Income Taxes	3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective tax rates for the three months ended March 31, 2018 and 2017 were 3% and 20%, respectively. The effective tax rates for the three months ended March 31, 2018 differed from the Federal statutory rate primarily due to the recognition of excess tax benefits of stock-based compensation and Federal and California research and development credits (“R&D”), partially offset by state taxes, foreign taxes, non-deductible expenses, and the international provisions from the U.S. tax reform enacted in December 2017. The effective tax rate for the three months ended March 31, 2017 differed from the Federal statutory rate primarily due to the recognition of excess tax benefits as a component of the provision for income taxes attributable to the adoption of ASU 2016-09 and Federal and California R&D credits offset by state taxes, foreign taxes and non-deductible expenses. The decrease in effective tax rate for the three months ended March 31, 2018 as compared to the same period in 2017 was due primarily to the reduction of the U.S. corporate tax rate from 35% to 21% as a result of the U.S. tax reform enacted in December 2017. For the three months ended March 31, 2018 and 2017, the Company recognized a discrete tax benefit related to the excess tax benefits from stock-based compensation of $60.7 million and $36.0 million, respectively. In December 2017, the Tax Cuts and Jobs Act of 2017 (the “Act”) was signed into law making significant changes to the Internal Revenue Code. Changes include, but are not limited to, a corporate tax rate decrease from 35% to 21% effective for tax years beginning after December 31, 2017, the transition of U.S. international taxation from a worldwide tax system to a territorial system, and a one-time transition tax on the mandatory deemed repatriation of cumulative foreign earnings as of December 31, 2017. On December 22, 2017, Staff Accounting Bulletin No. 118 (“SAB 118”) was issued to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Act. For the three months ended March 31, 2018, the Company obtained additional information affecting the provisional amount initially recorded for the transition tax for the three months ended December 31, 2017. As a result, the Company recorded an immaterial adjustment to the transition tax. Additional work is still necessary for a more detailed analysis of the Company's deferred tax assets and liabilities and its historical foreign earnings as well as potential correlative adjustments. Any subsequent adjustment to these amounts will be recorded to current tax expense in the quarter of 2018 when the analysis is complete. Gross unrecognized tax benefits were $47.8 million and $42.9 million as of March 31, 2018 and December 31, 2017, respectively. The gross unrecognized tax benefits, if recognized by the Company, will result in a reduction of approximately $44.5 million to the provision for income taxes thereby favorably impacting the Company’s effective tax rate. As of March 31, 2018, gross unrecognized tax benefits of $25.4 million was classified as “Other non-current liabilities” and $22.4 million as a reduction to deferred tax assets which was classified as "Other non-current assets" in the Consolidated Balance Sheets. The Company includes interest and penalties related to unrecognized tax benefits within the "Provision for income taxes" on the Consolidated Statements of Operations and “Other non-current liabilities” in the Consolidated Balance Sheets. Interest and penalties included in the Company’s “Provision for income taxes” were not material in any of the periods presented. Deferred tax assets of $500.6 million and $478.3 million were classified as “Other non-current assets” on the Consolidated Balance Sheets as of March 31, 2018 and December 31, 2017, respectively. In evaluating its ability to realize the net deferred tax assets, the Company considered all available positive and negative evidence, including its past operating results and the forecast of future market growth, forecasted earnings, future taxable income, and prudent and feasible tax planning strategies. The Company has a valuation allowance of $71.0 million and $49.4 million as of March 31, 2018 and December 31, 2017, respectively. The valuation allowance is primarily related to certain foreign tax credit carryovers that are not likely to be recognized. The Company files U.S. Federal, state and foreign tax returns. The Company is currently under examination by the IRS and the state of California for 2014 and 2015. The 2016 Federal tax return remains subject to examination by the IRS. The 2009 through 2016 state tax returns are subject to examination by state tax authorities. The Company has no significant foreign jurisdiction audits underway. The years 2012 through 2017 remain subject to examination by foreign tax authorities. Given the potential outcome of the current examinations as well as the impact of the current examinations on the potential expiration of the statute of limitations, it is reasonably possible that the balance of unrecognized tax benefits could significantly change within the next twelve months. At this time, an estimate of the range of reasonably possible adjustments to the balance of unrecognized tax benefits cannot be made.

