Stockholders' Equity (Dividends) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Class of Stock [Line Items]
Common stock dividends		$ 89,947	$ 83,935	$ 266,365	$ 245,574
Common stock dividends per share (in dollars per share)		$ 0.520	$ 0.515	$ 1.550	$ 1.515
Common stock dividends declared (in dollars per share)		$ 0.520	$ 0.515	$ 1.550	$ 1.515
Subsequent event
Class of Stock [Line Items]
Common stock dividends declared (in dollars per share)	$ 0.52
Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends		$ 0	$ 4,097	$ 0	$ 12,291
Preferred stock dividends per depositary share (in dollars per share)		$ 0	$ 0.356250	$ 0	$ 1.068750
Dividend rate					5.70%
Series F Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends		$ 4,485	$ 4,485	$ 13,455	$ 13,455
Preferred stock dividends per depositary share (in dollars per share)		$ 0.325000	$ 0.325000	$ 0.975000	$ 0.975000
Dividend rate				5.20%	5.20%