Gross Unrealized Investment Losses (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	$ (4,072)	$ (10,782)
Less than 80% of amortized cost
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	(547)
Less than 80% of amortized cost | Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	(547)
Less than 80% of amortized cost | > 12 months
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	(547)
Less than 80% of amortized cost | > 12 months | Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	$ (547)