Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
Mar. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies The accompanying condensed consolidated financial statements of Fitbit, Inc. (the “Company”) are unaudited. The condensed consolidated balance sheet at December 31, 2018 has been derived from the audited financial statements of the Company. The accompanying condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information, and in management’s opinion, includes all adjustments, consisting of only normal recurring adjustments, necessary for the fair statement of the Company’s financial position, its results of operations, and cash flows for the interim periods presented. The results of operations for the three months ended March 30, 2019 are not necessarily indicative of the results to be expected for the full fiscal year or any other period. The accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018, filed with the Securities and Exchange Commission (“SEC”) on March 1, 2019. The Company’s fiscal year ends on December 31 of each year. The Company is on a 4-4-5 week quarterly calendar. There were 89 and 90 days in each of the three months ended March 30, 2019 and March 31, 2018, respectively. The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated. Use of Estimates The preparation of condensed consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the condensed consolidated financial statements and accompanying notes. The primary estimates and assumptions made by management are related to revenue recognition, reserves for sales returns and incentives, reserves for warranty, valuation of stock-based awards, fair value of derivative assets and liabilities, allowance for doubtful accounts, inventory valuation, fair value of goodwill and acquired tangible and intangible assets and liabilities assumed during acquisitions, the number of reportable segments, the recoverability of intangible assets and their useful lives, contingencies, income taxes, and impairment of an equity investment. Actual results could differ from those estimates, and such differences may be material to the condensed consolidated financial statements. Significant Accounting Policies There have been no significant changes in the Company’s accounting policies from those disclosed in its Annual Report on Form 10-K, except for the policies described below in relation to the adoption of Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842), discussed below in the section titled “Accounting Pronouncements Recently Adopted.” Leases The Company determines if an arrangement is a lease at inception. Operating lease right-of-use assets (“ROU assets”) and short-term and long-term lease liabilities are included on the face of the condensed consolidated balance sheet. Finance lease ROU assets are presented within other assets, and finance lease liabilities are presented within accrued liabilities. ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset also excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has lease agreements with lease and non-lease components, which are accounted for as a single lease component. For lease agreements with terms less than 12 months, the Company has elected the short-term lease measurement and recognition exemption, and it recognizes such lease payments on a straight-line basis over the lease term. Customer Bankruptcy In September 2017, Wynit Distribution LLC (“Wynit”) filed for bankruptcy protection under Chapter 11 of the U.S. Bankruptcy Code. Wynit was previously the Company’s largest customer. The Company ceased to recognize revenue from Wynit, which totaled $8.1 million during the third quarter of 2017. Additionally, the Company recorded a charge of $35.8 million during the third quarter ended September 30, 2017 comprised of cost of revenue of $5.5 million associated with shipments to Wynit in the third quarter of 2017 and bad debt expense of $30.3 million associated with all of Wynit’s outstanding accounts receivables. The Company maintains credit insurance that covers a portion of the exposure related to its customer receivables. The Company recorded an insurance receivable based on an analysis of its insurance policies, including their exclusions, an assessment of the nature of the claim, and information from its insurance carrier. As of September 30, 2017, the Company had recorded an insurance receivable of $26.8 million, included in prepaid expenses and other current assets, associated with the amount it had concluded was probable related to the claim. The $26.8 million insurance receivable allowed the Company to recover $22.7 million of bad debt expense and $4.1 million of cost of revenue, resulting in a net charge of $9.0 million in the consolidated statement of operations comprised of net bad debt expense of $7.6 million and net cost of revenue of $1.4 million. The Company received $21.4 million of the insurance receivable during the fourth quarter of 2017 and the remaining $5.4 million in January 2018. During the three months ended March 31, 2018, the Company released $12.4 million in product return and rebate reserves related to Wynit, as it believed the possibility of future claims associated with these reserves was remote. This reserve release resulted in a $12.4 million increase in revenue during the three months ended March 31, 2018. Recent Accounting Pronouncements Accounting Pronouncements Not Yet Adopted In June 2016, the Financial Accounting Standards Board (the “FASB”) issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 provides for a new impairment model which requires measurement and recognition of expected credit losses for most financial assets and certain other instruments, including but not limited to accounts receivable and available for sale debt securities. ASU 2016-13 will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating the second step of the goodwill impairment test. The second step measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. Under ASU 2017-04, a company will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. ASU 2017-04 will be applied prospectively and is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements on fair value measurements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies the accounting for implementation costs in cloud computing arrangements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU 2016-02, Leases and subsequent amendments to the initial guidance; ASU 2017-13, ASU 2018-10 and ASU 2018-11 (collectively, “Topic 842”). Topic 842 requires lessees to recognize ROU assets and lease liabilities for operating leases, initially measured at the present value of the lease payments, on the balance sheet. The Company adopted the standard effective January 1, 2019 using a modified retrospective approach. Prior periods were not retrospectively adjusted. The cumulative effect upon adoption on the opening accumulated deficit balance was zero. The Company elected the available practical expedients, which allowed for carryforward of historical assessments of whether contracts contain or are leases, historical lease classification, and remaining lease terms. The standard had a material impact on the Company’s condensed consolidated balance sheets but did not have an impact on its condensed consolidated statements of operations. The most significant impact was the recognition of ROU assets and short-term and long-term lease liabilities for operating leases. The balances of operating lease ROU assets, operating lease liabilities, and long-term operating lease liabilities as of March 30, 2019 were $99.1 million, $30.2 million, and $98.2 million, respectively. The impact to other financial statement line items was immaterial. Adoption of the standard had no impact to net cash from or used in operating, investing, or financing activities in the Company’s consolidated statement of cash flows. Refer to Note 5 for further information on leases. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 amends the hedge accounting rules to simplify the application of hedge accounting standard and better portray the economic results of risk management activities in the financial statements. The standard expands the ability to hedge non-financial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. ASU 2017-12 became effective for the Company on January 1, 2019 with early adoption permitted. The Company early adopted this new standard in the first quarter of 2018. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 became effective for the Company on January 1, 2019. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements.

