Iberiabank (IBKC) 10-Q10 Nov 142014 Q3 Quarterly reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2014	Oct. 31, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'IBKC	'
Entity Registrant Name	'IBERIABANK CORP	'
Entity Central Index Key	'0000933141	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	33,446,577

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets	'	'
Cash and due from banks	$257,147	$238,672
Interest-bearing deposits in banks	410,860	152,724
Total cash and cash equivalents	668,007	391,396
Securities available for sale, at fair value	2,103,828	1,936,797
Securities held to maturity (fair values of $122,458 and $152,566, respectively)	120,520	154,109
Mortgage loans held for sale ($148,530 and $97,273 recorded at fair value, respectively)	148,530	128,442
Loans covered by loss share agreements	524,189	719,793
Non-covered loans, net of unearned income	10,555,010	8,772,226
Total loans, net of unearned income	11,079,199	9,492,019
Allowance for loan losses	-134,540	-143,074
Loans, net	10,944,659	9,348,945
FDIC loss share receivables	94,712	162,312
Premises and equipment, net	307,868	287,510
Goodwill	526,242	401,872
Other assets	602,243	554,167
Total Assets	15,516,609	13,365,550
Liabilities	'	'
Non-interest-bearing	3,157,453	2,575,939
Interest-bearing	9,220,322	8,161,061
Total deposits	12,377,775	10,737,000
Short-term borrowings	812,783	680,344
Long-term debt	355,569	280,699
Other liabilities	152,934	136,528
Total Liabilities	13,699,061	11,834,571
Shareholders' Equity	'	'
Preferred stock, $1 par value-5,000,000 shares authorized	'	'
Common stock, $1 par value-50,000,000 shares authorized; 35,262,901 and 31,917,385 shares issued, respectively	35,263	31,917
Additional paid-in capital	1,394,618	1,178,284
Retained earnings	473,885	436,141
Accumulated other comprehensive income (loss)	-256	-16,491
Treasury stock at cost-1,822,042 and 2,130,841 shares, respectively	-85,962	-98,872
Total Shareholders' Equity	1,817,548	1,530,979
Total Liabilities and Shareholders' Equity	$15,516,609	$13,365,550

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]	'	'
Securities held to maturity, fair values	$122,458	$152,566
Mortgage loans held for sale recorded at fair value	$148,530	$97,273
Preferred stock, par value	$1	$1
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, par value	$1	$1
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	35,262,901	31,917,385
Treasury stock, shares	1,822,042	2,130,841

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Loss) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Interest and Dividend Income	'	'	'	'
Loans, including fees	$144,846	$120,035	$389,124	$358,344
Mortgage loans held for sale, including fees	1,594	1,289	3,953	3,965
Investment securities:	'	'	'	'
Taxable interest	9,551	7,837	28,411	22,241
Tax-exempt interest	1,443	1,649	4,500	5,082
Amortization of FDIC loss share receivable	-25,120	-22,875	-61,393	-68,707
Other	853	577	2,024	2,180
Total interest and dividend income	133,167	108,512	366,619	323,105
Interest Expense	'	'	'	'
NOW and MMDA	5,046	4,441	13,353	14,462
Savings	88	71	235	238
Time deposits	4,067	4,012	10,093	13,038
Short-term borrowings	406	104	1,022	365
Long-term debt	2,519	2,432	7,489	8,196
Total interest expense	12,126	11,060	32,192	36,299
Net interest income	121,041	97,452	334,427	286,806
Provision for loan losses	5,714	2,014	12,565	445
Net interest income after provision for loan losses	115,327	95,438	321,862	286,361
Non-interest Income	'	'	'	'
Service charges on deposit accounts	10,205	7,512	25,421	21,415
Mortgage income	12,814	15,202	40,903	51,841
Title revenue	5,577	5,482	15,007	16,199
ATM/debit card fee income	3,287	2,476	8,691	7,017
Income from bank owned life insurance	1,047	908	4,423	2,747
Gain (loss) on sale of available for sale investments	582	-3	609	2,259
Derivative losses reclassified from other comprehensive income	'	'	'	-392
Broker commissions	5,297	3,950	14,823	11,347
Other income	6,854	7,736	19,430	17,809
Total non-interest income	45,663	43,263	129,307	130,242
Non-interest Expense	'	'	'	'
Salaries and employee benefits	64,934	59,234	193,641	185,578
Net occupancy and equipment	14,883	14,572	44,977	44,050
Impairment of FDIC loss share receivables and other long-lived assets	4,741	1,319	5,378	37,750
Communication and delivery	2,525	2,899	8,756	9,286
Marketing and business development	2,624	2,350	8,886	8,486
Data processing	5,693	4,837	21,196	13,093
Amortization of acquisition intangibles	1,493	1,179	3,954	3,543
Professional services	4,267	4,156	13,575	13,675
Costs of OREO property, net	-587	-359	1,070	980
Credit and other loan related expense	4,569	5,248	11,208	13,093
Insurance	3,846	3,125	10,518	8,408
Travel and entertainment	2,290	1,912	6,745	6,199
Other expenses	8,782	7,680	24,959	26,269
Total non-interest expense	120,060	108,152	354,863	370,410
Income before income tax expense	40,930	30,549	96,306	46,193
Income tax expense	11,186	7,357	25,619	6,694
Net Income	29,744	23,192	70,687	39,499
Income Available to Common Shareholders-Basic	29,744	23,192	70,687	39,499
Earnings Allocated to Unvested Restricted Stock	-448	-425	-1,159	-744
Earnings Available to Common Shareholders-Diluted	29,296	22,767	69,528	38,755
Earnings per common share-Basic	$0.89	$0.78	$2.26	$1.34
Earnings per common share-Diluted	$0.89	$0.78	$2.25	$1.33
Cash dividends declared per common share	$0.34	$0.34	$1.02	$1.02
Unrealized gains on securities:	'	'	'	'
Unrealized holding gains (losses) arising during the period	-7,032	5,528	25,586	-38,769
Less: reclassification adjustment for (gains) losses included in net income	-582	3	-609	-2,259
Net unrealized losses/gains, Before-Tax Amount	-7,614	5,531	24,977	-41,028
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	'	'	'	952
Less: reclassification adjustment for losses (gains) included in net income	'	'	'	392
Fair value of derivative instruments designated as cash flow hedges, before tax	'	'	'	1,344
Other comprehensive income (loss), before tax	-7,614	5,531	24,977	-39,684
Income tax expense (benefit) related to items of other comprehensive (loss) income	-2,665	1,936	8,742	-13,890
Other comprehensive income (loss), net of tax	-4,949	3,595	16,235	-25,794
Comprehensive income (loss)	$24,795	$26,787	$86,922	$13,705

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity (USD $)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning balance at Dec. 31, 2012	$1,529,868	$31,917	$1,176,180	$411,472	$24,477	($114,178)
Beginning balance, Shares at Dec. 31, 2012	'	31,917,385	'	'	'	2,427,640
Net income	39,499	'	'	39,499	'	'
Other comprehensive income (loss)	-25,794	'	'	'	-25,794	'
Cash dividends declared, $1.02 per share	-30,307	'	'	-30,307	'	'
Reissuance of treasury stock under incentive plans, net of shares surrendered in payment, including tax benefit	4,003	'	-966	'	'	4,969
Reissuance of treasury stock under incentive plans, Shares	'	'	'	'	'	-94,949
Treasury stock issued for recognition and retention plans	'	'	-8,016	'	'	8,016
Treasury stock issued for recognition and retention plans, Shares	'	'	'	'	'	-149,765
Share-based compensation cost	7,999	'	7,999	'	'	'
Ending balance at Sep. 30, 2013	1,525,268	31,917	1,175,197	420,664	-1,317	-101,193
Ending balance, Shares at Sep. 30, 2013	'	31,917,385	'	'	'	2,182,926
Beginning balance at Dec. 31, 2013	1,530,979	31,917	1,178,284	436,141	-16,491	-98,872
Beginning balance, Shares at Dec. 31, 2013	'	31,917,385	'	'	'	2,130,841
Net income	70,687	'	'	70,687	'	'
Other comprehensive income (loss)	16,235	'	'	'	16,235	'
Cash dividends declared, $1.02 per share	-32,943	'	'	-32,943	'	'
Reissuance of treasury stock under incentive plans, net of shares surrendered in payment, including tax benefit	8,998	'	2,168	'	'	6,830
Reissuance of treasury stock under incentive plans, Shares	'	'	'	'	'	-180,423
Common stock issued for acquisitions	214,665	3,346	211,319	'	'	'
Common stock issued for acquisitions, Shares	'	3,345,516	'	'	'	'
Treasury stock issued for recognition and retention plans	'	'	-6,080	'	'	6,080
Treasury stock issued for recognition and retention plans, Shares	'	'	'	'	'	-128,376
Share-based compensation cost	8,927	'	8,927	'	'	'
Ending balance at Sep. 30, 2014	$1,817,548	$35,263	$1,394,618	$473,885	($256)	($85,962)
Ending balance, Shares at Sep. 30, 2014	'	35,262,901	'	'	'	1,822,042

Consolidated_Statements_of_Sha1

Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash dividends declared per share	$1.02	$1.02
Retained Earnings [Member]	'	'
Cash dividends declared per share	$1.02	$1.02

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Cash Flows from Operating Activities	'	'
Net income	$70,687	$39,499
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	12,190	19,851
Amortization of purchase accounting adjustments, net	7,899	-1,186
Provision for loan losses	12,565	445
Share-based equity compensation expense	8,927	7,999
Loss (Gain) on sale of assets, net	7	-51
Gain on sale of available for sale investments	-609	-2,259
Gain on sale of OREO, net	-3,253	-5,211
Loss on abandonment of fixed assets	'	4,941
Impairment of FDIC loss share receivables	5,097	31,813
Amortization of premium/discount on investments	10,248	15,426
Derivative (gains) losses on swaps	1	-209
(Benefit) provision for deferred income taxes	-24,328	-7,802
Originations of mortgage loans held for sale	-1,218,684	-1,712,557
Proceeds from sales of mortgage loans held for sale	1,234,694	1,923,455
Gain on sale of mortgage loans held for sale, net	-41,412	-51,709
Tax benefit associated with share-based payment arrangements	-1,163	-495
Decrease (Increase) in other assets	21,553	-15,759
Other operating activities, net	-14,634	30,079
Net Cash Provided by Operating Activities	79,785	276,270
Cash Flows from Investing Activities	'	'
Proceeds from sales of securities available for sale	20,531	44,672
Proceeds from maturities, prepayments and calls of securities available for sale	413,069	618,059
Purchases of securities available for sale	-540,197	-935,341
Proceeds from maturities, prepayments and calls of securities held to maturity	32,880	54,372
Purchases of securities held to maturity	'	-5,901
Reimbursement of recoverable covered asset losses (to) from the FDIC	-457	56,311
Increase in loans receivable, net	-476,329	-595,315
Proceeds from sale of premises and equipment	6,217	7,371
Purchases of premises and equipment	-26,587	-12,592
Proceeds from disposition of real estate owned	69,124	76,150
Investment in tax credit entities	-10,384	-1,696
Cash received in excess of cash paid for acquisition	188,803	'
Other investing activities, net	-16,073	8,963
Net Cash Used in Investing Activities	-339,403	-684,947
Cash Flows from Financing Activities	'	'
Increase in deposits, net of deposits acquired	497,970	202,959
Net change in short-term borrowings, net of borrowings acquired	77,338	-44,196
Proceeds from long-term debt	4,637	2,230
Repayments of long-term debt	-21,012	-143,625
Dividends paid to shareholders	-31,701	-30,223
Proceeds from sale of treasury stock for stock options exercised	11,141	5,441
Payments to repurchase common stock	-3,307	-1,933
Common stock issued	'	'
Tax benefit associated with share-based payment arrangements	1,163	495
Net Cash Provided by (Used in) Financing Activities	536,229	-8,852
Net Increase (Decrease) In Cash and Cash Equivalents	276,611	-417,529
Cash and Cash Equivalents at Beginning of Period	391,396	970,977
Cash and Cash Equivalents at End of Period	668,007	553,448
Supplemental Schedule of Noncash Activities	'	'
Acquisition of real estate in settlement of loans	20,219	82,383
Common stock issued in acquisition	214,665	'
Transfers of property into Other Real Estate	30,442	82,383
Supplemental Disclosures Cash paid for:	'	'
Interest on deposits and borrowings	30,984	36,888
Income taxes, net	$42,933	$19,891

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	NOTE 1 – BASIS OF PRESENTATION
	The accompanying unaudited consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include information or footnotes necessary for a complete presentation of financial position, results of operations and cash flows in conformity with generally accepted accounting principles. These interim financial statements should be read in conjunction with the audited consolidated financial statements and note disclosures for IBERIABANK Corporation (the “Company”) previously filed with the Securities and Exchange Commission (the “SEC”) in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
	PRINCIPLES OF CONSOLIDATION
	The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, IBERIABANK, Lenders Title Company (“LTC”), IBERIA Capital Partners L.L.C. (“ICP”), IB Aircraft Holdings, LLC, 1887 Leasing LLC, IBERIA Asset Management, Inc. (“IAM”), and IBERIA CDE, L.L.C. (“CDE”). All significant intercompany balances and transactions have been eliminated in consolidation. All normal, recurring adjustments which, in the opinion of management, are necessary for a fair presentation of the financial statements have been included. Certain amounts reported in prior periods have been reclassified to conform to the current period presentation.
	NATURE OF OPERATIONS
	The Company offers commercial and retail banking products and services to customers throughout locations in six states through IBERIABANK. The Company also operates mortgage production offices in twelve states through IBERIABANK Mortgage Company (“IMC”), and offers a full line of title insurance and closing services throughout Arkansas and Louisiana through LTC and its subsidiaries. ICP provides equity research, institutional sales and trading, and corporate finance services. 1887 Leasing LLC owns an aircraft used by management of the Company, and IB Aircraft Holdings, LLC owns a fractional share of a separate aircraft also used by management. IAM provides wealth management and trust services for commercial and private banking clients. CDE is engaged in the purchase of tax credits.
	USE OF ESTIMATES
	The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Material estimates that are susceptible to significant change in the near term are the allowance for credit losses, valuation of and accounting for loans covered by loss sharing arrangements with the FDIC and the related loss share receivables, valuation of and accounting for acquired loans, and valuation of goodwill, intangible assets and other purchase accounting adjustments.
	CONCENTRATION OF CREDIT RISKS
	Most of the Company’s business activity is with customers located within the States of Louisiana, Florida, Arkansas, Alabama, Texas, and Tennessee. The Company’s lending activity is concentrated in its market areas in those states. The Company has emphasized originations of commercial loans and private banking loans, defined as loans to larger consumer 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 value of the collateral upon default of the borrowers. The Company does not have any significant concentrations to any one industry or customer.
	FAIR VALUE MEASUREMENTS
	The Company estimates fair value based on the assumptions market participants would use when selling an asset or transferring a liability and characterizes such measurements within the fair value hierarchy based on the inputs used to develop those assumptions and measure fair value. The hierarchy requires the Company to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows:

		•	Level 1—Quoted prices in active markets for identical assets or liabilities.

		•	Level 2—Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

		•	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
	A description of the valuation methodologies used for instruments measured at fair value follows, as well as the classification of such instruments within the valuation hierarchy.

	Investment securities
	Securities are classified within Level 1 where quoted market prices are available in an active market. Inputs include securities that have quoted prices in active markets for identical assets. If quoted market prices are unavailable, fair value is estimated using quoted prices of securities with similar characteristics, at which point the securities would be classified within Level 2 of the hierarchy. Examples may include certain collateralized mortgage and debt obligations.
	Mortgage loans held for sale
	Mortgage loans originated and held for sale are recorded at fair value under the fair value option, unless otherwise noted. When determining the fair value of loans held for sale, the Company obtains quotes or bids on these loans directly from the purchasing financial institutions (Level 2). See Note 17 for additional information related to mortgage loans held for sale.
	Impaired loans
	Loans are measured for impairment using the methods permitted by Accounting Standards Codification (‘‘ASC’’) Topic 310. Fair value measurements are used in determining impairment using either the loan’s observable market price (Level 1), if available, or the fair value of the collateral if the loan is collateral dependent (Level 2). Measuring the impairment of loans using the present value of expected future cash flows, discounted at the loan’s effective interest rate, is not considered a fair value measurement. Fair value of the collateral is determined by appraisals or independent valuation.
	Other real estate owned (OREO)
	Fair values of OREO at September 30, 2014 and December 31, 2013 are determined by sales agreement or appraisal, and costs to sell are based on estimation per the terms and conditions of the sales agreement or amounts commonly used in real estate transactions. Inputs include appraisal values on the properties or recent sales activity for similar assets in the property’s market, and thus OREO measured at fair value would be classified within Level 2 of the hierarchy. The Company included property write-downs of $0.5 million and $1.4 million in earnings for the three months ended September 30, 2014 and 2013, respectively, and $1.9 million and $4.0 million for the nine months ended September 30, 2014 and 2013, respectively.
	Derivative financial instruments
	The Company enters into commitments to originate loans whereby the interest rate on the prospective loan is determined prior to funding. Rate lock commitments on mortgage loans that are intended to be sold are considered to be derivatives. The Company offers its customers a certificate of deposit that provides the purchaser a guaranteed return of principal at maturity plus potential return, which allows the Company to identify a known cost of funds. The rate of return is based on an equity index, and as such represents an embedded derivative. Fair value of interest rate swaps, interest rate lock commitments, forward sales contracts, and equity-linked written and purchased options are estimated using prices of financial instruments with similar characteristics, and thus are classified within Level 2 of the fair value hierarchy. See Note 12 for further discussion and details related to derivative financial instruments.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	9 Months Ended
Recent Accounting Pronouncements	Sep. 30, 2014
Accounting Changes and Error Corrections [Abstract]	'
Recent Accounting Pronouncements	'

	NOTE 2 – RECENT ACCOUNTING PRONOUNCEMENTS

	ASU No. 2014-01

	In January 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-01, Investments – Equity Method and Joint Ventures, in order to provide guidance on accounting for investments in flow-through limited liability entities that manage or invest in affordable housing projects that qualify for low-income housing tax credit (“LIHTC”). Through the Company’s investments in these entities, the Company receives tax credits and/or tax deductions from operating losses, which are allowable on the Company’s filed income tax returns over a 10-year period, subject to recapture over a 15-year period beginning with the first year the tax credits are earned.

	Under current U.S. generally accepted accounting principles (“U.S. GAAP”), the Company may elect to account for the investments using the effective yield method if certain conditions are met, and if they are not met, the investments are accounted for under either the equity method or the cost method. The Company currently accounts for its investments under the equity method. Alternatively, the provisions of ASU No. 2014-01 permit the Company to make an accounting policy election to account for its investments in LIHTC entities using the proportional amortization method if certain conditions are met. Under the proportional amortization method, the Company would amortize the initial cost of the investment in proportion to the tax credits and other tax benefits received and recognize the net investment performance in the Company’s consolidated statements of comprehensive income as a component of income tax expense or benefit. ASU No. 2014-01 would also require the Company to disclose information that enables users of the consolidated financial statements to understand the nature of the Company’s investments, the measurement of these investments, and their effect on the Company’s financial position and results of operations.

	ASU No. 2014-01 is effective beginning with the Company’s first quarter ending March 31, 2015, with early adoption permitted. If adopted, the provisions of ASU No. 2014-01 would be applied retrospectively to all financial statement periods presented. The Company is currently assessing the effect that a change in accounting policy would have on its consolidated financial statements, but does not anticipate that the potential accounting policy change to the proportional amortization method would be material to the financial condition, results of operations, or liquidity of the Company. The expanded disclosures required by ASU No. 2014-01 will be incorporated in the Company’s future consolidated financial statements upon adoption.

	ASU No. 2014-04

	In January 2014, the FASB issued ASU No. 2014-04, Receivables-Troubled Debt Restructurings by Creditors: Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans Upon Foreclosure, in order to clarify when a creditor should reclassify mortgage loans collateralized by residential real estate from their loan portfolio to other real estate owned (“OREO”) upon foreclosure. ASU No. 2014-04 clarifies that an in-substance repossession or foreclosure has occurred when either the creditor obtains legal title to the property or the borrower conveys all interest in the property to the creditor to satisfy the loan through completion of a deed in-lieu-of foreclosure or similar legal agreement. Additionally, ASU No. 2014-04 requires the Company to disclose both the amount of foreclosed residential real estate property held and the investment in consumer mortgage loans collateralized by residential real estate that are in the process of foreclosure.

	ASU No. 2014-04 is effective beginning with the Company’s first quarter ending March 31, 2015, with early adoption permitted. When adopting the provisions of ASU No. 2014-04, the Company could apply the provisions using either a prospective transition method or a modified retrospective method. The Company is currently assessing the effect that the adoption would have on its consolidated financial statements, but does not anticipate that adoption would materially affect the Company’s financial condition, results of operations, or liquidity. The expanded disclosures required by this ASU will be incorporated in the Company’s future consolidated financial statements upon adoption.

	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. As part of that principle, the entity should identify the contract(s) with the customer, identify the performance obligations of the contract, determine the transaction price, allocate that transaction price to the performance obligation(s) of the contract, and then recognize revenue when or as the entity satisfies the performance obligation(s).

	ASU No. 2014-09 is effective beginning with the Company’s first quarter ending March 31, 2017. The Company is currently assessing the effect the adoption of this ASU will have on its consolidated financial statements, but the Company does not expect adoption will have a significant impact on the Company’s consolidated financial statements.

	ASU No. 2014-11

	In June 2014, the FASB issued ASU No. 2014-11, Repurchase-to-Maturity Transactions, Repurchase Financings, and Disclosure, which will implement two accounting changes.

	ASU No. 2014-11 changes the accounting for repurchase-to-maturity transactions to secured borrowing accounting. For repurchase financing arrangements, ASU 2014-11 requires separate accounting for a transfer of a financial asset executed contemporaneously with a repurchase agreement with the same counterparty, which will result in secured borrowing accounting for the repurchase agreement. The amendments in ASU 2014-11 also require certain disclosures for transfer of financial assets and repurchase agreements.

	ASU 2014-11 is effective beginning with the Company’s first quarter ending March 31, 2015. Early adoption is not permitted. Changes will be applied as a cumulative-effect adjustment to retained earnings at the beginning of the adoption period. The disclosures of certain transactions accounted for as a sale is required to be presented beginning with the Company’s first quarter ending March 31, 2015. The company is currently assessing the effect that the adoption of this ASU will have on its Consolidated financial statements, but the Company does not expect that such adoption will have a significant impact on the Company’s consolidated financial statements.

	ASU No. 2014-14

	In August 2014, the FASB issued ASU No. 2014-14, Receivables- Troubled Debt Restructurings by Creditors: Classification of Certain Government-Guaranteed Mortgage Loans Upon Foreclosure, in order to clarify how creditors classify government-guaranteed mortgage loans upon foreclosure, including loans guaranteed by the Federal Housing Administration (“FHA”) of the U.S. Department of Housing and Urban Development and the U.S. Department of Veteran Affairs (“VA”).

	ASU No. 2014-14 clarifies that a mortgage loan should be derecognized and that a separate other receivable be recognized upon foreclosure in creditor financial statements if 1) the loan has a government guarantee that is not separable from the loan before foreclosure, 2) at the time of foreclosure the creditor has the intent to convey the real estate property to the guarantor and make a claim on the guarantee, and 3) at the time of foreclosure, any amount of the claim that is determined on the basis of the fair value of the real estate is fixed. Upon foreclosure, the separate other receivable should be measured based on the amount of the loan balance, including principal and interest, expected to be recovered from the guarantor.

	ASU No. 2014-14 is effective beginning with the Company’s first quarter ending March 31, 2015, using either a prospective transition method (application of the amendments of the ASU to foreclosures occurring after the adoption date) or modified retrospective transition method (by means of a cumulative-effect adjustment through a reclassification to a separate other receivable). The Company is currently assessing the effect that the adoption of this ASU will have on its consolidated financial statements, but the Company does not expect that such adoption will have a significant impact on the Company’s consolidated financial statements.

Earnings_Per_Share

Earnings Per Share	9 Months Ended
Earnings Per Share	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	NOTE 3 – EARNINGS PER SHARE
	Share-based payment awards that entitle holders to receive non-forfeitable dividends before vesting are considered participating securities and thus included in the calculation of basic earnings per share. These awards are included in the calculation of basic earnings per share under the two-class method. The two-class method allocates earnings for the period between common shareholders and other participating securities holders. The participating awards receiving dividends will be allocated the same amount of income as if they were outstanding shares.
	The following table presents the calculation of basic and diluted earnings per share for the periods indicated.


			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2014			2013			2014			2013
	Income available to common shareholders		$	29,744		$	23,192		$	70,687		$	39,499
	Distributed earnings (capital) to unvested restricted stock			(444	)		(421	)		(1,134	)		(744	)

	Distributed earnings (capital) to common shareholders—basic			29,300			22,771			69,553			38,755
	Undistributed earnings reallocated to unvested restricted stock			(4	)		(4	)		(25	)		—

	Distributed and undistributed earnings to common shareholders—diluted		$	29,296		$	22,767		$	69,528		$	38,755

	Weighted average shares outstanding—basic (1)			33,309,881			29,631,799			31,316,267			29,582,081
	Weighted average shares outstanding—diluted			32,926,969			29,147,232			30,923,050			29,062,238
	Earnings per common share—basic		$	0.89		$	0.78		$	2.26		$	1.34
	Earnings per common share—diluted			0.89			0.78			2.25			1.33
	Earnings per unvested restricted stock share—basic			0.88			0.77			2.16			1.33
	Earnings per unvested restricted stock share—diluted			0.89			0.78			2.21			1.33

	-1	Weighted average basic shares outstanding include 506,464 and 547,155 shares of unvested restricted stock for the three months ended September 30, 2014 and 2013, respectively, and 525,441 and 559,556 shares for the nine months ended September 30, 2014 and 2013, respectively.

	Additional information on the Company’s basic earnings per common share is shown in the following table.


			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2014			2013			2014			2013
	Distributed earnings to common shareholders		$	11,200		$	9,926		$	32,430		$	29,736
	Undistributed earnings (distributed capital) to common shareholders			18,100			12,845			37,123			9,019

	Total earnings to common shareholders		$	29,300		$	22,771		$	69,553		$	38,755
	Distributed earnings to unvested restricted stock		$	170		$	183		$	529		$	571
	Undistributed earnings (distributed capital) to unvested restricted stock			274			238			605			173

	Total earnings allocated to restricted stock		$	444		$	421		$	1,134		$	744
	Distributed earnings per common share		$	0.34		$	0.34		$	1.05		$	1.03
	Undistributed earnings (distributed capital) per common share			0.55			0.44			1.21			0.31

	Total earnings per common share—basic		$	0.89		$	0.78		$	2.26		$	1.34
	Distributed earnings per unvested restricted stock share		$	0.34		$	0.34		$	1.01		$	1.02
	Undistributed earnings (distributed capital) per unvested restricted stock share			0.54			0.43			1.15			0.31

	Total earnings per unvested restricted stock share—basic		$	0.88		$	0.77		$	2.16		$	1.33
	For the three months ended September 30, 2014 and 2013, the calculations for basic shares outstanding exclude the weighted average shares owned by the Recognition and Retention Plan (“RRP”) of 621,341 and 642,764, respectively, and are adjusted for the weighted average shares in treasury stock of 1,838,144 and 2,189,978, respectively. For the nine months ended September 30, 2014 and 2013, basic shares outstanding exclude 630,320 and 645,793 shares owned by the RRP, respectively, and are adjusted for 1,901,277 and 2,249,068 shares, respectively, of weighted average shares of treasury stock.
	The effects from the assumed exercises of 12,765 and 402,344 stock options were not included in the computation of diluted earnings per share for the three months ended September 30, 2014 and 2013, respectively, because such amounts would have had an antidilutive effect on earnings per common share. For the nine months ended September 30, 2014 and 2013, the effects from the assumed exercise of 12,765 and 678,604 stock options, respectively, was not included in the computation of diluted earnings per share because such amounts would have had an antidilutive effect on earnings per common share.

Acquisition_Activity

Acquisition Activity	9 Months Ended
Acquisition Activity	Sep. 30, 2014
Business Combinations [Abstract]	'
Acquisition Activity	'
	NOTE 4 –ACQUISITION ACTIVITY
	Acquisition of Certain Assets and Liabilities of Trust One Bank
	On January 17, 2014, IBERIABANK acquired certain assets and assumed certain liabilities of the Memphis, Tennessee operations of Trust One Bank, a division of Synovus Bank (hereby referred to as “Trust One-Memphis”). Under terms of the agreement, Synovus Bank paid IBERIABANK $91.6 million in cash to acquire four Trust One-Memphis branches in the Memphis, Tennessee market, which resulted in goodwill of $8.6 million. With this acquisition, IBERIABANK expanded its presence in the Memphis, Tennessee Metropolitan Statistical Area (“MSA”) through the addition of four branches and an experienced in-market team that enhances IBERIABANK’s ability to compete in that market.

	Acquisition of Teche Holding Company
	On May 31, 2014, the Company acquired Teche Holding Company (“Teche”), the holding company of Teche Federal Bank, a New Iberia, Louisiana-based commercial bank servicing south Louisiana. Under terms of the agreement, for each share of Teche stock outstanding, Teche shareholders received 1.162 shares of the Company’s common stock, as well as a cash payment for any fractional share and unexercised option to purchase Teche stock. The Company acquired all of the outstanding common stock of the former Teche shareholders for total consideration of $156.7 million, which resulted in goodwill of $84.8 million, as shown in the table below. With this acquisition, IBERIABANK expanded its presence in the Acadiana region of Louisiana through the addition of 20 branches and an experienced in-market team that enhances IBERIABANK’s ability to compete in that market. The Company projects cost savings will be recognized in future periods through the elimination of redundant operations. The following summarizes consideration paid and a preliminary allocation of purchase price to net assets acquired.


	(Dollars in thousands)		Number of Shares			Amount
	Equity consideration
	Common stock issued			2,498,007		$	156,026

	Total equity consideration						156,026
	Non-Equity consideration
	Cash						714

	Total consideration paid						156,740
	Fair value of net assets assumed including identifiable intangible assets						71,954

	Goodwill					$	84,786
	Acquisition of First Private Holdings, Inc.
	On June 30, 2014, the Company acquired First Private Holdings, Inc. (“First Private”), the holding company of First Private Bank of Texas, a Dallas, Texas-based commercial bank with four branch locations, including two mobile branches. Under terms of the agreement, for each share of First Private stock outstanding, First Private shareholders received 0.27 of a share of the Company’s common stock, as well as a cash payment for any fractional share. The Company acquired all of the outstanding common stock of the former First Private shareholders for total consideration of $58.6 million, which resulted in goodwill of $30.6 million, as shown in the table below. With this acquisition, IBERIABANK expanded its presence into the Dallas, Texas MSA through the addition of branches and an experienced in-market team. The Company projects cost savings will be recognized in future periods through the elimination of redundant operations. The following summarizes consideration paid and a preliminary allocation of purchase price to net assets acquired.


	(Dollars in thousands)		Number of Shares			Amount
	Equity consideration
	Common stock issued			847,509		$	58,639

	Total equity consideration						58,639
	Non-Equity consideration
	Cash						1

	Total consideration paid						58,640
	Fair value of net liabilities assumed including identifiable intangible assets						28,029

	Goodwill					$	30,611
	The Company accounted for the aforementioned business combinations as purchase business combinations. Accordingly, the purchase price is allocated to the fair value of the assets acquired and liabilities assumed as of the date of acquisition. The following purchase price allocations on these acquisitions are preliminary and will be finalized upon the receipt of final valuations on certain assets and liabilities. Upon receipt of final fair value estimates, which must be within one year of the acquisition dates, the Company will make any final adjustments to the purchase price allocation and retrospectively adjust any goodwill recorded. Material adjustments to acquisition date estimated fair values would be recorded in the period in which the acquisition occurred, and as a result, previously reported results are subject to change. Information regarding the Company’s loan discount and related deferred tax asset, core deposit intangible asset and related deferred tax liability, as well as income taxes payable and the related deferred tax balances, recorded in the acquisitions may be adjusted as the Company refines its estimates of the current and deferred tax balances acquired, as well as the fair values of loans acquired, core deposit intangible asset, and the deferred tax assets or liabilities created from the acquisition. Determining the fair value of assets and liabilities, particularly illiquid assets and liabilities, is a complicated process involving significant judgment regarding estimates and assumptions used to calculate estimated fair value. Fair value adjustments based on updated estimates could materially affect the goodwill recorded on the acquisition. The Company may incur losses on the acquired loans that are materially different from losses the Company originally projected.

	The acquired assets and liabilities, as well as the preliminary adjustments to record the assets and liabilities at their estimated fair values, are presented in the following tables.


	Trust One - Memphis					Preliminary
						Fair Value				As recorded by
	(Dollars in thousands)		As Acquired			Adjustments				IBERIABANK
	Assets
	Cash and cash equivalents		$	92,060		$	—			$	92,060
	Loans			88,179			(1,726	)(1)			86,453
	Other real estate owned			1,325			—				1,325
	Core deposit intangible			—			2,597	(2)			2,597
	Other assets			368			—				368

	Total Assets		$	181,932		$	871			$	182,803
	Liabilities
	Interest-bearing deposits		$	164,942		$	—			$	164,942
	Non-interest-bearing deposits			26,373			—				26,373
	Deferred tax liability			—			—				—
	Other liabilities			84			—				84

	Total Liabilities		$	191,399		$	—			$	191,399
	Explanation of certain fair value adjustments
	(1)	The amount represents the adjustment of the book value of Trust One-Memphis loans to their estimated fair value based on current interest rates and expected cash flows, which includes estimates of expected credit losses inherent in the portfolio.
	(2)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.


Teche					Preliminary
					Fair Value				As recorded by
(Dollars in thousands)		As Acquired			Adjustments				IBERIABANK
Assets
Cash and cash equivalents		$	71,611		$	—			$	71,611
Investment securities			24,077			1,092	(1)			25,169
Loans			716,196			(16,636	)(2)			699,560
Other real estate owned			329			(153	)(3)			176
Core deposit intangible			—			2,055	(4)			2,055
Deferred tax asset			1,057			7,337	(5)			8,394
Other assets			56,752			(6,261	)(6)			50,491

Total Assets		$	870,022		$	(12,566	)		$	857,456
Liabilities
Interest-bearing deposits		$	520,446		$	902	(7)		$	521,348
Non-interest-bearing deposits			118,256			—				118,256
Borrowings			134,228			6,304	(8)			140,532
Other liabilities			5,366			—				5,366

Total Liabilities		$	778,296		$	7,206			$	785,502
Explanation of certain fair value adjustments
(1)	The amount represents the adjustment to the book value of Teche’s investments to their estimated fair value based on fair values on the date of acquisition.
(2)	The amount represents the adjustment of the book value of Teche loans to their estimated fair value based on current interest rates and expected cash flows, which includes estimates of expected credit losses inherent in the portfolio.
(3)	The amount represents the adjustment to the book value of Teche’s OREO to their estimated fair value on the date of acquisition.
(4)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.
(5)	The amount represents the deferred tax asset recognized on the fair value adjustment of Teche acquired assets and assumed liabilities.
(6)	The amount represents the write down of the book value of Teche’s property, equipment, and other assets to their estimated fair value at the acquisition date based on their appraised value.
(7)	The adjustment is necessary because the weighted average interest rate of Teche’s deposits exceeded the cost of similar funding at the time of acquisition. The fair value adjustment will be amortized to reduce future interest expense over the life of the portfolio, which is estimated at 85 months.
(8)	The adjustment is necessary because the interest rate of Teche’s borrowings exceeded current interest rates on similar borrowings.


First Private					Preliminary
					Fair Value				As recorded by
(Dollars in thousands)		As Acquired			Adjustments				IBERIABANK
Assets
Cash and cash equivalents		$	26,621		$	—			$	26,621
Investment securities			18,920			297	(1)			19,217
Loans			295,736			(910	)(2)			294,826
Other real estate owned			—			—				—
Core deposit intangible			—			506	(3)			506
Deferred tax asset (liability)			530			122	(4)			652
Other assets			5,230			—				5,230

Total Assets		$	347,037		$	15			$	347,052
Liabilities
Interest-bearing deposits		$	261,713		$	220	(5)		$	261,933
Non-interest-bearing deposits			50,333			—				50,333
Borrowings			6,451			—				6,451
Other liabilities			306			—				306

Total Liabilities		$	318,803		$	220			$	319,023
Explanation of certain fair value adjustments
(1)	The amount represents the adjustment to the book value of First Private’s investments to their estimated fair value based on fair values on the date of acquisition.
(2)	The amount represents the adjustment of the book value of First Private loans to their estimated fair value based on current interest rates and expected cash flows, which includes estimates of expected credit losses inherent in the portfolio.
(3)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.
(4)	The amount represents the deferred tax liability recognized on the fair value adjustment of First Private acquired assets and assumed liabilities.
(5)	The adjustment is necessary because the weighted average interest rate of First Private’s deposits exceeded the cost of similar funding at the time of acquisition. The fair value adjustment will be amortized to reduce future interest expense over the life of the portfolio, which is estimated at 85 months.

Acquisitions of LTC
On February 24, 2014, the Company’s subsidiary, LTC, acquired the assets of The Title Company LLC. Under terms of the agreement, LTC paid $0.4 million in cash to acquire a title office in Baton Rouge, Louisiana, which resulted in goodwill of $0.2 million.
On May 1, 2014, LTC acquired the assets of Louisiana Abstract and Title, LLC. Under terms of the agreement, LTC paid $0.2 million in cash to acquire a title office in Shreveport, Louisiana. In addition, the agreement provides for potential additional cash consideration based on earnings over a four-year period after the acquisition.
The acquisitions were accounted for under the purchase method of accounting in accordance with ASC Topic 805. Purchased assets were recorded at their acquisition date fair values. Identifiable intangible assets were recorded at fair value. Because the consideration paid was greater than the net fair value of the acquired assets, the Company recorded goodwill as part of the acquisitions. The goodwill recognized was the result of LTC’s expanded presence into the Baton Rouge and Shreveport Louisiana MSAs and experienced in-market teams that enhance its ability to compete in those markets. As part of the acquisitions, LTC also acquired or created the following other assets:


					Louisiana Abstract and Title
(Dollars in thousands)		The Title Company LLC			LLC
Goodwill		$	221		$	155
Non-compete agreement			63			100
Title plant			14			9
Other intangible assets			75			130
Other assets			3			6

Total Assets		$	376		$	400
Supplemental unaudited pro forma information
The following unaudited pro forma information for the nine months ended September 30, 2013 reflects the Company’s estimated consolidated results of operations as if the acquisitions of Trust One-Memphis, Teche, and First Private occurred at January 1, 2013, unadjusted for potential cost savings and preliminary purchase price adjustments.


