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 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Common Stock        
Dividends Payable [Line Items]        
Common Stock, dividends paid per share $ 0.375 $ 0.375 $ 1.125 $ 1.125
Senior Common Stock        
Dividends Payable [Line Items]        
Common Stock, dividends paid per share 0.2625 0.2625 0.7875 0.7875
Series A Preferred Stock        
Dividends Payable [Line Items]        
Preferred Stock, dividends paid per share 0.4843749 0.4843749 1.4531247 1.4531247
Series B Preferred Stock        
Dividends Payable [Line Items]        
Preferred Stock, dividends paid per share 0.4688 0.4688 1.4063 1.4063
Series C Preferred Stock        
Dividends Payable [Line Items]        
Preferred Stock, dividends paid per share 0 0.2424 0.0000 1.1330
Series D Preferred Stock        
Dividends Payable [Line Items]        
Preferred Stock, dividends paid per share $ 0.4375 $ 0.4375 $ 1.3125 $ 0.6163