Quarterly report pursuant to Section 13 or 15(d)

Subsequent Events - Monthly Distributions Declared by Company's Board of Directors (Detail)

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Subsequent Events - Monthly Distributions Declared by Company's Board of Directors (Detail) - $ / shares
 3 Months Ended
Apr. 11, 2017
Mar. 31, 2017
April 28, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Distributions Payable To Holders Of Records Months   April
May 31, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Distributions Payable To Holders Of Records Months   May
June 30, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Distributions Payable To Holders Of Records Months   June
Subsequent event | Series A Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.4843749  
Subsequent event | Series B Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.46875  
Subsequent event | Series D Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.4375  
Subsequent event | Senior Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.2625  
Subsequent event | Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.375  
Subsequent event | April 28, 2017    
Dividends Payable [Line Items]    
Record Date Apr. 21, 2017  
Payment Date Apr. 28, 2017  
Subsequent event | April 28, 2017 | Series A Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1614583  
Subsequent event | April 28, 2017 | Series B Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.15625  
Subsequent event | April 28, 2017 | Series D Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1458333  
Subsequent event | April 28, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Payment Date May 05, 2017  
Distribution per Share (in dollars per share) $ 0.0875  
Subsequent event | April 28, 2017 | Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.125  
Subsequent event | May 31, 2017    
Dividends Payable [Line Items]    
Record Date May 19, 2017  
Payment Date May 31, 2017  
Subsequent event | May 31, 2017 | Series A Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1614583  
Subsequent event | May 31, 2017 | Series B Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.15625  
Subsequent event | May 31, 2017 | Series D Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1458333  
Subsequent event | May 31, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Payment Date Jun. 07, 2017  
Distribution per Share (in dollars per share) $ 0.0875  
Subsequent event | May 31, 2017 | Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.125  
Subsequent event | June 30, 2017    
Dividends Payable [Line Items]    
Record Date Jun. 21, 2017  
Payment Date Jun. 30, 2017  
Subsequent event | June 30, 2017 | Series A Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1614583  
Subsequent event | June 30, 2017 | Series B Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.15625  
Subsequent event | June 30, 2017 | Series D Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1458333  
Subsequent event | June 30, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Payment Date Jul. 10, 2017  
Distribution per Share (in dollars per share) $ 0.0875  
Subsequent event | June 30, 2017 | Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.125