Trustmark (TRMK) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	TRUSTMARK CORP
Entity Central Index Key	36,146
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		67,088,861
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Trading Symbol	TRMK
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Cash and due from banks (noninterest-bearing)	$ 432,471	$ 335,768
Federal funds sold and securities purchased under reverse repurchase agreements	1,000	615
Securities available for sale (at fair value)	1,864,633	2,238,635
Securities held to maturity (fair value: $907,317-2018; $1,046,247-2017)	943,883	1,056,486
Loans held for sale (LHFS)	182,664	180,512
Loans held for investment (LHFI)	8,747,030	8,569,967
Less allowance for loan losses, LHFI	88,874	76,733
Net LHFI	8,658,156	8,493,234
Acquired loans	132,615	261,517
Less allowance for loan losses, acquired loans	1,714	4,079
Net acquired loans	130,901	257,438
Net LHFI and acquired loans	8,789,057	8,750,672
Premises and equipment, net	178,739	179,339
Mortgage servicing rights	101,374	84,269
Goodwill	379,627	379,627
Identifiable intangible assets, net	12,391	16,360
Other real estate	36,475	43,228
Other assets	517,498	532,442
Total Assets	13,439,812	13,797,953
Deposits:
Noninterest-bearing	2,786,539	2,978,074
Interest-bearing	8,170,371	7,599,438
Total deposits	10,956,910	10,577,512
Federal funds purchased and securities sold under repurchase agreements	486,865	469,827
Short-term borrowings	190,023	971,049
Long-term Federal Home Loan Bank (FHLB) advances	896	946
Junior subordinated debt securities	61,856	61,856
Other liabilities	143,658	145,062
Total Liabilities	11,840,208	12,226,252
Shareholders' Equity
Authorized: 250,000,000 shares Issued and outstanding: 67,621,369 shares - 2018; 67,746,094 shares - 2017	14,089	14,115
Capital surplus	362,868	369,124
Retained earnings	1,302,593	1,228,187
Accumulated other comprehensive loss, net of tax	(79,946)	(39,725)
Total Shareholders' Equity	1,599,604	1,571,701
Total Liabilities and Shareholders' Equity	$ 13,439,812	$ 13,797,953

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Securities held to maturity, fair value	$ 907,317	$ 1,046,247
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)	67,621,369	67,746,094
Common stock, outstanding (in shares)	67,621,369	67,746,094

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017
Interest Income
Interest and fees on LHFS & LHFI	$ 102,980	$ 89,112		$ 291,362	$ 253,507
Interest and fees on acquired loans	4,033	6,625		13,932	18,077
Interest on securities:
Taxable	16,186	19,291		50,586	57,865
Tax exempt	518	717		1,748	2,328
Interest on federal funds sold and securities purchased under reverse repurchase agreements	3	14		10	26
Other interest income	1,050	355		3,038	993
Total Interest Income	124,770	116,114		360,676	332,796
Interest Expense
Interest on deposits	14,972	6,381		36,602	15,433
Interest on federal funds purchased and securities sold under repurchase agreements	1,348	1,301		3,260	3,036
Other interest expense	1,467	4,520		6,574	10,821
Total Interest Expense	17,787	12,202		46,436	29,290
Net Interest Income	106,983	103,912		314,240	303,506
Provision for loan losses, LHFI	8,673	3,672		15,801	9,355
Provision for loan losses, acquired loans	(467)	(1,653)		(758)	(5,822)
Net Interest Income After Provision for Loan Losses	98,777	101,893		299,197	299,973
Noninterest Income
Service charges on deposit accounts	11,075	11,223	[1]	32,579	32,810	[1]
Bank card and other fees	7,459	7,150	[1]	21,155	21,020	[1]
Mortgage banking, net	8,647	4,425	[1]	28,958	23,618	[1]
Insurance commissions	10,765	10,398	[1]	30,919	29,355	[1]
Wealth management	7,789	7,530	[1]	22,834	22,617	[1]
Other, net	1,358	3,740	[1]	4,832	11,268	[1]
Security gains (losses), net		14	[1]	0	15	[1]
Total Noninterest Income	47,093	44,480	[1]	141,277	140,703	[1]
Noninterest Expense
Salaries and employee benefits	60,847	57,871		179,297	170,445
Defined benefit plan termination					17,644
Services and fees	16,404	15,133		48,472	45,474
Net occupancy - premises	6,910	6,702		19,962	19,150
Equipment expense	6,200	6,297		18,501	18,457
Other real estate expense, net	1,168	864		1,941	3,006
FDIC assessment expense	1,999	2,816		7,532	8,142
Other expense	11,695	13,403		35,783	44,900
Total Noninterest Expense	105,223	103,086		311,488	327,218
Income Before Income Taxes	40,647	43,287		128,986	113,458
Income taxes	4,394	8,708		16,090	23,596
Net Income	$ 36,253	$ 34,579		$ 112,896	$ 89,862
Earnings Per Share
Basic	$ 0.54	$ 0.51		$ 1.67	$ 1.33
Diluted	0.54	0.51		1.67	1.32
Dividends Per Share	$ 0.23	$ 0.23		$ 0.69	$ 0.69
[1]	Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may not be comparable to current year presentation.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income per consolidated statements of income	$ 36,253	$ 34,579	$ 112,896	$ 89,862
Net unrealized gains (losses) on available for sale securities and transferred securities:
Net unrealized holding gains (losses) arising during the period	(7,246)	(331)	(35,231)	3,912
Less: adjustment for net (gains) losses realized in net income	0	(8)	0	(9)
Change in net unrealized holding loss on securities transferred to held to maturity	730	698	2,182	2,193
Pension and other postretirement benefit plans:
Net change in prior service costs	47	39	140	116
Recognized net loss due to lump sum settlement	31	0	92	0
Change in net actuarial loss	271	219	819	1,187
Recognized net loss due to defined benefit plan termination	0	0	0	10,492
Derivatives:
Change in the accumulated gain (loss) on effective cash flow hedge derivatives	39	33	458	(61)
Less: adjustment for (gain) loss realized in net income	(79)	34	(157)	143
Other comprehensive income (loss), net of tax	(6,207)	684	(31,697)	17,973
Comprehensive income	$ 30,046	$ 35,263	$ 81,199	$ 107,835

Consolidated Condensed Statemen

Consolidated Condensed Statements of Changes in Shareholders' Equity (Unaudited) $ in Thousands	USD ($)
Balance at Dec. 31, 2016	$ 1,520,208
Statement Of Stockholders Equity [Abstract]
Net income per consolidated statements of income	89,862
Other comprehensive income (loss), net of tax	17,973
Common stock dividends paid	(47,099)
Shares withheld to pay taxes, long-term incentive plan	(1,659)
Compensation expense, long-term incentive plan	3,250
Balance at Sep. 30, 2017	1,582,535
Balance at Dec. 31, 2017	1,571,701
Statement Of Stockholders Equity [Abstract]
Net income per consolidated statements of income	112,896
Other comprehensive income (loss), net of tax	(31,697)
Common stock dividends paid	(47,014)
Shares withheld to pay taxes, long-term incentive plan	(1,427)
Repurchase and retirement of common stock	(7,877)
Compensation expense, long-term incentive plan	3,022
Balance at Sep. 30, 2018	$ 1,599,604

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities
Net income per consolidated statements of income	$ 112,896	$ 89,862
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses, net	15,043	3,533
Depreciation and amortization	29,512	28,781
Net amortization of securities	7,197	8,084
Securities (gains) losses, net	0	(15)	[1]
Gains on sales of loans, net	(16,409)	(13,633)
Deferred income tax provision	5,612	4,800
Proceeds from sales of loans held for sale	836,971	885,520
Purchases and originations of loans held for sale	(823,134)	(895,992)
Originations of mortgage servicing rights	(12,248)	(11,630)
Earnings on bank-owned life insurance	(3,994)	(3,753)
Net change in other assets	521	29,599
Net change in other liabilities	14	4,205
Other operating activities, net	(10,268)	6,280
Net cash provided by operating activities	141,713	135,641
Investing Activities
Proceeds from maturities, prepayments and calls of securities held to maturity	114,531	128,515
Proceeds from maturities, prepayments and calls of securities available for sale	334,852	351,817
Proceeds from sales of securities available for sale	0	27,682
Purchases of securities held to maturity	0	(69,989)
Purchases of securities available for sale	(14,040)	(338,532)
Net proceeds from bank-owned life insurance	1,843	3,630
Net change in federal funds sold and securities purchased under reverse repurchase agreements	(385)	4,185
Net change in member bank stock	26,970	739
Net change in loans	(63,796)	(457,292)
Purchases of premises and equipment	(10,870)	(10,963)
Proceeds from sales of premises and equipment	651	7,792
Proceeds from sales of other real estate	16,490	20,301
Purchases of software	(10,701)	(3,492)
Investments in tax credit and other partnerships	(17)	(5,213)
Net cash used in business acquisition	0	(19,775)
Net cash provided by (used in) investing activities	395,528	(360,595)
Financing Activities
Net change in deposits	379,398	9,572
Net change in federal funds purchased and securities sold under repurchase agreements	17,038	5,786
Net change in short-term borrowings	(780,606)	283,820
Payments on long-term FHLB advances	(50)	(49)
Redemption of junior subordinated debt securities	0	(3,000)
Common stock dividends	(47,014)	(47,099)
Repurchase and retirement of common stock	(7,877)	0
Shares withheld to pay taxes, long-term incentive plan	(1,427)	(1,659)
Net cash provided by (used in) financing activities	(440,538)	247,371
Net change in cash and cash equivalents	96,703	22,417
Cash and cash equivalents at beginning of period	335,768	327,706
Cash and cash equivalents at end of period	$ 432,471	$ 350,123
[1]	Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may not be comparable to current year presentation.

Business, Basis of Financial St

Business, Basis of Financial Statement Presentation and Principles of Consolidation	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Business, Basis of Financial Statement Presentation and Principles of Consolidation	Note 1 – Business, Basis of Financial Statement Presentation and Principles of Consolidation 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 at September 30, 2018 in Alabama, Florida, Mississippi, Tennessee and Texas. 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. Certain reclassifications have been made to prior period amounts to conform to the current period presentation. The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the consolidated financial statements, and notes thereto, included in Trustmark’s 2017 Annual Report on Form 10-K. Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period. In the opinion of Management, all adjustments (consisting of normal recurring accruals) considered necessary for the fair presentation of these consolidated financial statements have been included. 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. Subsequent Events On October 10, 2018, Hurricane Michael struck the Florida Panhandle causing significant damages. As of September 30, 2018, Trustmark had 1,787 loans with a balance of $239.7 million and exposure of $282.1 million in the Federal Emergency Management Agency (FEMA) designated disaster areas which includes 12 counties in Florida and 20 counties in Georgia. Immediately following the storm, Trustmark initiated a process to identify all customers in the FEMA disaster areas. Efforts are now ongoing to contact those borrowers to offer assistance as well as to establish reasonable estimates of uninsured damage and to adequately assess potential risk to Trustmark. Management continues to evaluate the impact of Hurricane Michael and is unable to provide a reasonable estimate of the financial impact on Trustmark’s consolidated financial statements at this time.

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2018
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 $24.8 million. The merger with Reliance was consistent with Trustmark’s strategic plan to selectively expand the Trustmark franchise and enhance the Trustmark franchise in north Alabama. This merger was accounted for in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 805, “Business Combinations.” Accordingly, the assets and liabilities, both tangible and intangible, were recorded at their estimated fair values as of the merger date. The statement of assets purchased and liabilities assumed in the Reliance merger is presented below at their estimated fair values as of the merger date of April 7, 2017 ($ 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 identifiable 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, “Loans and Debt Securities Acquired with Deteriorated Credit Quality.” See Note 5 – 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 inputs within Level 2 of the fair value hierarchy 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 17 – Fair Value for more information on Trustmark’s classification of financial instruments based on valuation inputs within the fair value hierarchy.

Securities Available for Sale a

Securities Available for Sale and Held to Maturity	9 Months Ended
	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Securities Available for Sale and Held to Maturity	Note 3 – 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 September 30, 2018 and December 31, 2017 ($ in thousands): Securities Available for Sale Securities Held to Maturity September 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. Government agency obligations $ 33,511 $ 126 $ (1,266 ) $ 32,371 $ 3,725 $ 26 $ — $ 3,751 Obligations of states and political subdivisions 57,127 201 (64 ) 57,264 42,623 173 (156 ) 42,640 Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 68,844 118 (3,115 ) 65,847 12,316 33 (389 ) 11,960 Issued by FNMA and FHLMC 713,673 125 (29,324 ) 684,474 119,040 3 (4,652 ) 114,391 Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 872,699 86 (32,712 ) 840,073 600,635 — (27,473 ) 573,162 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 189,248 154 (4,798 ) 184,604 165,544 41 (4,172 ) 161,413 Total $ 1,935,102 $ 810 $ (71,279 ) $ 1,864,633 $ 943,883 $ 276 $ (36,842 ) $ 907,317 December 31, 2017 U.S. Government agency obligations $ 45,763 $ 322 $ (800 ) $ 45,285 $ 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 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 September 30, 2018, the net unamortized, unrealized loss on the transferred securities included in accumulated other comprehensive loss in the accompanying balance sheet totaled approximately $16.6 million ($12.4 million, net of tax). Temporarily Impaired Securities The tables below include securities with gross unrealized losses segregated by length of impairment at September 30, 2018 and December 31, 2017 ($ in thousands): Less than 12 Months 12 Months or More Total September 30, 2018 Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses U.S. Government agency obligations $ — $ — $ 26,421 $ (1,266 ) $ 26,421 $ (1,266 ) Obligations of states and political subdivisions 29,786 (179 ) 3,791 (41 ) 33,577 (220 ) Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 24,843 (677 ) 49,000 (2,827 ) 73,843 (3,504 ) Issued by FNMA and FHLMC 134,720 (3,928 ) 655,161 (30,048 ) 789,881 (33,976 ) Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 531,793 (14,120 ) 865,762 (46,065 ) 1,397,555 (60,185 ) Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 168,750 (3,334 ) 158,538 (5,636 ) 327,288 (8,970 ) Total $ 889,892 $ (22,238 ) $ 1,758,673 $ (85,883 ) $ 2,648,565 $ (108,121 ) December 31, 2017 U.S. Government agency obligations $ 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 ) 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 September 30, 2018. There were no other-than-temporary impairments for the nine months ended September 30, 2018 and 2017. Security Gains and Losses Gross realized gains or losses as a result of calls and dispositions of securities, as well as any associated proceeds, were as follows for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, Available for Sale 2018 2017 2018 2017 Proceeds from calls and sales of securities $ — $ 1,273 $ — $ 27,682 Gross realized gains — 15 — 16 Gross realized (losses) — (1 ) — (1 ) Realized gains and losses are determined using the specific identification method and are included in noninterest income as security gains (losses), net. Securities Pledged Securities with a carrying value of $2.092 billion and $1.834 billion at September 30, 2018 and December 31, 2017, respectively, were pledged to collateralize public deposits and securities sold under repurchase agreements and for other purposes as permitted by law. At both September 30, 2018 and December 31, 2017, none of these securities were pledged under the Federal Reserve Discount Window program to provide additional contingency funding capacity. Contractual Maturities The amortized cost and estimated fair value of securities available for sale and held to maturity at September 30, 2018, by contractual maturity, are shown below ($ 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 Available for Sale Securities Held to Maturity Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Due in one year or less $ 25,525 $ 25,554 $ 170 $ 170 Due after one year through five years 37,426 37,661 41,912 41,934 Due after five years through ten years 3,124 3,054 4,266 4,287 Due after ten years 24,563 23,366 — — 90,638 89,635 46,348 46,391 Mortgage-backed securities 1,844,464 1,774,998 897,535 860,926 Total $ 1,935,102 $ 1,864,633 $ 943,883 $ 907,317

Loans Held for Investment (LHFI

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI	9 Months Ended
	Sep. 30, 2018
Accounts Notes Loans And Financing Receivable Gross Allowance And Net [Abstract]
Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI	Note 4 – Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI At September 30, 2018 and December 31, 2017, LHFI consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Loans secured by real estate: Construction, land development and other land $ 1,031,491 $ 987,624 Secured by 1-4 family residential properties 1,801,029 1,675,311 Secured by nonfarm, nonresidential properties 2,294,289 2,193,823 Other real estate secured 453,687 517,956 Commercial and industrial loans 1,565,922 1,570,345 Consumer loans 182,709 171,918 State and other political subdivision loans 929,178 952,483 Other loans 488,725 500,507 LHFI 8,747,030 8,569,967 Allowance for loan losses, LHFI (88,874 ) (76,733 ) Net LHFI $ 8,658,156 $ 8,493,234 Loan Concentrations Trustmark does not have any loan concentrations other than those reflected in the preceding table, which exceed 10% of total LHFI. At September 30, 2018, 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. Nonaccrual and Past Due LHFI At September 30, 2018 and December 31, 2017, the carrying amounts of nonaccrual LHFI were $67.8 million and $67.6 million, respectively. Included in these amounts were $33.6 million and $23.2 million, respectively, of nonaccrual LHFI classified as troubled debt restructurings (TDRs). No material interest income was recognized in the income statement on nonaccrual LHFI for each of the periods ended September 30, 2018 and 2017. The following tables provide an aging analysis of past due and nonaccrual LHFI by loan type at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Past Due 30-59 Days 60-89 Days 90 Days or (1) Total Nonaccrual Current Loans Total LHFI Loans secured by real estate: Construction, land development and other land $ 203 $ 5 $ — $ 208 $ 2,262 $ 1,029,021 $ 1,031,491 Secured by 1-4 family residential properties 5,626 1,304 447 7,377 15,164 1,778,488 1,801,029 Secured by nonfarm, nonresidential properties 256 280 — 536 5,389 2,288,364 2,294,289 Other real estate secured 5 — — 5 742 452,940 453,687 Commercial and industrial loans 1,727 9 21 1,757 33,870 1,530,295 1,565,922 Consumer loans 1,480 241 258 1,979 228 180,502 182,709 State and other political subdivision loans — — — — 8,762 920,416 929,178 Other loans 419 33 — 452 1,419 486,854 488,725 Total $ 9,716 $ 1,872 $ 726 $ 12,314 $ 67,836 $ 8,666,880 $ 8,747,030 (1) Past due 90 days or more but still accruing interest. December 31, 2017 Past Due 30-59 Days 60-89 Days 90 Days or (1) Total Nonaccrual Current Loans Total LHFI 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. Impaired LHFI Trustmark’s individually evaluated impaired LHFI include all commercial nonaccrual relationships of $500 thousand or more, which are specifically reviewed for impairment and deemed impaired, and all LHFI classified as TDRs in accordance with FASB ASC Topic 310-10-50-20 “Impaired Loans”, and are primarily collateral dependent loans. Fair value estimates for collateral dependent loans are derived from appraised values based on the current market value or as is value of the collateral, normally from recently received and reviewed appraisals. Current appraisals are ordered on an annual basis based on the inspection date or more often if market conditions necessitate. Appraisals are obtained from state-certified appraisers and are based on certain assumptions, which may include construction or development status and the highest and best use of the property. These appraisals are reviewed by Trustmark’s Appraisal Review Department to ensure they are acceptable, and values are adjusted down for costs associated with asset disposal. Once this estimated net realizable value has been determined, the value used in the impairment assessment is updated. At the time a LHFI that has been individually evaluated for impairment is deemed to be impaired, the full difference between book value and the most likely estimate of the collateral’s net realizable value is charged off. As subsequent events dictate and estimated net realizable values decline, required reserves may be established or further adjustments recorded. No material interest income was recognized in the income statement on impaired LHFI for each of the periods ended September 30, 2018 and 2017. At September 30, 2018 and December 31, 2017, individually evaluated impaired LHFI consisted of the following ($ in thousands): September 30, 2018 LHFI Unpaid Principal Balance With No Related Allowance Recorded With an Allowance Recorded Total Carrying Amount Related Allowance Average Recorded Investment Loans secured by real estate: Construction, land development and other land $ 1,801 $ 1,546 $ 26 $ 1,572 $ — $ 1,747 Secured by 1-4 family residential properties 4,771 126 3,614 3,740 43 4,217 Secured by nonfarm, nonresidential properties 3,585 3,010 360 3,370 78 5,845 Other real estate secured — — — — — — Commercial and industrial loans 39,845 14,657 19,045 33,702 13,869 28,218 Consumer loans 3 — 3 3 — 6 State and other political subdivision loans 8,765 4,079 4,683 8,762 683 4,381 Other loans 1,432 230 1,076 1,306 1,076 816 Total $ 60,202 $ 23,648 $ 28,807 $ 52,455 $ 15,749 $ 45,230 December 31, 2017 LHFI Unpaid Principal Balance With No Related Allowance Recorded With an Allowance Recorded Total Carrying Amount Related Allowance Average Recorded 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 Troubled Debt Restructurings 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 collectability 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. All loans whose terms have been modified in a TDR 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. At September 30, 2018 and December 31, 2017, Trustmark held $203 thousand and $366 thousand, respectively, of foreclosed residential real estate as a result of foreclosure or in substance repossession of consumer mortgage LHFI classified as TDRs. At September 30, 2018, Trustmark had $55 thousand of consumer mortgage LHFI classified as TDRs in the process of formal foreclosure proceedings compared to none at December 31, 2017. 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. At September 30, 2018 and 2017, LHFI classified as TDRs totaled $36.0 million and $24.4 million, respectively, and were primarily comprised of credits with interest-only payments for an extended period of time which totaled $24.7 million and $21.1 million, respectively. The remaining TDRs at September 30, 2018 and 2017 resulted from bankruptcies or from payment or maturity extensions. Trustmark had $7.7 million of unused commitments on TDRs at September 30, 2018 compared to no material unused commitments on TDRs at September 30, 2017. For TDRs, Trustmark had a related loan loss allowance of $14.3 million and $393 thousand at September 30, 2018 and 2017, respectively. 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 $4.7 million for the nine months ended September 30, 2018 compared to $126 thousand for the nine months ended September 30, 2017. The following tables illustrate the impact of modifications classified as TDRs as well as those TDRs modified within the last 12 months for which there was a payment default during the period for the periods presented ($ in thousands): Three Months Ended September 30, 2018 2017 Troubled Debt Restructurings Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by 1-4 family residential properties 3 $ 121 $ 121 1 $ 112 $ 113 Loans secured by nonfarm, nonresidential properties — — — 1 426 426 Commercial and industrial loans 9 11,153 10,062 6 12,500 12,500 Total 12 $ 11,274 $ 10,183 8 $ 13,038 $ 13,039 Nine Months Ended September 30, 2018 2017 Troubled Debt Restructurings Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Construction, land development and other land loans 1 $ 22 $ 22 1 $ 341 $ 325 Loans secured by 1-4 family residential properties 19 1,873 1,432 17 1,280 1,290 Loans secured by nonfarm, nonresidential properties — — — 1 426 426 Commercial and industrial loans 15 22,899 21,791 7 12,744 12,744 Consumer loans 3 4 4 — — — Total 38 $ 24,798 $ 23,249 26 $ 14,791 $ 14,785 Nine Months Ended September 30, 2018 2017 TDRs that Subsequently Defaulted Number of Contracts Recorded Investment Number of Contracts Recorded Investment Construction, land development and other land loans 1 $ 21 — $ — Loans secured by 1-4 family residential properties 6 321 4 64 Commercial and industrial loans 6 13,985 2 — Total 13 $ 14,327 6 $ 64 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 September 30, 2018 and 2017 ($ in thousands): September 30, 2018 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 26 $ 26 Secured by 1-4 family residential properties 563 3,052 3,615 Secured by nonfarm, nonresidential properties — 360 360 Commercial and industrial loans 1,783 29,636 31,419 Consumer loans — 3 3 Other loans — 540 540 Total TDRs $ 2,346 $ 33,617 $ 35,963 September 30, 2017 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 272 $ 272 Secured by 1-4 family residential properties 14 3,077 3,091 Secured by nonfarm, nonresidential properties 426 436 862 Commercial and industrial loans — 20,153 20,153 Consumer loans — 1 1 Total TDRs $ 440 $ 23,939 $ 24,379 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, nonaccrual 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 $100 thousand or more. In addition, a semi-annual review of significant development, commercial construction, multi-family and non-owner occupied projects is performed. The review assesses each particular project with respect to location, project valuations, progress of completion, leasing status, current financial information, rents, operating expenses, cash flow, adherence to budget and projections and other information as applicable. Summary results are reviewed by Senior and Regional Credit Officers in addition to the Chief Credit Officer with a determination as to the appropriateness of existing risk ratings and accrual status. Consumer Credits Consumer LHFI that do not meet a minimum custom credit score are reviewed quarterly by Management. The Retail Credit Review Committee reviews the volume and percentage of approvals that did not meet the minimum passing custom score by region, individual location, and officer to ensure that Trustmark continues to originate quality loans. Trustmark monitors the levels and severity of past due consumer LHFI on a daily basis through its collection activities. A detailed assessment of consumer LHFI delinquencies is performed monthly at both a product and market level by delivery channel, which incorporates the perceived level of risk at time of underwriting. The tables below present LHFI by loan type and credit quality indicator at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Commercial LHFI Pass - Categories 1-6 Special Mention - Category 7 Substandard - Category 8 Doubtful - Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 961,316 $ 78 $ 4,512 $ 208 $ 966,114 Secured by 1-4 family residential properties 125,998 175 2,960 60 129,193 Secured by nonfarm, nonresidential properties 2,259,388 3,052 31,302 484 2,294,226 Other real estate secured 452,095 454 515 — 453,064 Commercial and industrial loans 1,490,431 9,721 63,936 1,834 1,565,922 Consumer loans — — — — — State and other political subdivision loans 913,286 5,250 10,642 — 929,178 Other loans 458,118 15,597 10,469 77 484,261 Total $ 6,660,632 $ 34,327 $ 124,336 $ 2,663 $ 6,821,958 Consumer LHFI Current Past Due 30-89 Days Past Due 90 Days or More Nonaccrual Subtotal Total LHFI Loans secured by real estate: Construction, land development and other land $ 65,028 $ 3 $ — $ 346 $ 65,377 $ 1,031,491 Secured by 1-4 family residential properties 1,651,019 6,566 447 13,804 1,671,836 1,801,029 Secured by nonfarm, nonresidential properties 63 — — — 63 2,294,289 Other real estate secured 623 — — — 623 453,687 Commercial and industrial loans — — — — — 1,565,922 Consumer loans 180,503 1,721 258 227 182,709 182,709 State and other political subdivision loans — — — — — 929,178 Other loans 4,464 — — — 4,464 488,725 Total $ 1,901,700 $ 8,290 $ 705 $ 14,377 $ 1,925,072 $ 8,747,030 December 31, 2017 Commercial LHFI Pass - Categories 1-6 Special Mention - Category 7 Substandard Category 8 Doubtful - 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 Current Past Due 30-89 Days Past Due 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 Past Due Loans Held for Sale (LHFS) LHFS past due 90 days or more totaled $34.1 million and $35.5 million at September 30, 2018 and December 31, 2017, respectively. LHFS past due 90 days or more are serviced loans eligible for repurchase, which are fully guaranteed by the Government National Mortgage Association (GNMA). 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. 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 loans held for sale, regardless of whether Trustmark intends to exercise the buy-back option. These loans are reported as held for sale with the offsetting liability being reported as short-term borrowings. Trustmark did not exercise its buy-back option on any delinquent loans serviced for GNMA during the first nine months of 2018 or 2017. 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. 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. The allowance for loan loss methodology segregates the consumer LHFI portfolio into homogeneous pools of loans that contain similar structure, repayment, collateral and risk profiles. These homogeneous pools of loans are shown below: • Residential Mortgage • Direct Consumer • Junior Lien on 1-4 Family Residential Properties • Credit Cards • Overdrafts The historical loss experience for these pools is determined by calculating a 12-quarter rolling average of net charge-offs, which is applied to each pool to establish the quantitative aspect of the methodology. Where, in Management’s estimation, the calculated loss experience does not fully cover the anticipated loss for a pool, an estimate is also applied to each pool to establish the qualitative aspect of the methodology, which represents the perceived risks across the loan portfolio at the current point in time. This qualitative methodology utilizes five separate factors made up of unique components that when weighted and combined produce an estimated level of reserve for each of the loan pools. The five qualitative factors include the following: • Economic indicators • Performance trends • Management experience • Credit concentrations • Loan policy exceptions The risk measure for each factor is converted to a scale ranging from 0 (No risk) to 100 (High Risk) to ensure that the combination of such factors is proportional. The determination of the risk measurement for each qualitative factor is done for all markets combined. The resulting estimated reserve factor is then applied to each pool. The resulting ratings from the individual factors are weighted and summed to establish the weighted-average qualitative factor of a specific loan portfolio. This weighted-average qualitative factor is then applied over the five loan pools. Trustmark’s loan policy dictates the guidelines to be followed in determining when a loan is charged off. Commercial purpose loans are charged off when a determination is made that the loan is uncollectible and continuance as a bankable asset is not warranted or an impairment evaluation indicates that a value adjustment is necessary. Consumer loans secured by 1-4 family residential real estate are generally charged off or written down when the credit becomes severely delinquent and the balance exceeds the fair value of the property less costs to sell. Non-real estate consumer purpose loans, both secured and unsecured, are generally charged off in full during the month in which the loan becomes 120 days past due. Credit card loans are generally charged off in full when the loan becomes 180 days past due. 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 September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Individually Collectively Total Loans secured by real estate: Construction, land development and other land $ — $ 8,414 $ 8,414 Secured by 1-4 family residential properties 43 9,265 9,308 Secured by nonfarm, nonresidential properties 78 24,781 24,859 Other real estate secur

Acquired Loans

Acquired Loans	9 Months Ended
	Sep. 30, 2018
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities [Abstract]
Acquired Loans	Note 5 – Acquired Loans Trustmark’s loss-share agreement with the FDIC covering the acquired covered loans secured by 1-4 family residential properties will expire in 2021. 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 $7.9 million of the loans acquired in the Reliance merger exhibited evidence of significant credit deterioration since origination and for which it was probable at acquisition that Trustmark would not be able to collect all contractually required payments. These loans were accounted for as acquired impaired loans under FASB ASC Topic 310-30. At September 30, 2018 and December 31, 2017, acquired loans consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Loans secured by real estate: Construction, land development and other land $ 6,657 $ 23,586 Secured by 1-4 family residential properties 25,274 61,751 Secured by nonfarm, nonresidential properties 66,865 114,694 Other real estate secured 8,507 16,746 Commercial and industrial loans 16,610 31,506 Consumer loans 1,514 2,600 Other loans 7,188 10,634 Acquired loans 132,615 261,517 Allowance for loan losses, acquired loans (1,714 ) (4,079 ) Net acquired loans $ 130,901 $ 257,438 The following table presents changes in the net carrying value of the acquired loans for the periods presented ($ in thousands): Acquired Impaired Acquired Not ASC 310-30 (1) Carrying value, net at January 1, 2017 $ 218,107 $ 42,743 Transfers (2) — (36,719 ) Additions (3) 7,899 109,548 Accretion to interest income 14,924 1,578 Payments received, net (68,317 ) (39,208 ) Other (4) (361 ) (74 ) Change in allowance for loan losses, acquired loans 7,318 — Carrying value, net at December 31, 2017 179,570 77,868 Transfers (5)(2) (26,497 ) (43,922 ) Accretion to interest income 7,870 782 Payments received, net (50,940 ) (16,096 ) Other (4) (173 ) 74 Change in allowance for loan losses, acquired loans 2,365 — Carrying value, net at September 30, 2018 $ 112,195 $ 18,706 (1) “ (2) “Acquired Not ASC 310-30” (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. (5) During the second quarter of 2018, Trustmark transferred the remaining loans acquired in the Bay Bank merger on March 16, 2012 from acquired impaired loans to LHFI. During the third quarter of 2018, Trustmark transferred the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017 from acquired impaired loans to LHFI. 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): Nine Months Ended September 30, 2018 2017 Accretable yield at beginning of period $ (31,426 ) $ (38,918 ) Accretion to interest income 7,870 11,021 Additions due to acquisitions (1) — (784 ) Disposals, net 3,452 1,759 Transfers (2) 5,874 — Reclassification from nonaccretable difference (3) (4,204 ) (7,204 ) Accretable yield at end of period $ (18,434 ) $ (34,126 ) (1) Accretable yield on loans acquired from Reliance on April 7, 2017. (2) During the second quarter of 2018, Trustmark transferred the remaining loans acquired in the Bay Bank merger on March 16, 2012 from acquired impaired loans to LHFI. During the third quarter of 2018, Trustmark transferred the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017 from acquired impaired loans to LHFI. (3) 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 loans for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Balance at beginning of period $ 3,046 $ 7,423 $ 4,079 $ 11,397 Transfers (1) (772 ) — (1,554 ) — Net (charge-offs) recoveries (93 ) (2 ) (53 ) 193 Provision for loan losses, acquired loans (467 ) (1,653 ) (758 ) (5,822 ) Balance at end of period $ 1,714 $ 5,768 $ 1,714 $ 5,768 (1) The allowance for loan losses balance related to the remaining loans acquired in the Bay Bank merger, which were transferred from acquired impaired loans to LHFI during the second quarter of 2018, and the remaining loans acquired in the Heritage acquisition and the Reliance merger, which were transferred from acquired impaired loans to LHFI during the third quarter of 2018. As discussed in Note 4 - Loans Held for Investment (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 September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Commercial Loans Pass - Categories 1-6 Special Mention - Category 7 Substandard - Category 8 Doubtful - Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 5,541 $ 25 $ 296 $ 68 $ 5,930 Secured by 1-4 family residential properties 5,594 47 645 — 6,286 Secured by nonfarm, nonresidential properties 51,123 — 15,223 519 66,865 Other real estate secured 7,906 — 177 424 8,507 Commercial and industrial loans 7,366 — 6,832 2,412 16,610 Consumer loans — — — — — Other loans 4,536 — 2,652 — 7,188 Total acquired loans $ 82,066 $ 72 $ 25,825 $ 3,423 $ 111,386 Consumer Loans Current Past Due 30-89 Days Past Due 90 Days or More Nonaccrual (1) Subtotal Total Acquired Loans Loans secured by real estate: Construction, land development and other land $ 652 $ 75 $ — $ — $ 727 $ 6,657 Secured by 1-4 family residential properties 17,676 1,044 268 — 18,988 25,274 Secured by nonfarm, nonresidential properties — — — — — 66,865 Other real estate secured — — — — — 8,507 Commercial and industrial loans — — — — — 16,610 Consumer loans 1,473 41 — — 1,514 1,514 Other loans — — — — — 7,188 Total acquired loans $ 19,801 $ 1,160 $ 268 $ — $ 21,229 $ 132,615 (1) Acquired loans not accounted for under FASB ASC Topic 310-30. December 31, 2017 Commercial Loans Pass - Categories 1-6 Special Mention - Category 7 Substandard - Category 8 Doubtful - 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 Current Past Due 30-89 Days Past Due 90 Days or More Nonaccrual (1) Subtotal Total 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. The following tables provide an aging analysis of contractually past due and nonaccrual acquired loans by loan type at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 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 $ 103 $ — $ 25 $ 128 $ — $ 6,529 $ 6,657 Secured by 1-4 family residential properties 703 341 288 1,332 — 23,942 25,274 Secured by nonfarm, nonresidential properties 297 — 1,475 1,772 — 65,093 66,865 Other real estate secured 15 — — 15 — 8,492 8,507 Commercial and industrial loans — — 607 607 — 16,003 16,610 Consumer loans 39 2 — 41 — 1,473 1,514 Other loans — — — — — 7,188 7,188 Total acquired loans $ 1,157 $ 343 $ 2,395 $ 3,895 $ — $ 128,720 $ 132,615 (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, 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.

Mortgage Banking

Mortgage Banking	9 Months Ended
	Sep. 30, 2018
Mortgage Banking [Abstract]
Mortgage Banking	Note 6 – Mortgage Banking Mortgage Servicing Rights The activity in the mortgage servicing rights (MSR) is detailed in the table below for the periods presented ($ in thousands): Nine Months Ended September 30, 2018 2017 Balance at beginning of period $ 84,269 $ 80,239 Origination of servicing assets 12,248 11,630 Change in fair value: Due to market changes 13,879 (2,218 ) Due to run-off (9,022 ) (8,174 ) Balance at end of period $ 101,374 $ 81,477 Trustmark determines the fair value of the MSR using a valuation model administered by a third party that calculates the present value of estimated future net servicing income. 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 September 30, 2018, the fair value of the MSR included an assumed average prepayment speed of 6.86 CPR and an average discount rate of 10.04% compared to an assumed average prepayment speed of 9.25 CPR and an average discount rate of 10.28% at September 30, 2017. Mortgage Loans Serviced/Sold During the first nine months of 2018 and 2017, Trustmark sold $820.6 million and $871.9 million, respectively, of residential mortgage loans. Pretax gains on these sales were recorded to noninterest income in mortgage banking, net and totaled $16.4 million for the first nine months of 2018 compared to $13.6 million for the first nine months of 2017. The table below details the mortgage loans sold and serviced for others at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 December 31, 2017 Federal National Mortgage Association $ 4,174,961 $ 4,128,614 Government National Mortgage Association 2,492,009 2,421,456 Federal Home Loan Mortgage Corporation 69,617 47,071 Other 22,804 26,864 Total mortgage loans sold and serviced for others $ 6,759,391 $ 6,624,005 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 are 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): Nine Months Ended September 30, 2018 2017 Balance at beginning of period $ 1,000 $ 1,130 Provision for putback expenses — 164 Other (1) — 706 Balance at end of period $ 1,000 $ 2,000 (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.

Other Real Estate

Other Real Estate	9 Months Ended
	Sep. 30, 2018
Other Real Estate And Foreclosed Assets [Abstract]
Other Real Estate	Note 7 – Other Real Estate At September 30, 2018, 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 (losses), net on other real estate were as follows ($ in thousands): Nine Months Ended September 30, 2018 2017 Balance at beginning of period $ 43,228 $ 62,051 Additions (1) 10,368 7,481 Disposals (15,264 ) (18,583 ) Write-downs (1,857 ) (2,593 ) Balance at end of period $ 36,475 $ 48,356 Gains (losses), net on the sale of other real estate included in other real estate expense $ 1,226 $ 1,722 (1) Includes $475 thousand of other real estate acquired in the Reliance merger on April 7, 2017. At September 30, 2018 and December 31, 2017, other real estate by type of property consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Construction, land development and other land properties $ 18,976 $ 27,491 1-4 family residential properties 5,266 5,081 Nonfarm, nonresidential properties 12,050 10,468 Other real estate properties 183 188 Total other real estate $ 36,475 $ 43,228 At September 30, 2018 and December 31, 2017, other real estate by geographic location consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Alabama $ 7,526 $ 11,714 Florida 8,931 13,937 Mississippi (1) 18,191 14,260 Tennessee (2) 1,083 2,535 Texas 744 782 Total other real estate $ 36,475 $ 43,228 (1) Mississippi includes Central and Southern Mississippi Regions (2) Tennessee includes Memphis, Tennessee and Northern Mississippi Regions

Deposits

Deposits	9 Months Ended
	Sep. 30, 2018
Deposits [Abstract]
Deposits	Note 8 – Deposits At September 30, 2018 and December 31, 2017, deposits consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Noninterest-bearing demand $ 2,786,539 $ 2,978,074 Interest-bearing demand 2,739,245 2,432,814 Savings 3,538,125 3,408,183 Time 1,893,001 1,758,441 Total $ 10,956,910 $ 10,577,512

Securities Sold Under Repurchas

Securities Sold Under Repurchase Agreements	9 Months Ended
	Sep. 30, 2018
Securities Sold Under Agreements To Repurchase [Abstract]
Securities Sold Under Repurchase Agreements	Note 9 – 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 were secured by securities with a carrying amount of $167.1 million and $200.9 million at September 30, 2018 and December 31, 2017, respectively. Trustmark’s repurchase agreements are transacted under master repurchase agreements that give Trustmark, in the event of default by the counterparty, the right of offset with the same counterparty. As of September 30, 2018, all repurchase agreements were short-term and consisted primarily of sweep repurchase arrangements, under which excess deposits are “swept” into overnight repurchase agreements with Trustmark. The following table presents the securities sold under repurchase agreements by collateral pledged at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 December 31, 2017 Mortgage-backed securities Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA $ 41,650 $ 68,246 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 48,861 50,448 Total securities sold under repurchase agreements $ 90,511 $ 118,694

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2018
Revenue From Contract With Customer [Abstract]
Revenue from Contracts with Customers	Note 10 – Revenue from Contracts with Customers Effective January 1, 2018, Trustmark accounts for revenue from contracts with customers in accordance with FASB ASC Topic 606, “Revenue from Contracts with Customers,” which provides that revenue be recognized in a manner that depicts the transfer of goods or services to a customer in an amount that reflects the consideration Trustmark expects to be entitled to in exchange for those goods or services. Revenue from contracts with customers is recognized either over time in a manner that depicts Trustmark’s performance, or at a point in time when control of the goods or services are transferred to the customer. Trustmark’s noninterest income, excluding all of mortgage banking, net and securities gains (losses), net and portions of bank card and other fees and other income, are considered within the scope of FASB ASC Topic 606. Gains or losses on the sale of other real estate, which are included in Trustmark’s noninterest expense as other real estate expense, are also within the scope of FASB ASC Topic 606. General Banking Division Service Charges on Deposit Accounts In general, deposit accounts represent contracts with customers with no fixed duration and can be terminated or modified by either party at any time without compensation to the other party. According to FASB ASC Topic 606, a contract that can be terminated by either party without compensation does not exist for periods beyond the then-current period. Therefore, deposit contracts are considered to renew day-to-day if not minute-to-minute. Deposit contracts have a single continuous or stand-ready service obligation whereby Trustmark makes customer funds available for use by the customer as and when the customer chooses as well as other services such as statement rendering and online banking. The specific services provided vary based on the type of deposit account. These services are not individually distinct, but are distinct as a group, and therefore, constitute a single performance obligation which is satisfied over time and qualifies as a series of distinct service periods. Trustmark receives a fixed service charge amount as consideration monthly for services rendered. The service charge amount varies based on the type of deposit account. Some of the service charge revenue is subject to refund provisions, which is variable consideration under the guidelines of FASB ASC Topic 606. Trustmark has elected the ‘as-invoiced’ practical expedient permitted under FASB ASC Topic 606 for recognition of service charge revenue. Therefore, revenue is recognized at the time and in the amount the customer is charged. The service charge revenue is presented net of refunded amounts on Trustmark’s consolidated statements of income. Services related to non-sufficient funds, overdrafts, excess account activity, stop payments, dormant accounts, etc. are considered optional purchases for a deposit contract because there is no performance obligation for Trustmark until the service is requested by the customer or the occurrence of a triggering event. Fees for these services are fixed amounts and are charged to the customer when the service is performed. Revenue is recognized at the time the customer is charged. Bank Card and Other Fees Revenue from contracts with customers in bank card and other fees includes income related to interchange fees and various other contracts which primarily consists of contracts with a single performance obligation that is satisfied at a point in time. Trustmark receives a fixed consideration amount once the performance obligation is completed for these contracts. Trustmark reports revenue from these contracts net of amounts refunded or due to a third party. Interchange Fees As both a debit and credit card issuer, Trustmark receives an interchange fee for every card transaction completed by its customers with a merchant. Trustmark receives two types of interchange fees: point-of-sale transactions in which the customer must enter the PIN associated with the card to complete the transaction (a debit card transaction), and signature transactions in which the signature of the customer is required to complete the transaction (a credit card transaction). Trustmark, as the card issuing or settlement bank, has a contract (implied based on customary business practices) with the payment network in which Trustmark has a single continuous service obligation to make funds available for settlement of the card transaction. Trustmark’s service obligation is satisfied over time and qualifies as a series of distinct service periods. Trustmark receives interchange fees as consideration for services rendered in the amount established by the respective payment network. The interchange fees are established by the payment network based on the type of transaction and is posted on their website. Trustmark receives and records interchange fee revenue from the payment networks daily net of all fees and amounts due to the payment network. Other Income Revenue from contracts with customers in other income includes income related to cash management services and other contracts with a single performance obligation that is satisfied at a point in time. Trustmark receives a fixed consideration amount once the performance obligation is completed for these contracts. Trustmark reports revenue from these contracts net of amounts refunded or due to a third party. Cash Management Services Trustmark provides cash management services through the delivery of various products and services offered to its business and municipal customers including various departments of state, city and local governments, universities and other non-profit entities. Similar to the deposit account contracts, the cash management contracts primarily represent contracts with customers with no fixed duration and can be terminated or modified by either party at any time without compensation to the other party. Therefore, cash management contracts are generally considered to renew day-to-day if not minute-to-minute. Cash management contracts have a single continuous or stand-ready service obligation whereby Trustmark makes a specific service or group of services available for use by the customer as and when the customer chooses. The specific services provided vary based on the type of account or product. These services are not individually distinct, but are distinct as a group, and therefore, constitute a single performance obligation which is satisfied over time and qualifies as a series of distinct service periods. Trustmark receives a set service charge or maintenance fee amount as consideration monthly for services rendered. However, some of the fees are based on the number of transactions that occur (i.e. flat fee for a set number of transactions per month then an additional charge for each transaction after that) or the average daily account balance maintained by the customer during the month and a small amount of the cash management fee revenue is subject to refund provisions. These fees represent variable consideration under the guidelines of FASB ASC Topic 606. Trustmark has elected the ‘as-invoiced’ practical expedient permitted under FASB ASC Topic 606 for recognition of cash management fee revenue. The cash management revenue is presented net of any refunded amounts on Trustmark’s consolidated statements of income. Trustmark’s merchant services provider contracts directly with Trustmark business customers and provides Trustmark’s merchant customers card processing equipment and transaction processing services. Trustmark’s contract with the merchant services provider has a single-continuous service obligation to provide customer referrals for potential new accounts which is satisfied over time and qualifies as a series of distinct service periods. Trustmark receives a flat fee for each new account established and a percentage of the residual income related to transactions processed for Trustmark’s merchant customers each month as provided in the contract. Under the guidelines of FASB ASC Topic 606, the fee received for each new account and the profit sharing represent variable consideration. Revenue from merchant card services contracts is recognized monthly using a time-elapsed measure of progress. Trustmark has elected the ‘as-invoiced’ practical expedient permitted under FASB ASC Topic 606 for recognition of the merchant card services revenue. Other Real Estate Trustmark records a gain or loss from the sale of other real estate when control of the property transfers to the buyer. Trustmark records the gain or loss from the sale of other real estate in noninterest expense as other real estate expense. Other real estate sales for the three and nine months ended September 30, 2018 resulted in net gains of $224 thousand and $1.2 million, respectively, compared to $200 thousand and $1.7 million for the three and nine months ended September 30, 2017, respectively. In general, purchases of Trustmark’s other real estate property are not financed by Trustmark. Financing the purchase of other real estate is evaluated based upon the same lending policies and procedures as all other types of loans. Under FASB ASC Topic 610-20, “Other Income – Gains and Losses from the Derecognition of Nonfinancial Assets,” when Trustmark finances the sale of its other real estate to a buyer, Trustmark is required to assess whether the buyer is committed to perform their obligations under the contract and whether collectability of the transaction price is probable. Once these two criteria are met, Trustmark derecognizes the other real estate asset and records a gain or loss on the sale once control of the property is transferred to the buyer. Wealth Management Division Trust Management There are five categories of revenue included in trust management: personal trust and investments, retirement plan services, institutional custody, corporate trust and other. Each of these categories includes multiple types of contracts, service obligations and fee income. However, the majority of these contracts include a single service obligation that is satisfied over time, the customer is charged in arrears for services rendered and revenue is recognized when payment is received. In general, the time period between when the service obligation is completed and when payment from the customer is received is less than 30 days. Revenue from trust management contracts is primarily related to monthly service periods and based on the prior month-end’s market value. Some trust management revenue is mandated by a court order, while other revenue consists of flat fees. Trust management revenue based on an account’s market value represents variable consideration under the guidelines of FASB ASC Topic 606. Trustmark has elected the ‘as-invoiced’ practical expedient allowed under FASB ASC Topic 606 to account for the trust management revenue. Investment Services Investment services includes both brokerage and annuity income. Trustmark has a contract with a third-party investment services company which contains a single continuous service obligation, to provide broker-dealer and advisory services to customers on behalf of the third-party, which is satisfied over time and qualifies as a series of distinct service periods. Trustmark serves as the agent between the third-party investment services company, the principle, and the customer. In accordance with the contract, Trustmark receives a monthly payment from the investment services company for commissions and advisory fees (asset management fees) earned on transactions completed in the prior month net of all charges and fees due to the investment services company. Trustmark recognizes revenue from the investment services company, net of the revenue sharing expense due to the investment services company, when the payments are received. Commissions vary from month-to-month based on the specific products and transactions completed. The advisory fees vary based on the average daily balance of the managed assets for the period. The commissions and advisory fees represent variable consideration under FASB ASC Topic 606. Trustmark has elected the ‘as-invoiced’ practical expedient allowed under FASB ASC Topic 606 to recognize revenue from the investment services company. Insurance Division Fisher Brown Bottrell Insurance, Inc. (FBBI), a wholly-owned subsidiary of TNB, operates as an insurance broker representing the policyholder and has no allegiance with any one insurance provider. FBBI serves as the agent between the insurance provider (either insurance carrier or broker), the principal, and the policy holder, the customer. FBBI has four general categories of insurance contracts: commercial, commercial installments, personal and employee benefits. FBBI’s insurance contracts contain a single performance obligation, policy placement, which is satisfied at a point in time. FBBI’s performance obligation is satisfied as of the policy effective date. In addition to policy placement, FBBI provides various other periodic services to the policyholders for which no additional fee is charged. These additional services are not considered material to the overall contract. Trustmark has elected the immaterial promises practical expedient allowed under FASB ASC Topic 606, which allows Trustmark to not assess whether promised services are performance obligations if the promised services are immaterial in the context of the contract. Therefore, the immaterial additional services offered to policyholders are not considered a performance obligation and no amount of the contract transaction price is allocated to these services. In general, the transaction price for the insurance contracts is an established commission amount agreed upon by FBBI and the insurance provider. The commission amount varies based on the insurance provider and the type of policy. There are a small number of insurance contracts which FBBI does not receive a commission, but charges a fee directly to the policyholder. Most of the commissions from insurance contracts are subject to clawback provisions which require FBBI to refund a prorated amount of the commissions received as a result of policy cancellations or lapses. Commissions subject to clawback provisions are considered variable consideration under FASB ASC Topic 606. Trustmark believes the expected value method of estimating the commissions subject to clawback provisions would best predict the amount of commissions FBBI will be entitled to because of the large number of insurance contracts with similar characteristics and the number of possible outcomes. FBBI calculates a separate weighted-average percentage (returned commissions percentage) based on actual cancellations over the previous three years for commercial lines, bonds, and personal lines. FBBI applies the respective returned commissions percentage to the commission revenue earned related to insurance contracts within these three lines each month to calculate the estimated returned commissions amount, which represents the variable consideration subject to variable constraint. Revenue from insurance contracts is reported net of the variable consideration subject to variable constraint. FBBI performs an analysis of the returned commissions reserve quarterly and adjusts the reserve balance based on all available information including actual cancellations and the remaining term of the contract. The returned commissions percentage is updated annually. Insurance Producers at FBBI earn commission as compensation for each policy they are responsible for placing. Commissions are not paid to Producers immediately at the policy effective date, can be subject to clawback provisions and can vary by Producer. Producers receive the commissions for which they are entitled at the end of the month following the month in which the policy became effective. Effective April 1, 2018, FBBI implemented a ‘pay when paid’ system. Under the ‘pay when paid’ system, Producers receive the commissions for which they are entitled at the end of the month following the month in which FBBI receives payment from the insurance provider or customer. Under FASB ASC Subtopic 340-40, “Other Assets and Deferred Costs: Contracts with Customers,” the commission paid to the Producers is an incremental cost of obtaining a contract, which should be capitalized and amortized in a manner consistent with the pattern of transfer of the service related to the contract acquisition asset. Insurance contracts have a term of one year or less; therefore, Trustmark has elected the cost of obtaining a contract practical expedient allowed under FASB ASC Subtopic 340-40, which allows FBBI to recognize the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the contract asset that FBBI otherwise would have recognized is one year or less. Commission expense is recorded as noninterest expense in salaries and employee benefits when paid to the Producers. Commercial Insurance Revenue from FBBI’s commercial insurance contracts (both agency billed and direct billed) consists of a set commission amount, which is subject to clawback provisions. Revenue from commercial insurance contracts is recognized on the policy effective date, and a corresponding commission receivable is recorded concurrent with the revenue until payment is received by FBBI. Effective April 1, 2018, FBBI utilizes a ‘pay when paid’ system to account for commercial insurance contracts. Under the ‘pay when paid’ system, an estimated commission amount is entered in the system when a commercial insurance contract is placed. FBBI records a top line receivable based on the estimated commission amount entered in the system each month, along with a corresponding amount recognized as revenue, and then adjusts the estimated receivable when the commissions are received from the insurance provider or customer. Commercial Installment Insurance Revenue from commercial installment insurance contracts consists of a set commission amount, which is not subject to clawback provisions, and is recognized in twelve equal monthly installments when invoiced by FBBI in the agency management system. FBBI has only a small number of commercial installment insurance contracts and these contracts all have a term of one year; therefore, recognizing the revenue from these contracts over twelve months is not materially different than recognizing the revenue in full at the policy effective date for any given period. Effective April 1, 2018, as a result of implementing this ‘pay when paid’ system, as applied to insurance contracts, revenue from commercial installment contracts is recognized in the same manner as commercial insurance contracts. Personal Insurance Revenue from FBBI’s personal insurance contracts consists of a set commission amount, which is subject to clawback provisions, and is recognized when payment is received (generally 30-60 days after the policy effective date). Personal insurance contracts have a term of one year; therefore, recognizing the revenue from these contracts when payment is received is not materially different than recognizing the revenue at the policy effective date for any given period. Employee Benefits Insurance Revenue from FBBI’s employee benefits insurance contracts consists of a variable commission amount, which is not subject to clawback provisions, and is recognized when payment is received, typically on a monthly basis. Employee benefits insurance contracts have a set commission rate, but can vary from period to period based on changes in the number of employees covered by the policy (i.e. new hires and terminations). FBBI generally receives twelve monthly commission payments for these contracts with the initial payment being received approximately 60-90 days after the policy effective date. Under the guidelines of FASB ASC Topic 606, commissions from employee benefits insurance contracts represent fixed consideration because at contract inception (policy effective date) there is a set commission rate times a known number of covered employees. Changes in the number of covered employees are not known, nor can they be predicted, at contract inception. An increase or decrease in the number of covered employees after the policy effective date is considered a contract modification resulting from a change in scope and transaction price under FASB ASC Topic 606. This modification is treated as part of the existing contract because it does not add a distinct service. Employee benefits insurance contracts have a term of one year; therefore, recognizing the revenue from these contracts when payment is received is not materially different than recognizing the revenue at the policy effective date or the contract modification date for any given period. Contingency Commission Insurance In addition to the insurance contracts discussed above, FBBI has contracts with various insurance providers for which it receives contingency income based on volume of business and claims experience. FBBI is the principal and the insurance provider is the customer for these contingency commission insurance contracts. The contingency commission contracts have a single continuous or stand-ready service obligation whereby FBBI places policies with policyholders when acceptable to the insurance provider, which is satisfied over time. The contract term for these contingency commission contracts is one year. Revenue is recognized from the contingency commission contracts monthly using a time-elapsed measure of progress. FBBI accrues throughout the current year the amount of contingency commission income it expects to receive in the following year adjusted for a degree of uncertainty. FBBI updates a detail by insurance provider with the contingency commission income received, which is then compared to the total amount that was expected to be received. If actual receipts are higher or lower than the amount accrued in the prior year, the monthly accrual for the current year is adjusted accordingly. Under the guidelines of FASB ASC Topic 606, revenue from contingency commission insurance contracts represents variable consideration and should be estimated using one of the two allowable methods subject to the variable consideration constraint. FBBI believes the most likely amount method to be the most appropriate method for estimating the variable consideration as there are only a few possible outcomes for each contract. The following tables present noninterest income disaggregated by reportable operating segment and revenue stream for the periods presented ($ in thousands): Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 (1) Topic 606 Not Topic 606 (2) Total Topic 606 Not Topic 606 (2) Total General Banking Division Service charges on deposit accounts $ 11,074 $ — $ 11,074 $ 11,222 $ — $ 11,222 Bank card and other fees 6,503 937 7,440 7,104 23 7,127 Mortgage banking, net — 8,647 8,647 — 4,425 4,425 Wealth management 70 — 70 64 — 64 Other, net 1,685 (359 ) 1,326 1,495 2,223 3,718 Security gains (losses), net — — — — 14 14 Total noninterest income $ 19,332 $ 9,225 $ 28,557 $ 19,885 $ 6,685 $ 26,570 Wealth Management Division Service charges on deposit accounts $ 1 $ — $ 1 $ 1 $ — $ 1 Bank card and other fees 19 — 19 23 — 23 Wealth management 7,719 — 7,719 7,466 — 7,466 Other, net 1 29 30 — 22 22 Total noninterest income $ 7,740 $ 29 $ 7,769 $ 7,490 $ 22 $ 7,512 Insurance Division Insurance commissions $ 10,765 $ — $ 10,765 $ 10,398 $ — $ 10,398 Other, net 2 — 2 — — — Total noninterest income $ 10,767 $ — $ 10,767 $ 10,398 $ — $ 10,398 Consolidated Service charges on deposit accounts $ 11,075 $ — $ 11,075 $ 11,223 $ — $ 11,223 Bank card and other fees 6,522 937 7,459 7,127 23 7,150 Mortgage banking, net — 8,647 8,647 — 4,425 4,425 Insurance commissions 10,765 — 10,765 10,398 — 10,398 Wealth management 7,789 — 7,789 7,530 — 7,530 Other, net 1,688 (330 ) 1,358 1,495 2,245 3,740 Security gains (losses), net — — — — 14 14 Total noninterest income $ 37,839 $ 9,254 $ 47,093 $ 37,773 $ 6,707 $ 44,480 (1) Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may (2) Noninterest income not in scope for FASB ASC Topic 606 includes customer derivatives revenue and miscellaneous credit card fee income within bank card and other fees; mortgage banking, net; amortization of tax credits, accretion of the FDIC indemnification asset, cash surrender value on various life insurance policies, earnings on Trustmark’s non-qualified deferred compensation plans, other partnership investments and rental income within other, net; and security Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 (1) Topic 606 Not Topic 606 (2) Total Topic 606 Not Topic 606 (2) Total General Banking Division Service charges on deposit accounts $ 32,577 $ — $ 32,577 $ 32,809 $ — $ 32,809 Bank card and other fees 19,865 1,227 21,092 20,777 208 20,985 Mortgage banking, net — 28,958 28,958 — 23,618 23,618 Wealth management 210 — 210 210 — 210 Other, net 4,666 84 4,750 4,997 6,196 11,193 Security gains (losses), net — — — — 15 15 Total noninterest income $ 57,318 $ 30,269 $ 87,587 $ 58,793 $ 30,037 $ 88,830 Wealth Management Division Service charges on deposit accounts $ 2 $ — $ 2 $ 1 $ — $ 1 Bank card and other fees 63 — 63 35 — 35 Wealth management 22,624 — 22,624 22,407 — 22,407 Other, net 3 76 79 — 70 70 Total noninterest income $ 22,692 $ 76 $ 22,768 $ 22,443 $ 70 $ 22,513 Insurance Division Insurance commissions $ 30,919 $ — $ 30,919 $ 29,355 $ — $ 29,355 Other, net 3 — 3 5 — 5 Total noninterest income $ 30,922 $ — $ 30,922 $ 29,360 $ — $ 29,360 Consolidated Service charges on deposit accounts $ 32,579 $ — $ 32,579 $ 32,810 $ — $ 32,810 Bank card and other fees 19,928 1,227 21,155 20,812 208 21,020 Mortgage banking, net — 28,958 28,958 — 23,618 23,618 Insurance commissions 30,919 — 30,919 29,355 — 29,355 Wealth management 22,834 — 22,834 22,617 — 22,617 Other, net 4,672 160 4,832 5,002 6,266 11,268 Security gains (losses), net — — — — 15 15 Total noninterest income $ 110,932 $ 30,345 $ 141,277 $ 110,596 $ 30,107 $ 140,703 (1) Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may (2) Noninterest income not in scope for FASB ASC Topic 606 includes customer derivatives revenue and miscellaneous credit card fee income within bank card and other fees; mortgage banking, net; amortization of tax credits, accretion of the FDIC indemnification asset, cash surrender value on various life insurance policies, earnings on Trustmark’s non-qualified deferred compensation plans, other partnership investments and rental income within other, net; and security

