Iberiabank (IBKC) 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]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	IBKC
Entity Registrant Name	IBERIABANK CORP
Entity Central Index Key	933,141
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		55,544,035

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 291,083	$ 319,156
Interest-bearing deposits in other banks	184,852	306,568
Total cash and cash equivalents	475,935	625,724
Securities available for sale, at fair value	4,634,124	4,590,062
Securities held to maturity (fair values of $207,309 and $227,964, respectively)	213,561	227,318
Mortgage loans held for sale, at fair value	42,976	134,916
Loans and leases, net of unearned income	22,343,906	20,078,181
Allowance for loan and lease losses	(136,950)	(140,891)
Loans and leases, net	22,206,956	19,937,290
Premises and equipment, net	304,605	331,413
Goodwill	1,220,903	1,188,902
Other intangible assets	92,575	88,562
Other assets	926,752	779,942
Total Assets	30,118,387	27,904,129
Deposits:
Non-interest-bearing	6,544,926	6,209,925
Interest-bearing	16,648,520	15,256,792
Total deposits	23,193,446	21,466,717
Short-term borrowings	1,242,719	991,297
Long-term debt	1,466,810	1,495,835
Other liabilities	273,051	253,489
Total Liabilities	26,176,026	24,207,338
Shareholders’ Equity
Preferred stock, $1 par value - 5,000,000 shares authorized Non-cumulative perpetual, liquidation preference $10,000 per share; 13,750 and 13,750 shares issued and outstanding, respectively, including related surplus	132,097	132,097
Common stock, $1 par value - 100,000,000 shares authorized; 56,006,818 and 53,872,272 shares issued and outstanding, respectively	56,007	53,872
Additional paid-in capital	2,950,964	2,787,484
Retained earnings	936,657	769,226
Accumulated other comprehensive income (loss)	(133,364)	(45,888)
Total Shareholders’ Equity	3,942,361	3,696,791
Total Liabilities and Shareholders’ Equity	$ 30,118,387	$ 27,904,129

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Securities held to maturity, fair values	$ 207,309	$ 227,964
Preferred stock, par value (in usd per share)	$ 1	$ 1
Preferred stock, shares authorized	5,000,000	5,000,000
Liquidation preference (per share)	$ 10,000	$ 10,000
Preferred stock, shares issued	13,750	13,750
Preferred stock, shares outstanding	13,750	13,750
Common stock, par value (in usd per share)	$ 1	$ 1
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	56,006,818	53,872,272
Common stock, shares outstanding	56,006,818	53,872,272

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest and Dividend Income
Loans, including fees	$ 283,125	$ 216,888	$ 791,670	$ 565,130
Mortgage loans held for sale, including fees	1,037	1,209	3,027	3,429
Investment securities:
Taxable interest	27,113	24,067	79,058	62,177
Tax-exempt interest	2,680	2,179	8,154	6,303
Other	3,112	2,629	9,524	7,041
Total interest and dividend income	317,067	246,972	891,433	644,080
Deposits:
NOW and MMDA	31,367	15,633	79,128	38,940
Savings	550	401	1,503	1,050
Time deposits	12,484	5,766	28,173	14,980
Short-term borrowings	4,727	4,152	10,578	4,655
Long-term debt	8,714	4,137	23,824	11,111
Total interest expense	57,842	30,089	143,206	70,736
Net interest income	259,225	216,883	748,227	573,344
Provision for loan and lease losses	11,097	18,514	26,678	36,718
Net interest income after provision for loan and lease losses	248,128	198,369	721,549	536,626
Non-interest Income
Income from bank owned life insurance	1,744	1,263	4,287	3,815
Gain (loss) on sale of available for sale securities	0	(242)	(56)	(183)
Other non-interest income	6,607	5,481	17,502	15,291
Total non-interest income	53,087	50,843	151,593	149,805
Non-interest Expense
Salaries and employee benefits	101,159	106,970	313,190	275,140
Net occupancy and equipment	18,889	19,139	58,867	51,452
Communication and delivery	3,773	3,533	11,888	9,534
Marketing and business development	4,068	3,706	13,715	10,368
Data processing	9,036	12,300	30,738	25,374
Professional services	5,519	22,550	20,070	39,104
Credit and other loan related expense	5,117	7,532	14,925	15,838
Insurance	6,536	6,264	20,587	15,279
Travel and entertainment	1,846	2,601	7,880	7,837
Amortization of acquisition intangibles	5,382	4,527	16,595	7,948
Errors, fines, and losses	467	4,714	24,924	7,916
Other non-interest expense	7,557	6,926	21,143	19,148
Total non-interest expense	169,349	200,762	554,522	484,938
Income before income tax expense	131,866	48,450	318,620	201,493
Income tax expense	30,401	18,806	78,410	69,358
Net Income	101,465	29,644	240,210	132,135
Less: Preferred stock dividends	3,599	3,598	8,146	8,146
Net Income Available to Common Shareholders	97,866	26,046	232,064	123,989
Less: Earnings allocated to unvested restricted stock	908	283	2,341	1,052
Earnings allocated to common shareholders	$ 96,958	$ 25,763	$ 229,723	$ 122,937
Earnings per common share - Basic (in usd per share)	$ 1.74	$ 0.49	$ 4.17	$ 2.47
Earnings per common share - Diluted (in usd per share)	1.73	0.49	4.14	2.45
Cash dividends declared per common share (in usd per share)	$ 0.39	$ 0.37	$ 1.15	$ 1.09
Comprehensive Income
Net income	$ 101,465	$ 29,644	$ 240,210	$ 132,135
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during the period (net of tax effects of $5,906, $472, $24,578, and $7,430, respectively)	(22,220)	877	(92,460)	13,799
Less: Reclassification adjustment for gains (losses) included in net income (net of tax effects of $0, $85, $12, and $64, respectively)	0	(157)	(44)	(119)
Unrealized gains (losses) on securities, net of tax	(22,220)	1,034	(92,416)	13,918
Fair value of derivative instruments designated as cash flow hedges:
Change in fair value of derivative instruments designated as cash flow hedges during the period (net of tax effects of $217, $24, $1,266, and $314, respectively)	818	(158)	4,762	(1,081)
Less: Reclassification adjustment for gains (losses) included in net income (net of tax effects of $6, $55, $47, and $134, respectively)	(22)	(101)	(178)	(249)
Fair value of derivative instruments designated as cash flow hedges, net of tax	840	(57)	4,940	(832)
Other comprehensive income (loss), net of tax	(21,380)	977	(87,476)	13,086
Comprehensive income	80,085	30,621	152,734	145,221
Mortgage income
Non-interest Income
Non-interest Income	12,732	16,050	36,048	49,895
Service charges on deposit accounts
Non-interest Income
Non-interest Income	13,520	12,534	39,378	35,097
Title revenue
Non-interest Income
Non-interest Income	6,280	5,643	18,153	16,574
Broker commissions
Non-interest Income
Non-interest Income	2,627	2,094	7,244	7,203
ATM/debit card fee income
Non-interest Income
Non-interest Income	2,470	2,486	8,028	7,615
Credit card and merchant-related income
Non-interest Income
Non-interest Income	3,114	2,848	9,347	7,873
Trust department income
Non-interest Income
Non-interest Income	$ 3,993	$ 2,686	$ 11,662	$ 6,625

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Unrealized holding gains (losses), arising during the period taxes	$ 5,906	$ 472	$ 24,578	$ 7,430
Reclassification adjustment for gains (losses) included in net income, taxes	0	85	12	64
Change in fair value of derivative instruments designated as cash flow hedges, taxes	217	24	1,266	314
Reclassification adjustment for gains (losses) included in net income, taxes	$ 6	$ 55	$ 47	$ 134

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2016		13,750	44,795,386
Beginning balance at Dec. 31, 2016	$ 2,939,694	$ 132,097	$ 44,795	$ 2,084,446	$ 704,391	$ (26,035)
Increase (Decrease) in Shareholders' Equity
Net income	132,135				132,135
Other comprehensive income/(loss)	13,086					13,086
Cash dividends declared	(56,683)				(56,683)
Preferred stock dividends	(8,146)				(8,146)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			358,560
Common stock issued under incentive plans, net of shares surrendered in payment	(1,605)		$ 359	(1,964)
Shares issued (in shares)			8,710,304
Common stock issued	696,794		$ 8,710	688,084
Share-based compensation cost	11,499			11,499
Ending balance (in shares) at Sep. 30, 2017		13,750	53,864,250
Ending balance at Sep. 30, 2017	3,726,774	$ 132,097	$ 53,864	2,782,065	771,697	(12,949)
Beginning balance (in shares) at Dec. 31, 2017		13,750	53,872,272
Beginning balance at Dec. 31, 2017	3,696,791	$ 132,097	$ 53,872	2,787,484	769,226	(45,888)
Increase (Decrease) in Shareholders' Equity
Net income	240,210				240,210
Other comprehensive income/(loss)	(87,476)					(87,476)
Cash dividends declared	(64,288)				(64,288)
Preferred stock dividends	(8,146)				(8,146)
Common stock issued under incentive plans, net of shares surrendered in payment (in shares)			109,983
Common stock issued under incentive plans, net of shares surrendered in payment	(3,142)		$ 110	(3,252)
Common stock issued for acquisitions (in shares)			2,787,773
Common stock issued for acquisitions	214,659		$ 2,788	211,871
Common stock repurchases (in shares)			(763,210)
Common stock repurchases	(61,046)		$ (763)	(60,283)
Share-based compensation cost	15,144			15,144
Ending balance (in shares) at Sep. 30, 2018		13,750	56,006,818
Ending balance at Sep. 30, 2018	$ 3,942,361	$ 132,097	$ 56,007	$ 2,950,964	$ 936,657	$ (133,364)

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash dividends declared per common share (in usd per share)	$ 1.15	$ 1.09
Retained Earnings
Cash dividends declared per common share (in usd per share)	$ 1.15	$ 1.09

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities
Net income	$ 240,210	$ 132,135
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization, and accretion, including amortization of purchase accounting adjustments and market value adjustments	(1,644)	1,060
Provision for loan and lease losses	26,678	36,718
Share-based compensation cost - equity awards	15,144	11,499
Loss (gain) on sale of OREO and long-lived assets, net of impairment	6,831	675
Loss (gain) on sale of available for sale securities	56	183
(Gain) loss on early termination of FDIC loss share agreements	(2,708)	0
Cash paid for early termination of FDIC loss share agreements	(5,637)	0
Expense (benefit) for deferred income taxes	31,348	12,438
Originations of mortgage loans held for sale	(1,139,117)	(1,415,447)
Proceeds from sales of mortgage loans held for sale	1,260,962	1,475,038
Realized and unrealized (gain) loss on mortgage loans held for sale, net	(35,244)	(48,944)
Other operating activities, net	(35,778)	14,062
Net Cash Provided by Operating Activities	361,101	219,417
Cash Flows from Investing Activities
Proceeds from sales of available for sale securities	18,867	577,891
Proceeds from maturities, prepayments and calls of available for sale securities	493,095	410,419
Purchases of available for sale securities, net of available for sale securities acquired	(711,258)	(1,312,762)
Proceeds from maturities, prepayments and calls of held to maturity securities	11,464	6,714
Purchases of held to maturity securities	0	(94,179)
Purchases of equity securities, net of equity securities acquired	(21,090)	(40,749)
Proceeds from sales of equity securities	70,371	6,119
Increase in loans, net of loans acquired	(767,715)	(699,684)
Proceeds from sales of premises and equipment	5,698	2,750
Purchases of premises and equipment, net of premises and equipment acquired	(11,575)	(31,522)
Proceeds from dispositions of OREO	12,166	11,653
Cash paid for additional investment in tax credit entities	(6,059)	(7,160)
Cash received (paid) for acquisition of a business, net of cash paid	99,318	(490,509)
Purchase of bank owned life insurance policies	(50,000)	0
Other investing activities, net	595	893
Net Cash Used in Investing Activities	(856,123)	(1,660,126)
Cash Flows from Financing Activities
Increase (decrease) in deposits, net of deposits acquired	662,680	(456,350)
Net change in short-term borrowings, net of borrowings acquired	251,422	494,029
Proceeds from long-term debt, net of long-term debt acquired	927,884	516,620
Repayments of long-term debt	(1,361,482)	(17,342)
Cash dividends paid on common stock	(62,937)	(52,841)
Cash dividends paid on preferred stock	(8,146)	(8,146)
Net share-based compensation stock transactions	(3,142)	(1,922)
Payments to repurchase common stock	(61,046)	0
Net proceeds from issuance of common stock	0	485,751
Net Cash Provided by Financing Activities	345,233	959,799
Net Increase (Decrease) In Cash and Cash Equivalents	(149,789)	(480,910)
Cash and Cash Equivalents at Beginning of Period	625,724	1,362,126
Cash and Cash Equivalents at End of Period	475,935	881,216
Supplemental Schedule of Non-cash Activities
Acquisition of real estate in settlement of loans	13,066	6,873
Common stock issued in acquisitions	214,659	211,043
Cash paid for:
Interest on deposits and borrowings, net of acquired	137,727	69,057
Income taxes, net	$ 34,604	$ 67,434

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	BASIS OF PRESENTATION General IBERIABANK Corporation is a financial holding company with locations in Louisiana, Arkansas, Tennessee, Alabama, Texas, Florida, Georgia, South Carolina, North Carolina, Mississippi, Missouri, and New York offering commercial, private banking, consumer, small business, wealth and trust management, retail brokerage, mortgage, and title insurance services. The consolidated financial statements include the accounts of the Company and its subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. Certain amounts reported in prior periods have been reclassified to conform to the current period presentation. These reclassifications did not have a material effect on previously reported consolidated financial statements. The accompanying unaudited consolidated financial statements have been prepared in accordance with 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 information or footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments, consisting of normal and recurring items, necessary for a fair presentation of the consolidated financial statements have been made. These interim financial statements should be read in conjunction with the audited consolidated financial statements and footnote disclosures for the Company previously filed with the SEC in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 ("2017 10-K"). Operating results for the period ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. When we refer to the “Company,” “we,” “our,” or “us” in this Report, we mean IBERIABANK Corporation and subsidiaries (consolidated). When we refer to the “Parent,” we mean IBERIABANK Corporation. See the Glossary of Defined Terms at the end of this Report for terms used throughout this Report. Concentrations of Credit Risk Most of the Company’s business activity is with customers located in the southeastern United States. The Company’s lending activity is concentrated in its market areas within those states. The Company has emphasized originations of commercial loans and private banking loans, defined as loans to higher net worth clients. Repayments on loans are expected to come from cash flows of the borrower and/or guarantor. Losses on secured loans are limited by the net realizable value of the collateral upon default of the borrowers and guarantor support. The Company believes it does not have any excessive concentrations to any one industry, loan type, or customer.

Recent Accounting Pronouncement

Recent Accounting Pronouncements (Notes)	9 Months Ended
	Sep. 30, 2018
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncements	RECENT ACCOUNTING PRONOUNCEMENTS Pronouncements adopted during the nine months ended September 30, 2018: ASU No. 2014-09 In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , which implements a common revenue standard and clarifies the principles used for recognizing revenue. The amendments in the ASU clarify that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Revenue from Contracts with Customers The majority of the Company’s income streams (e.g., interest and dividend income and mortgage income) are accounted for in accordance with GAAP literature outside the scope of ASC 606, Revenue from Contracts with Customers . Details regarding income recognition for interest and non-interest streams can be found throughout the Company’s 2017 10-K (including Note 1 - Summary of Significant Accounting Policies). Impairment losses recognized against certain receivables (e.g., NSF fees) and capitalized costs (e.g., sales commissions) associated with contracts within the scope of ASC 606 are immaterial. Non-interest income from service charges on deposit accounts, broker commissions, ATM/debit card fee income, credit card and merchant-related income (e.g., interchange fees), and transactional income from traditional banking services (part of other non-interest income) are the significant income streams within the scope of ASC 606 associated with the IBERIABANK reportable segment. Non-interest income from title revenue is associated with the LTC reportable segment. Recognition of Revenue from Contracts with Customers The Company enters into various contracts with customers to provide traditional banking services, including asset management, on a routine basis. The Company’s performance obligations are generally service-related and provided on a daily or monthly basis. The Company does not typically have performance obligations which extend beyond a reporting period. The performance obligations are generally satisfied upon completion of service (i.e., as services are rendered) and the fees are collected at such time, or shortly thereafter. The fees are readily determinable and allocated individually to each service. It is not typical for contracts to require significant judgment to determine the transaction price. Some contracts contain variable consideration; however, the variable consideration is generally constrained (not estimable) as it is based on the occurrence or nonoccurence of a contingent event (or another constraint in some circumstances). The Company generally records the variable consideration when the contingent event occurs and the fee is determinable. The Company provides some services for customers in which it acts in an agent capacity, but generally acts in a principal capacity. Payment terms and conditions vary slightly amongst services; however, amounts are generally invoiced and due or collected by the Company within 30 days, although some fees may be prepaid. The Company bills the customer periodically as performance obligations are satisfied for most services. Therefore, revenue for services provided is generally recognized in the amount invoiced (except in circumstances of prepayment) as that amount corresponds directly to the value of the Company’s performance. In the normal course of business, the Company does not generally grant refunds for services provided. As such, the Company does not establish provisions for estimated returns. Title revenue associated with services provided by LTC, as well as broker commissions, ATM/debit card fee income, credit card and merchant-related income (e.g., interchange fees), and transactional fees from traditional banking services generated within IBERIABANK are generally recognized at the point-in-time the services are provided. The Company has determined this recognition to be appropriate as, upon completion of services, the Company has completed its performance obligations, has a present right to payment (or has collected the cash), and the customer is able to obtain (or has obtained) substantially all of the benefits from the performance obligation (i.e., the provided services). Revenues from service charges on deposit accounts are recognized at the end of the monthly service period (e.g., account service charges) or the date the performance obligation is satisfied (e.g., NSF, stop payment, wire transfer, etc.), except for deposit account services performed by Treasury Management which are recognized on a monthly basis, as these services are performed over that time. Asset management fees (e.g., trust fees) are generally recognized at the end of the monthly service period, but fees are not collected until the beginning of the subsequent month, although some contracts may have quarterly terms and/or be prepaid. NSF fees which are not initially paid are subsequently recorded as “loans” (along with the overdraft balance) and remain classified as such until the amount is paid or charged-off (generally after 60 days). Adoption of ASC 606 The Company adopted ASC 606 as of January 1, 2018 for all contracts as of the effective date. Prior period amounts have been reclassified to conform to current guidance requirements related to the net presentation of certain costs associated with interchange fees and rewards programs. The reclassification of prior period amounts reduced non-interest income and non-interest expense by an immaterial amount (approximately $2.2 million and $6.6 million for the three and nine months ended September 30, 2017, respectively) and had no impact on net income. There was no cumulative adjustment made to opening retained earnings as of January 1, 2018. ASU No. 2016-01 In January 2016, the FASB issued ASU No. 2016-01, Financial Statements - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , which impacts how the Company measures certain equity investments and discloses and presents certain financial instruments through the application of the “exit price” notion. The Company adopted the amendments beginning January 1, 2018. Under the new guidance, equity investments can no longer be classified as trading or available for sale (AFS), and related unrealized holding gains and losses can no longer be recognized in OCI. Per the ASU, such equity investments should be measured at fair value, with adjustments recognized in earnings at the end of each reporting period. As such, the Company reclassified its portfolio of equity investments (which were insignificant at the adoption date and at September 30, 2018) previously classified as AFS investment securities to “other assets.” As these equity investments were previously measured at fair value, implementation of the ASU did not impact the Company’s valuation method. In accordance with the adoption of the ASU, the Company recorded a cumulative-effect adjustment to retained earnings for previously recorded fair value adjustments related to these equity investments, which was insignificant. The Company elected the practical expedient measurement alternative to prospectively account for other equity investments that do not have readily determinable fair values at cost less impairment plus or minus observable price changes in orderly transactions for an identical or similar investment of the same issuer. These investments are insignificant overall and are classified within “other assets” on the Company’s consolidated balance sheets. The Company also modified its fair value methodology for loans measured at amortized cost whose fair values were previously disclosed using an “entry price” methodology to an “exit price” methodology, in accordance with the ASU. The Company’s “exit price” methodology estimates the fair value of these loans based on the present value of the future cash flows using the interest rate that would be charged for a similar loan to a borrower with similar risk at the indicated balance sheet date, adjusted for a liquidity discount based on the estimated time period to complete a sale transaction with a market participant. ASU No. 2016-15 In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (ASC 230): Classification of Certain Cash Receipts and Cash Payments , in order to reduce current diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The Company retrospectively adopted the amendments effective January 1, 2018. The adoption of these amendments did not impact the Company’s consolidated statements of cash flows. ASU No. 2017-04 In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (ASC 350): Simplifying the Test for Goodwill Impairment, which simplifies how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Therefore, any carrying amount which exceeds the reporting unit’s fair value (up to the amount of goodwill recorded) will be recognized as an impairment loss. The ASU is effective for annual reporting periods beginning after December 15, 2019, including interim periods within those periods. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company elected to early adopt the guidance, effective September 30, 2018. The adoption of the guidance did not impact the Company’s consolidated financial statements in the current period. The Company will apply the guidance prospectively, beginning with its annual impairment test as of October 1, 2018. ASU No. 2017-12 In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities, which amends the hedge accounting model to enable entities to better portray the economics of their risk management activities in the financial statements and enhance the transparency and understandability of hedge results. The Company elected to early adopt the amendments effective January 1, 2018. The modified-retrospective adoption of the amendments did not impact the Company’s consolidated financial statements in the current or prior periods. ASU 2018-15 In August 2018, the FASB issued ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The guidance requires customers in a cloud computing arrangement (i.e., hosting arrangement) that is a service contract to follow the internal-use software guidance in ASC 350-40 to determine which implementation costs to capitalize as assets or expense as incurred. ASC 350-40 requires the capitalization of certain costs incurred only during the application development stage (e.g., costs of integration with on-premises software, coding, configuration, and customization). ASC 350-40 also requires entities to expense costs during the preliminary project and post-implementation stages (e.g., costs of project planning, training, maintenance after implementation, data conversion) as they are incurred. The accounting for the service element of the arrangement is not affected by the ASU. Capitalized implementation costs related to a hosting arrangement that is a service contract should be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. The expense related to the capitalized implementation costs should be presented in the same line item in the income statement as the fees associated with the hosting element of the arrangement. Capitalized implementation costs should be presented in the same line item in the statement of financial position that a prepayment of the fees for the associated hosting arrangement would be presented. Payments for capitalized implementation costs should be classified in the statement of cash flows in the same manner as payments of the fees for the service component of the hosting arrangement (typically operating cash flows). The amendments further require entities to disclose the nature of their hosting arrangements that are service contracts and make the disclosures in ASC 360-10 as if the capitalized implementation costs were a separate major class of depreciable asset. The ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim period. Entities have the option to apply the guidance retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company elected to early adopt the guidance prospectively, effective August 31, 2018. The adoption of the guidance did not impact the Company’s consolidated financial statements in the current period. Pronouncements issued but not yet adopted: ASU No. 2016-02 and ASU No. 2018-11 In February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842) . A significant amendment to existing GAAP from this ASU is the recognition of lease assets (i.e., right of use assets) and liabilities on the balance sheet for leases that are classified as operating leases by lessees. The lessor model remains similar to the current accounting model in existing GAAP. Additional amendments include, but are not limited to, the elimination of leveraged leases; modification to the definition of a lease; amendments on sale and leaseback transactions; and disclosure of additional quantitative and qualitative information. ASU 2016-02 will be effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. In July 2018, the FASB issued ASU No. 2018-11, Leases (ASC 842): Targeted Improvements. The amendments include an optional transition method to apply ASU 2016-02 on a prospective basis as of the effective date, with a cumulative effect adjustment to retained earnings in the period of adoption, instead of applying the guidance using a modified retrospective approach as originally required under ASU 2016-02. ASU 2018-11 also provides lessors with a practical expedient, by class of underlying asset, to not separate nonlease components from the associated lease component under certain circumstances, and clarifies which guidance (ASC 842 or ASC 606) to apply to combined lease and nonlease components. The Company occupies certain banking offices and equipment under operating lease agreements, which currently are not recognized on the consolidated balance sheets. Based on the Company’s preliminary analysis of its current portfolio, the impact to the Company’s consolidated balance sheets is estimated to result in less than a 1% increase in assets and liabilities. The Company has developed an implementation plan and selected a third-party vendor to assist in the implementation and subsequent accounting for leases under the ASUs. The Company will elect the optional transition method and adopt ASU 2016-02 and ASU No. 2018-11 on January 1, 2019. The Company is still assessing other practical expedients it may elect at adoption, the final determination of the incremental borrowing rate, and the impact to regulatory capital ratios, amongst other matters associated with the ASUs. The adjustment to retained earnings is not expected to be significant based on the transition guidance associated with current sale-leaseback agreements. The Company also anticipates additional disclosures to be provided at adoption. ASU No. 2016-13 In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (ASC 326): Measurement of Credit Losses on Financial Instruments . The amendments introduce an impairment model that is based on expected credit losses (“ECL”), rather than incurred losses, to estimate credit losses on certain types of financial instruments (e.g., loans and held-to-maturity securities), including certain off-balance sheet financial instruments (e.g., loan commitments). The measurement of ECL should consider historical information, current information, and reasonable and supportable forecasts, including estimates of prepayments, over the contractual term. Financial instruments with similar risk characteristics must be grouped together when estimating ECL. The ASU also amends the current AFS security impairment model for debt securities. The new model will require an estimate of ECL when the fair value is below the amortized cost of the asset through the use of an allowance to record estimated credit losses (and subsequent recoveries). Non-credit related losses will continue to be recognized through OCI. In addition, the amendments provide for a simplified accounting model for purchased financial assets with a more-than-insignificant amount of credit deterioration since their origination. The initial estimate of expected credit losses would be recognized through an ALLL with an offset (i.e., increase) to the cost basis of the related financial asset at acquisition. ASU 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods. The amendments will be applied through a modified-retrospective approach, resulting in a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. A prospective transition approach is required for debt securities for which OTTI had been recognized before the effective date. Amounts previously recognized in AOCI as of the date of adoption that relate to improvements in cash flows expected to be collected should continue to be accreted into income over the remaining life of the asset. Recoveries of amounts previously written off relating to improvements in cash flows after the date of adoption should be recorded in earnings when received. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements. The Company has engaged third-party consultants to assist with the ASU and has developed an implementation plan. ASU No. 2018-13 In August 2018, the FASB released ASU No. 2018-13, Fair Value Measurement (ASC 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The amendments to the guidance on fair value disclosures eliminate the requirements for all entities to disclose (i) the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, (ii) the entity’s policy for the timing of transfers between levels of the fair value hierarchy, and (iii) the entity’s valuation processes for Level 3 fair value measurements. New disclosure requirements for public entities per the ASU include (i) the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements of instruments held at the end of the reporting period, and (ii) the range and weighted average used to develop significant unobservable inputs and how the weighted average was calculated for recurring and nonrecurring Level 3 fair value measurements, with certain exceptions. For derivative instruments and certain other assets and liabilities, entities are permitted to disclose other quantitative information (such as the median or arithmetic average) if doing so provides a more reasonable and rational reflection of the distribution of unobservable inputs used to develop Level 3 fair value measurements. The amendments also modified disclosure guidance within ASC 820 to clarify that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date, rather than a point in the future. Further, entities that use the practical expedient to measure the fair value of certain investments at their net asset values are required to disclose (i) the timing of liquidation of an investee’s assets, and (ii) the date when redemption restrictions will lapse only if the investee has communicated this information to the entity or announced the timing publicly. ASU 2018-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods. The guidance on changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 measurements, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty is applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted, including interim periods, and entities may elect to early adopt either (i) the entire standard, or (ii) only the provisions that eliminate or modify disclosure requirements. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements. ASU No. 2018-16 In October 2018, the FASB released ASU No. 2018-16, Derivatives and Hedging (ASC 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes , which permits the use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under ASC 815 in addition to the interest rates on direct Treasury obligations of the U.S. government (UST), the London Interbank Offered Rate (LIBOR) swap rate, the OIS Rate based on the Fed Funds Effective Rate, and the Securities Industry and Financial Markets Association (SIFMA) Municipal Swap Rate. For entities that have not already adopted ASU No. 2017-12, Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities, ASU 2018-16 is required to be adopted concurrently with the amendments in ASU 2017-12. For entities that already have adopted ASU 2017-12, ASU 2018-16 will be effective for fiscal years beginning after December 15, 2018, including interim periods. Early adoption is permitted in any interim period upon issuance of ASU 2018-16 if an entity already has adopted ASU 2017-12. The amendments should be adopted on a prospective basis for qualifying new or redesignated hedging relationships entered into, on, or after the date of adoption. The implementation of the amendments will not have a significant impact on the Company’s consolidated financial statements based upon its current hedging strategies. ASU No. 2018-17 In October 2018, the FASB released ASU No. 2018-17, Consolidation (ASC 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities, which improves the consistency of the application of the variable interest entity (VIE) related party guidance for common control arrangements. The amendments require reporting entities to consider indirect interests held through related parties under common control on a proportional basis rather than as the equivalent of a direct interest in its entirety (as currently required in GAAP) when determining whether a decision-making fee is a variable interest. ASU 2018-17 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The amendments should be applied retrospectively with a cumulative-effect adjustment to retained earnings at the beginning of the earliest period presented. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements.

Acquisition Activity

Acquisition Activity	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisition Activity	ACQUISITION ACTIVITY The acquisitions discussed below qualify as business combinations. The Company accounts for business combinations under the acquisition method in accordance with ASC Topic 805, Business Combinations . See Note 1, Summary of Significant Accounting Policies, in the 2017 10-K for a description of the Company's accounting for business combinations. 2018 Acquisitions Acquisition of Gibraltar The Company completed the acquisition of Gibraltar Private Bank & Trust Co. ("Gibraltar") on March 23, 2018. The acquisition added $1.5 billion in loans and $1.1 billion in deposits, based on preliminary purchase accounting adjustments. Gibraltar operated eight offices in total, with seven located in the Florida metropolitan statistical areas of Miami, Key West, and Naples and one in New York City. Under the terms of the Agreement and Plan of Merger, Gibraltar common shareholders received 1.9749 shares of IBERIABANK Corporation common stock for each outstanding share of Gibraltar common stock. Based on the Company's closing common stock price of $77.00 per share on March 23, 2018, the aggregate value of the acquisition consideration paid at the time of closing was approximately $214.7 million . During the first quarter of 2018, the Company recorded preliminary purchase price allocations related to Gibraltar. Throughout the second and third quarters of 2018, the Company continued to analyze the valuations assigned to the acquired assets and liabilities assumed. Based on new information relating to events or circumstances existing at the acquisition date and revised valuations, the Company updated estimated fair values decreasing goodwill by $2.9 million to $49.6 million during the third quarter of 2018. This decrease is primarily a result of an adjustment to the acquired lease liability. As of September 30, 2018, the Company continues to review its fair value estimates and additional adjustments may be required. The following table summarizes the consideration paid for Gibraltar's net assets and the preliminary fair value estimates of the identifiable assets acquired and liabilities assumed as of the acquisition date. (Dollars in thousands) Number of Shares Amount Equity consideration Common stock issued 2,787,773 $ 214,659 Total equity consideration 214,659 Non-equity consideration Cash 7 Total consideration paid 214,666 Fair value of net assets assumed including identifiable intangible assets 165,044 Goodwill $ 49,622 (Dollars in thousands) Gibraltar Fair Value (Preliminary) Assets Cash and cash equivalents $ 102,575 Investment securities 19,169 Equity securities 27,519 Loans 1,465,278 Core deposit intangible assets 18,529 Other assets 12,005 Total assets acquired $ 1,645,075 Liabilities Deposit liabilities $ 1,064,803 Long-term borrowings 405,107 Deferred tax liability, net 5,960 Other liabilities 4,161 Total liabilities assumed $ 1,480,031 The following is a description of the methods used to determine the fair values of significant assets acquired and liabilities assumed presented above. Cash and Cash Equivalents: The carrying amount of these assets is a reasonable estimate of fair value based on the short-term nature of these assets. Investment Securities: Fair values for securities were based on quoted market prices from multiple bond dealers. The simple average of the prices received was used to calculate the adjustments. Equity Securities: The carrying amount of these securities is a reasonable estimate of fair value based on the short-term nature of these assets. Loans: Fair values for loans were based on a discounted cash flow methodology that considered factors including loan type, classification status, remaining term of the loan, fixed or variable interest rate, amortization status and current discount rates. The discount rates used for loans were based on current market rates for new originations of comparable loans and included adjustments for any liquidity concerns. The discount rate did not include an explicit factor for credit losses, as that was included as a reduction to the estimated cash flows. Core Deposit Intangible Assets ("CDI"): The fair value for CDI was estimated based on a discounted cash flow methodology that gave appropriate consideration to expected customer attrition rates, net maintenance cost of the deposit base, alternative costs of funds, and the interest costs associated with the customer deposits. The CDI is being amortized over its estimated useful life of approximately ten years utilizing an accelerated method. Deposit Liabilities: The fair values used for the demand and savings deposits by definition equal the amount payable on demand at the acquisition date. Fair values for time deposits were estimated using a discounted cash flow analysis, that applied interest rates currently being offered to the contractual interest rates on such time deposits. Long-term Borrowings: The carrying amount of long-term borrowings at the acquisition date approximated fair value, as the Company immediately paid off the debt upon acquisition. Acquisition of SolomonParks On January 12, 2018, the Company's subsidiary, Lenders Title Company ("LTC"), acquired SolomonParks Title & Escrow, LLC ("SolomonParks"). Under the terms of the agreement, LTC paid $3.3 million in cash to acquire eight title offices in the Nashville, Tennessee area, which resulted in goodwill of $3.4 million . In addition, the agreement provides for potential additional cash consideration of up to $750 thousand based on gross revenues over a two-year period after the acquisition. Information regarding the preliminary allocation of goodwill recorded as a result of these acquisitions to the Company's reportable segments is provided in Note 7 "Goodwill and Other Intangible Assets." The goodwill recorded as a result of these acquisitions is not deductible for tax purposes. 2017 Acquisition Acquisition of Sabadell United The Company completed the acquisition of Sabadell United Bank, N.A. ("Sabadell United") from Banco de Sabadell, S.A. ("Banco Sabadell") on July 31, 2017. The acquisition added $4.0 billion in loans and $4.4 billion in deposits after fair value adjustments. The acquisition expanded the Company's presence in Southeast Florida adding 25 offices serving the Miami metropolitan area and three offices in Naples, Sarasota and Tampa. Under the terms of the Stock Purchase Agreement, Banco Sabadell received $809.2 million in cash and 2,610,304 shares of IBERIABANK Corporation common stock in exchange for 100 percent of Sabadell United's common stock. The cash consideration was financed through two public common stock offerings completed on December 7, 2016, and March 7, 2017. During the third quarter of 2017, the Company recorded preliminary purchase price allocations related to Sabadell United. Throughout the remainder of 2017 and the first six months of 2018, the Company continued to analyze the valuations assigned to the acquired assets and liabilities assumed. Based on new information relating to events or circumstances existing at the acquisition date and revised valuations, the Company updated estimated fair values decreasing goodwill by $21.0 million to $441.0 million during the first six months of 2018. This decrease was primarily a result of a change in the estimated fair value of the acquired loans and deferred tax asset. The valuation of the Sabadell United acquisition was final as of June 30, 2018, therefore there were no measurement period adjustments made during the third quarter of 2018. The following table summarizes the consideration paid for Sabadell United's net assets and the fair value estimates of identifiable assets acquired and liabilities assumed as of the acquisition date. See Note 3, Acquisition Activity, in the 2017 10-K for a description of the methods used to determine the fair values of significant assets acquired and liabilities assumed presented below. (Dollars in thousands) Number of Shares Amount Equity consideration Common stock issued 2,610,304 $ 211,043 Total equity consideration 211,043 Non-equity consideration Cash 809,159 Total consideration paid 1,020,202 Fair value of net assets assumed including identifiable intangible assets 579,157 Goodwill $ 441,045 (Dollars in thousands) Sabadell United Fair Value Assets Cash and cash equivalents $ 318,819 Investment securities 964,123 Loans 4,030,777 Core deposit intangible assets 66,600 Deferred tax asset, net 44,480 Other assets 92,820 Total assets acquired $ 5,517,619 Liabilities Deposit liabilities $ 4,382,780 Short-term borrowings 520,539 Other liabilities 35,143 Total liabilities assumed $ 4,938,462 Information regarding the allocation of goodwill recorded as a result of the acquisition to the Company's reportable segments is provided in Note 7 "Goodwill and Other Intangible Assets." The goodwill recorded as a result of the acquisition is not deductible for tax purposes. The Company's consolidated financial statements as of and for the period ended September 30, 2018 include the operating results of the acquired assets and liabilities assumed. Due to the system conversion of Sabadell United in October 2017 and subsequent streamlining and integration of the operating activities into those of the Company, historical reporting for the former Sabadell United operations is impracticable and thus disclosure of the revenue from the assets acquired and income before income taxes is impracticable for the period subsequent to acquisition. The following table presents unaudited pro forma information as if the acquisition occurred on January 1, 2016. The pro forma information does not necessarily reflect the results of operations that would have occurred had the Company acquired Sabadell United on January 1, 2016. Furthermore, cost savings and other business synergies related to the acquisition are not reflected in the pro forma amounts. Unaudited Pro Forma Information for the (Dollars in thousands) Three months ended September 30, 2017 Nine months ended September 30, 2017 Net interest income $ 232,828 $ 688,846 Non-interest income 54,511 164,360 Net income 30,825 163,968 This pro forma information combines the historical consolidated results of operations of IBERIABANK and Sabadell United for the periods presented and gives effect to the following non recurring adjustments: Fair value adjustments: Pro forma adjustment to net interest income of $3.0 million for the three months ended September 30, 2017 and $20.3 million for the nine months ended September 30, 2017 to record estimated amortization of premiums and accretion of discounts on acquired loans, securities, and deposits. Sabadell United accretion / amortization: Pro forma adjustment to net interest income of $22.3 thousand for the three months ended September 30, 2017 and $1.3 million for the nine months ended September 30, 2017 to eliminate Sabadell United's amortization of premiums and accretion of discounts on previously acquired loans, securities, FDIC indemnification asset, and deposits. Sabadell United provision for loan losses: Pro forma adjustments were made to provision for loan losses of $918.3 thousand for the three months ended September 30, 2017 and $6.4 million for the nine months ended September 30, 2017 to eliminate the reversal (benefit) of Sabadell United's release of provision for loan losses and to account for the provision for loan losses on new loans originated during the period presented. Amortization of acquired intangibles: Pro forma adjustment to non-interest expense of $846.6 thousand for the three months ended September 30, 2017 and $5.9 million for the nine months ended September 30, 2017 to record estimated amortization of acquired intangible assets. Other adjustments: Pro forma results also include adjustments related to the removal of benefit from release of reserve for unfunded lending commitments, removal of FDIC clawback liability expense, adjustments to FDIC insurance and other regulatory assessment expenses and related income tax effects.

