Revenue Recognition - Disaggregation of Revenue by Contract Type, Customer Information and Prime or Subcontractor (Detail) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Revenue	$ 1,165,864	$ 1,085,814
Prime contractor
Disaggregation Of Revenue [Line Items]
Revenue	1,089,872
Subcontractor
Disaggregation Of Revenue [Line Items]
Revenue	75,992
Department of Defense
Disaggregation Of Revenue [Line Items]
Revenue	818,266
Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenue	292,202
Commercial and other
Disaggregation Of Revenue [Line Items]
Revenue	55,396
Domestic
Disaggregation Of Revenue [Line Items]
Revenue	1,126,523	1,050,883
Domestic | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenue	1,050,531
Domestic | Subcontractor
Disaggregation Of Revenue [Line Items]
Revenue	75,992
Domestic | Department of Defense
Disaggregation Of Revenue [Line Items]
Revenue	818,266
Domestic | Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenue	292,202
Domestic | Commercial and other
Disaggregation Of Revenue [Line Items]
Revenue	16,055
International
Disaggregation Of Revenue [Line Items]
Revenue	39,341	$ 34,931
International | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenue	39,341
International | Commercial and other
Disaggregation Of Revenue [Line Items]
Revenue	39,341
Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenue	641,527
Cost-plus-fee | Domestic
Disaggregation Of Revenue [Line Items]
Revenue	641,527
Firm fixed-price
Disaggregation Of Revenue [Line Items]
Revenue	344,004
Firm fixed-price | Domestic
Disaggregation Of Revenue [Line Items]
Revenue	321,071
Firm fixed-price | International
Disaggregation Of Revenue [Line Items]
Revenue	22,933
Time and materials
Disaggregation Of Revenue [Line Items]
Revenue	180,333
Time and materials | Domestic
Disaggregation Of Revenue [Line Items]
Revenue	163,925
Time and materials | International
Disaggregation Of Revenue [Line Items]
Revenue	$ 16,408