Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income/(Loss)	Accumulated Deficit	Transition Adjustment	Transition Adjustment Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		39,303,710
Beginning balance at Dec. 31, 2018	$ 733,228	$ 395	$ 827,558	$ (459)	$ (94,266)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		1,161,580
Issuance of common stock	19,409	$ 11	19,398
Common stock repurchases (in shares)		(387,530)
Common stock repurchases	(7,207)	$ (4)	(7,203)
Common stock issued through distribution reinvestment plan (in shares)		180,906
Common stock issued through distribution reinvestment plan	3,392	$ 2	3,390
Share-based compensation	39		39
Offering costs	(382)		(382)
Net income/(loss)	19,890				19,890
Distributions declared	(17,449)				(17,449)
Other comprehensive income/(loss)	145			145
Ending balance (in shares) at Mar. 31, 2019		40,258,666
Ending balance at Mar. 31, 2019	751,065	$ 404	842,800	(314)	(91,825)
Beginning balance (in shares) at Dec. 31, 2018		39,303,710
Beginning balance at Dec. 31, 2018	733,228	$ 395	827,558	(459)	(94,266)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income/(loss)	60,329
Ending balance (in shares) at Sep. 30, 2019		43,021,064
Ending balance at Sep. 30, 2019	798,520	$ 432	888,208	(751)	(89,369)
Beginning balance (in shares) at Mar. 31, 2019		40,258,666
Beginning balance at Mar. 31, 2019	751,065	$ 404	842,800	(314)	(91,825)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		1,267,833
Issuance of common stock	21,188	$ 13	21,175
Common stock issued through distribution reinvestment plan (in shares)		187,146
Common stock issued through distribution reinvestment plan	3,492	$ 2	3,490
Share-based compensation (in shares)		6,400
Share-based compensation	39		39
Offering costs	(529)		(529)
Net income/(loss)	14,526				14,526
Distributions declared	(18,298)				(18,298)
Other comprehensive income/(loss)	(65)			(65)
Ending balance (in shares) at Jun. 30, 2019		41,720,045
Ending balance at Jun. 30, 2019	771,418	$ 419	866,975	(379)	(95,597)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		1,466,430
Issuance of common stock	24,485	$ 14	24,471
Common stock repurchases (in shares)		(354,323)
Common stock repurchases	(6,606)	$ (3)	(6,603)
Common stock issued through distribution reinvestment plan (in shares)		188,912
Common stock issued through distribution reinvestment plan	3,515	$ 2	3,513
Share-based compensation	39		39
Offering costs	(187)		(187)
Net income/(loss)	25,913				25,913
Distributions declared	(19,685)				(19,685)
Other comprehensive income/(loss)	(372)			(372)
Ending balance (in shares) at Sep. 30, 2019		43,021,064
Ending balance at Sep. 30, 2019	798,520	$ 432	888,208	(751)	(89,369)
Beginning balance (in shares) at Dec. 31, 2019		43,916,815
Beginning balance at Dec. 31, 2019	816,805	$ 441	903,310	(978)	(85,968)	$ (7,761)	$ (7,761)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		650,034
Issuance of common stock	10,862	$ 7	10,855
Common stock repurchases (in shares)		(361,829)
Common stock repurchases	(6,715)	$ (4)	(6,711)
Common stock issued through distribution reinvestment plan (in shares)		191,326
Common stock issued through distribution reinvestment plan	3,549	$ 1	3,548
Share-based compensation	39		39
Offering costs	(136)		(136)
Net income/(loss)	(7,400)				(7,400)
Distributions declared	(20,371)				(20,371)
Other comprehensive income/(loss)	(67,607)			(67,607)
Ending balance (in shares) at Mar. 31, 2020		44,396,346
Ending balance at Mar. 31, 2020	721,265	$ 445	910,905	(68,585)	(121,500)
Beginning balance (in shares) at Dec. 31, 2019		43,916,815
Beginning balance at Dec. 31, 2019	816,805	$ 441	903,310	(978)	(85,968)	$ (7,761)	$ (7,761)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income/(loss)	21,911
Ending balance (in shares) at Sep. 30, 2020		44,353,727
Ending balance at Sep. 30, 2020	$ 777,415	$ 445	910,040	(9,610)	(123,460)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance (in shares) at Mar. 31, 2020		44,396,346
Beginning balance at Mar. 31, 2020	$ 721,265	$ 445	910,905	(68,585)	(121,500)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		0
Issuance of common stock	25	$ 0	25
Common stock repurchases (in shares)		(11,306)
Common stock repurchases	(192)	$ 0	(192)
Common stock issued through distribution reinvestment plan (in shares)		6
Common stock issued through distribution reinvestment plan	(57)	$ 0	(57)
Share-based compensation (in shares)		10,770
Share-based compensation	57		57
Offering costs	(32)		(32)
Net income/(loss)	7,814				7,814
Distributions declared	(15,603)				(15,603)
Other comprehensive income/(loss)	40,319			40,319
Ending balance (in shares) at Jun. 30, 2020		44,395,816
Ending balance at Jun. 30, 2020	753,596	$ 445	910,706	(28,266)	(129,289)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock repurchases (in shares)		(206,332)
Common stock repurchases	(3,352)	$ (2)	(3,350)
Common stock issued through distribution reinvestment plan (in shares)		164,243
Common stock issued through distribution reinvestment plan	2,669	$ 2	2,667
Share-based compensation	40		40
Offering costs	(23)		(23)
Net income/(loss)	21,497				21,497
Distributions declared	(15,668)				(15,668)
Other comprehensive income/(loss)	18,656			18,656
Ending balance (in shares) at Sep. 30, 2020		44,353,727
Ending balance at Sep. 30, 2020	$ 777,415	$ 445	$ 910,040	$ (9,610)	$ (123,460)