Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 18,272	$ 10,556	$ 16,882	$ 17,624
Other comprehensive income (loss), net of tax:
Amortization of actuarial losses, net of taxes of ($31) and ($9) for the three months ended June 30, 2020 and 2019, respectively and of ($61) and ($19) for the six months ended June 30, 2020 and 2019, respectively.	67	22	134	44
Amortization of prior service credits, net of taxes of $8 and $6 for the three months ended June 30, 2020 and 2019, respectively and of $14 and $13 for six months ended June 30, 2020 and 2019, respectively.	(15)	(14)	(29)	(29)
Net unrealized gains on securities, net of taxes of ($5,193) and ($2,796) for the three months ended June 30, 2020 and 2019, respectively and of ($551) and ($5,320) for six months ended June 30, 2020 and 2019, respectively.	11,414	6,204	1,212	11,824
Reclassification adjustment for net losses included in income, net of taxes of ($17) and ($5) for three months ended June 30, 2020 and 2019, respectively and of ($29) and ($5) for the six months ended June 30, 2020 and 2019, respectively.	37	10	62	10
Net unrealized losses on cash flow hedges, net of taxes of $912 and $2,844 for the three months ended June 30, 2020 and 2019 respectively and of $7,102 and $4,419 for six months ended June 30, 2020 and 2019, respectively.	(2,005)	(6,331)	(15,610)	(9,836)
Change in fair value of liabilities related to instrument-specific credit risk, net of taxes of $259 and ($16) for the three months ended June 30, 2020 and 2019 respectively and of ($230) and ($55) for the six months ended June 30, 2020 and 2019, respectively.	(580)	35	516	123
Total other comprehensive income (loss) , net of tax	8,918	(74)	(13,715)	2,136
Comprehensive income	$ 27,190	$ 10,482	$ 3,167	$ 19,760