Note 9 - Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Net revenues	$ 58,865			$ 66,440			$ 171,157	$ 191,823
Operating income (loss)	3,341			3,047			6,783	9,007
Interest expense	169			216			482	605
Other income, net	(143)			(11)			(201)	(268)
Income before income tax expense	3,315			2,842			6,502	8,670
Income tax expense	870			760			1,830	2,745
Net income (loss)	2,445	$ 1,305	$ 922	2,082	$ 2,807	$ 1,036	4,672	5,925
Net income (loss) attributable to non-controlling interest	(1,301)			(1,175)			(3,335)	(2,880)
Total net income attributable to SPAR Group, Inc.	1,144			907			1,337	3,045
Depreciation and amortization	530			524			1,609	1,563
Capital expenditures	463			443			1,248	1,378
US Segment [Member]
Net revenues	27,041			26,480			72,453	73,142
Operating income (loss)	1,299			1,273			1,924	4,633
Interest expense	158			130			435	377
Other income, net	0			(1)			(2)	(2)
Income before income tax expense	1,141			1,144			1,491	4,258
Income tax expense	436			217			637	918
Net income (loss)	705			927			854	3,340
Net income (loss) attributable to non-controlling interest	(299)			(380)			(882)	(1,155)
Total net income attributable to SPAR Group, Inc.	406			547			(28)	2,185
Depreciation and amortization	399			390			1,231	1,144
Capital expenditures	417			418			1,085	1,140
International Segment [Member]
Net revenues	31,824			39,960			98,704	118,681
Operating income (loss)	2,042			1,774			4,859	4,374
Interest expense	11			86			47	228
Other income, net	(143)			(10)			(199)	(266)
Income before income tax expense	2,174			1,698			5,011	4,412
Income tax expense	434			543			1,193	1,827
Net income (loss)	1,740			1,155			3,818	2,585
Net income (loss) attributable to non-controlling interest	(1,002)			(795)			(2,453)	(1,725)
Total net income attributable to SPAR Group, Inc.	738			360			1,365	860
Depreciation and amortization	131			134			378	419
Capital expenditures	$ 46			$ 25			$ 163	$ 238