Employee Benefit Plans (Schedule of Assumptions used to Determine Net Periodic Cost and Benefit Obligations) (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Postretirement Medical and Life Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.81%	3.91%	3.35%

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration