CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Dividends declared and paid:
Common stock dividends (in dollars per share)	$ 0.515	$ 0.50	$ 1.515	$ 1.45
Issuance of common stock:
Director compensation (in shares)	6,964	9,308	21,933	31,941
Stock purchase plan (in shares)	1,716	2,923	5,872	8,429
ATM equity program and equity offering (in shares)	7,000,000		7,000,000
Restricted shares, net of buyback and surrender (in shares)	100,000		359,650	221,484
ATM equity program
Issuance of common stock:
ATM equity program and equity offering (in shares)	848,474	1,859,099	2,344,022	4,896,563
Series E Preferred Stock
Dividends declared and paid:
Preferred stock dividends (in dollars per share)	$ 0.356250	$ 0.356250	$ 1.068750	$ 1.068750
Series F Preferred Stock
Dividends declared and paid:
Preferred stock dividends (in dollars per share)	$ 0.32500	$ 0.32500	$ 0.975000	$ 0.975000