Comprehensive Income - Components of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 7.7	$ 4.5	$ 15.7	$ 16.8
Effective portion of unrealized gain (loss) on cash flow hedge	0.2	(0.2)	(0.1)	(0.5)
Foreign currency translation	(0.1)	(0.3)	(0.1)	(0.6)
Comprehensive income	7.8	4.0	15.5	15.7
Less: Comprehensive income attributable to noncontrolling interest	0.7	0.8	2.2	2.0
Comprehensive income attributable to SP Plus Corporation	$ 7.1	$ 3.2	$ 13.3	$ 13.7