Financial Instruments - Amounts of gains/(losses) recognized in income (Details) - Service revenue - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Forward sales commitments
Fair Value, Option, Quantitative Disclosures [Line Items]
Net gain recognized in earnings	$ 859	$ 553	$ 938	$ 442
IRLCs
Fair Value, Option, Quantitative Disclosures [Line Items]
Net gain recognized in earnings	$ (888)	$ (233)	$ (687)	$ 1,131