Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (33,183)
Investment securities losses (gains), net	(80)	$ 0
Personnel expense	(114,200)	(120,050)
Interest income	(556)	(69)
Total other comprehensive income (loss)	16,209	21,597
Ending Balance	(16,974)
Investment Securities Available For Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	3,989	(75,643)
Other comprehensive income (loss) before reclassifications	26,419	30,490
Investment securities losses (gains), net	(6,118)	(1,680)
Personnel expense	0	0
Other expense	0	0
Interest income	556	69
Income tax (expense) benefit	(5,225)	(7,301)
Total other comprehensive income (loss)	15,632	21,578
Ending Balance	19,620	(54,065)
Defined Benefit Pension and Postretirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(37,172)	(49,330)
Other comprehensive income (loss) before reclassifications	0	0
Investment securities losses (gains), net	0	0
Personnel expense	(38)	(38)
Other expense	808	64
Interest income	0	0
Income tax (expense) benefit	(193)	(7)
Total other comprehensive income (loss)	577	20
Ending Balance	(36,595)	(49,310)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(33,183)	(124,972)
Other comprehensive income (loss) before reclassifications	26,419	30,490
Investment securities losses (gains), net	(6,118)	(1,680)
Personnel expense	(38)	(38)
Other expense	808	64
Interest income	556	69
Income tax (expense) benefit	(5,418)	(7,308)
Total other comprehensive income (loss)	16,209	21,597
Ending Balance	$ (16,974)	$ (103,375)