Financial Instruments - Amounts of gains/(losses) recognized in income (Details) - Service revenue - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest rate lock commitments
Fair Value, Option, Quantitative Disclosures [Line Items]
Net gain recognized in earnings	$ (233)	$ (209)	$ 1,131	$ 225
Forward sales commitments
Fair Value, Option, Quantitative Disclosures [Line Items]
Net gain recognized in earnings	$ 553	$ 554	$ 442	$ 312