Business Unit Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Parking Services Revenue
Lease contracts	$ 138.5	$ 135.8
Management contracts	91.2	94.1
Total parking services revenue	229.7	229.9
Reimbursed management contract revenue	167.9	174.3
Total revenue	397.6	404.2
Gross Profit
Lease contracts	7.9	7.1
Management contracts	30.5	34.1
Total gross profit	38.4	41.2
Gross Margin
General and administrative expenses	$ 24.6	$ 25.7
General and administrative expense percentage of gross profit	64.00%	62.00%
Depreciation and amortization	$ 9.2	$ 7.9
Operating income	4.6	7.6
Other expenses (income)
Interest expense	2.8	4.1
Interest income	(0.2)	(0.1)
Equity in losses from investment in unconsolidated entity	0.5	0.5
Total other expenses (income)	3.1	4.5
Earnings before income taxes	1.5	3.1
Income tax expense	0.9	1.3
Net income	0.6	1.8
Less: Net income attributable to noncontrolling interest	0.6	0.5
Net income attributable to SP Plus Corporation	0.0	1.3
Operating segment \| Region One
Parking Services Revenue
Lease contracts	106.6	104.8
Management contracts	46.4	47.3
Total parking services revenue	153.0	152.1
Gross Profit
Lease contracts	7.2	5.5
Management contracts	19.5	20.8
Total gross profit	$ 26.7	$ 26.3
Gross Margin
Lease contracts (as a percent)	7.00%	5.00%
Management contracts (as a percent)	42.00%	44.00%
Operating segment \| Region Two
Parking Services Revenue
Lease contracts	$ 30.5	$ 29.7
Management contracts	24.2	25.5
Total parking services revenue	54.7	55.2
Gross Profit
Lease contracts	0.8	0.9
Management contracts	5.8	5.5
Total gross profit	$ 6.6	$ 6.4
Gross Margin
Lease contracts (as a percent)	3.00%	3.00%
Management contracts (as a percent)	24.00%	22.00%
Operating segment \| Region Three
Parking Services Revenue
Lease contracts	$ 1.3	$ 1.2
Management contracts	17.2	17.6
Total parking services revenue	18.5	18.8
Gross Profit
Lease contracts	0.2	0.2
Management contracts	3.9	3.8
Total gross profit	$ 4.1	$ 4.0
Gross Margin
Lease contracts (as a percent)	15.00%	17.00%
Management contracts (as a percent)	23.00%	22.00%
Operating segment \| Other
Parking Services Revenue
Lease contracts	$ 0.1	$ 0.1
Management contracts	3.4	3.7
Total parking services revenue	3.5	3.8
Gross Profit
Lease contracts	(0.3)	0.5
Management contracts	1.3	4.0
Total gross profit	$ 1.0	$ 4.5
Gross Margin
Lease contracts (as a percent)	(300.00%)	500.00%
Management contracts (as a percent)	38.00%	108.00%

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