CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Cumulative change in accounting principle (Note 1)	Balance, January 1, 2021 (as adjusted for change in accounting principle)	Paid In Capital [Member]	Paid In Capital [Member] Balance, January 1, 2021 (as adjusted for change in accounting principle)	Retained Earnings [Member]	Retained Earnings [Member] Cumulative change in accounting principle (Note 1)	Retained Earnings [Member] Balance, January 1, 2021 (as adjusted for change in accounting principle)	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Balance, January 1, 2021 (as adjusted for change in accounting principle)	Treasury Stock [Member]	Treasury Stock [Member] Balance, January 1, 2021 (as adjusted for change in accounting principle)	Maximum Cash Obligation Related To ESOP Shares [Member]	Maximum Cash Obligation Related To ESOP Shares [Member] Balance, January 1, 2021 (as adjusted for change in accounting principle)
Beginning Balance at Dec. 31, 2019	$ 375,211			$ 55,943		$ 409,509			$ 1,415		$ (39,830)		$ (51,826)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of 91,274 and 657 shares of common stock for 3 months ended March 31, 2020 and 2021, respectively	5,933			3,504							2,429
Issuance 1,712 and 2,018 shares of common stock under the employee stock purchase plan for 3 months ended March 31, 2020 and 2021, respectively	101			101
Unearned restricted stock compensation	202			202
Forfeiture of 443 and 300 shares of common stock for 3 months ended March 31, 2020 and 2021, respectively	(23)			(23)
Share-based compensation	6			6
Change related to ESOP shares	1,577												1,577
Net income	7,075					7,075
Cash dividends ($0.89 and $0.94 per share for 3 months ended March 31, 2020 and 2021, respectively)	(8,324)					(8,324)
Purchase of 68,881 and 20,852 shares of common stock for 3 months ended March 31, 2020 and 2021, respectively	(4,538)										(4,538)
Other comprehensive income (loss)	(409)								(409)
Ending Balance at Mar. 31, 2020	376,811			59,733		408,260			1,006		(41,939)		(50,249)
Beginning Balance at Dec. 31, 2020	416,076	$ (4,751)	$ 411,325	60,233	$ 60,233	439,831	$ (4,751)	$ 435,080	8,782	$ 8,782	(45,441)	$ (45,441)	(47,329)	$ (47,329)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of 91,274 and 657 shares of common stock for 3 months ended March 31, 2020 and 2021, respectively	41			24							17
Issuance 1,712 and 2,018 shares of common stock under the employee stock purchase plan for 3 months ended March 31, 2020 and 2021, respectively	114			114
Unearned restricted stock compensation	251			251
Forfeiture of 443 and 300 shares of common stock for 3 months ended March 31, 2020 and 2021, respectively	(17)			(17)
Share-based compensation	6			6
Change related to ESOP shares	(805)												(805)
Net income	15,197					15,197
Cash dividends ($0.89 and $0.94 per share for 3 months ended March 31, 2020 and 2021, respectively)	(8,773)					(8,773)
Purchase of 68,881 and 20,852 shares of common stock for 3 months ended March 31, 2020 and 2021, respectively	(1,311)										(1,311)
Other comprehensive income (loss)	(2,778)								(2,778)
Ending Balance at Mar. 31, 2021	$ 413,250			$ 60,611		$ 441,504			$ 6,004		$ (46,735)		$ (48,134)