6. Commitments and contingencies: Capital leasesfiber lease agreements The Company has entered into lease agreements with numerous providers of dark fiber primarily under 15-20 year IRUs typically with additional renewal terms. Once the Company has accepted the related fiber route, leases that meet the criteria for treatment as capital leases are recorded as a capital lease obligation and an IRU asset. The interest rate used in determining the present value of the aggregate future minimum lease payments is the lessee's incremental borrowing rate, interest rate for the lease term. The future minimum payments (principal and interest) under these agreements are as follows (in thousands): For the year ending December 31, 2016 $ 19,857 2017 18,450 2018 18,270 2019 18,144 2020 18,127 Thereafter 197,812 ? ? ? ? ? Total minimum lease obligations 290,660 Lessamounts representing interest (154,650 ) ? ? ? ? ? Present value of minimum lease obligations 136,010 Current maturities (6,247 ) ? ? ? ? ? Capital lease obligations, net of current maturities $ 129,763 ? ? ? ? ? ? ? ? ? ? Gains on capital lease terminations In March 2015 the Company elected to terminate certain IRU capital lease obligations in Spain with a vendor. The Company obtained alternative fiber to serve its customers in Spain. Under its estimate of the termination provisions of the related contracts the Company has recorded an estimated termination liability of $8.1 million included in accrued and other current liabilities. The difference between the remaining carrying amount of the related IRU capital lease liabilities ($29.9 million), the remaining net book value of the IRU assets ($10.0 million) and the termination liability and amounts due through the termination date was recorded as a gain on capital lease terminations of $10.1 million in 2015. In July 2015, the Company settled a dispute for the payment of the remaining balances for certain IRU capital lease obligations in Europe with a vendor. The IRU assets were fully depreciated in 2012 when the rel