Accounting Policies Recently Adopted and Pending Accounting Pronouncements	3 Months Ended
Mar. 31, 2019
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Accounting Policies Recently Adopted and Pending Accounting Pronouncements	Note 20 – Accounting Policies Recently Adopted and Pending Accounting Pronouncements Accounting Policies Recently Adopted Except for the changes detailed below, Trustmark has consistently applied its accounting policies to all periods presented in the accompanying consolidated financial statements. ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” Issued in August 2017, ASU 2017-12 aims to improve the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. The amendments in ASU 2017-12 aim to better align an entity’s risk management activities and financial reporting for hedging relationships by expanding and refining hedge accounting for both non-financial and financial risk components and aligning the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The amendments in ASU 2017-12 (i) permit hedge accounting for risk components in hedging relationships involving nonfinancial risk and interest rate risk; (ii) change the guidance for designating fair value hedges of interest rate risk and for measuring the change in fair value of the hedged item in fair value hedges of interest rate risk; (iii) continue to allow an entity to exclude option premiums and forward points from the assessment of hedge effectiveness; and (iv) permit an entity to exclude the portion of the change in fair value of a currency swap that is attributable to a cross-country basis spread from the assessment of hedge effectiveness. The amendments of ASU 2017-12 also include targeted improvements intended to simplify the application of hedge accounting. All transition requirements and elections must be applied to all hedging relationships existing at the date of adoption. The amendments of ASU 2017-12 became effective for Trustmark on January 1, 2019. ASU 2017-12 did not have any impact to Trustmark’s existing hedging relationships at adoption; therefore, the adoption of ASU 2017-12 did not have a material impact on Trustmark’s consolidated financial statements. ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” Issued in March 2017, ASU 2017-08 amends the amortization period for certain purchased callable debt securities held at a premium. In particular, the amendments in ASU 2017-08 require the premium to be amortized to the earliest call date. The amendments do not, however, require an accounting change for securities held at a discount; instead, the discount continues to be amortized to maturity. Notably, the amendments in this ASU more closely align the amortization period of premiums and discounts to expectations incorporated in market pricing on the underlying securities. Securities within the scope of ASU 2017-08 are purchased debt securities that have explicit, noncontingent call features that are callable at fixed prices and on preset dates. The amendments of ASU 2017-08 became effective for Trustmark on January 1, 2019. Trustmark’s total unamortized premium for purchased debt securities within the scope of ASU 2017-08 is immaterial; therefore, the adoption of ASU 2017-08 did not have a material impact on Trustmark’s consolidated financial statements. ASU 2016-02, “Leases (Topic 842).” Issued in February 2016, ASU 2016-02 was issued by the FASB to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and by disclosing key information about leasing arrangements. ASU 2016-02, among other things, requires lessees to recognize a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, the ASU contains some targeted improvements that are intended to align, where necessary, lessor accounting with the lessee accounting model and with the updated revenue recognition guidance issued in 2014. In July 2018, the FASB issued ASU 2018-10, “Codification Improvements to Topic 842: Leases,” which provides corrections or improvements to a number of areas within FASB ASC Topic 842 and has the same transition guidance and effective date as ASU 2016-02. The FASB also issued ASU 2018-11, “Leases (Topic 842)-Targeted Improvements”, in July 2018, which provides entities with an additional and optional transition method to adopt the new lease standard and, for lessors only, a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease component. The amendments in ASU 2018-11 allow an entity the option to initially apply the new lease standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption as opposed to at the beginning of the earliest period presented in the financial statements. The amendments of ASU 2018-11 have the same effective date as ASU 2016-02. In December 2018, the FASB issued ASU 2018-20, “Leases (Topic 842): Narrow-Scope Improvements for Lessors,” which provides targeted improvements and clarification to guidance with FASB ASC Topic 842 specific to lessors. The amendments of ASU 2018-20 have the same effective date as ASU 2016-02 and may be applied either retrospectively or prospectively to all new and existing leases. Trustmark has an immaterial amount of leases in which it is the lessor and adoption of ASU 2016-02 did not have a material impact to these leases or the related income. Trustmark obtained a third-party software application which will provide lease contract maintenance and lease accounting under the guidelines of FASB ASC Topic 842. All existing lease contracts, with the exception of short-term leases, were loaded into the software application and reviewed by Management. The amendments of ASU 2016-02 and subsequently issued ASUs, which provided additional guidance and clarifications to various aspects of FASB ASC Topic 842, became effective for Trustmark on January 1, 2019. Trustmark adopted the amendments in this ASU using the optional transition method allowable under ASU 2018-11, and was not required to recognize any cumulative-effect adjustment to the opening balance of retained earnings. During the first quarter of 2019, Trustmark recorded operating lease right-of-use assets and operating lease liabilities of $33.9 million and $34.9 million, respectively, in its consolidation balance sheet. Additionally, Trustmark recorded finance lease right-of-use assets, net of accumulated depreciation, of $11.2 million in premises and equipment, net and finance lease liabilities of $11.2 million in other borrowings. Trustmark’s total lease right-of-use assets, net represented approximately 0.3% of its total assets as of March 31, 2019; therefore, the adoption of ASU 2016-02 did not have a material impact on Trustmark’s consolidated financial statements. Disclosures required by the amendments of ASU 2016-02 are included in Note 7 – Leases of this report. Pending Accounting Pronouncements ASU 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).” Issued in August 2018, ASU 2018-15 aims to reduce complexity in the accounting for costs of implementing a cloud computing service arrangement. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The amendments of ASU 2018-15 require an entity to follow the guidance in FASB ASC Subtopic 350-40, “Intangibles-Goodwill and Other-Internal-Use Software,” in order to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. The amendments of ASU 2018-15 also require an entity to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement (i.e. the noncancellable period of the arrangement plus periods covered by (1) an option to extend the arrangement if the entity is reasonably certain to exercise that option, (2) an option to terminate the arrangement if the entity is reasonably certain not to exercise the option, and (3) an option to extend (or not to terminate) the arrangement in which exercise of the option is in the control of the vendor). ASU 2018-15 also requires an entity to present the expense related to the capitalized implementation costs in the same line item in the statement of income as the fees associated with the hosting element (service) of the arrangement, and to classify payments for capitalized implementation costs in the statement of cash flows in the same manner as payments made for fees associated with the hosting element. ASU 2018-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Trustmark does not currently have any material amount of implementation costs related to hosting arrangements that are service contracts and is not expected to have a material impact to Trustmark’s consolidated financial statements; however, Management will continue to evaluate the impact of this ASU on future hosting arrangements as well as Trustmark’s consolidated financial statements through its effective date. ASU 2018-14, “Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans.” Issued in August 2018, ASU 2018-14 modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. The amendments in ASU 2018-14 remove certain disclosure requirements that are no longer considered cost beneficial, clarify the specific requirements of disclosures and add disclosure requirements identified as relevant. The amendments of ASU 2018-14 become effective for fiscal years beginning after December 15, 2020. Trustmark plans to adopt these amendments during the first quarter of 2021. Management is currently assessing all the potential impacts of the amendments in ASU 2018-14 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-14 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement.” Issued in August 2018, the amendments in this ASU remove disclosure requirements in FASB ASC Topic 820 related to (1) the amount of, and reasons for, transfers between Level 1 and Level 2 of the fair value hierarchy; (2) the policy for timing of transfers between levels; (3) the valuation processes for Level 3 fair value measurements; and (4) for non-public entities, the changes in unrealized gains and losses for the period included in earnings for recurring Level 3 fair value measurements held at the end of the reporting period. The ASU also modifies disclosure requirements such that (1) in place of a rollforward for Level 3 fair value measurements, a non-public entity is required to disclose transfers into and out of Level 3 of the fair value hierarchy and purchases and issues of Level 3 assets and liabilities; (2) for investments in certain entities that calculate net asset value, an entity is required to disclose the timing of liquidation of an investee’s assets and the date that restrictions from redemption might lapse, only if the investee has communicated the timing to the entity or announced the timing publicly; and (3) it is clear that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. Additionally, this ASU adds disclosure requirements for public entities about (1) the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period, and (2) the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. The amendments of ASU 2018-13 are effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. Trustmark plans to adopt ASU 2018-13 during the first quarter of 2020. Management is currently assessing all the potential impacts of the amendments in ASU 2018-13 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-13 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2017-04, “Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” Issued in January 2017, ASU 2017-04 simplifies the manner in which an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount of that goodwill. In computing the implied fair value of goodwill under Step 2, an entity, prior to the amendments in ASU 2017-04, had to perform procedures to determine the fair value at the impairment testing date of its assets and liabilities, including unrecognized assets and liabilities, in accordance with the procedure that would be required in determining the fair value of assets acquired and liabilities assumed in a business combination. However, under the amendments in ASU 2017-04, an entity should (1) perform its annual or interim goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount, and (2) recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value, with the understanding that the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, ASU 2017-04 removes the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails such qualitative test, to perform Step 2 of the goodwill impairment test. ASU 2017-04 is effective prospectively for annual, or any interim, goodwill impairment tests in fiscal years beginning after December 15, 2019. Based on Trustmark’s annual goodwill impairment test performed as of October 1, 2018, the fair value of its reporting units exceeded the carrying value and, therefore, the related goodwill was not impaired. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements through its effective date; however, the adoption of ASU 2017-04 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2016-13, “Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” Issued in June 2016, ASU 2016-13 will add FASB ASC Topic 326, “Financial Instruments-Credit Losses” and finalizes amendments to FASB ASC Subtopic 825-15, “Financial Instruments-Credit Losses.” The amendments of ASU 2016-13 are intended to provide financial statement users with more decision-useful information related to expected credit losses on financial instruments and other commitments to extend credit by replacing the current incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to determine credit loss estimates. The amendments of ASU 2016-13 eliminate the probable initial recognition threshold and, in turn, reflect an entity’s current estimate of all expected credit losses. ASU 2016-13 does not specify the method for measuring expected credit losses, and an entity is allowed to apply methods that reasonably reflect its expectations of the credit loss estimate. Additionally, the amendments of ASU 2016-13 require that credit losses on available for sale debt securities be presented as an allowance rather than as a write-down. The amendments of ASU 2016-13 are effective for interim and annual periods beginning after December 15, 2019. Earlier application is permitted for interim and annual periods beginning after December 15, 2018. Trustmark has established a Current Expected Credit Loss (CECL) Steering Committee, a CECL Solution Development Working Group and a CECL Working Group which include the appropriate members of Management to evaluate the impact this ASU will have on Trustmark’s financial position, results of operations and financial statement disclosures and determine the most appropriate method of implementing the amendments in this ASU as well as any resources needed to implement the amendments. Trustmark intends to adopt the amendments of ASU 2016-13 during the first quarter of 2020. Trustmark selected a third-party vendor to provide allowance for loan loss software as well as advisory services in developing a new methodology that would be compliant with amendments of ASU 2016-13, and is working with the approved third-party vendor to develop the CECL model and evaluate the impact to Trustmark. Trustmark is on schedule to fully comply with all CECL requirements within its internally established timeframe for implementation. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements through its effective date.

