Iberiabank (IBKC) 10-Q 8 Aug 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 31, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
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	'	33,419,918

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets	'	'
Cash and due from banks	$286,615	$238,672
Interest-bearing deposits in banks	381,955	152,724
Total cash and cash equivalents	668,570	391,396
Securities available for sale, at fair value	2,008,953	1,936,797
Securities held to maturity (fair values of $134,063 and $152,566, respectively)	132,245	154,109
Mortgage loans held for sale ($178,380 and $97,273 recorded at fair value, respectively)	178,380	128,442
Loans covered by loss share agreements	585,439	719,793
Non-covered loans, net of unearned income	10,313,088	8,772,226
Total loans, net of unearned income	10,898,527	9,492,019
Allowance for loan losses	-133,519	-143,074
Loans, net	10,765,008	9,348,945
FDIC loss share receivables	120,532	162,312
Premises and equipment, net	307,090	287,510
Goodwill	524,154	401,872
Other assets	620,110	554,167
Total Assets	15,325,042	13,365,550
Liabilities	'	'
Non-interest-bearing	3,047,385	2,575,939
Interest-bearing	8,933,798	8,161,061
Total deposits	11,981,183	10,737,000
Short-term borrowings	1,034,741	680,344
Long-term debt	365,747	280,699
Other liabilities	144,065	136,528
Total Liabilities	13,525,736	11,834,571
Shareholders' Equity	'	'
Preferred stock, $1 par value - 5,000,000 shares authorized	0	0
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	1,391,097	1,178,284
Retained earnings	455,511	436,141
Accumulated other comprehensive income (loss)	4,693	-16,491
Treasury stock at cost - 1,852,819 and 2,130,841 shares, respectively	-87,258	-98,872
Total Shareholders' Equity	1,799,306	1,530,979
Total Liabilities and Shareholders' Equity	$15,325,042	$13,365,550

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Securities held to maturity, fair values	$134,063	$152,566
Mortgage loans held for sale recorded at fair value	$178,380	$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	1,852,819	2,130,841

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Loss) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Interest and Dividend Income	'	'	'	'
Loans, including fees	$123,124	$115,242	$244,278	$238,309
Mortgage loans held for sale, including fees	1,474	1,351	2,359	2,676
Investment securities:	'	'	'	'
Taxable interest	9,492	7,301	18,859	14,406
Tax-exempt interest	1,508	1,677	3,058	3,432
Amortization of FDIC loss share receivable	-17,009	-18,130	-36,273	-45,831
Other	631	736	1,170	1,601
Total interest and dividend income	119,220	108,177	233,451	214,593
Interest Expense	'	'	'	'
NOW and MMDA	4,123	4,614	8,307	10,021
Savings	83	74	147	167
Time deposits	3,089	4,372	6,026	9,026
Short-term borrowings	373	121	615	261
Long-term debt	2,573	2,514	4,970	5,764
Total interest expense	10,241	11,695	20,065	25,239
Net interest income	108,979	96,482	213,386	189,354
(Reversal of) Provision for loan losses	4,748	1,807	6,851	-1,569
Net interest income after provision for loan losses	104,231	94,675	206,535	190,923
Non-interest Income	'	'	'	'
Service charges on deposit accounts	8,203	7,106	15,216	13,903
Mortgage income	17,957	17,708	28,089	36,639
Title revenue	5,262	5,696	9,429	10,717
ATM/debit card fee income	2,937	2,357	5,404	4,541
Income from bank owned life insurance	935	901	3,376	1,840
Gain (loss) on sale of available for sale investments	8	-66	27	2,261
Derivative losses reclassified from other comprehensive income	'	33	'	-392
Broker commissions	5,479	3,863	9,526	7,397
Other income	7,182	4,891	12,577	10,074
Total non-interest income	47,963	42,489	83,644	86,980
Non-interest Expense	'	'	'	'
Salaries and employee benefits	68,846	63,815	128,707	126,344
Net occupancy and equipment	16,104	14,283	30,094	29,478
Impairment of FDIC loss share receivables and other long-lived assets	1,109	4,618	1,441	36,431
Communication and delivery	3,464	3,116	6,231	6,387
Marketing and business development	3,412	3,049	6,262	6,136
Data processing	10,121	4,264	15,503	8,256
Amortization of acquisition intangibles	1,244	1,181	2,461	2,364
Professional services	5,560	5,101	9,308	9,519
Costs of OREO property, net	497	367	1,657	1,339
Credit and other loan related expense	3,093	4,135	6,639	7,858
Insurance	3,255	2,782	6,672	5,283
Travel and entertainment	2,126	2,019	4,456	4,287
Other expenses	8,544	8,631	15,371	18,577
Total non-interest expense	127,375	117,361	234,802	262,259
Income before income tax expense	24,819	19,803	55,377	15,644
Income tax expense (benefit)	6,271	4,213	14,434	-663
Net Income	18,548	15,590	40,943	16,307
Income Available to Common Shareholders - Basic	18,548	15,590	40,943	16,307
Earnings Allocated to Unvested Restricted Stock	-298	-293	-699	-313
Earnings Available to Common Shareholders - Diluted	18,250	15,297	40,244	15,994
Earnings per common share - Basic	$0.60	$0.53	$1.35	$0.55
Earnings per common share - Diluted	$0.60	$0.53	$1.35	$0.55
Cash dividends declared per common share	$0.34	$0.34	$0.68	$0.68
Unrealized gains on securities:	'	'	'	'
Unrealized holding gains (losses) arising during the period	16,730	-42,303	32,618	-44,297
Less: reclassification adjustment for (gains) losses included in net income	-8	66	-27	-2,261
Net unrealized losses/gains, Before-Tax Amount	16,722	-42,237	32,591	-46,558
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	'	-1,121	'	952
Less: reclassification adjustment for losses (gains) included in net income	'	-33	'	392
Fair value of derivative instruments designated as cash flow hedges, before tax	'	-1,154	'	1,344
Other comprehensive income (loss), before tax	16,722	-43,391	32,591	-45,214
Income tax expense (benefit) related to items of other comprehensive (loss) income	5,853	-15,187	11,407	-15,825
Other comprehensive income (loss), net of tax	10,869	-28,204	21,184	-29,389
Comprehensive income (loss)	$29,417	($12,614)	$62,127	($13,082)

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
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	16,307	'	'	16,307	'	'
Other comprehensive income (loss)	-29,389	'	'	'	-29,389	'
Cash dividends declared, $0.68 and $0.68 per share for six months ended June 30,2013 and June 30,2014 respectively.	-20,197	'	'	-20,197	'	'
Reissuance of treasury stock under incentive plans, net of shares surrendered in payment, including tax benefit	2,911	'	-1,120	'	'	4,031
Reissuance of treasury stock under incentive plans, Shares	'	'	'	'	'	-220,313
Common stock issued for recognition and retention plans	'	'	-7,962	'	'	7,962
Share-based compensation cost	5,261	'	5,261	'	'	'
Ending balance at Jun. 30, 2013	1,504,761	31,917	1,172,359	407,582	-4,912	-102,185
Ending balance, Shares at Jun. 30, 2013	'	31,917,385	'	'	'	2,207,327
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	40,943	'	'	40,943	'	'
Other comprehensive income (loss)	21,184	'	'	'	21,184	'
Cash dividends declared, $0.68 and $0.68 per share for six months ended June 30,2013 and June 30,2014 respectively.	-21,573	'	'	-21,573	'	'
Reissuance of treasury stock under incentive plans, net of shares surrendered in payment, including tax benefit	7,186	'	1,797	'	'	5,389
Reissuance of treasury stock under incentive plans, Shares	'	'	'	'	'	-278,022
Common stock issued for acquisitions	214,665	3,346	211,319	'	'	'
Common stock issued for acquisitions, Shares	'	3,345,516	'	'	'	'
Common stock issued for recognition and retention plans	'	'	-6,225	'	'	6,225
Share-based compensation cost	5,922	'	5,922	'	'	'
Ending balance at Jun. 30, 2014	$1,799,306	$35,263	$1,391,097	$455,511	$4,693	($87,258)
Ending balance, Shares at Jun. 30, 2014	'	35,262,901	'	'	'	1,852,819

Consolidated_Statements_of_Sha1

Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash dividends declared per share	$0.68	$0.68
Retained Earnings [Member]	'	'
Cash dividends declared per share	$0.68	$0.68

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Cash Flows from Operating Activities	'	'
Net income	$40,943	$16,307
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	7,749	13,346
Amortization of purchase accounting adjustments, net	6,142	-10,879
Provision for (Reversal of) loan losses	6,851	-1,569
Share-based equity compensation expense	5,922	5,261
Gain on sale of assets	-16	-49
Gain on sale of available for sale investments	-27	-2,261
Gain on sale of OREO	-1,322	-2,975
Loss on abandonment of fixed assets	'	4,618
Impairment of FDIC loss share receivables	804	31,813
Amortization of premium/discount on investments	6,713	10,683
Derivative losses on swaps	'	-209
(Benefit) provision for deferred income taxes	-6,817	-12,198
Originations of mortgage loans held for sale	-760,658	-1,207,676
Proceeds from sales of mortgage loans held for sale	730,129	1,350,910
Gain on sale of mortgage loans held for sale, net	-24,397	-37,790
Tax benefit associated with share-based payment arrangements	-945	-417
(Increase) decrease in other assets	-26,251	732
Other operating activities, net	-780	5,798
Net Cash (Used in) Provided by Operating Activities	-15,960	163,445
Cash Flows from Investing Activities	'	'
Proceeds from sales of securities available for sale	14,050	44,675
Proceeds from maturities, prepayments and calls of securities available for sale	154,111	494,593
Purchases of securities available for sale	-169,807	-760,640
Proceeds from maturities, prepayments and calls of securities held to maturity	21,383	47,101
Purchases of securities held to maturity	'	-5,901
Reimbursement of recoverable covered asset losses from the FDIC	1,319	49,582
Increase in loans receivable, net	-306,593	-427,489
Proceeds from sale of premises and equipment	6,474	639
Purchases of premises and equipment	-21,297	-8,735
Proceeds from disposition of real estate owned	43,376	44,082
Investment in new market tax credit entities	-5,809	'
Cash received in excess of cash paid for acquisition	188,796	'
Other investing activities, net	-13,567	11,400
Net Cash Used in Investing Activities	-87,564	-510,693
Cash Flows from Financing Activities	'	'
Increase (Decrease) in deposits, net of deposits acquired	101,223	-106,219
Net change in short-term borrowings, net of borrowings acquired	299,296	-13,668
Proceeds from long-term debt	'	2,230
Repayments of long-term debt	-6,666	-141,296
Dividends paid to shareholders	-20,341	-20,122
Proceeds from sale of treasury stock for stock options exercised	9,240	4,238
Payments to repurchase common stock	-2,999	-1,744
Common stock issued	'	'
Tax benefit associated with share-based payment arrangements	945	417
Net Cash Provided by (Used in) Financing Activities	380,698	-276,164
Net Increase (Decrease) In Cash and Cash Equivalents	277,174	-623,412
Cash and Cash Equivalents at Beginning of Period	391,396	970,977
Cash and Cash Equivalents at End of Period	668,570	347,565
Supplemental Schedule of Noncash Activities	'	'
Acquisition of real estate in settlement of loans	16,851	51,733
Transfers of property into Other Real Estate	27,074	51,733
Supplemental Disclosures Cash paid for:	'	'
Interest on deposits and borrowings	19,277	25,797
Income taxes, net	$39,306	$19,558

Basis_of_Presentation

Basis of Presentation	6 Months Ended
	Jun. 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, excluding loans held for sale that are recorded at fair value under the fair value option, are carried at the lower of cost or estimated fair value. When determining the fair value of loans held for sale, the Company obtains quotes or bids on these loans directly from purchasing financial institutions (Level 2). Mortgage loans held for sale that were recorded at estimated fair value are included in Note 17.
	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 June 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 $0.6 million and $1.4 million in earnings for the three months ended June 30, 2014 and 2013, respectively, and $1.4 million and $2.6 million for the six months ended June 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.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	6 Months Ended
	Jun. 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. 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 also required 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 a change in accounting policy would have on its consolidated financial statements, but does not anticipate 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, 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. The amendments in the ASU deem 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 the adoption would have on its consolidated financial statements, but does not anticipate 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.

Earnings_Per_Share

Earnings Per Share	6 Months Ended
	Jun. 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 Six Months Ended
			June 30						June 30
			2014			2013			2014			2013
	(Dollars in thousands, except per share data)
	Income available to common shareholders		$	18,548		$	15,590		$	40,943		$	16,307
	Distributed earnings (capital) to unvested restricted stock			(286	)		(290	)		(681	)		(313	)
	Distributed earnings (capital) to common shareholders – basic			18,262			15,300			40,262			15,994
	Undistributed earnings reallocated to unvested restricted stock			(12	)		(3	)		(18	)		—
	Distributed and undistributed earnings to common shareholders – diluted		$	18,250		$	15,297		$	40,244		$	15,994
	Weighted average shares outstanding – basic (1)			30,787,520			29,610,315			30,303,294			29,556,810
	Weighted average shares outstanding – diluted			30,386,105			29,066,906			29,904,370			29,023,002
	Earnings per common share – basic		$	0.6		$	0.53		$	1.35		$	0.55
	Earnings per common share – diluted			0.6			0.53			1.35			0.55
	Earnings per unvested restricted stock share – basic			0.54			0.51			1.27			0.55
	Earnings per unvested restricted stock share – diluted			0.56			0.52			1.31			0.55
	-1	Weighted average basic shares outstanding include 527,605 and 567,162 shares of unvested restricted stock for the three months ended June 30, 2014 and 2013, respectively, and 535,442 and 565,860 shares for the six months ended June 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 Six Months Ended
			June 30						June 30
			2014			2013			2014			2013
	(Dollars in thousands, except per share data)
	Distributed earnings to common shareholders		$	11,184		$	9,914		$	21,214		$	19,810
	Undistributed earnings (distributed capital) to common shareholders			7,078			5,386			19,048			(3,816	)
	Total earnings to common shareholders		$	18,262		$	15,300		$	40,262		$	15,994
	Distributed earnings to unvested restricted stock		$	175		$	188		$	359		$	387
	Undistributed earnings (distributed capital) to unvested restricted stock			111			102			322			(74	)
	Total earnings allocated to restricted stock		$	286		$	290		$	681		$	313
	Distributed earnings per common share		$	0.37		$	0.34		$	0.71		$	0.68
	Undistributed earnings (distributed capital) per common share			0.23			0.19			0.64			(0.13	)
	Total earnings per common share – basic		$	0.6		$	0.53		$	1.35		$	0.55
	Distributed earnings per unvested restricted stock share		$	0.33		$	0.33		$	0.67		$	0.68
	Undistributed earnings (distributed capital) per unvested restricted stock share			0.21			0.18			0.6			(0.13	)
	Total earnings per unvested restricted stock share – basic		$	0.54		$	0.51		$	1.27		$	0.55
	For the three months ended June 30, 2014 and 2013, the calculations for basic shares outstanding exclude the weighted average shares owned by the Recognition and Retention Plan (“RRP”) of 629,055 and 652,683, respectively, and are adjusted for the weighted average shares in treasury stock of 1,861,247 and 2,221,550, respectively. For the six months ended June 30, 2014 and 2013, basic shares outstanding exclude 634,883 and 647,332 shares owned by the RRP, respectively, and are adjusted for 1,933,367 and 2,279,103 shares, respectively, of weighted average shares of treasury stock.
	The effects from the assumed exercises of 11,623 and 792,893 stock options were not included in the computation of diluted earnings per share for the three months ended June 30, 2014 and 2013, respectively, because such amounts would have had an antidilutive effect on earnings per common share. For the six months ended June 30, 2014 and 2013, the effects from the assumed exercise of 11,623 and 787,893 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	6 Months Ended
	Jun. 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 $8.4 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 $84.4 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					72,308
	Goodwill				$	84,432
	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 $28.7 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					29,980
	Goodwill				$	28,660
	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. Net assets acquired subject to finalization of fair value estimates include, but are not limited to, loans and core deposit intangibles and any related adjustments to deferred taxes associated with these fair value adjustments. 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 table.
	Trust One-Memphis
	(Dollars in thousands)		As Acquired		Preliminary			As recorded by
					Fair Value			IBERIABANK
					Adjustments
	Assets
	Cash and cash equivalents		$	92,060	$	—		$	92,060
	Loans			88,179		(1,290	)(1)		86,889
	Other real estate owned			1,325		—			1,325
	Core deposit intangible			—		2,597	(2)		2,597
	Other assets			368		—			368
	Total Assets		$	181,932	$	1,307		$	183,239
	Liabilities
	Interest-bearing deposits		$	164,942	$	—		$	164,942
	Non-interest-bearing deposits			26,373		—			26,373
	Deferred tax liability			—		654	(3)		654
	Other liabilities			84		—			84
	Total Liabilities		$	191,399	$	654		$	192,053
	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 estimated fair value of the core deposit intangible asset created in the acquisition.
	(3)	The amount represents the deferred tax liability recognized on the fair value adjustment of Trust One-Memphis acquired assets and assumed liabilities.
	Teche
	(Dollars in thousands)		As Acquired		Preliminary			As recorded
					Fair Value			by
					Adjustments			IBERIABANK
	Assets
	Cash and cash equivalents		$	71,606	$	—		$	71,606
	Investment securities			24,077		1,092	(1)		25,169
	Loans			716,587		(16,637	)(2)		699,950
	Other real estate owned			329		—			329
	Core deposit intangible			—		2,055	(3)		2,055
	Deferred tax asset			1,057		7,373	(4)		8,430
	Other assets			56,708		(6,512	)(5)		50,196
	Total Assets		$	870,364	$	(12,629	)	$	857,735
	Liabilities
	Interest-bearing deposits		$	520,446	$	902	(6)	$	521,348
Non-interest-bearing deposits			118,256		—			118,256
Borrowings			134,228		6,304	(7)		140,532
Other liabilities			5,291		—			5,291
Total Liabilities		$	778,221	$	7,206		$	785,427
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 estimated fair value of the core deposit intangible asset created in the acquisition.
(4)	The amount represents the deferred tax asset recognized on the fair value adjustment of Teche acquired assets and assumed liabilities.
(5)	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.
(6)	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.
(7)	The amount represents the estimated fair value adjustment for the debt assumed, primarily driven by the estimated market interest rate on the debt relative to the stated interest rate.
First Private
(Dollars in thousands)		As Acquired		Preliminary			As recorded by
				Fair Value			IBERIABANK
				Adjustments
Assets
Cash and cash equivalents		$	26,621	$	—		$	26,621
Investment securities			19,110		—			19,110
Loans			294,425		4,207	(1)		298,632
Other real estate owned			—		—			—
Core deposit intangible			—		506	(2)		506
Deferred tax asset (liability)			530		(1,676	) (3)		(1,146	)
Other assets			5,230		—			5,230
Total Assets		$	345,916	$	3,037		$	348,953
Liabilities
Interest-bearing deposits		$	261,713	$	220	(4)	$	261,933
Non-interest-bearing deposits			50,333		—			50,333
Borrowings			6,451		—			6,451
Other liabilities			256		—			256
Total Liabilities		$	318,753	$	220		$	318,973
Explanation of certain fair value adjustments
(1)	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.
(2)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.
(3)	The amount represents the deferred tax liability recognized on the fair value adjustment of First Private acquired assets and assumed liabilities.
(4)	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.
Acquisition of The Title Company LLC
On February 24, 2014, the Company’s subsidiary, LTC, acquired 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. The acquisition was 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 acquisition. The goodwill recognized was the result of LTC’s expanded presence into the Baton Rouge, Louisiana MSA and an experienced in-market team that enhances its ability to compete in that market. As part of the acquisition, LTC also acquired or created the following other assets:
(Dollars in thousands)		Amount
Non-compete agreement		$	63
Title plant			14
Other intangible assets			75
Other assets			2
Total Assets		$	154
Acquisition of Louisiana Abstract and Title, LLC
On May 1, 2014, LTC acquired Louisiana Abstract and Title, LLC. Under terms of the agreement, LTC paid $0.2 million in cash to acquire a title office in Baton Rouge, Louisiana, which resulted in goodwill of $0.2 million. In addition, the agreement provides for potential additional cash consideration based on earnings over a four-year period after the acquisition. The acquisition was 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 acquisition. The goodwill recognized was the result of LTC’s expanded presence in the Shreveport, Louisiana MSA and an experienced in-market team that enhances its ability to compete in that market. As part of the acquisition, LTC also acquired or created the following other assets:
(Dollars in thousands)		Amount
Non-compete agreement		$	100
Title plant			9
Other intangible assets			130
Other assets			6
Total Assets		$	245
Supplemental unaudited pro forma information
The following unaudited pro forma information for the six months ended June 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		$	332,674
Net income			20,022
Earnings per share – basic			0.68
Earnings per share – diluted			0.68
The Company’s consolidated financial statements as of and for the six months ended June 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 six-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	6 Months Ended
	Jun. 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:
			June 30, 2014
	(Dollars in thousands)		Amortized			Gross			Gross			Estimated
			Cost			Unrealized			Unrealized			Fair
						Gains			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations		$	371,703		$	1,702		$	(6,011	)	$	367,394
	Obligations of state and political obligations			98,833			3,944			(170	)		102,607
	Mortgage-backed securities			1,530,366			16,456			(9,357	)		1,537,465
	Other securities			1,460			27			—			1,487
	Total securities available for sale		$	2,002,362		$	22,129		$	(15,538	)	$	2,008,953
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations		$	17,499		$	214		$	—		$	17,713
	Obligations of state and political obligations			82,073			2,831			(324	)		84,580
	Mortgage-backed securities			32,673			234			(1,137	)		31,770
	Total securities held to maturity		$	132,245		$	3,279		$	(1,461	)	$	134,063
			31-Dec-13
	(Dollars in thousands)		Amortized			Gross			Gross			Estimated
			Cost			Unrealized			Unrealized			Fair
						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 $1.5 billion were pledged to secure public deposits and other borrowings at both June 30, 2014 and December 31, 2013.
	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:
			June 30, 2014
			Less Than Twelve Months						Over Twelve Months						Total
	(Dollars in thousands)		Gross			Estimated			Gross			Estimated			Gross			Estimated
			Unrealized			Fair			Unrealized			Fair			Unrealized			Fair
			Losses			Value			Losses			Value			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations		$	—		$	—		$	(6,011	)	$	258,673		$	(6,011	)	$	258,673
	Obligations of state and political obligations			—			—			(170	)		1,437			(170	)		1,437
	Mortgage-backed securities			(869	)		182,114			(8,488	)		354,316			(9,357	)		536,430
	Total securities available for sale		$	(869	)	$	182,114		$	(14,669	)	$	614,426		$	(15,538	)	$	796,540
	Securities held to maturity:
	Obligations of state and political obligations		$	—		$	569		$	(324	)	$	13,937		$	(324	)	$	14,506
	Mortgage-backed securities			—			—			(1,137	)		24,785			(1,137	)		24,785
	Total securities held to maturity		$	—		$	569		$	(1,461	)	$	38,722		$	(1,461	)	$	39,291
			31-Dec-13
			Less Than Twelve Months						Over Twelve Months						Total
	(Dollars in thousands)		Gross			Estimated			Gross			Estimated			Gross			Estimated
			Unrealized			Fair			Unrealized			Fair			Unrealized			Fair
			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 June 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 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 June 30, 2014, 113 debt securities had unrealized losses of 1.99% of the securities’ amortized cost basis and 0.80% 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 June 30, 2014 and December 31, 2013 is presented in the following table.
(Dollars in thousands)		June 30, 2014			December 31, 2013
Number of securities
Issued by Fannie Mae, Freddie Mac, or Ginnie Mae			80			20
Issued by political subdivisions			11			5
			91			25
Amortized Cost Basis
Issued by Fannie Mae, Freddie Mac, or Ginnie Mae		$	653,411		$	104,520
Issued by political subdivisions			15,867			7,956
		$	669,278		$	112,476
Unrealized Loss
Issued by Fannie Mae, Freddie Mac, or Ginnie Mae		$	15,636		$	5,519
Issued by political subdivisions			494			669
		$	16,130		$	6,188
The Fannie Mae, Freddie Mac, and Ginnie Mae securities are rated AA+ by S&P and Aaa by Moodys. Eleven of the securities in a continuous loss position for over twelve months were issued by political subdivisions. Ten of 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. The remaining security in a continuous unrealized loss position for over twelve months was issued by a political subdivision and is discussed in further detail below.
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 bonds that was consistent with current market pricing. During 2014, the Company continued to analyze the operating environment of the bond as it did in prior periods and noted no further deterioration in the operating environment of the bond issuer.
During the six months ended June 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 other declines in the estimated fair value of the Company’s investment securities were deemed to be other-than-temporary at June 30, 2014 or December 31, 2013.
The amortized cost and estimated fair value of investment securities by maturity at June 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
(Dollars in thousands)		Weighted			Amortized			Estimated			Weighted			Amortized			Estimated
		Average			Cost			Fair Value			Average			Cost			Fair Value
		Yield									Yield
Within one year or less			2	%	$	16,390		$	16,445			2.11	%	$	17,499		$	17,713
One through five years			1.55			262,494			263,033			3.24			13,510			13,867
After five through ten years			2.1			504,532			508,167			2.92			20,495			21,200
Over ten years			2.2			1,218,946			1,221,308			3.1			80,741			81,283
Total			2.09	%	$	2,002,362		$	2,008,953			2.95	%	$	132,245		$	134,063
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						Six Months Ended
		June 30						June 30
(Dollars in thousands)		2014			2013			2014			2013
Realized gains		$	8		$	4		$	27		$	2,369
Realized losses			—			(70	)		—			(108	)
Net realized gains (losses)		$	8		$	(66	)	$	27		$	2,261
In addition to the gains above, the Company realized certain immaterial gains on calls of held to maturity securities.
Other Equity Securities
At June 30, 2014 and December 31, 2013, the Company included the following securities in “Other assets” on the consolidated balance sheets:
(Dollars in thousands)		June 30			December 31
		2014			2013
Federal Home Loan Bank (FHLB) stock		$	44,715		$	24,369
Federal Reserve Bank (FRB) stock			28,098			28,098
Other investments			3,306			1,306
Total		$	76,119		$	53,773

Loans_Receivable

Loans Receivable	6 Months Ended
	Jun. 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:
			June 30, 2014
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	3,949,444		$	294,115		$	4,243,559
	Business			3,095,087			35,902			3,130,989
				7,044,531			330,017			7,374,548
	Residential mortgage loans:
	Residential 1-4 family			926,972			141,613			1,068,585
	Construction / Owner Occupied			56,039			—			56,039
				983,011			141,613			1,124,624
	Consumer and other loans:
	Home equity			1,357,073			110,068			1,467,141
	Indirect automobile			392,355			—			392,355
	Other			536,119			3,740			539,859
				2,285,547			113,808			2,399,355
	Total		$	10,313,089		$	585,438		$	10,898,527
			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 $19.1 million and $18.6 million and deferred loan expenses were $8.4 million and $7.6 million at June 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 June 30, 2014 and December 31, 2013, overdrafts of $6.4 million and $3.1 million, respectively, have been reclassified to loans receivable.
	Loans with carrying values of $2.4 billion and $2.3 billion were pledged to secure public deposits and other borrowings at June 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 June 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.
			June 30, 2014
			Non-covered loans excluding acquired loans
			Past Due (1)											Current		Total Non-covered			Recorded
																Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total				Unearned Income			and Accruing
	Commercial real estate construction		$	56		$	223		$	1,349		$	1,628	$	591,233	$	592,861		$	—
	Commercial real estate – other			387			112			4,331			4,830		2,828,295		2,833,125			—
	Commercial business			3,742			56			4,191			7,989		2,953,471		2,961,460			—
	Residential prime			2,581			1,455			10,593			14,629		326,077		340,706			20
	Residential subprime			—			—			3,111			3,111		115,835		118,946			—
	Home equity			1,518			703			7,949			10,170		1,163,216		1,173,386			—
	Indirect automobile			1,611			322			1,192			3,125		388,356		391,481			—
	Credit card			282			158			949			1,389		63,871		65,260			—
	Other			567			209			542			1,318		356,189		357,507			—
	Total		$	10,744		$	3,238		$	34,207		$	48,189	$	8,786,543	$	8,834,732		$	20
			31-Dec-13
			Non-covered loans excluding acquired loans
			Past Due (1)											Current		Total Non-covered			Recorded
																Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total				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.
		June 30, 2014
		Non-covered acquired loans
													Current		Discount/			Total Non-		Recorded
		Past Due (1)													Premium			covered		Investment
																		Loans, Net		> 90 days
																		of		and
																		Unearned		Accruing
(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total							Income
Commercial real estate construction		$	—		$	597		$	2,183		$	2,780	$	35,403	$	(2,536	)	$	35,647	$	2,090
Commercial real estate – other			3,584			628			23,144			27,356		511,672		(51,217	)		487,811		21,592
Commercial business			1,944			281			2,212			4,437		136,130		(6,941	)		133,626		2,172
Residential prime			331			1,378			6,703			8,412		508,678		6,269			523,359		525
Home equity			1,260			622			8,667			10,549		180,703		(7,565	)		183,687		4,629
Indirect automobile			28			—			59			87		850		(63	)		874		59
Other			1,004			395			2,096			3,495		122,011		(12,154	)		113,352		343
Total		$	8,151		$	3,901		$	45,064		$	57,116	$	1,495,447	$	(74,207	)	$	1,478,356	$	31,410
		31-Dec-13
		Non-covered acquired loans
													Current		Discount/			Total Non-		Recorded
		Past Due (1)													Premium			covered		Investment
																		Loans, Net		> 90 days
																		of		and
																		Unearned		Accruing
(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total							Income
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 includes 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 June 30, 2014 and December 31, 2013.
(Dollars in thousands)		June 30			December 31
		2014			2013
Commercial real estate construction		$	1,349		$	1,803
Commercial real estate – other			4,331			7,648
Commercial business			4,191			15,020
Residential prime			10,573			8,611
Residential subprime			3,111			1,626
Home equity			7,949			6,808
Indirect automobile			1,192			1,275
Credit card			949			411
Other			542			485
Total		$	34,187		$	43,687
Covered Loans
The carrying amount of the acquired covered loans at June 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.
		June 30, 2014
(Dollars in thousands)		Acquired			Acquired			Total
		Impaired			Performing			Covered
		Loans			Loans			Loans
Commercial loans:
Real estate		$	6,523		$	287,592		$	294,115
Business			—			35,902			35,902
			6,523			323,494			330,017
Residential mortgage loans:
Residential 1-4 family			28,273			113,340			141,613
Construction / Owner Occupied			—			—			—
			28,273			113,340			141,613
Consumer and other loans:
Home equity			13,879			96,189			110,068
Indirect automobile			—			—			—
Other			596			3,145			3,741
			14,475			99,334			113,809
Total		$	49,271		$	536,168		$	585,439
		31-Dec-13
(Dollars in thousands)		Acquired			Acquired			Total
		Impaired			Performing			Covered
		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 $86.9 million from Trust One-Memphis, $700.0 million from Teche, and $298.6 million for First Private in the current period. $1.0 billion in loans acquired 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 dates as information on these loans becomes available.
(Dollars in thousands)		Acquired			Acquired			Total
		Impaired			Performing			Acquired
		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 six months ended June 30, 2014 and 2013.
		June 30, 2014
(Dollars in thousands)		Acquired			Acquired			Total
		Impaired			Performing			Acquired
		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			4,128			13,517			17,645
Accretion			(4,089	)		(50,429	)		(54,518	)
Changes in expected cash flows not affecting nonaccretable differences (1)			(12,176	)		12,720			544
Balance at end of period		$	74,454		$	253,887		$	328,341
		June 30, 2013
		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			6,368			32,039			38,407
Accretion			(10,973	)		(81,227	)		(92,200	)
Changes in expected cash flows not affecting nonaccretable differences (1)			4,158			70,721			74,879
Balance at end of period		$	76,176		$	301,303		$	377,479
-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 June 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.
		June 30, 2014											June 30, 2013
		Accruing Loans											Accruing Loans
(Dollars in thousands)		Current			Past Due			Nonaccrual			Total		Current		Past Due			Nonaccrual		Total
					> 30 days			TDRs			TDRs				> 30 days			TDRs		TDRs
Commercial real estate construction		$	—		$	—		$	—		$	—	$	—		—			—		—
Commercial real estate – other			378			—			1,634			2,012		677		—			8,064		8,741
Commercial business			811			—			2,342			3,153		1,135		—			281		1,416
Residential prime			—			—			—			—		—		—			—		—
Residential subprime			—			—			—			—		—		—			—		—
Home equity			—			—			248			248		—		—			268		268
Indirect automobile			—			—			—			—		—		—			—		—
Credit card			—			—			—			—		—		—			—		—
Other			—			—			—			—		—		—			—		—
Total		$	1,189		$	—		$	4,224		$	5,413	$	1,812	$	—		$	8,613	$	10,425
At June 30, 2014, there were no TDRs that occurred during the first six months through modification of the original loan terms. TDRs totaling $1.5 million occurred during the six-month period ending June 30, 2013 and were subsequently charged off during the same period. The following table provides information on how the TDRs were modified during the six months ended June 30:
(Dollars in thousands)		2014			2013
Extended maturities		$	—		$	—
Interest rate adjustment			—			—
Maturity and interest rate adjustment			—			1,545
Movement to or extension of interest-rate only payments			—			—
Forbearance			—			—
Other concession(s) (1)			—			—
Total		$	—		$	1,545
-1	Other concessions include concessions or a combination of concessions that do not consist of maturity extensions, interest rate adjustments, forbearance or covenant modifications.
Information about the Company’s TDRs occurring in these periods is presented in the following table.
		June 30, 2014									June 30, 2013
(In thousands, except number of loans)		Number of			Pre-modification			Post-modification			Number of		Pre-modification		Post-modification
		Loans			Outstanding			Outstanding			Loans		Outstanding		Outstanding
					Recorded			Recorded					Recorded		Recorded
					Investment			Investment  (1)					Investment		Investment  (1)
Commercial real estate			—		$	—		$	—			1	$	1,545	$	1,545
Commercial business			—			—			—			—		—		—
Residential prime			—			—			—			—		—		—
Home Equity			—			—			—			—		—		—
Indirect automobile			—			—			—			—		—		—
Credit card			—			—			—			—		—		—
Other			—			—			—			—		—		—
Total			—		$	—		$	—			1	$	1,545	$	1,545
-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.
		June 30, 2014						June 30, 2013
(In thousands, except number of loans)		Number of			Recorded			Number of			Recorded
		Loans			Investment			Loans			Investment
Commercial real estate			31		$	1,635			48		$	8,673
Commercial business			11			2,115			8			1,417
Residential prime			—			—			—			—
Home Equity			1			40			1			49
Indirect automobile			—			—			—			—
Credit card			—			—			—			—
Other			1			—			1			—
Total			44		$	3,790			58		$	10,139

Allowance_for_Credit_Losses_an

Allowance for Credit Losses and Credit Quality	6 Months Ended
	Jun. 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 six months ended June 30, 2014 and 2013 is as follows:
		June 30, 2014
		Non-covered loans
	(Dollars in thousands)	Excluding			Acquired			Covered			Total
		Acquired			Loans			Loans
		Loans
	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		5,078			(1,085	)		(740	)		3,253
	Adjustment attributable to FDIC loss share arrangements		—			—			3,598			3,598
	Net (reversal of) provision for loan losses		5,078			(1,085	)		2,858			6,851
	Adjustment attributable to FDIC loss share arrangements		—			—			(3,598	)		(3,598	)
	Transfer of balance to OREO		—			(523	)		(5,085	)		(5,608	)
	Loans charged-off		(5,198	)		(182	)		(5,393	)		(10,773	)
	Recoveries		3,426			109			38			3,573
	Balance at end of period	$	70,648		$	2,876		$	59,995		$	133,519
	Reserve for unfunded lending commitments
	Balance, beginning of period	$	11,147		$	—		$	—		$	11,147
	Provision for unfunded lending commitments		113			—			—			113
	Balance at end of period	$	11,260		$	—		$	—		$	11,260
		30-Jun-13
		Non-covered loans
		Excluding			Acquired			Covered			Total
		Acquired			Loans			Loans
		Loans
	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		(585	)		(1,009	)		(55,060	)		(56,654	)
	Adjustment attributable to FDIC loss share arrangements		—			—			55,085			55,085
	Net (reversal of) provision for loan losses		(585	)		(1,009	)		25			(1,569	)
	Adjustment attributable to FDIC loss share arrangements		—			—			(55,085	)		(55,085	)
	Transfer of balance to OREO		—			(973	)		(16,712	)		(17,685	)
	Transfer of balance to the RULC		(9,828	)		—			—			(9,828	)
	Loans charged-off		(4,249	)		—			(2,334	)		(6,583	)
	Recoveries		2,050			—			—			2,050
	Balance at end of period		61,599			6,834		$	94,470		$	162,903
	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		514			—			—			514
	Balance at end of period	$	10,342		$	—		$	—		$	10,342
	A summary of changes in the allowance for credit losses for non-covered loans, by loan portfolio type, for the six months ended June 30, 2014 and 2013 is as follows:
		June 30, 2014
	(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
	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		585			782			171			2,455			—			3,993
	Transfer of balance to OREO		(108	)		(162	)		(253	)		—			—			(523	)
	Loans charged off		(660	)		(668	)		(435	)		(3,617	)		—			(5,380	)
	Recoveries		1,699			65			114			1,657			—			3,535
	Balance at end of period	$	28,106		$	28,532		$	2,143		$	14,743		$	—		$	73,524
	Reserve for unfunded commitments
	Balance at beginning of period	$	3,089		$	4,839		$	72		$	3,147		$	—		$	11,147
	(Reversal of) Provision for unfunded commitments		112			(43	)		4			40			—			113
	Balance at end of period	$	3,201		$	4,796		$	76		$	3,187		$	—		$	11,260
	Allowance on loans individually evaluated for impairment	$	—		$	31		$	171		$	—		$	—		$	202
	Allowance on loans collectively evaluated for impairment		28,105			28,501			1,972			14,743			—			73,321
	Loans, net of unearned income:
	Balance at end of period	$	3,949,444		$	3,095,087		$	983,011		$	2,285,547		$	—		$	10,313,089
	Balance at end of period individually evaluated for impairment		5,976			4,563			1,058			248			—			11,845
Balance at end of period collectively evaluated for impairment		3,943,468			3,090,524			981,953			2,285,299			—			10,301,244
Balance at end of period acquired with deteriorated credit quality		30,799			5,496			1,209			3,803			—			41,307
	June 30, 2013
(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
	real estate			business
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		(7,459	)		557			2,961			2,347			—			(1,594	)
Transfer of balance to OREO		(264	)		(90	)		(612	)		(7	)		—			(973	)
Transfer of balance to the RULC		(2,939	)		(3,497	)		(40	)		(3,352	)		—			(9,828	)
Loans charged off		(807	)		(395	)		(2,603	)		(444	)		—			(4,249	)
Recoveries		500			259			188			1,103			—			2,050
Balance at end of period	$	27,295		$	25,555		$	2,019		$	13,564		$	—		$	68,433
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
(Reversal of) Provision for unfunded commitments		545			12			—			(43	)					514
Balance at end of period	$	3,484		$	3,509		$	40		$	3,309		$	—		$	10,342
Allowance on loans individually evaluated for impairment	$	72		$	116		$	137		$	—		$	—		$	325
Allowance on loans collectively evaluated for impairment		27,223			25,439			1,882			13,564			—			68,108
Loans, net of unearned income:
Balance at end of period	$	3,224,078		$	2,618,963		$	350,842		$	1,790,939		$	—		$	7,984,822
Balance at end of period individually evaluated for impairment		16,525			14,014			1,152			267			—			31,958
Balance at end of period collectively evaluated for impairment		3,207,553			2,604,949			349,690			1,790,672			—			7,952,864
Balance at end of period acquired with deteriorated credit quality		40,015			3,468			383			3,287			—			47,153
A summary of changes in the allowance for credit losses for covered loans, by loan portfolio type, for the six months ended June 30, 2014 and 2013 is as follows:
	June 30, 2014
(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
	real estate			business
Allowance for loan losses
Balance at beginning of period	$	38,772		$	5,380		$	10,889		$	16,134		$	—		$	71,175
Provision for loan losses		1,474			313			592			479			—			2,858
(Decrease) Increase in FDIC loss share receivable		(2,121	)		749			(2,100	)		(126	)		—			(3,598	)
Transfer of balance to OREO		(1,857	)		(1,162	)		(534	)		(1,532	)		—			(5,085	)
Loans charged off		(3,726	)		(1,589	)		—			(78	)		—			(5,393	)
Recoveries		38			—			—			—			—			38
Balance at end of period	$	32,580		$	3,691		$	8,847		$	14,877		$	—		$	59,995
Allowance on loans individually evaluated for impairment	$	—		$	—		$	—		$	—		$	—		$	—
Allowance on loans collectively evaluated for impairment		32,580			3,691			8,847			14,877			—			59,995
Loans, net of unearned income:
Balance at end of period	$	294,115		$	35,902		$	141,613		$	113,809		$	—		$	585,439
Balance at end of period individually evaluated for impairment		—			—			—			—			—			—
Balance at end of period collectively evaluated for impairment		294,115			35,902			141,613			113,809			—			585,439
Balance at end of period acquired with deteriorated credit quality		6,523			—			28,273			14,475			—			49,271
	June 30, 2013
(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
	real estate			business
Allowance for credit losses
Balance at beginning of period	$	100,871		$	11,375		$	22,566		$	33,764		$	—		$	168,576
Provision for loan losses		27			—			(1	)		(1	)		—			25
(Decrease) Increase in FDIC loss share receivable		(26,737	)		(2,672	)		(7,073	)		(18,603	)		—			(55,085	)
Transfer of balance to OREO		(12,178	)		(314	)		(4,221	)		1			—			(16,712	)
Loans charged off		(2,334	)		—			—			—			—			(2,334	)
Balance at end of period	$	59,649		$	8,389		$	11,271		$	15,161		$	—		$	94,470
Allowance on loans individually evaluated for impairment	$	—		$	—		$	—		$	—		$	—		$	—
Allowance on loans collectively evaluated for impairment		59,649			8,389			11,271			15,161			—			94,470
Loans, net of unearned income:
Balance at end of period	$	520,160		$	68,957		$	167,654		$	161,444		$	—		$	918,215
Balance at end of period individually evaluated for impairment		—			—			—			—			—			—
Balance at end of period collectively evaluated for impairment		520,160			68,957			167,654			161,444			—			918,215
Balance at end of period acquired with deteriorated credit quality		132,565			2,005			17,969			19,504			—			172,043
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 June 30, 2014 and December 31, 2013, respectively. Credit quality information in the tables below include loans acquired at the gross loan balance, prior to the application of premiums/discounts, at June 30, 2014 and December 31, 2013.
	Non-covered loans excluding acquired loans
	30-Jun-14															31-Dec-13
(Dollars in thousands)	Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
				Mention															Mention
Commercial real estate construction	$	581,164		$	252		$	11,445		$	—		$	592,861		$	370,824		$	9,309		$	2,962	$	—	$	383,095
Commercial real estate – other		2,757,043			46,067			29,783			232			2,833,125			2,694,161			27,227			30,308		113		2,751,809
Commercial business		2,920,519			27,975			11,013			1,953			2,961,460			2,866,794			6,164			32,167		926		2,906,051
Total	$	6,258,726		$	74,294		$	52,241		$	2,185		$	6,387,446		$	5,931,779		$	42,700		$	65,437	$	1,039	$	6,040,955
	Non-covered loans excluding acquired loans
	30-Jun-14									31-Dec-13
(Dollars in thousands)	Current			30+ Days			Total			Current			30+ Days			Total
				Past Due									Past Due
Residential prime	$	326,077		$	14,629		$	340,706		$	286,167		$	11,640		$	297,807
Residential subprime		115,835			3,111			118,946			114,939			1,626			116,565
Home equity		1,163,216			10,170			1,173,386			1,091,894			9,333			1,101,227
Indirect automobile		388,356			3,125			391,481			370,388			2,995			373,383
Credit card		63,871			1,389			65,260			62,873			769			63,642
Consumer – other		356,189			1,318			357,507			293,693			1,049			294,742
Total	$	2,413,544		$	33,742		$	2,447,286		$	2,219,954		$	27,412		$	2,247,366
	Non-covered acquired loans
	30-Jun-14																		31-Dec-13
(Dollars in thousands)	Pass			Special			Substandard			Doubtful			Discount			Total			Pass			Special		Substandard		Doubtful			Discount			Total
				Mention																		Mention
Commercial real estate construction	$	31,269		$	1,541		$	5,373		$	—		$	(2,536	)	$	35,647		$	17,132		$	196	$	5,435	$	—		$	(2,532	)	$	20,231
Commercial real estate – other		482,016			13,816			42,866			330			(51,217	)		487,811			310,303			15,351		51,267		93			(52,176	)		324,838
Commercial business		132,151			2,916			4,571			929			(6,941	)		133,626			51,414			1,920		2,586		31			(2,914	)		53,037
Total	$	645,436		$	18,273		$	52,810		$	1,259		$	(60,694	)	$	657,084		$	378,849		$	17,467	$	59,288	$	124		$	(57,622	)	$	398,106
	Non-covered acquired loans
	30-Jun-14												31-Dec-13
(Dollars in thousands)	Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
				Past Due			(discount)									Past Due			(discount)
Residential prime	$	508,678		$	8,412		$	6,269		$	523,359		$	18,796		$	226		$	(887	)	$	18,135
Home equity		180,703			10,549			(7,565	)		183,687			53,995			5,071			(5,623	)		53,443
Indirect automobile		850			87			(63	)		874			1,725			128			—			1,853
Consumer – other		122,011			3,495			(12,154	)		113,352			12,598			1,251			(1,481	)		12,368
Total	$	812,242		$	22,543		$	(13,513	)	$	821,272		$	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, as adjusted for income accretion and changes in cash flow estimates in subsequent periods.
	Covered loans
	June 30, 2014															December 31, 2013
(Dollars in thousands)	Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
				Mention															Mention
Commercial real estate construction	$	39,482		$	1,997		$	14,476		$	—		$	55,955		$	42,886		$	7,401		$	23,891	$	497	$	74,675
Commercial real estate – other		119,489			40,291			104,527			821			265,128			148,579			49,699			144,680		3,267		346,225
Commercial business		25,592			930			9,334			46			35,902			30,710			780			14,556		984		47,030
		$184,563		$	43,218		$	128,337		$	867		$	356,985		$	222,175		$	57,880		$	183,127	$	4,748	$	467,930
Discount														(26,968	)												(43,573	)
Total													$	330,017												$	424,357
	Covered loans
	June 30, 2014												December 31, 2013
(Dollars in thousands)	Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
				Past Due			(discount)									Past Due			(discount)
Residential prime	$	149,945		$	30,381		$	(38,713	)	$	141,613		$	158,710		$	30,814		$	(35,499	)	$	154,025
Home equity		124,113			16,489			(30,534	)		110,068			143,236			35,811			(41,925	)		137,122
Credit card		582			50			—			632			648			31			—			679
Consumer – other		316			71			2,721			3,108			591			144			2,875			3,610
Total	$	274,956		$	46,991		$	(66,526	)	$	255,421		$	303,185		$	66,800		$	(74,549	)	$	295,436
Impaired Loans
Information on the Company’s investment in impaired loans is presented in the following tables as of and for the periods indicated.
	June 30, 2014									December 31, 2013
(Dollars in thousands)	Recorded			Unpaid			Related			Recorded			Unpaid			Related
	Investment			Principal			Allowance			Investment			Principal			Allowance
				Balance									Balance
With no related allowance recorded:
Commercial real estate	$	5,146		$	5,146		$	—		$	8,567		$	8,567		$	—
Commercial business		4,291			4,291			—			13,256			13,256			—
Home equity		248			248			—			258			258			—
With an allowance recorded:
Commercial real estate		905			912			(7	)		1,268			1,284			(16	)
Commercial business		675			710			(35	)		1,927			2,770			(843	)
Residential prime		10,362			10,573			(211	)		9,791			10,019			(228	)
Residential subprime		3,097			3,111			(14	)		1,617			1,626			(9	)
Home equity		7,663			7,701			(38	)		6,506			6,550			(44	)
Indirect automobile		1,185			1,192			(7	)		1,267			1,275			(8	)
Credit card		931			949			(18	)		404			411			(7	)
Other		537			542			(5	)		481			485			(4	)
Total	$	35,040		$	35,375		$	(335	)	$	45,342		$	46,501			(1,159	)
Total commercial loans		11,017			11,059			(42	)		25,018			25,877			(859	)
Total mortgage loans		13,459			13,684			(225	)		11,408			11,645			(237	)
Total consumer loans		10,564			10,632			(68	)		8,916			8,979			(63	)
	For the Three Months Ended June 30												For the Six Months Ended June 30
	2014						2013						2014						2013
(Dollars in thousands)	Average			Interest			Average			Interest			Average			Interest			Average			Interest
	Recorded			Income			Recorded			Income			Recorded			Income			Recorded			Income
	Investment			Recognized			Investment			Recognized			Investment			Recognized			Investment			Recognized
With no related allowance recorded:
Commercial real estate	$	5,228		$	6		$	21,452		$	24		$	5,178		$	14		$	22,871		$	63
Commercial business		5,128			9			10,942			17			5,006			22			6,891			73
Home equity		252			—			—			—			250			—			—			—
With an allowance recorded:
Commercial real estate		925						194			—			926			1			306			1
Commercial business		1,078			4			447			3			1,061			13			449			8
Residential prime		10,911			—			8,613			—			10,131			6			8,913			13
Residential subprime		3,139			—			—			—			3,127			—			—			—
Home equity		7,825			—			7,356			—			7,749			5			7,541			7
Indirect automobile		1,310			—			1,228			—			1,300			6			1,386			6
Credit card		750			—			448			—			560			—			427			—
Other		575			—			527			—			571			5			597			1
Total	$	37,121		$	19		$	51,207		$	44		$	35,859		$	72		$	49,381		$	172
Total commercial loans		12,359			19			33,035			44			12,171			50			30,517			145
Total mortgage loans		14,050			—			8,613			—			13,258			6			8,913			13
Total consumer loans		10,712			—			9,559			—			10,430			16			9,951			14
As of June 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	6 Months Ended
	Jun. 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 ends during the third quarter of 2014 for all covered assets excluding single family residential assets and during the third quarter of 2019 for single family residential assets. 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. However, the sum of the historical and remaining projected losses and recoveries under one agreement is less than the clawback threshold stated in that agreement. The Company has a liability of $0.8 million at both June 30, 2014 and December 31, 2013, to reserve for the amount of consideration due to the FDIC based on projected net losses. 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:
		Six Months Ended June 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		(3,598	)		(55,085	)
	Amortization		(36,273	)		(45,831	)
	Submission of reimbursable losses to (recoveries payable to) the FDIC		2,215			(42,043	)
	Impairment		(804	)		(31,813	)
	Changes due to a change in cash flow assumptions on OREO and other changes		(3,320	)		(7,257	)
	Balance at end of period	$	120,532		$	241,040
	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 six months ended June 30, 2014, the Company concluded that the $120.5 million FDIC loss share receivable is fully collectible as of June 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 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 Audit Committee 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 three-month period ended June 30, 2014 for $0.8 million.

