Other income and operating expenses - Paycheck Protection Program (Details) $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 28, 2020	Apr. 30, 2020 USD ($) Lender	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	May 31, 2020 USD ($)
Paycheck Protection Program (PPP)
Origination costs			$ 9,430	$ 2,734	$ 12,455	$ 3,923
PPP Loans
Paycheck Protection Program (PPP)
Number of non-bank SBA lenders | Lender		14
Loans funded		$ 114,700	2,700,000		$ 2,700,000
PPP processing fees		$ 5,200
Origination fee and fee income			32,300
Lender Service Provider Agreement
Paycheck Protection Program (PPP)
Fees received as a percentage of total fees received by third party from SBA	50.00%
Lender Service Provider Agreement | PPP Loans
Paycheck Protection Program (PPP)
Amount of PPP loans underwritten and sold to third party							$ 2,500,000
Origination fee and fee income			$ 27,100