Acquisitions - Summary of Pro Forma Adjustments to Pro Forma Condensed Statement of Earnings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements
Business Acquisition [Line Items]
Total income	$ 1,106,558	$ 1,175,187
Total expenses	(903,676)	(1,058,312)
Total noncontrolling interest	9,950	(13,487)
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements | Scenario, Adjustment
Business Acquisition [Line Items]
Total income	9,494
Total expenses	5,894	(3,026)
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements | Scenario, Adjustment | Reversal of Amortization of Fair Value Adjustments Related to Unearned Premiums
Business Acquisition [Line Items]
Total income	13,344
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements | Scenario, Adjustment | Amortization of Fair Value Adjustment to Unearned Premium
Business Acquisition [Line Items]
Total income	(3,850)	(14,557)
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements | Scenario, Adjustment | Adjustment to Interest Expense to Reflect Financing Costs of the Acquisition
Business Acquisition [Line Items]
Total expenses	(1,098)	(5,744)
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements | Scenario, Adjustment | Amortization of Fair Value Adjustments Related To Acquired Losses And Loss Adjustment Expense Liabilities And Reinsurance Balances Recoverable
Business Acquisition [Line Items]
Total expenses	(451)	(5,417)
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements | Scenario, Adjustment | Reversal of Amortization of Fair Value Adjustments Related to Acquisition Costs
Business Acquisition [Line Items]
Total expenses	16,173
Sussex Insurance Company, National Suisse Assurance S.A., and Wilton Relife Settlements | Scenario, Adjustment | Adjustments to Income Taxes Pro Forma Adjustments
Business Acquisition [Line Items]
Total expenses	$ (8,730)	8,135
StarStone
Business Acquisition [Line Items]
Total income		1,004,864	$ 1,042,886
Total expenses		(774,090)	(885,770)
Total noncontrolling interest		(14,938)	12,145
StarStone | Scenario, Adjustment
Business Acquisition [Line Items]
Total expenses		3,670	14,678
Total noncontrolling interest		(1,451)	27,363
StarStone | Scenario, Adjustment | Amortization of Fair Value Adjustment to Unearned Premium
Business Acquisition [Line Items]
Total income		(1,846)	(7,384)
StarStone | Scenario, Adjustment | Amortization of Finite Live Intangible Assets
Business Acquisition [Line Items]
Total expenses		(1,146)	(4,583)
StarStone | Scenario, Adjustment | Amortization of Fair Value Adjustments Related To Acquired Losses And Loss Adjustment Expense Liabilities And Reinsurance Balances Recoverable
Business Acquisition [Line Items]
Total expenses		$ 4,816	$ 19,261