Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 16.3	$ 9.8	$ 27.6	$ 13.7
Reclassification of de-designated interest rate collars	0.1	0.4	0.5	0.8
Foreign currency translation (loss) gain	(0.2)	0.1	(0.1)	0.1
Comprehensive income	16.2	10.3	28.0	14.6
Less: Comprehensive income attributable to noncontrolling interest	0.9	0.8	1.5	2.4
Comprehensive income attributable to SP Plus Corporation	$ 15.3	$ 9.5	$ 26.5	$ 12.2