Schedule of Dividends Authorized and Declared Cash Dividends to Common Stockholders (Detail) - $ / shares
6 Months Ended
Jun. 30, 2017
Apr. 26, 2017
Jan. 31, 2017
Dividends Payable [Line Items]      
Dividend Amount Per Share of Common Stock   $ 0.227 $ 0.227
Installment First Quarter Of Fiscal Year      
Dividends Payable [Line Items]      
Declaration Date Jan. 31, 2017    
Payment Date Mar. 15, 2017    
Record Date (close of business) Mar. 01, 2017    
Installment Second Quarter Of Fiscal Year      
Dividends Payable [Line Items]      
Declaration Date Apr. 26, 2017    
Payment Date May 31, 2017    
Record Date (close of business) May 17, 2017