Parent Company Only Financial Statements - Balance Sheets (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and equivalents	$ 220,337	$ 107,934	$ 113,032	$ 125,751
Investment in bank subsidiary	1,911	1,601
Other assets	9,477	8,391
Total assets	933,058	805,836
Liabilities
Junior subordinated debt securities (at fair value)	10,155	9,730
Total liabilities	823,818	704,484
Shareholders' Equity
Common stock, no par value; 20,000,000 shares authorized; issued and outstanding: 16,946,622 at December 31, 2018 and 16,885,615 at December 31, 2017	58,624	57,880
Retained earnings	49,942	44,182
Accumulated other comprehensive income (loss)	674	(710)
Total shareholders' equity	109,240	101,352	96,654	89,635
Total liabilities and shareholders' equity	$ 933,058	$ 805,836
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	16,946,622	16,885,615
Common stock, shares outstanding (in shares)	16,946,622	16,885,615
Parent Company
Assets
Cash and equivalents	$ 2,297	$ 1,656	$ 148	$ 140
Investment in bank subsidiary	117,831	109,472
Other assets	1,153	1,136
Total assets	121,281	112,264
Liabilities
Junior subordinated debt securities (at fair value)	10,155	9,730
Dividends declared	1,859	1,182
Other liabilities	27	0
Total liabilities	12,041	10,912
Shareholders' Equity
Common stock, no par value; 20,000,000 shares authorized; issued and outstanding: 16,946,622 at December 31, 2018 and 16,885,615 at December 31, 2017	58,624	57,880
Retained earnings	49,942	44,182
Accumulated other comprehensive income (loss)	674	(710)
Total shareholders' equity	109,240	101,352
Total liabilities and shareholders' equity	$ 121,281	$ 112,264
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	16,946,622	16,885,615
Common stock, shares outstanding (in shares)	16,946,622	16,885,615