Stockholders' Equity (Dividends) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Common stock dividends		$ 88,270	$ 81,074	$ 176,418	$ 161,639
Common stock dividends per share (in dollars per share)		$ 0.515	$ 0.500	$ 1.030	$ 1.000
Common stock dividends declared (in dollars per share)		$ 0.515	$ 0.500	$ 1.030	$ 1.000
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	$ 4,096	$ 0	$ 8,194
Preferred stock dividends per depositary share (in dollars per share)		$ 0	$ 0.356250	$ 0	$ 0.712500
Dividend rate				5.70%
Series F Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends		$ 4,485	$ 4,485	$ 8,970	$ 8,970
Preferred stock dividends per depositary share (in dollars per share)		$ 0.325000	$ 0.325000	$ 0.650000	$ 0.650000
Dividend rate				5.20%		5.20%