CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS EQUITY - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2017	$ 458,578	$ 10,438	$ 292	$ 391,586	$ 61,349	$ (5,087)
Beginning balance, shares at Dec. 31, 2017		10,438	29,317,298
Net income	6,768				6,768
Other comprehensive income (loss), net of tax	(3,564)					(3,564)
Issuance of common stock upon exercise of stock options	1,005		$ 1	1,004
Issuance of common stock upon exercise of stock options, shares			86,750
Reclassification of certain income tax effects from accumulated other comprehensive income (loss)					763	(763)
Cash dividends declared on preferred stock	(193)				(193)
Share-based compensation expense	342			342
Ending balance at Mar. 31, 2018	462,936	$ 10,438	$ 293	392,932	68,687	(9,414)
Ending balance, shares at Mar. 31, 2018		10,438	29,404,048
Beginning balance at Dec. 31, 2017	458,578	$ 10,438	$ 292	391,586	61,349	(5,087)
Beginning balance, shares at Dec. 31, 2017		10,438	29,317,298
Net income	24,072
Other comprehensive income (loss), net of tax	(6,512)
Reclassification of certain income tax effects from accumulated other comprehensive income (loss)	(763)
Ending balance at Sep. 30, 2018	629,861	$ 10,438	$ 361	545,827	85,597	(12,362)
Ending balance, shares at Sep. 30, 2018		10,438	36,279,600
Beginning balance at Dec. 31, 2017	458,578	$ 10,438	$ 292	391,586	61,349	(5,087)
Beginning balance, shares at Dec. 31, 2017		10,438	29,317,298
Ending balance at Dec. 31, 2018	650,672	$ 10,438	$ 361	546,849	102,522	(9,498)
Ending balance, shares at Dec. 31, 2018		10,438	36,343,239
Beginning balance at Mar. 31, 2018	462,936	$ 10,438	$ 293	392,932	68,687	(9,414)
Beginning balance, shares at Mar. 31, 2018		10,438	29,404,048
Net income	2,768				2,768
Other comprehensive income (loss), net of tax	(921)					(921)
Issuance of common stock upon exercise of stock options	130			130
Issuance of common stock upon exercise of stock options, shares			8,000
Issuance of common stock and stock options due to business combination, net of issuance costs	151,275		$ 67	151,208
Issuance of common stock and stock options due to business combination, net of issuance costs, shares			6,682,850
Issuance of common stock in connection with restricted stock awards, shares			126,157
Forfeiture of restricted stock awards, shares			(2,100)
Cash dividends declared on preferred stock	(198)				(198)
Share-based compensation expense	416			416
Ending balance at Jun. 30, 2018	616,406	$ 10,438	$ 360	544,686	71,257	(10,335)
Ending balance, shares at Jun. 30, 2018		10,438	36,218,955
Net income	14,536				14,536
Other comprehensive income (loss), net of tax	(2,027)					(2,027)
Issuance of common stock upon exercise of stock options	567		$ 1	566
Issuance of common stock upon exercise of stock options, shares			51,763
Issuance of common stock in connection with employee stock purchase plan	172			172
Issuance of common stock in connection with employee stock purchase plan, shares			8,882
Cash dividends declared on preferred stock	(196)				(196)
Share-based compensation expense	403			403
Ending balance at Sep. 30, 2018	629,861	$ 10,438	$ 361	545,827	85,597	(12,362)
Ending balance, shares at Sep. 30, 2018		10,438	36,279,600
Net income	17,121				17,121
Other comprehensive income (loss), net of tax	2,864					2,864
Issuance of common stock upon exercise of stock options	638			638
Issuance of common stock upon exercise of stock options, shares			58,639
Issuance of common stock in connection with restricted stock awards, shares			5,000
Issuance of common stock in connection with employee stock purchase plan	31			31
Cash dividends declared on preferred stock	(196)				(196)
Share-based compensation expense	353			353
Ending balance at Dec. 31, 2018	650,672	$ 10,438	$ 361	546,849	102,522	(9,498)
Ending balance, shares at Dec. 31, 2018		10,438	36,343,239
Net income	12,597				12,597
Other comprehensive income (loss), net of tax	4,519					4,519
Issuance of common stock upon exercise of stock options	636		$ 1	635
Issuance of common stock upon exercise of stock options, shares			50,662
Forfeiture of restricted stock awards, shares			(8,500)
Issuance of common stock in connection with employee stock purchase plan	291			291
Issuance of common stock in connection with employee stock purchase plan, shares			12,743
Cumulative-effect adjustment (ASU 2016-01) | ASU 2016-01					1,440	(1,440)
Cash dividends declared on preferred stock	(196)				(196)
Share-based compensation expense	230			230
Ending balance at Mar. 31, 2019	668,749	$ 10,438	$ 362	548,005	116,363	(6,419)
Ending balance, shares at Mar. 31, 2019		10,438	36,398,144
Beginning balance at Dec. 31, 2018	650,672	$ 10,438	$ 361	546,849	102,522	(9,498)
Beginning balance, shares at Dec. 31, 2018		10,438	36,343,239
Net income	41,150
Other comprehensive income (loss), net of tax	11,899
Cumulative-effect adjustment (ASU 2016-01)	(1,440)
Ending balance at Sep. 30, 2019	735,866	$ 10,438	$ 378	579,564	144,525	961
Ending balance, shares at Sep. 30, 2019		10,438	38,169,126
Beginning balance at Mar. 31, 2019	668,749	$ 10,438	$ 362	548,005	116,363	(6,419)
Beginning balance, shares at Mar. 31, 2019		10,438	36,398,144
Net income	13,211				13,211
Other comprehensive income (loss), net of tax	5,071					5,071
Issuance of common stock upon exercise of stock options	1,669		$ 1	1,668
Issuance of common stock upon exercise of stock options, shares			116,048
Issuance of common stock and stock options due to business combination, net of issuance costs	28,892		$ 15	28,877
Issuance of common stock and stock options due to business combination, net of issuance costs, shares			1,464,558
Issuance of common stock in connection with restricted stock awards, shares			141,207
Forfeiture of restricted stock awards, shares			(4,738)
Cash dividends declared on preferred stock	(195)				(195)
Share-based compensation expense	278			278
Ending balance at Jun. 30, 2019	717,675	$ 10,438	$ 378	578,828	129,379	(1,348)
Ending balance, shares at Jun. 30, 2019		10,438	38,115,219
Net income	15,342				15,342
Other comprehensive income (loss), net of tax	2,309					2,309
Issuance of common stock upon exercise of stock options	54			54
Issuance of common stock upon exercise of stock options, shares			3,472
Issuance cost in connection with business combination	(157)			(157)
Issuance of common stock in connection with restricted stock awards, shares			50,992
Forfeiture of restricted stock awards, shares			(14,642)
Issuance of common stock in connection with employee stock purchase plan	289			289
Issuance of common stock in connection with employee stock purchase plan, shares			14,085
Cash dividends declared on preferred stock	(196)				(196)
Share-based compensation expense	550			550
Ending balance at Sep. 30, 2019	$ 735,866	$ 10,438	$ 378	$ 579,564	$ 144,525	$ 961
Ending balance, shares at Sep. 30, 2019		10,438	38,169,126