11. Commitments and Contingencies The Company is involved in various claims, regulatory agency audits and pending or threatened legal actions involving a variety of matters. The Company has also assessed the potential for additional losses above the amounts accrued as well as potential losses for matters that are not probable but are reasonably possible. The total potential loss on these matters cannot be determined; however, in the Companys opinion, any ultimate liability, to the extent not otherwise recorded or accrued for, will not materially affect the Companys financial position, cash flow or results of operations. These estimated liabilities are based on the Companys assessment of the nature of these matters, their progress toward resolution, the advice of legal counsel and outside experts as well as managements intention and experience. The Companys business is affected both directly and indirectly by governmental laws and regulations relating to the oilfield service industry in general, as well as by environmental and safety regulations that specifically apply to the Companys business. Although the Company has not incurred material costs in connection with its compliance with such laws, there can be no assurance that other developments, such as new environmental laws, regulations and enforcement policies hereunder may not result in additional, presently unquantifiable, costs or liabilities to the Company. The Company does not accrue for contingent losses that, in its judgment, are considered to be reasonably possible, but not probable. Estimating reasonably possible losses also requires the analysis of multiple possible outcomes that often depend on judgments about potential actions by third parties. NOWs management currently estimates a range of loss for reasonably possible losses for which an estimate can be made is between zero and $ 16 million in the international segment primarily attributable to accounts receivable with one customer. The Company has accrued its best estimate for loss as of December 31, 2018. Factors underlying this estimated range of loss may change from time to time, and actual results may vary significantly from this estimate. The Company maintains credit arrangements with several banks providing for standby letters of credit, including bid and performance bonds, and other bonding requirements. As of December 31, 2018, the Company was contingently liable for approximately $10 million of outstanding standby letters of credit and surety bonds. The Company does not believe, based on historical experience and information currently available, that it is probable that any amounts will be required to be paid. The Company assumed leases with former owners of acquired entities for premises utilized by the acquired entities in the performance of their operations. Most of these leases are renewable at the Companys option and contain clauses for payment of real estate taxes, maintenance, insurance and certain other operating expenses of the properties. The aggregated rental expense was approximately $3 million, $3 million and $3 million for the years ended December 31, 2018, 2017, and 2016, respectively. Total future commitments related to these operating leases is approximately $6 million through 2023. The Company leases certain facilities and equipment under operating leases that expire at various dates through 2029. These leases generally contain renewal options and require the lessee to pay maintenance, insurance, taxes and other operating expenses in addition to the minimum annual rentals. Rental expense related to operating leases approximated $48 million, $50 million and $50 million in 2018, 2017 and 2016, respectively. Future minimum lease commitments under noncancellable operating leases with initial or remaining terms of one year or more as of December 31, 2018, are payable as follows ( in millions ): 2019 32 2020 25 2021 17 2022 9 2023 6 Thereafter 5 Total future lease commitments $ 94