Accumulated Other Comprehensive Income and Supplemental Equity Disclosure - Changes in AOCI (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 25, 2019	Jan. 26, 2018	Jan. 25, 2019	Jan. 26, 2018	Apr. 28, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance			$ 50,822,000,000	$ 50,416,000,000
Other comprehensive income (loss)	$ 154,000,000	$ 678,000,000	(722,000,000)	1,231,000,000
Cumulative effect of change in accounting principle					$ 296,000,000
Balance	49,941,000,000	50,340,000,000	49,941,000,000	50,340,000,000
Unrealized (Loss) Gain on Investment Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance			(194,000,000)	(69,000,000)
Other comprehensive (loss) income before reclassifications			(7,000,000)	50,000,000
Reclassifications			30,000,000	(9,000,000)
Other comprehensive income (loss)			23,000,000	41,000,000
Cumulative effect of change in accounting principle					47,000,000
Balance	(124,000,000)	(28,000,000)	(124,000,000)	(28,000,000)
Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)			(2,000,000)	33,000,000
Reclassifications, tax expense (benefit)			(2,000,000)	4,000,000
Cumulative Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance			(268,000,000)	(1,452,000,000)
Other comprehensive (loss) income before reclassifications			(1,124,000,000)	1,559,000,000
Reclassifications			0	(34,000,000)
Other comprehensive income (loss)			(1,124,000,000)	1,525,000,000
Cumulative effect of change in accounting principle					0
Balance	(1,392,000,000)	73,000,000	(1,392,000,000)	73,000,000
Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)			(8,000,000)
Net Change in Retirement Obligations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance			(1,117,000,000)	(1,129,000,000)
Other comprehensive (loss) income before reclassifications			0	(38,000,000)
Reclassifications			65,000,000	49,000,000
Other comprehensive income (loss)			65,000,000	11,000,000
Cumulative effect of change in accounting principle					0
Balance	(1,052,000,000)	(1,118,000,000)	(1,052,000,000)	(1,118,000,000)
Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)			0	(6,000,000)
Reclassifications, tax expense (benefit)			15,000,000	21,000,000
Unrealized (Loss) Gain on Derivative Financial Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance			(207,000,000)	37,000,000
Other comprehensive (loss) income before reclassifications			353,000,000	(351,000,000)
Reclassifications			(36,000,000)	5,000,000
Other comprehensive income (loss)			317,000,000	(346,000,000)
Cumulative effect of change in accounting principle					0
Balance	110,000,000	(309,000,000)	110,000,000	(309,000,000)
Other Comprehensive Income (Loss), Tax [Abstract]
Other comprehensive income (loss) before reclassifications, tax expense (benefit)			116,000,000	(156,000,000)
Reclassifications, tax expense (benefit)			16,000,000	0
Total Accumulated Other Comprehensive (Loss) Income
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance			(1,786,000,000)	(2,613,000,000)
Other comprehensive (loss) income before reclassifications			(778,000,000)	1,220,000,000
Reclassifications			59,000,000	11,000,000
Other comprehensive income (loss)			(719,000,000)	1,231,000,000
Cumulative effect of change in accounting principle					$ 47,000,000
Balance	$ (2,458,000,000)	$ (1,382,000,000)	$ (2,458,000,000)	$ (1,382,000,000)