Saul Centers (BFS) 10-K 25 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 18, 2021	Jun. 30, 2020
Document Information [Line Items]
Document type	10-K
Document Annual Report	true
Document period end date	Dec. 31, 2020
Current fiscal year end date	--12-31
Document Transition Report	false
Entity File Number	1-12254
Entity registrant name	SAUL CENTERS, INC.
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	52-1833074
Entity Address, Address Line One	7501 Wisconsin Avenue
Entity Address, Address Line Two	Suite 1500E
Entity Address, City or Town	Bethesda
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20814-6522
City Area Code	301
Local Phone Number	986-6200
Entity well-known seasoned issuer	Yes
Entity voluntary filers	No
Entity current reporting status	Yes
Entity Interactive Data Current	Yes
Entity filer category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity common stock, shares outstanding		23.5
Entity public float			$ 419.8
Documents Incorporated by Reference	Registrant incorporates by reference into Part III (Items 10, 11, 12, 13 and 14) of this Annual Report on Form 10-K portions of registrant’s definitive Proxy Statement for the 2021 Annual Meeting of Stockholders to be filed with the Securities Exchange Commission pursuant to Regulation 14A. The definitive Proxy Statement will be filed with the Commission not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
Amendment flag	false
Document fiscal year focus	2020
Document fiscal period focus	FY
Entity central index key	0000907254
Common Stock, Par Value $0.01 Per Share
Document Information [Line Items]
Title of 12(b) Security	Common Stock, Par Value $0.01 Per Share
Security Exchange Name	NYSE
Trading symbol	BFS
Depositary Shares each representing 1/100th of a share of 6.125% Series D Cumulative Redeemable Preferred Stock, Par Value $0.01 Per Share
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares each representing 1/100th of a share of 6.125% Series D Cumulative Redeemable Preferred Stock, Par Value $0.01 Per Share
Security Exchange Name	NYSE
Trading symbol	BFS/PRD
Depositary Shares each representing 1/100th of a share of 6.000% Series E Cumulative Redeemable Preferred Stock, Par Value $0.01 Per Share
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares each representing 1/100th of a share of 6.000% Series E Cumulative Redeemable Preferred Stock, Par Value $0.01 Per Share
Security Exchange Name	NYSE
Trading symbol	BFS/PRE

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Real estate investments
Land	$ 511,482	$ 453,322
Buildings and equipment	1,543,837	1,292,631
Construction in progress	69,477	335,644
Total Purchase Price	2,124,796	2,081,597
Accumulated depreciation	(607,706)	(563,474)
Book Value	1,517,090	1,518,123
Cash and cash equivalents	26,856	13,905
Accounts receivable and accrued income, net	64,917	52,311
Deferred leasing costs, net	26,872	24,083
Prepaid expenses, net	5,643	5,363
Other assets	4,194	4,555
Total assets	1,645,572	1,618,340
Liabilities
Mortgage notes payable	827,603	821,503
Term loan facility payable	74,791	74,691
Revolving credit facility payable	103,913	86,371
Construction loan payable	144,607	108,623
Dividends and distributions payable	19,448	19,291
Accounts payable, accrued expenses and other liabilities	24,384	35,199
Deferred income	23,293	29,306
Total liabilities	1,218,039	1,174,984
Equity
Common stock, $0.01 par value, 40,000,000 shares authorized, 23,476,626 and 23,231,240 shares issued and outstanding, respectively	235	232
Additional paid-in capital	420,625	410,926
Distributions in excess of accumulated earnings	(241,535)	(221,177)
Total Saul Centers, Inc. equity	364,325	374,981
Noncontrolling interests	63,208	68,375
Total equity	427,533	443,356
Total liabilities and equity	1,645,572	1,618,340
Series D Cumulative Redeemable Preferred Stock
Equity
Preferred stock, 1,000,000 shares authorized, Series D Cumulative Redeemable, 30,000 shares issued and outstanding, Series E Cumulative Redeemable, 44,000 and 0 shares issued and outstanding respectively	75,000	75,000
Series E Cumulative Redeemable Preferred Stock
Equity
Preferred stock, 1,000,000 shares authorized, Series D Cumulative Redeemable, 30,000 shares issued and outstanding, Series E Cumulative Redeemable, 44,000 and 0 shares issued and outstanding respectively	$ 110,000	$ 110,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
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)	23,476,626	23,231,240
Common stock, shares outstanding (in shares)	23,476,626	23,231,240
Series D Cumulative Redeemable Preferred Stock
Cumulative redeemable preferred stock, shares issued (in shares)	30,000	30,000
Cumulative redeemable preferred stock, shares outstanding (in shares)	30,000	30,000
Series E Cumulative Redeemable Preferred Stock
Cumulative redeemable preferred stock, shares issued (in shares)	44,000
Cumulative redeemable preferred stock, shares outstanding (in shares)	44,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue
Rental revenue	$ 220,281	$ 223,352	$ 221,734
Other	4,926	8,173	5,485
Total revenue	225,207	231,525	227,219
Expenses
Property operating expenses	28,857	29,946	28,202
Real estate taxes	29,560	27,987	27,376
Interest expense, net and amortization of deferred debt costs	46,519	41,834	44,768
Depreciation and amortization of deferred leasing costs	51,126	46,333	45,861
General and administrative	19,107	20,793	18,459
Total expenses	175,169	166,893	164,666
Change in fair value of derivatives	0	(436)	(3)
Gains on sales of properties	278	0	509
Net income (loss)	50,316	64,196	63,059
Income attributable to noncontrolling interests	(9,934)	(12,473)	(12,505)
Net income attributable to Saul Centers, Inc.	40,382	51,723	50,554
Preferred stock dividends	(11,194)	(12,235)	(12,262)
Extinguishment of issuance costs upon redemption of preferred shares	0	(3,235)	(2,328)
Net income available to common stockholders	$ 29,188	$ 36,253	$ 35,964
Per share net income available to common stockholders
Basic (in usd per share)	$ 1.25	$ 1.58	$ 1.61
Diluted (in usd per share)	$ 1.25	$ 1.57	$ 1.60

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 50,316	$ 64,196	$ 63,059
Other comprehensive income
Unrealized gain on cash flow hedge	0	93
Unrealized gain on cash flow hedge			594
Total comprehensive income	50,316	64,289	63,653
Comprehensive income attributable to noncontrolling interests	(9,934)	(12,561)	(12,658)
Total comprehensive income attributable to Saul Centers, Inc.	40,382	51,728	50,995
Preferred stock dividends	(11,194)	(12,235)	(12,262)
Extinguishment of issuance costs upon redemption of preferred shares	0	(3,235)	(2,328)
Total comprehensive income available to common stockholders	$ 29,188	$ 36,258	$ 36,405

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Dividend paid	Dividend declared	Series C Cumulative Preferred Stock	Series C Cumulative Preferred StockDividend paid	Series C Cumulative Preferred StockDividend declared	Series D Cumulative Redeemable Preferred Stock	Series D Cumulative Redeemable Preferred StockDividend paid	Series D Cumulative Redeemable Preferred StockDividend declared	Series E Cumulative Redeemable Preferred Stock	Series E Cumulative Redeemable Preferred StockDividend paid	Series E Cumulative Redeemable Preferred StockDividend declared	Preferred Stock	Preferred StockSeries C Cumulative Preferred Stock	Preferred StockSeries D Cumulative Redeemable Preferred Stock	Preferred StockSeries E Cumulative Redeemable Preferred Stock	Common Stock	Additional Paid-in Capital	Additional Paid-in CapitalSeries C Cumulative Preferred Stock	Additional Paid-in CapitalSeries D Cumulative Redeemable Preferred Stock	Additional Paid-in CapitalSeries E Cumulative Redeemable Preferred Stock	Distributions in Excess of Accumulated Earnings	Distributions in Excess of Accumulated EarningsDividend paid	Distributions in Excess of Accumulated EarningsDividend declared	Distributions in Excess of Accumulated EarningsSeries C Cumulative Preferred Stock	Distributions in Excess of Accumulated EarningsSeries C Cumulative Preferred StockDividend paid	Distributions in Excess of Accumulated EarningsSeries C Cumulative Preferred StockDividend declared	Distributions in Excess of Accumulated EarningsSeries D Cumulative Redeemable Preferred StockDividend paid	Distributions in Excess of Accumulated EarningsSeries D Cumulative Redeemable Preferred StockDividend declared	Distributions in Excess of Accumulated EarningsSeries E Cumulative Redeemable Preferred StockDividend paid	Distributions in Excess of Accumulated EarningsSeries E Cumulative Redeemable 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 Cumulative Preferred Stock	Total Saul Centers, Inc.Series C Cumulative Preferred StockDividend paid	Total Saul Centers, Inc.Series C Cumulative Preferred StockDividend declared	Total Saul Centers, Inc.Series D Cumulative Redeemable Preferred Stock	Total Saul Centers, Inc.Series D Cumulative Redeemable Preferred StockDividend paid	Total Saul Centers, Inc.Series D Cumulative Redeemable Preferred StockDividend declared	Total Saul Centers, Inc.Series E Cumulative Redeemable Preferred Stock	Total Saul Centers, Inc.Series E Cumulative Redeemable Preferred StockDividend paid	Total Saul Centers, Inc.Series E Cumulative Redeemable Preferred StockDividend declared	Noncontrolling Interests	Noncontrolling InterestsDividend paid	Noncontrolling InterestsDividend declared
Beginning balance at Dec. 31, 2017	$ 393,103												$ 180,000				$ 221	$ 352,590				$ (197,710)										$ (696)	$ 334,405												$ 58,698
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of cumulative preferred stock							$ 72,367								$ 75,000					$ (2,633)																			$ 72,367
Stock redeemed or called during period, value				$ (75,017)										$ (75,000)			0		$ 2,311						$ (2,328)											$ (75,017)
Issuance of common stock:
Shares issued pursuant to dividend reinvestment plan	28,823																6	28,817															28,823
Shares issued due to exercise of employee stock options and issuance of directors' deferred stock	3,448																0	3,448															3,448
Issuance of partnership units	14,159																																												14,159
Net income	63,059																					50,554											50,554												12,505
Change in unrealized loss on cash flow hedge	594																															441	441												153
Preferred stock distributions:
Preferred stock distributions			$ (46,900)		$ (6,145)	$ (1,805)		$ (3,164)	$ (1,148)															$ (34,841)		$ (6,145)	$ (1,805)	$ (3,164)	$ (1,148)						$ (34,841)		$ (6,145)	$ (1,805)		$ (3,164)	$ (1,148)
Common stock distributions																																														$ (12,059)
Distributions payable common stock and distributions payable partnership units			(16,154)																					(12,006)											(12,006)												$ (4,148)
Ending balance at Dec. 31, 2018	425,220												180,000				227	384,533				(208,593)										(255)	355,912												69,308
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of cumulative preferred stock										$ 106,265						$ 110,000					$ (3,735)																					$ 106,265
Stock redeemed or called during period, value				$ (105,000)										$ (105,000)					$ 3,235						$ (3,235)											$ (105,000)
Issuance of common stock:
Shares issued pursuant to dividend reinvestment plan	22,498																4	22,494															22,498
Shares issued due to exercise of employee stock options and issuance of directors' deferred stock	4,400																1	4,399															4,400
Issuance of partnership units	3,180																																												3,180
Net income	64,196																					51,723											51,723												12,473
Change in unrealized loss on cash flow hedge	343																															255	255												88
Preferred stock distributions:
Preferred stock distributions			(49,056)		$ (5,736)			(3,444)	(1,148)			$ (1,650)												(36,562)		$ (5,736)		(3,444)	(1,148)		$ (1,650)				(36,562)		$ (5,736)			(3,444)	(1,148)			$ (1,650)
Common stock distributions											$ (257)																			$ (257)													$ (257)			(12,494)
Distributions payable common stock and distributions payable partnership units			(16,455)																					(12,275)											(12,275)												(4,180)
Ending balance at Dec. 31, 2019	443,356												185,000				232	410,926				(221,177)										0	374,981												68,375
Issuance of common stock:
Shares issued pursuant to dividend reinvestment plan	7,735																3	7,732															7,735
Shares issued due to exercise of employee stock options and issuance of directors' deferred stock	1,967																0	1,967															1,967
Issuance of partnership units	1,677																																												1,677
Net income	50,316																					40,382											40,382												9,934
Preferred stock distributions:
Preferred stock distributions			(1,650)					$ (3,446)	$ (1,148)		$ (4,950)													(1,650)				$ (3,446)	$ (1,148)	$ (4,950)					(1,650)					$ (3,446)	$ (1,148)
Common stock distributions		$ (49,679)																					$ (37,108)											$ (37,108)												$ (12,571)
Distributions payable common stock and distributions payable partnership units			$ (16,645)																					$ (12,438)											$ (12,438)												$ (4,207)
Ending balance at Dec. 31, 2020	$ 427,533												$ 185,000				$ 235	$ 420,625				$ (241,535)										$ 0	$ 364,325												$ 63,208

Consolidated Statements of Eq_2

Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares issued pursuant to dividend reinvestment plan (in shares)	228,498,000	430,462,000	572,928,000
Shares due to exercise of employee stock options and issuance of directors' deferred stock (in shares)	16,887,000	61,571,000	43,150,000
Issuance of partnership units pursuant to dividend reinvestment plan (in shares)	51,579,000	60,936,000	107,433,000
Issuance of partnership units (in shares)	51,579,000	60,936,000	284,113,000
Series D Cumulative Redeemable Preferred Stock
Issuance of Series D Cumulative preferred stock (in shares)			30,000,000
Series C Cumulative Preferred Stock
Redemption of Series C Cumulative preferred stock (in shares)		42,000,000	30,000,000
Series E Cumulative Redeemable Preferred Stock
Issuance of Series D Cumulative preferred stock (in shares)		44,000,000
Dividend declared
Distributions payable common stock and partnership units (in usd per share)	$ 0.53	$ 0.53	$ 0.53
Dividend declared | Series D Cumulative Redeemable Preferred Stock
Distributions payable on preferred stock (in usd per share)	38.28	38.28	38.28
Dividend declared | Series C Cumulative Preferred Stock
Distributions payable on preferred stock (in usd per share)			$ 42.97
Dividend declared | Series E Cumulative Redeemable Preferred Stock
Distributions payable on preferred stock (in usd per share)	$ 37.50	$ 37.50

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income		$ 50,316	$ 64,196	$ 63,059
Adjustments to reconcile net income to net cash provided by operating activities:
Change in fair value of derivatives		0	436	3
Gains on sales of properties		(278)	0	(509)
Depreciation and amortization of deferred leasing costs		51,126	46,333	45,861
Amortization of deferred debt costs		1,570	1,518	1,610
Non cash compensation costs of stock grants and options		1,438	1,859	1,766
Credit losses on operating lease receivables		5,212	1,226	685
(Increase) decrease in accounts receivable and accrued income		(17,818)	339	(336)
Additions to deferred leasing costs		(8,050)	(1,843)	(6,034)
(Increase) decrease in prepaid expenses		(356)	(188)	73
Decrease in other assets		361	894	3,681
Increase in accounts payable, accrued expenses and other liabilities		875	158	225
Increase (decrease) in deferred income		(6,013)	455	255
Net cash provided by operating activities		78,383	115,383	110,339
Cash flows from investing activities:
Acquisitions of real estate investments	[1]	0	0	(40,836)
Additions to real estate investments		(19,484)	(21,891)	(12,883)
Additions to development and redevelopment projects		(37,060)	(113,772)	(76,257)
Proceeds from sale of properties	[2]	376	0	1,326
Net cash used in investing activities		(56,168)	(135,663)	(128,650)
Cash flows from financing activities:
Proceeds from mortgage notes payable		52,100	50,600	54,900
Repayments on mortgage notes payable		(45,654)	(109,235)	(72,572)
Proceeds from term loan facility		0	0	75,000
Proceeds from revolving credit facility		90,000	152,500	102,000
Repayments on revolving credit facility		(73,000)	(112,000)	(116,000)
Proceeds from construction loans payable		35,883	86,868	23,332
Additions to deferred debt costs		(1,206)	(1,010)	(3,233)
Proceeds from the issuance of:
Common stock		8,264	25,039	30,503
Partnership units	[1]	1,677	3,180	5,383
Preferred stock redemption costs		0	0	(12)
Distributions to:
Distributions to preferred stockholders		(11,194)	(12,390)	(12,402)
Common stockholders		(49,383)	(48,568)	(46,306)
Noncontrolling interests		(16,751)	(16,642)	(15,981)
Net cash provided by (used in) financing activities		(9,264)	19,607	21,981
Net increase (decrease) in cash and cash equivalents		12,951	(673)	3,670
Cash and cash equivalents, beginning of year		13,905	14,578	10,908
Cash and cash equivalents, end of year		26,856	13,905	14,578
Supplemental disclosure of cash flow information:
Cash paid for interest		44,990	40,434	43,561
Increase (decrease) in accrued real estate investments and development costs		(11,690)	303	9,663
Series C Cumulative Preferred Stock
Proceeds from the issuance of:
Series C preferred stock redemption		0	(105,000)	(75,000)
Distributions to:
Distributions to preferred stockholders		0	(7,541)	(9,238)
Series D Cumulative Redeemable Preferred Stock
Proceeds from the issuance of:
Preferred stock		0	0	72,369
Distributions to:
Distributions to preferred stockholders		(4,594)	(4,592)	(3,164)
Series E Cumulative Redeemable Preferred Stock
Proceeds from the issuance of:
Preferred stock		0	106,265	0
Distributions to:
Distributions to preferred stockholders		$ (6,600)	$ (257)	0
Ashbrook Marketplace
Supplemental disclosure of cash flow information:
Limited partnership units issued				8,776
Great Eastern Shopping Center
Supplemental disclosure of cash flow information:
Seller financing				1,275
Interest income				$ 51
[1]	The 2018 acquisition of real estate and proceeds from the issuance of partnership units each excludes $8,776 in connection with the acquisition of Ashbrook Marketplace in exchange for limited partnership units.
[2]	Proceeds from sale of property in 2018 includes $1,275 of seller financing in connection with the sale of the Company's Great Eastern property in 2017, which were received in 2018 plus accrued interest of $51.

Organization, Basis of Presenta

Organization, Basis of Presentation	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Basis of Presentation	ORGANIZATION, BASIS OF PRESENTATION 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, Chief Executive Officer and President of Saul Centers. 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 "Saul 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 Centers 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 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, 2020, 33 of the Shopping Centers were anchored by a grocery store and offer primarily day-to-day necessities and services. One retail tenant, Giant Food (5.4%), a tenant at 11 Shopping Centers, individually accounted for 2.5% or more of the Company’s total revenue for the year ended December 31, 2020. As of December 31, 2020, the Current Portfolio Properties consisted of 50 Shopping Centers, seven Mixed-Use Properties, and three (non-operating) development properties. The accompanying consolidated financial statements of the Company include the accounts of Saul Centers and its subsidiaries, including the Operating Partnership and Subsidiary Partnerships, which are majority owned by Saul Centers. Substantially all assets and liabilities of the Company as of December 31, 2020 and December 31, 2019, are comprised of the assets and liabilities of the Operating Partnership. The debt arrangements which are subject to recourse are described in Note 5. 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 74.6% 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.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates The preparation of financial statements in conformity with GAAP 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. The most significant estimates and assumptions relate to impairment of real estate properties and collectability of operating lease receivables. Actual results could differ from those estimates. Real Estate Investment Properties Real estate investment properties are stated at historic cost less depreciation. Although the Company intends to own its real estate investment properties over a long term, from time to time it will evaluate its market position, market conditions, and other factors and may elect to sell properties that do not conform to the Company’s investment profile. Management believes that the Company’s real estate assets have generally appreciated in value since their acquisition or development and, accordingly, the aggregate current value exceeds their aggregate net book value and also exceeds the value of the Company’s liabilities as reported in the financial statements. Because the financial statements are prepared in conformity with GAAP, they do not report the current value of the Company’s real estate investment properties. 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 2020, 2019, or 2018. 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, 2020, 2019, and 2018, was $45.9 million, $40.5 million, and $39.8 million, respectively. Repairs and maintenance expense totaled $11.1 million, $12.5 million, and $11.9 million for 2020, 2019, and 2018, respectively, and is included in property operating expenses in the accompanying consolidated financial statements. As of December 31, 2020, we have not identified any impairment triggering events, including the impact of COVID-19 and corresponding tenant requests for rent relief. Accordingly, under applicable GAAP guidance, no impairment charges were recorded. 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, 2020 and 2019, the Company had no assets designated as held for sale. 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. Accounts Receivable, Accrued Income, and Allowance for Doubtful Accounts Accounts receivable are primarily comprised of rental and reimbursement billings due from tenants, and straight-line rent receivables representing the cumulative amount of adjustments necessary to present rental income on a straight-line basis. Individual leases are assessed for collectability and, upon the determination that the collection of rents is not probable, accrued rent and accounts receivable are charged off, and the charge off is reflected as an adjustment to rental revenue. Revenue from leases where collection is not probable is recorded on a cash basis until collectability is determined to be probable. We also assess whether operating lease receivables, at the portfolio level, are appropriately valued based upon an analysis of balances outstanding, effects of tenant bankruptcies, historical levels of bad debt and current economic trends. Additionally, because of the uncertainties related to the impact of the COVID-19 pandemic, our assessment also takes into consideration the types of business conducted by tenants and current discussions with the tenants, as well as recent rent collection experience. Evaluating and estimating uncollectable lease payments and related receivables requires a significant amount of judgment by management and is based on the best information available to management at the time of evaluation. For the year-ended December 31, 2020, we reduced rental revenue by $3.5 million and $1.7 million, due to lease-related reserves and charge offs, respectively. Actual results could differ from these estimates. At December 31, 2020 and December 31, 2019, accounts receivable was comprised of: (In thousands) December 31, 2020 December 31, 2019 Rents currently due $ 13,321 $ 7,235 Deferred rents and payment plans 8,205 474 Straight-line rent 44,863 42,088 Other receivables 3,751 2,967 Credit losses on operating lease receivables (5,223) (453) Total $ 64,917 $ 52,311 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 $26.9 million and $24.1 million, net of accumulated amortization of approximately $44.5 million and $41.6 million, as of December 31, 2020 and 2019, respectively. Amortization expense, which is included in Depreciation and amortization of deferred leasing costs in the Consolidated Statements of Operations, totaled approximately $5.2 million, $5.8 million, and $6.1 million, for the years ended December 31, 2020, 2019, and 2018, respectively. 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, 2020 are held in 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 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. 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, 2020, 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 2020, 2019, and 2018. The tax basis of the Company’s real estate investments was approximately $1.55 billion and $1.33 billion as of December 31, 2020 and 2019, 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 2017. 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 February 2016, the Financial Accounting Standards Board (‘‘FASB’’) issued Accounting Standards Update (‘‘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. Upon adoption of ASU 2016-02 effective January 1, 2019, we elected the practical expedient for all leases with respect to lease identification, lease classification, and initial direct costs. We made a policy election not to separate lease and nonlease components and have accounted for each lease component and the related nonlease components together as a single component. There have been no significant changes to our lessor accounting for operating leases as a result of ASU 2016-02 We lease Shopping Centers and Mixed-Use Properties to lessees in exchange for monthly payments that cover rent, and where applicable, reimbursement for property taxes, insurance, and certain property operating expenses. Our leases were determined to be operating leases and generally range in term from one Some of our leases have termination options and/or extension options. Termination options allow the lessee to terminate the lease prior to the end of the lease term, provided certain conditions are met. Termination options generally require advance notification from the lessee and payment of a termination fee. Termination fees are recognized as revenue over the modified lease term. Extension options are subject to terms and conditions stated in the lease. On January 1, 2019, a right of use asset and corresponding lease liability related to our headquarters lease were recorded in other assets and other liabilities, respectively. The lease expires on February 28, 2022, with one option to renew for an additional five years. The right of use asset and corresponding lease liability totaled $0.9 million and $0.9 million, respectively, at December 31, 2020. Due to the business disruptions and challenges severely affecting the global economy caused by the novel strain of coronavirus (“COVID-19”) pandemic, many lessees have requested rent relief, including rent deferrals and other lease concessions. The lease modification guidance in ASU 2016-02 does not contemplate the rapid execution of concessions for multiple tenants in response to sudden liquidity constraints of lessees. In April 2020, the FASB staff issued a question and answer document that provided guidance allowing the Company to elect to either apply the lease modification accounting framework or not, with such election applied consistently to leases with similar characteristics and similar circumstances. The Company has elected to apply such relief, which, in the case of rent deferrals, results in the accrual of rent due from tenants and defers the payment of that rent to a future date, and will monitor the collectability of rent receivables. 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. The adoption of ASU 2016-13 effective January 1, 2020, had no material impact on our consolidated financial statements and related disclosures because the vast majority of the Company's receivables relate to operating leases which are accounted for under ASC 842. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging” (“ASU 2017-12”). ASU 2017-12 amends financial reporting for hedging activities to better align that reporting with risk management activities. ASU 2017-12 expands and refines hedge accounting for both financial and nonfinancial risk components and aligns the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. Effective with the adoption of ASU 2017-12 on January 1, 2019, changes in the fair value of the Company’s interest rate swap related to changes in the cash flow of the hedged item are reported as a component of interest expense and amortization of deferred debt costs in the Statements of Operations. Reclassifications

Real Estate

Real Estate	12 Months Ended
	Dec. 31, 2020
Real Estate [Abstract]
Real Estate	REAL ESTATE Construction in Progress Construction in progress includes land, 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) 2020 2019 Hampden House (formerly 7316 Wisconsin Avenue) $ 50,723 $ 44,638 The Waycroft 8,651 255,443 Ashbrook Marketplace 153 19,128 Other 9,950 16,435 Total $ 69,477 $ 335,644 Acquisitions Ashbrook Marketplace In May 2018, the Company acquired from the Saul Trust, in exchange for 176,680 limited partnership units, approximately 13.7 acres of land located at the intersection of Ashburn Village Boulevard and Russell Branch Parkway in Loudoun County, Virginia. Based on the closing price of the Company's common stock, the land and the limited partnership units were recorded at a value of $8.8 million. Acquisition costs related to the transaction totaled approximately $0.2 million. Hampden House (formerly 7316 Wisconsin Avenue) In September 2018, the Company purchased for $35.5 million, plus $0.7 million of acquisition costs, an office building and the underlying ground located at 7316 Wisconsin Avenue in Bethesda, Maryland. In December 2018, the Company purchased for $4.5 million, including acquisition costs, an interest in an adjacent parcel of land and retail building. The purchase price was funded through the Company's credit facility. Effective September 1, 2019, the asset was removed from service and transferred to construction in progress at its carrying value of $42.6 million. 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. During 2018, the Company acquired properties that had an aggregate cost of $49.5 million, including acquisition costs. The purchase price was allocated to assets acquired and liabilities assumed based on their relative fair values as shown in the following table. (in thousands) Ashbrook Marketplace Hampden House (formerly 7316 Wisconsin Avenue) Total Land $ 8,776 $ 38,662 $ 47,438 Buildings — 979 979 In-place Leases — 886 886 Above Market Rent — 168 168 Below Market Rent — (21) (21) Total Purchase Price $ 8,776 $ 40,674 $ 49,450 The gross carrying amount of lease intangible assets included in deferred leasing costs as of December 31, 2020 and 2019 was $11.0 million and $11.7 million, respectively, and accumulated amortization was $8.6 million and $8.5 million, respectively. Amortization expense totaled $0.6 million, $0.9 million and $1.3 million, for the years ended December 31, 2020, 2019, and 2018, respectively. The gross carrying amount of below market lease intangible liabilities included in deferred income as of December 31, 2020 and 2019 was $23.7 million and $24.1 million, respectively, and accumulated amortization was $15.0 million and $13.9 million, respectively. Accretion income totaled $1.4 million, $1.5 million, and $1.7 million, for the years ended December 31, 2020, 2019, and 2018, respectively. The gross carrying amount of above market lease intangible assets included in accounts receivable as of December 31, 2020 and 2019 was $0.6 million and $0.6 million, respectively, and accumulated amortization was $128,900 and $108,300, respectively. Amortization expense totaled $43,600, $109,600 and $110,500, for the years ended December 31, 2020, 2019 and 2018, respectively. The remaining weighted-average amortization period as of December 31, 2020 is 4.3 years, 7.0 years, and 5.0 years for lease acquisition costs, above market leases and below market leases, respectively. As of December 31, 2020, 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 2021 $ 495 $ 33 $ 1,409 2022 368 33 1,306 2023 317 33 1,297 2024 198 33 878 2025 153 33 601 Thereafter 843 309 3,253 Total $ 2,374 $ 474 $ 8,744

Noncontrolling Interests - Hold

Noncontrolling Interests - Holders of Convertible Limited Partnership Units in the Operating Partnership	12 Months Ended
	Dec. 31, 2020
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 Saul Centers is the sole general partner of the Operating Partnership, owning a 74.6% common interest as of December 31, 2020. 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. The Saul Organization holds a 25.4% limited partnership interest in the Operating Partnership represented by 7,938,495 limited partnership units, as of December 31, 2020. 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, 2020, approximately 1,947,000 units were eligible for conversion. The impact of the Saul Organization’s 25.4% 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, 2020, 2019, and 2018, were 31.3 million, 30.9 million, and 30.2 million, respectively.

Mortgage Notes Payable, Revolvi

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs	12 Months Ended
	Dec. 31, 2020
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, 2020, the principal amount of outstanding debt totaled $1.2 billion, of which $980.8 million was fixed rate debt and $179.5 million was variable rate debt. The principal amount of the Company’s outstanding debt totaled $1.1 billion at December 31, 2019, of which $938.4 million was fixed rate debt and $162.5 million was variable rate debt. At December 31, 2020, the Company had a $400.0 million unsecured credit facility, which can be used for working capital, property acquisitions or development projects, of which $325.0 million is a revolving credit facility and $75.0 million is a term loan. The revolving credit facility matures on January 26, 2022, and may be extended by the Company for one leverage ratio and which can range from 135 basis points to 195 basis points under the revolving facility and from 130 basis points to 190 basis points under the term loan. As of December 31, 2020, the margin was 140 basis points under the revolving facility and 135 basis points under the term loan. Saul Centers and certain consolidated subsidiaries of the Operating Partnership have guaranteed the payment obligations of the Operating Partnership under the credit facility. The Operating Partnership is the guarantor of (a) a portion of the Park Van Ness mortgage (approximately $3.3 million of the $66.4 million outstanding balance at December 31, 2020, which guarantee was reduced to (i) $3.3 million on October 1, 2020 and (ii) will be reduced to zero on October 1, 2021), (b) a portion of the Broadlands mortgage (approximately $3.8 million of the $30.5 million outstanding balance at December 31, 2020), (c) a portion of the Avenel Business Park mortgage (approximately $6.3 million of the $25.2 million outstanding balance at December 31, 2020), (d) a portion of The Waycroft mortgage (approximately $23.6 million of the $146.1 million outstanding balance at December 31, 2020), (e) the Ashbrook Marketplace mortgage (totaling $21.9 million at December 31, 2020), and (f) the mortgage secured by Kentlands Place, Kentlands Square I and Kentlands pad (totaling $29.7 million at December 31, 2020). All other notes payable are non-recourse. The guarantee on the Kentlands Square II mortgage loan was released on February 5, 2020. On January 4, 2019, the Company repaid in full the remaining principal balance of $12.7 million of the mortgage loan secured by Countryside Marketplace, which was scheduled to mature in July 2019. On January 10, 2019, the Company closed on a 15-year, non-recourse $22.1 million mortgage loan secured by Olde Forte Village. The loan matures in 2034, bears interest at a fixed-rate of 4.65%, requires monthly principal and interest payments of $124,700 based on a 25-year amortization schedule and requires a final payment of $12.1 million. Proceeds were partially used to repay in full the existing mortgage secured by Olde Forte Village, which was scheduled to mature in May 2019. On June 3, 2019, the Company repaid in full the remaining principal balance of $12.4 million of the mortgage loan secured by Briggs Chaney Marketplace, which was scheduled to mature in September 2019. On November 12, 2019, the Company closed on a 15-year, non-recourse $28.5 million mortgage loan secured by Shops at Monocacy. The loan matures in 2034, bears interest at a fixed-rate of 4.14%, requires monthly principal and interest payments of $152,600 based on a 25-year amortization schedule and requires a final payment of $15.1 million. Proceeds were partially used to repay in full the existing mortgage secured by Shops at Monocacy, which was scheduled to mature in January 2020. On November 21, 2019, the Company repaid in full the remaining principal balance of $35.6 million of the mortgage loan secured by Thruway, which was scheduled to mature in July 2020. The Company’s corresponding swap agreement was terminated on the same day. On February 10, 2020, the Company repaid in full the remaining principal balance of $9.2 million of the mortgage loan secured by Boca Valley Plaza, which was scheduled to mature on May 10, 2020. On March 3, 2020, the Company repaid in full the remaining principal balance of $7.1 million of the mortgage loan secured by Palm Springs Center, which was scheduled to mature on June 1, 2020. On July 14, 2020, the Company closed on a 15-year, $22.1 million mortgage loan secured by Ashbrook Marketplace. The loan matures in 2035, bears interest at a fixed rate of 3.80%, requires monthly principal and interest payments of $114,226 based on a 25-year amortization schedule and requires a final payment of $11.5 million at maturity. The proceeds from the loan were used to pay down the revolving credit facility. On July 24, 2020, the Company closed on a 15-year, $30.0 million mortgage loan secured by Kentlands Place, Kentlands Square I and Kentlands Pad. The loan matures in 2035, bears interest at a fixed rate of 3.43%, requires monthly principal and interest payments of $149,064 based on a 25-year amortization schedule and requires a final payment of $15.3 million at maturity. The proceeds from the loan were used to pay down the revolving credit facility. The carrying value of the properties collateralizing the mortgage notes payable totaled $1.2 billion and $1.1 billion, as of December 31, 2020 and 2019, 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, 2020. • 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 1.4x on a trailing four-quarter basis (fixed charge coverage). Mortgage notes payable totaling $41.0 million at each of December 31, 2020 and 2019, are guaranteed by members of the Saul Organization. As of December 31, 2020, the scheduled maturities of all debt including scheduled principal amortization for years ended December 31 are as follows: (in thousands) Balloon Scheduled Total 2021 $ 11,012 $ 30,355 $ 41,367 2022 141,002 (a) 31,017 172,019 2023 84,225 31,481 115,706 2024 66,164 30,856 97,020 2025 20,363 27,860 48,223 Thereafter 569,330 116,586 685,916 Principal amount $ 892,096 $ 268,155 1,160,251 Unamortized deferred debt costs 9,337 Net $ 1,150,914 (a) Includes $104.5 million outstanding under the revolving facility. 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 $9.3 million and $9.7 million, net of accumulated amortization of $8.7 million and $7.5 million at December 31, 2020 and 2019, respectively, and are reflected as a reduction of the related debt in the Consolidated Balance Sheets. The components of interest expense are set forth below. (in thousands) Year ended December 31, 2020 2019 2018 Interest incurred $ 51,705 $ 52,044 $ 49,652 Amortization of deferred debt costs 1,570 1,518 1,610 Capitalized interest (6,616) (11,480) (6,222) Interest expense 46,659 42,082 45,040 Less: Interest income 140 248 272 Interest expense, net and amortization of deferred debt costs $ 46,519 $ 41,834 $ 44,768

