Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Before Tax Amount
(Loss) income, Before Tax Amount		$ 14,778	$ 10,089
Net unrealized gains (losses) on available-for-sale investment securities, Before Tax Amount
Net unrealized holding gains arising during the period		420	2,218
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(15)	(44)
Total net unrealized gains on available-for-sale investment securities		405	2,174
Cash flow hedge derivative, Before Tax Amount
Net unrealized holding gains (losses) arising during the period		7	(626)
Less: reclassification adjustment for net losses realized in net income	[2]	71	81
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges		78	(545)
Defined benefit pension plans, Before Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	299	329
Accretion of prior service cost included in net periodic pension costs	[3]	(70)	(71)
Total defined benefit pension plans		229	258
Other comprehensive income, Before Tax Amount		712	1,887
Total comprehensive income, Before Tax Amount		15,490	11,976
Tax Expense (Benefit)
Income taxes		3,922	2,800
Net unrealized gains (losses) on available-for-sale investment securities, Tax Expense (Benefit)
Net unrealized holding gains arising during the period		147	776
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(5)	(15)
Total net unrealized gains on available-for-sale investment securities		142	761
Net unrealized losses on interest rate swaps used in cash flow hedges, Tax Expense (Benefit)
Net unrealized holding losses arising during the period		2	(219)
Less: reclassification adjustment for net losses realized in net income	[2]	25	28
Total net unrealized losses on interest rate swaps used in cash flow hedges		27	(191)
Defined benefit pension plans, Tax Expense (Benefit)
Amortization of net actuarial loss included in net periodic pension costs	[3]	105	115
Accretion of prior service cost included in net periodic pension costs	[3]	(24)	(25)
Total defined benefit pension plans		81	90
Other comprehensive income, Tax Expense (Benefit)		250	660
Total comprehensive income, Tax Expense (Benefit)		4,172	3,460
Net of Tax Amount
Net income		10,856	7,289
Net unrealized gains (losses) on available-for-sale investment securities, Net of Tax Amount
Net unrealized holding gains arising during the period		273	1,442
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(10)	(29)
Total net unrealized gains on available-for-sale investment securities		263	1,413
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		5	(407)
Less: reclassification adjustment for net losses realized in net income	[2]	46	53
Total net unrealized gains (losses) on interest rate swaps used in cash flow hedges		51	(354)
Defined benefit pension plans, Net of Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	194	214
Accretion of prior service cost included in net periodic pension costs	[3]	(46)	(46)
Total defined benefit pension plans		148	168
Other comprehensive income, Net of Tax Amount		462	1,227
Total comprehensive income, Net of Tax Amount		$ 11,318	$ 8,516

[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).