Investments and Fair Value Measurements Investments and Fair Value Measurements (Investment Maturities) (Details) - USD ($) $ in Thousands	Sep. 25, 2015	Sep. 26, 2014
Amortized Cost
Due within 1 year	$ 158,957	$ 232,944
Due in 1 to 2 years	173,571	179,177
Due in 2 to 3 years	143,879	116,204
Total	476,407	528,325
Fair Value
Due within 1 year	159,090	233,208
Due in 1 to 2 years	173,577	179,536
Due in 2 to 3 years	143,752	116,299
Total	$ 476,419	$ 529,043