Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value
Total	$ 3,167,095	$ 3,093,156
Amortized Cost
Amortized Cost	3,150,910	3,135,647
Fixed Maturities
Fair Value
Due in one year or less	145,022
Due after one year through five years	805,156
Due after five years through ten years	372,917
Due after ten years	621,505
Mortgage-Backed and Asset-Backed Securities	1,215,208
Total	3,159,808	3,082,923
Amortized Cost
Due in one year or less	145,859
Due after one year through five years	802,331
Due after five years through ten years	362,404
Due after ten years	609,527
Mortgage-Backed and Asset-Backed Securities	1,223,501
Amortized Cost	$ 3,143,622	$ 3,125,413