Accounting Policies Recently Adopted and Pending Accounting Pronouncements

3 Months Ended

Mar. 31, 2019

New Accounting Pronouncements And Changes In Accounting Principles [Abstract]

Accounting Policies Recently Adopted and Pending Accounting Pronouncements

Note 20 – Accounting Policies Recently Adopted and Pending Accounting Pronouncements

Accounting Policies Recently Adopted

Except for the changes detailed below, Trustmark has consistently applied its accounting policies to all periods presented in the accompanying consolidated financial statements.

ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” Issued in August 2017, ASU 2017-12 aims to improve the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. The amendments in ASU 2017-12 aim to better align an entity’s risk management activities and financial reporting for hedging relationships by expanding and refining hedge accounting for both non-financial and financial risk components and aligning the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The amendments in ASU 2017-12 (i) permit hedge accounting for risk components in hedging relationships involving nonfinancial risk and interest rate risk; (ii) change the guidance for designating fair value hedges of interest rate risk and for measuring the change in fair value of the hedged item in fair value hedges of interest rate risk; (iii) continue to allow an entity to exclude option premiums and forward points from the assessment of hedge effectiveness; and (iv) permit an entity to exclude the portion of the change in fair value of a currency swap that is attributable to a cross-country basis spread from the assessment of hedge effectiveness. The amendments of ASU 2017-12 also include targeted improvements intended to simplify the application of hedge accounting. All transition requirements and elections must be applied to all hedging relationships existing at the date of adoption. The amendments of ASU 2017-12 became effective for Trustmark on January 1, 2019. ASU 2017-12 did not have any impact to Trustmark’s existing hedging relationships at adoption; therefore, the adoption of ASU 2017-12 did not have a material impact on Trustmark’s consolidated financial statements.

ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” Issued in March 2017, ASU 2017-08 amends the amortization period for certain purchased callable debt securities held at a premium. In particular, the amendments in ASU 2017-08 require the premium to be amortized to the earliest call date. The amendments do not, however, require an accounting change for securities held at a discount; instead, the discount continues to be amortized to maturity. Notably, the amendments in this ASU more closely align the amortization period of premiums and discounts to expectations incorporated in market pricing on the underlying securities. Securities within the scope of ASU 2017-08 are purchased debt securities that have explicit, noncontingent call features that are callable at fixed prices and on preset dates. The amendments of ASU 2017-08 became effective for Trustmark on January 1, 2019. Trustmark’s total unamortized premium for purchased debt securities within the scope of ASU 2017-08 is immaterial; therefore, the adoption of ASU 2017-08 did not have a material impact on Trustmark’s consolidated financial statements.

ASU 2016-02, “Leases (Topic 842).” Issued in February 2016, ASU 2016-02 was issued by the FASB to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and by disclosing key information about leasing arrangements. ASU 2016-02, among other things, requires lessees to recognize a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, the ASU contains some targeted improvements that are intended to align, where necessary, lessor accounting with the lessee accounting model and with the updated revenue recognition guidance issued in 2014. In July 2018, the FASB issued ASU 2018-10, “Codification Improvements to Topic 842: Leases,” which provides corrections or improvements to a number of areas within FASB ASC Topic 842 and has the same transition guidance and effective date as ASU 2016-02. The FASB also issued ASU 2018-11, “Leases (Topic 842)-Targeted Improvements”, in July 2018, which provides entities with an additional and optional transition method to adopt the new lease standard and, for lessors only, a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease component. The amendments in ASU 2018-11 allow an entity the option to initially apply the new lease standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption as opposed to at the beginning of the earliest period presented in the financial statements. The amendments of ASU 2018-11 have the same effective date as ASU 2016-02. In December 2018, the FASB issued ASU 2018-20, “Leases (Topic 842): Narrow-Scope Improvements for Lessors,” which provides targeted improvements and clarification to guidance with FASB ASC Topic 842 specific to lessors. The amendments of ASU 2018-20 have the same effective date as ASU 2016-02 and may be applied either retrospectively or prospectively to all new and existing leases. Trustmark has an immaterial amount of leases in which it is the lessor and adoption of ASU 2016-02 did not have a material impact to these leases or the related income. Trustmark obtained a third-party software application which will provide lease contract maintenance and lease accounting under the guidelines of FASB ASC Topic 842. All existing lease contracts, with the exception of short-term leases, were loaded into the software application and reviewed by Management. The amendments of ASU 2016-02 and subsequently issued ASUs, which provided additional guidance and clarifications to various aspects of FASB ASC Topic 842, became effective for Trustmark on January 1, 2019. Trustmark adopted the amendments in this ASU using the optional transition method allowable under ASU 2018-11, and was not required to recognize any cumulative-effect adjustment to the opening balance of retained earnings. During the first quarter of 2019, Trustmark recorded operating lease right-of-use assets and operating lease liabilities of $33.9 million and $34.9 million, respectively, in its consolidation balance sheet. Additionally, Trustmark recorded finance lease right-of-use assets, net of accumulated depreciation, of $11.2 million in premises and equipment, net and finance lease liabilities of $11.2 million in other borrowings. Trustmark’s total lease right-of-use assets, net represented approximately 0.3% of its total assets as of March 31, 2019; therefore, the adoption of ASU 2016-02 did not have a material impact on Trustmark’s consolidated financial statements. Disclosures required by the amendments of ASU 2016-02 are included in Note 7 – Leases of this report.

Pending Accounting Pronouncements

ASU 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).” Issued in August 2018, ASU 2018-15 aims to reduce complexity in the accounting for costs of implementing a cloud computing service arrangement. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The amendments of ASU 2018-15 require an entity to follow the guidance in FASB ASC Subtopic 350-40, “Intangibles-Goodwill and Other-Internal-Use Software,” in order to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. The amendments of ASU 2018-15 also require an entity to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement (i.e. the noncancellable period of the arrangement plus periods covered by (1) an option to extend the arrangement if the entity is reasonably certain to exercise that option, (2) an option to terminate the arrangement if the entity is reasonably certain not to exercise the option, and (3) an option to extend (or not to terminate) the arrangement in which exercise of the option is in the control of the vendor). ASU 2018-15 also requires an entity to present the expense related to the capitalized implementation costs in the same line item in the statement of income as the fees associated with the hosting element (service) of the arrangement, and to classify payments for capitalized implementation costs in the statement of cash flows in the same manner as payments made for fees associated with the hosting element. ASU 2018-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Trustmark does not currently have any material amount of implementation costs related to hosting arrangements that are service contracts and is not expected to have a material impact to Trustmark’s consolidated financial statements; however, Management will continue to evaluate the impact of this ASU on future hosting arrangements as well as Trustmark’s consolidated financial statements through its effective date.

