Investments - Maturities of Available-for-sale and Held-to-maturity Securities (Details) $ in Millions	Feb. 17, 2019 USD ($)
Available-for-sale, Cost Basis
Due in one year or less	$ 403
Due after one year through five years	458
Due after five years	31
Available-for-sale, cost basis, total	892
Available-for-sale, Fair Value
Due in one year or less	401
Due after one year through five years	452
Due after five years	31
Available-for-sale, recorded basis, total	884
Held-to-maturity
Due in one year or less	158
Due after one year through five years	0
Due after five years	0
Held-to-maturity, cost basis, total	$ 158