Fair Value Measurements (Tables)

3 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Assets And Liabilities Measured At Fair Value On A Recurring Basis

Assets and Liabilities Measured at Fair Value on a Recurring Basis (in millions):

			Fair Value Measurements at Reporting Date Using
	Balance at Dec 31, 2017		Quoted Prices in Active Markets for  Identical Assets (Level 1)		Significant  Other Observable  Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)
Assets:
Cash and cash equivalents	$	3,661.4	$	3,661.4	$	—	$	—
Short-term investments:
Available-for-sale securities
Corporate debt securities	14.9		—		14.9		—
U.S. government treasury securities	10.5		10.5		—		—
Total available-for-sale securities	25.4		10.5		14.9		—
Trading securities	81.2		81.2		—		—
Total short-term investments	106.6		91.7		14.9		—
Prepaid expenses and other current assets:
Derivative assets	24.1		—		24.1		—
Long-term investments:
Available-for-sale securities
Agency obligations	8.5		—		8.5		—
Corporate debt securities	165.9		—		165.9		—
Auction rate securities	5.9		—		—		5.9
Foreign government obligations	12.0		—		12.0		—
U.S. government treasury securities	112.1		112.1		—		—
State and local government obligations	7.0		—		7.0		—
Mortgage and other asset-backed securities	52.1		—		52.1		—
Total long-term investments	363.5		112.1		245.5		5.9
Other long-term assets:
Derivative assets	16.2		—		16.2		—
Total assets	$	4,171.8	$	3,865.2	$	300.7	$	5.9
Liabilities:
Accrued liabilities:
Derivative liabilities	$	20.8	$	4.6	$	16.2	$	—
Other long-term liabilities:
Derivative liabilities	27.4		—		27.4		—
Total liabilities	$	48.2	$	4.6	$	43.6	$	—

			Fair Value Measurements at Reporting Date Using
	Balance at Oct 1, 2017		Quoted Prices in Active Markets for  Identical Assets (Level 1)		Significant  Other Observable  Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)
Assets:
Cash and cash equivalents	$	2,462.3	$	2,462.3	$	—	$	—
Short-term investments:
Available-for-sale securities
Agency obligations	7.5		—		7.5		—
Commercial paper	2.0		—		2.0		—
Corporate debt securities	49.4		—		49.4		—
Foreign government obligations	7.1		—		7.1		—
U.S. government treasury securities	81.4		81.4		—		—
State and local government obligations	2.0		—		2.0		—
Certificates of deposit	2.3		—		2.3		—
Total available-for-sale securities	151.7		81.4		70.3		—
Trading securities	76.9		76.9		—		—
Total short-term investments	228.6		158.3		70.3		—
Prepaid expenses and other current assets:
Derivative assets	13.4		0.1		13.3		—
Long-term investments:
Available-for-sale securities
Agency obligations	21.8		—		21.8		—
Corporate debt securities	207.4		—		207.4		—
Auction rate securities	5.9		—		—		5.9
Foreign government obligations	17.1		—		17.1		—
U.S. government treasury securities	127.4		127.4		—		—
State and local government obligations	7.0		—		7.0		—
Mortgage and other asset-backed securities	155.7		—		155.7		—
Total long-term investments	542.3		127.4		409.0		5.9
Other long-term assets:
Derivative assets	24.4		—		24.4		—
Total assets	$	3,271.0	$	2,748.1	$	517.0	$	5.9
Liabilities:
Accrued liabilities:
Derivative liabilities	$	16.4	$	2.5	$	13.9	$	—
Other long-term liabilities:
Derivative liabilities	22.1		—		22.1		—
Total	$	38.5	$	2.5	$	36.0	$	—