Iberiabank (IBKC) 10-Q 12 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 31, 2013
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
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	'	29,775,721

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Assets	'	'
Cash and due from banks	$260,742	$248,214
Interest-bearing deposits in banks	292,706	722,763
Total cash and cash equivalents	553,448	970,977
Securities available for sale, at fair value	1,964,389	1,745,004
Securities held to maturity, fair values of $155,310 and $211,498, respectively	155,678	205,062
Mortgage loans held for sale	108,285	267,475
Loans covered by loss share agreements	807,002	1,092,756
Non-covered loans, net of unearned income	8,236,035	7,405,824
Total loans, net of unearned income	9,043,037	8,498,580
Allowance for credit losses	-148,545	-251,603
Loans, net	8,894,492	8,246,977
FDIC loss share receivables	204,885	423,069
Premises and equipment, net	289,157	303,523
Goodwill	401,872	401,872
Other assets	572,871	565,719
Total Assets	13,145,077	13,129,678
Liabilities	'	'
Noninterest-bearing	2,529,296	1,967,662
Interest-bearing	8,421,468	8,780,615
Total deposits	10,950,764	10,748,277
Short-term borrowings	258,850	303,045
Long-term debt	281,101	423,377
Other liabilities	129,094	125,111
Total Liabilities	11,619,809	11,599,810
Shareholders' Equity	'	'
Common stock, $1 par value - 50,000,000 shares authorized; 31,917,385 shares issued	31,917	31,917
Additional paid-in capital	1,175,197	1,176,180
Retained earnings	420,664	411,472
Accumulated other comprehensive income (loss)	-1,317	24,477
Treasury stock at cost - 2,182,926 and 2,427,640 shares, respectively	-101,193	-114,178
Total Shareholders' Equity	1,525,268	1,529,868
Total Liabilities and Shareholders' Equity	$13,145,077	$13,129,678

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Securities held to maturity, fair values	$155,310	$211,498
Common stock, par value	$1	$1
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	31,917,385	31,917,385
Treasury stock, shares	2,182,926	2,427,640

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest and Dividend Income	'	'	'	'
Loans, including fees	$120,035	$133,397	$358,344	$382,212
Mortgage loans held for sale, including fees	1,289	1,466	3,965	3,747
Investment securities:	'	'	'	'
Taxable interest	7,837	8,133	22,241	26,745
Tax-exempt interest	1,649	1,809	5,082	5,589
Amortization of FDIC loss share receivable	-22,875	-33,488	-68,707	-89,899
Other	577	634	2,180	2,028
Total interest and dividend income	108,512	111,951	323,105	330,422
Interest Expense	'	'	'	'
NOW and MMDA	4,441	5,863	14,462	17,942
Savings	71	154	238	459
Time deposits	4,012	5,530	13,038	19,755
Short-term borrowings	104	197	365	507
Long-term debt	2,432	3,481	8,196	9,999
Total interest expense	11,060	15,225	36,299	48,662
Net interest income	97,452	96,726	286,806	281,760
Provision for loan losses	2,014	4,053	445	15,805
Net interest income after provision for loan losses	95,438	92,673	286,361	265,955
Noninterest Income	'	'	'	'
Service charges on deposit accounts	7,512	6,952	21,415	19,557
Mortgage income	15,202	23,215	51,841	55,118
Title revenue	5,482	5,623	16,199	15,495
ATM/debit card fee income	2,476	2,377	7,017	6,566
Income from bank owned life insurance	908	916	2,747	2,771
Gain (loss) on sale of available for sale investments	-3	41	2,259	3,743
Derivative losses reclassified from other comprehensive income	'	-409	-392	-1,195
Broker commissions	3,950	3,092	11,347	9,254
Other income	7,736	4,746	17,809	14,334
Total noninterest income	43,263	46,553	130,242	125,643
Noninterest Expense	'	'	'	'
Salaries and employee benefits	59,234	59,938	185,578	172,878
Net occupancy and equipment	14,572	13,869	44,050	39,496
Impairment of FDIC loss share receivables and other long-lived assets	1,319	'	37,750	2,743
Franchise and shares tax	911	1,023	2,986	3,664
Communication and delivery	2,899	3,152	9,286	9,424
Marketing and business development	2,350	2,189	8,486	7,964
Data processing	4,837	4,931	13,093	11,537
Printing, stationery and supplies	581	848	2,004	2,523
Amortization of acquisition intangibles	1,179	1,287	3,543	3,865
Professional services	4,156	5,947	13,675	15,665
Costs of OREO property, net	-359	270	980	4,453
Credit and other loan related expense	5,248	4,846	13,155	13,709
Insurance	3,125	2,615	8,408	7,745
Travel and entertainment	1,912	2,398	6,199	7,158
Other expenses	6,188	6,535	21,217	15,920
Total noninterest expense	108,152	109,848	370,410	318,744
Income before income tax expense	30,549	29,378	46,193	72,854
Income tax expense	7,357	8,144	6,694	19,667
Net Income	23,192	21,234	39,499	53,187
Income Available to Common Shareholders - Basic	23,192	21,234	39,499	53,187
Earnings Allocated to Unvested Restricted Stock	-425	-406	-744	-1,007
Earnings Available to Common Shareholders - Diluted	22,767	20,828	38,755	52,180
Earnings per common share - Basic	$0.78	$0.73	$1.34	$1.81
Earnings per common share - Diluted	$0.78	$0.73	$1.33	$1.81
Cash dividends declared per common share	$0.34	$0.34	$1.02	$1.02
Unrealized gains on securities:	'	'	'	'
Unrealized holding gains (losses) arising during the period	5,528	6,099	-38,769	8,236
Less: reclassification adjustment for gains (losses) included in net income	3	-41	-2,259	-3,743
Unrealized (loss) gain on securities, before tax	5,531	6,058	-41,028	4,493
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	'	800	952	-1,882
Less: reclassification adjustment for losses (gains) included in net income	'	409	392	1,195
Fair value of derivative instruments designated as cash flow hedges, before tax	'	1,209	1,344	-687
Other comprehensive income (loss), before tax	5,531	7,267	-39,684	3,806
Income tax expense (benefit) related to items of other comprehensive income (loss)	1,936	2,543	-13,890	1,332
Other comprehensive income (loss), net of tax	3,595	4,724	-25,794	2,474
Comprehensive income	$26,787	$25,958	$13,705	$55,661

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, 2011	$1,482,661	$31,163	$1,135,880	$375,184	$24,457	($84,023)
Beginning balance, shares at Dec. 31, 2011	'	31,163,070	'	'	'	1,789,165
Net income	53,187	'	'	53,187	'	'
Other comprehensive income (loss)	2,474	'	'	'	2,474	'
Cash dividends declared, $1.02 per share	-30,080	'	'	-30,080	'	'
Reissuance of treasury stock under incentive plan, net of shares surrendered in payment, including tax benefit	836	'	17	'	'	819
Reissuance of treasury stock under incentive plan, shares	'	'	'	'	'	-181,836
Common stock issued for acquisitions	39,203	754	38,449	'	'	'
Common stock issued for acquisitions, shares	'	754,334	'	'	'	'
Common stock issued for recognition and retention plan	'	'	-7,776	'	'	7,776
Share-based compensation cost	7,306	'	7,306	'	'	'
Treasury stock acquired at cost	-40,433	'	'	'	'	-40,433
Treasury stock acquired at cost, Shares	'	'	'	'	'	853,308
Ending balance at Sep. 30, 2012	1,515,154	31,917	1,173,876	398,291	26,931	-115,861
Ending balance, shares at Sep. 30, 2012	'	31,917,404	'	'	'	2,460,637
Beginning balance at Dec. 31, 2012	1,529,868	31,917	1,176,180	411,472	24,477	-114,178
Beginning balance, shares at Dec. 31, 2012	'	31,917,385	'	'	'	2,427,640
Net income	39,499	'	'	39,499	'	'
Other comprehensive income (loss)	-25,794	'	'	'	-25,794	'
Cash dividends declared, $1.02 per share	-30,307	'	'	-30,307	'	'
Reissuance of treasury stock under incentive plan, net of shares surrendered in payment, including tax benefit	4,003	'	-966	'	'	4,969
Reissuance of treasury stock under incentive plan, shares	'	'	'	'	'	-244,714
Common stock issued for recognition and retention plan	'	'	-8,016	'	'	8,016
Share-based compensation cost	7,999	'	7,999	'	'	'
Ending balance at Sep. 30, 2013	$1,525,268	$31,917	$1,175,197	$420,664	($1,317)	($101,193)
Ending balance, shares at Sep. 30, 2013	'	31,917,385	'	'	'	2,182,926

Consolidated_Statements_of_Sha1

Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash dividends declared per share	$1.02	$1.02
Retained Earnings [Member]	'	'
Cash dividends declared per share	$1.02	$1.02

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities	'	'
Net income	$39,499	$53,187
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	19,851	'
Amortization of purchase accounting adjustments, net	-1,186	'
Provision for loan losses	445	15,805
Share-based equity compensation expense	-7,999	-7,306
(Gain) loss on sale of assets	-51	'
Gain on sale of available for sale investments	-2,259	'
Gain on sale of OREO	-5,211	'
Loss on abandonment of fixed assets	4,941	'
Impairment	31,813	'
Amortization of premium/discount on investments	15,426	'
Derivative (gains) losses on swaps	-209	'
Benefit for deferred income taxes	-7,802	'
Originations of mortgage loans held for sale	-1,712,557	'
Proceeds from sales of mortgage loans held for sale	1,923,455	'
Gain on sale of mortgage loans held for sale, net	-51,709	'
Tax benefit associated with share-based payment arrangements	-495	'
(Increase) decrease in other assets	-15,759	'
Other operating activities, net	30,079	'
Net Cash Provided by Operating Activities	276,270	'
Cash Flows from Investing Activities	'	'
Proceeds from sales of securities available for sale	44,672	'
Proceeds from maturities, prepayments and calls of securities available for sale	618,059	'
Purchases of securities available for sale	-935,341	'
Proceeds from maturities, prepayments and calls of securities held to maturity	54,372	'
Purchases of securities held to maturity	-5,901	'
FDIC reimbursement of recoverable covered asset losses	56,311	'
Increase in loans receivable, net	-595,315	'
Proceeds from sale of premises and equipment	7,371	'
Purchases of premises and equipment	-12,592	'
Proceeds from disposition of real estate owned	76,150	'
Investment in new market tax credit entities	-1,696	'
Cash received in excess of cash paid for acquisition	'	'
Other investing activities, net	8,963	'
Net Cash Used in Investing Activities	-684,947	'
Cash Flows from Financing Activities	'	'
Increase in deposits, net of deposits acquired	202,959	'
Net change in short-term borrowings, net of borrowings acquired	-44,196	'
Proceeds from long-term debt	2,230	'
Repayments of long-term debt	-143,625	'
Dividends paid to shareholders	-30,223	'
Proceeds from sale of treasury stock for stock options exercised	5,441	1,541
Payments to repurchase common stock	-1,933	'
Tax benefit associated with share-based payment arrangements	495	940
Net Cash (Used in) Provided by Financing Activities	-8,852	'
Net (Decrease) Increase In Cash and Cash Equivalents	-417,529	'
Cash and Cash Equivalents at Beginning of Period	970,977	'
Cash and Cash Equivalents at End of Period	553,448	'
Supplemental Schedule of Noncash Activities	'	'
Acquisition of real estate in settlement of loans	82,383	'
Common stock issued in acquisition	'	'
Transfers of property into Other Real Estate	82,383	'
Supplemental Disclosures	'	'
Interest on deposits and borrowings	36,888	'
Income taxes, net	19,891	'
Restated [Member]	'	'
Cash Flows from Operating Activities	'	'
Net income	'	53,187
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	'	15,870
Amortization of purchase accounting adjustments, net	'	-27,896
Provision for loan losses	'	15,805
Share-based equity compensation expense	'	-7,306
(Gain) loss on sale of assets	'	144
Gain on sale of available for sale investments	'	-3,743
Gain on sale of OREO	'	-4,083
Loss on abandonment of fixed assets	'	2,743
Impairment	'	'
Amortization of premium/discount on investments	'	15,365
Derivative (gains) losses on swaps	'	1
Benefit for deferred income taxes	'	-5,264
Originations of mortgage loans held for sale	'	-1,749,121
Proceeds from sales of mortgage loans held for sale	'	1,742,830
Gain on sale of mortgage loans held for sale, net	'	-51,828
Tax benefit associated with share-based payment arrangements	'	-940
(Increase) decrease in other assets	'	9,823
Other operating activities, net	'	23,826
Net Cash Provided by Operating Activities	'	44,025
Cash Flows from Investing Activities	'	'
Proceeds from sales of securities available for sale	'	153,397
Proceeds from maturities, prepayments and calls of securities available for sale	'	739,734
Purchases of securities available for sale	'	-795,178
Proceeds from maturities, prepayments and calls of securities held to maturity	'	40,071
Purchases of securities held to maturity	'	-37,236
FDIC reimbursement of recoverable covered asset losses	'	114,564
Increase in loans receivable, net	'	-630,229
Proceeds from sale of premises and equipment	'	355
Purchases of premises and equipment	'	-22,922
Proceeds from disposition of real estate owned	'	80,282
Investment in new market tax credit entities	'	-20,000
Cash received in excess of cash paid for acquisition	'	32,425
Other investing activities, net	'	6,088
Net Cash Used in Investing Activities	'	-338,649
Cash Flows from Financing Activities	'	'
Increase in deposits, net of deposits acquired	'	339,379
Net change in short-term borrowings, net of borrowings acquired	'	126,136
Proceeds from long-term debt	'	23,449
Repayments of long-term debt	'	-74,920
Dividends paid to shareholders	'	-30,053
Proceeds from sale of treasury stock for stock options exercised	'	1,541
Payments to repurchase common stock	'	-42,078
Tax benefit associated with share-based payment arrangements	'	940
Net Cash (Used in) Provided by Financing Activities	'	344,394
Net (Decrease) Increase In Cash and Cash Equivalents	'	49,770
Cash and Cash Equivalents at Beginning of Period	'	573,296
Cash and Cash Equivalents at End of Period	'	623,066
Supplemental Schedule of Noncash Activities	'	'
Acquisition of real estate in settlement of loans	'	82,780
Common stock issued in acquisition	'	39,203
Transfers of property into Other Real Estate	'	82,780
Supplemental Disclosures	'	'
Interest on deposits and borrowings	'	49,529
Income taxes, net	'	$10,902

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2013
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, 2012.
	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, IBERIA Asset Management Inc. (“IAM”), and IBERIA CDE, LLC (“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. IB Aircraft Holdings, LLC owns a fractional share of an aircraft used by management of the Company and its subsidiaries. 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.
	SEGMENTS
	All of the Company’s banking operations are considered by management to be aggregated in one reportable operating segment. Because the overall banking operations comprise substantially all of the consolidated operations and none of the Company’s other subsidiaries, either individually or in the aggregate, meet quantitative materiality thresholds, no separate segment disclosures are presented in these consolidated financial statements. The Company has invested in its financial reporting infrastructure to report financial information associated with performance of segments. The Company anticipates reporting this information at the end of 2013.
	FDIC LOSS SHARE RECEIVABLE
	Because the FDIC reimburses the Company for losses on certain loans acquired in 2009 and 2010, indemnification assets were recorded at fair value as of the acquisition dates. The initial values of the indemnification assets were based on estimated cash flows to be received over the expected life of the acquired assets, not to exceed the term of the indemnification agreements. The loss sharing terms of the Company’s commercial and single family residential indemnification agreements are five years and ten years, respectively, from the date of acquisition.
	Because the indemnification assets are measured on the same basis as the indemnified loans, subject to contractual and collectability limitations, the indemnification assets are impacted by changes in expected cash flows on covered assets. Increases in credit losses expected to occur within the loss share term are recorded as current period increases to the allowance for credit losses and increase the amount collectible from the FDIC by the applicable loss share percentage. Decreases in credit losses expected to occur within loss share term reduce the amount collectible from the FDIC and increase the amount collectible from customers in the form of prospective accretion on loans. Increases in the portion of indemnification asset collectible from customers are amortized to income. Periodic amortization represents the amount that is expected to result in symmetrical recognition of pool-level accretion and amortization over the shorter of 1) the life of the loan or 2) the life of the shared loss agreement.
	The Company assesses the indemnification assets for collectability at the acquisition level based on three sources: 1) the FDIC, 2) OREO transactions, and 3) customers. Amounts collectible from the FDIC through loss reimbursements are comprised of losses currently expected within the loss share term. A current period impairment would be recorded to the extent that events or circumstances indicate that losses previously expected to occur within the loss share term are expected to occur subsequent to loss share termination. Amounts collectible through expected gains on the sale of OREO are written-up or impaired each period based on the best available information. Amounts collectible from customers in the form of accretion are deemed collectible to the extent that net acquisition-level yield, which primarily consists of accretion and indemnification asset amortization, are expected to remain positive over the life of the shared loss agreement. Impairment of amounts collectible from customers would be recorded as a current period charge to income, to the extent required to maintain the zero net yield floor.
	Loss assumptions used to measure the basis of the indemnified loans are consistent with the loss assumptions used to measure the indemnification assets.
	A claim receivable is established within other assets when a loss is incurred and the indemnification asset is reduced when cash is received from the FDIC.
	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
	As of September 30, 2013, the Company has $108,285,000 of conforming mortgage loans held for sale. Mortgage loans originated and held for sale are carried at the lower of cost or estimated fair value. The Company obtains quotes or bids on these loans directly from purchasing financial institutions. Mortgage loans held for sale that were recorded at estimated fair value are included in Note 16.
	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 obtainable market price, if available (Level 1) or the fair value of the collateral if the loan is collateral dependent (Level 2). Measuring the impairment of loans using the present value of expected future cash flows, discounted at the loan’s effective interest rate, is not considered a fair value measurement. Fair value of the collateral is determined by appraisals or independent valuation.
	Other real estate owned (OREO)
	Fair values of OREO at September 30, 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 $1,437,000 and $867,000 in earnings for the three months ended September 30, 2013 and 2012, respectively, and $3,993,000 and $4,900,000 for the nine months ended September 30, 2013 and 2012, respectively.
	Derivative financial instruments
	The Company may utilize interest rate swap agreements to convert a portion of its variable-rate debt to a fixed rate (cash flow hedge). The Company also enters into commitments to originate loans whereby the interest rate on the prospective loan is determined prior to funding (“rate lock commitments”). 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	9 Months Ended
	Sep. 30, 2013
Accounting Changes And Error Corrections [Abstract]	'
Recent Accounting Pronouncements	'
	NOTE 2 – RECENT ACCOUNTING PRONOUNCEMENTS
	ASU No. 2012-06
	For the quarter ended March 31, 2013, the Company adopted the provisions of ASU No. 2012-06, Business Combinations (Topic 805): Subsequent Accounting for an Indemnification Asset Recognized at the Acquisition Date as a Result of a Government-Assisted Acquisition of a Financial Institution, which clarifies the applicable guidance for subsequently measuring an indemnification asset recognized in a government-assisted acquisition of a financial institution that includes a loss-sharing agreement. The ASU addresses the diversity in practice regarding interpretation of the terms “on the same basis” and “contractual limitations” referred to by the applicable accounting guidance. Accounting principles require that an indemnification asset recognized at the acquisition date as a result of a government-assisted acquisition of a financial institution involving an indemnification agreement shall be subsequently measured on the same basis as the indemnified item. The provisions of ASU No. 2012-06 clarify that, upon subsequent remeasurement of an indemnification asset, the effect of the change in expected cash flows of the indemnification agreement shall be amortized. Any amortization of changes in value is limited to the lesser of the contractual term of the indemnification agreement or the remaining life of the indemnified assets. The ASU also clarifies that the pool level is the appropriate unit of account for determining the life of the indemnified loans. The ASU is to be applied prospectively and does not affect the guidance relating to the recognition or initial measurement of an indemnification asset.
	Application of the ASU’s provisions on a disaggregated basis had the effect of reducing the remaining period over which the indemnification assets will be amortized. As a result of the shortened amortization period, and based on current cash flow expectations and other assumptions, the Company’s indemnification asset amortization increased amortization expense for the three- and nine-month periods ended September 30, 2013 by $5,496,000 and $15,916,000, respectively, however the change in amortization period did not have a material impact on its financial position and liquidity. Adoption of the ASU also requires the Company to assess the indemnification assets for collectability on a standalone basis. Prior to adoption, the Company assessed collectability of the indemnification asset and the covered loans on a linked basis. The transition in collectability assessment methodology did not have an impact on the Company’s consolidated financial statements for the three months ended September 30, 2013. However, future changes in cash flow expectations and/or other assumptions could result in indemnification asset impairment.
	ASU No. 2013-02
	In 2013, the Company adopted the provisions of ASU No. 2013-06, Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, which requires the Company to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income on the Company’s consolidated statements of comprehensive income if the amount being reclassified is required under US GAAP to be reclassified in its entirety to net income. The ASU does not change the current requirements for reporting net income or other comprehensive income in the consolidated financial statements of the Company, but does require the Company to provide information about the amounts reclassified out of accumulated other comprehensive income by component.
	The adoption of the ASU affects the format and presentation of the Company’s consolidated financial statements and the footnotes to the consolidated financial statements, but does not represent a departure from accounting principles previously applied and thus the adoption did not have an effect on the Company’s operating results, financial position, or liquidity. The information required to be presented or disclosed by this ASU is incorporated in the Company’s statements of comprehensive income and Note 13 in these unaudited consolidated financial statements.
	ASU No. 2011-11 and ASU No. 2013-01
	In the first quarter of 2013, the Company adopted the provisions of ASU No. 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities, which requires an entity to disclose gross and net information about certain instruments and transactions eligible for offset in the statement of financial position and instruments and certain transactions subject to an agreement similar to a master netting arrangement. The Company also adopted ASU No. 2013-01, Balance Sheet (Topic 210): Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities, which clarifies the scope of ASU 2011-11. Because the guidance provided by the ASU’s is disclosure related, adoption resulted in additional disclosures incorporated in Note 12 of these unaudited consolidated financial statements.

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2013
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 Three Months Ended						For the Nine Months Ended
			30-Sep						30-Sep
	(Dollars in thousands, except per share data)		2013			2012			2013			2012
	Income available to common shareholders		$	23,192		$	21,234		$	39,499		$	53,187
	Distributed earnings to unvested restricted stock			(421	)		(401	)		(744	)		(1,009	)
	Distributed earnings to common shareholders - basic			22,771			20,833			38,755			52,178
	Undistributed earnings reallocated to unvested restricted stock			(4	)		(5	)		—			2
	Distributed and undistributed earnings to common shareholders - diluted		$	22,767		$	20,828		$	38,755		$	52,180
	Weighted average shares outstanding - basic (1)			29,631,799			29,066,000			29,582,081			29,303,849
	Weighted average shares outstanding - diluted			29,147,232			28,548,432			29,062,238			28,812,631
	Earnings per common share - basic		$	0.78		$	0.73		$	1.34		$	1.81
	Earnings per common share - diluted			0.78			0.73			1.33			1.81
	Earnings per unvested restricted stock share - basic			0.77			0.71			1.33			1.82
	Earnings per unvested restricted stock share - diluted			0.78			0.72			1.33			1.82
	-1	Weighted average basic shares outstanding include 547,155 and 563,061 shares of unvested restricted stock for the three months ended September 30, 2013 and 2012, respectively, and 559,556 and 554,041 shares for the nine months ended September 30, 2013 and 2012, respectively.
	Additional information on the Company’s basic earnings per common share is shown in the following table.
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2013			2012			2013			2012
	Distributed earnings to common shareholders		$	9,926		$	9,826		$	29,736		$	29,695
	Undistributed earnings to common shareholders			12,845			11,007			9,019			22,483
	Total earnings to common shareholders		$	22,771		$	20,833		$	38,755		$	52,178
	Distributed earnings to unvested restricted stock		$	183		$	189		$	571		$	574
	Undistributed earnings to unvested restricted stock			238			212			173			435
	Total earnings allocated to unvested restricted stock		$	421		$	401		$	744		$	1,009
	Distributed earnings per common share		$	0.34		$	0.34		$	1.03		$	1.03
	Undistributed earnings per common share			0.44			0.39			0.31			0.78
	Total earnings per common share - basic		$	0.78		$	0.73		$	1.34		$	1.81
	Distributed earnings per unvested restricted stock share		$	0.34		$	0.34		$	1.02		$	1.04
	Undistributed earnings per unvested restricted stock share			0.43			0.37			0.31			0.78
	Total earnings per unvested restricted stock share - basic		$	0.77		$	0.71		$	1.33		$	1.82
	For the three months ended September 30, 2013 and 2012, the calculations for basic shares outstanding exclude the weighted average shares owned by the Recognition and Retention Plan (“RRP”) of 642,764 and 624,000, respectively, and are adjusted for the weighted average shares in treasury stock of 2,189,978 and 2,036,132, respectively. For the nine months ended September 30, 2013 and 2012, basic shares outstanding exclude 645,793 and 611,646 shares owned by the RRP, respectively, and are adjusted for 2,249,068 and 1,801,572 shares, respectively, of weighted average shares of treasury stock.
	The effect from the assumed exercise of 402,344 and 834,559 stock options was not included in the computation of diluted earnings per share for three months ended September 30, 2013 and 2012, respectively, because such amounts would have had an antidilutive effect on earnings per common share. For the nine months ended September 30, 2013 and 2012, the effect from the assumed exercise of 678,604 and 703,346 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_and_Disposition_Ac

Acquisition and Disposition Activity	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]	'
Acquisition and Disposition Activity	'
	NOTE 4 –ACQUISITION AND DISPOSITION ACTIVITY
	Acquisitions
	During the third quarter of 2013, the Company announced the signing of a definitive agreement pursuant to which IBERIABANK will acquire certain assets and assume certain liabilities of the Memphis, Tennessee operations of Trust One Bank, a division of Synovus Bank. The transaction is expected to close in the first quarter of 2014 and is subject to customary closing conditions, including receipt of certain regulatory approvals.
	Branch Dispositions
	During the fourth quarter of 2012, the Company announced plans to close four branches during 2013 as part of its ongoing business strategy, which includes a periodic review of its branch network to maximize shareholder return. The Company closed these four branches during the first quarter of 2013. During the second quarter of 2013, the Company announced plans to close or consolidate ten additional branches. As part of these branch closures, the Company incurred various disposal costs during the three and nine months ended September 30, 2013, including personnel termination costs, contract termination costs, and fixed asset disposals. The following table shows the costs the Company incurred that are included in its statements of comprehensive income for the periods indicated.
		For the Three Months Ended					For the Nine Months Ended
		September 30					September 30
	(Dollars in thousands)	2013			2012		2013		2012
	Employee termination	$	(70	)	$	384	$	299	$	384
	Accelerated depreciation		352			284		1,033		284
	Contract termination		591			—		591		—
	Impairment		323			2,743		4,941		2,743
		$	1,196		$	3,411	$	6,864	$	3,411
	For the three months ended September 30, 2013, employee termination costs include an adjustment to record the difference between estimated severance costs at the end of the second quarter of 2013 and severance paid to employees during the third quarter of 2013. The difference is a result of a reduction in calculated severance payments due to employee acceptance of other opportunities. The Company estimates future exit costs, which would include additional employee termination costs, fixed asset disposals, and lease termination costs, will not be material.

Investment_Securities

Investment Securities	9 Months Ended
	Sep. 30, 2013
Investments Debt And Equity Securities [Abstract]	'
Investment Securities	'
	NOTE 5 – INVESTMENT SECURITIES
	The amortized cost and fair values of investment securities, with gross unrealized gains and losses, consist of the following:
			September 30, 2013
	(Dollars in thousands)		Amortized			Gross		Gross			Estimated
			Cost			Unrealized		Unrealized			Fair
						Gains		Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations		$	407,049		$	1,878	$	(7,127	)	$	401,800
	Obligations of state and political obligations			109,509			2,967		(235	)		112,241
	Mortgage-backed securities			1,449,275			14,928		(15,337	)		1,448,866
	Other securities			1,460			22		—			1,482
	Total securities available for sale		$	1,967,293		$	19,795	$	(22,699	)	$	1,964,389
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations		$	34,471		$	650	$	—		$	35,121
	Obligations of state and political obligations			84,471			1,735		(1,425	)		84,781
	Mortgage-backed securities			36,736			293		(1,621	)		35,408
	Total securities held to maturity		$	155,678		$	2,678	$	(3,046	)	$	155,310
			December 31, 2012
	(Dollars in thousands)		Amortized			Gross		Gross			Estimated
			Cost			Unrealized		Unrealized			Fair
						Gains		Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations		$	281,746		$	4,364	$	(386	)	$	285,724
	Obligations of state and political obligations			120,680			6,573		(178	)		127,075
	Mortgage-backed securities			1,303,030			29,108		(1,482	)		1,330,656
	Other securities			1,460			89		—			1,549
	Total securities available for sale		$	1,706,916		$	40,134	$	(2,046	)	$	1,745,004
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations		$	69,949		$	1,244	$	—		$	71,193
	Obligations of state and political obligations			88,909			4,730		(113	)		93,526
	Mortgage-backed securities			46,204			728		(153	)		46,779
	Total securities held to maturity		$	205,062		$	6,702	$	(266	)	$	211,498
	Securities with carrying values of $1.4 billion and $1.7 billion were pledged to secure public deposits and other borrowings at September 30, 2013 and December 31, 2012, respectively.
	Management evaluates securities for other-than-temporary impairment at least quarterly, and more frequently when economic or market concerns warrant such evaluation. Consideration is given to 1) the length of time and extent to which the estimated fair value has been less than amortized cost, 2) the financial condition and near-term prospects of the issuer, and 3) the intent and ability of the Company to retain the investment for a period of time sufficient to allow for any anticipated recovery in estimated fair value above amortized cost. In analyzing an issuer’s financial condition, management considers whether the securities are issued by the federal government or its agencies and whether downgrades by bond rating agencies have occurred, as well as review of issuer financial statements and industry analysts’ reports.
	Information pertaining to securities with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position, is as follows:
			September 30, 2013
			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		$	(7,127	)	$	274,195	$	—		$	—		$	(7,127	)	$	274,195
	Obligations of state and political obligations			(10	)		326		(225	)		1,047			(235	)		1,373
	Mortgage-backed securities			(14,096	)		671,684		(1,241	)		38,600			(15,337	)		710,284
	Total securities available for sale		$	(21,233	)	$	946,205	$	(1,466	)	$	39,647		$	(22,699	)	$	985,852
	Securities held to maturity:
	Obligations of state and political obligations		$	(1,308	)	$	28,433	$	(117	)	$	2,080		$	(1,425	)	$	30,513
	Mortgage-backed securities			(850	)		15,490		(771	)		9,805			(1,621	)		25,295
	Total securities held to maturity		$	(2,158	)	$	43,923	$	(888	)	$	11,885		$	(3,046	)	$	55,808
			December 31, 2012
			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		$	(386	)	$	59,741	$	—		$	—		$	(386	)	$	59,741
	Obligations of state and political obligations			—			—		(178	)		1,094			(178	)		1,094
	Mortgage-backed securities			(1,473	)		180,027		(9	)		3,919			(1,482	)		183,946
	Total securities available for sale		$	(1,859	)	$	239,768	$	(187	)	$	5,013		$	(2,046	)	$	244,781
	Securities held to maturity:
	Obligations of state and political obligations		$	(113	)	$	8,242	$	—		$	—		$	(113	)	$	8,242
	Mortgage-backed securities			(153	)		16,262		—			—			(153	)		16,262
	Total securities held to maturity		$	(266	)	$	24,504	$	—		$	—		$	(266	)	$	24,504
The Company assessed the nature of the losses in its portfolio as of September 30, 2013 and December, 31, 2012 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 and ability to hold debt securities until their maturity or anticipated recovery if the security is classified as available for sale. In addition, management does not believe the Company will be required to sell debt securities before the anticipated recovery of the amortized cost basis of the security.
At September 30, 2013, 151 debt securities had unrealized losses of 2.41% of the securities’ amortized cost basis and 1.21% of the Company’s total amortized cost basis. The unrealized losses for each of the 151 securities relate to market interest rate changes. 13 of the 151 securities have been in a continuous loss position for over twelve months at September 30, 2013. These 13 securities had an aggregate amortized cost basis and unrealized loss of $53,886,000 and $2,354,000, respectively. Ten of the 13 securities were issued by either the Federal National Mortgage Association (Fannie Mae), the Federal Home Loan Mortgage Corporation (Freddie Mac), or the Government National Mortgage Association (Ginnie Mae). The Fannie Mae, Freddie Mac, and Ginnie Mae securities are rated AA+ by S&P and Aaa by Moodys. Three of the securities in a continuous loss position for over twelve months were issued by political subdivisions. One of the bond issuers has a credit rating of A+ by S&P. In addition, the bond is insured by a Aaa rated insurer and as a result, the Company concluded that an other-than-temporary impairment charge was not required at September 30, 2013. The second bond in a continuous unrealized loss position for over twelve months carries an issue rating of Aa2 by Moody’s, and is also insured by the same Aaa rated insurer, and as a result, the Company concluded that an other-than-temporary impairment charge was not required at September 30, 2013. 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.
At December 31, 2012, 49 debt securities had unrealized losses of 0.85% of the securities’ amortized cost basis and 0.12% of the Company’s total amortized cost basis. The unrealized losses for each of the 49 securities relate to market interest rate changes. Three of the 49 securities had been in a continuous loss position for over twelve months at December 31, 2012. These three securities had an aggregate amortized cost basis and unrealized loss of $5,200,000 and $187,000, respectively. Two of the three securities were issued by either the Federal National Mortgage Association (Fannie Mae), Federal Home Loan Mortgage Corporation (Freddie Mac), or the Government National Mortgage Association (Ginnie Mae). The Fannie Mae, Freddie Mac, and Ginnie Mae securities are rated AA+ by S&P and Aaa by Moodys. One of the securities 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 2012, 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 for the year ended December 31, 2011. 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 the first nine months of 2013, the Company continued to analyze the operating environment of the bond as it did in 2012 and 2011 and noted no further deterioration in the operating environment of the bond issuer.
During the nine months ended September 30, 2013 and 2012, 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 September 30, 2013 or December 31, 2012.
The amortized cost and estimated fair value of investment securities by maturity at September 30, 2013 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.
		Securities Available for Sale								Securities Held to Maturity
(Dollars in thousands)		Weighted			Amortized		Estimated			Weighted			Amortized			Estimated
		Average			Cost		Fair			Average			Cost			Fair
		Yield					Value			Yield						Value
Within one year or less			1.99	%	$	16,230	$	16,430			1.85	%	$	24,541		$	24,815
One through five years			1.38			220,047		220,114			3.01			18,071			18,685
After five through ten years			1.98			596,282		597,600			2.6			24,599			25,040
Over ten years			1.92			1,134,734		1,130,245			2.92			88,467			86,770
			1.88	%	$	1,967,293	$	1,964,389			2.71	%	$	155,678		$	155,310
The following is a summary of realized gains and losses from the sale of securities classified as available for sale. Gains or losses on securities sold are recorded on the trade date, using the specific identification method.
		Three Months Ended September 30					Nine Months Ended September 30
(Dollars in thousands)		2013			2012		2013			2012
Realized gains		$	—		$	41	$	2,369		$	3,758
Realized losses			(3	)		—		(110	)		(15	)
		$	(3	)	$	41	$	2,259		$	3,743
In addition to the gains above, the Company realized certain immaterial gains on calls of held to maturity securities.
Other Equity Securities
The Company included the following securities in “Other assets” on the consolidated balance sheets:
(Dollars in thousands)		September 30			December 31
		2013			2012
Federal Home Loan Bank (FHLB) stock		$	12,759		$	16,860
Federal Reserve Bank (FRB) stock			28,098			28,155
Other investments			1,306			1,201
		$	42,163		$	46,216

Loans_Receivable

Loans Receivable	9 Months Ended
	Sep. 30, 2013
Receivables [Abstract]	'
Loans Receivable	'
	NOTE 6 – LOANS RECEIVABLE
	Loans receivable consist of the following, segregated into non-covered and covered loans, for the periods indicated:
			September 30, 2013
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	3,320,333		$	459,506		$	3,779,839
	Business			2,643,822			40,422			2,684,244
				5,964,155			499,928			6,464,083
	Residential mortgage loans:
	Residential 1-4 family			402,354			153,515			555,869
	Construction / Owner Occupied			7,586			—			7,586
				409,940			153,515			563,455
	Consumer and other loans:
	Home equity			1,131,870			149,144			1,281,014
	Indirect automobile			369,755			—			369,755
	Other			360,315			4,415			364,730
				1,861,940			153,559			2,015,499
			$	8,236,035		$	807,002		$	9,043,037
			December 31, 2012
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	2,990,700		$	640,843		$	3,631,543
	Business			2,450,667			87,051			2,537,718
				5,441,367			727,894			6,169,261
	Residential mortgage loans:
	Residential 1-4 family			284,019			187,164			471,183
	Construction / Owner Occupied			6,021			—			6,021
				290,040			187,164			477,204
	Consumer and other loans:
	Home equity			1,076,913			174,212			1,251,125
	Indirect automobile			327,985			—			327,985
	Other			269,519			3,486			273,005
				1,674,417			177,698			1,852,115
			$	7,405,824		$	1,092,756		$	8,498,580
	In 2009, the Company acquired substantially all of the assets and liabilities of CapitalSouth Bank (“CSB”), and certain assets and assumed certain deposit 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”). 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” in the information below and loans that are not subject to the loss share agreements as “non-covered loans.”
	Deferred loan origination fees were $16,445,000 and $14,040,000 and deferred loan expenses were $7,154,000 and $5,270,000 at September 30, 2013 and December 31, 2012, respectively. In addition to loans issued in the normal course of business, the Company considers overdrafts on customer deposit accounts to be loans and reclassifies these overdrafts as loans in its consolidated balance sheets. At September 30, 2013 and December 31, 2012, overdrafts of $2,319,000 and $3,231,000, respectively, have been reclassified to loans receivable.
	Loans with carrying values of $2.2 billion and $1.5 billion were pledged to secure public deposits and other borrowings at September 30, 2013 and December 31, 2012, respectively.
	Non-covered Loans
	The following tables provide an analysis of the aging of non-covered loans as of September 30, 2013 and December 31, 2012. Because of the difference in accounting for acquired loans, the tables below further segregate the Company’s non-covered loans receivable between loans acquired from Florida Gulf in 2012, as well as those acquired in 2011, and loans originated by the Company. For purposes of the following tables, subprime mortgage loans are defined as the Company’s mortgage loans that have FICO scores that are less than 620 at the time of origination or were purchased outside of a business combination.
			September 30, 2013
			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		$	—		$	—		$	2,430		$	2,430		$	380,665		$	383,095		$	—
	Commercial real estate - other			1,933			—			9,639			11,572			2,556,798			2,568,370			151
	Commercial business			1,743			6			14,591			16,340			2,573,065			2,589,405			—
	Residential prime			517			2,297			9,326			12,140			261,615			273,755			1,267
	Residential subprime			—			—			442			442			115,715			116,157			—
	Home equity			1,745			577			7,092			9,414			1,063,257			1,072,671			—
	Indirect automobile			1,719			439			1,056			3,214			364,094			367,308			—
	Credit card			184			102			425			711			59,225			59,936			—
	Other			684			460			255			1,399			287,477			288,876			—
			$	8,525		$	3,881		$	45,256		$	57,662		$	7,661,911		$	7,719,573		$	1,418
	(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.
			December 31, 2012
			Non-covered loans excluding acquired loans
			Past Due(1)															Total Non-covered			Recorded
																		Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Unearned Income			and Accruing
	Commercial real estate construction		$	60		$	—		$	5,479		$	5,539		$	288,137		$	293,676		$	—
	Commercial real estate - other			3,590			—			23,559			27,149			2,224,495			2,251,644			83
Commercial business			1,430			13			3,687			5,130			2,362,304			2,367,434			329
Residential prime			662			1,156			9,168			10,986			185,843			196,829			801
Residential subprime			—			—			—			—			60,454			60,454			—
Home equity			2,283			796			5,793			8,872			991,766			1,000,638			158
Indirect automobile			1,624			326			868			2,818			320,148			322,966			—
Credit card			130			51			424			605			51,117			51,722			—
Other			566			105			310			981			201,161			202,142			—
		$	10,345		$	2,447		$	49,288		$	62,080		$	6,685,425		$	6,747,505		$	1,371
(1)	Past due loans include loans on nonaccrual status as of the period indicated. Nonaccrual loans are presented separately in the “Nonaccrual Loans” section below.
		September 30, 2013
		Non-covered acquired loans
		Past Due (1)																		Total Non-covered		Recorded
																				Loans, Net of		Investment > 90 days
(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Discount			Unearned Income		and Accruing
Commercial real estate construction		$	97		$	—		$	3,457		$	3,554		$	15,020		$	(1,928	)	$	16,646	$	3,457
Commercial real estate - other			2,240			438			33,484			36,162			367,085			(51,025	)		352,222		33,484
Commercial business			444			246			1,880			2,570			59,949			(8,102	)		54,417		1,880
Residential prime			—			—			226			226			20,388			(586	)		20,028		226
Home equity			1,567			302			4,681			6,550			56,842			(4,193	)		59,199		4,681
Indirect automobile			86			1			102			189			2,258			—			2,447		102
Other			162			185			948			1,295			13,859			(3,651	)		11,503		948
		$	4,596		$	1,172		$	44,778		$	50,546		$	535,401		$	(69,485	)	$	516,462	$	44,778
(1)	Past due information includes loans acquired from OMNI, Cameron and Florida Gulf at the gross loan balance, prior to application of discounts.
		December 31, 2012
		Non-covered acquired loans
		Past Due (1)																		Total Non-covered		Recorded
																				Loans, Net of		Investment > 90 days
(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Discount			Unearned Income		and Accruing
Commercial real estate construction		$	369		$	—		$	4,067		$	4,436		$	29,098		$	(3,968	)	$	29,566	$	4,067
Commercial real estate - other			5,971			1,572			38,987			46,530			426,339			(57,055	)		415,814		38,987
Commercial business			1,410			524			3,953			5,887			89,490			(12,144	)		83,233		3,953
Residential prime			—			—			779			779			30,663			1,315			32,757		779
Home equity			2,379			382			4,354			7,115			73,658			(4,498	)		76,275		4,354
Indirect automobile			171			4			146			321			4,698			—			5,019		146
Other			202			17			495			714			21,746			(6,805	)		15,655		495
		$	10,502		$	2,499		$	52,781		$	65,782		$	675,692		$	(83,155	)	$	658,319	$	52,781
(1)	Past due information includes loans acquired from OMNI, Cameron and Florida Gulf at the gross loan balance, prior to application of discounts.
Nonaccrual Loans
The following table provides the recorded investment of non-covered loans on nonaccrual status at September 30, 2013 and December 31, 2012. Nonaccrual loans in the table exclude acquired loans.
(Dollars in thousands)		September 30, 2013			December 31, 2012
Commercial real estate construction		$	2,430		$	5,479
Commercial real estate - other			9,488			23,475
Commercial business			14,591			3,358
Residential prime			8,501			8,367
Home equity			7,092			5,635
Indirect automobile			1,056			868
Credit card			425			424
Other			255			310
		$	43,838		$	47,916
Covered Loans
The carrying amount of the acquired covered loans at September 30, 2013 and December 31, 2012 consisted of loans determined to be impaired at the acquisition date, which are accounted for in accordance with ASC Topic 310-30, and loans that were considered to be performing at the acquisition date, accounted for by analogy to ASC Topic 310-30, as detailed in the following tables.
		September 30, 2013
(Dollars in thousands)		Acquired			Acquired			Total
		Impaired			Performing			Covered
		Loans			Loans			Loans
Commercial loans:
Real estate		$	23,751		$	435,755		$	459,506
Business			—			40,422			40,422
			23,751			476,177			499,928
Residential mortgage loans:
Residential 1-4 family			28,333			125,182			153,515
Construction / Owner Occupied			—			—			—
			28,333			125,182			153,515
Consumer and other loans:
Home equity			25,195			123,949			149,144
Indirect automobile			—			—			—
Other			1,205			3,210			4,415
			26,400			127,159			153,559
		$	78,484		$	728,518		$	807,002
		December 31, 2012
(Dollars in thousands)		Acquired			Acquired			Total
		Impaired			Performing			Covered
		Loans			Loans			Loans
Commercial loans:
Real estate		$	167,742		$	473,101		$	640,843
Business			2,757			84,294			87,051
			170,499			557,395			727,894
Residential mortgage loans:
Residential 1-4 family			20,232			166,932			187,164
Construction / Owner Occupied			—			—			—
			20,232			166,932			187,164
Consumer and other loans:
Home equity			22,094			152,118			174,212
Indirect automobile			—			—			—
Other			820			2,666			3,486
			22,914			154,784			177,698
		$	213,645		$	879,111		$	1,092,756
ASC 310-30 loans
The Company acquired loans (both covered and non-covered) through previous acquisitions which are subject to ASC Topic 310-30.
The following is a summary of changes in the accretable yields of acquired loans during the nine months ended September 30, 2013 and 2012.
		September 30, 2013									September 30, 2012
(Dollars in thousands)		Acquired			Acquired			Total			Acquired			Acquired			Total
		Impaired			Performing			Acquired			Impaired			Performing			Acquired
		Loans			Loans			Loans			Loans			Loans			Loans
Balance at beginning of period		$	76,623		$	279,770		$	356,393		$	83,834		$	386,977		$	470,811
Transfers from nonaccretable difference to accretable yield			6,148			34,480			40,628			1,062			4,245			5,307
Accretion			(13,519	)		(119,193	)		(132,712	)		(21,924	)		(165,247	)		(187,171	)
Changes in expected cash flows not affecting nonaccretable differences (1)			10,561			81,173			91,734			10,964			46,197			57,161
Balance at end of period		$	79,813		$	276,230		$	356,043		$	73,936		$	272,172		$	346,108
-1	Includes changes in cash flows expected to be collected due to the impact of changes in actual or expected timing of liquidation events, loan modifications, changes in interest rates and changes in prepayment assumptions.
Accretable yield during the first nine months of 2013 increased primarily as a result of changes in expected cash flows not impacting the nonaccretable difference, offset by an increase in accretion recognized during the period. Accretable yield during the first nine months of 2012 decreased primarily as a result of the accretion recognized.
Troubled Debt Restructurings
Information about the Company’s TDRs at September 30, 2013 and 2012 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 the loans acquired in the OMNI and Cameron acquisitions completed during 2011 and certain loans acquired from Florida Gulf in 2012. 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 loans and loans acquired from OMNI and Cameron, and certain Florida Gulf loans that would otherwise meet the criteria for classification as a troubled debt restructuring are excluded from the tables below.
		September 30, 2013												September 30, 2012
		Accruing Loans												Accruing Loans
(Dollars in thousands)		Current			Past Due			Nonaccrual TDRs			Total TDRs			Current			Past Due			Nonaccrual TDRs		Total TDRs
					> 30 days												> 30 days
Commercial real estate construction		$	—		$	—		$	—		$	—		$	—		$	—		$	—	$	—
Commercial real estate - other			411			—			5,601			6,012			370			264			18,985		19,619
Commercial business			1,056			—			12,610			13,666			19			—			1,884		1,903
Residential prime			—			—			—			—			—			—			—		—
Residential subprime			—			—			—			—			—			—			—		—
Home equity			—			—			263			263			94			—			224		318
Indirect automobile			—			—			—			—			—			—			—		—
Credit card			—			—			—			—			—			—			—		—
Other			—			—			—			—			—			—			—		—
		$	1,467		$	—		$	18,474		$	19,941		$	483		$	264		$	21,093	$	21,840
At September 30, 2013, TDRs totaling $19,941,000 included $11,210,000 of TDRs that occurred during the current nine-month period through modification of the original loan terms. Total TDRs of $21,840,000 at September 30, 2012 included $4,391,000 of TDRs that occurred during the nine-month period ended September 30, 2012. The following table provides information on how the TDRs were modified during the periods indicated.
		Nine Months Ended
		September 30
(Dollars in thousands)		2013			2012
Extended maturities		$	—		$	412
Interest rate adjustment			—			481
Maturity and interest rate adjustment			—			2,389
Movement to or extension of interest-rate only payments			—			939
Forbearance			11,210			170
		$	11,210		$	4,391
Information about the Company’s non-covered TDRs occurring in these periods is presented in the following table.
		September 30, 2013									September 30, 2012
(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			5		$	12,507		$	12,329			14		$	4,478		$	3,707
Commercial business			—			—			—			1			27			—
Residential prime			—			—			—			—			—			—
Home Equity			—			—			—			1			94			51
Indirect automobile			—			—			—			—			—			—
Credit card			—			—			—			—			—			—
Other			—			—			—			1			—			—
			5		$	12,507		$	12,329			17		$	4,599		$	3,758
-1	Recorded investment includes any allowance for credit losses recorded on the TDRs at the dates indicated.
Information detailing non-covered TDRs that subsequently defaulted during the previous twelve months is presented in the following table. The Company has defined a default as any loan with a loan payment that is currently past due greater than 30 days, or was past due greater than 30 days at any point during the previous twelve months, or since the date of modification, whichever is shorter.
		September 30, 2013						September 30, 2012
(In thousands, except number of loans)		Number of			Recorded			Number of			Recorded
		Loans			Investment			Loans			Investment
Commercial real estate			45		$	6,012			46		$	19,048
Commercial business			13			12,370			8			1,883
Residential prime			—			—			—			—
Home Equity			1			47			2			275
Indirect automobile			—			—			—			—
Credit card			—			—			—			—
Other			1			—			1			—
			60		$	18,429			57		$	21,206

Allowance_for_Credit_Losses_an

Allowance for Credit Losses and Credit Quality	9 Months Ended
	Sep. 30, 2013
Receivables [Abstract]	'
Allowance for Credit Losses and Credit Quality	'
	NOTE 7 – ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY
	Change in Methodology
	During the nine-month period ended September 30, 2013, the Company modified its methodology for estimating its allowance for credit losses on its non-covered, non-acquired loan portfolio to incorporate practices, processes, and methodologies consistent with the guidance provided in the Office of the Comptroller of Currency’s (“OCC”) inter-agency policy statement 2006 SR 06-17. The methodology was modified to segregate the reserve for unfunded lending commitments (“RULC”), previously included in the Company’s allowance for credit losses, and to enhance the previous methodology around loss migration.
	As part of the modification, the Company’s calculation of its allowance for credit losses incorporates a new loss migration model designed by the Company to improve its estimates of credit losses by:
		•		Providing a greater degree of segmentation of the Company’s non-covered, non-acquired loan portfolio within its existing homogeneous pools with distinct risk characteristics;
		•		Improving the application of the Company’s specific historical loss rates to effectively generate estimated incurred loss rates for these various pools of the loan portfolio; and
		•		Facilitating future loan portfolio stress testing.
	The following changes were made from the Company’s previous methodology utilized through the three months ended March 31, 2013:
		•		Segregation of the RULC noted above;
		•		Creation of a transition matrix-based model that calculates current incurred loss estimates derived from Company-specific history of risk rating changes and net charge-offs across multiple loan pools in its portfolio; and
		•		Elimination of the use of published available expected default frequencies (“EDFs”) adjusted for the Company’s experience in estimating losses in the Company’s commercial real estate and business loan portfolios.
	The following table presents the effect of the change in methodology on the Company’s unaudited consolidated financial statements as of September 30, 2013.
	(Dollars in thousands)		Current Methodology			Previous Methodolgy			Difference			Per Share Difference
	Selected Data
	Allowance for loan losses		$	64,165		$	73,992		$	(9,827	)
	Reserve for unfunded lending commitments			11,959			—			11,959
	Allowance for credit losses		$	76,124		$	73,992		$	2,132
	(Reversal of)Provision for loan losses		$	2,884		$	2,883		$	1		$	(0.00	)
	Provision for unfunded lending commitments			2,131			—			2,131			0.05
	Total provision for credit losses		$	5,015		$	2,883		$	2,132		$	0.05
	Allowance for Credit Losses Activity
	A summary of changes in the allowance for credit losses for the covered loan and non-covered loan portfolios is as follows:
			September 30, 2013
			Non-covered loans
	(Dollars in thousands)		Excluding Acquired Loans			Acquired Loans			Covered Loans			Total
	Allowance for loan losses
	Balance at beginning of period		$	74,211		$	8,816		$	168,576		$	251,603
	(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements			2,884			(2,464	)		(58,540	)		(58,120	)
	Adjustment attributable to FDIC loss share arrangements			—			—			58,565			58,565
	Net (reversal of) provision for loan losses			2,884			(2,464	)		25			445
	Decrease in FDIC loss share receivable			—			—			(58,565	)		(58,565	)
	Transfer of balance to OREO			—			(1,013	)		(29,302	)		(30,315	)
	Transfer of balance to the RULC			(9,828	)		—			—			(9,828	)
	Loans charged-off			(7,455	)		(10	)		(1,683	)		(9,148	)
	Recoveries			4,353			—			—			4,353
	Balance at end of period		$	64,165		$	5,329		$	79,051		$	148,545
	Reserve for unfunded lending commitments
	Balance at beginning of period		$	—		$	—		$	—		$	—
	Transfer of balance from the allowance for loan losses			9,828			—			—			9,828
	Provision for unfunded lending commitments			2,131			—			—			2,131
	Balance at end of period		$	11,959		$	—		$	—		$	11,959
			September 30, 2012
			Non-covered loans
			Excluding Acquired Loans			Acquired Loans			Covered Loans			Total
	Allowance for loan losses
	Balance at beginning of period		$	74,861		$	—		$	118,900		$	193,761
	(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements			6,518			5,805			37,268			49,591
	Adjustment attributable to FDIC loss share arrangements			—			—			(33,786	)		(33,786	)
	Net (reversal of) provision for loan losses			6,518			5,805			3,482			15,805
	Increase in FDIC loss share receivable			—			—			33,786			33,786
	Transfer of balance to OREO			—			(408	)		(23,769	)		(24,177	)
	Loans charged-off			(6,818	)		(179	)		(13,283	)		(20,280	)
	Recoveries			2,455			18			19			2,492
	Balance at end of period		$	77,016		$	5,236		$	119,135		$	201,387
	A summary of changes in the allowance for credit losses for non-covered loans, by loan portfolio type, is as follows:
			September 30, 2013
	(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
			real estate			business
	Allowance for loan losses
	Balance at beginning of period		$	38,264		$	28,721		$	2,125		$	13,917		$	—		$	83,027
	(Reversal of) Provision for loan losses			(6,926	)		(582	)		1,048			6,880			—			420
	Transfer of balance to OREO			(279	)		(81	)		(646	)		(7	)		—			(1,013	)
	Transfer of balance to the RULC			(2,939	)		(3,497	)		(40	)		(3,352	)		—			(9,828	)
Loans charged off			(1,966	)		(531	)		(481	)		(4,487	)		—			(7,465	)
Recoveries			1,498			354			698			1,803			—			4,353
Balance at end of period		$	27,652		$	24,384		$	2,704		$	14,754			—		$	69,494
Reserve for unfunded commitments
Balance at beginning of period		$	—		$	—		$	—		$	—		$	—		$	—
Transfer of balance from the allowance for loan losses			2,939			3,497			40			3,352			—			9,828
Provision for unfunded commitments			1,207			610			38			276			—			2,131
Balance at end of period		$	4,146		$	4,107		$	78		$	3,628		$	—		$	11,959
Allowance on loans individually evaluated for impairment		$	8		$	801		$	283		$	—		$	—		$	1,092
Allowance on loans collectively evaluated for impairment			27,644			23,583			2,421			14,754			—			68,402
Loans, net of unearned income:
Balance at end of period		$	3,320,333		$	2,643,822		$	409,940		$	1,861,940		$	—		$	8,236,035
Balance at end of period individually evaluated for impairment			9,529			14,548			1,407			263			—			25,747
Balance at end of period collectively evaluated for impairment			3,310,804			2,629,274			408,533			1,861,677			—			8,210,288
Balance at end of period acquired with deteriorated credit quality			16,287			45			120			1,815			—			18,267
		September 30, 2012
(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
Allowance for credit losses
Balance at beginning of period		$	35,604		$	25,705		$	897		$	12,655		$	—		$	74,861
(Reversal of) Provision for loan losses			4,199			3,851			1,344			2,929			—			12,323
Transfer of balance to OREO			(62	)		—			(337	)		(9	)		—			(408	)
Loans charged off			(1,195	)		(769	)		(759	)		(4,274	)		—			(6,997	)
Recoveries			790			80			30			1,573			—			2,473
Balance at end of period		$	39,336		$	28,867		$	1,175		$	12,874		$	—		$	82,252
Allowance on loans individually evaluated for impairment		$	1,173		$	162		$	163		$	43		$	—		$	1,541
Allowance on loans collectively evaluated for impairment			38,163			28,705			1,012			12,831			—			80,711
Loans, net of unearned income:
Balance at end of period		$	2,879,836		$	2,357,303		$	266,069		$	1,587,488		$	—		$	7,090,696
Balance at end of period individually evaluated for impairment			26,353			1,888			1,703			318			—			30,262
Balance at end of period collectively evaluated for impairment			2,853,483			2,355,415			264,366			1,587,170			—			7,060,434
Balance at end of period acquired with deteriorated credit quality			60,360			3,675			430			5,334			—			69,799
A summary of changes in the allowance for credit losses for covered loans, by loan portfolio type, is as follows:
		September 30, 2013
(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
Allowance for loan losses
Balance at beginning of period		$	100,871		$	11,375		$	22,566		$	33,764		$	—		$	168,576
(Reversal of) Provision for loan losses			27			—			(1	)		(1	)		—			25
(Decrease) Increase in FDIC loss share receivable			(30,853	)		(3,137	)		(5,734	)		(18,841	)		—			(58,565	)
Transfer of balance to OREO			(22,375	)		(314	)		(6,614	)		1			—			(29,302	)
Loans charged off			(1,683	)		—			—			—			—			(1,683	)
Balance at end of period		$	45,987		$	7,924		$	10,217		$	14,923		$	—		$	79,051
Allowance on loans individually evaluated for impairment		$	—		$	—		$	—		$	—		$	—		$	—
Allowance on loans collectively evaluated for impairment			45,987			7,924			10,217			14,923			—			79,051
Loans, net of unearned income:
Balance at end of period		$	459,506		$	40,422		$	153,515		$	153,559		$	—		$	807,002
Balance at end of period individually evaluated for impairment			—			—			—			—			—			—
Balance at end of period collectively evaluated for impairment			459,506			40,422			153,515			153,559			—			807,002
Balance at end of period acquired with deteriorated credit quality			23,751			—			28,333			26,400			—			78,484
		September 30, 2012
(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
		real estate			business
Allowance for credit losses
Balance at beginning of period		$	69,175		$	9,788		$	21,184		$	18,753		$	—		$	118,900
(Reversal of) Provision for loan losses			3,550			922			(1,387	)		397			—			3,482
(Decrease) Increase in FDIC loss share receivable			24,229			2,398			4,277			2,882			—			33,786
Transfer of balance to OREO			(9,876	)		(2,475	)		(10,593	)		(825	)		—			(23,769	)
Loans charged off			(13,143	)		—			(131	)		(9	)		—			(13,283	)
Recoveries			16			—			—			3			—			19
Balance at end of period		$	73,951		$	10,633		$	13,350		$	21,201		$	—		$	119,135
Allowance on loans individually evaluated for impairment		$	—		$	—		$	—		$	—		$	—		$	—
Allowance on loans collectively evaluated for impairment			73,951			10,633			13,350			21,201			—			119,135
Loans, net of unearned income:
Balance at end of period		$	670,001		$	91,822		$	197,333		$	180,094		$	—		$	1,139,250
Balance at end of period individually evaluated for impairment			—			—			—			—			—			—
Balance at end of period collectively evaluated for impairment			670,001			91,822			197,333			180,094			—			1,139,250
Balance at end of period acquired with deteriorated credit quality			171,965			3,522			22,085			24,388			—			221,960
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 discounts in the tables below represent the adjustment of non-covered acquired loans to fair value at the acquisition date, as adjusted for income accretion and changes in cash flow estimates in subsequent periods. Asset risk classifications for commercial loans reflect the classification as of September 30, 2013 and December 31, 2012.
		Non-covered loans excluding acquired loans
		September 30, 2013															December 31, 2012
(Dollars in		Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
thousands)					Mention															Mention
Commercial real estate construction		$	374,458		$	4,800		$	3,837		$	—		$	383,095		$	269,842		$	16,767		$	7,067	$	—	$	293,676
Commercial real estate - other			2,503,820			37,537			26,896			117			2,568,370			2,162,989			40,547			47,710		398		2,251,644
Commercial business			2,546,614			9,013			32,825			953			2,589,405			2,295,788			21,640			49,958		48		2,367,434
Total		$	5,424,892		$	51,350		$	63,558		$	1,070			5,540,870		$	4,728,619		$	78,954		$	104,735	$	446	$	4,912,754
		Non-covered loans excluding acquired loans
		September 30, 2013									December 31, 2012
(Dollars in thousands)		Current			30+ Days			Total			Current			30+ Days			Total
					Past Due									Past Due
Residential prime		$	261,615		$	12,140		$	273,755		$	185,843		$	10,986		$	196,829
Residential subprime			115,715			442			116,157			60,454			—			60,454
Home equity			1,063,257			9,414			1,072,671			991,766			8,872			1,000,638
Indirect automobile			364,094			3,214			367,308			320,148			2,818			322,966
Credit card			59,225			711			59,936			51,117			605			51,722
Consumer - other			287,477			1,399			288,876			201,161			981			202,142
		$	2,151,383		$	27,320		$	2,178,703		$	1,810,489		$	24,262		$	1,834,751
		Non-covered acquired loans
		September 30, 2013																		December 31, 2012
(Dollars in		Pass			Special			Substandard			Doubtful			Discount			Total			Pass			Special		Substandard		Doubtful			Discount			Total
thousands)					Mention																		Mention
Commercial real estate construction		$	12,900		$	1,321		$	4,353		$	—		$	(1,928	)	$	16,646		$	25,896		$	2,410	$	5,228	$	—		$	(3,968	)	$	29,566
Commercial real estate - other			320,781			18,438			63,816			212			(51,025	)		352,222			359,046			28,185		85,420		218			(57,055	)		415,814
Commercial business			56,465			2,241			3,725			88			(8,102	)		54,417			86,201			2,159		4,808		2,209			(12,144	)		83,233
Total		$	390,146		$	22,000		$	71,894		$	300		$	(61,055	)	$	423,285		$	471,143		$	32,754	$	95,456	$	2,427		$	(73,167	)	$	528,613
		Non-covered acquired loans
		September 30, 2013												December 31, 2012
(Dollars in thousands)		Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
					Past Due			(discount)									Past Due			(discount)
Residential prime		$	20,388		$	226		$	(586	)	$	20,028		$	30,663		$	779		$	1,315		$	32,757
Home equity			56,842			6,550			(4,193	)		59,199			73,658			7,115			(4,498	)		76,275
Indirect automobile			2,258			189			—			2,447			4,698			321			—			5,019
Consumer - other			13,859			1,295			(3,651	)		11,503			21,746			714			(6,805	)		15,655
		$	93,347		$	8,260		$	(8,430	)	$	93,177		$	130,765		$	8,929		$	(9,988	)	$	129,706
Credit quality information in the table above includes loans acquired at the gross loan balance, prior to the application of discounts, at September 30, 2013 and December 31, 2012.
The Company’s investment in covered loans by credit quality indicator is presented in the following table. Loan 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
		September 30, 2013															December 31, 2012
(Dollars in thousands)		Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
					Mention															Mention
Commercial real estate construction		$	44,312		$	8,093		$	42,849		$	497		$	95,751		$	46,201		$	9,888		$	97,315	$	607	$	154,011
Commercial real estate - other			146,103			56,182			194,785			7,496			404,566			201,261			65,498			279,171		8,530		554,460
Commercial business			33,112			958			17,201			1,277			52,548			38,552			8,600			50,018		451		97,621
Total		$	223,527		$	65,233		$	254,835		$	9,270		$	552,865		$	286,014		$	83,986		$	426,504	$	9,588	$	806,092
Discount															(52,937	)												(78,198	)
														$	499,928												$	727,894
		Covered loans
		September 30, 2013												December 31, 2012
(Dollars in thousands)		Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
					Past Due			(discount)									Past Due			(discount)
Residential prime		$	164,214		$	33,114		$	(43,813	)	$	153,515		$	183,795		$	52,379		$	(49,010	)	$	187,164
Home equity			150,302			41,683			(42,841	)		149,144			168,729			65,997			(60,514	)		174,212
Credit card			665			36			—			701			841			65			—			906
Consumer - other			643			204			2,867			3,714			1,154			1,523			(97	)		2,580
		$	315,824		$	75,037		$	(83,787	)	$	307,074		$	354,519		$	119,964		$	(109,621	)	$	364,862
Impaired Loans
Information on the Company’s investment in impaired loans is presented in the following tables as of and for the periods indicated.
		September 30, 2013									December 31, 2012
(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		$	9,392		$	9,392		$	—		$	26,151		$	26,151		$	—
Commercial business			13,068			13,068			—			1,824			1,824			—
Home equity			263			263			—			—			—			—
With an allowance recorded:
Commercial real estate			2,913			2,937			(24	)		3,464			3,663			(199	)
Commercial business			2,569			2,579			(10	)		1,334			1,810			(476	)
Residential prime			9,575			9,908			(333	)		9,861			10,070			(209	)
Home equity			6,784			6,829			(45	)		5,860			5,951			(91	)
Indirect automobile			1,050			1,056			(6	)		865			868			(3	)
Credit card			417			425			(8	)		413			424			(11	)
Other			252			255			(3	)		307			310			(3	)
		$	46,283		$	46,712		$	(429	)	$	50,079		$	51,071		$	(992	)
Total commercial loans			27,942			27,976			(34	)		32,773			33,448			(675	)
Total mortgage loans			9,575			9,908			(333	)		9,861			10,070			(209	)
Total consumer loans			8,766			8,828			(62	)		7,445			7,553			(108	)
		For the Three Months Ended September 30												For the Nine Months Ended September 30
		2013						2012						2013						2012
(Dollars in thousands)		Average			Interest			Average			Interest			Average			Interest			Average			Interest
		Recorded			Income			Recorded			Income			Recorded			Income			Recorded			Income
		Investment			Recognized (1)			Investment			Recognized (1)			Investment			Recognized (1)			Investment			Recognized (1)
With no related allowance recorded:
Commercial real estate		$	10,703		$	6		$	27,547		$	15		$	12,787		$	22		$	29,872		$	651
Commercial business			13,218			17			2,451			—			8,608			59			3,387			71
Home Equity			265			—			225			—			287			—			227			—
With an allowance recorded:
Commercial real estate			4,346			—			2,731			8			6,092			5			2,866			22
Commercial business			2,739			—			209			1			2,746			3			215			1
Residential prime			9,650			—			9,248			—			9,380			7			7,439			148
Home equity			7,244			—			6,184			—			7,458			14			6,502			110
Indirect automobile			1,349			—			1,135			—			1,610			22			1,345			20
Credit card			424			—			387			—			426			—			354			—
Other			372			—			585			—			446			4			675			6
		$	50,310		$	23		$	50,702		$	24		$	49,840		$	136		$	52,882		$	1,029
Total commercial loans			31,006			23			32,938			24			30,233			89			36,340			745
Total mortgage loans			9,650			—			9,248			—			9,380			7			7,439			148
Total consumer loans			9,654			—			8,516			—			10,227			40			9,103			136
-1	Interest income recognized on impaired loans represents income recognized before loans were placed on nonaccrual status.
As of September 30, 2013 and December 31, 2012, the Company was not committed to lend additional funds to any customer whose loan was classified as impaired or as a troubled debt restructuring.

Loss_Sharing_Agreements_and_FD

Loss Sharing Agreements and FDIC Loss Share Receivable	9 Months Ended
	Sep. 30, 2013
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 and assumed certain deposit 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 significant 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 CapitalSouth reimbursable loss period ends during the third quarter of 2014 for all covered assets excluding single family residential loans and during the third quarter of 2019 for single family residential loans. The Century and Orion reimbursable loss periods end during the fourth quarter of 2014 for all covered assets excluding single family residential loans and during the fourth quarter of 2019 for single family residential loans. The Sterling reimbursable loss period ends during the third quarter of 2015 for all covered assets excluding single family residential loans and during the third quarter of 2020 for single family residential loans.
	In addition, all loans excluding single family residential loans 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, consistent with the covered loss reimbursement rates in effect during the reimbursable loss 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 incurred. Of the three loss share agreements that contain clawback provisions, cumulative losses under two of these agreements have exceeded the cumulative loss floors that would trigger a clawback payment. The loss floor has not yet been attained for the third agreement. However, the sum of the historical and remaining projected losses under the remaining agreement is in excess of the clawback amount stated in that agreement. The Company has recorded a liability of $797,000 at September 30, 2013 to reserve for the amount of consideration due to the FDIC based on cumulative losses to date. 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 receivable
	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. Note 1 to these unaudited consolidated financial statements provides additional information regarding the Company’s FDIC loss share receivable accounting policy and basis of presentation.
	The following is a summary of FDIC loss share receivable year-to-date activity:
		September 30
	(Dollars in thousands)	2013			2012
	Balance at beginning of period	$	423,069		$	591,844
	Change due to (reversal of) credit loss provision recorded on FDIC covered loans		(58,565	)		33,786
	Amortization		(68,707	)		(89,899	)
	Submission of reimbursable losses to the FDIC		(44,910	)		(97,511	)
	Impairment		(31,813	)		—
	Changes due to a change in cash flow assumptions on OREO and other		(14,189	)		(7,053	)
	Balance at end of period	$	204,885		$	431,167
	FDIC loss share receivables collectability assessment
	The Company assesses the FDIC loss share receivables for collectability on a quarterly basis. Note 1 provides a description of the Company’s policy for assessing the FDIC loss share receivables for collectability. Based on the collectability analysis completed for the three months ended September 30, 2013, the Company concluded that the $204.9 million FDIC loss share receivable is fully collectible as of September 30, 2013. See below for discussion of the impairment charge recognized for the three-month period ended March 31, 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 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, the Audit Committee and the Board of Directors concluded that an impairment charge was required under generally accepted accounting principles applicable to the Company and should be recognized in the Company’s unaudited 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 $31,813,000 through a charge to net income.
	Generally accepted accounting principles require that the tax effects of unusual or infrequent items, such as impairment of the FDIC loss share receivables, be recognized in the interim period in which they occur. Recognition of the tax effect of the impairment during the three-month period ended March 31, 2013 resulted in an effective tax rate for that period, and subsequent year to date periods in 2013, that is not customary of the Company’s effective tax rate without recognition of this infrequent item.

Transfers_and_Servicing_of_Fin

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity)	9 Months Ended
	Sep. 30, 2013
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 GSEs, but can also consist of junior lien loans secured by residential property. These sales are primarily to private companies that are unaffiliated with the GSEs on a servicing released basis. The following table details the mortgage banking activity as of and for the nine months ended September 30:
	(Dollars in thousands)	2013			2012
	Balance at beginning of period	$	267,475		$	153,013
	Originations		1,712,557			1,749,121
	Sales		(1,871,747	)		(1,691,002	)
	Balance at end of period	$	108,285		$	211,132
	(Dollars in thousands)	2013			2012
	Fair value changes of derivatives and mortgage loans held for sale, net	$	(270	)	$	2,954
	Gains on sales		51,709			51,828
	Servicing and other income, net		402			336
		$	51,841		$	55,118
	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:
		September 30, 2013								December 31, 2012
	(Dollars in thousands)	Gross			Accumulated			Net		Gross		Accumulated			Net
		Carrying Amount			Amortization			Carrying Amount		Carrying Amount		Amortization			Carrying Amount
	Mortgage servicing rights	$	1,816		$	(543	)	$	1,273	$	1,234	$	(304	)	$	930

Goodwill_and_Other_Acquired_In

Goodwill and Other Acquired Intangible Assets	9 Months Ended
	Sep. 30, 2013
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 for the year ended December 31, 2012 and the nine months ended September 30, 2013 are provided in the following table.
	(Dollars in thousands)
	Balance, December 31, 2011	$	369,811
	Goodwill acquired during the year		32,420
	Goodwill adjustment to correct an immaterial error		(359	)
	Balance, December 31, 2012		401,872
	Goodwill acquired during the period		—
	Balance, September 30, 2013	$	401,872
	The goodwill acquired during the year ended December 31, 2012 was a result of the Florida Gulf acquisition.
	The goodwill adjustment in 2012 was a result of the Company’s revised goodwill recorded on its OMNI and Cameron acquisitions. The Company has recorded the adjustment to account for the impact of an immaterial error in accounting for its OMNI and Cameron acquisitions that resulted in a decrease in goodwill of $359,000. The Company revised its valuation of acquired deferred tax assets and property during the first quarter of 2012 as a result of information that existed at the acquisition date but was not available during the prior period. The error was identified in 2012 through the operation of the Company’s internal controls over financial reporting as it related to the Company’s acquisition accounting.
	The Company performed the required annual goodwill impairment test as of October 1, 2012. The Company’s annual impairment test did not indicate impairment at any of the Company’s reporting units as of the testing date. The Company is in the process of performing its annual goodwill impairment test as of October 1, 2013.
	Prior to 2011, the Company recognized goodwill impairment of $9,681,000 at the Company’s LTC subsidiary based on a decrease in operating revenue and income, which resulted in the conclusion that the fair value of LTC may have been reduced below its carrying amount.
	Title plant
	The Company held title plant assets totaling $6,722,000 at September 30, 2013 and December 31, 2012, respectively. No events or changes in circumstances occurred during 2013 or 2012 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 for the periods indicated:
		September 30, 2013								December 31, 2012
	(Dollars in thousands)	Gross			Accumulated			Net		Gross		Accumulated			Net
		Carrying Amount			Amortization			Carrying Amount		Carrying Amount		Amortization			Carrying Amount
	Core deposit intangibles	$	45,406		$	(29,659	)	$	15,747	$	45,406	$	(26,284	)	$	19,122
	Customer relationship intangible asset		1,348			(579	)		769		1,348		(410	)		938
		$	46,754		$	(30,238	)	$	16,516	$	46,754	$	(26,694	)	$	20,060

Other_Real_Estate_Owned

Other Real Estate Owned	9 Months Ended
	Sep. 30, 2013
Banking And Thrift [Abstract]	'
Other Real Estate Owned	'
	NOTE 11 – OTHER REAL ESTATE OWNED
	Other real estate owned, segregated into non-covered and covered properties, consists of the following as of the periods indicated.
		September 30, 2013						December 31, 2012
	(Dollars in thousands)	Non-covered		Covered		Total		Non-covered		Covered		Total
	Real estate owned acquired by foreclosure	$	31,261	$	85,616	$	116,877	$	35,080	$	75,784	$	110,864
	Real estate acquired for development or resale		10,518		—		10,518		9,199		—		9,199
	Other foreclosed property		109		1,483		1,592		14		1,459		1,473
		$	41,888	$	87,099	$	128,987	$	44,293	$	77,243	$	121,536

Derivative_Instruments_and_Oth

Derivative Instruments and Other Hedging Activities	9 Months Ended
	Sep. 30, 2013
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:
			Balance Sheet		Asset Derivatives Fair Value								Balance Sheet		Liability Derivatives Fair Value
	(Dollars in thousands)		Location		September 30, 2013				December 31, 2012				Location		September 30, 2013				December 31, 2012
	Derivatives designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		Other assets		$	—			$	499			Other liabilities		$	—			$	1,843
	Total derivatives designated as hedging instruments under ASC Topic 815				$	—			$	499					$	—			$	1,843
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		Other assets		$	14,312			$	25,940			Other liabilities		$	14,312			$	25,940
	Forward sales contracts		Other assets			148				2,774			Other liabilities			5,289				343
	Written and purchased options		Other assets			18,009				12,906			Other liabilities			11,920				8,764
	Total derivatives not designated as hedging instruments under ASC Topic 815				$	32,469			$	41,620					$	31,521			$	35,047
	Total derivatives				$	32,469			$	42,119					$	31,521			$	36,890
			Asset Derivatives Notional Amount								Liability Derivatives Notional Amount
	(Dollars in thousands)		September 30, 2013				December 31, 2012				September 30, 2013				December 31, 2012
	Derivatives designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		$	—			$	35,000			$	—			$	35,000
	Total derivatives designated as hedging instruments under ASC Topic 815		$	—			$	35,000			$	—			$	35,000
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		$	376,374			$	374,536			$	376,374			$	374,536
	Forward sales contracts			8,218				212,028				253,051				53,269
	Written and purchased options			366,585				388,793				196,950				185,885
	Total derivatives not designated as hedging instruments under ASC Topic 815		$	751,177			$	975,357			$	826,375			$	613,690
	Total derivatives		$	751,177			$	1,010,357			$	826,375			$	648,690
	The Company is party to collateral agreements with certain derivative counterparties. Such agreements require that the Company maintain collateral based on the fair values of individual derivative transactions. In the event of default by the Company, the counterparty would be entitled to the collateral.
	At September 30, 2013 and December 31, 2012, the Company was required to post $5,630,000 and $2,650,000, respectively, in cash as collateral for its derivative transactions, which are included in interest-bearing deposits in banks on the Company’s consolidated balance sheets. The Company does not anticipate additional assets will be required to be posted as collateral, nor does it believe additional assets would be required to settle its derivative instruments immediately if contingent features were triggered at September 30, 2013. 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 generally-accepted accounting principles, the Company does not offset fair value amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral against recognized fair value amounts of derivatives executed with the same counterparty under a master netting agreement. The following table reconciles the gross amounts presented in the consolidated balance sheets to the net amounts that would result in the event of offset.
			September 30, 2013
			Gross Amounts				Gross Amounts Not Offset								Net
			Presented in the				in the Balance Sheet
	(Dollars in thousands)		Balance Sheet				Derivatives				Collateral (1)
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			14,312				—				—				14,312
	Written and purchased options			11,865				—				—				11,865
	Total derivative assets subject to master netting arrangements		$	26,177			$	—			$	—			$	26,177
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			14,312				—				(5,658	)			8,654
	Total derivative liabilities subject to master netting arrangements		$	14,312			$	—			$	(5,658	)		$	8,654
	-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
			December 31, 2012
			Gross Amounts				Gross Amounts Not Offset								Net
			Presented in the				in the Balance Sheet
	(Dollars in thousands)		Balance Sheet				Derivatives				Collateral (1)
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	499			$	(499	)		$	—			$	—
	Interest rate contracts not designated as hedging instruments			25,940				—				—				25,940
	Written and purchased options			8,763				—				—				8,763
	Total derivative assets subject to master netting arrangements		$	35,202			$	(499	)		$	—			$	34,703
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	1,843			$	(499	)		$	—			$	1,344
	Interest rate contracts not designated as hedging instruments			25,940				—				(13,350	)			12,590
	Total derivative liabilities subject to master netting arrangements		$	27,783			$	(499	)		$	(13,350	)		$	13,934
	-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
	During the nine months ended September 30, 2013 and 2012, the Company has not reclassified into earnings any gain or loss as a result of the discontinuance of cash flow hedges because it was probable the original forecasted transaction would not occur by the end of the originally specified term.
	At September 30, 2013, the fair value of derivatives that will mature within the next twelve months is $690,000. 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.
	Information pertaining to the effect of the hedging instruments on the consolidated financial statements is as follows:
			Amount of Gain (Loss)								Location of		Amount of Gain								Location of	Amount of Gain
			Recognized in OCI								Gain (Loss)		(Loss)								Gain (Loss)	(Loss)
			net of taxes								Reclassified		Reclassified								Recognized in	Recognized in
			(Effective Portion)								from		from								Income on	Income on
						Accumulated	Accumulated						Derivative	Derivative
						OCI into	OCI into						(Ineffective	(Ineffective
						Income	Income						Portion and	Portion and
						(Effective	(Effective Portion)						Amount	Amount
						Portion)							Excluded from	Excluded from
													(Effectiveness	Effectiveness Testing)
													Testing)
		As of September 30								For the Three Months Ended September 30
(Dollars in thousands)		2013				2012						2013				2012					2013		2012
Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
Interest rate contracts		$	—			$	(2,358	)		Other income		$	—			$	(408	)		Other income	$	—	$	—
										(expense)										(expense)
		$	—			$	(2,358	)				$	—			$	(408	)			$	—	$	—
		Amount of Gain								Location of		Amount of Gain								Location of	Amount of Gain
		(Loss) Recognized								Gain (Loss)		(Loss) Reclassified								Gain (Loss)	(Loss)
		in OCI net of								Reclassified		from Accumulated								Recognized in	Recognized in
		taxes								from		OCI into Income								Income on	Income on
		(Effective Portion)								Accumulated		(Effective Portion)								Derivative	Derivative
										OCI into										(Ineffective	(Ineffective
										Income										Portion and	Portion and
										(Effective										Amount	Amount
										Portion)										Excluded from	Excluded from
																				(Effectiveness	Effectiveness Testing)
																				Testing)
		As of September 30								For the Nine Months Ended September 30
(Dollars in thousands)		2013				2012						2013				2012					2013		2012
Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
Interest rate contracts		$	—			$	(2,358	)		Other income		$	(392	)		$	(1,195	)		Other income	$	—	$	—
										(expense)										(expense)
		$	—			$	(2,358	)				$	(392	)		$	(1,195	)			$	—	$	—
		Location of				Amount of Gain (Loss) Recognized in
		Gain (Loss)				Income on Derivatives
		Recognized in
		Income				For the Three Months Ended								For the Nine Months Ended
		on Derivatives				September 30								September 30
(Dollars in thousands)						2013				2012				2013				2012
Derivatives Not Designated as Hedging Instruments under ASC Topic 815
Interest rate contracts			Other income			$	2,061				247				2,542				627
			(expense)
Forward sales contracts			Mortgage Income				3,290				(1,887	)			897				(1,887	)
Written and purchased options			Mortgage Income				(7,896	)			3,378				(3,820	)			5,094
						$	(2,545	)		$	1,738			$	(381	)		$	3,834

Other_Comprehensive_Income

Other Comprehensive Income	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Other Comprehensive Income	'
	NOTE 13 –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
		September 30, 2013
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	5,528		$	(1,935	)	$	3,593
	Less: reclassification adjustment for losses included in net income		3			(1	)		2
	Net unrealized gains		5,531			(1,936	)		3,595
	Fair value of derivative instruments designated as cash flow hedges
	Change in fair value of derivative instruments designated as cash flow hedges during the period	$	—		$	—		$	—
	Less: reclassification adjustment for gains included in net income		—			—			—
	Fair value of derivative instruments designated as cash flow hedges		—			—			—
	Total other comprehensive income	$	5,531		$	(1,936	)	$	3,595
		Three Months Ended
		30-Sep-12
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	6,099		$	(2,135	)	$	3,964
	Less: reclassification adjustment for gains included in net income		(41	)		14			(27	)
	Net unrealized gains		6,058			(2,121	)		3,937
	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	$	800		$	(280	)	$	520
	Less: reclassification adjustment for losses included in net income		409			(142	)		267
	Fair value of derivative instruments designated as cash flow hedges		1,209			(422	)		787
	Total other comprehensive income	$	7,267		$	(2,543	)	$	4,724
		Nine Months Ended
		September 30, 2013
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized loss on securities:
	Unrealized holding losses arising during the period	$	(38,769	)	$	13,569		$	(25,200	)
	Less: reclassification adjustment for gains included in net income		(2,259	)		791			(1,468	)
	Net unrealized losses		(41,028	)		14,360			(26,668	)
	Fair value of derivative instruments designated as cash flow hedges
	Change in fair value of derivative instruments designated as cash flow hedges during the period	$	952		$	(333	)	$	619
	Less: reclassification adjustment for losses included in net income		392			(137	)		255
	Fair value of derivative instruments designated as cash flow hedges		1,344			(470	)		874
	Total other comprehensive loss	$	(39,684	)	$	13,890		$	(25,794	)
		Nine Months Ended
		30-Sep-12
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	8,236		$	(2,883	)	$	5,353
	Less: reclassification adjustment for gains included in net income		(3,743	)		1,310			(2,433	)
	Net unrealized gains		4,493			(1,573	)		2,920
	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	$	(1,882	)	$	659		$	(1,223	)
	Less: reclassification adjustment for losses included in net income		1,195			(418	)		777
	Fair value of derivative instruments designated as cash flow hedges		(687	)		241			(446	)
	Total other comprehensive income	$	3,806		$	(1,332	)	$	2,474

ShareBased_Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Share-Based Compensation	'
	NOTE 14 – SHARE-BASED COMPENSATION
	The Company has various types of share-based compensation plans. These plans are administered by the Compensation Committee of the Board of Directors, which selects persons eligible to receive awards and determines the number of shares and/or options subject to each award, the terms, conditions and other provisions of the awards. During the nine months ended September 30, 2013 and 2012, the Company did not have any equity awards that were settled in cash.
	Stock option plans
	The Company issues stock options under various plans to directors, officers and other key employees. The option exercise price cannot be less than the fair value of the underlying common stock as of the date of the option grant and the maximum option term cannot exceed ten years. The stock options granted were issued with vesting periods ranging from one-and-a half to seven years. At September 30, 2013, future option or restricted stock awards of 491,346 shares could be made under approved incentive compensation plans.
	The following table represents the compensation expense that is included in salaries and employee benefits expense and related income tax benefits in the accompanying consolidated statements of comprehensive income related to stock options.
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2013			2012			2013			2012
	Compensation expense related to stock options		$	526		$	334		$	1,592		$	1,317
	Income tax benefit related to stock options			184			117			557			461
	Impact on basic earnings per share			0.01			0.01			0.03			0.03
	Impact on diluted earnings per share			0.01			0.01			0.03			0.03
	The Company reported $495,000 and $940,000 of excess tax benefits as financing cash inflows during the nine months ended September 30, 2013 and 2012, respectively, related to the exercise and vesting of stock options. Net cash proceeds from the exercise of stock options were $5,441,000 and $1,541,000 for the nine months ended September 30, 2013 and 2012, respectively.
	The Company uses the Black-Scholes option pricing model to estimate the fair value of share-based awards. The following weighted-average assumptions were used for option awards outstanding during the nine-month periods ended September 30:
			2013			2012
	Expected dividends			2.6	%		2.3	%
	Expected volatility			34.8	%		33.9	%
	Risk-free interest rate			1.7	%		2.9	%
	Expected term (in years)			8.6			5.8
	Weighted-average grant-date fair value		$	15.37		$	13.58
	The assumptions above are based on multiple factors, including historical stock option exercise patterns and post-vesting employment termination behaviors, expected future exercise patterns and the expected volatility of the Company’s stock price.
	At September 30, 2013, there was $4,485,000 of unrecognized compensation cost related to stock options which is expected to be recognized over a weighted-average period of 4.7 years.
	The following table represents the activity related to stock options during the periods indicated.
			Number of			Weighted			Weighted Average
			shares			Average			Remaining Contract Life
						Exercise
						Price
	Oustanding options, December 31, 2011			1,097,620		$	50.14
	Granted			226,764			51.73
	Issued in connection with acquisition			32,863			41.3
	Exercised			(46,729	)		29.42
	Forfeited or expired			(29,410	)		57.39
	Outstanding options, September 30, 2012			1,281,108		$	50.78			4.8		Years
	Outstanding exercisable at September 30, 2012			822,410		$	48.94			3		Years
	Oustanding options, December 31, 2012			1,236,075		$	51.48
	Granted			75,722			52.36
	Exercised			(142,841	)		38.09
	Forfeited or expired			(36,608	)		56.01
	Outstanding options, September 30, 2013			1,132,348		$	53.09			4.7		Years
	Outstanding exercisable at September 30, 2013			749,545		$	52.94			3.2		Years
	At September 30, 2013, the aggregate intrinsic value of shares underlying outstanding stock options and underlying exercisable stock options was $2,090,000 and $1,951,000. Total intrinsic value of options exercised was $1,920,000 and $1,046,000 for the nine months ended September 30, 2013 and 2012, respectively.
	Restricted stock plans
	The Company issues restricted stock under various plans for certain officers and directors. A supplemental stock benefit plan adopted in 1999 and the 2001, 2005, 2008, and 2010 Incentive Plans allow grants of restricted stock. The plans allow for the issuance of restricted stock awards that may not be sold or otherwise transferred until certain restrictions have lapsed. The holders of the restricted stock receive dividends and have the right to vote the shares. The fair value of the restricted stock shares awarded under these plans is recorded as unearned share-based compensation, a contra-equity account. The unearned compensation related to these awards is amortized to compensation expense over the vesting period (generally three to seven years). The total share-based compensation expense for these awards is determined based on the market price of the Company’s common stock at the date of grant applied to the total number of shares granted and is amortized over the vesting period. As of September 30, 2013, unearned share-based compensation associated with these awards totaled $23,253,000.
	The following table represents the compensation expense that was included in salaries and employee benefits expense in the accompanying consolidated statements of income related to restricted stock grants:
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands)		2013			2012			2013			2012
	Compensation expense related to restricted stock		$	2,110		$	1,973		$	6,055		$	5,638
	The following table represents unvested restricted stock award activity for the nine months ended September 30:
			2013			2012
	Balance at beginning of period			538,202			512,112
	Granted			166,223			174,393
	Forfeited			(27,483	)		(8,736	)
	Earned and issued			(136,629	)		(120,644	)
	Balance at end of period			540,313			557,125
	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 period and the current market price of the Company’s stock.
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands)		2013			2012			2013			2012
	Compensation expense related to phantom stock		$	792		$	245		$	2,602		$	1,426
	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, 2011			232,921			8,942			241,863		$	11,924,000
Granted			117,506			6,852			124,358			5,696,000
Forfeited share equivalents			(8,052	)		(242	)		(8,294	)		(380,000	)
Vested share equivalents			(16,735	)		(1,144	)		(17,879	)		(894,000	)
Balance, September 30, 2012			325,640			14,408			340,048		$	15,574,000
Balance, December 31, 2012			318,729			16,035			334,764		$	16,444,000
Granted			166,664			8,793			175,457			9,108,000
Forfeited share equivalents			(16,381	)		(681	)		(17,062	)		(886,000	)
Vested share equivalents			(45,065	)		(3,327	)		(48,392	)		(2,453,000	)
Balance, September 30, 2013			423,947			20,820			444,767		$	23,088,000
(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 $51.91 and $45.80 on September 30, 2013 and 2012, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	NOTE 15 – COMMITMENTS AND CONTINGENCIES
	Off-balance sheet commitments
	The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. Such commitments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the consolidated balance sheets. The credit policies used for these commitments are consistent with those used for on-balance sheet instruments. The Company’s exposure to credit loss in the event of nonperformance by other parties represents the contractual amount of the financial instruments. At September 30, 2013, the fair value of guarantees under commercial and standby letters of credit was $1,067,000. 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.
	The Company had the following financial instruments outstanding, whose contract amounts represent credit risk:
	(Dollars in thousands)	September 30		December 31
		2013		2012
	Commitments to grant loans	$	342,494	$	192,295
	Unfunded commitments under lines of credit		2,972,046		2,372,971
	Commercial and standby letters of credit		106,652		62,207
	Reserve for unfunded lending commitments		11,959		—
	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 it is reasonably possible to incur losses above amounts already accrued associated with legal proceedings between $0.5 million and $2.2 million.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	NOTE 16 – FAIR VALUE MEASUREMENTS
	The Company has segregated all financial assets and liabilities that are measured at fair value on a recurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to estimate the fair value at the measurement date in the tables below.
	(Dollars in thousands)	September 30, 2013
	Assets	(Level 1)			(Level 2)			(Level 3)		Total
	Available for sale securities	$	15,220		$	1,949,169		$	—	$	1,964,389
	Derivative instruments		—			32,469			—		32,469
	Total	$	15,220		$	1,981,638		$	—	$	1,996,858
	Liabilities
	Derivative instruments		—			31,521			—		31,521
	Total	$	—		$	31,521		$	—	$	31,521
	(Dollars in thousands)	31-Dec-12
	Assets	(Level 1)			(Level 2)			(Level 3)		Total
	Available for sale securities	$	—		$	1,745,004		$	—	$	1,745,004
	Derivative instruments		—			42,119			—		42,119
	Total	$	—		$	1,787,123		$	—	$	1,787,123
	Liabilities
	Derivative instruments		—			36,890			—		36,890
	Total	$	—		$	36,890		$	—	$	36,890
	During 2013, available for sale securities with a market value of $15,220,000 were purchased and included in the Level 1 fair value measurement category in the table above. The security was issued by Fannie Mae and was included in the Level 1 category at September 30, 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) for the first nine months of 2013 related to assets and liabilities measured at fair value on a recurring basis are reported in noninterest income or other comprehensive income as follows:
	(Dollars in thousands)	Noninterest			Other
		income			comprehensive
					income
	Total gains (losses) included in earnings (or changes in net assets)	$	(1,056	)	$	—
	Change in unrealized gains (losses) relating to assets still held at September 30, 2013		—			(25,794	)
	The Company has segregated all financial assets and liabilities that are measured at fair value on a nonrecurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to determine the fair value at the measurement date in the tables below.
		September 30, 2013
	(Dollars in thousands)	(Level 1)			(Level 2)			(Level 3)		Total
	Assets
	Loans	$	—		$	1,932		$	—	$	1,932
	Mortgage loans held for sale		—			3,213			—		3,213
	OREO		—			20,427			—		20,427
	Total	$	—		$	25,572		$	—	$	25,572
		December 31, 2012
	(Dollars in thousands)	(Level 1)			(Level 2)			(Level 3)		Total
	Assets
	Loans	$	—		$	6,388		$	—	$	6,388
	Mortgage loans held for sale		—			32,753			—		32,753
	OREO		—			20,427			—		20,427
	Total	$	—		$	59,568		$	—	$	59,568
	The tables above exclude the initial measurement of assets and liabilities that were acquired as part of the Florida Gulf, OMNI, Cameron, and Florida Trust Company acquisitions completed in 2012 and 2011. These assets and liabilities were recorded at their fair value upon acquisition in accordance with generally-accepted accounting principles and were not re-measured during the periods presented unless specifically required by generally accepted accounting principles. 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, the Company records 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 $3,024,000 were recorded at their fair value at September 30, 2013. These loans include a reserve of $1,092,000 included in the Company’s allowance for credit losses at September 30, 2013. Impaired non-covered loans with an outstanding balance of $7,269,000 were recorded at their fair value at December 31, 2012. These loans include a reserve of $880,000 included in the Company’s allowance for credit losses at December 31, 2012.
	During the second quarter of 2013, the Company announced plans to close ten branches during the second and third quarters of 2013 as part of its business strategy. The Company has notified customers of these branches and has received the required regulatory approvals to proceed with closure. The Company reviewed the carrying amount of the owned properties and concluded it exceeded the fair value of these branches at that date. As a result, the Company recorded an impairment loss in other noninterest expense of $0 in its consolidated statement of comprehensive income for the nine months ended September 30, 2013. After the impairment loss, the carrying value of the branches was $0 and is included in OREO (as real estate acquired for development or resale) on the Company’s consolidated balance sheet at September 30, 2013.
	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.
	The Company did not record any liabilities at fair value for which measurement of the fair value was made on a nonrecurring basis during the nine months ended September 30, 2013 and 2012.
	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. The Company has currently chosen not to elect the fair value option for any items that are not already required to be measured at fair value in accordance with generally accepted accounting principles, and as such has not included any gains or losses in earnings for the nine months ended September 30, 2013 and 2012.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments	'
	NOTE 17 – FAIR VALUE OF FINANCIAL INSTRUMENTS
	The estimated fair value of a financial instrument is the current amount that would be exchanged between willing parties, other than in a forced liquidation. Fair value is best determined based upon quoted market prices. However, in many instances, there are no quoted market prices for the Company’s various financial instruments. In cases where quoted market prices are not available, fair values are based on estimates using present value or other valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Accordingly, the fair value estimates may not be realized in an immediate settlement of the instrument. ASC Topic 825 excludes certain financial instruments and all non-financial instruments from its disclosure requirements. Accordingly, the aggregate fair value amounts presented may not necessarily represent the underlying fair value of the Company.
	The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate that value. Refer to Note 1 to these financial statements for the methods and assumptions used to measure the fair value of investment securities and derivative instruments.
	Cash and cash equivalents
	The carrying amounts of cash and cash equivalents approximate their fair value.
	Loans
	The fair values of non-covered mortgage loans receivable are estimated based on present values using entry-value rates (the interest rate that would be charged for a similar loan to a borrower with similar risk at the indicated balance sheet date) at September 30, 2013 and December 31, 2012, weighted for varying maturity dates. Other non-covered loans receivable are valued based on present values using entry-value interest rates at September 30, 2013 and December 31, 2012 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. 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 September 30, 2013 and December 31, 2012 for deposits with similar remaining maturities. The fair value of the Company’s deposits would therefore be categorized within Level 3 of the fair value hierarchy.
	Short-term borrowings
	The carrying amounts of short-term borrowings maturing within ninety days approximate their fair values.
	Long-term debt
	The fair values of long-term debt are estimated using discounted cash flow analyses based on the Company’s current incremental borrowing rates for similar types of borrowing arrangements. The fair value of the Company’s long-term debt would therefore be categorized within Level 3 of the fair value hierarchy.
	Off-balance sheet items
	The Company has outstanding commitments to extend credit and standby letters of credit. These off-balance sheet financial instruments are generally exercisable at the market rate prevailing at the date the underlying transaction will be completed. At September 30, 2013 and December 31, 2012, the fair value of guarantees under commercial and standby letters of credit was immaterial.
	The estimated fair values and carrying amounts of the Company’s financial instruments are as follows:
		September 30, 2013				December 31, 2012
	(Dollars in thousands)	Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Financial Assets
	Cash and cash equivalents	$	553,447	$	553,447	$	970,977	$	970,977
	Investment securities		2,120,067		2,119,699		1,950,066		1,956,502
	Loans and loans held for sale		9,151,322		9,257,560		8,766,054		8,800,563
	FDIC loss share receivable		204,885		59,512		423,069		207,222
	Derivative instruments		32,469		32,469		42,119		42,119
	Accrued interest receivable		31,296		31,296		32,183		32,183
	Financial Liabilities
	Deposits	$	10,950,764	$	10,533,414	$	10,748,277	$	10,594,885
	Short-term borrowings		258,850		258,850		303,045		303,045
	Long-term debt		281,101		239,506		423,377		394,490
	Derivative instruments		31,521		31,521		36,890		36,890
	Accrued interest payable		6,026		6,026		6,615		6,615
	The fair value estimates presented herein are based upon pertinent information available to management as of September 30, 2013 and December 31, 2012. 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.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2013
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, IBERIA Asset Management Inc. (“IAM”), and IBERIA CDE, LLC (“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. IB Aircraft Holdings, LLC owns a fractional share of an aircraft used by management of the Company and its subsidiaries. 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.
Segments	'
	SEGMENTS
	All of the Company’s banking operations are considered by management to be aggregated in one reportable operating segment. Because the overall banking operations comprise substantially all of the consolidated operations and none of the Company’s other subsidiaries, either individually or in the aggregate, meet quantitative materiality thresholds, no separate segment disclosures are presented in these consolidated financial statements. The Company has invested in its financial reporting infrastructure to report financial information associated with performance of segments. The Company anticipates reporting this information at the end of 2013.
FDIC Loss Share Receivable	'
	FDIC LOSS SHARE RECEIVABLE
	Because the FDIC reimburses the Company for losses on certain loans acquired in 2009 and 2010, indemnification assets were recorded at fair value as of the acquisition dates. The initial values of the indemnification assets were based on estimated cash flows to be received over the expected life of the acquired assets, not to exceed the term of the indemnification agreements. The loss sharing terms of the Company’s commercial and single family residential indemnification agreements are five years and ten years, respectively, from the date of acquisition.
	Because the indemnification assets are measured on the same basis as the indemnified loans, subject to contractual and collectability limitations, the indemnification assets are impacted by changes in expected cash flows on covered assets. Increases in credit losses expected to occur within the loss share term are recorded as current period increases to the allowance for credit losses and increase the amount collectible from the FDIC by the applicable loss share percentage. Decreases in credit losses expected to occur within loss share term reduce the amount collectible from the FDIC and increase the amount collectible from customers in the form of prospective accretion on loans. Increases in the portion of indemnification asset collectible from customers are amortized to income. Periodic amortization represents the amount that is expected to result in symmetrical recognition of pool-level accretion and amortization over the shorter of 1) the life of the loan or 2) the life of the shared loss agreement.
	The Company assesses the indemnification assets for collectability at the acquisition level based on three sources: 1) the FDIC, 2) OREO transactions, and 3) customers. Amounts collectible from the FDIC through loss reimbursements are comprised of losses currently expected within the loss share term. A current period impairment would be recorded to the extent that events or circumstances indicate that losses previously expected to occur within the loss share term are expected to occur subsequent to loss share termination. Amounts collectible through expected gains on the sale of OREO are written-up or impaired each period based on the best available information. Amounts collectible from customers in the form of accretion are deemed collectible to the extent that net acquisition-level yield, which primarily consists of accretion and indemnification asset amortization, are expected to remain positive over the life of the shared loss agreement. Impairment of amounts collectible from customers would be recorded as a current period charge to income, to the extent required to maintain the zero net yield floor.
	Loss assumptions used to measure the basis of the indemnified loans are consistent with the loss assumptions used to measure the indemnification assets.
	A claim receivable is established within other assets when a loss is incurred and the indemnification asset is reduced when cash is received from the FDIC.
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
	As of September 30, 2013, the Company has $108,285,000 of conforming mortgage loans held for sale. Mortgage loans originated and held for sale are carried at the lower of cost or estimated fair value. The Company obtains quotes or bids on these loans directly from purchasing financial institutions. Mortgage loans held for sale that were recorded at estimated fair value are included in Note 16.
	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 obtainable market price, if available (Level 1) or the fair value of the collateral if the loan is collateral dependent (Level 2). Measuring the impairment of loans using the present value of expected future cash flows, discounted at the loan’s effective interest rate, is not considered a fair value measurement. Fair value of the collateral is determined by appraisals or independent valuation.
	Other real estate owned (OREO)
	Fair values of OREO at September 30, 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 $1,437,000 and $867,000 in earnings for the three months ended September 30, 2013 and 2012, respectively, and $3,993,000 and $4,900,000 for the nine months ended September 30, 2013 and 2012, respectively.
	Derivative financial instruments
	The Company may utilize interest rate swap agreements to convert a portion of its variable-rate debt to a fixed rate (cash flow hedge). The Company also enters into commitments to originate loans whereby the interest rate on the prospective loan is determined prior to funding (“rate lock commitments”). 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)	9 Months Ended
	Sep. 30, 2013
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 Three Months Ended						For the Nine Months Ended
			30-Sep						30-Sep
	(Dollars in thousands, except per share data)		2013			2012			2013			2012
	Income available to common shareholders		$	23,192		$	21,234		$	39,499		$	53,187
	Distributed earnings to unvested restricted stock			(421	)		(401	)		(744	)		(1,009	)
	Distributed earnings to common shareholders - basic			22,771			20,833			38,755			52,178
	Undistributed earnings reallocated to unvested restricted stock			(4	)		(5	)		—			2
	Distributed and undistributed earnings to common shareholders - diluted		$	22,767		$	20,828		$	38,755		$	52,180
	Weighted average shares outstanding - basic (1)			29,631,799			29,066,000			29,582,081			29,303,849
	Weighted average shares outstanding - diluted			29,147,232			28,548,432			29,062,238			28,812,631
	Earnings per common share - basic		$	0.78		$	0.73		$	1.34		$	1.81
	Earnings per common share - diluted			0.78			0.73			1.33			1.81
	Earnings per unvested restricted stock share - basic			0.77			0.71			1.33			1.82
	Earnings per unvested restricted stock share - diluted			0.78			0.72			1.33			1.82
	-1	Weighted average basic shares outstanding include 547,155 and 563,061 shares of unvested restricted stock for the three months ended September 30, 2013 and 2012, respectively, and 559,556 and 554,041 shares for the nine months ended September 30, 2013 and 2012, respectively.
Schedule of Basic Earnings Per Common Share	'
	Additional information on the Company’s basic earnings per common share is shown in the following table.
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2013			2012			2013			2012
	Distributed earnings to common shareholders		$	9,926		$	9,826		$	29,736		$	29,695
	Undistributed earnings to common shareholders			12,845			11,007			9,019			22,483
	Total earnings to common shareholders		$	22,771		$	20,833		$	38,755		$	52,178
	Distributed earnings to unvested restricted stock		$	183		$	189		$	571		$	574
	Undistributed earnings to unvested restricted stock			238			212			173			435
	Total earnings allocated to unvested restricted stock		$	421		$	401		$	744		$	1,009
	Distributed earnings per common share		$	0.34		$	0.34		$	1.03		$	1.03
	Undistributed earnings per common share			0.44			0.39			0.31			0.78
	Total earnings per common share - basic		$	0.78		$	0.73		$	1.34		$	1.81
	Distributed earnings per unvested restricted stock share		$	0.34		$	0.34		$	1.02		$	1.04
	Undistributed earnings per unvested restricted stock share			0.43			0.37			0.31			0.78
	Total earnings per unvested restricted stock share - basic		$	0.77		$	0.71		$	1.33		$	1.82

Acquisition_and_Disposition_Ac1

Acquisition and Disposition Activity (Tables)	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]	'
Schedule of Branch Closure Costs	'
	The following table shows the costs the Company incurred that are included in its statements of comprehensive income for the periods indicated.
		For the Three Months Ended					For the Nine Months Ended
		September 30					September 30
	(Dollars in thousands)	2013			2012		2013		2012
	Employee termination	$	(70	)	$	384	$	299	$	384
	Accelerated depreciation		352			284		1,033		284
	Contract termination		591			—		591		—
	Impairment		323			2,743		4,941		2,743
		$	1,196		$	3,411	$	6,864	$	3,411

Investment_Securities_Tables

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2013
Investments Debt And Equity Securities [Abstract]	'
Schedule of Amortized Cost and Fair Values of Investment Securities, with Gross Unrealized Gains and Losses	'
	The amortized cost and fair values of investment securities, with gross unrealized gains and losses, consist of the following:
		September 30, 2013
	(Dollars in thousands)	Amortized			Gross		Gross			Estimated
		Cost			Unrealized		Unrealized			Fair
					Gains		Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	407,049		$	1,878	$	(7,127	)	$	401,800
	Obligations of state and political obligations		109,509			2,967		(235	)		112,241
	Mortgage-backed securities		1,449,275			14,928		(15,337	)		1,448,866
	Other securities		1,460			22		—			1,482
	Total securities available for sale	$	1,967,293		$	19,795	$	(22,699	)	$	1,964,389
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations	$	34,471		$	650	$	—		$	35,121
	Obligations of state and political obligations		84,471			1,735		(1,425	)		84,781
	Mortgage-backed securities		36,736			293		(1,621	)		35,408
	Total securities held to maturity	$	155,678		$	2,678	$	(3,046	)	$	155,310
		December 31, 2012
	(Dollars in thousands)	Amortized			Gross		Gross			Estimated
		Cost			Unrealized		Unrealized			Fair
					Gains		Losses			Value
	Securities available for sale:
	U.S. Government-sponsored enterprise obligations	$	281,746		$	4,364	$	(386	)	$	285,724
	Obligations of state and political obligations		120,680			6,573		(178	)		127,075
	Mortgage-backed securities		1,303,030			29,108		(1,482	)		1,330,656
	Other securities		1,460			89		—			1,549
	Total securities available for sale	$	1,706,916		$	40,134	$	(2,046	)	$	1,745,004
	Securities held to maturity:
	U.S. Government-sponsored enterprise obligations	$	69,949		$	1,244	$	—		$	71,193
	Obligations of state and political obligations		88,909			4,730		(113	)		93,526
	Mortgage-backed securities		46,204			728		(153	)		46,779
	Total securities held to maturity	$	205,062		$	6,702	$	(266	)	$	211,498
Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category	'
	Information pertaining to securities with gross unrealized losses aggregated by investment category and length of time that individual securities have been in a continuous loss position, is as follows:
		September 30, 2013
		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	$	(7,127	)	$	274,195	$	—		$	—		$	(7,127	)	$	274,195
	Obligations of state and political obligations		(10	)		326		(225	)		1,047			(235	)		1,373
	Mortgage-backed securities		(14,096	)		671,684		(1,241	)		38,600			(15,337	)		710,284
	Total securities available for sale	$	(21,233	)	$	946,205	$	(1,466	)	$	39,647		$	(22,699	)	$	985,852
	Securities held to maturity:
	Obligations of state and political obligations	$	(1,308	)	$	28,433	$	(117	)	$	2,080		$	(1,425	)	$	30,513
	Mortgage-backed securities		(850	)		15,490		(771	)		9,805			(1,621	)		25,295
	Total securities held to maturity	$	(2,158	)	$	43,923	$	(888	)	$	11,885		$	(3,046	)	$	55,808
		December 31, 2012
		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	$	(386	)	$	59,741	$	—		$	—		$	(386	)	$	59,741
	Obligations of state and political obligations		—			—		(178	)		1,094			(178	)		1,094
	Mortgage-backed securities		(1,473	)		180,027		(9	)		3,919			(1,482	)		183,946
	Total securities available for sale	$	(1,859	)	$	239,768	$	(187	)	$	5,013		$	(2,046	)	$	244,781
	Securities held to maturity:
	Obligations of state and political obligations	$	(113	)	$	8,242	$	—		$	—		$	(113	)	$	8,242
	Mortgage-backed securities		(153	)		16,262		—			—			(153	)		16,262
	Total securities held to maturity	$	(266	)	$	24,504	$	—		$	—		$	(266	)	$	24,504
Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Maturity	'
	The amortized cost and estimated fair value of investment securities by maturity at September 30, 2013 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.
		Securities Available for Sale								Securities Held to Maturity
	(Dollars in thousands)	Weighted			Amortized		Estimated			Weighted			Amortized			Estimated
		Average			Cost		Fair			Average			Cost			Fair
		Yield					Value			Yield						Value
	Within one year or less		1.99	%	$	16,230	$	16,430			1.85	%	$	24,541		$	24,815
	One through five years		1.38			220,047		220,114			3.01			18,071			18,685
	After five through ten years		1.98			596,282		597,600			2.6			24,599			25,040
	Over ten years		1.92			1,134,734		1,130,245			2.92			88,467			86,770
			1.88	%	$	1,967,293	$	1,964,389			2.71	%	$	155,678		$	155,310
Schedule of Realized Gains and Losses from Sale of Securities Classified as Available for Sale	'
	The following is a summary of realized gains and losses from the sale of securities classified as available for sale. Gains or losses on securities sold are recorded on the trade date, using the specific identification method.
		Three Months Ended September 30					Nine Months Ended September 30
	(Dollars in thousands)	2013			2012		2013			2012
	Realized gains	$	—		$	41	$	2,369		$	3,758
	Realized losses		(3	)		—		(110	)		(15	)
		$	(3	)	$	41	$	2,259		$	3,743
Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets	'
	The Company included the following securities in “Other assets” on the consolidated balance sheets:
	(Dollars in thousands)	September 30			December 31
		2013			2012
	Federal Home Loan Bank (FHLB) stock	$	12,759		$	16,860
	Federal Reserve Bank (FRB) stock		28,098			28,155
	Other investments		1,306			1,201
		$	42,163		$	46,216

Loans_Receivable_Tables

Loans Receivable (Tables)	9 Months Ended
	Sep. 30, 2013
Schedule of Non-Covered Loans Outstanding	'
	Loans receivable consist of the following, segregated into non-covered and covered loans, for the periods indicated:
			September 30, 2013
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	3,320,333		$	459,506		$	3,779,839
	Business			2,643,822			40,422			2,684,244
				5,964,155			499,928			6,464,083
	Residential mortgage loans:
	Residential 1-4 family			402,354			153,515			555,869
	Construction / Owner Occupied			7,586			—			7,586
				409,940			153,515			563,455
	Consumer and other loans:
	Home equity			1,131,870			149,144			1,281,014
	Indirect automobile			369,755			—			369,755
	Other			360,315			4,415			364,730
				1,861,940			153,559			2,015,499
			$	8,236,035		$	807,002		$	9,043,037
			December 31, 2012
	(Dollars in thousands)		Non-covered loans			Covered loans			Total
	Commercial loans:
	Real estate		$	2,990,700		$	640,843		$	3,631,543
	Business			2,450,667			87,051			2,537,718
				5,441,367			727,894			6,169,261
	Residential mortgage loans:
	Residential 1-4 family			284,019			187,164			471,183
	Construction / Owner Occupied			6,021			—			6,021
				290,040			187,164			477,204
	Consumer and other loans:
	Home equity			1,076,913			174,212			1,251,125
	Indirect automobile			327,985			—			327,985
	Other			269,519			3,486			273,005
				1,674,417			177,698			1,852,115
			$	7,405,824		$	1,092,756		$	8,498,580
Schedule of Non-Covered Loans on Nonaccrual Status	'
	The following table provides the recorded investment of non-covered loans on nonaccrual status at September 30, 2013 and December 31, 2012. Nonaccrual loans in the table exclude acquired loans.
	(Dollars in thousands)		September 30, 2013			December 31, 2012
	Commercial real estate construction		$	2,430		$	5,479
	Commercial real estate - other			9,488			23,475
	Commercial business			14,591			3,358
	Residential prime			8,501			8,367
	Home equity			7,092			5,635
	Indirect automobile			1,056			868
	Credit card			425			424
	Other			255			310
			$	43,838		$	47,916
Schedule of Carrying Amount of Acquired Covered Loans	'
	The carrying amount of the acquired covered loans at September 30, 2013 and December 31, 2012 consisted of loans determined to be impaired at the acquisition date, which are accounted for in accordance with ASC Topic 310-30, and loans that were considered to be performing at the acquisition date, accounted for by analogy to ASC Topic 310-30, as detailed in the following tables.
			September 30, 2013
	(Dollars in thousands)		Acquired			Acquired			Total
			Impaired			Performing			Covered
			Loans			Loans			Loans
	Commercial loans:
	Real estate		$	23,751		$	435,755		$	459,506
	Business			—			40,422			40,422
				23,751			476,177			499,928
	Residential mortgage loans:
	Residential 1-4 family			28,333			125,182			153,515
	Construction / Owner Occupied			—			—			—
				28,333			125,182			153,515
	Consumer and other loans:
	Home equity			25,195			123,949			149,144
	Indirect automobile			—			—			—
	Other			1,205			3,210			4,415
				26,400			127,159			153,559
			$	78,484		$	728,518		$	807,002
			December 31, 2012
	(Dollars in thousands)		Acquired			Acquired			Total
			Impaired			Performing			Covered
			Loans			Loans			Loans
	Commercial loans:
	Real estate		$	167,742		$	473,101		$	640,843
	Business			2,757			84,294			87,051
				170,499			557,395			727,894
	Residential mortgage loans:
	Residential 1-4 family			20,232			166,932			187,164
	Construction / Owner Occupied			—			—			—
				20,232			166,932			187,164
	Consumer and other loans:
	Home equity			22,094			152,118			174,212
	Indirect automobile			—			—			—
	Other			820			2,666			3,486
				22,914			154,784			177,698
			$	213,645		$	879,111		$	1,092,756
Summary of Changes in Accretable Yields of Acquired Loans	'
	The following is a summary of changes in the accretable yields of acquired loans during the nine months ended September 30, 2013 and 2012.
			September 30, 2013									September 30, 2012
	(Dollars in thousands)		Acquired			Acquired			Total			Acquired			Acquired			Total
			Impaired			Performing			Acquired			Impaired			Performing			Acquired
			Loans			Loans			Loans			Loans			Loans			Loans
	Balance at beginning of period		$	76,623		$	279,770		$	356,393		$	83,834		$	386,977		$	470,811
	Transfers from nonaccretable difference to accretable yield			6,148			34,480			40,628			1,062			4,245			5,307
	Accretion			(13,519	)		(119,193	)		(132,712	)		(21,924	)		(165,247	)		(187,171	)
	Changes in expected cash flows not affecting nonaccretable differences (1)			10,561			81,173			91,734			10,964			46,197			57,161
	Balance at end of period		$	79,813		$	276,230		$	356,043		$	73,936		$	272,172		$	346,108
	-1	Includes changes in cash flows expected to be collected due to the impact of changes in actual or expected timing of liquidation events, loan modifications, changes in interest rates and changes in prepayment assumptions.
Schedule of Troubled Debt Restructurings	'
	Information about the Company’s TDRs at September 30, 2013 and 2012 is presented in the following tables.
			September 30, 2013												September 30, 2012
			Accruing Loans												Accruing Loans
	(Dollars in thousands)		Current			Past Due			Nonaccrual TDRs			Total TDRs			Current			Past Due			Nonaccrual TDRs		Total TDRs
						> 30 days												> 30 days
	Commercial real estate construction		$	—		$	—		$	—		$	—		$	—		$	—		$	—	$	—
	Commercial real estate - other			411			—			5,601			6,012			370			264			18,985		19,619
	Commercial business			1,056			—			12,610			13,666			19			—			1,884		1,903
	Residential prime			—			—			—			—			—			—			—		—
	Residential subprime			—			—			—			—			—			—			—		—
	Home equity			—			—			263			263			94			—			224		318
	Indirect automobile			—			—			—			—			—			—			—		—
	Credit card			—			—			—			—			—			—			—		—
	Other			—			—			—			—			—			—			—		—
			$	1,467		$	—		$	18,474		$	19,941		$	483		$	264		$	21,093	$	21,840
Schedule of Modified TDRs	'
	The following table provides information on how the TDRs were modified during the periods indicated.
			Nine Months Ended
			September 30
	(Dollars in thousands)		2013			2012
	Extended maturities		$	—		$	412
	Interest rate adjustment			—			481
	Maturity and interest rate adjustment			—			2,389
	Movement to or extension of interest-rate only payments			—			939
	Forbearance			11,210			170
			$	11,210		$	4,391
Non-Covered Loans Excluding Acquired Loans [Member]	'
Schedule of Aging of Non-Covered Loans	'
	The following tables provide an analysis of the aging of non-covered loans as of September 30, 2013 and December 31, 2012.
			September 30, 2013
			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		$	—		$	—		$	2,430		$	2,430		$	380,665		$	383,095		$	—
	Commercial real estate - other			1,933			—			9,639			11,572			2,556,798			2,568,370			151
	Commercial business			1,743			6			14,591			16,340			2,573,065			2,589,405			—
	Residential prime			517			2,297			9,326			12,140			261,615			273,755			1,267
	Residential subprime			—			—			442			442			115,715			116,157			—
	Home equity			1,745			577			7,092			9,414			1,063,257			1,072,671			—
	Indirect automobile			1,719			439			1,056			3,214			364,094			367,308			—
	Credit card			184			102			425			711			59,225			59,936			—
	Other			684			460			255			1,399			287,477			288,876			—
			$	8,525		$	3,881		$	45,256		$	57,662		$	7,661,911		$	7,719,573		$	1,418
	(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.
			December 31, 2012
			Non-covered loans excluding acquired loans
			Past Due(1)															Total Non-covered			Recorded
																		Loans, Net of			Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Unearned Income			and Accruing
	Commercial real estate construction		$	60		$	—		$	5,479		$	5,539		$	288,137		$	293,676		$	—
	Commercial real estate - other			3,590			—			23,559			27,149			2,224,495			2,251,644			83
	Commercial business			1,430			13			3,687			5,130			2,362,304			2,367,434			329
	Residential prime			662			1,156			9,168			10,986			185,843			196,829			801
	Residential subprime			—			—			—			—			60,454			60,454			—
	Home equity			2,283			796			5,793			8,872			991,766			1,000,638			158
	Indirect automobile			1,624			326			868			2,818			320,148			322,966			—
	Credit card			130			51			424			605			51,117			51,722			—
	Other			566			105			310			981			201,161			202,142			—
			$	10,345		$	2,447		$	49,288		$	62,080		$	6,685,425		$	6,747,505		$	1,371
	(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	'
	The following tables provide an analysis of the aging of non-covered loans as of September 30, 2013 and December 31, 2012.
			September 30, 2013
			Non-covered acquired loans
			Past Due (1)																		Total Non-covered		Recorded
																					Loans, Net of		Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Discount			Unearned Income		and Accruing
	Commercial real estate construction		$	97		$	—		$	3,457		$	3,554		$	15,020		$	(1,928	)	$	16,646	$	3,457
	Commercial real estate - other			2,240			438			33,484			36,162			367,085			(51,025	)		352,222		33,484
	Commercial business			444			246			1,880			2,570			59,949			(8,102	)		54,417		1,880
	Residential prime			—			—			226			226			20,388			(586	)		20,028		226
	Home equity			1,567			302			4,681			6,550			56,842			(4,193	)		59,199		4,681
	Indirect automobile			86			1			102			189			2,258			—			2,447		102
	Other			162			185			948			1,295			13,859			(3,651	)		11,503		948
			$	4,596		$	1,172		$	44,778		$	50,546		$	535,401		$	(69,485	)	$	516,462	$	44,778
	(1)	Past due information includes loans acquired from OMNI, Cameron and Florida Gulf at the gross loan balance, prior to application of discounts.
			December 31, 2012
			Non-covered acquired loans
			Past Due (1)																		Total Non-covered		Recorded
																					Loans, Net of		Investment > 90 days
	(Dollars in thousands)		30-59 days			60-89 days			> 90 days			Total			Current			Discount			Unearned Income		and Accruing
	Commercial real estate construction		$	369		$	—		$	4,067		$	4,436		$	29,098		$	(3,968	)	$	29,566	$	4,067
	Commercial real estate - other			5,971			1,572			38,987			46,530			426,339			(57,055	)		415,814		38,987
	Commercial business			1,410			524			3,953			5,887			89,490			(12,144	)		83,233		3,953
	Residential prime			—			—			779			779			30,663			1,315			32,757		779
	Home equity			2,379			382			4,354			7,115			73,658			(4,498	)		76,275		4,354
	Indirect automobile			171			4			146			321			4,698			—			5,019		146
	Other			202			17			495			714			21,746			(6,805	)		15,655		495
			$	10,502		$	2,499		$	52,781		$	65,782		$	675,692		$	(83,155	)	$	658,319	$	52,781
	(1)	Past due information includes loans acquired from OMNI, Cameron and Florida Gulf at the gross loan balance, prior to application of discounts.
TDRs [Member]	'
Schedule of Subsequently Defaulted TDRs	'
	Information about the Company’s non-covered TDRs occurring in these periods is presented in the following table.
			September 30, 2013									September 30, 2012
	(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			5		$	12,507		$	12,329			14		$	4,478		$	3,707
	Commercial business			—			—			—			1			27			—
	Residential prime			—			—			—			—			—			—
	Home Equity			—			—			—			1			94			51
	Indirect automobile			—			—			—			—			—			—
	Credit card			—			—			—			—			—			—
	Other			—			—			—			1			—			—
				5		$	12,507		$	12,329			17		$	4,599		$	3,758
			September 30, 2013						September 30, 2012
	(In thousands, except number of loans)		Number of			Recorded			Number of			Recorded
			Loans			Investment			Loans			Investment
	Commercial real estate			45		$	6,012			46		$	19,048
	Commercial business			13			12,370			8			1,883
	Residential prime			—			—			—			—
	Home Equity			1			47			2			275
	Indirect automobile			—			—			—			—
	Credit card			—			—			—			—
	Other			1			—			1			—
				60		$	18,429			57		$	21,206
	-1	Recorded investment includes any allowance for credit losses recorded on the TDRs at the dates indicated.

