Cover - USD ($) shares in Millions, $ in Billions	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-35580
Entity Registrant Name	SERVICENOW, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-2056195
Entity Address, Address Line One	2225 Lawson Lane
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95054
City Area Code	408
Local Phone Number	501-8550
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	NOW
Security Exchange Name	NYSE
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			$ 37.7
Entity Common Stock, Shares Outstanding		189.8
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement for its 2020 Annual Meeting of Stockholders (Proxy Statement) to be filed within 120 days of the Registrant’s fiscal year ended December 31, 2019, are incorporated by reference in Part III of this Report on Form 10-K. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.
Entity Central Index Key	0001373715
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31