(Dollars in thousands, except per share data)		2013
Interest and non-interest income		$	500,638
Net income			46,139
Earnings per share—basic			1.4
Earnings per share—diluted			1.4
The Company’s consolidated financial statements as of and for the nine months ended September 30, 2014 include the operating results of the acquired assets and assumed liabilities for the days subsequent to the respective acquisition dates. Due to the system conversion of the acquired entities throughout the current nine-month period and subsequent integration of the operating activities of the acquired branches into existing Company markets, historical reporting for the former Trust One-Memphis, Teche, and First Private branches 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.

Investment_Securities

Investment Securities	9 Months Ended
Investment Securities	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Investment Securities	'
	NOTE 5 – INVESTMENT SECURITIES
	The amortized cost and fair values of investment securities, with gross unrealized gains and losses, consist of the following:


			September 30, 2014
							Gross			Gross				Estimated
			Amortized				Unrealized			Unrealized				Fair
	(Dollars in thousands)		Cost				Gains			Losses				Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations		$	359,404			$	1,465		$	(5,926	)		$	354,943
	Obligations of state and political obligations			87,895				3,891			—				91,786
	Mortgage-backed securities			1,656,341				11,613			(12,338	)			1,655,616
	Other securities			1,460				23			—				1,483

	Total securities available for sale		$	2,105,100			$	16,992		$	(18,264	)		$	2,103,828
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations		$	10,000			$	157		$	—			$	10,157
	Obligations of state and political obligations			79,309				3,044			(266	)			82,087
	Mortgage-backed securities			31,211				197			(1,194	)			30,214

	Total securities held to maturity		$	120,520			$	3,398		$	(1,460	)		$	122,458

			31-Dec-13
							Gross			Gross				Estimated
			Amortized				Unrealized			Unrealized				Fair
	(Dollars in thousands)		Cost				Gains			Losses				Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations		$	406,092			$	1,382		$	(11,913	)		$	395,561
	Obligations of state and political obligations			105,300				2,435			(256	)			107,479
	Mortgage-backed securities			1,450,194				10,031			(27,947	)			1,432,278
	Other securities			1,460				19			—				1,479

	Total securities available for sale		$	1,963,046			$	13,867		$	(40,116	)		$	1,936,797
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations		$	34,478			$	484		$	—			$	34,962
	Obligations of state and political obligations			84,290				1,463			(1,624	)			84,129
	Mortgage-backed securities			35,341				258			(2,124	)			33,475

	Total securities held to maturity		$	154,109			$	2,205		$	(3,748	)		$	152,566
	Securities with carrying values of $1.4 billion and $1.5 billion were pledged to secure public deposits and other borrowings at September 30, 2014 and December 31, 2013, respectively.
	Management evaluates securities for other-than-temporary impairment at least quarterly, and more frequently when economic or market concerns warrant such evaluation. Consideration is given to 1) the length of time and extent to which the estimated fair value has been less than amortized cost, 2) the financial condition and near-term prospects of the issuer, and 3) the intent of the Company to retain the investment for a period of time sufficient to allow for any anticipated recovery in estimated fair value above amortized cost. In analyzing an issuer’s financial condition, management considers whether the securities are issued by the federal government or its agencies and whether downgrades by bond rating agencies have occurred, as well as review of issuer financial statements and industry analysts’ reports.

	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, 2014
			Less Than Twelve Months							Over Twelve Months							Total
			Gross				Estimated			Gross				Estimated			Gross				Estimated
			Unrealized				Fair			Unrealized				Fair			Unrealized				Fair
	(Dollars in thousands)		Losses				Value			Losses				Value			Losses				Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations		$	—			$	—		$	(5,926	)		$	258,521		$	(5,926	)		$	258,521
	Obligations of state and political obligations			—				186			—				—			—				186
	Mortgage-backed securities			(2,846	)			552,357			(9,492	)			333,795			(12,338	)			886,152

	Total securities available for sale		$	(2,846	)		$	552,543		$	(15,418	)		$	592,316		$	(18,264	)		$	1,144,859
	Securities held to maturity:
	Obligations of state and political obligations		$	(1	)		$	564		$	(265	)		$	10,811		$	(266	)		$	11,375
	Mortgage-backed securities			—				72			(1,194	)			24,303			(1,194	)			24,375

	Total securities held to maturity		$	(1	)		$	636		$	(1,459	)		$	35,114		$	(1,460	)		$	35,750

			31-Dec-13
		Less Than Twelve Months							Over Twelve Months							Total
		Gross				Estimated			Gross				Estimated			Gross				Estimated
		Unrealized				Fair			Unrealized				Fair			Unrealized				Fair
(Dollars in thousands)		Losses				Value			Losses				Value			Losses				Value
Securities available for sale:
U.S. Government-sponsored enterprise obligations		$	(11,764	)		$	298,515		$	(149	)		$	5,515		$	(11,913	)		$	304,030
Obligations of state and political obligations			(30	)			2,415			(226	)			1,047			(256	)			3,462
Mortgage-backed securities			(23,749	)			864,899			(4,198	)			81,870			(27,947	)			946,769

Total securities available for sale		$	(35,543	)		$	1,165,829		$	(4,573	)		$	88,432		$	(40,116	)		$	1,254,261
Securities held to maturity:
Obligations of state and political obligations		$	(1,181	)		$	29,355		$	(443	)		$	6,240		$	(1,624	)		$	35,595
Mortgage-backed securities			(952	)			12,913			(1,172	)			11,616			(2,124	)			24,529

Total securities held to maturity		$	(2,133	)		$	42,268		$	(1,615	)		$	17,856		$	(3,748	)		$	60,124
The Company assessed the nature of the losses in its portfolio as of September 30, 2014 and December, 31, 2013 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, including 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. Except for the particular municipal bond discussed below, 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.

At September 30, 2014, 162 debt securities had unrealized losses of 1.64% of the securities’ amortized cost basis and 0.89% of the Company’s total amortized cost basis. At December 31, 2013, 207 debt securities had unrealized losses of 3.23% of the securities’ amortized cost basis and 2.07% of the Company’s total amortized cost basis. The unrealized losses for each of the securities related to market interest rate changes. Additional information on securities that have been in a continuous loss position for over twelve months at September 30, 2014 and December 31, 2013 is presented in the following table.


(Dollars in thousands)		September 30, 2014				December 31, 2013
Number of securities
Issued by Fannie Mae, Freddie Mac, or Ginnie Mae			78				20
Issued by political subdivisions			6				5

			84				25
Amortized Cost Basis
Issued by Fannie Mae, Freddie Mac, or Ginnie Mae		$	633,230			$	104,520
Issued by political subdivisions			11,076				7,956

		$	644,306			$	112,476
Unrealized Loss
Issued by Fannie Mae, Freddie Mac, or Ginnie Mae		$	16,611			$	5,519
Issued by political subdivisions			265				669

		$	16,876			$	6,188
The Fannie Mae, Freddie Mac, and Ginnie Mae securities are rated AA+ by S&P and Aaa by Moodys. Six of the securities in a continuous loss position for over twelve months were issued by political subdivisions. The securities issued by political subdivisions have credit ratings by S&P ranging from A+ to AAA and credit ratings from Moody’s ranging from A2 to Aaa.
Prior to 2013, management assessed the operating environment of a bond issuer as adverse and concluded that the Company had one unrated revenue municipal bond that warranted an other-than-temporary impairment charge. The specific impairment was related to the loss of the contracted revenue source required for bond repayment. The Company determined the impairment charge using observable market data for similar assets, including third party valuation of the security, as well as information from unobservable inputs, including its best estimate of the recoverability of the amortized cost of the security as outlined above. Changes to the unobservable inputs used by the Company would have resulted in a higher or lower impairment charge, but the unobservable inputs were not highly sensitive and would not result in a material difference in the impairment charge recorded. The Company recorded total impairment of 50% of the par value of the bond and provided a fair value of the bond that was consistent with current market pricing. During the third quarter of 2014, the Company sold the municipal bond and recorded a gain of $0.6 million in the Company’s unaudited consolidated statements of comprehensive income for the three and nine months ended September 30, 2014.
During the nine months ended September 30, 2014 and 2013, there was no activity related to credit losses on the other-than temporarily impaired investment security where a portion of the unrealized loss was recognized in other comprehensive income.
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, 2014 or December 31, 2013.
The amortized cost and estimated fair value of investment securities by maturity at September 30, 2014 are shown 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
		Weighted							Estimated				Weighted							Estimated
		Average				Amortized			Fair				Average			Amortized				Fair
(Dollars in thousands)		Yield				Cost			Value				Yield			Cost				Value
Within one year or less			1.27	%		$	15,397		$	15,488				2.65	%	$	10,000			$	10,157
One through five years			1.54				241,992			241,502				2.84			12,968				13,352
After five through ten years			2.1				474,758			476,954				2.97			17,983				18,591
Over ten years			2.18				1,372,953			1,369,884				3.05			79,569				80,358

Total			2.08	%		$	2,105,100		$	2,103,828				2.98	%	$	120,520			$	122,458

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							Nine Months Ended
		September 30							September 30
(Dollars in thousands)		2014				2013			2014				2013
Realized gains		$	582			$	—		$	609			$	2,369
Realized losses			—				(3	)		—				(110	)

Net realized gains (losses)		$	582			$	(3	)	$	609			$	2,259
In addition to the gains above, the Company realized certain immaterial gains on calls of held to maturity securities.
Other Equity Securities
At September 30, 2014 and December 31, 2013, the Company included the following securities in “Other assets” on the consolidated balance sheets:


		September 30				December 31
(Dollars in thousands)		2014				2013
Federal Home Loan Bank (FHLB) stock		$	41,011			$	24,369
Federal Reserve Bank (FRB) stock			34,348				28,098
Other investments			1,306				1,306

Total		$	76,665			$	53,773

Loans_Receivable

Loans Receivable	9 Months Ended
Loans Receivable	Sep. 30, 2014
Receivables [Abstract]	'
Loans Receivable	'
	NOTE 6 – LOANS RECEIVABLE
	Loans receivable consist of the following, segregated into non-covered and covered loans, for the periods indicated:


			September 30, 2014
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	4,032,419		$	247,156		$	4,279,575
	Business			3,193,098			34,234			3,227,332

				7,225,517			281,390			7,506,907
	Residential mortgage loans:
	Residential 1-4 family			911,099			130,976			1,042,075
	Construction / Owner Occupied			27,888			—			27,888

				938,987			130,976			1,069,963
	Consumer and other loans:
	Home equity			1,458,067			107,811			1,565,878
	Indirect automobile			394,691			—			394,691
	Other			537,748			4,012			541,760

				2,390,506			111,823			2,502,329

	Total		$	10,555,010		$	524,189		$	11,079,199

			31-Dec-13
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	3,479,973		$	387,332		$	3,867,305
	Business			2,959,088			37,025			2,996,113

				6,439,061			424,357			6,863,418
	Residential mortgage loans:
	Residential 1-4 family			423,057			154,025			577,082
	Construction / Owner Occupied			9,450			—			9,450

				432,507			154,025			586,532
	Consumer and other loans:
	Home equity			1,154,670			137,122			1,291,792
	Indirect automobile			375,236			—			375,236
	Other			370,752			4,289			375,041

				1,900,658			141,411			2,042,069

	Total		$	8,772,226		$	719,793		$	9,492,019
	In 2009, the Company acquired substantially all of the assets and liabilities of CapitalSouth Bank (“CSB”), and certain assets deposits, and other liabilities of Orion Bank (“Orion”) and Century Bank (“Century”). In 2010, the Company acquired certain assets and assumed certain deposit and other liabilities of Sterling Bank (“Sterling”). Substantially all of the loans and foreclosed real estate that were acquired in these transactions are covered by loss sharing agreements between the FDIC and IBERIABANK, which afford IBERIABANK loss protection. Refer to Note 8 for additional information regarding the Company’s loss sharing agreements.
	Because of the loss protection provided by the FDIC, the risks of the CSB, Orion, Century, and Sterling loans and foreclosed real estate are significantly different from those assets not covered under the loss share agreements. Accordingly, the Company presents loans subject to the loss share agreements as “covered loans” and loans that are not subject to the loss share agreements as “non-covered loans.”
	Deferred loan origination fees were $19.4 million and $18.6 million and deferred loan expenses were $9.0 million and $7.6 million at September 30, 2014 and December 31, 2013, respectively. 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, 2014 and December 31, 2013, overdrafts of $3.7 million and $3.1 million, respectively, have been reclassified to loans receivable.
	Loans with carrying values of $2.7 billion and $2.3 billion were pledged to secure public deposits and other borrowings at September 30, 2014 and December 31, 2013, respectively.

	Non-covered Loans
	The following tables provide an analysis of the aging of non-covered loans as of September 30, 2014 and December 31, 2013. Because of the difference in accounting for acquired loans, the tables below further segregate the Company’s non-covered loans receivable between acquired loans and loans originated by the Company. For purposes of the following tables, subprime mortgage loans are defined as the Company’s mortgage loans that have FICO scores that are less than 620 at the time of origination or were purchased outside of a business combination.


			September 30, 2014
			Non-covered loans excluding acquired loans
																		Total Non-covered			Recorded
			Past Due (1)															Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Unearned Income			and Accruing
	Commercial real estate construction		$	84		$	—		$	1,317		$	1,401		$	634,593		$	635,994		$	—
	Commercial real estate—other			1,347			640			6,789			8,776			2,882,842			2,891,618			—
	Commercial business			1,475			44			2,737			4,256			3,089,617			3,093,873			—
	Residential prime			1,859			1,349			10,973			14,181			362,513			376,694			—
Residential subprime			—			2			6,197			6,199			114,182			120,381			—
Home equity			1,783			201			7,310			9,294			1,220,704			1,229,998			4
Indirect automobile			1,825			502			1,338			3,665			390,413			394,078			—
Credit card			149			123			987			1,259			67,472			68,731			—
Other			720			337			416			1,473			367,102			368,575			—

Total		$	9,242		$	3,198		$	38,064		$	50,504		$	9,129,438		$	9,179,942		$	4

		December 31, 2013
		Non-covered loans excluding acquired loans
																	Total Non-covered			Recorded
		Past Due (1)															Loans, Net of			Investment > 90 days
(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Unearned Income			and Accruing
Commercial real estate construction		$	—		$	—		$	1,803		$	1,803		$	381,292		$	383,095		$	—
Commercial real estate—other			6,098			5,630			7,650			19,378			2,732,431			2,751,809			2
Commercial business			2,117			423			15,020			17,560			2,888,491			2,906,051			—
Residential prime			1,104			852			9,684			11,640			286,167			297,807			1,073
Residential subprime			—			—			1,626			1,626			114,939			116,565			—
Home equity			1,956			569			6,808			9,333			1,091,894			1,101,227			—
Indirect automobile			1,427			293			1,275			2,995			370,388			373,383			—
Credit card			266			92			411			769			62,873			63,642			—
Other			458			106			485			1,049			293,693			294,742			—

Total		$	13,426		$	7,965		$	44,762		$	66,153		$	8,222,168		$	8,288,321		$	1,075

(1)	Past due loans include loans on nonaccrual status as of the period indicated. Nonaccrual loans are presented separately in the “Nonaccrual Loans” section below.


		September 30, 2014
		Non-covered acquired loans
																				Total Non-covered			Recorded
		Past Due (1)																		Loans, Net of			Investment > 90 days
(Dollars in		30-59 days			60-89 days			> 90 days			Total			Current			Discount/ Premium			Unearned Income			and Accruing
thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Discount/ Premium			Unearned Income			and Accruing
Commercial real estate construction		$	340		$	45		$	2,118		$	2,503		$	36,832		$	(2,061	)	$	37,274		$	1,821
Commercial real estate—other			1,464			277			22,081			23,822			486,238			(42,527	)		467,533			20,614
Commercial business			717			25			1,905			2,647			101,722			(5,144	)		99,225			1,892
Residential prime			76			931			7,437			8,444			432,837			631			441,912			369
Home equity			1,615			1,003			8,203			10,821			228,051			(10,803	)		228,069			4,102
Indirect automobile			7			1			43			51			606			(44	)		613			43
Other			337			7			2,051			2,395			109,599			(11,552	)		100,442			389

Total		$	4,556		$	2,289		$	43,838		$	50,683		$	1,395,885		$	(71,500	)	$	1,375,068		$	29,230

		December 31, 2013
		Non-covered acquired loans
																				Total Non-covered			Recorded
		Past Due (1)																		Loans, Net of			Investment > 90 days
(Dollars in		30-59 days			60-89 days			> 90 days			Total			Current			Discount/ Premium			Unearned Income			and Accruing
thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Discount/ Premium			Unearned Income			and Accruing
Commercial real estate construction		$	388		$	—		$	2,542		$	2,930		$	19,833		$	(2,532	)	$	20,231		$	2,542
Commercial real estate—other			1,798			1,963			27,967			31,728			345,286			(52,176	)		324,838			27,967
Commercial business			544			—			1,218			1,762			54,189			(2,914	)		53,037			1,218
Residential prime			—			—			226			226			18,796			(887	)		18,135			226
Home equity			313			516			4,242			5,071			53,995			(5,623	)		53,443			4,242
Indirect automobile			33			—			95			128			1,725			—			1,853			95
Other			175			101			975			1,251			12,598			(1,481	)		12,368			975

Total		$	3,251		$	2,580		$	37,265		$	43,096		$	506,422		$	(65,613	)	$	483,905		$	37,265

(1)	Past due information presents acquired loans at the gross loan balance, prior to application of discounts.
Non-accrual Loans
The following table provides the recorded investment of non-covered loans, excluding acquired loans, on non-accrual status at September 30, 2014 and December 31, 2013.


		September 30			December 31
(Dollars in thousands)		2014			2013
Commercial real estate construction		$	1,317		$	1,803
Commercial real estate—other			6,789			7,648
Commercial business			2,737			15,020
Residential prime			10,973			8,611
Residential subprime			6,197			1,626
Home equity			7,306			6,808
Indirect automobile			1,338			1,275
Credit card			987			411
Other			416			485

Total		$	38,060		$	43,687

Covered Loans
The carrying amount of the acquired covered loans at September 30, 2014 and December 31, 2013 consisted of loans determined to be impaired at the acquisition date, which are accounted for in accordance with ASC Topic 310-30, and loans that were considered to be performing at the acquisition date, accounted for by analogy to ASC Topic 310-30, as detailed in the following tables.


		September 30, 2014
		Acquired			Acquired			Total
		Impaired			Performing			Covered
(Dollars in thousands)		Loans			Loans			Loans
Commercial loans:
Real estate		$	4,678		$	242,478		$	247,156
Business			620			33,614			34,234

			5,298			276,092			281,390
Residential mortgage loans:
Residential 1-4 family			24,304			106,672			130,976
Construction / Owner Occupied			—			—			—

			24,304			106,672			130,976
Consumer and other loans:
Home equity			16,210			91,601			107,811
Indirect automobile			—			—			—
Other			489			3,523			4,012

			16,699			95,124			111,823

Total		$	46,301		$	477,888		$	524,189

		31-Dec-13
		Acquired			Acquired			Total
		Impaired			Performing			Covered
(Dollars in thousands)		Loans			Loans			Loans
Commercial loans:
Real estate		$	14,904		$	372,428		$	387,332
Business			—			37,025			37,025

			14,904			409,453			424,357
Residential mortgage loans:
Residential 1-4 family			28,223			125,802			154,025
Construction / Owner Occupied			—			—			—

			28,223			125,802			154,025
Consumer and other loans:
Home equity			21,768			115,354			137,122
Indirect automobile			—			—			—
Other			1,182			3,107			4,289

			22,950			118,461			141,411

Total		$	66,077		$	653,716		$	719,793

Loans Acquired
The Company acquired loans (both covered and non-covered) through previous acquisitions, which are subject to ASC Topic 310-30.
As discussed in Note 4, during 2014, the Company acquired loans of $86.5 million from Trust One-Memphis, $699.6 million from Teche, and $294.8 million from First Private in the current period. Acquired loans totaling $1.1 billion are accounted for under ASC Topic 310-10, while the carrying amounts of the loans acquired in the current period subject to ASC Topic 310-30 are detailed in the following table as of the purchase date. The allocation of loans acquired from both Teche and First Private between loans subject to ASC Topic 310-30 and those subject to ASC Topic 310-10 is preliminary and subject to change up to one year after the acquisition date as information on these loans becomes available.


		Acquired			Acquired			Total
		Impaired			Performing			Acquired
(Dollars in thousands)		Loans			Loans			Loans
Contractually required principal and interest at acquisition		$	82,967		$	15,130		$	98,097
Nonaccretable difference (expected losses and foregone interest)			(4,197	)		(361	)		(4,558	)

Cash flows expected to be collected at acquisition			78,770			14,769			93,539
Accretable yield			(8,242	)		(1,536	)		(9,778	)

Basis in acquired loans at acquisition		$	70,528		$	13,233		$	83,761
The following is a summary of changes in the accretable difference of acquired loans during the nine months ended September 30, 2014 and 2013.


		September 30, 2014
		Acquired			Acquired			Total
		Impaired			Performing			Acquired
(Dollars in thousands)		Loans			Loans			Loans
Balance at beginning of period		$	78,349		$	276,543		$	354,892
Acquisition			8,242			1,536			9,778
Transfers from nonaccretable difference to accretable yield			3,952			13,872			17,824
Accretion			(12,766	)		(66,590	)		(79,356	)
Changes in expected cash flows not affecting nonaccretable differences (1)			(6,873	)		(19,377	)		(26,250	)

Balance at end of period		$	70,904		$	205,984		$	276,888

		30-Sep-13
		Acquired			Acquired			Total
		Impaired			Performing			Acquired
		Loans			Loans			Loans
Balance at beginning of period		$	76,623		$	279,770		$	356,393
Transfers from nonaccretable difference to accretable yield			6,148			34,480			40,628
Accretion			(13,519	)		(119,193	)		(132,712	)
Changes in expected cash flows not affecting nonaccretable differences (1)			10,561			81,173			91,734

Balance at end of period		$	79,813		$	276,230		$	356,043

(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, 2014 and 2013 is presented in the following tables. The Company excludes as TDRs modifications of loans that are accounted for within a pool under ASC Topic 310-30, which include the covered loans above, as well as acquired loans. 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 covered and acquired loans that would otherwise meet the criteria for classification as a TDR are excluded from the tables below.


		September 30, 2014												September 30, 2013
		Accruing Loans												Accruing Loans
					Past Due			Nonaccrual									Past Due			Nonaccrual
(Dollars in thousands)		Current			> 30 days			TDRs			Total TDRs			Current			> 30 days			TDRs			Total TDRs
Commercial real estate construction		$	—		$	—		$	—		$	—		$	—			—			—			—
Commercial real estate—other			367			—			58			425			411			—			5,601			6,012
Commercial business			726			—			2,027			2,753			1,056			—			12,610			13,666
Residential prime			—			—			—			—			—			—			—			—
Residential subprime			—			—			—			—			—			—			—			—
Home equity			—			—			243			243			—			—			263			263
Indirect automobile			—			—			—			—			—			—			—			—
Credit card			—			—			—			—			—			—			—			—
Other			—			—			—			—			—			—			—			—

Total		$	1,093		$	—		$	2,328		$	3,421		$	1,467		$	—		$	18,474		$	19,941
At September 30, 2014, there were no TDRs that occurred during the first nine months through modification of the original loan terms. TDRs totaling $11.2 million occurred during the nine-month period ending September 30, 2013 and were subsequently charged off during the same period. The following table provides information on how the TDRs were modified during the nine months ended September 30:


(Dollars in thousands)		2014			2013
Extended maturities		$	—		$	—
Interest rate adjustment			—			—
Maturity and interest rate adjustment			—			—
Movement to or extension of interest-rate only payments			—			—
Forbearance			—			—
Other concession(s) (1)			—			11,210

Total		$	—		$	11,210

(1)	Other concessions include concessions or a combination of concessions that do not consist of maturity extensions, interest rate adjustments, forbearance or covenant modifications.
The Company had no commercial business, mortgage or consumer TDRs that were added during the nine month periods for September 30, 2014 and 2013. Information about the Company’s TDRs occurring in these periods is presented in the following table.


		September 30, 2014									September 30, 2013
					Pre-modification			Post-modification						Pre-modification			Post-modification
					Outstanding			Outstanding						Outstanding			Outstanding
		Number of			Recorded			Recorded			Number of			Recorded			Recorded
(In thousands, except number of loans)		Loans			Investment			Investment (1)			Loans			Investment			Investment (1)
Commercial real estate			—		$	—		$	—			5		$	12,507		$	12,329

Total			—		$	—		$	—			5		$	12,507		$	12,329

(1)	Recorded investment includes any allowance for credit losses recorded on the TDRs at the dates indicated.
Information detailing non-covered TDRs that subsequently defaulted during the previous twelve months is presented in the following table. The Company has defined a default as any loan with a loan payment that is currently past due greater than 30 days, or was past due greater than 30 days at any point during the previous twelve months, or since the date of modification, whichever is shorter.


		September 30, 2014						September 30, 2013
		Number of			Recorded			Number of			Recorded
(In thousands, except number of loans)		Loans			Investment			Loans			Investment
Commercial real estate			31		$	58			45		$	6,012
Commercial business			11			1,767			13			12,370
Residential prime			—			—			—			—
Home Equity			—			—			1			47
Indirect automobile			—			—			—			—
Credit card			—			—			—			—
Other			1			—			1			—

Total			43		$	1,825			60		$	18,429

Allowance_for_Credit_Losses_an

Allowance for Credit Losses and Credit Quality	9 Months Ended
Allowance for Credit Losses and Credit Quality	Sep. 30, 2014
Receivables [Abstract]	'
Allowance for Credit Losses and Credit Quality	'
	NOTE 7 – ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY
	Allowance for Credit Losses Activity
	A summary of changes in the allowance for credit losses for the covered loan and non-covered loan portfolios for the nine months ended September 30, 2014 and 2013 is as follows:


			September 30, 2014
			Non-covered loans
			Excluding
	(Dollars in thousands)		Acquired Loans				Acquired Loans				Covered Loans				Total
	Allowance for credit losses
	Balance at beginning of period		$	67,342			$	4,557			$	71,175			$	143,074
	(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements			9,099				(1,259	)			5,878				13,718
	Adjustment attributable to FDIC loss share arrangements			—				—				(1,153	)			(1,153	)

	Net (reversal of) provision for loan losses			9,099				(1,259	)			4,725				12,565
	Adjustment attributable to FDIC loss share arrangements			—				—				1,153				1,153
	Transfer of balance to OREO			—				(207	)			(5,171	)			(5,378	)
	Loans charged-off			(8,242	)			(586	)			(12,823	)			(21,651	)
	Recoveries			4,338				401				38				4,777

	Balance at end of period		$	72,537			$	2,906			$	59,097			$	134,540
	Reserve for unfunded lending commitments
	Balance, beginning of period		$	11,147			$	—			$	—			$	11,147
	Provision for unfunded lending commitments			952				—				—				952

	Balance at end of period		$	12,099			$	—			$	—			$	12,099

			September 30, 2013
			Non-covered loans
			Excluding
			Acquired Loans				Acquired Loans				Covered Loans				Total
	Allowance for loan losses
	Balance at beginning of period		$	74,211			$	8,816			$	168,576			$	251,603
	(Reversal of) Provision for loan losses before adjustment attributable to FDIC loss share agreements			2,884				(2,464	)			(58,540	)			(58,120	)
	Adjustment attributable to FDIC loss share arrangements			—				—				58,565				58,565

	Net (reversal of) provision for loan losses			2,884				(2,464	)			25				445
	Adjustment attributable to FDIC loss share arrangements			—				—				(58,565	)			(58,565	)
	Transfer of balance to OREO			—				(1,013	)			(29,302	)			(30,315	)
	Transfer of balance to the RULC			(9,828	)			—				—				(9,828	)
	Loans charged-off			(7,455	)			(10	)			(1,683	)			(9,148	)
	Recoveries			4,353				—				—				4,353

	Balance at end of period			64,165				5,329			$	79,051			$	148,545
	Reserve for unfunded lending commitments
	Balance, beginning of period			—				—				—				—
	Transfer of balance from the allowance for loan losses			9,828				—				—				9,828
	Provision for unfunded lending commitments			2,131				—				—				2,131

	Balance at end of period		$	11,959			$	—			$	—			$	11,959

	A summary of changes in the allowance for credit losses for non-covered loans, by loan portfolio type, for the nine months ended September 30, 2014 and 2013 is as follows:


			September 30, 2014
			Commercial				Commercial
	(Dollars in thousands)		real estate				business				Mortgage				Consumer				Unallocated			Total
	Allowance for loan losses
	Balance at beginning of period		$	26,590			$	28,515			$	2,546			$	14,248			$	—		$	71,899
	(Reversal of) Provision for loan losses			611				2,187				514				4,528				—			7,840
	Transfer of balance to OREO			—				(130	)			(12	)			(65	)			—			(207	)
	Loans charged off			(1,214	)			(1,097	)			(607	)			(5,910	)			—			(8,828	)
	Recoveries			2,209				93				134				2,303				—			4,739

Balance at end of period		$	28,196			$	29,568			$	2,575			$	15,104			$	—		$	75,443
Reserve for unfunded commitments
Balance at beginning of period		$	3,089			$	4,839			$	72			$	3,147			$	—		$	11,147
(Reversal of) Provision for unfunded commitments			726				192				11				23				—			952

Balance at end of period		$	3,815			$	5,031			$	83			$	3,170			$	—		$	12,099
Allowance on loans individually evaluated for impairment		$	25			$	—			$	—			$	—			$	—		$	25
Allowance on loans collectively evaluated for impairment			28,171				29,568				2,575				15,104				—			75,418
Loans, net of unearned income:
Balance at end of period		$	4,032,419			$	3,193,098			$	938,987			$	2,390,506			$	—		$	10,555,010
Balance at end of period individually evaluated for impairment			7,357				3,276				—				706				—			11,339
Balance at end of period collectively evaluated for impairment			4,025,062				3,189,822				938,987				2,389,800				—			10,543,671
Balance at end of period acquired with deteriorated credit quality			15,061				2,562				160				1,707				—			19,490

		September 30, 2013
		Commercial				Commercial
(Dollars in thousands)		real estate				business				Mortgage				Consumer				Unallocated			Total
Allowance for credit losses
Balance at beginning of period		$	38,264			$	28,721			$	2,125			$	13,917			$	—		$	83,027
(Reversal of) Provision for loan losses			(6,926	)			(582	)			1,048				6,880				—			420
Transfer of balance to OREO			(279	)			(81	)			(646	)			(7	)			—			(1,013	)
Transfer of balance to the RULC			(2,939	)			(3,497	)			(40	)			(3,352	)			—			(9,828	)
Loans charged off			(1,966	)			(531	)			(481	)			(4,487	)			—			(7,465	)
Recoveries			1,498				354				698				1,803				—			4,353

Balance at end of period		$	27,652			$	24,384			$	2,704			$	14,754			$	—		$	69,494
Reserve for unfunded commitments
Balance at beginning of period		$	—			$	—			$	—			$	—			$	—		$	—
Transfer of balance from the allowance for loan losses			2,939				3,497				40				3,352							9,828
Provision for unfunded commitments			1,207				610				38				276							2,131

Balance at end of period		$	4,146			$	4,107			$	78			$	3,628			$	—		$	11,959

Allowance on loans individually evaluated for impairment		$	8			$	801			$	283			$	—			$	—		$	1,092
Allowance on loans collectively evaluated for impairment			27,644				23,583				2,421				14,754				—			68,402
Loans, net of unearned income:
Balance at end of period		$	3,320,333			$	2,643,822			$	409,940			$	1,861,940			$	—		$	8,236,035
Balance at end of period individually evaluated for impairment			9,529				14,548				1,407				263				—			25,747
Balance at end of period collectively evaluated for impairment			3,310,804				2,629,274				408,533				1,861,677				—			8,210,288
Balance at end of period acquired with deteriorated credit quality			16,287				45				120				1,815				—			18,267

A summary of changes in the allowance for credit losses for covered loans, by loan portfolio type, for the nine months ended September 30, 2014 and 2013 is as follows:


		September 30, 2014
		Commercial				Commercial
(Dollars in thousands)		real estate				business				Mortgage				Consumer				Unallocated			Total
Allowance for loan losses
Balance at beginning of period		$	38,772			$	5,380			$	10,889			$	16,134			$	—		$	71,175
Provision for loan losses			2,544				376				971				834				—			4,725
(Decrease) Increase in FDIC loss share receivable			734				609				(2,911	)			2,721				—			1,153
Transfer of balance to OREO			(1,874	)			(1,162	)			(648	)			(1,487	)			—			(5,171	)
Loans charged off			(9,578	)			(2,192	)			(90	)			(963	)			—			(12,823	)
Recoveries			38				—				—				—				—			38

Balance at end of period		$	30,636			$	3,011			$	8,211			$	17,239			$	—		$	59,097
Allowance on loans individually evaluated for impairment		$	—			$	—			$	—			$	—			$	—		$	—
Allowance on loans collectively evaluated for impairment			30,636				3,011				8,211				17,239				—			59,097
Loans, net of unearned income:
Balance at end of period		$	247,156			$	34,234			$	130,976			$	111,823			$	—		$	524,189
Balance at end of period individually evaluated for impairment			—				—				—				—				—			—
Balance at end of period collectively evaluated for impairment			247,156				34,234				130,976				111,823				—			524,189
Balance at end of period acquired with deteriorated credit quality			4,678				620				24,304				16,699				—			46,301

		30-Sep-13
		Commercial				Commercial
(Dollars in thousands)		real estate				business				Mortgage				Consumer				Unallocated			Total
Allowance for credit losses
Balance at beginning of period		$	100,871			$	11,375			$	22,566			$	33,764			$	—		$	168,576
(Reversal of) Provision for loan losses			27				—				(1	)			(1	)			—			25
(Decrease) Increase in FDIC loss share receivable			(30,853	)			(3,137	)			(5,734	)			(18,841	)			—			(58,565	)
Transfer of balance to OREO			(22,375	)			(314	)			(6,614	)			1				—			(29,302	)
Loans charged off			(1,683	)			—				—				—				—			(1,683	)

Balance at end of period		$	45,987			$	7,924			$	10,217			$	14,923			$	—		$	79,051
Allowance on loans individually evaluated for impairment		$	—			$	—			$	—			$	—			$	—		$	—
Allowance on loans collectively evaluated for impairment			45,987				7,924				10,217				14,923				—			79,051
Loans, net of unearned income:
Balance at end of period		$	459,506			$	40,422			$	153,515			$	153,559			$	—		$	807,002
Balance at end of period individually evaluated for impairment			—				—				—				—				—			—
Balance at end of period collectively evaluated for impairment			459,506				40,422				153,515				153,559				—			807,002
Balance at end of period acquired with deteriorated credit quality			23,751				—				28,333				26,400				—			78,484

Credit Quality
The Company’s investment in non-covered loans by credit quality indicator is presented in the following tables. Because of the difference in accounting for acquired loans, the tables below further segregate the Company’s non-covered loans receivable between acquired loans and loans that were not acquired. Loan premiums/discounts in the tables below represent the adjustment of non-covered acquired loans to fair value at the acquisition date, as adjusted for income accretion and changes in cash flow estimates in subsequent periods. Asset risk classifications for commercial loans reflect the classification as of September 30, 2014 and December 31, 2013, respectively. Credit quality information in the tables below includes loans acquired at the gross loan balance, prior to the application of premiums/discounts, at September 30, 2014 and December 31, 2013.


		Non-covered loans excluding acquired loans
		September 30, 2014																			December 31, 2013
						Special																			Special
(Dollars in thousands)		Pass				Mention				Substandard				Doubtful				Total			Pass				Mention			Substandard		Doubtful		Total
Commercial real estate construction		$	624,592			$	249			$	11,153			$	—			$	635,994		$	370,824			$	9,309		$	2,962	$	—	$	383,095
Commercial real estate—other			2,817,777				46,718				26,700				423				2,891,618			2,694,161				27,227			30,308		113		2,751,809
Commercial business			3,047,885				23,093				20,921				1,974				3,093,873			2,866,794				6,164			32,167		926		2,906,051

Total		$	6,490,254			$	70,060			$	58,774			$	2,397			$	6,621,485		$	5,931,779			$	42,700		$	65,437	$	1,039	$	6,040,955


		Non-covered loans excluding acquired loans
		30-Sep-14												31-Dec-13
						30+ Days												30+ Days
(Dollars in thousands)		Current				Past Due				Total				Current				Past Due			Total
Residential prime		$	362,513			$	14,181			$	376,694			$	286,167			$	11,640		$	297,807
Residential subprime			114,182				6,199				120,381				114,939				1,626			116,565
Home equity			1,220,704				9,294				1,229,998				1,091,894				9,333			1,101,227
Indirect automobile			390,413				3,665				394,078				370,388				2,995			373,383
Credit card			67,472				1,259				68,731				62,873				769			63,642
Consumer—other			367,102				1,473				368,575				293,693				1,049			294,742

Total		$	2,522,386			$	36,071			$	2,558,457			$	2,219,954			$	27,412		$	2,247,366


		Non-covered acquired loans
		September 30, 2014																							December 31, 2013
						Special																						Special
(Dollars in thousands)		Pass				Mention				Substandard				Doubtful				Discount			Total				Pass			Mention		Substandard		Doubtful			Discount			Total
Commercial real estate construction		$	30,675			$	3,671			$	4,989			$	—			$	(2,061	)	$	37,274			$	17,132		$	196	$	5,435	$	—		$	(2,532	)	$	20,231
Commercial real estate—other			456,790				11,065				42,027				178				(42,527	)		467,533				310,303			15,351		51,267		93			(52,176	)		324,838
Commercial business			97,383				2,203				4,571				212				(5,144	)		99,225				51,414			1,920		2,586		31			(2,914	)		53,037

Total		$	584,848			$	16,939			$	51,587			$	390			$	(49,732	)	$	604,032			$	378,849		$	17,467	$	59,288	$	124		$	(57,622	)	$	398,106


		Non-covered acquired loans
		September 30, 2014																December 31, 2013
						30+ Days				Premium											30+ Days				Premium
(Dollars in thousands)		Current				Past Due				(discount)				Total				Current			Past Due				(discount)			Total
Residential prime		$	432,837			$	8,444			$	631			$	441,912			$	18,796		$	226			$	(887	)	$	18,135
Home equity			228,051				10,821				(10,803	)			228,069				53,995			5,071				(5,623	)		53,443
Indirect automobile			606				51				(44	)			613				1,725			128				—			1,853
Consumer—other			109,599				2,395				(11,552	)			100,442				12,598			1,251				(1,481	)		12,368

Total		$	771,093			$	21,711			$	(21,768	)		$	771,036			$	87,114		$	6,676			$	(7,991	)	$	85,799
The Company’s investment in covered loans by credit quality indicator is presented in the following table. Loan premiums/discounts in the tables below represent the adjustment of covered loans to fair value at the date indicated, as adjusted for income accretion and changes in cash flow estimates in subsequent periods.


		Covered loans
		30-Sep-14																			31-Dec-13
						Special																			Special
(Dollars in thousands)		Pass				Mention				Substandard				Doubtful				Total			Pass				Mention			Substandard		Doubtful		Total
Commercial real estate construction		$	40,754			$	1,822			$	9,285			$	—			$	51,861		$	42,886			$	7,401		$	23,891	$	497	$	74,675
Commercial real estate—other			113,309				22,277				75,353				—				210,939			148,579				49,699			144,680		3,267		346,225
Commercial business			26,087				887				8,814				46				35,834			30,710				780			14,556		984		47,030

		$	180,150			$	24,986			$	93,452			$	46			$	298,634		$	222,175			$	57,880		$	183,127	$	4,748	$	467,930

Discount																			(17,244	)													(43,573	)

Total																		$	281,390													$	424,357


		Covered loans
		September 30, 2014																December 31, 2013
						30+ Days				Premium											30+ Days				Premium
(Dollars in thousands)		Current				Past Due				(discount)				Total				Current			Past Due				(discount)			Total
Residential prime		$	143,529			$	23,993			$	(36,546	)		$	130,976			$	158,710		$	30,814			$	(35,499	)	$	154,025
Home equity			115,813				19,403				(27,405	)			107,811				143,236			35,811				(41,925	)		137,122
Credit card			588				33				—				621				648			31				—			679
Consumer—other			498				23				2,870				3,391				591			144				2,875			3,610

Total		$	260,428			$	43,452			$	(61,081	)		$	242,799			$	303,185		$	66,800			$	(74,549	)	$	295,436

Legacy Impaired Loans
Information on the Company’s investment in legacy impaired loans is presented in the following tables as of and for the periods indicated.


		September 30, 2014												December 31, 2013
						Unpaid												Unpaid
		Recorded				Principal				Related				Recorded				Principal			Related
(Dollars in thousands)		Investment				Balance				Allowance				Investment				Balance			Allowance
With no related allowance recorded:
Commercial real estate		$	6,990			$	6,990			$	—			$	8,567			$	8,567		$	—
Commercial business			3,276				3,276				—				13,256				13,256			—
Home equity			689				689				—				258				258			—
With an allowance recorded:
Commercial real estate			1,450				1,483				(33	)			1,268				1,284			(16	)
Commercial business			186				188				(2	)			1,927				2,770			(843	)
Residential prime			10,746				10,973				(227	)			9,791				10,019			(228	)
Residential subprime			6,169				6,197				(28	)			1,617				1,626			(9	)
Home equity			7,017				7,064				(47	)			6,506				6,550			(44	)
Indirect automobile			1,330				1,338				(8	)			1,267				1,275			(8	)
Credit card			968				987				(19	)			404				411			(7	)
Other			429				433				(4	)			481				485			(4	)

Total		$	39,250			$	39,618			$	(368	)		$	45,342			$	46,501			(1,159	)
Total commercial loans			11,902				11,937				(35	)			25,018				25,877			(859	)
Total mortgage loans			16,915				17,170				(255	)			11,408				11,645			(237	)
Total consumer loans			10,433				10,511				(78	)			8,916				8,979			(63	)


		For the Three Months Ended September 30																For the Nine Months Ended September 30
		2014								2013								2014							2013
		Average				Interest				Average				Interest				Average			Interest				Average			Interest
		Recorded				Income				Recorded				Income				Recorded			Income				Recorded			Income
(Dollars in thousands)		Investment				Recognized				Investment				Recognized				Investment			Recognized				Investment			Recognized
With no related allowance recorded:
Commercial real estate		$	7,026			$	6			$	10,703			$	6			$	7,114		$	20			$	12,787		$	22
Commercial business			3,553				11				13,218				17				4,417			48				8,608			59
Home equity			692				—				265				—				700			14				287			—
With an allowance recorded:
Commercial real estate			1,631				—				4,346				—				1,533			91				6,092			5
Commercial business			312				—				2,739				—				584			9				2,746			3
Residential prime			11,077				—				9,650				—				10,226			119				9,380			7
Residential subprime			6,228				—				—				—				6,115			—				—			—
Home equity			7,177				5				7,244				—				7,404			40				7,458			14
Indirect automobile			1,544				—				1,349				—				1,720			27				1,610			22
Credit card			1,051				—				424				—				724			—				426			—
Other			470				—				372				—				489			11				446			4

Total		$	40,761			$	22			$	50,310			$	23			$	41,026		$	379			$	49,840		$	136
Total commercial loans			12,522				17				31,006				23				13,648			168				30,233			89
Total mortgage loans			17,305				—				9,650				—				16,341			119				9,380			7
Total consumer loans			10,934				5				9,654				—				11,037			92				10,227			40

As of September 30, 2014 and December 31, 2013, the Company was not committed to lend additional funds to any customer whose loan was classified as impaired or as a troubled debt restructuring.

Loss_Sharing_Agreements_and_FD

Loss Sharing Agreements and FDIC Loss Share Receivable	9 Months Ended
Loss Sharing Agreements and FDIC Loss Share Receivable	Sep. 30, 2014
Text Block [Abstract]	'
Loss Sharing Agreements and FDIC Loss Share Receivable	'
	NOTE 8 – LOSS SHARING AGREEMENTS AND FDIC LOSS SHARE RECEIVABLE
	Loss Sharing Agreements
	In 2009, the Company acquired substantially all of the assets and liabilities of CSB, and certain assets and assumed certain deposit and other liabilities of Orion and Century. In 2010, the Company acquired certain assets, deposits, and other liabilities of Sterling. Excluding consumer loans acquired from Sterling, the loans and foreclosed real estate that were acquired in these transactions are covered by loss share agreements between the FDIC and IBERIABANK, which afford IBERIABANK loss protection.
	During the reimbursable loss periods, the FDIC will cover 80% of covered loan and foreclosed real estate losses up to certain thresholds for all four acquisitions, and 95% of losses that exceed contractual thresholds for CSB, Orion, and Century. The CSB reimbursable loss period ended as of October 1, 2014 for all covered assets excluding single family residential assets. The CSB reimbursable loss period for single family residential assets will end during the third quarter of 2019. The Century and Orion reimbursable loss periods end during the fourth quarter of 2014 for all covered assets excluding single family residential assets and during the fourth quarter of 2019 for single family residential assets. The Sterling reimbursable loss period ends during the third quarter of 2015 for all covered assets excluding single family residential assets and during the third quarter of 2020 for single family residential assets. To the extent that loss share coverage ends prior to triggering events on covered assets that would enable the Company to collect these amounts from the FDIC, future impairments may be required.
	In addition, all covered assets, excluding single family residential assets, have a three year recovery period, which begins upon expiration of the reimbursable loss period. During the recovery periods, the Company must reimburse the FDIC for its share of any recovered losses, net of certain expenses, consistent with the covered loss reimbursement rates in effect during the recovery periods.
	The Orion, Century, and Sterling loss share agreements include “clawback” provisions. The clawback provisions require the Company to make payments to the FDIC to the extent that specified cumulative loss floors are not met. For each of the three loss share agreements that contain clawback provisions, cumulative losses have exceeded the cumulative loss floors that would trigger a clawback payment. Previously, the sum of the historical and remaining projected losses and recoveries under one agreement was less than the clawback threshold stated in that agreement. The Company had $0.8 million recorded at December 31, 2013, to reserve for the amount of clawback consideration due to the FDIC based on projected net losses. As of September 30, 2014, projected net losses indicate that a clawback payment is no longer probable. Accordingly, the reserve balance was reversed in the third quarter of 2014 through a reduction of expense in the Company’s statement of comprehensive income for the three and nine months ended September 30, 2014. Improvement in the performance of covered assets in excess of current expectations, particularly in regard to improvements in recoveries and/or reduced losses, through expiration of the recovery periods could result in reduced levels of cumulative losses that trigger the clawback provisions within any or all of the applicable loss share agreements.

	FDIC loss share receivables
	The Company recorded indemnification assets in the form of FDIC loss share receivables as of the acquisition date of each of the four banks covered by loss share agreements. At acquisition, the indemnification assets represented the fair value of the expected cash flows to be received from the FDIC under the loss share agreements. Subsequent to acquisition, the FDIC loss share receivables are updated to reflect changes in actual and expected amounts collectible adjusted for amortization.
	The following is a summary of FDIC loss share receivables year-to-date activity:


		Nine Months Ended
		September 30
	(Dollars in thousands)	2014			2013
	Balance at beginning of period	$	162,312		$	423,069
	Change due to (reversal of) loan loss provision recorded on FDIC covered loans		1,153			(58,565	)
	Amortization		(61,393	)		(68,707	)
	Submission of reimbursable losses to (recoveries payable to) the FDIC		4,901			(44,910	)
	Impairment		(5,097	)		(31,813	)
	Changes due to a change in cash flow assumptions on OREO and other changes		(7,164	)		(14,189	)

	Balance at end of period	$	94,712		$	204,885
	FDIC loss share receivables collectability assessment
	The Company assesses the FDIC loss share receivables for collectability on a quarterly basis. Based on the collectability analysis completed for the nine months ended September 30, 2014, the Company concluded that the $94.7 million FDIC loss share receivable is fully collectible as of September 30, 2014. See below for discussion of the impairment charges recognized in 2014 and 2013.
	Impairment of FDIC loss share receivables
	Based on improving economic trends, their impact on the amount and timing of expected future cash flows, and delays in the foreclosure process, during the loss share receivable collectability assessment completed for the three-months ended September 30, 2014, June 30, 2014 and March 31, 2013, the Company concluded that certain expected losses were probable of not being collected from either the FDIC or the customer because such projected losses were no longer expected to occur or were expected to occur beyond the reimbursable loss periods specified within the loss share agreements.
	On April 10, 2013, management concluded and the Board of Directors agreed that an impairment charge was required under generally accepted accounting principles applicable to the Company and should be recognized in the Company’s consolidated financial statements during the three-month period ended March 31, 2013. Therefore, the Company recognized a valuation allowance against the indemnification assets in the amount of $31.8 million through a charge to net income.
	Management deemed an impairment charge necessary for the nine-month period ended September 30, 2014 for $5.1 million.

Transfers_and_Servicing_of_Fin

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity)	9 Months Ended
	Sep. 30, 2014
Transfers and Servicing [Abstract]	'
Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity)	'
	NOTE 9 –TRANSFERS AND SERVICING OF FINANCIAL ASSETS (INCLUDING MORTGAGE BANKING ACTIVITY)
	Mortgage Banking Activity
	IBERIABANK through its subsidiary, IMC, originates mortgage loans for sale into the secondary market. The loans originated primarily consist of residential first mortgages that conform to standards established by the government-sponsored enterprises (“GSEs”), but can also consist of junior lien loans secured by residential property. These sales are primarily to private companies that are unaffiliated with the GSEs on a servicing released basis. The following table details the mortgage banking activity as of and for the nine months ended September 30:


	(Dollars in thousands)	2014			2013
	Balance at beginning of period	$	128,442		$	267,475
	Originations and purchases		1,218,684			1,712,557
	Sales, net of gains		(1,193,282	)		(1,871,747	)
	Other		(5,314	)		—

	Balance at end of period	$	148,530		$	108,285


	(Dollars in thousands)	2014			2013
	Fair value changes of derivatives and mortgage loans held for sale, net	$	(1,081	)	$	(270	)
	Gains on sales		41,412			51,709
	Servicing and other income, net		572			402

	Total mortgage income	$	40,903		$	51,841
	Mortgage Servicing Rights
	Mortgage servicing rights are 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, 2014								December 31, 2013
		Gross Carrying			Accumulated			Net Carrying		Gross Carrying		Accumulated			Net Carrying
	(Dollars in thousands)	Amount			Amortization			Amount		Amount		Amortization			Amount
	Mortgage servicing rights	$	2,787		$	(1,020	)	$	1,767	$	2,146	$	(638	)	$	1,508

Goodwill_and_Other_Acquired_In

Goodwill and Other Acquired Intangible Assets	9 Months Ended
Goodwill and Other Acquired Intangible Assets	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill and Other Acquired Intangible Assets	'
	NOTE 10 – GOODWILL AND OTHER ACQUIRED INTANGIBLE ASSETS
	Goodwill
	Changes to the carrying amount of goodwill by reportable segment for the nine months ended September 30, 2014 and the year ended December 31, 2013 are provided in the following table.


	(Dollars in thousands)	IBERIABANK		IMC			LTC		Total
	Balance, December 31, 2012	$	373,905	$	23,178		$	4,789	$	401,872
	Goodwill acquired during the year		—		—			—		—

	Balance, December 31, 2013		373,905	$	23,178		$	4,789		401,872
	Goodwill acquired during the period		123,995		—			375		124,370

	Balance, September 30, 2014	$	497,900	$	23,178		$	5,164	$	526,242
	The goodwill acquired during the nine months ended September 30, 2014 was a result of the Trust One-Memphis, Teche, First Private, and The Title Company LLC acquisitions. See Note 4 for further information. Allocation of the goodwill acquired during the nine months ended September 30, 2014 to reportable segments is preliminary and subject to change.
	The Company performed the required annual goodwill impairment test as of October 1, 2013. The Company’s annual impairment test did not indicate impairment in any of the Company’s reporting units as of the testing date. Subsequent to the testing date, management has not become aware of any events or changes in circumstances that would indicate that goodwill might be impaired. The Company is currently in the process of performing its annual impairment tests as of October 1, 2014.
	Title Plant
	The Company held title plant assets totaling $6.7 million at both September 30, 2014 and December 31, 2013. No events or changes in circumstances occurred during 2014 or 2013 to suggest the carrying value of the title plant was not recoverable.

	Intangible assets subject to amortization
	Definite-lived intangible assets had the following carrying values included in Other assets on the Company’s consolidated balance sheet as of the periods indicated:


		September 30, 2014							December 31, 2013
		Gross		Accumulated			Net		Gross		Accumulated			Net
		Carrying		Accumulated			Carrying		Carrying		Accumulated			Carrying
	(Dollars in thousands)	Amount		Amortization			Amount		Amount		Amortization			Amount
	Core deposit intangibles	$	50,564	$	(34,564	)	$	16,000	$	45,406	$	(30,784	)	$	14,622
	Customer relationship intangible asset		1,348		(777	)		571		1,348		(631	)		717
	Non-compete agreement		163		(53	)		110		—		—			—
	Other intangible assets		205		(29	)		176		—		—			—

	Total	$	52,280	$	(35,423	)	$	16,857	$	46,754	$	(31,415	)	$	15,339

Other_Real_Estate_Owned

Other Real Estate Owned	9 Months Ended
Other Real Estate Owned	Sep. 30, 2014
Banking and Thrift [Abstract]	'
Other Real Estate Owned	'
	NOTE 11 – OTHER REAL ESTATE OWNED
	Other real estate owned is included in Other assets on the Company’s consolidated balance sheet. Other real estate owned, segregated into non-covered and covered properties, consists of the following for the periods indicated. For further discussion of loss share coverage periods applicable to the covered foreclosed assets, see Note 8 to these consolidated financial statements.


			September 30, 2014						December 31, 2013
	(Dollars in thousands)		Non-covered		Covered(1)		Total		Non-covered		Covered		Total
	Real estate owned acquired by foreclosure		$	18,627	$	30,991	$	49,618	$	28,072	$	60,474	$	88,546
	Real estate acquired for development or resale			12,734		—		12,734		9,206		—		9,206
	Other foreclosed property			63		971		1,034		93		1,328		1,421

	Total		$	31,424	$	31,962	$	63,386	$	37,371	$	61,802	$	99,173

	(1)	Included in covered OREO at September 30, 2014 is $20.6 million that will lose loss share coverage within the next 12 months.

Derivative_Instruments_and_Oth

Derivative Instruments and Other Hedging Activities	9 Months Ended
Derivative Instruments and Other Hedging Activities	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments and Other Hedging Activities	'
	NOTE 12 – DERIVATIVE INSTRUMENTS AND OTHER HEDGING ACTIVITIES
	Information pertaining to outstanding derivative instruments is as follows:


	(Dollars in thousands)		Balance Sheet				Asset Derivatives Fair Value								Balance Sheet				Liability Derivatives Fair Value
			Location				September 30, 2014				December 31, 2013				Location				September 30, 2014			December 31, 2013
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts			Other assets			$	11,839			$	10,621				Other liabilities			$	11,839		$	10,620
	Forward sales contracts			Other assets				104				1,468				Other liabilities				2,215			287
	Written and purchased options			Other assets				20,347				17,987				Other liabilities				15,786			15,828

	Total derivatives not designated as hedging instruments under ASC Topic 815							32,290				30,076								29,840			26,735

	Total						$	32,290			$	30,076							$	29,840		$	26,735

	(Dollars in thousands)						Asset Derivatives Notional Amount												Liability Derivatives Notional Amount
							30-Sep-14				31-Dec-13								30-Sep-14			31-Dec-13
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts						$	421,523			$	380,303							$	421,523		$	380,303
	Forward sales contracts							88,190				192,876								351,861			45,091
	Written and purchased options							363,239				295,425								197,044			199,061

	Total derivatives not designated as hedging instruments under ASC Topic 815							872,952				868,604								970,428			624,455

	Total						$	872,952			$	868,604							$	970,428		$	624,455
	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, 2014 and December 31, 2013, the Company was required to post $8.4 and $5.0 million, respectively, in cash as collateral for its derivative transactions, which are included in interest-bearing deposits in banks on the Company’s 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, 2014. 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, 2014
	(Dollars in thousands)		Gross Amounts				Gross Amounts Not Offset
			Presented in the				in the Balance Sheet
			Balance Sheet				Derivatives				Collateral (1)				Net
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			11,839				—				—				11,839
	Written and purchased options			15,423				—				—				15,423

	Total derivative assets subject to master netting arrangements		$	27,262			$	—			$	—			$	27,262
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			11,839				—				(3,892	)			7,947

	Total derivative liabilities subject to master netting arrangements		$	11,839			$	—			$	(3,892	)		$	7,947

	-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.


			December 31, 2013
	(Dollars in thousands)		Gross Amounts				Gross Amounts Not Offset
			Presented in the				in the Balance Sheet
			Balance Sheet				Derivatives				Collateral (1)				Net
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			10,621				—				—				10,621
	Written and purchased options			15,801				—				—				15,801

	Total derivative assets subject to master netting arrangements		$	26,422			$	—			$	—			$	26,422
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			10,620				—				(5,419	)			5,201

Total derivative liabilities subject to master netting arrangements		$	10,620			$	—			$	(5,419	)		$	5,201

-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
During the nine months ended September 30, 2014 and 2013, 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, 2014, the fair value of derivatives that will mature within the next twelve months is $0.1 million. The Company does not expect to reclassify any amount from accumulated other comprehensive income into interest income over the next twelve months for derivatives that will be settled.

At September 30, 2014 and 2013, 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:


(Dollars in thousands)		Amount of Gain (Loss)								Location of Gain		Amount of								Location of	Amount of Gain (Loss)
		Recognized								(Loss)		Gain (Loss)								Gain (Loss)	Recognized in Income
		in OCI net of taxes								Reclassified		Reclassified								Recognized	on Derivative (Ineffective
		(Effective Portion)								from		from								in Income on	Portion and Amount
										Accumulated		Accumulated								Derivative	Excluded from
										OCI into Income		OCI into								(Ineffective	Effectiveness Testing)
										(Effective		Income								Portion and
										Portion)		(Effective								Amount
												Portion)								Excluded from
																				Effectiveness
																				Testing
		As of September 30										For the Three Months Ended September 30
Derivatives in ASC Topic 815 Cash
Flow Hedging Relationships		2014				2013						2014				2013					2014			2013
Interest rate contracts		$	—			$	—			Other income		$	—			$	—			Other income	$	—		$	—
Interest rate contracts		$	—			$	—			(expense)		$	—			$	—			(expense)	$	—		$	—

Total		$	—			$	—					$	—			$	—				$	—		$	—



																		Location of Gain			Amount of Gain
																		(Loss)			Amount of Gain
																		Recognized in			(Loss)
																		Income on			Recognized in
						Location of Gain				Amount of Gain								Derivative (Ineffective			Income on
Amount of Gain (Loss)						(Loss) Reclassified				(Loss) Reclassified								Portion and Amount			Derivative (Ineffective
Recognized in OCI net of						from Accumulated				from Accumulated OCI								Excluded from			Portion and Amount
taxes (Effective						OCI into Income				into Income								Effectiveness			Excluded from
Portion)						(Effective Portion)				(Effective Portion)								Testing			Effectiveness Testing)
As of September 30										For the Nine Months Ended September 30
2014		2013								2014				2013							2014			2013
$ —		$	—				Other income			$	—			$	(392	)			Other income		$	(1	)	$	—
$ —		$	—				(expense	)		$	—			$	(392	)			(expense	)	$	(1	)	$	—

$ —		$	—							$	—			$	(392	)					$	(1	)	$	—



(Dollars in thousands)		Amount of Gain (Loss) Recognized in Income on Derivatives
Derivatives Not Designated as		Location of Gain (Loss)
Hedging Instruments under ASC		Recognized in Income on		For the Three Months Ended								For the Nine Months Ended
Topic 815		Derivatives		September 30								September 30
				2014				2013				2014				2013
Interest rate contracts		Other income (expense)		$	406			$	2,061				1,971				2,542
Forward sales contracts		Mortgage Income			(3,648	)			3,290				(7,512	)			897
Written and purchased options		Mortgage Income			773				(7,896	)			2,401				(3,820	)

Total				$	(2,469	)		$	(2,545	)		$	(3,140	)		$	(381	)

Shareholders_Equity_and_Other_

Shareholders' Equity and Other Comprehensive Income (Loss)	9 Months Ended
Shareholders' Equity and Other Comprehensive Income (Loss)	Sep. 30, 2014
Equity [Abstract]	'
Shareholders' Equity and Other Comprehensive Income (Loss)	'
	NOTE 13 – SHAREHOLDERS’ EQUITY AND OTHER COMPREHENSIVE INCOME (LOSS)
	Other Comprehensive Income
	The following is a summary of the tax effects of each component of other comprehensive income for the periods indicated:


			Three Months Ended
			30-Sep-14
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized gain on securities:
	Unrealized holding losses arising during the period		$	(7,032	)		$	2,461			$	(4,571	)
	Less: reclassification adjustment for gains included in net income			(582	)			204				(378	)

	Net unrealized losses			(7,614	)			2,665				(4,949	)
	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		$	—			$	—			$	—
	Less: reclassification adjustment for losses (gains) included in net income			—				—				—

	Fair value of derivative instruments designated as cash flow hedges			—				—				—

	Total other comprehensive loss		$	(7,614	)		$	2,665			$	(4,949	)


			Three Months Ended
			30-Sep-13
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period		$	5,528			$	(1,935	)		$	3,593
	Less: reclassification adjustment for losses included in net income			3				(1	)			2

	Net unrealized losses			5,531				(1,936	)			3,595
	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		$	—			$	—			$	—
	Less: reclassification adjustment for gains included in net income			—				—				—

	Fair value of derivative instruments designated as cash flow hedges			—				—				—

	Total other comprehensive income		$	5,531			$	(1,936	)		$	3,595


			Nine Months Ended
			30-Sep-14
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized loss on securities:
	Unrealized holding gains arising during the period		$	25,586			$	(8,955	)		$	16,631
	Less: reclassification adjustment for gains included in net income			(609	)			213				(396	)

	Net unrealized gains			24,977				(8,742	)			16,235
	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		$	—			$	—			$	—
	Less: reclassification adjustment for losses (gains) included in net income			—				—				—

	Fair value of derivative instruments designated as cash flow hedges			—				—				—

	Total other comprehensive income		$	24,977			$	(8,742	)		$	16,235

			Nine Months Ended
			30-Sep-13
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized gain on securities:
Unrealized holding losses arising during the period		$	(38,769	)		$	13,569			$	(25,200	)
Less: reclassification adjustment for gains included in net income			(2,259	)			791				(1,468	)

Net unrealized losses			(41,028	)			14,360				(26,668	)
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		$	952			$	(333	)		$	619
Less: reclassification adjustment for losses included in net income			392				(137	)			255

Fair value of derivative instruments designated as cash flow hedges			1,344				(470	)			874

Total other comprehensive loss		$	(39,684	)		$	13,890			$	(25,794	)

Capital_Requirements_and_Other

Capital Requirements and Other Regulatory Matters	9 Months Ended
Capital Requirements and Other Regulatory Matters	Sep. 30, 2014
Banking and Thrift [Abstract]	'
Capital Requirements and Other Regulatory Matters	'
	NOTE 14 – CAPITAL REQUIREMENTS AND OTHER REGULATORY MATTERS
	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 financial statements. Under capital adequacy guidelines 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.
	Quantitative measures established by regulation to ensure capital adequacy require the Company and IBERIABANK to maintain minimum amounts and ratios of total and Tier 1 capital to risk-weighted assets and of Tier 1 capital to average assets. Management believes, as of September 30, 2014 and December 31, 2013, that the Company and IBERIABANK met all capital adequacy requirements to which they are subject.

	As of September 30, 2014, the most recent notification from the Federal Deposit Insurance Corporation 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, 2014 and December 31, 2013 are presented in the following table.


	(Dollars in thousands)	September 30, 2014
		Minimum					Well Capitalized					Actual
		Amount		Ratio			Amount		Ratio			Amount		Ratio
	Tier 1 Leverage
	Consolidated	$	596,945		4	%	$	N/A		N/A	%	$	1,376,283		9.22	%
	IBERIABANK		594,578		4			743,223		5			1,225,980		8.25
	Tier 1 risk-based capital
	Consolidated		490,391		4	%	$	N/A		N/A	%	$	1,376,283		11.23	%
	IBERIABANK		489,049		4			733,574		6			1,225,980		10.03
	Total risk-based capital
	Consolidated		980,781		8	%	$	N/A		N/A	%	$	1,522,932		12.42	%
	IBERIABANK		978,099		8			1,222,624		10			1,372,629		11.23


		December 31, 2013
		Minimum					Well Capitalized					Actual
		Amount		Ratio			Amount		Ratio			Amount		Ratio
	Tier 1 Leverage
	Consolidated	$	507,760		4	%	$	N/A		N/A	%	$	1,231,886		9.7	%
	IBERIABANK		505,723		4			632,154		5			1,069,783		8.46
	Tier 1 risk-based capital
	Consolidated	$	426,002		4	%	$	N/A		N/A	%	$	1,231,886		11.57	%
	IBERIABANK		424,578		4			636,868		6			1,069,783		10.08
	Total risk-based capital
	Consolidated	$	852,005		8	%	$	N/A		N/A	%	$	1,365,280		12.82	%
	IBERIABANK		849,157		8			1,061,446		10			1,202,738		11.33

ShareBased_Compensation

Share-Based Compensation	9 Months Ended
Share-Based Compensation	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-Based Compensation	'
	NOTE 15 – SHARE-BASED COMPENSATION
	The Company has various types of share-based compensation plans. These plans are administered by the Compensation Committee of the Board of Directors, which selects persons eligible to receive awards and determines the number of shares and/or options subject to each award, the terms, conditions and other provisions of the awards. During the nine months ended September 30, 2014 and 2013, the Company did not have any equity awards that were settled in cash.
	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 stock options granted were issued with vesting periods ranging from one-and-a half to seven years. At September 30, 2014, future option or restricted stock awards of 1,040,092 shares could be made under approved incentive compensation plans.

	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 three-month and nine-month periods ended September 30:


			For the Three Months Ended								For the Nine Months Ended
			September 30								September 30
	(Dollars in thousands, except per share data)		2014				2013				2014			2013
	Compensation expense related to stock options		$	508			$	526			$	1,545		$	1,592
	Income tax benefit related to stock options			178				184				541			557
	Impact on basic earnings per share			0.01				0.01				0.03			0.03
	Impact on diluted earnings per share			0.01				0.01				0.03			0.03
	The Company reported $1.2 million and $0.5 million of excess tax benefits as financing cash inflows during the nine months ended September 30, 2014 and 2013, respectively, related to the exercise and vesting of stock options. Net cash proceeds from the exercise of stock options were $11.1 million and $5.4 million for the nine months ended September 30, 2014 and 2013, respectively.
	The Company uses the Black-Scholes option pricing model to estimate the fair value of share-based awards. The following weighted-average assumptions were used for option awards outstanding during the nine-month periods ended September 30:


			2014				2013
	Expected dividends			2.1	%			2.6	%
	Expected volatility			35.8	%			34.8	%
	Risk-free interest rate			2.3	%			1.7	%
	Expected term (in years)			7.5				8.6
	Weighted-average grant-date fair value		$	21.25			$	15.37
	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.
	At September 30, 2014, there was $3.7 million of unrecognized compensation cost related to stock options that is expected to be recognized over a weighted-average period of 5.2 years.
	The following table represents the activity related to stock options during the periods indicated.


							Weighted Average				Weighted Average
			Number of shares				Exercise Price				Remaining Contract Life
	Outstanding options, December 31, 2012			1,236,075			$	51.48
	Granted			75,722				52.36
	Exercised			(142,841	)			38.09
	Forfeited or expired			(36,608	)			56.01

	Outstanding options, September 30, 2013			1,132,348			$	53.09				4.7 Years
	Exercisable options, September 30, 2013			749,545				52.94				3.2 Years
	Outstanding options, December 31, 2013			1,072,829			$	53.47
	Granted			77,098				65.3
	Exercised			(234,363	)			48.36
	Forfeited or expired			(13,446	)			60.82

	Outstanding options, September 30, 2014			902,118			$	55.7				5.2 Years
	Exercisable options, September 30, 2014			581,423				55.65				3.8 Years
	At September 30, 2014, the aggregate intrinsic value of shares underlying outstanding stock options and underlying exercisable stock options was $6.8 million and $4.4 million, respectively. Total intrinsic value of options exercised was $4.1 million and $1.9 million for the nine months ended September 30, 2014 and 2013, respectively.

	Restricted stock awards
	The Company issues restricted stock under various plans for certain officers and directors. A supplemental stock benefit plan adopted in 1999 and the 2001, 2005, 2008, and 2010 Incentive Plans allow grants of restricted stock. The plans allow for the issuance of restricted stock awards that 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 fair value of the restricted stock shares awarded under these plans is recorded as unearned share-based compensation, a contra-equity account. The unearned compensation related to these awards is amortized to compensation expense over the vesting period (generally three to seven years). The total share-based 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 amortized over the vesting period. As of September 30, 2014 and 2013, unearned share-based compensation associated with these awards totaled $22.2 million and $23.3 million, respectively.
	The following table represents the compensation expense that was included in non-interest expense in the accompanying consolidated statements of comprehensive income related to restricted stock grants:


			For the Three Months Ended								For the Nine Months Ended
			September 30								September 30
	(Dollars in thousands)		2014				2013				2014			2013
	Compensation expense related to restricted stock		$	2,497			$	2,212			$	7,382		$	6,407
	The following table represents unvested restricted stock award activity for the nine months ended September 30:


			2014				2013
	Balance at beginning of period			523,756				538,202
	Granted			146,547				166,223
Forfeited			(18,171	)			(27,483	)
Earned and issued			(152,112	)			(136,629	)

Balance at end of period			500,020				540,313
Phantom stock awards
As part of the IBKC Phantom Award Plan and 2009 Phantom Stock Plan, the Company issues phantom stock awards to certain key officers and employees. The award is subject to a vesting period of five to seven years and is 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 will be deemed to be 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 acquired 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 the end of the periods indicated and the current market price of the Company’s stock at that time.


		For the Three Months Ended								For the Nine Months Ended
		September 30								September 30
(Dollars in thousands)		2014				2013				2014			2013
Compensation expense related to phantom stock		$	619			$	792			$	3,692		$	2,602

The following table represents phantom stock award activity during the periods indicated.


		Number of share				Dividend				Total share			Value of share
		equivalents				equivalents				equivalents			equivalents (1)
Balance, December 31, 2012			318,729				16,035				334,764		$	16,444,000
Granted			166,664				8,793				175,457			9,108,000
Forfeited share equivalents			(16,381	)			(681	)			(17,062	)		(886,000	)
Vested share equivalents			(45,065	)			(3,327	)			(48,392	)		(2,453,000	)

Balance, September 30, 2013			423,947				20,820				444,767		$	23,088,000

Balance, December 31, 2013			417,238				22,351				439,589		$	27,628,000
Granted			115,620				7,147				122,767			7,674,000
Forfeited share equivalents			(19,498	)			(1,751	)			(21,249	)		(1,328,000	)
Vested share equivalents			(68,480	)			(6,615	)			(75,095	)		(5,002,000	)

Balance, September 30, 2014			444,880				21,132				466,012		$	29,130,000

(1)	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 $62.51 and $51.91 on September 30, 2014 and 2013, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	NOTE 16 – COMMITMENTS AND CONTINGENCIES
	Off-balance sheet commitments
	The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby 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 nonperformance by other parties represents the contractual amount of the financial instruments. At September 30, 2014, and December 31, 2013, the fair value of guarantees under commercial and standby letters of credit was $1.3 million and $1.1 million, respectively. This amount represents the unamortized fee associated with these guarantees and is included in the consolidated balance sheets of the Company. This fair value will decrease as the existing commercial and standby letters of credit approach their expiration dates.
	At September 30, 2014 and December 31, 2013, the Company had the following financial instruments outstanding, whose contract amounts represent credit risk:


	(Dollars in thousands)	September 30		December 31
		2014		2013
	Commitments to grant loans	$	242,137	$	221,627
	Unfunded commitments under lines of credit		3,834,107		3,326,448
	Commercial and standby letters of credit		131,347		105,026
	Reserve for unfunded lending commitments		12,099		11,147
	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. 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 counterparty.
	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 7 for additional discussion related to the Company’s 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 or credit is essentially the same as that involved in extending loan facilities to customers and as such, are collateralized when necessary, 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, all of 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, and certain of these claims will be covered by loss sharing agreements with the FDIC. The Company has asserted defenses to these litigations 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.
	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, advice of counsel and available insurance coverage, the Company’s management believes that it has established appropriate legal reserves. Any 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, in the event of unexpected future developments, 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 is immaterial.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	NOTE 17 – FAIR VALUE MEASUREMENTS
	Fair value option
	The Company may elect the fair value option, which permits the Company to choose to measure eligible financial assets and liabilities at fair value at specified election dates and recognize prospective changes in unrealized gains and losses on items for which the fair value option has been elected in earnings at each reporting date.
	Beginning in 2013, the Company has elected the fair value option for certain 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 following table summarizes the difference between the aggregate fair value and the aggregate unpaid principal balance for mortgage loans held for sale measured at fair value:


			September 30, 2014										December 31, 2013
	(Dollars in thousands)		Aggregate				Aggregate			Aggregate			Aggregate		Aggregate		Aggregate
			Fair Value				Unpaid			Fair Value			Fair Value		Unpaid		Fair Value
							Principal			Less Unpaid					Principal		Less Unpaid
										Principal							Principal
	Mortgage loans held for sale, at fair value		$	148,530			$	142,381		$	6,149		$	97,273	$	96,875	$	398
	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. Net losses resulting from the change in fair value of these loans that were recorded in mortgage income in the consolidated statement of comprehensive income for the three-month period ended September 30, 2014 totaled $1.6 million, while net gains resulting from the change in fair value of these loans were $4.0 million for the nine-month period ended September 30, 2014. There were no net gains or losses recorded in mortgage income for the corresponding periods ended September 30, 2013 resulting from the change in fair value of loans accounted for under the fair value option. The changes in fair value are mostly offset by economic hedging activities, with an immaterial portion of these changes attributable to changes in instrument-specific credit risk.

	Items measured at fair value on a 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.


	(Dollars in thousands)		September 30, 2014
			(Level 1)				(Level 2)			(Level 3)			Total
	Assets
	Available for sale securities		$	46,261			$	2,057,567		$	—		$	2,103,828
	Mortgage loans held for sale			—				148,530			—			148,530
	Derivative instruments			—				32,290			—			32,290

	Total		$	46,261			$	2,238,387		$	—		$	2,284,648
	Liabilities
	Derivative instruments			—				29,840			—			29,840

	Total		$	—			$	29,840		$	—		$	29,840

			31-Dec-13
			(Level 1)				(Level 2)			(Level 3)			Total
	Assets
	Available for sale securities		$	15,496			$	1,921,301		$	—		$	1,936,797
	Mortgage loans held for sale			—				97,273			—			97,273
	Derivative instruments			—				30,076			—			30,076

	Total		$	15,496			$	2,048,650		$	—		$	2,064,146
	Liabilities
	Derivative instruments			—				26,735			—			26,735

	Total		$	—			$	26,735		$	—		$	26,735
	Available for sale securities with a market value of $14.7 million at September 30, 2014 were transferred from the Level 1 to Level 2 fair value category in the table above. The security was issued by Freddie Mac and was included in the Level 1 category at December 31, 2013 based on a recent trade price in the open market.
	Gains and losses (realized and unrealized) included in earnings (or changes in net assets) during 2014 related to assets and liabilities measured at fair value on a recurring basis are reported in non-interest income or other comprehensive income as follows:


	(Dollars in thousands)		Noninterest				Other
			income				comprehensive
							income
	Total gains (losses) included in earnings (or changes in net assets)		$	(1,697	)		$	—
	Change in unrealized gains (losses) relating to assets still held at September 30, 2014			—				16,235

	Items measured at fair value on a non-recurring basis
	The Company has segregated all financial 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.


	(Dollars in thousands)		September 30, 2014
			(Level 1)				(Level 2)			(Level 3)			Total
	Assets
	Loans		$	—			$	1,086		$	—		$	1,086
	OREO			—				6,974			—			6,974

Total		$	—			$	8,060		$	—		$	8,060


(Dollars in thousands)		December 31, 2013
		(Level 1)				(Level 2)			(Level 3)			Total
Assets
Loans		$	—			$	3,070		$	—		$	3,070
Mortgage loans held for sale			—				11,876			—			11,876
OREO			—				14,598			—			14,598

Total		$	—			$	29,544		$	—		$	29,544

The tables above exclude the initial measurement of assets and liabilities that were acquired as part of the acquisitions completed in 2011 through 2014. 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, OREO, property, equipment, and debt) or Level 3 fair value measurements (loans, deposits, and core deposit intangible asset).
In accordance with the provisions of ASC Topic 310-30, the Company records certain loans considered impaired at their estimated fair value. A loan is considered impaired if it is probable the Company will be unable to collect all amounts due according to the contractual terms of the loan agreement. Fair value is measured at the estimated fair value of the collateral for collateral-dependent loans. Impaired non-covered loans with an outstanding balance of $1.1 million and $4.1 million were recorded at their fair value at September 30, 2014 and December 31, 2013, respectively. These loans include a reserve of $25 thousand and $1.0 million included in the Company’s allowance for credit losses at September 30, 2014 and December 31, 2013, respectively.
During the second quarter of 2013, the Company announced plans to close ten branches as part of its business strategy. In addition, during the second quarter of 2014, the Company closed nine branches as part of its acquisition of Teche. The Company notified customers of these branch closings and received the required regulatory approvals to proceed with closure. The Company reviewed the carrying amount of the owned properties and concluded carrying amounts exceeded the fair value of certain branches at that date. Fair value of the branches was based on a third-party broker opinion of value using both a comparable sales and cash flow approach. The Company did not modify the third-party pricing information for unobservable inputs. As a result, the Company recorded impairment losses in other non-interest expense in its consolidated statement of comprehensive income for the nine months ended September 30, 2014 and the year ended December 31, 2013. After the impairment losses, the carrying value of the closed branches was $3.1 million and $5.1 million at September 30, 2014 and December 31, 2013, respectively, and is included in OREO (as real estate acquired for development or resale) on the Company’s consolidated balance sheet.
The Company did not record any liabilities at fair value for which measurement of the fair value was made on a nonrecurring basis at September 30, 2014 and December 31, 2013.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
Fair Value of Financial Instruments	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments	'
	NOTE 18 – 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 excludes certain financial instruments and all non-financial instruments from its disclosure requirements. Accordingly, the aggregate fair value amounts presented may not necessarily represent the underlying fair value of the Company.
	The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate that value. Refer to Note 1 to these financial statements for the methods and assumptions used to measure the fair value of investment securities and derivative instruments.

	Cash and cash equivalents
	The carrying amounts of cash and cash equivalents approximate their fair value.
	Loans
	The fair values of non-covered mortgage loans receivable are estimated based on present values using entry-value rates (the interest rate that would be charged for a similar loan to a borrower with similar risk at the indicated balance sheet date) at September 30, 2014 and December 31, 2013, weighted for varying maturity dates. Other non-covered loans receivable are valued based on present values using entry-value interest rates at September 30, 2014 and December 31, 2013 applicable to each category of loans, which would be classified within Level 3 of the hierarchy. Fair values of mortgage loans held for sale are based on commitments on hand from investors or prevailing market prices, a Level 2 measurement. Covered loans are measured using projections of expected cash flows, exclusive of the shared-loss agreements with the FDIC. Fair value of the covered loans included in the table below reflects the current fair value of these loans, which is based on an updated estimate of the projected cash flow as of the dates indicated. The fair value associated with the loans includes estimates related to expected prepayments and the amount and timing of undiscounted expected principal, interest and other cash flows, which also would be classified within Level 3 of the hierarchy.
	Accrued Interest Receivable and Accrued Interest Payable
	The carrying amount of accrued interest approximates fair value because of the short maturity of these financial instruments.
	FDIC Loss Share Receivable
	The fair value is determined using projected cash flows from loss sharing agreements based on expected reimbursements for losses at the applicable loss sharing percentages based on the terms of the loss share agreements. Cash flows are discounted to reflect the timing and receipt of the loss sharing reimbursements from the FDIC. The fair value of the Company’s FDIC loss share receivable would be categorized within Level 3 of the hierarchy.
	Deposits
	The fair values of NOW accounts, money market deposits and savings accounts are the amounts payable on demand at the reporting date. Certificates of deposit were valued using a discounted cash flow model based on the weighted-average rate at September 30, 2014 and December 31, 2013 for deposits with similar remaining maturities. The fair value of the Company’s deposits would therefore be categorized within Level 3 of the fair value hierarchy.
	Short-term borrowings
	The carrying amounts of short-term borrowings maturing within ninety days approximate their fair values.
	Long-term debt
	The fair values of long-term debt are estimated using discounted cash flow analyses based on the Company’s current incremental borrowing rates for similar types of borrowing arrangements. The fair value of the Company’s long-term debt would therefore be categorized within Level 3 of the fair value hierarchy.
	Off-balance sheet items
	The Company has outstanding commitments to extend credit and standby letters of credit. These off-balance sheet financial instruments are generally exercisable at the market rate prevailing at the date the underlying transaction will be completed. At September 30, 2014 and December 31, 2013, the fair value of guarantees under commercial and standby letters of credit was immaterial.
	The estimated fair values and carrying amounts of the Company’s financial instruments are as follows:


		September 30, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
	(Dollars in thousands)	Amount		Value		Amount		Value
	Financial Assets
	Cash and cash equivalents	$	668,007	$	668,007	$	391,396	$	391,396
	Investment securities		2,224,348		2,226,286		2,090,906		2,089,363
	Loans and loans held for sale		11,227,729		11,247,080		9,620,461		9,724,432
	FDIC loss share receivable		94,712		27,922		162,312		21,918
	Derivative instruments		32,290		32,290		30,076		30,076
	Accrued interest receivable		37,143		37,143		32,143		32,143
	Financial Liabilities
	Deposits	$	12,377,775	$	11,986,233	$	10,737,000	$	10,226,573
	Short-term borrowings		812,783		812,783		680,344		680,344
	Long-term debt		355,569		324,282		280,699		235,503
	Derivative instruments		29,840		29,840		26,735		26,735
	Accrued interest payable		7,972		7,972		6,102		6,102

	The fair value estimates presented herein are based upon pertinent information available to management as of September 30, 2014 and December 31, 2013. 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 that date and, therefore, current estimates of fair value may differ significantly from the amounts presented herein.

Business_Segments

Business Segments	9 Months Ended
Business Segments	Sep. 30, 2014
Segment Reporting [Abstract]	'
Business Segments	'
	NOTE 19 – BUSINESS SEGMENTS
	Each of the Company’s reportable operating segments is a business unit that 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 are subject to evaluation by the chief operating decision maker in deciding how to allocate resources to segments. The Company reports the results of its operations through three business segments: IBERIABANK, IMC, 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 that are not specifically related to a strategic business unit. The IMC 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 means that reflect utilization.
	Also within IBERIABANK are certain reconciling items in order to 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.
	IBERIABANK is considered a reportable segment based on the quantitative thresholds specified within ASC Topic 280, Segment Reporting (“ASC 280”). The Company’s wealth management, capital markets and trust operating segments are aggregated within the IBERIABANK reportable operating segment because they do not meet the thresholds specified by ASC 280 and based on the qualitative factors presented within ASC 280. The Company’s IMC and LTC segments do not meet the quantitative thresholds specified by ASC 280, but are reported because management believes information about those segments is useful to users of the financial statements.


			Three Months Ended September 30, 2014
	(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
	Interest income		$	131,362			$	1,804			$	1			$	133,167
	Interest expense			11,501				625				—				12,126

	Net interest income			119,861				1,179				1				121,041
	Provision for loan losses			5,621				93				—				5,714
	Mortgage income			(5	)			12,819				—				12,814
	Title income			—				—				5,577				5,577
	Other non-interest income			27,311				(37	)			(2	)			27,272
	Core deposit intangible amortization			1,429				—				—				1,429
	Allocated expenses			(2,386	)			1,697				689				—
	Other non-interest expenses			102,692				11,624				4,315				118,631

	Income before income taxes			39,811				547				572				40,930
	Income tax expense			10,739				217				230				11,186

	Net income		$	29,072			$	330			$	342			$	29,744
	Total loans and loans held for sale		$	11,055,809			$	171,920			$	—			$	11,227,729
	Total assets			15,288,157				202,923				25,529				15,516,609
	Total deposits			12,371,606				6,169				—				12,377,775
	Average assets			15,239,174				213,936				25,296				15,478,406


			Three Months Ended September 30, 2013
	(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
	Interest income		$	107,051			$	1,459			$	2			$	108,512
	Interest expense			10,731				329				—				11,060

	Net interest income			96,320				1,130				2				97,452
	Provision for loan losses			1,868				146				—				2,014
	Mortgage income			5				15,197				—				15,202
	Title income			—				—				5,482				5,482
	Other non-interest income			22,579				—				—				22,579
	Core deposit intangible amortization			1,125				—				—				1,125
	Allocated expenses			(2,658	)			1,933				725				—
	Other non-interest expenses			90,858				12,016				4,153				107,027

	Income before income taxes			27,711				2,232				606				30,549
	Income tax expense			6,228				877				252				7,357

	Net income		$	21,483			$	1,355			$	354			$	23,192
	Total loans and loans held for sale		$	9,024,959			$	126,363			$	—			$	9,151,322
	Total assets			12,965,373				153,402				26,302				13,145,077
	Total deposits			10,946,453				4,311				—				10,950,764
	Average assets			12,761,165				157,144				26,126				12,944,435


			Nine Months Ended September 30, 2014
	(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
Interest income		$	362,054			$	4,563			$	2			$	366,619
Interest expense			30,869				1,323				—				32,192

Net interest income			331,185				3,240				2				334,427
Provision for loan losses			12,481				84				—				12,565
Mortgage income			80				40,823				—				40,903
Title income			—				—				15,007				15,007
Other non-interest income			73,460				(61	)			(2	)			73,397
Core deposit intangible amortization			3,779				—				—				3,779
Allocated expenses			(9,110	)			6,432				2,678				—
Other non-interest expenses			305,121				33,558				12,405				351,084

Income (loss) before income taxes			92,454				3,928				(76	)			96,306
Income tax expense (benefit)			24,081				1,552				(14	)			25,619

Net income (loss)		$	68,373			$	2,376			$	(62	)		$	70,687
Total loans and loans held for sale		$	11,055,809			$	171,920			$	—			$	11,227,729
Total assets			15,288,157				202,923				25,529				15,516,609
Total deposits			12,371,606				6,169				—				12,377,775
Average assets			14,097,930				179,218				25,003				14,302,151


		Nine Months Ended September 30, 2013
(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
Interest income		$	318,646			$	4,428			$	31			$	323,105
Interest expense			34,786				1,513				—				36,299

Net interest income			283,860				2,915				31				286,806
Provision for loan losses			320				125				—				445
Mortgage income			2				51,839				—				51,841
Title income			—				—				16,199				16,199
Other non-interest income			62,206				(4	)			—				62,202
Core deposit intangible amortization			3,375				—				—				3,375
Allocated expenses			(4,402	)			3,213				1,189				—
Other non-interest expenses			315,332				38,942				12,761				367,035

Income before income taxes			31,443				12,470				2,280				46,193
Income tax expense (benefit)			884				4,897				913				6,694

Net income		$	30,559			$	7,573			$	1,367			$	39,499
Total loans and loans held for sale		$	9,024,959			$	126,363			$	—			$	9,151,322
Total assets			12,965,373				153,402				26,302				13,145,077
Total deposits			10,946,453				4,311				—				10,950,764
Average assets			12,747,602				193,463				25,454				12,966,519

Subsequent_Events

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	NOTE 20 – SUBSEQUENT EVENTS
	Acquisition of Florida Bank Group, Inc.
	During the forth quarter of 2014, the Company announced the signing of a definitive agreement pursuant to which IBERIABANK will acquire Florida Bank Group, Inc. (“Florida Bank Group”). The proposed acquisition of Florida Bank Group has been approved by the Board of Directors of each company and is expected to close in the first quarter of 2015, subject to customary closing conditions, including the receipt of required regulatory approvals and the approval of Florida Bank Group’s shareholders.
	Under the terms of the agreement, Florida Bank Group shareholders will receive a combination of cash and shares of the Company’s common stock. Florida Bank Group shareholders will receive cash equal to $7.81 per share of then outstanding Florida Bank Group common stock, including shares of preferred stock that will convert to common shares in the acquisition. Each Florida Bank Group common share will be exchanged for 0.149 share of the Company’s common stock, subject to certain market price adjustments provided for in the agreement. All unexercised Florida Bank Group stock options, whether or not vested, will be cashed out.
	Acquisition of Old Florida Bancshares, Inc.
	During the fourth quarter of 2014, the Company announced the signing of a definitive agreement pursuant to which IBERIABANK will acquire Old Florida Bancshares, Inc. (“Old Florida”), holding company of Old Florida Bank and New Traditions Bank. The proposed acquisition has been approved by the Board of Directors of each company and is expected to close in the first quarter of 2015, subject to customary closing conditions, including the receipt of required regulatory approvals and the approval of Old Florida’s shareholders.
	Under the terms of the agreement, Old Florida shareholders will receive 0.34 share of the Company’s common stock for each of the Old Florida common stock shares outstanding, subject to certain market price adjustments provided for in the agreement. All unexercised Old Florida stock options, whether or not vested, will be cashed out.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Principles of Consolidation	'
	PRINCIPLES OF CONSOLIDATION
	The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, IBERIABANK, Lenders Title Company (“LTC”), IBERIA Capital Partners L.L.C. (“ICP”), IB Aircraft Holdings, LLC, 1887 Leasing LLC, IBERIA Asset Management, Inc. (“IAM”), and IBERIA CDE, L.L.C. (“CDE”). All significant intercompany balances and transactions have been eliminated in consolidation. All normal, recurring adjustments which, in the opinion of management, are necessary for a fair presentation of the financial statements have been included. Certain amounts reported in prior periods have been reclassified to conform to the current period presentation.
Nature of Operations	'
	NATURE OF OPERATIONS
	The Company offers commercial and retail banking products and services to customers throughout locations in six states through IBERIABANK. The Company also operates mortgage production offices in twelve states through IBERIABANK Mortgage Company (“IMC”), and offers a full line of title insurance and closing services throughout Arkansas and Louisiana through LTC and its subsidiaries. ICP provides equity research, institutional sales and trading, and corporate finance services. 1887 Leasing LLC owns an aircraft used by management of the Company, and IB Aircraft Holdings, LLC owns a fractional share of a separate aircraft also used by management. IAM provides wealth management and trust services for commercial and private banking clients. CDE is engaged in the purchase of tax credits.
Use of Estimates	'
	USE OF ESTIMATES
	The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Material estimates that are susceptible to significant change in the near term are the allowance for credit losses, valuation of and accounting for loans covered by loss sharing arrangements with the FDIC and the related loss share receivables, valuation of and accounting for acquired loans, and valuation of goodwill, intangible assets and other purchase accounting adjustments.
Concentration of Credit Risks	'
	CONCENTRATION OF CREDIT RISKS
	Most of the Company’s business activity is with customers located within the States of Louisiana, Florida, Arkansas, Alabama, Texas, and Tennessee. The Company’s lending activity is concentrated in its market areas in those states. The Company has emphasized originations of commercial loans and private banking loans, defined as loans to larger consumer 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 value of the collateral upon default of the borrowers. The Company does not have any significant concentrations to any one industry or customer.
Fair Value Measurements	'
	FAIR VALUE MEASUREMENTS
	The Company estimates fair value based on the assumptions market participants would use when selling an asset or transferring a liability and characterizes such measurements within the fair value hierarchy based on the inputs used to develop those assumptions and measure fair value. The hierarchy requires the Company to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows:

		•	Level 1—Quoted prices in active markets for identical assets or liabilities.

		•	Level 2—Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

		•	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
	A description of the valuation methodologies used for instruments measured at fair value follows, as well as the classification of such instruments within the valuation hierarchy.

	Investment securities
	Securities are classified within Level 1 where quoted market prices are available in an active market. Inputs include securities that have quoted prices in active markets for identical assets. If quoted market prices are unavailable, fair value is estimated using quoted prices of securities with similar characteristics, at which point the securities would be classified within Level 2 of the hierarchy. Examples may include certain collateralized mortgage and debt obligations.
	Mortgage loans held for sale
	Mortgage loans originated and held for sale are recorded at fair value under the fair value option, unless otherwise noted. When determining the fair value of loans held for sale, the Company obtains quotes or bids on these loans directly from the purchasing financial institutions (Level 2). See Note 17 for additional information related to mortgage loans held for sale.
	Impaired loans
	Loans are measured for impairment using the methods permitted by Accounting Standards Codification (‘‘ASC’’) Topic 310. Fair value measurements are used in determining impairment using either the loan’s observable market price (Level 1), if available, or the fair value of the collateral if the loan is collateral dependent (Level 2). Measuring the impairment of loans using the present value of expected future cash flows, discounted at the loan’s effective interest rate, is not considered a fair value measurement. Fair value of the collateral is determined by appraisals or independent valuation.
	Other real estate owned (OREO)
	Fair values of OREO at September 30, 2014 and December 31, 2013 are determined by sales agreement or appraisal, and costs to sell are based on estimation per the terms and conditions of the sales agreement or amounts commonly used in real estate transactions. Inputs include appraisal values on the properties or recent sales activity for similar assets in the property’s market, and thus OREO measured at fair value would be classified within Level 2 of the hierarchy. The Company included property write-downs of $0.5 million and $1.4 million in earnings for the three months ended September 30, 2014 and 2013, respectively, and $1.9 million and $4.0 million for the nine months ended September 30, 2014 and 2013, respectively.
	Derivative financial instruments
	The Company enters into commitments to originate loans whereby the interest rate on the prospective loan is determined prior to funding. Rate lock commitments on mortgage loans that are intended to be sold are considered to be derivatives. The Company offers its customers a certificate of deposit that provides the purchaser a guaranteed return of principal at maturity plus potential return, which allows the Company to identify a known cost of funds. The rate of return is based on an equity index, and as such represents an embedded derivative. Fair value of interest rate swaps, interest rate lock commitments, forward sales contracts, and equity-linked written and purchased options are estimated using prices of financial instruments with similar characteristics, and thus are classified within Level 2 of the fair value hierarchy. See Note 12 for further discussion and details related to derivative financial instruments.

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
Earnings Per Share (Tables)	Sep. 30, 2014
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.


			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2014			2013			2014			2013
	Income available to common shareholders		$	29,744		$	23,192		$	70,687		$	39,499
	Distributed earnings (capital) to unvested restricted stock			(444	)		(421	)		(1,134	)		(744	)

	Distributed earnings (capital) to common shareholders—basic			29,300			22,771			69,553			38,755
	Undistributed earnings reallocated to unvested restricted stock			(4	)		(4	)		(25	)		—

	Distributed and undistributed earnings to common shareholders—diluted		$	29,296		$	22,767		$	69,528		$	38,755

	Weighted average shares outstanding—basic (1)			33,309,881			29,631,799			31,316,267			29,582,081
	Weighted average shares outstanding—diluted			32,926,969			29,147,232			30,923,050			29,062,238
	Earnings per common share—basic		$	0.89		$	0.78		$	2.26		$	1.34
	Earnings per common share—diluted			0.89			0.78			2.25			1.33
	Earnings per unvested restricted stock share—basic			0.88			0.77			2.16			1.33
	Earnings per unvested restricted stock share—diluted			0.89			0.78			2.21			1.33

	-1	Weighted average basic shares outstanding include 506,464 and 547,155 shares of unvested restricted stock for the three months ended September 30, 2014 and 2013, respectively, and 525,441 and 559,556 shares for the nine months ended September 30, 2014 and 2013, respectively.
Schedule of Basic Earnings Per Common Share	'
	Additional information on the Company’s basic earnings per common share is shown in the following table.


			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2014			2013			2014			2013
	Distributed earnings to common shareholders		$	11,200		$	9,926		$	32,430		$	29,736
	Undistributed earnings (distributed capital) to common shareholders			18,100			12,845			37,123			9,019

	Total earnings to common shareholders		$	29,300		$	22,771		$	69,553		$	38,755
	Distributed earnings to unvested restricted stock		$	170		$	183		$	529		$	571
	Undistributed earnings (distributed capital) to unvested restricted stock			274			238			605			173

	Total earnings allocated to restricted stock		$	444		$	421		$	1,134		$	744
	Distributed earnings per common share		$	0.34		$	0.34		$	1.05		$	1.03
	Undistributed earnings (distributed capital) per common share			0.55			0.44			1.21			0.31

	Total earnings per common share—basic		$	0.89		$	0.78		$	2.26		$	1.34
	Distributed earnings per unvested restricted stock share		$	0.34		$	0.34		$	1.01		$	1.02
	Undistributed earnings (distributed capital) per unvested restricted stock share			0.54			0.43			1.15			0.31

	Total earnings per unvested restricted stock share—basic		$	0.88		$	0.77		$	2.16		$	1.33

Acquisition_Activity_Tables

Acquisition Activity (Tables)	9 Months Ended
Acquisition Activity (Tables)	Sep. 30, 2014
Schedule of Assets Acquired under Business Acquisitions	'
	As part of the acquisitions, LTC also acquired or created the following other assets:


					Louisiana Abstract and Title
	(Dollars in thousands)		The Title Company LLC		LLC
	Goodwill		$	221	$	155
	Non-compete agreement			63		100
	Title plant			14		9
	Other intangible assets			75		130
	Other assets			3		6

	Total Assets		$	376	$	400
Supplemental Pro Forma Information	'
	The following unaudited pro forma information for the nine months ended September 30, 2013 reflects the Company’s estimated consolidated results of operations as if the acquisitions of Trust One-Memphis, Teche, and First Private occurred at January 1, 2013, unadjusted for potential cost savings and preliminary purchase price adjustments.


	(Dollars in thousands, except per share data)		2013
	Interest and non-interest income		$	500,638
	Net income			46,139
	Earnings per share—basic			1.4
	Earnings per share—diluted			1.4
Teche [Member]	'
Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable	'
	The following summarizes consideration paid and a preliminary allocation of purchase price to net assets acquired.


	(Dollars in thousands)		Number of Shares		Amount
	Equity consideration
	Common stock issued			2,498,007	$	156,026

	Total equity consideration					156,026
	Non-Equity consideration
	Cash					714

	Total consideration paid					156,740
	Fair value of net assets assumed including identifiable intangible assets					71,954

	Goodwill				$	84,786
Schedule of Business Acquisitions, by Acquisition	'
	Teche				Preliminary
					Fair Value			As recorded by
	(Dollars in thousands)		As Acquired		Adjustments			IBERIABANK
	Assets
	Cash and cash equivalents		$	71,611	$	—		$	71,611
	Investment securities			24,077		1,092	(1)		25,169
	Loans			716,196		(16,636	)(2)		699,560
	Other real estate owned			329		(153	)(3)		176
	Core deposit intangible			—		2,055	(4)		2,055
	Deferred tax asset			1,057		7,337	(5)		8,394
	Other assets			56,752		(6,261	)(6)		50,491

	Total Assets		$	870,022	$	(12,566	)	$	857,456
	Liabilities
	Interest-bearing deposits		$	520,446	$	902	(7)	$	521,348
	Non-interest-bearing deposits			118,256		—			118,256
	Borrowings			134,228		6,304	(8)		140,532
	Other liabilities			5,366		—			5,366

	Total Liabilities		$	778,296	$	7,206		$	785,502
	Explanation of certain fair value adjustments
	(1)	The amount represents the adjustment to the book value of Teche’s investments to their estimated fair value based on fair values on the date of acquisition.
	(2)	The amount represents the adjustment of the book value of Teche loans to their estimated fair value based on current interest rates and expected cash flows, which includes estimates of expected credit losses inherent in the portfolio.
	(3)	The amount represents the adjustment to the book value of Teche’s OREO to their estimated fair value on the date of acquisition.
	(4)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.
	(5)	The amount represents the deferred tax asset recognized on the fair value adjustment of Teche acquired assets and assumed liabilities.
	(6)	The amount represents the write down of the book value of Teche’s property, equipment, and other assets to their estimated fair value at the acquisition date based on their appraised value.
	(7)	The adjustment is necessary because the weighted average interest rate of Teche’s deposits exceeded the cost of similar funding at the time of acquisition. The fair value adjustment will be amortized to reduce future interest expense over the life of the portfolio, which is estimated at 85 months.
	(8)	The adjustment is necessary because the interest rate of Teche’s borrowings exceeded current interest rates on similar borrowings.
First Private [Member]	'
Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable	'
	The following summarizes consideration paid and a preliminary allocation of purchase price to net assets acquired.


	(Dollars in thousands)		Number of Shares		Amount
	Equity consideration
	Common stock issued			847,509	$	58,639

	Total equity consideration					58,639
	Non-Equity consideration
	Cash					1

	Total consideration paid					58,640
	Fair value of net liabilities assumed including identifiable intangible assets					28,029

	Goodwill				$	30,611
Schedule of Business Acquisitions, by Acquisition	'
	First Private				Preliminary
					Fair Value			As recorded by
	(Dollars in thousands)		As Acquired		Adjustments			IBERIABANK
	Assets
	Cash and cash equivalents		$	26,621	$	—		$	26,621
	Investment securities			18,920		297	(1)		19,217
	Loans			295,736		(910	)(2)		294,826
	Other real estate owned			—		—			—
	Core deposit intangible			—		506	(3)		506
	Deferred tax asset (liability)			530		122	(4)		652
	Other assets			5,230		—			5,230

	Total Assets		$	347,037	$	15		$	347,052
	Liabilities
	Interest-bearing deposits		$	261,713	$	220	(5)	$	261,933
	Non-interest-bearing deposits			50,333		—			50,333
	Borrowings			6,451		—			6,451
	Other liabilities			306		—			306

	Total Liabilities		$	318,803	$	220		$	319,023
	Explanation of certain fair value adjustments
	(1)	The amount represents the adjustment to the book value of First Private’s investments to their estimated fair value based on fair values on the date of acquisition.
	(2)	The amount represents the adjustment of the book value of First Private loans to their estimated fair value based on current interest rates and expected cash flows, which includes estimates of expected credit losses inherent in the portfolio.
	(3)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.
	(4)	The amount represents the deferred tax liability recognized on the fair value adjustment of First Private acquired assets and assumed liabilities.
	(5)	The adjustment is necessary because the weighted average interest rate of First Private’s deposits exceeded the cost of similar funding at the time of acquisition. The fair value adjustment will be amortized to reduce future interest expense over the life of the portfolio, which is estimated at 85 months.
Trust One- Memphis [Member]	'
Schedule of Business Acquisitions, by Acquisition	'
	The acquired assets and liabilities, as well as the preliminary adjustments to record the assets and liabilities at their estimated fair values, are presented in the following tables.


	Trust One - Memphis				Preliminary
					Fair Value			As recorded by
	(Dollars in thousands)		As Acquired		Adjustments			IBERIABANK
	Assets
	Cash and cash equivalents		$	92,060	$	—		$	92,060
	Loans			88,179		(1,726	)(1)		86,453
	Other real estate owned			1,325		—			1,325
	Core deposit intangible			—		2,597	(2)		2,597
	Other assets			368		—			368

	Total Assets		$	181,932	$	871		$	182,803
	Liabilities
	Interest-bearing deposits		$	164,942	$	—		$	164,942
	Non-interest-bearing deposits			26,373		—			26,373
	Deferred tax liability			—		—			—
	Other liabilities			84		—			84

	Total Liabilities		$	191,399	$	—		$	191,399
	Explanation of certain fair value adjustments
	(1)	The amount represents the adjustment of the book value of Trust One-Memphis loans to their estimated fair value based on current interest rates and expected cash flows, which includes estimates of expected credit losses inherent in the portfolio.
	(2)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.

Investment_Securities_Tables

Investment Securities (Tables)	9 Months Ended
Investment Securities (Tables)	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Schedule of Amortized Cost and Fair Values of Investment Securities, with Gross Unrealized Gains and Losses	'
	The amortized cost and fair values of investment securities, with gross unrealized gains and losses, consist of the following:


		September 30, 2014
					Gross			Gross			Estimated
		Amortized			Unrealized			Unrealized			Fair
	(Dollars in thousands)	Cost			Gains			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	359,404		$	1,465		$	(5,926	)	$	354,943
	Obligations of state and political obligations		87,895			3,891			—			91,786
	Mortgage-backed securities		1,656,341			11,613			(12,338	)		1,655,616
	Other securities		1,460			23			—			1,483

	Total securities available for sale	$	2,105,100		$	16,992		$	(18,264	)	$	2,103,828
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations	$	10,000		$	157		$	—		$	10,157
	Obligations of state and political obligations		79,309			3,044			(266	)		82,087
	Mortgage-backed securities		31,211			197			(1,194	)		30,214

	Total securities held to maturity	$	120,520		$	3,398		$	(1,460	)	$	122,458

		31-Dec-13
					Gross			Gross			Estimated
		Amortized			Unrealized			Unrealized			Fair
	(Dollars in thousands)	Cost			Gains			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	406,092		$	1,382		$	(11,913	)	$	395,561
	Obligations of state and political obligations		105,300			2,435			(256	)		107,479
	Mortgage-backed securities		1,450,194			10,031			(27,947	)		1,432,278
	Other securities		1,460			19			—			1,479

	Total securities available for sale	$	1,963,046		$	13,867		$	(40,116	)	$	1,936,797
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations	$	34,478		$	484		$	—		$	34,962
	Obligations of state and political obligations		84,290			1,463			(1,624	)		84,129
	Mortgage-backed securities		35,341			258			(2,124	)		33,475

	Total securities held to maturity	$	154,109		$	2,205		$	(3,748	)	$	152,566
Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category	'
	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, 2014
		Less Than Twelve Months						Over Twelve Months						Total
		Gross			Estimated			Gross			Estimated			Gross			Estimated
		Unrealized			Fair			Unrealized			Fair			Unrealized			Fair
	(Dollars in thousands)	Losses			Value			Losses			Value			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	—		$	—		$	(5,926	)	$	258,521		$	(5,926	)	$	258,521
	Obligations of state and political obligations		—			186			—			—			—			186
	Mortgage-backed securities		(2,846	)		552,357			(9,492	)		333,795			(12,338	)		886,152

	Total securities available for sale	$	(2,846	)	$	552,543		$	(15,418	)	$	592,316		$	(18,264	)	$	1,144,859
	Securities held to maturity:
	Obligations of state and political obligations	$	(1	)	$	564		$	(265	)	$	10,811		$	(266	)	$	11,375
	Mortgage-backed securities		—			72			(1,194	)		24,303			(1,194	)		24,375

	Total securities held to maturity	$	(1	)	$	636		$	(1,459	)	$	35,114		$	(1,460	)	$	35,750

		31-Dec-13
		Less Than Twelve Months						Over Twelve Months						Total
		Gross			Estimated			Gross			Estimated			Gross			Estimated
		Unrealized			Fair			Unrealized			Fair			Unrealized			Fair
	(Dollars in thousands)	Losses			Value			Losses			Value			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	(11,764	)	$	298,515		$	(149	)	$	5,515		$	(11,913	)	$	304,030
	Obligations of state and political obligations		(30	)		2,415			(226	)		1,047			(256	)		3,462
	Mortgage-backed securities		(23,749	)		864,899			(4,198	)		81,870			(27,947	)		946,769

	Total securities available for sale	$	(35,543	)	$	1,165,829		$	(4,573	)	$	88,432		$	(40,116	)	$	1,254,261
	Securities held to maturity:
	Obligations of state and political obligations	$	(1,181	)	$	29,355		$	(443	)	$	6,240		$	(1,624	)	$	35,595
	Mortgage-backed securities		(952	)		12,913			(1,172	)		11,616			(2,124	)		24,529

	Total securities held to maturity	$	(2,133	)	$	42,268		$	(1,615	)	$	17,856		$	(3,748	)	$	60,124
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, 2014 and December 31, 2013 is presented in the following table.


	(Dollars in thousands)	September 30, 2014			December 31, 2013
	Number of securities
	Issued by Fannie Mae, Freddie Mac, or Ginnie Mae		78			20
	Issued by political subdivisions		6			5

			84			25
	Amortized Cost Basis
	Issued by Fannie Mae, Freddie Mac, or Ginnie Mae	$	633,230		$	104,520
	Issued by political subdivisions		11,076			7,956

		$	644,306		$	112,476
	Unrealized Loss
	Issued by Fannie Mae, Freddie Mac, or Ginnie Mae	$	16,611		$	5,519
	Issued by political subdivisions		265			669

		$	16,876		$	6,188
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, 2014 are shown 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
		Weighted						Estimated			Weighted						Estimated
		Average			Amortized			Fair			Average			Amortized			Fair
	(Dollars in thousands)	Yield			Cost			Value			Yield			Cost			Value
	Within one year or less		1.27	%	$	15,397		$	15,488			2.65	%	$	10,000		$	10,157
	One through five years		1.54			241,992			241,502			2.84			12,968			13,352
	After five through ten years		2.1			474,758			476,954			2.97			17,983			18,591
	Over ten years		2.18			1,372,953			1,369,884			3.05			79,569			80,358

	Total		2.08	%	$	2,105,100		$	2,103,828			2.98	%	$	120,520		$	122,458
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						Nine Months Ended
		September 30						September 30
	(Dollars in thousands)	2014			2013			2014			2013
	Realized gains	$	582		$	—		$	609		$	2,369
	Realized losses		—			(3	)		—			(110	)

	Net realized gains (losses)	$	582		$	(3	)	$	609		$	2,259
Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets	'
	At September 30, 2014 and December 31, 2013, the Company included the following securities in “Other assets” on the consolidated balance sheets:


		September 30			December 31
	(Dollars in thousands)	2014			2013
	Federal Home Loan Bank (FHLB) stock	$	41,011		$	24,369
	Federal Reserve Bank (FRB) stock		34,348			28,098
	Other investments		1,306			1,306

	Total	$	76,665		$	53,773

Loans_Receivable_Tables

Loans Receivable (Tables)	9 Months Ended
Loans Receivable (Tables)	Sep. 30, 2014
Schedule of Non-Covered and Covered Loans	'
	Loans receivable consist of the following, segregated into non-covered and covered loans, for the periods indicated:


			September 30, 2014
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	4,032,419		$	247,156		$	4,279,575
	Business			3,193,098			34,234			3,227,332

				7,225,517			281,390			7,506,907
	Residential mortgage loans:
	Residential 1-4 family			911,099			130,976			1,042,075
	Construction / Owner Occupied			27,888			—			27,888

				938,987			130,976			1,069,963
	Consumer and other loans:
	Home equity			1,458,067			107,811			1,565,878
	Indirect automobile			394,691			—			394,691
	Other			537,748			4,012			541,760

				2,390,506			111,823			2,502,329

	Total		$	10,555,010		$	524,189		$	11,079,199

			31-Dec-13
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	3,479,973		$	387,332		$	3,867,305
	Business			2,959,088			37,025			2,996,113

				6,439,061			424,357			6,863,418
	Residential mortgage loans:
	Residential 1-4 family			423,057			154,025			577,082
	Construction / Owner Occupied			9,450			—			9,450

				432,507			154,025			586,532
	Consumer and other loans:
	Home equity			1,154,670			137,122			1,291,792
	Indirect automobile			375,236			—			375,236
	Other			370,752			4,289			375,041

				1,900,658			141,411			2,042,069

	Total		$	8,772,226		$	719,793		$	9,492,019
Schedule of Non-Covered Loans on Nonaccrual Status	'
	The following table provides the recorded investment of non-covered loans, excluding acquired loans, on non-accrual status at September 30, 2014 and December 31, 2013.


			September 30			December 31
	(Dollars in thousands)		2014			2013
	Commercial real estate construction		$	1,317		$	1,803
	Commercial real estate—other			6,789			7,648
	Commercial business			2,737			15,020
	Residential prime			10,973			8,611
	Residential subprime			6,197			1,626
	Home equity			7,306			6,808
	Indirect automobile			1,338			1,275
	Credit card			987			411
	Other			416			485

	Total		$	38,060		$	43,687
Schedule of Carrying Amount of Acquired Covered Loans	'
	The carrying amount of the acquired covered loans at September 30, 2014 and December 31, 2013 consisted of loans determined to be impaired at the acquisition date, which are accounted for in accordance with ASC Topic 310-30, and loans that were considered to be performing at the acquisition date, accounted for by analogy to ASC Topic 310-30, as detailed in the following tables.


