. ( 4 ) port facilities are for our usage of certain port facilities . ( 5 ) interest includes fixed and variable rates with libor held constant as of december 31 , 2018 . ( 6 ) other includes future commitments for service , maintenance and other business enhancement capital expenditure contracts . ( 7 ) total excludes $ 0.5 million of unrecognized tax benefits as of december 31 , 2018 , because an estimate of the timing of future tax settlements cannot be reasonably determined. .