Unaudited Quarterly Results (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Parking services revenue:
Lease contracts	$ 126,027	$ 129,004	$ 124,958	$ 116,635	$ 122,487	$ 122,771	$ 123,232	$ 121,085	$ 496,624	$ 489,575	$ 250,355
Management contracts	85,519	77,878	84,931	89,955	90,911	77,681	88,659	90,095	338,283	347,346	230,501
Reimbursed management contract revenue	172,663	173,405	164,539	169,178	157,141	154,858	158,402	159,477	679,785	629,878	473,082
Total revenue	384,209	380,287	374,428	375,768	370,539	355,310	370,293	370,657	1,514,692	1,466,799	953,938
Cost of parking services:
Lease contracts	115,077	116,520	111,979	112,084	116,262	115,696	112,014	112,118	455,660	456,090	231,781
Management contracts	51,940	46,741	50,016	59,214	51,480	44,680	53,833	58,737	207,911	208,730	141,949
Reimbursed management contract expense	172,663	173,405	164,539	169,178	157,141	154,858	158,402	159,477	679,785	629,878	473,082
Total cost of parking services	339,680	336,666	326,534	340,476	324,883	315,234	324,249	330,332	1,343,356	1,294,698	846,812
Gross profit:
Lease contracts	10,950	12,484	12,979	4,551	6,225	7,075	11,218	8,967	40,964	33,485	18,574
Management contracts	33,579	31,137	34,915	30,741	39,431	33,001	34,826	31,358	130,372	138,616	88,552
Total gross profit	44,529	43,621	47,894	35,292	45,656	40,076	46,044	40,325	171,336	172,101	107,126
General and administrative expenses	26,331	24,123	24,996	26,066	23,621	20,494	26,868	27,948	101,516	98,931	86,540
Depreciation and amortization	7,826	7,630	7,730	7,163	7,489	7,959	8,252	7,493	30,349	31,193	13,513
Operating income	10,372	11,868	15,168	2,063	14,546	11,623	10,924	4,884	39,471	41,977	7,073
Other expense (income):
Interest expense	4,033	4,162	4,811	4,809	4,613	4,818	4,763	4,840	17,815	19,034	8,616
Interest income	(66)	(144)	(94)	(98)	(296)	(108)	(128)	(111)	(402)	(643)	(297)
Gain on contribution of a business to an unconsolidated entity	(4,161)								(4,161)
Equity in losses from investment in unconsolidated entity	283								(283)
Total other expenses (income)	89	4,018	4,717	4,711	4,317	4,710	4,635	4,729	13,535	18,391	8,319
Income (loss) before income taxes	10,283	7,850	10,451	(2,648)	10,229	6,913	6,289	155	25,936	23,586	(1,246)
Income tax expense (reversal)	224	2,763	4,254	(7,438)	4,462	2,448	2,065	(154)	(197)	8,821	(3,620)
Net income	10,059	5,087	6,197	4,790	5,767	4,465	4,224	309	26,133	14,765	2,374
Less: Net income attributable to noncontrolling interest	873	785	890	487	606	721	780	569	3,035	2,676	1,034
Net income attributable to SP Plus Corporation	$ 9,186	$ 4,302	$ 5,307	$ 4,303	$ 5,161	$ 3,744	$ 3,444	$ (260)	$ 23,098	$ 12,089	$ 1,340
Net income per share:
Basic (in dollars per share)	$ 0.42	$ 0.20	$ 0.24	$ 0.20	$ 0.24	$ 0.17	$ 0.16	$ (0.01)	$ 1.05	$ 0.55	$ 0.08
Diluted (in dollars per share)	$ 0.41	$ 0.19	$ 0.24	$ 0.19	$ 0.23	$ 0.17	$ 0.15	$ (0.01)	$ 1.03	$ 0.54	$ 0.08
Weighted average shares outstanding:
Basic (in shares)	22,071,706	21,997,394	21,991,965	21,977,836	21,938,377	21,911,574	21,889,777	21,870,771	22,009,800	21,902,870	17,179,606
Diluted (in shares)	22,451,557	22,426,787	22,398,886	22,351,845	22,319,723	22,285,723	22,221,102	21,870,771	22,407,343	22,249,584	17,490,204
Common stock, shares issued in conjunction with the Central Merger	22,127,725				21,977,311				22,127,725	21,977,311