Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Stock-Based Compensation
Increase in deferred compensation expense	$ 6.2
Unrecognized compensation costs related to unvested share-based compensation arrangements	$ 24.0
Weighted-average period for recognition of unrecognized stock-based compensation expense	2 years 7 months 6 days
Restricted Stock Units
Stock-Based Compensation
Awarded (in shares)	133,424
Weighted average granted date fair value (in dollars per share)	$ 100.26
Vesting period	3 years
Employees
Stock-Based Compensation
Stock-based compensation expense	$ 6.5	$ 0.3
Employees \| Restricted Stock Units
Stock-Based Compensation
Vesting period	4 years

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

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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