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Commitments and Contingencies - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]      
Initial term of leases 20 years    
Renewal terms of leases 10 years    
Notice period upon cancellation of leases 90 days    
Rental expenses $ 9,421us-gaap_LeaseAndRentalExpense $ 8,829us-gaap_LeaseAndRentalExpense $ 8,879us-gaap_LeaseAndRentalExpense