Subordinated debt (Details) - Subordinate 2020 Notes Due 2030 $ in Millions	Jun. 01, 2020 USD ($)
Debt Instrument
Aggregate principal amount	$ 33.0
Rate of interest for first five years	5.375%
Duration interest rate in effect	5 years
Percentage of debt redeemed	100.00%
Minimum
Debt Instrument
Floated interest rate	4.75%
Number of days notice to redeem debt	10 days