Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021
Disaggregation Of Revenue [Line Items]
Revenues	$ 6,702,546	$ 6,202,917	$ 6,044,135
Expertise
Disaggregation Of Revenue [Line Items]
Revenues	3,091,372	2,869,317	2,972,966
Technology
Disaggregation Of Revenue [Line Items]
Revenues	3,611,174	3,333,600	3,071,169
Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	5,973,700	5,564,922	5,449,590
Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	728,846	637,995	594,545
Department of Defense
Disaggregation Of Revenue [Line Items]
Revenues	4,817,470	4,331,327	4,185,292
Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenues	1,533,295	1,549,791	1,585,672
Commercial and other
Disaggregation Of Revenue [Line Items]
Revenues	351,781	321,799	273,171
Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	3,896,725	3,632,359	3,504,838
Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	2,023,968	1,823,221	1,769,841
Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	781,853	747,337	769,456
Domestic
Disaggregation Of Revenue [Line Items]
Revenues	6,512,938	6,011,059	5,868,392
Domestic | Expertise
Disaggregation Of Revenue [Line Items]
Revenues	3,021,621	2,796,038	2,901,204
Domestic | Technology
Disaggregation Of Revenue [Line Items]
Revenues	3,491,317	3,215,021	2,967,188
Domestic | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	5,801,840	5,389,870	5,284,761
Domestic | Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	711,098	621,189	583,631
Domestic | Department of Defense
Disaggregation Of Revenue [Line Items]
Revenues	4,817,470	4,331,327	4,185,292
Domestic | Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenues	1,533,295	1,549,791	1,585,672
Domestic | Commercial and other
Disaggregation Of Revenue [Line Items]
Revenues	162,173	129,941	97,428
Domestic | Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	3,896,725	3,632,359	3,504,838
Domestic | Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	1,888,414	1,690,480	1,651,343
Domestic | Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	727,799	688,220	712,211
International
Disaggregation Of Revenue [Line Items]
Revenues	189,608	191,858	175,743
International | Expertise
Disaggregation Of Revenue [Line Items]
Revenues	69,751	73,279	71,762
International | Technology
Disaggregation Of Revenue [Line Items]
Revenues	119,857	118,579	103,981
International | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	171,860	175,052	164,829
International | Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	17,748	16,806	10,914
International | Department of Defense
Disaggregation Of Revenue [Line Items]
Revenues	0	0	0
International | Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenues	0	0	0
International | Commercial and other
Disaggregation Of Revenue [Line Items]
Revenues	189,608	191,858	175,743
International | Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	0	0	0
International | Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	135,554	132,741	118,498
International | Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	$ 54,054	$ 59,117	$ 57,245