Commitments and Contingencies	6 Months Ended
Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments The Company’s principal commitments consist of future payment obligations under capital leases to finance data centers and other computer and networking equipment purchases, debt agreements (see Note 6), operating lease agreements for office space, research and development, and sales and marketing facilities, and agreements with third parties to provide co-location hosting, telecommunication usage and equipment maintenance services. These commitments as of December 31, 2017 are disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017, and did not change materially during the six months ended June 30, 2018 except for the acquisition of certain additional data center and network equipment and software under multiple capital leases, and certain hosting and telecommunications agreements. As of June 30, 2018, the total minimum future payment commitments under these capital leases added during the six months ended June 30, 2018 were approximately $6.9 million, of which $1.4 million is due during the remainder of 2018, with the remaining $5.5 million due in 2019 to 2021. During the six months ended June 30, 2018, the Company entered into or renewed various hosting and telecommunications agreements for terms of 12 to 36 months commencing on various dates in 2018. These agreements require the Company to make monthly payments over the service term in exchange for certain network services. The Company’s total minimum future payment commitments under these agreements are $2.5 million. Universal Services Fund Liability During the third quarter of 2012, the Company determined that based on its business activities, it is classified as a telecommunications service provider for regulatory purposes and it should make direct contributions to the federal USF and related funds based on revenues it receives from the resale of interstate and international telecommunications services. In order to comply with the obligation to make direct contributions, the Company made a voluntary self-disclosure to the FCC Enforcement Bureau and registered with the USAC, which is charged by the FCC with administering the USF. The Company filed exemption certificates with its wholesale telecommunications service providers in order to eliminate its obligation to reimburse such wholesale telecommunications service providers for their USF contributions calculated on services sold to the Company. In April 2013, the Company began remitting required contributions on a prospective basis directly to USAC. The Company’s registration with USAC subjects it to assessments for unpaid USF contributions, as well as interest thereon and civil penalties, due to its late registration and past failure to recognize its obligation as a USF contributor and as an international carrier. The Company is required to pay assessments for periods prior to the Company’s registration. As of December 31, 2012, the total past due USF contribution being imposed by USAC and accrued by the Company for the period from 2003 through 2012 was $8.1 million, of which $4.7 million was undisputed and $3.4 million was disputed. The Company subsequently updated its filings and increased the liability related to 2008 through 2012 by $0.5 million, arriving at a new total of $3.9 million in disputed liability. In July 2013, the Company and USAC agreed to a financing arrangement for $4.1 million of the undisputed $4.7 million of the unpaid USF contributions whereby the Company issued to USAC a promissory note payable in the principal amount of the $4.1 million and paid off the remaining undisputed $0.6 million. The Company had fully paid the promissory note as of January 2017. In January 2017, the FCC’s Wireline Competition Bureau ruled in the Company’s favor with respect to most of the disputed amount. In September 2017, USAC issued a credit to the Company reflecting the FCC’s ruling for the $3.1 million of the $3.9 million in disputed liability. In addition, USAC reversed the interest and penalties related to the disputed liability of $3.1 million. The remaining $0.8 million in dispute involves USAC’s assessment of liability for the period of 2003 through 2007, which was prior to the five year window during which the Company was required to maintain financial records for USF contribution purposes. The Company filed a Request for Review (a form of appeal) of this disputed amount with the FCC’s Wireline Competition Bureau in 2013, which remains pending. If the Request for Review is not resolved in the Company’s favor, it is possible that the Company will be held to the back assessments of $0.8 million, which includes interest and penalties on that amount. As of June 30, 2018, the accrued liability on the remaining disputed assessments, including interest and penalties for the period of 2003 through 2007, was $0.8 million offset by $0.7 million in other USF credits. State and Local Taxes and Surcharges In April 2012, the Company commenced collecting and remitting sales taxes on sales of subscription services in all the U.S. states in which it determined it was obligated to do so. During the first quarter of 2015, the Company conducted an updated sales tax review of the taxability of sales of its subscription services. As a result, the Company determined that it may be obligated to collect and remit sales taxes on such sales in four additional states. Based on its best estimate of the probable sales tax liability in those four states relating to its sales of subscription services during the