Dropbox (DBX) 10-K 21 Feb 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 18, 2020	Jun. 28, 2019
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-38434
Entity Registrant Name	Dropbox, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-0138832
Entity Address, Address Line One	1800 Owens Street
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94158
City Area Code	415
Local Phone Number	857-6800
Title of 12(b) Security	Class A Common Stock, par value $0.00001 per share
Trading Symbol	DBX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 5,833.9
Documents Incorporated by Reference	Portions of the registrant's definitive Proxy Statement relating to the 2020 Annual Meeting of Stockholders are incorporated herein by references in Part II and Part III of this Annual Report on Form 10-K to the extent stated herein. Such Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 31, 2019.
Entity Central Index Key	0001467623
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		258,155,253
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		160,699,326
Class C Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		0

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 551.3	$ 519.3
Short-term investments	607.7	570
Trade and other receivables, net	36.7	28.6
Prepaid expenses and other current assets	47.5	92.3
Total current assets	1,243.2	1,210.2
Property and equipment, net	445.3	310.6
Operating lease right-of-use asset	657.9
Intangible assets, net	47.4	14.7
Goodwill	234.5	96.5
Other assets	70.9	62.1
Total assets	2,699.2	1,694.1
Current liabilities:
Accounts payable	40.7	33.3
Accrued and other current liabilities	161.9	164.5
Accrued compensation and benefits	101.4	80.9
Operating lease liability	79.9
Finance lease obligation	76.7
Finance lease obligation		73.8
Deferred revenue	554.2	485
Total current liabilities	1,014.8	837.5
Operating lease liability, non-current	711.9
Finance lease liability, non-current	138.2
Finance lease liability, non-current		89.9
Other non-current liabilities	25.9	89.9
Total liabilities	1,890.8	1,017.3
Commitments and contingencies (Note 10)
Stockholders’ equity:
Preferred stock value	0	0
Common stock, $0.00001 par value; Class A common stock - 2,400.0 million shares authorized and 255.8 million shares issued and outstanding as of December 31, 2019; 2,400.0 million shares authorized and 211.0 million shares issued and outstanding as of December 31, 2018; Class B common stock - 475.0 million shares authorized and 161.2 million shares issued and outstanding as of December 31, 2019; 475.0 million shares authorized and 198.6 issued and outstanding as of December 31, 2018; Class C common stock	0	0
Additional paid-in capital	2,531.3	2,337.5
Accumulated deficit	(1,726.2)	(1,659.5)
Accumulated other comprehensive income (loss)	3.3	(1.2)
Total stockholders’ equity	808.4	676.8
Total liabilities and stockholders’ equity	2,699.2	1,694.1
Convertible Preferred Stock
Stockholders’ equity:
Preferred stock value		$ 0

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Preferred stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	240,000,000	240,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Convertible Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	0	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Class A Common Stock
Common stock, par value (in dollars per share)	$ 0.00001
Common stock, shares authorized	2,400,000,000	2,400,000,000
Common stock, shares issued	255,800,000	211,000,000
Common stock, shares outstanding	255,800,000	211,000,000
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.00001
Common stock, shares authorized	475,000,000	475,000,000
Common stock, shares issued	161,200,000	198,600,000
Common stock, shares outstanding	161,200,000	198,600,000
Class C Common Stock
Common stock, par value (in dollars per share)	$ 0.00001
Common stock, shares authorized	800,000,000	800,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue		$ 1,661.3	$ 1,391.7	$ 1,106.8
Cost of revenue	[1]	411	394.7	368.9
Gross profit		1,250.3	997	737.9
Operating expenses
Research and development	[1],[2]	662.1	768.2	380.3
Sales and marketing	[1],[2]	423.3	439.6	314
General and administrative	[1],[2],[3]	245.4	283.2	157.3
Total operating expenses		1,330.8	1,491	851.6
Loss from operations		(80.5)	(494)	(113.7)
Interest income (expense), net		12.5	7.1	(11)
Other income (expense), net		16	6.8	13.2
Loss before income taxes		(52)	(480.1)	(111.5)
Benefit from (provision for) income taxes		(0.7)	(4.8)	(0.2)
Net loss		$ (52.7)	$ (484.9)	$ (111.7)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)		$ (0.13)	$ (1.35)	$ (0.57)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)		411.6	358.6	195.9
[1]	(1) Includes stock-based compensation as follows (in millions): Year ended December 31, 2019 2018 2017 Cost of revenue $ 15.8 $ 47.0 $ 12.2 Research and development 147.6 368.2 93.1 Sales and marketing 31.4 94.3 33.7 General and administrative 66.4 140.6 25.6
[2]	During the year ended December 31, 2018, the Company recognized the cumulative unrecognized stock-based compensation of $418.7 million related to the two-tier restricted stock units upon the effectiveness of the Company's registration statement for its initial public offering. See Note 1, "Description of the Business and Summary of Significant Accounting Policies "
[3]	During the year ended the year ended December 31, 2017, general and administrative expense includes $9.4 million for a non-cash charitable contribution and $1.9 million of cash contributions to the Dropbox Charitable Foundation, a related party. See Note 15, "Related Party Transactions" for further details.

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Donation of common stock to charitable foundation	$ 0	$ 0	$ 9.4
Cash contributions to charitable foundation			1.9
Two-Tier RSUs
Recognized cumulative unrecognized stock-based compensation		418.7
Cost of revenue
Allocated share-based compensation expense	15.8	47	12.2
Research and development
Allocated share-based compensation expense	147.6	368.2	93.1
Sales and marketing
Allocated share-based compensation expense	31.4	94.3	33.7
General and administrative
Allocated share-based compensation expense	$ 66.4	$ 140.6	25.6
Donation of common stock to charitable foundation			$ 9.4

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (52.7)	$ (484.9)	$ (111.7)
Other comprehensive income (loss), net of tax:
Change in foreign currency translation adjustments	2.9	(4.9)	5.2
Change in net unrealized losses on short-term investments	1.6	(0.5)	0
Total other comprehensive income (loss), net of tax	4.5	(5.4)	5.2
Comprehensive loss	$ (48.2)	$ (490.3)	$ (106.5)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($)	Total	Convertible preferred stock	Class A and Class B common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)
Shares outstanding, beginning balance (in shares) at Dec. 31, 2016		147,600,000	187,100,000
Shareholders equity, beginning balance at Dec. 31, 2016	$ 122,800,000	$ 615,300,000	$ 0	$ 446,000,000	$ (937,500,000)	$ (1,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Release of restricted stock units (in shares)			14,600,000
RSUs repurchased for tax withholdings on release of restricted stock (in shares)			(5,500,000)
RSUs repurchased for tax withholdings on release of restricted stock	(87,900,000)			(87,900,000)
Donation of common stock to charitable foundation (in shares)			600,000
Donation of common stock to charitable foundation	9,400,000			9,400,000
Exercise of stock options and awards (in shares)			200,000
Exercise of stock options and awards	500,000			500,000
Repurchase of unvested common stock (related to early exercised stock options) (in shares)			(200,000)
Repurchase of unvested common stock (related to early exercised stock options)	0
Stock-based compensation	164,600,000			164,600,000
Other comprehensive income (loss)	5,200,000					5,200,000
Net loss	(111,700,000)				(111,700,000)
Shares outstanding, ending balance (in shares) at Dec. 31, 2017		147,600,000	196,800,000
Shareholders equity, ending balance at Dec. 31, 2017	$ 102,900,000	$ 615,300,000	$ 0	533,100,000	(1,049,700,000)	4,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Release of restricted stock units (in shares)			40,400,000
RSUs repurchased for tax withholdings on release of restricted stock (in shares)	(15,600,000)		15,600,000
RSUs repurchased for tax withholdings on release of restricted stock	$ (351,800,000)			226,900,000	124,900,000
Exercise of stock options and awards (in shares)	3,400,000		3,400,000
Exercise of stock options and awards	$ 26,200,000			26,200,000
Conversion of preferred stock to common stock in connection with initial public offering (in shares)		147,600,000	(147,600,000)
Conversion of preferred stock to common stock in connection with initial public offering	0	$ (615,300,000)		615,300,000
Issuance of common stock in connection with initial public offering and private placement, net of underwriters' discounts and commissions and issuance costs (in shares)			37,000,000
Issuance of common stock in connection with initial public offering and private placement, net of underwriters' discounts and commissions and issuance costs	739,700,000			739,700,000
Stock-based compensation	650,100,000			650,100,000
Other comprehensive income (loss)	(5,400,000)					(5,400,000)
Net loss	(484,900,000)				(484,900,000)
Shares outstanding, ending balance (in shares) at Dec. 31, 2018		0	409,600,000
Shareholders equity, ending balance at Dec. 31, 2018	$ 676,800,000	$ 0	$ 0	2,337,500,000	(1,659,500,000)	(1,200,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Release of restricted stock units (in shares)			11,200,000
RSUs repurchased for tax withholdings on release of restricted stock (in shares)	(4,100,000)		(4,100,000)
RSUs repurchased for tax withholdings on release of restricted stock	$ (85,400,000)			(70,400,000)	(15,000,000)
Exercise of stock options and awards (in shares)	300,000		300,000
Exercise of stock options and awards	$ 2,200,000			2,200,000
Assumed stock options in connection with acquisition	800,000			800,000
Stock-based compensation	261,200,000			261,200,000
Other comprehensive income (loss)	4,500,000					4,500,000
Net loss	(52,700,000)				(52,700,000)
Shares outstanding, ending balance (in shares) at Dec. 31, 2019		0	417,000,000
Shareholders equity, ending balance at Dec. 31, 2019	$ 808,400,000	$ 0	$ 0	$ 2,531,300,000	$ (1,726,200,000)	$ 3,300,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flow from operating activities
Net loss		$ (52.7)	$ (484.9)	$ (111.7)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization		173.5	166.8	181.8
Stock-based compensation		261.2	650.1	164.6
Amortization of deferred commissions		17.5	12.1	6.6
Donation of common stock to charitable foundation		0	0	9.4
Other		(16.6)	(1.9)	(1.7)
Changes in operating assets and liabilities:
Trade and other receivables, net		(7.5)	0.1	(14.4)
Prepaid expenses and other current assets		(18.2)	(47.9)	(18.2)
Other assets		61.2	(11.2)	(10.6)
Accounts payable		6.4	(1.7)	16.2
Accrued and other current liabilities		23	40.3	34
Accrued compensation and benefits		19.1	25	14.4
Deferred revenue		68.7	66.4	64.3
Other non-current liabilities		(62.4)	12.2	(4.4)
Tenant improvement allowance reimbursement		55.3	0	0
Net cash provided by operating activities		528.5	425.4	330.3
Cash flow from investing activities
Capital expenditures		(136.1)	(63)	(25.3)
Purchase of intangible assets		(1.7)	(3)	(0.8)
Business combinations, net of cash acquired		(173.9)	0	0
Purchases of short-term investments		(775.4)	(850.4)	0
Proceeds from maturities of short-term investments		294.8	212.4	0
Proceeds from sales of short-term investments		456.1	71.2	0
Other		16.2	(1)	2.2
Net cash used in investing activities		(320)	(633.8)	(23.9)
Cash flow from financing activities
Proceeds from initial public offering and private placement, net of underwriters' discounts and commissions		0	746.6	0
Payments of deferred offering costs		0	(4.5)	(2.5)
Shares repurchased for tax withholdings on release of restricted stock		(85.4)	(351.9)	(87.9)
Proceeds from issuance of common stock, net of repurchases		2.2	26.2	0.5
Principal payments on capital lease obligations	[1]	(92.9)	(109.1)	(133)
Other		(0.6)	(6.5)	(8.8)
Net cash (used in) provided by financing activities		(176.7)	300.8	(231.7)
Effect of exchange rate changes on cash and cash equivalents		0.2	(3.1)	2.6
Change in cash and cash equivalents		32	89.3	77.3
Cash and cash equivalents—beginning of period		519.3	430	352.7
Cash and cash equivalents—end of period		551.3	519.3	430
Supplemental cash flow data:
Interest		9.8	8.3	10.8
Income taxes		0.6	1.4	3.4
Non-cash investing and financing activities:
Property and equipment received and accrued in accounts payable and accrued liabilities		19.9	7.3	2.4
Property and equipment acquired under finance leases		144.1	98.5	44.9
Deferred offering costs accrued in accounts payable and accrued liabilities		$ 0	$ 0	$ 1.6
[1]	Includes amounts attributable to related party transactions. See Note 15, "Related Party Transactions" for further details.

