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Actual Income Tax Expense Differs from Expected Amounts Computed by Applying U.S. Federal Income Tax Rate to Earnings Before Income Taxes (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Reconciliation of Provision of Income Taxes [Line Items]      
Expected income tax expense at statutory rate $ 62,910 $ 221,429 $ 38,830
Increase (decrease) in taxes resulting from:      
Domestic production activities (2,450) (2,625) (1,050)
Valuation allowance     27
State and local income taxes, net of federal benefit 4,766 22,275 3,759
Tax credits (128) (140) (109)
Tax exempt interest income   (2) (81)
Other items, net 1,216 6,313 2,799
Income tax expense $ 66,314 $ 247,250 $ 44,175