Recent Developments (Details) - $ / shares	Feb. 02, 2021	Jun. 01, 2020	Sep. 19, 2018	Sep. 15, 2016	Jun. 15, 2015
Series C Preferred Stock
Recent Developments [Line Items]
Preferred Stock, Dividend Rate, Percentage					6.125%
Series D Preferred Stock
Recent Developments [Line Items]
Preferred Stock, Dividend Rate, Percentage				5.375%
Series E Preferred Stock
Recent Developments [Line Items]
Preferred Stock, Dividend Rate, Percentage			5.875%
Series F Preferred Stock [Member]
Recent Developments [Line Items]
Preferred Stock, Dividend Rate, Percentage		5.625%
Subsequent Event [Member]
Recent Developments [Line Items]
Dividends Payable, Date Declared	Feb. 02, 2021
Subsequent Event [Member] | Common Stock [Member]
Recent Developments [Line Items]
Dividends Payable, Date to be Paid	Mar. 15, 2021
Dividends Payable, Date of Record	Mar. 01, 2021
Subsequent Event [Member] | Common Stock [Member] | Dividend Declared [Member]
Recent Developments [Line Items]
Common stock, dividends declared ($ per share)	$ 0.18
Subsequent Event [Member] | Series C Preferred Stock
Recent Developments [Line Items]
Dividends Payable, Date to be Paid	Mar. 15, 2021
Dividends Payable, Date of Record	Mar. 01, 2021
Subsequent Event [Member] | Series C Preferred Stock | Dividend Declared [Member]
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	$ 0.3828125
Subsequent Event [Member] | Series D Preferred Stock
Recent Developments [Line Items]
Dividends Payable, Date to be Paid	Mar. 15, 2021
Dividends Payable, Date of Record	Mar. 01, 2021
Subsequent Event [Member] | Series D Preferred Stock | Dividend Declared [Member]
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	$ 0.3359375
Subsequent Event [Member] | Series E Preferred Stock
Recent Developments [Line Items]
Dividends Payable, Date to be Paid	Mar. 15, 2021
Dividends Payable, Date of Record	Mar. 01, 2021
Subsequent Event [Member] | Series E Preferred Stock | Dividend Declared [Member]
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	$ 0.3671875
Subsequent Event [Member] | Series F Preferred Stock [Member] | Dividend Declared [Member]
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	$ 0.3515625
Preferred Stock, Dividend Rate, Percentage	5.625%