Basis of Presentation and Summary of Significant Accounting Policies

The accompanying condensed consolidated financial statements of Fitbit, Inc. (the “Company”) are unaudited. The condensed consolidated balance sheet at December 31, 2018 has been derived from the audited financial statements of the Company. The accompanying condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information, and in management’s opinion, includes all adjustments, consisting of only normal recurring adjustments, necessary for the fair statement of the Company’s financial position, its results of operations, and cash flows for the interim periods presented. The results of operations for the three months ended March 30, 2019 are not necessarily indicative of the results to be expected for the full fiscal year or any other period.

The accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018, filed with the Securities and Exchange Commission (“SEC”) on March 1, 2019.

The Company’s fiscal year ends on December 31 of each year. The Company is on a 4-4-5 week quarterly calendar. There were 89 and 90 days in each of the three months ended March 30, 2019 and March 31, 2018, respectively.

The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated.

Use of Estimates

The preparation of condensed consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the condensed consolidated financial statements and accompanying notes. The primary estimates and assumptions made by management are related to revenue recognition, reserves for sales returns and incentives, reserves for warranty, valuation of stock-based awards, fair value of derivative assets and liabilities, allowance for doubtful accounts, inventory valuation, fair value of goodwill and acquired tangible and intangible assets and liabilities assumed during acquisitions, the number of reportable segments, the recoverability of intangible assets and their useful lives, contingencies, income taxes, and impairment of an equity investment. Actual results could differ from those estimates, and such differences may be material to the condensed consolidated financial statements.

Significant Accounting Policies

There have been no significant changes in the Company’s accounting policies from those disclosed in its Annual Report on Form 10-K, except for the policies described below in relation to the adoption of Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842), discussed below in the section titled “Accounting Pronouncements Recently Adopted.”

Leases

The Company determines if an arrangement is a lease at inception. Operating lease right-of-use assets (“ROU assets”) and short-term and long-term lease liabilities are included on the face of the condensed consolidated balance sheet. Finance lease ROU assets are presented within other assets, and finance lease liabilities are presented within accrued liabilities.

ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset also excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has lease agreements with lease and non-lease components, which are accounted for as a single lease component. For lease agreements with terms less than 12 months, the Company has elected the short-term lease measurement and recognition exemption, and it recognizes such lease payments on a straight-line basis over the lease term.

Customer Bankruptcy

In September 2017, Wynit Distribution LLC (“Wynit”) filed for bankruptcy protection under Chapter 11 of the U.S. Bankruptcy Code. Wynit was previously the Company’s largest customer. The Company ceased to recognize revenue from Wynit, which totaled $8.1 million during the third quarter of 2017. Additionally, the Company recorded a charge of $35.8 million during the third quarter ended September 30, 2017 comprised of cost of revenue of $5.5 million associated with shipments to Wynit in the third quarter of 2017 and bad debt expense of $30.3 million associated with all of Wynit’s outstanding accounts receivables. The Company maintains credit insurance that covers a portion of the exposure related to its customer receivables. The Company recorded an insurance receivable based on an analysis of its insurance policies, including their exclusions, an assessment of the nature of the claim, and information from its insurance carrier. As of September 30, 2017, the Company had recorded an insurance receivable of $26.8 million, included in prepaid expenses and other current assets, associated with the amount it had concluded was probable related to the claim. The $26.8 million insurance receivable allowed the Company to recover $22.7 million of bad debt expense and $4.1 million of cost of revenue, resulting in a net charge of $9.0 million in the consolidated statement of operations comprised of net bad debt expense of $7.6 million and net cost of revenue of $1.4 million. The Company received $21.4 million of the insurance receivable during the fourth quarter of 2017 and the remaining $5.4 million in January 2018.

During the three months ended March 31, 2018, the Company released $12.4 million in product return and rebate reserves related to Wynit, as it believed the possibility of future claims associated with these reserves was remote. This reserve release resulted in a $12.4 million increase in revenue during the three months ended March 31, 2018.

Recent Accounting Pronouncements

Accounting Pronouncements Not Yet Adopted

In June 2016, the Financial Accounting Standards Board (the “FASB”) issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 provides for a new impairment model which requires measurement and recognition of expected credit losses for most financial assets and certain other instruments, including but not limited to accounts receivable and available for sale debt securities. ASU 2016-13 will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.

In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating the second step of the goodwill impairment test. The second step measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. Under ASU 2017-04, a company will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. ASU 2017-04 will be applied prospectively and is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements on fair value measurements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies the accounting for implementation costs in cloud computing arrangements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.

Accounting Pronouncements Recently Adopted

In February 2016, the FASB issued ASU 2016-02, Leases and subsequent amendments to the initial guidance; ASU 2017-13, ASU 2018-10 and ASU 2018-11 (collectively, “Topic 842”). Topic 842 requires lessees to recognize ROU assets and lease liabilities for operating leases, initially measured at the present value of the lease payments, on the balance sheet. The Company adopted the standard effective January 1, 2019 using a modified retrospective approach. Prior periods were not retrospectively adjusted. The cumulative effect upon adoption on the opening accumulated deficit balance was zero. The Company elected the available practical expedients, which allowed for carryforward of historical assessments of whether contracts contain or are leases, historical lease classification, and remaining lease terms.

The standard had a material impact on the Company’s condensed consolidated balance sheets but did not have an impact on its condensed consolidated statements of operations. The most significant impact was the recognition of ROU assets and short-term and long-term lease liabilities for operating leases. The balances of operating lease ROU assets, operating lease liabilities, and long-term operating lease liabilities as of March 30, 2019 were $99.1 million, $30.2 million, and $98.2 million, respectively. The impact to other financial statement line items was immaterial. Adoption of the standard had no impact to net cash from or used in operating, investing, or financing activities in the Company’s consolidated statement of cash flows. Refer to Note 5 for further information on leases.

In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 amends the hedge accounting rules to simplify the application of hedge accounting standard and better portray the economic results of risk management activities in the financial statements. The standard expands the ability to hedge non-financial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. ASU 2017-12 became effective for the Company on January 1, 2019 with early adoption permitted. The Company early adopted this new standard in the first quarter of 2018. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements.

In June 2018, the FASB issued ASU 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 became effective for the Company on January 1, 2019. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements.