Organization, Business and Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares		Sep. 30, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares		Sep. 30, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2018 USD ($) segment $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares	Mar. 31, 2019 USD ($)
Organization Consolidation and Presentation of Financial Statements [Line Items]
Revenues											$ 50,312	$ 29,558	$ 38,754
Net income	$ 10,651	[1]	$ 7,957	$ 6,835	$ 5,644	$ 13,579	[1]	$ 5,145	$ 1,230	$ 1,200	$ 31,087	$ 21,154	$ 21,431
Diluted earnings per share attributable to MYR Group (in dollars per share) | $ / shares	$ 0.64	[1]	$ 0.48	$ 0.41	$ 0.34	$ 0.82	[1]	$ 0.31	$ 0.07	$ 0.07	$ 1.87	$ 1.28	$ 1.23
Revenues recognized	$ 446,345	[1]	$ 399,537	$ 339,676	$ 345,611	$ 373,501	[1]	$ 373,502	$ 356,185	$ 300,129	$ 1,531,169	$ 1,403,317	$ 1,142,487
Advertising cost											$ 700	700	$ 600
Concentration Risk, Percentage											100.00%
Number of Segments Repotable | segment											2
Retention Provision											10.00%
Contract with Customer, Asset, Net, Current	160,281					120,992					$ 160,281	120,992
Contingencies Excluding Wildfire and Health Insurance [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Insurance Policy Deductible amount	1,000										1,000
Wildfire [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Insurance Policy Deductible amount	2,000										2,000
Health Insurance [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Insurance Policy Deductible amount	$ 200										200
Accounting Standards Update 606 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Contract with Customer, Asset, Net, Current						$ 42,700						$ 42,700
Significant Change Orders Or Claims [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Revenues recognized											$ 3,400
Maximum [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Term of Contract	10 years										10 years
Maximum [Member] | Scenario, Forecast [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Operating Lease, Liability														$ 17,000
Minimum [Member] | Scenario, Forecast [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Operating Lease, Liability														$ 19,000
Sales Revenue, Net [Member] | Top Ten Customers [Member] | Customer Concentration Risk [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage											32.90%	40.40%	46.40%
Sales Revenue, Net [Member] | Top Ten Customers [Member] | Customer Concentration Risk [Member] | TD member [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage											10.70%
Labor employees covered by collective bargaining agreements [Member] | Labor Force Concentration Risk [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage											88.00%
Contracts Accounted for under Percentage of Completion [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Cost Estimate Revision Gross Margin Increase (Decrease) Percentage											(0.70%)	(0.70%)	(0.20%)
Revenues											$ (10,500)	$ (10,400)	$ (2,600)
Net income											$ (8,200)	$ (6,200)	$ (1,400)
Diluted earnings per share attributable to MYR Group (in dollars per share) | $ / shares											$ (0.49)	$ (0.38)	$ (0.08)

[1] Results for the fourth quarter of 2017 include a net 2017 Tax Act benefit of $7.8 million, or $0.48 and $0.47 per basic and diluted share, respectively.