Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Before Tax Amount
Income (loss), before tax amount		$ 232	$ 19,578
Net unrealized gains (losses) on available-for-sale investment securities, before tax amount
Other comprehensive income (loss), securities, available-for-sale, unrealized holding gain (loss) arising during period, before tax		(4,965)	5,120
Other comprehensive (income) loss, reclassification adjustment from AOCI for write-down of securities, before tax		597
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(695)	(1)
Other comprehensive income (loss), securities, available-for-sale, adjustment, before tax		(5,063)	5,119
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, before tax amount
Net unrealized holding losses arising during the period		(497)	(168)
Less: reclassification adjustment for net (gains) losses realized in net income	[2]	29	(16)
Other comprehensive income (loss), derivatives qualifying as hedges, before tax		(468)	(184)
Defined benefit pension plans, Before Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	297	294
Accretion of prior service cost included in net periodic pension costs	[3]	0	(45)
Total defined benefit pension plans		297	249
Other comprehensive income (loss), before tax amount		(5,234)	5,184
Total comprehensive income (loss), before tax amount		(5,002)	24,762
Tax Expense (Benefit)
Income tax (benefit) expense		(606)	3,499
Net unrealized gains (losses) on available-for-sale investment securities, tax expense (benefit)
Other comprehensive income (loss), securities, available-for-sale, unrealized holding gain (loss) arising during period, tax		(1,042)	1,075
Other comprehensive (income) loss, reclassification adjustment from AOCI for write-down of securities, tax		125
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(146)	0
Total net unrealized (losses) gains on available-for-sale investment securities		(1,063)	1,075
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, tax expense (benefit)
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, tax		(104)	(36)
Less: reclassification adjustment for net (gains) losses realized in net income	[2]	6	(3)
Other comprehensive income (loss), derivatives qualifying as hedges, tax		(98)	(39)
Defined benefit pension plans, tax expense (benefit)
Amortization of net actuarial loss included in net periodic pension costs	[3]	62	62
Accretion of prior service cost included in net periodic pension costs	[3]	0	(9)
Other comprehensive (income) loss, defined benefit plan, after reclassification adjustment, tax		62	53
Other comprehensive income (loss), tax expense (benefit)		(1,099)	1,089
Total comprehensive income (loss), tax expense (benefit)		(1,705)	4,588
Net of Tax Amount
Net income		838	16,079
Net unrealized gains (losses) on available-for-sale investment securities, net of tax amount
Net unrealized holding (losses) gains arising during the period		(3,923)	4,045
Other comprehensive (income) loss, reclassification adjustment from AOCI for write-down of securities, net of tax, total		472
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(549)	(1)
Other comprehensive income (loss), securities, available-for-sale, adjustment, after tax		(4,000)	4,044
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, net of tax amount
Other comprehensive income (loss), unrealized gain (loss) on derivatives arising during period, net of tax		(393)	(132)
Less: reclassification adjustment for net (gains) losses realized in net income	[2]	23	(13)
Total net unrealized losses on interest rate swaps used in cash flow hedges		(370)	(145)
Defined benefit pension plans, net of tax amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	235	232
Accretion of prior service cost included in net periodic pension costs	[3]	0	(36)
Other comprehensive (income) loss, defined benefit plan, after reclassification adjustment, after tax		235	196
Other comprehensive income (loss), net of tax amount		(4,135)	4,095
Total comprehensive income (loss), net of tax amount		$ (3,297)	$ 20,174

[1] (1) Included in net gain on sales of investment securities on the consolidated statements of income (before tax amount).

[2] (2) Included in interest expense on deposits on the consolidated statements of income (before tax amount).

[3] (3) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (before tax amount). See Note 8, "Retirement Plans and Other Postretirement Benefits" for additional details.