Transfers_and_Servicing_of_Fin

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity)	6 Months Ended
	Jun. 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 six months ended June 30:
	(Dollars in thousands)	2014			2013
	Balance at beginning of period	$	128,442		$	267,475
	Originations and purchases		760,658			1,207,676
	Sales, net of gains		(705,732	)		(1,313,120	)
	Other		(4,988	)		—
	Balance at end of period	$	178,380		$	162,031
	(Dollars in thousands)	2014			2013
	Fair value changes of derivatives and mortgage loans held for sale, net	$	3,383		$	(1,431	)
	Gains on sales		24,397			37,790
	Servicing and other income, net		309			280
	Total mortgage income	$	28,089		$	36,639
	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:
		June 30, 2014								December 31, 2013
	(Dollars in thousands)	Gross			Accumulated			Net Carrying		Gross		Accumulated			Net Carrying
		Carrying			Amortization			Amount		Carrying		Amortization			Amount
		Amount								Amount
	Mortgage servicing rights	$	2,484		$	(887	)	$	1,597	$	2,146	$	(638	)	$	1,508

Goodwill_and_Other_Acquired_In

Goodwill and Other Acquired Intangible Assets	6 Months Ended
	Jun. 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 six months ended June 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		121,906		—			376		122,282
	Balance, June 30, 2014	$	495,811	$	23,178		$	5,165	$	524,154
	The goodwill acquired during the six months ended June 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 six months ended June 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.
	Title Plant
	The Company held title plant assets totaling $6.7 million at both June 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:
		June 30, 2014							December 31, 2013
	(Dollars in thousands)	Gross		Accumulated			Net Carrying		Gross		Accumulated			Net Carrying
		Carrying		Amortization			Amount		Carrying		Amortization			Amount
		Amount							Amount
	Core deposit intangibles	$	50,564	$	(33,135	)	$	17,429	$	45,406	$	(30,784	)	$	14,622
	Customer relationship intangible asset		1,398		(780	)		618		1,348		(631	)		717
	Non-compete agreement		163		(25	)		138		—		—			—
	Other intangible assets		255		(62	)		193		—		—			—
	Total	$	52,380	$	(34,002	)	$	18,378	$	46,754	$	(31,415	)	$	15,339

Other_Real_Estate_Owned

Other Real Estate Owned	6 Months Ended
	Jun. 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.
		June 30, 2014						December 31, 2013
	(Dollars in thousands)	Non-covered		Covered		Total		Non-covered		Covered		Total
	Real estate owned acquired by foreclosure	$	25,135	$	39,571	$	64,706	$	28,072	$	60,474	$	88,546
	Real estate acquired for development or resale		18,586		—		18,586		9,206		—		9,206
	Other foreclosed property		216		971		1,187		93		1,328		1,421
	Total	$	43,937	$	40,542	$	84,479	$	37,371	$	61,802	$	99,173

Derivative_Instruments_and_Oth

Derivative Instruments and Other Hedging Activities	6 Months Ended
	Jun. 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				June 30, 2014				December 31, 2013				Location				June 30, 2014			December 31, 2013
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts			Other assets			$	14,653			$	10,621				Other liabilities			$	14,653		$	10,620
	Forward sales contracts			Other assets				2,414				1,468				Other liabilities				4,163			287
	Written and purchased options			Other assets				23,224				17,987				Other liabilities				18,752			15,828
	Total derivatives not designated as hedging instruments under ASC Topic 815							40,291				30,076								37,568			26,735
	Total						$	40,291			$	30,076							$	37,568		$	26,735
							Asset Derivatives Notional Amount												Liability Derivatives Notional Amount
	(Dollars in thousands)						June 30, 2014				December 31, 2013								June 30, 2014			December 31, 2013
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts						$	493,924			$	380,303							$	493,924		$	380,303
	Forward sales contracts							3,123				192,876								384,907			45,091
	Written and purchased options							375,495				295,425								200,126			199,061
	Total derivatives not designated as hedging instruments under ASC Topic 815							872,542				868,604								1,078,957			624,455
	Total						$	872,542			$	868,604							$	1,078,957		$	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 June 30, 2014 and December 31, 2013, the Company was required to post $8.7 million 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 June 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 agreement to the non-defaulting entity upon an event of default of the counterparty, including bankruptcy, insolvency, or similar proceeding, and (2) provide the non-defaulting entity the right to accelerate, terminate, and close-out on a net basis all transactions under the agreement and to liquidate or set-off collateral promptly upon an event of default of the 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.
			June 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			14,653				—				—				14,653
	Written and purchased options			18,645				—				—				18,645
	Total derivative assets subject to master netting arrangements		$	33,298			$	—			$	—			$	33,298
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			14,653				—				(4,060	)			10,593
	Total derivative liabilities subject to master netting arrangements		$	14,653			$	—			$	(4,060	)		$	10,593
			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 six months ended June 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 June 30, 2014, the fair value of derivatives that will mature within the next twelve months is $0.3 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 June 30, 2014 and 2013, and for the three and six months then ended, information pertaining to the effect of the hedging instruments on the consolidated financial statements is as follows:
			Amount of Gain								Location of Gain		Amount of Gain								Location of Gain	Amount of Gain
			(Loss) Recognized in								(Loss) Reclassified		(Loss) Reclassified								(Loss) Recognized	(Loss) Recognized in
			OCI net of taxes								from		from								in Income on	Income on
			(Effective Portion)								Accumulated		Accumulated								Derivative	Derivative
											OCI into Income		OCI into Income								(Ineffective	(Ineffective Portion
											(Effective Portion)		(Effective Portion)								Portion and	and Amount
																					Amount	Excluded from
																					Excluded from	Effectiveness
																					Effectiveness	Testing)
																					Testing
			As of June 30										For the Three Months Ended June 30
(Dollars in thousands)		2014				2013						2014				2013					2014		2013
Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
Interest rate contracts		$	—			$	—			Other income		$	—			$	32			Other income	$	—	$	—
										(expense)										(expense)
Total		$	—			$	—					$	—			$	32				$	—	$	—
		Amount of Gain								Location of Gain		Amount of Gain								Location of Gain	Amount of Gain
		(Loss) Recognized in								(Loss) Reclassified		(Loss) Reclassified								(Loss) Recognized	(Loss) Recognized in
		OCI net of taxes								from		from								in Income on	Income on
		(Effective Portion)								Accumulated		Accumulated								Derivative	Derivative
										OCI into Income		OCI into Income								(Ineffective	(Ineffective Portion
										(Effective Portion)		(Effective Portion)								Portion and	and Amount
																				Amount	Excluded from
																				Excluded from	Effectiveness
																				Effectiveness	Testing)
																				Testing
		As of June 30										For the Six Months Ended June 30
(Dollars in thousands)		2014				2013						2014				2013					2014		2013
Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
Interest rate contracts		$	—			$	—			Other income		$	—			$	(392	)		Other income	$	—	$	—
										(expense)										(expense)
Total		$	—			$	—					$	—			$	(392	)			$	—	$	—
				Amount of Gain (Loss) Recognized in Income on Derivatives
		Location of Gain (Loss)		For the Three Months Ended June 30								For the Six Months Ended June 30
		Recognized in Income
		on Derivatives
(Dollars in thousands)				2014				2013				2014				2013
Derivatives Not Designated as Hedging Instruments under ASC Topic 815
Interest rate contracts		Other income		$	1,027			$	471				1,565				688
		(expense)
Forward sales contracts		Mortgage Income			(859	)			8,320				(3,864	)			5,408
Written and purchased options		Mortgage Income			(205	)			(4,815	)			1,628				(3,730	)
Total				$	(37	)		$	3,976			$	(671	)		$	2,366

Shareholders_Equity_and_Other_

Shareholders' Equity and Other Comprehensive Income (Loss)	6 Months Ended
	Jun. 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-Jun-14
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	16,730		$	(5,856	)	$	10,874
	Less: reclassification adjustment for gains included in net income		(8	)		3			(5	)
	Net unrealized gains		16,722			(5,853	)		10,869
	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	$	16,722		$	(5,853	)	$	10,869
		Three Months Ended
		30-Jun-13
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding losses arising during the period	$	(42,303	)	$	14,806		$	(27,497	)
	Less: reclassification adjustment for losses included in net income		66			(23	)		43
	Net unrealized losses		(42,237	)		14,783			(27,454	)
	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	$	(1,121	)	$	392		$	(729	)
	Less: reclassification adjustment for gains included in net income		(33	)		12			(21	)
	Fair value of derivative instruments designated as cash flow hedges		(1,154	)		404			(750	)
	Total other comprehensive loss	$	(43,391	)	$	15,187		$	(28,204	)
		Six Months Ended June 30, 2014
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized loss on securities:
	Unrealized holding gains arising during the period	$	32,618		$	(11,416	)	$	21,202
	Less: reclassification adjustment for gains included in net income		(27	)		9			(18	)
	Net unrealized gains		32,591			(11,407	)		21,184
	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	$	32,591		$	(11,407	)	$	21,184
		Six Months Ended June 30, 2013
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding losses arising during the period	$	(44,297	)	$	15,504		$	(28,793	)
	Less: reclassification adjustment for gains included in net income		(2,261	)		791			(1,470	)
	Net unrealized losses		(46,558	)		16,295			(30,263	)
	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	$	(45,214	)	$	15,825		$	(29,389	)

Capital_Requirements_and_Other

Capital Requirements and Other Regulatory Matters	6 Months Ended
	Jun. 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 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. Prompt corrective action provisions are not applicable to bank holding companies.
	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 June 30, 2014 and December 31, 2013, that the Company and IBERIABANK met all capital adequacy requirements to which they are subject.
	As of June 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. 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 June 30, 2014 and December 31, 2013 are presented in the following table.
		June 30, 2014
		Minimum					Well Capitalized					Actual
	(Dollars in thousands)	Amount		Ratio			Amount		Ratio			Amount		Ratio
	Tier 1 Leverage
	Consolidated	$	539,674		4	%	$	N/A		N/A	%	$	1,353,676		10.03	%
	IBERIABANK		537,718		4			672,147		5			1,196,630		8.9
	Tier 1 risk-based capital
	Consolidated	$	481,972		4	%	$	N/A		N/A	%	$	1,353,676		11.23	%
	IBERIABANK		480,157		4			720,236		6			1,196,630		9.97
	Total risk-based capital
	Consolidated	$	963,943		8	%	$	N/A		N/A	%	$	1,498,467		12.44	%
	IBERIABANK		960,315		8			1,200,393		10			1,341,421		11.17
		31-Dec-13
		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	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased 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 six months ended June 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 June 30, 2014, future option or restricted stock awards of 1,033,625 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 six-month periods ended June 30:
			For the Three Months						For the Six Months Ended
			Ended June 30						June 30
	(Dollars in thousands, except per share data)		2014			2013			2014			2013
	Compensation expense related to stock options		$	518		$	533		$	1,037		$	1,066
	Income tax benefit related to stock options			182			187			363			374
	Impact on basic earnings per share			0.01			0.01			0.02			0.02
	Impact on diluted earnings per share			0.01			0.01			0.02			0.02
	The Company reported $0.9 million and $0.4 million of excess tax benefits as financing cash inflows during the six months ended June 30, 2014 and 2013, respectively, related to the exercise and vesting of stock options. Net cash proceeds from the exercise of stock options were $9.2 million and $4.2 million for the six months ended June 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 six-month periods ended June 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		$	21.23		$	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 June 30, 2014, there was $4.2 million of unrecognized compensation cost related to stock options that is expected to be recognized over a weighted-average period of 5.3 years.
	The following table represents the activity related to stock options during the periods indicated.
			Number of shares			Weighted Average			Weighted Average
						Exercise Price			Remaining Contract Life
	Outstanding options, December 31, 2012			1,236,075		$	51.48
	Granted			75,722			52.36
	Exercised			(116,324	)		36.43
	Forfeited or expired			(31,270	)		55.39
	Outstanding options, June 30, 2013			1,164,203		$	52.94			4.9 Years
	Exercisable options, June 30, 2013			774,446			52.73			3.4 Years
	Outstanding options, December 31, 2013			1,072,829		$	53.47
	Granted			75,956			65.23
	Exercised			(196,734	)		47.98
	Forfeited or expired			(8,577	)		64.82
	Outstanding options, June 30, 2014			943,474		$	55.46			5.3 Years
	Exercisable options, June 30, 2014			614,361			55.37			3.8 Years
	At June 30, 2014, the aggregate intrinsic value of shares underlying outstanding stock options and underlying exercisable stock options was $13.3 million and $8.9 million, respectively. Total intrinsic value of options exercised was $3.5 million and $1.6 million for the six months ended June 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 June 30, 2014 and 2013, unearned share-based compensation associated with these awards totaled $24.8 million and $25.4 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 Six Months Ended
			June 30						June 30
	(Dollars in thousands)		2014			2013			2014			2013
	Compensation expense related to restricted stock		$	2,569		$	2,216		$	4,885		$	4,195
	The following table represents unvested restricted stock award activity for the six months ended June 30:
			2014			2013
	Balance at beginning of period			523,756			538,202
	Granted			141,377			164,151
	Forfeited			(9,631	)		(26,866	)
	Earned and issued			(140,616	)		(123,328	)
	Balance at end of period			514,886			552,159
	Phantom stock awards
	As part of the 2008 Incentive Compensation 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						For the Six Months
			Ended June 30						Ended June 30
	(Dollars in thousands)		2014			2013			2014			2013
	Compensation expense related to phantom stock		$	1,022		$	1,112		$	3,073		$	1,811
	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			163,498			5,899			169,397			9,081,000
Forfeited share equivalents			(15,121	)		(641	)		(15,762	)		(845,000	)
Vested share equivalents			(40,185	)		(2,876	)		(43,061	)		(2,156,000	)
Balance, June 30, 2013			426,921			18,417			445,338		$	23,875,000
Balance, December 31, 2013			417,238			22,351			439,589		$	27,628,000
Granted			105,043			4,626			109,669			7,588,000
Forfeited share equivalents			(12,656	)		(1,424	)		(14,080	)		(974,000	)
Vested share equivalents			(60,970	)		(5,724	)		(66,694	)		(4,451,000	)
Balance, June 30, 2014			448,655			19,829			468,484		$	32,414,000
(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 $69.19 and $53.61 on June 30, 2014 and 2013, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 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 June 30, 2014, and December 31, 2013, the fair value of guarantees under commercial and standby letters of credit was $1.2 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 June 30, 2014 and December 31, 2013, the Company had the following financial instruments outstanding, whose contract amounts represent credit risk:
	(Dollars in thousands)	June 30		December 31
		2014		2013
	Commitments to grant loans	$	334,186	$	221,627
	Unfunded commitments under lines of credit		3,534,055		3,326,448
	Commercial and standby letters of credit		124,870		105,026
	Reserve for unfunded lending commitments		11,260		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	6 Months Ended
	Jun. 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:
		June 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	$	178,380	$	170,527	$	7,853	$	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 gains 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 and six-month periods ended June 30, 2014 totaled $3.6 million and $5.6 million, respectively. There were no net gains or losses recorded in mortgage income for the corresponding periods ended June 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)	June 30, 2014
		(Level 1)		(Level 2)		(Level 3)		Total
	Assets
	Available for sale securities	$	—	$	2,008,953	$	—	$	2,008,953
	Mortgage loans held for sale		—		178,380		—		178,380
	Derivative instruments		—		40,291		—		40,291
	Total	$	—	$	2,227,624	$	—	$	2,227,624
	Liabilities
	Derivative instruments		—		37,568		—		37,568
	Total	$	—	$	37,568	$	—	$	37,568
		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 $15.1 million at June 30, 2014 were transferred from the Level 1 to Level 2 fair value category in the table above. The security was issued by Fannie Mae 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)	$	3,410	$	—
	Change in unrealized gains (losses) relating to assets still held at June 30, 2014		—		21,184
	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)	June 30, 2014
		(Level 1)		(Level 2)		(Level 3)		Total
	Assets
	Loans	$	—	$	2,045	$	—	$	2,045
	Mortgage loans held for sale		—		200		—		200
	OREO		—		10,407		—		10,407
	Total	$	—	$	12,452	$	—	$	12,452
	(Dollars in thousands)	31-Dec-13
		(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 $2.2 million and $4.1 million were recorded at their fair value at June 30, 2014 and December 31, 2013, respectively. These loans include a reserve of $0.2 million and $1.0 million included in the Company’s allowance for credit losses at June 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 9 branches as part of its acquisition of Teche. The Company notified customers of these branches 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 statements of comprehensive income for the year ended December 31, 2013 and the six months ended June 30, 2014. After the impairment losses, the carrying value of the branches was $3.9 million and $5.1 million at June 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 June 30, 2014 and December 31, 2013.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	6 Months Ended
	Jun. 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 June 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 June 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 include 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 June 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 June 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:
		June 30, 2014				December 31, 2013
	(Dollars in thousands)	Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Financial Assets
	Cash and cash equivalents	$	668,570	$	668,570	$	391,396	$	391,396
	Investment securities		2,141,198		2,143,016		2,090,906		2,089,363
	Loans and loans held for sale		11,076,907		11,006,250		9,620,461		9,724,432
	FDIC loss share receivable		120,532		21,965		162,312		21,918
	Derivative instruments		40,291		40,291		30,076		30,076
	Accrued interest receivable		36,043		36,043		32,143		32,143
	Financial Liabilities
	Deposits	$	11,981,183	$	11,749,790	$	10,737,000	$	10,226,573
	Short-term borrowings		1,034,741		1,034,741		680,344		680,344
	Long-term debt		365,747		336,326		280,699		235,503
	Derivative instruments		37,568		37,568		26,735		26,735
	Accrued interest payable		7,552		7,552		6,102		6,102
	The fair value estimates presented herein are based upon pertinent information available to management as of June 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	6 Months Ended
	Jun. 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 June 30, 2014
	(Dollars in thousands)		IBERIABANK			IMC			LTC			Consolidated
	Interest income		$	117,544		$	1,676		$	—		$	119,220
	Interest expense			9,764			477			—			10,241
	Net interest income			107,780			1,199			—			108,979
	(Reversal of) Provision for loan losses			4,764			(16	)		—			4,748
	Mortgage income			88			17,869			—			17,957
	Title income			—			—			5,262			5,262
	Other non-interest income			24,757			(13	)		—			24,744
	Core deposit intangible amortization			1,185			—			—			1,185
	Allocated expenses			(3,595	)		2,544			1,051			—
	Other non-interest expenses			110,355			11,635			4,200			126,190
	Income before income taxes			19,916			4,892			11			24,819
	Income tax expense			4,339			1,923			9			6,271
	Net income		$	15,577		$	2,969		$	2		$	18,548
	Total loans and loans held for sale		$	10,875,895		$	201,012		$	—		$	11,076,907
	Total assets			15,067,545			232,403			25,094			15,325,042
	Total deposits			11,976,403			4,780			—			11,981,183
	Average assets			13,832,987			183,838			24,737			14,041,562
			Three Months Ended June 30, 2013
	(Dollars in thousands)		IBERIABANK			IMC			LTC			Consolidated
	Interest income		$	106,668		$	1,495		$	14		$	108,177
	Interest expense			11,106			589			—			11,695
	Net interest income			95,562			906			14			96,482
	Provision for loan losses			1,807			—			—			1,807
	Mortgage income			(2	)		17,710			—			17,708
	Title income			—			—			5,696			5,696
	Other non-interest income			19,084			1			—			19,085
	Core deposit intangible amortization			1,125			—			—			1,125
	Allocated expenses			(882	)		649			233			—
	Other non-interest expenses			97,435			14,469			4,332			116,236
	Income before income taxes			15,159			3,499			1,145			19,803
	Income tax expense			2,389			1,374			450			4,213
	Net income		$	12,770		$	2,125		$	695		$	15,590
	Total loans and loans held for sale		$	8,889,618		$	175,449		$	—		$	9,065,068
	Total assets			12,592,635			205,069			25,799			12,823,503
	Total deposits			10,638,853			2,865			—			10,641,718
	Average assets			12,650,402			205,677			25,472			12,881,551
			Six Months Ended June 30, 2014
	(Dollars in thousands)		IBERIABANK			IMC			LTC			Consolidated
	Interest income		$	230,692		$	2,758		$	1		$	233,451
	Interest expense			19,367			698			—			20,065
	Net interest income			211,325			2,060			1			213,386
	(Reversal of) Provision for loan losses			6,860			(9	)		—			6,851
	Mortgage income			85			28,004			—			28,089
	Title income			—			—			9,429			9,429
	Other non-interest income			46,150			(24	)		—			46,126
	Core deposit intangible amortization			2,350			—			—			2,350
	Allocated expenses			(6,725	)		4,735			1,990			—
	Other non-interest expenses			202,429			21,934			8,089			232,452
	Income (loss) before income taxes			52,646			3,380			(649	)		55,377
	Income tax expense (benefit)			13,343			1,335			(244	)		14,434
	Net income (loss)		$	39,303		$	2,045		$	(405	)	$	40,943
	Total loans and loans held for sale		$	10,875,895		$	201,012		$	—		$	11,076,907
	Total assets			15,067,545			232,403			25,094			15,325,042
Total deposits			11,976,403			4,780			—			11,981,183
Average assets			13,517,696			161,571			24,854			13,704,121
		Six Months Ended June 30, 2013
(Dollars in thousands)		IBERIABANK			IMC			LTC			Consolidated
Interest income		$	211,595		$	2,969		$	29		$	214,593
Interest expense			24,055			1,184			—			25,239
Net interest income			187,540			1,785			29			189,354
(Reversal of) Provision for loan losses			(1,548	)		(21	)		—			(1,569	)
Mortgage income			(3	)		36,642			—			36,639
Title income			—			—			10,717			10,717
Other non-interest income			39,628			(4	)		—			39,624
Core deposit intangible amortization			2,250			—			—			2,250
Allocated expenses			(1,745	)		1,280			465			—
Other non-interest expenses			224,476			26,926			8,607			260,009
Income before income taxes			3,732			10,238			1,674			15,644
Income tax expense (benefit)			(5,343	)		4,019			661			(663	)
Net income		$	9,075		$	6,219		$	1,013		$	16,307
Total loans and loans held for sale		$	8,889,619		$	175,449		$	—		$	9,065,068
Total assets			12,592,635			205,069			25,799			12,823,503
Total deposits			10,638,853			2,865			—			10,641,718
Average assets			12,740,709			211,923			25,113			12,977,745

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	6 Months Ended
	Jun. 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, excluding loans held for sale that are recorded at fair value under the fair value option, are carried at the lower of cost or estimated fair value. When determining the fair value of loans held for sale, the Company obtains quotes or bids on these loans directly from purchasing financial institutions (Level 2). Mortgage loans held for sale that were recorded at estimated fair value are included in Note 17.
	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 June 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 $0.6 million and $1.4 million in earnings for the three months ended June 30, 2014 and 2013, respectively, and $1.4 million and $2.6 million for the six months ended June 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.

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	6 Months Ended
	Jun. 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 Six Months Ended
			June 30						June 30
			2014			2013			2014			2013
	(Dollars in thousands, except per share data)
	Income available to common shareholders		$	18,548		$	15,590		$	40,943		$	16,307
	Distributed earnings (capital) to unvested restricted stock			(286	)		(290	)		(681	)		(313	)
	Distributed earnings (capital) to common shareholders – basic			18,262			15,300			40,262			15,994
	Undistributed earnings reallocated to unvested restricted stock			(12	)		(3	)		(18	)		—
	Distributed and undistributed earnings to common shareholders – diluted		$	18,250		$	15,297		$	40,244		$	15,994
	Weighted average shares outstanding – basic (1)			30,787,520			29,610,315			30,303,294			29,556,810
	Weighted average shares outstanding – diluted			30,386,105			29,066,906			29,904,370			29,023,002
	Earnings per common share – basic		$	0.6		$	0.53		$	1.35		$	0.55
	Earnings per common share – diluted			0.6			0.53			1.35			0.55
	Earnings per unvested restricted stock share – basic			0.54			0.51			1.27			0.55
	Earnings per unvested restricted stock share – diluted			0.56			0.52			1.31			0.55
	-1	Weighted average basic shares outstanding include 527,605 and 567,162 shares of unvested restricted stock for the three months ended June 30, 2014 and 2013, respectively, and 535,442 and 565,860 shares for the six months ended June 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 Six Months Ended
			June 30						June 30
			2014			2013			2014			2013
	(Dollars in thousands, except per share data)
	Distributed earnings to common shareholders		$	11,184		$	9,914		$	21,214		$	19,810
	Undistributed earnings (distributed capital) to common shareholders			7,078			5,386			19,048			(3,816	)
	Total earnings to common shareholders		$	18,262		$	15,300		$	40,262		$	15,994
	Distributed earnings to unvested restricted stock		$	175		$	188		$	359		$	387
	Undistributed earnings (distributed capital) to unvested restricted stock			111			102			322			(74	)
	Total earnings allocated to restricted stock		$	286		$	290		$	681		$	313
	Distributed earnings per common share		$	0.37		$	0.34		$	0.71		$	0.68
	Undistributed earnings (distributed capital) per common share			0.23			0.19			0.64			(0.13	)
	Total earnings per common share – basic		$	0.6		$	0.53		$	1.35		$	0.55
	Distributed earnings per unvested restricted stock share		$	0.33		$	0.33		$	0.67		$	0.68
	Undistributed earnings (distributed capital) per unvested restricted stock share			0.21			0.18			0.6			(0.13	)
	Total earnings per unvested restricted stock share – basic		$	0.54		$	0.51		$	1.27		$	0.55

Acquisition_Activity_Tables

Acquisition Activity (Tables)	6 Months Ended
	Jun. 30, 2014
Supplemental Pro Forma Information	'
	The following unaudited pro forma information for the six months ended June 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		$	332,674
	Net income			20,022
	Earnings per share – basic			0.68
	Earnings per share – diluted			0.68
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					72,308
	Goodwill				$	84,432
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 table.
	Teche
	(Dollars in thousands)		As Acquired		Preliminary			As recorded
					Fair Value			by
					Adjustments			IBERIABANK
	Assets
	Cash and cash equivalents		$	71,606	$	—		$	71,606
	Investment securities			24,077		1,092	(1)		25,169
	Loans			716,587		(16,637	)(2)		699,950
	Other real estate owned			329		—			329
	Core deposit intangible			—		2,055	(3)		2,055
	Deferred tax asset			1,057		7,373	(4)		8,430
	Other assets			56,708		(6,512	)(5)		50,196
	Total Assets		$	870,364	$	(12,629	)	$	857,735
	Liabilities
	Interest-bearing deposits		$	520,446	$	902	(6)	$	521,348
	Non-interest-bearing deposits			118,256		—			118,256
	Borrowings			134,228		6,304	(7)		140,532
	Other liabilities			5,291		—			5,291
	Total Liabilities		$	778,221	$	7,206		$	785,427
	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 estimated fair value of the core deposit intangible asset created in the acquisition.
	(4)	The amount represents the deferred tax asset recognized on the fair value adjustment of Teche acquired assets and assumed liabilities.
	(5)	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.
	(6)	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.
	(7)	The amount represents the estimated fair value adjustment for the debt assumed, primarily driven by the estimated market interest rate on the debt relative to the stated interest rate.
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					29,980
	Goodwill				$	28,660
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 table.
	First Private
	(Dollars in thousands)		As Acquired		Preliminary			As recorded by
					Fair Value			IBERIABANK
					Adjustments
	Assets
	Cash and cash equivalents		$	26,621	$	—		$	26,621
	Investment securities			19,110		—			19,110
	Loans			294,425		4,207	(1)		298,632
	Other real estate owned			—		—			—
	Core deposit intangible			—		506	(2)		506
	Deferred tax asset (liability)			530		(1,676	) (3)		(1,146	)
	Other assets			5,230		—			5,230
	Total Assets		$	345,916	$	3,037		$	348,953
	Liabilities
	Interest-bearing deposits		$	261,713	$	220	(4)	$	261,933
	Non-interest-bearing deposits			50,333		—			50,333
	Borrowings			6,451		—			6,451
	Other liabilities			256		—			256
	Total Liabilities		$	318,753	$	220		$	318,973
	Explanation of certain fair value adjustments
	(1)	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.
	(2)	The amount represents the fair value of the core deposit intangible asset created in the acquisition.
	(3)	The amount represents the deferred tax liability recognized on the fair value adjustment of First Private acquired assets and assumed liabilities.
	(4)	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.
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 table.
	Trust One-Memphis
	(Dollars in thousands)		As Acquired		Preliminary			As recorded by
					Fair Value			IBERIABANK
					Adjustments
	Assets
	Cash and cash equivalents		$	92,060	$	—		$	92,060
	Loans			88,179		(1,290	)(1)		86,889
	Other real estate owned			1,325		—			1,325
	Core deposit intangible			—		2,597	(2)		2,597
	Other assets			368		—			368
	Total Assets		$	181,932	$	1,307		$	183,239
	Liabilities
	Interest-bearing deposits		$	164,942	$	—		$	164,942
	Non-interest-bearing deposits			26,373		—			26,373
	Deferred tax liability			—		654	(3)		654
	Other liabilities			84		—			84
	Total Liabilities		$	191,399	$	654		$	192,053
	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 estimated fair value of the core deposit intangible asset created in the acquisition.
	(3)	The amount represents the deferred tax liability recognized on the fair value adjustment of Trust One-Memphis acquired assets and assumed liabilities.
Title Company LLC [Member]	'
Schedule of Assets Acquired under Business Acquisitions	'
	As part of the acquisition, LTC also acquired or created the following other assets:
	(Dollars in thousands)		Amount
	Non-compete agreement		$	63
	Title plant			14
	Other intangible assets			75
	Other assets			2
	Total Assets		$	154
Louisiana Abstract and Title, LLC [Member]	'
Schedule of Assets Acquired under Business Acquisitions	'
	As part of the acquisition, LTC also acquired or created the following other assets:
	(Dollars in thousands)		Amount
	Non-compete agreement		$	100
	Title plant			9
	Other intangible assets			130
	Other assets			6
	Total Assets		$	245

Investment_Securities_Tables

Investment Securities (Tables)	6 Months Ended
	Jun. 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:
		June 30, 2014
	(Dollars in thousands)	Amortized			Gross			Gross			Estimated
		Cost			Unrealized			Unrealized			Fair
					Gains			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	371,703		$	1,702		$	(6,011	)	$	367,394
	Obligations of state and political obligations		98,833			3,944			(170	)		102,607
	Mortgage-backed securities		1,530,366			16,456			(9,357	)		1,537,465
	Other securities		1,460			27			—			1,487
	Total securities available for sale	$	2,002,362		$	22,129		$	(15,538	)	$	2,008,953
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations	$	17,499		$	214		$	—		$	17,713
	Obligations of state and political obligations		82,073			2,831			(324	)		84,580
	Mortgage-backed securities		32,673			234			(1,137	)		31,770
	Total securities held to maturity	$	132,245		$	3,279		$	(1,461	)	$	134,063
		31-Dec-13
	(Dollars in thousands)	Amortized			Gross			Gross			Estimated
		Cost			Unrealized			Unrealized			Fair
					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:
		June 30, 2014
		Less Than Twelve Months						Over Twelve Months						Total
	(Dollars in thousands)	Gross			Estimated			Gross			Estimated			Gross			Estimated
		Unrealized			Fair			Unrealized			Fair			Unrealized			Fair
		Losses			Value			Losses			Value			Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	—		$	—		$	(6,011	)	$	258,673		$	(6,011	)	$	258,673
	Obligations of state and political obligations		—			—			(170	)		1,437			(170	)		1,437
	Mortgage-backed securities		(869	)		182,114			(8,488	)		354,316			(9,357	)		536,430
	Total securities available for sale	$	(869	)	$	182,114		$	(14,669	)	$	614,426		$	(15,538	)	$	796,540
	Securities held to maturity:
	Obligations of state and political obligations	$	—		$	569		$	(324	)	$	13,937		$	(324	)	$	14,506
	Mortgage-backed securities		—			—			(1,137	)		24,785			(1,137	)		24,785
	Total securities held to maturity	$	—		$	569		$	(1,461	)	$	38,722		$	(1,461	)	$	39,291
		31-Dec-13
		Less Than Twelve Months						Over Twelve Months						Total
	(Dollars in thousands)	Gross			Estimated			Gross			Estimated			Gross			Estimated
		Unrealized			Fair			Unrealized			Fair			Unrealized			Fair
		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 June 30, 2014 and December 31, 2013 is presented in the following table.
	(Dollars in thousands)	June 30, 2014			December 31, 2013
	Number of securities
	Issued by Fannie Mae, Freddie Mac, or Ginnie Mae		80			20
	Issued by political subdivisions		11			5
			91			25
	Amortized Cost Basis
	Issued by Fannie Mae, Freddie Mac, or Ginnie Mae	$	653,411		$	104,520
	Issued by political subdivisions		15,867			7,956
		$	669,278		$	112,476
	Unrealized Loss
	Issued by Fannie Mae, Freddie Mac, or Ginnie Mae	$	15,636		$	5,519
	Issued by political subdivisions		494			669
		$	16,130		$	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 June 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
	(Dollars in thousands)	Weighted			Amortized			Estimated			Weighted			Amortized			Estimated
		Average			Cost			Fair Value			Average			Cost			Fair Value
		Yield									Yield
	Within one year or less		2	%	$	16,390		$	16,445			2.11	%	$	17,499		$	17,713
	One through five years		1.55			262,494			263,033			3.24			13,510			13,867
	After five through ten years		2.1			504,532			508,167			2.92			20,495			21,200
	Over ten years		2.2			1,218,946			1,221,308			3.1			80,741			81,283
	Total		2.09	%	$	2,002,362		$	2,008,953			2.95	%	$	132,245		$	134,063
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						Six Months Ended
		June 30						June 30
	(Dollars in thousands)	2014			2013			2014			2013
	Realized gains	$	8		$	4		$	27		$	2,369
	Realized losses		—			(70	)		—			(108	)
	Net realized gains (losses)	$	8		$	(66	)	$	27		$	2,261
Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets	'
	At June 30, 2014 and December 31, 2013, the Company included the following securities in “Other assets” on the consolidated balance sheets:
	(Dollars in thousands)	June 30			December 31
		2014			2013
	Federal Home Loan Bank (FHLB) stock	$	44,715		$	24,369
	Federal Reserve Bank (FRB) stock		28,098			28,098
	Other investments		3,306			1,306
	Total	$	76,119		$	53,773

Loans_Receivable_Tables

Loans Receivable (Tables)	6 Months Ended
	Jun. 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:
			June 30, 2014
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	3,949,444		$	294,115		$	4,243,559
	Business			3,095,087			35,902			3,130,989
				7,044,531			330,017			7,374,548
	Residential mortgage loans:
	Residential 1-4 family			926,972			141,613			1,068,585
	Construction / Owner Occupied			56,039			—			56,039
				983,011			141,613			1,124,624
	Consumer and other loans:
	Home equity			1,357,073			110,068			1,467,141
	Indirect automobile			392,355			—			392,355
	Other			536,119			3,740			539,859
				2,285,547			113,808			2,399,355
	Total		$	10,313,089		$	585,438		$	10,898,527
			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 June 30, 2014 and December 31, 2013.
	(Dollars in thousands)		June 30			December 31
			2014			2013
	Commercial real estate construction		$	1,349		$	1,803
	Commercial real estate – other			4,331			7,648
	Commercial business			4,191			15,020
	Residential prime			10,573			8,611
	Residential subprime			3,111			1,626
	Home equity			7,949			6,808
	Indirect automobile			1,192			1,275
	Credit card			949			411
	Other			542			485
	Total		$	34,187		$	43,687
Schedule of Carrying Amount of Acquired Covered Loans	'
	The carrying amount of the acquired covered loans at June 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.
			June 30, 2014
	(Dollars in thousands)		Acquired			Acquired			Total
			Impaired			Performing			Covered
			Loans			Loans			Loans
	Commercial loans:
	Real estate		$	6,523		$	287,592		$	294,115
	Business			—			35,902			35,902
				6,523			323,494			330,017
	Residential mortgage loans:
	Residential 1-4 family			28,273			113,340			141,613
	Construction / Owner Occupied			—			—			—
				28,273			113,340			141,613
	Consumer and other loans:
	Home equity			13,879			96,189			110,068
	Indirect automobile			—			—			—
	Other			596			3,145			3,741
				14,475			99,334			113,809
	Total		$	49,271		$	536,168		$	585,439
			31-Dec-13
	(Dollars in thousands)		Acquired			Acquired			Total
			Impaired			Performing			Covered
			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 $86.9 million from Trust One-Memphis, $700.0 million from Teche, and $298.6 million for First Private in the current period. $1.0 billion in loans acquired 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 dates as information on these loans becomes available.
	(Dollars in thousands)		Acquired			Acquired			Total
			Impaired			Performing			Acquired
			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 six months ended June 30, 2014 and 2013.
			June 30, 2014
	(Dollars in thousands)		Acquired			Acquired			Total
			Impaired			Performing			Acquired
			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			4,128			13,517			17,645
	Accretion			(4,089	)		(50,429	)		(54,518	)
	Changes in expected cash flows not affecting nonaccretable differences (1)			(12,176	)		12,720			544
	Balance at end of period		$	74,454		$	253,887		$	328,341
			June 30, 2013
			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			6,368			32,039			38,407
	Accretion			(10,973	)		(81,227	)		(92,200	)
	Changes in expected cash flows not affecting nonaccretable differences (1)			4,158			70,721			74,879
	Balance at end of period		$	76,176		$	301,303		$	377,479
	-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 June 30, 2014 and 2013 is presented in the following tables.
			June 30, 2014											June 30, 2013
			Accruing Loans											Accruing Loans
	(Dollars in thousands)		Current			Past Due			Nonaccrual			Total		Current		Past Due			Nonaccrual		Total
						> 30 days			TDRs			TDRs				> 30 days			TDRs		TDRs
	Commercial real estate construction		$	—		$	—		$	—		$	—	$	—		—			—		—
	Commercial real estate – other			378			—			1,634			2,012		677		—			8,064		8,741
	Commercial business			811			—			2,342			3,153		1,135		—			281		1,416
	Residential prime			—			—			—			—		—		—			—		—
	Residential subprime			—			—			—			—		—		—			—		—
	Home equity			—			—			248			248		—		—			268		268
	Indirect automobile			—			—			—			—		—		—			—		—
	Credit card			—			—			—			—		—		—			—		—
	Other			—			—			—			—		—		—			—		—
	Total		$	1,189		$	—		$	4,224		$	5,413	$	1,812	$	—		$	8,613	$	10,425
Schedule of Modified TDRs	'
	The following table provides information on how the TDRs were modified during the six months ended June 30:
	(Dollars in thousands)		2014			2013
	Extended maturities		$	—		$	—
	Interest rate adjustment			—			—
	Maturity and interest rate adjustment			—			1,545
	Movement to or extension of interest-rate only payments			—			—
	Forbearance			—			—
	Other concession(s) (1)			—			—
	Total		$	—		$	1,545
	-1	Other concessions include concessions or a combination of concessions that do not consist of maturity extensions, interest rate adjustments, forbearance or covenant modifications.
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 June 30, 2014 and December 31, 2013.
			June 30, 2014
			Non-covered loans excluding acquired loans
			Past Due (1)											Current		Total Non-covered			Recorded
																Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total				Unearned Income			and Accruing
	Commercial real estate construction		$	56		$	223		$	1,349		$	1,628	$	591,233	$	592,861		$	—
	Commercial real estate – other			387			112			4,331			4,830		2,828,295		2,833,125			—
	Commercial business			3,742			56			4,191			7,989		2,953,471		2,961,460			—
	Residential prime			2,581			1,455			10,593			14,629		326,077		340,706			20
	Residential subprime			—			—			3,111			3,111		115,835		118,946			—
	Home equity			1,518			703			7,949			10,170		1,163,216		1,173,386			—
	Indirect automobile			1,611			322			1,192			3,125		388,356		391,481			—
	Credit card			282			158			949			1,389		63,871		65,260			—
	Other			567			209			542			1,318		356,189		357,507			—
	Total		$	10,744		$	3,238		$	34,207		$	48,189	$	8,786,543	$	8,834,732		$	20
			31-Dec-13
			Non-covered loans excluding acquired loans
			Past Due (1)											Current		Total Non-covered			Recorded
																Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total				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	'
			June 30, 2014
			Non-covered acquired loans
														Current		Discount/			Total Non-		Recorded
			Past Due (1)													Premium			covered		Investment
																			Loans, Net		> 90 days
																			of		and
																			Unearned		Accruing
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total							Income
	Commercial real estate construction		$	—		$	597		$	2,183		$	2,780	$	35,403	$	(2,536	)	$	35,647	$	2,090
	Commercial real estate – other			3,584			628			23,144			27,356		511,672		(51,217	)		487,811		21,592
	Commercial business			1,944			281			2,212			4,437		136,130		(6,941	)		133,626		2,172
	Residential prime			331			1,378			6,703			8,412		508,678		6,269			523,359		525
	Home equity			1,260			622			8,667			10,549		180,703		(7,565	)		183,687		4,629
	Indirect automobile			28			—			59			87		850		(63	)		874		59
	Other			1,004			395			2,096			3,495		122,011		(12,154	)		113,352		343
	Total		$	8,151		$	3,901		$	45,064		$	57,116	$	1,495,447	$	(74,207	)	$	1,478,356	$	31,410
			31-Dec-13
			Non-covered acquired loans
														Current		Discount/			Total Non-		Recorded
			Past Due (1)													Premium			covered		Investment
																			Loans, Net		> 90 days
																			of		and
																			Unearned		Accruing
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total							Income
	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 includes acquired loans at the gross loan balance, prior to application of discounts.
TDRs [Member]	'
Schedule of Subsequently Defaulted TDRs	'
	Information about the Company’s TDRs occurring in these periods is presented in the following table.
			June 30, 2014									June 30, 2013
	(In thousands, except number of loans)		Number of			Pre-modification			Post-modification			Number of		Pre-modification		Post-modification
			Loans			Outstanding			Outstanding			Loans		Outstanding		Outstanding
						Recorded			Recorded					Recorded		Recorded
						Investment			Investment  (1)					Investment		Investment  (1)
	Commercial real estate			—		$	—		$	—			1	$	1,545	$	1,545
	Commercial business			—			—			—			—		—		—
	Residential prime			—			—			—			—		—		—
	Home Equity			—			—			—			—		—		—
	Indirect automobile			—			—			—			—		—		—
	Credit card			—			—			—			—		—		—
	Other			—			—			—			—		—		—
	Total			—		$	—		$	—			1	$	1,545	$	1,545
	-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.
			June 30, 2014						June 30, 2013
	(In thousands, except number of loans)		Number of			Recorded			Number of			Recorded
			Loans			Investment			Loans			Investment
	Commercial real estate			31		$	1,635			48		$	8,673
	Commercial business			11			2,115			8			1,417
	Residential prime			—			—			—			—
	Home Equity			1			40			1			49
	Indirect automobile			—			—			—			—
	Credit card			—			—			—			—
	Other			1			—			1			—
	Total			44		$	3,790			58		$	10,139

Allowance_for_Credit_Losses_an1

Allowance for Credit Losses and Credit Quality (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2014 and 2013 is as follows:
		June 30, 2014
		Non-covered loans
	(Dollars in thousands)	Excluding			Acquired			Covered			Total
		Acquired			Loans			Loans
		Loans
	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		5,078			(1,085	)		(740	)		3,253
	Adjustment attributable to FDIC loss share arrangements		—			—			3,598			3,598
	Net (reversal of) provision for loan losses		5,078			(1,085	)		2,858			6,851
	Adjustment attributable to FDIC loss share arrangements		—			—			(3,598	)		(3,598	)
	Transfer of balance to OREO		—			(523	)		(5,085	)		(5,608	)
	Loans charged-off		(5,198	)		(182	)		(5,393	)		(10,773	)
	Recoveries		3,426			109			38			3,573
	Balance at end of period	$	70,648		$	2,876		$	59,995		$	133,519
	Reserve for unfunded lending commitments
	Balance, beginning of period	$	11,147		$	—		$	—		$	11,147
	Provision for unfunded lending commitments		113			—			—			113
	Balance at end of period	$	11,260		$	—		$	—		$	11,260
		30-Jun-13
		Non-covered loans
		Excluding			Acquired			Covered			Total
		Acquired			Loans			Loans
		Loans
	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		(585	)		(1,009	)		(55,060	)		(56,654	)
	Adjustment attributable to FDIC loss share arrangements		—			—			55,085			55,085
	Net (reversal of) provision for loan losses		(585	)		(1,009	)		25			(1,569	)
	Adjustment attributable to FDIC loss share arrangements		—			—			(55,085	)		(55,085	)
	Transfer of balance to OREO		—			(973	)		(16,712	)		(17,685	)
	Transfer of balance to the RULC		(9,828	)		—			—			(9,828	)
	Loans charged-off		(4,249	)		—			(2,334	)		(6,583	)
	Recoveries		2,050			—			—			2,050
	Balance at end of period		61,599			6,834		$	94,470		$	162,903
	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		514			—			—			514
	Balance at end of period	$	10,342		$	—		$	—		$	10,342
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 six months ended June 30, 2014 and 2013 is as follows:
		June 30, 2014
	(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
	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		585			782			171			2,455			—			3,993
	Transfer of balance to OREO		(108	)		(162	)		(253	)		—			—			(523	)
	Loans charged off		(660	)		(668	)		(435	)		(3,617	)		—			(5,380	)
	Recoveries		1,699			65			114			1,657			—			3,535
	Balance at end of period	$	28,106		$	28,532		$	2,143		$	14,743		$	—		$	73,524
	Reserve for unfunded commitments
	Balance at beginning of period	$	3,089		$	4,839		$	72		$	3,147		$	—		$	11,147
	(Reversal of) Provision for unfunded commitments		112			(43	)		4			40			—			113
	Balance at end of period	$	3,201		$	4,796		$	76		$	3,187		$	—		$	11,260
	Allowance on loans individually evaluated for impairment	$	—		$	31		$	171		$	—		$	—		$	202
	Allowance on loans collectively evaluated for impairment		28,105			28,501			1,972			14,743			—			73,321
	Loans, net of unearned income:
	Balance at end of period	$	3,949,444		$	3,095,087		$	983,011		$	2,285,547		$	—		$	10,313,089
	Balance at end of period individually evaluated for impairment		5,976			4,563			1,058			248			—			11,845
	Balance at end of period collectively evaluated for impairment		3,943,468			3,090,524			981,953			2,285,299			—			10,301,244
	Balance at end of period acquired with deteriorated credit quality		30,799			5,496			1,209			3,803			—			41,307
		June 30, 2013
	(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
	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		(7,459	)		557			2,961			2,347			—			(1,594	)
	Transfer of balance to OREO		(264	)		(90	)		(612	)		(7	)		—			(973	)
	Transfer of balance to the RULC		(2,939	)		(3,497	)		(40	)		(3,352	)		—			(9,828	)
	Loans charged off		(807	)		(395	)		(2,603	)		(444	)		—			(4,249	)
	Recoveries		500			259			188			1,103			—			2,050
	Balance at end of period	$	27,295		$	25,555		$	2,019		$	13,564		$	—		$	68,433
	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
	(Reversal of) Provision for unfunded commitments		545			12			—			(43	)					514
	Balance at end of period	$	3,484		$	3,509		$	40		$	3,309		$	—		$	10,342
	Allowance on loans individually evaluated for impairment	$	72		$	116		$	137		$	—		$	—		$	325
	Allowance on loans collectively evaluated for impairment		27,223			25,439			1,882			13,564			—			68,108
	Loans, net of unearned income:
	Balance at end of period	$	3,224,078		$	2,618,963		$	350,842		$	1,790,939		$	—		$	7,984,822
	Balance at end of period individually evaluated for impairment		16,525			14,014			1,152			267			—			31,958
	Balance at end of period collectively evaluated for impairment		3,207,553			2,604,949			349,690			1,790,672			—			7,952,864
	Balance at end of period acquired with deteriorated credit quality		40,015			3,468			383			3,287			—			47,153
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 six months ended June 30, 2014 and 2013 is as follows:
		June 30, 2014
	(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
	Allowance for loan losses
	Balance at beginning of period	$	38,772		$	5,380		$	10,889		$	16,134		$	—		$	71,175
	Provision for loan losses		1,474			313			592			479			—			2,858
	(Decrease) Increase in FDIC loss share receivable		(2,121	)		749			(2,100	)		(126	)		—			(3,598	)
	Transfer of balance to OREO		(1,857	)		(1,162	)		(534	)		(1,532	)		—			(5,085	)
	Loans charged off		(3,726	)		(1,589	)		—			(78	)		—			(5,393	)
	Recoveries		38			—			—			—			—			38
	Balance at end of period	$	32,580		$	3,691		$	8,847		$	14,877		$	—		$	59,995
	Allowance on loans individually evaluated for impairment	$	—		$	—		$	—		$	—		$	—		$	—
	Allowance on loans collectively evaluated for impairment		32,580			3,691			8,847			14,877			—			59,995
	Loans, net of unearned income:
	Balance at end of period	$	294,115		$	35,902		$	141,613		$	113,809		$	—		$	585,439
	Balance at end of period individually evaluated for impairment		—			—			—			—			—			—
	Balance at end of period collectively evaluated for impairment		294,115			35,902			141,613			113,809			—			585,439
	Balance at end of period acquired with deteriorated credit quality		6,523			—			28,273			14,475			—			49,271
		June 30, 2013
	(Dollars in thousands)	Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
	Allowance for credit losses
	Balance at beginning of period	$	100,871		$	11,375		$	22,566		$	33,764		$	—		$	168,576
	Provision for loan losses		27			—			(1	)		(1	)		—			25
	(Decrease) Increase in FDIC loss share receivable		(26,737	)		(2,672	)		(7,073	)		(18,603	)		—			(55,085	)
	Transfer of balance to OREO		(12,178	)		(314	)		(4,221	)		1			—			(16,712	)
	Loans charged off		(2,334	)		—			—			—			—			(2,334	)
	Balance at end of period	$	59,649		$	8,389		$	11,271		$	15,161		$	—		$	94,470
	Allowance on loans individually evaluated for impairment	$	—		$	—		$	—		$	—		$	—		$	—
	Allowance on loans collectively evaluated for impairment		59,649			8,389			11,271			15,161			—			94,470
	Loans, net of unearned income:
	Balance at end of period	$	520,160		$	68,957		$	167,654		$	161,444		$	—		$	918,215
	Balance at end of period individually evaluated for impairment		—			—			—			—			—			—
	Balance at end of period collectively evaluated for impairment		520,160			68,957			167,654			161,444			—			918,215
	Balance at end of period acquired with deteriorated credit quality		132,565			2,005			17,969			19,504			—			172,043
Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator	'
	Credit quality information in the tables below include loans acquired at the gross loan balance, prior to the application of premiums/discounts, at June 30, 2014 and December 31, 2013.
		Non-covered loans excluding acquired loans
		30-Jun-14															31-Dec-13
	(Dollars in thousands)	Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
					Mention															Mention
	Commercial real estate construction	$	581,164		$	252		$	11,445		$	—		$	592,861		$	370,824		$	9,309		$	2,962	$	—	$	383,095
	Commercial real estate – other		2,757,043			46,067			29,783			232			2,833,125			2,694,161			27,227			30,308		113		2,751,809
	Commercial business		2,920,519			27,975			11,013			1,953			2,961,460			2,866,794			6,164			32,167		926		2,906,051
	Total	$	6,258,726		$	74,294		$	52,241		$	2,185		$	6,387,446		$	5,931,779		$	42,700		$	65,437	$	1,039	$	6,040,955
		Non-covered loans excluding acquired loans
		30-Jun-14									31-Dec-13
	(Dollars in thousands)	Current			30+ Days			Total			Current			30+ Days			Total
					Past Due									Past Due
	Residential prime	$	326,077		$	14,629		$	340,706		$	286,167		$	11,640		$	297,807
	Residential subprime		115,835			3,111			118,946			114,939			1,626			116,565
	Home equity		1,163,216			10,170			1,173,386			1,091,894			9,333			1,101,227
	Indirect automobile		388,356			3,125			391,481			370,388			2,995			373,383
	Credit card		63,871			1,389			65,260			62,873			769			63,642
	Consumer – other		356,189			1,318			357,507			293,693			1,049			294,742
	Total	$	2,413,544		$	33,742		$	2,447,286		$	2,219,954		$	27,412		$	2,247,366
Schedule of Investment in Impaired Loan	'
	Information on the Company’s investment in impaired loans is presented in the following tables as of and for the periods indicated.
		June 30, 2014									December 31, 2013
	(Dollars in thousands)	Recorded			Unpaid			Related			Recorded			Unpaid			Related
		Investment			Principal			Allowance			Investment			Principal			Allowance
					Balance									Balance
	With no related allowance recorded:
	Commercial real estate	$	5,146		$	5,146		$	—		$	8,567		$	8,567		$	—
	Commercial business		4,291			4,291			—			13,256			13,256			—
	Home equity		248			248			—			258			258			—
	With an allowance recorded:
	Commercial real estate		905			912			(7	)		1,268			1,284			(16	)
	Commercial business		675			710			(35	)		1,927			2,770			(843	)
	Residential prime		10,362			10,573			(211	)		9,791			10,019			(228	)
	Residential subprime		3,097			3,111			(14	)		1,617			1,626			(9	)
	Home equity		7,663			7,701			(38	)		6,506			6,550			(44	)
	Indirect automobile		1,185			1,192			(7	)		1,267			1,275			(8	)
	Credit card		931			949			(18	)		404			411			(7	)
	Other		537			542			(5	)		481			485			(4	)
	Total	$	35,040		$	35,375		$	(335	)	$	45,342		$	46,501			(1,159	)
	Total commercial loans		11,017			11,059			(42	)		25,018			25,877			(859	)
	Total mortgage loans		13,459			13,684			(225	)		11,408			11,645			(237	)
	Total consumer loans		10,564			10,632			(68	)		8,916			8,979			(63	)
		For the Three Months Ended June 30												For the Six Months Ended June 30
		2014						2013						2014						2013
	(Dollars in thousands)	Average			Interest			Average			Interest			Average			Interest			Average			Interest
		Recorded			Income			Recorded			Income			Recorded			Income			Recorded			Income
		Investment			Recognized			Investment			Recognized			Investment			Recognized			Investment			Recognized
	With no related allowance recorded:
	Commercial real estate	$	5,228		$	6		$	21,452		$	24		$	5,178		$	14		$	22,871		$	63
	Commercial business		5,128			9			10,942			17			5,006			22			6,891			73
	Home equity		252			—			—			—			250			—			—			—
	With an allowance recorded:
	Commercial real estate		925						194			—			926			1			306			1
	Commercial business		1,078			4			447			3			1,061			13			449			8
	Residential prime		10,911			—			8,613			—			10,131			6			8,913			13
	Residential subprime		3,139			—			—			—			3,127			—			—			—
	Home equity		7,825			—			7,356			—			7,749			5			7,541			7
	Indirect automobile		1,310			—			1,228			—			1,300			6			1,386			6
	Credit card		750			—			448			—			560			—			427			—
	Other		575			—			527			—			571			5			597			1
	Total	$	37,121		$	19		$	51,207		$	44		$	35,859		$	72		$	49,381		$	172
	Total commercial loans		12,359			19			33,035			44			12,171			50			30,517			145
	Total mortgage loans		14,050			—			8,613			—			13,258			6			8,913			13
	Total consumer loans		10,712			—			9,559			—			10,430			16			9,951			14
Covered Loans [Member]	'
Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator	'
	Non-covered acquired loans
		30-Jun-14																		31-Dec-13
	(Dollars in thousands)	Pass			Special			Substandard			Doubtful			Discount			Total			Pass			Special		Substandard		Doubtful			Discount			Total
					Mention																		Mention
	Commercial real estate construction	$	31,269		$	1,541		$	5,373		$	—		$	(2,536	)	$	35,647		$	17,132		$	196	$	5,435	$	—		$	(2,532	)	$	20,231
	Commercial real estate – other		482,016			13,816			42,866			330			(51,217	)		487,811			310,303			15,351		51,267		93			(52,176	)		324,838
	Commercial business		132,151			2,916			4,571			929			(6,941	)		133,626			51,414			1,920		2,586		31			(2,914	)		53,037
	Total	$	645,436		$	18,273		$	52,810		$	1,259		$	(60,694	)	$	657,084		$	378,849		$	17,467	$	59,288	$	124		$	(57,622	)	$	398,106
		Non-covered acquired loans
		30-Jun-14												31-Dec-13
	(Dollars in thousands)	Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
					Past Due			(discount)									Past Due			(discount)
	Residential prime	$	508,678		$	8,412		$	6,269		$	523,359		$	18,796		$	226		$	(887	)	$	18,135
	Home equity		180,703			10,549			(7,565	)		183,687			53,995			5,071			(5,623	)		53,443
	Indirect automobile		850			87			(63	)		874			1,725			128			—			1,853
	Consumer – other		122,011			3,495			(12,154	)		113,352			12,598			1,251			(1,481	)		12,368
	Total	$	812,242		$	22,543		$	(13,513	)	$	821,272		$	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, as adjusted for income accretion and changes in cash flow estimates in subsequent periods.
		Covered loans
		June 30, 2014															December 31, 2013
	(Dollars in thousands)	Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
					Mention															Mention
	Commercial real estate construction	$	39,482		$	1,997		$	14,476		$	—		$	55,955		$	42,886		$	7,401		$	23,891	$	497	$	74,675
	Commercial real estate – other		119,489			40,291			104,527			821			265,128			148,579			49,699			144,680		3,267		346,225
	Commercial business		25,592			930			9,334			46			35,902			30,710			780			14,556		984		47,030
			$184,563		$	43,218		$	128,337		$	867		$	356,985		$	222,175		$	57,880		$	183,127	$	4,748	$	467,930
	Discount														(26,968	)												(43,573	)
	Total													$	330,017												$	424,357
		Covered loans
		June 30, 2014												December 31, 2013
	(Dollars in thousands)	Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
					Past Due			(discount)									Past Due			(discount)
	Residential prime	$	149,945		$	30,381		$	(38,713	)	$	141,613		$	158,710		$	30,814		$	(35,499	)	$	154,025
	Home equity		124,113			16,489			(30,534	)		110,068			143,236			35,811			(41,925	)		137,122
	Credit card		582			50			—			632			648			31			—			679
	Consumer – other		316			71			2,721			3,108			591			144			2,875			3,610
	Total	$	274,956		$	46,991		$	(66,526	)	$	255,421		$	303,185		$	66,800		$	(74,549	)	$	295,436

