Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 9.3	$ 11.3
Reclassification of de-designated interest rate collars		0.4
Foreign currency translation gain	0.2	0.1
Comprehensive income	9.5	11.8
Less: Comprehensive income attributable to noncontrolling interest	0.9	0.6
Comprehensive income attributable to SP Plus Corporation	$ 8.6	$ 11.2