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Reportable Segments - Revenue By Client Sector (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Jul. 02, 2017 | Jun. 26, 2016 | Jul. 02, 2017 | Jun. 26, 2016
Revenue by client sector |  |  |  |
Revenue | $ 685,539 | $ 666,869 | $ 2,018,171 | $ 1,854,961
U.S. federal government |  |  |  |
Revenue by client sector |  |  |  |
Revenue | 224,343 | 203,663 | 665,086 | 546,700
International |  |  |  |
Revenue by client sector |  |  |  |
Revenue | 178,415 | 194,616 | 547,986 | 537,324
U.S. state and local government |  |  |  |
Revenue by client sector |  |  |  |
Revenue | 83,716 | 74,501 | 250,392 | 214,302
U.S. commercial |  |  |  |
Revenue by client sector |  |  |  |
Revenue | $ 199,065 | $ 194,089 | $ 554,707 | $ 556,635

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