Components of Net Realized Investment Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Total net realized investment gains (losses)	$ (7,493)	$ (2,970)
Not Designated as Hedging Instrument | Interest Rate Swap
Schedule of Available-for-sale Securities [Line Items]
Gross realized losses	(8,978)	(5,882)
Total net realized investment gains (losses)	(8,978)	(5,882)
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	180	733
Gross realized losses	(72)	(131)
Total net realized investment gains (losses)	108	602
Common Shares
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	2,564	2,552
Gross realized losses	(1,187)	(338)
Total net realized investment gains (losses)	$ 1,377	2,214
Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains		96
Total net realized investment gains (losses)		$ 96