			September 30, 2014
			Acquired			Acquired			Total
			Impaired			Performing			Covered
	(Dollars in thousands)		Loans			Loans			Loans
	Commercial loans:
	Real estate		$	4,678		$	242,478		$	247,156
	Business			620			33,614			34,234

				5,298			276,092			281,390
	Residential mortgage loans:
	Residential 1-4 family			24,304			106,672			130,976
	Construction / Owner Occupied			—			—			—

				24,304			106,672			130,976
	Consumer and other loans:
	Home equity			16,210			91,601			107,811
	Indirect automobile			—			—			—
	Other			489			3,523			4,012

				16,699			95,124			111,823

	Total		$	46,301		$	477,888		$	524,189

			31-Dec-13
			Acquired			Acquired			Total
			Impaired			Performing			Covered
	(Dollars in thousands)		Loans			Loans			Loans
	Commercial loans:
	Real estate		$	14,904		$	372,428		$	387,332
	Business			—			37,025			37,025

				14,904			409,453			424,357
	Residential mortgage loans:
	Residential 1-4 family			28,223			125,802			154,025
	Construction / Owner Occupied			—			—			—

				28,223			125,802			154,025
	Consumer and other loans:
	Home equity			21,768			115,354			137,122
	Indirect automobile			—			—			—
	Other			1,182			3,107			4,289

				22,950			118,461			141,411

	Total		$	66,077		$	653,716		$	719,793
Schedule of Carrying Amount of Loans Acquired	'
	The Company acquired loans (both covered and non-covered) through previous acquisitions, which are subject to ASC Topic 310-30.
	As discussed in Note 4, during 2014, the Company acquired loans of $86.5 million from Trust One-Memphis, $699.6 million from Teche, and $294.8 million from First Private in the current period. Acquired loans totaling $1.0 billion are accounted for under ASC Topic 310-10, while the carrying amounts of the loans acquired in the current period subject to ASC Topic 310-30 are detailed in the following table as of the purchase date. The allocation of loans acquired from both Teche and First Private between loans subject to ASC Topic 310-30 and those subject to ASC Topic 310-10 is preliminary and subject to change up to one year after the acquisition date as information on these loans becomes available.


			Acquired			Acquired			Total
			Impaired			Performing			Acquired
	(Dollars in thousands)		Loans			Loans			Loans
	Contractually required principal and interest at acquisition		$	82,967		$	15,130		$	98,097
	Nonaccretable difference (expected losses and foregone interest)			(4,197	)		(361	)		(4,558	)

	Cash flows expected to be collected at acquisition			78,770			14,769			93,539
	Accretable yield			(8,242	)		(1,536	)		(9,778	)

	Basis in acquired loans at acquisition		$	70,528		$	13,233		$	83,761
Summary of Changes in Accretable Yields of Acquired Loans	'
	The following is a summary of changes in the accretable difference of acquired loans during the nine months ended September 30, 2014 and 2013.


			September 30, 2014
			Acquired			Acquired			Total
			Impaired			Performing			Acquired
	(Dollars in thousands)		Loans			Loans			Loans
	Balance at beginning of period		$	78,349		$	276,543		$	354,892
	Acquisition			8,242			1,536			9,778
	Transfers from nonaccretable difference to accretable yield			3,952			13,872			17,824
	Accretion			(12,766	)		(66,590	)		(79,356	)
	Changes in expected cash flows not affecting nonaccretable differences (1)			(6,873	)		(19,377	)		(26,250	)

	Balance at end of period		$	70,904		$	205,984		$	276,888

			30-Sep-13
			Acquired			Acquired			Total
			Impaired			Performing			Acquired
			Loans			Loans			Loans
	Balance at beginning of period		$	76,623		$	279,770		$	356,393
	Transfers from nonaccretable difference to accretable yield			6,148			34,480			40,628
	Accretion			(13,519	)		(119,193	)		(132,712	)
	Changes in expected cash flows not affecting nonaccretable differences (1)			10,561			81,173			91,734

	Balance at end of period		$	79,813		$	276,230		$	356,043

	(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 Troubled Debt Restructurings	'
	Information about the Company’s troubled debt restructurings (“TDRs”) at September 30, 2014 and 2013 is presented in the following tables.

			September 30, 2014											September 30, 2013
			Accruing Loans											Accruing Loans
						Past Due			Nonaccrual							Past Due			Nonaccrual
	(Dollars in thousands)		Current			> 30 days			TDRs			Total TDRs		Current		> 30 days			TDRs		Total TDRs
	Commercial real estate construction		$	—		$	—		$	—		$	—	$	—		—			—		—
	Commercial real estate—other			367			—			58			425		411		—			5,601		6,012
	Commercial business			726			—			2,027			2,753		1,056		—			12,610		13,666
	Residential prime			—			—			—			—		—		—			—		—
	Residential subprime			—			—			—			—		—		—			—		—
	Home equity			—			—			243			243		—		—			263		263
	Indirect automobile			—			—			—			—		—		—			—		—
	Credit card			—			—			—			—		—		—			—		—
	Other			—			—			—			—		—		—			—		—

	Total		$	1,093		$	—		$	2,328		$	3,421	$	1,467	$	—		$	18,474	$	19,941
TroubledDebtRestructuringsOnFinancingReceivablesTableTextBlock	'
	The following table provides information on how the TDRs were modified during the nine months ended September 30:


	(Dollars in thousands)		2014			2013
	Extended maturities		$	—		$	—
	Interest rate adjustment			—			—
	Maturity and interest rate adjustment			—			—
	Movement to or extension of interest-rate only payments			—			—
	Forbearance			—			—
	Other concession(s) (1)			—			11,210

	Total		$	—		$	11,210

	(1)	Other concessions include concessions or a combination of concessions that do not consist of maturity extensions, interest rate adjustments, forbearance or covenant modifications.
TDRs [Member]	'
Schedule of Subsequently Defaulted TDRs	'
	Information about the Company’s TDRs occurring in these periods is presented in the following table.


			September 30, 2014									September 30, 2013
						Pre-modification			Post-modification					Pre-modification		Post-modification
						Outstanding			Outstanding					Outstanding		Outstanding
			Number of			Recorded			Recorded			Number of		Recorded		Recorded
	(In thousands, except number of loans)		Loans			Investment			Investment (1)			Loans		Investment		Investment (1)
	Commercial real estate			—		$	—		$	—			5	$	12,507	$	12,329

	Total			—		$	—		$	—			5	$	12,507	$	12,329

	(1)	Recorded investment includes any allowance for credit losses recorded on the TDRs at the dates indicated.
	Information detailing non-covered TDRs that subsequently defaulted during the previous twelve months is presented in the following table. The Company has defined a default as any loan with a loan payment that is currently past due greater than 30 days, or was past due greater than 30 days at any point during the previous twelve months, or since the date of modification, whichever is shorter.


			September 30, 2014						September 30, 2013
			Number of			Recorded			Number of			Recorded
	(In thousands, except number of loans)		Loans			Investment			Loans			Investment
	Commercial real estate			31		$	58			45		$	6,012
	Commercial business			11			1,767			13			12,370
	Residential prime			—			—			—			—
	Home Equity			—			—			1			47
	Indirect automobile			—			—			—			—
	Credit card			—			—			—			—
	Other			1			—			1			—

	Total			43		$	1,825			60		$	18,429
Non-Covered Loans Excluding Acquired Loans [Member]	'
Schedule of Aging of Non-Covered Loans	'
	The following tables provide an analysis of the aging of non-covered loans as of September 30, 2014 and December 31, 2013.

			September 30, 2014
			Non-covered loans excluding acquired loans
																Total Non-covered			Recorded
			Past Due (1)													Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total		Current		Unearned Income			and Accruing
	Commercial real estate construction		$	84		$	—		$	1,317		$	1,401	$	634,593	$	635,994		$	—
	Commercial real estate—other			1,347			640			6,789			8,776		2,882,842		2,891,618			—
	Commercial business			1,475			44			2,737			4,256		3,089,617		3,093,873			—
	Residential prime			1,859			1,349			10,973			14,181		362,513		376,694			—
	Residential subprime			—			2			6,197			6,199		114,182		120,381			—
	Home equity			1,783			201			7,310			9,294		1,220,704		1,229,998			4
	Indirect automobile			1,825			502			1,338			3,665		390,413		394,078			—
	Credit card			149			123			987			1,259		67,472		68,731			—
	Other			720			337			416			1,473		367,102		368,575			—

	Total		$	9,242		$	3,198		$	38,064		$	50,504	$	9,129,438	$	9,179,942		$	4

			December 31, 2013
			Non-covered loans excluding acquired loans
																Total Non-covered			Recorded
			Past Due (1)													Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total		Current		Unearned Income			and Accruing
	Commercial real estate construction		$	—		$	—		$	1,803		$	1,803	$	381,292	$	383,095		$	—
	Commercial real estate—other			6,098			5,630			7,650			19,378		2,732,431		2,751,809			2
	Commercial business			2,117			423			15,020			17,560		2,888,491		2,906,051			—
	Residential prime			1,104			852			9,684			11,640		286,167		297,807			1,073
	Residential subprime			—			—			1,626			1,626		114,939		116,565			—
	Home equity			1,956			569			6,808			9,333		1,091,894		1,101,227			—
	Indirect automobile			1,427			293			1,275			2,995		370,388		373,383			—
	Credit card			266			92			411			769		62,873		63,642			—
	Other			458			106			485			1,049		293,693		294,742			—

	Total		$	13,426		$	7,965		$	44,762		$	66,153	$	8,222,168	$	8,288,321		$	1,075

	(1)	Past due loans include loans on nonaccrual status as of the period indicated. Nonaccrual loans are presented separately in the “Nonaccrual Loans” section below.
Non-Covered Acquired Loans [Member]	'
Schedule of Aging of Non-Covered Loans	'

			September 30, 2014
			Non-covered acquired loans
																			Total Non-covered		Recorded
			Past Due (1)																Loans, Net of		Investment > 90 days
	(Dollars in		30-59 days			60-89 days			> 90 days			Total		Current		Discount/ Premium			Unearned Income		and Accruing
	thousands)		30-59 days			60-89 days			> 90 days			Total		Current		Discount/ Premium			Unearned Income		and Accruing
	Commercial real estate construction		$	340		$	45		$	2,118		$	2,503	$	36,832	$	(2,061	)	$	37,274	$	1,821
	Commercial real estate—other			1,464			277			22,081			23,822		486,238		(42,527	)		467,533		20,614
	Commercial business			717			25			1,905			2,647		101,722		(5,144	)		99,225		1,892
	Residential prime			76			931			7,437			8,444		432,837		631			441,912		369
	Home equity			1,615			1,003			8,203			10,821		228,051		(10,803	)		228,069		4,102
	Indirect automobile			7			1			43			51		606		(44	)		613		43
	Other			337			7			2,051			2,395		109,599		(11,552	)		100,442		389

	Total		$	4,556		$	2,289		$	43,838		$	50,683	$	1,395,885	$	(71,500	)	$	1,375,068	$	29,230

			December 31, 2013
			Non-covered acquired loans
																			Total Non-covered		Recorded
			Past Due (1)																Loans, Net of		Investment > 90 days
	(Dollars in		30-59 days			60-89 days			> 90 days			Total		Current		Discount/ Premium			Unearned Income		and Accruing
	thousands)		30-59 days			60-89 days			> 90 days			Total		Current		Discount/ Premium			Unearned Income		and Accruing
	Commercial real estate construction		$	388		$	—		$	2,542		$	2,930	$	19,833	$	(2,532	)	$	20,231	$	2,542
	Commercial real estate—other			1,798			1,963			27,967			31,728		345,286		(52,176	)		324,838		27,967
	Commercial business			544			—			1,218			1,762		54,189		(2,914	)		53,037		1,218
	Residential prime			—			—			226			226		18,796		(887	)		18,135		226
	Home equity			313			516			4,242			5,071		53,995		(5,623	)		53,443		4,242
	Indirect automobile			33			—			95			128		1,725		—			1,853		95
	Other			175			101			975			1,251		12,598		(1,481	)		12,368		975

	Total		$	3,251		$	2,580		$	37,265		$	43,096	$	506,422	$	(65,613	)	$	483,905	$	37,265


	(1)	Past due information presents acquired loans at the gross loan balance, prior to application of discounts.

Allowance_for_Credit_Losses_an1

Allowance for Credit Losses and Credit Quality (Tables)	9 Months Ended
Allowance for Credit Losses and Credit Quality (Tables)	Sep. 30, 2014
Schedule of Allowance for Loan Losses for Covered Loan and Non-Covered Loan Portfolios	'
	A summary of changes in the allowance for credit losses for the covered loan and non-covered loan portfolios for the nine months ended September 30, 2014 and 2013 is as follows:


		September 30, 2014
		Non-covered loans
		Excluding
	(Dollars in thousands)	Acquired Loans			Acquired Loans			Covered Loans			Total
	Allowance for credit losses
	Balance at beginning of period	$	67,342		$	4,557		$	71,175		$	143,074
	(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements		9,099			(1,259	)		5,878			13,718
	Adjustment attributable to FDIC loss share arrangements		—			—			(1,153	)		(1,153	)

	Net (reversal of) provision for loan losses		9,099			(1,259	)		4,725			12,565
	Adjustment attributable to FDIC loss share arrangements		—			—			1,153			1,153
	Transfer of balance to OREO		—			(207	)		(5,171	)		(5,378	)
	Loans charged-off		(8,242	)		(586	)		(12,823	)		(21,651	)
	Recoveries		4,338			401			38			4,777

	Balance at end of period	$	72,537		$	2,906		$	59,097		$	134,540
	Reserve for unfunded lending commitments
	Balance, beginning of period	$	11,147		$	—		$	—		$	11,147
	Provision for unfunded lending commitments		952			—			—			952

	Balance at end of period	$	12,099		$	—		$	—		$	12,099

		September 30, 2013
		Non-covered loans
		Excluding
		Acquired Loans			Acquired Loans			Covered Loans			Total
	Allowance for loan losses
	Balance at beginning of period	$	74,211		$	8,816		$	168,576		$	251,603
	(Reversal of) Provision for loan losses before adjustment attributable to FDIC loss share agreements		2,884			(2,464	)		(58,540	)		(58,120	)
	Adjustment attributable to FDIC loss share arrangements		—			—			58,565			58,565

	Net (reversal of) provision for loan losses		2,884			(2,464	)		25			445
	Adjustment attributable to FDIC loss share arrangements		—			—			(58,565	)		(58,565	)
	Transfer of balance to OREO		—			(1,013	)		(29,302	)		(30,315	)
	Transfer of balance to the RULC		(9,828	)		—			—			(9,828	)
	Loans charged-off		(7,455	)		(10	)		(1,683	)		(9,148	)
	Recoveries		4,353			—			—			4,353

	Balance at end of period		64,165			5,329		$	79,051		$	148,545
	Reserve for unfunded lending commitments
	Balance, beginning of period		—			—			—			—
	Transfer of balance from the allowance for loan losses		9,828			—			—			9,828
	Provision for unfunded lending commitments		2,131			—			—			2,131

	Balance at end of period	$	11,959		$	—		$	—		$	11,959
Schedule of Allowance for Loan Losses for Non-Covered Loans, by Loan Portfolio	'
	A summary of changes in the allowance for credit losses for non-covered loans, by loan portfolio type, for the nine months ended September 30, 2014 and 2013 is as follows:


		September 30, 2014
		Commercial			Commercial
	(Dollars in thousands)	real estate			business			Mortgage			Consumer			Unallocated			Total
	Allowance for loan losses
	Balance at beginning of period	$	26,590		$	28,515		$	2,546		$	14,248		$	—		$	71,899
	(Reversal of) Provision for loan losses		611			2,187			514			4,528			—			7,840
	Transfer of balance to OREO		—			(130	)		(12	)		(65	)		—			(207	)
	Loans charged off		(1,214	)		(1,097	)		(607	)		(5,910	)		—			(8,828	)
	Recoveries		2,209			93			134			2,303			—			4,739

	Balance at end of period	$	28,196		$	29,568		$	2,575		$	15,104		$	—		$	75,443
	Reserve for unfunded commitments
	Balance at beginning of period	$	3,089		$	4,839		$	72		$	3,147		$	—		$	11,147
	(Reversal of) Provision for unfunded commitments		726			192			11			23			—			952

	Balance at end of period	$	3,815		$	5,031		$	83		$	3,170		$	—		$	12,099
	Allowance on loans individually evaluated for impairment	$	25		$	—		$	—		$	—		$	—		$	25
	Allowance on loans collectively evaluated for impairment		28,171			29,568			2,575			15,104			—			75,418
	Loans, net of unearned income:
	Balance at end of period	$	4,032,419		$	3,193,098		$	938,987		$	2,390,506		$	—		$	10,555,010
	Balance at end of period individually evaluated for impairment		7,357			3,276			—			706			—			11,339
	Balance at end of period collectively evaluated for impairment		4,025,062			3,189,822			938,987			2,389,800			—			10,543,671
	Balance at end of period acquired with deteriorated credit quality		15,061			2,562			160			1,707			—			19,490

		September 30, 2013
		Commercial			Commercial
	(Dollars in thousands)	real estate			business			Mortgage			Consumer			Unallocated			Total
	Allowance for credit losses
	Balance at beginning of period	$	38,264		$	28,721		$	2,125		$	13,917		$	—		$	83,027
	(Reversal of) Provision for loan losses		(6,926	)		(582	)		1,048			6,880			—			420
	Transfer of balance to OREO		(279	)		(81	)		(646	)		(7	)		—			(1,013	)
	Transfer of balance to the RULC		(2,939	)		(3,497	)		(40	)		(3,352	)		—			(9,828	)
	Loans charged off		(1,966	)		(531	)		(481	)		(4,487	)		—			(7,465	)
	Recoveries		1,498			354			698			1,803			—			4,353

	Balance at end of period	$	27,652		$	24,384		$	2,704		$	14,754		$	—		$	69,494
	Reserve for unfunded commitments
	Balance at beginning of period	$	—		$	—		$	—		$	—		$	—		$	—
	Transfer of balance from the allowance for loan losses		2,939			3,497			40			3,352						9,828
	Provision for unfunded commitments		1,207			610			38			276						2,131

	Balance at end of period	$	4,146		$	4,107		$	78		$	3,628		$	—		$	11,959

	Allowance on loans individually evaluated for impairment	$	8		$	801		$	283		$	—		$	—		$	1,092
	Allowance on loans collectively evaluated for impairment		27,644			23,583			2,421			14,754			—			68,402
	Loans, net of unearned income:
	Balance at end of period	$	3,320,333		$	2,643,822		$	409,940		$	1,861,940		$	—		$	8,236,035
	Balance at end of period individually evaluated for impairment		9,529			14,548			1,407			263			—			25,747
	Balance at end of period collectively evaluated for impairment		3,310,804			2,629,274			408,533			1,861,677			—			8,210,288
	Balance at end of period acquired with deteriorated credit quality		16,287			45			120			1,815			—			18,267
Schedule of Allowance for Loan Losses for Covered Loans, by Loan Portfolio	'
	A summary of changes in the allowance for credit losses for covered loans, by loan portfolio type, for the nine months ended September 30, 2014 and 2013 is as follows:


		September 30, 2014
		Commercial			Commercial
	(Dollars in thousands)	real estate			business			Mortgage			Consumer			Unallocated			Total
	Allowance for loan losses
	Balance at beginning of period	$	38,772		$	5,380		$	10,889		$	16,134		$	—		$	71,175
	Provision for loan losses		2,544			376			971			834			—			4,725
	(Decrease) Increase in FDIC loss share receivable		734			609			(2,911	)		2,721			—			1,153
	Transfer of balance to OREO		(1,874	)		(1,162	)		(648	)		(1,487	)		—			(5,171	)
	Loans charged off		(9,578	)		(2,192	)		(90	)		(963	)		—			(12,823	)
	Recoveries		38			—			—			—			—			38

	Balance at end of period	$	30,636		$	3,011		$	8,211		$	17,239		$	—		$	59,097
	Allowance on loans individually evaluated for impairment	$	—		$	—		$	—		$	—		$	—		$	—
	Allowance on loans collectively evaluated for impairment		30,636			3,011			8,211			17,239			—			59,097
	Loans, net of unearned income:
	Balance at end of period	$	247,156		$	34,234		$	130,976		$	111,823		$	—		$	524,189
	Balance at end of period individually evaluated for impairment		—			—			—			—			—			—
	Balance at end of period collectively evaluated for impairment		247,156			34,234			130,976			111,823			—			524,189
	Balance at end of period acquired with deteriorated credit quality		4,678			620			24,304			16,699			—			46,301

		30-Sep-13
		Commercial			Commercial
	(Dollars in thousands)	real estate			business			Mortgage			Consumer			Unallocated			Total
	Allowance for credit losses
	Balance at beginning of period	$	100,871		$	11,375		$	22,566		$	33,764		$	—		$	168,576
	(Reversal of) Provision for loan losses		27			—			(1	)		(1	)		—			25
	(Decrease) Increase in FDIC loss share receivable		(30,853	)		(3,137	)		(5,734	)		(18,841	)		—			(58,565	)
	Transfer of balance to OREO		(22,375	)		(314	)		(6,614	)		1			—			(29,302	)
	Loans charged off		(1,683	)		—			—			—			—			(1,683	)

	Balance at end of period	$	45,987		$	7,924		$	10,217		$	14,923		$	—		$	79,051
	Allowance on loans individually evaluated for impairment	$	—		$	—		$	—		$	—		$	—		$	—
	Allowance on loans collectively evaluated for impairment		45,987			7,924			10,217			14,923			—			79,051
	Loans, net of unearned income:
	Balance at end of period	$	459,506		$	40,422		$	153,515		$	153,559		$	—		$	807,002
	Balance at end of period individually evaluated for impairment		—			—			—			—			—			—
	Balance at end of period collectively evaluated for impairment		459,506			40,422			153,515			153,559			—			807,002
	Balance at end of period acquired with deteriorated credit quality		23,751			—			28,333			26,400			—			78,484
Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator	'
	Credit quality information in the tables below includes loans acquired at the gross loan balance, prior to the application of premiums/discounts, at September 30, 2014 and December 31, 2013.


		Non-covered loans excluding acquired loans
		September 30, 2014															December 31, 2013
					Special															Special
	(Dollars in thousands)	Pass			Mention			Substandard			Doubtful			Total			Pass			Mention			Substandard		Doubtful		Total
	Commercial real estate construction	$	624,592		$	249		$	11,153		$	—		$	635,994		$	370,824		$	9,309		$	2,962	$	—	$	383,095
	Commercial real estate—other		2,817,777			46,718			26,700			423			2,891,618			2,694,161			27,227			30,308		113		2,751,809
	Commercial business		3,047,885			23,093			20,921			1,974			3,093,873			2,866,794			6,164			32,167		926		2,906,051

	Total	$	6,490,254		$	70,060		$	58,774		$	2,397		$	6,621,485		$	5,931,779		$	42,700		$	65,437	$	1,039	$	6,040,955


		Non-covered loans excluding acquired loans
		30-Sep-14									31-Dec-13
					30+ Days									30+ Days
	(Dollars in thousands)	Current			Past Due			Total			Current			Past Due			Total
	Residential prime	$	362,513		$	14,181		$	376,694		$	286,167		$	11,640		$	297,807
	Residential subprime		114,182			6,199			120,381			114,939			1,626			116,565
	Home equity		1,220,704			9,294			1,229,998			1,091,894			9,333			1,101,227
	Indirect automobile		390,413			3,665			394,078			370,388			2,995			373,383
	Credit card		67,472			1,259			68,731			62,873			769			63,642
	Consumer—other		367,102			1,473			368,575			293,693			1,049			294,742

	Total	$	2,522,386		$	36,071		$	2,558,457		$	2,219,954		$	27,412		$	2,247,366
Schedule of Investment in Legacy Impaired Loan	'
	Information on the Company’s investment in legacy impaired loans is presented in the following tables as of and for the periods indicated.


		September 30, 2014									December 31, 2013
					Unpaid									Unpaid
		Recorded			Principal			Related			Recorded			Principal			Related
	(Dollars in thousands)	Investment			Balance			Allowance			Investment			Balance			Allowance
	With no related allowance recorded:
	Commercial real estate	$	6,990		$	6,990		$	—		$	8,567		$	8,567		$	—
	Commercial business		3,276			3,276			—			13,256			13,256			—
	Home equity		689			689			—			258			258			—
	With an allowance recorded:
	Commercial real estate		1,450			1,483			(33	)		1,268			1,284			(16	)
	Commercial business		186			188			(2	)		1,927			2,770			(843	)
	Residential prime		10,746			10,973			(227	)		9,791			10,019			(228	)
	Residential subprime		6,169			6,197			(28	)		1,617			1,626			(9	)
	Home equity		7,017			7,064			(47	)		6,506			6,550			(44	)
	Indirect automobile		1,330			1,338			(8	)		1,267			1,275			(8	)
	Credit card		968			987			(19	)		404			411			(7	)
	Other		429			433			(4	)		481			485			(4	)

	Total	$	39,250		$	39,618		$	(368	)	$	45,342		$	46,501			(1,159	)
	Total commercial loans		11,902			11,937			(35	)		25,018			25,877			(859	)
	Total mortgage loans		16,915			17,170			(255	)		11,408			11,645			(237	)
	Total consumer loans		10,433			10,511			(78	)		8,916			8,979			(63	)


		For the Three Months Ended September 30												For the Nine Months Ended September 30
		2014						2013						2014						2013
		Average			Interest			Average			Interest			Average			Interest			Average			Interest
		Recorded			Income			Recorded			Income			Recorded			Income			Recorded			Income
	(Dollars in thousands)	Investment			Recognized			Investment			Recognized			Investment			Recognized			Investment			Recognized
	With no related allowance recorded:
	Commercial real estate	$	7,026		$	6		$	10,703		$	6		$	7,114		$	20		$	12,787		$	22
	Commercial business		3,553			11			13,218			17			4,417			48			8,608			59
	Home equity		692			—			265			—			700			14			287			—
	With an allowance recorded:
	Commercial real estate		1,631			—			4,346			—			1,533			91			6,092			5
	Commercial business		312			—			2,739			—			584			9			2,746			3
	Residential prime		11,077			—			9,650			—			10,226			119			9,380			7
	Residential subprime		6,228			—			—			—			6,115			—			—			—
	Home equity		7,177			5			7,244			—			7,404			40			7,458			14
	Indirect automobile		1,544			—			1,349			—			1,720			27			1,610			22
	Credit card		1,051			—			424			—			724			—			426			—
	Other		470			—			372			—			489			11			446			4

	Total	$	40,761		$	22		$	50,310		$	23		$	41,026		$	379		$	49,840		$	136
	Total commercial loans		12,522			17			31,006			23			13,648			168			30,233			89
	Total mortgage loans		17,305			—			9,650			—			16,341			119			9,380			7
	Total consumer loans		10,934			5			9,654			—			11,037			92			10,227			40
Covered Loans [Member]	'
Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator	'

		Non-covered acquired loans
		September 30, 2014																		December 31, 2013
					Special																		Special
	(Dollars in thousands)	Pass			Mention			Substandard			Doubtful			Discount			Total			Pass			Mention		Substandard		Doubtful			Discount			Total
	Commercial real estate construction	$	30,675		$	3,671		$	4,989		$	—		$	(2,061	)	$	37,274		$	17,132		$	196	$	5,435	$	—		$	(2,532	)	$	20,231
	Commercial real estate—other		456,790			11,065			42,027			178			(42,527	)		467,533			310,303			15,351		51,267		93			(52,176	)		324,838
	Commercial business		97,383			2,203			4,571			212			(5,144	)		99,225			51,414			1,920		2,586		31			(2,914	)		53,037

	Total	$	584,848		$	16,939		$	51,587		$	390		$	(49,732	)	$	604,032		$	378,849		$	17,467	$	59,288	$	124		$	(57,622	)	$	398,106


		Non-covered acquired loans
		September 30, 2014												December 31, 2013
					30+ Days			Premium									30+ Days			Premium
	(Dollars in thousands)	Current			Past Due			(discount)			Total			Current			Past Due			(discount)			Total
	Residential prime	$	432,837		$	8,444		$	631		$	441,912		$	18,796		$	226		$	(887	)	$	18,135
	Home equity		228,051			10,821			(10,803	)		228,069			53,995			5,071			(5,623	)		53,443
	Indirect automobile		606			51			(44	)		613			1,725			128			—			1,853
	Consumer—other		109,599			2,395			(11,552	)		100,442			12,598			1,251			(1,481	)		12,368

	Total	$	771,093		$	21,711		$	(21,768	)	$	771,036		$	87,114		$	6,676		$	(7,991	)	$	85,799
Acquired Loans [Member]	'
Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator	'
	The Company’s investment in covered loans by credit quality indicator is presented in the following table. Loan premiums/discounts in the tables below represent the adjustment of covered loans to fair value at the date indicated, as adjusted for income accretion and changes in cash flow estimates in subsequent periods.


		Covered loans
		30-Sep-14															31-Dec-13
					Special															Special
	(Dollars in thousands)	Pass			Mention			Substandard			Doubtful			Total			Pass			Mention			Substandard		Doubtful		Total
	Commercial real estate construction	$	40,754		$	1,822		$	9,285		$	—		$	51,861		$	42,886		$	7,401		$	23,891	$	497	$	74,675
	Commercial real estate—other		113,309			22,277			75,353			—			210,939			148,579			49,699			144,680		3,267		346,225
	Commercial business		26,087			887			8,814			46			35,834			30,710			780			14,556		984		47,030

		$	180,150		$	24,986		$	93,452		$	46		$	298,634		$	222,175		$	57,880		$	183,127	$	4,748	$	467,930

	Discount														(17,244	)												(43,573	)

	Total													$	281,390												$	424,357


		Covered loans
		September 30, 2014												December 31, 2013
					30+ Days			Premium									30+ Days			Premium
	(Dollars in thousands)	Current			Past Due			(discount)			Total			Current			Past Due			(discount)			Total
	Residential prime	$	143,529		$	23,993		$	(36,546	)	$	130,976		$	158,710		$	30,814		$	(35,499	)	$	154,025
	Home equity		115,813			19,403			(27,405	)		107,811			143,236			35,811			(41,925	)		137,122
	Credit card		588			33			—			621			648			31			—			679
	Consumer—other		498			23			2,870			3,391			591			144			2,875			3,610

	Total	$	260,428		$	43,452		$	(61,081	)	$	242,799		$	303,185		$	66,800		$	(74,549	)	$	295,436

Loss_Sharing_Agreements_and_FD1

Loss Sharing Agreements and FDIC Loss Share Receivable (Tables)	9 Months Ended
	Sep. 30, 2014
Text Block [Abstract]	'
Schedule of FDIC Loss Share Receivables	'
	The following is a summary of FDIC loss share receivables year-to-date activity:


		Nine Months Ended
		September 30
	(Dollars in thousands)	2014			2013
	Balance at beginning of period	$	162,312		$	423,069
	Change due to (reversal of) loan loss provision recorded on FDIC covered loans		1,153			(58,565	)
	Amortization		(61,393	)		(68,707	)
	Submission of reimbursable losses to (recoveries payable to) the FDIC		4,901			(44,910	)
	Impairment		(5,097	)		(31,813	)
	Changes due to a change in cash flow assumptions on OREO and other changes		(7,164	)		(14,189	)

	Balance at end of period	$	94,712		$	204,885

Transfers_and_Servicing_of_Fin1

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) (Tables)	9 Months Ended
	Sep. 30, 2014
Transfers and Servicing [Abstract]	'
Components of Mortgage Banking Activity	'
	The following table details the mortgage banking activity as of and for the nine months ended September 30:


	(Dollars in thousands)	2014			2013
	Balance at beginning of period	$	128,442		$	267,475
	Originations and purchases		1,218,684			1,712,557
	Sales, net of gains		(1,193,282	)		(1,871,747	)
	Other		(5,314	)		—

	Balance at end of period	$	148,530		$	108,285


	(Dollars in thousands)	2014			2013
	Fair value changes of derivatives and mortgage loans held for sale, net	$	(1,081	)	$	(270	)
	Gains on sales		41,412			51,709
	Servicing and other income, net		572			402

	Total mortgage income	$	40,903		$	51,841

Goodwill_and_Other_Acquired_In1

Goodwill and Other Acquired Intangible Assets (Tables)	9 Months Ended
Goodwill and Other Acquired Intangible Assets (Tables)	Sep. 30, 2014
Schedule of Definite-Lived Intangible Assets	'
	Definite-lived intangible assets had the following carrying values included in Other assets on the Company’s consolidated balance sheet as of the periods indicated:


		September 30, 2014							December 31, 2013
		Gross		Accumulated			Net		Gross		Accumulated			Net
		Carrying		Accumulated			Carrying		Carrying		Accumulated			Carrying
	(Dollars in thousands)	Amount		Amortization			Amount		Amount		Amortization			Amount
	Core deposit intangibles	$	50,564	$	(34,564	)	$	16,000	$	45,406	$	(30,784	)	$	14,622
	Customer relationship intangible asset		1,348		(777	)		571		1,348		(631	)		717
	Non-compete agreement		163		(53	)		110		—		—			—
	Other intangible assets		205		(29	)		176		—		—			—

	Total	$	52,280	$	(35,423	)	$	16,857	$	46,754	$	(31,415	)	$	15,339
Schedule of Carrying Amount of Goodwill	'
	Changes to the carrying amount of goodwill by reportable segment for the nine months ended September 30, 2014 and the year ended December 31, 2013 are provided in the following table.


	(Dollars in thousands)	IBERIABANK		IMC			LTC		Total
	Balance, December 31, 2012	$	373,905	$	23,178		$	4,789	$	401,872
	Goodwill acquired during the year		—		—			—		—

	Balance, December 31, 2013		373,905	$	23,178		$	4,789		401,872
	Goodwill acquired during the period		123,995		—			375		124,370

	Balance, September 30, 2014	$	497,900	$	23,178		$	5,164	$	526,242
Mortgage Servicing Rights [Member]	'
Schedule of Definite-Lived Intangible Assets	'
	Mortgage servicing rights had the following carrying values as of the periods indicated:


		September 30, 2014							December 31, 2013
		Gross Carrying		Accumulated			Net Carrying		Gross Carrying		Accumulated			Net Carrying
	(Dollars in thousands)	Amount		Amortization			Amount		Amount		Amortization			Amount
	Mortgage servicing rights	$	2,787	$	(1,020	)	$	1,767	$	2,146	$	(638	)	$	1,508

Other_Real_Estate_Owned_Tables

Other Real Estate Owned (Tables)	9 Months Ended
Other Real Estate Owned (Tables)	Sep. 30, 2014
Banking and Thrift [Abstract]	'
Schedule of Other Real Estate Owned Segregated Into Non-Covered and Covered Properties	'
	Other real estate owned is included in Other assets on the Company’s consolidated balance sheet. Other real estate owned, segregated into non-covered and covered properties, consists of the following for the periods indicated. For further discussion of loss share coverage periods applicable to the covered foreclosed assets, see Note 8 to these consolidated financial statements.


			September 30, 2014						December 31, 2013
	(Dollars in thousands)		Non-covered		Covered(1)		Total		Non-covered		Covered		Total
	Real estate owned acquired by foreclosure		$	18,627	$	30,991	$	49,618	$	28,072	$	60,474	$	88,546
	Real estate acquired for development or resale			12,734		—		12,734		9,206		—		9,206
	Other foreclosed property			63		971		1,034		93		1,328		1,421

	Total		$	31,424	$	31,962	$	63,386	$	37,371	$	61,802	$	99,173

	(1)	Included in covered OREO at September 30, 2014 is $20.6 million that will lose loss share coverage within the next 12 months.

Derivative_Instruments_and_Oth1

Derivative Instruments and Other Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Schedule of Outstanding Derivative Instruments	'
	Information pertaining to outstanding derivative instruments is as follows:


	(Dollars in thousands)		Balance Sheet				Asset Derivatives Fair Value								Balance Sheet				Liability Derivatives Fair Value
			Location				September 30, 2014				December 31, 2013				Location				September 30, 2014			December 31, 2013
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts			Other assets			$	11,839			$	10,621				Other liabilities			$	11,839		$	10,620
	Forward sales contracts			Other assets				104				1,468				Other liabilities				2,215			287
	Written and purchased options			Other assets				20,347				17,987				Other liabilities				15,786			15,828

	Total derivatives not designated as hedging instruments under ASC Topic 815							32,290				30,076								29,840			26,735

	Total						$	32,290			$	30,076							$	29,840		$	26,735

	(Dollars in thousands)						Asset Derivatives Notional Amount												Liability Derivatives Notional Amount
							30-Sep-14				31-Dec-13								30-Sep-14			31-Dec-13
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts						$	421,523			$	380,303							$	421,523		$	380,303
	Forward sales contracts							88,190				192,876								351,861			45,091
	Written and purchased options							363,239				295,425								197,044			199,061

	Total derivatives not designated as hedging instruments under ASC Topic 815							872,952				868,604								970,428			624,455

	Total						$	872,952			$	868,604							$	970,428		$	624,455
Reconciliation of Gross Amounts in Consolidated Balance Sheets	'
	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, 2014
	(Dollars in thousands)		Gross Amounts				Gross Amounts Not Offset
			Presented in the				in the Balance Sheet
			Balance Sheet				Derivatives				Collateral (1)				Net
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			11,839				—				—				11,839
	Written and purchased options			15,423				—				—				15,423

	Total derivative assets subject to master netting arrangements		$	27,262			$	—			$	—			$	27,262
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			11,839				—				(3,892	)			7,947

	Total derivative liabilities subject to master netting arrangements		$	11,839			$	—			$	(3,892	)		$	7,947

	-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.


