MARKETABLE SECURITIES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Marketable Securities, Restricted	$ 439.5		$ 439.5		$ 436.9
Available For Sale Securities Debt Maturities Fair Value Abstract
Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value	47.2		47.2
Available For Sale Securities Debt Maturities After Ten Years Fair Value	132.6		132.6
Available For Sale Securities Debt Maturities After One Year Through Five Years Fair Value	62.4		62.4
Available For Sale Securities Debt Maturities Within One Year Fair Value	27.2		27.2
Available For Sale Securities Debt Maturities Fair Value	269.4		269.4
Available For Sale Securities Debt Maturities Amortized Cost Abstract
Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost	61.6		61.6
Available For Sale Securities Debt Maturities Within One Year Amortized Cost	27.2		27.2
Available For Sale Securities Debt Maturities After Ten Years Amortized Cost	126.8		126.8
Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost	45.4		45.4
Available For Sale Securities Debt Maturities Amortized Cost	261.0		261.0
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	544.0		544.0		545.7
TradingSecuritiesEquity	10.6		10.6		14.2
IncreaseDecreaseInTradingSecurities	0.2	$ 0.5	0.5	$ 2.1
Fair Value Inputs Level 1 Member
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	295.7		295.7		312.2
Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	248.3		248.3		233.5
US Government Debt Securities Member | Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	70.8		70.8		46.6
Corporate Bond Securities Member | Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	39.5		39.5		43.9
Asset Backed Securities Member | Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	18.8		18.8		20.0
Municipal Bonds Member | Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	109.9		109.9		111.4
Other Debt Securities Member | Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	9.3		9.3		11.6
Cash And Cash Equivalents Member | Fair Value Inputs Level 1 Member
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	21.1		21.1		26.9
Mutual Funds [Member] | Fair Value Inputs Level 1 Member
Fair Value Assets And Liabilities Measured On Recurring Basis Abstract
Investments Fair Value Disclosure	274.6		274.6		285.3
Debt Securities
Investments, Debt and Equity Securities [Abstract]
Available For Sale Securities Fair Value Disclosure	269.4		269.4		260.4
Available-for-sale Securities, Gross Unrealized Gains			8.4		4.5
AvailableForSaleSecuritiesGrossUnrealizedLoss			0.0		(0.6)
Available For Sale Securities Amortized Cost	261.0		261.0		256.5
Equity Securities
Investments, Debt and Equity Securities [Abstract]
Available For Sale Securities Fair Value Disclosure	264.0		264.0		271.1
Available-for-sale Securities, Gross Unrealized Gains			58.5		59.2
AvailableForSaleSecuritiesGrossUnrealizedLoss			(2.3)		(3.4)
Available For Sale Securities Amortized Cost	$ 207.8		$ 207.8		$ 215.3