Saul Centers (BFS) 10-K 27 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Feb. 20, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document type	10-K
Amendment flag	false
Document period end date	Dec. 31, 2017
Document fiscal year focus	2,017
Document fiscal period focus	FY
Trading symbol	BFS
Entity registrant name	SAUL CENTERS INC
Entity central index key	907,254
Current fiscal year end date	--12-31
Entity well-known seasoned issuer	Yes
Entity current reporting status	Yes
Entity voluntary filers	No
Entity filer category	Large Accelerated Filer
Entity common stock, shares outstanding		22
Entity public float			$ 714.6

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Real estate investments
Land	$ 450,256	$ 422,546
Buildings and equipment	1,261,830	1,214,697
Construction in progress	91,114	63,570
Total Purchase Price	1,803,200	1,700,813
Accumulated depreciation	(488,166)	(458,279)
Real estate investments, net	1,315,034	1,242,534
Cash and cash equivalents	10,908	8,322
Accounts receivable and accrued income, net	54,057	52,774
Deferred leasing costs, net	27,255	25,983
Prepaid expenses, net	5,248	5,057
Other assets	9,950	8,355
Total assets	1,422,452	1,343,025
Liabilities
Mortgage notes payable	897,888	783,400
Revolving credit facility payable	60,734	48,217
Construction loan payable	0	68,672
Dividends and distributions payable	18,520	17,953
Accounts payable, accrued expenses and other liabilities	23,123	20,838
Deferred income	29,084	30,696
Total liabilities	1,029,349	969,776
Preferred stock, 1,000,000 shares authorized:
Series C Cumulative Redeemable, 72,000 shares issued and outstanding	180,000	180,000
Common stock, $0.01 par value, 40,000,000 shares authorized, 22,123,128 and 21,704,359 shares issued and outstanding, respectively	221	217
Additional paid-in capital	352,590	328,171
Accumulated deficit	(197,710)	(188,584)
Accumulated other comprehensive loss	(696)	(1,299)
Total Saul Centers, Inc. equity	334,405	318,505
Noncontrolling interests	58,698	54,744
Total equity	393,103	373,249
Total liabilities and equity	$ 1,422,452	$ 1,343,025

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Cumulative redeemable preferred stock, shares issued (in shares)	72,000	72,000
Cumulative redeemable preferred stock, shares outstanding (in shares)	72,000	72,000
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	22,123,128	21,704,359
Common stock, shares outstanding (in shares)	22,123,128	21,704,359

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Base rent	$ 181,141	$ 172,381	$ 168,303
Expense recoveries	35,347	34,269	32,911
Percentage rent	1,458	1,379	1,608
Other	9,339	9,041	6,255
Total revenue	227,285	217,070	209,077
Operating expenses
Property operating expenses	27,689	27,527	26,565
Provision for credit losses	906	1,494	915
Real estate taxes	26,997	24,680	23,663
Interest expense and amortization of deferred debt costs	47,225	45,683	45,165
Depreciation and amortization of deferred leasing costs	45,694	44,417	43,270
General and administrative	18,176	17,496	16,353
Acquisition related costs	0	60	84
Predevelopment expenses	0	0	132
Total operating expenses	166,687	161,357	156,147
Operating income	60,598	55,713	52,930
Change in fair value of derivatives	70	(6)	(10)
Gains on sales of properties	0	1,013	11
Net income (loss)	60,668	56,720	52,931
Income attributable to noncontrolling interests	(12,411)	(11,441)	(10,463)
Net income attributable to Saul Centers, Inc.	48,257	45,279	42,468
Preferred dividends	(12,375)	(12,375)	(12,375)
Net income available to common stockholders	$ 35,882	$ 32,904	$ 30,093
Per share net income available to common stockholders
Basic (in usd per share)	$ 1.64	$ 1.53	$ 1.42
Diluted (in usd per share)	$ 1.63	$ 1.52	$ 1.42

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 60,668	$ 56,720	$ 52,931
Other comprehensive income
Unrealized gain on cash flow hedge	812	678	124
Total comprehensive income	61,480	57,398	53,055
Comprehensive income attributable to noncontrolling interests	(12,620)	(11,616)	(10,495)
Total comprehensive income attributable to Saul Centers, Inc.	48,860	45,782	42,560
Preferred dividends	(12,375)	(12,375)	(12,375)
Total comprehensive income available to common stockholders	$ 36,485	$ 33,407	$ 30,185

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Dividend paid	Dividend declared	Series C Preferred StockDividend paid	Series C Preferred StockDividend declared	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated DeficitDividend paid	Accumulated DeficitDividend declared	Accumulated DeficitSeries C Preferred StockDividend paid	Accumulated DeficitSeries C Preferred StockDividend declared	Accumulated Other Comprehensive (Loss)	Total Saul Centers, Inc.	Total Saul Centers, Inc.Dividend paid	Total Saul Centers, Inc.Dividend declared	Total Saul Centers, Inc.Series C Preferred StockDividend paid	Total Saul Centers, Inc.Series C Preferred StockDividend declared	Noncontrolling Interests	Noncontrolling InterestsDividend paid	Noncontrolling InterestsDividend declared
Beginning balance at Dec. 31, 2014	$ 339,257					$ 180,000	$ 209	$ 287,995	$ (173,774)					$ (1,894)	$ 292,536					$ 46,721
Issuance of common stock:
Shares issued pursuant to dividend reinvestment plan	10,650						3	10,647							10,650
Shares issued due to exercise of employee stock options and issuance of directors' deferred stock	6,367						1	6,366							6,367
Issuance of partnership units pursuant to dividend reinvestment plan	5,673																			5,673
Net income	52,931								42,468						42,468					10,463
Change in unrealized loss on cash flow hedge	124													92	92					32
Preferred stock distributions:
Preferred stock distributions				$ (9,282)	$ (3,093)							$ (9,282)	$ (3,093)					$ (9,282)	$ (3,093)
Common stock distributions		$ (36,614)								$ (27,265)						$ (27,265)					$ (9,349)
Distributions payable common stock and distributions payable partnership units			$ (12,286)								$ (9,145)						$ (9,145)					$ (3,141)
Ending balance at Dec. 31, 2015	353,727					180,000	213	305,008	(180,091)					(1,802)	303,328					50,399
Issuance of common stock:
Shares issued pursuant to dividend reinvestment plan	10,311						2	10,309							10,311
Shares issued due to exercise of employee stock options and issuance of directors' deferred stock	12,856						2	12,854							12,856
Issuance of partnership units pursuant to dividend reinvestment plan	6,910																			6,910
Net income	56,720								45,279						45,279					11,441
Change in unrealized loss on cash flow hedge	678													503	503					175
Preferred stock distributions:
Preferred stock distributions				(9,282)	(3,093)							(9,282)	(3,093)					(9,282)	(3,093)
Common stock distributions		(40,720)								(30,328)						(30,328)					(10,392)
Distributions payable common stock and distributions payable partnership units			(14,858)								(11,069)						(11,069)					(3,789)
Ending balance at Dec. 31, 2016	373,249					180,000	217	328,171	(188,584)					(1,299)	318,505					54,744
Issuance of common stock:
Shares issued pursuant to dividend reinvestment plan	15,750						2	15,748							15,750
Shares issued due to exercise of employee stock options and issuance of directors' deferred stock	8,673						2	8,671							8,673
Issuance of partnership units pursuant to dividend reinvestment plan	6,735																			6,735
Net income	60,668								48,257						48,257					12,411
Change in unrealized loss on cash flow hedge	812													603	603					209
Preferred stock distributions:
Preferred stock distributions				$ (9,282)	$ (3,093)							$ (9,282)	$ (3,093)					$ (9,282)	$ (3,093)
Common stock distributions		$ (44,969)								$ (33,490)						$ (33,490)					$ (11,479)
Distributions payable common stock and distributions payable partnership units			$ (15,440)								$ (11,518)						$ (11,518)					$ (3,922)
Ending balance at Dec. 31, 2017	$ 393,103					$ 180,000	$ 221	$ 352,590	$ (197,710)					$ (696)	$ 334,405					$ 58,698

Consolidated Statements of Equ7

Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock Shares Issued (in shares)	266,011	186,797	201,212
Shares issued to directors (in shares)	152,758	251,323	117,886
Issuance of partnership units pursuant to dividend reinvestment plan (in shares)	111,351	124,758	107,037
Dividend declared
Distributions payable common stock and partnership units (in usd per share)	$ 0.52	$ 0.51	$ 0.43
Dividend declared | Series C Preferred Stock
Distributions payable on preferred stock (in usd per share)	$ 42.97	$ 42.97	$ 42.97

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income		$ 60,668	$ 56,720	$ 52,931
Adjustments to reconcile net income to net cash provided by operating activities:
Change in fair value of derivatives		(70)	6	10
Gains on sales of properties		0	(1,013)	(11)
Depreciation and amortization of deferred leasing costs		45,694	44,417	43,270
Amortization of deferred debt costs		1,392	1,343	1,433
Non cash compensation costs of stock grants and options		1,672	1,603	1,434
Provision for credit losses		906	1,494	915
Increase in accounts receivable and accrued income		(1,643)	(3,525)	(5,216)
Additions to deferred leasing costs		(4,615)	(4,633)	(5,563)
Increase in prepaid expenses		(294)	(399)	(570)
(Increase) decrease in other assets		1,374	(6,368)	1,544
Increase (decrease) in accounts payable, accrued expenses and other liabilities		1,125	921	(937)
Decrease in deferred income		(2,759)	(1,476)	(344)
Net cash provided by operating activities		103,450	89,090	88,896
Cash flows from investing activities:
Acquisitions of real estate investments		(79,499)	(48,250)	(4,894)
Additions to real estate investments		(17,653)	(15,564)	(18,855)
Additions to development and redevelopment projects		(22,842)	(27,231)	(45,870)
Proceeds from sale of properties	[1]	6,688	4,771	32
Net cash used in investing activities		(113,306)	(86,274)	(69,587)
Cash flows from financing activities:
Proceeds from mortgage notes payable		100,000	11,250	46,000
Repayments on mortgage notes payable		(55,679)	(24,653)	(52,963)
Proceeds from construction loans payable		1,437	24,937	39,817
Proceeds from revolving credit facility		63,000	78,500	20,000
Repayments on revolving credit facility		(51,000)	(57,500)	(35,000)
Additions to deferred debt costs		(2,583)	(125)	(296)
Proceeds from the issuance of:
Common stock		22,751	21,564	15,583
Partnership units		6,735	6,910	5,673
Distributions to:
Series C preferred stockholders		(12,375)	(12,375)	(12,375)
Common stockholders		(44,576)	(39,472)	(35,645)
Noncontrolling interests		(15,268)	(13,533)	(12,228)
Net cash provided by (used in) financing activities		12,442	(4,497)	(21,434)
Net increase (decrease) in cash and cash equivalents		2,586	(1,681)	(2,125)
Cash and cash equivalents, beginning of year		8,322	10,003	12,128
Cash and cash equivalents, end of year		10,908	8,322	10,003
Supplemental disclosure of cash flow information:
Cash paid for interest		45,713	44,066	43,799
Increase (decrease) in accrued real estate investments and development costs		2,097	$ (7,098)	$ 5,201
Great Eastern Shopping Center
Property, Plant and Equipment [Line Items]
Seller financing		$ 1,275
[1]	Proceeds from sales of property excludes $1,275 of seller financing in connection with the sale of the Company's Great Eastern property.

Organization, Formation, and Ba

Organization, Formation, and Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Formation, and Basis of Presentation	ORGANIZATION, FORMATION, AND BASIS OF PRESENTATION Organization Saul Centers, Inc. (“Saul Centers”) was incorporated under the Maryland General Corporation Law on June 10, 1993. Saul Centers operates as a real estate investment trust (a “REIT”) under the Internal Revenue Code of 1986, as amended (the “Code”). The Company is required to annually distribute at least 90% of its REIT taxable income (excluding net capital gains) to its stockholders and meet certain organizational and other requirements. Saul Centers has made and intends to continue to make regular quarterly distributions to its stockholders. Saul Centers, together with its wholly owned subsidiaries and the limited partnerships of which Saul Centers or one of its subsidiaries is the sole general partner, are referred to collectively as the “Company.” B. Francis Saul II serves as Chairman of the Board of Directors and Chief Executive Officer of Saul Centers. Formation and Structure of Company Saul Centers was formed to continue and expand the shopping center business previously owned and conducted by the B. F. Saul Real Estate Investment Trust (the "Trust"), the B. F. Saul Company and certain other affiliated entities, each of which is controlled by B. Francis Saul II and his family members (collectively, the “Saul Organization”). On August 26, 1993, members of the Saul Organization transferred to Saul Holdings Limited Partnership, a newly formed Maryland limited partnership (the “Operating Partnership”), and two newly formed subsidiary limited partnerships (the “Subsidiary Partnerships,” and collectively with the Operating Partnership, the “Partnerships”), shopping center and mixed-used properties, and the management functions related to the transferred properties. Since its formation, the Company has developed and purchased additional properties. The following table lists the significant properties acquired, developed and/or disposed of by the Company since January 1, 2015 . Name of Property Location Type Year of Acquisition/ Development/ Disposal Acquisitions 726 N. Glebe Road* Arlington, Virginia Shopping Center September 2015 700 N. Glebe Road Arlington, Virginia Development August 2016 Burtonsville Town Square Burtonsville, Maryland Shopping Center January 2017 Developments Park Van Ness Washington, DC Mixed-Use 2013-2016 750 N. Glebe Road Arlington, Virginia Mixed-Use 2017 Dispositions Crosstown Business Center Tulsa, Oklahoma Mixed-Use December 2016 Great Eastern District Heights, Maryland Shopping Center September 2017 *As of August 2016, this property was removed from operations and reclassified to development. As of December 31, 2017 , the Company’s properties (the “Current Portfolio Properties”) consisted of 49 shopping center properties (the “Shopping Centers”), six mixed-use properties, which are comprised of office, retail and multi-family residential uses (the “Mixed-Use Properties”) and three (non-operating) development properties. Basis of Presentation The accompanying financial statements are presented on the historical cost basis of the Saul Organization because of affiliated ownership and common management and because the assets and liabilities were the subject of a business combination with the Operating Partnership, the Subsidiary Partnerships and Saul Centers, all newly formed entities with no prior operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations The Company, which conducts all of its activities through its subsidiaries, the Operating Partnership and Subsidiary Partnerships, engages in the ownership, operation, management, leasing, acquisition, renovation, expansion, development and financing of community and neighborhood shopping centers and mixed-used properties, primarily in the Washington, DC/Baltimore metropolitan area. Because the properties are located primarily in the Washington, DC/Baltimore metropolitan area, a disproportionate economic downturn in the local economy would have a greater negative impact on our overall financial performance than on the overall financial performance of a company with a portfolio that is more geographically diverse. A majority of the Shopping Centers are anchored by several major tenants. As of December 31, 2017 , 32 of the Shopping Centers were anchored by a grocery store and offer primarily day-to-day necessities and services. Two retail tenants, Giant Food ( 4.7% ), a tenant at ten Shopping Centers and Capital One Bank ( 2.8% ), a tenant at 18 properties, individually accounted for 2.5% or more of the Company’s total revenue for the year ended December 31, 2017 . Principles of Consolidation The accompanying consolidated financial statements include the accounts of Saul Centers, its subsidiaries, and the Operating Partnership and Subsidiary Partnerships which are majority owned by Saul Centers. All significant intercompany balances and transactions have been eliminated in consolidation. The Operating Partnership is a variable interest entity ("VIE") of the Company because the limited partners do not have substantive kick-out or participating rights. The Company is the primary beneficiary of the Operating Partnership because it has the power to direct the activities of the Operating Partnership and the rights to absorb 74.4% of the net income of the Operating Partnership. Because the Operating Partnership was already consolidated into the financial statements of the Company, the identification of it as a VIE has no impact on the consolidated financial statements of the Company. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates. Real Estate Investment Properties The Company purchases real estate investment properties from time to time and records assets acquired and liabilities assumed, including land, buildings, and intangibles related to in-place leases and customer relationships, based on their relative fair values. The fair value of buildings generally is determined as if the buildings were vacant upon acquisition and then subsequently leased at market rental rates and considers the present value of all cash flows expected to be generated by the property including an initial lease up period. From time to time the Company may purchase a property for future development purposes. The property may be improved with an existing structure that would be demolished as part of the development. In such cases, the fair value of the building may be determined based only on existing leases and not include estimated cash flows related to future leases. In certain circumstances, such as if the building is vacant and the Company intends to demolish the building in the near term, the entire purchase price will be allocated to land. The Company determines the fair value of above and below market intangibles associated with in-place leases by assessing the net effective rent and remaining term of the lease relative to market terms for similar leases at acquisition taking into consideration the remaining contractual lease period, renewal periods, and the likelihood of the tenant exercising its renewal options. The fair value of a below market lease component is recorded as deferred income and accreted as additional lease revenue over the remaining contractual lease period. If the fair value of the below market lease intangible includes fair value associated with a renewal option, such amounts are not accreted until the renewal option is exercised. If the renewal option is not exercised the value is recognized at that time. The fair value of above market lease intangibles is recorded as a deferred asset and is amortized as a reduction of lease revenue over the remaining contractual lease term. The Company determines the fair value of at-market in-place leases considering the cost of acquiring similar leases, the foregone rents associated with the lease-up period and carrying costs associated with the lease-up period. Intangible assets associated with at-market in-place leases are amortized as additional expense over the remaining contractual lease term. To the extent customer relationship intangibles are present in an acquisition, the fair values of the intangibles are amortized over the lives of the customer relationships. The Company has never recorded a customer relationship intangible asset. Acquisition-related transaction costs are either (a) expensed as incurred when related to business combinations or (b) capitalized to land and/or building when related to asset acquisitions. If there is an event or change in circumstance that indicates a potential impairment in the value of a real estate investment property, the Company prepares an analysis to determine whether the carrying value of the real estate investment property exceeds its estimated fair value. The Company considers both quantitative and qualitative factors including recurring operating losses, significant decreases in occupancy, and significant adverse changes in legal factors and business climate. If impairment indicators are present, the Company compares the projected cash flows of the property over its remaining useful life, on an undiscounted basis, to the carrying value of that property. The Company assesses its undiscounted projected cash flows based upon estimated capitalization rates, historic operating results and market conditions that may affect the property. If the carrying value is greater than the undiscounted projected cash flows, the Company would recognize an impairment loss equivalent to an amount required to adjust the carrying amount to its then estimated fair value. The fair value of any property is sensitive to the actual results of any of the aforementioned estimated factors, either individually or taken as a whole. Should the actual results differ from management’s projections, the valuation could be negatively or positively affected. The Company did not recognize an impairment loss on any of its real estate in 2017 , 2016 , or 2015 . Interest, real estate taxes, development related salary costs and other carrying costs are capitalized on projects under development and construction. Once construction is substantially completed and the assets are placed in service, their rental income, real estate tax expense, property operating expenses (consisting of payroll, repairs and maintenance, utilities, insurance and other property related expenses) and depreciation are included in current operations. Property operating expenses are charged to operations as incurred. Interest expense capitalized totaled $3.5 million , $2.5 million , and $ 2.2 million during 2017 , 2016 , and 2015 , respectively. Commercial development projects are considered substantially complete and available for occupancy upon completion of tenant improvements, but no later than one year from the cessation of major construction activity. Multi-family residential development projects are considered substantially complete and available for occupancy upon receipt of the certificate of occupancy from the appropriate licensing authority. Substantially completed portions of a project are accounted for as separate projects. Depreciation is calculated using the straight-line method and estimated useful lives of generally between 35 and 50 years for base buildings, or a shorter period if management determines that the building has a shorter useful life, and up to 20 years for certain other improvements that extend the useful lives. Leasehold improvements expenditures are capitalized when certain criteria are met, including when the Company supervises construction and will own the improvements. Tenant improvements are amortized, over the shorter of the lives of the related leases or the useful life of the improvement, using the straight-line method. Depreciation expense, which is included in Depreciation and amortization of deferred leasing costs in the Consolidated Statements of Operations, for the years ended December 31, 2017 , 2016 , and 2015 , was $40.2 million , $38.8 million , and $37.7 million , respectively. Repairs and maintenance expense totaled $11.6 million , $11.8 million , and $11.6 million for 2017 , 2016 , and 2015 , respectively, and is included in property operating expenses in the accompanying consolidated financial statements. Deferred Leasing Costs Deferred leasing costs consist of commissions paid to third-party leasing agents, internal direct costs such as employee compensation and payroll-related fringe benefits directly related to time spent performing leasing-related activities for successful commercial leases and amounts attributed to in place leases associated with acquired properties and are amortized, using the straight-line method, over the term of the lease or the remaining term of an acquired lease. Leasing related activities include evaluating the prospective tenant’s financial condition, evaluating and recording guarantees, collateral and other security arrangements, negotiating lease terms, preparing lease documents and closing the transaction. Unamortized deferred costs are charged to expense if the applicable lease is terminated prior to expiration of the initial lease term. Collectively, deferred leasing costs totaled $27.3 million and $26.0 million , net of accumulated amortization of approximately $35.3 million and $30.4 million , as of December 31, 2017 and 2016 , respectively. Amortization expense, which is included in Depreciation and amortization of deferred leasing costs in the Consolidated Statements of Operations, totaled approximately $5.5 million , $5.6 million , and $5.6 million , for the years ended December 31, 2017 , 2016 , and 2015 , respectively. Construction in Progress Construction in progress includes preconstruction and development costs of active projects. Preconstruction costs include legal, zoning and permitting costs and other project carrying costs incurred prior to the commencement of construction. Development costs include direct construction costs and indirect costs incurred subsequent to the start of construction such as architectural, engineering, construction management and carrying costs consisting of interest, real estate taxes and insurance. The following table shows the components of construction in progress. December 31, (in thousands) 2017 2016 N. Glebe Road $ 83,462 $ 58,147 Other 7,652 5,423 Total $ 91,114 $ 63,570 Accounts Receivable and Accrued Income Accounts receivable primarily represent amounts currently due from tenants in accordance with the terms of the respective leases. Receivables are reviewed monthly and reserves are established with a charge to current period operations when, in the opinion of management, collection of the receivable is doubtful. Accounts receivable in the accompanying consolidated financial statements are shown net of an allowance for doubtful accounts of $0.4 million and $2.0 million , at December 31, 2017 and 2016 , respectively. (In thousands) Year ended December 31, 2017 2016 2015 Beginning Balance $ 1,958 $ 1,263 $ 677 Provision for Credit Losses 906 1,494 915 Charge-offs (2,459 ) (799 ) (329 ) Ending Balance $ 405 $ 1,958 $ 1,263 In addition to rents due currently, accounts receivable also includes $44.1 million and $43.1 million , at December 31, 2017 and 2016 , respectively, net of allowance for doubtful accounts totaling $0.2 million and $0.5 million , respectively, representing minimum rental income accrued on a straight-line basis to be paid by tenants over the remaining term of their respective leases. Assets Held for Sale The Company considers properties to be assets held for sale when all of the following criteria are met: • management commits to a plan to sell a property; • it is unlikely that the disposal plan will be significantly modified or discontinued; • the property is available for immediate sale in its present condition; • actions required to complete the sale of the property have been initiated; • sale of the property is probable and the Company expects the completed sale will occur within one year; and • the property is actively being marketed for sale at a price that is reasonable given its current market value. The Company must make a determination as to the point in time that it is probable that a sale will be consummated, which generally occurs when an executed sales contract has no contingencies and the prospective buyer has significant funds at risk to ensure performance. Upon designation as an asset held for sale, the Company records the carrying value of each property at the lower of its carrying value or its estimated fair value, less estimated costs to sell, and ceases depreciation. As of December 31, 2015, the Company has classified as held-for-sale one operating property, comprising 197,100 square feet of gross leasable area. The book value of this property, which is included in Other Assets, was $3.4 million , net of accumulated depreciation of $7.0 million , which does not exceed its estimated fair value, less costs to sell, and liabilities were $0.2 million . The asset was sold in 2016. Cash and Cash Equivalents Cash and cash equivalents include short-term investments. Short-term investments include money market accounts and other investments which generally mature within three months, measured from the acquisition date, and/or are readily convertible to cash. Substantially all of the Company’s cash balances at December 31, 2017 are held in non-interest bearing accounts at various banks. From time to time the Company may maintain deposits with financial institutions in amounts in excess of federally insured limits. The Company has not experienced any losses on such deposits and believes it is not exposed to any significant credit risk on those deposits. Deferred Debt Costs Deferred debt costs consist of fees and costs incurred to obtain long-term financing, construction financing and the revolving line of credit. These fees and costs are being amortized on a straight-line basis over the terms of the respective loans or agreements, which approximates the effective interest method. Deferred debt costs totaled $6.9 million and $7.5 million , net of accumulated amortization of $8.2 million and $7.3 million at December 31, 2017 and 2016 , respectively, and are reflected as a reduction of the related debt in the Consolidated Balance Sheets. At December 31, 2017 , deferred debt costs totaling $1.8 million , related to the Glebe Road construction loan, which has no outstanding balance, are included in Other Assets in the Consolidated Balance Sheets. Deferred Income Deferred income consists of payments received from tenants prior to the time they are earned and recognized by the Company as revenue, including tenant prepayment of rent for future periods, real estate taxes when the taxing jurisdiction has a fiscal year differing from the calendar year reimbursements specified in the lease agreement and tenant construction work provided by the Company. In addition, deferred income includes the fair value of certain below market leases. Derivative Financial Instruments The Company may, when appropriate, employ derivative instruments, such as interest-rate swaps, to mitigate the risk of interest rate fluctuations. The Company does not enter into derivative or other financial instruments for trading or speculative purposes. Derivative financial instruments are carried at fair value as either assets or liabilities on the consolidated balance sheets. For those derivative instruments that qualify, the Company may designate the hedging instrument, based upon the exposure being hedged, as a fair value hedge or a cash flow hedge. Derivative instruments that are designated as a hedge are evaluated to ensure they continue to qualify for hedge accounting. The effective portion of any gain or loss on the hedge instruments is reported as a component of accumulated other comprehensive income (loss) and recognized in earnings within the same line item associated with the forecasted transaction in the same period or periods during which the hedged transaction affects earnings. Any ineffective portion of the change in fair value of a derivative instrument is immediately recognized in earnings. For derivative instruments that do not meet the criteria for hedge accounting, or that qualify and are not designated, changes in fair value are immediately recognized in earnings. Revenue Recognition Rental and interest income are accrued as earned. Recognition of rental income commences when control of the space has been given to the tenant. When rental payments due under leases vary from a straight-line basis because of free rent periods or stepped increases, income is recognized on a straight-line basis. Expense recoveries represent a portion of property operating expenses billed to the tenants, including common area maintenance, real estate taxes and other recoverable costs. Expense recoveries are recognized in the period in which the expenses are incurred. Rental income based on a tenant’s revenue (“percentage rent”) is accrued when a tenant reports sales that exceed a specified breakpoint, pursuant to the terms of their respective leases. Income Taxes The Company made an election to be treated, and intends to continue operating so as to qualify, as a REIT under the Code, commencing with its taxable year ended December 31, 1993 . A REIT generally will not be subject to federal income taxation, provided that distributions to its stockholders equal or exceed its REIT taxable income and complies with certain other requirements. Therefore, no provision has been made for federal income taxes in the accompanying consolidated financial statements. As of December 31, 2017 , the Company had no material unrecognized tax benefits and there exist no potentially significant unrecognized tax benefits which are reasonably expected to occur within the next twelve months. The Company recognizes penalties and interest accrued related to unrecognized tax benefits, if any, as general and administrative expense. No penalties and interest have been accrued in years 2017 , 2016 , and 2015 . The tax basis of the Company’s real estate investments was approximately $1.32 billion and $1.26 billion as of December 31, 2017 and 2016 , respectively. With few exceptions, the Company is no longer subject to U.S. federal, state, and local tax examinations by tax authorities for years before 2013. Stock Based Employee Compensation, Deferred Compensation and Stock Plan for Directors The Company uses the fair value method to value and account for employee stock options. The fair value of options granted is determined at the time of each award using the Black-Scholes model, a widely used method for valuing stock based employee compensation, and the following assumptions: (1) Expected Volatility determined using the most recent trading history of the Company’s common stock (month-end closing prices) corresponding to the average expected term of the options; (2) Average Expected Term of the options is based on prior exercise history, scheduled vesting and the expiration date; (3) Expected Dividend Yield determined by management after considering the Company’s current and historic dividend yield rates, the Company’s yield in relation to other retail REITs and the Company’s market yield at the grant date; and (4) a Risk-free Interest Rate based upon the market yields of US Treasury obligations with maturities corresponding to the average expected term of the options at the grant date. The Company amortizes the value of options granted ratably over the vesting period and includes the amounts as compensation in general and administrative expenses. The Company has a stock plan, which was originally approved in 2004, amended in 2008 and 2013 and which expires in 2023, for the purpose of attracting and retaining executive officers, directors and other key personnel (the "Stock Plan"). Pursuant to the Stock Plan, the Compensation Committee established a Deferred Compensation Plan for Directors for the benefit of its directors and their beneficiaries, which replaced a previous Deferred Compensation and Stock Plan for Directors. A director may make an annual election to defer all or part of his or her director’s fees and has the option to have the fees paid in cash, in shares of common stock or in a combination of cash and shares of common stock upon separation from the Board. If the director elects to have fees paid in stock, fees earned during a calendar quarter are aggregated and divided by the common stock’s closing market price on the first trading day of the following quarter to determine the number of shares to be allocated to the director. As of December 31, 2017 , the directors’ deferred fee accounts comprise 183,818 shares. The Compensation Committee has also approved an annual award of shares of the Company’s common stock as additional compensation to each director serving on the Board of Directors as of the record date for the Annual Meeting of Stockholders. The shares are awarded as of each Annual Meeting of Shareholders, and their issuance may not be deferred. Each director was issued 200 shares for each of the years ended December 31, 2017 , 2016 , and 2015 . The shares were valued at the closing stock price on the dates the shares were awarded and included in general and administrative expenses in the total amounts of $130,700 , $150,100 , and $143,000 , for the years ended December 31, 2017 , 2016 , and 2015 , respectively. Noncontrolling Interest Saul Centers is the sole general partner of the Operating Partnership, owning a 74.4% common interest as of December 31, 2017 . Noncontrolling interest in the Operating Partnership is comprised of limited partnership units owned by the Saul Organization. Noncontrolling interest reflected on the accompanying consolidated balance sheets is increased for earnings allocated to limited partnership interests and distributions reinvested in additional units, and is decreased for limited partner distributions. Noncontrolling interest reflected on the consolidated statements of operations represents earnings allocated to limited partnership interests held by the Saul Organization. Per Share Data Per share data for net income (basic and diluted) is computed using weighted average shares of common stock. Convertible limited partnership units and employee stock options are the Company’s potentially dilutive securities. For all periods presented, the convertible limited partnership units are anti-dilutive. The treasury stock method was used to measure the effect of the dilution. December 31, (Shares in thousands) 2017 2016 2015 Weighted average common shares outstanding - Basic 21,901 21,505 21,127 Effect of dilutive options 107 110 69 Weighted average common shares outstanding - Diluted 22,008 21,615 21,196 Average share price $ 61.63 $ 58.96 $ 53.38 Non-dilutive options — 129 111 Years non-dilutive options were issued 2007, 2015, and 2016 2007 and 2015 Legal Contingencies The Company is subject to various legal proceedings and claims that arise in the ordinary course of business, which are generally covered by insurance. Upon determination that a loss is probable to occur and can be reasonably estimated, the estimated amount of the loss is recorded in the financial statements. Recently Issued Accounting Standards In May 2014, the FASB issued ASU No. 2014-09 titled “Revenue from Contracts with Customers” and subsequently issued several related ASUs (collectively “ASU 2014-09”). ASU 2014-09 will replace most existing revenue recognition guidance and will require an entity to recognize the amount of revenue which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 is effective for annual periods beginning after December 15, 2017, and interim periods within those years and early adoption is not permitted. ASU 2014-09 must be applied retrospectively by either restating prior periods or by recognizing the cumulative effect as of the first date of application. Management believes the majority of the Company's revenue falls outside of the scope of this guidance and does not anticipate any significant changes to the timing of the Company's revenue recognition. The Company intends to implement the standard retrospectively with the cumulative effect recognized in retained earnings at the date of adoption. In February 2015, the FASB issued ASU No. 2015-02, “Consolidation” ("ASU 2015-02"). ASU 2015-02 modifies existing consolidation guidance for reporting organizations that are required to evaluate whether they should consolidate certain legal entities. All legal entities are subject to reevaluation under the revised consolidation model. ASU 2015-02 is effective for annual periods beginning after December 15, 2015, and interim periods within those years. The adoption of ASU 2015-02 effective January 1, 2016, resulted in the Operating Partnership being classified as a variable interest entity. Because the Operating Partnership was already consolidated into the financial statements, adoption had no impact on the Company’s consolidated financial statements or disclosures. In April 2015, the FASB issued ASU No. 2015-03, “Interest - Imputation of Interest” (“ASU 2015-03”). ASU 2015-03 simplifies the presentation of debt issuance costs and will require an entity to deduct transaction costs from the carrying value of the related financial liability and not record those transaction costs as a separate asset. Recognition and measurement guidance for debt issuance costs are not affected by ASU 2015-03. ASU 2015-03 is effective for annual periods beginning after December 15, 2015, and interim periods within those years, and must be applied retrospectively by adjusting the balance sheet of each individual period presented. The Company retrospectively adopted ASU 2015-03 effective January 1, 2016. As a result of the adoption of ASU 2015-03, the Company no longer reports its net deferred debt costs as an asset and instead reports those amounts as reduction of the carrying value of the associated debt. In February 2016, the FASB issued ASU 2016-02, ‘‘Leases’’ (“ASU 2016-02”). ASU 2016-02 amends the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. ASU 2016-02 is effective for annual periods beginning after December 15, 2018, interim periods within those years, and requires a modified retrospective transition approach for all leases existing at the date of initial application, with an option to use certain practical expedients for those existing leases. We are evaluating the impact that ASU 2016-02 will have on our consolidated financial statements and related disclosures. In March 2016, the FASB issued ASU 2016-09, "Compensation-Stock Compensation" ("ASU 2016-09"). ASU 2016-09 simplifies the accounting for several aspects of share-based payments including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for annual periods beginning after December 15, 2016 and interim periods within those years. The transition method varies based on the specific amendment. The adoption of ASU 2016-09 effective January 1, 2017, did not have a material impact on our consolidated financial statements or related disclosures. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments-Credit Losses" ("ASU 2016-13"). ASU 2016-13 replaces the incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of information to support credit loss estimates. ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within those years. We are evaluating the impact that ASU 2016-13 will have on our consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-01, "Clarifying the Definition of a Business" ("ASU 2017-01"). ASU 2017-01 provides that when substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, the set is not a business. ASU 2017-01 is effective prospectively for annual periods beginning after December 15, 2017, and interim periods within those years. Early application is permitted for transactions for which the acquisition date occurs before the effective date provided the transaction has not been reported in the financial statements. The Company adopted ASU 2017-01 during the first quarter of 2017, the effect of which, for asset acquisitions, was (a) the capitalization of acquisition costs, instead of expense, and (b) recordation of acquired assets and assessment liabilities at relative fair value, instead of fair value. Reclassifications Certain reclassifications have been made to prior years to conform to the presentation used for year ended December 31, 2017 .

