Consolidated Statements of Equity (Unaudited) (Parentheticals) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class A
Statements of Equity
Distributions declared per share (in dollars per share)	$ 0.1563	$ 0.1563
Class C
Statements of Equity
Distributions declared per share (in dollars per share)	0.1375	0.1380
Common Stock | Class A
Statements of Equity
Distributions declared per share (in dollars per share)	0.1563	0.1563
Common Stock | Class C
Statements of Equity
Distributions declared per share (in dollars per share)	$ 0.1375	$ 0.1380