FINANCIAL INSTRUMENTS: (Tables)

9 Months Ended

Sep. 30, 2015

FINANCIAL INSTRUMENTS:

Schedule of carrying amount and estimated fair values of the Company's financial instruments

Consequently, such financial instruments are not included in the following table that provides information about the carrying amounts and estimated fair values of other financial instruments that are not measured at fair value in the condensed consolidated balance sheet as of September 30, 2015 and December 31, 2014 (in millions):

	At September 30, 2015				At December 31, 2014
	Carrying Value		Fair Value		Carrying Value		Fair Value
Liabilities:
Long-term debt	$	5,950.9	$	5,338.4	$	4,180.9	$	4,369.6

Schedule of fair values of assets and liabilities measured at fair value on a recurring basis

			Fair Value at Measurement Date Using:
Description	Fair Value as of September 30, 2015		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Assets:
Short-term investment:
- Trading securities	$	878.0	$	878.0	$	—	$	—
- Available-for-sale debt securities:
Corporate bonds	0.2		—		0.2		—
Mortgage backed securities	3.9		—		3.9		—
Accounts receivable:
- Embedded derivatives - Not classified as hedges:
Provisionally priced sales:
Copper	189.3		189.3		—		—
Molybdenum	64.6		64.6		—		—
Total	$	1,136.0	$	1,131.9	$	4.1	$	—

			Fair Value at Measurement Date Using:
Description	Fair Value as of December 31, 2014		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Assets:
Short-term investment:
- Trading securities	$	333.7	$	333.7	$	—	$	—
- Available-for-sale debt securities:
Corporate bonds	0.3		—		0.3		—
Mortgage backed securities	4.6		—		4.6		—
Accounts receivable:
- Embedded derivatives - Not classified as hedges:
Provisionally priced sales:
Copper	202.2		202.2		—		—
Molybdenum	105.5		105.5		—		—
Total	$	646.3	$	641.4	$	4.9	$	—