Consolidated Statement of Equity (Unaudited) - USD ($) $ in Thousands	Total	Series C Cumulative Preferred Stock	Series D Cumulative Redeemable Preferred Stock	Series E Cumulative Redeemable Preferred Stock	Total Saul Centers, Inc.	Total Saul Centers, Inc. Series C Cumulative Preferred Stock	Total Saul Centers, Inc. Series D Cumulative Redeemable Preferred Stock	Total Saul Centers, Inc. Series E Cumulative Redeemable Preferred Stock	Preferred Stock	Common Stock	Additional Paid-in Capital	Distributions in Excess of Accumulated Earnings	Distributions in Excess of Accumulated Earnings Series C Cumulative Preferred Stock	Distributions in Excess of Accumulated Earnings Series D Cumulative Redeemable Preferred Stock	Distributions in Excess of Accumulated Earnings Series E Cumulative Redeemable Preferred Stock	Accumulated Other Comprehensive (Loss)	Noncontrolling Interests
Beginning Balance at Dec. 31, 2018	$ 425,220				$ 355,912				$ 180,000	$ 227	$ 384,533	$ (208,593)				$ (255)	$ 69,308
Issuance of shares of common stock:
Issuance of shares pursuant to dividend reinvestment plan	6,171				6,171					1	6,170
Issuance of shares due to exercise of employee stock options and issuance of directors’ deferred shares	420				420					1	419
Issuance of partnership units pursuant to dividend reinvestment plan	705																705
Net income	17,077				13,447							13,447					3,630
Change in unrealized loss on cash flow hedge	(46)				(34)											(34)	(12)
Distributions payable preferred stock:
Preferred stock distributions		$ (1,805)	$ (1,148)			$ (1,805)	$ (1,148)						$ (1,805)	$ (1,148)
Distributions payable, common stock and partnership units	(16,263)				(12,108)							(12,108)					(4,155)
Ending Balance at Mar. 31, 2019	430,331				360,855				180,000	229	391,122	(210,207)				(289)	69,476
Beginning Balance at Dec. 31, 2018	425,220				355,912				180,000	227	384,533	(208,593)				(255)	69,308
Issuance of shares of common stock:
Net income	49,155
Change in unrealized loss on cash flow hedge	(118)
Ending Balance at Sep. 30, 2019	545,437				475,949				290,000	231	401,395	(215,334)				(343)	69,488
Beginning Balance at Mar. 31, 2019	430,331				360,855				180,000	229	391,122	(210,207)				(289)	69,476
Issuance of shares of common stock:
Issuance of shares pursuant to dividend reinvestment plan	5,128				5,128					1	5,127
Issuance of shares due to exercise of employee stock options and issuance of directors’ deferred shares	2,798				2,798					0	2,798
Issuance of partnership units pursuant to dividend reinvestment plan	1,029																1,029
Net income	16,750				13,232							13,232					3,518
Change in unrealized loss on cash flow hedge	(127)				(95)											(95)	(32)
Distributions payable preferred stock:
Preferred stock distributions		(1,805)	(1,148)			(1,805)	(1,148)						(1,805)	(1,148)
Distributions payable, common stock and partnership units	(16,347)				(12,181)							(12,181)					(4,166)
Ending Balance at Jun. 30, 2019	436,609				366,784				180,000	230	399,047	(212,109)				(384)	69,825
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of cumulative preferred stock	106,269				106,269				110,000		(3,731)
Issuance of shares of common stock:
Issuance of shares pursuant to dividend reinvestment plan	5,674				5,674					1	5,673
Issuance of shares due to exercise of employee stock options and issuance of directors’ deferred shares	406				406					0	406
Issuance of partnership units pursuant to dividend reinvestment plan	720																720
Net income	15,328				12,226							12,226					3,102
Change in unrealized loss on cash flow hedge	55				41											41	14
Distributions payable preferred stock:
Preferred stock distributions		$ (1,805)	(1,148)	$ (257)		$ (1,805)	(1,148)	$ (257)					$ (1,805)	(1,148)	$ (257)
Distributions payable, common stock and partnership units	(16,414)				(12,241)							(12,241)					(4,173)
Ending Balance at Sep. 30, 2019	545,437				475,949				290,000	231	401,395	(215,334)				(343)	69,488
Beginning Balance at Dec. 31, 2019	443,356				374,981				185,000	232	410,926	(221,177)				0	68,375
Issuance of shares of common stock:
Issuance of shares pursuant to dividend reinvestment plan	4,081				4,081					1	4,080
Issuance of shares due to exercise of employee stock options and issuance of directors’ deferred shares	956				956					0	956
Issuance of partnership units pursuant to dividend reinvestment plan	734																734
Net income	16,829				13,264							13,264					3,565
Distributions payable preferred stock:
Preferred stock distributions			(1,148)	(1,650)			(1,148)	(1,650)						(1,148)	(1,650)
Distributions payable, common stock and partnership units	(16,552)				(12,364)							(12,364)					(4,188)
Ending Balance at Mar. 31, 2020	446,606				378,120				185,000	233	415,962	(223,075)				0	68,486
Beginning Balance at Dec. 31, 2019	443,356				374,981				185,000	232	410,926	(221,177)				0	68,375
Issuance of shares of common stock:
Net income	38,640
Change in unrealized loss on cash flow hedge	0
Ending Balance at Sep. 30, 2020	431,617				367,018				185,000	234	417,504	(235,720)				0	64,599
Beginning Balance at Mar. 31, 2020	446,606				378,120				185,000	233	415,962	(223,075)				0	68,486
Issuance of shares of common stock:
Issuance of shares pursuant to dividend reinvestment plan	407				407					0	407
Issuance of shares due to exercise of employee stock options and issuance of directors’ deferred shares	424				424					0	424
Net income	10,208				8,328							8,328					1,880
Distributions payable preferred stock:
Preferred stock distributions			(1,148)	(1,650)			(1,148)	(1,650)						(1,148)	(1,650)
Distributions payable, common stock and partnership units	(16,561)				(12,373)							(12,373)					(4,188)
Ending Balance at Jun. 30, 2020	438,286				372,108				185,000	233	416,793	(229,918)				0	66,178
Issuance of shares of common stock:
Issuance of shares pursuant to dividend reinvestment plan	422				422					1	421
Issuance of shares due to exercise of employee stock options and issuance of directors’ deferred shares	290				290					0	290
Issuance of partnership units pursuant to dividend reinvestment plan	380																380
Net income	11,603				9,367							9,367					2,236
Change in unrealized loss on cash flow hedge	0
Distributions payable preferred stock:
Preferred stock distributions			$ (1,148)	$ (1,650)			$ (1,148)	$ (1,650)						$ (1,148)	$ (1,650)
Distributions payable, common stock and partnership units	(16,566)				(12,371)							(12,371)					(4,195)
Ending Balance at Sep. 30, 2020	$ 431,617				$ 367,018				$ 185,000	$ 234	$ 417,504	$ (235,720)				$ 0	$ 64,599