Consolidated statements of changes in shareholders' equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss), Net
Balance at Dec. 31, 2016	$ 330,498	$ 24,108	$ 213,480	$ 93,784	$ (874)
Initial fair value election on mortgage servicing rights, net of taxes of $396 (See Note 1)	615			615
Net income	9,753			9,753
Other comprehensive income (loss), net of taxes	549				549
Stock-based compensation expense	1,352		1,352
Restricted stock units vested and distributed, net of shares withheld for taxes	(625)	47	(672)
Balance at Mar. 31, 2017	342,142	24,155	214,160	104,152	(325)
Balance at Dec. 31, 2017	596,729	30,536	418,596	147,449	148
Initial adoption of ASU 2016-01 (See Note 1)				(109)	109
Net income	19,754			19,754
Other comprehensive income (loss), net of taxes	(5,758)				(5,758)
Stock-based compensation expense	1,958	4	1,954
Restricted stock units vested and distributed, net of shares withheld for taxes	(2,277)	115	(2,392)
Shares issued under employee stock purchase program	669	17	652
Balance at Mar. 31, 2018	$ 611,075	$ 30,672	$ 418,810	$ 167,094	$ (5,501)