Benefit Plans - Defined Benefit Plans - Nonqualified Defined Benefit Pension Plan (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) item
Supplemental Retirement Plan
Combined number of active and retired/terminated participants in the defined benefit plan \| item	52
Supplemental Retirement Plan
Supplemental Retirement Plan
Plan assets associated with the plan \| $	$ 0
Vesting period of defined benefit stated amount, minimum	9 years

Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant