Investments - Summary of Amortized Cost and Estimated Fair Value of Fixed Maturities by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]
Due in one year or less, Amortized Cost	$ 22,554	$ 17,541
Due after one year through five years, Amortized Cost	82,988	87,698
Due after five years through ten years, Amortized Cost	131,317	133,102
Due after ten years, Amortized Cost	619,359	621,046
Amortized cost due in years, Total	856,218	859,387
Due in one year or less, Fair Value	22,591	17,579
Due after one year through five years, Fair Value	82,574	86,611
Due after five years through ten years, Fair Value	127,759	126,541
Due after ten years, Fair Value	594,467	568,828
Fair value due in years, Total	$ 827,391	$ 799,559
Due in one year or less, Percentage of Total Fair Value	2.70%	2.20%
Due after one year through five years, Percentage of Total Fair Value	10.00%	10.80%
Due after five years through ten years, Percentage of Total Fair Value	15.40%	15.80%
Due after ten years, Percentage of Total Fair Value	71.90%	71.20%
Percentage of Fair Value, Total	100.00%	100.00%