Income Taxes	3 Months Ended
Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company recorded a provision for (benefit from) income taxes of $0.3 million and $(3.2) million for the three months ended March 31, 2019 and 2018, respectively. The provision for income taxes for the three months ended March 31, 2019 is driven by a combination of the valuation allowance recorded on U.S. deferred tax assets and the projected annual effective tax rate for the foreign jurisdictions for 2019. The benefit from income taxes for the three months ended March 31, 2018 is mainly due to projected pretax losses from which the company can benefit from. During the three months ended March 31, 2019 and 2018, the Company paid withholding taxes of $4.3 million and $6.1 million, respectively. As of March 31, 2019, the Company’s unaudited condensed consolidated balance sheets included net deferred tax assets, before valuation allowance, of approximately $165.6 million, which consists of net operating loss carryovers, tax credit carryovers, amortization, employee stock-based compensation expenses and certain liabilities. The Company periodically evaluates the realizability of its net deferred tax assets based on all available evidence, both positive and negative. During the third quarter of 2018, the Company assessed the changes in its underlying facts and circumstances and evaluated the realizability of its existing deferred tax assets based on all available evidence, both positive and negative, and the weight accorded to each, and concluded a full valuation allowance associated with U.S. federal and state deferred tax assets was appropriate. The basis for this conclusion was derived primarily from the fact that the Company completed its forecasting process during the third quarter of 2018. At a domestic level, losses are expected in future periods in part due to the impact of the adoption of ASC 606. In addition, the decrease in the U.S. federal tax rate from 35% to 21% as a result of U.S. tax reform has further reduced the Company's ability to utilize its deferred tax assets. In light of the above factors, the Company concluded that it is not more likely than not that it can realize its U.S. deferred tax assets. As such, during the third quarter of 2018, the Company set up and continues to maintain a full valuation allowance against its U.S. federal deferred tax assets. The Company has U.S. federal deferred tax assets related to research and development credits, foreign tax credits and other tax attributes that can be used to offset federal taxable income in future periods. These credit carryforwards will expire if they are not used within certain time periods. It is possible that some or all of these attributes could ultimately expire unused. The Company has U.S. federal deferred tax assets related to research and development credits, foreign tax credits and other tax attributes that can be used to offset federal taxable income in future periods. These credit carryforwards will expire if they are not used within certain time periods. It is possible that some or all of these attributes could ultimately expire unused. As of March 31, 2019, the Company has a total valuation allowance of $179.9 million on U.S. federal, state and foreign deferred tax assets, resulting in net deferred tax liability of $14.3 million. The Company maintains liabilities for uncertain tax positions within its long-term income taxes payable accounts and as a reduction to existing deferred tax assets to the extent tax attributes are available to offset such liabilities. These liabilities involve judgment and estimation and are monitored by management based on the best information available including changes in tax regulations, the outcome of relevant court cases and other information. As of March 31, 2019, the Company had approximately $24.5 million of unrecognized tax benefits, including $22.2 million recorded as a reduction of long-term deferred tax assets and $2.3 million in long-term income taxes payable. If recognized, approximately $2.3 million would be recorded as an income tax benefit. As of December 31, 2018, the Company had $23.5 million of unrecognized tax benefits, including $21.4 million recorded as a reduction of long-term deferred tax assets and $2.1 million recorded in long-term income taxes payable. Although it is possible that some of the unrecognized tax benefits could be settled within the next 12 months, the Company cannot reasonably estimate the outcome at this time. The Company recognizes interest and penalties related to uncertain tax positions as a component of the income tax provision. At March 31, 2019 and December 31, 2018, an immaterial amount of interest and penalties is included in long-term income taxes payable. Rambus files income tax returns for the U.S., California, India, the U.K., the Netherlands and various other state and foreign jurisdictions. The U.S. federal returns are subject to examination from 2015 and forward. The California returns are subject to examination from 2010 and forward. In addition, any research and development credit carryforward or net operating loss carryforward generated in prior years and utilized in these or future years may also be subject to examination. The India returns are subject to examination from fiscal year ending March 2012 and forward. The Company is currently under examination by the IRS for the 2015 tax year and California for the 2010 and 2011 tax years. The Company’s India subsidiary is under examination by the Indian tax administration for tax years beginning with 2011, except for 2014, which was assessed in the Company's favor. The Company’s France subsidiary is under examination by the French tax agency for the 2013 to 2017 tax years. These examinations may result in proposed adjustments to the income taxes as filed during these periods. Management regularly assesses the likelihood of outcomes resulting from income tax examinations to determine the adequacy of their provision for income taxes and believes their provision for unrecognized tax benefits is adequate. Additionally, the Company's future effective tax rates could be adversely affected by earnings being higher than anticipated in countries where the Company has higher statutory rates or lower than anticipated in countries where it has lower statutory rates, by changes in valuation of its deferred tax assets and liabilities or by changes in tax laws or interpretations of those laws.

