Investments in affiliates (Narrative) (Details) - USD ($) $ in Thousands				12 Months Ended
	Nov. 07, 2014	Oct. 02, 2014	Dec. 20, 2011	Dec. 31, 2015
Aquiline Financial Services Fund II LP
Schedule of Equity Method Investments [Line Items]
Percentage of interest assumed				100.00%
Capital commitment		$ 10,000	$ 50,000
Investment time lag reporting				3 months
Aquiline Financial Services Fund III LP
Schedule of Equity Method Investments [Line Items]
Capital commitment	$ 100,000
Investment time lag reporting				3 months