Summary of Amortized Cost and Estimated Fair Value Through Fixed Maturities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	$ 48,262
Due in one year through five years, Amortized Cost	345,085
Due in five years through ten years, Amortized Cost	121,987
Due in ten years through fifteen years, Amortized Cost	15,388
Due after fifteen years, Amortized Cost	46,052
Fixed maturities, Amortized Cost	1,175,646	$ 1,257,830
Due in one year or less, Estimated Fair value	48,230
Due in one year through five years, Estimated Fair value	350,697
Due in five years through ten years, Estimated Fair value	126,075
Due in ten years through fifteen years, Estimated Fair value	16,136
Due after fifteen years, Estimated Fair value	49,031
Fixed Maturities, estimated fair value	1,196,276	1,235,155
Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	183,430
Fixed maturities, Amortized Cost	183,430	119,327
Estimated Fair value	185,754
Fixed Maturities, estimated fair value	185,754	117,854
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	175,979
Fixed maturities, Amortized Cost	175,979	185,430
Estimated Fair value	176,944
Fixed Maturities, estimated fair value	176,944	183,754
Commercial Mortgage-Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	239,463
Fixed maturities, Amortized Cost	239,463	206,236
Estimated Fair value	243,409
Fixed Maturities, estimated fair value	$ 243,409	$ 202,722

Available For Sale Securities Debt Maturities After Ten Through Fifteen Years Amortized Cost

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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