Description of the Business and

Description of the Business and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business and Summary of Significant Accounting Policies	Description of the Business and Summary of Significant Accounting Policies Business Dropbox, Inc. (the “Company” or “Dropbox”) is the world’s first smart workspace. Dropbox was incorporated in May 2007 as Evenflow, Inc., a Delaware corporation, and changed its name to Dropbox, Inc. in October 2009. The Company is headquartered in San Francisco, California. Basis of presentation and consolidation The accompanying consolidated financial statements have been prepared in accordance with the United States of America generally accepted accounting principles (“GAAP”). The accompanying consolidated financial statements include the accounts of Dropbox and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Initial public offering and private placement On March 27, 2018, the Company closed its initial public offering ("IPO"), in which the Company issued and sold 26,822,409 shares of Class A common stock at $21.00 per share. The Company received aggregate proceeds of $538.2 million, net of underwriters' discounts and commissions, before deducting offering costs of $6.9 million, net of reimbursements. Immediately prior to the closing of the Company’s IPO, 147,310,563 shares of convertible preferred stock outstanding converted into an equivalent number of shares of Class B common stock. Further, pursuant to transfer agreements with certain of the Company’s stockholders, 258,620 shares of the Company’s convertible preferred stock and 2,609,951 shares of the Company’s Class B common stock automatically converted into an equivalent number of shares of Class A common stock. Immediately subsequent to the closing of the Company's IPO, Salesforce Ventures LLC purchased 4,761,905 shares of Class A common stock from the Company at $21.00 per share. The Company received aggregate proceeds of $100.0 million and did not pay any underwriting discounts or commissions with respect to the shares that were sold in the private placement. On March 28, 2018, the underwriters exercised their option to purchase an additional 5,400,000 shares of the Company's Class A common stock at $21.00 per share. This transaction closed on April 3, 2018, resulting in additional proceeds of $108.4 million, net of underwriters' discounts and commissions. The Company’s net proceeds from the IPO, the concurrent private placement, and underwriters' option totaled $746.6 million, before deducting offering costs of $6.9 million, net of reimbursements. Upon the effectiveness of the registration statement for the Company's IPO, which was March 22, 2018, the liquidity event-related performance vesting condition, referred to as the Performance Vesting Condition, associated with the Company's two-tier restricted stock units ("RSUs") was satisfied. As a result, the Company recognized the cumulative unrecognized stock-based compensation related to its two-tier RSUs using the accelerated attribution method of $418.7 million attributable to service prior to such effective date. The remaining unamortized stock-based compensation as of December 31, 2018 related to the two-tier RSUs of $0.1 million was recognized in 2019. During the first quarter of 2018, the Company's Board of Directors approved the acceleration of the Performance Vesting Condition for which the service condition was satisfied, to occur upon the effectiveness of the registration statement for the Company's IPO, rather than six months following an IPO. As a result, the Company released 26.8 million shares of common stock underlying the two-tier RSUs for which the Performance Vesting Condition was satisfied, and recorded $13.9 million in employer related payroll tax expenses associated with these same awards. See "—Stock-based compensation" for further discussion regarding the Company's two-tier RSUs. Stock Split On March 7, 2018, the Company effected a 1-for-1.5 reverse stock split of its capital stock. All of the share and per share information referenced throughout the consolidated financial statements and notes to the consolidated financial statements have been retroactively adjusted to reflect this reverse stock split. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the consolidated financial statements. Management evaluates these estimates and assumptions on a regular basis. Actual results may differ materially from these estimates. The Company’s most significant estimate and use of judgment involves the valuation of acquired intangible assets and goodwill from business combinations. Financial information about segments and geographic areas The Company manages its operations and allocates resources as a single operating segment. Further, the Company manages, monitors, and reports its financials as a single reporting segment. The Company’s chief operating decision-maker is its Chief Executive Officer, who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources. See Note 16, "Geographic Areas" for information regarding the Company's long-lived assets and revenue by geography. Foreign currency transactions The assets and liabilities of the Company’s foreign subsidiaries are translated from their respective functional currencies into U.S. dollars at the exchange rates in effect at the balance sheet date. Revenue and expense amounts are translated at the average exchange rate for the period. Foreign currency translation gains and losses are recorded in other comprehensive income (loss). Gains and losses realized from foreign currency transactions (those transactions denominated in currencies other than the foreign subsidiaries’ functional currency) are included in other income, net. Monetary assets and liabilities are remeasured using foreign currency exchange rates at the end of the period, and non-monetary assets are remeasured based on historical exchange rates. The Company recorded net foreign currency transaction losses of $ 0.8 million and $ 1.9 million in the years ended December 31, 2019 and 2018 , respectively. Revenue recognition The Company derives its revenue from subscription fees from customers for access to its platform. The Company’s policy is to exclude sales and other indirect taxes when measuring the transaction price of its subscription agreements. The Company accounts for revenue contracts with customers through the following steps: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, the Company satisfies a performance obligation The Company’s subscription agreements generally have monthly or annual contractual terms and a small percentage have multi-year contractual terms. Revenue is recognized ratably over the related contractual term beginning on the date that the platform is made available to a customer. Access to the platform represents a series of distinct services as the Company continually provides access to, and fulfills its obligation to the end customer over the subscription term. The series of distinct services represents a single performance obligation that is satisfied over time. The Company recognizes revenue ratably because the customer receives and consumes the benefits of the platform throughout the contract period. The Company’s contracts are generally non-cancelable. The Company bills in advance for monthly contracts and typically bills annually in advance for contracts with terms of one year or longer . The Company also recognizes an immaterial amount of contract assets, or unbilled receivables, primarily relating to consideration for services completed but not billed at the reporting date. Unbilled receivables are classified as receivables when the Company has the right to invoice the customer. The Company records contract liabilities when cash payments are received or due in advance of performance to deferred revenue. Deferred revenue primarily relates to the advance consideration received from the customer. The price of subscriptions is generally fixed at contract inception and therefore, the Company’s contracts do not contain a significant amount of variable consideration. As a result, the amount of revenue recognized in the periods presented from performance obligations satisfied (or partially satisfied) in previous periods was not material. The Company recognized $ 481.1 million, $ 411.6 million, and $ 353.0 million of revenue during the years ended December 31, 2019 , 2018 and 2017 , respectively, that was included in the deferred revenue balances at the beginning of their respective periods. As of December 31, 2019 , future estimated revenue related to performance obligations that were unsatisfied or partially unsatisfied at the end of the reporting period was $ 613.4 million. The substantial majority of the unsatisfied performance obligations will be satisfied over the next twelve months . Stock-based compensation The Company has granted RSUs to its employees and members of the Board of Directors under the 2008 Equity Incentive Plan (“2008 Plan”), the 2017 Equity Incentive Plan (“2017 Plan”), and the 2018 Equity Incentive Plan ("2018 Plan" and together with the 2008 Plan and 2017 Plan, the "Dropbox Equity Incentive Plans"). The Company has granted the following types of RSUs under the Dropbox Equity Incentives Plans: • One-tier RSUs, which have a service-based vesting condition over a four-year period. These awards typically have a cliff vesting period of one year and continue to vest quarterly thereafter. The Company began granting one-tier RSUs under its 2008 Plan in August 2015, and it continues to grant one-tier RSUs under its 2018 Plan. The Company recognizes compensation expense associated with one-tier RSUs ratably on a straight-line basis over the requisite service period and accounts for forfeitures in the period in which they occur. • Two-tier RSUs, which had both a service-based vesting condition and a Performance Vesting Condition. The Performance Vesting Condition was satisfied on the effectiveness of the registration statement related to the Company's IPO. Prior to August 2015, the Company granted two-tier RSUs under the 2008 Plan. The last grant date for two-tier RSUs was in May 2015. The Company recognized compensation expense associated with two-tier RSUs using the accelerated attribution method over the requisite service period. As of December 31, 2019 , the Company only had one -tier RSUs outstanding under the Dropbox Equity Incentive Plans. Since August 2015, the Company has granted one-tier RSUs as the only stock-based payment awards to its employees, with the exception of awards granted to its co-founders and certain executives, and has not granted any stock options to employees since then. The fair values of the common stock underlying the RSUs granted in periods prior to the date of the Company's IPO were determined by the Board of Directors, with input from management and contemporaneous third-party valuations, which were performed at least quarterly. For valuations after the Company's IPO, the Board of Directors determines the fair value of each share of underlying common stock based on the closing price of the Company's Class A common stock as reported on the Nasdaq Global Select Market on the date of the grant. In connection with the acquisition of JN Projects, Inc. (d/b/a HelloSign) ("HelloSign"), the Company assumed unvested stock options that had been granted under the HelloSign's 2011 Equity Incentive Plan. The fair value of options assumed were based upon the Black-Scholes option-pricing model, see Note 12, "Stockholders' Equity" for further information. In December 2017 , the Board of Directors approved a grant to the Company’s co-founders of restricted stock awards (“RSAs”) with respect to 14.7 million shares of Class A Common Stock in the aggregate (collectively, the “Co-Founder Grants”), of which 10.3 million RSAs were granted to Mr. Houston, the Company’s co-founder and Chief Executive Officer, and 4.4 million RSAs were granted to Mr. Ferdowsi, the Company’s co-founder and Director. These Co-Founder Grants have service-based, market-based, and performance-based vesting conditions. The Company estimated the grant date fair value of the Co-Founder Grants using a model based on multiple stock price paths developed through the use of a Monte Carlo simulation that incorporates into the valuation the possibility that the Stock Price Targets may not be satisfied. See Note 12, "Stockholders' Equity" for further information. Cost of revenue Cost of revenue consists primarily of expenses associated with the storage, delivery, and distribution of the Company’s platform for both paying users and free users, also known as Basic users. These costs, which are referred to as infrastructure costs, include depreciation of servers located in co-location facilities that the Company leases and operates, rent and facilities expense for those datacenters, network and bandwidth costs, support and maintenance costs for infrastructure equipment, and payments to third-party datacenter service providers. Cost of revenue also includes costs, such as salaries, bonuses, benefits, travel-related expenses, and stock-based compensation, which are referred to as employee-related costs, for employees whose primary responsibilities relate to supporting the Company’s infrastructure and delivering user support. Other non-employee costs included in cost of revenue include credit card fees related to processing customer transactions and allocated overhead, such as facilities, including rent, utilities, depreciation on leasehold improvements and other equipment shared by all departments, and shared information technology costs. In addition, cost of revenue includes amortization of developed technologies, professional fees related to user support initiatives, and property taxes related to the datacenters. Advertising and promotional expense Advertising and promotional expenses are included in sales and marketing expenses within the consolidated statements of operations and are expensed when incurred. Advertising and promotional expenses were $88.8 million , $100.9 million , and $80.1 million in the years ended December 31, 2019, 2018, and 2017, respectively. Cash and cash equivalents Cash consists primarily of cash on deposit with banks and includes amounts in transit from payment processors for credit and debit card transactions, which typically settle within five business days. Cash equivalents include highly liquid investments purchased with an original maturity date of 90 days or less from the date of purchase. Short-term investments The Company’s short-term investments are primarily comprised of corporate notes and obligations, U.S. Treasury securities, certificates of deposit, asset-backed securities, commercial paper, U.S. agency obligations, supranational securities, and municipal securities. The Company determines the appropriate classification of its short-term investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its short-term investments as available-for-sale securities as the Company may sell these securities at any time for use in its current operations or for other purposes, even prior to maturity. As a result, the Company classifies its short-term investments, including securities with stated maturities beyond twelve months, within current assets in the consolidated balance sheets. The Company's short-term investments are classified as available-for-sale securities and are recorded at fair value each reporting period. Unrealized gains and losses on these short-term investments are reported as a separate component of accumulated other comprehensive income (loss) in the consolidated balance sheets until realized. Interest income is reported within interest income, net in the consolidated statements of operations. The Company periodically evaluates its short-term investments to assess whether those with unrealized loss positions are other-than-temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value is less than the Company’s cost basis, and the financial condition and near-term prospects of the investee. Realized gains and losses are determined based on the specific identification method and are reported in other income, net in the consolidated statements of operations. If the Company determines that the decline in an investment’s fair value is other-than-temporary, the difference is recognized as an impairment loss in the consolidated statements of operations. Concentrations of credit risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, accounts receivable, and short-term investments. The Company places its cash and cash equivalents, and short-term investments with well-established financial institutions. Trade accounts receivables are typically unsecured and are derived from revenue earned from customers located around the world. Two distribution partners accounted for 10% and 27% of total trade and other receivables, net as of December 31, 2019 . Two distribution partners accounted for 14% and 23% of total trade and other receivables, net as of December 31, 2018 . No customer accounted for more than 10% of the Company’s revenue in the periods presented. Trade and other receivables, net Trade and other receivables, net consists primarily of trade receivables that are recorded at the invoice amount, net of an allowance for doubtful accounts. The allowance for doubtful accounts is based on the Company’s assessment of the collectability of accounts. The Company regularly reviews the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice, the collection history of each customer, and other relevant factors to determine the appropriate amount of the allowance. Accounts receivable deemed uncollectable are charged against the allowance for doubtful accounts when identified. The Company's allowance for doubtful accounts was $0.5 million and $1.2 million as of December 31, 2019 and 2018, respectively. Non-trade receivables The Company records non-trade receivables to reflect amounts due for activities outside of its subscription agreements, such as non-current notes receivable. Non-trade receivables totaled $ 7.4 million and $ 46.2 million, as of December 31, 2019 and 2018 , respectively, and are classified within prepaid expenses and other current assets in the accompanying consolidated balance sheets. See "—Lease obligations” for further discussion. Deferred commissions, net Deferred commissions, net is stated as gross deferred commissions less accumulated amortization. Sales commissions earned by the Company’s sales force and third-party resellers, as well as related payroll taxes, are considered to be incremental and recoverable costs of obtaining a contract with a customer. These amounts have been capitalized as deferred commissions within prepaid and other current assets and other assets on the consolidated balance sheets. The Company deferred incremental costs of obtaining a contract of $28.1 million and $32.0 million during the years ended December 31, 2019 and 2018 , respectively. Deferred commissions, net included in prepaid and other current assets were $ 19.9 million and $14.5 million as of December 31, 2019 and 2018 , respectively. Deferred commissions, net included in other assets were $ 43.5 million and $38.3 million as of December 31, 2019 and 2018 , respectively. Deferred commissions are typically amortized over a period of benefit of five years . The period of benefit was estimated by considering factors such as historical customer attrition rates, the useful life of the Company’s technology, and the impact of competition in its industry. Amortized costs were $17.5 million, $12.1 million, and $6.6 million for the years ended December 31, 2019 , 2018 , and 2017 , respectively. Amortized costs are included in sales and marketing expense in the accompanying consolidated statements of operations. There was no impairment loss in relation to the deferred costs for any period presented. Property and equipment, net Equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful life of the related asset, which is generally three to seven years . Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the related lease. The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Equity investments The Company holds an equity investment in a publicly traded company in which the Company does not have a controlling interest or significant influence. The investment is measured using quoted prices in its active market with changes recorded in other income, net, in the condensed consolidated statement of operations. As of December 31, 2019 , the Company's equity investment had a carrying value of $ 9.8 million and is included in other assets in the condensed consolidated balance sheet. The Company recognized net gains of $ 4.5 million related to changes in quoted prices in the investment’s active market during the twelve month period ended December 31, 2019 . The investment is classified as a Level 1 investment within the fair value hierarchy. Lease obligations The Company leases office space, datacenters, and equipment under non-cancelable finance operating leases with various expiration dates through 2033. The Company determines if an arrangement contains a lease at inception. Operating lease right-of-use assets and lease liabilities are recognized at the present value of the future lease payments at commencement date. The interest rate implicit in the Company’s operating leases is not readily determinable, and therefore an incremental borrowing rate is estimated to determine the present value of future payments. The estimated incremental borrowing rate factors in a hypothetical interest rate on a collateralized basis with similar terms, payments, and economic environments. Operating lease right-of-use assets also include any prepaid lease payments and lease incentives. Certain of the operating lease agreements contain rent concession, rent escalation, and option to renew provisions. Rent concession and rent escalation provisions are considered in determining the single lease cost to be recorded over the lease term. Single lease cost is recognized on a straight-line basis over the lease term commencing on the date the Company has the right to use the leased property. The lease terms may include options to extend or terminate the lease. The Company generally uses the base, non-cancelable, lease term when recognizing the lease assets and liabilities, unless it is reasonably certain that the option will be exercised. In addition, certain of the Company’s operating lease agreements contain tenant improvement allowances from its landlords. These allowances are accounted for as lease incentives and decrease the Company's right-of-use asset and reduce single lease cost over the lease term. The Company leases certain equipment from various third parties, through equipment finance leases. These leases either include a bargain purchase option, a full transfer of ownership at the completion of the lease term, or the terms of the leases are at least 75 percent of the useful lives of the assets and are therefore classified as finance leases. These leases are capitalized in property and equipment, net and the related amortization of assets under finance leases is included in depreciation and amortization expense in the Company’s consolidated statements of operations. Initial asset values and finance lease obligations are based on the present value of future minimum lease payments. The Company’s finance lease agreements may contain lease and non-lease components. The non-lease components include payments for support on infrastructure equipment obtained via finance leases, which when not significant in relation to the overall agreement, are combined with the lease components and accounted for together as a single lease component. Internal use software The Company capitalizes certain costs related to developed or modified software solely for its internal use and cloud based applications used to deliver its platform. The Company capitalizes costs during the application development stage once the preliminary project stage is complete, management authorizes and commits to funding the project, and it is probable that the project will be completed and that the software will be used to perform the function intended. Costs related to preliminary project activities and post implementation activities are expensed as incurred. Capitalized internal use software costs were not material to the Company’s consolidated financial statements during the years ended December 31, 2019, 2018, and 2017. Business combinations The Company uses best estimates and assumptions, including but not limited to, future expected cash flows, expected asset lives, and discount rates, to assign a fair value to the tangible and intangible assets acquired and liabilities assumed in business combinations as of the acquisition date. These estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed may be recorded, with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the Company’s consolidated statements of operations. Long-lived assets, including goodwill and other acquired intangible assets, net The Company evaluates the recoverability of its property and equipment and finite-lived intangible assets for possible impairment whenever events or circumstances indicate that the carrying amount of such assets may not be recoverable. The evaluation is performed at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If such review determines that the carrying amount of specific property and equipment or intangible assets is not recoverable, the carrying amount of such assets is reduced to its fair value. The Company reviews goodwill for impairment at least annually in the fourth quarter, or more frequently if events or changes in circumstances would more likely than not reduce the fair value of its single reporting unit below its carrying value. The Company has not recorded impairment charges on property and equipment, goodwill, or intangible assets for the periods presented in these consolidated financial statements. Acquired property and equipment and finite-lived intangible assets are amortized over their useful lives. The Company evaluates the estimated remaining useful life of these assets when events or changes in circumstances warrant a revision to the remaining period of amortization. If the Company revises the estimated useful life assumption for any asset, the remaining unamortized balance is amortized or depreciated over the revised estimated useful life on a prospective basis. Income taxes Deferred income tax balances reflect the effects of temporary differences between the financial reporting and tax bases of the Company’s assets and liabilities using enacted tax rates expected to apply when taxes are actually paid or recovered. In addition, deferred tax assets are recorded for net operating loss and credit carryforwards. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized based on all available positive and negative evidence. Such evidence includes, but is not limited to, recent cumulative earnings or losses, expectations of future taxable income by taxing jurisdiction, and the carry-forward periods available for the utilization of deferred tax assets. The Company uses a two-step approach to recognizing and measuring uncertain income tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates it is more likely than not that the position will be sustained on audit. The second step is to measure the tax benefit as the largest amount, which is more than 50% likely of being realized upon ultimate settlement. The Company recognizes interest and penalties related to unrecognized tax benefits as income tax expense. Although the Company believes that it has adequately reserved for its uncertain tax positions, it can provide no assurance that the final tax outcome of these matters will not be materially different. The Company evaluates its uncertain tax positions on a regular basis and evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, such as the 2017 Tax Cuts and Jobs Act ("2017 Tax Reform Act"), correspondence with tax authorities during the course of an audit, and effective settlement of audit issues. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made and could have a material impact on the Company’s financial condition and results of operations. Fair value measurement The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value measurements for assets and liabilities, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions, and credit risk. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Recently issued accounting pronouncements not yet adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires the measurement and recognition of expected credit losses for financial assets held

Cash, Cash Equivalents and Shor

Cash, Cash Equivalents and Short-Term Investments	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Short-Term Investments	Cash, Cash Equivalents and Short-Term Investments The amortized cost, unrealized gains and losses and estimated fair value of the Company's cash, cash equivalents and short-term investments as of December 31, 2019 consisted of the following: Amortized cost Unrealized gain Unrealized loss Estimated fair value Cash $ 105.0 $ — $ — $ 105.0 Cash equivalents Money market funds 444.3 — — 444.3 Commercial paper 2.0 — — 2.0 Total cash and cash equivalents $ 551.3 $ — $ — $ 551.3 Short-term investments Corporate notes and obligations 285.5 1.2 (0.1 ) 286.6 U.S. Treasury securities 171.0 0.3 — 171.3 Asset backed securities 53.8 — — 53.8 Certificates of deposit 38.2 — — 38.2 U.S. agency obligations 27.2 — — 27.2 Commercial paper 24.2 — — 24.2 Supranational securities 4.0 — — 4.0 Municipal securities 2.4 — — 2.4 Total short-term investments 606.3 1.5 (0.1 ) 607.7 Total $ 1,157.6 $ 1.5 $ (0.1 ) $ 1,159.0 The amortized cost, unrealized gains and losses and estimated fair value of the Company's cash, cash equivalents and short-term investments as of December 31, 2018 consisted of the following: Amortized cost Unrealized gain Unrealized loss Estimated fair value Cash $ 103.0 $ — $ — $ 103.0 Cash equivalents Money market funds 355.5 — — 355.5 Commercial paper 27.4 — — 27.4 U.S. Treasury securities 33.4 33.4 Total cash and cash equivalents $ 519.3 $ — $ — $ 519.3 Short-term investments Corporate notes and obligations 269.6 0.1 (0.5 ) 269.2 U.S. Treasury securities 176 — (0.1 ) 175.9 Certificates of deposit 70.6 — — 70.6 U.S. agency obligations 37.1 — — 37.1 Commercial paper 17.2 — — 17.2 Total short-term investments 570.5 0.1 (0.6 ) 570.0 Total $ 1,089.8 $ 0.1 $ (0.6 ) $ 1,089.3 Included in cash and cash equivalents is cash in transit from payment processors for credit and debit card transactions of $11.5 million and $ 11.9 million as of December 31, 2019 and December 31, 2018 , respectively. All short-term investments were designated as available-for-sale securities as of December 31, 2019 . The following table presents the contractual maturities of the Company’s short-term investments as of December 31, 2019 : Amortized cost Estimated fair value Due within one year $ 275.9 $ 276.5 Due between one to three years 310.7 311.5 Due after three years 19.7 19.7 Total $ 606.3 $ 607.7 The Company had 62 short-term investments in unrealized loss positions as of December 31, 2019 . The short-term investments have been in unrealized loss positions for less than twelve months. The total fair value of such investments is $125.6 million with unrealized losses of $0.1 million . There were no material gross unrealized losses from available-for-sale securities and no material realized gains or losses from available-for-sale securities that were reclassified out of accumulated other comprehensive income for the year ended December 31, 2019 . For investments in available-for-sale debt securities that have unrealized losses, the Company evaluates whether (i) it has the intention to sell any of these investments and (ii) whether it is not more likely than not that it will be required to sell any of these investments before recovery of the entire amortized cost basis. Based on this evaluation, the Company determined that there were no other-than-temporary impairments associated with short-term investments as of December 31, 2019 . The Company recorded $ 22.8 million, $ 16.8 million, and $ 3.0 million in interest income from its cash, cash equivalents and short-term investments for the years ended December 31, 2019 , 2018 and 2017

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures its financial instruments at fair value each reporting period using a fair value hierarchy that prioritizes the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value. A financial instrument’s classification within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following table presents information about the Company’s financial instruments that are measured at fair value on a recurring basis using the input categories discussed in Note 1: As of December 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 444.3 $ — $ — $ 444.3 Commercial paper — 2.0 — 2.0 Total Cash Equivalents $ 444.3 $ 2.0 $ — $ 446.3 Short-term investments Corporate notes and obligations — 286.6 — 286.6 U.S. Treasury securities — 171.3 — 171.3 Certificates of deposit — 38.2 — 38.2 Asset-backed securities — 53.8 — 53.8 Commercial paper — 24.2 — 24.2 U.S. agency obligations — 27.2 — 27.2 Supranational securities — 4.0 — 4.0 Municipal securities — 2.4 — 2.4 Total short-term investments — 607.7 — 607.7 Equity Investments 9.8 — — 9.8 Total $ 454.1 $ 609.7 $ — $ 1,063.8 As of December 31, 2018 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 355.5 $ — $ — $ 355.5 U.S Treasury securities — 33.4 33.4 Commercial paper — 27.4 — 27.4 Total Cash Equivalents $ 355.5 $ 60.8 $ — $ 416.3 Short-term investments Corporate notes and obligations — 269.2 — 269.2 U.S. Treasury securities — 175.9 — 175.9 Certificates of deposit — 70.6 — 70.6 U.S agency obligations — 37.1 — 37.1 Commercial paper 17.2 17.2 Total short-term investments — 570.0 — 570.0 Total $ 355.5 $ 630.8 $ — $ 986.3 The Company had no transfers between levels of the fair value hierarchy. The carrying amounts of certain financial instruments, including cash held in banks, accounts receivable and accounts payable approximate fair value due to their short-term maturities and are excluded from the fair value table above.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following: As of December 31, 2019 2018 Datacenter and other computer equipment $ 749.3 $ 667.4 Furniture and fixtures 35.5 23.8 Leasehold improvements 211.4 150.5 Construction in progress 36.3 32.8 Total property and equipment 1,032.5 874.5 Accumulated depreciation and amortization (587.2 ) (563.9 ) Property and equipment, net $ 445.3 $ 310.6 The Company leases certain infrastructure from various third parties, through equipment finance leases. Infrastructure assets as of December 31, 2019 and 2018 , respectively, included a total of $321.8 million and $362.8 million acquired under finance lease agreements. These leases are capitalized in property and equipment, and the related amortization of assets under finance leases is included in depreciation and amortization expense. The accumulated depreciation of the infrastructure assets under finance leases totaled $ 124.6 million and $211.7 million as of December 31, 2019 and 2018 , respectively. Construction in progress includes costs primarily related to construction of leasehold improvements for office buildings and datacenters. In the third quarter of 2019, the Company relocated from its former corporate headquarters to its new corporate headquarters. During the third quarter, the Company completed recognizing depreciation expense on assets related to its former headquarters, and commenced depreciation expense related to assets for its new corporate headquarters. Depreciation expense related to property and equipment was $159.9 million and $ 158.6 million for the years ended December 31, 2019 and 2018 respectively.