Loss_Sharing_Agreements_and_FD1

Loss Sharing Agreements and FDIC Loss Share Receivable (Tables)	6 Months Ended
	Jun. 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:
		Six Months Ended June 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		(3,598	)		(55,085	)
	Amortization		(36,273	)		(45,831	)
	Submission of reimbursable losses to (recoveries payable to) the FDIC		2,215			(42,043	)
	Impairment		(804	)		(31,813	)
	Changes due to a change in cash flow assumptions on OREO and other changes		(3,320	)		(7,257	)
	Balance at end of period	$	120,532		$	241,040

Transfers_and_Servicing_of_Fin1

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) (Tables)	6 Months Ended
	Jun. 30, 2014
Components of Mortgage Banking Activity	'
	The following table details the mortgage banking activity as of and for the six months ended June 30:
	(Dollars in thousands)	2014			2013
	Balance at beginning of period	$	128,442		$	267,475
	Originations and purchases		760,658			1,207,676
	Sales, net of gains		(705,732	)		(1,313,120	)
	Other		(4,988	)		—
	Balance at end of period	$	178,380		$	162,031
	(Dollars in thousands)	2014			2013
	Fair value changes of derivatives and mortgage loans held for sale, net	$	3,383		$	(1,431	)
	Gains on sales		24,397			37,790
	Servicing and other income, net		309			280
	Total mortgage income	$	28,089		$	36,639
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:
		June 30, 2014								December 31, 2013
	(Dollars in thousands)	Gross			Accumulated			Net Carrying		Gross		Accumulated			Net Carrying
		Carrying			Amortization			Amount		Carrying		Amortization			Amount
		Amount								Amount
	Core deposit intangibles	$	50,564		$	(33,135	)	$	17,429	$	45,406	$	(30,784	)	$	14,622
	Customer relationship intangible asset		1,398			(780	)		618		1,348		(631	)		717
	Non-compete agreement		163			(25	)		138		—		—			—
	Other intangible assets		255			(62	)		193		—		—			—
	Total	$	52,380		$	(34,002	)	$	18,378	$	46,754	$	(31,415	)	$	15,339
Mortgage Servicing Rights [Member]	'
Schedule of Definite-Lived Intangible Assets	'
	Mortgage servicing rights had the following carrying values as of the periods indicated:
		June 30, 2014								December 31, 2013
	(Dollars in thousands)	Gross			Accumulated			Net Carrying		Gross		Accumulated			Net Carrying
		Carrying			Amortization			Amount		Carrying		Amortization			Amount
		Amount								Amount
	Mortgage servicing rights	$	2,484		$	(887	)	$	1,597	$	2,146	$	(638	)	$	1,508

Goodwill_and_Other_Acquired_In1

Goodwill and Other Acquired Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2014
Goodwill And Intangible Assets Disclosure [Abstract]	'
Schedule of Carrying Amount of Goodwill	'
	Changes to the carrying amount of goodwill by reportable segment for the six months ended June 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		121,906		—		376		122,282
	Balance, June 30, 2014	$	495,811	$	23,178	$	5,165	$	524,154

Other_Real_Estate_Owned_Tables

Other Real Estate Owned (Tables)	6 Months Ended
	Jun. 30, 2014
Banking And Thrift [Abstract]	'
Schedule of Other Real Estate Owned Segregated Into Non-Covered and Covered Properties	'
	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.
		June 30, 2014						December 31, 2013
	(Dollars in thousands)	Non-covered		Covered		Total		Non-covered		Covered		Total
	Real estate owned acquired by foreclosure	$	25,135	$	39,571	$	64,706	$	28,072	$	60,474	$	88,546
	Real estate acquired for development or resale		18,586		—		18,586		9,206		—		9,206
	Other foreclosed property		216		971		1,187		93		1,328		1,421
	Total	$	43,937	$	40,542	$	84,479	$	37,371	$	61,802	$	99,173

Derivative_Instruments_and_Oth1

Derivative Instruments and Other Hedging Activities (Tables)	6 Months Ended
	Jun. 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				June 30, 2014				December 31, 2013				Location				June 30, 2014			December 31, 2013
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts			Other assets			$	14,653			$	10,621				Other liabilities			$	14,653		$	10,620
	Forward sales contracts			Other assets				2,414				1,468				Other liabilities				4,163			287
	Written and purchased options			Other assets				23,224				17,987				Other liabilities				18,752			15,828
	Total derivatives not designated as hedging instruments under ASC Topic 815							40,291				30,076								37,568			26,735
	Total						$	40,291			$	30,076							$	37,568		$	26,735
							Asset Derivatives Notional Amount												Liability Derivatives Notional Amount
	(Dollars in thousands)						June 30, 2014				December 31, 2013								June 30, 2014			December 31, 2013
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts						$	493,924			$	380,303							$	493,924		$	380,303
	Forward sales contracts							3,123				192,876								384,907			45,091
	Written and purchased options							375,495				295,425								200,126			199,061
	Total derivatives not designated as hedging instruments under ASC Topic 815							872,542				868,604								1,078,957			624,455
	Total						$	872,542			$	868,604							$	1,078,957		$	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.
			June 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			14,653				—				—				14,653
	Written and purchased options			18,645				—				—				18,645
	Total derivative assets subject to master netting arrangements		$	33,298			$	—			$	—			$	33,298
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			14,653				—				(4,060	)			10,593
	Total derivative liabilities subject to master netting arrangements		$	14,653			$	—			$	(4,060	)		$	10,593
			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 June 30, 2014 and 2013, and for the three and six months then ended, information pertaining to the effect of the hedging instruments on the consolidated financial statements is as follows:
			Amount of Gain								Location of Gain		Amount of Gain								Location of Gain	Amount of Gain
			(Loss) Recognized in								(Loss) Reclassified		(Loss) Reclassified								(Loss) Recognized	(Loss) Recognized in
			OCI net of taxes								from		from								in Income on	Income on
			(Effective Portion)								Accumulated		Accumulated								Derivative	Derivative
											OCI into Income		OCI into Income								(Ineffective	(Ineffective Portion
											(Effective Portion)		(Effective Portion)								Portion and	and Amount
																					Amount	Excluded from
																					Excluded from	Effectiveness
																					Effectiveness	Testing)
																					Testing
			As of June 30										For the Three Months Ended June 30
	(Dollars in thousands)		2014				2013						2014				2013					2014		2013
	Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
	Interest rate contracts		$	—			$	—			Other income		$	—			$	32			Other income	$	—	$	—
											(expense)										(expense)
	Total		$	—			$	—					$	—			$	32				$	—	$	—
			Amount of Gain								Location of Gain		Amount of Gain								Location of Gain	Amount of Gain
			(Loss) Recognized in								(Loss) Reclassified		(Loss) Reclassified								(Loss) Recognized	(Loss) Recognized in
			OCI net of taxes								from		from								in Income on	Income on
			(Effective Portion)								Accumulated		Accumulated								Derivative	Derivative
											OCI into Income		OCI into Income								(Ineffective	(Ineffective Portion
											(Effective Portion)		(Effective Portion)								Portion and	and Amount
																					Amount	Excluded from
																					Excluded from	Effectiveness
																					Effectiveness	Testing)
																					Testing
			As of June 30										For the Six Months Ended June 30
	(Dollars in thousands)		2014				2013						2014				2013					2014		2013
	Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
	Interest rate contracts		$	—			$	—			Other income		$	—			$	(392	)		Other income	$	—	$	—
											(expense)										(expense)
	Total		$	—			$	—					$	—			$	(392	)			$	—	$	—
					Amount of Gain (Loss) Recognized in Income on Derivatives
			Location of Gain (Loss)		For the Three Months Ended June 30								For the Six Months Ended June 30
			Recognized in Income
			on Derivatives
	(Dollars in thousands)				2014				2013				2014				2013
	Derivatives Not Designated as Hedging Instruments under ASC Topic 815
	Interest rate contracts		Other income		$	1,027			$	471				1,565				688
			(expense)
	Forward sales contracts		Mortgage Income			(859	)			8,320				(3,864	)			5,408
	Written and purchased options		Mortgage Income			(205	)			(4,815	)			1,628				(3,730	)
	Total				$	(37	)		$	3,976			$	(671	)		$	2,366

Shareholders_Equity_and_Other_1

Shareholders' Equity and Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 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-Jun-14
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	16,730		$	(5,856	)	$	10,874
	Less: reclassification adjustment for gains included in net income		(8	)		3			(5	)
	Net unrealized gains		16,722			(5,853	)		10,869
	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	$	16,722		$	(5,853	)	$	10,869
		Three Months Ended
		30-Jun-13
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding losses arising during the period	$	(42,303	)	$	14,806		$	(27,497	)
	Less: reclassification adjustment for losses included in net income		66			(23	)		43
	Net unrealized losses		(42,237	)		14,783			(27,454	)
	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	$	(1,121	)	$	392		$	(729	)
	Less: reclassification adjustment for gains included in net income		(33	)		12			(21	)
	Fair value of derivative instruments designated as cash flow hedges		(1,154	)		404			(750	)
	Total other comprehensive loss	$	(43,391	)	$	15,187		$	(28,204	)
		Six Months Ended June 30, 2014
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized loss on securities:
	Unrealized holding gains arising during the period	$	32,618		$	(11,416	)	$	21,202
	Less: reclassification adjustment for gains included in net income		(27	)		9			(18	)
	Net unrealized gains		32,591			(11,407	)		21,184
	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	$	32,591		$	(11,407	)	$	21,184
		Six Months Ended June 30, 2013
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding losses arising during the period	$	(44,297	)	$	15,504		$	(28,793	)
	Less: reclassification adjustment for gains included in net income		(2,261	)		791			(1,470	)
	Net unrealized losses		(46,558	)		16,295			(30,263	)
	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	$	(45,214	)	$	15,825		$	(29,389	)

Capital_Requirements_and_Other1

Capital Requirements and Other Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 2014
Banking And Thrift [Abstract]	'
Actual Capital Amounts and Ratios	'
	The Company’s and IBERIABANK’s actual capital amounts and ratios as of June 30, 2014 and December 31, 2013 are presented in the following table.
		June 30, 2014
		Minimum					Well Capitalized					Actual
	(Dollars in thousands)	Amount		Ratio			Amount		Ratio			Amount		Ratio
	Tier 1 Leverage
	Consolidated	$	539,674		4	%	$	N/A		N/A	%	$	1,353,676		10.03	%
	IBERIABANK		537,718		4			672,147		5			1,196,630		8.9
	Tier 1 risk-based capital
	Consolidated	$	481,972		4	%	$	N/A		N/A	%	$	1,353,676		11.23	%
	IBERIABANK		480,157		4			720,236		6			1,196,630		9.97
	Total risk-based capital
	Consolidated	$	963,943		8	%	$	N/A		N/A	%	$	1,498,467		12.44	%
	IBERIABANK		960,315		8			1,200,393		10			1,341,421		11.17
		31-Dec-13
		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)	6 Months Ended
	Jun. 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 six-month periods ended June 30:
			For the Three Months						For the Six Months Ended
			Ended June 30						June 30
	(Dollars in thousands, except per share data)		2014			2013			2014			2013
	Compensation expense related to stock options		$	518		$	533		$	1,037		$	1,066
	Income tax benefit related to stock options			182			187			363			374
	Impact on basic earnings per share			0.01			0.01			0.02			0.02
	Impact on diluted earnings per share			0.01			0.01			0.02			0.02
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 six-month periods ended June 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		$	21.23		$	15.37
Activity Related to Stock Options	'
	The following table represents the activity related to stock options during the periods indicated.
			Number of shares			Weighted Average			Weighted Average
						Exercise Price			Remaining Contract Life
	Outstanding options, December 31, 2012			1,236,075		$	51.48
	Granted			75,722			52.36
	Exercised			(116,324	)		36.43
	Forfeited or expired			(31,270	)		55.39
	Outstanding options, June 30, 2013			1,164,203		$	52.94			4.9 Years
	Exercisable options, June 30, 2013			774,446			52.73			3.4 Years
	Outstanding options, December 31, 2013			1,072,829		$	53.47
	Granted			75,956			65.23
	Exercised			(196,734	)		47.98
	Forfeited or expired			(8,577	)		64.82
	Outstanding options, June 30, 2014			943,474		$	55.46			5.3 Years
	Exercisable options, June 30, 2014			614,361			55.37			3.8 Years
Unvested Restricted Stock Award Activity	'
	The following table represents unvested restricted stock award activity for the six months ended June 30:
			2014			2013
	Balance at beginning of period			523,756			538,202
	Granted			141,377			164,151
	Forfeited			(9,631	)		(26,866	)
	Earned and issued			(140,616	)		(123,328	)
	Balance at end of period			514,886			552,159
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			163,498			5,899			169,397			9,081,000
	Forfeited share equivalents			(15,121	)		(641	)		(15,762	)		(845,000	)
	Vested share equivalents			(40,185	)		(2,876	)		(43,061	)		(2,156,000	)
	Balance, June 30, 2013			426,921			18,417			445,338		$	23,875,000
	Balance, December 31, 2013			417,238			22,351			439,589		$	27,628,000
	Granted			105,043			4,626			109,669			7,588,000
	Forfeited share equivalents			(12,656	)		(1,424	)		(14,080	)		(974,000	)
	Vested share equivalents			(60,970	)		(5,724	)		(66,694	)		(4,451,000	)
	Balance, June 30, 2014			448,655			19,829			468,484		$	32,414,000
	(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 $69.19 and $53.61 on June 30, 2014 and 2013, respectively.
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						For the Six Months
			Ended June 30						Ended June 30
	(Dollars in thousands)		2014			2013			2014			2013
	Compensation expense related to phantom stock		$	1,022		$	1,112		$	3,073		$	1,811
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 Six Months Ended
			June 30						June 30
	(Dollars in thousands)		2014			2013			2014			2013
	Compensation expense related to restricted stock		$	2,569		$	2,216		$	4,885		$	4,195

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Summary of Financial Instruments Outstanding	'
	At June 30, 2014 and December 31, 2013, the Company had the following financial instruments outstanding, whose contract amounts represent credit risk:
	(Dollars in thousands)	June 30		December 31
		2014		2013
	Commitments to grant loans	$	334,186	$	221,627
	Unfunded commitments under lines of credit		3,534,055		3,326,448
	Commercial and standby letters of credit		124,870		105,026
	Reserve for unfunded lending commitments		11,260		11,147

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 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:
		June 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	$	178,380	$	170,527	$	7,853	$	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)	June 30, 2014
		(Level 1)		(Level 2)		(Level 3)		Total
	Assets
	Available for sale securities	$	—	$	2,008,953	$	—	$	2,008,953
	Mortgage loans held for sale		—		178,380		—		178,380
	Derivative instruments		—		40,291		—		40,291
	Total	$	—	$	2,227,624	$	—	$	2,227,624
	Liabilities
	Derivative instruments		—		37,568		—		37,568
	Total	$	—	$	37,568	$	—	$	37,568
		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)	$	3,410	$	—
	Change in unrealized gains (losses) relating to assets still held at June 30, 2014		—		21,184
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)	June 30, 2014
		(Level 1)		(Level 2)		(Level 3)		Total
	Assets
	Loans	$	—	$	2,045	$	—	$	2,045
	Mortgage loans held for sale		—		200		—		200
	OREO		—		10,407		—		10,407
	Total	$	—	$	12,452	$	—	$	12,452
	(Dollars in thousands)	31-Dec-13
		(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)	6 Months Ended
	Jun. 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:
		June 30, 2014				December 31, 2013
	(Dollars in thousands)	Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Financial Assets
	Cash and cash equivalents	$	668,570	$	668,570	$	391,396	$	391,396
	Investment securities		2,141,198		2,143,016		2,090,906		2,089,363
	Loans and loans held for sale		11,076,907		11,006,250		9,620,461		9,724,432
	FDIC loss share receivable		120,532		21,965		162,312		21,918
	Derivative instruments		40,291		40,291		30,076		30,076
	Accrued interest receivable		36,043		36,043		32,143		32,143
	Financial Liabilities
	Deposits	$	11,981,183	$	11,749,790	$	10,737,000	$	10,226,573
	Short-term borrowings		1,034,741		1,034,741		680,344		680,344
	Long-term debt		365,747		336,326		280,699		235,503
	Derivative instruments		37,568		37,568		26,735		26,735
	Accrued interest payable		7,552		7,552		6,102		6,102

Business_Segments_Tables

Business Segments (Tables)	6 Months Ended
	Jun. 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 June 30, 2014
	(Dollars in thousands)	IBERIABANK			IMC			LTC			Consolidated
	Interest income	$	117,544		$	1,676		$	—		$	119,220
	Interest expense		9,764			477			—			10,241
	Net interest income		107,780			1,199			—			108,979
	(Reversal of) Provision for loan losses		4,764			(16	)		—			4,748
	Mortgage income		88			17,869			—			17,957
	Title income		—			—			5,262			5,262
	Other non-interest income		24,757			(13	)		—			24,744
	Core deposit intangible amortization		1,185			—			—			1,185
	Allocated expenses		(3,595	)		2,544			1,051			—
	Other non-interest expenses		110,355			11,635			4,200			126,190
	Income before income taxes		19,916			4,892			11			24,819
	Income tax expense		4,339			1,923			9			6,271
	Net income	$	15,577		$	2,969		$	2		$	18,548
	Total loans and loans held for sale	$	10,875,895		$	201,012		$	—		$	11,076,907
	Total assets		15,067,545			232,403			25,094			15,325,042
	Total deposits		11,976,403			4,780			—			11,981,183
	Average assets		13,832,987			183,838			24,737			14,041,562
		Three Months Ended June 30, 2013
	(Dollars in thousands)	IBERIABANK			IMC			LTC			Consolidated
	Interest income	$	106,668		$	1,495		$	14		$	108,177
	Interest expense		11,106			589			—			11,695
	Net interest income		95,562			906			14			96,482
	Provision for loan losses		1,807			—			—			1,807
	Mortgage income		(2	)		17,710			—			17,708
	Title income		—			—			5,696			5,696
	Other non-interest income		19,084			1			—			19,085
	Core deposit intangible amortization		1,125			—			—			1,125
	Allocated expenses		(882	)		649			233			—
	Other non-interest expenses		97,435			14,469			4,332			116,236
	Income before income taxes		15,159			3,499			1,145			19,803
	Income tax expense		2,389			1,374			450			4,213
	Net income	$	12,770		$	2,125		$	695		$	15,590
	Total loans and loans held for sale	$	8,889,618		$	175,449		$	—		$	9,065,068
	Total assets		12,592,635			205,069			25,799			12,823,503
	Total deposits		10,638,853			2,865			—			10,641,718
	Average assets		12,650,402			205,677			25,472			12,881,551
		Six Months Ended June 30, 2014
	(Dollars in thousands)	IBERIABANK			IMC			LTC			Consolidated
	Interest income	$	230,692		$	2,758		$	1		$	233,451
	Interest expense		19,367			698			—			20,065
	Net interest income		211,325			2,060			1			213,386
	(Reversal of) Provision for loan losses		6,860			(9	)		—			6,851
	Mortgage income		85			28,004			—			28,089
	Title income		—			—			9,429			9,429
	Other non-interest income		46,150			(24	)		—			46,126
	Core deposit intangible amortization		2,350			—			—			2,350
	Allocated expenses		(6,725	)		4,735			1,990			—
	Other non-interest expenses		202,429			21,934			8,089			232,452
	Income (loss) before income taxes		52,646			3,380			(649	)		55,377
	Income tax expense (benefit)		13,343			1,335			(244	)		14,434
	Net income (loss)	$	39,303		$	2,045		$	(405	)	$	40,943
	Total loans and loans held for sale	$	10,875,895		$	201,012		$	—		$	11,076,907
	Total assets		15,067,545			232,403			25,094			15,325,042
	Total deposits		11,976,403			4,780			—			11,981,183
	Average assets		13,517,696			161,571			24,854			13,704,121
		Six Months Ended June 30, 2013
	(Dollars in thousands)	IBERIABANK			IMC			LTC			Consolidated
	Interest income	$	211,595		$	2,969		$	29		$	214,593
	Interest expense		24,055			1,184			—			25,239
	Net interest income		187,540			1,785			29			189,354
(Reversal of) Provision for loan losses		(1,548	)		(21	)		—			(1,569	)
Mortgage income		(3	)		36,642			—			36,639
Title income		—			—			10,717			10,717
Other non-interest income		39,628			(4	)		—			39,624
Core deposit intangible amortization		2,250			—			—			2,250
Allocated expenses		(1,745	)		1,280			465			—
Other non-interest expenses		224,476			26,926			8,607			260,009
Income before income taxes		3,732			10,238			1,674			15,644
Income tax expense (benefit)		(5,343	)		4,019			661			(663	)
Net income	$	9,075		$	6,219		$	1,013		$	16,307
Total loans and loans held for sale	$	8,889,619		$	175,449		$	—		$	9,065,068
Total assets		12,592,635			205,069			25,799			12,823,503
Total deposits		10,638,853			2,865			—			10,641,718
Average assets		12,740,709			211,923			25,113			12,977,745

Basis_of_Presentation_Addition

Basis of Presentation - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Schedule Of Significant Accounting Policies [Line Items]	'	'	'	'
Property write-downs	$0.60	$1.40	$1.40	$2.60
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)	6 Months Ended
	Jun. 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		6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]	'	'	'	'
Income available to common shareholders	$18,548	$15,590	$40,943	$16,307
Distributed earnings (capital) to common shareholders - basic	18,262	15,300	40,262	15,994
Distributed and undistributed earnings to common shareholders - diluted	18,250	15,297	40,244	15,994
Weighted average shares outstanding - basic	30,787,520	29,610,315	30,303,294	29,556,810
Weighted average shares outstanding - diluted	30,386,105	29,066,906	29,904,370	29,023,002
Earnings per common share - Basic	$0.60	$0.53	$1.35	$0.55
Earnings per common share - Diluted	$0.60	$0.53	$1.35	$0.55
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	-286	-290	-681	-313
Undistributed earnings reallocated to unvested restricted stock	($12)	($3)	($18)	'
Earnings per common share - Basic	$0.54	$0.51	$1.27	$0.55
Earnings per common share - Diluted	$0.56	$0.52	$1.31	$0.55

Earnings_Per_Share_Schedule_of1

Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Weighted average basic shares outstanding, unvested restricted stock	527,605	567,162	535,442	565,860

Earnings_Per_Share_Schedule_of2

Earnings Per Share - Schedule of Basic Earnings Per Common Share (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings to common shareholders	$11,184	$9,914	$21,214	$19,810
Undistributed earnings (distributed capital) to common shareholders	7,078	5,386	19,048	-3,816
Total earnings to common shareholders	18,262	15,300	40,262	15,994
Distributed earnings per common share	$0.37	$0.34	$0.71	$0.68
Undistributed earnings (distributed capital) per common share	$0.23	$0.19	$0.64	($0.13)
Total earnings per common share - basic	$0.60	$0.53	$1.35	$0.55
Unvested Restricted Stock [Member]	'	'	'	'
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings to common shareholders	175	188	359	387
Undistributed earnings (distributed capital) to common shareholders	111	102	322	-74
Total earnings allocated to restricted stock	$286	$290	$681	$313
Distributed earnings per common share	$0.33	$0.33	$0.67	$0.68
Undistributed earnings (distributed capital) per common share	$0.21	$0.18	$0.60	($0.13)
Total earnings per common share - basic	$0.54	$0.51	$1.27	$0.55

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share Basic And Diluted [Line Items]	'	'	'	'
Weighted average number of shares, Recognition and Retention Plan	629,055	652,683	634,883	647,332
Weighted average number of shares, treasury stock	1,861,247	2,221,550	1,933,367	2,279,103
Stock Options [Member]	'	'	'	'
Earnings Per Share Basic And Diluted [Line Items]	'	'	'	'
Stock options having antidilutive effect on earnings per share	11,623	792,893	11,623	787,893

Acquisition_Activity_Additiona

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

0 Months Ended

6 Months Ended

0 Months Ended

6 Months Ended

0 Months Ended

6 Months Ended

0 Months Ended

0 Months Ended

Jan. 17, 2014

Jun. 30, 2014

Dec. 31, 2013

Dec. 31, 2012

31-May-14

Jun. 30, 2014

31-May-14

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Feb. 24, 2014

Feb. 24, 2014

1-May-14

1-May-14

Trust

Teche [Member]

Teche [Member]

Teche [Member]

First Private [Member]

First Private [Member]

First Private [Member]

Title Company LLC [Member]

Title Company LLC [Member]

Louisiana Abstract and Title, LLC [Member]

Louisiana Abstract and Title, LLC [Member]

Branch

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

8,400,000

524,154,000

401,872,000

401,872,000

'

84,432,000

84,400,000

'

28,660,000

'

'

200,000

'

200,000

Number of branches acquired

4

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'1 year

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'

'

'

20

'

4

'

2

'

'

'

'

Goodwill created in the acquisition deductible for income tax purposes

'

'

'

'

'

'

$0

'

$0

'

'

'

'

'

Acquisition_Activity_Schedule_

Acquisition Activity - Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable (Detail) (USD $)	0 Months Ended				0 Months Ended	6 Months Ended		0 Months Ended	6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jan. 17, 2014	Jun. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-14	Jun. 30, 2014	31-May-14	Jun. 30, 2014	Jun. 30, 2014
					Teche [Member]	Teche [Member]	Teche [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	'	'	'	'	'	72,308	'	'	'
Fair value of net liabilities assumed including identifiable intangible assets	'	'	'	'	'	'	'	'	29,980
Goodwill	$8,400	$524,154	$401,872	$401,872	'	$84,432	$84,400	'	$28,660

Acquisition_Activity_Schedule_1

Acquisition Activity - Schedule of Business Acquisitions, by Acquisition (Detail) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
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
As Acquired [Member] | Teche [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	71,606
Investment securities	24,077
Loans	716,587
Other real estate owned	329
Core deposit intangible	'
Deferred tax asset (liability)	1,057
Other assets	56,708
Total Assets	870,364
Interest-bearing deposits	520,446
Non-interest-bearing deposits	118,256
Borrowings	134,228
Other liabilities	5,291
Total Liabilities	778,221
As Acquired [Member] | First Private [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	26,621
Investment securities	19,110
Loans	294,425
Other real estate owned	'
Core deposit intangible	'
Deferred tax asset (liability)	530
Other assets	5,230
Total Assets	345,916
Interest-bearing deposits	261,713
Non-interest-bearing deposits	50,333
Borrowings	6,451
Other liabilities	256
Total Liabilities	318,753
Preliminary Fair Value Adjustments [Member] | Trust One-Memphis [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	'
Loans	-1,290
Other real estate owned	'
Core deposit intangible	2,597
Other assets	'
Total Assets	1,307
Interest-bearing deposits	'
Non-interest-bearing deposits	'
Deferred tax liability	654
Other liabilities	'
Total Liabilities	654
Preliminary Fair Value Adjustments [Member] | Teche [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	'
Investment securities	1,092
Loans	-16,637
Other real estate owned	'
Core deposit intangible	2,055
Deferred tax asset (liability)	7,373
Other assets	-6,512
Total Assets	-12,629
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	'
Loans	4,207
Other real estate owned	'
Core deposit intangible	506
Deferred tax asset (liability)	-1,676
Other assets	'
Total Assets	3,037
Interest-bearing deposits	220
Non-interest-bearing deposits	'
Borrowings	'
Other liabilities	'
Total Liabilities	220
As Recorded by IBERIABANK [Member] | Trust One-Memphis [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	92,060
Loans	86,889
Other real estate owned	1,325
Core deposit intangible	2,597
Other assets	368
Total Assets	183,239
Interest-bearing deposits	164,942
Non-interest-bearing deposits	26,373
Deferred tax liability	654
Other liabilities	84
Total Liabilities	192,053
As Recorded by IBERIABANK [Member] | Teche [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	71,606
Investment securities	25,169
Loans	699,950
Other real estate owned	329
Core deposit intangible	2,055
Deferred tax asset (liability)	8,430
Other assets	50,196
Total Assets	857,735
Interest-bearing deposits	521,348
Non-interest-bearing deposits	118,256
Borrowings	140,532
Other liabilities	5,291
Total Liabilities	785,427
As Recorded by IBERIABANK [Member] | First Private [Member]	'
Business Acquisition [Line Items]	'
Cash and cash equivalents	26,621
Investment securities	19,110
Loans	298,632
Other real estate owned	'
Core deposit intangible	506
Deferred tax asset (liability)	-1,146
Other assets	5,230
Total Assets	348,953
Interest-bearing deposits	261,933
Non-interest-bearing deposits	50,333
Borrowings	6,451
Other liabilities	256
Total Liabilities	$318,973

Acquisition_Activity_Schedule_2

Acquisition Activity - Schedule of Business Acquisitions, by Acquisition (Parenthetical) (Detail) (Teche [Member])	6 Months Ended
	Jun. 30, 2014
Teche [Member]	'
Business Acquisition [Line Items]	'
Estimated amortized period for fair value adjustment	'85 months

Acquisition_Activity_Schedule_3

Acquisition Activity - Schedule of Assets Acquired under Business Acquisitions (Detail) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Title Company LLC [Member]	'
Business Acquisition [Line Items]	'
Non-compete agreement	$63
Title plant	14
Other intangible assets	75
Other assets	2
Total Assets	154
Louisiana Abstract and Title, LLC [Member]	'
Business Acquisition [Line Items]	'
Non-compete agreement	100
Title plant	9
Other intangible assets	130
Other assets	6
Total Assets	$245

Acquisition_Activity_Supplemen

Acquisition Activity - Supplemental Pro Forma Information (Detail) (USD $)	6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2013
Business Acquisition Pro Forma Information [Abstract]	'
Interest and non-interest income	$332,674
Net income	$20,022
Earnings per share - basic	$0.68
Earnings per share - diluted	$0.68

Investment_Securities_Schedule

Investment Securities - Schedule of Amortized Cost and Fair Values of Investment Securities, with Gross Unrealized Gains and Losses (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	$2,002,362	$1,963,046
Securities available for sale, Gross Unrealized Gains	22,129	13,867
Securities available for sale, Gross Unrealized Losses	-15,538	-40,116
Securities available for sale, Estimated Fair Value	2,008,953	1,936,797
Securities held to maturity, Amortized Cost	132,245	154,109
Securities held to maturity, Gross Unrealized Gains	3,279	2,205
Securities held to maturity, Gross Unrealized Losses	-1,461	-3,748
Securities held to maturity, Estimated Fair Value	134,063	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	371,703	406,092
Securities available for sale, Gross Unrealized Gains	1,702	1,382
Securities available for sale, Gross Unrealized Losses	-6,011	-11,913
Securities available for sale, Estimated Fair Value	367,394	395,561
Securities held to maturity, Amortized Cost	17,499	34,478
Securities held to maturity, Gross Unrealized Gains	214	484
Securities held to maturity, Gross Unrealized Losses	'	'
Securities held to maturity, Estimated Fair Value	17,713	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	98,833	105,300
Securities available for sale, Gross Unrealized Gains	3,944	2,435
Securities available for sale, Gross Unrealized Losses	-170	-256
Securities available for sale, Estimated Fair Value	102,607	107,479
Securities held to maturity, Amortized Cost	82,073	84,290
Securities held to maturity, Gross Unrealized Gains	2,831	1,463
Securities held to maturity, Gross Unrealized Losses	-324	-1,624
Securities held to maturity, Estimated Fair Value	84,580	84,129
Mortgage-Backed Securities [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	1,530,366	1,450,194
Securities available for sale, Gross Unrealized Gains	16,456	10,031
Securities available for sale, Gross Unrealized Losses	-9,357	-27,947
Securities available for sale, Estimated Fair Value	1,537,465	1,432,278
Securities held to maturity, Amortized Cost	32,673	35,341
Securities held to maturity, Gross Unrealized Gains	234	258
Securities held to maturity, Gross Unrealized Losses	-1,137	-2,124
Securities held to maturity, Estimated Fair Value	31,770	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	27	19
Securities available for sale, Gross Unrealized Losses	'	'
Securities available for sale, Estimated Fair Value	$1,487	$1,479

Investment_Securities_Addition

Investment Securities - Additional Information (Detail) (USD $)	6 Months Ended	12 Months Ended
In Billions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
	Security	Bonds
		Security
Net Investment Income [Line Items]	'	'
Pledged securities, carrying values	$1.50	$1.50
Number of debt securities, held	113	207
Unrealized losses on debt securities, percent of amortized cost	1.99%	3.23%
Unrealized losses on debt securities, percent of Company's total amortized cost	0.80%	2.07%
Unrated revenue municipal bond	'	1
Impairment of par value bond, percentage	50.00%	'
Obligations of State and Political Obligations [Member]	'	'
Net Investment Income [Line Items]	'	'
Number of securities, continuous loss position, over twelve months	11	'
Number of securities, credit ratings	10	'

Investment_Securities_Schedule1

Investment Securities - Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category (Detail) (USD $)	6 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Net Investment Income [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	($869)	($35,543)
Securities available for sale, Less Than Twelve Months, Estimated Fair Value	182,114	1,165,829
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-14,669	-4,573
Securities available for sale, Over Twelve Months, Estimated Fair Value	614,426	88,432
Securities available for sale, Gross Unrealized Losses, Total	-15,538	-40,116
Securities available for sale, Estimated Fair Value, Total	796,540	1,254,261
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	'	-2,133
Securities held to maturity, Less Than Twelve Months, Estimated Fair Value	569	42,268
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-1,461	-1,615
Securities held to maturity, Over Twelve Months, Estimated Fair Value	38,722	17,856
Securities held to maturity, Gross Unrealized Losses, Total	-1,461	-3,748
Securities held to maturity, Estimated Fair Value, Total	39,291	60,124
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	-6,011	-149
Securities available for sale, Over Twelve Months, Estimated Fair Value	258,673	5,515
Securities available for sale, Gross Unrealized Losses, Total	-6,011	-11,913
Securities available for sale, Estimated Fair Value, Total	258,673	304,030
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	'	2,415
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-170	-226
Securities available for sale, Over Twelve Months, Estimated Fair Value	1,437	1,047
Securities available for sale, Gross Unrealized Losses, Total	-170	-256
Securities available for sale, Estimated Fair Value, Total	1,437	3,462
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	'	-1,181
Securities held to maturity, Less Than Twelve Months, Estimated Fair Value	569	29,355
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-324	-443
Securities held to maturity, Over Twelve Months, Estimated Fair Value	13,937	6,240
Securities held to maturity, Gross Unrealized Losses, Total	-324	-1,624
Securities held to maturity, Estimated Fair Value, Total	14,506	35,595
Mortgage-Backed Securities [Member]	'	'
Net Investment Income [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	-869	-23,749
Securities available for sale, Less Than Twelve Months, Estimated Fair Value	182,114	864,899
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-8,488	-4,198
Securities available for sale, Over Twelve Months, Estimated Fair Value	354,316	81,870
Securities available for sale, Gross Unrealized Losses, Total	-9,357	-27,947
Securities available for sale, Estimated Fair Value, Total	536,430	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	'	12,913
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-1,137	-1,172
Securities held to maturity, Over Twelve Months, Estimated Fair Value	24,785	11,616
Securities held to maturity, Gross Unrealized Losses, Total	-1,137	-2,124
Securities held to maturity, Estimated Fair Value, Total	$24,785	$24,529

Investment_Securities_Addition1

Investment Securities - Additional Information on Securities in a Continuous Loss Position (Detail) (USD $)	6 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
	Securities	Securities
Schedule of Available-for-sale Securities [Line Items]	'	'
Number of securities, available for sale securities	91	25
Number of securities, amortized costs	$669,278	$112,476
Number of securities, unrealized loss	16,130	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	80	20
Number of securities, amortized costs	653,411	104,520
Number of securities, unrealized loss	15,636	5,519
Political Subdivisions [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Number of securities, available for sale securities	11	5
Number of securities, amortized costs	15,867	7,956
Number of securities, unrealized loss	$494	$669

Investment_Securities_Schedule2

Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Maturity (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Investments Debt And Equity Securities [Abstract]	'	'
Securities Available for Sale, Weighted Average Yield, Within one year or less	2.00%	'
Securities Available for Sale, Weighted Average Yield, One through five years	1.55%	'
Securities Available for Sale, Weighted Average Yield, After five through ten years	2.10%	'
Securities Available for Sale, Weighted Average Yield, Over ten years	2.20%	'
Securities Available for Sale, Weighted Average Yield, Total	2.09%	'
Securities Available for Sale, Amortized Cost, Within one year or less	$16,390	'
Securities Available for Sale, Amortized Cost, One through five years	262,494	'
Securities Available for Sale, Amortized Cost, After five through ten years	504,532	'
Securities Available for Sale, Amortized Cost, Over ten years	1,218,946	'
Securities Available for Sale, Amortized Cost, Total	2,002,362	'
Securities Available for Sale, Estimated Fair Value, Within one year or less	16,445	'
Securities Available for Sale, Estimated Fair Value, One through five years	263,033	'
Securities Available for Sale, Estimated Fair Value, After five through ten years	508,167	'
Securities Available for Sale, Estimated Fair Value, Over ten years	1,221,308	'
Securities Available for Sale, Estimated Fair Value, Totals	2,008,953	'
Securities Held to Maturity, Weighted Average Yield, Within one year or less	2.11%	'
Securities Held to Maturity, Weighted Average Yield, One through five years	3.24%	'
Securities Held to Maturity, Weighted Average Yield, After five through ten years	2.92%	'
Securities Held to Maturity, Weighted Average Yield, Over ten years	3.10%	'
Securities Held to Maturity, Weighted Average Yield, Totals	2.95%	'
Securities Held to Maturity, Amortized Cost, Within one year or less	17,499	'
Securities Held to Maturity, Amortized Cost, One through five years	13,510	'
Securities Held to Maturity, Amortized Cost, After five through ten years	20,495	'
Securities Held to Maturity, Amortized Cost, Over ten years	80,741	'
Securities Held to Maturity, Amortized Cost, Totals	132,245	154,109
Securities Held to Maturity, Estimated Fair Value, Within one year or less	17,713	'
Securities Held to Maturity, Estimated Fair Value, One through five years	13,867	'
Securities Held to Maturity, Estimated Fair Value, After five through ten years	21,200	'
Securities Held to Maturity, Estimated Fair Value, Over ten years	81,283	'
Securities held to maturity, Estimated Fair Value	$134,063	$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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Investments Debt And Equity Securities [Abstract]	'	'	'	'
Realized gains	$8	$4	$27	$2,369
Realized losses	'	-70	'	-108
Net realized gains (losses)	$8	($66)	$27	$2,261

Investment_Securities_Schedule4

Investment Securities - Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Investments Debt And Equity Securities [Abstract]	'	'
Federal Home Loan Bank (FHLB) stock	$44,715	$24,369
Federal Reserve Bank (FRB) stock	28,098	28,098
Other investments	3,306	1,306
Total	$76,119	$53,773

Loans_Receivable_Schedule_of_N

Loans Receivable - Schedule of Non-Covered and Covered Loans (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	$10,313,088	$8,772,226	'
Covered loans receivable	585,439	719,793	'
Total loans receivable	10,898,527	9,492,019	'
Commercial Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	330,017	424,357	'
Total loans receivable	7,374,548	6,863,418	'
Commercial Loans [Member] | Real Estate [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	294,115	387,332	'
Total loans receivable	4,243,559	3,867,305	'
Commercial Loans [Member] | Business [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	35,902	37,025	'
Total loans receivable	3,130,989	2,996,113	'
Residential Mortgage Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	141,613	154,025	'
Total loans receivable	1,124,624	586,532	'
Residential Mortgage Loans [Member] | Residential 1-4 Family [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	141,613	154,025	'
Total loans receivable	1,068,585	577,082	'
Residential Mortgage Loans [Member] | Construction / Owner Occupied [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	'	'	'
Total loans receivable	56,039	9,450	'
Consumer and Other Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	113,809	141,411	'
Total loans receivable	2,399,355	2,042,069	'
Consumer and Other Loans [Member] | Home Equity [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	110,068	137,122	'
Total loans receivable	1,467,141	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	392,355	375,236	'
Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	3,741	4,289	'
Total loans receivable	539,859	375,041	'
Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	585,438	719,793	918,215
Covered Loans [Member] | Commercial Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	330,017	424,357	'
Covered Loans [Member] | Commercial Loans [Member] | Real Estate [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	294,115	387,332	'
Covered Loans [Member] | Commercial Loans [Member] | Business [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	35,902	37,025	'
Covered Loans [Member] | Residential Mortgage Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	141,613	154,025	'
Covered Loans [Member] | Residential Mortgage Loans [Member] | Residential 1-4 Family [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	141,613	154,025	'
Covered Loans [Member] | Residential Mortgage Loans [Member] | Construction / Owner Occupied [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	'	'	'
Covered Loans [Member] | Consumer and Other Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	113,808	141,411	'
Covered Loans [Member] | Consumer and Other Loans [Member] | Home Equity [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	110,068	137,122	'
Covered Loans [Member] | Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	'	'	'
Covered Loans [Member] | Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Covered loans receivable	3,740	4,289	'
Non-Covered Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	10,313,089	8,772,226	'
Non-Covered Loans [Member] | Commercial Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	7,044,531	6,439,061	'
Non-Covered Loans [Member] | Commercial Loans [Member] | Real Estate [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	3,949,444	3,479,973	'
Non-Covered Loans [Member] | Commercial Loans [Member] | Business [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	3,095,087	2,959,088	'
Non-Covered Loans [Member] | Residential Mortgage Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	983,011	432,507	'
Non-Covered Loans [Member] | Residential Mortgage Loans [Member] | Residential 1-4 Family [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	926,972	423,057	'
Non-Covered Loans [Member] | Residential Mortgage Loans [Member] | Construction / Owner Occupied [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	56,039	9,450	'
Non-Covered Loans [Member] | Consumer and Other Loans [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	2,285,547	1,900,658	'
Non-Covered Loans [Member] | Consumer and Other Loans [Member] | Home Equity [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	1,357,073	1,154,670	'
Non-Covered Loans [Member] | Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	392,355	375,236	'
Non-Covered Loans [Member] | Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Non-Covered loans receivable	$536,119	$370,752	'

Loans_Receivable_Additional_In

Loans Receivable - Additional Information (Detail) (USD $)	6 Months Ended		6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014
			Troubled Debt Restructurings [Member]	Troubled Debt Restructurings [Member]	Trust One-Memphis [Member]	Teche [Member]	First Private [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'	'	'	'	'
Deferred loan origination fees	$19,100,000	$18,600,000	'	'	'	'	'
Deferred loan expenses	8,400,000	7,600,000	'	'	'	'	'
Deposit liabilities reclassified as loans receivable	6,400,000	3,100,000	'	'	'	'	'
Loans with carrying value pledged to secure public deposits and other borrowings	2,400,000,000	2,300,000,000	'	'	'	'	'
Acquired loans	'	'	'	'	86,900,000	700,000,000	298,600,000
Carrying amounts of loans acquired	1,000,000,000	'	'	'	'	'	'
Maximum period for subject to change estimated fair values after acquisition date	'1 year	'	'	'	'	'	'
Total TDRs	'	'	$0	$1,500,000	'	'	'

Loans_Receivable_Schedule_of_A

Loans Receivable - Schedule of Aging of Non-Covered Loans (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	$10,744	$13,426
Past Due, 60-89 days	3,238	7,965
Past Due, Greater than 90 days	34,207	44,762
Total Past Due	48,189	66,153
Current	8,786,543	8,222,168
Total Non-covered Loans, Net of Unearned Income	8,834,732	8,288,321
Recorded Investment > 90 days and Accruing	20	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	56	'
Past Due, 60-89 days	223	'
Past Due, Greater than 90 days	1,349	1,803
Total Past Due	1,628	1,803
Current	591,233	381,292
Total Non-covered Loans, Net of Unearned Income	592,861	383,095
Recorded Investment > 90 days and Accruing	'	'
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	387	6,098
Past Due, 60-89 days	112	5,630
Past Due, Greater than 90 days	4,331	7,650
Total Past Due	4,830	19,378
Current	2,828,295	2,732,431
Total Non-covered Loans, Net of Unearned Income	2,833,125	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	3,742	2,117
Past Due, 60-89 days	56	423
Past Due, Greater than 90 days	4,191	15,020
Total Past Due	7,989	17,560
Current	2,953,471	2,888,491
Total Non-covered Loans, Net of Unearned Income	2,961,460	2,906,051
Recorded Investment > 90 days and Accruing	'	'
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	2,581	1,104
Past Due, 60-89 days	1,455	852
Past Due, Greater than 90 days	10,593	9,684
Total Past Due	14,629	11,640
Current	326,077	286,167
Total Non-covered Loans, Net of Unearned Income	340,706	297,807
Recorded Investment > 90 days and Accruing	20	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	1,518	1,956
Past Due, 60-89 days	703	569
Past Due, Greater than 90 days	7,949	6,808
Total Past Due	10,170	9,333
Current	1,163,216	1,091,894
Total Non-covered Loans, Net of Unearned Income	1,173,386	1,101,227
Recorded Investment > 90 days and Accruing	'	'
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	1,611	1,427
Past Due, 60-89 days	322	293
Past Due, Greater than 90 days	1,192	1,275
Total Past Due	3,125	2,995
Current	388,356	370,388
Total Non-covered Loans, Net of Unearned Income	391,481	373,383
Recorded Investment > 90 days and Accruing	'	'
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	567	458
Past Due, 60-89 days	209	106
Past Due, Greater than 90 days	542	485
Total Past Due	1,318	1,049
Current	356,189	293,693
Total Non-covered Loans, Net of Unearned Income	357,507	294,742
Recorded Investment > 90 days and Accruing	'	'
Non-Covered Loans Excluding Acquired Loans [Member] | Residential Subprime [Member] | Residential Mortgage Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	'	'
Past Due, 60-89 days	'	'
Past Due, Greater than 90 days	3,111	1,626
Total Past Due	3,111	1,626
Current	115,835	114,939
Total Non-covered Loans, Net of Unearned Income	118,946	116,565
Recorded Investment > 90 days and Accruing	'	'
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	282	266
Past Due, 60-89 days	158	92
Past Due, Greater than 90 days	949	411
Total Past Due	1,389	769
Current	63,871	62,873
Total Non-covered Loans, Net of Unearned Income	65,260	63,642
Recorded Investment > 90 days and Accruing	'	'
Non-Covered Acquired Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Past Due, 30-59 days	8,151	3,251
Past Due, 60-89 days	3,901	2,580
Past Due, Greater than 90 days	45,064	37,265
Total Past Due	57,116	43,096
Current	1,495,447	506,422
Discount	-74,207	-65,613
Total Non-covered Loans, Net of Unearned Income	1,478,356	483,905
Recorded Investment > 90 days and Accruing	31,410	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	'	388
Past Due, 60-89 days	597	'
Past Due, Greater than 90 days	2,183	2,542
Total Past Due	2,780	2,930
Current	35,403	19,833
Discount	-2,536	-2,532
Total Non-covered Loans, Net of Unearned Income	35,647	20,231
Recorded Investment > 90 days and Accruing	2,090	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	3,584	1,798
Past Due, 60-89 days	628	1,963
Past Due, Greater than 90 days	23,144	27,967
Total Past Due	27,356	31,728
Current	511,672	345,286
Discount	-51,217	-52,176
Total Non-covered Loans, Net of Unearned Income	487,811	324,838
Recorded Investment > 90 days and Accruing	21,592	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	1,944	544
Past Due, 60-89 days	281	'
Past Due, Greater than 90 days	2,212	1,218
Total Past Due	4,437	1,762
Current	136,130	54,189
Discount	-6,941	-2,914
Total Non-covered Loans, Net of Unearned Income	133,626	53,037
Recorded Investment > 90 days and Accruing	2,172	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	331	'
Past Due, 60-89 days	1,378	'
Past Due, Greater than 90 days	6,703	226
Total Past Due	8,412	226
Current	508,678	18,796
Discount	6,269	-887
Total Non-covered Loans, Net of Unearned Income	523,359	18,135
Recorded Investment > 90 days and Accruing	525	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	1,260	313
Past Due, 60-89 days	622	516
Past Due, Greater than 90 days	8,667	4,242
Total Past Due	10,549	5,071
Current	180,703	53,995
Discount	-7,565	-5,623
Total Non-covered Loans, Net of Unearned Income	183,687	53,443
Recorded Investment > 90 days and Accruing	4,629	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	28	33
Past Due, 60-89 days	'	'
Past Due, Greater than 90 days	59	95
Total Past Due	87	128
Current	850	1,725
Discount	-63	'
Total Non-covered Loans, Net of Unearned Income	874	1,853
Recorded Investment > 90 days and Accruing	59	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	1,004	175
Past Due, 60-89 days	395	101
Past Due, Greater than 90 days	2,096	975
Total Past Due	3,495	1,251
Current	122,011	12,598
Discount	-12,154	-1,481
Total Non-covered Loans, Net of Unearned Income	113,352	12,368
Recorded Investment > 90 days and Accruing	$343	$975

Loans_Receivable_Schedule_of_N1

Loans Receivable - Schedule of Non-Covered Loans on Nonaccrual Status (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	$34,187	$43,687
Commercial Loans [Member] | Commercial Real Estate Construction [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	1,349	1,803
Commercial Loans [Member] | Commercial Real Estate - Other [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	4,331	7,648
Commercial Loans [Member] | Business [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	4,191	15,020
Residential Mortgage Loans [Member] | Residential Prime [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	10,573	8,611
Residential Mortgage Loans [Member] | Residential Subprime [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	3,111	1,626
Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	7,949	6,808
Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	1,192	1,275
Consumer and Other Loans [Member] | Credit Card [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	949	411
Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	$542	$485

Loans_Receivable_Schedule_of_C

Loans Receivable - Schedule of Carrying Amount of Acquired Covered Loans (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	$49,271	$66,077
Acquired Performing Loans	536,168	653,716
Balance at end of period	585,439	719,793
Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	6,523	14,904
Acquired Performing Loans	323,494	409,453
Balance at end of period	330,017	424,357
Commercial Loans [Member] | Real Estate [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	6,523	14,904
Acquired Performing Loans	287,592	372,428
Balance at end of period	294,115	387,332
Commercial Loans [Member] | Business [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	'	'
Acquired Performing Loans	35,902	37,025
Balance at end of period	35,902	37,025
Residential Mortgage Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	28,273	28,223
Acquired Performing Loans	113,340	125,802
Balance at end of period	141,613	154,025
Residential Mortgage Loans [Member] | Residential 1-4 Family [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	28,273	28,223
Acquired Performing Loans	113,340	125,802
Balance at end of period	141,613	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	14,475	22,950
Acquired Performing Loans	99,334	118,461
Balance at end of period	113,809	141,411
Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Acquired Impaired Loans	13,879	21,768
Acquired Performing Loans	96,189	115,354
Balance at end of period	110,068	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	596	1,182
Acquired Performing Loans	3,145	3,107
Balance at end of period	$3,741	$4,289

Loans_Receivable_Schedule_of_C1

Loans Receivable - Schedule of Carrying Amount of Loans Acquired (Detail) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
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 $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 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	17,645	38,407
Accretion	-54,518	-92,200
Changes in expected cash flows not affecting nonaccretable differences	544	74,879
Balance at end of period	328,341	377,479
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	4,128	6,368
Accretion	-4,089	-10,973
Changes in expected cash flows not affecting nonaccretable differences	-12,176	4,158
Balance at end of period	74,454	76,176
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	13,517	32,039
Accretion	-50,429	-81,227
Changes in expected cash flows not affecting nonaccretable differences	12,720	70,721
Balance at end of period	$253,887	$301,303

Loans_Receivable_Schedule_of_T

Loans Receivable - Schedule of Troubled Debt Restructurings (Detail) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Commercial Loans [Member] | Commercial Real Estate Construction [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'
Commercial Loans [Member] | Real Estate [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	378	677
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	1,634	8,064
Total TDRs	2,012	8,741
Commercial Loans [Member] | Business [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	811	1,135
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	2,342	281
Total TDRs	3,153	1,416
Residential Mortgage Loans [Member] | Residential Prime [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'
Residential Mortgage Loans [Member] | Residential Subprime [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'
Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	1,189	1,812
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	4,224	8,613
Total TDRs	5,413	10,425
Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	0	0
Accruing Loans, Past Due Greater than 30 Days	0	0
Nonaccrual TDRs	248	268
Total TDRs	248	268
Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'
Consumer and Other Loans [Member] | Credit Card [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'
Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'

Loans_Receivable_Schedule_of_M

Loans Receivable - Schedule of Modified TDRs (Detail) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Receivables [Abstract]	'	'
Extended maturities	'	'
Interest rate adjustment	'	'
Maturity and interest rate adjustment	'	1,545
Movement to or extension of interest-rate only payments	'	'
Forbearance	'	'
Other concession(s)	'	'
Total	'	$1,545

Loans_Receivable_Schedule_of_S

Loans Receivable - Schedule of Subsequently Defaulted TDRs (Detail) (TDRs Occurring During The Period [Member], Non-Covered TDRs [Member], USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
	SecurityLoan	SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	1
Pre-modification Outstanding Recorded Investment	'	$1,545
Post-modification Outstanding Recorded Investment	'	1,545
Number of Loans	44	58
Recorded Investment	3,790	10,139
Real Estate [Member] | Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	1
Pre-modification Outstanding Recorded Investment	'	1,545
Post-modification Outstanding Recorded Investment	'	1,545
Number of Loans	31	48
Recorded Investment	1,635	8,673
Business [Member] | Commercial Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Number of Loans	11	8
Recorded Investment	2,115	1,417
Residential Prime [Member] | Residential Mortgage Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Number of Loans	'	'
Recorded Investment	'	'
Home Equity [Member] | Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Number of Loans	1	1
Recorded Investment	40	49
Indirect Automobile [Member] | Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Number of Loans	'	'
Recorded Investment	'	'
Credit Card [Member] | Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Number of Loans	'	'
Recorded Investment	'	'
Consumer - Other [Member] | Consumer and Other Loans [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Number of Loans	1	1
Recorded Investment	'	'

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 $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 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 benefit/adjustment attributable to FDIC loss share agreements	3,253	-56,654
Adjustment attributable to FDIC loss share arrangements	3,598	55,085
Net (reversal of) provision for loan losses	6,851	-1,569
Adjustment attributable to FDIC loss share arrangements	-3,598	-55,085
Transfer of balance to OREO	-5,608	-17,685
Transfer of balance to the RULC	'	-9,828
Loans charged-off	-10,773	-6,583
Recoveries	3,573	2,050
Balance at end of period	133,519	162,903
Balance at beginning of period	11,147	0
Transfer of balance from the allowance for loan losses	'	9,828
Provision for unfunded lending commitments	113	514
Balance at end of period	11,260	10,342
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 benefit/adjustment attributable to FDIC loss share agreements	5,078	-585
Adjustment attributable to FDIC loss share arrangements	'	'
Net (reversal of) provision for loan losses	5,078	-585
Adjustment attributable to FDIC loss share arrangements	'	'
Transfer of balance to OREO	'	'
Transfer of balance to the RULC	'	-9,828
Loans charged-off	-5,198	-4,249
Recoveries	3,426	2,050
Balance at end of period	70,648	61,599
Balance at beginning of period	11,147	0
Transfer of balance from the allowance for loan losses	'	9,828
Provision for unfunded lending commitments	113	514
Balance at end of period	11,260	10,342
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 benefit/adjustment attributable to FDIC loss share agreements	-1,085	-1,009
Adjustment attributable to FDIC loss share arrangements	'	'
Net (reversal of) provision for loan losses	-1,085	-1,009
Adjustment attributable to FDIC loss share arrangements	'	'
Transfer of balance to OREO	-523	-973
Transfer of balance to the RULC	'	'
Loans charged-off	-182	'
Recoveries	109	'
Balance at end of period	2,876	6,834
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 benefit/adjustment attributable to FDIC loss share agreements	-740	-55,060
Adjustment attributable to FDIC loss share arrangements	3,598	55,085
Net (reversal of) provision for loan losses	2,858	25
Adjustment attributable to FDIC loss share arrangements	-3,598	-55,085
Transfer of balance to OREO	-5,085	-16,712
Transfer of balance to the RULC	'	'
Loans charged-off	-5,393	-2,334
Recoveries	38	'
Balance at end of period	59,995	94,470
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 $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Transfer of balance to OREO	($5,608)	($17,685)	'
Transfer of balance to the RULC	'	-9,828	'
Loans charged off	-10,773	-6,583	'
Recoveries	3,573	2,050	'
Balance at beginning of period	11,147	0	'
Transfer of balance from the allowance for loan losses	'	9,828	'
Balance at end of period	11,260	10,342	'
Balance at end of period	585,439	'	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	3,993	-1,594	'
Transfer of balance to OREO	-523	-973	'
Transfer of balance to the RULC	'	-9,828	'
Loans charged off	-5,380	-4,249	'
Recoveries	3,535	2,050	'
Balance at end of period	73,524	68,433	'
Balance at beginning of period	11,147	'	'
Transfer of balance from the allowance for loan losses	'	9,828	'
(Reversal of) Provision for unfunded commitments	113	514	'
Balance at end of period	11,260	10,342	'
Allowance on loans individually evaluated for impairment	202	325	'
Allowance on loans collectively evaluated for impairment	73,321	68,108	'
Balance at end of period	10,313,089	7,984,822	'
Balance at end of period individually evaluated for impairment	11,845	31,958	'
Balance at end of period collectively evaluated for impairment	10,301,244	7,952,864	'
Balance at end of period acquired with deteriorated credit quality	41,307	47,153	'
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	2,858	25	'
(Decrease) Increase in FDIC loss share receivable	-3,598	-55,085	'
Transfer of balance to OREO	-5,085	-16,712	'
Transfer of balance to the RULC	'	'	'
Loans charged off	-5,393	-2,334	'
Recoveries	38	'	'
Balance at end of period	59,995	94,470	'
Balance at beginning of period	'	'	'
Transfer of balance from the allowance for loan losses	'	'	'
Balance at end of period	'	'	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	59,995	94,470	'
Balance at end of period	585,438	918,215	719,793
Balance at end of period individually evaluated for impairment	'	'	'
Balance at end of period collectively evaluated for impairment	585,439	918,215	'
Balance at end of period acquired with deteriorated credit quality	49,271	172,043	'
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	585	-7,459	'
Transfer of balance to OREO	-108	-264	'
Transfer of balance to the RULC	'	-2,939	'
Loans charged off	-660	-807	'
Recoveries	1,699	500	'
Balance at end of period	28,106	27,295	'
Balance at beginning of period	3,089	'	'
Transfer of balance from the allowance for loan losses	'	2,939	'
(Reversal of) Provision for unfunded commitments	112	545	'
Balance at end of period	3,201	3,484	'
Allowance on loans individually evaluated for impairment	'	72	'
Allowance on loans collectively evaluated for impairment	28,105	27,223	'
Balance at end of period	3,949,444	3,224,078	'
Balance at end of period individually evaluated for impairment	5,976	16,525	'
Balance at end of period collectively evaluated for impairment	3,943,468	3,207,553	'
Balance at end of period acquired with deteriorated credit quality	30,799	40,015	'
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	1,474	27	'
(Decrease) Increase in FDIC loss share receivable	-2,121	-26,737	'
Transfer of balance to OREO	-1,857	-12,178	'
Loans charged off	-3,726	-2,334	'
Recoveries	38	'	'
Balance at end of period	32,580	59,649	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	32,580	59,649	'
Balance at end of period	294,115	520,160	'
Balance at end of period individually evaluated for impairment	'	'	'
Balance at end of period collectively evaluated for impairment	294,115	520,160	'
Balance at end of period acquired with deteriorated credit quality	6,523	132,565	'
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	782	557	'
Transfer of balance to OREO	-162	-90	'
Transfer of balance to the RULC	'	-3,497	'
Loans charged off	-668	-395	'
Recoveries	65	259	'
Balance at end of period	28,532	25,555	'
Balance at beginning of period	4,839	'	'
Transfer of balance from the allowance for loan losses	'	3,497	'
(Reversal of) Provision for unfunded commitments	-43	12	'
Balance at end of period	4,796	3,509	'
Allowance on loans individually evaluated for impairment	31	116	'
Allowance on loans collectively evaluated for impairment	28,501	25,439	'
Balance at end of period	3,095,087	2,618,963	'
Balance at end of period individually evaluated for impairment	4,563	14,014	'
Balance at end of period collectively evaluated for impairment	3,090,524	2,604,949	'
Balance at end of period acquired with deteriorated credit quality	5,496	3,468	'
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	313	'	'
(Decrease) Increase in FDIC loss share receivable	749	-2,672	'
Transfer of balance to OREO	-1,162	-314	'
Loans charged off	-1,589	'	'
Recoveries	'	'	'
Balance at end of period	3,691	8,389	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	3,691	8,389	'
Balance at end of period	35,902	68,957	'
Balance at end of period individually evaluated for impairment	'	'	'
Balance at end of period collectively evaluated for impairment	35,902	68,957	'
Balance at end of period acquired with deteriorated credit quality	'	2,005	'
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	171	2,961	'
Transfer of balance to OREO	-253	-612	'
Transfer of balance to the RULC	'	-40	'
Loans charged off	-435	-2,603	'
Recoveries	114	188	'
Balance at end of period	2,143	2,019	'
Balance at beginning of period	72	'	'
Transfer of balance from the allowance for loan losses	'	40	'
(Reversal of) Provision for unfunded commitments	4	'	'
Balance at end of period	76	40	'
Allowance on loans individually evaluated for impairment	171	137	'
Allowance on loans collectively evaluated for impairment	1,972	1,882	'
Balance at end of period	983,011	350,842	'
Balance at end of period individually evaluated for impairment	1,058	1,152	'
Balance at end of period collectively evaluated for impairment	981,953	349,690	'
Balance at end of period acquired with deteriorated credit quality	1,209	383	'
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	2,455	2,347	'
Transfer of balance to OREO	'	-7	'
Transfer of balance to the RULC	'	-3,352	'
Loans charged off	-3,617	-444	'
Recoveries	1,657	1,103	'
Balance at end of period	14,743	13,564	'
Balance at beginning of period	3,147	'	'
Transfer of balance from the allowance for loan losses	'	3,352	'
(Reversal of) Provision for unfunded commitments	40	-43	'
Balance at end of period	3,187	3,309	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	14,743	13,564	'
Balance at end of period	2,285,547	1,790,939	'
Balance at end of period individually evaluated for impairment	248	267	'
Balance at end of period collectively evaluated for impairment	2,285,299	1,790,672	'
Balance at end of period acquired with deteriorated credit quality	3,803	3,287	'
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	479	-1	'
(Decrease) Increase in FDIC loss share receivable	-126	-18,603	'
Transfer of balance to OREO	-1,532	1	'
Loans charged off	-78	'	'
Recoveries	'	'	'
Balance at end of period	14,877	15,161	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	14,877	15,161	'
Balance at end of period	113,809	161,444	'
Balance at end of period individually evaluated for impairment	'	'	'
Balance at end of period collectively evaluated for impairment	113,809	161,444	'
Balance at end of period acquired with deteriorated credit quality	14,475	19,504	'
Unallocated [Member] | Non-Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	'	'	'
(Reversal of) Provision for loan losses	'	'	'
Transfer of balance to OREO	'	'	'
Loans charged off	'	'	'
Recoveries	'	'	'
Balance at end of period	'	'	'
Balance at beginning of period	'	'	'
(Reversal of) Provision for unfunded commitments	'	'	'
Balance at end of period	'	'	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	'	'	'
Balance at end of period	'	'	'
Balance at end of period individually evaluated for impairment	'	'	'
Balance at end of period collectively evaluated for impairment	'	'	'
Balance at end of period acquired with deteriorated credit quality	'	'	'
Unallocated [Member] | Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Balance at beginning of period	'	'	'
(Reversal of) Provision for loan losses	'	'	'
(Decrease) Increase in FDIC loss share receivable	'	'	'
Transfer of balance to OREO	'	'	'
Loans charged off	'	'	'
Recoveries	'	'	'
Balance at end of period	'	'	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	'	'	'
Balance at end of period	'	'	'
Balance at end of period individually evaluated for impairment	'	'	'
Balance at end of period collectively evaluated for impairment	'	'	'
Balance at end of period acquired with deteriorated credit quality	'	'	'
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	592	-1	'
(Decrease) Increase in FDIC loss share receivable	-2,100	-7,073	'
Transfer of balance to OREO	-534	-4,221	'
Loans charged off	'	'	'
Recoveries	'	'	'
Balance at end of period	8,847	11,271	'
Allowance on loans individually evaluated for impairment	'	'	'
Allowance on loans collectively evaluated for impairment	8,847	11,271	'
Balance at end of period	141,613	167,654	'
Balance at end of period individually evaluated for impairment	'	'	'
Balance at end of period collectively evaluated for impairment	141,613	167,654	'
Balance at end of period acquired with deteriorated credit quality	$28,273	$17,969	'

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 $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
In Thousands, unless otherwise specified
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	$10,313,088	$8,772,226	'
Total	585,439	719,793	'
Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	812,242	87,114	'
30+ Days Past Due	22,543	6,676	'
Discount	-13,513	-7,991	'
Total	821,272	85,799	'
Residential Prime [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	508,678	18,796	'
30+ Days Past Due	8,412	226	'
Discount	6,269	-887	'
Total	523,359	18,135	'
Home Equity [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	180,703	53,995	'
30+ Days Past Due	10,549	5,071	'
Discount	-7,565	-5,623	'
Total	183,687	53,443	'
Indirect Automobile [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	850	1,725	'
30+ Days Past Due	87	128	'
Discount	-63	'	'
Total	874	1,853	'
Consumer - Other [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	122,011	12,598	'
30+ Days Past Due	3,495	1,251	'
Discount	-12,154	-1,481	'
Total	113,352	12,368	'
Internally Assigned Grade Loss [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Discount	-60,694	-57,622	'
Total	657,084	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	-2,536	-2,532	'
Total	35,647	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	-51,217	-52,176	'
Total	487,811	324,838	'
Internally Assigned Grade Loss [Member] | Commercial Business [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Discount	-6,941	-2,914	'
Total	133,626	53,037	'
Pass [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	645,436	378,849	'
Pass [Member] | Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	31,269	17,132	'
Pass [Member] | Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	482,016	310,303	'
Pass [Member] | Commercial Business [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	132,151	51,414	'
Special Mention [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	18,273	17,467	'
Special Mention [Member] | Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	1,541	196	'
Special Mention [Member] | Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	13,816	15,351	'
Special Mention [Member] | Commercial Business [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	2,916	1,920	'
Substandard [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	52,810	59,288	'
Substandard [Member] | Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	5,373	5,435	'
Substandard [Member] | Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	42,866	51,267	'
Substandard [Member] | Commercial Business [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	4,571	2,586	'
Doubtful [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	1,259	124	'
Doubtful [Member] | Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	'	'	'
Doubtful [Member] | Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	330	93	'
Doubtful [Member] | Commercial Business [Member] | Non-Covered Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	929	31	'
Covered Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	585,438	719,793	918,215
Covered Loans [Member] | Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	274,956	303,185	'
30+ Days Past Due	46,991	66,800	'
Discount	-66,526	-74,549	'
Covered Loans [Member] | Residential Prime [Member] | Mortgage [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	149,945	158,710	'
30+ Days Past Due	30,381	30,814	'
Discount	-38,713	-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	124,113	143,236	'
30+ Days Past Due	16,489	35,811	'
Discount	-30,534	-41,925	'
Covered Loans [Member] | Consumer - Other [Member] | Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	316	591	'
30+ Days Past Due	71	144	'
Discount	2,721	2,875	'
Covered Loans [Member] | Credit Card [Member] | Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Credit risk by payment status, Current	582	648	'
30+ Days Past Due	50	31	'
Discount	'	'	'
Covered Loans [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	35,902	'	68,957
Covered Loans [Member] | Internally Assigned Grade Loss [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	356,985	467,930	'
Discount	-26,968	-43,573	'
Total	330,017	424,357	'
Covered Loans [Member] | Internally Assigned Grade Loss [Member] | Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	255,421	295,436	'
Covered Loans [Member] | Internally Assigned Grade Loss [Member] | Residential Prime [Member] | Mortgage [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	141,613	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	110,068	137,122	'
Covered Loans [Member] | Internally Assigned Grade Loss [Member] | Consumer - Other [Member] | Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	3,108	3,610	'
Covered Loans [Member] | Internally Assigned Grade Loss [Member] | Credit Card [Member] | Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	632	679	'
Covered Loans [Member] | Internally Assigned Grade Loss [Member] | Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	55,955	74,675	'
Covered Loans [Member] | Internally Assigned Grade Loss [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	265,128	346,225	'
Covered Loans [Member] | Internally Assigned Grade Loss [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	35,902	47,030	'
Covered Loans [Member] | Pass [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	184,563	222,175	'
Covered Loans [Member] | Pass [Member] | Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	39,482	42,886	'
Covered Loans [Member] | Pass [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	119,489	148,579	'
Covered Loans [Member] | Pass [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	25,592	30,710	'
Covered Loans [Member] | Special Mention [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	43,218	57,880	'
Covered Loans [Member] | Special Mention [Member] | Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	1,997	7,401	'
Covered Loans [Member] | Special Mention [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	40,291	49,699	'
Covered Loans [Member] | Special Mention [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	930	780	'
Covered Loans [Member] | Substandard [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	128,337	183,127	'
Covered Loans [Member] | Substandard [Member] | Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	14,476	23,891	'
Covered Loans [Member] | Substandard [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	104,527	144,680	'
Covered Loans [Member] | Substandard [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	9,334	14,556	'
Covered Loans [Member] | Doubtful [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	867	4,748	'
Covered Loans [Member] | Doubtful [Member] | Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	'	497	'
Covered Loans [Member] | Doubtful [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	821	3,267	'
Covered Loans [Member] | Doubtful [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	46	984	'
Non-Covered Loans Excluding Acquired Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	2,413,544	2,219,954	'
30+ Days Past Due	33,742	27,412	'
Total	2,447,286	2,247,366	'
Credit risk by payment status, Current	8,786,543	8,222,168	'
Non-Covered Loans Excluding Acquired Loans [Member] | Residential Prime [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	326,077	286,167	'
30+ Days Past Due	14,629	11,640	'
Total	340,706	297,807	'
Non-Covered Loans Excluding Acquired Loans [Member] | Home Equity [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	1,163,216	1,091,894	'
30+ Days Past Due	10,170	9,333	'
Total	1,173,386	1,101,227	'
Non-Covered Loans Excluding Acquired Loans [Member] | Indirect Automobile [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	388,356	370,388	'
30+ Days Past Due	3,125	2,995	'
Total	391,481	373,383	'
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	356,189	293,693	'
30+ Days Past Due	1,318	1,049	'
Total	357,507	294,742	'
Non-Covered Loans Excluding Acquired Loans [Member] | Credit Card [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	63,871	62,873	'
30+ Days Past Due	1,389	769	'
Total	65,260	63,642	'
Non-Covered Loans Excluding Acquired Loans [Member] | Residential Subprime [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Current	115,835	114,939	'
30+ Days Past Due	3,111	1,626	'
Total	118,946	116,565	'
Non-Covered Loans Excluding Acquired Loans [Member] | Internally Assigned Grade Loss [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Total	6,387,446	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	592,861	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	2,833,125	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	2,961,460	2,906,051	'
Non-Covered Loans Excluding Acquired Loans [Member] | Pass [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	6,258,726	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]	'	'	'
Doubtful	581,164	370,824	'
Non-Covered Loans Excluding Acquired Loans [Member] | Pass [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	2,757,043	2,694,161	'
Non-Covered Loans Excluding Acquired Loans [Member] | Pass [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	2,920,519	2,866,794	'
Non-Covered Loans Excluding Acquired Loans [Member] | Special Mention [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	74,294	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]	'	'	'
Doubtful	252	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]	'	'	'
Doubtful	46,067	27,227	'
Non-Covered Loans Excluding Acquired Loans [Member] | Special Mention [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	27,975	6,164	'
Non-Covered Loans Excluding Acquired Loans [Member] | Substandard [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	52,241	65,437	'
Non-Covered Loans Excluding Acquired Loans [Member] | Substandard [Member] | Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	11,445	2,962	'
Non-Covered Loans Excluding Acquired Loans [Member] | Substandard [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	29,783	30,308	'
Non-Covered Loans Excluding Acquired Loans [Member] | Substandard [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	11,013	32,167	'
Non-Covered Loans Excluding Acquired Loans [Member] | Doubtful [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	2,185	1,039	'
Non-Covered Loans Excluding Acquired Loans [Member] | Doubtful [Member] | Commercial Real Estate Construction [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	'	'	'
Non-Covered Loans Excluding Acquired Loans [Member] | Doubtful [Member] | Commercial Real Estate - Other [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	232	113	'
Non-Covered Loans Excluding Acquired Loans [Member] | Doubtful [Member] | Commercial Business [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Doubtful	$1,953	$926	'

Allowance_for_Credit_Losses_an5

Allowance for Credit Losses and Credit Quality - Schedule of Investment in Impaired Loan (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	$35,040	'	$35,040	'	$45,342
Unpaid Principal Balance	35,375	'	35,375	'	46,501
Related Allowance	-335	'	-335	'	-1,159
Average Recorded Investment	37,121	51,207	35,859	49,381	'
Interest Income Recognized	19	44	72	172	'
Commercial Loans [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	11,017	'	11,017	'	25,018
Unpaid Principal Balance	11,059	'	11,059	'	25,877
Related Allowance	-42	'	-42	'	-859
Average Recorded Investment	12,359	33,035	12,171	30,517	'
Interest Income Recognized	19	44	50	145	'
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Real Estate [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	5,146	'	5,146	'	8,567
Unpaid Principal Balance	5,146	'	5,146	'	8,567
Related Allowance	'	'	'	'	'
Average Recorded Investment	5,228	21,452	5,178	22,871	'
Interest Income Recognized	6	24	14	63	'
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Business [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	4,291	'	4,291	'	13,256
Unpaid Principal Balance	4,291	'	4,291	'	13,256
Related Allowance	'	'	'	'	'
Average Recorded Investment	5,128	10,942	5,006	6,891	'
Interest Income Recognized	9	17	22	73	'
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Home Equity [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	248	'	248	'	258
Unpaid Principal Balance	248	'	248	'	258
Related Allowance	'	'	'	'	'
Average Recorded Investment	252	'	250	'	'
Interest Income Recognized	'	'	'	'	'
Commercial Loans [Member] | With An Allowance Recorded [Member] | Real Estate [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	905	'	905	'	1,268
Unpaid Principal Balance	912	'	912	'	1,284
Related Allowance	-7	'	-7	'	-16
Average Recorded Investment	925	194	926	306	'
Interest Income Recognized	'	'	1	1	'
Commercial Loans [Member] | With An Allowance Recorded [Member] | Business [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	675	'	675	'	1,927
Unpaid Principal Balance	710	'	710	'	2,770
Related Allowance	-35	'	-35	'	-843
Average Recorded Investment	1,078	447	1,061	449	'
Interest Income Recognized	4	3	13	8	'
Mortgage Loans [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	13,459	'	13,459	'	11,408
Unpaid Principal Balance	13,684	'	13,684	'	11,645
Related Allowance	-225	'	-225	'	-237
Average Recorded Investment	14,050	8,613	13,258	8,913	'
Interest Income Recognized	'	'	6	13	'
Mortgage Loans [Member] | With An Allowance Recorded [Member] | Residential Prime [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	10,362	'	10,362	'	9,791
Unpaid Principal Balance	10,573	'	10,573	'	10,019
Related Allowance	-211	'	-211	'	-228
Average Recorded Investment	10,911	8,613	10,131	8,913	'
Interest Income Recognized	'	'	6	13	'
Mortgage Loans [Member] | With An Allowance Recorded [Member] | Residential Subprime [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	3,097	'	3,097	'	1,617
Unpaid Principal Balance	3,111	'	3,111	'	1,626
Related Allowance	-14	'	-14	'	-9
Average Recorded Investment	3,139	'	3,127	'	'
Interest Income Recognized	'	'	'	'	'
Consumer Loans [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	10,564	'	10,564	'	8,916
Unpaid Principal Balance	10,632	'	10,632	'	8,979
Related Allowance	-68	'	-68	'	-63
Average Recorded Investment	10,712	9,559	10,430	9,951	'
Interest Income Recognized	'	'	16	14	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Home Equity [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	7,663	'	7,663	'	6,506
Unpaid Principal Balance	7,701	'	7,701	'	6,550
Related Allowance	-38	'	-38	'	-44
Average Recorded Investment	7,825	7,356	7,749	7,541	'
Interest Income Recognized	'	'	5	7	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Indirect Automobile [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	1,185	'	1,185	'	1,267
Unpaid Principal Balance	1,192	'	1,192	'	1,275
Related Allowance	-7	'	-7	'	-8
Average Recorded Investment	1,310	1,228	1,300	1,386	'
Interest Income Recognized	'	'	6	6	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Credit Card [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	931	'	931	'	404
Unpaid Principal Balance	949	'	949	'	411
Related Allowance	-18	'	-18	'	-7
Average Recorded Investment	750	448	560	427	'
Interest Income Recognized	'	'	'	'	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Consumer - Other [Member]	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'
Recorded Investment	537	'	537	'	481
Unpaid Principal Balance	542	'	542	'	485
Related Allowance	-5	'	-5	'	-4
Average Recorded Investment	575	527	571	597	'
Interest Income Recognized	'	'	$5	$1	'

Loss_Sharing_Agreements_and_FD2

Loss Sharing Agreements and FDIC Loss Share Receivable - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
			Business
Receivables [Abstract]	'	'	'	'	'
Percentage of covered loan and foreclosed real estate losses	'	'	80.00%	'	'
Losses that exceed contractual thresholds	95.00%	'	95.00%	'	'
Number of acquisitions	'	'	4	'	'
Recovery period for covered assets	'	'	'3 years	'	'
Liability for reserve for amount of consideration	$800,000	'	$800,000	'	$800,000
FDIC loss share receivables	120,500,000	'	120,500,000	'	'
Valuation allowance against indemnification assets	$800,000	$31,800,000	($804,000)	($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			6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013
FDIC Loss Share Receivable [Line Items]	'	'	'	'	'
Balance at beginning of period	'	'	'	$162,312	'
Change due to (reversal of) loan loss provision recorded on FDIC covered loans	'	'	'	-3,598	-55,085
Amortization	-17,009	-18,130	'	-36,273	-45,831
Impairment	-800	'	-31,800	804	31,813
Balance at end of period	120,532	'	'	120,532	'
FDIC Loss Share Receivables [Member]	'	'	'	'	'
FDIC Loss Share Receivable [Line Items]	'	'	'	'	'
Balance at beginning of period	'	'	423,069	162,312	423,069
Change due to (reversal of) loan loss provision recorded on FDIC covered loans	'	'	'	-3,598	-55,085
Amortization	'	'	'	-36,273	-45,831
Submission of reimbursable losses to (recoveries payable to) the FDIC	'	'	'	2,215	-42,043
Impairment	'	'	'	-804	-31,813
Changes due to a change in cash flow assumptions on OREO and other changes	'	'	'	-3,320	-7,257
Balance at end of period	$120,532	$241,040	'	$120,532	$241,040

