Affiliated Purchasing and Selling of Investments Between Affiliated Companies (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Investments purchased from related parties, Mortgages		$ 106,949		$ 92,914
Investments purchased from related parties, Limited partnerships		11,145
Affiliated companies
Related Party Transaction [Line Items]
Investments purchased from related parties, Fixed maturities			$ 30,356
Investments purchased from related parties, Mortgages	$ 4,000		4,000
Investments purchased from related parties, Limited partnerships		10,000
Investments sold to related parties, Fixed maturities	$ 3,475	$ 62,859	$ 24,878