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Business Combinations	Business Combinations On February 8, 2019, the Company acquired all outstanding stock of JN Projects, Inc. (d/b/a HelloSign) ("HelloSign"), which provides an e-signature and document workflow platform. The acquisition of HelloSign expands the Company's content collaboration capabilities to include additional business-critical workflows. The results of HelloSign operations have been included in the Company’s consolidated results of operations since the date of acquisition. The purchase consideration transferred consisted of the following: Purchase consideration Cash paid to common and preferred stockholders and vested option holders $ 175.2 Transaction costs paid by Dropbox on behalf of HelloSign 2.4 Fair value of assumed HelloSign options attributable to pre-combination services (1) 0.8 Purchase price adjustments (0.5 ) Total purchase consideration $ 177.9 (1) The fair value of options assumed were based upon the Black-Scholes option-pricing model. In addition to the total purchase consideration above, the Company has compensation agreements with key HelloSign personnel consisting of $48.5 million in future cash payments subject to on-going employee service. The related expense will be recognized within research and development expenses over the required service period of three years , and the payments will begin in the first quarter of 2020 if the requisite service is provided. The purchase consideration was preliminarily allocated to the tangible and intangible assets and liabilities acquired as of the acquisition date, with the excess recorded to goodwill as shown below. The fair value of assets and liabilities acquired may change as additional information is received during the measurement period. The measurement period will end no later than one-year from the acquisition date. Assets acquired: Cash and cash equivalents $ 5.5 Short-term investments 7.8 Acquisition-related intangible assets 44.6 Accounts receivable, prepaid and other assets 5.0 Total assets acquired $ 62.9 Liabilities assumed: Accounts payable, accrued and other liabilities $ 6.3 Deferred revenue 4.8 Deferred tax liability 6.9 Total liabilities assumed 18.0 Net assets acquired, excluding goodwill 44.9 Total purchase consideration 177.9 Estimated goodwill (2) $ 133.0 (2) The goodwill recognized was primarily attributable to the opportunity to expand the user base of the Company's platform. The goodwill is not deductible for U.S. federal income tax purposes. The fair value of the separately identifiable finite-lived intangible assets acquired and estimated weighted average useful lives are as follows: Estimated fair values Estimated weighted average useful lives (In years) Customer relationships $ 20.5 4.9 Developed technology 19.6 5.0 Trade name 4.5 5.0 Total acquisition-related intangible assets $ 44.6 The fair values of the acquisition-related intangibles were determined using the following methodologies: the multi-period excess earnings method, replacement cost method, and the relief from royalty method, for customer relationships, developed technology, and the trade name, respectively. The valuation model inputs required the application of significant judgment by management. The acquired intangible assets have a total weighted average amortization period of 4.9 years . One-time acquisition-related diligence costs of $1.0 million were expensed within general and administrative expenses as incurred for the year ended December 31, 2019

Intangible Assets, Net

Intangible Assets, Net	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets, Net	Intangible Assets, Net Intangible assets consisted of the following: As of December 31, Weighted- (In years) 2019 2018 Developed technology $ 25.8 $ 47.0 4.0 Customer relationships 20.5 0.0 4.1 Software 20.0 19.2 1.7 Patents 13.0 13.0 7.6 Assembled workforce in asset acquisitions 12.6 12.6 1.0 Licenses 4.6 4.6 1.5 Trademarks and trade names 5.2 0.7 4.1 Other 3.3 3.3 5.6 Total intangibles 105.0 100.4 Accumulated amortization (57.6 ) (85.7 ) Intangible assets, net $ 47.4 $ 14.7 During the first quarter of 2019 the Company retired $ 41.7 million in fully amortized developed technology assets. Amortization expense was $13.6 million, $ 6.1 million, and $ 10.5 million for the years ended December 31, 2019 , 2018 , and 2017 , respectively. Expected future amortization expense for intangible assets as of December 31, 2019 , is as follows: 2020 $ 13.9 2021 11.6 2022 8.3 2023 7.7 2024 3.3 Thereafter 2.6 Total $ 47.4

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Goodwill represents the excess of the purchase price in a business combination over the fair value of net tangible and intangible assets acquired. The changes in the carrying amounts of goodwill were as follows: Balance at December 31, 2018 $ 96.5 HelloSign acquisition 133.0 Other acquisition 2.4 Effect of foreign currency translation 2.6 Balance at December 31, 2019 $ 234.5 The goodwill acquired from HelloSign and our other acquisition is carried in U.S. dollars, while goodwill from previous acquisitions is denominated in other foreign currencies. Goodwill amounts are not amortized, but tested for impairment on an annual basis. There was no impairment of goodwill as of December 31, 2019 , 2018 , and 2017

Revolving Credit Facility

Revolving Credit Facility	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Revolving Credit Facility	Revolving Credit Facility In April 2017, the Company entered into an amended and restated credit and guaranty agreement which provided for a $ 600.0 million revolving loan facility (the “revolving credit facility”). In conjunction with the revolving credit facility, the Company paid upfront issuance fees of $ 2.6 million, which are being amortized over the five -year term of the agreement. In February 2018, the Company amended its revolving credit facility to, among other things, permit the Company to make certain investments, enter into an unsecured standby letter of credit facility and increase its standby letter of credit sublimit to $ 187.5 million. The Company increased its borrowing capacity under the revolving credit facility from $600.0 million to $725.0 million. The Company may from time to time request increases in its borrowing capacity under the revolving credit facility of up to $275.0 million, provided no event of default has occurred or is continuing or would result from such increase. In conjunction with the amendment, the Company paid upfront issuance fees of $0.4 million, which are being amortized over the remaining term of the agreement. Pursuant to the terms of the revolving credit facility, the Company may issue letters of credit under the revolving credit facility, which reduce the total amount available for borrowing. Pursuant to the terms of the revolving credit facility, the Company is required to pay an annual commitment fee that accrues at a rate of 0.20% per annum on the unused portion of the borrowing commitments under the revolving credit facility. In addition, the Company is required to pay a fee in connection with letters of credit issued under the revolving credit facility, which accrues at a rate of 1.5% per annum on the amount of such letters of credit outstanding. There is an additional fronting fee of 0.125% per annum multiplied by the average aggregate daily maximum amount available under all letters of credit. Borrowings under the revolving credit facility bear interest, at the Company’s option, at an annual rate based on LIBOR plus a spread of 1.50% or at an alternative base rate plus a spread of 0.50% . The revolving credit facility contains customary conditions to borrowing, events of default and covenants, including covenants that restrict the Company’s ability to incur indebtedness, grant liens, make distributions to holders of the Company or its subsidiaries’ equity interests, make investments, or engage in transactions with its affiliates. In addition, the revolving credit facility contains financial covenants, including a consolidated leverage ratio covenant and a minimum liquidity balance of $100.0 million, which includes any available borrowing capacity. The Company was in compliance with the covenants of the revolving credit facility as of December 31, 2019 and December 31, 2018 , respectively. The Company had an aggregate of $59.7 million of letters of credit outstanding under the revolving credit facility as of December 31, 2019 , and the Company’s total available borrowing capacity under the revolving credit facility was $665.3 million as of December 31, 2019 . The Company’s letters of credit expire between April 2020 and April 2022 .

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	Leases Leases The Company has operating leases for corporate offices and datacenters, and finance leases for infrastructure equipment. The Company’s leases have remaining lease terms of 1 year to 14 years , some of which include options to extend the leases for up to 5 years . The Company also has subleases of former corporate offices. Subleases have remaining lease terms of 1 year to 4 years . Sublease income, which is recorded as a reduction of rental expense, was $7.1 million for the year ended December 31, 2019 and $ 11.8 million for the year ended December 31, 2018. The components of single lease cost were as follows: Year ended December 31, 2019 2018 Operating lease cost (1) 103.2 85.9 Finance lease cost: Amortization of assets under finance lease 80.3 87.6 Interest 9.2 8.0 Total finance lease cost 89.5 95.6 (1) Is presented gross of sublease income and includes short-term leases, which are immaterial Other information related to leases was as follows: Year ended December 31, 2019 Supplemental Cash Flow Information: Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases included in cash from operating activities $ 102.8 Payments for finance leases included in cash from operating activities 9.2 Payments for finance leases included in cash from financing activities 92.9 Assets obtained in exchange for lease obligations: Operating leases (2) 297.0 Finance leases $ 144.1 (2) Includes the impact of the Company taking initial possession of the second and third phases of its new corporate headquarters in April and December of 2019, respectively, of $ 260.0 million. As of December 31, 2019 Weighted Average Remaining Lease Term (in years) Operating leases 11.3 Finance leases 3.0 Weighted Average Discount Rate Operating leases 4.3 % Finance leases 4.3 % Future minimum lease payments under non-cancellable leases as of December 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2020 $ 115.9 $ 84.1 2021 108.0 68.9 2022 98.2 54.8 2023 82.0 21.1 2024 74.2 0.1 Thereafter 583.0 0.0 Total future minimum lease payments 1,061.3 229.0 Less imputed interest (250.2 ) (14.1 ) Less tenant incentive receivables (19.3 ) — Total liability $ 791.8 $ 214.9 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of December 31, 2019 , the Company is entitled to non-cancelable rent payments from its sub-tenants of $ 34.5 million, which will be collected over the next 1 to 4 years . In 2017, the Company entered into a lease agreement for office space in San Francisco, California, to serve as its new corporate headquarters. The Company took initial possession of the first phase of its new corporate headquarters in June 2018, and began to recognize single lease cost related to the first phase. In that same period, the Company recorded a lease incentive obligation related to tenant improvement reimbursements associated with the first phase. In April 2019, the Company took possession of the second phase, and began to recognize additional lease costs and recorded an additional lease obligation, net of tenant improvement reimbursements expected to be received in the second phase. In December 2019, the Company took possession of the third phase, and began to recognize additional lease costs and recorded an additional lease obligation, net of tenant improvement reimbursements expected to be received in the third phase. The Company's total expected minimum obligations for all three phases of the lease are $ 836.4 million, which exclude expected tenant improvement reimbursements from the landlord of approximately $75.0 million and variable operating expenses. The Company’s obligations under the lease are supported by a $ 34.2 million letter of credit, which reduced the borrowing capacity under the revolving credit facility. For the twelve month period ended December 31, 2019 , the Company collected tenant improvement reimbursements from the landlord totaling $ 55.3 million. The Company moved into its new corporate headquarters and vacated its old corporate headquarters in the third quarter of 2019, at which time the Company began to make recurring rental payments for its new corporate headquarters and stopped incurring expense on its old headquarters. The Company will continue to pay cash rental payments for its old corporate headquarters until the first quarter of 2020. As of December 31, 2019 , the Company had commitments of $ 91.9 million for operating leases that have not yet commenced, and therefore are not included in the right-of-use asset or operating lease liability. These operating leases will commence between 2019 and 2021 with lease terms of 4 years to 12 years
Leases	Leases Leases The Company has operating leases for corporate offices and datacenters, and finance leases for infrastructure equipment. The Company’s leases have remaining lease terms of 1 year to 14 years , some of which include options to extend the leases for up to 5 years . The Company also has subleases of former corporate offices. Subleases have remaining lease terms of 1 year to 4 years . Sublease income, which is recorded as a reduction of rental expense, was $7.1 million for the year ended December 31, 2019 and $ 11.8 million for the year ended December 31, 2018. The components of single lease cost were as follows: Year ended December 31, 2019 2018 Operating lease cost (1) 103.2 85.9 Finance lease cost: Amortization of assets under finance lease 80.3 87.6 Interest 9.2 8.0 Total finance lease cost 89.5 95.6 (1) Is presented gross of sublease income and includes short-term leases, which are immaterial Other information related to leases was as follows: Year ended December 31, 2019 Supplemental Cash Flow Information: Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases included in cash from operating activities $ 102.8 Payments for finance leases included in cash from operating activities 9.2 Payments for finance leases included in cash from financing activities 92.9 Assets obtained in exchange for lease obligations: Operating leases (2) 297.0 Finance leases $ 144.1 (2) Includes the impact of the Company taking initial possession of the second and third phases of its new corporate headquarters in April and December of 2019, respectively, of $ 260.0 million. As of December 31, 2019 Weighted Average Remaining Lease Term (in years) Operating leases 11.3 Finance leases 3.0 Weighted Average Discount Rate Operating leases 4.3 % Finance leases 4.3 % Future minimum lease payments under non-cancellable leases as of December 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2020 $ 115.9 $ 84.1 2021 108.0 68.9 2022 98.2 54.8 2023 82.0 21.1 2024 74.2 0.1 Thereafter 583.0 0.0 Total future minimum lease payments 1,061.3 229.0 Less imputed interest (250.2 ) (14.1 ) Less tenant incentive receivables (19.3 ) — Total liability $ 791.8 $ 214.9 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of December 31, 2019 , the Company is entitled to non-cancelable rent payments from its sub-tenants of $ 34.5 million, which will be collected over the next 1 to 4 years . In 2017, the Company entered into a lease agreement for office space in San Francisco, California, to serve as its new corporate headquarters. The Company took initial possession of the first phase of its new corporate headquarters in June 2018, and began to recognize single lease cost related to the first phase. In that same period, the Company recorded a lease incentive obligation related to tenant improvement reimbursements associated with the first phase. In April 2019, the Company took possession of the second phase, and began to recognize additional lease costs and recorded an additional lease obligation, net of tenant improvement reimbursements expected to be received in the second phase. In December 2019, the Company took possession of the third phase, and began to recognize additional lease costs and recorded an additional lease obligation, net of tenant improvement reimbursements expected to be received in the third phase. The Company's total expected minimum obligations for all three phases of the lease are $ 836.4 million, which exclude expected tenant improvement reimbursements from the landlord of approximately $75.0 million and variable operating expenses. The Company’s obligations under the lease are supported by a $ 34.2 million letter of credit, which reduced the borrowing capacity under the revolving credit facility. For the twelve month period ended December 31, 2019 , the Company collected tenant improvement reimbursements from the landlord totaling $ 55.3 million. The Company moved into its new corporate headquarters and vacated its old corporate headquarters in the third quarter of 2019, at which time the Company began to make recurring rental payments for its new corporate headquarters and stopped incurring expense on its old headquarters. The Company will continue to pay cash rental payments for its old corporate headquarters until the first quarter of 2020. As of December 31, 2019 , the Company had commitments of $ 91.9 million for operating leases that have not yet commenced, and therefore are not included in the right-of-use asset or operating lease liability. These operating leases will commence between 2019 and 2021 with lease terms of 4 years to 12 years

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Other commitments Other commitments include payments to third-party vendors for services related to the Company's infrastructure, infrastructure warranty contracts, and asset retirement obligations for office modifications. Future minimum payments under the Company's non-cancelable leases, finance lease obligations, and other commitments as of December 31, 2019, are as follows, and exclude non-cancelable rent payments from the Company's sub-tenants: Finance lease commitments Operating lease commitments (1) Other commitments (2) Year ended December 31: 2020 $ 84.1 $ 119.5 $ 48.8 2021 68.9 116.4 6.7 2022 54.8 108.1 0.7 2023 21.1 91.6 0.4 2024 0.1 83.9 — Thereafter — 636.2 16.7 Future minimum payments 229.0 $ 1,155.7 $ 73.3 Less interest and taxes (14.1 ) Less current portion of the present value of minimum lease payments (76.7 ) Financing lease obligations, net of current portion $ 138.2 (1) This balance includes short-term lease obligations and operating leases that we have entered into but have not yet commenced. (2) This balance excludes founder holdbacks related to our acquisition of HelloSign. See Note 5, "Business Combinations" for further details. Legal matters From time to time, the Company is a party to a variety of claims, lawsuits, and proceedings which arise in the ordinary course of business, including claims of alleged infringement of intellectual property rights. The matters described in Item 3. ("Legal Proceedings") are examples of the types of claims Dropbox is currently defending. The Company records a liability when it believes that it is probable that a loss will be incurred and the amount of loss or range of loss can be reasonably estimated. In its opinion, resolution of pending matters is not likely to have a material adverse impact on its condensed consolidated results of operations, cash flows, or its financial position. Given the unpredictable nature of legal proceedings, the Company bases its estimate on the information available at the time of the assessment. As additional information becomes available, the Company reassesses the potential liability and may revise the estimate. We are currently involved in four putative class action lawsuits alleging violations of the federal securities laws that were filed on August 30, 2019, September 5, 2019, September 13, 2019, and October 3, 2019, in the Superior Court of the State of California, San Mateo County, against us, certain of our officers and directors, underwriters of our IPO, and Sequoia Capital XII, L.P. and certain of its affiliated entities (collectively, the “Dropbox Defendants”). On October 4, 2019, two putative class action lawsuits alleging violations of the federal securities laws were filed against the Dropbox Defendants in the U.S. District Court for the Northern District of California. The six lawsuits each make the same or similar allegations of violations of the Securities Act of 1933, as amended, for allegedly making materially false and misleading statements in, or omitting material information from, our IPO registration statement. The plaintiffs seek unspecified monetary damages and other relief. We do not currently believe that this matter is likely to have a material adverse impact on our consolidated results of operations, cash flows, or our financial position. Indemnification The Company’s arrangements generally include certain provisions for indemnifying customers against liabilities if its products or services infringe a third party’s intellectual property rights. It is not possible to determine the maximum potential amount under these indemnification obligations due to the limited history of prior indemnification claims.