Defined Benefit and Other Postr

Defined Benefit and Other Postretirement Benefits	9 Months Ended
	Sep. 30, 2018
Compensation And Retirement Disclosure [Abstract]
Defined Benefit and Other Postretirement Benefits	Note 11 – 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. 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. Final distributions were completed during the second quarter of 2017. 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 table presents information regarding the net periodic benefit cost for the Plan and the Continuing Plan for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost $ 69 $ 64 $ 208 $ 190 Interest cost 83 102 249 1,394 Expected return on plan assets (57 ) (51 ) (171 ) (267 ) Recognized net loss due to lump sum settlements 41 — 121 — Recognized net loss due to defined benefit plan termination — — — 17,644 Recognized net actuarial loss 143 142 428 1,272 Net periodic benefit cost $ 279 $ 257 $ 835 $ 20,233 For the plan year ending December 31, 2018, Trustmark’s minimum required contribution to the Continuing Plan is expected to be $243 thousand; however, Management and the Board of Directors of Trustmark will monitor the Continuing Plan throughout 2018 to determine any additional funding requirements by the plan’s measurement date, which is December 31. Supplemental Retirement Plans Trustmark maintains a nonqualified supplemental retirement plan covering key executive officers and senior officers as well as directors who have elected to defer fees. The plan provides for retirement and/or death benefits based on a participant’s covered salary or deferred fees. Although plan benefits may be paid from Trustmark’s general assets, Trustmark has purchased life insurance contracts on the participants covered under the plan, which may be used to fund future benefit payments under the plan. The measurement date for the plan is December 31. As a result of mergers prior to 2014, Trustmark became the administrator of small nonqualified supplemental retirement plans, for which the plan benefits were frozen prior to the merger date. The following table presents information regarding the net periodic benefit cost for Trustmark’s nonqualified supplemental retirement plans for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost $ 29 $ 36 $ 87 $ 106 Interest cost 457 514 1,409 1,589 Amortization of prior service cost 63 63 188 188 Recognized net actuarial loss 218 214 664 651 Net periodic benefit cost $ 767 $ 827 $ 2,348 $ 2,534

Stock and Incentive Compensatio

Stock and Incentive Compensation Plans	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock and Incentive Compensation Plans	Note 12 – 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. 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. 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. 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 tables summarize the Stock Plan activity for the periods presented: Three Months Ended September 30, 2018 Performance Awards Time-Vested Awards Nonvested shares, beginning of period 177,695 322,528 Granted — 1,500 Released from restriction — (400 ) Forfeited — (764 ) Nonvested shares, end of period 177,695 322,864 Nine Months Ended September 30, 2018 Performance Awards Time-Vested Awards Nonvested shares, beginning of period 213,516 320,357 Granted 51,174 118,325 Released from restriction (55,351 ) (107,180 ) Forfeited (31,644 ) (8,638 ) Nonvested shares, end of period 177,695 322,864 The following table presents information regarding compensation expense for awards under the Stock Plan for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Performance awards $ 435 $ 435 $ 725 $ 959 Time-vested awards 723 641 2,297 2,291 Total compensation expense $ 1,158 $ 1,076 $ 3,022 $ 3,250

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Contingencies	Note 13 – 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 fully 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 September 30, 2018 and 2017, Trustmark had unused commitments to extend credit of $3.666 billion and $3.143 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 September 30, 2018 and 2017, Trustmark’s maximum exposure to credit loss in the event of nonperformance by the other party for letters of credit was $102.9 million and $105.6 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 September 30, 2018 and 2017, the fair value of collateral held was $31.2 million and $30.2 million, respectively. 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.

Earnings Per Share (EPS)

Earnings Per Share (EPS)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share (EPS)	Note 14 – Earnings Per Share (EPS) The following table reflects weighted-average shares used to calculate basic and diluted EPS for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Basic shares 67,621 67,742 67,729 67,722 Dilutive shares 175 174 147 154 Diluted shares 67,796 67,916 67,876 67,876 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): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Weighted-average antidilutive stock awards 8 6 87 72

Statements of Cash Flows

Statements of Cash Flows	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Statements of Cash Flows	Note 15 – Statements of Cash Flows The following table reflects specific transaction amounts for the periods presented ($ in thousands): Nine Months Ended September 30, 2018 2017 Income taxes paid $ 11,629 $ 1,423 Interest expense paid on deposits and borrowings 46,506 28,266 Noncash transfers from loans to other real estate 10,368 7,006 Transfer of long-term FHLB advances to short-term — 250,038 Assets acquired in business combination — 196,265 Liabilities acquired in business combination — 184,949

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2018
Stockholders Equity Note [Abstract]
Shareholders' Equity	Note 16 – 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 Trustmark’s 2017 Annual Report on Form 10-K, 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 1.875% at September 30, 2018 and 1.250% at December 31, 2017. 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 September 30, 2018, Trustmark and TNB exceeded all applicable minimum capital standards. In addition, Trustmark and TNB met applicable regulatory guidelines to be considered well-capitalized at September 30, 2018. 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 September 30, 2018, which Management believes have affected Trustmark’s or TNB’s present classification. The following table provides Trustmark’s and TNB’s actual regulatory capital amounts and ratios under regulatory capital standards in effect at September 30, 2018 and December 31, 2017 ($ in thousands): Actual Regulatory Capital Minimum To Be Well Amount Ratio Requirement Capitalized At September 30, 2018: Common Equity Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,302,859 12.20 % 6.375 % n/a Trustmark National Bank 1,344,029 12.59 % 6.375 % 6.50 % Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,362,859 12.76 % 7.875 % n/a Trustmark National Bank 1,344,029 12.59 % 7.875 % 8.00 % Total Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,453,447 13.61 % 9.875 % n/a Trustmark National Bank 1,434,617 13.44 % 9.875 % 10.00 % Tier 1 Leverage (to Average Assets) Trustmark Corporation $ 1,362,859 10.41 % 4.00 % n/a Trustmark National Bank 1,344,029 10.29 % 4.00 % 5.00 % 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 % 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 repurchased approximately 243 thousand shares of its common stock valued at $7.9 million during the nine months ended September 30, 2018, compared to no shares repurchased during the nine months ended September 30, 2017. Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss The following tables present the net change in the components of accumulated other comprehensive loss and the related tax effects allocated to each component for the periods presented ($ in thousands). Reclassification adjustments related to securities available for sale are included in security 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 on pension and other postretirement benefit plans are included in the computation of net periodic benefit cost (see Note 11 – 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. Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Securities available for sale and transferred securities: Net unrealized holding gains (losses) arising during the period $ (9,660 ) $ 2,414 $ (7,246 ) $ (535 ) $ 204 $ (331 ) Reclassification adjustment for net (gains) losses realized in net income — — — (14 ) 6 (8 ) Change in net unrealized holding loss on securities transferred to held to maturity 973 (243 ) 730 1,130 (432 ) 698 Total securities available for sale and transferred securities (8,687 ) 2,171 (6,516 ) 581 (222 ) 359 Pension and other postretirement benefit plans: Net change in prior service costs 63 (16 ) 47 63 (24 ) 39 Recognized net loss due to lump sum settlements 41 (10 ) 31 — — — Change in net actuarial loss 361 (90 ) 271 356 (137 ) 219 Total pension and other postretirement benefit plans 465 (116 ) 349 419 (161 ) 258 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives 52 (13 ) 39 53 (20 ) 33 Reclassification adjustment for (gain) loss realized in net income (104 ) 25 (79 ) 55 (21 ) 34 Total cash flow hedge derivatives (52 ) 12 (40 ) 108 (41 ) 67 Total other comprehensive income (loss) $ (8,274 ) $ 2,067 $ (6,207 ) $ 1,108 $ (424 ) $ 684 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Securities available for sale and transferred securities: Net unrealized holding gains (losses) arising during the period $ (46,974 ) $ 11,743 $ (35,231 ) $ 6,335 $ (2,423 ) $ 3,912 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 2,909 (727 ) 2,182 3,551 (1,358 ) 2,193 Total securities available for sale and transferred securities (44,065 ) 11,016 (33,049 ) 9,871 (3,775 ) 6,096 Pension and other postretirement benefit plans: Net change in prior service costs 188 (48 ) 140 188 (72 ) 116 Recognized net loss due to lump sum settlements 121 (29 ) 92 — — — Change in net actuarial loss 1,092 (273 ) 819 1,923 (736 ) 1,187 Recognized net loss due to defined benefit plan termination — — — 16,991 (6,499 ) 10,492 Total pension and other postretirement benefit plans 1,401 (350 ) 1,051 19,102 (7,307 ) 11,795 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives 611 (153 ) 458 (99 ) 38 (61 ) Reclassification adjustment for (gain) loss realized in net income (209 ) 52 (157 ) 232 (89 ) 143 Total cash flow hedge derivatives 402 (101 ) 301 133 (51 ) 82 Total other comprehensive income (loss) $ (42,262 ) $ 10,565 $ (31,697 ) $ 29,106 $ (11,133 ) $ 17,973 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 Transferred Securities Defined Benefit Pension Items Cash Flow Hedge Derivatives Total Balance at January 1, 2018 $ (26,535 ) $ (13,468 ) $ 278 $ (39,725 ) Other comprehensive income (loss) before reclassification (33,049 ) — 458 (32,591 ) Amounts reclassified from accumulated other comprehensive loss — 1,051 (157 ) 894 Net other comprehensive income (loss) (33,049 ) 1,051 301 (31,697 ) Reclassification of certain income tax effects related to the change in the federal statutory income tax rate under the Tax Cuts and Jobs Act of 2017 (Tax Reform Act) (5,694 ) (2,890 ) 60 (8,524 ) Balance at September 30, 2018 $ (65,278 ) $ (15,307 ) $ 639 $ (79,946 ) Balance at January 1, 2017 $ (20,800 ) $ (24,980 ) $ (18 ) $ (45,798 ) Other comprehensive income (loss) before reclassification 6,105 — (61 ) 6,044 Amounts reclassified from accumulated other comprehensive loss (9 ) 11,795 143 11,929 Net other comprehensive income (loss) 6,096 11,795 82 17,973 Balance at September 30, 2017 $ (14,704 ) $ (13,185 ) $ 64 $ (27,825 )

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value	Note 17 – 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 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 September 30, 2018 and December 31, 2017, 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 nine months ended September 30, 2018 and the year ended December 31, 2017. September 30, 2018 Total Level 1 Level 2 Level 3 U.S. Government agency obligations $ 32,371 $ — $ 32,371 $ — Obligations of states and political subdivisions 57,264 — 57,264 — Mortgage-backed securities 1,774,998 — 1,774,998 — Securities available for sale 1,864,633 — 1,864,633 — Loans held for sale 182,664 — 182,664 — Mortgage servicing rights 101,374 — — 101,374 Other assets - derivatives 3,287 (1,531 ) 3,925 893 Other liabilities - derivatives 4,311 1,070 3,241 — 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 — The changes in Level 3 assets measured at fair value on a recurring basis for the nine months ended September 30, 2018 and 2017 are summarized as follows ($ in thousands): MSR Other Assets - Derivatives Balance, January 1, 2018 $ 84,269 $ 900 Total net (loss) gain included in Mortgage banking, net (1) 4,857 3,345 Additions 12,248 — Sales — (3,352 ) Balance, September 30, 2018 $ 101,374 $ 893 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 September 30, 2018 $ 13,879 $ 247 Balance, January 1, 2017 $ 80,239 $ 1,001 Total net (loss) gain included in Mortgage banking, net (1) (10,392 ) 3,436 Additions 11,630 — Sales — (3,431 ) Balance, September 30, 2017 $ 81,477 $ 1,006 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 September 30, 2017 $ (2,218 ) $ (1,483 ) (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 September 30, 2018, 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 September 30, 2018, Trustmark had outstanding balances of $52.5 million in impaired LHFI that were individually evaluated for impairment and written down to the fair value of the underlying collateral less cost to sell based on the fair value of the collateral or other unobservable input compared to $48.9 million at December 31, 2017. 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 $18.4 million were remeasured during the first nine months of 2018, requiring write-downs of $1.9 million to reach their current fair values compared to $22.0 million of foreclosed assets that were remeasured during the first nine months of 2017, requiring write-downs of $2.6 million. Fair Value of Financial Instruments FASB ASC Topic 825, “Financial Instruments,” requires disclosure of the fair value of financial assets and financial liabilities, including those financial assets and financial liabilities that are not measured and reported at fair value on a recurring basis or non-recurring basis. A detailed description of the valuation methodologies used in estimating the fair value of financial instruments can be found in Note 18 – Fair Value included in Item 8 of Trustmark’s Annual Report on Form 10-K for the year ended December 31, 2017. The carrying amounts and estimated fair values of financial instruments at September 30, 2018 and December 31, 2017, are as follows ($ in thousands): September 30, 2018 December 31, 2017 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Financial Assets: Level 2 Inputs: Cash and short-term investments $ 433,471 $ 433,471 $ 336,383 $ 336,383 Securities held to maturity 943,883 907,317 1,056,486 1,046,247 Level 3 Inputs: Net LHFI 8,658,156 8,560,091 8,493,234 8,507,469 Net acquired loans 130,901 130,901 257,438 257,438 Financial Liabilities: Level 2 Inputs: Deposits 10,956,910 10,953,348 10,577,512 10,577,858 Short-term liabilities 676,888 676,888 1,440,876 1,440,876 Long-term FHLB advances 896 831 946 946 Junior subordinated debt securities 61,856 53,815 61,856 45,773 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 necessarily be 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. On January 1, 2018, Trustmark adopted 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)” Fair Value Option Trustmark has elected to account for its mortgage LHFS under the fair value option, with interest income on these mortgage LHFS reported in interest and fees on LHFS and LHFI. The fair value of the mortgage LHFS is determined using quoted prices for a similar asset, adjusted for specific attributes of that loan. The mortgage 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 in 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 three and nine months ended September 30, 2018, a net loss of $1.3 million and a net gain of $416 thousand, respectively, was recorded in noninterest income in mortgage banking, net for changes in the fair value of the LHFS accounted for under the fair value option, compared to a net loss of $202 thousand and a net gain of $3.5 million for the three and nine months ended September 30, 2017, respectively. Interest and fees on LHFS and LHFI for the three and nine months ended September 30, 2018 included $1.5 million and $3.8 million, respectively, of interest earned on the LHFS accounted for under the fair value option, compared to $1.4 million and $3.7 million for the three and nine months ended September 30, 2017, respectively. 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 $47.8 million and $48.2 million at September 30, 2018 and December 31, 2017, respectively, and are included in LHFS on the accompanying consolidated balance sheets. The following table provides information about the fair value and the contractual principal outstanding of the LHFS accounted for under the fair value option as of September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 December 31, 2017 Fair value of LHFS $ 134,874 $ 132,300 LHFS contractual principal outstanding 134,598 129,347 Fair value less unpaid principal $ 276 $ 2,953

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Note 18 – 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, “Derivatives and Hedging,” 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 nine months ended September 30, 2018 and 2017. The accumulated net after-tax gain related to the effective cash flow hedge included in accumulated other comprehensive loss totaled $639 thousand at September 30, 2018 compared to a net after-tax gain of $278 thousand at December 31, 2017. 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 $644 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 were $252.0 million at September 30, 2018 compared to $349.0 million at December 31, 2017. Changes in the fair value of these exchange-traded derivative instruments are recorded in 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 $72 thousand and a net negative ineffectiveness of $2.6 million for the three months ended September 30, 2018 and 2017, respectively. For the nine months ended September 30, 2018 and 2017, the impact was a net positive ineffectiveness of $3.5 million and $1.0 million, respectively. 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 in 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 $199.5 million at September 30, 2018, with a positive valuation adjustment of $930 thousand, compared to $182.1 million, with a negative valuation adjustment of $237 thousand, at December 31, 2017. 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 in 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 $102.9 million at September 30, 2018, with a positive valuation adjustment of $893 thousand, compared to $83.0 million, with a positive valuation adjustment of $900 thousand, as of December 31, 2017. 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 September 30, 2018, Trustmark had interest rate swaps with an aggregate notional amount of $410.2 million related to this program, compared to $351.9 million as of December 31, 2017. 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 September 30, 2018, Trustmark had no 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 compared to $80 thousand at December 31, 2017. As of September 30, 2018, Trustmark had no posted collateral against its obligations because of negotiated thresholds and minimum transfer amounts under these agreements. If Trustmark had breached any of these triggering provisions at September 30, 2018, 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 both September 30, 2018 and December 31, 2017, Trustmark had entered into two risk participation agreements as a beneficiary with an aggregate notional amount of $13.2 million and $13.7 million, respectively. Trustmark had entered into seven risk participation agreements as a guarantor with an aggregate notional amount of $40.3 million at September 30, 2018 compared to six risk participation agreements as a guarantor with an aggregate notional amount of $37.1 million at December 31, 2017. The aggregate fair values of these risk participation agreements were immaterial at September 30, 2018 and December 31, 2017. Tabular Disclosures The following tables disclose the fair value of derivative instruments in Trustmark’s consolidated balance sheets as of September 30, 2018 and December 31, 2017 as well as the effect of these derivative instruments on Trustmark’s results of operations for the periods presented ($ in thousands): September 30, 2018 December 31, 2017 Derivatives in hedging relationships Interest rate contracts: Interest rate swaps included in other assets $ 852 $ 451 Derivatives not designated as hedging instruments Interest rate contracts: Futures contracts included in other assets $ (1,569 ) $ (1,088 ) Exchange traded purchased options included in other assets 38 75 OTC written options (rate locks) included in other assets 893 900 Interest rate swaps included in other assets 3,073 1,175 Credit risk participation agreements included in other assets — 3 Forward contracts included in other liabilities (930 ) 237 Exchange traded written options included in other liabilities 1,070 616 Interest rate swaps included in other liabilities 4,170 1,819 Credit risk participation agreements included in other liabilities 1 6 Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Derivatives in hedging relationships Amount of gain (loss) reclassified from accumulated other comprehensive loss and recognized in other interest expense $ 104 $ (55 ) $ 209 $ (232 ) Derivatives not designated as hedging instruments Amount of gain (loss) recognized in mortgage banking, net $ (1,302 ) $ (466 ) $ (9,243 ) $ 688 Amount of gain (loss) recognized in bank card and other fees (86 ) (10 ) (41 ) (63 ) 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): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Derivatives in cash flow hedging relationship Amount of gain (loss) recognized in other comprehensive income (loss), net of tax $ 39 $ 33 $ 458 $ (61 ) 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. Information about financial instruments that are eligible for offset in the consolidated balance sheets as of September 30, 2018 and December 31, 2017 is presented in the following tables ($ in thousands): Offsetting of Derivative Assets As of September 30, 2018 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 the Statement of Financial Position Financial Instruments Cash Collateral Received Net Amount Derivatives $ 3,925 $ — $ 3,925 $ (84 ) $ (950 ) $ 2,891 Offsetting of Derivative Liabilities As of September 30, 2018 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 $ 4,170 $ — $ 4,170 $ (84 ) $ — $ 4,086 Offsetting of Derivative Assets As of December 31, 2017 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 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

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	Note 19 – Segment Information Trustmark’s management reporting structure includes three segments: General Banking, Wealth Management and Insurance. For a complete overview of Trustmark’s operating segments, see Note 20 – Segment Information included in Part II. Item 8. – Financial Statements and Supplementary Data, of Trustmark’s 2017 Annual Report on Form 10-K. There have been no significant changes in Trustmark’s operating segments during the periods presented. 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 segment, 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): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 General Banking Net interest income $ 106,784 $ 103,408 $ 313,299 $ 302,613 Provision for loan losses, net 8,206 2,019 15,043 3,533 Noninterest income 28,557 26,570 87,587 88,830 Noninterest expense 89,889 88,814 267,462 284,420 Income before income taxes 37,246 39,145 118,381 103,490 Income taxes 3,536 7,130 13,430 19,772 General banking net income $ 33,710 $ 32,015 $ 104,951 $ 83,718 Selected Financial Information Total assets $ 13,364,636 $ 13,811,335 $ 13,364,636 $ 13,811,335 Depreciation and amortization $ 9,759 $ 9,863 $ 28,959 $ 28,196 Wealth Management Net interest income $ 134 $ 434 $ 771 $ 718 Noninterest income 7,769 7,512 22,768 22,513 Noninterest expense 7,194 6,791 19,996 20,361 Income before income taxes 709 1,155 3,543 2,870 Income taxes 177 441 886 1,098 Wealth management net income $ 532 $ 714 $ 2,657 $ 1,772 Selected Financial Information Total assets $ 9,411 $ 6,635 $ 9,411 $ 6,635 Depreciation and amortization $ 64 $ 30 $ 116 $ 104 Insurance Net interest income $ 65 $ 70 $ 170 $ 175 Noninterest income 10,767 10,398 30,922 29,360 Noninterest expense 8,140 7,481 24,030 22,437 Income before income taxes 2,692 2,987 7,062 7,098 Income taxes 681 1,137 1,774 2,726 Insurance net income $ 2,011 $ 1,850 $ 5,288 $ 4,372 Selected Financial Information Total assets $ 65,765 $ 66,685 $ 65,765 $ 66,685 Depreciation and amortization $ 155 $ 159 $ 437 $ 481 Consolidated Net interest income $ 106,983 $ 103,912 $ 314,240 $ 303,506 Provision for loan losses, net 8,206 2,019 15,043 3,533 Noninterest income 47,093 44,480 141,277 140,703 Noninterest expense 105,223 103,086 311,488 327,218 Income before income taxes 40,647 43,287 128,986 113,458 Income taxes 4,394 8,708 16,090 23,596 Consolidated net income $ 36,253 $ 34,579 $ 112,896 $ 89,862 Selected Financial Information Total assets $ 13,439,812 $ 13,884,655 $ 13,439,812 $ 13,884,655 Depreciation and amortization $ 9,978 $ 10,052 $ 29,512 $ 28,781