			December 31, 2013
	(Dollars in thousands)		Gross Amounts				Gross Amounts Not Offset
			Presented in the				in the Balance Sheet
			Balance Sheet				Derivatives				Collateral (1)				Net
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			10,621				—				—				10,621
	Written and purchased options			15,801				—				—				15,801

	Total derivative assets subject to master netting arrangements		$	26,422			$	—			$	—			$	26,422
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			10,620				—				(5,419	)			5,201

	Total derivative liabilities subject to master netting arrangements		$	10,620			$	—			$	(5,419	)		$	5,201

	-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
Effect of Hedging Instruments on Consolidated Financial Statements	'
	At September 30, 2014 and 2013, 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:


	(Dollars in thousands)		Amount of Gain (Loss)								Location of Gain		Amount of								Location of	Amount of Gain (Loss)
			Recognized								(Loss)		Gain (Loss)								Gain (Loss)	Recognized in Income
			in OCI net of taxes								Reclassified		Reclassified								Recognized	on Derivative (Ineffective
			(Effective Portion)								from		from								in Income on	Portion and Amount
											Accumulated		Accumulated								Derivative	Excluded from
											OCI into Income		OCI into								(Ineffective	Effectiveness Testing)
											(Effective		Income								Portion and
											Portion)		(Effective								Amount
													Portion)								Excluded from
																					Effectiveness
																					Testing
			As of September 30										For the Three Months Ended September 30
	Derivatives in ASC Topic 815 Cash
	Flow Hedging Relationships		2014				2013						2014				2013					2014			2013
	Interest rate contracts		$	—			$	—			Other income		$	—			$	—			Other income	$	—		$	—
	Interest rate contracts		$	—			$	—			(expense)		$	—			$	—			(expense)	$	—		$	—

	Total		$	—			$	—					$	—			$	—				$	—		$	—



																			Location of Gain			Amount of Gain
																			(Loss)			Amount of Gain
																			Recognized in			(Loss)
																			Income on			Recognized in
							Location of Gain				Amount of Gain								Derivative (Ineffective			Income on
	Amount of Gain (Loss)						(Loss) Reclassified				(Loss) Reclassified								Portion and Amount			Derivative (Ineffective
	Recognized in OCI net of						from Accumulated				from Accumulated OCI								Excluded from			Portion and Amount
	taxes (Effective						OCI into Income				into Income								Effectiveness			Excluded from
	Portion)						(Effective Portion)				(Effective Portion)								Testing			Effectiveness Testing)
	As of September 30										For the Nine Months Ended September 30
	2014		2013								2014				2013							2014			2013
	$ —		$	—				Other income			$	—			$	(392	)			Other income		$	(1	)	$	—
	$ —		$	—				(expense	)		$	—			$	(392	)			(expense	)	$	(1	)	$	—

	$ —		$	—							$	—			$	(392	)					$	(1	)	$	—



	(Dollars in thousands)		Amount of Gain (Loss) Recognized in Income on Derivatives
	Derivatives Not Designated as		Location of Gain (Loss)
	Hedging Instruments under ASC		Recognized in Income on		For the Three Months Ended								For the Nine Months Ended
	Topic 815		Derivatives		September 30								September 30
					2014				2013				2014				2013
	Interest rate contracts		Other income (expense)		$	406			$	2,061				1,971				2,542
	Forward sales contracts		Mortgage Income			(3,648	)			3,290				(7,512	)			897
	Written and purchased options		Mortgage Income			773				(7,896	)			2,401				(3,820	)

	Total				$	(2,469	)		$	(2,545	)		$	(3,140	)		$	(381	)

Shareholders_Equity_and_Other_1

Shareholders' Equity and Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Summary of Tax Effects of Each Component of Other Comprehensive Income	'
	The following is a summary of the tax effects of each component of other comprehensive income for the periods indicated:


			Three Months Ended
			30-Sep-14
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized gain on securities:
	Unrealized holding losses arising during the period		$	(7,032	)		$	2,461			$	(4,571	)
	Less: reclassification adjustment for gains included in net income			(582	)			204				(378	)

	Net unrealized losses			(7,614	)			2,665				(4,949	)
	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		$	—			$	—			$	—
	Less: reclassification adjustment for losses (gains) included in net income			—				—				—

	Fair value of derivative instruments designated as cash flow hedges			—				—				—

	Total other comprehensive loss		$	(7,614	)		$	2,665			$	(4,949	)


			Three Months Ended
			30-Sep-13
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period		$	5,528			$	(1,935	)		$	3,593
	Less: reclassification adjustment for losses included in net income			3				(1	)			2

	Net unrealized losses			5,531				(1,936	)			3,595
	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		$	—			$	—			$	—
	Less: reclassification adjustment for gains included in net income			—				—				—

	Fair value of derivative instruments designated as cash flow hedges			—				—				—

	Total other comprehensive income		$	5,531			$	(1,936	)		$	3,595


			Nine Months Ended
			30-Sep-14
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized loss on securities:
	Unrealized holding gains arising during the period		$	25,586			$	(8,955	)		$	16,631
	Less: reclassification adjustment for gains included in net income			(609	)			213				(396	)

	Net unrealized gains			24,977				(8,742	)			16,235
	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		$	—			$	—			$	—
	Less: reclassification adjustment for losses (gains) included in net income			—				—				—

	Fair value of derivative instruments designated as cash flow hedges			—				—				—

	Total other comprehensive income		$	24,977			$	(8,742	)		$	16,235

			Nine Months Ended
			30-Sep-13
			Before				Tax Expense				Net-of-Tax
	(Dollars in thousands)		Tax				(Benefit)				Amount
	Unrealized gain on securities:
	Unrealized holding losses arising during the period		$	(38,769	)		$	13,569			$	(25,200	)
	Less: reclassification adjustment for gains included in net income			(2,259	)			791				(1,468	)

Net unrealized losses			(41,028	)			14,360				(26,668	)
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		$	952			$	(333	)		$	619
Less: reclassification adjustment for losses included in net income			392				(137	)			255

Fair value of derivative instruments designated as cash flow hedges			1,344				(470	)			874

Total other comprehensive loss		$	(39,684	)		$	13,890			$	(25,794	)

Capital_Requirements_and_Other1

Capital Requirements and Other Regulatory Matters (Tables)	9 Months Ended
Capital Requirements and Other Regulatory Matters (Tables)	Sep. 30, 2014
Banking and Thrift [Abstract]	'
Actual Capital Amounts and Ratios	'
	The Company’s and IBERIABANK’s actual capital amounts and ratios as of September 30, 2014 and December 31, 2013 are presented in the following table.


	(Dollars in thousands)	September 30, 2014
		Minimum					Well Capitalized					Actual
		Amount		Ratio			Amount		Ratio			Amount		Ratio
	Tier 1 Leverage
	Consolidated	$	596,945		4	%	$	N/A		N/A	%	$	1,376,283		9.22	%
	IBERIABANK		594,578		4			743,223		5			1,225,980		8.25
	Tier 1 risk-based capital
	Consolidated		490,391		4	%	$	N/A		N/A	%	$	1,376,283		11.23	%
	IBERIABANK		489,049		4			733,574		6			1,225,980		10.03
	Total risk-based capital
	Consolidated		980,781		8	%	$	N/A		N/A	%	$	1,522,932		12.42	%
	IBERIABANK		978,099		8			1,222,624		10			1,372,629		11.23


		December 31, 2013
		Minimum					Well Capitalized					Actual
		Amount		Ratio			Amount		Ratio			Amount		Ratio
	Tier 1 Leverage
	Consolidated	$	507,760		4	%	$	N/A		N/A	%	$	1,231,886		9.7	%
	IBERIABANK		505,723		4			632,154		5			1,069,783		8.46
	Tier 1 risk-based capital
	Consolidated	$	426,002		4	%	$	N/A		N/A	%	$	1,231,886		11.57	%
	IBERIABANK		424,578		4			636,868		6			1,069,783		10.08
	Total risk-based capital
	Consolidated	$	852,005		8	%	$	N/A		N/A	%	$	1,365,280		12.82	%
	IBERIABANK		849,157		8			1,061,446		10			1,202,738		11.33

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	9 Months Ended
Share-Based Compensation (Tables)	Sep. 30, 2014
Compensation Expense Included in Non-Interest Expense and Related Income Tax Benefits	'
	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 three-month and nine-month periods ended September 30:


			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2014			2013			2014			2013
	Compensation expense related to stock options		$	508		$	526		$	1,545		$	1,592
	Income tax benefit related to stock options			178			184			541			557
	Impact on basic earnings per share			0.01			0.01			0.03			0.03
	Impact on diluted earnings per share			0.01			0.01			0.03			0.03
Estimate Fair Value of Share-Based Awards with Weighted-Average Assumptions	'
	The Company uses the Black-Scholes option pricing model to estimate the fair value of share-based awards. The following weighted-average assumptions were used for option awards outstanding during the nine-month periods ended September 30:


			2014			2013
	Expected dividends			2.1	%		2.6	%
	Expected volatility			35.8	%		34.8	%
	Risk-free interest rate			2.3	%		1.7	%
	Expected term (in years)			7.5			8.6
	Weighted-average grant-date fair value		$	21.25		$	15.37
Activity Related to Stock Options	'
	The following table represents the activity related to stock options during the periods indicated.


						Weighted Average			Weighted Average
			Number of shares			Exercise Price			Remaining Contract Life
	Outstanding options, December 31, 2012			1,236,075		$	51.48
	Granted			75,722			52.36
	Exercised			(142,841	)		38.09
	Forfeited or expired			(36,608	)		56.01

	Outstanding options, September 30, 2013			1,132,348		$	53.09			4.7 Years
	Exercisable options, September 30, 2013			749,545			52.94			3.2 Years
	Outstanding options, December 31, 2013			1,072,829		$	53.47
	Granted			77,098			65.3
	Exercised			(234,363	)		48.36
	Forfeited or expired			(13,446	)		60.82

	Outstanding options, September 30, 2014			902,118		$	55.7			5.2 Years
	Exercisable options, September 30, 2014			581,423			55.65			3.8 Years
Unvested Restricted Stock Award Activity	'
	The following table represents unvested restricted stock award activity for the nine months ended September 30:


			2014			2013
	Balance at beginning of period			523,756			538,202
	Granted			146,547			166,223
	Forfeited			(18,171	)		(27,483	)
	Earned and issued			(152,112	)		(136,629	)

	Balance at end of period			500,020			540,313
Schedule of Share and Dividend Equivalent Share Award Activity	'
	The following table represents phantom stock award activity during the periods indicated.


			Number of share			Dividend			Total share			Value of share
			equivalents			equivalents			equivalents			equivalents (1)
	Balance, December 31, 2012			318,729			16,035			334,764		$	16,444,000
	Granted			166,664			8,793			175,457			9,108,000
	Forfeited share equivalents			(16,381	)		(681	)		(17,062	)		(886,000	)
	Vested share equivalents			(45,065	)		(3,327	)		(48,392	)		(2,453,000	)

	Balance, September 30, 2013			423,947			20,820			444,767		$	23,088,000

	Balance, December 31, 2013			417,238			22,351			439,589		$	27,628,000
	Granted			115,620			7,147			122,767			7,674,000
	Forfeited share equivalents			(19,498	)		(1,751	)		(21,249	)		(1,328,000	)
	Vested share equivalents			(68,480	)		(6,615	)		(75,095	)		(5,002,000	)

	Balance, September 30, 2014			444,880			21,132			466,012		$	29,130,000

	(1)	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 $62.51 and $51.91 on September 30, 2014 and 2013, respectively.
Restricted Stock [Member]	'
Compensation Expense Included in Non-Interest Expense and Related Income Tax Benefits	'
	The following table represents the compensation expense that was included in non-interest expense in the accompanying consolidated statements of comprehensive income related to restricted stock grants:


			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands)		2014			2013			2014			2013
	Compensation expense related to restricted stock		$	2,497		$	2,212		$	7,382		$	6,407
Phantom Stock Awards [Member]	'
Compensation Expense Included in Non-Interest Expense and Related Income Tax Benefits	'
	The following table indicates compensation expense recorded for phantom stock based on the number of share equivalents vested at the end of the periods indicated and the current market price of the Company’s stock at that time.


			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands)		2014			2013			2014			2013
	Compensation expense related to phantom stock		$	619		$	792		$	3,692		$	2,602

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
Commitments and Contingencies (Tables)	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Summary of Financial Instruments Outstanding	'
	At September 30, 2014 and December 31, 2013, the Company had the following financial instruments outstanding, whose contract amounts represent credit risk:


	(Dollars in thousands)	September 30		December 31
	(Dollars in thousands)	2014		2013
	Commitments to grant loans	$	242,137	$	221,627
	Unfunded commitments under lines of credit		3,834,107		3,326,448
	Commercial and standby letters of credit		131,347		105,026
	Reserve for unfunded lending commitments		12,099		11,147

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
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 measured at fair value:


		September 30, 2014							December 31, 2013
	(Dollars in thousands)	Aggregate			Aggregate		Aggregate		Aggregate		Aggregate		Aggregate
		Fair Value			Unpaid		Fair Value		Fair Value		Unpaid		Fair Value
					Principal		Less Unpaid				Principal		Less Unpaid
							Principal						Principal
	Mortgage loans held for sale, at fair value	$	148,530		$	142,381	$	6,149	$	97,273	$	96,875	$	398
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.


	(Dollars in thousands)	September 30, 2014
		(Level 1)			(Level 2)		(Level 3)		Total
	Assets
	Available for sale securities	$	46,261		$	2,057,567	$	—	$	2,103,828
	Mortgage loans held for sale		—			148,530		—		148,530
	Derivative instruments		—			32,290		—		32,290

	Total	$	46,261		$	2,238,387	$	—	$	2,284,648
	Liabilities
	Derivative instruments		—			29,840		—		29,840

	Total	$	—		$	29,840	$	—	$	29,840

		31-Dec-13
		(Level 1)			(Level 2)		(Level 3)		Total
	Assets
	Available for sale securities	$	15,496		$	1,921,301	$	—	$	1,936,797
	Mortgage loans held for sale		—			97,273		—		97,273
	Derivative instruments		—			30,076		—		30,076

	Total	$	15,496		$	2,048,650	$	—	$	2,064,146
	Liabilities
	Derivative instruments		—			26,735		—		26,735

	Total	$	—		$	26,735	$	—	$	26,735
Gains and Losses Included in Earnings Related to Asset and Liabilities Measured at Fair Value on Recurring Basis	'
	Gains and losses (realized and unrealized) included in earnings (or changes in net assets) during 2014 related to assets and liabilities measured at fair value on a recurring basis are reported in non-interest income or other comprehensive income as follows:


	(Dollars in thousands)	Noninterest			Other
		income			comprehensive
					income
	Total gains (losses) included in earnings (or changes in net assets)	$	(1,697	)	$	—
	Change in unrealized gains (losses) relating to assets still held at September 30, 2014		—			16,235
Financial Asset and Liabilities Measured at Fair Value on Nonrecurring Basis	'
	The Company has segregated all financial 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.


	(Dollars in thousands)	September 30, 2014
		(Level 1)			(Level 2)		(Level 3)		Total
	Assets
	Loans	$	—		$	1,086	$	—	$	1,086
	OREO		—			6,974		—		6,974

	Total	$	—		$	8,060	$	—	$	8,060


	(Dollars in thousands)	December 31, 2013
		(Level 1)			(Level 2)		(Level 3)		Total
	Assets
	Loans	$	—		$	3,070	$	—	$	3,070
	Mortgage loans held for sale		—			11,876		—		11,876
	OREO		—			14,598		—		14,598

	Total	$	—		$	29,544	$	—	$	29,544

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	9 Months Ended
Fair Value of Financial Instruments (Tables)	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Estimated Fair Values and Carrying Amounts of Financial Instruments	'
	The estimated fair values and carrying amounts of the Company’s financial instruments are as follows:


		September 30, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
	(Dollars in thousands)	Amount		Value		Amount		Value
	Financial Assets
	Cash and cash equivalents	$	668,007	$	668,007	$	391,396	$	391,396
	Investment securities		2,224,348		2,226,286		2,090,906		2,089,363
	Loans and loans held for sale		11,227,729		11,247,080		9,620,461		9,724,432
	FDIC loss share receivable		94,712		27,922		162,312		21,918
	Derivative instruments		32,290		32,290		30,076		30,076
	Accrued interest receivable		37,143		37,143		32,143		32,143
	Financial Liabilities
	Deposits	$	12,377,775	$	11,986,233	$	10,737,000	$	10,226,573
	Short-term borrowings		812,783		812,783		680,344		680,344
	Long-term debt		355,569		324,282		280,699		235,503
	Derivative instruments		29,840		29,840		26,735		26,735
	Accrued interest payable		7,972		7,972		6,102		6,102

Business_Segments_Tables

Business Segments (Tables)	9 Months Ended
Business Segments (Tables)	Sep. 30, 2014
Segment Reporting [Abstract]	'
Schedule of Segment Reporting Information	'
	The Company’s wealth management, capital markets and trust operating segments are aggregated within the IBERIABANK reportable operating segment because they do not meet the thresholds specified by ASC 280 and based on the qualitative factors presented within ASC 280. The Company’s IMC and LTC segments do not meet the quantitative thresholds specified by ASC 280, but are reported because management believes information about those segments is useful to users of the financial statements.


			Three Months Ended September 30, 2014
	(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
	Interest income		$	131,362			$	1,804			$	1			$	133,167
	Interest expense			11,501				625				—				12,126

	Net interest income			119,861				1,179				1				121,041
	Provision for loan losses			5,621				93				—				5,714
	Mortgage income			(5	)			12,819				—				12,814
	Title income			—				—				5,577				5,577
	Other non-interest income			27,311				(37	)			(2	)			27,272
	Core deposit intangible amortization			1,429				—				—				1,429
	Allocated expenses			(2,386	)			1,697				689				—
	Other non-interest expenses			102,692				11,624				4,315				118,631

	Income before income taxes			39,811				547				572				40,930
	Income tax expense			10,739				217				230				11,186

	Net income		$	29,072			$	330			$	342			$	29,744
	Total loans and loans held for sale		$	11,055,809			$	171,920			$	—			$	11,227,729
	Total assets			15,288,157				202,923				25,529				15,516,609
	Total deposits			12,371,606				6,169				—				12,377,775
	Average assets			15,239,174				213,936				25,296				15,478,406


			Three Months Ended September 30, 2013
	(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
	Interest income		$	107,051			$	1,459			$	2			$	108,512
	Interest expense			10,731				329				—				11,060

	Net interest income			96,320				1,130				2				97,452
	Provision for loan losses			1,868				146				—				2,014
	Mortgage income			5				15,197				—				15,202
	Title income			—				—				5,482				5,482
	Other non-interest income			22,579				—				—				22,579
	Core deposit intangible amortization			1,125				—				—				1,125
	Allocated expenses			(2,658	)			1,933				725				—
	Other non-interest expenses			90,858				12,016				4,153				107,027

	Income before income taxes			27,711				2,232				606				30,549
	Income tax expense			6,228				877				252				7,357

	Net income		$	21,483			$	1,355			$	354			$	23,192
	Total loans and loans held for sale		$	9,024,959			$	126,363			$	—			$	9,151,322
	Total assets			12,965,373				153,402				26,302				13,145,077
	Total deposits			10,946,453				4,311				—				10,950,764
	Average assets			12,761,165				157,144				26,126				12,944,435


			Nine Months Ended September 30, 2014
	(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
	Interest income		$	362,054			$	4,563			$	2			$	366,619
	Interest expense			30,869				1,323				—				32,192

	Net interest income			331,185				3,240				2				334,427
	Provision for loan losses			12,481				84				—				12,565
	Mortgage income			80				40,823				—				40,903
	Title income			—				—				15,007				15,007
	Other non-interest income			73,460				(61	)			(2	)			73,397
	Core deposit intangible amortization			3,779				—				—				3,779
	Allocated expenses			(9,110	)			6,432				2,678				—
Other non-interest expenses			305,121				33,558				12,405				351,084

Income (loss) before income taxes			92,454				3,928				(76	)			96,306
Income tax expense (benefit)			24,081				1,552				(14	)			25,619

Net income (loss)		$	68,373			$	2,376			$	(62	)		$	70,687
Total loans and loans held for sale		$	11,055,809			$	171,920			$	—			$	11,227,729
Total assets			15,288,157				202,923				25,529				15,516,609
Total deposits			12,371,606				6,169				—				12,377,775
Average assets			14,097,930				179,218				25,003				14,302,151


		Nine Months Ended September 30, 2013
(Dollars in thousands)		IBERIABANK				IMC				LTC				Consolidated
Interest income		$	318,646			$	4,428			$	31			$	323,105
Interest expense			34,786				1,513				—				36,299

Net interest income			283,860				2,915				31				286,806
Provision for loan losses			320				125				—				445
Mortgage income			2				51,839				—				51,841
Title income			—				—				16,199				16,199
Other non-interest income			62,206				(4	)			—				62,202
Core deposit intangible amortization			3,375				—				—				3,375
Allocated expenses			(4,402	)			3,213				1,189				—
Other non-interest expenses			315,332				38,942				12,761				367,035

Income before income taxes			31,443				12,470				2,280				46,193
Income tax expense (benefit)			884				4,897				913				6,694

Net income		$	30,559			$	7,573			$	1,367			$	39,499
Total loans and loans held for sale		$	9,024,959			$	126,363			$	—			$	9,151,322
Total assets			12,965,373				153,402				26,302				13,145,077
Total deposits			10,946,453				4,311				—				10,950,764
Average assets			12,747,602				193,463				25,454				12,966,519

Basis_of_Presentation_Addition

Basis of Presentation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule Of Significant Accounting Policies [Line Items]	'	'	'	'
Property write-downs	$0.50	$1.40	$1.90	$4
IBERIABANK Corporation [Member]	'	'	'	'
Schedule Of Significant Accounting Policies [Line Items]	'	'	'	'
Number of operating states	6	'	6	'
IMC [Member]	'	'	'	'
Schedule Of Significant Accounting Policies [Line Items]	'	'	'	'
Number of operating states	12	'	12	'

Recent_Accounting_Pronouncemen1

Recent Accounting Pronouncements - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2014
Equity Method Investments and Joint Ventures [Abstract]	'
Income tax examination description	'The Company receives tax credits and/or tax deductions from operating losses, which are allowable on the Company's filed income tax returns over a 10-year period, subject to recapture over a 15-year period beginning with the first year the tax credits are earned.

Earnings_Per_Share_Schedule_of

Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]	'	'	'	'
Income available to common shareholders	$29,744	$23,192	$70,687	$39,499
Distributed earnings (capital) to common shareholders-basic	29,300	22,771	69,553	38,755
Distributed and undistributed earnings to common shareholders-diluted	29,296	22,767	69,528	38,755
Weighted average shares outstanding-basic	33,309,881	29,631,799	31,316,267	29,582,081
Weighted average shares outstanding-diluted	32,926,969	29,147,232	30,923,050	29,062,238
Earnings per common share - Basic	$0.89	$0.78	$2.26	$1.34
Earnings per common share - Diluted	$0.89	$0.78	$2.25	$1.33
Unvested Restricted Stock [Member]	'	'	'	'
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings (capital) to unvested restricted stock	-444	-421	-1,134	-744
Undistributed earnings reallocated to unvested restricted stock	($4)	($4)	($25)	'
Earnings per common share - Basic	$0.88	$0.77	$2.16	$1.33
Earnings per common share - Diluted	$0.89	$0.78	$2.21	$1.33

Earnings_Per_Share_Schedule_of1

Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Weighted average basic shares outstanding, unvested restricted stock	506,464	547,155	525,441	559,556

Earnings_Per_Share_Schedule_of2

Earnings Per Share - Schedule of Basic Earnings Per Common Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings to common shareholders	$11,200	$9,926	$32,430	$29,736
Undistributed earnings (distributed capital) to common shareholders	18,100	12,845	37,123	9,019
Total earnings to common shareholders	29,300	22,771	69,553	38,755
Distributed earnings per common share	$0.34	$0.34	$1.05	$1.03
Undistributed earnings (distributed capital) per common share	$0.55	$0.44	$1.21	$0.31
Total earnings per common share-basic	$0.89	$0.78	$2.26	$1.34
Unvested Restricted Stock [Member]	'	'	'	'
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings to common shareholders	170	183	529	571
Undistributed earnings (distributed capital) to common shareholders	274	238	605	173
Total earnings allocated to restricted stock	$444	$421	$1,134	$744
Distributed earnings per common share	$0.34	$0.34	$1.01	$1.02
Undistributed earnings (distributed capital) per common share	$0.54	$0.43	$1.15	$0.31
Total earnings per common share-basic	$0.88	$0.77	$2.16	$1.33

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail)	3 Months Ended		9 Months Ended
Earnings Per Share - Additional Information (Detail)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share Basic And Diluted [Line Items]	'	'	'	'
Weighted average number of shares, Recognition and Retention Plan	621,341	642,764	630,320	645,793
Weighted average number of shares, treasury stock	1,838,144	2,189,978	1,901,277	2,249,068
Stock Options [Member]	'	'	'	'
Earnings Per Share Basic And Diluted [Line Items]	'	'	'	'
Stock options having antidilutive effect on earnings per share	12,765	402,344	12,765	678,604

Acquisition_Activity_Additiona

Acquisition Activity - Additional Information (Detail) (USD $)

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

Jan. 17, 2014

Sep. 30, 2014

Dec. 31, 2013

Dec. 31, 2012

31-May-14

Sep. 30, 2014

31-May-14

Jun. 30, 2014

Sep. 30, 2014

Jun. 30, 2014

Feb. 24, 2014

Sep. 30, 2014

Feb. 24, 2014

1-May-14

Sep. 30, 2014

Trust

Teche [Member]

First Private [Member]

Title Company LLC [Member]

Louisiana Abstract and Title Llc [Member]

Branch

Mobile Branches [Member]

Branch

Business Acquisition [Line Items]

Cash payment to acquire business

$91,600,000

$714,000

$1,000

$400,000

$200,000

Goodwill

8,600,000

526,242,000

401,872,000

84,786,000

84,800,000

30,611,000

30,600,000

221,000

200,000

155,000

Number of branches acquired

Shares received

1.162

0.27

Total consideration paid

156,700,000

156,740,000

58,600,000

58,640,000

Business combination date of acquisition

31-May-14

30-Jun-14

Number of branches

Goodwill created in the acquisition deductible for income tax purposes

Maximum period for subject to change estimated fair values after acquisition date

'1 year

Acquisition_Activity_Schedule_

Acquisition Activity - Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable (Detail) (USD $)	0 Months Ended				0 Months Ended	9 Months Ended		0 Months Ended	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Jan. 17, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-14	Sep. 30, 2014	31-May-14	Jun. 30, 2014	Sep. 30, 2014	Jun. 30, 2014
	Jan. 17, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Teche [Member]	Teche [Member]	Teche [Member]	First Private [Member]	First Private [Member]	First Private [Member]
Equity consideration	'	'	'	'	'	'	'	'	'	'
Common stock issued, Amount	'	'	'	'	'	$156,026	'	'	$58,639	'
Common stock issued, Number of Shares	'	'	'	'	'	2,498,007	'	'	847,509	'
Total equity consideration	'	'	'	'	'	156,026	'	'	58,639	'
Non-Equity consideration	'	'	'	'	'	'	'	'	'	'
Cash	91,600	'	'	'	'	714	'	'	1	'
Total consideration paid	'	'	'	'	156,700	156,740	'	58,600	58,640	'
Fair value of net assets assumed including identifiable intangible assets	'	'	'	'	'	71,954	'	'	'	'
Fair value of net liabilities assumed including identifiable intangible assets	'	'	'	'	'	'	'	'	28,029	'
Goodwill	$8,600	$526,242	$401,872	$401,872	'	$84,786	$84,800	'	$30,611	$30,600

Acquisition_Activity_Schedule_1

Acquisition Activity - Schedule of Business Acquisitions, by Acquisition (Detail) (USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified	Sep. 30, 2014
As Acquired [Member] \| Teche [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	$71,611
Investment securities	24,077
Loans	716,196
Other real estate owned	329
Core deposit intangible	'
Deferred tax asset (liability)	1,057
Other assets	56,752
Total Assets	870,022
Interest-bearing deposits	520,446
Non-interest-bearing deposits	118,256
Borrowings	134,228
Other liabilities	5,366
Total Liabilities	778,296
As Acquired [Member] \| First Private [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	26,621
Investment securities	18,920
Loans	295,736
Other real estate owned	'
Core deposit intangible	'
Deferred tax asset (liability)	530
Other assets	5,230
Total Assets	347,037
Interest-bearing deposits	261,713
Non-interest-bearing deposits	50,333
Borrowings	6,451
Other liabilities	306
Total Liabilities	318,803
As Acquired [Member] \| Trust One- Memphis [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	92,060
Loans	88,179
Other real estate owned	1,325
Core deposit intangible	'
Other assets	368
Total Assets	181,932
Interest-bearing deposits	164,942
Non-interest-bearing deposits	26,373
Deferred tax liability	'
Other liabilities	84
Total Liabilities	191,399
Preliminary Fair Value Adjustments [Member] \| Teche [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	'
Investment securities	1,092
Loans	-16,636
Other real estate owned	-153
Core deposit intangible	2,055
Deferred tax asset (liability)	7,337
Other assets	-6,261
Total Assets	-12,566
Interest-bearing deposits	902
Non-interest-bearing deposits	'
Borrowings	6,304
Other liabilities	'
Total Liabilities	7,206
Preliminary Fair Value Adjustments [Member] \| First Private [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	'
Investment securities	297
Loans	-910
Other real estate owned	'
Core deposit intangible	506
Deferred tax asset (liability)	122
Other assets	'
Total Assets	15
Interest-bearing deposits	220
Non-interest-bearing deposits	'
Borrowings	'
Other liabilities	'
Total Liabilities	220
Preliminary Fair Value Adjustments [Member] \| Trust One- Memphis [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	'
Loans	-1,726
Other real estate owned	'
Core deposit intangible	2,597
Other assets	'
Total Assets	871
Interest-bearing deposits	'
Non-interest-bearing deposits	'
Deferred tax liability	'
Other liabilities	'
Total Liabilities	'
As Recorded by IBERIABANK [Member] \| Teche [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	71,611
Investment securities	25,169
Loans	699,560
Other real estate owned	176
Core deposit intangible	2,055
Deferred tax asset (liability)	8,394
Other assets	50,491
Total Assets	857,456
Interest-bearing deposits	521,348
Non-interest-bearing deposits	118,256
Borrowings	140,532
Other liabilities	5,366
Total Liabilities	785,502
As Recorded by IBERIABANK [Member] \| First Private [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	26,621
Investment securities	19,217
Loans	294,826
Other real estate owned	'
Core deposit intangible	506
Deferred tax asset (liability)	652
Other assets	5,230
Total Assets	347,052
Interest-bearing deposits	261,933
Non-interest-bearing deposits	50,333
Borrowings	6,451
Other liabilities	306
Total Liabilities	319,023
As Recorded by IBERIABANK [Member] \| Trust One- Memphis [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	92,060
Loans	86,453
Other real estate owned	1,325
Core deposit intangible	2,597
Other assets	368
Total Assets	182,803
Interest-bearing deposits	164,942
Non-interest-bearing deposits	26,373
Deferred tax liability	'
Other liabilities	84
Total Liabilities	$191,399

Acquisition_Activity_Schedule_2

Acquisition Activity - Schedule of Assets Acquired under Business Acquisitions (Detail) (USD $)	Sep. 30, 2014	Jan. 17, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Feb. 24, 2014	Sep. 30, 2014
In Thousands, unless otherwise specified	Sep. 30, 2014	Jan. 17, 2014	Dec. 31, 2013	Dec. 31, 2012	Title Company LLC [Member]	Title Company LLC [Member]	Louisiana Abstract and Title Llc [Member]
Business Acquisition [Line Items]	'	'	'	'	'	'	'
Goodwill	$526,242	$8,600	$401,872	$401,872	$221	$200	$155
Non-compete agreement	'	'	'	'	63	'	100
Title plant	'	'	'	'	14	'	9
Other intangible assets	'	'	'	'	75	'	130
Other assets	'	'	'	'	3	'	6
Total Assets	'	'	'	'	$376	'	$400

Acquisition_Activity_Supplemen

Acquisition Activity - Supplemental Pro Forma Information (Detail) (USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013
Business Acquisition, Pro Forma Information [Abstract]	'
Interest and non-interest income	$500,638
Net income	$46,139
Earnings per share-basic	$1.40
Earnings per share-diluted	$1.40

Investment_Securities_Schedule

Investment Securities - Schedule of Amortized Cost and Fair Values of Investment Securities, with Gross Unrealized Gains and Losses (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	$2,105,100	$1,963,046
Securities available for sale, Gross Unrealized Gains	16,992	13,867
Securities available for sale, Gross Unrealized Losses	-18,264	-40,116
Securities available for sale, Estimated Fair Value	2,103,828	1,936,797
Securities held to maturity, Amortized Cost	120,520	154,109
Securities held to maturity, Gross Unrealized Gains	3,398	2,205
Securities held to maturity, Gross Unrealized Losses	-1,460	-3,748
Securities held to maturity, Estimated Fair Value	122,458	152,566
U.S. Government-Sponsored Enterprise Obligations [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	359,404	406,092
Securities available for sale, Gross Unrealized Gains	1,465	1,382
Securities available for sale, Gross Unrealized Losses	-5,926	-11,913
Securities available for sale, Estimated Fair Value	354,943	395,561
Securities held to maturity, Amortized Cost	10,000	34,478
Securities held to maturity, Gross Unrealized Gains	157	484
Securities held to maturity, Gross Unrealized Losses	'	'
Securities held to maturity, Estimated Fair Value	10,157	34,962
Obligations of State and Political Obligations [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	87,895	105,300
Securities available for sale, Gross Unrealized Gains	3,891	2,435
Securities available for sale, Gross Unrealized Losses	'	-256
Securities available for sale, Estimated Fair Value	91,786	107,479
Securities held to maturity, Amortized Cost	79,309	84,290
Securities held to maturity, Gross Unrealized Gains	3,044	1,463
Securities held to maturity, Gross Unrealized Losses	-266	-1,624
Securities held to maturity, Estimated Fair Value	82,087	84,129
Mortgage-Backed Securities [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	1,656,341	1,450,194
Securities available for sale, Gross Unrealized Gains	11,613	10,031
Securities available for sale, Gross Unrealized Losses	-12,338	-27,947
Securities available for sale, Estimated Fair Value	1,655,616	1,432,278
Securities held to maturity, Amortized Cost	31,211	35,341
Securities held to maturity, Gross Unrealized Gains	197	258
Securities held to maturity, Gross Unrealized Losses	-1,194	-2,124
Securities held to maturity, Estimated Fair Value	30,214	33,475
Other Securities [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	1,460	1,460
Securities available for sale, Gross Unrealized Gains	23	19
Securities available for sale, Gross Unrealized Losses	'	'
Securities available for sale, Estimated Fair Value	$1,483	$1,479

Investment_Securities_Addition

Investment Securities - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
	Security		Security		Bonds
					Security
Net Investment Income [Line Items]	'	'	'	'	'
Pledged securities, carrying values	$1,400,000,000	'	$1,400,000,000	'	$1,500,000,000
Number of debt securities, held	162	'	162	'	207
Unrealized losses on debt securities, percent of amortized cost	1.64%	'	1.64%	'	3.23%
Unrealized losses on debt securities, percent of Company's total amortized cost	0.89%	'	0.89%	'	2.07%
Unrated revenue municipal bond	'	'	'	'	1
Impairment of par value bond, percentage	'	'	50.00%	'	'
Gain (loss) on sale of available for sale investments	$582,000	($3,000)	$609,000	$2,259,000	'
Obligations of State and Political Obligations [Member]	'	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'	'
Number of securities, continuous loss position, over twelve months	6	'	6	'	'

Investment_Securities_Schedule1

Investment Securities - Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Net Investment Income [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	($2,846)	($35,543)
Securities available for sale, Less Than Twelve Months, Estimated Fair Value	552,543	1,165,829
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-15,418	-4,573
Securities available for sale, Over Twelve Months, Estimated Fair Value	592,316	88,432
Securities available for sale, Gross Unrealized Losses, Total	-18,264	-40,116
Securities available for sale, Estimated Fair Value, Total	1,144,859	1,254,261
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	-1	-2,133
Securities held to maturity, Less Than Twelve Months, Estimated Fair Value	636	42,268
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-1,459	-1,615
Securities held to maturity, Over Twelve Months, Estimated Fair Value	35,114	17,856
Securities held to maturity, Gross Unrealized Losses, Total	-1,460	-3,748
Securities held to maturity, Estimated Fair Value, Total	35,750	60,124
Obligations of State and Political Obligations [Member]	'	'
Net Investment Income [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	'	-30
Securities available for sale, Less Than Twelve Months, Estimated Fair Value	186	2,415
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	'	-226
Securities available for sale, Over Twelve Months, Estimated Fair Value	'	1,047
Securities available for sale, Gross Unrealized Losses, Total	'	-256
Securities available for sale, Estimated Fair Value, Total	186	3,462
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	-1	-1,181
Securities held to maturity, Less Than Twelve Months, Estimated Fair Value	564	29,355
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-265	-443
Securities held to maturity, Over Twelve Months, Estimated Fair Value	10,811	6,240
Securities held to maturity, Gross Unrealized Losses, Total	-266	-1,624
Securities held to maturity, Estimated Fair Value, Total	11,375	35,595
Mortgage-Backed Securities [Member]	'	'
Net Investment Income [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	-2,846	-23,749
Securities available for sale, Less Than Twelve Months, Estimated Fair Value	552,357	864,899
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-9,492	-4,198
Securities available for sale, Over Twelve Months, Estimated Fair Value	333,795	81,870
Securities available for sale, Gross Unrealized Losses, Total	-12,338	-27,947
Securities available for sale, Estimated Fair Value, Total	886,152	946,769
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	'	-952
Securities held to maturity, Less Than Twelve Months, Estimated Fair Value	72	12,913
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-1,194	-1,172
Securities held to maturity, Over Twelve Months, Estimated Fair Value	24,303	11,616
Securities held to maturity, Gross Unrealized Losses, Total	-1,194	-2,124
Securities held to maturity, Estimated Fair Value, Total	24,375	24,529
U.S. Government-Sponsored Enterprise Obligations [Member]	'	'
Net Investment Income [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	'	-11,764
Securities available for sale, Less Than Twelve Months, Estimated Fair Value	'	298,515
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-5,926	-149
Securities available for sale, Over Twelve Months, Estimated Fair Value	258,521	5,515
Securities available for sale, Gross Unrealized Losses, Total	-5,926	-11,913
Securities available for sale, Estimated Fair Value, Total	$258,521	$304,030

Investment_Securities_Addition1

Investment Securities - Additional Information on Securities in a Continuous Loss Position (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
	Securities	Securities
Schedule of Available-for-sale Securities [Line Items]	'	'
Number of securities, available for sale securities	84	25
Number of securities, amortized costs	$644,306	$112,476
Number of securities, unrealized loss	16,876	6,188
Fannie Mae Freddie Mac or Ginnie Mae [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Number of securities, available for sale securities	78	20
Number of securities, amortized costs	633,230	104,520
Number of securities, unrealized loss	16,611	5,519
Political Subdivisions [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Number of securities, available for sale securities	6	5
Number of securities, amortized costs	11,076	7,956
Number of securities, unrealized loss	$265	$669

Investment_Securities_Schedule2

Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Maturity (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'	'
Securities Available for Sale, Weighted Average Yield, Within one year or less	1.27%	'
Securities Available for Sale, Weighted Average Yield, One through five years	1.54%	'
Securities Available for Sale, Weighted Average Yield, After five through ten years	2.10%	'
Securities Available for Sale, Weighted Average Yield, Over ten years	2.18%	'
Securities Available for Sale, Weighted Average Yield, Total	2.08%	'
Securities Available for Sale, Amortized Cost, Within one year or less	$15,397	'
Securities Available for Sale, Amortized Cost, One through five years	241,992	'
Securities Available for Sale, Amortized Cost, After five through ten years	474,758	'
Securities Available for Sale, Amortized Cost, Over ten years	1,372,953	'
Securities Available for Sale, Amortized Cost, Total	2,105,100	'
Securities Available for Sale, Estimated Fair Value, Within one year or less	15,488	'
Securities Available for Sale, Estimated Fair Value, One through five years	241,502	'
Securities Available for Sale, Estimated Fair Value, After five through ten years	476,954	'
Securities Available for Sale, Estimated Fair Value, Over ten years	1,369,884	'
Securities Available for Sale, Estimated Fair Value, Totals	2,103,828	1,936,797
Securities Held to Maturity, Weighted Average Yield, Within one year or less	2.65%	'
Securities Held to Maturity, Weighted Average Yield, One through five years	2.84%	'
Securities Held to Maturity, Weighted Average Yield, After five through ten years	2.97%	'
Securities Held to Maturity, Weighted Average Yield, Over ten years	3.05%	'
Securities Held to Maturity, Weighted Average Yield, Totals	2.98%	'
Securities Held to Maturity, Amortized Cost, Within one year or less	10,000	'
Securities Held to Maturity, Amortized Cost, One through five years	12,968	'
Securities Held to Maturity, Amortized Cost, After five through ten years	17,983	'
Securities Held to Maturity, Amortized Cost, Over ten years	79,569	'
Securities Held to Maturity, Amortized Cost, Totals	120,520	154,109
Securities Held to Maturity, Estimated Fair Value, Within one year or less	10,157	'
Securities Held to Maturity, Estimated Fair Value, One through five years	13,352	'
Securities Held to Maturity, Estimated Fair Value, After five through ten years	18,591	'
Securities Held to Maturity, Estimated Fair Value, Over ten years	80,358	'
Securities held to maturity, Estimated Fair Value	$122,458	$152,566

Investment_Securities_Schedule3

Investment Securities - Schedule of Realized Gains and Losses from Sale of Securities Classified as Available for Sale (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments, Debt and Equity Securities [Abstract]	'	'	'	'
Realized gains	$582	'	$609	$2,369
Realized losses	'	-3	'	-110
Net realized gains (losses)	$582	($3)	$609	$2,259

Investment_Securities_Schedule4

Investment Securities - Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'	'
Federal Home Loan Bank (FHLB) stock	$41,011	$24,369
Federal Reserve Bank (FRB) stock	34,348	28,098
Other investments	1,306	1,306
Total	$76,665	$53,773

Loans_Receivable_Schedule_of_N

Loans Receivable - Schedule of Non-Covered and Covered Loans (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	$10,555,010	$8,772,226	'
Covered loans receivable	524,189	719,793	'
Total loans receivable	11,079,199	9,492,019	'
Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	524,189	719,793	807,002
Non-Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	10,555,010	8,772,226	'
Commercial Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	281,390	424,357	'
Total loans receivable	7,506,907	6,863,418	'
Commercial Loans [Member] \| Real Estate [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	247,156	387,332	'
Total loans receivable	4,279,575	3,867,305	'
Commercial Loans [Member] \| Business [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	34,234	37,025	'
Total loans receivable	3,227,332	2,996,113	'
Commercial Loans [Member] \| Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	281,390	424,357	'
Commercial Loans [Member] \| Covered Loans [Member] \| Real Estate [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	247,156	387,332	'
Commercial Loans [Member] \| Covered Loans [Member] \| Business [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	34,234	37,025	'
Commercial Loans [Member] \| Non-Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	7,225,517	6,439,061	'
Commercial Loans [Member] \| Non-Covered Loans [Member] \| Real Estate [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	4,032,419	3,479,973	'
Commercial Loans [Member] \| Non-Covered Loans [Member] \| Business [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	3,193,098	2,959,088	'
Residential Mortgage Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	130,976	154,025	'
Total loans receivable	1,069,963	586,532	'
Residential Mortgage Loans [Member] \| Residential 1-4 Family [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	130,976	154,025	'
Total loans receivable	1,042,075	577,082	'
Residential Mortgage Loans [Member] \| Construction / Owner Occupied [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	'	'	'
Total loans receivable	27,888	9,450	'
Residential Mortgage Loans [Member] \| Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	130,976	154,025	'
Residential Mortgage Loans [Member] \| Covered Loans [Member] \| Residential 1-4 Family [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	130,976	154,025	'
Residential Mortgage Loans [Member] \| Non-Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	938,987	432,507	'
Residential Mortgage Loans [Member] \| Non-Covered Loans [Member] \| Residential 1-4 Family [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	911,099	423,057	'
Residential Mortgage Loans [Member] \| Non-Covered Loans [Member] \| Construction / Owner Occupied [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	27,888	9,450	'
Consumer and Other Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	111,823	141,411	'
Total loans receivable	2,502,329	2,042,069	'
Consumer and Other Loans [Member] \| Home Equity [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	107,811	137,122	'
Total loans receivable	1,565,878	1,291,792	'
Consumer and Other Loans [Member] \| Indirect Automobile [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	'	'	'
Total loans receivable	394,691	375,236	'
Consumer and Other Loans [Member] \| Consumer - Other [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	4,012	4,289	'
Total loans receivable	541,760	375,041	'
Consumer and Other Loans [Member] \| Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	111,823	141,411	'
Consumer and Other Loans [Member] \| Covered Loans [Member] \| Home Equity [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	107,811	137,122	'
Consumer and Other Loans [Member] \| Covered Loans [Member] \| Consumer - Other [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	4,012	4,289	'
Consumer and Other Loans [Member] \| Non-Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	2,390,506	1,900,658	'
Consumer and Other Loans [Member] \| Non-Covered Loans [Member] \| Home Equity [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	1,458,067	1,154,670	'
Consumer and Other Loans [Member] \| Non-Covered Loans [Member] \| Indirect Automobile [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	394,691	375,236	'
Consumer and Other Loans [Member] \| Non-Covered Loans [Member] \| Consumer - Other [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	$537,748	$370,752	'

Loans_Receivable_Additional_In

Loans Receivable - Additional Information (Detail) (USD $)	9 Months Ended					9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013
	Sep. 30, 2014	Dec. 31, 2013	Trust One- Memphis [Member]	Teche [Member]	First Private [Member]	Troubled Debt Restructurings [Member]	Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'	'	'	'	'
Deferred loan origination fees	$19,400,000	$18,600,000	'	'	'	'	'
Deferred loan expenses	9,000,000	7,600,000	'	'	'	'	'
Deposit liabilities reclassified as loans receivable	3,700,000	3,100,000	'	'	'	'	'
Loans with carrying value pledged to secure public deposits and other borrowings	2,700,000,000	2,300,000,000	'	'	'	'	'
Acquired loans	'	'	86,500,000	699,600,000	294,800,000	'	'
Carrying amounts of loans acquired	1,100,000,000	'	'	'	'	'	'
Maximum period for subject to change estimated fair values after acquisition date	'1 year	'	'	'	'	'	'
Total TDRs	'	'	'	'	'	$0	$11,200,000

Loans_Receivable_Schedule_of_A

Loans Receivable - Schedule of Aging of Non-Covered Loans (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Non-Covered Acquired Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	$4,556	$3,251
Past Due, 60-89 days	2,289	2,580
Past Due, Greater than 90 days	43,838	37,265
Total Past Due	50,683	43,096
Current	1,395,885	506,422
Discount	-71,500	-65,613
Total Non-covered Loans, Net of Unearned Income	1,375,068	483,905
Recorded Investment > 90 days and Accruing	29,230	37,265
Non-Covered Acquired Loans [Member] \| Commercial Real Estate Construction [Member] \| Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	340	388
Past Due, 60-89 days	45	'
Past Due, Greater than 90 days	2,118	2,542
Total Past Due	2,503	2,930
Current	36,832	19,833
Discount	-2,061	-2,532
Total Non-covered Loans, Net of Unearned Income	37,274	20,231
Recorded Investment > 90 days and Accruing	1,821	2,542
Non-Covered Acquired Loans [Member] \| Commercial Real Estate - Other [Member] \| Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	1,464	1,798
Past Due, 60-89 days	277	1,963
Past Due, Greater than 90 days	22,081	27,967
Total Past Due	23,822	31,728
Current	486,238	345,286
Discount	-42,527	-52,176
Total Non-covered Loans, Net of Unearned Income	467,533	324,838
Recorded Investment > 90 days and Accruing	20,614	27,967
Non-Covered Acquired Loans [Member] \| Commercial Business [Member] \| Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	717	544
Past Due, 60-89 days	25	'
Past Due, Greater than 90 days	1,905	1,218
Total Past Due	2,647	1,762
Current	101,722	54,189
Discount	-5,144	-2,914
Total Non-covered Loans, Net of Unearned Income	99,225	53,037
Recorded Investment > 90 days and Accruing	1,892	1,218
Non-Covered Acquired Loans [Member] \| Residential Prime [Member] \| Residential Mortgage Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	76	'
Past Due, 60-89 days	931	'
Past Due, Greater than 90 days	7,437	226
Total Past Due	8,444	226
Current	432,837	18,796
Discount	631	-887
Total Non-covered Loans, Net of Unearned Income	441,912	18,135
Recorded Investment > 90 days and Accruing	369	226
Non-Covered Acquired Loans [Member] \| Home Equity [Member] \| Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	1,615	313
Past Due, 60-89 days	1,003	516
Past Due, Greater than 90 days	8,203	4,242
Total Past Due	10,821	5,071
Current	228,051	53,995
Discount	-10,803	-5,623
Total Non-covered Loans, Net of Unearned Income	228,069	53,443
Recorded Investment > 90 days and Accruing	4,102	4,242
Non-Covered Acquired Loans [Member] \| Indirect Automobile [Member] \| Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	7	33
Past Due, 60-89 days	1	'
Past Due, Greater than 90 days	43	95
Total Past Due	51	128
Current	606	1,725
Discount	-44	'
Total Non-covered Loans, Net of Unearned Income	613	1,853
Recorded Investment > 90 days and Accruing	43	95
Non-Covered Acquired Loans [Member] \| Consumer - Other [Member] \| Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	337	175
Past Due, 60-89 days	7	101
Past Due, Greater than 90 days	2,051	975
Total Past Due	2,395	1,251
Current	109,599	12,598
Discount	-11,552	-1,481
Total Non-covered Loans, Net of Unearned Income	100,442	12,368
Recorded Investment > 90 days and Accruing	389	975
Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	9,242	13,426
Past Due, 60-89 days	3,198	7,965
Past Due, Greater than 90 days	38,064	44,762
Total Past Due	50,504	66,153
Current	9,129,438	8,222,168
Total Non-covered Loans, Net of Unearned Income	9,179,942	8,288,321
Recorded Investment > 90 days and Accruing	4	1,075
Non-Covered Loans Excluding Acquired Loans [Member] \| Commercial Real Estate Construction [Member] \| Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	84	'
Past Due, Greater than 90 days	1,317	1,803
Total Past Due	1,401	1,803
Current	634,593	381,292
Total Non-covered Loans, Net of Unearned Income	635,994	383,095
Non-Covered Loans Excluding Acquired Loans [Member] \| Commercial Real Estate - Other [Member] \| Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	1,347	6,098
Past Due, 60-89 days	640	5,630
Past Due, Greater than 90 days	6,789	7,650
Total Past Due	8,776	19,378
Current	2,882,842	2,732,431
Total Non-covered Loans, Net of Unearned Income	2,891,618	2,751,809
Recorded Investment > 90 days and Accruing	'	2
Non-Covered Loans Excluding Acquired Loans [Member] \| Commercial Business [Member] \| Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	1,475	2,117
Past Due, 60-89 days	44	423
Past Due, Greater than 90 days	2,737	15,020
Total Past Due	4,256	17,560
Current	3,089,617	2,888,491
Total Non-covered Loans, Net of Unearned Income	3,093,873	2,906,051
Non-Covered Loans Excluding Acquired Loans [Member] \| Residential Prime [Member] \| Residential Mortgage Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	1,859	1,104
Past Due, 60-89 days	1,349	852
Past Due, Greater than 90 days	10,973	9,684
Total Past Due	14,181	11,640
Current	362,513	286,167
Total Non-covered Loans, Net of Unearned Income	376,694	297,807
Recorded Investment > 90 days and Accruing	'	1,073
Non-Covered Loans Excluding Acquired Loans [Member] \| Home Equity [Member] \| Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	1,783	1,956
Past Due, 60-89 days	201	569
Past Due, Greater than 90 days	7,310	6,808
Total Past Due	9,294	9,333
Current	1,220,704	1,091,894
Total Non-covered Loans, Net of Unearned Income	1,229,998	1,101,227
Recorded Investment > 90 days and Accruing	4	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Indirect Automobile [Member] \| Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	1,825	1,427
Past Due, 60-89 days	502	293
Past Due, Greater than 90 days	1,338	1,275
Total Past Due	3,665	2,995
Current	390,413	370,388
Total Non-covered Loans, Net of Unearned Income	394,078	373,383
Non-Covered Loans Excluding Acquired Loans [Member] \| Consumer - Other [Member] \| Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	720	458
Past Due, 60-89 days	337	106
Past Due, Greater than 90 days	416	485
Total Past Due	1,473	1,049
Current	367,102	293,693
Total Non-covered Loans, Net of Unearned Income	368,575	294,742
Non-Covered Loans Excluding Acquired Loans [Member] \| Residential Subprime [Member] \| Residential Mortgage Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 60-89 days	2	'
Past Due, Greater than 90 days	6,197	1,626
Total Past Due	6,199	1,626
Current	114,182	114,939
Total Non-covered Loans, Net of Unearned Income	120,381	116,565
Non-Covered Loans Excluding Acquired Loans [Member] \| Credit Card [Member] \| Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	149	266
Past Due, 60-89 days	123	92
Past Due, Greater than 90 days	987	411
Total Past Due	1,259	769
Current	67,472	62,873
Total Non-covered Loans, Net of Unearned Income	$68,731	$63,642

Loans_Receivable_Schedule_of_N1

Loans Receivable - Schedule of Non-Covered Loans on Nonaccrual Status (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	$38,060	$43,687
Commercial Loans [Member] \| Commercial Real Estate Construction [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	1,317	1,803
Commercial Loans [Member] \| Commercial Real Estate - Other [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	6,789	7,648
Commercial Loans [Member] \| Business [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	2,737	15,020
Residential Mortgage Loans [Member] \| Residential Prime [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	10,973	8,611
Residential Mortgage Loans [Member] \| Residential Subprime [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	6,197	1,626
Consumer and Other Loans [Member] \| Home Equity [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	7,306	6,808
Consumer and Other Loans [Member] \| Indirect Automobile [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	1,338	1,275
Consumer and Other Loans [Member] \| Credit Card [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	987	411
Consumer and Other Loans [Member] \| Consumer - Other [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	$416	$485

Loans_Receivable_Schedule_of_C

Loans Receivable - Schedule of Carrying Amount of Acquired Covered Loans (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	$46,301	$66,077
Acquired Performing Loans	477,888	653,716
Balance at end of period	524,189	719,793
Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	5,298	14,904
Acquired Performing Loans	276,092	409,453
Balance at end of period	281,390	424,357
Commercial Loans [Member] \| Real Estate [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	4,678	14,904
Acquired Performing Loans	242,478	372,428
Balance at end of period	247,156	387,332
Commercial Loans [Member] \| Business [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	620	'
Acquired Performing Loans	33,614	37,025
Balance at end of period	34,234	37,025
Residential Mortgage Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	24,304	28,223
Acquired Performing Loans	106,672	125,802
Balance at end of period	130,976	154,025
Residential Mortgage Loans [Member] \| Residential 1-4 Family [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	24,304	28,223
Acquired Performing Loans	106,672	125,802
Balance at end of period	130,976	154,025
Residential Mortgage Loans [Member] \| Construction / Owner Occupied [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	'	'
Acquired Performing Loans	'	'
Balance at end of period	'	'
Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	16,699	22,950
Acquired Performing Loans	95,124	118,461
Balance at end of period	111,823	141,411
Consumer and Other Loans [Member] \| Home Equity [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	16,210	21,768
Acquired Performing Loans	91,601	115,354
Balance at end of period	107,811	137,122
Consumer and Other Loans [Member] \| Indirect Automobile [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	'	'
Acquired Performing Loans	'	'
Balance at end of period	'	'
Consumer and Other Loans [Member] \| Consumer - Other [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	489	1,182
Acquired Performing Loans	3,523	3,107
Balance at end of period	$4,012	$4,289

Loans_Receivable_Schedule_of_C1

Loans Receivable - Schedule of Carrying Amount of Loans Acquired (Detail) (USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified	Sep. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Contractually required principal and interest at acquisition	$98,097
Nonaccretable difference (expected losses and foregone interest)	-4,558
Cash flows expected to be collected at acquisition	93,539
Accretable yield	-9,778
Basis in acquired loans at acquisition	83,761
Acquired Impaired Loans [Member]	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Contractually required principal and interest at acquisition	82,967
Nonaccretable difference (expected losses and foregone interest)	-4,197
Cash flows expected to be collected at acquisition	78,770
Accretable yield	-8,242
Basis in acquired loans at acquisition	70,528
Acquired Performing Loans [Member]	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Contractually required principal and interest at acquisition	15,130
Nonaccretable difference (expected losses and foregone interest)	-361
Cash flows expected to be collected at acquisition	14,769
Accretable yield	-1,536
Basis in acquired loans at acquisition	$13,233

Loans_Receivable_Summary_of_Ch

Loans Receivable - Summary of Changes in Accretable Yields of Acquired Loans (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Balance at beginning of period	$354,892	$356,393
Acquisition	9,778	'
Transfers from nonaccretable difference to accretable yield	17,824	40,628
Accretion	-79,356	-132,712
Changes in expected cash flows not affecting nonaccretable differences	-26,250	91,734
Balance at end of period	276,888	356,043
Acquired Impaired Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Balance at beginning of period	78,349	76,623
Acquisition	8,242	'
Transfers from nonaccretable difference to accretable yield	3,952	6,148
Accretion	-12,766	-13,519
Changes in expected cash flows not affecting nonaccretable differences	-6,873	10,561
Balance at end of period	70,904	79,813
Acquired Performing Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Balance at beginning of period	276,543	279,770
Acquisition	1,536	'
Transfers from nonaccretable difference to accretable yield	13,872	34,480
Accretion	-66,590	-119,193
Changes in expected cash flows not affecting nonaccretable differences	-19,377	81,173
Balance at end of period	$205,984	$276,230

Loans_Receivable_Schedule_of_T

Loans Receivable - Schedule of Troubled Debt Restructurings (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Commercial Loans [Member] \| Commercial Real Estate Construction [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Commercial Loans [Member] \| Real Estate [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	367	411
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	58	5,601
Total TDRs	425	6,012
Commercial Loans [Member] \| Business [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	726	1,056
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	2,027	12,610
Total TDRs	2,753	13,666
Residential Mortgage Loans [Member] \| Residential Prime [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Residential Mortgage Loans [Member] \| Residential Subprime [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	1,093	1,467
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	2,328	18,474
Total TDRs	3,421	19,941
Consumer and Other Loans [Member] \| Home Equity [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	243	263
Total TDRs	243	263
Consumer and Other Loans [Member] \| Indirect Automobile [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Consumer and Other Loans [Member] \| Credit Card [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Consumer and Other Loans [Member] \| Consumer - Other [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'

Loans_Receivable_Schedule_of_M

Loans Receivable - Schedule of Modified TDRs (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Receivables [Abstract]	'	'
Extended maturities	'	'
Interest rate adjustment	'	'
Maturity and interest rate adjustment	'	'
Movement to or extension of interest-rate only payments	'	'
Forbearance	'	'
Other concession(s)	'	11,210
Total	'	$11,210

Loans_Receivable_Schedule_of_S

Loans Receivable - Schedule of Subsequently Defaulted TDRs (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
	SecurityLoan	SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	5
Pre-modification Outstanding Recorded Investment	'	$12,507
Post-modification Outstanding Recorded Investment	'	12,329
TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	43	60
Recorded Investment	1,825	18,429
Real Estate [Member] \| Commercial Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	5
Pre-modification Outstanding Recorded Investment	'	12,507
Post-modification Outstanding Recorded Investment	'	12,329
Number of Loans	31	45
Recorded Investment	58	6,012
Business [Member] \| Commercial Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	11	13
Recorded Investment	1,767	12,370
Home Equity [Member] \| Consumer and Other Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	1
Recorded Investment	'	$47
Consumer - Other [Member] \| Consumer and Other Loans [Member] \| TDRs Occurring During The Period [Member] \| Non-Covered TDRs [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	1	1

Allowance_for_Credit_Losses_an2

Allowance for Credit Losses and Credit Quality - Schedule of Allowance for Loan Losses for Covered Loan and Non-Covered Loan Portfolios (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	$143,074	$251,603
(Reversal of) Provision for loan losses before adjustment attributable to FDIC loss share agreements	13,718	-58,120
Adjustment attributable to FDIC loss share arrangements	-1,153	58,565
Net (reversal of) provision for loan losses	12,565	445
Adjustment attributable to FDIC loss share arrangements	1,153	-58,565
Transfer of balance to OREO	-5,378	-30,315
Transfer of balance to the RULC	'	-9,828
Loans charged-off	-21,651	-9,148
Recoveries	4,777	4,353
Balance at end of period	134,540	148,545
Balance at beginning of period	11,147	'
Transfer of balance from the allowance for loan losses	'	9,828
Provision for unfunded lending commitments	952	2,131
Balance at end of period	12,099	11,959
Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	67,342	74,211
(Reversal of) Provision for loan losses before adjustment attributable to FDIC loss share agreements	9,099	2,884
Adjustment attributable to FDIC loss share arrangements	'	'
Net (reversal of) provision for loan losses	9,099	2,884
Adjustment attributable to FDIC loss share arrangements	'	'
Transfer of balance to OREO	'	'
Transfer of balance to the RULC	'	-9,828
Loans charged-off	-8,242	-7,455
Recoveries	4,338	4,353
Balance at end of period	72,537	64,165
Balance at beginning of period	11,147	'
Transfer of balance from the allowance for loan losses	'	9,828
Provision for unfunded lending commitments	952	2,131
Balance at end of period	12,099	11,959
Non-Covered Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	4,557	8,816
(Reversal of) Provision for loan losses before adjustment attributable to FDIC loss share agreements	-1,259	-2,464
Adjustment attributable to FDIC loss share arrangements	'	'
Net (reversal of) provision for loan losses	-1,259	-2,464
Adjustment attributable to FDIC loss share arrangements	'	'
Transfer of balance to OREO	-207	-1,013
Transfer of balance to the RULC	'	'
Loans charged-off	-586	-10
Recoveries	401	'
Balance at end of period	2,906	5,329
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	'	'
Provision for unfunded lending commitments	'	'
Balance at end of period	'	'
Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	71,175	168,576
(Reversal of) Provision for loan losses before adjustment attributable to FDIC loss share agreements	5,878	-58,540
Adjustment attributable to FDIC loss share arrangements	-1,153	58,565
Net (reversal of) provision for loan losses	4,725	25
Adjustment attributable to FDIC loss share arrangements	1,153	-58,565
Transfer of balance to OREO	-5,171	-29,302
Transfer of balance to the RULC	'	'
Loans charged-off	-12,823	-1,683
Recoveries	38	'
Balance at end of period	59,097	79,051
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	'	'
Provision for unfunded lending commitments	'	'
Balance at end of period	'	'

Allowance_for_Credit_Losses_an3

Allowance for Credit Losses and Credit Quality - Schedule of Allowance for Loan Losses for Covered Loans, by Loan Portfolio (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Transfer of balance to OREO	($5,378)	($30,315)	'
Transfer of balance to the RULC	'	-9,828	'
Loans charged off	-21,651	-9,148	'
Recoveries	4,777	4,353	'
Balance at beginning of period	11,147	'	'
Transfer of balance from the allowance for loan losses	'	9,828	'
Balance at end of period	12,099	11,959	'
Balance at end of period	524,189	'	719,793
Non-Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	71,899	83,027	'
(Reversal of) Provision for loan losses	7,840	420	'
Transfer of balance to OREO	-207	-1,013	'
Transfer of balance to the RULC	'	-9,828	'
Loans charged off	-8,828	-7,465	'
Recoveries	4,739	4,353	'
Balance at end of period	75,443	69,494	'
Balance at beginning of period	11,147	'	'
Transfer of balance from the allowance for loan losses	'	9,828	'
(Reversal of) Provision for unfunded commitments	952	2,131	'
Balance at end of period	12,099	11,959	'
Allowance on loans individually evaluated for impairment	25	1,092	'
Allowance on loans collectively evaluated for impairment	75,418	68,402	'
Balance at end of period	10,555,010	8,236,035	'
Balance at end of period individually evaluated for impairment	11,339	25,747	'
Balance at end of period collectively evaluated for impairment	10,543,671	8,210,288	'
Balance at end of period acquired with deteriorated credit quality	19,490	18,267	'
Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	71,175	168,576	'
(Reversal of) Provision for loan losses	4,725	25	'
(Decrease) Increase in FDIC loss share receivable	1,153	-58,565	'
Transfer of balance to OREO	-5,171	-29,302	'
Transfer of balance to the RULC	'	'	'
Loans charged off	-12,823	-1,683	'
Recoveries	38	'	'
Balance at end of period	59,097	79,051	'
Balance at beginning of period	'	'	'
Transfer of balance from the allowance for loan losses	'	'	'
Balance at end of period	'	'	'
Allowance on loans collectively evaluated for impairment	59,097	79,051	'
Balance at end of period	524,189	807,002	719,793
Balance at end of period collectively evaluated for impairment	524,189	807,002	'
Balance at end of period acquired with deteriorated credit quality	46,301	78,484	'
Commercial Real Estate [Member] \| Non-Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	26,590	38,264	'
(Reversal of) Provision for loan losses	611	-6,926	'
Transfer of balance to OREO	'	-279	'
Transfer of balance to the RULC	'	-2,939	'
Loans charged off	-1,214	-1,966	'
Recoveries	2,209	1,498	'
Balance at end of period	28,196	27,652	'
Balance at beginning of period	3,089	'	'
Transfer of balance from the allowance for loan losses	'	2,939	'
(Reversal of) Provision for unfunded commitments	726	1,207	'
Balance at end of period	3,815	4,146	'
Allowance on loans individually evaluated for impairment	25	8	'
Allowance on loans collectively evaluated for impairment	28,171	27,644	'
Balance at end of period	4,032,419	3,320,333	'
Balance at end of period individually evaluated for impairment	7,357	9,529	'
Balance at end of period collectively evaluated for impairment	4,025,062	3,310,804	'
Balance at end of period acquired with deteriorated credit quality	15,061	16,287	'
Commercial Real Estate [Member] \| Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	38,772	100,871	'
(Reversal of) Provision for loan losses	2,544	27	'
(Decrease) Increase in FDIC loss share receivable	734	-30,853	'
Transfer of balance to OREO	-1,874	-22,375	'
Loans charged off	-9,578	-1,683	'
Recoveries	38	'	'
Balance at end of period	30,636	45,987	'
Allowance on loans collectively evaluated for impairment	30,636	45,987	'
Balance at end of period	247,156	459,506	'
Balance at end of period collectively evaluated for impairment	247,156	459,506	'
Balance at end of period acquired with deteriorated credit quality	4,678	23,751	'
Commercial Business [Member] \| Non-Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	28,515	28,721	'
(Reversal of) Provision for loan losses	2,187	-582	'
Transfer of balance to OREO	-130	-81	'
Transfer of balance to the RULC	'	-3,497	'
Loans charged off	-1,097	-531	'
Recoveries	93	354	'
Balance at end of period	29,568	24,384	'
Balance at beginning of period	4,839	'	'
Transfer of balance from the allowance for loan losses	'	3,497	'
(Reversal of) Provision for unfunded commitments	192	610	'
Balance at end of period	5,031	4,107	'
Allowance on loans individually evaluated for impairment	'	801	'
Allowance on loans collectively evaluated for impairment	29,568	23,583	'
Balance at end of period	3,193,098	2,643,822	'
Balance at end of period individually evaluated for impairment	3,276	14,548	'
Balance at end of period collectively evaluated for impairment	3,189,822	2,629,274	'
Balance at end of period acquired with deteriorated credit quality	2,562	45	'
Commercial Business [Member] \| Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	5,380	11,375	'
(Reversal of) Provision for loan losses	376	'	'
(Decrease) Increase in FDIC loss share receivable	609	-3,137	'
Transfer of balance to OREO	-1,162	-314	'
Loans charged off	-2,192	'	'
Balance at end of period	3,011	7,924	'
Allowance on loans collectively evaluated for impairment	3,011	7,924	'
Balance at end of period	34,234	40,422	'
Balance at end of period collectively evaluated for impairment	34,234	40,422	'
Balance at end of period acquired with deteriorated credit quality	620	'	'
Mortgage [Member] \| Non-Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	2,546	2,125	'
(Reversal of) Provision for loan losses	514	1,048	'
Transfer of balance to OREO	-12	-646	'
Transfer of balance to the RULC	'	-40	'
Loans charged off	-607	-481	'
Recoveries	134	698	'
Balance at end of period	2,575	2,704	'
Balance at beginning of period	72	'	'
Transfer of balance from the allowance for loan losses	'	40	'
(Reversal of) Provision for unfunded commitments	11	38	'
Balance at end of period	83	78	'
Allowance on loans individually evaluated for impairment	'	283	'
Allowance on loans collectively evaluated for impairment	2,575	2,421	'
Balance at end of period	938,987	409,940	'
Balance at end of period individually evaluated for impairment	'	1,407	'
Balance at end of period collectively evaluated for impairment	938,987	408,533	'
Balance at end of period acquired with deteriorated credit quality	160	120	'
Consumer [Member] \| Non-Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	14,248	13,917	'
(Reversal of) Provision for loan losses	4,528	6,880	'
Transfer of balance to OREO	-65	-7	'
Transfer of balance to the RULC	'	-3,352	'
Loans charged off	-5,910	-4,487	'
Recoveries	2,303	1,803	'
Balance at end of period	15,104	14,754	'
Balance at beginning of period	3,147	'	'
Transfer of balance from the allowance for loan losses	'	3,352	'
(Reversal of) Provision for unfunded commitments	23	276	'
Balance at end of period	3,170	3,628	'
Allowance on loans collectively evaluated for impairment	15,104	14,754	'
Balance at end of period	2,390,506	1,861,940	'
Balance at end of period individually evaluated for impairment	706	263	'
Balance at end of period collectively evaluated for impairment	2,389,800	1,861,677	'
Balance at end of period acquired with deteriorated credit quality	1,707	1,815	'
Consumer [Member] \| Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	16,134	33,764	'
(Reversal of) Provision for loan losses	834	-1	'
(Decrease) Increase in FDIC loss share receivable	2,721	-18,841	'
Transfer of balance to OREO	-1,487	1	'
Loans charged off	-963	'	'
Balance at end of period	17,239	14,923	'
Allowance on loans collectively evaluated for impairment	17,239	14,923	'
Balance at end of period	111,823	153,559	'
Balance at end of period collectively evaluated for impairment	111,823	153,559	'
Balance at end of period acquired with deteriorated credit quality	16,699	26,400	'
Mortgage [Member] \| Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	10,889	22,566	'
(Reversal of) Provision for loan losses	971	-1	'
(Decrease) Increase in FDIC loss share receivable	-2,911	-5,734	'
Transfer of balance to OREO	-648	-6,614	'
Loans charged off	-90	'	'
Balance at end of period	8,211	10,217	'
Allowance on loans collectively evaluated for impairment	8,211	10,217	'
Balance at end of period	130,976	153,515	'
Balance at end of period collectively evaluated for impairment	130,976	153,515	'
Balance at end of period acquired with deteriorated credit quality	$24,304	$28,333	'

Allowance_for_Credit_Losses_an4

Allowance for Credit Losses and Credit Quality - Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	$10,555,010	$8,772,226	'
Total	524,189	719,793	'
Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	771,093	87,114	'
30+ Days Past Due	21,711	6,676	'
Discount	-21,768	-7,991	'
Total	771,036	85,799	'
Residential Prime [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	432,837	18,796	'
30+ Days Past Due	8,444	226	'
Discount	631	-887	'
Total	441,912	18,135	'
Home Equity [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	228,051	53,995	'
30+ Days Past Due	10,821	5,071	'
Discount	-10,803	-5,623	'
Total	228,069	53,443	'
Indirect Automobile [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	606	1,725	'
30+ Days Past Due	51	128	'
Discount	-44	'	'
Total	613	1,853	'
Consumer - Other [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	109,599	12,598	'
30+ Days Past Due	2,395	1,251	'
Discount	-11,552	-1,481	'
Total	100,442	12,368	'
Internally Assigned Grade Loss [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Discount	-49,732	-57,622	'
Total	604,032	398,106	'
Internally Assigned Grade Loss [Member] \| Commercial Real Estate Construction [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Discount	-2,061	-2,532	'
Total	37,274	20,231	'
Internally Assigned Grade Loss [Member] \| Commercial Real Estate - Other [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Discount	-42,527	-52,176	'
Total	467,533	324,838	'
Internally Assigned Grade Loss [Member] \| Commercial Business [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Discount	-5,144	-2,914	'
Total	99,225	53,037	'
Pass [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	584,848	378,849	'
Pass [Member] \| Commercial Real Estate Construction [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	30,675	17,132	'
Pass [Member] \| Commercial Real Estate - Other [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	456,790	310,303	'
Pass [Member] \| Commercial Business [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	97,383	51,414	'
Special Mention [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	16,939	17,467	'
Special Mention [Member] \| Commercial Real Estate Construction [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	3,671	196	'
Special Mention [Member] \| Commercial Real Estate - Other [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	11,065	15,351	'
Special Mention [Member] \| Commercial Business [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	2,203	1,920	'
Substandard [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	51,587	59,288	'
Substandard [Member] \| Commercial Real Estate Construction [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	4,989	5,435	'
Substandard [Member] \| Commercial Real Estate - Other [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	42,027	51,267	'
Substandard [Member] \| Commercial Business [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	4,571	2,586	'
Doubtful [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	390	124	'
Doubtful [Member] \| Commercial Real Estate - Other [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	178	93	'
Doubtful [Member] \| Commercial Business [Member] \| Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	212	31	'
Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	524,189	719,793	807,002
Covered Loans [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	260,428	303,185	'
30+ Days Past Due	43,452	66,800	'
Discount	-61,081	-74,549	'
Covered Loans [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	34,234	'	40,422
Covered Loans [Member] \| Residential Prime [Member] \| Mortgage [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	143,529	158,710	'
30+ Days Past Due	23,993	30,814	'
Discount	-36,546	-35,499	'
Covered Loans [Member] \| Home Equity [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	115,813	143,236	'
30+ Days Past Due	19,403	35,811	'
Discount	-27,405	-41,925	'
Covered Loans [Member] \| Credit Card [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	588	648	'
30+ Days Past Due	33	31	'
Covered Loans [Member] \| Consumer - Other [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	498	591	'
30+ Days Past Due	23	144	'
Discount	2,870	2,875	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	298,634	467,930	'
Discount	-17,244	-43,573	'
Total	281,390	424,357	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	242,799	295,436	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	51,861	74,675	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	210,939	346,225	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	35,834	47,030	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Residential Prime [Member] \| Mortgage [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	130,976	154,025	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Home Equity [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	107,811	137,122	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Credit Card [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	621	679	'
Covered Loans [Member] \| Internally Assigned Grade Loss [Member] \| Consumer - Other [Member] \| Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	3,391	3,610	'
Covered Loans [Member] \| Pass [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	180,150	222,175	'
Covered Loans [Member] \| Pass [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	40,754	42,886	'
Covered Loans [Member] \| Pass [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	113,309	148,579	'
Covered Loans [Member] \| Pass [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	26,087	30,710	'
Covered Loans [Member] \| Special Mention [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	24,986	57,880	'
Covered Loans [Member] \| Special Mention [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	1,822	7,401	'
Covered Loans [Member] \| Special Mention [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	22,277	49,699	'
Covered Loans [Member] \| Special Mention [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	887	780	'
Covered Loans [Member] \| Substandard [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	93,452	183,127	'
Covered Loans [Member] \| Substandard [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	9,285	23,891	'
Covered Loans [Member] \| Substandard [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	75,353	144,680	'
Covered Loans [Member] \| Substandard [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	8,814	14,556	'
Covered Loans [Member] \| Doubtful [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	46	4,748	'
Covered Loans [Member] \| Doubtful [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	'	497	'
Covered Loans [Member] \| Doubtful [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	'	3,267	'
Covered Loans [Member] \| Doubtful [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	46	984	'
Non-Covered Loans Excluding Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	2,522,386	2,219,954	'
30+ Days Past Due	36,071	27,412	'
Total	2,558,457	2,247,366	'
Credit risk by payment status, Current	9,129,438	8,222,168	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Residential Prime [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	362,513	286,167	'
30+ Days Past Due	14,181	11,640	'
Total	376,694	297,807	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Residential Subprime [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	114,182	114,939	'
30+ Days Past Due	6,199	1,626	'
Total	120,381	116,565	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Home Equity [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	1,220,704	1,091,894	'
30+ Days Past Due	9,294	9,333	'
Total	1,229,998	1,101,227	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Indirect Automobile [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	390,413	370,388	'
30+ Days Past Due	3,665	2,995	'
Total	394,078	373,383	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Credit Card [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	67,472	62,873	'
30+ Days Past Due	1,259	769	'
Total	68,731	63,642	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Consumer - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	367,102	293,693	'
30+ Days Past Due	1,473	1,049	'
Total	368,575	294,742	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Internally Assigned Grade Loss [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	6,621,485	6,040,955	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Internally Assigned Grade Loss [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	635,994	383,095	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Internally Assigned Grade Loss [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	2,891,618	2,751,809	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Internally Assigned Grade Loss [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	3,093,873	2,906,051	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Pass [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	6,490,254	5,931,779	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Pass [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	624,592	370,824	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Pass [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	2,817,777	2,694,161	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Pass [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	3,047,885	2,866,794	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Special Mention [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	70,060	42,700	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Special Mention [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	249	9,309	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Special Mention [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	46,718	27,227	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Special Mention [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	23,093	6,164	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Substandard [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	58,774	65,437	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Substandard [Member] \| Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	11,153	2,962	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Substandard [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	26,700	30,308	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Substandard [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	20,921	32,167	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Doubtful [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	2,397	1,039	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Doubtful [Member] \| Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	423	113	'
Non-Covered Loans Excluding Acquired Loans [Member] \| Doubtful [Member] \| Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit quality indicator by asset risk classification	$1,974	$926	'

