Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Jan. 27, 2021	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity [Abstract]
Unrecognized prior service cost and net actuarial (losses) on pension plans	$ (20,134)		$ (21,677)	$ (27,689)
Unrealized (losses) gains on derivatives (cash flow hedges)	(16)		(32)	1,821
Unrealized net holding gains (losses) on AFS securities	20,567		2,683	(17,306)
AOCI	$ 417		$ (19,026)	$ (43,174)
Preceding period of retained net profits for approval of Office of Comptroller of the Currency	2 years
Statutory amount available for dividend payments	$ 194,200
Stock Repurchase Program [Abstract]
Purchase of common stock (in shares)	263,507
Purchase of common stock value	$ 7,980
Average price per share (in dollars per share)	$ 30.28
Number of shares available for repurchase under stock repurchase program (in shares)	736,493
Number of shares authorized under stock repurchase program (in shares)	1,000,000
Subsequent Event [Member]
Stock Repurchase Program [Abstract]
Number of shares authorized under stock repurchase program (in shares)		2,000,000