Accounting Policies Recently Ad

Accounting Policies Recently Adopted and Pending Accounting Pronouncements	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Accounting Policies Recently Adopted and Pending Accounting Pronouncements	Note 20 – Accounting Policies Recently Adopted and Pending Accounting Pronouncements Accounting Policies Recently Adopted Except for the changes detailed below, Trustmark has consistently applied its accounting policies to all periods presented in the accompanying consolidated financial statements. ASU 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 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 early adopted the amendments of 2018-02 during the first quarter of 2018 and elected to reclassify the stranded tax effects from accumulated other comprehensive loss to retained earnings at the beginning of the period of adoption. The reclassification of the stranded tax effects resulted in an $8.5 million increase in accumulated other comprehensive loss, net of tax and a corresponding increase in retained earnings. 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 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 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. As a result of the adoption of ASU 2017-07, Trustmark reclassified $885 thousand and $2.7 million of the net periodic benefit cost from salaries and employee benefits to other expense in the accompanying consolidated statements of income for the three and nine months ended September 30, 2018, respectively, compared to $966 thousand and $4.8 million for the three and nine months ended September 30, 2017, respectively. 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” included in Item 8 of Trustmark’s 2017 Annual Report on Form 10-K for information regarding Trustmark’s investment in member bank stock. Adoption of the amendments of ASU 2016-01 resulted in changes to Trustmark’s fair value related disclosures, specifically amendments (iii) which eliminated 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 and (iv) which required the use of the exit price notion when measuring the fair value of the LHFI portfolio. Changes to Trustmark’s fair value related disclosures are presented in Note 17 – Fair Value of this report. The adoption of ASU 2016-01 did not have a material impact on Trustmark’s consolidated financial statements. 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 (cumulative effect method) of application for only those contracts not completed as of the date of adoption; therefore, comparative information has not been adjusted and continues to be reported under legacy GAAP. 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 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. No cumulative adjustment was recorded as a result of the adoption of ASU 2014-09. Disclosures required by the amendments of ASU 2014-09 are presented in Note 10 – Revenue from Contracts with Customers of this report. The adoption of ASU 2014-09 did not have a material impact on Trustmark’s consolidated financial statements. Changes in Trustmark’s accounting policies as a result of adopting the amendments of ASU 2014-09 included the following: Bank Card and Other Fees Previously, Trustmark recognized interchange fee revenue from point of sale transactions in full as noninterest income in bank card and other fees and recorded a separate expense as noninterest expense in other expense for the amounts payable to the payment network. Under the guidelines of FASB ASC Topic 606, Trustmark records the amounts payable to the payment network for point of sale transactions as noninterest income in bank card and other fees and, therefore, reports revenue from interchange fee contracts net of the considered for which Trustmark is not entitled. Insurance Commissions Commissions subject to clawback provisions are considered variable consideration subject to variable constraint under FASB ASC Topic 606. Previously, FBBI recognized revenue from insurance contracts in full when the commissions were invoiced or received and recorded a negative commission amount at the time the commissions were paid back to the insurance provider as a result of a policy cancellation or lapse. No allowance for doubtful accounts was previously recorded related to the commission revenue subject to clawback provisions. As a result of the adoption of FASB ASC Topic 606, FBBI calculates a separate weighted-average percentage (returned commissions percentage) based on actual cancellations over the previous three years for commercial lines, bonds, and personal lines. FBBI applies the respective returned commissions percentage to the commission revenue earned related to insurance contracts within these three lines each month to calculate the estimated returned commissions amount, which represents the variable consideration subject to variable constraint. Revenue from insurance contracts is reported net of the estimated returned commissions amount (contra-revenue) and a corresponding liability is recorded in other liabilities. FBBI performs an analysis of the returned commissions reserve quarterly and adjusts the reserve balance based on all available information including actual cancellations and the remaining term of the contract. The returned commissions percentage is updated annually. Wealth Management A portion of the revenue received by Trustmark from investment services and trust tax contracts are payable to third-parties for related services rendered and represents consideration for which Trustmark is not entitled under FASB ASC Topic 606. Previously, Trustmark recognized revenue from investment services and trust tax contracts in full as noninterest income in wealth management and recorded a separate expense for services rendered related to these contracts as noninterest expense in other expense. Under FASB ASC Topic 606, Trustmark records expenses for services rendered related to these contracts as noninterest income in wealth management (contra-revenue) and, as a result, revenue from wealth management contracts is reported net of the amount for which Trustmark is not entitled. Pending Accounting Pronouncements ASU 2018-15, “Intangibles-Goodwill and Other–Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force).” Issued in August 2018, ASU 2018-15 aims to reduce complexity in the accounting for costs of implementing a cloud computing service arrangement. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The amendments of ASU 2018-15 require an entity to follow the guidance in FASB ASC Subtopic 350-40, “Intangibles-Goodwill and Other-Internal-Use Software,” in order to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. The amendments of ASU 2018-15 also require an entity to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement (i.e. the noncancellable period of the arrangement plus periods covered by (1) an option to extend the arrangement if the entity is reasonably certain to exercise that option, (2) an option to terminate the arrangement if the entity is reasonably certain not to exercise the option, and (3) an option to extend (or not to terminate) the arrangement in which exercise of the option is in the control of the vendor). ASU 2018-15 also requires an entity to present the expense related to the capitalized implementation costs in the same line item in the statement of income as the fees associated with the hosting element (service) of the arrangement, and to classify payments for capitalized implementation costs in the statement of cash flows in the same manner as payments made for fees associated with the hosting element. ASU 2018-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Trustmark does not currently have any material amount of implementation costs related to hosting arrangements that are service contracts and is not expected to have a material impact to Trustmark’s consolidated financial statements; however, Management will continue to evaluate the impact of this ASU on future hosting arrangements as well as Trustmark’s consolidated financial statements through its effective date. ASU 2018-14, “Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans.” Issued in August 2018, ASU 2018-14 modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. The amendments in ASU 2018-14 remove certain disclosure requirements that are no longer considered cost beneficial, clarify the specific requirements of disclosures and add disclosure requirements identified as relevant. T he amendments of ASU 2018-14 become effective for fiscal years beginning after December 15, 2020. Trustmark plans to adopt these amendments during the first quarter of 2021. Management is currently assessing all the potential impacts of the amendments in ASU 2018-14 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-14 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement.” Issued in August 2018, the amendments in this ASU remove disclosure requirements in FASB ASC Topic 820 related to (1) the amount of, and reasons for, transfers between Level 1 and Level 2 of the fair value hierarchy; (2) the policy for timing of transfers between levels; (3) the valuation processes for Level 3 fair value measurements; and (4) for non-public entities, the changes in unrealized gains and losses for the period included in earnings for recurring Level 3 fair value measurements held at the end of the reporting period. The ASU also modifies disclosure requirements such that (1) in place of a rollforward for Level 3 fair value measurements, a non-public entity is required to disclose transfers into and out of Level 3 of the fair value hierarchy and purchases and issues of Level 3 assets and liabilities; (2) for investments in certain entities that calculate net asset value, an entity is required to disclose the timing of liquidation of an investee’s assets and the date that restrictions from redemption might lapse, only if the investee has communicated the timing to the entity or announced the timing publicly; and (3) it is clear that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. Additionally, this ASU adds disclosure requirements for public entities about (1) the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period, and (2) the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. The amendments of ASU 2018-13 are effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. Trustmark plans to adopt ASU 2018-13 during the first quarter of 2020. Management is currently assessing all the potential impacts of the amendments in ASU 2018-13 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-13 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2017-12, “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 2017-08, “ 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 September 30, 2018, 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 2017-04, “ 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 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 intends to adopt the amendments of ASU 2016-13 during the first quarter of 2020. Trustmark selected a third-party vendor to provide allowance for loan loss software as well as advisory services in developing a new methodology that would be compliant with amendments of ASU 2016-13, and is working with the approved third-party vendor to develop the CECL model and evaluate the impact to Trustmark. Trustmark is working with the third-party vendor on developing various modeling techniques and methodologies, which Management will review to determine the most appropriate model for Trustmark. Trustmark is on schedule to fully comply with all CECL requirements within its internally established timeframe for implementation. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements through its effective date. 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. In July 2018, the FASB issued ASU 2018-10, “Codification Improvements to Topic 842: Leases,” which provides corrections or improvements to a number of areas within Topic 842 and has the same transition guidance and effective date as ASU 2016-02. The FASB also issued ASU 2018-11, “Leases (Topic 842)-Targeted Improvements”, in July 2018, which provides entities with an additional and optional transition method to adopt the new lease standard and, for lessors only, a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease component. The amendments in ASU 2018-11 allow an entity the option to initially apply the new lease standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption as opposed to at the beginning of the earliest period presented in the financial statements. The amendments of ASU 2018-11 have the same effective date as ASU 2016-02. 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 evaluatio

Accounting Policies Recently _2

Accounting Policies Recently Adopted and Pending Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Accounting Policies Recently Adopted and Pending Accounting Pronouncements	Accounting Policies Recently Adopted Except for the changes detailed below, Trustmark has consistently applied its accounting policies to all periods presented in the accompanying consolidated financial statements. ASU 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 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 early adopted the amendments of 2018-02 during the first quarter of 2018 and elected to reclassify the stranded tax effects from accumulated other comprehensive loss to retained earnings at the beginning of the period of adoption. The reclassification of the stranded tax effects resulted in an $8.5 million increase in accumulated other comprehensive loss, net of tax and a corresponding increase in retained earnings. 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 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 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. As a result of the adoption of ASU 2017-07, Trustmark reclassified $885 thousand and $2.7 million of the net periodic benefit cost from salaries and employee benefits to other expense in the accompanying consolidated statements of income for the three and nine months ended September 30, 2018, respectively, compared to $966 thousand and $4.8 million for the three and nine months ended September 30, 2017, respectively. 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” included in Item 8 of Trustmark’s 2017 Annual Report on Form 10-K for information regarding Trustmark’s investment in member bank stock. Adoption of the amendments of ASU 2016-01 resulted in changes to Trustmark’s fair value related disclosures, specifically amendments (iii) which eliminated 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 and (iv) which required the use of the exit price notion when measuring the fair value of the LHFI portfolio. Changes to Trustmark’s fair value related disclosures are presented in Note 17 – Fair Value of this report. The adoption of ASU 2016-01 did not have a material impact on Trustmark’s consolidated financial statements. 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 (cumulative effect method) of application for only those contracts not completed as of the date of adoption; therefore, comparative information has not been adjusted and continues to be reported under legacy GAAP. 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 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. No cumulative adjustment was recorded as a result of the adoption of ASU 2014-09. Disclosures required by the amendments of ASU 2014-09 are presented in Note 10 – Revenue from Contracts with Customers of this report. The adoption of ASU 2014-09 did not have a material impact on Trustmark’s consolidated financial statements. Changes in Trustmark’s accounting policies as a result of adopting the amendments of ASU 2014-09 included the following: Bank Card and Other Fees Previously, Trustmark recognized interchange fee revenue from point of sale transactions in full as noninterest income in bank card and other fees and recorded a separate expense as noninterest expense in other expense for the amounts payable to the payment network. Under the guidelines of FASB ASC Topic 606, Trustmark records the amounts payable to the payment network for point of sale transactions as noninterest income in bank card and other fees and, therefore, reports revenue from interchange fee contracts net of the considered for which Trustmark is not entitled. Insurance Commissions Commissions subject to clawback provisions are considered variable consideration subject to variable constraint under FASB ASC Topic 606. Previously, FBBI recognized revenue from insurance contracts in full when the commissions were invoiced or received and recorded a negative commission amount at the time the commissions were paid back to the insurance provider as a result of a policy cancellation or lapse. No allowance for doubtful accounts was previously recorded related to the commission revenue subject to clawback provisions. As a result of the adoption of FASB ASC Topic 606, FBBI calculates a separate weighted-average percentage (returned commissions percentage) based on actual cancellations over the previous three years for commercial lines, bonds, and personal lines. FBBI applies the respective returned commissions percentage to the commission revenue earned related to insurance contracts within these three lines each month to calculate the estimated returned commissions amount, which represents the variable consideration subject to variable constraint. Revenue from insurance contracts is reported net of the estimated returned commissions amount (contra-revenue) and a corresponding liability is recorded in other liabilities. FBBI performs an analysis of the returned commissions reserve quarterly and adjusts the reserve balance based on all available information including actual cancellations and the remaining term of the contract. The returned commissions percentage is updated annually. Wealth Management A portion of the revenue received by Trustmark from investment services and trust tax contracts are payable to third-parties for related services rendered and represents consideration for which Trustmark is not entitled under FASB ASC Topic 606. Previously, Trustmark recognized revenue from investment services and trust tax contracts in full as noninterest income in wealth management and recorded a separate expense for services rendered related to these contracts as noninterest expense in other expense. Under FASB ASC Topic 606, Trustmark records expenses for services rendered related to these contracts as noninterest income in wealth management (contra-revenue) and, as a result, revenue from wealth management contracts is reported net of the amount for which Trustmark is not entitled. Pending Accounting Pronouncements ASU 2018-15, “Intangibles-Goodwill and Other–Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force).” Issued in August 2018, ASU 2018-15 aims to reduce complexity in the accounting for costs of implementing a cloud computing service arrangement. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The amendments of ASU 2018-15 require an entity to follow the guidance in FASB ASC Subtopic 350-40, “Intangibles-Goodwill and Other-Internal-Use Software,” in order to determine which implementation costs to capitalize as an asset related to the service contract and which costs to expense. The amendments of ASU 2018-15 also require an entity to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement (i.e. the noncancellable period of the arrangement plus periods covered by (1) an option to extend the arrangement if the entity is reasonably certain to exercise that option, (2) an option to terminate the arrangement if the entity is reasonably certain not to exercise the option, and (3) an option to extend (or not to terminate) the arrangement in which exercise of the option is in the control of the vendor). ASU 2018-15 also requires an entity to present the expense related to the capitalized implementation costs in the same line item in the statement of income as the fees associated with the hosting element (service) of the arrangement, and to classify payments for capitalized implementation costs in the statement of cash flows in the same manner as payments made for fees associated with the hosting element. ASU 2018-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Trustmark does not currently have any material amount of implementation costs related to hosting arrangements that are service contracts and is not expected to have a material impact to Trustmark’s consolidated financial statements; however, Management will continue to evaluate the impact of this ASU on future hosting arrangements as well as Trustmark’s consolidated financial statements through its effective date. ASU 2018-14, “Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans.” Issued in August 2018, ASU 2018-14 modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. The amendments in ASU 2018-14 remove certain disclosure requirements that are no longer considered cost beneficial, clarify the specific requirements of disclosures and add disclosure requirements identified as relevant. T he amendments of ASU 2018-14 become effective for fiscal years beginning after December 15, 2020. Trustmark plans to adopt these amendments during the first quarter of 2021. Management is currently assessing all the potential impacts of the amendments in ASU 2018-14 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-14 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement.” Issued in August 2018, the amendments in this ASU remove disclosure requirements in FASB ASC Topic 820 related to (1) the amount of, and reasons for, transfers between Level 1 and Level 2 of the fair value hierarchy; (2) the policy for timing of transfers between levels; (3) the valuation processes for Level 3 fair value measurements; and (4) for non-public entities, the changes in unrealized gains and losses for the period included in earnings for recurring Level 3 fair value measurements held at the end of the reporting period. The ASU also modifies disclosure requirements such that (1) in place of a rollforward for Level 3 fair value measurements, a non-public entity is required to disclose transfers into and out of Level 3 of the fair value hierarchy and purchases and issues of Level 3 assets and liabilities; (2) for investments in certain entities that calculate net asset value, an entity is required to disclose the timing of liquidation of an investee’s assets and the date that restrictions from redemption might lapse, only if the investee has communicated the timing to the entity or announced the timing publicly; and (3) it is clear that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. Additionally, this ASU adds disclosure requirements for public entities about (1) the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period, and (2) the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. The amendments of ASU 2018-13 are effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. Trustmark plans to adopt ASU 2018-13 during the first quarter of 2020. Management is currently assessing all the potential impacts of the amendments in ASU 2018-13 on Trustmark’s consolidated financial statements; however, the adoption of ASU 2018-13 is not expected to have a material impact on Trustmark’s consolidated financial statements. ASU 2017-12, “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 2017-08, “ 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 September 30, 2018, 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 2017-04, “ 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 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 intends to adopt the amendments of ASU 2016-13 during the first quarter of 2020. Trustmark selected a third-party vendor to provide allowance for loan loss software as well as advisory services in developing a new methodology that would be compliant with amendments of ASU 2016-13, and is working with the approved third-party vendor to develop the CECL model and evaluate the impact to Trustmark. Trustmark is working with the third-party vendor on developing various modeling techniques and methodologies, which Management will review to determine the most appropriate model for Trustmark. Trustmark is on schedule to fully comply with all CECL requirements within its internally established timeframe for implementation. Management will continue to evaluate the impact this ASU will have on Trustmark’s consolidated financial statements through its effective date. 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. In July 2018, the FASB issued ASU 2018-10, “Codification Improvements to Topic 842: Leases,” which provides corrections or improvements to a number of areas within Topic 842 and has the same transition guidance and effective date as ASU 2016-02. The FASB also issued ASU 2018-11, “Leases (Topic 842)-Targeted Improvements”, in July 2018, which provides entities with an additional and optional transition method to adopt the new lease standard and, for lessors only, a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease component. The amendments in ASU 2018-11 allow an entity the option to initially apply the new lease standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption as opposed to at the beginning of the earliest period presented in the financial statements. The amendments of ASU 2018-11 have the same effective date as ASU 2016-02. 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 materi

Business Combinations (Tables)

Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2018
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 identifiable assets acquired at fair value 11,316 Goodwill 13,471 Total consideration paid $ 24,787

Securities Available for Sale_2

Securities Available for Sale and Held to Maturity (Tables)	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017 ($ in thousands): Securities Available for Sale Securities Held to Maturity September 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. Government agency obligations $ 33,511 $ 126 $ (1,266 ) $ 32,371 $ 3,725 $ 26 $ — $ 3,751 Obligations of states and political subdivisions 57,127 201 (64 ) 57,264 42,623 173 (156 ) 42,640 Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 68,844 118 (3,115 ) 65,847 12,316 33 (389 ) 11,960 Issued by FNMA and FHLMC 713,673 125 (29,324 ) 684,474 119,040 3 (4,652 ) 114,391 Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 872,699 86 (32,712 ) 840,073 600,635 — (27,473 ) 573,162 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 189,248 154 (4,798 ) 184,604 165,544 41 (4,172 ) 161,413 Total $ 1,935,102 $ 810 $ (71,279 ) $ 1,864,633 $ 943,883 $ 276 $ (36,842 ) $ 907,317 December 31, 2017 U.S. Government agency obligations $ 45,763 $ 322 $ (800 ) $ 45,285 $ 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
Securities with Gross Unrealized Losses, Segregated by Length of Impairment	The tables below include securities with gross unrealized losses segregated by length of impairment at September 30, 2018 and December 31, 2017 ($ in thousands): Less than 12 Months 12 Months or More Total September 30, 2018 Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses U.S. Government agency obligations $ — $ — $ 26,421 $ (1,266 ) $ 26,421 $ (1,266 ) Obligations of states and political subdivisions 29,786 (179 ) 3,791 (41 ) 33,577 (220 ) Mortgage-backed securities Residential mortgage pass-through securities Guaranteed by GNMA 24,843 (677 ) 49,000 (2,827 ) 73,843 (3,504 ) Issued by FNMA and FHLMC 134,720 (3,928 ) 655,161 (30,048 ) 789,881 (33,976 ) Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 531,793 (14,120 ) 865,762 (46,065 ) 1,397,555 (60,185 ) Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 168,750 (3,334 ) 158,538 (5,636 ) 327,288 (8,970 ) Total $ 889,892 $ (22,238 ) $ 1,758,673 $ (85,883 ) $ 2,648,565 $ (108,121 ) December 31, 2017 U.S. Government agency obligations $ 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 )
Gains and Losses as a Result of Calls and Disposition of Securities	Gross realized gains or losses as a result of calls and dispositions of securities, as well as any associated proceeds, were as follows for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, Available for Sale 2018 2017 2018 2017 Proceeds from calls and sales of securities $ — $ 1,273 $ — $ 27,682 Gross realized gains — 15 — 16 Gross realized (losses) — (1 ) — (1 )
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 September 30, 2018, 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 Available for Sale Securities Held to Maturity Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Due in one year or less $ 25,525 $ 25,554 $ 170 $ 170 Due after one year through five years 37,426 37,661 41,912 41,934 Due after five years through ten years 3,124 3,054 4,266 4,287 Due after ten years 24,563 23,366 — — 90,638 89,635 46,348 46,391 Mortgage-backed securities 1,844,464 1,774,998 897,535 860,926 Total $ 1,935,102 $ 1,864,633 $ 943,883 $ 907,317

Loans Held for Investment (LH_2

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (Tables)	9 Months Ended
	Sep. 30, 2018
Accounts Notes Loans And Financing Receivable Gross Allowance And Net [Abstract]
Loan Portfolio Held for Investment	At September 30, 2018 and December 31, 2017, LHFI consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Loans secured by real estate: Construction, land development and other land $ 1,031,491 $ 987,624 Secured by 1-4 family residential properties 1,801,029 1,675,311 Secured by nonfarm, nonresidential properties 2,294,289 2,193,823 Other real estate secured 453,687 517,956 Commercial and industrial loans 1,565,922 1,570,345 Consumer loans 182,709 171,918 State and other political subdivision loans 929,178 952,483 Other loans 488,725 500,507 LHFI 8,747,030 8,569,967 Allowance for loan losses, LHFI (88,874 ) (76,733 ) Net LHFI $ 8,658,156 $ 8,493,234
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 September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Past Due 30-59 Days 60-89 Days 90 Days or (1) Total Nonaccrual Current Loans Total LHFI Loans secured by real estate: Construction, land development and other land $ 203 $ 5 $ — $ 208 $ 2,262 $ 1,029,021 $ 1,031,491 Secured by 1-4 family residential properties 5,626 1,304 447 7,377 15,164 1,778,488 1,801,029 Secured by nonfarm, nonresidential properties 256 280 — 536 5,389 2,288,364 2,294,289 Other real estate secured 5 — — 5 742 452,940 453,687 Commercial and industrial loans 1,727 9 21 1,757 33,870 1,530,295 1,565,922 Consumer loans 1,480 241 258 1,979 228 180,502 182,709 State and other political subdivision loans — — — — 8,762 920,416 929,178 Other loans 419 33 — 452 1,419 486,854 488,725 Total $ 9,716 $ 1,872 $ 726 $ 12,314 $ 67,836 $ 8,666,880 $ 8,747,030 (1) Past due 90 days or more but still accruing interest. December 31, 2017 Past Due 30-59 Days 60-89 Days 90 Days or (1) Total Nonaccrual Current Loans Total LHFI 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.
Impaired Financing Receivables	At September 30, 2018 and December 31, 2017, individually evaluated impaired LHFI consisted of the following ($ in thousands): September 30, 2018 LHFI Unpaid Principal Balance With No Related Allowance Recorded With an Allowance Recorded Total Carrying Amount Related Allowance Average Recorded Investment Loans secured by real estate: Construction, land development and other land $ 1,801 $ 1,546 $ 26 $ 1,572 $ — $ 1,747 Secured by 1-4 family residential properties 4,771 126 3,614 3,740 43 4,217 Secured by nonfarm, nonresidential properties 3,585 3,010 360 3,370 78 5,845 Other real estate secured — — — — — — Commercial and industrial loans 39,845 14,657 19,045 33,702 13,869 28,218 Consumer loans 3 — 3 3 — 6 State and other political subdivision loans 8,765 4,079 4,683 8,762 683 4,381 Other loans 1,432 230 1,076 1,306 1,076 816 Total $ 60,202 $ 23,648 $ 28,807 $ 52,455 $ 15,749 $ 45,230 December 31, 2017 LHFI Unpaid Principal Balance With No Related Allowance Recorded With an Allowance Recorded Total Carrying Amount Related Allowance Average Recorded 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
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): Three Months Ended September 30, 2018 2017 Troubled Debt Restructurings Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Loans secured by 1-4 family residential properties 3 $ 121 $ 121 1 $ 112 $ 113 Loans secured by nonfarm, nonresidential properties — — — 1 426 426 Commercial and industrial loans 9 11,153 10,062 6 12,500 12,500 Total 12 $ 11,274 $ 10,183 8 $ 13,038 $ 13,039 Nine Months Ended September 30, 2018 2017 Troubled Debt Restructurings Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Construction, land development and other land loans 1 $ 22 $ 22 1 $ 341 $ 325 Loans secured by 1-4 family residential properties 19 1,873 1,432 17 1,280 1,290 Loans secured by nonfarm, nonresidential properties — — — 1 426 426 Commercial and industrial loans 15 22,899 21,791 7 12,744 12,744 Consumer loans 3 4 4 — — — Total 38 $ 24,798 $ 23,249 26 $ 14,791 $ 14,785
Troubled Debt Restructuring Subsequently Defaulted	Nine Months Ended September 30, 2018 2017 TDRs that Subsequently Defaulted Number of Contracts Recorded Investment Number of Contracts Recorded Investment Construction, land development and other land loans 1 $ 21 — $ — Loans secured by 1-4 family residential properties 6 321 4 64 Commercial and industrial loans 6 13,985 2 — Total 13 $ 14,327 6 $ 64
Troubled Debt Restructuring Related to Loans Held for Investment by Loan Type	The following tables detail LHFI classified as TDRs by loan type at September 30, 2018 and 2017 ($ in thousands): September 30, 2018 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 26 $ 26 Secured by 1-4 family residential properties 563 3,052 3,615 Secured by nonfarm, nonresidential properties — 360 360 Commercial and industrial loans 1,783 29,636 31,419 Consumer loans — 3 3 Other loans — 540 540 Total TDRs $ 2,346 $ 33,617 $ 35,963 September 30, 2017 Accruing Nonaccrual Total Loans secured by real estate: Construction, land development and other land $ — $ 272 $ 272 Secured by 1-4 family residential properties 14 3,077 3,091 Secured by nonfarm, nonresidential properties 426 436 862 Commercial and industrial loans — 20,153 20,153 Consumer loans — 1 1 Total TDRs $ 440 $ 23,939 $ 24,379
Carrying Amount of Loans by Credit Quality Indicator	The tables below present LHFI by loan type and credit quality indicator at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Commercial LHFI Pass - Categories 1-6 Special Mention - Category 7 Substandard - Category 8 Doubtful - Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 961,316 $ 78 $ 4,512 $ 208 $ 966,114 Secured by 1-4 family residential properties 125,998 175 2,960 60 129,193 Secured by nonfarm, nonresidential properties 2,259,388 3,052 31,302 484 2,294,226 Other real estate secured 452,095 454 515 — 453,064 Commercial and industrial loans 1,490,431 9,721 63,936 1,834 1,565,922 Consumer loans — — — — — State and other political subdivision loans 913,286 5,250 10,642 — 929,178 Other loans 458,118 15,597 10,469 77 484,261 Total $ 6,660,632 $ 34,327 $ 124,336 $ 2,663 $ 6,821,958 Consumer LHFI Current Past Due 30-89 Days Past Due 90 Days or More Nonaccrual Subtotal Total LHFI Loans secured by real estate: Construction, land development and other land $ 65,028 $ 3 $ — $ 346 $ 65,377 $ 1,031,491 Secured by 1-4 family residential properties 1,651,019 6,566 447 13,804 1,671,836 1,801,029 Secured by nonfarm, nonresidential properties 63 — — — 63 2,294,289 Other real estate secured 623 — — — 623 453,687 Commercial and industrial loans — — — — — 1,565,922 Consumer loans 180,503 1,721 258 227 182,709 182,709 State and other political subdivision loans — — — — — 929,178 Other loans 4,464 — — — 4,464 488,725 Total $ 1,901,700 $ 8,290 $ 705 $ 14,377 $ 1,925,072 $ 8,747,030 December 31, 2017 Commercial LHFI Pass - Categories 1-6 Special Mention - Category 7 Substandard Category 8 Doubtful - 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 Current Past Due 30-89 Days Past Due 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
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 September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Individually Collectively Total Loans secured by real estate: Construction, land development and other land $ — $ 8,414 $ 8,414 Secured by 1-4 family residential properties 43 9,265 9,308 Secured by nonfarm, nonresidential properties 78 24,781 24,859 Other real estate secured — 2,949 2,949 Commercial and industrial loans 13,869 19,448 33,317 Consumer loans — 3,394 3,394 State and other political subdivision loans 683 510 1,193 Other loans 1,076 4,364 5,440 Total allowance for loan losses, LHFI $ 15,749 $ 73,125 $ 88,874 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 Changes in the allowance for loan losses, LHFI were as follows for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Balance at beginning of period $ 83,566 $ 76,184 $ 76,733 $ 71,265 Transfers (1) 772 — 1,554 — Loans charged-off (7,017 ) (2,752 ) (12,980 ) (9,072 ) Recoveries 2,880 3,228 7,766 8,784 Net (charge-offs) recoveries (4,137 ) 476 (5,214 ) (288 ) Provision for loan losses, LHFI 8,673 3,672 15,801 9,355 Balance at end of period $ 88,874 $ 80,332 $ 88,874 $ 80,332 (1) The allowance for loan losses balance related to the remaining loans acquired in the Bay Bank & Trust Company (Bay Bank) merger on March 16, 2012, which were transferred from acquired impaired loans to LHFI during the second quarter of 2018, and the remaining loans acquired in the Heritage Banking Group (Heritage) acquisition on April 15, 2011 and the Reliance merger on April 7, 2017, which were transferred from acquired impaired loans to LHFI during the third quarter of 2018. The following tables detail changes in the allowance for loan losses, LHFI by loan type for the periods ended September 30, 2018 and 2017 ($ in thousands): 2018 Balance January 1, Transfers (1) Charge-offs Recoveries Provision for Loan Losses Balance September 30, Loans secured by real estate: Construction, land development and other land $ 7,865 $ 584 $ (123 ) $ 1,039 $ (951 ) $ 8,414 Secured by 1-4 family residential properties 10,874 182 (1,435 ) 439 (752 ) 9,308 Secured by nonfarm, nonresidential properties 23,428 446 (1,117 ) 120 1,982 24,859 Other real estate secured 2,790 291 — 17 (149 ) 2,949 Commercial and industrial loans 22,851 46 (4,658 ) 2,285 12,793 33,317 Consumer loans 3,470 5 (1,585 ) 1,545 (41 ) 3,394 State and other political subdivision loans 789 — — — 404 1,193 Other loans 4,666 — (4,062 ) 2,321 2,515 5,440 Total allowance for loan losses, LHFI $ 76,733 $ 1,554 $ (12,980 ) $ 7,766 $ 15,801 $ 88,874 (1) The allowance for loan losses balance related to the remaining loans acquired in the Bay Bank merger on March 16, 2012, which were transferred from acquired impaired loans to LHFI during the second quarter of 2018, and the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017, which were transferred from acquired impaired loans to LHFI during the third quarter of 2018. 2017 Balance January 1, Charge-offs Recoveries Provision for Loan Losses Balance September 30, Loans secured by real estate: Construction, land development and other land loans $ 9,085 $ (79 ) $ 1,257 $ (1,615 ) $ 8,648 Secured by 1-4 family residential properties 10,347 (753 ) 1,429 (743 ) 10,280 Secured by nonfarm, nonresidential properties 20,967 (50 ) 289 7,542 28,748 Other real estate secured 2,263 — 31 1,111 3,405 Commercial and industrial loans 22,011 (2,624 ) 1,813 (1,420 ) 19,780 Consumer loans 3,241 (1,809 ) 1,427 1,597 4,456 State and other political subdivision loans 859 — — (48 ) 811 Other loans 2,492 (3,757 ) 2,538 2,931 4,204 Total allowance for loan losses, LHFI $ 71,265 $ (9,072 ) $ 8,784 $ 9,355 $ 80,332
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 September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 LHFI Evaluated for Impairment Individually Collectively Total Loans secured by real estate: Construction, land development and other land $ 1,572 $ 1,029,919 $ 1,031,491 Secured by 1-4 family residential properties 3,740 1,797,289 1,801,029 Secured by nonfarm, nonresidential properties 3,370 2,290,919 2,294,289 Other real estate secured — 453,687 453,687 Commercial and industrial loans 33,702 1,532,220 1,565,922 Consumer loans 3 182,706 182,709 State and other political subdivision loans 8,762 920,416 929,178 Other loans 1,306 487,419 488,725 Total $ 52,455 $ 8,694,575 $ 8,747,030 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