Accrued and Other Current Liabi

Accrued and Other Current Liabilities	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued and Other Current Liabilities	Accrued and Other Current Liabilities Accrued and other current liabilities consisted of the following: As of December 31, 2019 2018 Non-income taxes payable $ 92.2 $ 75.7 Accrued legal and other external fees 29.2 28.1 Deferred rent — 41.0 Other accrued and current liabilities 40.5 19.7 Total accrued and other current liabilities $ 161.9 $ 164.5 The decrease in deferred rent from December 31, 2018 is due to the Company's adoption of ASC 842 on January 1, 2019 using the modified retrospective approach. As of December 31, 2019

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Common stock The Company’s amended and restated certificate of incorporation authorizes the issuance of Class A common stock, Class B common stock, and Class C common stock. Holders of Class A common stock, Class B common stock, and Class C common stock are entitled to dividends on a pro rata basis, when, as, and if declared by the Company’s Board of Directors, subject to the rights of the holders of the Company’s preferred stock. Holders of Class A common stock are entitled to one vote per share, holders of Class B common stock are entitled to 10 votes per share, and holders of Class C common stock are entitled to zero votes per share. Holders of Class B common stock voluntarily converted 38.9 million and 157.0 million shares into an equivalent number shares of Class A common stock during the years ended December 31, 2019 and December 31, 2018 respectively. As of December 31, 2019 , the Company had authorized 2,400.0 million shares of Class A common stock, 475.0 million shares of Class B common stock, and 800.0 million shares of Class C common stock, each at par value of $0.00001 . As of December 31, 2019 , 255.8 million shares of Class A common stock, 161.2 million shares of Class B common stock, and no shares of Class C common stock were issued and outstanding. As of December 31, 2018 , 211.0 million shares of Class A common stock, 198.6 million shares of Class B common stock, and no shares of Class C common stock were issued and outstanding. Class A shares issued and outstanding as of December 31, 2019 exclude restricted stock awards granted to certain executives during the year. Class A shares issued and outstanding as of December 31, 2019 and 2018 exclude 14.7 million unvested restricted stock awards granted to the Company's founders. See "Co-Founder Grants" section below for further details. Convertible preferred stock Immediately prior to the closing of the Company’s IPO, all of the 147.3 million shares of convertible preferred stock converted into an equivalent number of shares of Class B common stock. Further, pursuant to transfer agreements with certain of the Company’s stockholders, 0.3 million shares of the Company’s convertible preferred stock automatically converted into an equivalent number of shares of Class A common stock. As of December 31, 2019 the Company has zero authorized, issued and outstanding shares of convertible preferred stock. Preferred stock The Company's Board of Directors will have the authority, without further action by the Company's stockholders, to issue up to 240.0 million shares of undesignated preferred stock with rights and preferences, including voting rights, designated from time to time by the Board of Directors. Equity incentive plans Under the 2018 Plan, the Company may grant stock-based awards to purchase or directly issue shares of common stock to employees, directors, and consultants. Options are granted at a price per share equal to the fair market value of the Company's common stock at the date of grant. Options granted are exercisable over a maximum term of 10 years from the date of grant and generally vest over a period of four years . RSUs and RSAs are also granted under the 2018 Plan. The 2018 Plan will terminate 10 years after the later of (i) its adoption or (ii) the most recent stockholder-approved increase in the number of shares reserved under the 2018 Plan, unless terminated earlier by the Company's Board of Directors. The 2018 Plan was adopted on March 22, 2018. In connection with the acquisition of HelloSign, the Company assumed unvested stock options that had been granted under HelloSign's 2011 Equity Incentive Plan. As of December 31, 2019 , there were 32.7 million stock-based awards issued and outstanding and 66.2 million shares available for issuance under the Dropbox Equity Incentive Plans and HelloSign's 2011 Equity Incentive Plan (collectively, the "Plans"). Stock option and restricted stock activity for the Plans was as follows for the years ended December 31, 2019 and 2018 : Options outstanding Restricted stock outstanding Number of shares available for issuance under the Plans Number of shares outstanding under the Plans Weighted- average exercise price per share Weighted- average remaining contractual term (In years) Aggregate Intrinsic Value Number of Plan shares outstanding Weighted- average grant date fair value per share Balance at December 31, 2017 9.0 5.0 $ 10.52 5.5 54.9 $ 15.6 Reserved for issuance under the 2018 Plan 41.4 Additional shares authorized 1.3 Options exercised and RSUs released — (3.4 ) $ 7.75 (40.4 ) 15.42 Options and RSUs canceled 6.0 (0.3 ) $ 22.90 (5.7 ) 16.78 Shares repurchased for tax withholdings on release of restricted stock 15.6 15.45 Restricted stock granted (16.2 ) 16.2 20.26 Balance at December 31, 2018 57.1 1.3 $ 14.68 5.0 9.1 25.0 $ 18.68 Additional shares authorized 21.2 — — — — Stock options assumed 0.9 0.9 6.02 — — Options exercised and RSUs released — (0.3 ) 6.82 (11.2 ) 19.01 Options and RSUs canceled 7.1 (0.2 ) 18.89 (6.9 ) 19.32 Shares repurchased for tax withholdings on release of restricted stock 4.1 — — — 18.87 Restricted stock, awards and options granted (24.2 ) 0.3 23.09 23.8 21.34 Balance as of December 31, 2019 66.2 2.0 $ 12.28 6.5 16.40 30.7 $ 20.48 Vested at December 31, 2019 1.3 $ 16.01 5.4 7.90 — $ — Unvested at December 31, 2019 0.7 $ 5.76 8.50 30.7 $ 20.48 The following table summarizes information about the pre-tax intrinsic value of options exercised during the years ended December 31, 2019 and 2018 : Year ended December 31, 2019 2018 Intrinsic value of options exercised $ 5.3 $ 59.0 As of December 31, 2019 , unamortized stock-based compensation related to unvested stock options, restricted stock awards (excluding the Co-Founder Grants), and RSUs was $597.7 million. The weighted-average period over which such compensation expense will be recognized if the requisite service is provided is approximately 2.9 years as of December 31, 2019 . The total fair value of released RSUs, as of their respective vesting dates, during the years ended December 31, 2019 , 2018 and 2017 were $235.0 million, $913.5 million, and $232.5 million, respectively. Assumed stock options In connection with the acquisition of HelloSign the Company assumed 0.9 million unvested stock options which were valued using the Black-Scholes option-pricing model. The fair value of stock options assumed were estimated using the following assumptions: Expected volatility 51.6 % Expected term (in years) 3.4 - 7.0 Risk-free interest rate 2.42% - 2.51% Dividend yield — % Expected volatility. The expected volatility is based on the Company's historical volatility. Management believes this is the best estimate of the expected volatility over the expected life of its stock options. Expected term. The Company determines the expected term based on the average period the stock options are expected to remain outstanding, generally calculated as the midpoint of the stock options’ remaining vesting term and contractual expiration period, as the Company does not have sufficient historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior. Risk-free interest rate . The risk-free interest rate is based on the U.S. Treasury security in effect at the time the options were assumed for maturities corresponding with the expected term of the option. Expected dividend yield . The Company has not paid and does not expect to pay dividends. Consequently, the Company uses an expected dividend yield of zero . The estimated weighted-average grant date fair value for stock options assumed was $ 21.60 per share and total fair value of $ 19.4 million, of which, $ 18.6 million will be recognized as post-combination stock-based compensation expense. Co-Founder Grants In December 2017, the Board of Directors approved a grant to the Company’s co-founders of non-Plan RSAs with respect to 14.7 million shares of Class A Common Stock in the aggregate (collectively, the “Co-Founder Grants”), of which 10.3 million RSAs were granted to Mr. Houston, the Company’s co-founder and Chief Executive Officer, and 4.4 million RSAs were granted to Mr. Ferdowsi, the Company’s co-founder and Director. These Co-Founder Grants have service-based, market-based, and performance-based vesting conditions. The Co-Founder Grants are excluded from Class A common stock issued and outstanding until the satisfaction of these vesting conditions. The Co-Founder Grants also provide the holders with certain stockholder rights, such as the right to vote the shares with the other holders of Class A common stock and a right to cumulative declared dividends. However, the Co-Founder Grants are not considered a participating security for purposes of calculating net loss per share attributable to common stockholders in Note 13, "Net Loss Per Share", as the right to the cumulative declared dividends is forfeitable if the service condition is not met. The Co-Founder Grants are eligible to vest over the ten-year period following the date the Company’s shares of Class A common stock commenced trading on the Nasdaq Global Select Market in connection with the Company’s IPO. The Co-Founder Grants comprise nine tranches that are eligible to vest based on the achievement of stock price goals ranging from $30 to $90 per share, each of which are referred to as a Stock Price Target, measured over a consecutive thirty-day trading period during the Performance Period. The Performance Period began on January 1, 2019. During the first four years of the Performance Period, no more than 20% of the shares subject to each Co-Founder Grant would be eligible to vest in any calendar year. After the first four years , all shares are eligible to vest based on the achievement of the Stock Price Targets. The Company calculated the grant date fair value of the Co-Founder Grants based on multiple stock price paths developed through the use of a Monte Carlo simulation. A Monte Carlo simulation also calculates a derived service period for each of the nine vesting tranches, which is the measure of the expected time to achieve each Stock Price Target. A Monte Carlo simulation requires the use of various assumptions, including the underlying stock price, volatility, and the risk-free interest rate as of the valuation date, corresponding to the length of time remaining in the performance period, and expected dividend yield. The weighted-average grant date fair value of each Co-Founder Grant was estimated to be $ 10.60 per share. The weighted-average derived service period of each Co-Founder Grant was estimated to be 5.2 years , and ranged from 2.9 - 6.9 years . The Company will recognize aggregate stock-based compensation expense of $156.2 million over the derived service period of each tranche using the accelerated attribution method as long as the co-founders satisfy their service-based vesting conditions. If the Stock Price Targets are met sooner than the derived service period, the Company will adjust its stock-based compensation to reflect the cumulative expense associated with the vested awards. The Company will recognize expense if the requisite service is provided, regardless of whether the market conditions are achieved. The Performance Vesting Condition for the Co-Founder Grants was satisfied on the date the Company’s shares of Class A common stock commenced trading on the Nasdaq Global Select Market in connection with the Company’s IPO, which was March 23, 2018. The Company recognized stock-based compensation expense related to the Co-Founder Grants of $ 34.9 and $37.0 million during the years ended December 31, 2019 and December 31, 2018 , respectively. Unamortized stock-based compensation expense related to the Co-Founder Grants was $ 84.2 million and $ 119.3 million for the years ended December 31, 2019 and December 31, 2018 , respectively. Award modifications During the year ended December 31, 2017, the Company's Board of Directors voted to approve a modification of vesting schedules for certain unvested one-tier and two-tier RSUs to align the vesting schedules for all RSUs to vest once per quarter. The modification was effective February 15, 2018, which resulted in accelerated vesting of impacted RSUs that had met their service requirement as of that date. As a result, the Company recognized an incremental $10.0 million in stock-based compensation during the first quarter of 2018, related to these modified one-tier and two-tier RSUs.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The Company computes net loss per share using the two-class method required for multiple classes of common stock and participating securities. The rights, including the liquidation and dividend rights, of the Class A common stock and Class B common stock are substantially identical, other than voting rights. Accordingly, the Class A common stock and Class B common stock share equally in the Company’s net losses. Before the IPO, the Company’s outstanding securities also included convertible preferred stock. The holders of convertible preferred stock did not have a contractual obligation to share in the Company’s losses, and as a result, net losses were not allocated to these securities. The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented. The shares issued in the IPO and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below weighted for the period outstanding in the year ended December 31, 2018 . Additionally, the voluntary conversions of Class B common stock into Class A common stock are included in the table below weighted for the period outstanding in the years ended December 31, 2019 and December 31, 2018 : Year ended December 31, 2019 2018 2017 Class A Class B Class A Class B Class A Class B Numerator: Net loss attributable to common stockholders $ (30.3 ) $ (22.4 ) $ (138.7 ) $ (346.2 ) $ (3.6 ) $ (108.1 ) Denominator: Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share 236.8 174.8 102.6 256.0 6.3 189.6 Net loss per common share, basic and diluted $ (0.13 ) $ (0.13 ) $ (1.35 ) $ (1.35 ) $ (0.57 ) $ (0.57 ) Since the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. The weighted-average impact of potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive was as follows: Year ended December 31, 2019 2018 2017 Convertible preferred stock — — 147.6 Restricted stock units 28.9 35.0 52.7 Restricted stock awards 0.4 — 0.0 Options to purchase shares of common stock 1.9 4.0 5.1 Co-Founder Grants 14.7 14.7 0.8 Shares subject to repurchase from early-exercised options and unvested restricted stock — 0.1 0.2 Total 45.9 53.8 206.4

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the years ended December 31, 2019 , 2018 , and 2017 , the Company’s loss from continuing operations before provision for income taxes was as follows: Year ended December 31, 2019 2018 2017 Domestic $ (98.8 ) $ (497.1 ) $ (76.9 ) Foreign 46.8 17.0 (34.6 ) Loss before income taxes $ (52.0 ) $ (480.1 ) $ (111.5 ) The components of the benefit from (provision for) income taxes in the years ended December 31, 2019 , 2018 , and 2017 , were as follows: Year ended December 31, 2019 2018 2017 Current: Federal $ 0.1 $ (0.1 ) $ 0.1 State (0.6 ) (0.2 ) (0.3 ) Foreign (7.7 ) (4.6 ) (2.3 ) Deferred: Federal 6.6 — 1.4 State 0.6 — — Foreign 0.3 0.1 0.9 Benefit from (provision for) income taxes $ (0.7 ) $ (4.8 ) $ (0.2 ) A reconciliation of income taxes at the statutory federal income tax rate to the benefit from (provision for) income taxes included in the accompanying consolidated statements of operations is as follows (in millions): Year ended December 31, 2019 2018 2017 Tax benefit at federal statutory rate $ 10.9 $ 100.8 $ 37.9 State taxes, net of federal benefit 2.4 10.7 1.7 Foreign rate differential (0.9 ) 1.8 (12.3 ) Research and other credits 30.2 86.5 25.4 Non-deductible compensation (3.4 ) — — Meals & entertainment (2.5 ) (2.2 ) (0.2 ) Permanent differences (2.1 ) (16.2 ) (8.8 ) Tax Cuts and Jobs Act impact — — (61.7 ) Change in valuation allowance (32.2 ) (240.7 ) 38.9 Stock-based compensation 1.8 57.3 (20.1 ) Other non-deductible items (4.9 ) (2.8 ) (1.0 ) Benefit from (provision for) income taxes $ (0.7 ) $ (4.8 ) $ (0.2 ) The significant components of the Company’s deferred tax assets and liabilities as of December 31, 2019 and 2018 were as follows: As of December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 257.2 $ 264.8 Research credit carryforwards 188.6 157.3 Stock-based compensation 29.3 11.1 Accruals and reserves 32.3 42.0 Fixed assets and intangible assets — 0.7 Lease liability 189.8 — Other 1.0 1.1 Gross deferred tax assets 698.2 477.0 Valuation allowance (510.8 ) (476.0 ) Total deferred tax assets, net of valuation allowance 187.4 1.0 Deferred tax liabilities: Fixed assets and intangible assets 13.1 — Right of use assets 172.7 — Other 0.3 — Total deferred tax liability 186.1 — Net deferred tax assets $ 1.3 $ 1.0 For the years ended December 31, 2019 and 2018 , based on all available objective evidence, including the existence of cumulative losses, the Company determined that it was not more likely than not that the U.S., Ireland, and Israel net deferred tax assets were fully realizable as of December 31, 2019 and 2018 . Accordingly, the Company established a full valuation allowance against its U.S. and Ireland deferred tax assets and a partial valuation allowance against its Israeli deferred tax assets. As of December 31, 2019 , the Company had $916.9 million of federal, $390.8 million of state, and $244.3 million of foreign net operating loss carryforwards available to reduce future taxable income. Of the federal net operating loss carryforwards, $288.9 million will begin to expire in 2032 and $628.0 million will carryforward indefinitely, while state net operating losses begin to expire in 2026 . As of December 31, 2019 , the Company had research credit carryforwards of $171.7 million and $94.6 million for federal and state income tax purposes, respectively, of which $42.8 million and $23.6 million is the unrecognized tax benefit portion related to the research credit carryforwards for federal and state, respectively. The federal credit carryforward will begin to expire in 2027. The state research credits have no expiration date. The Company also had $3.6 million of state enterprise zone credit carryforwards, which will begin to expire in 2023. As of December 31, 2019 , the Company also had $221.4 million of foreign net operating loss carryforwards available to reduce future taxable income, which will carryforward indefinitely. In addition, the Company had $22.9 million of foreign acquired net operating losses, which will carryforward indefinitely. The Company also had $0.7 million of foreign tax credit carryforwards, which will carryforward indefinitely. Under Section 382 and 383 of the Internal Revenue Code of 1986, as amended, or the Code, if a corporation undergoes an “ownership change,” the corporation’s ability to use its pre-change net operating loss carryforwards and other pre-change attributes, such as research tax credits, to offset its post-change income may be limited. In general, an “ownership change” will occur if there is a cumulative change in our ownership by “5-percent shareholders” that exceeds 50 percentage points over a rolling three-year period. Similar rules may apply under state tax laws. The Company has determined that it has experienced multiple ownership changes and, as a result, the annual utilization of our net operating loss carryforwards and other pre-change attributes will be subject to limitation. However, the Company does not expect that the annual limitations will significantly impact its ability to utilize our net operating loss or tax credit carryforwards prior to expiration. As of December 31, 2019 , the balance of unrecognized tax benefits was $74.5 million of which $8.1 million, if recognized, would affect the effective tax rate and $66.4 million would result in adjustment to deferred tax assets with corresponding adjustments to the valuation allowance. A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows: Year ended December 31, 2019 2018 2017 Balance of gross unrecognized tax benefits at the beginning of the fiscal year $ 59.8 $ 25.6 $ 15.7 Gross increases related to prior period tax positions 0.1 1.1 — Gross increases related to current period tax positions 14.6 33.1 9.9 Balance of gross unrecognized tax benefits at the end of the fiscal year $ 74.5 $ 59.8 $ 25.6 The Company recognizes interest and/or penalties related to income tax matters as a component of income tax expense. As of December 31, 2019 , the amount of accrued interest and penalties related to uncertain tax positions was $2.6 million. Interest and penalties recognized for the year ended December 31, 2019 , 2018 , and 2017 was $1.3 million, $0.7 million, and $0.2 million, respectively. The amount of unrecognized tax benefits could be reduced upon expiration of the applicable statutes of limitations and resolution and/or closure of audits. As of December 31, 2019, the Company anticipates the gross unrecognized tax benefits would not significantly change in the next 12 months. The Company files income tax returns in the U.S. federal, multiple states, and foreign jurisdictions. All of the Company’s tax years from 2007 remain open for examination by the federal and state authorities, and from 2013 by foreign authorities. The Company generally does not provide deferred income taxes for the undistributed earnings of its foreign subsidiaries as the Company intends to reinvest such earnings indefinitely. Should circumstances change and it becomes apparent that some or all of the undistributed earnings will no longer be indefinitely reinvested, the Company will accrue for income taxes not previously recognized. As of December 31, 2019 , there were no cumulative undistributed earnings in its Irish subsidiary and, as a result, there were no unrecorded deferred tax liabilities. The amount of undistributed earnings in the Company’s other foreign subsidiaries, if any, are immaterial.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Dropbox Charitable Foundation During the year ended December 31, 2016, two of the Company’s controlling shareholders formed the Dropbox Charitable Foundation, a Delaware non-stock corporation (the “Foundation”). The primary purpose of the Foundation is to engage in charitable and educational activities within the meaning of Section 501(c)(3) of the Code. The Foundation is governed by a Board of Directors, a majority of which are independent. Both shareholders made contributions to the Foundation during the year ended December 31, 2016, comprised entirely of shares of Dropbox common stock. The Company has not consolidated the Foundation in the accompanying consolidated financial statements, as the Company does not have control of the entity. During the year ended December 31, 2017, the Company donated shares of Class B common stock to initially fund the Foundation and recorded $9.4 million of expense to general and administrative expenses based on the Company’s estimate of the then current fair value of the contributed shares. The Company made additional cash contributions to the Foundation of $1.9 million during year ended December 31, 2017. There were no contributions to the Foundations during the years ended December 31, 2019 and December 31, 2018

Geographic Areas

Geographic Areas	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Geographic Areas	Geographic Areas Long-lived assets The following table sets forth long-lived assets by geographic area: As of December 31, 2019 2018 United States $ 431.9 $ 293.6 International (1) 13.4 17.0 Total property and equipment, net $ 445.3 $ 310.6 (1) No single country other than the United States had a property and equipment balance greater than 10% of total property and equipment, net, as of December 31, 2019 and 2018 . Revenue Revenue by geography is generally based on the address of the customer as defined in the Company’s subscription agreement. The following table sets forth revenue by geographic area for the years ended December 31, 2019 , 2018 , and 2017 : Year ended December 31, 2019 2018 2017 United States $ 854.1 $ 706.5 $ 575.7 International (1) 807.2 685.2 531.1 Total revenue $ 1,661.3 $ 1,391.7 $ 1,106.8 (1) No single country outside of the United States accounted for more than 10 percent of total revenue during the years ended December 31, 2019 , 2018 , and 2017

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 19, 2020, our Board of Directors authorized the repurchase of up to $600 million of the Company’s outstanding shares of Class A common stock. Under the stock repurchase program, the Company is authorized to repurchase, from time-to-time, shares of its outstanding common stock through open market purchases or in privately negotiated transactions, in accordance with applicable rules and regulations, at such time and such prices as management may decide. The program does not obligate the Company to repurchase any specific number of shares and may be discontinued at any time. There have been no purchases of common stock executed under the repurchase program as of the date of this filing.

