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Exchangeable Senior Notes - Additional Information (Detail)
1 Months Ended 3 Months Ended
Jun. 21, 2013
USD ($)
Feb. 29, 2016
USD ($)
shares
Sep. 30, 2015
USD ($)
Mar. 31, 2017
USD ($)
d
Dec. 31, 2016
USD ($)
Par Value [Member]          
Debt Instrument [Line Items]          
Shares issued for value of notes in excess of principal amount | shares   130,909      
Value of notes in excess of principal amount   $ 11,380,000      
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member]          
Debt Instrument [Line Items]          
Effective interest rate on the liability component       4.00%  
Exchangeable Senior Notes 2.375% due 2033 (the 2013 Notes) [Member]          
Debt Instrument [Line Items]          
Notes exchange, threshold percentage       130.00%  
Notes exchange, threshold trading days | d       20  
Notes exchange, threshold consecutive trading days       30 days  
Effective interest rate on the liability component       4.00%  
Operating Partnership [Member]          
Debt Instrument [Line Items]          
Related debt issuance costs       $ 8,430,000 $ 9,033,000
Operating Partnership [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member]          
Debt Instrument [Line Items]          
Principal amount of notes issued     $ 575,000,000    
Interest rate     3.125% 3.125%  
Underwriting fee percentage     2.00%    
Amortization period     5 years    
Conversion ratio, number of shares per $1,000 principal amount, numerator       10.58  
Principal amount used for debt instrument conversion ratio       $ 1,000  
Redemption price as percentage of principal amount of notes plus accrued and unpaid interest     100.00%    
Redemption price as percentage of principal amount of notes at request of debt holders and upon occurrence of designated event     100.00%    
Related debt issuance costs     $ 11,992,000    
Operating Partnership [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
Number of days of written notice to holders of notes required for redemption     30 days    
Operating Partnership [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member] | Maximum [Member]          
Debt Instrument [Line Items]          
Number of days of written notice to holders of notes required for redemption     60 days    
Operating Partnership [Member] | Exchangeable Senior Notes 2.375% due 2033 (the 2013 Notes) [Member]          
Debt Instrument [Line Items]          
Principal amount of notes issued $ 250,000,000        
Interest rate 2.375%     2.375%  
Conversion ratio, number of shares per $1,000 principal amount, numerator       18.58  
Principal amount used for debt instrument conversion ratio       $ 1,000  
Redemption price as percentage of principal amount of notes plus accrued and unpaid interest 100.00%        
Redemption price as percentage of principal amount of notes at request of debt holders and upon occurrence of designated event 100.00%        
Discount rate 1.50%        
Unamortized cash discount $ 3,750,000 716,000   $ 234,000 $ 281,000
Related debt issuance costs $ 1,672,000 36,000      
Amortization period 5 years        
Principal amount repurchased   $ 19,639,000      
Operating Partnership [Member] | Exchangeable Senior Notes 2.375% due 2033 (the 2013 Notes) [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
Number of days of written notice to holders of notes required for redemption 30 days        
Operating Partnership [Member] | Exchangeable Senior Notes 2.375% due 2033 (the 2013 Notes) [Member] | Maximum [Member]          
Debt Instrument [Line Items]          
Number of days of written notice to holders of notes required for redemption 60 days