Acquired Loans (Tables)

Acquired Loans (Tables)	9 Months Ended
	Sep. 30, 2018
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities [Abstract]
Schedule of Acquired Loans	At September 30, 2018 and December 31, 2017, acquired loans consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Loans secured by real estate: Construction, land development and other land $ 6,657 $ 23,586 Secured by 1-4 family residential properties 25,274 61,751 Secured by nonfarm, nonresidential properties 66,865 114,694 Other real estate secured 8,507 16,746 Commercial and industrial loans 16,610 31,506 Consumer loans 1,514 2,600 Other loans 7,188 10,634 Acquired loans 132,615 261,517 Allowance for loan losses, acquired loans (1,714 ) (4,079 ) Net acquired loans $ 130,901 $ 257,438
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 Impaired Acquired Not ASC 310-30 (1) Carrying value, net at January 1, 2017 $ 218,107 $ 42,743 Transfers (2) — (36,719 ) Additions (3) 7,899 109,548 Accretion to interest income 14,924 1,578 Payments received, net (68,317 ) (39,208 ) Other (4) (361 ) (74 ) Change in allowance for loan losses, acquired loans 7,318 — Carrying value, net at December 31, 2017 179,570 77,868 Transfers (5)(2) (26,497 ) (43,922 ) Accretion to interest income 7,870 782 Payments received, net (50,940 ) (16,096 ) Other (4) (173 ) 74 Change in allowance for loan losses, acquired loans 2,365 — Carrying value, net at September 30, 2018 $ 112,195 $ 18,706 (1) “ (2) “Acquired Not ASC 310-30” (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. (5) During the second quarter of 2018, Trustmark transferred the remaining loans acquired in the Bay Bank merger on March 16, 2012 from acquired impaired loans to LHFI. During the third quarter of 2018, Trustmark transferred the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017 from acquired impaired loans to LHFI.
Changes in Accretable Yield of Acquired Loans	The following table presents changes in the accretable yield for the periods presented ($ in thousands): Nine Months Ended September 30, 2018 2017 Accretable yield at beginning of period $ (31,426 ) $ (38,918 ) Accretion to interest income 7,870 11,021 Additions due to acquisitions (1) — (784 ) Disposals, net 3,452 1,759 Transfers (2) 5,874 — Reclassification from nonaccretable difference (3) (4,204 ) (7,204 ) Accretable yield at end of period $ (18,434 ) $ (34,126 ) (1) Accretable yield on loans acquired from Reliance on April 7, 2017. (2) During the second quarter of 2018, Trustmark transferred the remaining loans acquired in the Bay Bank merger on March 16, 2012 from acquired impaired loans to LHFI. During the third quarter of 2018, Trustmark transferred the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017 from acquired impaired loans to LHFI. (3) 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 loans for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Balance at beginning of period $ 3,046 $ 7,423 $ 4,079 $ 11,397 Transfers (1) (772 ) — (1,554 ) — Net (charge-offs) recoveries (93 ) (2 ) (53 ) 193 Provision for loan losses, acquired loans (467 ) (1,653 ) (758 ) (5,822 ) Balance at end of period $ 1,714 $ 5,768 $ 1,714 $ 5,768 (1) The allowance for loan losses balance related to the remaining loans acquired in the Bay Bank merger, which were transferred from acquired impaired loans to LHFI during the second quarter of 2018, and the remaining loans acquired in the Heritage acquisition and the Reliance merger, which were transferred from acquired impaired loans to LHFI during the third quarter of 2018.
Acquired Loans by Loan Type and Credit Quality Indicator	The tables below present the acquired loans by loan type and credit quality indicator at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 Commercial Loans Pass - Categories 1-6 Special Mention - Category 7 Substandard - Category 8 Doubtful - Category 9 Subtotal Loans secured by real estate: Construction, land development and other land $ 5,541 $ 25 $ 296 $ 68 $ 5,930 Secured by 1-4 family residential properties 5,594 47 645 — 6,286 Secured by nonfarm, nonresidential properties 51,123 — 15,223 519 66,865 Other real estate secured 7,906 — 177 424 8,507 Commercial and industrial loans 7,366 — 6,832 2,412 16,610 Consumer loans — — — — — Other loans 4,536 — 2,652 — 7,188 Total acquired loans $ 82,066 $ 72 $ 25,825 $ 3,423 $ 111,386 Consumer Loans Current Past Due 30-89 Days Past Due 90 Days or More Nonaccrual (1) Subtotal Total Acquired Loans Loans secured by real estate: Construction, land development and other land $ 652 $ 75 $ — $ — $ 727 $ 6,657 Secured by 1-4 family residential properties 17,676 1,044 268 — 18,988 25,274 Secured by nonfarm, nonresidential properties — — — — — 66,865 Other real estate secured — — — — — 8,507 Commercial and industrial loans — — — — — 16,610 Consumer loans 1,473 41 — — 1,514 1,514 Other loans — — — — — 7,188 Total acquired loans $ 19,801 $ 1,160 $ 268 $ — $ 21,229 $ 132,615 (1) Acquired loans not accounted for under FASB ASC Topic 310-30. December 31, 2017 Commercial Loans Pass - Categories 1-6 Special Mention - Category 7 Substandard - Category 8 Doubtful - 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 Current Past Due 30-89 Days Past Due 90 Days or More Nonaccrual (1) Subtotal Total 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.
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 September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 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 $ 103 $ — $ 25 $ 128 $ — $ 6,529 $ 6,657 Secured by 1-4 family residential properties 703 341 288 1,332 — 23,942 25,274 Secured by nonfarm, nonresidential properties 297 — 1,475 1,772 — 65,093 66,865 Other real estate secured 15 — — 15 — 8,492 8,507 Commercial and industrial loans — — 607 607 — 16,003 16,610 Consumer loans 39 2 — 41 — 1,473 1,514 Other loans — — — — — 7,188 7,188 Total acquired loans $ 1,157 $ 343 $ 2,395 $ 3,895 $ — $ 128,720 $ 132,615 (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, 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.

Mortgage Banking (Tables)

Mortgage Banking (Tables)	9 Months Ended
	Sep. 30, 2018
Mortgage Banking [Abstract]
Schedule of Activity in the Mortgage Servicing Rights	The activity in the mortgage servicing rights (MSR) is detailed in the table below for the periods presented ($ in thousands): Nine Months Ended September 30, 2018 2017 Balance at beginning of period $ 84,269 $ 80,239 Origination of servicing assets 12,248 11,630 Change in fair value: Due to market changes 13,879 (2,218 ) Due to run-off (9,022 ) (8,174 ) Balance at end of period $ 101,374 $ 81,477
Schedule of Mortgage Loans Sold and Serviced for Others	The table below details the mortgage loans sold and serviced for others at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 December 31, 2017 Federal National Mortgage Association $ 4,174,961 $ 4,128,614 Government National Mortgage Association 2,492,009 2,421,456 Federal Home Loan Mortgage Corporation 69,617 47,071 Other 22,804 26,864 Total mortgage loans sold and serviced for others $ 6,759,391 $ 6,624,005
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): Nine Months Ended September 30, 2018 2017 Balance at beginning of period $ 1,000 $ 1,130 Provision for putback expenses — 164 Other (1) — 706 Balance at end of period $ 1,000 $ 2,000 (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.

Other Real Estate (Tables)

Other Real Estate (Tables)	9 Months Ended
	Sep. 30, 2018
Other Real Estate And Foreclosed Assets [Abstract]
Changes and Gains (Losses), Net on Other Real Estate	For the periods presented, changes and gains (losses), net on other real estate were as follows ($ in thousands): Nine Months Ended September 30, 2018 2017 Balance at beginning of period $ 43,228 $ 62,051 Additions (1) 10,368 7,481 Disposals (15,264 ) (18,583 ) Write-downs (1,857 ) (2,593 ) Balance at end of period $ 36,475 $ 48,356 Gains (losses), net on the sale of other real estate included in other real estate expense $ 1,226 $ 1,722 (1) Includes $475 thousand of other real estate acquired in the Reliance merger on April 7, 2017.
Other Real Estate, By Type of Property	At September 30, 2018 and December 31, 2017, other real estate by type of property consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Construction, land development and other land properties $ 18,976 $ 27,491 1-4 family residential properties 5,266 5,081 Nonfarm, nonresidential properties 12,050 10,468 Other real estate properties 183 188 Total other real estate $ 36,475 $ 43,228
Other Real Estate, By Geographic Location	At September 30, 2018 and December 31, 2017, other real estate by geographic location consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Alabama $ 7,526 $ 11,714 Florida 8,931 13,937 Mississippi (1) 18,191 14,260 Tennessee (2) 1,083 2,535 Texas 744 782 Total other real estate $ 36,475 $ 43,228 (1) Mississippi includes Central and Southern Mississippi Regions (2) Tennessee includes Memphis, Tennessee and Northern Mississippi Regions

Deposits (Tables)

Deposits (Tables)	9 Months Ended
	Sep. 30, 2018
Deposits [Abstract]
Deposits Summary	At September 30, 2018 and December 31, 2017, deposits consisted of the following ($ in thousands): September 30, 2018 December 31, 2017 Noninterest-bearing demand $ 2,786,539 $ 2,978,074 Interest-bearing demand 2,739,245 2,432,814 Savings 3,538,125 3,408,183 Time 1,893,001 1,758,441 Total $ 10,956,910 $ 10,577,512

Securities Sold Under Repurch_2

Securities Sold Under Repurchase Agreements (Tables)	9 Months Ended
	Sep. 30, 2018
Securities Sold Under Agreements To Repurchase [Abstract]
Schedule of Securities Sold Under Repurchase Agreements	The following table presents the securities sold under repurchase agreements by collateral pledged at September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 December 31, 2017 Mortgage-backed securities Other residential mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA $ 41,650 $ 68,246 Commercial mortgage-backed securities Issued or guaranteed by FNMA, FHLMC or GNMA 48,861 50,448 Total securities sold under repurchase agreements $ 90,511 $ 118,694

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue From Contract With Customer [Abstract]
Summary of Noninterest Income Disaggregated by Reportable Operating Segment and Revenue Stream	The following tables present noninterest income disaggregated by reportable operating segment and revenue stream for the periods presented ($ in thousands): Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 (1) Topic 606 Not Topic 606 (2) Total Topic 606 Not Topic 606 (2) Total General Banking Division Service charges on deposit accounts $ 11,074 $ — $ 11,074 $ 11,222 $ — $ 11,222 Bank card and other fees 6,503 937 7,440 7,104 23 7,127 Mortgage banking, net — 8,647 8,647 — 4,425 4,425 Wealth management 70 — 70 64 — 64 Other, net 1,685 (359 ) 1,326 1,495 2,223 3,718 Security gains (losses), net — — — — 14 14 Total noninterest income $ 19,332 $ 9,225 $ 28,557 $ 19,885 $ 6,685 $ 26,570 Wealth Management Division Service charges on deposit accounts $ 1 $ — $ 1 $ 1 $ — $ 1 Bank card and other fees 19 — 19 23 — 23 Wealth management 7,719 — 7,719 7,466 — 7,466 Other, net 1 29 30 — 22 22 Total noninterest income $ 7,740 $ 29 $ 7,769 $ 7,490 $ 22 $ 7,512 Insurance Division Insurance commissions $ 10,765 $ — $ 10,765 $ 10,398 $ — $ 10,398 Other, net 2 — 2 — — — Total noninterest income $ 10,767 $ — $ 10,767 $ 10,398 $ — $ 10,398 Consolidated Service charges on deposit accounts $ 11,075 $ — $ 11,075 $ 11,223 $ — $ 11,223 Bank card and other fees 6,522 937 7,459 7,127 23 7,150 Mortgage banking, net — 8,647 8,647 — 4,425 4,425 Insurance commissions 10,765 — 10,765 10,398 — 10,398 Wealth management 7,789 — 7,789 7,530 — 7,530 Other, net 1,688 (330 ) 1,358 1,495 2,245 3,740 Security gains (losses), net — — — — 14 14 Total noninterest income $ 37,839 $ 9,254 $ 47,093 $ 37,773 $ 6,707 $ 44,480 (1) Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may (2) Noninterest income not in scope for FASB ASC Topic 606 includes customer derivatives revenue and miscellaneous credit card fee income within bank card and other fees; mortgage banking, net; amortization of tax credits, accretion of the FDIC indemnification asset, cash surrender value on various life insurance policies, earnings on Trustmark’s non-qualified deferred compensation plans, other partnership investments and rental income within other, net; and security Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 (1) Topic 606 Not Topic 606 (2) Total Topic 606 Not Topic 606 (2) Total General Banking Division Service charges on deposit accounts $ 32,577 $ — $ 32,577 $ 32,809 $ — $ 32,809 Bank card and other fees 19,865 1,227 21,092 20,777 208 20,985 Mortgage banking, net — 28,958 28,958 — 23,618 23,618 Wealth management 210 — 210 210 — 210 Other, net 4,666 84 4,750 4,997 6,196 11,193 Security gains (losses), net — — — — 15 15 Total noninterest income $ 57,318 $ 30,269 $ 87,587 $ 58,793 $ 30,037 $ 88,830 Wealth Management Division Service charges on deposit accounts $ 2 $ — $ 2 $ 1 $ — $ 1 Bank card and other fees 63 — 63 35 — 35 Wealth management 22,624 — 22,624 22,407 — 22,407 Other, net 3 76 79 — 70 70 Total noninterest income $ 22,692 $ 76 $ 22,768 $ 22,443 $ 70 $ 22,513 Insurance Division Insurance commissions $ 30,919 $ — $ 30,919 $ 29,355 $ — $ 29,355 Other, net 3 — 3 5 — 5 Total noninterest income $ 30,922 $ — $ 30,922 $ 29,360 $ — $ 29,360 Consolidated Service charges on deposit accounts $ 32,579 $ — $ 32,579 $ 32,810 $ — $ 32,810 Bank card and other fees 19,928 1,227 21,155 20,812 208 21,020 Mortgage banking, net — 28,958 28,958 — 23,618 23,618 Insurance commissions 30,919 — 30,919 29,355 — 29,355 Wealth management 22,834 — 22,834 22,617 — 22,617 Other, net 4,672 160 4,832 5,002 6,266 11,268 Security gains (losses), net — — — — 15 15 Total noninterest income $ 110,932 $ 30,345 $ 141,277 $ 110,596 $ 30,107 $ 140,703 (1) Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may (2) Noninterest income not in scope for FASB ASC Topic 606 includes customer derivatives revenue and miscellaneous credit card fee income within bank card and other fees; mortgage banking, net; amortization of tax credits, accretion of the FDIC indemnification asset, cash surrender value on various life insurance policies, earnings on Trustmark’s non-qualified deferred compensation plans, other partnership investments and rental income within other, net; and security

Defined Benefit and Other Pos_2

Defined Benefit and Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2018
Trustmark Capital Accumulation Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Benefit Cost for Plan and Continuing Plan	The following table presents information regarding the net periodic benefit cost for the Plan and the Continuing Plan for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost $ 69 $ 64 $ 208 $ 190 Interest cost 83 102 249 1,394 Expected return on plan assets (57 ) (51 ) (171 ) (267 ) Recognized net loss due to lump sum settlements 41 — 121 — Recognized net loss due to defined benefit plan termination — — — 17,644 Recognized net actuarial loss 143 142 428 1,272 Net periodic benefit cost $ 279 $ 257 $ 835 $ 20,233
Supplemental Retirement Plan [Member]
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Benefit Cost for Plan and Continuing Plan	The following table presents information regarding the net periodic benefit cost for Trustmark’s nonqualified supplemental retirement plans for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Service cost $ 29 $ 36 $ 87 $ 106 Interest cost 457 514 1,409 1,589 Amortization of prior service cost 63 63 188 188 Recognized net actuarial loss 218 214 664 651 Net periodic benefit cost $ 767 $ 827 $ 2,348 $ 2,534

Stock and Incentive Compensat_2

Stock and Incentive Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Plan Activity	The following tables summarize the Stock Plan activity for the periods presented: Three Months Ended September 30, 2018 Performance Awards Time-Vested Awards Nonvested shares, beginning of period 177,695 322,528 Granted — 1,500 Released from restriction — (400 ) Forfeited — (764 ) Nonvested shares, end of period 177,695 322,864 Nine Months Ended September 30, 2018 Performance Awards Time-Vested Awards Nonvested shares, beginning of period 213,516 320,357 Granted 51,174 118,325 Released from restriction (55,351 ) (107,180 ) Forfeited (31,644 ) (8,638 ) Nonvested shares, end of period 177,695 322,864
Compensation Expense for Awards Under Stock Plan	The following table presents information regarding compensation expense for awards under the Stock Plan for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Performance awards $ 435 $ 435 $ 725 $ 959 Time-vested awards 723 641 2,297 2,291 Total compensation expense $ 1,158 $ 1,076 $ 3,022 $ 3,250

Earnings Per Share (EPS) (Table

Earnings Per Share (EPS) (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
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): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Basic shares 67,621 67,742 67,729 67,722 Dilutive shares 175 174 147 154 Diluted shares 67,796 67,916 67,876 67,876
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): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Weighted-average antidilutive stock awards 8 6 87 72

Statements of Cash Flows (Table

Statements of Cash Flows (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Cash Flows Supplementary Disclosures	The following table reflects specific transaction amounts for the periods presented ($ in thousands): Nine Months Ended September 30, 2018 2017 Income taxes paid $ 11,629 $ 1,423 Interest expense paid on deposits and borrowings 46,506 28,266 Noncash transfers from loans to other real estate 10,368 7,006 Transfer of long-term FHLB advances to short-term — 250,038 Assets acquired in business combination — 196,265 Liabilities acquired in business combination — 184,949

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Stockholders Equity Note [Abstract]
Table of Actual Regulatory Capital Amounts and Ratios	The following table provides Trustmark’s and TNB’s actual regulatory capital amounts and ratios under regulatory capital standards in effect at September 30, 2018 and December 31, 2017 ($ in thousands): Actual Regulatory Capital Minimum To Be Well Amount Ratio Requirement Capitalized At September 30, 2018: Common Equity Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,302,859 12.20 % 6.375 % n/a Trustmark National Bank 1,344,029 12.59 % 6.375 % 6.50 % Tier 1 Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,362,859 12.76 % 7.875 % n/a Trustmark National Bank 1,344,029 12.59 % 7.875 % 8.00 % Total Capital (to Risk Weighted Assets) Trustmark Corporation $ 1,453,447 13.61 % 9.875 % n/a Trustmark National Bank 1,434,617 13.44 % 9.875 % 10.00 % Tier 1 Leverage (to Average Assets) Trustmark Corporation $ 1,362,859 10.41 % 4.00 % n/a Trustmark National Bank 1,344,029 10.29 % 4.00 % 5.00 % 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 %
Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects	Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Securities available for sale and transferred securities: Net unrealized holding gains (losses) arising during the period $ (9,660 ) $ 2,414 $ (7,246 ) $ (535 ) $ 204 $ (331 ) Reclassification adjustment for net (gains) losses realized in net income — — — (14 ) 6 (8 ) Change in net unrealized holding loss on securities transferred to held to maturity 973 (243 ) 730 1,130 (432 ) 698 Total securities available for sale and transferred securities (8,687 ) 2,171 (6,516 ) 581 (222 ) 359 Pension and other postretirement benefit plans: Net change in prior service costs 63 (16 ) 47 63 (24 ) 39 Recognized net loss due to lump sum settlements 41 (10 ) 31 — — — Change in net actuarial loss 361 (90 ) 271 356 (137 ) 219 Total pension and other postretirement benefit plans 465 (116 ) 349 419 (161 ) 258 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives 52 (13 ) 39 53 (20 ) 33 Reclassification adjustment for (gain) loss realized in net income (104 ) 25 (79 ) 55 (21 ) 34 Total cash flow hedge derivatives (52 ) 12 (40 ) 108 (41 ) 67 Total other comprehensive income (loss) $ (8,274 ) $ 2,067 $ (6,207 ) $ 1,108 $ (424 ) $ 684 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Before Tax Amount Tax (Expense) Benefit Net of Tax Amount Securities available for sale and transferred securities: Net unrealized holding gains (losses) arising during the period $ (46,974 ) $ 11,743 $ (35,231 ) $ 6,335 $ (2,423 ) $ 3,912 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 2,909 (727 ) 2,182 3,551 (1,358 ) 2,193 Total securities available for sale and transferred securities (44,065 ) 11,016 (33,049 ) 9,871 (3,775 ) 6,096 Pension and other postretirement benefit plans: Net change in prior service costs 188 (48 ) 140 188 (72 ) 116 Recognized net loss due to lump sum settlements 121 (29 ) 92 — — — Change in net actuarial loss 1,092 (273 ) 819 1,923 (736 ) 1,187 Recognized net loss due to defined benefit plan termination — — — 16,991 (6,499 ) 10,492 Total pension and other postretirement benefit plans 1,401 (350 ) 1,051 19,102 (7,307 ) 11,795 Cash flow hedge derivatives: Change in accumulated gain (loss) on effective cash flow hedge derivatives 611 (153 ) 458 (99 ) 38 (61 ) Reclassification adjustment for (gain) loss realized in net income (209 ) 52 (157 ) 232 (89 ) 143 Total cash flow hedge derivatives 402 (101 ) 301 133 (51 ) 82 Total other comprehensive income (loss) $ (42,262 ) $ 10,565 $ (31,697 ) $ 29,106 $ (11,133 ) $ 17,973
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 Transferred Securities Defined Benefit Pension Items Cash Flow Hedge Derivatives Total Balance at January 1, 2018 $ (26,535 ) $ (13,468 ) $ 278 $ (39,725 ) Other comprehensive income (loss) before reclassification (33,049 ) — 458 (32,591 ) Amounts reclassified from accumulated other comprehensive loss — 1,051 (157 ) 894 Net other comprehensive income (loss) (33,049 ) 1,051 301 (31,697 ) Reclassification of certain income tax effects related to the change in the federal statutory income tax rate under the Tax Cuts and Jobs Act of 2017 (Tax Reform Act) (5,694 ) (2,890 ) 60 (8,524 ) Balance at September 30, 2018 $ (65,278 ) $ (15,307 ) $ 639 $ (79,946 ) Balance at January 1, 2017 $ (20,800 ) $ (24,980 ) $ (18 ) $ (45,798 ) Other comprehensive income (loss) before reclassification 6,105 — (61 ) 6,044 Amounts reclassified from accumulated other comprehensive loss (9 ) 11,795 143 11,929 Net other comprehensive income (loss) 6,096 11,795 82 17,973 Balance at September 30, 2017 $ (14,704 ) $ (13,185 ) $ 64 $ (27,825 )

