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Fair Value Measurements - Additional Information (Detail) (USD $)
Jun. 30, 2012
Dec. 31, 2011
Fair Value, Measurement Inputs, Disclosure [Line Items]    
Long-term debt, carrying value $ 1,200,767,000 $ 808,448,000
Long-term debt, fair value 1,248,500,000 856,900,000
Capital lease obligation, carrying value $ 26,300,000 $ 21,800,000