Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2023
Disaggregation Of Revenue [Line Items]
Revenues	$ 8,627,824	$ 7,659,832	$ 6,702,546
Expertise
Disaggregation Of Revenue [Line Items]
Revenues	3,849,841	3,556,989	3,091,372
Technology
Disaggregation Of Revenue [Line Items]
Revenues	4,777,983	4,102,843	3,611,174
Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	7,783,908	6,849,849	5,973,700
Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	843,916	809,983	728,846
DoD
Disaggregation Of Revenue [Line Items]
Revenues	6,507,728	5,695,408	4,817,470
Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenues	1,751,973	1,588,262	1,533,295
Commercial and other
Disaggregation Of Revenue [Line Items]
Revenues	368,123	376,162	351,781
Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	5,221,011	4,654,689	3,896,725
Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	2,271,602	2,091,179	2,023,968
Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	1,135,211	913,964	781,853
Domestic
Disaggregation Of Revenue [Line Items]
Revenues	8,370,361	7,432,745	6,512,938
Domestic | Expertise
Disaggregation Of Revenue [Line Items]
Revenues	3,714,545	3,473,434	3,021,621
Domestic | Technology
Disaggregation Of Revenue [Line Items]
Revenues	4,655,816	3,959,311	3,491,317
Domestic | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	7,553,566	6,649,114	5,801,840
Domestic | Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	816,795	783,631	711,098
Domestic | DoD
Disaggregation Of Revenue [Line Items]
Revenues	6,507,728	5,695,408	4,817,470
Domestic | Federal civilian agencies
Disaggregation Of Revenue [Line Items]
Revenues	1,751,973	1,588,262	1,533,295
Domestic | Commercial and other
Disaggregation Of Revenue [Line Items]
Revenues	110,660	149,075	162,173
Domestic | Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	5,221,011	4,654,689	3,896,725
Domestic | Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	2,112,490	1,950,286	1,888,414
Domestic | Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	1,036,860	827,770	727,799
International
Disaggregation Of Revenue [Line Items]
Revenues	257,463	227,087	189,608
International | Expertise
Disaggregation Of Revenue [Line Items]
Revenues	135,296	83,555	69,751
International | Technology
Disaggregation Of Revenue [Line Items]
Revenues	122,167	143,532	119,857
International | Prime contractor
Disaggregation Of Revenue [Line Items]
Revenues	230,342	200,735	171,860
International | Subcontractor
Disaggregation Of Revenue [Line Items]
Revenues	27,121	26,352	17,748
International | DoD
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	257,463	227,087	189,608
International | Cost-plus-fee
Disaggregation Of Revenue [Line Items]
Revenues	0	0	0
International | Fixed-price
Disaggregation Of Revenue [Line Items]
Revenues	159,112	140,893	135,554
International | Time-and-materials
Disaggregation Of Revenue [Line Items]
Revenues	$ 98,351	$ 86,194	$ 54,054