Allowance_for_Credit_Losses_an1

Allowance for Credit Losses and Credit Quality (Tables)	9 Months Ended
	Sep. 30, 2013
Effect of Change in Methodology on the Company's Unaudited Consolidated Financial Statements	'
	The following table presents the effect of the change in methodology on the Company’s unaudited consolidated financial statements as of September 30, 2013.
	(Dollars in thousands)		Current Methodology			Previous Methodolgy			Difference			Per Share Difference
	Selected Data
	Allowance for loan losses		$	64,165		$	73,992		$	(9,827	)
	Reserve for unfunded lending commitments			11,959			—			11,959
	Allowance for credit losses		$	76,124		$	73,992		$	2,132
	(Reversal of)Provision for loan losses		$	2,884		$	2,883		$	1		$	(0.00	)
	Provision for unfunded lending commitments			2,131			—			2,131			0.05
	Total provision for credit losses		$	5,015		$	2,883		$	2,132		$	0.05
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 is as follows:
			September 30, 2013
			Non-covered loans
	(Dollars in thousands)		Excluding Acquired Loans			Acquired Loans			Covered Loans			Total
	Allowance for loan losses
	Balance at beginning of period		$	74,211		$	8,816		$	168,576		$	251,603
	(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements			2,884			(2,464	)		(58,540	)		(58,120	)
	Adjustment attributable to FDIC loss share arrangements			—			—			58,565			58,565
	Net (reversal of) provision for loan losses			2,884			(2,464	)		25			445
	Decrease in FDIC loss share receivable			—			—			(58,565	)		(58,565	)
	Transfer of balance to OREO			—			(1,013	)		(29,302	)		(30,315	)
	Transfer of balance to the RULC			(9,828	)		—			—			(9,828	)
	Loans charged-off			(7,455	)		(10	)		(1,683	)		(9,148	)
	Recoveries			4,353			—			—			4,353
	Balance at end of period		$	64,165		$	5,329		$	79,051		$	148,545
	Reserve for unfunded lending commitments
	Balance at beginning of period		$	—		$	—		$	—		$	—
	Transfer of balance from the allowance for loan losses			9,828			—			—			9,828
	Provision for unfunded lending commitments			2,131			—			—			2,131
	Balance at end of period		$	11,959		$	—		$	—		$	11,959
			September 30, 2012
			Non-covered loans
			Excluding Acquired Loans			Acquired Loans			Covered Loans			Total
	Allowance for loan losses
	Balance at beginning of period		$	74,861		$	—		$	118,900		$	193,761
	(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements			6,518			5,805			37,268			49,591
	Adjustment attributable to FDIC loss share arrangements			—			—			(33,786	)		(33,786	)
	Net (reversal of) provision for loan losses			6,518			5,805			3,482			15,805
	Increase in FDIC loss share receivable			—			—			33,786			33,786
	Transfer of balance to OREO			—			(408	)		(23,769	)		(24,177	)
	Loans charged-off			(6,818	)		(179	)		(13,283	)		(20,280	)
	Recoveries			2,455			18			19			2,492
	Balance at end of period		$	77,016		$	5,236		$	119,135		$	201,387
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, is as follows:
			September 30, 2013
	(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
			real estate			business
	Allowance for loan losses
	Balance at beginning of period		$	38,264		$	28,721		$	2,125		$	13,917		$	—		$	83,027
	(Reversal of) Provision for loan losses			(6,926	)		(582	)		1,048			6,880			—			420
	Transfer of balance to OREO			(279	)		(81	)		(646	)		(7	)		—			(1,013	)
	Transfer of balance to the RULC			(2,939	)		(3,497	)		(40	)		(3,352	)		—			(9,828	)
	Loans charged off			(1,966	)		(531	)		(481	)		(4,487	)		—			(7,465	)
	Recoveries			1,498			354			698			1,803			—			4,353
	Balance at end of period		$	27,652		$	24,384		$	2,704		$	14,754			—		$	69,494
	Reserve for unfunded commitments
	Balance at beginning of period		$	—		$	—		$	—		$	—		$	—		$	—
	Transfer of balance from the allowance for loan losses			2,939			3,497			40			3,352			—			9,828
	Provision for unfunded commitments			1,207			610			38			276			—			2,131
	Balance at end of period		$	4,146		$	4,107		$	78		$	3,628		$	—		$	11,959
	Allowance on loans individually evaluated for impairment		$	8		$	801		$	283		$	—		$	—		$	1,092
	Allowance on loans collectively evaluated for impairment			27,644			23,583			2,421			14,754			—			68,402
	Loans, net of unearned income:
	Balance at end of period		$	3,320,333		$	2,643,822		$	409,940		$	1,861,940		$	—		$	8,236,035
	Balance at end of period individually evaluated for impairment			9,529			14,548			1,407			263			—			25,747
	Balance at end of period collectively evaluated for impairment			3,310,804			2,629,274			408,533			1,861,677			—			8,210,288
	Balance at end of period acquired with deteriorated credit quality			16,287			45			120			1,815			—			18,267
			September 30, 2012
	(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
			real estate			business
	Allowance for credit losses
	Balance at beginning of period		$	35,604		$	25,705		$	897		$	12,655		$	—		$	74,861
	(Reversal of) Provision for loan losses			4,199			3,851			1,344			2,929			—			12,323
	Transfer of balance to OREO			(62	)		—			(337	)		(9	)		—			(408	)
	Loans charged off			(1,195	)		(769	)		(759	)		(4,274	)		—			(6,997	)
	Recoveries			790			80			30			1,573			—			2,473
	Balance at end of period		$	39,336		$	28,867		$	1,175		$	12,874		$	—		$	82,252
	Allowance on loans individually evaluated for impairment		$	1,173		$	162		$	163		$	43		$	—		$	1,541
	Allowance on loans collectively evaluated for impairment			38,163			28,705			1,012			12,831			—			80,711
	Loans, net of unearned income:
	Balance at end of period		$	2,879,836		$	2,357,303		$	266,069		$	1,587,488		$	—		$	7,090,696
	Balance at end of period individually evaluated for impairment			26,353			1,888			1,703			318			—			30,262
	Balance at end of period collectively evaluated for impairment			2,853,483			2,355,415			264,366			1,587,170			—			7,060,434
	Balance at end of period acquired with deteriorated credit quality			60,360			3,675			430			5,334			—			69,799
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, is as follows:
			September 30, 2013
	(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
			real estate			business
	Allowance for loan losses
	Balance at beginning of period		$	100,871		$	11,375		$	22,566		$	33,764		$	—		$	168,576
	(Reversal of) Provision for loan losses			27			—			(1	)		(1	)		—			25
	(Decrease) Increase in FDIC loss share receivable			(30,853	)		(3,137	)		(5,734	)		(18,841	)		—			(58,565	)
	Transfer of balance to OREO			(22,375	)		(314	)		(6,614	)		1			—			(29,302	)
	Loans charged off			(1,683	)		—			—			—			—			(1,683	)
	Balance at end of period		$	45,987		$	7,924		$	10,217		$	14,923		$	—		$	79,051
	Allowance on loans individually evaluated for impairment		$	—		$	—		$	—		$	—		$	—		$	—
	Allowance on loans collectively evaluated for impairment			45,987			7,924			10,217			14,923			—			79,051
	Loans, net of unearned income:
	Balance at end of period		$	459,506		$	40,422		$	153,515		$	153,559		$	—		$	807,002
	Balance at end of period individually evaluated for impairment			—			—			—			—			—			—
	Balance at end of period collectively evaluated for impairment			459,506			40,422			153,515			153,559			—			807,002
	Balance at end of period acquired with deteriorated credit quality			23,751			—			28,333			26,400			—			78,484
			September 30, 2012
	(Dollars in thousands)		Commercial			Commercial			Mortgage			Consumer			Unallocated			Total
			real estate			business
	Allowance for credit losses
	Balance at beginning of period		$	69,175		$	9,788		$	21,184		$	18,753		$	—		$	118,900
	(Reversal of) Provision for loan losses			3,550			922			(1,387	)		397			—			3,482
	(Decrease) Increase in FDIC loss share receivable			24,229			2,398			4,277			2,882			—			33,786
	Transfer of balance to OREO			(9,876	)		(2,475	)		(10,593	)		(825	)		—			(23,769	)
	Loans charged off			(13,143	)		—			(131	)		(9	)		—			(13,283	)
	Recoveries			16			—			—			3			—			19
	Balance at end of period		$	73,951		$	10,633		$	13,350		$	21,201		$	—		$	119,135
	Allowance on loans individually evaluated for impairment		$	—		$	—		$	—		$	—		$	—		$	—
	Allowance on loans collectively evaluated for impairment			73,951			10,633			13,350			21,201			—			119,135
	Loans, net of unearned income:
	Balance at end of period		$	670,001		$	91,822		$	197,333		$	180,094		$	—		$	1,139,250
	Balance at end of period individually evaluated for impairment			—			—			—			—			—			—
	Balance at end of period collectively evaluated for impairment			670,001			91,822			197,333			180,094			—			1,139,250
	Balance at end of period acquired with deteriorated credit quality			171,965			3,522			22,085			24,388			—			221,960
Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator	'
	Asset risk classifications for commercial loans reflect the classification as of September 30, 2013 and December 31, 2012.
			Non-covered loans excluding acquired loans
			September 30, 2013															December 31, 2012
	(Dollars in		Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
	thousands)					Mention															Mention
	Commercial real estate construction		$	374,458		$	4,800		$	3,837		$	—		$	383,095		$	269,842		$	16,767		$	7,067	$	—	$	293,676
	Commercial real estate - other			2,503,820			37,537			26,896			117			2,568,370			2,162,989			40,547			47,710		398		2,251,644
	Commercial business			2,546,614			9,013			32,825			953			2,589,405			2,295,788			21,640			49,958		48		2,367,434
	Total		$	5,424,892		$	51,350		$	63,558		$	1,070			5,540,870		$	4,728,619		$	78,954		$	104,735	$	446	$	4,912,754
			Non-covered loans excluding acquired loans
			September 30, 2013									December 31, 2012
	(Dollars in thousands)		Current			30+ Days			Total			Current			30+ Days			Total
						Past Due									Past Due
	Residential prime		$	261,615		$	12,140		$	273,755		$	185,843		$	10,986		$	196,829
	Residential subprime			115,715			442			116,157			60,454			—			60,454
	Home equity			1,063,257			9,414			1,072,671			991,766			8,872			1,000,638
	Indirect automobile			364,094			3,214			367,308			320,148			2,818			322,966
	Credit card			59,225			711			59,936			51,117			605			51,722
	Consumer - other			287,477			1,399			288,876			201,161			981			202,142
			$	2,151,383		$	27,320		$	2,178,703		$	1,810,489		$	24,262		$	1,834,751
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.
			September 30, 2013									December 31, 2012
	(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		$	9,392		$	9,392		$	—		$	26,151		$	26,151		$	—
	Commercial business			13,068			13,068			—			1,824			1,824			—
	Home equity			263			263			—			—			—			—
	With an allowance recorded:
	Commercial real estate			2,913			2,937			(24	)		3,464			3,663			(199	)
	Commercial business			2,569			2,579			(10	)		1,334			1,810			(476	)
	Residential prime			9,575			9,908			(333	)		9,861			10,070			(209	)
	Home equity			6,784			6,829			(45	)		5,860			5,951			(91	)
	Indirect automobile			1,050			1,056			(6	)		865			868			(3	)
	Credit card			417			425			(8	)		413			424			(11	)
	Other			252			255			(3	)		307			310			(3	)
			$	46,283		$	46,712		$	(429	)	$	50,079		$	51,071		$	(992	)
	Total commercial loans			27,942			27,976			(34	)		32,773			33,448			(675	)
	Total mortgage loans			9,575			9,908			(333	)		9,861			10,070			(209	)
	Total consumer loans			8,766			8,828			(62	)		7,445			7,553			(108	)
			For the Three Months Ended September 30												For the Nine Months Ended September 30
			2013						2012						2013						2012
	(Dollars in thousands)		Average			Interest			Average			Interest			Average			Interest			Average			Interest
			Recorded			Income			Recorded			Income			Recorded			Income			Recorded			Income
			Investment			Recognized (1)			Investment			Recognized (1)			Investment			Recognized (1)			Investment			Recognized (1)
	With no related allowance recorded:
	Commercial real estate		$	10,703		$	6		$	27,547		$	15		$	12,787		$	22		$	29,872		$	651
	Commercial business			13,218			17			2,451			—			8,608			59			3,387			71
	Home Equity			265			—			225			—			287			—			227			—
	With an allowance recorded:
	Commercial real estate			4,346			—			2,731			8			6,092			5			2,866			22
	Commercial business			2,739			—			209			1			2,746			3			215			1
	Residential prime			9,650			—			9,248			—			9,380			7			7,439			148
	Home equity			7,244			—			6,184			—			7,458			14			6,502			110
	Indirect automobile			1,349			—			1,135			—			1,610			22			1,345			20
	Credit card			424			—			387			—			426			—			354			—
	Other			372			—			585			—			446			4			675			6
			$	50,310		$	23		$	50,702		$	24		$	49,840		$	136		$	52,882		$	1,029
	Total commercial loans			31,006			23			32,938			24			30,233			89			36,340			745
	Total mortgage loans			9,650			—			9,248			—			9,380			7			7,439			148
	Total consumer loans			9,654			—			8,516			—			10,227			40			9,103			136
	-1	Interest income recognized on impaired loans represents income recognized before loans were placed on nonaccrual status.
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 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
			September 30, 2013															December 31, 2012
	(Dollars in thousands)		Pass			Special			Substandard			Doubtful			Total			Pass			Special			Substandard		Doubtful		Total
						Mention															Mention
	Commercial real estate construction		$	44,312		$	8,093		$	42,849		$	497		$	95,751		$	46,201		$	9,888		$	97,315	$	607	$	154,011
	Commercial real estate - other			146,103			56,182			194,785			7,496			404,566			201,261			65,498			279,171		8,530		554,460
	Commercial business			33,112			958			17,201			1,277			52,548			38,552			8,600			50,018		451		97,621
	Total		$	223,527		$	65,233		$	254,835		$	9,270		$	552,865		$	286,014		$	83,986		$	426,504	$	9,588	$	806,092
	Discount															(52,937	)												(78,198	)
															$	499,928												$	727,894
			Covered loans
			September 30, 2013												December 31, 2012
	(Dollars in thousands)		Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
						Past Due			(discount)									Past Due			(discount)
	Residential prime		$	164,214		$	33,114		$	(43,813	)	$	153,515		$	183,795		$	52,379		$	(49,010	)	$	187,164
	Home equity			150,302			41,683			(42,841	)		149,144			168,729			65,997			(60,514	)		174,212
	Credit card			665			36			—			701			841			65			—			906
	Consumer - other			643			204			2,867			3,714			1,154			1,523			(97	)		2,580
			$	315,824		$	75,037		$	(83,787	)	$	307,074		$	354,519		$	119,964		$	(109,621	)	$	364,862
Covered Loans [Member]	'
Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator	'
			Non-covered acquired loans
			September 30, 2013																		December 31, 2012
	(Dollars in		Pass			Special			Substandard			Doubtful			Discount			Total			Pass			Special		Substandard		Doubtful			Discount			Total
	thousands)					Mention																		Mention
	Commercial real estate construction		$	12,900		$	1,321		$	4,353		$	—		$	(1,928	)	$	16,646		$	25,896		$	2,410	$	5,228	$	—		$	(3,968	)	$	29,566
	Commercial real estate - other			320,781			18,438			63,816			212			(51,025	)		352,222			359,046			28,185		85,420		218			(57,055	)		415,814
	Commercial business			56,465			2,241			3,725			88			(8,102	)		54,417			86,201			2,159		4,808		2,209			(12,144	)		83,233
	Total		$	390,146		$	22,000		$	71,894		$	300		$	(61,055	)	$	423,285		$	471,143		$	32,754	$	95,456	$	2,427		$	(73,167	)	$	528,613
			Non-covered acquired loans
			September 30, 2013												December 31, 2012
	(Dollars in thousands)		Current			30+ Days			Premium			Total			Current			30+ Days			Premium			Total
						Past Due			(discount)									Past Due			(discount)
	Residential prime		$	20,388		$	226		$	(586	)	$	20,028		$	30,663		$	779		$	1,315		$	32,757
	Home equity			56,842			6,550			(4,193	)		59,199			73,658			7,115			(4,498	)		76,275
	Indirect automobile			2,258			189			—			2,447			4,698			321			—			5,019
	Consumer - other			13,859			1,295			(3,651	)		11,503			21,746			714			(6,805	)		15,655
			$	93,347		$	8,260		$	(8,430	)	$	93,177		$	130,765		$	8,929		$	(9,988	)	$	129,706

Loss_Sharing_Agreements_and_FD1

Loss Sharing Agreements and FDIC Loss Share Receivable (Tables)	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]	'
Schedule of FDIC Loss Share Receivable	'
	The following is a summary of FDIC loss share receivable year-to-date activity:
		September 30
	(Dollars in thousands)	2013			2012
	Balance at beginning of period	$	423,069		$	591,844
	Change due to (reversal of) credit loss provision recorded on FDIC covered loans		(58,565	)		33,786
	Amortization		(68,707	)		(89,899	)
	Submission of reimbursable losses to the FDIC		(44,910	)		(97,511	)
	Impairment		(31,813	)		—
	Changes due to a change in cash flow assumptions on OREO and other		(14,189	)		(7,053	)
	Balance at end of period	$	204,885		$	431,167

Transfers_and_Servicing_of_Fin1

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) (Tables)	9 Months Ended
	Sep. 30, 2013
Components of Mortgage Banking Activity	'
	The following table details the mortgage banking activity as of and for the nine months ended September 30:
	(Dollars in thousands)	2013			2012
	Balance at beginning of period	$	267,475		$	153,013
	Originations		1,712,557			1,749,121
	Sales		(1,871,747	)		(1,691,002	)
	Balance at end of period	$	108,285		$	211,132
	(Dollars in thousands)	2013			2012
	Fair value changes of derivatives and mortgage loans held for sale, net	$	(270	)	$	2,954
	Gains on sales		51,709			51,828
	Servicing and other income, net		402			336
		$	51,841		$	55,118
Schedule of Definite-Lived Intangible Assets	'
	Definite-lived intangible assets had the following carrying values for the periods indicated:
		September 30, 2013								December 31, 2012
	(Dollars in thousands)	Gross			Accumulated			Net		Gross		Accumulated			Net
		Carrying Amount			Amortization			Carrying Amount		Carrying Amount		Amortization			Carrying Amount
	Core deposit intangibles	$	45,406		$	(29,659	)	$	15,747	$	45,406	$	(26,284	)	$	19,122
	Customer relationship intangible asset		1,348			(579	)		769		1,348		(410	)		938
		$	46,754		$	(30,238	)	$	16,516	$	46,754	$	(26,694	)	$	20,060
Mortgage Servicing Rights [Member]	'
Schedule of Definite-Lived Intangible Assets	'
	Mortgage servicing rights had the following carrying values:
		September 30, 2013								December 31, 2012
	(Dollars in thousands)	Gross			Accumulated			Net		Gross		Accumulated			Net
		Carrying Amount			Amortization			Carrying Amount		Carrying Amount		Amortization			Carrying Amount
	Mortgage servicing rights	$	1,816		$	(543	)	$	1,273	$	1,234	$	(304	)	$	930

Goodwill_and_Other_Acquired_In1

Goodwill and Other Acquired Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'
Schedule of Carrying Amount of Goodwill	'
	Changes to the carrying amount of goodwill for the year ended December 31, 2012 and the nine months ended September 30, 2013 are provided in the following table.
	(Dollars in thousands)
	Balance, December 31, 2011	$	369,811
	Goodwill acquired during the year		32,420
	Goodwill adjustment to correct an immaterial error		(359	)
	Balance, December 31, 2012		401,872
	Goodwill acquired during the period		—
	Balance, September 30, 2013	$	401,872

Other_Real_Estate_Owned_Tables

Other Real Estate Owned (Tables)	9 Months Ended
	Sep. 30, 2013
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 as of the periods indicated.
		September 30, 2013						December 31, 2012
	(Dollars in thousands)	Non-covered		Covered		Total		Non-covered		Covered		Total
	Real estate owned acquired by foreclosure	$	31,261	$	85,616	$	116,877	$	35,080	$	75,784	$	110,864
	Real estate acquired for development or resale		10,518		—		10,518		9,199		—		9,199
	Other foreclosed property		109		1,483		1,592		14		1,459		1,473
		$	41,888	$	87,099	$	128,987	$	44,293	$	77,243	$	121,536

Derivative_Instruments_and_Oth1

Derivative Instruments and Other Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Schedule of Outstanding Derivative Instruments	'
	Information pertaining to outstanding derivative instruments is as follows:
			Balance Sheet		Asset Derivatives Fair Value								Balance Sheet		Liability Derivatives Fair Value
	(Dollars in thousands)		Location		September 30, 2013				December 31, 2012				Location		September 30, 2013				December 31, 2012
	Derivatives designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		Other assets		$	—			$	499			Other liabilities		$	—			$	1,843
	Total derivatives designated as hedging instruments under ASC Topic 815				$	—			$	499					$	—			$	1,843
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		Other assets		$	14,312			$	25,940			Other liabilities		$	14,312			$	25,940
	Forward sales contracts		Other assets			148				2,774			Other liabilities			5,289				343
	Written and purchased options		Other assets			18,009				12,906			Other liabilities			11,920				8,764
	Total derivatives not designated as hedging instruments under ASC Topic 815				$	32,469			$	41,620					$	31,521			$	35,047
	Total derivatives				$	32,469			$	42,119					$	31,521			$	36,890
			Asset Derivatives Notional Amount								Liability Derivatives Notional Amount
	(Dollars in thousands)		September 30, 2013				December 31, 2012				September 30, 2013				December 31, 2012
	Derivatives designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		$	—			$	35,000			$	—			$	35,000
	Total derivatives designated as hedging instruments under ASC Topic 815		$	—			$	35,000			$	—			$	35,000
	Derivatives not designated as hedging instruments under ASC Topic 815:
	Interest rate contracts		$	376,374			$	374,536			$	376,374			$	374,536
	Forward sales contracts			8,218				212,028				253,051				53,269
	Written and purchased options			366,585				388,793				196,950				185,885
	Total derivatives not designated as hedging instruments under ASC Topic 815		$	751,177			$	975,357			$	826,375			$	613,690
	Total derivatives		$	751,177			$	1,010,357			$	826,375			$	648,690
Reconciliation of Gross Amounts in Consolidated Balance Sheets	'
	The following table reconciles the gross amounts presented in the consolidated balance sheets to the net amounts that would result in the event of offset.
			September 30, 2013
			Gross Amounts				Gross Amounts Not Offset								Net
			Presented in the				in the Balance Sheet
	(Dollars in thousands)		Balance Sheet				Derivatives				Collateral (1)
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			14,312				—				—				14,312
	Written and purchased options			11,865				—				—				11,865
	Total derivative assets subject to master netting arrangements		$	26,177			$	—			$	—			$	26,177
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	—			$	—			$	—			$	—
	Interest rate contracts not designated as hedging instruments			14,312				—				(5,658	)			8,654
	Total derivative liabilities subject to master netting arrangements		$	14,312			$	—			$	(5,658	)		$	8,654
	-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
			December 31, 2012
			Gross Amounts				Gross Amounts Not Offset								Net
			Presented in the				in the Balance Sheet
	(Dollars in thousands)		Balance Sheet				Derivatives				Collateral (1)
	Derivatives subject to master netting arrangements
	Derivative assets
	Interest rate contracts designated as hedging instruments		$	499			$	(499	)		$	—			$	—
	Interest rate contracts not designated as hedging instruments			25,940				—				—				25,940
	Written and purchased options			8,763				—				—				8,763
	Total derivative assets subject to master netting arrangements		$	35,202			$	(499	)		$	—			$	34,703
	Derivative liabilities
	Interest rate contracts designated as hedging instruments		$	1,843			$	(499	)		$	—			$	1,344
	Interest rate contracts not designated as hedging instruments			25,940				—				(13,350	)			12,590
	Total derivative liabilities subject to master netting arrangements		$	27,783			$	(499	)		$	(13,350	)		$	13,934
	-1	Consists of cash collateral recorded at cost, which approximates fair value, and investment securities.
Schedule of Derivative Instruments on Consolidated Financial Statements	'
	Information pertaining to the effect of the hedging instruments on the consolidated financial statements is as follows:
			Amount of Gain (Loss)								Location of		Amount of Gain								Location of	Amount of Gain
			Recognized in OCI								Gain (Loss)		(Loss)								Gain (Loss)	(Loss)
			net of taxes								Reclassified		Reclassified								Recognized in	Recognized in
			(Effective Portion)								from		from								Income on	Income on
											Accumulated		Accumulated								Derivative	Derivative
											OCI into		OCI into								(Ineffective	(Ineffective
											Income		Income								Portion and	Portion and
											(Effective		(Effective Portion)								Amount	Amount
											Portion)										Excluded from	Excluded from
																					(Effectiveness	Effectiveness Testing)
																					Testing)
			As of September 30								For the Three Months Ended September 30
	(Dollars in thousands)		2013				2012						2013				2012					2013		2012
	Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
	Interest rate contracts		$	—			$	(2,358	)		Other income		$	—			$	(408	)		Other income	$	—	$	—
											(expense)										(expense)
			$	—			$	(2,358	)				$	—			$	(408	)			$	—	$	—
			Amount of Gain								Location of		Amount of Gain								Location of	Amount of Gain
			(Loss) Recognized								Gain (Loss)		(Loss) Reclassified								Gain (Loss)	(Loss)
			in OCI net of								Reclassified		from Accumulated								Recognized in	Recognized in
			taxes								from		OCI into Income								Income on	Income on
			(Effective Portion)								Accumulated		(Effective Portion)								Derivative	Derivative
											OCI into										(Ineffective	(Ineffective
											Income										Portion and	Portion and
											(Effective										Amount	Amount
											Portion)										Excluded from	Excluded from
																					(Effectiveness	Effectiveness Testing)
																					Testing)
			As of September 30								For the Nine Months Ended September 30
	(Dollars in thousands)		2013				2012						2013				2012					2013		2012
	Derivatives in ASC Topic 815 Cash Flow Hedging Relationships
	Interest rate contracts		$	—			$	(2,358	)		Other income		$	(392	)		$	(1,195	)		Other income	$	—	$	—
											(expense)										(expense)
			$	—			$	(2,358	)				$	(392	)		$	(1,195	)			$	—	$	—
			Location of				Amount of Gain (Loss) Recognized in
			Gain (Loss)				Income on Derivatives
			Recognized in
			Income				For the Three Months Ended								For the Nine Months Ended
			on Derivatives				September 30								September 30
	(Dollars in thousands)						2013				2012				2013				2012
	Derivatives Not Designated as Hedging Instruments under ASC Topic 815
	Interest rate contracts			Other income			$	2,061				247				2,542				627
				(expense)
	Forward sales contracts			Mortgage Income				3,290				(1,887	)			897				(1,887	)
	Written and purchased options			Mortgage Income				(7,896	)			3,378				(3,820	)			5,094
							$	(2,545	)		$	1,738			$	(381	)		$	3,834

Other_Comprehensive_Income_Tab

Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2013
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
		September 30, 2013
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	5,528		$	(1,935	)	$	3,593
	Less: reclassification adjustment for losses included in net income		3			(1	)		2
	Net unrealized gains		5,531			(1,936	)		3,595
	Fair value of derivative instruments designated as cash flow hedges
	Change in fair value of derivative instruments designated as cash flow hedges during the period	$	—		$	—		$	—
	Less: reclassification adjustment for gains included in net income		—			—			—
	Fair value of derivative instruments designated as cash flow hedges		—			—			—
	Total other comprehensive income	$	5,531		$	(1,936	)	$	3,595
		Three Months Ended
		30-Sep-12
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	6,099		$	(2,135	)	$	3,964
	Less: reclassification adjustment for gains included in net income		(41	)		14			(27	)
	Net unrealized gains		6,058			(2,121	)		3,937
	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	$	800		$	(280	)	$	520
	Less: reclassification adjustment for losses included in net income		409			(142	)		267
	Fair value of derivative instruments designated as cash flow hedges		1,209			(422	)		787
	Total other comprehensive income	$	7,267		$	(2,543	)	$	4,724
		Nine Months Ended
		September 30, 2013
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized loss on securities:
	Unrealized holding losses arising during the period	$	(38,769	)	$	13,569		$	(25,200	)
	Less: reclassification adjustment for gains included in net income		(2,259	)		791			(1,468	)
	Net unrealized losses		(41,028	)		14,360			(26,668	)
	Fair value of derivative instruments designated as cash flow hedges
	Change in fair value of derivative instruments designated as cash flow hedges during the period	$	952		$	(333	)	$	619
	Less: reclassification adjustment for losses included in net income		392			(137	)		255
	Fair value of derivative instruments designated as cash flow hedges		1,344			(470	)		874
	Total other comprehensive loss	$	(39,684	)	$	13,890		$	(25,794	)
		Nine Months Ended
		30-Sep-12
	(Dollars in thousands)	Before			Tax Expense			Net-of-Tax
		Tax			(Benefit)			Amount
	Unrealized gain on securities:
	Unrealized holding gains arising during the period	$	8,236		$	(2,883	)	$	5,353
	Less: reclassification adjustment for gains included in net income		(3,743	)		1,310			(2,433	)
	Net unrealized gains		4,493			(1,573	)		2,920
	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	$	(1,882	)	$	659		$	(1,223	)
	Less: reclassification adjustment for losses included in net income		1,195			(418	)		777
	Fair value of derivative instruments designated as cash flow hedges		(687	)		241			(446	)
	Total other comprehensive income	$	3,806		$	(1,332	)	$	2,474

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
Compensation Expense Included in Salaries and Employee Benefits Expense and Related Income Tax Benefits	'
	The following table represents the compensation expense that is included in salaries and employee benefits expense and related income tax benefits in the accompanying consolidated statements of comprehensive income related to stock options.
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands, except per share data)		2013			2012			2013			2012
	Compensation expense related to stock options		$	526		$	334		$	1,592		$	1,317
	Income tax benefit related to stock options			184			117			557			461
	Impact on basic earnings per share			0.01			0.01			0.03			0.03
	Impact on diluted earnings per share			0.01			0.01			0.03			0.03
Estimate Fair Value of Share-Based Awards with Weighted-Average Assumptions	'
	The Company uses the Black-Scholes option pricing model to estimate the fair value of share-based awards. The following weighted-average assumptions were used for option awards outstanding during the nine-month periods ended September 30:
			2013			2012
	Expected dividends			2.6	%		2.3	%
	Expected volatility			34.8	%		33.9	%
	Risk-free interest rate			1.7	%		2.9	%
	Expected term (in years)			8.6			5.8
	Weighted-average grant-date fair value		$	15.37		$	13.58
Activity Related to Stock Options	'
	The following table represents the activity related to stock options during the periods indicated.
			Number of			Weighted			Weighted Average
			shares			Average			Remaining Contract Life
						Exercise
						Price
	Oustanding options, December 31, 2011			1,097,620		$	50.14
	Granted			226,764			51.73
	Issued in connection with acquisition			32,863			41.3
	Exercised			(46,729	)		29.42
	Forfeited or expired			(29,410	)		57.39
	Outstanding options, September 30, 2012			1,281,108		$	50.78			4.8		Years
	Outstanding exercisable at September 30, 2012			822,410		$	48.94			3		Years
	Oustanding options, December 31, 2012			1,236,075		$	51.48
	Granted			75,722			52.36
	Exercised			(142,841	)		38.09
	Forfeited or expired			(36,608	)		56.01
	Outstanding options, September 30, 2013			1,132,348		$	53.09			4.7		Years
	Outstanding exercisable at September 30, 2013			749,545		$	52.94			3.2		Years
Compensation Expense Included in Salaries and Employee Benefits Expense Related to Restricted Stock Grants	'
	The following table represents the compensation expense that was included in salaries and employee benefits expense in the accompanying consolidated statements of income related to restricted stock grants:
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands)		2013			2012			2013			2012
	Compensation expense related to restricted stock		$	2,110		$	1,973		$	6,055		$	5,638
Unvested Restricted Stock Award Activity	'
	The following table represents unvested restricted stock award activity for the nine months ended September 30:
			2013			2012
	Balance at beginning of period			538,202			512,112
	Granted			166,223			174,393
	Forfeited			(27,483	)		(8,736	)
	Earned and issued			(136,629	)		(120,644	)
	Balance at end of period			540,313			557,125
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, 2011			232,921			8,942			241,863		$	11,924,000
	Granted			117,506			6,852			124,358			5,696,000
	Forfeited share equivalents			(8,052	)		(242	)		(8,294	)		(380,000	)
	Vested share equivalents			(16,735	)		(1,144	)		(17,879	)		(894,000	)
	Balance, September 30, 2012			325,640			14,408			340,048		$	15,574,000
	Balance, December 31, 2012			318,729			16,035			334,764		$	16,444,000
	Granted			166,664			8,793			175,457			9,108,000
	Forfeited share equivalents			(16,381	)		(681	)		(17,062	)		(886,000	)
	Vested share equivalents			(45,065	)		(3,327	)		(48,392	)		(2,453,000	)
	Balance, September 30, 2013			423,947			20,820			444,767		$	23,088,000
	(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 $51.91 and $45.80 on September 30, 2013 and 2012, respectively.
Phantom Stock Awards [Member]	'
Compensation Expense Included in Salaries and Employee Benefits 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 period and the current market price of the Company’s stock.
			For the Three Months Ended						For the Nine Months Ended
			September 30						September 30
	(Dollars in thousands)		2013			2012			2013			2012
	Compensation expense related to phantom stock		$	792		$	245		$	2,602		$	1,426

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Summary of Financial Instruments Outstanding	'
	The Company had the following financial instruments outstanding, whose contract amounts represent credit risk:
	(Dollars in thousands)	September 30		December 31
		2013		2012
	Commitments to grant loans	$	342,494	$	192,295
	Unfunded commitments under lines of credit		2,972,046		2,372,971
	Commercial and standby letters of credit		106,652		62,207
	Reserve for unfunded lending commitments		11,959		—

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Financial Asset and Liabilities Measured at Fair Value on Recurring Basis	'
	The Company has segregated all financial assets and liabilities that are measured at fair value on a recurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to estimate the fair value at the measurement date in the tables below.
	(Dollars in thousands)	September 30, 2013
	Assets	(Level 1)			(Level 2)			(Level 3)		Total
	Available for sale securities	$	15,220		$	1,949,169		$	—	$	1,964,389
	Derivative instruments		—			32,469			—		32,469
	Total	$	15,220		$	1,981,638		$	—	$	1,996,858
	Liabilities
	Derivative instruments		—			31,521			—		31,521
	Total	$	—		$	31,521		$	—	$	31,521
	(Dollars in thousands)	31-Dec-12
	Assets	(Level 1)			(Level 2)			(Level 3)		Total
	Available for sale securities	$	—		$	1,745,004		$	—	$	1,745,004
	Derivative instruments		—			42,119			—		42,119
	Total	$	—		$	1,787,123		$	—	$	1,787,123
	Liabilities
	Derivative instruments		—			36,890			—		36,890
	Total	$	—		$	36,890		$	—	$	36,890
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) for the first nine months of 2013 related to assets and liabilities measured at fair value on a recurring basis are reported in noninterest income or other comprehensive income as follows:
	(Dollars in thousands)	Noninterest			Other
		income			comprehensive
					income
	Total gains (losses) included in earnings (or changes in net assets)	$	(1,056	)	$	—
	Change in unrealized gains (losses) relating to assets still held at September 30, 2013		—			(25,794	)
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 nonrecurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to determine the fair value at the measurement date in the tables below.
		September 30, 2013
	(Dollars in thousands)	(Level 1)			(Level 2)			(Level 3)		Total
	Assets
	Loans	$	—		$	1,932		$	—	$	1,932
	Mortgage loans held for sale		—			3,213			—		3,213
	OREO		—			20,427			—		20,427
	Total	$	—		$	25,572		$	—	$	25,572
		December 31, 2012
	(Dollars in thousands)	(Level 1)			(Level 2)			(Level 3)		Total
	Assets
	Loans	$	—		$	6,388		$	—	$	6,388
	Mortgage loans held for sale		—			32,753			—		32,753
	OREO		—			20,427			—		20,427
	Total	$	—		$	59,568		$	—	$	59,568

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Estimated Fair Values and Carrying Amounts of Financial Instruments	'
	The estimated fair values and carrying amounts of the Company’s financial instruments are as follows:
		September 30, 2013				December 31, 2012
	(Dollars in thousands)	Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Financial Assets
	Cash and cash equivalents	$	553,447	$	553,447	$	970,977	$	970,977
	Investment securities		2,120,067		2,119,699		1,950,066		1,956,502
	Loans and loans held for sale		9,151,322		9,257,560		8,766,054		8,800,563
	FDIC loss share receivable		204,885		59,512		423,069		207,222
	Derivative instruments		32,469		32,469		42,119		42,119
	Accrued interest receivable		31,296		31,296		32,183		32,183
	Financial Liabilities
	Deposits	$	10,950,764	$	10,533,414	$	10,748,277	$	10,594,885
	Short-term borrowings		258,850		258,850		303,045		303,045
	Long-term debt		281,101		239,506		423,377		394,490
	Derivative instruments		31,521		31,521		36,890		36,890
	Accrued interest payable		6,026		6,026		6,615		6,615

Basis_of_Presentation_Addition

Basis of Presentation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basis Of Presentation [Line Items]	'	'	'	'
Company mortgage loans held for sale	$108,285,000	'	$108,285,000	'
Property write-downs	$1,437,000	$867,000	$3,993,000	$4,900,000
Commercial [Member]	'	'	'	'
Basis Of Presentation [Line Items]	'	'	'	'
Loss sharing indemnification agreements, terms	'	'	'5 years	'
Single family residential [Member]	'	'	'	'
Basis Of Presentation [Line Items]	'	'	'	'
Loss sharing indemnification agreements, terms	'	'	'10 years	'
IBERIABANK Corporation [Member]	'	'	'	'
Basis Of Presentation [Line Items]	'	'	'	'
Number of operating states	6	'	6	'
IBERIABANK Mortgage Company [Member]	'	'	'	'
Basis Of Presentation [Line Items]	'	'	'	'
Number of operating states	12	'	12	'

Recent_Accounting_Pronouncemen1

Recent Accounting Pronouncements - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Accounting Policies [Abstract]	'	'
Amortization expense	$5,496,000	$15,916,000

Earnings_Per_Share_Schedule_of

Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]	'	'	'	'
Income available to common shareholders	$23,192	$21,234	$39,499	$53,187
Distributed earnings to common shareholders - basic	22,771	20,833	38,755	52,178
Distributed and undistributed earnings to common shareholders - diluted	22,767	20,828	38,755	52,180
Weighted average shares outstanding - basic	29,631,799	29,066,000	29,582,081	29,303,849
Weighted average shares outstanding - diluted	29,147,232	28,548,432	29,062,238	28,812,631
Earnings per common share - Basic	$0.78	$0.73	$1.34	$1.81
Earnings per common share - diluted	$0.78	$0.73	$1.33	$1.81
Unvested Restricted Stock [Member]	'	'	'	'
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings to unvested restricted stock	-421	-401	-744	-1,009
Undistributed earnings reallocated to unvested restricted stock	($4)	($5)	'	$2
Earnings per common share - Basic	$0.77	$0.71	$1.33	$1.82
Earnings per common share - diluted	$0.78	$0.72	$1.33	$1.82

Earnings_Per_Share_Schedule_of1

Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]	'	'	'	'
Weighted average basic shares outstanding, unvested restricted stock	547,155	563,061	559,556	554,041

Earnings_Per_Share_Schedule_of2

Earnings Per Share - Schedule of Basic Earnings Per Common Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings	$9,926	$9,826	$29,736	$29,695
Undistributed earnings to common shareholders	12,845	11,007	9,019	22,483
Total earnings to common shareholders	22,771	20,833	38,755	52,178
Distributed earnings	$0.34	$0.34	$1.03	$1.03
Undistributed earnings per common share	$0.44	$0.39	$0.31	$0.78
Total earnings per common share - basic	$0.78	$0.73	$1.34	$1.81
Unvested Restricted Stock [Member]	'	'	'	'
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]	'	'	'	'
Distributed earnings	183	189	571	574
Undistributed earnings to common shareholders	238	212	173	435
Total earnings allocated to unvested restricted stock	$421	$401	$744	$1,009
Distributed earnings	$0.34	$0.34	$1.02	$1.04
Undistributed earnings per common share	$0.43	$0.37	$0.31	$0.78
Total earnings per common share - basic	$0.77	$0.71	$1.33	$1.82

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]	'	'	'	'
Weighted average number of shares, Recognition and Retention Plan	642,764	624,000	645,793	611,646
Weighted average number of shares, treasury stock	2,189,978	2,036,132	2,249,068	1,801,572
Stock options having antidilutive effect on earnings per share	402,344	834,559	678,604	703,346

Acquisition_and_Disposition_Ac2

Acquisition and Disposition Activity - Schedule of Branch Closure Costs (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Business Combinations [Abstract]	'	'	'	'
Employee termination	($70)	$384	$299	$384
Accelerated depreciation	352	284	1,033	284
Contract termination	591	'	591	'
Impairment	323	2,743	4,941	2,743
Total	$1,196	$3,411	$6,864	$3,411

Investment_Securities_Schedule

Investment Securities - Schedule of Amortized Cost and Fair Values of Investment Securities, with Gross Unrealized Gains and Losses (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	$1,967,293	$1,706,916
Securities available for sale, Gross Unrealized Gains	19,795	40,134
Securities available for sale, Gross Unrealized Losses	-22,699	-2,046
Securities available for sale, Estimated Fair Value	1,964,389	1,745,004
Securities held to maturity, Amortized Cost	155,678	205,062
Securities held to maturity, Gross Unrealized Gains	2,678	6,702
Securities held to maturity, Gross Unrealized Losses	-3,046	-266
Securities held to maturity, Estimated Fair Value	155,310	211,498
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	407,049	281,746
Securities available for sale, Gross Unrealized Gains	1,878	4,364
Securities available for sale, Gross Unrealized Losses	-7,127	-386
Securities available for sale, Estimated Fair Value	401,800	285,724
Securities held to maturity, Amortized Cost	34,471	69,949
Securities held to maturity, Gross Unrealized Gains	650	1,244
Securities held to maturity, Gross Unrealized Losses	'	'
Securities held to maturity, Estimated Fair Value	35,121	71,193
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	109,509	120,680
Securities available for sale, Gross Unrealized Gains	2,967	6,573
Securities available for sale, Gross Unrealized Losses	-235	-178
Securities available for sale, Estimated Fair Value	112,241	127,075
Securities held to maturity, Amortized Cost	84,471	88,909
Securities held to maturity, Gross Unrealized Gains	1,735	4,730
Securities held to maturity, Gross Unrealized Losses	-1,425	-113
Securities held to maturity, Estimated Fair Value	84,781	93,526
Mortgage-Backed Securities [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Amortized Cost	1,449,275	1,303,030
Securities available for sale, Gross Unrealized Gains	14,928	29,108
Securities available for sale, Gross Unrealized Losses	-15,337	-1,482
Securities available for sale, Estimated Fair Value	1,448,866	1,330,656
Securities held to maturity, Amortized Cost	36,736	46,204
Securities held to maturity, Gross Unrealized Gains	293	728
Securities held to maturity, Gross Unrealized Losses	-1,621	-153
Securities held to maturity, Estimated Fair Value	35,408	46,779
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	22	89
Securities available for sale, Gross Unrealized Losses	'	'
Securities available for sale, Estimated Fair Value	$1,482	$1,549

Investment_Securities_Addition

Investment Securities - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
	Security	Bonds
		Security
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'	'
Pledged securities, carrying values	$1,400,000,000	$1,700,000,000	'
Number of debt securities, held	151	49	'
Unrealized losses on debt securities, percent of amortized cost	2.41%	0.85%	'
Unrealized losses on debt securities, percent of Company's total amortized cost	1.21%	0.12%	'
Number of debt securities having unrealized losses	151	49	'
Number of securities recorded with an aggregate amortized cost	13	3	'
Number of securities, continuous unrealized loss position, twelve months or longer, fair value	13	3	'
Available-for-sale securities, amortized cost basis	53,886,000	5,200,000	'
Unrealized loss on securities	$2,354,000	$187,000	'
Unrated revenue municipal bond	'	1	'
Impairment of par value bond, percentage	'	'	50.00%
Rated AAA by Fannie Mae Freddie Mac and Ginnie Mae Securities [Member]	'	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'	'
Number of securities issued	13	'	'
Rated AAA by Fannie Mae Freddie Mac and Ginnie Mae Securities [Member] | Maximum [Member]	'	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'	'
Number of securities issued	10	3	'
Rated AAA by Fannie Mae Freddie Mac and Ginnie Mae Securities [Member] | Minimum [Member]	'	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'	'
Number of securities issued	'	2	'

Investment_Securities_Schedule1

Investment Securities - Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	($21,233)	($1,859)
Securities available for sale, Less Than Twelve Months, Fair Value	946,205	239,768
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-1,466	-187
Securities available for sale, Over Twelve Months, Fair Value	39,647	5,013
Securities available for sale, Gross Unrealized Losses, Total	-22,699	-2,046
Securities available for sale, Fair Value, Total	985,852	244,781
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	-2,158	-266
Securities held to maturity, Less Than Twelve Months, Fair Value	43,923	24,504
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-888	'
Securities held to maturity, Over Twelve Months, Fair Value	11,885	'
Securities held to maturity, Gross Unrealized Losses, Total	-3,046	-266
Securities held to maturity, Fair Value, Total	55,808	24,504
U.S. Government-Sponsored Enterprise Obligations [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	-7,127	-386
Securities available for sale, Less Than Twelve Months, Fair Value	274,195	59,741
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	'	'
Securities available for sale, Over Twelve Months, Fair Value	'	'
Securities available for sale, Gross Unrealized Losses, Total	-7,127	-386
Securities available for sale, Fair Value, Total	274,195	59,741
Obligations of State and Political Obligations [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	-10	'
Securities available for sale, Less Than Twelve Months, Fair Value	326	'
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-225	-178
Securities available for sale, Over Twelve Months, Fair Value	1,047	1,094
Securities available for sale, Gross Unrealized Losses, Total	-235	-178
Securities available for sale, Fair Value, Total	1,373	1,094
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	-1,308	-113
Securities held to maturity, Less Than Twelve Months, Fair Value	28,433	8,242
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-117	'
Securities held to maturity, Over Twelve Months, Fair Value	2,080	'
Securities held to maturity, Gross Unrealized Losses, Total	-1,425	-113
Securities held to maturity, Fair Value, Total	30,513	8,242
Mortgage-Backed Securities [Member]	'	'
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]	'	'
Securities available for sale, Less Than Twelve Months, Gross Unrealized Losses	-14,096	-1,473
Securities available for sale, Less Than Twelve Months, Fair Value	671,684	180,027
Securities available for sale, Over Twelve Months, Gross Unrealized Losses	-1,241	-9
Securities available for sale, Over Twelve Months, Fair Value	38,600	3,919
Securities available for sale, Gross Unrealized Losses, Total	-15,337	-1,482
Securities available for sale, Fair Value, Total	710,284	183,946
Securities held to maturity, Less Than Twelve Months, Gross Unrealized Losses	-850	-153
Securities held to maturity, Less Than Twelve Months, Fair Value	15,490	16,262
Securities held to maturity, Over Twelve Months, Gross Unrealized Losses	-771	'
Securities held to maturity, Over Twelve Months, Fair Value	9,805	'
Securities held to maturity, Gross Unrealized Losses, Total	-1,621	-153
Securities held to maturity, Fair Value, Total	$25,295	$16,262

Investment_Securities_Schedule2

Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Maturity (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments Debt And Equity Securities [Abstract]	'	'
Securities Available for Sale, Weighted Average Yield, Within one year or less	1.99%	'
Securities Available for Sale, Weighted Average Yield, One through five years	1.38%	'
Securities Available for Sale, Weighted Average Yield, After five through ten years	1.98%	'
Securities Available for Sale, Weighted Average Yield, Over ten years	1.92%	'
Securities Available for Sale, Weighted Average Yield, Totals	1.88%	'
Securities Available for Sale, Amortized Cost, Within one year or less	$16,230	'
Securities Available for Sale, Amortized Cost, One through five years	220,047	'
Securities Available for Sale, Amortized Cost, After five through ten years	596,282	'
Securities Available for Sale, Amortized Cost, Over ten years	1,134,734	'
Securities Available for Sale, Amortized Cost, Totals	1,967,293	'
Securities Available for Sale, Fair Value, Within one year or less	16,430	'
Securities Available for Sale, Fair Value, One through five years	220,114	'
Securities Available for Sale, Fair Value, After five through ten years	597,600	'
Securities Available for Sale, Fair Value, Over ten years	1,130,245	'
Securities Available for Sale, Fair Value, Totals	1,964,389	'
Securities Held to Maturity, Weighted Average Yield, Within one year or less	1.85%	'
Securities Held to Maturity, Weighted Average Yield, One through five years	3.01%	'
Securities Held to Maturity, Weighted Average Yield, After five through ten years	2.60%	'
Securities Held to Maturity, Weighted Average Yield, Over ten years	2.92%	'
Securities Held to Maturity, Weighted Average Yield, Totals	2.71%	'
Securities Held to Maturity, Amortized Cost, Within one year or less	24,541	'
Securities Held to Maturity, Amortized Cost, One through five years	18,071	'
Securities Held to Maturity, Amortized Cost, After five through ten years	24,599	'
Securities Held to Maturity, Amortized Cost, Over ten years	88,467	'
Securities Held to Maturity, Amortized Cost, Totals	155,678	205,062
Securities Held to Maturity, Fair Value, Within one year or less	24,815	'
Securities Held to Maturity, Fair Value, One through five years	18,685	'
Securities Held to Maturity, Fair Value, After five through ten years	25,040	'
Securities Held to Maturity, Fair Value, Over ten years	86,770	'
Securities Held to Maturity, Fair Value, Totals	$155,310	$211,498

Investment_Securities_Schedule3

Investment Securities - Schedule of Realized Gains and Losses from Sale of Securities Classified as Available for Sale (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Investments Debt And Equity Securities [Abstract]	'	'	'	'
Realized gains	'	$41	$2,369	$3,758
Realized losses	-3	'	-110	-15
Net realized gains	($3)	$41	$2,259	$3,743

Investment_Securities_Schedule4

Investment Securities - Schedule of Securities in Other Assets on Company's Consolidated Balance Sheets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments Debt And Equity Securities [Abstract]	'	'
Federal Home Loan Bank (FHLB) stock	$12,759	$16,860
Federal Reserve Bank (FRB) stock	28,098	28,155
Other investments	1,306	1,201
Total equity securities	$42,163	$46,216

Loans_Receivable_Schedule_of_L

Loans Receivable - Schedule of Loans Receivable (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Loans Receivable [Line Items]	'	'
Total loans receivable	$9,043,037	$8,498,580
Commercial Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	6,464,083	6,169,261
Commercial Loans [Member] | Real Estate [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	3,779,839	3,631,543
Commercial Loans [Member] | Business [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	2,684,244	2,537,718
Residential Mortgage Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	563,455	477,204
Residential Mortgage Loans [Member] | Residential 1-4 Family [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	555,869	471,183
Residential Mortgage Loans [Member] | Construction/ Owner Occupied [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	7,586	6,021
Consumer and Other Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	2,015,499	1,852,115
Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	1,281,014	1,251,125
Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	369,755	327,985
Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	364,730	273,005
Non-Covered Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	8,236,035	7,405,824
Non-Covered Loans [Member] | Commercial Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	5,964,155	5,441,367
Non-Covered Loans [Member] | Commercial Loans [Member] | Real Estate [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	3,320,333	2,990,700
Non-Covered Loans [Member] | Commercial Loans [Member] | Business [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	2,643,822	2,450,667
Non-Covered Loans [Member] | Residential Mortgage Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	409,940	290,040
Non-Covered Loans [Member] | Residential Mortgage Loans [Member] | Residential 1-4 Family [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	402,354	284,019
Non-Covered Loans [Member] | Residential Mortgage Loans [Member] | Construction/ Owner Occupied [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	7,586	6,021
Non-Covered Loans [Member] | Consumer and Other Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	1,861,940	1,674,417
Non-Covered Loans [Member] | Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	1,131,870	1,076,913
Non-Covered Loans [Member] | Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	369,755	327,985
Non-Covered Loans [Member] | Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	360,315	269,519
Covered Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	807,002	1,092,756
Covered Loans [Member] | Commercial Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	499,928	727,894
Covered Loans [Member] | Commercial Loans [Member] | Real Estate [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	459,506	640,843
Covered Loans [Member] | Commercial Loans [Member] | Business [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	40,422	87,051
Covered Loans [Member] | Residential Mortgage Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	153,515	187,164
Covered Loans [Member] | Residential Mortgage Loans [Member] | Residential 1-4 Family [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	153,515	187,164
Covered Loans [Member] | Residential Mortgage Loans [Member] | Construction/ Owner Occupied [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	'	'
Covered Loans [Member] | Consumer and Other Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	153,559	177,698
Covered Loans [Member] | Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	149,144	174,212
Covered Loans [Member] | Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	'	'
Covered Loans [Member] | Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Loans Receivable [Line Items]	'	'
Total loans receivable	$4,415	$3,486

Loans_Receivable_Additional_In

Loans Receivable - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Loans Receivable [Line Items]	'	'	'
Deferred loan origination fees	$16,445,000	'	$14,040,000
Deferred loan expenses	7,154,000	'	5,270,000
Deposit liabilities reclassified as loans receivable	2,319,000	'	3,231,000
Loans with carrying value pledged to secure public deposits and other borrowings	2,200,000,000	'	1,500,000,000
Non-covered troubled debt restructurings modified during the current period	11,210,000	4,391,000	'
Troubled Debt Restructurings [Member]	'	'	'
Loans Receivable [Line Items]	'	'	'
Total TDRs	$19,941,000	$21,840,000	'