Investment Securities

Investment Securities	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	INVESTMENT SECURITIES The amortized cost and fair values of investment securities, with gross unrealized gains and losses, consist of the following: September 30, 2018 (Dollars in thousands) Amortized Gross Gross Estimated Securities available for sale: U.S. Government-sponsored enterprise obligations $ 40,996 $ 5 $ (740 ) $ 40,261 Obligations of state and political subdivisions 265,565 694 (4,852 ) 261,407 Mortgage-backed securities: Residential agency 3,654,417 68 (140,816 ) 3,513,669 Commercial agency 721,899 — (26,513 ) 695,386 Other securities 126,098 — (2,697 ) 123,401 Total securities available for sale $ 4,808,975 $ 767 $ (175,618 ) $ 4,634,124 Securities held to maturity: Obligations of state and political subdivisions $ 194,382 $ 349 $ (5,277 ) $ 189,454 Mortgage-backed securities: Residential agency 19,179 28 (1,352 ) 17,855 Total securities held to maturity $ 213,561 $ 377 $ (6,629 ) $ 207,309 December 31, 2017 (Dollars in thousands) Amortized Gross Gross Estimated Securities available for sale: U.S. Government-sponsored enterprise obligations $ 41,003 $ 18 $ (406 ) $ 40,615 Obligations of state and political subdivisions 271,451 4,246 (1,493 ) 274,204 Mortgage-backed securities: Residential agency 3,675,367 1,233 (52,090 ) 3,624,510 Commercial agency 546,105 228 (8,938 ) 537,395 Other securities 114,005 247 (914 ) 113,338 Total securities available for sale $ 4,647,931 $ 5,972 $ (63,841 ) $ 4,590,062 Securities held to maturity: Obligations of state and political subdivisions $ 206,736 $ 1,530 $ (275 ) $ 207,991 Mortgage-backed securities: Residential agency 20,582 41 (650 ) 19,973 Total securities held to maturity $ 227,318 $ 1,571 $ (925 ) $ 227,964 Securities with carrying values of $2.3 billion were pledged to support repurchase transactions, public funds deposits and certain long-term borrowings at September 30, 2018 compared to $2.1 billion at December 31, 2017 . Information pertaining to securities with gross unrealized losses, aggregated by investment category and length of time that individual securities have been in a continuous loss position, is as follows: September 30, 2018 Less Than Twelve Months Twelve Months or More Total (Dollars in thousands) Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Securities available for sale: U.S. Government-sponsored enterprise obligations $ — $ — $ (740 ) $ 39,259 $ (740 ) $ 39,259 Obligations of state and political subdivisions (839 ) 107,014 (4,013 ) 90,761 (4,852 ) 197,775 Mortgage-backed securities: Residential agency (23,673 ) 1,009,754 (117,143 ) 2,482,730 (140,816 ) 3,492,484 Commercial agency (4,657 ) 268,207 (21,856 ) 418,295 (26,513 ) 686,502 Other securities (1,310 ) 93,529 (1,387 ) 29,872 (2,697 ) 123,401 Total securities available for sale $ (30,479 ) $ 1,478,504 $ (145,139 ) $ 3,060,917 $ (175,618 ) $ 4,539,421 Securities held to maturity: Obligations of state and political subdivisions $ (3,725 ) $ 115,138 $ (1,552 ) $ 40,960 $ (5,277 ) $ 156,098 Mortgage-backed securities: Residential agency — — (1,352 ) 17,544 (1,352 ) 17,544 Total securities held to maturity $ (3,725 ) $ 115,138 $ (2,904 ) $ 58,504 $ (6,629 ) $ 173,642 December 31, 2017 Less Than Twelve Months Twelve Months or More Total (Dollars in thousands) Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Securities available for sale: U.S. Government-sponsored enterprise obligations $ (254 ) $ 29,744 $ (152 ) $ 9,848 $ (406 ) $ 39,592 Obligations of state and political subdivisions (326 ) 31,601 (1,167 ) 68,609 (1,493 ) 100,210 Mortgage-backed securities: Residential agency (22,760 ) 2,366,569 (29,330 ) 1,061,588 (52,090 ) 3,428,157 Commercial agency (3,503 ) 310,769 (5,435 ) 164,470 (8,938 ) 475,239 Other securities (914 ) 75,302 — — (914 ) 75,302 Total securities available for sale $ (27,757 ) $ 2,813,985 $ (36,084 ) $ 1,304,515 $ (63,841 ) $ 4,118,500 Securities held to maturity: Obligations of state and political subdivisions $ (263 ) $ 65,817 $ (12 ) $ 3,031 $ (275 ) $ 68,848 Mortgage-backed securities: Residential agency (2 ) 333 (648 ) 19,269 (650 ) 19,602 Total securities held to maturity $ (265 ) $ 66,150 $ (660 ) $ 22,300 $ (925 ) $ 88,450 The Company assessed the nature of the unrealized losses in its portfolio as of September 30, 2018 and December 31, 2017 to determine if there are losses that should be deemed other-than-temporary. In its analysis of these securities, management considered numerous factors to determine whether there were instances where the amortized cost basis of the debt securities would not be fully recoverable, including, but not limited to: • The length of time and extent to which the estimated fair value of the securities was less than their amortized cost; • Whether adverse conditions were present in the operations, geographic area, or industry of the issuer; • The payment structure of the security, including scheduled interest and principal payments, the issuer’s failures to make scheduled payments, if any, and the likelihood of failure to make scheduled payments in the future; • Changes to the rating of the security by a rating agency; and • Subsequent recoveries or additional declines in fair value after the balance sheet date. Management believes it has considered these factors, as well as all relevant information available, when determining the expected future cash flows of the securities in question. In each instance, management has determined the cost basis of the securities would be fully recoverable. Management also has the intent to hold debt securities until their maturity or anticipated recovery if the security is classified as available for sale. In addition, management does not believe the Company will be required to sell debt securities before the anticipated recovery of the amortized cost basis of the security. As a result of the Company's analysis, no declines in the estimated fair value of the Company's investment securities were deemed to be other-than-temporary at September 30, 2018 or December 31, 2017 . At September 30, 2018 , 719 debt securities had unrealized losses of 3.72% of the securities’ amortized cost basis. At December 31, 2017 , 544 debt securities had unrealized losses of 1.52% of the securities’ amortized cost basis. The unrealized losses for each of the securities related to market interest rate changes and not credit concerns of the issuers. Additional information on securities that have been in a continuous loss position for over twelve months at September 30, 2018 and December 31, 2017 is presented in the following table: (Dollars in thousands) September 30, 2018 December 31, 2017 Number of securities: Mortgage-backed securities: Residential agency 336 153 Commercial agency 65 28 Obligations of state and political subdivisions 53 28 U.S. Government-sponsored enterprise obligations 3 1 Other securities 7 — 464 210 Amortized Cost Basis: Mortgage-backed securities: Residential agency $ 2,618,769 $ 1,110,834 Commercial agency 440,151 169,905 Obligations of state and political subdivisions 137,286 72,820 U.S. Government-sponsored enterprise obligations 39,999 10,000 Other securities 31,259 — $ 3,267,464 $ 1,363,559 Unrealized Loss: Mortgage-backed securities: Residential agency $ 118,495 $ 29,977 Commercial agency 21,856 5,435 Obligations of state and political subdivisions 5,565 1,180 U.S. Government-sponsored enterprise obligations 740 152 Other securities 1,387 — $ 148,043 $ 36,744 The Fannie Mae, Freddie Mac, and Ginnie Mae securities noted above carry a rating of AA+/Aaa by S&P and Moody's. The amortized cost and estimated fair value of investment securities by maturity at September 30, 2018 are presented in the following table. Securities are classified according to their contractual maturities without consideration of principal amortization, potential prepayments or call options. Accordingly, actual maturities may differ from contractual maturities. Weighted average yields are calculated on the basis of the yield to maturity based on the amortized cost of each security. Securities Available for Sale Securities Held to Maturity (Dollars in thousands) Weighted Amortized Estimated Weighted Amortized Estimated Within one year or less 1.90 % $ 19,161 $ 19,056 4.00 % $ 435 $ 436 One through five years 2.25 150,119 147,472 2.80 8,776 8,751 After five through ten years 2.47 1,104,969 1,069,983 2.58 45,368 44,690 Over ten years 2.45 3,534,726 3,397,613 2.60 158,982 153,432 2.44 % $ 4,808,975 $ 4,634,124 2.61 % $ 213,561 $ 207,309 The following is a summary of realized gains and losses from the sale of securities classified as available for sale. Gains or losses on securities sold are recorded on the trade date, using the specific identification method. Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Realized gains $ — $ 667 $ 39 $ 909 Realized losses — (909 ) (95 ) (1,092 ) $ — $ (242 ) $ (56 ) $ (183 ) In addition to the gains above, the Company realized certain gains on calls of securities held to maturity that were not significant to the consolidated financial statements. Other Equity Securities The Company accounts for the following securities at cost less impairment plus or minus any observable price changes, which approximates fair value, with the exception of CRA and Community Development Investment Funds, which are recorded at fair value. Other Equity Securities, which are presented in “other assets” on the consolidated balance sheets, are as follows: (Dollars in thousands) September 30, 2018 December 31, 2017 Federal Home Loan Bank (FHLB) stock $ 102,508 $ 95,171 Federal Reserve Bank (FRB) stock 85,630 79,191 CRA and Community Development Investment Funds 1,866 — Other investments 9,838 3,008 $ 199,842 $ 177,370

Loans and Leases

Loans and Leases	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Loans	LOANS AND LEASES Loans and leases consist of the following for the periods indicated: (Dollars in thousands) September 30, 2018 December 31, 2017 Commercial loans and leases: Real estate - construction $ 1,127,988 $ 1,240,396 Real estate - owner-occupied 2,458,964 2,375,321 Real estate - non-owner-occupied 5,794,931 5,322,513 Commercial and industrial (1) 5,581,040 5,135,067 14,962,923 14,073,297 Residential mortgage loans 4,300,163 3,056,352 Consumer loans: Home equity 2,350,176 2,292,275 Other 730,644 656,257 3,080,820 2,948,532 Total $ 22,343,906 $ 20,078,181 (1) Includes equipment financing leases Net deferred loan origination fees were $29.6 million and $29.3 million at September 30, 2018 and December 31, 2017 , respectively. Total net discount on the Company's loans was $143.2 million and $159.3 million at September 30, 2018 and December 31, 2017 , respectively, of which $75.6 million and $94.7 million was related to non-impaired loans. Net loan discounts include preliminary discounts recorded on Gibraltar loans, which are subject to change upon receipt of final fair value estimates during the measurement period. In addition to loans issued in the normal course of business, the Company considers overdrafts on customer deposit accounts to be loans and reclassifies these overdrafts as loans in its consolidated balance sheets. At September 30, 2018 and December 31, 2017 , overdrafts of $6.3 million and $7.4 million , respectively, have been reclassified to loans. Loans with carrying values of $7.5 billion and $6.6 billion were pledged as collateral for borrowings at September 30, 2018 and December 31, 2017 , respectively. Aging Analysis The following tables provide an analysis of the aging of loans as of September 30, 2018 and December 31, 2017 . Past due and non-accrual loan amounts exclude acquired impaired loans, even if contractually past due or if the Company does not expect to receive payment in full, as the Company is currently accreting interest income over the expected life of the loans. September 30, 2018 Accruing (Dollars in thousands) Current or Less Than 30 days Past Due 30-59 days 60-89 days > 90 days Total Past Due Non-accrual Acquired Impaired Total Real estate- construction $ 1,105,488 $ 75 $ 830 $ — $ 905 $ 1,122 $ 20,473 $ 1,127,988 Real estate- owner-occupied 2,353,176 1,792 872 2,930 5,594 19,089 81,105 2,458,964 Real estate- non-owner-occupied 5,678,485 10,995 4,266 505 15,766 20,497 80,183 5,794,931 Commercial and industrial 5,474,922 8,083 3,568 614 12,265 66,815 27,038 5,581,040 Residential mortgage 4,132,941 4,597 18,915 8,403 31,915 15,898 119,409 4,300,163 Consumer - home equity 2,246,693 8,727 2,963 — 11,690 17,854 73,939 2,350,176 Consumer - other 720,666 3,934 1,007 — 4,941 2,320 2,717 730,644 Total $ 21,712,371 $ 38,203 $ 32,421 $ 12,452 $ 83,076 $ 143,595 $ 404,864 $ 22,343,906 December 31, 2017 Accruing (Dollars in thousands) Current or Less Than 30 days Past Due 30-59 days 60-89 days > 90 days Total Past Due Non-accrual Acquired Impaired Total Real estate- construction $ 1,197,766 $ 269 $ — $ 458 $ 727 $ 2,635 $ 39,268 $ 1,240,396 Real estate- owner-occupied 2,243,923 1,631 659 74 2,364 24,457 104,577 2,375,321 Real estate- non-owner-occupied 5,220,648 2,086 6,405 887 9,378 6,811 85,676 5,322,513 Commercial and industrial 5,014,438 5,788 5,726 146 11,660 77,823 31,146 5,135,067 Residential mortgage 2,877,048 10,083 8,136 5,317 23,536 17,387 138,381 3,056,352 Consumer - home equity 2,186,554 11,675 2,947 18 14,640 12,365 78,716 2,292,275 Consumer - other 642,244 5,286 1,026 — 6,312 3,910 3,791 656,257 Total $ 19,382,621 $ 36,818 $ 24,899 $ 6,900 $ 68,617 $ 145,388 $ 481,555 $ 20,078,181 Acquired Loans As discussed in Note 3, during the third quarter of 2017, the Company acquired loans with fair values of $4.0 billion from Sabadell United. Certain loans that were acquired in this transaction were covered by loss share agreements between the FDIC and Sabadell United, which were assumed in connection with the Company's acquisition of Sabadell United and afforded IBERIABANK loss protection. In September 2018, the Company terminated its loss share agreements with the FDIC. As a result, there were no covered loans at September 30, 2018. Covered loans were $158.6 million at December 31, 2017. Certain acquired loans from Sabadell United were to customers with addresses outside of the United States. Foreign loans, denominated in U.S. dollars, totaled $228.2 million and $325.5 million at September 30, 2018 and December 31, 2017, respectively. During the first quarter of 2018, the Company acquired loans with fair values of $1.5 billion from Gibraltar based on preliminary purchase accounting adjustments. Of the total loans acquired from Gibraltar, $1.46 billion were determined to have no evidence of deteriorated credit quality and are accounted for under ASC Topics 310-10 and 310-20. The remaining $10.2 million were determined to exhibit deteriorated credit quality since origination under ASC 310-30. The tables below show the fair value estimates of loans acquired from Gibraltar for these two subsections of the portfolio as of the acquisition date. These amounts are subject to change due to the finalization of purchase accounting adjustments. (Dollars in thousands) Acquired Non-Impaired Loans Contractually required principal and interest at acquisition $ 1,695,918 Expected losses and foregone interest (19,952 ) Cash flows expected to be collected at acquisition 1,675,966 Fair value of acquired loans at acquisition $ 1,455,044 (Dollars in thousands) Acquired Impaired Loans Contractually required principal and interest at acquisition $ 43,779 Non-accretable difference (expected losses and foregone interest) (31,174 ) Cash flows expected to be collected at acquisition 12,605 Accretable yield (2,371 ) Basis in acquired loans at acquisition $ 10,234 The following is a summary of changes in the accretable difference for all loans accounted for under ASC 310-30 during the nine months ended September 30 : (Dollars in thousands) 2018 2017 Balance at beginning of period $ 152,623 $ 175,054 Additions 2,371 32,937 Transfers from non-accretable difference to accretable yield (4 ) 4,977 Accretion (37,115 ) (42,435 ) Changes in expected cash flows not affecting non-accretable differences (1) 21,092 (242 ) Balance at end of period $ 138,967 $ 170,291 (1) Includes changes in cash flows expected to be collected due to the impact of changes in actual or expected timing of liquidation events, modifications, changes in interest rates and changes in prepayment assumptions. Troubled Debt Restructurings Information about the Company’s troubled debt restructurings ("TDRs") at September 30, 2018 and 2017 is presented in the following tables. Modifications of loans that are accounted for within a pool under ASC Topic 310-30 are excluded as TDRs. Accordingly, such modifications do not result in the removal of those loans from the pool, even if the modification of those loans would otherwise be considered a TDR. As a result, all such acquired loans that would otherwise meet the criteria for classification as a TDR are excluded from the tables below. TDRs totaling $46.0 million and $51.5 million occurred during the nine months ended September 30, 2018 and 2017, respectively, through modification of the original loan terms. The following table provides information on how the TDRs were modified during the periods indicated: Three Months Ended September 30 Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Extended maturities $ 3,658 $ 3,184 $ 10,020 $ 18,177 Maturity and interest rate adjustment 267 204 368 5,151 Movement to or extension of interest-rate only payments — 3,560 48 3,692 Interest rate adjustment — — 101 25 Forbearance 802 841 14,386 5,528 Other concession(s) (1) 1,810 16,797 21,031 18,944 Total $ 6,537 $ 24,586 $ 45,954 $ 51,517 (1) Other concessions may include covenant waivers, forgiveness of principal or interest associated with a customer bankruptcy, or a combination of any of the above concessions. Of the $46.0 million of TDRs occurring during the nine months ended September 30, 2018 , $20.2 million are on accrual status and $25.8 million are on non-accrual status. Of the $51.5 million of TDRs occurring during the nine months ended September 30, 2017 , $40.5 million were on accrual status and $11.0 million were on non-accrual status. The following table presents the end of period balance for loans modified in a TDR during the periods indicated: Three Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Real estate- construction — $ — $ — 2 $ 1,166 $ 1,164 Real estate- owner-occupied 1 2,312 2,312 3 717 713 Real estate- non-owner-occupied 6 1,818 1,790 10 5,306 5,298 Commercial and industrial 9 829 804 11 11,650 12,502 Residential mortgage 3 257 255 7 409 392 Consumer - home equity 15 1,152 1,124 38 3,495 3,479 Consumer - other 11 352 252 36 1,078 1,038 Total 45 $ 6,720 $ 6,537 107 $ 23,821 $ 24,586 Nine Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Real estate- construction 1 $ 1,950 $ 976 2 $ 1,166 $ 1,164 Real estate- owner-occupied 8 15,233 13,373 5 2,447 2,411 Real estate- non-owner-occupied 13 3,228 3,064 21 9,645 11,505 Commercial and industrial 32 32,827 22,769 44 18,743 19,399 Residential mortgage 9 898 837 16 1,126 1,030 Consumer - home equity 47 4,130 4,047 99 13,573 13,471 Consumer - other 53 1,056 888 106 2,745 2,537 Total 163 $ 59,322 $ 45,954 293 $ 49,445 $ 51,517 Information detailing TDRs that defaulted during the three-month and nine-month periods ended September 30, 2018 and 2017, and were modified in the previous twelve months (i.e., the twelve months prior to the default) is presented in the following tables. The Company has defined a default as any loan with a payment that is currently past due greater than 30 days , or was past due greater than 30 days at any point during the respective periods, or since the date of modification, whichever is shorter. Three Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Recorded Investment Number of Loans Recorded Investment Real estate- construction — $ — 2 $ 1,164 Real estate- owner-occupied 1 929 4 1,304 Real estate- non-owner-occupied 1 7 11 2,206 Commercial and industrial 2 127 16 1,008 Residential mortgage — — 13 819 Consumer - home equity 4 380 23 2,150 Consumer - other 6 86 49 795 Total 14 $ 1,529 118 $ 9,446 Nine Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Recorded Investment Number of Loans Recorded Investment Real estate- construction — $ — 2 $ 1,164 Real estate- owner-occupied 6 10,101 8 3,234 Real estate- non-owner-occupied 6 1,084 16 4,929 Commercial and industrial 12 3,632 31 5,939 Residential mortgage 8 912 18 1,243 Consumer - home equity 17 1,978 34 3,215 Consumer - other 39 488 65 1,264 Total 88 $ 18,195 174 $ 20,988

Allowance for Credit Losses and

Allowance for Credit Losses and Credit Quality	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Allowance for Credit Losses and Credit Quality	ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY Allowance for Credit Losses Activity A summary of changes in the allowance for credit losses for the nine months ended September 30 is as follows: (Dollars in thousands) 2018 2017 Allowance for credit losses Allowance for loan and lease losses at beginning of period $ 140,891 $ 144,719 Provision for loan and lease losses 26,678 36,718 Transfer of balance to OREO and other (5,709 ) 963 Charge-offs (34,740 ) (49,939 ) Recoveries 9,830 4,167 Allowance for loan and lease losses at end of period $ 136,950 $ 136,628 Reserve for unfunded commitments at beginning of period $ 13,208 $ 11,241 Balance created in acquisition accounting 900 7,626 Provision for unfunded lending commitments 613 2,165 Reserve for unfunded commitments at end of period $ 14,721 $ 21,032 Allowance for credit losses at end of period $ 151,671 $ 157,660 A summary of changes in the allowance for credit losses, by loan portfolio type, for the nine months ended September 30 is as follows: 2018 (Dollars in thousands) Commercial Real Estate Commercial and Industrial Residential Mortgage Consumer Total Allowance for loan and lease losses at beginning of period $ 54,201 $ 53,916 $ 9,117 $ 23,657 $ 140,891 Provision for (Reversal of) loan and lease losses (4,020 ) 20,372 2,318 8,008 26,678 Transfer of balance to OREO and other (1,556 ) (814 ) (45 ) (3,294 ) (5,709 ) Charge-offs (1,281 ) (22,447 ) (365 ) (10,647 ) (34,740 ) Recoveries 1,019 5,665 53 3,093 9,830 Allowance for loan and lease losses at end of period $ 48,363 $ 56,692 $ 11,078 $ 20,817 $ 136,950 Reserve for unfunded commitments at beginning of period $ 4,531 $ 5,309 $ 555 $ 2,813 $ 13,208 Balance created in acquisition accounting 129 81 — 690 900 Provision for (Reversal of) unfunded commitments (134 ) 169 246 332 613 Reserve for unfunded commitments at end of period $ 4,526 $ 5,559 $ 801 $ 3,835 $ 14,721 Allowance on loans individually evaluated for impairment $ 2,650 $ 10,471 $ 154 $ 2,973 $ 16,248 Allowance on loans collectively evaluated for impairment 40,519 44,727 5,063 17,661 107,970 Allowance on loans acquired with deteriorated credit quality 5,194 1,494 5,861 183 12,732 Loans and leases, net of unearned income: Balance at end of period $ 9,381,883 $ 5,581,040 $ 4,300,163 $ 3,080,820 $ 22,343,906 Balance at end of period individually evaluated for impairment 73,469 75,625 6,230 33,863 189,187 Balance at end of period collectively evaluated for impairment 9,126,653 5,478,377 4,174,524 2,970,301 21,749,855 Balance at end of period acquired with deteriorated credit quality 181,761 27,038 119,409 76,656 404,864 2017 (Dollars in thousands) Commercial Real Estate Commercial and Industrial Residential Mortgage Consumer Total Allowance for loan losses at beginning of period $ 49,231 $ 60,939 $ 11,249 $ 23,300 $ 144,719 Provision for (Reversal of) loan and lease losses 4,888 23,574 (1,333 ) 9,589 36,718 Transfer of balance to OREO and other 879 (69 ) 2 151 963 Charge-offs (1,410 ) (37,110 ) (265 ) (11,154 ) (49,939 ) Recoveries 668 605 148 2,746 4,167 Allowance for loan losses at end of period $ 54,256 $ 47,939 $ 9,801 $ 24,632 $ 136,628 Reserve for unfunded commitments at beginning of period $ 3,207 $ 4,537 $ 657 $ 2,840 $ 11,241 Balance created in acquisition accounting 1,358 4,903 1,303 62 7,626 Provision for (Reversal of) unfunded commitments 1,239 752 (30 ) 204 2,165 Reserve for unfunded commitments at end of period $ 5,804 $ 10,192 $ 1,930 $ 3,106 $ 21,032 Allowance on loans individually evaluated for impairment $ 1,957 $ 9,744 $ 164 $ 2,445 $ 14,310 Allowance on loans collectively evaluated for impairment 30,016 35,964 3,801 18,768 88,549 Allowance on loans acquired with deteriorated credit quality 22,283 2,231 5,836 3,419 33,769 Loans, net of unearned income: Balance at end of period 8,767,886 5,016,437 3,024,970 2,985,792 19,795,085 Balance at end of period individually evaluated for impairment 68,241 85,054 5,384 29,140 187,819 Balance at end of period collectively evaluated for impairment 8,457,950 4,899,842 2,890,206 2,877,383 19,125,381 Balance at end of period acquired with deteriorated credit quality 241,695 31,541 129,380 79,269 481,885 Portfolio Segment Risk Factors Commercial real estate loans include loans to commercial customers for long-term financing of land and buildings or for land development or construction of a building. These loans are repaid through revenues from operations of the businesses, rents of properties, sales of properties and refinances. Commercial and industrial loans and leases represent loans to commercial customers to finance general working capital needs, equipment purchases and leases and other projects where repayment is derived from cash flows resulting from business operations. The Company originates commercial business loans on a secured and, to a lesser extent, unsecured basis. Residential mortgage loans consist of loans to consumers to finance a primary residence. The vast majority of the residential mortgage loan portfolio is comprised of non-conforming 1-4 family mortgage loans secured by properties located in the Company's market areas and originated under terms and documentation that permit their sale in a secondary market. Consumer loans are offered by the Company in order to provide a full range of retail financial services to its customers and include home equity, credit card and other direct consumer installment loans. The Company originates substantially all of its consumer loans in its primary market areas. Loans in the consumer segment are sensitive to unemployment and other key consumer economic measures. Credit Quality The Company utilizes an asset risk classification system in accordance with guidelines established by the Federal Reserve Board as part of its efforts to monitor commercial asset quality. “Special mention” loans are defined as loans with potential weaknesses that may, if not corrected, result in future deterioration of the loan. Special mention loans do not expose the Company to sufficient risk to warrant adverse classification. For problem assets with identified credit issues, the Company has two primary classifications: “substandard” and “doubtful.” Substandard assets have one or more defined weaknesses and are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Doubtful assets have the weaknesses of substandard assets with the additional characteristic that the weaknesses make collection or liquidation in full satisfaction of the loan balance outstanding questionable, which makes probability of loss higher based on currently existing facts, conditions, and values. Loans classified as substandard, doubtful, and loss are collectively referred to as classified loans. Criticized loans include all classified loans, as well as loans classified as special mention loans. Loans classified as “Pass” do not meet the criteria set forth for special mention, substandard, or doubtful classification and are not considered criticized. Asset risk classifications are determined at origination or acquisition and reviewed on an ongoing basis. Risk classifications are changed if, in the opinion of management, the risk profile of the customer has changed since the last review of the loan relationship. The Company’s investment in loans by credit quality indicator is presented in the following tables. Asset risk classifications for commercial loans and leases reflect the classification as of September 30, 2018 and December 31, 2017 . Credit quality information in the tables below includes total loans acquired (including acquired impaired loans) at the net loan balance, after the application of premiums/discounts, at September 30, 2018 and December 31, 2017 . Loan premiums/discounts represent the adjustment of acquired loans to fair value at the acquisition date, as adjusted for income accretion and changes in cash flow estimates in subsequent periods. Loan premiums/discounts include preliminary discounts recorded on acquired Gibraltar loans, which are subject to change upon receipt of final fair value estimates during the measurement period. Loan delinquency is the primary credit quality indicator that the Company utilizes to monitor consumer asset quality. September 30, 2018 December 31, 2017 (Dollars in thousands) Pass Special Mention Sub- Doubtful Total Pass Special Mention Sub- Doubtful Loss Total Commercial real estate - construction $ 1,094,240 $ 19,033 $ 14,704 $ 11 $ 1,127,988 $ 1,189,490 $ 20,351 $ 30,541 $ 14 $ — $ 1,240,396 Commercial real estate - owner-occupied 2,382,053 31,588 45,058 265 2,458,964 2,234,151 82,114 56,590 2,466 — 2,375,321 Commercial real estate - non-owner-occupied 5,692,007 49,121 49,415 4,388 5,794,931 5,258,638 19,311 42,702 1,744 118 5,322,513 Commercial and industrial 5,366,990 96,303 86,903 30,844 5,581,040 4,882,554 88,149 128,961 35,403 — 5,135,067 Total $ 14,535,290 $ 196,045 $ 196,080 $ 35,508 $ 14,962,923 $ 13,564,833 $ 209,925 $ 258,794 $ 39,627 $ 118 $ 14,073,297 September 30, 2018 December 31, 2017 (Dollars in thousands) Current 30+ Days Past Due Total Current 30+ Days Past Due Total Residential mortgage $ 4,212,447 $ 87,716 $ 4,300,163 $ 2,962,043 $ 94,309 $ 3,056,352 Consumer - home equity 2,306,712 43,464 2,350,176 2,250,205 42,070 2,292,275 Consumer - other 723,183 7,461 730,644 645,498 10,759 656,257 Total $ 7,242,342 $ 138,641 $ 7,380,983 $ 5,857,746 $ 147,138 $ 6,004,884 Impaired Loans Information on the Company’s investment in impaired loans, which include all TDRs and all other non-accrual loans evaluated or measured individually for impairment for purposes of determining the ALLL, is presented in the following tables as of and for the periods indicated. September 30, 2018 December 31, 2017 Unpaid Principal Balance Recorded Investment Related Allowance Unpaid Principal Balance Recorded Investment Related Allowance (Dollars in thousands) With no related allowance recorded: Commercial real estate - construction $ 11,176 $ 11,176 $ — $ 13,763 $ 13,013 $ — Commercial real estate - owner-occupied 33,816 33,816 — 50,867 44,482 — Commercial real estate - non-owner-occupied 21,996 21,996 — 15,370 14,975 — Commercial and industrial 41,717 41,717 — 103,013 70,254 — Residential mortgage 1,254 1,241 — 2,004 2,001 — Consumer - home equity 701 701 — 5,906 5,634 — Consumer - other — — — 75 75 — With an allowance recorded: Commercial real estate - construction 146 146 (11 ) 238 156 (19 ) Commercial real estate - owner-occupied 3,987 3,987 (535 ) 13,314 13,287 (949 ) Commercial real estate - non-owner-occupied 2,348 2,348 (2,104 ) 6,051 5,872 (620 ) Commercial and industrial 33,894 33,908 (10,471 ) 35,306 32,162 (12,736 ) Residential mortgage 5,420 4,989 (154 ) 5,179 4,748 (172 ) Consumer - home equity 28,700 28,695 (2,469 ) 27,189 26,575 (2,358 ) Consumer - other 4,526 4,467 (504 ) 5,354 4,893 (498 ) Total $ 189,681 $ 189,187 $ (16,248 ) $ 283,629 $ 238,127 $ (17,352 ) Total commercial loans and leases $ 149,080 $ 149,094 $ (13,121 ) $ 237,922 $ 194,201 $ (14,324 ) Total mortgage loans 6,674 6,230 (154 ) 7,183 6,749 (172 ) Total consumer loans 33,927 33,863 (2,973 ) 38,524 37,177 (2,856 ) Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Average Interest Average Interest Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (Dollars in thousands) With no related allowance recorded: Commercial real estate - construction $ 10,806 $ 164 $ 2,722 $ 11 $ 10,371 $ 460 $ 2,538 $ 57 Commercial real estate - owner-occupied 34,118 209 36,850 88 34,505 903 37,185 517 Commercial real estate - non-owner-occupied 22,091 249 7,858 83 22,988 746 7,908 231 Commercial and industrial 43,409 523 64,863 240 40,564 1,543 71,611 975 Residential mortgage 1,254 9 1,114 13 1,271 36 1,129 36 Consumer - home equity 705 2 364 6 708 16 367 18 With an allowance recorded: Commercial real estate - construction 148 — 166 1 151 1 209 5 Commercial real estate - owner-occupied 4,006 83 11,154 89 4,044 102 11,206 269 Commercial real estate - non-owner-occupied 2,398 20 4,874 29 2,442 76 4,808 109 Commercial and industrial 40,357 150 55,042 261 47,098 720 57,020 788 Residential mortgage 5,014 50 4,290 38 5,066 149 4,338 115 Consumer - home equity 28,577 305 23,730 254 27,905 892 21,639 690 Consumer - other 4,710 65 4,330 64 4,884 208 4,010 180 Total $ 197,593 $ 1,829 $ 217,357 $ 1,177 $ 201,997 $ 5,852 $ 223,968 $ 3,990 Total commercial loans and leases $ 157,333 $ 1,398 $ 183,529 $ 802 $ 162,163 $ 4,551 $ 192,485 $ 2,951 Total mortgage loans 6,268 59 5,404 51 6,337 185 5,467 151 Total consumer loans 33,992 372 28,424 324 33,497 1,116 26,016 888 As of September 30, 2018 and December 31, 2017 , the Company was not committed to lend a material amount of additional funds to any customer whose loan was classified as impaired or as a troubled debt restructuring.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill Changes to the carrying amount of goodwill by reporting unit for the nine months ended September 30, 2018, and the year ended December 31, 2017 are provided in the following table: (Dollars in thousands) IBERIABANK Mortgage LTC Total Balance, December 31, 2016 $ 698,513 $ 23,178 $ 5,165 $ 726,856 Goodwill acquired during the year 462,046 — — 462,046 Balance, December 31, 2017 $ 1,160,559 $ 23,178 $ 5,165 $ 1,188,902 Goodwill acquired during the year (preliminary allocation) and adjustments 28,621 — 3,380 32,001 Balance, September 30, 2018 $ 1,189,180 $ 23,178 $ 8,545 $ 1,220,903 On March 23, 2018, the Company completed its acquisition of Gibraltar. In connection with the acquisition, the Company recorded $49.6 million of goodwill based on preliminary fair value estimates of the assets acquired and liabilities assumed in the business combination as of September 30, 2018. On January 12, 2018, the Company's subsidiary, LTC, completed its acquisition of SolomonParks. In connection with the acquisition, LTC recorded $3.4 million of goodwill based on preliminary estimates. In addition, measurement period adjustments to preliminary fair value estimates related to the acquisition of Sabadell United were updated during the six months ended June 30, 2018, reducing goodwill by $21.0 million . The accounting for the acquisition of Sabadell United was complete as of June 30, 2018. See Note 3 for additional information regarding these acquisitions. The Company performed the required annual goodwill impairment test as of October 1, 2017. The Company’s annual impairment test did not indicate impairment in any of the Company’s reporting units as of the testing date. Following the testing date, management evaluated the events and changes that could indicate that goodwill might be impaired and concluded that a subsequent interim test was not necessary. The Company is currently in the process of performing its annual impairment test as of October 1, 2018. Mortgage Servicing Rights Mortgage servicing rights are recorded at the lower of cost or market value in “other intangible assets” on the Company's consolidated balance sheets and amortized over the remaining servicing life of the loans, with consideration given to prepayment assumptions. Mortgage servicing rights had the following carrying values as of the periods indicated: September 30, 2018 December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (Dollars in thousands) Mortgage servicing rights $ 12,125 $ (4,562 ) $ 7,563 $ 9,588 $ (3,931 ) $ 5,657 Title Plant The Company held title plant assets recorded in “other intangible assets” on the Company's consolidated balance sheets totaling $6.8 million on September 30, 2018 and $6.7 million on December 31, 2017. The increase in title plant assets was the result of the SolomonParks acquisition during the first quarter of 2018. No events or changes in circumstances occurred during the nine months ended September 30, 2018 to suggest the carrying value of the title plant was not recoverable. Intangible assets subject to amortization In connection with the acquisition of Gibraltar, the Company recorded $18.5 million of core deposit intangible assets. Core deposit intangible assets are subject to amortization over a ten year period. In connection with the acquisition of SolomonParks, the Company recorded $156 thousand of non-compete agreement intangible assets. Non-compete agreement intangible assets are subject to amortization over a five year period. Definite-lived intangible assets had the following carrying values included in “other intangible assets” on the Company’s consolidated balance sheets as of the periods indicated: September 30, 2018 December 31, 2017 (Dollars in thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Core deposit intangible assets $ 136,183 $ (58,161 ) $ 78,022 $ 127,957 $ (51,971 ) $ 75,986 Customer relationship intangible asset 1,385 (1,305 ) 80 1,143 (996 ) 147 Non-compete agreement 206 (60 ) 146 63 (39 ) 24 Total $ 137,774 $ (59,526 ) $ 78,248 $ 129,163 $ (53,006 ) $ 76,157

Derivative Instruments and Othe

Derivative Instruments and Other Hedging Activities	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Other Hedging Activities	DERIVATIVE INSTRUMENTS AND OTHER HEDGING ACTIVITIES The Company enters into derivative financial instruments to manage interest rate risk, exposures related to liquidity and credit risk, and to facilitate customer transactions. The primary types of derivatives used by the Company include interest rate swap agreements, foreign exchange contracts, interest rate lock commitments, forward sales commitments, written and purchased options and credit derivatives. All derivative instruments are recognized on the consolidated balance sheets as "other assets" or "other liabilities" at fair value, as required by ASC Topic 815, Derivatives and Hedging . Cash flow hedge relationships mitigate exposure to the variability of future cash flows or other forecasted transactions. The Company enters into interest rate swap agreements in a cash flow hedge to convert forecasted variable interest payments to a fixed rate on its junior subordinated debt. In addition, the Company has entered into an interest rate collar and designated the instrument as a cash flow hedge of the risk of fluctuations in interest rates, thereby reducing the Company's exposure to variability in cash flows from variable-rate loans. For cash flow hedges, the effective and ineffective portions of the gain or loss related to the derivative instrument is initially reported as a component of other comprehensive income and subsequently reclassified into earnings when the forecasted transaction affects earnings or when the hedge is terminated, per the Company’s early adoption of ASU No. 2017-12, Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities, as of January 1, 2018. In applying hedge accounting for derivatives, the Company establishes and documents a method for assessing the effectiveness of the hedging derivative and a measurement approach for determining the ineffective aspect of the hedge upon the inception of the hedge. For derivative instruments that are not designated as hedging instruments, changes in the fair value of the derivatives are recognized in earnings immediately. Information pertaining to outstanding derivative instruments is as follows: Balance Sheet Location Derivative Assets - Fair Value Balance Sheet Location Derivative Liabilities - Fair Value (Dollars in thousands) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 Derivatives designated as hedging instruments under ASC Topic 815: Interest rate contracts Other assets $ 48 $ — Other liabilities $ — $ — Total derivatives designated as hedging instruments under ASC Topic 815 $ 48 $ — $ — $ — Derivatives not designated as hedging instruments under ASC Topic 815: Interest rate contracts Other assets $ 3,665 $ 20,446 Other liabilities $ 37,417 $ 16,191 Foreign exchange contracts Other assets 13 7 Other liabilities 13 7 Forward sales contracts Other assets 1,084 136 Other liabilities 44 279 Written and purchased options Other assets 7,754 10,654 Other liabilities 5,282 8,656 Other contracts Other assets 6 22 Other liabilities 8 21 Total derivatives not designated as hedging instruments under ASC Topic 815 $ 12,522 $ 31,265 $ 42,764 $ 25,154 Total $ 12,570 $ 31,265 $ 42,764 $ 25,154 Derivative Assets - Notional Amount Derivative Liabilities - Notional Amount (Dollars in thousands) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 Derivatives designated as hedging instruments under ASC Topic 815: Interest rate contracts $ 258,500 $ — $ — $ 108,500 Total derivatives designated as hedging instruments under ASC Topic 815 $ 258,500 $ — $ — $ 108,500 Derivatives not designated as hedging instruments under ASC Topic 815: Interest rate contracts $ 1,489,111 $ 1,218,464 $ 1,489,111 $ 1,218,464 Foreign exchange contracts 933 268 933 268 Forward sales contracts 169,276 82,347 21,684 142,578 Written and purchased options 275,473 278,638 143,912 165,198 Other contracts 33,570 29,755 62,142 86,744 Total derivatives not designated as hedging instruments under ASC Topic 815 $ 1,968,363 $ 1,609,472 $ 1,717,782 $ 1,613,252 Total $ 2,226,863 $ 1,609,472 $ 1,717,782 $ 1,721,752 The Company has entered into risk participation agreements with counterparties to transfer or assume credit exposures related to interest rate derivatives. The notional amounts of risk participation agreements sold were $62.1 million and $86.7 million at September 30, 2018 and December 31, 2017, respectively. Assuming all underlying third party customers referenced in the swap contracts defaulted at September 30, 2018 and December 31, 2017, the exposure from these agreements would not be material based on the fair value of the underlying swaps. The Company is party to collateral agreements with certain derivative counterparties. Such agreements require that the Company maintain collateral based on the fair values of individual derivative transactions. In the event of default by the Company, the counterparty would be entitled to the collateral. At September 30, 2018, the Company was not required to post collateral due to the Company's derivative position at the balance sheet date. At December 31, 2017, the Company was required to post $552 thousand in cash or securities as collateral for its derivative transactions, which is included in "interest-bearing deposits in banks" on the Company’s consolidated balance sheets. Effective January 3, 2017, the Chicago Mercantile Exchange and LCH.Clearnet Limited amended their rulebooks to legally characterize variation margin payments for over-the-counter derivatives they clear as settlements of the derivatives' exposure rather than collateral against the exposures. In light of changes to the aforementioned rulebooks, the Board of Governors of the Federal Reserve System, the OCC and the FDIC issued guidance effective August 14, 2017, which is consistent with the SEC's accounting guidance, that allows institutions to treat centrally-cleared derivatives as settled for purposes of the capital rule. At September 30, 2018 and December 31, 2017, the Company was required to post $44.4 million and $5.1 million , respectively, in variation margin payments for its derivative transactions, which is required to be netted against the fair value of the derivatives in "other assets/other liabilities" on the consolidated balance sheets. The Company does not anticipate additional assets will be required to be posted as collateral, nor does it believe additional assets would be required to settle its derivative instruments immediately if contingent features were triggered at September 30, 2018. The Company’s master netting agreements represent written, legally enforceable bilateral agreements that (1) create a single legal obligation for all individual transactions covered by the master agreement and (2) in the event of default, provide the non-defaulting counterparty the right to accelerate, terminate, and close-out on a net basis all transactions under the agreement and to promptly liquidate or set-off collateral posted by the defaulting counterparty. As permitted by U.S. GAAP, the Company does not offset fair value amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral against recognized fair value amounts of derivatives executed with the same counterparty under a master netting agreement. The following table reconciles the gross amounts presented in the consolidated balance sheets to the net amounts that would result in the event of offset. September 30, 2018 Gross Amounts Presented in the Balance Sheet Gross Amounts Not Offset in the Balance Sheet Net (Dollars in thousands) Derivatives Collateral (1) Derivatives subject to master netting arrangements Derivative assets Interest rate contracts designated as hedging instruments $ 48 $ — $ — $ 48 Interest rate contracts not designated as hedging instruments 3,665 (248 ) — 3,417 Written and purchased options 5,267 — — 5,267 Total derivative assets subject to master netting arrangements $ 8,980 $ (248 ) $ — $ 8,732 Derivative liabilities Interest rate contracts not designated as hedging instruments $ 37,417 $ (248 ) $ — $ 37,169 Written and purchased options 5,267 — — 5,267 Total derivative liabilities subject to master netting arrangements $ 42,684 $ (248 ) $ — $ 42,436 (1) Consists of cash collateral recorded at cost, which approximates fair value, and investment securities. December 31, 2017 Gross Amounts Presented in the Balance Sheet Gross Amounts Not Offset in the Balance Sheet Net (Dollars in thousands) Derivatives Collateral (1) Derivatives subject to master netting arrangements Derivative assets Interest rate contracts not designated as hedging instruments $ 20,446 $ (12,469 ) $ — $ 7,977 Written and purchased options 8,610 — — 8,610 Total derivative assets subject to master netting arrangements $ 29,056 $ (12,469 ) $ — $ 16,587 Derivative liabilities Interest rate contracts designated as hedging instruments $ — $ — $ — $ — Interest rate contracts not designated as hedging instruments 16,191 (12,469 ) (552 ) 3,170 Total derivative liabilities subject to master netting arrangements $ 16,191 $ (12,469 ) $ (552 ) $ 3,170 (1) Consists of cash collateral recorded at cost, which approximates fair value, and investment securities. During the nine months ended September 30, 2018 and 2017 , the Company has not reclassified into earnings any gain or loss as a result of the discontinuance of cash flow hedges because it was probable the original forecasted transaction would not occur by the end of the originally specified term. At September 30, 2018 , the Company does not expect to reclassify a material amount from accumulated other comprehensive income into interest income over the next twelve months for derivatives that will be settled. At September 30, 2018 and 2017 , and for the three and nine months then ended, information pertaining to the effect of the hedging instruments on the consolidated financial statements is as follows: Location of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in OCI, net of taxes Location of Gain (Loss) Reclassified from Accumulated OCI into Income Amount of Gain (Loss) Reclassified from Accumulated OCI into Income, net of taxes (Dollars in thousands) For the Three Months Ended September 30, Derivatives in ASC Topic 815 Cash Flow Hedging Relationships 2018 2017 2018 2017 2018 2017 Interest rate contracts $ 818 $ (158 ) Interest expense $ (22 ) $ (101 ) Interest expense $ — $ — Total $ 818 $ (158 ) $ (22 ) $ (101 ) $ — $ — Location of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in OCI, net of taxes Location of Gain (Loss) Reclassified from Accumulated OCI into Income Amount of Gain (Loss) Reclassified from Accumulated OCI into Income, net of taxes (Dollars in thousands) For the Nine Months Ended September 30, Derivatives in ASC Topic 815 Cash Flow Hedging Relationships 2018 2017 2018 2017 2018 2017 Interest rate contracts $ 4,762 $ (1,081 ) Other income (expense) $ (178 ) $ (249 ) Other income (expense) $ — $ — Total $ 4,762 $ (1,081 ) $ (178 ) $ (249 ) $ — $ — Information pertaining to the effect of derivatives not designated as hedging instruments on the consolidated financial statements as of September 30, is as follows: Location of Gain (Loss) Recognized in Income on Derivatives Amount of Gain (Loss) Recognized in Income on Derivatives For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Interest rate contracts (1) Other income $ 2,586 $ 743 $ 5,093 $ 3,159 Foreign exchange contracts Other income 7 24 17 38 Forward sales contracts Mortgage income 948 (2,007 ) 4,563 (3,893 ) Written and purchased options Mortgage income (692 ) (462 ) 473 (1,393 ) Other contracts Other income 1 8 (4 ) 17 Total $ 2,850 $ (1,694 ) $ 10,142 $ (2,072 ) (1) Includes fees associated with customer interest rate contracts.

Income Taxes (Notes)

Income Taxes (Notes)	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	INCOME TAXES The Company's provision for income taxes for the three and nine months ended September 30, 2018 and 2017 is based on the estimated annual effective tax rate, plus discrete items. The following table presents the provision for income taxes and the effective tax rates for the periods indicated. Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Income before income tax expense $ 131,866 $ 48,450 $ 318,620 $ 201,493 Income tax expense 30,401 18,806 78,410 69,358 Effective tax rate 23.1 % 38.8 % 24.6 % 34.4 % The difference between the Company's effective tax rate for the three and nine months ended September 30, 2018 and 2017 and the U.S. statutory tax rates of 21% and 35%, respectively, primarily relates to tax-exempt income, non-deductible expenses, state income taxes (net of federal income tax benefit), and the recognition of tax credits. The effective tax rate may vary significantly due to fluctuations in the amount and source of pretax income, changes in amounts of non-deductible expenses, and timing of the recognition of tax credits. In addition, the difference between the Company's effective tax rate for the nine months ended September 30, 2018 and the U.S. statutory tax rate of 21% primarily relates to the discrete item of $6.6 million in income tax expense due to the write-down of deferred tax assets in the second quarter of 2018 associated with the finalization of the accounting for the Sabadell United acquisition and the related impact of the Tax Act on those adjustments. This adjustment increased the effective tax rate for the nine months ended September 30, 2018 by 2.1% from 22.5% to 24.6% . Provisional amounts in effective tax rate On December 22, 2017, President Trump signed the Tax Cuts and Jobs Act (the "Tax Act") into law. Under ASC 740, the effects of changes in tax rates and laws are recognized in the period in which the new legislation is enacted. In the case of U.S. federal income taxes, the enactment date is the date the bill becomes law (i.e., upon presidential signature). Among other provisions, the most significant to the Company is the reduction of the corporate income tax rate from 35% to 21%. With respect to the legislation, the Company recognized a provisional one-time increase in tax expense of $51.0 million as of December 31, 2017 due to a re-measurement of deferred tax assets and liabilities resulting from the decrease in the corporate income tax rate. The Company made no adjustment to the provisional amounts during the third quarter of 2018. During the nine months ended September 30, 2018, the Company recognized an adjustment of $6.6 million in income tax expense due to the write-down of deferred tax assets associated with the finalization of the accounting for the Sabadell United acquisition and the related impact of the Tax Act on those adjustments. This adjustment increased the year-to-date effective tax rate by 2.1% from 22.5% to 24.6% . The accounting for the tax effects of the Tax Act remained incomplete as of September 30, 2018. The Company is in the process of analyzing certain aspects of the Tax Act, obtaining additional information, and refining its calculations, which could potentially affect the measurement of these balances. Information which could result in adjustment to the provisional amount includes, but is not limited to, the filing of the Sabadell United tax returns, elections or changes in IRS tax methods, and further analysis of tax positions. Our estimates may also be affected as we gain a more thorough understanding of the Tax Act. Consistent with the guidance provided under ASC 740, the Company recorded impacts from enactment of the Tax Act in the fourth quarter of 2017 subject to Staff Accounting Bulletin 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act ("SAB 118"). SAB 118 provides a measurement period not to extend beyond one year of the enactment date to adjust the accounting for certain elements of the tax reform.

Shareholders' Equity, Capital R

Shareholders' Equity, Capital Ratios and Other Regulatory Matters	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Shareholders' Equity, Capital Ratios and Other Regulatory Matters	SHAREHOLDERS' EQUITY, CAPITAL RATIOS AND OTHER REGULATORY MATTERS Preferred Stock The following table presents a summary of the Company's non-cumulative perpetual preferred stock: September 30, 2018 December 31, 2017 Issuance Date Earliest Redemption Date Annual Dividend Rate Liquidation Amount Carrying Amount Carrying Amount (Dollars in thousands) Series B Preferred Stock 8/5/2015 8/1/2025 6.625 % $ 80,000 $ 76,812 $ 76,812 Series C Preferred Stock 5/9/2016 5/1/2026 6.600 % 57,500 55,285 55,285 $ 137,500 $ 132,097 $ 132,097 Common Stock During the second quarter of 2018, the Company's Board of Directors authorized the repurchase of up to 1,137,500 shares of IBERIABANK Corporation's outstanding common stock. Stock repurchases under this program will be made from time to time, on the open market or in privately negotiated transactions. The timing of these repurchases will depend on market conditions and other requirements. The share repurchase program does not obligate the Company to repurchase any dollar amount or number of shares, and expires during the second quarter of 2020. The program may be extended, modified, suspended, or discontinued at any time. During the first nine months of 2018, the Company repurchased 763,210 common shares for approximately $61.0 million at a weighted average cost of $79.99 per share, which included 335,000 common shares repurchased under a plan previously approved by the Board of Directors that has subsequently expired. At September 30, 2018 , the remaining common shares that could be repurchased under the current Board-approved plan was 709,290 shares. Subsequent to quarter-end and through November 5, 2018, the Company repurchased the remaining common shares for approximately $52.6 million . On March 23, 2018, as part of the Gibraltar acquisition, the Company issued 2,787,773 shares of common stock. The aggregate value of the acquisition consideration paid by the Company at the time of closing was approximately $214.7 million based on the Company's closing common stock price of $77.00 per share on March 23, 2018. Gibraltar common shareholders received 1.9749 shares of IBERIABANK Corporation common stock for each outstanding share of Gibraltar common stock. Refer to Note 3, Acquisition Activity, for further detail regarding the Gibraltar acquisition. Regulatory Capital The Company and IBERIABANK are subject to various regulatory capital requirements administered by the federal and state banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company’s consolidated financial statements. Under capital adequacy regulations and the regulatory framework for prompt corrective action, the Company and IBERIABANK, as applicable, must meet specific capital guidelines that involve quantitative measures of their assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings and other factors. Management believes that, as of September 30, 2018 , the Company and IBERIABANK met all capital adequacy requirements to which they are subject. As of September 30, 2018 , the most recent notification from the FRB categorized IBERIABANK as well-capitalized under the regulatory framework for prompt corrective action (the prompt corrective action requirements are not applicable to the Company). To be categorized as well-capitalized, an institution must maintain minimum total risk-based, Tier 1 risk-based and Tier 1 leverage ratios as set forth in the following table. There are no conditions or events since the notification that management believes have changed that categorization. The Company’s and IBERIABANK’s actual capital amounts and ratios as of September 30, 2018 and December 31, 2017 are presented in the following tables: (Dollars in thousands) September 30, 2018 Minimum Well-Capitalized Actual Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Consolidated $ 1,156,436 4.00 % N/A N/A $ 2,789,740 9.65 % IBERIABANK 1,153,671 4.00 1,442,089 5.00 2,768,917 9.60 Common Equity Tier 1 (CET1) (1) Consolidated $ 1,107,934 4.50 % N/A N/A $ 2,657,643 10.79 % IBERIABANK 1,105,391 4.50 1,596,676 6.50 2,768,917 11.27 Tier 1 Risk-Based Capital (1) Consolidated $ 1,477,245 6.00 % N/A N/A $ 2,789,740 11.33 % IBERIABANK 1,473,855 6.00 1,965,140 8.00 2,768,917 11.27 Total Risk-Based Capital (1) Consolidated $ 1,969,660 8.00 % N/A N/A $ 3,057,911 12.42 % IBERIABANK 1,965,140 8.00 2,456,425 10.00 2,920,587 11.89 December 31, 2017 Minimum Well-Capitalized Actual Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Consolidated $ 1,073,381 4.00 % N/A N/A $ 2,509,496 9.35 % IBERIABANK 1,070,789 4.00 1,338,487 5.00 2,437,275 9.10 Common Equity Tier 1 (CET1) (1) Consolidated $ 1,011,732 4.50 % N/A N/A $ 2,377,398 10.57 % IBERIABANK 1,009,553 4.50 1,458,243 6.50 2,437,275 10.86 Tier 1 Risk-Based Capital (1) Consolidated $ 1,348,977 6.00 % N/A N/A $ 2,509,496 11.16 % IBERIABANK 1,346,070 6.00 1,794,760 8.00 2,437,275 10.86 Total Risk-Based Capital (1) Consolidated $ 1,798,635 8.00 % N/A N/A $ 2,780,095 12.37 % IBERIABANK 1,794,760 8.00 2,243,450 10.00 2,591,374 11.55 (1) Minimum capital ratios are subject to a capital conservation buffer. In order to avoid limitations on distributions, including dividend payments, and certain discretionary bonus payments to executive officers, an institution must hold a capital conservation buffer above its minimum risk-based capital requirements. This capital conservation buffer is calculated as the lowest of the differences between the actual CET1 ratio, Tier 1 Risk-Based Capital Ratio, and Total Risk-Based Capital ratio and the corresponding minimum ratios. At September 30, 2018 , the required minimum capital conservation buffer was 1.875% , and will increase by 0.625% and be fully phased-in on January 1, 2019 at 2.50% . At September 30, 2018 , the capital conservation buffers of the Company and IBERIABANK were 4.42% and 3.89% , respectively.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Share-based payment awards that entitle holders to receive non-forfeitable dividends before vesting are considered participating securities that are included in the calculation of earnings per share using the two-class method. The two-class method is an earnings allocation formula under which earnings per share is calculated for common stock and participating securities according to dividends declared and participating rights in undistributed earnings. Under this method, all earnings, distributed and undistributed, are allocated to common shares and participating securities based on their respective rights to receive dividends. The following table presents the calculation of basic and diluted earnings per share for the periods indicated. Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2018 2017 2018 2017 Earnings per common share - basic: Net income $ 101,465 $ 29,644 $ 240,210 $ 132,135 Less: Preferred stock dividends 3,599 3,598 8,146 8,146 Less: Dividends and undistributed earnings allocated to unvested restricted shares 908 283 2,341 1,052 Net income allocated to common shareholders - basic $ 96,958 $ 25,763 $ 229,723 $ 122,937 Weighted average common shares outstanding 55,571 52,424 55,047 49,749 Earnings per common share - basic 1.74 0.49 4.17 2.47 Earnings per common share - diluted: Net income allocated to common shareholders - basic $ 96,958 $ 25,763 $ 229,723 $ 122,937 Adjustment for undistributed earnings allocated to unvested restricted shares (25 ) 8 (49 ) — Net income allocated to common shareholders - diluted $ 96,933 $ 25,771 $ 229,674 $ 122,937 Weighted average common shares outstanding 55,571 52,424 55,047 49,749 Dilutive potential common shares 374 346 360 357 Weighted average common shares outstanding - diluted 55,945 52,770 55,407 50,106 Earnings per common share - diluted $ 1.73 $ 0.49 $ 4.14 $ 2.45 For the three months ended September 30, 2018 , and 2017 , the calculations for basic shares outstanding exclude the weighted average shares owned by the RRP of 542,796 and 511,562 , respectively. For the nine months ended September 30, 2018 , and 2017 , basic shares outstanding exclude 581,397 and 428,232 shares owned by the RRP, respectively. The effects from the assumed exercises of 60,931 and 72,239 stock options were not included in the computation of diluted earnings per share for the three months ended September 30, 2018 and 2017 , respectively, because such amounts would have had an antidilutive effect on earnings per common share. For the nine months ended September 30, 2018 and 2017, the effects from the assumed exercise of 147,834 and 69,289 stock options, respectively, were not included in the computation of diluted earnings per share because such amounts would have had an antidilutive effect on earnings per common share.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION The Company has various types of share-based compensation plans that permit the granting of awards in the form of stock options, restricted stock, restricted share units and phantom stock. These plans are administered by the Compensation Committee of the Board of Directors, which selects persons eligible to receive awards and determines the terms, conditions and other provisions of the awards. At September 30, 2018, awards of 1,163,414 shares could be made under approved incentive compensation plans. The Company issues shares to fulfill stock option exercises and restricted share units and restricted stock awards vesting from available authorized common shares. At September 30, 2018, the Company believes there are adequate authorized shares to satisfy anticipated stock option exercises and restricted share unit and restricted stock award vesting. Stock option awards The Company issues stock options under various plans to directors, officers and other key employees. The option exercise price cannot be less than the fair value of the underlying common stock as of the date of the option grant and the maximum option term cannot exceed ten years . The following table represents the activity related to stock options during the periods indicated: Number of Shares Weighted Average Exercise Price Outstanding options, December 31, 2016 721,538 $ 55.38 Granted 78,434 85.03 Exercised (74,236 ) 55.77 Forfeited or expired (26,675 ) 68.93 Outstanding options, September 30, 2017 699,061 $ 58.15 Exercisable options, September 30, 2017 463,326 $ 55.68 Outstanding options, December 31, 2017 686,366 $ 58.24 Granted 97,620 82.02 Exercised (41,697 ) 53.12 Forfeited or expired (27,328 ) 68.19 Outstanding options, September 30, 2018 714,961 $ 61.41 Exercisable options, September 30, 2018 500,349 $ 56.70 The Company uses the Black-Scholes option pricing model to estimate the fair value of stock option awards. The following weighted-average assumptions were used for option awards issued during the following periods: For the Nine Months Ended September 30, 2018 2017 Expected dividends 1.8 % 1.7 % Expected volatility 24.3 % 25.0 % Risk-free interest rate 2.7 % 2.1 % Expected term (in years) 5.8 5.8 Weighted-average grant-date fair value $ 18.48 $ 18.87 The assumptions above are based on multiple factors, including historical stock option exercise patterns and post-vesting employment termination behaviors, expected future exercise patterns and the expected volatility of the Company’s stock price. The following table represents the compensation expense that is included in non-interest expense and related income tax benefits in the accompanying consolidated statements of comprehensive income related to stock options for the following periods: For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Compensation expense related to stock options $ 322 $ 343 $ 952 $ 1,131 Income tax benefit related to stock options 23 46 70 161 At September 30, 2018, there was $2.2 million of unrecognized compensation expense related to stock options that is expected to be recognized over a weighted-average period of 2.9 years . Restricted stock awards The Company issues restricted stock under various plans for certain officers and directors. The restricted stock awards may not be sold or otherwise transferred until certain restrictions have lapsed. The holders of the restricted stock receive dividends and have the right to vote the shares. The compensation expense for these awards is determined based on the market price of the Company's common stock at the date of grant applied to the total number of shares granted and is recognized over the vesting period (generally three to five years). As of September 30, 2018 and 2017, unrecognized share-based compensation expense associated with these awards totaled $30.9 million and $35.7 million , respectively. The unrecognized compensation expense related to restricted stock awards at September 30, 2018 is expected to be recognized over a weighted-average period of 1.4 years . Restricted share units During the first nine months of 2018 and 2017, the Company issued restricted share units to certain of its executive officers. Restricted share units vest after the end of a three year performance period, based on satisfaction of the market and performance conditions set forth in the restricted share unit agreements. Recipients do not possess voting or investment power over the common stock underlying such units until vesting. The grant date fair value of these restricted share units is the same as the value of the corresponding number of shares of common stock, adjusted for assumptions surrounding the market-based conditions contained in the respective agreements. See Note 1, Summary of Significant Accounting Policies, in the 2017 10-K for further discussion of restricted share units with market or performance conditions. The following table represents the compensation expense that was included in non-interest expense and related income tax benefits in the accompanying consolidated statements of comprehensive income related to restricted stock awards and restricted share units for the periods indicated: For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Compensation expense related to restricted stock awards and restricted share units $ 4,843 $ 4,046 $ 14,192 $ 10,368 Income tax benefit related to restricted stock awards and restricted share units 1,017 1,416 2,980 3,629 The following table represents unvested restricted stock award and restricted share unit activity for the following periods: For the Nine Months Ended September 30, 2018 2017 Number of shares at beginning of period 738,187 543,258 Granted 229,181 411,957 Forfeited (70,981 ) (21,272 ) Vested (192,217 ) (191,222 ) Number of shares at end of period 704,170 742,721 Phantom stock awards The Company issues phantom stock awards to certain key officers and employees. The awards are subject to a vesting period of five years and are paid out in cash upon vesting. The amount paid per vesting period is calculated as the number of vested “share equivalents” multiplied by the closing market price of a share of the Company’s common stock on the vesting date. Share equivalents are calculated on the date of grant as the total award’s dollar value divided by the closing market price of a share of the Company’s common stock on the grant date. Award recipients are also entitled to a “dividend equivalent” on each unvested share equivalent held by the award recipient. A dividend equivalent is a dollar amount equal to the cash dividends that the participant would have been entitled to receive if the participant’s share equivalents were issued in shares of common stock. Dividend equivalents are reinvested as share equivalents that will vest and be paid out on the same date as the underlying share equivalents on which the dividend equivalents were paid. The number of share equivalents accumulated with a dividend equivalent is determined by dividing the aggregate of dividend equivalents paid on the unvested share equivalents by the closing price of a share of the Company’s common stock on the dividend payment date. The following table indicates compensation expense recorded for phantom stock based on the number of share equivalents vested at September 30 of the periods indicated and the current market price of the Company’s stock at that time: For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Compensation expense related to phantom stock $ 2,375 $ 2,747 $ 7,388 $ 8,689 The following table represents phantom stock award activity during the periods indicated: (Dollars in thousands) Number of share equivalents (1) Value of share equivalents (2) Balance, December 31, 2016 472,830 $ 39,600 Granted 111,119 9,128 Forfeited share equivalents (22,956 ) 1,886 Vested share equivalents (158,573 ) 13,212 Balance, September 30, 2017 402,420 $ 33,059 Balance, December 31, 2017 393,844 $ 30,523 Granted 151,908 12,358 Forfeited share equivalents (59,550 ) 4,844 Vested share equivalents (130,497 ) 10,871 Balance, September 30, 2018 355,705 $ 28,937 (1) Number of share equivalents includes all reinvested dividend equivalents for the periods indicated. (2) Except for share equivalents at the beginning of each period, which are based on the value at that time, and vested share payments, which are based on the cash paid at the time of vesting, the value of share equivalents is calculated based on the market price of the Company’s stock at the end of the respective periods. The market price of the Company’s stock was $81.35 and $82.15 on September 30, 2018, and 2017, respectively.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS See Note 1, Summary of Significant Accounting Policies, to the consolidated financial statements of the 2017 10-K for a description of valuation methodologies for assets and liabilities measured at fair value on a recurring and non-recurring basis. Recurring fair value measurements The Company has segregated all financial assets and liabilities that are measured at fair value on a recurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to estimate the fair value at the measurement date in the tables below. September 30, 2018 (Dollars in thousands) Level 1 Level 2 Level 3 Total Assets Securities available for sale $ — $ 4,634,124 $ — $ 4,634,124 CRA and Community Development Investment Funds — 1,866 — 1,866 Mortgage loans held for sale — 42,976 — 42,976 Mortgage loans held for investment, at fair value option — 7,249 — 7,249 Derivative instruments — 12,570 — 12,570 Total $ — $ 4,698,785 $ — $ 4,698,785 Liabilities Derivative instruments $ — $ 42,764 $ — $ 42,764 Total $ — $ 42,764 $ — $ 42,764 December 31, 2017 Level 1 Level 2 Level 3 Total Assets Securities available for sale $ — $ 4,590,062 $ — $ 4,590,062 Mortgage loans held for sale — 134,916 — 134,916 Mortgage loans held for investment, at fair value option — 14,953 — 14,953 Derivative instruments — 31,265 — 31,265 Total $ — $ 4,771,196 $ — $ 4,771,196 Liabilities Derivative instruments $ — $ 25,154 $ — $ 25,154 Total $ — $ 25,154 $ — $ 25,154 During the nine months ended September 30, 2018 , there were no transfers between the Level 1 and Level 2 fair value categories. Non-recurring fair value measurements The Company has segregated all assets and liabilities that are measured at fair value on a non-recurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to determine the fair value at the measurement date in the tables below. September 30, 2018 (Dollars in thousands) Level 1 Level 2 Level 3 Total Assets Loans $ — $ — $ 60,307 $ 60,307 OREO, net — — 5,148 5,148 Total $ — $ — $ 65,455 $ 65,455 December 31, 2017 (Dollars in thousands) Level 1 Level 2 Level 3 Total Assets Loans $ — $ — $ 71,210 $ 71,210 OREO, net — — 3,029 3,029 Total $ — $ — $ 74,239 $ 74,239 The tables above exclude the initial measurement of assets and liabilities that were acquired as part of the business combinations disclosed in Note 3, Acquisition Activity. These assets and liabilities were recorded at their fair value upon acquisition in accordance with U.S. GAAP and were not re-measured during the periods presented unless specifically required by U.S. GAAP. Acquisition date fair values represent either Level 2 fair value measurements (investment securities, deposits, property, and equipment) or Level 3 fair value measurements (loans, core deposit intangible assets, and debt.) Refer to Note 3, Acquisition Activity, for further detail. The Company did not record any liabilities at fair value for which measurement of the fair value was made on a non-recurring basis as of September 30, 2018 and December 31, 2017 . Fair value option The Company has elected the fair value option for originated residential mortgage loans held for sale, which allows for a more effective offset of the changes in fair values of the loans and the derivative instruments used to hedge them without the burden of complying with the requirements for hedge accounting. The Company also has a portion of mortgage loans held for investment for which the fair value option was elected upon origination and continue to be accounted for at fair value at September 30, 2018 and December 31, 2017, respectively. The following table summarizes the difference between the aggregate fair value and the aggregate unpaid principal balance for mortgage loans held for sale and mortgage loans held for investment measured at fair value: September 30, 2018 December 31, 2017 (Dollars in thousands) Aggregate Fair Value Aggregate Unpaid Principal Aggregate Fair Value Less Unpaid Principal Aggregate Fair Value Aggregate Unpaid Principal Aggregate Fair Value Less Unpaid Principal Mortgage loans held for sale, at fair value $ 42,976 $ 41,848 $ 1,128 $ 134,916 $ 131,276 $ 3,640 Mortgage loans held for investment, at fair value 7,249 8,666 (1,417 ) 14,953 16,306 (1,353 ) Interest income on mortgage loans held for sale is recognized based on contractual rates and is reflected in interest income on loans held for sale in the consolidated statements of comprehensive income. The following table details net gains (losses) resulting from the change in fair value of loans that were recorded in mortgage income in the consolidated statements of comprehensive income for the three and nine months ended September 30, 2018 and 2017. The changes in fair value are mostly offset by economic hedging activities, with an insignificant portion of these changes attributable to changes in instrument-specific credit risk. Net Gains (Losses) Resulting From Changes in Fair Value For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Fair value option Mortgage loans held for sale, at fair value $ (1,041 ) $ 251 $ (2,513 ) $ 1,121 Mortgage loans held for investment, at fair value (296 ) (62 ) (1,217 ) (127 )

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	FAIR VALUE OF FINANCIAL INSTRUMENTS The estimated fair value of a financial instrument is the current amount that would be exchanged between willing parties, other than in a forced liquidation. Fair value is best determined based upon quoted market prices. However, in many instances, there are no quoted market prices for the Company’s various financial instruments. In cases where quoted market prices are not available, fair values are based on estimates using present value or other valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Accordingly, the fair value estimates may not be realized in an immediate settlement of the instrument. ASC Topic 825, Financial Instruments , excludes certain financial instruments and all non-financial instruments from its disclosure requirements. Consequently, the aggregate fair value amounts presented may not necessarily represent the underlying fair value of the Company. The carrying amount and estimated fair values, as well as the level within the fair value hierarchy, of the Company’s financial instruments are included in the tables below. See Note 1, Summary of Significant Accounting Policies, in the 2017 10-K for a description of how fair value measurements are determined, except for loans, amended upon implementation of ASU 2016-01, Financial Statements - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. See Note 2, Recent Accounting Pronouncements, in this Report for a description of how the fair value measurement is determined for loans beginning January 1, 2018. September 30, 2018 (Dollars in thousands) Carrying Amount Fair Value Level 1 Level 2 Level 3 Measurement Category Fair Value Financial Assets Securities available for sale $ 4,634,124 $ 4,634,124 $ — $ 4,634,124 $ — CRA and Community Development Investment Funds 1,866 1,866 — 1,866 — Mortgage loans held for sale 42,976 42,976 — 42,976 — Derivative instruments 12,570 12,570 — 12,570 — Financial Liabilities Derivative instruments 42,764 42,764 — 42,764 — Amortized Cost Financial Assets Cash and cash equivalents $ 475,935 $ 475,935 $ 475,935 $ — $ — Securities held to maturity 213,561 207,309 — 207,309 — Loans and leases, net of unearned income and allowance for loan and lease losses 22,206,956 22,014,886 — — 22,014,886 Financial Liabilities Deposits 23,193,446 23,181,429 — 23,181,429 — Short-term borrowings 1,242,719 1,242,719 452,719 790,000 — Long-term debt 1,466,810 1,449,018 — — 1,449,018 December 31, 2017 (Dollars in thousands) Carrying Amount Fair Value Level 1 Level 2 Level 3 Measurement Category Fair Value Financial Assets Securities available for sale $ 4,590,062 $ 4,590,062 $ — $ 4,590,062 $ — Mortgage loans held for sale 134,916 134,916 — 134,916 — Derivative instruments 31,265 31,265 — 31,265 — Financial Liabilities Derivative instruments 25,154 25,154 — 25,154 — Amortized Cost Financial Assets Cash and cash equivalents $ 625,724 $ 625,724 $ 625,724 $ — $ — Securities held to maturity 227,318 227,964 — 227,964 — Loans and leases, net of unearned income and allowance for loan and lease losses 19,937,290 19,826,857 — — 19,826,857 Financial Liabilities Deposits 21,466,717 21,460,782 — 21,460,782 — Short-term borrowings 991,297 991,297 516,297 475,000 — Long-term debt 1,495,835 1,476,899 — — 1,476,899 The fair value estimates presented herein are based upon pertinent information available to management as of September 30, 2018 and December 31, 2017 . Although management is not aware of any factors that would significantly affect the estimated fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since these dates and, therefore, current estimates of fair value may differ significantly from the amounts presented herein.

Business Segments

Business Segments	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Business Segments	BUSINESS SEGMENTS Each of the Company’s reportable operating segments serves the specific needs of the Company’s customers based on the products and services it offers. The reportable segments are based upon those revenue-producing components for which separate financial information is produced internally and primarily reflect the manner in which resources are allocated and performance is assessed. Further, the reportable operating segments are also determined based on the quantitative thresholds prescribed within ASC Topic 280, Segment Reporting , and consideration of the usefulness of the information to the users of the consolidated financial statements. The Company reports the results of its operations through three reportable segments: IBERIABANK, Mortgage, and LTC. The IBERIABANK segment represents the Company’s commercial and retail banking functions, including its lending, investment, and deposit activities. IBERIABANK also includes the Company’s wealth management, capital markets, and other corporate functions. The Mortgage segment represents the Company’s origination, funding, and subsequent sale of one-to-four family residential mortgage loans. The LTC segment represents the Company’s title insurance and loan closing services. Certain expenses not directly attributable to a specific reportable segment are allocated to segments based on pre-determined methods that reflect utilization. Also within IBERIABANK are certain reconciling items that translate reportable segment results into consolidated results. The following tables present certain information regarding our operations by reportable segment, including a reconciliation of segment results to reported consolidated results for the periods presented. Reconciling items between segment results and reported results include: • Elimination of interest income and interest expense representing interest earned by IBERIABANK on interest-bearing checking accounts held by related companies, as well as the elimination of the related deposit balances at the IBERIABANK segment; • Elimination of investment in subsidiary balances on certain operating segments included in total and average segment assets; and • Elimination of intercompany due to and due from balances on certain operating segments that are included in total and average segment assets. Three Months Ended September 30, 2018 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 315,467 $ 1,599 $ 1 $ 317,067 Interest expense 57,842 — — 57,842 Net interest income 257,625 1,599 1 259,225 Provision for/(reversal of) loan and lease losses 11,099 (2 ) — 11,097 Mortgage income — 12,732 — 12,732 Title revenue — — 6,280 6,280 Other non-interest income/(expense) 33,591 (16 ) 500 34,075 Allocated expenses/(income) (3,691 ) 2,680 1,011 — Non-interest expense 154,287 10,223 4,839 169,349 Income/(loss) before income tax expense 129,521 1,414 931 131,866 Income tax expense/(benefit) 29,765 386 250 30,401 Net income/(loss) $ 99,756 $ 1,028 $ 681 $ 101,465 Total loans, leases, and loans held for sale, net of unearned income $ 22,302,679 $ 84,203 $ — $ 22,386,882 Total assets 29,974,065 119,322 25,000 30,118,387 Total deposits 23,179,549 13,897 — 23,193,446 Average assets 29,863,742 158,464 24,025 30,046,231 Three Months Ended September 30, 2017 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 245,166 $ 1,805 $ 1 $ 246,972 Interest expense 30,089 — — 30,089 Net interest income 215,077 1,805 1 216,883 Provision for/(reversal of) loan and lease losses 18,524 (10 ) — 18,514 Mortgage income — 16,050 — 16,050 Title revenue — — 5,643 5,643 Other non-interest income/(expense) 29,163 (9 ) (4 ) 29,150 Allocated expenses/(income) (3,881 ) 2,911 970 — Non-interest expense 174,306 22,170 4,286 200,762 Income/(loss) before income tax expense 55,291 (7,225 ) 384 48,450 Income tax expense/(benefit) 21,076 (2,424 ) 154 18,806 Net income/(loss) $ 34,215 $ (4,801 ) $ 230 $ 29,644 Total loans, leases, and loans held for sale, net of unearned income $ 19,743,749 $ 192,554 $ — $ 19,936,303 Total assets 27,738,588 217,056 20,991 27,976,635 Total deposits 21,333,190 1,081 — 21,334,271 Average assets 25,869,559 204,920 22,442 26,096,921 Nine Months Ended September 30, 2018 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 886,629 $ 4,802 $ 2 $ 891,433 Interest expense 143,206 — — 143,206 Net interest income 743,423 4,802 2 748,227 Provision for/(reversal of) loan losses 26,704 (26 ) — 26,678 Mortgage income — 36,048 — 36,048 Title revenue — — 18,153 18,153 Other non-interest income/(expense) 96,978 (83 ) 497 97,392 Allocated expenses/(income) (9,043 ) 6,714 2,329 — Non-interest expense 506,035 34,105 14,382 554,522 Income/(loss) before income tax expense 316,705 (26 ) 1,941 318,620 Income tax expense/(benefit) 78,516 (7 ) (99 ) 78,410 Net income/(loss) $ 238,189 $ (19 ) $ 2,040 $ 240,210 Total loans and loans held for sale, net of unearned income $ 22,302,679 $ 84,203 $ — $ 22,386,882 Total assets 29,974,065 119,322 25,000 30,118,387 Total deposits 23,179,549 13,897 — 23,193,446 Average assets 29,136,369 164,039 23,037 29,323,445 Nine Months Ended September 30, 2017 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 638,683 $ 5,395 $ 2 $ 644,080 Interest expense 70,736 — — 70,736 Net interest income 567,947 5,395 2 573,344 Provision for/(reversal of) loan losses 36,816 (98 ) — 36,718 Mortgage income — 49,895 — 49,895 Title revenue — — 16,574 16,574 Other non-interest income/(expense) 83,376 (30 ) (10 ) 83,336 Allocated expenses/(income) (9,377 ) 7,057 2,320 — Non-interest expense 412,305 59,754 12,879 484,938 Income/(loss) before income tax expense 211,579 (11,453 ) 1,367 201,493 Income tax expense/(benefit) 72,650 (3,840 ) 548 69,358 Net income/(loss) $ 138,929 $ (7,613 ) $ 819 $ 132,135 Total loans and loans held for sale, net of unearned income $ 19,743,749 $ 192,554 $ — $ 19,936,303 Total assets 27,738,588 217,056 20,991 27,976,635 Total deposits 21,333,190 1,081 — 21,334,271 Average assets 23,020,324 239,014 23,496 23,282,834

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Off-balance sheet commitments In the normal course of business, to meet the financing needs of its customers, the Company is a party to credit-related financial instruments, with risk not reflected in the consolidated financial statements. These financial instruments include commitments to extend credit, standby letters of credit, and commercial letters of credit. Such commitments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the consolidated balance sheets. The credit policies used for these commitments are consistent with those used for on-balance sheet instruments. The Company’s exposure to credit loss in the event of non-performance by its customers under such commitments or letters of credit represents the contractual amount of the financial instruments as indicated in the table below. At September 30, 2018, the fair value of guarantees under commercial and standby letters of credit was $2.4 million compared to $2.1 million at December 31, 2017. This fair value will decrease as the existing commercial and standby letters of credit approach their expiration dates. At September 30, 2018 and December 31, 2017, respectively, the Company had the following financial instruments outstanding and related reserves, whose contract amounts represent credit risk: (Dollars in thousands) September 30, 2018 December 31, 2017 Commitments to extend credit $ 824,472 $ 342,305 Unfunded commitments under lines of credit 6,610,843 6,060,034 Commercial and standby letters of credit 235,730 210,002 Reserve for unfunded lending commitments 14,721 13,208 Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee by the borrower. Since many of the commitments are expected to be drawn upon, the total commitment amounts generally represent future cash requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral, if any, is based on management’s credit evaluation of the customer. Unfunded commitments under commercial lines of credit, revolving credit lines, and overdraft protection agreements are commitments for possible future extensions of credit to existing customers. Many of these types of commitments do not contain a specified maturity date and may not be drawn upon to the total extent to which the Company is committed. See Note 6, Allowance for Credit Losses and Credit Quality, for additional information related to the Company’s reserve for unfunded lending commitments. Commercial and standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. These guarantees are primarily issued to support public and private borrowing arrangements, including commercial paper issuance, bond financing, and similar transactions. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers. When necessary they are collateralized, generally in the form of marketable securities and cash equivalents. Legal proceedings The nature of the business of the Company’s banking and other subsidiaries ordinarily results in a certain amount of claims, litigation, investigations, and legal and administrative cases and proceedings, which are considered incidental to the normal conduct of business. Some of these claims are against entities or assets of which the Company is a successor or acquired in business acquisitions. The Company has asserted defenses to these claims and, with respect to such legal proceedings, intends to continue to defend itself vigorously, litigating or settling cases according to management’s judgment as to what is in the best interest of the Company and its shareholders. In July of 2016, the Company received a subpoena from the Office of Inspector General of the U.S. Department of Housing and Urban Development (“HUD”) requesting information on certain previously originated loans insured by the Federal Housing Administration ("FHA") as well as other documents regarding the Company's FHA-related policies and practices. After the Company complied with the subpoena, attorneys from the Department of Justice (“DOJ”) informed the Company in late March of 2017 that a civil qui tam suit had been filed against the Company in federal court involving the subject matter of the HUD subpoena. The HUD lawsuit was settled on December 11, 2017 in the amount of $11.7 million . On February 2, 2018, IBERIABANK filed a lawsuit in the United States District Court for the Eastern District of Louisiana (New Orleans) against Illinois Union Insurance Company and Travelers Casualty and Surety Company of America in an effort to recover the $11.7 million it paid to settle the HUD matter. IBERIABANK filed that lawsuit to recover the insurance proceeds to which it claims to be entitled under certain Bankers’ Professional Liability insurance policies issued by defendants Illinois Union and Travelers. More specifically, IBERIABANK alleges that the insurers have failed to honor their obligations under the policies to pay IBERIABANK’s losses in connection with the $11.7 million settlement of disputed allegations relating to IBERIABANK’s professional services in connection with certain mortgage loans insured by the FHA. The Company assesses its liabilities and contingencies in connection with outstanding legal proceedings utilizing the latest information available. Where it is probable that the Company will incur a loss and the amount of the loss can be reasonably estimated, the Company records a liability in its consolidated financial statements. These legal reserves may be increased or decreased to reflect any relevant developments on a quarterly basis. Where a loss is not probable or the amount of loss is not estimable, the Company does not accrue legal reserves. While the outcome of legal proceedings is inherently uncertain, based on information currently available and available insurance coverage, the Company’s management believes that it has established appropriate legal reserves. Any incremental liabilities arising from pending legal proceedings are not expected to have a material adverse effect on the Company’s consolidated financial position, consolidated results of operations, or consolidated cash flows. However, it is possible that the ultimate resolution of these matters, if unfavorable, may be material to the Company’s consolidated financial position, consolidated results of operations, or consolidated cash flows. As of the date of this filing, the Company believes the amount of losses associated with legal proceedings that it is reasonably possible to incur above amounts already accrued and reported as of September 30, 2018 is not material.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS In the ordinary course of business, the Company may execute transactions with various related parties. Examples of such transactions may include lending or deposit arrangements, transfers of financial assets, services for administrative support, and other miscellaneous items. The Company has granted loans to executive officers and directors and their affiliates. These loans, including the related principal additions, principal payments, and unfunded commitments are not material to the consolidated financial statements at September 30, 2018 and December 31, 2017. There were no outstanding loans to such related parties classified as non-accrual, past due, or troubled debt restructurings at September 30, 2018. Deposits from related parties held by the Company were not material at September 30, 2018 and December 31, 2017.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Principles of Consolidation	The consolidated financial statements include the accounts of the Company and its subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
Reclassification	Certain amounts reported in prior periods have been reclassified to conform to the current period presentation. These reclassifications did not have a material effect on previously reported consolidated financial statements.
Concentration of Credit Risks	Concentrations of Credit Risk Most of the Company’s business activity is with customers located in the southeastern United States. The Company’s lending activity is concentrated in its market areas within those states. The Company has emphasized originations of commercial loans and private banking loans, defined as loans to higher net worth clients. Repayments on loans are expected to come from cash flows of the borrower and/or guarantor. Losses on secured loans are limited by the net realizable value of the collateral upon default of the borrowers and guarantor support. The Company believes it does not have any excessive concentrations to any one industry, loan type, or customer.
Recent Accounting Pronouncements	RECENT ACCOUNTING PRONOUNCEMENTS Pronouncements adopted during the nine months ended September 30, 2018: ASU No. 2014-09 In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , which implements a common revenue standard and clarifies the principles used for recognizing revenue. The amendments in the ASU clarify that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Revenue from Contracts with Customers The majority of the Company’s income streams (e.g., interest and dividend income and mortgage income) are accounted for in accordance with GAAP literature outside the scope of ASC 606, Revenue from Contracts with Customers . Details regarding income recognition for interest and non-interest streams can be found throughout the Company’s 2017 10-K (including Note 1 - Summary of Significant Accounting Policies). Impairment losses recognized against certain receivables (e.g., NSF fees) and capitalized costs (e.g., sales commissions) associated with contracts within the scope of ASC 606 are immaterial. Non-interest income from service charges on deposit accounts, broker commissions, ATM/debit card fee income, credit card and merchant-related income (e.g., interchange fees), and transactional income from traditional banking services (part of other non-interest income) are the significant income streams within the scope of ASC 606 associated with the IBERIABANK reportable segment. Non-interest income from title revenue is associated with the LTC reportable segment. Recognition of Revenue from Contracts with Customers The Company enters into various contracts with customers to provide traditional banking services, including asset management, on a routine basis. The Company’s performance obligations are generally service-related and provided on a daily or monthly basis. The Company does not typically have performance obligations which extend beyond a reporting period. The performance obligations are generally satisfied upon completion of service (i.e., as services are rendered) and the fees are collected at such time, or shortly thereafter. The fees are readily determinable and allocated individually to each service. It is not typical for contracts to require significant judgment to determine the transaction price. Some contracts contain variable consideration; however, the variable consideration is generally constrained (not estimable) as it is based on the occurrence or nonoccurence of a contingent event (or another constraint in some circumstances). The Company generally records the variable consideration when the contingent event occurs and the fee is determinable. The Company provides some services for customers in which it acts in an agent capacity, but generally acts in a principal capacity. Payment terms and conditions vary slightly amongst services; however, amounts are generally invoiced and due or collected by the Company within 30 days, although some fees may be prepaid. The Company bills the customer periodically as performance obligations are satisfied for most services. Therefore, revenue for services provided is generally recognized in the amount invoiced (except in circumstances of prepayment) as that amount corresponds directly to the value of the Company’s performance. In the normal course of business, the Company does not generally grant refunds for services provided. As such, the Company does not establish provisions for estimated returns. Title revenue associated with services provided by LTC, as well as broker commissions, ATM/debit card fee income, credit card and merchant-related income (e.g., interchange fees), and transactional fees from traditional banking services generated within IBERIABANK are generally recognized at the point-in-time the services are provided. The Company has determined this recognition to be appropriate as, upon completion of services, the Company has completed its performance obligations, has a present right to payment (or has collected the cash), and the customer is able to obtain (or has obtained) substantially all of the benefits from the performance obligation (i.e., the provided services). Revenues from service charges on deposit accounts are recognized at the end of the monthly service period (e.g., account service charges) or the date the performance obligation is satisfied (e.g., NSF, stop payment, wire transfer, etc.), except for deposit account services performed by Treasury Management which are recognized on a monthly basis, as these services are performed over that time. Asset management fees (e.g., trust fees) are generally recognized at the end of the monthly service period, but fees are not collected until the beginning of the subsequent month, although some contracts may have quarterly terms and/or be prepaid. NSF fees which are not initially paid are subsequently recorded as “loans” (along with the overdraft balance) and remain classified as such until the amount is paid or charged-off (generally after 60 days). Adoption of ASC 606 The Company adopted ASC 606 as of January 1, 2018 for all contracts as of the effective date. Prior period amounts have been reclassified to conform to current guidance requirements related to the net presentation of certain costs associated with interchange fees and rewards programs. The reclassification of prior period amounts reduced non-interest income and non-interest expense by an immaterial amount (approximately $2.2 million and $6.6 million for the three and nine months ended September 30, 2017, respectively) and had no impact on net income. There was no cumulative adjustment made to opening retained earnings as of January 1, 2018. ASU No. 2016-01 In January 2016, the FASB issued ASU No. 2016-01, Financial Statements - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , which impacts how the Company measures certain equity investments and discloses and presents certain financial instruments through the application of the “exit price” notion. The Company adopted the amendments beginning January 1, 2018. Under the new guidance, equity investments can no longer be classified as trading or available for sale (AFS), and related unrealized holding gains and losses can no longer be recognized in OCI. Per the ASU, such equity investments should be measured at fair value, with adjustments recognized in earnings at the end of each reporting period. As such, the Company reclassified its portfolio of equity investments (which were insignificant at the adoption date and at September 30, 2018) previously classified as AFS investment securities to “other assets.” As these equity investments were previously measured at fair value, implementation of the ASU did not impact the Company’s valuation method. In accordance with the adoption of the ASU, the Company recorded a cumulative-effect adjustment to retained earnings for previously recorded fair value adjustments related to these equity investments, which was insignificant. The Company elected the practical expedient measurement alternative to prospectively account for other equity investments that do not have readily determinable fair values at cost less impairment plus or minus observable price changes in orderly transactions for an identical or similar investment of the same issuer. These investments are insignificant overall and are classified within “other assets” on the Company’s consolidated balance sheets. The Company also modified its fair value methodology for loans measured at amortized cost whose fair values were previously disclosed using an “entry price” methodology to an “exit price” methodology, in accordance with the ASU. The Company’s “exit price” methodology estimates the fair value of these loans based on the present value of the future cash flows using the interest rate that would be charged for a similar loan to a borrower with similar risk at the indicated balance sheet date, adjusted for a liquidity discount based on the estimated time period to complete a sale transaction with a market participant. ASU No. 2016-15 In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (ASC 230): Classification of Certain Cash Receipts and Cash Payments , in order to reduce current diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The Company retrospectively adopted the amendments effective January 1, 2018. The adoption of these amendments did not impact the Company’s consolidated statements of cash flows. ASU No. 2017-04 In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (ASC 350): Simplifying the Test for Goodwill Impairment, which simplifies how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Therefore, any carrying amount which exceeds the reporting unit’s fair value (up to the amount of goodwill recorded) will be recognized as an impairment loss. The ASU is effective for annual reporting periods beginning after December 15, 2019, including interim periods within those periods. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company elected to early adopt the guidance, effective September 30, 2018. The adoption of the guidance did not impact the Company’s consolidated financial statements in the current period. The Company will apply the guidance prospectively, beginning with its annual impairment test as of October 1, 2018. ASU No. 2017-12 In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities, which amends the hedge accounting model to enable entities to better portray the economics of their risk management activities in the financial statements and enhance the transparency and understandability of hedge results. The Company elected to early adopt the amendments effective January 1, 2018. The modified-retrospective adoption of the amendments did not impact the Company’s consolidated financial statements in the current or prior periods. ASU 2018-15 In August 2018, the FASB issued ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The guidance requires customers in a cloud computing arrangement (i.e., hosting arrangement) that is a service contract to follow the internal-use software guidance in ASC 350-40 to determine which implementation costs to capitalize as assets or expense as incurred. ASC 350-40 requires the capitalization of certain costs incurred only during the application development stage (e.g., costs of integration with on-premises software, coding, configuration, and customization). ASC 350-40 also requires entities to expense costs during the preliminary project and post-implementation stages (e.g., costs of project planning, training, maintenance after implementation, data conversion) as they are incurred. The accounting for the service element of the arrangement is not affected by the ASU. Capitalized implementation costs related to a hosting arrangement that is a service contract should be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. The expense related to the capitalized implementation costs should be presented in the same line item in the income statement as the fees associated with the hosting element of the arrangement. Capitalized implementation costs should be presented in the same line item in the statement of financial position that a prepayment of the fees for the associated hosting arrangement would be presented. Payments for capitalized implementation costs should be classified in the statement of cash flows in the same manner as payments of the fees for the service component of the hosting arrangement (typically operating cash flows). The amendments further require entities to disclose the nature of their hosting arrangements that are service contracts and make the disclosures in ASC 360-10 as if the capitalized implementation costs were a separate major class of depreciable asset. The ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim period. Entities have the option to apply the guidance retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company elected to early adopt the guidance prospectively, effective August 31, 2018. The adoption of the guidance did not impact the Company’s consolidated financial statements in the current period. Pronouncements issued but not yet adopted: ASU No. 2016-02 and ASU No. 2018-11 In February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842) . A significant amendment to existing GAAP from this ASU is the recognition of lease assets (i.e., right of use assets) and liabilities on the balance sheet for leases that are classified as operating leases by lessees. The lessor model remains similar to the current accounting model in existing GAAP. Additional amendments include, but are not limited to, the elimination of leveraged leases; modification to the definition of a lease; amendments on sale and leaseback transactions; and disclosure of additional quantitative and qualitative information. ASU 2016-02 will be effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. In July 2018, the FASB issued ASU No. 2018-11, Leases (ASC 842): Targeted Improvements. The amendments include an optional transition method to apply ASU 2016-02 on a prospective basis as of the effective date, with a cumulative effect adjustment to retained earnings in the period of adoption, instead of applying the guidance using a modified retrospective approach as originally required under ASU 2016-02. ASU 2018-11 also provides lessors with a practical expedient, by class of underlying asset, to not separate nonlease components from the associated lease component under certain circumstances, and clarifies which guidance (ASC 842 or ASC 606) to apply to combined lease and nonlease components. The Company occupies certain banking offices and equipment under operating lease agreements, which currently are not recognized on the consolidated balance sheets. Based on the Company’s preliminary analysis of its current portfolio, the impact to the Company’s consolidated balance sheets is estimated to result in less than a 1% increase in assets and liabilities. The Company has developed an implementation plan and selected a third-party vendor to assist in the implementation and subsequent accounting for leases under the ASUs. The Company will elect the optional transition method and adopt ASU 2016-02 and ASU No. 2018-11 on January 1, 2019. The Company is still assessing other practical expedients it may elect at adoption, the final determination of the incremental borrowing rate, and the impact to regulatory capital ratios, amongst other matters associated with the ASUs. The adjustment to retained earnings is not expected to be significant based on the transition guidance associated with current sale-leaseback agreements. The Company also anticipates additional disclosures to be provided at adoption. ASU No. 2016-13 In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (ASC 326): Measurement of Credit Losses on Financial Instruments . The amendments introduce an impairment model that is based on expected credit losses (“ECL”), rather than incurred losses, to estimate credit losses on certain types of financial instruments (e.g., loans and held-to-maturity securities), including certain off-balance sheet financial instruments (e.g., loan commitments). The measurement of ECL should consider historical information, current information, and reasonable and supportable forecasts, including estimates of prepayments, over the contractual term. Financial instruments with similar risk characteristics must be grouped together when estimating ECL. The ASU also amends the current AFS security impairment model for debt securities. The new model will require an estimate of ECL when the fair value is below the amortized cost of the asset through the use of an allowance to record estimated credit losses (and subsequent recoveries). Non-credit related losses will continue to be recognized through OCI. In addition, the amendments provide for a simplified accounting model for purchased financial assets with a more-than-insignificant amount of credit deterioration since their origination. The initial estimate of expected credit losses would be recognized through an ALLL with an offset (i.e., increase) to the cost basis of the related financial asset at acquisition. ASU 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods. The amendments will be applied through a modified-retrospective approach, resulting in a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. A prospective transition approach is required for debt securities for which OTTI had been recognized before the effective date. Amounts previously recognized in AOCI as of the date of adoption that relate to improvements in cash flows expected to be collected should continue to be accreted into income over the remaining life of the asset. Recoveries of amounts previously written off relating to improvements in cash flows after the date of adoption should be recorded in earnings when received. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements. The Company has engaged third-party consultants to assist with the ASU and has developed an implementation plan. ASU No. 2018-13 In August 2018, the FASB released ASU No. 2018-13, Fair Value Measurement (ASC 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The amendments to the guidance on fair value disclosures eliminate the requirements for all entities to disclose (i) the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, (ii) the entity’s policy for the timing of transfers between levels of the fair value hierarchy, and (iii) the entity’s valuation processes for Level 3 fair value measurements. New disclosure requirements for public entities per the ASU include (i) the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements of instruments held at the end of the reporting period, and (ii) the range and weighted average used to develop significant unobservable inputs and how the weighted average was calculated for recurring and nonrecurring Level 3 fair value measurements, with certain exceptions. For derivative instruments and certain other assets and liabilities, entities are permitted to disclose other quantitative information (such as the median or arithmetic average) if doing so provides a more reasonable and rational reflection of the distribution of unobservable inputs used to develop Level 3 fair value measurements. The amendments also modified disclosure guidance within ASC 820 to clarify that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date, rather than a point in the future. Further, entities that use the practical expedient to measure the fair value of certain investments at their net asset values are required to disclose (i) the timing of liquidation of an investee’s assets, and (ii) the date when redemption restrictions will lapse only if the investee has communicated this information to the entity or announced the timing publicly. ASU 2018-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods. The guidance on changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 measurements, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty is applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted, including interim periods, and entities may elect to early adopt either (i) the entire standard, or (ii) only the provisions that eliminate or modify disclosure requirements. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements. ASU No. 2018-16 In October 2018, the FASB released ASU No. 2018-16, Derivatives and Hedging (ASC 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes , which permits the use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under ASC 815 in addition to the interest rates on direct Treasury obligations of the U.S. government (UST), the London Interbank Offered Rate (LIBOR) swap rate, the OIS Rate based on the Fed Funds Effective Rate, and the Securities Industry and Financial Markets Association (SIFMA) Municipal Swap Rate. For entities that have not already adopted ASU No. 2017-12, Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities, ASU 2018-16 is required to be adopted concurrently with the amendments in ASU 2017-12. For entities that already have adopted ASU 2017-12, ASU 2018-16 will be effective for fiscal years beginning after December 15, 2018, including interim periods. Early adoption is permitted in any interim period upon issuance of ASU 2018-16 if an entity already has adopted ASU 2017-12. The amendments should be adopted on a prospective basis for qualifying new or redesignated hedging relationships entered into, on, or after the date of adoption. The implementation of the amendments will not have a significant impact on the Company’s consolidated financial statements based upon its current hedging strategies. ASU No. 2018-17 In October 2018, the FASB released ASU No. 2018-17, Consolidation (ASC 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities, which improves the consistency of the application of the variable interest entity (VIE) related party guidance for common control arrangements. The amendments require reporting entities to consider indirect interests held through related parties under common control on a proportional basis rather than as the equivalent of a direct interest in its entirety (as currently required in GAAP) when determining whether a decision-making fee is a variable interest. ASU 2018-17 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The amendments should be applied retrospectively with a cumulative-effect adjustment to retained earnings at the beginning of the earliest period presented. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements.