period 2011 through 2014, during the three months ended March 31, 2015, the Company recorded a general and administrative expense of $0.6 million to accrue for such taxes. During 2013, the Company analyzed its activities and determined it may be obligated to collect and remit various state and local taxes and surcharges on its usage-based fees. The Company had not remitted state and local taxes on usage-based fees in any of the periods prior to 2014 and therefore accrued a sales tax liability for this contingency. In January 2014, the Company commenced paying such taxes and surcharges to certain state authorities. In June 2014, the Company commenced collecting state and local taxes or surcharges on usage-based fees from its clients on a current basis and remitting such taxes to the applicable U.S. state taxing authorities. As of June 30, 2018 and December 31, 2017, the Company had accrued liabilities of $1.3 million and $1.5 million, respectively, for such contingent sales taxes and surcharges that were not being collected from its clients but may be imposed by various taxing authorities, of which $0.3 million and $0.4 million, respectively, were included in current “Sales tax liability” on the condensed consolidated balance sheets, and the remaining were included in non-current “Sales tax liability” on the condensed consolidated balance sheets. The Company’s estimate of the probable loss incurred under this contingency is based on its analysis of the source location of its usage-based fees and the regulations and rules in each tax jurisdiction. Legal Matters The Company is involved in various legal and regulatory matters arising in the normal course of business. In management’s opinion, resolution of these matters is not expected to have a material impact on the Company’s consolidated results of operations, cash flows, or its financial position. However, due to the uncertain nature of legal matters, an unfavorable resolution of a matter could materially affect the Company’s future consolidated results of operations, cash flows or financial position in a particular period. The Company expenses legal fees as incurred. Indemnification Agreements In the ordinary course of business, the Company enters into agreements of varying scope and terms pursuant to which it agrees to indemnify clients, vendors, lessors, business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of breach of such agreements, services to be provided by the Company or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with directors and certain officers and employees that will require it, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. Other than as described below, no demands have been made upon the Company to provide indemnification under such agreements and there are no claims that it is aware of that could have a material effect on the consolidated balance sheet, consolidated statement of operations and comprehensive loss, or consolidated statements of cash flows. On October 27, 2016, the Company received notice from Lance Fried, a former officer and director of Face It, Corp., of his claim for indemnification by the Company (as successor in interest to Face It), and for advancement of all legal fees and expenses he incurs in connection with the defense of a lawsuit captioned Melcher, et al. v. Five9, Inc., et al., No. 16-cv-02440, in the U.S. District Court for the Southern District of California. In the lawsuit, plaintiff Carl Melcher, a purported former stockholder of Face It, and his related investment entity Melcher Family Limited Partnership, allege that Face It repurchased the plaintiffs’ stock in September 2013 before Five9 acquired Face It, and that in connection with the repurchase, Fried made material misstatements or omissions to Melcher, by failing to disclose that Face It allegedly was in concurrent discussions about a potential sale of the company to Five9. The lawsuit alleges violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder, as well as various claims under state law and common law. To date, the Company has advanced Mr. Fried $62 thousand in connection with this claim. However, the Company disputes that Mr. Fried is entitled to advancement in connection with the Melcher litigation. On January 9, 2018, Mr. Fried initiated an arbitration against the Company in which he alleged that the Company breached advancement obligations to him. On June 11, 2018, the arbitrator ordered the Company to advance the fees Mr. Fried incurs (and has already incurred) in connection with the defense of the Melcher litigation. After the arbitrator’s order, Fried claimed that he is entitled to approximately $0.2 million of fees incurred to date. The Company disputes that amount. Regardless of the arbitrator’s order, Mr. Fried is required to reimburse the Company for any amounts advanced to him if it is ultimately determined that Mr. Fried is not entitled to indemnification in connection with the Melcher litigation. In addition, the Company believes that it has indemnification rights against the former stockholders of Face It (including Mr. Fried) for all losses that are incurred by the Company in connection with the Melcher litigation, including without limitation, amounts incurred to indemnify or advance the legal fees and expenses of Mr. Fried pursuant to his indemnification claim against the Company. The Company has asserted claims in arbitration against both Mr. Fried and the representative of the former Face It stockholders to recoup these losses. These claims are stayed pending the resolution of the Melcher litigation.

