Debt Investment Maturities (Detail) $ in Millions	Jun. 30, 2018 USD ($)
Cost Basis
Due in one year or less	$ 31,590
Due after one year through five years	76,422
Due after five years through 10 years	21,765
Due after 10 years	924
Total	130,701
Estimated Fair Value
Due in one year or less	31,451
Due after one year through five years	75,810
Due after five years through 10 years	21,396
Due after 10 years	922
Total	$ 129,579