FINANCING ARRANGEMENTS (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Unsecured Debt [Member] Unsecured Senior Notes 2020 [Member]	Dec. 31, 2012 Unsecured Debt [Member] Unsecured Senior Notes 2020 [Member]	Sep. 30, 2013 Unsecured Debt [Member] Unsecured Senior Notes 2021 [Member]	Dec. 31, 2012 Unsecured Debt [Member] Unsecured Senior Notes 2021 [Member]	Jan. 17, 2013 Line of Credit [Member]	Jan. 17, 2013 Letter of Credit [Member]
Financing arrangements
Senior unsecured notes			$ 800,000,000	$ 800,000,000	$ 600,000,000	$ 600,000,000
Revolving credit facility due January 17, 2018	0	0
Long-term obligations	1,400,000,000	1,400,000,000
Revolving credit facility, maximum borrowing capacity							400,000,000.0	325,000,000
Line of credit facility available borrowing capacity	262,300,000
Letters of credit amount outstanding	137,700,000
Senior unsecured notes principal amount			$ 800,000,000		$ 600,000,000
Stated interest rate			5.25%		5.125%