Investments - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) Security	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Security	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Investments Schedule [Abstract]
Individual fixed maturity held in unrealized loss position | Security	187		187
Individual fixed maturity held in unrealized loss position longer than 12 months | Security	21		21
Carrying value of investments	$ 7,038,000		$ 7,038,000		$ 13,330,000
Impairment losses recognized			0	$ 0
Net realized gains (losses) on investments	$ (388,000)	$ 545,000	$ (569,000)	$ 793,000