Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Available-for-sale securities:
Available-for-sale securities	$ 2,887.5		$ 2,748.5
Trading securities:
Trading securities	15.1	[1]	12.6	[1]
Fair Value Measurements (Textuals)
Restricted investments	88.1		102.6
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	2,905.4		2,764.6
Liabilities measured at fair value:
Other accrued liabilities	(3.4)		0.1
Total liabilities measured at fair value	(3.4)		0.1
Cash equivalents measured at fair value	1,049.7		1,225.9
Restricted investments measured at fair value	90.6		105.6
Short-term investments measured at fair value	573.7		441.5
Long-term investments measured at fair value	1,188.6		988.1
Prepaid expenses and other current assets measured at fair value	2.8		3.5
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	1,370.6		1,692.5
Liabilities measured at fair value:
Other accrued liabilities	0		0
Total liabilities measured at fair value	0		0
Cash equivalents measured at fair value	961.0		1,048.7
Restricted investments measured at fair value	90.6		103.6
Short-term investments measured at fair value	259.1		224.4
Long-term investments measured at fair value	59.9		315.8
Prepaid expenses and other current assets measured at fair value	0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	1,534.8		1,072.1
Liabilities measured at fair value:
Other accrued liabilities	(3.4)		0.1
Total liabilities measured at fair value	(3.4)		0.1
Cash equivalents measured at fair value	88.7		177.2
Restricted investments measured at fair value	0		2.0
Short-term investments measured at fair value	314.6		217.1
Long-term investments measured at fair value	1,128.7		672.3
Prepaid expenses and other current assets measured at fair value	2.8		3.5
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	0		0
Liabilities measured at fair value:
Other accrued liabilities	0		0
Total liabilities measured at fair value	0		0
Cash equivalents measured at fair value	0		0
Restricted investments measured at fair value	0		0
Short-term investments measured at fair value	0		0
Long-term investments measured at fair value	0		0
Prepaid expenses and other current assets measured at fair value	0		0
Foreign exchange contract [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Derivative assets	2.8		3.5
Liabilities measured at fair value:
Derivative liabilities	(3.4)		0.1
Foreign exchange contract [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Derivative assets	0		0
Liabilities measured at fair value:
Derivative liabilities	0		0
Foreign exchange contract [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Derivative assets	2.8		3.5
Liabilities measured at fair value:
Derivative liabilities	(3.4)		0.1
Foreign exchange contract [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Derivative assets	0		0
Liabilities measured at fair value:
Derivative liabilities	0		0
Asset-backed Securities [Member]
Available-for-sale securities:
Available-for-sale securities	253.7		226.4
Asset-backed Securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	253.7		226.4
Asset-backed Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	253.7		226.4
Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Certificates of deposit [Member]
Available-for-sale securities:
Available-for-sale securities	24.8		41.9
Certificates of deposit [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	24.9		42.5
Certificates of deposit [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Certificates of deposit [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	24.9		42.5
Certificates of deposit [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Commercial paper [Member]
Available-for-sale securities:
Available-for-sale securities	11.5		11.6
Commercial paper [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	11.5		22.4
Commercial paper [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Commercial paper [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	11.5		22.4
Commercial paper [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Corporate debt securities [Member]
Available-for-sale securities:
Available-for-sale securities	769.1		535.6
Corporate debt securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	769.1		535.6
Corporate debt securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Corporate debt securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	769.1		535.6
Corporate debt securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Foreign government debt securities [Member]
Available-for-sale securities:
Available-for-sale securities	15.8		5.0
Foreign government debt securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	15.8		5.0
Foreign government debt securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Foreign government debt securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	15.8		5.0
Foreign government debt securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Government-sponsored enterprise obligations [Member]
Available-for-sale securities:
Available-for-sale securities	315.1		264.9
Government-sponsored enterprise obligations [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	323.7		271.0
Government-sponsored enterprise obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		254.9
Government-sponsored enterprise obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	323.7		16.1
Government-sponsored enterprise obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Money market funds [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1,044.1	[2]	1,145.2	[3]
Money market funds [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1,044.1	[2]	1,145.2	[3]
Money market funds [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0	[2]	0	[3]
Money market funds [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0	[2]	0	[3]
Mutual funds [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	2.5	[4]	3.0	[4]
Trading securities:
Trading securities	15.1	[5]	12.6	[5]
Mutual funds [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	2.5	[4]	1.0	[4]
Trading securities:
Trading securities	15.1	[5]	12.6	[5]
Mutual funds [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0	[4]	2.0	[4]
Trading securities:
Trading securities	0	[5]	0	[5]
Mutual funds [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0	[4]	0	[4]
Trading securities:
Trading securities	0	[5]	0	[5]
Publicly-traded equity securities [Member]
Available-for-sale securities:
Available-for-sale securities	126.7		2.9
Publicly-traded equity securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	126.7		2.9
Publicly-traded equity securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	126.7		2.9
Publicly-traded equity securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Publicly-traded equity securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
US government securities [Member]
Available-for-sale securities:
Available-for-sale securities	230.5		328.7
US government securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	315.5		494.5
US government securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	182.2		275.9
US government securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	133.3		218.6
US government securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Available-for-sale securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	2,887.5		2,748.5
Available-for-sale securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1,355.5		1,679.9
Available-for-sale securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1,532.0		1,068.6
Available-for-sale securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	$ 0		$ 0

[1] Balance includes the Company's non-qualified deferred compensation plan assets.

[2] Balance includes $88.1 million of restricted investments measured at fair market value, related to the Company's D&O trust and acquisition-related escrows.

[3] Balance includes $102.6 million of restricted investments measured at fair market value, related to the Company's D&O trust and acquisition-related escrows.

[4] Balance relates to the restricted investments measured at fair market value of the Company's India Gratuity Trust.

[5] Balance relates to investments measured at fair value related to the Company's non-qualified deferred compensation plan assets.