Quarterly report pursuant to Section 13 or 15(d)

Other Assets

Other Assets
9 Months Ended
Sep. 30, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]  
Other Assets Other Assets
Other assets consist of the following (in thousands): 
September 30, 2021 December 31, 2020
Costs to obtain contracts - customer agreements $ 626,484  $ 377,839 
Costs to obtain contracts - incentives 2,481  2,481 
Accumulated amortization of costs to obtain contracts (67,218) (51,365)
Unbilled receivables 195,066  150,603 
Allowance for credit losses on unbilled receivables (2,198) (1,731)
Operating lease right-of-use assets 90,070  81,516 
Equity security investment 63,826  65,356 
Other assets 104,838  56,966 
Total $ 1,013,349  $ 681,665 
The Company recorded amortization of costs to obtain contracts of $6.5 million and $3.7 million for the three months ended September 30, 2021 and 2020,respectively, and $16.1 million and $10.7 million for the nine months ended September 30, 2021 and 2020, respectively, in Sales and marketing in the consolidated statements of operations.

The majority of unbilled receivables arise from fixed price escalators included in the Company's long-term Customer Agreements.  The escalator is included in calculating the total estimated transaction value for an individual Customer Agreement.  The total estimated transaction value is then recognized over the term of the Customer Agreement.  The amount of unbilled receivables increases while cumulative billings for an individual Customer Agreement are less than the cumulative revenue recognized for that Customer Agreement.  Conversely, the amount of unbilled receivables decreases when the actual cumulative billings becomes higher than the cumulative revenue recognized. At the end of the initial term of a Customer Agreement, the cumulative amounts recognized as revenue and billed to date are the same, therefore the unbilled receivable balance for an individual Customer Agreement will be zero. As a result of the adoption of ASU No. 2016-13, an allowance for credit loss on unbilled receivables was established as of January 1, 2020. The Company applies an estimated loss-rate in order to determine the current expected credit loss for unbilled receivables. The estimated loss-rate is determined by analyzing historical credit losses, residential first and second mortgage foreclosures and consumers' utility default rates, as well as current economic conditions. The Company reviews individual customer collection status of electricity billings to determine whether the unbilled receivables for an individual customer should be written off, including the possibility of a service transfer to a potential new homeowner.