Net Income per Common Share Net Income per Common Share - Weighted Average Common Shares Outstanding (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to SP Plus Corporation	$ 0.0	$ 1.3
Basic weighted average common shares outstanding (in shares)	22,328,578	22,127,725
Dilutive impact of share-based awards (in shares)	300,000	400,000
Diluted weighted average common shares outstanding (in shares)	22,593,505	22,528,609
Net income per common share
Basic (in dollars per share)	$ 0.00	$ 0.06
Diluted (in dollars per share)	$ 0.00	$ 0.06