Other comprehensive income (loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains (losses) arising during the period, before income taxes	$ 19,190	$ (6,664)	$ 9,563
Income taxes	(4,029)	1,399	(3,094)
Unrealized gains (losses) arising during the period, net of income tax	15,161	(5,265)	6,469
Less reclassification adjustment [Abstract]
Net realized investment gains (losses)	489	258	132
Income taxes	(102)	(54)	(47)
Reclassification adjustment included in net income	387	204	85
Other comprehensive income (loss)	14,774	(5,469)	6,384
Fixed Maturities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains (losses) arising during the period, before income taxes	19,190	(6,664)	5,371
Equity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains (losses) arising during the period, before income taxes	$ 0	$ 0	$ 4,192