Commitments and contingencies (Other commitments) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Remaining commitment		$ 222,806	$ 234,775
Capital commitment		268,000	268,000
Fixed maturity investments
Other Commitments [Line Items]
Remaining commitment	[1]	28,067	22,082
Other investments
Other Commitments [Line Items]
Remaining commitment	[2]	87,353	86,697
Investment affiliate
Other Commitments [Line Items]
Remaining commitment		$ 107,386	$ 125,996

[1] The Company has an outstanding commitment to participate in certain secured loan facilities through participation agreements with an established loan originator

[2] The Company’s total capital commitments related to other investments as at March 31, 2018 was $268,000 (December 31, 2017: $268,000).