Debt Investment Maturities (Detail) $ in Millions	Dec. 31, 2016 USD ($)
Cost Basis
Due in one year or less	$ 16,027
Due after one year through five years	94,925
Due after five years through 10 years	4,470
Due after 10 years	1,294
Total	116,716
Estimated Fair Value
Due in one year or less	16,026
Due after one year through five years	94,669
Due after five years through 10 years	4,402
Due after 10 years	1,287
Total	$ 116,384