Change in Carrying Amount of Value of Business Acquired (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Business Acquisition, Acquisition Related Costs [Line Items]
Net realized investment gains (losses)	$ 31	$ (134)
Adjustment related to unrealized (gains) losses and OTTI on investments	871	5,098
Valuation of business acquired
Business Acquisition, Acquisition Related Costs [Line Items]
Amortization expense	(2,227)	(5,371)
Unlocking	(137)	(9)
Net realized investment gains (losses)	(104)	(59)
Adjustment related to unrealized (gains) losses and OTTI on investments	(871)	(5,098)
Change in VOBA carrying amount	$ (3,339)	$ (10,537)