Stockholder's Equity (Summary of Dividend Payments) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Per Share
Common Stock (in USD per share)	$ 3.4800	$ 3.4800	$ 3.4800
Amount
Common Stock	$ 1,404,977	$ 1,300,141	$ 1,277,321
Totals	$ 1,404,977	$ 1,346,845	$ 1,326,731
Series I Preferred Stock
Per Share
Preferred Stock (in USD per share)	$ 0	$ 3.2500	$ 3.2500
Amount
Preferred Stock	$ 0	$ 46,704	$ 46,711
Series J Preferred Stock
Per Share
Preferred Stock (in USD per share)	$ 0	$ 0	$ 0.2347
Amount
Preferred Stock	$ 0	$ 0	$ 2,699