Real Estate Acquired

Real Estate Acquired	12 Months Ended
	Dec. 31, 2017
Real Estate [Abstract]
Real Estate Acquired	REAL ESTATE ACQUIRED 700, 726, 730 and 750 N. Glebe Road In August 2014, the Company purchased for $40.0 million , 750 N. Glebe Road and incurred acquisition costs of $0.4 million . In December 2014, the Company purchased for $2.8 million 730 N. Glebe Road and incurred acquisition costs of $40,400 . In September 2015, the Company purchased for $4.0 million 726 N. Glebe Road and incurred acquisition costs of $0.1 million . In August 2016 , the Company purchased for $7.2 million , including acquisition costs, 700 N. Glebe Road . These properties are contiguous and are located in Arlington, Virginia. Westview pad In February 2015 , the Company purchased for $0.9 million including acquisition costs, a 1.1 acre retail pad site in Frederick, Maryland, which is contiguous with and an expansion of the Company's other Westview asset. Thruway pad In August 2016 , the Company purchased for $3.1 million , a retail pad site with an occupied bank building in Winston Salem, North Carolina , and incurred acquisition costs of $60,400 . The property is contiguous with and an expansion of the Company's Thruway asset. Beacon Center In the fourth quarter of 2016, the Company purchased for $22.7 million , including acquisition costs, the land underlying Beacon Center. The land was previously leased by the Company with an annual rent of approximately $60,000 . The purchase price was funded in part by an $11.25 million increase to the existing mortgage collateralized by Beacon Center and in part by the Company’s revolving credit facility. Southdale In the fourth quarter of 2016, the Company purchased for $15.3 million , including acquisition costs, the land underlying Southdale. The land was previously leased by the Company with an annual rent of approximately $60,000 . The purchase price was funded by the Company’s revolving credit facility. Burtonsville Town Square In January 2017 , the Company purchased for $76.4 million , including acquisition costs, Burtonsville Town Square located in Burtonsville, Maryland . Olney Shopping Center In March 2017, the Company purchased for $3.1 million , including acquisition costs, the land underlying Olney Shopping Center. The land was previously leased by the Company with an annual rent of approximately $56,000 . The purchase price was funded by the revolving credit facility. Allocation of Purchase Price of Real Estate Acquired The Company allocates the purchase price of real estate investment properties to various components, such as land, buildings and intangibles related to in-place leases and customer relationships, based on their relative fair values. See Note 2. Summary of Significant Accounting Policies-Real Estate Investment Properties. During 2017, the Company purchased one property, Burtonsville Town Square, at a cost of $76.4 million , including acquisition costs. Of the total acquisition cost, $28.4 million was allocated to land, $45.8 million was allocated to buildings, $2.2 million was allocated to in-place leases, $0.6 million was allocated to above-market rent, and $(0.6) million was allocated to below-market rent, based on their relative fair values. During 2016, the Company purchased two properties at an aggregate cost of $10.3 million , and incurred acquisition costs totaling $60,400 . The purchase price was allocated to the assets acquired and liabilities assumed based on their fair value as shown in the following table. (in thousands) 700 N. Glebe Road Thruway Pad Total Land $ 7,236 $ 2,196 $ 9,432 Buildings — 874 874 In-place Leases — 93 93 Above Market Rent — — — Below Market Rent — (63 ) (63 ) Total Purchase Price $ 7,236 $ 3,100 $ 10,336 During 2015, the Company purchased one property, 726 N. Glebe Road, at a cost of $4.0 million and incurred acquisition costs of $0.1 million . Of the total purchase price, $3.9 million was allocated to land and $0.1 million was allocated to building. No amounts were allocated to in-place, above-market or below-market leases. The gross carrying amount of lease intangible assets included in deferred leasing costs as of December 31, 2017 and 2016 was $12.3 million and $10.1 million , respectively, and accumulated amortization was $7.5 million and $6.4 million , respectively. Amortization expense totaled $1.1 million , $1.0 million and $1.3 million , for the years ended December 31, 2017 , 2016 , and 2015 , respectively. The gross carrying amount of below market lease intangible liabilities included in deferred income as of December 31, 2017 and 2016 was $25.1 million and $25.1 million , respectively, and accumulated amortization was $11.8 million and $10.6 million , respectively. Accretion income totaled $1.7 million , $1.8 million , and $1.8 million , for the years ended December 31, 2017 , 2016 , and 2015 , respectively. The gross carrying amount of above market lease intangible assets included in accounts receivable as of December 31, 2017 and 2016 was $0.6 million and $10,200 , respectively, and accumulated amortization was $39,500 and $7,800 , respectively. Amortization expense totaled $31,600 , $1,500 and $1,500 , for the years ended December 31, 2017 , 2016 and 2015 , respectively. The remaining weighted-average amortization period as of December 31, 2017 is 4.6 years, 5.8 years, and 8.8 years for lease acquisition costs, above market leases and below market leases, respectively. As of December 31, 2017 , scheduled amortization of intangible assets and deferred income related to in place leases is as follows: (In thousands) Lease acquisition costs Above market leases Below market leases 2018 $ 982 $ 33 $ 1,652 2019 780 33 1,515 2020 653 33 1,433 2021 530 33 1,409 2022 390 33 1,306 Thereafter 1,547 409 6,029 Total $ 4,882 $ 574 $ 13,344

Noncontrolling Interests - Hold

Noncontrolling Interests - Holders of Convertible Limited Partnership Units in the Operating Partnership	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Noncontrolling Interests - Holders of Convertible Limited Partnership Units in the Operating Partnership	NONCONTROLLING INTERESTS - HOLDERS OF CONVERTIBLE LIMITED PARTNERSHIP UNITS IN THE OPERATING PARTNERSHIP The Saul Organization holds a 25.6% limited partnership interest in the Operating Partnership represented by 7,541,867 limited partnership units, as of December 31, 2017 . The units are convertible into shares of Saul Centers’ common stock, at the option of the unit holder, on a one -for-one basis provided that, in accordance with the Saul Centers, Inc. Articles of Incorporation, the rights may not be exercised at any time that the Saul Organization beneficially owns, directly or indirectly, in the aggregate more than 39.9% of the value of the outstanding common stock and preferred stock of Saul Centers (the “Equity Securities”). As of December 31, 2017 , approximately 740,000 units were eligible for conversion. The impact of the Saul Organization’s 25.6% limited partnership interest in the Operating Partnership is reflected as Noncontrolling Interests in the accompanying consolidated financial statements. Fully converted partnership units and diluted weighted average shares outstanding for the years ended December 31, 2017 , 2016 , and 2015 , were 29,510,900 , 28,989,900 , and 28,449,400 , respectively.

Mortgage Notes Payable, Revolvi

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs	MORTGAGE NOTES PAYABLE, REVOLVING CREDIT FACILITY, INTEREST EXPENSE AND AMORTIZATION OF DEFERRED DEBT COSTS At December 31, 2017 , the principal amount of outstanding debt totaled $965.5 million , of which $890.4 million was fixed rate debt and $75.1 million was variable rate debt. The principal amount of the Company’s outstanding debt totaled $907.8 million at December 31, 2016 , of which $844.3 million was fixed rate debt and $63.5 million was variable rate debt. At December 31, 2017 , the Company had a $275.0 million unsecured revolving credit facility, which can be used for working capital, property acquisitions or development projects. The revolving credit facility matures on June 23, 2018, and may be extended by the Company for one additional year subject to the Company’s satisfaction of certain conditions. Saul Centers and certain consolidated subsidiaries of the Operating Partnership have guaranteed the payment obligations of the Operating Partnership under the revolving credit facility. Letters of credit may be issued under the revolving credit facility. On December 31, 2017 , based on the value of the Company's unencumbered properties, approximately $213.8 million was available under the line, $61.0 million was outstanding and approximately $185,000 was committed for letters of credit. The interest rate under the facility is variable and equals the sum of one-month LIBOR and a margin that is based on the Company’s leverage ratio and which can range from 145 basis points to 200 basis points. As of December 31, 2017 , the margin was 145 basis points. Saul Centers is a guarantor of the revolving credit facility, of which the Operating Partnership is the borrower, a portion of the Metro Pike Center bank loan (approximately $7.8 million of the $14.1 million outstanding at December 31, 2017 ), a portion of the Park Van Ness construction-to-permanent loan (approximately $53.7 million of the $71.2 million outstanding balance at December 31, 2017), and a portion of the Kentlands Square II mortgage loan (approximately $9.2 million of the $36.5 million outstanding at December 31, 2017). All other notes payable are non-recourse. On March 3, 2015 , the Company closed on a 15 -year, non-recourse $30.0 million mortgage loan secured by Shops at Fairfax and Boulevard. The loan matures in 2030 , bears interest at a fixed rate of 3.69% , requires monthly principal and interest payments totaling $153,300 based on a 25 -year amortization schedule and requires a final payment of $15.5 million at maturity. Proceeds were used to repay in full the $15.2 million remaining balance of existing debt secured by Shops at Fairfax and Boulevard and to reduce outstanding borrowings under the revolving credit facility. On April 1, 2015 , the Company closed on a 15 -year, non-recourse $16.0 million mortgage loan secured by Northrock. The loan matures in 2030 , bears interest at a fixed rate of 3.99% , requires monthly principal and interest payments totaling $84,400 based on a 25 -year amortization schedule and requires a final payment of $8.4 million at maturity. Proceeds were used to repay in full the $14.5 million remaining balance of existing debt secured by Northrock. In November 2016, the existing loan secured by Beacon Center was increased by $11.25 million . The interest rate, amortization period and maturity date did not change; the required monthly payment was increased to $268,500 . Proceeds were used to partially fund the purchase of the ground which underlies Beacon Center. On January 18, 2017 , the Company closed on a 15 -year, non-recourse $40.0 million mortgage loan secured by Burtonsville Town Square. The loan matures in 2032 , bears interest at a fixed rate of 3.39% , requires monthly principal and interest payments of $197,900 based on a 25 -year amortization schedule and requires a final payment of $20.3 million million at maturity. On August 14, 2017, the Company closed on a $157.0 million construction-to-permanent loan, the proceeds of which will be used to partially fund the Glebe Road development project. The loan matures in 2035, bears interest at a fixed rate of 4.67% , requires interest only payments, which will be funded by the loan, until conversion to permanent. The conversion is expected in the fourth quarter of 2021, and thereafter, monthly principal and interest payments of $887,900 based on a 25 -year amortization schedule will be required. Effective September 1, 2017 , the Company's $71.6 million construction-to-permanent loan, which is fully drawn and secured by Park Van Ness, converted to permanent financing. The loan matures in 2032 , bears interest at a fixed rate of 4.88% , requires monthly principal and interest payments of $413,460 based on a 25 -year amortization schedule and requires a final payment of $39.6 million at maturity. On November 20, 2017 , the Company closed on a 15 -year, non-recourse $60.0 million mortgage loan secured by Washington Square. The loan matures in 2032 , bears interest at a fixed rate of 3.75% , requires monthly principal and interest payments of $308,500 based on a 25 -year amortization schedule and requires a final payment of $31.1 million . Proceeds were used to repay the remaining balance of approximately $28.1 million on the existing mortgage and reduce the outstanding balance of the revolving credit facility. The following is a summary of notes payable as of December 31, 2017 and 2016 . Notes Payable December 31, Interest Scheduled (Dollars in thousands) 2017 2016 Rate * Maturity * Fixed rate mortgages: $ — (a) $ 29,428 6.01 % Feb-2018 30,201 (b) 32,036 5.88 % Jan-2019 9,783 (c) 10,372 5.76 % May-2019 13,529 (d) 14,335 5.62 % Jul-2019 13,543 (e) 14,325 5.79 % Sep-2019 12,029 (f) 12,725 5.22 % Jan-2020 9,948 (g) 10,277 5.60 % May-2020 8,244 (h) 8,697 5.30 % Jun-2020 37,998 (i) 39,213 5.83 % Jul-2020 7,325 (j) 7,685 5.81 % Feb-2021 5,649 (k) 5,808 6.01 % Aug-2021 32,673 (l) 33,571 5.62 % Jun-2022 9,999 (m) 10,253 6.08 % Sep-2022 10,877 (n) 11,129 6.43 % Apr-2023 12,577 (o) 13,401 6.28 % Feb-2024 15,452 (p) 15,917 7.35 % Jun-2024 13,438 (q) 13,832 7.60 % Jun-2024 23,873 (r) 24,504 7.02 % Jul-2024 28,115 (s) 28,945 7.45 % Jul-2024 28,025 (t) 28,822 7.30 % Jan-2025 14,537 (u) 14,961 6.18 % Jan-2026 105,817 (v) 109,144 5.31 % Apr-2026 32,016 (w) 33,097 4.30 % Oct-2026 36,507 (x) 37,701 4.53 % Nov-2026 17,086 (y) 17,630 4.70 % Dec-2026 64,472 (z) 66,210 5.84 % May-2027 15,859 (aa) 16,352 4.04 % Apr-2028 39,968 (bb) 41,753 3.51 % Jun-2028 16,055 (cc) 16,543 3.99 % Sep-2028 27,884 (dd) 28,679 3.69 % Mar-2030 14,950 (ee) 15,357 3.99 % Apr-2030 39,140 (ff) — 3.39 % Feb-2032 71,211 (gg) 70,144 4.88 % Sep-2032 60,000 (hh) — 3.75 % Dec-2032 11,613 (ii) 11,446 8.00 % Apr-2034 Total fixed rate 890,393 844,292 5.25 % 8.6 Years Variable rate loans: 61,000 (jj) 49,000 LIBOR + 1.45 % Jun-2018 14,135 (kk) 14,482 LIBOR + 1.65 % Feb-2018 Total variable rate $ 75,135 $ 63,482 2.86 % 0.4 Years Total notes payable $ 965,528 $ 907,774 5.07 % 7.9 Years * Interest rate and scheduled maturity data presented as of December 31, 2017 . Totals computed using weighted averages. Amounts shown are principal amounts and have not been reduced by any deferred debt issuance costs. (a) The loan was collateralized by Washington Square and required equal monthly principal and interest payments of $264,000 based upon a 27.5 -year amortization schedule and a final payment of $28.0 million at loan maturity. In 2017, the loan was repaid in full and replaced with a new $60.0 million loan. See (hh) below. (b) The loan is collateralized by three shopping centers, Broadlands Village, The Glen and Kentlands Square I, and requires equal monthly principal and interest payments of $306,000 based upon a 25 -year amortization schedule and a final payment of $28.4 million at loan maturity. Principal of $1.8 million was amortized during 2017 . (c) The loan is collateralized by Olde Forte Village and requires equal monthly principal and interest payments of $98,000 based upon a 25 -year amortization schedule and a final payment of $9.0 million at loan maturity. Principal of $589,000 was amortized during 2017 . (d) The loan is collateralized by Countryside and requires equal monthly principal and interest payments of $133,000 based upon a 25 -year amortization schedule and a final payment of $12.3 million at loan maturity. Principal of $806,000 was amortized during 2017 . (e) The loan is collateralized by Briggs Chaney MarketPlace and requires equal monthly principal and interest payments of $133,000 based upon a 25 -year amortization schedule and a final payment of $12.2 million at loan maturity. Principal of $782,000 was amortized during 2017 . (f) The loan is collateralized by Shops at Monocacy and requires equal monthly principal and interest payments of $112,000 based upon a 25 -year amortization schedule and a final payment of $10.6 million at loan maturity. Principal of $696,000 was amortized during 2017 . (g) The loan is collateralized by Boca Valley Plaza and requires equal monthly principal and interest payments of $75,000 based upon a 30 -year amortization schedule and a final payment of $9.1 million at loan maturity. Principal of $329,000 was amortized during 2017 . (h) The loan is collateralized by Palm Springs Center and requires equal monthly principal and interest payments of $75,000 based upon a 25 -year amortization schedule and a final payment of $7.1 million at loan maturity. Principal of $453,000 was amortized during 2017 . (i) The loan and a corresponding interest-rate swap closed on June 29, 2010 and are collateralized by Thruway. On a combined basis, the loan and the interest-rate swap require equal monthly principal and interest payments of $289,000 based upon a 25 -year amortization schedule and a final payment of $34.8 million at loan maturity. Principal of $1.2 million was amortized during 2017 . (j) The loan is collateralized by Jamestown Place and requires equal monthly principal and interest payments of $66,000 based upon a 25 -year amortization schedule and a final payment of $6.1 million at loan maturity. Principal of $360,000 was amortized during 2017 . (k) The loan is collateralized by Hunt Club Corners and requires equal monthly principal and interest payments of $42,000 based upon a 30 -year amortization schedule and a final payment of $5.0 million , at loan maturity. Principal of $159,000 was amortized during 2017 . (l) The loan is collateralized by Lansdowne Town Center and requires monthly principal and interest payments of $230,000 based on a 30 -year amortization schedule and a final payment of $28.2 million at loan maturity. Principal of $898,000 was amortized during 2017 . (m) The loan is collateralized by Orchard Park and requires equal monthly principal and interest payments of $73,000 based upon a 30 -year amortization schedule and a final payment of $8.6 million at loan maturity. Principal of $254,000 was amortized during 2017 . (n) The loan is collateralized by BJ’s Wholesale and requires equal monthly principal and interest payments of $80,000 based upon a 30 -year amortization schedule and a final payment of $9.3 million at loan maturity. Principal of $252,000 was amortized during 2017 . (o) The loan is collateralized by Great Falls shopping center. The loan consists of three notes which require equal monthly principal and interest payments of $138,000 based upon a weighted average 26 -year amortization schedule and a final payment of $6.3 million at maturity. Principal of $824,000 was amortized during 2017 . (p) The loan is collateralized by Leesburg Pike and requires equal monthly principal and interest payments of $135,000 based upon a 25 -year amortization schedule and a final payment of $11.5 million at loan maturity. Principal of $465,000 was amortized during 2017 . (q) The loan is collateralized by Village Center and requires equal monthly principal and interest payments of $119,000 based upon a 25 -year amortization schedule and a final payment of $10.1 million at loan maturity. Principal of $394,000 was amortized during 2017 . (r) The loan is collateralized by White Oak and requires equal monthly principal and interest payments of $193,000 based upon a 24.4 year weighted amortization schedule and a final payment of $18.5 million at loan maturity. The loan was previously collateralized by Van Ness Square. During 2012, the Company substituted White Oak as the collateral and borrowed an additional $10.5 million . Principal of $631,000 was amortized during 2017 . (s) The loan is collateralized by Avenel Business Park and requires equal monthly principal and interest payments of $246,000 based upon a 25 -year amortization schedule and a final payment of $20.9 million at loan maturity. Principal of $830,000 was amortized during 2017 . (t) The loan is collateralized by Ashburn Village and requires equal monthly principal and interest payments of $240,000 based upon a 25 -year amortization schedule and a final payment of $20.5 million at loan maturity. Principal of $797,000 was amortized during 2017 . (u) The loan is collateralized by Ravenwood and requires equal monthly principal and interest payments of $111,000 based upon a 25 -year amortization schedule and a final payment of $10.1 million at loan maturity. Principal of $424,000 was amortized during 2017 . (v) The loan is collateralized by Clarendon Center and requires equal monthly principal and interest payments of $753,000 based upon a 25 -year amortization schedule and a final payment of $70.5 million at loan maturity. Principal of $3.3 million was amortized during 2017 . (w) The loan is collateralized by Severna Park MarketPlace and requires equal monthly principal and interest payments of $207,000 based upon a 25 -year amortization schedule and a final payment of $20.3 million at loan maturity. Principal of $1.1 million was amortized during 2017 . (x) The loan is collateralized by Kentlands Square II and requires equal monthly principal and interest payments of $240,000 based upon a 25 -year amortization schedule and a final payment of $23.1 million at loan maturity. Principal of $1.2 million was amortized during 2017 . (y) The loan is collateralized by Cranberry Square and requires equal monthly principal and interest payments of $113,000 based upon a 25 -year amortization schedule and a final payment of $10.9 million at loan maturity. Principal of $544,000 was amortized during 2017 . (z) 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 $1.7 million was amortized during 2017 . (aa) 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 $493,000 was amortized in 2017 . (bb) The loan is collateralized by Beacon Center and requires equal monthly principal and interest payments of $268,500 based upon a 20 -year amortization schedule and a final payment of $17.1 million at loan maturity. Principal of $1.8 million was amortized in 2017 . (cc) 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 $488,000 was amortized in 2017 . (dd) The loan is collateralized by Shops at Fairfax and Boulevard shopping centers and requires equal monthly principal and interest payments totaling $153,300 based upon a 25 -year amortization schedule and a final payment of $15.5 million at maturity. Principal of $795,000 was amortized in 2017 . (ee) The loan is collateralized by Northrock and requires equal monthly principal and interest payments totaling $84,400 based upon a 25 -year amortization schedule and a final payment of $8.4 million at maturity. Principal of $407,000 was amortized in 2017 . (ff) The loan is collateralized by Burtonsville Town Square and requires equal monthly principal and interest payments of $198,000 based on a 25 -year amortization schedule and a final payment of $20.3 million at loan maturity. Principal of $860,000 was amortized in 2017. (gg) The loan is a $71.6 million construction-to-permanent facility that is collateralized by and financed a portion of the construction costs of Park Van Ness. During the construction period, interest was funded by the loan. Effective September 1, 2017, the loan converted to permanent financing and requires monthly principal and interest payments totaling $413,500 based upon a 25 -year amortization schedule. A final payment of $39.6 million will be due at maturity. Principal of $369,000 was amortized in 2017. (hh) The loan is collateralized by Washington Square and requires equal monthly principal and interest payments of $308,000 based upon a 25 -year amortization schedule and a final payment of $31.1 million at loan maturity. (ii) The Company entered into a sale-leaseback transaction with its Olney property and is accounting for that transaction as a secured financing. The arrangement requires monthly payments of $60,400 which increase by 1.5% on May 1, 2015, and every May 1 thereafter. The arrangement provides for a final payment of $14.7 million and has an implicit interest rate of 8.0% . Negative amortization in 2017 totaled $167,000 . (jj) 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. (kk) The loan is collateralized by Metro Pike Center and requires monthly principal and interest payments of approximately $48,000 and a final payment of $14.2 million at loan maturity. Principal of $347,000 was amortized during 2017 . The carrying value of the properties collateralizing the mortgage notes payable totaled $1.0 billion and $957.2 million , as of December 31, 2017 and 2016 , respectively. The Company’s credit facility requires the Company and its subsidiaries to maintain certain financial covenants, which are summarized below. The Company was in compliance as of December 31, 2017 . • maintain tangible net worth, as defined in the loan agreement, of at least $542.1 million plus 80% of the Company’s net equity proceeds received after March 2014; • limit the amount of debt as a percentage of gross asset value, as defined in the loan agreement, to less than 60% (leverage ratio); • limit the amount of debt so that interest coverage will exceed 2.0 x on a trailing four-quarter basis (interest expense coverage); and • limit the amount of debt so that interest, scheduled principal amortization and preferred dividend coverage exceeds 1.3 x on a trailing four-quarter basis (fixed charge coverage). Mortgage notes payable at each of December 31, 2017 and 2016 , totaling $51.0 million , are guaranteed by members of the Saul Organization. As of December 31, 2017 , the scheduled maturities of all debt including scheduled principal amortization for years ended December 31 are as follows: (in thousands) Balloon Payments Scheduled Principal Amortization Total 2018 $ 75,105 (a) $ 30,160 $ 105,265 2019 60,793 29,272 90,065 2020 61,163 26,743 87,906 2021 11,012 26,456 37,468 2022 36,503 26,958 63,461 Thereafter 436,325 145,038 581,363 Principal amount $ 680,901 $ 284,627 965,528 Unamortized deferred debt costs 6,906 Net $ 958,622 (a) Includes $61.0 million outstanding under the line of credit. The components of interest expense are set forth below. (in thousands) Year ended December 31, 2017 2016 2015 Interest incurred $ 49,322 $ 46,867 $ 45,898 Amortization of deferred debt costs 1,392 1,343 1,433 Capitalized interest (3,489 ) (2,527 ) (2,166 ) Total $ 47,225 $ 45,683 $ 45,165 Deferred debt costs capitalized during the years ending December 31, 2017 , 2016 and 2015 totaled $2.6 million , $0.1 million and $0.3 million , respectively.

Lease Agreements

Lease Agreements	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Lease Agreements	LEASE AGREEMENTS Lease income includes primarily base rent arising from noncancelable leases. Base rent (including straight-line rent) for the years ended December 31, 2017 , 2016 , and 2015 , amounted to $181.1 million , $172.4 million , and $168.3 million , respectively. Future contractual payments under noncancelable leases for years ended December 31 (which exclude the effect of straight-line rents), are as follows: (in thousands) 2018 $ 160,025 2019 141,097 2020 120,369 2021 100,766 2022 77,312 Thereafter 245,103 $ 844,672 The majority of the leases provide for rental increases and expense recoveries based on fixed annual increases or increases in the Consumer Price Index and increases in operating expenses. The expense recoveries generally are payable in equal installments throughout the year based on estimates, with adjustments made in the succeeding year. Expense recoveries for the years ended December 31, 2017 , 2016 , and 2015 , amounted to $35.3 million , $34.3 million , and $32.9 million , respectively. In addition, certain retail leases provide for percentage rent based on sales in excess of the minimum specified in the tenant’s lease. Percentage rent amounted to $1.5 million , $1.4 million , and $1.6 million , for the years ended December 31, 2017 , 2016 , and 2015 , respectively.

Long-Term Lease Obligations

Long-Term Lease Obligations	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Long-Term Lease Obligations	LONG-TERM LEASE OBLIGATIONS During 2016 and 2017, the Company purchased the land underlying Olney, Beacon Center and Southdale - See Note 3. As a result, at December 31, 2017, no properties are subject to noncancelable long-term leases which apply to underlying land. Reflected in the accompanying consolidated financial statements is minimum ground rent expense of $10,500 , $159,000 , $176,000 , for the years ended December 31, 2017 , 2016 , and 2015 , respectively. Flagship Center consists of two developed out parcels that are part of a larger adjacent community shopping center formerly owned by the Saul Organization and sold to an affiliate of a tenant in 1991. The Company has a 90 -year ground leasehold interest which commenced in September 1991 with a minimum rent of one dollar per year. Countryside shopping center was acquired in February 2004. Because of certain land use considerations, approximately 3.4% of the underlying land is held under a 99 -year ground lease. The lease requires the Company to pay minimum rent of one dollar per year as well as its pro-rata share of the real estate taxes. The Company’s corporate headquarters space is leased by a member of the Saul Organization. The lease commenced in March 2002, and expires in February 2022. The Company and the Saul Organization entered into a Shared Services Agreement whereby each party pays an allocation of total rental payments based on a percentage proportionate to the number of employees employed by each party. The Company’s rent expense for the years ended December 31, 2017 , 2016 , and 2015 was $774,700 , $843,300 , and $904,900 , respectively. Expenses arising from the lease are included in general and administrative expense (see Note 9 – Related Party Transactions).

Equity and Noncontrolling Inter

Equity and Noncontrolling Interest	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Equity and Noncontrolling Interest	EQUITY AND NONCONTROLLING INTEREST The Consolidated Statements of Operations for the years ended December 31, 2017 , 2016 , and 2015 reflect noncontrolling interest of $12.4 million , $11.4 million , and $10.5 million , respectively, representing the Saul Organization’s share of the net income for the year. The Company has outstanding, 7.2 million depositary shares, each representing 1/100 th of a share of 6.875% Series C Cumulative Redeemable Preferred Stock ("Series C Stock"). The depositary shares may be redeemed on or after February 12, 2018 at the Company’s option, in whole or in part, at the $25.00 liquidation preference plus accrued but unpaid dividends. The depositary shares pay an annual dividend of $1.71875 per share, equivalent to 6.875% of the $25.00 liquidation preference. The Series C Stock has no stated maturity, is not subject to any sinking fund or mandatory redemption and is not convertible into any other securities of the Company except in connection with certain changes of control or delisting events. Investors in the depositary shares generally have no voting rights, but will have limited voting rights if the Company fails to pay dividends for six or more quarters (whether or not declared or consecutive) and in certain other events.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS The Chairman and Chief Executive Officer, the President and Chief Operating Officer, the Executive Vice President-Chief Legal and Administrative Officer and the Senior Vice President-Chief Accounting Officer of the Company are also officers of various members of the Saul Organization and their management time is shared with the Saul Organization. Their annual compensation is fixed by the Compensation Committee of the Board of Directors, with the exception of the Senior Vice President-Chief Accounting Officer whose share of annual compensation allocated to the Company is determined by the shared services agreement (described below). The Company participates in a multiemployer 401K plan with entities in the Saul Organization which covers those full-time employees who meet the requirements as specified in the plan. Company contributions, which are included in general and administrative expense or property operating expenses in the consolidated statements of operations, at the discretionary amount of up to six percent of the employee’s cash compensation, subject to certain limits, were $349,500 , $329,000 , and $400,000 , for 2017 , 2016 , and 2015 , respectively. All amounts deferred by employees and contributed by the Company are fully vested. The Company also participates in a multiemployer nonqualified deferred compensation plan with entities in the Saul Organization which covers those full-time employees who meet the requirements as specified in the plan. According to the plan, which can be modified or discontinued at any time, participating employees defer 2% of their compensation in excess of a specified amount. For the years ended December 31, 2017 , 2016 , and 2015 , the Company contributed three times the amount deferred by employees. The Company’s expense, included in general and administrative expense, totaled $228,500 , $250,800 , and $224,900 , for the years ended December 31, 2017 , 2016 , and 2015 , respectively. All amounts deferred by employees and the Company are fully vested. The cumulative unfunded liability under this plan was $2.4 million and $2.1 million , at December 31, 2017 and 2016 , respectively, and is included in accounts payable, accrued expenses and other liabilities in the consolidated balance sheets. The Company has entered into a shared services agreement (the “Agreement”) with the Saul Organization that provides for the sharing of certain personnel and ancillary functions such as computer hardware, software, and support services and certain direct and indirect administrative personnel. The method for determining the cost of the shared services is provided for in the Agreement and is based upon head count, estimates of usage or estimates of time incurred, as applicable. Senior management has determined that the final allocations of shared costs are reasonable. The terms of the Agreement and the payments made thereunder are reviewed annually by the Audit Committee of the Board of Directors, which consists entirely of independent directors. Net billings by the Saul Organization for the Company’s share of these ancillary costs and expenses for the years ended December 31, 2017 , 2016 , and 2015 , which included rental expense for the Company’s headquarters lease (see Note 7. Long Term Lease Obligations), totaled $8.1 million , $7.2 million , and $8.2 million , respectively. The amounts are expensed when incurred and are primarily reported as general and administrative expenses or capitalized to specific development projects in these consolidated financial statements. As of December 31, 2017 and 2016 , accounts payable, accrued expenses and other liabilities included $993,200 and $829,000 , respectively, representing billings due to the Saul Organization for the Company’s share of these ancillary costs and expenses. The Company has entered into a shared third-party predevelopment cost agreement with the Trust (the “Predevelopment Agreement”). The Predevelopment Agreement, which expired on December 31, 2015 and was extended to December 31, 2016, relates to the sharing of third-party predevelopment costs incurred in connection with the planning of the future redevelopment of certain adjacent real estate assets in the Twinbrook area of Rockville, Maryland. On December 8, 2016, the Company entered into a replacement agreement with the Saul Trust which extended the expiration date to December 31, 2017 and provides for automatic twelve month renewals unless either party provides notice of termination. The costs will be shared on a pro rata basis based on the acreage owned by each entity and neither party is obligated to advance funds to the other. The B. F. Saul Insurance Agency of Maryland, Inc., a subsidiary of the B. F. Saul Company and a member of the Saul Organization, is a general insurance agency that receives commissions and counter-signature fees in connection with the Company’s insurance program. Such commissions and fees amounted to approximately $288,400 , $360,500 , and $443,500 , for the years ended December 31, 2017 , 2016 , and 2015 , respectively. In August 2016, the Company entered into an agreement to acquire from the Trust, for an initial purchase price of $8.8 million , approximately 14.3 acres of land located at the intersection of Ashburn Village Boulevard and Russell Branch Parkway in Loudoun County, Virginia. In order to allow the Company time to pre-lease and complete project plans and specifications, the parties have agreed to a closing date in the second quarter of 2018, at which time the Company will exchange limited partnership units for the land. The number of limited partnership units to be exchanged will be based on the initial purchase price and the average share value (as defined in the agreement) of the Company’s common stock at the time of the exchange. The Company intends to construct a shopping center and, upon stabilization, may be obligated to issue additional limited partnership units to the Trust.

Stock Option Plan

Stock Option Plan	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Plan	STOCK OPTION PLAN The Company established a stock option plan in 1993 (the “1993 Plan”) for the purpose of attracting and retaining executive officers and other key personnel. The 1993 Plan provides for grants of options to purchase up to 400,000 shares of common stock. The 1993 Plan authorizes the Compensation Committee of the Board of Directors to grant options at an exercise price which may not be less than the market value of the common stock on the date the option is granted. At the annual meeting of the Company’s stockholders in 2004, the stockholders approved the adoption of the 2004 stock plan for the purpose of attracting and retaining executive officers, directors and other key personnel. The 2004 stock plan was subsequently amended by the Company’s stockholders at the 2008 Annual Meeting and further amended at the 2013 Annual Meeting (the “Amended 2004 Plan”). The Amended 2004 Plan, which terminates in 2023, provides for grants of options to purchase up to 2,000,000 shares of common stock as well as grants of up to 200,000 shares of common stock to directors. The Amended 2004 Plan authorizes the Compensation Committee of the Board of Directors to grant options at an exercise price which may not be less than the market value of the common stock on the date the option is granted. Effective April 25, 2008 , the Compensation Committee granted options to purchase 30,000 shares (all nonqualified stock options) to 12 Company directors (the “2008 Options”), which were immediately exercisable and expire on April 24, 2018 . The exercise price of $50.15 per share was the closing market price of the Company’s common stock on the date of the award. Using the Black-Scholes model, the Company determined the total fair value of the 2008 Options to be $254,700 . Because the directors’ options vested immediately, the entire $254,700 was expensed as of the date of grant. No options were granted to the Company’s officers in 2008. Effective April 24, 2009 , the Compensation Committee granted options to purchase 32,500 shares (all nonqualified stock options) to 13 Company directors (the “2009 Options”), which were immediately exercisable and expire on April 23, 2019 . The exercise price of $32.68 per share was the closing market price of the Company’s common stock on the date of the award. Using the Black-Scholes model, the Company determined the total fair value of the 2009 Options to be $222,950 . Because the directors’ options vested immediately, the entire $222,950 was expensed as of the date of grant. No options were granted to the Company’s officers in 2009. Effective May 7, 2010 , the Compensation Committee granted options to purchase 32,500 shares (all nonqualified stock options) to 13 Company directors (the “2010 Options”), which were immediately exercisable and expire on May 6, 2020 . The exercise price of $38.76 per share was the closing market price of the Company’s common stock on the date of the award. Using the Black-Scholes model, the Company determined the total fair value of the 2010 Options to be $287,950 . Because the directors’ options vested immediately, the entire $287,950 was expensed as of the date of grant. No options were granted to the Company’s officers in 2010. Effective May 13, 2011 , the Compensation Committee granted options to purchase 195,000 shares ( 65,300 incentive stock options and 129,700 nonqualified stock options) to 15 Company officers and 13 Company Directors (the “2011 options”), which expire on May 12, 2021 . The officers’ 2011 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2011 options were immediately exercisable. The exercise price of $41.82 per share was the closing market price of the Company’s common stock on the date of award. Using the Black-Scholes model, the Company determined the total fair value of the 2011 Options to be $1.6 million , of which $1.3 million and $297,375 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $297,375 was expensed as of the date of grant. The expense for the officers’ options is being recognized as compensation expense monthly during the four years the options vest. Effective May 4, 2012 , the Compensation Committee granted options to purchase 277,500 shares ( 26,157 incentive stock options and 251,343 nonqualified stock options) to 15 Company officers and 14 Company Directors (the “2012 options”), which expire on May 3, 2022 . The officers’ 2012 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2012 Options were immediately exercisable. The exercise price of $39.29 per share was the closing market price of the Company’s common stock on the date of award. Using the Black-Scholes model, the Company determined the total fair value of the 2012 Options to be $1.7 million , of which $1.4 million and $257,250 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $257,250 was expensed as of the date of grant. The expense for the officers’ options is being recognized as compensation expense monthly during the four years the options vest. Effective May 10, 2013 , the Compensation Committee granted options to purchase 237,500 shares ( 35,592 incentive stock options and 201,908 nonqualified stock options) to 15 Company officers and 14 Company Directors (the "2013 options"), which expire on May 9, 2023 . The officers' 2013 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors' 2013 options were immediately exercisable. The exercise price of $44.42 per share was the closing market price of the Company's common stock on the date of award. Using the Black-Scholes model, the Company determined the total fair value of the 2013 Options to be $1.5 million , of which $1.2 million and $278,250 were assigned to the officer options and director options, respectively. Because the directors' options vested immediately, the entire $278,250 was expensed as of the date of grant. The expense for the officers' options is being recognized as compensation expense monthly during the four years the option was vested. Effective May 9, 2014 , the Compensation Committee granted options to purchase 200,000 shares ( 29,300 incentive stock options and 170,700 nonqualified stock options) to 18 Company officers and 12 Company Directors (the “2014 options”), which expire on May 8, 2024 . The officers’ 2014 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2014 Options were immediately exercisable. The exercise price of $47.03 per share was the closing market price of the Company’s common stock on the date of award. Using the Black-Scholes model, the Company determined the total fair value of the 2014 Options to be $1.3 million , of which $1.2 million and $109,500 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $109,500 was expensed as of the date of grant. The expense for the officers’ options is being recognized as compensation expense monthly during the four years the options vest. Effective May 8, 2015 , the Compensation Committee granted options to purchase 225,000 shares ( 33,690 incentive stock options and 191,310 nonqualified stock options) to 19 Company officers and 14 Company Directors (the “2015 options”), which expire on May 7, 2025 . The officers’ 2015 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2015 Options were immediately exercisable. The exercise price of $51.07 per share was the closing market price of the Company’s common stock on the date of award. Using the Black-Scholes model, the Company determined the total fair value of the 2015 Options to be $1.57 million , of which $1.44 million and $125,300 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $125,300 was expensed as of the date of grant. The expense for the officers’ options is being recognized as compensation expense monthly during the four years the options vest. Effective May 6, 2016 , the Compensation Committee granted options to purchase 226,500 shares ( 24,248 incentive stock options and 202,252 nonqualified stock options) to 19 Company officers and 13 Company Directors (the “2016 options”), which expire on May 5, 2026 . The officers’ 2016 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2016 Options were immediately exercisable. The exercise price of $57.74 per share was the closing market price of the Company’s common stock on the date of award. Using the Black-Scholes model, the Company determined the total fair value of the 2016 Options to be $1.2 million , of which $1.0 million and $151,125 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $151,125 was expensed as of the date of grant. The expense for the officers’ options is being recognized as compensation expense monthly during the four years the options vest. Effective May 5, 2017 , the Compensation Committee granted options to purchase 232,500 shares ( 21,492 incentive stock options and 211,008 nonqualified stock options) to 20 Company officers and 11 Company Directors (the “2017 options”), which expire on May 4, 2027 . The officers’ 2017 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2017 Options were immediately exercisable. The exercise price of $59.41 per share was the closing market price of the Company’s common stock on the date of award. Using the Black-Scholes model, the Company determined the total fair value of the 2017 Options to be $1.4 million , of which $1.2 million and $165,550 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $165,550 was expensed as of the date of grant. The expense for the officers’ options is being recognized as compensation expense monthly during the four years the options vest. The following table summarizes the amount and activity of each grant, the total value and variables used in the computation and the amount expensed and included in general and administrative expense in the Consolidated Statements of Operations for the years ended December 31, 2017 , 2016 and 2015 . SAUL CENTERS, INC. (Dollars in thousands, except per share data) Stock options issued Directors Grant date 4/25/2008 4/24/2009 5/7/2010 5/13/2011 5/4/2012 5/10/2013 5/9/2014 5/8/2015 5/6/2016 5/5/2017 Subtotals Total grant 30,000 32,500 32,500 32,500 35,000 35,000 30,000 35,000 32,500 27,500 322,500 Vested 30,000 32,500 32,500 32,500 35,000 35,000 30,000 35,000 32,500 27,500 322,500 Exercised 20,000 27,500 25,000 22,500 22,500 22,500 17,500 12,500 7,500 — 177,500 Forfeited 7,500 — 2,500 2,500 — — — — — — 12,500 Exercisable at December 31, 2017 2,500 5,000 5,000 7,500 12,500 12,500 12,500 22,500 25,000 27,500 132,500 Remaining unexercised 2,500 5,000 5,000 7,500 12,500 12,500 12,500 22,500 25,000 27,500 132,500 Exercise price $ 50.15 $ 32.68 $ 38.76 $ 41.82 $ 39.29 $ 44.42 $ 47.03 $ 51.07 $ 57.74 $ 59.41 Volatility 0.237 0.344 0.369 0.358 0.348 0.333 0.173 0.166 0.166 0.173 Expected life (years) 7.0 6.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Assumed yield 4.09 % 4.54 % 4.23 % 4.16 % 4.61 % 4.53 % 4.48 % 4.54 % 3.75 % 3.45 % Risk-free rate 3.49 % 2.19 % 2.17 % 1.86 % 0.78 % 0.82 % 1.63 % 1.50 % 1.23 % 1.89 % Total value at grant date $ 255 $ 223 $ 288 $ 297 $ 257 $ 278 $ 110 $ 125 $ 151 $ 166 $ 2,150 Expensed in previous years 255 223 288 297 257 278 110 — — — 1,708 Expensed in 2015 — — — — — — — 125 — — 125 Expensed in 2016 — — — — — — — — 151 — 151 Expensed in 2017 — — — — — — — — — 166 166 Future expense — — — — — — — — — — — Officers Grant date 5/13/2011 5/4/2012 5/10/2013 5/9/2014 5/8/2015 5/6/2016 5/5/2017 Subtotals Grand Totals Total grant 162,500 242,500 202,500 170,000 190,000 194,000 205,000 1,366,500 1,689,000 Vested 118,750 107,500 171,875 126,875 94,375 48,500 — 667,875 990,375 Exercised 96,100 91,830 116,500 41,250 20,000 3,750 — 369,430 546,930 Forfeited 43,750 135,000 30,625 1,875 3,125 1,875 — 216,250 228,750 Exercisable at December 31, 2017 22,650 15,670 55,375 85,625 74,375 44,750 — 298,445 430,945 Remaining unexercised 22,650 15,670 55,375 126,875 166,875 188,375 205,000 780,820 913,320 Exercise price $ 41.82 $ 39.29 $ 44.42 $ 47.03 $ 51.07 $ 57.74 $ 59.41 Volatility 0.330 0.315 0.304 0.306 0.298 0.185 0.170 Expected life (years) 8.0 8.0 8.0 7.0 7.0 7.0 7.0 Assumed yield 4.81 % 5.28 % 5.12 % 4.89 % 4.94 % 3.80 % 3.50 % Risk-free rate 2.75 % 1.49 % 1.49 % 2.17 % 1.89 % 1.55 % 2.17 % Gross value at grant date $ 1,366 $ 1,518 $ 1,401 $ 1,350 $ 1,585 $ 1,137 $ 1,324 $ 9,681 $ 11,831 Estimated forfeitures 368 845 212 169 142 86 92 1,914 1,914 Expensed in previous years 909 419 493 197 — — — 2,018 3,726 Expensed in 2015 89 157 269 296 240 — — 1,051 1,176 Expensed in 2016 — 97 269 295 361 175 — 1,197 1,348 Expensed in 2017 — — 158 295 361 263 205 1,282 1,448 Future expense — — — 98 481 613 1,027 2,219 2,219 Weighted average term of remaining future expense 2.5 years The table below summarizes the option activity for the years 2017 , 2016 , and 2015 : 2017 2016 2015 Shares Weighted Shares Weighted Shares Weighted Outstanding at January 1 833,630 $ 49.92 860,274 $ 46.58 748,208 $ 44.79 Granted 232,500 59.41 226,500 57.74 225,000 51.07 Exercised (149,060 ) 46.97 (246,894 ) 45.59 (112,934 ) 43.67 Expired/Forfeited (3,750 ) 53.73 (6,250 ) 45.31 — — Outstanding December 31 913,320 52.80 833,630 49.92 860,274 46.58 Exercisable at December 31 430,945 48.94 375,255 46.68 435,899 45.33 The intrinsic value of options exercised in 2017 , 2016 , and 2015 , was $2.2 million , $3.4 million and $1.5 million , respectively. The intrinsic value of options outstanding and exercisable at year end 2017 was $8.2 million and $5.5 million , respectively. The intrinsic value measures the difference between the options’ exercise price and the closing share price quoted by the New York Stock Exchange as of the date of measurement. The date of exercise was the measurement date for shares exercised during the period. At December 29, 2017, the final trading day of calendar 2017 , the closing price of $61.75 per share was used for the calculation of aggregate intrinsic value of options outstanding and exercisable at that date. The weighted average remaining contractual life of the Company’s exercisable and outstanding options at December 31, 2017 are 6.5 and 7.5 years, respectively.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	FAIR VALUE OF FINANCIAL INSTRUMENTS The carrying values of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses are reasonable estimates of their fair value. The aggregate fair value of the notes payable with fixed-rate payment terms was determined using Level 3 data in a discounted cash flow approach, which is based upon management’s estimate of borrowing rates and loan terms currently available to the Company for fixed rate financing, and assuming long term interest rates of approximately 3.90% and 4.25% , would be approximately $951.7 million and $851.3 million as of December 31, 2017 and 2016 , respectively, compared to the principal balance of $890.4 million and $844.3 million at December 31, 2017 and 2016 , respectively. A change in any of the significant inputs may lead to a change in the Company’s fair value measurement of its debt. Effective June 30, 2011, the Company determined that one of its interest-rate swap arrangements was a highly effective hedge of the cash flows under one of its variable-rate mortgage loans and designated the swap as a cash flow hedge of that mortgage. The swap is carried at fair value with changes in fair value recognized either in income or comprehensive income depending on the effectiveness of the swap. The following chart summarizes the changes in fair value of the Company’s swap for the indicated periods. (Dollars in thousands) Year ended December 31, 2017 2016 2015 Increase (decrease) in fair value: Recognized in earnings $ 70 $ (6 ) $ (10 ) Recognized in other comprehensive income 812 678 124 Total $ 882 $ 672 $ 114 The Company carries its interest rate swaps at fair value. The Company has determined the majority of the inputs used to value its derivative fall within Level 2 of the fair value hierarchy with the exception of the impact of counter-party risk, which was determined using Level 3 inputs and are not significant. Derivative instruments are classified within Level 2 of the fair value hierarchy because their values are determined using third-party pricing models which contain inputs that are derived from observable market data. Where possible, the values produced by the pricing models are verified by the market prices. Valuation models require a variety of inputs, including contractual terms, market prices, yield curves, credit spreads, measure of volatility, and correlations of such inputs. The swap agreement terminates on July 1, 2020 . As of December 31, 2017 , the fair value of the interest-rate swap was approximately $1.1 million and is included in “Accounts payable, accrued expenses and other liabilities” in the consolidated balance sheets. The decrease in value from inception of the swap designated as a cash flow hedge is reflected in “Other Comprehensive Income” in the Consolidated Statements of Comprehensive Income.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Neither the Company nor the Current Portfolio Properties are subject to any material litigation, nor, to management’s knowledge, is any material litigation currently threatened against the Company, other than routine litigation and administrative proceedings arising in the ordinary course of business. Management believes that these items, individually or in the aggregate, will not have a material adverse impact on the Company or the Current Portfolio Properties.

Distributions

Distributions	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Distributions	DISTRIBUTIONS In December 1995, the Company established a Dividend Reinvestment and Stock Purchase Plan (the “Plan”), to allow its stockholders and holders of limited partnership interests an opportunity to buy additional shares of common stock by reinvesting all or a portion of their dividends or distributions. The Plan provides for investing in newly issued shares of common stock at a 3% discount from market price without payment of any brokerage commissions, service charges or other expenses. All expenses of the Plan are paid by the Company. The Operating Partnership also maintains a similar dividend reinvestment plan that mirrors the Plan, which allows holders of limited partnership interests the opportunity to buy either additional limited partnership units or common stock shares of the Company. The Company paid common stock distributions of $2.04 per share in 2017 , $1.84 per share in 2016 , and $1.69 per share during 2015 and Series C preferred stock dividends of $1.72 per depositary share during each of 2017 , 2016 , and 2015 . Of the common stock dividends paid, $1.70 per share, $1.75 per share, and $1.69 per share, represented ordinary dividend income in 2017 , 2016 , and 2015 , respectively, and $0.34 per share and $0.09 per share represented return of capital to the shareholders in 2017 and 2016, respectively. All of the preferred stock dividends paid were considered ordinary dividend income. The following summarizes distributions paid during the years ended December 31, 2017 , 2016 , and 2015 , and includes activity in the Plan as well as limited partnership units issued from the reinvestment of unit distributions: Total Distributions to Dividend Reinvestments (Dollars in thousands, except per share amounts) Preferred Common Limited Common Discounted Limited Partnership Units Issued Average Unit Price Distributions during 2017 October 31 $ 3,094 $ 11,221 $ 3,838 82,991 $ 59.33 15,596 $ 60.08 July 31 3,094 11,160 3,830 85,731 57.40 16,021 58.13 April 30 3,094 11,119 3,810 51,003 59.64 40,623 59.96 January 31 3,093 11,076 3,790 46,286 61.85 39,111 62.15 Total 2017 $ 12,375 $ 44,576 $ 15,268 266,011 111,351 Distributions during 2016 October 31 $ 3,094 $ 10,168 $ 3,478 44,176 $ 57.18 30,891 $ 57.18 July 31 3,094 10,133 3,465 39,487 65.64 26,897 65.64 April 30 3,094 10,029 3,449 48,854 51.59 34,201 51.59 January 31 3,093 9,142 3,141 54,280 49.24 32,769 49.24 Total 2016 $ 12,375 $ 39,472 $ 13,533 186,797 124,758 Distributions during 2015 October 31 $ 3,094 $ 9,106 $ 3,129 47,313 $ 55.73 28,936 $ 55.73 July 31 3,094 9,081 3,115 56,003 50.30 32,041 50.30 April 30 3,094 9,055 3,104 54,921 50.21 25,264 50.21 January 31 3,093 8,403 2,880 42,975 56.74 20,796 56.74 Total 2015 $ 12,375 $ 35,645 $ 12,228 201,212 107,037 In December 2017 , the Board of Directors of the Company authorized a distribution of $0.52 per common share payable in January 2018, to holders of record on January 17, 2018 . As a result, $11.5 million was paid to common shareholders on January 31, 2018 . Also, $3.9 million was paid to limited partnership unitholders on January 31, 2018 ( $0.52 per Operating Partnership unit). The Board of Directors authorized preferred stock dividends of $0.4297 per Series C depositary share to holders of record on January 2, 2018 . As a result, $3.1 million was paid to preferred shareholders on January 15, 2018 . These amounts are reflected as a reduction of stockholders’ equity in the case of common stock and preferred stock dividends and noncontrolling interests deductions in the case of limited partner distributions and are included in dividends and distributions payable in the accompanying consolidated financial statements.

Interim Results (Unaudited)

Interim Results (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interim Results (Unaudited)	INTERIM RESULTS (Unaudited) The following summary presents the results of operations of the Company for the quarterly periods of calendar years 2017 and 2016 . (In thousands, except per share amounts) 2017 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Revenue $ 58,466 $ 55,907 $ 56,237 $ 56,675 Operating income before loss on early extinguishment of debt, gain on casualty settlement, and noncontrolling interests 17,374 14,422 14,386 14,416 Gain on sales of properties — — — — Net income attributable to Saul Centers, Inc. 13,704 11,510 11,483 11,560 Net income available to common stockholders 10,610 8,416 8,390 8,466 Net income available to common stockholders per diluted share 0.49 0.38 0.38 0.38 (In thousands, except per share amounts) 2016 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Revenue $ 56,926 $ 52,710 $ 53,233 $ 54,201 Operating income before loss on early extinguishment of debt, gain on casualty settlement, and noncontrolling interests 16,381 13,250 12,722 13,360 Gain on sales of properties — — — 1,013 Net income attributable to Saul Centers, Inc. 12,948 10,627 10,239 11,465 Net income available to common stockholders 9,854 7,533 7,146 8,371 Net income available to common stockholders per diluted share 0.46 0.35 0.33 0.38

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segments	BUSINESS SEGMENTS The Company has two reportable business segments: Shopping Centers and Mixed-Use Properties. The accounting policies of the segments are the same as those described in the summary of significant accounting policies (see Note 2). The Company evaluates performance based upon income and cash flows from real estate for the combined properties in each segment. All of our properties within each segment generate similar types of revenues and expenses related to tenant rent, reimbursements and operating expenses. Although services are provided to a range of tenants, the types of services provided to them are similar within each segment. The properties in each portfolio have similar economic characteristics and the nature of the products and services provided to our tenants and the method to distribute such services are consistent throughout the portfolio. Certain reclassifications have been made to prior year information to conform to the 2017 presentation. SAUL CENTERS, INC. Notes to Consolidated Financial Statements (In thousands) Shopping Mixed-Use Corporate Consolidated As of or for the year ended December 31, 2017 Centers Properties and Other Totals Real estate rental operations: Revenue $ 165,853 $ 61,352 $ 80 $ 227,285 Expenses (34,675 ) (20,917 ) — (55,592 ) Income from real estate 131,178 40,435 80 171,693 Interest expense and amortization of deferred debt costs — — (47,225 ) (47,225 ) General and administrative — — (18,176 ) (18,176 ) Subtotal 131,178 40,435 (65,321 ) 106,292 Depreciation and amortization of deferred leasing costs (29,977 ) (15,717 ) — (45,694 ) Change in fair value of derivatives — — 70 70 Net income (loss) $ 101,201 $ 24,718 $ (65,251 ) $ 60,668 Capital investment $ 90,896 $ 29,098 $ — $ 119,994 Total assets $ 974,061 $ 438,283 $ 10,108 $ 1,422,452 As of or for the year ended December 31, 2016 Real estate rental operations: Revenue $ 160,179 $ 56,840 $ 51 $ 217,070 Expenses (34,931 ) (18,770 ) — (53,701 ) Income from real estate 125,248 38,070 51 163,369 Interest expense and amortization of deferred debt costs — — (45,683 ) (45,683 ) General and administrative — — (17,496 ) (17,496 ) Subtotal 125,248 38,070 (63,128 ) 100,190 Depreciation and amortization of deferred leasing costs (29,964 ) (14,453 ) — (44,417 ) Acquisition related costs (60 ) — — (60 ) Change in fair value of derivatives — — (6 ) (6 ) Gain on sale of property — 1,013 — 1,013 Net income (loss) $ 95,224 $ 24,630 $ (63,134 ) $ 56,720 Capital investment $ 64,044 $ 27,001 $ — $ 91,045 Total assets $ 976,545 $ 358,419 $ 8,061 $ 1,343,025 SAUL CENTERS, INC. Notes to Consolidated Financial Statements (continued) (In thousands) Shopping Mixed-Use Corporate Consolidated As of or for the year ended December 31, 2015 Centers Properties and Other Totals Real estate rental operations: Revenue $ 156,110 $ 52,916 $ 51 $ 209,077 Expenses (33,877 ) (17,266 ) — (51,143 ) Income from real estate 122,233 35,650 51 157,934 Interest expense and amortization of deferred debt costs — — (45,165 ) (45,165 ) General and administrative — — (16,353 ) (16,353 ) Subtotal 122,233 35,650 (61,467 ) 96,416 Depreciation and amortization of deferred leasing costs (30,171 ) (13,099 ) — (43,270 ) Acquisition related costs (84 ) — — (84 ) Predevelopment expenses (57 ) (75 ) — (132 ) Change in fair value of derivatives — — (10 ) (10 ) Gain on sale of property 11 — — 11 Net income (loss) $ 91,932 $ 22,476 $ (61,477 ) $ 52,931 Capital investment $ 17,159 $ 52,460 $ — $ 69,619 Total assets $ 931,256 $ 354,254 $ 9,898 $ 1,295,408

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 12, 2018, the Company entered into an agreement to purchase for $35.5 million , plus approximately $0.7 million of acquisition costs, an office building and the underlying ground located at 7316 Wisconsin Avenue in Bethesda, Montgomery County, Maryland and has an earnest money deposit of $3.5 million at risk. The purchase price will be funded through the Company's revolving credit facility. The Company anticipates closing the acquisition on or before January 12, 2019. On January 23, 2018, the Company sold, in an underwritten public offering, 3.0 million depositary shares, each representing 1/100 th of a share of 6.125% Series D Cumulative Redeemable Preferred Stock (the “Series D Stock”) and received net cash proceeds totaling approximately $72.6 million . The depositary shares may be redeemed at the Company’s option, in whole or in part, on or after January 23, 2023, at the $25.00 liquidation preference, plus accrued but unpaid dividends. The depositary shares pay an annual dividend of $1.53125 per share, equivalent to 6.125% of the $25.00 liquidation preference. The first dividend is scheduled to be paid on April 15, 2018, and cover the period from January 23, 2018, through March 31, 2018. The Series D Stock has no stated maturity, is not subject to any sinking fund or mandatory redemption and is not convertible into any other securities of the Company except in connection with certain changes of control or delisting events. Investors in the depositary shares generally have no voting rights, but will have limited voting rights if the Company fails to pay dividends for six or more quarters (whether or not declared or consecutive) and in certain other events. On January 26, 2018, the Company replaced its revolving credit facility, which was scheduled to expire on June 23, 2018, with a new credit facility. The new credit facility is comprised of a $75.0 million term facility that matures on January 26, 2023, and a $325.0 million revolving facility that matures on January 26, 2022, and can be extended for one year at the Company’s option, subject to satisfaction of certain conditions. The terms, conditions and covenants of the new credit facility are substantially the same as the existing credit facility. On February 22, 2018, the Company used the net proceeds from the sale of the Series D Stock, together with cash on hand, to redeem 3.0 million depositary shares, each representing 1/100 th of a share of Series C Stock at a price of $25.00 per depositary share, plus accrued dividends.

Real Estate and Accumulated Dep

Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2017
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real estate and accumulated depreciation	SAUL CENTERS, INC. Real Estate and Accumulated Depreciation December 31, 2017 (Dollars in Thousands) Costs Buildings Capitalized Basis at Close of Period and Initial Basis Subsequent to Acquisition Land Buildings and Improvements Total Accumulated Depreciation Book Value Related Debt Date of Construction Date Acquired Improvements Depreciable Lives in Years Shopping Centers Ashburn Village, Ashburn, VA $ 11,431 $ 20,278 $ 6,764 $ 24,945 $ 31,709 $ 12,993 $ 18,716 $ 28,025 1994 & 2000-6 3/94 40 Ashland Square Phase I, Dumfries, VA 1,178 7,503 1,178 7,503 8,681 1,764 6,917 — 2007, 2013 12/04 20 & 50 Beacon Center, Alexandria, VA 24,161 18,426 22,674 19,913 42,587 14,288 28,299 39,968 1960 & 1974 1/72, 11/16 40 & 50 BJ’s Wholesale Club, Alexandria, VA 22,623 — 22,623 — 22,623 — 22,623 10,877 3/08 — Boca Valley Plaza, Boca Raton, FL 16,720 1,768 5,735 12,753 18,488 4,424 14,064 9,948 2/04 40 Boulevard, Fairfax, VA 4,883 4,461 3,687 5,657 9,344 2,808 6,536 16,730 1969, 1999 & 2009 4/94 40 Briggs Chaney MarketPlace, Silver Spring, MD 27,037 4,143 9,789 21,391 31,180 7,908 23,272 13,543 4/04 40 Broadlands Village, Ashburn, VA 5,316 27,954 5,300 27,970 33,270 10,933 22,337 16,082 2003, 2004 & 2006 3/02 40 & 50 Burtonsville Town Square, Burtonsville, MD 74,212 342 28,401 46,153 74,554 1,095 73,459 39,140 2010 1/17 20 & 45 Countryside Marketplace, Sterling, VA 28,912 3,752 7,666 24,998 32,664 8,838 23,826 13,529 2/04 40 Cranberry Square, Westminster, MD 31,578 640 6,700 25,518 32,218 4,105 28,113 17,086 9/11 40 Cruse MarketPlace, Cumming, GA 12,226 448 3,901 8,773 12,674 3,057 9,617 — 3/04 40 Flagship Center, Rockville, MD 160 9 169 — 169 — 169 — 1972 1/72 — French Market, Oklahoma City, OK 5,781 13,829 1,118 18,492 19,610 11,191 8,419 — 1972 & 1998 3/74 50 Germantown, Germantown, MD 2,034 567 2,034 567 2,601 297 2,304 — 1990 8/93 40 The Glen, Woodbridge, VA 12,918 8,098 5,300 15,716 21,016 9,026 11,990 7,696 1993 & 2005 6/94 40 Great Falls Center, Great Falls, VA 41,750 3,178 14,766 30,162 44,928 7,719 37,209 12,577 3/08 40 Hampshire Langley, Takoma, MD 3,159 3,499 1,856 4,802 6,658 3,702 2,956 15,859 1960 1/72 40 Hunt Club Corners, Apopka, FL 12,584 4,034 4,822 11,796 16,618 3,801 12,817 5,649 6/06, 12/12 40 Jamestown Place, Altamonte Springs, FL 14,055 1,603 4,455 11,203 15,658 3,477 12,181 7,325 11/05 40 Kentlands Square I, Gaithersburg, MD 14,379 507 5,006 9,880 14,886 3,713 11,173 6,423 2002 9/02 40 Kentlands Square II, Gaithersburg, MD 76,723 1,602 22,800 55,525 78,325 9,092 69,233 36,507 9/11, 9/13 40 Kentlands Place, Gaithersburg, MD 1,425 7,255 1,425 7,255 8,680 3,744 4,936 — 2005 1/04 50 Lansdowne Town Center, Leesburg, VA 6,545 37,312 6,546 37,311 43,857 13,727 30,130 32,673 2006 11/02 50 Leesburg Pike Plaza, Baileys Crossroads, VA 2,418 6,243 1,132 7,529 8,661 5,934 2,727 15,452 1965 2/66 40 Lumberton Plaza, Lumberton, NJ 4,400 11,220 950 14,670 15,620 12,751 2,869 — 1975 12/75 40 Metro Pike Center, Rockville, MD 33,123 4,095 26,064 11,154 37,218 1,375 35,843 14,135 12/10 40 Shops at Monocacy, Frederick, MD 9,541 13,926 9,260 14,207 23,467 5,565 17,902 12,029 2004 11/03 50 Northrock, Warrenton, VA 12,686 15,414 12,686 15,414 28,100 3,871 24,229 14,950 2009 01/08 50 Olde Forte Village, Ft. Washington, MD 15,933 6,643 5,409 17,167 22,576 7,158 15,418 9,783 2004 07/03 40 Olney, Olney, MD 4,963 1,961 3,079 3,845 6,924 3,318 3,606 11,613 1972 11/75 40 Orchard Park, Dunwoody, GA 19,377 1,014 7,751 12,640 20,391 3,432 16,959 9,999 7/07 40 Palm Springs Center, Altamonte Springs, FL 18,365 1,435 5,739 14,061 19,800 4,606 15,194 8,244 3/05 40 Ravenwood, Baltimore, MD 1,245 4,227 703 4,769 5,472 3,067 2,405 14,537 1959 & 2006 1/72 40 11503 Rockville Pike/5541 Nicholson Lane, Rockville, MD 26,561 24 22,113 4,472 26,585 806 25,779 — 10/10 40 1500/1580/1582/1584 Rockville Pike, Rockville, MD 51,149 1,553 43,863 8,839 52,702 5,656 47,046 — 12/12, 1/14, 4/14, 12/14 5, 10, 5, 4 Seabreeze Plaza, Palm Harbor, FL 24,526 1,960 8,665 17,821 26,486 5,611 20,875 16,055 11/05 40 Market Place at Sea Colony, Bethany Beach, DE 2,920 203 1,147 1,976 3,123 491 2,632 — 3/08 40 Seven Corners, Falls Church, VA 4,848 44,108 4,913 44,043 48,956 28,790 20,166 64,472 1956 & 1997 7/73 40 Severna Park Marketplace, Severna Park, MD 63,254 232 12,700 50,786 63,486 7,927 55,559 32,016 9/11 40 Shops at Fairfax, Fairfax, VA 2,708 9,924 992 11,640 12,632 7,989 4,643 11,154 1975 & 1999 6/75 50 Smallwood Village Center, Waldorf, MD 17,819 7,975 6,402 19,392 25,794 7,278 18,516 — 1/06 40 Southdale, Glen Burnie, MD 18,895 24,345 15,254 27,986 43,240 21,333 21,907 — 1962 & 1986 1/72 40 Southside Plaza, Richmond, VA 6,728 10,695 1,878 15,545 17,423 12,280 5,143 — 1958 1/72 40 South Dekalb Plaza, Atlanta, GA 2,474 4,359 703 6,130 6,833 4,792 2,041 — 1970 2/76 40 Thruway, Winston-Salem, NC 7,848 24,821 7,693 24,976 32,669 16,735 15,934 37,998 1955 & 1965 5/72 40 Village Center, Centreville, VA 16,502 2,495 7,851 11,146 18,997 6,688 12,309 13,438 1990 8/93 40 Westview Village, Frederick, MD 6,047 25,227 6,047 25,227 31,274 7,511 23,763 — 2009 11/07, 02/15 50 White Oak, Silver Spring, MD 6,277 5,366 4,649 6,994 11,643 6,043 5,600 23,873 1958 & 1967 1/72 40 Other Buildings / Improvements 423 423 423 109 314 — Total Shopping Centers 832,397 401,096 412,358 821,135 1,233,493 332,818 900,675 639,385 Mixed-Use Properties Avenel Business Park, Gaithersburg, MD 21,459 30,409 3,756 48,112 51,868 36,469 15,399 28,115 1981-2000 12/84 35 & 40 Clarendon Center, Arlington, VA (1) 12,753 185,904 16,287 182,370 198,657 37,242 161,415 105,817 2010 7/73, 1/96 & 4/02 50 Park Van Ness, Washington, DC 2,242 91,617 2,242 91,617 93,859 4,801 89,058 71,211 2016 7/73 & 2/11 50 601 Pennsylvania Ave., Washington, DC 5,479 67,995 5,667 67,807 73,474 52,194 21,280 — 1986 7/73 35 Washington Square, Alexandria, VA 2,034 56,735 544 58,225 58,769 24,642 34,127 60,000 2000 7/73 50 Total Mixed-Use Properties 43,967 432,660 28,496 448,131 476,627 155,348 321,279 265,143 Development Land Ashland Square Phase II, Manassas, VA 5,292 1,917 7,028 181 7,209 — 7,209 — 12/04 New Market, New Market, MD 2,088 286 2,374 — 2,374 — 2,374 — 9/05 North Glebe Road, Arlington, VA 52,067 31,430 — 83,497 83,497 — 83,497 — — 8/14-8/16 Total Development Land 59,447 33,633 9,402 83,678 93,080 — 93,080 — Total $ 935,811 $ 867,389 $ 450,256 $ 1,352,944 $ 1,803,200 $ 488,166 $ 1,315,034 $ 904,528 (1) Includes the North and South Blocks and Residential Depreciation and amortization related to the real estate investments reflected in the statements of operations is calculated over the estimated useful lives of the assets as follows: Base building Generally 35 - 50 years or a shorter period if management determines that the building has a shorter useful life. Building components Up to 20 years Tenant improvements The shorter of the term of the lease or the useful life of the improvements The aggregate remaining net basis of the real estate investments for federal income tax purposes was approximately $1.3 billion at December 31, 2017 . Depreciation and amortization are provided on the declining balance and straight-line methods over the estimated useful lives of the assets. The changes in total real estate investments and related accumulated depreciation for each of the years in the three year period ended December 31, 2017 are summarized as follows: (In thousands) 2017 2016 2015 Total real estate investments: Balance, beginning of year $ 1,700,813 $ 1,622,710 $ 1,560,159 Acquisitions 77,258 48,123 4,894 Improvements 42,640 35,826 70,067 Retirements (17,511 ) (5,846 ) (1,981 ) Transfers to assets held for sale — — (10,429 ) Balance, end of year $ 1,803,200 $ 1,700,813 $ 1,622,710 Total accumulated depreciation: Balance, beginning of year $ 458,279 $ 425,370 $ 396,617 Depreciation expense 40,197 38,755 37,698 Retirements (10,310 ) (5,846 ) (1,911 ) Transfers to assets held for sale — $ — (7,034 ) Balance, end of year $ 488,166 $ 458,279 $ 425,370

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations The Company, which conducts all of its activities through its subsidiaries, the Operating Partnership and Subsidiary Partnerships, engages in the ownership, operation, management, leasing, acquisition, renovation, expansion, development and financing of community and neighborhood shopping centers and mixed-used properties, primarily in the Washington, DC/Baltimore metropolitan area. Because the properties are located primarily in the Washington, DC/Baltimore metropolitan area, a disproportionate economic downturn in the local economy would have a greater negative impact on our overall financial performance than on the overall financial performance of a company with a portfolio that is more geographically diverse. A majority of the Shopping Centers are anchored by several major tenants.
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Saul Centers, its subsidiaries, and the Operating Partnership and Subsidiary Partnerships which are majority owned by Saul Centers. All significant intercompany balances and transactions have been eliminated in consolidation. The Operating Partnership is a variable interest entity ("VIE") of the Company because the limited partners do not have substantive kick-out or participating rights. The Company is the primary beneficiary of the Operating Partnership because it has the power to direct the activities of the Operating Partnership and the rights to absorb 74.4% of the net income of the Operating Partnership. Because the Operating Partnership was already consolidated into the financial statements of the Company, the identification of it as a VIE has no impact on the consolidated financial statements of the Company.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates.
Real Estate Investment Properties	Real Estate Investment Properties The Company purchases real estate investment properties from time to time and records assets acquired and liabilities assumed, including land, buildings, and intangibles related to in-place leases and customer relationships, based on their relative fair values. The fair value of buildings generally is determined as if the buildings were vacant upon acquisition and then subsequently leased at market rental rates and considers the present value of all cash flows expected to be generated by the property including an initial lease up period. From time to time the Company may purchase a property for future development purposes. The property may be improved with an existing structure that would be demolished as part of the development. In such cases, the fair value of the building may be determined based only on existing leases and not include estimated cash flows related to future leases. In certain circumstances, such as if the building is vacant and the Company intends to demolish the building in the near term, the entire purchase price will be allocated to land. The Company determines the fair value of above and below market intangibles associated with in-place leases by assessing the net effective rent and remaining term of the lease relative to market terms for similar leases at acquisition taking into consideration the remaining contractual lease period, renewal periods, and the likelihood of the tenant exercising its renewal options. The fair value of a below market lease component is recorded as deferred income and accreted as additional lease revenue over the remaining contractual lease period. If the fair value of the below market lease intangible includes fair value associated with a renewal option, such amounts are not accreted until the renewal option is exercised. If the renewal option is not exercised the value is recognized at that time. The fair value of above market lease intangibles is recorded as a deferred asset and is amortized as a reduction of lease revenue over the remaining contractual lease term. The Company determines the fair value of at-market in-place leases considering the cost of acquiring similar leases, the foregone rents associated with the lease-up period and carrying costs associated with the lease-up period. Intangible assets associated with at-market in-place leases are amortized as additional expense over the remaining contractual lease term. To the extent customer relationship intangibles are present in an acquisition, the fair values of the intangibles are amortized over the lives of the customer relationships. The Company has never recorded a customer relationship intangible asset. Acquisition-related transaction costs are either (a) expensed as incurred when related to business combinations or (b) capitalized to land and/or building when related to asset acquisitions. If there is an event or change in circumstance that indicates a potential impairment in the value of a real estate investment property, the Company prepares an analysis to determine whether the carrying value of the real estate investment property exceeds its estimated fair value. The Company considers both quantitative and qualitative factors including recurring operating losses, significant decreases in occupancy, and significant adverse changes in legal factors and business climate. If impairment indicators are present, the Company compares the projected cash flows of the property over its remaining useful life, on an undiscounted basis, to the carrying value of that property. The Company assesses its undiscounted projected cash flows based upon estimated capitalization rates, historic operating results and market conditions that may affect the property. If the carrying value is greater than the undiscounted projected cash flows, the Company would recognize an impairment loss equivalent to an amount required to adjust the carrying amount to its then estimated fair value. The fair value of any property is sensitive to the actual results of any of the aforementioned estimated factors, either individually or taken as a whole. Should the actual results differ from management’s projections, the valuation could be negatively or positively affected. The Company did not recognize an impairment loss on any of its real estate in 2017 , 2016 , or 2015 . Interest, real estate taxes, development related salary costs and other carrying costs are capitalized on projects under development and construction. Once construction is substantially completed and the assets are placed in service, their rental income, real estate tax expense, property operating expenses (consisting of payroll, repairs and maintenance, utilities, insurance and other property related expenses) and depreciation are included in current operations. Property operating expenses are charged to operations as incurred. Interest expense capitalized totaled $3.5 million , $2.5 million , and $ 2.2 million during 2017 , 2016 , and 2015 , respectively. Commercial development projects are considered substantially complete and available for occupancy upon completion of tenant improvements, but no later than one year from the cessation of major construction activity. Multi-family residential development projects are considered substantially complete and available for occupancy upon receipt of the certificate of occupancy from the appropriate licensing authority. Substantially completed portions of a project are accounted for as separate projects. Depreciation is calculated using the straight-line method and estimated useful lives of generally between 35 and 50 years for base buildings, or a shorter period if management determines that the building has a shorter useful life, and up to 20 years for certain other improvements that extend the useful lives. Leasehold improvements expenditures are capitalized when certain criteria are met, including when the Company supervises construction and will own the improvements. Tenant improvements are amortized, over the shorter of the lives of the related leases or the useful life of the improvement, using the straight-line method.
Deferred Leasing Costs	Deferred Leasing Costs Deferred leasing costs consist of commissions paid to third-party leasing agents, internal direct costs such as employee compensation and payroll-related fringe benefits directly related to time spent performing leasing-related activities for successful commercial leases and amounts attributed to in place leases associated with acquired properties and are amortized, using the straight-line method, over the term of the lease or the remaining term of an acquired lease. Leasing related activities include evaluating the prospective tenant’s financial condition, evaluating and recording guarantees, collateral and other security arrangements, negotiating lease terms, preparing lease documents and closing the transaction. Unamortized deferred costs are charged to expense if the applicable lease is terminated prior to expiration of the initial lease term.
Construction in Progress	Construction in Progress Construction in progress includes preconstruction and development costs of active projects. Preconstruction costs include legal, zoning and permitting costs and other project carrying costs incurred prior to the commencement of construction. Development costs include direct construction costs and indirect costs incurred subsequent to the start of construction such as architectural, engineering, construction management and carrying costs consisting of interest, real estate taxes and insurance.
Accounts Receivable and Accrued Income	Accounts Receivable and Accrued Income Accounts receivable primarily represent amounts currently due from tenants in accordance with the terms of the respective leases. Receivables are reviewed monthly and reserves are established with a charge to current period operations when, in the opinion of management, collection of the receivable is doubtful.
Assets Held for Sale	Assets Held for Sale The Company considers properties to be assets held for sale when all of the following criteria are met: • management commits to a plan to sell a property; • it is unlikely that the disposal plan will be significantly modified or discontinued; • the property is available for immediate sale in its present condition; • actions required to complete the sale of the property have been initiated; • sale of the property is probable and the Company expects the completed sale will occur within one year; and • the property is actively being marketed for sale at a price that is reasonable given its current market value. The Company must make a determination as to the point in time that it is probable that a sale will be consummated, which generally occurs when an executed sales contract has no contingencies and the prospective buyer has significant funds at risk to ensure performance. Upon designation as an asset held for sale, the Company records the carrying value of each property at the lower of its carrying value or its estimated fair value, less estimated costs to sell, and ceases depreciation.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include short-term investments. Short-term investments include money market accounts and other investments which generally mature within three months, measured from the acquisition date, and/or are readily convertible to cash. Substantially all of the Company’s cash balances at December 31, 2017 are held in non-interest bearing accounts at various banks. From time to time the Company may maintain deposits with financial institutions in amounts in excess of federally insured limits. The Company has not experienced any losses on such deposits and believes it is not exposed to any significant credit risk on those deposits.
Deferred Debt Costs	Deferred Debt Costs Deferred debt costs consist of fees and costs incurred to obtain long-term financing, construction financing and the revolving line of credit. These fees and costs are being amortized on a straight-line basis over the terms of the respective loans or agreements, which approximates the effective interest method.
Deferred Income	Deferred Income Deferred income consists of payments received from tenants prior to the time they are earned and recognized by the Company as revenue, including tenant prepayment of rent for future periods, real estate taxes when the taxing jurisdiction has a fiscal year differing from the calendar year reimbursements specified in the lease agreement and tenant construction work provided by the Company. In addition, deferred income includes the fair value of certain below market leases.
Derivative Financial Instruments	Derivative Financial Instruments The Company may, when appropriate, employ derivative instruments, such as interest-rate swaps, to mitigate the risk of interest rate fluctuations. The Company does not enter into derivative or other financial instruments for trading or speculative purposes. Derivative financial instruments are carried at fair value as either assets or liabilities on the consolidated balance sheets. For those derivative instruments that qualify, the Company may designate the hedging instrument, based upon the exposure being hedged, as a fair value hedge or a cash flow hedge. Derivative instruments that are designated as a hedge are evaluated to ensure they continue to qualify for hedge accounting. The effective portion of any gain or loss on the hedge instruments is reported as a component of accumulated other comprehensive income (loss) and recognized in earnings within the same line item associated with the forecasted transaction in the same period or periods during which the hedged transaction affects earnings. Any ineffective portion of the change in fair value of a derivative instrument is immediately recognized in earnings. For derivative instruments that do not meet the criteria for hedge accounting, or that qualify and are not designated, changes in fair value are immediately recognized in earnings.
Revenue Recognition	Revenue Recognition Rental and interest income are accrued as earned. Recognition of rental income commences when control of the space has been given to the tenant. When rental payments due under leases vary from a straight-line basis because of free rent periods or stepped increases, income is recognized on a straight-line basis. Expense recoveries represent a portion of property operating expenses billed to the tenants, including common area maintenance, real estate taxes and other recoverable costs. Expense recoveries are recognized in the period in which the expenses are incurred. Rental income based on a tenant’s revenue (“percentage rent”) is accrued when a tenant reports sales that exceed a specified breakpoint, pursuant to the terms of their respective leases.
Income Taxes	Income Taxes The Company made an election to be treated, and intends to continue operating so as to qualify, as a REIT under the Code, commencing with its taxable year ended December 31, 1993 . A REIT generally will not be subject to federal income taxation, provided that distributions to its stockholders equal or exceed its REIT taxable income and complies with certain other requirements. Therefore, no provision has been made for federal income taxes in the accompanying consolidated financial statements. As of December 31, 2017 , the Company had no material unrecognized tax benefits and there exist no potentially significant unrecognized tax benefits which are reasonably expected to occur within the next twelve months. The Company recognizes penalties and interest accrued related to unrecognized tax benefits, if any, as general and administrative expense.
Stock Based Employee Compensation, Deferred Compensation and Stock Plan for Directors	Stock Based Employee Compensation, Deferred Compensation and Stock Plan for Directors The Company uses the fair value method to value and account for employee stock options. The fair value of options granted is determined at the time of each award using the Black-Scholes model, a widely used method for valuing stock based employee compensation, and the following assumptions: (1) Expected Volatility determined using the most recent trading history of the Company’s common stock (month-end closing prices) corresponding to the average expected term of the options; (2) Average Expected Term of the options is based on prior exercise history, scheduled vesting and the expiration date; (3) Expected Dividend Yield determined by management after considering the Company’s current and historic dividend yield rates, the Company’s yield in relation to other retail REITs and the Company’s market yield at the grant date; and (4) a Risk-free Interest Rate based upon the market yields of US Treasury obligations with maturities corresponding to the average expected term of the options at the grant date. The Company amortizes the value of options granted ratably over the vesting period and includes the amounts as compensation in general and administrative expenses. The Company has a stock plan, which was originally approved in 2004, amended in 2008 and 2013 and which expires in 2023, for the purpose of attracting and retaining executive officers, directors and other key personnel (the "Stock Plan"). Pursuant to the Stock Plan, the Compensation Committee established a Deferred Compensation Plan for Directors for the benefit of its directors and their beneficiaries, which replaced a previous Deferred Compensation and Stock Plan for Directors. A director may make an annual election to defer all or part of his or her director’s fees and has the option to have the fees paid in cash, in shares of common stock or in a combination of cash and shares of common stock upon separation from the Board. If the director elects to have fees paid in stock, fees earned during a calendar quarter are aggregated and divided by the common stock’s closing market price on the first trading day of the following quarter to determine the number of shares to be allocated to the director. As of December 31, 2017 , the directors’ deferred fee accounts comprise 183,818 shares. The Compensation Committee has also approved an annual award of shares of the Company’s common stock as additional compensation to each director serving on the Board of Directors as of the record date for the Annual Meeting of Stockholders. The shares are awarded as of each Annual Meeting of Shareholders, and their issuance may not be deferred.
Noncontrolling Interest	Noncontrolling Interest Saul Centers is the sole general partner of the Operating Partnership, owning a 74.4% common interest as of December 31, 2017 . Noncontrolling interest in the Operating Partnership is comprised of limited partnership units owned by the Saul Organization. Noncontrolling interest reflected on the accompanying consolidated balance sheets is increased for earnings allocated to limited partnership interests and distributions reinvested in additional units, and is decreased for limited partner distributions. Noncontrolling interest reflected on the consolidated statements of operations represents earnings allocated to limited partnership interests held by the Saul Organization.
Per Share Data	Per Share Data Per share data for net income (basic and diluted) is computed using weighted average shares of common stock. Convertible limited partnership units and employee stock options are the Company’s potentially dilutive securities. For all periods presented, the convertible limited partnership units are anti-dilutive. The treasury stock method was used to measure the effect of the dilution.
Legal Contingencies	Legal Contingencies The Company is subject to various legal proceedings and claims that arise in the ordinary course of business, which are generally covered by insurance. Upon determination that a loss is probable to occur and can be reasonably estimated, the estimated amount of the loss is recorded in the financial statements.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the FASB issued ASU No. 2014-09 titled “Revenue from Contracts with Customers” and subsequently issued several related ASUs (collectively “ASU 2014-09”). ASU 2014-09 will replace most existing revenue recognition guidance and will require an entity to recognize the amount of revenue which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 is effective for annual periods beginning after December 15, 2017, and interim periods within those years and early adoption is not permitted. ASU 2014-09 must be applied retrospectively by either restating prior periods or by recognizing the cumulative effect as of the first date of application. Management believes the majority of the Company's revenue falls outside of the scope of this guidance and does not anticipate any significant changes to the timing of the Company's revenue recognition. The Company intends to implement the standard retrospectively with the cumulative effect recognized in retained earnings at the date of adoption. In February 2015, the FASB issued ASU No. 2015-02, “Consolidation” ("ASU 2015-02"). ASU 2015-02 modifies existing consolidation guidance for reporting organizations that are required to evaluate whether they should consolidate certain legal entities. All legal entities are subject to reevaluation under the revised consolidation model. ASU 2015-02 is effective for annual periods beginning after December 15, 2015, and interim periods within those years. The adoption of ASU 2015-02 effective January 1, 2016, resulted in the Operating Partnership being classified as a variable interest entity. Because the Operating Partnership was already consolidated into the financial statements, adoption had no impact on the Company’s consolidated financial statements or disclosures. In April 2015, the FASB issued ASU No. 2015-03, “Interest - Imputation of Interest” (“ASU 2015-03”). ASU 2015-03 simplifies the presentation of debt issuance costs and will require an entity to deduct transaction costs from the carrying value of the related financial liability and not record those transaction costs as a separate asset. Recognition and measurement guidance for debt issuance costs are not affected by ASU 2015-03. ASU 2015-03 is effective for annual periods beginning after December 15, 2015, and interim periods within those years, and must be applied retrospectively by adjusting the balance sheet of each individual period presented. The Company retrospectively adopted ASU 2015-03 effective January 1, 2016. As a result of the adoption of ASU 2015-03, the Company no longer reports its net deferred debt costs as an asset and instead reports those amounts as reduction of the carrying value of the associated debt. In February 2016, the FASB issued ASU 2016-02, ‘‘Leases’’ (“ASU 2016-02”). ASU 2016-02 amends the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. ASU 2016-02 is effective for annual periods beginning after December 15, 2018, interim periods within those years, and requires a modified retrospective transition approach for all leases existing at the date of initial application, with an option to use certain practical expedients for those existing leases. We are evaluating the impact that ASU 2016-02 will have on our consolidated financial statements and related disclosures. In March 2016, the FASB issued ASU 2016-09, "Compensation-Stock Compensation" ("ASU 2016-09"). ASU 2016-09 simplifies the accounting for several aspects of share-based payments including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for annual periods beginning after December 15, 2016 and interim periods within those years. The transition method varies based on the specific amendment. The adoption of ASU 2016-09 effective January 1, 2017, did not have a material impact on our consolidated financial statements or related disclosures. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments-Credit Losses" ("ASU 2016-13"). ASU 2016-13 replaces the incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of information to support credit loss estimates. ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within those years. We are evaluating the impact that ASU 2016-13 will have on our consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-01, "Clarifying the Definition of a Business" ("ASU 2017-01"). ASU 2017-01 provides that when substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, the set is not a business. ASU 2017-01 is effective prospectively for annual periods beginning after December 15, 2017, and interim periods within those years. Early application is permitted for transactions for which the acquisition date occurs before the effective date provided the transaction has not been reported in the financial statements. The Company adopted ASU 2017-01 during the first quarter of 2017, the effect of which, for asset acquisitions, was (a) the capitalization of acquisition costs, instead of expense, and (b) recordation of acquired assets and assessment liabilities at relative fair value, instead of fair value.
Reclassifications	Reclassifications Certain reclassifications have been made to prior years to conform to the presentation used for year ended December 31, 2017 .

