Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 51.7	$ 56.4	$ 44.5
Other comprehensive (loss) income	(0.3)	(0.6)	0.2
Comprehensive income	51.4	55.8	44.7
Less: Comprehensive income attributable to noncontrolling interest	2.9	3.2	3.3
Comprehensive income attributable to SP Plus Corporation	$ 48.5	$ 52.6	$ 41.4