Reconciliations of Changes in Level Three Assets Measured at Fair Value (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 214.3		$ 23.6
Net realized/unrealized gains (losses) included in:
Net earnings	3.8	[1]	5.9	[1]
Other comprehensive income	8.6		12.5
Purchases	500.1	[2]	152.0	[2]
Sales	(45.2)		(6.5)
Issuances
Settlements	(46.2)		(15.1)
Transfers into Level 3	173.1	[3]	41.9	[3]
Transfers out of Level 3	(100.0)
Ending balance	708.5		214.3
Debt Securities | Foreign corporate bonds
Net realized/unrealized gains (losses) included in:
Purchases	1.0	[2]
Issuances
Ending balance	1.0
Debt Securities | U.S. corporate bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	30.4
Net realized/unrealized gains (losses) included in:
Net earnings	0.3	[1]	(0.1)	[1]
Other comprehensive income	(0.5)		0.7
Purchases	22.9	[2]	31.5	[2]
Sales	(23.8)
Issuances
Settlements	(1.8)		(1.7)
Ending balance	27.5		30.4
Debt Securities | Mortgage and asset backed securities | RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	59.6
Net realized/unrealized gains (losses) included in:
Net earnings	2.9	[1]	5.1	[1]
Other comprehensive income	5.7		7.9
Purchases			55.1	[2]
Issuances
Settlements	(10.7)		(8.5)
Transfers into Level 3	21.3	[3]
Ending balance	78.8		59.6
Debt Securities | Mortgage and asset backed securities | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	76.1
Net realized/unrealized gains (losses) included in:
Net earnings	0.1	[1]	1.0	[1]
Other comprehensive income	(0.4)
Purchases	22.9	[2]	37.2	[2]
Sales	(21.4)
Issuances
Settlements	(16.6)		(4.0)
Transfers into Level 3	0.1	[3]	41.9	[3]
Ending balance	60.8		76.1
Debt Securities | Mortgage and asset backed securities | Other asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	5.9
Net realized/unrealized gains (losses) included in:
Net earnings	0.2	[1]	0.1	[1]
Other comprehensive income	(0.5)		0.2
Purchases	103.3	[2]	6.5	[2]
Issuances
Settlements	(2.2)		(0.9)
Transfers into Level 3	151.7	[3]
Ending balance	258.4		5.9
Other invested assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	42.3	[4]	23.6	[4]
Net realized/unrealized gains (losses) included in:
Net earnings	0.3	[1],[4]	(0.2)	[1],[4]
Other comprehensive income	4.3	[4]	3.7	[4]
Purchases	350.0	[2],[4]	21.7	[2],[4]
Sales			(6.5)	[4]
Issuances		[4]		[4]
Settlements	(14.9)	[4]
Transfers out of Level 3	(100.0)	[4]
Ending balance	$ 282.0	[4]	$ 42.3	[4]

[1] There were no OTTI losses recorded in net earnings related to level 3 instruments still held as of December 31, 2013 and 2012.

[2] For 2013, principally due to an investment in Ares Management LLC ("Ares"); See note 4(h) for a more detailed description of this investment. For 2012, principally consists of Level 3 assets acquired as part of the merger.

[3] Principally due to a decrease in observable inputs related to the valuation of such securities.

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