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Stock Plans - Stock-based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total stock-based compensation expense	$ 11,137	$ 22,250	$ 27,604
Tax benefit	1,815	3,455	5,387
Stock-based compensation cost related to non-vested equity awards not yet recognized as an expense	$ 12,800
Weighted-average period over which stock-based compensation cost related to non-vested equity awards is expected to be recognized	9 months 18 days
Stock options
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total stock-based compensation expense	$ 1,308	7,348	7,368
Restricted stock awards
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total stock-based compensation expense	9,743	14,775	20,216
Performance Based Cash Units
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total stock-based compensation expense	86	127	20
Stock-based compensation cost related to non-vested equity awards not yet recognized as an expense	$ 300
Weighted-average period over which stock-based compensation cost related to non-vested equity awards is expected to be recognized	1 year 7 months 6 days
Cost of revenues
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total stock-based compensation expense	$ 2,409	2,929	4,370
Research and development
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total stock-based compensation expense	4,380	4,227	6,055
Selling, general and administrative
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total stock-based compensation expense	$ 4,348	$ 15,094	$ 17,179

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