v3.22.0.1

Summary of Significant Accounting Policies - Investments (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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Accounting Policies [Abstract] |  |
Accrued interest, net of allowance for credit losses | $ 12 | $ 13

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- Definition Debt Securities, Available-for-sale, Accrued Interest Net Of Credit Loss + References No definition available. + Details
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Namespace Prefix: | now_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration