Derivative Instruments and Hedging Activities	12 Months Ended
Dec. 31, 2017
Derivative Instruments and Hedging Activities [Abstract]
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities We manage our exposure to foreign exchange and interest rate risk through various strategies, including the use of derivative financial instruments. We use forward foreign exchange contracts as economic hedges to manage the cash flow volatility arising from foreign exchange rate fluctuations. We use interest rate swaps to manage our interest expense and structure our long-term debt portfolio to achieve a mix of fixed rate and floating rate debt. We do not use derivatives for trading or speculative purposes. Using derivatives exposes us to the risk that counterparties to the derivative contracts will fail to meet their contractual obligations. We manage that risk through careful selection and ongoing evaluation of the counterparty financial institutions based on specific minimum credit standards and other factors. We evaluate the effects of changes in foreign currency exchange rates, interest rates and other relevant market risks on our derivatives. We periodically determine the potential loss from market risk on our derivatives by performing a value-at-risk, or VaR, analysis. VaR is a statistical model that uses historical currency exchange and interest rate data to measure the potential impact on future earnings of our derivative financial instruments assuming normal market conditions. The VaR model is not intended to represent actual losses but is used as a risk estimation and management tool. Based on the results of the model, we estimate with 95% confidence a maximum one-day change in the net fair value of our derivative financial instruments at December 31, 2017 was not significant. Foreign Exchange Risk As an integral part of our global treasury operations, we centralize our cash and use multicurrency pools to manage the foreign exchange risk that arises from imbalances between subsidiaries and their respective treasury centers from which they borrow or invest funds. However, in certain circumstances, subsidiaries borrowing or investing with a treasury center operating in a different currency creates foreign exchange exposure. To manage that risk, we had outstanding forward foreign exchange contracts with an aggregate notional amount of $92.8 million and $99.0 million at December 31, 2017 and 2016, respectively. Additionally, there are circumstances where revenue and expense transactions are not denominated in the same currency. In these instances, amounts are either promptly settled or hedged with forward foreign exchange contracts. To manage that risk, we had outstanding forward foreign exchange contracts with an aggregate notional amount of $136.3 million and $94.0 million at December 31, 2017 and 2016, respectively. The net fair value of the forward foreign contracts at December 31, 2017 and 2016 was a current asset of $0.9 million and a current liability of $1.1 million, respectively. Foreign currency derivatives are designated as fair value hedges; therefore, any gain or loss in fair value incurred on those instruments is recorded in results of operations and is generally offset by decreases or increases in the fair value of the underlying exposures. By using these financial instruments, we reduced financial risk of adverse foreign exchange changes by foregoing any gain which might have occurred if the markets moved favorably. The terms of our forward foreign exchange contracts are generally less than 90 days. Interest Rate Risk We use interest rate swaps to manage our interest cost and structure our long-term debt portfolio to achieve a mix of fixed rate and floating rate debt. Based on market conditions, we may terminate the swaps to reduce our exposure to rising interest rates or to monetize any gain and lock in a reduction in interest expense over the term of the underlying debt. The total notional amount of the outstanding fixed-to-floating interest rate swaps at December 31, 2017 and 2016, was $1.25 billion. See Note 6 for a discussion of our interest rate swaps.

Derivative Instruments and Hedging Activities

We manage our exposure to foreign exchange and interest rate risk through various strategies, including the use of derivative financial instruments. We use forward foreign exchange contracts as economic hedges to manage the cash flow volatility arising from foreign exchange rate fluctuations. We use interest rate swaps to manage our interest expense and structure our long-term debt portfolio to achieve a mix of fixed rate and floating rate debt. We do not use derivatives for trading or speculative purposes. Using derivatives exposes us to the risk that counterparties to the derivative contracts will fail to meet their contractual obligations. We manage that risk through careful selection and ongoing evaluation of the counterparty financial institutions based on specific minimum credit standards and other factors.

We evaluate the effects of changes in foreign currency exchange rates, interest rates and other relevant market risks on our derivatives. We periodically determine the potential loss from market risk on our derivatives by performing a value-at-risk, or VaR, analysis. VaR is a statistical model that uses historical currency exchange and interest rate data to measure the potential impact on future earnings of our derivative financial instruments assuming normal market conditions. The VaR model is not intended to represent actual losses but is used as a risk estimation and management tool. Based on the results of the model, we estimate with 95% confidence a maximum one-day change in the net fair value of our derivative financial instruments at December 31, 2017 was not significant.

Foreign Exchange Risk

As an integral part of our global treasury operations, we centralize our cash and use multicurrency pools to manage the foreign exchange risk that arises from imbalances between subsidiaries and their respective treasury centers from which they borrow or invest funds. However, in certain circumstances, subsidiaries borrowing or investing with a treasury center operating in a different currency creates foreign exchange exposure. To manage that risk, we had outstanding forward foreign exchange contracts with an aggregate notional amount of $92.8 million and $99.0 million at December 31, 2017 and 2016, respectively. Additionally, there are circumstances where revenue and expense transactions are not denominated in the same currency. In these instances, amounts are either promptly settled or hedged with forward foreign exchange contracts. To manage that risk, we had outstanding forward foreign exchange contracts with an aggregate notional amount of $136.3 million and $94.0 million at December 31, 2017 and 2016, respectively. The net fair value of the forward foreign contracts at December 31, 2017 and 2016 was a current asset of $0.9 million and a current liability of $1.1 million, respectively.

Foreign currency derivatives are designated as fair value hedges; therefore, any gain or loss in fair value incurred on those instruments is recorded in results of operations and is generally offset by decreases or increases in the fair value of the underlying exposures. By using these financial instruments, we reduced financial risk of adverse foreign exchange changes by foregoing any gain which might have occurred if the markets moved favorably. The terms of our forward foreign exchange contracts are generally less than 90 days.

Interest Rate Risk

We use interest rate swaps to manage our interest cost and structure our long-term debt portfolio to achieve a mix of fixed rate and floating rate debt. Based on market conditions, we may terminate the swaps to reduce our exposure to rising interest rates or to monetize any gain and lock in a reduction in interest expense over the term of the underlying debt. The total notional amount of the outstanding fixed-to-floating interest rate swaps at December 31, 2017 and 2016, was $1.25 billion. See Note 6 for a discussion of our interest rate swaps.