Other comprehensive income (loss) (accumulated other comprehensive loss) (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2024		Jun. 30, 2023
Postretirement benefit plans [Member]
Accumulated other comprehensive loss [Line Items]
Balance, beginning of period		$ (19,824)		$ (26,872)
Other comprehensive income (loss) before reclassifications		0		0
Amounts reclassified from accumulated other comprehensive loss		45		394
Net current-period other comprehensive income (loss)		45		394
Balance, end of period		(19,779)		(26,478)
Net unrealized loss on debt securities [Member]
Accumulated other comprehensive loss [Line Items]
Balance, beginning of period				(909)
Other comprehensive income (loss) before reclassifications	[1]			(8)
Amounts reclassified from accumulated other comprehensive loss				0
Net current-period other comprehensive income (loss)				(8)
Balance, end of period				(917)
Unrealized gain on debt securities arising during the period, tax benefit				(3)
Net unrealized gain on cash flow hedges [Member]
Accumulated other comprehensive loss [Line Items]
Balance, beginning of period		(286)		2,593
Other comprehensive income (loss) before reclassifications		6,903	[2]	4,858	[3]
Amounts reclassified from accumulated other comprehensive loss		(1,321)		(883)
Net current-period other comprehensive income (loss)		5,582		3,975
Balance, end of period		5,296		6,568
Unrealized loss on cash flow hedge arising during the period, tax expense		2,553		1,768
Currency translation adjustment [Member]
Accumulated other comprehensive loss [Line Items]
Balance, beginning of period		(9,918)		(12,076)
Other comprehensive income (loss) before reclassifications		(1,499)		1,149
Amounts reclassified from accumulated other comprehensive loss		0		863
Net current-period other comprehensive income (loss)		(1,499)		2,012
Balance, end of period		(11,417)		(10,064)
Accumulated other comprehensive loss [Member]
Accumulated other comprehensive loss [Line Items]
Balance, beginning of period		(30,028)		(37,264)
Other comprehensive income (loss) before reclassifications		5,404		5,999
Amounts reclassified from accumulated other comprehensive loss		(1,276)		374
Net current-period other comprehensive income (loss)		4,128		6,373
Balance, end of period		$ (25,900)		$ (30,891)

[1] Other comprehensive loss before reclassifications is net of an income tax benefit of $3.

[2] Other comprehensive income before reclassifications is net of income tax expense of $2,553.

[3] Other comprehensive income before reclassifications is net of income tax expense of $1,768.