Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Before Tax Amount
(Loss) income, Before Tax Amount		$ 15,995	$ 7,286	$ 30,773	$ 17,375
Net unrealized gains (losses) on available-for-sale investment securities, Before Tax Amount
Net unrealized holding gains arising during the period		2,632	2,084	3,052	4,302
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(21)	(413)	(36)	(457)
Total net unrealized gains on available-for-sale investment securities		2,611	1,671	3,016	3,845
Cash flow hedge derivative, Before Tax Amount
Net unrealized holding losses arising during the period		(92)	(300)	(85)	(926)
Less: reclassification adjustment for net losses realized in net income	[2]	36	80	107	161
Total net unrealized losses on interest rate swaps used in cash flow hedges		(56)	(220)	22	(765)
Defined benefit pension plans, Before Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	299	329	598	658
Accretion of prior service cost included in net periodic pension costs	[3]	(71)	(70)	(141)	(141)
Total defined benefit pension plans		228	259	457	517
Other comprehensive income, Before Tax Amount		2,783	1,710	3,495	3,597
Total comprehensive income, Before Tax Amount		18,778	8,996	34,268	20,972
Tax Expense (Benefit)
Income taxes		4,217	2,046	8,139	4,846
Net unrealized gains (losses) on available-for-sale investment securities, Tax Expense (Benefit)
Net unrealized holding gains arising during the period		921	730	1,068	1,506
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(8)	(145)	(13)	(160)
Total net unrealized gains on available-for-sale investment securities		913	585	1,055	1,346
Net unrealized losses on interest rate swaps used in cash flow hedges, Tax Expense (Benefit)
Net unrealized holding losses arising during the period		(31)	(105)	(29)	(324)
Less: reclassification adjustment for net losses realized in net income	[2]	12	28	37	56
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges		(19)	(77)	8	(268)
Defined benefit pension plans, Tax Expense (Benefit)
Amortization of net actuarial loss included in net periodic pension costs	[3]	104	115	209	230
Accretion of prior service cost included in net periodic pension costs	[3]	(25)	(24)	(49)	(49)
Total defined benefit pension plans		79	91	160	181
Other comprehensive income, Tax Expense (Benefit)		973	599	1,223	1,259
Total comprehensive income, Tax Expense (Benefit)		5,190	2,645	9,362	6,105
Net of Tax Amount
Net income		11,778	5,240	22,634	12,529
Net unrealized gains (losses) on available-for-sale investment securities, Net of Tax Amount
Net unrealized holding gains arising during the period		1,711	1,354	1,984	2,796
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(13)	(268)	(23)	(297)
Total net unrealized gains on available-for-sale investment securities		1,698	1,086	1,961	2,499
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges, Net of Tax Amount
Net unrealized holding losses arising during the period		(61)	(195)	(56)	(602)
Less: reclassification adjustment for net losses realized in net income	[2]	24	52	70	105
Total net unrealized losses on interest rate swaps used in cash flow hedges		(37)	(143)	14	(497)
Defined benefit pension plans, Net of Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	195	214	389	428
Accretion of prior service cost included in net periodic pension costs	[3]	(46)	(46)	(92)	(92)
Total defined benefit pension plans		149	168	297	336
Other comprehensive income, Net of Tax Amount		1,810	1,111	2,272	2,338
Total comprehensive income, Net of Tax Amount		$ 13,588	$ 6,351	$ 24,906	$ 14,867

[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.