Net Investment Income (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Net Investment Income [Line Items]
Interest income	$ 348,000,000		$ 306,100,000	$ 100,000,000
Dividend income	59,600,000		24,900,000	37,800,000
Investment expenses	(20,300,000)		(16,800,000)	(6,800,000)
Other investment results	200,000		10,200,000	(1,200,000)
Net investment income	465,664,000		312,998,000	108,910,000
Homesite
Net Investment Income [Line Items]
Equity results	42,900,000		(6,900,000)	(20,200,000)
ORX
Net Investment Income [Line Items]
Equity results	(1,000,000)		(4,500,000)	(700,000)
Pillar Holdings and Funds | Pillar Capital Holdings Limited And Managed Funds
Net Investment Income [Line Items]
Equity results	27,200,000	[1]
Ares Management Limited Liability Company
Net Investment Income [Line Items]
Net investment income	$ 9,100,000	[1]

[1] See Note 4(h) for discussion of the Pillar Investments and the investment in Ares.