Investments - Major Categories of Net Investment Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Net Investment Income [Line Items]
Net amortization of bond premiums and discounts	$ (12,462)	$ (8,513)
Dividends from equities	1,404	1,091
Other investments	92	61
Interest on other receivables	226	618
Other income	22	1,397
Interest on deposits held with clients	730	1,194
Investment expenses	(1,806)	(1,591)
Interest from investments	24,348	17,963
Fixed Maturity Investments [Member]
Net Investment Income [Line Items]
Interest from investments	34,206	20,625
Cash and Cash Equivalents and Short-term Investments [Member]
Net Investment Income [Line Items]
Interest from investments	1,625	3,081
Policy Loan Interest [Member]
Net Investment Income [Line Items]
Interest from investments	$ 311	$ 0