Trustmark (TRMK) 10-K 20 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	TRUSTMARK CORP
Entity Central Index Key	36,146
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,306
Entity Common Stock, Shares Outstanding		67,818,093
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Trading Symbol	TRMK

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and due from banks (noninterest-bearing)		$ 335,768	$ 327,706
Federal funds sold and securities purchased under reverse repurchase agreements		615	500
Securities available for sale (at fair value)		2,238,635	2,356,682
Securities held to maturity (fair value: $1,046,247-2017; $1,157,046-2016)		1,056,486	1,158,643
Loans held for sale (LHFS)		180,512	175,927
Loans held for investment (LHFI)	[1]	8,569,967	7,851,213
Less allowance for loan losses, LHFI		76,733	71,265
Net LHFI		8,493,234	7,779,948
Acquired loans		261,517	272,247
Less allowance for loan losses, acquired loans		4,079	11,397
Net acquired loans		257,438	260,850
Net LHFI and acquired loans		8,750,672	8,040,798
Premises and equipment, net		179,339	184,987
Mortgage servicing rights		84,269	80,239
Goodwill		379,627	366,156
Identifiable intangible assets, net		16,360	20,680
Other real estate		43,228	62,051
Other assets		532,442	577,964
Total Assets		13,797,953	13,352,333
Deposits:
Noninterest-bearing		2,978,074	2,973,238
Interest-bearing		7,599,438	7,082,774
Total deposits		10,577,512	10,056,012
Federal funds purchased and securities sold under repurchase agreements		469,827	539,817
Short-term borrowings		971,049	769,778
Long-term Federal Home Loan Bank (FHLB) advances		946	251,049
Junior subordinated debt securities		61,856	61,856
Other liabilities		145,062	153,613
Total Liabilities		12,226,252	11,832,125
Shareholders' Equity
Common stock, no par value: Authorized: 250,000,000 shares Issued and outstanding: 67,746,094 shares - 2017; 67,628,618 shares - 2016		14,115	14,091
Capital surplus		369,124	366,563
Retained earnings		1,228,187	1,185,352
Accumulated other comprehensive loss, net of tax		(39,725)	(45,798)
Total Shareholders' Equity		1,571,701	1,520,208
Total Liabilities and Shareholders' Equity		$ 13,797,953	$ 13,352,333
[1]	During the first quarter of 2017, Trustmark reclassified $36.7 million of acquired loans not accounted for under FASB ASC Topic 310-30 to LHFI due to the discount on these loans being fully amortized.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Securities held to maturity, fair value	$ 1,046,247	$ 1,157,046
Shareholders' Equity
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, authorized (in shares)	250,000,000	250,000,000
Common stock, issued (in shares)	67,746,094	67,628,618
Common stock, outstanding (in shares)	67,746,094	67,628,618

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Income
Interest and fees on LHFS & LHFI	$ 344,625	$ 299,645	$ 274,433
Interest and fees on acquired loans	24,478	30,144	51,152
Interest on securities:
Taxable	76,192	77,614	80,730
Tax exempt	3,001	3,675	4,323
Interest on federal funds sold and securities purchased under reverse repurchase agreements	33	14	8
Other interest income	1,466	988	1,579
Total Interest Income	449,795	412,080	412,225
Interest Expense
Interest on deposits	22,717	12,748	12,598
Interest on federal funds purchased and securities sold under repurchase agreements	4,152	1,717	801
Other interest expense	15,376	10,082	7,061
Total Interest Expense	42,245	24,547	20,460
Net Interest Income	407,550	387,533	391,765
Provision for loan losses, LHFI	15,094	10,957	8,375
Provision for loan losses, acquired loans	(7,395)	3,757	3,425
Net Interest Income After Provision for Loan Losses	399,851	372,819	379,965
Noninterest Income
Service charges on deposit accounts	44,003	45,253	47,366
Bank card and other fees	28,286	27,906	28,298
Mortgage banking, net	29,902	28,212	30,176
Insurance commissions	38,168	36,764	36,424
Wealth management	30,340	30,492	31,369
Other, net	13,949	5,626	(484)
Securities gains (losses), net	15	(310)	0
Total Noninterest Income	184,663	173,943	173,149
Noninterest Expense
Salaries and employee benefits	234,987	239,637	230,198
Defined benefit plan termination	17,644
Services and fees	60,893	58,695	57,534
Net occupancy - premises	25,767	24,982	25,318
Equipment expense	24,453	24,225	23,859
Other real estate expense	3,672	586	4,903
FDIC assessment expense	11,010	11,243	10,728
Other expense	51,743	47,930	49,122
Total Noninterest Expense	430,169	407,298	401,662
Income Before Income Taxes	154,345	139,464	151,452
Income taxes	48,715	31,053	35,414
Net Income	$ 105,630	$ 108,411	$ 116,038
Earnings Per Share
Basic	$ 1.56	$ 1.60	$ 1.72
Diluted	$ 1.56	$ 1.60	$ 1.71

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income per consolidated statements of income	$ 105,630	$ 108,411	$ 116,038
Net unrealized gains (losses) on available for sale securities and transferred securities:
Net unrealized holding gains (losses) arising during the period	(8,641)	(9,667)	(10,309)
Less: adjustment for net (gains) losses realized in net income	(9)	191	0
Change in net unrealized holding loss on securities transferred to held to maturity	2,915	6,070	3,918
Pension and other postretirement benefit plans:
Net change in prior service costs	154	154	154
Recognized net loss due to lump sum settlements	0	2,412	1,371
Change in net actuarial loss	451	294	2,252
Recognized net loss due to defined benefit plan termination	10,907	0	0
Derivatives:
Change in the accumulated gain (loss) on effective cash flow hedge derivatives	122	(228)	(812)
Less: adjustment for loss realized in net income	174	370	516
Other comprehensive income (loss), net of tax	6,073	(404)	(2,910)
Comprehensive income	$ 111,703	$ 108,007	$ 113,128

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2014	$ 1,419,940	$ 14,060	$ 356,244	$ 1,092,120	$ (42,484)
Balance (in shares) at Dec. 31, 2014		67,481,992
Net income per consolidated statements of income	116,038	$ 0	0	116,038	0
Other comprehensive income (loss), net of tax	(2,910)				(2,910)
Cash dividends paid on common stock ($0.92 per share)	(62,605)	0	0	(62,605)	0
Common stock issued, long-term incentive plan	(1,074)	$ 16	1,555	(2,645)	0
Common stock issued, long-term incentive plan (in shares)		77,136
Compensation expense, long-term incentive plan	3,668	$ 0	3,668	0	0
Balance at Dec. 31, 2015	1,473,057	$ 14,076	361,467	1,142,908	(45,394)
Balance (in shares) at Dec. 31, 2015		67,559,128
Net income per consolidated statements of income	108,411	$ 0	0	108,411	0
Other comprehensive income (loss), net of tax	(404)				(404)
Cash dividends paid on common stock ($0.92 per share)	(62,666)	0	0	(62,666)	0
Common stock issued, long-term incentive plan	(1,124)	$ 22	2,155	(3,301)	0
Common stock issued, long-term incentive plan (in shares)		103,112
Repurchase and retirement of common stock	(750)	$ (7)	(743)
Repurchase and retirement of common stock (in shares)		(33,622)
Compensation expense, long-term incentive plan	3,684	$ 0	3,684	0	0
Balance at Dec. 31, 2016	$ 1,520,208	$ 14,091	366,563	1,185,352	(45,798)
Balance (in shares) at Dec. 31, 2016	67,628,618	67,628,618
Net income per consolidated statements of income	$ 105,630			105,630
Other comprehensive income (loss), net of tax	6,073				6,073
Cash dividends paid on common stock ($0.92 per share)	(62,795)			(62,795)
Common stock issued, long-term incentive plan	(1,724)	$ 24	(1,748)
Common stock issued, long-term incentive plan (in shares)		117,476
Compensation expense, long-term incentive plan	4,309		4,309
Balance at Dec. 31, 2017	$ 1,571,701	$ 14,115	$ 369,124	$ 1,228,187	$ (39,725)
Balance (in shares) at Dec. 31, 2017	67,746,094	67,746,094

Consolidated Statements of Cha7

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Stockholders Equity [Abstract]
Cash dividends paid on common stock (in dollars per share)	$ 0.92	$ 0.92	$ 0.92

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income per consolidated statements of income	$ 105,630	$ 108,411	$ 116,038
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses, net	7,699	14,714	11,800
Depreciation and amortization	38,471	36,613	37,056
Net amortization of securities	10,964	9,664	7,793
Securities (gains) losses, net	(15)	310	0
Gains on sales of loans, net	(18,933)	(20,531)	(17,953)
Deferred income tax provision	26,068	18,000	14,800
Proceeds from sales of loans held for sale	1,197,821	1,404,852	1,264,303
Purchases and originations of loans held for sale	(1,179,187)	(1,392,155)	(1,279,321)
Originations of mortgage servicing rights	(15,860)	(16,745)	(17,598)
Earnings on bank-owned life insurance	(5,025)	(4,883)	(4,824)
Net change in other assets	23,451	(20,129)	28,794
Net change in other liabilities	9,093	7,284	6,608
Other operating activities, net	6,430	2,932	5,043
Net cash provided by operating activities	206,607	148,337	172,539
Investing Activities
Proceeds from maturities, prepayments and calls of securities held to maturity	174,976	277,373	126,546
Proceeds from maturities, prepayments and calls of securities available for sale	467,194	486,915	479,927
Proceeds from sales of securities available for sale	27,682	24,693	0
Purchases of securities held to maturity	(69,989)	(239,446)	(107,679)
Purchases of securities available for sale	(346,159)	(547,112)	(504,920)
Net proceeds from bank-owned life insurance	3,623	2,585	648
Net change in federal funds sold and securities purchased under reverse repurchase agreements	6,785	(250)	1,635
Net change in member bank stock	4,474	(8,386)	(18,480)
Net change in loans	(608,886)	(677,296)	(528,050)
Purchases of premises and equipment	(13,219)	(10,208)	(12,757)
Proceeds from sales of premises and equipment	8,377	6,799	3,061
Proceeds from sales of other real estate	26,849	42,809	48,898
Purchases of software	(5,498)	(8,024)	(8,741)
Investments in tax credit and other partnerships	(5,296)	(116)	(4,578)
Purchase of insurance book of business	0	0	(2,787)
Net cash used in business acquisition	(19,775)	0	0
Net cash used in investing activities	(348,862)	(649,664)	(527,277)
Financing Activities
Net change in deposits	355,342	467,782	(110,128)
Net change in federal funds purchased and securities sold under repurchase agreements	(69,990)	98,775	(2,501)
Net change in short-term borrowings	(67,451)	(150,748)	(7,293)
Payments on long-term FHLB advances	(65)	(94)	(94)
Proceeds from long-term FHLB advances	0	250,000	500,000
Redemption of junior subordinated debt securities	(3,000)	0	0
Payment of subordinated debt	0	(50,000)	0
Common stock dividends	(62,795)	(62,666)	(62,605)
Repurchase and retirement of common stock	0	(750)	0
Shares withheld to pay taxes, long-term incentive plan	(1,724)	(1,017)	(863)
Net cash provided by financing activities	150,317	551,282	316,516
Net change in cash and cash equivalents	8,062	49,955	(38,222)
Cash and cash equivalents at beginning of year	327,706	277,751	315,973
Cash and cash equivalents at end of year	$ 335,768	$ 327,706	$ 277,751

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Note 1 – Significant Accounting Policies Business Trustmark Corporation (Trustmark) is a bank holding company headquartered in Jackson, Mississippi. Through its subsidiaries, Trustmark operates as a financial services organization providing banking and financial solutions to corporate institutions and individual customers through 198 offices in Alabama, Florida, Mississippi, Tennessee and Texas. Basis of Financial Statement Presentation The consolidated financial statements include the accounts of Trustmark and all other entities in which Trustmark has a controlling financial interest. All significant intercompany accounts and transactions have been eliminated in consolidation. The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (GAAP). The preparation of financial statements in conformity with these accounting principles requires Management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and income and expense during the reporting periods and the related disclosures. Although Management’s estimates contemplate current conditions and how they are expected to change in the future, it is reasonably possible that in 2018 actual conditions could vary from those anticipated, which could affect Trustmark’s financial condition and results of operations. Actual results could differ from those estimates. Securities Securities are classified as either held to maturity or available for sale. Securities are classified as held to maturity and carried at amortized cost when Management has the positive intent and the ability to hold them until maturity. Securities to be held for indefinite periods of time are classified as available for sale and carried at fair value, with the unrealized holding gains and losses reported as a component of other comprehensive income (loss), net of tax. Securities available for sale are used as part of Trustmark’s interest rate risk management strategy and may be sold in response to changes in interest rates, changes in prepayment rates and other factors. Management determines the appropriate classification of securities at the time of purchase. The amortized cost of debt securities classified as securities held to maturity or securities available for sale is adjusted for amortization of premiums and accretion of discounts to maturity of the security using the interest method. Such amortization or accretion is included in interest on securities. Realized gains and losses are determined using the specific identification method and are included in noninterest income as securities gains (losses), net. Securities transferred from the available for sale category to the held to maturity category are recorded at fair value at the date of transfer. Unrealized holding gains or losses associated with the transfer of securities from available for sale to held to maturity are included in the balance of accumulated other comprehensive income (loss), net of tax, in the consolidated balance sheets. These unrealized holding gains or losses are amortized over the remaining life of the security as a yield adjustment in a manner consistent with the amortization or accretion of the original purchase premium or discount on the associated security. Trustmark reviews securities for impairment quarterly. Declines in the fair value of held to maturity and available for sale securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of the impairment related to other factors is recognized as a component of other comprehensive income (loss), net of tax. In estimating other-than-temporary impairment losses, Management considers, among other things, the length of time and the extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer and Trustmark’s intent and ability to hold the security for a period of time sufficient to allow for any anticipated recovery in fair value. Loans Held for Sale (LHFS) Primarily, all mortgage loans purchased from wholesale customers or originated in Trustmark’s General Banking Division are considered to be held for sale. In certain circumstances, Trustmark will retain a mortgage loan in its portfolio based on banking relationships or certain investment strategies. Trustmark has elected to account for its LHFS under the fair value option permitted by Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 825, “Financial Instruments,” with interest income on the LHFS reported in interest and fees on LHFS and LHFI. Trustmark reports unrealized gains and losses resulting from changes in the fair value of the LHFS accounted for under the fair value option as noninterest income in mortgage banking, net. LHFS are actively managed and monitored and certain market risks of the loans may be mitigated through the use of derivatives. These derivative instruments are carried at fair value with changes in the fair value reported as noninterest income in mortgage banking, net. Changes in the fair value of the LHFS are largely offset by changes in the fair value of the derivative instruments. Election of the fair value option allows Trustmark to reduce the accounting volatility that would otherwise result from the asymmetry created by accounting for its LHFS at the lower of cost or fair value and the derivative instruments at fair value. Realized gains and losses upon ultimate sale of the loans are reported as noninterest income in mortgage banking, net. Government National Mortgage Association (GNMA) optional repurchase programs allow financial institutions to buy back individual delinquent mortgage loans that meet certain criteria from the securitized loan pool for which the institution provides servicing. At the servicer’s option and without GNMA’s prior authorization, the servicer may repurchase such a delinquent loan for an amount equal to 100 percent of the remaining principal balance of the loan. Under FASB ASC Topic 860, “Transfers and Servicing,” this buy-back option is considered a conditional option until the delinquency criteria are met, at which time the option becomes unconditional. When Trustmark is deemed to have regained effective control over these loans under the unconditional buy-back option, the loans can no longer be reported as sold and must be brought back onto the balance sheet as LHFS, regardless of whether Trustmark intends to exercise the buy-back option. These loans are reported as LHFS with the offsetting liability being reported as short-term borrowings. The fair value option election does not apply to the GNMA optional repurchase loans which do not meet the requirements under FASB ASC Topic 825 to be accounted for under the fair value option. Trustmark defers the upfront loan fees and costs related to the LHFS. In general, the LHFS are only retained on Trustmark’s balance sheet for 30 to 45 days before they are pooled and sold in the secondary market. The difference between deferring these loan fees and costs until the loans are sold and recognizing them in earnings as incurred as required by FASB ASC Topic 825-10 is considered immaterial. Deferred loan fees and costs are reflected in the basis of the LHFS and, as such, impact the resulting gain or loss when the loans are sold. Loans Held for Investment (LHFI) LHFI are stated at the amount of unpaid principal, adjusted for the net amount of direct costs and nonrefundable loan fees associated with lending. The net amount of nonrefundable loan origination fees and direct costs associated with the lending process, including commitment fees, is deferred and accreted to interest income over the lives of the loans using a method that approximates the interest method. Interest on LHFI is accrued and recorded as interest income based on the outstanding principal balance. Past due LHFI are loans contractually past due 30 days or more as to principal or interest payments. A LHFI is classified as nonaccrual, and the accrual of interest on such loan is discontinued, when the contractual payment of principal or interest becomes 90 days past due on commercial credits and 120 days past due on non-business purpose credits. In addition, a credit may be placed on nonaccrual at any other time Management has serious doubts about further collectibility of principal or interest according to the contractual terms, even though the loan is currently performing. A LHFI may remain in accrual status if it is in the process of collection and well secured. When a LHFI is placed in nonaccrual status, interest accrued but not received is reversed against interest income. Interest payments received on nonaccrual LHFI are applied against principal under the cost-recovery method, until qualifying for return to accrual status. Under the cost-recovery method, interest income is not recognized until the principal balance is reduced to zero. LHFI are restored to accrual status when the obligation is brought current or has performed in accordance with the contractual terms for a reasonable period of time and the ultimate collectibility of the total contractual principal and interest is no longer in doubt. A LHFI is considered impaired when, based on current information and events, it is probable that Trustmark will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. Trustmark considers all nonaccrual LHFI and LHFI classified as a troubled debt restructuring (TDR) to be impaired loans. All commercial nonaccrual relationships of $500 thousand or more and all LHFI classified as TDRs are individually reviewed for impairment (individually evaluated impaired LHFI). If a LHFI is deemed impaired, a specific valuation allowance is allocated, if necessary, so that the loan is reported net, at the present value of estimated future cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Commercial nonaccrual relationships under $500 thousand are not individually evaluated for impairment due to the insignificant number and dollar amount of these types of loans. Nonaccrual LHFI includes both individually evaluated impaired LHFI as well as smaller balance homogeneous loans that are collectively evaluated for impairment. Consistent with the policy for nonaccrual LHFI, interest payments on impaired LHFI are applied to principal. Impaired LHFI, or portions thereof, are charged off when deemed uncollectible. Troubled Debt Restructuring A TDR occurs when a borrower is experiencing financial difficulties, and for related economic or legal reasons, a concession is granted to the borrower that Trustmark would not otherwise consider. Whatever the form of concession that might be granted by Trustmark, Management’s objective is to enhance collectibility by obtaining more cash or other value from the borrower or by increasing the probability of receipt by granting the concession than by not granting it. Other concessions may arise from court proceedings or may be imposed by law. In addition, TDRs also include those credits that are extended or renewed to a borrower who is not able to obtain funds from sources other than Trustmark at a market interest rate for new debt with similar risk. A formal TDR may include, but is not necessarily limited to, one or a combination of the following situations: • Trustmark accepts a third-party receivable or other asset(s) of the borrower, in lieu of the receivable from the borrower. • Trustmark accepts an equity interest in the borrower in lieu of the receivable. • Trustmark accepts modification of the terms of the debt including but not limited to: o Reduction (absolute or contingent) of the stated interest rate to below the current market rate. o Extension of the maturity date or dates at a stated interest rate lower than the current market rate for new debt with similar risk. o Reduction (absolute or contingent) of the face amount or maturity amount of the debt as stated in the note or other agreement. o Reduction (absolute or contingent) of accrued interest. Troubled debt restructurings are addressed in Trustmark’s loan policy, and in accordance with that policy, any modifications or concessions that may result in a TDR are subject to a special approval process which allows for control, identification, and monitoring of these arrangements. Prior to granting a concession, a revised borrowing arrangement is proposed which is structured so as to improve collectability of the loan in accordance with a reasonable repayment schedule with any loss promptly identified. It is supported by a thorough evaluation of the borrower’s financial condition and prospects for repayment under those revised terms. Other TDRs arising from renewals or extensions of existing debt are routinely identified through the processes utilized in the Problem Loan Committees and in the Credit Quality Review Committee. TDRs are subsequently reported to the Director Credit Policy Committee on a quarterly basis and are disclosed in Trustmark’s consolidated financial statements in accordance with GAAP and regulatory reporting guidance. All loans whose terms have been modified in a troubled debt restructuring are evaluated for impairment under FASB ASC Topic 310, “Receivables.” Accordingly, Trustmark measures any loss on the restructuring in accordance with that guidance. A TDR in which Trustmark receives physical possession of the borrower’s assets, regardless of whether formal foreclosure or repossession proceedings take place, is accounted for in accordance with FASB ASC Subtopic 310-40, “Troubled Debt Restructurings by Creditors.” Thus, the loan is treated as if assets have been received in satisfaction of the loan and reported as a foreclosed asset. A TDR may be returned to accrual status if Trustmark is reasonably assured of repayment of principal and interest under the modified terms and the borrower has demonstrated sustained performance under those terms for a period of at least six months. Otherwise, the restructured loan must remain on nonaccrual. Allowance for Loan Losses, LHFI The allowance for loan losses, LHFI is established through provisions for estimated loan losses charged against net income. The allowance account is maintained at a level which is believed to be adequate by Management based on estimated probable losses within the LHFI portfolio. Evaluations of the portfolio and individual credits are inherently subjective, as they require estimates, assumptions and judgments as to the facts and circumstances of particular situations. Some of the factors considered, such as amounts and timing of future cash flows expected to be received, may be susceptible to significant change. Trustmark’s allowance methodology is based on guidance provided in Securities and Exchange Commission (SEC) Staff Accounting Bulletin (SAB) No. 102, “Selected Loan Loss Allowance Methodology and Documentation Issues,” as well as other regulatory guidance. The allowance for loan losses, LHFI consists of three components: (i) a historical valuation allowance determined in accordance with FASB ASC Topic 450, “Contingencies,” based on historical loan loss experience for LHFI with similar characteristics and trends, (ii) a specific valuation allowance determined in accordance with FASB ASC Topic 310 based on probable losses on specific LHFI and (iii) a qualitative risk valuation allowance determined in accordance with FASB ASC Topic 450 based on general economic conditions and other specific internal and external qualitative risk factors. Each of these components calls for estimates, assumptions and judgments as described below. Historical Valuation Allowance The historical valuation allowance is derived by application of a historical net loss percentage to the outstanding balances of LHFI contained in designated pools and risk rating categories. Pools are established by grouping credits that display similar characteristics and trends such as commercial LHFI for working capital purposes and non-working capital purposes, commercial purpose LHFI secured by real estate (which are further segregated into 1-4 family construction, non 1-4 family construction, land, lots and development, owner-occupied and non-owner occupied categories), other commercial loans, 1-4 family LHFI, 1-4 family LHFI secured by junior liens and other consumer LHFI. Within these pools, LHFI are further segregated based on Trustmark’s internal credit risk rating process that evaluates, among other things: the obligor’s ability and willingness to pay, the value of underlying collateral, the ability of guarantors to meet their payment obligations, management experience and effectiveness, and the economic environment and industry in which the borrower operates. The historical net loss percentages, calculated on a quarterly basis, are proportionally distributed to each risk rate within loan groups based upon degree of risk. Using third-party default data, which is updated annually to incorporate the most recent year’s information, average cumulative issuer-weighted global default rates by alphanumeric rating are aggregated by Trustmark’s commercial loan risk rates. Management uses the long-term default rates to measure the relative risk across the risk rates while the 12-quarter quantitative loss rate sets the absolute level of allowance for loan loss reserve. Further, given the volatility in the default data, the longer look-back period provides for a more stable allowance for loan loss estimate which better reflects the incremental risk across the risk rates. The historical net loss percentages are calculated using a 12 quarter look-back period, which is the period that best reflects losses inherent in the current loan portfolio. The look-back period sufficiently captures the volatility in net charge-off rates from quarter to quarter and affects the qualitative adjustments that are required to capture the differences in conditions between the current period and those that were prevailing during the look-back period. The loss emergence period (LEP) refers to the period of time between the events that trigger a loss and charge-off of that loss. Losses are usually not immediately known and determining the loss event can be difficult. It takes time for the borrower and extent of loss to be identified and determined. Management may not be aware that the loss event has occurred until the borrower exhibits the inability to pay or other evidence of credit deterioration. The LEP is evaluated annually to incorporate the most recent year’s data and adjusted as necessary. Loans-Specific Valuation Allowance Once a LHFI is classified, it is subject to periodic review to determine whether or not the loan is impaired. If determined to be impaired, the loan is evaluated using one of the valuation criteria contained in FASB ASC Topic 310 (i.e., individually or collectively evaluated), and a specific valuation allowance is allocated, if necessary, so that the loan is reported at the net realizable value. Qualitative Risk Valuation Allowance The qualitative risk valuation allowance is based on general economic conditions and other internal and external factors affecting Trustmark as a whole as well as specific LHFI. Factors considered include the following within Trustmark’s five key market regions: the experience, ability, and effectiveness of Trustmark’s lending management and staff; adherence to Trustmark’s loans policies, procedures and internal controls; the volume of exceptions relating to collateral, underwriting and financial documentation; credit concentrations; recent performance trends; regional economic trends; the impact of recent acquisitions; and the impact of significant natural disasters. These factors are evaluated on a quarterly basis with the results representing Trustmark’s qualitative risk profile in the current period which is used to establish an appropriate allowance. The qualitative portion of the commercial and consumer LHFI allowance for loan loss methodology also incorporates the use of maximum observed gross historical losses observed through the last economic cycle as a way to calculate a maximum qualitative reserve limit. The maximum observed gross historical losses as a percentage of the loan balances results in a maximum observed gross historical loss rate. Once the quantitative component of the allowance for loan loss methodology is calculated, the quantitative reserve percentage is deducted from the maximum observed gross historical loss rate to determine the maximum possible qualitative reserve limit. Management uses its qualitative factor evaluation process in conjunction with this maximum to determine the appropriate estimate of the qualitative considerations not captured by Trustmark’s historical loss rates. Other factors included in the qualitative risk valuation allowance include consideration of: commercial loan facility risk that embodies the nature, frequency and duration of the repayment structure as it pertains to the actual source of loan repayment, commercial nonaccrual relationships under $500 thousand which are below the threshold to perform a specific impairment analysis, and independent consumer credit bureau scores that are monitored to identify shifts in risk that are represented in the retail portfolio. These factors are also evaluated on a quarterly basis with the exception of the commercial nonaccrual relationships under $500 thousand which are evaluated monthly. Commercial purpose LHFI are charged off when a determination is made that the loan is uncollectible and continuance as a bankable asset is not warranted. Consumer LHFI secured by 1-4 family residential real estate are generally charged off or written down to the fair value of the collateral less cost to sell at no later than 180 days of delinquency. Non-real estate consumer purpose LHFI, including both secured and unsecured loans, are generally charged off by 120 days of delinquency. Consumer revolving lines of credit and credit card debt are generally charged off on or prior to 180 days of delinquency. LHFI are charged off against the allowance for loan losses, LHFI, with any subsequent recoveries credited back to the allowance account. Acquired Loans Acquired loans are accounted for under the acquisition method of accounting. The acquired loans are recorded at their estimated fair value at the time of acquisition. The fair value of acquired loans is determined using a discounted cash flow model based on assumptions regarding the amount and timing of principal and interest payments, estimated prepayments, estimated default rates, estimated loss severity in the event of defaults and current market rates. Estimated credit losses are included in the determination of fair value; therefore, an allowance for loan losses is not recorded on the acquisition date. Trustmark accounts for acquired impaired loans under FASB ASC Topic 310-30, “Loans and Debt Securities Acquired with Deteriorated Credit Quality.” An acquired loan is considered impaired when there is evidence of credit deterioration since origination and it is probable at the date of acquisition that Trustmark would be unable to collect all contractually required payments. Acquired loans accounted for under FASB ASC Topic 310-30 are referred to as “acquired impaired loans.” Revolving credit agreements, such as home equity lines, and commercial leases are excluded from acquired impaired loan accounting requirements. For acquired impaired loans, Trustmark (i) calculates the contractual amount and timing of undiscounted principal and interest payments (the “undiscounted contractual cash flows”) and (ii) estimates the amount and timing of undiscounted expected principal and interest payments (the “undiscounted expected cash flows”). Under FASB ASC Topic 310-30, the difference between the undiscounted contractual cash flows and the undiscounted expected cash flows is the nonaccretable difference. The nonaccretable difference represents an estimate of the loss exposure of principal and interest related to the acquired impaired loan portfolio, and such amount is subject to change over time based on the performance of such loans. The excess of undiscounted expected cash flows at acquisition over the initial fair value of acquired impaired loans is referred to as the “accretable yield” and is recorded as interest income over the estimated life of the loans using the effective yield method if the timing and amount of the future cash flows is reasonably estimable. Under the effective yield method, the accretable yield is recorded as an accretion of interest income over the life of the loan. Trustmark aggregates certain acquired impaired loans into pools of loans with common credit risk characteristics such as loan type and risk rating. To establish accounting pools of acquired impaired loans, loans are first categorized by similar purpose, collateral and geographic region. Within each category, the acquired impaired loans are further segmented by ranges of risk determinants observed at the time of acquisition. For commercial loans, the primary risk determinant is the risk rating as assigned by Trustmark. For consumer loans, the risk determinants include delinquency, delinquency history and FICO scores. Statistical comparison of the pools reflect that each pool is comprised of acquired impaired loans generally of similar characteristics, including loan type, loan risk and weighted average life. Each pool is then reviewed for similarity of the pool constituents, including standard deviation of purchase price, weighted average life and concentration of the largest loans. Loan pools are initially booked at the aggregate fair value of the loan pool constituents, based on the present value of Trustmark's expected cash flows from the acquired impaired loans. An acquired impaired loan is removed from a pool of loans only if the loan is sold, foreclosed, payment is received in full satisfaction of the loan or the loan is fully charged off. The acquired impaired loan is removed from the pool at the carrying value. When an individual acquired impaired loan is removed from a pool of loans, the difference between its relative carrying amount and the cash, collateral (measured at fair value) or other assets received will be recognized as a gain or loss immediately in interest income on acquired loans and would not affect the effective yield used to recognize the accretable yield on the remaining pool. Certain acquired impaired loans are not pooled and are accounted for individually. Such acquired impaired loans are withheld from pools due to the inherent uncertainty of the timing and amount of their cash flows or because they are not a suitable similar constituent to the established pools. As required by FASB ASC Topic 310-30, Trustmark periodically re-estimates the expected cash flows to be collected over the life of the acquired impaired loans. If, based on current information and events, it is probable that Trustmark will be unable to collect all cash flows expected at acquisition plus additional cash flows expected to be collected arising from changes in estimate after acquisition, the acquired loans are considered impaired. The decrease in the expected cash flows reduces the carrying value of the acquired impaired loans as well as the accretable yield and results in a charge-off through the allowance for loan losses, acquired loans or the establishment of an allowance for loan losses, acquired loans with a charge to income through the provision for loan losses, acquired loans. If, based on current information and events, it is probable that there is a significant increase in the cash flows previously expected to be collected or if actual cash flows are significantly greater than cash flows previously expected, Trustmark will reduce any remaining allowance for loan losses, acquired loans established on the acquired impaired loans for the increase in the present value of cash flows expected to be collected. The increase in the expected cash flows for the acquired impaired loans over those originally estimated at acquisition increases the carrying value of the acquired impaired loans as well as the accretable yield. The increase in the accretable yield is recognized as interest income prospectively over the remaining life of the acquired impaired loans. The carrying value of acquired impaired loans is reduced by payments received, both principal and interest, and increased by the portion of the accretable yield recognized as interest income. Under FASB ASC Topic 310-30, acquired impaired loans are generally considered accruing and performing loans as the loans accrete interest income over the estimated life of the loan when expected cash flows are reasonably estimable. Accordingly, acquired impaired loans that are contractually past due are still considered to be accruing and performing loans as long as the estimated cash flows are received as expected. If the timing and amount of cash flows is not reasonably estimable, the loans may be classified as nonaccrual loans and interest income may be recognized on a cash basis or as a reduction of the principal amount outstanding. Premises and Equipment, Net Premises and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is charged to expense over the estimated useful lives of the assets, which are up to thirty-nine years for buildings and three to ten years for furniture and equipment. Leasehold improvements are amortized over the terms of the respective leases or the estimated useful lives of the improvements, whichever is shorter. In cases where Trustmark has the right to renew the lease for additional periods, the lease term for the purpose of calculating amortization of the capitalized cost of the leasehold improvements is extended when Trustmark is “reasonably assured” that it will renew the lease. Depreciation and amortization expenses are computed using the straight-line method. Trustmark continually evaluates whether events and circumstances have occurred that indicate that such long-lived assets have become impaired. Measurement of any impairment of such long-lived assets is based on the fair values of those assets. Branch closures and purchased land held for future branch expansion for more than five years are evaluated to determine if the related land, buildings and building improvements should be transferred to assets held for sale in accordance with FASB ASC Topic 360, “Property, Plant and Equipment.” The property is transferred to assets held for sale at the lower of its carrying value or fair value less cost to sell. An impairment loss is recorded at the time of transfer if the carrying value of the assets exceeds the fair value. Impairment losses are recorded as non-interest expense in other expense. Mortgage Servicing Rights (MSR) Trustmark recognizes as assets the rights to service mortgage loans based on the estimated fair value of the MSR when loans are sold and the associated servicing rights are retained. Trustmark has elected to account for the MSR at fair value. The fair value of the MSR is determined using discounted cash flow techniques benchmarked against third-party valuations. Estimates of fair value involve several assumptions, including the key valuation assumptions about market expectations of future prepayment rates, interest rates and discount rates which are provided by a third-party firm. Prepayment rates are projected using an industry standard prepayment model. The model considers other key factors, such as a wide range of standard industry assumptions tied to specific portfolio characteristics such as remittance cycles, escrow payment requirements, geographic factors, foreclosure loss exposure, VA no-bid exposure, delinquency rates and cost of servicing, including base cost and cost to service delinquent mortgages. Prevailing market conditions at the time of analysis are factored into the accumulation of assumptions and determination of servicing value. Trustmark economically hedges changes in the fair value of the MSR attributable to interest rates. See Note 1 – Significant Accounting Policies, “Derivative Financial Instruments – Derivatives not Designated as Hedging Instruments” for information regarding these derivative instruments. Trustmark receives annual servicing fee income for loa

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Business Combinations	Note 2 – Business Combinations On April 7, 2017, Trustmark completed its merger with RB Bancorporation (Reliance), the holding company for Reliance Bank, which had seven offices serving the Huntsville, Alabama metropolitan service area (MSA). Reliance Bank was merged into Trustmark National Bank simultaneously with the merger of Trustmark and Reliance. Under the terms of the Merger Agreement dated November 14, 2016, Trustmark paid $22.00 in cash for each share of Reliance common stock outstanding, which represented payment to Reliance common shareholders of approximately $23.7 million. In addition, Trustmark paid off Reliance Preferred Stock of $1.1 million bringing the total consideration paid to $24.8 million. The merger with Reliance was consistent with Trustmark’s strategic plan to selectively expand the Trustmark franchise and enhance the Trustmark franchise in north Alabama. This merger was accounted for in accordance with FASB ASC Topic 805, “Business Combinations.” Accordingly, the assets and liabilities, both tangible and intangible, were recorded at their estimated fair values as of the merger date. The fair values of the assets acquired and liabilities assumed are subject to adjustment if additional information relative to the closing date fair values becomes available through the measurement period, which is not to exceed one year from the merger date of April 7, 2017 The statement of assets purchased and liabilities assumed in the Reliance merger is presented below at their estimated fair values as of the merger date of April 7, 2017 ($ in thousands): Assets: Cash and due from banks $ 5,013 Federal funds sold and securities purchased under reverse repurchase agreements 6,900 Securities 54,843 Acquired loans 117,447 Premises and equipment, net 3,700 Identifiable intangible assets 1,850 Other real estate 475 Other assets 6,037 Total Assets 196,265 Liabilities: Deposits 166,158 Other borrowings 17,469 Other liabilities 1,322 Total Liabilities 184,949 Net identified assets acquired at fair value 11,316 Goodwill 13,471 Total consideration paid $ 24,787 The excess of the consideration paid over the estimated fair value of the net assets acquired was $13.5 million, which was recorded as goodwill under FASB ASC Topic 805. The identifiable intangible assets acquired represent the core deposit intangible at fair value at the merger date. The core deposit intangible is being amortized on an accelerated basis over the estimated useful life, currently expected to be approximately ten years. Loans acquired from Reliance were evaluated under a fair value process. Loans with evidence of deterioration in credit quality and for which it was probable at acquisition that Trustmark would not be able to collect all contractually required payments are referred to as acquired impaired loans and accounted for in accordance with FASB ASC Topic 310-30. See Note 6 – Acquired Loans for additional information on acquired loans. The operations of Reliance are included in Trustmark’s operating results from April 7, 2017 and did not have a material impact on Trustmark’s results of operations. During the second quarter of 2017, Trustmark included merger transaction expenses in other noninterest expense totaling $3.2 million (change in control expense of $1.3 million; professional fees, contract termination and other expenses of $1.9 million). Fair Value of Acquired Financial Instruments For financial instruments measured at fair value, Trustmark utilized Level 2 inputs to determine the fair value of securities available for sale (included in securities above), time deposits (included in deposits above) and FHLB advances (included in other borrowings above). Level 3 inputs were used to determine the fair value of acquired loans, identifiable intangible assets and other real estate. The methodology and significant assumptions used in estimating the fair values of these financial assets and liabilities are as follows: Securities Available for Sale Estimated fair values for securities available for sale are based on quoted market prices where available. If quoted market prices are not available, estimated fair values are based on quoted market prices of comparable instruments. Acquired Loans Fair value of acquired loans is determined using a discounted cash flow model based on assumptions regarding the amount and timing of principal and interest payments, estimated prepayments, estimated default rates, estimated loss severity in the event of default and current market rates. Identifiable Intangible Assets The fair value assigned to the identifiable intangible assets, in this case the core deposit intangible, represents the future economic benefits of the potential cost savings from acquiring core deposits in the merger compared to the cost of obtaining alternative funding from market sources. Other Real Estate Other real estate was initially recorded at its estimated fair value on the merger date based on independent appraisals less estimated selling costs. Time Deposits Time deposits were valued by projecting expected cash flows into the future based on each account’s contracted rate and then determining the present value of those expected cash flows using current rates for deposits with similar maturities. FHLB Advances FHLB advances were valued by projecting expected cash flows into the future based on each advance’s contracted rate and then determining the present value of those expected cash flows using current rates for advances with similar maturities. Please refer to Note 18 – Fair Value for more information on Trustmark’s classification of financial instruments based on valuation inputs within the fair value hierarchy.

Cash and Due from Banks

Cash and Due from Banks	12 Months Ended
	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash and Due from Banks	Note 3 – Cash and Due from Banks Trustmark is required to maintain average reserve balances with the Federal Reserve Bank of Atlanta based on a percentage of deposits. The average amounts of those reserves for the years ended December 31, 2017 and 2016 were $100.8 million and $94.7 million, respectively.

Securities Available for Sale a

Securities Available for Sale and Held to Maturity	12 Months Ended
	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Securities Available for Sale and Held to Maturity	Note 4 – Securities Available for Sale and Held to Maturity The following tables are a summary of the amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2017 and 2016 ($ in thousands): Securities Available for Sale Securities Held to Maturity Gross Gross Estimated Gross Gross Estimated Amortized Unrealized Unrealized Fair Amortized Unrealized Unrealized Fair December 31, 2017 Cost Gains Losses Value Cost Gains Losses Value U.S. Government agency obligations Issued by U.S. Government agencies $ 45,508 $ 310 $ (800 ) $ 45,018 $ — $ — $ — $ — Issued by U.S. Government sponsored agencies 255 12 — 267 3,692 182 — 3,874 Obligations of states and political subdivisions 78,433 850 (54 ) 79,229 46,039 1,044 (59 ) 47,024 Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 66,634 215 (1,103 ) 65,746 13,539 207 (73 ) 13,673 Issued by FNMA and FHLMC 824,872 827 (11,249 ) 814,450 133,975 210 (1,559 ) 132,626 Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 1,028,176 1,808 (13,194 ) 1,016,790 678,926 1,209 (11,065 ) 669,070 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 218,252 426 (1,543 ) 217,135 180,315 1,102 (1,437 ) 179,980 Total $ 2,262,130 $ 4,448 $ (27,943 ) $ 2,238,635 $ 1,056,486 $ 3,954 $ (14,193 ) $ 1,046,247 December 31, 2016 U.S. Government agency obligations Issued by U.S. Government agencies $ 56,272 $ 416 $ (925 ) $ 55,763 $ — $ — $ — $ — Issued by U.S. Government sponsored agencies 257 19 — 276 3,647 355 — 4,002 Obligations of states and political subdivisions 113,541 1,945 (113 ) 115,373 46,303 1,476 (27 ) 47,752 Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 43,222 340 (776 ) 42,786 15,478 280 (52 ) 15,706 Issued by FNMA and FHLMC 638,809 1,773 (9,498 ) 631,084 81,299 223 (1,084 ) 80,438 Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 1,271,198 5,865 (9,112 ) 1,267,951 803,474 3,208 (6,519 ) 800,163 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 242,869 1,766 (1,186 ) 243,449 208,442 1,758 (1,215 ) 208,985 Total $ 2,366,168 $ 12,124 $ (21,610 ) $ 2,356,682 $ 1,158,643 $ 7,300 $ (8,897 ) $ 1,157,046 During 2013, Trustmark reclassified approximately $1.099 billion of securities available for sale to securities held to maturity. The securities were transferred at fair value, which became the cost basis for the securities held to maturity. At the date of transfer, the net unrealized holding loss on the available for sale securities totaled approximately $46.6 million ($28.8 million, net of tax). The net unrealized holding loss is amortized over the remaining life of the securities as a yield adjustment in a manner consistent with the amortization or accretion of the original purchase premium or discount on the associated security. There were no gains or losses recognized as a result of the transfer. At December 31, 2017, the net unamortized, unrealized loss on the transferred securities included in accumulated other comprehensive loss in the accompanying balance sheet totaled approximately $19.5 million ($12.0 million, net of tax). Temporarily Impaired Securities The table below includes securities with gross unrealized losses segregated by length of impairment at December 31, 2017 and 2016 ($ in thousands): Less than 12 Months 12 Months or More Total Gross Gross Gross Estimated Unrealized Estimated Unrealized Estimated Unrealized December 31, 2017 Fair Value Losses Fair Value Losses Fair Value Losses U.S. Government agency obligations Issued by U.S. Government agencies $ 5,214 $ (113 ) $ 29,432 $ (687 ) $ 34,646 $ (800 ) Obligations of states and political subdivisions 19,345 (80 ) 3,874 (33 ) 23,219 (113 ) Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 37,304 (351 ) 29,446 (825 ) 66,750 (1,176 ) Issued by FNMA and FHLMC 506,410 (4,219 ) 369,060 (8,589 ) 875,470 (12,808 ) Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 755,013 (7,668 ) 534,955 (16,591 ) 1,289,968 (24,259 ) Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 230,898 (1,719 ) 55,288 (1,261 ) 286,186 (2,980 ) Total $ 1,554,184 $ (14,150 ) $ 1,022,055 $ (27,986 ) $ 2,576,239 $ (42,136 ) December 31, 2016 U.S. Government agency obligations Issued by U.S. Government agencies $ 9,420 $ (142 ) $ 33,248 $ (783 ) $ 42,668 $ (925 ) Obligations of states and political subdivisions 20,539 (135 ) 654 (5 ) 21,193 (140 ) Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 43,615 (822 ) 222 (6 ) 43,837 (828 ) Issued by FNMA and FHLMC 588,352 (10,582 ) — — 588,352 (10,582 ) Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 1,127,501 (12,722 ) 76,196 (2,909 ) 1,203,697 (15,631 ) Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 244,050 (2,311 ) 4,655 (90 ) 248,705 (2,401 ) Total $ 2,033,477 $ (26,714 ) $ 114,975 $ (3,793 ) $ 2,148,452 $ (30,507 ) The unrealized losses shown above are due to increases in market rates over the yields available at the time of purchase of the underlying securities and not credit quality. Because Trustmark does not intend to sell these securities and it is more likely than not that Trustmark will not be required to sell the investments before recovery of their amortized cost bases, which may be maturity, Trustmark does not consider these investments to be other-than-temporarily impaired at December 31, 2017. There were no other-than-temporary impairments for the years ended December 31, 2017, 2016 and 2015. Security Gains and Losses For the periods presented, gains and losses as a result of calls and dispositions of securities, as well as any associated proceeds, were as follows ($ in thousands): Years Ended December 31, Available for Sale 2017 2016 2015 Proceeds from calls and sales of securities $ 27,682 $ 24,693 $ — Gross realized gains 16 32 — Gross realized losses (1 ) (342 ) — Securities Pledged Securities with a carrying value of $1.834 billion and $1.999 billion at December 31, 2017 and 2016, respectively, were pledged to collateralize public deposits and securities sold under repurchase agreements and for other purposes as permitted by law. At both December 31, 2017 and 2016, none of these securities were pledged under the Federal Reserve Discount Window program to provide additional contingency funding capacity. Contractual Maturities The amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2017, by contractual maturity, are shown below ($ in thousands). Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities Securities Available for Sale Held to Maturity Amortized Estimated Amortized Estimated Cost Fair Value Cost Fair Value Due in one year or less $ 31,376 $ 31,525 $ 155 $ 155 Due after one year through five years 57,372 58,343 40,594 41,450 Due after five years through ten years 3,866 3,845 8,982 9,293 Due after ten years 31,582 30,801 — — 124,196 124,514 49,731 50,898 Mortgage-backed securities 2,137,934 2,114,121 1,006,755 995,349 Total $ 2,262,130 $ 2,238,635 $ 1,056,486 $ 1,046,247

