Stock-Based Compensation - Expense (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock-Based Compensation
Total non-recognized non-cash compensation expense	$ 24.2
Weighted-average period	2 years 6 months
Selling, general and administrative expense and operating expenses (excluding depreciation and amortization)
Stock-Based Compensation
Non-cash compensation expense	$ 11.1	$ 10.1	$ 13.0

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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