Investments - Additional Information (Detail)	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Security Fund	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) Security
Investments Debt And Equity Securities [Abstract]
Number of securities | Security		1		0
OTTI charges recognized in net income (loss)	$ 147,000	$ 0	$ 147,000
Number of investment funds | Fund		3
Unfunded commitments		$ 2,500,000
Fixed maturities and cash equivalents on deposit with various insurance departments at fair value and amortized cost		6,400,000
Cash equivalents on deposit with another insurance company at fair value and amortized cost		17,200,000
Non credit other than temporary impairment for securities		$ 1,100,000		$ 1,100,000