Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended						12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Other comprehensive income, tax expense (benefit)	$ (37)	$ 2	$ 220	$ 52	$ 164	$ 167
Income tax benefit	$ 226			$ 191
Stock options exercised				17,773
ESOP, shares earned	1,984	1,984	1,984	1,984	1,983	1,984
Compensation plan shares granted			20,830			5,186
Compensation plan shares forfeited		332			760
Compensation plan shares earned	3,327	3,299	1,889	4,277	6,107	5,518
Purchase of treasury stock, shares	42,100	40,600	26,900	16,990	43,900	7,300
Cash dividends declared, value per share	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.12
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-02 [Member]
Income tax benefit							$ (2)