Special Charge (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 27, 2017	Jan. 29, 2016	Jan. 27, 2017	Jan. 29, 2016
Commitments and Contingencies Disclosure [Abstract]
Charitable cash contribution	$ 100,000,000		$ 100,000,000
Special charge	$ 100,000,000	$ 0	$ 100,000,000	$ 0