Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 17.3	$ 7.4	$ 24.0	$ 8.0
Other comprehensive income (expense)	0.1	(0.2)	0.1	(0.3)
Comprehensive income	17.4	7.2	24.1	7.7
Less: Comprehensive income attributable to noncontrolling interest	1.1	0.9	1.8	1.5
Comprehensive income attributable to SP Plus Corporation	$ 16.3	$ 6.3	$ 22.3	$ 6.2