Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Additional Information (Detail) - USD ($)											12 Months Ended
		Apr. 01, 2015	Mar. 03, 2015	Jun. 24, 2014	Oct. 25, 2013	Sep. 04, 2013	May. 28, 2013	Apr. 10, 2013	Mar. 19, 2013	Feb. 27, 2013	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Outstanding debt											$ 875,200,000
Fixed rate mortgages											802,034,000		$ 808,997,000
Debt outstanding											875,242,000		857,400,000
Debt outstanding with fixed-rate													784,800,000
Debt outstanding with variable-rate													72,600,000
Line of credit facility, maximum borrowing capacity											246,552,000
Outstanding line of credit											28,000,000		43,000,000
Letter of credit facility											448,000
Guarantor obligations, maximum exposure											51,000,000		$ 51,000,000
Long-term debt											$ 250,543,000
Debt instrument fixed interest rate											3.75%		3.65%
Capitalization of debt issuance cost											$ 300,000		$ 1,300,000	$ 3,200,000
Metro Pike Center
Debt Instrument [Line Items]
Interest rate spread on LIBOR										1.65%
Debt instrument amount										$ 15,600,000
Principal amortization period										25 years
Debt instrument required final principal payment										$ 14,800,000
Debt instrument, term										3 years
Existing loan extension period										1 year
Repayment of debt										$ 15,900,000
Northrock
Debt Instrument [Line Items]
Interest rate spread on LIBOR										1.65%
Debt instrument amount										$ 15,000,000
Principal amortization period										25 years
Debt instrument required final principal payment										$ 14,200,000
Debt instrument, term										3 years
Repayment of debt										$ 15,000,000
Cruse Market Place
Debt Instrument [Line Items]
Repayment of debt								$ 6,900,000
4.04% due April 2028 | Hampshire Langley
Debt Instrument [Line Items]
Debt instrument amount									$ 18,000,000
Debt instrument required periodic principal and interest payment									95,400
Debt instrument required final principal payment									$ 9,500,000
Debt instrument fixed interest rate									4.04%
Debt instrument, term									15 years
3.51% due June 2028 | Beacon Center
Debt Instrument [Line Items]
Debt instrument amount							$ 35,000,000
Debt instrument required periodic principal and interest payment							$ 203,200
Principal amortization period							20 years
Debt instrument required final principal payment							$ 11,400,000
Debt instrument fixed interest rate							3.51%
Debt instrument, term							15 years
3.99% due September 2028 | Seabreeze Plaza
Debt Instrument [Line Items]
Debt instrument amount						$ 18,000,000
Debt instrument fixed interest rate						3.99%
Debt instrument, term						15 years
Repayment of debt						$ 13,500,000
Payments of debt extinguishment costs						497,000
4.88% due September 2032 | Park Van Ness
Debt Instrument [Line Items]
Principal amortization period					25 years
Debt instrument fixed interest rate					4.88%
Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 275,000,000.0
Extension in line of credit facility period				1 year							1 year
Interest rate spread on LIBOR											1.45%
Fixed Rate Mortgage Notes Payable
Debt Instrument [Line Items]
Fixed rate mortgages											$ 832,441,000		784,757,000
Debt instrument fixed interest rate	[1]										5.53%
Fixed Rate Mortgage Notes Payable | Metro Pike Center Bank Loan
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure											$ 7,800,000
Fixed Rate Mortgage Notes Payable | 5.84% due May 2027
Debt Instrument [Line Items]
Fixed rate mortgages											$ 67,850,000	[2]	69,397,000
Debt instrument fixed interest rate	[1]										5.84%
Fixed Rate Mortgage Notes Payable | 5.84% due May 2027 | Seven Corners Shopping Center
Debt Instrument [Line Items]
Debt instrument amount											$ 73,000,000
Debt instrument required periodic principal and interest payment											$ 463,200
Principal amortization period											25 years
Debt instrument required final principal payment											$ 42,300,000
Fixed Rate Mortgage Notes Payable | 4.04% due April 2028
Debt Instrument [Line Items]
Fixed rate mortgages											$ 16,826,000	[3]	17,281,000
Debt instrument fixed interest rate	[1]										4.04%
Fixed Rate Mortgage Notes Payable | 4.04% due April 2028 | Hampshire Langley
Debt Instrument [Line Items]
Debt instrument required periodic principal and interest payment											$ 95,400
Principal amortization period									25 years
Debt instrument required final principal payment											9,500,000
Fixed Rate Mortgage Notes Payable | 3.51% due June 2028
Debt Instrument [Line Items]
Fixed rate mortgages											$ 31,844,000	[4]	33,140,000
Debt instrument fixed interest rate	[1]										3.51%
Fixed Rate Mortgage Notes Payable | 3.51% due June 2028 | Beacon Center
Debt Instrument [Line Items]
Debt instrument required periodic principal and interest payment											$ 203,200
Principal amortization period											20 years
Debt instrument required final principal payment											$ 11,400,000
Fixed Rate Mortgage Notes Payable | 3.99% due September 2028
Debt Instrument [Line Items]
Fixed rate mortgages											$ 17,011,000	[5]	17,462,000
Debt instrument fixed interest rate	[1]										3.99%
Fixed Rate Mortgage Notes Payable | 3.99% due September 2028 | Seabreeze Plaza
Debt Instrument [Line Items]
Debt instrument required periodic principal and interest payment						$ 94,900					$ 94,900
Principal amortization period						25 years					25 years
Debt instrument required final principal payment						$ 9,500,000					$ 9,500,000
Fixed Rate Mortgage Notes Payable | 4.88% due September 2032
Debt Instrument [Line Items]
Fixed rate mortgages											$ 45,208,000	[6]	5,391,000
Debt instrument fixed interest rate	[1]										4.88%
Fixed Rate Mortgage Notes Payable | 4.88% due September 2032 | Park Van Ness
Debt Instrument [Line Items]
Debt instrument amount					$ 71,600,000						$ 71,600,000
Debt instrument required periodic principal and interest payment											$ 413,500
Principal amortization period											25 years
Debt instrument required final principal payment											$ 39,600,000
Variable Rate Loans Payable
Debt Instrument [Line Items]
Variable rate loans											$ 42,801,000		72,631,000
Interest rate spread on LIBOR	[1]										1.94%
Variable Rate Loans Payable | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Variable rate loans											$ 28,000,000	[7]	43,000,000
Line of credit facility, maximum borrowing capacity											$ 275,000,000
Interest rate spread on LIBOR	[1]										1.45%
Variable Rate Loans Payable | Northrock Loan
Debt Instrument [Line Items]
Variable rate loans											$ 0	[8]	14,525,000
Interest rate spread on LIBOR	[1]										1.65%
Variable Rate Loans Payable | Northrock Loan | Northrock
Debt Instrument [Line Items]
Debt instrument required periodic principal and interest payment											$ 47,000
Debt instrument required final principal payment											14,200,000
Variable Rate Loans Payable | Metro Pike Center Bank Loan
Debt Instrument [Line Items]
Variable rate loans											$ 14,801,000	[9]	15,106,000
Interest rate spread on LIBOR	[1]										1.65%
Variable Rate Loans Payable | Metro Pike Center Bank Loan | Metro Pike Center
Debt Instrument [Line Items]
Debt instrument required periodic principal and interest payment											$ 48,000
Debt instrument required final principal payment											14,800,000
Debt Covenant
Debt Instrument [Line Items]
Carrying value of properties collateralized											$ 856,800,000		$ 895,500,000
Debt covenant, percentage of net proceeds of additional equity issuance											80.00%
Credit agreement leverage ratio											60.00%
Interest coverage ratio required minimum											2.0
Required fixed charge coverage ratio											1.3
Minimum | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate spread on LIBOR											1.45%
Minimum | Debt Covenant
Debt Instrument [Line Items]
Debt covenant required net assets											$ 542,100,000
Maximum | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate spread on LIBOR											2.00%
Shops at Fairfax and Boulevard
Debt Instrument [Line Items]
Debt instrument amount			$ 30,000,000
Debt instrument fixed interest rate			3.69%
Debt instrument, term			15 years
Shops at Fairfax and Boulevard | Fixed Rate Mortgage Notes Payable
Debt Instrument [Line Items]
Debt instrument required periodic principal and interest payment			$ 153,300
Debt instrument required final principal payment			$ 15,500,000
Debt instrument amortization period			25 years
Long-term debt			$ 15,200,000
Northrock
Debt Instrument [Line Items]
Debt instrument amount		$ 16,000,000
Debt instrument fixed interest rate		3.99%
Debt instrument, term		15 years
Northrock | Fixed Rate Mortgage Notes Payable
Debt Instrument [Line Items]
Debt instrument required periodic principal and interest payment		$ 84,400
Debt instrument required final principal payment		$ 8,400,000
Debt instrument amortization period		25 years
Long-term debt		$ 14,500,000

[1] Interest rate and scheduled maturity data presented as of December 31, 2015. Totals computed using weighted averages.

[2] The loan in the original amount of $73.0 million closed in May 2012, is collateralized by Seven Corners and requires equal monthly principal and interest payments of $463,200 based upon a 25-year amortization schedule and a final payment of $42.3 million at loan maturity. Principal of $1.5 million was amortized during 2015.

[3] The loan is collateralized by Hampshire Langley and requires equal monthly principal and interest payments of $95,400 based upon a 25 -year amortization schedule and a final payment of $9.5 million at loan maturity. Principal of $455,000 was amortized in 2015.

[4] The loan is collateralized by Beacon Center and requires equal monthly principal and interest payments of $203,200 based upon a 20-year amortization schedule and a final payment of $11.4 million at loan maturity. Principal of $1,296,000 was amortized in 2015.

[5] The loan is collateralized by Seabreeze Plaza and requires equal monthly principal and interest payments of $94,900 based upon a 25-year amortization schedule and a final payment of $9.5 million at loan maturity. Principal of $451,000 was amortized in 2015.

[6] The loan is a $71.6 million construction-to-permanent facility that is collateralized by and will finance a portion of the construction costs of Park Van Ness. During the construction period, interest will be funded by the loan. After conversion to a permanent loan, monthly principal and interest payments totaling $413,500 will be required based upon a 25-year amortization schedule. A final payment of $39.6 million will be due at maturity.

[7] The loan is a $275.0 million unsecured revolving credit facility. Interest accrues at a rate equal to the sum of one-month LIBOR plus a spread of 145 basis points. The line may be extended at the Company’s option for one year with payment of a fee of 0.15%. Monthly payments, if required, are interest only and vary depending upon the amount outstanding and the applicable interest rate for any given month.

[8] The loan was collateralized by Northrock and required monthly principal and interest payments of approximately $47,000 and a final payment of $14.2 million at maturity. In 2015 the loan was repaid in full and replaced with a new $16.0 million loan. See (ff) above.

[9] The loan is collateralized by Metro Pike Center and requires monthly principal and interest payments of approximately $48,000 and a final payment of $14.8 million at loan maturity. Principal of $305,000 was amortized during 2015.