Commitments And Contingencies	3 Months Ended
Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	COMMITMENTS AND CONTINGENCIES Litigation. In the ordinary course of business, we are subject to actions for damages alleging personal injury under the general maritime laws of the United States, including the Jones Act, for alleged negligence. We report actions for personal injury to our insurance carriers and believe that the settlement or disposition of those claims will not have a material adverse effect on our consolidated financial position, results of operations or cash flows. Various other actions and claims are pending against us, most of which are covered by insurance. Although we cannot predict the ultimate outcome of these matters, we believe that our ultimate liability, if any, that may result from these other actions and claims will not materially affect our results of operations, cash flows or financial position. Financial Instruments and Risk Concentration. In the normal course of business, we manage risks associated with foreign exchange rates and interest rates through a variety of strategies, including the use of hedging transactions. As a matter of policy, we do not use derivative instruments unless we have an underlying exposure. Other financial instruments that potentially subject us to concentrations of credit risk are principally cash and cash equivalents and accounts receivable. The carrying values of cash and cash equivalents approximate their fair values due to the short-term maturity of the underlying instruments. Accounts receivable are generated from a broad group of customers, primarily from within the energy industry, which is our major source of revenue. Due to their short-term nature, carrying values of our accounts receivable and accounts payable approximate fair market values. We estimated the aggregate fair market value of the Senior Notes to be $791 million as of March 31, 2018, based on quoted prices. Since the market for the Senior Notes is not an active market, the fair value of the Senior Notes is classified within Level 2 in the fair value hierarchy under U.S. GAAP (inputs other than quoted prices in active markets for similar assets and liabilities that are observable or can be corroborated by observable market data for substantially the full terms for the assets or liabilities). We have two interest rate swaps in place on a total of $200 million of the 2024 Senior Notes for the period to November 2024. The agreements swap the fixed interest rate of 4.650% on $100 million of the 2024 Senior Notes to the floating rate of one month LIBOR plus 2.426% and on another $100 million to one month LIBOR plus 2.823%. We estimate the combined fair value of the interest rate swaps to be a net liability of $6.4 million as of March 31, 2018, which is included on our balance sheet in our Other Long-term Liabilities. These values were arrived at based on a discounted cash flow model using Level 2 inputs. Since the second quarter of 2015, the exchange rate for the Angolan kwanza relative to the U.S. dollar generally has been declining, although the exchange rate was relatively stable during 2017. As our functional currency in Angola is the U.S. dollar, we recorded foreign currency transaction losses related to the kwanza of $7.7 million and $0.5 million in the three-month periods ended March 31, 2018 and 2017, respectively, as a component of Other income (expense), net in our Consolidated Statements of Operations for those respective periods. Our foreign currency transaction gains or losses related primarily to the remeasurement of our Angolan kwanza cash balances to U.S. dollars. Conversion of cash balances from kwanza to U.S. dollars is controlled by the central bank in Angola, and the central bank has slowed this process since mid-2015, causing our kwanza cash balances to subsequently increase. As of March 31, 2018, we had the equivalent of approximately $22 million of kwanza cash balances in Angola reflected on our balance sheet. To mitigate our currency exposure risk in Angola, through March 31, 2018, we used kwanza to purchase $68 million equivalent Angolan central bank (Banco Nacional de Angola) bonds, with maturities of $58 million in 2018 and $10 million in 2020. The bonds are denominated as U.S. dollar equivalents, so that, upon payment of semi-annual interest and principal upon maturity, payment is made in kwanza, equivalent to the respective U.S. dollars at the then-current exchange rate. The entire $68 million was classified as Other non-current assets on our Consolidated Balance Sheet as of December 31, 2017, as our intention was to reinvest funds from maturing bonds in similar long-term assets. However, the market to purchase similar long-term bonds is limited. As a result, we have classified the $58 million bonds due to mature in 2018 as Other current assets in our Consolidated Balance Sheet as of March 31, 2018. We estimated the fair market value of the Angolan bonds to be $68 million as of March 31, 2018 using quoted prices. Since the market for the Angolan bonds is not an active market, the fair value of the Angolan bonds is classified within Level 2 in the fair value hierarchy under U.S. GAAP.

COMMITMENTS AND CONTINGENCIES

Litigation. In the ordinary course of business, we are subject to actions for damages alleging personal injury under the general maritime laws of the United States, including the Jones Act, for alleged negligence. We report actions for personal injury to our insurance carriers and believe that the settlement or disposition of those claims will not have a material adverse effect on our consolidated financial position, results of operations or cash flows.

Various other actions and claims are pending against us, most of which are covered by insurance. Although we cannot predict the ultimate outcome of these matters, we believe that our ultimate liability, if any, that may result from these other actions and claims will not materially affect our results of operations, cash flows or financial position.

Financial Instruments and Risk Concentration. In the normal course of business, we manage risks associated with foreign exchange rates and interest rates through a variety of strategies, including the use of hedging transactions. As a matter of policy, we do not use derivative instruments unless we have an underlying exposure. Other financial instruments that potentially subject us to concentrations of credit risk are principally cash and cash equivalents and accounts receivable.

The carrying values of cash and cash equivalents approximate their fair values due to the short-term maturity of the underlying instruments. Accounts receivable are generated from a broad group of customers, primarily from within the energy industry, which is our major source of revenue. Due to their short-term nature, carrying values of our accounts receivable and accounts payable approximate fair market values.

We estimated the aggregate fair market value of the Senior Notes to be $791 million as of March 31, 2018, based on quoted prices. Since the market for the Senior Notes is not an active market, the fair value of the Senior Notes is classified within Level 2 in the fair value hierarchy under U.S. GAAP (inputs other than quoted prices in active markets for similar assets and liabilities that are observable or can be corroborated by observable market data for substantially the full terms for the assets or liabilities).

We have two interest rate swaps in place on a total of $200 million of the 2024 Senior Notes for the period to November 2024. The agreements swap the fixed interest rate of 4.650% on $100 million of the 2024 Senior Notes to the floating rate of one month LIBOR plus 2.426% and on another $100 million to one month LIBOR plus 2.823%. We estimate the combined fair value of the interest rate swaps to be a net liability of $6.4 million as of March 31, 2018, which is included on our balance sheet in our Other Long-term Liabilities. These values were arrived at based on a discounted cash flow model using Level 2 inputs.

Since the second quarter of 2015, the exchange rate for the Angolan kwanza relative to the U.S. dollar generally has been declining, although the exchange rate was relatively stable during 2017. As our functional currency in Angola is the U.S. dollar, we recorded foreign currency transaction losses related to the kwanza of $7.7 million and $0.5 million in the three-month periods ended March 31, 2018 and 2017, respectively, as a component of Other income (expense), net in our Consolidated Statements of Operations for those respective periods. Our foreign currency transaction gains or losses related primarily to the remeasurement of our Angolan kwanza cash balances to U.S. dollars. Conversion of cash balances from kwanza to U.S. dollars is controlled by the central bank in Angola, and the central bank has slowed this process since mid-2015, causing our kwanza cash balances to subsequently increase. As of March 31, 2018, we had the equivalent of approximately $22 million of kwanza cash balances in Angola reflected on our balance sheet.

To mitigate our currency exposure risk in Angola, through March 31, 2018, we used kwanza to purchase $68 million equivalent Angolan central bank (Banco Nacional de Angola) bonds, with maturities of $58 million in 2018 and $10 million in 2020. The bonds are denominated as U.S. dollar equivalents, so that, upon payment of semi-annual interest and principal upon maturity, payment is made in kwanza, equivalent to the respective U.S. dollars at the then-current exchange rate. The entire $68 million was classified as Other non-current assets on our Consolidated Balance Sheet as of December 31, 2017, as our intention was to reinvest funds from maturing bonds in similar long-term assets. However, the market to purchase similar long-term bonds is limited. As a result, we have classified the $58 million bonds due to mature in 2018 as Other current assets in our Consolidated Balance Sheet as of March 31, 2018. We estimated the fair market value of the Angolan bonds to be $68 million as of March 31, 2018 using quoted prices. Since the market for the Angolan bonds is not an active market, the fair value of the Angolan bonds is classified within Level 2 in the fair value hierarchy under U.S. GAAP.