Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Before Tax Amount
(Loss) income, Before Tax Amount		$ 4,548	$ 15,995	$ 20,224	$ 30,773
Net unrealized gains (losses) on available-for-sale investment securities, Before Tax Amount
Net unrealized holding (losses) gains arising during the period		(1,911)	2,632	(8,249)	3,052
Less: reclassification adjustment for net gains on sales realized in net income	[1]	0	(21)	(10)	(36)
Total net unrealized (losses) gains on available-for-sale investment securities		(1,911)	2,611	(8,259)	3,016
Cash flow hedge derivative, Before Tax Amount
Net unrealized holding gains (losses) arising during the period		154	(92)	366	(85)
Less: reclassification adjustment for net losses realized in net income	[2]	6	36	26	107
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges		160	(56)	392	22
Defined benefit pension plans, Before Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	282	299	563	598
Accretion of prior service cost included in net periodic pension costs	[3]	(71)	(71)	(142)	(141)
Total defined benefit pension plans		211	228	421	457
Other comprehensive income, Before Tax Amount		(1,540)	2,783	(7,446)	3,495
Total comprehensive income (loss), Before Tax Amount		3,008	18,778	12,778	34,268
Tax Expense (Benefit)
Income tax expense		191	4,217	3,017	8,139
Net unrealized gains (losses) on available-for-sale investment securities, Tax Expense (Benefit)
Net unrealized holding (losses) gains arising during the period		(401)	921	(1,732)	1,068
Less: reclassification adjustment for net gains on sales realized in net income	[1]	0	(8)	(2)	(13)
Total net unrealized (losses) gains on available-for-sale investment securities		(401)	913	(1,734)	1,055
Net unrealized losses on interest rate swaps used in cash flow hedges, Tax Expense (Benefit)
Net unrealized holding gains (losses) arising during the period		32	(31)	77	(29)
Less: reclassification adjustment for net losses realized in net income	[2]	1	12	5	37
Total net unrealized gains on interest rate swaps used in cash flow hedges		33	(19)	82	8
Defined benefit pension plans, Tax Expense (Benefit)
Amortization of net actuarial loss included in net periodic pension costs	[3]	58	104	117	209
Accretion of prior service cost included in net periodic pension costs	[3]	(14)	(25)	(29)	(49)
Total defined benefit pension plans		44	79	88	160
Other comprehensive income, Tax Expense (Benefit)		(324)	973	(1,564)	1,223
Total comprehensive income (loss), Tax Expense (Benefit)		(133)	5,190	1,453	9,362
Net of Tax Amount
Net income		4,357	11,778	17,207	22,634
Net unrealized gains (losses) on available-for-sale investment securities, Net of Tax Amount
Net unrealized holding (losses) gains arising during the period		(1,510)	1,711	(6,517)	1,984
Less: reclassification adjustment for net gains on sales realized in net income	[1]	0	(13)	(8)	(23)
Total net unrealized (losses) gains on available-for-sale investment securities		(1,510)	1,698	(6,525)	1,961
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges, Net of Tax Amount
Net unrealized holding gains (losses) arising during the period		122	(61)	289	(56)
Less: reclassification adjustment for net losses realized in net income	[2]	5	24	21	70
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges		127	(37)	310	14
Defined benefit pension plans, Net of Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	224	195	446	389
Accretion of prior service cost included in net periodic pension costs	[3]	(57)	(46)	(113)	(92)
Total defined benefit pension plans		167	149	333	297
Other comprehensive income, Net of Tax Amount		(1,216)	1,810	(5,882)	2,272
Total comprehensive income (loss), Net of Tax Amount		$ 3,141	$ 13,588	$ 11,325	$ 24,906

[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.