LHFI and Allowance for Loan Los

LHFI and Allowance for Loan Losses, LHFI	12 Months Ended
	Dec. 31, 2017
Accounts Notes Loans And Financing Receivable Gross Allowance And Net [Abstract]
LHFI and Allowance for Loan Losses, LHFI	Note 5 – LHFI and Allowance for Loan Losses, LHFI At December 31, 2017 and 2016, LHFI consisted of the following ($ in thousands): December 31, 2017 2016 Loans secured by real estate: Construction, land development and other land $ 987,624 $ 831,437 Secured by 1-4 family residential properties 1,675,311 1,660,043 Secured by nonfarm, nonresidential properties 2,193,823 2,034,176 Other real estate secured 517,956 318,148 Commercial and industrial loans 1,570,345 1,528,434 Consumer loans 171,918 170,562 State and other political subdivision loans 952,483 917,515 Other loans 500,507 390,898 LHFI (1) 8,569,967 7,851,213 Less allowance for loan losses, LHFI 76,733 71,265 Net LHFI $ 8,493,234 $ 7,779,948 (1) During the first quarter of 2017, Trustmark reclassified $36.7 million of acquired loans not accounted for under FASB ASC Topic 310-30 to LHFI due to the discount on these loans being fully amortized. Loan Concentrations Trustmark does not have any loan concentrations other than those reflected in the preceding table, which exceed 10% of total LHFI. At December 31, 2017, Trustmark’s geographic loan distribution was concentrated primarily in its five key market regions: Alabama, Florida, Mississippi, Tennessee and Texas. Accordingly, the ultimate collectability of a substantial portion of these loans is susceptible to changes in market conditions in these areas. Related Party Loans At December 31, 2017 and 2016, loans to certain executive officers and directors, including their immediate families and companies in which they are principal owners, totaled $59.9 million and $47.1 million, respectively. During 2017, $418.5 million of new loan advances were made, while repayments were Nonaccrual and Past Due LHFI At December 31, 2017 and 2016, the carrying amounts of nonaccrual LHFI were $67.6 million and $49.2 million, respectively. Included in these amounts were $23.2 million and $14.4 million, respectively, of nonaccrual LHFI classified as TDRs. No material interest income was recognized in the income statement on nonaccrual LHFI for each of the years in the three-year period ended December 31, 2017. The following table details nonaccrual LHFI by loan type at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Loans secured by real estate: Construction, land development and other land $ 2,105 $ 3,323 Secured by 1-4 family residential properties 19,022 20,329 Secured by nonfarm, nonresidential properties 12,608 8,482 Other real estate secured 212 402 Commercial and industrial loans 33,338 15,824 Consumer loans 135 300 State and other political subdivision loans — — Other loans 155 574 Total nonaccrual LHFI $ 67,575 $ 49,234 The following tables provide an aging analysis of past due and nonaccrual LHFI by loan type at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Past Due 90 Days Current 30-59 Days 60-89 Days or More (1) Total Nonaccrual Loans Total Loans secured by real estate: Construction, land development and other land $ 391 $ 1 $ — $ 392 $ 2,105 $ 985,127 $ 987,624 Secured by 1-4 family residential properties 6,412 2,084 1,917 10,413 19,022 1,645,876 1,675,311 Secured by nonfarm, nonresidential properties 2,319 256 — 2,575 12,608 2,178,640 2,193,823 Other real estate secured — — — — 212 517,744 517,956 Commercial and industrial loans 759 1,233 12 2,004 33,338 1,535,003 1,570,345 Consumer loans 2,141 255 242 2,638 135 169,145 171,918 State and other political subdivision loans 350 39 — 389 — 952,094 952,483 Other loans 18 4 — 22 155 500,330 500,507 Total $ 12,390 $ 3,872 $ 2,171 $ 18,433 $ 67,575 $ 8,483,959 $ 8,569,967 (1) Past due 90 days or more but still accruing interest. December 31, 2016 Past Due 90 Days Current 30-59 Days 60-89 Days or More (1) Total Nonaccrual Loans Total Loans secured by real estate: Construction, land development and other land $ 248 $ 37 $ 54 $ 339 $ 3,323 $ 827,775 $ 831,437 Secured by 1-4 family residential properties 5,308 2,434 1,436 9,178 20,329 1,630,536 1,660,043 Secured by nonfarm, nonresidential properties 606 100 — 706 8,482 2,024,988 2,034,176 Other real estate secured 179 — — 179 402 317,567 318,148 Commercial and industrial loans 571 213 — 784 15,824 1,511,826 1,528,434 Consumer loans 1,561 330 341 2,232 300 168,030 170,562 State and other political subdivision loans 1,035 — — 1,035 — 916,480 917,515 Other loans 178 53 — 231 574 390,093 390,898 Total $ 9,686 $ 3,167 $ 1,831 $ 14,684 $ 49,234 $ 7,787,295 $ 7,851,213 (1) Past due 90 days or more but still accruing interest. Impaired LHFI As of January 1, 2017, Trustmark modified its presentation of individually evaluated impaired LHFI in the accompanying notes to the consolidated financial statements to include all commercial nonaccrual relationships of $500 thousand or more, which are specifically reviewed for impairment and deemed impaired, and all LHFI classified as TDRs in accordance with FASB ASC Topic 310-10-50-20. Previously, Trustmark presented all nonaccrual LHFI and LHFI classified as TDRs as impaired loans. Nonaccrual LHFI includes both individually evaluated impaired LHFI as well as smaller balance homogeneous loans that are collectively evaluated for impairment. As a result of this change in presentation, these smaller balance homogenous nonaccrual LHFI are included within the LHFI collectively evaluated for impairment category. All prior period information has been reclassified to conform to the current period presentation. Trustmark’s individually evaluated impaired LHFI are primarily collateral dependent loans. Fair value estimates for collateral dependent loans are derived from appraised values based on the current market value or as is value of the collateral, normally from recently received and reviewed appraisals. Current appraisals are ordered on an annual basis based on the inspection date or more often if market conditions necessitate. Appraisals are obtained from state-certified appraisers and are based on certain assumptions, which may include construction or development status and the highest and best use of the property. These appraisals are reviewed by Trustmark’s Appraisal Review Department to ensure they are acceptable, and values are adjusted down for costs associated with asset disposal. Once this estimated net realizable value has been determined, the value used in the impairment assessment is updated. At the time a LHFI that has been individually evaluated for impairment is deemed to be impaired, the full difference between book value and the most likely estimate of the collateral’s net realizable value is charged off. As subsequent events dictate and estimated net realizable values decline, required reserves may be established or further adjustments recorded. No material interest income was recognized in the accompanying consolidated statements of income on impaired LHFI for each of the years in the three-year period ended December 31, 2017. At December 31, 2017 and 2016, the carrying amount of LHFI individually evaluated for impairment consisted of the following ($ in thousands): December 31, 2017 LHFI Unpaid Wit h o With an Total Average Principal Allowance Allowance Carrying Related Recorded Balance Recorded Recorded Amount Allowance Investment Loans secured by real estate: Construction, land development and other land $ 1,704 $ 1,206 $ 199 $ 1,405 $ 75 $ 1,923 Secured by 1-4 family residential properties 6,031 160 4,576 4,736 1,331 4,693 Secured by nonfarm, nonresidential properties 15,205 10,027 396 10,423 165 8,321 Other real estate secured — — — — — — Commercial and industrial loans 36,874 31,281 518 31,799 131 22,734 Consumer loans 17 — 17 17 — 9 State and other political subdivision loans — — — — — — Other loans 556 — 556 556 41 325 Total $ 60,387 $ 42,674 $ 6,262 $ 48,936 $ 1,743 $ 38,005 December 31, 2016 LHFI Unpaid Wit h o With an Total Average Principal Allowance Allowance Carrying Related Recorded Balance Recorded Recorded Amount Allowance Investment Loans secured by real estate: Construction, land development and other land $ 5,691 $ 2,213 $ 228 $ 2,441 $ 103 $ 2,943 Secured by 1-4 family residential properties 6,134 221 4,428 4,649 960 4,639 Secured by nonfarm, nonresidential properties 8,562 5,784 435 6,219 221 6,703 Other real estate secured — — — — — 500 Commercial and industrial loans 14,593 11,222 2,447 13,669 1,976 14,258 Consumer loans 2 — 2 2 — 2 State and other political subdivision loans — — — — — — Other loans 95 — 95 95 — 95 Total $ 35,077 $ 19,440 $ 7,635 $ 27,075 $ 3,260 $ 29,140 Troubled Debt Restructurings At December 31, 2017, 2016 and 2015, LHFI classified as TDRs totaled $23.9 million, $14.5 million and $9.7 million, respectively, and were primarily comprised of credits with interest-only payments for an extended period of time which totaled $20.5 million, $9.8 million and $5.9 million, respectively. The remaining TDRs at December 31, 2017, 2016 and 2015 resulted from real estate loans discharged through Chapter 7 bankruptcy that were not reaffirmed or from payment or maturity extensions. For TDRs, Trustmark had a related loan loss allowance of $458 thousand at December 31, 2017, $2.2 million at December 31, 2016 and $1.8 million at December 31, 2015. LHFI classified as TDRs are charged down to the most likely fair value estimate less an estimated cost to sell for collateral dependent loans, which would approximate net realizable value. Specific charge-offs related to TDRs totaled $127 thousand, $1.0 million and $806 thousand for the years ended December 31, 2017, 2016 and 2015, respectively. At December 31, 2017 and 2016, Trustmark held $366 thousand and $269 thousand, respectively, of foreclosed residential real estate as a result of foreclosure or in substance repossession of consumer mortgage LHFI classified as TDRs. There were no consumer mortgage LHFI classified as TDRs in the process of formal foreclosure proceedings at December 31, 2017 compared to $101 thousand at December 31, 2016. The following tables illustrate the impact of modifications classified as TDRs as well as those TDRs modified within the last 12 months for which there was a payment default during the period for the periods presented ($ in thousands): Year Ended December 31, 2017 Modifications Classified as TDRs Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by real estate: Construction, land development and other land 1 $ 341 $ 325 Secured by 1-4 family residential properties 22 1,478 1,487 Secured by nonfarm, nonresidential properties 1 426 426 Commercial and industrial loans 8 12,836 12,836 Other loans 1 556 556 Total 33 $ 15,637 $ 15,630 Year Ended December 31, 2016 Modifications Classified as TDRs Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by real estate: Construction, land development and other land 1 $ 14 $ 14 Secured by 1-4 family residential properties 18 1,386 1,391 Secured by nonfarm, nonresidential properties 2 717 717 Commercial and industrial loans 5 10,043 9,982 Consumer loans 1 2 2 Total 27 $ 12,162 $ 12,106 Year Ended December 31, 2015 Modifications Classified as TDRs Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by real estate: Secured by 1-4 family residential properties 13 $ 688 $ 688 Secured by nonfarm, nonresidential properties 5 3,613 3,613 Total 18 $ 4,301 $ 4,301 Years Ended December 31, 2017 2016 2015 TDRs that Subsequently Defaulted Number of Contracts Recorded Investment Number of Contracts Recorded Investment Number of Contracts Recorded Investment Loans secured by 1-4 family residential properties 4 $ 78 1 $ — 5 $ 260 Commercial and industrial loans 3 9,526 2 2,154 — — Total 7 $ 9,604 3 $ 2,154 5 $ 260 Trustmark’s TDRs have resulted primarily from allowing the borrower to pay interest-only for an extended period of time rather than from forgiveness. Accordingly, as shown above, these TDRs have a similar recorded investment for both the pre-modification and post-modification disclosure. Trustmark has utilized loans 90 days or more past due to define payment default in determining TDRs that have subsequently defaulted. The following tables detail LHFI classified as TDRs by loan type at December 31, 2017, 2016 and 2015 ($ in thousands): December 31, 2017 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 199 $ 199 Secured by 1-4 family residential properties 51 3,140 3,191 Secured by nonfarm, nonresidential properties — 421 421 Commercial and industrial loans 53 19,434 19,487 Consumer loans — 17 17 Other loans 556 — 556 Total TDRs $ 660 $ 23,211 $ 23,871 December 31, 2016 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 405 $ 405 Secured by 1-4 family residential properties — 2,873 2,873 Secured by nonfarm, nonresidential properties — 881 881 Commercial and industrial loans 53 10,266 10,319 Consumer loans — 2 2 Total TDRs $ 53 $ 14,427 $ 14,480 December 31, 2015 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 869 $ 869 Secured by 1-4 family residential properties 1,426 2,424 3,850 Secured by nonfarm, nonresidential properties 809 3,662 4,471 Commercial and industrial loans — 463 463 Total TDRs $ 2,235 $ 7,418 $ 9,653 Credit Quality Indicators Trustmark’s loan portfolio credit quality indicators focus on six key quality ratios that are compared against bank tolerances. The loan indicators are total classified outstanding, total criticized outstanding, nonperforming loans, nonperforming assets, delinquencies and net loan losses. Due to the homogenous nature of consumer loans, Trustmark does not assign a formal internal risk rating to each credit and therefore the criticized and classified measures are primarily composed of commercial loans. In addition to monitoring portfolio credit quality indicators, Trustmark also measures how effectively the lending process is being managed and risks are being identified. As part of an ongoing monitoring process, Trustmark grades the commercial portfolio as it relates to credit file completion and financial statement exceptions, underwriting, collateral documentation and compliance with law as shown below: • Credit File Completeness and Financial Statement Exceptions – evaluates the quality and condition of credit files in terms of content and completeness and focuses on efforts to obtain and document sufficient information to determine the quality and status of credits. Also included is an evaluation of the systems/procedures used to insure compliance with policy. • Underwriting – evaluates whether credits are adequately analyzed, appropriately structured and properly approved within loan policy requirements. A properly approved credit is approved by adequate authority in a timely manner with all conditions of approval fulfilled. Total policy exceptions measure the level of underwriting and other policy exceptions within a loan portfolio. • Collateral Documentation – focuses on the adequacy of documentation to perfect Trustmark’s collateral position and substantiate collateral value. Collateral exceptions measure the level of documentation exceptions within a loan portfolio. Collateral exceptions occur when certain collateral documentation is either not present or not current. • Compliance with Law – focuses on underwriting, documentation, approval and reporting in compliance with banking laws and regulations. Primary emphasis is directed to the Financial Institutions Reform, Recovery and Enforcement Act of 1989 (FIRREA), Regulation O requirements and regulations governing appraisals. Commercial Credits Trustmark has established a loan grading system that consists of ten individual credit risk grades (risk ratings) that encompass a range from loans where the expectation of loss is negligible to loans where loss has been established. The model is based on the risk of default for an individual credit and establishes certain criteria to delineate the level of risk across the ten unique credit risk grades. Credit risk grade definitions are as follows: • Risk Rate (RR) 1 through RR 6 – Grades one through six represent groups of loans that are not subject to criticism as defined in regulatory guidance. Loans in these groups exhibit characteristics that represent low to moderate risk measured by using a variety of credit risk criteria such as cash flow coverage, debt service coverage, balance sheet leverage, liquidity, management experience, industry position, prevailing economic conditions, support from secondary sources of repayment and other credit factors that may be relevant to a specific loan. In general, these loans are supported by properly margined collateral and guarantees of principal parties. • Other Assets Especially Mentioned (Special Mention) - (RR 7) – a loan that has a potential weakness that if not corrected will lead to a more severe rating. This rating is for credits that are currently protected but potentially weak because of an adverse feature or condition that if not corrected will lead to a further downgrade. • Substandard (RR 8) – a loan that has at least one identified weakness that is well defined. This rating is for credits where the primary sources of repayment are not viable at the time of evaluation or where either the capital or collateral is not adequate to support the loan and the secondary means of repayment do not provide a sufficient level of support to offset the identified weakness. Loss potential exists in the aggregate amount of substandard loans but does not necessarily exist in individual loans. • Doubtful (RR 9) – a loan with an identified weakness that does not have a valid secondary source of repayment. Generally these credits have an impaired primary source of repayment and secondary sources are not sufficient to prevent a loss in the credit. The exact amount of the loss has not been determined at this time. • Loss (RR 10) – a loan or a portion of a loan that is deemed to be uncollectible. By definition, credit risk grades special mention (RR 7), substandard (RR 8), doubtful (RR 9) and loss (RR 10) are criticized loans while substandard (RR 8), doubtful (RR 9) and loss (RR 10) are classified loans. These definitions are standardized by all bank regulatory agencies and are generally equally applied to each individual lending institution. The remaining credit risk grades are considered pass credits and are solely defined by Trustmark. Each commercial loan is assigned a credit risk grade that is an indication for the likelihood of default and is not a direct indication of loss at default. The loss at default aspect of the subject risk ratings is neither uniform across the nine primary commercial loan groups or constant between the geographic areas. To account for the variance in the loss at default aspects of the risk rating system, the loss expectations for each risk rating are integrated into the allowance for loan loss methodology where the calculated loss at default is allotted for each individual risk rating with respect to the individual loan group and unique geographic area. The loss at default aspect of the reserve methodology is calculated each quarter as a component of the overall reserve factor for each risk grade by loan group and geographic area. To enhance this process, relationships of $500 thousand or more that are rated in one of the criticized categories are routinely reviewed to establish an expectation of loss, if any, and if such examination indicates that the level of reserve is not adequate to cover the expectation of loss, a special reserve or impairment is generally applied. The distribution of the losses is accomplished by means of a loss distribution model that assigns a loss factor to each risk rating (1 to 9) in each commercial loan pool. A factor is not applied to risk rate 10 as loans classified as losses are charged off within the period that the loss is determined and are not carried on Trustmark’s books over quarter-end. The expected loss distribution is spread across the various risk ratings by the perceived level of risk for loss. The nine grade scale described above ranges from a negligible risk of loss to an identified loss across its breadth. The loss distribution factors are graduated through the scale on a basis proportional to the degree of risk that appears manifest in each individual rating and assumes that migration through the loan grading system will occur. Each loan officer assesses the appropriateness of the internal risk rating assigned to their credits on an ongoing basis. Trustmark’s Asset Review area conducts independent credit quality reviews of the majority of Trustmark’s commercial loan portfolio both on the underlying credit quality of each individual loan portfolio as well as the adherence to Trustmark’s loan policy and the loan administration process. In general, Asset Review conducts reviews of each lending area within a six to eighteen month window depending on the overall credit quality results of the individual area. In addition to the ongoing internal risk rate monitoring described above, Trustmark’s Credit Quality Review Committee meets monthly and performs a review of all loans of $100 thousand or more that are either delinquent thirty days or more or on nonaccrual. This review includes recommendations regarding risk ratings, accrual status, charge-offs and appropriate servicing officer as well as evaluation of problem credits for determination of TDRs. Quarterly, the Credit Quality Review Committee reviews and modifies continuous action plans for all credits risk rated seven or worse for relationships of $100 thousand or more. In addition, a semi-annual review of significant development, commercial construction, multi-family and non-owner occupied projects is performed. This review assesses each particular project with respect to location, project valuations, progress of completion, leasing status, current financial information, rents, operating expenses, cash flow, adherence to budget and projections and other information as applicable. Summary results are reviewed by Senior and Regional Credit Officers in addition to the Chief Credit Officer with a determination made as to the appropriateness of existing risk ratings and accrual status. Consumer Credits Consumer LHFI that do not meet a minimum custom credit score are reviewed quarterly by Management. The Retail Credit Review Committee reviews the volume and percentage of approvals that did not meet the minimum passing custom score by region, individual location, and officer to ensure that Trustmark continues to originate quality loans. Trustmark monitors the levels and severity of past due consumer LHFI on a daily basis through its collection activities. A detailed assessment of consumer LHFI delinquencies is performed monthly at both a product and market level by delivery channel, which incorporates the perceived level of risk at time of underwriting. The tables below present LHFI by loan type and credit quality indicator at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Commercial LHFI Pass - Special Mention - Substandard - Doubtful - Categories Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 922,563 $ 316 $ 3,780 $ 222 $ 926,881 Secured by 1-4 family residential properties 127,405 134 4,948 76 132,563 Secured by nonfarm, nonresidential properties 2,135,749 6,684 50,785 527 2,193,745 Other real estate secured 517,036 — 517 — 517,553 Commercial and industrial loans 1,437,590 28,780 103,089 886 1,570,345 Consumer loans — — — — — State and other political subdivision loans 936,420 5,850 10,213 — 952,483 Other loans 478,083 — 16,390 108 494,581 Total $ 6,554,846 $ 41,764 $ 189,722 $ 1,819 $ 6,788,151 Consumer LHFI Past Due Past Due Current 30-89 Days 90 Days or More Nonaccrual Subtotal Total LHFI Loans secured by real estate: Construction, land development and other land $ 60,240 $ 342 $ — $ 161 $ 60,743 $ 987,624 Secured by 1-4 family residential properties 1,516,691 7,874 1,809 16,374 1,542,748 1,675,311 Secured by nonfarm, nonresidential properties 78 — — — 78 2,193,823 Other real estate secured 403 — — — 403 517,956 Commercial and industrial loans — — — — — 1,570,345 Consumer loans 169,146 2,396 242 134 171,918 171,918 State and other political subdivision loans — — — — — 952,483 Other loans 5,926 — — — 5,926 500,507 Total $ 1,752,484 $ 10,612 $ 2,051 $ 16,669 $ 1,781,816 $ 8,569,967 December 31, 2016 Commercial LHFI Pass - Special Mention - Substandard - Doubtful - Categories 1-6 Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 752,318 $ 9,567 $ 8,086 $ 465 $ 770,436 Secured by 1-4 family residential properties 124,615 170 6,162 129 131,076 Secured by nonfarm, nonresidential properties 1,989,554 4,394 38,913 584 2,033,445 Other real estate secured 315,829 762 890 — 317,481 Commercial and industrial loans 1,386,155 7,095 134,199 985 1,528,434 Consumer loans — — — — — State and other political subdivision loans 899,935 6,450 11,130 — 917,515 Other loans 382,890 — 2,685 350 385,925 Total $ 5,851,296 $ 28,438 $ 202,065 $ 2,513 $ 6,084,312 Consumer LHFI Past Due Past Due Current 30-89 Days 90 Nonaccrual Subtotal Total LHFI Loans secured by real estate: Construction, land development and other land $ 60,701 $ 188 $ 54 $ 58 $ 61,001 $ 831,437 Secured by 1-4 family residential properties 1,503,096 7,377 1,436 17,058 1,528,967 1,660,043 Secured by nonfarm, nonresidential properties 731 — — — 731 2,034,176 Other real estate secured 667 — — — 667 318,148 Commercial and industrial loans — — — — — 1,528,434 Consumer loans 168,031 1,891 341 299 170,562 170,562 State and other political subdivision loans — — — — — 917,515 Other loans 4,940 33 — — 4,973 390,898 Total $ 1,738,166 $ 9,489 $ 1,831 $ 17,415 $ 1,766,901 $ 7,851,213 Past Due LHFS LHFS past due 90 days or more totaled $35.5 million and $28.3 million at December 31, 2017 and 2016, respectively. Trustmark did not exercise its buy-back option on any delinquent loans serviced for GNMA during 2017 or 2016. Allowance for Loan Losses, LHFI Trustmark’s allowance for loan loss methodology for commercial LHFI is based upon regulatory guidance from its primary regulator and GAAP. The methodology segregates the commercial purpose and commercial construction LHFI portfolios into nine separate loan types (or pools) which have similar characteristics such as repayment, collateral and risk profiles. The nine basic loan pools are further segregated into Trustmark’s five key market regions, Alabama, Florida, Mississippi, Tennessee and Texas, to take into consideration the uniqueness of each market. A 10-point risk rating system is utilized for each separate loan pool to apply a reserve factor consisting of quantitative and qualitative components to determine the needed allowance by each loan type. As a result, there are 450 risk rate factors for commercial loan types. The nine separate pools are shown below: Commercial Purpose LHFI • Real Estate – Owner-Occupied • Real Estate – Non-Owner Occupied • Working Capital • Non-Working Capital • Land • Lots and Development • Political Subdivisions Commercial Construction LHFI • 1 to 4 Family • Non-1 to 4 Family The quantitative factors of the allowance methodology reflect a twelve-quarter rolling average of net charge-offs by loan type within each key market region. This allows for a greater sensitivity to current trends, such as economic changes, as well as current loss profiles and creates a more accurate depiction of historical losses. During 2015, the LEP, a component of the quantitative portion of the allowance for loan loss methodology for commercial LHFI, was revised to reflect a 1.5 year period rather than a one year period. An additional provision of approximately $2.3 million was recorded in 2015 as result of this revision to the quantitative portion of the allowance for loan loss methodology for commercial LHFI. The LEP refers to the period of time between the events that trigger a loss and a charge-off of that loss. Losses are usually not immediately known, and determining the loss event can be challenging. It takes time for the borrower and extent of loss to be identified and determined. Trustmark may not be aware that the loss trigger has occurred until the borrower exhibits the inability to pay or other evidence of credit deterioration. Trustmark estimates the loss event to have occurred within a nine month period prior to the event of default. The charge-off of the loss occurs within a ten month period after the event of default, resulting in a 1.5 year LEP. During 2015, Trustmark also revised the quantitative portion of the allowance for loan loss methodology for commercial LHFI to incorporate third-party default data. The default data is used in conjunction with each market/commercial loan pool’s loss rate and the commercial loan LEP in calculating a total quantitative loss factor for each risk rating within each market and pool. The quantitative reserves are a result of the total quantitative loss factor multiplied by the outstanding balances within each loan group and risk rate. An additional provision of approximately $1.3 million was recorded in 2015 as a result of this revision to the quantitative portion of the allowance for loan loss methodology for commercial LHFI. Qualitative factors used in the allowance methodology include the following: • National and regional economic trends and conditions • Impact of recent performance trends • Experience, ability and effectiveness of management • Adherence to Trustmark’s loan policies, procedures and internal controls • Collateral, financial and underwriting exception trends • Credit concentrations • Loan facility risk • Acquisitions • Catastrophe Each qualitative factor is converted to a scale ranging from 0 (No risk) to 100 (High Risk), other than the last two factors, which are applied on a dollar-for-dollar basis to ensure that the combination of such factors is proportional. The resulting ratings from the individual factors are weighted and summed to establish the weighted-average qualitative factor within each key market region. During 2015, Trustmark eliminated caps and floors from the criticized risk grades in the qualitative portion and adjusted the Florida market region’s distribution factors in the qualitative and quantitative portions of the allowance for loan loss methodology for commercial LHFI. The caps and floors for criticized risk ratings were eliminated in order to allow the risk associated with those credits to be reflected without constraint of pre-existing limits (caps or floors) on the risk ratings. When the current allowance for loan loss methodology was originally established, the vast majority of the reserve for the Florida market region’s assets was covered by the quantitative features of the allowance for loan loss methodology due to the amount of gross charge-offs at that time and captured the vast majority of the embedded risk in the portfolio. The distribution for the Florida market region was adjusted to be the same as Trustmark’s other key market regions since the credit metrics in the Florida market region now more closely resemble Trustmark as a whole. The elimination of the caps and floors for criticized risk ratings in the qualitative portion of the allowance for loan loss methodology for commercial LHFI resulted in a provision recapture of $1.8 million in 2015. The change in the Florida market region distribution resulted in an additional provision expense of $2.1 million related to the qualitative portion and an additional provision expense of $785 thousand related to the quantitative portion of the allowance for loan loss methodology for commercial LHFI in 2015. Combined, these revisions to the allowance for loan loss methodology for commercial LHFI resulted in an additional provision of approximately $1.1 million recorded during 2015. In addition, Trustmark revised the qualitative portion of the commercial LHFI allowance for loan loss methodology to incorporate the use of maximum observed gross historical losses as a way to calculate a maximum qualitative reserve limit. The maximum observed gross historical losses for each market were observed for a three-year period reflecting the last economic downturn (i.e., 2008-2010). The aggregate of these losses as a percentage of the three-year ave

Acquired Loans

Acquired Loans	12 Months Ended
	Dec. 31, 2017
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities [Abstract]
Acquired Loans	Note 6 – Acquired Loans During the first quarter of 2017, Trustmark modified the presentation of the acquired loans disclosures to eliminate the segmentation of acquired noncovered loans and acquired covered loans due to the significantly reduced size of the acquired covered loan portfolio. Trustmark’s loss share agreement with the FDIC covering the acquired covered loans other than loans secured by 1-4 family residential properties expired on June 30, 2016. Trustmark’s loss share agreement with the FDIC covering the acquired covered loans secured by 1-4 family residential properties will expire in 2021. Effective July 1, 2016, all acquired covered loans excluding the acquired covered loans secured by 1-4 family residential properties were reclassified to acquired noncovered loans. The revised presentation reflects total acquired loan information in the accompanying consolidated balance sheets and tables below. All prior period information has been reclassified to conform to the current period presentation. Loans acquired in the Reliance merger completed on April 7, 2017 were evaluated using a fair value process to determine the degree of credit deterioration since origination and the collectibility of contractually required payments. Approximately $7.9 million of the loans acquired in the Reliance merger exhibited evidence of significant credit deterioration since origination and for which it was probable at acquisition that Trustmark would not be able to collect all contractually required payments. These loans are accounted for as acquired impaired loans under FASB ASC Topic 310-30. At December 31, 2017 and 2016, acquired loans consisted of the following ($ in thousands): December 31, 2017 2016 Loans secured by real estate: Construction, land development and other land $ 23,586 $ 20,850 Secured by 1-4 family residential properties 61,751 69,540 Secured by nonfarm, nonresidential properties 114,694 103,820 Other real estate secured 16,746 19,010 Commercial and industrial loans 31,506 36,896 Consumer loans 2,600 3,365 Other loans 10,634 18,766 Acquired loans 261,517 272,247 Less allowance for loan losses, acquired loans 4,079 11,397 Net acquired loans $ 257,438 $ 260,850 The following table presents changes in the net carrying value of the acquired loans for the periods presented ($ in thousands): Acquired Acquired Impaired Not (1) Carrying value, net at January 1, 2016 $ 310,762 $ 67,657 Accretion to interest income 18,405 40 Payments received, net (111,522 ) (24,953 ) Other (2) (134 ) — Change in allowance for loan losses, acquired loans 596 (1 ) Carrying value, net at December 31, 2016 218,107 42,743 Transfers (3) — (36,719 ) Additions (4) 7,899 109,548 Accretion to interest income 14,924 1,578 Payments received, net (68,317 ) (39,208 ) Other (2) (361 ) (74 ) Change in allowance for loan losses, acquired loans 7,318 — Carrying value, net at December 31, 2017 $ 179,570 $ 77,868 (1) “Acquired Not ASC 310-30” loans consist of loans that are not in scope for FASB ASC Topic 310-30. (2) Includes miscellaneous timing adjustments as well as acquired loan terminations through foreclosure, charge-off and other terminations. (3) “Acquired Not ASC 310-20” loans transferred to LHFI due to the discount on these loans being fully amortized. (4) Loans acquired in the Reliance merger on April 7, 2017. Under FASB ASC Topic 310-30, the accretable yield is the excess of expected cash flows at acquisition over the initial fair value of acquired impaired loans and is recorded as interest income over the estimated life of the loans using the effective yield method if the timing and amount of the future cash flows is reasonably estimable. The following table presents changes in the accretable yield for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Accretable yield at beginning of period $ (38,918 ) $ (52,672 ) $ (77,149 ) Additions due to acquisition (1) (784 ) — — Accretion to interest income 14,924 18,405 30,501 Disposals 2,868 6,488 10,013 Reclassification from nonaccretable difference (2) (9,516 ) (11,139 ) (16,037 ) Accretable yield at end of period $ (31,426 ) $ (38,918 ) $ (52,672 ) (1) Accretable yield on loans acquired from Reliance on April 7, 2017. (2) Reclassifications from nonaccretable difference are due to lower loss expectations and improvements in expected cash flows. The following tables present the components of the allowance for loan losses on acquired impaired loans for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Balance at beginning of period $ 11,397 $ 11,992 $ 12,059 Provision for loan losses, acquired loans (7,395 ) 3,757 3,425 Loans charged-off — (6,616 ) (7,200 ) Recoveries 77 2,264 3,708 Net (charge-offs) recoveries 77 (4,352 ) (3,492 ) Balance at end of period $ 4,079 $ 11,397 $ 11,992 As discussed in Note 5 - LHFI and Allowance for Loan Losses, LHFI, Trustmark has established a loan grading system that consists of ten individual credit risk grades (risk ratings) that encompass a range from loans where the expectation of loss is negligible to loans where loss has been established. The model is based on the risk of default for an individual credit and establishes certain criteria to segregate the level of risk across the ten unique risk ratings. These credit quality measures are unique to commercial loans. Credit quality for consumer loans is based on individual credit scores, aging status of the loan and payment activity. The tables below present the acquired loans by loan type and credit quality indicator at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Commercial Loans Pass - Special Mention - Substandard - Doubtful - Categories 1-6 Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 17,150 $ 234 $ 4,690 $ 264 $ 22,338 Secured by 1-4 family residential properties 14,021 298 3,029 — 17,348 Secured by nonfarm, nonresidential properties 95,147 1,400 17,583 530 114,660 Other real estate secured 12,730 102 3,031 477 16,340 Commercial and industrial loans 22,157 15 7,585 1,749 31,506 Consumer loans — — — — — Other loans 5,874 18 4,742 — 10,634 Total acquired loans $ 167,079 $ 2,067 $ 40,660 $ 3,020 $ 212,826 Consumer Loans Past Due Past Due Total Current 30-89 Days 90 Days or More Nonaccrual (1) Subtotal Acquired Loans Loans secured by real estate: Construction, land development and other land $ 1,188 $ 46 $ 14 $ — $ 1,248 $ 23,586 Secured by 1-4 family residential properties 42,008 1,687 584 124 44,403 61,751 Secured by nonfarm, nonresidential properties 34 — — — 34 114,694 Other real estate secured 406 — — — 406 16,746 Commercial and industrial loans — — — — — 31,506 Consumer loans 2,428 172 — — 2,600 2,600 Other loans — — — — — 10,634 Total acquired loans $ 46,064 $ 1,905 $ 598 $ 124 $ 48,691 $ 261,517 (1) Acquired loans not accounted for under FASB ASC Topic 310-30. December 31, 2016 Commercial Loans Pass - Special Mention - Substandard - Doubtful - Categories 1-6 Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 12,148 $ 99 $ 6,469 $ 322 $ 19,038 Secured by 1-4 family residential properties 14,552 61 4,066 69 18,748 Secured by nonfarm, nonresidential properties 83,271 435 19,553 511 103,770 Other real estate secured 15,344 — 2,673 565 18,582 Commercial and industrial loans 22,024 18 13,494 1,354 36,890 Consumer loans — — — — — Other loans 12,954 — 5,649 161 18,764 Total acquired loans $ 160,293 $ 613 $ 51,904 $ 2,982 $ 215,792 Consumer Loans Past Due Past Due Total Current 30-89 Days 90 Days or More Nonaccrual (1) Subtotal Acquired Loans Loans secured by real estate: Construction, land development and other land $ 1,801 $ — $ 11 $ — $ 1,812 $ 20,850 Secured by 1-4 family residential properties 48,695 1,364 709 24 50,792 69,540 Secured by nonfarm, nonresidential properties 50 — — — 50 103,820 Other real estate secured 428 — — — 428 19,010 Commercial and industrial loans 6 — — — 6 36,896 Consumer loans 3,250 51 64 — 3,365 3,365 Other loans 2 — — — 2 18,766 Total acquired loans $ 54,232 $ 1,415 $ 784 $ 24 $ 56,455 $ 272,247 (1) Acquired loans not accounted for under FASB ASC Topic 310-30 . At December 31, 2017 and 2016, there were no acquired impaired loans accounted for under FASB ASC Topic 310-30 classified as nonaccrual loans. At December 31, 2017, approximately $304 thousand of acquired loans not accounted for under FASB ASC Topic 310-30 were classified as nonaccrual loans, compared to approximately $631 thousand of acquired loans at December 31, 2016. The following tables provide an aging analysis of contractually past due and nonaccrual acquired loans by loan type at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Past Due 30-59 Days 60-89 Days 90 Days or More (1) Total Nonaccrual (2) Current Loans Total Acquired Loans Loans secured by real estate: Construction, land development and other land $ 34 $ 90 $ 861 $ 985 $ — $ 22,601 $ 23,586 Secured by 1-4 family residential properties 1,691 614 654 2,959 302 58,490 61,751 Secured by nonfarm, nonresidential properties 467 73 898 1,438 — 113,256 114,694 Other real estate secured 132 — — 132 — 16,614 16,746 Commercial and industrial loans — — — — 2 31,504 31,506 Consumer loans 16 156 — 172 — 2,428 2,600 Other loans — — 21 21 — 10,613 10,634 Total acquired loans $ 2,340 $ 933 $ 2,434 $ 5,707 $ 304 $ 255,506 $ 261,517 (1) Past due 90 days or more but still accruing interest. (2) Acquired loans not accounted for under FASB ASC Topic 310-30. December 31, 2016 Past Due 30-59 Days 60-89 Days 90 Days or More (1) Total Nonaccrual (2) Current Loans Total Acquired Loans Loans secured by real estate: Construction, land development and other land $ 321 $ 100 $ 821 $ 1,242 $ — $ 19,608 $ 20,850 Secured by 1-4 family residential properties 1,495 412 1,057 2,964 41 66,535 69,540 Secured by nonfarm, nonresidential properties 1,658 38 343 2,039 328 101,453 103,820 Other real estate secured 769 — 1,445 2,214 — 16,796 19,010 Commercial and industrial loans 60 39 — 99 262 36,535 36,896 Consumer loans 51 — 64 115 — 3,250 3,365 Other loans — — — — — 18,766 18,766 Total acquired loans $ 4,354 $ 589 $ 3,730 $ 8,673 $ 631 $ 262,943 $ 272,247 (1) Past due 90 days or more but still accruing interest. (2) Acquired loans not accounted for under FASB ASC Topic 310-30.

Premises and Equipment, Net

Premises and Equipment, Net	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Premises and Equipment, Net	Note 7 – Premises and Equipment, Net At December 31, 2017 and 2016, premises and equipment consisted of the following ($ in thousands): December 31, 2017 2016 Land $ 52,335 $ 51,097 Buildings and leasehold improvements 197,372 195,296 Furniture and equipment 166,071 172,170 Total cost of premises and equipment 415,778 418,563 Less accumulated depreciation and amortization 237,425 239,319 Premises and equipment, net 178,353 179,244 Assets held for sale 986 5,743 Total premises and equipment, net $ 179,339 $ 184,987 Assets held for sale consisted of three closed branches at December 31, 2017 compared to five closed branches and two parcels of land previously purchased for expansion at December 31, 2016. These properties were transferred from land and premises to assets held for sale due to Trustmark’s intent to sell these properties over the next twelve months as a result of its strategic branch initiatives. As a result, property valuation adjustments of $338 thousand and $750 thousand were recognized and included in other expense for 2017 and 2016, respectively, with no property valuation adjustments recognized in 2015. Depreciation and amortization of premises and equipment totaled $14.3 million in 2017, $13.2 million in 2016 and $14.0 million in 2015.

Mortgage Banking

Mortgage Banking	12 Months Ended
	Dec. 31, 2017
Mortgage Banking [Abstract]
Mortgage Banking	Note 8 – Mortgage Banking Mortgage Servicing Rights The activity in the MSR is detailed in the table below for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 Balance at beginning of period $ 80,239 $ 74,007 Origination of servicing assets 15,860 16,745 Change in fair value: Due to market changes (1,050 ) (407 ) Due to runoff (10,780 ) (10,106 ) Balance at end of period $ 84,269 $ 80,239 In the determination of the fair value of the MSR at the date of securitization, certain key economic assumptions are made. For instance, Trustmark considers the conditional prepayment rate (CPR), which is an estimated loan prepayment rate that uses historical prepayment rates for previous loans similar to the loans being evaluated, and the discount rate in determining the fair value of the MSR. An increase in either the CPR or discount rate assumption will result in a decrease in the fair value of the MSR, while a decrease in either assumption will result in an increase in the fair value of the MSR. At December 31, 2017, the fair value of the MSR included an assumed average prepayment speed of 9.14 CPR and an average discount rate of 10.28% compared to an assumed average prepayment speed of 7.94 CPR and an average discount rate of 10.32% at December 31, 2016. In recent years, there have been significant market-driven fluctuations in loan prepayment speeds and discount rates. These fluctuations can be rapid and may continue to be significant. Therefore, estimating prepayment speed and/or discount rates within ranges that market participants would use in determining the fair value of the MSR requires significant management judgment. Mortgage Loans Sold/Serviced During 2017, 2016 and 2015, Trustmark sold $1.179 billion, $1.384 billion and $1.246 billion, respectively, of residential mortgage loans. Pretax gains on these sales totaled $18.9 million in 2017, $20.5 million in 2016 and $18.0 million in 2015. Trustmark receives annual servicing fee income approximating 0.33% of the outstanding balance of the underlying loans, which totaled $21.4 million in 2017, $20.4 million in 2016 and $19.3 million in 2015. The pretax gains on the sale of residential mortgage loans and the annual servicing fee are both recorded to noninterest income in mortgage banking, net in the accompanying consolidated statements of income. The investors and the securitization trusts have no recourse to the assets of Trustmark for failure of debtors to pay when due. The table below details the mortgage loans sold and serviced for others at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Federal National Mortgage Association $ 4,128,614 $ 3,992,349 Government National Mortgage Association 2,421,456 2,291,398 Federal Home Loan Mortgage Corporation 47,071 55,006 Other 26,864 32,589 Total mortgage loans sold and serviced for others $ 6,624,005 $ 6,371,342 Trustmark is subject to losses in its loan servicing portfolio due to loan foreclosures. Trustmark has obligations to either repurchase the outstanding principal balance of a loan or make the purchaser whole for the economic benefits of a loan if it is determined that the loan sold was in violation of representations or warranties made by Trustmark at the time of the sale, herein referred to as mortgage loan servicing putback expenses. Such representations and warranties typically include those made regarding loans that had missing or insufficient file documentation, loans that do not meet investor guidelines, loans in which the appraisal does not support the value and/or loans obtained through fraud by the borrowers or other third parties. Generally, putback requests may be made until the loan is paid in full. However, mortgage loans delivered to Federal National Mortgage Association (FNMA) and Federal Home Loan Mortgage Corporation (FHLMC) on or after January 1, 2013 are subject to the Lending and Selling Representations and Warranties Framework updated in May 2014, which provides certain instances in which FNMA and FHLMC will not exercise their remedies, including a putback request, for breaches of certain selling representations and warranties, such as payment history and quality control review. When a putback request is received, Trustmark evaluates the request and takes appropriate actions based on the nature of the request. Trustmark is required by FNMA and FHLMC to provide a response to putback requests within 60 days of the date of receipt. Currently, putback requests primarily relate to 2009 through 2013 vintage mortgage loans. The total mortgage loan servicing putback expenses were included in other expense. Changes in the reserve for mortgage loan servicing putback expense for mortgage loans were as follows for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Balance at beginning of period $ 1,130 $ 1,685 $ 1,170 Provision for putback expenses (836 ) 420 315 Other (1) 706 (975 ) 200 Balance at end of period $ 1,000 $ 1,130 $ 1,685 (1) Includes fair value adjustments for loans transferred due to underwriting issues as well as adjustments based on Trustmark’s mortgage loan servicing putback reserve analysis. There is inherent uncertainty in reasonably estimating the requirement for reserves against potential future mortgage loan servicing putback expenses. Future putback expenses are dependent on many subjective factors, including the review procedures of the purchasers and the potential refinance activity on loans sold with servicing released and the subsequent consequences under the representations and warranties. Trustmark believes that it has appropriately reserved for potential mortgage loan servicing putback requests.

Goodwill and Identifiable Intan

Goodwill and Identifiable Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Identifiable Intangible Assets	Note 9 – Goodwill and Identifiable Intangible Assets Goodwill The table below illustrates goodwill by segment for the years ended December 31, 2017 and 2016 ($ in thousands): General Banking Insurance Total Balance as of January 1, 2016 $ 321,132 $ 45,024 $ 366,156 Adjustment during 2016 — — — Balance as of December 31, 2016 321,132 45,024 366,156 Goodwill from Reliance merger during 2017 13,471 — 13,471 Balance as of December 31, 2017 $ 334,603 $ 45,024 $ 379,627 Trustmark’s General Banking Division delivers a full range of banking services to consumer, corporate, small and middle-market businesses through its extensive branch network. During 2017, Trustmark recorded $13.5 million as goodwill from its merger with Reliance. The Insurance Division includes TNB’s wholly-owned retail insurance subsidiary that offers a diverse mix of insurance products and services. Trustmark performed goodwill impairment tests for the General Banking and Insurance Divisions during 2017, 2016 and 2015. Based on these tests, Trustmark concluded that the fair value of both the General Banking and Insurance Divisions substantially exceeded the book value and no impairment charge was required. Identifiable Intangible Assets At December 31, 2017 and 2016, identifiable intangible assets consisted of the following ($ in thousands): December 31, 2017 December 31, 2016 Gross Accumulated Net Carrying Gross Carrying Accumulated Net Carrying Amount Amortization Amount Amount Amortization Amount Core deposit intangibles $ 87,674 $ 73,494 $ 14,180 $ 85,824 $ 67,843 $ 17,981 Insurance intangibles 13,824 12,026 1,798 13,824 11,615 2,209 Banking charters 1,325 943 382 1,325 877 448 Borrower relationship intangible 690 690 — 690 648 42 Total $ 103,513 $ 87,153 $ 16,360 $ 101,663 $ 80,983 $ 20,680 Trustmark recorded $6.2 million of amortization of identifiable intangible assets in 2017, $6.9 million in 2016 and $7.8 million in 2015. Trustmark estimates that amortization expense for identifiable intangible assets will be $5.2 million in 2018, $4.0 million in 2019, $2.7 million in 2020, $1.9 million in 2021 and $1.1 million in 2022. Trustmark continually evaluates whether events and circumstances have occurred that indicate that identifiable intangible assets have become impaired. Measurement of any impairment of such identifiable intangible assets is based on the fair values of those assets. There were no impairment losses on identifiable intangible assets recorded during 2017, 2016 or 2015. The following table illustrates the carrying amounts and remaining weighted-average amortization periods of identifiable intangible assets as of December 31, 2017 ($ in thousands): Remaining Weighted- Average Net Carrying Amortization Amount Period in Core deposit intangibles $ 14,180 5.2 Insurance intangibles 1,798 15.3 Banking charters 382 5.7 Total $ 16,360 6.3

Other Real Estate

Other Real Estate	12 Months Ended
	Dec. 31, 2017
Other Real Estate And Foreclosed Assets [Abstract]
Other Real Estate	Note 10 – Other Real Estate At December 31, 2017, Trustmark’s geographic other real estate distribution was concentrated primarily in its five key market regions: Alabama, Florida, Mississippi, Tennessee and Texas. The ultimate recovery of a substantial portion of the carrying amount of other real estate is susceptible to changes in market conditions in these areas. For the periods presented, changes and gains, net on other real estate were as follows ($ in thousands): Years Ended December 31, 2017 2016 (1) 2015 (1) Balance at beginning of period $ 62,051 $ 78,828 $ 98,569 Additions (2) 9,235 24,525 32,782 Disposals (24,762 ) (36,801 ) (48,352 ) Write-downs (3,296 ) (4,501 ) (4,171 ) Balance at end of period $ 43,228 $ 62,051 $ 78,828 Gain, net on the sale of other real estate included in other real estate expense $ 2,087 $ 7,031 $ 4,041 (1) The changes and gains, net on other real estate for the years ended December 31, 2016 and 2015 include covered other real estate. (2) For the year ended December 31, 2017, additions to other real estate included $475 thousand of other real estate acquired in the Reliance merger on April 7, 2017. At December 31, 2017 and 2016, other real estate by type of property consisted of the following ($ in thousands): December 31, 2017 2016 Construction, land development and other land properties $ 27,491 $ 36,871 1-4 family residential properties 5,081 7,926 Nonfarm, nonresidential properties 10,468 16,817 Other real estate properties 188 437 Total other real estate $ 43,228 $ 62,051 At December 31, 2017 and 2016, other real estate by geographic location consisted of the following ($ in thousands): December 31, 2017 2016 Alabama $ 11,714 $ 15,989 Florida 13,937 22,582 Mississippi (1) 14,260 15,646 Tennessee (2) 2,535 6,183 Texas 782 1,651 Total other real estate $ 43,228 $ 62,051 (1) Mississippi includes Central and Southern Mississippi Regions (2) Tennessee includes Memphis, Tennessee and Northern Mississippi Regions

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Deposits	Note 11 – Deposits At December 31, 2017 and 2016, deposits consisted of the following ($ in thousands): December 2017 2016 Noninterest-bearing demand $ 2,978,074 $ 2,973,238 Interest-bearing demand 2,432,814 1,875,312 Savings 3,408,183 3,586,369 Time 1,758,441 1,621,093 Total $ 10,577,512 $ 10,056,012 Interest expense on deposits by type consisted of the following for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Interest-bearing demand $ 6,820 $ 3,297 $ 3,235 Savings 6,047 2,657 2,547 Time 9,850 6,794 6,816 Total $ 22,717 $ 12,748 $ 12,598 Time deposits that exceed the FDIC insurance limit of $250 thousand totaled $342.3 million and $229.9 million at December 31, 2017 and 2016, respectively. The maturities of time deposits of $100 thousand or more at December 31, 2017 and 2016 are as follows ($ in thousands): December 2017 2016 3 months or less $ 203,679 $ 150,991 Over 3 months through 6 months 183,679 147,089 Over 6 months through 12 months 276,944 204,944 Over 12 months 179,237 179,469 Total $ 843,539 $ 682,493 The maturities of interest-bearing deposits at December 31, 2017, are as follows ($ in thousands): 2018 $ 1,356,448 2019 268,989 2020 73,745 2021 23,191 2022 and thereafter 36,068 Total time deposits 1,758,441 Interest-bearing deposits with no stated maturity 5,840,997 Total interest-bearing deposits $ 7,599,438

