Debt Investment Maturities (Detail) $ in Millions	Dec. 31, 2018 USD ($)
Cost Basis
Due in one year or less	$ 39,245
Due after one year through five years	58,499
Due after five years through 10 years	26,009
Due after 10 years	878
Debt investments, Cost Basis	124,631
Estimated Fair Value
Due in one year or less	39,040
Due after one year through five years	58,306
Due after five years through 10 years	26,077
Due after 10 years	870
Total	$ 124,293