Reinsurance Balances Recoverable - Summary of Reinsurance Reserves Recoverable (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Effects of Reinsurance [Line Items]
Recoverable from reinsurers on outstanding losses	$ 778,663	$ 828,038
Recoverable from reinsurers on losses incurred but not reported	359,068	413,344
Recoverable from reinsurers on fair value adjustments	(55,020)	(65,456)
Total reinsurance reserves recoverable	1,082,711	1,175,926
Paid losses recoverable	173,519	187,893
Total reinsurance recoverable	1,256,230	1,363,819
Non-Life Run-Off [Member]
Effects of Reinsurance [Line Items]
Recoverable from reinsurers on outstanding losses	741,055	788,705
Recoverable from reinsurers on losses incurred but not reported	346,518	402,675
Recoverable from reinsurers on fair value adjustments	(59,411)	(69,847)
Total reinsurance reserves recoverable	1,028,162	1,121,533
Paid losses recoverable	168,756	177,459
Total reinsurance recoverable	1,196,918	1,298,992
Active Underwriting [Member]
Effects of Reinsurance [Line Items]
Recoverable from reinsurers on outstanding losses	9,436	10,777
Recoverable from reinsurers on losses incurred but not reported	11,799	9,887
Recoverable from reinsurers on fair value adjustments	4,391	4,391
Total reinsurance reserves recoverable	25,626	25,055
Paid losses recoverable	1,129	7,845
Total reinsurance recoverable	26,755	32,900
Life and Annuities [Member]
Effects of Reinsurance [Line Items]
Recoverable from reinsurers on outstanding losses	28,172	28,556
Recoverable from reinsurers on losses incurred but not reported	751	782
Recoverable from reinsurers on fair value adjustments
Total reinsurance reserves recoverable	28,923	29,338
Paid losses recoverable	3,634	2,589
Total reinsurance recoverable	$ 32,557	$ 31,927