Allowance_for_Credit_Losses_an5

Allowance for Credit Losses and Credit Quality - Schedule of Investment in Impaired Loan (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	$39,250	'	$39,250	'	$45,342
Unpaid Principal Balance	39,618	'	39,618	'	46,501
Related Allowance	-368	'	-368	'	-1,159
Average Recorded Investment	40,761	50,310	41,026	49,840	'
Interest Income Recognized	22	23	379	136	'
Commercial Loans [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	11,902	'	11,902	'	25,018
Unpaid Principal Balance	11,937	'	11,937	'	25,877
Related Allowance	-35	'	-35	'	-859
Average Recorded Investment	12,522	31,006	13,648	30,233	'
Interest Income Recognized	17	23	168	89	'
Commercial Loans [Member] \| With No Related Allowance Recorded [Member] \| Real Estate [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	6,990	'	6,990	'	8,567
Unpaid Principal Balance	6,990	'	6,990	'	8,567
Related Allowance	'	'	'	'	'
Average Recorded Investment	7,026	10,703	7,114	12,787	'
Interest Income Recognized	6	6	20	22	'
Commercial Loans [Member] \| With No Related Allowance Recorded [Member] \| Business [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	3,276	'	3,276	'	13,256
Unpaid Principal Balance	3,276	'	3,276	'	13,256
Related Allowance	'	'	'	'	'
Average Recorded Investment	3,553	13,218	4,417	8,608	'
Interest Income Recognized	11	17	48	59	'
Commercial Loans [Member] \| With No Related Allowance Recorded [Member] \| Home Equity [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	689	'	689	'	258
Unpaid Principal Balance	689	'	689	'	258
Related Allowance	'	'	'	'	'
Average Recorded Investment	692	265	700	287	'
Interest Income Recognized	'	'	14	'	'
Commercial Loans [Member] \| With An Allowance Recorded [Member] \| Real Estate [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	1,450	'	1,450	'	1,268
Unpaid Principal Balance	1,483	'	1,483	'	1,284
Related Allowance	-33	'	-33	'	-16
Average Recorded Investment	1,631	4,346	1,533	6,092	'
Interest Income Recognized	'	'	91	5	'
Commercial Loans [Member] \| With An Allowance Recorded [Member] \| Business [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	186	'	186	'	1,927
Unpaid Principal Balance	188	'	188	'	2,770
Related Allowance	-2	'	-2	'	-843
Average Recorded Investment	312	2,739	584	2,746	'
Interest Income Recognized	'	'	9	3	'
Mortgage Loans [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	16,915	'	16,915	'	11,408
Unpaid Principal Balance	17,170	'	17,170	'	11,645
Related Allowance	-255	'	-255	'	-237
Average Recorded Investment	17,305	9,650	16,341	9,380	'
Interest Income Recognized	'	'	119	7	'
Mortgage Loans [Member] \| With An Allowance Recorded [Member] \| Residential Prime [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	10,746	'	10,746	'	9,791
Unpaid Principal Balance	10,973	'	10,973	'	10,019
Related Allowance	-227	'	-227	'	-228
Average Recorded Investment	11,077	9,650	10,226	9,380	'
Interest Income Recognized	'	'	119	7	'
Mortgage Loans [Member] \| With An Allowance Recorded [Member] \| Residential Subprime [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	6,169	'	6,169	'	1,617
Unpaid Principal Balance	6,197	'	6,197	'	1,626
Related Allowance	-28	'	-28	'	-9
Average Recorded Investment	6,228	'	6,115	'	'
Interest Income Recognized	'	'	'	'	'
Consumer Loans [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	10,433	'	10,433	'	8,916
Unpaid Principal Balance	10,511	'	10,511	'	8,979
Related Allowance	-78	'	-78	'	-63
Average Recorded Investment	10,934	9,654	11,037	10,227	'
Interest Income Recognized	5	'	92	40	'
Consumer Loans [Member] \| With An Allowance Recorded [Member] \| Home Equity [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	7,017	'	7,017	'	6,506
Unpaid Principal Balance	7,064	'	7,064	'	6,550
Related Allowance	-47	'	-47	'	-44
Average Recorded Investment	7,177	7,244	7,404	7,458	'
Interest Income Recognized	5	'	40	14	'
Consumer Loans [Member] \| With An Allowance Recorded [Member] \| Indirect Automobile [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	1,330	'	1,330	'	1,267
Unpaid Principal Balance	1,338	'	1,338	'	1,275
Related Allowance	-8	'	-8	'	-8
Average Recorded Investment	1,544	1,349	1,720	1,610	'
Interest Income Recognized	'	'	27	22	'
Consumer Loans [Member] \| With An Allowance Recorded [Member] \| Credit Card [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	968	'	968	'	404
Unpaid Principal Balance	987	'	987	'	411
Related Allowance	-19	'	-19	'	-7
Average Recorded Investment	1,051	424	724	426	'
Interest Income Recognized	'	'	'	'	'
Consumer Loans [Member] \| With An Allowance Recorded [Member] \| Consumer - Other [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	429	'	429	'	481
Unpaid Principal Balance	433	'	433	'	485
Related Allowance	-4	'	-4	'	-4
Average Recorded Investment	470	372	489	446	'
Interest Income Recognized	'	'	$11	$4	'

Loss_Sharing_Agreements_and_FD2

Loss Sharing Agreements and FDIC Loss Share Receivable - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Mar. 31, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
	Mar. 31, 2014	Business	Sep. 30, 2013	Dec. 31, 2013
Receivables [Abstract]	'	'	'	'
Percentage of covered loan and foreclosed real estate losses	'	80.00%	'	'
Losses that exceed contractual thresholds	'	95.00%	'	'
Number of acquisitions	'	4	'	'
Recovery period for covered assets	'	'3 years	'	'
Liability for reserve for amount of consideration	'	'	'	$800,000
FDIC loss share receivables	'	94,700,000	'	'
Valuation allowance against indemnification assets	$31,800,000	($5,097,000)	($31,813,000)	'

Loss_Sharing_Agreements_and_FD3

Loss Sharing Agreements and FDIC Loss Share Receivable - Schedule of FDIC Loss Share Receivables (Detail) (USD $)	3 Months Ended			9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
FDIC Loss Share Receivable [Line Items]	'	'	'	'	'
Balance at beginning of period	'	$162,312	'	$162,312	'
Change due to (reversal of) loan loss provision recorded on FDIC covered loans	'	'	'	1,153	-58,565
Amortization	-25,120	'	-22,875	-61,393	-68,707
Impairment	'	-31,800	'	5,097	31,813
Balance at end of period	94,712	'	'	94,712	'
FDIC Loss Share Receivables [Member]	'	'	'	'	'
FDIC Loss Share Receivable [Line Items]	'	'	'	'	'
Balance at beginning of period	'	162,312	'	162,312	423,069
Change due to (reversal of) loan loss provision recorded on FDIC covered loans	'	'	'	1,153	-58,565
Amortization	'	'	'	-61,393	-68,707
Submission of reimbursable losses to (recoveries payable to) the FDIC	'	'	'	4,901	-44,910
Impairment	'	'	'	-5,097	-31,813
Changes due to a change in cash flow assumptions on OREO and other changes	'	'	'	-7,164	-14,189
Balance at end of period	$94,712	'	$204,885	$94,712	$204,885

Transfers_and_Servicing_of_Fin2

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) - Components of Mortgage Banking Activity (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Participating Mortgage Loans [Line Items]	'	'	'	'
Balance at beginning of period	'	'	$128,442	'
Originations and purchases	'	'	1,218,684	1,712,557
Balance at end of period	148,530	'	148,530	'
Gains on sales	'	'	41,412	51,709
Total mortgage income	12,814	15,202	40,903	51,841
Mortgage Loans Held for Sale [Member]	'	'	'	'
Participating Mortgage Loans [Line Items]	'	'	'	'
Balance at beginning of period	'	'	128,442	267,475
Originations and purchases	'	'	1,218,684	1,712,557
Sales, net of gains	'	'	-1,193,282	-1,871,747
Other	'	'	-5,314	'
Balance at end of period	148,530	108,285	148,530	108,285
Mortgage Income [Member]	'	'	'	'
Participating Mortgage Loans [Line Items]	'	'	'	'
Fair value changes of derivatives and mortgage loans held for sale, net	'	'	-1,081	-270
Gains on sales	'	'	41,412	51,709
Servicing and other income, net	'	'	572	402
Total mortgage income	'	'	$40,903	$51,841

Transfers_and_Servicing_of_Fin3

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) - Schedule of Mortgage Servicing Rights at Carrying Values (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Acquired Indefinite-lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	$52,280	$46,754
Accumulated Amortization	-35,423	-31,415
Net Carrying Amount	16,857	15,339
Mortgage Servicing Rights [Member]	'	'
Acquired Indefinite-lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	2,787	2,146
Accumulated Amortization	-1,020	-638
Net Carrying Amount	$1,767	$1,508

Goodwill_and_Other_Acquired_In2

Goodwill and Other Acquired Intangible Assets - Schedule of Carrying Amount of Goodwill (Detail) (USD $)	9 Months Ended			9 Months Ended					9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Jan. 17, 2014	Dec. 31, 2012	Sep. 30, 2014	Dec. 31, 2012	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Dec. 31, 2012
	Sep. 30, 2014	Jan. 17, 2014	Dec. 31, 2012	IBERIABANK [Member]	IBERIABANK [Member]	IMC [Member]	IMC [Member]	IMC [Member]	LTC [Member]	LTC [Member]
Goodwill And Other Intangibles [Line Items]	'	'	'	'	'	'	'	'	'	'
Balance, December 31, 2012	$401,872	$8,600	$401,872	$373,905	$373,905	$23,178	$23,178	$23,178	$4,789	$4,789
Goodwill acquired during the period	124,370	'	'	123,995	'	'	'	'	375	'
Balance, December 31, 2013	$526,242	$8,600	$401,872	$497,900	$373,905	$23,178	$23,178	$23,178	$5,164	$4,789

Goodwill_and_Other_Acquired_In3

Goodwill and Other Acquired Intangible Assets - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]	'	'
Title plant assets	$6.70	$6.70

Goodwill_and_Other_Acquired_In4

Goodwill and Other Acquired Intangible Assets - Schedule of Definite-Lived Intangible Assets (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	$52,280	$46,754
Accumulated Amortization	-35,423	-31,415
Net Carrying Amount	16,857	15,339
Core Deposit Intangibles [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	50,564	45,406
Accumulated Amortization	-34,564	-30,784
Net Carrying Amount	16,000	14,622
Customer Relationship Intangible Asset [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	1,348	1,348
Accumulated Amortization	-777	-631
Net Carrying Amount	571	717
Noncompete Agreements [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	163	'
Accumulated Amortization	-53	'
Net Carrying Amount	110	'
Other Intangible Assets [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	205	'
Accumulated Amortization	-29	'
Net Carrying Amount	$176	'

Other_Real_Estate_Owned_Schedu

Other Real Estate Owned - Schedule of Other Real Estate Owned Segregated into Non-Covered and Covered Properties (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	$49,618	$88,546
Real estate acquired for development or resale	12,734	9,206
Other foreclosed property	1,034	1,421
Total other real estate owned and foreclosed property	63,386	99,173
Non-covered Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	18,627	28,072
Real estate acquired for development or resale	12,734	9,206
Other foreclosed property	63	93
Total other real estate owned and foreclosed property	31,424	37,371
Covered Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	30,991	60,474
Real estate acquired for development or resale	'	'
Other foreclosed property	971	1,328
Total other real estate owned and foreclosed property	$31,962	$61,802

Other_Real_Estate_Owned_Schedu1

Other Real Estate Owned - Schedule of Other Real Estate Owned Segregated into Non-Covered and Covered Properties (Parenthetical) (Detail) (USD $)	Sep. 30, 2014
In Millions, unless otherwise specified	Sep. 30, 2014
Statement of Financial Position [Abstract]	'
Covered other real estate owned	$20.60

Derivative_Instruments_and_Oth2

Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	$872,952	$868,604
Derivative Liability, Notional Amount	970,428	624,455
Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	872,952	868,604
Derivative Liability, Notional Amount	970,428	624,455
Not Designated as Hedging Instruments [Member] \| Interest Rate Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	421,523	380,303
Derivative Liability, Notional Amount	421,523	380,303
Not Designated as Hedging Instruments [Member] \| Forward Sales Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	88,190	192,876
Derivative Liability, Notional Amount	351,861	45,091
Not Designated as Hedging Instruments [Member] \| Written and Purchased Options [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	363,239	295,425
Derivative Liability, Notional Amount	197,044	199,061
Other Assets [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	32,290	30,076
Other Assets [Member] \| Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	32,290	30,076
Other Assets [Member] \| Not Designated as Hedging Instruments [Member] \| Interest Rate Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	11,839	10,621
Other Assets [Member] \| Not Designated as Hedging Instruments [Member] \| Forward Sales Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	104	1,468
Other Assets [Member] \| Not Designated as Hedging Instruments [Member] \| Written and Purchased Options [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	20,347	17,987
Other Liabilities [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	29,840	26,735
Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	29,840	26,735
Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member] \| Interest Rate Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	11,839	10,620
Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member] \| Forward Sales Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	2,215	287
Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member] \| Written and Purchased Options [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	$15,786	$15,828

Derivative_Instruments_and_Oth3

Derivative Instruments and Other Hedging Activities - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'	'
Cash as collateral for derivative transactions	$8.40	$5
Fair value of derivatives	$0.10	'

Derivative_Instruments_and_Oth4

Derivative Instruments and Other Hedging Activities - Reconciliation of Gross Amounts in Consolidated Balance Sheets (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	$27,262	$26,422
Derivative liabilities subject to master netting arrangements, Gross Amounts	11,839	10,620
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	27,262	26,422
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	7,947	5,201
Collateral [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	-3,892	-5,419
Interest Rate Contracts [Member] \| Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	11,839	10,621
Derivative liabilities subject to master netting arrangements, Gross Amounts	11,839	10,620
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	11,839	10,621
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	7,947	5,201
Interest Rate Contracts [Member] \| Collateral [Member] \| Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	-3,892	-5,419
Written and Purchased Options [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	15,423	15,801
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	$15,423	$15,801

Derivative_Instruments_and_Oth5

Derivative Instruments and Other Hedging Activities - Effect of Hedging Instruments on Consolidated Financial Statements (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI net of taxes (Effective Portion)	'	'	'	'
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	'	'	'	-392
Amount of Gain (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)	'	'	-1	'
Amount of Gain (Loss) Recognized in Income on Derivatives	'	'	-1	209
Not Designated as Hedging Instruments [Member]	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	-2,469	-2,545	-3,140	-381
Not Designated as Hedging Instruments [Member] \| Interest Rate Contracts [Member] \| Other Income (Expense) [Member]	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	406	2,061	1,971	2,542
Not Designated as Hedging Instruments [Member] \| Forward Sale Contracts [Member] \| Mortgage Income [Member]	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	-3,648	3,290	-7,512	897
Not Designated as Hedging Instruments [Member] \| Written and Purchased Options [Member] \| Mortgage Income [Member]	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	773	-7,896	2,401	-3,820
Cash Flow Hedging [Member] \| Interest Rate Contracts [Member]	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI net of taxes (Effective Portion)	'	'	'	'
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	'	'	'	-392
Amount of Gain (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)	'	'	($1)	'

Shareholders_Equity_and_Other_2

Shareholders' Equity and Other Comprehensive Income (Loss) - Summary of Tax Effects of Each Component of Other Comprehensive Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]	'	'	'	'
Unrealized holding gains/losses arising during the period, Before-Tax Amount	($7,032)	$5,528	$25,586	($38,769)
Less: reclassification adjustment for losses/gains included in net income, Before-Tax Amount	-582	3	-609	-2,259
Net unrealized losses/gains, Before-Tax Amount	-7,614	5,531	24,977	-41,028
Change in fair value of derivative instruments designated as cash flow hedges during the period, Before-Tax Amount	'	'	'	952
Less: reclassification adjustment for gains/losses included in net income, Before-Tax Amount	'	'	'	392
Fair value of derivative instruments designated as cash flow hedges, Before-Tax Amount	'	'	'	1,344
Total other comprehensive income/loss, Before-Tax Amount	-7,614	5,531	24,977	-39,684
Unrealized holding gains/losses arising during the period, Tax Expense (Benefit)	2,461	-1,935	-8,955	13,569
Less: reclassification adjustment for losses/gain included in net income, Tax Expense (Benefit)	204	-1	213	791
Net unrealized gains/losses, Tax Expense (Benefit)	2,665	-1,936	-8,742	14,360
Change in fair value of derivative instruments designated as cash flow hedges during the period, Tax Expense (Benefit)	'	'	'	-333
Less: reclassification adjustment for gains/losses included in net income, Tax Expense (Benefit)	'	'	'	-137
Fair value of derivative instruments designated as cash flow hedges, Tax Expense (Benefit)	'	'	'	-470
Total other comprehensive income/loss, Tax Expense (Benefit)	2,665	-1,936	-8,742	13,890
Unrealized holding gains/losses arising during the period, Net-of-Tax Amount	-4,571	3,593	16,631	-25,200
Less: reclassification adjustment for gains/losses included in net income, Net-of-Tax Amount	-378	2	-396	-1,468
Net unrealized gains/losses, Net-of-Tax Amount	-4,949	3,595	16,235	-26,668
Change in fair value of derivative instruments designated as cash flow hedges during the period, Net-of-Tax Amount	'	'	'	619
Less: reclassification adjustment for gains/losses included in net income, Net-of-Tax Amount	'	'	'	255
Fair value of derivative instruments designated as cash flow hedges, Net-of-Tax Amount	'	'	'	874
Other comprehensive income (loss), net of tax	($4,949)	$3,595	$16,235	($25,794)

Capital_Requirements_and_Other2

Capital Requirements and Other Regulatory Matters - Actual Capital Amounts and Ratios (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Consolidated [Member]	'	'
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Tier 1 Leverage, Minimum Amount	$596,945	$507,760
Tier 1 risk-based capital, Minimum Amount	490,391	426,002
Total risk-based capital, Minimum Amount	980,781	852,005
Tier 1 Leverage capital, Minimum Ratio	4.00%	4.00%
Tier 1 risk-based capital, Minimum Ratio	4.00%	4.00%
Total risk-based capital, Minimum Ratio	8.00%	8.00%
Tier 1 Leverage, Actual Amount	1,376,283	1,231,886
Tier 1 risk-based capital, Actual Amount	1,376,283	1,231,886
Total risk-based capital, Actual Amount	1,522,932	1,365,280
Tier 1 Leverage, Actual Ratio	9.22%	9.70%
Tier 1 risk-based capital, Actual Ratio	11.23%	11.57%
Total risk-based capital, Actual Ratio	12.42%	12.82%
IBERIABANK [Member]	'	'
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Tier 1 Leverage, Minimum Amount	594,578	505,723
Tier 1 risk-based capital, Minimum Amount	489,049	424,578
Total risk-based capital, Minimum Amount	978,099	849,157
Tier 1 Leverage capital, Minimum Ratio	4.00%	4.00%
Tier 1 risk-based capital, Minimum Ratio	4.00%	4.00%
Total risk-based capital, Minimum Ratio	8.00%	8.00%
Tier 1 Leverage capital, Well Capitalized Amount	743,223	632,154
Tier 1 risk-based capital, Well Capitalized Amount	733,574	636,868
Total risk-based capital, Well Capitalized Amount	1,222,624	1,061,446
Tier 1 Leverage capital, Well Capitalized Ratio	5.00%	5.00%
Tier 1 risk-based capital, Well Capitalized Ratio	6.00%	6.00%
Total risk-based capital, Well Capitalized Ratio	10.00%	10.00%
Tier 1 Leverage, Actual Amount	1,225,980	1,069,783
Tier 1 risk-based capital, Actual Amount	1,225,980	1,069,783
Total risk-based capital, Actual Amount	$1,372,629	$1,202,738
Tier 1 Leverage, Actual Ratio	8.25%	8.46%
Tier 1 risk-based capital, Actual Ratio	10.03%	10.08%
Total risk-based capital, Actual Ratio	11.23%	11.33%

ShareBased_Compensation_Additi

Share-Based Compensation - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Equity awards settled in cash	$0	$0
Share-based compensation maximum option term (in years)	'10 years	'
Future awards shares under approved incentive compensation plans	1,040,092	'
Minimum vesting period (in years)	'1 year 6 months	'
Maximum vesting period (in years)	'7 years	'
Excess tax benefits as financing cash inflows	1,163,000	495,000
Net cash proceeds from exercise of stock options	11,141,000	5,441,000
Aggregate intrinsic value of shares underlying outstanding stock options	6,800,000	'
Aggregate intrinsic value of shares underlying exercisable stock options	4,400,000	'
Total intrinsic value of options exercised	4,100,000	1,900,000
Maximum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned compensation vesting period (in years)	'7 years	'
Minimum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned compensation vesting period (in years)	'3 years	'
Employee Stock Option [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned share-based compensation associated with awards	3,700,000	'
Unrecognized compensation cost related to stock options expected to be recognized over a weighted-average period	'5 years 2 months 12 days	'
Restricted Stock [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned share-based compensation associated with awards	$22,200,000	$23,300,000
Phantom Stock Awards [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Minimum vesting period (in years)	'5 years	'
Maximum vesting period (in years)	'7 years	'

ShareBased_Compensation_Compen

Share-Based Compensation - Compensation Expense Included in Non-Interest Expense and Related Income Tax Benefits (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'	'	'
Compensation expense related to stock options	$508	$526	$1,545	$1,592
Income tax benefit related to stock options	$178	$184	$541	$557
Impact on basic earnings per share	$0.01	$0.01	$0.03	$0.03
Impact on diluted earnings per share	$0.01	$0.01	$0.03	$0.03

ShareBased_Compensation_Estima

Share-Based Compensation - Estimate Fair Value of Share-Based Awards with Weighted-Average Assumptions (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]	'	'
Expected dividends	2.10%	2.60%
Expected volatility	35.80%	34.80%
Risk-free interest rate	2.30%	1.70%
Expected term (in years)	'7 years 6 months	'8 years 7 months 6 days
Weighted-average grant-date fair value	$21.25	$15.37

ShareBased_Compensation_Activi

Share-Based Compensation - Activity Related to Stock Options (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]	'	'
Number of shares, Outstanding options, Beginning balance	1,072,829	1,236,075
Number of shares, Outstanding options, Granted	77,098	75,722
Number of shares, Outstanding options, Exercised	-234,363	-142,841
Number of shares, Outstanding options, Forfeited or expired	-13,446	-36,608
Number of shares, Outstanding options, Ending balance	902,118	1,132,348
Number of shares, Exercisable options	581,423	749,545
Weighted Average Exercise Price, Outstanding options, Beginning balance	$53.47	$51.48
Weighted Average Exercise Price, Outstanding options, Granted	$65.30	$52.36
Weighted Average Exercise Price, Outstanding options, Exercised	$48.36	$38.09
Weighted Average Exercise Price, Outstanding options, Forfeited or expired	$60.82	$56.01
Weighted Average Exercise Price, Outstanding options, Ending balance	$55.70	$53.09
Weighted Average Exercise Price, Exercisable options	$55.65	$52.94
Weighted Average Remaining Contract Life, Outstanding options	'5 years 2 months 12 days	'4 years 8 months 12 days
Weighted Average Remaining Contract Life, Exercisable options	'3 years 9 months 18 days	'3 years 2 months 12 days

ShareBased_Compensation_Compen1

Share-Based Compensation - Compensation Expense Included in Salaries and Employee Benefits Expense Related to Restricted Stock Grants (Detail) (Restricted Stock [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Restricted Stock [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to restricted stock	$2,497	$2,212	$7,382	$6,407

ShareBased_Compensation_Unvest

Share-Based Compensation - Unvested Restricted Stock Award Activity (Detail)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Balance at beginning of period	523,756	538,202
Granted	146,547	166,223
Forfeited	-18,171	-27,483
Earned and issued	-152,112	-136,629
Balance at end of period	500,020	540,313

ShareBased_Compensation_Compen2

Share-Based Compensation - Compensation Expense of Phantom Stock (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to phantom stock	$508	$526	$1,545	$1,592
Phantom Stock Awards [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to phantom stock	$619	$792	$3,692	$2,602

ShareBased_Compensation_Schedu

Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Number of share equivalents, Beginning Balance	417,238	318,729
Number of share equivalents, Granted	115,620	166,664
Number of share equivalents, Forfeited share equivalents	-19,498	-16,381
Number of share equivalents, Vested share equivalents	-68,480	-45,065
Number of share equivalents, Ending Balance	444,880	423,947
Dividend equivalents, Beginning Balance	22,351	16,035
Dividend equivalents, Granted	7,147	8,793
Dividend equivalents, Forfeited share equivalents	-1,751	-681
Dividend equivalents, Vested share equivalents	-6,615	-3,327
Dividend equivalents, Ending Balance	21,132	20,820
Total share equivalents, Beginning Balance	439,589	334,764
Total share equivalents, Granted	122,767	175,457
Total share equivalents, Forfeited share equivalents	-21,249	-17,062
Total share equivalents, Vested share equivalents	-75,095	-48,392
Total share equivalents, Ending Balance	466,012	444,767
Value of share equivalents, Beginning Balance	$27,628,000	$16,444,000
Value of share equivalents, Granted	7,674,000	9,108,000
Value of share equivalents, Forfeited share equivalents	-1,328,000	-886,000
Value of share equivalents, Vested share equivalents	-5,002,000	-2,453,000
Value of share equivalents, Ending Balance	$29,130,000	$23,088,000

ShareBased_Compensation_Schedu1

Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Parenthetical) (Detail) (USD $)	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Market price of Company's stock	$62.51	$51.91

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'	'
Fair value of guarantees under commercial and standby letters of credit	$1.30	$1.10

Commitments_and_Contingencies_2

Commitments and Contingencies - Summary of Financial Instruments Outstanding (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Loss Contingencies [Line Items]	'	'	'
Reserve for unfunded lending commitments	$12,099	$11,147	$11,959
Credit Risk Contract [Member]	'	'	'
Loss Contingencies [Line Items]	'	'	'
Commitments to grant loans	242,137	221,627	'
Unfunded commitments under lines of credit	3,834,107	3,326,448	'
Commercial and standby letters of credit	131,347	105,026	'
Reserve for unfunded lending commitments	$12,099	$11,147	'

Fair_Value_Measurements_Summar

Fair Value Measurements - Summary of Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance for Mortgage Loans Held for Sale (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'	'
Mortgage loans held for sale, at fair value, Aggregate Fair Value	$148,530	$97,273
Mortgage loans held for sale, at fair value, Aggregate Unpaid Principal	142,381	96,875
Mortgage loans held for sale, at fair value, Aggregate Fair Value Less Unpaid Principal	$6,149	$398

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014	Dec. 31, 2013
	Sep. 30, 2014	Sep. 30, 2013	Branch	Sep. 30, 2014	Sep. 30, 2013	Branch	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'	'	'
Total mortgage income (loss) in the consolidated statement of comprehensive income	($1,600,000)	$0	'	$4,000,000	$0	'	'
Impaired non-covered loans with an outstanding balance	1,100,000	'	'	1,100,000	'	'	4,100,000
Reserve in allowance for credit losses	25,000	'	'	25,000	'	'	1,000,000
Company announced plans to close branches	'	'	10	'	'	'	'
Number of branches closed	'	'	'	'	'	9	'
Book value of company's closed branches after impairment losses	3,100,000	'	'	3,100,000	'	'	5,100,000
Available-for-sale Securities [Member]	'	'	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'	'	'
Fair value assets transferred from Level 1 to Level 2	14,700,000	'	'	14,700,000	'	'	'
Fair Value, Measurements, Nonrecurring [Member]	'	'	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'	'	'
Fair value of liabilities	$0	'	'	$0	'	'	$0

Fair_Value_Measurements_Financ

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available for sale securities, Assets	$2,103,828,000	$1,936,797,000
Mortgage loans held for sale, Assets	148,530,000	97,273,000
Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available for sale securities, Assets	2,103,828,000	1,936,797,000
Mortgage loans held for sale, Assets	148,530,000	97,273,000
Derivative instruments, Assets	32,290,000	30,076,000
Total, Assets	2,284,648,000	2,064,146,000
Derivative instruments, Liabilities	29,840,000	26,735,000
Total, Liabilities	29,840,000	26,735,000
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available for sale securities, Assets	46,261,000	15,496,000
Mortgage loans held for sale, Assets	'	'
Derivative instruments, Assets	'	'
Total, Assets	46,261,000	15,496,000
Derivative instruments, Liabilities	'	'
Total, Liabilities	'	'
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available for sale securities, Assets	2,057,567,000	1,921,301,000
Mortgage loans held for sale, Assets	148,530,000	97,273,000
Derivative instruments, Assets	32,290,000	30,076,000
Total, Assets	2,238,387,000	2,048,650,000
Derivative instruments, Liabilities	29,840,000	26,735,000
Total, Liabilities	29,840,000	26,735,000
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available for sale securities, Assets	'	'
Mortgage loans held for sale, Assets	'	'
Derivative instruments, Assets	'	'
Total, Assets	'	'
Derivative instruments, Liabilities	'	'
Total, Liabilities	'	'

Fair_Value_Measurements_Gains_

Fair Value Measurements - Gains and Losses Included in Earnings Related to Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014
Noninterest Income [Member]	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Total gains (losses) included in earnings (or changes in net assets)	($1,697)
Other Comprehensive Income [Member]	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Change in unrealized gains (losses) relating to assets still held at September 30, 2014	$16,235

Fair_Value_Measurements_Financ1

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Mortgage loans held for sale, Assets	$148,530	$97,273
Fair Value, Measurements, Nonrecurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Loans, Assets	1,086	3,070
Mortgage loans held for sale, Assets	'	11,876
OREO, Assets	6,974	14,598
Total, Assets	8,060	29,544
Fair Value, Measurements, Nonrecurring [Member] \| Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Loans, Assets	'	'
Mortgage loans held for sale, Assets	'	'
OREO, Assets	'	'
Total, Assets	'	'
Fair Value, Measurements, Nonrecurring [Member] \| Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Loans, Assets	1,086	3,070
Mortgage loans held for sale, Assets	'	11,876
OREO, Assets	6,974	14,598
Total, Assets	8,060	29,544
Fair Value, Measurements, Nonrecurring [Member] \| Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Loans, Assets	'	'
Mortgage loans held for sale, Assets	'	'
OREO, Assets	'	'
Total, Assets	'	'

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Short-term borrowings maturity period	'90 days

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments - Estimated Fair Values and Carrying Amounts of Financial Instruments (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Financial Assets	'	'	'	'
Cash and cash equivalents	$668,007	$391,396	$553,448	$970,977
Loans and loans held for sale	11,227,729	'	9,151,322	'
FDIC loss share receivable	94,712	162,312	'	'
Financial Liabilities	'	'	'	'
Deposits	12,377,775	10,737,000	10,950,764	'
Short-term borrowings	812,783	680,344	'	'
Long-term debt	355,569	280,699	'	'
Carrying Amount [Member]	'	'	'	'
Financial Assets	'	'	'	'
Cash and cash equivalents	668,007	391,396	'	'
Investment securities	2,224,348	2,090,906	'	'
Loans and loans held for sale	11,227,729	9,620,461	'	'
FDIC loss share receivable	94,712	162,312	'	'
Derivative instruments	32,290	30,076	'	'
Accrued interest receivable	37,143	32,143	'	'
Financial Liabilities	'	'	'	'
Deposits	12,377,775	10,737,000	'	'
Short-term borrowings	812,783	680,344	'	'
Long-term debt	355,569	280,699	'	'
Derivative instruments	29,840	26,735	'	'
Accrued interest payable	7,972	6,102	'	'
Fair Value [Member]	'	'	'	'
Financial Assets	'	'	'	'
Cash and cash equivalents	668,007	391,396	'	'
Investment securities	2,226,286	2,089,363	'	'
Loans and loans held for sale	11,247,080	9,724,432	'	'
FDIC loss share receivable	27,922	21,918	'	'
Derivative instruments	32,290	30,076	'	'
Accrued interest receivable	37,143	32,143	'	'
Financial Liabilities	'	'	'	'
Deposits	11,986,233	10,226,573	'	'
Short-term borrowings	812,783	680,344	'	'
Long-term debt	324,282	235,503	'	'
Derivative instruments	29,840	26,735	'	'
Accrued interest payable	$7,972	$6,102	'	'

Business_Segments_Additional_I

Business Segments - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2014
	Segment
Segment Reporting [Abstract]	'
No of business segments	3

Business_Segments_Schedule_of_

Business Segments - Schedule of Segment Reporting Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	$133,167	$108,512	$366,619	$323,105	'
Interest expense	12,126	11,060	32,192	36,299	'
Net interest income	121,041	97,452	334,427	286,806	'
Provision for loan losses	5,714	2,014	12,565	445	'
Mortgage income	12,814	15,202	40,903	51,841	'
Title income	5,577	5,482	15,007	16,199	'
Other non-interest income	27,272	22,579	73,397	62,202	'
Core deposit intangible amortization	1,429	1,125	3,779	3,375	'
Other non-interest expenses	118,631	107,027	351,084	367,035	'
Income before income tax expense	40,930	30,549	96,306	46,193	'
Income tax expense (benefit)	11,186	7,357	25,619	6,694	'
Net income (loss)	29,744	23,192	70,687	39,499	'
Total loans and loans held for sale	11,227,729	9,151,322	11,227,729	9,151,322	'
Total assets	15,516,609	13,145,077	15,516,609	13,145,077	13,365,550
Total deposits	12,377,775	10,950,764	12,377,775	10,950,764	10,737,000
Average assets	15,478,406	12,944,435	14,302,151	12,966,519	'
IBERIABANK [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	131,362	107,051	362,054	318,646	'
Interest expense	11,501	10,731	30,869	34,786	'
Net interest income	119,861	96,320	331,185	283,860	'
Provision for loan losses	5,621	1,868	12,481	320	'
Mortgage income	-5	5	80	2	'
Other non-interest income	27,311	22,579	73,460	62,206	'
Core deposit intangible amortization	1,429	1,125	3,779	3,375	'
Allocated expenses	-2,386	-2,658	-9,110	-4,402	'
Other non-interest expenses	102,692	90,858	305,121	315,332	'
Income before income tax expense	39,811	27,711	92,454	31,443	'
Income tax expense (benefit)	10,739	6,228	24,081	884	'
Net income (loss)	29,072	21,483	68,373	30,559	'
Total loans and loans held for sale	11,055,809	9,024,959	11,055,809	9,024,959	'
Total assets	15,288,157	12,965,373	15,288,157	12,965,373	'
Total deposits	12,371,606	10,946,453	12,371,606	10,946,453	'
Average assets	15,239,174	12,761,165	14,097,930	12,747,602	'
IMC [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	1,804	1,459	4,563	4,428	'
Interest expense	625	329	1,323	1,513	'
Net interest income	1,179	1,130	3,240	2,915	'
Provision for loan losses	93	146	84	125	'
Mortgage income	12,819	15,197	40,823	51,839	'
Other non-interest income	-37	'	-61	-4	'
Allocated expenses	1,697	1,933	6,432	3,213	'
Other non-interest expenses	11,624	12,016	33,558	38,942	'
Income before income tax expense	547	2,232	3,928	12,470	'
Income tax expense (benefit)	217	877	1,552	4,897	'
Net income (loss)	330	1,355	2,376	7,573	'
Total loans and loans held for sale	171,920	126,363	171,920	126,363	'
Total assets	202,923	153,402	202,923	153,402	'
Total deposits	6,169	4,311	6,169	4,311	'
Average assets	213,936	157,144	179,218	193,463	'
LTC [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	1	2	2	31	'
Net interest income	1	2	2	31	'
Title income	5,577	5,482	15,007	16,199	'
Other non-interest income	-2	'	-2	'	'
Allocated expenses	689	725	2,678	1,189	'
Other non-interest expenses	4,315	4,153	12,405	12,761	'
Income before income tax expense	572	606	-76	2,280	'
Income tax expense (benefit)	230	252	-14	913	'
Net income (loss)	342	354	-62	1,367	'
Total assets	25,529	26,302	25,529	26,302	'
Average assets	$25,296	$26,126	$25,003	$25,454	'

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (Subsequent Events [Member], USD $)	3 Months Ended
	Dec. 30, 2014	Dec. 31, 2014
	Florida Bank Group, Inc. [Member]	Old Florida Bancshares, Inc. [Member]
Subsequent Event [Line Items]	'	'
Cash paid per share	$7.81	'
Shares received	0.149	0.34