Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Total Shareholders’ Equity	Common Shares	Additional Paid - In Capital	Retained earnings (distributions in excess of retained earnings)	Noncontrolling Interest in Operating Partnership
Beginning Balance (in shares) at Dec. 31, 2015			38,308,937
Beginning Balance at Dec. 31, 2015	$ 697,002	$ 692,871	$ 379	$ 719,773	$ (27,281)	$ 4,131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares pursuant to Equity Incentive Plan (in shares)			26,488
Issuance of shares pursuant to Equity Incentive Plan	550	550		550
Issuance of shares, net of offering costs (in shares)			16,454
Issuance of shares, net of offering costs	337	337	$ 1	336
Issuance of restricted time-based (in shares)			7,851
Issuance of restricted time-based shares	0
Amortization of share based compensation	1,879	963		963		916
Dividends declared on common shares	(37,266)	(37,266)			(37,266)
Distributions declared on LTIP units	(537)					(537)
Reallocation of noncontrolling interest	0	11		11		(11)
Net income	29,018	28,823			28,823	195
Ending Balance (in shares) at Sep. 30, 2016			38,359,730
Ending Balance at Sep. 30, 2016	690,983	686,289	$ 380	721,633	(35,724)	4,694
Beginning Balance (in shares) at Dec. 31, 2016			38,367,014
Beginning Balance at Dec. 31, 2016	681,590	676,742	$ 380	722,019	(45,657)	4,848
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares pursuant to Equity Incentive Plan (in shares)			23,980
Issuance of shares pursuant to Equity Incentive Plan	500	500		500
Issuance of shares, net of offering costs (in shares)			1,443,482
Issuance of shares, net of offering costs	28,924	28,924	$ 15	28,909
Issuance of restricted time-based (in shares)			5,000
Amortization of share based compensation	2,410	619		619		1,791
Dividends declared on common shares	(38,495)	(38,495)			(38,495)
Distributions declared on LTIP units	(721)					(721)
Reallocation of noncontrolling interest	0	101		101		(101)
Net income	24,222	24,055			24,055	167
Ending Balance (in shares) at Sep. 30, 2017			39,839,476
Ending Balance at Sep. 30, 2017	$ 698,430	$ 692,446	$ 395	$ 752,148	$ (60,097)	$ 5,984