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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Participating Mortgage Loans [Line Items]	'	'	'	'
Balance at beginning of period	'	'	$128,442	'
Originations and purchases	'	'	-760,658	-1,207,676
Sales, net of gains	'	'	-730,129	-1,350,910
Balance at end of period	178,380	'	178,380	'
Gains on sales	'	'	24,397	37,790
Total mortgage income	17,957	17,708	28,089	36,639
Mortgage Loans Held for Sale [Member]	'	'	'	'
Participating Mortgage Loans [Line Items]	'	'	'	'
Balance at beginning of period	'	'	128,442	267,475
Originations and purchases	'	'	760,658	1,207,676
Sales, net of gains	'	'	-705,732	-1,313,120
Other	'	'	-4,988	'
Balance at end of period	178,380	162,031	178,380	162,031
Mortgage Income [Member]	'	'	'	'
Participating Mortgage Loans [Line Items]	'	'	'	'
Fair value changes of derivatives and mortgage loans held for sale, net	'	'	3,383	-1,431
Gains on sales	'	'	24,397	37,790
Servicing and other income, net	'	'	309	280
Total mortgage income	'	'	$28,089	$36,639

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 $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Acquired Indefinite-lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	$52,380	$46,754
Accumulated Amortization	-34,002	-31,415
Net Carrying Amount	18,378	15,339
Mortgage Servicing Rights [Member]	'	'
Acquired Indefinite-lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	2,484	2,146
Accumulated Amortization	-887	-638
Net Carrying Amount	$1,597	$1,508

Goodwill_and_Other_Acquired_In2

Goodwill and Other Acquired Intangible Assets - Schedule of Carrying Amount of Goodwill (Detail) (USD $)	6 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jan. 17, 2014
Goodwill And Other Intangibles [Line Items]	'	'	'
Beginning Balance	$401,872	$401,872	$8,400
Goodwill acquired during the period	122,282	0	'
Ending Balance	524,154	401,872	8,400
IBERIABANK [Member]	'	'	'
Goodwill And Other Intangibles [Line Items]	'	'	'
Beginning Balance	373,905	373,905	'
Goodwill acquired during the period	121,906	0	'
Ending Balance	495,811	373,905	'
IMC [Member]	'	'	'
Goodwill And Other Intangibles [Line Items]	'	'	'
Beginning Balance	23,178	23,178	'
Goodwill acquired during the period	0	0	'
Ending Balance	23,178	23,178	'
LTC [Member]	'	'	'
Goodwill And Other Intangibles [Line Items]	'	'	'
Beginning Balance	4,789	4,789	'
Goodwill acquired during the period	376	0	'
Ending Balance	$5,165	$4,789	'

Goodwill_and_Other_Acquired_In3

Goodwill and Other Acquired Intangible Assets - Additional Information (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
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 $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	$52,380	$46,754
Accumulated Amortization	-34,002	-31,415
Net Carrying Amount	18,378	15,339
Core Deposit Intangibles [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	50,564	45,406
Accumulated Amortization	-33,135	-30,784
Net Carrying Amount	17,429	14,622
Customer Relationship Intangible Asset [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	1,398	1,348
Accumulated Amortization	-780	-631
Net Carrying Amount	618	717
Non-compete Agreement [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	163	'
Accumulated Amortization	-25	'
Net Carrying Amount	138	'
Other Intangible Assets [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	255	'
Accumulated Amortization	-62	'
Net Carrying Amount	$193	'

Other_Real_Estate_Owned_Schedu

Other Real Estate Owned - Schedule of Other Real Estate Owned Segregated into Non-Covered and Covered Properties (Detail) (USD $)	Jun. 30, 2014	Jun. 30, 2013
In Thousands, unless otherwise specified
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	$64,706	$88,546
Real estate acquired for development or resale	18,586	9,206
Other foreclosed property	1,187	1,421
Total other real estate owned and foreclosed property	84,479	99,173
Non-covered Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	25,135	28,072
Real estate acquired for development or resale	18,586	9,206
Other foreclosed property	216	93
Total other real estate owned and foreclosed property	43,937	37,371
Covered Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	39,571	60,474
Real estate acquired for development or resale	'	'
Other foreclosed property	971	1,328
Total other real estate owned and foreclosed property	$40,542	$61,802

Derivative_Instruments_and_Oth2

Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	$872,542	$868,604
Derivative Liability, Notional Amount	1,078,957	624,455
Other Assets [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	40,291	30,076
Other Liabilities [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	37,568	26,735
Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	872,542	868,604
Derivative Liability, Notional Amount	1,078,957	624,455
Not Designated as Hedging Instruments [Member] | Other Assets [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	40,291	30,076
Not Designated as Hedging Instruments [Member] | Other Liabilities [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	37,568	26,735
Not Designated as Hedging Instruments [Member] | Interest Rate Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	493,924	380,303
Derivative Liability, Notional Amount	493,924	380,303
Not Designated as Hedging Instruments [Member] | Interest Rate Contracts [Member] | Other Assets [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	14,653	10,621
Not Designated as Hedging Instruments [Member] | Interest Rate Contracts [Member] | Other Liabilities [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	14,653	10,620
Not Designated as Hedging Instruments [Member] | Forward Sales Contracts [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	3,123	192,876
Derivative Liability, Notional Amount	384,907	45,091
Not Designated as Hedging Instruments [Member] | Forward Sales Contracts [Member] | Other Assets [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	2,414	1,468
Not Designated as Hedging Instruments [Member] | Forward Sales Contracts [Member] | Other Liabilities [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	4,163	287
Not Designated as Hedging Instruments [Member] | Written and Purchased Options [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Notional Amount	375,495	295,425
Derivative Liability, Notional Amount	200,126	199,061
Not Designated as Hedging Instruments [Member] | Written and Purchased Options [Member] | Other Assets [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Asset, Fair Value	23,224	17,987
Not Designated as Hedging Instruments [Member] | Written and Purchased Options [Member] | Other Liabilities [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative Liability, Fair Value	$18,752	$15,828

Derivative_Instruments_and_Oth3

Derivative Instruments and Other Hedging Activities - Additional Information (Detail) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'	'
Cash as collateral for derivative transactions	$8.70	$5
Fair value of derivatives	$0.30	'

Derivative_Instruments_and_Oth4

Derivative Instruments and Other Hedging Activities - Reconciliation of Gross Amounts in Consolidated Balance Sheets (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	$33,298	$26,422
Derivative liabilities subject to master netting arrangements, Gross Amounts	14,653	10,620
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	33,298	26,422
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	10,593	5,201
Derivatives [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	'	'
Collateral [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	-4,060	-5,419
Interest Rate Contracts [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts	0	0
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	0	0
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	14,653	10,621
Derivative liabilities subject to master netting arrangements, Gross Amounts	14,653	10,620
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	14,653	10,621
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	10,593	5,201
Interest Rate Contracts [Member] | Derivatives [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	'	'
Interest Rate Contracts [Member] | Derivatives [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	'	'
Interest Rate Contracts [Member] | Collateral [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	0	'
Interest Rate Contracts [Member] | Collateral [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	-4,060	-5,419
Written and Purchased Options [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	18,645	15,801
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	18,645	15,801
Written and Purchased Options [Member] | Derivatives [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Written and Purchased Options [Member] | Collateral [Member]	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'

Derivative_Instruments_and_Oth5

Derivative Instruments and Other Hedging Activities - Effect of Hedging Instruments on Consolidated Financial Statements (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 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)	'	32	'	-392
Amount of Gain (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	'	'	'	209
Not Designated as Hedging Instruments [Member]	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	-37	3,976	-671	2,366
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	1,027	471	1,565	688
Not Designated as Hedging Instruments [Member] | Forward Sales Contracts [Member] | Mortgage Income [Member]	'	'	'	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	-859	8,320	-3,864	5,408
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	-205	-4,815	1,628	-3,730
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)	'	32	'	-392
Amount of Gain (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)	'	'	'	'

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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Equity [Abstract]	'	'	'	'
Unrealized holding gains/losses arising during the period, Before-Tax Amount	$16,730	($42,303)	$32,618	($44,297)
Less: reclassification adjustment for losses/gains included in net income, Before-Tax Amount	-8	66	-27	-2,261
Net unrealized losses/gains, Before-Tax Amount	16,722	-42,237	32,591	-46,558
Change in fair value of derivative instruments designated as cash flow hedges during the period, Before-Tax Amount	'	-1,121	'	952
Less: reclassification adjustment for gains/losses included in net income, Before-Tax Amount	'	-33	'	392
Fair value of derivative instruments designated as cash flow hedges, Before-Tax Amount	'	-1,154	'	1,344
Total other comprehensive income/loss, Before-Tax Amount	16,722	-43,391	32,591	-45,214
Unrealized holding gains/losses arising during the period, Tax Expense (Benefit)	-5,856	14,806	-11,416	15,504
Less: reclassification adjustment for losses/gain included in net income, Tax Expense (Benefit)	3	-23	9	791
Net unrealized gains/losses, Tax Expense (Benefit)	-5,853	14,783	-11,407	16,295
Change in fair value of derivative instruments designated as cash flow hedges during the period, Tax Expense (Benefit)	'	392	'	-333
Less: reclassification adjustment for gains/losses included in net income, Tax Expense (Benefit)	'	12	'	-137
Fair value of derivative instruments designated as cash flow hedges, Tax Expense (Benefit)	'	404	'	-470
Total other comprehensive income/loss, Tax Expense (Benefit)	-5,853	15,187	-11,407	15,825
Unrealized holding gains/losses arising during the period, Net-of-Tax Amount	10,874	-27,497	21,202	-28,793
Less: reclassification adjustment for gains/losses included in net income, Net-of-Tax Amount	-5	43	-18	-1,470
Net unrealized gains/losses, Net-of-Tax Amount	10,869	-27,454	21,184	-30,263
Change in fair value of derivative instruments designated as cash flow hedges during the period, Net-of-Tax Amount	'	-729	'	619
Less: reclassification adjustment for gains/losses included in net income, Net-of-Tax Amount	'	-21	'	255
Fair value of derivative instruments designated as cash flow hedges, Net-of-Tax Amount	'	-750	'	874
Other comprehensive income (loss), net of tax	$10,869	($28,204)	$21,184	($29,389)

Capital_Requirements_and_Other2

Capital Requirements and Other Regulatory Matters - Actual Capital Amounts and Ratios (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Consolidated [Member]	'	'
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Tier 1 Leverage, Minimum Amount	$539,674	$507,760
Tier 1 risk-based capital, Minimum Amount	481,972	426,002
Total risk-based capital, Minimum Amount	963,943	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	1,353,676	1,231,886
Tier 1 risk-based capital, Actual Amount	1,353,676	1,231,886
Total risk-based capital, Actual Amount	1,498,467	1,365,280
Tier 1 Leverage, Actual Ratio	10.03%	9.70%
Tier 1 risk-based capital, Actual Ratio	11.23%	11.57%
Total risk-based capital, Actual Ratio	12.44%	12.82%
IBERIABANK [Member]	'	'
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Tier 1 Leverage, Minimum Amount	537,718	505,723
Tier 1 risk-based capital, Minimum Amount	480,157	424,578
Total risk-based capital, Minimum Amount	960,315	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	672,147	632,154
Tier 1 risk-based capital, Well Capitalized Amount	720,236	636,868
Total risk-based capital, Well Capitalized Amount	1,200,393	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	1,196,630	1,069,783
Tier 1 risk-based capital, Actual Amount	1,196,630	1,069,783
Total risk-based capital, Actual Amount	$1,341,421	$1,202,738
Tier 1 Leverage, Actual Ratio	8.90%	8.46%
Tier 1 risk-based capital, Actual Ratio	9.97%	10.08%
Total risk-based capital, Actual Ratio	11.17%	11.33%

ShareBased_Compensation_Additi

Share-Based Compensation - Additional Information (Detail) (USD $)	6 Months Ended							3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Mar. 31, 2014
			Maximum [Member]	Minimum [Member]	Employee Stock Option [Member]	Restricted Stock [Member]	Restricted Stock [Member]	Phantom Stock Awards [Member]
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	1,033,625	'	'	'	'	'	'	'
Minimum vesting period (in years)	'1 year 6 months	'	'	'	'	'	'	'5 years
Maximum vesting period (in years)	'7 years	'	'	'	'	'	'	'7 years
Excess tax benefits as financing cash inflows	945,000	417,000	'	'	'	'	'	'
Net cash proceeds from exercise of stock options	9,240,000	4,238,000	'	'	'	'	'	'
Unearned share-based compensation associated with awards	'	'	'	'	4,200,000	24,800,000	25,400,000	'
Unrecognized compensation cost related to stock options expected to be recognized over a weighted-average period	'	'	'	'	'5 years 3 months 18 days	'	'	'
Aggregate intrinsic value of shares underlying outstanding stock options	13,300,000	'	'	'	'	'	'	'
Aggregate intrinsic value of shares underlying exercisable stock options	8,900,000	'	'	'	'	'	'	'
Total intrinsic value of options exercised	$3,500,000	$1,600,000	'	'	'	'	'	'
Unearned compensation vesting period (in years)	'	'	'7 years	'3 years	'	'	'	'

ShareBased_Compensation_Compen

Share-Based Compensation - Compensation Expense Included in Non-Interest Expense and Related Income Tax Benefits (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'	'
Compensation expense related to stock options	$518	$533	$1,037	$1,066
Income tax benefit related to stock options	$182	$187	$363	$374
Impact on basic earnings per share	$0.01	$0.01	$0.02	$0.02
Impact on diluted earnings per share	$0.01	$0.01	$0.02	$0.02

ShareBased_Compensation_Estima

Share-Based Compensation - Estimate Fair Value of Share-Based Awards with Weighted-Average Assumptions (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 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	$21.23	$15.37

ShareBased_Compensation_Activi

Share-Based Compensation - Activity Related to Stock Options (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 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	75,956	75,722
Number of shares, Outstanding options, Exercised	-196,734	-116,324
Number of shares, Outstanding options, Forfeited or expired	-8,577	-31,270
Number of shares, Outstanding options, Ending balance	943,474	1,164,203
Number of shares, Exercisable options	614,361	774,446
Weighted Average Exercise Price, Outstanding options, Beginning balance	$53.47	$51.48
Weighted Average Exercise Price, Outstanding options, Granted	$65.23	$52.36
Weighted Average Exercise Price, Outstanding options, Exercised	$47.98	$36.43
Weighted Average Exercise Price, Outstanding options, Forfeited or expired	$64.82	$55.39
Weighted Average Exercise Price, Outstanding options, Ending balance	$55.46	$52.94
Weighted Average Exercise Price, Exercisable options	$55.37	$52.73
Weighted Average Remaining Contract Life, Outstanding options	'5 years 3 months 18 days	'4 years 10 months 24 days
Weighted Average Remaining Contract Life, Exercisable options	'3 years 9 months 18 days	'3 years 4 months 24 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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Restricted Stock [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to restricted stock	$2,569	$2,216	$4,885	$4,195

ShareBased_Compensation_Unvest

Share-Based Compensation - Unvested Restricted Stock Award Activity (Detail)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Balance at beginning of period	523,756	538,202
Granted	141,377	164,151
Forfeited	-9,631	-26,866
Earned and issued	-140,616	-123,328
Balance at end of period	514,886	552,159

ShareBased_Compensation_Compen2

Share-Based Compensation - Compensation Expense of Phantom Stock (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to stock options	$518	$533	$1,037	$1,066
Phantom Stock Awards [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to stock options	$1,022	$1,112	$3,073	$1,811

ShareBased_Compensation_Schedu

Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Number of share equivalents, Beginning Balance	417,238	318,729
Number of share equivalents, Granted	105,043	163,498
Number of share equivalents, Forfeited share equivalents	-12,656	-15,121
Number of share equivalents, Vested share equivalents	-60,970	-40,185
Number of share equivalents, Ending Balance	448,655	426,921
Dividend equivalents, Beginning Balance	22,351	16,035
Dividend equivalents, Granted	4,626	5,899
Dividend equivalents, Forfeited share equivalents	-1,424	-641
Dividend equivalents, Vested share equivalents	-5,724	-2,876
Dividend equivalents, Ending Balance	19,829	18,417
Total share equivalents, Beginning Balance	439,589	334,764
Total share equivalents, Granted	109,669	169,397
Total share equivalents, Forfeited share equivalents	-14,080	-15,762
Total share equivalents, Vested share equivalents	-66,694	-43,061
Total share equivalents, Ending Balance	468,484	445,338
Value of share equivalents, Beginning Balance	$27,628,000	$16,444,000
Value of share equivalents, Granted	7,588,000	9,081,000
Value of share equivalents, Forfeited share equivalents	-974,000	-845,000
Value of share equivalents, Vested share equivalents	-4,451,000	-2,156,000
Value of share equivalents, Ending Balance	$32,414,000	$23,875,000

ShareBased_Compensation_Schedu1

Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Parenthetical) (Detail) (USD $)	Jun. 30, 2014	Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Market price of Company's stock	$69.19	$53.61

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'	'
Fair value of guarantees under commercial and standby letters of credit	$1.20	$1.10

Commitments_and_Contingencies_2

Commitments and Contingencies - Summary of Financial Instruments Outstanding (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Loss Contingencies [Line Items]	'	'	'	'
Reserve for unfunded lending commitments	$11,260	$11,147	$10,342	$0
Credit Risk Contract [Member]	'	'	'	'
Loss Contingencies [Line Items]	'	'	'	'
Commitments to grant loans	334,186	221,627	'	'
Unfunded commitments under lines of credit	3,534,055	3,326,448	'	'
Commercial and standby letters of credit	124,870	105,026	'	'
Reserve for unfunded lending commitments	$11,260	$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 $)	6 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'	'
Mortgage loans held for sale, at fair value, Aggregate Fair Value	$178,380	$97,273
Mortgage loans held for sale, at fair value, Aggregate Unpaid Principal	170,527	96,875
Mortgage loans held for sale, at fair value, Aggregate Fair Value Less Unpaid Principal	$7,853	$398

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
	Branch	Branch	Branch
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Total mortgage income in the consolidated statement of comprehensive income	$3,600,000	$0	$5,600,000	$0	'
Impaired non-covered loans with an outstanding balance	2,200,000	'	2,200,000	'	4,100,000
Reserve in allowance for credit losses	200,000	'	200,000	'	1,000,000
Company announced plans to close branches	'	10	'	'	'
Number of branches closed	9	'	9	'	'
Book value of company owned branches after impairment losses	3,900,000	'	3,900,000	'	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	15,100,000	'	15,100,000	'	'
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 $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available for sale securities, Assets	$2,008,953	$1,936,797
Mortgage loans held for sale, Assets	178,380	97,273
Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available for sale securities, Assets	2,008,953	1,936,797
Mortgage loans held for sale, Assets	178,380	97,273
Derivative instruments, Assets	40,291	30,076
Total, Assets	2,227,624	2,064,146
Derivative instruments, Liabilities	37,568	26,735
Total, Liabilities	37,568	26,735
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	'	15,496
Mortgage loans held for sale, Assets	'	'
Derivative instruments, Assets	'	'
Total, Assets	'	15,496
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	2,008,953	1,921,301
Mortgage loans held for sale, Assets	178,380	97,273
Derivative instruments, Assets	40,291	30,076
Total, Assets	2,227,624	2,048,650
Derivative instruments, Liabilities	37,568	26,735
Total, Liabilities	37,568	26,735
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 $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014
Other Comprehensive 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)	'
Change in unrealized gains (losses) relating to assets still held at June 30, 2014	21,184
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)	3,410
Change in unrealized gains (losses) relating to assets still held at June 30, 2014	'

Fair_Value_Measurements_Financ1

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Mortgage loans held for sale, Assets	$178,380	$97,273
Fair Value, Measurements, Nonrecurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Loans, Assets	2,045	3,070
Mortgage loans held for sale, Assets	200	11,876
OREO, Assets	10,407	14,598
Total, Assets	12,452	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	2,045	3,070
Mortgage loans held for sale, Assets	200	11,876
OREO, Assets	10,407	14,598
Total, Assets	12,452	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)	6 Months Ended
	Mar. 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 $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financial Assets	'	'	'	'
Cash and cash equivalents	$668,570	$391,396	$347,565	$970,977
Loans and loans held for sale	11,076,907	'	9,065,068	'
FDIC loss share receivable	120,532	162,312	'	'
Financial Liabilities	'	'	'	'
Deposits	11,981,183	10,737,000	10,641,718	'
Short-term borrowings	1,034,741	680,344	'	'
Long-term debt	365,747	280,699	'	'
Carrying Amount [Member]	'	'	'	'
Financial Assets	'	'	'	'
Cash and cash equivalents	668,570	391,396	'	'
Investment securities	2,141,198	2,090,906	'	'
Loans and loans held for sale	11,076,907	9,620,461	'	'
FDIC loss share receivable	120,532	162,312	'	'
Derivative instruments	40,291	30,076	'	'
Accrued interest receivable	36,043	32,143	'	'
Financial Liabilities	'	'	'	'
Deposits	11,981,183	10,737,000	'	'
Short-term borrowings	1,034,741	680,344	'	'
Long-term debt	365,747	280,699	'	'
Derivative instruments	37,568	26,735	'	'
Accrued interest payable	7,552	6,102	'	'
Fair Value [Member]	'	'	'	'
Financial Assets	'	'	'	'
Cash and cash equivalents	668,570	391,396	'	'
Investment securities	2,143,016	2,089,363	'	'
Loans and loans held for sale	11,006,250	9,724,432	'	'
FDIC loss share receivable	21,965	21,918	'	'
Derivative instruments	40,291	30,076	'	'
Accrued interest receivable	36,043	32,143	'	'
Financial Liabilities	'	'	'	'
Deposits	11,749,790	10,226,573	'	'
Short-term borrowings	1,034,741	680,344	'	'
Long-term debt	336,326	235,503	'	'
Derivative instruments	37,568	26,735	'	'
Accrued interest payable	$7,552	$6,102	'	'

Business_Segments_Additional_I

Business Segments - Additional Information (Detail)	6 Months Ended
	Jun. 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		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	$119,220	$108,177	$233,451	$214,593	'
Interest expense	10,241	11,695	20,065	25,239	'
Net interest income	108,979	96,482	213,386	189,354	'
(Reversal of) Provision for loan losses	4,748	1,807	6,851	-1,569	'
Mortgage income	17,957	17,708	28,089	36,639	'
Title income	5,262	5,696	9,429	10,717	'
Other non-interest income	24,744	19,085	46,126	39,624	'
Core deposit intangible amortization	1,185	1,125	2,350	2,250	'
Allocated expenses	'	'	'	'	'
Other non-interest expenses	126,190	116,236	232,452	260,009	'
Income before income tax expense	24,819	19,803	55,377	15,644	'
Income tax expense (benefit)	6,271	4,213	14,434	-663	'
Net income (loss)	18,548	15,590	40,943	16,307	'
Total loans and loans held for sale	11,076,907	9,065,068	11,076,907	9,065,068	'
Total assets	15,325,042	12,823,503	15,325,042	12,823,503	13,365,550
Total deposits	11,981,183	10,641,718	11,981,183	10,641,718	10,737,000
Average assets	14,041,562	12,881,551	13,704,121	12,977,745	'
IBERIABANK [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	117,544	106,668	230,692	211,595	'
Interest expense	9,764	11,106	19,367	24,055	'
Net interest income	107,780	95,562	211,325	187,540	'
(Reversal of) Provision for loan losses	4,764	1,807	6,860	-1,548	'
Mortgage income	88	-2	85	-3	'
Title income	'	'	'	'	'
Other non-interest income	24,757	19,084	46,150	39,628	'
Core deposit intangible amortization	1,185	1,125	2,350	2,250	'
Allocated expenses	-3,595	-882	-6,725	-1,745	'
Other non-interest expenses	110,355	97,435	202,429	224,476	'
Income before income tax expense	19,916	15,159	52,646	3,732	'
Income tax expense (benefit)	4,339	2,389	13,343	-5,343	'
Net income (loss)	15,577	12,770	39,303	9,075	'
Total loans and loans held for sale	10,875,895	8,889,618	10,875,895	8,889,618	'
Total assets	15,067,545	12,592,635	15,067,545	12,592,635	'
Total deposits	11,976,403	10,638,853	11,976,403	10,638,853	'
Average assets	13,832,987	12,650,402	13,517,696	12,740,709	'
IMC [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	1,676	1,495	2,758	2,969	'
Interest expense	477	589	698	1,184	'
Net interest income	1,199	906	2,060	1,785	'
(Reversal of) Provision for loan losses	-16	'	-9	-21	'
Mortgage income	17,869	17,710	28,004	36,642	'
Title income	'	'	'	'	'
Other non-interest income	-13	1	-24	-4	'
Core deposit intangible amortization	'	'	'	'	'
Allocated expenses	2,544	649	4,735	1,280	'
Other non-interest expenses	11,635	14,469	21,934	26,926	'
Income before income tax expense	4,892	3,499	3,380	10,238	'
Income tax expense (benefit)	1,923	1,374	1,335	4,019	'
Net income (loss)	2,969	2,125	2,045	6,219	'
Total loans and loans held for sale	201,012	175,449	201,012	175,449	'
Total assets	232,403	205,069	232,403	205,069	'
Total deposits	4,780	2,865	4,780	2,865	'
Average assets	183,838	205,677	161,571	211,923	'
LTC [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Interest income	'	14	1	29	'
Interest expense	'	'	'	'	'
Net interest income	'	14	1	29	'
(Reversal of) Provision for loan losses	'	'	'	'	'
Mortgage income	'	'	'	'	'
Title income	5,262	5,696	9,429	10,717	'
Other non-interest income	'	'	'	'	'
Core deposit intangible amortization	'	'	'	'	'
Allocated expenses	1,051	233	1,990	465	'
Other non-interest expenses	4,200	4,332	8,089	8,607	'
Income before income tax expense	11	1,145	-649	1,674	'
Income tax expense (benefit)	9	450	-244	661	'
Net income (loss)	2	695	-405	1,013	'
Total loans and loans held for sale	'	'	'	'	'
Total assets	25,094	25,799	25,094	25,799	'
Total deposits	'	'	'	'	'
Average assets	$24,737	$25,472	$24,854	$25,113	'