Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2019
Accounting Policies [Abstract]
Business Combinations	Business Combinations Pursuant to the guidance of ASC Topic 805 ("ASC 805"), TCF recognized assets acquired, including identified intangible assets, and the liabilities assumed in mergers and acquisitions at their fair values as of the acquisition date, with the acquisition and merger-related transaction and restructuring costs expensed in the period incurred. ASC 805 affords a measurement period beyond the acquisition date that allows the opportunity to finalize the acquisition accounting in the event that new information is identified that existed as of the acquisition date but was not known or available at that time. This measurement period ends on the earlier of one year after the acquisition or the date information about the facts and circumstances that existed at the acquisition are available. TCF anticipates that measurement period adjustments may arise from adjustments to the fair values of Chemical's assets and liabilities recorded at the Merger Date, as additional information and evidence is obtained. In the event that a measurement period adjustment is identified, TCF will recognize the adjustment as part of its acquisition accounting, which may result in an adjustment to goodwill in the period the adjustment was identified. See Note 2. Merger for further information. Loans and Leases Acquired in a Business Combination We record loans and leases acquired in a business combination at fair value at the acquisition date and the fair value discount or premium is recognized as an adjustment to yield over the remaining life of each loan or lease. Credit discounts are included in the determination of fair value; therefore, an allowance for loan and lease losses is not recorded at the acquisition date. Purchased loans are evaluated at the acquisition date and classified as either (i) loans purchased without evidence of deteriorated credit quality since origination, referred to as purchased loans, or (ii) loans purchased with evidence of deteriorated credit quality since origination for which it is probable that all contractually required payments will not be collected, referred to as PCI loans. PCI loans are considered to be impaired and are accounted for under ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality ("ASC 310-30"). In determining whether a purchased loan should be classified as a PCI loan, we must make numerous assumptions, interpretations and judgments using internal and third-party credit quality information to determine whether or not it is probable that we will be able to collect all contractually required payments. This is a point in time assessment and is inherently subjective due to the nature of the available information and judgment involved. Evidence of credit quality deterioration as of the acquisition date may include statistics such as past due and nonaccrual status, recent borrower credit scores and loan-to-value percentages. The excess of cash flows expected to be collected over the estimated fair value of PCI loans is referred to as the accretable yield and is accreted into interest income over the estimated remaining life of the loan using the effective yield method. We estimate the expected cash flows based on the expected remaining life of the loans, which includes the effects of estimated prepayments and estimates of future credit losses. Cash flow evaluations are inherently subjective as they require material estimates, all of which may be susceptible to significant change. The difference between the contractually required payments and the cash flows expected to be collected at acquisition, is referred to as the nonaccretable difference. We do not classify PCI loans as nonaccrual loans subsequent to acquisition because the loans are recorded at net realizable value based on the principal and interest expected to be collected on the loan. Judgment is required to estimate the timing and amount of cash flows expected to be collected when the loans are not performing in accordance with the original contractual terms. Purchased loans outside the scope of ASC 310-30 are accounted for under ASC 310-20, Receivables - Nonrefundable Fees and Other Costs. For purchased loans, credit discounts representing the principal losses expected over the life of the loan are a component of the initial fair value and the discount is accreted to interest income over the life of the loan. Subsequent to the purchase date, the method used to evaluate the sufficiency of the credit discount is similar to originated loans, and if necessary, additional reserves are recognized in the allowance for loan and lease losses.
Leases	Leases TCF enters into lease contracts as both a lessor and a lessee. A contract, or part of a contract, is considered a lease if it conveys the right to obtain substantially all of the economic benefits from, and the right to direct and use, an identified asset for a period of time in exchange for consideration. The determination of lease classification requires various judgments and estimates by management which may include the fair value of the equipment at lease inception, useful life of the equipment under lease, estimate of the lease residual value and collectability of minimum lease payments. Management has policies and procedures in place for the determination of lease classification and review of the related judgments and estimates for all leases. As a lessor, TCF provides various types of lease financing that are classified for accounting purposes as direct financing, sales-type or operating leases. Leases that transfer substantially all of the benefits and risks of ownership to the lessee are classified as direct financing or sales-type leases and are recorded in loans and leases. Direct financing and sales-type leases are carried at the combined present value of future minimum lease payments and lease residual values. Interest income on net investment in direct financing and sales-type leases is recognized using methods that approximate a level yield over the fixed, non-cancelable term of the lease, including pro rata rent payments received for the interim period until the lease contract commences and the fixed, non-cancelable lease term begins. Sales-type leases generate selling profit (loss), which is recognized on the commencement date by recording lease revenue net of lease cost. Lease revenue consists of the present value of the future minimum lease payments and lease cost consists of the leased equipment's net book value, less the present value of its residual. Some lease financing contracts include a residual value component, which represents the estimated fair value of the leased equipment at the expiration of the initial term of the transaction. The estimation of residual values involves judgment regarding product and technology changes, customer behavior, shifts in supply and demand and other economic assumptions. TCF reviews residual assumptions when assessing potential impairment of the net investment in direct financing and sales-type leases each quarter. Decreases in the expected residual value are reflected through an increase in the provision for credit losses, which results in an increase to the allowance for loan and lease losses. TCF may sell minimum lease payment receivables, primarily as a credit risk reduction tool, to third-party financial institutions at fixed rates, on a non-recourse basis, with its underlying equipment as collateral. For those transactions that qualify for sale accounting, the related lease cash flow stream and the non-recourse financing are derecognized. For those transactions that do not qualify for sale accounting, the underlying lease remains on TCF's Consolidated Statements of Financial Condition and non-recourse debt is recorded in the amount of the proceeds received. TCF retains servicing of these leases and bills, collects and remits funds to the third-party financial institution. Upon default by the lessee, the third-party financial institutions may take control of the underlying collateral which TCF would otherwise retain as residual value. Leases that do not transfer substantially all benefits and risks of ownership to the lessee are classified as operating leases. Such leased equipment and related initial direct costs are included in other assets and depreciated to their estimated salvage value on a straight-line basis over the term of the lease. Lease financing equipment depreciation is recorded in noninterest expense. Operating lease payments received are recognized as lease income when due and recorded as a component of leasing and equipment finance noninterest income. An allowance for lease losses is not provided on operating leases. See Note 7. Loans and Leases for further information. As a lessee, TCF enters into contracts to lease real estate, information technology equipment and various other types of equipment. Leases that transfer substantially all of the benefits and risks of ownership to TCF are classified as finance leases, while all others are classified as operating leases. At lease commencement, a lease liability and right-of-use asset are calculated and recognized for both types of leases. The lease liability is equal to the present value of future minimum lease payments. The right-of-use asset is equal to the lease liability, plus any initial direct costs and prepaid lease payments, less any lease incentives received. Operating lease right-of-use assets are recorded in other assets and finance lease right-of-use assets are recorded in premises and equipment, net. TCF uses the appropriate term Federal Home Loan Bank ("FHLB") rate to determine the discount rate for the present value calculation of future minimum payments when an implicit rate is not known for a given lease. The lease term used in the calculation includes any options to extend that TCF is reasonably certain to exercise. Subsequent to lease commencement, lease liabilities recorded for finance leases are measured using the effective interest rate method and the related right-of-use assets are amortized on a straight-line basis over the lease term. Interest expense and amortization expense are recorded separately in the income statement in interest expense on borrowings and occupancy and equipment noninterest expense, respectively. For operating leases, total lease cost is comprised of lease expense, short-term lease cost, variable lease cost and sublease income. Lease expense includes future minimum lease payments, which are recognized on a straight-line basis over the lease term, as well as common area maintenance charges, real estate taxes, insurance and other expenses, where applicable, which are expensed as incurred. Total lease cost for operating leases is recorded in occupancy and equipment noninterest expense. See Note 12. Operating Lease Right-of-Use Assets and Liabilities for further information.
Leases	Leases TCF enters into lease contracts as both a lessor and a lessee. A contract, or part of a contract, is considered a lease if it conveys the right to obtain substantially all of the economic benefits from, and the right to direct and use, an identified asset for a period of time in exchange for consideration. The determination of lease classification requires various judgments and estimates by management which may include the fair value of the equipment at lease inception, useful life of the equipment under lease, estimate of the lease residual value and collectability of minimum lease payments. Management has policies and procedures in place for the determination of lease classification and review of the related judgments and estimates for all leases. As a lessor, TCF provides various types of lease financing that are classified for accounting purposes as direct financing, sales-type or operating leases. Leases that transfer substantially all of the benefits and risks of ownership to the lessee are classified as direct financing or sales-type leases and are recorded in loans and leases. Direct financing and sales-type leases are carried at the combined present value of future minimum lease payments and lease residual values. Interest income on net investment in direct financing and sales-type leases is recognized using methods that approximate a level yield over the fixed, non-cancelable term of the lease, including pro rata rent payments received for the interim period until the lease contract commences and the fixed, non-cancelable lease term begins. Sales-type leases generate selling profit (loss), which is recognized on the commencement date by recording lease revenue net of lease cost. Lease revenue consists of the present value of the future minimum lease payments and lease cost consists of the leased equipment's net book value, less the present value of its residual. Some lease financing contracts include a residual value component, which represents the estimated fair value of the leased equipment at the expiration of the initial term of the transaction. The estimation of residual values involves judgment regarding product and technology changes, customer behavior, shifts in supply and demand and other economic assumptions. TCF reviews residual assumptions when assessing potential impairment of the net investment in direct financing and sales-type leases each quarter. Decreases in the expected residual value are reflected through an increase in the provision for credit losses, which results in an increase to the allowance for loan and lease losses. TCF may sell minimum lease payment receivables, primarily as a credit risk reduction tool, to third-party financial institutions at fixed rates, on a non-recourse basis, with its underlying equipment as collateral. For those transactions that qualify for sale accounting, the related lease cash flow stream and the non-recourse financing are derecognized. For those transactions that do not qualify for sale accounting, the underlying lease remains on TCF's Consolidated Statements of Financial Condition and non-recourse debt is recorded in the amount of the proceeds received. TCF retains servicing of these leases and bills, collects and remits funds to the third-party financial institution. Upon default by the lessee, the third-party financial institutions may take control of the underlying collateral which TCF would otherwise retain as residual value. Leases that do not transfer substantially all benefits and risks of ownership to the lessee are classified as operating leases. Such leased equipment and related initial direct costs are included in other assets and depreciated to their estimated salvage value on a straight-line basis over the term of the lease. Lease financing equipment depreciation is recorded in noninterest expense. Operating lease payments received are recognized as lease income when due and recorded as a component of leasing and equipment finance noninterest income. An allowance for lease losses is not provided on operating leases. See Note 7. Loans and Leases for further information. As a lessee, TCF enters into contracts to lease real estate, information technology equipment and various other types of equipment. Leases that transfer substantially all of the benefits and risks of ownership to TCF are classified as finance leases, while all others are classified as operating leases. At lease commencement, a lease liability and right-of-use asset are calculated and recognized for both types of leases. The lease liability is equal to the present value of future minimum lease payments. The right-of-use asset is equal to the lease liability, plus any initial direct costs and prepaid lease payments, less any lease incentives received. Operating lease right-of-use assets are recorded in other assets and finance lease right-of-use assets are recorded in premises and equipment, net. TCF uses the appropriate term Federal Home Loan Bank ("FHLB") rate to determine the discount rate for the present value calculation of future minimum payments when an implicit rate is not known for a given lease. The lease term used in the calculation includes any options to extend that TCF is reasonably certain to exercise. Subsequent to lease commencement, lease liabilities recorded for finance leases are measured using the effective interest rate method and the related right-of-use assets are amortized on a straight-line basis over the lease term. Interest expense and amortization expense are recorded separately in the income statement in interest expense on borrowings and occupancy and equipment noninterest expense, respectively. For operating leases, total lease cost is comprised of lease expense, short-term lease cost, variable lease cost and sublease income. Lease expense includes future minimum lease payments, which are recognized on a straight-line basis over the lease term, as well as common area maintenance charges, real estate taxes, insurance and other expenses, where applicable, which are expensed as incurred. Total lease cost for operating leases is recorded in occupancy and equipment noninterest expense. See Note 12. Operating Lease Right-of-Use Assets and Liabilities for further information.
Loan Servicing Rights	Loan Servicing Rights Loan servicing rights ("LSRs") are recognized as assets or liabilities as a result of selling residential mortgage and commercial real estate loans in the secondary market while retaining the right to service these loans and receive servicing income over the life of the loan, and from acquisitions of other banks that had LSRs. An LSR is recorded at estimated fair value when initially recognized. Fair value is determined by the present value of expected cash flows received in excess of a market servicing rate. If the amount earned to service assets is equal to the market rate, no value is recorded. Subsequently, LSRs are accounted for at the lower of amortized cost or fair value and amortized in proportion to and over the period of net servicing income. Unexpected prepayments of mortgage loans result in increased amortization of LSRs, as the remaining book value of the LSRs is expensed at the time of prepayment. LSRs are assessed quarterly for impairment. See Note 11. Loan Servicing Rights for further information.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements Effective January 1, 2019, TCF adopted ASU No. 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes, which permits the use of the OIS Rate based on the SOFR as a U.S. benchmark interest rate for hedge accounting purposes under Topic 815 in addition to the interest rates on direct Treasury obligations of the U.S. government, the London Interbank Offered Rate ("LIBOR") swap rate, the OIS Rate based on the Fed Funds Effective Rate and the Securities Industry and Financial Markets Association Municipal Swap Rate. The adoption of this ASU was on a prospective basis for qualifying new or redesignated hedging relationships entered into on or after January 1, 2019. The adoption of this guidance did not have a material impact on our consolidated financial statements. Effective January 1, 2019, TCF adopted ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force), which requires the decision to capitalize or expense implementation costs incurred in a cloud computing arrangement (i.e. a hosting arrangement) that is a service contract to follow the internal-use software guidance in ASC 350-40. TCF's policy had been to expense these costs as incurred. The adoption of this ASU was on a prospective basis. The adoption of this guidance did not have a material impact on our consolidated financial statements. Effective January 1, 2019, TCF adopted ASU No. 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which simplifies the accounting for share-based payments to nonemployees by aligning it more consistently with the accounting for share-based payments to employees. The new guidance in ASC 718 supersedes the guidance in ASC 505-50. The adoption of this ASU was on a modified retrospective basis with no cumulative effect adjustment recorded. The adoption of this guidance did not have a material impact on our consolidated financial statements. Effective January 1, 2019, TCF adopted ASU No. 2017-11, Earnings Per Share (Topic 260): Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features, which simplifies the accounting for certain equity-linked financial instruments and embedded features with the down round features that reduce the exercise price when the pricing of a future round of financing is lower. The adoption of this ASU was on a modified retrospective basis. The adoption of this guidance did not have a material impact on our consolidated financial statements. Effective January 1, 2019, TCF adopted ASU No. 2016-02, Leases (Topic 842), which, along with other amendments, requires lessees to recognize most leases on their balance sheet. Lessor accounting is largely unchanged. The ASU requires both quantitative and qualitative disclosure regarding key information about leasing arrangements from both lessees and lessors. Effective January 1, 2019, TCF also adopted the following ASUs, which further amend the original lease guidance in Topic 842: (i) ASU No. 2017-13, Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840) and Leases (Topic 842): Amendments to SEC Paragraphs, which rescinds certain SEC Observer comments and staff announcements from the lease guidance and incorporates SEC staff announcements on the effect of a change in tax law on leveraged leases from ASC 840 into ASC 842; (ii) ASU No. 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842, which amends the new lease guidance to add an optional transition practical expedient that permits an entity to continue applying its current accounting policy for land easements that existed or expired before January 1, 2019; (iii) ASU No. 2018-10, Codification Improvements to Topic 842, Leases, which makes narrow scope improvements to the standard for specific issues; (iv) ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, which provides an optional transition method allowing the standard to be applied at the adoption date and provides a practical expedient related to separating components of a contract for lessors; (v) ASU No. 2018-20, Leases (Topic 842): Narrow-Scope Improvements for Lessors, which allows lessors to elect to account for all sales taxes as lessee costs, instead of determining whether they are lessee or lessor costs in each individual jurisdiction. It requires lessor costs paid by lessees directly to third parties to be excluded from revenue, requires lessors to account for costs excluded from the consideration of a contract that are paid by the lessor as revenue and requires certain variable payments to be allocated (rather than recognized) to lease and nonlease components when changes occur in the facts and circumstances on which the variable payments are based; and (vi) ASU No. 2019-01, Leases (Topic 842): Codification Improvements, which allows lessors that are not manufacturers or dealers to calculate the fair value of an underlying asset as its cost less any volume or trade discount, requires lessors to classify principal payments received from direct financing and sales-type leases as investing activities in the statement of cash flows and clarifies that certain disclosure requirements that were explicitly excluded from annual reporting during the year of adoption are also excluded from interim reporting during the same year. These ASUs were adopted on a modified retrospective basis. Management elected the practical expedients and optional transition method, which allow for leases entered into prior to January 1, 2019 to be accounted for consistent with prior guidance. Management evaluated TCF's leasing contracts and activities, and developed methodologies and processes to estimate and account for the right-of-use assets and lease liabilities based on the present value of future lease payments. On January 1, 2019, TCF recorded right-of-use assets and lease liabilities totaling $91.9 million and $112.8 million, respectively. TCF also recorded additional right-of-use assets and lease liabilities totaling $39.8 million and $41.6 million on August 1, 2019 as a result of the Merger. The impact to capital ratios as a result of increased risk-weighted assets is immaterial. The adoption of this guidance did not result in a material change to lessee expense recognition. The changes to lessor accounting, as well as changes in customer behavior driven by the adoption of these ASUs, impacts the results of TCF's leasing and equipment financing businesses, including earlier recognition of expense due to a narrower definition of initial direct costs and the timing of revenue recognition for certain leases, resulting in more revenue being deferred over the lease term. Recently Issued but Not Yet Adopted Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606, which makes targeted improvements to the accounting for collaborative arrangements in response to questions raised as a result of the issuance of ASU 2014-09, Revenue from Contracts with Customers (Topic 606). The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. Early adoption is allowed. The adoption of this guidance will not have a material impact on our consolidated financial statements. In October 2018, the FASB issued ASU No. 2018-17, Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities, which provides an elective exemption to private companies from applying variable interest entities ("VIE") guidance to all entities under common control if certain criteria are met. In addition, this ASU contains an amendment applicable to all entities which amends how a decision maker or service provider determines whether its fee is a variable interest in a VIE when a related party under common control also has an interest in the VIE. The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. Early adoption is allowed. The adoption of this guidance will not have a material impact on our consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. Certain of the amendments require prospective application, while the remainder require retrospective application. Early adoption is allowed either for the entire standard or only the provisions that eliminate or modify the requirements. Management is currently evaluating which adoption method will be selected as well as the related potential impact of this guidance on our consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. This ASU simplifies the accounting for goodwill impairment by removing Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. Subsequent to adoption, goodwill impairment will be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. All other goodwill impairment guidance largely remains unchanged. The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020 on a prospective basis. Early adoption is allowed. The adoption of this guidance will not have a material impact on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which changes the impairment model for most financial assets (including off-balance sheet exposure), including trade and other receivables, debt securities held to maturity, loans, net investments in leases and purchased financial assets with credit deterioration. The ASU requires the use of a current expected credit loss ("CECL") methodology to determine the allowance for credit losses for loans and debt securities held to maturity. CECL requires loss estimates for the remaining estimated life of the asset to be measured using historical loss data as well as reasonable and supportable forecasts based on current and forecasted economic conditions. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses, which clarifies that receivables arising from operating leases are not within the scope of Subtopic 326-20 and should be accounted for in accordance with Topic 842. In April 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, which clarifies and corrects certain unintended applications of the guidance contained in each of the amended Topics. In May 2019, the FASB issued ASU No. 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief, which provides an option to irrevocably elect the fair value option in Subtopic 825-10 to certain instruments within the scope of Subtopic 326-20 upon adoption of Topic 326. The adoption of these ASUs will be required on a modified retrospective basis with a cumulative effect adjustment required beginning January 1, 2020 with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. CECL represents a significant change in GAAP and is expected to result in a material impact to our consolidated financial statements and capital ratios. The impact of these ASUs will depend on the composition of TCF's portfolios, the current economic conditions, and forecasted macroeconomic conditions at the date of adoption. Additionally, industry practice and interpretation of the ASUs continues to evolve which may impact management's implementation of the standard. TCF has established a governance structure to implement these ASUs and has developed a majority of the methodology and models to be used upon adoption. Based on parallel runs of the CECL process that TCF has performed alongside our current allowance for loan and lease losses process, we preliminarily estimated that the adoption of the standard will increase the allowance for loan and lease losses between 35% to 45% on Legacy TCF portfolios, when compared to current allowance for loan and lease loss levels. At September 30, 2019, Legacy TCF loan and lease portfolios totaled approximately $17.8 billion with a corresponding allowance for loans and lease losses of approximately $117.1 million. The largest impact is anticipated to be to our consumer segment given the longer duration of the portfolios. Management is in the process of finalizing model validations and approval of all key design decisions through its governance structure, which includes decisions about the methodology for estimating reserves for unfunded commitments and disclosures. The estimated impact of the standard depends on the composition of the portfolio, credit quality, economic conditions and forecasts at the time of adoption, as well as final decisions by management, all of which could result in a change to management’s estimate. With the close of the Merger on August 1, 2019, management is evaluating the impact of CECL on the acquired legacy Chemical portfolio which will then be included in the combined portfolio of TCF upon adoption. The loans and leases acquired in the Merger were recorded at estimated fair value on the Merger Date, which includes an estimate of credit losses. Under current GAAP, an allowance for loan and lease losses is not recorded on these loans and leases until there is evidence of credit deterioration post acquisition. However, upon adoption of CECL an allowance for loan and lease loss will need to be recorded for the acquired loans based on the lifetime loss concept within CECL. We are in the process of developing CECL assumptions on the acquired Chemical portfolios with those used by Legacy TCF. Since these assumptions could materially impact the estimate of the allowance for loan and lease losses under CECL, we are unable to estimate the impact on the Chemical portfolio at this time. The initial increase to TCF's allowance for loan and lease losses will be recorded as an adjustment to beginning of the year retained earnings. Post adoption, as loans and leases are added to the portfolio, we expect higher levels of allowance for loan and lease losses determined by CECL assumptions, resulting in higher levels of provision for credit losses. Management will continue to refine this process during the fourth quarter of 2019 as well as consider the impacts the Merger will have on the adoption of the standard.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2019