Acquisition Activity (Tables)

Acquisition Activity (Tables)	9 Months Ended
	Sep. 30, 2018
Gibraltar Private Bank & Trust Company
Business Acquisition [Line Items]
Schedule of Business Acquisitions	(Dollars in thousands) Number of Shares Amount Equity consideration Common stock issued 2,787,773 $ 214,659 Total equity consideration 214,659 Non-equity consideration Cash 7 Total consideration paid 214,666 Fair value of net assets assumed including identifiable intangible assets 165,044 Goodwill $ 49,622 (Dollars in thousands) Gibraltar Fair Value (Preliminary) Assets Cash and cash equivalents $ 102,575 Investment securities 19,169 Equity securities 27,519 Loans 1,465,278 Core deposit intangible assets 18,529 Other assets 12,005 Total assets acquired $ 1,645,075 Liabilities Deposit liabilities $ 1,064,803 Long-term borrowings 405,107 Deferred tax liability, net 5,960 Other liabilities 4,161 Total liabilities assumed $ 1,480,031
Sabadell United
Business Acquisition [Line Items]
Schedule of Business Acquisitions	(Dollars in thousands) Number of Shares Amount Equity consideration Common stock issued 2,610,304 $ 211,043 Total equity consideration 211,043 Non-equity consideration Cash 809,159 Total consideration paid 1,020,202 Fair value of net assets assumed including identifiable intangible assets 579,157 Goodwill $ 441,045 (Dollars in thousands) Sabadell United Fair Value Assets Cash and cash equivalents $ 318,819 Investment securities 964,123 Loans 4,030,777 Core deposit intangible assets 66,600 Deferred tax asset, net 44,480 Other assets 92,820 Total assets acquired $ 5,517,619 Liabilities Deposit liabilities $ 4,382,780 Short-term borrowings 520,539 Other liabilities 35,143 Total liabilities assumed $ 4,938,462
Schedule of Pro Forma Information	The following table presents unaudited pro forma information as if the acquisition occurred on January 1, 2016. The pro forma information does not necessarily reflect the results of operations that would have occurred had the Company acquired Sabadell United on January 1, 2016. Furthermore, cost savings and other business synergies related to the acquisition are not reflected in the pro forma amounts. Unaudited Pro Forma Information for the (Dollars in thousands) Three months ended September 30, 2017 Nine months ended September 30, 2017 Net interest income $ 232,828 $ 688,846 Non-interest income 54,511 164,360 Net income 30,825 163,968

Investment Securities (Tables)

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities	The amortized cost and fair values of investment securities, with gross unrealized gains and losses, consist of the following: September 30, 2018 (Dollars in thousands) Amortized Gross Gross Estimated Securities available for sale: U.S. Government-sponsored enterprise obligations $ 40,996 $ 5 $ (740 ) $ 40,261 Obligations of state and political subdivisions 265,565 694 (4,852 ) 261,407 Mortgage-backed securities: Residential agency 3,654,417 68 (140,816 ) 3,513,669 Commercial agency 721,899 — (26,513 ) 695,386 Other securities 126,098 — (2,697 ) 123,401 Total securities available for sale $ 4,808,975 $ 767 $ (175,618 ) $ 4,634,124 Securities held to maturity: Obligations of state and political subdivisions $ 194,382 $ 349 $ (5,277 ) $ 189,454 Mortgage-backed securities: Residential agency 19,179 28 (1,352 ) 17,855 Total securities held to maturity $ 213,561 $ 377 $ (6,629 ) $ 207,309 December 31, 2017 (Dollars in thousands) Amortized Gross Gross Estimated Securities available for sale: U.S. Government-sponsored enterprise obligations $ 41,003 $ 18 $ (406 ) $ 40,615 Obligations of state and political subdivisions 271,451 4,246 (1,493 ) 274,204 Mortgage-backed securities: Residential agency 3,675,367 1,233 (52,090 ) 3,624,510 Commercial agency 546,105 228 (8,938 ) 537,395 Other securities 114,005 247 (914 ) 113,338 Total securities available for sale $ 4,647,931 $ 5,972 $ (63,841 ) $ 4,590,062 Securities held to maturity: Obligations of state and political subdivisions $ 206,736 $ 1,530 $ (275 ) $ 207,991 Mortgage-backed securities: Residential agency 20,582 41 (650 ) 19,973 Total securities held to maturity $ 227,318 $ 1,571 $ (925 ) $ 227,964 Information pertaining to securities with gross unrealized losses, aggregated by investment category and length of time that individual securities have been in a continuous loss position, is as follows: September 30, 2018 Less Than Twelve Months Twelve Months or More Total (Dollars in thousands) Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Securities available for sale: U.S. Government-sponsored enterprise obligations $ — $ — $ (740 ) $ 39,259 $ (740 ) $ 39,259 Obligations of state and political subdivisions (839 ) 107,014 (4,013 ) 90,761 (4,852 ) 197,775 Mortgage-backed securities: Residential agency (23,673 ) 1,009,754 (117,143 ) 2,482,730 (140,816 ) 3,492,484 Commercial agency (4,657 ) 268,207 (21,856 ) 418,295 (26,513 ) 686,502 Other securities (1,310 ) 93,529 (1,387 ) 29,872 (2,697 ) 123,401 Total securities available for sale $ (30,479 ) $ 1,478,504 $ (145,139 ) $ 3,060,917 $ (175,618 ) $ 4,539,421 Securities held to maturity: Obligations of state and political subdivisions $ (3,725 ) $ 115,138 $ (1,552 ) $ 40,960 $ (5,277 ) $ 156,098 Mortgage-backed securities: Residential agency — — (1,352 ) 17,544 (1,352 ) 17,544 Total securities held to maturity $ (3,725 ) $ 115,138 $ (2,904 ) $ 58,504 $ (6,629 ) $ 173,642 December 31, 2017 Less Than Twelve Months Twelve Months or More Total (Dollars in thousands) Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Securities available for sale: U.S. Government-sponsored enterprise obligations $ (254 ) $ 29,744 $ (152 ) $ 9,848 $ (406 ) $ 39,592 Obligations of state and political subdivisions (326 ) 31,601 (1,167 ) 68,609 (1,493 ) 100,210 Mortgage-backed securities: Residential agency (22,760 ) 2,366,569 (29,330 ) 1,061,588 (52,090 ) 3,428,157 Commercial agency (3,503 ) 310,769 (5,435 ) 164,470 (8,938 ) 475,239 Other securities (914 ) 75,302 — — (914 ) 75,302 Total securities available for sale $ (27,757 ) $ 2,813,985 $ (36,084 ) $ 1,304,515 $ (63,841 ) $ 4,118,500 Securities held to maturity: Obligations of state and political subdivisions $ (263 ) $ 65,817 $ (12 ) $ 3,031 $ (275 ) $ 68,848 Mortgage-backed securities: Residential agency (2 ) 333 (648 ) 19,269 (650 ) 19,602 Total securities held to maturity $ (265 ) $ 66,150 $ (660 ) $ 22,300 $ (925 ) $ 88,450
Held-to-maturity Securities	Information pertaining to securities with gross unrealized losses, aggregated by investment category and length of time that individual securities have been in a continuous loss position, is as follows: September 30, 2018 Less Than Twelve Months Twelve Months or More Total (Dollars in thousands) Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Securities available for sale: U.S. Government-sponsored enterprise obligations $ — $ — $ (740 ) $ 39,259 $ (740 ) $ 39,259 Obligations of state and political subdivisions (839 ) 107,014 (4,013 ) 90,761 (4,852 ) 197,775 Mortgage-backed securities: Residential agency (23,673 ) 1,009,754 (117,143 ) 2,482,730 (140,816 ) 3,492,484 Commercial agency (4,657 ) 268,207 (21,856 ) 418,295 (26,513 ) 686,502 Other securities (1,310 ) 93,529 (1,387 ) 29,872 (2,697 ) 123,401 Total securities available for sale $ (30,479 ) $ 1,478,504 $ (145,139 ) $ 3,060,917 $ (175,618 ) $ 4,539,421 Securities held to maturity: Obligations of state and political subdivisions $ (3,725 ) $ 115,138 $ (1,552 ) $ 40,960 $ (5,277 ) $ 156,098 Mortgage-backed securities: Residential agency — — (1,352 ) 17,544 (1,352 ) 17,544 Total securities held to maturity $ (3,725 ) $ 115,138 $ (2,904 ) $ 58,504 $ (6,629 ) $ 173,642 December 31, 2017 Less Than Twelve Months Twelve Months or More Total (Dollars in thousands) Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Securities available for sale: U.S. Government-sponsored enterprise obligations $ (254 ) $ 29,744 $ (152 ) $ 9,848 $ (406 ) $ 39,592 Obligations of state and political subdivisions (326 ) 31,601 (1,167 ) 68,609 (1,493 ) 100,210 Mortgage-backed securities: Residential agency (22,760 ) 2,366,569 (29,330 ) 1,061,588 (52,090 ) 3,428,157 Commercial agency (3,503 ) 310,769 (5,435 ) 164,470 (8,938 ) 475,239 Other securities (914 ) 75,302 — — (914 ) 75,302 Total securities available for sale $ (27,757 ) $ 2,813,985 $ (36,084 ) $ 1,304,515 $ (63,841 ) $ 4,118,500 Securities held to maturity: Obligations of state and political subdivisions $ (263 ) $ 65,817 $ (12 ) $ 3,031 $ (275 ) $ 68,848 Mortgage-backed securities: Residential agency (2 ) 333 (648 ) 19,269 (650 ) 19,602 Total securities held to maturity $ (265 ) $ 66,150 $ (660 ) $ 22,300 $ (925 ) $ 88,450 The amortized cost and fair values of investment securities, with gross unrealized gains and losses, consist of the following: September 30, 2018 (Dollars in thousands) Amortized Gross Gross Estimated Securities available for sale: U.S. Government-sponsored enterprise obligations $ 40,996 $ 5 $ (740 ) $ 40,261 Obligations of state and political subdivisions 265,565 694 (4,852 ) 261,407 Mortgage-backed securities: Residential agency 3,654,417 68 (140,816 ) 3,513,669 Commercial agency 721,899 — (26,513 ) 695,386 Other securities 126,098 — (2,697 ) 123,401 Total securities available for sale $ 4,808,975 $ 767 $ (175,618 ) $ 4,634,124 Securities held to maturity: Obligations of state and political subdivisions $ 194,382 $ 349 $ (5,277 ) $ 189,454 Mortgage-backed securities: Residential agency 19,179 28 (1,352 ) 17,855 Total securities held to maturity $ 213,561 $ 377 $ (6,629 ) $ 207,309 December 31, 2017 (Dollars in thousands) Amortized Gross Gross Estimated Securities available for sale: U.S. Government-sponsored enterprise obligations $ 41,003 $ 18 $ (406 ) $ 40,615 Obligations of state and political subdivisions 271,451 4,246 (1,493 ) 274,204 Mortgage-backed securities: Residential agency 3,675,367 1,233 (52,090 ) 3,624,510 Commercial agency 546,105 228 (8,938 ) 537,395 Other securities 114,005 247 (914 ) 113,338 Total securities available for sale $ 4,647,931 $ 5,972 $ (63,841 ) $ 4,590,062 Securities held to maturity: Obligations of state and political subdivisions $ 206,736 $ 1,530 $ (275 ) $ 207,991 Mortgage-backed securities: Residential agency 20,582 41 (650 ) 19,973 Total securities held to maturity $ 227,318 $ 1,571 $ (925 ) $ 227,964
Additional Information on Securities in a Continuous Loss Position	Additional information on securities that have been in a continuous loss position for over twelve months at September 30, 2018 and December 31, 2017 is presented in the following table: (Dollars in thousands) September 30, 2018 December 31, 2017 Number of securities: Mortgage-backed securities: Residential agency 336 153 Commercial agency 65 28 Obligations of state and political subdivisions 53 28 U.S. Government-sponsored enterprise obligations 3 1 Other securities 7 — 464 210 Amortized Cost Basis: Mortgage-backed securities: Residential agency $ 2,618,769 $ 1,110,834 Commercial agency 440,151 169,905 Obligations of state and political subdivisions 137,286 72,820 U.S. Government-sponsored enterprise obligations 39,999 10,000 Other securities 31,259 — $ 3,267,464 $ 1,363,559 Unrealized Loss: Mortgage-backed securities: Residential agency $ 118,495 $ 29,977 Commercial agency 21,856 5,435 Obligations of state and political subdivisions 5,565 1,180 U.S. Government-sponsored enterprise obligations 740 152 Other securities 1,387 — $ 148,043 $ 36,744
Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Maturity	The amortized cost and estimated fair value of investment securities by maturity at September 30, 2018 are presented in the following table. Securities are classified according to their contractual maturities without consideration of principal amortization, potential prepayments or call options. Accordingly, actual maturities may differ from contractual maturities. Weighted average yields are calculated on the basis of the yield to maturity based on the amortized cost of each security. Securities Available for Sale Securities Held to Maturity (Dollars in thousands) Weighted Amortized Estimated Weighted Amortized Estimated Within one year or less 1.90 % $ 19,161 $ 19,056 4.00 % $ 435 $ 436 One through five years 2.25 150,119 147,472 2.80 8,776 8,751 After five through ten years 2.47 1,104,969 1,069,983 2.58 45,368 44,690 Over ten years 2.45 3,534,726 3,397,613 2.60 158,982 153,432 2.44 % $ 4,808,975 $ 4,634,124 2.61 % $ 213,561 $ 207,309
Schedule of Realized Gains and Losses from Sale of Securities Classified as Available for Sale	The following is a summary of realized gains and losses from the sale of securities classified as available for sale. Gains or losses on securities sold are recorded on the trade date, using the specific identification method. Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Realized gains $ — $ 667 $ 39 $ 909 Realized losses — (909 ) (95 ) (1,092 ) $ — $ (242 ) $ (56 ) $ (183 )
Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets	The Company accounts for the following securities at cost less impairment plus or minus any observable price changes, which approximates fair value, with the exception of CRA and Community Development Investment Funds, which are recorded at fair value. Other Equity Securities, which are presented in “other assets” on the consolidated balance sheets, are as follows: (Dollars in thousands) September 30, 2018 December 31, 2017 Federal Home Loan Bank (FHLB) stock $ 102,508 $ 95,171 Federal Reserve Bank (FRB) stock 85,630 79,191 CRA and Community Development Investment Funds 1,866 — Other investments 9,838 3,008 $ 199,842 $ 177,370

Loans (Tables)

Loans (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Schedule of Non-Covered and Covered Loans	Loans and leases consist of the following for the periods indicated: (Dollars in thousands) September 30, 2018 December 31, 2017 Commercial loans and leases: Real estate - construction $ 1,127,988 $ 1,240,396 Real estate - owner-occupied 2,458,964 2,375,321 Real estate - non-owner-occupied 5,794,931 5,322,513 Commercial and industrial (1) 5,581,040 5,135,067 14,962,923 14,073,297 Residential mortgage loans 4,300,163 3,056,352 Consumer loans: Home equity 2,350,176 2,292,275 Other 730,644 656,257 3,080,820 2,948,532 Total $ 22,343,906 $ 20,078,181 (1) Includes equipment financing leases
Schedule of Aging of Loans	The following tables provide an analysis of the aging of loans as of September 30, 2018 and December 31, 2017 . Past due and non-accrual loan amounts exclude acquired impaired loans, even if contractually past due or if the Company does not expect to receive payment in full, as the Company is currently accreting interest income over the expected life of the loans. September 30, 2018 Accruing (Dollars in thousands) Current or Less Than 30 days Past Due 30-59 days 60-89 days > 90 days Total Past Due Non-accrual Acquired Impaired Total Real estate- construction $ 1,105,488 $ 75 $ 830 $ — $ 905 $ 1,122 $ 20,473 $ 1,127,988 Real estate- owner-occupied 2,353,176 1,792 872 2,930 5,594 19,089 81,105 2,458,964 Real estate- non-owner-occupied 5,678,485 10,995 4,266 505 15,766 20,497 80,183 5,794,931 Commercial and industrial 5,474,922 8,083 3,568 614 12,265 66,815 27,038 5,581,040 Residential mortgage 4,132,941 4,597 18,915 8,403 31,915 15,898 119,409 4,300,163 Consumer - home equity 2,246,693 8,727 2,963 — 11,690 17,854 73,939 2,350,176 Consumer - other 720,666 3,934 1,007 — 4,941 2,320 2,717 730,644 Total $ 21,712,371 $ 38,203 $ 32,421 $ 12,452 $ 83,076 $ 143,595 $ 404,864 $ 22,343,906 December 31, 2017 Accruing (Dollars in thousands) Current or Less Than 30 days Past Due 30-59 days 60-89 days > 90 days Total Past Due Non-accrual Acquired Impaired Total Real estate- construction $ 1,197,766 $ 269 $ — $ 458 $ 727 $ 2,635 $ 39,268 $ 1,240,396 Real estate- owner-occupied 2,243,923 1,631 659 74 2,364 24,457 104,577 2,375,321 Real estate- non-owner-occupied 5,220,648 2,086 6,405 887 9,378 6,811 85,676 5,322,513 Commercial and industrial 5,014,438 5,788 5,726 146 11,660 77,823 31,146 5,135,067 Residential mortgage 2,877,048 10,083 8,136 5,317 23,536 17,387 138,381 3,056,352 Consumer - home equity 2,186,554 11,675 2,947 18 14,640 12,365 78,716 2,292,275 Consumer - other 642,244 5,286 1,026 — 6,312 3,910 3,791 656,257 Total $ 19,382,621 $ 36,818 $ 24,899 $ 6,900 $ 68,617 $ 145,388 $ 481,555 $ 20,078,181
Schedule of Carrying Amount of Loans Acquired	The tables below show the fair value estimates of loans acquired from Gibraltar for these two subsections of the portfolio as of the acquisition date. These amounts are subject to change due to the finalization of purchase accounting adjustments. (Dollars in thousands) Acquired Non-Impaired Loans Contractually required principal and interest at acquisition $ 1,695,918 Expected losses and foregone interest (19,952 ) Cash flows expected to be collected at acquisition 1,675,966 Fair value of acquired loans at acquisition $ 1,455,044 (Dollars in thousands) Acquired Impaired Loans Contractually required principal and interest at acquisition $ 43,779 Non-accretable difference (expected losses and foregone interest) (31,174 ) Cash flows expected to be collected at acquisition 12,605 Accretable yield (2,371 ) Basis in acquired loans at acquisition $ 10,234
Summary of Changes in Accretable Yields of Acquired Loans	The following is a summary of changes in the accretable difference for all loans accounted for under ASC 310-30 during the nine months ended September 30 : (Dollars in thousands) 2018 2017 Balance at beginning of period $ 152,623 $ 175,054 Additions 2,371 32,937 Transfers from non-accretable difference to accretable yield (4 ) 4,977 Accretion (37,115 ) (42,435 ) Changes in expected cash flows not affecting non-accretable differences (1) 21,092 (242 ) Balance at end of period $ 138,967 $ 170,291 (1) Includes changes in cash flows expected to be collected due to the impact of changes in actual or expected timing of liquidation events, modifications, changes in interest rates and changes in prepayment assumptions.
Schedule of Modified TDRs	The following table provides information on how the TDRs were modified during the periods indicated: Three Months Ended September 30 Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Extended maturities $ 3,658 $ 3,184 $ 10,020 $ 18,177 Maturity and interest rate adjustment 267 204 368 5,151 Movement to or extension of interest-rate only payments — 3,560 48 3,692 Interest rate adjustment — — 101 25 Forbearance 802 841 14,386 5,528 Other concession(s) (1) 1,810 16,797 21,031 18,944 Total $ 6,537 $ 24,586 $ 45,954 $ 51,517 (1) Other concessions may include covenant waivers, forgiveness of principal or interest associated with a customer bankruptcy, or a combination of any of the above concessions.
Schedule of Subsequently Defaulted TDRs	The following table presents the end of period balance for loans modified in a TDR during the periods indicated: Three Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Real estate- construction — $ — $ — 2 $ 1,166 $ 1,164 Real estate- owner-occupied 1 2,312 2,312 3 717 713 Real estate- non-owner-occupied 6 1,818 1,790 10 5,306 5,298 Commercial and industrial 9 829 804 11 11,650 12,502 Residential mortgage 3 257 255 7 409 392 Consumer - home equity 15 1,152 1,124 38 3,495 3,479 Consumer - other 11 352 252 36 1,078 1,038 Total 45 $ 6,720 $ 6,537 107 $ 23,821 $ 24,586 Nine Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Number of Loans Pre-modification Outstanding Recorded Investment Post-modification Outstanding Recorded Investment Real estate- construction 1 $ 1,950 $ 976 2 $ 1,166 $ 1,164 Real estate- owner-occupied 8 15,233 13,373 5 2,447 2,411 Real estate- non-owner-occupied 13 3,228 3,064 21 9,645 11,505 Commercial and industrial 32 32,827 22,769 44 18,743 19,399 Residential mortgage 9 898 837 16 1,126 1,030 Consumer - home equity 47 4,130 4,047 99 13,573 13,471 Consumer - other 53 1,056 888 106 2,745 2,537 Total 163 $ 59,322 $ 45,954 293 $ 49,445 $ 51,517 Information detailing TDRs that defaulted during the three-month and nine-month periods ended September 30, 2018 and 2017, and were modified in the previous twelve months (i.e., the twelve months prior to the default) is presented in the following tables. The Company has defined a default as any loan with a payment that is currently past due greater than 30 days , or was past due greater than 30 days at any point during the respective periods, or since the date of modification, whichever is shorter. Three Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Recorded Investment Number of Loans Recorded Investment Real estate- construction — $ — 2 $ 1,164 Real estate- owner-occupied 1 929 4 1,304 Real estate- non-owner-occupied 1 7 11 2,206 Commercial and industrial 2 127 16 1,008 Residential mortgage — — 13 819 Consumer - home equity 4 380 23 2,150 Consumer - other 6 86 49 795 Total 14 $ 1,529 118 $ 9,446 Nine Months Ended September 30, 2018 2017 (In thousands, except number of loans) Number of Loans Recorded Investment Number of Loans Recorded Investment Real estate- construction — $ — 2 $ 1,164 Real estate- owner-occupied 6 10,101 8 3,234 Real estate- non-owner-occupied 6 1,084 16 4,929 Commercial and industrial 12 3,632 31 5,939 Residential mortgage 8 912 18 1,243 Consumer - home equity 17 1,978 34 3,215 Consumer - other 39 488 65 1,264 Total 88 $ 18,195 174 $ 20,988

Allowance for Credit Losses a_2

Allowance for Credit Losses and Credit Quality (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Schedule of Allowance for Loan Losses for Covered and Non-Covered Loan Portfolios	A summary of changes in the allowance for credit losses for the nine months ended September 30 is as follows: (Dollars in thousands) 2018 2017 Allowance for credit losses Allowance for loan and lease losses at beginning of period $ 140,891 $ 144,719 Provision for loan and lease losses 26,678 36,718 Transfer of balance to OREO and other (5,709 ) 963 Charge-offs (34,740 ) (49,939 ) Recoveries 9,830 4,167 Allowance for loan and lease losses at end of period $ 136,950 $ 136,628 Reserve for unfunded commitments at beginning of period $ 13,208 $ 11,241 Balance created in acquisition accounting 900 7,626 Provision for unfunded lending commitments 613 2,165 Reserve for unfunded commitments at end of period $ 14,721 $ 21,032 Allowance for credit losses at end of period $ 151,671 $ 157,660 A summary of changes in the allowance for credit losses, by loan portfolio type, for the nine months ended September 30 is as follows: 2018 (Dollars in thousands) Commercial Real Estate Commercial and Industrial Residential Mortgage Consumer Total Allowance for loan and lease losses at beginning of period $ 54,201 $ 53,916 $ 9,117 $ 23,657 $ 140,891 Provision for (Reversal of) loan and lease losses (4,020 ) 20,372 2,318 8,008 26,678 Transfer of balance to OREO and other (1,556 ) (814 ) (45 ) (3,294 ) (5,709 ) Charge-offs (1,281 ) (22,447 ) (365 ) (10,647 ) (34,740 ) Recoveries 1,019 5,665 53 3,093 9,830 Allowance for loan and lease losses at end of period $ 48,363 $ 56,692 $ 11,078 $ 20,817 $ 136,950 Reserve for unfunded commitments at beginning of period $ 4,531 $ 5,309 $ 555 $ 2,813 $ 13,208 Balance created in acquisition accounting 129 81 — 690 900 Provision for (Reversal of) unfunded commitments (134 ) 169 246 332 613 Reserve for unfunded commitments at end of period $ 4,526 $ 5,559 $ 801 $ 3,835 $ 14,721 Allowance on loans individually evaluated for impairment $ 2,650 $ 10,471 $ 154 $ 2,973 $ 16,248 Allowance on loans collectively evaluated for impairment 40,519 44,727 5,063 17,661 107,970 Allowance on loans acquired with deteriorated credit quality 5,194 1,494 5,861 183 12,732 Loans and leases, net of unearned income: Balance at end of period $ 9,381,883 $ 5,581,040 $ 4,300,163 $ 3,080,820 $ 22,343,906 Balance at end of period individually evaluated for impairment 73,469 75,625 6,230 33,863 189,187 Balance at end of period collectively evaluated for impairment 9,126,653 5,478,377 4,174,524 2,970,301 21,749,855 Balance at end of period acquired with deteriorated credit quality 181,761 27,038 119,409 76,656 404,864 2017 (Dollars in thousands) Commercial Real Estate Commercial and Industrial Residential Mortgage Consumer Total Allowance for loan losses at beginning of period $ 49,231 $ 60,939 $ 11,249 $ 23,300 $ 144,719 Provision for (Reversal of) loan and lease losses 4,888 23,574 (1,333 ) 9,589 36,718 Transfer of balance to OREO and other 879 (69 ) 2 151 963 Charge-offs (1,410 ) (37,110 ) (265 ) (11,154 ) (49,939 ) Recoveries 668 605 148 2,746 4,167 Allowance for loan losses at end of period $ 54,256 $ 47,939 $ 9,801 $ 24,632 $ 136,628 Reserve for unfunded commitments at beginning of period $ 3,207 $ 4,537 $ 657 $ 2,840 $ 11,241 Balance created in acquisition accounting 1,358 4,903 1,303 62 7,626 Provision for (Reversal of) unfunded commitments 1,239 752 (30 ) 204 2,165 Reserve for unfunded commitments at end of period $ 5,804 $ 10,192 $ 1,930 $ 3,106 $ 21,032 Allowance on loans individually evaluated for impairment $ 1,957 $ 9,744 $ 164 $ 2,445 $ 14,310 Allowance on loans collectively evaluated for impairment 30,016 35,964 3,801 18,768 88,549 Allowance on loans acquired with deteriorated credit quality 22,283 2,231 5,836 3,419 33,769 Loans, net of unearned income: Balance at end of period 8,767,886 5,016,437 3,024,970 2,985,792 19,795,085 Balance at end of period individually evaluated for impairment 68,241 85,054 5,384 29,140 187,819 Balance at end of period collectively evaluated for impairment 8,457,950 4,899,842 2,890,206 2,877,383 19,125,381 Balance at end of period acquired with deteriorated credit quality 241,695 31,541 129,380 79,269 481,885
Investment in Legacy and Acquired Loans by Credit Quality Indicator	The Company’s investment in loans by credit quality indicator is presented in the following tables. Asset risk classifications for commercial loans and leases reflect the classification as of September 30, 2018 and December 31, 2017 . Credit quality information in the tables below includes total loans acquired (including acquired impaired loans) at the net loan balance, after the application of premiums/discounts, at September 30, 2018 and December 31, 2017 . Loan premiums/discounts represent the adjustment of acquired loans to fair value at the acquisition date, as adjusted for income accretion and changes in cash flow estimates in subsequent periods. Loan premiums/discounts include preliminary discounts recorded on acquired Gibraltar loans, which are subject to change upon receipt of final fair value estimates during the measurement period. Loan delinquency is the primary credit quality indicator that the Company utilizes to monitor consumer asset quality. September 30, 2018 December 31, 2017 (Dollars in thousands) Pass Special Mention Sub- Doubtful Total Pass Special Mention Sub- Doubtful Loss Total Commercial real estate - construction $ 1,094,240 $ 19,033 $ 14,704 $ 11 $ 1,127,988 $ 1,189,490 $ 20,351 $ 30,541 $ 14 $ — $ 1,240,396 Commercial real estate - owner-occupied 2,382,053 31,588 45,058 265 2,458,964 2,234,151 82,114 56,590 2,466 — 2,375,321 Commercial real estate - non-owner-occupied 5,692,007 49,121 49,415 4,388 5,794,931 5,258,638 19,311 42,702 1,744 118 5,322,513 Commercial and industrial 5,366,990 96,303 86,903 30,844 5,581,040 4,882,554 88,149 128,961 35,403 — 5,135,067 Total $ 14,535,290 $ 196,045 $ 196,080 $ 35,508 $ 14,962,923 $ 13,564,833 $ 209,925 $ 258,794 $ 39,627 $ 118 $ 14,073,297 September 30, 2018 December 31, 2017 (Dollars in thousands) Current 30+ Days Past Due Total Current 30+ Days Past Due Total Residential mortgage $ 4,212,447 $ 87,716 $ 4,300,163 $ 2,962,043 $ 94,309 $ 3,056,352 Consumer - home equity 2,306,712 43,464 2,350,176 2,250,205 42,070 2,292,275 Consumer - other 723,183 7,461 730,644 645,498 10,759 656,257 Total $ 7,242,342 $ 138,641 $ 7,380,983 $ 5,857,746 $ 147,138 $ 6,004,884
Schedule of Investment in Legacy Impaired Loans	Information on the Company’s investment in impaired loans, which include all TDRs and all other non-accrual loans evaluated or measured individually for impairment for purposes of determining the ALLL, is presented in the following tables as of and for the periods indicated. September 30, 2018 December 31, 2017 Unpaid Principal Balance Recorded Investment Related Allowance Unpaid Principal Balance Recorded Investment Related Allowance (Dollars in thousands) With no related allowance recorded: Commercial real estate - construction $ 11,176 $ 11,176 $ — $ 13,763 $ 13,013 $ — Commercial real estate - owner-occupied 33,816 33,816 — 50,867 44,482 — Commercial real estate - non-owner-occupied 21,996 21,996 — 15,370 14,975 — Commercial and industrial 41,717 41,717 — 103,013 70,254 — Residential mortgage 1,254 1,241 — 2,004 2,001 — Consumer - home equity 701 701 — 5,906 5,634 — Consumer - other — — — 75 75 — With an allowance recorded: Commercial real estate - construction 146 146 (11 ) 238 156 (19 ) Commercial real estate - owner-occupied 3,987 3,987 (535 ) 13,314 13,287 (949 ) Commercial real estate - non-owner-occupied 2,348 2,348 (2,104 ) 6,051 5,872 (620 ) Commercial and industrial 33,894 33,908 (10,471 ) 35,306 32,162 (12,736 ) Residential mortgage 5,420 4,989 (154 ) 5,179 4,748 (172 ) Consumer - home equity 28,700 28,695 (2,469 ) 27,189 26,575 (2,358 ) Consumer - other 4,526 4,467 (504 ) 5,354 4,893 (498 ) Total $ 189,681 $ 189,187 $ (16,248 ) $ 283,629 $ 238,127 $ (17,352 ) Total commercial loans and leases $ 149,080 $ 149,094 $ (13,121 ) $ 237,922 $ 194,201 $ (14,324 ) Total mortgage loans 6,674 6,230 (154 ) 7,183 6,749 (172 ) Total consumer loans 33,927 33,863 (2,973 ) 38,524 37,177 (2,856 ) Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Average Interest Average Interest Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (Dollars in thousands) With no related allowance recorded: Commercial real estate - construction $ 10,806 $ 164 $ 2,722 $ 11 $ 10,371 $ 460 $ 2,538 $ 57 Commercial real estate - owner-occupied 34,118 209 36,850 88 34,505 903 37,185 517 Commercial real estate - non-owner-occupied 22,091 249 7,858 83 22,988 746 7,908 231 Commercial and industrial 43,409 523 64,863 240 40,564 1,543 71,611 975 Residential mortgage 1,254 9 1,114 13 1,271 36 1,129 36 Consumer - home equity 705 2 364 6 708 16 367 18 With an allowance recorded: Commercial real estate - construction 148 — 166 1 151 1 209 5 Commercial real estate - owner-occupied 4,006 83 11,154 89 4,044 102 11,206 269 Commercial real estate - non-owner-occupied 2,398 20 4,874 29 2,442 76 4,808 109 Commercial and industrial 40,357 150 55,042 261 47,098 720 57,020 788 Residential mortgage 5,014 50 4,290 38 5,066 149 4,338 115 Consumer - home equity 28,577 305 23,730 254 27,905 892 21,639 690 Consumer - other 4,710 65 4,330 64 4,884 208 4,010 180 Total $ 197,593 $ 1,829 $ 217,357 $ 1,177 $ 201,997 $ 5,852 $ 223,968 $ 3,990 Total commercial loans and leases $ 157,333 $ 1,398 $ 183,529 $ 802 $ 162,163 $ 4,551 $ 192,485 $ 2,951 Total mortgage loans 6,268 59 5,404 51 6,337 185 5,467 151 Total consumer loans 33,992 372 28,424 324 33,497 1,116 26,016 888

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Carrying Amount of Goodwill	Changes to the carrying amount of goodwill by reporting unit for the nine months ended September 30, 2018, and the year ended December 31, 2017 are provided in the following table: (Dollars in thousands) IBERIABANK Mortgage LTC Total Balance, December 31, 2016 $ 698,513 $ 23,178 $ 5,165 $ 726,856 Goodwill acquired during the year 462,046 — — 462,046 Balance, December 31, 2017 $ 1,160,559 $ 23,178 $ 5,165 $ 1,188,902 Goodwill acquired during the year (preliminary allocation) and adjustments 28,621 — 3,380 32,001 Balance, September 30, 2018 $ 1,189,180 $ 23,178 $ 8,545 $ 1,220,903
Schedule of Mortgage Servicing Rights	Mortgage Servicing Rights Mortgage servicing rights are recorded at the lower of cost or market value in “other intangible assets” on the Company's consolidated balance sheets and amortized over the remaining servicing life of the loans, with consideration given to prepayment assumptions. Mortgage servicing rights had the following carrying values as of the periods indicated: September 30, 2018 December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (Dollars in thousands) Mortgage servicing rights $ 12,125 $ (4,562 ) $ 7,563 $ 9,588 $ (3,931 ) $ 5,657
Schedule of Definite-Lived Intangible Assets	Definite-lived intangible assets had the following carrying values included in “other intangible assets” on the Company’s consolidated balance sheets as of the periods indicated: September 30, 2018 December 31, 2017 (Dollars in thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Core deposit intangible assets $ 136,183 $ (58,161 ) $ 78,022 $ 127,957 $ (51,971 ) $ 75,986 Customer relationship intangible asset 1,385 (1,305 ) 80 1,143 (996 ) 147 Non-compete agreement 206 (60 ) 146 63 (39 ) 24 Total $ 137,774 $ (59,526 ) $ 78,248 $ 129,163 $ (53,006 ) $ 76,157

