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Derivative Financial Instruments (Textuals) (Details) € in Millions, ¥ in Millions, $ in Millions, $ in Millions | 6 Months Ended |  |  |
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Jun. 30, 2019 EUR (€) MBbls $ / bbl | Jun. 30, 2019 JPY (¥) | Jun. 30, 2019 USD ($) | Jun. 30, 2019 SGD ($) MBbls $ / bbl | Jun. 30, 2019 JPY (¥) MBbls $ / bbl | Jun. 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 |  | $ 23.9 |  |  |  |  |  |  |
Cumulative foreign currency translation loss |  |  |  |  |  | $ 0.4 |  |  |  |
Cumulative foreign currency translation loss, net of tax |  |  |  |  |  | 0.3 |  |  |  |
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 | 105,891 |  |  | 105,891 | 105,891 | 105,891 |  |  |  | 262,269
Derivative, Average Price Risk Option Strike Price | $ / bbl | 64.02 |  |  | 64.02 | 64.02 | 64.02 |  |  |  |
Euro Member Countries, Euro | Forward Contracts [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount | € |  |  |  |  |  |  | € 10.0 |  |  |
Singapore, Dollars | Forward Contracts [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  | $ 601.5 |  |  |  | $ 601.5 |  |
United States of America, Dollars | Forward Contracts [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  |  |  | $ 13.4 |  |  | $ 13.4 |
Long [Member] | Designated as Hedging Instrument [Member] | Singapore, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  | $ 23.8 |  |  |  |  |  |
Long [Member] | Designated as Hedging Instrument [Member] | United States of America, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  |  |  | 35.1 |  |  |  |
Long [Member] | Designated as Hedging Instrument [Member] | Japan, Yen | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount | ¥ |  |  |  |  | ¥ 5,992.8 |  |  |  |  |
Short [Member] | Designated as Hedging Instrument [Member] | Singapore, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount | € 1.9 |  |  |  |  | 15.4 |  |  |  |
Short [Member] | Designated as Hedging Instrument [Member] | United States of America, Dollars | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount | 30.2 |  |  |  |  | 0.0 |  |  |  |
Short [Member] | Designated as Hedging Instrument [Member] | Japan, Yen | Foreign Exchange Forward [Member] |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount | € 19.8 |  |  |  |  | $ 32.3 |  |  |  |

X
- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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