Revenue Recognition (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues [Abstract]
Concentration risk, percentage	34.00%	33.00%	32.00%
Concentration risk second customer			10.00%
Deferred Revenue, Revenue Recognized	$ 729.0

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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