2013 Debt Securities Mortgage and asset backed securities CMBS		Sep. 30, 2014 Debt Securities Mortgage and asset backed securities Other asset-backed securities		Sep. 30, 2013 Debt Securities Mortgage and asset backed securities Other asset-backed securities		Sep. 30, 2013 Other invested assets		Sep. 30, 2014 Other invested assets		Sep. 30, 2013 Other invested assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance		$ 708.5		$ 214.3			$ 27.5		$ 30.4		$ 1.0		$ 78.8		$ 59.6		$ 60.8		$ 76.1		$ 258.4		$ 5.9				$ 282.0	[1]	$ 42.3	[1]
Net realized/unrealized gains (losses) included in:
Net earnings		3.6	[2]	2.3	[2]		(0.9)	[2]	0.3	[2]			4.1	[2]	1.6	[2]	(0.3)	[2]	0.1	[2]	0.5	[2]	0.1	[2]			0.2	[1],[2]	0.2	[1],[2]
Other comprehensive income		(4.6)		7.0			(0.3)		(0.6)				2.5		4.2		(1.3)		0.1		(6.9)		(0.3)				1.4	[1]	3.6	[1]
Purchases		781.1		371.5		4.5	21.6				2.5						22.0		20.3		730.5		1.2						350.0	[1]
Sales		(104.3)		(34.6)			(9.0)		(23.8)		(1.2)		(12.2)				(3.0)		(10.8)		(78.7)						(0.2)	[1]
Issuances																												[1]		[1]
Settlements		(91.0)		(27.2)			(7.6)		(0.7)		(1.5)		(8.3)		(7.8)		(41.4)		(9.5)		(11.2)		(2.2)				(21.0)	[1]	(7.0)	[1]
Transfers into Level 3	6.3	44.4		21.7			15.0				0.3				21.3				0.1		29.1		0.3
Transfers out of Level 3		(238.1)		(100.0)																					(100.0)		(238.1)	[1]	(100.0)	[1]
Ending balance	$ 1,099.6	$ 1,099.6		$ 455.0		$ 4.5	$ 46.3		$ 5.6		$ 1.1		$ 64.9		$ 78.9		$ 36.8		$ 76.4		$ 921.7		$ 5.0		$ 289.1	[1]	$ 24.3	[1]	$ 289.1	[1]

[1] Includes partnership and certain non-marketable equity investments accounted for on an AFS basis.

[2] There were no other than temporary impairment ("OTTI") losses recorded in net earnings related to Level 3 investments still held as of September 30, 2014 and 2013.