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowings	Note 12 - Borrowings Securities Sold Under Repurchase Agreements Trustmark utilizes securities sold under repurchase agreements as a source of borrowing in connection with overnight repurchase agreements offered to commercial deposit customers by using its unencumbered investment securities as collateral. Trustmark accounts for its securities sold under repurchase agreements as secured borrowings in accordance with FASB ASC Topic 860-30, “Transfers and Servicing – Secured Borrowing and Collateral.” Securities sold under repurchase agreements are stated at the amount of cash received in connection with the transaction. Trustmark monitors collateral levels on a continual basis and may be required to provide additional collateral based on the fair value of the underlying securities. Securities sold under repurchase agreements are secured by securities with a carrying amount of $200.9 million and $284.4 million at December 31, 2017 and 2016, respectively. As of December 31, 2017, all repurchase agreements were short-term and consisted primarily of sweep repurchase arrangements, under which excess deposits are “swept” into overnight repurchase agreements with Trustmark. The following table presents the securities sold under repurchase agreements by collateral pledged at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Mortgage-backed securities Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA $ 68,246 $ 75,795 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 50,448 51,212 Total securities sold under repurchase agreements $ 118,694 $ 127,007 Short-Term Borrowings At December 31, 2017 and 2016, short-term borrowings consisted of the following ($ in thousands): December 2017 2016 FHLB advances $ 900,013 $ 700,008 Serviced GNMA loans eligible for repurchase 48,211 43,925 Other 22,825 25,845 Total short-term borrowings $ 971,049 $ 769,778 At December 31, 2017, Trustmark had four outstanding short-term FHLB advances totaling $900.0 million with the FHLB of Dallas. Two of these outstanding advances with the FHLB of Dallas had fixed interest rates 1.44% and 1.48% and balances of $250.0 million and $150.0 million, respectively. At December 31, 2017, these two fixed rate advances had a weighted-average remaining maturity of 58 days with a weighted-average cost of 1.45% during 2017. At December 31, 2017, Trustmark had two outstanding short-term FHLB advances with a balance of $250.0 million each with the FHLB of Dallas that reprice on a monthly basis and are set to mature on May 25, 2018 and October 19, 2018. These advances have a weighted-average remaining maturity of 219 days and had a weighted-average cost of 1.20% during 2017. Trustmark had three outstanding short-term FHLB advances totaling $700.0 million with the FHLB of Dallas at December 31, 2016. Two of these outstanding advances with the FHLB of Dallas had fixed interest rates of 0.55% and 0.80% and balances of $100.0 million each. At December 31, 2016, these two fixed rate advances had a weighted-average remaining maturity of seven days with a weighted-average cost of 0.68% during 2016. At December 31, 2016, Trustmark had one outstanding short-term FHLB advance with a balance of $500.0 million with the FHLB of Dallas that repriced on a monthly basis and matured on December 20, 2017. At December 31, 2017 and 2016, Trustmark had $1.771 billion and $1.511 billion, respectively, available in additional short and long-term borrowing capacity from the FHLB of Dallas. At both December 31, 2017 and 2016, Trustmark had one outstanding short-term FHLB advance with the FHLB of Atlanta, which was assumed through the BancTrust merger. The short-term FHLB advance outstanding at December 31, 2017 had a balance of $13 thousand with a fixed interest rate of 6.12% and a remaining maturity of 72 days. The short-term FHLB advance outstanding at December 31, 2016 had a balance of $8 thousand with a fixed interest rate of 6.50% and a remaining maturity of 310 days. Trustmark has a non-member status and no additional borrowing capacity with the FHLB of Atlanta. Interest expense on short-term FHLB advances totaled $11.4 million in 2017, $1.8 million in 2016 and $727 thousand in 2015. Long-Term FHLB Advances At December 31, 2017, Trustmark had no outstanding long-term FHLB advances with the FHLB of Dallas. At December 31, 2016, Trustmark had one outstanding long-term FHLB advance with the FHLB of Dallas totaling $250.0 million. The long-term FHLB advance outstanding at December 31, 2016 repriced on a monthly basis and is set to mature on May 25, 2018. At December 31, 2016, this advance had a remaining maturity of 1.4 years and had an average cost of 0.24% during 2016. At December 31, 2017, Trustmark had two outstanding long-term FHLB advances totaling $946 thousand with the FHLB of Atlanta, compared to three outstanding long-term FHLB advances totaling $1.0 million with the FHLB of Atlanta at December 31, 2016. All of these advances were assumed through the BancTrust merger. The advances outstanding had fixed interest rates of 0.08% and 0.75% with outstanding balances of $171 thousand to $775 thousand at December 31, 2017. At December 31, 2017, these advances had a weighted-average remaining maturity of 4.44 years with a weighted-average cost of 0.63% during 2017. At December 31, 2016, the three outstanding long-term FHLB advances with the FHLB of Atlanta had interest rates ranging from 0.08% to 6.12% with outstanding balances ranging from $38 thousand to $800 thousand. At December 31, 2016, the outstanding long-term advances had a weighted-average remaining maturity of 5.32 years with a weighted-average cost of 0.82% during 2016. There was no fair market value adjustment associated with the BancTrust merger included in the long-term FHLB advances at December 31, 2017, compared to a fair mark value adjustment of $1 thousand at December 31, 2016. Trustmark’s long-term FHLB advances are collateralized by securities held in safekeeping with the FHLB of Atlanta. Trustmark incurred $566 thousand of interest expense on long-term FHLB advances in 2017, compared to $2.1 million of interest expense in 2016 and $49 thousand of interest expense in 2015. Junior Subordinated Debt Securities On August 18, 2006, Trustmark completed a private placement of $60.0 million of trust preferred securities through a newly formed Delaware trust affiliate, Trustmark Preferred Capital Trust I (the Trust). The trust preferred securities mature September 30, 2036, are redeemable at Trustmark’s option and bear interest at a variable rate per annum equal to the three-month LIBOR plus 1.72%. Under applicable regulatory guidelines, these trust preferred securities qualify as Tier 1 capital. The proceeds from the sale of the trust preferred securities were used by the Trust to purchase $61.9 million in aggregate principal amount of Trustmark’s junior subordinated debentures. The debentures were issued pursuant to a Junior Subordinated Indenture, dated August 18, 2006, between Trustmark, as issuer, and Wilmington Trust Company, National Association, as trustee. Like the trust preferred securities, the debentures bear interest at a variable rate per annum equal to the three-month LIBOR plus 1.72% and mature on September 30, 2036. The debentures may be redeemed at Trustmark’s option at any time. The interest payments by Trustmark will be used to pay the quarterly distributions payable by the Trust to the holder of the trust preferred securities. However, so long as no event of default has occurred under the debentures, Trustmark may defer interest payments on the debentures (in which case the Trust will also defer distributions otherwise due on the trust preferred securities) for up to 20 consecutive quarters. The debentures are subordinated to the prior payment of any other indebtedness of Trustmark that, by its terms, is not similarly subordinated. The trust preferred securities are recorded as a long-term liability on Trustmark’s balance sheet; however, for regulatory purposes the trust preferred securities are treated as Tier 1 capital under the rules of the FRB, Trustmark’s primary federal regulatory agency. Trustmark also entered into a Guarantee Agreement, dated August 18, 2006, pursuant to which it has agreed to guarantee the payment by the Trust of distributions on the trust preferred securities and the payment of principal of the trust preferred securities when due, either at maturity or on redemption, but only if and to the extent that the Trust fails to pay distributions on or principal of the trust preferred securities after having received interest payments or principal payments on the junior subordinated debentures from Trustmark for the purpose of paying those distributions or the principal amount of the trust preferred securities. As defined in applicable accounting standards, the Trust, a wholly-owned subsidiary of Trustmark, is considered a variable interest entity for which Trustmark is not the primary beneficiary. Accordingly, the accounts of the Trust are not included in Trustmark’s consolidated financial statements. At December 31, 2017 and 2016, assets for the Trust totaled $61.9 million, resulting from the investment in junior subordinated debentures issued by Trustmark. Liabilities and shareholder’s equity for the Trust also totaled $61.9 million at December 31, 2017 and 2016, resulting from the issuance of trust preferred securities in the amount of $60.0 million as well as $1.9 million in common securities issued to Trustmark. During 2017, net income for the Trust equaled $55 thousand resulting from interest income from the junior subordinated debt securities issued by Trustmark to the Trust, compared with net income of $45 thousand during 2016 and $38 thousand during 2015. Dividends issued to Trustmark by the Trust during 2017 totaled $55 thousand, compared to $45 thousand during 2016 and $38 thousand during 2015.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 13 – Income Taxes The income tax provision included in the consolidated statements of income was as follows for the periods presented ($ in thousands): Years Ended December 31, Current 2017 2016 2015 Federal $ 16,959 $ 10,355 $ 18,448 State 5,687 2,698 2,166 Deferred Federal 7,280 15,647 12,865 State 1,820 2,353 1,935 Income tax provision excluding deferred tax asset revaluation and reversal of valuation allowance 31,746 31,053 35,414 Deferred tax expense (benefit) - re-measurement of deferred tax assets 25,619 — — Deferred tax expense (benefit) - reversal of valuation allowance (8,650 ) — — Income tax provision $ 48,715 $ 31,053 $ 35,414 Trustmark maintained a valuation allowance for deferred tax assets of $8.7 million at December 31, 2016 that was related to unrealized built-in losses from a prior acquisition. Trustmark has determined that based on the weight of the available evidence that it is more likely than not that all deferred tax assets will be realized as of December 31, 2017. Therefore, the valuation allowance was reversed as of December 31, 2017, resulting in a decrease of $8.7 million to income tax expense for the year. The re-measurement of the deferred tax assets and liabilities during 2017 resulted from the enactment of the Tax Reform Act, which was signed into law on December 22, 2017. Under the Tax Reform Act, corporate statutory income tax rates were reduced from 35.0% to 21.0% effective January 1, 2018. Trustmark re-measured its deferred tax assets and liabilities to reflect the future realization of these assets and liabilities at the lower tax rate. This re-measurement resulted in an increase to tax expense and a decrease to the net deferred tax asset of $25.6 million for the year ended December 31, 2017. For the periods presented, the income tax provision differs from the amount computed by applying the statutory federal income tax rate of 35.0% to income before income taxes as a result of the following ($ in thousands): Years Ended December 31, 2017 2016 2015 Income tax computed at statutory tax rate $ 54,021 $ 48,812 $ 53,008 Tax exempt interest (7,611 ) (6,780 ) (5,908 ) Nondeductible interest expense 407 201 119 State income taxes, net 3,697 1,754 1,408 Income tax credits, net (15,793 ) (16,183 ) (15,283 ) Death benefit gains (3,268 ) — — Reversal of valuation allowance (8,650 ) — — Re-measurement of deferred tax assets 25,619 — — Other 293 3,249 2,070 Income tax provision $ 48,715 $ 31,053 $ 35,414 Temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities gave rise to the following net deferred tax assets at December 31, 2017 and 2016, which are included in other assets ($ in thousands): December 31, 2017 2016 Deferred tax assets: Loan purchase accounting $ 3,638 $ 9,341 Other real estate 13,403 25,750 Allowance for loan losses 20,203 31,618 Deferred compensation 15,184 21,893 Realized built-in losses 12,932 18,699 Securities 4,869 9,256 Pension and other postretirement benefit plans 5,453 15,545 Interest on nonaccrual loans 774 2,093 Unrealized losses on securities available for sale 5,874 3,629 Stock-based compensation 2,067 3,031 Federal carryovers 4,569 — Other 8,964 13,731 Gross deferred tax asset 97,930 154,586 Valuation allowance — (8,650 ) Deferred tax asset net of valuation allowance 97,930 145,936 Deferred tax liabilities: Goodwill and other identifiable intangibles 16,729 25,666 Premises and equipment 11,877 19,391 Mortgage servicing rights 9,964 12,159 Securities 1,345 1,697 Leases — 60 Other 5,040 6,891 Gross deferred tax liability 44,955 65,864 Net deferred tax asset $ 52,975 $ 80,072 Trustmark has completed its accounting for the effects of the Tax Reform Act on its deferred tax assets and liabilities. In the course of normal operations, Trustmark is required to make reasonable estimates for certain tax items which could not be fully determined at year-end, but will be finalized when its tax return is filed in October 2018. However, Trustmark does not believe that any adjustments resulting from the finalization of the tax return will have a material impact on its financial statements. The following table provides a summary of the changes during the 2017 calendar year in the amount of unrecognized tax benefits that are included in other liabilities in the consolidated balance sheet ($ in thousands): Balance at January 1, 2017 $ 1,734 Increases due to tax positions taken during the current year 303 Decreases due to tax positions taken during a prior year (853 ) Decreases due to the lapse of applicable statute of limitations during the current year (79 ) Decreases due to settlements with taxing authorities during the current year — Balance at December 31, 2017 $ 1,105 Accrued interest, net of federal benefit, at December 31, 2017 $ 217 Unrecognized tax benefits that would impact the effective tax rate, if recognized, at December 31, 2017 $ 883 Interest and penalties related to unrecognized tax benefits, if any, are recorded in income tax expense. With limited exception, Trustmark is no longer subject to U.S. federal, state and local audits by tax authorities for 2011 and earlier tax years. Trustmark does not anticipate a significant change to the total amount of unrecognized tax benefits within the next twelve months.

Defined Benefit and Other Postr

Defined Benefit and Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Defined Benefit and Other Postretirement Benefits	Note 14 – Defined Benefit and Other Postretirement Benefits Qualified Pension Plans Trustmark Capital Accumulation Plan Trustmark maintained a noncontributory tax-qualified defined benefit pension plan titled the Trustmark Capital Accumulation Plan (the “Plan”) in which substantially all associates who began employment prior to 2007 participated. The Plan provided for retirement benefits based on the length of credited service and final average compensation, as defined in the Plan, which vested upon three years of service. Benefit accruals under the Plan were frozen in 2009, with the exception of benefit accruals for certain employees of acquired financial institutions covered through plans that were subsequently merged into the Plan. Other than certain employees of acquired financial institutions, associates have not earned additional benefits, except for interest as required by law, since the Plan was frozen. Current and former associates who participated in the Plan retained their right to receive benefits that accrued before the Plan was frozen. As previously reported, on July 26, 2016 the Board of Directors of Trustmark authorized the termination of the Plan, effective as of December 31, 2016. As a result of the termination of the Plan, each participant became fully vested in their accrued benefits under the Plan. During the second quarter of 2017, Trustmark fully funded the Plan on a termination basis by contributing additional assets in the amount of $17.6 million in accordance with Internal Revenue Service (IRS) and Pension Benefit Guaranty Corporation requirements. Participants in the Plan elected to receive either a lump sum cash payment or annuity payments under a group annuity contract purchased from an insurance carrier. Final distributions were made to participants from plan assets and a one-time pension settlement expense was recognized totaling $17.6 million. Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions To satisfy commitments made by Trustmark to associates covered through plans obtained in acquisitions and subsequently merged into the Plan (collectively, the “Continuing Associates”), on July 26, 2016, the Board of Directors of Trustmark also approved the spin-off of the portion of the Plan associated with the accrued benefits of the Continuing Associates into a new plan titled the Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions (the “Continuing Plan”), effective as of December 30, 2016, immediately prior to the termination of the Plan. The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s tax-qualified defined benefit pension plans (the Continuing Plan and the Plan) for the periods presented ($ in thousands): December 31, 2017 2016 Change in benefit obligation: Benefit obligation, beginning of year $ 75,900 $ 91,403 Service cost 253 428 Interest cost 1,461 3,355 Actuarial loss (gain) 391 (893 ) Benefits paid for the Plan (68,583 ) (18,393 ) Settlement loss 680 — Benefit obligation, end of year $ 10,102 $ 75,900 Change in plan assets: Fair value of plan assets, beginning of year $ 54,734 $ 74,137 Actual return on plan assets 481 (1,079 ) Employer contributions 17,964 69 Benefit payments for the Plan (68,583 ) (18,393 ) Fair value of plan assets, end of year $ 4,596 $ 54,734 Funded status at end of year - net liability $ (5,506 ) $ (21,166 ) Amounts recognized in accumulated other comprehensive loss: Net loss - amount recognized $ 3,187 $ 21,355 Years Ended December 31, 2017 2016 2015 Net periodic benefit cost: Service cost $ 253 $ 428 $ 513 Interest cost 1,461 3,355 3,461 Expected return on plan assets (317 ) (2,897 ) (5,187 ) Recognized net loss due to defined benefit plan termination 17,662 — — Recognized net loss due to lump sum settlements — 3,906 2,221 Recognized net actuarial loss 1,414 2,749 3,878 Net periodic benefit cost $ 20,473 $ 7,541 $ 4,886 Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes: Net loss - Total recognized in other comprehensive income (loss) $ (18,168 ) $ (3,572 ) $ (3,173 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 2,305 $ 3,969 $ 1,713 Weighted-average assumptions as of end of year: Discount rate for benefit obligation 3.32 % 3.71 % 3.86 % Discount rate for net periodic benefit cost 3.71 % 3.86 % 3.57 % Expected long-term return on plan assets 5.00 % 4.25 % 7.00 % Plan Assets The weighted-average asset allocations by asset category are presented below for the Continuing Plan at December 31, 2017 and 2016, and for the Plan at December 31, 2016. No assets remained in the Plan at December 31, 2017. December 31, 2017 2016 Money market fund 6.0 % 13.0 % U.S. Treasuries — 87.0 % Exchange traded funds: Equity securities 48.0 % — Fixed income 32.0 % — International 14.0 % — Total 100.0 % 100.0 % The strategic objective of the investments of the assets in the Continuing Plan aims to provide long-term capital growth with moderate income. The allocation is managed on a total return basis with the average participant age in mind. It is constructed with an intermediate investment time frame with a moderate to high risk tolerance or a long-term investment time frame with a low to moderate risk tolerance. The plan allocation is typically balanced between equity and fixed income. The equity exposure has the potential to earn a return greater than inflation while the fixed income exposure may reduce the risk and volatility of the portfolio to which the equity allocation contributes. The strategic objective of the investments of the assets in the Plan was changed significantly after the decision to terminate the Plan. The Plan was no longer managed on a total return basis. The Plan was managed with as little market value fluctuation as possible. Given the known fixed actuarial discount rate used until termination to match liabilities, the asset allocation of the Plan was changed to reflect a very conservative posture. Money market and individual U.S. Treasury securities were used solely to maintain a stable market value and achieve a small level of interest income. The Treasury securities matured at or before the projected distribution date. Similarly, a money market allocation was maintained for liquidity purposes due to monthly reoccurring distributions and lump sum distributions until final termination. Fair Value Measurements At this time, Trustmark presents no fair values that are derived through internal modeling. Should positions requiring fair valuation arise that are not relevant to existing methodologies, Trustmark will make every reasonable effort to obtain market participant assumptions, or independent evaluation. The following table sets forth by level, within the fair value hierarchy, the Continuing Plan’s assets measured at fair value at December 31, 2017 and 2016 and the Plan’s assets at December 31, 2016 ($ in thousands): December 31, 2017 Total Level 1 Level 2 Level 3 Money market fund $ 269 $ 269 $ — $ — Exchange traded funds: Equity securities 2,199 2,199 — — Fixed income 1,462 1,462 — — International 666 666 — — Total assets at fair value $ 4,596 $ 4,596 $ — $ — December 31, 2016 Total Level 1 Level 2 Level 3 Money market fund $ 6,859 $ 6,859 $ — $ — U.S. Treasuries 47,875 47,875 — — Total assets at fair value $ 54,734 $ 54,734 $ — $ — There have been no changes in the methodologies used in estimating the fair value of plan assets at December 31, 2017. The money market fund approximates fair value due to its immediate maturity. The preceding methods described may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, although Trustmark believes their valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date. Contributions The range of potential contributions to the Continuing Plan is determined annually by the Continuing Plan’s actuary in accordance with applicable IRS rules and regulations. Trustmark’s policy is to fund amounts that are sufficient to satisfy the annual minimum funding requirements and do not exceed the maximum that is deductible for federal income tax purposes. The actual amount of the contribution is determined annually based on the Continuing Plan’s funded status and return on plan assets as of the measurement date, which is December 31. For the plan year ending December 31, 2017, Trustmark’s minimum required contribution to the Continuing Plan was $113 thousand. During 2017, Trustmark contributed $200 thousand to the Continuing Plan for the plan year ending December 31, 2017. For the plan year ending December 31, 2018, Trustmark’s minimum required contribution to the Continuing Plan is expected to be $175 thousand; however, Management and the Board of Directors of Trustmark will monitor the Continuing Plan throughout 2018 to determine any additional funding requirements by the plan’s measurement date. For the plan year ending December 31, 2016, Trustmark’s minimum required contribution to the Plan was zero. Since the Plan was terminated, there were no additional contributions required other than amounts necessary to facilitate the Plan termination. Estimated Future Benefit Payments and Other Disclosures The following table presents the expected benefit payments, which reflect expected future service, for the Continuing Plan ($ in thousands): Year Amount 2018 $ 196 2019 282 2020 333 2021 394 2022 453 2023 - 2027 2,961 Amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during 2018 include a net loss of $571 thousand. Supplemental Retirement Plans Trustmark maintains a nonqualified supplemental retirement plan covering key executive officers and senior officers as well as directors who have elected to defer fees. The plan provides for retirement and/or death benefits based on a participant’s covered salary or deferred fees. Although plan benefits may be paid from Trustmark’s general assets, Trustmark has purchased life insurance contracts on the participants covered under the plan, which may be used to fund future benefit payments under the plan. The measurement date for the plan is December 31. As a result of mergers prior to 2014, Trustmark became the administrator of small nonqualified supplemental retirement plans, for which the plan benefits were frozen prior to the merger date. The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s nonqualified supplemental retirement plans ($ in thousands): December 31, 2017 2016 Change in benefit obligation: Benefit obligation, beginning of year $ 58,495 $ 57,766 Service cost 141 295 Interest cost 2,103 2,223 Actuarial loss 642 1,537 Benefits paid (3,451 ) (3,326 ) Benefit obligation, end of year $ 57,930 $ 58,495 Change in plan assets: Fair value of plan assets, beginning of year $ — $ — Employer contributions 3,451 3,326 Benefit payments (3,451 ) (3,326 ) Fair value of plan assets, end of year $ — $ — Funded status at end of year - net liability $ (57,930 ) $ (58,495 ) Amounts recognized in accumulated other comprehensive loss: Net loss $ 17,514 $ 17,739 Prior service cost 1,109 1,359 Amounts recognized $ 18,623 $ 19,098 Years Ended December 31, 2017 2016 2015 Net periodic benefit cost: Service cost $ 141 $ 295 $ 431 Interest cost 2,103 2,223 2,082 Amortization of prior service cost 250 250 250 Recognized net actuarial loss 866 864 992 Net periodic benefit cost $ 3,360 $ 3,632 $ 3,755 Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes: Net (gain) loss $ (224 ) $ (810 ) $ (2,694 ) Amortization of prior service cost (250 ) (250 ) (250 ) Total recognized in other comprehensive income (loss) $ (474 ) $ (1,060 ) $ (2,944 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 2,886 $ 2,572 $ 811 Weighted-average assumptions as of end of year: Discount rate for benefit obligation 3.32 % 3.71 % 3.86 % Discount rate for net periodic benefit cost 3.71 % 3.86 % 3.57 % Estimated Supplemental Retirement Plan Payments and Other Disclosures The following table presents the expected benefits payments for Trustmark’s supplemental retirement plans ($ in thousands): Year Amount 2018 $ 3,475 2019 3,591 2020 4,047 2021 4,105 2022 4,262 2023 - 2027 19,230 Amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during 2018 include a loss of $884 thousand and prior service cost of $250 thousand. Other Benefit Plans Defined Contribution Plan Trustmark provides associates with a self-directed 401(k) retirement plan that allows associates to contribute a percentage of base pay, within limits provided by the Internal Revenue Code and accompanying regulations, into the plan. Trustmark matches 100% of associate contributions to the plan based on the amount of each participant’s contributions up to a maximum of 6% of eligible compensation. Associates may become eligible to make elective deferral contributions the first of the month following 30 days of employment. Eligible associates must complete one year of service in order to vest in Trustmark’s matching contributions. Trustmark’s contributions to this plan were $7.5 million in 2017, $7.2 million in 2016 and $7.0 million in 2015.

Stock and Incentive Compensatio

Stock and Incentive Compensation Plans	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock and Incentive Compensation Plans	Note 15 – Stock and Incentive Compensation Plans Trustmark has granted stock and incentive compensation awards subject to the provisions of the Stock and Incentive Compensation Plan (the Stock Plan). Current outstanding and future grants of stock and incentive compensation awards are subject to the provisions of the Stock Plan, which is designed to provide flexibility to Trustmark regarding its ability to motivate, attract and retain the services of key associates and directors. The Stock Plan also allows Trustmark to grant nonqualified stock options, incentive stock options, stock appreciation rights, restricted stock, restricted stock units and performance units to key associates and directors. At December 31, 2017, the maximum number of shares of Trustmark’s common stock available for issuance under the Plan was 1,110,739 shares. Restricted Stock Grants Performance Awards Trustmark’s performance awards vest over three years and are granted to Trustmark’s executive and senior management teams. Performance awards granted vest based on performance goals of return on average tangible equity and total shareholder return compared to a defined peer group. Performance awards are valued utilizing a Monte Carlo simulation model to estimate fair value of the awards at the grant date. These awards are recognized using the straight-line method over the requisite service period. These awards provide for achievement shares if performance measures exceed 100%. The restricted share agreement provides for voting rights and dividend privileges. The following table summarizes Trustmark’s performance award activity for the periods presented: Years Ended December 31, 2017 2016 2015 Weighted- Weighted- Weighted- Average Average Average Grant-Date Grant-Date Grant-Date Shares Fair Value Shares Fair Value Shares Fair Value Nonvested shares, beginning of year 237,136 $ 26.27 212,309 $ 24.14 181,195 $ 24.98 Granted 58,406 33.31 99,116 20.18 84,899 22.71 Released from restriction (67,279 ) 34.78 (40,888 ) 32.84 (47,360 ) 24.97 Forfeited (14,747 ) 28.42 (33,401 ) 30.01 (6,425 ) 24.97 Nonvested shares, end of year 213,516 $ 25.37 237,136 $ 26.27 212,309 $ 24.14 Time-Vested Awards Trustmark’s time-vested awards vest over three years and are granted to members of Trustmark’s Board of Directors as well as Trustmark’s executive and senior management teams. Time-vested awards are valued utilizing the fair value of Trustmark’s stock at the grant date. These awards are recognized on the straight-line method over the requisite service period. The following table summarizes Trustmark’s time-vested award activity for the periods presented: Years Ended December 31, 2017 2016 2015 Weighted- Weighted- Weighted- Average Average Average Grant-Date Grant-Date Grant-Date Shares Fair Value Shares Fair Value Shares Fair Value Nonvested shares, beginning of year 322,056 $ 22.65 306,657 $ 24.56 263,905 $ 24.66 Granted 105,524 33.79 139,791 20.66 121,314 23.61 Released from restriction (101,289 ) 25.35 (108,241 ) 23.74 (67,087 ) 24.31 Forfeited (5,934 ) 26.52 (16,151 ) 22.24 (11,475 ) 24.22 Nonvested shares, end of year 320,357 $ 25.40 322,056 $ 22.65 306,657 $ 24.56 The following table presents information regarding compensation expense for awards under the Plan for the periods presented ($ in thousands): Weighted Average Life Recognized Compensation Expense Unrecognized of for Years Ended December 31, Compensation Compensation 2017 2016 2015 Expense Expense Performance awards $ 1,387 $ 1,171 $ 1,201 $ 1,783 1.66 Time-vested awards 2,922 2,513 2,467 3,058 1.80 Total $ 4,309 $ 3,684 $ 3,668 $ 4,841

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 16 – Commitments and Contingencies Lending Related Trustmark makes commitments to extend credit and issues standby and commercial letters of credit (letters of credit) in the normal course of business in order to fulfill the financing needs of its customers. The carrying amount of commitments to extend credit and letters of credit approximates the fair value of such financial instruments. Commitments to extend credit are agreements to lend money to customers pursuant to certain specified conditions. Commitments generally have fixed expiration dates or other termination clauses. Because many of these commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The exposure to credit loss in the event of nonperformance by the other party to the commitments to extend credit is represented by the contract amount of those instruments. Trustmark applies the same credit policies and standards as it does in the lending process when making these commitments. The collateral obtained is based upon the nature of the transaction and the assessed creditworthiness of the borrower. At December 31, 2017 and 2016, Trustmark had unused commitments to extend credit of $3.172 billion and $3.131 billion, respectively. Letters of credit are conditional commitments issued by Trustmark to insure the performance of a customer to a third-party. A financial standby letter of credit irrevocably obligates Trustmark to pay a third-party beneficiary when a customer fails to repay an outstanding loan or debt instrument. A performance standby letter of credit irrevocably obligates Trustmark to pay a third-party beneficiary when a customer fails to perform some contractual, nonfinancial obligation. When issuing letters of credit, Trustmark uses the same policies regarding credit risk and collateral which are followed in the lending process. At December 31, 2017 and 2016, Trustmark’s maximum exposure to credit loss in the event of nonperformance by the other party for letters of credit was $104.1 million and $111.3 million, respectively. These amounts consist primarily of commitments with maturities of less than three years, which have an immaterial carrying value. Trustmark holds collateral to support standby letters of credit when deemed necessary. As of December 31, 2017 and 2016, the fair value of collateral held was $28.4 million and $32.7 million, respectively. Lease Commitments Trustmark currently has operating lease commitments for banking premises and equipment, which expire from 2018 to 2038. It is expected that certain leases will be renewed, or equipment replaced, as leases expire. Rental expense totaled $9.3 million in 2017, $9.8 million in 2016 and $9.3 million in 2015. At December 31, 2017, future minimum rental commitments under non-cancellable operating leases are as follows ($ in thousands): Year Amount 2018 12,031 2019 10,436 2020 6,642 2021 5,197 2022 5,039 Thereafter 28,518 Total $ 67,863 Legal Proceedings Trustmark’s wholly-owned subsidiary, TNB, has been named as a defendant in three lawsuits related to the collapse of the Stanford Financial Group. The first is a purported class action complaint that was filed on August 23, 2009 in the District Court of Harris County, Texas, by Peggy Roif Rotstain, Guthrie Abbott, Catherine Burnell, Steven Queyrouze, Jaime Alexis Arroyo Bornstein and Juan C. Olano (collectively, Class Plaintiffs), on behalf of themselves and all others similarly situated, naming TNB and four other financial institutions unaffiliated with Trustmark as defendants. The complaint seeks to recover (i) alleged fraudulent transfers from each of the defendants in the amount of fees and other monies received by each defendant from entities controlled by R. Allen Stanford (collectively, the Stanford Financial Group) and (ii) damages allegedly attributable to alleged conspiracies by one or more of the defendants with the Stanford Financial Group to commit fraud and/or aid and abet fraud on the asserted grounds that defendants knew or should have known the Stanford Financial Group was conducting an illegal and fraudulent scheme. Plaintiffs have demanded a jury trial. Plaintiffs did not quantify damages. In November 2009, the lawsuit was removed to federal court by certain defendants and then transferred by the United States Panel on Multidistrict Litigation to federal court in the Northern District of Texas (Dallas) where multiple Stanford related matters are being consolidated for pre-trial proceedings. In May 2010, all defendants (including TNB) filed motions to dismiss the lawsuit. In August 2010, the court authorized and approved the formation of an Official Stanford Investors Committee (OSIC) to represent the interests of Stanford investors and, under certain circumstances, to file legal actions for the benefit of Stanford investors. In December 2011, the OSIC filed a motion to intervene in this action. In September 2012, the district court referred the case to a magistrate judge for hearing and determination of certain pretrial issues. In December 2012, the court granted the OSIC’s motion to intervene, and the OSIC filed an Intervenor Complaint against one of the other defendant financial institutions. In February 2013, the OSIC filed a second Intervenor Complaint that asserts claims against TNB and the remaining defendant financial institutions. The OSIC seeks to recover: (i) alleged fraudulent transfers in the amount of the fees each of the defendants allegedly received from Stanford Financial Group, the profits each of the defendants allegedly made from Stanford Financial Group deposits, and other monies each of the defendants allegedly received from Stanford Financial Group; (ii) damages attributable to alleged conspiracies by each of the defendants with the Stanford Financial Group to commit fraud and/or aid and abet fraud and conversion on the asserted grounds that the defendants knew or should have known the Stanford Financial Group was conducting an illegal and fraudulent scheme; and (iii) punitive damages. The OSIC did not quantify damages. In July 2013, all defendants (including TNB) filed motions to dismiss the OSIC’s claims. In March 2015, the court entered an order authorizing the parties to conduct discovery regarding class certification, staying all other discovery and setting a deadline for the parties to complete briefing on class certification issues. In April 2015, the court granted in part and denied in part the defendants’ motions to dismiss the Class Plaintiffs’ claims and the OSIC’s claims. The court dismissed all of the Class Plaintiffs’ fraudulent transfer claims and dismissed certain of the OSIC’s claims. The court denied the motions by TNB and the other financial institution defendants to dismiss the OSIC’s constructive fraudulent transfer claims. On June 23, 2015, the court allowed the Class Plaintiffs to file a Second Amended Class Action Complaint (SAC), which asserted new claims against TNB and certain of the other defendants for (i) aiding, abetting and participating in a fraudulent scheme, (ii) aiding, abetting and participating in violations of the Texas Securities Act, (iii) aiding, abetting and participating in breaches of fiduciary duty, (iv) aiding, abetting and participating in conversion and (v) conspiracy. On July 14, 2015, the defendants (including TNB) filed motions to dismiss the SAC and to reconsider the court’s prior denial to dismiss the OSIC’s constructive fraudulent transfer claims against TNB and the other financial institutions that are defendants in the action. On July 27, 2016, the court denied the motion by TNB and the other financial institution defendants to dismiss the SAC and also denied the motion by TNB and the other financial institution defendants to reconsider the court’s prior denial to dismiss the OSIC’s constructive fraudulent transfer claims. On August 24, 2016, TNB filed its answer to the SAC. On October 20, 2017, the OSIC filed a motion seeking an order lifting the discovery stay and establishing a trial schedule. On November 7, 2017, the court denied the OSIC's motion seeking class certification and designation of class representatives and counsel, finding that common issues of fact did not predominate. The court granted the OSIC's motion to lift the discovery stay that it had previously ordered. The second Stanford-related lawsuit was filed on December 14, 2009 in the District Court of Ascension Parish, Louisiana, individually by Harold Jackson, Paul Blaine, Carolyn Bass Smith, Christine Nichols, and Ronald and Ramona Hebert naming TNB (misnamed as Trust National Bank) and other individuals and entities not affiliated with Trustmark as defendants. The complaint seeks to recover the money lost by these individual plaintiffs as a result of the collapse of the Stanford Financial Group (in addition to other damages) under various theories and causes of action, including negligence, breach of contract, breach of fiduciary duty, negligent misrepresentation, detrimental reliance, conspiracy, and violation of Louisiana’s uniform fiduciary, securities, and racketeering laws. The complaint does not quantify the amount of money the plaintiffs seek to recover. In January 2010, the lawsuit was removed to federal court by certain defendants and then transferred by the United States Panel on Multidistrict Litigation to federal court in the Northern District of Texas (Dallas) where multiple Stanford related matters are being consolidated for pre-trial proceedings. On March 29, 2010, the court stayed the case. TNB filed a motion to lift the stay, which was denied on February 28, 2012. In September 2012, the district court referred the case to a magistrate judge for hearing and determination of certain pretrial issues. On April 11, 2016, Trustmark learned that a third Stanford-related lawsuit had been filed on that date in the Superior Court of Justice in Ontario, Canada, by The Toronto-Dominion Bank (“TD Bank”), naming TNB and three other financial institutions not affiliated with Trustmark as defendants. The complaint seeks a declaration specifying the degree to which each of TNB and the other defendants are liable in respect of any loss and damage for which TD Bank is found to be liable in a litigation commenced against TD Bank brought by the Joint Liquidators of Stanford International Bank Limited in the Superior Court of Justice, Commercial List in Ontario, Canada (the “Joint Liquidators’ Action”), as well as contribution and indemnity in respect of any judgment, interest and costs TD Bank is ordered to pay in the Joint Liquidators’ Action. To date, TNB has not been served in connection with this action. TNB’s relationship with the Stanford Financial Group began as a result of Trustmark’s acquisition of a Houston-based bank in August 2006, and consisted of correspondent banking and other traditional banking services in the ordinary course of business. All Stanford-related lawsuits are in pre-trial stages. Trustmark and its subsidiaries are also parties to other lawsuits and other claims that arise in the ordinary course of business. Some of the lawsuits assert claims related to the lending, collection, servicing, investment, trust and other business activities, and some of the lawsuits allege substantial claims for damages. All pending legal proceedings described above are being vigorously contested. In accordance FASB ASC Topic 450-20, “Loss Contingencies,” Trustmark will establish an accrued liability for litigation matters when those matters present loss contingencies that are both probable and reasonably estimable. At the present time, Trustmark believes, based on its evaluation and the advice of legal counsel, that a loss in any such proceeding is not probable and a reasonable estimate cannot reasonably be made.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
Stockholders Equity Note [Abstract]
Shareholders' Equity	Note 17 – Shareholders’ Equity Regulatory Capital Trustmark and TNB are subject to minimum risk-based capital and leverage capital requirements, as described in the section captioned “Capital Adequacy” included in Part I. Item 1. – Business of this report, which are administered by the federal bank regulatory agencies. These capital requirements, as defined by federal regulations, involve quantitative and qualitative measures of assets, liabilities and certain off-balance sheet instruments. Trustmark’s and TNB’s minimum risk-based capital requirements include the phased in capital conservation buffer of 1.250% at December 31, 2017 and 0.625% at December 31, 2016. Accumulated other comprehensive loss, net of tax, is not included in computing regulatory capital. Failure to meet minimum capital requirements can result in certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the financial statements of Trustmark and TNB and limit Trustmark’s and TNB’s ability to pay dividends. As of December 31, 2017, Trustmark and TNB exceeded all applicable minimum capital standards. In addition, Trustmark and TNB met applicable regulatory guidelines to be considered well-capitalized at December 31, 2017. To be categorized in this manner, Trustmark and TNB maintained minimum common equity Tier 1 risk-based capital, Tier 1 risk-based capital, total risk-based capital and Tier 1 leverage ratios as set forth in the accompanying table, and were not subject to any written agreement, order or capital directive, or prompt corrective action directive issued by their primary federal regulators to meet and maintain a specific capital level for any capital measures. There are no significant conditions or events that have occurred since December 31, 2017, which Management believes have affected Trustmark’s or TNB’s present classification. The regulatory capital ratios for December 31, 2017 contain a reclassification adjustment of $8.5 million from accumulated other comprehensive loss to retained earnings as allowed by regulatory agencies in an interagency statement released January 18, 2018 to address disproportionate tax effect in accumulated other comprehensive loss resulting from the recent enactment of the Tax Reform Act and the application of FASB ASC Topic 740. The following table provides Trustmark’s and TNB’s actual regulatory capital amounts and ratios under regulatory capital standards in effect at December 31, 2017 and 2016 ($ in thousands): Actual Regulatory Capital Minimum To Be Well Amount Ratio Requirement Capitalized At December 31, 2017: Common Equity Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,243,240 11.77 % 5.750 % n/a Trustmark National Bank 1,284,575 12.16 % 5.750 % 6.50 % Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,303,238 12.33 % 7.250 % n/a Trustmark National Bank 1,284,575 12.16 % 7.250 % 8.00 % Total Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,384,050 13.10 % 9.250 % n/a Trustmark National Bank 1,365,387 12.93 % 9.250 % 10.00 % Tier 1 Leverage (to Average Assets) Trustmark Corporation $ 1,303,238 9.67 % 4.00 % n/a Trustmark National Bank 1,284,575 9.54 % 4.00 % 5.00 % At December 31, 2016: Common Equity Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,209,927 12.16 % 5.125 % n/a Trustmark National Bank 1,251,329 12.58 % 5.125 % 6.50 % Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,269,660 12.76 % 6.625 % n/a Trustmark National Bank 1,251,329 12.58 % 6.625 % 8.00 % Total Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,352,322 13.59 % 8.625 % n/a Trustmark National Bank 1,333,991 13.41 % 8.625 % 10.00 % Tier 1 Leverage (to Average Assets) Trustmark Corporation $ 1,269,660 9.90 % 4.00 % n/a Trustmark National Bank 1,251,329 9.77 % 4.00 % 5.00 % Dividends on Common Stock Dividends paid by Trustmark are substantially funded from dividends received from TNB. Approval by TNB’s regulators is required if the total of all dividends declared in any calendar year exceeds the total of its net income for that year combined with its retained net income of the preceding two years. TNB will have available in 2018 approximately $87.0 million plus its net income for that year to pay as dividends. Stock Repurchase Program On March 11, 2016, the Board of Directors of Trustmark authorized a stock repurchase program under which $100.0 million of Trustmark’s outstanding common stock may be acquired through March 31, 2019. The shares may be purchased from time to time at prevailing market prices, through open market or privately negotiated transactions, depending on market conditions. Trustmark did not repurchase any of its common stock during the year ended December 31, 2017, compared to approximately 34 thousand shares of its common stock valued at approximately $750 thousand repurchased during the year ended December 31, 2016. Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss The following tables present the net change in the components of accumulated other comprehensive loss and the related tax effects allocated to each component for the years ended December 31, 2017, 2016 and 2015 ($ in thousands). Reclassification adjustments related to securities available for sale are included in securities gains (losses), net in the accompanying consolidated statements of income. The amortization of prior service cost, recognized net loss due to lump sum settlements, change in net actuarial loss and recognized net loss due to defined benefit plan termination for pension and other postretirement benefit plans are included in the computation of net periodic benefit cost (see Note 14 – Defined Benefit and Other Postretirement Benefits for additional details). Reclassification adjustments related to pension and other postretirement benefit plans are included in salaries and employee benefits, defined benefit plan termination and other expense in the accompanying consolidated statements of income. Reclassification adjustments related to the cash flow hedge derivative are included in other interest expense in the accompanying consolidated statements of income. Before Tax Tax Net of Tax Amount Benefit Amount Year Ended December 31, 2017 Securities available for sale and transferred securities: Unrealized holding gains (losses) arising during the period $ (13,994 ) $ 5,353 $ (8,641 ) Reclassification adjustment for net (gains) losses realized in net income (15 ) 6 (9 ) Change in net unrealized holding loss on securities transferred to held to maturity 4,721 (1,806 ) 2,915 Total securities available for sale and transferred securities (9,288 ) 3,553 (5,735 ) Pension and other postretirement benefit plans: Net change in prior service costs 250 (96 ) 154 Change in net actuarial loss 731 (280 ) 451 Recognized net loss due to defined benefit plan termination 17,662 (6,755 ) 10,907 Total pension and other postretirement benefit plans 18,643 (7,131 ) 11,512 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives 198 (76 ) 122 Reclassification adjustment for loss realized in net income 282 (108 ) 174 Total cash flow hedge derivatives 480 (184 ) 296 Total other comprehensive income (loss) $ 9,835 $ (3,762 ) $ 6,073 Year Ended December 31, 2016 Securities available for sale and transferred securities: Unrealized holding gains (losses) arising during the period $ (15,656 ) $ 5,989 $ (9,667 ) Reclassification adjustment for net (gains) losses realized in net income 310 (119 ) 191 Change in net unrealized holding loss on securities transferred to held to maturity 9,830 (3,760 ) 6,070 Total securities available for sale and transferred securities (5,516 ) 2,110 (3,406 ) Pension and other postretirement benefit plans: Net change in prior service costs 250 (96 ) 154 Recognized net loss due to lump sum settlements 3,906 (1,494 ) 2,412 Change in net actuarial loss 476 (182 ) 294 Total pension and other postretirement benefit plans 4,632 (1,772 ) 2,860 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives (369 ) 141 (228 ) Reclassification adjustment for loss realized in net income 599 (229 ) 370 Total cash flow hedge derivatives 230 (88 ) 142 Total other comprehensive income (loss) $ (654 ) $ 250 $ (404 ) Year Ended December 31, 2015 Securities available for sale and transferred securities: Unrealized holding gains (losses) arising during the period $ (16,695 ) $ 6,386 $ (10,309 ) Reclassification adjustment for net (gains) losses realized in net income — — — Change in net unrealized holding loss on securities transferred to held to maturity 6,345 (2,427 ) 3,918 Total securities available for sale and transferred securities (10,350 ) 3,959 (6,391 ) Pension and other postretirement benefit plans: Net change in prior service costs 250 (96 ) 154 Recognized net loss due to lump sum settlements 2,221 (850 ) 1,371 Change in net actuarial loss 3,647 (1,395 ) 2,252 Total pension and other postretirement benefit plans 6,118 (2,341 ) 3,777 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives (1,315 ) 503 (812 ) Reclassification adjustment for loss realized in net income 836 (320 ) 516 Total cash flow hedge derivatives (479 ) 183 (296 ) Total other comprehensive income (loss) $ (4,711 ) $ 1,801 $ (2,910 ) The following table presents the changes in the balances of each component of accumulated other comprehensive loss for the periods presented ($ in thousands). All amounts are presented net of tax. Securities Available and Securities Defined Benefit Pension Items Cash Flow Hedge Derivative Total Balance, January 1, 2015 $ (11,003 ) $ (31,617 ) $ 136 $ (42,484 ) Other comprehensive income (loss) before reclassification (6,391 ) 3,777 (812 ) (3,426 ) Amounts reclassified from accumulated other comprehensive loss — — 516 516 Net other comprehensive income (loss) (6,391 ) 3,777 (296 ) (2,910 ) Balance, December 31, 2015 (17,394 ) (27,840 ) (160 ) (45,394 ) Other comprehensive income (loss) before reclassification (3,597 ) (148 ) (228 ) (3,973 ) Amounts reclassified from accumulated other comprehensive loss 191 3,008 370 3,569 Net other comprehensive income (loss) (3,406 ) 2,860 142 (404 ) Balance, December 31, 2016 (20,800 ) (24,980 ) (18 ) (45,798 ) Other comprehensive income (loss) before reclassification (5,726 ) (760 ) 122 (6,364 ) Amounts reclassified from accumulated other comprehensive loss (9 ) 12,272 174 12,437 Net other comprehensive income (loss) (5,735 ) 11,512 296 6,073 Balance, December 31, 2017 $ (26,535 ) $ (13,468 ) $ 278 $ (39,725 )

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value	Note 18 – Fair Value Financial Instruments Measured at Fair Value The methodologies Trustmark uses in determining the fair values are based primarily on the use of independent, market-based data to reflect a value that would be reasonably expected upon exchange of the position in an orderly transaction between market participants at the measurement date. The predominant portion of assets that are stated at fair value are of a nature that can be valued using prices or inputs that are readily observable through a variety of independent data providers. The providers selected by Trustmark for fair valuation data are widely recognized and accepted vendors whose evaluations support the pricing functions of financial institutions, investment and mutual funds, and portfolio managers. Trustmark has documented and evaluated the pricing methodologies used by the vendors and maintains internal processes that regularly test valuations for anomalies. Trustmark utilizes an independent pricing service to advise it on the carrying value of the securities available for sale portfolio. As part of Trustmark’s procedures, the price provided from the service is evaluated for reasonableness given market changes. When a questionable price exists, Trustmark investigates further to determine if the price is valid. If needed, other market participants may be utilized to determine the correct fair value. Trustmark has also reviewed and confirmed its determinations in thorough discussions with the pricing source regarding their methods of price discovery. Mortgage loan commitments are valued based on the securities prices of similar collateral, term, rate and delivery for which the loan is eligible to deliver in place of the particular security. Trustmark acquires a broad array of mortgage security prices that are supplied by a market data vendor, which in turn accumulates prices from a broad list of securities dealers. Prices are processed through a mortgage pipeline management system that accumulates and segregates all loan commitment and forward-sale transactions according to the similarity of various characteristics (maturity, term, rate, and collateral). Prices are matched to those positions that are deemed to be an eligible substitute or offset (i.e., “deliverable”) for a corresponding security observed in the market place. Trustmark estimates fair value of the MSR through the use of prevailing market participant assumptions and market participant valuation processes. This valuation is periodically tested and validated against other third-party firm valuations. Trustmark obtains the fair value of interest rate swaps from a third-party pricing service that uses an industry standard discounted cash flow methodology. In addition, credit valuation adjustments are incorporated in the fair values to account for potential nonperformance risk. In adjusting the fair value of its interest rate swap contracts for the effect of nonperformance risk, Trustmark has considered any applicable credit enhancements such as collateral postings, thresholds, mutual puts, and guarantees. In conjunction with the FASB’s fair value measurement guidance, Trustmark made an accounting policy election to measure the credit risk of these derivative financial instruments, which are subject to master netting agreements, on a net basis by counterparty portfolio. Trustmark has determined that the majority of the inputs used to value its interest rate swaps offered to qualified commercial borrowers fall within Level 2 of the fair value hierarchy, while the credit valuation adjustments associated with these derivatives utilize Level 3 inputs, such as estimates of current credit spreads. Trustmark has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its interest rate swaps and has determined that the credit valuation adjustment is not significant to the overall valuation of these derivatives. As a result, Trustmark classifies its interest rate swap valuations in Level 2 of the fair value hierarchy. Trustmark also utilizes exchange-traded derivative instruments such as Treasury note futures contracts and option contracts to achieve a fair value return that offsets the changes in fair value of the MSR attributable to interest rates. Fair values of these derivative instruments are determined from quoted prices in active markets for identical assets therefore allowing them to be classified within Level 1 of the fair value hierarchy. In addition, Trustmark utilizes derivative instruments such as interest rate lock commitments in its mortgage banking area which lack observable inputs for valuation purposes resulting in their inclusion in Level 3 of the fair value hierarchy. At this time, Trustmark presents no fair values that are derived through internal modeling. Should positions requiring fair valuation arise that are not relevant to existing methodologies, Trustmark will make every reasonable effort to obtain market participant assumptions, or independent evaluation. Financial Assets and Liabilities The following tables summarize financial assets and financial liabilities measured at fair value on a recurring basis as of December 31, 2017 and 2016, segregated by the level of valuation inputs within the fair value hierarchy utilized to measure fair value ($ in thousands). There were no transfers between fair value levels for the years ended December 31, 2017 and 2016. December 31, 2017 Total Level 1 Level 2 Level 3 U.S. Government agency obligations $ 45,285 $ — $ 45,285 $ — Obligations of states and political subdivisions 79,229 — 79,229 — Mortgage-backed securities 2,114,121 — 2,114,121 — Securities available for sale 2,238,635 — 2,238,635 — Loans held for sale 180,512 — 180,512 — Mortgage servicing rights 84,269 — — 84,269 Other assets - derivatives 1,516 (1,013 ) 1,629 900 Other liabilities - derivatives 2,678 616 2,062 — December 31, 2016 Total Level 1 Level 2 Level 3 U.S. Government agency obligations $ 56,039 $ — $ 56,039 $ — Obligations of states and political subdivisions 115,373 — 115,373 — Mortgage-backed securities 2,185,270 — 2,185,270 — Securities available for sale 2,356,682 — 2,356,682 — Loans held for sale 175,927 — 175,927 — Mortgage servicing rights 80,239 — — 80,239 Other assets - derivatives 2,518 (524 ) 2,041 1,001 Other liabilities - derivatives 412 1,174 (762 ) — The changes in Level 3 assets measured at fair value on a recurring basis for the years ended December 31, 2017 and 2016 are summarized as follows ($ in thousands): MSR Other Assets - Derivatives Balance, January 1, 2017 $ 80,239 $ 1,001 Total net (loss) gain included in Mortgage banking, net (1) (11,830 ) 4,165 Additions 15,860 — Sales — (4,266 ) Balance, December 31, 2017 $ 84,269 $ 900 The amount of total gains (losses) for the period included in earnings that are attributable to the change in unrealized gains or losses still held at December 31, 2017 $ (1,050 ) $ (1,569 ) Balance, January 1, 2016 $ 74,007 $ 1,113 Total net (loss) gain included in Mortgage banking, net (1) (10,513 ) 10,128 Additions 16,745 — Sales — (10,240 ) Balance, December 31, 2016 $ 80,239 $ 1,001 The amount of total gains (losses) for the period included in earnings that are attributable to the change in unrealized gains or losses still held at December 31, 2016 $ (407 ) $ 753 (1) Total net (loss) gain included in Mortgage banking, net relating to the MSR includes changes in fair value due to market changes and due to run-off. Trustmark may be required, from time to time, to measure certain assets at fair value on a nonrecurring basis in accordance with GAAP. Assets at December 31, 2017, which have been measured at fair value on a nonrecurring basis, include impaired LHFI. Loans for which it is probable Trustmark will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement are considered impaired. Specific allowances for impaired LHFI are based on comparisons of the recorded carrying values of the loans to the present value of the estimated cash flows of these loans at each loan’s original effective interest rate, the fair value of the collateral or the observable market prices of the loans. Impaired LHFI are primarily collateral dependent loans and are assessed using a fair value approach. Fair value estimates for collateral dependent loans are derived from appraised values based on the current market value or as-is value of the property being appraised, normally from recently received and reviewed appraisals. Appraisals are obtained from state-certified appraisers and are based on certain assumptions, which may include construction or development status and the highest and best use of the property. These appraisals are reviewed by Trustmark’s Appraisal Review Department to ensure they are acceptable. Appraised values are adjusted down for costs associated with asset disposal. At December 31, 2017, Trustmark had outstanding balances of $48.9 million in impaired LHFI that were individually evaluated for impairment and written down to fair value of the underlying collateral less cost to sell based on the fair value of the collateral or other unobservable input compared to $27.1 million at December 31, 2016. These individually evaluated impaired LHFI are classified as Level 3 in the fair value hierarchy. Impaired LHFI are periodically reviewed and evaluated for additional impairment and adjusted accordingly based on the same factors identified above. Nonfinancial Assets and Liabilities Certain nonfinancial assets measured at fair value on a nonrecurring basis include foreclosed assets (upon initial recognition or subsequent impairment), nonfinancial assets and nonfinancial liabilities measured at fair value in the second step of a goodwill impairment test, and intangible assets and other nonfinancial long-lived assets measured at fair value for impairment assessment. Other real estate includes assets that have been acquired in satisfaction of debt through foreclosure and is carried at the lower of cost or estimated fair value. Fair value is based on independent appraisals and other relevant factors. In the determination of fair value subsequent to foreclosure, Management also considers other factors or recent developments, such as changes in market conditions from the time of valuation and anticipated sales values considering plans for disposition, which could result in an adjustment to lower the collateral value estimates indicated in the appraisals. Periodic revaluations are classified as Level 3 in the fair value hierarchy since assumptions are used that may not be observable in the market. Foreclosed assets of $26.6 million were re-measured during 2017 requiring write-downs of $3.3 million to reach their current fair values compared to $32.2 million of foreclosed assets that were re-measured during 2016, requiring write-downs of $4.4 million. Fair Value of Financial Instruments The carrying amounts and estimated fair values of financial instruments at December 31, 2017 and 2016 were as follows ($ in thousands): December 31, 2017 December 31, 2016 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Financial Assets: Level 2 Inputs: Cash and short-term investments $ 336,383 $ 336,383 $ 328,206 $ 328,206 Securities held to maturity 1,056,486 1,046,247 1,158,643 1,157,046 Level 3 Inputs: Net LHFI 8,493,234 8,507,469 7,779,948 7,825,009 Net acquired loans 257,438 257,438 260,850 260,850 Financial Liabilities: Level 2 Inputs: Deposits 10,577,512 10,577,858 10,056,012 10,059,794 Short-term liabilities 1,440,876 1,440,876 1,309,595 1,309,595 Long-term FHLB advances 946 946 251,049 251,050 Junior subordinated debt securities 61,856 45,773 61,856 41,057 FASB ASC Topic 825 requires disclosure of the fair value of financial assets and financial liabilities, including those financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis. The methodology and significant assumptions used in estimating the fair values presented above are as follows: In cases where quoted market prices are not available, fair values are generally based on estimates using present value techniques. Trustmark’s premise in present value techniques is to represent the fair values on a basis of replacement value of the existing instrument given observed market rates on the measurement date. These techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. In that regard, the derived fair value estimates for those assets or liabilities cannot be necessarily substantiated by comparison to independent markets and, in many cases, may not be realizable in immediate settlement of the instruments. The estimated fair value of financial instruments with immediate and shorter-term maturities (generally 90 days or less) is assumed to be the same as the recorded book value. All nonfinancial instruments, by definition, have been excluded from these disclosure requirements. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of Trustmark. Cash and Short-Term Investments The carrying amounts for cash and due from banks and short-term investments (federal funds sold and securities purchased under reverse repurchase agreements) approximate fair values due to their immediate and shorter-term maturities. Securities Held to Maturity Estimated fair values for securities held to maturity are based on quoted market prices where available. If quoted market prices are not available, estimated fair values are based on quoted market prices of comparable instruments. Net LHFI The fair values of net LHFI are estimated for portfolios of loans with similar financial characteristics. For variable rate LHFI that reprice frequently with no significant change in credit risk, fair values are based on carrying values. The fair values of certain mortgage LHFI, such as 1-4 family residential properties, are based on quoted market prices of similar loans sold in conjunction with securitization transactions, adjusted for differences in loan characteristics. The fair values of other types of LHFI are estimated by discounting the future cash flows using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities. The processes for estimating the fair value of net LHFI described above do not represent an exit price under FASB ASC Topic 820 and such an exit price could potentially produce a different fair value estimate at December 31, 2017 and 2016. Net Acquired Loans The fair value of net acquired loans is based on estimates of future loan cash flows and appropriate discount rates, which incorporate Trustmark’s assumptions about market funding cost and liquidity premium. The estimates of future loan cash flows are determined using Trustmark’s assumptions concerning the amount and timing of principal and interest payments, prepayments and credit losses. Deposits The fair values of deposits with no stated maturity, such as noninterest-bearing demand deposits, NOW accounts, MMDA products and savings accounts are, by definition, equal to the amount payable on demand, which is the carrying value. Fair values for certificates of deposit are based on the discounted value of contractual cash flows. The discount rate is estimated using the rates currently offered for deposits with similar remaining maturities. Short-Term Liabilities The carrying amounts for federal funds purchased, securities sold under repurchase agreements and other borrowings, including short-term FHLB advances, approximate their fair values. Long-Term FHLB Advances FHLB advances were valued by projecting expected cash flows into the future based on each advance’s contracted rate and then determining the present value of those expected cash flows using current rates for advances with similar maturities. Junior Subordinated Debt Securities The fair value of the junior subordinated debt securities equals quoted market prices, if available. If a quoted market price is not available, the fair value is estimated using quoted market prices for similar junior subordinated debt securities. Fair Value Option Trustmark has elected to account for its LHFS under the fair value option, with interest income on these LHFS reported in interest and fees on LHFS and LHFI. The fair value of the LHFS is determined using quoted prices for a similar asset, adjusted for specific attributes of that loan. The LHFS are actively managed and monitored and certain market risks of the loans may be mitigated through the use of derivatives. These derivative instruments are carried at fair value with changes in fair value recorded as noninterest income in mortgage banking, net. The changes in the fair value of the LHFS are largely offset by changes in the fair value of the derivative instruments. For the years ended December 31, 2017, 2016 and 2015, a net gain of $3.0 million, a net loss of $2.5 million and a net loss of $857 thousand, respectively, was recorded as noninterest income in mortgage banking, net for changes in the fair value of the LHFS accounted for under the fair value option. Interest and fees on LHFS and LHFI for the years ended December 31, 2017, 2016 and 2015 included $4.9 million, $5.0 million and $4.7 million, respectively, of interest earned on the LHFS accounted for under the fair value option. Election of the fair value option allows Trustmark to reduce the accounting volatility that would otherwise result from the asymmetry created by accounting for the financial instruments at the lower of cost or fair value and the derivatives at fair value. The fair value option election does not apply to the GNMA optional repurchase loans which do not meet the requirements under FASB ASC Topic 825 to be accounted for under the fair value option. GNMA optional repurchase loans totaled $48.2 million and $43.9 million at December 31, 2017 and 2016, respectively, and are included in LHFS on the accompanying consolidated balance sheets. The following table provides information about the fair value and the contractual principal outstanding of the LHFS accounted for under the fair value option as of December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Fair value of LHFS $ 132,300 $ 132,002 LHFS contractual principal outstanding 129,347 132,047 Fair value less unpaid principal $ 2,953 $ (45 )

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Note 19 – Derivative Financial Instruments Derivatives Designated as Hedging Instruments On April 4, 2013, Trustmark entered into a forward interest rate swap contract on junior subordinated debentures with a total notional amount of $60.0 million. The interest rate swap contract was designated as a derivative instrument in a cash flow hedge under FASB ASC Topic 815 with the objective of protecting the quarterly interest payments on Trustmark’s $60.0 million of junior subordinated debentures issued to Trustmark Preferred Capital Trust I throughout the five-year period beginning December 31, 2014 and ending December 31, 2019 from the risk of variability of those payments resulting from changes in the three-month LIBOR interest rate. Under the swap, which became effective on December 31, 2014, Trustmark will pay a fixed interest rate of 1.66% and receive a variable interest rate based on three-month LIBOR on a total notional amount of $60.0 million, with quarterly net settlements. No ineffectiveness related to the interest rate swap designated as a cash flow hedge was recognized in the consolidated statements of income for the years ended December 31, 2017, 2016 and 2015. The accumulated net after-tax gain related to the effective cash flow hedge included in accumulated other comprehensive loss totaled $278 thousand at December 31, 2017 compared to a net after-tax loss of $18 thousand at December 31, 2016. Amounts reported in accumulated other comprehensive loss related to this derivative are reclassified to other interest expense as interest payments are made on Trustmark’s variable rate junior subordinated debentures. During the next twelve months, Trustmark estimates that $125 thousand will be reclassified as a decrease to other interest expense. Derivatives not Designated as Hedging Instruments Trustmark utilizes a portfolio of exchange-traded derivative instruments, such as Treasury note futures contracts and option contracts, to achieve a fair value return that economically hedges changes in the fair value of the MSR attributable to interest rates. These transactions are considered freestanding derivatives that do not otherwise qualify for hedge accounting. The total notional amount of these derivative instruments was $349.0 million at December 31, 2017 compared to $262.0 million at December 31, 2016. Changes in the fair value of these exchange-traded derivative instruments are recorded as noninterest income in mortgage banking, net and are offset by changes in the fair value of the MSR. The impact of this strategy resulted in a net positive ineffectiveness of $254 thousand for the year ended December 31, 2017, compared to a net negative ineffectiveness of $2.9 million for the year ended December 31, 2016 and a net positive ineffectiveness of $1.9 million for the year ended December 31, 2015. As part of Trustmark’s risk management strategy in the mortgage banking area, derivative instruments such as forward sales contracts are utilized. Trustmark’s obligations under forward sales contracts consist of commitments to deliver mortgage loans, originated and/or purchased, in the secondary market at a future date. Changes in the fair value of these derivative instruments are recorded as noninterest income in mortgage banking, net and are offset by changes in the fair value of LHFS. Trustmark’s off-balance sheet obligations under these derivative instruments totaled $182.1 million at December 31, 2017, with a negative valuation adjustment of $237 thousand, compared to $195.0 million at December 31, 2016, with a positive valuation adjustment of $2.8 million. Trustmark also utilizes derivative instruments such as interest rate lock commitments in its mortgage banking area. Interest rate lock commitments are residential mortgage loan commitments with customers, which guarantee a specified interest rate for a specified time period. Changes in the fair value of these derivative instruments are recorded as noninterest income in mortgage banking, net and are offset by the changes in the fair value of forward sales contracts. Trustmark’s off-balance sheet obligations under these derivative instruments totaled $83.0 million at December 31, 2017, with a positive valuation adjustment of $900 thousand, compared to $97.9 million at December 31, 2016, with a positive valuation adjustment of $1.0 million. Trustmark offers certain derivatives products directly to qualified commercial lending clients seeking to manage their interest rate risk. Trustmark economically hedges interest rate swap transactions executed with commercial lending clients by entering into offsetting interest rate swap transactions with institutional derivatives market participants. Derivatives transactions executed as part of this program are not designated as qualifying hedging relationships and are, therefore, carried at fair value with the change in fair value recorded in noninterest income in bank card and other fees. Because these derivatives have mirror-image contractual terms, in addition to collateral provisions which mitigate the impact of non-performance risk, the changes in fair value are expected to substantially offset. As of December 31, 2017, Trustmark had interest rate swaps with an aggregate notional amount of $351.9 million related to this program, compared to $340.2 million as of December 31, 2016. Credit-risk-related Contingent Features Trustmark has agreements with its financial institution counterparties that contain provisions where if Trustmark defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then Trustmark could also be declared in default on its derivatives obligations. As of December 31, 2017 and 2016, the termination value of interest rate swaps in a liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $80 thousand and $1.2 million, respectively. As of December 31, 2017, Trustmark had posted collateral of $100 thousand against its obligations because of negotiated thresholds and minimum transfer amounts under these agreements. If Trustmark had breached any of these triggering provisions at December 31, 2017, it could have been required to settle its obligations under the agreements at the termination value. Credit risk participation agreements arise when Trustmark contracts with other financial institutions, as a guarantor or beneficiary, to share credit risk associated with certain interest rate swaps. These agreements provide for reimbursement of losses resulting from a third party default on the underlying swap. At December 31, 2017 and 2016, Trustmark had entered into two risk participation agreements as a beneficiary with an aggregate notional amount of $13.7 million and $14.2 million, respectively. At December 31, 2017, Trustmark had entered into six risk participation agreements as a guarantor with an aggregate notional amount of $37.1 million compared to five risk participation agreements as a guarantor with an aggregate notional amount of $28.0 million at December 31, 2016. The aggregate fair values of these risk participation agreements were immaterial at December 31, 2017 and 2016. Tabular Disclosures The following tables disclose the fair value of derivative instruments in Trustmark’s balance sheets as of December 31, 2017 and 2016 as well as the effect of these derivative instruments on Trustmark’s results of operations for the periods presented ($ in thousands): December 31, 2017 2016 Derivatives in hedging relationships Interest rate contracts: Interest rate swaps included in other assets $ 451 $ (28 ) Derivatives not designated as hedging instruments Interest rate contracts: Futures contracts included in other assets $ (1,088 ) $ (626 ) Exchange traded purchased options included in other assets 75 102 OTC written options (rate locks) included in other assets 900 1,001 Interest rate swaps included in other assets 1,175 2,060 Credit risk participation agreements included in other assets 3 9 Forward contracts included in other liabilities 237 (2,838 ) Exchange traded written options included in other liabilities 616 1,174 Interest rate swaps included in other liabilities 1,819 2,065 Credit risk participation agreements included in other liabilities 6 11 Years Ended December 31, 2017 2016 2015 Derivatives in hedging relationships Amount of loss reclassified from accumulated other comprehensive loss and recognized in other interest expense $ (282 ) $ (599 ) $ (836 ) Derivatives not designated as hedging instruments Amount of gain (loss) recognized in mortgage banking, net $ (1,873 ) $ 13 $ 1,392 Amount of gain (loss) recognized in bank card and other fees (31 ) 60 (49 ) The following table discloses the amount included in other comprehensive income (loss), net of tax for derivative instruments designated as cash flow hedges for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Derivatives in cash flow hedging relationship Amount of gain (loss) recognized in other comprehensive income (loss), net of tax $ 122 $ (228 ) $ (812 ) Information about financial instruments that are eligible for offset in the consolidated balance sheets as of December 31, 2017 and 2016 is presented in the following tables ($ in thousands): Offsetting of Derivative Assets As of December 31, 2017 Gross Statement of Financial Position Gross Amounts of Recognized Assets Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets presented in the Statement of Financial Position Financial Instruments Cash Collateral Received Net Amount Derivatives $ 1,626 $ — $ 1,626 $ (311 ) $ — $ 1,315 Offsetting of Derivative Liabilities As of December 31, 2017 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Statement of Financial Position Net Amounts of Liabilities presented in the Statement of Financial Position Financial Instruments Cash Collateral Posted Net Amount Derivatives $ 1,819 $ — $ 1,819 $ (311 ) $ (100 ) $ 1,408 Offsetting of Derivative Assets As of December 31, 2016 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets presented in Financial Position Financial Instruments Cash Collateral Received Net Amount Derivatives $ 2,032 $ — $ 2,032 $ (499 ) $ — $ 1,533 Offsetting of Derivative Liabilities As of December 31, 2016 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Statement of Financial Position Net Amounts of Liabilities presented in the Statement of Financial Position Financial Instruments Cash Collateral Posted Net Amount Derivatives $ 2,065 $ — $ 2,065 $ (499 ) $ (937 ) $ 629

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	Note 20 – Segment Information Trustmark’s management reporting structure includes three segments: General Banking, Wealth Management and Insurance. The General Banking Division is responsible for all traditional banking products and services, including loans and deposits. The General Banking Division also consists of internal operations such as Human Resources, Executive Administration, Treasury (Funds Management), Public Affairs and Corporate Finance. The Wealth Management Division provides customized solutions for customers by integrating financial services with traditional banking products and services such as money management, full-service brokerage, financial planning, personal and institutional trust and retirement services. Through Fisher Brown Bottrell Insurance, Inc. (FBBI), a wholly owned subsidiary of TNB, Trustmark’s Insurance Division provides a full range of retail insurance products including commercial risk management products, bonding, group benefits and personal lines coverage. The accounting policies of each reportable segment are the same as those of Trustmark except for its internal allocations. Noninterest expenses for back-office operations support are allocated to segments based on estimated uses of those services. Trustmark measures the net interest income of its business segments with a process that assigns cost of funds or earnings credit on a matched-term basis. This process, called “funds transfer pricing”, charges an appropriate cost of funds to assets held by a business unit, or credits the business unit for potential earnings for carrying liabilities. The net of these charges and credits flows through to the General Banking Division, which contains the management team responsible for determining TNB’s funding and interest rate risk strategies. The following table discloses financial information by reportable segment for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 General Banking Net interest income $ 406,406 $ 386,596 $ 391,092 Provision for loan losses, net 7,699 14,714 11,800 Noninterest income 116,180 107,059 105,477 Noninterest expense 373,221 354,555 348,270 Income before income taxes 141,666 124,386 136,499 Income taxes 43,960 25,303 29,761 General banking net income $ 97,706 $ 99,083 $ 106,738 Selected Financial Information Total assets $ 13,724,193 $ 13,278,668 $ 12,604,112 Depreciation and amortization $ 37,710 $ 35,692 $ 36,072 Wealth Management Net interest income $ 910 $ 726 $ 337 Noninterest income 30,285 30,117 31,245 Noninterest expense 27,561 24,165 25,346 Income before income taxes 3,634 6,678 6,236 Income taxes 1,390 2,554 2,386 Wealth Management net income $ 2,244 $ 4,124 $ 3,850 Selected Financial Information Total assets $ 5,592 $ 7,501 $ 7,471 Depreciation and amortization $ 131 $ 174 $ 183 Insurance Net interest income $ 234 $ 211 $ 336 Noninterest income 38,198 36,767 36,427 Noninterest expense 29,387 28,578 28,046 Income before income taxes 9,045 8,400 8,717 Income taxes 3,365 3,196 3,267 Insurance net income $ 5,680 $ 5,204 $ 5,450 Selected Financial Information Total assets $ 68,168 $ 66,164 $ 67,313 Depreciation and amortization $ 630 $ 747 $ 801 Consolidated Net interest income $ 407,550 $ 387,533 $ 391,765 Provision for loan losses, net 7,699 14,714 11,800 Noninterest income 184,663 173,943 173,149 Noninterest expense 430,169 407,298 401,662 Income before income taxes 154,345 139,464 151,452 Income taxes 48,715 31,053 35,414 Consolidated net income $ 105,630 $ 108,411 $ 116,038 Selected Financial Information Total assets $ 13,797,953 $ 13,352,333 $ 12,678,896 Depreciation and amortization $ 38,471 $ 36,613 $ 37,056

Parent Company Only Financial I

Parent Company Only Financial Information	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Parent Company Only Financial Information	Note 21 – Parent Company Only Financial Information ($ in thousands) Condensed Balance Sheets December 31, 2017 2016 Assets: Investment in banks $ 1,617,238 $ 1,566,186 Other assets 17,349 16,756 Total Assets $ 1,634,587 $ 1,582,942 Liabilities and Shareholders' Equity: Accrued expense $ 1,030 $ 878 Junior subordinated debt securities 61,856 61,856 Shareholders' equity 1,571,701 1,520,208 Total Liabilities and Shareholders' Equity $ 1,634,587 $ 1,582,942 Condensed Statements of Income Years Ended December 31, 2017 2016 2015 Revenue: Dividends received from banks $ 65,663 $ 65,987 $ 64,752 Earnings of subsidiaries over distributions 42,211 44,756 53,562 Other income 71 60 55 Total Revenue 107,945 110,803 118,369 Expense: Other expense 2,315 2,392 2,331 Total Expense 2,315 2,392 2,331 Net Income $ 105,630 $ 108,411 $ 116,038 Condensed Statements of Cash Flows Years Ended December 31, 2017 2016 2015 Operating Activities: Net income $ 105,630 $ 108,411 $ 116,038 Adjustments to reconcile net income to net cash provided by operating activities: Net change in investment in subsidiaries (42,211 ) (44,756 ) (53,562 ) Other (1,697 ) (739 ) (761 ) Net cash provided by operating activities 61,722 62,916 61,715 Investing Activities: Payment for investments in subsidiaries (30,755 ) — — Repayment for investments in subsidiaries 32,000 — — Net cash provided by investing activities 1,245 — — Financing Activities: Cash dividends paid on common stock (62,795 ) (62,666 ) (62,605 ) Other common stock transactions, net — (857 ) (211 ) Net cash used in financing activities (62,795 ) (63,523 ) (62,816 ) Net change in cash and cash equivalents 172 (607 ) (1,101 ) Cash and cash equivalents at beginning of year 16,713 17,320 18,421 Cash and cash equivalents at end of year $ 16,885 $ 16,713 $ 17,320 Trustmark (parent company only) paid income taxes of approximately $7.4 million in 2017, $24.8 million in 2016 and $16.3 million in 2015. During 2017, interest paid was $283 thousand compared to $600 thousand of interest paid in 2016 and $837 thousand of interest paid during 2015.

Significant Accounting Polici30

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Business	Business Trustmark Corporation (Trustmark) is a bank holding company headquartered in Jackson, Mississippi. Through its subsidiaries, Trustmark operates as a financial services organization providing banking and financial solutions to corporate institutions and individual customers through 198 offices in Alabama, Florida, Mississippi, Tennessee and Texas.
Basis of Financial Statement Presentation	Basis of Financial Statement Presentation The consolidated financial statements include the accounts of Trustmark and all other entities in which Trustmark has a controlling financial interest. All significant intercompany accounts and transactions have been eliminated in consolidation. The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (GAAP). The preparation of financial statements in conformity with these accounting principles requires Management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and income and expense during the reporting periods and the related disclosures. Although Management’s estimates contemplate current conditions and how they are expected to change in the future, it is reasonably possible that in 2018 actual conditions could vary from those anticipated, which could affect Trustmark’s financial condition and results of operations. Actual results could differ from those estimates.
Securities	Securities Securities are classified as either held to maturity or available for sale. Securities are classified as held to maturity and carried at amortized cost when Management has the positive intent and the ability to hold them until maturity. Securities to be held for indefinite periods of time are classified as available for sale and carried at fair value, with the unrealized holding gains and losses reported as a component of other comprehensive income (loss), net of tax. Securities available for sale are used as part of Trustmark’s interest rate risk management strategy and may be sold in response to changes in interest rates, changes in prepayment rates and other factors. Management determines the appropriate classification of securities at the time of purchase. The amortized cost of debt securities classified as securities held to maturity or securities available for sale is adjusted for amortization of premiums and accretion of discounts to maturity of the security using the interest method. Such amortization or accretion is included in interest on securities. Realized gains and losses are determined using the specific identification method and are included in noninterest income as securities gains (losses), net. Securities transferred from the available for sale category to the held to maturity category are recorded at fair value at the date of transfer. Unrealized holding gains or losses associated with the transfer of securities from available for sale to held to maturity are included in the balance of accumulated other comprehensive income (loss), net of tax, in the consolidated balance sheets. These unrealized holding gains or losses are amortized over the remaining life of the security as a yield adjustment in a manner consistent with the amortization or accretion of the original purchase premium or discount on the associated security. Trustmark reviews securities for impairment quarterly. Declines in the fair value of held to maturity and available for sale securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of the impairment related to other factors is recognized as a component of other comprehensive income (loss), net of tax. In estimating other-than-temporary impairment losses, Management considers, among other things, the length of time and the extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer and Trustmark’s intent and ability to hold the security for a period of time sufficient to allow for any anticipated recovery in fair value.
Loans Held for Sale (LHFS)	Loans Held for Sale (LHFS) Primarily, all mortgage loans purchased from wholesale customers or originated in Trustmark’s General Banking Division are considered to be held for sale. In certain circumstances, Trustmark will retain a mortgage loan in its portfolio based on banking relationships or certain investment strategies. Trustmark has elected to account for its LHFS under the fair value option permitted by Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 825, “Financial Instruments,” with interest income on the LHFS reported in interest and fees on LHFS and LHFI. Trustmark reports unrealized gains and losses resulting from changes in the fair value of the LHFS accounted for under the fair value option as noninterest income in mortgage banking, net. LHFS are actively managed and monitored and certain market risks of the loans may be mitigated through the use of derivatives. These derivative instruments are carried at fair value with changes in the fair value reported as noninterest income in mortgage banking, net. Changes in the fair value of the LHFS are largely offset by changes in the fair value of the derivative instruments. Election of the fair value option allows Trustmark to reduce the accounting volatility that would otherwise result from the asymmetry created by accounting for its LHFS at the lower of cost or fair value and the derivative instruments at fair value. Realized gains and losses upon ultimate sale of the loans are reported as noninterest income in mortgage banking, net. Government National Mortgage Association (GNMA) optional repurchase programs allow financial institutions to buy back individual delinquent mortgage loans that meet certain criteria from the securitized loan pool for which the institution provides servicing. At the servicer’s option and without GNMA’s prior authorization, the servicer may repurchase such a delinquent loan for an amount equal to 100 percent of the remaining principal balance of the loan. Under FASB ASC Topic 860, “Transfers and Servicing,” this buy-back option is considered a conditional option until the delinquency criteria are met, at which time the option becomes unconditional. When Trustmark is deemed to have regained effective control over these loans under the unconditional buy-back option, the loans can no longer be reported as sold and must be brought back onto the balance sheet as LHFS, regardless of whether Trustmark intends to exercise the buy-back option. These loans are reported as LHFS with the offsetting liability being reported as short-term borrowings. The fair value option election does not apply to the GNMA optional repurchase loans which do not meet the requirements under FASB ASC Topic 825 to be accounted for under the fair value option. Trustmark defers the upfront loan fees and costs related to the LHFS. In general, the LHFS are only retained on Trustmark’s balance sheet for 30 to 45 days before they are pooled and sold in the secondary market. The difference between deferring these loan fees and costs until the loans are sold and recognizing them in earnings as incurred as required by FASB ASC Topic 825-10 is considered immaterial. Deferred loan fees and costs are reflected in the basis of the LHFS and, as such, impact the resulting gain or loss when the loans are sold.
Loans Held for Investment (LHFI)	Loans Held for Investment (LHFI) LHFI are stated at the amount of unpaid principal, adjusted for the net amount of direct costs and nonrefundable loan fees associated with lending. The net amount of nonrefundable loan origination fees and direct costs associated with the lending process, including commitment fees, is deferred and accreted to interest income over the lives of the loans using a method that approximates the interest method. Interest on LHFI is accrued and recorded as interest income based on the outstanding principal balance. Past due LHFI are loans contractually past due 30 days or more as to principal or interest payments. A LHFI is classified as nonaccrual, and the accrual of interest on such loan is discontinued, when the contractual payment of principal or interest becomes 90 days past due on commercial credits and 120 days past due on non-business purpose credits. In addition, a credit may be placed on nonaccrual at any other time Management has serious doubts about further collectibility of principal or interest according to the contractual terms, even though the loan is currently performing. A LHFI may remain in accrual status if it is in the process of collection and well secured. When a LHFI is placed in nonaccrual status, interest accrued but not received is reversed against interest income. Interest payments received on nonaccrual LHFI are applied against principal under the cost-recovery method, until qualifying for return to accrual status. Under the cost-recovery method, interest income is not recognized until the principal balance is reduced to zero. LHFI are restored to accrual status when the obligation is brought current or has performed in accordance with the contractual terms for a reasonable period of time and the ultimate collectibility of the total contractual principal and interest is no longer in doubt. A LHFI is considered impaired when, based on current information and events, it is probable that Trustmark will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. Trustmark considers all nonaccrual LHFI and LHFI classified as a troubled debt restructuring (TDR) to be impaired loans. All commercial nonaccrual relationships of $500 thousand or more and all LHFI classified as TDRs are individually reviewed for impairment (individually evaluated impaired LHFI). If a LHFI is deemed impaired, a specific valuation allowance is allocated, if necessary, so that the loan is reported net, at the present value of estimated future cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Commercial nonaccrual relationships under $500 thousand are not individually evaluated for impairment due to the insignificant number and dollar amount of these types of loans. Nonaccrual LHFI includes both individually evaluated impaired LHFI as well as smaller balance homogeneous loans that are collectively evaluated for impairment. Consistent with the policy for nonaccrual LHFI, interest payments on impaired LHFI are applied to principal. Impaired LHFI, or portions thereof, are charged off when deemed uncollectible. Troubled Debt Restructuring A TDR occurs when a borrower is experiencing financial difficulties, and for related economic or legal reasons, a concession is granted to the borrower that Trustmark would not otherwise consider. Whatever the form of concession that might be granted by Trustmark, Management’s objective is to enhance collectibility by obtaining more cash or other value from the borrower or by increasing the probability of receipt by granting the concession than by not granting it. Other concessions may arise from court proceedings or may be imposed by law. In addition, TDRs also include those credits that are extended or renewed to a borrower who is not able to obtain funds from sources other than Trustmark at a market interest rate for new debt with similar risk. A formal TDR may include, but is not necessarily limited to, one or a combination of the following situations: • Trustmark accepts a third-party receivable or other asset(s) of the borrower, in lieu of the receivable from the borrower. • Trustmark accepts an equity interest in the borrower in lieu of the receivable. • Trustmark accepts modification of the terms of the debt including but not limited to: o Reduction (absolute or contingent) of the stated interest rate to below the current market rate. o Extension of the maturity date or dates at a stated interest rate lower than the current market rate for new debt with similar risk. o Reduction (absolute or contingent) of the face amount or maturity amount of the debt as stated in the note or other agreement. o Reduction (absolute or contingent) of accrued interest. Troubled debt restructurings are addressed in Trustmark’s loan policy, and in accordance with that policy, any modifications or concessions that may result in a TDR are subject to a special approval process which allows for control, identification, and monitoring of these arrangements. Prior to granting a concession, a revised borrowing arrangement is proposed which is structured so as to improve collectability of the loan in accordance with a reasonable repayment schedule with any loss promptly identified. It is supported by a thorough evaluation of the borrower’s financial condition and prospects for repayment under those revised terms. Other TDRs arising from renewals or extensions of existing debt are routinely identified through the processes utilized in the Problem Loan Committees and in the Credit Quality Review Committee. TDRs are subsequently reported to the Director Credit Policy Committee on a quarterly basis and are disclosed in Trustmark’s consolidated financial statements in accordance with GAAP and regulatory reporting guidance. All loans whose terms have been modified in a troubled debt restructuring are evaluated for impairment under FASB ASC Topic 310, “Receivables.” Accordingly, Trustmark measures any loss on the restructuring in accordance with that guidance. A TDR in which Trustmark receives physical possession of the borrower’s assets, regardless of whether formal foreclosure or repossession proceedings take place, is accounted for in accordance with FASB ASC Subtopic 310-40, “Troubled Debt Restructurings by Creditors.” Thus, the loan is treated as if assets have been received in satisfaction of the loan and reported as a foreclosed asset. A TDR may be returned to accrual status if Trustmark is reasonably assured of repayment of principal and interest under the modified terms and the borrower has demonstrated sustained performance under those terms for a period of at least six months. Otherwise, the restructured loan must remain on nonaccrual.
Allowance for Loan Losses, LHFI	Allowance for Loan Losses, LHFI The allowance for loan losses, LHFI is established through provisions for estimated loan losses charged against net income. The allowance account is maintained at a level which is believed to be adequate by Management based on estimated probable losses within the LHFI portfolio. Evaluations of the portfolio and individual credits are inherently subjective, as they require estimates, assumptions and judgments as to the facts and circumstances of particular situations. Some of the factors considered, such as amounts and timing of future cash flows expected to be received, may be susceptible to significant change. Trustmark’s allowance methodology is based on guidance provided in Securities and Exchange Commission (SEC) Staff Accounting Bulletin (SAB) No. 102, “Selected Loan Loss Allowance Methodology and Documentation Issues,” as well as other regulatory guidance. The allowance for loan losses, LHFI consists of three components: (i) a historical valuation allowance determined in accordance with FASB ASC Topic 450, “Contingencies,” based on historical loan loss experience for LHFI with similar characteristics and trends, (ii) a specific valuation allowance determined in accordance with FASB ASC Topic 310 based on probable losses on specific LHFI and (iii) a qualitative risk valuation allowance determined in accordance with FASB ASC Topic 450 based on general economic conditions and other specific internal and external qualitative risk factors. Each of these components calls for estimates, assumptions and judgments as described below. Historical Valuation Allowance The historical valuation allowance is derived by application of a historical net loss percentage to the outstanding balances of LHFI contained in designated pools and risk rating categories. Pools are established by grouping credits that display similar characteristics and trends such as commercial LHFI for working capital purposes and non-working capital purposes, commercial purpose LHFI secured by real estate (which are further segregated into 1-4 family construction, non 1-4 family construction, land, lots and development, owner-occupied and non-owner occupied categories), other commercial loans, 1-4 family LHFI, 1-4 family LHFI secured by junior liens and other consumer LHFI. Within these pools, LHFI are further segregated based on Trustmark’s internal credit risk rating process that evaluates, among other things: the obligor’s ability and willingness to pay, the value of underlying collateral, the ability of guarantors to meet their payment obligations, management experience and effectiveness, and the economic environment and industry in which the borrower operates. The historical net loss percentages, calculated on a quarterly basis, are proportionally distributed to each risk rate within loan groups based upon degree of risk. Using third-party default data, which is updated annually to incorporate the most recent year’s information, average cumulative issuer-weighted global default rates by alphanumeric rating are aggregated by Trustmark’s commercial loan risk rates. Management uses the long-term default rates to measure the relative risk across the risk rates while the 12-quarter quantitative loss rate sets the absolute level of allowance for loan loss reserve. Further, given the volatility in the default data, the longer look-back period provides for a more stable allowance for loan loss estimate which better reflects the incremental risk across the risk rates. The historical net loss percentages are calculated using a 12 quarter look-back period, which is the period that best reflects losses inherent in the current loan portfolio. The look-back period sufficiently captures the volatility in net charge-off rates from quarter to quarter and affects the qualitative adjustments that are required to capture the differences in conditions between the current period and those that were prevailing during the look-back period. The loss emergence period (LEP) refers to the period of time between the events that trigger a loss and charge-off of that loss. Losses are usually not immediately known and determining the loss event can be difficult. It takes time for the borrower and extent of loss to be identified and determined. Management may not be aware that the loss event has occurred until the borrower exhibits the inability to pay or other evidence of credit deterioration. The LEP is evaluated annually to incorporate the most recent year’s data and adjusted as necessary. Loans-Specific Valuation Allowance Once a LHFI is classified, it is subject to periodic review to determine whether or not the loan is impaired. If determined to be impaired, the loan is evaluated using one of the valuation criteria contained in FASB ASC Topic 310 (i.e., individually or collectively evaluated), and a specific valuation allowance is allocated, if necessary, so that the loan is reported at the net realizable value. Qualitative Risk Valuation Allowance The qualitative risk valuation allowance is based on general economic conditions and other internal and external factors affecting Trustmark as a whole as well as specific LHFI. Factors considered include the following within Trustmark’s five key market regions: the experience, ability, and effectiveness of Trustmark’s lending management and staff; adherence to Trustmark’s loans policies, procedures and internal controls; the volume of exceptions relating to collateral, underwriting and financial documentation; credit concentrations; recent performance trends; regional economic trends; the impact of recent acquisitions; and the impact of significant natural disasters. These factors are evaluated on a quarterly basis with the results representing Trustmark’s qualitative risk profile in the current period which is used to establish an appropriate allowance. The qualitative portion of the commercial and consumer LHFI allowance for loan loss methodology also incorporates the use of maximum observed gross historical losses observed through the last economic cycle as a way to calculate a maximum qualitative reserve limit. The maximum observed gross historical losses as a percentage of the loan balances results in a maximum observed gross historical loss rate. Once the quantitative component of the allowance for loan loss methodology is calculated, the quantitative reserve percentage is deducted from the maximum observed gross historical loss rate to determine the maximum possible qualitative reserve limit. Management uses its qualitative factor evaluation process in conjunction with this maximum to determine the appropriate estimate of the qualitative considerations not captured by Trustmark’s historical loss rates. Other factors included in the qualitative risk valuation allowance include consideration of: commercial loan facility risk that embodies the nature, frequency and duration of the repayment structure as it pertains to the actual source of loan repayment, commercial nonaccrual relationships under $500 thousand which are below the threshold to perform a specific impairment analysis, and independent consumer credit bureau scores that are monitored to identify shifts in risk that are represented in the retail portfolio. These factors are also evaluated on a quarterly basis with the exception of the commercial nonaccrual relationships under $500 thousand which are evaluated monthly. Commercial purpose LHFI are charged off when a determination is made that the loan is uncollectible and continuance as a bankable asset is not warranted. Consumer LHFI secured by 1-4 family residential real estate are generally charged off or written down to the fair value of the collateral less cost to sell at no later than 180 days of delinquency. Non-real estate consumer purpose LHFI, including both secured and unsecured loans, are generally charged off by 120 days of delinquency. Consumer revolving lines of credit and credit card debt are generally charged off on or prior to 180 days of delinquency. LHFI are charged off against the allowance for loan losses, LHFI, with any subsequent recoveries credited back to the allowance account.
Acquired Loans	Acquired Loans Acquired loans are accounted for under the acquisition method of accounting. The acquired loans are recorded at their estimated fair value at the time of acquisition. The fair value of acquired loans is determined using a discounted cash flow model based on assumptions regarding the amount and timing of principal and interest payments, estimated prepayments, estimated default rates, estimated loss severity in the event of defaults and current market rates. Estimated credit losses are included in the determination of fair value; therefore, an allowance for loan losses is not recorded on the acquisition date. Trustmark accounts for acquired impaired loans under FASB ASC Topic 310-30, “Loans and Debt Securities Acquired with Deteriorated Credit Quality.” An acquired loan is considered impaired when there is evidence of credit deterioration since origination and it is probable at the date of acquisition that Trustmark would be unable to collect all contractually required payments. Acquired loans accounted for under FASB ASC Topic 310-30 are referred to as “acquired impaired loans.” Revolving credit agreements, such as home equity lines, and commercial leases are excluded from acquired impaired loan accounting requirements. For acquired impaired loans, Trustmark (i) calculates the contractual amount and timing of undiscounted principal and interest payments (the “undiscounted contractual cash flows”) and (ii) estimates the amount and timing of undiscounted expected principal and interest payments (the “undiscounted expected cash flows”). Under FASB ASC Topic 310-30, the difference between the undiscounted contractual cash flows and the undiscounted expected cash flows is the nonaccretable difference. The nonaccretable difference represents an estimate of the loss exposure of principal and interest related to the acquired impaired loan portfolio, and such amount is subject to change over time based on the performance of such loans. The excess of undiscounted expected cash flows at acquisition over the initial fair value of acquired impaired loans is referred to as the “accretable yield” and is recorded as interest income over the estimated life of the loans using the effective yield method if the timing and amount of the future cash flows is reasonably estimable. Under the effective yield method, the accretable yield is recorded as an accretion of interest income over the life of the loan. Trustmark aggregates certain acquired impaired loans into pools of loans with common credit risk characteristics such as loan type and risk rating. To establish accounting pools of acquired impaired loans, loans are first categorized by similar purpose, collateral and geographic region. Within each category, the acquired impaired loans are further segmented by ranges of risk determinants observed at the time of acquisition. For commercial loans, the primary risk determinant is the risk rating as assigned by Trustmark. For consumer loans, the risk determinants include delinquency, delinquency history and FICO scores. Statistical comparison of the pools reflect that each pool is comprised of acquired impaired loans generally of similar characteristics, including loan type, loan risk and weighted average life. Each pool is then reviewed for similarity of the pool constituents, including standard deviation of purchase price, weighted average life and concentration of the largest loans. Loan pools are initially booked at the aggregate fair value of the loan pool constituents, based on the present value of Trustmark's expected cash flows from the acquired impaired loans. An acquired impaired loan is removed from a pool of loans only if the loan is sold, foreclosed, payment is received in full satisfaction of the loan or the loan is fully charged off. The acquired impaired loan is removed from the pool at the carrying value. When an individual acquired impaired loan is removed from a pool of loans, the difference between its relative carrying amount and the cash, collateral (measured at fair value) or other assets received will be recognized as a gain or loss immediately in interest income on acquired loans and would not affect the effective yield used to recognize the accretable yield on the remaining pool. Certain acquired impaired loans are not pooled and are accounted for individually. Such acquired impaired loans are withheld from pools due to the inherent uncertainty of the timing and amount of their cash flows or because they are not a suitable similar constituent to the established pools. As required by FASB ASC Topic 310-30, Trustmark periodically re-estimates the expected cash flows to be collected over the life of the acquired impaired loans. If, based on current information and events, it is probable that Trustmark will be unable to collect all cash flows expected at acquisition plus additional cash flows expected to be collected arising from changes in estimate after acquisition, the acquired loans are considered impaired. The decrease in the expected cash flows reduces the carrying value of the acquired impaired loans as well as the accretable yield and results in a charge-off through the allowance for loan losses, acquired loans or the establishment of an allowance for loan losses, acquired loans with a charge to income through the provision for loan losses, acquired loans. If, based on current information and events, it is probable that there is a significant increase in the cash flows previously expected to be collected or if actual cash flows are significantly greater than cash flows previously expected, Trustmark will reduce any remaining allowance for loan losses, acquired loans established on the acquired impaired loans for the increase in the present value of cash flows expected to be collected. The increase in the expected cash flows for the acquired impaired loans over those originally estimated at acquisition increases the carrying value of the acquired impaired loans as well as the accretable yield. The increase in the accretable yield is recognized as interest income prospectively over the remaining life of the acquired impaired loans. The carrying value of acquired impaired loans is reduced by payments received, both principal and interest, and increased by the portion of the accretable yield recognized as interest income. Under FASB ASC Topic 310-30, acquired impaired loans are generally considered accruing and performing loans as the loans accrete interest income over the estimated life of the loan when expected cash flows are reasonably estimable. Accordingly, acquired impaired loans that are contractually past due are still considered to be accruing and performing loans as long as the estimated cash flows are received as expected. If the timing and amount of cash flows is not reasonably estimable, the loans may be classified as nonaccrual loans and interest income may be recognized on a cash basis or as a reduction of the principal amount outstanding.
Premises and Equipment, Net	Premises and Equipment, Net Premises and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is charged to expense over the estimated useful lives of the assets, which are up to thirty-nine years for buildings and three to ten years for furniture and equipment. Leasehold improvements are amortized over the terms of the respective leases or the estimated useful lives of the improvements, whichever is shorter. In cases where Trustmark has the right to renew the lease for additional periods, the lease term for the purpose of calculating amortization of the capitalized cost of the leasehold improvements is extended when Trustmark is “reasonably assured” that it will renew the lease. Depreciation and amortization expenses are computed using the straight-line method. Trustmark continually evaluates whether events and circumstances have occurred that indicate that such long-lived assets have become impaired. Measurement of any impairment of such long-lived assets is based on the fair values of those assets. Branch closures and purchased land held for future branch expansion for more than five years are evaluated to determine if the related land, buildings and building improvements should be transferred to assets held for sale in accordance with FASB ASC Topic 360, “Property, Plant and Equipment.” The property is transferred to assets held for sale at the lower of its carrying value or fair value less cost to sell. An impairment loss is recorded at the time of transfer if the carrying value of the assets exceeds the fair value. Impairment losses are recorded as non-interest expense in other expense.
Mortgage Servicing Rights (MSR)	Mortgage Servicing Rights (MSR) Trustmark recognizes as assets the rights to service mortgage loans based on the estimated fair value of the MSR when loans are sold and the associated servicing rights are retained. Trustmark has elected to account for the MSR at fair value. The fair value of the MSR is determined using discounted cash flow techniques benchmarked against third-party valuations. Estimates of fair value involve several assumptions, including the key valuation assumptions about market expectations of future prepayment rates, interest rates and discount rates which are provided by a third-party firm. Prepayment rates are projected using an industry standard prepayment model. The model considers other key factors, such as a wide range of standard industry assumptions tied to specific portfolio characteristics such as remittance cycles, escrow payment requirements, geographic factors, foreclosure loss exposure, VA no-bid exposure, delinquency rates and cost of servicing, including base cost and cost to service delinquent mortgages. Prevailing market conditions at the time of analysis are factored into the accumulation of assumptions and determination of servicing value. Trustmark economically hedges changes in the fair value of the MSR attributable to interest rates. See Note 1 – Significant Accounting Policies, “Derivative Financial Instruments – Derivatives not Designated as Hedging Instruments” for information regarding these derivative instruments. Trustmark receives annual servicing fee income for loans serviced, which is recorded as noninterest income in mortgage banking, net. The fees are based on a contractual percentage of the outstanding principal or a fixed amount per loan and are recorded as income when earned. Late fees and ancillary fees related to loan servicing are not considered material.
Goodwill and Identifiable Intangible Assets	Goodwill and Identifiable Intangible Assets Trustmark accounts for goodwill and other intangible assets in accordance with FASB ASC Topic 350, “Intangibles – Goodwill and Other.” Goodwill, which represents the excess of cost over the fair value of the net assets of an acquired business, is not amortized but tested for impairment on an annual basis, which is October 1 for Trustmark, or more often if events or circumstances indicate that there may be impairment. Identifiable intangible assets are acquired assets that lack physical substance but can be distinguished from goodwill because of contractual or legal rights or because the assets are capable of being sold or exchanged either on their own or in combination with a related contract, asset or liability. Trustmark’s identifiable intangible assets primarily relate to core deposits, insurance customer relationships and borrower relationships. These intangibles, which have definite useful lives, are amortized on an accelerated basis over their estimated useful lives. In addition, these intangibles are evaluated for impairment whenever events and changes in circumstances indicate that the carrying amount should be reevaluated. Trustmark also purchased banking charters in order to facilitate its entry into the states of Florida and Texas. These identifiable intangible assets are being amortized on a straight-line method over 20 years.
Other Real Estate	Other Real Estate Other real estate includes assets that have been acquired in satisfaction of debt through foreclosure and is carried at the lower of cost or estimated fair value. Fair value is based on independent appraisals and other relevant factors. Valuation adjustments required at foreclosure are charged to the allowance for loan losses. Other real estate is revalued on an annual basis or more often if market conditions necessitate. An other real estate specific reserve may be recorded through other real estate expense for declines in fair value subsequent to foreclosure based on recent appraisals or changes in market conditions. Subsequent to foreclosure, losses on the periodic revaluation of the property are charged against an existing other real estate specific reserve or as noninterest expense in other real estate expense if a reserve does not exist. Costs of operating and maintaining the properties as well as gains or losses on their disposition are also included in other real estate expense as incurred. Improvements made to properties are capitalized if the expenditures are expected to be recovered upon the sale of the properties.
Federal Home Loan Bank (FHLB) and Federal Reserve Bank of Atlanta Stock	Federal Home Loan Bank (FHLB) and Federal Reserve Bank of Atlanta Stock Securities with limited marketability, such as stock in the Federal Reserve Bank of Atlanta and the FHLB, are carried at cost. Trustmark’s investment in member bank stock is included in other assets in the accompanying consolidated balance sheets because these equity securities do not have a readily determinable fair value, which places them outside the scope of FASB ASC Topic 320, “Investments – Debt and Equity Securities.” At December 31, 2017 and 2016, Trustmark’s investment in member bank stock totaled $67.7 million and $71.0 million, respectively. The carrying value of Trustmark’s member bank stock gave rise to no other-than-temporary impairment for the years ended December 31, 2017, 2016 and 2015.
Insurance Commissions	Insurance Commissions Commission revenue is recognized as of the effective date of the insurance policy or the date the customer is billed, whichever is later. Trustmark also receives contingent commissions from insurance companies as additional incentive for achieving specified premium volume goals and/or the loss experience of the insurance placed by Trustmark. Contingent commissions from insurance companies are recognized throughout the calendar year using reasonable estimates that are continuously reviewed and revised to reflect current experience. Trustmark maintains reserves for commission adjustments and doubtful accounts receivable which were not considered significant at December 31, 2017 or 2016.
Wealth Management	Wealth Management Assets under administration held by Trustmark in a fiduciary or agency capacity for customers are not included in Trustmark’s consolidated balance sheets. Investment management and trust fee income is recorded on a cash basis, which because of the regularity of the billing cycles, approximates the accrual method, in accordance with industry practice.
Derivative Financial Instruments	Derivative Financial Instruments Trustmark maintains an overall interest rate risk management strategy that incorporates the use of derivative instruments to minimize significant unplanned fluctuations in earnings and cash flows caused by interest rate volatility. Trustmark’s interest rate risk management strategy involves modifying the repricing characteristics of certain assets and liabilities so that changes in interest rates do not adversely affect the net interest margin and cash flows. Under the guidelines of FASB ASC Topic 815, “Derivatives and Hedging,” all derivative instruments are required to be recognized as either assets or liabilities and carried at fair value on the balance sheet. The fair value of derivative positions outstanding is included in other assets and/or other liabilities in the accompanying consolidated balance sheets and in the net change in these financial statement line items in the accompanying consolidated statements of cash flows as well as included in noninterest income in the accompanying consolidated statements of income and other comprehensive income (loss), net of tax in the accompanying consolidated statements of comprehensive income. Trustmark’s interest rate swap derivative instruments are subject to master netting agreements, and therefore, eligible for offsetting in the consolidated balance sheets. Trustmark has elected to not offset any derivative instruments in its consolidated balance sheets. Derivatives Designated as Hedging Instruments Trustmark has entered into a forward interest rate swap contract on its junior subordinated debentures, with the objective of protecting the quarterly interest payments from the risk of variability of those payments resulting from changes in the three-month LIBOR interest rate for the five-year period beginning December 31, 2014 and ending December 31, 2019. This derivative instrument is designated as a cash flow hedge under FASB ASC Topic 815. Any accumulated net after-tax gains or losses related to effective cash flow hedge are included in accumulated other comprehensive income (loss), net of tax. Any ineffective portion of the interest rate swap is reclassified from accumulated other comprehensive income (loss), net of tax to noninterest expense in the consolidated statements of income for the relevant periods. Amounts reported in accumulated other comprehensive income (loss), net of tax related to this derivative are reclassified to other interest expense as interest payments are made on Trustmark’s variable rate junior subordinated debentures. Derivatives not Designated as Hedging Instruments As part of Trustmark’s risk management strategy in the mortgage banking area, derivative instruments such as forward sales contracts are utilized. Trustmark’s obligations under forward contracts consist of commitments to deliver mortgage loans, originated and/or purchased, in the secondary market at a future date. Changes in the fair value of these derivative instruments are recorded as noninterest income in mortgage banking, net and are offset by changes in the fair value of LHFS. See Note 1 – Significant Accounting Policies, “Loans Held for Sale (LHFS)” for information regarding the fair value option election. Trustmark also utilizes derivative instruments such as interest rate lock commitments in its mortgage banking area. Rate lock commitments are residential mortgage loan commitments with customers, which guarantee a specified interest rate for a specified time period. Changes in the fair value of these derivative instruments are recorded as noninterest income in mortgage banking, net and are offset by the changes in the fair value of forward sales contracts. Trustmark utilizes a portfolio of exchange-traded derivative instruments, such as Treasury note futures contracts and option contracts, to achieve a fair value return that economically hedges changes in the fair value of the MSR attributable to interest rates. These transactions are considered freestanding derivatives that do not otherwise qualify for hedge accounting. These exchange-traded derivative instruments are accounted for at fair value with changes in the fair value recorded as noninterest income in mortgage banking, net and are offset by changes in the fair value of the MSR. The MSR fair value represents the present value of future cash flows, which among other things includes decay and the effect of changes in interest rates. Ineffectiveness of hedging the MSR fair value is measured by comparing the change in the fair value of the hedge instruments to the change in the fair value of the MSR asset attributable to changes in interest rates and other market driven changes in valuation inputs and assumptions. Trustmark offers certain derivatives products directly to qualified commercial lending clients seeking to manage their interest rate risk. Trustmark economically hedges interest rate swap transactions executed with commercial lending clients by entering into offsetting interest rate swap transactions with institutional derivatives market participants. Derivative transactions executed as part of this program are not designated as qualifying hedging relationships and are, therefore, carried at fair value with the change in fair value recorded as noninterest income in bank card and other fees. Because these derivatives have mirror-image contractual terms, in addition to collateral provisions which mitigate the impact of non-performance risk, the changes in fair value are expected to substantially offset.
Income Taxes	Income Taxes Trustmark accounts for uncertain tax positions in accordance with FASB ASC Topic 740, “Income Taxes,” which clarifies the accounting and disclosure for uncertainty in tax positions. Under the guidance of FASB ASC Topic 740, Trustmark accounts for deferred income taxes using the liability method. Deferred tax assets and liabilities are based on temporary differences between the financial statement carrying amounts and the tax basis of Trustmark’s assets and liabilities. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be realized or settled and are presented net in the accompanying consolidated balance sheets in other assets.
Stock-Based Compensation	Stock-Based Compensation Trustmark accounts for the stock and incentive compensation under the provisions of FASB ASC Topic 718, “Compensation – Stock Compensation.” Under this accounting guidance, fair value is established as the measurement objective in accounting for stock awards and requires the application of a fair value based measurement method in accounting for compensation cost, which is recognized over the requisite service period. Trustmark has elected to account for forfeitures of stock awards as they occur.
Statements of Cash Flows	Statements of Cash Flows For purposes of reporting cash flows, cash and cash equivalents include cash on hand and amounts due from banks. The following table reflects specific transaction amounts for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Income taxes paid $ 7,371 $ 24,836 $ 16,321 Interest expense paid on deposits and borrowings 41,472 24,312 20,733 Noncash transfers from loans to other real estate (1) 8,760 23,965 32,782 Transfer of long-term FHLB advances to short-term 250,038 500,009 — Assets acquired in business combination 196,265 — — Liabilities assumed in business combination 184,949 — — (1) Includes transfers from covered loans to foreclosed properties.
Per Share Data	Per Share Data Trustmark accounts for per share data in accordance with FASB ASC Topic 260, “Earnings Per Share,” which provides that unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and shall be included in the computation of earnings per share (EPS) pursuant to the two-class method. Trustmark has determined that its outstanding unvested stock awards and deferred stock units are not participating securities. Based on this determination, no change has been made to Trustmark’s current computation for basic and diluted EPS. Basic EPS is computed by dividing net income by the weighted-average shares of common stock outstanding. Diluted EPS is computed by dividing net income by the weighted-average shares of common stock outstanding, adjusted for the effect of potentially dilutive stock awards outstanding during the period. The following table reflects weighted-average shares used to calculate basic and diluted EPS for the periods presented (in thousands): Years Ended December 31, 2017 2016 2015 Basic shares 67,727 67,620 67,550 Dilutive shares 160 164 142 Diluted shares 67,887 67,784 67,692 Weighted-average antidilutive stock awards were excluded in determining diluted EPS. The following table reflects weighted-average antidilutive stock awards for the periods presented (in thousands): Years Ended December 31, 2017 2016 2015 Weighted-average antidilutive stock awards 74 2 1
Fair Value Measurements	Fair Value Measurements FASB ASC Topic 820, “Fair Value Measurements and Disclosures,” defines fair value, establishes a framework for measuring fair value in generally accepted accounting principles, and requires certain disclosures about fair value measurements. The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. Depending on the nature of the asset or liability, Trustmark uses various valuation techniques and assumptions when estimating fair value. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. FASB ASC Topic 820 establishes a fair value hierarchy for valuation inputs that gives the highest priority to quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The fair value hierarchy is as follows: Level 1 Inputs – Valuation is based upon quoted prices (unadjusted) in active markets for identical assets or liabilities that Trustmark has the ability to access at the measurement date. Level 2 Inputs – Valuation is based upon quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability such as interest rates, yield curves, volatilities and default rates and inputs that are derived principally from or corroborated by observable market data. Level 3 Inputs – Unobservable inputs reflecting the reporting entity’s own determination about the assumptions that market participants would use in pricing the asset or liability based on the best information available. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the fair value measurement in its entirety is classified is based on the lowest level input that is significant to the fair value measurement in its entirety. Trustmark’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability. Transfers between levels of the fair value hierarchy are recognized on the actual date of the event or circumstances that caused the transfer.
Accounting Policies Recently Adopted and Pending Accounting Pronouncements	Accounting Policies Recently Adopted and Pending Accounting Pronouncements ASU 2018-02, “Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” Issued in February 2018, ASU 2018-02 seeks to help entities reclassify certain stranded income tax effects in accumulated other comprehensive income resulting from the Tax Cuts and Jobs Act of 2017 (Tax Reform Act), enacted on December 22, 2017. ASU 2018-02 was issued in response to concerns regarding current guidance in GAAP that requires deferred tax liabilities and assets to be adjusted for the effect of a change in tax laws or rates with the effect included in income from continuing operations in the reporting period that includes the enactment date, even in situations in which the related income tax effects of items in accumulated other comprehensive income were originally recognized in other comprehensive income, rather than net income, and as a result the stranded tax effects would not reflect the appropriate tax rate. The amendments of ASU 2018-02 allow an entity to make a reclassification from accumulated other comprehensive income to retained earnings for the stranded tax effects, which is the difference between the historical corporate income tax rate of 35.0% and the newly enacted corporate income tax rate of 21.0%. ASU 2018-02 is effective for fiscal years, and interim periods within those years, beginning after December 31, 2018; however, public business entities are allowed to early adopt the amendments of ASU 2018-02 in any interim period for which the financial statements have not yet been issued. The amendments of ASU 2018-02 may be applied either at the beginning of the period (annual or interim) of adoption or retrospectively to each of the period(s) in which the effect of the change in the U.S. federal corporate tax rate in the Tax Reform Act is recognized. As a result of the re-measurement of Trustmark’s deferred tax assets following the enactment of the Tax Reform Act, accumulated other comprehensive loss included $8.5 million of stranded tax effects at December 31, 2017. Trustmark intends to early adopt the amendments of 2018-02 during the first quarter of 2018 and plans to make an election to reclassify the stranded tax effects from accumulated other comprehensive loss to retaining earnings at the beginning of the period of adoption. The reclassification of the stranded tax effects will result in an increase in accumulated other comprehensive loss and a corresponding increase in retained earnings. Disclosures required by the amendments of ASU 2018-02 will be presented in the Quarterly Report on Form 10-Q for the period ending March 31, 2018. Adoption of ASU 2018-02 is not expected to have a material impact on Trustmark’s 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. The amendments of ASU 2017-12 are effective for fiscal years, and interim periods within those years, beginning after December 15, 2018. All transition requirements and elections must be applied to all hedging relationships existing at the date of adoption. Trustmark plans to adopt ASU 2017-12 during the first quarter of 2019 using the required modified retrospective transition method. Trustmark will recognize the cumulative effect of the change, if any, in the beginning balance of each affected component of equity as of January 1, 2019. Management is currently assessing all the potential impacts of the amendments in ASU 2017-12 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2017-12 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2017-09, “Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting.” ASU 2017-09 seeks to provide clarity, reduce diversity in practice, and reduce cost and complexity when applying the guidance in Topic 718, Compensation-Stock Compensation, regarding a change to the terms or conditions of a share-based payment award. In fact, ASU 2017-09 provides guidance concerning which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. Specifically, an entity is to account for the effects of a modification, unless all of the following are satisfied: (1) the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the modified award is the same as the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the original award immediately before the original award is modified; (2) the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; and (3) the classification of the modified award as an equity instrument or as a liability instrument is the same as the classification of the original award immediately before the original award is modified. Note that the current disclosure requirements in Topic 718 apply regardless of whether an entity is required to apply modification accounting under the amendments in this ASU. The amendments of ASU 2017-09 became effective for Trustmark on January 1, 2018 and had no impact on Trustmark’s consolidated financial statements. However, should Trustmark modify the terms or conditions of any share-based payment award in the future, this modification would be evaluated and disclosed as appropriate based on the amendments of ASU 2017-09. 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 become effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018. Trustmark plans to adopt these amendments during the first quarter of 2019. As of December 31, 2017, Trustmark’s total unamortized premium for purchased debt securities within the scope of ASU 2017-08 was immaterial. 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 2017-08 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2017-07, “ Compensation-Retirement Benefits (Topic 715)-Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” Issued in March 2017, ASU 2017-07 is designed to improve guidance related to the presentation of defined benefit costs in the income statement. In particular, ASU No. 2017-07 requires that an employer report the service cost component in the same line item(s) as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations, if one is presented. If a separate line item or items are used to present the other components of net benefit cost, then that line item or items must be appropriately described. However, if a separate line item or items are not used, then the line item(s) used in the income statement to present the other components of net benefit cost must be disclosed. Additionally, ASU 2017-07 allows only the service cost component to be eligible for capitalization, when applicable. The amendments of ASU 2017-07 must be applied retrospectively for the presentation of the service cost component and the other components of net periodic benefit cost in the income statement and prospectively, on or after the adoption date, for capitalization of the service cost component in assets. Management has evaluated the amendments of this ASU and determined that the amendments of ASU 2017-07 would require a reclassification of the net periodic benefit cost, with the exception of the service cost component, from salaries and employee benefits to other expense on the consolidated statements of income for each period presented, which is not considered material to Trustmark’s consolidated financial statements. Trustmark adopted the amendments of ASU 2017-07 effective January 1, 2018. Trustmark has elected the available practical expedient which allows Trustmark to use the amounts disclosed in its pension and other postretirement benefits footnote for the prior comparative periods for applying the retrospective presentation requirements This change in presentation will be presented beginning with the Quarterly Report on Form 10-Q for the period ending March 31, 2018. 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, 2017, 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 2017-01, “Business Combinations (Topic 805) - Clarifying the Definition of a Business.” Issued in January 2017, ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses, which determines whether goodwill should be recorded or not. The amendments in ASU No. 2017-01 provide a screen to determine when a set of assets and activities (collectively, a “set”) is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. This screen reduces the number of transactions that need to be further evaluated. If, however, the screen is not met, then the amendments in ASU 2017-01 require that to be considered a business, a set must include, at a minimum, an input and a substantive process that together significantly contribute to the ability to create output and remove the evaluation of whether a market participant could replace missing elements. The revised definition will result in more transactions being recorded as asset acquisitions or dispositions as opposed to business acquisitions or dispositions. The amendments of ASU 2017-01 must be applied prospectively to transactions occurring on or after the adoption date. The amendments of ASU 2017-01 became effective for Trustmark on January 1, 2018 and did not have any impact to Trustmark’s consolidated financial statements; however, any future business combinations will be evaluated and disclosed as appropriate based on the amendments of ASU 2017-01. ASU 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” Issued in August 2016, ASU 2016-15 provides guidance to reduce the diversity in practice of how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The amendments of ASU 2016-15 provide guidance on eight specific cash flow: (i) debt prepayment or debt extinguishment costs; (ii) settlement of zero-coupon bonds; (iii) contingent consideration payments made after a business combination; (iv) proceeds from the settlement of insurance claims; (v) proceeds from the settlement of corporate-owned life insurance policies, including bank-owned life insurance policies; (vi) distributions received from equity method investees; (vii) beneficial interests in securitization transactions and (viii) separately identifiable cash flows and application of the predominance principle. Trustmark adopted the amendments of ASU 2016-15 effective January 1, 2018, and adoption of this ASU did not have any impact to Trustmark’s existing presentation of the applicable cash receipts and cash payments on its consolidated statements of cash flows. 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 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 selected a third-party vendor to provide an automated allowance for loan loss software as well as advisory services in developing a new allowance for loan loss 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 intends to adopt the amendments of ASU 2016-13 during the first quarter of 2020. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements through its effective date. ASU 2016-09, “Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” Issued in March 2016, ASU 2016-09 seeks to reduce complexity in accounting standards by simplifying several aspects of the accounting for share-based payment transactions. The amendments of ASU 2016-09 include: (i) requiring all excess tax benefits and tax deficiencies to be recognized as income tax expense or benefit in the income statement; (ii) requiring excess tax benefits to be classified along with other income tax cash flows as an operating activity on the statement of cash flow; (iii) allowing an entity to make an entity-wide accounting policy election to either estimate the number of awards that expect to vest or account for forfeitures when they occur; (iv) change the threshold to qualify for equity classification to permit withholding up to the maximum statutory tax rates in the applicable jurisdictions; and (v) requiring that cash paid by an employer when directly withholding shares for tax-withholding purposes to be classified as a financing activity on the statement of cash flows. The amendments of ASU 2016-09 became effective for Trustmark on January 1, 2017. Trustmark elected to present changes to the consolidated statements of cash flows on a retrospective basis, which resulted in $107 thousand and $211 thousand of excess tax expense from stock-based compensation arrangements being reclassified from financing activities to other operating activities, net and $1.0 million and $863 thousand of withholding taxes paid for shares directly withheld being reclassified from other operating activities, net to financing activities for the years ended December 31, 2016 and 2015, respectively. Adoption of ASU 2016-09 did not materially affect Trustmark’s consolidated financial statements. Trustmark has made an entity-wide accounting policy election to account for forfeitures of stock awards as they occur. Changes as required by the amendments of ASU 2016-09 are presented in the accompanying consolidated statements of cash flows. 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 will, among other things, require 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. The amendments of ASU 2016-02 are effective for interim and annual periods beginning after December 15, 2018. Trustmark plans to adopt the amendments of ASU 2016-02 beginning in the first quarter of 2019. At adoption, Trustmark will recognize a lease asset and a corresponding lease liability on its consolidated balance sheet for its total lease obligation measured on a discounted basis. As of December 31, 2017, all leases in which Trustmark was the lessee were classified as operating leases and the total outstanding lease obligation was $67.9 million, or 0.5% of total assets. Management is currently evaluating these lease obligations as potential lease assets and liabilities as defined by ASU 2016-02. Trustmark does not anticipant any material impact to its consolidated statements of income as a result of the adoption of this ASU. Trustmark has an immaterial amount of leases in which it is the lessor. Based on Management’s evaluation to date, Trustmark does not expect the amendments of ASU 2016-02 to have any material impact to these leases or the related income. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements; however, the adoption of ASU 2016-02 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2016-01, “Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (An Amendment of the FASB Accounting Standards Codification).” Issued in January 2016, ASU 2016-01 is intended to enhance the reporting model for financial instruments to provide users of financial statements with improved decision-making information. The amendments of ASU 2016-01 include: (i) requiring equity investments, except those accounted for under the equity method of accounting or those that result in the consolidation of an investee, to be measured at fair value with changes in fair value recognized in net income; (ii) requiring a qualitative assessment to identify impairment of equity investments without readily determinable fair values; (iii) eliminating the requirement to disclose the method and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost on the balance sheet; (iv) requiring the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes; (v) requiring an entity that has elected the fair value option to measure the fair value of a liability to present separately in other comprehensive income the portion of the change in the fair value resulting from a change in the instrument-specific credit risk; (vi) requiring separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or the accompanying notes to the financial statements and (vii) clarifying that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available for sale securities in combination with the entity’s other deferred tax assets. The amendments of ASU 2016-01 became effective for Trustmark on January 1, 2018. Trustmark’s investments in member bank stock, which are equity securities that do not have readily determinable fair values, are not within the scope of ASU 2016-01. See Note 1 – Significant Accounting Policies, “Federal Home Loan Bank (FHLB) and Federal Reserve Bank of Atlanta Stock” for information regarding Trustmark’s investment in member bank stock. The amendments of ASU 2016-01, specifically amendments (iii) and (iv) described above, will require changes to Trustmark’s fair value related disclosures. Trustmark has selected a third-party vendor to measure the fair value of the LHFI portfolio using the exit price notion as required by amendment (iv) above. The adoption of ASU 2016-01 did not have a material impact on Trustmark’s consolidated financial statements. Changes to Trustmark’s fair value related disclosures will be presented beginning with the Quarterly Report on Form 10-Q as of March 31, 2018. ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).” Issued in May 2014, ASU 2014-09 will add FASB ASC Topic 606, “Revenue from Contracts with Customers,” and will supersede revenue recognition requirements in FASB ASC Topic 605, “Revenue Recognition,” as well as certain cost guidance in FASB ASC Topic 605-35, “Revenue Recognition – Construction-Type and Production-Type Contracts.” ASU 2014-09 provides a framework for revenue recognition that replaces the existing industry and transaction specific requirements under the existing standards. ASU 2014-09 requires an entity to apply a five-step model to determine when to recognize revenue and at what amount. The model specifies that revenue should be recognized when (or as) an entity transfers control of goods or services to a customer at the amount in which the entity expects to be entitled. Depending on whether certain criteria are met, revenue should be recognized either over time, in a manner that depicts the entity’s performance, or at a point in time, when control of the goods or services are transferred to the customer. ASU 2014-09 provides that an entity should apply the following steps: (1) identify the contract(s) with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when, or as, the entity satisfies a performance obligation. In addition, the existing requirements for the recognition of a gain or loss on the transfer of non-financial assets that are not in a contract with a customer are amended to be consistent with the guidance on recognition and measurement in ASU 2014-09. The amendments of ASU 2014-09 may be applied either retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying ASU 2014-09 recognized at the date of initial application. If the transition method of application is elected, the entity should also provide the additional disclosures in reporting periods that include the date of initial application of (1) the amount by which each financial statement line item is affected in the current reporting period, as compared to the guidance that was in effect before the change, and (2) an explanation of the reasons for significant changes. The amendments of ASU 2014-09 and all subsequently issued ASUs, which provided additional guidance and clarifications to various aspects of FASB ASC Topic 606, became effective for Trustmark on January 1, 2018. Trustmark elected to adopt these amendments using the modified retrospective method of application for only those contracts not completed as of the date of adoption. Trustmark’s contracts with customers are primarily for a term of one year or less and substantially all of Trustmark’s contracts were completed as of January 1, 2018. Management has determined that approximately 23% of the revenues earned by Trustmark are within the scope of ASU 2014-09, and, for most of the revenue streams within the scope of ASU 2014-09, the amendments do not change the timing or amount of revenue recognized. The adoption of ASU 2014-09 did not have a material impact on Trustmark’s consolidated financial statements. No cumulative adjustment was recorded as a result of the adoption of ASU 2014-09. Disclosures required by the amendments of ASU 2014-09 will be presented beginning with the Quarterly Report on Form 10-Q for the period ending March 31, 2018.

Significant Accounting Polici31

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Cash Flows Supplementary Disclosures	For purposes of reporting cash flows, cash and cash equivalents include cash on hand and amounts due from banks. The following table reflects specific transaction amounts for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Income taxes paid $ 7,371 $ 24,836 $ 16,321 Interest expense paid on deposits and borrowings 41,472 24,312 20,733 Noncash transfers from loans to other real estate (1) 8,760 23,965 32,782 Transfer of long-term FHLB advances to short-term 250,038 500,009 — Assets acquired in business combination 196,265 — — Liabilities assumed in business combination 184,949 — — (1) Includes transfers from covered loans to foreclosed properties.
Weighted-Average Shares Used to Calculate Basic and Diluted EPS	The following table reflects weighted-average shares used to calculate basic and diluted EPS for the periods presented (in thousands): Years Ended December 31, 2017 2016 2015 Basic shares 67,727 67,620 67,550 Dilutive shares 160 164 142 Diluted shares 67,887 67,784 67,692
Weighted-Average Antidilutive Stock Awards Excluded from Determining Diluted EPS	Weighted-average antidilutive stock awards were excluded in determining diluted EPS. The following table reflects weighted-average antidilutive stock awards for the periods presented (in thousands): Years Ended December 31, 2017 2016 2015 Weighted-average antidilutive stock awards 74 2 1

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2017
Reliance [Member]
Business Acquisition [Line Items]
Summary of Estimated Fair Values of Assets Purchased and Liabilities Assumed	The statement of assets purchased and liabilities assumed in the Reliance merger is presented below at their estimated fair values as of the merger date of April 7, 2017 ($ in thousands): Assets: Cash and due from banks $ 5,013 Federal funds sold and securities purchased under reverse repurchase agreements 6,900 Securities 54,843 Acquired loans 117,447 Premises and equipment, net 3,700 Identifiable intangible assets 1,850 Other real estate 475 Other assets 6,037 Total Assets 196,265 Liabilities: Deposits 166,158 Other borrowings 17,469 Other liabilities 1,322 Total Liabilities 184,949 Net identified assets acquired at fair value 11,316 Goodwill 13,471 Total consideration paid $ 24,787

Securities Available for Sale33

Securities Available for Sale and Held to Maturity (Tables)	12 Months Ended
	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Amortized Cost and Estimated Fair Value of Available for Sale and Held to Maturity Securities	The following tables are a summary of the amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2017 and 2016 ($ in thousands): Securities Available for Sale Securities Held to Maturity Gross Gross Estimated Gross Gross Estimated Amortized Unrealized Unrealized Fair Amortized Unrealized Unrealized Fair December 31, 2017 Cost Gains Losses Value Cost Gains Losses Value U.S. Government agency obligations Issued by U.S. Government agencies $ 45,508 $ 310 $ (800 ) $ 45,018 $ — $ — $ — $ — Issued by U.S. Government sponsored agencies 255 12 — 267 3,692 182 — 3,874 Obligations of states and political subdivisions 78,433 850 (54 ) 79,229 46,039 1,044 (59 ) 47,024 Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 66,634 215 (1,103 ) 65,746 13,539 207 (73 ) 13,673 Issued by FNMA and FHLMC 824,872 827 (11,249 ) 814,450 133,975 210 (1,559 ) 132,626 Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 1,028,176 1,808 (13,194 ) 1,016,790 678,926 1,209 (11,065 ) 669,070 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 218,252 426 (1,543 ) 217,135 180,315 1,102 (1,437 ) 179,980 Total $ 2,262,130 $ 4,448 $ (27,943 ) $ 2,238,635 $ 1,056,486 $ 3,954 $ (14,193 ) $ 1,046,247 December 31, 2016 U.S. Government agency obligations Issued by U.S. Government agencies $ 56,272 $ 416 $ (925 ) $ 55,763 $ — $ — $ — $ — Issued by U.S. Government sponsored agencies 257 19 — 276 3,647 355 — 4,002 Obligations of states and political subdivisions 113,541 1,945 (113 ) 115,373 46,303 1,476 (27 ) 47,752 Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 43,222 340 (776 ) 42,786 15,478 280 (52 ) 15,706 Issued by FNMA and FHLMC 638,809 1,773 (9,498 ) 631,084 81,299 223 (1,084 ) 80,438 Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 1,271,198 5,865 (9,112 ) 1,267,951 803,474 3,208 (6,519 ) 800,163 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 242,869 1,766 (1,186 ) 243,449 208,442 1,758 (1,215 ) 208,985 Total $ 2,366,168 $ 12,124 $ (21,610 ) $ 2,356,682 $ 1,158,643 $ 7,300 $ (8,897 ) $ 1,157,046
Securities with Gross Unrealized Losses, Segregated by Length of Impairment	The table below includes securities with gross unrealized losses segregated by length of impairment at December 31, 2017 and 2016 ($ in thousands): Less than 12 Months 12 Months or More Total Gross Gross Gross Estimated Unrealized Estimated Unrealized Estimated Unrealized December 31, 2017 Fair Value Losses Fair Value Losses Fair Value Losses U.S. Government agency obligations Issued by U.S. Government agencies $ 5,214 $ (113 ) $ 29,432 $ (687 ) $ 34,646 $ (800 ) Obligations of states and political subdivisions 19,345 (80 ) 3,874 (33 ) 23,219 (113 ) Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 37,304 (351 ) 29,446 (825 ) 66,750 (1,176 ) Issued by FNMA and FHLMC 506,410 (4,219 ) 369,060 (8,589 ) 875,470 (12,808 ) Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 755,013 (7,668 ) 534,955 (16,591 ) 1,289,968 (24,259 ) Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 230,898 (1,719 ) 55,288 (1,261 ) 286,186 (2,980 ) Total $ 1,554,184 $ (14,150 ) $ 1,022,055 $ (27,986 ) $ 2,576,239 $ (42,136 ) December 31, 2016 U.S. Government agency obligations Issued by U.S. Government agencies $ 9,420 $ (142 ) $ 33,248 $ (783 ) $ 42,668 $ (925 ) Obligations of states and political subdivisions 20,539 (135 ) 654 (5 ) 21,193 (140 ) Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 43,615 (822 ) 222 (6 ) 43,837 (828 ) Issued by FNMA and FHLMC 588,352 (10,582 ) — — 588,352 (10,582 ) Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 1,127,501 (12,722 ) 76,196 (2,909 ) 1,203,697 (15,631 ) Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 244,050 (2,311 ) 4,655 (90 ) 248,705 (2,401 ) Total $ 2,033,477 $ (26,714 ) $ 114,975 $ (3,793 ) $ 2,148,452 $ (30,507 )
Gains and Losses as a Result of Calls and Disposition of Securities	For the periods presented, gains and losses as a result of calls and dispositions of securities, as well as any associated proceeds, were as follows ($ in thousands): Years Ended December 31, Available for Sale 2017 2016 2015 Proceeds from calls and sales of securities $ 27,682 $ 24,693 $ — Gross realized gains 16 32 — Gross realized losses (1 ) (342 ) —
Contractual Maturities of Available for Sale and Held to Maturity Securities	The amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2017, by contractual maturity, are shown below ($ in thousands). Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities Securities Available for Sale Held to Maturity Amortized Estimated Amortized Estimated Cost Fair Value Cost Fair Value Due in one year or less $ 31,376 $ 31,525 $ 155 $ 155 Due after one year through five years 57,372 58,343 40,594 41,450 Due after five years through ten years 3,866 3,845 8,982 9,293 Due after ten years 31,582 30,801 — — 124,196 124,514 49,731 50,898 Mortgage-backed securities 2,137,934 2,114,121 1,006,755 995,349 Total $ 2,262,130 $ 2,238,635 $ 1,056,486 $ 1,046,247

LHFI and Allowance for Loan L34

LHFI and Allowance for Loan Losses, LHFI (Tables)	12 Months Ended
	Dec. 31, 2017
Accounts Notes Loans And Financing Receivable Gross Allowance And Net [Abstract]
Loan Portfolio Held for Investment	At December 31, 2017 and 2016, LHFI consisted of the following ($ in thousands): December 31, 2017 2016 Loans secured by real estate: Construction, land development and other land $ 987,624 $ 831,437 Secured by 1-4 family residential properties 1,675,311 1,660,043 Secured by nonfarm, nonresidential properties 2,193,823 2,034,176 Other real estate secured 517,956 318,148 Commercial and industrial loans 1,570,345 1,528,434 Consumer loans 171,918 170,562 State and other political subdivision loans 952,483 917,515 Other loans 500,507 390,898 LHFI (1) 8,569,967 7,851,213 Less allowance for loan losses, LHFI 76,733 71,265 Net LHFI $ 8,493,234 $ 7,779,948
Nonaccrual LHFI by Loan Type	The following table details nonaccrual LHFI by loan type at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Loans secured by real estate: Construction, land development and other land $ 2,105 $ 3,323 Secured by 1-4 family residential properties 19,022 20,329 Secured by nonfarm, nonresidential properties 12,608 8,482 Other real estate secured 212 402 Commercial and industrial loans 33,338 15,824 Consumer loans 135 300 State and other political subdivision loans — — Other loans 155 574 Total nonaccrual LHFI $ 67,575 $ 49,234
Aging Analysis of Past Due and Nonaccrual LHFI by Loan Type	The following tables provide an aging analysis of past due and nonaccrual LHFI by loan type at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Past Due 90 Days Current 30-59 Days 60-89 Days or More (1) Total Nonaccrual Loans Total Loans secured by real estate: Construction, land development and other land $ 391 $ 1 $ — $ 392 $ 2,105 $ 985,127 $ 987,624 Secured by 1-4 family residential properties 6,412 2,084 1,917 10,413 19,022 1,645,876 1,675,311 Secured by nonfarm, nonresidential properties 2,319 256 — 2,575 12,608 2,178,640 2,193,823 Other real estate secured — — — — 212 517,744 517,956 Commercial and industrial loans 759 1,233 12 2,004 33,338 1,535,003 1,570,345 Consumer loans 2,141 255 242 2,638 135 169,145 171,918 State and other political subdivision loans 350 39 — 389 — 952,094 952,483 Other loans 18 4 — 22 155 500,330 500,507 Total $ 12,390 $ 3,872 $ 2,171 $ 18,433 $ 67,575 $ 8,483,959 $ 8,569,967 (1) Past due 90 days or more but still accruing interest. December 31, 2016 Past Due 90 Days Current 30-59 Days 60-89 Days or More (1) Total Nonaccrual Loans Total Loans secured by real estate: Construction, land development and other land $ 248 $ 37 $ 54 $ 339 $ 3,323 $ 827,775 $ 831,437 Secured by 1-4 family residential properties 5,308 2,434 1,436 9,178 20,329 1,630,536 1,660,043 Secured by nonfarm, nonresidential properties 606 100 — 706 8,482 2,024,988 2,034,176 Other real estate secured 179 — — 179 402 317,567 318,148 Commercial and industrial loans 571 213 — 784 15,824 1,511,826 1,528,434 Consumer loans 1,561 330 341 2,232 300 168,030 170,562 State and other political subdivision loans 1,035 — — 1,035 — 916,480 917,515 Other loans 178 53 — 231 574 390,093 390,898 Total $ 9,686 $ 3,167 $ 1,831 $ 14,684 $ 49,234 $ 7,787,295 $ 7,851,213 (1) Past due 90 days or more but still accruing interest.
Impaired Financing Receivables	At December 31, 2017 and 2016, the carrying amount of LHFI individually evaluated for impairment consisted of the following ($ in thousands): December 31, 2017 LHFI Unpaid Wit h o With an Total Average Principal Allowance Allowance Carrying Related Recorded Balance Recorded Recorded Amount Allowance Investment Loans secured by real estate: Construction, land development and other land $ 1,704 $ 1,206 $ 199 $ 1,405 $ 75 $ 1,923 Secured by 1-4 family residential properties 6,031 160 4,576 4,736 1,331 4,693 Secured by nonfarm, nonresidential properties 15,205 10,027 396 10,423 165 8,321 Other real estate secured — — — — — — Commercial and industrial loans 36,874 31,281 518 31,799 131 22,734 Consumer loans 17 — 17 17 — 9 State and other political subdivision loans — — — — — — Other loans 556 — 556 556 41 325 Total $ 60,387 $ 42,674 $ 6,262 $ 48,936 $ 1,743 $ 38,005 December 31, 2016 LHFI Unpaid Wit h o With an Total Average Principal Allowance Allowance Carrying Related Recorded Balance Recorded Recorded Amount Allowance Investment Loans secured by real estate: Construction, land development and other land $ 5,691 $ 2,213 $ 228 $ 2,441 $ 103 $ 2,943 Secured by 1-4 family residential properties 6,134 221 4,428 4,649 960 4,639 Secured by nonfarm, nonresidential properties 8,562 5,784 435 6,219 221 6,703 Other real estate secured — — — — — 500 Commercial and industrial loans 14,593 11,222 2,447 13,669 1,976 14,258 Consumer loans 2 — 2 2 — 2 State and other political subdivision loans — — — — — — Other loans 95 — 95 95 — 95 Total $ 35,077 $ 19,440 $ 7,635 $ 27,075 $ 3,260 $ 29,140
Impact of Modifications Classified as Troubled Debt Restructurings	The following tables illustrate the impact of modifications classified as TDRs as well as those TDRs modified within the last 12 months for which there was a payment default during the period for the periods presented ($ in thousands): Year Ended December 31, 2017 Modifications Classified as TDRs Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by real estate: Construction, land development and other land 1 $ 341 $ 325 Secured by 1-4 family residential properties 22 1,478 1,487 Secured by nonfarm, nonresidential properties 1 426 426 Commercial and industrial loans 8 12,836 12,836 Other loans 1 556 556 Total 33 $ 15,637 $ 15,630 Year Ended December 31, 2016 Modifications Classified as TDRs Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by real estate: Construction, land development and other land 1 $ 14 $ 14 Secured by 1-4 family residential properties 18 1,386 1,391 Secured by nonfarm, nonresidential properties 2 717 717 Commercial and industrial loans 5 10,043 9,982 Consumer loans 1 2 2 Total 27 $ 12,162 $ 12,106 Year Ended December 31, 2015 Modifications Classified as TDRs Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by real estate: Secured by 1-4 family residential properties 13 $ 688 $ 688 Secured by nonfarm, nonresidential properties 5 3,613 3,613 Total 18 $ 4,301 $ 4,301
Troubled Debt Restructuring Subsequently Defaulted	Years Ended December 31, 2017 2016 2015 TDRs that Subsequently Defaulted Number of Contracts Recorded Investment Number of Contracts Recorded Investment Number of Contracts Recorded Investment Loans secured by 1-4 family residential properties 4 $ 78 1 $ — 5 $ 260 Commercial and industrial loans 3 9,526 2 2,154 — — Total 7 $ 9,604 3 $ 2,154 5 $ 260
Troubled Debt Restructuring Related to Loans Held for Investment by Loan Type	The following tables detail LHFI classified as TDRs by loan type at December 31, 2017, 2016 and 2015 ($ in thousands): December 31, 2017 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 199 $ 199 Secured by 1-4 family residential properties 51 3,140 3,191 Secured by nonfarm, nonresidential properties — 421 421 Commercial and industrial loans 53 19,434 19,487 Consumer loans — 17 17 Other loans 556 — 556 Total TDRs $ 660 $ 23,211 $ 23,871 December 31, 2016 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 405 $ 405 Secured by 1-4 family residential properties — 2,873 2,873 Secured by nonfarm, nonresidential properties — 881 881 Commercial and industrial loans 53 10,266 10,319 Consumer loans — 2 2 Total TDRs $ 53 $ 14,427 $ 14,480 December 31, 2015 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 869 $ 869 Secured by 1-4 family residential properties 1,426 2,424 3,850 Secured by nonfarm, nonresidential properties 809 3,662 4,471 Commercial and industrial loans — 463 463 Total TDRs $ 2,235 $ 7,418 $ 9,653
Carrying Amount of Loans by Credit Quality Indicator	The tables below present LHFI by loan type and credit quality indicator at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Commercial LHFI Pass - Special Mention - Substandard - Doubtful - Categories Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 922,563 $ 316 $ 3,780 $ 222 $ 926,881 Secured by 1-4 family residential properties 127,405 134 4,948 76 132,563 Secured by nonfarm, nonresidential properties 2,135,749 6,684 50,785 527 2,193,745 Other real estate secured 517,036 — 517 — 517,553 Commercial and industrial loans 1,437,590 28,780 103,089 886 1,570,345 Consumer loans — — — — — State and other political subdivision loans 936,420 5,850 10,213 — 952,483 Other loans 478,083 — 16,390 108 494,581 Total $ 6,554,846 $ 41,764 $ 189,722 $ 1,819 $ 6,788,151 Consumer LHFI Past Due Past Due Current 30-89 Days 90 Days or More Nonaccrual Subtotal Total LHFI Loans secured by real estate: Construction, land development and other land $ 60,240 $ 342 $ — $ 161 $ 60,743 $ 987,624 Secured by 1-4 family residential properties 1,516,691 7,874 1,809 16,374 1,542,748 1,675,311 Secured by nonfarm, nonresidential properties 78 — — — 78 2,193,823 Other real estate secured 403 — — — 403 517,956 Commercial and industrial loans — — — — — 1,570,345 Consumer loans 169,146 2,396 242 134 171,918 171,918 State and other political subdivision loans — — — — — 952,483 Other loans 5,926 — — — 5,926 500,507 Total $ 1,752,484 $ 10,612 $ 2,051 $ 16,669 $ 1,781,816 $ 8,569,967 December 31, 2016 Commercial LHFI Pass - Special Mention - Substandard - Doubtful - Categories 1-6 Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 752,318 $ 9,567 $ 8,086 $ 465 $ 770,436 Secured by 1-4 family residential properties 124,615 170 6,162 129 131,076 Secured by nonfarm, nonresidential properties 1,989,554 4,394 38,913 584 2,033,445 Other real estate secured 315,829 762 890 — 317,481 Commercial and industrial loans 1,386,155 7,095 134,199 985 1,528,434 Consumer loans — — — — — State and other political subdivision loans 899,935 6,450 11,130 — 917,515 Other loans 382,890 — 2,685 350 385,925 Total $ 5,851,296 $ 28,438 $ 202,065 $ 2,513 $ 6,084,312 Consumer LHFI Past Due Past Due Current 30-89 Days 90 Nonaccrual Subtotal Total LHFI Loans secured by real estate: Construction, land development and other land $ 60,701 $ 188 $ 54 $ 58 $ 61,001 $ 831,437 Secured by 1-4 family residential properties 1,503,096 7,377 1,436 17,058 1,528,967 1,660,043 Secured by nonfarm, nonresidential properties 731 — — — 731 2,034,176 Other real estate secured 667 — — — 667 318,148 Commercial and industrial loans — — — — — 1,528,434 Consumer loans 168,031 1,891 341 299 170,562 170,562 State and other political subdivision loans — — — — — 917,515 Other loans 4,940 33 — — 4,973 390,898 Total $ 1,738,166 $ 9,489 $ 1,831 $ 17,415 $ 1,766,901 $ 7,851,213
Change in Allowance for Loan Losses	The following tables detail the balance in the allowance for loan losses, LHFI allocated to each loan type segmented by the impairment evaluation methodology used at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Individually Collectively Total Loans secured by real estate: Construction, land development and other land $ 75 $ 7,790 $ 7,865 Secured by 1-4 family residential properties 1,331 9,543 10,874 Secured by nonfarm, nonresidential properties 165 23,263 23,428 Other real estate secured — 2,790 2,790 Commercial and industrial loans 131 22,720 22,851 Consumer loans — 3,470 3,470 State and other political subdivision loans — 789 789 Other loans 41 4,625 4,666 Total allowance for loan losses, LHFI $ 1,743 $ 74,990 $ 76,733 December 31, 2016 Individually Collectively Total Loans secured by real estate: Construction, land development and other land $ 103 $ 8,982 $ 9,085 Secured by 1-4 family residential properties 960 9,387 10,347 Secured by nonfarm, nonresidential properties 221 20,746 20,967 Other real estate secured — 2,263 2,263 Commercial and industrial loans 1,976 20,035 22,011 Consumer loans — 3,241 3,241 State and other political subdivision loans — 859 859 Other loans — 2,492 2,492 Total allowance for loan losses, LHFI $ 3,260 $ 68,005 $ 71,265 Changes in the allowance for loan losses, LHFI were as follows for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Balance at beginning of period $ 71,265 $ 67,619 $ 69,616 Loans charged-off (21,147 ) (18,930 ) (22,469 ) Recoveries 11,521 11,619 12,097 Net (charge-offs) recoveries (9,626 ) (7,311 ) (10,372 ) Provision for loan losses, LHFI 15,094 10,957 8,375 Balance at end of period $ 76,733 $ 71,265 $ 67,619 The following tables detail changes in the allowance for loan losses, LHFI by loan type for the years ended December 31, 2017 and 2016, respectively ($ in thousands): 2017 Balance Provision for Balance January 1, Charge-offs Recoveries Loan Losses December 31, Loans secured by real estate: Construction, land development and other land $ 9,085 $ (79 ) $ 1,428 $ (2,569 ) $ 7,865 Secured by 1-4 family residential properties 10,347 (950 ) 1,833 (356 ) 10,874 Secured by nonfarm, nonresidential properties 20,967 (4,231 ) 396 6,296 23,428 Other real estate secured 2,263 (5 ) 69 463 2,790 Commercial and industrial loans 22,011 (8,286 ) 2,578 6,548 22,851 Consumer loans 3,241 (2,546 ) 1,938 837 3,470 State and other political subdivision loans 859 — — (70 ) 789 Other loans 2,492 (5,050 ) 3,279 3,945 4,666 Total allowance for loan losses, LHFI $ 71,265 $ (21,147 ) $ 11,521 $ 15,094 $ 76,733 2016 Balance Provision for Balance January 1, Charge-offs Recoveries Loan Losses December 31, Loans secured by real estate: Construction, land development and other land $ 11,587 $ (311 ) $ 1,380 $ (3,571 ) $ 9,085 Secured by 1-4 family residential properties 10,678 (1,319 ) 1,122 (134 ) 10,347 Secured by nonfarm, nonresidential properties 21,563 (3,067 ) 976 1,495 20,967 Other real estate secured 2,467 (27 ) 7 (184 ) 2,263 Commercial and industrial loans 15,815 (6,602 ) 732 12,066 22,011 Consumer loans 2,879 (1,864 ) 4,007 (1,781 ) 3,241 State and other political subdivision loans 809 — — 50 859 Other loans 1,821 (5,740 ) 3,395 3,016 2,492 Total allowance for loan losses, LHFI $ 67,619 $ (18,930 ) $ 11,619 $ 10,957 $ 71,265
Summary Of LHFI Evaluated For Impairment	The following tables detail LHFI by loan type related to each balance in the allowance for loan losses, LHFI segregated by the impairment evaluation methodology used at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 LHFI Evaluated for Impairment Individually Collectively Total Loans secured by real estate: Construction, land development and other land $ 1,405 $ 986,219 $ 987,624 Secured by 1-4 family residential properties 4,736 1,670,575 1,675,311 Secured by nonfarm, nonresidential properties 10,423 2,183,400 2,193,823 Other real estate secured — 517,956 517,956 Commercial and industrial loans 31,799 1,538,546 1,570,345 Consumer loans 17 171,901 171,918 State and other political subdivision loans — 952,483 952,483 Other loans 556 499,951 500,507 Total $ 48,936 $ 8,521,031 $ 8,569,967 December 31, 2016 LHFI Evaluated for Impairment Individually Collectively Total Loans secured by real estate: Construction, land development and other land $ 2,441 $ 828,996 $ 831,437 Secured by 1-4 family residential properties 4,649 1,655,394 1,660,043 Secured by nonfarm, nonresidential properties 6,219 2,027,957 2,034,176 Other real estate secured — 318,148 318,148 Commercial and industrial loans 13,669 1,514,765 1,528,434 Consumer loans 2 170,560 170,562 State and other political subdivision loans — 917,515 917,515 Other loans 95 390,803 390,898 Total $ 27,075 $ 7,824,138 $ 7,851,213

Acquired Loans (Tables)

Acquired Loans (Tables)	12 Months Ended
	Dec. 31, 2017
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities [Abstract]
Schedule of Acquired Loans	At December 31, 2017 and 2016, acquired loans consisted of the following ($ in thousands): December 31, 2017 2016 Loans secured by real estate: Construction, land development and other land $ 23,586 $ 20,850 Secured by 1-4 family residential properties 61,751 69,540 Secured by nonfarm, nonresidential properties 114,694 103,820 Other real estate secured 16,746 19,010 Commercial and industrial loans 31,506 36,896 Consumer loans 2,600 3,365 Other loans 10,634 18,766 Acquired loans 261,517 272,247 Less allowance for loan losses, acquired loans 4,079 11,397 Net acquired loans $ 257,438 $ 260,850
Changes in the Carrying Value of Acquired Loans	The following table presents changes in the net carrying value of the acquired loans for the periods presented ($ in thousands): Acquired Acquired Impaired Not (1) Carrying value, net at January 1, 2016 $ 310,762 $ 67,657 Accretion to interest income 18,405 40 Payments received, net (111,522 ) (24,953 ) Other (2) (134 ) — Change in allowance for loan losses, acquired loans 596 (1 ) Carrying value, net at December 31, 2016 218,107 42,743 Transfers (3) — (36,719 ) Additions (4) 7,899 109,548 Accretion to interest income 14,924 1,578 Payments received, net (68,317 ) (39,208 ) Other (2) (361 ) (74 ) Change in allowance for loan losses, acquired loans 7,318 — Carrying value, net at December 31, 2017 $ 179,570 $ 77,868 (1) “Acquired Not ASC 310-30” loans consist of loans that are not in scope for FASB ASC Topic 310-30. (2) Includes miscellaneous timing adjustments as well as acquired loan terminations through foreclosure, charge-off and other terminations. (3) “Acquired Not ASC 310-20” loans transferred to LHFI due to the discount on these loans being fully amortized. (4) Loans acquired in the Reliance merger on April 7, 2017.
Changes in Accretable Yield of Acquired Loans	The following table presents changes in the accretable yield for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Accretable yield at beginning of period $ (38,918 ) $ (52,672 ) $ (77,149 ) Additions due to acquisition (1) (784 ) — — Accretion to interest income 14,924 18,405 30,501 Disposals 2,868 6,488 10,013 Reclassification from nonaccretable difference (2) (9,516 ) (11,139 ) (16,037 ) Accretable yield at end of period $ (31,426 ) $ (38,918 ) $ (52,672 ) (1) Accretable yield on loans acquired from Reliance on April 7, 2017. (2) Reclassifications from nonaccretable difference are due to lower loss expectations and improvements in expected cash flows.
Components of the Allowance for Loan Losses on Acquired Loans	The following tables present the components of the allowance for loan losses on acquired impaired loans for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Balance at beginning of period $ 11,397 $ 11,992 $ 12,059 Provision for loan losses, acquired loans (7,395 ) 3,757 3,425 Loans charged-off — (6,616 ) (7,200 ) Recoveries 77 2,264 3,708 Net (charge-offs) recoveries 77 (4,352 ) (3,492 ) Balance at end of period $ 4,079 $ 11,397 $ 11,992
Acquired Loans by Loan Type and Credit Quality Indicator	The tables below present the acquired loans by loan type and credit quality indicator at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Commercial Loans Pass - Special Mention - Substandard - Doubtful - Categories 1-6 Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 17,150 $ 234 $ 4,690 $ 264 $ 22,338 Secured by 1-4 family residential properties 14,021 298 3,029 — 17,348 Secured by nonfarm, nonresidential properties 95,147 1,400 17,583 530 114,660 Other real estate secured 12,730 102 3,031 477 16,340 Commercial and industrial loans 22,157 15 7,585 1,749 31,506 Consumer loans — — — — — Other loans 5,874 18 4,742 — 10,634 Total acquired loans $ 167,079 $ 2,067 $ 40,660 $ 3,020 $ 212,826 Consumer Loans Past Due Past Due Total Current 30-89 Days 90 Days or More Nonaccrual (1) Subtotal Acquired Loans Loans secured by real estate: Construction, land development and other land $ 1,188 $ 46 $ 14 $ — $ 1,248 $ 23,586 Secured by 1-4 family residential properties 42,008 1,687 584 124 44,403 61,751 Secured by nonfarm, nonresidential properties 34 — — — 34 114,694 Other real estate secured 406 — — — 406 16,746 Commercial and industrial loans — — — — — 31,506 Consumer loans 2,428 172 — — 2,600 2,600 Other loans — — — — — 10,634 Total acquired loans $ 46,064 $ 1,905 $ 598 $ 124 $ 48,691 $ 261,517 (1) Acquired loans not accounted for under FASB ASC Topic 310-30. December 31, 2016 Commercial Loans Pass - Special Mention - Substandard - Doubtful - Categories 1-6 Category 7 Category 8 Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 12,148 $ 99 $ 6,469 $ 322 $ 19,038 Secured by 1-4 family residential properties 14,552 61 4,066 69 18,748 Secured by nonfarm, nonresidential properties 83,271 435 19,553 511 103,770 Other real estate secured 15,344 — 2,673 565 18,582 Commercial and industrial loans 22,024 18 13,494 1,354 36,890 Consumer loans — — — — — Other loans 12,954 — 5,649 161 18,764 Total acquired loans $ 160,293 $ 613 $ 51,904 $ 2,982 $ 215,792 Consumer Loans Past Due Past Due Total Current 30-89 Days 90 Days or More Nonaccrual (1) Subtotal Acquired Loans Loans secured by real estate: Construction, land development and other land $ 1,801 $ — $ 11 $ — $ 1,812 $ 20,850 Secured by 1-4 family residential properties 48,695 1,364 709 24 50,792 69,540 Secured by nonfarm, nonresidential properties 50 — — — 50 103,820 Other real estate secured 428 — — — 428 19,010 Commercial and industrial loans 6 — — — 6 36,896 Consumer loans 3,250 51 64 — 3,365 3,365 Other loans 2 — — — 2 18,766 Total acquired loans $ 54,232 $ 1,415 $ 784 $ 24 $ 56,455 $ 272,247 (1) Acquired loans not accounted for under FASB ASC Topic 310-30 .
Aging Analysis of Past Due and Nonaccrual Acquired Loans, by Class	The following tables provide an aging analysis of contractually past due and nonaccrual acquired loans by loan type at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 Past Due 30-59 Days 60-89 Days 90 Days or More (1) Total Nonaccrual (2) Current Loans Total Acquired Loans Loans secured by real estate: Construction, land development and other land $ 34 $ 90 $ 861 $ 985 $ — $ 22,601 $ 23,586 Secured by 1-4 family residential properties 1,691 614 654 2,959 302 58,490 61,751 Secured by nonfarm, nonresidential properties 467 73 898 1,438 — 113,256 114,694 Other real estate secured 132 — — 132 — 16,614 16,746 Commercial and industrial loans — — — — 2 31,504 31,506 Consumer loans 16 156 — 172 — 2,428 2,600 Other loans — — 21 21 — 10,613 10,634 Total acquired loans $ 2,340 $ 933 $ 2,434 $ 5,707 $ 304 $ 255,506 $ 261,517 (1) Past due 90 days or more but still accruing interest. (2) Acquired loans not accounted for under FASB ASC Topic 310-30. December 31, 2016 Past Due 30-59 Days 60-89 Days 90 Days or More (1) Total Nonaccrual (2) Current Loans Total Acquired Loans Loans secured by real estate: Construction, land development and other land $ 321 $ 100 $ 821 $ 1,242 $ — $ 19,608 $ 20,850 Secured by 1-4 family residential properties 1,495 412 1,057 2,964 41 66,535 69,540 Secured by nonfarm, nonresidential properties 1,658 38 343 2,039 328 101,453 103,820 Other real estate secured 769 — 1,445 2,214 — 16,796 19,010 Commercial and industrial loans 60 39 — 99 262 36,535 36,896 Consumer loans 51 — 64 115 — 3,250 3,365 Other loans — — — — — 18,766 18,766 Total acquired loans $ 4,354 $ 589 $ 3,730 $ 8,673 $ 631 $ 262,943 $ 272,247 (1) Past due 90 days or more but still accruing interest. (2) Acquired loans not accounted for under FASB ASC Topic 310-30.

Premises and Equipment, Net (Ta

Premises and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Premises and Equipment	At December 31, 2017 and 2016, premises and equipment consisted of the following ($ in thousands): December 31, 2017 2016 Land $ 52,335 $ 51,097 Buildings and leasehold improvements 197,372 195,296 Furniture and equipment 166,071 172,170 Total cost of premises and equipment 415,778 418,563 Less accumulated depreciation and amortization 237,425 239,319 Premises and equipment, net 178,353 179,244 Assets held for sale 986 5,743 Total premises and equipment, net $ 179,339 $ 184,987

Mortgage Banking (Tables)

Mortgage Banking (Tables)	12 Months Ended
	Dec. 31, 2017
Mortgage Banking [Abstract]
Schedule of Activity in the Mortgage Servicing Rights	The activity in the MSR is detailed in the table below for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 Balance at beginning of period $ 80,239 $ 74,007 Origination of servicing assets 15,860 16,745 Change in fair value: Due to market changes (1,050 ) (407 ) Due to runoff (10,780 ) (10,106 ) Balance at end of period $ 84,269 $ 80,239
Schedule of Mortgage Loans Sold and Serviced for Others	The table below details the mortgage loans sold and serviced for others at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Federal National Mortgage Association $ 4,128,614 $ 3,992,349 Government National Mortgage Association 2,421,456 2,291,398 Federal Home Loan Mortgage Corporation 47,071 55,006 Other 26,864 32,589 Total mortgage loans sold and serviced for others $ 6,624,005 $ 6,371,342
Changes In The Reserve For Mortgage Loan Servicing Putback Expense	Changes in the reserve for mortgage loan servicing putback expense for mortgage loans were as follows for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Balance at beginning of period $ 1,130 $ 1,685 $ 1,170 Provision for putback expenses (836 ) 420 315 Other (1) 706 (975 ) 200 Balance at end of period $ 1,000 $ 1,130 $ 1,685 (1) Includes fair value adjustments for loans transferred due to underwriting issues as well as adjustments based on Trustmark’s mortgage loan servicing putback reserve analysis.

Goodwill and Identifiable Int38

Goodwill and Identifiable Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill by segment	The table below illustrates goodwill by segment for the years ended December 31, 2017 and 2016 ($ in thousands): General Banking Insurance Total Balance as of January 1, 2016 $ 321,132 $ 45,024 $ 366,156 Adjustment during 2016 — — — Balance as of December 31, 2016 321,132 45,024 366,156 Goodwill from Reliance merger during 2017 13,471 — 13,471 Balance as of December 31, 2017 $ 334,603 $ 45,024 $ 379,627
Schedule of identifiable intangible assets	At December 31, 2017 and 2016, identifiable intangible assets consisted of the following ($ in thousands): December 31, 2017 December 31, 2016 Gross Accumulated Net Carrying Gross Carrying Accumulated Net Carrying Amount Amortization Amount Amount Amortization Amount Core deposit intangibles $ 87,674 $ 73,494 $ 14,180 $ 85,824 $ 67,843 $ 17,981 Insurance intangibles 13,824 12,026 1,798 13,824 11,615 2,209 Banking charters 1,325 943 382 1,325 877 448 Borrower relationship intangible 690 690 — 690 648 42 Total $ 103,513 $ 87,153 $ 16,360 $ 101,663 $ 80,983 $ 20,680 The following table illustrates the carrying amounts and remaining weighted-average amortization periods of identifiable intangible assets as of December 31, 2017 ($ in thousands): Remaining Weighted- Average Net Carrying Amortization Amount Period in Core deposit intangibles $ 14,180 5.2 Insurance intangibles 1,798 15.3 Banking charters 382 5.7 Total $ 16,360 6.3

Other Real Estate (Tables)

Other Real Estate (Tables)	12 Months Ended
	Dec. 31, 2017
Other Real Estate And Foreclosed Assets [Abstract]
Changes and Gains, Net on Other Real Estate	For the periods presented, changes and gains, net on other real estate were as follows ($ in thousands): Years Ended December 31, 2017 2016 (1) 2015 (1) Balance at beginning of period $ 62,051 $ 78,828 $ 98,569 Additions (2) 9,235 24,525 32,782 Disposals (24,762 ) (36,801 ) (48,352 ) Write-downs (3,296 ) (4,501 ) (4,171 ) Balance at end of period $ 43,228 $ 62,051 $ 78,828 Gain, net on the sale of other real estate included in other real estate expense $ 2,087 $ 7,031 $ 4,041 (1) The changes and gains, net on other real estate for the years ended December 31, 2016 and 2015 include covered other real estate. (2) For the year ended December 31, 2017, additions to other real estate included $475 thousand of other real estate acquired in the Reliance merger on April 7, 2017.
Other Real Estate, By Type of Property	At December 31, 2017 and 2016, other real estate by type of property consisted of the following ($ in thousands): December 31, 2017 2016 Construction, land development and other land properties $ 27,491 $ 36,871 1-4 family residential properties 5,081 7,926 Nonfarm, nonresidential properties 10,468 16,817 Other real estate properties 188 437 Total other real estate $ 43,228 $ 62,051
Other Real Estate, By Geographic Location	At December 31, 2017 and 2016, other real estate by geographic location consisted of the following ($ in thousands): December 31, 2017 2016 Alabama $ 11,714 $ 15,989 Florida 13,937 22,582 Mississippi (1) 14,260 15,646 Tennessee (2) 2,535 6,183 Texas 782 1,651 Total other real estate $ 43,228 $ 62,051 (1) Mississippi includes Central and Southern Mississippi Regions (2) Tennessee includes Memphis, Tennessee and Northern Mississippi Regions

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Deposits Summary	At December 31, 2017 and 2016, deposits consisted of the following ($ in thousands): December 2017 2016 Noninterest-bearing demand $ 2,978,074 $ 2,973,238 Interest-bearing demand 2,432,814 1,875,312 Savings 3,408,183 3,586,369 Time 1,758,441 1,621,093 Total $ 10,577,512 $ 10,056,012
Interest Expense on Deposits by Type	Interest expense on deposits by type consisted of the following for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Interest-bearing demand $ 6,820 $ 3,297 $ 3,235 Savings 6,047 2,657 2,547 Time 9,850 6,794 6,816 Total $ 22,717 $ 12,748 $ 12,598
Maturities on Outstanding Time Deposits of $100 thousand or More	The maturities of time deposits of $100 thousand or more at December 31, 2017 and 2016 are as follows ($ in thousands): December 2017 2016 3 months or less $ 203,679 $ 150,991 Over 3 months through 6 months 183,679 147,089 Over 6 months through 12 months 276,944 204,944 Over 12 months 179,237 179,469 Total $ 843,539 $ 682,493
Maturities of Interest-Bearing Deposits	The maturities of interest-bearing deposits at December 31, 2017, are as follows ($ in thousands): 2018 $ 1,356,448 2019 268,989 2020 73,745 2021 23,191 2022 and thereafter 36,068 Total time deposits 1,758,441 Interest-bearing deposits with no stated maturity 5,840,997 Total interest-bearing deposits $ 7,599,438

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Securities Sold Under Repurchase Agreements	The following table presents the securities sold under repurchase agreements by collateral pledged at December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Mortgage-backed securities Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA $ 68,246 $ 75,795 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 50,448 51,212 Total securities sold under repurchase agreements $ 118,694 $ 127,007
Summary of Short-Term Borrowings	At December 31, 2017 and 2016, short-term borrowings consisted of the following ($ in thousands): December 2017 2016 FHLB advances $ 900,013 $ 700,008 Serviced GNMA loans eligible for repurchase 48,211 43,925 Other 22,825 25,845 Total short-term borrowings $ 971,049 $ 769,778

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Tax Provision	The income tax provision included in the consolidated statements of income was as follows for the periods presented ($ in thousands): Years Ended December 31, Current 2017 2016 2015 Federal $ 16,959 $ 10,355 $ 18,448 State 5,687 2,698 2,166 Deferred Federal 7,280 15,647 12,865 State 1,820 2,353 1,935 Income tax provision excluding deferred tax asset revaluation and reversal of valuation allowance 31,746 31,053 35,414 Deferred tax expense (benefit) - re-measurement of deferred tax assets 25,619 — — Deferred tax expense (benefit) - reversal of valuation allowance (8,650 ) — — Income tax provision $ 48,715 $ 31,053 $ 35,414
Income Tax Reconciliation	For the periods presented, the income tax provision differs from the amount computed by applying the statutory federal income tax rate of 35.0% to income before income taxes as a result of the following ($ in thousands): Years Ended December 31, 2017 2016 2015 Income tax computed at statutory tax rate $ 54,021 $ 48,812 $ 53,008 Tax exempt interest (7,611 ) (6,780 ) (5,908 ) Nondeductible interest expense 407 201 119 State income taxes, net 3,697 1,754 1,408 Income tax credits, net (15,793 ) (16,183 ) (15,283 ) Death benefit gains (3,268 ) — — Reversal of valuation allowance (8,650 ) — — Re-measurement of deferred tax assets 25,619 — — Other 293 3,249 2,070 Income tax provision $ 48,715 $ 31,053 $ 35,414
Deferred Tax Assets and Liabilities	Temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities gave rise to the following net deferred tax assets at December 31, 2017 and 2016, which are included in other assets ($ in thousands): December 31, 2017 2016 Deferred tax assets: Loan purchase accounting $ 3,638 $ 9,341 Other real estate 13,403 25,750 Allowance for loan losses 20,203 31,618 Deferred compensation 15,184 21,893 Realized built-in losses 12,932 18,699 Securities 4,869 9,256 Pension and other postretirement benefit plans 5,453 15,545 Interest on nonaccrual loans 774 2,093 Unrealized losses on securities available for sale 5,874 3,629 Stock-based compensation 2,067 3,031 Federal carryovers 4,569 — Other 8,964 13,731 Gross deferred tax asset 97,930 154,586 Valuation allowance — (8,650 ) Deferred tax asset net of valuation allowance 97,930 145,936 Deferred tax liabilities: Goodwill and other identifiable intangibles 16,729 25,666 Premises and equipment 11,877 19,391 Mortgage servicing rights 9,964 12,159 Securities 1,345 1,697 Leases — 60 Other 5,040 6,891 Gross deferred tax liability 44,955 65,864 Net deferred tax asset $ 52,975 $ 80,072
Changes in Unrecognized Tax Benefits	The following table provides a summary of the changes during the 2017 calendar year in the amount of unrecognized tax benefits that are included in other liabilities in the consolidated balance sheet ($ in thousands): Balance at January 1, 2017 $ 1,734 Increases due to tax positions taken during the current year 303 Decreases due to tax positions taken during a prior year (853 ) Decreases due to the lapse of applicable statute of limitations during the current year (79 ) Decreases due to settlements with taxing authorities during the current year — Balance at December 31, 2017 $ 1,105 Accrued interest, net of federal benefit, at December 31, 2017 $ 217 Unrecognized tax benefits that would impact the effective tax rate, if recognized, at December 31, 2017 $ 883

Defined Benefit and Other Pos43

Defined Benefit and Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Trustmark Capital Accumulation Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan Benefit Obligation, Plan Assets and Funded Status of the Plan	The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s tax-qualified defined benefit pension plans (the Continuing Plan and the Plan) for the periods presented ($ in thousands): December 31, 2017 2016 Change in benefit obligation: Benefit obligation, beginning of year $ 75,900 $ 91,403 Service cost 253 428 Interest cost 1,461 3,355 Actuarial loss (gain) 391 (893 ) Benefits paid for the Plan (68,583 ) (18,393 ) Settlement loss 680 — Benefit obligation, end of year $ 10,102 $ 75,900 Change in plan assets: Fair value of plan assets, beginning of year $ 54,734 $ 74,137 Actual return on plan assets 481 (1,079 ) Employer contributions 17,964 69 Benefit payments for the Plan (68,583 ) (18,393 ) Fair value of plan assets, end of year $ 4,596 $ 54,734 Funded status at end of year - net liability $ (5,506 ) $ (21,166 ) Amounts recognized in accumulated other comprehensive loss: Net loss - amount recognized $ 3,187 $ 21,355
Net Periodic Benefit Cost	Years Ended December 31, 2017 2016 2015 Net periodic benefit cost: Service cost $ 253 $ 428 $ 513 Interest cost 1,461 3,355 3,461 Expected return on plan assets (317 ) (2,897 ) (5,187 ) Recognized net loss due to defined benefit plan termination 17,662 — — Recognized net loss due to lump sum settlements — 3,906 2,221 Recognized net actuarial loss 1,414 2,749 3,878 Net periodic benefit cost $ 20,473 $ 7,541 $ 4,886 Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes: Net loss - Total recognized in other comprehensive income (loss) $ (18,168 ) $ (3,572 ) $ (3,173 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 2,305 $ 3,969 $ 1,713 Weighted-average assumptions as of end of year: Discount rate for benefit obligation 3.32 % 3.71 % 3.86 % Discount rate for net periodic benefit cost 3.71 % 3.86 % 3.57 % Expected long-term return on plan assets 5.00 % 4.25 % 7.00 %
Weighted-Average Asset Allocation	The weighted-average asset allocations by asset category are presented below for the Continuing Plan at December 31, 2017 and 2016, and for the Plan at December 31, 2016. No assets remained in the Plan at December 31, 2017. December 31, 2017 2016 Money market fund 6.0 % 13.0 % U.S. Treasuries — 87.0 % Exchange traded funds: Equity securities 48.0 % — Fixed income 32.0 % — International 14.0 % — Total 100.0 % 100.0 %
Plan Assets Measured at Fair Value	The following table sets forth by level, within the fair value hierarchy, the Continuing Plan’s assets measured at fair value at December 31, 2017 and 2016 and the Plan’s assets at December 31, 2016 ($ in thousands): December 31, 2017 Total Level 1 Level 2 Level 3 Money market fund $ 269 $ 269 $ — $ — Exchange traded funds: Equity securities 2,199 2,199 — — Fixed income 1,462 1,462 — — International 666 666 — — Total assets at fair value $ 4,596 $ 4,596 $ — $ — December 31, 2016 Total Level 1 Level 2 Level 3 Money market fund $ 6,859 $ 6,859 $ — $ — U.S. Treasuries 47,875 47,875 — — Total assets at fair value $ 54,734 $ 54,734 $ — $ —
Estimated Future Benefit Payments and Other Disclosures	The following table presents the expected benefit payments, which reflect expected future service, for the Continuing Plan ($ in thousands): Year Amount 2018 $ 196 2019 282 2020 333 2021 394 2022 453 2023 - 2027 2,961
Supplemental Retirement Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan Benefit Obligation, Plan Assets and Funded Status of the Plan	The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s nonqualified supplemental retirement plans ($ in thousands): December 31, 2017 2016 Change in benefit obligation: Benefit obligation, beginning of year $ 58,495 $ 57,766 Service cost 141 295 Interest cost 2,103 2,223 Actuarial loss 642 1,537 Benefits paid (3,451 ) (3,326 ) Benefit obligation, end of year $ 57,930 $ 58,495 Change in plan assets: Fair value of plan assets, beginning of year $ — $ — Employer contributions 3,451 3,326 Benefit payments (3,451 ) (3,326 ) Fair value of plan assets, end of year $ — $ — Funded status at end of year - net liability $ (57,930 ) $ (58,495 ) Amounts recognized in accumulated other comprehensive loss: Net loss $ 17,514 $ 17,739 Prior service cost 1,109 1,359 Amounts recognized $ 18,623 $ 19,098
Net Periodic Benefit Cost	Years Ended December 31, 2017 2016 2015 Net periodic benefit cost: Service cost $ 141 $ 295 $ 431 Interest cost 2,103 2,223 2,082 Amortization of prior service cost 250 250 250 Recognized net actuarial loss 866 864 992 Net periodic benefit cost $ 3,360 $ 3,632 $ 3,755 Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes: Net (gain) loss $ (224 ) $ (810 ) $ (2,694 ) Amortization of prior service cost (250 ) (250 ) (250 ) Total recognized in other comprehensive income (loss) $ (474 ) $ (1,060 ) $ (2,944 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 2,886 $ 2,572 $ 811 Weighted-average assumptions as of end of year: Discount rate for benefit obligation 3.32 % 3.71 % 3.86 % Discount rate for net periodic benefit cost 3.71 % 3.86 % 3.57 %
Estimated Future Benefit Payments and Other Disclosures	The following table presents the expected benefits payments for Trustmark’s supplemental retirement plans ($ in thousands): Year Amount 2018 $ 3,475 2019 3,591 2020 4,047 2021 4,105 2022 4,262 2023 - 2027 19,230

Stock and Incentive Compensat44

Stock and Incentive Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Restricted Stock Grants	The following table summarizes Trustmark’s performance award activity for the periods presented: Years Ended December 31, 2017 2016 2015 Weighted- Weighted- Weighted- Average Average Average Grant-Date Grant-Date Grant-Date Shares Fair Value Shares Fair Value Shares Fair Value Nonvested shares, beginning of year 237,136 $ 26.27 212,309 $ 24.14 181,195 $ 24.98 Granted 58,406 33.31 99,116 20.18 84,899 22.71 Released from restriction (67,279 ) 34.78 (40,888 ) 32.84 (47,360 ) 24.97 Forfeited (14,747 ) 28.42 (33,401 ) 30.01 (6,425 ) 24.97 Nonvested shares, end of year 213,516 $ 25.37 237,136 $ 26.27 212,309 $ 24.14 The following table summarizes Trustmark’s time-vested award activity for the periods presented: Years Ended December 31, 2017 2016 2015 Weighted- Weighted- Weighted- Average Average Average Grant-Date Grant-Date Grant-Date Shares Fair Value Shares Fair Value Shares Fair Value Nonvested shares, beginning of year 322,056 $ 22.65 306,657 $ 24.56 263,905 $ 24.66 Granted 105,524 33.79 139,791 20.66 121,314 23.61 Released from restriction (101,289 ) 25.35 (108,241 ) 23.74 (67,087 ) 24.31 Forfeited (5,934 ) 26.52 (16,151 ) 22.24 (11,475 ) 24.22 Nonvested shares, end of year 320,357 $ 25.40 322,056 $ 22.65 306,657 $ 24.56
Compensation Expense for Stock and Incentive Plans	The following table presents information regarding compensation expense for awards under the Plan for the periods presented ($ in thousands): Weighted Average Life Recognized Compensation Expense Unrecognized of for Years Ended December 31, Compensation Compensation 2017 2016 2015 Expense Expense Performance awards $ 1,387 $ 1,171 $ 1,201 $ 1,783 1.66 Time-vested awards 2,922 2,513 2,467 3,058 1.80 Total $ 4,309 $ 3,684 $ 3,668 $ 4,841

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Rental Commitments Under Non-cancellable Operating Leases	At December 31, 2017, future minimum rental commitments under non-cancellable operating leases are as follows ($ in thousands): Year Amount 2018 12,031 2019 10,436 2020 6,642 2021 5,197 2022 5,039 Thereafter 28,518 Total $ 67,863

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Stockholders Equity Note [Abstract]
Table of Actual Regulatory Capital Amounts and Ratios	The regulatory capital ratios for December 31, 2017 contain a reclassification adjustment of $8.5 million from accumulated other comprehensive loss to retained earnings as allowed by regulatory agencies in an interagency statement released January 18, 2018 to address disproportionate tax effect in accumulated other comprehensive loss resulting from the recent enactment of the Tax Reform Act and the application of FASB ASC Topic 740. The following table provides Trustmark’s and TNB’s actual regulatory capital amounts and ratios under regulatory capital standards in effect at December 31, 2017 and 2016 ($ in thousands): Actual Regulatory Capital Minimum To Be Well Amount Ratio Requirement Capitalized At December 31, 2017: Common Equity Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,243,240 11.77 % 5.750 % n/a Trustmark National Bank 1,284,575 12.16 % 5.750 % 6.50 % Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,303,238 12.33 % 7.250 % n/a Trustmark National Bank 1,284,575 12.16 % 7.250 % 8.00 % Total Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,384,050 13.10 % 9.250 % n/a Trustmark National Bank 1,365,387 12.93 % 9.250 % 10.00 % Tier 1 Leverage (to Average Assets) Trustmark Corporation $ 1,303,238 9.67 % 4.00 % n/a Trustmark National Bank 1,284,575 9.54 % 4.00 % 5.00 % At December 31, 2016: Common Equity Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,209,927 12.16 % 5.125 % n/a Trustmark National Bank 1,251,329 12.58 % 5.125 % 6.50 % Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,269,660 12.76 % 6.625 % n/a Trustmark National Bank 1,251,329 12.58 % 6.625 % 8.00 % Total Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,352,322 13.59 % 8.625 % n/a Trustmark National Bank 1,333,991 13.41 % 8.625 % 10.00 % Tier 1 Leverage (to Average Assets) Trustmark Corporation $ 1,269,660 9.90 % 4.00 % n/a Trustmark National Bank 1,251,329 9.77 % 4.00 % 5.00 %
Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects	Before Tax Tax Net of Tax Amount Benefit Amount Year Ended December 31, 2017 Securities available for sale and transferred securities: Unrealized holding gains (losses) arising during the period $ (13,994 ) $ 5,353 $ (8,641 ) Reclassification adjustment for net (gains) losses realized in net income (15 ) 6 (9 ) Change in net unrealized holding loss on securities transferred to held to maturity 4,721 (1,806 ) 2,915 Total securities available for sale and transferred securities (9,288 ) 3,553 (5,735 ) Pension and other postretirement benefit plans: Net change in prior service costs 250 (96 ) 154 Change in net actuarial loss 731 (280 ) 451 Recognized net loss due to defined benefit plan termination 17,662 (6,755 ) 10,907 Total pension and other postretirement benefit plans 18,643 (7,131 ) 11,512 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives 198 (76 ) 122 Reclassification adjustment for loss realized in net income 282 (108 ) 174 Total cash flow hedge derivatives 480 (184 ) 296 Total other comprehensive income (loss) $ 9,835 $ (3,762 ) $ 6,073 Year Ended December 31, 2016 Securities available for sale and transferred securities: Unrealized holding gains (losses) arising during the period $ (15,656 ) $ 5,989 $ (9,667 ) Reclassification adjustment for net (gains) losses realized in net income 310 (119 ) 191 Change in net unrealized holding loss on securities transferred to held to maturity 9,830 (3,760 ) 6,070 Total securities available for sale and transferred securities (5,516 ) 2,110 (3,406 ) Pension and other postretirement benefit plans: Net change in prior service costs 250 (96 ) 154 Recognized net loss due to lump sum settlements 3,906 (1,494 ) 2,412 Change in net actuarial loss 476 (182 ) 294 Total pension and other postretirement benefit plans 4,632 (1,772 ) 2,860 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives (369 ) 141 (228 ) Reclassification adjustment for loss realized in net income 599 (229 ) 370 Total cash flow hedge derivatives 230 (88 ) 142 Total other comprehensive income (loss) $ (654 ) $ 250 $ (404 ) Year Ended December 31, 2015 Securities available for sale and transferred securities: Unrealized holding gains (losses) arising during the period $ (16,695 ) $ 6,386 $ (10,309 ) Reclassification adjustment for net (gains) losses realized in net income — — — Change in net unrealized holding loss on securities transferred to held to maturity 6,345 (2,427 ) 3,918 Total securities available for sale and transferred securities (10,350 ) 3,959 (6,391 ) Pension and other postretirement benefit plans: Net change in prior service costs 250 (96 ) 154 Recognized net loss due to lump sum settlements 2,221 (850 ) 1,371 Change in net actuarial loss 3,647 (1,395 ) 2,252 Total pension and other postretirement benefit plans 6,118 (2,341 ) 3,777 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives (1,315 ) 503 (812 ) Reclassification adjustment for loss realized in net income 836 (320 ) 516 Total cash flow hedge derivatives (479 ) 183 (296 ) Total other comprehensive income (loss) $ (4,711 ) $ 1,801 $ (2,910 )
Components of Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	The following table presents the changes in the balances of each component of accumulated other comprehensive loss for the periods presented ($ in thousands). All amounts are presented net of tax. Securities Available and Securities Defined Benefit Pension Items Cash Flow Hedge Derivative Total Balance, January 1, 2015 $ (11,003 ) $ (31,617 ) $ 136 $ (42,484 ) Other comprehensive income (loss) before reclassification (6,391 ) 3,777 (812 ) (3,426 ) Amounts reclassified from accumulated other comprehensive loss — — 516 516 Net other comprehensive income (loss) (6,391 ) 3,777 (296 ) (2,910 ) Balance, December 31, 2015 (17,394 ) (27,840 ) (160 ) (45,394 ) Other comprehensive income (loss) before reclassification (3,597 ) (148 ) (228 ) (3,973 ) Amounts reclassified from accumulated other comprehensive loss 191 3,008 370 3,569 Net other comprehensive income (loss) (3,406 ) 2,860 142 (404 ) Balance, December 31, 2016 (20,800 ) (24,980 ) (18 ) (45,798 ) Other comprehensive income (loss) before reclassification (5,726 ) (760 ) 122 (6,364 ) Amounts reclassified from accumulated other comprehensive loss (9 ) 12,272 174 12,437 Net other comprehensive income (loss) (5,735 ) 11,512 296 6,073 Balance, December 31, 2017 $ (26,535 ) $ (13,468 ) $ 278 $ (39,725 )

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value Recurring Basis	The following tables summarize financial assets and financial liabilities measured at fair value on a recurring basis as of December 31, 2017 and 2016, segregated by the level of valuation inputs within the fair value hierarchy utilized to measure fair value ($ in thousands). There were no transfers between fair value levels for the years ended December 31, 2017 and 2016. December 31, 2017 Total Level 1 Level 2 Level 3 U.S. Government agency obligations $ 45,285 $ — $ 45,285 $ — Obligations of states and political subdivisions 79,229 — 79,229 — Mortgage-backed securities 2,114,121 — 2,114,121 — Securities available for sale 2,238,635 — 2,238,635 — Loans held for sale 180,512 — 180,512 — Mortgage servicing rights 84,269 — — 84,269 Other assets - derivatives 1,516 (1,013 ) 1,629 900 Other liabilities - derivatives 2,678 616 2,062 — December 31, 2016 Total Level 1 Level 2 Level 3 U.S. Government agency obligations $ 56,039 $ — $ 56,039 $ — Obligations of states and political subdivisions 115,373 — 115,373 — Mortgage-backed securities 2,185,270 — 2,185,270 — Securities available for sale 2,356,682 — 2,356,682 — Loans held for sale 175,927 — 175,927 — Mortgage servicing rights 80,239 — — 80,239 Other assets - derivatives 2,518 (524 ) 2,041 1,001 Other liabilities - derivatives 412 1,174 (762 ) —
Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis	The changes in Level 3 assets measured at fair value on a recurring basis for the years ended December 31, 2017 and 2016 are summarized as follows ($ in thousands): MSR Other Assets - Derivatives Balance, January 1, 2017 $ 80,239 $ 1,001 Total net (loss) gain included in Mortgage banking, net (1) (11,830 ) 4,165 Additions 15,860 — Sales — (4,266 ) Balance, December 31, 2017 $ 84,269 $ 900 The amount of total gains (losses) for the period included in earnings that are attributable to the change in unrealized gains or losses still held at December 31, 2017 $ (1,050 ) $ (1,569 ) Balance, January 1, 2016 $ 74,007 $ 1,113 Total net (loss) gain included in Mortgage banking, net (1) (10,513 ) 10,128 Additions 16,745 — Sales — (10,240 ) Balance, December 31, 2016 $ 80,239 $ 1,001 The amount of total gains (losses) for the period included in earnings that are attributable to the change in unrealized gains or losses still held at December 31, 2016 $ (407 ) $ 753 (1) Total net (loss) gain included in Mortgage banking, net relating to the MSR includes changes in fair value due to market changes and due to run-off.
Carrying Amounts and Estimated Fair Values of Financial Instruments	The carrying amounts and estimated fair values of financial instruments at December 31, 2017 and 2016 were as follows ($ in thousands): December 31, 2017 December 31, 2016 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Financial Assets: Level 2 Inputs: Cash and short-term investments $ 336,383 $ 336,383 $ 328,206 $ 328,206 Securities held to maturity 1,056,486 1,046,247 1,158,643 1,157,046 Level 3 Inputs: Net LHFI 8,493,234 8,507,469 7,779,948 7,825,009 Net acquired loans 257,438 257,438 260,850 260,850 Financial Liabilities: Level 2 Inputs: Deposits 10,577,512 10,577,858 10,056,012 10,059,794 Short-term liabilities 1,440,876 1,440,876 1,309,595 1,309,595 Long-term FHLB advances 946 946 251,049 251,050 Junior subordinated debt securities 61,856 45,773 61,856 41,057
Fair Value and the Contractual Principal Outstanding of the LHFS	The following table provides information about the fair value and the contractual principal outstanding of the LHFS accounted for under the fair value option as of December 31, 2017 and 2016 ($ in thousands): December 31, 2017 2016 Fair value of LHFS $ 132,300 $ 132,002 LHFS contractual principal outstanding 129,347 132,047 Fair value less unpaid principal $ 2,953 $ (45 )

Derivative Financial Instrume48

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Fair Value of Derivative Instruments	The following tables disclose the fair value of derivative instruments in Trustmark’s balance sheets as of December 31, 2017 and 2016 as well as the effect of these derivative instruments on Trustmark’s results of operations for the periods presented ($ in thousands): December 31, 2017 2016 Derivatives in hedging relationships Interest rate contracts: Interest rate swaps included in other assets $ 451 $ (28 ) Derivatives not designated as hedging instruments Interest rate contracts: Futures contracts included in other assets $ (1,088 ) $ (626 ) Exchange traded purchased options included in other assets 75 102 OTC written options (rate locks) included in other assets 900 1,001 Interest rate swaps included in other assets 1,175 2,060 Credit risk participation agreements included in other assets 3 9 Forward contracts included in other liabilities 237 (2,838 ) Exchange traded written options included in other liabilities 616 1,174 Interest rate swaps included in other liabilities 1,819 2,065 Credit risk participation agreements included in other liabilities 6 11
Effects of Derivative Instruments on Statements of Operations	Years Ended December 31, 2017 2016 2015 Derivatives in hedging relationships Amount of loss reclassified from accumulated other comprehensive loss and recognized in other interest expense $ (282 ) $ (599 ) $ (836 ) Derivatives not designated as hedging instruments Amount of gain (loss) recognized in mortgage banking, net $ (1,873 ) $ 13 $ 1,392 Amount of gain (loss) recognized in bank card and other fees (31 ) 60 (49 )
Schedule of Amount Included in Other Comprehensive Income for Derivative Instruments Designated as Hedges of Cash Flows	The following table discloses the amount included in other comprehensive income (loss), net of tax for derivative instruments designated as cash flow hedges for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 Derivatives in cash flow hedging relationship Amount of gain (loss) recognized in other comprehensive income (loss), net of tax $ 122 $ (228 ) $ (812 )
Information about Financial Instruments that are Eligible for Offset in the Consolidated Balance Sheets	Information about financial instruments that are eligible for offset in the consolidated balance sheets as of December 31, 2017 and 2016 is presented in the following tables ($ in thousands): Offsetting of Derivative Assets As of December 31, 2017 Gross Statement of Financial Position Gross Amounts of Recognized Assets Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets presented in the Statement of Financial Position Financial Instruments Cash Collateral Received Net Amount Derivatives $ 1,626 $ — $ 1,626 $ (311 ) $ — $ 1,315 Offsetting of Derivative Liabilities As of December 31, 2017 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Statement of Financial Position Net Amounts of Liabilities presented in the Statement of Financial Position Financial Instruments Cash Collateral Posted Net Amount Derivatives $ 1,819 $ — $ 1,819 $ (311 ) $ (100 ) $ 1,408 Offsetting of Derivative Assets As of December 31, 2016 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets Gross Amounts Offset in the Statement of Financial Position Net Amounts of Assets presented in Financial Position Financial Instruments Cash Collateral Received Net Amount Derivatives $ 2,032 $ — $ 2,032 $ (499 ) $ — $ 1,533 Offsetting of Derivative Liabilities As of December 31, 2016 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Liabilities Gross Amounts Offset in the Statement of Financial Position Net Amounts of Liabilities presented in the Statement of Financial Position Financial Instruments Cash Collateral Posted Net Amount Derivatives $ 2,065 $ — $ 2,065 $ (499 ) $ (937 ) $ 629

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of Segment Information	The following table discloses financial information by reportable segment for the periods presented ($ in thousands): Years Ended December 31, 2017 2016 2015 General Banking Net interest income $ 406,406 $ 386,596 $ 391,092 Provision for loan losses, net 7,699 14,714 11,800 Noninterest income 116,180 107,059 105,477 Noninterest expense 373,221 354,555 348,270 Income before income taxes 141,666 124,386 136,499 Income taxes 43,960 25,303 29,761 General banking net income $ 97,706 $ 99,083 $ 106,738 Selected Financial Information Total assets $ 13,724,193 $ 13,278,668 $ 12,604,112 Depreciation and amortization $ 37,710 $ 35,692 $ 36,072 Wealth Management Net interest income $ 910 $ 726 $ 337 Noninterest income 30,285 30,117 31,245 Noninterest expense 27,561 24,165 25,346 Income before income taxes 3,634 6,678 6,236 Income taxes 1,390 2,554 2,386 Wealth Management net income $ 2,244 $ 4,124 $ 3,850 Selected Financial Information Total assets $ 5,592 $ 7,501 $ 7,471 Depreciation and amortization $ 131 $ 174 $ 183 Insurance Net interest income $ 234 $ 211 $ 336 Noninterest income 38,198 36,767 36,427 Noninterest expense 29,387 28,578 28,046 Income before income taxes 9,045 8,400 8,717 Income taxes 3,365 3,196 3,267 Insurance net income $ 5,680 $ 5,204 $ 5,450 Selected Financial Information Total assets $ 68,168 $ 66,164 $ 67,313 Depreciation and amortization $ 630 $ 747 $ 801 Consolidated Net interest income $ 407,550 $ 387,533 $ 391,765 Provision for loan losses, net 7,699 14,714 11,800 Noninterest income 184,663 173,943 173,149 Noninterest expense 430,169 407,298 401,662 Income before income taxes 154,345 139,464 151,452 Income taxes 48,715 31,053 35,414 Consolidated net income $ 105,630 $ 108,411 $ 116,038 Selected Financial Information Total assets $ 13,797,953 $ 13,352,333 $ 12,678,896 Depreciation and amortization $ 38,471 $ 36,613 $ 37,056

Parent Company Only Financial50

Parent Company Only Financial Information (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Parent Only Financial Statements	Condensed Balance Sheets December 31, 2017 2016 Assets: Investment in banks $ 1,617,238 $ 1,566,186 Other assets 17,349 16,756 Total Assets $ 1,634,587 $ 1,582,942 Liabilities and Shareholders' Equity: Accrued expense $ 1,030 $ 878 Junior subordinated debt securities 61,856 61,856 Shareholders' equity 1,571,701 1,520,208 Total Liabilities and Shareholders' Equity $ 1,634,587 $ 1,582,942 Condensed Statements of Income Years Ended December 31, 2017 2016 2015 Revenue: Dividends received from banks $ 65,663 $ 65,987 $ 64,752 Earnings of subsidiaries over distributions 42,211 44,756 53,562 Other income 71 60 55 Total Revenue 107,945 110,803 118,369 Expense: Other expense 2,315 2,392 2,331 Total Expense 2,315 2,392 2,331 Net Income $ 105,630 $ 108,411 $ 116,038 Condensed Statements of Cash Flows Years Ended December 31, 2017 2016 2015 Operating Activities: Net income $ 105,630 $ 108,411 $ 116,038 Adjustments to reconcile net income to net cash provided by operating activities: Net change in investment in subsidiaries (42,211 ) (44,756 ) (53,562 ) Other (1,697 ) (739 ) (761 ) Net cash provided by operating activities 61,722 62,916 61,715 Investing Activities: Payment for investments in subsidiaries (30,755 ) — — Repayment for investments in subsidiaries 32,000 — — Net cash provided by investing activities 1,245 — — Financing Activities: Cash dividends paid on common stock (62,795 ) (62,666 ) (62,605 ) Other common stock transactions, net — (857 ) (211 ) Net cash used in financing activities (62,795 ) (63,523 ) (62,816 ) Net change in cash and cash equivalents 172 (607 ) (1,101 ) Cash and cash equivalents at beginning of year 16,713 17,320 18,421 Cash and cash equivalents at end of year $ 16,885 $ 16,713 $ 17,320

Significant Accounting Polici51

Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017USD ($)OfficeFactorRegion	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of offices | Office		198
Percentage of outstanding principal to be repurchased under GNMA optional repurchase program		100.00%
Number of days to pass to be classified as past due LHFI		30 days
Balance of commercial nonaccrual loans identified for impairment analysis, minimum		$ 500,000
Components in allowance for loan losses methodology | Factor		3
Key market regions | Region		5
Finite-lived intangible assets, average useful life		20 years
Securities with limited marketability		$ 67,700,000	$ 71,000,000
Effective income tax rate		35.00%	35.00%	35.00%
Amount be reclassified from AOCI to retained earnings		$ 8,500
Excess tax expense from stock-based compensation arrangements being reclassified from financing activities to other operating activities, net			$ 107,000	$ 211,000
Taxes paid for shares directly withheld being reclassified from other operating activities, net to financing activities		1,724,000	$ 1,017,000	$ 863,000
Total outstanding operating lease obligation		67,863,000
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Total outstanding operating lease obligation		$ 67,900
Percentage of total outstanding operating lease obligation of total assets		0.50%
Accounting Standards Update 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative adjustment		$ 0
Percentage of revenues earned		23.00%
Scenario Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
Effective income tax rate	21.00%
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Summary Of Significant Accounting Policies [Line Items]
Description of variable rate basis for derivative		three-month LIBOR
Period for which cash flow hedges will be used to hedge quarterly interest payments		5 years
Derivative inception date		Dec. 31, 2014
Derivative maturity date		Dec. 31, 2019
Credit Card Loans [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due loans are to be charged-off		180 days
Commercial Credits [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due for loan to be classified as nonaccrual		90 days
Non-Business Purpose Credits [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due for loan to be classified as nonaccrual		120 days
Number of days past due loans are to be charged-off		120 days
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days mortgage LHFS are retained on balance sheet		30 days
Minimum [Member] | Furniture and Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets		3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days mortgage LHFS are retained on balance sheet		45 days
Period for which cash flow hedges will be used to hedge quarterly interest payments		90 days
Maximum [Member] | Buildings [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets		39 years
Maximum [Member] | Furniture and Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets		10 years
Maximum [Member] | 1-4 Family Residential Real Estate [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days past due loans are to be charged-off		180 days

Significant Accounting Polici52

Significant Accounting Policies - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of cash flows specific transaction amounts [Abstract]
Income taxes paid		$ 7,371	$ 24,836	$ 16,321
Interest expense paid on deposits and borrowings		41,472	24,312	20,733
Noncash transfers from loans to other real estate	[1]	8,760	23,965	$ 32,782
Transfer of long-term FHLB advances to short-term		250,038	$ 500,009
Assets acquired in business combination		196,265
Liabilities assumed in business combination		$ 184,949
[1]	Includes transfers from covered loans to foreclosed properties.

Significant Accounting Polici53

Significant Accounting Policies - Weighted-Average Shares Used to Calculate Basic and Diluted EPS (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share (EPS) [Abstract]
Basic shares	67,727	67,620	67,550
Dilutive shares	160	164	142
Diluted shares	67,887	67,784	67,692

Significant Accounting Polici54

Significant Accounting Policies - Weighted-Average Antidilutive Stock Awards Excluded from Determining Diluted EPS (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Weighted-average antidilutive stock awards (in shares)	74	2	1

Business Combinations - Additio

Business Combinations - Additional Information (Details) $ / shares in Units, $ in Thousands	Apr. 07, 2017USD ($)Office	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Nov. 14, 2016$ / shares	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Goodwill			$ 379,627	$ 366,156		$ 366,156
Intangible asset estimated useful life			20 years
Reliance [Member]
Business Acquisition [Line Items]
Number of offices | Office	7
Business acquisition agreement date	Nov. 14, 2016
Business acquisition, share price | $ / shares					$ 22
Total consideration paid	$ 24,800
Fair value measurement period from acquisition date, maximum	1 year
Goodwill	$ 13,471		$ 13,500
Intangible asset estimated useful life	10 years
Reliance [Member] | Other Noninterest Expense [Member]
Business Acquisition [Line Items]
Merger transaction expense		$ 3,200
Reliance [Member] | Other Noninterest Expense [Member] | Change In Control Expense [Member]
Business Acquisition [Line Items]
Merger transaction expense		1,300
Reliance [Member] | Other Noninterest Expense [Member] | Professional Fees and Contract Termination and Other Expenses [Member]
Business Acquisition [Line Items]
Merger transaction expense		$ 1,900
Reliance [Member] | Reliance Common Stock [Member]
Business Acquisition [Line Items]
Business acquisition, payment for equity	$ 23,700
Reliance [Member] | Reliance Preferred Stock [Member]
Business Acquisition [Line Items]
Business acquisition, payment for equity	$ 1,100

Business Combinations - Summary

Business Combinations - Summary of Estimated Fair Values of Assets Purchased and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Apr. 07, 2017	Dec. 31, 2016	Dec. 31, 2015
Liabilities:
Goodwill	$ 379,627		$ 366,156	$ 366,156
Reliance [Member]
Assets:
Cash and due from banks		$ 5,013
Federal funds sold and securities purchased under reverse repurchase agreements		6,900
Securities		54,843
Acquired loans		117,447
Premises and equipment, net		3,700
Identifiable intangible assets		1,850
Other real estate		475
Other assets		6,037
Total Assets		196,265
Liabilities:
Deposits		166,158
Other borrowings		17,469
Other liabilities		1,322
Total Liabilities		184,949
Net identified assets acquired at fair value		11,316
Goodwill	$ 13,500	13,471
Total consideration paid		$ 24,787

Cash and Due from Banks - Addit

Cash and Due from Banks - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Average reserve balances with Federal Reserve Bank	$ 100.8	$ 94.7

Securities Available for Sale58

Securities Available for Sale and Held to Maturity - Amortized Cost and Estimated Fair Value of Available for Sale and Held to Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	$ 2,262,130	$ 2,366,168
Securities Available for Sale, Gross Unrealized Gains	4,448	12,124
Securities Available for Sale, Gross Unrealized (Losses)	(27,943)	(21,610)
Securities Available for Sale, Estimated Fair Value	2,238,635	2,356,682
Securities Held to Maturity, Amortized Cost	1,056,486	1,158,643
Securities Held to Maturity, Gross Unrealized Gains	3,954	7,300
Securities Held to Maturity, Gross Unrealized (Losses)	(14,193)	(8,897)
Securities Held to Maturity, Estimated Fair Value	1,046,247	1,157,046
U.S. Government Agency Obligations Issued by U.S. Government Agencies [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	45,508	56,272
Securities Available for Sale, Gross Unrealized Gains	310	416
Securities Available for Sale, Gross Unrealized (Losses)	(800)	(925)
Securities Available for Sale, Estimated Fair Value	45,018	55,763
Securities Held to Maturity, Amortized Cost	0	0
Securities Held to Maturity, Gross Unrealized Gains	0	0
Securities Held to Maturity, Gross Unrealized (Losses)	0	0
Securities Held to Maturity, Estimated Fair Value	0	0
U.S. Government Agency Obligations Issued by U.S. Government Sponsored Agencies [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	255	257
Securities Available for Sale, Gross Unrealized Gains	12	19
Securities Available for Sale, Gross Unrealized (Losses)	0	0
Securities Available for Sale, Estimated Fair Value	267	276
Securities Held to Maturity, Amortized Cost	3,692	3,647
Securities Held to Maturity, Gross Unrealized Gains	182	355
Securities Held to Maturity, Gross Unrealized (Losses)	0	0
Securities Held to Maturity, Estimated Fair Value	3,874	4,002
Obligations of States and Political Subdivisions [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	78,433	113,541
Securities Available for Sale, Gross Unrealized Gains	850	1,945
Securities Available for Sale, Gross Unrealized (Losses)	(54)	(113)
Securities Available for Sale, Estimated Fair Value	79,229	115,373
Securities Held to Maturity, Amortized Cost	46,039	46,303
Securities Held to Maturity, Gross Unrealized Gains	1,044	1,476
Securities Held to Maturity, Gross Unrealized (Losses)	(59)	(27)
Securities Held to Maturity, Estimated Fair Value	47,024	47,752
Residential Mortgage Pass-Through Securities Guaranteed by GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	66,634	43,222
Securities Available for Sale, Gross Unrealized Gains	215	340
Securities Available for Sale, Gross Unrealized (Losses)	(1,103)	(776)
Securities Available for Sale, Estimated Fair Value	65,746	42,786
Securities Held to Maturity, Amortized Cost	13,539	15,478
Securities Held to Maturity, Gross Unrealized Gains	207	280
Securities Held to Maturity, Gross Unrealized (Losses)	(73)	(52)
Securities Held to Maturity, Estimated Fair Value	13,673	15,706
Residential Mortgage Pass-Through Securities Issued by FNMA and FHLMC [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	824,872	638,809
Securities Available for Sale, Gross Unrealized Gains	827	1,773
Securities Available for Sale, Gross Unrealized (Losses)	(11,249)	(9,498)
Securities Available for Sale, Estimated Fair Value	814,450	631,084
Securities Held to Maturity, Amortized Cost	133,975	81,299
Securities Held to Maturity, Gross Unrealized Gains	210	223
Securities Held to Maturity, Gross Unrealized (Losses)	(1,559)	(1,084)
Securities Held to Maturity, Estimated Fair Value	132,626	80,438
Other Residential Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	1,028,176	1,271,198
Securities Available for Sale, Gross Unrealized Gains	1,808	5,865
Securities Available for Sale, Gross Unrealized (Losses)	(13,194)	(9,112)
Securities Available for Sale, Estimated Fair Value	1,016,790	1,267,951
Securities Held to Maturity, Amortized Cost	678,926	803,474
Securities Held to Maturity, Gross Unrealized Gains	1,209	3,208
Securities Held to Maturity, Gross Unrealized (Losses)	(11,065)	(6,519)
Securities Held to Maturity, Estimated Fair Value	669,070	800,163
Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	218,252	242,869
Securities Available for Sale, Gross Unrealized Gains	426	1,766
Securities Available for Sale, Gross Unrealized (Losses)	(1,543)	(1,186)
Securities Available for Sale, Estimated Fair Value	217,135	243,449
Securities Held to Maturity, Amortized Cost	180,315	208,442
Securities Held to Maturity, Gross Unrealized Gains	1,102	1,758
Securities Held to Maturity, Gross Unrealized (Losses)	(1,437)	(1,215)
Securities Held to Maturity, Estimated Fair Value	$ 179,980	$ 208,985

Securities Available for Sale59

Securities Available for Sale and Held to Maturity - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]
Reclassification of Securities available for sale to securities held to maturity				$ 1,099,000,000
Net unrealized holding loss on AFS Securities at date of transfer				46,600,000
Net unrealized holding losses on AFS Securities, net of tax at date of transfer				$ 28,800,000
Net unamortized, unrealized loss on transfer of securities	$ 19,500,000
Net unamortized, unrealized loss on transfer of securities, net of tax	12,000,000
Other-than-temporary impairments	0	$ 0	$ 0
Pledged to collateralize public deposits and securities sold under repurchase agreements and for other purposes as permitted by law	1,834,000,000	1,999,000,000
Pledged securities providing additional contingency funding	$ 0	$ 0

Securities Available for Sale60

Securities Available for Sale and Held to Maturity - Securities with Gross Unrealized Losses, Segregated by Length of Impairment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	$ 1,554,184	$ 2,033,477
Estimated Fair Value, 12 Months or More	1,022,055	114,975
Estimated Fair Value, Total	2,576,239	2,148,452
Gross Unrealized (Losses), Less than 12 Months	(14,150)	(26,714)
Gross Unrealized (Losses), 12 Months or More	(27,986)	(3,793)
Gross Unrealized (Losses), Total	(42,136)	(30,507)
U.S. Government Agency Obligations Issued by U.S. Government Agencies [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	5,214	9,420
Estimated Fair Value, 12 Months or More	29,432	33,248
Estimated Fair Value, Total	34,646	42,668
Gross Unrealized (Losses), Less than 12 Months	(113)	(142)
Gross Unrealized (Losses), 12 Months or More	(687)	(783)
Gross Unrealized (Losses), Total	(800)	(925)
Obligations of States and Political Subdivisions [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	19,345	20,539
Estimated Fair Value, 12 Months or More	3,874	654
Estimated Fair Value, Total	23,219	21,193
Gross Unrealized (Losses), Less than 12 Months	(80)	(135)
Gross Unrealized (Losses), 12 Months or More	(33)	(5)
Gross Unrealized (Losses), Total	(113)	(140)
Residential Mortgage Pass-Through Securities Guaranteed by GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	37,304	43,615
Estimated Fair Value, 12 Months or More	29,446	222
Estimated Fair Value, Total	66,750	43,837
Gross Unrealized (Losses), Less than 12 Months	(351)	(822)
Gross Unrealized (Losses), 12 Months or More	(825)	(6)
Gross Unrealized (Losses), Total	(1,176)	(828)
Residential Mortgage Pass-Through Securities Issued by FNMA and FHLMC [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	506,410	588,352
Estimated Fair Value, 12 Months or More	369,060	0
Estimated Fair Value, Total	875,470	588,352
Gross Unrealized (Losses), Less than 12 Months	(4,219)	(10,582)
Gross Unrealized (Losses), 12 Months or More	(8,589)	0
Gross Unrealized (Losses), Total	(12,808)	(10,582)
Other Residential Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	755,013	1,127,501
Estimated Fair Value, 12 Months or More	534,955	76,196
Estimated Fair Value, Total	1,289,968	1,203,697
Gross Unrealized (Losses), Less than 12 Months	(7,668)	(12,722)
Gross Unrealized (Losses), 12 Months or More	(16,591)	(2,909)
Gross Unrealized (Losses), Total	(24,259)	(15,631)
Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	230,898	244,050
Estimated Fair Value, 12 Months or More	55,288	4,655
Estimated Fair Value, Total	286,186	248,705
Gross Unrealized (Losses), Less than 12 Months	(1,719)	(2,311)
Gross Unrealized (Losses), 12 Months or More	(1,261)	(90)
Gross Unrealized (Losses), Total	$ (2,980)	$ (2,401)

Securities Available for Sale61

Securities Available for Sale and Held to Maturity - Gains and Losses as a Result of Calls and Disposition of Securities (Details) - Available for Sale [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gains (losses) on Investments [Abstract]
Proceeds from calls and sales of securities	$ 27,682	$ 24,693	$ 0
Gross realized gains	16	32	0
Gross realized losses	$ (1)	$ (342)	$ 0

Securities Available for Sale62

Securities Available for Sale and Held to Maturity - Contractual Maturities of Available for Sale and Held to Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Securities Available for Sale, Amortized Cost [Abstract]
Due in one year or less	$ 31,376
Due after one year through five years	57,372
Due after five years through ten years	3,866
Due after ten years	31,582
Total amortized cost, before mortgage-backed securities	124,196
Mortgage-backed securities	2,137,934
Total	2,262,130
Securities Available for Sale, Estimated Fair Value [Abstract]
Due in one year or less	31,525
Due after one year through five years	58,343
Due after five years through ten years	3,845
Due after ten years	30,801
Total fair value, before mortgage-backed securities	124,514
Mortgage-backed securities	2,114,121
Total	2,238,635	$ 2,356,682
Securities Held to Maturity, Amortized Cost [Abstract]
Due in one year or less	155
Due after one year through five years	40,594
Due after five years through ten years	8,982
Due after ten years	0
Total amortized cost, before mortgage-backed securities	49,731
Mortgage-backed securities	1,006,755
Securities Held to Maturity, Amortized Cost	1,056,486	1,158,643
Securities Held to Maturity, Estimated Fair Value [Abstract]
Due in one year or less	155
Due after one year through five years	41,450
Due after five years through ten years	9,293
Due after ten years	0
Total fair value, before mortgage-backed securities	50,898
Mortgage-backed securities	995,349
Total	$ 1,046,247	$ 1,157,046

LHFI and Allowance for Loan L63

LHFI and Allowance for Loan Losses, LHFI - Loan Portfolio Held for Investment (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Loan Portfolio [Abstract]
Total LHFI	[1]	$ 8,569,967	$ 7,851,213
Less allowance for loan losses, LHFI		76,733	71,265
Net LHFI		8,493,234	7,779,948
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI		987,624	831,437
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI		1,675,311	1,660,043
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI		517,956	318,148
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI		2,193,823	2,034,176
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI		1,570,345	1,528,434
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI		171,918	170,562
State and Other Political Subdivision Loans [Member]
Loan Portfolio [Abstract]
Total LHFI		952,483	917,515
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI		$ 500,507	$ 390,898
[1]	During the first quarter of 2017, Trustmark reclassified $36.7 million of acquired loans not accounted for under FASB ASC Topic 310-30 to LHFI due to the discount on these loans being fully amortized.

LHFI and Allowance for Loan L64

LHFI and Allowance for Loan Losses, LHFI - Loan Portfolio Held for Investment (Parenthetical) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Accounts Notes Loans And Financing Receivable Gross Allowance And Net [Abstract]
Reclassification of acquired loans	$ 36.7

LHFI and Allowance for Loan L65

LHFI and Allowance for Loan Losses, LHFI - Additional Information (Details 1)	12 Months Ended
	Dec. 31, 2017USD ($)Region	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jan. 01, 2017USD ($)
Financing Receivable Impaired [Line Items]
Maximum concentration of loan as a percentage of total LHFI	10.00%
Key market regions | Region	5
Loans and Leases Receivable, Related Parties	$ 59,900,000	$ 47,100,000
New loan advances to related party	418,500,000
Loan repayment by related party	405,800,000
Loan increase (decreases) from changes in executive officers and directors	12,000,000
Carrying amounts of nonaccrual LHFI considered for impairment analysis	67,600,000	49,200,000
Nonaccrual	67,575,000	49,234,000
Minimum loan amount for loan to be specifically reviewed for impairment and deemed impaired				$ 500,000
LHFI Classified as TDRs	23,900,000	14,500,000	$ 9,700,000
LHFI classified as TDRs from credits with interest only payments	20,500,000	9,800,000	5,900,000
Financing receivable, related allowance	458,000	2,200,000	1,800,000
Financing receivable, related charge-offs	127,000	1,000,000	806,000
Amount held by company of foreclosure or in substance repossession of consumer mortgage LHFI classified as TDRs	366,000	269,000
TDRs Classified as Consumer mortgage LHFI in the process of formal disclosure	0	101,000
Troubled Debt Restructurings [Member]
Financing Receivable Impaired [Line Items]
Nonaccrual	$ 23,211,000	$ 14,427,000	$ 7,418,000

LHFI and Allowance for Loan L66

LHFI and Allowance for Loan Losses, LHFI - Nonaccrual LHFI by Loan Type (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loan Portfolio [Abstract]
Total nonaccrual LHFI	$ 67,575	$ 49,234
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	2,105	3,323
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	19,022	20,329
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	12,608	8,482
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	212	402
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	33,338	15,824
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	135	300
Other Loans [Member]
Loan Portfolio [Abstract]
Total nonaccrual LHFI	$ 155	$ 574

LHFI and Allowance for Loan L67

LHFI and Allowance for Loan Losses, LHFI - Aging Analysis of Past Due and Nonaccrual LHFI by Loan Type (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		$ 18,433	$ 14,684
Nonaccrual		67,575	49,234
Current Loans		8,483,959	7,787,295
Total LHFI	[1]	8,569,967	7,851,213
Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		12,390	9,686
Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		3,872	3,167
Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[2]	2,171	1,831
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		392	339
Nonaccrual		2,105	3,323
Current Loans		985,127	827,775
Total LHFI		987,624	831,437
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		391	248
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1	37
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[2]		54
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		10,413	9,178
Nonaccrual		19,022	20,329
Current Loans		1,645,876	1,630,536
Total LHFI		1,675,311	1,660,043
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		6,412	5,308
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,084	2,434
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[2]	1,917	1,436
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,575	706
Nonaccrual		12,608	8,482
Current Loans		2,178,640	2,024,988
Total LHFI		2,193,823	2,034,176
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,319	606
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		256	100
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due			179
Nonaccrual		212	402
Current Loans		517,744	317,567
Total LHFI		517,956	318,148
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due			179
Commercial and Industrial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,004	784
Nonaccrual		33,338	15,824
Current Loans		1,535,003	1,511,826
Total LHFI		1,570,345	1,528,434
Commercial and Industrial Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		759	571
Commercial and Industrial Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,233	213
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[2]	12
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,638	2,232
Nonaccrual		135	300
Current Loans		169,145	168,030
Total LHFI		171,918	170,562
Consumer Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		2,141	1,561
Consumer Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		255	330
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[2]	242	341
State and Other Political Subdivision Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		389	1,035
Current Loans		952,094	916,480
Total LHFI		952,483	917,515
State and Other Political Subdivision Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		350	1,035
State and Other Political Subdivision Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		39
Other Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		22	231
Nonaccrual		155	574
Current Loans		500,330	390,093
Total LHFI		500,507	390,898
Other Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		18	178
Other Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		$ 4	$ 53
[1]	During the first quarter of 2017, Trustmark reclassified $36.7 million of acquired loans not accounted for under FASB ASC Topic 310-30 to LHFI due to the discount on these loans being fully amortized.
[2]	Past due 90 days or more but still accruing interest.

LHFI and Allowance for Loan L68

LHFI and Allowance for Loan Losses, LHFI - Impaired Financing Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	$ 60,387	$ 35,077
Total LHFI With No Related Allowance Recorded	42,674	19,440
Total LHFI With an Allowance Recorded	6,262	7,635
Total LHFI Carrying Amount	48,936	27,075
Related Allowance	1,743	3,260
Average Recorded Investment	38,005	29,140
Commercial and Industrial Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	36,874	14,593
Total LHFI With No Related Allowance Recorded	31,281	11,222
Total LHFI With an Allowance Recorded	518	2,447
Total LHFI Carrying Amount	31,799	13,669
Related Allowance	131	1,976
Average Recorded Investment	22,734	14,258
Consumer Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	17	2
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	17	2
Total LHFI Carrying Amount	17	2
Related Allowance	0	0
Average Recorded Investment	9	2
State and Other Political Subdivision Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	0	0
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	0	0
Total LHFI Carrying Amount	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Other Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	556	95
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	556	95
Total LHFI Carrying Amount	556	95
Related Allowance	41	0
Average Recorded Investment	325	95
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	1,704	5,691
Total LHFI With No Related Allowance Recorded	1,206	2,213
Total LHFI With an Allowance Recorded	199	228
Total LHFI Carrying Amount	1,405	2,441
Related Allowance	75	103
Average Recorded Investment	1,923	2,943
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	6,031	6,134
Total LHFI With No Related Allowance Recorded	160	221
Total LHFI With an Allowance Recorded	4,576	4,428
Total LHFI Carrying Amount	4,736	4,649
Related Allowance	1,331	960
Average Recorded Investment	4,693	4,639
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	15,205	8,562
Total LHFI With No Related Allowance Recorded	10,027	5,784
Total LHFI With an Allowance Recorded	396	435
Total LHFI Carrying Amount	10,423	6,219
Related Allowance	165	221
Average Recorded Investment	8,321	6,703
Loans Secured by Real Estate [Member] | Other Real Estate Secured [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	0	0
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	0	0
Total LHFI Carrying Amount	0	0
Related Allowance	0	0
Average Recorded Investment	$ 0	$ 500

LHFI and Allowance for Loan L69

LHFI and Allowance for Loan Losses, LHFI - Impact of Modifications Classified as Troubled Debt Restructurings (Details) - Troubled Debt Restructurings [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Contract	Dec. 31, 2016USD ($)Contract	Dec. 31, 2015USD ($)Contract
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	33	27	18
Pre-Modification Outstanding Recorded Investment	$ 15,637	$ 12,162	$ 4,301
Post-Modification Outstanding Recorded Investment	$ 15,630	$ 12,106	$ 4,301
Secured by 1-4 Family Residential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	22	18	13
Pre-Modification Outstanding Recorded Investment	$ 1,478	$ 1,386	$ 688
Post-Modification Outstanding Recorded Investment	$ 1,487	$ 1,391	$ 688
Construction, Land Development and Other Land [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	1	1
Pre-Modification Outstanding Recorded Investment	$ 341	$ 14
Post-Modification Outstanding Recorded Investment	$ 325	$ 14
Secured by Nonfarm, Nonresidential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	1	2	5
Pre-Modification Outstanding Recorded Investment	$ 426	$ 717	$ 3,613
Post-Modification Outstanding Recorded Investment	$ 426	$ 717	$ 3,613
Commercial and Industrial Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	8	5
Pre-Modification Outstanding Recorded Investment	$ 12,836	$ 10,043
Post-Modification Outstanding Recorded Investment	$ 12,836	$ 9,982
Other Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	1
Pre-Modification Outstanding Recorded Investment	$ 556
Post-Modification Outstanding Recorded Investment	$ 556
Consumer Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract		1
Pre-Modification Outstanding Recorded Investment		$ 2
Post-Modification Outstanding Recorded Investment		$ 2

LHFI and Allowance for Loan L70

LHFI and Allowance for Loan Losses, LHFI - Troubled Debt Restructuring Subsequently Defaulted (Details) - Troubled Debt Restructurings that Subsequently Defaulted [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Contract	Dec. 31, 2016USD ($)Contract	Dec. 31, 2015USD ($)Contract
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	7	3	5
Recorded Investment | $	$ 9,604	$ 2,154	$ 260
Commercial and Industrial [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	3	2
Recorded Investment | $	$ 9,526	$ 2,154
Secured by 1-4 Family Residential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	4	1	5
Recorded Investment | $	$ 78		$ 260

LHFI and Allowance for Loan L71

LHFI and Allowance for Loan Losses, LHFI - Troubled Debt Restructuring Related to Loans Held for Investment, Excluding Covered Loans, by Loan Type (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable Modifications [Line Items]
Nonaccrual	$ 67,575	$ 49,234
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	2,105	3,323
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	19,022	20,329
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	12,608	8,482
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	212	402
Commercial and Industrial Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	33,338	15,824
Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	135	300
Other Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	155	574
Troubled Debt Restructurings [Member]
Financing Receivable Modifications [Line Items]
Accruing	660	53	$ 2,235
Nonaccrual	23,211	14,427	7,418
Total	23,871	14,480	9,653
Troubled Debt Restructurings [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	0	0	0
Nonaccrual	199	405	869
Total	199	405	869
Troubled Debt Restructurings [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	51	0	1,426
Nonaccrual	3,140	2,873	2,424
Total	3,191	2,873	3,850
Troubled Debt Restructurings [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	0	0	809
Nonaccrual	421	881	3,662
Total	421	881	4,471
Troubled Debt Restructurings [Member] | Commercial and Industrial Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	53	53	0
Nonaccrual	19,434	10,266	463
Total	19,487	10,319	$ 463
Troubled Debt Restructurings [Member] | Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	0	0
Nonaccrual	17	2
Total	17	$ 2
Troubled Debt Restructurings [Member] | Other Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	556
Nonaccrual	0
Total	$ 556

LHFI and Allowance for Loan L72

LHFI and Allowance for Loan Losses, LHFI - Additional Information (Details 2)	12 Months Ended
	Dec. 31, 2017USD ($)KeyRatioLoanPoolCreditRiskGrade	Dec. 31, 2016USD ($)
Financing Receivable, Recorded Investment, Aging [Abstract]
Number of days used as baseline in evaluating collateral documentation exceptions for loan policy	90 days
Number of key quality ratios | KeyRatio	6
LHFS past due 90 days or more	$ 35,500,000	$ 28,300,000
Financing Receivable [Abstract]
Number of primary commercial loan groups | LoanPool	9
Number of individual credit risk grades | CreditRiskGrade	10
Minimum [Member]
Financing Receivable [Abstract]
Period to conduct asset review	6 months
Credit amount used as baseline in evaluating loan policy	$ 100,000
Maximum [Member]
Financing Receivable [Abstract]
Period to conduct asset review	18 months

LHFI and Allowance for Loan L73

LHFI and Allowance for Loan Losses, LHFI - Summary of LHFI by Loan Type and Credit Quality Indicator (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable [Abstract]
Current		$ 8,483,959	$ 7,787,295
Financing Receivable, Recorded Investment, Past Due		18,433	14,684
Nonaccrual		67,575	49,234
Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]	2,171	1,831
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		1,645,876	1,630,536
Financing Receivable, Recorded Investment, Past Due		10,413	9,178
Nonaccrual		19,022	20,329
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]	1,917	1,436
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		2,178,640	2,024,988
Financing Receivable, Recorded Investment, Past Due		2,575	706
Nonaccrual		12,608	8,482
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		517,744	317,567
Financing Receivable, Recorded Investment, Past Due			179
Nonaccrual		212	402
Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Current		1,535,003	1,511,826
Financing Receivable, Recorded Investment, Past Due		2,004	784
Nonaccrual		33,338	15,824
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]	12
Consumer Loans [Member]
Financing Receivable [Abstract]
Current		169,145	168,030
Financing Receivable, Recorded Investment, Past Due		2,638	2,232
Nonaccrual		135	300
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]	242	341
State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Current		952,094	916,480
Financing Receivable, Recorded Investment, Past Due		389	1,035
Other Loans [Member]
Financing Receivable [Abstract]
Current		500,330	390,093
Financing Receivable, Recorded Investment, Past Due		22	231
Nonaccrual		155	574
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		985,127	827,775
Financing Receivable, Recorded Investment, Past Due		392	339
Nonaccrual		2,105	3,323
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]		54
Commercial LHFI [Member]
Financing Receivable [Abstract]
Financing receivable commercial		6,788,151	6,084,312
Commercial LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		132,563	131,076
Commercial LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		2,193,745	2,033,445
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		517,553	317,481
Commercial LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,570,345	1,528,434
Commercial LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		952,483	917,515
Commercial LHFI [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		494,581	385,925
Commercial LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		926,881	770,436
Commercial LHFI [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial		6,554,846	5,851,296
Commercial LHFI [Member] | Pass [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		127,405	124,615
Commercial LHFI [Member] | Pass [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		2,135,749	1,989,554
Commercial LHFI [Member] | Pass [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		517,036	315,829
Commercial LHFI [Member] | Pass [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,437,590	1,386,155
Commercial LHFI [Member] | Pass [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		936,420	899,935
Commercial LHFI [Member] | Pass [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		478,083	382,890
Commercial LHFI [Member] | Pass [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		922,563	752,318
Commercial LHFI [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial		41,764	28,438
Commercial LHFI [Member] | Special Mention [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		134	170
Commercial LHFI [Member] | Special Mention [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		6,684	4,394
Commercial LHFI [Member] | Special Mention [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial			762
Commercial LHFI [Member] | Special Mention [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		28,780	7,095
Commercial LHFI [Member] | Special Mention [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		5,850	6,450
Commercial LHFI [Member] | Special Mention [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		316	9,567
Commercial LHFI [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial		189,722	202,065
Commercial LHFI [Member] | Substandard [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		4,948	6,162
Commercial LHFI [Member] | Substandard [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		50,785	38,913
Commercial LHFI [Member] | Substandard [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		517	890
Commercial LHFI [Member] | Substandard [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		103,089	134,199
Commercial LHFI [Member] | Substandard [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		10,213	11,130
Commercial LHFI [Member] | Substandard [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		16,390	2,685
Commercial LHFI [Member] | Substandard [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		3,780	8,086
Commercial LHFI [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,819	2,513
Commercial LHFI [Member] | Doubtful [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		76	129
Commercial LHFI [Member] | Doubtful [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		527	584
Commercial LHFI [Member] | Doubtful [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		886	985
Commercial LHFI [Member] | Doubtful [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		108	350
Commercial LHFI [Member] | Doubtful [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		222	465
Consumer LHFI [Member]
Financing Receivable [Abstract]
Financing receivable commercial		8,569,967	7,851,213
Current		1,752,484	1,738,166
Nonaccrual		16,669	17,415
Subtotal		1,781,816	1,766,901
Consumer LHFI [Member] | Past Due 30-89 Days [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		10,612	9,489
Consumer LHFI [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		2,051	1,831
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,675,311	1,660,043
Current		1,516,691	1,503,096
Nonaccrual		16,374	17,058
Subtotal		1,542,748	1,528,967
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30-89 Days [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		7,874	7,377
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		1,809	1,436
Consumer LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		2,193,823	2,034,176
Current		78	731
Subtotal		78	731
Consumer LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		517,956	318,148
Current		403	667
Subtotal		403	667
Consumer LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,570,345	1,528,434
Consumer LHFI [Member] | Consumer Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		171,918	170,562
Current		169,146	168,031
Nonaccrual		134	299
Subtotal		171,918	170,562
Consumer LHFI [Member] | Consumer Loans [Member] | Past Due 30-89 Days [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		2,396	1,891
Consumer LHFI [Member] | Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		242	341
Consumer LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		952,483	917,515
Consumer LHFI [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		500,507	390,898
Current		5,926	4,940
Subtotal		5,926	4,973
Consumer LHFI [Member] | Other Loans [Member] | Past Due 30-89 Days [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due			33
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		987,624	831,437
Current		60,240	60,701
Nonaccrual		161	58
Subtotal		60,743	61,001
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 30-89 Days [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		$ 342	188
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due			$ 54
[1]	Past due 90 days or more but still accruing interest.

LHFI and Allowance for Loan L74

LHFI and Allowance for Loan Losses, LHFI - Additional Information (Details 3) $ in Thousands	12 Months Ended
	Dec. 31, 2017FactorLoanScale	Dec. 31, 2015USD ($)
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Number of loan types for commercial portfolio | Loan	9
Number of risk rate factors for commercial loans | Factor	450
Length of loss emergence period in the quantitative portion of the allowance for loan loss methodology for commercial LHFI		1 year 6 months
Additional provision amount quantitative portion of the allowance for loan loss methodology for commercial LHFI		$ 2,300
Additional provision amount quantitative portion of the allowance for loan loss methodology for commercial LHFI due to incorporate third-party default data		1,300
Minimum score for qualitative risk factor | Scale	0
Maximum score for qualitative risk factor | Scale	100
Amount of provision recapture resulting from the elimination of cap and floors for criticized risk ratings in the qualitative portion of the allowance for loan loss methodology for commercial LHFI		1,800
Amount of additional provision expense resulting from market region distribution related to qualitative portion of the allowance for loan loss methodology for commercial LHFI		2,100
Amount of additional provision recapture resulting from market region distribution related to quantitative portion of the allowance for loan loss methodology for commercial LHFI		785
Length of loss emergence period in the qualitative portion of the allowance for loan loss methodology for commercial LHFI to observe the maximum observed gross historical losses	3 years
Additional provision due to revision of methodology to incorporate the use of maximum observed gross historical losses		4,400
Amount of provision recapture resulting from revision to loan facility risk component related to qualitative portion of the allowance for loan loss methodology for commercial LHFI		2,100
Amount of provision recapture resulting from market region distribution related to quantitative portion of the allowance for loan loss methodology for consumer LHFI regarding consumer mortgage portfolio		455
Additional provision amount qualitative portion of the allowance for loan loss methodology for consumer LHFI to incorporate the use of maximum observed gross historical losses		750
Number of unique qualitative factors used to analyze consumer loans | Factor	5
Number of loan types for consumer portfolio | Loan	5
Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Additional provision due to revision of methodology		1,100
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Additional provision due to revision of methodology		$ 2,200

LHFI and Allowance for Loan L75

LHFI and Allowance for Loan Losses, LHFI - Summary of Balance in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Total	$ 76,733	$ 71,265
Allowance for Loan Losses, LHFI [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	1,743	3,260
Collectively	74,990	68,005
Total	76,733	71,265	$ 67,619	$ 69,616
Allowance for Loan Losses, LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	131	1,976
Collectively	22,720	20,035
Total	22,851	22,011	15,815
Allowance for Loan Losses, LHFI [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	3,470	3,241
Total	3,470	3,241	2,879
Allowance for Loan Losses, LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	789	859
Total	789	859	809
Allowance for Loan Losses, LHFI [Member] | Other Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	41
Collectively	4,625	2,492
Total	4,666	2,492	1,821
Allowance for Loan Losses, LHFI [Member] | Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	75	103
Collectively	7,790	8,982
Total	7,865	9,085	11,587
Allowance for Loan Losses, LHFI [Member] | Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	1,331	960
Collectively	9,543	9,387
Total	10,874	10,347	10,678
Allowance for Loan Losses, LHFI [Member] | Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	165	221
Collectively	23,263	20,746
Total	23,428	20,967	21,563
Allowance for Loan Losses, LHFI [Member] | Loans Secured by Real Estate [Member] | Other Real Estate Secured [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	2,790	2,263
Total	$ 2,790	$ 2,263	$ 2,467

LHFI and Allowance for Loan L76

LHFI and Allowance for Loan Losses, LHFI - Summary of Loan Type Related to Each Balance in Allowance for Loan Losses (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		$ 48,900	$ 27,100
Total LHFI	[1]	8,569,967	7,851,213
Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		48,936	27,075
LHFI, Collectively Evaluated For Impairment		8,521,031	7,824,138
Total LHFI		8,569,967	7,851,213
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		987,624	831,437
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		1,405	2,441
LHFI, Collectively Evaluated For Impairment		986,219	828,996
Total LHFI		987,624	831,437
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		1,675,311	1,660,043
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		4,736	4,649
LHFI, Collectively Evaluated For Impairment		1,670,575	1,655,394
Total LHFI		1,675,311	1,660,043
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		2,193,823	2,034,176
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		10,423	6,219
LHFI, Collectively Evaluated For Impairment		2,183,400	2,027,957
Total LHFI		2,193,823	2,034,176
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		517,956	318,148
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Collectively Evaluated For Impairment		517,956	318,148
Total LHFI		517,956	318,148
Commercial and Industrial Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		1,570,345	1,528,434
Commercial and Industrial Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		31,799	13,669
LHFI, Collectively Evaluated For Impairment		1,538,546	1,514,765
Total LHFI		1,570,345	1,528,434
Consumer Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		171,918	170,562
Consumer Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		17	2
LHFI, Collectively Evaluated For Impairment		171,901	170,560
Total LHFI		171,918	170,562
State and Other Political Subdivision Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		952,483	917,515
State and Other Political Subdivision Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Collectively Evaluated For Impairment		952,483	917,515
Total LHFI		952,483	917,515
Other Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI		500,507	390,898
Other Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment		556	95
LHFI, Collectively Evaluated For Impairment		499,951	390,803
Total LHFI		$ 500,507	$ 390,898
[1]	During the first quarter of 2017, Trustmark reclassified $36.7 million of acquired loans not accounted for under FASB ASC Topic 310-30 to LHFI due to the discount on these loans being fully amortized.

LHFI and Allowance for Loan L77

LHFI and Allowance for Loan Losses, LHFI - Change in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 71,265
Provision for loan losses, LHFI	15,094	$ 10,957	$ 8,375
Balance at end of period	76,733	71,265
Allowance for Loan Losses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	71,265	67,619	69,616
Loans charged-off	(21,147)	(18,930)	(22,469)
Recoveries	11,521	11,619	12,097
Net (charge-offs) recoveries	(9,626)	(7,311)	(10,372)
Provision for loan losses, LHFI	15,094	10,957	8,375
Balance at end of period	76,733	71,265	67,619
Allowance for Loan Losses, LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	9,085	11,587
Loans charged-off	(79)	(311)
Recoveries	1,428	1,380
Provision for loan losses, LHFI	(2,569)	(3,571)
Balance at end of period	7,865	9,085	11,587
Allowance for Loan Losses, LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	10,347	10,678
Loans charged-off	(950)	(1,319)
Recoveries	1,833	1,122
Provision for loan losses, LHFI	(356)	(134)
Balance at end of period	10,874	10,347	10,678
Allowance for Loan Losses, LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	20,967	21,563
Loans charged-off	(4,231)	(3,067)
Recoveries	396	976
Provision for loan losses, LHFI	6,296	1,495
Balance at end of period	23,428	20,967	21,563
Allowance for Loan Losses, LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	2,263	2,467
Loans charged-off	(5)	(27)
Recoveries	69	7
Provision for loan losses, LHFI	463	(184)
Balance at end of period	2,790	2,263	2,467
Allowance for Loan Losses, LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	22,011	15,815
Loans charged-off	(8,286)	(6,602)
Recoveries	2,578	732
Provision for loan losses, LHFI	6,548	12,066
Balance at end of period	22,851	22,011	15,815
Allowance for Loan Losses, LHFI [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	3,241	2,879
Loans charged-off	(2,546)	(1,864)
Recoveries	1,938	4,007
Provision for loan losses, LHFI	837	(1,781)
Balance at end of period	3,470	3,241	2,879
Allowance for Loan Losses, LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	859	809
Provision for loan losses, LHFI	(70)	50
Balance at end of period	789	859	809
Allowance for Loan Losses, LHFI [Member] | Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	2,492	1,821
Loans charged-off	(5,050)	(5,740)
Recoveries	3,279	3,395
Provision for loan losses, LHFI	3,945	3,016
Balance at end of period	$ 4,666	$ 2,492	$ 1,821

Acquired Loans - Additional Inf

Acquired Loans - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)CreditRiskGrade	Apr. 07, 2017USD ($)	Dec. 31, 2016USD ($)
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities [Abstract]
Loans acquired in merger accounted for under FASB ASC Topic 310 30		$ 7,900
Number of individual credit risk grades | CreditRiskGrade	10
Nonaccrual loans not accounted for under FASB ASC Topic 310 30	$ 304		$ 631

Acquired Loans - Schedule of Ac

Acquired Loans - Schedule of Acquired Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	$ 261,517	$ 272,247
Less allowance for loan losses, acquired loans	4,079	11,397	$ 11,992	$ 12,059
Net acquired loans	257,438	260,850
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	23,586	20,850
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	61,751	69,540
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	114,694	103,820
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	16,746	19,010
Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	31,506	36,896
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	2,600	3,365
Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	$ 10,634	$ 18,766

Acquired Loans - Changes in the

Acquired Loans - Changes in the Carrying Value of Acquired Loans (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 07, 2017
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		$ 260,850
Additions					$ 7,900
Accretion to interest income		14,924	$ 18,405	$ 30,501
Carrying value, net, ending		257,438	260,850
Acquired Not ASC 310-30 [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning	[1]	42,743	67,657
Transfers	[1],[2]	(36,719)
Additions	[1],[3]	109,548
Accretion to interest income	[1]	1,578	40
Payments received, net	[1]	(39,208)	(24,953)
Other	[1],[4]	(74)	0
Change in allowance for loan losses, acquired loans	[1]	0	(1)
Carrying value, net, ending	[1]	77,868	42,743	67,657
Acquired Impaired [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		218,107	310,762
Transfers	[2]	0
Additions	[3]	7,899
Accretion to interest income		14,924	18,405
Payments received, net		(68,317)	(111,522)
Other	[4]	(361)	(134)
Change in allowance for loan losses, acquired loans		7,318	596
Carrying value, net, ending		$ 179,570	$ 218,107	$ 310,762
[1]	“Acquired Not ASC 310-30” loans consist of loans that are not in scope for FASB ASC Topic 310-30.
[2]	“Acquired Not ASC 310-20” loans transferred to LHFI due to the discount on these loans being fully amortized.
[3]	Loans acquired in the Reliance merger on April 7, 2017
[4]	Includes miscellaneous timing adjustments as well as acquired loan terminations through foreclosure, charge-off and other terminations.

Acquired Loans - Changes in Acc

Acquired Loans - Changes in Accretable Yield of Acquired Loans (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in accretable difference on acquired loans [Abstract]
Accretable yield at beginning of period		$ (38,918)	$ (52,672)	$ (77,149)
Additions due to acquisition	[1]	(784)
Accretion to interest income		14,924	18,405	30,501
Disposals		2,868	6,488	10,013
Reclassification from nonaccretable difference	[2]	(9,516)	(11,139)	(16,037)
Accretable yield at end of period		$ (31,426)	$ (38,918)	$ (52,672)
[1]	Accretable yield on loans acquired from Reliance on April 7, 2017
[2]	Reclassifications from nonaccretable difference are due to lower loss expectations and improvements in expected cash flows.

Acquired Loans - Components of

Acquired Loans - Components of the Allowance for Loan Losses on Acquired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 11,397	$ 11,992	$ 12,059
Provision for loan losses, acquired loans	(7,395)	3,757	3,425
Loans charged-off		(6,616)	(7,200)
Recoveries	77	2,264	3,708
Net (charge-offs) recoveries	77	(4,352)	(3,492)
Balance at end of period	$ 4,079	$ 11,397	$ 11,992

Acquired Loans - Acquired Loans

Acquired Loans - Acquired Loans by Loan Type and Credit Quality Indicator (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		$ 257,438	$ 260,850
Acquired Loans, Aging [Abstract]
Current		255,506	262,943
Acquired Loans, Past Due		5,707	8,673
Nonaccrual	[1]	304	631
Total Acquired Loans		261,517	272,247
Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	2,434	3,730
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		22,601	19,608
Acquired Loans, Past Due		985	1,242
Nonaccrual	[1]	0	0
Total Acquired Loans		23,586	20,850
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	861	821
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		58,490	66,535
Acquired Loans, Past Due		2,959	2,964
Nonaccrual	[1]	302	41
Total Acquired Loans		61,751	69,540
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	654	1,057
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		113,256	101,453
Acquired Loans, Past Due		1,438	2,039
Nonaccrual	[1]	0	328
Total Acquired Loans		114,694	103,820
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	898	343
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		16,614	16,796
Acquired Loans, Past Due		132	2,214
Nonaccrual	[1]	0	0
Total Acquired Loans		16,746	19,010
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	1,445
Commercial and Industrial Loans [Member]
Acquired Loans, Aging [Abstract]
Current		31,504	36,535
Acquired Loans, Past Due		0	99
Nonaccrual	[1]	2	262
Total Acquired Loans		31,506	36,896
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	0
Consumer Loans [Member]
Acquired Loans, Aging [Abstract]
Current		2,428	3,250
Acquired Loans, Past Due		172	115
Nonaccrual	[1]	0	0
Total Acquired Loans		2,600	3,365
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	64
Other Loans [Member]
Acquired Loans, Aging [Abstract]
Current		10,613	18,766
Acquired Loans, Past Due		21	0
Nonaccrual	[1]	0	0
Total Acquired Loans		10,634	18,766
Other Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	21	0
Commercial LHFI [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		212,826	215,792
Commercial LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		22,338	19,038
Commercial LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		17,348	18,748
Commercial LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		114,660	103,770
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		16,340	18,582
Commercial LHFI [Member] | Commercial and Industrial Loans [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		31,506	36,890
Commercial LHFI [Member] | Other Loans [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		10,634	18,764
Commercial LHFI [Member] | Pass [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		167,079	160,293
Commercial LHFI [Member] | Pass [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		17,150	12,148
Commercial LHFI [Member] | Pass [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		14,021	14,552
Commercial LHFI [Member] | Pass [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		95,147	83,271
Commercial LHFI [Member] | Pass [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		12,730	15,344
Commercial LHFI [Member] | Pass [Member] | Commercial and Industrial Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		22,157	22,024
Commercial LHFI [Member] | Pass [Member] | Other Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		5,874	12,954
Commercial LHFI [Member] | Special Mention [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		2,067	613
Commercial LHFI [Member] | Special Mention [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		234	99
Commercial LHFI [Member] | Special Mention [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		298	61
Commercial LHFI [Member] | Special Mention [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		1,400	435
Commercial LHFI [Member] | Special Mention [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		102
Commercial LHFI [Member] | Special Mention [Member] | Commercial and Industrial Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		15	18
Commercial LHFI [Member] | Special Mention [Member] | Other Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		18
Commercial LHFI [Member] | Substandard [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		40,660	51,904
Commercial LHFI [Member] | Substandard [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		4,690	6,469
Commercial LHFI [Member] | Substandard [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		3,029	4,066
Commercial LHFI [Member] | Substandard [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		17,583	19,553
Commercial LHFI [Member] | Substandard [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		3,031	2,673
Commercial LHFI [Member] | Substandard [Member] | Commercial and Industrial Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		7,585	13,494
Commercial LHFI [Member] | Substandard [Member] | Other Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		4,742	5,649
Commercial LHFI [Member] | Doubtful [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		3,020	2,982
Commercial LHFI [Member] | Doubtful [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		264	322
Commercial LHFI [Member] | Doubtful [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans			69
Commercial LHFI [Member] | Doubtful [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		530	511
Commercial LHFI [Member] | Doubtful [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		477	565
Commercial LHFI [Member] | Doubtful [Member] | Commercial and Industrial Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		1,749	1,354
Commercial LHFI [Member] | Doubtful [Member] | Other Loans [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans			161
Consumer LHFI [Member]
Acquired Loans, Aging [Abstract]
Current		46,064	54,232
Nonaccrual	[1]	124	24
Subtotal		48,691	56,455
Total Acquired Loans		261,517	272,247
Consumer LHFI [Member] | Past Due 30-89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,905	1,415
Consumer LHFI [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		598	784
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		1,188	1,801
Subtotal		1,248	1,812
Total Acquired Loans		23,586	20,850
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 30-89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		46
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		14	11
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		42,008	48,695
Nonaccrual	[1]	124	24
Subtotal		44,403	50,792
Total Acquired Loans		61,751	69,540
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30-89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,687	1,364
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		584	709
Consumer LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		34	50
Subtotal		34	50
Total Acquired Loans		114,694	103,820
Consumer LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		406	428
Subtotal		406	428
Total Acquired Loans		16,746	19,010
Consumer LHFI [Member] | Commercial and Industrial Loans [Member]
Acquired Loans, Aging [Abstract]
Current			6
Subtotal			6
Total Acquired Loans		31,506	36,896
Consumer LHFI [Member] | Consumer Loans [Member]
Acquired Loans, Aging [Abstract]
Current		2,428	3,250
Subtotal		2,600	3,365
Total Acquired Loans		2,600	3,365
Consumer LHFI [Member] | Consumer Loans [Member] | Past Due 30-89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		172	51
Consumer LHFI [Member] | Consumer Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due			64
Consumer LHFI [Member] | Other Loans [Member]
Acquired Loans, Aging [Abstract]
Current			2
Subtotal			2
Total Acquired Loans		$ 10,634	$ 18,766
[1]	Acquired loans not accounted for under FASB ASC Topic 310-30.
[2]	Past due 90 days or more but still accruing interest.

Acquired Loans - Aging Analysis

Acquired Loans - Aging Analysis of Past Due and Nonaccrual Acquired Loans, by Class (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		$ 5,707	$ 8,673
Nonaccrual	[1]	304	631
Current		255,506	262,943
Acquired Loans		261,517	272,247
Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		2,340	4,354
Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		933	589
Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	2,434	3,730
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		985	1,242
Nonaccrual	[1]	0	0
Current		22,601	19,608
Acquired Loans		23,586	20,850
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		34	321
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		90	100
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	861	821
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		2,959	2,964
Nonaccrual	[1]	302	41
Current		58,490	66,535
Acquired Loans		61,751	69,540
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,691	1,495
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		614	412
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	654	1,057
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,438	2,039
Nonaccrual	[1]	0	328
Current		113,256	101,453
Acquired Loans		114,694	103,820
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		467	1,658
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		73	38
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	898	343
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		132	2,214
Nonaccrual	[1]	0	0
Current		16,614	16,796
Acquired Loans		16,746	19,010
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		132	769
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	0
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	1,445
Commercial and Industrial Loans [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	99
Nonaccrual	[1]	2	262
Current		31,504	36,535
Acquired Loans		31,506	36,896
Commercial and Industrial Loans [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	60
Commercial and Industrial Loans [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	39
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	0
Consumer Loans [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		172	115
Nonaccrual	[1]	0	0
Current		2,428	3,250
Acquired Loans		2,600	3,365
Consumer Loans [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		16	51
Consumer Loans [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		156	0
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	64
Other Loans [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		21	0
Nonaccrual	[1]	0	0
Current		10,613	18,766
Acquired Loans		10,634	18,766
Other Loans [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	0
Other Loans [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	0
Other Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	$ 21	$ 0
[1]	Acquired loans not accounted for under FASB ASC Topic 310-30.
[2]	Past due 90 days or more but still accruing interest.

Premises and Equipment, Net - P

Premises and Equipment, Net - Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	$ 415,778	$ 418,563
Less accumulated depreciation and amortization	237,425	239,319
Premises and equipment, net	178,353	179,244
Assets held for sale	986	5,743
Total premises and equipment, net	179,339	184,987
Land [Member]
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	52,335	51,097
Building and Leasehold Improvements [Member]
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	197,372	195,296
Furniture and Equipment [Member]
Premises and Equipment, Net, by Type [Abstract]
Total cost of premises and equipment	$ 166,071	$ 172,170

Premises and Equipment, Net - A

Premises and Equipment, Net - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017USD ($)Branch	Dec. 31, 2016USD ($)BranchLand	Dec. 31, 2015USD ($)
Property Plant And Equipment [Abstract]
Number of branches held for sale | Branch	3	5
Number of land held for sale | Land		2
Property valuation adjustments	$ 338,000	$ 750,000	$ 0
Premises and Equipment, Net, by Type [Abstract]
Depreciation and amortization of premises and equipment	$ 14,300,000	$ 13,200,000	$ 14,000,000

Mortgage Banking - Schedule of

Mortgage Banking - Schedule of Activity in the Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Mortgage servicing rights [Abstract]
Balance at beginning of period	$ 80,239	$ 74,007
Origination of servicing assets	15,860	16,745
Change in fair value [Abstract]
Due to market changes	(1,050)	(407)
Due to runoff	(10,780)	(10,106)
Balance at end of period	$ 84,269	$ 80,239

Mortgage Banking - Additional I

Mortgage Banking - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)CPR	Dec. 31, 2016USD ($)CPR	Dec. 31, 2015USD ($)
Schedule of changes in the reserve for mortgage loan [Abstract]
Assumed average prepayment speed | CPR	9.14	7.94
Average discount rate (in hundredths)	10.28%	10.32%
Annual servicing fee	$ 21.4	$ 20.4	$ 19.3
Servicing fee income percentage of outstanding balance of underlying loans (in hundredths)	0.33%
Mortgage servicing rights [Abstract]
Residential mortgage loans sold	$ 1,179	1,384	1,246
Gains on sales of residential mortgage loans, before tax	$ 18.9	$ 20.5	$ 18
Period of putback response	60 days

Mortgage Banking - Schedule o89

Mortgage Banking - Schedule of Mortgage Loans Sold and Serviced for Others (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 6,624,005	$ 6,371,342
Federal National Mortgage Association [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	4,128,614	3,992,349
Government National Mortgage Association [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	2,421,456	2,291,398
Federal Home Loan Mortgage Corporation [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	47,071	55,006
Other [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 26,864	$ 32,589

Mortgage Banking - Changes in t

Mortgage Banking - Changes in the Reserve for Mortgage Loan Servicing Putback Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of changes in the reserve for mortgage loan [Abstract]
Balance at beginning of period		$ 1,130	$ 1,685	$ 1,170
Provision for putback expenses		(836)	420	315
Other	[1]	706	(975)	200
Balance at end of period		$ 1,000	$ 1,130	$ 1,685
[1]	Includes fair value adjustments for loans transferred due to underwriting issues as well as adjustments based on Trustmark’s mortgage loan servicing putback reserve analysis.

Goodwill and Identifiable Int91

Goodwill and Identifiable Intangible Assets - Goodwill by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 366,156	$ 366,156
Adjustment during 2016		0
Balance, end of period	379,627	366,156
Goodwill from Reliance merger during 2017	13,471
General Banking [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	321,132	321,132
Adjustment during 2016		0
Balance, end of period	334,603	321,132
Goodwill from Reliance merger during 2017	13,471
Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	45,024	45,024
Adjustment during 2016		0
Balance, end of period	45,024	$ 45,024
Goodwill from Reliance merger during 2017	$ 0

Goodwill and Identifiable Int92

Goodwill and Identifiable Intangible Assets - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 07, 2017
Goodwill [Line Items]
Impairment charge	$ 338,000	$ 750,000	$ 0
Goodwill	379,627,000	366,156,000	366,156,000
Amortization expense of identifiable intangible assets	6,200,000	6,900,000	7,800,000
Impairment losses on identifiable intangible assets	0	0	0
Future amortization expense for identifiable intangible assets [Abstract]
2,018	5,200,000
2,019	4,000,000
2,020	2,700,000
2,021	1,900,000
2,022	1,100,000
Reliance [Member]
Goodwill [Line Items]
Goodwill	13,500,000			$ 13,471,000
General Banking And Insurance [Member]
Goodwill [Line Items]
Impairment charge	$ 0	$ 0	$ 0

Goodwill and Identifiable Int93

Goodwill and Identifiable Intangible Assets - Schedule of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 103,513	$ 101,663
Accumulated Amortization	87,153	80,983
Net Carrying Amount	$ 16,360	20,680
Remaining Weighted-Average Amortization Periods in Years	6 years 3 months 18 days
Core Deposit Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 87,674	85,824
Accumulated Amortization	73,494	67,843
Net Carrying Amount	$ 14,180	17,981
Remaining Weighted-Average Amortization Periods in Years	5 years 2 months 12 days
Insurance Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 13,824	13,824
Accumulated Amortization	12,026	11,615
Net Carrying Amount	$ 1,798	2,209
Remaining Weighted-Average Amortization Periods in Years	15 years 3 months 18 days
Banking Charters [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,325	1,325
Accumulated Amortization	943	877
Net Carrying Amount	$ 382	448
Remaining Weighted-Average Amortization Periods in Years	5 years 8 months 12 days
Borrower Relationship Intangible [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 690	690
Accumulated Amortization	690	648
Net Carrying Amount	$ 0	$ 42

Other Real Estate - Changes and

Other Real Estate - Changes and Gains, Net on Other Real Estate (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Reconciliation Of Carrying Amount Of Real Estate Investments Roll Forward
Balance at beginning of period	[1]	$ 62,051	$ 78,828		$ 98,569
Additions	[2]	9,235	24,525	[1]	32,782	[1]
Disposals		(24,762)	(36,801)	[1]	(48,352)	[1]
Write-downs		(3,296)	(4,501)	[1]	(4,171)	[1]
Balance at end of period		43,228	62,051	[1]	78,828	[1]
Gain, net on the sale of other real estate included in other real estate expense		$ 2,087	$ 7,031	[1]	$ 4,041	[1]
[1]	The changes and gains, net on other real estate for the years ended December 31, 2016 and 2015 include covered other real estate.
[2]	For the year ended December 31, 2017, additions to other real estate included $475 thousand of other real estate acquired in the Reliance merger on April 7, 2017

Other Real Estate - Changes a95

Other Real Estate - Changes and Gains, Net on Other Real Estate (Parenthetical) (Details) $ in Thousands	Apr. 07, 2017USD ($)
Reliance [Member]
Business Acquisition [Line Items]
Other real estate acquired	$ 475

Other Real Estate - Other Real

Other Real Estate - Other Real Estate, By Type of Property (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	[1]	Dec. 31, 2014	[1]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	$ 43,228	$ 62,051	[1]	$ 78,828		$ 98,569
Construction, Land Development And Other Land Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	27,491	36,871
1 - 4 Family Residential Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	5,081	7,926
Nonfarm, Nonresidential Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	10,468	16,817
Other Real Estate Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	$ 188	$ 437
[1]	The changes and gains, net on other real estate for the years ended December 31, 2016 and 2015 include covered other real estate.