Commitments and Contingencies

Commitments

The Company’s principal commitments consist of future payment obligations under capital leases to finance data centers and other computer and networking equipment purchases, debt agreements (see Note 6), operating lease agreements for office space, research and development, and sales and marketing facilities, and agreements with third parties to provide co-location hosting, telecommunication usage and equipment maintenance services. These commitments as of December 31, 2017 are disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017, and did not change materially during the six months ended June 30, 2018 except for the acquisition of certain additional data center and network equipment and software under multiple capital leases, and certain hosting and telecommunications agreements. As of June 30, 2018, the total minimum future payment commitments under these capital leases added during the six months ended June 30, 2018 were approximately $6.9 million, of which $1.4 million is due during the remainder of 2018, with the remaining $5.5 million due in 2019 to 2021.

During the six months ended June 30, 2018, the Company entered into or renewed various hosting and telecommunications agreements for terms of 12 to 36 months commencing on various dates in 2018. These agreements require the Company to make monthly payments over the service term in exchange for certain network services. The Company’s total minimum future payment commitments under these agreements are $2.5 million.

Universal Services Fund Liability

During the third quarter of 2012, the Company determined that based on its business activities, it is classified as a telecommunications service provider for regulatory purposes and it should make direct contributions to the federal USF and related funds based on revenues it receives from the resale of interstate and international telecommunications services. In order to comply with the obligation to make direct contributions, the Company made a voluntary self-disclosure to the FCC Enforcement Bureau and registered with the USAC, which is charged by the FCC with administering the USF. The Company filed exemption certificates with its wholesale telecommunications service providers in order to eliminate its obligation to reimburse such wholesale telecommunications service providers for their USF contributions calculated on services sold to the Company. In April 2013, the Company began remitting required contributions on a prospective basis directly to USAC.

The Company’s registration with USAC subjects it to assessments for unpaid USF contributions, as well as interest thereon and civil penalties, due to its late registration and past failure to recognize its obligation as a USF contributor and as an international carrier. The Company is required to pay assessments for periods prior to the Company’s registration. As of December 31, 2012, the total past due USF contribution being imposed by USAC and accrued by the Company for the period from 2003 through 2012 was $8.1 million, of which $4.7 million was undisputed and $3.4 million was disputed. The Company subsequently updated its filings and increased the liability related to 2008 through 2012 by $0.5 million, arriving at a new total of $3.9 million in disputed liability. In July 2013, the Company and USAC agreed to a financing arrangement for $4.1 million of the undisputed $4.7 million of the unpaid USF contributions whereby the Company issued to USAC a promissory note payable in the principal amount of the $4.1 million and paid off the remaining undisputed $0.6 million. The Company had fully paid the promissory note as of January 2017.

In January 2017, the FCC’s Wireline Competition Bureau ruled in the Company’s favor with respect to most of the disputed amount. In September 2017, USAC issued a credit to the Company reflecting the FCC’s ruling for the $3.1 million of the $3.9 million in disputed liability. In addition, USAC reversed the interest and penalties related to the disputed liability of $3.1 million. The remaining $0.8 million in dispute involves USAC’s assessment of liability for the period of 2003 through 2007, which was prior to the five year window during which the Company was required to maintain financial records for USF contribution purposes. The Company filed a Request for Review (a form of appeal) of this disputed amount with the FCC’s Wireline Competition Bureau in 2013, which remains pending. If the Request for Review is not resolved in the Company’s favor, it is possible that the Company will be held to the back assessments of $0.8 million, which includes interest and penalties on that amount.

As of June 30, 2018, the accrued liability on the remaining disputed assessments, including interest and penalties for the period of 2003 through 2007, was $0.8 million offset by $0.7 million in other USF credits.

State and Local Taxes and Surcharges

In April 2012, the Company commenced collecting and remitting sales taxes on sales of subscription services in all the U.S. states in which it determined it was obligated to do so. During the first quarter of 2015, the Company conducted an updated sales tax review of the taxability of sales of its subscription services. As a result, the Company determined that it may be obligated to collect and remit sales taxes on such sales in four additional states. Based on its best estimate of the probable sales tax liability in those four states relating to its sales of subscription services during the period 2011 through 2014, during the three months ended March 31, 2015, the Company recorded a general and administrative expense of $0.6 million to accrue for such taxes.

During 2013, the Company analyzed its activities and determined it may be obligated to collect and remit various state and local taxes and surcharges on its usage-based fees. The Company had not remitted state and local taxes on usage-based fees in any of the periods prior to 2014 and therefore accrued a sales tax liability for this contingency. In January 2014, the Company commenced paying such taxes and surcharges to certain state authorities. In June 2014, the Company commenced collecting state and local taxes or surcharges on usage-based fees from its clients on a current basis and remitting such taxes to the applicable U.S. state taxing authorities.

As of June 30, 2018 and December 31, 2017, the Company had accrued liabilities of $1.3 million and $1.5 million, respectively, for such contingent sales taxes and surcharges that were not being collected from its clients but may be imposed by various taxing authorities, of which $0.3 million and $0.4 million, respectively, were included in current “Sales tax liability” on the condensed consolidated balance sheets, and the remaining were included in non-current “Sales tax liability” on the condensed consolidated balance sheets. The Company’s estimate of the probable loss incurred under this contingency is based on its analysis of the source location of its usage-based fees and the regulations and rules in each tax jurisdiction.

Legal Matters

The Company is involved in various legal and regulatory matters arising in the normal course of business. In management’s opinion, resolution of these matters is not expected to have a material impact on the Company’s consolidated results of operations, cash flows, or its financial position. However, due to the uncertain nature of legal matters, an unfavorable resolution of a matter could materially affect the Company’s future consolidated results of operations, cash flows or financial position in a particular period. The Company expenses legal fees as incurred.

Indemnification Agreements

In the ordinary course of business, the Company enters into agreements of varying scope and terms pursuant to which it agrees to indemnify clients, vendors, lessors, business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of breach of such agreements, services to be provided by the Company or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with directors and certain officers and employees that will require it, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. Other than as described below, no demands have been made upon the Company to provide indemnification under such agreements and there are no claims that it is aware of that could have a material effect on the consolidated balance sheet, consolidated statement of operations and comprehensive loss, or consolidated statements of cash flows.

On October 27, 2016, the Company received notice from Lance Fried, a former officer and director of Face It, Corp., of his claim for indemnification by the Company (as successor in interest to Face It), and for advancement of all legal fees and expenses he incurs in connection with the defense of a lawsuit captioned Melcher, et al. v. Five9, Inc., et al., No. 16-cv-02440, in the U.S. District Court for the Southern District of California. In the lawsuit, plaintiff Carl Melcher, a purported former stockholder of Face It, and his related investment entity Melcher Family Limited Partnership, allege that Face It repurchased the plaintiffs’ stock in September 2013 before Five9 acquired Face It, and that in connection with the repurchase, Fried made material misstatements or omissions to Melcher, by failing to disclose that Face It allegedly was in concurrent discussions about a potential sale of the company to Five9. The lawsuit alleges violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder, as well as various claims under state law and common law. To date, the Company has advanced Mr. Fried $62 thousand in connection with this claim. However, the Company disputes that Mr. Fried is entitled to advancement in connection with the Melcher litigation. On January 9, 2018, Mr. Fried initiated an arbitration against the Company in which he alleged that the Company breached advancement obligations to him. On June 11, 2018, the arbitrator ordered the Company to advance the fees Mr. Fried incurs (and has already incurred) in connection with the defense of the Melcher litigation. After the arbitrator’s order, Fried claimed that he is entitled to approximately $0.2 million of fees incurred to date. The Company disputes that amount.

Regardless of the arbitrator’s order, Mr. Fried is required to reimburse the Company for any amounts advanced to him if it is ultimately determined that Mr. Fried is not entitled to indemnification in connection with the Melcher litigation. In addition, the Company believes that it has indemnification rights against the former stockholders of Face It (including Mr. Fried) for all losses that are incurred by the Company in connection with the Melcher litigation, including without limitation, amounts incurred to indemnify or advance the legal fees and expenses of Mr. Fried pursuant to his indemnification claim against the Company. The Company has asserted claims in arbitration against both Mr. Fried and the representative of the former Face It stockholders to recoup these losses. These claims are stayed pending the resolution of the Melcher litigation.