Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 13.3	$ 16.3	$ 22.6	$ 27.6
Reclassification of de-designated interest rate collars		0.1		0.5
Foreign currency translation gain (loss)	0.5	(0.2)	0.7	(0.1)
Comprehensive income	13.8	16.2	23.3	28.0
Less: Comprehensive income attributable to noncontrolling interests	1.0	0.9	1.9	1.5
Comprehensive income attributable to SP Plus Corporation	$ 12.8	$ 15.3	$ 21.4	$ 26.5