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Represents general and administrative expenses expressed as a percentage of gross profit.

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Gross Margin Percentage

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The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount of Net Income (Loss) attributable to noncontrolling interest.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

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The net result for the period of deducting operating expenses from operating revenues.

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Amount of income related to nonoperating activities, classified as other.

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Business Unit Segment Information - Schedule of Revenues and Gross Profit by Regions (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Parking Services Revenue
Total Services Revenue	$ 414.2		$ 362.2		$ 823.6	$ 729.0
Gross Profit
Total gross profit	61.9		51.1		115.1	90.6
General and administrative expenses	$ 27.7		$ 22.3		$ 54.8	$ 44.6
General and administrative expense percentage of gross profit	45.00%		44.00%		48.00%	49.00%
Depreciation and amortization	$ 7.3		$ 4.5		$ 14.5	$ 8.5
Operating income	26.9		24.3		45.8	37.5
Other expenses (income)
Interest expense	4.9		2.2		9.9	4.3
Interest expense	(0.1)		(0.1)		(0.2)	(0.2)
Equity earnings from investment in unconsolidated entity	0.0		0.0		0.0	(10.0)
Total other expenses (income)	4.8		2.1		9.7	(5.9)
Earnings before income taxes	22.1		22.2		36.1	43.4
Income tax expense	5.8		6.0		8.9	11.3
Net income	16.3	$ 10.9	16.2	$ 15.9	27.2	32.1
Less: Net income attributable to noncontrolling interest	1.1		0.9		1.4	1.5
Net income attributable to SP Plus Corporation	15.2		15.3		25.8	30.6
Operating segment \| Segment One
Parking Services Revenue
Total Services Revenue	158.0		162.3		316.1	325.0
Gross Profit
Total gross profit	33.3		33.5		61.7	59.6
Operating segment \| Segment Two
Parking Services Revenue
Total Services Revenue	74.9		29.8		145.2	58.5
Gross Profit
Total gross profit	22.1		9.8		39.3	17.1
Segment Reconciling Items
Parking Services Revenue
Total Services Revenue	2.2		3.0		4.5	5.6
Gross Profit
Total gross profit	6.5		7.8		14.1	13.9
Lease type contracts
Parking Services Revenue
Total Services Revenue	105.2		107.4		203.0	206.9
Gross Profit
Total gross profit	13.4		12.9		21.5	17.9
Lease type contracts \| Operating segment \| Segment One
Parking Services Revenue
Total Services Revenue	96.9		100.2		187.4	193.3
Gross Profit
Total gross profit	$ 9.8		$ 9.6		$ 14.4	$ 12.0
Gross margin percentage	10.00%		10.00%		8.00%	6.00%
Lease type contracts \| Operating segment \| Segment Two
Parking Services Revenue
Total Services Revenue	$ 8.2		$ 7.0		$ 15.3	$ 13.4
Gross Profit
Total gross profit	$ 2.5		$ 2.1		$ 4.0	$ 3.5
Gross margin percentage	31.00%		30.00%		26.00%	26.00%
Lease type contracts \| Segment Reconciling Items
Parking Services Revenue
Total Services Revenue	$ 0.1		$ 0.2		$ 0.3	$ 0.2
Gross Profit
Total gross profit	$ 1.1		$ 1.2		$ 3.1	$ 2.4
Gross margin percentage	1100.00%		600.00%		1033.00%	1200.00%
Management type contracts
Parking Services Revenue
Total Services Revenue	$ 129.9		$ 87.7		$ 262.8	$ 182.2
Gross Profit
Total gross profit	48.5		38.2		93.6	72.7
Management type contracts \| Operating segment \| Segment One
Parking Services Revenue
Total Services Revenue	61.1		62.1		128.7	131.7
Gross Profit
Total gross profit	$ 23.5		$ 23.9		$ 47.3	$ 47.6
Gross margin percentage	39.00%		38.00%		37.00%	36.00%
Management type contracts \| Operating segment \| Segment Two
Parking Services Revenue
Total Services Revenue	$ 66.7		$ 22.8		$ 129.9	$ 45.1
Gross Profit
Total gross profit	$ 19.6		$ 7.7		$ 35.3	$ 13.6
Gross margin percentage	29.00%		34.00%		27.00%	30.00%
Management type contracts \| Segment Reconciling Items
Parking Services Revenue
Total Services Revenue	$ 2.1		$ 2.8		$ 4.2	$ 5.4
Gross Profit
Total gross profit	$ 5.4		$ 6.6		$ 11.0	$ 11.5
Gross margin percentage	257.00%		236.00%		262.00%	213.00%
Reimbursed management type contract expense
Parking Services Revenue
Total Services Revenue	$ 179.1		$ 167.1		$ 357.8	$ 339.9