v2.4.0.6
Summary of Fair Value Transfers Between Level I and Level II (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Transfers from Level I into Level II $ 15,924 [1] $ 45,440 [1]
Transfers from Level II into Level I $ 529 [2] $ 801 [2]
[1] Transfers out of Level I represent those financial instruments for which restrictions exist and adjustments were made to an otherwise observable price to reflect fair value at the reporting date.
[2] Transfers into Level I represent those financial instruments for which an unadjusted quoted price in an active market became available for the identical asset.