Consolidated Statements of Changes In Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Unallocated Common Stock Held by the Employee Stock Ownership Plan	Retained Earnings	Accumulated Other Comprehensive Income (loss) Net of tax	Treasury Stock
Beginning Balance (shares) at Dec. 31, 2018		49,635,673
Beginning Balance at Dec. 31, 2018	$ 666,439	$ 609	$ 546,219	$ (20,992)	$ 302,544	$ (9,147)	$ (152,794)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	8,771				8,771
Other comprehensive income, net of tax	6,198					6,198
ESOP shares allocated or committed to be released	436		187	249
Stock compensation expense	1,328		1,328
Exercise of stock options, net (shares)		138,123
Exercise of stock options, net	995		(873)				1,868
Cash dividends declared and paid	(4,727)				(4,727)
Ending Balance (shares) at Mar. 31, 2019		49,773,796
Ending Balance at Mar. 31, 2019	679,440	$ 609	546,861	(20,743)	306,588	(2,949)	(150,926)
Beginning Balance (shares) at Dec. 31, 2019		49,175,347
Beginning Balance at Dec. 31, 2019	695,853	$ 609	548,486	(19,740)	322,581	4,699	(160,782)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,551				4,551
Other comprehensive income, net of tax	5,994					5,994
ESOP shares allocated or committed to be released	446		198	248
Stock compensation expense	448		448
Issuance of restricted stock (shares)		103,581
Issuance of restricted stock	$ 0		(1,416)				1,416
Exercise of stock options, net (shares)	13,000	13,000
Exercise of stock options, net	$ 175		(4)				179
Cash dividends declared and paid	(5,151)				(5,151)
Ending Balance (shares) at Mar. 31, 2020		49,291,928
Ending Balance at Mar. 31, 2020	$ 702,316	$ 609	$ 547,712	$ (19,492)	$ 321,981	$ 10,693	$ (159,187)