ilim holding s.a . shareholder 2019s agreement in october 2007 , in connection with the formation of the ilim holding s.a . joint venture , international paper entered into a shareholder 2019s agreement that includes provisions relating to the reconciliation of disputes among the partners . this agreement provides that at any time , either the company or its partners may commence procedures specified under the deadlock agreement . if these or any other deadlock procedures under the shareholder's agreement are commenced , although it is not obligated to do so , the company may in certain situations choose to purchase its partners' 50% ( 50 % ) interest in ilim . any such transaction would be subject to review and approval by russian and other relevant anti-trust authorities . based on the provisions of the agreement , the company estimates that the current purchase price for its partners' 50% ( 50 % ) interests would be approximately $ 1.5 billion , which could be satisfied by payment of cash or international paper common stock , or some combination of the two , at the company's option . the purchase by the company of its partners 2019 50% ( 50 % ) interest in ilim would result in the consolidation of ilim's financial position and results of operations in all subsequent periods . the parties have informed each other that they have no current intention to commence procedures specified under the deadlock provisions of the shareholder 2019s agreement . critical accounting policies and significant accounting estimates the preparation of financial statements in conformity with accounting principles generally accepted in the united states requires international paper to establish accounting policies and to make estimates that affect both the amounts and timing of the recording of assets , liabilities , revenues and expenses . some of these estimates require judgments about matters that are inherently uncertain . accounting policies whose application may have a significant effect on the reported results of operations and financial position of international paper , and that can require judgments by management that affect their application , include the accounting for contingencies , impairment or disposal of long-lived assets and goodwill , pensions and postretirement benefit obligations , stock options and income taxes . the company has discussed the selection of critical accounting policies and the effect of significant estimates with the audit and finance committee of the company 2019s board of directors . contingent liabilities accruals for contingent liabilities , including legal and environmental matters , are recorded when it is probable that a liability has been incurred or an asset impaired and the amount of the loss can be reasonably estimated . liabilities accrued for legal matters require judgments regarding projected outcomes and range of loss based on historical experience and recommendations of legal counsel . liabilities for environmental matters require evaluations of relevant environmental regulations and estimates of future remediation alternatives and costs . impairment of long-lived assets and goodwill an impairment of a long-lived asset exists when the asset 2019s carrying amount exceeds its fair value , and is recorded when the carrying amount is not recoverable through cash flows from future operations . a goodwill impairment exists when the carrying amount of goodwill exceeds its fair value . assessments of possible impairments of long-lived assets and goodwill are made when events or changes in circumstances indicate that the carrying value of the asset may not be recoverable through future operations . additionally , testing for possible impairment of goodwill and intangible asset balances is required annually . the amount and timing of any impairment charges based on these assessments require the estimation of future cash flows and the fair market value of the related assets based on management 2019s best estimates of certain key factors , including future selling prices and volumes , operating , raw material , energy and freight costs , and various other projected operating economic factors . as these key factors change in future periods , the company will update its impairment analyses to reflect its latest estimates and projections . under the provisions of accounting standards codification ( asc ) 350 , 201cintangibles 2013 goodwill and other , 201d the testing of goodwill for possible impairment is a two-step process . in the first step , the fair value of the company 2019s reporting units is compared with their carrying value , including goodwill . if fair value exceeds the carrying value , goodwill is not considered to be impaired . if the fair value of a reporting unit is below the carrying value , then step two is performed to measure the amount of the goodwill impairment loss for the reporting unit . this analysis requires the determination of the fair value of all of the individual assets and liabilities of the reporting unit , including any currently unrecognized intangible assets , as if the reporting unit had been purchased on the analysis date . once these fair values have been determined , the implied fair value of the unit 2019s goodwill is calculated as the excess , if any , of the fair value of the reporting unit determined in step one over the fair value of the net assets determined in step two . the carrying value of goodwill is then reduced to this implied value , or to zero if the fair value of the assets exceeds the fair value of the reporting unit , through a goodwill impairment charge . the impairment analysis requires a number of judgments by management . in calculating the estimated fair value of its reporting units in step one , a total debt-to-capital ratio of less than 60% ( 60 % ) . net worth is defined as the sum of common stock , paid-in capital and retained earnings , less treasury stock plus any cumulative goodwill impairment charges . the calculation also excludes accumulated other comprehensive income/loss and nonrecourse financial liabilities of special purpose entities . the total debt-to-capital ratio is defined as total debt divided by the sum of total debt plus net worth . the company was in compliance with all its debt covenants at december 31 , 2016 and was well below the thresholds stipulated under the covenants as defined in the credit agreements . the company will continue to rely upon debt and capital markets for the majority of any necessary long-term funding not provided by operating cash flows . funding decisions will be guided by our capital structure planning objectives . the primary goals of the company 2019s capital structure planning are to maximize financial flexibility and preserve liquidity while reducing interest expense . the majority of international paper 2019s debt is accessed through global public capital markets where we have a wide base of investors . maintaining an investment grade credit rating is an important element of international paper 2019s financing strategy . at december 31 , 2016 , the company held long-term credit ratings of bbb ( stable outlook ) and baa2 ( stable outlook ) by s&p and moody 2019s , respectively . contractual obligations for future payments under existing debt and lease commitments and purchase obligations at december 31 , 2016 , were as follows: .
in 2018 what percentage of contractual obligations for future payments under existing debt and lease commitments and purchase obligations at december 31 , 2016 is due to maturities of long-term debt?
( a ) total debt includes scheduled principal payments only . ( b ) includes $ 2 billion relating to fiber supply agreements entered into at the time of the 2006 transformation plan forestland sales and in conjunction with the 2008 acquisition of weyerhaeuser company 2019s containerboard , packaging and recycling business . also includes $ 1.1 billion relating to fiber supply agreements assumed in conjunction with the 2016 acquisition of weyerhaeuser's pulp business . ( c ) not included in the above table due to the uncertainty as to the amount and timing of the payment are unrecognized tax benefits of approximately $ 77 million . we consider the undistributed earnings of our foreign subsidiaries as of december 31 , 2016 , to be indefinitely reinvested and , accordingly , no u.s . income taxes have been provided thereon . as of december 31 , 2016 , the amount of cash associated with indefinitely reinvested foreign earnings was approximately $ 620 million . we do not anticipate the need to repatriate funds to the united states to satisfy domestic liquidity needs arising in the ordinary course of business , including liquidity needs associated with our domestic debt service requirements . pension obligations and funding at december 31 , 2016 , the projected benefit obligation for the company 2019s u.s . defined benefit plans determined under u.s . gaap was approximately $ 3.4 billion higher than the fair value of plan assets . approximately $ 3.0 billion of this amount relates to plans that are subject to minimum funding requirements . under current irs funding rules , the calculation of minimum funding requirements differs from the calculation of the present value of plan benefits ( the projected benefit obligation ) for accounting purposes . in december 2008 , the worker , retiree and employer recovery act of 2008 ( wera ) was passed by the u.s . congress which provided for pension funding relief and technical corrections . funding contributions depend on the funding method selected by the company , and the timing of its implementation , as well as on actual demographic data and the targeted funding level . the company continually reassesses the amount and timing of any discretionary contributions and elected to make contributions totaling $ 750 million for both years ended december 31 , 2016 and 2015 . at this time , we do not expect to have any required contributions to our plans in 2017 , although the company may elect to make future voluntary contributions . the timing and amount of future contributions , which could be material , will depend on a number of factors , including the actual earnings and changes in values of plan assets and changes in interest rates . international paper announced a voluntary , limited-time opportunity for former employees who are participants in the retirement plan of international paper company ( the pension plan ) to request early payment of their entire pension plan benefit in the form of a single lump sum payment . the amount of total payments under this program was approximately $ 1.2 billion , and were made from plan trust assets on june 30 , 2016 . based on the level of payments made , settlement accounting rules applied and resulted in a plan remeasurement as of the june 30 , 2016 payment date . as a result of settlement accounting , the company recognized a pro-rata portion of the unamortized net actuarial loss , after remeasurement , resulting in a $ 439 million non-cash charge to the company's earnings in the second quarter of 2016 . additional payments of $ 8 million and $ 9 million were made during the third and fourth quarters , respectively , due to mandatory cash payouts and a small lump sum payout , and the pension plan was subsequently remeasured at september 30 , 2016 and december 31 , 2016 . as a result of settlement accounting , the company recognized non-cash settlement charges of $ 3 million in both the third and fourth quarters of 2016. .