Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Stock-Based Compensation
Stock-based compensation expense	$ 1,700	$ 1,700
Proceeds from exercise of stock options	$ 4,499	$ 1,828
Common Stock
Stock-Based Compensation
Exercise of stock options (in shares)	540,000	288,000
Common Stock \| Employee stock purchase plan
Stock-Based Compensation
Exercise of stock options (in shares)	600,000	300,000
Proceeds from exercise of stock options	$ 4,500	$ 1,800
2000 Stock Plan
Stock-Based Compensation
Number of shares of common stock available for future grants	0

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

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