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Income Taxes - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Disclosure [Abstract]      
Net unrealized holding gains in available for sale securities, excluded from deferred tax assets (liabilities) calculation $ 7,500,000 $ 4,300,000  
Employee benefit plan deferred tax assets, excluded from deferred tax asset calculation 12,900,000 12,600,000  
Federal tax reform remeasurement of AOCI deferred tax asset 0 9,958,000 $ 0
Deferred tax assets, valuation allowance 0 0  
Unrecognized tax benefits $ 0 0  
Re-measurement of net deferred tax asset resulting in additional income tax expense   $ 14,900,000