Loans_Receivable_Schedule_of_A

Loans Receivable - Schedule of Aging of Non-Covered Loans (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	$8,525	$10,345
Past Due, 60-89 days	3,881	2,447
Past Due, Greater than 90 days	45,256	49,288
Total past due	57,662	62,080
Current	7,661,911	6,685,425
Total Non-covered loans, Net of Unearned Income	7,719,573	6,747,505
Recorded investment > 90 days and Accruing	1,418	1,371
Non-Covered Loans Excluding Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate Construction [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	'	60
Past Due, 60-89 days	'	'
Past Due, Greater than 90 days	2,430	5,479
Total past due	2,430	5,539
Current	380,665	288,137
Total Non-covered loans, Net of Unearned Income	383,095	293,676
Recorded investment > 90 days and Accruing	'	'
Non-Covered Loans Excluding Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate - Other [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	1,933	3,590
Past Due, 60-89 days	'	'
Past Due, Greater than 90 days	9,639	23,559
Total past due	11,572	27,149
Current	2,556,798	2,224,495
Total Non-covered loans, Net of Unearned Income	2,568,370	2,251,644
Recorded investment > 90 days and Accruing	151	83
Non-Covered Loans Excluding Acquired Loans [Member] | Commercial Loans [Member] | Commercial Business [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	1,743	1,430
Past Due, 60-89 days	6	13
Past Due, Greater than 90 days	14,591	3,687
Total past due	16,340	5,130
Current	2,573,065	2,362,304
Total Non-covered loans, Net of Unearned Income	2,589,405	2,367,434
Recorded investment > 90 days and Accruing	'	329
Non-Covered Loans Excluding Acquired Loans [Member] | Residential Mortgage Loans [Member] | Residential Prime [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	517	662
Past Due, 60-89 days	2,297	1,156
Past Due, Greater than 90 days	9,326	9,168
Total past due	12,140	10,986
Current	261,615	185,843
Total Non-covered loans, Net of Unearned Income	273,755	196,829
Recorded investment > 90 days and Accruing	1,267	801
Non-Covered Loans Excluding Acquired Loans [Member] | Residential Mortgage Loans [Member] | Residential Subprime [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	'	'
Past Due, 60-89 days	'	'
Past Due, Greater than 90 days	442	'
Total past due	442	'
Current	115,715	60,454
Total Non-covered loans, Net of Unearned Income	116,157	60,454
Recorded investment > 90 days and Accruing	'	'
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	1,745	2,283
Past Due, 60-89 days	577	796
Past Due, Greater than 90 days	7,092	5,793
Total past due	9,414	8,872
Current	1,063,257	991,766
Total Non-covered loans, Net of Unearned Income	1,072,671	1,000,638
Recorded investment > 90 days and Accruing	'	158
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	1,719	1,624
Past Due, 60-89 days	439	326
Past Due, Greater than 90 days	1,056	868
Total past due	3,214	2,818
Current	364,094	320,148
Total Non-covered loans, Net of Unearned Income	367,308	322,966
Recorded investment > 90 days and Accruing	'	'
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer and Other Loans [Member] | Credit Card [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	184	130
Past Due, 60-89 days	102	51
Past Due, Greater than 90 days	425	424
Total past due	711	605
Current	59,225	51,117
Total Non-covered loans, Net of Unearned Income	59,936	51,722
Recorded investment > 90 days and Accruing	'	'
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	684	566
Past Due, 60-89 days	460	105
Past Due, Greater than 90 days	255	310
Total past due	1,399	981
Current	287,477	201,161
Total Non-covered loans, Net of Unearned Income	288,876	202,142
Recorded investment > 90 days and Accruing	'	'
Non-Covered Acquired Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	4,596	10,502
Past Due, 60-89 days	1,172	2,499
Past Due, Greater than 90 days	44,778	52,781
Total past due	50,546	65,782
Current	535,401	675,692
Discount	-69,485	-83,155
Total Non-covered loans, Net of Unearned Income	516,462	658,319
Recorded investment > 90 days and Accruing	44,778	52,781
Non-Covered Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate Construction [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	97	369
Past Due, 60-89 days	'	'
Past Due, Greater than 90 days	3,457	4,067
Total past due	3,554	4,436
Current	15,020	29,098
Discount	-1,928	-3,968
Total Non-covered loans, Net of Unearned Income	16,646	29,566
Recorded investment > 90 days and Accruing	3,457	4,067
Non-Covered Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate - Other [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	2,240	5,971
Past Due, 60-89 days	438	1,572
Past Due, Greater than 90 days	33,484	38,987
Total past due	36,162	46,530
Current	367,085	426,339
Discount	-51,025	-57,055
Total Non-covered loans, Net of Unearned Income	352,222	415,814
Recorded investment > 90 days and Accruing	33,484	38,987
Non-Covered Acquired Loans [Member] | Commercial Loans [Member] | Commercial Business [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	444	1,410
Past Due, 60-89 days	246	524
Past Due, Greater than 90 days	1,880	3,953
Total past due	2,570	5,887
Current	59,949	89,490
Discount	-8,102	-12,144
Total Non-covered loans, Net of Unearned Income	54,417	83,233
Recorded investment > 90 days and Accruing	1,880	3,953
Non-Covered Acquired Loans [Member] | Residential Mortgage Loans [Member] | Residential Prime [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	'	'
Past Due, 60-89 days	'	'
Past Due, Greater than 90 days	226	779
Total past due	226	779
Current	20,388	30,663
Discount	-586	1,315
Total Non-covered loans, Net of Unearned Income	20,028	32,757
Recorded investment > 90 days and Accruing	226	779
Non-Covered Acquired Loans [Member] | Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	1,567	2,379
Past Due, 60-89 days	302	382
Past Due, Greater than 90 days	4,681	4,354
Total past due	6,550	7,115
Current	56,842	73,658
Discount	-4,193	-4,498
Total Non-covered loans, Net of Unearned Income	59,199	76,275
Recorded investment > 90 days and Accruing	4,681	4,354
Non-Covered Acquired Loans [Member] | Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	86	171
Past Due, 60-89 days	1	4
Past Due, Greater than 90 days	102	146
Total past due	189	321
Current	2,258	4,698
Discount	'	'
Total Non-covered loans, Net of Unearned Income	2,447	5,019
Recorded investment > 90 days and Accruing	102	146
Non-Covered Acquired Loans [Member] | Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Loans Receivable [Line Items]	'	'
Past Due, 30-59 days	162	202
Past Due, 60-89 days	185	17
Past Due, Greater than 90 days	948	495
Total past due	1,295	714
Current	13,859	21,746
Discount	-3,651	-6,805
Total Non-covered loans, Net of Unearned Income	11,503	15,655
Recorded investment > 90 days and Accruing	$948	$495

Loans_Receivable_Schedule_of_N

Loans Receivable - Schedule of Non-Covered Loans on Nonaccrual Status (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	$43,838	$47,916
Commercial Loans [Member] | Commercial Real Estate Construction [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	2,430	5,479
Commercial Loans [Member] | Commercial Real Estate - Other [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	9,488	23,475
Commercial Loans [Member] | Business [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	14,591	3,358
Residential Mortgage Loans [Member] | Residential Prime [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	8,501	8,367
Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	7,092	5,635
Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	1,056	868
Consumer and Other Loans [Member] | Credit Card [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	425	424
Consumer and Other Loans [Member] | Consumer - Other [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total loans on nonaccrual status	$255	$310

Loans_Receivable_Schedule_of_C

Loans Receivable - Schedule of Carrying Amount of Acquired Covered Loans (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	$78,484	$213,645
Acquired Performing Loans	728,518	879,111
Total Covered Loans	807,002	1,092,756
Commercial Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	23,751	170,499
Acquired Performing Loans	476,177	557,395
Total Covered Loans	499,928	727,894
Residential Mortgage Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	28,333	20,232
Acquired Performing Loans	125,182	166,932
Total Covered Loans	153,515	187,164
Consumer and Other Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	26,400	22,914
Acquired Performing Loans	127,159	154,784
Total Covered Loans	153,559	177,698
Real Estate [Member] | Commercial Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	23,751	167,742
Acquired Performing Loans	435,755	473,101
Total Covered Loans	459,506	640,843
Business [Member] | Commercial Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	'	2,757
Acquired Performing Loans	40,422	84,294
Total Covered Loans	40,422	87,051
Residential 1-4 Family [Member] | Residential Mortgage Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	28,333	20,232
Acquired Performing Loans	125,182	166,932
Total Covered Loans	153,515	187,164
Home Equity [Member] | Consumer and Other Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	25,195	22,094
Acquired Performing Loans	123,949	152,118
Total Covered Loans	149,144	174,212
Consumer - Other [Member] | Consumer and Other Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Acquired Impaired Loans	1,205	820
Acquired Performing Loans	3,210	2,666
Total Covered Loans	$4,415	$3,486

Loans_Receivable_Summary_of_Ch

Loans Receivable - Summary of Changes in Accretable Yields of Acquired Loans (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Loans Receivable [Line Items]	'	'
Balance	$356,393	$470,811
Transfers from nonaccretable difference to accretable yield	40,628	5,307
Accretion	-132,712	-187,171
Changes in expected cash flows not affecting nonaccretable differences	91,734	57,161
Balance	356,043	346,108
Acquired Impaired Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Balance	76,623	83,834
Transfers from nonaccretable difference to accretable yield	6,148	1,062
Accretion	-13,519	-21,924
Changes in expected cash flows not affecting nonaccretable differences	10,561	10,964
Balance	79,813	73,936
Acquired Performing Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Balance	279,770	386,977
Transfers from nonaccretable difference to accretable yield	34,480	4,245
Accretion	-119,193	-165,247
Changes in expected cash flows not affecting nonaccretable differences	81,173	46,197
Balance	$276,230	$272,172

Loans_Receivable_Schedule_of_T

Loans Receivable - Schedule of Troubled Debt Restructurings (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Commercial Loans [Member] | Commercial Real Estate Construction [Member]	'	'
Loans Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'
Commercial Loans [Member] | Real Estate [Member]	'	'
Loans Receivable [Line Items]	'	'
Accruing Loans, Current	411,000	370,000
Accruing Loans, Past Due Greater than 30 Days	'	264,000
Nonaccrual TDRs	5,601,000	18,985,000
Total TDRs	6,012,000	19,619,000
Commercial Loans [Member] | Business [Member]	'	'
Loans Receivable [Line Items]	'	'
Accruing Loans, Current	1,056,000	19,000
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	12,610,000	1,884,000
Total TDRs	13,666,000	1,903,000
Residential Mortgage Loans [Member] | Residential Prime [Member]	'	'
Loans 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]	'	'
Loans Receivable [Line Items]	'	'
Accruing Loans, Current	'	'
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	'	'
Total TDRs	'	'
Consumer and Other Loans [Member]	'	'
Loans Receivable [Line Items]	'	'
Accruing Loans, Current	1,467,000	483,000
Accruing Loans, Past Due Greater than 30 Days	'	264,000
Nonaccrual TDRs	18,474,000	21,093,000
Total TDRs	19,941,000	21,840,000
Consumer and Other Loans [Member] | Home Equity [Member]	'	'
Loans Receivable [Line Items]	'	'
Accruing Loans, Current	'	94,000
Accruing Loans, Past Due Greater than 30 Days	'	'
Nonaccrual TDRs	263,000	224,000
Total TDRs	263,000	318,000
Consumer and Other Loans [Member] | Indirect Automobile [Member]	'	'
Loans 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]	'	'
Loans 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]	'	'
Loans 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 $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Receivables [Abstract]	'	'
Extended maturities	'	$412,000
Interest rate adjustment	'	481,000
Maturity and interest rate adjustment	'	2,389,000
Movement to or extension of interest-rate only payments	'	939,000
Forbearance	11,210,000	170,000
Total	$11,210,000	$4,391,000

Loans_Receivable_Schedule_of_S

Loans Receivable - Schedule of Subsequently Defaulted TDRs (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
	SecurityLoan	SecurityLoan
TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	5	17
Pre-modification Outstanding Recorded Investment	$12,507	$4,599
Post-modification Outstanding Recorded Investment	12,329	3,758
TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	60	57
Recorded Investment	18,429	21,206
Real Estate [Member] | Commercial Loans [Member] | TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	5	14
Pre-modification Outstanding Recorded Investment	12,507	4,478
Post-modification Outstanding Recorded Investment	12,329	3,707
Real Estate [Member] | Commercial Loans [Member] | TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	45	46
Recorded Investment	6,012	19,048
Business [Member] | Commercial Loans [Member] | TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	1
Pre-modification Outstanding Recorded Investment	'	27
Post-modification Outstanding Recorded Investment	'	'
Business [Member] | Commercial Loans [Member] | TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	13	8
Recorded Investment	12,370	1,883
Residential Prime [Member] | Residential Mortgage Loans [Member] | TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Residential Prime [Member] | Residential Mortgage Loans [Member] | TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	'
Recorded Investment	'	'
Home Equity [Member] | Consumer and Other Loans [Member] | TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	1
Pre-modification Outstanding Recorded Investment	'	94
Post-modification Outstanding Recorded Investment	'	51
Home Equity [Member] | Consumer and Other Loans [Member] | TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	1	2
Recorded Investment	47	275
Indirect Automobile [Member] | Consumer and Other Loans [Member] | TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Indirect Automobile [Member] | Consumer and Other Loans [Member] | TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	'
Recorded Investment	'	'
Credit Card [Member] | Consumer and Other Loans [Member] | TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	'
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Credit Card [Member] | Consumer and Other Loans [Member] | TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	'
Recorded Investment	'	'
Consumer - Other [Member] | Consumer and Other Loans [Member] | TDRs Occurring During The Period [Member] | Non-Covered TDRs [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	'	1
Pre-modification Outstanding Recorded Investment	'	'
Post-modification Outstanding Recorded Investment	'	'
Consumer - Other [Member] | Consumer and Other Loans [Member] | TDRs That Subsequently Defaulted In Past 12 Months [Member]	'	'
Loans Receivable [Line Items]	'	'
Number of Loans	1	1
Recorded Investment	'	'

Allowance_for_Credit_Losses_an2

Allowance for Credit Losses and Credit Quality - Effect of Change in Methodology on Company's Unaudited Consolidated Financial Statements (Detail) (USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Loan Lease Allowance For Credit Losses Loan Activity And Report By Impairment Methodology [Line Items]	'	'	'	'
Allowance for loan losses	$148,545	$201,387	$251,603	$193,761
(Reversal of) Provision for loan losses	-445	-15,805	'	'
Provision for unfunded lending commitments	2,131	'	'	'
(Reversal of) Provision for loan losses	$0	'	'	'
Provision for unfunded lending commitments	$0.05	'	'	'
Total provision for credit losses	$0.05	'	'	'
Current Methodology [Member]	'	'	'	'
Loan Lease Allowance For Credit Losses Loan Activity And Report By Impairment Methodology [Line Items]	'	'	'	'
Allowance for loan losses	64,165	'	'	'
Reserve for unfunded lending commitments	11,959	'	'	'
Allowance for credit losses	76,124	'	'	'
(Reversal of) Provision for loan losses	2,884	'	'	'
Provision for unfunded lending commitments	2,131	'	'	'
Total provision for credit losses	5,015	'	'	'
Previous Methodology [Member]	'	'	'	'
Loan Lease Allowance For Credit Losses Loan Activity And Report By Impairment Methodology [Line Items]	'	'	'	'
Allowance for loan losses	73,992	'	'	'
Reserve for unfunded lending commitments	'	'	'	'
Allowance for credit losses	73,992	'	'	'
(Reversal of) Provision for loan losses	2,883	'	'	'
Provision for unfunded lending commitments	'	'	'	'
Total provision for credit losses	2,883	'	'	'
Difference of New And Previous Methodology [Member]	'	'	'	'
Loan Lease Allowance For Credit Losses Loan Activity And Report By Impairment Methodology [Line Items]	'	'	'	'
Allowance for loan losses	-9,827	'	'	'
Reserve for unfunded lending commitments	11,959	'	'	'
Allowance for credit losses	2,132	'	'	'
(Reversal of) Provision for loan losses	1	'	'	'
Provision for unfunded lending commitments	2,131	'	'	'
Total provision for credit losses	$2,132	'	'	'

Allowance_for_Credit_Losses_an3

Allowance for Credit Losses and Credit Quality - Schedule of Allowance for Loan Losses for Covered Loan and Non-Covered Loan Portfolios (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	$251,603	$193,761
(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements	-58,120	49,591
Adjustment attributable to FDIC loss share arrangements	58,565	-33,786
Net (reversal of) provision for loan losses	445	15,805
Increase (Decrease) in FDIC loss share receivable	-58,565	33,786
Transfer of balance to OREO	-30,315	-24,177
Transfer of balance to the RULC	-9,828	'
Loans charged-off	-9,148	-20,280
Recoveries	4,353	2,492
Balance at end of period	148,545	201,387
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	9,828	'
Provision for unfunded lending commitments	2,131	'
Balance at end of period	11,959	'
Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	74,211	74,861
(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements	2,884	6,518
Adjustment attributable to FDIC loss share arrangements	'	'
Net (reversal of) provision for loan losses	2,884	6,518
Increase (Decrease) in FDIC loss share receivable	'	'
Transfer of balance to OREO	'	'
Transfer of balance to the RULC	-9,828	'
Loans charged-off	-7,455	-6,818
Recoveries	4,353	2,455
Balance at end of period	64,165	77,016
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	9,828	'
Provision for unfunded lending commitments	2,131	'
Balance at end of period	11,959	'
Non-Covered Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	8,816	'
(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements	-2,464	5,805
Adjustment attributable to FDIC loss share arrangements	'	'
Net (reversal of) provision for loan losses	-2,464	5,805
Increase (Decrease) in FDIC loss share receivable	'	'
Transfer of balance to OREO	-1,013	-408
Transfer of balance to the RULC	'	'
Loans charged-off	-10	-179
Recoveries	'	18
Balance at end of period	5,329	5,236
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	168,576	118,900
(Reversal of) Provision for loan losses before benefit attributable to FDIC loss share agreements	-58,540	37,268
Adjustment attributable to FDIC loss share arrangements	58,565	-33,786
Net (reversal of) provision for loan losses	25	3,482
Increase (Decrease) in FDIC loss share receivable	-58,565	33,786
Transfer of balance to OREO	-29,302	-23,769
Transfer of balance to the RULC	'	'
Loans charged-off	-1,683	-13,283
Recoveries	'	19
Balance at end of period	79,051	119,135
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_an4

Allowance for Credit Losses and Credit Quality - Schedule of Allowance for Loan Losses for Covered Loans, by Loan Portfolio (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	$251,603	$193,761
(Reversal of) Provision for loan losses	445	15,805
(Decrease) Increase in FDIC loss share receivable	-58,565	33,786
Transfer of balance to OREO	-30,315	-24,177
Transfer of balance to the RULC	-9,828	'
Loans charged off	-9,148	-20,280
Recoveries	4,353	2,492
Balance at end of period	148,545	201,387
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	9,828	'
Provision for unfunded commitments	2,131	'
Balance at end of period	11,959	'
Balance at end of period	8,894,492	'
Balance at end of period	8,246,977	'
Non-Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	83,027	74,861
(Reversal of) Provision for loan losses	420	12,323
Transfer of balance to OREO	-1,013	-408
Transfer of balance to the RULC	-9,828	'
Loans charged off	-7,465	-6,997
Recoveries	4,353	2,473
Balance at end of period	69,494	82,252
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	9,828	'
Provision for unfunded commitments	2,131	'
Balance at end of period	11,959	'
Allowance on loans individually evaluated for impairment	1,092	1,541
Allowance on loans collectively evaluated for impairment	68,402	80,711
Balance at end of period	8,236,035	7,090,696
Balance at end of period individually evaluated for impairment	25,747	30,262
Balance at end of period collectively evaluated for impairment	8,210,288	7,060,434
Balance at end of period acquired with deteriorated credit quality	18,267	69,799
Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	168,576	118,900
(Reversal of) Provision for loan losses	25	3,482
(Decrease) Increase in FDIC loss share receivable	-58,565	33,786
Transfer of balance to OREO	-29,302	-23,769
Transfer of balance to the RULC	'	'
Loans charged off	-1,683	-13,283
Recoveries	'	19
Balance at end of period	79,051	119,135
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	'	'
Provision for unfunded commitments	'	'
Balance at end of period	'	'
Allowance on loans individually evaluated for impairment	'	'
Allowance on loans collectively evaluated for impairment	79,051	119,135
Balance at end of period	'	1,139,250
Balance at end of period	807,002	'
Balance at end of period individually evaluated for impairment	'	'
Balance at end of period collectively evaluated for impairment	807,002	1,139,250
Balance at end of period acquired with deteriorated credit quality	78,484	221,960
Commercial Real Estate [Member] | Non-Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	38,264	35,604
(Reversal of) Provision for loan losses	-6,926	4,199
Transfer of balance to OREO	-279	-62
Transfer of balance to the RULC	-2,939	'
Loans charged off	-1,966	-1,195
Recoveries	1,498	790
Balance at end of period	27,652	39,336
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	2,939	'
Provision for unfunded commitments	1,207	'
Balance at end of period	4,146	'
Allowance on loans individually evaluated for impairment	8	1,173
Allowance on loans collectively evaluated for impairment	27,644	38,163
Balance at end of period	3,320,333	2,879,836
Balance at end of period individually evaluated for impairment	9,529	26,353
Balance at end of period collectively evaluated for impairment	3,310,804	2,853,483
Balance at end of period acquired with deteriorated credit quality	16,287	60,360
Commercial Real Estate [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	100,871	69,175
(Reversal of) Provision for loan losses	27	3,550
(Decrease) Increase in FDIC loss share receivable	-30,853	24,229
Transfer of balance to OREO	-22,375	-9,876
Loans charged off	-1,683	-13,143
Recoveries	'	16
Balance at end of period	45,987	73,951
Allowance on loans individually evaluated for impairment	'	'
Allowance on loans collectively evaluated for impairment	45,987	73,951
Balance at end of period	'	670,001
Balance at end of period	459,506	'
Balance at end of period individually evaluated for impairment	'	'
Balance at end of period collectively evaluated for impairment	459,506	670,001
Balance at end of period acquired with deteriorated credit quality	23,751	171,965
Commercial Business [Member] | Non-Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	28,721	25,705
(Reversal of) Provision for loan losses	-582	3,851
Transfer of balance to OREO	-81	'
Transfer of balance to the RULC	-3,497	'
Loans charged off	-531	-769
Recoveries	354	80
Balance at end of period	24,384	28,867
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	3,497	'
Provision for unfunded commitments	610	'
Balance at end of period	4,107	'
Allowance on loans individually evaluated for impairment	801	162
Allowance on loans collectively evaluated for impairment	23,583	28,705
Balance at end of period	2,643,822	2,357,303
Balance at end of period individually evaluated for impairment	14,548	1,888
Balance at end of period collectively evaluated for impairment	2,629,274	2,355,415
Balance at end of period acquired with deteriorated credit quality	45	3,675
Commercial Business [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	11,375	9,788
(Reversal of) Provision for loan losses	'	922
(Decrease) Increase in FDIC loss share receivable	-3,137	2,398
Transfer of balance to OREO	-314	-2,475
Loans charged off	'	'
Recoveries	'	'
Balance at end of period	7,924	10,633
Allowance on loans individually evaluated for impairment	'	'
Allowance on loans collectively evaluated for impairment	7,924	10,633
Balance at end of period	'	91,822
Balance at end of period	40,422	'
Balance at end of period individually evaluated for impairment	'	'
Balance at end of period collectively evaluated for impairment	40,422	91,822
Balance at end of period acquired with deteriorated credit quality	'	3,522
Mortgage [Member] | Non-Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	2,125	897
(Reversal of) Provision for loan losses	1,048	1,344
Transfer of balance to OREO	-646	-337
Transfer of balance to the RULC	-40	'
Loans charged off	-481	-759
Recoveries	698	30
Balance at end of period	2,704	1,175
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	40	'
Provision for unfunded commitments	38	'
Balance at end of period	78	'
Allowance on loans individually evaluated for impairment	283	163
Allowance on loans collectively evaluated for impairment	2,421	1,012
Balance at end of period	409,940	266,069
Balance at end of period individually evaluated for impairment	1,407	1,703
Balance at end of period collectively evaluated for impairment	408,533	264,366
Balance at end of period acquired with deteriorated credit quality	120	430
Consumer [Member] | Non-Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	13,917	12,655
(Reversal of) Provision for loan losses	6,880	2,929
Transfer of balance to OREO	-7	-9
Transfer of balance to the RULC	-3,352	'
Loans charged off	-4,487	-4,274
Recoveries	1,803	1,573
Balance at end of period	14,754	12,874
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	3,352	'
Provision for unfunded commitments	276	'
Balance at end of period	3,628	'
Allowance on loans individually evaluated for impairment	'	43
Allowance on loans collectively evaluated for impairment	14,754	12,831
Balance at end of period	1,861,940	1,587,488
Balance at end of period individually evaluated for impairment	263	318
Balance at end of period collectively evaluated for impairment	1,861,677	1,587,170
Balance at end of period acquired with deteriorated credit quality	1,815	5,334
Consumer [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Balance at beginning of period	33,764	18,753
(Reversal of) Provision for loan losses	-1	397
(Decrease) Increase in FDIC loss share receivable	-18,841	2,882
Transfer of balance to OREO	1	-825
Loans charged off	'	-9
Recoveries	'	3
Balance at end of period	14,923	21,201
Allowance on loans individually evaluated for impairment	'	'
Allowance on loans collectively evaluated for impairment	14,923	21,201
Balance at end of period	'	180,094
Balance at end of period	153,559	'
Balance at end of period individually evaluated for impairment	'	'
Balance at end of period collectively evaluated for impairment	153,559	180,094
Balance at end of period acquired with deteriorated credit quality	26,400	24,388
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	'	'
Transfer of balance to the RULC	'	'
Loans charged off	'	'
Recoveries	'	'
Balance at end of period	'	'
Balance at beginning of period	'	'
Transfer of balance from the allowance for loan losses	'	'
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	'	'
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	22,566	21,184
(Reversal of) Provision for loan losses	-1	-1,387
(Decrease) Increase in FDIC loss share receivable	-5,734	4,277
Transfer of balance to OREO	-6,614	-10,593
Loans charged off	'	-131
Recoveries	'	'
Balance at end of period	10,217	13,350
Allowance on loans individually evaluated for impairment	'	'
Allowance on loans collectively evaluated for impairment	10,217	13,350
Balance at end of period	'	197,333
Balance at end of period	153,515	'
Balance at end of period individually evaluated for impairment	'	'
Balance at end of period collectively evaluated for impairment	153,515	197,333
Balance at end of period acquired with deteriorated credit quality	$28,333	$22,085

Allowance_for_Credit_Losses_an5

Allowance for Credit Losses and Credit Quality - Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	$8,236,035	$7,405,824
Total	807,002	1,092,756
Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	7,661,911	6,685,425
30+ Days Past Due	57,662	62,080
Total	2,178,703	1,834,751
Internally Assigned Grade Loss [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	5,540,870	4,912,754
Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	552,865	806,092
Discount	-52,937	-78,198
Total	499,928	727,894
Pass [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	5,424,892	4,728,619
Pass [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	223,527	286,014
Special Mention [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	51,350	78,954
Special Mention [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	65,233	83,986
Substandard [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	63,558	104,735
Substandard [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	254,835	426,504
Doubtful [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	1,070	446
Doubtful [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	9,270	9,588
Residential Prime [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	261,615	185,843
30+ Days Past Due	12,140	10,986
Total	273,755	196,829
Home Equity [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	1,063,257	991,766
30+ Days Past Due	9,414	8,872
Total	1,072,671	1,000,638
Indirect Automobile [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	364,094	320,148
30+ Days Past Due	3,214	2,818
Total	367,308	322,966
Consumer - Other [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	287,477	201,161
30+ Days Past Due	1,399	981
Total	288,876	202,142
Commercial Real Estate Construction [Member] | Internally Assigned Grade Loss [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	383,095	293,676
Commercial Real Estate Construction [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	95,751	154,011
Commercial Real Estate Construction [Member] | Pass [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	374,458	269,842
Commercial Real Estate Construction [Member] | Pass [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	44,312	46,201
Commercial Real Estate Construction [Member] | Special Mention [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	4,800	16,767
Commercial Real Estate Construction [Member] | Special Mention [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	8,093	9,888
Commercial Real Estate Construction [Member] | Substandard [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	3,837	7,067
Commercial Real Estate Construction [Member] | Substandard [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	42,849	97,315
Commercial Real Estate Construction [Member] | Doubtful [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	'	'
Commercial Real Estate Construction [Member] | Doubtful [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	497	607
Commercial Real Estate - Other [Member] | Internally Assigned Grade Loss [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	2,568,370	2,251,644
Commercial Real Estate - Other [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	404,566	554,460
Commercial Real Estate - Other [Member] | Pass [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	2,503,820	2,162,989
Commercial Real Estate - Other [Member] | Pass [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	146,103	201,261
Commercial Real Estate - Other [Member] | Special Mention [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	37,537	40,547
Commercial Real Estate - Other [Member] | Special Mention [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	56,182	65,498
Commercial Real Estate - Other [Member] | Substandard [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	26,896	47,710
Commercial Real Estate - Other [Member] | Substandard [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	194,785	279,171
Commercial Real Estate - Other [Member] | Doubtful [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	117	398
Commercial Real Estate - Other [Member] | Doubtful [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	7,496	8,530
Commercial Business [Member] | Internally Assigned Grade Loss [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	2,589,405	2,367,434
Commercial Business [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	52,548	97,621
Commercial Business [Member] | Pass [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	2,546,614	2,295,788
Commercial Business [Member] | Pass [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	33,112	38,552
Commercial Business [Member] | Special Mention [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	9,013	21,640
Commercial Business [Member] | Special Mention [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	958	8,600
Commercial Business [Member] | Substandard [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	32,825	49,958
Commercial Business [Member] | Substandard [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	17,201	50,018
Commercial Business [Member] | Doubtful [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	953	48
Commercial Business [Member] | Doubtful [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	1,277	451
Residential Subprime [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	115,715	60,454
30+ Days Past Due	442	'
Total	116,157	60,454
Credit Card [Member] | Non-Covered Loans Excluding Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	59,225	51,117
30+ Days Past Due	711	605
Total	59,936	51,722
Non-Covered Acquired Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	93,347	130,765
30+ Days Past Due	8,260	8,929
Discount	-8,430	-9,988
Total	93,177	129,706
Non-Covered Acquired Loans [Member] | Internally Assigned Grade Loss [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Discount	-61,055	-73,167
Total	423,285	528,613
Non-Covered Acquired Loans [Member] | Pass [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	390,146	471,143
Non-Covered Acquired Loans [Member] | Special Mention [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	22,000	32,754
Non-Covered Acquired Loans [Member] | Substandard [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	71,894	95,456
Non-Covered Acquired Loans [Member] | Doubtful [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	300	2,427
Non-Covered Acquired Loans [Member] | Residential Prime [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	20,388	30,663
30+ Days Past Due	226	779
Discount	-586	1,315
Total	20,028	32,757
Non-Covered Acquired Loans [Member] | Home Equity [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	56,842	73,658
30+ Days Past Due	6,550	7,115
Discount	-4,193	-4,498
Total	59,199	76,275
Non-Covered Acquired Loans [Member] | Indirect Automobile [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	2,258	4,698
30+ Days Past Due	189	321
Discount	'	'
Total	2,447	5,019
Non-Covered Acquired Loans [Member] | Consumer - Other [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	13,859	21,746
30+ Days Past Due	1,295	714
Discount	-3,651	-6,805
Total	11,503	15,655
Non-Covered Acquired Loans [Member] | Commercial Real Estate Construction [Member] | Internally Assigned Grade Loss [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Discount	-1,928	-3,968
Total	16,646	29,566
Non-Covered Acquired Loans [Member] | Commercial Real Estate Construction [Member] | Pass [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	12,900	25,896
Non-Covered Acquired Loans [Member] | Commercial Real Estate Construction [Member] | Special Mention [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	1,321	2,410
Non-Covered Acquired Loans [Member] | Commercial Real Estate Construction [Member] | Substandard [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	4,353	5,228
Non-Covered Acquired Loans [Member] | Commercial Real Estate Construction [Member] | Doubtful [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	'	'
Non-Covered Acquired Loans [Member] | Commercial Real Estate - Other [Member] | Internally Assigned Grade Loss [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Discount	-51,025	-57,055
Total	352,222	415,814
Non-Covered Acquired Loans [Member] | Commercial Real Estate - Other [Member] | Pass [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	320,781	359,046
Non-Covered Acquired Loans [Member] | Commercial Real Estate - Other [Member] | Special Mention [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	18,438	28,185
Non-Covered Acquired Loans [Member] | Commercial Real Estate - Other [Member] | Substandard [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	63,816	85,420
Non-Covered Acquired Loans [Member] | Commercial Real Estate - Other [Member] | Doubtful [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	212	218
Non-Covered Acquired Loans [Member] | Commercial Business [Member] | Internally Assigned Grade Loss [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Discount	-8,102	-12,144
Total	54,417	83,233
Non-Covered Acquired Loans [Member] | Commercial Business [Member] | Pass [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	56,465	86,201
Non-Covered Acquired Loans [Member] | Commercial Business [Member] | Special Mention [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	2,241	2,159
Non-Covered Acquired Loans [Member] | Commercial Business [Member] | Substandard [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	3,725	4,808
Non-Covered Acquired Loans [Member] | Commercial Business [Member] | Doubtful [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit quality indicator by asset risk classification	88	2,209
Mortgage [Member] | Residential Prime [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	164,214	183,795
30+ Days Past Due	33,114	52,379
Discount	-43,813	-49,010
Mortgage [Member] | Residential Prime [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	153,515	187,164
Consumer Loans [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	315,824	354,519
30+ Days Past Due	75,037	119,964
Discount	-83,787	-109,621
Consumer Loans [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	307,074	364,862
Consumer Loans [Member] | Home Equity [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	150,302	168,729
30+ Days Past Due	41,683	65,997
Discount	-42,841	-60,514
Consumer Loans [Member] | Home Equity [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	149,144	174,212
Consumer Loans [Member] | Consumer - Other [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	643	1,154
30+ Days Past Due	204	1,523
Discount	2,867	-97
Consumer Loans [Member] | Consumer - Other [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	3,714	2,580
Consumer Loans [Member] | Credit Card [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Credit risk by payment status, Current	665	841
30+ Days Past Due	36	65
Discount	'	'
Consumer Loans [Member] | Credit Card [Member] | Internally Assigned Grade Loss [Member] | Covered Loans [Member]	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'
Total	$701	$906

