Amount and Percentage of Fixed Maturities by Rating (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Investment Securities [Line Items]
Rating	AA
Fair Value	$ 2,047,873	$ 2,121,833
Percent of Total	100.00%
Extremely strong
Investment Securities [Line Items]
Rating	AAA
Fair Value	348,908
Percent of Total	17.00%
Very strong
Investment Securities [Line Items]
Rating	AA
Fair Value	1,047,155
Percent of Total	51.00%
Strong
Investment Securities [Line Items]
Rating	A
Fair Value	452,455
Percent of Total	22.00%
Adequate
Investment Securities [Line Items]
Rating	BBB
Fair Value	184,302
Percent of Total	9.00%
Speculative
Investment Securities [Line Items]
Rating	BB & Below
Fair Value	11,500
Percent of Total	1.00%
Not rated
Investment Securities [Line Items]
Rating	NR
Fair Value	$ 3,553
Percent of Total	0.00%