Investments - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($) Security	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) Security	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) Security
Schedule of Investments [Line Items]
Non-credit OTTI on fixed maturities in an unrealized gain position			$ 400		$ 500
Gross Unrealized Loss	$ 10,497		10,497		$ 29,398
OTTI losses	$ 150	$ 423	$ 150	$ 423
Equity Securities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security	30		30		57
Gross Unrealized Loss	$ 2,222		$ 2,222		$ 3,013
Fixed maturities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security	140		140		368
Gross Unrealized Loss	$ 8,275		$ 8,275		$ 26,385
OTTI losses	200		200
Equity Portfolio
Schedule of Investments [Line Items]
OTTI losses		$ 400		$ 400
Non-government-backed securities
Schedule of Investments [Line Items]
Gross Unrealized Loss	$ 1,000		$ 1,000		$ 2,600
Non-government-backed securities | Maximum
Schedule of Investments [Line Items]
Percentage of investment	5.00%		5.00%		5.00%
Mortgage-backed and asset-backed securities
Schedule of Investments [Line Items]
Securities, effective maturities			4 years 2 months 12 days
Mortgage-backed and asset-backed securities | Fixed maturities
Schedule of Investments [Line Items]
Gross Unrealized Loss	$ 2,177		$ 2,177		$ 5,652