Lease Agreements

Lease Agreements	12 Months Ended
	Dec. 31, 2020
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, 2020, 2019, and 2018, amounted to $188.6 million, $185.7 million, and $184.7 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) 2021 $ 163,862 2022 146,574 2023 126,550 2024 102,118 2025 80,366 Thereafter 351,968 $ 971,438 The majority of the leases provide for rental increases based on fixed annual increases or increases in the Consumer Price Index and expense recoveries based on 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, 2020, 2019, and 2018, amounted to $34.7 million, $36.5 million, and $35.5 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 $0.9 million, $0.9 million, and $1.0 million, for the years ended December 31, 2020, 2019, and 2018, respectively.

Long-Term Lease Obligations

Long-Term Lease Obligations	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Long-Term Lease Obligations	LONG-TERM LEASE OBLIGATIONS At December 31, 2020 and 2019, no properties were situated upon land subject to noncancelable long- term leases. 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, 2020, 2019, and 2018 was $799,300, $806,500, and $779,800, 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, 2020
Noncontrolling Interest [Abstract]
Equity and Noncontrolling Interest	EQUITY AND NONCONTROLLING INTEREST The Consolidated Statements of Operations for the years ended December 31, 2020, 2019, and 2018 reflect noncontrolling interest of $9.9 million, $12.5 million, and $12.5 million, respectively, representing the Saul Organization’s share of the net income for the year. At December 31, 2020, the Company had outstanding 3.0 million depositary shares, each representing 1/100th of a share of 6.125% Series D Cumulative Redeemable Preferred Stock (the "Series D Stock"). 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 to but not including the redemption date. The depositary shares pay an annual dividend of $1.53125 per share, equivalent to 6.125% of the $25.00 liquidation preference. 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 in 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. At December 31, 2020, the Company had outstanding 4.4 million depositary shares, each representing 1/100th of a share of 6.000% Series E Cumulative Redeemable Preferred Stock (the “Series E Stock”). The depositary shares may be redeemed at the Company’s option, in whole or in part, on or after September 17, 2024, at the $25.00 liquidation preference, plus accrued but unpaid dividends to but not including the redemption date. The depositary shares pay an annual dividend of $1.50 per share, equivalent to 6.000% of the $25.00 liquidation preference. The Series E 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 in 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. 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) 2020 2019 2018 Weighted average common shares outstanding - Basic 23,356 23,009 22,383 Effect of dilutive options 1 44 42 Weighted average common shares outstanding - Diluted 23,357 23,053 22,425 Average share price $ 33.84 $ 53.41 $ 52.50 Non-dilutive options 1,439 633 492 Years non-dilutive options were issued 2014 through 2020 2016, 2017 and 2019 2015, 2016 and 2017

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS The Chairman, Chief Executive Officer and President, the Executive Vice President of Real Estate, 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 6% of the employee’s cash compensation, subject to certain limits, were $302,000, $322,200, and $345,900, for 2020, 2019, and 2018, 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 and the Company matches those deferrals up to three times the amount deferred by employees. The Company’s expense, included in general and administrative expense, totaled $241,300, $345,200, and $282,500, for the years ended December 31, 2020, 2019, and 2018, respectively. All amounts deferred by employees and the Company are fully vested. The cumulative unfunded liability under this plan was $2.9 million and $3.1 million, at December 31, 2020 and 2019, 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, 2020, 2019, and 2018, which included rental expense for the Company’s headquarters lease (see Note 7. Long Term Lease Obligations), totaled $7.4 million, $8.4 million, and $8.4 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, 2020 and 2019, accounts payable, accrued expenses and other liabilities included $782,700 and $918,700, 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 Saul 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. On November 5, 2019, the Company entered into a Contribution Agreement to acquire the Contributed Property from the Saul Trust. In exchange for the Contributed Property, the Company will issue to the Saul Trust 1,416,071 limited partnership units. In connection with the contribution, the Company is obligated to reimburse the Saul Trust for certain pre-development and carrying costs incurred by the Saul Trust subsequent to the date of the Contribution Agreement, which total approximately $6.1 million as of December 31, 2020. Deed to the Contributed Property and the units were placed in escrow until certain conditions of the Contribution Agreement are satisfied. 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 $427,700, $399,600, and $407,900, for the years ended December 31, 2020, 2019, and 2018, respectively. In August 2016, the Company entered into an agreement to acquire from the Saul Trust approximately 13.7 acres of land located at the intersection of Ashburn Village Boulevard and Russell Branch Parkway in Ashburn, Virginia. The transaction closed on May 9, 2018, and the Company issued 176,680 limited partnership units to the Saul Trust. The Company constructed a shopping center, Ashbrook Marketplace, and may be obligated to issue additional limited partnership units to the Saul Trust in the second quarter of 2021. As of December 31, 2020, the Company estimates this obligation to range in value from $3.3 million to $3.6 million, based on projected net operating income of Ashbrook Marketplace for the 12 months ending May 31, 2021.

Stock Option Plan

Stock Option Plan	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Option Plan	STOCK OPTION PLAN Stock Based Employee Compensation, Deferred Compensation and Stock Plan for Directors In 2004, the Company established a stock incentive plan (the "Plan"), as amended. Under the Plan, options were granted at an exercise price not less than the market value of the common stock on the date of grant and expire ten years from the date of grant. Officer options vest ratably over four years following the grant and are charged to expense using the straight-line method over the vesting period. Director options vest immediately and are charged to expense as of the date of grant. 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 expense in general and administrative expenses. Pursuant to the Plan, the Compensation Committee established a Deferred Compensation Plan for Directors for the benefit of the Company’s directors and their beneficiaries, which replaced a previous Deferred Compensation and Stock Plan for Directors. Annually, directors are given the ability to make an election to defer all or part of their fees and have the option to have their 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 a director elects to their have fees paid in stock, fees earned during a calendar quarter are aggregated and divided by the closing market price of the Company’s common stock on the first trading day of the following quarter to determine the number of shares to be credited to the director. During the twelve months ended December 31, 2020, 11,574 shares were credited to director's deferred fee accounts and 7,354 shares were issued. As of December 31, 2020, the director's deferred fee accounts comprise 118,628 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 Stockholders, and their issuance may not be deferred. 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, further amended at the 2013 Annual Meeting, and further amended at the 2019 Annual Meeting (the “Amended 2004 Plan”). The Amended 2004 Plan, which terminates in 2029, provides for grants of options to purchase up to 3,400,000 shares of common stock. 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 May 11, 2018, the Compensation Committee granted options to purchase 245,000 shares (25,914 incentive stock options and 219,086 nonqualified stock options) to 22 Company officers and 11 Company Directors (the “2018 options”), which expire on May 10, 2028. The officers’ 2018 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2018 Options were immediately exercisable. The exercise price of $49.46 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 2018 Options to be $1.4 million, of which $1.2 million and $169,400 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $169,400 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 3, 2019, the Compensation Committee granted options to purchase 260,000 shares (34,651 incentive stock options and 225,349 nonqualified stock options) to 23 Company officers and 11 Company Directors (the “2019 options”), which expire on May 2, 2029. The officers’ 2019 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2019 Options were immediately exercisable. The exercise price of $55.71 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 2019 Options to be $1.9 million, of which $1.7 million and $226,600 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $226,600 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 April 24, 2020, the Compensation Committee granted options to purchase 238,000 shares (29,624 incentive stock options and 208,376 nonqualified stock options) to 20 Company officers and 11 Company Directors (the “2020 options”), which expire on April 23, 2030. The officers’ 2020 Options vest 25% per year over four years and are subject to early expiration upon termination of employment. The directors’ 2020 Options were immediately exercisable. The exercise price of $50.00 per share was determined by the compensation committee. The exercise price was greater than the closing market price of the Company's common stock on the date of award, which was $28.02. Using the Black-Scholes model, the Company determined the total fair value of the 2020 Options to be $0.2 million, of which $0.2 million and $23,100 were assigned to the officer options and director options, respectively. Because the directors’ options vested immediately, the entire $23,100 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 assumptions used in the valuation of the 2018, 2019, and 2020 option grants. During the twelve months ended December 31, 2020, stock option expense totaling $1.2 million was included in general and administrative expense in the Consolidated Statements of Operations. As of December 31, 2020, the estimated future expense related to unvested stock options was $1.6 million. Directors Officers Grant date May 11, 2018 May 3, 2019 April 24, 2020 May 11, 2018 May 3, 2019 April 24, 2020 Exercise price $ 49.46 $ 55.71 $ 50.00 $ 49.46 $ 55.71 $ 50.00 Volatility 0.192 0.236 0.258 0.177 0.206 0.240 Expected life (years) 5.0 5.0 5.0 7.0 7.0 7.0 Assumed yield 3.70 % 3.75 % 3.80 % 3.75 % 3.80 % 3.85 % Risk-free rate 2.84 % 2.33 % 0.36 % 2.94 % 2.43 % 0.51 % The table below summarizes the option activity for the years 2020, 2019, and 2018: 2020 2019 2018 Shares Weighted Shares Weighted Shares Weighted Outstanding at January 1 1,309,614 $ 53.38 1,114,169 $ 52.40 913,320 $ 52.80 Granted 238,000 50.00 260,000 55.71 245,000 49.46 Exercised (10,749) 49.19 (57,055) 44.53 (39,151) 42.98 Expired/Forfeited (34,195) 54.09 (7,500) 56.07 (5,000) 54.78 Outstanding December 31 1,502,670 52.86 1,309,614 53.38 1,114,169 52.40 Exercisable at December 31 971,545 53.01 763,614 52.43 600,919 50.93

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	FAIR VALUE OF FINANCIAL INSTRUMENTSThe carrying values of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses and floating rate debt 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 3.40% and 3.55%, would be approximately $981.0 million and $957.4 million as of December 31, 2020 and 2019, respectively, compared to the principal balance of $980.8 million and $938.4 million at December 31, 2020 and 2019, 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 was carried at fair value with changes in fair value recognized either in income or comprehensive income depending on the effectiveness of the swap. The swap was terminated on November 21, 2019.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIESNeither 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, 2020
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 $2.12 per share in 2020, $2.12 per share in 2019, and $2.08 per share in 2018, Series C preferred stock dividends of $1.80 and $1.72, respectively, per depositary share in 2019 and 2018, Series D preferred stock dividends of $1.53, $1.53 and $1.05, respectively, per depositary share in 2020, 2019, and 2018, and Series E preferred stock dividends of $1.50 and $0.06, respectively, per depositary share in 2020 and 2019. Of the common stock dividends paid, $1.43 per share, $2.00 per share, and $1.61 per share, represented ordinary dividend income in 2020, 2019, and 2018, respectively, and $0.69 per share, $0.12 per share, and $0.47 per share represented return of capital to the shareholders in 2020, 2019, and 2018, respectively. All of the preferred dividends paid represented ordinary dividend income. The following summarizes distributions paid during the years ended December 31, 2020, 2019, and 2018, 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 2020 4th Quarter $ 2,798 $ 12,371 $ 4,195 117,368 $ 24.08 23,370 $ 24.35 3rd Quarter 2,798 12,373 4,188 14,525 28.98 13,108 29.47 2nd Quarter 2,799 12,364 4,188 12,627 32.22 — — 1st Quarter 2,799 12,275 4,180 83,978 48.59 15,101 49.40 Total 2020 $ 11,194 $ 49,383 $ 16,751 228,498 51,579 Distributions during 2019 4th Quarter $ 3,531 $ 12,251 $ 4,173 104,558 $ 52.84 13,747 $ 53.73 3rd Quarter 2,953 12,195 4,166 105,753 53.66 13,406 54.56 2nd Quarter 2,953 12,116 4,155 99,804 51.38 20,041 51.99 1st Quarter 2,953 12,006 4,148 120,347 51.28 13,742 52.16 Total 2019 $ 12,390 $ 48,568 $ 16,642 430,462 60,936 Distributions during 2018 4th Quarter $ 2,953 $ 11,706 $ 4,062 216,476 $ 49.34 13,867 $ 50.20 3rd Quarter 2,953 11,590 4,055 201,500 51.68 13,107 52.60 2nd Quarter 2,672 11,545 3,942 85,202 47.54 42,422 47.83 1st Quarter 3,824 11,465 3,922 69,750 52.71 38,037 53.03 Total 2018 $ 12,402 $ 46,306 $ 15,981 572,928 107,433 In December 2020, the Board of Directors of the Company authorized a distribution of $0.53 per common share payable in January 2021 to holders of record on January 15, 2021. As a result, $12.4 million was paid to common shareholders on January 29, 2021. Also, $4.2 million was paid to limited partnership unitholders on January 29, 2021 ($0.53 per Operating Partnership unit). The Board of Directors authorized preferred stock dividends of (a) $0.3750 per Series E depositary share and (b) $0.3828 per Series D depositary share to holders of record on January 4, 2021. As a result, $2.8 million was paid to preferred shareholders on January 15, 2021. 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, 2020
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 2020 and 2019. (In thousands, except per share amounts) 2020 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total revenue $ 56,943 $ 53,220 $ 56,760 $ 58,284 Net Income 16,829 10,208 11,603 11,676 Net income attributable to Saul Centers, Inc. 13,264 8,328 9,367 9,423 Net income available to common stockholders 10,466 5,530 6,569 6,623 Net income available to common stockholders per diluted share 0.45 0.24 0.28 0.28 (In thousands, except per share amounts) 2019 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total revenue $ 59,750 $ 58,141 $ 57,052 $ 56,582 Net Income 17,077 16,750 15,328 15,041 Net income attributable to Saul Centers, Inc. 13,447 13,232 12,226 12,818 Net income available to common stockholders 10,494 10,279 9,016 6,464 Net income available to common stockholders per basic and diluted share 0.46 0.45 0.39 0.27

