Note 9 - Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Net revenues	$ 67,176		$ 50,944		$ 128,273	$ 112,292
Operating income (loss)	1,887		1,963		4,606	3,440
Interest expense	129		84		277	312
Other income, net	5		(50)		(70)	(58)
Income before income tax expense	1,753		1,929		4,399	3,186
Income tax expense	621		624		1,486	959
Net income	1,132	$ 1,781	1,305	$ 922	2,913	2,227
Net income (loss) attributable to non-controlling interest	(618)		(1,408)		(1,482)	(2,034)
Net income (loss) attributable to SPAR Group, Inc.	514		(103)		1,431	193
Depreciation and amortization	534		539		1,064	1,079
Capital expenditures	559		444		890	786
US Segment [Member]
Net revenues	27,252		22,123		50,927	45,412
Operating income (loss)	332		315		1,090	623
Interest expense	151		144		289	276
Other income, net	(1)		(1)		(3)	(1)
Income before income tax expense	182		172		804	348
Income tax expense	7		124		176	199
Net income	175		48		628	149
Net income (loss) attributable to non-controlling interest	(2)		(519)		(82)	(583)
Net income (loss) attributable to SPAR Group, Inc.	173		(471)		546	(434)
Depreciation and amortization	385		419		775	832
Capital expenditures	352		288		637	669
International Segment [Member]
Net revenues	39,924		28,821		77,346	66,880
Operating income (loss)	1,555		1,648		3,516	2,817
Interest expense	(22)		(60)		(12)	36
Other income, net	6		(49)		(67)	(57)
Income before income tax expense	1,571		1,757		3,595	2,838
Income tax expense	614		500		1,310	760
Net income	957		1,257		2,285	2,078
Net income (loss) attributable to non-controlling interest	(616)		(889)		(1,400)	(1,451)
Net income (loss) attributable to SPAR Group, Inc.	341		368		885	627
Depreciation and amortization	149		120		289	247
Capital expenditures	$ 207		$ 156		$ 253	$ 117