Reinsurance Balances Recoverable - Reinsurance Balances Recoverable by Reinsurer (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Ceded Credit Risk [Line Items]
Reinsurance balances recoverable	$ 1,256,230	$ 1,363,819
% of Total	100.00%	100.00%
Ceded Credit Risk, Concentrated Credit Risk [Member] | Top Ten Reinsurers [Member]
Ceded Credit Risk [Line Items]
Reinsurance balances recoverable	862,124	930,943
% of Total	68.60%	68.30%
Ceded Credit Risk, Not Concentrated Credit Risk [Member] | Other Reinsurers' Balances Greater Than $1 Million [Member]
Ceded Credit Risk [Line Items]
Reinsurance balances recoverable	386,362	423,013
% of Total	30.80%	31.00%
Ceded Credit Risk, Not Concentrated Credit Risk [Member] | Other Reinsurers' Balances Less Than $1 Million [Member]
Ceded Credit Risk [Line Items]
Reinsurance balances recoverable	$ 7,744	$ 9,863
% of Total	0.60%	0.70%