Contract Assets and Liabilities - Contracts in process (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Abstract]
Costs and estimated earnings on uncompleted contracts	$ 3,969,565	$ 3,921,376
Less: billings to date	3,983,570	3,979,403
Net asset position for contracts in process	$ (14,005)	$ (58,027)

Represents the net costs and estimated earnings in excess of billings on uncompleted contracts accounted for under the percentage-of-completion method.

No definition available.

Name:	myrg_NetCostsAndEstimatedEarningsInExcessOfBillings
Namespace Prefix:	myrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant