Summarized Condensed Consolidating Information - Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands				12 Months Ended
	Nov. 18, 2016	Mar. 28, 2016	Aug. 18, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net cash (used in) provided by operating activities				$ 88,800	$ 64,431	$ 40,254
Cash flows from investing activities:
Acquisitions of real estate				(296,517)	(281,228)	(232,466)
Improvements to real estate				(748)	(762)	(187)
Purchases of equipment, furniture and fixtures				(403)	(151)	(276)
Preferred equity investments				0	(4,656)	0
Investment in real estate mortgage loan receivable				(12,416)	0	0
Sale of other real estate investment				7,500	0	0
Principal payments received on mortgage loan receivable				25	0	0
Escrow deposits for acquisition of real estate				0	(700)	(1,750)
Net proceeds from the sale of real estate				0	2,855	30
Distribution from subsidiary				0	0	0
Intercompany financing				0	0	0
Net cash used in investing activities				(302,559)	(284,642)	(234,649)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	$ 80,900	$ 105,800	$ 163,000	170,323	200,402	162,963
Proceeds from the issuance of senior unsecured notes payable				300,000	0	0
Proceeds from the issuance of senior unsecured term loan				0	100,000	0
Borrowings under unsecured revolving credit facility				238,000	255,000	45,000
Payments on senior unsecured notes payable				(267,639)	0	0
Payments on unsecured revolving credit facility				(168,000)	(205,000)	0
Borrowings under senior secured revolving credit facility				0	0	35,000
Repayments of borrowings under senior secured revolving credit facility				0	0	(35,000)
Payments on the mortgage notes payable				0	(95,022)	(3,183)
Payments of deferred financing costs				(6,063)	(1,352)	(2,303)
Net-settle adjustment on restricted stock				(866)	(515)	(145)
Dividends paid on common stock				(52,587)	(37,269)	(21,790)
Distribution to Parent				0	0	0
Intercompany financing				0	0	0
Net cash provided by financing activities				213,168	216,244	180,542
Net decrease in cash and cash equivalents				(591)	(3,967)	(13,853)
Cash and cash equivalents, beginning of period				7,500	11,467	25,320
Cash and cash equivalents, end of period				6,909	7,500	11,467
Reportable Legal Entities | Parent Guarantor
Cash flows from operating activities:
Net cash (used in) provided by operating activities				(222)	(91)	(15)
Cash flows from investing activities:
Acquisitions of real estate				0	0	0
Improvements to real estate				0	0	0
Purchases of equipment, furniture and fixtures				0	0	0
Preferred equity investments					0
Investment in real estate mortgage loan receivable				0
Sale of other real estate investment				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	0
Distribution from subsidiary				52,587	37,269	21,790
Intercompany financing				(169,235)	(199,796)	(162,803)
Net cash used in investing activities				(116,648)	(162,527)	(141,013)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net				170,323	200,402	162,963
Proceeds from the issuance of senior unsecured notes payable				0
Proceeds from the issuance of senior unsecured term loan					0
Borrowings under unsecured revolving credit facility				0	0	0
Payments on senior unsecured notes payable				0
Payments on unsecured revolving credit facility				0	0
Borrowings under senior secured revolving credit facility						0
Repayments of borrowings under senior secured revolving credit facility						0
Payments on the mortgage notes payable					0	0
Payments of deferred financing costs				0	0	0
Net-settle adjustment on restricted stock				(866)	(515)	(145)
Dividends paid on common stock				(52,587)	(37,269)	(21,790)
Distribution to Parent				0	0	0
Intercompany financing				0	0	0
Net cash provided by financing activities				116,870	162,618	141,028
Net decrease in cash and cash equivalents				0	0	0
Cash and cash equivalents, beginning of period				0	0	0
Cash and cash equivalents, end of period				0	0	0
Reportable Legal Entities | Issuers
Cash flows from operating activities:
Net cash (used in) provided by operating activities				25,745	9,253	(9,894)
Cash flows from investing activities:
Acquisitions of real estate				(296,517)	(281,228)	(232,466)
Improvements to real estate				(681)	(485)	(19)
Purchases of equipment, furniture and fixtures				(309)	(81)	(195)
Preferred equity investments					0
Investment in real estate mortgage loan receivable				(12,416)
Sale of other real estate investment				0
Principal payments received on mortgage loan receivable				25
Escrow deposits for acquisition of real estate					(700)	(1,750)
Net proceeds from the sale of real estate					0	0
Distribution from subsidiary				0	0	0
