Merger and Acquisition - Additional Information (Details) - USD ($) $ in Thousands				3 Months Ended		9 Months Ended
	Apr. 06, 2018	Mar. 01, 2018	May 31, 2017	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Payable to related party for the recapitalization related to the working capital adjustment				$ 7,001		$ 7,001
Decrease to the additional paid-in capital account				(796)	$ (6,205)
ATS Merger
Business Acquisition [Line Items]
Purchase price before adjustments			$ 550,000
Purchase price			548,200
Costs recognized related to merger			9,900
ATS Merger | Acquisition Advisory Services
Business Acquisition [Line Items]
Costs recognized related to merger			8,000
ATS Merger | Professional Fees And Other Expenses
Business Acquisition [Line Items]
Costs recognized related to merger			$ 1,900
HTA Merger
Business Acquisition [Line Items]
Purchase price		$ 603,300
Cash purchase price		525,000
Business combination adjustments		9,700
Payable to sellers for certain tax items		$ 11,300
Shares issued in acquisition		5.26
Shares issued in acquisition, fair value		$ 57,300
Enterprise value		2,100,000
Value of debt deducted		1,000,000
Equity value		1,100,000
Immaterial adjustments to the preliminary purchase price allocation resulting in net reduction to goodwill		$ (1,200)
HTA Merger | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Costs recognized related to the merger							$ 15,600
HTA Merger | Acquisition Advisory Services
Business Acquisition [Line Items]
Costs recognized related to the merger							7,200
HTA Merger | Professional Fees And Other Expenses
Business Acquisition [Line Items]
Costs recognized related to the merger							8,400
HTA Merger | Customer Relationships
Business Acquisition [Line Items]
Identifiable intangible assets useful life		9 years
HTA Merger | Developed Technology
Business Acquisition [Line Items]
Identifiable intangible assets useful life		5 years 6 months
HTA Merger | Non-compete Agreements
Business Acquisition [Line Items]
Identifiable intangible assets useful life		5 years
HTA Merger | Trademarks
Business Acquisition [Line Items]
Identifiable intangible assets useful life		3 years
EPC Merger
Business Acquisition [Line Items]
Purchase price	$ 62,900
Business combination adjustments	$ 2,600
Shares issued in acquisition	5.54
Enterprise value	$ 2,100,000
Value of debt deducted	1,000,000
Equity value	$ 1,100,000
Costs recognized related to the merger							3,000
EPC Merger | Acquisition Advisory Services
Business Acquisition [Line Items]
Costs recognized related to the merger							2,500
EPC Merger | Professional Fees And Other Expenses
Business Acquisition [Line Items]
Costs recognized related to the merger							$ 500
EPC Merger | Customer Relationships
Business Acquisition [Line Items]
Identifiable intangible assets useful life	10 years
EPC Merger | Developed Technology
Business Acquisition [Line Items]
Identifiable intangible assets useful life	4 years 6 months
EPC Merger | Trademarks
Business Acquisition [Line Items]
Identifiable intangible assets useful life	5 years
Platinum
Business Acquisition [Line Items]
Payable to related party for the recapitalization related to the working capital adjustment				$ 7,000		7,000
Decrease to the additional paid-in capital account						(7,000)
Increase in accrued liabilities						$ 7,000