Fair Value Measurements and Investments - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Dec. 31, 2015	Mar. 31, 2016	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-marketable equity investments		$ 45,000,000	$ 45,000,000
Carrying value of cost method investments, reclassified as available for sale		4,000,000
Fair value of available for sale securities previously classified as cost method investments		64,000,000
Pre-tax unrealized gain on available-for-sale securities, previously classified as cost method investments		60,000,000
Principal Amount		16,000,000,000
Long-term Debt		15,876,000,000	0
Long-term Debt, Fair Value		16,798,000,000
Available-for-sale securities, gross unrealized gains		65,000,000	7,000,000
Available-for-sale securities, gross unrealized losses		$ 2,000,000	0
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, stated maturities		1 year
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, stated maturities		2 years
Senior Notes | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt maturity period		2 years
Senior Notes | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt maturity period		30 years
Senior Notes | 2017 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal Amount		$ 1,750,000,000
Long-term Debt		1,745,000,000
Long-term Debt, Fair Value		1,760,000,000
Senior Notes | 2020 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal Amount		3,000,000,000
Long-term Debt		2,986,000,000
Long-term Debt, Fair Value		3,075,000,000
Senior Notes | 2022 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal Amount		2,250,000,000
Long-term Debt		2,237,000,000
Long-term Debt, Fair Value		2,346,000,000
Senior Notes | 2025 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal Amount		4,000,000,000
Long-term Debt		3,962,000,000
Long-term Debt, Fair Value		4,176,000,000
Senior Notes | 2035 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal Amount		1,500,000,000
Long-term Debt		1,485,000,000
Long-term Debt, Fair Value		1,612,000,000
Senior Notes | 2045 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal Amount		3,500,000,000
Long-term Debt		3,461,000,000
Long-term Debt, Fair Value		3,829,000,000
Level 3 | Visa Europe put option | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Visa Europe put option		$ 0	$ 255,000,000
Non-cash decrease in the fair value of the put	$ (255,000,000)