Fair Value Measurements and Investments (Tables)

12 Months Ended

Sep. 30, 2017

Fair Value Measurements and Investments [Abstract]

Fair Value, Assets and Liabilities Measured on Recurring Basis

Assets and Liabilities Measured at Fair Value on a Recurring Basis

	Fair Value Measurements at September 30 Using Inputs Considered as
	Level 1				Level 2
	September 30, 2017		September 30, 2016		September 30, 2017		September 30, 2016
	(in millions)
Assets
Cash equivalents and restricted cash:
Money market funds	$	5,935	$	4,537
U.S. government-sponsored debt securities					$	2,870	$	196
Investment securities, trading:
Equity securities	$	82	$	71
Investment securities, available-for-sale:
U.S. government-sponsored debt securities					3,663		4,699
U.S. Treasury securities	1,621		2,178
Equity securities	124		53
Corporate debt securities					—		249
Prepaid and other current assets:
Foreign exchange derivative instruments					18		50
Other Assets:
Foreign exchange derivative instruments							6
Total	$	7,762	$	6,839	$	6,551	$	5,200
Liabilities
Accrued liabilities:
Foreign exchange derivative instruments					$	98	$	116
Other liabilities:
Foreign exchange derivative instruments					—		20
Total	$	—	$	—	$	98	$	136

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments

The following table presents the carrying amount and estimated fair value of the Company’s debt in order of maturity:

	September 30, 2017				September 30, 2016
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
	(in millions)
1.20% Senior Notes due December 2017	$	1,749	$	1,751	$	1,746	$	1,754
2.20% Senior Notes due December 2020	2,990		3,031		2,988		3,077
2.15% Senior Notes due September 2022	993		997		—		—
2.80% Senior Notes due December 2022	2,240		2,301		2,238		2,359
3.15% Senior Notes due December 2025	3,967		4,098		3,964		4,225
2.75% Senior Notes due September 2027	740		737		—		—
4.15% Senior Notes due December 2035	1,485		1,637		1,485		1,698
4.30% Senior Notes due December 2045	3,463		3,873		3,461		4,045
3.65% Senior Notes due September 2047	740		746		—		—
Total	$	18,367	$	19,171	$	15,882	$	17,158

Available-for-sale Investment Securities

The amortized cost, unrealized gains and losses and fair value of available-for-sale investment securities are as follows:

	September 30, 2017										September 30, 2016
	Amortized Cost		Gross Unrealized					Fair Value			Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses								Gains		Losses
	(in millions)
U.S. government-sponsored debt securities	$	3,664	$	1	$	(2	)	$	3,663		$	4,693	$	6	$	—	$	4,699
U.S. Treasury securities	1,623		—		(2		)	1,621			2,176		3		—		2,179
Equity securities	5		119		—			124			7		46		—		53
Corporate debt securities	—		—		—			—			248		—		—		248
Auction rate securities	—		—		—			—			—		—		—		—
Total	$	5,292	$	120	$	(4	)	$	5,408		$	7,124	$	55	$	—	$	7,179
Less: current portion of available-for-sale investment securities								$	(3,482	)							$	(3,248	)
Long-term available-for-sale investment securities								$	1,926								$	3,931

Available for Sale Investments Classified by Contractual Maturity Date

	Amortized Cost		Fair Value
	(in millions)
September 30, 2017:
Due within one year	$	3,360	$	3,358
Due after 1 year through 5 years	1,927		1,926
Due after 5 years through 10 years	—		—
Due after 10 years	—		—
Total	$	5,287	$	5,284

Investment Income

Investment income is recorded as non-operating income in the Company's consolidated statements of operations and consisted of the following:

	For the Years Ended September 30,
	2017			2016			2015
	(in millions)
Interest and dividend income on cash and investments	$	92		$	75		$	31
Gain on other investments	6			5			3
Investment securities, trading:
Unrealized gains (losses), net	6			3			(6		)
Realized gains, net	2			—			2
Investment securities, available-for-sale:
Realized (losses) gains, net	(1		)	3			21
Other-than-temporary impairment on investments	—			(4		)	(5		)
Investment income	$	105		$	82		$	46