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Segment Financial Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement [Line Items]
Number of Reportable Segments	4
UNITED STATES
Statement [Line Items]
Disclosure on Geographic Areas Percentage of Revenue from External Customers	97.00%	96.00%	96.00%
Disclosure on Geographic Areas Percentage of Long Lived Assets	75.00%	72.00%
Revenues [Member] | CMS [Member]
Statement [Line Items]
Concentration Risk, Percentage	36.00%	33.00%	30.00%

X

- Definition

Disclosures about long-lived assets (except financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets) that are (1) located in the entity's country of domicile, and (2) located in all foreign countries in which the entity holds assets.

+ References

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- Definition

Disclosure about revenues from external customers (1) attributed to the entity's country of domicile and (2) attributed to all foreign countries in total from which the entity derives revenues.

+ References

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
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-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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-Section 50
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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

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- 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.

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