CONDENSED FINANCIAL STATEMENTS OF PARENT COMPANY - Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES
Net income	$ 11,838	$ 6,491	$ 18,034	$ 1,048	$ 4,095	$ 4,327	$ 15,377	$ 3,192	$ 37,411	$ 26,991	$ 12,003
Equity in undistributed earnings of subsidiaries									(24,174)	0	0
Stock-based compensation									2,353	1,759	1,267
Other assets									(27,286)	(14,753)	(3,013)
Net cash from operating activities									112,235	(8,062)	6,694
INVESTING ACTIVITIES
Net cash from investing activities									(294,111)	(120,055)	(209,977)
FINANCING ACTIVITIES
Common stock repurchased									(15,746)	0	0
Preferred stock redemption									0	(500)	0
Common stock options exercised									4,464	2,164	2,129
Cash dividends paid on common stock									(4,275)	(2,290)	(1,220)
Cash dividends paid on preferred stock									(461)	(479)	(489)
Net cash from financing activities									417,767	133,898	205,199
Net change in cash									235,891	5,781	1,916
Cash and cash equivalents at beginning of period				28,002				22,221	28,002	22,221	20,305
Cash and cash equivalents at end of period	263,893				28,002				263,893	28,002	22,221
Noncash common stock converted from subordinated debt									0	1,000	15,965
Parent Company
OPERATING ACTIVITIES
Net income									37,411	26,991	12,003
Equity in undistributed earnings of subsidiaries									(45,445)	(32,700)	(14,967)
Stock-based compensation									2,353	1,759	1,267
Other assets									(2,101)	(4,104)	1,997
Other liabilities									1,767	344	1,311
Net cash from operating activities									(6,015)	(7,710)	1,611
INVESTING ACTIVITIES
Investment in subsidiaries									(2,982)	16,791	(2,194)
Net cash from investing activities									(2,982)	16,791	(2,194)
FINANCING ACTIVITIES
Proceeds from stock issuance									240	1,033	0
AOCI reclassification of pension and available-for-sale investments									0	0	743
Subordinated debt issuance (redemption)									40,000	(12,400)	(35)
Common stock repurchased									(15,746)	0	0
Preferred stock redemption									0	(500)	0
Common stock options exercised									4,464	2,164	2,129
Cash dividends paid on common stock									(4,275)	(2,290)	(1,220)
Cash dividends paid on preferred stock									(461)	(479)	(489)
Net cash from financing activities									24,222	(12,472)	1,128
Net change in cash									15,225	(3,391)	545
Cash and cash equivalents at beginning of period				$ 1,058				$ 4,449	1,058	4,449	3,904
Cash and cash equivalents at end of period	$ 16,283				$ 1,058				16,283	1,058	4,449
Noncash common stock converted from subordinated debt									$ 0	$ 1,000	$ 15,965