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Revenue and Contract Balances - Disaggregation of Revenue (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 29, 2020 | Mar. 31, 2019 | Mar. 29, 2020 | Mar. 31, 2019
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 734,133 | $ 722,621 | $ 1,531,756 | $ 1,440,052
Fixed-price |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 255,613 | 247,831 | 526,668 | 488,764
Time-and-materials |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 350,618 | 345,626 | 738,776 | 682,163
Cost-plus |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 127,902 | 129,164 | 266,312 | 269,125
U.S. state and local government |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 102,260 | 129,868 | 224,616 | 253,147
U.S. federal government |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 243,261 | 216,498 | 488,564 | 441,256
U.S. commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | 162,198 | 165,970 | 345,169 | 338,758
International |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue | $ 226,414 | $ 210,285 | $ 473,407 | $ 406,891

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- Definition Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045 + Details
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