Quarterly report pursuant to Section 13 or 15(d)

Stockholders' and Mezzanine Equity - Dividends Paid (Detail)

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Stockholders' and Mezzanine Equity - Dividends Paid (Detail) - $ / shares
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Senior Common Stock    
Dividends Payable [Line Items]    
Common Stock, dividends paid per share $ 0.2625 $ 0.2625
Series A Preferred Stock    
Dividends Payable [Line Items]    
Preferred Stock, dividends paid per share 0.4843749 0.4843749
Series B Preferred Stock    
Dividends Payable [Line Items]    
Preferred Stock, dividends paid per share 0.46875 0.46875
Series D Preferred Stock    
Dividends Payable [Line Items]    
Preferred Stock, dividends paid per share 0.4374999 0.4374999
Common Stock    
Dividends Payable [Line Items]    
Common Stock, dividends paid per share $ 0.375 $ 0.375