Accumulated Other Comprehensive (Loss) Income - Components of Accumulated Other Comprehensive (Loss) Income, Net of Taxes (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance				$ (17,771)	$ (19,454)
Net Change		$ (1,216)	$ 1,810	(5,882)	2,272
Ending balance		(28,007)	(17,182)	(28,007)	(17,182)
Accounting Standards Update 2016-01 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption						$ 0
Accounting Standards Update 2018-02 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption						0
Net Unrealized Holding (Losses) Gains on Available-for-Sale Investment Securities [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance				(4,061)	(4,988)
Net Change				(6,525)	1,961
Ending balance		(11,987)	(3,027)	(11,987)	(3,027)
Net Unrealized Holding (Losses) Gains on Available-for-Sale Investment Securities [Member] | Accounting Standards Update 2016-01 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1]					(433)
Net Unrealized Holding (Losses) Gains on Available-for-Sale Investment Securities [Member] | Accounting Standards Update 2018-02 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1]					(968)
Net Change Related to Derivative Used for Cash Flow Hedge [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance				9	(141)
Net Change				310	14
Ending balance		321	(127)	321	(127)
Net Change Related to Derivative Used for Cash Flow Hedge [Member] | Accounting Standards Update 2016-01 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1]					0
Net Change Related to Derivative Used for Cash Flow Hedge [Member] | Accounting Standards Update 2018-02 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1]					2
Net Change Related to Defined Benefit Pension Plan [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance				(13,719)	(14,325)
Net Change				333	297
Ending balance		$ (16,341)	$ (14,028)	(16,341)	(14,028)
Net Change Related to Defined Benefit Pension Plan [Member] | Accounting Standards Update 2016-01 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1]					0
Net Change Related to Defined Benefit Pension Plan [Member] | Accounting Standards Update 2018-02 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1]					(2,955)
Accumulated Other Comprehensive (Loss) Income [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Net Change				$ (5,882)	$ 2,272
Accumulated Other Comprehensive (Loss) Income [Member] | Accounting Standards Update 2016-01 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1],[2]					(433)
Accumulated Other Comprehensive (Loss) Income [Member] | Accounting Standards Update 2018-02 [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Cumulative Effect of New Accounting Pronouncement in Period of Adoption	[1],[2]					$ (3,921)

[1] (1) See Note 1, "Summary of Significant Accounting Policies - Accounting Pronouncements Adopted in 2018" for additional information.

[2] (1) See Note 1, "Summary of Significant Accounting Policies - Accounting Pronouncements Adopted in 2018" for additional information.