Quarterly report pursuant to Section 13 or 15(d)

Unsecured Line of Credit and Term Notes - Additional Information (Detail)

v3.19.1
Unsecured Line of Credit and Term Notes - Additional Information (Detail) - USD ($)
3 Months Ended 12 Months Ended
Dec. 07, 2017
Jul. 21, 2016
Jun. 20, 2016
Apr. 08, 2014
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2011
Dec. 31, 2018
Debt Instrument [Line Items]                
Amount available on unsecured revolving line of credit         $ 322,700,000      
Unamortized senior term note discount         4,266,000     $ 4,402,000
Amortization expense related to deferred debt issuance costs         $ 903,000 $ 891,000    
Maximum [Member]                
Debt Instrument [Line Items]                
Leverage ratio percentage         60.00%      
Indenture covenant percentage on unencumbered assets         150.00%      
Minimum [Member]                
Debt Instrument [Line Items]                
Interest coverage ratio on debt         150.00%      
Secured Debt [Member] | Maximum [Member]                
Debt Instrument [Line Items]                
Leverage ratio percentage         40.00%      
Senior Term Note Due December 15, 2027 [Member] | Unsecured Senior Notes [Member]                
Debt Instrument [Line Items]                
Debt instrument principal amount $ 450,000,000              
Debt instrument,maturity date Dec. 15, 2027              
Debt instrument stated interest rate 3.875%              
Debt instrument percentage discount to par 0.477%              
Debt instrument, interest payable description         Interest on the 2027 Senior Notes is payable semi-annually in arrears on each June 15 and December 15.      
Unamortized senior term note discount $ 2,100,000              
Underwriting discount and other offering expenses 4,000,000.0              
Proceeds from senior notes, net $ 443,900,000              
Senior Term Note Due July 1, 2026 [Member] | Unsecured Senior Notes [Member]                
Debt Instrument [Line Items]                
Debt instrument principal amount     $ 600,000,000          
Debt instrument,maturity date     Jul. 01, 2026          
Debt instrument stated interest rate     3.50%          
Debt instrument percentage discount to par     0.553%          
Debt instrument, interest payable description         Interest on the 2026 Senior Notes is payable semi-annually in arrears on each January 1 and July 1.      
Unamortized senior term note discount     $ 3,300,000          
Underwriting discount and other offering expenses     5,500,000          
Proceeds from senior notes, net     $ 591,200,000          
Term Note Due July 21, 2028 [Member]                
Debt Instrument [Line Items]                
Debt instrument,maturity date   Jul. 21, 2028            
Debt instrument stated interest rate   3.67%            
Additional secured term note   $ 200,000,000            
Term Note Due April 8, 2024 [Member]                
Debt Instrument [Line Items]                
Debt instrument,maturity date       Apr. 08, 2024        
Debt instrument stated interest rate       4.533%        
Additional secured term note       $ 175,000,000        
Term Note Due April 8, 2024 [Member] | Maximum [Member]                
Debt Instrument [Line Items]                
Debt instrument stated interest rate       6.283%        
Term Note Due August 5, 2021 [Member]                
Debt Instrument [Line Items]                
Line of credit facility, expiration date             Aug. 05, 2021  
Debt instrument stated interest rate             5.54%  
Additional secured term note             $ 100,000,000  
Term Note Due August 5, 2021 [Member] | Maximum [Member]                
Debt Instrument [Line Items]                
Debt instrument stated interest rate             7.29%  
Senior Notes and Term Notes [Member]                
Debt Instrument [Line Items]                
Amortization expense related to deferred debt issuance costs         $ 500,000 $ 500,000    
Revolving Credit Facility [Member]                
Debt Instrument [Line Items]                
Revolving credit limit         $ 500,000,000      
Line of credit facility, expiration date         Mar. 10, 2023      
Basis spread over LIBOR         0.95%      
Facility fee         0.15%      
Interest rate, line of credit facility         3.45%     3.47%
Revolving Credit Facility [Member] | Term Note Due June 4, 2020 [Member]                
Debt Instrument [Line Items]                
Debt instrument principal amount         $ 100,000,000      
Debt instrument,maturity date         Jun. 04, 2020      
Basis spread over LIBOR         1.00%      
Debt instrument variable interest rate         3.50%     3.52%
Revolving Credit Facility [Member] | Term Note [Member]                
Debt Instrument [Line Items]                
Revolving credit limit         $ 900,000,000