Acquisitions - Narrative (Details) £ / shares in Units, $ in Thousands, £ in Millions, $ in Millions		3 Months Ended		6 Months Ended			12 Months Ended
	Sep. 23, 2022 employee £ / shares	Jan. 31, 2023 GBP (£)	Sep. 27, 2020 USD ($)	Mar. 29, 2020 USD ($)	Mar. 31, 2019 USD ($)	Apr. 01, 2018 AUD ($)	Oct. 02, 2022 USD ($) acquisition	Oct. 03, 2021 USD ($) employee	Sep. 27, 2020 USD ($) acquisition	Sep. 27, 2020 AUD ($) acquisition	Sep. 29, 2019 USD ($)	Sep. 29, 2019 AUD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 AUD ($)	Sep. 27, 2020 AUD ($)
Business Acquisition [Line Items]
Number Of Acquisitions | acquisition							4
Contingent earn-out liability							$ 65,600
Fair value adjustments to contingent consideration liabilities							$ (329)	$ 3,273	$ 14,971
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]							Foreign currency translation adjustments, net of tax	Foreign currency translation adjustments, net of tax	Foreign currency translation adjustments, net of tax	Foreign currency translation adjustments, net of tax
Interest expense | Contingent consideration
Business Acquisition [Line Items]
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]							Interest Expense	Interest Expense	Interest Expense	Interest Expense
Operating income | Contingent consideration
Business Acquisition [Line Items]
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]							Income from operations	Income from operations	Income from operations	Income from operations
Minimum
Business Acquisition [Line Items]
Earn-out period							3 years
Significant unobservable input, earn-out period							3 years
Maximum
Business Acquisition [Line Items]
Earn-out period							5 years
Significant unobservable input, earn-out period							5 years
Existing customer contracts | Minimum
Business Acquisition [Line Items]
Useful life of intangible assets							1 year
Existing customer contracts | Maximum
Business Acquisition [Line Items]
Useful life of intangible assets							10 years
Technology and trade names | Minimum
Business Acquisition [Line Items]
Useful life of intangible assets							3 years
Technology and trade names | Maximum
Business Acquisition [Line Items]
Useful life of intangible assets							5 years
RPS Group plc
Business Acquisition [Line Items]
Pence per share expected to be acquired | £ / shares	£ 2.22
Number of employees | employee	5,000
RPS Group plc | Forecast | Subsequent Event
Business Acquisition [Line Items]
Percentage of outstanding shares expected to be acquired		100.00%
Expected consideration received upon closing of acquisition | £		£ 636
Business acquisitions
Business Acquisition [Line Items]
Fair value of acquisition purchase price							$ 88,300	$ 151,700	$ 88,600
Initial cash payments							44,000	101,400	71,400
Payables related to estimated post-closing adjustments							(2,500)		700
Promissory note							15,500
Contingent earn-out liability			$ 16,500				31,300	50,300	16,500
Aggregate maximum of contingent consideration			28,000				47,000	$ 74,000	$ 28,000
Earn-out period									3 years	3 years
Number of acquisitions | acquisition									2	2
Business acquisitions | Minimum
Business Acquisition [Line Items]
Earn-out period								3 years
Business acquisitions | Maximum
Business Acquisition [Line Items]
Earn-out period								4 years
Hoare Lea
Business Acquisition [Line Items]
Number of employees | employee								900
NDY
Business Acquisition [Line Items]
Contingent earn-out liability			1,800			$ 9.4			$ 1,800						$ 2.6
Aggregate maximum of contingent consideration						$ 25.0
Earn-out period						3 years
Fair value adjustments to contingent consideration liabilities									3,700	$ 5.2	$ (5,400)	$ (7.9)	$ (2,100)	$ (3.0)
Maximum contingent consideration, year one						$ 7.4
Maximum contingent consideration, year two						8.8
Maximum contingent consideration, year three						$ 8.8
Percentage of maximum potential earn-out						38.00%
EGT
Business Acquisition [Line Items]
Contingent earn-out liability			7,500		$ 21,100				7,500
Aggregate maximum of contingent consideration					$ 25,000
Earn-out period					3 years
Fair value adjustments to contingent consideration liabilities									4,700
Maximum contingent consideration, year one					$ 8,500
Maximum contingent consideration, year two					9,000
Maximum contingent consideration, year three					$ 7,500
Percentage of maximum potential earn-out					84.00%
SEG
Business Acquisition [Line Items]
Contingent earn-out liability			8,100	$ 11,300					$ 8,100
Aggregate maximum of contingent consideration				$ 20,000
Earn-out period				3 years
Fair value adjustments to contingent consideration liabilities			$ 3,400
Maximum contingent consideration, year one				$ 5,000
Maximum contingent consideration, year two				7,000
Maximum contingent consideration, year three				$ 8,000
Percentage of maximum potential earn-out				57.00%
All acquisitions
Business Acquisition [Line Items]
Aggregate maximum of contingent consideration							$ 120,900