Fair Value Measurements, Valuation Techniques (Details) (Recurring, Level 3, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 23, 2015	Jan. 24, 2014	Jan. 23, 2015	Jan. 24, 2014
Reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs (level3)
Beginning balance	$ 108	$ 118	$ 106	$ 127
Total realized losses and other-than-temporary impairment losses included in income		(3)		(5)
Total unrealized gains/(losses) included in other comprehensive income	0	(3)	2	3
Settlements		(7)		(20)
Ending balance	108	105	108	105
Corporate Debt Securities
Reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs (level3)
Beginning balance	9	9	9	10
Total realized losses and other-than-temporary impairment losses included in income		0		0
Total unrealized gains/(losses) included in other comprehensive income	0	0	0	0
Settlements		0		(1)
Ending balance	9	9	9	9
Auction Rate Securities
Reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs (level3)
Beginning balance	99	105	97	103
Total realized losses and other-than-temporary impairment losses included in income		(3)		(5)
Total unrealized gains/(losses) included in other comprehensive income	0	(3)	2	2
Settlements		(3)		(4)
Ending balance	99	96	99	96
Auction Rate Securities | Discounted Cash Flow
Fair Value Inputs
Illiquidity Premium			6.00%
Auction Rate Securities | Discounted Cash Flow | Minimum
Fair Value Inputs
Years to Principal Recovery			2 years
Auction Rate Securities | Discounted Cash Flow | Maximum
Fair Value Inputs
Years to Principal Recovery			12 years
Auction Rate Securities | Discounted Cash Flow | Weighted Average
Fair Value Inputs
Years to Principal Recovery			3 years
Mortgage Backed Securities
Reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs (level3)
Beginning balance	0	4	0	14
Total realized losses and other-than-temporary impairment losses included in income		0		0
Total unrealized gains/(losses) included in other comprehensive income	0	0	0	1
Settlements		(4)		(15)
Ending balance	$ 0	$ 0	$ 0	$ 0