Fair Value Measurements, Valuation Techniques (Details) (Recurring, Level 3, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 25, 2013	Jan. 27, 2012	Jan. 25, 2013	Jan. 27, 2012
Reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs
Beginning balance	$ 171	$ 174	$ 172	$ 191
Total realized losses and other-than-temporary impairment losses included in earnings		(1)		(3)
Total unrealized gains/(losses) included in other comprehensive income	5	6	6	1
Settlements		(1)	(2)	(11)
Ending balance	176	178	176	178
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
Beginning balance	10	10	10	17
Total realized losses and other-than-temporary impairment losses included in earnings		0		(1)
Total unrealized gains/(losses) included in other comprehensive income	(1)	0	(1)	1
Settlements		0	0	(7)
Ending balance	9	10	9	10
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
Beginning balance	129	127	127	133
Total realized losses and other-than-temporary impairment losses included in earnings		0		0
Total unrealized gains/(losses) included in other comprehensive income	5	6	7	0
Settlements		0	0	0
Ending balance	134	133	134	133
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
Beginning balance	27	31	29	35
Total realized losses and other-than-temporary impairment losses included in earnings		(1)		(1)
Total unrealized gains/(losses) included in other comprehensive income	0	0	0	(1)
Settlements		(1)	(2)	(4)
Ending balance	27	29	27	29
Other Asset-backed Securities
Reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs
Beginning balance	5	6	6	6
Total realized losses and other-than-temporary impairment losses included in earnings		0		(1)
Total unrealized gains/(losses) included in other comprehensive income	1	0	0	1
Settlements		0	0	0
Ending balance	$ 6	$ 6	$ 6	$ 6