CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Dividends declared and paid:
Common stock dividends (in dollars per share)	$ 0.50	$ 0.475
Issuance of common stock:
Director compensation and other (in shares)	8,007	9,597
Stock purchase plan (in shares)	2,324	2,537
Issuance of restricted common stock (in shares)	259,650	222,684
Series E Preferred Stock
Dividends declared and paid:
Preferred stock dividends (in dollars per share)	$ 0.356250	$ 0.356250
Series F Preferred Stock
Dividends declared and paid:
Preferred stock dividends (in dollars per share)	$ 0.32500	$ 0.32500