XML 44 R42.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Significant Accounting Policies (Schedule Of Securities Segregated For Regulatory Purposes) (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Marketable Securities [Line Items] |  |  |
Securities - segregated for regulatory purposes |  | $ 17,824 | $ 15,595
US Government Securities [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Securities - segregated for regulatory purposes |  | 3,800 | 4,200
Securities Purchased Under Agreement To Resell [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Securities - segregated for regulatory purposes | [1] | $ 14,000 | $ 11,400
[1] | These balances are collateralized by U.S. government securities.

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_MarketableSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Securities deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations. + References No definition available. + Details
Name: | us-gaap_SecuritiesReserveDepositRequiredAndMade
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ibkr_SecuritiesPurchasedUnderAgreementToResellMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |