Statutory financial information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract]
Statutory net income	$ 40,917	$ 34,206	$ 23,841
Statutory capital and surplus	$ 348,811	$ 233,500	$ 213,833
Percentage of policyholder surplus as of end of prior year used in determining maximum dividend distribution	10.00%
Maximum dividend distribution that can be paid without prior approval	$ 40,700