v3.26.1
Segment Information - Schedule of Total Revenues, Segment Operating Profit and Total Asset for Reporting Segment (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Jun. 26, 2026
Jun. 27, 2025
Jun. 26, 2026
Jun. 27, 2025
Segment Reporting [Line Items]        
Revenues from External Customers $ 4,076,410 $ 3,031,768 $ 11,064,572 $ 8,875,139
Direct cost of contracts (3,265,707) (2,273,358) (8,693,726) (6,657,118)
Selling, general and administrative expenses (524,000) (523,396) (1,932,758) (1,565,942)
Segment Operating Profit 286,703 235,014 438,088 652,079
Restructuring, Transaction and Other Charges (21,613) (34,134) (402,889) (87,991)
Amortization of Intangible Assets (33,452) (39,245) (105,511) (115,946)
Total Other (Expense) Income, net (45,456) 10,090 (121,226) (298,006)
Earnings from Continuing Operations Before Taxes 241,247 245,104 316,862 354,073
Restructuring and other charges 21,395 22,254 39,565 47,657
Other income, net of mark-to-market losses related to a fair value investment in equity securities 6,200   6,200  
Allocated share-based compensation expense   6,800   20,700
Equity method investment retained after disposal, mark-to market losses   (27,400)   227,300
Loss on extinguishment of debt 0 $ 0 0 $ (20,510)
Joint Venture        
Segment Reporting [Line Items]        
Ownership percentage   50.00%   50.00%
Amentum Holdings, Inc.        
Segment Reporting [Line Items]        
Restructuring and other charges   $ 4,700   $ 20,900
Amentum Holdings, Inc. | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | SpinCo Business        
Segment Reporting [Line Items]        
Discontinued operation, transition services agreement, income (expenses)   9,800   31,500
Foreign Exchange Forward        
Segment Reporting [Line Items]        
Gain (loss) on derivatives, before taxes     (20,500)  
Equity-Based Incentive Grants        
Segment Reporting [Line Items]        
Allocated share-based compensation expense     237,500 20,600
PA Consulting Group Limited        
Segment Reporting [Line Items]        
Pre-tax transaction costs     122,700  
Restructuring and other charges 13,800   22,000  
Professional Services and Employee Seperation        
Segment Reporting [Line Items]        
Restructuring and other charges 7,600 22,000 17,500 47,100
Operating Segments        
Segment Reporting [Line Items]        
Revenues from External Customers 4,076,410 3,031,768 11,064,572 8,875,139
Direct cost of contracts (3,265,707) (2,273,358) (8,693,726) (6,657,118)
Selling, general and administrative expenses (468,935) (450,017) (1,424,358) (1,362,005)
Segment Operating Profit 341,768 308,393 946,488 856,016
Infrastructure & Advanced Facilities | Operating Segments        
Segment Reporting [Line Items]        
Revenues from External Customers 3,746,900 2,699,062 10,022,055 7,928,023
Direct cost of contracts (3,037,800) (2,052,021) (7,997,201) (6,052,299)
Selling, general and administrative expenses (440,975) (411,066) (1,316,765) (1,226,210)
Segment Operating Profit 268,125 235,975 708,089 649,514
Restructuring and other charges 7,627 22,254 17,518 47,398
PA Consulting | Operating Segments        
Segment Reporting [Line Items]        
Revenues from External Customers 329,510 332,706 1,042,517 947,116
Direct cost of contracts (227,907) (221,337) (696,525) (604,819)
Selling, general and administrative expenses (27,960) (38,951) (107,593) (135,795)
Segment Operating Profit 73,643 72,418 238,399 206,502
Restructuring and other charges $ 13,768 $ 0 $ 22,047 $ 259