Intercompany financing				70,616	(41,901)	46,761
Net cash used in investing activities				(239,282)	(324,395)	(187,669)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net				0	0	0
Proceeds from the issuance of senior unsecured notes payable				300,000
Proceeds from the issuance of senior unsecured term loan					100,000
Borrowings under unsecured revolving credit facility				238,000	255,000	45,000
Payments on senior unsecured notes payable				(267,639)
Payments on unsecured revolving credit facility				(168,000)	(205,000)
Borrowings under senior secured revolving credit facility						35,000
Repayments of borrowings under senior secured revolving credit facility						(35,000)
Payments on the mortgage notes payable					0	0
Payments of deferred financing costs				(6,063)	(1,352)	(2,303)
Net-settle adjustment on restricted stock				0	0	0
Dividends paid on common stock				0	0	0
Distribution to Parent				(52,587)	(37,269)	(21,790)
Intercompany financing				169,235	199,796	162,803
Net cash provided by financing activities				212,946	311,175	183,710
Net decrease in cash and cash equivalents				(591)	(3,967)	(13,853)
Cash and cash equivalents, beginning of period				7,500	11,467	25,320
Cash and cash equivalents, end of period				6,909	7,500	11,467
Reportable Legal Entities | Combined Subsidiary Guarantors
Cash flows from operating activities:
Net cash (used in) provided by operating activities				63,277	55,269	50,163
Cash flows from investing activities:
Acquisitions of real estate				0	0	0
Improvements to real estate				(67)	(277)	(168)
Purchases of equipment, furniture and fixtures				(94)	(70)	(81)
Preferred equity investments					(4,656)
Investment in real estate mortgage loan receivable				0
Sale of other real estate investment				7,500
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					2,855	30
Distribution from subsidiary				0	0	0
Intercompany financing				0	0	0
Net cash used in investing activities				7,339	(2,148)	(219)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net				0	0	0
Proceeds from the issuance of senior unsecured notes payable				0
Proceeds from the issuance of senior unsecured term loan					0
Borrowings under unsecured revolving credit facility				0	0	0
Payments on senior unsecured notes payable				0
Payments on unsecured revolving credit facility				0	0
Borrowings under senior secured revolving credit facility						0
Repayments of borrowings under senior secured revolving credit facility						0
Payments on the mortgage notes payable					(95,022)	(3,183)
Payments of deferred financing costs				0	0	0
Net-settle adjustment on restricted stock				0	0	0
Dividends paid on common stock				0	0	0
Distribution to Parent				0	0	0
Intercompany financing				(70,616)	41,901	(46,761)
Net cash provided by financing activities				(70,616)	(53,121)	(49,944)
Net decrease in cash and cash equivalents				0	0	0
Cash and cash equivalents, beginning of period				0	0	0
Cash and cash equivalents, end of period				0	0	0
Elimination
Cash flows from operating activities:
Net cash (used in) provided by operating activities				0	0	0
Cash flows from investing activities:
Acquisitions of real estate				0	0	0
Improvements to real estate				0	0	0
Purchases of equipment, furniture and fixtures				0	0	0
Preferred equity investments					0
Investment in real estate mortgage loan receivable				0
Sale of other real estate investment				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	0
Distribution from subsidiary				(52,587)	(37,269)	(21,790)
Intercompany financing				98,619	241,697	116,042
Net cash used in investing activities				46,032	204,428	94,252
Cash flows from financing activities:
Proceeds from the issuance of common stock, net				0	0	0
Proceeds from the issuance of senior unsecured notes payable				0
Proceeds from the issuance of senior unsecured term loan					0
Borrowings under unsecured revolving credit facility				0	0	0
Payments on senior unsecured notes payable				0
Payments on unsecured revolving credit facility				0	0
Borrowings under senior secured revolving credit facility						0
Repayments of borrowings under senior secured revolving credit facility						0
Payments on the mortgage notes payable					0	0
Payments of deferred financing costs				0	0	0
Net-settle adjustment on restricted stock				0	0	0
Dividends paid on common stock				0	0	0
Distribution to Parent				52,587	37,269	21,790
Intercompany financing				(98,619)	(241,697)	(116,042)
Net cash provided by financing activities				(46,032)	(204,428)	(94,252)
Net decrease in cash and cash equivalents				0	0	0
Cash and cash equivalents, beginning of period				0	0	0
Cash and cash equivalents, end of period				$ 0	$ 0	$ 0