Stockholders' Equity - Dividends (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividends
Common stock dividends declared (in dollars per share)	$ 0.74	$ 0.69	$ 0.73
Series E Cumulative Redeemable Preferred Stock
Dividends
Preferred stock dividends and dividends payable (in dollars per share)	1.7375	1.7375	1.7375
Series F Cumulative Redeemable Preferred Stock
Dividends
Preferred stock dividends and dividends payable (in dollars per share)	1.6125	1.6125	1.6125
Common Stock
Dividends
Common stock dividends declared (in dollars per share)	$ 0.7400	$ 0.6900	$ 0.7300