Fair Value Measurements (Details) - USD ($) $ in Thousands	Jul. 25, 2015	Apr. 25, 2015
Assets
Transfers from Level 1 to Level 2	$ 0	$ 0
Transfers from Level 2 to Level 1	0	0
Level 1 | Fair Value, Measurements, Recurring [Member]
Assets
Available-for-sale Securities	1,239	1,552
Total	1,239	1,552
Level 2 | Fair Value, Measurements, Recurring [Member]
Assets
Available-for-sale Securities	49,892	58,516
Trading securities	7	1,127
Total	$ 49,899	$ 59,643