Hedging Transactions and Derivative Financial Instruments (Notional Values of Derivative Instruments) (Details)	Mar. 31, 2017 JPY (¥) T	Mar. 31, 2017 EUR (€) T	Mar. 31, 2017 USD ($) T	Mar. 31, 2017 KRW (₩) T
Contracts designated as hedging instruments | April 2017 - June 2017
Derivative [Line Items]
Notional Value of Copper Derivatives	122	122	122	122
Contracts designated as hedging instruments | July 2017 - September 2017
Derivative [Line Items]
Notional Value of Copper Derivatives	122	122	122	122
Contracts designated as hedging instruments | October 2017 - December 2017
Derivative [Line Items]
Notional Value of Copper Derivatives	122	122	122	122
Contracts designated as hedging instruments | January 2018 - March 2018
Derivative [Line Items]
Notional Value of Copper Derivatives	56	56	56	56
Contracts designated as hedging instruments | April 2018 - June 2018
Derivative [Line Items]
Notional Value of Copper Derivatives	25	25	25	25
Contracts not designated as hedging instruments | KRW/USD | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | ₩				₩ 5,291,766,000
Contracts not designated as hedging instruments | USD/JPY | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | $			$ 512,637
Contracts not designated as hedging instruments | JPY/EUR | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | ¥	¥ 338,000,000
Contracts not designated as hedging instruments | EUR/USD | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | €		€ 3,914,930
Contracts not designated as hedging instruments | EUR/HUF | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | €		€ 586,678
Contracts not designated as hedging instruments | USD/CNY | Foreign Exchange Forward
Derivative [Line Items]
Notional Values of Foreign Currency Derivatives | $			$ 6,083,500