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Segment Reporting (Revenue by Geographical Areas) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2020 | Mar. 31, 2019
Revenues from External Customers [Line Items] |  |
Revenues | $ 990.5 | $ 923.7
Revenue as Percentage of Consolidated Revenue | 100.00% | 100.00%
Domestic |  |
Revenues from External Customers [Line Items] |  |
Revenues | $ 945.4 | $ 881.1
Revenue as Percentage of Consolidated Revenue | 95.40% | 95.40%
Foreign |  |
Revenues from External Customers [Line Items] |  |
Revenues | $ 45.1 | $ 42.6
Revenue as Percentage of Consolidated Revenue | 4.60% | 4.60%

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