Deposit contracts (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Deposit Contracts, Liabilities [Roll Forward]
Balance, beginning of period	$ 104,905	$ 83,955
Consideration received	9,143	22,463
Consideration receivable	13,520	0
Net investment expense (income) allocation and change in fair value of embedded derivatives	1,472	(164)
Payments	(2,763)	(915)
Foreign currency translation	214	(434)
Balance, end of period	$ 126,491	$ 104,905