ACCOUTNING POLICIES (Derivative financial instruments and hedging activities) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Cash flow hedges
Derivative instruments, gain (loss) [Line Items]
Effective portion of hedge	$ (0.1)	$ 0.5

Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion

No definition available.

Name:	tx_DerivativeInstrumentsGainRecognizedinOtherComprehensiveIncomeLossEffectivePortion
Namespace Prefix:	tx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration