Reinsurance - Additional Information (Detail)	Dec. 31, 2011
Number of companies that make up reinsurance recoverable	91
Number of companies that make up majority of reinsurance recoverable	14
Percent of reinsurance recoverable made up by majority of companies	92.00%
Remaining companies rated A- or better by AM best	7.00%
Percent of recoverable held with companies less than A-	1.00%