Annual report pursuant to Section 13 and 15(d)

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

v3.8.0.1
Unsecured Line of Credit and Term Notes - Additional Information (Detail)
12 Months Ended
Dec. 07, 2017
USD ($)
Jul. 21, 2016
USD ($)
Jun. 20, 2016
USD ($)
May 17, 2016
USD ($)
Bridge_Loan
Apr. 08, 2014
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2011
USD ($)
Jan. 31, 2016
USD ($)
Unsecured Line Of Credit And Term Notes [Line Items]                    
Unsecured term note           $ 1,625,000,000 $ 1,400,000,000      
Term notes, outstanding amount           1,742,674,000        
Unamortized senior term note discount           4,949,000 3,152,000      
Underwriting discount and other offering expenses           $ 3,961,000 15,273,000      
Interest expense - bridge financing commitment fee             7,329,000      
Interest coverage ratio on debt           150.00%        
Amortization expense related to deferred debt issuance costs           $ 4,289,000 9,688,000 $ 1,184,000    
Maximum [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Leverage ratio percentage           60.00%        
Indenture covenant percentage on unencumbered assets           150.00%        
Bridge Facilities [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Number of bridge facilities | Bridge_Loan       2            
Senior unsecured acquisition bridge facilities, amount       $ 1,675,000,000            
Interest expense - bridge financing commitment fee             7,300,000      
Bridge loan, termination date       Jun. 29, 2016            
Secured Debt [Member] | Maximum [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Leverage ratio percentage           40.00%        
Senior Term Note Due December 15, 2027 [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Unsecured term note           $ 450,000,000        
Senior Term Note Due December 15, 2027 [Member] | Unsecured Senior Notes [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Debt instrument principal amount $ 450,000,000                  
Debt instrument stated interest rate 3.875%                  
Debt instrument percentage discount to par 0.477%                  
Unamortized senior term note discount $ 2,100,000                  
Underwriting discount and other offering expenses 4,000,000                  
Proceeds from senior notes, net $ 443,900,000                  
Senior Term Note Due July 1, 2026 [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Unsecured term note           600,000,000 600,000,000      
Senior Term Note Due July 1, 2026 [Member] | Unsecured Senior Notes [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Debt instrument principal amount     $ 600,000,000              
Debt instrument stated interest rate     3.50%              
Debt instrument percentage discount to par     0.553%              
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]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Unsecured term note           200,000,000 200,000,000      
Line of credit facility, expiration date   Jul. 21, 2028                
Debt instrument stated interest rate   3.67%                
Additional secured term note   $ 200,000,000                
Maturity in April 8, 2024 [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Line of credit facility, expiration date         Apr. 08, 2024          
Debt instrument stated interest rate         4.533%          
Additional secured term note         $ 175,000,000          
Maturity in April 8, 2024 [Member] | Maximum [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Debt instrument stated interest rate         6.283%          
Maturity in August 2021 [Member]                    
Unsecured Line Of Credit And Term Notes [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  
Maturity in August 2021 [Member] | Maximum [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Debt instrument stated interest rate                 7.29%  
Senior Notes and Term Notes [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Amortization expense related to deferred debt issuance costs           3,000,000 $ 1,700,000 $ 1,200,000    
Revolving Credit Facility [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Revolving credit limit           $ 500,000,000       $ 300,000,000
Maturity on December 10, 2019 [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Basis spread over LIBOR           1.10%        
Facility fee           0.15%        
Interest rate, line of credit facility           2.63% 1.79%      
Amount available on unsecured revolving line of credit           $ 395,000,000        
Line of credit facility, expiration date           Dec. 10, 2019        
Maturity on June 4, 2020 [Member]                    
Unsecured Line Of Credit And Term Notes [Line Items]                    
Basis spread over LIBOR           1.15%        
Unsecured term note           $ 325,000,000        
Repayments of unsecured term note           225,000,000        
Term notes, outstanding amount           $ 100,000,000