Annual report pursuant to Section 13 and 15(d)

Interest Rate Swap Agreements - Additional Information (Detail)

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Interest Rate Swap Agreements - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Agreement
Dec. 31, 2011
Dec. 31, 2010
Derivative [Line Items]      
Number of interest rate swap agreements 3    
Changes in fair values are reclassified from accumulated other comprehensive income (loss) into earnings $ 12,979 $ 15,929 $ 11,771
Losses accumulated in other comprehensive income related to a previously terminated interest rate swap agreement 18,147    
Amortized Interest Expenses related to a previously terminated interest rate swap agreement $ 2,470 $ 4,236 $ 4,633