ASU 2018-14, “Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans.” Issued in August 2018, ASU 2018-14 modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. The amendments in ASU 2018-14 remove certain disclosure requirements that are no longer considered cost beneficial, clarify the specific requirements of disclosures and add disclosure requirements identified as relevant. The amendments of ASU 2018-14 become effective for fiscal years beginning after December 15, 2020. Trustmark plans to adopt these amendments during the first quarter of 2021. Management is currently assessing all the potential impacts of the amendments in ASU 2018-14 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-14 is not expected to have a material impact on Trustmark’s consolidated financial statements.

ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement.” Issued in August 2018, the amendments in this ASU remove disclosure requirements in FASB ASC Topic 820 related to (1) the amount of, and reasons for, transfers between Level 1 and Level 2 of the fair value hierarchy; (2) the policy for timing of transfers between levels; (3) the valuation processes for Level 3 fair value measurements; and (4) for non-public entities, the changes in unrealized gains and losses for the period included in earnings for recurring Level 3 fair value measurements held at the end of the reporting period. The ASU also modifies disclosure requirements such that (1) in place of a rollforward for Level 3 fair value measurements, a non-public entity is required to disclose transfers into and out of Level 3 of the fair value hierarchy and purchases and issues of Level 3 assets and liabilities; (2) for investments in certain entities that calculate net asset value, an entity is required to disclose the timing of liquidation of an investee’s assets and the date that restrictions from redemption might lapse, only if the investee has communicated the timing to the entity or announced the timing publicly; and (3) it is clear that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. Additionally, this ASU adds disclosure requirements for public entities about (1) the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period, and (2) the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. The amendments of ASU 2018-13 are effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. Trustmark plans to adopt ASU 2018-13 during the first quarter of 2020. Management is currently assessing all the potential impacts of the amendments in ASU 2018-13 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-13 is not expected to have a material impact on Trustmark’s consolidated financial statements.

ASU 2017-04, “Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” Issued in January 2017, ASU 2017-04 simplifies the manner in which an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount of that goodwill. In computing the implied fair value of goodwill under Step 2, an entity, prior to the amendments in ASU 2017-04, had to perform procedures to determine the fair value at the impairment testing date of its assets and liabilities, including unrecognized assets and liabilities, in accordance with the procedure that would be required in determining the fair value of assets acquired and liabilities assumed in a business combination. However, under the amendments in ASU 2017-04, an entity should (1) perform its annual or interim goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount, and (2) recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value, with the understanding that the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, ASU 2017-04 removes the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails such qualitative test, to perform Step 2 of the goodwill impairment test. ASU 2017-04 is effective prospectively for annual, or any interim, goodwill impairment tests in fiscal years beginning after December 15, 2019. Based on Trustmark’s annual goodwill impairment test performed as of October 1, 2018, the fair value of its reporting units exceeded the carrying value and, therefore, the related goodwill was not impaired. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements through its effective date; however, the adoption of ASU 2017-04 is not expected to have a material impact on Trustmark’s consolidated financial statements.

ASU 2016-13, “Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” Issued in June 2016, ASU 2016-13 will add FASB ASC Topic 326, “Financial Instruments-Credit Losses” and finalizes amendments to FASB ASC Subtopic 825-15, “Financial Instruments-Credit Losses.” The amendments of ASU 2016-13 are intended to provide financial statement users with more decision-useful information related to expected credit losses on financial instruments and other commitments to extend credit by replacing the current incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to determine credit loss estimates. The amendments of ASU 2016-13 eliminate the probable initial recognition threshold and, in turn, reflect an entity’s current estimate of all expected credit losses. ASU 2016-13 does not specify the method for measuring expected credit losses, and an entity is allowed to apply methods that reasonably reflect its expectations of the credit loss estimate. Additionally, the amendments of ASU 2016-13 require that credit losses on available for sale debt securities be presented as an allowance rather than as a write-down. The amendments of ASU 2016-13 are effective for interim and annual periods beginning after December 15, 2019. Earlier application is permitted for interim and annual periods beginning after December 15, 2018. Trustmark has established a Current Expected Credit Loss (CECL) Steering Committee, a CECL Solution Development Working Group and a CECL Working Group which include the appropriate members of Management to evaluate the impact this ASU will have on Trustmark’s financial position, results of operations and financial statement disclosures and determine the most appropriate method of implementing the amendments in this ASU as well as any resources needed to implement the amendments. Trustmark intends to adopt the amendments of ASU 2016-13 during the first quarter of 2020. Trustmark selected a third-party vendor to provide allowance for loan loss software as well as advisory services in developing a new methodology that would be compliant with amendments of ASU 2016-13, and is working with the approved third-party vendor to develop the CECL model and evaluate the impact to Trustmark. Trustmark is on schedule to fully comply with all CECL requirements within its internally established timeframe for implementation. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements through its effective date.