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Derivative Financial Instruments - Summary of Aggregate Amount and Estimated Net Fair Value of Derivative Instruments (Detail) - USD ($)
Jun. 30, 2018
Dec. 31, 2017
Nov. 17, 2017
Jun. 24, 2016
Derivative Instruments Gain Loss [Line Items]        
Derivative, notional amount $ 250,000,000 $ 250,000,000    
Fair Value of Assets 11,755,000 7,291,000    
Fair Value of Assets   7,291,000    
Interest Rate Swap        
Derivative Instruments Gain Loss [Line Items]        
Derivative, notional amount       $ 150,000
Cash Flow Hedge        
Derivative Instruments Gain Loss [Line Items]        
Derivative, notional amount 250,000,000 200,000,000    
Fair Value of Assets 11,755,000 5,997,000    
Cash Flow Hedge | Interest Rate Swap        
Derivative Instruments Gain Loss [Line Items]        
Derivative, notional amount 150,000,000 150,000,000    
Fair Value of Assets 6,697,000 4,700,000    
Cash Flow Hedge | Interest Rate Collar        
Derivative Instruments Gain Loss [Line Items]        
Derivative, notional amount 100,000,000 50,000,000 $ 100,000,000  
Fair Value of Assets $ 5,058,000 1,297,000    
Freestanding Derivatives | Interest Rate Collar        
Derivative Instruments Gain Loss [Line Items]        
Derivative, notional amount   50,000,000 $ 50,000,000  
Fair Value of Assets   $ 1,294,000