FAIR VALUE MEASUREMENT: (Tables)

12 Months Ended

Dec. 31, 2022

FAIR VALUE MEASUREMENT:

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 consolidated balance sheet as of December 31, 2022 and December 31, 2020 (in millions):

	At December 31, 2022				At December 31, 2021
	Carrying Value		Fair Value		Carrying Value		Fair Value
Liabilities:
Long-term debt level 1	$	6,200.0	$	6,372.6	$	6,496.4	$	8,506.0
Long-term debt level 2		51.2		54.2		51.2		67.2
Total long-term debt	$	6,251.2	$	6,426.8	$	6,547.6	$	8,573.2

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

Fair values of assets and liabilities measured at fair value on a recurring basis were calculated as of December 31, 2022 and 2021, as follows (in millions):

	Fair Value at Measurement Date Using:
					Significant
	Fair Value		Quoted prices in		other		Significant
	as of		active markets for		observable		unobservable
	December 31,		identical assets		inputs		inputs
Description	2022		(Level 1)		(Level 2)		(Level 3)
Assets:
Short term investment:
—Trading securities	$	208.0	$	208.0	$	—	$	—
—Available-for-sale debt securities:
Asset backed securities		0.1		—		0.1		—
Mortgage backed securities		0.2		—		0.2		—
Accounts receivable:
—Embedded derivatives—Not classified as hedges:
Provisionally priced sales:
Copper		1,052.0		1,052.0		—		—
Molybdenum		456.9		456.9		—		—
Total	$	1,717.2	$	1,716.9	$	0.3	$	—

	Fair Value at Measurement Date Using:
					Significant
	Fair Value		Quoted prices in		other		Significant
	as of		active markets for		observable		unobservable
	December 31,		identical assets		inputs		inputs
Description	2021		(Level 1)		(Level 2)		(Level 3)
Assets:
Short term investment:
—Trading securities	$	486.5	$	486.5	$	—	$	—
—Available-for-sale debt securities:
Corporate bonds		—		—		—		—
Asset backed securities		0.2		—		0.2		—
Mortgage backed securities		0.2		—		0.2		—
Accounts receivable:
—Embedded derivatives-Not classified as hedges:
Provisionally priced sales:
Copper		876.2		876.2		—		—
Molybdenum		288.3		288.3		—		—
Total	$	1,651.4	$	1,651.0	$	0.4	$	—