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Pension Plan and Other Postretirement Benefits - Asset Allocation Ranges By Asset Class and PBO Funded Status (Details) - Pension Plan	Dec. 31, 2020
Equity | Less Than 85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	39.00%
Equity | Less Than 85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	59.00%
Equity | >=85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	34.00%
Equity | >=85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	54.00%
Equity | >=90% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	24.00%
Equity | >=90% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	44.00%
Equity | >=95% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	14.00%
Equity | >=95% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	34.00%
Equity | >=100% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Equity | >=100% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	20.00%
Investment Grade Fixed Income | Less Than 85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	22.00%
Investment Grade Fixed Income | Less Than 85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	42.00%
Investment Grade Fixed Income | >=85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	30.00%
Investment Grade Fixed Income | >=85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	50.00%
Investment Grade Fixed Income | >=90% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	40.00%
Investment Grade Fixed Income | >=90% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	60.00%
Investment Grade Fixed Income | >=95% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	53.00%
Investment Grade Fixed Income | >=95% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	73.00%
Investment Grade Fixed Income | >=100% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	70.00%
Investment Grade Fixed Income | >=100% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	100.00%
Below Investment Grade Fixed Income1 | Less Than 85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Below Investment Grade Fixed Income1 | Less Than 85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	15.00%
Below Investment Grade Fixed Income1 | >=85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Below Investment Grade Fixed Income1 | >=85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	15.00%
Below Investment Grade Fixed Income1 | >=90% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Below Investment Grade Fixed Income1 | >=90% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	15.00%
Below Investment Grade Fixed Income1 | >=95% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Below Investment Grade Fixed Income1 | >=95% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	10.00%
Below Investment Grade Fixed Income1 | >=100% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Below Investment Grade Fixed Income1 | >=100% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	10.00%
Other2 | Less Than 85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	5.00%
Other2 | Less Than 85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	20.00%
Other2 | >=85% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	5.00%
Other2 | >=85% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	20.00%
Other2 | >=90% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	5.00%
Other2 | >=90% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	20.00%
Other2 | >=95% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Other2 | >=95% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	15.00%
Other2 | >=100% PBO | Minimum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	0.00%
Other2 | >=100% PBO | Maximum
Defined Benefit Plan Disclosure [Line Items]
Permitted Range	15.00%

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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