CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Maximum Cash Obligation Related To ESOP Shares [Member]
Beginning Balance at Dec. 31, 2018	$ 334,882	$ 52,122	$ 371,848	$ (3,250)	$ (36,968)	$ (48,870)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of 2,327, 1,148, 86,491 and 92,422 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	5,279	3,016			2,263
Issuance 2,106, 1,857, 4,035, and 3,569 shares of common stock under the employee stock purchase plan for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	223	223
Unearned restricted stock compensation	407	407
Forfeiture of 4,418, 580, 5,121 and 1,023 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(254)	(254)
Share-based compensation	1	1
Change related to ESOP shares	(1,355)					(1,355)
Net income	22,423		22,423
Cash dividends ($0.82 and $0.89 per share for 6 months ended June 30, 2019 and 2020, respectively)	(7,657)		(7,657)
Purchase of 5,626, 13,719, 75,397 and 82,600 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(4,647)				(4,647)
Other comprehensive income	4,222			4,222
Ending Balance at Jun. 30, 2019	353,524	55,515	386,614	972	(39,352)	(50,225)
Beginning Balance at Mar. 31, 2019	340,780	55,295	375,394	(1,001)	(39,057)	(49,851)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of 2,327, 1,148, 86,491 and 92,422 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	145	84			61
Issuance 2,106, 1,857, 4,035, and 3,569 shares of common stock under the employee stock purchase plan for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	118	118
Unearned restricted stock compensation	237	237
Forfeiture of 4,418, 580, 5,121 and 1,023 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(220)	(220)
Share-based compensation	1	1
Change related to ESOP shares	(374)					(374)
Net income	11,220		11,220
Purchase of 5,626, 13,719, 75,397 and 82,600 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(356)				(356)
Other comprehensive income	1,973			1,973
Ending Balance at Jun. 30, 2019	353,524	55,515	386,614	972	(39,352)	(50,225)
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 2,327, 1,148, 86,491 and 92,422 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	6,006	3,547			2,459
Issuance 2,106, 1,857, 4,035, and 3,569 shares of common stock under the employee stock purchase plan for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	200	200
Unearned restricted stock compensation	393	393
Forfeiture of 4,418, 580, 5,121 and 1,023 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(52)	(52)
Share-based compensation	12	12
Change related to ESOP shares	6,497					6,497
Net income	18,786		18,786
Cash dividends ($0.82 and $0.89 per share for 6 months ended June 30, 2019 and 2020, respectively)	(8,325)		(8,325)
Purchase of 5,626, 13,719, 75,397 and 82,600 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(5,416)				(5,416)
Other comprehensive income	5,406			5,406
Ending Balance at Jun. 30, 2020	398,718	60,043	419,970	6,821	(42,787)	(45,329)
Beginning Balance at Mar. 31, 2020	376,810	59,733	408,259	1,006	(41,939)	(50,249)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of 2,327, 1,148, 86,491 and 92,422 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	73	43			30
Issuance 2,106, 1,857, 4,035, and 3,569 shares of common stock under the employee stock purchase plan for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	99	99
Unearned restricted stock compensation	191	191
Forfeiture of 4,418, 580, 5,121 and 1,023 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(29)	(29)
Share-based compensation	6	6
Change related to ESOP shares	4,920					4,920
Net income	11,711		11,711
Purchase of 5,626, 13,719, 75,397 and 82,600 shares of common stock for 3 months ended June 30, 2019 and 2020 and the 6 months ended June 30, 2019 and 2020, respectively	(878)				(878)
Other comprehensive income	5,815			5,815
Ending Balance at Jun. 30, 2020	$ 398,718	$ 60,043	$ 419,970	$ 6,821	$ (42,787)	$ (45,329)