Corporate debt, Movement in corporate debt, split between cash and non-cash items (Details) $ in Thousands |
12 Months Ended |
|---|---|
|
Dec. 31, 2017
USD ($)
| |
| Corporate debt [Abstract] | |
| Beginning balance | $ 668,201 |
| Cash flow | (68,372) |
| Non-cash changes | 43,254 |
| Ending balance | $ 643,083 |