Income Taxes

The Company recorded a provision for (benefit from) income taxes of $0.3 million and $(3.2) million for the three months ended March 31, 2019 and 2018, respectively. The provision for income taxes for the three months ended March 31, 2019 is driven by a combination of the valuation allowance recorded on U.S. deferred tax assets and the projected annual effective tax rate for the foreign jurisdictions for 2019. The benefit from income taxes for the three months ended March 31, 2018 is mainly due to projected pretax losses from which the company can benefit from.

During the three months ended March 31, 2019 and 2018, the Company paid withholding taxes of $4.3 million and $6.1 million, respectively.

As of March 31, 2019, the Company’s unaudited condensed consolidated balance sheets included net deferred tax assets, before valuation allowance, of approximately $165.6 million, which consists of net operating loss carryovers, tax credit carryovers, amortization, employee stock-based compensation expenses and certain liabilities.

The Company periodically evaluates the realizability of its net deferred tax assets based on all available evidence, both positive and negative. During the third quarter of 2018, the Company assessed the changes in its underlying facts and circumstances and evaluated the realizability of its existing deferred tax assets based on all available evidence, both positive and negative, and the weight accorded to each, and concluded a full valuation allowance associated with U.S. federal and state deferred tax assets was appropriate. The basis for this conclusion was derived primarily from the fact that the Company completed its forecasting process during the third quarter of 2018. At a domestic level, losses are expected in future periods in part due to the impact of the adoption of ASC 606. In addition, the decrease in the U.S. federal tax rate from 35% to 21% as a result of U.S. tax reform has further reduced the Company's ability to utilize its deferred tax assets. In light of the above factors, the Company concluded that it is not more likely than not that it can realize its U.S. deferred tax assets. As such, during the third quarter of 2018, the Company set up and continues to maintain a full valuation allowance against its U.S. federal deferred tax assets. The Company has U.S. federal deferred tax assets related to research and development credits, foreign tax credits and other tax attributes that can be used to offset federal taxable income in future periods. These credit carryforwards will expire if they are not used within certain time periods. It is possible that some or all of these attributes could ultimately expire unused.

The Company has U.S. federal deferred tax assets related to research and development credits, foreign tax credits and other tax attributes that can be used to offset federal taxable income in future periods. These credit carryforwards will expire if they are not used within certain time periods. It is possible that some or all of these attributes could ultimately expire unused.

As of March 31, 2019, the Company has a total valuation allowance of $179.9 million on U.S. federal, state and foreign deferred tax assets, resulting in net deferred tax liability of $14.3 million.

The Company maintains liabilities for uncertain tax positions within its long-term income taxes payable accounts and as a reduction to existing deferred tax assets to the extent tax attributes are available to offset such liabilities. These liabilities involve judgment and estimation and are monitored by management based on the best information available including changes in tax regulations, the outcome of relevant court cases and other information.

As of March 31, 2019, the Company had approximately $24.5 million of unrecognized tax benefits, including $22.2 million recorded as a reduction of long-term deferred tax assets and $2.3 million in long-term income taxes payable. If recognized, approximately $2.3 million would be recorded as an income tax benefit. As of December 31, 2018, the Company had $23.5 million of unrecognized tax benefits, including $21.4 million recorded as a reduction of long-term deferred tax assets and $2.1 million recorded in long-term income taxes payable.

Although it is possible that some of the unrecognized tax benefits could be settled within the next 12 months, the Company cannot reasonably estimate the outcome at this time.

The Company recognizes interest and penalties related to uncertain tax positions as a component of the income tax provision. At March 31, 2019 and December 31, 2018, an immaterial amount of interest and penalties is included in long-term income taxes payable.

Rambus files income tax returns for the U.S., California, India, the U.K., the Netherlands and various other state and foreign jurisdictions. The U.S. federal returns are subject to examination from 2015 and forward. The California returns are subject to examination from 2010 and forward. In addition, any research and development credit carryforward or net operating loss carryforward generated in prior years and utilized in these or future years may also be subject to examination. The India returns are subject to examination from fiscal year ending March 2012 and forward. The Company is currently under examination by the IRS for the 2015 tax year and California for the 2010 and 2011 tax years. The Company’s India subsidiary is under examination by the Indian tax administration for tax years beginning with 2011, except for 2014, which was assessed in the Company's favor. The Company’s France subsidiary is under examination by the French tax agency for the 2013 to 2017 tax years. These examinations may result in proposed adjustments to the income taxes as filed during these periods. Management regularly assesses the likelihood of outcomes resulting from income tax examinations to determine the adequacy of their provision for income taxes and believes their provision for unrecognized tax benefits is adequate.

Additionally, the Company's future effective tax rates could be adversely affected by earnings being higher than anticipated in countries where the Company has higher statutory rates or lower than anticipated in countries where it has lower statutory rates, by changes in valuation of its deferred tax assets and liabilities or by changes in tax laws or interpretations of those laws.