Derivative Instruments and Ot_2

Derivative Instruments and Other Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Outstanding Derivative Instruments	Information pertaining to outstanding derivative instruments is as follows: Balance Sheet Location Derivative Assets - Fair Value Balance Sheet Location Derivative Liabilities - Fair Value (Dollars in thousands) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 Derivatives designated as hedging instruments under ASC Topic 815: Interest rate contracts Other assets $ 48 $ — Other liabilities $ — $ — Total derivatives designated as hedging instruments under ASC Topic 815 $ 48 $ — $ — $ — Derivatives not designated as hedging instruments under ASC Topic 815: Interest rate contracts Other assets $ 3,665 $ 20,446 Other liabilities $ 37,417 $ 16,191 Foreign exchange contracts Other assets 13 7 Other liabilities 13 7 Forward sales contracts Other assets 1,084 136 Other liabilities 44 279 Written and purchased options Other assets 7,754 10,654 Other liabilities 5,282 8,656 Other contracts Other assets 6 22 Other liabilities 8 21 Total derivatives not designated as hedging instruments under ASC Topic 815 $ 12,522 $ 31,265 $ 42,764 $ 25,154 Total $ 12,570 $ 31,265 $ 42,764 $ 25,154 Derivative Assets - Notional Amount Derivative Liabilities - Notional Amount (Dollars in thousands) September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 Derivatives designated as hedging instruments under ASC Topic 815: Interest rate contracts $ 258,500 $ — $ — $ 108,500 Total derivatives designated as hedging instruments under ASC Topic 815 $ 258,500 $ — $ — $ 108,500 Derivatives not designated as hedging instruments under ASC Topic 815: Interest rate contracts $ 1,489,111 $ 1,218,464 $ 1,489,111 $ 1,218,464 Foreign exchange contracts 933 268 933 268 Forward sales contracts 169,276 82,347 21,684 142,578 Written and purchased options 275,473 278,638 143,912 165,198 Other contracts 33,570 29,755 62,142 86,744 Total derivatives not designated as hedging instruments under ASC Topic 815 $ 1,968,363 $ 1,609,472 $ 1,717,782 $ 1,613,252 Total $ 2,226,863 $ 1,609,472 $ 1,717,782 $ 1,721,752
Offsetting Assets	The following table reconciles the gross amounts presented in the consolidated balance sheets to the net amounts that would result in the event of offset. September 30, 2018 Gross Amounts Presented in the Balance Sheet Gross Amounts Not Offset in the Balance Sheet Net (Dollars in thousands) Derivatives Collateral (1) Derivatives subject to master netting arrangements Derivative assets Interest rate contracts designated as hedging instruments $ 48 $ — $ — $ 48 Interest rate contracts not designated as hedging instruments 3,665 (248 ) — 3,417 Written and purchased options 5,267 — — 5,267 Total derivative assets subject to master netting arrangements $ 8,980 $ (248 ) $ — $ 8,732 Derivative liabilities Interest rate contracts not designated as hedging instruments $ 37,417 $ (248 ) $ — $ 37,169 Written and purchased options 5,267 — — 5,267 Total derivative liabilities subject to master netting arrangements $ 42,684 $ (248 ) $ — $ 42,436 (1) Consists of cash collateral recorded at cost, which approximates fair value, and investment securities. December 31, 2017 Gross Amounts Presented in the Balance Sheet Gross Amounts Not Offset in the Balance Sheet Net (Dollars in thousands) Derivatives Collateral (1) Derivatives subject to master netting arrangements Derivative assets Interest rate contracts not designated as hedging instruments $ 20,446 $ (12,469 ) $ — $ 7,977 Written and purchased options 8,610 — — 8,610 Total derivative assets subject to master netting arrangements $ 29,056 $ (12,469 ) $ — $ 16,587 Derivative liabilities Interest rate contracts designated as hedging instruments $ — $ — $ — $ — Interest rate contracts not designated as hedging instruments 16,191 (12,469 ) (552 ) 3,170 Total derivative liabilities subject to master netting arrangements $ 16,191 $ (12,469 ) $ (552 ) $ 3,170 (1) Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
Offsetting Liabilities	The following table reconciles the gross amounts presented in the consolidated balance sheets to the net amounts that would result in the event of offset. September 30, 2018 Gross Amounts Presented in the Balance Sheet Gross Amounts Not Offset in the Balance Sheet Net (Dollars in thousands) Derivatives Collateral (1) Derivatives subject to master netting arrangements Derivative assets Interest rate contracts designated as hedging instruments $ 48 $ — $ — $ 48 Interest rate contracts not designated as hedging instruments 3,665 (248 ) — 3,417 Written and purchased options 5,267 — — 5,267 Total derivative assets subject to master netting arrangements $ 8,980 $ (248 ) $ — $ 8,732 Derivative liabilities Interest rate contracts not designated as hedging instruments $ 37,417 $ (248 ) $ — $ 37,169 Written and purchased options 5,267 — — 5,267 Total derivative liabilities subject to master netting arrangements $ 42,684 $ (248 ) $ — $ 42,436 (1) Consists of cash collateral recorded at cost, which approximates fair value, and investment securities. December 31, 2017 Gross Amounts Presented in the Balance Sheet Gross Amounts Not Offset in the Balance Sheet Net (Dollars in thousands) Derivatives Collateral (1) Derivatives subject to master netting arrangements Derivative assets Interest rate contracts not designated as hedging instruments $ 20,446 $ (12,469 ) $ — $ 7,977 Written and purchased options 8,610 — — 8,610 Total derivative assets subject to master netting arrangements $ 29,056 $ (12,469 ) $ — $ 16,587 Derivative liabilities Interest rate contracts designated as hedging instruments $ — $ — $ — $ — Interest rate contracts not designated as hedging instruments 16,191 (12,469 ) (552 ) 3,170 Total derivative liabilities subject to master netting arrangements $ 16,191 $ (12,469 ) $ (552 ) $ 3,170 (1) Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
Effect of Derivatives on the Consolidated Financial Statements	At September 30, 2018 and 2017 , and for the three and nine months then ended, information pertaining to the effect of the hedging instruments on the consolidated financial statements is as follows: Location of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in OCI, net of taxes Location of Gain (Loss) Reclassified from Accumulated OCI into Income Amount of Gain (Loss) Reclassified from Accumulated OCI into Income, net of taxes (Dollars in thousands) For the Three Months Ended September 30, Derivatives in ASC Topic 815 Cash Flow Hedging Relationships 2018 2017 2018 2017 2018 2017 Interest rate contracts $ 818 $ (158 ) Interest expense $ (22 ) $ (101 ) Interest expense $ — $ — Total $ 818 $ (158 ) $ (22 ) $ (101 ) $ — $ — Location of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing) Amount of Gain (Loss) Recognized in OCI, net of taxes Location of Gain (Loss) Reclassified from Accumulated OCI into Income Amount of Gain (Loss) Reclassified from Accumulated OCI into Income, net of taxes (Dollars in thousands) For the Nine Months Ended September 30, Derivatives in ASC Topic 815 Cash Flow Hedging Relationships 2018 2017 2018 2017 2018 2017 Interest rate contracts $ 4,762 $ (1,081 ) Other income (expense) $ (178 ) $ (249 ) Other income (expense) $ — $ — Total $ 4,762 $ (1,081 ) $ (178 ) $ (249 ) $ — $ — Information pertaining to the effect of derivatives not designated as hedging instruments on the consolidated financial statements as of September 30, is as follows: Location of Gain (Loss) Recognized in Income on Derivatives Amount of Gain (Loss) Recognized in Income on Derivatives For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Interest rate contracts (1) Other income $ 2,586 $ 743 $ 5,093 $ 3,159 Foreign exchange contracts Other income 7 24 17 38 Forward sales contracts Mortgage income 948 (2,007 ) 4,563 (3,893 ) Written and purchased options Mortgage income (692 ) (462 ) 473 (1,393 ) Other contracts Other income 1 8 (4 ) 17 Total $ 2,850 $ (1,694 ) $ 10,142 $ (2,072 ) (1) Includes fees associated with customer interest rate contracts.

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The following table presents the provision for income taxes and the effective tax rates for the periods indicated. Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Income before income tax expense $ 131,866 $ 48,450 $ 318,620 $ 201,493 Income tax expense 30,401 18,806 78,410 69,358 Effective tax rate 23.1 % 38.8 % 24.6 % 34.4 %

Shareholders' Equity, Capital_2

Shareholders' Equity, Capital Ratios and Other Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Schedule of Preferred Stock	The following table presents a summary of the Company's non-cumulative perpetual preferred stock: September 30, 2018 December 31, 2017 Issuance Date Earliest Redemption Date Annual Dividend Rate Liquidation Amount Carrying Amount Carrying Amount (Dollars in thousands) Series B Preferred Stock 8/5/2015 8/1/2025 6.625 % $ 80,000 $ 76,812 $ 76,812 Series C Preferred Stock 5/9/2016 5/1/2026 6.600 % 57,500 55,285 55,285 $ 137,500 $ 132,097 $ 132,097
Actual Capital Amounts and Ratios	The Company’s and IBERIABANK’s actual capital amounts and ratios as of September 30, 2018 and December 31, 2017 are presented in the following tables: (Dollars in thousands) September 30, 2018 Minimum Well-Capitalized Actual Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Consolidated $ 1,156,436 4.00 % N/A N/A $ 2,789,740 9.65 % IBERIABANK 1,153,671 4.00 1,442,089 5.00 2,768,917 9.60 Common Equity Tier 1 (CET1) (1) Consolidated $ 1,107,934 4.50 % N/A N/A $ 2,657,643 10.79 % IBERIABANK 1,105,391 4.50 1,596,676 6.50 2,768,917 11.27 Tier 1 Risk-Based Capital (1) Consolidated $ 1,477,245 6.00 % N/A N/A $ 2,789,740 11.33 % IBERIABANK 1,473,855 6.00 1,965,140 8.00 2,768,917 11.27 Total Risk-Based Capital (1) Consolidated $ 1,969,660 8.00 % N/A N/A $ 3,057,911 12.42 % IBERIABANK 1,965,140 8.00 2,456,425 10.00 2,920,587 11.89 December 31, 2017 Minimum Well-Capitalized Actual Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Consolidated $ 1,073,381 4.00 % N/A N/A $ 2,509,496 9.35 % IBERIABANK 1,070,789 4.00 1,338,487 5.00 2,437,275 9.10 Common Equity Tier 1 (CET1) (1) Consolidated $ 1,011,732 4.50 % N/A N/A $ 2,377,398 10.57 % IBERIABANK 1,009,553 4.50 1,458,243 6.50 2,437,275 10.86 Tier 1 Risk-Based Capital (1) Consolidated $ 1,348,977 6.00 % N/A N/A $ 2,509,496 11.16 % IBERIABANK 1,346,070 6.00 1,794,760 8.00 2,437,275 10.86 Total Risk-Based Capital (1) Consolidated $ 1,798,635 8.00 % N/A N/A $ 2,780,095 12.37 % IBERIABANK 1,794,760 8.00 2,243,450 10.00 2,591,374 11.55 (1) Minimum capital ratios are subject to a capital conservation buffer. In order to avoid limitations on distributions, including dividend payments, and certain discretionary bonus payments to executive officers, an institution must hold a capital conservation buffer above its minimum risk-based capital requirements. This capital conservation buffer is calculated as the lowest of the differences between the actual CET1 ratio, Tier 1 Risk-Based Capital Ratio, and Total Risk-Based Capital ratio and the corresponding minimum ratios. At September 30, 2018 , the required minimum capital conservation buffer was 1.875% , and will increase by 0.625% and be fully phased-in on January 1, 2019 at 2.50% . At September 30, 2018 , the capital conservation buffers of the Company and IBERIABANK were 4.42% and 3.89% , respectively.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Calculation of Basic and Diluted Earnings Per Share	The following table presents the calculation of basic and diluted earnings per share for the periods indicated. Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2018 2017 2018 2017 Earnings per common share - basic: Net income $ 101,465 $ 29,644 $ 240,210 $ 132,135 Less: Preferred stock dividends 3,599 3,598 8,146 8,146 Less: Dividends and undistributed earnings allocated to unvested restricted shares 908 283 2,341 1,052 Net income allocated to common shareholders - basic $ 96,958 $ 25,763 $ 229,723 $ 122,937 Weighted average common shares outstanding 55,571 52,424 55,047 49,749 Earnings per common share - basic 1.74 0.49 4.17 2.47 Earnings per common share - diluted: Net income allocated to common shareholders - basic $ 96,958 $ 25,763 $ 229,723 $ 122,937 Adjustment for undistributed earnings allocated to unvested restricted shares (25 ) 8 (49 ) — Net income allocated to common shareholders - diluted $ 96,933 $ 25,771 $ 229,674 $ 122,937 Weighted average common shares outstanding 55,571 52,424 55,047 49,749 Dilutive potential common shares 374 346 360 357 Weighted average common shares outstanding - diluted 55,945 52,770 55,407 50,106 Earnings per common share - diluted $ 1.73 $ 0.49 $ 4.14 $ 2.45

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation Arrangements by Share-based Payment Award	The following table represents phantom stock award activity during the periods indicated: (Dollars in thousands) Number of share equivalents (1) Value of share equivalents (2) Balance, December 31, 2016 472,830 $ 39,600 Granted 111,119 9,128 Forfeited share equivalents (22,956 ) 1,886 Vested share equivalents (158,573 ) 13,212 Balance, September 30, 2017 402,420 $ 33,059 Balance, December 31, 2017 393,844 $ 30,523 Granted 151,908 12,358 Forfeited share equivalents (59,550 ) 4,844 Vested share equivalents (130,497 ) 10,871 Balance, September 30, 2018 355,705 $ 28,937 (1) Number of share equivalents includes all reinvested dividend equivalents for the periods indicated. (2) Except for share equivalents at the beginning of each period, which are based on the value at that time, and vested share payments, which are based on the cash paid at the time of vesting, the value of share equivalents is calculated based on the market price of the Company’s stock at the end of the respective periods. The market price of the Company’s stock was $81.35 and $82.15 on September 30, 2018, and 2017, respectively. The following table represents the activity related to stock options during the periods indicated: Number of Shares Weighted Average Exercise Price Outstanding options, December 31, 2016 721,538 $ 55.38 Granted 78,434 85.03 Exercised (74,236 ) 55.77 Forfeited or expired (26,675 ) 68.93 Outstanding options, September 30, 2017 699,061 $ 58.15 Exercisable options, September 30, 2017 463,326 $ 55.68 Outstanding options, December 31, 2017 686,366 $ 58.24 Granted 97,620 82.02 Exercised (41,697 ) 53.12 Forfeited or expired (27,328 ) 68.19 Outstanding options, September 30, 2018 714,961 $ 61.41 Exercisable options, September 30, 2018 500,349 $ 56.70 The following table represents unvested restricted stock award and restricted share unit activity for the following periods: For the Nine Months Ended September 30, 2018 2017 Number of shares at beginning of period 738,187 543,258 Granted 229,181 411,957 Forfeited (70,981 ) (21,272 ) Vested (192,217 ) (191,222 ) Number of shares at end of period 704,170 742,721
Schedule of Valuation Assumptions	The following weighted-average assumptions were used for option awards issued during the following periods: For the Nine Months Ended September 30, 2018 2017 Expected dividends 1.8 % 1.7 % Expected volatility 24.3 % 25.0 % Risk-free interest rate 2.7 % 2.1 % Expected term (in years) 5.8 5.8 Weighted-average grant-date fair value $ 18.48 $ 18.87
Schedule of Allocation for Share-based Compensation Expense	The following table represents the compensation expense that is included in non-interest expense and related income tax benefits in the accompanying consolidated statements of comprehensive income related to stock options for the following periods: For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Compensation expense related to stock options $ 322 $ 343 $ 952 $ 1,131 Income tax benefit related to stock options 23 46 70 161 The following table indicates compensation expense recorded for phantom stock based on the number of share equivalents vested at September 30 of the periods indicated and the current market price of the Company’s stock at that time: For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Compensation expense related to phantom stock $ 2,375 $ 2,747 $ 7,388 $ 8,689 The following table represents the compensation expense that was included in non-interest expense and related income tax benefits in the accompanying consolidated statements of comprehensive income related to restricted stock awards and restricted share units for the periods indicated: For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Compensation expense related to restricted stock awards and restricted share units $ 4,843 $ 4,046 $ 14,192 $ 10,368 Income tax benefit related to restricted stock awards and restricted share units 1,017 1,416 2,980 3,629

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Financial Asset and Liabilities Measured at Fair Value on Recurring Basis	The Company has segregated all financial assets and liabilities that are measured at fair value on a recurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to estimate the fair value at the measurement date in the tables below. September 30, 2018 (Dollars in thousands) Level 1 Level 2 Level 3 Total Assets Securities available for sale $ — $ 4,634,124 $ — $ 4,634,124 CRA and Community Development Investment Funds — 1,866 — 1,866 Mortgage loans held for sale — 42,976 — 42,976 Mortgage loans held for investment, at fair value option — 7,249 — 7,249 Derivative instruments — 12,570 — 12,570 Total $ — $ 4,698,785 $ — $ 4,698,785 Liabilities Derivative instruments $ — $ 42,764 $ — $ 42,764 Total $ — $ 42,764 $ — $ 42,764 December 31, 2017 Level 1 Level 2 Level 3 Total Assets Securities available for sale $ — $ 4,590,062 $ — $ 4,590,062 Mortgage loans held for sale — 134,916 — 134,916 Mortgage loans held for investment, at fair value option — 14,953 — 14,953 Derivative instruments — 31,265 — 31,265 Total $ — $ 4,771,196 $ — $ 4,771,196 Liabilities Derivative instruments $ — $ 25,154 $ — $ 25,154 Total $ — $ 25,154 $ — $ 25,154
Financial Asset and Liabilities Measured at Fair Value on Nonrecurring Basis	The Company has segregated all assets and liabilities that are measured at fair value on a non-recurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to determine the fair value at the measurement date in the tables below. September 30, 2018 (Dollars in thousands) Level 1 Level 2 Level 3 Total Assets Loans $ — $ — $ 60,307 $ 60,307 OREO, net — — 5,148 5,148 Total $ — $ — $ 65,455 $ 65,455 December 31, 2017 (Dollars in thousands) Level 1 Level 2 Level 3 Total Assets Loans $ — $ — $ 71,210 $ 71,210 OREO, net — — 3,029 3,029 Total $ — $ — $ 74,239 $ 74,239
Summary of Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance for Mortgage Loans Held for Sale	The following table summarizes the difference between the aggregate fair value and the aggregate unpaid principal balance for mortgage loans held for sale and mortgage loans held for investment measured at fair value: September 30, 2018 December 31, 2017 (Dollars in thousands) Aggregate Fair Value Aggregate Unpaid Principal Aggregate Fair Value Less Unpaid Principal Aggregate Fair Value Aggregate Unpaid Principal Aggregate Fair Value Less Unpaid Principal Mortgage loans held for sale, at fair value $ 42,976 $ 41,848 $ 1,128 $ 134,916 $ 131,276 $ 3,640 Mortgage loans held for investment, at fair value 7,249 8,666 (1,417 ) 14,953 16,306 (1,353 )
Fair Value Option, Disclosures	The following table details net gains (losses) resulting from the change in fair value of loans that were recorded in mortgage income in the consolidated statements of comprehensive income for the three and nine months ended September 30, 2018 and 2017. The changes in fair value are mostly offset by economic hedging activities, with an insignificant portion of these changes attributable to changes in instrument-specific credit risk. Net Gains (Losses) Resulting From Changes in Fair Value For the Three Months Ended September 30, For the Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Fair value option Mortgage loans held for sale, at fair value $ (1,041 ) $ 251 $ (2,513 ) $ 1,121 Mortgage loans held for investment, at fair value (296 ) (62 ) (1,217 ) (127 )

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Estimated Fair Values and Carrying Amounts of Financial Instruments	The carrying amount and estimated fair values, as well as the level within the fair value hierarchy, of the Company’s financial instruments are included in the tables below. See Note 1, Summary of Significant Accounting Policies, in the 2017 10-K for a description of how fair value measurements are determined, except for loans, amended upon implementation of ASU 2016-01, Financial Statements - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. See Note 2, Recent Accounting Pronouncements, in this Report for a description of how the fair value measurement is determined for loans beginning January 1, 2018. September 30, 2018 (Dollars in thousands) Carrying Amount Fair Value Level 1 Level 2 Level 3 Measurement Category Fair Value Financial Assets Securities available for sale $ 4,634,124 $ 4,634,124 $ — $ 4,634,124 $ — CRA and Community Development Investment Funds 1,866 1,866 — 1,866 — Mortgage loans held for sale 42,976 42,976 — 42,976 — Derivative instruments 12,570 12,570 — 12,570 — Financial Liabilities Derivative instruments 42,764 42,764 — 42,764 — Amortized Cost Financial Assets Cash and cash equivalents $ 475,935 $ 475,935 $ 475,935 $ — $ — Securities held to maturity 213,561 207,309 — 207,309 — Loans and leases, net of unearned income and allowance for loan and lease losses 22,206,956 22,014,886 — — 22,014,886 Financial Liabilities Deposits 23,193,446 23,181,429 — 23,181,429 — Short-term borrowings 1,242,719 1,242,719 452,719 790,000 — Long-term debt 1,466,810 1,449,018 — — 1,449,018 December 31, 2017 (Dollars in thousands) Carrying Amount Fair Value Level 1 Level 2 Level 3 Measurement Category Fair Value Financial Assets Securities available for sale $ 4,590,062 $ 4,590,062 $ — $ 4,590,062 $ — Mortgage loans held for sale 134,916 134,916 — 134,916 — Derivative instruments 31,265 31,265 — 31,265 — Financial Liabilities Derivative instruments 25,154 25,154 — 25,154 — Amortized Cost Financial Assets Cash and cash equivalents $ 625,724 $ 625,724 $ 625,724 $ — $ — Securities held to maturity 227,318 227,964 — 227,964 — Loans and leases, net of unearned income and allowance for loan and lease losses 19,937,290 19,826,857 — — 19,826,857 Financial Liabilities Deposits 21,466,717 21,460,782 — 21,460,782 — Short-term borrowings 991,297 991,297 516,297 475,000 — Long-term debt 1,495,835 1,476,899 — — 1,476,899

Business Segments (Tables)

Business Segments (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information	The following tables present certain information regarding our operations by reportable segment, including a reconciliation of segment results to reported consolidated results for the periods presented. Reconciling items between segment results and reported results include: • Elimination of interest income and interest expense representing interest earned by IBERIABANK on interest-bearing checking accounts held by related companies, as well as the elimination of the related deposit balances at the IBERIABANK segment; • Elimination of investment in subsidiary balances on certain operating segments included in total and average segment assets; and • Elimination of intercompany due to and due from balances on certain operating segments that are included in total and average segment assets. Three Months Ended September 30, 2018 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 315,467 $ 1,599 $ 1 $ 317,067 Interest expense 57,842 — — 57,842 Net interest income 257,625 1,599 1 259,225 Provision for/(reversal of) loan and lease losses 11,099 (2 ) — 11,097 Mortgage income — 12,732 — 12,732 Title revenue — — 6,280 6,280 Other non-interest income/(expense) 33,591 (16 ) 500 34,075 Allocated expenses/(income) (3,691 ) 2,680 1,011 — Non-interest expense 154,287 10,223 4,839 169,349 Income/(loss) before income tax expense 129,521 1,414 931 131,866 Income tax expense/(benefit) 29,765 386 250 30,401 Net income/(loss) $ 99,756 $ 1,028 $ 681 $ 101,465 Total loans, leases, and loans held for sale, net of unearned income $ 22,302,679 $ 84,203 $ — $ 22,386,882 Total assets 29,974,065 119,322 25,000 30,118,387 Total deposits 23,179,549 13,897 — 23,193,446 Average assets 29,863,742 158,464 24,025 30,046,231 Three Months Ended September 30, 2017 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 245,166 $ 1,805 $ 1 $ 246,972 Interest expense 30,089 — — 30,089 Net interest income 215,077 1,805 1 216,883 Provision for/(reversal of) loan and lease losses 18,524 (10 ) — 18,514 Mortgage income — 16,050 — 16,050 Title revenue — — 5,643 5,643 Other non-interest income/(expense) 29,163 (9 ) (4 ) 29,150 Allocated expenses/(income) (3,881 ) 2,911 970 — Non-interest expense 174,306 22,170 4,286 200,762 Income/(loss) before income tax expense 55,291 (7,225 ) 384 48,450 Income tax expense/(benefit) 21,076 (2,424 ) 154 18,806 Net income/(loss) $ 34,215 $ (4,801 ) $ 230 $ 29,644 Total loans, leases, and loans held for sale, net of unearned income $ 19,743,749 $ 192,554 $ — $ 19,936,303 Total assets 27,738,588 217,056 20,991 27,976,635 Total deposits 21,333,190 1,081 — 21,334,271 Average assets 25,869,559 204,920 22,442 26,096,921 Nine Months Ended September 30, 2018 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 886,629 $ 4,802 $ 2 $ 891,433 Interest expense 143,206 — — 143,206 Net interest income 743,423 4,802 2 748,227 Provision for/(reversal of) loan losses 26,704 (26 ) — 26,678 Mortgage income — 36,048 — 36,048 Title revenue — — 18,153 18,153 Other non-interest income/(expense) 96,978 (83 ) 497 97,392 Allocated expenses/(income) (9,043 ) 6,714 2,329 — Non-interest expense 506,035 34,105 14,382 554,522 Income/(loss) before income tax expense 316,705 (26 ) 1,941 318,620 Income tax expense/(benefit) 78,516 (7 ) (99 ) 78,410 Net income/(loss) $ 238,189 $ (19 ) $ 2,040 $ 240,210 Total loans and loans held for sale, net of unearned income $ 22,302,679 $ 84,203 $ — $ 22,386,882 Total assets 29,974,065 119,322 25,000 30,118,387 Total deposits 23,179,549 13,897 — 23,193,446 Average assets 29,136,369 164,039 23,037 29,323,445 Nine Months Ended September 30, 2017 (Dollars in thousands) IBERIABANK Mortgage LTC Consolidated Interest and dividend income $ 638,683 $ 5,395 $ 2 $ 644,080 Interest expense 70,736 — — 70,736 Net interest income 567,947 5,395 2 573,344 Provision for/(reversal of) loan losses 36,816 (98 ) — 36,718 Mortgage income — 49,895 — 49,895 Title revenue — — 16,574 16,574 Other non-interest income/(expense) 83,376 (30 ) (10 ) 83,336 Allocated expenses/(income) (9,377 ) 7,057 2,320 — Non-interest expense 412,305 59,754 12,879 484,938 Income/(loss) before income tax expense 211,579 (11,453 ) 1,367 201,493 Income tax expense/(benefit) 72,650 (3,840 ) 548 69,358 Net income/(loss) $ 138,929 $ (7,613 ) $ 819 $ 132,135 Total loans and loans held for sale, net of unearned income $ 19,743,749 $ 192,554 $ — $ 19,936,303 Total assets 27,738,588 217,056 20,991 27,976,635 Total deposits 21,333,190 1,081 — 21,334,271 Average assets 23,020,324 239,014 23,496 23,282,834

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of Financial Instruments Outstanding	At September 30, 2018 and December 31, 2017, respectively, the Company had the following financial instruments outstanding and related reserves, whose contract amounts represent credit risk: (Dollars in thousands) September 30, 2018 December 31, 2017 Commitments to extend credit $ 824,472 $ 342,305 Unfunded commitments under lines of credit 6,610,843 6,060,034 Commercial and standby letters of credit 235,730 210,002 Reserve for unfunded lending commitments 14,721 13,208

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in non-interest income and non-interest expense	$ 2.2	$ 6.6

Acquisition Activity - Addition

Acquisition Activity - Additional Information (Details)	Mar. 23, 2018USD ($)$ / sharesshares	Jul. 31, 2017USD ($)bankshares	Sep. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Business Acquisition [Line Items]
Increase in goodwill due to adjustments							$ 32,001,000
Goodwill			$ 1,220,903,000				1,220,903,000		$ 1,188,902,000	$ 726,856,000
Amortization of intangible assets acquired			5,382,000		$ 4,527,000		16,595,000	$ 7,948,000
Gibraltar Private Bank & Trust Company
Business Acquisition [Line Items]
Loans acquired	$ 1,465,278,000
Interest-bearing deposits acquired	1,064,803,000
Consideration paid	214,666,000
Cash consideration	7,000
Increase in goodwill due to adjustments			2,900,000
Goodwill	$ 49,622,000		$ 49,600,000				49,600,000
Gibraltar Private Bank & Trust Company | Common Stock
Business Acquisition [Line Items]
Number of shares issued per share acquired | $ / shares	$ 1.9749
Common stock issued (in dollars per share) | $ / shares	$ 77
Common stock issued (shares) | shares	2,787,773
Solomon Parks Title & Escrow
Business Acquisition [Line Items]
Cash consideration				$ 3,300,000
Increase in goodwill due to adjustments				3,400,000			$ 3,400,000
Other payments to acquire businesses				$ 750,000
Sabadell United
Business Acquisition [Line Items]
Loans acquired		$ 4,030,777,000
Interest-bearing deposits acquired		4,382,780,000
Consideration paid		1,020,202,000
Cash consideration		809,159,000
Increase in goodwill due to adjustments						$ 21,000,000
Goodwill		$ 441,045,000				$ 441,000,000
Number of offices acquired | bank		25
Percentage of voting interests acquired		100.00%
Sabadell United | Fair Value Adjustments
Business Acquisition [Line Items]
amortization of premiums and accretion of discounts on acquired loans, securities, and deposits					3,000,000			20,300,000
Elimination of amortization of premiums and accretion of discounts on previously acquired loans, securities, FDIC indemnification asset, and deposits					22,300			1,300,000
Allowance for loan and lease losses acquired					918,300			6,400,000
Amortization of intangible assets acquired					$ 846,600			$ 5,900,000
Sabadell United | Common Stock
Business Acquisition [Line Items]
Common stock issued (shares) | shares		2,610,304

Acquisition Activity - Consider

Acquisition Activity - Consideration (Details) - USD ($) $ in Thousands	Mar. 23, 2018	Jul. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Total equity consideration			$ 214,659	$ 211,043
Goodwill			1,220,903			$ 1,188,902	$ 726,856
Gibraltar Private Bank & Trust Company
Business Acquisition [Line Items]
Total equity consideration	$ 214,659
Cash	7
Total consideration paid	214,666
Fair value of net assets assumed including identifiable intangible assets	165,044
Goodwill	$ 49,622		$ 49,600
Gibraltar Private Bank & Trust Company | Common Stock
Business Acquisition [Line Items]
Common stock issued (shares)	2,787,773
Common stock issued	$ 214,659
Sabadell United
Business Acquisition [Line Items]
Total equity consideration		$ 211,043
Cash		809,159
Total consideration paid		1,020,202
Fair value of net assets assumed including identifiable intangible assets		579,157
Goodwill		$ 441,045			$ 441,000
Sabadell United | Common Stock
Business Acquisition [Line Items]
Common stock issued (shares)		2,610,304
Common stock issued		$ 211,043

Acquisition Activity - Assets A

Acquisition Activity - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Mar. 23, 2018	Jan. 12, 2018	Dec. 31, 2017	Jul. 31, 2017	Dec. 31, 2016
Assets
Non-compete agreement				$ 156
Liabilities
Goodwill	$ 1,220,903				$ 1,188,902		$ 726,856
Gibraltar Private Bank & Trust Company
Assets
Cash and cash equivalents			$ 102,575
Investment securities			19,169
Equity securities			27,519
Loans			1,465,278
Core deposit intangible assets			18,529
Other assets			12,005
Total assets acquired			1,645,075
Liabilities
Deposit liabilities			1,064,803
Long-term borrowings			405,107
Deferred tax liability, net			5,960
Other liabilities			4,161
Total liabilities assumed			1,480,031
Goodwill	$ 49,600		$ 49,622
Sabadell United
Assets
Cash and cash equivalents						$ 318,819
Investment securities						964,123
Loans						4,030,777
Core deposit intangible assets						66,600
Deferred tax asset, net						44,480
Other assets						92,820
Total assets acquired						5,517,619
Liabilities
Deposit liabilities						4,382,780
Short-term borrowings						520,539
Other liabilities						35,143
Total liabilities assumed						4,938,462
Goodwill		$ 441,000				$ 441,045

Acquisition Activity - Pro Form

Acquisition Activity - Pro Forma Information (Details) - Sabadell United - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Business Acquisition [Line Items]
Net interest income	$ 232,828	$ 688,846
Non-interest income	54,511	164,360
Net income	$ 30,825	$ 163,968

Investment Securities - Schedul

Investment Securities - Schedule of Amortized Cost and Fair Values of Investment Securities, with Gross Unrealized Gains and Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities
Amortized Cost	$ 4,808,975	$ 4,647,931
Gross Unrealized Gains	767	5,972
Gross Unrealized Losses	(175,618)	(63,841)
Estimated Fair Value	4,634,124	4,590,062
Schedule of Held-to-maturity Securities
Amortized Cost	213,561	227,318
Gross Unrealized Gains	377	1,571
Gross Unrealized Losses	(6,629)	(925)
Estimated Fair Value	207,309	227,964
Fair value of securities held as collateral	2,300,000	2,100,000
U.S. Government-sponsored enterprise obligations
Schedule of Available-for-sale Securities
Amortized Cost	40,996	41,003
Gross Unrealized Gains	5	18
Gross Unrealized Losses	(740)	(406)
Estimated Fair Value	40,261	40,615
Obligations of state and political subdivisions
Schedule of Available-for-sale Securities
Amortized Cost	265,565	271,451
Gross Unrealized Gains	694	4,246
Gross Unrealized Losses	(4,852)	(1,493)
Estimated Fair Value	261,407	274,204
Schedule of Held-to-maturity Securities
Amortized Cost	194,382	206,736
Gross Unrealized Gains	349	1,530
Gross Unrealized Losses	(5,277)	(275)
Estimated Fair Value	189,454	207,991
Mortgage-backed securities: Residential agency
Schedule of Available-for-sale Securities
Amortized Cost	3,654,417	3,675,367
Gross Unrealized Gains	68	1,233
Gross Unrealized Losses	(140,816)	(52,090)
Estimated Fair Value	3,513,669	3,624,510
Schedule of Held-to-maturity Securities
Amortized Cost	19,179	20,582
Gross Unrealized Gains	28	41
Gross Unrealized Losses	(1,352)	(650)
Estimated Fair Value	17,855	19,973
Mortgage-backed securities: Commercial agency
Schedule of Available-for-sale Securities
Amortized Cost	721,899	546,105
Gross Unrealized Gains	0	228
Gross Unrealized Losses	(26,513)	(8,938)
Estimated Fair Value	695,386	537,395
Other securities
Schedule of Available-for-sale Securities
Amortized Cost	126,098	114,005
Gross Unrealized Gains	0	247
Gross Unrealized Losses	(2,697)	(914)
Estimated Fair Value	$ 123,401	$ 113,338