Organization, Formation, and 27

Organization, Formation, and Basis of Presentation (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Significant Properties Acquired, Developed and/or Disposed	The following table lists the significant properties acquired, developed and/or disposed of by the Company since January 1, 2015 . Name of Property Location Type Year of Acquisition/ Development/ Disposal Acquisitions 726 N. Glebe Road* Arlington, Virginia Shopping Center September 2015 700 N. Glebe Road Arlington, Virginia Development August 2016 Burtonsville Town Square Burtonsville, Maryland Shopping Center January 2017 Developments Park Van Ness Washington, DC Mixed-Use 2013-2016 750 N. Glebe Road Arlington, Virginia Mixed-Use 2017 Dispositions Crosstown Business Center Tulsa, Oklahoma Mixed-Use December 2016 Great Eastern District Heights, Maryland Shopping Center September 2017 *As of August 2016, this property was removed from operations and reclassified to development.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Schedule of construction in progress	The following table shows the components of construction in progress. December 31, (in thousands) 2017 2016 N. Glebe Road $ 83,462 $ 58,147 Other 7,652 5,423 Total $ 91,114 $ 63,570
Allowance for doubtful accounts	Accounts receivable in the accompanying consolidated financial statements are shown net of an allowance for doubtful accounts of $0.4 million and $2.0 million , at December 31, 2017 and 2016 , respectively. (In thousands) Year ended December 31, 2017 2016 2015 Beginning Balance $ 1,958 $ 1,263 $ 677 Provision for Credit Losses 906 1,494 915 Charge-offs (2,459 ) (799 ) (329 ) Ending Balance $ 405 $ 1,958 $ 1,263
Basic and diluted shares outstanding	December 31, (Shares in thousands) 2017 2016 2015 Weighted average common shares outstanding - Basic 21,901 21,505 21,127 Effect of dilutive options 107 110 69 Weighted average common shares outstanding - Diluted 22,008 21,615 21,196 Average share price $ 61.63 $ 58.96 $ 53.38 Non-dilutive options — 129 111 Years non-dilutive options were issued 2007, 2015, and 2016 2007 and 2015

Real Estate Acquired (Tables)

Real Estate Acquired (Tables)	12 Months Ended
	Dec. 31, 2017
Real Estate [Abstract]
Allocation of purchase prices to acquired assets and liabilities	The purchase price was allocated to the assets acquired and liabilities assumed based on their fair value as shown in the following table. (in thousands) 700 N. Glebe Road Thruway Pad Total Land $ 7,236 $ 2,196 $ 9,432 Buildings — 874 874 In-place Leases — 93 93 Above Market Rent — — — Below Market Rent — (63 ) (63 ) Total Purchase Price $ 7,236 $ 3,100 $ 10,336
Amortization of intangible assets and deferred income related to in place leases	As of December 31, 2017 , scheduled amortization of intangible assets and deferred income related to in place leases is as follows: (In thousands) Lease acquisition costs Above market leases Below market leases 2018 $ 982 $ 33 $ 1,652 2019 780 33 1,515 2020 653 33 1,433 2021 530 33 1,409 2022 390 33 1,306 Thereafter 1,547 409 6,029 Total $ 4,882 $ 574 $ 13,344

Mortgage Notes Payable, Revol30

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Summary of notes payable	The following is a summary of notes payable as of December 31, 2017 and 2016 . Notes Payable December 31, Interest Scheduled (Dollars in thousands) 2017 2016 Rate * Maturity * Fixed rate mortgages: $ — (a) $ 29,428 6.01 % Feb-2018 30,201 (b) 32,036 5.88 % Jan-2019 9,783 (c) 10,372 5.76 % May-2019 13,529 (d) 14,335 5.62 % Jul-2019 13,543 (e) 14,325 5.79 % Sep-2019 12,029 (f) 12,725 5.22 % Jan-2020 9,948 (g) 10,277 5.60 % May-2020 8,244 (h) 8,697 5.30 % Jun-2020 37,998 (i) 39,213 5.83 % Jul-2020 7,325 (j) 7,685 5.81 % Feb-2021 5,649 (k) 5,808 6.01 % Aug-2021 32,673 (l) 33,571 5.62 % Jun-2022 9,999 (m) 10,253 6.08 % Sep-2022 10,877 (n) 11,129 6.43 % Apr-2023 12,577 (o) 13,401 6.28 % Feb-2024 15,452 (p) 15,917 7.35 % Jun-2024 13,438 (q) 13,832 7.60 % Jun-2024 23,873 (r) 24,504 7.02 % Jul-2024 28,115 (s) 28,945 7.45 % Jul-2024 28,025 (t) 28,822 7.30 % Jan-2025 14,537 (u) 14,961 6.18 % Jan-2026 105,817 (v) 109,144 5.31 % Apr-2026 32,016 (w) 33,097 4.30 % Oct-2026 36,507 (x) 37,701 4.53 % Nov-2026 17,086 (y) 17,630 4.70 % Dec-2026 64,472 (z) 66,210 5.84 % May-2027 15,859 (aa) 16,352 4.04 % Apr-2028 39,968 (bb) 41,753 3.51 % Jun-2028 16,055 (cc) 16,543 3.99 % Sep-2028 27,884 (dd) 28,679 3.69 % Mar-2030 14,950 (ee) 15,357 3.99 % Apr-2030 39,140 (ff) — 3.39 % Feb-2032 71,211 (gg) 70,144 4.88 % Sep-2032 60,000 (hh) — 3.75 % Dec-2032 11,613 (ii) 11,446 8.00 % Apr-2034 Total fixed rate 890,393 844,292 5.25 % 8.6 Years Variable rate loans: 61,000 (jj) 49,000 LIBOR + 1.45 % Jun-2018 14,135 (kk) 14,482 LIBOR + 1.65 % Feb-2018 Total variable rate $ 75,135 $ 63,482 2.86 % 0.4 Years Total notes payable $ 965,528 $ 907,774 5.07 % 7.9 Years * Interest rate and scheduled maturity data presented as of December 31, 2017 . Totals computed using weighted averages. Amounts shown are principal amounts and have not been reduced by any deferred debt issuance costs. (a) The loan was collateralized by Washington Square and required equal monthly principal and interest payments of $264,000 based upon a 27.5 -year amortization schedule and a final payment of $28.0 million at loan maturity. In 2017, the loan was repaid in full and replaced with a new $60.0 million loan. See (hh) below. (b) The loan is collateralized by three shopping centers, Broadlands Village, The Glen and Kentlands Square I, and requires equal monthly principal and interest payments of $306,000 based upon a 25 -year amortization schedule and a final payment of $28.4 million at loan maturity. Principal of $1.8 million was amortized during 2017 . (c) The loan is collateralized by Olde Forte Village and requires equal monthly principal and interest payments of $98,000 based upon a 25 -year amortization schedule and a final payment of $9.0 million at loan maturity. Principal of $589,000 was amortized during 2017 . (d) The loan is collateralized by Countryside and requires equal monthly principal and interest payments of $133,000 based upon a 25 -year amortization schedule and a final payment of $12.3 million at loan maturity. Principal of $806,000 was amortized during 2017 . (e) The loan is collateralized by Briggs Chaney MarketPlace and requires equal monthly principal and interest payments of $133,000 based upon a 25 -year amortization schedule and a final payment of $12.2 million at loan maturity. Principal of $782,000 was amortized during 2017 . (f) The loan is collateralized by Shops at Monocacy and requires equal monthly principal and interest payments of $112,000 based upon a 25 -year amortization schedule and a final payment of $10.6 million at loan maturity. Principal of $696,000 was amortized during 2017 . (g) The loan is collateralized by Boca Valley Plaza and requires equal monthly principal and interest payments of $75,000 based upon a 30 -year amortization schedule and a final payment of $9.1 million at loan maturity. Principal of $329,000 was amortized during 2017 . (h) The loan is collateralized by Palm Springs Center and requires equal monthly principal and interest payments of $75,000 based upon a 25 -year amortization schedule and a final payment of $7.1 million at loan maturity. Principal of $453,000 was amortized during 2017 . (i) The loan and a corresponding interest-rate swap closed on June 29, 2010 and are collateralized by Thruway. On a combined basis, the loan and the interest-rate swap require equal monthly principal and interest payments of $289,000 based upon a 25 -year amortization schedule and a final payment of $34.8 million at loan maturity. Principal of $1.2 million was amortized during 2017 . (j) The loan is collateralized by Jamestown Place and requires equal monthly principal and interest payments of $66,000 based upon a 25 -year amortization schedule and a final payment of $6.1 million at loan maturity. Principal of $360,000 was amortized during 2017 . (k) The loan is collateralized by Hunt Club Corners and requires equal monthly principal and interest payments of $42,000 based upon a 30 -year amortization schedule and a final payment of $5.0 million , at loan maturity. Principal of $159,000 was amortized during 2017 . (l) The loan is collateralized by Lansdowne Town Center and requires monthly principal and interest payments of $230,000 based on a 30 -year amortization schedule and a final payment of $28.2 million at loan maturity. Principal of $898,000 was amortized during 2017 . (m) The loan is collateralized by Orchard Park and requires equal monthly principal and interest payments of $73,000 based upon a 30 -year amortization schedule and a final payment of $8.6 million at loan maturity. Principal of $254,000 was amortized during 2017 . (n) The loan is collateralized by BJ’s Wholesale and requires equal monthly principal and interest payments of $80,000 based upon a 30 -year amortization schedule and a final payment of $9.3 million at loan maturity. Principal of $252,000 was amortized during 2017 . (o) The loan is collateralized by Great Falls shopping center. The loan consists of three notes which require equal monthly principal and interest payments of $138,000 based upon a weighted average 26 -year amortization schedule and a final payment of $6.3 million at maturity. Principal of $824,000 was amortized during 2017 . (p) The loan is collateralized by Leesburg Pike and requires equal monthly principal and interest payments of $135,000 based upon a 25 -year amortization schedule and a final payment of $11.5 million at loan maturity. Principal of $465,000 was amortized during 2017 . (q) The loan is collateralized by Village Center and requires equal monthly principal and interest payments of $119,000 based upon a 25 -year amortization schedule and a final payment of $10.1 million at loan maturity. Principal of $394,000 was amortized during 2017 . (r) The loan is collateralized by White Oak and requires equal monthly principal and interest payments of $193,000 based upon a 24.4 year weighted amortization schedule and a final payment of $18.5 million at loan maturity. The loan was previously collateralized by Van Ness Square. During 2012, the Company substituted White Oak as the collateral and borrowed an additional $10.5 million . Principal of $631,000 was amortized during 2017 . (s) The loan is collateralized by Avenel Business Park and requires equal monthly principal and interest payments of $246,000 based upon a 25 -year amortization schedule and a final payment of $20.9 million at loan maturity. Principal of $830,000 was amortized during 2017 . (t) The loan is collateralized by Ashburn Village and requires equal monthly principal and interest payments of $240,000 based upon a 25 -year amortization schedule and a final payment of $20.5 million at loan maturity. Principal of $797,000 was amortized during 2017 . (u) The loan is collateralized by Ravenwood and requires equal monthly principal and interest payments of $111,000 based upon a 25 -year amortization schedule and a final payment of $10.1 million at loan maturity. Principal of $424,000 was amortized during 2017 . (v) The loan is collateralized by Clarendon Center and requires equal monthly principal and interest payments of $753,000 based upon a 25 -year amortization schedule and a final payment of $70.5 million at loan maturity. Principal of $3.3 million was amortized during 2017 . (w) The loan is collateralized by Severna Park MarketPlace and requires equal monthly principal and interest payments of $207,000 based upon a 25 -year amortization schedule and a final payment of $20.3 million at loan maturity. Principal of $1.1 million was amortized during 2017 . (x) The loan is collateralized by Kentlands Square II and requires equal monthly principal and interest payments of $240,000 based upon a 25 -year amortization schedule and a final payment of $23.1 million at loan maturity. Principal of $1.2 million was amortized during 2017 . (y) The loan is collateralized by Cranberry Square and requires equal monthly principal and interest payments of $113,000 based upon a 25 -year amortization schedule and a final payment of $10.9 million at loan maturity. Principal of $544,000 was amortized during 2017 . (z) 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 $1.7 million was amortized during 2017 . (aa) 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 $493,000 was amortized in 2017 . (bb) The loan is collateralized by Beacon Center and requires equal monthly principal and interest payments of $268,500 based upon a 20 -year amortization schedule and a final payment of $17.1 million at loan maturity. Principal of $1.8 million was amortized in 2017 . (cc) 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 $488,000 was amortized in 2017 . (dd) The loan is collateralized by Shops at Fairfax and Boulevard shopping centers and requires equal monthly principal and interest payments totaling $153,300 based upon a 25 -year amortization schedule and a final payment of $15.5 million at maturity. Principal of $795,000 was amortized in 2017 . (ee) The loan is collateralized by Northrock and requires equal monthly principal and interest payments totaling $84,400 based upon a 25 -year amortization schedule and a final payment of $8.4 million at maturity. Principal of $407,000 was amortized in 2017 . (ff) The loan is collateralized by Burtonsville Town Square and requires equal monthly principal and interest payments of $198,000 based on a 25 -year amortization schedule and a final payment of $20.3 million at loan maturity. Principal of $860,000 was amortized in 2017. (gg) The loan is a $71.6 million construction-to-permanent facility that is collateralized by and financed a portion of the construction costs of Park Van Ness. During the construction period, interest was funded by the loan. Effective September 1, 2017, the loan converted to permanent financing and requires monthly principal and interest payments totaling $413,500 based upon a 25 -year amortization schedule. A final payment of $39.6 million will be due at maturity. Principal of $369,000 was amortized in 2017. (hh) The loan is collateralized by Washington Square and requires equal monthly principal and interest payments of $308,000 based upon a 25 -year amortization schedule and a final payment of $31.1 million at loan maturity. (ii) The Company entered into a sale-leaseback transaction with its Olney property and is accounting for that transaction as a secured financing. The arrangement requires monthly payments of $60,400 which increase by 1.5% on May 1, 2015, and every May 1 thereafter. The arrangement provides for a final payment of $14.7 million and has an implicit interest rate of 8.0% . Negative amortization in 2017 totaled $167,000 . (jj) 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. (kk) The loan is collateralized by Metro Pike Center and requires monthly principal and interest payments of approximately $48,000 and a final payment of $14.2 million at loan maturity. Principal of $347,000 was amortized during 2017 .
Scheduled maturities of all debt, including scheduled principal amortization	As of December 31, 2017 , the scheduled maturities of all debt including scheduled principal amortization for years ended December 31 are as follows: (in thousands) Balloon Payments Scheduled Principal Amortization Total 2018 $ 75,105 (a) $ 30,160 $ 105,265 2019 60,793 29,272 90,065 2020 61,163 26,743 87,906 2021 11,012 26,456 37,468 2022 36,503 26,958 63,461 Thereafter 436,325 145,038 581,363 Principal amount $ 680,901 $ 284,627 965,528 Unamortized deferred debt costs 6,906 Net $ 958,622 (a) Includes $61.0 million outstanding under the line of credit.
Components of interest expense	The components of interest expense are set forth below. (in thousands) Year ended December 31, 2017 2016 2015 Interest incurred $ 49,322 $ 46,867 $ 45,898 Amortization of deferred debt costs 1,392 1,343 1,433 Capitalized interest (3,489 ) (2,527 ) (2,166 ) Total $ 47,225 $ 45,683 $ 45,165

Lease Agreements (Tables)

Lease Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Future contractual payments under noncancelable leases	Future contractual payments under noncancelable leases for years ended December 31 (which exclude the effect of straight-line rents), are as follows: (in thousands) 2018 $ 160,025 2019 141,097 2020 120,369 2021 100,766 2022 77,312 Thereafter 245,103 $ 844,672

Stock Option Plan (Tables)

Stock Option Plan (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Options Issued	The following table summarizes the amount and activity of each grant, the total value and variables used in the computation and the amount expensed and included in general and administrative expense in the Consolidated Statements of Operations for the years ended December 31, 2017 , 2016 and 2015 . SAUL CENTERS, INC. (Dollars in thousands, except per share data) Stock options issued Directors Grant date 4/25/2008 4/24/2009 5/7/2010 5/13/2011 5/4/2012 5/10/2013 5/9/2014 5/8/2015 5/6/2016 5/5/2017 Subtotals Total grant 30,000 32,500 32,500 32,500 35,000 35,000 30,000 35,000 32,500 27,500 322,500 Vested 30,000 32,500 32,500 32,500 35,000 35,000 30,000 35,000 32,500 27,500 322,500 Exercised 20,000 27,500 25,000 22,500 22,500 22,500 17,500 12,500 7,500 — 177,500 Forfeited 7,500 — 2,500 2,500 — — — — — — 12,500 Exercisable at December 31, 2017 2,500 5,000 5,000 7,500 12,500 12,500 12,500 22,500 25,000 27,500 132,500 Remaining unexercised 2,500 5,000 5,000 7,500 12,500 12,500 12,500 22,500 25,000 27,500 132,500 Exercise price $ 50.15 $ 32.68 $ 38.76 $ 41.82 $ 39.29 $ 44.42 $ 47.03 $ 51.07 $ 57.74 $ 59.41 Volatility 0.237 0.344 0.369 0.358 0.348 0.333 0.173 0.166 0.166 0.173 Expected life (years) 7.0 6.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Assumed yield 4.09 % 4.54 % 4.23 % 4.16 % 4.61 % 4.53 % 4.48 % 4.54 % 3.75 % 3.45 % Risk-free rate 3.49 % 2.19 % 2.17 % 1.86 % 0.78 % 0.82 % 1.63 % 1.50 % 1.23 % 1.89 % Total value at grant date $ 255 $ 223 $ 288 $ 297 $ 257 $ 278 $ 110 $ 125 $ 151 $ 166 $ 2,150 Expensed in previous years 255 223 288 297 257 278 110 — — — 1,708 Expensed in 2015 — — — — — — — 125 — — 125 Expensed in 2016 — — — — — — — — 151 — 151 Expensed in 2017 — — — — — — — — — 166 166 Future expense — — — — — — — — — — — Officers Grant date 5/13/2011 5/4/2012 5/10/2013 5/9/2014 5/8/2015 5/6/2016 5/5/2017 Subtotals Grand Totals Total grant 162,500 242,500 202,500 170,000 190,000 194,000 205,000 1,366,500 1,689,000 Vested 118,750 107,500 171,875 126,875 94,375 48,500 — 667,875 990,375 Exercised 96,100 91,830 116,500 41,250 20,000 3,750 — 369,430 546,930 Forfeited 43,750 135,000 30,625 1,875 3,125 1,875 — 216,250 228,750 Exercisable at December 31, 2017 22,650 15,670 55,375 85,625 74,375 44,750 — 298,445 430,945 Remaining unexercised 22,650 15,670 55,375 126,875 166,875 188,375 205,000 780,820 913,320 Exercise price $ 41.82 $ 39.29 $ 44.42 $ 47.03 $ 51.07 $ 57.74 $ 59.41 Volatility 0.330 0.315 0.304 0.306 0.298 0.185 0.170 Expected life (years) 8.0 8.0 8.0 7.0 7.0 7.0 7.0 Assumed yield 4.81 % 5.28 % 5.12 % 4.89 % 4.94 % 3.80 % 3.50 % Risk-free rate 2.75 % 1.49 % 1.49 % 2.17 % 1.89 % 1.55 % 2.17 % Gross value at grant date $ 1,366 $ 1,518 $ 1,401 $ 1,350 $ 1,585 $ 1,137 $ 1,324 $ 9,681 $ 11,831 Estimated forfeitures 368 845 212 169 142 86 92 1,914 1,914 Expensed in previous years 909 419 493 197 — — — 2,018 3,726 Expensed in 2015 89 157 269 296 240 — — 1,051 1,176 Expensed in 2016 — 97 269 295 361 175 — 1,197 1,348 Expensed in 2017 — — 158 295 361 263 205 1,282 1,448 Future expense — — — 98 481 613 1,027 2,219 2,219 Weighted average term of remaining future expense 2.5 years
Summary of Option Activity	The table below summarizes the option activity for the years 2017 , 2016 , and 2015 : 2017 2016 2015 Shares Weighted Shares Weighted Shares Weighted Outstanding at January 1 833,630 $ 49.92 860,274 $ 46.58 748,208 $ 44.79 Granted 232,500 59.41 226,500 57.74 225,000 51.07 Exercised (149,060 ) 46.97 (246,894 ) 45.59 (112,934 ) 43.67 Expired/Forfeited (3,750 ) 53.73 (6,250 ) 45.31 — — Outstanding December 31 913,320 52.80 833,630 49.92 860,274 46.58 Exercisable at December 31 430,945 48.94 375,255 46.68 435,899 45.33

Fair Value of Financial Instr33

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Changes in Fair Value of Swaps	The following chart summarizes the changes in fair value of the Company’s swap for the indicated periods. (Dollars in thousands) Year ended December 31, 2017 2016 2015 Increase (decrease) in fair value: Recognized in earnings $ 70 $ (6 ) $ (10 ) Recognized in other comprehensive income 812 678 124 Total $ 882 $ 672 $ 114

Distributions (Tables)

Distributions (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of distributions paid including activity in plan as well as limited partnership units issued from reinvestment of unit distributions	The following summarizes distributions paid during the years ended December 31, 2017 , 2016 , and 2015 , and includes activity in the Plan as well as limited partnership units issued from the reinvestment of unit distributions: Total Distributions to Dividend Reinvestments (Dollars in thousands, except per share amounts) Preferred Common Limited Common Discounted Limited Partnership Units Issued Average Unit Price Distributions during 2017 October 31 $ 3,094 $ 11,221 $ 3,838 82,991 $ 59.33 15,596 $ 60.08 July 31 3,094 11,160 3,830 85,731 57.40 16,021 58.13 April 30 3,094 11,119 3,810 51,003 59.64 40,623 59.96 January 31 3,093 11,076 3,790 46,286 61.85 39,111 62.15 Total 2017 $ 12,375 $ 44,576 $ 15,268 266,011 111,351 Distributions during 2016 October 31 $ 3,094 $ 10,168 $ 3,478 44,176 $ 57.18 30,891 $ 57.18 July 31 3,094 10,133 3,465 39,487 65.64 26,897 65.64 April 30 3,094 10,029 3,449 48,854 51.59 34,201 51.59 January 31 3,093 9,142 3,141 54,280 49.24 32,769 49.24 Total 2016 $ 12,375 $ 39,472 $ 13,533 186,797 124,758 Distributions during 2015 October 31 $ 3,094 $ 9,106 $ 3,129 47,313 $ 55.73 28,936 $ 55.73 July 31 3,094 9,081 3,115 56,003 50.30 32,041 50.30 April 30 3,094 9,055 3,104 54,921 50.21 25,264 50.21 January 31 3,093 8,403 2,880 42,975 56.74 20,796 56.74 Total 2015 $ 12,375 $ 35,645 $ 12,228 201,212 107,037

Interim Results (Unaudited) (Ta

Interim Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of results of operations for quarterly periods	The following summary presents the results of operations of the Company for the quarterly periods of calendar years 2017 and 2016 . (In thousands, except per share amounts) 2017 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Revenue $ 58,466 $ 55,907 $ 56,237 $ 56,675 Operating income before loss on early extinguishment of debt, gain on casualty settlement, and noncontrolling interests 17,374 14,422 14,386 14,416 Gain on sales of properties — — — — Net income attributable to Saul Centers, Inc. 13,704 11,510 11,483 11,560 Net income available to common stockholders 10,610 8,416 8,390 8,466 Net income available to common stockholders per diluted share 0.49 0.38 0.38 0.38 (In thousands, except per share amounts) 2016 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Revenue $ 56,926 $ 52,710 $ 53,233 $ 54,201 Operating income before loss on early extinguishment of debt, gain on casualty settlement, and noncontrolling interests 16,381 13,250 12,722 13,360 Gain on sales of properties — — — 1,013 Net income attributable to Saul Centers, Inc. 12,948 10,627 10,239 11,465 Net income available to common stockholders 9,854 7,533 7,146 8,371 Net income available to common stockholders per diluted share 0.46 0.35 0.33 0.38

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segments	SAUL CENTERS, INC. Notes to Consolidated Financial Statements (In thousands) Shopping Mixed-Use Corporate Consolidated As of or for the year ended December 31, 2017 Centers Properties and Other Totals Real estate rental operations: Revenue $ 165,853 $ 61,352 $ 80 $ 227,285 Expenses (34,675 ) (20,917 ) — (55,592 ) Income from real estate 131,178 40,435 80 171,693 Interest expense and amortization of deferred debt costs — — (47,225 ) (47,225 ) General and administrative — — (18,176 ) (18,176 ) Subtotal 131,178 40,435 (65,321 ) 106,292 Depreciation and amortization of deferred leasing costs (29,977 ) (15,717 ) — (45,694 ) Change in fair value of derivatives — — 70 70 Net income (loss) $ 101,201 $ 24,718 $ (65,251 ) $ 60,668 Capital investment $ 90,896 $ 29,098 $ — $ 119,994 Total assets $ 974,061 $ 438,283 $ 10,108 $ 1,422,452 As of or for the year ended December 31, 2016 Real estate rental operations: Revenue $ 160,179 $ 56,840 $ 51 $ 217,070 Expenses (34,931 ) (18,770 ) — (53,701 ) Income from real estate 125,248 38,070 51 163,369 Interest expense and amortization of deferred debt costs — — (45,683 ) (45,683 ) General and administrative — — (17,496 ) (17,496 ) Subtotal 125,248 38,070 (63,128 ) 100,190 Depreciation and amortization of deferred leasing costs (29,964 ) (14,453 ) — (44,417 ) Acquisition related costs (60 ) — — (60 ) Change in fair value of derivatives — — (6 ) (6 ) Gain on sale of property — 1,013 — 1,013 Net income (loss) $ 95,224 $ 24,630 $ (63,134 ) $ 56,720 Capital investment $ 64,044 $ 27,001 $ — $ 91,045 Total assets $ 976,545 $ 358,419 $ 8,061 $ 1,343,025 SAUL CENTERS, INC. Notes to Consolidated Financial Statements (continued) (In thousands) Shopping Mixed-Use Corporate Consolidated As of or for the year ended December 31, 2015 Centers Properties and Other Totals Real estate rental operations: Revenue $ 156,110 $ 52,916 $ 51 $ 209,077 Expenses (33,877 ) (17,266 ) — (51,143 ) Income from real estate 122,233 35,650 51 157,934 Interest expense and amortization of deferred debt costs — — (45,165 ) (45,165 ) General and administrative — — (16,353 ) (16,353 ) Subtotal 122,233 35,650 (61,467 ) 96,416 Depreciation and amortization of deferred leasing costs (30,171 ) (13,099 ) — (43,270 ) Acquisition related costs (84 ) — — (84 ) Predevelopment expenses (57 ) (75 ) — (132 ) Change in fair value of derivatives — — (10 ) (10 ) Gain on sale of property 11 — — 11 Net income (loss) $ 91,932 $ 22,476 $ (61,477 ) $ 52,931 Capital investment $ 17,159 $ 52,460 $ — $ 69,619 Total assets $ 931,256 $ 354,254 $ 9,898 $ 1,295,408

Organization, Formation And Bas

Organization, Formation And Basis of Presentation - Additional Information (Detail)	Dec. 31, 2017partnershipproperty
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Distribution of REIT taxable income (excluding net capital gains) to its stockholders	90.00%
Number of partnerships | partnership	2
Shopping Centers
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	49
Mixed-Use Properties
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	6
Non-operating Development Properties
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	3

