Stockholders' Equity - ESPP Activity (Details) - ESPP - shares	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-Based Compensation Arrangement By Share-Based Payment Award, Shares Available [Roll Forward]
Beginning balance, equity securities available (in shares)	149,199	184,860	208,159
Less: common stock purchased by eligible employees (shares)	(16,015)	(35,661)	(23,299)
Ending balance, equity securities available (in shares)	133,184	149,199	184,860

Number of share options (or share units) exercised during the current period.

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