Variable interest entities - Carrying amounts and maximum exposure to loss for E&O joint venture (Details) - Eastern and Oriental Express Ltd. - Variable interest entity, not primary beneficiary - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity
Carrying Amounts, Total	$ 8,760	$ 8,944
Maximum exposure	8,760	8,944
Investment
Variable Interest Entity
Carrying Amounts, Assets	2,603	2,642
Maximum exposure	2,603	2,642
Due from unconsolidated company
Variable Interest Entity
Carrying Amounts, Assets	6,157	6,302
Maximum exposure	$ 6,157	$ 6,302