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Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Summary of Notes Payable (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Notes Payable [Line Items]
Fixed rate mortgages	$ 880,271	$ 897,888
Interest rate	4.40%	3.90%
Variable rate debt	$ 74,591	$ 0
Scheduled maturity period	7 years 11 months 14 days
Total notes payable	$ 1,032,189	965,528
Interest rate during period	5.02%
Fixed rate mortgage notes payable
Notes Payable [Line Items]
Fixed rate mortgages	$ 910,189	890,393
Interest rate	5.18%
Scheduled maturity period	8 years 6 months 10 days
Fixed rate mortgage notes payable | 5.88% due January 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 0	30,201
Interest rate	5.88%
Fixed rate mortgage notes payable | 5.76% due May 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 9,159	9,783
Interest rate	5.76%
Fixed rate mortgage notes payable | 5.62% due July 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 12,676	13,529
Interest rate	5.62%
Fixed rate mortgage notes payable | 5.79% due September 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 12,714	13,543
Interest rate	5.79%
Fixed rate mortgage notes payable | 5.22% due January 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 11,295	12,029
Interest rate	5.22%
Fixed rate mortgage notes payable | 5.60% due May 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 9,601	9,948
Interest rate	5.60%
Fixed rate mortgage notes payable | 5.30% due June 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 7,766	8,244
Interest rate	5.30%
Fixed rate mortgage notes payable | 5.83% due July 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 36,711	37,998
Interest rate	5.83%
Fixed rate mortgage notes payable | 5.81% due February 2021
Notes Payable [Line Items]
Fixed rate mortgages	$ 6,943	7,325
Interest rate	5.81%
Fixed rate mortgage notes payable | 6.01% due August 2021
Notes Payable [Line Items]
Fixed rate mortgages	$ 5,480	5,649
Interest rate	6.01%
Fixed rate mortgage notes payable | 5.62% due June 2022
Notes Payable [Line Items]
Fixed rate mortgages	$ 31,723	32,673
Interest rate	5.62%
Fixed rate mortgage notes payable | 6.08% due September 2022
Notes Payable [Line Items]
Fixed rate mortgages	$ 9,728	9,999
Interest rate	6.08%
Fixed rate mortgage notes payable | 6.43% due April 2023
Notes Payable [Line Items]
Fixed rate mortgages	$ 10,609	10,877
Interest rate	6.43%
Fixed rate mortgage notes payable | 6.28% due February 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 11,702	12,577
Interest rate	6.28%
Fixed rate mortgage notes payable | 7.35% due June 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 14,952	15,452
Interest rate	7.35%
Fixed rate mortgage notes payable | 7.60% due June 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 13,013	13,438
Interest rate	7.60%
Fixed rate mortgage notes payable | 7.02% due July 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 23,198	23,873
Interest rate	7.02%
Fixed rate mortgage notes payable | 7.45% due July 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 27,222	28,115
Interest rate	7.45%
Fixed rate mortgage notes payable | 7.30% due January 2025
Notes Payable [Line Items]
Fixed rate mortgages	$ 27,168	28,025
Interest rate	7.30%
Fixed rate mortgage notes payable | 6.18% due January 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 14,086	14,537
Interest rate	6.18%
Fixed rate mortgage notes payable | 5.31% due April 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 102,310	105,817
Interest rate	5.31%
Fixed rate mortgage notes payable | 4.30% due October 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 30,888	32,016
Interest rate	4.30%
Fixed rate mortgage notes payable | 4.53% due November 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 35,258	36,507
Interest rate	4.53%
Fixed rate mortgage notes payable | 4.70% due December 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 16,515	17,086
Interest rate	4.70%
Fixed rate mortgage notes payable | 5.84% due May 2027
Notes Payable [Line Items]
Fixed rate mortgages	$ 62,630	64,472
Interest rate	5.84%
Fixed rate mortgage notes payable | 4.04% due April 2028
Notes Payable [Line Items]
Fixed rate mortgages	$ 15,345	15,859
Interest rate	4.04%
Fixed rate mortgage notes payable | 3.51% due June 2028
Notes Payable [Line Items]
Fixed rate mortgages	$ 38,120	39,968
Interest rate	3.51%
Fixed rate mortgage notes payable | 3.99% due September 2028
Notes Payable [Line Items]
Fixed rate mortgages	$ 15,547	16,055
Interest rate	3.99%
Fixed rate mortgage notes payable | 3.69% Due March 2030
Notes Payable [Line Items]
Fixed rate mortgages	$ 27,060	27,884
Interest rate	3.69%
Fixed rate mortgage notes payable | 3.99% Due April 2030
Notes Payable [Line Items]
Fixed rate mortgages	$ 14,526	14,950
Interest rate	3.99%
Fixed rate mortgage notes payable | 3.39% due January 2032
Notes Payable [Line Items]
Fixed rate mortgages	$ 38,076	39,140
Interest rate	3.39%
Fixed rate mortgage notes payable | 4.88% due September 2032
Notes Payable [Line Items]
Fixed rate mortgages	$ 69,691	71,211
Interest rate	4.88%
Fixed rate mortgage notes payable | 3.75% due December 2032
Notes Payable [Line Items]
Fixed rate mortgages	$ 58,523	60,000
Interest rate	3.75%
Fixed rate mortgage notes payable | 4.41% mortgage maturing 2033
Notes Payable [Line Items]
Fixed rate mortgages	$ 31,941	0
Interest rate	4.41%
Fixed rate mortgage notes payable | 4.69% fixed rate loan maturing in 2034
Notes Payable [Line Items]
Fixed rate mortgages	$ 22,900	0
Interest rate	4.69%
Fixed rate mortgage notes payable | 8.00% due April 2034
Notes Payable [Line Items]
Fixed rate mortgages	$ 11,781	11,613
Interest rate	8.00%
Fixed rate mortgage notes payable | 4.67% Construction To Permanent Loan Due 2035
Notes Payable [Line Items]
Fixed rate mortgages	$ 23,332	0
Interest rate	4.67%
Variable rate loans payable
Notes Payable [Line Items]
Variable rate debt	$ 122,000	75,135
Interest rate spread on LIBOR	3.84%
Scheduled maturity period	3 years 8 months 8 days
Variable rate loans payable | Metro Pike Center Bank Loan
Notes Payable [Line Items]
Variable rate debt	$ 0	14,135
Interest rate spread on LIBOR	1.65%
Revolving Credit Facility | New Facility | Line of Credit
Notes Payable [Line Items]
Variable rate debt	$ 47,000	61,000
Interest rate spread on LIBOR	1.35%
Revolving Credit Facility | New Facility | Term Facility
Notes Payable [Line Items]
Interest rate spread on LIBOR	1.30%
Term Facility | New Facility | Line of Credit
Notes Payable [Line Items]
Variable rate debt	$ 75,000	$ 0
Interest rate spread on LIBOR	1.30%

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