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	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	$ 32,980	$ 1,261
Percent of Total Gross Unrealized Loss	100.00%
Fair Value Amount	934,607	156,071
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	1
Percent of Total Gross Unrealized Loss	0.00%
Fair Value Amount	7,687
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	2,152
Percent of Total Gross Unrealized Loss	7.00%
Fair Value Amount	242,879
Percent of Total Fair Value	26.00%
Due After Five Years Through Ten Years
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	13,585
Percent of Total Gross Unrealized Loss	41.00%
Fair Value Amount	262,989
Percent of Total Fair Value	28.00%
Due After Ten Years
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	10,211
Percent of Total Gross Unrealized Loss	31.00%
Fair Value Amount	178,428
Percent of Total Fair Value	19.00%
Mortgage- and asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Loss Amount	7,031
Percent of Total Gross Unrealized Loss	21.00%
Fair Value Amount	$ 242,624
Percent of Total Fair Value	26.00%