CONDENSED CONSOLIDATED STATEMENT OF EQUITY - USD ($) $ in Thousands	Total	Class A Common Shares [Member]	Class B Common Shares [Member]	Class C Common Shares [Member]	Series A Preferred Shares [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Non-Controlling Interest [Member]
Beginning balance at Dec. 31, 2016	$ 1,424,311	$ 258	$ 16	$ 58		$ 925,563	$ (121,338)	$ 619,754
Beginning balance, shares at Dec. 31, 2016		25,843,000	1,589,000	5,755,000
Net income (loss)	(50,435)						(30,543)	(19,892)
Common dividends and distributions declared	(41,907)						(25,513)	(16,394)
Vesting of restricted share units, shares		11,000
Vesting of restricted share units	(13)	$ 0				(13)
Stock-based compensation	1,166					1,166
Stock issued in conversion of securities				$ 1
Stock issued in conversion securities, shares				197,176
Stock sold in conversion of securities		$ (1)
Stock sold in conversion of securities, shares		(197,000)
Share class surrenders			$ (2)			2
Share class surrenders, shares			(154,000)
OP Unit exchanges		$ 23				69,329		(69,352)
OP Unit exchanges, shares		2,344,589
Ending balance at Sep. 30, 2017	1,333,122	$ 280	$ 14	$ 59		996,047	(177,394)	514,116
Ending balance, shares at Sep. 30, 2017		28,001,000	1,435,000	5,952,000
Beginning balance at Dec. 31, 2017	1,320,860	$ 324	$ 13	$ 31	$ 28	1,116,060	(229,760)	434,164
Beginning balance, shares at Dec. 31, 2017		32,415,734	1,328,866	3,151,131	2,800,000
Net income (loss)	(29,145)						(18,659)	(10,486)
Common dividends and distributions declared	(42,109)						(26,995)	(15,114)
Preferred dividends declared	(3,678)						(3,678)
Vesting of restricted share units, shares		2,000
Vesting of restricted share units		$ 0				0
Stock-based compensation	5,589					5,589
Preferred stock offering costs	(113)					(113)
Stock issued in conversion of securities	1	$ 32
Stock issued in conversion securities, shares		3,151,131
Stock sold in conversion of securities				$ (31)
Stock sold in conversion of securities, shares				(3,151,000)
Share class surrenders, shares			(7,000)
OP Unit exchanges		$ 1				2,925		(2,926)
OP Unit exchanges, shares		98,923
Ending balance at Sep. 30, 2018	$ 1,251,405	$ 357	$ 13		$ 28	$ 1,124,461	$ (279,092)	$ 405,638
Ending balance, shares at Sep. 30, 2018		35,667,521	1,322,365		2,800,000