Statutory Financial Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
United States Traditional Insurance Subsidiaries [Member]
Statutory Accounting Practices [Line Items]
Statutory Net Income	$ 584.5	$ 624.5	$ 642.9
Statutory Combined Net Gain from Operations	617.5	649.8	664.0
CaptiveReinsurers [Domain]
Statutory Accounting Practices [Line Items]
Statutory Net Income	13.3	40.8	64.6
Statutory Combined Net Gain from Operations	$ 13.6	$ 37.4	$ 55.4