Summary of Significant Accoun38

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)ft²tenantstorepropertyshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)
Significant Accounting Policies [Line Items]
Number of shopping centers | store	32
Percentage of ownership in operating partnership	74.41803%
Interest expense capitalized	$ 3,489,000	$ 2,527,000	$ 2,166,000
Depreciation and amortization of deferred leasing costs	40,197,000	38,755,000	37,698,000
Repairs and maintenance expense	11,600,000	11,800,000	11,600,000
Deferred leasing costs, net	27,255,000	25,983,000
Accumulated amortization deferred leasing cost	35,300,000	30,400,000
Amortization expense deferred leasing cost	5,500,000	5,600,000	5,600,000
Allowance for doubtful accounts receivables	405,000	1,958,000	1,263,000	$ 677,000
Accounts receivable, net representing rental income accrued	44,100,000	43,100,000
Allowance for doubtful accounts receivables representing rental income accrued	200,000	500,000
Real estate held-for-sale	3,400,000
Real estate, accumulated depreciation	488,166,000	458,279,000	425,370,000	$ 396,617,000
Real estate, costs to sell and liabilities	200,000
Unamortized deferred debt costs	6,906,000	7,500,000
Accumulated amortization	8,200,000	7,300,000
Accrued penalties and interest	0	0	$ 0
Tax basis of the company's real estate investments	$ 1,320,000,000	$ 1,260,000,000
Shares issued to directors (in shares) | shares	152,758	251,323	117,886
Shares issued to directors	$ 1,448,000	$ 1,348,000	$ 1,176,000
Director
Significant Accounting Policies [Line Items]
Shares credited to deferred fee accounts (in shares) | shares	183,818
Shares issued to directors (in shares) | shares	200	200	200
Shares issued to directors	$ 130,700	$ 150,100	$ 143,000
Property Held-for-sale
Significant Accounting Policies [Line Items]
Number of real estate properties | property	1
Net rentable area (in square feet) | ft²	197,100
Real estate, accumulated depreciation	$ 7,000,000
Minimum | Building
Significant Accounting Policies [Line Items]
Estimated useful life	35 years
Maximum | Building
Significant Accounting Policies [Line Items]
Estimated useful life	50 years
Maximum | Building Improvements
Significant Accounting Policies [Line Items]
Estimated useful life	20 years
Revenue
Significant Accounting Policies [Line Items]
Number of tenants | tenant	2
Revenue | Minimum
Significant Accounting Policies [Line Items]
Percentage of total revenue	2.50%
Revenue | Giant Food
Significant Accounting Policies [Line Items]
Percentage of total revenue	4.70%
Number of shopping centers | store	10
Revenue | Capital One
Significant Accounting Policies [Line Items]
Percentage of total revenue	2.80%
Number of shopping centers | store	18
Glebe Road Construction Loan
Significant Accounting Policies [Line Items]
Unamortized deferred debt costs	$ 1,800,000

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Construction in Progress (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Construction in progress	$ 91,114	$ 63,570
N. Glebe Road
Property, Plant and Equipment [Line Items]
Construction in progress	83,462	58,147
Other
Property, Plant and Equipment [Line Items]
Construction in progress	$ 7,652	$ 5,423

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning Balance	$ 1,958	$ 1,263	$ 677
Provision for Credit Losses	906	1,494	915
Charge-offs	(2,459)	(799)	(329)
Ending Balance	$ 405	$ 1,958	$ 1,263

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Basic and Diluted Shares Outstanding (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding - basic (in shares)	21,901	21,505	21,127
Effect of dilutive options (in shares)	107	110	69
Weighted average common shares outstanding - diluted (in shares)	22,008	21,615	21,196
Average share price (in usd per share)	$ 61.63	$ 58.96	$ 53.38
Options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive options (in shares)	0	129	111

Real Estate Acquired - Addition

Real Estate Acquired - Additional Information (Detail)	1 Months Ended							3 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)	Jan. 31, 2017USD ($)	Aug. 31, 2016USD ($)	Sep. 30, 2015USD ($)	Feb. 28, 2015USD ($)a	Dec. 31, 2014USD ($)	Aug. 31, 2014USD ($)	Dec. 31, 2016USD ($)property	Dec. 31, 2017USD ($)property	Dec. 31, 2016USD ($)property	Dec. 31, 2015USD ($)property
Real Estate Properties [Line Items]
Payments to acquire real estate									$ 17,653,000	$ 15,564,000	$ 18,855,000
Acquisition costs										60,400
Rent expense									$ 774,700	$ 843,300	$ 904,900
Number of properties acquired | property								2	1	2	1
Purchase price allocated to land									$ 450,256,000
Purchase price allocated to buildings									1,352,944,000
Below market lease, carrying amount								$ 25,100,000	25,100,000	$ 25,100,000
Below market lease, accumulated amortization								10,600,000	11,800,000	10,600,000
Accretion income, intangible liabilities									1,700,000	1,800,000	$ 1,800,000
Lease acquisition costs
Real Estate Properties [Line Items]
Intangible assets gross carrying amount								10,100,000	12,300,000	10,100,000
Intangible assets, accumulated amortization								6,400,000	7,500,000	6,400,000
Amortization expense									$ 1,100,000	1,000,000	1,300,000
Weighted-average amortization period									4 years 6 months 26 days
Above Market Rent
Real Estate Properties [Line Items]
Intangible assets gross carrying amount								10,200	$ 600,000	10,200
Intangible assets, accumulated amortization								7,800	39,500	7,800
Amortization expense									$ 31,600	1,500	1,500
Weighted-average amortization period									8 years 9 months 9 days
Below Market Rent
Real Estate Properties [Line Items]
Weighted-average amortization period									5 years 9 months 10 days
750 N. Glebe Road
Real Estate Properties [Line Items]
Payments to acquire real estate							$ 40,000,000
Acquisition costs							$ 400,000
730 N. Glebe Road
Real Estate Properties [Line Items]
Payments to acquire real estate						$ 2,800,000
Acquisition costs						$ 40,400
726 N Glebe Road
Real Estate Properties [Line Items]
Payments to acquire real estate				$ 4,000,000							4,000,000
Acquisition costs				$ 100,000							100,000
Purchase price allocated to land											3,900,000
Purchase price allocated to buildings											$ 100,000
700 N. Glebe Road
Real Estate Properties [Line Items]
Payments to acquire real estate			$ 7,200,000
Purchase price allocated to land								7,236,000		7,236,000
Purchase price allocated to buildings								0		0
700 N. Glebe Road | In-place Leases
Real Estate Properties [Line Items]
Leasehold Interests								0		0
700 N. Glebe Road | Above Market Rent
Real Estate Properties [Line Items]
Leasehold Interests								0		0
700 N. Glebe Road | Below Market Rent
Real Estate Properties [Line Items]
Leasehold Interests								0		0
Westview Pad
Real Estate Properties [Line Items]
Payments to acquire real estate					$ 900,000
Area of real estate property (in square feet) | a					1.1
Thruway Pad
Real Estate Properties [Line Items]
Payments to acquire real estate			3,100,000
Acquisition costs			$ 60,400
Purchase price allocated to land								2,196,000		2,196,000
Purchase price allocated to buildings								874,000		874,000
Thruway Pad | In-place Leases
Real Estate Properties [Line Items]
Leasehold Interests								93,000		93,000
Thruway Pad | Above Market Rent
Real Estate Properties [Line Items]
Leasehold Interests								0		0
Thruway Pad | Below Market Rent
Real Estate Properties [Line Items]
Leasehold Interests								63,000		63,000
Beacon Center
Real Estate Properties [Line Items]
Payments to acquire real estate								22,700,000
Rent expense										60,000
Mortgage loans on real estate, period increase (decrease)								11,250,000
Southdale
Real Estate Properties [Line Items]
Payments to acquire real estate								15,300,000
Rent expense										60,000
Burtonsville Town Square
Real Estate Properties [Line Items]
Payments to acquire real estate		$ 76,400,000
Purchase price allocated to land									$ 28,400,000
Purchase price allocated to buildings									45,800,000
Burtonsville Town Square | In-place Leases
Real Estate Properties [Line Items]
Leasehold Interests									2,200,000
Burtonsville Town Square | Above Market Rent
Real Estate Properties [Line Items]
Leasehold Interests									600,000
Burtonsville Town Square | Below Market Rent
Real Estate Properties [Line Items]
Leasehold Interests									$ 600,000
2016 Acquisitions
Real Estate Properties [Line Items]
Payments to acquire real estate										10,300,000
Purchase price allocated to land								9,432,000		9,432,000
Purchase price allocated to buildings								874,000		874,000
2016 Acquisitions | In-place Leases
Real Estate Properties [Line Items]
Leasehold Interests								93,000		93,000
2016 Acquisitions | Above Market Rent
Real Estate Properties [Line Items]
Leasehold Interests								0		0
2016 Acquisitions | Below Market Rent
Real Estate Properties [Line Items]
Leasehold Interests								$ 63,000		$ 63,000
Olney
Real Estate Properties [Line Items]
Payments to acquire real estate	$ 3,100,000
Rent expense	$ 56,000

Real Estate Acquired - Allocati

Real Estate Acquired - Allocation of Purchase Prices to Acquired Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Real Estate Properties [Line Items]
Land	$ 450,256
Buildings	1,352,944
Total Purchase Price	$ 1,803,200	$ 1,700,813	$ 1,622,710	$ 1,560,159
700 N. Glebe Road
Real Estate Properties [Line Items]
Land		7,236
Buildings		0
Total Purchase Price		7,236
700 N. Glebe Road | In-place Leases
Real Estate Properties [Line Items]
Intangible assets		0
700 N. Glebe Road | Above Market Rent
Real Estate Properties [Line Items]
Intangible assets		0
700 N. Glebe Road | Below Market Rent
Real Estate Properties [Line Items]
Intangible assets		0
Thruway Pad
Real Estate Properties [Line Items]
Land		2,196
Buildings		874
Total Purchase Price		3,100
Thruway Pad | In-place Leases
Real Estate Properties [Line Items]
Intangible assets		93
Thruway Pad | Above Market Rent
Real Estate Properties [Line Items]
Intangible assets		0
Thruway Pad | Below Market Rent
Real Estate Properties [Line Items]
Intangible assets		63
2016 Acquisitions
Real Estate Properties [Line Items]
Land		9,432
Buildings		874
Total Purchase Price		10,336
2016 Acquisitions | In-place Leases
Real Estate Properties [Line Items]
Intangible assets		93
2016 Acquisitions | Above Market Rent
Real Estate Properties [Line Items]
Intangible assets		0
2016 Acquisitions | Below Market Rent
Real Estate Properties [Line Items]
Intangible assets		$ 63

Real Estate Acquired - Amortiza

Real Estate Acquired - Amortization of Intangible Assets and Deferred Income Related to in Place Leases (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Below market leases
2,018	$ 1,652
2,019	1,515
2,020	1,433
2,021	1,409
2,022	1,306
Thereafter	6,029
Total	13,344
Lease acquisition costs
Finite-Lived Intangible Assets [Line Items]
2,018	982
2,019	780
2,020	653
2,021	530
2,022	390
Thereafter	1,547
Total	4,882
Above market leases
Finite-Lived Intangible Assets [Line Items]
2,018	33
2,019	33
2,020	33
2,021	33
2,022	33
Thereafter	409
Total	$ 574

Noncontrolling Interests - Ho45

Noncontrolling Interests - Holders of Convertible Limited Partnership Units in Operating Partnership - Additional Information (Detail) - Noncontrolling Interests	12 Months Ended
	Dec. 31, 2017shares	Dec. 31, 2016shares	Dec. 31, 2015shares
Noncontrolling Interest [Line Items]
Percentage of ownership interest of noncontrolling interest	25.60%
Limited partnership units (in shares)	7,541,867
Limited partnership units, conversion ratio	1
Outstanding stock percent that should be acquired for rights to be exercised	39.90%
Limited partnership units convertible to shares of common stock, eligible for conversion (in partnership units)	740,000
Fully converted partnership units and diluted weighted average shares outstanding (in shares)	29,510,900	28,989,900	28,449,400

Mortgage Notes Payable, Revol46

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Additional Information (Detail) - USD ($)

Nov. 20, 2017

Aug. 14, 2017

Jan. 18, 2017

Apr. 01, 2015

Mar. 03, 2015

Sep. 30, 2017

Dec. 31, 2021

Dec. 31, 2017

Sep. 01, 2017

Dec. 31, 2016

Nov. 30, 2016

Dec. 31, 2015

Debt Instrument [Line Items]

Outstanding debt

$ 965,500,000

Fixed rate mortgages

897,888,000

$ 783,400,000

Principal amount

965,528,000

907,800,000

Debt outstanding with fixed-rate

844,300,000

Debt outstanding with variable-rate

63,500,000

Remaining loan balance

284,627,000

Capitalization of debt issuance cost

2,600,000

100,000

$ 300,000

3.69% Due March 2030 | Shops at Fairfax and Boulevard

Debt Instrument [Line Items]

Loan term

15 years

Loan amount

$ 30,000,000

Loan fixed interest rate

3.69%

Loan required periodic principal and interest payment

$ 153,300

Amortization schedule

25 years

Balloon payment to be paid

$ 15,500,000

3.99% Due April 2030 | Northrock

Debt Instrument [Line Items]

Loan term

15 years

Loan amount

$ 16,000,000

Loan fixed interest rate

3.99%

Mortgage Notes Payable

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

$ 51,000,000

51,000,000

Revolving Credit Facility | Line of Credit

Debt Instrument [Line Items]

Extension in line of credit facility period

1 year

Available borrowing capacity

$ 213,800,000

Outstanding line of credit

61,000,000

Letter of credit available borrowing capacity

$ 185,000

Interest rate spread on LIBOR

1.45%

Revolving Credit Facility | Line of Credit | Minimum

Debt Instrument [Line Items]

Interest rate spread on LIBOR

1.45%

Revolving Credit Facility | Line of Credit | Maximum

Debt Instrument [Line Items]

Interest rate spread on LIBOR

2.00%

Fixed rate mortgage notes payable

Debt Instrument [Line Items]

Fixed rate mortgages

$ 890,393,000

844,292,000

Fixed rate mortgage notes payable | Shops at Fairfax and Boulevard

Debt Instrument [Line Items]

Remaining loan balance

$ 15,200,000

Fixed rate mortgage notes payable | Northrock

Debt Instrument [Line Items]

Remaining loan balance

$ 14,500,000

Fixed rate mortgage notes payable | Washington Square

Debt Instrument [Line Items]

Remaining loan balance

$ 28,100,000

Fixed rate mortgage notes payable | 3.69% Due March 2030

Debt Instrument [Line Items]

Fixed rate mortgages

27,884,000

28,679,000

Fixed rate mortgage notes payable | 3.99% Due April 2030

Debt Instrument [Line Items]

Fixed rate mortgages

14,950,000

15,357,000

Fixed rate mortgage notes payable | 3.99% Due April 2030 | Northrock

Debt Instrument [Line Items]

Loan required periodic principal and interest payment

$ 84,400

Amortization schedule

25 years

Balloon payment to be paid

$ 8,400,000

Fixed rate mortgage notes payable | 3.51% due June 2028

Debt Instrument [Line Items]

Fixed rate mortgages

39,968,000

41,753,000

Fixed rate mortgage notes payable | 3.51% due June 2028 | Beacon Center

Debt Instrument [Line Items]

Loan amount

$ 11,250,000

Loan required periodic principal and interest payment

268,500

Fixed rate mortgage notes payable | 3.39% due January 2032

Debt Instrument [Line Items]

Fixed rate mortgages

39,140,000

0

Fixed rate mortgage notes payable | 4.88% due September 2032

Debt Instrument [Line Items]

Fixed rate mortgages

71,211,000

70,144,000

Fixed rate mortgage notes payable | 3.75% due December 2032

Debt Instrument [Line Items]

Fixed rate mortgages

60,000,000

0

Variable rate loans payable

Debt Instrument [Line Items]

Variable rate debt

$ 75,135,000

63,482,000

Interest rate spread on LIBOR

2.86%

Variable rate loans payable | Revolving Credit Facility | Line of Credit

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 275,000,000

Metro Pike Center Bank Loan | Fixed rate mortgage notes payable

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

7,800,000

Remaining loan balance

14,100,000

Kentlands Square II Bank Loan | Fixed rate mortgage notes payable

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

9,200,000

Remaining loan balance

36,500,000

Burtonsville Fixed Rate Mortgage | 3.39% due January 2032

Debt Instrument [Line Items]

Loan term

15 years

Loan amount

$ 40,000,000

Loan fixed interest rate

3.39%

Loan required periodic principal and interest payment

$ 197,900

Amortization schedule

25 years

Balloon payment to be paid

$ 20,300,000

Glebe Road Construction Loan | 4.67% Construction To Permanent Loan Due 2035

Debt Instrument [Line Items]

Loan amount

$ 157,000,000

Loan fixed interest rate

4.67%

Amortization schedule

25 years

Park Van Ness Loan | Fixed rate mortgage notes payable

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

53,700,000

Remaining loan balance

71,200,000

Park Van Ness Loan | 4.88% due September 2032

Debt Instrument [Line Items]

Fixed rate mortgages

$ 71,600,000

Loan fixed interest rate

4.88%

Loan required periodic principal and interest payment

$ 413,460

Amortization schedule

25 years

Balloon payment to be paid

$ 39,600,000

Washington Square 2017 Mortgage | 3.75% due December 2032

Debt Instrument [Line Items]

Loan term

15 years

Loan amount

$ 60,000,000

Loan fixed interest rate

3.75%

Loan required periodic principal and interest payment

$ 308,500

Amortization schedule

25 years

Balloon payment to be paid

$ 31,100,000

Debt Covenant

Debt Instrument [Line Items]

Carrying value of properties collateralized

$ 1,000,000,000

$ 957,200,000

Debt covenant, percentage of net proceeds of additional equity issuance

80.00%

Credit agreement leverage ratio

60.00%

Interest coverage ratio required minimum

2

Required fixed charge coverage ratio

1.3

Debt Covenant | Minimum

Debt Instrument [Line Items]

Debt covenant required net assets

$ 542,100,000

Scenario, Forecast | Glebe Road Construction Loan | 4.67% Construction To Permanent Loan Due 2035

Debt Instrument [Line Items]

Loan required periodic principal and interest payment

$ 887,900

Mortgage Notes Payable, Revol47

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, 2017	Dec. 31, 2016
Notes Payable [Line Items]
Fixed rate mortgages	$ 897,888	$ 783,400
Interest rate	3.90%	4.25%
Scheduled maturity period	7 years 11 months 6 days
Total notes payable	$ 965,528	$ 907,774
Interest rate during period	5.07%
Fixed rate mortgage notes payable
Notes Payable [Line Items]
Fixed rate mortgages	$ 890,393	844,292
Interest rate	5.25%
Scheduled maturity period	8 years 6 months 26 days
Fixed rate mortgage notes payable | 6.01% due February 2018
Notes Payable [Line Items]
Fixed rate mortgages	$ 0	29,428
Interest rate	6.01%
Fixed rate mortgage notes payable | 5.88% due January 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 30,201	32,036
Interest rate	5.88%
Fixed rate mortgage notes payable | 5.76% due May 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 9,783	10,372
Interest rate	5.76%
Fixed rate mortgage notes payable | 5.62% due July 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 13,529	14,335
Interest rate	5.62%
Fixed rate mortgage notes payable | 5.79% due September 2019
Notes Payable [Line Items]
Fixed rate mortgages	$ 13,543	14,325
Interest rate	5.79%
Fixed rate mortgage notes payable | 5.22% due January 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 12,029	12,725
Interest rate	5.22%
Fixed rate mortgage notes payable | 5.60% due May 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 9,948	10,277
Interest rate	5.60%
Fixed rate mortgage notes payable | 5.30% due June 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 8,244	8,697
Interest rate	5.30%
Fixed rate mortgage notes payable | 5.83% due July 2020
Notes Payable [Line Items]
Fixed rate mortgages	$ 37,998	39,213
Interest rate	5.83%
Fixed rate mortgage notes payable | 5.81% due February 2021
Notes Payable [Line Items]
Fixed rate mortgages	$ 7,325	7,685
Interest rate	5.81%
Fixed rate mortgage notes payable | 6.01% due August 2021
Notes Payable [Line Items]
Fixed rate mortgages	$ 5,649	5,808
Interest rate	6.01%
Fixed rate mortgage notes payable | 5.62% due June 2022
Notes Payable [Line Items]
Fixed rate mortgages	$ 32,673	33,571
Interest rate	5.62%
Fixed rate mortgage notes payable | 6.08% due September 2022
Notes Payable [Line Items]
Fixed rate mortgages	$ 9,999	10,253
Interest rate	6.08%
Fixed rate mortgage notes payable | 6.43% due April 2023
Notes Payable [Line Items]
Fixed rate mortgages	$ 10,877	11,129
Interest rate	6.43%
Fixed rate mortgage notes payable | 6.28% due February 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 12,577	13,401
Interest rate	6.28%
Fixed rate mortgage notes payable | 7.35% due June 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 15,452	15,917
Interest rate	7.35%
Fixed rate mortgage notes payable | 7.60% due June 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 13,438	13,832
Interest rate	7.60%
Fixed rate mortgage notes payable | 7.02% due July 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 23,873	24,504
Interest rate	7.02%
Fixed rate mortgage notes payable | 7.45% due July 2024
Notes Payable [Line Items]
Fixed rate mortgages	$ 28,115	28,945
Interest rate	7.45%
Fixed rate mortgage notes payable | 7.30% due January 2025
Notes Payable [Line Items]
Fixed rate mortgages	$ 28,025	28,822
Interest rate	7.30%
Fixed rate mortgage notes payable | 6.18% due January 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 14,537	14,961
Interest rate	6.18%
Fixed rate mortgage notes payable | 5.31% due April 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 105,817	109,144
Interest rate	5.31%
Fixed rate mortgage notes payable | 4.30% due October 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 32,016	33,097
Interest rate	4.30%
Fixed rate mortgage notes payable | 4.53% due November 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 36,507	37,701
Interest rate	4.53%
Fixed rate mortgage notes payable | 4.70% due December 2026
Notes Payable [Line Items]
Fixed rate mortgages	$ 17,086	17,630
Interest rate	4.70%
Fixed rate mortgage notes payable | 5.84% due May 2027
Notes Payable [Line Items]
Fixed rate mortgages	$ 64,472	66,210
Interest rate	5.84%
Fixed rate mortgage notes payable | 4.04% due April 2028
Notes Payable [Line Items]
Fixed rate mortgages	$ 15,859	16,352
Interest rate	4.04%
Fixed rate mortgage notes payable | 3.51% due June 2028
Notes Payable [Line Items]
Fixed rate mortgages	$ 39,968	41,753
Interest rate	3.51%
Fixed rate mortgage notes payable | 3.99% due September 2028
Notes Payable [Line Items]
Fixed rate mortgages	$ 16,055	16,543
Interest rate	3.99%
Fixed rate mortgage notes payable | 3.69% Due March 2030
Notes Payable [Line Items]
Fixed rate mortgages	$ 27,884	28,679
Interest rate	3.69%
Fixed rate mortgage notes payable | 3.99% Due April 2030
Notes Payable [Line Items]
Fixed rate mortgages	$ 14,950	15,357
Interest rate	3.99%
Fixed rate mortgage notes payable | 3.39% due January 2032
Notes Payable [Line Items]
Fixed rate mortgages	$ 39,140	0
Interest rate	3.39%
Fixed rate mortgage notes payable | 4.88% due September 2032
Notes Payable [Line Items]
Fixed rate mortgages	$ 71,211	70,144
Interest rate	4.88%
Fixed rate mortgage notes payable | 3.75% due December 2032
Notes Payable [Line Items]
Fixed rate mortgages	$ 60,000	0
Interest rate	3.75%
Fixed rate mortgage notes payable | 8.00% due April 2034
Notes Payable [Line Items]
Fixed rate mortgages	$ 11,613	11,446
Interest rate	8.00%
Variable rate loans payable
Notes Payable [Line Items]
Variable rate debt	$ 75,135	63,482
Interest rate spread on LIBOR	2.86%
Scheduled maturity period	4 months 8 days
Variable rate loans payable | Revolving credit facility
Notes Payable [Line Items]
Variable rate debt	$ 61,000	49,000
Interest rate spread on LIBOR	1.45%
Variable rate loans payable | Metro Pike Center Bank Loan
Notes Payable [Line Items]
Variable rate debt	$ 14,135	$ 14,482
Interest rate spread on LIBOR	1.65%

Mortgage Notes Payable, Revol48

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Summary of Notes Payable (Additional Information) (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)noteshopping_center	Dec. 31, 2016	Dec. 31, 2012USD ($)
Notes Payable [Line Items]
Interest rate	3.90%	4.25%
Fixed rate mortgage notes payable
Notes Payable [Line Items]
Interest rate	5.25%
Fixed rate mortgage notes payable | 6.01% due February 2018
Notes Payable [Line Items]
Interest rate	6.01%
Fixed rate mortgage notes payable | 6.01% due February 2018 | Washington Square
Notes Payable [Line Items]
Principal and interest payments	$ 264,000
Balloon payment to be paid	$ 28,000,000
Amortization period	27 years 6 months
Loan amount	$ 60,000,000
Fixed rate mortgage notes payable | 5.88% due January 2019
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 28,400,000
Amortization period	25 years
Number of shopping centers | shopping_center	3
Amortization of principal	$ 1,800,000
Fixed rate mortgage notes payable | 5.76% due May 2019
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 9,000,000
Amortization period	25 years
Amortization of principal	$ 589,000
Fixed rate mortgage notes payable | 5.62% due July 2019
Notes Payable [Line Items]
Interest rate	5.62%
Fixed rate mortgage notes payable | 5.62% due July 2019 | Countryside
Notes Payable [Line Items]
Principal and interest payments	$ 133,000
Balloon payment to be paid	$ 12,300,000
Amortization period	25 years
Amortization of principal	$ 806,000
Fixed rate mortgage notes payable | 5.79% due September 2019
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 12,200,000
Amortization period	25 years
Amortization of principal	$ 782,000
Fixed rate mortgage notes payable | 5.22% due January 2020
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 10,600,000
Amortization period	25 years
Amortization of principal	$ 696,000
Fixed rate mortgage notes payable | 5.60% due May 2020
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 9,100,000
Amortization period	30 years
Amortization of principal	$ 329,000
Fixed rate mortgage notes payable | 5.30% due June 2020
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 7,100,000
Amortization period	25 years
Amortization of principal	$ 453,000
Fixed rate mortgage notes payable | 5.83% due July 2020
Notes Payable [Line Items]
Interest rate	5.83%
Fixed rate mortgage notes payable | 5.83% due July 2020 | Thruway
Notes Payable [Line Items]
Principal and interest payments	$ 289,000
Balloon payment to be paid	$ 34,800,000
Amortization period	25 years
Amortization of principal	$ 1,200,000
Fixed rate mortgage notes payable | 5.81% due February 2021
Notes Payable [Line Items]
Interest rate	5.81%
Fixed rate mortgage notes payable | 5.81% due February 2021 | Jamestown Place
Notes Payable [Line Items]
Principal and interest payments	$ 66,000
Balloon payment to be paid	$ 6,100,000
Amortization period	25 years
Amortization of principal	$ 360,000
Fixed rate mortgage notes payable | 6.01% due August 2021
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 5,000,000
Amortization period	30 years
Amortization of principal	$ 159,000
Fixed rate mortgage notes payable | 5.62% due June 2022
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 28,200,000
Amortization period	30 years
Amortization of principal	$ 898,000
Fixed rate mortgage notes payable | 6.08% due September 2022
Notes Payable [Line Items]
Interest rate	6.08%
Fixed rate mortgage notes payable | 6.08% due September 2022 | Orchard Park
Notes Payable [Line Items]
Principal and interest payments	$ 73,000
Balloon payment to be paid	$ 8,600,000
Amortization period	30 years
Amortization of principal	$ 254,000
Fixed rate mortgage notes payable | 6.43% due April 2023
Notes Payable [Line Items]
Interest rate	6.43%
Fixed rate mortgage notes payable | 6.43% due April 2023 | BJs Wholesale
Notes Payable [Line Items]
Principal and interest payments	$ 80,000
Balloon payment to be paid	$ 9,300,000
Amortization period	30 years
Amortization of principal	$ 252,000
Fixed rate mortgage notes payable | 6.28% due February 2024
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 6,300,000
Amortization period	26 years
Amortization of principal	$ 824,000
Number of notes | note	3
Fixed rate mortgage notes payable | 7.35% due June 2024
Notes Payable [Line Items]
Interest rate	7.35%
Fixed rate mortgage notes payable | 7.35% due June 2024 | Leesburg Pike
Notes Payable [Line Items]
Principal and interest payments	$ 135,000
Balloon payment to be paid	$ 11,500,000
Amortization period	25 years
Amortization of principal	$ 465,000
Fixed rate mortgage notes payable | 7.60% due June 2024
Notes Payable [Line Items]
Interest rate	7.60%
Fixed rate mortgage notes payable | 7.60% due June 2024 | Village Center
Notes Payable [Line Items]
Principal and interest payments	$ 119,000
Balloon payment to be paid	$ 10,100,000
Amortization period	25 years
Amortization of principal	$ 394,000
Fixed rate mortgage notes payable | 7.02% due July 2024
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 18,500,000
Amortization period	24 years 4 months 24 days
Loan amount			$ 10,500,000
Amortization of principal	$ 631,000
Fixed rate mortgage notes payable | 7.45% due July 2024
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 20,900,000
Amortization period	25 years
Amortization of principal	$ 830,000
Fixed rate mortgage notes payable | 7.30% due January 2025
Notes Payable [Line Items]
Interest rate	7.30%
Fixed rate mortgage notes payable | 7.30% due January 2025 | Ashburn Village
Notes Payable [Line Items]
Principal and interest payments	$ 240,000
Balloon payment to be paid	$ 20,500,000
Amortization period	25 years
Amortization of principal	$ 797,000
Fixed rate mortgage notes payable | 6.18% due January 2026
Notes Payable [Line Items]
Interest rate	6.18%
Fixed rate mortgage notes payable | 6.18% due January 2026 | Ravenwood
Notes Payable [Line Items]
Principal and interest payments	$ 111,000
Balloon payment to be paid	$ 10,100,000
Amortization period	25 years
Amortization of principal	$ 424,000
Fixed rate mortgage notes payable | 5.31% due April 2026
Notes Payable [Line Items]
Interest rate	5.31%
Fixed rate mortgage notes payable | 5.31% due April 2026 | Clarendon Center
Notes Payable [Line Items]
Principal and interest payments	$ 753,000
Balloon payment to be paid	$ 70,500,000
Amortization period	25 years
Amortization of principal	$ 3,300,000
Fixed rate mortgage notes payable | 4.30% due October 2026
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 20,300,000
Amortization period	25 years
Amortization of principal	$ 1,100,000
Fixed rate mortgage notes payable | 4.53% due November 2026
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 23,100,000
Amortization period	25 years
Amortization of principal	$ 1,200,000
Fixed rate mortgage notes payable | 4.70% due December 2026
Notes Payable [Line Items]
Interest rate	4.70%
Fixed rate mortgage notes payable | 4.70% due December 2026 | Cranberry Square
Notes Payable [Line Items]
Principal and interest payments	$ 113,000
Balloon payment to be paid	$ 10,900,000
Amortization period	25 years
Amortization of principal	$ 544,000
Fixed rate mortgage notes payable | 5.84% due May 2027
Notes Payable [Line Items]
Interest rate	5.84%
Fixed rate mortgage notes payable | 5.84% due May 2027 | Seven Corners
Notes Payable [Line Items]
Principal and interest payments	$ 463,200
Balloon payment to be paid	$ 42,300,000
Amortization period	25 years
Loan amount	$ 73,000,000
Amortization of principal	$ 1,700,000
Fixed rate mortgage notes payable | 4.04% due April 2028
Notes Payable [Line Items]
Interest rate	4.04%
Fixed rate mortgage notes payable | 4.04% due April 2028 | Hampshire Langley
Notes Payable [Line Items]
Principal and interest payments	$ 95,400
Balloon payment to be paid	$ 9,500,000
Amortization period	25 years
Amortization of principal	$ 493,000
Fixed rate mortgage notes payable | 3.51% due June 2028
Notes Payable [Line Items]
Interest rate	3.51%
Fixed rate mortgage notes payable | 3.51% due June 2028 | Beacon Center
Notes Payable [Line Items]
Balloon payment to be paid	$ 17,100,000
Amortization period	20 years
Amortization of principal	$ 1,800,000
Fixed rate mortgage notes payable | 3.99% due September 2028
Notes Payable [Line Items]
Interest rate	3.99%
Fixed rate mortgage notes payable | 3.99% due September 2028 | Seabreeze Plaza
Notes Payable [Line Items]
Principal and interest payments	$ 94,900
Balloon payment to be paid	$ 9,500,000
Amortization period	25 years
Amortization of principal	$ 488,000
Fixed rate mortgage notes payable | 3.69% Due March 2030
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 15,500,000
Amortization period	25 years
Amortization of principal	$ 795,000
Fixed rate mortgage notes payable | 3.99% Due April 2030
Notes Payable [Line Items]
Interest rate	3.99%
Fixed rate mortgage notes payable | 3.99% Due April 2030 | Northrock
Notes Payable [Line Items]
Principal and interest payments	$ 84,400
Balloon payment to be paid	$ 8,400,000
Amortization period	25 years
Amortization of principal	$ 407,000
Fixed rate mortgage notes payable | 3.39% due January 2032
Notes Payable [Line Items]
Interest rate	3.39%
Fixed rate mortgage notes payable | 3.39% due January 2032 | Burtonsville Town Square
Notes Payable [Line Items]
Principal and interest payments	$ 198,000
Balloon payment to be paid	$ 20,300,000
Amortization period	25 years
Amortization of principal	$ 860,000
Fixed rate mortgage notes payable | 4.88% due September 2032
Notes Payable [Line Items]
Interest rate	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
Balloon payment to be paid	$ 39,600,000
Amortization period	25 years
Amortization of principal	$ 369,000
Fixed rate mortgage notes payable | 3.75% due December 2032
Notes Payable [Line Items]
Interest rate	3.75%
Fixed rate mortgage notes payable | 3.75% due December 2032 | Washington Square
Notes Payable [Line Items]
Principal and interest payments	$ 308,000
Balloon payment to be paid	$ 31,100,000
Amortization period	25 years
Fixed rate mortgage notes payable | 8.00% due April 2034
Notes Payable [Line Items]
Interest rate	8.00%
Fixed rate mortgage notes payable | 8.00% due April 2034 | Olney
Notes Payable [Line Items]
Principal and interest payments	$ 60,400
Balloon payment to be paid	$ 14,700,000
Fixed rate increase on note	1.50%
Interest rate	8.00%
Negative amortization	$ (167,000)
Variable rate loans payable
Notes Payable [Line Items]
Interest rate spread on LIBOR	2.86%
Variable rate loans payable | Revolving credit facility
Notes Payable [Line Items]
Debt maturity extension period	1 year
Debt instrument fee	0.15%
Interest rate spread on LIBOR	1.45%
Variable rate loans payable | Metro Pike Center Bank Loan
Notes Payable [Line Items]
Interest rate spread on LIBOR	1.65%
Variable rate loans payable | Metro Pike Center Bank Loan | Metro Pike Center
Notes Payable [Line Items]
Principal and interest payments	$ 48,000
Balloon payment to be paid	14,200,000
Amortization of principal	$ 347,000

