Accumulated Other Comprehensive Loss Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains on sale of investment securities									$ (62)	$ (69)	$ 0
Actual gain (loss) on plan assets									(1,324)	(880)
Income tax expense	$ 4,565	$ 5,098	$ 4,732	$ 7,322	$ 6,319	$ 6,193	$ 5,813	$ 5,810	21,717	24,135	18,015
Net Income Available to Common Shareholders	$ (22,222)	$ (20,126)	$ (18,251)	$ (28,996)	$ (22,611)	$ (22,371)	$ (22,751)	$ (21,619)	(89,595)	(89,352)	(70,002)
Unrealized Gains (Losses) on Securities Available-for-Sale | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains on sale of investment securities									(62)	(69)	0
Income tax expense									15	15	0
Net Income Available to Common Shareholders									(47)	(54)	0
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actual gain (loss) on plan assets									0	0	163
Income tax expense									0	0	(38)
Net Income Available to Common Shareholders									$ 0	$ 0	$ 125