Business Combinations Pursuant to the guidance of ASC Topic 805 ("ASC 805"), TCF recognized assets acquired, including identified intangible assets, and the liabilities assumed in mergers and acquisitions at their fair values as of the acquisition date, with the acquisition and merger-related transaction and restructuring costs expensed in the period incurred.

ASC 805 affords a measurement period beyond the acquisition date that allows the opportunity to finalize the acquisition accounting in the event that new information is identified that existed as of the acquisition date but was not known or available at that time. This measurement period ends on the earlier of one year after the acquisition or the date information about the facts and circumstances that existed at the acquisition are available. TCF anticipates that measurement period adjustments may arise from adjustments to the fair values of Chemical's assets and liabilities recorded at the Merger Date, as additional information and evidence is obtained. In the event that a measurement period adjustment is identified, TCF will recognize the adjustment as part of its acquisition accounting, which may result in an adjustment to goodwill in the period the adjustment was identified.

See Note 2. Merger for further information.

Loans and Leases Acquired in a Business Combination We record loans and leases acquired in a business combination at fair value at the acquisition date and the fair value discount or premium is recognized as an adjustment to yield over the remaining life of each loan or lease. Credit discounts are included in the determination of fair value; therefore, an allowance for loan and lease losses is not recorded at the acquisition date. Purchased loans are evaluated at the acquisition date and classified as either (i) loans purchased without evidence of deteriorated credit quality since origination, referred to as purchased loans, or (ii) loans purchased with evidence of deteriorated credit quality since origination for which it is probable that all contractually required payments will not be collected, referred to as PCI loans. PCI loans are considered to be impaired and are accounted for under ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality ("ASC 310-30"). In determining whether a purchased loan should be classified as a PCI loan, we must make numerous assumptions, interpretations and judgments using internal and third-party credit quality information to determine whether or not it is probable that we will be able to collect all contractually required payments. This is a point in time assessment and is inherently subjective due to the nature of the available information and judgment involved. Evidence of credit quality deterioration as of the acquisition date may include statistics such as past due and nonaccrual status, recent borrower credit scores and loan-to-value percentages. The excess of cash flows expected to be collected over the estimated fair value of PCI loans is referred to as the accretable yield and is accreted into interest income over the estimated remaining life of the loan using the effective yield method. We estimate the expected cash flows based on the expected remaining life of the loans, which includes the effects of estimated prepayments and estimates of future credit losses. Cash flow evaluations are inherently subjective as they require material estimates, all of which may be susceptible to significant change. The difference between the contractually required payments and the cash flows expected to be collected at acquisition, is referred to as the nonaccretable difference.

We do not classify PCI loans as nonaccrual loans subsequent to acquisition because the loans are recorded at net realizable value based on the principal and interest expected to be collected on the loan. Judgment is required to estimate the timing and amount of cash flows expected to be collected when the loans are not performing in accordance with the original contractual terms.

Purchased loans outside the scope of ASC 310-30 are accounted for under ASC 310-20, Receivables - Nonrefundable Fees and Other Costs. For purchased loans, credit discounts representing the principal losses expected over the life of the loan are a component of the initial fair value and the discount is accreted to interest income over the life of the loan. Subsequent to the purchase date, the method used to evaluate the sufficiency of the credit discount is similar to originated loans, and if necessary, additional reserves are recognized in the allowance for loan and lease losses.

