Income Taxes	3 Months Ended
Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to U.S. federal, state, and foreign income taxes. For the three months ended March 31, 2019, the Company recorded a provision for income taxes of $51.5 million. The Company’s effective tax rate for the three months ended March 31, 2019 is lower than the U.S. statutory rate primarily due to excess tax benefits related to stock-based compensation and utilization of net operating losses to offset pre-tax operating income. The Company’s provision for income taxes for the three months ended March 31, 2019 increased compared to historical amounts due to the release of the Company’s valuation allowance on the majority of its net operating losses and other deferred tax assets as of December 31, 2018. Starting in the three months ended March 31, 2019, the Company began recording a provision for income taxes on its pre-tax income using an estimated effective tax rate that approximates statutory rates. Due to the Company's ability to offset its pre-tax income against previously benefited net operating losses, it expects the majority of its tax provision to represent a non-cash expense until its net operating losses have been fully utilized. During the three months ended March 31, 2018, the Company’s benefit from income taxes of $12.7 million included a benefit from income taxes of $21.9 million from excess tax benefits related to stock-based compensation partially offset by provisions for income taxes of $6.4 million related to BioAxone’s income taxes (as a result of an increase in the fair value of the contingent payments payable by the Company to BioAxone) and the Company’s U.S. state and foreign taxes. As noted above, the Company released the valuation allowance on the majority of net operating losses and other deferred tax assets and maintained a valuation allowance of $168.5 million related primarily to U.S. state and foreign tax attributes as of December 31, 2018. On a periodic basis, the Company reassesses any valuation allowances that it maintains on its deferred tax assets, weighing positive and negative evidence to assess the recoverability of the deferred tax assets. The Company has reviewed the tax positions taken, or to be taken, in its tax returns for all tax years currently open to examination by a taxing authority. Unrecognized tax benefits represent the aggregate tax effect of differences between tax return positions and the benefits recognized in the financial statements. As of March 31, 2019 and December 31, 2018, the Company had $25.2 million and $19.5 million, respectively, of gross unrecognized tax benefits, which would affect the Company’s tax rate if recognized. The Company does not expect that its unrecognized tax benefits will materially increase within the next twelve months. The Company accrues interest and penalties related to unrecognized tax benefits as a component of its provision for income taxes. As of March 31, 2019, no significant interest or penalties were accrued. The Company did not recognize any material interest or penalties related to uncertain tax positions during the three months ended March 31, 2019 and 2018. As of March 31, 2019, foreign earnings, which were not significant, have been retained indefinitely by foreign subsidiaries for indefinite reinvestment. Upon repatriation of those earnings, in the form of dividends or otherwise, the Company could be subject to withholding taxes payable to the various foreign countries. The Company files U.S. federal income tax returns and income tax returns in various state, local and foreign jurisdictions. The Company is no longer subject to any tax assessment from an income tax examination in the United States or any other major taxing jurisdiction for years before 2011, except where the Company has net operating losses or tax credit carryforwards that originate before 2011. The Company has various income tax audits ongoing at any time throughout the world. No adjustments have been reported for any jurisdiction under audit.

Income Taxes

The Company is subject to U.S. federal, state, and foreign income taxes. For the three months ended March 31, 2019, the Company recorded a provision for income taxes of $51.5 million. The Company’s effective tax rate for the three months ended March 31, 2019 is lower than the U.S. statutory rate primarily due to excess tax benefits related to stock-based compensation and utilization of net operating losses to offset pre-tax operating income. The Company’s provision for income taxes for the three months ended March 31, 2019 increased compared to historical amounts due to the release of the Company’s valuation allowance on the majority of its net operating losses and other deferred tax assets as of December 31, 2018. Starting in the three months ended March 31, 2019, the Company began recording a provision for income taxes on its pre-tax income using an estimated effective tax rate that approximates statutory rates. Due to the Company's ability to offset its pre-tax income against previously benefited net operating losses, it expects the majority of its tax provision to represent a non-cash expense until its net operating losses have been fully utilized.

During the three months ended March 31, 2018, the Company’s benefit from income taxes of $12.7 million included a benefit from income taxes of $21.9 million from excess tax benefits related to stock-based compensation partially offset by provisions for income taxes of $6.4 million related to BioAxone’s income taxes (as a result of an increase in the fair value of the contingent payments payable by the Company to BioAxone) and the Company’s U.S. state and foreign taxes.

As noted above, the Company released the valuation allowance on the majority of net operating losses and other deferred tax assets and maintained a valuation allowance of $168.5 million related primarily to U.S. state and foreign tax attributes as of December 31, 2018. On a periodic basis, the Company reassesses any valuation allowances that it maintains on its deferred tax assets, weighing positive and negative evidence to assess the recoverability of the deferred tax assets.

The Company has reviewed the tax positions taken, or to be taken, in its tax returns for all tax years currently open to examination by a taxing authority. Unrecognized tax benefits represent the aggregate tax effect of differences between tax return positions and the benefits recognized in the financial statements. As of March 31, 2019 and December 31, 2018, the Company had $25.2 million and $19.5 million, respectively, of gross unrecognized tax benefits, which would affect the Company’s tax rate if recognized. The Company does not expect that its unrecognized tax benefits will materially increase within the next twelve months. The Company accrues interest and penalties related to unrecognized tax benefits as a component of its provision for income taxes. As of March 31, 2019, no significant interest or penalties were accrued. The Company did not recognize any material interest or penalties related to uncertain tax positions during the three months ended March 31, 2019 and 2018.

As of March 31, 2019, foreign earnings, which were not significant, have been retained indefinitely by foreign subsidiaries for indefinite reinvestment. Upon repatriation of those earnings, in the form of dividends or otherwise, the Company could be subject to withholding taxes payable to the various foreign countries.

The Company files U.S. federal income tax returns and income tax returns in various state, local and foreign jurisdictions. The Company is no longer subject to any tax assessment from an income tax examination in the United States or any other major taxing jurisdiction for years before 2011, except where the Company has net operating losses or tax credit carryforwards that originate before 2011. The Company has various income tax audits ongoing at any time throughout the world. No adjustments have been reported for any jurisdiction under audit.