Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	$ 269,584	$ 249,603
Other comprehensive income before reclassifications	2,080	(2,485)
Amounts reclassified from accumulated other comprehensive income	163	45
Net current-period other comprehensive income (loss)	2,243	(2,440)
Reclassification due to the adoption of ASU 2016-01		(331)
Stockholders' equity, ending balance	276,609	252,734
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(13,810)	(8,514)
Net current-period other comprehensive income (loss)	2,243	(2,440)
Stockholders' equity, ending balance	(11,567)	(11,285)
Unrealized Gains and Losses on Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(3,697)	(1,250)
Other comprehensive income before reclassifications	2,080	(2,485)
Amounts reclassified from accumulated other comprehensive income		0
Net current-period other comprehensive income (loss)	2,080	(2,485)
Reclassification due to the adoption of ASU 2016-01		(331)
Stockholders' equity, ending balance	(1,617)	(4,066)
Amortization of Net Retirement Plan Actuarial Gain (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(8,971)	(6,380)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	121	46
Net current-period other comprehensive income (loss)	121	46
Stockholders' equity, ending balance	(8,850)	(6,334)
Accretion of Net Retirement Plan Prior Service (Cost) Credit
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(1,142)	(884)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	42	(1)
Net current-period other comprehensive income (loss)	42	(1)
Stockholders' equity, ending balance	$ (1,100)	$ (885)

Tax Cuts And Jobs Act, Reclassification From AOCI To Retained Earnings, Tax Effect

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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