Acquisitions - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended
	Jul. 31, 2018	Feb. 01, 2018	Sep. 30, 2018	Jul. 18, 2018	Jun. 30, 2018
Business Acquisition [Line Items]
Estimated fair value of goodwill			$ 520,589		$ 497,442
Germane Systems
Business Acquisition [Line Items]
Total purchase price	$ 45,000,000
Estimated fair value of goodwill	$ 23,847
Acquired goodwill, amortization period	15 years
Tax deductible goodwill			23,554
Revenue of acquiree since acquisition date			8,994
Net income (loss) of acquiree since acquisition date			$ (400)
Estimated fair value of assets acquired	$ 46,973
Germane Systems | Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 8,500,000
Useful life of acquired assets	11 years
Germane Systems | Developed Technology Rights
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 4,200,000
Useful life of acquired assets	8 years
Germane Systems | Backlog
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 210,000
Useful life of acquired assets	1 year
Themis Computer Acquisition
Business Acquisition [Line Items]
Estimated fair value of goodwill		$ 112,148
Estimated fair value of assets acquired		185,815
Themis Computer Acquisition | Acquisition-related Costs
Business Acquisition [Line Items]
Estimated fair value of assets acquired				$ 700
Themis Computer Acquisition | Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangible assets acquired		$ 52,600
Useful life of acquired assets		12 years 6 months
Themis Computer Acquisition | Developed Technology Rights
Business Acquisition [Line Items]
Finite-lived intangible assets acquired		$ 17,150
Useful life of acquired assets		9 years 6 months
Themis Computer Acquisition | Backlog
Business Acquisition [Line Items]
Finite-lived intangible assets acquired		$ 1,970
Useful life of acquired assets		1 year