Income Taxes - Deferred tax assets (liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Accrued expenses	$ 2,839	$ 1,717	$ 1,802
Net operating loss	3,977	5,192	2,703
Allowance for loan losses, net of bad debt charge-offs	8,061	6,252	5,158
Deferred compensation	2,348	2,547	1,750
State taxes	1,879	1,451	1,238
Depreciation	1,090	651	321
Loan discount	3,477	0	0
Stock based compensation	1,108	639	313
Unrealized loss on available for sale securities	1,939	0	0
Total deferred tax assets	26,718	18,449	13,285
Deferred tax liabilities:
Deferred FDIC gain	(1,675)	(1,656)	(1,731)
Core deposit intangibles	(3,331)	(2,266)	(1,518)
Unrealized loss on available for sale securities	0	(231)	(362)
Loan origination costs	(4,208)	0	0
Other	(697)	(2,785)	(291)
Total deferred tax liabilities	(9,911)	(6,938)	(3,902)
Net deferred tax asset	$ 16,807	$ 11,511	$ 9,383