Components of Net Realized Investment Gains (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Total net realized investment gains	$ 1,158	$ 1,641	$ 40,226	$ 10,204
Not Designated as Hedging Instrument | Interest Rate Swap
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	147
Gross realized losses	(1,339)		(13,552)
Total net realized investment gains	(1,192)		(13,552)
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	262	105	2,651	779
Gross realized losses	(471)	(195)	(697)	(591)
Total net realized investment gains	(209)	(90)	1,954	188
Common Shares
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	2,559	2,383	52,434	12,396
Gross realized losses		(652)	(610)	(2,380)
Total net realized investment gains	$ 2,559	$ 1,731	$ 51,824	$ 10,016