Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 25,413	$ 14,331	$ 63,710	$ 31,213
Other comprehensive income (loss), net of tax:
Amortization of actuarial losses, net of taxes of ($39) and ($30) for the three months ended September 30, 2021 and 2020, respectively, and of ($116) and ($91) for the nine months ended September 30, 2021 and 2020, respectively.	86	67	259	201
Amortization of prior service credits, net of taxes of $7 and $6 for the three months ended September 30, 2021 and 2020, respectively, and of $19 and $20 for the nine months ended September 30, 2021 and 2020, respectively.	(14)	(15)	(44)	(44)
Net unrealized gains (losses) on securities, net of taxes of $1,209 and ($1,449) for the three months ended September 30, 2021 and 2020, respectively, and of $1,518 and ($2,000) for the nine months ended September 30, 2021 and 2020, respectively.	(2,645)	3,185	(3,365)	4,397
Reclassification adjustment for net losses (gains) included in income, net of taxes of ($3) for the three months ended September 30, 2021, and net of taxes of $35 and ($29) for the nine months ended September 30, 2021 and 2020, respectively.	7		(78)	62
Net unrealized gains (losses) on cash flow hedges, net of taxes of ($910) and ($849) for the three months ended September 30, 2021 and 2020 respectively, and of ($4,485) and $6,253 for the nine months ended September 30, 2021 and 2020 respectively.	1,991	1,866	10,310	(13,744)
Change in fair value of liabilities related to instrument-specific credit risk, net of taxes of ($27) and ($50) for the three months ended September 30, 2021 and 2020, respectively, and of ($139) and ($280) for the nine months ended September 30, 2021 and 2020, respectively.	58	111	250	627
Total other comprehensive income (loss), net of tax	(517)	5,214	7,332	(8,501)
Comprehensive income	$ 24,896	$ 19,545	$ 71,042	$ 22,712