Summarized Condensed Consolidating Information - Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net cash (used in) provided by operating activities	$ 44,901	$ 28,113
Cash flows from investing activities:
Acquisitions of real estate	(96,641)	(144,149)
Improvements to real estate	(598)	(170)
Purchases of equipment, furniture and fixtures	(233)	(89)
Escrow deposit for acquisitions of real estate	(4,335)	0
Sale of other real estate investment	7,500	0
Distribution from subsidiary	0	0
Intercompany financing	0	0
Net cash used in investing activities	(94,307)	(144,408)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	170,485	105,889
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	63,000	115,000
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	(5,511)	(1,332)
Net-settle adjustment on restricted stock	(866)	(515)
Dividends paid on common stock	(24,497)	(17,548)
Distribution to Parent	0	0
Intercompany financing	0	0
Net cash provided by financing activities	76,972	114,472
Net increase (decrease) in cash and cash equivalents	27,566	(1,823)
Cash and cash equivalents beginning of period	7,500	11,467
Cash and cash equivalents end of period	35,066	9,644
Reportable Legal Entities [Member] | Parent Guarantor [Member]
Cash flows from operating activities:
Net cash (used in) provided by operating activities	(141)	466
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
Escrow deposit for acquisitions of real estate	0
Sale of other real estate investment	0
Distribution from subsidiary	24,497	17,548
Intercompany financing	(169,478)	(105,840)
Net cash used in investing activities	(144,981)	(88,292)
Cash flows from financing activities:
Proceeds from the issuance of common stock, net	170,485	105,889
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	(24,497)	(17,548)
Distribution to Parent	0	0
Intercompany financing	0	0
Net cash provided by financing activities	145,122	87,826
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 [Member] | Issuers [Member]
Cash flows from operating activities:
Net cash (used in) provided by operating activities	10,517	396
Cash flows from investing activities:
Acquisitions of real estate	(96,641)	(144,149)
Improvements to real estate	(556)	(56)
Purchases of equipment, furniture and fixtures	(169)	(31)
Escrow deposit for acquisitions of real estate	(4,335)
Sale of other real estate investment	0
Distribution from subsidiary	0	0
Intercompany financing	41,919	(67,943)
Net cash used in investing activities	(59,782)	(212,179)
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	63,000	115,000
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	(5,511)	(1,332)
Net-settle adjustment on restricted stock	0	0
Dividends paid on common stock	0	0
Distribution to Parent	(24,497)	(17,548)
Intercompany financing	169,478	105,840
Net cash provided by financing activities	76,831	209,960
Net increase (decrease) in cash and cash equivalents	27,566	(1,823)
Cash and cash equivalents beginning of period	7,500	11,467
Cash and cash equivalents end of period	35,066	9,644
Reportable Legal Entities [Member] | Combined Subsidiary Guarantors [Member]
Cash flows from operating activities:
Net cash (used in) provided by operating activities	34,525	27,251
Cash flows from investing activities:
Acquisitions of real estate	0	0
Improvements to real estate	(42)	(114)
Purchases of equipment, furniture and fixtures	(64)	(58)
Escrow deposit for acquisitions of real estate	0
Sale of other real estate investment	7,500
Distribution from subsidiary	0	0
Intercompany financing	0	0
Net cash used in investing activities	7,394	(172)
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	(41,919)	67,943
Net cash provided by financing activities	(41,919)	(27,079)
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 [Member]
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
Escrow deposit for acquisitions of real estate	0
Sale of other real estate investment	0
Distribution from subsidiary	(24,497)	(17,548)
Intercompany financing	127,559	173,783
Net cash used in investing activities	103,062	156,235
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	24,497	17,548
Intercompany financing	(127,559)	(173,783)
Net cash provided by financing activities	(103,062)	(156,235)
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