Description of the Business a_2

Description of the Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying consolidated financial statements have been prepared in accordance with the United States of America generally accepted accounting principles (“GAAP”). The accompanying consolidated financial statements include the accounts of Dropbox and its wholly owned subsidiaries.
Consolidation	All intercompany balances and transactions have been eliminated in consolidation.
Use of estimates	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the consolidated financial statements. Management evaluates these estimates and assumptions on a regular basis. Actual results may differ materially from these estimates.
Financial information about segments and geographic areas	The Company manages its operations and allocates resources as a single operating segment. Further, the Company manages, monitors, and reports its financials as a single reporting segment. The Company’s chief operating decision-maker is its Chief Executive Officer, who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources.
Foreign currency transactions	The assets and liabilities of the Company’s foreign subsidiaries are translated from their respective functional currencies into U.S. dollars at the exchange rates in effect at the balance sheet date. Revenue and expense amounts are translated at the average exchange rate for the period. Foreign currency translation gains and losses are recorded in other comprehensive income (loss).
Revenue recognition and deferred commissions, net	Deferred commissions, net is stated as gross deferred commissions less accumulated amortization. Sales commissions earned by the Company’s sales force and third-party resellers, as well as related payroll taxes, are considered to be incremental and recoverable costs of obtaining a contract with a customer. These amounts have been capitalized as deferred commissions within prepaid and other current assets and other assets on the consolidated balance sheets. The Company derives its revenue from subscription fees from customers for access to its platform. The Company’s policy is to exclude sales and other indirect taxes when measuring the transaction price of its subscription agreements. The Company accounts for revenue contracts with customers through the following steps: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, the Company satisfies a performance obligation The Company’s subscription agreements generally have monthly or annual contractual terms and a small percentage have multi-year contractual terms. Revenue is recognized ratably over the related contractual term beginning on the date that the platform is made available to a customer. Access to the platform represents a series of distinct services as the Company continually provides access to, and fulfills its obligation to the end customer over the subscription term. The series of distinct services represents a single performance obligation that is satisfied over time. The Company recognizes revenue ratably because the customer receives and consumes the benefits of the platform throughout the contract period. The Company’s contracts are generally non-cancelable. The Company bills in advance for monthly contracts and typically bills annually in advance for contracts with terms of one year or longer . The Company also recognizes an immaterial amount of contract assets, or unbilled receivables, primarily relating to consideration for services completed but not billed at the reporting date. Unbilled receivables are classified as receivables when the Company has the right to invoice the customer. The Company records contract liabilities when cash payments are received or due in advance of performance to deferred revenue. Deferred revenue primarily relates to the advance consideration received from the customer. The price of subscriptions is generally fixed at contract inception and therefore, the Company’s contracts do not contain a significant amount of variable consideration. As a result, the amount of revenue recognized in the periods presented from performance obligations satisfied (or partially satisfied) in previous periods was not material.
Stock-based compensation	The Company has granted RSUs to its employees and members of the Board of Directors under the 2008 Equity Incentive Plan (“2008 Plan”), the 2017 Equity Incentive Plan (“2017 Plan”), and the 2018 Equity Incentive Plan ("2018 Plan" and together with the 2008 Plan and 2017 Plan, the "Dropbox Equity Incentive Plans"). The Company has granted the following types of RSUs under the Dropbox Equity Incentives Plans: • One-tier RSUs, which have a service-based vesting condition over a four-year period. These awards typically have a cliff vesting period of one year and continue to vest quarterly thereafter. The Company began granting one-tier RSUs under its 2008 Plan in August 2015, and it continues to grant one-tier RSUs under its 2018 Plan. The Company recognizes compensation expense associated with one-tier RSUs ratably on a straight-line basis over the requisite service period and accounts for forfeitures in the period in which they occur. • Two-tier RSUs, which had both a service-based vesting condition and a Performance Vesting Condition. The Performance Vesting Condition was satisfied on the effectiveness of the registration statement related to the Company's IPO. Prior to August 2015, the Company granted two-tier RSUs under the 2008 Plan. The last grant date for two-tier RSUs was in May 2015. The Company recognized compensation expense associated with two-tier RSUs using the accelerated attribution method over the requisite service period. As of December 31, 2019 , the Company only had one -tier RSUs outstanding under the Dropbox Equity Incentive Plans. Since August 2015, the Company has granted one-tier RSUs as the only stock-based payment awards to its employees, with the exception of awards granted to its co-founders and certain executives, and has not granted any stock options to employees since then. The fair values of the common stock underlying the RSUs granted in periods prior to the date of the Company's IPO were determined by the Board of Directors, with input from management and contemporaneous third-party valuations, which were performed at least quarterly. For valuations after the Company's IPO, the Board of Directors determines the fair value of each share of underlying common stock based on the closing price of the Company's Class A common stock as reported on the Nasdaq Global Select Market on the date of the grant. In connection with the acquisition of JN Projects, Inc. (d/b/a HelloSign) ("HelloSign"), the Company assumed unvested stock options that had been granted under the HelloSign's 2011 Equity Incentive Plan. The fair value of options assumed were based upon the Black-Scholes option-pricing model, see Note 12, "Stockholders' Equity" for further information. In December 2017 , the Board of Directors approved a grant to the Company’s co-founders of restricted stock awards (“RSAs”) with respect to 14.7 million shares of Class A Common Stock in the aggregate (collectively, the “Co-Founder Grants”), of which 10.3 million RSAs were granted to Mr. Houston, the Company’s co-founder and Chief Executive Officer, and 4.4 million RSAs were granted to Mr. Ferdowsi, the Company’s co-founder and Director. These Co-Founder Grants have service-based, market-based, and performance-based vesting conditions. The Company estimated the grant date fair value of the Co-Founder Grants using a model based on multiple stock price paths developed through the use of a Monte Carlo simulation that incorporates into the valuation the possibility that the Stock Price Targets may not be satisfied. See Note 12, "Stockholders' Equity" for further information.
Cost of revenue	Cost of revenue consists primarily of expenses associated with the storage, delivery, and distribution of the Company’s platform for both paying users and free users, also known as Basic users. These costs, which are referred to as infrastructure costs, include depreciation of servers located in co-location facilities that the Company leases and operates, rent and facilities expense for those datacenters, network and bandwidth costs, support and maintenance costs for infrastructure equipment, and payments to third-party datacenter service providers. Cost of revenue also includes costs, such as salaries, bonuses, benefits, travel-related expenses, and stock-based compensation, which are referred to as employee-related costs, for employees whose primary responsibilities relate to supporting the Company’s infrastructure and delivering user support. Other non-employee costs included in cost of revenue include credit card fees related to processing customer transactions and allocated overhead, such as facilities, including rent, utilities, depreciation on leasehold improvements and other equipment shared by all departments, and shared information technology costs. In addition, cost of revenue includes amortization of developed technologies, professional fees related to user support initiatives, and property taxes related to the datacenters.
Advertising and promotional expense	Advertising and promotional expenses are included in sales and marketing expenses within the consolidated statements of operations and are expensed when incurred. Advertising and promotional expenses were $88.8 million , $100.9 million , and $80.1 million in the years ended December 31, 2019, 2018, and 2017, respectively.
Cash and cash equivalents	Cash consists primarily of cash on deposit with banks and includes amounts in transit from payment processors for credit and debit card transactions, which typically settle within five business days. Cash equivalents include highly liquid investments purchased with an original maturity date of 90 days or less from the date of purchase.
Short-term investments	The Company’s short-term investments are primarily comprised of corporate notes and obligations, U.S. Treasury securities, certificates of deposit, asset-backed securities, commercial paper, U.S. agency obligations, supranational securities, and municipal securities. The Company determines the appropriate classification of its short-term investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its short-term investments as available-for-sale securities as the Company may sell these securities at any time for use in its current operations or for other purposes, even prior to maturity. As a result, the Company classifies its short-term investments, including securities with stated maturities beyond twelve months, within current assets in the consolidated balance sheets. The Company's short-term investments are classified as available-for-sale securities and are recorded at fair value each reporting period. Unrealized gains and losses on these short-term investments are reported as a separate component of accumulated other comprehensive income (loss) in the consolidated balance sheets until realized. Interest income is reported within interest income, net in the consolidated statements of operations. The Company periodically evaluates its short-term investments to assess whether those with unrealized loss positions are other-than-temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value is less than the Company’s cost basis, and the financial condition and near-term prospects of the investee. Realized gains and losses are determined based on the specific identification method and are reported in other income, net in the consolidated statements of operations. If the Company determines that the decline in an investment’s fair value is other-than-temporary, the difference is recognized as an impairment loss in the consolidated statements of operations.
Concentrations of credit risk	Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, accounts receivable, and short-term investments. The Company places its cash and cash equivalents, and short-term investments with well-established financial institutions.
Receivables	Trade and other receivables, net Trade and other receivables, net consists primarily of trade receivables that are recorded at the invoice amount, net of an allowance for doubtful accounts. The allowance for doubtful accounts is based on the Company’s assessment of the collectability of accounts. The Company regularly reviews the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice, the collection history of each customer, and other relevant factors to determine the appropriate amount of the allowance. Accounts receivable deemed uncollectable are charged against the allowance for doubtful accounts when identified. The Company's allowance for doubtful accounts was $0.5 million and $1.2 million as of December 31, 2019 and 2018, respectively. Non-trade receivables The Company records non-trade receivables to reflect amounts due for activities outside of its subscription agreements, such as non-current notes receivable. Non-trade receivables totaled $ 7.4 million and $ 46.2 million, as of December 31, 2019 and 2018 , respectively, and are classified within prepaid expenses and other current assets in the accompanying consolidated balance sheets. See "—Lease obligations” for further discussion.
Property and equipment, net	Equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful life of the related asset, which is generally three to seven years
Equity investments	The Company holds an equity investment in a publicly traded company in which the Company does not have a controlling interest or significant influence. The investment is measured using quoted prices in its active market with changes recorded in other income, net, in the condensed consolidated statement of operations. As of December 31, 2019 , the Company's equity investment had a carrying value of $ 9.8 million and is included in other assets in the condensed consolidated balance sheet. The Company recognized net gains of $ 4.5 million related to changes in quoted prices in the investment’s active market during the twelve month period ended December 31, 2019 . The investment is classified as a Level 1 investment within the fair value hierarchy.
Lease obligations	The Company leases office space, datacenters, and equipment under non-cancelable finance operating leases with various expiration dates through 2033. The Company determines if an arrangement contains a lease at inception. Operating lease right-of-use assets and lease liabilities are recognized at the present value of the future lease payments at commencement date. The interest rate implicit in the Company’s operating leases is not readily determinable, and therefore an incremental borrowing rate is estimated to determine the present value of future payments. The estimated incremental borrowing rate factors in a hypothetical interest rate on a collateralized basis with similar terms, payments, and economic environments. Operating lease right-of-use assets also include any prepaid lease payments and lease incentives. Certain of the operating lease agreements contain rent concession, rent escalation, and option to renew provisions. Rent concession and rent escalation provisions are considered in determining the single lease cost to be recorded over the lease term. Single lease cost is recognized on a straight-line basis over the lease term commencing on the date the Company has the right to use the leased property. The lease terms may include options to extend or terminate the lease. The Company generally uses the base, non-cancelable, lease term when recognizing the lease assets and liabilities, unless it is reasonably certain that the option will be exercised. In addition, certain of the Company’s operating lease agreements contain tenant improvement allowances from its landlords. These allowances are accounted for as lease incentives and decrease the Company's right-of-use asset and reduce single lease cost over the lease term. The Company leases certain equipment from various third parties, through equipment finance leases. These leases either include a bargain purchase option, a full transfer of ownership at the completion of the lease term, or the terms of the leases are at least 75 percent of the useful lives of the assets and are therefore classified as finance leases. These leases are capitalized in property and equipment, net and the related amortization of assets under finance leases is included in depreciation and amortization expense in the Company’s consolidated statements of operations. Initial asset values and finance lease obligations are based on the present value of future minimum lease payments. The Company’s finance lease agreements may contain lease and non-lease components. The non-lease components include payments for support on infrastructure equipment obtained via finance leases, which when not significant in relation to the overall agreement, are combined with the lease components and accounted for together as a single lease component.
Internal use software	The Company capitalizes certain costs related to developed or modified software solely for its internal use and cloud based applications used to deliver its platform. The Company capitalizes costs during the application development stage once the preliminary project stage is complete, management authorizes and commits to funding the project, and it is probable that the project will be completed and that the software will be used to perform the function intended. Costs related to preliminary project activities and post implementation activities are expensed as incurred. Capitalized internal use software costs were not material to the Company’s consolidated financial statements during the years ended December 31, 2019, 2018, and 2017.
Business combinations	The Company uses best estimates and assumptions, including but not limited to, future expected cash flows, expected asset lives, and discount rates, to assign a fair value to the tangible and intangible assets acquired and liabilities assumed in business combinations as of the acquisition date. These estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed may be recorded, with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the Company’s consolidated statements of operations.
Long-lived assets, including goodwill and other acquired intangible assets, net	The Company evaluates the recoverability of its property and equipment and finite-lived intangible assets for possible impairment whenever events or circumstances indicate that the carrying amount of such assets may not be recoverable. The evaluation is performed at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If such review determines that the carrying amount of specific property and equipment or intangible assets is not recoverable, the carrying amount of such assets is reduced to its fair value. The Company reviews goodwill for impairment at least annually in the fourth quarter, or more frequently if events or changes in circumstances would more likely than not reduce the fair value of its single reporting unit below its carrying value. The Company has not recorded impairment charges on property and equipment, goodwill, or intangible assets for the periods presented in these consolidated financial statements. Acquired property and equipment and finite-lived intangible assets are amortized over their useful lives. The Company evaluates the estimated remaining useful life of these assets when events or changes in circumstances warrant a revision to the remaining period of amortization. If the Company revises the estimated useful life assumption for any asset, the remaining unamortized balance is amortized or depreciated over the revised estimated useful life on a prospective basis.
Income taxes	Deferred income tax balances reflect the effects of temporary differences between the financial reporting and tax bases of the Company’s assets and liabilities using enacted tax rates expected to apply when taxes are actually paid or recovered. In addition, deferred tax assets are recorded for net operating loss and credit carryforwards. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized based on all available positive and negative evidence. Such evidence includes, but is not limited to, recent cumulative earnings or losses, expectations of future taxable income by taxing jurisdiction, and the carry-forward periods available for the utilization of deferred tax assets. The Company uses a two-step approach to recognizing and measuring uncertain income tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates it is more likely than not that the position will be sustained on audit. The second step is to measure the tax benefit as the largest amount, which is more than 50% likely of being realized upon ultimate settlement. The Company recognizes interest and penalties related to unrecognized tax benefits as income tax expense. Although the Company believes that it has adequately reserved for its uncertain tax positions, it can provide no assurance that the final tax outcome of these matters will not be materially different. The Company evaluates its uncertain tax positions on a regular basis and evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, such as the 2017 Tax Cuts and Jobs Act ("2017 Tax Reform Act"), correspondence with tax authorities during the course of an audit, and effective settlement of audit issues. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made and could have a material impact on the Company’s financial condition and results of operations.
Fair value measurement	The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value measurements for assets and liabilities, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions, and credit risk. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability.
Recently issued accounting pronouncements not yet adopted and Recently adopted accounting pronouncements	Recently issued accounting pronouncements not yet adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses rather than as a reduction in the amortized cost basis of the securities. These changes will result in more timely recognition of credit losses. The guidance is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The Company does not expect the adoption of ASU No. 2016-13 to have a significant impact on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), which amends disclosure requirements for fair value measurements by requiring new disclosures, modifying existing requirements, and eliminating others. The amendments are the result of a broader disclosure project, which aims to improve the effectiveness of disclosures. ASU No. 2018-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. The Company does not expect the adoption of ASU No. 2018-13 to have a significant impact on its disclosures. In August 2018, the FASB issued ASU No. 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. Under existing U.S. GAAP, there is diversity in practice in accounting for the costs of implementing cloud computing arrangements that are service contracts. The amendments in ASU No. 2018-15 amend the definition of a hosting arrangement and requires a customer in a hosting arrangement that is a service contract to capitalize certain costs as if the arrangement were an internal-use software project. The guidance is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. The Company does not expect the adoption of ASU No. 2018-15 to have a significant impact on its consolidated financial statements. Recently adopted accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . Most prominent among the changes in the standard is the recognition of right-of-use assets (“ROU assets”) and lease liabilities by lessees for certain leases classified as operating leases under current GAAP. The Company made the policy election to not recognize a lease liability or right-of-use asset for short-term operating leases. The Company adopted the standard as of January 1, 2019, using the modified retrospective approach and has elected to use the optional transition method which allows the Company to apply the guidance of ASC 840, including disclosure requirements, in the comparative periods presented. In addition, the Company elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed the Company to carry forward the historical lease classification related to agreements entered prior to adoption. The most significant impact was the recognition of ROU assets and lease liabilities for operating leases. The adoption of the new standard resulted in the recording of operating ROU assets and lease liabilities of approximately $431.7 million and $502.4 million , respectively, as of January 1, 2019. The accounting for finance leases remained unchanged, except for the accounting for certain non-lease components. Lease and non-lease components will be accounted for as a single lease component if the non-lease component is determined to be insignificant to the total agreement. The cumulative impact of transition to retained earnings, recorded as of the adoption date, was not material. The standard did not materially impact consolidated net earnings and had no impact on cash flows. In February 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . Under existing U.S. GAAP, the effects of changes in tax rates and laws on deferred tax balances are recorded as a component of income tax expense in the period in which the law was enacted. When deferred tax balances related to items originally recorded in accumulated other comprehensive income are adjusted, certain tax effects become stranded in accumulated other comprehensive income. The amendments in ASU No. 2018-02 allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the 2017 Tax Reform Act. The amendments in ASU No. 2018-02 also require certain disclosures about stranded tax effects. The Company adopted ASU No. 2018-02 on January 1, 2019. The adoption of the standard did not have a material impact on the Company's consolidated financial statements. In June 2018, the FASB issued ASU No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting. Under existing U.S. GAAP, the measurement date for equity awards granted to nonemployees is the earlier of the performance commitment date or the date the performance is complete. The amendments in ASU No. 2018-07 allow for measurement of these awards on the grant date, consistent with equity awards granted to employees. The Company adopted ASU No. 2019-07 on January 1, 2019. The adoption of the standard did not have a material impact on the Company's consolidated financial statements. Prior Period Reclassifications Certain amounts in prior periods have been reclassified to conform with current period presentation.

