Old National Bancorp (ONB) 10-K 15 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	ONB
Entity Registrant Name	Old National Bancorp /IN/
Entity Central Index Key	707,179
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		152,061,000
Entity Public Float			$ 2,295,172,245

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 222,753	$ 209,381
Money market and other interest-earning investments	67,679	46,138
Total cash and cash equivalents	290,432	255,519
Trading securities, at fair value	5,584	4,982
Investment securities - available-for-sale, at fair value	3,196,207	2,797,174
Investment securities - held-to-maturity, at amortized cost (fair value $727,703 and $784,172, respectively)	684,063	745,090
Federal Home Loan Bank/Federal Reserve Bank stock, at cost	119,686	101,716
Loans held for sale, at fair value	17,930	90,682
Loans, net of unearned income	11,118,121	9,010,512
Allowance for loan losses	(50,381)	(49,808)
Net loans	11,067,740	8,960,704
Premises and equipment, net	458,074	429,622
Accrued interest receivable	87,102	81,381
Goodwill	828,051	655,018
Other intangible assets	53,096	37,677
Company-owned life insurance	403,753	352,956
Net deferred tax assets	110,857	181,863
Loan servicing rights	24,661	25,561
Assets held for sale	7,180	5,970
Other real estate owned and repossessed personal property	8,810	18,546
Other assets	155,066	115,776
Total assets	17,518,292	14,860,237
Deposits:
Noninterest-bearing demand	3,680,807	3,016,093
Interest-bearing:
NOW	3,115,822	2,596,595
Savings	3,035,622	2,954,709
Money market	1,139,077	707,748
Time	1,634,436	1,468,108
Total deposits	12,605,764	10,743,253
Federal funds purchased and interbank borrowings	335,033	213,003
Securities sold under agreements to repurchase	384,810	367,052
Federal Home Loan Bank advances	1,609,579	1,353,092
Other borrowings	248,782	218,939
Accrued expenses and other liabilities	179,927	150,481
Total liabilities	15,363,895	13,045,820
Commitments and contingencies (Note 22)
Shareholders' Equity
Preferred stock, series A, 2,000 shares authorized, no shares issued or outstanding
Common stock, $1.00 per share stated value, 300,000 shares authorized, 152,040 and 135,159 shares issued and outstanding, respectively	152,040	135,159
Capital surplus	1,639,499	1,348,338
Retained earnings	413,130	390,292
Accumulated other comprehensive income (loss), net of tax	(50,272)	(59,372)
Total shareholders' equity	2,154,397	1,814,417
Total liabilities and shareholders' equity	$ 17,518,292	$ 14,860,237

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment securities - held-to-maturity, fair value	$ 727,703	$ 784,172
Common stock, stated value	$ 1	$ 1
Authorized and unissued common shares reserved for issuance	300,000,000	300,000,000
Common stock, shares issued	152,040,000	135,159,000
Common stock, shares outstanding	152,040,000	135,159,000
Series A Preferred Stock [Member]
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans including fees:
Taxable	$ 389,219	$ 349,095	$ 304,452
Nontaxable	13,970	12,287	11,566
Investment securities:
Taxable	63,031	57,005	57,336
Nontaxable	28,858	28,617	25,788
Money market and other interest-earning investments	258	130	47
Total interest income	495,336	447,134	399,189
Interest Expense
Deposits	20,356	17,283	14,168
Federal funds purchased and interbank borrowings	1,966	673	265
Securities sold under agreements to repurchase	1,270	1,509	1,488
Federal Home Loan Bank advances	24,818	15,547	8,121
Other borrowings	9,758	9,419	9,031
Total interest expense	58,168	44,431	33,073
Net interest income	437,168	402,703	366,116
Provision for loan losses	3,050	960	2,923
Net interest income after provision for loan losses	434,118	401,743	363,193
Noninterest Income
Wealth management fees	37,316	34,641	34,395
Service charges on deposit accounts	41,331	41,578	43,372
Debit card and ATM fees	17,676	16,769	21,340
Mortgage banking revenue	18,449	20,240	12,540
Insurance premiums and commissions	617	20,527	42,714
Investment product fees	20,977	18,822	17,924
Capital markets income	6,544	3,227	1,082
Company-owned life insurance	8,654	8,479	8,604
Net securities gains (losses)	9,135	5,848	5,718
Recognition of deferred gain on sale leaseback transactions	2,080	16,057	16,444
Gain on sale of ONB Insurance Group, Inc.		41,864
Net gain on branch divestitures			15,627
Change in FDIC indemnification asset		233	(9,034)
Other income	20,603	24,545	19,906
Total noninterest income	183,382	252,830	230,632
Noninterest Expense
Salaries and employee benefits	246,738	252,892	243,875
Occupancy	46,511	50,947	53,239
Equipment	13,560	13,448	13,183
Marketing	13,172	14,620	10,410
Data processing	32,306	32,002	27,309
Communication	9,284	9,959	9,586
Professional fees	16,840	15,705	11,756
Loan expense	6,596	7,632	6,373
Supplies	2,406	2,865	2,275
FDIC assessment	9,480	8,681	7,503
Other real estate owned expense	3,376	4,195	2,703
Amortization of intangibles	11,841	12,486	11,746
Amortization of tax credit investments	11,733
Other expense	24,993	28,715	30,974
Total noninterest expense	448,836	454,147	430,932
Income before income taxes	168,664	200,426	162,893
Income tax expense	72,939	66,162	46,177
Net income	$ 95,725	$ 134,264	$ 116,716
Net income per common share - basic	$ 0.69	$ 1.05	$ 1.01
Net income per common share - diluted	$ 0.69	$ 1.05	$ 1
Weighted average number of common shares outstanding - basic	137,821	127,705	115,726
Weighted average number of common shares outstanding - diluted	138,513	128,301	116,255
Dividends per common share	$ 0.52	$ 0.52	$ 0.48

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 95,725	$ 134,264	$ 116,716
Change in securities available-for-sale:
Unrealized holding gains (losses) for the period	14,259	(49,813)	1,173
Reclassification adjustment for securities gains realized in income	(9,135)	(5,848)	(5,718)
Income tax effect	(1,669)	20,455	1,487
Unrealized gains (losses) on available-for-sale securities	3,455	(35,206)	(3,058)
Change in securities held-to-maturity:
Amortization of fair value for securities held-to-maturity previously recognized into accumulated other comprehensive income	1,830	1,776	1,692
Income tax effect	(627)	(606)	(396)
Changes from securities held-to-maturity	1,203	1,170	1,296
Cash flow hedges:
Net unrealized derivative gains (losses) on cash flow hedges	927	(2,323)	(8,107)
Reclassification adjustment for losses realized in net income	6,135	6,453	2,719
Income tax effect	(2,684)	(1,569)	2,047
Changes from cash flow hedges	4,378	2,561	(3,341)
Defined benefit pension plans:
Amortization of net (gain) loss and settlement cost recognized in income	159	11,203	3,002
Income tax effect	(95)	(4,303)	(1,141)
Changes from defined benefit pension plans	64	6,900	1,861
Other comprehensive income (loss), net of tax	9,100	(24,575)	(3,242)
Comprehensive income	$ 104,825	$ 109,689	$ 113,474

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Founders Financial Corporation [Member]	AnchorBank WI [Member]	Common Stock [Member]	Common Stock [Member]Founders Financial Corporation [Member]	Capital Surplus [Member]	Capital Surplus [Member]Founders Financial Corporation [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]AnchorBank WI [Member]
Beginning Balance at Dec. 31, 2014	$ 1,465,764			$ 116,847		$ 1,118,292		$ 262,180	$ (31,555)
Net income	116,716							116,716
Other comprehensive income (loss)	(3,242)								(3,242)
Acquisition		$ 50,626			$ 3,402		$ 47,224
Dividends - common stock	(55,552)							(55,552)
Common stock issued	391			29		362
Common stock repurchased	(88,695)			(6,399)		(82,296)
Stock based compensation expense	4,255					4,255
Stock activity under incentive compensation plans	907			418		74		415
Ending Balance at Dec. 31, 2015	1,491,170			114,297		1,087,911		323,759	(34,797)
Net income	134,264							134,264
Other comprehensive income (loss)	(24,575)		$ (24,575)							$ (24,575)
Acquisition	273,565		$ 273,565	20,415		253,150
Dividends - common stock	(67,536)							(67,536)
Common stock issued	388			32		356
Common stock repurchased	(2,044)			(154)		(1,890)
Stock based compensation expense	7,318					7,318
Stock activity under incentive compensation plans	1,867			569		1,493		(195)
Ending Balance at Dec. 31, 2016	1,814,417			135,159		1,348,338		390,292	(59,372)
Net income	95,725							95,725
Other comprehensive income (loss)	9,100								9,100
Acquisition	300,828			16,527		284,301
Dividends - common stock	(72,604)							(72,604)
Common stock issued	404			24		380
Common stock repurchased	(2,761)			(153)		(2,608)
Stock based compensation expense	6,275					6,275
Stock activity under incentive compensation plans	3,013			483		2,813		(283)
Ending Balance at Dec. 31, 2017	$ 2,154,397			$ 152,040		$ 1,639,499		$ 413,130	$ (50,272)

Consolidated Statements of Cha7

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Common stock, dividends per share	$ 0.52	$ 0.52	$ 0.48

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities
Net income	$ 95,725	$ 134,264	$ 116,716
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation	22,183	16,558	14,101
Amortization of other intangible assets	11,841	12,486	11,746
Amortization of tax credit investments	11,733
Net premium amortization on investment securities	15,302	18,633	18,609
Amortization of and net gains on termination of FDIC indemnification asset		(458)	9,034
Stock-based compensation expense	6,275	7,318	4,255
Excess tax (benefit) expense on stock-based compensation	79
Provision for loan losses	3,050	960	2,923
Net securities (gains) losses	(9,135)	(5,848)	(5,718)
Recognition of deferred gain on sale leaseback transactions	(2,080)	(16,057)	(16,444)
Gain on sale of ONB Insurance Group, Inc.		(41,864)
Net gain on branch divestitures			(15,627)
Net gains on sales of loans and other assets	(6,421)	(4,741)	(5,232)
Increase in cash surrender value of company-owned life insurance	(8,654)	(8,479)	(8,604)
Residential real estate loans originated for sale	(452,604)	(637,639)	(350,846)
Proceeds from sale of residential real estate loans	535,271	578,653	362,157
(Increase) decrease in interest receivable	151	(4,974)	(7,523)
