Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Reconciliation and Income Statement Classification of Gains and Losses for All Assets and Liabilities (Parenthetical) (Detail)

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Fair Value Measurements - Reconciliation and Income Statement Classification of Gains and Losses for All Assets and Liabilities (Parenthetical) (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2012
Municipal Bonds-Tax Exempt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Par value of bond $ 451,060,000 $ 381,862,000 $ 700,000
Amortized value     $ 698,000
Useful remaining life intangible assets     2 years 2 months 12 days
Exercise price of stock warrants 9.60