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Business Segments	BUSINESS SEGMENTSThe 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 2020 presentation. SAUL CENTERS, INC. (In thousands) Shopping Mixed-Use Corporate Consolidated As of or for the year ended December 31, 2020 Centers Properties and Other Totals Real estate rental operations: Revenue $ 161,854 $ 63,353 $ — $ 225,207 Expenses (35,198) (23,219) — (58,417) Income from real estate 126,656 40,134 — 166,790 Interest expense, net and amortization of deferred debt costs — — (46,519) (46,519) General and administrative — — (19,107) (19,107) Depreciation and amortization of deferred leasing costs (30,891) (20,235) — (51,126) Gain on sale of property 278 — — 278 Net income (loss) $ 96,043 $ 19,899 $ (65,626) $ 50,316 Capital investment $ 15,203 $ 40,965 $ — $ 56,168 Total assets $ 975,195 $ 643,503 $ 26,874 $ 1,645,572 As of or for the year ended December 31, 2019 Real estate rental operations: Revenue $ 167,888 $ 63,637 $ — $ 231,525 Expenses (36,119) (21,814) — (57,933) Income from real estate 131,769 41,823 — 173,592 Interest expense, net and amortization of deferred debt costs — — (41,834) (41,834) General and administrative — — (20,793) (20,793) Depreciation and amortization of deferred leasing costs (29,112) (17,221) — (46,333) Change in fair value of derivatives — — (436) (436) Net income (loss) $ 102,657 $ 24,602 $ (63,063) $ 64,196 Capital investment $ 33,968 $ 101,695 $ — $ 135,663 Total assets $ 980,096 $ 625,183 $ 13,061 $ 1,618,340 As of or for the year ended December 31, 2018 Real estate rental operations: Revenue $ 164,344 $ 62,875 $ — $ 227,219 Expenses (34,643) (20,935) — (55,578) Income from real estate 129,701 41,940 — 171,641 Interest expense, net and amortization of deferred debt costs — — (44,768) (44,768) General and administrative — — (18,459) (18,459) Depreciation and amortization of deferred leasing costs (29,251) (16,610) — (45,861) Change in fair value of derivatives — — (3) (3) Gain on sale of property 509 — — 509 Net income (loss) $ 100,959 $ 25,330 $ (63,230) $ 63,059 Capital investment $ 13,485 $ 115,165 $ — $ 128,650 Total assets $ 971,321 $ 537,500 $ 18,668 $ 1,527,489

Impact of COVID-19

Impact of COVID-19	12 Months Ended
	Dec. 31, 2020
Unusual or Infrequent Items, or Both [Abstract]
Impact of COVID-19	Impact of COVID-19 On March 11, 2020, the World Health Organization declared a novel strain of coronavirus ("COVID-19") a pandemic, and on March 13, 2020, the United States declared a national emergency with respect to COVID-19. As a result, the COVID-19 pandemic is negatively affecting almost every industry directly or indirectly. The actions taken by federal, state and local governments to mitigate the spread of COVID-19 by ordering closure of nonessential businesses and ordering residents to generally stay at home, and subsequent phased re-openings, have resulted in many of our tenants announcing mandated or temporary closures of their operations and/or requesting adjustments to their lease terms. Experts predict that the COVID-19 pandemic will trigger a period of global economic slowdown or a global recession. COVID-19 could have a material and adverse effect on or cause disruption to our business or financial condition, results from operations, cash flows and the market value and trading price of our securities. While the Company’s grocery stores, pharmacies, banks and home improvement stores generally remain open, restaurants, if open, are operating at limited capacity, with many offering only delivery and curbside pick-up, and most health, beauty supply and services, fitness centers, and other non-essential businesses are in various phases of re-opening depending on location. The Company is generally not charging late fees or delinquent interest on past due rent payments and, in many cases, rent deferral agreements are being negotiated to allow tenants temporary relief where needed. As of February 23, 2021, payments by tenants of contractual base rent and operating expense and real estate tax recoveries totaled approximately 94% for the fourth quarter of 2020. The following is a summary of the Company's consolidated total collections of fourth quarter 2020 rent billings, including minimum rent, operating expense recoveries, and real estate tax reimbursements as of February 23, 2021: 2020 fourth quarter • 94% of 2020 fourth quarter total billings has been paid by our tenants. ▪ 94% of retail ▪ 93% of office ▪ 100% of residential ▪ Additionally, rent deferral agreements comprising approximately 0.5% of 2020 fourth quarter total billings have been executed. The executed deferrals typically cover three months of rent and are generally scheduled to be repaid during 2021 and 2022. As a condition to granted rent deferrals, we have sought, and in some cases received, extended lease terms, or waivers of certain adjacent use or common area restrictions. ▪ Through February 23, 2021, no fourth quarter deferred rents have come due. Deferrals represent 9% of the total unpaid balance for the quarter.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe Company has reviewed operating activities for the period subsequent to December 31, 2020 and prior to the date that financial statements are issued, February 25, 2021, and determined there are no subsequent events that are required to be disclosed.

Real Estate and Accumulated Dep

Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real estate and accumulated depreciation	SAUL CENTERS, INC. Real Estate and Accumulated Depreciation December 31, 2020 (Dollars in Thousands) Costs Buildings Capitalized Basis at Close of Period and Initial Subsequent Land Buildings Construction in Progress Total Accumulated Book Related Date of Date Improvements Shopping Centers Ashbrook Marketplace, Ashburn, VA $ 8,938 $ 19,897 $ 8,938 $ 19,744 $ 153 $ 28,835 $ 453 $ 28,382 $ 21,922 2019 05/18 50 Ashburn Village, Ashburn, VA 11,431 20,493 6,764 25,138 22 31,924 14,989 16,935 25,253 1994 & 2000-6 3/94 40 Ashland Square Phase I, Dumfries, VA 1,178 5,298 1,178 5,298 — 6,476 2,438 4,038 — 2007, 2013 12/04 20 & 50 Beacon Center, Alexandria, VA 24,161 18,485 22,691 19,955 — 42,646 15,823 26,823 34,223 1960 & 1974 1/72 , 11/16 40 & 50 BJ’s Wholesale Club, Alexandria, VA 22,623 — 22,623 — — 22,623 — 22,623 10,018 3/08 — Boca Valley Plaza, Boca Raton, FL 16,720 2,614 5,735 13,599 — 19,334 5,681 13,653 — 2/04 40 Boulevard, Fairfax, VA 4,883 4,709 3,687 5,905 — 9,592 3,466 6,126 15,191 1969, 1999 & 2009 4/94 40 Briggs Chaney MarketPlace, Silver Spring, MD 27,037 4,711 9,789 21,959 — 31,748 9,966 21,782 — 4/04 40 Broadlands Village, Ashburn, VA 5,316 35,823 5,300 35,826 13 41,139 13,811 27,328 30,467 2002-3, 2004 & 2006 3/02 40 & 50 Burtonsville Town Square, Burtonsville, MD 74,212 6,261 28,401 51,821 251 80,473 5,184 75,289 35,836 2010 1/17 20 & 45 Countryside Marketplace, Sterling, VA 28,912 4,156 7,666 25,402 — 33,068 11,364 21,704 — 2/04 40 Cranberry Square, Westminster, MD 31,578 692 6,700 25,570 — 32,270 6,166 26,104 15,290 9/11 40 Cruse MarketPlace, Cumming, GA 12,226 688 3,901 9,013 — 12,914 3,914 9,000 — 3/04 40 Flagship Center, Rockville, MD 160 9 169 — — 169 — 169 — 1972 1/72 — French Market, Oklahoma City, OK 5,781 15,984 1,118 20,647 — 21,765 13,133 8,632 — 1972 & 1998 3/74 50 Germantown, Germantown, MD 2,034 566 2,034 566 — 2,600 455 2,145 — 1990 34,208 40 The Glen, Woodbridge, VA 12,918 8,466 5,300 16,084 — 21,384 10,659 10,725 21,933 1993 & 2005 6/94 40 Great Falls Center, Great Falls, VA 41,750 3,203 14,766 30,187 — 44,953 10,378 34,575 9,788 3/08 40 Hampshire Langley, Takoma, MD 3,159 3,368 1,892 4,635 — 6,527 4,008 2,519 13,480 1960 1/72 40 Hunt Club Corners, Apopka, FL 12,584 4,519 4,822 12,281 — 17,103 5,250 11,853 5,109 6/06, 12/12 40 Jamestown Place, Altamonte Springs, FL 14,055 2,245 4,455 11,845 — 16,300 4,694 11,606 6,110 11/05 40 Kentlands Square I, Gaithersburg, MD 14,379 2,996 5,006 12,369 — 17,375 4,474 12,901 22,012 2002 9/02 40 Kentlands Square II, Gaithersburg, MD 76,723 2,774 23,133 56,364 — 79,497 15,220 64,277 32,585 9/11, 9/13 40 Kentlands Place, Gaithersburg, MD 1,425 7,404 1,425 7,404 — 8,829 4,479 4,350 7,734 2005 1/04 50 Lansdowne Town Center, Leesburg, VA 6,545 43,227 6,546 43,220 6 49,772 17,708 32,064 29,657 2006 11/02 50 Leesburg Pike Plaza, Baileys Crossroads, VA 2,418 6,294 1,132 7,580 — 8,712 6,266 2,446 13,836 1965 2/66 40 Lumberton Plaza, Lumberton, NJ 4,400 11,612 950 15,041 21 16,012 13,709 2,303 — 1975 12/75 40 Metro Pike Center, Rockville, MD 33,123 4,832 26,064 7,944 3,947 37,955 2,046 35,909 — 12/10 40 Shops at Monocacy, Frederick, MD 9,541 14,385 9,260 14,666 — 23,926 6,643 17,283 27,836 2003-4 11/03 50 Northrock, Warrenton, VA 12,686 15,428 12,686 15,422 6 28,114 5,386 22,728 13,626 2009 01/08 50 Olde Forte Village, Ft. Washington, MD 15,933 6,795 5,409 17,319 — 22,728 8,646 14,082 21,204 2003-4 07/03 40 Olney, Olney, MD 4,963 2,623 3,079 4,507 — 7,586 3,487 4,099 12,125 1972 11/75 40 Orchard Park, Dunwoody, GA 19,377 1,553 7,751 13,179 — 20,930 4,457 16,473 9,136 7/07 40 Palm Springs Center, Altamonte Springs, FL 18,365 2,029 5,739 14,655 — 20,394 6,088 14,306 — 3/05 40 Ravenwood, Baltimore, MD 1,245 4,256 703 4,798 — 5,501 3,435 2,066 13,095 1959 & 2006 1/72 40 11503 Rockville Pike/5541 Nicholson Lane, Rockville, MD 26,561 24 22,113 4,472 — 26,585 1,146 25,439 — 10/10, 12/12 40 1500/1580/1582/1584 Rockville Pike, Rockville, MD 51,149 2,750 43,863 7,490 2,546 53,899 6,677 47,222 — 12/12, 1/14, 4/14, 12/14 5, 10, 5, 4 Seabreeze Plaza, Palm Harbor, FL 24,526 2,502 8,665 18,363 — 27,028 7,323 19,705 14,469 11/05 40 Market Place at Sea Colony, Bethany Beach, DE 2,920 261 1,147 2,034 — 3,181 674 2,507 — 3/08 40 Seven Corners, Falls Church, VA 4,848 45,770 4,929 45,689 — 50,618 32,078 18,540 58,607 1956 & 1997 26,846 40 Severna Park Marketplace, Severna Park, MD 63,254 526 12,700 51,080 — 63,780 11,856 51,924 28,480 9/11 40 Shops at Fairfax, Fairfax, VA 2,708 11,062 992 12,778 — 13,770 8,939 4,831 10,127 1975 & 1999 6/75 50 Smallwood Village Center, Waldorf, MD 17,819 8,345 6,402 19,762 — 26,164 9,655 16,509 — 1/06 40 Southdale, Glen Burnie, MD 18,895 25,098 15,254 28,739 — 43,993 23,105 20,888 — 1962 & 1986 1/72 , 11/16 40 Southside Plaza, Richmond, VA 6,728 11,381 1,878 16,231 — 18,109 13,105 5,004 — 1958 1/72 40 South Dekalb Plaza, Atlanta, GA 2,474 4,563 703 6,334 — 7,037 5,228 1,809 — 1970 2/76 40 Thruway, Winston-Salem, NC 7,848 26,569 7,693 26,693 31 34,417 19,638 14,779 — 1955 & 1965 5/72 40 Village Center, Centreville, VA 16,502 2,636 7,851 11,287 — 19,138 7,761 11,377 12,061 1990 34,208 40 Westview Village, Frederick, MD 6,047 25,265 6,047 25,265 — 31,312 10,448 20,864 — 2009 11/07 , 02/15 50 White Oak, Silver Spring, MD 6,277 6,020 4,649 7,446 202 12,297 6,307 5,990 21,704 1958 & 1967 1/72 40 Other Buildings / Improvements — 182 — 182 — 182 102 80 — Total Shopping Centers 841,335 461,349 421,698 873,788 7,198 1,302,684 407,918 894,766 592,914 Mixed-Use Properties Avenel Business Park, Gaithersburg, MD 21,459 33,526 3,756 51,229 — 54,985 40,108 14,877 25,224 1984, 1986,1990, 1998 & 2000 12/84, 8/85, 2/86, 4/98 & 10/2000 35 & 40 Clarendon Center, Arlington, VA (1) 12,753 186,314 16,287 182,780 — 199,067 51,725 147,342 94,712 2010 7/73, 1/96 & 4/02 50 Park Van Ness, Washington, DC 2,242 91,715 2,242 91,715 — 93,957 13,739 80,218 66,420 2016 7/73, 2/11 50 601 Pennsylvania Ave., Washington, DC 5,479 69,328 5,667 69,140 — 74,807 59,413 15,394 — 1986 26846 35 The Waycroft, Arlington, VA 52,067 225,226 52,025 216,617 8,651 277,293 4,722 272,571 146,083 2017 8/14, 12/14, 9/15, 8/16, 50 Washington Square, Alexandria, VA 2,034 57,078 544 58,568 — 59,112 30,081 29,031 55,398 1952 & 2000 26,846 50 Total Mixed-Use Properties 96,034 663,187 80,521 670,049 8,651 759,221 199,788 559,433 387,837 Development Land Ashland Square Phase II, Manassas, VA 5,292 4,642 7,029 — 2,905 9,934 — 9,934 — 12/04 New Market, New Market, MD 2,088 146 2,234 — — 2,234 — 2,234 — 9/05 Hampden House (formerly 7316 Wisconsin Avenue), Bethesda, MD 39,641 11,082 — 50,723 50,723 — 50,723 — 10/18, 12/18 Total Development Land 47,021 15,870 9,263 — 53,628 62,891 — 62,891 — Total $ 984,390 $ 1,140,406 $ 511,482 $ 1,543,837 $ 69,477 $ 2,124,796 $ 607,706 $ 1,517,090 $ 980,751 (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 $1.55 billion at December 31, 2020. 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, 2020 are summarized as follows: (In thousands) 2020 2019 2018 Total real estate investments: Balance, beginning of year $ 2,081,597 $ 1,948,165 $ 1,803,200 Acquisitions — — 48,579 Improvements 45,396 135,966 98,917 Retirements (2,197) (2,534) (2,531) Balance, end of year $ 2,124,796 $ 2,081,597 $ 1,948,165 Total accumulated depreciation: Balance, beginning of year $ 563,474 $ 525,518 $ 488,166 Depreciation expense 45,865 40,490 39,768 Retirements (1,633) (2,534) (2,416) Balance, end of year $ 607,706 $ 563,474 $ 525,518

