Acquisitions - Estimated Fair Values of Identifiable Intangible Assets and Related Weighted Average Amortization (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2019
Business Acquisition [Line Items]
Estimated fair value at acquisition date		$ 39,900
Acquisitions 2019
Business Acquisition [Line Items]
Estimated fair value at acquisition date	$ 7,337
Weighted average amortization period at acquisition date	5 years 3 months 18 days
Customer relationships | Acquisitions 2019
Business Acquisition [Line Items]
Estimated fair value at acquisition date	$ 3,996
Weighted average amortization period at acquisition date	5 years
Backlog | Acquisitions 2019
Business Acquisition [Line Items]
Estimated fair value at acquisition date	$ 1,058
Weighted average amortization period at acquisition date	1 year
Trade names | Acquisitions 2019
Business Acquisition [Line Items]
Estimated fair value at acquisition date	$ 908
Weighted average amortization period at acquisition date	15 years
Non-compete agreements | Acquisitions 2019
Business Acquisition [Line Items]
Estimated fair value at acquisition date	$ 1,375
Weighted average amortization period at acquisition date	3 years