Summarized Condensed Consolidating Information - Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net cash provided by operating activities	$ 22,059	$ 20,166
Cash flows from investing activities:
Acquisitions of real estate	(47,103)	(54,568)
Improvements to real estate	(11)	(89)
Purchases of equipment, furniture and fixtures	(27)	(117)
Principal payments received on mortgage loan receivable	23	0
Escrow deposits for acquisition of real estate	(1,000)	(700)
Net proceeds from the sale of real estate	13,004
Net proceeds from the sale of real estate	13,004	0
Distribution from subsidiary	0	0
Intercompany financing	0	0
Net cash used in investing activities	(35,114)	(55,474)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	(10)	108,166
Borrowings under unsecured revolving credit facility	60,000	45,000
Payments on unsecured revolving credit facility	(25,000)	(113,000)
Net-settle adjustment on restricted stock	(605)	0
Dividends paid on common stock	(14,044)	(11,075)
Distribution to Parent	0	0
Distribution to Parent	0	0
Net cash provided by financing activities	20,341	29,091
Net increase (decrease) in cash and cash equivalents	7,286	(6,217)
Cash and cash equivalents, beginning of period	6,909	7,500
Cash and cash equivalents, end of period	14,195	1,283
Reportable Legal Entities | Parent Guarantor
Cash flows from operating activities:
Net cash provided by operating activities	0	(14)
Cash flows from investing activities:
Acquisitions of real estate	0	0
Improvements to real estate	0	0
Purchases of equipment, furniture and fixtures	0	0
Principal payments received on mortgage loan receivable	0
Escrow deposits for acquisition of real estate	0	0
Net proceeds from the sale of real estate	0
Net proceeds from the sale of real estate		0
Distribution from subsidiary	14,044	11,075
Intercompany financing	615	(108,152)
Net cash used in investing activities	14,659	(97,077)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	(10)	108,166
Borrowings under unsecured revolving credit facility	0	0
Payments on unsecured revolving credit facility	0	0
Net-settle adjustment on restricted stock	(605)
Dividends paid on common stock	(14,044)	(11,075)
Distribution to Parent	0	0
Distribution to Parent	0	0
Net cash provided by financing activities	(14,659)	97,091
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Reportable Legal Entities | Issuers
Cash flows from operating activities:
Net cash provided by operating activities	7,295	6,001
Cash flows from investing activities:
Acquisitions of real estate	(47,103)	(54,568)
Improvements to real estate	0	(64)
Purchases of equipment, furniture and fixtures	(23)	(93)
Principal payments received on mortgage loan receivable	23
Escrow deposits for acquisition of real estate	(1,000)	(700)
Net proceeds from the sale of real estate	13,004
Net proceeds from the sale of real estate		0
Distribution from subsidiary	0	0
Intercompany financing	14,749	14,130
Net cash used in investing activities	(20,350)	(41,295)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	0	0
Borrowings under unsecured revolving credit facility	60,000	45,000
Payments on unsecured revolving credit facility	(25,000)	(113,000)
Net-settle adjustment on restricted stock	0
Dividends paid on common stock	0	0
Distribution to Parent	(14,044)	(11,075)
Distribution to Parent	(615)	108,152
Net cash provided by financing activities	20,341	29,077
Net increase (decrease) in cash and cash equivalents	7,286	(6,217)
Cash and cash equivalents, beginning of period	6,909	7,500
Cash and cash equivalents, end of period	14,195	1,283
Reportable Legal Entities | Combined Subsidiary Guarantors
Cash flows from operating activities:
Net cash provided by operating activities	14,764	14,179
Cash flows from investing activities:
Acquisitions of real estate	0	0
Improvements to real estate	(11)	(25)
Purchases of equipment, furniture and fixtures	(4)	(24)
Principal payments received on mortgage loan receivable	0
Escrow deposits for acquisition of real estate	0	0
Net proceeds from the sale of real estate	0
Net proceeds from the sale of real estate		0
Distribution from subsidiary	0	0
Intercompany financing	0	0
Net cash used in investing activities	(15)	(49)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	0	0
Borrowings under unsecured revolving credit facility	0	0
Payments on unsecured revolving credit facility	0	0
Net-settle adjustment on restricted stock	0
Dividends paid on common stock	0	0
Distribution to Parent	0	0
Distribution to Parent	(14,749)	(14,130)
Net cash provided by financing activities	(14,749)	(14,130)
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Elimination
Cash flows from operating activities:
Net cash provided by operating activities	0	0
Cash flows from investing activities:
Acquisitions of real estate	0	0
Improvements to real estate	0	0
Purchases of equipment, furniture and fixtures	0	0
Principal payments received on mortgage loan receivable	0
Escrow deposits for acquisition of real estate	0	0
Net proceeds from the sale of real estate	0
Net proceeds from the sale of real estate		0
Distribution from subsidiary	(14,044)	(11,075)
Intercompany financing	(15,364)	94,022
Net cash used in investing activities	(29,408)	82,947
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	0	0
Borrowings under unsecured revolving credit facility	0	0
Payments on unsecured revolving credit facility	0	0
Net-settle adjustment on restricted stock	0
Dividends paid on common stock	0	0
Distribution to Parent	14,044	11,075
Distribution to Parent	15,364	(94,022)
Net cash provided by financing activities	29,408	(82,947)
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 0	$ 0