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Reportable Segments - Revenue By Sector (Details) - USD ($) $ in Thousands | 3 Months Ended
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Jan. 01, 2017 | Dec. 27, 2015
Revenue by client sector |  |
Revenue | $ 668,851 | $ 560,708
International |  |
Revenue by client sector |  |
Revenue | 172,457 | 135,807
U.S. commercial |  |
Revenue by client sector |  |
Revenue | 190,266 | 188,164
U.S. federal government |  |
Revenue by client sector |  |
Revenue | 222,634 | 165,022
U.S. state and local government |  |
Revenue by client sector |  |
Revenue | $ 83,494 | $ 71,715

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