Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 11.3	$ 3.9
Reclassification of de-designated interest rate collars	0.4	0.4
Foreign currency translation gain	0.1
Comprehensive income	11.8	4.3
Less: Comprehensive income attributable to noncontrolling interest	0.6	1.6
Comprehensive income attributable to SP Plus Corporation	$ 11.2	$ 2.7