Income Taxes - Deferred tax assets (liabilities) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Accrued expenses	$ 2,126,000	$ 3,239,000
Net operating loss	4,765,000	6,115,000
Allowance for loan losses, net of bad debt charge-offs	10,415,000	10,709,000
Deferred compensation	3,616,000	3,649,000
State taxes	3,746,000	2,707,000
Loan discount	11,634,000	17,677,000
Stock-based compensation	3,535,000	3,234,000
Unrealized loss on available for sale securities	0	2,308,000
Operating lease liabilities	13,334,000
AMT credit and other state tax credit carryovers	416,000	96,000
Total deferred tax assets	53,587,000	49,734,000
Deferred tax liabilities:
Operating lease right-of-use assets	(12,382,000)
Deferred FDIC gain	(228,000)	(364,000)
Core deposit intangibles	(22,415,000)	(27,388,000)
Loan origination costs	(4,828,000)	(4,760,000)
Depreciation	(1,814,000)	(1,192,000)
Unrealized gain on available for sale securities	(8,639,000)	0
Other	(4,652,000)	(403,000)
Total deferred tax liabilities	(54,958,000)	(34,107,000)
Valuation allowance	0	0
Net deferred tax (liabilities) asset	$ (1,371,000)
Net deferred tax (liabilities) asset		$ 15,627,000