Derivative Instruments (Detail) - Hedged Items - Amount of Gain/(Loss) Recognized in Income Attributable to Risk (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Gain Loss Recognized In Income On Derivative [Member]
Interest rate exposure	$ (5,457)	$ (874)
Foreign exchange exposure	(15,100)	(20,425)
Total	(20,557)	(21,299)
Deposit Liabilities [Member]
Total	3,607	2,381
Fixed Maturity Investments [Member]
Total	14,511	20,139
Notes Payable and Debt [Member]
Total	$ (2,439)	$ 1,221