Mortgage Notes Payable, Revol49

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Scheduled Maturities of All Debt, Including Scheduled Principal Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Balloon Payments
2,018	$ 75,105
2,019	60,793
2,020	61,163
2,021	11,012
2,022	36,503
Thereafter	436,325
Balloon Payments	680,901
Scheduled Principal Amortization
2,018	30,160
2,019	29,272
2,020	26,743
2,021	26,456
2,022	26,958
Thereafter	145,038
Scheduled Principal Amortization	284,627
Total
2,018	105,265
2,019	90,065
2,020	87,906
2,021	37,468
2,022	63,461
Thereafter	581,363
Principal amount	965,528	$ 907,800
Unamortized deferred debt costs	6,906	$ 7,500
Net	$ 958,622

Mortgage Notes Payable, Revol50

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs - Interest Expense and Amortization of Deferred Debt Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Interest incurred	$ 49,322	$ 46,867	$ 45,898
Amortization of deferred debt costs	1,392	1,343	1,433
Capitalized interest	(3,489)	(2,527)	(2,166)
Total	$ 47,225	$ 45,683	$ 45,165

Lease Agreements - Additional I

Lease Agreements - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Abstract]
Base rent (including straight-line rent)	$ 181,141	$ 172,381	$ 168,303
Expense recoveries	35,347	34,269	32,911
Percentage rent	$ 1,458	$ 1,379	$ 1,608

Lease Agreements - Future Contr

Lease Agreements - Future Contractual Payments Under Noncancelable Leases (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 160,025
2,019	141,097
2,020	120,369
2,021	100,766
2,022	77,312
Thereafter	245,103
Total future contractual payments	$ 844,672

Long Term Lease Obligations - A

Long Term Lease Obligations - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)property	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Leases Disclosure [Line Items]
Number of properties subject to noncancelable long-term lease | property	0
Minimum rental obligations	$ 10,500	$ 159,000	$ 176,000
Rent expense	$ 774,700	$ 843,300	$ 904,900
90-year Ground Leasehold Interest
Leases Disclosure [Line Items]
Ground leasehold interest period	90 years
Minimum annual lease rent over lease term	$ 1
99-year Ground Lease
Leases Disclosure [Line Items]
Ground leasehold interest period	99 years
Minimum annual lease rent over lease term	$ 1
Percent of underlying land held under a 99-year ground lease	3.40%
Flagship Center
Leases Disclosure [Line Items]
Number of developed parcels | property	2

Equity and Noncontrolling Int54

Equity and Noncontrolling Interest - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	Feb. 12, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Income attributable to noncontrolling interests		$ 12,411	$ 11,441	$ 10,463
Depositary shares outstanding (in shares)		7.2
Series C Preferred Stock
Class of Stock [Line Items]
Depository shares to cumulative redeemable preferred stock ratio		1.00%
Dividend rate on preferred stock		6.875%
Liquidation preference (in usd per share)	$ 25
Annual dividend on depositary shares (in usd per share)	$ 1.71875
Percentage of redeemable preferred stock	6.875%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail)	Dec. 08, 2016	Aug. 31, 2016USD ($)a	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Related Party Transactions [Abstract]
Company contribution to a multi employer 401K plan at discretionary amount of employee's cash compensation, maximum percentage			6.00%
Company contribution to a multi employer 401K plan at discretionary amount of employee's cash compensation, amount			$ 349,500	$ 329,000	$ 400,000
Deferred compensation, employee contribution, percentage			2.00%
Deferred compensation, employer contribution, percentage			3	3	3
Deferred compensation, company contribution, amount			$ 228,500	$ 250,800	$ 224,900
Deferred compensation, cumulative unfunded liability			2,400,000	2,100,000
Ancillary costs and expenses			8,100,000	7,200,000	8,200,000
Liability due to the Saul Organization for the company's share of these ancillary costs and expenses			993,200	829,000
Automatic renewal period	12 months
Insurance commissions and fees expense			$ 288,400	$ 360,500	$ 443,500
Initial purchase price		$ 8,800,000
Area of real estate property (in square feet) | a		14.3

Stock Option Plan - Additional

Stock Option Plan - Additional Information (Detail)

May 05, 2017USD ($)person$ / sharesshares

May 06, 2016USD ($)person$ / sharesshares

May 08, 2015USD ($)person$ / sharesshares

May 09, 2014USD ($)person$ / sharesshares

May 10, 2013USD ($)person$ / sharesshares

May 04, 2012USD ($)person$ / sharesshares

May 13, 2011USD ($)person$ / sharesshares

May 07, 2010USD ($)person$ / sharesshares

Apr. 24, 2009USD ($)person$ / sharesshares

Apr. 25, 2008USD ($)person$ / sharesshares

Dec. 31, 2017USD ($)$ / shares

Dec. 31, 2016$ / shares

Dec. 31, 2015$ / shares

Dec. 31, 2004shares

Dec. 31, 1993shares

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 59.41

$ 57.74

$ 51.07

Fair value stock option grant | $

$ 11,831,000

the 1993 Plan | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Authorized shares for a grant (in shares)

400,000

Amended 2004 Plan | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Authorized shares for a grant (in shares)

2,000,000

Amended 2004 Plan | Stock options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Authorized shares for a grant (in shares)

200,000

2008 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 50.15

Fair value stock option grant | $

$ 254,700

2008 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

12

2008 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

0

2008 Options | Stock options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

30,000

2009 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 32.68

Fair value stock option grant | $

$ 222,950

2009 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

13

2009 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

0

2009 Options | Stock options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

32,500

2010 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 38.76

Fair value stock option grant | $

$ 287,950

2010 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

13

2010 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

0

2010 Options | Stock options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

32,500

2011 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 41.82

Fair value stock option grant | $

$ 1,600,000

2011 Options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

15

Fair value stock option grant | $

$ 1,300,000

Options vested

25.00%

2011 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

13

Fair value stock option grant | $

$ 297,375

2011 Options | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

195,000

2011 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Option vesting period

4 years

2011 Options | Incentive stock option

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

65,300

2011 Options | Nonqualified stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

129,700

2012 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 39.29

Fair value stock option grant | $

$ 1,700,000

2012 Options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

15

Fair value stock option grant | $

$ 1,400,000

Options vested

25.00%

2012 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

14

Fair value stock option grant | $

$ 257,250

2012 Options | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

277,500

2012 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Option vesting period

4 years

2012 Options | Incentive stock option

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

26,157

2012 Options | Nonqualified stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

251,343

2013 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

15

Exercise price of options (in usd per share) | $ / shares

$ 44.42

Fair value stock option grant | $

$ 1,500,000

2013 Options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Fair value stock option grant | $

$ 1,200,000

Options vested

25.00%

2013 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

14

Fair value stock option grant | $

$ 278,250

2013 Options | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

237,500

2013 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Option vesting period

4 years

2013 Options | Incentive stock option

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

35,592

2013 Options | Nonqualified stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

201,908

2014 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 47.03

Fair value stock option grant | $

$ 1,300,000

2014 Options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

18

Fair value stock option grant | $

$ 1,200,000

Options vested

25.00%

2014 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

12

Fair value stock option grant | $

$ 109,500

2014 Options | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

200,000

2014 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Option vesting period

4 years

2014 Options | Incentive stock option

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

29,300

2014 Options | Nonqualified stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

170,700

2015 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 51.07

Fair value stock option grant | $

$ 1,570,000

2015 Options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

19

Fair value stock option grant | $

$ 1,440,000

Options vested

25.00%

2015 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

14

Fair value stock option grant | $

$ 125,300

2015 Options | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

225,000

2015 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Option vesting period

4 years

2015 Options | Incentive stock option

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

33,690

2015 Options | Nonqualified stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

191,310

2016 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 57.74

Fair value stock option grant | $

$ 1,200,000

2016 Options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

19

Fair value stock option grant | $

$ 1,000,000

Options vested

25.00%

2016 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

13

Fair value stock option grant | $

$ 151,125

2016 Options | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

226,500

2016 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Option vesting period

4 years

2016 Options | Incentive stock option

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

24,248

2016 Options | Nonqualified stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

202,252

2017 Options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Exercise price of options (in usd per share) | $ / shares

$ 59.41

Fair value stock option grant | $

$ 1,400,000

2017 Options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

20

Fair value stock option grant | $

$ 1,200,000

Options vested

25.00%

2017 Options | Director

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Number of individuals granted options | person

11

Fair value stock option grant | $

$ 165,550

2017 Options | Stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

232,500

2017 Options | Stock options | Officer

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Option vesting period

4 years

2017 Options | Incentive stock option

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

21,492

2017 Options | Nonqualified stock options

Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]

Options granted to purchase stocks (in shares)

211,008

Stock Option Plan - Stock Optio

Stock Option Plan - Stock Options Issued (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	1,689,000
Vested (in shares)	990,375
Exercised (in shares)	546,930
Forfeited (in shares)	228,750
Exercisable at December 31 (in shares)	430,945	375,255	435,899
Remaining unexercised (in shares)	913,320
Exercise price (in usd per share) | $ / shares	$ 46.97	$ 45.59	$ 43.67
Total value at grant date | $	$ 11,831,000
Estimated forfeitures | $	1,914,000
Expensed in previous years | $	3,726,000
Allocated share based compensation | $	1,448,000	$ 1,348,000	$ 1,176,000
Future expense | $	2,219,000
Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation | $	$ 130,700	150,100	143,000
Directors | 4/25/2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	30,000
Vested (in shares)	30,000
Exercised (in shares)	20,000
Forfeited (in shares)	7,500
Exercisable at December 31 (in shares)	2,500
Remaining unexercised (in shares)	2,500
Exercise price (in usd per share) | $ / shares	$ 50.15
Volatility	0.237
Expected life (years)	7 years
Assumed yield	4.09%
Risk-free rate	3.49%
Total value at grant date | $	$ 255,000
Expensed in previous years | $	255,000
Allocated share based compensation | $	0	0	0
Future expense | $	$ 0
Directors | 4/24/2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	32,500
Vested (in shares)	32,500
Exercised (in shares)	27,500
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	5,000
Remaining unexercised (in shares)	5,000
Exercise price (in usd per share) | $ / shares	$ 32.68
Volatility	0.344
Expected life (years)	6 years
Assumed yield	4.54%
Risk-free rate	2.19%
Total value at grant date | $	$ 223,000
Expensed in previous years | $	223,000
Allocated share based compensation | $	0	0	0
Future expense | $	$ 0
Directors | 5/7/2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	32,500
Vested (in shares)	32,500
Exercised (in shares)	25,000
Forfeited (in shares)	2,500
Exercisable at December 31 (in shares)	5,000
Remaining unexercised (in shares)	5,000
Exercise price (in usd per share) | $ / shares	$ 38.76
Volatility	0.369
Expected life (years)	5 years
Assumed yield	4.23%
Risk-free rate	2.17%
Total value at grant date | $	$ 288,000
Expensed in previous years | $	288,000
Allocated share based compensation | $	0	0	0
Future expense | $	$ 0
Directors | 5/13/2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	32,500
Vested (in shares)	32,500
Exercised (in shares)	22,500
Forfeited (in shares)	2,500
Exercisable at December 31 (in shares)	7,500
Remaining unexercised (in shares)	7,500
Exercise price (in usd per share) | $ / shares	$ 41.82
Volatility	0.358
Expected life (years)	5 years
Assumed yield	4.16%
Risk-free rate	1.86%
Total value at grant date | $	$ 297,000
Expensed in previous years | $	297,000
Allocated share based compensation | $	0	0	0
Future expense | $	$ 0
Directors | 5/4/2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	35,000
Vested (in shares)	35,000
Exercised (in shares)	22,500
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	12,500
Remaining unexercised (in shares)	12,500
Exercise price (in usd per share) | $ / shares	$ 39.29
Volatility	0.348
Expected life (years)	5 years
Assumed yield	4.61%
Risk-free rate	0.78%
Total value at grant date | $	$ 257,000
Expensed in previous years | $	257,000
Allocated share based compensation | $	0	0	0
Future expense | $	$ 0
Directors | 5/10/2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	35,000
Vested (in shares)	35,000
Exercised (in shares)	22,500
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	12,500
Remaining unexercised (in shares)	12,500
Exercise price (in usd per share) | $ / shares	$ 44.42
Volatility	0.333
Expected life (years)	5 years
Assumed yield	4.53%
Risk-free rate	0.82%
Total value at grant date | $	$ 278,000
Expensed in previous years | $	278,000
Allocated share based compensation | $	0	0	0
Future expense | $	$ 0
Directors | 5/9/2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	30,000
Vested (in shares)	30,000
Exercised (in shares)	17,500
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	12,500
Remaining unexercised (in shares)	12,500
Exercise price (in usd per share) | $ / shares	$ 47.03
Volatility	0.173
Expected life (years)	5 years
Assumed yield	4.48%
Risk-free rate	1.63%
Total value at grant date | $	$ 110,000
Expensed in previous years | $	110,000
Allocated share based compensation | $	0	0	0
Future expense | $	$ 0
Directors | 5/8/2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	35,000
Vested (in shares)	35,000
Exercised (in shares)	12,500
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	22,500
Remaining unexercised (in shares)	22,500
Exercise price (in usd per share) | $ / shares	$ 51.07
Volatility	0.166
Expected life (years)	5 years
Assumed yield	4.54%
Risk-free rate	1.50%
Total value at grant date | $	$ 125,000
Expensed in previous years | $	0
Allocated share based compensation | $	0	0	125,000
Future expense | $	$ 0
Directors | 5/6/2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	32,500
Vested (in shares)	32,500
Exercised (in shares)	7,500
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	25,000
Remaining unexercised (in shares)	25,000
Exercise price (in usd per share) | $ / shares	$ 57.74
Volatility	0.166
Expected life (years)	5 years
Assumed yield	3.75%
Risk-free rate	1.23%
Total value at grant date | $	$ 151,000
Expensed in previous years | $	0
Allocated share based compensation | $	0	151,000	0
Future expense | $	$ 0
Directors | 5/5/2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	27,500
Vested (in shares)	27,500
Exercised (in shares)	0
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	27,500
Remaining unexercised (in shares)	27,500
Exercise price (in usd per share) | $ / shares	$ 59.41
Volatility	0.173
Expected life (years)	5 years
Assumed yield	3.45%
Risk-free rate	1.89%
Total value at grant date | $	$ 166,000
Expensed in previous years | $	0
Allocated share based compensation | $	166,000	0	0
Future expense | $	$ 0
Directors | Subtotals
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	322,500
Vested (in shares)	322,500
Exercised (in shares)	177,500
Forfeited (in shares)	12,500
Exercisable at December 31 (in shares)	132,500
Remaining unexercised (in shares)	132,500
Total value at grant date | $	$ 2,150,000
Expensed in previous years | $	1,708,000
Allocated share based compensation | $	166,000	151,000	125,000
Future expense | $	$ 0
Officers | 5/13/2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	162,500
Vested (in shares)	118,750
Exercised (in shares)	96,100
Forfeited (in shares)	43,750
Exercisable at December 31 (in shares)	22,650
Remaining unexercised (in shares)	22,650
Exercise price (in usd per share) | $ / shares	$ 41.82
Volatility	0.330
Expected life (years)	8 years
Assumed yield	4.81%
Risk-free rate	2.75%
Total value at grant date | $	$ 1,366,000
Estimated forfeitures | $	368,000
Expensed in previous years | $	909,000
Allocated share based compensation | $	0	0	89,000
Future expense | $	$ 0
Weighted average term of remaining future expense	2 years 5 months 27 days
Officers | 5/4/2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	242,500
Vested (in shares)	107,500
Exercised (in shares)	91,830
Forfeited (in shares)	135,000
Exercisable at December 31 (in shares)	15,670
Remaining unexercised (in shares)	15,670
Exercise price (in usd per share) | $ / shares	$ 39.29
Volatility	0.315
Expected life (years)	8 years
Assumed yield	5.28%
Risk-free rate	1.49%
Total value at grant date | $	$ 1,518,000
Estimated forfeitures | $	845,000
Expensed in previous years | $	419,000
Allocated share based compensation | $	0	97,000	157,000
Future expense | $	$ 0
Officers | 5/10/2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	202,500
Vested (in shares)	171,875
Exercised (in shares)	116,500
Forfeited (in shares)	30,625
Exercisable at December 31 (in shares)	55,375
Remaining unexercised (in shares)	55,375
Exercise price (in usd per share) | $ / shares	$ 44.42
Volatility	0.304
Expected life (years)	8 years
Assumed yield	5.12%
Risk-free rate	1.49%
Total value at grant date | $	$ 1,401,000
Estimated forfeitures | $	212,000
Expensed in previous years | $	493,000
Allocated share based compensation | $	158,000	269,000	269,000
Future expense | $	$ 0
Officers | 5/9/2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	170,000
Vested (in shares)	126,875
Exercised (in shares)	41,250
Forfeited (in shares)	1,875
Exercisable at December 31 (in shares)	85,625
Remaining unexercised (in shares)	126,875
Exercise price (in usd per share) | $ / shares	$ 47.03
Volatility	0.306
Expected life (years)	7 years
Assumed yield	4.89%
Risk-free rate	2.17%
Total value at grant date | $	$ 1,350,000
Estimated forfeitures | $	169,000
Expensed in previous years | $	197,000
Allocated share based compensation | $	295,000	295,000	296,000
Future expense | $	$ 98,000
Officers | 5/8/2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	190,000
Vested (in shares)	94,375
Exercised (in shares)	20,000
Forfeited (in shares)	3,125
Exercisable at December 31 (in shares)	74,375
Remaining unexercised (in shares)	166,875
Exercise price (in usd per share) | $ / shares	$ 51.07
Volatility	0.298
Expected life (years)	7 years
Assumed yield	4.94%
Risk-free rate	1.89%
Total value at grant date | $	$ 1,585,000
Estimated forfeitures | $	142,000
Expensed in previous years | $	0
Allocated share based compensation | $	361,000	361,000		$ 240,000
Future expense | $	$ 481,000
Officers | 5/6/2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	194,000
Vested (in shares)	48,500
Exercised (in shares)	3,750
Forfeited (in shares)	1,875
Exercisable at December 31 (in shares)	44,750
Remaining unexercised (in shares)	188,375
Exercise price (in usd per share) | $ / shares	$ 57.74
Volatility	0.185
Expected life (years)	7 years
Assumed yield	3.80%
Risk-free rate	1.55%
Total value at grant date | $	$ 1,137,000
Estimated forfeitures | $	86,000
Expensed in previous years | $	0
Allocated share based compensation | $	263,000	175,000	0
Future expense | $	$ 613,000
Officers | 5/5/2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	205,000
Vested (in shares)	0
Exercised (in shares)	0
Forfeited (in shares)	0
Exercisable at December 31 (in shares)	0
Remaining unexercised (in shares)	205,000
Exercise price (in usd per share) | $ / shares	$ 59.41
Volatility	0.170
Expected life (years)	7 years
Assumed yield	3.50%
Risk-free rate	2.17%
Total value at grant date | $	$ 1,324,000
Estimated forfeitures | $	92,000
Expensed in previous years | $	0
Allocated share based compensation | $	205,000	0	0
Future expense | $	$ 1,027,000
Officers | Subtotals
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant (in shares)	1,366,500
Vested (in shares)	667,875
Exercised (in shares)	369,430
Forfeited (in shares)	216,250
Exercisable at December 31 (in shares)	298,445
Remaining unexercised (in shares)	780,820
Total value at grant date | $	$ 9,681,000
Estimated forfeitures | $	1,914,000
Expensed in previous years | $	2,018,000
Allocated share based compensation | $	1,282,000	$ 1,197,000	$ 1,051,000
Future expense | $	$ 2,219,000

Stock Option Plan - Summary of

Stock Option Plan - Summary of Option Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares
Outstanding at January 1 (in shares)	833,630	860,274	748,208
Granted (in shares)	232,500	226,500	225,000
Exercised (in shares)	(149,060)	(246,894)	(112,934)
Expired/Forfeited (in shares)	(3,750)	(6,250)	0
Outstanding December 31 (in shares)	913,320	833,630	860,274
Options exercisable (in shares)	430,945	375,255	435,899
Weighted Average Exercise Price
Outstanding at January 1 (in usd per share)	$ 49.92	$ 46.58	$ 44.79
Granted (in usd per share)	59.41	57.74	51.07
Exercised (in usd per share)	46.97	45.59	43.67
Expired/Forfeited (in usd per share)	53.73	45.31	0
Outstanding December 31 (in usd per share)	52.80	49.92	46.58
Exercisable at December 31 (in usd per share)	$ 48.94	$ 46.68	$ 45.33
Intrinsic value of options exercised	$ 2.2	$ 3.4	$ 1.5
Intrinsic value of options outstanding	8.2
Intrinsic value of options exercisable	$ 5.5
Closing price (in usd per share)	$ 61.75
Weighted average remaining life of options exercisable	6 years 5 months 13 days
Weighted average remaining life of options outstanding	7 years 5 months 24 days

Fair Value of Financial Instr59

Fair Value of Financial Instruments - Additional Information (Detail) $ in Thousands	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jun. 30, 2011instrument
Fair Value of Financial Instruments [Line Items]
Interest rate	3.90%	4.25%
Notes payable, fair value	$ 951,700	$ 851,300
Fixed rate mortgages	897,888	783,400
Interest rate swap
Fair Value of Financial Instruments [Line Items]
Fair value of derivative liability	$ 1,100
Cash flow hedging | Designated as hedging instrument | Interest rate swap
Fair Value of Financial Instruments [Line Items]
Derivative, number of instruments held | instrument			1
Fixed rate mortgage notes payable
Fair Value of Financial Instruments [Line Items]
Interest rate	5.25%
Fixed rate mortgages	$ 890,393	$ 844,292

Fair Value of Financial Instr60

Fair Value of Financial Instruments - Changes in Fair Value of Swaps (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (decrease) in fair value:
Recognized in earnings	$ 70	$ (6)	$ (10)
Recognized in other comprehensive income	812	678	124
Total	$ 882	$ 672	$ 114

Distributions - Additional Info

Distributions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 31, 2018	Jan. 15, 2018	Jan. 02, 2018	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends [Line Items]
Common stock issued, discount rate					3.00%
Common stock distributions (in usd per share)					$ 2.04	$ 1.84	$ 1.69
Dividends declared per common share outstanding (in usd per share)				$ 0.52
Distribution to limited partnership unitholders					$ 15,268	$ 13,533	$ 12,228
Dividend Income
Dividends [Line Items]
Common stock distributions (in usd per share)					$ 1.7	$ 1.75	$ 1.69
Return on Invested Capital
Dividends [Line Items]
Return of capital (in usd per share)				$ 0.34	0.34	0.09
Series C Preferred Stock
Dividends [Line Items]
Preferred stock dividend (in usd per share)					$ 1.72	$ 1.72	$ 1.72
Subsequent Event
Dividends [Line Items]
Common stock dividend paid	$ 11,500
Distribution to limited partnership unitholders	$ 3,900
Distributions partnership units (in usd per share)	$ 0.52
Subsequent Event | Series C Preferred Stock
Dividends [Line Items]
Dividends declared per preferred share outstanding (in usd per share)			$ 0.4297
Preferred stock distributions		$ 3,100

Distributions - Summary of Dist

Distributions - Summary of Distributions Paid Including Activity in Plan as well as Limited Partnership Units Issued from Reinvestment of Unit Distributions (Detail) - USD ($) $ / shares in Units, $ in Thousands	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Jan. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends [Line Items]
Preferred Stockholders													$ 12,375	$ 12,375	$ 12,375
Common Stockholders													44,576	39,472	35,645
Limited Partnership Unitholders													$ 15,268	$ 13,533	$ 12,228
Common Stock Shares Issued (in shares)													266,011	186,797	201,212
Limited Partnership Units Issued (in shares)													111,351	124,758	107,037
October 31
Dividends [Line Items]
Preferred Stockholders	$ 3,094			$ 3,094				$ 3,094
Common Stockholders	11,221			10,168				9,106
Limited Partnership Unitholders	$ 3,838			$ 3,478				$ 3,129
Common Stock Shares Issued (in shares)	82,991			44,176				47,313
Discounted Share Price (in usd per share)	$ 59.33			$ 57.18				$ 55.73
Limited Partnership Units Issued (in shares)	15,596			30,891				28,936
Average Unit Price (in usd per share)	$ 60.08			$ 57.18				$ 55.73
July 31
Dividends [Line Items]
Preferred Stockholders		$ 3,094			$ 3,094				$ 3,094
Common Stockholders		11,160			10,133				9,081
Limited Partnership Unitholders		$ 3,830			$ 3,465				$ 3,115
Common Stock Shares Issued (in shares)		85,731			39,487				56,003
Discounted Share Price (in usd per share)		$ 57.40			$ 65.64				$ 50.30
Limited Partnership Units Issued (in shares)		16,021			26,897				32,041
Average Unit Price (in usd per share)		$ 58.13			$ 65.64				$ 50.30
April 30
Dividends [Line Items]
Preferred Stockholders			$ 3,094			$ 3,094				$ 3,094
Common Stockholders			11,119			10,029				9,055
Limited Partnership Unitholders			$ 3,810			$ 3,449				$ 3,104
Common Stock Shares Issued (in shares)			51,003			48,854				54,921
Discounted Share Price (in usd per share)			$ 59.64			$ 51.59				$ 50.21
Limited Partnership Units Issued (in shares)			40,623			34,201				25,264
Average Unit Price (in usd per share)			$ 59.96			$ 51.59				$ 50.21
January 31
Dividends [Line Items]
Preferred Stockholders							$ 3,093				$ 3,093	$ 3,093
Common Stockholders							9,142				8,403	11,076
Limited Partnership Unitholders							$ 3,141				$ 2,880	$ 3,790
Common Stock Shares Issued (in shares)							54,280				42,975	46,286
Discounted Share Price (in usd per share)							$ 49.24				$ 56.74	$ 61.85
Limited Partnership Units Issued (in shares)							32,769				20,796	39,111
Average Unit Price (in usd per share)							$ 49.24				$ 56.74	$ 62.15