Allowance_for_Credit_Losses_an6

Allowance for Credit Losses and Credit Quality - Schedule of Investment in Impaired Loan (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 23, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	$46,283	$50,079
Unpaid Principal Balance	'	'	'	'	46,712	51,071
Related Allowance	'	'	'	'	-429	-992
Average Recorded Investment	50,310	50,702	49,840	52,882	'	'
Interest Income Recognized	23	24	136	1,029	'	'
Commercial Loans [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	27,942	32,773
Unpaid Principal Balance	'	'	'	'	27,976	33,448
Related Allowance	'	'	'	'	-34	-675
Average Recorded Investment	31,006	32,938	30,233	36,340	'	'
Interest Income Recognized	23	24	89	745	'	'
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Real Estate [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	9,392	26,151
Unpaid Principal Balance	'	'	'	'	9,392	26,151
Related Allowance	'	'	'	'	'	'
Average Recorded Investment	10,703	27,547	12,787	29,872	'	'
Interest Income Recognized	6	15	22	651	'	'
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Business [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	13,068	1,824
Unpaid Principal Balance	'	'	'	'	13,068	1,824
Related Allowance	'	'	'	'	'	'
Average Recorded Investment	13,218	2,451	8,608	3,387	'	'
Interest Income Recognized	17	'	59	71	'	'
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Home Equity [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	263	'
Unpaid Principal Balance	'	'	'	'	263	'
Related Allowance	'	'	'	'	'	'
Commercial Loans [Member] | With An Allowance Recorded [Member] | Real Estate [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	2,913	3,464
Unpaid Principal Balance	'	'	'	'	2,937	3,663
Related Allowance	'	'	'	'	-24	-199
Average Recorded Investment	4,346	2,731	6,092	2,866	'	'
Interest Income Recognized	'	8	5	22	'	'
Commercial Loans [Member] | With An Allowance Recorded [Member] | Business [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	2,569	1,334
Unpaid Principal Balance	'	'	'	'	2,579	1,810
Related Allowance	'	'	'	'	-10	-476
Average Recorded Investment	2,739	209	2,746	215	'	'
Interest Income Recognized	'	1	3	1	'	'
Consumer Loans [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	8,766	7,445
Unpaid Principal Balance	'	'	'	'	8,828	7,553
Related Allowance	'	'	'	'	-62	-108
Average Recorded Investment	9,654	8,516	10,227	9,103	'	'
Interest Income Recognized	'	'	40	136	'	'
Consumer Loans [Member] | With No Related Allowance Recorded [Member] | Home Equity [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Average Recorded Investment	265	225	287	227	'	'
Interest Income Recognized	'	'	'	'	'	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Home Equity [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	6,784	5,860
Unpaid Principal Balance	'	'	'	'	6,829	5,951
Related Allowance	'	'	'	'	-45	-91
Average Recorded Investment	7,244	6,184	7,458	6,502	'	'
Interest Income Recognized	'	'	14	110	'	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Indirect Automobile [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	1,050	865
Unpaid Principal Balance	'	'	'	'	1,056	868
Related Allowance	'	'	'	'	-6	-3
Average Recorded Investment	1,349	1,135	1,610	1,345	'	'
Interest Income Recognized	'	'	22	20	'	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Credit Card [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	417	413
Unpaid Principal Balance	'	'	'	'	425	424
Related Allowance	'	'	'	'	-8	-11
Average Recorded Investment	424	387	426	354	'	'
Interest Income Recognized	'	'	'	'	'	'
Consumer Loans [Member] | With An Allowance Recorded [Member] | Consumer - Other [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	252	307
Unpaid Principal Balance	'	'	'	'	255	310
Related Allowance	'	'	'	'	-3	-3
Average Recorded Investment	372	585	446	675	'	'
Interest Income Recognized	'	'	4	6	'	'
Mortgage Loans [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	9,575	9,861
Unpaid Principal Balance	'	'	'	'	9,908	10,070
Related Allowance	'	'	'	'	-333	-209
Average Recorded Investment	9,650	9,248	9,380	7,439	'	'
Interest Income Recognized	'	'	7	148	'	'
Mortgage Loans [Member] | With An Allowance Recorded [Member] | Residential Prime [Member]	'	'	'	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'	'	'	'
Recorded Investment	'	'	'	'	9,575	9,861
Unpaid Principal Balance	'	'	'	'	9,908	10,070
Related Allowance	'	'	'	'	-333	-209
Average Recorded Investment	9,650	9,248	9,380	7,439	'	'
Interest Income Recognized	'	'	$7	$148	'	'

Loss_Sharing_Agreements_and_FD2

Loss Sharing Agreements and FDIC Loss Share Receivables - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Mar. 31, 2013	Sep. 30, 2013
		Business
Receivables [Abstract]	'	'
Percentage of covered loan and foreclosed real estate losses	'	80.00%
Losses that exceed contractual thresholds	'	95.00%
Number of acquisitions	'	4
Recovery period for loans	'	'3 years
Liability for reserve for amount of consideration	'	$797,000
FDIC loss share receivables	'	204,900,000
Valuation allowance against indemnification assets	$31,813,000	$31,813,000

Loss_Sharing_Agreements_and_FD3

Loss Sharing Agreements and FDIC Loss Share Receivables - Schedule of FDIC Loss Share Receivable (Detail) (USD $)	3 Months Ended			9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
FDIC Loss Share Receivable [Line Items]	'	'	'	'	'
Balance	'	$423,069	'	$423,069	'
Amortization	-22,875	'	-33,488	-68,707	-89,899
Impairment	'	31,813	'	31,813	'
Balance	204,885	'	'	204,885	'
FDIC Loss Share Receivable [Member]	'	'	'	'	'
FDIC Loss Share Receivable [Line Items]	'	'	'	'	'
Balance	'	423,069	'	423,069	591,844
Change due to (reversal of) credit loss provision recorded on FDIC covered loans	'	'	'	-58,565	33,786
Amortization	'	'	'	-68,707	-89,899
Submission of reimbursable losses to the FDIC	'	'	'	-44,910	-97,511
Impairment	'	'	'	-31,813	'
Changes due to a change in cash flow assumptions on OREO and other	'	'	'	-14,189	-7,053
Balance	$204,885	'	$431,167	$204,885	$431,167

Transfers_and_Servicing_of_Fin2

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) - Components of Mortgage Banking Activity (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Mortgage Loan Activity [Line Items]	'	'	'	'
Balance at beginning of period	'	'	$267,475	'
Originations	'	'	1,712,557	'
Sales	'	'	-1,923,455	'
Balance at end of period	108,285	'	108,285	'
Gains on sales	'	'	51,709	'
Total mortgage income	15,202	23,215	51,841	55,118
Mortgage Loans Held for Sale [Member]	'	'	'	'
Mortgage Loan Activity [Line Items]	'	'	'	'
Balance at beginning of period	'	'	267,475	153,013
Originations	'	'	1,712,557	1,749,121
Sales	'	'	-1,871,747	-1,691,002
Balance at end of period	108,285	211,132	108,285	211,132
Mortgage Income [Member]	'	'	'	'
Mortgage Loan Activity [Line Items]	'	'	'	'
Fair value changes of derivatives and mortgage loans held for sale, net	'	'	-270	2,954
Gains on sales	'	'	51,709	51,828
Servicing and other income, net	'	'	402	336
Total mortgage income	'	'	$51,841	$55,118

Transfers_and_Servicing_of_Fin3

Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) - Schedule of Mortgage Servicing Rights at Carrying Values (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Acquired Indefinite-lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	$46,754	$46,754
Accumulated Amortization	-30,238	-26,694
Net Carrying Amount	16,516	20,060
Mortgage Servicing Rights [Member]	'	'
Acquired Indefinite-lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	1,816	1,234
Accumulated Amortization	-543	-304
Net Carrying Amount	$1,273	$930

Goodwill_and_Other_Acquired_In2

Goodwill and Other Acquired Intangible Assets - Schedule of Carrying Amount of Goodwill (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
Beginning Balance	$401,872	$369,811
Goodwill acquired during the period	'	32,420
Goodwill adjustment to correct an immaterial error	'	-359
Ending Balance	$401,872	$401,872

Goodwill_and_Other_Acquired_In3

Goodwill and Other Acquired Intangible Assets - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
Decrease in goodwill	$359,000	'
Impairment of goodwill	'	9,681,000
Title plant assets	$6,722,000	$6,722,000

Goodwill_and_Other_Acquired_In4

Goodwill and Other Acquired Intangible Assets - Schedule of Definite-Lived Intangible Assets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Goodwill [Line Items]	'	'
Gross Carrying Amount	$46,754	$46,754
Accumulated Amortization	-30,238	-26,694
Net Carrying Amount	16,516	20,060
Core Deposit Intangibles [Member]	'	'
Goodwill [Line Items]	'	'
Gross Carrying Amount	45,406	45,406
Accumulated Amortization	-29,659	-26,284
Net Carrying Amount	15,747	19,122
Customer Relationship Intangible Asset [Member]	'	'
Goodwill [Line Items]	'	'
Gross Carrying Amount	1,348	1,348
Accumulated Amortization	-579	-410
Net Carrying Amount	$769	$938

Other_Real_Estate_Owned_Schedu

Other Real Estate Owned - Schedule of Other Real Estate Owned Segregated into Non-Covered and Covered Properties (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	$116,877	$110,864
Real estate acquired for development or resale	10,518	9,199
Other foreclosed property	1,592	1,473
Total other real estate owned and foreclosed property	128,987	121,536
Non-covered Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	31,261	35,080
Real estate acquired for development or resale	10,518	9,199
Other foreclosed property	109	14
Total other real estate owned and foreclosed property	41,888	44,293
Covered Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Real estate owned acquired by foreclosure	85,616	75,784
Other foreclosed property	1,483	1,459
Total other real estate owned and foreclosed property	$87,099	$77,243

Derivative_Instruments_and_Oth2

Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	$26,177	$35,202
Derivative Liability, Fair Value	14,312	27,783
Derivative Asset, Notional Amount	751,177	1,010,357
Derivative Liability, Notional Amount	826,375	648,690
Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Notional Amount	'	35,000
Derivative Liability, Notional Amount	'	35,000
Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Notional Amount	751,177	975,357
Derivative Liability, Notional Amount	826,375	613,690
Other Assets [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	32,469	42,119
Other Assets [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	'	499
Other Assets [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	32,469	41,620
Other Liabilities [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Liability, Fair Value	31,521	36,890
Other Liabilities [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Liability, Fair Value	'	1,843
Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Liability, Fair Value	31,521	35,047
Interest Rate Contracts [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Notional Amount	'	35,000
Derivative Liability, Notional Amount	'	35,000
Interest Rate Contracts [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Notional Amount	376,374	374,536
Derivative Liability, Notional Amount	376,374	374,536
Interest Rate Contracts [Member] | Other Assets [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	'	499
Interest Rate Contracts [Member] | Other Assets [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	14,312	25,940
Interest Rate Contracts [Member] | Other Liabilities [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Liability, Fair Value	'	1,843
Interest Rate Contracts [Member] | Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Liability, Fair Value	14,312	25,940
Forward Sale Contracts [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Notional Amount	8,218	212,028
Derivative Liability, Notional Amount	253,051	53,269
Forward Sale Contracts [Member] | Other Assets [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	148	2,774
Forward Sale Contracts [Member] | Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Liability, Fair Value	5,289	343
Written and Purchased Options [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Notional Amount	366,585	388,793
Derivative Liability, Notional Amount	196,950	185,885
Written and Purchased Options [Member] | Other Assets [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Asset, Fair Value	18,009	12,906
Written and Purchased Options [Member] | Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative Liability, Fair Value	$11,920	$8,764

Derivative_Instruments_and_Oth3

Derivative Instruments and Other Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'	'
Cash as collateral for derivative transactions	$5,630,000	$2,650,000
Fair value of derivatives	$690,000	'

Derivative_Instruments_and_Oth4

Derivative Instruments and Other Hedging Activities - Reconciliation of Gross Amounts in Consolidated Balance Sheets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	$26,177	$35,202
Derivative liabilities subject to master netting arrangements, Gross Amounts	14,312	27,783
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	26,177	34,703
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	8,654	13,934
Derivatives [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	-499
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	'	-499
Collateral [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	-5,658	-13,350
Interest Rate Contracts [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	'	499
Derivative liabilities subject to master netting arrangements, Gross Amounts	'	1,843
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	'	1,344
Interest Rate Contracts [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	14,312	25,940
Derivative liabilities subject to master netting arrangements, Gross Amounts	14,312	25,940
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	14,312	25,940
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	8,654	12,590
Interest Rate Contracts [Member] | Derivatives [Member] | Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	-499
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	'	-499
Interest Rate Contracts [Member] | Derivatives [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [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 [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] | Not Designated as Hedging Instruments [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'
Derivative liabilities subject to master netting arrangements, Gross Amounts Not Offset	-5,658	-13,350
Written and Purchased Options [Member]	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts	11,865	8,763
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	11,865	8,763
Written and Purchased Options [Member] | Derivatives [Member]	'	'
Derivative Instruments And Hedging Activities [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 [Line Items]	'	'
Derivative assets subject to master netting arrangements, Gross Amounts Not Offset	'	'

Derivative_Instruments_and_Oth5

Derivative Instruments and Other Hedging Activities - Schedule of Derivative Instruments on Consolidated Financial Statements (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments And Hedging Activities [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI, net of taxes (Effective Portion)	'	($2,358)	'	($2,358)
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	'	-408	-392	-1,195
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 [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	-2,545	1,738	-381	3,834
Not Designated as Hedging Instruments [Member] | Forward Sale Contracts [Member]	'	'	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	3,290	-1,887	897	-1,887
Not Designated as Hedging Instruments [Member] | Written and Purchased Options [Member]	'	'	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	-7,896	3,378	-3,820	5,094
Interest Rate Contracts [Member] | Not Designated as Hedging Instruments [Member] | Other Income (Expense) [Member]	'	'	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in Income on Derivatives	2,061	247	2,542	627
Interest Rate Contracts [Member] | Cash Flow Hedging [Member]	'	'	'	'
Derivative Instruments And Hedging Activities [Line Items]	'	'	'	'
Amount of Gain (Loss) Recognized in OCI, net of taxes (Effective Portion)	'	-2,358	'	-2,358
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	'	-408	-392	-1,195
Amount of Gain (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)	'	'	'	'

Other_Comprehensive_Income_Sum

Other Comprehensive Income - Summary of Tax Effects of Each Component of Other Comprehensive Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other Comprehensive Income Loss [Abstract]	'	'	'	'
Unrealized holding gains/losses arising during the period, Before-Tax Amount	$5,528	$6,099	($38,769)	$8,236
Less: reclassification adjustment for losses/gains included in net income, Before-Tax Amount	3	-41	-2,259	-3,743
Net unrealized gains/losses, Before-Tax Amount	5,531	6,058	-41,028	4,493
Change in fair value of derivative instruments designated as cash flow hedges during the period, Before-Tax Amount	'	800	952	-1,882
Less: reclassification adjustment for gains/losses included in net income, Before-Tax Amount	'	409	392	1,195
Fair value of derivative instruments designated as cash flow hedges, Before-Tax Amount	'	1,209	1,344	-687
Total other comprehensive income/loss, Before-Tax Amount	5,531	7,267	-39,684	3,806
Unrealized holding gains/losses arising during the period, Tax (Expense) Benefit	-1,935	-2,135	13,569	-2,883
Less: reclassification adjustment for gains/losses included in net income, Tax (Expense) Benefit	-1	14	791	1,310
Net unrealized gains/losses, Tax (Expense) Benefit	-1,936	-2,121	14,360	-1,573
Change in fair value of derivative instruments designated as cash flow hedges during the period, Tax (Expense) Benefit	'	-280	-333	659
Less: reclassification adjustment for gains/losses included in net income, Tax Expense (Benefit)	'	-142	-137	-418
Fair value of derivative instruments designated as cash flow hedges, Tax (Expense) Benefit	'	-422	-470	241
Total other comprehensive income/loss, Tax Expense (Benefit)	-1,936	-2,543	13,890	-1,332
Unrealized holding gains/losses arising during the period, Net-of-Tax Amount	3,593	3,964	-25,200	5,353
Less: reclassification adjustment for losses/gains included in net income, Net-of-Tax Amount	2	-27	-1,468	-2,433
Net unrealized gains/losses, Net-of-Tax Amount	3,595	3,937	-26,668	2,920
Change in fair value of derivative instruments designated as cash flow hedges during the period, Net-of-Tax Amount	'	520	619	-1,223
Less: reclassification adjustment for gains/losses included in net income, Net-of-Tax Amount	'	267	255	777
Fair value of derivative instruments designated as cash flow hedges, Net-of-Tax Amount	'	787	874	-446
Total other comprehensive income/loss, Net-of-Tax Amount	$3,595	$4,724	($25,794)	$2,474

ShareBased_Compensation_Additi

Share-Based Compensation - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Share-based compensation maximum option term (in years)	'10 years	'
Future awards shares under approved incentive compensation plans	491,346	'
Minimum vesting period (in years)	'1 year 6 months	'
Maximum vesting period (in years)	'7 years	'
Excess tax benefits as financing cash inflows	$495,000	$940,000
Net cash proceeds from exercise of stock options	5,441,000	1,541,000
Aggregate intrinsic value of shares underlying outstanding stock options	2,090,000	'
Aggregate intrinsic value of shares underlying exercisable stock options	1,951,000	'
Total intrinsic value of options exercised	1,920,000	1,046,000
Maximum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned compensation vesting period (in years)	7	'
Minimum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned compensation vesting period (in years)	3	'
Phantom Stock Awards [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Minimum vesting period (in years)	'5 years	'
Maximum vesting period (in years)	'7 years	'
Employee Stock Option [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned share-based compensation associated with awards	4,485,000	'
Unrecognized compensation cost related to stock options expected to be recognized over a weighted-average period	'4 years 8 months 12 days	'
Restricted Stock [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Unearned share-based compensation associated with awards	$23,253,000	'

ShareBased_Compensation_Compen

Share-Based Compensation - Compensation Expense Included in Salaries and Employee Benefits Expense and Related Income Tax Benefits (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'	'
Compensation expense related to stock options	$526	$334	$1,592	$1,317
Income tax benefit related to stock options	$184	$117	$557	$461
Impact on basic earnings per share	$0.01	$0.01	$0.03	$0.03
Impact on diluted earnings per share	$0.01	$0.01	$0.03	$0.03

ShareBased_Compensation_Estima

Share-Based Compensation - Estimate Fair Value of Share-Based Awards with Weighted-Average Assumptions (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]	'	'
Expected dividends	2.60%	2.30%
Expected volatility	34.80%	33.90%
Risk-free interest rate	1.70%	2.90%
Expected term (in years)	'8 years 7 months 6 days	'5 years 9 months 18 days
Weighted-average grant-date fair value	$15.37	$13.58

ShareBased_Compensation_Activi

Share-Based Compensation - Activity Related to Stock Options (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract]	'	'
Number of shares, Outstanding options, Beginning balance	1,236,075	1,097,620
Number of shares, Outstanding options, Granted	75,722	226,764
Number of shares, Issued in connection with acquisition	'	32,863
Number of shares, Outstanding options, Exercised	-142,841	-46,729
Number of shares, Outstanding options, Forfeited or expired	-36,608	-29,410
Number of shares, Outstanding options, Ending balance	1,132,348	1,281,108
Number of shares, Exercisable options	749,545	822,410
Weighted average exercise price, Outstanding options, Beginning balance	$51.48	$50.14
Weighted average exercise price, Outstanding options, Granted	$52.36	$51.73
Weighted average exercise price, Issued in connection with acquisition	'	$41.30
Weighted average exercise price, Outstanding options, Exercised	$38.09	$29.42
Weighted average exercise price, Outstanding options, Forfeited or expired	$56.01	$57.39
Weighted average exercise price, Outstanding options, Ending balance	$53.09	$50.78
Weighted average exercise price, Exercisable options	$52.94	$48.94
Weighted average remaining contract life, Outstanding options, Ending period	'4 years 8 months 12 days	'4 years 9 months 18 days
Weighted average remaining contract life, Outstanding exercisable, Ending period	'3 years 2 months 12 days	'
Weighted average remaining contract life, Exercisable options	'	'3 years

ShareBased_Compensation_Compen1

Share-Based Compensation - Compensation Expense Included in Salaries and Employee Benefits Expense Related to Restricted Stock Grants (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'	'
Compensation expense related to restricted stock/phantom stock	$2,110	$1,973	$6,055	$5,638

ShareBased_Compensation_Unvest

Share-Based Compensation - Unvested Restricted Stock Award Activity (Detail)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Balance at beginning of period	538,202	512,112
Granted	166,223	174,393
Forfeited	-27,483	-8,736
Earned and issued	-136,629	-120,644
Balance at end of period	540,313	557,125

ShareBased_Compensation_Compen2

Share-Based Compensation - Compensation Expense of Phantom Stock (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to restricted stock/phantom stock	$2,110	$1,973	$6,055	$5,638
Phantom Stock Awards [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation expense related to restricted stock/phantom stock	$792	$245	$2,602	$1,426

ShareBased_Compensation_Schedu

Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Number of share equivalents, Beginning Balance	318,729	232,921
Number of share equivalents, Granted	166,664	117,506
Number of share equivalents, Forfeited share equivalents	-16,381	-8,052
Number of share equivalents, Vested share equivalents	-45,065	-16,735
Number of share equivalents, Ending Balance	423,947	325,640
Dividend equivalents, Beginning Balance	16,035	8,942
Dividend equivalents, Granted	8,793	6,852
Dividend equivalents, Forfeited share equivalents	-681	-242
Dividend equivalents, Vested share equivalents	-3,327	-1,144
Dividend equivalents, Ending Balance	20,820	14,408
Dividend equivalents, Beginning Balance	334,764	241,863
Dividend equivalents, Granted	175,457	124,358
Dividend equivalents, Forfeited share equivalents	-17,062	-8,294
Dividend equivalents, Vested share equivalents	-48,392	-17,879
Dividend equivalents, Ending Balance	444,767	340,048
Value of share equivalents, Beginning Balance	$16,444,000	$11,924,000
Value of share equivalents, Granted	9,108,000	5,696,000
Value of share equivalents, Forfeited share equivalents	-886,000	-380,000
Value of share equivalents, Vested share equivalents	-2,453,000	-894,000
Value of share equivalents, Ending Balance	$23,088,000	$15,574,000

ShareBased_Compensation_Schedu1

Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Parenthetical) (Detail) (USD $)	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Market price of Company's stock	$51.91	$45.80

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	Sep. 30, 2013
Commitments Contingencies And Guarantees [Line Items]	'
Fair value of guarantees under commercial and standby letters of credit	$1,067,000
Minimum [Member]	'
Commitments Contingencies And Guarantees [Line Items]	'
Estimated losses associated with legal proceedings	500,000
Maximum [Member]	'
Commitments Contingencies And Guarantees [Line Items]	'
Estimated losses associated with legal proceedings	$2,200,000

Commitments_and_Contingencies_2

Commitments and Contingencies - Summary of Financial Instruments Outstanding (Detail) (Credit Risk Contract [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Credit Risk Contract [Member]	'	'
Commitments Contingencies And Guarantees [Line Items]	'	'
Commitments to grant loans	$342,494	$192,295
Unfunded commitments under lines of credit	2,972,046	2,372,971
Commercial and standby letters of credit	106,652	62,207
Reserve for unfunded lending commitments	$11,959	'

Fair_Value_Measurements_Financ

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Available-for-sale securities, Assets	$1,964,389	$1,745,004
Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Available-for-sale securities, Assets	1,964,389	1,745,004
Derivative instruments, Assets	32,469	42,119
Total, Assets	1,996,858	1,787,123
Derivative instruments, Liabilities	31,521	36,890
Total, Liabilities	31,521	36,890
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Available-for-sale securities, Assets	15,220	'
Derivative instruments, Assets	'	'
Total, Assets	15,220	'
Derivative instruments, Liabilities	'	'
Total, Liabilities	'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Available-for-sale securities, Assets	1,949,169	1,745,004
Derivative instruments, Assets	32,469	42,119
Total, Assets	1,981,638	1,787,123
Derivative instruments, Liabilities	31,521	36,890
Total, Liabilities	31,521	36,890
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Available-for-sale securities, Assets	'	'
Derivative instruments, Assets	'	'
Total, Assets	'	'
Derivative instruments, Liabilities	'	'
Total, Liabilities	'	'

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]	'	'
Fair value assets additions to Level 1 purchases	$15,220,000	'
Impaired non-covered loans with an outstanding balance	3,024,000	7,269,000
Reserve in allowance for credit losses	1,092,000	880,000
Asset impairment loss	4,941,000	'
Book value of company owned branches after impairment loss	$0	'

Fair_Value_Measurements_Gains_

Fair Value Measurements - Gains and Losses Included in Earnings Related to Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Noninterest Income [Member]	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Total gains (losses) included in earnings (or changes in net assets)	($1,056)
Change in unrealized gains (losses) relating to assets still held at September 30, 2013	'
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 September 30, 2013	($25,794)

Fair_Value_Measurements_Financ1

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Detail) (Fair Value, Measurements, Nonrecurring [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value Measurements [Line Items]	'	'
Loans, Assets	$1,932	$6,388
Mortgage loans held for sale, Assets	3,213	32,753
OREO, Assets	20,427	20,427
Total, Assets	25,572	59,568
Level 1 [Member]	'	'
Fair Value Measurements [Line Items]	'	'
Loans, Assets	'	'
Mortgage loans held for sale, Assets	'	'
OREO, Assets	'	'
Total, Assets	'	'
Level 2 [Member]	'	'
Fair Value Measurements [Line Items]	'	'
Loans, Assets	1,932	6,388
Mortgage loans held for sale, Assets	3,213	32,753
OREO, Assets	20,427	20,427
Total, Assets	25,572	59,568
Level 3 [Member]	'	'
Fair Value Measurements [Line Items]	'	'
Loans, Assets	'	'
Mortgage loans held for sale, Assets	'	'
OREO, Assets	'	'
Total, Assets	'	'

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Short-term borrowings maturity period	'90 days

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments - Estimated Fair Values and Carrying Amounts of Financial Instruments (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financial Assets	'	'
Cash and cash equivalents	$553,448	$970,977
FDIC loss share receivable	204,885	423,069
Financial Liabilities	'	'
Deposits	10,950,764	10,748,277
Short-term borrowings	258,850	303,045
Long-term debt	281,101	423,377
Carrying Amount [Member]	'	'
Financial Assets	'	'
Cash and cash equivalents	553,447	970,977
Investment securities	2,120,067	1,950,066
Loans and loans held for sale	9,151,322	8,766,054
FDIC loss share receivable	204,885	423,069
Derivative instruments	32,469	42,119
Accrued interest receivable	31,296	32,183
Financial Liabilities	'	'
Deposits	10,950,764	10,748,277
Short-term borrowings	258,850	303,045
Long-term debt	281,101	423,377
Derivative instruments	31,521	36,890
Accrued interest payable	6,026	6,615
Fair Value [Member]	'	'
Financial Assets	'	'
Cash and cash equivalents	553,447	970,977
Investment securities	2,119,699	1,956,502
Loans and loans held for sale	9,257,560	8,800,563
FDIC loss share receivable	59,512	207,222
Derivative instruments	32,469	42,119
Accrued interest receivable	31,296	32,183
Financial Liabilities	'	'
Deposits	10,533,414	10,594,885
Short-term borrowings	258,850	303,045
Long-term debt	239,506	394,490
Derivative instruments	31,521	36,890
Accrued interest payable	$6,026	$6,615