Summary of significant accounting policies - Concentrations of credit risk (Details) |
12 Months Ended | ||||
|---|---|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Total Revenue | Entities affiliated with T-Mobile | |||||
| Concentrations of credit risk | |||||
| Concentration risk percentage | 21.00% | 20.00% | 26.00% | ||
| Total Revenue | Entities affiliated with AT&T Inc. | |||||
| Concentrations of credit risk | |||||
| Concentration risk percentage | 13.00% | 12.00% | |||
| Total Revenue | Entities affiliated with Verizon Communications Inc. | |||||
| Concentrations of credit risk | |||||
| Concentration risk percentage | 11.00% | 11.00% | 11.00% | ||
| Total accounts receivable | Entities affiliated with T-Mobile | |||||
| Concentrations of credit risk | |||||
| Concentration risk percentage | 13.00% | 13.00% | |||
| Total accounts receivable | Entities affiliated with AT&T Inc. | |||||
| Concentrations of credit risk | |||||
| Concentration risk percentage | 27.00% | 34.00% | |||
| Total accounts receivable | Entities affiliated with Verizon Communications Inc. | |||||
| Concentrations of credit risk | |||||
| Concentration risk percentage | 11.00% | ||||