Other comprehensive income (reclassification adjustments) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2022		Jun. 30, 2021	Jun. 30, 2022		Jun. 30, 2021
Reclassifications from accumulated other comprehensive loss
Prior service credit	$ 355		$ 355	$ 711		$ 711
Net actuarial loss	(225)		(407)	(450)		(814)
Total amortization	130		(52)	261		(103)
Tax expense	(79)		(31)	(157)		(63)
Amortization of postretirement benefit plan items, net of tax	51		(83)	104		(166)
Realized loss on debt securities	(8)		0	(8)		0
Tax benefit	2		0	2		0
Realized loss on debt securities, net of tax	(6)		0	(6)		0
Realized loss on interest rate swap	(144)		(330)	(464)		(664)
Tax benefit	38		87	123		174
Realized loss on interest rate swap, net of tax	(106)		(243)	(341)		(490)
Foreign currency translation adjustment	(5,550)	[1]	0	(5,550)	[1]	0
Total reclassifications, net of tax	$ (5,611)		$ (326)	$ (5,793)		$ (656)

[1] Relates to the sale of our Australian web hosting business during the quarter ended June 30, 2022. Further information can be found in Note 6.