Gross Unrealized Investment Losses (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	$ 2,837	$ 10,782
Less than 80% of amortized cost
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	698
Less than 80% of amortized cost | Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	230
Less than 80% of amortized cost | Equity Securities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	468
Less than 80% of amortized cost | 6-12 months
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	468
Less than 80% of amortized cost | 6-12 months | Equity Securities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	468
Less than 80% of amortized cost | > 12 months
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	230
Less than 80% of amortized cost | > 12 months | Fixed maturities
Gain (Loss) on Investments [Line Items]
Gross Unrealized Loss	$ 230