Commitments and Contingent Liabilities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments and Contingencies Disclosure [Line Items]
Operating Leases, Future Minimum Payments Due	$ 213.9
Operating Leases, Future Minimum Payments Due, Next Twelve Months	40.7
Operating Leases, Future Minimum Payments, Due in Two Years	27.9
Operating Leases, Future Minimum Payments, Due in Three Years	22.4
Operating Leases, Future Minimum Payments, Due in Four Years	17.7
Operating Leases, Future Minimum Payments, Due in Five Years	16.6
Operating Leases, Future Minimum Payments, Due Thereafter	88.6
Operating Leases, Rent Expense, Minimum Rentals	44.1	41.6	36.1
Commitment to fund partnership Equity Investments	158.4
Commitment to fund private placement fixed maturity securities	58.0
Committments to Fund Commercial Mortgage Loans	83.9
Interest on undrawn retained asset account funds			18.00%
Loss Contingency, Damages Awarded, Value	12.1
Loss Contingency, Prejudgment Interest Awarded	$ 1.3