Investments - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) Security Fund	Dec. 31, 2016 USD ($) Security
Investments Debt And Equity Securities [Abstract]
Number of securities | Security	1	0
OTTI charges recognized in net income (loss)	$ 0
Number of investment funds | Fund	2
Unfunded commitment	$ 2,500,000
Fixed maturities and cash equivalents on deposit with various insurance departments at fair value and amortized cost	6,300,000
Cash equivalents on deposit with another insurance company at fair value and amortized cost	17,100,000
Non credit other than temporary impairment for securities	$ 1,100,000	$ 1,100,000