ACQUISITIONS Narrative (Detail) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Apr. 04, 2017	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Net cash paid				$ 0	$ 235,856	$ 2,504
Equity issued as part of acquisitions, net						$ 1,130
Sotera [Member]
Business Acquisition [Line Items]
Net cash paid	$ 236,100			235,856
Escrow holdback funds	200
Tax deductible goodwill	103,500
Intangible assets	60,590
Integration related expenses				$ 2,000	13,900
Acquisition related expenses					$ 4,300
Milestone [Member]
Business Acquisition [Line Items]
Equity issued (in shares)			129,530
Equity issued as part of acquisitions, net			$ 1,000
Geospacial Intelligence Collection Business [Member]
Business Acquisition [Line Items]
Business purchase price		$ 3,900
Backlog and Customer Relationships | Sotera [Member]
Business Acquisition [Line Items]
Intangible assets	$ 60,600