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Other liabilities - RSU's and SAR's (Details) | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) EquityInstruments shares | Dec. 31, 2017 USD ($) EquityInstruments Option shares
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Share options exercised | Option |  | 30,000
Restricted stock units |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Share options exercised | EquityInstruments | 7,031 | 371,570
Outstanding | 0 | 13,340
Share based compensation expense | $ 584,000 | $ 343,000
Share based compensation expense, after tax | 376,000 | 202,000
Liability from share based payments | $ 41,000 | 626,000
Vesting life | 3 years |
Employee stock option |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Share based compensation expense | $ 2,798,000 | $ 2,405,000
Stock appreciation rights |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Outstanding | EquityInstruments | 610,021 | 1,182,871
Share based compensation expense | $ 5,848,000 | $ 3,429,000
Share based compensation expense, after tax | 3,762,000 | 2,023,000
Liability from share based payments | $ 62,000 | 5,911,000
Non current liability from share based payments |  | $ 111,000
Vesting percentage of share-based awards | 33.33% |
Vesting life | 3 years |
Exercised | EquityInstruments | 498,476 | 168,135
Cancelled | shares | 74,373 | 209,451

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