Summary of Amortized Cost and Estimated Fair Value Through Fixed Maturities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	$ 149,020
Due in one year through five years, Amortized Cost	513,595
Due in five years through ten years, Amortized Cost	57,556
Due in ten years through fifteen years, Amortized Cost	4,403
Due after fifteen years, Amortized Cost	17,616
Fixed maturities, amortized cost	1,187,660	1,187,685
Due in one year or less, Estimated Fair value	151,466
Due in one year through five years, Estimated Fair value	523,822
Due in five years through ten years, Estimated Fair value	58,800
Due in ten years through fifteen years, Estimated Fair value	4,814
Due after fifteen years, Estimated Fair value	17,244
Fixed Maturities, estimated fair value	1,205,713	1,204,364
Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	218,030
Estimated Fair value	221,304
Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	166,315
Estimated Fair value	167,329
Commercial Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	61,125
Estimated Fair value	$ 60,934