| In millions, except per share items | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 20-F | 20-F | 20-F | 20-F |
| Statement1 [Table] | | | | |
| Statement1 [Line Items] | | | | |
| Total operating revenues | | | | |
| Other operating income | | | | |
| Service costs | | | | |
| Cost of equipment and accessories | | | | |
| Selling, general and administrative expenses | | | | |
| Depreciation | | | | |
| Amortization | | | | |
| Impairment (loss) / reversal | | | | |
| Gain / (loss) on disposal of non-current assets | | | | |
| Gain / (loss) on disposal of subsidiaries | 30 | | | |
| |
| Operating (loss) / profit | | | | |
| Finance costs | | | | |
| Finance income | | | | |
| |
| Net foreign exchange gain / (loss) | | | | |
| Profit / (loss) before tax from continuing operations | | | | |
| Income tax expense | | | | |
| Profit / (loss) from continuing operations | | | | |
| Profit / (loss) after tax from discontinued operations | | | | |
| Profit / (loss) for the period | | | | |
| Attributable to: | | | | |
| The owners of the parent (continuing operations) | | | | |
| The owners of the parent (discontinued operations) | | | | |
| Non-controlling interest | | | | |
| Profit / (loss) for the period | | | | |
| Basic and diluted gain / (loss) per share attributable to ordinary equity holders of the parent: | | | | |
| Diluted gain (loss) per share from continuing operations (in dollars per share) | | | | |
| Basic gain (loss) from continuing operations per share (in dollars per share) | | | | |
| Diluted gain | | | | |
| Basic gain (loss) from discontinued operations per share (in dollars per share) | | | | |
| Diluted gain (loss) per share | | | | |
| Basic gain (loss) per share | | | | |