Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified From Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest income	$ 37,650	$ 43,621	$ 75,300	$ 89,728
Income tax expense	5,988	4,010	11,070	1,053
Other operating expenses	5,421	5,927	11,227	9,198
Net income	21,342	15,035	38,425	3,872
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Net unrealized losses on interest rate swaps used in cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest income	(413)	0	(599)	0
Income tax expense	87	0	126	0
Net income	(326)	0	(473)	0
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Net Change in Unfunded Pension Liability
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income tax expense	(7)	(3)	(14)	(7)
Other operating expenses	34	17	69	35
Net income	$ 27	$ 14	$ 55	$ 28