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP 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. The most significant estimates and assumptions relate to impairment of real estate properties and collectability of operating lease receivables. Actual results could differ from those estimates.
Real Estate Investment Properties	Real Estate Investment Properties Real estate investment properties are stated at historic cost less depreciation. Although the Company intends to own its real estate investment properties over a long term, from time to time it will evaluate its market position, market conditions, and other factors and may elect to sell properties that do not conform to the Company’s investment profile. Management believes that the Company’s real estate assets have generally appreciated in value since their acquisition or development and, accordingly, the aggregate current value exceeds their aggregate net book value and also exceeds the value of the Company’s liabilities as reported in the financial statements. Because the financial statements are prepared in conformity with GAAP, they do not report the current value of the Company’s real estate investment properties. 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 2020, 2019, or 2018. 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, 2020, 2019, and 2018, was $45.9 million, $40.5 million, and $39.8 million, respectively. Repairs and maintenance expense totaled $11.1 million, $12.5 million, and $11.9 million for 2020, 2019, and 2018, respectively, and is included in property operating expenses in the accompanying consolidated financial statements.
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.
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.
Accounts Receivable, Accrued Income, and Allowance for Doubtful Accounts	Accounts Receivable, Accrued Income, and Allowance for Doubtful AccountsAccounts receivable are primarily comprised of rental and reimbursement billings due from tenants, and straight-line rent receivables representing the cumulative amount of adjustments necessary to present rental income on a straight-line basis. Individual leases are assessed for collectability and, upon the determination that the collection of rents is not probable, accrued rent and accounts receivable are charged off, and the charge off is reflected as an adjustment to rental revenue. Revenue from leases where collection is not probable is recorded on a cash basis until collectability is determined to be probable. We also assess whether operating lease receivables, at the portfolio level, are appropriately valued based upon an analysis of balances outstanding, effects of tenant bankruptcies, historical levels of bad debt and current economic trends. Additionally, because of the uncertainties related to the impact of the COVID-19 pandemic, our assessment also takes into consideration the types of business conducted by tenants and current discussions with the tenants, as well as recent rent collection experience. Evaluating and estimating uncollectable lease payments and related receivables requires a significant amount of judgment by management and is based on the best information available to management at the time of evaluation.
Deferred Leasing Costs	Deferred Leasing CostsDeferred 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.
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, 2020 are held in 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 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.
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.
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 February 2016, the Financial Accounting Standards Board (‘‘FASB’’) issued Accounting Standards Update (‘‘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. Upon adoption of ASU 2016-02 effective January 1, 2019, we elected the practical expedient for all leases with respect to lease identification, lease classification, and initial direct costs. We made a policy election not to separate lease and nonlease components and have accounted for each lease component and the related nonlease components together as a single component. There have been no significant changes to our lessor accounting for operating leases as a result of ASU 2016-02 We lease Shopping Centers and Mixed-Use Properties to lessees in exchange for monthly payments that cover rent, and where applicable, reimbursement for property taxes, insurance, and certain property operating expenses. Our leases were determined to be operating leases and generally range in term from one Some of our leases have termination options and/or extension options. Termination options allow the lessee to terminate the lease prior to the end of the lease term, provided certain conditions are met. Termination options generally require advance notification from the lessee and payment of a termination fee. Termination fees are recognized as revenue over the modified lease term. Extension options are subject to terms and conditions stated in the lease. On January 1, 2019, a right of use asset and corresponding lease liability related to our headquarters lease were recorded in other assets and other liabilities, respectively. The lease expires on February 28, 2022, with one option to renew for an additional five years. The right of use asset and corresponding lease liability totaled $0.9 million and $0.9 million, respectively, at December 31, 2020. Due to the business disruptions and challenges severely affecting the global economy caused by the novel strain of coronavirus (“COVID-19”) pandemic, many lessees have requested rent relief, including rent deferrals and other lease concessions. The lease modification guidance in ASU 2016-02 does not contemplate the rapid execution of concessions for multiple tenants in response to sudden liquidity constraints of lessees. In April 2020, the FASB staff issued a question and answer document that provided guidance allowing the Company to elect to either apply the lease modification accounting framework or not, with such election applied consistently to leases with similar characteristics and similar circumstances. The Company has elected to apply such relief, which, in the case of rent deferrals, results in the accrual of rent due from tenants and defers the payment of that rent to a future date, and will monitor the collectability of rent receivables. 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. The adoption of ASU 2016-13 effective January 1, 2020, had no material impact on our consolidated financial statements and related disclosures because the vast majority of the Company's receivables relate to operating leases which are accounted for under ASC 842. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging” (“ASU 2017-12”). ASU 2017-12 amends financial reporting for hedging activities to better align that reporting with risk management activities. ASU 2017-12 expands and refines hedge accounting for both financial and nonfinancial risk components and aligns the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. Effective with the adoption of ASU 2017-12 on January 1, 2019, changes in the fair value of the Company’s interest rate swap related to changes in the cash flow of the hedged item are reported as a component of interest expense and amortization of deferred debt costs in the Statements of Operations.
Reclassifications	ReclassificationsCertain reclassifications have been made to prior years to conform to the presentation used for year ended December 31, 2020.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	At December 31, 2020 and December 31, 2019, accounts receivable was comprised of: (In thousands) December 31, 2020 December 31, 2019 Rents currently due $ 13,321 $ 7,235 Deferred rents and payment plans 8,205 474 Straight-line rent 44,863 42,088 Other receivables 3,751 2,967 Credit losses on operating lease receivables (5,223) (453) Total $ 64,917 $ 52,311

Real Estate (Tables)

Real Estate (Tables)	12 Months Ended
	Dec. 31, 2020
Real Estate [Abstract]
Schedule of Construction in Progress	The following table shows the components of construction in progress. December 31, (in thousands) 2020 2019 Hampden House (formerly 7316 Wisconsin Avenue) $ 50,723 $ 44,638 The Waycroft 8,651 255,443 Ashbrook Marketplace 153 19,128 Other 9,950 16,435 Total $ 69,477 $ 335,644
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The purchase price was allocated to assets acquired and liabilities assumed based on their relative fair values as shown in the following table. (in thousands) Ashbrook Marketplace Hampden House (formerly 7316 Wisconsin Avenue) Total Land $ 8,776 $ 38,662 $ 47,438 Buildings — 979 979 In-place Leases — 886 886 Above Market Rent — 168 168 Below Market Rent — (21) (21) Total Purchase Price $ 8,776 $ 40,674 $ 49,450
Amortization of intangible assets and deferred income related to in place leases	As of December 31, 2020, 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 2021 $ 495 $ 33 $ 1,409 2022 368 33 1,306 2023 317 33 1,297 2024 198 33 878 2025 153 33 601 Thereafter 843 309 3,253 Total $ 2,374 $ 474 $ 8,744

Mortgage Notes Payable, Revol_2

Mortgage Notes Payable, Revolving Credit Facility, Interest Expense and Amortization of Deferred Debt Costs (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Scheduled maturities of all debt, including scheduled principal amortization	As of December 31, 2020, the scheduled maturities of all debt including scheduled principal amortization for years ended December 31 are as follows: (in thousands) Balloon Scheduled Total 2021 $ 11,012 $ 30,355 $ 41,367 2022 141,002 (a) 31,017 172,019 2023 84,225 31,481 115,706 2024 66,164 30,856 97,020 2025 20,363 27,860 48,223 Thereafter 569,330 116,586 685,916 Principal amount $ 892,096 $ 268,155 1,160,251 Unamortized deferred debt costs 9,337 Net $ 1,150,914 (a) Includes $104.5 million outstanding under the revolving facility.
Components of interest expense	The components of interest expense are set forth below. (in thousands) Year ended December 31, 2020 2019 2018 Interest incurred $ 51,705 $ 52,044 $ 49,652 Amortization of deferred debt costs 1,570 1,518 1,610 Capitalized interest (6,616) (11,480) (6,222) Interest expense 46,659 42,082 45,040 Less: Interest income 140 248 272 Interest expense, net and amortization of deferred debt costs $ 46,519 $ 41,834 $ 44,768

Lease Agreements (Tables)

Lease Agreements (Tables)	12 Months Ended
	Dec. 31, 2020
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) 2021 $ 163,862 2022 146,574 2023 126,550 2024 102,118 2025 80,366 Thereafter 351,968 $ 971,438

Equity and Noncontrolling Int_2

Equity and Noncontrolling Interest Equity Weighted Average Shares Outstanding (Tables)	12 Months Ended
	Dec. 31, 2020
Noncontrolling Interest [Abstract]
Schedule of Weighted Average Number of Shares	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) 2020 2019 2018 Weighted average common shares outstanding - Basic 23,356 23,009 22,383 Effect of dilutive options 1 44 42 Weighted average common shares outstanding - Diluted 23,357 23,053 22,425 Average share price $ 33.84 $ 53.41 $ 52.50 Non-dilutive options 1,439 633 492 Years non-dilutive options were issued 2014 through 2020 2016, 2017 and 2019 2015, 2016 and 2017

Stock Option Plan (Tables)

Stock Option Plan (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Options Issued	Directors Officers Grant date May 11, 2018 May 3, 2019 April 24, 2020 May 11, 2018 May 3, 2019 April 24, 2020 Exercise price $ 49.46 $ 55.71 $ 50.00 $ 49.46 $ 55.71 $ 50.00 Volatility 0.192 0.236 0.258 0.177 0.206 0.240 Expected life (years) 5.0 5.0 5.0 7.0 7.0 7.0 Assumed yield 3.70 % 3.75 % 3.80 % 3.75 % 3.80 % 3.85 % Risk-free rate 2.84 % 2.33 % 0.36 % 2.94 % 2.43 % 0.51 %
Summary of Option Activity	The table below summarizes the option activity for the years 2020, 2019, and 2018: 2020 2019 2018 Shares Weighted Shares Weighted Shares Weighted Outstanding at January 1 1,309,614 $ 53.38 1,114,169 $ 52.40 913,320 $ 52.80 Granted 238,000 50.00 260,000 55.71 245,000 49.46 Exercised (10,749) 49.19 (57,055) 44.53 (39,151) 42.98 Expired/Forfeited (34,195) 54.09 (7,500) 56.07 (5,000) 54.78 Outstanding December 31 1,502,670 52.86 1,309,614 53.38 1,114,169 52.40 Exercisable at December 31 971,545 53.01 763,614 52.43 600,919 50.93

Distributions (Tables)

Distributions (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020, 2019, and 2018, 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 2020 4th Quarter $ 2,798 $ 12,371 $ 4,195 117,368 $ 24.08 23,370 $ 24.35 3rd Quarter 2,798 12,373 4,188 14,525 28.98 13,108 29.47 2nd Quarter 2,799 12,364 4,188 12,627 32.22 — — 1st Quarter 2,799 12,275 4,180 83,978 48.59 15,101 49.40 Total 2020 $ 11,194 $ 49,383 $ 16,751 228,498 51,579 Distributions during 2019 4th Quarter $ 3,531 $ 12,251 $ 4,173 104,558 $ 52.84 13,747 $ 53.73 3rd Quarter 2,953 12,195 4,166 105,753 53.66 13,406 54.56 2nd Quarter 2,953 12,116 4,155 99,804 51.38 20,041 51.99 1st Quarter 2,953 12,006 4,148 120,347 51.28 13,742 52.16 Total 2019 $ 12,390 $ 48,568 $ 16,642 430,462 60,936 Distributions during 2018 4th Quarter $ 2,953 $ 11,706 $ 4,062 216,476 $ 49.34 13,867 $ 50.20 3rd Quarter 2,953 11,590 4,055 201,500 51.68 13,107 52.60 2nd Quarter 2,672 11,545 3,942 85,202 47.54 42,422 47.83 1st Quarter 3,824 11,465 3,922 69,750 52.71 38,037 53.03 Total 2018 $ 12,402 $ 46,306 $ 15,981 572,928 107,433

Interim Results (Unaudited) (Ta

Interim Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
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 2020 and 2019. (In thousands, except per share amounts) 2020 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total revenue $ 56,943 $ 53,220 $ 56,760 $ 58,284 Net Income 16,829 10,208 11,603 11,676 Net income attributable to Saul Centers, Inc. 13,264 8,328 9,367 9,423 Net income available to common stockholders 10,466 5,530 6,569 6,623 Net income available to common stockholders per diluted share 0.45 0.24 0.28 0.28 (In thousands, except per share amounts) 2019 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Total revenue $ 59,750 $ 58,141 $ 57,052 $ 56,582 Net Income 17,077 16,750 15,328 15,041 Net income attributable to Saul Centers, Inc. 13,447 13,232 12,226 12,818 Net income available to common stockholders 10,494 10,279 9,016 6,464 Net income available to common stockholders per basic and diluted share 0.46 0.45 0.39 0.27

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule of Business Segments	SAUL CENTERS, INC. (In thousands) Shopping Mixed-Use Corporate Consolidated As of or for the year ended December 31, 2020 Centers Properties and Other Totals Real estate rental operations: Revenue $ 161,854 $ 63,353 $ — $ 225,207 Expenses (35,198) (23,219) — (58,417) Income from real estate 126,656 40,134 — 166,790 Interest expense, net and amortization of deferred debt costs — — (46,519) (46,519) General and administrative — — (19,107) (19,107) Depreciation and amortization of deferred leasing costs (30,891) (20,235) — (51,126) Gain on sale of property 278 — — 278 Net income (loss) $ 96,043 $ 19,899 $ (65,626) $ 50,316 Capital investment $ 15,203 $ 40,965 $ — $ 56,168 Total assets $ 975,195 $ 643,503 $ 26,874 $ 1,645,572 As of or for the year ended December 31, 2019 Real estate rental operations: Revenue $ 167,888 $ 63,637 $ — $ 231,525 Expenses (36,119) (21,814) — (57,933) Income from real estate 131,769 41,823 — 173,592 Interest expense, net and amortization of deferred debt costs — — (41,834) (41,834) General and administrative — — (20,793) (20,793) Depreciation and amortization of deferred leasing costs (29,112) (17,221) — (46,333) Change in fair value of derivatives — — (436) (436) Net income (loss) $ 102,657 $ 24,602 $ (63,063) $ 64,196 Capital investment $ 33,968 $ 101,695 $ — $ 135,663 Total assets $ 980,096 $ 625,183 $ 13,061 $ 1,618,340 As of or for the year ended December 31, 2018 Real estate rental operations: Revenue $ 164,344 $ 62,875 $ — $ 227,219 Expenses (34,643) (20,935) — (55,578) Income from real estate 129,701 41,940 — 171,641 Interest expense, net and amortization of deferred debt costs — — (44,768) (44,768) General and administrative — — (18,459) (18,459) Depreciation and amortization of deferred leasing costs (29,251) (16,610) — (45,861) Change in fair value of derivatives — — (3) (3) Gain on sale of property 509 — — 509 Net income (loss) $ 100,959 $ 25,330 $ (63,230) $ 63,059 Capital investment $ 13,485 $ 115,165 $ — $ 128,650 Total assets $ 971,321 $ 537,500 $ 18,668 $ 1,527,489

Organization, Basis of Presen_2

Organization, Basis of Presentation - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020propertystoretenantpartnership
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
Number of stores | store	33
Saul Holdings Limited Partnership
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Percentage of ownership in operating partnership	74.60%
Shopping Centers
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	50
Mixed-Use Properties
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	7
Non-operating Development Properties
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of real estate properties	3
Revenue Benchmark
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of tenants | tenant	1
Percentage of total revenue	2.50%
Revenue Benchmark | Giant Food
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of stores | store	11
Percentage of total revenue	5.40%

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jan. 01, 2019lease_option
Significant Accounting Policies [Line Items]
Depreciation and amortization of deferred leasing costs	$ 45,865,000	$ 40,490,000	$ 39,768,000
Repairs and maintenance expense	11,100,000	12,500,000	11,900,000
Impairment of real estate	0
Rental revenue, lease related reserves	3,500,000
Rental revenue, charge offs	1,700,000
Deferred leasing costs, net	26,872,000	24,083,000
Accumulated amortization deferred leasing cost	(44,500,000)	(41,600,000)
Amortization expense deferred leasing cost	5,200,000	5,800,000	6,100,000
Accrued penalties and interest	0	0	$ 0
Tax basis of the company's real estate investments	1,550,000,000	$ 1,330,000,000
Right-of-use asset	900,000
Operating lease liability	$ 900,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:LiabilitiesAbstract
Corporate Headquarters
Significant Accounting Policies [Line Items]
Number of options to extend lease | lease_option				1
Lease renewal term				5 years
Minimum
Significant Accounting Policies [Line Items]
Operating lease term of contract				1 year
Minimum | Building
Significant Accounting Policies [Line Items]
Estimated useful life	35 years
Maximum
Significant Accounting Policies [Line Items]
Operating lease term of contract				15 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

