Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pre-Tax Amount
Other Comprehensive Income/(Loss), Pre-Tax Amount	$ (5,891)	$ 281	$ (12,714)	$ 26,833
Tax (Expense) Benefit
Other Comprehensive Income/(Loss), Tax (Expense) Benefit	1,257	(60)	2,714	(5,710)
Net of Tax Amount
Other Comprehensive (Loss)/Income, Net of Tax Amount	(4,634)	221	(10,000)	21,123
Pension settlement charge	400		1,300
Accumulated Net Investment Gain (Loss) on Debt Securities Available-for-sale
Pre-Tax Amount
Change in net unrealized gains/(losses) on debt securities available-for-sale	(5,676)	(882)	(15,065)	24,883
Reclassification adjustment for net (gains)/losses on debt securities available-for-sale included in net income			0	(142)
Tax (Expense) Benefit
Change in net unrealized gains/(losses) on debt securities available-for-sale	1,211	188	3,215	(5,294)
Reclassification adjustment for net (gains)/losses on debt securities available-for-sale included in net income			0	30
Net of Tax Amount
Change in net unrealized gains/(losses) on debt securities available-for-sale	(4,465)	(694)	(11,850)	19,589
Reclassification adjustment for net (gains)/losses on debt securities available-for-sale included in net income			0	(112)
Adjustment to Funded Status of Employee Benefit Plans
Pre-Tax Amount
Other Comprehensive Income/(Loss), Pre-Tax Amount	(215)	1,163	2,351	2,092
Tax (Expense) Benefit
Other Comprehensive Income/(Loss), Tax (Expense) Benefit	46	(248)	(501)	(446)
Net of Tax Amount
Other Comprehensive (Loss)/Income, Net of Tax Amount	$ (169)	$ 915	$ 1,850	$ 1,646