CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Cash and Cash Equivalents [Abstract]
Cash	$ 23.2		$ 23.2		$ 62.1
Money market funds	12.2		12.2		40.1
Cash and cash equivalents	35.4	67.0	35.4	67.0	102.2	89.5
Available-for-sale Securities, Current [Abstract]
Marketable securities, Cost Basis	1,139.0		1,139.0		1,029.5
Marketable securities, Unrealized Gains	11.6		11.6		12.2
Marketable securities, Unrealized Losses	(0.6)		(0.6)		(3.0)
Marketable securities, Fair Value	1,150.0		1,150.0		1,038.7
Cash and marketables securities, Cost Basis	1,174.4		1,174.4		1,131.7
Total cash and marketable securities	1,185.4		1,185.4		1,140.9
Available-for-sale Securities, Activity [Abstract]
Proceeds from sales and maturities	242.3	145.0	430.4	459.0
Gross realized gains	2.0	1.4	3.6	3.3
Gross realized losses	0.5	0.4	0.8	1.7
Other-than-temporary impairments on investments	0	0	0.3	0
Percentage of marketable securities maturing in 2012	9.80%		9.80%
Percentage of marketable securities maturing in 2013	29.50%		29.50%
Percentage of marketable securities maturing after 2013	60.70%		60.70%
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Investments with continuous unrealized losses, Less than 12 months, Fair Value	132.6		132.6		204.2
Investments with continuous unrealized losses, Less than 12 months, Unrealized Losses	(0.6)		(0.6)		(2.7)
Investments with continuous unrealized losses, Greater than 12 months, Fair Value	0		0		4.0
Investments with continuous unrealized losses, Greater than 12 months, Unrealized Losses	0		0		(0.3)
Investments with continuous unrealized losses, Total Fair Value	132.6		132.6		208.2
Investments with continuous unrealized losses, Total Unrealized Losses	(0.6)		(0.6)		(3.0)
U.S. government and agency securities [Member]
Available-for-sale Securities, Current [Abstract]
Marketable securities, Cost Basis	366.0		366.0		292.5
Marketable securities, Unrealized Gains	2.8		2.8		3.4
Marketable securities, Unrealized Losses	0		0		0
Marketable securities, Fair Value	368.8		368.8		295.9
Foreign government bonds [Member]
Available-for-sale Securities, Current [Abstract]
Marketable securities, Cost Basis	41.4		41.4		24.9
Marketable securities, Unrealized Gains	0.9		0.9		0.5
Marketable securities, Unrealized Losses	0		0		0
Marketable securities, Fair Value	42.3		42.3		25.4
Asset-backed securities [Member]
Available-for-sale Securities, Current [Abstract]
Marketable securities, Cost Basis	90.3		90.3		58.2
Marketable securities, Unrealized Gains	0.4		0.4		0.1
Marketable securities, Unrealized Losses	0		0		(0.3)
Marketable securities, Fair Value	90.7		90.7		58.0
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Investments with continuous unrealized losses, Less than 12 months, Fair Value					31.7
Investments with continuous unrealized losses, Less than 12 months, Unrealized Losses					(0.1)
Investments with continuous unrealized losses, Greater than 12 months, Fair Value					1.1
Investments with continuous unrealized losses, Greater than 12 months, Unrealized Losses					(0.2)
Investments with continuous unrealized losses, Total Fair Value					32.8
Investments with continuous unrealized losses, Total Unrealized Losses					(0.3)
Mortgage-backed securities [Member]
Available-for-sale Securities, Current [Abstract]
Marketable securities, Cost Basis	109.6		109.6		124.1
Marketable securities, Unrealized Gains	0.9		0.9		1.1
Marketable securities, Unrealized Losses	(0.1)		(0.1)		(0.3)
Marketable securities, Fair Value	110.4		110.4		124.9
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Investments with continuous unrealized losses, Less than 12 months, Fair Value	26.3		26.3		35.1
Investments with continuous unrealized losses, Less than 12 months, Unrealized Losses	(0.1)		(0.1)		(0.2)
Investments with continuous unrealized losses, Greater than 12 months, Fair Value	0		0		1.9
Investments with continuous unrealized losses, Greater than 12 months, Unrealized Losses	0		0		(0.1)
Investments with continuous unrealized losses, Total Fair Value	26.3		26.3		37.0
Investments with continuous unrealized losses, Total Unrealized Losses	(0.1)		(0.1)		(0.3)
Corporate notes and bonds [Member]
Available-for-sale Securities, Current [Abstract]
Marketable securities, Cost Basis	516.8		516.8		518.0
Marketable securities, Unrealized Gains	6.5		6.5		7.0
Marketable securities, Unrealized Losses	(0.5)		(0.5)		(2.4)
Marketable securities, Fair Value	522.8		522.8		522.6
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Investments with continuous unrealized losses, Less than 12 months, Fair Value	106.3		106.3		137.4
Investments with continuous unrealized losses, Less than 12 months, Unrealized Losses	(0.5)		(0.5)		(2.4)
Investments with continuous unrealized losses, Greater than 12 months, Fair Value	0		0		1.0
Investments with continuous unrealized losses, Greater than 12 months, Unrealized Losses	0		0		0
Investments with continuous unrealized losses, Total Fair Value	106.3		106.3		138.4
Investments with continuous unrealized losses, Total Unrealized Losses	(0.5)		(0.5)		(2.4)
Municipal securities [Member]
Available-for-sale Securities, Current [Abstract]
Marketable securities, Cost Basis	14.9		14.9		11.8
Marketable securities, Unrealized Gains	0.1		0.1		0.1
Marketable securities, Unrealized Losses	0		0		0
Marketable securities, Fair Value	$ 15.0		$ 15.0		$ 11.9