Income Taxes - Variation Between Expected and Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%	35.00%
State income taxes (net of federal benefit)	3.60%	5.30%	2.50%
Foreign derived intangible income deduction	(0.012)	(0.000)	(0.000)
Qualified domestic production activities	(0.00%)	(0.00%)	(2.60%)
Stock-based compensation expense	(2.10%)	(1.90%)	(8.20%)
Research and development tax credits	(7.80%)	(32.00%)	(50.60%)
Other tax credits	(0.00%)	(1.20%)	(7.50%)
Changes in valuation allowance	(1.60%)	0.70%	10.60%
Non-deductible book expenses	3.90%	8.20%	1.10%
Changes in deferred tax assets	(2.20%)	12.10%	15.40%
Re-measurement of deferred taxes for 2017 Tax Act	(0.000)	(0.000)	(1.713)
Changes in tax reserves	1.20%	1.20%	11.40%
Other	(0.80%)	(1.40%)	0.40%
Effective income tax (benefit) rate	14.00%	12.00%	(163.80%)