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Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Summary of Notes Payable (Additional Information) (Detail) |  | 12 Months Ended |  |
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Feb. 27, 2013 | Dec. 31, 2016 USD ($) shopping_center note | Dec. 31, 2015 | Dec. 31, 2012 USD ($)
Notes Payable [Line Items] |  |  |  |  |
Interest rate |  |  | 4.25% | 3.75% |
Line of credit facility, maximum borrowing capacity |  |  | $ 225,600,000 |  |
Northrock |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate spread on LIBOR |  | 1.65% |  |  |
Metro Pike Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate spread on LIBOR |  | 1.65% |  |  |
Fixed rate mortgage notes payable |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.48% |  |
Fixed rate mortgage notes payable | 6.01% due February 2018 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 6.01% |  |
Fixed rate mortgage notes payable | 6.01% due February 2018 | Washington Square |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 264,000 |  |
Amortization period |  |  | 27 years 6 months |  |
Debt instrument final payment |  |  | $ 28,000,000 |  |
Amortization of principal |  |  | $ 1,400,000 |  |
Fixed rate mortgage notes payable | 5.88% due January 2019 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.88% |  |
Fixed rate mortgage notes payable | 5.88% due January 2019 | Broadlands Village, The Glen and Kentlands Square I |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 306,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 28,400,000 |  |
Amortization of principal |  |  | $ 1,700,000 |  |
Number of shopping centers | shopping_center |  |  | 3 |  |
Fixed rate mortgage notes payable | 5.76% due May 2019 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.76% |  |
Fixed rate mortgage notes payable | 5.76% due May 2019 | Olde Forte Village |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 98,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 9,000,000 |  |
Amortization of principal |  |  | $ 556,000 |  |
Fixed rate mortgage notes payable | 5.62% due July 2019 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.62% |  |
Fixed rate mortgage notes payable | 5.62% due July 2019 | Countryside |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 133,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 12,300,000 |  |
Amortization of principal |  |  | $ 763,000 |  |
Fixed rate mortgage notes payable | 5.79% due September 2019 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.79% |  |
Fixed rate mortgage notes payable | 5.79% due September 2019 | Briggs Chancy MarketPlace |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 133,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 12,200,000 |  |
Amortization of principal |  |  | $ 739,000 |  |
Fixed rate mortgage notes payable | 5.22% due January 2020 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.22% |  |
Fixed rate mortgage notes payable | 5.22% due January 2020 | Shops at Monocacy |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 112,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 10,600,000 |  |
Amortization of principal |  |  | $ 662,000 |  |
Fixed rate mortgage notes payable | 5.60% due May 2020 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.60% |  |
Fixed rate mortgage notes payable | 5.60% due May 2020 | Boca Valley Plaza |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 75,000 |  |
Amortization period |  |  | 30 years |  |
Debt instrument final payment |  |  | $ 9,100,000 |  |
Amortization of principal |  |  | $ 310,000 |  |
Fixed rate mortgage notes payable | 5.30% due June 2020 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.30% |  |
Fixed rate mortgage notes payable | 5.30% due June 2020 | Palm Springs Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 75,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 7,100,000 |  |
Amortization of principal |  |  | $ 430,000 |  |
Fixed rate mortgage notes payable | 5.83% due July 2020 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.83% |  |
Fixed rate mortgage notes payable | 5.83% due July 2020 | Thruway |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 289,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 34,800,000 |  |
Amortization of principal |  |  | $ 1,147,000 |  |
Fixed rate mortgage notes payable | 5.81% due February 2021 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.81% |  |
Fixed rate mortgage notes payable | 5.81% due February 2021 | Jamestown Place |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 66,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 6,100,000 |  |
Amortization of principal |  |  | $ 340,000 |  |
Fixed rate mortgage notes payable | 6.01% due August 2021 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 6.01% |  |
Fixed rate mortgage notes payable | 6.01% due August 2021 | Hunt Club Corners |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 42,000 |  |
Amortization period |  |  | 30 years |  |
Debt instrument final payment |  |  | $ 5,000,000 |  |
Amortization of principal |  |  | $ 151,000 |  |
Fixed rate mortgage notes payable | 5.62% due June 2022 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.62% |  |
Fixed rate mortgage notes payable | 5.62% due June 2022 | Landsowne Town Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 230,000 |  |
Amortization period |  |  | 30 years |  |
Debt instrument final payment |  |  | $ 28,200,000 |  |
Amortization of principal |  |  | $ 849,000 |  |
Fixed rate mortgage notes payable | 6.08% due September 2022 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 6.08% |  |
Fixed rate mortgage notes payable | 6.08% due September 2022 | Orchard Park |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 73,000 |  |
Amortization period |  |  | 30 years |  |
Debt instrument final payment |  |  | $ 8,600,000 |  |
Amortization of principal |  |  | $ 239,000 |  |
Fixed rate mortgage notes payable | 6.43% due April 2023 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 6.43% |  |
Fixed rate mortgage notes payable | 6.43% due April 2023 | BJs Wholesale |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 80,000 |  |
Amortization period |  |  | 30 years |  |
Debt instrument final payment |  |  | $ 9,300,000 |  |
Amortization of principal |  |  | $ 236,000 |  |
Fixed rate mortgage notes payable | 6.28% due February 2024 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 6.28% |  |
Fixed rate mortgage notes payable | 6.28% due February 2024 | Great Falls Shopping Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 138,000 |  |
Amortization period |  |  | 26 years |  |
Debt instrument final payment |  |  | $ 6,300,000 |  |
Amortization of principal |  |  | $ 776,000 |  |
Number of notes | note |  |  | 3 |  |
Fixed rate mortgage notes payable | 7.35% due June 2024 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 7.35% |  |
Fixed rate mortgage notes payable | 7.35% due June 2024 | Leesburg Pike |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 135,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 11,500,000 |  |
Amortization of principal |  |  | $ 431,000 |  |
Fixed rate mortgage notes payable | 7.60% due June 2024 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 7.60% |  |
Fixed rate mortgage notes payable | 7.60% due June 2024 | Village Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 119,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 10,100,000 |  |
Amortization of principal |  |  | $ 365,000 |  |
Fixed rate mortgage notes payable | 7.02% due July 2024 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 7.02% |  |
Fixed rate mortgage notes payable | 7.02% due July 2024 | White Oak Shopping Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 193,000 |  |
Amortization period |  |  | 24 years 4 months 24 days |  |
Debt instrument final payment |  |  | $ 18,500,000 |  |
Loan amount |  |  |  |  | $ 10,500,000
Amortization of principal |  |  | $ 584,000 |  |
Fixed rate mortgage notes payable | 7.45% due July 2024 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 7.45% |  |
Fixed rate mortgage notes payable | 7.45% due July 2024 | Avenel Business Park |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 246,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 20,900,000 |  |
Amortization of principal |  |  | $ 769,000 |  |
Fixed rate mortgage notes payable | 7.30% due January 2025 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 7.30% |  |
Fixed rate mortgage notes payable | 7.30% due January 2025 | Ashburn Village |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 240,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 20,500,000 |  |
Amortization of principal |  |  | $ 742,000 |  |
Fixed rate mortgage notes payable | 6.18% due January 2026 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 6.18% |  |
Fixed rate mortgage notes payable | 6.18% due January 2026 | Ravenwood |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 111,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 10,100,000 |  |
Amortization of principal |  |  | $ 399,000 |  |
Fixed rate mortgage notes payable | 5.31% due April 2026 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.31% |  |
Fixed rate mortgage notes payable | 5.31% due April 2026 | Clarendon Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 753,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 70,500,000 |  |
Amortization of principal |  |  | $ 3,200,000 |  |
Fixed rate mortgage notes payable | 4.30% due October 2026 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 4.30% |  |
Fixed rate mortgage notes payable | 4.30% due October 2026 | Severna Park Market Place |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 207,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 20,300,000 |  |
Amortization of principal |  |  | $ 1,036,000 |  |
Fixed rate mortgage notes payable | 4.53% due November 2026 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 4.53% |  |
Fixed rate mortgage notes payable | 4.53% due November 2026 | Kentlands Square II |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 240,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 23,100,000 |  |
Amortization of principal |  |  | $ 1,141,000 |  |
Fixed rate mortgage notes payable | 4.70% due December 2026 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 4.70% |  |
Fixed rate mortgage notes payable | 4.70% due December 2026 | Cranberry Square |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 113,000 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 10,900,000 |  |
Amortization of principal |  |  | $ 520,000 |  |
Fixed rate mortgage notes payable | 5.84% due May 2027 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 5.84% |  |
Fixed rate mortgage notes payable | 5.84% due May 2027 | Seven Corners |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 463,200 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 42,300,000 |  |
Loan amount |  |  | 73,000,000 |  |
Amortization of principal |  |  | $ 1,600,000 |  |
Fixed rate mortgage notes payable | 4.04% due April 2028 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 4.04% |  |
Fixed rate mortgage notes payable | 4.04% due April 2028 | Hampshire Langley |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 95,400 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 9,500,000 |  |
Amortization of principal |  |  | $ 474,000 |  |
Fixed rate mortgage notes payable | 3.51% due June 2028 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 3.51% |  |
Fixed rate mortgage notes payable | 3.51% due June 2028 | Beacon Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 268,500 |  |
Amortization period |  |  | 20 years |  |
Debt instrument final payment |  |  | $ 17,100,000 |  |
Amortization of principal |  |  | $ 1,300,000 |  |
Fixed rate mortgage notes payable | 3.99% due September 2028 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 3.99% |  |
Fixed rate mortgage notes payable | 3.99% due September 2028 | Seabreeze Plaza |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 94,900 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 9,500,000 |  |
Amortization of principal |  |  | $ 468,000 |  |
Fixed rate mortgage notes payable | 3.69% Due March 2030 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 3.69% |  |
Fixed rate mortgage notes payable | 3.69% Due March 2030 | Shops at Fairfax and Boulevard |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 153,300 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 15,500,000 |  |
Amortization of principal |  |  | $ 765,000 |  |
Fixed rate mortgage notes payable | 3.99% Due April 2030 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 3.99% |  |
Fixed rate mortgage notes payable | 3.99% Due April 2030 | Northrock |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 84,400 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 8,400,000 |  |
Amortization of principal |  |  | $ 391,000 |  |
Fixed rate mortgage notes payable | 4.88% due September 2032 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 4.88% |  |
Fixed rate mortgage notes payable | 4.88% due September 2032 | Park Van Ness |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 413,500 |  |
Amortization period |  |  | 25 years |  |
Debt instrument final payment |  |  | $ 39,600,000 |  |
Loan amount |  |  | $ 71,600,000 |  |
Fixed rate mortgage notes payable | 8.00% due April 2034 |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate | [1] |  | 8.00% |  |
Fixed rate mortgage notes payable | 8.00% due April 2034 | Olney |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 60,400 |  |
Debt instrument final payment |  |  | $ 14,700,000 |  |
Fixed rate increase on note |  |  | 1.50% |  |
Interest rate |  |  | 8.00% |  |
Negative amortization |  |  | $ 164,000 |  |
Variable rate loans payable |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate spread on LIBOR | [1] |  | 2.22% |  |
Variable rate loans payable | Revolving credit facility |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  |  | $ 275,000,000 |  |
Debt maturity extension period |  |  | 1 year |  |
Debt instrument fee |  |  | 0.15% |  |
Interest rate spread on LIBOR | [1] |  | 1.45% |  |
Variable rate loans payable | Metro Pike Center Bank Loan |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Interest rate spread on LIBOR | [1] |  | 1.65% |  |
Variable rate loans payable | Metro Pike Center Bank Loan | Metro Pike Center |  |  |  |  |
Notes Payable [Line Items] |  |  |  |  |
Principal and interest payments |  |  | $ 48,000 |  |
Debt instrument final payment |  |  | 14,200,000 |  |
Amortization of principal |  |  | $ 319,000 |  |
[1] | Interest rate and scheduled maturity data presented as of December 31, 2016. Totals computed using weighted averages. Amounts shown are principal amounts and have not been reduced by any deferred debt issuance costs.

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