Other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Before-Tax Amount
Other comprehensive income (loss)	$ 2,508	$ 26,306	$ (6,914)	$ 9,279
Tax Expense (Benefit)
Other comprehensive income (loss)	538	5,418	(1,450)	2,493
Net-of-Tax Amount
Other comprehensive income (loss), net of taxes:	1,970	20,888	(5,464)	6,786
Net unrealized gains and losses on investments
Before-Tax Amount
Change in net unrealized gains and losses on investments	1,277	21,159	(10,312)	17,892
Reclassification adjustment for realized gains and losses on investments	(529)	(27)	(713)	(128)
Other comprehensive income (loss)	748	21,132	(11,025)	17,764
Tax Expense (Benefit)
Change in net unrealized gains and losses on investments	268	4,444	(2,165)	3,757
Reclassification adjustment for realized gains and losses on investments	(111)	(6)	(150)	(27)
Other comprehensive income (loss)	157	4,438	(2,315)	3,730
Net-of-Tax Amount
Change in net unrealized gains and losses on investments	1,009	16,715	(8,147)	14,135
Reclassification adjustment for realized gains and losses on investments	(418)	(21)	(563)	(101)
Other comprehensive income (loss), net of taxes:	591	16,694	(8,710)	14,034
Foreign currency translation adjustments
Before-Tax Amount
Other comprehensive income (loss)	1,760	5,174	4,111	(8,485)
Tax Expense (Benefit)
Other comprehensive income (loss)	381	980	865	(1,237)
Net-of-Tax Amount
Other comprehensive income (loss), net of taxes:	$ 1,379	$ 4,194	$ 3,246	$ (7,248)