Debt Investment Maturities (Detail) $ in Millions	Sep. 30, 2019 USD ($)
Cost Basis
Due in one year or less	$ 44,950
Due after one year through five years	46,544
Due after five years through 10 years	36,438
Due after 10 years	1,376
Debt investments, Cost Basis	129,308
Estimated Fair Value
Due in one year or less	44,929
Due after one year through five years	47,525
Due after five years through 10 years	37,990
Due after 10 years	1,467
Total	$ 131,911