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017, 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 nine months ended September 30, 2018 and the year ended December 31, 2017. September 30, 2018 Total Level 1 Level 2 Level 3 U.S. Government agency obligations $ 32,371 $ — $ 32,371 $ — Obligations of states and political subdivisions 57,264 — 57,264 — Mortgage-backed securities 1,774,998 — 1,774,998 — Securities available for sale 1,864,633 — 1,864,633 — Loans held for sale 182,664 — 182,664 — Mortgage servicing rights 101,374 — — 101,374 Other assets - derivatives 3,287 (1,531 ) 3,925 893 Other liabilities - derivatives 4,311 1,070 3,241 — 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 —
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 nine months ended September 30, 2018 and 2017 are summarized as follows ($ in thousands): MSR Other Assets - Derivatives Balance, January 1, 2018 $ 84,269 $ 900 Total net (loss) gain included in Mortgage banking, net (1) 4,857 3,345 Additions 12,248 — Sales — (3,352 ) Balance, September 30, 2018 $ 101,374 $ 893 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 September 30, 2018 $ 13,879 $ 247 Balance, January 1, 2017 $ 80,239 $ 1,001 Total net (loss) gain included in Mortgage banking, net (1) (10,392 ) 3,436 Additions 11,630 — Sales — (3,431 ) Balance, September 30, 2017 $ 81,477 $ 1,006 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 September 30, 2017 $ (2,218 ) $ (1,483 ) (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 September 30, 2018 and December 31, 2017, are as follows ($ in thousands): September 30, 2018 December 31, 2017 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Financial Assets: Level 2 Inputs: Cash and short-term investments $ 433,471 $ 433,471 $ 336,383 $ 336,383 Securities held to maturity 943,883 907,317 1,056,486 1,046,247 Level 3 Inputs: Net LHFI 8,658,156 8,560,091 8,493,234 8,507,469 Net acquired loans 130,901 130,901 257,438 257,438 Financial Liabilities: Level 2 Inputs: Deposits 10,956,910 10,953,348 10,577,512 10,577,858 Short-term liabilities 676,888 676,888 1,440,876 1,440,876 Long-term FHLB advances 896 831 946 946 Junior subordinated debt securities 61,856 53,815 61,856 45,773
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 September 30, 2018 and December 31, 2017 ($ in thousands): September 30, 2018 December 31, 2017 Fair value of LHFS $ 134,874 $ 132,300 LHFS contractual principal outstanding 134,598 129,347 Fair value less unpaid principal $ 276 $ 2,953

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
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 consolidated balance sheets as of September 30, 2018 and December 31, 2017 as well as the effect of these derivative instruments on Trustmark’s results of operations for the periods presented ($ in thousands): September 30, 2018 December 31, 2017 Derivatives in hedging relationships Interest rate contracts: Interest rate swaps included in other assets $ 852 $ 451 Derivatives not designated as hedging instruments Interest rate contracts: Futures contracts included in other assets $ (1,569 ) $ (1,088 ) Exchange traded purchased options included in other assets 38 75 OTC written options (rate locks) included in other assets 893 900 Interest rate swaps included in other assets 3,073 1,175 Credit risk participation agreements included in other assets — 3 Forward contracts included in other liabilities (930 ) 237 Exchange traded written options included in other liabilities 1,070 616 Interest rate swaps included in other liabilities 4,170 1,819 Credit risk participation agreements included in other liabilities 1 6
Effects of Derivative Instruments on Statements of Operations	Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Derivatives in hedging relationships Amount of gain (loss) reclassified from accumulated other comprehensive loss and recognized in other interest expense $ 104 $ (55 ) $ 209 $ (232 ) Derivatives not designated as hedging instruments Amount of gain (loss) recognized in mortgage banking, net $ (1,302 ) $ (466 ) $ (9,243 ) $ 688 Amount of gain (loss) recognized in bank card and other fees (86 ) (10 ) (41 ) (63 )
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): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Derivatives in cash flow hedging relationship Amount of gain (loss) recognized in other comprehensive income (loss), net of tax $ 39 $ 33 $ 458 $ (61 )
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 September 30, 2018 and December 31, 2017 is presented in the following tables ($ in thousands): Offsetting of Derivative Assets As of September 30, 2018 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 the Statement of Financial Position Financial Instruments Cash Collateral Received Net Amount Derivatives $ 3,925 $ — $ 3,925 $ (84 ) $ (950 ) $ 2,891 Offsetting of Derivative Liabilities As of September 30, 2018 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 $ 4,170 $ — $ 4,170 $ (84 ) $ — $ 4,086 Offsetting of Derivative Assets As of December 31, 2017 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 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

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Segment Information	The following table discloses financial information by reportable segment for the periods presented ($ in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 General Banking Net interest income $ 106,784 $ 103,408 $ 313,299 $ 302,613 Provision for loan losses, net 8,206 2,019 15,043 3,533 Noninterest income 28,557 26,570 87,587 88,830 Noninterest expense 89,889 88,814 267,462 284,420 Income before income taxes 37,246 39,145 118,381 103,490 Income taxes 3,536 7,130 13,430 19,772 General banking net income $ 33,710 $ 32,015 $ 104,951 $ 83,718 Selected Financial Information Total assets $ 13,364,636 $ 13,811,335 $ 13,364,636 $ 13,811,335 Depreciation and amortization $ 9,759 $ 9,863 $ 28,959 $ 28,196 Wealth Management Net interest income $ 134 $ 434 $ 771 $ 718 Noninterest income 7,769 7,512 22,768 22,513 Noninterest expense 7,194 6,791 19,996 20,361 Income before income taxes 709 1,155 3,543 2,870 Income taxes 177 441 886 1,098 Wealth management net income $ 532 $ 714 $ 2,657 $ 1,772 Selected Financial Information Total assets $ 9,411 $ 6,635 $ 9,411 $ 6,635 Depreciation and amortization $ 64 $ 30 $ 116 $ 104 Insurance Net interest income $ 65 $ 70 $ 170 $ 175 Noninterest income 10,767 10,398 30,922 29,360 Noninterest expense 8,140 7,481 24,030 22,437 Income before income taxes 2,692 2,987 7,062 7,098 Income taxes 681 1,137 1,774 2,726 Insurance net income $ 2,011 $ 1,850 $ 5,288 $ 4,372 Selected Financial Information Total assets $ 65,765 $ 66,685 $ 65,765 $ 66,685 Depreciation and amortization $ 155 $ 159 $ 437 $ 481 Consolidated Net interest income $ 106,983 $ 103,912 $ 314,240 $ 303,506 Provision for loan losses, net 8,206 2,019 15,043 3,533 Noninterest income 47,093 44,480 141,277 140,703 Noninterest expense 105,223 103,086 311,488 327,218 Income before income taxes 40,647 43,287 128,986 113,458 Income taxes 4,394 8,708 16,090 23,596 Consolidated net income $ 36,253 $ 34,579 $ 112,896 $ 89,862 Selected Financial Information Total assets $ 13,439,812 $ 13,884,655 $ 13,439,812 $ 13,884,655 Depreciation and amortization $ 9,978 $ 10,052 $ 29,512 $ 28,781

Business, Basis of Financial _2

Business, Basis of Financial Statement Presentation and Principles of Consolidation (Details) $ in Millions	Oct. 10, 2018USD ($)LoanCounty	Sep. 30, 2018Office
Loans And Leases Receivable Disclosure [Line Items]
Number of offices | Office		198
Subsequent Events [Member]
Loans And Leases Receivable Disclosure [Line Items]
Number of loans held by Trustmark | Loan	1,787
Balance of outstanding loans | $	$ 239.7
Credit exposure of loans in FEMA designated disaster areas | $	$ 282.1
Florida [Member] | Subsequent Events [Member]
Loans And Leases Receivable Disclosure [Line Items]
Number of designated disaster area | County	12
Georgia [Member] | Subsequent Events [Member]
Loans And Leases Receivable Disclosure [Line Items]
Number of designated disaster area | County	20

Business Combinations - Additio

Business Combinations - Additional Information (Details) $ / shares in Units, $ in Thousands	Apr. 07, 2017USD ($)Office	Jun. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Dec. 31, 2017USD ($)	Nov. 14, 2016$ / shares
Business Acquisition [Line Items]
Goodwill			$ 379,627	$ 379,627
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
Goodwill	$ 13,471
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	Sep. 30, 2018	Dec. 31, 2017	Apr. 07, 2017
Liabilities:
Goodwill	$ 379,627	$ 379,627
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 identifiable assets acquired at fair value			11,316
Goodwill			13,471
Total consideration paid			$ 24,787

Securities Available for Sale_3

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	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	$ 1,935,102	$ 2,262,130
Securities Available for Sale, Gross Unrealized Gains	810	4,448
Securities Available for Sale, Gross Unrealized (Losses)	(71,279)	(27,943)
Securities Available for Sale, Estimated Fair Value	1,864,633	2,238,635
Securities Held to Maturity, Amortized Cost	943,883	1,056,486
Securities Held to Maturity, Gross Unrealized Gains	276	3,954
Securities Held to Maturity, Gross Unrealized (Losses)	(36,842)	(14,193)
Securities Held to Maturity, Estimated Fair Value	907,317	1,046,247
U.S. Government Agency Obligations [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	33,511	45,763
Securities Available for Sale, Gross Unrealized Gains	126	322
Securities Available for Sale, Gross Unrealized (Losses)	(1,266)	(800)
Securities Available for Sale, Estimated Fair Value	32,371	45,285
Securities Held to Maturity, Amortized Cost	3,725	3,692
Securities Held to Maturity, Gross Unrealized Gains	26	182
Securities Held to Maturity, Gross Unrealized (Losses)	0	0
Securities Held to Maturity, Estimated Fair Value	3,751	3,874
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	57,127	78,433
Securities Available for Sale, Gross Unrealized Gains	201	850
Securities Available for Sale, Gross Unrealized (Losses)	(64)	(54)
Securities Available for Sale, Estimated Fair Value	57,264	79,229
Securities Held to Maturity, Amortized Cost	42,623	46,039
Securities Held to Maturity, Gross Unrealized Gains	173	1,044
Securities Held to Maturity, Gross Unrealized (Losses)	(156)	(59)
Securities Held to Maturity, Estimated Fair Value	42,640	47,024
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	68,844	66,634
Securities Available for Sale, Gross Unrealized Gains	118	215
Securities Available for Sale, Gross Unrealized (Losses)	(3,115)	(1,103)
Securities Available for Sale, Estimated Fair Value	65,847	65,746
Securities Held to Maturity, Amortized Cost	12,316	13,539
Securities Held to Maturity, Gross Unrealized Gains	33	207
Securities Held to Maturity, Gross Unrealized (Losses)	(389)	(73)
Securities Held to Maturity, Estimated Fair Value	11,960	13,673
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	713,673	824,872
Securities Available for Sale, Gross Unrealized Gains	125	827
Securities Available for Sale, Gross Unrealized (Losses)	(29,324)	(11,249)
Securities Available for Sale, Estimated Fair Value	684,474	814,450
Securities Held to Maturity, Amortized Cost	119,040	133,975
Securities Held to Maturity, Gross Unrealized Gains	3	210
Securities Held to Maturity, Gross Unrealized (Losses)	(4,652)	(1,559)
Securities Held to Maturity, Estimated Fair Value	114,391	132,626
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	872,699	1,028,176
Securities Available for Sale, Gross Unrealized Gains	86	1,808
Securities Available for Sale, Gross Unrealized (Losses)	(32,712)	(13,194)
Securities Available for Sale, Estimated Fair Value	840,073	1,016,790
Securities Held to Maturity, Amortized Cost	600,635	678,926
Securities Held to Maturity, Gross Unrealized Gains	0	1,209
Securities Held to Maturity, Gross Unrealized (Losses)	(27,473)	(11,065)
Securities Held to Maturity, Estimated Fair Value	573,162	669,070
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	189,248	218,252
Securities Available for Sale, Gross Unrealized Gains	154	426
Securities Available for Sale, Gross Unrealized (Losses)	(4,798)	(1,543)
Securities Available for Sale, Estimated Fair Value	184,604	217,135
Securities Held to Maturity, Amortized Cost	165,544	180,315
Securities Held to Maturity, Gross Unrealized Gains	41	1,102
Securities Held to Maturity, Gross Unrealized (Losses)	(4,172)	(1,437)
Securities Held to Maturity, Estimated Fair Value	$ 161,413	$ 179,980

Securities Available for Sale_4

Securities Available for Sale and Held to Maturity - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	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	$ 16,600,000
Net unamortized, unrealized loss on transfer of securities, net of tax	12,400,000
Other-than-temporary impairments	0	$ 0
Pledged to collateralize public deposits and securities sold under repurchase agreements and for other purposes as permitted by law	2,092,000,000		$ 1,834,000,000
Pledged securities providing additional contingency funding	$ 0		$ 0

Securities Available for Sale_5

Securities Available for Sale and Held to Maturity - Securities with Gross Unrealized Losses, Segregated by Length of Impairment (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	$ 889,892	$ 1,554,184
Estimated Fair Value, 12 Months or More	1,758,673	1,022,055
Estimated Fair Value, Total	2,648,565	2,576,239
Gross Unrealized (Losses), Less than 12 Months	(22,238)	(14,150)
Gross Unrealized (Losses), 12 Months or More	(85,883)	(27,986)
Gross Unrealized (Losses), Total	(108,121)	(42,136)
U.S. Government Agency Obligations [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Estimated Fair Value, Less than 12 Months	0	5,214
Estimated Fair Value, 12 Months or More	26,421	29,432
Estimated Fair Value, Total	26,421	34,646
Gross Unrealized (Losses), Less than 12 Months	0	(113)
Gross Unrealized (Losses), 12 Months or More	(1,266)	(687)
Gross Unrealized (Losses), Total	(1,266)	(800)
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	29,786	19,345
Estimated Fair Value, 12 Months or More	3,791	3,874
Estimated Fair Value, Total	33,577	23,219
Gross Unrealized (Losses), Less than 12 Months	(179)	(80)
Gross Unrealized (Losses), 12 Months or More	(41)	(33)
Gross Unrealized (Losses), Total	(220)	(113)
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	24,843	37,304
Estimated Fair Value, 12 Months or More	49,000	29,446
Estimated Fair Value, Total	73,843	66,750
Gross Unrealized (Losses), Less than 12 Months	(677)	(351)
Gross Unrealized (Losses), 12 Months or More	(2,827)	(825)
Gross Unrealized (Losses), Total	(3,504)	(1,176)
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	134,720	506,410
Estimated Fair Value, 12 Months or More	655,161	369,060
Estimated Fair Value, Total	789,881	875,470
Gross Unrealized (Losses), Less than 12 Months	(3,928)	(4,219)
Gross Unrealized (Losses), 12 Months or More	(30,048)	(8,589)
Gross Unrealized (Losses), Total	(33,976)	(12,808)
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	531,793	755,013
Estimated Fair Value, 12 Months or More	865,762	534,955
Estimated Fair Value, Total	1,397,555	1,289,968
Gross Unrealized (Losses), Less than 12 Months	(14,120)	(7,668)
Gross Unrealized (Losses), 12 Months or More	(46,065)	(16,591)
Gross Unrealized (Losses), Total	(60,185)	(24,259)
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	168,750	230,898
Estimated Fair Value, 12 Months or More	158,538	55,288
Estimated Fair Value, Total	327,288	286,186
Gross Unrealized (Losses), Less than 12 Months	(3,334)	(1,719)
Gross Unrealized (Losses), 12 Months or More	(5,636)	(1,261)
Gross Unrealized (Losses), Total	$ (8,970)	$ (2,980)

Securities Available for Sale_6

Securities Available for Sale and Held to Maturity - Gains and Losses as a Result of Calls and Disposition of Securities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Gain Loss On Investments [Abstract]
Proceeds from calls and sales of securities	$ 0	$ 1,273	$ 0	$ 27,682
Gross realized gains	0	15	0	16
Gross realized (losses)	$ 0	$ (1)	$ 0	$ (1)

Securities Available for Sale_7

Securities Available for Sale and Held to Maturity - Contractual Maturities of Available for Sale and Held to Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities Available for Sale, Amortized Cost [Abstract]
Due in one year or less	$ 25,525
Due after one year through five years	37,426
Due after five years through ten years	3,124
Due after ten years	24,563
Total amortized cost, before mortgage-backed securities	90,638
Mortgage-backed securities	1,844,464
Total	1,935,102
Securities Available for Sale, Estimated Fair Value [Abstract]
Due in one year or less	25,554
Due after one year through five years	37,661
Due after five years through ten years	3,054
Due after ten years	23,366
Total fair value, before mortgage-backed securities	89,635
Mortgage-backed securities	1,774,998
Total	1,864,633	$ 2,238,635
Securities Held to Maturity, Amortized Cost [Abstract]
Due in one year or less	170
Due after one year through five years	41,912
Due after five years through ten years	4,266
Due after ten years	0
Total amortized cost, before mortgage-backed securities	46,348
Mortgage-backed securities	897,535
Securities Held to Maturity, Amortized Cost	943,883	1,056,486
Securities Held to Maturity, Estimated Fair Value [Abstract]
Due in one year or less	170
Due after one year through five years	41,934
Due after five years through ten years	4,287
Due after ten years	0
Total fair value, before mortgage-backed securities	46,391
Mortgage-backed securities	860,926
Total	$ 907,317	$ 1,046,247

Loans Held for Investment (LH_3

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Loan Portfolio Held for Investment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Loan Portfolio [Abstract]
Total LHFI	$ 8,747,030	$ 8,569,967
Allowance for loan losses, LHFI	(88,874)	(76,733)
Net LHFI	8,658,156	8,493,234
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	1,031,491	987,624
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	1,801,029	1,675,311
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	453,687	517,956
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	2,294,289	2,193,823
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,565,922	1,570,345
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	182,709	171,918
State and Other Political Subdivision Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	929,178	952,483
Other Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	$ 488,725	$ 500,507

Loans Held for Investment (LH_4

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Additional Information (Details 1)	9 Months Ended
	Sep. 30, 2018USD ($)Region	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Financing Receivable Impaired [Line Items]
Maximum concentration of loan as a percentage of total LHFI	10.00%
Key market regions | Region	5
Carrying amounts of nonaccrual LHFI considered for impairment analysis	$ 67,800,000		$ 67,600,000
Nonaccrual	67,836,000		67,575,000
Minimum loan amount for loan to be specifically reviewed for impairment and deemed impaired	500,000
Amount held by company of foreclosure or in substance repossession of consumer mortgage LHFI classified as TDRs	203,000		366,000
TDRs Classified as Consumer mortgage LHFI in the process of formal disclosure	55,000		0
LHFI Classified as TDRs	36,000,000	$ 24,400,000
LHFI classified as TDRs from credits with interest only payments	24,700,000	21,100,000
Unused Commitments on Troubled Debt Restructurings	7,700,000	0
Financing receivable, related allowance	14,300,000	393,000
Financing receivable, related charge-offs	4,700,000	126,000
Troubled Debt Restructurings [Member]
Financing Receivable Impaired [Line Items]
Nonaccrual	$ 33,617,000	$ 23,939,000	$ 23,200,000

Loans Held for Investment (LH_5

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Aging Analysis of Past Due and Nonaccrual LHFI by Loan Type (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		$ 12,314	$ 18,433
Nonaccrual		67,836	67,575
Current Loans		8,666,880	8,483,959
Total LHFI		8,747,030	8,569,967
Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		9,716	12,390
Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,872	3,872
Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[1]	726	2,171
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		208	392
Nonaccrual		2,262	2,105
Current Loans		1,029,021	985,127
Total LHFI		1,031,491	987,624
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		203	391
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		5	1
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		7,377	10,413
Nonaccrual		15,164	19,022
Current Loans		1,778,488	1,645,876
Total LHFI		1,801,029	1,675,311
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		5,626	6,412
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		1,304	2,084
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	[1]	447	1,917
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		536	2,575
Nonaccrual		5,389	12,608
Current Loans		2,288,364	2,178,640
Total LHFI		2,294,289	2,193,823
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		256	2,319
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		280	256
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		5
Nonaccrual		742	212
Current Loans		452,940	517,744
Total LHFI		453,687	517,956
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		5
Commercial and Industrial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,757	2,004
Nonaccrual		33,870	33,338
Current Loans		1,530,295	1,535,003
Total LHFI		1,565,922	1,570,345
Commercial and Industrial Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,727	759
Commercial and Industrial Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		9	1,233
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[1]	21	12
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,979	2,638
Nonaccrual		228	135
Current Loans		180,502	169,145
Total LHFI		182,709	171,918
Consumer Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		1,480	2,141
Consumer Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		241	255
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due	[1]	258	242
State and Other Political Subdivision Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due			389
Nonaccrual		8,762
Current Loans		920,416	952,094
Total LHFI		929,178	952,483
State and Other Political Subdivision Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due			350
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		452	22
Nonaccrual		1,419	155
Current Loans		486,854	500,330
Total LHFI		488,725	500,507
Other Loans [Member] | Past Due 30 to 59 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		419	18
Other Loans [Member] | Past Due 60 to 89 Days [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Past Due		$ 33	$ 4
[1]	Past due 90 days or more but still accruing interest.

Loans Held for Investment (LH_6

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Impaired Financing Receivables (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	$ 60,202	$ 60,387
Total LHFI With No Related Allowance Recorded	23,648	42,674
Total LHFI With an Allowance Recorded	28,807	6,262
Total LHFI Carrying Amount	52,455	48,936
Related Allowance	15,749	1,743
Average Recorded Investment	45,230	38,005
Commercial and Industrial Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	39,845	36,874
Total LHFI With No Related Allowance Recorded	14,657	31,281
Total LHFI With an Allowance Recorded	19,045	518
Total LHFI Carrying Amount	33,702	31,799
Related Allowance	13,869	131
Average Recorded Investment	28,218	22,734
Consumer Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	3	17
Total LHFI With No Related Allowance Recorded	0	0
Total LHFI With an Allowance Recorded	3	17
Total LHFI Carrying Amount	3	17
Related Allowance	0	0
Average Recorded Investment	6	9
State and Other Political Subdivision Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	8,765	0
Total LHFI With No Related Allowance Recorded	4,079	0
Total LHFI With an Allowance Recorded	4,683	0
Total LHFI Carrying Amount	8,762	0
Related Allowance	683	0
Average Recorded Investment	4,381	0
Other Loans [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	1,432	556
Total LHFI With No Related Allowance Recorded	230	0
Total LHFI With an Allowance Recorded	1,076	556
Total LHFI Carrying Amount	1,306	556
Related Allowance	1,076	41
Average Recorded Investment	816	325
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	1,801	1,704
Total LHFI With No Related Allowance Recorded	1,546	1,206
Total LHFI With an Allowance Recorded	26	199
Total LHFI Carrying Amount	1,572	1,405
Related Allowance	0	75
Average Recorded Investment	1,747	1,923
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	4,771	6,031
Total LHFI With No Related Allowance Recorded	126	160
Total LHFI With an Allowance Recorded	3,614	4,576
Total LHFI Carrying Amount	3,740	4,736
Related Allowance	43	1,331
Average Recorded Investment	4,217	4,693
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member]
Loan and Lease Receivables, Impaired [Abstract]
Total LHFI Unpaid Principal Balance	3,585	15,205
Total LHFI With No Related Allowance Recorded	3,010	10,027
Total LHFI With an Allowance Recorded	360	396
Total LHFI Carrying Amount	3,370	10,423
Related Allowance	78	165
Average Recorded Investment	5,845	8,321
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	$ 0

Loans Held for Investment (LH_7

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Impact of Modifications Classified as Troubled Debt Restructurings (Details) - Troubled Debt Restructurings [Member] $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)Contract	Sep. 30, 2017USD ($)Contract	Sep. 30, 2018USD ($)Contract	Sep. 30, 2017USD ($)Contract
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	12	8	38	26
Pre-Modification Outstanding Recorded Investment	$ 11,274	$ 13,038	$ 24,798	$ 14,791
Post-Modification Outstanding Recorded Investment	$ 10,183	$ 13,039	$ 23,249	$ 14,785
Secured by 1-4 Family Residential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	3	1	19	17
Pre-Modification Outstanding Recorded Investment	$ 121	$ 112	$ 1,873	$ 1,280
Post-Modification Outstanding Recorded Investment	$ 121	$ 113	$ 1,432	$ 1,290
Secured by Nonfarm, Nonresidential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract		1		1
Pre-Modification Outstanding Recorded Investment		$ 426		$ 426
Post-Modification Outstanding Recorded Investment		$ 426		$ 426
Commercial and Industrial Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	9	6	15	7
Pre-Modification Outstanding Recorded Investment	$ 11,153	$ 12,500	$ 22,899	$ 12,744
Post-Modification Outstanding Recorded Investment	$ 10,062	$ 12,500	$ 21,791	$ 12,744
Construction, Land Development and Other Land [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract			1	1
Pre-Modification Outstanding Recorded Investment			$ 22	$ 341
Post-Modification Outstanding Recorded Investment			$ 22	$ 325
Consumer Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract			3
Pre-Modification Outstanding Recorded Investment			$ 4
Post-Modification Outstanding Recorded Investment			$ 4

Loans Held for Investment (LH_8

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Troubled Debt Restructuring Subsequently Defaulted (Details) - Troubled Debt Restructurings that Subsequently Defaulted [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)Contract	Sep. 30, 2017USD ($)Contract
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	13	6
Recorded Investment | $	$ 14,327	$ 64
Construction, Land Development and Other Land [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	1	0
Recorded Investment | $	$ 21	$ 0
Secured by 1-4 Family Residential Properties [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	6	4
Recorded Investment | $	$ 321	$ 64
Commercial and Industrial Loans [Member]
Troubled Debt Restructurings [Abstract]
Number of Contracts | Contract	6	2
Recorded Investment | $	$ 13,985	$ 0

Loans Held for Investment (LH_9

Loans Held for Investment (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	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Financing Receivable Modifications [Line Items]
Nonaccrual	$ 67,836	$ 67,575
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	2,262	2,105
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	15,164	19,022
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	5,389	12,608
Commercial and Industrial Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	33,870	33,338
Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	228	135
Other Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	1,419	155
Troubled Debt Restructurings [Member]
Financing Receivable Modifications [Line Items]
Accruing	2,346		$ 440
Nonaccrual	33,617	$ 23,200	23,939
Total	35,963		24,379
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
Nonaccrual	26		272
Total	26		272
Troubled Debt Restructurings [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	563		14
Nonaccrual	3,052		3,077
Total	3,615		3,091
Troubled Debt Restructurings [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	0		426
Nonaccrual	360		436
Total	360		862
Troubled Debt Restructurings [Member] | Commercial and Industrial Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	1,783		0
Nonaccrual	29,636		20,153
Total	31,419		20,153
Troubled Debt Restructurings [Member] | Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	0		0
Nonaccrual	3		1
Total	3		$ 1
Troubled Debt Restructurings [Member] | Other Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	0
Nonaccrual	540
Total	$ 540

Loans Held for Investment (L_10

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Additional Information (Details 2)	9 Months Ended
	Sep. 30, 2018USD ($)KeyRatioLoanPoolCreditRiskGrade	Dec. 31, 2017USD ($)
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	$ 34,100,000	$ 35,500,000
Percentage of outstanding principal to be repurchased under GNMA optional repurchase program	100.00%
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

