Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Available-for-sale securities:
Available-for-sale securities	$ 2,089.1		$ 2,882.2
Trading securities:
Trading securities	16.1	[1]	15.4	[1]
Fair Value Measurements (Textuals)
Restricted investments	66.7		83.6
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	2,108.9		2,900.6
Liabilities measured at fair value:
Other accrued liabilities	(0.1)		(0.7)
Total liabilities measured at fair value	(0.1)		(0.7)
Cash equivalents	1,135.1		996.2
Restricted investments measured at fair value	70.8		87.6
Short-term investments measured at fair value	378.1		561.9
Long-term investments measured at fair value	521.2		1,251.9
Prepaid expenses and other current assets measured at fair value	3.7		3.0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	1,350.5		1,374.9
Liabilities measured at fair value:
Other accrued liabilities	0		0
Total liabilities measured at fair value	0		0
Cash equivalents	1,116.3		965.1
Restricted investments measured at fair value	70.8		87.6
Short-term investments measured at fair value	135.7		246.5
Long-term investments measured at fair value	27.7		75.7
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	758.4		1,525.7
Liabilities measured at fair value:
Other accrued liabilities	(0.1)		(0.7)
Total liabilities measured at fair value	(0.1)		(0.7)
Cash equivalents	18.8		31.1
Restricted investments measured at fair value	0		0
Short-term investments measured at fair value	242.4		315.4
Long-term investments measured at fair value	493.5		1,176.2
Prepaid expenses and other current assets measured at fair value	3.7		3.0
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	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	3.7		3.0
Liabilities measured at fair value:
Derivative liabilities	(0.1)		(0.7)
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	3.7		3.0
Liabilities measured at fair value:
Derivative liabilities	(0.1)		(0.7)
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	135.3		249.9
Asset-backed Securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	135.3		249.9
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	135.3		249.9
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	12.0		27.6
Certificates of deposit [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	12.0		27.6
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	12.0		27.6
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	1.2		6.9
Commercial paper [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1.2		6.9
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	1.2		6.9
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	412.2		815.3
Corporate debt securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	412.2		815.3
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	412.2		815.3
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	5.0		10.7
Foreign government debt securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	5.0		10.7
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	5.0		10.7
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	88.3		306.2
Government-sponsored enterprise obligations [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	88.3		306.2
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		0
Government-sponsored enterprise obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	88.3		306.2
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]
Available-for-sale securities:
Available-for-sale securities	1,183.0		1,043.7
Money market funds [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1,183.0	[2]	1,043.7	[3]
Money market funds [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1,183.0	[2]	1,043.7	[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]
Available-for-sale securities:
Available-for-sale securities	4.1		4.0
Mutual funds [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	4.1	[4]	4.0	[4]
Trading securities:
Trading securities	16.1	[5]	15.4	[5]
Mutual funds [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	4.1	[4]	4.0	[4]
Trading securities:
Trading securities	16.1	[5]	15.4	[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]	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	6.4		114.6
Publicly-traded equity securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	6.4		114.6
Publicly-traded equity securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	6.4		114.6
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	241.6		303.3
US government securities [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	241.6		303.3
US government securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	140.9		197.2
US government securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	100.7		106.1
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	2,089.1		2,882.2
Available-for-sale securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	1,334.4		1,359.5
Available-for-sale securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	754.7		1,522.7
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 $66.7 million of restricted investments measured at fair market value related to the Company's D&O Trust and acquisitions related escrows.

[3] Balance includes $83.6 million of restricted investments measured at fair market value related to the Company's D&O Trust and acquisitions related escrows.

[4] Balance relates to restricted investments measured at fair market value related to 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.