Income Taxes - Significant Components of The Company's Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred tax assets
Allowance for credit losses	$ 30,528	$ 14,304
Loans	11,573	10,284
Deferred compensation	9,213	12,050
Impairment of assets	1,141	1,108
Net operating loss carryforwards	6,916	9,387
Lease liabilities under operating leases	22,745	22,686
Other	1,635	934
Total deferred tax assets	83,751	70,753
Deferred tax liabilities
Net unrealized gains on securities	4,880	190
Investment in partnerships	877	967
Fixed assets	2,951	2,952
Mortgage servicing rights	11,718	13,472
Junior subordinated debt	2,282	2,304
Lease right-of-use asset	21,747	21,727
Other	1,760	1,859
Total deferred tax liabilities	46,215	43,471
Net deferred tax assets	$ 37,536	$ 27,282