Investments (Maturities of fixed income securities) (Details) - USD ($) $ in Millions	Jul. 30, 2016	Jul. 25, 2015
Investment [Line Items]
Total, fair value	$ 58,125	$ 53,539
Fixed Income Securities
Investment [Line Items]
Less than 1 year, cost	15,473
Due in 1 to 2 years, cost	17,791
Due in 2 to 5 years, cost	20,870
Due after 5 years, cost	288
With no single maturity, mortgage-backed securities, cost	1,846
Total, Cost	56,268
Less than 1 year, fair value	15,485
Due in 1 to 2 years, fair Value	17,847
Due in 2 to 5 year, fair Value	21,128
Due after 5 years, fair value	293
With no single maturity, mortgage-backed securities, fair value	1,868
Total, fair value	$ 56,621