Other comprehensive income (loss) - Reclassification out of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification out of accumulated other comprehensive loss
Income tax (benefit) expense	$ (3,097)	$ (50,223)
Net income	34,302	167,925
Reclassification out of accumulated other comprehensive income
Reclassification out of accumulated other comprehensive loss
Net income	(4,192)	(4,317)
Reclassification out of accumulated other comprehensive income | Adjustment of pension and postretirement benefit plan
Reclassification out of accumulated other comprehensive loss
Income (loss) before tax	(5,362)	(5,876)
Income tax (benefit) expense	2,011	2,203
Net income	(3,351)	(3,673)
Reclassification out of accumulated other comprehensive income | Amortization of net Loss | Personnel costs
Reclassification out of accumulated other comprehensive loss
Income (loss) before tax	(5,362)	(5,876)
Reclassification out of accumulated other comprehensive income | Unrealized net (losses) gains on cash flow hedges | Forward contracts
Reclassification out of accumulated other comprehensive loss
Income (loss) before tax	(1,327)	(1,030)
Income tax (benefit) expense	(486)	(386)
Other Operating Income	(31)	0
Net income	(841)	(644)
Reclassification out of accumulated other comprehensive income | Unrealized net (losses) gains on cash flow hedges | Forward contracts | Mortgage banking activities
Reclassification out of accumulated other comprehensive loss
Income (loss) before tax	$ (1,296)	$ (1,030)