Investments - Maturities of Available-for-sale and Held-to-maturity Securities (Details) $ in Millions	May 07, 2017 USD ($)
Available-for-sale, Cost Basis
Due in one year or less	$ 145
Due after one year through five years	748
Due after five years	50
Available-for-sale, cost basis, total	943
Available-for-sale, Fair Value
Due in one year or less	146
Due after one year through five years	746
Due after five years	49
Available-for-sale, recorded basis, total	941
Held-to-maturity
Due in one year or less	246
Due after one year through five years	0
Due after five years	0
Held-to-maturity, cost basis, total	$ 246