Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 10.1	$ 15.1	$ 32.7	$ 42.7
Reclassification of de-designated interest rate collars				0.5
Foreign currency translation loss	(0.9)	(0.6)	(0.2)	(0.7)
Comprehensive income	9.2	14.5	32.5	42.5
Less: Comprehensive income attributable to noncontrolling interests	0.9	0.8	2.8	2.3
Comprehensive income attributable to SP Plus Corporation	$ 8.3	$ 13.7	$ 29.7	$ 40.2