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit losses on operating lease receivables	$ (5,223)	$ (453)
Total	64,917	52,311
Rents currently due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	13,321	7,235
Deferred rents and payment plans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	8,205	474
Straight-line rent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	44,863	42,088
Other receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	$ 3,751	$ 2,967

Real Estate - Schedule of Const

Real Estate - Schedule of Construction in Progress (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Sep. 01, 2019
Real Estate [Line Items]
Development in process	$ 69,477	$ 335,644
Hampden House (formerly 7316 Wisconsin Avenue)
Real Estate [Line Items]
Development in process	50,723	44,638	$ 42,600
The Waycroft
Real Estate [Line Items]
Development in process	8,651	255,443
Ashbrook Marketplace
Real Estate [Line Items]
Development in process	153	19,128
Other
Real Estate [Line Items]
Development in process	$ 9,950	$ 16,435

Real Estate - Additional Inform

Real Estate - Additional Information (Detail)	1 Months Ended				12 Months Ended
	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	May 31, 2018USD ($)ashares	Aug. 31, 2016shares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 01, 2019USD ($)	Dec. 31, 2017USD ($)
Real Estate Properties [Line Items]
Acquisition costs			$ 200,000
Development in process					$ 69,477,000	$ 335,644,000
Total purchase price	$ 1,948,165,000				2,124,796,000	2,081,597,000	$ 1,948,165,000		$ 1,803,200,000
Below market lease, carrying amount					23,700,000	24,100,000
Below market lease, accumulated amortization					15,000,000	13,900,000
Accretion income, intangible liabilities					1,400,000	1,500,000	1,700,000
Above Market Rent
Real Estate Properties [Line Items]
Intangible assets gross carrying amount					600,000	600,000
Intangible assets, accumulated amortization					128,900	108,300
Amortization expense					$ 43,600	109,600	110,500
Weighted-average amortization period					7 years
Below Market Rent
Real Estate Properties [Line Items]
Weighted-average amortization period					5 years
Lease acquisition costs
Real Estate Properties [Line Items]
Intangible assets gross carrying amount					$ 11,000,000	11,700,000
Intangible assets, accumulated amortization					8,600,000	8,500,000
Amortization expense					$ 600,000	900,000	1,300,000
Weighted-average amortization period					4 years 3 months 18 days
Ashbrook Marketplace
Real Estate Properties [Line Items]
Limited partnership units issued			$ 8,800,000				8,776,000
Development in process					$ 153,000	19,128,000
Hampden House (formerly 7316 Wisconsin Avenue)
Real Estate Properties [Line Items]
Acquisition costs		$ 700,000
Payments to acquire real estate		$ 35,500,000
Development in process					$ 50,723,000	$ 44,638,000		$ 42,600,000
Parcel Adjacent to 7316 Wisconsin Avenue
Real Estate Properties [Line Items]
Payments to acquire real estate	4,500,000
BF Saul Real Estate Investment Trust | Ashbrook Marketplace
Real Estate Properties [Line Items]
Limited partnership units issued (in shares) | shares			176,680	176,680
Area of land | a			13.7
2018 Acquisitions
Real Estate Properties [Line Items]
Total purchase price	49,450,000						49,450,000
2018 Acquisitions | In-place Leases
Real Estate Properties [Line Items]
Intangible assets	886,000						886,000
2018 Acquisitions | Above Market Rent
Real Estate Properties [Line Items]
Intangible assets	168,000						168,000
2018 Acquisitions | Below Market Rent
Real Estate Properties [Line Items]
Intangible assets	$ 21,000						$ 21,000

Real Estate - Allocation of Pur

Real Estate - Allocation of Purchase Prices to Acquired Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Real Estate Properties [Line Items]
Land	$ 511,482
Buildings	1,543,837
Total Purchase Price	$ 2,124,796	$ 2,081,597	$ 1,948,165	$ 1,803,200
Ashbrook Marketplace
Real Estate Properties [Line Items]
Land			8,776
Buildings			0
Total Purchase Price			8,776
Ashbrook Marketplace | In-place Leases
Real Estate Properties [Line Items]
Intangible assets			0
Ashbrook Marketplace | Above Market Rent
Real Estate Properties [Line Items]
Intangible assets			0
Ashbrook Marketplace | Below Market Rent
Real Estate Properties [Line Items]
Intangible assets			0
Hampden House (formerly 7316 Wisconsin Avenue)
Real Estate Properties [Line Items]
Land			38,662
Buildings			979
Total Purchase Price			40,674
Hampden House (formerly 7316 Wisconsin Avenue) | In-place Leases
Real Estate Properties [Line Items]
Intangible assets			(886)
Hampden House (formerly 7316 Wisconsin Avenue) | Above Market Rent
Real Estate Properties [Line Items]
Intangible assets			(168)
Hampden House (formerly 7316 Wisconsin Avenue) | Below Market Rent
Real Estate Properties [Line Items]
Intangible assets			(21)
2018 Acquisitions
Real Estate Properties [Line Items]
Land			47,438
Buildings			979
Total Purchase Price			49,450
2018 Acquisitions | In-place Leases
Real Estate Properties [Line Items]
Intangible assets			(886)
2018 Acquisitions | Above Market Rent
Real Estate Properties [Line Items]
Intangible assets			(168)
2018 Acquisitions | Below Market Rent
Real Estate Properties [Line Items]
Intangible assets			$ (21)

Real Estate - Amortization of I

Real Estate - Amortization of Intangible Assets and Deferred Income Related to in Place Leases (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Below market leases
2021	$ 1,409
2022	1,306
2023	1,297
2024	878
2025	601
Thereafter	3,253
Total	8,744
Lease acquisition costs
Finite-Lived Intangible Assets [Line Items]
2021	495
2022	368
2023	317
2024	198
2025	153
Thereafter	843
Total	2,374
Above market leases
Finite-Lived Intangible Assets [Line Items]
2021	33
2022	33
2023	33
2024	33
2025	33
Thereafter	309
Total	$ 474

Noncontrolling Interests - Ho_2

Noncontrolling Interests - Holders of Convertible Limited Partnership Units in the Operating Partnership - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Noncontrolling Interests
Noncontrolling Interest [Line Items]
Limited partnership units (in shares)	7,938,495
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 shares)	1,947,000
Fully converted partnership units and diluted weighted average shares outstanding (in shares)	31,300,000	30,900,000	30,200,000
Saul Holdings Limited Partnership
Noncontrolling Interest [Line Items]
Percentage of ownership in operating partnership	74.60%
Saul Holdings Limited Partnership | Noncontrolling Interests
Noncontrolling Interest [Line Items]
Percentage of ownership interest of noncontrolling interest	25.40%

Mortgage Notes Payable, Revol_3

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

Jul. 24, 2020

Jul. 14, 2020

Nov. 12, 2019

Jan. 10, 2019

Dec. 31, 2020

Oct. 01, 2021

Oct. 01, 2020

Mar. 03, 2020

Feb. 10, 2020

Dec. 31, 2019

Nov. 21, 2019

Jun. 03, 2019

Jan. 04, 2019

Dec. 31, 2018

Debt Instrument [Line Items]

Outstanding debt

$ 1,200,000,000

Fixed rate mortgages

827,603,000

$ 821,503,000

Variable rate debt

74,791,000

74,691,000

Principal amount

1,160,251,000

1,100,000,000

Debt outstanding with fixed-rate

938,400,000

Debt outstanding with variable-rate

162,500,000

Remaining loan balance

268,155,000

Unamortized deferred debt costs

9,337,000

9,700,000

Accumulated amortization

8,700,000

7,500,000

Capitalization of debt issuance cost

1,200,000

1,000,000

$ 3,200,000

Mortgage Notes Payable

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

41,000,000

41,000,000

Fixed rate mortgage notes payable

Debt Instrument [Line Items]

Fixed rate mortgages

980,800,000

938,400,000

Variable rate loans payable

Debt Instrument [Line Items]

Variable rate debt

179,500,000

New Facility | Line of Credit

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 400,000,000

Extension in line of credit facility period

1 year

Available borrowing capacity

$ 220,300,000

Outstanding line of credit

104,500,000

Letter of credit available borrowing capacity

185,000

New Facility | Line of Credit | Revolving Credit Facility

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 325,000,000

Interest rate spread on LIBOR

1.40%

New Facility | Line of Credit | Revolving Credit Facility | Minimum

Debt Instrument [Line Items]

Interest rate spread on LIBOR

1.35%

New Facility | Line of Credit | Revolving Credit Facility | Maximum

Debt Instrument [Line Items]

Interest rate spread on LIBOR

1.95%

New Facility | Line of Credit | Term Facility

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 75,000,000

New Facility | Term Facility | Revolving Credit Facility

Debt Instrument [Line Items]

Interest rate spread on LIBOR

1.35%

New Facility | Term Facility | Revolving Credit Facility | Minimum

Debt Instrument [Line Items]

Interest rate spread on LIBOR

1.30%

New Facility | Term Facility | Revolving Credit Facility | Maximum

Debt Instrument [Line Items]

Interest rate spread on LIBOR

1.90%

Park Van Ness Loan

Debt Instrument [Line Items]

Fixed rate mortgages

$ 66,400,000

Guarantor obligations, maximum exposure

3,300,000

$ 3,300,000

Park Van Ness Loan | Scenario, Forecast

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

$ 0

Kentlands Square I

Debt Instrument [Line Items]

Remaining loan balance

29,700,000

Waycroft Construction Loan

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

23,600,000

Remaining loan balance

146,100,000

Broadlands Village

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

3,800,000

Remaining loan balance

30,500,000

Avenel Business Park

Debt Instrument [Line Items]

Guarantor obligations, maximum exposure

6,300,000

Remaining loan balance

25,200,000

Countryside

Debt Instrument [Line Items]

Remaining loan balance

$ 12,700,000

Olde Forte Village | Four Point Six Five Maturing January Twenty Thirty Four

Debt Instrument [Line Items]

Loan amount

$ 22,100,000

Loan required periodic principal and interest payment

$ 124,700

Loan term

15 years

Loan fixed interest rate

4.65%

Amortization schedule

25 years

Balloon payment to be paid

$ 12,100,000

Briggs Chancy MarketPlace

Debt Instrument [Line Items]

Remaining loan balance

$ 12,400,000

Shops at Monocacy | Four Point Six Five Maturing January Twenty Thirty Four

Debt Instrument [Line Items]

Loan amount

$ 28,500,000

Loan required periodic principal and interest payment

$ 152,600

Loan term

15 years

Loan fixed interest rate

4.14%

Amortization schedule

25 years

Shops at Monocacy | 4.69% fixed rate loan maturing in 2034

Debt Instrument [Line Items]

Balloon payment to be paid

$ 15,100,000

Thruway

Debt Instrument [Line Items]

Remaining loan balance

$ 35,600,000

Ashbrook Marketplace

Debt Instrument [Line Items]

Remaining loan balance

21,900,000

Ashbrook Marketplace | 3.80% Fixed Rate Loan Maturing In 2035

Debt Instrument [Line Items]

Loan amount

$ 22,100,000

Loan required periodic principal and interest payment

$ 114,226

Loan term

15 years

Loan fixed interest rate

3.80%

Amortization schedule

25 years

Balloon payment to be paid

$ 11,500,000

Ashbrook Marketplace | 3.43% Fixed Rate Loan Maturing in 2035

Debt Instrument [Line Items]

Loan amount

$ 30,000,000

Loan required periodic principal and interest payment

$ 149,064

Loan term

15 years

Loan fixed interest rate

3.43%

Amortization schedule

25 years

Balloon payment to be paid

$ 15,300,000

Debt Covenant

Debt Instrument [Line Items]

Carrying value of properties collateralized

$ 1,200,000,000

$ 1,100,000,000

Credit agreement leverage ratio

60.00%

Interest coverage ratio required minimum

2

Required fixed charge coverage ratio

1.4

Boca Valley Plaza

Debt Instrument [Line Items]

Remaining loan balance

$ 9,200,000

Palm Springs Center

Debt Instrument [Line Items]

Remaining loan balance

$ 7,100,000

Mortgage Notes Payable, Revol_4

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, 2020	Dec. 31, 2019
Balloon Payments
2021	$ 11,012
2022	141,002
2023	84,225
2024	66,164
2025	20,363
Thereafter	569,330
Balloon Payments	892,096
Scheduled Principal Amortization
2021	30,355
2022	31,017
2023	31,481
2024	30,856
2025	27,860
Thereafter	116,586
Scheduled Principal Amortization	268,155
Total
2021	41,367
2022	172,019
2023	115,706
2024	97,020
2025	48,223
Thereafter	685,916
Principal amount	1,160,251	$ 1,100,000
Unamortized deferred debt costs	9,337	$ 9,700
Net	$ 1,150,914

Mortgage Notes Payable, Revol_5

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Interest incurred	$ 51,705	$ 52,044	$ 49,652
Amortization of deferred debt costs	1,570	1,518	1,610
Capitalized interest	(6,616)	(11,480)	(6,222)
Interest expense	46,659	42,082	45,040
Less: Interest income	140	248	272
Interest expense, net and amortization of deferred debt costs	$ 46,519	$ 41,834	$ 44,768

Lease Agreements - Additional I

Lease Agreements - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Base rent	$ 188.6	$ 185.7
Base rent (including straight-line rent)			$ 184.7
Expense recoveries	34.7	36.5	35.5
Payments for rent	$ 0.9	$ 0.9
Percentage rent			$ 1

Lease Agreements - Future Contr

Lease Agreements - Future Contractual Payments Under Noncancelable Leases (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Leases [Abstract]
2021	$ 163,862
2022	146,574
2023	126,550
2024	102,118
2025	80,366
Thereafter	351,968
Total future contractual payments	$ 971,438

Long-Term Lease Obligations - A

Long-Term Lease Obligations - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)property	Dec. 31, 2019USD ($)property	Dec. 31, 2018USD ($)
Leases Disclosure [Line Items]
Number of properties subject to noncancelable long-term lease | property	0	0
Rent expense	$ 799,300	$ 806,500
Rent expense			$ 779,800
Flagship Center
Leases Disclosure [Line Items]
Number of developed parcels | property	2
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%

Equity and Noncontrolling Int_3

Equity and Noncontrolling Interest - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Income (loss) attributable to noncontrolling interest, before tax	$ 9.9	$ 12.5	$ 12.5
Series D Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Depositary shares outstanding (in shares)	3
Percentage of redeemable preferred stock	6.125%
Liquidation preference (in usd per share)	$ 25
Annual dividend on depositary shares (in usd per share)	$ 1.53125
Depository shares to cumulative redeemable preferred stock ratio	1.00%
Series E Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Depositary shares outstanding (in shares)	4.4
Percentage of redeemable preferred stock	6.00%
Liquidation preference (in usd per share)	$ 25
Annual dividend on depositary shares (in usd per share)	$ 1.50
Depository shares to cumulative redeemable preferred stock ratio	1.00%

Equity and Noncontrolling Int_4

Equity and Noncontrolling Interest - Per Share Data (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Weighted average common shares outstanding - basic (in shares)	23,356	23,009	22,383
Effect of dilutive options (in shares)	1	44	42
Weighted average common shares outstanding - diluted (in shares)	23,357	23,053	22,425
Average share price (in usd per share)	$ 33.84	$ 53.41	$ 52.50
Options
Class of Stock [Line Items]
Non-dilutive options (in shares)	1,439	633	492

