Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.8
Subsequent Events - Monthly Distributions Declared by Company's Board of Directors (Detail) (USD $)
 0 Months Ended
Jul. 09, 2013
Common Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.3750000
Subsequent Event A [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Record Date Jul. 19, 2013
Payment Date Jul. 31, 2013
Payable to the Holders of Records During the Month July
Subsequent Event A [Member] | Common Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1250000
Subsequent Event B [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Record Date Aug. 21, 2013
Payment Date Aug. 30, 2013
Payable to the Holders of Records During the Month August
Subsequent Event B [Member] | Common Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1250000
Subsequent Event C [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Record Date Sep. 18, 2013
Payment Date Sep. 30, 2013
Payable to the Holders of Records During the Month September
Subsequent Event C [Member] | Common Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1250000
Senior Common Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.2625
Senior Common Stock [Member] | Subsequent Event A [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Payment Date Aug. 07, 2013
Distribution per Share $ 0.0875
Senior Common Stock [Member] | Subsequent Event B [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Payment Date Sep. 09, 2013
Distribution per Share $ 0.0875
Senior Common Stock [Member] | Subsequent Event C [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Payment Date Oct. 07, 2013
Distribution per Share $ 0.0875
Series A Preferred Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.4843749
Series A Preferred Stock [Member] | Subsequent Event A [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1614583
Series A Preferred Stock [Member] | Subsequent Event B [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1614583
Series A Preferred Stock [Member] | Subsequent Event C [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1614583
Series B Preferred Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.4687500
Series B Preferred Stock [Member] | Subsequent Event A [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1562500
Series B Preferred Stock [Member] | Subsequent Event B [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1562500
Series B Preferred Stock [Member] | Subsequent Event C [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1562500
Series C Preferred Stock [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.4453125
Series C Preferred Stock [Member] | Subsequent Event A [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1484375
Series C Preferred Stock [Member] | Subsequent Event B [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1484375
Series C Preferred Stock [Member] | Subsequent Event C [Member]
  
Schedule Of Performance Share Units Activity [Line Items]  
Distribution per Share $ 0.1484375