Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Common Stock Dividends in Excess of Earnings	Accumulated Other Comprehensive Income (Loss)	Total Stockholders' Equity	Noncontrolling Interest - Unit holders in Operating Partnership
Balance, beginning of period at Dec. 31, 2013	$ 674,564	$ 139,000	$ 447	$ 577,039	$ (116,877)	$ 3,440	$ 603,049	$ 71,515
Balance, beginning of period (in shares) at Dec. 31, 2013			44,764,377
Increase (Decrease) in Stockholders' Equity
Proceeds from sale of common stock	164,077		$ 72	164,005			164,077
Proceeds from sale of common stock (in shares)			7,191,537
Offering costs	(2,731)			(2,731)			(2,731)
Issuance of restricted stock, net			$ 1	(1)
Issuance of restricted stock, net (in shares)			101,934
Issuance of common stock (in shares)			9,488
Issuance of equity pursuant to outperformance program	(475)		$ 1	(1,491)			(1,490)	1,015
Issuance of equity pursuant to outperformance program (in shares)			43,657
Dividends and distributions, net	(61,935)	(8,136)			(50,227)		(58,363)	(3,572)
Non-cash compensation	5,306			1,546			1,546	3,760
Redemption of common units to common stock			$ 51	54,681			54,732	(54,732)
Redemption of common units to common stock (in shares)			5,105,584
Redemption of common units for cash	(342)							(342)
Rebalancing of noncontrolling interest				(9,530)			(9,530)	9,530
Other comprehensive income (loss)	(1,959)					(1,813)	(1,813)	(146)
Net income (loss)	(2,395)	8,136			(9,747)		(1,611)	(784)
Balance, end of period at Sep. 30, 2014	774,110	139,000	$ 572	783,518	(176,851)	1,627	747,866	26,244
Balance, end of period (in shares) at Sep. 30, 2014			57,216,577
Balance, beginning of period at Dec. 31, 2013	674,564	139,000	$ 447	577,039	(116,877)	3,440	603,049	71,515
Balance, beginning of period (in shares) at Dec. 31, 2013			44,764,377
Balance, end of period at Dec. 31, 2014	891,524	139,000	$ 644	928,242	(203,241)	(489)	864,156	27,368
Balance, end of period (in shares) at Dec. 31, 2014			64,434,852
Increase (Decrease) in Stockholders' Equity
Proceeds from sale of common stock	74,892		$ 35	74,857			74,892
Proceeds from sale of common stock (in shares)			3,456,403
Offering costs	(1,229)			(1,229)			(1,229)
Issuance of restricted stock, net			$ 1	(1)
Issuance of restricted stock, net (in shares)			83,756
Issuance of common stock (in shares)			11,277
Dividends and distributions, net	(79,402)	(8,136)			(67,652)		(75,788)	(3,614)
Non-cash compensation	5,667			2,115			2,115	3,552
Redemption of common units to common stock			$ 1	1,002			1,003	(1,003)
Redemption of common units to common stock (in shares)			90,824
Redemption of common units for cash	(64)							(64)
Issuance of units	21,902							21,902
Rebalancing of noncontrolling interest				10,141			10,141	(10,141)
Other comprehensive income (loss)	(7,019)					(6,676)	(6,676)	(343)
Net income (loss)	(11,335)	8,136			(18,520)		(10,384)	(951)
Balance, end of period at Sep. 30, 2015	$ 894,936	$ 139,000	$ 681	$ 1,015,127	$ (289,413)	$ (7,165)	$ 858,230	$ 36,706
Balance, end of period (in shares) at Sep. 30, 2015			68,077,112