Hedging Transactions and Derivative Financial Instruments (Notional Values of Derivative Instruments) (Details)	Mar. 31, 2019 KRW (₩) T / mo	Mar. 31, 2019 USD ($) T / mo
Contracts not designated as hedging instruments | USD/CNY | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | $		$ 17,470,003
Contracts not designated as hedging instruments | KRW/USD | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | ₩	₩ 4,539,600,000
Contract designated as hedging instrument | April 2019 - June 2019
Derivative [Line Items]
Volume of Copper Derivatives (in metric tons per month)	188	188
Contract designated as hedging instrument | July 2019 - September 2019
Derivative [Line Items]
Volume of Copper Derivatives (in metric tons per month)	191	191
Contract designated as hedging instrument | October 2019 - December 2019
Derivative [Line Items]
Volume of Copper Derivatives (in metric tons per month)	195	195
Contract designated as hedging instrument | January 2020 - March 2020
Derivative [Line Items]
Volume of Copper Derivatives (in metric tons per month)	202	202
Contract designated as hedging instrument | April 2020 - June 2020
Derivative [Line Items]
Volume of Copper Derivatives (in metric tons per month)	134	134