Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 34,674	$ 41,279	$ 55,090
Other comprehensive income (loss), net of tax:
Amortization of prior service credits, net of taxes of $26, $26 and $12 for the years ended December 31, 2020, 2019 and 2018, respectively	(59)	(59)	(27)
Amortization of net actuarial losses, net of taxes of ($120), ($40) and ($167) for the years ended December 31, 2020, 2019 and 2018, respectively	270	88	363
Unrecognized actuarial gains (losses), net of taxes of $484, ($290) and ($1,162) for the years ended December 31, 2020, 2019 and 2018, respectively	(1,112)	661	2,484
Change in net unrealized gains (losses) on securities available for sale, net of taxes of ($2,169), ($5,211) and $4,473 for the years ended December 31, 2020, 2019 and 2018, respectively	4,787	11,657	(10,127)
Reclassification adjustment for net losses included in net income, net of taxes of ($216), ($5) and ($595) for the years ended December 31, 2020, 2019 and 2018, respectively	485	10	1,325
Net unrealized (loss) gain on cash flow hedges, net of taxes of $5,177, $4,353 and ($1,538) for the years ended December 31, 2020, 2019 and 2018, respectively	(11,658)	(9,567)	3,423
Change in fair value of liabilities related to instrument-specific credit risk, net of taxes of ($367), ($74) and ($35) for the years ended December 31, 2020, 2019 and 2018, respectively	828	155	87
Total other comprehensive income (loss) , net of tax	(6,459)	2,945	(2,472)
Comprehensive net income	$ 28,215	$ 44,224	$ 52,618