Recent Developments (Details) - $ / shares	Feb. 04, 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%
Subsequent Event [Member]
Recent Developments [Line Items]
Dividends Payable, Date Declared	Feb. 04, 2020
Subsequent Event [Member] | Common Stock [Member]
Recent Developments [Line Items]
Dividends Payable, Date to be Paid	Mar. 16, 2020
Dividends Payable, Date of Record	Mar. 02, 2020
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. 16, 2020
Dividends Payable, Date of Record	Mar. 02, 2020
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. 16, 2020
Dividends Payable, Date of Record	Mar. 02, 2020
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. 16, 2020
Dividends Payable, Date of Record	Mar. 02, 2020
Subsequent Event [Member] | Series E Preferred Stock | Dividend Declared [Member]
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	$ 0.3671875