Description of the Business a_3

Description of the Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Estimated Useful Lives of Property and Equipment	The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Property and equipment, net consisted of the following: As of December 31, 2019 2018 Datacenter and other computer equipment $ 749.3 $ 667.4 Furniture and fixtures 35.5 23.8 Leasehold improvements 211.4 150.5 Construction in progress 36.3 32.8 Total property and equipment 1,032.5 874.5 Accumulated depreciation and amortization (587.2 ) (563.9 ) Property and equipment, net $ 445.3 $ 310.6

Cash, Cash Equivalents and Sh_2

Cash, Cash Equivalents and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Schedule of Cash, Cash Equivalents and Short-Term Investments	The amortized cost, unrealized gains and losses and estimated fair value of the Company's cash, cash equivalents and short-term investments as of December 31, 2019 consisted of the following: Amortized cost Unrealized gain Unrealized loss Estimated fair value Cash $ 105.0 $ — $ — $ 105.0 Cash equivalents Money market funds 444.3 — — 444.3 Commercial paper 2.0 — — 2.0 Total cash and cash equivalents $ 551.3 $ — $ — $ 551.3 Short-term investments Corporate notes and obligations 285.5 1.2 (0.1 ) 286.6 U.S. Treasury securities 171.0 0.3 — 171.3 Asset backed securities 53.8 — — 53.8 Certificates of deposit 38.2 — — 38.2 U.S. agency obligations 27.2 — — 27.2 Commercial paper 24.2 — — 24.2 Supranational securities 4.0 — — 4.0 Municipal securities 2.4 — — 2.4 Total short-term investments 606.3 1.5 (0.1 ) 607.7 Total $ 1,157.6 $ 1.5 $ (0.1 ) $ 1,159.0 The amortized cost, unrealized gains and losses and estimated fair value of the Company's cash, cash equivalents and short-term investments as of December 31, 2018 consisted of the following: Amortized cost Unrealized gain Unrealized loss Estimated fair value Cash $ 103.0 $ — $ — $ 103.0 Cash equivalents Money market funds 355.5 — — 355.5 Commercial paper 27.4 — — 27.4 U.S. Treasury securities 33.4 33.4 Total cash and cash equivalents $ 519.3 $ — $ — $ 519.3 Short-term investments Corporate notes and obligations 269.6 0.1 (0.5 ) 269.2 U.S. Treasury securities 176 — (0.1 ) 175.9 Certificates of deposit 70.6 — — 70.6 U.S. agency obligations 37.1 — — 37.1 Commercial paper 17.2 — — 17.2 Total short-term investments 570.5 0.1 (0.6 ) 570.0 Total $ 1,089.8 $ 0.1 $ (0.6 ) $ 1,089.3
Contractual Maturities of Short Term Investments	The following table presents the contractual maturities of the Company’s short-term investments as of December 31, 2019 : Amortized cost Estimated fair value Due within one year $ 275.9 $ 276.5 Due between one to three years 310.7 311.5 Due after three years 19.7 19.7 Total $ 606.3 $ 607.7

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value on Recurring Basis	The following table presents information about the Company’s financial instruments that are measured at fair value on a recurring basis using the input categories discussed in Note 1: As of December 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 444.3 $ — $ — $ 444.3 Commercial paper — 2.0 — 2.0 Total Cash Equivalents $ 444.3 $ 2.0 $ — $ 446.3 Short-term investments Corporate notes and obligations — 286.6 — 286.6 U.S. Treasury securities — 171.3 — 171.3 Certificates of deposit — 38.2 — 38.2 Asset-backed securities — 53.8 — 53.8 Commercial paper — 24.2 — 24.2 U.S. agency obligations — 27.2 — 27.2 Supranational securities — 4.0 — 4.0 Municipal securities — 2.4 — 2.4 Total short-term investments — 607.7 — 607.7 Equity Investments 9.8 — — 9.8 Total $ 454.1 $ 609.7 $ — $ 1,063.8 As of December 31, 2018 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 355.5 $ — $ — $ 355.5 U.S Treasury securities — 33.4 33.4 Commercial paper — 27.4 — 27.4 Total Cash Equivalents $ 355.5 $ 60.8 $ — $ 416.3 Short-term investments Corporate notes and obligations — 269.2 — 269.2 U.S. Treasury securities — 175.9 — 175.9 Certificates of deposit — 70.6 — 70.6 U.S agency obligations — 37.1 — 37.1 Commercial paper 17.2 17.2 Total short-term investments — 570.0 — 570.0 Total $ 355.5 $ 630.8 $ — $ 986.3

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Property and equipment, net consisted of the following: As of December 31, 2019 2018 Datacenter and other computer equipment $ 749.3 $ 667.4 Furniture and fixtures 35.5 23.8 Leasehold improvements 211.4 150.5 Construction in progress 36.3 32.8 Total property and equipment 1,032.5 874.5 Accumulated depreciation and amortization (587.2 ) (563.9 ) Property and equipment, net $ 445.3 $ 310.6

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Schedule of Purchase Consideration Transferred	The purchase consideration transferred consisted of the following: Purchase consideration Cash paid to common and preferred stockholders and vested option holders $ 175.2 Transaction costs paid by Dropbox on behalf of HelloSign 2.4 Fair value of assumed HelloSign options attributable to pre-combination services (1) 0.8 Purchase price adjustments (0.5 ) Total purchase consideration $ 177.9 (1) The fair value of options assumed were based upon the Black-Scholes option-pricing model.
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The purchase consideration was preliminarily allocated to the tangible and intangible assets and liabilities acquired as of the acquisition date, with the excess recorded to goodwill as shown below. The fair value of assets and liabilities acquired may change as additional information is received during the measurement period. The measurement period will end no later than one-year from the acquisition date. Assets acquired: Cash and cash equivalents $ 5.5 Short-term investments 7.8 Acquisition-related intangible assets 44.6 Accounts receivable, prepaid and other assets 5.0 Total assets acquired $ 62.9 Liabilities assumed: Accounts payable, accrued and other liabilities $ 6.3 Deferred revenue 4.8 Deferred tax liability 6.9 Total liabilities assumed 18.0 Net assets acquired, excluding goodwill 44.9 Total purchase consideration 177.9 Estimated goodwill (2) $ 133.0 (2) The goodwill recognized was primarily attributable to the opportunity to expand the user base of the Company's platform. The goodwill is not deductible for U.S. federal income tax purposes.
Schedule of Identifiable Finite-lived Intangible Assets Acquired and Estimated Weighted Average Useful Lives	The fair value of the separately identifiable finite-lived intangible assets acquired and estimated weighted average useful lives are as follows: Estimated fair values Estimated weighted average useful lives (In years) Customer relationships $ 20.5 4.9 Developed technology 19.6 5.0 Trade name 4.5 5.0 Total acquisition-related intangible assets $ 44.6

Intangible Assets, Net (Tables)

Intangible Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Intangible assets consisted of the following: As of December 31, Weighted- (In years) 2019 2018 Developed technology $ 25.8 $ 47.0 4.0 Customer relationships 20.5 0.0 4.1 Software 20.0 19.2 1.7 Patents 13.0 13.0 7.6 Assembled workforce in asset acquisitions 12.6 12.6 1.0 Licenses 4.6 4.6 1.5 Trademarks and trade names 5.2 0.7 4.1 Other 3.3 3.3 5.6 Total intangibles 105.0 100.4 Accumulated amortization (57.6 ) (85.7 ) Intangible assets, net $ 47.4 $ 14.7
Schedule of Expected Future Amortization Expense	Expected future amortization expense for intangible assets as of December 31, 2019 , is as follows: 2020 $ 13.9 2021 11.6 2022 8.3 2023 7.7 2024 3.3 Thereafter 2.6 Total $ 47.4

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Amounts of Goodwill	The changes in the carrying amounts of goodwill were as follows: Balance at December 31, 2018 $ 96.5 HelloSign acquisition 133.0 Other acquisition 2.4 Effect of foreign currency translation 2.6 Balance at December 31, 2019 $ 234.5

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Components of Single Lease Cost and Other Information	The components of single lease cost were as follows: Year ended December 31, 2019 2018 Operating lease cost (1) 103.2 85.9 Finance lease cost: Amortization of assets under finance lease 80.3 87.6 Interest 9.2 8.0 Total finance lease cost 89.5 95.6 (1) Is presented gross of sublease income and includes short-term leases, which are immaterial Other information related to leases was as follows: Year ended December 31, 2019 Supplemental Cash Flow Information: Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases included in cash from operating activities $ 102.8 Payments for finance leases included in cash from operating activities 9.2 Payments for finance leases included in cash from financing activities 92.9 Assets obtained in exchange for lease obligations: Operating leases (2) 297.0 Finance leases $ 144.1 (2) Includes the impact of the Company taking initial possession of the second and third phases of its new corporate headquarters in April and December of 2019, respectively, of $ 260.0 million. As of December 31, 2019 Weighted Average Remaining Lease Term (in years) Operating leases 11.3 Finance leases 3.0 Weighted Average Discount Rate Operating leases 4.3 % Finance leases 4.3 %
Maturities of Operating Lease Liabilities	Future minimum lease payments under non-cancellable leases as of December 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2020 $ 115.9 $ 84.1 2021 108.0 68.9 2022 98.2 54.8 2023 82.0 21.1 2024 74.2 0.1 Thereafter 583.0 0.0 Total future minimum lease payments 1,061.3 229.0 Less imputed interest (250.2 ) (14.1 ) Less tenant incentive receivables (19.3 ) — Total liability $ 791.8 $ 214.9 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of December 31, 2019 , the Company is entitled to non-cancelable rent payments from its sub-tenants of $ 34.5 million, which will be collected over the next 1 to 4 years . Future minimum payments under the Company's non-cancelable leases, finance lease obligations, and other commitments as of December 31, 2019, are as follows, and exclude non-cancelable rent payments from the Company's sub-tenants: Finance lease commitments Operating lease commitments (1) Other commitments (2) Year ended December 31: 2020 $ 84.1 $ 119.5 $ 48.8 2021 68.9 116.4 6.7 2022 54.8 108.1 0.7 2023 21.1 91.6 0.4 2024 0.1 83.9 — Thereafter — 636.2 16.7 Future minimum payments 229.0 $ 1,155.7 $ 73.3 Less interest and taxes (14.1 ) Less current portion of the present value of minimum lease payments (76.7 ) Financing lease obligations, net of current portion $ 138.2 (1) This balance includes short-term lease obligations and operating leases that we have entered into but have not yet commenced. (2) This balance excludes founder holdbacks related to our acquisition of HelloSign. See Note 5, "Business Combinations" for further details.
Maturities of Finance Lease Liabilities	Future minimum lease payments under non-cancellable leases as of December 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2020 $ 115.9 $ 84.1 2021 108.0 68.9 2022 98.2 54.8 2023 82.0 21.1 2024 74.2 0.1 Thereafter 583.0 0.0 Total future minimum lease payments 1,061.3 229.0 Less imputed interest (250.2 ) (14.1 ) Less tenant incentive receivables (19.3 ) — Total liability $ 791.8 $ 214.9 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of December 31, 2019 , the Company is entitled to non-cancelable rent payments from its sub-tenants of $ 34.5 million, which will be collected over the next 1 to 4 years . Future minimum payments under the Company's non-cancelable leases, finance lease obligations, and other commitments as of December 31, 2019, are as follows, and exclude non-cancelable rent payments from the Company's sub-tenants: Finance lease commitments Operating lease commitments (1) Other commitments (2) Year ended December 31: 2020 $ 84.1 $ 119.5 $ 48.8 2021 68.9 116.4 6.7 2022 54.8 108.1 0.7 2023 21.1 91.6 0.4 2024 0.1 83.9 — Thereafter — 636.2 16.7 Future minimum payments 229.0 $ 1,155.7 $ 73.3 Less interest and taxes (14.1 ) Less current portion of the present value of minimum lease payments (76.7 ) Financing lease obligations, net of current portion $ 138.2 (1) This balance includes short-term lease obligations and operating leases that we have entered into but have not yet commenced.

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of Other Commitments	Future minimum payments under the Company's non-cancelable leases, finance lease obligations, and other commitments as of December 31, 2019, are as follows, and exclude non-cancelable rent payments from the Company's sub-tenants: Finance lease commitments Operating lease commitments (1) Other commitments (2) Year ended December 31: 2020 $ 84.1 $ 119.5 $ 48.8 2021 68.9 116.4 6.7 2022 54.8 108.1 0.7 2023 21.1 91.6 0.4 2024 0.1 83.9 — Thereafter — 636.2 16.7 Future minimum payments 229.0 $ 1,155.7 $ 73.3 Less interest and taxes (14.1 ) Less current portion of the present value of minimum lease payments (76.7 ) Financing lease obligations, net of current portion $ 138.2 (1) This balance includes short-term lease obligations and operating leases that we have entered into but have not yet commenced.
Maturities of Finance Lease Liabilities	Future minimum lease payments under non-cancellable leases as of December 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2020 $ 115.9 $ 84.1 2021 108.0 68.9 2022 98.2 54.8 2023 82.0 21.1 2024 74.2 0.1 Thereafter 583.0 0.0 Total future minimum lease payments 1,061.3 229.0 Less imputed interest (250.2 ) (14.1 ) Less tenant incentive receivables (19.3 ) — Total liability $ 791.8 $ 214.9 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of December 31, 2019 , the Company is entitled to non-cancelable rent payments from its sub-tenants of $ 34.5 million, which will be collected over the next 1 to 4 years . Future minimum payments under the Company's non-cancelable leases, finance lease obligations, and other commitments as of December 31, 2019, are as follows, and exclude non-cancelable rent payments from the Company's sub-tenants: Finance lease commitments Operating lease commitments (1) Other commitments (2) Year ended December 31: 2020 $ 84.1 $ 119.5 $ 48.8 2021 68.9 116.4 6.7 2022 54.8 108.1 0.7 2023 21.1 91.6 0.4 2024 0.1 83.9 — Thereafter — 636.2 16.7 Future minimum payments 229.0 $ 1,155.7 $ 73.3 Less interest and taxes (14.1 ) Less current portion of the present value of minimum lease payments (76.7 ) Financing lease obligations, net of current portion $ 138.2 (1) This balance includes short-term lease obligations and operating leases that we have entered into but have not yet commenced.
Maturities of Operating Lease Liabilities	Future minimum lease payments under non-cancellable leases as of December 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2020 $ 115.9 $ 84.1 2021 108.0 68.9 2022 98.2 54.8 2023 82.0 21.1 2024 74.2 0.1 Thereafter 583.0 0.0 Total future minimum lease payments 1,061.3 229.0 Less imputed interest (250.2 ) (14.1 ) Less tenant incentive receivables (19.3 ) — Total liability $ 791.8 $ 214.9 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of December 31, 2019 , the Company is entitled to non-cancelable rent payments from its sub-tenants of $ 34.5 million, which will be collected over the next 1 to 4 years . Future minimum payments under the Company's non-cancelable leases, finance lease obligations, and other commitments as of December 31, 2019, are as follows, and exclude non-cancelable rent payments from the Company's sub-tenants: Finance lease commitments Operating lease commitments (1) Other commitments (2) Year ended December 31: 2020 $ 84.1 $ 119.5 $ 48.8 2021 68.9 116.4 6.7 2022 54.8 108.1 0.7 2023 21.1 91.6 0.4 2024 0.1 83.9 — Thereafter — 636.2 16.7 Future minimum payments 229.0 $ 1,155.7 $ 73.3 Less interest and taxes (14.1 ) Less current portion of the present value of minimum lease payments (76.7 ) Financing lease obligations, net of current portion $ 138.2 (1) This balance includes short-term lease obligations and operating leases that we have entered into but have not yet commenced. (2) This balance excludes founder holdbacks related to our acquisition of HelloSign. See Note 5, "Business Combinations" for further details.

Accrued and Other Current Lia_2

Accrued and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Schedule of Accrued and Other Current Liabilities	Accrued and other current liabilities consisted of the following: As of December 31, 2019 2018 Non-income taxes payable $ 92.2 $ 75.7 Accrued legal and other external fees 29.2 28.1 Deferred rent — 41.0 Other accrued and current liabilities 40.5 19.7 Total accrued and other current liabilities $ 161.9 $ 164.5

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Schedule of Stock Option and Restricted Stock Activity	Stock option and restricted stock activity for the Plans was as follows for the years ended December 31, 2019 and 2018 : Options outstanding Restricted stock outstanding Number of shares available for issuance under the Plans Number of shares outstanding under the Plans Weighted- average exercise price per share Weighted- average remaining contractual term (In years) Aggregate Intrinsic Value Number of Plan shares outstanding Weighted- average grant date fair value per share Balance at December 31, 2017 9.0 5.0 $ 10.52 5.5 54.9 $ 15.6 Reserved for issuance under the 2018 Plan 41.4 Additional shares authorized 1.3 Options exercised and RSUs released — (3.4 ) $ 7.75 (40.4 ) 15.42 Options and RSUs canceled 6.0 (0.3 ) $ 22.90 (5.7 ) 16.78 Shares repurchased for tax withholdings on release of restricted stock 15.6 15.45 Restricted stock granted (16.2 ) 16.2 20.26 Balance at December 31, 2018 57.1 1.3 $ 14.68 5.0 9.1 25.0 $ 18.68 Additional shares authorized 21.2 — — — — Stock options assumed 0.9 0.9 6.02 — — Options exercised and RSUs released — (0.3 ) 6.82 (11.2 ) 19.01 Options and RSUs canceled 7.1 (0.2 ) 18.89 (6.9 ) 19.32 Shares repurchased for tax withholdings on release of restricted stock 4.1 — — — 18.87 Restricted stock, awards and options granted (24.2 ) 0.3 23.09 23.8 21.34 Balance as of December 31, 2019 66.2 2.0 $ 12.28 6.5 16.40 30.7 $ 20.48 Vested at December 31, 2019 1.3 $ 16.01 5.4 7.90 — $ — Unvested at December 31, 2019 0.7 $ 5.76 8.50 30.7 $ 20.48
Schedule of Pre-Tax Intrinsic Value of Options Exercised	The following table summarizes information about the pre-tax intrinsic value of options exercised during the years ended December 31, 2019 and 2018 : Year ended December 31, 2019 2018 Intrinsic value of options exercised $ 5.3 $ 59.0
Fair Value of Stock Options Assumptions Used	The fair value of stock options assumed were estimated using the following assumptions: Expected volatility 51.6 % Expected term (in years) 3.4 - 7.0 Risk-free interest rate 2.42% - 2.51% Dividend yield — %

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Additionally, the voluntary conversions of Class B common stock into Class A common stock are included in the table below weighted for the period outstanding in the years ended December 31, 2019 and December 31, 2018 : Year ended December 31, 2019 2018 2017 Class A Class B Class A Class B Class A Class B Numerator: Net loss attributable to common stockholders $ (30.3 ) $ (22.4 ) $ (138.7 ) $ (346.2 ) $ (3.6 ) $ (108.1 ) Denominator: Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share 236.8 174.8 102.6 256.0 6.3 189.6 Net loss per common share, basic and diluted $ (0.13 ) $ (0.13 ) $ (1.35 ) $ (1.35 ) $ (0.57 ) $ (0.57 )
Schedule of Potentially Dilutive Securities Excluded from Computation of Earnings Per Share	The weighted-average impact of potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive was as follows: Year ended December 31, 2019 2018 2017 Convertible preferred stock — — 147.6 Restricted stock units 28.9 35.0 52.7 Restricted stock awards 0.4 — 0.0 Options to purchase shares of common stock 1.9 4.0 5.1 Co-Founder Grants 14.7 14.7 0.8 Shares subject to repurchase from early-exercised options and unvested restricted stock — 0.1 0.2 Total 45.9 53.8 206.4

