Acquisitions and Dispositions - Summary of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	6 Months Ended	9 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Jun. 28, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Final Valuation
Goodwill	$ 738,369			$ 404,713		$ 394,919
Clean Earth
Final Valuation
Intangible assets	242,200		$ 261,100
Altek
Final Valuation
Cash and cash equivalents		$ 1,700			$ 1,700
Net working capital		(1,300)			(1,500)
Property, plant and equipment		3,300			3,300
Intangible assets		52,700			52,500
Goodwill		22,500			20,900
Net deferred tax liabilities		(8,500)			(8,500)
Other liabilities		(300)			(300)
Total identifiable net assets of Altek		70,100			$ 68,100
Measurement Period Adjustments
Net working capital		200
Intangible assets		200
Goodwill		1,600
Total identifiable net assets of Altek		$ 2,000
Clean Earth
Final Valuation
Goodwill	330,230			$ 0		$ 0
Measurement Period Adjustments
Intangible assets	(18,900)
Clean Earth | Clean Earth
Final Valuation
Cash and cash equivalents	3,600		42,800
Property, plant and equipment	77,300		75,600
Intangible assets	242,200		261,100
Goodwill	330,200		313,800
Net deferred tax liabilities	(45,800)		(51,200)
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Current Assets, Trade Receivables	62,500		63,700
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Current Assets, Other Receivables	2,100		800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	7,300		8,700
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Operating Lease, Right-of-Use Asset	25,800		14,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	1,000		4,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	(23,100)		(23,000)
Business Combination, Provisional Information Initial Accounting Incomplete, Adjustment, Accounts Payable	(100)
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Current Liabilities, Acquisition Consideration Payable	0		(39,200)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	(19,300)		(18,000)
Business Combination, Recognized Identifiable Asset Acquired and Liability Assumed, Lease Obligation	(19,500)		(11,100)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	(8,600)		(6,500)
Total identifiable net assets of Altek	635,700		$ 635,900
Measurement Period Adjustments
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Cash	(39,200)
Business Combination Provisional Information Initial Accounting Incomplete Adjustment	(1,200)
Business Combination Provisional Information Initial Accounting Incomplete Adjustment, Other Receivables	1,300
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Other Current Assets	(1,400)
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment	1,700
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Right of Use Asset	11,400
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Other Assets	(3,000)
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Acquisition Consideration Payable	39,200
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Other Current Liabilities	(1,300)
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Net deferred Taxes Liability	5,400
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Operating lease liabilities	(8,400)
Business Combination Provisional Information Initial Accounting Incomplete Adjustment Other Liabilities	(2,100)
Intangible assets	(18,900)
Goodwill	16,400
Total identifiable net assets of Altek	$ (200)