Investments - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) Security	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Security	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) Security
Schedule of Investments [Line Items]
Other Invested Assets	$ 1,781		$ 1,781		$ 1,960
Non-credit OTTI on fixed maturities in a net unrealized gain position			400		400
Gross Unrealized Loss	15,865		$ 15,865		$ 30,199
OTTI losses	$ 0
Equity Securities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security	40		40		75
Gross Unrealized Loss	$ 1,522		$ 1,522		$ 5,785
OTTI losses			$ 1,100
Fixed Maturities
Schedule of Investments [Line Items]
Number of securities in unrealized loss position | Security	321		321		413
Gross Unrealized Loss	$ 14,343		$ 14,343		$ 24,414
OTTI losses		$ 200		$ 200
Non-government-backed securities | Maximum
Schedule of Investments [Line Items]
Percentage of investment	5.00%		5.00%		5.00%
Gross Unrealized Loss	$ 900		$ 900		$ 1,000
Mortgage-Backed and Asset-Backed Securities
Schedule of Investments [Line Items]
Securities, effective maturities			4 years 10 months 24 days
Mortgage-Backed and Asset-Backed Securities | Fixed Maturities
Schedule of Investments [Line Items]
Gross Unrealized Loss	$ 7,324		$ 7,324		$ 9,722