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	For the years ended December 31, 2019 , 2018 , and 2017 , the Company’s loss from continuing operations before provision for income taxes was as follows: Year ended December 31, 2019 2018 2017 Domestic $ (98.8 ) $ (497.1 ) $ (76.9 ) Foreign 46.8 17.0 (34.6 ) Loss before income taxes $ (52.0 ) $ (480.1 ) $ (111.5 )
Schedule of Components of Income Tax Expense (Benefit)	The components of the benefit from (provision for) income taxes in the years ended December 31, 2019 , 2018 , and 2017 , were as follows: Year ended December 31, 2019 2018 2017 Current: Federal $ 0.1 $ (0.1 ) $ 0.1 State (0.6 ) (0.2 ) (0.3 ) Foreign (7.7 ) (4.6 ) (2.3 ) Deferred: Federal 6.6 — 1.4 State 0.6 — — Foreign 0.3 0.1 0.9 Benefit from (provision for) income taxes $ (0.7 ) $ (4.8 ) $ (0.2 )
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of income taxes at the statutory federal income tax rate to the benefit from (provision for) income taxes included in the accompanying consolidated statements of operations is as follows (in millions): Year ended December 31, 2019 2018 2017 Tax benefit at federal statutory rate $ 10.9 $ 100.8 $ 37.9 State taxes, net of federal benefit 2.4 10.7 1.7 Foreign rate differential (0.9 ) 1.8 (12.3 ) Research and other credits 30.2 86.5 25.4 Non-deductible compensation (3.4 ) — — Meals & entertainment (2.5 ) (2.2 ) (0.2 ) Permanent differences (2.1 ) (16.2 ) (8.8 ) Tax Cuts and Jobs Act impact — — (61.7 ) Change in valuation allowance (32.2 ) (240.7 ) 38.9 Stock-based compensation 1.8 57.3 (20.1 ) Other non-deductible items (4.9 ) (2.8 ) (1.0 ) Benefit from (provision for) income taxes $ (0.7 ) $ (4.8 ) $ (0.2 )
Schedule of Deferred Tax Assets and Liabilities	The significant components of the Company’s deferred tax assets and liabilities as of December 31, 2019 and 2018 were as follows: As of December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 257.2 $ 264.8 Research credit carryforwards 188.6 157.3 Stock-based compensation 29.3 11.1 Accruals and reserves 32.3 42.0 Fixed assets and intangible assets — 0.7 Lease liability 189.8 — Other 1.0 1.1 Gross deferred tax assets 698.2 477.0 Valuation allowance (510.8 ) (476.0 ) Total deferred tax assets, net of valuation allowance 187.4 1.0 Deferred tax liabilities: Fixed assets and intangible assets 13.1 — Right of use assets 172.7 — Other 0.3 — Total deferred tax liability 186.1 — Net deferred tax assets $ 1.3 $ 1.0
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows: Year ended December 31, 2019 2018 2017 Balance of gross unrecognized tax benefits at the beginning of the fiscal year $ 59.8 $ 25.6 $ 15.7 Gross increases related to prior period tax positions 0.1 1.1 — Gross increases related to current period tax positions 14.6 33.1 9.9 Balance of gross unrecognized tax benefits at the end of the fiscal year $ 74.5 $ 59.8 $ 25.6

Geographic Areas (Tables)

Geographic Areas (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Long-lived Assets by Geographic Areas	The following table sets forth long-lived assets by geographic area: As of December 31, 2019 2018 United States $ 431.9 $ 293.6 International (1) 13.4 17.0 Total property and equipment, net $ 445.3 $ 310.6 (1) No single country other than the United States had a property and equipment balance greater than 10% of total property and equipment, net, as of December 31, 2019 and 2018 .
Revenue by Geographic Areas	The following table sets forth revenue by geographic area for the years ended December 31, 2019 , 2018 , and 2017 : Year ended December 31, 2019 2018 2017 United States $ 854.1 $ 706.5 $ 575.7 International (1) 807.2 685.2 531.1 Total revenue $ 1,661.3 $ 1,391.7 $ 1,106.8 (1) No single country outside of the United States accounted for more than 10 percent of total revenue during the years ended December 31, 2019 , 2018 , and 2017

Description of the Business a_4

Description of the Business and Summary of Significant Accounting Policies - Initial Public Offering and Private Placement (Details) $ / shares in Units, $ in Millions	Apr. 03, 2018USD ($)	Mar. 28, 2018USD ($)$ / sharesshares	Mar. 27, 2018USD ($)$ / sharesshares	Mar. 26, 2018shares	Mar. 22, 2018USD ($)	Mar. 07, 2018	Mar. 31, 2018USD ($)shares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)
Conversion of Stock [Line Items]
Stock issued in IPO (in shares)			26,822,409
Share price of stock issued in IPO (in dollars per share) | $ / shares			$ 21
Proceeds from initial public offering and private placement | $		$ 746.6	$ 538.2					$ 0	$ 746.6	$ 0
Offering costs | $		6.9						$ 0	$ 4.5	$ 2.5
Reverse stock split ratio						0.6667
Convertible Preferred Stock | Conversion of Convertible Preferred Stock to Class B Common Stock
Conversion of Stock [Line Items]
Shares converted in conversion				147,310,563
Convertible Preferred Stock | Conversion of Convertible Preferred Stock to Class A Common Stock
Conversion of Stock [Line Items]
Shares converted in conversion				258,620
Class B Common Stock
Conversion of Stock [Line Items]
Shares converted in conversion								38,900,000	157,000,000
Class B Common Stock | Conversion of Convertible Preferred Stock to Class B Common Stock
Conversion of Stock [Line Items]
Shares issued in conversion				147,310,563
Class B Common Stock | Conversion of Class B Common Stock to Class A Common Stock
Conversion of Stock [Line Items]
Shares converted in conversion				2,609,951
Class A Common Stock
Conversion of Stock [Line Items]
Shares issued in conversion								38,900,000	157,000,000
Class A Common Stock | Conversion of Convertible Preferred Stock to Class A Common Stock
Conversion of Stock [Line Items]
Shares issued in conversion				258,620
Class A Common Stock | Conversion of Class B Common Stock to Class A Common Stock
Conversion of Stock [Line Items]
Shares issued in conversion				2,609,951
Private Placement
Conversion of Stock [Line Items]
Proceeds from initial public offering and private placement | $		$ 100
Private Placement | Class A Common Stock
Conversion of Stock [Line Items]
Sale of stock (in shares)		4,761,905
Share price of stock sold (in dollars per share) | $ / shares		$ 21
Underwriters Over-allotment Option | Class A Common Stock
Conversion of Stock [Line Items]
Sale of stock (in shares)		5,400,000
Proceeds received in sale of stock | $	$ 108.4
Two-Tier RSUs
Conversion of Stock [Line Items]
Recognized cumulative unrecognized stock-based compensation | $					$ 418.7				$ 418.7
Remaining unamortized stock-based compensation | $								$ 0.1
Unamortized stock-based compensation, requisite service period								2 months 12 days
Shares released							26,800,000
Employer related payroll expense | $							$ 13.9

Description of the Business a_5

Description of the Business and Summary of Significant Accounting Policies - Foreign Currency Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net foreign currency transaction losses	$ (0.8)	$ (1.9)

Description of the Business a_6

Description of the Business and Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue, performance obligation, description of timing	one year or longer
Revenue recognized	$ 481.1	$ 411.6	$ 353
Remaining performance obligation	$ 613.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Remaining performance obligation, expected timing of satisfaction	12 months

Description of the Business a_7

Description of the Business and Summary of Significant Accounting Policies - Stock-based Compensation (Details) shares in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2017shares	Dec. 31, 2019awardshares	Dec. 31, 2018shares
One-Tier RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Number of award types | award		1
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted		23.8	16.2
Tranche One | One-Tier RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year
Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	14.7		14.7
Co-Founder Grants | Tranche One | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Chief Executive Officer | Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	10.3
Director | Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	4.4

Description of the Business a_8

Description of the Business and Summary of Significant Accounting Policies - Advertising and promotional expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Advertising and promotional expense	$ 88.8	$ 100.9	$ 80.1

Description of the Business a_9

Description of the Business and Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details) - Customer Concentration Risk - Trade and Other Receivables	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	14.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	27.00%	23.00%

Description of the Business _10

Description of the Business and Summary of Significant Accounting Policies - Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Allowance for doubtful accounts	$ 0.5	$ 1.2
Non-trade receivables	$ 7.4	$ 46.2

Description of the Business _11

Description of the Business and Summary of Significant Accounting Policies - Deferred Commissions, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Capitalized Contract Cost [Line Items]
Additional contract costs deferred	$ 28,100,000	$ 32,000,000
Deferred contract costs, amortization period	5 years
Amortization of deferred commissions	$ 17,500,000	12,100,000	$ 6,600,000
Impairment loss related to deferred costs	0	0	$ 0
Prepaid Expenses and Other Current Assets | Deferred Commissions
Capitalized Contract Cost [Line Items]
Deferred contract costs	19,900,000	14,500,000
Other Assets | Deferred Commissions
Capitalized Contract Cost [Line Items]
Deferred contract costs	$ 43,500,000	$ 38,300,000

Description of the Business _12

Description of the Business and Summary of Significant Accounting Policies - Property and Equipment, Net (Details)	12 Months Ended
	Dec. 31, 2019
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Minimum | Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	20 years
Minimum | Datacenter and other computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Minimum | Office equipment and other
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	7 years
Maximum | Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	30 years
Maximum | Datacenter and other computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Maximum | Office equipment and other
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	7 years

Description of the Business _13

Description of the Business and Summary of Significant Accounting Policies - Equity investments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Equity investments	$ 9.8
Gain on equity investments	$ 4.5

Description of the Business _14

Description of the Business and Summary of Significant Accounting Policies - Recently Issued Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset	$ 657.9
Total liability	$ 791.8
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		$ 431.7
Total liability		$ 502.4

Cash, Cash Equivalents and Sh_3

Cash, Cash Equivalents and Short-Term Investments - Schedule of Cash, Cash Equivalents and Short-Term Investments (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	$ 551,300,000	$ 519,300,000
Cash and cash equivalents, estimated fair value	551,300,000	519,300,000
Short-term investments, amortized cost	606,300,000	570,500,000
Short-term investments, unrealized gain	1,500,000	100,000
Short-term investments, unrealized loss	(100,000)	(600,000)
Short-term investments, estimated fair value	607,700,000	570,000,000
Total cash, cash equivalents, and short term investments, before unrealized gain (loss) on investments	1,157,600,000	1,089,800,000
Total cash, cash equivalents, and short term investments	1,159,000,000	1,089,300,000
Corporate notes and obligations
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	285,500,000	269,600,000
Short-term investments, unrealized gain	1,200,000	100,000
Short-term investments, unrealized loss	(100,000)	(500,000)
Short-term investments, estimated fair value	286,600,000	269,200,000
U.S. Treasury securities
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	171,000,000	176,000,000
Short-term investments, unrealized gain	300,000	0
Short-term investments, unrealized loss	0	(100,000)
Short-term investments, estimated fair value	171,300,000	175,900,000
Asset backed securities
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	53,800,000
Short-term investments, unrealized gain	0
Short-term investments, unrealized loss	0
Short-term investments, estimated fair value	53,800,000
Certificates of deposit
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	38,200,000	70,600,000
Short-term investments, unrealized gain	0	0
Short-term investments, unrealized loss	0	0
Short-term investments, estimated fair value	38,200,000	70,600,000
U.S. agency obligations
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	27,200,000	37,100,000
Short-term investments, unrealized gain	0	0
Short-term investments, unrealized loss	0	0
Short-term investments, estimated fair value	27,200,000	37,100,000
Commercial paper
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	24,200,000	17,200,000
Short-term investments, unrealized gain	0	0
Short-term investments, unrealized loss	0	0
Short-term investments, estimated fair value	24,200,000	17,200,000
Supranational securities
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	4,000,000
Short-term investments, unrealized gain	0
Short-term investments, unrealized loss	0
Short-term investments, estimated fair value	4,000,000
Municipal securities
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	2,400,000
Short-term investments, unrealized gain	0
Short-term investments, unrealized loss	0
Short-term investments, estimated fair value	2,400,000
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	105,000,000	103,000,000
Cash and cash equivalents, estimated fair value	105,000,000	103,000,000
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	444,300,000	355,500,000
Cash and cash equivalents, estimated fair value	444,300,000	355,500,000
Commercial paper
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost	2,000,000	27,400,000
Cash and cash equivalents, estimated fair value	$ 2,000,000	27,400,000
U.S. Treasury securities
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, amortized cost		33,400,000
Cash and cash equivalents, estimated fair value		$ 33,400,000

Cash, Cash Equivalents and Sh_4

Cash, Cash Equivalents and Short-Term Investments - Narrative (Details)	12 Months Ended
	Dec. 31, 2019USD ($)investment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Cash and Cash Equivalents [Abstract]
Cash in transit for credit and debit card transactions	$ 11,500,000	$ 11,900,000
Number of investments in unrealized loss positions | investment	62
Securities in an unrealized loss position for less than twelve months, fair value	$ 125,600,000
Securities in an unrealized loss position for less than twelve months, unrealized loss amount	100,000
Other-than-temporary impairment loss	0
Investment income	$ 22,800,000	$ 16,800,000	$ 3,000,000

Cash, Cash Equivalents and Sh_5

Cash, Cash Equivalents and Short-Term Investments - Contractual Maturities of Short Term Investments (Details) $ in Millions	Dec. 31, 2019USD ($)
Amortized cost
Due within one year	$ 275.9
Due between one to three years	310.7
Due after three years	19.7
Total	606.3
Estimated fair value
Due within one year	276.5
Due between one to three years	311.5
Due after three years	19.7
Total	$ 607.7

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	$ 551.3	$ 519.3
Total short-term investments	607.7	570
Equity Investments	9.8
U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	171.3	175.9
Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	38.2	70.6
Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	53.8
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	24.2	17.2
U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	27.2	37.1
Supranational securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	4
Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	2.4
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	444.3	355.5
U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents		33.4
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	2	27.4
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	446.3	416.3
Total short-term investments	607.7	570
Equity Investments	9.8
Total	1,063.8	986.3
Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	286.6	269.2
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	171.3	175.9
Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	38.2	70.6
Fair Value, Measurements, Recurring | Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	53.8
Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	24.2	17.2
Fair Value, Measurements, Recurring | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	27.2	37.1
Fair Value, Measurements, Recurring | Supranational securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	4
Fair Value, Measurements, Recurring | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	2.4
Fair Value, Measurements, Recurring | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	444.3	355.5
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents		33.4
Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	2	27.4
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	444.3	355.5
Total short-term investments	0	0
Equity Investments	9.8
Total	454.1	355.5
Fair Value, Measurements, Recurring | Level 1 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 1 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 1 | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Supranational securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 1 | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 1 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	444.3	355.5
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents		0
Fair Value, Measurements, Recurring | Level 1 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	2	60.8
Total short-term investments	607.7	570
Equity Investments	0
Total	609.7	630.8
Fair Value, Measurements, Recurring | Level 2 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	286.6	269.2
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	171.3	175.9
Fair Value, Measurements, Recurring | Level 2 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	38.2	70.6
Fair Value, Measurements, Recurring | Level 2 | Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	53.8
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	24.2	17.2
Fair Value, Measurements, Recurring | Level 2 | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	27.2	37.1
Fair Value, Measurements, Recurring | Level 2 | Supranational securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	4
Fair Value, Measurements, Recurring | Level 2 | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	2.4
Fair Value, Measurements, Recurring | Level 2 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	0	0
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents		33.4
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	2	27.4
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	0	0
Total short-term investments	0	0
Equity Investments	0
Total	0	0
Fair Value, Measurements, Recurring | Level 3 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 3 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 3 | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Supranational securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 3 | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0
Fair Value, Measurements, Recurring | Level 3 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	0	0
Fair Value, Measurements, Recurring | Level 3 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Cash Equivalents	$ 0	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,032.5	$ 874.5
Accumulated depreciation and amortization	(587.2)	(563.9)
Property and equipment, net	445.3	310.6
Datacenter and other computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	749.3	667.4
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	35.5	23.8
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	211.4	150.5
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 36.3	$ 32.8

Property and Equipment, Net - N

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,032.5	$ 874.5
Accumulated depreciation and amortization	(587.2)	(563.9)
Depreciation	159.9	158.6
Infrastructure Assets Held Under Capital Leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross	321.8	362.8
Infrastructure Assets Held Under Finance Leases
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (124.6)	$ (211.7)

Business Combinations - Schedul

Business Combinations - Schedule of Purchase Consideration (Details) - HelloSign Inc. $ in Millions	Feb. 08, 2019USD ($)
Business Acquisition [Line Items]
Fair value of assumed HelloSign options attributable to pre-combination services	$ 0.8
Purchase price adjustments	(0.5)
Total purchase consideration	177.9
Preferred Stockholders and Vested Option Holders
Business Acquisition [Line Items]
Cash and transaction costs paid	175.2
HelloSign
Business Acquisition [Line Items]
Cash and transaction costs paid	$ 2.4

Business Combinations - Narrati

Business Combinations - Narrative (Details) - HelloSign Inc. - USD ($) $ in Millions	Feb. 08, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Purchase consideration, agreements with key personnel	$ 48.5
Acquired finite-lived intangible assets weighted average amortization period	4 years 10 months 24 days
Acquisition-related diligence costs		$ 1
Required service period	3 years

Business Combinations - Sched_2

Business Combinations - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Dec. 31, 2019	Feb. 08, 2019	Dec. 31, 2018
Liabilities assumed:
Estimated goodwill	$ 234.5		$ 96.5
HelloSign Inc.
Assets acquired:
Cash and cash equivalents		$ 5.5
Short-term investments		7.8
Acquisition-related intangible assets		44.6
Accounts receivable, prepaid and other assets		5
Total assets acquired		62.9
Liabilities assumed:
Accounts payable, accrued and other liabilities		6.3
Deferred revenue		4.8
Deferred tax liability		6.9
Total liabilities assumed		18
Net assets acquired, excluding goodwill		44.9
Total purchase consideration		177.9
Estimated goodwill		$ 133

Business Combinations - Sched_3

Business Combinations - Schedule of Identifiable Finite-lived Intangible Assets Acquired and Estimated Weighted Average Useful Lives (Details) - HelloSign Inc. $ in Millions	Feb. 08, 2019USD ($)
Business Acquisition [Line Items]
Estimated fair values	$ 44.6
Estimated weighted average useful lives (In years)	4 years 10 months 24 days
Customer relationships
Business Acquisition [Line Items]
Estimated fair values	$ 20.5
Estimated weighted average useful lives (In years)	4 years 10 months 24 days
Developed technology
Business Acquisition [Line Items]
Estimated fair values	$ 19.6
Estimated weighted average useful lives (In years)	5 years
Trade name
Business Acquisition [Line Items]
Estimated fair values	$ 4.5
Estimated weighted average useful lives (In years)	5 years

