Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Tenant and other receivables allowance	$ 1,422	$ 3,333
Deferred rent receivables allowance	$ 185	$ 390
Preferred stock, par value (USD per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Private perpetual preferred units, liquidation preference per share (in dollars per share)	$ 16.62	$ 16.62
Private perpetual preferred units, issued, shares	1,560,360	1,560,360
Private perpetual preferred units, outstanding, shares	1,560,360	1,560,360
Common Class A [Member]
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares issued (in shares)	160,424,575	154,744,740
Common stock, shares outstanding (in shares)	160,424,575	154,744,740
Common Class B [Member]
Common stock, par value (USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	1,052,469	1,095,737
Common stock, shares outstanding (in shares)	1,052,469	1,095,737