CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common stock dividends declared and paid (in dollars per share)	$ 1.95	$ 1.86	$ 1.78
Issuance of stock (in shares)	40,371	35,456	31,807
Issuance of stock - stock purchase plan (in shares)	10,101	13,695	8,444
Issuance of stock - ATM equity program (in shares)	7,378,163	5,821,366	5,716,222
Issuance of stock - restricted common stock (in shares)	221,484	274,102	222,157
Series D Depositary Share
Preferred stock dividends declared and paid (in dollars per share)		$ 0.312847	$ 1.65625
Redemption of stock (in shares)		11,500,000
Series E Depositary Share
Preferred stock dividends declared and paid (in dollars per share)	$ 1.42500	$ 1.42500	1.42500
Series F Preferred Stock
Preferred stock dividends declared and paid (in dollars per share)	$ 1.30000	$ 1.30000	$ 0.231111
Issuance of stock (in shares)			13,800,000