Debt Investment Maturities (Detail) $ in Millions	Mar. 31, 2019 USD ($)
Cost Basis
Due in one year or less	$ 48,902
Due after one year through five years	51,977
Due after five years through 10 years	24,920
Due after 10 years	904
Debt investments, Cost Basis	126,703
Estimated Fair Value
Due in one year or less	48,729
Due after one year through five years	52,189
Due after five years through 10 years	25,428
Due after 10 years	921
Total	$ 127,267