v2.4.0.6
Reconciliation of Assets Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs Level Three (Detail) (Corporate Securities [Member], USD $)
In Thousands, unless otherwise specified
9 Months Ended 12 Months Ended
Sep. 30, 2012
Dec. 31, 2011
Corporate Securities [Member]
   
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]    
Balance of recurring Level 3 assets at January 1 $ 1,060 $ 1,060
Purchases 0 0
Sales 0 0
Issuances 0 0
Settlements 0 0
Transfers into Level 3 0 0
Transfers out of Level 3 0 0
Balance of recurring Level 3 assets at December 31 $ 1,060 $ 1,060