Acquisitions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Net tangible assets acquired	$ 87,600			$ 87,600
Other intangible assets acquired				190,000
Goodwill acquired	10,069			100,700	$ 110,383
Bargain purchase gain, net of deferred tax		$ (3,100)		(3,100)
Acquisitions 2020
Business Acquisition [Line Items]
Cash consideration	$ 19,377
Number of shares granted for acquired companies (in shares)	116,812
Value of Quanta common stock issued	$ 4,158
Other intangible assets acquired	4,561
Goodwill acquired	10,069
Bargain purchase gain, net of deferred tax	0
Goodwill expected to be deductible for income tax	3,800			$ 3,800
Revenues included in consolidated results of operations	1,900
Income (loss) before taxes	(900)
Acquisition costs	$ 800
Acquisitions 2019
Business Acquisition [Line Items]
Cash consideration			$ 399,300		$ 399,279
Number of shares granted for acquired companies (in shares)					60,860
Value of Quanta common stock issued					$ 1,791
Goodwill acquired					110,137
Bargain purchase gain, net of deferred tax					(3,139)
Goodwill expected to be deductible for income tax					$ 90,600
Revenues included in consolidated results of operations			7,400
Income (loss) before taxes			(1,000)
Acquisition costs			$ 2,400