Summarized Condensed Consolidating Information - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Assets:
Real estate investments, net	$ 1,167,001	$ 1,152,261
Other real estate investments, net	18,108	17,949
Cash and cash equivalents	11,560	6,909	$ 35,066	$ 7,500
Accounts and other receivables, net	9,023	5,254
Prepaid expenses and other assets	4,972	895
Deferred financing costs, net	1,176	1,718
Investment in subsidiaries	0	0
Intercompany	0	0
Total assets	1,211,840	1,184,986
Liabilities and Equity:
Senior unsecured notes payable, net	294,774	294,395
Senior unsecured term loan, net	99,564	99,517
Unsecured revolving credit facility	150,000	165,000
Accounts payable and accrued liabilities	12,515	17,413
Dividends payable	16,249	14,044
Intercompany	0	0
Total liabilities	573,102	590,369
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 78,550,687 and 75,478,202 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	785	755
Additional paid-in capital	831,286	783,237
Cumulative distributions in excess of earnings	(193,333)	(189,375)
Total equity	638,738	594,617		452,430
Total liabilities and equity	1,211,840	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	654,987	619,075
Intercompany	0	0
Total assets	654,987	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	16,249	14,044
Intercompany	0	0
Total liabilities	16,249	14,044
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 78,550,687 and 75,478,202 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	785	755
Additional paid-in capital	831,286	783,237
Cumulative distributions in excess of earnings	(193,333)	(178,961)
Total equity	638,738	605,031
Total liabilities and equity	654,987	619,075
Reportable Legal Entities | Issuers
Assets:
Real estate investments, net	829,720	805,826
Other real estate investments, net	12,362	12,399
Cash and cash equivalents	11,560	6,909	35,066	7,500
Accounts and other receivables, net	7,101	2,945
Prepaid expenses and other assets	4,970	893
Deferred financing costs, net	1,176	1,718
Investment in subsidiaries	464,159	444,120
Intercompany	0	0
Total assets	1,331,048	1,274,810
Liabilities and Equity:
Senior unsecured notes payable, net	294,774	294,395
Senior unsecured term loan, net	99,564	99,517
Unsecured revolving credit facility	150,000	165,000
Accounts payable and accrued liabilities	10,364	15,176
Dividends payable	0	0
Intercompany	121,358	92,061
Total liabilities	676,060	666,149
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 78,550,687 and 75,478,202 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	0	0
Additional paid-in capital	562,714	546,097
Cumulative distributions in excess of earnings	92,274	62,564
Total equity	654,988	608,661
Total liabilities and equity	1,331,048	1,274,810
Reportable Legal Entities | Combined Subsidiary Guarantors
Assets:
Real estate investments, net	337,281	346,435
Other real estate investments, net	5,746	5,550
Cash and cash equivalents	0	0	0	0
Accounts and other receivables, net	1,922	2,309
Prepaid expenses and other assets	2	2
Deferred financing costs, net	0	0
Investment in subsidiaries	0	0
Intercompany	121,358	92,061
Total assets	466,309	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	2,151	2,237
Dividends payable	0	0
Intercompany	0	0
Total liabilities	2,151	2,237
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 78,550,687 and 75,478,202 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	0	0
Additional paid-in capital	321,761	321,761
Cumulative distributions in excess of earnings	142,397	122,359
Total equity	464,158	444,120
Total liabilities and equity	466,309	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	(1,119,146)	(1,063,195)
Intercompany	(121,358)	(92,061)
Total assets	(1,240,504)	(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	(121,358)	(92,061)
Total liabilities	(121,358)	(92,061)
Equity:
Common stock, $0.01 par value; 500,000,000 shares authorized, 78,550,687 and 75,478,202 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	0	0
Additional paid-in capital	(884,475)	(867,858)
Cumulative distributions in excess of earnings	(234,671)	(195,337)
Total equity	(1,119,146)	(1,063,195)
Total liabilities and equity	$ (1,240,504)	$ (1,155,256)