Consolidated Balance Sheets (Parentheticals) - $ / shares	Jun. 30, 2019	Dec. 31, 2018	Jun. 28, 2017
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01		$ 0.01
Common stock, shares authorized (in shares)	1,000,000,000		125,000,000
Convertible Stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000	50,000
Preferred stock, shares issued (in shares)	50,000	50,000
Preferred stock, shares outstanding (in shares)	50,000	50,000
Class A Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	623,238	634,493
Common stock, shares outstanding (in shares)	623,238	634,493
Class T Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	1,099,414	1,111,394
Common stock, shares outstanding (in shares)	1,099,414	1,111,394
Class R Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	750,000,000	750,000,000
Common stock, shares issued (in shares)	9,294,218	7,181,534
Common stock, shares outstanding (in shares)	9,294,218	7,181,534
Class I Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	614,262	329,604
Common stock, shares outstanding (in shares)	614,262	329,604