Leases

Leases TCF enters into lease contracts as both a lessor and a lessee. A contract, or part of a contract, is considered a lease if it conveys the right to obtain substantially all of the economic benefits from, and the right to direct and use, an identified asset for a period of time in exchange for consideration. The determination of lease classification requires various judgments and estimates by management which may include the fair value of the equipment at lease inception, useful life of the equipment under lease, estimate of the lease residual value and collectability of minimum lease payments. Management has policies and procedures in place for the determination of lease classification and review of the related judgments and estimates for all leases.

As a lessor, TCF provides various types of lease financing that are classified for accounting purposes as direct financing, sales-type or operating leases. Leases that transfer substantially all of the benefits and risks of ownership to the lessee are classified as direct financing or sales-type leases and are recorded in loans and leases. Direct financing and sales-type leases are carried at the combined present value of future minimum lease payments and lease residual values.

Interest income on net investment in direct financing and sales-type leases is recognized using methods that approximate a level yield over the fixed, non-cancelable term of the lease, including pro rata rent payments received for the interim period until the lease contract commences and the fixed, non-cancelable lease term begins. Sales-type leases generate selling profit (loss), which is recognized on the commencement date by recording lease revenue net of lease cost. Lease revenue consists of the present value of the future minimum lease payments and lease cost consists of the leased equipment's net book value, less the present value of its residual.

Some lease financing contracts include a residual value component, which represents the estimated fair value of the leased equipment at the expiration of the initial term of the transaction. The estimation of residual values involves judgment regarding product and technology changes, customer behavior, shifts in supply and demand and other economic assumptions. TCF reviews residual assumptions when assessing potential impairment of the net investment in direct financing and sales-type leases each quarter. Decreases in the expected residual value are reflected through an increase in the provision for credit losses, which results in an increase to the allowance for loan and lease losses.

TCF may sell minimum lease payment receivables, primarily as a credit risk reduction tool, to third-party financial institutions at fixed rates, on a non-recourse basis, with its underlying equipment as collateral. For those transactions that qualify for sale accounting, the related lease cash flow stream and the non-recourse financing are derecognized. For those transactions that do not qualify for sale accounting, the underlying lease remains on TCF's Consolidated Statements of Financial Condition and non-recourse debt is recorded in the amount of the proceeds received. TCF retains servicing of these leases and bills, collects and remits funds to the third-party financial institution. Upon default by the lessee, the third-party financial institutions may take control of the underlying collateral which TCF would otherwise retain as residual value.

Leases that do not transfer substantially all benefits and risks of ownership to the lessee are classified as operating leases. Such leased equipment and related initial direct costs are included in other assets and depreciated to their estimated salvage value on a straight-line basis over the term of the lease. Lease financing equipment depreciation is recorded in noninterest expense. Operating lease payments received are recognized as lease income when due and recorded as a component of leasing and equipment finance noninterest income. An allowance for lease losses is not provided on operating leases.

See Note 7. Loans and Leases for further information.

As a lessee, TCF enters into contracts to lease real estate, information technology equipment and various other types of equipment. Leases that transfer substantially all of the benefits and risks of ownership to TCF are classified as finance leases, while all others are classified as operating leases. At lease commencement, a lease liability and right-of-use asset are calculated and recognized for both types of leases. The lease liability is equal to the present value of future minimum lease payments. The right-of-use asset is equal to the lease liability, plus any initial direct costs and prepaid lease payments, less any lease incentives received. Operating lease right-of-use assets are recorded in other assets and finance lease right-of-use assets are recorded in premises and equipment, net. TCF uses the appropriate term Federal Home Loan Bank ("FHLB") rate to determine the discount rate for the present value calculation of future minimum payments when an implicit rate is not known for a given lease. The lease term used in the calculation includes any options to extend that TCF is reasonably certain to exercise.

Subsequent to lease commencement, lease liabilities recorded for finance leases are measured using the effective interest rate method and the related right-of-use assets are amortized on a straight-line basis over the lease term. Interest expense and amortization expense are recorded separately in the income statement in interest expense on borrowings and occupancy and equipment noninterest expense, respectively. For operating leases, total lease cost is comprised of lease expense, short-term lease cost, variable lease cost and sublease income. Lease expense includes future minimum lease payments, which are recognized on a straight-line basis over the lease term, as well as common area maintenance charges, real estate taxes, insurance and other expenses, where applicable, which are expensed as incurred. Total lease cost for operating leases is recorded in occupancy and equipment noninterest expense.

See Note 12. Operating Lease Right-of-Use Assets and Liabilities for further information.

Leases

See Note 7. Loans and Leases for further information.

See Note 12. Operating Lease Right-of-Use Assets and Liabilities for further information.

Loan Servicing Rights

Loan Servicing Rights Loan servicing rights ("LSRs") are recognized as assets or liabilities as a result of selling residential mortgage and commercial real estate loans in the secondary market while retaining the right to service these loans and receive servicing income over the life of the loan, and from acquisitions of other banks that had LSRs. An LSR is recorded at estimated fair value when initially recognized. Fair value is determined by the present value of expected cash flows received in excess of a market servicing rate. If the amount earned to service assets is equal to the market rate, no value is recorded. Subsequently, LSRs are accounted for at the lower of amortized cost or fair value and amortized in proportion to and over the period of net servicing income. Unexpected prepayments of mortgage loans result in increased amortization of LSRs, as the remaining book value of the LSRs is expensed at the time of prepayment. LSRs are assessed quarterly for impairment. See Note 11. Loan Servicing Rights for further information.

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Effective January 1, 2019, TCF adopted ASU No. 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes, which permits the use of the OIS Rate based on the SOFR as a U.S. benchmark interest rate for hedge accounting purposes under Topic 815 in addition to the interest rates on direct Treasury obligations of the U.S. government, the London Interbank Offered Rate ("LIBOR") swap rate, the OIS Rate based on the Fed Funds Effective Rate and the Securities Industry and Financial Markets Association Municipal Swap Rate. The adoption of this ASU was on a prospective basis for qualifying new or redesignated hedging relationships entered into on or after January 1, 2019. The adoption of this guidance did not have a material impact on our consolidated financial statements.

Effective January 1, 2019, TCF adopted ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force), which requires the decision to capitalize or expense implementation costs incurred in a cloud computing arrangement (i.e. a hosting arrangement) that is a service contract to follow the internal-use software guidance in ASC 350-40. TCF's policy had been to expense these costs as incurred. The adoption of this ASU was on a prospective basis. The adoption of this guidance did not have a material impact on our consolidated financial statements.

Effective January 1, 2019, TCF adopted ASU No. 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which simplifies the accounting for share-based payments to nonemployees by aligning it more consistently with the accounting for share-based payments to employees. The new guidance in ASC 718 supersedes the guidance in ASC 505-50. The adoption of this ASU was on a modified retrospective basis with no cumulative effect adjustment recorded. The adoption of this guidance did not have a material impact on our consolidated financial statements.

Effective January 1, 2019, TCF adopted ASU No. 2017-11, Earnings Per Share (Topic 260): Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features, which simplifies the accounting for certain equity-linked financial instruments and embedded features with the down round features that reduce the exercise price when the pricing of a future round of financing is lower. The adoption of this ASU was on a modified retrospective basis. The adoption of this guidance did not have a material impact on our consolidated financial statements.

Effective January 1, 2019, TCF adopted ASU No. 2016-02, Leases (Topic 842), which, along with other amendments, requires lessees to recognize most leases on their balance sheet. Lessor accounting is largely unchanged. The ASU requires both quantitative and qualitative disclosure regarding key information about leasing arrangements from both lessees and lessors. Effective January 1, 2019, TCF also adopted the following ASUs, which further amend the original lease guidance in Topic 842: (i) ASU No. 2017-13, Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840) and Leases (Topic 842): Amendments to SEC Paragraphs, which rescinds certain SEC Observer comments and staff announcements from the lease guidance and incorporates SEC staff announcements on the effect of a change in tax law on leveraged leases from ASC 840 into ASC 842; (ii) ASU No. 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842, which amends the new lease guidance to add an optional transition practical expedient that permits an entity to continue applying its current accounting policy for land easements that existed or expired before January 1, 2019; (iii) ASU No. 2018-10, Codification Improvements to Topic 842, Leases, which makes narrow scope improvements to the standard for specific issues; (iv) ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, which provides an optional transition method allowing the standard to be applied at the adoption date and provides a practical expedient related to separating components of a contract for lessors; (v) ASU No. 2018-20, Leases (Topic 842): Narrow-Scope Improvements for Lessors, which allows lessors to elect to account for all sales taxes as lessee costs, instead of determining whether they are lessee or lessor costs in each individual jurisdiction. It requires lessor costs paid by lessees directly to third parties to be excluded from revenue, requires lessors to account for costs excluded from the consideration of a contract that are paid by the lessor as revenue and requires certain variable payments to be allocated (rather than recognized) to lease and nonlease components when changes occur in the facts and circumstances on which the variable payments are based; and (vi) ASU No. 2019-01, Leases (Topic 842): Codification Improvements, which allows lessors that are not manufacturers or dealers to calculate the fair value of an underlying asset as its cost less any volume or trade discount, requires lessors to classify principal payments received from direct financing and sales-type leases as investing activities in the statement of cash flows and clarifies that certain disclosure requirements that were explicitly excluded from annual reporting during the year of adoption are also excluded from interim reporting during the same year. These

ASUs were adopted on a modified retrospective basis. Management elected the practical expedients and optional transition method, which allow for leases entered into prior to January 1, 2019 to be accounted for consistent with prior guidance. Management evaluated TCF's leasing contracts and activities, and developed methodologies and processes to estimate and account for the right-of-use assets and lease liabilities based on the present value of future lease payments. On January 1, 2019, TCF recorded right-of-use assets and lease liabilities totaling $91.9 million and $112.8 million, respectively. TCF also recorded additional right-of-use assets and lease liabilities totaling $39.8 million and $41.6 million on August 1, 2019 as a result of the Merger. The impact to capital ratios as a result of increased risk-weighted assets is immaterial. The adoption of this guidance did not result in a material change to lessee expense recognition. The changes to lessor accounting, as well as changes in customer behavior driven by the adoption of these ASUs, impacts the results of TCF's leasing and equipment financing businesses, including earlier recognition of expense due to a narrower definition of initial direct costs and the timing of revenue recognition for certain leases, resulting in more revenue being deferred over the lease term.