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail)	Nov. 05, 2019shares	Dec. 08, 2016	May 31, 2018shares	Aug. 31, 2016USD ($)ashares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Related Party Transaction [Line Items]
Company contribution to a multi employer 401K plan at discretionary amount of employee's cash compensation, maximum percentage					6.00%	6.00%	6.00%
Company contribution to a multi employer 401K plan at discretionary amount of employee's cash compensation, amount					$ 302,000	$ 322,200	$ 345,900
Deferred compensation, employee contribution, percentage					2.00%
Deferred compensation, employer contribution, percentage					3	3	3
Deferred compensation, company contribution, amount					$ 241,300	$ 345,200	$ 282,500
Deferred compensation, cumulative unfunded liability					2,900,000	3,100,000
Ancillary costs and expenses					7,400,000	8,400,000	8,400,000
Liability due to the Saul Organization for the company's share of these ancillary costs and expenses					782,700	918,700
Automatic renewal period		12 months
Insurance commissions and fees expense					427,700	$ 399,600	$ 407,900
Contribution Agreement
Related Party Transaction [Line Items]
Number of partnership units issued in transaction (in shares) | shares	1,416,071
Estimated reimbursement of costs incurred					$ 6,100,000
BF Saul Real Estate Investment Trust | Ashbrook Marketplace
Related Party Transaction [Line Items]
Area of real estate property (in square feet) | a				13.7
Limited partnership units issued (in shares) | shares			176,680	176,680
BF Saul Real Estate Investment Trust | Ashbrook Marketplace | Minimum
Related Party Transaction [Line Items]
Noncash financial or equity instrument consideration, future shares issued estimated value				$ 3,300,000
BF Saul Real Estate Investment Trust | Ashbrook Marketplace | Maximum
Related Party Transaction [Line Items]
Noncash financial or equity instrument consideration, future shares issued estimated value				$ 3,600,000

Stock Option Plan - Additional

Stock Option Plan - Additional Information (Detail)	Dec. 31, 2020USD ($)$ / sharesshares	Apr. 24, 2020USD ($)person$ / shares	May 03, 2019USD ($)person$ / sharesshares	May 11, 2018USD ($)person$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019$ / shares	Dec. 31, 2018$ / shares	Dec. 31, 2004shares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Deferred compensation (in shares)	118,628				11,574
Exercise price of options (in usd per share) | $ / shares					$ 50	$ 55.71	$ 49.46
Closing price (in usd per share) | $ / shares	$ 31.68				$ 31.68
Allocated share based compensation | $					$ 1,200,000
Future expense | $	$ 1,600,000				$ 1,600,000
2017 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price of options (in usd per share) | $ / shares				$ 49.46
Fair value stock option grant | $				$ 1,400,000
2018 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price of options (in usd per share) | $ / shares			$ 55.71
Fair value stock option grant | $			$ 1,900,000
2019 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price of options (in usd per share) | $ / shares		$ 50
Closing price (in usd per share) | $ / shares		$ 28.02
Fair value stock option grant | $		$ 200,000
Common Stock
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Shares due to exercise of employee stock options and issuance of directors' deferred stock (in shares)					7,354
Officer | 2017 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of individuals granted options | person				22
Options vested				25.00%
Fair value stock option grant | $				$ 1,200,000
Officer | 2018 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of individuals granted options | person			23
Options vested			25.00%
Fair value stock option grant | $			$ 1,700,000
Officer | 2019 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of individuals granted options | person		20
Options vested		25.00%
Fair value stock option grant | $		$ 200,000
Director | 2017 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of individuals granted options | person				11
Fair value stock option grant | $				$ 169,400
Director | 2018 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of individuals granted options | person			11
Fair value stock option grant | $			$ 226,600
Director | 2019 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of individuals granted options | person		11
Fair value stock option grant | $		$ 23,100
Stock options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Expiration period								10 years
Stock options | Amended 2004 Plan
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Authorized shares for a grant (in shares)								3,400,000
Stock options | 2017 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)				245,000
Stock options | 2018 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)			260,000
Stock options | 2019 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)			238,000
Stock options | Officer
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Option vesting period								4 years
Stock options | Officer | 2017 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Option vesting period				4 years
Stock options | Officer | 2018 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Option vesting period			4 years
Stock options | Officer | 2019 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Option vesting period		4 years
Incentive stock option | 2017 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)				25,914
Incentive stock option | 2018 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)			34,651
Incentive stock option | 2019 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)			29,624
Nonqualified stock options | 2017 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)				219,086
Nonqualified stock options | 2018 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)			225,349
Nonqualified stock options | 2019 Options
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options granted to purchase stocks (in shares)			208,376

Stock Option Plan - Stock Optio

Stock Option Plan - Stock Options Issued (Detail)	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2019$ / shares	Dec. 31, 2018$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 49.19	$ 44.53	$ 42.98
Directors | May 11, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 49.46
Volatility	0.192
Expected life (years)	5 years
Assumed yield	3.70%
Risk-free rate	2.84%
Directors | May 3, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 55.71
Volatility	0.236
Expected life (years)	5 years
Assumed yield	3.75%
Risk-free rate	2.33%
Directors | April, 24 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 50
Volatility	0.258
Expected life (years)	5 years
Assumed yield	3.80%
Risk-free rate	0.36%
Officers | May 11, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 49.46
Volatility	0.177
Expected life (years)	7 years
Assumed yield	3.75%
Risk-free rate	2.94%
Officers | May 3, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 55.71
Volatility	0.206
Expected life (years)	7 years
Assumed yield	3.80%
Risk-free rate	2.43%
Officers | April, 24 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in usd per share)	$ 50
Volatility	0.240
Expected life (years)	7 years
Assumed yield	3.85%
Risk-free rate	0.51%

Stock Option Plan - Summary of

Stock Option Plan - Summary of Option Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Outstanding at January 1 (in shares)	1,309,614	1,114,169	913,320
Granted (in shares)	238,000	260,000	245,000
Exercised (in shares)	(10,749)	(57,055)	(39,151)
Expired/Forfeited (in shares)	(34,195)	(7,500)	(5,000)
Outstanding December 31 (in shares)	1,502,670	1,309,614	1,114,169
Options exercisable (in shares)	971,545	763,614	600,919
Weighted Average Exercise Price
Outstanding at January 1 (in usd per share)	$ 53.38	$ 52.40	$ 52.80
Granted (in usd per share)	50	55.71	49.46
Exercised (in usd per share)	49.19	44.53	42.98
Expired/Forfeited (in usd per share)	54.09	56.07	54.78
Outstanding December 31 (in usd per share)	52.86	53.38	52.40
Exercisable at December 31 (in usd per share)	$ 53.01	$ 52.43	$ 50.93
Intrinsic value of options exercised	$ 0.1	$ 0.6	$ 0.5
Closing price (in usd per share)	$ 31.68
Weighted average remaining life of options exercisable	5 years 2 months 12 days
Weighted average remaining life of options outstanding	5 years

Fair Value of Financial Instr_2

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value of Financial Instruments [Line Items]
Interest rate	3.40%	3.55%
Notes payable, fair value	$ 981,000	$ 957,400
Fixed rate mortgages	827,603	821,503
Fixed rate mortgage notes payable
Fair Value of Financial Instruments [Line Items]
Fixed rate mortgages	$ 980,800	$ 938,400

Distributions - Additional Info

Distributions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 31, 2020	Jan. 15, 2020	Jan. 02, 2020	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends [Line Items]
Common stock issued, discount rate					3.00%
Common stock distributions (in usd per share)					$ 2.12	$ 2.12	$ 2.08
Dividends declared per common share outstanding (in usd per share)				$ 0.53
Common stock dividend paid	$ 12,400
Distribution to limited partnership unitholders	$ 4,200				$ 16,751	$ 16,642	$ 15,981
Distributions partnership units (in usd per share)	$ 0.53
Preferred stock distributions		$ 2,800
Dividend Income
Dividends [Line Items]
Common stock distributions (in usd per share)					$ 1.43	$ 2	$ 1.61
Return on Invested Capital
Dividends [Line Items]
Return of capital (in usd per share)				$ 0.69	0.69	0.12	0.47
Series C Preferred Stock
Dividends [Line Items]
Preferred stock dividend (in usd per share)						1.80	1.72
Depositary Shares each representing 1/100th of a share of 6.125% Series D Cumulative Redeemable Preferred Stock, Par Value $0.01 Per Share
Dividends [Line Items]
Preferred stock dividend (in usd per share)					1.53	1.53	$ 1.05
Dividends declared per preferred share outstanding (in usd per share)			$ 0.3828
Depositary Shares each representing 1/100th of a share of 6.000% Series E Cumulative Redeemable Preferred Stock, Par Value $0.01 Per Share
Dividends [Line Items]
Preferred stock dividend (in usd per share)					$ 1.50	$ 0.06
Dividends declared per preferred share outstanding (in usd per share)			$ 0.3750

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	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends [Line Items]
Preferred Stockholders													$ 11,194	$ 12,390	$ 12,402
Common Stockholders													49,383	48,568	46,306
Limited Partnership Unitholders													$ 16,751	$ 16,642	$ 15,981
Common Stock Shares Issued (in shares)													228,498,000	430,462,000	572,928,000
Limited Partnership Units Issued (in shares)													51,579,000	60,936,000	107,433,000
4th Quarter
Dividends [Line Items]
Preferred Stockholders	$ 2,798				$ 3,531				$ 2,953
Common Stockholders	12,371				12,251				11,706
Limited Partnership Unitholders	$ 4,195				$ 4,173				$ 4,062
Common Stock Shares Issued (in shares)	117,368,000				104,558,000				216,476,000
Discounted Share Price (in usd per share)	$ 24.08				$ 52.84				$ 49.34				$ 24.08	$ 52.84	$ 49.34
Limited Partnership Units Issued (in shares)	23,370,000				13,747,000				13,867,000
Average Unit Price (in usd per share)	$ 24.35				$ 53.73				$ 50.20				$ 24.35	$ 53.73	$ 50.20
3rd Quarter
Dividends [Line Items]
Preferred Stockholders		$ 2,798				$ 2,953				$ 2,953
Common Stockholders		12,373				12,195				11,590
Limited Partnership Unitholders		$ 4,188				$ 4,166				$ 4,055
Common Stock Shares Issued (in shares)		14,525,000				105,753,000				201,500,000
Discounted Share Price (in usd per share)		$ 28.98				$ 53.66				$ 51.68
Limited Partnership Units Issued (in shares)		13,108,000				13,406,000				13,107,000
Average Unit Price (in usd per share)		$ 29.47				$ 54.56				$ 52.60
2nd Quarter
Dividends [Line Items]
Preferred Stockholders			$ 2,799				$ 2,953				$ 2,672
Common Stockholders			12,364				12,116				11,545
Limited Partnership Unitholders			$ 4,188				$ 4,155				$ 3,942
Common Stock Shares Issued (in shares)			12,627,000				99,804,000				85,202,000
Discounted Share Price (in usd per share)			$ 32.22				$ 51.38				$ 47.54
Limited Partnership Units Issued (in shares)			0				20,041,000				42,422,000
Average Unit Price (in usd per share)			$ 0				$ 51.99				$ 47.83
1st Quarter
Dividends [Line Items]
Preferred Stockholders				$ 2,799				$ 2,953				$ 3,824
Common Stockholders				12,275				12,006				11,465
Limited Partnership Unitholders				$ 4,180				$ 4,148				$ 3,922
Common Stock Shares Issued (in shares)				83,978,000				120,347,000				69,750,000
Discounted Share Price (in usd per share)				$ 48.59				$ 51.28				$ 52.71
Limited Partnership Units Issued (in shares)				15,101,000				13,742,000				38,037,000
Average Unit Price (in usd per share)				$ 49.40				$ 52.16				$ 53.03

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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 58,284	$ 56,760	$ 53,220	$ 56,943	$ 56,582	$ 57,052	$ 58,141	$ 59,750	$ 225,207	$ 231,525	$ 227,219
Net Income	11,676	11,603	10,208	16,829	15,041	15,328	16,750	17,077
Net income attributable to Saul Centers, Inc.	9,423	9,367	8,328	13,264	12,818	12,226	13,232	13,447	40,382	51,723	50,554
Net income available to common stockholders	$ 6,623	$ 6,569	$ 5,530	$ 10,466	$ 6,464	$ 9,016	$ 10,279	$ 10,494	$ 29,188	$ 36,253	$ 35,964
Net income available to common stockholders per diluted share (in usd per share)	$ 0.28	$ 0.28	$ 0.24	$ 0.45					$ 1.25	$ 1.57	$ 1.60
Net income available to common stockholders per basic and diluted share (in usd per share)					$ 0.27	$ 0.39	$ 0.45	$ 0.46

Business Segments - Additional

Business Segments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020segment
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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total revenue	$ 58,284	$ 56,760	$ 53,220	$ 56,943	$ 56,582	$ 57,052	$ 58,141	$ 59,750	$ 225,207	$ 231,525	$ 227,219
Expenses									(58,417)	(57,933)	(55,578)
Income from real estate									166,790	173,592	171,641
Interest expense, net and amortization of deferred debt costs									(46,519)	(41,834)	(44,768)
General and administrative									(19,107)	(20,793)	(18,459)
Depreciation and amortization of deferred leasing costs									(51,126)	(46,333)	(45,861)
Change in fair value of derivatives									0	(436)	(3)
Gain on sale of property									278	0	509
Net income (loss)									50,316	64,196	63,059
Capital investment									56,168	135,663	128,650
Total assets	1,645,572				1,618,340				1,645,572	1,618,340	1,527,489
Operating Segments | Shopping Centers
Segment Reporting Information [Line Items]
Total revenue									161,854	167,888	164,344
Expenses									(35,198)	(36,119)	(34,643)
Income from real estate									126,656	131,769	129,701
Interest expense, net and amortization of deferred debt costs									0	0	0
General and administrative									0	0	0
Depreciation and amortization of deferred leasing costs									(30,891)	(29,112)	(29,251)
Change in fair value of derivatives										0	0
Gain on sale of property									278		509
Net income (loss)									96,043	102,657	100,959
Capital investment									15,203	33,968	13,485
Total assets	975,195				980,096				975,195	980,096	971,321
Operating Segments | Mixed-Use Properties
Segment Reporting Information [Line Items]
Total revenue									63,353	63,637	62,875
Expenses									(23,219)	(21,814)	(20,935)
Income from real estate									40,134	41,823	41,940
Interest expense, net and amortization of deferred debt costs									0	0	0
General and administrative									0	0	0
Depreciation and amortization of deferred leasing costs									(20,235)	(17,221)	(16,610)
Change in fair value of derivatives										0	0
Gain on sale of property									0		0
Net income (loss)									19,899	24,602	25,330
Capital investment									40,965	101,695	115,165
Total assets	643,503				625,183				643,503	625,183	537,500
Corporate
Segment Reporting Information [Line Items]
Total revenue									0	0	0
Expenses									0	0	0
Income from real estate									0	0	0
Interest expense, net and amortization of deferred debt costs									(46,519)	(41,834)	(44,768)
General and administrative									(19,107)	(20,793)	(18,459)
Depreciation and amortization of deferred leasing costs									0	0	0
Change in fair value of derivatives										(436)	(3)
Gain on sale of property									0		0
Net income (loss)									(65,626)	(63,063)	(63,230)
Capital investment									0	0	0
Total assets	$ 26,874				$ 13,061				$ 26,874	$ 13,061	$ 18,668

Impact of COVID-19 - Narrative

Impact of COVID-19 - Narrative (Details)	3 Months Ended	14 Months Ended
	Dec. 31, 2020	Feb. 22, 2022
Subsequent Event [Line Items]
Rent deferral period	3 months
Subsequent Event
Subsequent Event [Line Items]
Deferred Rent, Percent Due		0
Contractual Base Rent, Operating Expense And Real Estate Recoveries Collected | Revenue
Subsequent Event [Line Items]
Percentage of total revenue	94.00%
Operating lease income subject to deferral agreements | Outstanding Billings | Revenue
Subsequent Event [Line Items]
Percentage of total revenue	0.50%
Operating lease income subject to deferral agreements | April, May, June 2020 unpaid balance as percent of total unpaid balance | Revenue
Subsequent Event [Line Items]
Percentage of total revenue	9.00%
Retail Real Estate | Contractual Base Rent, Operating Expense And Real Estate Recoveries Collected | Revenue
Subsequent Event [Line Items]
Percentage of total revenue	94.00%
Office Real Estate | Contractual Base Rent, Operating Expense And Real Estate Recoveries Collected | Revenue
Subsequent Event [Line Items]
Percentage of total revenue	93.00%
Residential Real Estate | Contractual Base Rent, Operating Expense And Real Estate Recoveries Collected | Revenue
Subsequent Event [Line Items]
Percentage of total revenue	100.00%

