Financial Instruments - Amounts of gains/(losses) recognized in income (Details) - Service revenue - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Forward sales commitments
Fair Value, Option, Quantitative Disclosures [Line Items]
Net gain recognized in earnings	$ (1,849)	$ (142)	$ 79	$ 1,053
IRLCs
Fair Value, Option, Quantitative Disclosures [Line Items]
Net gain recognized in earnings	$ 35	$ 1,460	$ 201	$ (110)