Loans Held for Investment (L_11

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Summary of LHFI by Loan Type and Credit Quality Indicator (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Financing Receivable [Abstract]
Current		$ 8,666,880	$ 8,483,959
Financing Receivable, Recorded Investment, Past Due		12,314	18,433
Nonaccrual		67,836	67,575
Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]	726	2,171
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		1,029,021	985,127
Financing Receivable, Recorded Investment, Past Due		208	392
Nonaccrual		2,262	2,105
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		1,778,488	1,645,876
Financing Receivable, Recorded Investment, Past Due		7,377	10,413
Nonaccrual		15,164	19,022
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]	447	1,917
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		2,288,364	2,178,640
Financing Receivable, Recorded Investment, Past Due		536	2,575
Nonaccrual		5,389	12,608
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Current		452,940	517,744
Financing Receivable, Recorded Investment, Past Due		5
Nonaccrual		742	212
Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Current		1,530,295	1,535,003
Financing Receivable, Recorded Investment, Past Due		1,757	2,004
Nonaccrual		33,870	33,338
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]	21	12
Consumer Loans [Member]
Financing Receivable [Abstract]
Current		180,502	169,145
Financing Receivable, Recorded Investment, Past Due		1,979	2,638
Nonaccrual		228	135
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due	[1]	258	242
State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Current		920,416	952,094
Financing Receivable, Recorded Investment, Past Due			389
Nonaccrual		8,762
Other Loans [Member]
Financing Receivable [Abstract]
Current		486,854	500,330
Financing Receivable, Recorded Investment, Past Due		452	22
Nonaccrual		1,419	155
Commercial LHFI [Member]
Financing Receivable [Abstract]
Financing receivable commercial		6,821,958	6,788,151
Commercial LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		966,114	926,881
Commercial LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		129,193	132,563
Commercial LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		2,294,226	2,193,745
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		453,064	517,553
Commercial LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,565,922	1,570,345
Commercial LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		929,178	952,483
Commercial LHFI [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		484,261	494,581
Commercial LHFI [Member] | Pass [Member]
Financing Receivable [Abstract]
Financing receivable commercial		6,660,632	6,554,846
Commercial LHFI [Member] | Pass [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		961,316	922,563
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		125,998	127,405
Commercial LHFI [Member] | Pass [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		2,259,388	2,135,749
Commercial LHFI [Member] | Pass [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		452,095	517,036
Commercial LHFI [Member] | Pass [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,490,431	1,437,590
Commercial LHFI [Member] | Pass [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		913,286	936,420
Commercial LHFI [Member] | Pass [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		458,118	478,083
Commercial LHFI [Member] | Special Mention [Member]
Financing Receivable [Abstract]
Financing receivable commercial		34,327	41,764
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		78	316
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		175	134
Commercial LHFI [Member] | Special Mention [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		3,052	6,684
Commercial LHFI [Member] | Special Mention [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		454
Commercial LHFI [Member] | Special Mention [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		9,721	28,780
Commercial LHFI [Member] | Special Mention [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		5,250	5,850
Commercial LHFI [Member] | Special Mention [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		15,597
Commercial LHFI [Member] | Substandard [Member]
Financing Receivable [Abstract]
Financing receivable commercial		124,336	189,722
Commercial LHFI [Member] | Substandard [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		4,512	3,780
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		2,960	4,948
Commercial LHFI [Member] | Substandard [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		31,302	50,785
Commercial LHFI [Member] | Substandard [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		515	517
Commercial LHFI [Member] | Substandard [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		63,936	103,089
Commercial LHFI [Member] | Substandard [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		10,642	10,213
Commercial LHFI [Member] | Substandard [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		10,469	16,390
Commercial LHFI [Member] | Doubtful [Member]
Financing Receivable [Abstract]
Financing receivable commercial		2,663	1,819
Commercial LHFI [Member] | Doubtful [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		208	222
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		60	76
Commercial LHFI [Member] | Doubtful [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		484	527
Commercial LHFI [Member] | Doubtful [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,834	886
Commercial LHFI [Member] | Doubtful [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		77	108
Consumer LHFI [Member]
Financing Receivable [Abstract]
Financing receivable commercial		8,747,030	8,569,967
Current		1,901,700	1,752,484
Nonaccrual		14,377	16,669
Subtotal		1,925,072	1,781,816
Consumer LHFI [Member] | Past Due 30-89 Days [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		8,290	10,612
Consumer LHFI [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		705	2,051
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,031,491	987,624
Current		65,028	60,240
Nonaccrual		346	161
Subtotal		65,377	60,743
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		3	342
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,801,029	1,675,311
Current		1,651,019	1,516,691
Nonaccrual		13,804	16,374
Subtotal		1,671,836	1,542,748
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		6,566	7,874
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		447	1,809
Consumer LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		2,294,289	2,193,823
Current		63	78
Subtotal		63	78
Consumer LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable [Abstract]
Financing receivable commercial		453,687	517,956
Current		623	403
Subtotal		623	403
Consumer LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		1,565,922	1,570,345
Consumer LHFI [Member] | Consumer Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		182,709	171,918
Current		180,503	169,146
Nonaccrual		227	134
Subtotal		182,709	171,918
Consumer LHFI [Member] | Consumer Loans [Member] | Past Due 30-89 Days [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		1,721	2,396
Consumer LHFI [Member] | Consumer Loans [Member] | Past Due 90 Days or More [Member]
Financing Receivable [Abstract]
Financing Receivable, Recorded Investment, Past Due		258	242
Consumer LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		929,178	952,483
Consumer LHFI [Member] | Other Loans [Member]
Financing Receivable [Abstract]
Financing receivable commercial		488,725	500,507
Current		4,464	5,926
Subtotal		$ 4,464	$ 5,926
[1]	Past due 90 days or more but still accruing interest.

Loans Held for Investment (L_12

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Additional Information (Details 3)	9 Months Ended
	Sep. 30, 2018LoanFactorScale
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
Minimum score for qualitative risk factor | Scale	0
Maximum score for qualitative risk factor | Scale	100
Number of loan types for consumer portfolio | Loan	5
Number of unique qualitative factors used to analyze consumer loans | Factor	5

Loans Held for Investment (L_13

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Summary of Balance in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Total	$ 88,874		$ 76,733
Allowance for Loan Losses, LHFI [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	15,749		1,743
Collectively	73,125		74,990
Total	88,874	$ 83,566	76,733	$ 80,332	$ 76,184	$ 71,265
Allowance for Loan Losses, LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	13,869		131
Collectively	19,448		22,720
Total	33,317		22,851	19,780		22,011
Allowance for Loan Losses, LHFI [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively	3,394		3,470
Total	3,394		3,470	4,456		3,241
Allowance for Loan Losses, LHFI [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	683
Collectively	510		789
Total	1,193		789	811		859
Allowance for Loan Losses, LHFI [Member] | Other Loans [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually	1,076		41
Collectively	4,364		4,625
Total	5,440		4,666	4,204		2,492
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
Collectively	8,414		7,790
Total	8,414		7,865	8,648		9,085
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	43		1,331
Collectively	9,265		9,543
Total	9,308		10,874	10,280		10,347
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	78		165
Collectively	24,781		23,263
Total	24,859		23,428	28,748		20,967
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	2,949		2,790
Total	$ 2,949		$ 2,790	$ 3,405		$ 2,263

Loans Held for Investment (L_14

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Summary of Loan Type Related to Each Balance in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	$ 52,500	$ 48,900
Total LHFI	8,747,030	8,569,967
Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	52,455	48,936
LHFI, Collectively Evaluated For Impairment	8,694,575	8,521,031
Total LHFI	8,747,030	8,569,967
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	1,031,491	987,624
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	1,572	1,405
LHFI, Collectively Evaluated For Impairment	1,029,919	986,219
Total LHFI	1,031,491	987,624
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	1,801,029	1,675,311
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	3,740	4,736
LHFI, Collectively Evaluated For Impairment	1,797,289	1,670,575
Total LHFI	1,801,029	1,675,311
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	2,294,289	2,193,823
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	3,370	10,423
LHFI, Collectively Evaluated For Impairment	2,290,919	2,183,400
Total LHFI	2,294,289	2,193,823
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	453,687	517,956
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	453,687	517,956
Total LHFI	453,687	517,956
Commercial and Industrial Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	1,565,922	1,570,345
Commercial and Industrial Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	33,702	31,799
LHFI, Collectively Evaluated For Impairment	1,532,220	1,538,546
Total LHFI	1,565,922	1,570,345
Consumer Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	182,709	171,918
Consumer Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	3	17
LHFI, Collectively Evaluated For Impairment	182,706	171,901
Total LHFI	182,709	171,918
State and Other Political Subdivision Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	929,178	952,483
State and Other Political Subdivision Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	8,762
LHFI, Collectively Evaluated For Impairment	920,416	952,483
Total LHFI	929,178	952,483
Other Loans [Member]
Loans and Leases Receivable, Other Information [Abstract]
Total LHFI	488,725	500,507
Other Loans [Member] | Allowance for Loan Losses, LHFI [Member]
Loans and Leases Receivable, Other Information [Abstract]
LHFI, Individually Evaluated For Impairment	1,306	556
LHFI, Collectively Evaluated For Impairment	487,419	499,951
Total LHFI	$ 488,725	$ 500,507

Loans Held for Investment (L_15

Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Change in Allowance for Loan Losses (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				$ 76,733
Provision for loan losses, LHFI		$ 8,673	$ 3,672	15,801	$ 9,355
Balance at end of period		88,874		88,874
Allowance for Loan Losses, LHFI [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period		83,566	76,184	76,733	71,265
Transfers	[1]	772		1,554
Loans charged-off		(7,017)	(2,752)	(12,980)	(9,072)
Recoveries		2,880	3,228	7,766	8,784
Net (charge-offs) recoveries		(4,137)	476	(5,214)	(288)
Provision for loan losses, LHFI		8,673	3,672	15,801	9,355
Balance at end of period		88,874	80,332	88,874	80,332
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				7,865	9,085
Transfers	[2]			584
Loans charged-off				(123)	(79)
Recoveries				1,039	1,257
Provision for loan losses, LHFI				(951)	(1,615)
Balance at end of period		8,414	8,648	8,414	8,648
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				10,874	10,347
Transfers	[2]			182
Loans charged-off				(1,435)	(753)
Recoveries				439	1,429
Provision for loan losses, LHFI				(752)	(743)
Balance at end of period		9,308	10,280	9,308	10,280
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				23,428	20,967
Transfers	[2]			446
Loans charged-off				(1,117)	(50)
Recoveries				120	289
Provision for loan losses, LHFI				1,982	7,542
Balance at end of period		24,859	28,748	24,859	28,748
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				2,790	2,263
Transfers	[2]			291
Recoveries				17	31
Provision for loan losses, LHFI				(149)	1,111
Balance at end of period		2,949	3,405	2,949	3,405
Allowance for Loan Losses, LHFI [Member] | Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				22,851	22,011
Transfers	[2]			46
Loans charged-off				(4,658)	(2,624)
Recoveries				2,285	1,813
Provision for loan losses, LHFI				12,793	(1,420)
Balance at end of period		33,317	19,780	33,317	19,780
Allowance for Loan Losses, LHFI [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				3,470	3,241
Transfers	[2]			5
Loans charged-off				(1,585)	(1,809)
Recoveries				1,545	1,427
Provision for loan losses, LHFI				(41)	1,597
Balance at end of period		3,394	4,456	3,394	4,456
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				789	859
Provision for loan losses, LHFI				404	(48)
Balance at end of period		1,193	811	1,193	811
Allowance for Loan Losses, LHFI [Member] | Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				4,666	2,492
Loans charged-off				(4,062)	(3,757)
Recoveries				2,321	2,538
Provision for loan losses, LHFI				2,515	2,931
Balance at end of period		$ 5,440	$ 4,204	$ 5,440	$ 4,204
[1]	The allowance for loan losses balance related to the remaining loans acquired in the Bay Bank & Trust Company (Bay Bank) merger on March 16, 2012, which were transferred from acquired impaired loans to LHFI during the second quarter of 2018, and the remaining loans acquired in the Heritage Banking Group (Heritage) acquisition on April 15, 2011 and the Reliance merger on April 7, 2017, which were transferred from acquired impaired loans to LHFI during the third quarter of 2018.
[2]	The allowance for loan losses balance related to the remaining loans acquired in the Bay Bank merger on March 16, 2012, which were transferred from acquired impaired loans to LHFI during the second quarter of 2018, and the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017, which were transferred from acquired impaired loans to LHFI during the third quarter of 2018.

Acquired Loans - Additional Inf

Acquired Loans - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018CreditRiskGrade	Apr. 07, 2017USD ($)
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities [Abstract]
Loans acquired in merger accounted for under FASB ASC Topic 310 30 | $		$ 7.9
Number of individual credit risk grades | CreditRiskGrade	10

Acquired Loans - Schedule of Ac

Acquired Loans - Schedule of Acquired Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	$ 132,615		$ 261,517
Allowance for loan losses, acquired loans	(1,714)	$ (3,046)	(4,079)	$ (5,768)	$ (7,423)	$ (11,397)
Net acquired loans	130,901		257,438
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	6,657		23,586
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	25,274		61,751
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	66,865		114,694
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	8,507		16,746
Commercial and Industrial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	16,610		31,506
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	1,514		2,600
Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Acquired loans	$ 7,188		$ 10,634

Acquired Loans - Changes in the

Acquired Loans - Changes in the Carrying Value of Acquired Loans (Details) - USD ($) $ in Thousands		9 Months Ended			12 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Dec. 31, 2017	Apr. 07, 2017
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		$ 257,438
Additions						$ 7,900
Accretion to interest income		7,870		$ 11,021
Carrying value, net, ending		130,901			$ 257,438
Acquired Not ASC 310-30 [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning	[1]	77,868		42,743	42,743
Transfers	[1],[2]	(43,922)			(36,719)
Additions	[1],[3]				109,548
Accretion to interest income	[1]	782			1,578
Payments received, net	[1]	(16,096)			(39,208)
Other	[1],[4]	74			(74)
Change in allowance for loan losses, acquired loans	[1]	0			0
Carrying value, net, ending	[1]	18,706			77,868
Acquired Impaired [Member]
Carrying value of acquired loans [Abstract]
Carrying value, net, beginning		179,570		$ 218,107	218,107
Transfers		(26,497)	[5]		0
Additions	[3]				7,899
Accretion to interest income		7,870			14,924
Payments received, net		(50,940)			(68,317)
Other	[4]	(173)			(361)
Change in allowance for loan losses, acquired loans		2,365			7,318
Carrying value, net, ending		$ 112,195			$ 179,570
[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 310-30” 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.
[5]	During the second quarter of 2018, Trustmark transferred the remaining loans acquired in the Bay Bank merger on March 16, 2012 from acquired impaired loans to LHFI. During the third quarter of 2018, Trustmark transferred the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017 from acquired impaired loans to LHFI.

Acquired Loans - Changes in Acc

Acquired Loans - Changes in Accretable Yield of Acquired Loans (Details) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Change in accretable difference on acquired loans [Abstract]
Accretable yield at beginning of period		$ (31,426)	$ (38,918)	$ (38,918)
Accretion to interest income		7,870	11,021
Additions due to acquisitions	[1]		(784)
Disposals, net		3,452	1,759
Transfers	[2]	5,874
Reclassification from nonaccretable difference	[3]	(4,204)	(7,204)
Accretable yield at end of period		$ (18,434)	$ (34,126)	$ (31,426)
[1]	Accretable yield on loans acquired from Reliance on April 7, 2017.
[2]	During the second quarter of 2018, Trustmark transferred the remaining loans acquired in the Bay Bank merger on March 16, 2012 from acquired impaired loans to LHFI. During the third quarter of 2018, Trustmark transferred the remaining loans acquired in the Heritage acquisition on April 15, 2011 and the Reliance merger on April 7, 2017 from acquired impaired loans to LHFI.
[3]	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		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		$ 3,046	$ 7,423	$ 4,079	$ 11,397
Transfers	[1]	(772)		(1,554)
Net (charge-offs) recoveries		(93)	(2)	(53)	193
Provision for loan losses, acquired loans		(467)	(1,653)	(758)	(5,822)
Balance at end of period		$ 1,714	$ 5,768	$ 1,714	$ 5,768
[1]	The allowance for loan losses balance related to the remaining loans acquired in the Bay Bank merger, which were transferred from acquired impaired loans to LHFI during the second quarter of 2018, and the remaining loans acquired in the Heritage acquisition and the Reliance merger, which were transferred from acquired impaired loans to LHFI during the third quarter of 2018.

Acquired Loans - Acquired Loans

Acquired Loans - Acquired Loans by Loan Type and Credit Quality Indicator (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		$ 130,901	$ 257,438
Acquired Loans, Aging [Abstract]
Current		128,720	255,506
Acquired Loans, Past Due		3,895	5,707
Nonaccrual	[1]	0	304
Total Acquired Loans		132,615	261,517
Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	2,395	2,434
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		6,529	22,601
Acquired Loans, Past Due		128	985
Nonaccrual	[1]	0	0
Total Acquired Loans		6,657	23,586
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]	25	861
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		23,942	58,490
Acquired Loans, Past Due		1,332	2,959
Nonaccrual	[1]	0	302
Total Acquired Loans		25,274	61,751
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]	288	654
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		65,093	113,256
Acquired Loans, Past Due		1,772	1,438
Nonaccrual	[1]	0	0
Total Acquired Loans		66,865	114,694
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]	1,475	898
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		8,492	16,614
Acquired Loans, Past Due		15	132
Nonaccrual	[1]	0	0
Total Acquired Loans		8,507	16,746
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	0
Commercial and Industrial Loans [Member]
Acquired Loans, Aging [Abstract]
Current		16,003	31,504
Acquired Loans, Past Due		607	0
Nonaccrual	[1]	0	2
Total Acquired Loans		16,610	31,506
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	607	0
Consumer Loans [Member]
Acquired Loans, Aging [Abstract]
Current		1,473	2,428
Acquired Loans, Past Due		41	172
Nonaccrual	[1]	0	0
Total Acquired Loans		1,514	2,600
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	0
Other Loans [Member]
Acquired Loans, Aging [Abstract]
Current		7,188	10,613
Acquired Loans, Past Due		0	21
Nonaccrual	[1]	0	0
Total Acquired Loans		7,188	10,634
Other Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	21
Commercial LHFI [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		111,386	212,826
Commercial LHFI [Member] | Pass [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		82,066	167,079
Commercial LHFI [Member] | Special Mention [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		72	2,067
Commercial LHFI [Member] | Substandard [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		25,825	40,660
Commercial LHFI [Member] | Doubtful [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		3,423	3,020
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		5,930	22,338
Commercial LHFI [Member] | Construction, Land Development and Other Land [Member] | Pass [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		5,541	17,150
Commercial LHFI [Member] | Construction, Land Development and Other Land [Member] | Special Mention [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		25	234
Commercial LHFI [Member] | Construction, Land Development and Other Land [Member] | Substandard [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		296	4,690
Commercial LHFI [Member] | Construction, Land Development and Other Land [Member] | Doubtful [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		68	264
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		6,286	17,348
Commercial LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Pass [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		5,594	14,021
Commercial LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Special Mention [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		47	298
Commercial LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Substandard [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		645	3,029
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		66,865	114,660
Commercial LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Pass [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		51,123	95,147
Commercial LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Special Mention [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans			1,400
Commercial LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Substandard [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		15,223	17,583
Commercial LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Doubtful [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		519	530
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		8,507	16,340
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Pass [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		7,906	12,730
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Special Mention [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans			102
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Substandard [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		177	3,031
Commercial LHFI [Member] | Other Real Estate Secured [Member] | Doubtful [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		424	477
Commercial LHFI [Member] | Commercial and Industrial Loans [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		16,610	31,506
Commercial LHFI [Member] | Commercial and Industrial Loans [Member] | Pass [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		7,366	22,157
Commercial LHFI [Member] | Commercial and Industrial Loans [Member] | Special Mention [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans			15
Commercial LHFI [Member] | Commercial and Industrial Loans [Member] | Substandard [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		6,832	7,585
Commercial LHFI [Member] | Commercial and Industrial Loans [Member] | Doubtful [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		2,412	1,749
Commercial LHFI [Member] | Other Loans [Member] | Commercial Loan [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		7,188	10,634
Commercial LHFI [Member] | Other Loans [Member] | Pass [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		4,536	5,874
Commercial LHFI [Member] | Other Loans [Member] | Special Mention [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans			18
Commercial LHFI [Member] | Other Loans [Member] | Substandard [Member]
Acquired Loans, Commercial Loans [Abstract]
Acquired loans		2,652	4,742
Consumer LHFI [Member]
Acquired Loans, Aging [Abstract]
Current		19,801	46,064
Nonaccrual	[1]		124
Subtotal		21,229	48,691
Total Acquired Loans		132,615	261,517
Consumer LHFI [Member] | Past Due 30-89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,160	1,905
Consumer LHFI [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		268	598
Consumer LHFI [Member] | Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		652	1,188
Subtotal		727	1,248
Total Acquired Loans		6,657	23,586
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		75	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
Consumer LHFI [Member] | Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current		17,676	42,008
Nonaccrual	[1]		124
Subtotal		18,988	44,403
Total Acquired Loans		25,274	61,751
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		1,044	1,687
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		268	584
Consumer LHFI [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current			34
Subtotal			34
Total Acquired Loans		66,865	114,694
Consumer LHFI [Member] | Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Current			406
Subtotal			406
Total Acquired Loans		8,507	16,746
Consumer LHFI [Member] | Commercial and Industrial Loans [Member]
Acquired Loans, Aging [Abstract]
Total Acquired Loans		16,610	31,506
Consumer LHFI [Member] | Consumer Loans [Member]
Acquired Loans, Aging [Abstract]
Current		1,473	2,428
Subtotal		1,514	2,600
Total Acquired Loans		1,514	2,600
Consumer LHFI [Member] | Consumer Loans [Member] | Past Due 30-89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		41	172
Consumer LHFI [Member] | Other Loans [Member]
Acquired Loans, Aging [Abstract]
Total Acquired Loans		$ 7,188	$ 10,634
[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		Sep. 30, 2018	Dec. 31, 2017
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		$ 3,895	$ 5,707
Nonaccrual	[1]	0	304
Current		128,720	255,506
Acquired Loans		132,615	261,517
Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,157	2,340
Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		343	933
Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	2,395	2,434
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		128	985
Nonaccrual	[1]	0	0
Current		6,529	22,601
Acquired Loans		6,657	23,586
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		103	34
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		0	90
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]	25	861
Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,332	2,959
Nonaccrual	[1]	0	302
Current		23,942	58,490
Acquired Loans		25,274	61,751
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		703	1,691
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		341	614
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]	288	654
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		1,772	1,438
Nonaccrual	[1]	0	0
Current		65,093	113,256
Acquired Loans		66,865	114,694
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		297	467
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		0	73
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]	1,475	898
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		15	132
Nonaccrual	[1]	0	0
Current		8,492	16,614
Acquired Loans		8,507	16,746
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		15	132
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	0
Commercial and Industrial Loans [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		607	0
Nonaccrual	[1]	0	2
Current		16,003	31,504
Acquired Loans		16,610	31,506
Commercial and Industrial Loans [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	0
Commercial and Industrial Loans [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	0
Commercial and Industrial Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	607	0
Consumer Loans [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		41	172
Nonaccrual	[1]	0	0
Current		1,473	2,428
Acquired Loans		1,514	2,600
Consumer Loans [Member] | Past Due 30 to 59 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		39	16
Consumer Loans [Member] | Past Due 60 to 89 Days [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		2	156
Consumer Loans [Member] | Past Due 90 Days or More [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due	[2]	0	0
Other Loans [Member]
Acquired Loans, Aging [Abstract]
Acquired Loans, Past Due		0	21
Nonaccrual	[1]	0	0
Current		7,188	10,613
Acquired Loans		7,188	10,634
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]	$ 0	$ 21
[1]	Acquired loans not accounted for under FASB ASC Topic 310-30.
[2]	Past due 90 days or more but still accruing interest.

Mortgage Banking - Schedule of

Mortgage Banking - Schedule of Activity in the Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Mortgage servicing rights [Abstract]
Balance at beginning of period	$ 84,269	$ 80,239
Origination of servicing assets	12,248	11,630
Change in fair value [Abstract]
Due to market changes	13,879	(2,218)
Due to run-off	(9,022)	(8,174)
Balance at end of period	$ 101,374	$ 81,477

Mortgage Banking - Additional I

Mortgage Banking - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)CPR	Sep. 30, 2017USD ($)CPR
Schedule of changes in the reserve for mortgage loan [Abstract]
Assumed average prepayment speed | CPR	6.86	9.25
Average discount rate (in hundredths)	10.04%	10.28%
Mortgage servicing rights [Abstract]
Residential mortgage loans sold	$ 820.6	$ 871.9
Gains on sales of residential mortgage loans, before tax	$ 16.4	$ 13.6
Period of putback response	60 days

Mortgage Banking - Schedule o_2

Mortgage Banking - Schedule of Mortgage Loans Sold and Serviced for Others (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 6,759,391	$ 6,624,005
Federal National Mortgage Association [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	4,174,961	4,128,614
Government National Mortgage Association [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	2,492,009	2,421,456
Federal Home Loan Mortgage Corporation [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	69,617	47,071
Other [Member]
Mortgage Loans On Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 22,804	$ 26,864

Mortgage Banking - Changes in t

Mortgage Banking - Changes in the Reserve for Mortgage Loan Servicing Putback Expense (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Schedule of changes in the reserve for mortgage loan [Abstract]
Balance at beginning of period		$ 1,000	$ 1,130
Provision for putback expenses		0	164
Other	[1]	0	706
Balance at end of period		$ 1,000	$ 2,000
[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.

Other Real Estate - Changes and

Other Real Estate - Changes and Gains (Losses), Net on Other Real Estate (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation Of Carrying Amount Of Real Estate Investments Roll Forward
Balance at beginning of period				$ 43,228	$ 62,051
Additions	[1]			10,368	7,481
Disposals				(15,264)	(18,583)
Write-downs				(1,857)	(2,593)
Balance at end of period		$ 36,475	$ 48,356	36,475	48,356
Gains (losses), net on the sale of other real estate included in other real estate expense		$ 224	$ 200	$ 1,226	$ 1,722
[1]	Includes $475 thousand of other real estate acquired in the Reliance merger on April 7, 2017.

