Organization and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The financial information presented in the accompanying unaudited condensed consolidated financial statements has been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and in accordance with rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Accordingly, the financial statements do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The condensed consolidated balance sheet data as of December 31, 2019 was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments, consisting primarily of normal recurring accruals, necessary for a fair presentation of our financial position and results of operations. The operating results for the three and six months ended June 30, 2020 are not necessarily indicative of the results expected for the full year ending December 31, 2020.
Principles of Consolidation	All intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States requires us to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. We base our estimates on historical experience and various other assumptions believed to be reasonable. These estimates include, but are not limited to, the allowance for doubtful accounts, the determination of the relative selling prices of our services, the measurement of material rights, health insurance claims incurred but not yet reported, valuation of available-for-sale marketable securities, useful lives of deferred contract costs, intangible assets and property and equipment, income taxes, discount rates used in the valuation of right-of-use assets and lease liabilities, the fair value of the liability and equity components of the convertible senior notes, and certain assumptions used in the valuation of equity awards. While these estimates are based on our best knowledge of current events and actions that may affect us in the future, actual results may differ materially from these estimates.
Recently Adopted Accounting Pronouncements	In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which amends the current accounting guidance and requires the measurement of all expected losses based on historical experience, current conditions and reasonable and supportable forecasts. For trade receivables, loans, and other financial instruments, we are required to use a forward-looking expected loss model that reflects probable losses rather than the incurred loss model for recognizing credit losses. The standard became effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted. Application of the amendments is through a cumulative-effect adjustment to retained earnings as of the effective date. Effective January 1, 2020, we adopted this standard. The adoption of this new standard did not have a material impact on our consolidated financial statements.
Fair Value of Financial Instruments	Cash equivalents primarily consist of AAA-rated money market funds with overnight liquidity and no stated maturities. We classified cash equivalents as Level 1 due to the short-term nature of these instruments and measured the fair value based on quoted prices in active markets for identical assets. When available, our marketable securities are valued using quoted prices for identical instruments in active markets. If we are unable to value our marketable securities using quoted prices for identical instruments in active markets, we value our investments using broker reports that utilize quoted market prices for comparable instruments. We validate, on a sample basis, the derived prices provided by the brokers by comparing their assessment of the fair values of our investments against the fair values of the portfolio balances of another third-party professional pricing service.
Stock-based Compensation	The fair value of each share issued under the ESPP is estimated on the date of grant using the Black-Scholes option-pricing model. Expected volatility is based on the historical volatility of our common stock. The expected term represents the period of time the ESPP purchase rights are expected to be outstanding. The expected term for the ESPP purchase rights approximates the offering period. The risk-free interest rate is based on yields on U.S. Treasury STRIPS (Separate Trading of Registered Interest and Principal of Securities) with a maturity similar to the estimated expected term of the ESPP purchase rights.