Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.2
Unsecured Line of Credit and Term Notes - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 03, 2019
Dec. 07, 2017
Jul. 21, 2016
Jun. 20, 2016
Apr. 08, 2014
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2011
Dec. 31, 2019
Debt Instrument [Line Items]                      
Amount available on unsecured revolving line of credit           $ 341,900,000   $ 341,900,000      
Unamortized senior term note discount           5,218,000   5,218,000     $ 5,583,000
Underwriting discount and other offering expenses                 $ 3,099,000    
Amortization expense related to deferred debt issuance costs               $ 2,025,000 1,846,000    
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 June 15, 2029 [Member] | Unsecured Senior Notes [Member]                      
Debt Instrument [Line Items]                      
Debt instrument principal amount $ 350,000,000                    
Debt instrument,maturity date Jun. 15, 2029                    
Debt instrument stated interest rate 4.00%                    
Debt instrument percentage discount to par 0.524%                    
Debt instrument, interest payable description               Interest on the 2029 Senior Notes is payable semi-annually in arrears on each June 15 and December 15.      
Unamortized senior term note discount $ 1,800,000                    
Underwriting discount and other offering expenses 3,100,000                    
Proceeds from senior notes, net $ 345,100,000                    
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]                      
Debt instrument,maturity 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           600,000 $ 600,000 $ 1,200,000 $ 1,100,000    
Revolving Credit Facility [Member]                      
Debt Instrument [Line Items]                      
Revolving credit limit           $ 500,000,000   $ 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           1.13%   1.13%     2.75%
Revolving Credit Facility [Member] | Term Note Due June 4, 2020 [Member]                      
Debt Instrument [Line Items]                      
Debt instrument principal amount           $ 100,000,000   $ 100,000,000      
Basis spread over LIBOR               1.00%      
Debt instrument variable interest rate           1.18%   1.18%     2.80%
Principal amount paid off               $ 100,000,000      
Revolving Credit Facility [Member] | Term Note [Member]                      
Debt Instrument [Line Items]                      
Revolving credit limit           $ 900,000,000   $ 900,000,000