(Increase) decrease in other real estate owned	10,794	11,301	4,538
(Increase) decrease in other assets	45,008	46,462	16,079
Increase (decrease) in accrued expenses and other liabilities	12,141	(24,524)	(26,408)
Total adjustments	194,934	(52,213)	7,040
Net cash flows provided by (used in) operating activities	290,659	82,051	123,756
Cash Flows From Investing Activities
Cash portion of bank purchase price, net of cash acquired	2,564	(62,532)	(37,098)
Proceeds from sale of ONB Insurance Group, Inc.		91,771
Payments related to branch divestitures			(333,095)
Purchases of investment securities available-for-sale	(874,555)	(1,625,746)	(832,419)
Purchases of investment securities held-to-maturity			(74,862)
Purchases of Federal Home Loan Bank/Federal Reserve Bank stock	(17,979)	(10,974)	(21,872)
Proceeds from maturities, prepayments, and calls of investment securities available-for-sale	438,818	1,177,130	764,649
Proceeds from sales of investment securities available-for-sale	342,233	243,312	343,486
Proceeds from maturities, prepayments, and calls of investment securities held-to-maturity	57,682	120,954	39,799
Proceeds from sales of investment securities held-to-maturity			855
Proceeds from sales of Federal Home Loan Bank/Federal Reserve Bank stock	6,594		8,711
Proceeds from sales of trading securities	127
Reimbursements under FDIC loss share agreements		10,000	3,548
Net principal collected from (loans made to) loan customers	(516,095)	(427,686)	(285,875)
Proceeds from settlements on company-owned life insurance	2,347	4,095	1,224
Proceeds from sale of premises and equipment and other assets	18,592	6,332	7,714
Purchases of premises and equipment and other assets	(37,303)	(224,659)	(85,661)
Net cash flows provided by (used in) investing activities	(576,975)	(698,003)	(500,896)
Cash Flows From Financing Activities
Deposits	85,062	489,680	89,328
Federal funds purchased and interbank borrowings	76,430	(78,087)	95,903
Securities sold under agreements to repurchase	(5,207)	(23,489)	(31,205)
Payments for maturities of Federal Home Loan Bank advances	(947,694)	(594,541)	(229,109)
Payments for maturities/redemptions of other borrowings	(20,056)	(67)	(63)
Proceeds from Federal Home Loan Bank advances	1,205,000	925,000	575,000
Cash dividends paid on common stock	(72,604)	(67,536)	(55,552)
Common stock repurchased	(2,761)	(2,044)	(88,695)
Proceeds from exercise of stock options	2,655	2,349	997
Common stock issued	404	388	391
Net cash flows provided by (used in) financing activities	321,229	651,653	356,995
Net increase (decrease) in cash and cash equivalents	34,913	35,701	(20,145)
Cash and cash equivalents at beginning of period	255,519	219,818	239,963
Cash and cash equivalents at end of period	$ 290,432	$ 255,519	$ 219,818

Nature of Operations

Nature of Operations	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	NATURE OF OPERATIONS Old National Bancorp, a financial holding company headquartered in Evansville, Indiana, operates primarily in Indiana, Kentucky, Michigan, Wisconsin, and Minnesota. Its principal subsidiary is Old National Bank. Through its bank and non-bank

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	NOTE 1 – BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying consolidated financial statements include the accounts of Old National Bancorp and its wholly-owned affiliates (hereinafter collectively referred to as “Old National”) and have been prepared in conformity with accounting principles generally accepted in the United States of America and prevailing practices within the banking industry. Such principles require management to make estimates and assumptions that affect the reported amounts of assets, liabilities and the disclosures of contingent assets and liabilities at the date of the financial statements and amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. All significant intercompany transactions and balances have been eliminated. Certain prior year amounts have been reclassified to conform to the 2017 presentation. Such reclassifications had no effect on net income or shareholders’ equity and were insignificant amounts. Trading Securities Trading securities consist of mutual funds held in trusts associated with deferred compensation plans for former directors and executives. These mutual funds are recorded as trading securities at fair value. Gains and losses are included in net securities gains. Investment Securities Old National classifies investment securities as available-for-sale held-to-maturity available-for-sale held-to-maturity, available-for-sale Other-Than-Temporary Impairment Federal Home Loan Bank Stock Old National is a member of the FHLB system. Members are required to own a certain amount of stock based on the level of borrowings and other factors and may invest in additional amounts. FHLB stock is carried at cost, classified as a restricted security, and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income. Loans Held for Sale Loans that Old National has