Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Before Tax Amount
(Loss) income, Before Tax Amount		$ 15,612	$ (1,475)	$ 46,385	$ 15,900
Net unrealized gains (losses) on available-for-sale investment securities, Before Tax Amount
Net unrealized holding gains (losses) arising during the period		1,030	(151)	4,082	4,151
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(7)	(30)	(43)	(487)
Total net unrealized gains (losses) on available-for-sale investment securities		1,023	(181)	4,039	3,664
Cash flow hedge derivative, Before Tax Amount
Net unrealized holding (losses) gains arising during the period		(20)	101	(105)	(825)
Less: reclassification adjustment for net losses realized in net income	[2]	41	76	148	237
Total net unrealized gains on interest rate swaps used in cash flow hedges		21	177	43	(588)
Defined benefit pension plans, Before Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	320	330	918	988
Accretion of prior service cost included in net periodic pension costs	[3]	(71)	(71)	(212)	(212)
Total defined benefit pension plans		249	259	706	776
Other comprehensive income, Before Tax Amount		1,293	255	4,788	3,852
Total comprehensive income (loss), Before Tax Amount		16,905	(1,220)	51,173	19,752
Tax Expense (Benefit)
Income tax expense (benefit)		4,416	(1,533)	12,555	3,313
Net unrealized gains (losses) on available-for-sale investment securities, Tax Expense (Benefit)
Net unrealized holding gains (losses) arising during the period		362	(53)	1,430	1,453
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(2)	(10)	(15)	(170)
Total net unrealized gains (losses) on available-for-sale investment securities		360	(63)	1,415	1,283
Net unrealized losses on interest rate swaps used in cash flow hedges, Tax Expense (Benefit)
Net unrealized holding losses arising during the period		(7)	35	(37)	(289)
Less: reclassification adjustment for net losses realized in net income	[2]	14	27	52	83
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges		7	62	15	(206)
Defined benefit pension plans, Tax Expense (Benefit)
Amortization of net actuarial loss included in net periodic pension costs	[3]	112	115	321	345
Accretion of prior service cost included in net periodic pension costs	[3]	(25)	(25)	(74)	(74)
Total defined benefit pension plans		87	90	247	271
Other comprehensive income, Tax Expense (Benefit)		454	89	1,677	1,348
Total comprehensive income (loss), Tax Expense (Benefit)		4,870	(1,444)	14,232	4,661
Net of Tax Amount
Net income		11,196	58	33,830	12,587
Net unrealized gains (losses) on available-for-sale investment securities, Net of Tax Amount
Net unrealized holding gains (losses) arising during the period		668	(98)	2,652	2,698
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(5)	(20)	(28)	(317)
Total net unrealized gains (losses) on available-for-sale investment securities		663	(118)	2,624	2,381
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges, Net of Tax Amount
Net unrealized holding (losses) gains arising during the period		(13)	66	(68)	(536)
Less: reclassification adjustment for net losses realized in net income	[2]	27	49	96	154
Total net unrealized gains on interest rate swaps used in cash flow hedges		14	115	28	(382)
Defined benefit pension plans, Net of Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	208	215	597	643
Accretion of prior service cost included in net periodic pension costs	[3]	(46)	(46)	(138)	(138)
Total defined benefit pension plans		162	169	459	505
Other comprehensive income, Net of Tax Amount		839	166	3,111	2,504
Total comprehensive income (loss), Net of Tax Amount		$ 12,035	$ 224	$ 36,941	$ 15,091

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

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

[3] These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (before tax amount). See Note 7—Retirement Plans and Other Postretirement Benefits for additional details.