Other Balance Sheet Items (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Reston Building Purchase Price	$ 19.8
Reston Building Purchase Price Allocation - Buildings	13.0
Reston Building Purchase Price Allocation - Land	6.8
Deposits Assets, Noncurrent	145.0	$ 145.0
Amortization of Other Deferred Charges	$ 39.5

Amount of amortization of other deferred costs recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration