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Debt - Additional Information (Detail) - Senior Unsecured Credit Facilities - USD ($)
Dec. 31, 2015
Oct. 12, 2012
Debt Instrument [Line Items]    
Remaining borrowing capacity $ 162,697,000  
Borrowings outstanding 0  
Amount of outstanding letter of credit $ 5,113,000  
Key Bank Credit Facility [Member]    
Debt Instrument [Line Items]    
Line of Credit Facility, Maximum Borrowing Capacity   $ 200,000,000