originated with an intent to sell are classified as loans held for sale and are recorded in accordance with FASB ASC 825-10 Loans Loans that Old National intends to hold for investment purposes are classified as portfolio loans. Portfolio loans are carried at the principal balance outstanding, net of earned interest, purchase premiums or discounts, deferred loan fees and costs, and an allowance for loan losses. Interest income is accrued on the principal balances of loans outstanding. For all loan classes, a loan is generally placed on nonaccrual status when principal or interest becomes 90 days past due unless it is well secured and in the process of collection, or earlier when concern exists as to the ultimate collectibility of principal or interest. Interest accrued during the current year on such loans is reversed against earnings. Interest accrued in the prior year, if any, is charged to the allowance for loan losses. Cash interest received on these loans is applied to the principal balance until the principal is recovered or until the loan returns to accrual status. Loans may be returned to accrual status when all the principal and interest amounts contractually due are brought current, remain current for a prescribed period, and future payments are reasonably assured. Purchased loans acquired in a business combination are recorded at estimated fair value on their purchase date with no carryover of the related allowance for loan and lease losses. In determining the estimated fair value of purchased loans, management considers a number of factors including, among others, the remaining life of the acquired loans, estimated prepayments, estimated loss ratios, estimated value of the underlying collateral, and net present value of cash flows expected to be received. Purchased loans are accounted for in accordance with guidance for certain loans acquired in a transfer (ASC 310-30), non-accretable Allowance for Loan Losses The allowance for loan losses is maintained at a level believed adequate by management to absorb probable losses incurred in the consolidated loan portfolio. Management’s evaluation of the adequacy of the allowance is an estimate based on reviews of individual loans, pools of homogeneous loans, assessments of the impact of current and anticipated economic conditions on the portfolio, and historical loss experience. The allowance is increased through a provision charged to operating expense. Loans deemed to be uncollectible are charged to the allowance. Recoveries of loans previously charged-off For all loan classes, a loan is considered impaired when it is probable that contractual interest and principal payments will not be collected either for the amounts or by the dates as scheduled in the loan agreement. If a loan is impaired, a portion of the allowance is allocated so that the loan is reported net, at the present value of estimated cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Old National’s policy, for all but PCI loans, is to recognize interest income on impaired loans unless the loan is placed on nonaccrual status. Acquired loans accounted for under ASC Topic 310-30 re-estimation Old National charges off small commercial loans scored through our small business credit center with contractual balances under $250,000 that are 90 days or more delinquent and do not have adequate collateral support. For all portfolio segments, the general component covers non-impaired Further information regarding Old National’s policies and methodology used to estimate the allowance for loan losses is presented in Note 5. Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation. Land is stated at cost. Depreciation is charged to operating expense over the useful lives of the assets, principally on the straight-line method. Useful lives for premises and equipment are as follows: buildings and building improvements – 15 to 39 years; and furniture and equipment – 3 to 10 years. Leasehold improvements are depreciated over the lesser of their useful lives or the term of the lease. Maintenance and repairs are expensed as incurred while major additions and improvements are capitalized. Interest costs on construction of qualifying assets are capitalized. Premises and equipment are reviewed for impairment when events indicate their carrying amount may not be recoverable from future undiscounted cash flows. If impaired, the assets are adjusted to fair value. Such impairments are included in other expense. Goodwill and Other Intangible Assets The excess of the cost of acquired entities over the fair value of identifiable assets acquired less liabilities assumed is recorded as goodwill. In accordance with FASB ASC 350, Intangibles – Goodwill and Other Company-Owned Life Insurance Old National has purchased life insurance policies on certain key executives. Old National records company-owned life insurance at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value adjusted for other charges or other amounts due that