Summary of Securities with Gross Unrealized Losses (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 135,832		$ 347,857
Less than 12 months, Gross Unrealized Losses	(1,309)		(7,318)
12 months or longer, Fair Value	147,662	[1]	10,443	[2]
12 months or longer, Gross Unrealized Losses	(1,896)	[1]	(260)	[2]
Total, Fair Value	283,494		358,300
Total, Gross Unrealized Losses	(3,205)		(7,578)
U.S. Treasury and Agency Obligations
Schedule of Available-for-sale Securities [Line Items]
Total, Gross Unrealized Losses	(97)
Obligations of States and Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Total, Gross Unrealized Losses	(794)
Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Total, Gross Unrealized Losses	(1,040)
Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Total, Gross Unrealized Losses	(59)
Commercial Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Total, Gross Unrealized Losses	(239)
Corporate bonds and loans
Schedule of Available-for-sale Securities [Line Items]
Total, Gross Unrealized Losses	(111)
Common Shares
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	9,777		18,622
Less than 12 months, Gross Unrealized Losses	(465)		(627)
12 months or longer, Fair Value			140	[2]
12 months or longer, Gross Unrealized Losses			(9)	[2]
Total, Fair Value	9,777		18,762
Total, Gross Unrealized Losses	(465)		(636)
Other Invested Assets
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	11,524
Less than 12 months, Gross Unrealized Losses	(397)
Total, Fair Value	11,524
Total, Gross Unrealized Losses	(397)
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	114,531		329,235
Less than 12 months, Gross Unrealized Losses	(447)		(6,691)
12 months or longer, Fair Value	147,662	[1]	10,303	[2]
12 months or longer, Gross Unrealized Losses	(1,896)	[1]	(251)	[2]
Total, Fair Value	262,193		339,538
Total, Gross Unrealized Losses	(2,343)		(6,942)
Fixed Maturities | U.S. Treasury and Agency Obligations
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	998		9,335
Less than 12 months, Gross Unrealized Losses	(1)		(166)
12 months or longer, Fair Value	3,317	[1]
12 months or longer, Gross Unrealized Losses	(96)	[1]
Total, Fair Value	4,315		9,335
Total, Gross Unrealized Losses	(97)		(166)
Fixed Maturities | Obligations of States and Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	14,983		61,401
Less than 12 months, Gross Unrealized Losses	(153)		(2,000)
12 months or longer, Fair Value	32,643	[1]	9,922	[2]
12 months or longer, Gross Unrealized Losses	(641)	[1]	(241)	[2]
Total, Fair Value	47,626		71,323
Total, Gross Unrealized Losses	(794)		(2,241)
Fixed Maturities | Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	27,222		110,304
Less than 12 months, Gross Unrealized Losses	(204)		(2,859)
12 months or longer, Fair Value	70,731	[1]	2	[2]
12 months or longer, Gross Unrealized Losses	(836)	[1]
Total, Fair Value	97,953		110,306
Total, Gross Unrealized Losses	(1,040)		(2,859)
Fixed Maturities | Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	19,812		42,247
Less than 12 months, Gross Unrealized Losses	(23)		(228)
12 months or longer, Fair Value	8,617	[1]	3	[2]
12 months or longer, Gross Unrealized Losses	(36)	[1]
Total, Fair Value	28,429		42,250
Total, Gross Unrealized Losses	(59)		(228)
Fixed Maturities | Commercial Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	7,712		45,642
Less than 12 months, Gross Unrealized Losses	(19)		(856)
12 months or longer, Fair Value	27,169	[1]
12 months or longer, Gross Unrealized Losses	(220)	[1]
Total, Fair Value	34,881		45,642
Total, Gross Unrealized Losses	(239)		(856)
Fixed Maturities | Corporate bonds and loans
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	33,764		60,306
Less than 12 months, Gross Unrealized Losses	(44)		(582)
12 months or longer, Fair Value	5,185	[1]	376	[2]
12 months or longer, Gross Unrealized Losses	(67)	[1]	(10)	[2]
Total, Fair Value	38,949		60,682
Total, Gross Unrealized Losses	(111)		(592)
Fixed Maturities | Foreign Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	10,040
Less than 12 months, Gross Unrealized Losses	(3)
Total, Fair Value	10,040
Total, Gross Unrealized Losses	$ (3)

[1] Fixed maturities in a gross unrealized loss position for twelve months or longer are primarily comprised of non-credit losses on investment grade securities where management does not intend to sell, and it is more likely than not that the Company will not be forced to sell the security before recovery. The Company has analyzed these securities and has determined that they are not other than temporarily impaired.

[2] Fixed maturities in a gross unrealized loss position for twelve months or longer are primarily comprised of non-credit losses on investment grade securities where management does not intend to sell, and it is more likely than not that the Company will not be forced to sell the security before recovery. The Company has analyzed these securities and has determined that they are not other than temporarily impaired