Intangible Assets, Net - Schedu

Intangible Assets, Net - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 105		$ 100.4
Accumulated amortization	(57.6)		(85.7)
Intangible assets, net	47.4		14.7
Developed technology
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 25.8		47
Intangible assets, retired		$ 41.7
Developed technology | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	4 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 20.5		0
Customer relationships | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	4 years 1 month 6 days
Software
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 20		19.2
Software | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	1 year 8 months 12 days
Patents
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 13		13
Patents | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	7 years 7 months 6 days
Assembled workforce in asset acquisitions
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 12.6		12.6
Assembled workforce in asset acquisitions | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	1 year
Licenses
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 4.6		4.6
Licenses | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	1 year 6 months
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 5.2		0.7
Trademarks and trade names | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	4 years 1 month 6 days
Other
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 3.3		$ 3.3
Other | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	5 years 7 months 6 days

Intangible Assets, Net - Sche_2

Intangible Assets, Net - Schedule of Future Amortization Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 13.6	$ 6.1	$ 10.5
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2020	13.9
2021	11.6
2022	8.3
2023	7.7
2024	3.3
Thereafter	2.6
Total	$ 47.4

Goodwill (Details)

Goodwill (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Balance at December 31, 2018	$ 96,500,000	$ 96,500,000
Effect of foreign currency translation		2,600,000
Balance at December 31, 2019		234,500,000	$ 96,500,000
Goodwill impairment	$ 0		$ 0	$ 0
HelloSign
Goodwill [Roll Forward]
Acquisitions		133,000,000
Other Acquisition
Goodwill [Roll Forward]
Acquisitions		$ 2,400,000

Revolving Credit Facility (Deta

Revolving Credit Facility (Details) - Credit and Guarantee Agreement - Line of Credit - USD ($)	Apr. 30, 2017	Feb. 28, 2018	Dec. 31, 2019
Revolving Credit Facility
Line of Credit Facility [Line Items]
Letter of credit	$ 600,000,000	$ 725,000,000
Debt issuance fees	$ 2,600,000	400,000
Debt instrument, term	5 years
Line of credit facility, accordion feature, increase limit		$ 275,000,000
Unused capacity, commitment fee percentage		0.20%
Covenant terms, minimum liquidity balance		$ 100,000,000
Aggregate letters of credit outstanding amount			$ 59,700,000
Remaining borrowing capacity			$ 665,300,000
Revolving Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.50%
Revolving Credit Facility | Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.50%
Letter of Credit
Line of Credit Facility [Line Items]
Letter of credit		$ 187,500,000
Commitment fee percentage		1.50%
Fronting fee		0.125%

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lessee, Lease, Description [Line Items]
Lease, renewal term	5 years
Sublease income	$ (7,100,000)	$ (11,800,000)
Minimum obligations	836,400,000
Tenant improvements	75,000,000
Tenant improvement allowance reimbursement	55,300,000	$ 0	$ 0
Operating leases, not yet commenced, value	$ 91,900,000
Minimum
Lessee, Lease, Description [Line Items]
Lease, remaining lease term	1 year
Operating sublease, term	1 year
Operating leases, not yet commenced, term of contract	4 years
Maximum
Lessee, Lease, Description [Line Items]
Lease, remaining lease term	14 years
Operating sublease, term	4 years
Operating leases, not yet commenced, term of contract	12 years
Corporate Headquarters Lease | Line of Credit | Letter of Credit
Lessee, Lease, Description [Line Items]
Letter of credit	$ 34,200,000

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease cost	$ 103.2	$ 85.9
Finance lease cost:
Amortization of assets under finance lease	80.3	87.6
Interest	9.2	8
Total finance lease cost	$ 89.5	$ 95.6

Leases - Other Lease Informatio

Leases - Other Lease Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2019	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Payments for operating leases included in cash from operating activities		$ 102.8
Payments for finance leases included in cash from operating activities		9.2
Payments for finance leases included in cash from financing activities		92.9
Assets obtained in exchange for lease obligations: operating leases		297
Assets obtained in exchange for lease obligations: finance leases		$ 144.1
Weighted average remaining lease term (in years) - operating leases		11 years 3 months 18 days
Weighted average remaining lease term (in years) - finance leases		3 years
Weighted average discount rate - operating leases		4.30%
Weighted average discount rate - finance leases		4.30%
Corporate Headquarters Lease
Lessee, Lease, Description [Line Items]
Assets obtained in exchange for lease obligations: operating leases	$ 260

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Payments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Operating leases
2020	$ 115.9
2021	108
2022	98.2
2023	82
2024	74.2
Thereafter	583
Total future minimum lease payments	1,061.3
Less imputed interest	(250.2)
Less tenant incentive receivables	(19.3)
Total liability	791.8
Finance leases
2020	84.1
2021	68.9
2022	54.8
2023	21.1
2024	0.1
Thereafter	0
Total future minimum lease payments	229
Less imputed interest	(14.1)
Less tenant incentive receivables	0
Total liability	214.9
Rent payments from sub-tenants	$ 34.5
Minimum
Finance leases
Rent payments from sub-tenants, term	1 year
Maximum
Finance leases
Rent payments from sub-tenants, term	4 years

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	Dec. 31, 2019USD ($)
Finance lease commitments
2020	$ 84.1
2021	68.9
2022	54.8
2023	21.1
2024	0.1
Thereafter	0
Total future minimum lease payments	229
Less interest and taxes	(14.1)
Less current portion of the present value of minimum lease payments	(76.7)
Finance lease liability, non-current	138.2
Operating lease commitments
2020	119.5
2021	116.4
2022	108.1
2023	91.6
2024	83.9
Thereafter	636.2
Future minimum payments	1,155.7
Other commitments
2020	48.8
2021	6.7
2022	0.7
2023	0.4
2024	0
Thereafter	16.7
Future minimum payments	$ 73.3

Accrued and Other Current Lia_3

Accrued and Other Current Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Non-income taxes payable	$ 92.2	$ 75.7
Accrued legal and other external fees	29.2	28.1
Deferred rent	0	41
Other accrued and current liabilities	40.5	19.7
Total accrued and other current liabilities	$ 161.9	$ 164.5

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details)	1 Months Ended	12 Months Ended
	Dec. 31, 2017shares	Dec. 31, 2019vote$ / sharesshares	Dec. 31, 2018$ / sharesshares
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001	$ 0.00001
Restricted Stock
Class of Stock [Line Items]
Shares granted		23,800,000	16,200,000
Co-Founder Grants | Restricted Stock
Class of Stock [Line Items]
Shares granted	14,700,000		14,700,000
Class A Common Stock
Class of Stock [Line Items]
Votes per share | vote		1
Shares issued in conversion		38,900,000	157,000,000
Common stock, shares authorized		2,400,000,000	2,400,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001
Common stock, shares issued		255,800,000	211,000,000
Common stock, shares outstanding		255,800,000	211,000,000
Class B Common Stock
Class of Stock [Line Items]
Votes per share | vote		10
Shares converted in conversion		38,900,000	157,000,000
Common stock, shares authorized		475,000,000	475,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001
Common stock, shares issued		161,200,000	198,600,000
Common stock, shares outstanding		161,200,000	198,600,000
Class C Common Stock
Class of Stock [Line Items]
Votes per share | vote		0
Common stock, shares authorized		800,000,000	800,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001
Common stock, shares issued		0	0
Common stock, shares outstanding		0	0

Stockholders' Equity - Converti

Stockholders' Equity - Convertible Preferred Stock and Preferred Stock (Details) - shares	Mar. 26, 2018	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock, shares authorized		240,000,000	240,000,000
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized		0	0
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Class A Common Stock
Class of Stock [Line Items]
Shares issued in conversion		38,900,000	157,000,000
Class B Common Stock
Class of Stock [Line Items]
Shares converted in conversion		38,900,000	157,000,000
Conversion of Convertible Preferred Stock to Class B Common Stock | Convertible Preferred Stock
Class of Stock [Line Items]
Shares converted in conversion	147,310,563
Conversion of Convertible Preferred Stock to Class B Common Stock | Class B Common Stock
Class of Stock [Line Items]
Shares issued in conversion	147,310,563
Conversion of Convertible Preferred Stock to Class A Common Stock | Convertible Preferred Stock
Class of Stock [Line Items]
Shares converted in conversion	258,620
Conversion of Convertible Preferred Stock to Class A Common Stock | Class A Common Stock
Class of Stock [Line Items]
Shares issued in conversion	258,620

Stockholders' Equity - Equity I

Stockholders' Equity - Equity Incentive Plans (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued and outstanding	2	1.3	5
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of RSUs	$ 235	$ 913.5	$ 232.5
2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Remaining unamortized stock-based compensation	$ 597.7
Unamortized stock-based compensation, requisite service period	2 years 10 months 24 days
2018 Plan | Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Vesting period	4 years
2008 Equity Incentive Plan, 2017 Equity Incentive Plan, and 2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued and outstanding	32.7
Shares available for grant	66.2

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Stock Option and Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of shares available for issuance under the Plans
Beginning balance (in shares)	57,100,000	9,000,000
Reserved for issuance under the 2018 Plan (in shares)			41,400,000
Additional shares authorized (in shares)	21,200,000	1,300,000
Stock options assumed (in shares)	900,000
Options canceled (in shares)	7,100,000	6,000,000
Shares repurchased for tax withholdings on release of restricted stock (in shares)	4,100,000	15,600,000
Options granted (in shares)	(24,200,000)	(16,200,000)
Ending balance (in shares)	66,200,000	57,100,000	9,000,000
Options outstanding, Number of shares outstanding under the Plans
Beginning balance (in shares)	1,300,000	5,000,000
Stock options assumed (in shares)	900,000
Options exercised (in shares)	(300,000)	(3,400,000)
Options canceled (in shares)	(200,000)	(300,000)
Options granted (in shares)	300,000
Ending balance (in shares)	2,000,000	1,300,000	5,000,000
Vested at December 31, 2019 (in shares)	1,300,000
Unvested at December 31, 2019 (in shares)	700,000
Options outstanding, Weighted- average exercise price per share
Beginning balance (in dollars per share)	$ 14.68	$ 10.52
Stock options assumed (in dollars per share)	6.02
Options exercised (in dollars per share)	6.82	7.75
Options canceled (in dollars per share)	18.89	22.90
Options granted (in dollars per share)	23.09
Ending balance (in dollars per share)	12.28	$ 14.68	$ 10.52
Vested at December 31, 2019 (in dollars per share)	16.01
Unvested at December 31, 2019 (in dollars per share)	$ 5.76
Options outstanding, Weighted- average remaining contractual term (In years)
Weighted-average contractual term	6 years 6 months	5 years	5 years 6 months
Weighted-average contractual term, Vested at December 31, 2019	5 years 4 months 24 days
Options outstanding, aggregate intrinsic value	$ 16.4	$ 9.1
Vested during period, aggregate intrinsic value	7.9
Unvested during period, aggregate intrinsic value	$ 8.5
Restricted Stock
Restricted Stock Outstanding, Number of Plan shares outstanding
Beginning balance (in shares)	25,000,000	54,900,000
RSUs released (in shares)	(11,200,000)	(40,400,000)
RSUs canceled (in shares)	(6,900,000)	(5,700,000)
Restricted stock granted (in shares)	23,800,000	16,200,000
Ending balance (in shares)	30,700,000	25,000,000	54,900,000
Restricted Stock Outstanding, Weighted- average grant date fair value per share
Beginning balance (in dollars per share)	$ 18.68	$ 15.6
RSUs released (in dollars per share)	19.01	15.42
RSUs canceled (in dollars per share)	19.32	16.78
Shares repurchased for tax withholdings on release of restricted stock (in dollars per share)	18.87	15.45
Restricted stock granted (in dollars per share)	21.34	20.26
Ending balance (in dollars per share)	$ 20.48	$ 18.68	$ 15.6

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Pre-Tax Intrinsic Value of Options Exercised (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Intrinsic value of options exercised	$ 5.3	$ 59

Stockholders' Equity - Assumed

Stockholders' Equity - Assumed Stock Options (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Feb. 08, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options assumed (in shares)		0.9
Dividend yield		0.00%
Weighted average grant date fair value of stock options assumed (in dollars per share)		$ 21.60
Fair value of options assumed in business combination		$ 19.4
Post combination, stock-based compensation expense		$ 18.6
HelloSign Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options assumed (in shares)	0.9

Stockholders' Equity - Fair Val

Stockholders' Equity - Fair Value of Stock Option Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	51.60%
Risk-free interest rate, minimum	2.00%
Risk-free interest rate, maximum	3.00%
Dividend yield	0.00%
Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 years 4 months 24 days
Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	7 years

Stockholders' Equity - Co-Found

Stockholders' Equity - Co-Founder Grants (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2017tranche$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 5.76
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted | shares		23.8	16.2
Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted | shares	14.7		14.7
Expiration period	10 years
Number of tranches | tranche	9
Weighted average grant date fair value (in dollars per share) | $ / shares			$ 10.60
Award requisite period		5 years 2 months 12 days
Aggregate unamortized stock-based compensation expense | $		$ 156.2
Remaining unamortized stock-based compensation | $		84.2	$ 119.3
Stock-based compensation related to the Co-Founder Grants | $		$ 34.9	$ 37
Co-Founder Grants | Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price target (in dollars per share) | $ / shares	$ 30
Award requisite period			2 years 10 months 24 days
Co-Founder Grants | Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price target (in dollars per share) | $ / shares	$ 90
Award requisite period			6 years 10 months 24 days
Co-Founder Grants | Restricted Stock | Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Co-Founder Grants | Restricted Stock | Tranche One | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage vested maximum	20.00%
Co-Founder Grants | Chief Executive Officer | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted | shares	10.3
Co-Founder Grants | Director | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted | shares	4.4

Stockholders' Equity - Award Mo

Stockholders' Equity - Award Modifications (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan modification, stock-based compensation	$ 10

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (52.7)	$ (484.9)	$ (111.7)
Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share	411.6	358.6	195.9
Net loss per common share, basic and diluted (in dollars per share)	$ (0.13)	$ (1.35)	$ (0.57)
Class A
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (30.3)	$ (138.7)	$ (3.6)
Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share	236.8	102.6	6.3
Net loss per common share, basic and diluted (in dollars per share)	$ (0.13)	$ (1.35)	$ (0.57)
Class B
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (22.4)	$ (346.2)	$ (108.1)
Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share	174.8	256	189.6
Net loss per common share, basic and diluted (in dollars per share)	$ (0.13)	$ (1.35)	$ (0.57)

Net Loss Per Share - Schedule_2

Net Loss Per Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	45.9	53.8	206.4
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	0	147.6
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	28.9	35	52.7
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0.4	0	0
Options to purchase shares of common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1.9	4	5.1
Co-Founder Grants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	14.7	14.7	0.8
Shares subject to repurchase from early-exercised options and unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	0.1	0.2

Income Taxes - Schedule of Loss

Income Taxes - Schedule of Loss from Continuing Operations Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ (98.8)	$ (497.1)	$ (76.9)
Foreign	46.8	17	(34.6)
Loss before income taxes	$ (52)	$ (480.1)	$ (111.5)

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 0.1	$ (0.1)	$ 0.1
State	(0.6)	(0.2)	(0.3)
Foreign	(7.7)	(4.6)	(2.3)
Deferred:
Federal	6.6	0	1.4
State	0.6	0	0
Foreign	0.3	0.1	0.9
Benefit from (provision for) income taxes	$ (0.7)	$ (4.8)	$ (0.2)

Income Taxes - Income Tax Rate

Income Taxes - Income Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax benefit at federal statutory rate	$ 10.9	$ 100.8	$ 37.9
State taxes, net of federal benefit	2.4	10.7	1.7
Foreign rate differential	(0.9)	1.8	(12.3)
Research and other credits	30.2	86.5	25.4
Non-deductible compensation	(3.4)	0	0
Meals & entertainment	(2.5)	(2.2)	(0.2)
Permanent differences	(2.1)	(16.2)	(8.8)
Tax Cuts and Jobs Act impact	0	0	(61.7)
Change in valuation allowance	(32.2)	(240.7)	38.9
Stock-based compensation	1.8	57.3	(20.1)
Other nondeductible items	(4.9)	(2.8)	(1)
Benefit from (provision for) income taxes	$ (0.7)	$ (4.8)	$ (0.2)

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 257.2	$ 264.8
Research credit carryforwards	188.6	157.3
Stock-based compensation	29.3	11.1
Accruals and reserves	32.3	42
Fixed assets and intangible assets	0	0.7
Lease liability	189.8	0
Other	1	1.1
Gross deferred tax assets	698.2	477
Valuation allowance	(510.8)	(476)
Total deferred tax assets, net of valuation allowance	187.4	1
Deferred tax liabilities:
Fixed assets and intangible assets	13.1	0
Right of use assets	172.7	0
Other	0.3	0
Total deferred tax liability	186.1	0
Net deferred tax assets	$ 1.3	$ 1

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Research credit carryforwards	$ 188.6	$ 157.3
Unrecognized tax benefits	74.5	59.8	$ 25.6	$ 15.7
Unrecognized tax benefits that would impact effective tax rate	8.1
Income tax benefit (expense)	(0.7)	(4.8)	(0.2)
Unrecognized tax benefit that would result in adjustment to deferred tax assets	66.4
Penalties and interest accrued	2.6
Penalties and interest expense	1.3	$ 0.7	$ 0.2
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	916.9
Operating loss carryforwards, subject to expiration	288.9
Operating loss carryforwards, not subject to expiration	628
Research credit carryforwards	171.7
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	390.8
Research credit carryforwards	94.6
Foreign
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	244.3
Tax credit carryforward	0.7
Operating loss carryforwards, not subject to expiration, available to reduce future taxable income	221.4
Deferred tax assets, acquired operating loss carryforwards, not subject to expiration	22.9
Research Tax Credit Carryforward | Federal
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	42.8
Research Tax Credit Carryforward | State
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	23.6
State Enterprise Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	$ 3.6

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance of gross unrecognized tax benefits at the beginning of the fiscal year	$ 59.8	$ 25.6	$ 15.7
Gross increases related to prior period tax positions	0.1	1.1	0
Gross increases related to current period tax positions	14.6	33.1	9.9
Balance of gross unrecognized tax benefits at the end of the fiscal year	$ 74.5	$ 59.8	$ 25.6

Related Party Transactions (Det

Related Party Transactions (Details)	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016shareholder
Related Party Transaction [Line Items]
Cash contributions to charitable foundation			$ 1,900,000
Controlling Shareholders | Dropbox Charitable Foundation
Related Party Transaction [Line Items]
Number of controlling shareholders in related party transaction | shareholder				2
Payments to related party	$ 0	$ 0
Dropbox Charitable Foundation
Related Party Transaction [Line Items]
Fair value of shares contributed to charitable foundation			9,400,000
Cash contributions to charitable foundation			$ 1,900,000

Geographic Areas (Details)

Geographic Areas (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property and equipment, net	$ 445.3	$ 310.6
Revenue	1,661.3	1,391.7	$ 1,106.8
United States
Segment Reporting Information [Line Items]
Property and equipment, net	431.9	293.6
Revenue	854.1	706.5	575.7
International
Segment Reporting Information [Line Items]
Property and equipment, net	13.4	17
Revenue	$ 807.2	$ 685.2	$ 531.1

Subsequent Events (Details)

Subsequent Events (Details) $ in Millions	Feb. 19, 2020USD ($)
Subsequent Event
Subsequent Event [Line Items]
Stock repurchase program, authorized amount	$ 600

Uncategorized Items - a12311910

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 1,000,000
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	0
Additional Paid-in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	500,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	1,000,000
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (500,000)