Quarterly report pursuant to Section 13 or 15(d)

Equity - Monthly Distributions Declared and Paid by Company's Board of Directors (Detail)

v3.7.0.1
Equity - Monthly Distributions Declared and Paid by Company's Board of Directors (Detail) - $ / shares
 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Class of Stock [Line Items]    
Distributions per Common Share (in dollars per share) $ 0.2595 $ 0.24375
2017-01-31    
Class of Stock [Line Items]    
Declaration Date Jan. 10, 2017  
Record Date Jan. 20, 2017  
Payment Date Jan. 31, 2017  
Distributions per Common Share (in dollars per share) $ 0.043  
2017-02-28    
Class of Stock [Line Items]    
Declaration Date Jan. 10, 2017  
Record Date Feb. 16, 2017  
Payment Date Feb. 28, 2017  
Distributions per Common Share (in dollars per share) $ 0.043  
2017-03-31    
Class of Stock [Line Items]    
Declaration Date Jan. 10, 2017  
Record Date Mar. 22, 2017  
Payment Date Mar. 31, 2017  
Distributions per Common Share (in dollars per share) $ 0.043  
2017-04-28    
Class of Stock [Line Items]    
Declaration Date Apr. 11, 2017  
Record Date Apr. 21, 2017  
Payment Date Apr. 28, 2017  
Distributions per Common Share (in dollars per share) $ 0.04350  
2017-05-31    
Class of Stock [Line Items]    
Declaration Date Apr. 11, 2017  
Record Date May 19, 2017  
Payment Date May 31, 2017  
Distributions per Common Share (in dollars per share) $ 0.0435  
2017-06-30    
Class of Stock [Line Items]    
Declaration Date Apr. 11, 2017  
Record Date Jun. 21, 2017  
Payment Date Jun. 30, 2017  
Distributions per Common Share (in dollars per share) $ 0.0435  
2016-02-02    
Class of Stock [Line Items]    
Declaration Date   Jan. 12, 2016
Record Date   Jan. 22, 2016
Payment Date   Feb. 02, 2016
Distributions per Common Share (in dollars per share)   $ 0.040
2016-02-29    
Class of Stock [Line Items]    
Declaration Date   Jan. 12, 2016
Record Date   Feb. 18, 2016
Payment Date   Feb. 29, 2016
Distributions per Common Share (in dollars per share)   $ 0.040
2016-03-31    
Class of Stock [Line Items]    
Declaration Date   Jan. 12, 2016
Record Date   Mar. 21, 2016
Payment Date   Mar. 31, 2016
Distributions per Common Share (in dollars per share)   $ 0.040
2016-05-02    
Class of Stock [Line Items]    
Declaration Date   Apr. 12, 2016
Record Date   Apr. 22, 2016
Payment Date   May 02, 2016
Distributions per Common Share (in dollars per share)   $ 0.04125
2016-05-31    
Class of Stock [Line Items]    
Declaration Date   Apr. 12, 2016
Record Date   May 19, 2016
Payment Date   May 31, 2016
Distributions per Common Share (in dollars per share)   $ 0.04125
2016-06-30    
Class of Stock [Line Items]    
Declaration Date   Apr. 12, 2016
Record Date   Jun. 17, 2016
Payment Date   Jun. 30, 2016
Distributions per Common Share (in dollars per share)   $ 0.04125