Description of Business and Basis of Presentation - Schedule of Percentage Revenues Realized by Contract (Details)	12 Months Ended
Sep. 27, 2019 Lines_of_Business	Sep. 27, 2019	Sep. 27, 2019 Business	Sep. 28, 2018 Business	Sep. 29, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of lines of business	2		3	3
Cost-reimbursable		76.00%		74.00%	76.00%
Fixed-price		24.00%		26.00%	24.00%

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration