CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common stock dividends declared and paid (in dollars per share)	$ 2.07	$ 2.03	$ 1.95
Redemption of depositary shares (in shares)		11,500,000
Issuance of common stock - Director compensation (in shares)	35,351	28,287	40,731
Issuance of common stock - Stock purchase plan (in shares)	8,079	6,986	10,101
Issuance of common stock - ATM equity program (in shares)	3,119,153	2,344,022	7,378,163
Issuance of common stock - Equity offering (in shares)		7,000,000
Issuance of common stock - restricted shares, net (in shares)	263,406	359,650	221,484
Series E Preferred Stock
Preferred stock dividends declared and paid (in dollars per share)		$ 1.47917	$ 1.42500
Series F Preferred Stock
Preferred stock dividends declared and paid (in dollars per share)	$ 1.30000	$ 1.30000	$ 1.30000