Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022
Disaggregation Of Revenue [Line Items]
Revenues	$ 7,659,832	$ 6,702,546	$ 6,202,917
Expertise
Disaggregation Of Revenue [Line Items]
Revenues	3,556,989	3,091,372	2,869,317
Technology
Disaggregation Of Revenue [Line Items]
Revenues	4,102,843	3,611,174	3,333,600
Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	6,849,849	5,973,700	5,564,922
Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	809,983	728,846	637,995
Department of Defense
Disaggregation Of Revenue [Line Items]
Revenues	5,695,408	4,817,470	4,331,327
Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenues	1,588,262	1,533,295	1,549,791
Commercial and other
Disaggregation Of Revenue [Line Items]
Revenues	376,162	351,781	321,799
Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	4,654,689	3,896,725	3,632,359
Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	2,091,179	2,023,968	1,823,221
Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	913,964	781,853	747,337
Domestic
Disaggregation Of Revenue [Line Items]
Revenues	7,432,745	6,512,938	6,011,059
Domestic | Expertise
Disaggregation Of Revenue [Line Items]
Revenues	3,473,434	3,021,621	2,796,038
Domestic | Technology
Disaggregation Of Revenue [Line Items]
Revenues	3,959,311	3,491,317	3,215,021
Domestic | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	6,649,114	5,801,840	5,389,870
Domestic | Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	783,631	711,098	621,189
Domestic | Department of Defense
Disaggregation Of Revenue [Line Items]
Revenues	5,695,408	4,817,470	4,331,327
Domestic | Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenues	1,588,262	1,533,295	1,549,791
Domestic | Commercial and other
Disaggregation Of Revenue [Line Items]
Revenues	149,075	162,173	129,941
Domestic | Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	4,654,689	3,896,725	3,632,359
Domestic | Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	1,950,286	1,888,414	1,690,480
Domestic | Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	827,770	727,799	688,220
International
Disaggregation Of Revenue [Line Items]
Revenues	227,087	189,608	191,858
International | Expertise
Disaggregation Of Revenue [Line Items]
Revenues	83,555	69,751	73,279
International | Technology
Disaggregation Of Revenue [Line Items]
Revenues	143,532	119,857	118,579
International | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	200,735	171,860	175,052
International | Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	26,352	17,748	16,806
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	227,087	189,608	191,858
International | Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	0	0	0
International | Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	140,893	135,554	132,741
International | Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	$ 86,194	$ 54,054	$ 59,117