Other Real Estate - Changes a_2

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

Other Real Estate - Other Real

Other Real Estate - Other Real Estate, By Type of Property (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	$ 36,475	$ 43,228	$ 48,356	$ 62,051
Construction, Land Development And Other Land Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	18,976	27,491
1 - 4 Family Residential Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	5,266	5,081
Nonfarm, Nonresidential Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	12,050	10,468
Other Real Estate Properties [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	$ 183	$ 188

Other Real Estate - Other Rea_2

Other Real Estate - Other Real Estate, By Geographic Location (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		$ 36,475	$ 43,228	$ 48,356	$ 62,051
Alabama [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		7,526	11,714
Florida [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		8,931	13,937
Mississippi [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	[1]	18,191	14,260
Tennessee [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate	[2]	1,083	2,535
Texas [Member]
Other real estate, excluding covered other real estate [Line Items]
Total other real estate		$ 744	$ 782
[1]	Mississippi includes Central and Southern Mississippi Regions
[2]	Tennessee includes Memphis, Tennessee and Northern Mississippi Regions

Deposits - Deposits Summary (De

Deposits - Deposits Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deposits [Abstract]
Noninterest-bearing demand	$ 2,786,539	$ 2,978,074
Interest-bearing demand	2,739,245	2,432,814
Savings	3,538,125	3,408,183
Time	1,893,001	1,758,441
Total deposits	$ 10,956,910	$ 10,577,512

Securities Sold Under Repurch_3

Securities Sold Under Repurchase Agreement - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Securities sold under repurchase agreements, secured by securities carrying amount	$ 167.1	$ 200.9

Securities Sold Under Repurch_4

Securities Sold Under Repurchase Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities sold under repurchase agreements by collateral pledged
Total securities sold under repurchase agreements	$ 90,511	$ 118,694
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	41,650	68,246
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	$ 48,861	$ 50,448

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)Contract	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)ContractFeeRevenueCategory	Sep. 30, 2017USD ($)
Revenue From Contract With Customer [Line Items]
Number of types of interchange fees | Fee			2
Other real estate sales, net gains | $	$ 224	$ 200	$ 1,226	$ 1,722
Number of trust management revenue categories | RevenueCategory			5
Time period between service obligation completed and payment received from trust customer			30 days
Number of general categories of insurance contracts | Contract	4		4
Commercial Installment Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Personal Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Employee Benefits Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Contingency Commission Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Maximum [Member] | Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Maximum [Member] | Personal Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			60 days
Maximum [Member] | Employee Benefits Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			90 days
Minimum [Member] | Personal Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			30 days
Minimum [Member] | Employee Benefits Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			60 days

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Summary of Noninterest Income Disaggregated by Reportable Operating Segment and Revenue Stream (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		$ 11,075	$ 11,223	[1]	$ 32,579	$ 32,810	[1]
Bank card and other fees		7,459	7,150	[1]	21,155	21,020	[1]
Mortgage banking, net		8,647	4,425	[1]	28,958	23,618	[1]
Insurance commissions		10,765	10,398	[1]	30,919	29,355	[1]
Wealth management		7,789	7,530	[1]	22,834	22,617	[1]
Other, net		1,358	3,740	[1]	4,832	11,268	[1]
Security gains (losses), net			14	[1]	0	15	[1]
Total Noninterest Income		47,093	44,480	[1]	141,277	140,703	[1]
Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		11,075	11,223	[1]	32,579	32,810	[1]
Bank card and other fees		6,522	7,127	[1]	19,928	20,812	[1]
Insurance commissions		10,765	10,398	[1]	30,919	29,355	[1]
Wealth management		7,789	7,530	[1]	22,834	22,617	[1]
Other, net		1,688	1,495	[1]	4,672	5,002	[1]
Total Noninterest Income		37,839	37,773	[1]	110,932	110,596	[1]
Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	937	23	[1]	1,227	208	[1]
Mortgage banking, net	[2]	8,647	4,425	[1]	28,958	23,618	[1]
Other, net	[2]	(330)	2,245	[1]	160	6,266	[1]
Security gains (losses), net	[1],[2]		14			15
Total Noninterest Income	[2]	9,254	6,707	[1]	30,345	30,107	[1]
General Banking Division [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		11,074	11,222	[1]	32,577	32,809	[1]
Bank card and other fees		7,440	7,127	[1]	21,092	20,985	[1]
Mortgage banking, net		8,647	4,425	[1]	28,958	23,618	[1]
Wealth management		70	64	[1]	210	210	[1]
Other, net		1,326	3,718	[1]	4,750	11,193	[1]
Security gains (losses), net	[1]		14			15
Total Noninterest Income		28,557	26,570	[1]	87,587	88,830	[1]
General Banking Division [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		11,074	11,222	[1]	32,577	32,809	[1]
Bank card and other fees		6,503	7,104	[1]	19,865	20,777	[1]
Wealth management		70	64	[1]	210	210	[1]
Other, net		1,685	1,495	[1]	4,666	4,997	[1]
Total Noninterest Income		19,332	19,885	[1]	57,318	58,793	[1]
General Banking Division [Member] | Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	937	23	[1]	1,227	208	[1]
Mortgage banking, net	[2]	8,647	4,425	[1]	28,958	23,618	[1]
Other, net	[2]	(359)	2,223	[1]	84	6,196	[1]
Security gains (losses), net	[1],[2]		14			15
Total Noninterest Income	[2]	9,225	6,685	[1]	30,269	30,037	[1]
Wealth Management Division [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		1	1	[1]	2	1	[1]
Bank card and other fees		19	23	[1]	63	35	[1]
Wealth management		7,719	7,466	[1]	22,624	22,407	[1]
Other, net		30	22	[1]	79	70	[1]
Total Noninterest Income		7,769	7,512	[1]	22,768	22,513	[1]
Wealth Management Division [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		1	1	[1]	2	1	[1]
Bank card and other fees		19	23	[1]	63	35	[1]
Wealth management		7,719	7,466	[1]	22,624	22,407	[1]
Other, net		1			3
Total Noninterest Income		7,740	7,490	[1]	22,692	22,443	[1]
Wealth Management Division [Member] | Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Other, net	[2]	29	22	[1]	76	70	[1]
Total Noninterest Income	[2]	29	22	[1]	76	70	[1]
Insurance Division [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		10,765	10,398	[1]	30,919	29,355	[1]
Other, net		2			3	5	[1]
Total Noninterest Income		10,767	10,398	[1]	30,922	29,360	[1]
Insurance Division [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		10,765	10,398	[1]	30,919	29,355	[1]
Other, net		2			3	5	[1]
Total Noninterest Income		$ 10,767	$ 10,398	[1]	$ 30,922	$ 29,360	[1]
[1]	Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may not be comparable to current year presentation.
[2]	Noninterest income not in scope for FASB ASC Topic 606 includes customer derivatives revenue and miscellaneous credit card fee income within bank card and other fees; mortgage banking, net; amortization of tax credits, accretion of the FDIC indemnification asset, cash surrender value on various life insurance policies, earnings on Trustmark’s non-qualified deferred compensation plans, other partnership investments and rental income within other, net; and security gains (losses), net.

Defined Benefit and Other Pos_3

Defined Benefit and Other Postretirement Benefits - Additional Information (Details) - Trustmark Capital Accumulation Plan [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Years of service required to vest	3 years
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		$ 243

Defined Benefit and Other Pos_4

Defined Benefit and Other Postretirement Benefits - Net Periodic Benefit Cost for Plan and Continuing plan (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
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	$ 69	$ 64	$ 208	190
Interest cost	83	102	249	1,394
Expected return on plan assets	(57)	(51)	(171)	(267)
Recognized net loss due to lump sum settlements	41	0	121	0
Recognized net loss due to defined benefit plan termination	0	0	0	17,644
Recognized net actuarial loss	143	142	428	1,272
Net periodic benefit cost	$ 279	$ 257	$ 835	$ 20,233

Defined Benefit and Other Pos_5

Defined Benefit and Other Postretirement Benefits - Net Periodic Benefit Cost (Details) - Supplemental Retirement Plan [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net periodic benefit cost [Abstract]
Service cost	$ 29	$ 36	$ 87	$ 106
Interest cost	457	514	1,409	1,589
Amortization of prior service cost	63	63	188	188
Recognized net actuarial loss	218	214	664	651
Net periodic benefit cost	$ 767	$ 827	$ 2,348	$ 2,534

Stock and Incentive Compensat_3

Stock and Incentive Compensation Plans - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018
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 Compensat_4

Stock and Incentive Compensation Plans - Summary of Stock Plan Activity (Details) - Stock and Incentive Compensation Plan [Member] - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Performance Based Award [Member]
Shares [Roll Forward]
Nonvested shares, beginning of period (in shares)	177,695	213,516
Granted (in shares)		51,174
Released from restriction (in shares)		(55,351)
Forfeited (in shares)		(31,644)
Nonvested shares, end of period (in shares)	177,695	177,695
Time-Vested Awards [Member]
Shares [Roll Forward]
Nonvested shares, beginning of period (in shares)	322,528	320,357
Granted (in shares)	1,500	118,325
Released from restriction (in shares)	(400)	(107,180)
Forfeited (in shares)	(764)	(8,638)
Nonvested shares, end of period (in shares)	322,864	322,864

Stock and Incentive Compensat_5

Stock and Incentive Compensation Plans - Compensation Expense for Awards Under Stock Plan (Details) - Stock and Incentive Compensation Plan [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total compensation expense	$ 1,158	$ 1,076	$ 3,022	$ 3,250
Performance Based Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total compensation expense	435	435	725	959
Time-Vested Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total compensation expense	$ 723	$ 641	$ 2,297	$ 2,291

Contingencies - Additional Info

Contingencies - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)Lawsuit	Sep. 30, 2017USD ($)
Loss Contingencies [Line Items]
Unused commitments to extend credit	$ 3,666	$ 3,143
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	$ 102.9	105.6
Letters of credit, maturity term - maximum	3 years
Collateral held, fair value	$ 31.2	$ 30.2

Earnings Per Share (EPS) - Weig

Earnings Per Share (EPS) - Weighted-Average Shares Used to Calculate Basic and Diluted EPS (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Basic shares (in shares)	67,621	67,742	67,729	67,722
Dilutive shares (in shares)	175	174	147	154
Diluted shares (in shares)	67,796	67,916	67,876	67,876

Earnings Per Share (EPS) - We_2

Earnings Per Share (EPS) - Weighted-Average Antidilutive Stock Awards Excluded from Determining Diluted EPS (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Weighted-average antidilutive stock awards	8	6	87	72

Statements of Cash Flows (Detai

Statements of Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement of cash flows specific transaction amounts [Abstract]
Income taxes paid	$ 11,629	$ 1,423
Interest expense paid on deposits and borrowings	46,506	28,266
Noncash transfers from loans to other real estate	$ 10,368	7,006
Transfer of long-term FHLB advances to short-term		250,038
Assets acquired in business combination		196,265
Liabilities acquired in business combination		$ 184,949

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Mar. 11, 2016
Stockholders Equity [Line items]
Capital conservation buffer rate	1.875%		1.25%
Stock Repurchase Program
Stockholders Equity [Line items]
Amount of stock authorized for repurchase				$ 100
Repurchase shares of common stock	243,000	0
Repurchase shares of common stock, value	$ 7.9

Shareholders' Equity - Table of

Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
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		$ 1,302,859	$ 1,243,240
Actual Regulatory Capital Ratio		12.20%	11.77%
Minimum Regulatory Capital Required Ratio		6.375%	5.75%
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		$ 1,362,859	$ 1,303,238
Actual Regulatory Capital Ratio		12.76%	12.33%
Minimum Regulatory Capital Required Ratio		7.875%	7.25%
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		$ 1,453,447	$ 1,384,050
Actual Regulatory Capital Ratio		13.61%	13.10%
Minimum Regulatory Capital Required Ratio		9.875%	9.25%
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		$ 1,362,859	$ 1,303,238
Actual Regulatory Capital Ratio		10.41%	9.67%
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		$ 1,344,029	$ 1,284,575
Actual Regulatory Capital Ratio		12.59%	12.16%
Minimum Regulatory Capital Required Ratio		6.375%	5.75%
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		$ 1,344,029	$ 1,284,575
Actual Regulatory Capital Ratio		12.59%	12.16%
Minimum Regulatory Capital Required Ratio		7.875%	7.25%
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		$ 1,434,617	$ 1,365,387
Actual Regulatory Capital Ratio		13.44%	12.93%
Minimum Regulatory Capital Required Ratio		9.875%	9.25%
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		$ 1,344,029	$ 1,284,575
Actual Regulatory Capital Ratio		10.29%	9.54%
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 - Net Chan

Shareholders' Equity - Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Securities available for sale and transferred securities:
Net unrealized holding gains (losses) arising during the period, Before tax amount	$ (9,660)	$ (535)	$ (46,974)	$ 6,335
Reclassification adjustment for net (gains) losses realized in net income, Before tax amount	0	(14)	0	(15)
Change in net unrealized holding loss on securities transferred to held to maturity, Before tax amount	973	1,130	2,909	3,551
Total securities available for sale and transferred securities, Before tax amount	(8,687)	581	(44,065)	9,871
Pension and other postretirement benefit plans:
Net change in prior service costs, Before tax amount	63	63	188	188
Recognized net loss due to lump sum settlements, Before tax amount	41	0	121	0
Change in net actuarial loss, Before tax amount	361	356	1,092	1,923
Recognized net loss due to defined benefit plan termination, Before tax amount			0	16,991
Total pension and other postretirement benefit plans, Before tax amount	465	419	1,401	19,102
Cash flow hedge derivatives:
Change in accumulated gain (loss) on effective cash flow hedge derivatives, Before tax amount	52	53	611	(99)
Reclassification adjustment for (gain) loss realized in net income, Before tax amount	(104)	55	(209)	232
Total cash flow hedge derivatives, Before tax amount	(52)	108	402	133
Total other comprehensive income (loss), Before tax amount	(8,274)	1,108	(42,262)	29,106
Securities available for sale and transferred securities:
Net unrealized holding gains (losses) arising during the period, tax (expense) benefit	2,414	204	11,743	(2,423)
Reclassification adjustment for net (gains) losses realized in net income, tax (expense) benefit	0	(6)	0	(6)
Change in net unrealized holding loss on securities transferred to held to maturity, tax (expense) benefit	(243)	(432)	(727)	(1,358)
Total securities available for sale and transferred securities, tax (expense) benefit	2,171	(222)	11,016	(3,775)
Reclassification adjustment for net (gains) losses realized in net income, tax (expense) benefit	0	6	0	6
Pension and other postretirement benefit plans:
Net change in prior service costs, tax (expense) benefit	(16)	(24)	(48)	(72)
Recognized net loss due to lump sum settlements, tax (expense) benefit	(10)	0	(29)	0
Change in net actuarial loss, tax (expense) benefit	(90)	(137)	(273)	(736)
Recognized net loss due to defined benefit plan termination, tax (expense) benefit			0	(6,499)
Total pension and other postretirement benefit plans, tax (expense) benefit	(116)	(161)	(350)	(7,307)
Cash flow hedge derivatives:
Change in accumulated gain (loss) on effective cash flow hedge derivatives, tax (expense) benefit	(13)	(20)	(153)	38
Reclassification adjustment for (gain) loss realized in net income, tax (expense) benefit	25	(21)	52	(89)
Total cash flow hedge derivatives, tax (expense) benefit	12	(41)	(101)	(51)
Total other comprehensive income (loss), tax (expense) benefit	2,067	(424)	10,565	(11,133)
Net unrealized gains (losses) on available for sale securities and transferred securities:
Net unrealized holding gains (losses) arising during the period, net of tax amount	(7,246)	(331)	(35,231)	3,912
Reclassification adjustment for net (gains) losses realized in net income, net of tax amount	0	(8)	0	(9)
Change in net unrealized holding loss on securities transferred to held to maturity, net of tax amount	730	698	2,182	2,193
Total securities available for sale and transferred securities, net of tax amount	(6,516)	359	(33,049)	6,096
Pension and other postretirement benefit plans:
Net change in prior service costs, net of tax amount	47	39	140	116
Recognized net loss due to lump sum settlements, net of tax amount	31	0	92	0
Change in net actuarial loss, net of tax amount	271	219	819	1,187
Recognized net loss due to defined benefit plan termination, net of tax amount	0	0	0	10,492
Total pension and other postretirement benefit plans, net of tax amount	349	258	1,051	11,795
Cash flow hedge derivatives:
Change in accumulated gain (loss) on effective cash flow hedge derivatives, net of tax amount	39	33	458	(61)
Reclassification adjustment for (gain) loss realized in net income, net of tax amount	(79)	34	(157)	143
Total cash flow hedge derivatives, net of tax amount	(40)	67	301	82
Total other comprehensive income (loss), net of tax amount	$ (6,207)	$ 684	$ (31,697)	$ 17,973

Shareholders' Equity - Changes

Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 1,599,604	$ 1,582,535	$ 1,599,604	$ 1,582,535	$ 1,571,701	$ 1,520,208
Other comprehensive income (loss) before reclassification			(32,591)	6,044
Amounts reclassified from accumulated other comprehensive loss			894	11,929
Total other comprehensive income (loss), net of tax amount	(6,207)	684	(31,697)	17,973
Reclassification of certain income tax effects related to the change in the federal statutory income tax rate under the Tax Cuts and Jobs Act of 2017 (Tax Reform Act)			(8,524)
Securities Available for Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(65,278)	(14,704)	(65,278)	(14,704)	(26,535)	(20,800)
Other comprehensive income (loss) before reclassification			(33,049)	6,105
Amounts reclassified from accumulated other comprehensive loss				(9)
Total other comprehensive income (loss), net of tax amount			(33,049)	6,096
Reclassification of certain income tax effects related to the change in the federal statutory income tax rate under the Tax Cuts and Jobs Act of 2017 (Tax Reform Act)			(5,694)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(15,307)	(13,185)	(15,307)	(13,185)	(13,468)	(24,980)
Amounts reclassified from accumulated other comprehensive loss			1,051	11,795
Total other comprehensive income (loss), net of tax amount			1,051	11,795
Reclassification of certain income tax effects related to the change in the federal statutory income tax rate under the Tax Cuts and Jobs Act of 2017 (Tax Reform Act)			(2,890)
Cash Flow Hedge Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	639	64	639	64	278	(18)
Other comprehensive income (loss) before reclassification			458	(61)
Amounts reclassified from accumulated other comprehensive loss			(157)	143
Total other comprehensive income (loss), net of tax amount			301	82
Reclassification of certain income tax effects related to the change in the federal statutory income tax rate under the Tax Cuts and Jobs Act of 2017 (Tax Reform Act)			60
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ (79,946)	$ (27,825)	$ (79,946)	$ (27,825)	$ (39,725)	$ (45,798)

Fair Value - Financial Assets a

Fair Value - Financial Assets and Liabilities Measured at Fair Value Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 1,864,633	$ 2,238,635
Loans held for sale	182,664	180,512
Mortgage servicing rights	101,374	84,269	$ 81,477	$ 80,239
U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	32,371	45,285
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	57,264	79,229
Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,864,633	2,238,635
Loans held for sale	182,664	180,512
Mortgage servicing rights	101,374	84,269
Other assets - derivatives	3,287	1,516
Other liabilities - derivatives	4,311	2,678
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	32,371	45,285
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	57,264	79,229
Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,774,998	2,114,121
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	(1,531)	(1,013)
Other liabilities - derivatives	1,070	616
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	1,864,633	2,238,635
Loans held for sale	182,664	180,512
Mortgage servicing rights	0	0
Other assets - derivatives	3,925	1,629
Other liabilities - derivatives	3,241	2,062
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	32,371	45,285
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	57,264	79,229
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	1,774,998	2,114,121
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	101,374	84,269
Other assets - derivatives	893	900
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		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
MSR [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ 84,269	$ 80,239
Total net (loss) gain included in Mortgage banking, net	[1]	4,857	(10,392)
Additions		12,248	11,630
Sales		0	0
Ending Balance		101,374	81,477
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		13,879	(2,218)
Other Assets - Derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		900	1,001
Total net (loss) gain included in Mortgage banking, net	[1]	3,345	3,436
Additions		0	0
Sales		(3,352)	(3,431)
Ending Balance		893	1,006
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		$ 247	$ (1,483)
[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	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Nonfinancial Assets and Liabilities [Abstract]
Outstanding balances in impaired loans	$ 52,500		$ 52,500		$ 48,900
Foreclosed assets re-measured after initial recognition			18,400	$ 22,000
Write-downs of allowance for foreclosed assets after initial recognition			1,900	2,600
Noninterest gain (loss) Mortgage banking, net for changes in fair value of LHFS	(1,300)	$ (202)	416,000	3,500
Interest earned on LHFS included in Interest and fees on LHFS and LHFI	1,500	$ 1,400	3,800	$ 3,700
GNMA optional repurchase loans	$ 47,800		$ 47,800		$ 48,200
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	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	$ 943,883	$ 1,056,486
Net LHFI	8,658,156	8,493,234
Acquired loans	130,901	257,438
Deposits	10,956,910	10,577,512
Long-term FHLB advances	896	946
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	433,471	336,383
Securities held to maturity	943,883	1,056,486
Deposits	10,956,910	10,577,512
Short-term liabilities	676,888	1,440,876
Long-term FHLB advances	896	946
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	433,471	336,383
Securities held to maturity	907,317	1,046,247
Deposits	10,953,348	10,577,858
Short-term liabilities	676,888	1,440,876
Long-term FHLB advances	831	946
Junior subordinated debt securities	53,815	45,773
Level 3 [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	8,658,156	8,493,234
Acquired loans	130,901	257,438
Level 3 [Member] | Estimate Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net LHFI	8,560,091	8,507,469
Acquired loans	$ 130,901	$ 257,438

Fair Value - Fair Value and the

Fair Value - Fair Value and the Contractual Principal Outstanding of the LHFS (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair value and the contractual principal outstanding of the LHFS [Abstract]
Fair value of LHFS	$ 134,874	$ 132,300
LHFS contractual principal outstanding	134,598	129,347
Fair value less unpaid principal	$ 276	$ 2,953

Derivative Financial Instrume_3

Derivative Financial Instruments - Additional Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)Contract	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)Contract	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)Contract	Apr. 04, 2013USD ($)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Accumulated net, after tax gain included in accumulated other comprehensive loss	$ 52,000	$ 53,000	$ 611,000	$ (99,000)
Mortgage Servicing Rights Hedge [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total notional amount	252,000,000		252,000,000		$ 349,000,000
Net (negative) positive ineffectiveness on MSR fair value	72,000	$ (2,600,000)	$ 3,500,000	1,000,000
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
Accumulated net, after tax gain included in accumulated other comprehensive loss			$ 639,000		$ 278,000
The period over which OCI will be reclassified as interest expense			12 months
Estimated amount to be reclassified as a decrease to interest expense	$ 644,000		$ 644,000
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%		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		2
Aggregate notional amount of credit risk participation agreements	$ 13,200,000		$ 13,200,000		$ 13,700,000
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	7		7		6
Aggregate notional amount of credit risk participation agreements	$ 40,300,000		$ 40,300,000		$ 37,100,000
Derivatives not Designated as Hedging Instruments [Member] | Interest Rate Swap [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total notional amount	410,200,000		410,200,000		351,900,000
Termination value of derivatives	0		0		80,000
Collateral Posted	0		0
Derivatives not Designated as Hedging Instruments [Member] | Forward Contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance sheet obligations	199,500,000		199,500,000		182,100,000
Valuation adjustment			930,000		(237,000)
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	$ 102,900,000		102,900,000		83,000,000
Valuation adjustment			$ 893,000		$ 900,000

Derivative Financial Instrume_4

Derivative Financial Instruments - Fair Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	$ 3,925	$ 1,626
Fair value of derivative liability	4,170	1,819
Derivatives in Hedging Relationships [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	852	451
Derivatives not Designated as Hedging Instruments [Member] | Future Contracts [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	(1,569)	(1,088)
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
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	1	6
Derivatives not Designated as Hedging Instruments [Member] | Forward Contracts [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	(930)	237
Derivatives not Designated as Hedging Instruments [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	3,073	1,175
Derivatives not Designated as Hedging Instruments [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	4,170	1,819
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	38	75
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	893	900
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	$ 1,070	$ 616

Derivative Financial Instrume_5

Derivative Financial Instruments - Effects of Derivative Instruments on Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivatives in Hedging Relationships [Member] | Accumulated Other Comprehensive Loss and Other Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Amount of gain (loss) reclassified from accumulated other comprehensive loss and recognized in other interest expense	$ 104	$ (55)	$ 209	$ (232)
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	(1,302)	(466)	(9,243)	688
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	$ (86)	$ (10)	$ (41)	$ (63)

Derivative Financial Instrume_6

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	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivatives, Fair Value [Line Items]
Change in the accumulated gain (loss) on effective cash flow hedge derivatives	$ 39	$ 33	$ 458	$ (61)
Derivatives in Hedging Relationships [Member]
Derivatives, Fair Value [Line Items]
Change in the accumulated gain (loss) on effective cash flow hedge derivatives	$ 39	$ 33	$ 458	$ (61)

Derivative Financial Instrume_7

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	Sep. 30, 2018	Dec. 31, 2017
Offsetting Derivative Assets
Gross Amounts of Recognized Assets, Offsetting of Derivative Assets	$ 3,925	$ 1,626
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	3,925	1,626
Financial Instruments, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Assets	(84)	(311)
Cash Collateral Received, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Assets	(950)	0
Net Amount, Offsetting of Derivative Assets	2,891	1,315
Offsetting Derivative Liabilities
Gross Amounts of Recognized Liabilities, Offsetting of Derivative Liabilities	4,170	1,819
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	4,170	1,819
Financial Instruments, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Liabilities	(84)	(311)
Cash Collateral Posted, Gross Amounts Not Offset in the Statement of Financial Position, Offsetting of Derivative Liabilities		(100)
Net Amount, Offsetting of Derivative Liabilities	$ 4,086	$ 1,408

Segment Information - Additiona

Segment Information - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018Segment
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	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017		Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 106,983	$ 103,912		$ 314,240	$ 303,506
Provision for loan losses, net	8,206	2,019		15,043	3,533
Noninterest income	47,093	44,480	[1]	141,277	140,703	[1]
Noninterest expense	105,223	103,086		311,488	327,218
Income Before Income Taxes	40,647	43,287		128,986	113,458
Income taxes	4,394	8,708		16,090	23,596
Net Income	36,253	34,579		112,896	89,862
Selected Financial Information
Total assets	13,439,812	13,884,655		13,439,812	13,884,655		$ 13,797,953
Depreciation and amortization	9,978	10,052		29,512	28,781
General Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	106,784	103,408		313,299	302,613
Provision for loan losses, net	8,206	2,019		15,043	3,533
Noninterest income	28,557	26,570	[1]	87,587	88,830	[1]
Noninterest expense	89,889	88,814		267,462	284,420
Income Before Income Taxes	37,246	39,145		118,381	103,490
Income taxes	3,536	7,130		13,430	19,772
Net Income	33,710	32,015		104,951	83,718
Selected Financial Information
Total assets	13,364,636	13,811,335		13,364,636	13,811,335
Depreciation and amortization	9,759	9,863		28,959	28,196
Wealth Management [Member]
Segment Reporting Information [Line Items]
Net interest income	134	434		771	718
Noninterest income	7,769	7,512	[1]	22,768	22,513	[1]
Noninterest expense	7,194	6,791		19,996	20,361
Income Before Income Taxes	709	1,155		3,543	2,870
Income taxes	177	441		886	1,098
Net Income	532	714		2,657	1,772
Selected Financial Information
Total assets	9,411	6,635		9,411	6,635
Depreciation and amortization	64	30		116	104
Insurance [Member]
Segment Reporting Information [Line Items]
Net interest income	65	70		170	175
Noninterest income	10,767	10,398	[1]	30,922	29,360	[1]
Noninterest expense	8,140	7,481		24,030	22,437
Income Before Income Taxes	2,692	2,987		7,062	7,098
Income taxes	681	1,137		1,774	2,726
Net Income	2,011	1,850		5,288	4,372
Selected Financial Information
Total assets	65,765	66,685		65,765	66,685
Depreciation and amortization	$ 155	$ 159		$ 437	$ 481
[1]	Trustmark elected the modified retrospective approach of adoption; therefore, prior period balances are presented under legacy GAAP and may not be comparable to current year presentation.

Accounting Policies Recently _3

Accounting Policies Recently Adopted and Pending Accounting Pronouncements - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Corporate income tax rate			21.00%		35.00%
Stranded tax effects, reclassify from accumulated other comprehensive loss to retained earnings			$ 8,500,000		$ 8,500,000
Topic 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Percentage of revenues earned			23.00%
Cumulative adjustment	$ 0		$ 0
Topic 606 [Member] | Before adoption of Topic 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for doubtful accounts related to commission revenue subject to clawback provisions	0		0
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Total outstanding operating lease obligation					$ 67,900,000
Percentage of total outstanding operating lease obligation of total assets					0.50%
Other Expense [Member] | Accounting Standard Update 2017-07 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net periodic benefit cost	$ 885,000	$ 966,000	$ 2,700,000	$ 4,800,000