Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 553,334	$ 546,526
Cost of revenue	481,457	487,095
Gross profit	71,877	59,431
Operating expenses:
Selling, general and administrative	63,168	57,089
Amortization of intangibles	642	1,272
Total operating expenses	63,810	58,361
Operating income	8,067	1,070
Other income (expense):
Interest income (expense), net	(6,285)	(3,305)
Loss on debt modification	0	(335)
Loss on debt extinguishment	(513)	0
Gain on sale of property and equipment	57	90
Gain on change in fair value of warrant liability	588	0
Gain on embedded derivative	(388)	0
Impairment of goodwill	(4,359)	0
Total other expenses	(10,124)	(3,550)
Loss before income taxes	(2,057)	(2,480)
Income tax benefit	(282)	(635)
Net loss	(1,775)	(1,845)
Dividends on cumulative redeemable convertible preferred stock	0	113
Premium paid on partial preferred redemption	0	(2,219)
Net loss attributable to Limbach Holdings, Inc. common stockholders	$ (1,775)	$ (3,951)
Net loss per share attributable to Limbach Holdings, Inc. common stockholders:
Basic (usd per share)	$ (0.23)	$ (0.52)
Diluted (usd per share)	$ (0.23)	$ (0.52)
Weighted average number of shares outstanding:
Basic (in shares)	7,662,362	7,562,586
Diluted (in shares)	7,662,362	7,562,586