Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2020
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The unaudited interim consolidated financial statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Accordingly, they do not include all information and disclosures necessary for a presentation of our financial position, results of operations and cash flows in conformity with generally accepted accounting principles in the United States of America (GAAP) for annual financial statements. In the opinion of management, these unaudited interim consolidated financial statements reflect the elimination of all intercompany accounts and transactions and all adjustments, consisting primarily of normal recurring accruals, necessary for a fair presentation of our financial position and results of operations and cash flows for the periods presented. The results of operations for interim periods are not necessarily indicative of the results for the full year. These unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2019 and accompanying notes thereto included in our annual report on Form 10-K filed with the SEC on March 16, 2020. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Actual results could differ from such estimates. New Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The ASU replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. We adopted the ASU effective as of January 1, 2020. Our cash equivalents and short-term investments are accounted for as available-for-sale debt instruments and certificates of deposit, recorded at fair value. Interest income on these instruments is recorded as “Other income” on the interim consolidated statements of operations and comprehensive loss. We have never experienced a credit loss on the principal or interest receivable of our cash equivalents or short-term investments. Our available-for-sale debt securities represent United States (U.S.) treasury securities, and our certificates of deposit are each individually and fully insured by the Federal Deposit Insurance Corporation (FDIC). Accordingly, we did not measure an allowance for credit losses on these securities and we did not record a cumulative-effect adjustment to accumulated deficit during the three months ended March 31, 2020 upon adoption of ASU No. 2016-13.

2. Summary of Significant Accounting Policies

Basis of Presentation

The unaudited interim consolidated financial statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Accordingly, they do not include all information and disclosures necessary for a presentation of our financial position, results of operations and cash flows in conformity with generally accepted accounting principles in the United States of America (GAAP) for annual financial statements. In the opinion of management, these unaudited interim consolidated financial statements reflect the elimination of all intercompany accounts and transactions and all adjustments, consisting primarily of normal recurring accruals, necessary for a fair presentation of our financial position and results of operations and cash flows for the periods presented. The results of operations for interim periods are not necessarily indicative of the results for the full year. These unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2019 and accompanying notes thereto included in our annual report on Form 10-K filed with the SEC on March 16, 2020.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Actual results could differ from such estimates.

New Accounting Pronouncements

In June 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The ASU replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. We adopted the ASU effective as of January 1, 2020.

Our cash equivalents and short-term investments are accounted for as available-for-sale debt instruments and certificates of deposit, recorded at fair value. Interest income on these instruments is recorded as “Other income” on the interim consolidated statements of operations and comprehensive loss. We have never experienced a credit loss on the principal or interest receivable of our cash equivalents or short-term investments. Our available-for-sale debt securities represent United States (U.S.) treasury securities, and our certificates of deposit are each individually and fully insured by the Federal Deposit Insurance Corporation (FDIC). Accordingly, we did not measure an allowance for credit losses on these securities and we did not record a cumulative-effect adjustment to accumulated deficit during the three months ended March 31, 2020 upon adoption of ASU No. 2016-13.