Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 02, 2020
Entity Listings [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-35493
Entity Registrant Name	STEEL PARTNERS HOLDINGS L.P.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3727655
Entity Address, Address Line One	590 Madison Avenue, 32nd Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10022
City Area Code	212
Local Phone Number	520-2300
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		25,207,175
Entity Central Index Key	0001452857
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Stock
Entity Listings [Line Items]
Title of 12(b) Security	Common Units, $0 par
Trading Symbol	SPLP
Security Exchange Name	NYSE
Series A Preferred Units
Entity Listings [Line Items]
Title of 12(b) Security	6.0% Series A Preferred Units
Trading Symbol	SPLP-PRA
Security Exchange Name	NYSE