Contractual Maturity by Number of Years Until Maturity for Fixed Maturity Securities with Gross Unrealized Loss (Detail) (Fixed maturities, USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	$ 10,747	$ 32,980
Percent of Total Gross Unrealized Loss	100.00%
Fair Value Amount	645,099	934,607
Percent of Total Fair Value	100.00%
Due in one year or less
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	417
Percent of Total Gross Unrealized Loss	4.00%
Fair Value Amount	8,486
Percent of Total Fair Value	1.00%
Due After One Year Through Five Years
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	2,009
Percent of Total Gross Unrealized Loss	19.00%
Fair Value Amount	157,888
Percent of Total Fair Value	25.00%
Due After Five Years Through Ten Years
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	3,877
Percent of Total Gross Unrealized Loss	36.00%
Fair Value Amount	182,500
Percent of Total Fair Value	28.00%
Due After Ten Years
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	2,078
Percent of Total Gross Unrealized Loss	19.00%
Fair Value Amount	140,813
Percent of Total Fair Value	22.00%
Mortgage- and asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	2,366
Percent of Total Gross Unrealized Loss	22.00%
Fair Value Amount	$ 155,412
Percent of Total Fair Value	24.00%