Real Estate and Accumulated D_2

Real Estate and Accumulated Depreciation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Real Estate Properties [Line Items]
Initial Basis	$ 984,390
Cost capitalized subsequent to acquisition	1,140,406
Land	511,482
Buildings	1,543,837
Construction in progress	69,477	$ 335,644
Total Purchase Price	2,124,796	2,081,597	$ 1,948,165	$ 1,803,200
Accumulated Depreciation	607,706	563,474	$ 525,518	$ 488,166
Book Value	1,517,090	1,518,123
Fixed rate mortgages	827,603	821,503
Development land, related debt	144,607	$ 108,623
Total, related debt	980,751
Shopping Centers
Real Estate Properties [Line Items]
Initial Basis	841,335
Cost capitalized subsequent to acquisition	461,349
Land	421,698
Buildings	873,788
Construction in progress	7,198
Total Purchase Price	1,302,684
Accumulated Depreciation	407,918
Book Value	894,766
Fixed rate mortgages	592,914
Shopping Centers | Ashbrook Marketplace, Ashburn, VA
Real Estate Properties [Line Items]
Initial Basis	8,938
Cost capitalized subsequent to acquisition	19,897
Land	8,938
Buildings	19,744
Construction in progress	153
Total Purchase Price	28,835
Accumulated Depreciation	453
Book Value	28,382
Fixed rate mortgages	$ 21,922
Buildings and Improvements Depreciable Lives in Years	50 years
Shopping Centers | Ashburn Village, Ashburn, VA
Real Estate Properties [Line Items]
Initial Basis	$ 11,431
Cost capitalized subsequent to acquisition	20,493
Land	6,764
Buildings	25,138
Construction in progress	22
Total Purchase Price	31,924
Accumulated Depreciation	14,989
Book Value	16,935
Fixed rate mortgages	$ 25,253
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	5,298
Land	1,178
Buildings	5,298
Construction in progress	0
Total Purchase Price	6,476
Accumulated Depreciation	2,438
Book Value	4,038
Fixed rate mortgages	$ 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	18,485
Land	22,691
Buildings	19,955
Construction in progress	0
Total Purchase Price	42,646
Accumulated Depreciation	15,823
Book Value	26,823
Fixed rate mortgages	$ 34,223
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
Construction in progress	0
Total Purchase Price	22,623
Accumulated Depreciation	0
Book Value	22,623
Fixed rate mortgages	$ 10,018
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	2,614
Land	5,735
Buildings	13,599
Construction in progress	0
Total Purchase Price	19,334
Accumulated Depreciation	5,681
Book Value	13,653
Fixed rate mortgages	$ 0
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	4,709
Land	3,687
Buildings	5,905
Construction in progress	0
Total Purchase Price	9,592
Accumulated Depreciation	3,466
Book Value	6,126
Fixed rate mortgages	$ 15,191
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	4,711
Land	9,789
Buildings	21,959
Construction in progress	0
Total Purchase Price	31,748
Accumulated Depreciation	9,966
Book Value	21,782
Fixed rate mortgages	$ 0
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	35,823
Land	5,300
Buildings	35,826
Construction in progress	13
Total Purchase Price	41,139
Accumulated Depreciation	13,811
Book Value	27,328
Fixed rate mortgages	$ 30,467
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	6,261
Land	28,401
Buildings	51,821
Construction in progress	251
Total Purchase Price	80,473
Accumulated Depreciation	5,184
Book Value	75,289
Fixed rate mortgages	$ 35,836
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	4,156
Land	7,666
Buildings	25,402
Construction in progress	0
Total Purchase Price	33,068
Accumulated Depreciation	11,364
Book Value	21,704
Fixed rate mortgages	$ 0
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	692
Land	6,700
Buildings	25,570
Construction in progress	0
Total Purchase Price	32,270
Accumulated Depreciation	6,166
Book Value	26,104
Fixed rate mortgages	$ 15,290
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	688
Land	3,901
Buildings	9,013
Construction in progress	0
Total Purchase Price	12,914
Accumulated Depreciation	3,914
Book Value	9,000
Fixed rate mortgages	$ 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
Construction in progress	0
Total Purchase Price	169
Accumulated Depreciation	0
Book Value	169
Fixed rate mortgages	$ 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	15,984
Land	1,118
Buildings	20,647
Construction in progress	0
Total Purchase Price	21,765
Accumulated Depreciation	13,133
Book Value	8,632
Fixed rate mortgages	$ 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	566
Land	2,034
Buildings	566
Construction in progress	0
Total Purchase Price	2,600
Accumulated Depreciation	455
Book Value	2,145
Fixed rate mortgages	$ 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	8,466
Land	5,300
Buildings	16,084
Construction in progress	0
Total Purchase Price	21,384
Accumulated Depreciation	10,659
Book Value	10,725
Fixed rate mortgages	$ 21,933
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	3,203
Land	14,766
Buildings	30,187
Construction in progress	0
Total Purchase Price	44,953
Accumulated Depreciation	10,378
Book Value	34,575
Fixed rate mortgages	$ 9,788
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	3,368
Land	1,892
Buildings	4,635
Construction in progress	0
Total Purchase Price	6,527
Accumulated Depreciation	4,008
Book Value	2,519
Fixed rate mortgages	$ 13,480
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	4,519
Land	4,822
Buildings	12,281
Construction in progress	0
Total Purchase Price	17,103
Accumulated Depreciation	5,250
Book Value	11,853
Fixed rate mortgages	$ 5,109
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	2,245
Land	4,455
Buildings	11,845
Construction in progress	0
Total Purchase Price	16,300
Accumulated Depreciation	4,694
Book Value	11,606
Fixed rate mortgages	$ 6,110
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	2,996
Land	5,006
Buildings	12,369
Construction in progress	0
Total Purchase Price	17,375
Accumulated Depreciation	4,474
Book Value	12,901
Fixed rate mortgages	$ 22,012
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	2,774
Land	23,133
Buildings	56,364
Construction in progress	0
Total Purchase Price	79,497
Accumulated Depreciation	15,220
Book Value	64,277
Fixed rate mortgages	$ 32,585
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	7,404
Land	1,425
Buildings	7,404
Construction in progress	0
Total Purchase Price	8,829
Accumulated Depreciation	4,479
Book Value	4,350
Fixed rate mortgages	$ 7,734
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	43,227
Land	6,546
Buildings	43,220
Construction in progress	6
Total Purchase Price	49,772
Accumulated Depreciation	17,708
Book Value	32,064
Fixed rate mortgages	$ 29,657
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	6,294
Land	1,132
Buildings	7,580
Construction in progress	0
Total Purchase Price	8,712
Accumulated Depreciation	6,266
Book Value	2,446
Fixed rate mortgages	$ 13,836
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	11,612
Land	950
Buildings	15,041
Construction in progress	21
Total Purchase Price	16,012
Accumulated Depreciation	13,709
Book Value	2,303
Fixed rate mortgages	$ 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	4,832
Land	26,064
Buildings	7,944
Construction in progress	3,947
Total Purchase Price	37,955
Accumulated Depreciation	2,046
Book Value	35,909
Fixed rate mortgages	$ 0
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	14,385
Land	9,260
Buildings	14,666
Construction in progress	0
Total Purchase Price	23,926
Accumulated Depreciation	6,643
Book Value	17,283
Fixed rate mortgages	$ 27,836
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	15,428
Land	12,686
Buildings	15,422
Construction in progress	6
Total Purchase Price	28,114
Accumulated Depreciation	5,386
Book Value	22,728
Fixed rate mortgages	$ 13,626
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	6,795
Land	5,409
Buildings	17,319
Construction in progress	0
Total Purchase Price	22,728
Accumulated Depreciation	8,646
Book Value	14,082
Fixed rate mortgages	$ 21,204
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	2,623
Land	3,079
Buildings	4,507
Construction in progress	0
Total Purchase Price	7,586
Accumulated Depreciation	3,487
Book Value	4,099
Fixed rate mortgages	$ 12,125
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	1,553
Land	7,751
Buildings	13,179
Construction in progress	0
Total Purchase Price	20,930
Accumulated Depreciation	4,457
Book Value	16,473
Fixed rate mortgages	$ 9,136
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	2,029
Land	5,739
Buildings	14,655
Construction in progress	0
Total Purchase Price	20,394
Accumulated Depreciation	6,088
Book Value	14,306
Fixed rate mortgages	$ 0
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	4,256
Land	703
Buildings	4,798
Construction in progress	0
Total Purchase Price	5,501
Accumulated Depreciation	3,435
Book Value	2,066
Fixed rate mortgages	$ 13,095
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
Construction in progress	0
Total Purchase Price	26,585
Accumulated Depreciation	1,146
Book Value	25,439
Fixed rate mortgages	$ 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	2,750
Land	43,863
Buildings	7,490
Construction in progress	2,546
Total Purchase Price	53,899
Accumulated Depreciation	6,677
Book Value	47,222
Fixed rate mortgages	0
Shopping Centers | Seabreeze Plaza, Palm Harbor, FL
Real Estate Properties [Line Items]
Initial Basis	24,526
Cost capitalized subsequent to acquisition	2,502
Land	8,665
Buildings	18,363
Construction in progress	0
Total Purchase Price	27,028
Accumulated Depreciation	7,323
Book Value	19,705
Fixed rate mortgages	$ 14,469
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	261
Land	1,147
Buildings	2,034
Construction in progress	0
Total Purchase Price	3,181
Accumulated Depreciation	674
Book Value	2,507
Fixed rate mortgages	$ 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	45,770
Land	4,929
Buildings	45,689
Construction in progress	0
Total Purchase Price	50,618
Accumulated Depreciation	32,078
Book Value	18,540
Fixed rate mortgages	$ 58,607
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	526
Land	12,700
Buildings	51,080
Construction in progress	0
Total Purchase Price	63,780
Accumulated Depreciation	11,856
Book Value	51,924
Fixed rate mortgages	$ 28,480
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	11,062
Land	992
Buildings	12,778
Construction in progress	0
Total Purchase Price	13,770
Accumulated Depreciation	8,939
Book Value	4,831
Fixed rate mortgages	$ 10,127
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	8,345
Land	6,402
Buildings	19,762
Construction in progress	0
Total Purchase Price	26,164
Accumulated Depreciation	9,655
Book Value	16,509
Fixed rate mortgages	$ 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	25,098
Land	15,254
Buildings	28,739
Construction in progress	0
Total Purchase Price	43,993
Accumulated Depreciation	23,105
Book Value	20,888
Fixed rate mortgages	$ 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	11,381
Land	1,878
Buildings	16,231
Construction in progress	0
Total Purchase Price	18,109
Accumulated Depreciation	13,105
Book Value	5,004
Fixed rate mortgages	$ 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	4,563
Land	703
Buildings	6,334
Construction in progress	0
Total Purchase Price	7,037
Accumulated Depreciation	5,228
Book Value	1,809
Fixed rate mortgages	$ 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	26,569
Land	7,693
Buildings	26,693
Construction in progress	31
Total Purchase Price	34,417
Accumulated Depreciation	19,638
Book Value	14,779
Fixed rate mortgages	$ 0
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	2,636
Land	7,851
Buildings	11,287
Construction in progress	0
Total Purchase Price	19,138
Accumulated Depreciation	7,761
Book Value	11,377
Fixed rate mortgages	$ 12,061
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	25,265
Land	6,047
Buildings	25,265
Construction in progress	0
Total Purchase Price	31,312
Accumulated Depreciation	10,448
Book Value	20,864
Fixed rate mortgages	$ 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	6,020
Land	4,649
Buildings	7,446
Construction in progress	202
Total Purchase Price	12,297
Accumulated Depreciation	6,307
Book Value	5,990
Fixed rate mortgages	$ 21,704
Buildings and Improvements Depreciable Lives in Years	40 years
Shopping Centers | Other Buildings / Improvements
Real Estate Properties [Line Items]
Cost capitalized subsequent to acquisition	$ 182
Buildings	182
Construction in progress	0
Total Purchase Price	182
Accumulated Depreciation	102
Book Value	80
Fixed rate mortgages	0
Mixed-Use Properties
Real Estate Properties [Line Items]
Initial Basis	96,034
Cost capitalized subsequent to acquisition	663,187
Land	80,521
Buildings	670,049
Construction in progress	8,651
Total Purchase Price	759,221
Accumulated Depreciation	199,788
Book Value	559,433
Fixed rate mortgages	387,837
Mixed-Use Properties | Avenel Business Park, Gaithersburg, MD
Real Estate Properties [Line Items]
Initial Basis	21,459
Cost capitalized subsequent to acquisition	33,526
Land	3,756
Buildings	51,229
Construction in progress	0
Total Purchase Price	54,985
Accumulated Depreciation	40,108
Book Value	14,877
Fixed rate mortgages	$ 25,224
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	186,314
Land	16,287
Buildings	182,780
Construction in progress	0
Total Purchase Price	199,067
Accumulated Depreciation	51,725
Book Value	147,342
Fixed rate mortgages	$ 94,712
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	91,715
Land	2,242
Buildings	91,715
Construction in progress	0
Total Purchase Price	93,957
Accumulated Depreciation	13,739
Book Value	80,218
Fixed rate mortgages	$ 66,420
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	69,328
Land	5,667
Buildings	69,140
Construction in progress	0
Total Purchase Price	74,807
Accumulated Depreciation	59,413
Book Value	15,394
Fixed rate mortgages	$ 0
Buildings and Improvements Depreciable Lives in Years	35 years
Mixed-Use Properties | The Waycroft, Arlington, VA
Real Estate Properties [Line Items]
Initial Basis	$ 52,067
Cost capitalized subsequent to acquisition	225,226
Land	52,025
Buildings	216,617
Construction in progress	8,651
Total Purchase Price	277,293
Accumulated Depreciation	4,722
Book Value	272,571
Fixed rate mortgages	$ 146,083
Buildings and Improvements Depreciable Lives in Years	50 years
Mixed-Use Properties | Washington Square, Alexandria, VA
Real Estate Properties [Line Items]
Initial Basis	$ 2,034
Cost capitalized subsequent to acquisition	57,078
Land	544
Buildings	58,568
Construction in progress	0
Total Purchase Price	59,112
Accumulated Depreciation	30,081
Book Value	29,031
Fixed rate mortgages	$ 55,398
Buildings and Improvements Depreciable Lives in Years	50 years
Development Land
Real Estate Properties [Line Items]
Initial Basis	$ 47,021
Cost capitalized subsequent to acquisition	15,870
Land	9,263
Buildings	0
Construction in progress	53,628
Total Purchase Price	62,891
Accumulated Depreciation	0
Book Value	62,891
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	4,642
Land	7,029
Buildings	0
Construction in progress	2,905
Total Purchase Price	9,934
Accumulated Depreciation	0
Book Value	9,934
Development land, related debt	$ 0
Buildings and Improvements Depreciable Lives in Years
Development Land | New Market, New Market, MD
Real Estate Properties [Line Items]
Initial Basis	$ 2,088
Cost capitalized subsequent to acquisition	146
Land	2,234
Buildings	0
Construction in progress	0
Total Purchase Price	2,234
Accumulated Depreciation	0
Book Value	2,234
Development land, related debt	$ 0
Buildings and Improvements Depreciable Lives in Years
Development Land | Hampden House (formerly 7316 Wisconsin Avenue), Bethesda, MD
Real Estate Properties [Line Items]
Initial Basis	$ 39,641
Cost capitalized subsequent to acquisition	11,082
Land
Buildings	0
Construction in progress	50,723
Total Purchase Price	50,723
Accumulated Depreciation	0
Book Value	50,723
Development land, related debt	$ 0
Buildings and Improvements Depreciable Lives in Years

Real Estate and Accumulated D_3

Real Estate and Accumulated Depreciation - Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2020
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 D_4

Real Estate and Accumulated Depreciation - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real estate investments for federal income tax	$ 1,550	$ 1,330

Real Estate and Accumulated D_5

Real Estate and Accumulated Depreciation - Changes in Total Real Estate Investments and Related Accumulated Depreciation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Total real estate investments:
Balance, beginning of year	$ 2,081,597	$ 1,948,165	$ 1,803,200
Acquisitions	0	0	48,579
Improvements	45,396	135,966	98,917
Retirements	(2,197)	(2,534)	(2,531)
Balance, end of year	2,124,796	2,081,597	1,948,165
Total accumulated depreciation:
Balance, beginning of year	563,474	525,518	488,166
Depreciation expense	45,865	40,490	39,768
Retirements	(1,633)	(2,534)	(2,416)
Balance, end of year	$ 607,706	$ 563,474	$ 525,518