Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Available-for-sale securities:
Available-for-sale securities	$ 2,755.8		$ 2,748.5
Trading securities:
Trading securities	13.8	[1]	12.6	[1]
Fair Value Measurements (Textuals)
Restricted investments	89.5		102.6
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	2,770.9		2,764.6
Liabilities measured at fair value:
Other accrued liabilities	(2.7)		0.1
Total liabilities measured at fair value	(2.7)		0.1
Cash equivalents measured at fair value	1,108.1		1,225.9
Restricted investments measured at fair value	92.2		105.6
Short-term investments measured at fair value	542.9		441.5
Long-term investments measured at fair value	1,026.4		988.1
Prepaid expenses and other current assets measured at fair value	1.3		3.5
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative assets:
Total assets measured at fair value	1,637.9		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	1,011.5		1,048.7
Restricted investments measured at fair value	92.2		103.6
Short-term investments measured at fair value	272.7		224.4
Long-term investments measured at fair value	261.5		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	1,133.0		1,072.1
Liabilities measured at fair value:
Other accrued liabilities	(2.7)		0.1
Total liabilities measured at fair value	(2.7)		0.1
Cash equivalents measured at fair value	96.6		177.2
Restricted investments measured at fair value	0		2.0
Short-term investments measured at fair value	270.2		217.1
Long-term investments measured at fair value	764.9		672.3
Prepaid expenses and other current assets measured at fair value	1.3		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	1.3		3.5
Liabilities measured at fair value:
Derivative liabilities	(2.7)		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	1.3		3.5
Liabilities measured at fair value:
Derivative liabilities	(2.7)		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	237.4		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	237.4		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	237.4		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
Certificate of deposit [Member]
Available-for-sale securities:
Available-for-sale securities	36.0		41.9
Certificate of deposit [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	36.3		42.5
Certificate of deposit [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	0		0
Certificate of deposit [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	36.3		42.5
Certificate 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	6.6		11.6
Commercial paper [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Available-for-sale securities	6.6		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	6.6		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	652.2		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	652.2		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	652.2		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	292.4		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	292.4		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	287.4		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	5.0		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	1,101.0	[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	1,101.0	[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	2.7	[4]	3.0	[4]
Trading securities:
Trading securities	13.8	[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	2.7	[4]	1.0	[4]
Trading securities:
Trading securities	13.8	[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	19.1		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	19.1		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	19.1		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	296.0		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	392.3		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	213.9		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	178.4		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	2,755.8		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	1,624.1		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	1,131.7		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 $89.5 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.