Credit Loss Impairments on Fixed Maturity Securities, Other-Than-Temporary Impairment Loss Recognized in Other Comprehensive Income, and Corresponding Changes (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Balance at beginning of period	$ (935)	$ (185)
Additional credit loss impairments recognized in the current period on securities previously impaired through other comprehensive income	121	109
Accretion of credit loss impairments previously recognized	(502)	(859)
Balance at end of period	$ (1,316)	$ (935)