Quarterly report pursuant to Section 13 or 15(d)

Equity - Summary of Dividends Declared by Board of Directors (Detail)

v3.8.0.1
Equity - Summary of Dividends Declared by Board of Directors (Detail) - $ / shares
 9 Months Ended
Oct. 16, 2017
Jul. 13, 2017
Apr. 13, 2017
Jan. 12, 2017
Oct. 13, 2016
Jul. 14, 2016
Apr. 07, 2016
Sep. 30, 2017
3/30/2016 Record Date [Member]                
Dividends Payable [Line Items]                
Announced Date               Mar. 15, 2016
Record Date               Mar. 30, 2016
Pay Date               Apr. 07, 2016
Amount per share             $ 0.30  
07/06/16 Record Date [Member]                
Dividends Payable [Line Items]                
Announced Date               Jun. 07, 2016
Record Date               Jul. 06, 2016
Pay Date               Jul. 14, 2016
Amount per share           $ 0.30    
10/05/16 Record Date [Member]                
Dividends Payable [Line Items]                
Announced Date               Sep. 15, 2016
Record Date               Oct. 05, 2016
Pay Date               Oct. 13, 2016
Amount per share         $ 0.30      
12/29/16 Record Date [Member]                
Dividends Payable [Line Items]                
Announced Date               Dec. 13, 2016
Record Date [1]               Dec. 29, 2016
Pay Date               Jan. 12, 2017
Amount per share       $ 0.33        
4/05/2017 Record Date [Member]                
Dividends Payable [Line Items]                
Announced Date               Mar. 15, 2017
Record Date               Apr. 05, 2017
Pay Date               Apr. 13, 2017
Amount per share     $ 0.33          
7/06/2017 Record Date [Member]                
Dividends Payable [Line Items]                
Announced Date               Jun. 01, 2017
Record Date               Jul. 06, 2017
Pay Date               Jul. 13, 2017
Amount per share   $ 0.33            
10/05/2017 Record Date [Member]                
Dividends Payable [Line Items]                
Announced Date               Sep. 12, 2017
Record Date               Oct. 05, 2017
Pay Date               Oct. 16, 2017
10/05/2017 Record Date [Member] | Subsequent Event [Member]                
Dividends Payable [Line Items]                
Amount per share $ 0.33              
[1] This dividend was treated as a distribution in 2017 for tax purposes.