Accumulated Other Comprehensive (Loss) Income - Components of Accumulated Other Comprehensive (Loss) Income, Net of Taxes (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 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		$ (657)	$ 839	(6,539)	3,111
Ending balance		(28,664)	(16,343)	(28,664)	(16,343)
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				(7,411)	2,624
Ending balance		(12,873)	(2,364)	(12,873)	(2,364)
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				373	28
Ending balance		384	(113)	384	(113)
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				499	459
Ending balance		$ (16,175)	$ (13,866)	(16,175)	(13,866)
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				$ (6,539)	$ 3,111
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.