Summarized Condensed Consolidating Information - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Assets:
Real estate investments, net	$ 1,189,449	$ 1,152,261
Other real estate investments, net	18,083	17,949
Cash and cash equivalents	15,745	6,909	$ 14,808	$ 7,500
Accounts and other receivables, net	12,384	5,254
Prepaid expenses and other assets	3,792	895
Deferred financing costs, net	904	1,718
Investment in subsidiaries	0	0
Intercompany	0	0
Total assets	1,240,357	1,184,986
Liabilities and Equity:
Senior unsecured notes payable, net	294,963	294,395
Senior unsecured term loan, net	99,588	99,517
Unsecured revolving credit facility	90,000	165,000
Accounts payable and accrued liabilities	18,510	17,413
Dividends payable	17,246	14,044
Intercompany	0	0
Total liabilities	520,307	590,369
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 83,353,226 and 75,478,202 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	834	755
Additional paid-in capital	915,235	783,237
Cumulative distributions in excess of earnings	(196,019)	(189,375)
Total equity	720,050	594,617		452,430
Total liabilities and equity	1,240,357	1,184,986
Reportable Legal Entities | Parent Guarantor
Assets:
Real estate investments, net	0	0
Other real estate investments, net	0	0
Cash and cash equivalents	0	0	0	0
Accounts and other receivables, net	0	0
Prepaid expenses and other assets	0	0
Deferred financing costs, net	0	0
Investment in subsidiaries	737,296	619,075
Intercompany	0	0
Total assets	737,296	619,075
Liabilities and Equity:
Senior unsecured notes payable, net	0	0
Senior unsecured term loan, net	0	0
Unsecured revolving credit facility	0	0
Accounts payable and accrued liabilities	0	0
Dividends payable	17,246	14,044
Intercompany	0	0
Total liabilities	17,246	14,044
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 83,353,226 and 75,478,202 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	834	755
Additional paid-in capital	915,235	783,237
Cumulative distributions in excess of earnings	(196,019)	(178,961)
Total equity	720,050	605,031
Total liabilities and equity	737,296	619,075
Reportable Legal Entities | Issuers
Assets:
Real estate investments, net	856,659	805,826
Other real estate investments, net	12,337	12,399
Cash and cash equivalents	15,745	6,909	14,808	7,500
Accounts and other receivables, net	9,567	2,945
Prepaid expenses and other assets	3,789	893
Deferred financing costs, net	904	1,718
Investment in subsidiaries	474,524	444,120
Intercompany	0	0
Total assets	1,373,525	1,274,810
Liabilities and Equity:
Senior unsecured notes payable, net	294,963	294,395
Senior unsecured term loan, net	99,588	99,517
Unsecured revolving credit facility	90,000	165,000
Accounts payable and accrued liabilities	15,401	15,176
Dividends payable	0	0
Intercompany	136,277	92,061
Total liabilities	636,229	666,149
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 83,353,226 and 75,478,202 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	0	0
Additional paid-in capital	629,525	546,097
Cumulative distributions in excess of earnings	107,771	62,564
Total equity	737,296	608,661
Total liabilities and equity	1,373,525	1,274,810
Reportable Legal Entities | Combined Subsidiary Guarantors
Assets:
Real estate investments, net	332,790	346,435
Other real estate investments, net	5,746	5,550
Cash and cash equivalents	0	0	0	0
Accounts and other receivables, net	2,817	2,309
Prepaid expenses and other assets	3	2
Deferred financing costs, net	0	0
Investment in subsidiaries	0	0
Intercompany	136,277	92,061
Total assets	477,633	446,357
Liabilities and Equity:
Senior unsecured notes payable, net	0	0
Senior unsecured term loan, net	0	0
Unsecured revolving credit facility	0	0
Accounts payable and accrued liabilities	3,109	2,237
Dividends payable	0	0
Intercompany	0	0
Total liabilities	3,109	2,237
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 83,353,226 and 75,478,202 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	0	0
Additional paid-in capital	321,761	321,761
Cumulative distributions in excess of earnings	152,763	122,359
Total equity	474,524	444,120
Total liabilities and equity	477,633	446,357
Elimination
Assets:
Real estate investments, net	0	0
Other real estate investments, net	0	0
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts and other receivables, net	0	0
Prepaid expenses and other assets	0	0
Deferred financing costs, net	0	0
Investment in subsidiaries	(1,211,820)	(1,063,195)
Intercompany	(136,277)	(92,061)
Total assets	(1,348,097)	(1,155,256)
Liabilities and Equity:
Senior unsecured notes payable, net	0	0
Senior unsecured term loan, net	0	0
Unsecured revolving credit facility	0	0
Accounts payable and accrued liabilities	0	0
Dividends payable	0	0
Intercompany	(136,277)	(92,061)
Total liabilities	(136,277)	(92,061)
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 83,353,226 and 75,478,202 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	0	0
Additional paid-in capital	(951,286)	(867,858)
Cumulative distributions in excess of earnings	(260,534)	(195,337)
Total equity	(1,211,820)	(1,063,195)
Total liabilities and equity	$ (1,348,097)	$ (1,155,256)