Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value
Due in one year or less	$ 63,670
Due after one year through five years	765,084
Due after five years through ten years	356,929
Due after ten years	368,811
Mortgage- and asset-backed securities	811,440
Total	2,365,934	2,047,873
Amortized Cost
Due in one year or less	65,643
Due after one year through five years	758,064
Due after five years through ten years	348,195
Due after ten years	355,058
Mortgage- and asset-backed securities	796,999
Total	$ 2,323,959	$ 2,036,999