Summarized Condensed Consolidating Information - Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net cash (used in) provided by operating activities	$ 66,933	$ 49,513
Cash flows from investing activities:
Acquisitions of real estate	(222,463)	(185,284)
Improvements to real estate	(621)	(258)
Purchases of equipment, furniture and fixtures	(359)	(139)
Preferred equity investments	0	(4,531)
Escrow deposits for acquisition of real estate	(1,000)	(1,000)
Sale of other real estate investment	7,500	0
Distribution from subsidiary	0	0
Intercompany financing	0	0
Net cash used in investing activities	(216,943)	(191,212)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	170,414	108,395
Proceeds from the issuance of senior unsecured notes payable	300,000	0
Proceeds from the issuance of senior unsecured term loan	0	100,000
Borrowings under unsecured revolving credit facility	158,000	150,000
Payments on senior unsecured notes payable	(267,639)	0
Payments on unsecured revolving credit facility	(158,000)	(92,000)
Payments on the mortgage notes payable	0	(95,022)
Payments of deferred financing costs	(6,047)	(1,352)
Net-settle adjustment on restricted stock	(866)	(515)
Dividends paid on common stock	(38,544)	(27,396)
Distribution to Parent	0	0
Intercompany financing	0	0
Net cash provided by financing activities	157,318	142,110
Net increase in cash and cash equivalents	7,308	411
Cash and cash equivalents, beginning of period	7,500	11,467
Cash and cash equivalents, end of period	14,808	11,878
Reportable Legal Entities | Parent Guarantor
Cash flows from operating activities:
Net cash (used in) provided by operating activities	(157)	(73)
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
Preferred equity investments		0
Escrow deposits for acquisition of real estate	0	0
Sale of other real estate investment	0
Distribution from subsidiary	38,544	27,396
Intercompany financing	(169,391)	(107,807)
Net cash used in investing activities	(130,847)	(80,411)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	170,414	108,395
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
Payments on senior unsecured notes payable	0
Payments on unsecured revolving credit facility	0	0
Payments on the mortgage notes payable		0
Payments of deferred financing costs	0	0
Net-settle adjustment on restricted stock	(866)	(515)
Dividends paid on common stock	(38,544)	(27,396)
Distribution to Parent	0	0
Intercompany financing	0	0
Net cash provided by financing activities	131,004	80,484
Net increase 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 (used in) provided by operating activities	17,946	8,332
Cash flows from investing activities:
Acquisitions of real estate	(222,463)	(185,284)
Improvements to real estate	(571)	(56)
Purchases of equipment, furniture and fixtures	(292)	(70)
Preferred equity investments		0
Escrow deposits for acquisition of real estate	(1,000)	(1,000)
Sale of other real estate investment	0
Distribution from subsidiary	0	0
Intercompany financing	56,527	(58,570)
Net cash used in investing activities	(167,799)	(244,980)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	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	158,000	150,000
Payments on senior unsecured notes payable	(267,639)
Payments on unsecured revolving credit facility	(158,000)	(92,000)
Payments on the mortgage notes payable		0
Payments of deferred financing costs	(6,047)	(1,352)
Net-settle adjustment on restricted stock	0	0
Dividends paid on common stock	0	0
Distribution to Parent	(38,544)	(27,396)
Intercompany financing	169,391	107,807
Net cash provided by financing activities	157,161	237,059
Net increase in cash and cash equivalents	7,308	411
Cash and cash equivalents, beginning of period	7,500	11,467
Cash and cash equivalents, end of period	14,808	11,878
Reportable Legal Entities | Combined Subsidiary Guarantors
Cash flows from operating activities:
Net cash (used in) provided by operating activities	49,144	41,254
Cash flows from investing activities:
Acquisitions of real estate	0	0
Improvements to real estate	(50)	(202)
Purchases of equipment, furniture and fixtures	(67)	(69)
Preferred equity investments		(4,531)
Escrow deposits for acquisition of real estate	0	0
Sale of other real estate investment	7,500
Distribution from subsidiary	0	0
Intercompany financing	0	0
Net cash used in investing activities	7,383	(4,802)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	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
Payments on senior unsecured notes payable	0
Payments on unsecured revolving credit facility	0	0
Payments on the mortgage notes payable		(95,022)
Payments of deferred financing costs	0	0
Net-settle adjustment on restricted stock	0	0
Dividends paid on common stock	0	0
Distribution to Parent	0	0
Intercompany financing	(56,527)	58,570
Net cash provided by financing activities	(56,527)	(36,452)
Net increase 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 (used in) 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
Preferred equity investments		0
Escrow deposits for acquisition of real estate	0	0
Sale of other real estate investment	0
Distribution from subsidiary	(38,544)	(27,396)
Intercompany financing	112,864	166,377
Net cash used in investing activities	74,320	138,981
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	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
Payments on senior unsecured notes payable	0
Payments on unsecured revolving credit facility	0	0
Payments on the mortgage notes payable		0
Payments of deferred financing costs	0	0
Net-settle adjustment on restricted stock	0	0
Dividends paid on common stock	0	0
Distribution to Parent	38,544	27,396
Intercompany financing	(112,864)	(166,377)
Net cash provided by financing activities	(74,320)	(138,981)
Net increase 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