Investment Securities - Sched_2

Investment Securities - Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Gross Unrealized Losses
Less Than Twelve Months	$ (30,479)	$ (27,757)
Twelve Months or More	(145,139)	(36,084)
Total	(175,618)	(63,841)
Estimated Fair Value
Less Than Twelve Months	1,478,504	2,813,985
Twelve Months or More	3,060,917	1,304,515
Total	4,539,421	4,118,500
Gross Unrealized Losses
Less than twelve months	(3,725)	(265)
Over twelve months	(2,904)	(660)
Total	(6,629)	(925)
Estimated Fair Value
Less than twelve months	115,138	66,150
Over twelve months	58,504	22,300
Total	173,642	88,450
U.S. Government-sponsored enterprise obligations
Gross Unrealized Losses
Less Than Twelve Months	0	(254)
Twelve Months or More	(740)	(152)
Total	(740)	(406)
Estimated Fair Value
Less Than Twelve Months	0	29,744
Twelve Months or More	39,259	9,848
Total	39,259	39,592
Obligations of state and political subdivisions
Gross Unrealized Losses
Less Than Twelve Months	(839)	(326)
Twelve Months or More	(4,013)	(1,167)
Total	(4,852)	(1,493)
Estimated Fair Value
Less Than Twelve Months	107,014	31,601
Twelve Months or More	90,761	68,609
Total	197,775	100,210
Gross Unrealized Losses
Less than twelve months	(3,725)	(263)
Over twelve months	(1,552)	(12)
Total	(5,277)	(275)
Estimated Fair Value
Less than twelve months	115,138	65,817
Over twelve months	40,960	3,031
Total	156,098	68,848
Mortgage-backed securities: Residential agency
Gross Unrealized Losses
Less Than Twelve Months	(23,673)	(22,760)
Twelve Months or More	(117,143)	(29,330)
Total	(140,816)	(52,090)
Estimated Fair Value
Less Than Twelve Months	1,009,754	2,366,569
Twelve Months or More	2,482,730	1,061,588
Total	3,492,484	3,428,157
Gross Unrealized Losses
Less than twelve months	0	(2)
Over twelve months	(1,352)	(648)
Total	(1,352)	(650)
Estimated Fair Value
Less than twelve months	0	333
Over twelve months	17,544	19,269
Total	17,544	19,602
Mortgage-backed securities: Commercial agency
Gross Unrealized Losses
Less Than Twelve Months	(4,657)	(3,503)
Twelve Months or More	(21,856)	(5,435)
Total	(26,513)	(8,938)
Estimated Fair Value
Less Than Twelve Months	268,207	310,769
Twelve Months or More	418,295	164,470
Total	686,502	475,239
Other securities
Gross Unrealized Losses
Less Than Twelve Months	(1,310)	(914)
Twelve Months or More	(1,387)	0
Total	(2,697)	(914)
Estimated Fair Value
Less Than Twelve Months	93,529	75,302
Twelve Months or More	29,872	0
Total	$ 123,401	$ 75,302

Investment Securities - Additio

Investment Securities - Additional Information on Securities in a Continuous Loss Position (Detail) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018USD ($)Security	Dec. 31, 2017USD ($)Security
Schedule of Available-for-sale Securities
Number of debt securities with unrealized losses | Security	719	544
Debt securities with unrealized losses (percentage of amortized cost)	3.72%	1.52%
Number of securities | Security	464	210
Amortized cost basis	$ 3,267,464	$ 1,363,559
Unrealized loss	$ 148,043	$ 36,744
Mortgage-backed securities: Residential agency
Schedule of Available-for-sale Securities
Number of securities | Security	336	153
Amortized cost basis	$ 2,618,769	$ 1,110,834
Unrealized loss	$ 118,495	$ 29,977
Mortgage-backed securities: Commercial agency
Schedule of Available-for-sale Securities
Number of securities | Security	65	28
Amortized cost basis	$ 440,151	$ 169,905
Unrealized loss	$ 21,856	$ 5,435
Obligations of state and political subdivisions
Schedule of Available-for-sale Securities
Number of securities | Security	53	28
Amortized cost basis	$ 137,286	$ 72,820
Unrealized loss	$ 5,565	$ 1,180
U.S. Government-sponsored enterprise obligations
Schedule of Available-for-sale Securities
Number of securities | Security	3	1
Amortized cost basis	$ 39,999	$ 10,000
Unrealized loss	$ 740	$ 152
Other securities
Schedule of Available-for-sale Securities
Number of securities | Security	7	0
Amortized cost basis	$ 31,259	$ 0
Unrealized loss	$ 1,387	$ 0

Investment Securities - Sched_3

Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Weighted Average Yield
Within one year or less	1.90%
One through five years	2.25%
After five through ten years	2.47%
Over ten years	2.45%
Weighted average yield	2.44%
Amortized Cost
Within one year or less	$ 19,161
One through five years	150,119
After five through ten years	1,104,969
Over ten years	3,534,726
Amortized Cost	4,808,975	$ 4,647,931
Estimated Fair Value
Within one year or less	19,056
One through five years	147,472
After five through ten years	1,069,983
Over ten years	3,397,613
Estimated fair value	$ 4,634,124	4,590,062
Weighted Average Yield
Within one year or less	4.00%
One through five years	2.80%
After five through ten years	2.58%
Over ten years	2.60%
Weighted average yield	2.61%
Amortized Cost
Within one year or less	$ 435
One through five years	8,776
After five through ten years	45,368
Over ten years	158,982
Amortized Cost	213,561	227,318
Estimated Fair Value
Within one year or less	436
One through five years	8,751
After five through ten years	44,690
Over ten years	153,432
Estimated fair value	$ 207,309	$ 227,964

Investment Securities - Sched_4

Investment Securities - Schedule of Realized Gains and Losses from Sale of Securities Classified as Available for Sale (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Realized gains	$ 0	$ 667	$ 39	$ 909
Realized losses	0	(909)	(95)	(1,092)
Realized gains (losses)	$ 0	$ (242)	$ (56)	$ (183)

Investment Securities - Sched_5

Investment Securities - Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Federal Home Loan Bank (FHLB) stock	$ 102,508	$ 95,171
Federal Reserve Bank Stock	85,630	79,191
CRA and Community Development Investment Funds	1,866	0
Other Investments	9,838	3,008
Marketable Securities	$ 199,842	$ 177,370

Loans and Leases - Schedule of

Loans and Leases - Schedule of Non-Covered Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	$ 22,343,906	$ 20,078,181
Commercial Loans
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	14,962,923	14,073,297
Commercial Loans | Commercial real estate - Construction
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	1,127,988	1,240,396
Commercial Loans | Commercial real estate - owner-occupied
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	2,458,964	2,375,321
Commercial Loans | Commercial real estate - non-owner-occupied
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	5,794,931	5,322,513
Commercial Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	5,581,040	5,135,067
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	4,300,163	3,056,352
Consumer and Other Loans
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	3,080,820	2,948,532
Consumer and Other Loans | Home Equity
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	2,350,176	2,292,275
Consumer and Other Loans | Other
Accounts, Notes, Loans and Financing Receivable
Loans and leases, net of unearned income	$ 730,644	$ 656,257

Loans (Detail)

Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 23, 2018	Dec. 31, 2017	Jul. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Net deferred loan origination fees	$ 29,600		$ 29,600			$ 29,300
Net discount	143,200		143,200			159,300
Deposit liabilities reclassified as loans receivable	6,300		6,300			7,400
Loans with carrying value pledged to secure public deposits and other borrowings	7,500,000		7,500,000			6,600,000
Loans acquired with no evidence of deteriorated credit quality	7,249		7,249			14,953
Acquired Loans
Accounts, Notes, Loans and Financing Receivable
Net discount	75,600		75,600			94,700
Sabadell United
Accounts, Notes, Loans and Financing Receivable
Loans acquired							$ 4,030,777
Covered loans acquired						158,600
Sabadell United | Non-US
Accounts, Notes, Loans and Financing Receivable
Covered loans acquired	228,200		228,200			$ 325,500
Gibraltar Private Bank & Trust Company
Accounts, Notes, Loans and Financing Receivable
Loans acquired					$ 1,465,278
Loans acquired with no evidence of deteriorated credit quality	1,455,044		1,455,044
Loans acquired with deteriorated credit quality	10,234		10,234
TDRs Occurring during the Period | TDRs
Accounts, Notes, Loans and Financing Receivable
TDRs during period	$ 6,537	$ 24,586	45,954	$ 51,517
TDRs during period on accrual status			20,200	40,500
TDRs during period on non-accrual status			$ 25,800	$ 11,000

Loans and Leases - Schedule o_2

Loans and Leases - Schedule of Aging of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Accruing	$ 83,076	$ 68,617
Non-accrual Loans	143,595	145,388
Acquired Impaired Loans	189,187	238,127
Total Loans	22,343,906	20,078,181
Commercial Loans
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	149,094	194,201
Total Loans	14,962,923	14,073,297
Commercial Loans | Commercial real estate - Construction
Accounts, Notes, Loans and Financing Receivable
Accruing	905	727
Non-accrual Loans	1,122	2,635
Total Loans	1,127,988	1,240,396
Commercial Loans | Commercial real estate - owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	5,594	2,364
Non-accrual Loans	19,089	24,457
Total Loans	2,458,964	2,375,321
Commercial Loans | Commercial real estate - non-owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	15,766	9,378
Non-accrual Loans	20,497	6,811
Total Loans	5,794,931	5,322,513
Commercial Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Accruing	12,265	11,660
Non-accrual Loans	66,815	77,823
Total Loans	5,581,040	5,135,067
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	6,230	6,749
Residential Mortgage | Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Current	4,212,447	2,962,043
Accruing	31,915	23,536
Non-accrual Loans	15,898	17,387
Total Loans	4,300,163	3,056,352
Consumer and Other Loans
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	33,863	37,177
Consumer and Other Loans | Consumer - Home equity
Accounts, Notes, Loans and Financing Receivable
Current	2,306,712	2,250,205
Accruing	11,690	14,640
Non-accrual Loans	17,854	12,365
Total Loans	2,350,176	2,292,275
Consumer and Other Loans | Consumer - Other
Accounts, Notes, Loans and Financing Receivable
Current	723,183	645,498
Accruing	4,941	6,312
Non-accrual Loans	2,320	3,910
Total Loans	730,644	656,257
Current or Less Than 30 days past due
Accounts, Notes, Loans and Financing Receivable
Current	21,712,371	19,382,621
Current or Less Than 30 days past due | Commercial Loans | Commercial real estate - Construction
Accounts, Notes, Loans and Financing Receivable
Current	1,105,488	1,197,766
Current or Less Than 30 days past due | Commercial Loans | Commercial real estate - owner-occupied
Accounts, Notes, Loans and Financing Receivable
Current	2,353,176	2,243,923
Current or Less Than 30 days past due | Commercial Loans | Commercial real estate - non-owner-occupied
Accounts, Notes, Loans and Financing Receivable
Current	5,678,485	5,220,648
Current or Less Than 30 days past due | Commercial Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Current	5,474,922	5,014,438
Current or Less Than 30 days past due | Residential Mortgage | Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Current	4,132,941	2,877,048
Current or Less Than 30 days past due | Consumer and Other Loans | Consumer - Home equity
Accounts, Notes, Loans and Financing Receivable
Current	2,246,693	2,186,554
Current or Less Than 30 days past due | Consumer and Other Loans | Consumer - Other
Accounts, Notes, Loans and Financing Receivable
Current	720,666	642,244
30-59 days
Accounts, Notes, Loans and Financing Receivable
Accruing	38,203	36,818
30-59 days | Commercial Loans | Commercial real estate - Construction
Accounts, Notes, Loans and Financing Receivable
Accruing	75	269
30-59 days | Commercial Loans | Commercial real estate - owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	1,792	1,631
30-59 days | Commercial Loans | Commercial real estate - non-owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	10,995	2,086
30-59 days | Commercial Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Accruing	8,083	5,788
30-59 days | Residential Mortgage | Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Accruing	4,597	10,083
30-59 days | Consumer and Other Loans | Consumer - Home equity
Accounts, Notes, Loans and Financing Receivable
Accruing	8,727	11,675
30-59 days | Consumer and Other Loans | Consumer - Other
Accounts, Notes, Loans and Financing Receivable
Accruing	3,934	5,286
60-89 days
Accounts, Notes, Loans and Financing Receivable
Accruing	32,421	24,899
60-89 days | Commercial Loans | Commercial real estate - Construction
Accounts, Notes, Loans and Financing Receivable
Accruing	830	0
60-89 days | Commercial Loans | Commercial real estate - owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	872	659
60-89 days | Commercial Loans | Commercial real estate - non-owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	4,266	6,405
60-89 days | Commercial Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Accruing	3,568	5,726
60-89 days | Residential Mortgage | Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Accruing	18,915	8,136
60-89 days | Consumer and Other Loans | Consumer - Home equity
Accounts, Notes, Loans and Financing Receivable
Accruing	2,963	2,947
60-89 days | Consumer and Other Loans | Consumer - Other
Accounts, Notes, Loans and Financing Receivable
Accruing	1,007	1,026
Greater than 90 days
Accounts, Notes, Loans and Financing Receivable
Accruing	12,452	6,900
Greater than 90 days | Commercial Loans | Commercial real estate - Construction
Accounts, Notes, Loans and Financing Receivable
Accruing	0	458
Greater than 90 days | Commercial Loans | Commercial real estate - owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	2,930	74
Greater than 90 days | Commercial Loans | Commercial real estate - non-owner-occupied
Accounts, Notes, Loans and Financing Receivable
Accruing	505	887
Greater than 90 days | Commercial Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Accruing	614	146
Greater than 90 days | Residential Mortgage | Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Accruing	8,403	5,317
Greater than 90 days | Consumer and Other Loans | Consumer - Home equity
Accounts, Notes, Loans and Financing Receivable
Accruing	0	18
Greater than 90 days | Consumer and Other Loans | Consumer - Other
Accounts, Notes, Loans and Financing Receivable
Accruing	0	0
Acquired Loans
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	404,864	481,555
Acquired Loans | Commercial Loans | Commercial real estate - Construction
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	20,473	39,268
Acquired Loans | Commercial Loans | Commercial real estate - owner-occupied
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	81,105	104,577
Acquired Loans | Commercial Loans | Commercial real estate - non-owner-occupied
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	80,183	85,676
Acquired Loans | Commercial Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	27,038	31,146
Acquired Loans | Residential Mortgage | Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	119,409	138,381
Acquired Loans | Consumer and Other Loans | Consumer - Home equity
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	73,939	78,716
Acquired Loans | Consumer and Other Loans | Consumer - Other
Accounts, Notes, Loans and Financing Receivable
Acquired Impaired Loans	$ 2,717	$ 3,791

Loans and Leases - Schedule o_3

Loans and Leases - Schedule of Carrying Amount of Loans Acquired (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 23, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Expected losses and foregone interest	$ (151,671)			$ (157,660)
Loans acquired with no evidence of deteriorated credit quality	7,249		$ 14,953
Related allowance	(16,248)		(17,352)
Sabadell United
Accounts, Notes, Loans and Financing Receivable
Loans acquired					$ 4,030,777
Covered loans acquired			$ 158,600
Gibraltar Private Bank & Trust Company
Accounts, Notes, Loans and Financing Receivable
Loans acquired		$ 1,465,278
Contractually required principal and interest at acquisition	1,695,918
Expected losses and foregone interest	(19,952)
Cash flows expected to be collected at acquisition	1,675,966
Loans acquired with no evidence of deteriorated credit quality	1,455,044
Impaired Financing Receivable, with Related Allowance, Recorded Investment	43,779
Related allowance	(31,174)
Impaired Financing Receivable, Expected Cash Flow	12,605
Accretable yield	(2,371)
Loans acquired with deteriorated credit quality	$ 10,234

Loans and Leases - Summary of C

Loans and Leases - Summary of Changes in Accretable Yields of Acquired Loans (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 152,623	$ 175,054
Additions	2,371	32,937
Transfers from non-accretable difference to accretable yield	(4)	4,977
Accretion	(37,115)	(42,435)
Changes in expected cash flows not affecting non-accretable differences	21,092	(242)
Balance at end of period	$ 138,967	$ 170,291

Loans and Leases - Schedule o_4

Loans and Leases - Schedule of Modified TDRs (Detail) - TDRs Occurring during the Period - TDRs - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Modifications
TDRs during period on accrual status			$ 20,200	$ 40,500
TDRs during period on non-accrual status			25,800	11,000
Extended maturities	$ 3,658	$ 3,184	10,020	18,177
Maturity and interest rate adjustment	267	204	368	5,151
Movement to or extension of interest-rate only payments	0	3,560	48	3,692
Interest rate adjustment	0	0	101	25
Financing Receivable Modifications Forbearance	802	841	14,386	5,528
Other concession(s)	1,810	16,797	21,031	18,944
TDRs during period	6,537	24,586	45,954	51,517
Commercial Loans | Commercial real estate - Construction
Financing Receivable, Modifications
TDRs during period	0	1,164	976	1,164
Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Modifications
TDRs during period	2,312	713	13,373	2,411
Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Modifications
TDRs during period	1,790	5,298	3,064	11,505
Commercial Loans | Commercial and industrial
Financing Receivable, Modifications
TDRs during period	804	12,502	22,769	19,399
Residential Mortgage | Residential mortgage
Financing Receivable, Modifications
TDRs during period	255	392	837	1,030
Consumer and Other Loans | Consumer - Home equity
Financing Receivable, Modifications
TDRs during period	1,124	3,479	4,047	13,471
Consumer and Other Loans | Consumer - Other
Financing Receivable, Modifications
TDRs during period	$ 252	$ 1,038	$ 888	$ 2,537

Loans and Leases - Schedule o_5

Loans and Leases - Schedule of Subsequently Defaulted TDRs (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)SecurityLoan	Sep. 30, 2017USD ($)SecurityLoan	Sep. 30, 2018USD ($)SecurityLoan	Sep. 30, 2017USD ($)SecurityLoan
Accounts, Notes, Loans and Financing Receivable
Threshold period for loans in default (in days)			30 days
TDRs | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	45	107	163	293
Pre-modification Outstanding Recorded Investment	$ 6,720	$ 23,821	$ 59,322	$ 49,445
Post-modification Outstanding Recorded Investment	$ 6,537	$ 24,586	$ 45,954	$ 51,517
Number of loans | SecurityLoan	14	118	88	174
Recorded investment	$ 1,529	$ 9,446	$ 18,195	$ 20,988
TDRs | Commercial Loans | Commercial real estate - Construction | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	0	2	1	2
Pre-modification Outstanding Recorded Investment	$ 0	$ 1,166	$ 1,950	$ 1,166
Post-modification Outstanding Recorded Investment	$ 0	$ 1,164	$ 976	$ 1,164
Number of loans | SecurityLoan	0	2	0	2
Recorded investment	$ 0	$ 1,164	$ 0	$ 1,164
TDRs | Commercial Loans | Commercial real estate - owner-occupied | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	1	3	8	5
Pre-modification Outstanding Recorded Investment	$ 2,312	$ 717	$ 15,233	$ 2,447
Post-modification Outstanding Recorded Investment	$ 2,312	$ 713	$ 13,373	$ 2,411
Number of loans | SecurityLoan	1	4	6	8
Recorded investment	$ 929	$ 1,304	$ 10,101	$ 3,234
TDRs | Commercial Loans | Commercial real estate - non-owner-occupied | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	6	10	13	21
Pre-modification Outstanding Recorded Investment	$ 1,818	$ 5,306	$ 3,228	$ 9,645
Post-modification Outstanding Recorded Investment	$ 1,790	$ 5,298	$ 3,064	$ 11,505
Number of loans | SecurityLoan	1	11	6	16
Recorded investment	$ 7	$ 2,206	$ 1,084	$ 4,929
TDRs | Commercial Loans | Commercial and industrial | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	9	11	32	44
Pre-modification Outstanding Recorded Investment	$ 829	$ 11,650	$ 32,827	$ 18,743
Post-modification Outstanding Recorded Investment	$ 804	$ 12,502	$ 22,769	$ 19,399
Number of loans | SecurityLoan	2	16	12	31
Recorded investment	$ 127	$ 1,008	$ 3,632	$ 5,939
TDRs | Residential Mortgage | Residential mortgage | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	3	7	9	16
Pre-modification Outstanding Recorded Investment	$ 257	$ 409	$ 898	$ 1,126
Post-modification Outstanding Recorded Investment	$ 255	$ 392	$ 837	$ 1,030
Number of loans | SecurityLoan	0	13	8	18
Recorded investment	$ 0	$ 819	$ 912	$ 1,243
TDRs | Consumer and Other Loans | Consumer - Home equity | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	15	38	47	99
Pre-modification Outstanding Recorded Investment	$ 1,152	$ 3,495	$ 4,130	$ 13,573
Post-modification Outstanding Recorded Investment	$ 1,124	$ 3,479	$ 4,047	$ 13,471
Number of loans | SecurityLoan	4	23	17	34
Recorded investment	$ 380	$ 2,150	$ 1,978	$ 3,215
TDRs | Consumer and Other Loans | Consumer - Other | TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans | SecurityLoan	11	36	53	106
Pre-modification Outstanding Recorded Investment	$ 352	$ 1,078	$ 1,056	$ 2,745
Post-modification Outstanding Recorded Investment	$ 252	$ 1,038	$ 888	$ 2,537
Number of loans | SecurityLoan	6	49	39	65
Recorded investment	$ 86	$ 795	$ 488	$ 1,264

Allowance for Credit Losses a_3

Allowance for Credit Losses and Credit Quality - Schedule of Allowance for Loan Losses for Covered and Non-Covered Loan Portfolios (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Allowance for credit losses
Allowance for loan losses at beginning of period	$ 140,891	$ 144,719
Provision for loan and lease losses	26,678	36,718
Transfer of balance to OREO and other	(5,709)	963
Loans charged-off	(34,740)	(49,939)
Recoveries	9,830	4,167
Allowance for loan losses at end of period	136,950	136,628
Reserve For Unfunded Commitments
Reserve for unfunded commitments at beginning of period	13,208	11,241
provision for unfunded commitment, acquired	900	7,626
Provision For Unfunded Commitments	613	2,165
Reserve for unfunded commitments at end of period	14,721	21,032
Allowance for credit losses at end of period	$ 151,671	$ 157,660

Allowance for Credit Losses a_4

Allowance for Credit Losses and Credit Quality - Schedule of Allowance for Loan Losses for Legacy and Acquired Loans, by Loan Portfolio (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses
provision for unfunded commitment, acquired	$ 900	$ 7,626
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses at beginning of period	140,891	144,719
Provision for (Reversal of) loan losses	26,678	36,718
Transfer of balance to OREO and other	(5,709)	963
Loans charged-off	(34,740)	(49,939)
Recoveries	9,830	4,167
Allowance for loan losses at end of period	136,950	136,628
Financing Receivable, Reserve For Unfunded Commitments
Reserve for unfunded commitments at beginning of period	13,208	11,241
Provision for (Reversal of) unfunded commitments	613	2,165
Reserve for unfunded commitments at end of period	14,721	21,032
Allowance on loans individually evaluated for impairment	16,248	14,310
Allowance on loans collectively evaluated for impairment	107,970	88,549
Allowance on loans acquired with deteriorated credit quality	151,671	157,660
Loans, net of unearned income:
Loans, net of unearned income	22,343,906	19,795,085
Balance at end of period individually evaluated for impairment	189,187	187,819
Balance at end of period collectively evaluated for impairment	21,749,855	19,125,381
Commercial Loans | Real Estate
Financing Receivable, Allowance for Credit Losses
provision for unfunded commitment, acquired	129	1,358
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses at beginning of period	54,201	49,231
Provision for (Reversal of) loan losses	(4,020)	4,888
Transfer of balance to OREO and other	(1,556)	879
Loans charged-off	(1,281)	(1,410)
Recoveries	1,019	668
Allowance for loan losses at end of period	48,363	54,256
Financing Receivable, Reserve For Unfunded Commitments
Reserve for unfunded commitments at beginning of period	4,531	3,207
Provision for (Reversal of) unfunded commitments	(134)	1,239
Reserve for unfunded commitments at end of period	4,526	5,804
Allowance on loans individually evaluated for impairment	2,650	1,957
Allowance on loans collectively evaluated for impairment	40,519	30,016
Loans, net of unearned income:
Loans, net of unearned income	9,381,883	8,767,886
Balance at end of period individually evaluated for impairment	73,469	68,241
Balance at end of period collectively evaluated for impairment	9,126,653	8,457,950
Commercial Loans | Commercial and industrial
Financing Receivable, Allowance for Credit Losses
provision for unfunded commitment, acquired	81	4,903
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses at beginning of period	53,916	60,939
Provision for (Reversal of) loan losses	20,372	23,574
Transfer of balance to OREO and other	(814)	(69)
Loans charged-off	(22,447)	(37,110)
Recoveries	5,665	605
Allowance for loan losses at end of period	56,692	47,939
Financing Receivable, Reserve For Unfunded Commitments
Reserve for unfunded commitments at beginning of period	5,309	4,537
Provision for (Reversal of) unfunded commitments	169	752
Reserve for unfunded commitments at end of period	5,559	10,192
Allowance on loans individually evaluated for impairment	10,471	9,744
Allowance on loans collectively evaluated for impairment	44,727	35,964
Loans, net of unearned income:
Loans, net of unearned income	5,581,040	5,016,437
Balance at end of period individually evaluated for impairment	75,625	85,054
Balance at end of period collectively evaluated for impairment	5,478,377	4,899,842
Residential Mortgage
Financing Receivable, Allowance for Credit Losses
provision for unfunded commitment, acquired	0	1,303
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses at beginning of period	9,117	11,249
Provision for (Reversal of) loan losses	2,318	(1,333)
Transfer of balance to OREO and other	(45)	2
Loans charged-off	(365)	(265)
Recoveries	53	148
Allowance for loan losses at end of period	11,078	9,801
Financing Receivable, Reserve For Unfunded Commitments
Reserve for unfunded commitments at beginning of period	555	657
Provision for (Reversal of) unfunded commitments	246	(30)
Reserve for unfunded commitments at end of period	801	1,930
Allowance on loans individually evaluated for impairment	154	164
Allowance on loans collectively evaluated for impairment	5,063	3,801
Loans, net of unearned income:
Loans, net of unearned income	4,300,163	3,024,970
Balance at end of period individually evaluated for impairment	6,230	5,384
Balance at end of period collectively evaluated for impairment	4,174,524	2,890,206
Consumer and Other Loans
Financing Receivable, Allowance for Credit Losses
provision for unfunded commitment, acquired	690	62
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses at beginning of period	23,657	23,300
Provision for (Reversal of) loan losses	8,008	9,589
Transfer of balance to OREO and other	(3,294)	151
Loans charged-off	(10,647)	(11,154)
Recoveries	3,093	2,746
Allowance for loan losses at end of period	20,817	24,632
Financing Receivable, Reserve For Unfunded Commitments
Reserve for unfunded commitments at beginning of period	2,813	2,840
Provision for (Reversal of) unfunded commitments	332	204
Reserve for unfunded commitments at end of period	3,835	3,106
Allowance on loans individually evaluated for impairment	2,973	2,445
Allowance on loans collectively evaluated for impairment	17,661	18,768
Loans, net of unearned income:
Loans, net of unearned income	3,080,820	2,985,792
Balance at end of period individually evaluated for impairment	33,863	29,140
Balance at end of period collectively evaluated for impairment	2,970,301	2,877,383
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Reserve For Unfunded Commitments
Allowance on loans acquired with deteriorated credit quality	12,732	33,769
Loans, net of unearned income:
Balance at end of period acquired with deteriorated credit quality	404,864	481,885
Receivables Acquired with Deteriorated Credit Quality | Commercial Loans | Real Estate
Financing Receivable, Reserve For Unfunded Commitments
Allowance on loans acquired with deteriorated credit quality	5,194	22,283
Loans, net of unearned income:
Balance at end of period acquired with deteriorated credit quality	181,761	241,695
Receivables Acquired with Deteriorated Credit Quality | Commercial Loans | Commercial and industrial
Financing Receivable, Reserve For Unfunded Commitments
Allowance on loans acquired with deteriorated credit quality	1,494	2,231
Loans, net of unearned income:
Balance at end of period acquired with deteriorated credit quality	27,038	31,541
Receivables Acquired with Deteriorated Credit Quality | Residential Mortgage
Financing Receivable, Reserve For Unfunded Commitments
Allowance on loans acquired with deteriorated credit quality	5,861	5,836
Loans, net of unearned income:
Balance at end of period acquired with deteriorated credit quality	119,409	129,380
Receivables Acquired with Deteriorated Credit Quality | Consumer and Other Loans
Financing Receivable, Reserve For Unfunded Commitments
Allowance on loans acquired with deteriorated credit quality	183	3,419
Loans, net of unearned income:
Balance at end of period acquired with deteriorated credit quality	$ 76,656	$ 79,269

Allowance for Credit Losses a_5

Allowance for Credit Losses and Credit Quality - Investment in Legacy and Acquired Loans by Credit Quality Indicator (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses
Total Loans	$ 22,343,906	$ 20,078,181
Commercial Loans
Financing Receivable, Allowance for Credit Losses
Total Loans	14,962,923	14,073,297
Commercial Loans | Commercial real estate - Construction
Financing Receivable, Allowance for Credit Losses
Total Loans	1,127,988	1,240,396
Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Allowance for Credit Losses
Total Loans	2,458,964	2,375,321
Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Allowance for Credit Losses
Total Loans	5,794,931	5,322,513
Commercial Loans | Commercial and industrial
Financing Receivable, Allowance for Credit Losses
Total Loans	5,581,040	5,135,067
Residential and Consumer Portfolio
Financing Receivable, Allowance for Credit Losses
Current	7,242,342	5,857,746
30 or more days past due	138,641	147,138
Total Loans	7,380,983	6,004,884
Residential Mortgage | Residential mortgage
Financing Receivable, Allowance for Credit Losses
Current	4,212,447	2,962,043
30 or more days past due	87,716	94,309
Total Loans	4,300,163	3,056,352
Consumer and Other Loans | Consumer - Home equity
Financing Receivable, Allowance for Credit Losses
Current	2,306,712	2,250,205
30 or more days past due	43,464	42,070
Total Loans	2,350,176	2,292,275
Consumer and Other Loans | Consumer - Other
Financing Receivable, Allowance for Credit Losses
Current	723,183	645,498
30 or more days past due	7,461	10,759
Total Loans	730,644	656,257
Pass | Commercial Loans
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	14,535,290	13,564,833
Pass | Commercial Loans | Commercial real estate - Construction
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	1,094,240	1,189,490
Pass | Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	2,382,053	2,234,151
Pass | Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	5,692,007	5,258,638
Pass | Commercial Loans | Commercial and industrial
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	5,366,990	4,882,554
Special Mention | Commercial Loans
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	196,045	209,925
Special Mention | Commercial Loans | Commercial real estate - Construction
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	19,033	20,351
Special Mention | Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	31,588	82,114
Special Mention | Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	49,121	19,311
Special Mention | Commercial Loans | Commercial and industrial
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	96,303	88,149
Substandard | Commercial Loans
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	196,080	258,794
Substandard | Commercial Loans | Commercial real estate - Construction
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	14,704	30,541
Substandard | Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	45,058	56,590
Substandard | Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	49,415	42,702
Substandard | Commercial Loans | Commercial and industrial
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	86,903	128,961
Doubtful | Commercial Loans
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	35,508	39,627
Doubtful | Commercial Loans | Commercial real estate - Construction
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	11	14
Doubtful | Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	265	2,466
Doubtful | Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	4,388	1,744
Doubtful | Commercial Loans | Commercial and industrial
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable	$ 30,844	35,403
Loss | Commercial Loans
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable		118
Loss | Commercial Loans | Commercial real estate - Construction
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable		0
Loss | Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable		0
Loss | Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable		118
Loss | Commercial Loans | Commercial and industrial
Financing Receivable, Allowance for Credit Losses
Gross loans and leases receivable		$ 0

Allowance for Credit Losses a_6

Allowance for Credit Losses and Credit Quality - Schedule of Investment in Legacy Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Impaired
Unpaid Principal Balance	$ 189,681		$ 189,681		$ 283,629
Recorded Investment	189,187		189,187		238,127
Related allowance	(16,248)		(16,248)		(17,352)
Average Recorded Investment	197,593	$ 217,357	201,997	$ 223,968
Interest Income Recognized	1,829	1,177	5,852	3,990
Commercial Loans
Financing Receivable, Impaired
Unpaid Principal Balance	149,080		149,080		237,922
Recorded Investment	149,094		149,094		194,201
Related allowance	(13,121)		(13,121)		(14,324)
Average Recorded Investment	157,333	183,529	162,163	192,485
Interest Income Recognized	1,398	802	4,551	2,951
Residential Mortgage
Financing Receivable, Impaired
Unpaid Principal Balance	6,674		6,674		7,183
Recorded Investment	6,230		6,230		6,749
Related allowance	(154)		(154)		(172)
Average Recorded Investment	6,268	5,404	6,337	5,467
Interest Income Recognized	59	51	185	151
Consumer and Other Loans
Financing Receivable, Impaired
Unpaid Principal Balance	33,927		33,927		38,524
Recorded Investment	33,863		33,863		37,177
Related allowance	(2,973)		(2,973)		(2,856)
Average Recorded Investment	33,992	28,424	33,497	26,016
Interest Income Recognized	372	324	1,116	888
With No Related Allowance Recorded | Commercial Loans | Commercial real estate - Construction
Financing Receivable, Impaired
Unpaid Principal Balance	11,176		11,176		13,763
Recorded Investment	11,176		11,176		13,013
Average Recorded Investment	10,806	2,722	10,371	2,538
Interest Income Recognized	164	11	460	57
With No Related Allowance Recorded | Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Impaired
Unpaid Principal Balance	33,816		33,816		50,867
Recorded Investment	33,816		33,816		44,482
Average Recorded Investment	34,118	36,850	34,505	37,185
Interest Income Recognized	209	88	903	517
With No Related Allowance Recorded | Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Impaired
Unpaid Principal Balance	21,996		21,996		15,370
Recorded Investment	21,996		21,996		14,975
Average Recorded Investment	22,091	7,858	22,988	7,908
Interest Income Recognized	249	83	746	231
With No Related Allowance Recorded | Commercial Loans | Commercial and industrial
Financing Receivable, Impaired
Unpaid Principal Balance	41,717		41,717		103,013
Recorded Investment	41,717		41,717		70,254
Average Recorded Investment	43,409	64,863	40,564	71,611
Interest Income Recognized	523	240	1,543	975
With No Related Allowance Recorded | Commercial Loans | Residential mortgage
Financing Receivable, Impaired
Unpaid Principal Balance	1,254		1,254		2,004
Recorded Investment	1,241		1,241		2,001
Average Recorded Investment	1,254	1,114	1,271	1,129
Interest Income Recognized	9	13	36	36
With No Related Allowance Recorded | Consumer and Other Loans | Consumer - Home equity
Financing Receivable, Impaired
Unpaid Principal Balance	701		701		5,906
Recorded Investment	701		701		5,634
Average Recorded Investment	705	364	708	367
Interest Income Recognized	2	6	16	18
With No Related Allowance Recorded | Consumer and Other Loans | Consumer - Other
Financing Receivable, Impaired
Unpaid Principal Balance	0		0		75
Recorded Investment	0		0		75
With An Allowance Recorded | Commercial Loans | Commercial real estate - Construction
Financing Receivable, Impaired
Unpaid Principal Balance	146		146		238
Recorded Investment	146		146		156
Related allowance	(11)		(11)		(19)
Average Recorded Investment	148	166	151	209
Interest Income Recognized	0	1	1	5
With An Allowance Recorded | Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Impaired
Unpaid Principal Balance	3,987		3,987		13,314
Recorded Investment	3,987		3,987		13,287
Related allowance	(535)		(535)		(949)
Average Recorded Investment	4,006	11,154	4,044	11,206
Interest Income Recognized	83	89	102	269
With An Allowance Recorded | Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Impaired
Unpaid Principal Balance	2,348		2,348		6,051
Recorded Investment	2,348		2,348		5,872
Related allowance	(2,104)		(2,104)		(620)
Average Recorded Investment	2,398	4,874	2,442	4,808
Interest Income Recognized	20	29	76	109
With An Allowance Recorded | Commercial Loans | Commercial and industrial
Financing Receivable, Impaired
Unpaid Principal Balance	33,894		33,894		35,306
Recorded Investment	33,908		33,908		32,162
Related allowance	(10,471)		(10,471)		(12,736)
Average Recorded Investment	40,357	55,042	47,098	57,020
Interest Income Recognized	150	261	720	788
With An Allowance Recorded | Residential Mortgage | Residential mortgage
Financing Receivable, Impaired
Unpaid Principal Balance	5,420		5,420		5,179
Recorded Investment	4,989		4,989		4,748
Related allowance	(154)		(154)		(172)
Average Recorded Investment	5,014	4,290	5,066	4,338
Interest Income Recognized	50	38	149	115
With An Allowance Recorded | Consumer and Other Loans | Consumer - Home equity
Financing Receivable, Impaired
Unpaid Principal Balance	28,700		28,700		27,189
Recorded Investment	28,695		28,695		26,575
Related allowance	(2,469)		(2,469)		(2,358)
Average Recorded Investment	28,577	23,730	27,905	21,639
Interest Income Recognized	305	254	892	690
With An Allowance Recorded | Consumer and Other Loans | Consumer - Other
Financing Receivable, Impaired
Unpaid Principal Balance	4,526		4,526		5,354
Recorded Investment	4,467		4,467		4,893
Related allowance	(504)		(504)		$ (498)
Average Recorded Investment	4,710	4,330	4,884	4,010
Interest Income Recognized	$ 65	$ 64	$ 208	$ 180

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Schedule of Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Goodwill
Balance at beginning of the period			$ 1,188,902	$ 1,188,902	$ 726,856
Goodwill acquired during the year					462,046
Goodwill acquired during the year (preliminary allocation) and adjustments				32,001
Balance at end of the period	$ 1,220,903			1,220,903	1,188,902
Operating Segments | IBERIABANK
Goodwill
Balance at beginning of the period			1,160,559	1,160,559	698,513
Goodwill acquired during the year					462,046
Goodwill acquired during the year (preliminary allocation) and adjustments				28,621
Balance at end of the period	1,189,180			1,189,180	1,160,559
Operating Segments | IMC
Goodwill
Balance at beginning of the period			23,178	23,178	23,178
Goodwill acquired during the year					0
Goodwill acquired during the year (preliminary allocation) and adjustments				0
Balance at end of the period	23,178			23,178	23,178
Operating Segments | LTC
Goodwill
Balance at beginning of the period			5,165	5,165	5,165
Goodwill acquired during the year					0
Goodwill acquired during the year (preliminary allocation) and adjustments				3,380
Balance at end of the period	8,545			8,545	$ 5,165
Gibraltar Private Bank & Trust Company
Goodwill
Goodwill acquired during the year (preliminary allocation) and adjustments	2,900
Balance at end of the period	49,600			49,600
Solomon Parks Title & Escrow
Goodwill
Goodwill acquired during the year (preliminary allocation) and adjustments		$ 3,400		$ 3,400
Sabadell United
Goodwill
Balance at beginning of the period	$ 441,000
Goodwill acquired during the year (preliminary allocation) and adjustments			21,000
Balance at end of the period			$ 441,000

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2018	Mar. 23, 2018	Jan. 12, 2018	Dec. 31, 2017	Jul. 31, 2017
Goodwill
Goodwill acquired during the year (preliminary allocation) and adjustments			$ 32,001
Non-compete agreement					$ 156
Title plant assets	$ 6,800		$ 6,800			$ 6,700
Gibraltar Private Bank & Trust Company
Goodwill
Goodwill acquired during the year (preliminary allocation) and adjustments	$ 2,900
Core deposit intangible assets				$ 18,529
Sabadell United
Goodwill
Goodwill acquired during the year (preliminary allocation) and adjustments		$ 21,000
Core deposit intangible assets							$ 66,600

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Schedule of Mortgage Servicing Rights at Carrying Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 137,774	$ 129,163
Accumulated Amortization	(59,526)	(53,006)
Net Carrying Amount	78,248	76,157
Mortgage servicing rights
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	12,125	9,588
Accumulated Amortization	(4,562)	(3,931)
Net Carrying Amount	$ 7,563	$ 5,657

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Schedule of Definite-Lived Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 137,774	$ 129,163
Accumulated Amortization	(59,526)	(53,006)
Net Carrying Amount	78,248	76,157
Core deposit intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	136,183	127,957
Accumulated Amortization	(58,161)	(51,971)
Net Carrying Amount	78,022	75,986
Customer relationship intangible asset
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,385	1,143
Accumulated Amortization	(1,305)	(996)
Net Carrying Amount	80	147
Non-compete agreement
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	206	63
Accumulated Amortization	(60)	(39)
Net Carrying Amount	$ 146	$ 24

Derivative Instruments and Ot_3

Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value of Derivatives
Derivative instruments	$ 12,570	$ 31,265
Derivative Liability	42,764	25,154
Notional Amount of Derivatives
Derivative assets	2,226,863	1,609,472
Derivative liabilities	1,717,782	1,721,752
Designated as Hedging Instruments
Fair Value of Derivatives
Derivative instruments	48	0
Derivative Liability	0	0
Notional Amount of Derivatives
Derivative assets	258,500	0
Derivative liabilities	0	108,500
Designated as Hedging Instruments | Interest rate contracts
Notional Amount of Derivatives
Derivative assets	258,500	0
Derivative liabilities	0	108,500
Designated as Hedging Instruments | Interest rate contracts | Other Assets
Fair Value of Derivatives
Derivative instruments	48	0
Designated as Hedging Instruments | Interest rate contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	0	0
Not Designated as Hedging Instruments
Notional Amount of Derivatives
Derivative assets	1,968,363	1,609,472
Derivative liabilities	1,717,782	1,613,252
Not Designated as Hedging Instruments | Other Assets
Fair Value of Derivatives
Derivative instruments	12,522	31,265
Not Designated as Hedging Instruments | Other Liabilities
Fair Value of Derivatives
Derivative Liability	42,764	25,154
Not Designated as Hedging Instruments | Interest rate contracts
Notional Amount of Derivatives
Derivative assets	1,489,111	1,218,464
Derivative liabilities	1,489,111	1,218,464
Not Designated as Hedging Instruments | Interest rate contracts | Other Assets
Fair Value of Derivatives
Derivative instruments	3,665	20,446
Not Designated as Hedging Instruments | Interest rate contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	37,417	16,191
Not Designated as Hedging Instruments | Foreign exchange contracts
Notional Amount of Derivatives
Derivative assets	933	268
Derivative liabilities	933	268
Not Designated as Hedging Instruments | Foreign exchange contracts | Other Assets
Fair Value of Derivatives
Derivative instruments	13	7
Not Designated as Hedging Instruments | Foreign exchange contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	13	7
Not Designated as Hedging Instruments | Forward sales contracts
Notional Amount of Derivatives
Derivative assets	169,276	82,347
Derivative liabilities	21,684	142,578
Not Designated as Hedging Instruments | Forward sales contracts | Other Assets
Fair Value of Derivatives
Derivative instruments	1,084	136
Not Designated as Hedging Instruments | Forward sales contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	44	279
Not Designated as Hedging Instruments | Written and purchased options
Notional Amount of Derivatives
Derivative assets	275,473	278,638
Derivative liabilities	143,912	165,198
Not Designated as Hedging Instruments | Written and purchased options | Other Assets
Fair Value of Derivatives
Derivative instruments	7,754	10,654
Not Designated as Hedging Instruments | Written and purchased options | Other Liabilities
Fair Value of Derivatives
Derivative Liability	5,282	8,656
Not Designated as Hedging Instruments | Other contracts
Notional Amount of Derivatives
Derivative assets	33,570	29,755
Derivative liabilities	62,142	86,744
Not Designated as Hedging Instruments | Other contracts | Other Assets
Fair Value of Derivatives
Derivative instruments	6	22
Not Designated as Hedging Instruments | Other contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liability	$ 8	$ 21

Derivative Instruments and Ot_4

Derivative Instruments and Other Hedging Activities - Narrative (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional amount of derivative liabilities	$ 1,717,782	$ 1,721,752
Cash as collateral for derivative transactions	0	(552)
Cash Posted As Variation Margin for Derivatives	44,400	5,100
Not Designated as Hedging Instruments
Derivative [Line Items]
Notional amount of derivative liabilities	1,717,782	1,613,252
Not Designated as Hedging Instruments | Other contracts
Derivative [Line Items]
Notional amount of derivative liabilities	$ 62,142	$ 86,744

Derivative Instruments and Ot_5

Derivative Instruments and Other Hedging Activities - Reconciliation of Gross Amounts in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative assets
Gross derivative assets	$ 8,980	$ 29,056
Gross amounts not offset in the Balance Sheet, derivatives	(248)	(12,469)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	8,732	16,587
Derivative liabilities
Gross derivative liabilities	42,684	16,191
Gross amounts not offset in the Balance Sheet, derivatives	(248)	(12,469)
Gross amounts not offset in the Balance Sheet, collateral	0	(552)
Net derivative liabilities	42,436	3,170
Written and purchased options
Derivative assets
Gross derivative assets	5,267	8,610
Gross amounts not offset in the Balance Sheet, derivatives	0	0
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	5,267	8,610
Derivative liabilities
Gross derivative liabilities	5,267
Gross amounts not offset in the Balance Sheet, derivatives	0
Gross amounts not offset in the Balance Sheet, collateral	0
Net derivative liabilities	5,267
Designated as Hedging Instruments | Interest rate contracts
Derivative assets
Gross derivative assets	48
Gross amounts not offset in the Balance Sheet, derivatives	0
Gross amounts not offset in the Balance Sheet, collateral	0
Net derivative assets	48
Derivative liabilities
Gross derivative liabilities		0
Gross amounts not offset in the Balance Sheet, derivatives		0
Gross amounts not offset in the Balance Sheet, collateral		0
Net derivative liabilities		0
Not Designated as Hedging Instruments | Interest rate contracts
Derivative assets
Gross derivative assets	3,665	20,446
Gross amounts not offset in the Balance Sheet, derivatives	(248)	(12,469)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	3,417	7,977
Derivative liabilities
Gross derivative liabilities	37,417	16,191
Gross amounts not offset in the Balance Sheet, derivatives	(248)	(12,469)
Gross amounts not offset in the Balance Sheet, collateral	0	(552)
Net derivative liabilities	$ 37,169	$ 3,170

Derivative Instruments and Ot_6

Derivative Instruments and Other Hedging Activities - Effect of Hedging Instruments on Consolidated Financial Statements (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Designated as Hedging Instruments | Cash Flow Hedging | Interest rate contracts | Interest expense
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	$ (22)	$ (101)	$ (178)	$ (249)
Amount of Gain (Loss) Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing)	0	0	0	0
Not Designated as Hedging Instruments
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	2,850	(1,694)	10,142	(2,072)
Not Designated as Hedging Instruments | Interest rate contracts | Other income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	2,586	743	5,093	3,159
Not Designated as Hedging Instruments | Foreign exchange contracts | Other income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	7	24	17	38
Not Designated as Hedging Instruments | Forward sales contracts | Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	948	(2,007)	4,563	(3,893)
Not Designated as Hedging Instruments | Written and purchased options | Mortgage income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	(692)	(462)	473	(1,393)
Not Designated as Hedging Instruments | Other contracts | Other income
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	1	8	(4)	17
OCI | Designated as Hedging Instruments | Cash Flow Hedging | Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures
Amount of Gain (Loss) Recognized	$ 818	$ (158)	$ 4,762	$ (1,081)

Income Taxes Schedule of Effect

Income Taxes Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income before income tax expense	$ 131,866	$ 48,450	$ 318,620	$ 201,493
Income tax expense	$ 30,401	$ 18,806	$ 78,410	$ 69,358
Effective tax rate	23.10%	38.80%	24.60%	34.40%

Income Taxes Income Taxes (Deta

Income Taxes Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Discrete tax items		$ 6.6
Change in enacted tax rate				2.10%
Effective tax rate prior to impact of change in enacted tax rate				22.50%
Effective tax rate	23.10%		38.80%	24.60%	34.40%
TCJA one-time tax expense				$ 51

Shareholders' Equity, Capital_3

Shareholders' Equity, Capital Ratios and Other Regulatory Matters - Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 06, 2018	Mar. 23, 2018	May 09, 2016	Aug. 05, 2015	Sep. 30, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Liquidation preference value			$ 137,500
Carrying Amount					$ 132,097	$ 132,097
Number of shares authorized to be repurchased					1,137,500
Common stock repurchases					$ 61,046
Shares authorized to be repurchased					709,290
Series B Preferred Stock
Class of Stock [Line Items]
Ownership per share				6.625%
Liquidation preference value				$ 80,000
Carrying Amount					$ 76,812	76,812
Series C Preferred Stock
Class of Stock [Line Items]
Ownership per share			6.60%
Liquidation preference value			$ 57,500
Carrying Amount					$ 55,285	$ 55,285
Gibraltar Private Bank & Trust Company
Class of Stock [Line Items]
Consideration paid		$ 214,666
Cash consideration		$ 7
Gibraltar Private Bank & Trust Company | Common Stock
Class of Stock [Line Items]
Common stock issued (shares)		2,787,773
Common stock issued (in dollars per share)		$ 77
Number of shares issued per share acquired		$ 1.9749
Subsequent Event
Class of Stock [Line Items]
Treasury stock acquired (shares)	709,290
Treasury stock acquired	$ 52,600
Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)					763,210
Common stock repurchases					$ 763
2016 and 2018 Share Repurchase Program
Class of Stock [Line Items]
Common stock repurchases					$ 61,000
Average cost of common stock shares repurchased (in usd per share)					$ 79.99
2016 and 2018 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)					763,210
2016 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)					335,000

Shareholders' Equity, Capital_4

Shareholders' Equity, Capital Ratios and Other Regulatory Matters - Actual Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Consolidated
Tier 1 Leverage
Minimum amount	$ 1,156,436	$ 1,073,381
Minimum ratio	4.00%	4.00%
Actual amount	$ 2,789,740	$ 2,509,496
Actual ratio	9.65%	9.35%
Common Equity Tier 1 (CET1)
Minimum amount	$ 1,107,934	$ 1,011,732
Minimum ratio	4.50%	4.50%
Actual amount	$ 2,657,643	$ 2,377,398
Actual ratio	10.79%	10.57%
Tier 1 Risk-Based Capital (1)
Minimum amount	$ 1,477,245	$ 1,348,977
Minimum ratio	6.00%	6.00%
Actual amount	$ 2,789,740	$ 2,509,496
Actual ratio	11.33%	11.16%
Total Risk-Based Capital (1)
Minimum amount	$ 1,969,660	$ 1,798,635
Minimum ratio	8.00%	8.00%
Actual amount	$ 3,057,911	$ 2,780,095
Actual ratio	12.42%	12.37%
IBERIABANK
Tier 1 Leverage
Minimum amount	$ 1,153,671	$ 1,070,789
Minimum ratio	4.00%	4.00%
Well capitalized amount	$ 1,442,089	$ 1,338,487
Well capitalized ratio	5.00%	5.00%
Actual amount	$ 2,768,917	$ 2,437,275
Actual ratio	9.60%	9.10%
Common Equity Tier 1 (CET1)
Minimum amount	$ 1,105,391	$ 1,009,553
Minimum ratio	4.50%	4.50%
Well capitalized amount	$ 1,596,676	$ 1,458,243
Well capitalized ratio	6.50%	6.50%
Actual amount	$ 2,768,917	$ 2,437,275
Actual ratio	11.27%	10.86%
Tier 1 Risk-Based Capital (1)
Minimum amount	$ 1,473,855	$ 1,346,070
Minimum ratio	6.00%	6.00%
Well capitalized amount	$ 1,965,140	$ 1,794,760
Well capitalized ratio	8.00%	8.00%
Actual amount	$ 2,768,917	$ 2,437,275
Actual ratio	11.27%	10.86%
Total Risk-Based Capital (1)
Minimum amount	$ 1,965,140	$ 1,794,760
Minimum ratio	8.00%	8.00%
Well capitalized amount	$ 2,456,425	$ 2,243,450
Well capitalized ratio	10.00%	10.00%
Actual amount	$ 2,920,587	$ 2,591,374
Actual ratio	11.89%	11.55%

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings per common share - basic:
Net income	$ 101,465	$ 29,644	$ 240,210	$ 132,135
Less: Preferred stock dividends	3,599	3,598	8,146	8,146
Less: Dividends and undistributed earnings allocated to unvested restricted shares	908	283	2,341	1,052
Net income allocated to common shareholders - basic	$ 96,958	$ 25,763	$ 229,723	$ 122,937
Weighted average common shares outstanding	55,571	52,424	55,047	49,749
Earnings per common share - basic (in usd per share)	$ 1.74	$ 0.49	$ 4.17	$ 2.47
Earnings per common share - diluted:
Net income allocated to common shareholders - basic	$ 96,958	$ 25,763	$ 229,723	$ 122,937
Adjustment for undistributed earnings allocated to unvested restricted shares	(25)	8	(49)	0
Net income allocated to common shareholders - diluted	$ 96,933	$ 25,771	$ 229,674	$ 122,937
Weighted average common shares outstanding	55,571	52,424	55,047	49,749
Dilutive potential common shares	374	346	360	357
Weighted average common shares outstanding - diluted	55,945	52,770	55,407	50,106
Earnings per common share - diluted (in usd per share)	$ 1.73	$ 0.49	$ 4.14	$ 2.45

Earnings Per Share - Narrative

Earnings Per Share - Narrative (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share
Weighted average number of shares held by Recognition and Retention Plan excluded from the calculation for basic shares outstanding	542,796	511,562	581,397	428,232
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from the computation of earnings per share	60,931	72,239	147,834	69,289

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Future awards shares under approved incentive compensation plans	1,163,414
Share-based compensation maximum option term (in years)	10 years
Stock Option Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned share-based compensation associated with awards	$ 2.2
Unrecognized compensation cost related to stock options expected to be recognized over a weighted-average period	2 years 11 months
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned share-based compensation associated with awards	$ 30.9	$ 35.7
Unrecognized compensation cost related to stock options expected to be recognized over a weighted-average period	1 year 5 months
Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Phantom Stock Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	5 years

Share-Based Compensation - Acti

Share-Based Compensation - Activity Related to Stock Options (Detail) - Stock Option Awards - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Number of shares
Balance at beginning of the period (in shares)	686,366,000	721,538,000
Granted (in shares)	97,620,000	78,434,000
Exercised (in shares)	(41,697,000)	(74,236,000)
Forfeited or expired (in shares)	(27,328,000)	(26,675,000)
Balance at end of the period (in shares)	714,961,000	699,061,000
Exercisable at period end (in shares)	500,349,000	463,326,000
Weighted Average Exercise Price
Balance at beginning of the period (in usd per share)	$ 58.24	$ 55.38
Granted (in usd per share)	82.02	85.03
Exercised (in usd per share)	53.12	55.77
Forfeited or expired (in usd per share)	68.19	68.93
Balance at end of the period (in usd per share)	61.41	58.15
Exercisable at period end (in usd per share)	$ 56.70	$ 55.68

Share-Based Compensation - Esti

Share-Based Compensation - Estimate Fair Value of Stock Option Awards with Weighted-Average Assumptions (Detail) - Stock Option Awards - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends	1.80%	1.70%
Expected volatility	24.30%	25.00%
Risk-free interest rate	2.70%	2.10%
Expected term (in years)	5 years 9 months 18 days	5 years 9 months 18 days
Weighted-average grant-date fair value	$ 18.48	$ 18.87

Share-Based Compensation - Comp

Share-Based Compensation - Compensation Expense Included in Non-Interest Expense and Related Income Tax Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock Option Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 322	$ 343	$ 952	$ 1,131
Income tax benefit	23	46	70	161
Restricted Stock And Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	4,843	4,046	14,192	10,368
Income tax benefit	1,017	1,416	2,980	3,629
Phantom Stock and Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 2,375	$ 2,747	$ 7,388	$ 8,689

Share-Based Compensation - Unve

Share-Based Compensation - Unvested Restricted Stock Award Activity (Detail) - Restricted Stock And Restricted Stock Units - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at beginning of the period (in shares)	738,187,000	543,258,000
Granted (in shares)	229,181,000	411,957,000
Forfeited (in shares)	(70,981,000)	(21,272,000)
Earned and issued (in shares)	(192,217,000)	(191,222,000)
Balance at end of the period (in shares)	704,170,000	742,721,000

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Value of share equivalents
Market price of Company's stock	$ 81.35	$ 82.15
Phantom Stock and Performance Stock Units
Number of share equivalents
Balance at beginning of the period (in shares)	393,844,000	472,830,000
Granted (in shares)	151,908,000	111,119,000
Forfeited share equivalents (in shares)	(59,550,000)	(22,956,000)
Vested share equivalents (in shares)	(130,497,000)	(158,573,000)
Balance at end of the period (in shares)	355,705,000	402,420,000
Value of share equivalents
Balance at beginning of the period (in shares)	$ 30,523	$ 39,600
Granted (in shares)	12,358	9,128
Forfeited share equivalents (in shares)	4,844	1,886
Vested share equivalents (in shares)	10,871	13,212
Balance at end of the period (in shares)	$ 28,937	$ 33,059

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Assets
Securities available for sale, at fair value	$ 4,634,124,000	$ 4,590,062,000
CRA and Community Development Investment Funds	1,866,000	0
Mortgage loans held for sale	42,976,000	134,916,000
Mortgage loans held for investment, at fair value option	7,249,000	14,953,000
Derivative instruments	8,980,000	29,056,000
Liabilities
Derivative instruments	42,684,000	16,191,000
Fair value assets transferred from Level 1 to Level 2	0
Level 1
Assets
Securities available for sale, at fair value	0	0
CRA and Community Development Investment Funds	0
Level 2
Assets
Securities available for sale, at fair value	4,634,124,000	4,590,062,000
CRA and Community Development Investment Funds	1,866,000
Level 3
Assets
Securities available for sale, at fair value	0	0
CRA and Community Development Investment Funds	0
Recurring
Assets
Securities available for sale, at fair value	4,634,124,000	4,590,062,000
CRA and Community Development Investment Funds	1,866,000
Mortgage loans held for sale	42,976,000	134,916,000
Mortgage loans held for investment, at fair value option	7,249,000	14,953,000
Derivative instruments	12,570,000	31,265,000
Total, Assets	4,698,785,000	4,771,196,000
Liabilities
Derivative instruments	42,764,000	25,154,000
Total	42,764,000	25,154,000
Recurring | Level 1
Assets
Securities available for sale, at fair value	0	0
CRA and Community Development Investment Funds	0
Mortgage loans held for sale	0	0
Mortgage loans held for investment, at fair value option	0	0
Derivative instruments	0	0
Total, Assets	0	0
Liabilities
Derivative instruments	0	0
Total	0	0
Recurring | Level 2
Assets
Securities available for sale, at fair value	4,634,124,000	4,590,062,000
CRA and Community Development Investment Funds	1,866,000
Mortgage loans held for sale	42,976,000	134,916,000
Mortgage loans held for investment, at fair value option	7,249,000	14,953,000
Derivative instruments	12,570,000	31,265,000
Total, Assets	4,698,785,000	4,771,196,000
Liabilities
Derivative instruments	42,764,000	25,154,000
Total	42,764,000	25,154,000
Recurring | Level 3
Assets
Securities available for sale, at fair value	0	0
CRA and Community Development Investment Funds	0
Mortgage loans held for sale	0	0
Mortgage loans held for investment, at fair value option	0	0
Derivative instruments	0	0
Total, Assets	0	0
Liabilities
Derivative instruments	0	0
Total	$ 0	$ 0

Fair Value Measurements - Fin_2

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Detail) - Nonrecurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Loans	$ 60,307	$ 71,210
OREO, net	5,148	3,029
Total	65,455	74,239
Level 1
Assets
Loans	0	0
OREO, net	0	0
Total	0	0
Level 2
Assets
Loans	0	0
OREO, net	0	0
Total	0	0
Level 3
Assets
Loans	60,307	71,210
OREO, net	5,148	3,029
Total	$ 65,455	$ 74,239

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance for Mortgage Loans Held for Sale and Mortgage Loans Held for Investment (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Mortgage loans held for sale, at fair value
Aggregate Fair Value	$ 42,976	$ 134,916
Aggregate Unpaid Principal	41,848	131,276
Aggregate Fair Value Less Unpaid Principal	1,128	3,640
Mortgage loans held for investment, at fair value
Aggregate Fair Value	7,249	14,953
Aggregate Unpaid Principal	8,666	16,306
Aggregate Fair Value Less Unpaid Principal	$ (1,417)	$ (1,353)

Fair Value Measurements - Amoun

Fair Value Measurements - Amount of Net Gains (Losses) from Fair Value Changes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Net Gains (Losses) Resulting From Changes in Fair Value - Mortgage loans held for sale, at fair value	$ (1,041)	$ 251	$ (2,513)	$ 1,121
Net Gains (Losses) Resulting From Changes in Fair Value - Mortgage loans held for investment, at fair value	$ (296)	$ (62)	$ (1,217)	$ (127)

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Estimated Fair Values and Carrying Amounts of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Financial Assets
Securities available for sale, at fair value	$ 4,634,124	$ 4,590,062
CRA and Community Development Investment Funds	1,866	0
Mortgage loans held for sale	42,976	134,916
Derivative instruments	12,570	31,265
Cash and cash equivalents	475,935	625,724	$ 881,216	$ 1,362,126
Securities held to maturity	213,561	227,318
Financial Liabilities
Derivative instruments	42,764	25,154
Deposits	23,193,446	21,466,717	$ 21,334,271
Short-term borrowings	1,242,719	991,297
Long-term debt	1,466,810	1,495,835
Level 1
Financial Assets
Securities available for sale, at fair value	0	0
CRA and Community Development Investment Funds	0
Mortgage loans held for sale	0	0
Derivative instruments	0	0
Cash and cash equivalents	475,935	625,724
Securities held to maturity	0	0
Loans and leases, net of unearned income and allowance for loan and lease losses	0	0
Financial Liabilities
Derivative instruments	0	0
Deposits	0	0
Short-term borrowings	452,719	516,297
Long-term debt	0	0
Level 2
Financial Assets
Securities available for sale, at fair value	4,634,124	4,590,062
CRA and Community Development Investment Funds	1,866
Mortgage loans held for sale	42,976	134,916
Derivative instruments	12,570	31,265
Cash and cash equivalents	0	0
Securities held to maturity	207,309	227,964
Loans and leases, net of unearned income and allowance for loan and lease losses	0	0
Financial Liabilities
Derivative instruments	42,764	25,154
Deposits	23,181,429	21,460,782
Short-term borrowings	790,000	475,000
Long-term debt	0	0
Level 3
Financial Assets
Securities available for sale, at fair value	0	0
CRA and Community Development Investment Funds	0
Mortgage loans held for sale	0	0
Derivative instruments	0	0
Cash and cash equivalents	0	0
Securities held to maturity	0	0
Loans and leases, net of unearned income and allowance for loan and lease losses	22,014,886	19,826,857
Financial Liabilities
Derivative instruments	0	0
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	1,449,018	1,476,899
Carrying Amount
Financial Assets
Securities available for sale, at fair value	4,634,124	4,590,062
CRA and Community Development Investment Funds	1,866
Mortgage loans held for sale	42,976	134,916
Derivative instruments	12,570	31,265
Cash and cash equivalents	475,935	625,724
Securities held to maturity	213,561	227,318
Loans and leases, net of unearned income and allowance for loan and lease losses	22,206,956	19,937,290
Financial Liabilities
Derivative instruments	42,764	25,154
Deposits	23,193,446	21,466,717
Short-term borrowings	1,242,719	991,297
Long-term debt	1,466,810	1,495,835
Fair Value
Financial Assets
Securities available for sale, at fair value	4,634,124	4,590,062
CRA and Community Development Investment Funds	1,866
Mortgage loans held for sale	42,976	134,916
Derivative instruments	12,570	31,265
Cash and cash equivalents	475,935	625,724
Securities held to maturity	207,309	227,964
Loans and leases, net of unearned income and allowance for loan and lease losses	22,014,886	19,826,857
Financial Liabilities
Derivative instruments	42,764	25,154
Deposits	23,181,429	21,460,782
Short-term borrowings	1,242,719	991,297
Long-term debt	$ 1,449,018	$ 1,476,899

Business Segments (Detail)

Business Segments (Detail)	9 Months Ended
	Sep. 30, 2018Segment
Segment Reporting [Abstract]
Number of business segments	3

Business Segments - Schedule of

Business Segments - Schedule of Segment Reporting Information (Detail) - 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
Interest and dividend income	$ 317,067	$ 246,972	$ 891,433	$ 644,080
Interest expense	57,842	30,089	143,206	70,736
Net interest income	259,225	216,883	748,227	573,344
Provision for/(reversal of) loan losses	11,097	18,514	26,678	36,718
Other non-interest income/(expense)	34,075	29,150	97,392	83,336
Allocated expenses/(income)	0	0	0	0
Non-interest expense	169,349	200,762	554,522	484,938
Income before income tax expense	131,866	48,450	318,620	201,493
Income tax expense	30,401	18,806	78,410	69,358
Net income	101,465	29,644	240,210	132,135
Total loans, leases, and loans held for sale, net of unearned income	22,386,882	19,936,303	22,386,882	19,936,303
Total assets	30,118,387	27,976,635	30,118,387	27,976,635	$ 27,904,129
Total deposits	23,193,446	21,334,271	23,193,446	21,334,271	$ 21,466,717
Average assets	30,046,231	26,096,921	29,323,445	23,282,834
Operating Segments | IBERIABANK
Segment Reporting Information
Interest and dividend income	315,467	245,166	886,629	638,683
Interest expense	57,842	30,089	143,206	70,736
Net interest income	257,625	215,077	743,423	567,947
Provision for/(reversal of) loan losses	11,099	18,524	26,704	36,816
Other non-interest income/(expense)	33,591	29,163	96,978	83,376
Allocated expenses/(income)	(3,691)	(3,881)	(9,043)	(9,377)
Non-interest expense	154,287	174,306	506,035	412,305
Income before income tax expense	129,521	55,291	316,705	211,579
Income tax expense	29,765	21,076	78,516	72,650
Net income	99,756	34,215	238,189	138,929
Total loans, leases, and loans held for sale, net of unearned income	22,302,679	19,743,749	22,302,679	19,743,749
Total assets	29,974,065	27,738,588	29,974,065	27,738,588
Total deposits	23,179,549	21,333,190	23,179,549	21,333,190
Average assets	29,863,742	25,869,559	29,136,369	23,020,324
Operating Segments | IMC
Segment Reporting Information
Interest and dividend income	1,599	1,805	4,802	5,395
Interest expense	0	0	0	0
Net interest income	1,599	1,805	4,802	5,395
Provision for/(reversal of) loan losses	(2)	(10)	(26)	(98)
Other non-interest income/(expense)	(16)	(9)	(83)	(30)
Allocated expenses/(income)	2,680	2,911	6,714	7,057
Non-interest expense	10,223	22,170	34,105	59,754
Income before income tax expense	1,414	(7,225)	(26)	(11,453)
Income tax expense	386	(2,424)	(7)	(3,840)
Net income	1,028	(4,801)	(19)	(7,613)
Total loans, leases, and loans held for sale, net of unearned income	84,203	192,554	84,203	192,554
Total assets	119,322	217,056	119,322	217,056
Total deposits	13,897	1,081	13,897	1,081
Average assets	158,464	204,920	164,039	239,014
Operating Segments | LTC
Segment Reporting Information
Interest and dividend income	1	1	2	2
Interest expense	0	0	0	0
Net interest income	1	1	2	2
Provision for/(reversal of) loan losses	0	0	0	0
Other non-interest income/(expense)	500	(4)	497	(10)
Allocated expenses/(income)	1,011	970	2,329	2,320
Non-interest expense	4,839	4,286	14,382	12,879
Income before income tax expense	931	384	1,941	1,367
Income tax expense	250	154	(99)	548
Net income	681	230	2,040	819
Total loans, leases, and loans held for sale, net of unearned income	0	0	0	0
Total assets	25,000	20,991	25,000	20,991
Total deposits	0	0	0	0
Average assets	24,025	22,442	23,037	23,496
Mortgage income
Segment Reporting Information
Non-interest Income	12,732	16,050	36,048	49,895
Mortgage income | Operating Segments | IBERIABANK
Segment Reporting Information
Non-interest Income	0	0	0	0
Mortgage income | Operating Segments | IMC
Segment Reporting Information
Non-interest Income	12,732	16,050	36,048	49,895
Mortgage income | Operating Segments | LTC
Segment Reporting Information
Non-interest Income	0	0	0	0
Title revenue
Segment Reporting Information
Non-interest Income	6,280	5,643	18,153	16,574
Title revenue | Operating Segments | IBERIABANK
Segment Reporting Information
Non-interest Income	0	0	0	0
Title revenue | Operating Segments | IMC
Segment Reporting Information
Non-interest Income	0	0	0	0
Title revenue | Operating Segments | LTC
Segment Reporting Information
Non-interest Income	$ 6,280	$ 5,643	$ 18,153	$ 16,574

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Detail) - USD ($) $ in Millions	Dec. 11, 2017	Sep. 30, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Fair value of guarantees under commercial and standby letters of credit		$ 2.4	$ 2.1
Settled Litigation
Loss Contingencies [Line Items]
Settlement amount	$ 11.7
Pending Litigation
Loss Contingencies [Line Items]
Damages sought		$ 11.7

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Financial Instruments Outstanding (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 824,472	$ 342,305
Unfunded commitments under lines of credit	6,610,843	6,060,034
Commercial and standby letters of credit	235,730	210,002
Reserve for unfunded lending commitments	$ 14,721	$ 13,208	$ 21,032	$ 11,241

Uncategorized Items - ibkc-2018

Label	Element	Value	[1]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (345,000)
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (345,000)
[1]	Cumulative-effect adjustment to beginning retained earnings for fair value adjustments related to the reclassification of certain equity investments in accordance with ASU 2016-01, adopted as of January 1, 2018.