Income Taxes

The effective tax rates for the three months ended March 31, 2018 and 2017 were 3% and 20%, respectively. The effective tax rates for the three months ended March 31, 2018 differed from the Federal statutory rate primarily due to the recognition of excess tax benefits of stock-based compensation and Federal and California research and development credits (“R&D”), partially offset by state taxes, foreign taxes, non-deductible expenses, and the international provisions from the U.S. tax reform enacted in December 2017. The effective tax rate for the three months ended March 31, 2017 differed from the Federal statutory rate primarily due to the recognition of excess tax benefits as a component of the provision for income taxes attributable to the adoption of ASU 2016-09 and Federal and California R&D credits offset by state taxes, foreign taxes and non-deductible expenses. The decrease in effective tax rate for the three months ended March 31, 2018 as compared to the same period in 2017 was due primarily to the reduction of the U.S. corporate tax rate from 35% to 21% as a result of the U.S. tax reform enacted in December 2017. For the three months ended March 31, 2018 and 2017, the Company recognized a discrete tax benefit related to the excess tax benefits from stock-based compensation of $60.7 million and $36.0 million, respectively.

In December 2017, the Tax Cuts and Jobs Act of 2017 (the “Act”) was signed into law making significant changes to the Internal Revenue Code. Changes include, but are not limited to, a corporate tax rate decrease from 35% to 21% effective for tax years beginning after December 31, 2017, the transition of U.S. international taxation from a worldwide tax system to a territorial system, and a one-time transition tax on the mandatory deemed repatriation of cumulative foreign earnings as of December 31, 2017.

On December 22, 2017, Staff Accounting Bulletin No. 118 (“SAB 118”) was issued to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Act. For the three months ended March 31, 2018, the Company obtained additional information affecting the provisional amount initially recorded for the transition tax for the three months ended December 31, 2017. As a result, the Company recorded an immaterial adjustment to the transition tax. Additional work is still necessary for a more detailed analysis of the Company's deferred tax assets and liabilities and its historical foreign earnings as well as potential correlative adjustments. Any subsequent adjustment to these amounts will be recorded to current tax expense in the quarter of 2018 when the analysis is complete.

Gross unrecognized tax benefits were $47.8 million and $42.9 million as of March 31, 2018 and December 31, 2017, respectively. The gross unrecognized tax benefits, if recognized by the Company, will result in a reduction of approximately $44.5 million to the provision for income taxes thereby favorably impacting the Company’s effective tax rate. As of March 31, 2018, gross unrecognized tax benefits of $25.4 million was classified as “Other non-current liabilities” and $22.4 million as a reduction to deferred tax assets which was classified as "Other non-current assets" in the Consolidated Balance Sheets. The Company includes interest and penalties related to unrecognized tax benefits within the "Provision for income taxes" on the Consolidated Statements of Operations and “Other non-current liabilities” in the Consolidated Balance Sheets. Interest and penalties included in the Company’s “Provision for income taxes” were not material in any of the periods presented.

Deferred tax assets of $500.6 million and $478.3 million were classified as “Other non-current assets” on the Consolidated Balance Sheets as of March 31, 2018 and December 31, 2017, respectively. In evaluating its ability to realize the net deferred tax assets, the Company considered all available positive and negative evidence, including its past operating results and the forecast of future market growth, forecasted earnings, future taxable income, and prudent and feasible tax planning strategies. The Company has a valuation allowance of $71.0 million and $49.4 million as of March 31, 2018 and December 31, 2017, respectively. The valuation allowance is primarily related to certain foreign tax credit carryovers that are not likely to be recognized.

The Company files U.S. Federal, state and foreign tax returns. The Company is currently under examination by the IRS and the state of California for 2014 and 2015. The 2016 Federal tax return remains subject to examination by the IRS. The 2009 through 2016 state tax returns are subject to examination by state tax authorities. The Company has no significant foreign jurisdiction audits underway. The years 2012 through 2017 remain subject to examination by foreign tax authorities.

Given the potential outcome of the current examinations as well as the impact of the current examinations on the potential expiration of the statute of limitations, it is reasonably possible that the balance of unrecognized tax benefits could significantly change within the next twelve months. At this time, an estimate of the range of reasonably possible adjustments to the balance of unrecognized tax benefits cannot be made.