XML 53 R44.htm IDEA: XBRL DOCUMENT
v3.22.1

Investment Securities (Narrative) (Detail) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2022 USD ($) security | Mar. 31, 2021 USD ($) | Dec. 31, 2021 USD ($)
Investments, Debt and Equity Securities [Abstract] |  |  |
Equity securities without readily determinable fair value | $ 38,400,000 |  |
Upward adjustments of equity securities without readily determinable fair values | 0 | $ 0 |
Downward adjustments of equity securities without readily determinable fair values | 0 | 0 |
Impairment of equity securities without readily determinable fair values | 571,000 | 30,000 |
Pledged securities | $ 2,500,000,000 | $ 2,100,000,000 | $ 2,600,000,000
Number of securities by a single non-government sponsored issuer exceeding 10% of shareholders' equity | security | 0 |  |

X
- Definition Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 210 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120413173&loc=SL6242262-115580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 210 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120413209&loc=SL6242269-115581 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleRestricted
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123583765&loc=SL75117539-209714 + Details
Name: | us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of loss from downward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123583765&loc=SL75117539-209714 + Details
Name: | us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueDownwardPriceAdjustmentAnnualAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of impairment loss on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123583765&loc=SL75117539-209714 + Details
Name: | us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123583765&loc=SL75117539-209714 + Details
Name: | us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition Securities By A Single Non-government Sponsored Issuer Exceeding Ten Percent Of Shareholders' Equity + References No definition available. + Details
Name: | wtfc_SecuritiesByASingleNongovernmentSponsoredIssuerExceedingTenPercentOfShareholdersEquity
Namespace Prefix: | wtfc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant