Reinsurance Recoverables (Detail) (USD $)	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009		Dec. 31, 2008
Ceded Credit Risk [Line Items]
Reinsurance recoverables on paid losses	$ 21,000,000		$ 25,900,000
Ceded outstanding loss and loss adjustment expenses	831,800,000	[1]	847,400,000	[1]	947,700,000	[1]	1,008,300,000	[1]
Reinsurance Recoverable	$ 852,845,000	[2],[3]	$ 873,295,000

[1] Reinsurance recoverables in this table include only ceded loss reserves.

[2] Approximately 99.0 percent of AIHL's reinsurance recoverables balance as of December 31, 2011 was due from reinsurers having an A.M. Best financial strength rating of A (Excellent) or higher.

[3] Reinsurance recoverables reflect amounts due from one or more reinsurance subsidiaries of the listed company.