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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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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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Net number of non-option equity instruments granted to participants.

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Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-Based Compensation
Weighted average granted date fair value (in dollars per share)			$ 114.60
Allocated share based compensation expense			$ 690
Equity instruments granted (in shares)			6,601
Compensation expense			$ 756
Unrecognized compensation costs related to unvested share-based compensation arrangements	$ 20,300		$ 20,300
Weighted-average period for recognition of unrecognized stock-based compensation expense	2 years 3 months 18 days
Restricted Stock Units
Stock-Based Compensation
Awarded (in shares)			133,717
Weighted average granted date fair value (in dollars per share)			$ 100.93
Vesting period			3 years
Employees
Stock-Based Compensation
Stock-based compensation expense	$ 2,600	$ 4,000	$ 12,400	$ 9,500
Employees \| Restricted Stock Units
Stock-Based Compensation
Vesting period			4 years