Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock Shares Issued (in shares)	266,011	186,797	201,212
Shares issued to directors (in shares)	152,758	251,323	117,886
Issuance of partnership units pursuant to dividend reinvestment plan (in shares)	111,351	124,758	107,037
Dividend declared
Distributions payable common stock and partnership units (in usd per share)	$ 0.52	$ 0.51	$ 0.43
Dividend declared | Series C Preferred Stock
Distributions payable on preferred stock (in usd per share)	$ 42.97	$ 42.97	$ 42.97