Interim Results (Unaudited) - S

Interim Results (Unaudited) - Summary of Results of Operations for Quarterly Periods (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 56,675	$ 56,237	$ 55,907	$ 58,466	$ 54,201	$ 53,233	$ 52,710	$ 56,926	$ 227,285	$ 217,070	$ 209,077
Operating income before loss on early extinguishment of debt, gain on casualty settlement, and noncontrolling interests	14,416	14,386	14,422	17,374	13,360	12,722	13,250	16,381	60,598	55,713	52,930
Gains on sales of properties	0	0	0	0	1,013	0	0	0	0	1,013	11
Net income attributable to Saul Centers, Inc.	11,560	11,483	11,510	13,704	11,465	10,239	10,627	12,948	48,257	45,279	42,468
Net income available to common stockholders	$ 8,466	$ 8,390	$ 8,416	$ 10,610	$ 8,371	$ 7,146	$ 7,533	$ 9,854	$ 35,882	$ 32,904	$ 30,093
Net income available to common stockholders per diluted share (in usd per share)	$ 0.38	$ 0.38	$ 0.38	$ 0.49	$ 0.38	$ 0.33	$ 0.35	$ 0.46	$ 1.63	$ 1.52	$ 1.42

Business Segments - Additional

Business Segments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017segment
Segment Reporting [Abstract]
Number of reportable business segments	2

Business Segments (Detail)

Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	$ 56,675	$ 56,237	$ 55,907	$ 58,466	$ 54,201	$ 53,233	$ 52,710	$ 56,926	$ 227,285	$ 217,070	$ 209,077
Expenses									(55,592)	(53,701)	(51,143)
Income from real estate									171,693	163,369	157,934
Interest expense and amortization of deferred debt costs									(47,225)	(45,683)	(45,165)
General and administrative									(18,176)	(17,496)	(16,353)
Subtotal									106,292	100,190	96,416
Depreciation and amortization of deferred leasing costs									(45,694)	(44,417)	(43,270)
Acquisition related costs									0	(60)	(84)
Predevelopment expenses									0	0	(132)
Change in fair value of derivatives									70	(6)	(10)
Gain on sale of property	0	$ 0	$ 0	$ 0	1,013	$ 0	$ 0	$ 0	0	1,013	11
Net income (loss)									60,668	56,720	52,931
Capital investment									119,994	91,045	69,619
Total assets	1,422,452				1,343,025				1,422,452	1,343,025	1,295,408
Operating Segments | Shopping Centers
Segment Reporting Information [Line Items]
Revenue									165,853	160,179	156,110
Expenses									(34,675)	(34,931)	(33,877)
Income from real estate									131,178	125,248	122,233
Interest expense and amortization of deferred debt costs									0	0	0
General and administrative									0	0	0
Subtotal									131,178	125,248	122,233
Depreciation and amortization of deferred leasing costs									(29,977)	(29,964)	(30,171)
Acquisition related costs										(60)	(84)
Predevelopment expenses											(57)
Change in fair value of derivatives									0	0	0
Gain on sale of property										0	11
Net income (loss)									101,201	95,224	91,932
Capital investment									90,896	64,044	17,159
Total assets	974,061				976,545				974,061	976,545	931,256
Operating Segments | Mixed-Use Properties
Segment Reporting Information [Line Items]
Revenue									61,352	56,840	52,916
Expenses									(20,917)	(18,770)	(17,266)
Income from real estate									40,435	38,070	35,650
Interest expense and amortization of deferred debt costs									0	0	0
General and administrative									0	0	0
Subtotal									40,435	38,070	35,650
Depreciation and amortization of deferred leasing costs									(15,717)	(14,453)	(13,099)
Acquisition related costs										0	0
Predevelopment expenses											(75)
Change in fair value of derivatives									0	0	0
Gain on sale of property										1,013	0
Net income (loss)									24,718	24,630	22,476
Capital investment									29,098	27,001	52,460
Total assets	438,283				358,419				438,283	358,419	354,254
Corporate
Segment Reporting Information [Line Items]
Revenue									80	51	51
Expenses									0	0	0
Income from real estate									80	51	51
Interest expense and amortization of deferred debt costs									(47,225)	(45,683)	(45,165)
General and administrative									(18,176)	(17,496)	(16,353)
Subtotal									(65,321)	(63,128)	(61,467)
Depreciation and amortization of deferred leasing costs									0	0	0
Acquisition related costs										0	0
Predevelopment expenses											0
Change in fair value of derivatives									70	(6)	(10)
Gain on sale of property										0	0
Net income (loss)									(65,251)	(63,134)	(61,477)
Capital investment									0	0	0
Total assets	$ 10,108				$ 8,061				$ 10,108	$ 8,061	$ 9,898

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, shares in Millions	Feb. 22, 2018	Jan. 23, 2018	Jan. 12, 2018	Feb. 12, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 26, 2018
Class of Stock [Line Items]
Payments to acquire real estate					$ 17,653,000	$ 15,564,000	$ 18,855,000
Series C Preferred Stock
Class of Stock [Line Items]
Depository shares to cumulative redeemable preferred stock ratio					1.00%
Dividend rate on preferred stock					6.875%
Percentage of redeemable preferred stock				6.875%
Liquidation preference (in usd per share)				$ 25
Annual dividend on depositary shares (in usd per share)				$ 1.71875
Subsequent Event | Series D Preferred Stock
Class of Stock [Line Items]
Depositary shares issued (in shares)		3
Depository shares to cumulative redeemable preferred stock ratio		1.00%
Dividend rate on preferred stock		6.125%
Percentage of redeemable preferred stock		6.125%
Net proceeds from shares sold		$ 72,600,000
Liquidation preference (in usd per share)		$ 25
Annual dividend on depositary shares (in usd per share)		$ 1.53125
Subsequent Event | Series C Preferred Stock
Class of Stock [Line Items]
Depository shares to cumulative redeemable preferred stock ratio	1.00%
Liquidation preference (in usd per share)	$ 25
Stock redeemed during period (in shares)	3
Line of Credit | Term Facility | Subsequent Event
Class of Stock [Line Items]
Line of credit facility, maximum borrowing capacity								$ 75,000,000
Line of Credit | Revolving Credit Facility | Subsequent Event
Class of Stock [Line Items]
Line of credit facility, maximum borrowing capacity								$ 325,000,000
7316 Wisconsin Avenue | Subsequent Event
Class of Stock [Line Items]
Payments to acquire real estate			$ 35,500,000
Acquisition costs			700,000
Earnest money deposit			$ 3,500,000

Real Estate and Accumulated D67

Real Estate and Accumulated Depreciation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Real Estate Properties [Line Items]
Initial Basis	$ 935,811
Cost capitalized subsequent to acquisition	867,389
Land	450,256
Buildings	1,352,944
Total Purchase Price	1,803,200	$ 1,700,813	$ 1,622,710	$ 1,560,159
Accumulated Depreciation	488,166	458,279	$ 425,370	$ 396,617
Book Value	1,315,034	1,242,534
Related Debt	897,888	783,400
Development land, related debt	0	$ 68,672
Total, related debt	904,528
Shopping Centers
Real Estate Properties [Line Items]
Initial Basis	832,397
Cost capitalized subsequent to acquisition	401,096
Land	412,358
Buildings	821,135
Total Purchase Price	1,233,493
Accumulated Depreciation	332,818
Book Value	900,675
Related Debt	639,385
Shopping Centers | Ashburn Village, Ashburn, VA
Real Estate Properties [Line Items]
Initial Basis	11,431
Cost capitalized subsequent to acquisition	20,278
Land	6,764
Buildings	24,945
Total Purchase Price	31,709
Accumulated Depreciation	12,993
Book Value	18,716
Related Debt	$ 28,025
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Ashland Square Phase I, Dumfries, VA
Real Estate Properties [Line Items]
Initial Basis	$ 1,178
Cost capitalized subsequent to acquisition	7,503
Land	1,178
Buildings	7,503
Total Purchase Price	8,681
Accumulated Depreciation	1,764
Book Value	6,917
Related Debt	$ 0
Shopping Centers | Ashland Square Phase I, Dumfries, VA | Minimum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	20 years
Shopping Centers | Ashland Square Phase I, Dumfries, VA | Maximum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Beacon Center, Alexandria, VA
Real Estate Properties [Line Items]
Initial Basis	$ 24,161
Cost capitalized subsequent to acquisition	18,426
Land	22,674
Buildings	19,913
Total Purchase Price	42,587
Accumulated Depreciation	14,288
Book Value	28,299
Related Debt	$ 39,968
Shopping Centers | Beacon Center, Alexandria, VA | Minimum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Beacon Center, Alexandria, VA | Maximum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | BJ’s Wholesale Club, Alexandria, VA
Real Estate Properties [Line Items]
Initial Basis	$ 22,623
Cost capitalized subsequent to acquisition	0
Land	22,623
Buildings	0
Total Purchase Price	22,623
Accumulated Depreciation	0
Book Value	22,623
Related Debt	$ 10,877
Buildings and Improvements Depreciable Lives in Years	0 years
Shopping Centers | Boca Valley Plaza, Boca Raton, FL
Real Estate Properties [Line Items]
Initial Basis	$ 16,720
Cost capitalized subsequent to acquisition	1,768
Land	5,735
Buildings	12,753
Total Purchase Price	18,488
Accumulated Depreciation	4,424
Book Value	14,064
Related Debt	$ 9,948
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Boulevard, Fairfax, VA
Real Estate Properties [Line Items]
Initial Basis	$ 4,883
Cost capitalized subsequent to acquisition	4,461
Land	3,687
Buildings	5,657
Total Purchase Price	9,344
Accumulated Depreciation	2,808
Book Value	6,536
Related Debt	$ 16,730
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Briggs Chaney MarketPlace, Silver Spring, MD
Real Estate Properties [Line Items]
Initial Basis	$ 27,037
Cost capitalized subsequent to acquisition	4,143
Land	9,789
Buildings	21,391
Total Purchase Price	31,180
Accumulated Depreciation	7,908
Book Value	23,272
Related Debt	$ 13,543
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Broadlands Village, Ashburn, VA
Real Estate Properties [Line Items]
Initial Basis	$ 5,316
Cost capitalized subsequent to acquisition	27,954
Land	5,300
Buildings	27,970
Total Purchase Price	33,270
Accumulated Depreciation	10,933
Book Value	22,337
Related Debt	$ 16,082
Shopping Centers | Broadlands Village, Ashburn, VA | Minimum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Broadlands Village, Ashburn, VA | Maximum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Burtonsville Town Square, Burtonsville, MD
Real Estate Properties [Line Items]
Initial Basis	$ 74,212
Cost capitalized subsequent to acquisition	342
Land	28,401
Buildings	46,153
Total Purchase Price	74,554
Accumulated Depreciation	1,095
Book Value	73,459
Related Debt	$ 39,140
Shopping Centers | Burtonsville Town Square, Burtonsville, MD | Minimum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	20 years
Shopping Centers | Burtonsville Town Square, Burtonsville, MD | Maximum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	45 years
Shopping Centers | Countryside Marketplace, Sterling, VA
Real Estate Properties [Line Items]
Initial Basis	$ 28,912
Cost capitalized subsequent to acquisition	3,752
Land	7,666
Buildings	24,998
Total Purchase Price	32,664
Accumulated Depreciation	8,838
Book Value	23,826
Related Debt	$ 13,529
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Cranberry Square, Westminster, MD
Real Estate Properties [Line Items]
Initial Basis	$ 31,578
Cost capitalized subsequent to acquisition	640
Land	6,700
Buildings	25,518
Total Purchase Price	32,218
Accumulated Depreciation	4,105
Book Value	28,113
Related Debt	$ 17,086
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Cruse MarketPlace, Cumming, GA
Real Estate Properties [Line Items]
Initial Basis	$ 12,226
Cost capitalized subsequent to acquisition	448
Land	3,901
Buildings	8,773
Total Purchase Price	12,674
Accumulated Depreciation	3,057
Book Value	9,617
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Flagship Center, Rockville, MD
Real Estate Properties [Line Items]
Initial Basis	$ 160
Cost capitalized subsequent to acquisition	9
Land	169
Buildings	0
Total Purchase Price	169
Accumulated Depreciation	0
Book Value	169
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	0 years
Shopping Centers | French Market, Oklahoma City, OK
Real Estate Properties [Line Items]
Initial Basis	$ 5,781
Cost capitalized subsequent to acquisition	13,829
Land	1,118
Buildings	18,492
Total Purchase Price	19,610
Accumulated Depreciation	11,191
Book Value	8,419
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Germantown, Germantown, MD
Real Estate Properties [Line Items]
Initial Basis	$ 2,034
Cost capitalized subsequent to acquisition	567
Land	2,034
Buildings	567
Total Purchase Price	2,601
Accumulated Depreciation	297
Book Value	2,304
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | The Glen, Woodbridge, VA
Real Estate Properties [Line Items]
Initial Basis	$ 12,918
Cost capitalized subsequent to acquisition	8,098
Land	5,300
Buildings	15,716
Total Purchase Price	21,016
Accumulated Depreciation	9,026
Book Value	11,990
Related Debt	$ 7,696
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Great Falls Center, Great Falls, VA
Real Estate Properties [Line Items]
Initial Basis	$ 41,750
Cost capitalized subsequent to acquisition	3,178
Land	14,766
Buildings	30,162
Total Purchase Price	44,928
Accumulated Depreciation	7,719
Book Value	37,209
Related Debt	$ 12,577
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Hampshire Langley, Takoma, MD
Real Estate Properties [Line Items]
Initial Basis	$ 3,159
Cost capitalized subsequent to acquisition	3,499
Land	1,856
Buildings	4,802
Total Purchase Price	6,658
Accumulated Depreciation	3,702
Book Value	2,956
Related Debt	$ 15,859
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Hunt Club Corners, Apopka, FL
Real Estate Properties [Line Items]
Initial Basis	$ 12,584
Cost capitalized subsequent to acquisition	4,034
Land	4,822
Buildings	11,796
Total Purchase Price	16,618
Accumulated Depreciation	3,801
Book Value	12,817
Related Debt	$ 5,649
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Jamestown Place, Altamonte Springs, FL
Real Estate Properties [Line Items]
Initial Basis	$ 14,055
Cost capitalized subsequent to acquisition	1,603
Land	4,455
Buildings	11,203
Total Purchase Price	15,658
Accumulated Depreciation	3,477
Book Value	12,181
Related Debt	$ 7,325
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Kentlands Square I, Gaithersburg, MD
Real Estate Properties [Line Items]
Initial Basis	$ 14,379
Cost capitalized subsequent to acquisition	507
Land	5,006
Buildings	9,880
Total Purchase Price	14,886
Accumulated Depreciation	3,713
Book Value	11,173
Related Debt	$ 6,423
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Kentlands Square II, Gaithersburg, MD
Real Estate Properties [Line Items]
Initial Basis	$ 76,723
Cost capitalized subsequent to acquisition	1,602
Land	22,800
Buildings	55,525
Total Purchase Price	78,325
Accumulated Depreciation	9,092
Book Value	69,233
Related Debt	$ 36,507
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Kentlands Place, Gaithersburg, MD
Real Estate Properties [Line Items]
Initial Basis	$ 1,425
Cost capitalized subsequent to acquisition	7,255
Land	1,425
Buildings	7,255
Total Purchase Price	8,680
Accumulated Depreciation	3,744
Book Value	4,936
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Lansdowne Town Center, Leesburg, VA
Real Estate Properties [Line Items]
Initial Basis	$ 6,545
Cost capitalized subsequent to acquisition	37,312
Land	6,546
Buildings	37,311
Total Purchase Price	43,857
Accumulated Depreciation	13,727
Book Value	30,130
Related Debt	$ 32,673
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Leesburg Pike Plaza, Baileys Crossroads, VA
Real Estate Properties [Line Items]
Initial Basis	$ 2,418
Cost capitalized subsequent to acquisition	6,243
Land	1,132
Buildings	7,529
Total Purchase Price	8,661
Accumulated Depreciation	5,934
Book Value	2,727
Related Debt	$ 15,452
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Lumberton Plaza, Lumberton, NJ
Real Estate Properties [Line Items]
Initial Basis	$ 4,400
Cost capitalized subsequent to acquisition	11,220
Land	950
Buildings	14,670
Total Purchase Price	15,620
Accumulated Depreciation	12,751
Book Value	2,869
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Metro Pike Center, Rockville, MD
Real Estate Properties [Line Items]
Initial Basis	$ 33,123
Cost capitalized subsequent to acquisition	4,095
Land	26,064
Buildings	11,154
Total Purchase Price	37,218
Accumulated Depreciation	1,375
Book Value	35,843
Related Debt	$ 14,135
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Shops at Monocacy, Frederick, MD
Real Estate Properties [Line Items]
Initial Basis	$ 9,541
Cost capitalized subsequent to acquisition	13,926
Land	9,260
Buildings	14,207
Total Purchase Price	23,467
Accumulated Depreciation	5,565
Book Value	17,902
Related Debt	$ 12,029
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Northrock, Warrenton, VA
Real Estate Properties [Line Items]
Initial Basis	$ 12,686
Cost capitalized subsequent to acquisition	15,414
Land	12,686
Buildings	15,414
Total Purchase Price	28,100
Accumulated Depreciation	3,871
Book Value	24,229
Related Debt	$ 14,950
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Olde Forte Village, Ft. Washington, MD
Real Estate Properties [Line Items]
Initial Basis	$ 15,933
Cost capitalized subsequent to acquisition	6,643
Land	5,409
Buildings	17,167
Total Purchase Price	22,576
Accumulated Depreciation	7,158
Book Value	15,418
Related Debt	$ 9,783
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Olney, Olney, MD
Real Estate Properties [Line Items]
Initial Basis	$ 4,963
Cost capitalized subsequent to acquisition	1,961
Land	3,079
Buildings	3,845
Total Purchase Price	6,924
Accumulated Depreciation	3,318
Book Value	3,606
Related Debt	$ 11,613
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Orchard Park, Dunwoody, GA
Real Estate Properties [Line Items]
Initial Basis	$ 19,377
Cost capitalized subsequent to acquisition	1,014
Land	7,751
Buildings	12,640
Total Purchase Price	20,391
Accumulated Depreciation	3,432
Book Value	16,959
Related Debt	$ 9,999
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Palm Springs Center, Altamonte Springs, FL
Real Estate Properties [Line Items]
Initial Basis	$ 18,365
Cost capitalized subsequent to acquisition	1,435
Land	5,739
Buildings	14,061
Total Purchase Price	19,800
Accumulated Depreciation	4,606
Book Value	15,194
Related Debt	$ 8,244
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Ravenwood, Baltimore, MD
Real Estate Properties [Line Items]
Initial Basis	$ 1,245
Cost capitalized subsequent to acquisition	4,227
Land	703
Buildings	4,769
Total Purchase Price	5,472
Accumulated Depreciation	3,067
Book Value	2,405
Related Debt	$ 14,537
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | 11503 Rockville Pike/5541 Nicholson Lane, Rockville, MD
Real Estate Properties [Line Items]
Initial Basis	$ 26,561
Cost capitalized subsequent to acquisition	24
Land	22,113
Buildings	4,472
Total Purchase Price	26,585
Accumulated Depreciation	806
Book Value	25,779
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | 1500/1580/1582/1584 Rockville Pike, Rockville, MD
Real Estate Properties [Line Items]
Initial Basis	$ 51,149
Cost capitalized subsequent to acquisition	1,553
Land	43,863
Buildings	8,839
Total Purchase Price	52,702
Accumulated Depreciation	5,656
Book Value	47,046
Related Debt	0
Shopping Centers | Seabreeze Plaza, Palm Harbor, FL
Real Estate Properties [Line Items]
Initial Basis	24,526
Cost capitalized subsequent to acquisition	1,960
Land	8,665
Buildings	17,821
Total Purchase Price	26,486
Accumulated Depreciation	5,611
Book Value	20,875
Related Debt	$ 16,055
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Market Place at Sea Colony, Bethany Beach, DE
Real Estate Properties [Line Items]
Initial Basis	$ 2,920
Cost capitalized subsequent to acquisition	203
Land	1,147
Buildings	1,976
Total Purchase Price	3,123
Accumulated Depreciation	491
Book Value	2,632
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Seven Corners, Falls Church, VA
Real Estate Properties [Line Items]
Initial Basis	$ 4,848
Cost capitalized subsequent to acquisition	44,108
Land	4,913
Buildings	44,043
Total Purchase Price	48,956
Accumulated Depreciation	28,790
Book Value	20,166
Related Debt	$ 64,472
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Severna Park Marketplace, Severna Park, MD
Real Estate Properties [Line Items]
Initial Basis	$ 63,254
Cost capitalized subsequent to acquisition	232
Land	12,700
Buildings	50,786
Total Purchase Price	63,486
Accumulated Depreciation	7,927
Book Value	55,559
Related Debt	$ 32,016
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Shops at Fairfax, Fairfax, VA
Real Estate Properties [Line Items]
Initial Basis	$ 2,708
Cost capitalized subsequent to acquisition	9,924
Land	992
Buildings	11,640
Total Purchase Price	12,632
Accumulated Depreciation	7,989
Book Value	4,643
Related Debt	$ 11,154
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Smallwood Village Center, Waldorf, MD
Real Estate Properties [Line Items]
Initial Basis	$ 17,819
Cost capitalized subsequent to acquisition	7,975
Land	6,402
Buildings	19,392
Total Purchase Price	25,794
Accumulated Depreciation	7,278
Book Value	18,516
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Southdale, Glen Burnie, MD
Real Estate Properties [Line Items]
Initial Basis	$ 18,895
Cost capitalized subsequent to acquisition	24,345
Land	15,254
Buildings	27,986
Total Purchase Price	43,240
Accumulated Depreciation	21,333
Book Value	21,907
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Southside Plaza, Richmond, VA
Real Estate Properties [Line Items]
Initial Basis	$ 6,728
Cost capitalized subsequent to acquisition	10,695
Land	1,878
Buildings	15,545
Total Purchase Price	17,423
Accumulated Depreciation	12,280
Book Value	5,143
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | South Dekalb Plaza, Atlanta, GA
Real Estate Properties [Line Items]
Initial Basis	$ 2,474
Cost capitalized subsequent to acquisition	4,359
Land	703
Buildings	6,130
Total Purchase Price	6,833
Accumulated Depreciation	4,792
Book Value	2,041
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Thruway, Winston-Salem, NC
Real Estate Properties [Line Items]
Initial Basis	$ 7,848
Cost capitalized subsequent to acquisition	24,821
Land	7,693
Buildings	24,976
Total Purchase Price	32,669
Accumulated Depreciation	16,735
Book Value	15,934
Related Debt	$ 37,998
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Village Center, Centreville, VA
Real Estate Properties [Line Items]
Initial Basis	$ 16,502
Cost capitalized subsequent to acquisition	2,495
Land	7,851
Buildings	11,146
Total Purchase Price	18,997
Accumulated Depreciation	6,688
Book Value	12,309
Related Debt	$ 13,438
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Westview Village, Frederick, MD
Real Estate Properties [Line Items]
Initial Basis	$ 6,047
Cost capitalized subsequent to acquisition	25,227
Land	6,047
Buildings	25,227
Total Purchase Price	31,274
Accumulated Depreciation	7,511
Book Value	23,763
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | White Oak, Silver Spring, MD
Real Estate Properties [Line Items]
Initial Basis	$ 6,277
Cost capitalized subsequent to acquisition	5,366
Land	4,649
Buildings	6,994
Total Purchase Price	11,643
Accumulated Depreciation	6,043
Book Value	5,600
Related Debt	$ 23,873
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Other Buildings / Improvements
Real Estate Properties [Line Items]
Cost capitalized subsequent to acquisition	$ 423
Buildings	423
Total Purchase Price	423
Accumulated Depreciation	109
Book Value	314
Related Debt	0
Mixed-Use Properties
Real Estate Properties [Line Items]
Initial Basis	43,967
Cost capitalized subsequent to acquisition	432,660
Land	28,496
Buildings	448,131
Total Purchase Price	476,627
Accumulated Depreciation	155,348
Book Value	321,279
Related Debt	$ 265,143
Mixed-Use Properties | 1500/1580/1582/1584 Rockville Pike, Rockville, MD | Acquisition Date One
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	5 years
Mixed-Use Properties | 1500/1580/1582/1584 Rockville Pike, Rockville, MD | Acquisition Date Two
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	10 years
Mixed-Use Properties | 1500/1580/1582/1584 Rockville Pike, Rockville, MD | Acquisition Date Three
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	5 years
Mixed-Use Properties | 1500/1580/1582/1584 Rockville Pike, Rockville, MD | Acquisition Date Four
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	4 years
Mixed-Use Properties | Avenel Business Park, Gaithersburg, MD
Real Estate Properties [Line Items]
Initial Basis	$ 21,459
Cost capitalized subsequent to acquisition	30,409
Land	3,756
Buildings	48,112
Total Purchase Price	51,868
Accumulated Depreciation	36,469
Book Value	15,399
Related Debt	$ 28,115
Mixed-Use Properties | Avenel Business Park, Gaithersburg, MD | Minimum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	35 years
Mixed-Use Properties | Avenel Business Park, Gaithersburg, MD | Maximum
Real Estate Properties [Line Items]
Buildings and Improvements Depreciable Lives in Years	40 years
Mixed-Use Properties | Clarendon Center, Arlington, VA (1)
Real Estate Properties [Line Items]
Initial Basis	$ 12,753
Cost capitalized subsequent to acquisition	185,904
Land	16,287
Buildings	182,370
Total Purchase Price	198,657
Accumulated Depreciation	37,242
Book Value	161,415
Related Debt	$ 105,817
Buildings and Improvements Depreciable Lives in Years	50 years
Mixed-Use Properties | Park Van Ness, Washington, DC
Real Estate Properties [Line Items]
Initial Basis	$ 2,242
Cost capitalized subsequent to acquisition	91,617
Land	2,242
Buildings	91,617
Total Purchase Price	93,859
Accumulated Depreciation	4,801
Book Value	89,058
Development land, related debt	$ 71,211
Buildings and Improvements Depreciable Lives in Years	50 years
Mixed-Use Properties | 601 Pennsylvania Ave., Washington, DC
Real Estate Properties [Line Items]
Initial Basis	$ 5,479
Cost capitalized subsequent to acquisition	67,995
Land	5,667
Buildings	67,807
Total Purchase Price	73,474
Accumulated Depreciation	52,194
Book Value	21,280
Related Debt	$ 0
Buildings and Improvements Depreciable Lives in Years	35 years
Mixed-Use Properties | Washington Square, Alexandria, VA
Real Estate Properties [Line Items]
Initial Basis	$ 2,034
Cost capitalized subsequent to acquisition	56,735
Land	544
Buildings	58,225
Total Purchase Price	58,769
Accumulated Depreciation	24,642
Book Value	34,127
Related Debt	$ 60,000
Buildings and Improvements Depreciable Lives in Years	50 years
Development Land
Real Estate Properties [Line Items]
Initial Basis	$ 59,447
Cost capitalized subsequent to acquisition	33,633
Land	9,402
Buildings	83,678
Total Purchase Price	93,080
Accumulated Depreciation	0
Book Value	93,080
Development land, related debt	0
Development Land | Ashland Square Phase II, Manassas, VA
Real Estate Properties [Line Items]
Initial Basis	5,292
Cost capitalized subsequent to acquisition	1,917
Land	7,028
Buildings	181
Total Purchase Price	7,209
Accumulated Depreciation	0
Book Value	7,209
Development land, related debt	0
Development Land | New Market, New Market, MD
Real Estate Properties [Line Items]
Initial Basis	2,088
Cost capitalized subsequent to acquisition	286
Land	2,374
Buildings	0
Total Purchase Price	2,374
Accumulated Depreciation	0
Book Value	2,374
Development land, related debt	0
Development Land | North Glebe Road, Arlington, VA
Real Estate Properties [Line Items]
Initial Basis	52,067
Cost capitalized subsequent to acquisition	31,430
Land	0
Buildings	83,497
Total Purchase Price	83,497
Accumulated Depreciation	0
Book Value	83,497
Development land, related debt	$ 0

Real Estate and Accumulated D68

Real Estate and Accumulated Depreciation - Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2017
Base building | Minimum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	35 years
Base building | Maximum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	50 years
Building components | Maximum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	20 years

Real Estate and Accumulated D69

Real Estate and Accumulated Depreciation - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real estate investments for federal income tax	$ 1,320	$ 1,260

Real Estate and Accumulated D70

Real Estate and Accumulated Depreciation - Changes in Total Real Estate Investments and Related Accumulated Depreciation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total real estate investments:
Balance, beginning of year	$ 1,700,813	$ 1,622,710	$ 1,560,159
Acquisitions	77,258	48,123	4,894
Improvements	42,640	35,826	70,067
Retirements	(17,511)	(5,846)	(1,981)
Transfers to assets held for sale	0	0	(10,429)
Balance, end of year	1,803,200	1,700,813	1,622,710
Total accumulated depreciation:
Balance, beginning of year	458,279	425,370	396,617
Depreciation expense	40,197	38,755	37,698
Retirements	(10,310)	(5,846)	(1,911)
Transfers to assets held for sale	0	0	(7,034)
Balance, end of year	$ 488,166	$ 458,279	$ 425,370