Property and equipment:	9 Months Ended
Sep. 30, 2020
Property and equipment:
Property and equipment:	2. Property and equipment: Depreciation and amortization expense related to property and equipment and finance leases was $21.6 million and $20.0 million for the three months ended September 30, 2020, and 2019 respectively, and $61.0 million and $60.2 million for the nine months ended September 30, 2020 and 2019, respectively. The Company capitalized salaries and related benefits of employees working directly on the construction and build-out of its network of $3.0 million and $2.7 million for the three months ended September 30, 2020 and 2019, respectively, and $8.9 million and $8.0 million for the nine months ended September 30, 2020 and 2019, respectively. Exchange agreement In the three and nine months ended September 30, 2020 and 2019, the Company exchanged certain used network equipment and cash consideration for new network equipment. The fair value of the equipment received was estimated to be $0.2 million and $0.3 million for the three months ended September 30, 2020 and 2019, respectively, and $1.1 million and $2.6 million for the nine months ended September 30, 2020 and 2019, respectively. After considering the cash component the transactions resulted in gains of $0.1 million and $0.1 million for the three months ended September 30, 2020 and 2019, respectively, and $0.3 million and $0.8 million for the nine months ended September 30, 2020 and 2019, respectively. The estimated fair value of the equipment received was based upon the cash consideration price the Company pays for the new network equipment on a standalone basis (Level 3). Installment payment agreement In March 2015, the Company entered into an installment payment agreement (“IPA”) with a vendor. Under the IPA the Company was allowed to purchase network equipment in exchange for interest free note obligations each with a twenty-four month term until July 2020 when additional borrowings under the IPA expired. There are no payments under each note obligation for the first six months followed by eighteen equal installment payments for the remaining eighteen month term. As of September 30, 2020, and December 31, 2019 there was $10.4 million and $12.5 million, respectively, of note obligations outstanding under the IPA, secured by the related equipment. The Company recorded the assets purchased and the net present value of the note obligation utilizing an imputed interest rate. The resulting discount was $0.3 million and $0.4 million as of September 30, 2020 and December 31, 2019, respectively, and is being amortized over the note term using the effective interest rate method.

Property and equipment:

9 Months Ended

Sep. 30, 2020

2. Property and equipment:

Depreciation and amortization expense related to property and equipment and finance leases was $21.6 million and $20.0 million for the three months ended September 30, 2020, and 2019 respectively, and $61.0 million and $60.2 million for the nine months ended September 30, 2020 and 2019, respectively. The Company capitalized salaries and related benefits of employees working directly on the construction and build-out of its network of $3.0 million and $2.7 million for the three months ended

September 30, 2020 and 2019, respectively, and $8.9 million and $8.0 million for the nine months ended September 30, 2020 and 2019, respectively.

Exchange agreement

In the three and nine months ended September 30, 2020 and 2019, the Company exchanged certain used network equipment and cash consideration for new network equipment. The fair value of the equipment received was estimated to be $0.2 million and $0.3 million for the three months ended September 30, 2020 and 2019, respectively, and $1.1 million and $2.6 million for the nine months ended September 30, 2020 and 2019, respectively. After considering the cash component the transactions resulted in gains of $0.1 million and $0.1 million for the three months ended September 30, 2020 and 2019, respectively, and $0.3 million and $0.8 million for the nine months ended September 30, 2020 and 2019, respectively. The estimated fair value of the equipment received was based upon the cash consideration price the Company pays for the new network equipment on a standalone basis (Level 3).

Installment payment agreement

In March 2015, the Company entered into an installment payment agreement (“IPA”) with a vendor. Under the IPA the Company was allowed to purchase network equipment in exchange for interest free note obligations each with a twenty-four month term until July 2020 when additional borrowings under the IPA expired. There are no payments under each note obligation for the first six months followed by eighteen equal installment payments for the remaining eighteen month term. As of September 30, 2020, and December 31, 2019 there was $10.4 million and $12.5 million, respectively, of note obligations outstanding under the IPA, secured by the related equipment. The Company recorded the assets purchased and the net present value of the note obligation utilizing an imputed interest rate. The resulting discount was $0.3 million and $0.4 million as of September 30, 2020 and December 31, 2019, respectively, and is being amortized over the note term using the effective interest rate method.