Cover shares in Millions	9 Months Ended
	Sep. 30, 2021 shares
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
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 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 Common Stock, Shares Outstanding	199
Entity Central Index Key	0001373715
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31