Financial Data by Segment (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Net earned premiums		$ 264,358	$ 236,132
Net losses and LAE		(152,956)	(130,198)
Commission expenses		(37,554)	(32,905)
Other operating expenses		(60,809)	(54,909)
Other underwriting income (expense)		9	55
Underwriting profit (loss)		13,048	18,175
Net investment income		19,594	16,253
Net realized gains (losses)		1,597	5,596
Interest expense		(3,858)	(3,855)
Other income (loss)		2,540	2,187
Income before income taxes		32,921	38,356
Income tax (expense) benefit		(9,989)	(12,427)
Net income		$ 22,932	$ 25,929
Losses and LAE ratio		57.90%	55.10%
Commission expense ratio		14.20%	13.90%
Other operating expense ratio	[1]	23.00%	23.30%
Combined ratio		95.10%	92.30%
U.S.Insurance
Segment Reporting Information [Line Items]
Net earned premiums		$ 148,340	$ 131,091
Net losses and LAE		(91,512)	(77,799)
Commission expenses		(14,855)	(14,345)
Other operating expenses		(33,761)	(33,688)
Other underwriting income (expense)		361	196
Underwriting profit (loss)		8,573	5,455
Income before income taxes		$ 8,573	$ 5,455
Losses and LAE ratio		61.70%	59.30%
Commission expense ratio		10.00%	10.90%
Other operating expense ratio	[1]	22.50%	25.60%
Combined ratio		94.20%	95.80%
International Insurance
Segment Reporting Information [Line Items]
Net earned premiums		$ 78,008	$ 65,525
Net losses and LAE		(40,410)	(29,691)
Commission expenses		(15,355)	(11,413)
Other operating expenses		(21,771)	(17,009)
Underwriting profit (loss)		472	7,412
Income before income taxes		$ 472	$ 7,412
Losses and LAE ratio		51.80%	45.30%
Commission expense ratio		19.70%	17.40%
Other operating expense ratio	[1]	27.90%	26.00%
Combined ratio		99.40%	88.70%
Global Reinsurance
Segment Reporting Information [Line Items]
Net earned premiums		$ 38,010	$ 39,516
Net losses and LAE		(21,034)	(22,708)
Commission expenses		(7,745)	(7,298)
Other operating expenses		(5,277)	(4,212)
Other underwriting income (expense)		49	10
Underwriting profit (loss)		4,003	5,308
Income before income taxes		$ 4,003	$ 5,308
Losses and LAE ratio		55.30%	57.50%
Commission expense ratio		20.40%	18.50%
Other operating expense ratio	[1]	13.80%	10.60%
Combined ratio		89.50%	86.60%
Corporate
Segment Reporting Information [Line Items]
Commission expenses	[2]	$ 401	$ 151
Other underwriting income (expense)	[2]	(401)	(151)
Net investment income	[2]	19,594	16,253
Net realized gains (losses)	[2]	1,597	5,596
Interest expense	[2]	(3,858)	(3,855)
Other income (loss)	[2]	2,540	2,187
Income before income taxes	[2]	19,873	20,181
Income tax (expense) benefit	[2]	$ (9,989)	$ (12,427)

[1] Includes Other operating expenses and Other underwriting income (expense).

[2] Includes Corporate segment intercompany eliminations.