COMMITMENTS AND CONTINGENCIES Contingencies We have contingent liabilities resulting from various litigation, claims and commitments. We record accruals for loss contingencies when losses are considered probable and can be reasonably estimated. Legal fees associated with defending the Partnership in legal matters are expensed as incurred. We accrued $7.3 million for contingent losses as of December 31, 2017 , and had no accrual for contingent losses as of December 31, 2016 . The amount that will ultimately be paid related to such matters may differ from the recorded accruals, and the timing of such payments is uncertain. In addition, due to the inherent uncertainty of litigation, there can be no assurance that the resolution of any particular claim or proceeding would not have a material adverse effect on our results of operations, financial position or liquidity. Commitments Lessee Commitments. Future minimum rental payments applicable to all noncancellable operating leases and purchase obligations as of December 31, 2017 are as follows: Payments Due by Period 2018 2019 2020 2021 2022 There- after Total (Thousands of Dollars) Operating leases $ 39,236 $ 34,203 $ 19,541 $ 13,324 $ 7,295 $ 68,386 $ 181,985 Purchase obligations $ 6,963 $ 6,133 $ 4,686 $ 4,690 $ 4,480 $ 300 $ 27,252 Rental expense for all operating leases totaled $36.2 million , $37.0 million and $39.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Our operating leases consist primarily of the following:  a ten-year lease for tugs and barges utilized at our St. Eustatius facility for bunker fuel sales, with two five-year renewal options ; and  land leases at various terminal facilities, with original terms ranging from 10 to 100 years. Our purchase obligations primarily consist of an eleven-year chemical supply agreement related to our pipelines. Lessor Revenues. We have entered into certain revenue arrangements where we are considered to be the lessor in accordance with GAAP. Under these arrangements we lease certai