Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Subsequent Events - Monthly Distributions Declared by Company's Board of Directors (Detail) - $ / shares
 6 Months Ended
Jul. 11, 2017
Jun. 30, 2017
July 31, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Distributions Payable To Holders Of Records Months   July
August 31, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Distributions Payable To Holders Of Records Months   August
September 29, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Distributions Payable To Holders Of Records Months   September
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 | July 31, 2017    
Dividends Payable [Line Items]    
Record Date Jul. 21, 2017  
Payment Date Jul. 31, 2017  
Subsequent event | July 31, 2017 | Series A Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1614583  
Subsequent event | July 31, 2017 | Series B Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.15625  
Subsequent event | July 31, 2017 | Series D Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1458333  
Subsequent event | July 31, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Payment Date Aug. 07, 2017  
Distribution per Share (in dollars per share) $ 0.0875  
Subsequent event | July 31, 2017 | Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.125  
Subsequent event | August 31, 2017    
Dividends Payable [Line Items]    
Record Date Aug. 21, 2017  
Payment Date Aug. 31, 2017  
Subsequent event | August 31, 2017 | Series A Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1614583  
Subsequent event | August 31, 2017 | Series B Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.15625  
Subsequent event | August 31, 2017 | Series D Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1458333  
Subsequent event | August 31, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Payment Date Sep. 08, 2017  
Distribution per Share (in dollars per share) $ 0.0875  
Subsequent event | August 31, 2017 | Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.125  
Subsequent event | September 29, 2017    
Dividends Payable [Line Items]    
Record Date Sep. 20, 2017  
Payment Date Sep. 29, 2017  
Subsequent event | September 29, 2017 | Series A Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1614583  
Subsequent event | September 29, 2017 | Series B Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) 0.15625  
Subsequent event | September 29, 2017 | Series D Preferred Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.1458333  
Subsequent event | September 29, 2017 | Senior Common Stock    
Dividends Payable [Line Items]    
Payment Date Oct. 06, 2017  
Distribution per Share (in dollars per share) $ 0.0875  
Subsequent event | September 29, 2017 | Common Stock    
Dividends Payable [Line Items]    
Distribution per Share (in dollars per share) $ 0.125