Other assets - Narratives (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure Abstract
Hosting arrangement service contract implementation cost capitalized	$ 16,800	$ 16,800
Hosting arrangement service contract accumulated amortization	4,200	4,200
Hosting arrangement service contract, net value	12,600	12,600
Hosting arrangement service amortization expense	500	1,500
Other assets
Principal, interest and escrow servicing advances	$ 72,721	$ 72,721	$ 77,800