Recently Issued but Not Yet Adopted Accounting Pronouncements

In November 2018, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606, which makes targeted improvements to the accounting for collaborative arrangements in response to questions raised as a result of the issuance of ASU 2014-09, Revenue from Contracts with Customers (Topic 606). The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. Early adoption is allowed. The adoption of this guidance will not have a material impact on our consolidated financial statements.

In October 2018, the FASB issued ASU No. 2018-17, Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities, which provides an elective exemption to private companies from applying variable interest entities ("VIE") guidance to all entities under common control if certain criteria are met. In addition, this ASU contains an amendment applicable to all entities which amends how a decision maker or service provider determines whether its fee is a variable interest in a VIE when a related party under common control also has an interest in the VIE. The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. Early adoption is allowed. The adoption of this guidance will not have a material impact on our consolidated financial statements.

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. Certain of the amendments require prospective application, while the remainder require retrospective application. Early adoption is allowed either for the entire standard or only the provisions that eliminate or modify the requirements. Management is currently evaluating which adoption method will be selected as well as the related potential impact of this guidance on our consolidated financial statements.

In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. This ASU simplifies the accounting for goodwill impairment by removing Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. Subsequent to adoption, goodwill impairment will be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. All other goodwill impairment guidance largely remains unchanged. The adoption of this ASU will be required beginning with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020 on a prospective basis. Early adoption is allowed. The adoption of this guidance will not have a material impact on our consolidated financial statements.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which changes the impairment model for most financial assets (including off-balance sheet exposure), including trade and other receivables, debt securities held to maturity, loans, net investments in leases and purchased financial assets with credit deterioration. The ASU requires the use of a current expected credit loss ("CECL") methodology to determine the allowance for credit losses for loans and debt securities held to maturity. CECL requires loss estimates for the remaining estimated life of the asset to be measured using historical loss data as well as reasonable and supportable forecasts based on current and forecasted economic conditions. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses, which clarifies that receivables arising from operating leases are not within the scope of Subtopic 326-20 and should be accounted for in accordance with Topic 842. In April 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments - Credit Losses, Topic 815, Derivatives and

Hedging, and Topic 825, Financial Instruments, which clarifies and corrects certain unintended applications of the guidance contained in each of the amended Topics. In May 2019, the FASB issued ASU No. 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief, which provides an option to irrevocably elect the fair value option in Subtopic 825-10 to certain instruments within the scope of Subtopic 326-20 upon adoption of Topic 326. The adoption of these ASUs will be required on a modified retrospective basis with a cumulative effect adjustment required beginning January 1, 2020 with TCF's Quarterly Report on Form 10-Q for the quarter ending March 31, 2020. CECL represents a significant change in GAAP and is expected to result in a material impact to our consolidated financial statements and capital ratios. The impact of these ASUs will depend on the composition of TCF's portfolios, the current economic conditions, and forecasted macroeconomic conditions at the date of adoption. Additionally, industry practice and interpretation of the ASUs continues to evolve which may impact management's implementation of the standard.

TCF has established a governance structure to implement these ASUs and has developed a majority of the methodology and models to be used upon adoption. Based on parallel runs of the CECL process that TCF has performed alongside our current allowance for loan and lease losses process, we preliminarily estimated that the adoption of the standard will increase the allowance for loan and lease losses between 35% to 45% on Legacy TCF portfolios, when compared to current allowance for loan and lease loss levels. At September 30, 2019, Legacy TCF loan and lease portfolios totaled approximately $17.8 billion with a corresponding allowance for loans and lease losses of approximately $117.1 million. The largest impact is anticipated to be to our consumer segment given the longer duration of the portfolios. Management is in the process of finalizing model validations and approval of all key design decisions through its governance structure, which includes decisions about the methodology for estimating reserves for unfunded commitments and disclosures. The estimated impact of the standard depends on the composition of the portfolio, credit quality, economic conditions and forecasts at the time of adoption, as well as final decisions by management, all of which could result in a change to management’s estimate.

With the close of the Merger on August 1, 2019, management is evaluating the impact of CECL on the acquired legacy Chemical portfolio which will then be included in the combined portfolio of TCF upon adoption. The loans and leases acquired in the Merger were recorded at estimated fair value on the Merger Date, which includes an estimate of credit losses. Under current GAAP, an allowance for loan and lease losses is not recorded on these loans and leases until there is evidence of credit deterioration post acquisition. However, upon adoption of CECL an allowance for loan and lease loss will need to be recorded for the acquired loans based on the lifetime loss concept within CECL. We are in the process of developing CECL assumptions on the acquired Chemical portfolios with those used by Legacy TCF. Since these assumptions could materially impact the estimate of the allowance for loan and lease losses under CECL, we are unable to estimate the impact on the Chemical portfolio at this time.

The initial increase to TCF's allowance for loan and lease losses will be recorded as an adjustment to beginning of the year retained earnings. Post adoption, as loans and leases are added to the portfolio, we expect higher levels of allowance for loan and lease losses determined by CECL assumptions, resulting in higher levels of provision for credit losses. Management will continue to refine this process during the fourth quarter of 2019 as well as consider the impacts the Merger will have on the adoption of the standard.