Income taxes - Schedule of Net Deferred Tax (Liabilities) Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Allowance for credit losses	$ 35,233	$ 48,409
Operating lease liabilities	12,478	14,496
Federal net operating loss	1,370	1,753
Deferred compensation	5,484	8,872
Unrealized loss on cash flow hedges	205	499
Other assets	8,301	19,101
Subtotal	63,071	93,130
Deferred tax liabilities:
FHLB stock dividends	(484)	(561)
Operating leases - right of use assets	(11,287)	(13,197)
Depreciation	(7,938)	(7,491)
Amortization of core deposit intangibles	(116)	(684)
Unrealized gain on equity securities	(2,407)	(17)
Unrealized gain on debt securities	(1,324)	(13,027)
Mortgage servicing rights	(30,098)	(20,803)
Goodwill	(13,743)	(11,301)
Other liabilities	(2,494)	(9,653)
Subtotal	(69,891)	(76,734)
Net deferred tax (liabilities) assets	$ (6,820)
Net deferred tax assets		$ 16,396