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Derivative Financial Instruments (Textuals) (Details) € in Millions, ¥ in Millions, $ in Millions, $ in Millions | 9 Months Ended |  |  |
--- | --- | --- | --- | ---
Sep. 30, 2019 EUR (€) MBbls $ / bbl | Sep. 30, 2019 JPY (¥) | Sep. 30, 2019 USD ($) | Sep. 30, 2019 SGD ($) MBbls $ / bbl | Sep. 30, 2019 JPY (¥) MBbls $ / bbl | Sep. 30, 2019 USD ($) MBbls $ / bbl | Dec. 31, 2018 EUR (€) | Dec. 31, 2018 SGD ($) | Dec. 31, 2018 USD ($) | Nov. 22, 2017 MBbls
Debt EUR Denominated [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount, nonderivative instruments | € 21.0 |  | $ 23.0 |  |  |  |  |  |  |
Cumulative foreign currency translation loss |  |  |  |  |  | $ 0.6 |  |  |  |
Cumulative foreign currency translation loss, net of tax |  |  |  |  |  | 0.5 |  |  |  |
Debt Yen Denominated [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount, nonderivative instruments |  | ¥ 500.0 | $ 4.6 |  |  |  |  |  |  |
Cumulative foreign currency translation loss |  |  |  |  |  | 0.5 |  |  |  |
Cumulative foreign currency translation loss, net of tax |  |  |  |  |  | $ 0.4 |  |  |  |
Options Held [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Nonmonetary Notional Amount | MBbls | 107,909 |  |  | 107,909 | 107,909 | 107,909 |  |  |  | 301,326
Derivative, Average Price Risk Option Strike Price | $ / bbl | 71.15 |  |  | 71.15 | 71.15 | 71.15 |  |  |  |
Euro Member Countries, Euro | Forward Contracts [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount | € |  |  |  |  |  |  | € 10.0 |  |  |
Singapore, Dollars | Forward Contracts [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount |  |  |  | $ 601.5 |  |  |  | $ 601.5 |  |
United States of America, Dollars | Forward Contracts [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount |  |  |  |  |  | $ 13.4 |  |  | $ 13.4 |
Long [Member] | Designated as Hedging Instrument [Member] | Singapore, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount |  |  |  | $ 31.9 |  |  |  |  |  |
Long [Member] | Designated as Hedging Instrument [Member] | United States of America, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount |  |  |  |  |  | 39.3 |  |  |  |
Long [Member] | Designated as Hedging Instrument [Member] | Japan, Yen | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount | ¥ |  |  |  |  | ¥ 5,921.1 |  |  |  |  |
Short [Member] | Designated as Hedging Instrument [Member] | Singapore, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount | € 4.3 |  |  |  |  | 18.7 |  |  |  |
Short [Member] | Designated as Hedging Instrument [Member] | United States of America, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount | 34.2 |  |  |  |  | 0.0 |  |  |  |
Short [Member] | Designated as Hedging Instrument [Member] | Japan, Yen | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount | € 20.2 |  |  |  |  | $ 31.8 |  |  |  |

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