Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Remaining Weighted Average Amortization Period	7 years 6 months
Intangible Assets	$ 839,211	$ 848,620
Accumulated Amortization	(446,573)	(437,886)
Intangible Assets, Net	392,638	410,734
Indefinite-lived Intangible Assets [Line Items]
Intangible Assets	842,211	851,620
Intangible Assets, Net	395,638	413,734
Engineering license
Indefinite-lived Intangible Assets [Line Items]
Intangible Assets	$ 3,000	3,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Remaining Weighted Average Amortization Period	6 years 2 months 12 days
Intangible Assets	$ 527,298	532,808
Accumulated Amortization	(223,606)	(213,915)
Intangible Assets, Net	$ 303,692	318,893
Backlog
Finite-Lived Intangible Assets [Line Items]
Remaining Weighted Average Amortization Period	2 years 6 months
Intangible Assets	$ 142,144	144,704
Accumulated Amortization	(139,330)	(141,580)
Intangible Assets, Net	$ 2,814	3,124
Trade names
Finite-Lived Intangible Assets [Line Items]
Remaining Weighted Average Amortization Period	14 years 6 months
Intangible Assets	$ 92,182	93,396
Accumulated Amortization	(27,400)	(26,145)
Intangible Assets, Net	$ 64,782	67,251
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Remaining Weighted Average Amortization Period	3 years 1 month 6 days
Intangible Assets	$ 43,459	43,281
Accumulated Amortization	(33,234)	(32,868)
Intangible Assets, Net	$ 10,225	10,413
Patented rights and developed technology
Finite-Lived Intangible Assets [Line Items]
Remaining Weighted Average Amortization Period	2 years 1 month 6 days
Intangible Assets	$ 22,416	22,719
Accumulated Amortization	(20,789)	(20,682)
Intangible Assets, Net	$ 1,627	2,037
Curriculum
Finite-Lived Intangible Assets [Line Items]
Remaining Weighted Average Amortization Period	8 years 1 month 6 days
Intangible Assets	$ 11,712	11,712
Accumulated Amortization	(2,214)	(2,696)
Intangible Assets, Net	$ 9,498	$ 9,016