Financial Data by Segment (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net earned premiums		$ 286,131	$ 264,358
Net losses and LAE		(169,600)	(152,956)
Commission expenses		(47,844)	(37,554)
Other operating expenses		(58,538)	(60,809)
Other underwriting income (expense)		21	9
Underwriting profit (loss)		10,170	13,048
Net investment income		21,448	19,594
Net realized gains (losses)		(44)	1,597
Interest expense		(3,861)	(3,858)
Other income		1,047	2,540
Income before income taxes		28,760	32,921
Income tax expense		(7,650)	(9,989)
Net income		$ 21,110	$ 22,932
Losses and LAE ratio		59.30%	57.90%
Commission expense ratio		16.70%	14.20%
Other operating expense ratio	[1]	20.40%	23.00%
Combined ratio		96.40%	95.10%
Goodwill and other intangible assets		$ 6,442	$ 6,746	$ 6,451
U.S.Insurance
Segment Reporting Information [Line Items]
Net earned premiums		164,004	148,340
Net losses and LAE		(98,826)	(91,512)
Commission expenses		(20,384)	(14,855)
Other operating expenses		(33,472)	(33,761)
Other underwriting income (expense)		110	361
Underwriting profit (loss)		11,432	8,573
Income before income taxes		$ 11,432	$ 8,573
Losses and LAE ratio		60.30%	61.70%
Commission expense ratio		12.40%	10.00%
Other operating expense ratio	[1]	20.30%	22.50%
Combined ratio		93.00%	94.20%
Goodwill and other intangible assets		$ 2,534	$ 2,534
International Insurance
Segment Reporting Information [Line Items]
Net earned premiums		84,086	78,008
Net losses and LAE		(50,705)	(40,410)
Commission expenses		(19,233)	(15,355)
Other operating expenses		(19,793)	(21,771)
Underwriting profit (loss)		(5,645)	472
Income before income taxes		$ (5,645)	$ 472
Losses and LAE ratio		60.30%	51.80%
Commission expense ratio		22.90%	19.70%
Other operating expense ratio	[1]	23.50%	27.90%
Combined ratio		106.70%	99.40%
Goodwill and other intangible assets		$ 3,908	$ 4,212
Global Reinsurance
Segment Reporting Information [Line Items]
Net earned premiums		38,041	38,010
Net losses and LAE		(20,069)	(21,034)
Commission expenses		(8,492)	(7,745)
Other operating expenses		(5,273)	(5,277)
Other underwriting income (expense)		176	49
Underwriting profit (loss)		4,383	4,003
Income before income taxes		$ 4,383	$ 4,003
Losses and LAE ratio		52.80%	55.30%
Commission expense ratio		22.30%	20.40%
Other operating expense ratio	[1]	13.40%	13.80%
Combined ratio		88.50%	89.50%
Corporate
Segment Reporting Information [Line Items]
Net investment income	[2]	$ 21,448	$ 19,594
Net realized gains (losses)	[2]	(44)	1,597
Interest expense	[2]	(3,861)	(3,858)
Other income	[2]	1,047	2,540
Income before income taxes	[2]	18,590	19,873
Income tax expense	[2]	(7,650)	(9,989)
Intersegment Elimination
Segment Reporting Information [Line Items]
Commission expenses	[2]	265	401
Other underwriting income (expense)	[2]	$ (265)	$ (401)

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

[2] Includes Corporate segment intercompany eliminations.