Business Unit Segment Information - Schedule of Revenues and Gross Profit by Regions (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Parking Services Revenue
Lease contracts	$ 130.8	$ 138.5
Management contracts	92.1	91.2
Total parking services revenue	222.9	229.7
Reimbursed management contract revenue	191.6	167.9
Total parking services revenue	414.5	397.6
Gross Profit
Lease contracts	5.0	7.9
Management contracts	35.5	30.5
Total gross profit	40.5	38.4
Gross Margin
General and administrative expenses	$ 21.2	$ 24.6
General and administrative expense percentage of gross profit	52.00%	64.00%
Depreciation and amortization	$ 6.6	$ 9.2
Operating income	12.7	4.6
Other expenses (income)
Interest expense	2.6	2.8
Interest income	(0.1)	(0.2)
Equity in losses from investment in unconsolidated entity	0.2	0.5
Total other expenses (income)	2.7	3.1
Earnings before income taxes	10.0	1.5
Income tax expense	3.3	0.9
Net income	6.7	0.6
Less: Net income attributable to noncontrolling interest	0.7	0.6
Net income attributable to SP Plus Corporation	6.0	0.0
Operating segment \| Region One
Parking Services Revenue
Lease contracts	99.8	108.0
Management contracts	68.1	64.5
Total parking services revenue	167.9	172.5
Gross Profit
Lease contracts	3.3	6.7
Management contracts	24.6	22.2
Total gross profit	$ 27.9	$ 28.9
Gross Margin
Lease contracts (as a percent)	3.00%	6.00%
Management contracts (as a percent)	36.00%	34.00%
Operating segment \| Region Two
Parking Services Revenue
Lease contracts	$ 31.0	$ 30.5
Management contracts	21.8	24.1
Total parking services revenue	52.8	54.6
Gross Profit
Lease contracts	1.2	0.7
Management contracts	6.3	4.4
Total gross profit	$ 7.5	$ 5.1
Gross Margin
Lease contracts (as a percent)	4.00%	2.00%
Management contracts (as a percent)	29.00%	18.00%
Corporate, Non-Segment
Parking Services Revenue
Lease contracts	$ 0.0	$ 0.0
Management contracts	2.2	2.6
Total parking services revenue	2.2	2.6
Gross Profit
Lease contracts	0.5	0.5
Management contracts	4.6	3.9
Total gross profit	$ 5.1	$ 4.4
Gross Margin
Lease contracts (as a percent)	0.00%	0.00%
Management contracts (as a percent)	209.00%	150.00%

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