Losses and Loss Adjustment Expenses - Net (Reduction) Increase in Ultimate Losses and Loss Adjustment Expense Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Effects of Reinsurance [Line Items]
Net (reduction) increase in ultimate losses and loss adjustment expense liabilities, Current Period	$ (29,182)
Net losses paid	100,522	83,674
Net change in case and LAE reserves	(61,623)	(57,500)
Net change in IBNR reserves	(33,879)	(2,702)
(Reduction) increase in estimates of net ultimate losses	(5,020)	23,472
Reduction in provisions for unallocated loss adjustment expense liabilities	(13,307)	(16,404)
Amortization of fair value adjustments	(3,764)	2,093
Total net (reduction) increase in ultimate losses and loss adjustment expense liabilities	(12,051)	9,161
Non-Life Run-Off [Member]
Effects of Reinsurance [Line Items]
Net (reduction) increase in ultimate losses and loss adjustment expense liabilities, Current Period	(29,182)	9,161
Net losses paid	87,687	83,674
Net change in case and LAE reserves	(62,398)	(57,500)
Net change in IBNR reserves	(37,348)	(2,702)
(Reduction) increase in estimates of net ultimate losses	(12,059)	23,472
Reduction in provisions for unallocated loss adjustment expense liabilities	(13,359)	(16,404)
Amortization of fair value adjustments	(3,764)	2,093
Total net (reduction) increase in ultimate losses and loss adjustment expense liabilities	(29,182)	9,161
Active Underwriting [Member]
Effects of Reinsurance [Line Items]
Net losses paid, Prior Period	8,151
Net change in case and LAE reserves, Prior Period	(3,985)
Net change in IBNR reserves, Prior Period	(8,401)
(Reduction) increase in estimates of net ultimate losses, Prior Period	(4,235)
Reduction in provisions for unallocated loss adjustment expense liabilities, Prior Period	52
Net (reduction) increase in ultimate losses and loss adjustment expense liabilities, Prior Period	(4,183)
Net losses paid, Current Period	4,684
Net change in case and LAE reserves, Current Period	4,760
Net change in IBNR reserves, Current Period	11,870
(Reduction) increase in estimates of net ultimate losses, Current Period	21,314
Reduction in provisions for unallocated loss adjustment expense liabilities, Current Period
Net (reduction) increase in ultimate losses and loss adjustment expense liabilities, Current Period	21,314
Net losses paid	12,835
Net change in case and LAE reserves	775
Net change in IBNR reserves	3,469
(Reduction) increase in estimates of net ultimate losses	17,079
Reduction in provisions for unallocated loss adjustment expense liabilities	52
Amortization of fair value adjustments
Total net (reduction) increase in ultimate losses and loss adjustment expense liabilities	17,131
Non-Life Run-Off Segment [Member]
Effects of Reinsurance [Line Items]
Net losses paid, Prior Period	87,155	81,134
Net change in case and LAE reserves, Prior Period	(63,249)	(62,745)
Net change in IBNR reserves, Prior Period	(37,397)	(23,450)
(Reduction) increase in estimates of net ultimate losses, Prior Period	(13,491)	(5,061)
Reduction in provisions for unallocated loss adjustment expense liabilities, Prior Period	(13,359)	(16,404)
Amortization of fair value adjustments, Prior Period	(3,764)	2,093
Net (reduction) increase in ultimate losses and loss adjustment expense liabilities, Prior Period	(30,614)	(19,372)
Net losses paid, Current Period	532	2,540
Net change in case and LAE reserves, Current Period	851	5,245
Net change in IBNR reserves, Current Period	49	20,748
(Reduction) increase in estimates of net ultimate losses, Current Period	1,432	28,533
Reduction in provisions for unallocated loss adjustment expense liabilities, Current Period
Amortization of fair value adjustments, Current Period
Net (reduction) increase in ultimate losses and loss adjustment expense liabilities, Current Period	1,432	28,533
Net losses paid	87,687	83,674
Net change in case and LAE reserves	(62,398)	(57,500)
Net change in IBNR reserves	(37,348)	(2,702)
(Reduction) increase in estimates of net ultimate losses	(12,059)	23,472
Reduction in provisions for unallocated loss adjustment expense liabilities	(13,359)	(16,404)
Amortization of fair value adjustments	(3,764)	2,093
Total net (reduction) increase in ultimate losses and loss adjustment expense liabilities	$ (29,182)	$ 9,161