Other Real Estate - Other Rea97

Other Real Estate - Other Real Estate, By Geographic Location (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	[1]	Dec. 31, 2014	[1]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		$ 43,228	$ 62,051	[1]	$ 78,828		$ 98,569
Alabama [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		11,714	15,989
Florida [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		13,937	22,582
Mississippi [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	[2]	14,260	15,646
Tennessee [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	[3]	2,535	6,183
Texas [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		$ 782	$ 1,651
[1]	The changes and gains, net on other real estate for the years ended December 31, 2016 and 2015 include covered other real estate.
[2]	Mississippi includes Central and Southern Mississippi Regions
[3]	Tennessee includes Memphis, Tennessee and Northern Mississippi Regions

Deposits - Deposits Summary (De

Deposits - Deposits Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Noninterest-bearing demand	$ 2,978,074	$ 2,973,238
Interest-bearing demand	2,432,814	1,875,312
Savings	3,408,183	3,586,369
Time	1,758,441	1,621,093
Total deposits	$ 10,577,512	$ 10,056,012

Deposits - Interest Expense on

Deposits - Interest Expense on Deposits by Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest expense on deposits by type [Abstract]
Interest-bearing demand	$ 6,820	$ 3,297	$ 3,235
Savings	6,047	2,657	2,547
Time	9,850	6,794	6,816
Total	$ 22,717	$ 12,748	$ 12,598

Deposits - Additional Informati

Deposits - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Time deposits that exceed the FDIC insurance limit of $250 thousand	$ 342.3	$ 229.9

Deposits - Maturities on Outsta

Deposits - Maturities on Outstanding Time Deposits of $100 thousand or More (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Maturities of time deposits of $ 100 thousand or more [Abstract]
3 months or less	$ 203,679	$ 150,991
Over 3 months through 6 months	183,679	147,089
Over 6 months through 12 months	276,944	204,944
Over 12 months	179,237	179,469
Total	$ 843,539	$ 682,493

Deposits - Maturities of Intere

Deposits - Maturities of Interest-Bearing Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Maturities of interest-bearing deposits [Abstract]
2,018	$ 1,356,448
2,019	268,989
2,020	73,745
2,021	23,191
2022 and thereafter	36,068
Total time deposits	1,758,441	$ 1,621,093
Interest-bearing deposits with no stated maturity	5,840,997
Total interest-bearing deposits	$ 7,599,438	$ 7,082,774

Borrowings - Securities Sold Un

Borrowings - Securities Sold Under Repurchase Agreement - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Securities sold under repurchase agreements, secured by securities carrying amount	$ 200.9	$ 284.4

Borrowings - Securities Sold104

Borrowings - Securities Sold Under Repurchase Agreement (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Securities sold under repurchase agreements by collateral pledged
Total securities sold under repurchase agreements	$ 118,694	$ 127,007
Other Residential Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Securities sold under repurchase agreements by collateral pledged
Total securities sold under repurchase agreements	68,246	75,795
Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]
Securities sold under repurchase agreements by collateral pledged
Total securities sold under repurchase agreements	$ 50,448	$ 51,212

Borrowings - Summary of Short-T

Borrowings - Summary of Short-Term Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short Term Debt [Line Items]
Total short-term borrowings	$ 971,049	$ 769,778
Federal Home Loan Bank Advances [Member]
Short Term Debt [Line Items]
Total short-term borrowings	900,013	700,008
Serviced GNMA Loans Eligible for Repurchase [Member]
Short Term Debt [Line Items]
Total short-term borrowings	48,211	43,925
Other [Member]
Short Term Debt [Line Items]
Total short-term borrowings	$ 22,825	$ 25,845

Borrowings - Short-Term Borrowi

Borrowings - Short-Term Borrowings - Additional information (Details)	12 Months Ended
	Dec. 31, 2017USD ($)Loan	Dec. 31, 2016USD ($)Loan	Dec. 31, 2015USD ($)
Short-term Debt [Abstract]
Total short-term borrowings	$ 971,049,000	$ 769,778,000
Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Total short-term borrowings	900,013,000	700,008,000
Dallas [Member]
Short-term Debt [Abstract]
Additional debt instrument borrowing capacity	$ 1,771,000,000	$ 1,511,000,000
Dallas [Member] | Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Number of outstanding short-term FHLB advances | Loan	4	3
Total short-term borrowings	$ 900,000,000	$ 700,000,000
Dallas [Member] | Federal Home Loan Bank Advances [Member] | Advance Four [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 250,000,000
Weighted average remaining maturity	219 days
Weighted-average cost related to FHLB advances (in hundredths)	1.20%
Maturity date	Oct. 19, 2018
Dallas [Member] | Federal Home Loan Bank Advances [Member] | Advance One [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 250,000,000	$ 100,000,000
Interest rate (in hundredths)	1.44%	0.55%
Weighted average remaining maturity	58 days	7 days
Weighted-average cost related to FHLB advances (in hundredths)	1.45%	0.68%
Dallas [Member] | Federal Home Loan Bank Advances [Member] | Advance Three [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 250,000,000	$ 500,000,000
Weighted average remaining maturity	219 days
Weighted-average cost related to FHLB advances (in hundredths)	1.20%
Maturity date	May 25, 2018	Dec. 20, 2017
Dallas [Member] | Federal Home Loan Bank Advances [Member] | Advance Two [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 150,000,000	$ 100,000,000
Interest rate (in hundredths)	1.48%	0.80%
Weighted average remaining maturity	58 days	7 days
Weighted-average cost related to FHLB advances (in hundredths)	1.45%	0.68%
Atlanta [Member]
Short-term Debt [Abstract]
Additional debt instrument borrowing capacity	$ 0	$ 0
Atlanta [Member] | Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Number of outstanding short-term FHLB advances | Loan	1	1
Total short-term borrowings	$ 13,000	$ 8,000
Interest rate (in hundredths)	6.12%	6.50%
Remaining maturity	72 days	310 days
Atlanta and Dallas [Member]
Short-term Debt [Abstract]
Interest expense, short-term borrowings	$ 11,400,000	$ 1,800,000	$ 727,000

Borrowings - Long-term Debt Ins

Borrowings - Long-term Debt Instruments - Additional information (Details) - Federal Home Loan Bank Advances [Member]	12 Months Ended
	Dec. 31, 2017USD ($)Loan	Dec. 31, 2016USD ($)Loan	Dec. 31, 2015USD ($)
Dallas [Member]
Long-Term Borrowings [Abstract]
Number of outstanding long-term FHLB advances | Loan	0	1
Weighted average remaining maturity		1 year 4 months 24 days
Weighted-average cost related to FHLB advances (in hundredths)		0.24%
Maturity date		May 25, 2018
Atlanta [Member]
Long-Term Borrowings [Abstract]
Number of outstanding long-term FHLB advances | Loan	2	3
Weighted average remaining maturity	4 years 5 months 8 days	5 years 3 months 25 days
Weighted-average cost related to FHLB advances (in hundredths)	0.63%	0.82%
Atlanta [Member] | Minimum [Member]
Long-Term Borrowings [Abstract]
Interest rate (in hundredths)	0.08%	0.08%
Atlanta [Member] | Maximum [Member]
Long-Term Borrowings [Abstract]
Interest rate (in hundredths)	0.75%	6.12%
Atlanta and Dallas [Member]
Long-Term Borrowings [Abstract]
Interest expense, long-term	$ 566,000	$ 2,100,000	$ 49,000
Long Term Borrowing [Member] | BancTrust [Member] | Fair Market Value Adjustment [Member]
Long-Term Borrowings [Abstract]
Long-term FHLB advances	0	1,000
Long Term Borrowing [Member] | Dallas [Member]
Long-Term Borrowings [Abstract]
Long-term FHLB advances		250,000,000
Long Term Borrowing [Member] | Atlanta [Member] | BancTrust [Member]
Long-Term Borrowings [Abstract]
Long-term FHLB advances	946,000	1,000,000
Long Term Borrowing [Member] | Atlanta [Member] | BancTrust [Member] | Minimum [Member]
Long-Term Borrowings [Abstract]
Long-term FHLB advances	171,000	38,000
Long Term Borrowing [Member] | Atlanta [Member] | BancTrust [Member] | Maximum [Member]
Long-Term Borrowings [Abstract]
Long-term FHLB advances	$ 775,000	$ 800,000

Borrowings - Junior Subordinate

Borrowings - Junior Subordinated Debt Securities - Additional information (Details) $ in Thousands	Aug. 18, 2006USD ($)Quarter	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Variable Interest Entity [Line Items]
Junior subordinated debt securities		$ 61,856	$ 61,856
Total assets		13,797,953	13,352,333	$ 12,678,896
Total liabilities and shareholders' equity		13,797,953	13,352,333
Common securities		14,115	14,091
Net income		$ 105,630	108,411	116,038
Trustmark Preferred Capital Trust I [Member] | Junior Subordinated Debt Securities [Member]
Variable Interest Entity [Line Items]
Face amount of debt issued	$ 60,000
Maturity date	Sep. 30, 2036
Variable interest rate, description		three-month LIBOR
Basis spread over LIBOR rate (in hundredths)	1.72%
Junior subordinated debt securities	$ 61,900
Consecutive quarters that Trustmark may defer interest payments | Quarter	20
Total assets		$ 61,900	61,900
Total liabilities and shareholders' equity		61,900	61,900
Trust preferred securities		60,000	60,000
Common securities		1,900	1,900
Net income		55	45	38
Dividends paid		$ 55	$ 45	$ 38

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current [Abstract]
Federal	$ 16,959	$ 10,355	$ 18,448
State	5,687	2,698	2,166
Deferred [Abstract]
Federal	7,280	15,647	12,865
State	1,820	2,353	1,935
Income tax provision excluding deferred tax asset revaluation and reversal of valuation allowance	31,746	31,053	35,414
Deferred tax expense (benefit) - re-measurement of deferred tax assets	25,619
Deferred tax expense (benefit) - reversal of valuation allowance	(8,650)
Income tax provision	$ 48,715	$ 31,053	$ 35,414

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Valuation allowance for deferred tax assets			$ 8,650
Decrease in valuation allowance resulting in income tax expense		$ (8,700)
Statutory income tax rate		35.00%	35.00%	35.00%
Remeasurement result in decrease to net deferred tax asset		$ 25,600
Scenario Forecast [Member]
Income Tax Disclosure [Line Items]
Statutory income tax rate	21.00%

Income Taxes - Income Tax Recon

Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of provision for tax from the federal rate to the effective tax rate [Abstract]
Income tax computed at statutory tax rate	$ 54,021	$ 48,812	$ 53,008
Tax exempt interest	(7,611)	(6,780)	(5,908)
Nondeductible interest expense	407	201	119
State income taxes, net	3,697	1,754	1,408
Income tax credits, net	(15,793)	(16,183)	(15,283)
Death benefit gains	(3,268)
Reversal of valuation allowance	(8,650)
Re-measurement of deferred tax assets	25,619
Other	293	3,249	2,070
Income tax provision	$ 48,715	$ 31,053	$ 35,414

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets [Abstract]
Loan purchase accounting	$ 3,638	$ 9,341
Other real estate	13,403	25,750
Allowance for loan losses	20,203	31,618
Deferred compensation	15,184	21,893
Realized built-in losses	12,932	18,699
Securities	4,869	9,256
Pension and other postretirement benefit plans	5,453	15,545
Interest on nonaccrual loans	774	2,093
Unrealized losses on securities available for sale	5,874	3,629
Stock-based compensation	2,067	3,031
Federal carryovers	4,569
Other	8,964	13,731
Gross deferred tax asset	97,930	154,586
Valuation allowance		(8,650)
Deferred tax asset net of valuation allowance	97,930	145,936
Deferred tax liabilities [Abstract]
Goodwill and other identifiable intangibles	16,729	25,666
Premises and equipment	11,877	19,391
Mortgage servicing rights	9,964	12,159
Securities	1,345	1,697
Leases		60
Other	5,040	6,891
Gross deferred tax liability	44,955	65,864
Net deferred tax asset	$ 52,975	$ 80,072

Income Taxes - Changes in Unrec

Income Taxes - Changes in Unrecognized Tax Benefits (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Changes in unrecognized tax benefits [Roll Forward]
Balance at beginning of period	$ 1,734
Increases due to tax positions taken during the current year	303
Decreases due to tax positions taken during a prior year	(853)
Decreases due to the lapse of applicable statute of limitations during the current year	(79)
Balance at end of period	1,105
Accrued interest, net of federal benefit, at end of period	217
Unrecognized tax benefits that would impact the effective tax rate, if recognized, at end of period	$ 883

Defined Benefit and Other Po114

Defined Benefit and Other Postretirement Benefits - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Recognized net loss due to defined benefit plan termination			$ 17,644,000
Trustmark Capital Accumulation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Years of service required to vest			3 years
Defined benefit plan, additional asset contributions on termination basis	$ 17,600,000
Trustmark's minimum required contribution to the Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions			$ 113,000	$ 0
Trustmark's contribution to the Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions			200,000
Trustmark Capital Accumulation Plan [Member] | Scenario Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Trustmark's minimum required contribution to the Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions		$ 175,000
Trustmark Capital Accumulation Plan [Member] | Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, additional asset contributions on termination basis			17,964,000	69,000
Recognized net loss due to defined benefit plan termination	$ 17,600,000		17,662,000	0	$ 0
Assets remained in this plan			0
Estimated future benefit payments [Abstract]
Accumulated other comprehensive loss expected to be recognized during next fiscal year as components of net periodic benefit cost			(571,000)
Supplemental Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, additional asset contributions on termination basis			3,451,000	3,326,000
Estimated future benefit payments [Abstract]
Accumulated other comprehensive loss expected to be recognized during next fiscal year as components of net periodic benefit cost			(884,000)
Accumulated other comprehensive loss expected to be recognized during next fiscal year as prior service cost			250,000
Defined Contribution Plan [Member]
Other Benefit Plans - Defined Contribution Plan [Abstract]
Trustmarks contribution to defined contribution plan			$ 7,500,000	$ 7,200,000	$ 7,000,000
Contributions up to a maximum of eligible compensation			6.00%
Trustmark contributions to the plan			100.00%
Period when associates may become eligible to make elective deferral contributions after employment			30 days
Eligible associates must complete number of years of service			1 year

Defined Benefit and Other Po115

Defined Benefit and Other Postretirement Benefits - Plan Benefit Obligation, Plan Assets and Funded Status of the Plan (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Trustmark Capital Accumulation Plan [Member]
Change in plan assets [ Roll Forward]
Employer contributions	$ 17,600
Trustmark Capital Accumulation Plan [Member] | Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year		$ 75,900	$ 91,403
Service cost		253	428	$ 513
Interest cost		1,461	3,355	3,461
Actuarial loss (gain)		391	(893)
Benefits paid		(68,583)	(18,393)
Settlement loss		680	0
Benefit obligation, end of year		10,102	75,900	91,403
Change in plan assets [ Roll Forward]
Fair value of plan assets, beginning of year		54,734	74,137
Actual return on plan assets		481	(1,079)
Employer contributions		17,964	69
Benefits paid		(68,583)	(18,393)
Fair value of plan assets, end of year		4,596	54,734	74,137
Funded status at end of year - net liability		(5,506)	(21,166)
Amounts recognized in accumulated other comprehensive income (loss) [Abstract]
Net loss		3,187	21,355
Supplemental Retirement Plan [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year		58,495	57,766
Service cost		141	295	431
Interest cost		2,103	2,223	2,082
Actuarial loss (gain)		642	1,537
Benefits paid		(3,451)	(3,326)
Benefit obligation, end of year		57,930	58,495	57,766
Change in plan assets [ Roll Forward]
Fair value of plan assets, beginning of year		0	0
Employer contributions		3,451	3,326
Benefits paid		(3,451)	(3,326)
Fair value of plan assets, end of year		0	0	$ 0
Funded status at end of year - net liability		(57,930)	(58,495)
Amounts recognized in accumulated other comprehensive income (loss) [Abstract]
Net loss		17,514	17,739
Prior service cost		1,109	1,359
Amounts recognized		$ 18,623	$ 19,098

Defined Benefit and Other Po116

Defined Benefit and Other Postretirement Benefits - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net periodic benefit cost [Abstract]
Recognized net loss due to defined benefit plan termination		$ 17,644
Trustmark Capital Accumulation Plan [Member] | Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member]
Net periodic benefit cost [Abstract]
Service cost		253	$ 428	$ 513
Interest cost		1,461	3,355	3,461
Expected return on plan assets		(317)	(2,897)	(5,187)
Recognized net loss due to defined benefit plan termination	$ 17,600	17,662	0	0
Recognized net loss due to lump sum settlements		0	3,906	2,221
Recognized net actuarial loss		1,414	2,749	3,878
Net periodic benefit cost		20,473	7,541	4,886
Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes:
Net (gain) loss - Total recognized in other comprehensive income (loss)		(18,168)	(3,572)	(3,173)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		$ 2,305	$ 3,969	$ 1,713
Weighted-average assumptions as of end of year [Abstract]
Discount rate for benefit obligation (in hundredths)		3.32%	3.71%	3.86%
Discount rate for net periodic benefit cost (in hundredths)		3.71%	3.86%	3.57%
Expected long-term return on plan assets (in hundredths)		5.00%	4.25%	7.00%
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost		$ 141	$ 295	$ 431
Interest cost		2,103	2,223	2,082
Amortization of prior service credits		250	250	250
Recognized net actuarial loss		866	864	992
Net periodic benefit cost		3,360	3,632	3,755
Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes:
Net loss (gain)		(224)	(810)	(2,694)
Net (gain) loss - Total recognized in other comprehensive income (loss)		(474)	(1,060)	(2,944)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		2,886	2,572	811
Amortization of prior service cost		$ (250)	$ (250)	$ (250)
Weighted-average assumptions as of end of year [Abstract]
Discount rate for benefit obligation (in hundredths)		3.32%	3.71%	3.86%
Discount rate for net periodic benefit cost (in hundredths)		3.71%	3.86%	3.57%

Defined Benefit and Other Po117

Defined Benefit and Other Postretirement Benefits - Weighted-Average Asset Allocation (Details) - Trustmark Capital Accumulation Plan [Member] - Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member]	Dec. 31, 2017	Dec. 31, 2016
Asset target allocations [Abstract]
Weighted-average asset allocation (in hundredths)	100.00%	100.00%
Money Market Funds [Member]
Asset target allocations [Abstract]
Weighted-average asset allocation (in hundredths)	6.00%	13.00%
Equity Securities [Member]
Asset target allocations [Abstract]
Weighted-average asset allocation (in hundredths)	48.00%	0.00%
U.S. Treasuries [Member]
Asset target allocations [Abstract]
Weighted-average asset allocation (in hundredths)	0.00%	87.00%
Fixed Income [Member]
Asset target allocations [Abstract]
Weighted-average asset allocation (in hundredths)	32.00%	0.00%
International [Member]
Asset target allocations [Abstract]
Weighted-average asset allocation (in hundredths)	14.00%	0.00%

Defined Benefit and Other Po118

Defined Benefit and Other Postretirement Benefits - Plan Assets Measured at Fair Value (Details) - Trustmark Capital Accumulation Plan [Member] - Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Asset target allocations [Abstract]
Fair value of plan assets	$ 4,596	$ 54,734	$ 74,137
Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	4,596	54,734
Level 2 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0	0
Level 3 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0	0
Money Market Funds [Member]
Asset target allocations [Abstract]
Fair value of plan assets	269	6,859
Money Market Funds [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	269	6,859
Money Market Funds [Member] | Level 2 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0	0
Money Market Funds [Member] | Level 3 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0	0
Equity Securities [Member]
Asset target allocations [Abstract]
Fair value of plan assets	2,199
Equity Securities [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	2,199
Equity Securities [Member] | Level 2 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0
Equity Securities [Member] | Level 3 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0
Fixed Income [Member]
Asset target allocations [Abstract]
Fair value of plan assets	1,462
Fixed Income [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	1,462
Fixed Income [Member] | Level 2 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0
Fixed Income [Member] | Level 3 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0
International [Member]
Asset target allocations [Abstract]
Fair value of plan assets	666
International [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	666
International [Member] | Level 2 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	0
International [Member] | Level 3 [Member]
Asset target allocations [Abstract]
Fair value of plan assets	$ 0
U.S. Treasuries [Member]
Asset target allocations [Abstract]
Fair value of plan assets		47,875
U.S. Treasuries [Member] | Level 1 [Member]
Asset target allocations [Abstract]
Fair value of plan assets		47,875
U.S. Treasuries [Member] | Level 2 [Member]
Asset target allocations [Abstract]
Fair value of plan assets		0
U.S. Treasuries [Member] | Level 3 [Member]
Asset target allocations [Abstract]
Fair value of plan assets		$ 0

Defined Benefit and Other Po119

Defined Benefit and Other Postretirement Benefits - Estimated Future Benefit Payments and Other Disclosures (Details) $ in Thousands	Dec. 31, 2017USD ($)
Supplemental Retirement Plan [Member]
Estimated future benefit payments [Abstract]
2,018	$ 3,475
2,019	3,591
2,020	4,047
2,021	4,105
2,022	4,262
2023 - 2027	19,230
Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member] | Trustmark Capital Accumulation Plan [Member]
Estimated future benefit payments [Abstract]
2,018	196
2,019	282
2,020	333
2,021	394
2,022	453
2023 - 2027	$ 2,961

Stock and Incentive Compensa120

Stock and Incentive Compensation Plans - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017shares
Performance Based Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Return on average tangible equity, performance measure	100.00%
Total shareholder return, performance measure	100.00%
Time-Vested Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Stock and Incentive Compensation Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock available for issuance (in shares)	1,110,739

Stock and Incentive Compensa121

Stock and Incentive Compensation Plans - Summary of Performance Award Activity (Details) - Stock and Incentive Compensation Plan [Member] - Performance Based Award [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares [Roll Forward]
Nonvested shares, beginning of year (in shares)	237,136	212,309	181,195
Granted (in shares)	58,406	99,116	84,899
Released from restriction (in shares)	(67,279)	(40,888)	(47,360)
Forfeited (in shares)	(14,747)	(33,401)	(6,425)
Nonvested shares, end of year (in shares)	213,516	237,136	212,309
Weighted-Average Grant Date Fair Value [Abstract]
Nonvested shares, beginning of year (in dollars per share)	$ 26.27	$ 24.14	$ 24.98
Granted (in dollars per share)	33.31	20.18	22.71
Released from restriction (in dollars per share)	34.78	32.84	24.97
Forfeited (in dollars per share)	28.42	30.01	24.97
Nonvested shares, end of year (in dollars per share)	$ 25.37	$ 26.27	$ 24.14

Stock and Incentive Compensa122

Stock and Incentive Compensation Plans - Summary of Time-Vested Award Activity (Details) - Stock and Incentive Compensation Plan [Member] - Time-Vested Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares [Roll Forward]
Nonvested shares, beginning of year (in shares)	322,056	306,657	263,905
Granted (in shares)	105,524	139,791	121,314
Released from restriction (in shares)	(101,289)	(108,241)	(67,087)
Forfeited (in shares)	(5,934)	(16,151)	(11,475)
Nonvested shares, end of year (in shares)	320,357	322,056	306,657
Weighted-Average Grant Date Fair Value [Abstract]
Nonvested shares, beginning of year (in dollars per share)	$ 22.65	$ 24.56	$ 24.66
Granted (in dollars per share)	33.79	20.66	23.61
Released from restriction (in dollars per share)	25.35	23.74	24.31
Forfeited (in dollars per share)	26.52	22.24	24.22
Nonvested shares, end of year (in dollars per share)	$ 25.40	$ 22.65	$ 24.56

Stock and Incentive Compensa123

Stock and Incentive Compensation Plans - Compensation Expense for Stock and Incentive Plans (Details) - Stock and Incentive Compensation Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation expense [Abstract]
Recognized compensation expense	$ 4,309	$ 3,684	$ 3,668
Unrecognized compensation expense	4,841
Performance Based Award [Member]
Compensation expense [Abstract]
Recognized compensation expense	1,387	1,171	1,201
Unrecognized compensation expense	$ 1,783
Weighted average life of unrecognized compensation expense	1 year 7 months 28 days
Time-Vested Awards [Member]
Compensation expense [Abstract]
Recognized compensation expense	$ 2,922	$ 2,513	$ 2,467
Unrecognized compensation expense	$ 3,058
Weighted average life of unrecognized compensation expense	1 year 9 months 18 days

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)Lawsuit	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Loss Contingencies [Line Items]
Unused commitments to extend credit	$ 3,172	$ 3,131
Lease Commitments [Abstract]
Rental expense	$ 9.3	9.8	$ 9.3
Pending or Threatened Litigation, Stanford Financial Group [Member]
Legal Proceedings [Abstract]
Lawsuits naming entity as defendant, number | Lawsuit	3
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Potential exposure to credit loss in the event of nonperformance	$ 104.1	111.3
Letters of credit, maturity term - maximum	3 years
Collateral held, fair value	$ 28.4	$ 32.7

Commitments and Contingencie125

Commitments and Contingencies - Future Minimum Rental Commitments Under Non-cancellable Operating Leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2,018	$ 12,031
2,019	10,436
2,020	6,642
2,021	5,197
2,022	5,039
Thereafter	28,518
Total	$ 67,863

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Mar. 11, 2016
Stockholders Equity [Line Items]
Capital conservation buffer rate	1.25%	0.625%
Reclassification adjustment from accumulated other comprehensive loss to retained earnings	$ 8,500
Dividends on common stock [Abstract]
Dividend potential for next fiscal year	$ 87,000
Period for which retained net income considered for approval	2 years
Stock Repurchase Program
Dividends on common stock [Abstract]
Amount of stock authorized for repurchase			$ 100,000
Repurchase shares of common stock	0	34,000
Repurchase shares of common stock, value		$ 750

Shareholders' Equity - Table of

Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Trustmark Corporation [Member] | Common Equity Tier 1 Capital (to Risk Weighted Assets) [Member]
Common Equity Tier One Risk Based Capital [Abstract]
Actual Regulatory Capital Amount		$ 1,243,240	$ 1,209,927
Actual Regulatory Capital Ratio		11.77%	12.16%
Minimum Regulatory Capital Required Ratio		5.75%	5.125%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,303,238	$ 1,269,660
Actual Regulatory Capital Ratio		12.33%	12.76%
Minimum Regulatory Capital Required Ratio		7.25%	6.625%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,384,050	$ 1,352,322
Actual Regulatory Capital Ratio		13.10%	13.59%
Minimum Regulatory Capital Required Ratio		9.25%	8.625%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark Corporation [Member] | Tier 1 Leverage (to Average Assets) [Member]
Tier 1 Leverage (to Average Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,303,238	$ 1,269,660
Actual Regulatory Capital Ratio		9.67%	9.90%
Minimum Regulatory Capital Required Ratio		4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio	[1]
Trustmark National Bank [Member] | Common Equity Tier 1 Capital (to Risk Weighted Assets) [Member]
Common Equity Tier One Risk Based Capital [Abstract]
Actual Regulatory Capital Amount		$ 1,284,575	$ 1,251,329
Actual Regulatory Capital Ratio		12.16%	12.58%
Minimum Regulatory Capital Required Ratio		5.75%	5.125%
Minimum Regulatory Provision to be Well-Capitalized Ratio		6.50%	6.50%
Trustmark National Bank [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,284,575	$ 1,251,329
Actual Regulatory Capital Ratio		12.16%	12.58%
Minimum Regulatory Capital Required Ratio		7.25%	6.625%
Minimum Regulatory Provision to be Well-Capitalized Ratio		8.00%	8.00%
Trustmark National Bank [Member] | Total Capital (to Risk Weighted Assets) [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,365,387	$ 1,333,991
Actual Regulatory Capital Ratio		12.93%	13.41%
Minimum Regulatory Capital Required Ratio		9.25%	8.625%
Minimum Regulatory Provision to be Well-Capitalized Ratio		10.00%	10.00%
Trustmark National Bank [Member] | Tier 1 Leverage (to Average Assets) [Member]
Tier 1 Leverage (to Average Assets) [Abstract]
Actual Regulatory Capital Amount		$ 1,284,575	$ 1,251,329
Actual Regulatory Capital Ratio		9.54%	9.77%
Minimum Regulatory Capital Required Ratio		4.00%	4.00%
Minimum Regulatory Provision to be Well-Capitalized Ratio		5.00%	5.00%
[1]	n/a

Shareholders' Equity - Componen

Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Securities available for sale and transferred securities, Before tax amount [Abstract]
Unrealized holding gains (losses) arising during the period, Before tax amount	$ (13,994)	$ (15,656)	$ (16,695)
Reclassification adjustment for net (gains) losses realized in net income, Before tax amount	(15)	310	0
Change in net unrealized holding loss on securities transferred to held to maturity, Before tax amount	4,721	9,830	6,345
Total securities available for sale and transferred securities, Before tax amount	(9,288)	(5,516)	(10,350)
Securities available for sale and transferred securities, Tax (expense) benefit [Abstract]
Unrealized holding gains (losses) arising during the period, Tax (expense) benefit	5,353	5,989	6,386
Reclassification adjustment for net (gains) losses realized in net income, Tax (expense) benefit	6	(119)	0
Change in net unrealized holding loss on securities transferred to held to maturity, Tax (expense) benefit	(1,806)	(3,760)	(2,427)
Total securities available for sale and transferred securities, Tax (expense) benefit	3,553	2,110	3,959
Securities available for sale and transferred securities, Net of tax amount [Abstract]
Unrealized holding gains (losses) arising during the period, net of tax amount	(8,641)	(9,667)	(10,309)
Reclassification adjustment for net (gains) losses realized in net income, net of tax amount	(9)	191	0
Change in net unrealized holding loss on securities transferred to held to maturity, net of tax amount	2,915	6,070	3,918
Total securities available for sale and transferred securities, net of tax amount	(5,735)	(3,406)	(6,391)
Pension and other postretirement benefit plans, Before tax amount [Abstract]
Net change in prior service costs, before tax amount	250	250	250
Recognized net loss due to lump sum settlements, before tax amount		3,906	2,221
Change in net actuarial loss, before tax amount	731	476	3,647
Recognized net loss due to defined benefit plan termination, before tax amount	17,662
Total pension and other postretirement benefit plans, before tax amount	18,643	4,632	6,118
Pension and other postretirement benefit plans, Tax (expense) benefit [Abstract]
Net change in prior service costs, tax (expense) benefit	(96)	(96)	(96)
Recognized net loss due to lump sum settlements, tax (expense) benefit		(1,494)	(850)
Change in net actuarial loss, tax (expense) benefit	(280)	(182)	(1,395)
Recognized net loss due to defined benefit plan termination, tax (expense) benefit	(6,755)
Total pension and other postretirement benefit plans, tax (expense) benefit	(7,131)	(1,772)	(2,341)
Pension and other postretirement benefit plans, Net of tax amount [Abstract]
Net change in prior service costs, net of tax amount	154	154	154
Recognized net loss due to lump sum settlements, net of tax amount	0	2,412	1,371
Change in net actuarial loss, net of tax amount	451	294	2,252
Recognized net loss due to defined benefit plan termination, net of tax	10,907	0	0
Total pension and other postretirement benefit plans, net of tax amount	11,512	2,860	3,777
Cash flow hedge derivatives, Before tax amount [Abstract]
Change in accumulated gain (loss) on effective cash flow hedge derivatives, before tax amount	198	(369)	(1,315)
Reclassification adjustment for loss realized in net income, before tax amount	282	599	836
Total cash flow hedge derivatives, before tax benefit	480	230	(479)
Total other comprehensive income (loss), Before tax amount	9,835	(654)	(4,711)
Cash flow hedge derivatives, Tax (expense) benefit [Abstract]
Change in accumulated loss on effective cash flow hedge derivatives, tax (expense) benefit	(76)	141	503
Reclassification adjustment for loss realized in net income, tax (expense) benefit	(108)	(229)	(320)
Total cash flow hedge derivatives, tax (expense) benefit	(184)	(88)	183
Total other comprehensive income (loss), Tax expense (benefit)	(3,762)	250	1,801
Cash flow hedge derivatives, Net of tax amount [Abstract]
Change in the accumulated loss on effective cash flow hedge derivatives, net of tax amount	122	(228)	(812)
Reclassification adjustment for loss realized in net income, net of tax amount	174	370	516
Total cash flow hedge derivatives, net of tax amount	296	142	(296)
Total other comprehensive income (loss), net of tax amount	$ 6,073	$ (404)	$ (2,910)

Shareholders' Equity - Changes

Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,520,208	$ 1,473,057	$ 1,419,940
Other comprehensive income (loss) before reclassification	(6,364)	(3,973)	(3,426)
Amounts reclassified from accumulated other comprehensive loss	12,437	3,569	516
Total other comprehensive income (loss), net of tax amount	6,073	(404)	(2,910)
Balance	1,571,701	1,520,208	1,473,057
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(20,800)	(17,394)	(11,003)
Other comprehensive income (loss) before reclassification	(5,726)	(3,597)	(6,391)
Amounts reclassified from accumulated other comprehensive loss	(9)	191
Total other comprehensive income (loss), net of tax amount	(5,735)	(3,406)	(6,391)
Balance	(26,535)	(20,800)	(17,394)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(24,980)	(27,840)	(31,617)
Other comprehensive income (loss) before reclassification	(760)	(148)	3,777
Amounts reclassified from accumulated other comprehensive loss	12,272	3,008
Total other comprehensive income (loss), net of tax amount	11,512	2,860	3,777
Balance	(13,468)	(24,980)	(27,840)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(18)	(160)	136
Other comprehensive income (loss) before reclassification	122	(228)	(812)
Amounts reclassified from accumulated other comprehensive loss	174	370	516
Total other comprehensive income (loss), net of tax amount	296	142	(296)
Balance	278	(18)	(160)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(45,798)	(45,394)	(42,484)
Balance	$ (39,725)	$ (45,798)	$ (45,394)

Fair Value - Financial Assets a

Fair Value - Financial Assets and Liabilities Measured at Fair Value Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 2,238,635	$ 2,356,682
Loans held for sale	180,512	175,927
Mortgage servicing rights	84,269	80,239	$ 74,007
U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	45,018	55,763
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	79,229	115,373
Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,238,635	2,356,682
Loans held for sale	180,512	175,927
Mortgage servicing rights	84,269	80,239
Other assets - derivatives	1,516	2,518
Other liabilities - derivatives	2,678	412
Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	45,285	56,039
Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	79,229	115,373
Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,114,121	2,185,270
Level 1 [Member] | Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Loans held for sale	0	0
Mortgage servicing rights	0	0
Other assets - derivatives	(1,013)	(524)
Other liabilities - derivatives	616	1,174
Level 1 [Member] | Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 1 [Member] | Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 1 [Member] | Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 2 [Member] | Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,238,635	2,356,682
Loans held for sale	180,512	175,927
Mortgage servicing rights	0	0
Other assets - derivatives	1,629	2,041
Other liabilities - derivatives	2,062	(762)
Level 2 [Member] | Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	45,285	56,039
Level 2 [Member] | Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	79,229	115,373
Level 2 [Member] | Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,114,121	2,185,270
Level 3 [Member] | Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Loans held for sale	0	0
Mortgage servicing rights	84,269	80,239
Other assets - derivatives	900	1,001
Other liabilities - derivatives	0	0
Level 3 [Member] | Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 3 [Member] | Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 3 [Member] | Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 0	$ 0

Fair Value - Changes in Level 3

Fair Value - Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis (Details) - Recurring Basis [Member] - Level 3 [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
MSR [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ 80,239	$ 74,007
Total net (loss) gain included in Mortgage banking, net	[1]	(11,830)	(10,513)
Additions		15,860	16,745
Sales		0	0
Ending Balance		84,269	80,239
The amount of total gains (losses) for the period included in earnings that are attributable to the change in unrealized gains or losses still held, end of period		(1,050)	(407)
Other Assets - Derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		1,001	1,113
Total net (loss) gain included in Mortgage banking, net	[1]	4,165	10,128
Additions		0	0
Sales		(4,266)	(10,240)
Ending Balance		900	1,001
The amount of total gains (losses) for the period included in earnings that are attributable to the change in unrealized gains or losses still held, end of period		$ (1,569)	$ 753
[1]	Total net (loss) gain included in Mortgage banking, net relating to the MSR includes changes in fair value due to market changes and due to run-off.

Fair Value - Additional Informa

Fair Value - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Nonfinancial Assets and Liabilities [Abstract]
Outstanding balances in impaired loans	$ 48,900	$ 27,100
Foreclosed assets re-measured after initial recognition	26,600	32,200
Write-downs of allowance for foreclosed assets after initial recognition	3,300	4,400
Noninterest gain (loss) Mortgage banking, net for changes in fair value of LHFS	3,000	(2,500)	$ (857)
Interest earned on LHFS included in Interest and fees on LHFS and LHFI	4,900	5,000	$ 4,700
GNMA optional repurchase loans	$ 48,200	$ 43,900
Maximum [Member]
Nonfinancial Assets and Liabilities [Abstract]
Estimated fair value of financial instruments with immediate and shorter-term maturities	90 days

Fair Value - Carrying Amounts a

Fair Value - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	$ 1,056,486	$ 1,158,643
Net LHFI	8,493,234	7,779,948
Acquired loans	257,438	260,850
Deposits	10,577,512	10,056,012
Long-term FHLB advances	946	251,049
Junior subordinated debt securities	61,856	61,856
Level 2 [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	336,383	328,206
Securities held to maturity	1,056,486	1,158,643
Deposits	10,577,512	10,056,012
Short-term liabilities	1,440,876	1,309,595
Long-term FHLB advances	946	251,049
Junior subordinated debt securities	61,856	61,856
Level 2 [Member] | Estimate Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	336,383	328,206
Securities held to maturity	1,046,247	1,157,046
Deposits	10,577,858	10,059,794
Short-term liabilities	1,440,876	1,309,595
Long-term FHLB advances	946	251,050
Junior subordinated debt securities	45,773	41,057
Level 3 [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	8,493,234	7,779,948
Acquired loans	257,438	260,850
Level 3 [Member] | Estimate Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	8,507,469	7,825,009
Acquired loans	$ 257,438	$ 260,850

Fair Value - Fair Value and the

Fair Value - Fair Value and the Contractual Principal Outstanding of the LHFS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair value and the contractual principal outstanding of the LHFS [Abstract]
Fair value of LHFS	$ 132,300	$ 132,002
LHFS contractual principal outstanding	129,347	132,047
Fair value less unpaid principal	$ 2,953	$ (45)

Derivative Financial Instrum135

Derivative Financial Instruments - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017USD ($)Contract	Dec. 31, 2016USD ($)Contract	Dec. 31, 2015USD ($)	Apr. 04, 2013USD ($)
Mortgage Servicing Rights Hedge [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total notional amount	$ 349,000,000	$ 262,000,000
Net (negative) positive ineffectiveness on MSR fair value	254,000	(2,900,000)	$ 1,900,000
Designated as Hedging Instrument [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Accumulated net, after tax (loss) gain included in other comprehensive loss	$ 122,000	(228,000)	(812,000)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Period for which cash flow hedges will be used to hedge quarterly interest payments	5 years
Derivative inception date	Dec. 31, 2014
Derivative maturity date	Dec. 31, 2019
Description of variable rate basis for derivative	three-month LIBOR
Ineffectiveness related to interest rate swap designated as a cash flow hedge	$ 0	0	$ 0
Accumulated net, after tax (loss) gain included in other comprehensive loss	$ 278,000	$ (18,000)
The period over which OCI will be reclassified as interest expense	12 months
Estimated amount to be reclassified as a decrease to interest expense	$ 125,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Junior Subordinated Debentures [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total notional amount				$ 60,000,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Three-month LIBOR [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Swap fixed interest rate to be paid	1.66%
Derivatives not Designated as Hedging Instruments [Member] | Beneficiary [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Number of risk participation agreements | Contract	2	2
Aggregate notional amount of credit risk participation agreements	$ 13,700,000	$ 14,200,000
Derivatives not Designated as Hedging Instruments [Member] | Guarantor [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Number of risk participation agreements | Contract	6	5
Aggregate notional amount of credit risk participation agreements	$ 37,100,000	$ 28,000,000
Derivatives not Designated as Hedging Instruments [Member] | Interest Rate Swap [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total notional amount	351,900,000	340,200,000
Termination value of derivatives	80,000	1,200,000
Collateral Posted	100,000
Derivatives not Designated as Hedging Instruments [Member] | Forward Contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet obligations	182,100,000	195,000,000
Valuation adjustment	(237,000)	2,800,000
Derivatives not Designated as Hedging Instruments [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet obligations	83,000,000	97,900,000
Valuation adjustment	$ 900,000	$ 1,000,000

Derivative Financial Instrum136

Derivative Financial Instruments - Fair Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	$ 1,626	$ 2,032
Fair value of derivative liability	1,819	2,065
Derivatives in Hedging Relationships [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	451	(28)
Derivatives not Designated as Hedging Instruments [Member] | Future Contracts [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	(1,088)	(626)
Derivatives not Designated as Hedging Instruments [Member] | Credit Risk Participation Agreement [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	3	9
Derivatives not Designated as Hedging Instruments [Member] | Credit Risk Participation Agreement [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	6	11
Derivatives not Designated as Hedging Instruments [Member] | Forward Contracts [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	237	(2,838)
Derivatives not Designated as Hedging Instruments [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	1,175	2,060
Derivatives not Designated as Hedging Instruments [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	1,819	2,065
Derivatives not Designated as Hedging Instruments [Member] | Exchange Traded Purchased Options [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	75	102
Derivatives not Designated as Hedging Instruments [Member] | OTC Written Options (Rate Locks) [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	900	1,001
Derivatives not Designated as Hedging Instruments [Member] | Exchange Traded Written Options [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	$ 616	$ 1,174

Derivative Financial Instrum137

Derivative Financial Instruments - Effects of Derivative Instruments on Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivatives in Hedging Relationships [Member] | Accumulated Other Comprehensive Loss and Other Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Amount of loss reclassified from accumulated other comprehensive loss and recognized in other interest expense	$ (282)	$ (599)	$ (836)
Derivatives not Designated as Hedging Instruments [Member] | Mortgage Banking, Net [Member]
Derivatives, Fair Value [Line Items]
Amount of gain (loss) recognized in mortgage banking, net	(1,873)	13	1,392
Derivatives not Designated as Hedging Instruments [Member] | Bank Card and Other Fees [Member]
Derivatives, Fair Value [Line Items]
Amount of gain (loss) recognized in bank card and other fees	$ (31)	$ 60	$ (49)

Derivative Financial Instrum138

Derivative Financial Instruments - Schedule of Amount Included in Other Comprehensive Income (Loss) for Derivative Instruments Designated as Hedges of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivatives in Hedging Relationships [Member]
Derivatives in cash flow hedging relationship
Amount of gain (loss) recognized in other comprehensive income (loss), net of tax	$ 122	$ (228)	$ (812)

Derivative Financial Instrum139

Derivative Financial Instruments - Information about Financial Instruments that are Eligible for Offset in the Consolidated Balance Sheets (Details) - Interest Rate Swap [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Offsetting Derivative Assets
Gross Amounts of Recognized Assets, Offsetting of Derivative Assets	$ 1,626	$ 2,032
Gross Amounts Offset in the Statement of Financial Position, Offsetting of Derivative Assets	0	0
Net Amounts of Assets presented in the Statement of Financial Position, Offsetting of Derivative Assets	1,626	2,032
Financial Instruments, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Assets	(311)	(499)
Cash Collateral Received, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Assets	0	0
Net Amount, Offsetting of Derivative Assets	1,315	1,533
Offsetting Derivative Liabilities
Gross Amounts of Recognized Liabilities, Offsetting of Derivative Liabilities	1,819	2,065
Gross Amounts Offset in the Statement of Financial Position, Offsetting of Derivative Liabilities	0	0
Net Amounts of Liabilities presented in the Statement of Financial Position, Offsetting of Derivative Liabilities	1,819	2,065
Financial Instruments, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Liabilities	(311)	(499)
Cash Collateral Posted, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Liabilities	(100)	(937)
Net Amount, Offsetting of Derivative Liabilities	$ 1,408	$ 629

Segment Information - Additiona

Segment Information - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017Segment
Segment Reporting [Abstract]
Number of segments in which the business operates	3

Segment Information - Schedule

Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net interest income	$ 407,550	$ 387,533	$ 391,765
Provision for loan losses, net	7,699	14,714	11,800
Noninterest income	184,663	173,943	173,149
Noninterest expense	430,169	407,298	401,662
Income Before Income Taxes	154,345	139,464	151,452
Income taxes	48,715	31,053	35,414
Net Income	105,630	108,411	116,038
Selected Financial Information
Total assets	13,797,953	13,352,333	12,678,896
Depreciation and amortization	38,471	36,613	37,056
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	406,406	386,596	391,092
Provision for loan losses, net	7,699	14,714	11,800
Noninterest income	116,180	107,059	105,477
Noninterest expense	373,221	354,555	348,270
Income Before Income Taxes	141,666	124,386	136,499
Income taxes	43,960	25,303	29,761
Net Income	97,706	99,083	106,738
Selected Financial Information
Total assets	13,724,193	13,278,668	12,604,112
Depreciation and amortization	37,710	35,692	36,072
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	910	726	337
Noninterest income	30,285	30,117	31,245
Noninterest expense	27,561	24,165	25,346
Income Before Income Taxes	3,634	6,678	6,236
Income taxes	1,390	2,554	2,386
Net Income	2,244	4,124	3,850
Selected Financial Information
Total assets	5,592	7,501	7,471
Depreciation and amortization	131	174	183
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	234	211	336
Noninterest income	38,198	36,767	36,427
Noninterest expense	29,387	28,578	28,046
Income Before Income Taxes	9,045	8,400	8,717
Income taxes	3,365	3,196	3,267
Net Income	5,680	5,204	5,450
Selected Financial Information
Total assets	68,168	66,164	67,313
Depreciation and amortization	$ 630	$ 747	$ 801

Parent Company Only Financia142

Parent Company Only Financial Information - Parent Only Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Other assets	$ 532,442	$ 577,964
Total Assets	13,797,953	13,352,333	$ 12,678,896
Liabilities and Shareholders' Equity:
Junior subordinated debt securities	61,856	61,856
Shareholders' equity	1,571,701	1,520,208	1,473,057	$ 1,419,940
Total Liabilities and Shareholders' Equity	13,797,953	13,352,333
Expense:
Net Income	105,630	108,411	116,038
Operating Activities
Net income	105,630	108,411	116,038
Adjustments to reconcile net income to net cash provided by operating activities:
Other	6,430	2,932	5,043
Net cash provided by operating activities	206,607	148,337	172,539
Investing Activities
Net cash used in investing activities	(348,862)	(649,664)	(527,277)
Financing Activities
Cash dividends paid on common stock	(62,795)	(62,666)	(62,605)
Net cash provided by financing activities	150,317	551,282	316,516
Net change in cash and cash equivalents	8,062	49,955	(38,222)
Cash and cash equivalents at beginning of year	327,706	277,751	315,973
Cash and cash equivalents at end of year	335,768	327,706	277,751
Trustmark Corp (Parent Company Only) [Member]
Assets
Investment in banks	1,617,238	1,566,186
Other assets	17,349	16,756
Total Assets	1,634,587	1,582,942
Liabilities and Shareholders' Equity:
Accrued expense	1,030	878
Junior subordinated debt securities	61,856	61,856
Shareholders' equity	1,571,701	1,520,208
Total Liabilities and Shareholders' Equity	1,634,587	1,582,942
Revenue:
Dividends received from banks	65,663	65,987	64,752
Earnings of subsidiaries over distributions	42,211	44,756	53,562
Other income	71	60	55
Total Revenue	107,945	110,803	118,369
Expense:
Other expense	2,315	2,392	2,331
Total Expense	2,315	2,392	2,331
Net Income	105,630	108,411	116,038
Operating Activities
Net income	105,630	108,411	116,038
Adjustments to reconcile net income to net cash provided by operating activities:
Net change in investment in subsidiaries	(42,211)	(44,756)	(53,562)
Other	(1,697)	(739)	(761)
Net cash provided by operating activities	61,722	62,916	61,715
Investing Activities
Payment for investments in subsidiaries	30,755
Repayment for investments in subsidiaries	32,000
Net cash used in investing activities	1,245
Financing Activities
Cash dividends paid on common stock	(62,795)	(62,666)	(62,605)
Other common stock transactions, net		(857)	(211)
Net cash provided by financing activities	(62,795)	(63,523)	(62,816)
Net change in cash and cash equivalents	172	(607)	(1,101)
Cash and cash equivalents at beginning of year	16,713	17,320	18,421
Cash and cash equivalents at end of year	$ 16,885	$ 16,713	$ 17,320

Parent Company Only Financia143

Parent Company Only Financial Information - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements Captions [Line Items]
Income taxes paid	$ 7,371	$ 24,836	$ 16,321
Interest paid	41,472	24,312	20,733
Trustmark Corp (Parent Company Only) [Member]
Condensed Financial Statements Captions [Line Items]
Income taxes paid	7,400	24,800	16,300
Interest paid	$ 283	$ 600	$ 837