are probable at settlement. Loan Servicing Rights When loans are sold with servicing retained, servicing rights are initially recorded at fair value with the income statement effect recorded in gain on sales of loans. Fair value is based on market prices for comparable servicing contracts, when available or alternatively, is based on a valuation model that calculates the present value of estimated future net servicing income. All classes of servicing assets are subsequently measured using the amortization method which requires servicing rights to be amortized into noninterest income in proportion to, and over the period of, the estimated future net servicing income of the underlying loans. Loan servicing rights are evaluated for impairment based upon the fair value of the rights as compared to carrying amount. Impairment is determined by stratifying rights into groupings based on predominant risk characteristics, such as interest rate, loan type, term, and investor type. Impairment is recognized through a valuation allowance for an individual grouping, to the extent that fair value is less than the carrying amount. If Old National later determines that all or a portion of the impairment no longer exists for a particular grouping, a reduction of the allowance may be recorded as an increase to income. Changes in valuation allowances are reported with mortgage banking revenue on the income statement. The fair values of servicing rights are subject to significant fluctuations as a result of changes in estimated and actual prepayment speeds and default rates and losses. Servicing fee income, which is reported on the income statement as mortgage banking revenue, is recorded for fees earned for servicing loans. The fees are based on a contractual percentage of the outstanding principal, or a fixed amount per loan and are recorded as income when earned. Derivative Financial Instruments As part of Old National’s overall interest rate risk management, Old National uses derivative instruments, including TBA forward agreements and interest rate swaps, caps, and floors. All derivative instruments are recognized on the balance sheet at their fair value in accordance with ASC 815, as amended. At the inception of the derivative contract, Old National will designate the derivative as (1) a hedge of the fair value of a recognized asset or liability or of an unrecognized firm commitment (“fair value hedge”), (2) a hedge of a forecasted transaction or of the variability of cash flows to be received or paid related to a recognized asset or liability (“cash flow hedge”), or (3) an instrument with no hedging designation (“stand-alone derivative”). For derivatives that are designated and qualify as a fair value hedge, the change in value of the derivative, as well as the offsetting change in value of the hedged item attributable to the hedged risk, are recognized in current earnings during the period of the change in fair values. For derivatives that are designated and qualify as a cash flow hedge, the effective portion of the change in value on the derivative is reported as a component of other comprehensive income and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. For all hedging relationships, changes in fair value of derivatives that are not effective in hedging the changes in fair value or expected cash flows of the hedged item are recognized immediately in current earnings during the period of the change. Similarly, the changes in the fair value of derivatives that do not qualify for hedge accounting under ASC Topic 815 are also reported currently in earnings, in noninterest income. The accrued net settlements on derivatives that qualify for hedge accounting are recorded in interest income or interest expense, consistent with the item being hedged. Old National formally documents all relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking various hedge transactions. This process includes linking all derivative instruments that are designated as fair-value or cash-flow hedges to specific assets and liabilities on the balance sheet or to specific firm commitments or forecasted transactions. Old National also formally assesses, both at the hedge’s inception and on an ongoing basis, whether the derivative instruments that are used in hedging transactions are highly effective in offsetting changes in fair values or cash flows of hedged items. Old National discontinues hedge accounting prospectively when it is determined that (1) the derivative is no longer effective in offsetting changes in the fair value or cash flows of the hedged item; (2) the derivative expires, is sold, or terminated; (3) the derivative instrument is de-designated When hedge accounting is discontinued, the future changes in fair value of the derivative are recorded as noninterest income. When a fair value hedge is discontinued, the hedged asset or liability is no longer adjusted for changes in fair value and the existing basis adjustment is amortized or accreted over the remaining life of the asset or liability. When a cash flow hedge is discontinued but the hedged cash flows or forecasted transaction is still expected to occur, changes in value that were accumulated in other comprehensive income are amortized or accreted into earnings over the same periods which the hedged transactions will affect earnings. Old National enters into various stand-alone mortgage-banking derivatives in order to hedge the risk associated with the fluctuation of interest rates. Changes in fair value are recorded as mortgage banking revenue. Old National also enters into various stand-alone derivative contracts to provide derivative products to customers which are carried at fair value with changes in fair value recorded as other noninterest income. Old National is exposed to losses if a counterparty fails to make its payments under a contract in which Old National is in the net receiving position. Old National anticipates that the counterparties will be able to fully satisfy their obligations under the agreements. In addition, Old National obtains collateral above certain thresholds of the fair value of its hedges for each counterparty based upon their credit standing. All of the contracts to which Old National is a party settle monthly, quarterly, or semiannually. Further, Old National has netting agreements with the dealers with which it does business. Credit-Related Financial Instruments In the ordinary course of business, Old National’s affiliate bank has entered into credit-related financial instruments consisting of commitments to extend credit, commercial letters of credit, and standby letters of credit. The notional amount of these commitments is not reflected in the consolidated financial statements until they are funded. Foreclosed Assets Other assets include real estate properties acquired as a result of foreclosure and repossessed personal property and are initially recorded at the fair value of the property less estimated cost to sell. Any excess recorded investment over the fair value of the property received is charged to the allowance for loan losses. Any subsequent write-downs are charged to expense, as are the costs of operating the properties. Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase We purchase certain securities, generally U.S. government-sponsored entity and agency securities, under agreements to resell. The amounts advanced under these agreements represent short-term secured loans and are reflected as assets in the accompanying consolidated balance sheets. We also sell certain securities under agreements to repurchase. These agreements are treated as collateralized financing transactions. These secured borrowings are reflected as liabilities in the accompanying consolidated balance sheets and are recorded at the amount of cash received in connection with the transaction. Short-term securities sold under agreements to repurchase generally mature within one to four days from the transaction date. Securities, generally U.S. government and federal agency securities, pledged as collateral under these financing arrangements can be repledged by the secured party. Additional collateral may be required based on the fair value of the underlying securities. Covered Assets, Loss Share Agreements, and Indemnification Asset On July 29, 2011, Old National acquired the banking operations of Integra in an FDIC assisted transaction. As part of the purchase and assumption agreement, Old National and the FDIC entered into loss sharing agreements (each, a “loss sharing agreement” and collectively, the “loss sharing agreements”), whereby the FDIC would cover a substantial portion of any future losses on loans (and related unfunded commitments), OREO and up to 90 days of certain accrued interest on loans. The acquired loans and OREO subject to the loss sharing agreements are referred to collectively as “covered assets.” Old National entered into an agreement with the FDIC on June 22, 2016 to terminate its loss share agreements. As a result of the termination of the loss share agreements, the remaining covered assets that were covered by the loss share arrangements were reclassified to noncovered assets effective June 22, 2016. Prior to the termination of the loss share agreements, the FDIC would have reimbursed us for 80% of expenses and valuation write-downs related to covered assets up to $275.0 million, an amount which we never reached. Net Income per Share Basic net income per share is computed by dividing net income by the weighted-average number of common shares outstanding during each year. Diluted net income per share is computed as above and assumes the conversion of outstanding stock options and restricted stock. The following table reconciles basic and diluted net income per share for the years ended December 31. (dollars and shares in thousands, except per share data) Years Ended December 31, 2017 2016 2015 Basic Earnings Per Share Net income $ 95,725 $ 134,264 $ 116,716 Weighted average common shares outstanding 137,821 127,705 115,726 Basic Net Income Per Share $ 0.69 $ 1.05 $ 1.01 Diluted Earnings Per Share Net income $ 95,725 $ 134,264 $ 116,716 Weighted average common shares outstanding 137,821 127,705 115,726 Effect of dilutive securities: Restricted stock (1) 599 543 440 Stock options (2) 93 53 89 Weighted average shares outstanding 138,513 128,301 116,255 Diluted Earnings Per Share $ 0.69 $ 1.05 $ 1.00 (1) 8 thousand shares and 3 thousand shares of restricted stock at December 31, 2017 and 2016, respectively, were not included in the computation of net income per diluted share because the effect would be antidilutive. There were no shares of restricted stock excluded at December 31, 2015 because the effect would be antidilutive. (2) Options to purchase 0.1 million shares, 0.5 million shares, and 0.7 million shares outstanding at December 31, 2017, 2016, and 2015, respectively, were not included in the computation of net income per diluted share because the exercise price of these options was greater than the average market price of the common shares and, therefore, the effect would be antidilutive. Stock-Based Compensation Compensation cost is recognized for stock options and restricted stock awards and units issued to employees based on the fair value of these awards at the date of grant. A Black-Scholes model is utilized to estimate the fair value of stock options, while the market price of our Common Stock at the date of grant is used for restricted stock awards. A third party provider is used to value certain restricted stock units where the performance measure is based on total shareholder return. Compensation expense is recognized over the requisite service period. Income Taxes Income tax expense is the total of the current year income tax due or refundable and the change in deferred tax assets and liabilities. Deferred tax assets and liabilities are the expected future tax amounts for the temporary differences between carrying amounts and tax bases of assets and liabilities, computed using enacted tax rates. A valuation allowance, if needed, reduces deferred tax assets to the amount expected to be realized. We recognize a tax position as a benefit only if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit that is greater than 50% likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded. We recognize interest and/or penalties related to income tax matters in income tax expense. Old National is a limited partner in several tax-advantaged pre-tax Loss Contingencies Loss contingencies, including claims and legal actions arising in the normal course of business, are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated. See Note 22 to the consolidated financial statements for further disclosure. Statement of Cash Flows Data For the purpose of presentation in the accompanying consolidated statement of cash flows, cash and cash equivalents are defined as cash, due from banks, federal funds sold and resell agreements, and money market investments, which have maturities less than 90 days. The following table summarizes the supplemental cash flow information for the years ended December 31: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Cash payments: Interest $ 56,682 $ 43,698 $ 32,712 Income taxes (net of refunds) 4,326 23,636 14,824 Noncash Investing and Financing Activities: Transfer of premises and equipment to assets held for sale 16,617 4,620 9,070 The following table summarizes the common shares issued and resultant value of total shareholders’ equity associated with acquisitions for the years ended December 31: (dollars and shares in thousands) Shares of Total 2017 Acquisition of Anchor (MN) 16,527 $ 300,828 2016 Acquisition of Anchor (WI) 20,415 $ 273,565 2015 Acquisition of Founders 3,402 $ 50,626 Impact of Accounting Changes FASB ASC 606 – No. 2014-09, Revenue from Contracts with Customers Revenue from Contracts with Customers in-depth In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) No. 2014-09 No. 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing No. 2014-09 No. 2014-09. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients In December 2016, the FASB issued ASU No. 2016-20, Revenue from Contracts with Customers (Topic 606): Technical Corrections and Improvements No. 2014-09 No. 2014-09. No. 2014-09. FASB ASC 825 No. 2016-01, Financial Instruments – Overall (Subtopic 825-10): available-for-sale FASB ASC 842 – No. 2016-02, Leases (Topic 842) right-of-use FASB ASC 815 No. 2016-05, Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships de-designation In March 2016, the FASB issued ASU No. 2016-06, Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments Derivatives and Hedging In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. held-to-maturity available-for-sale FASB ASC 323 No. 2016-07, Investments—Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting step-by-step available-for-sale FASB ASC 718 – No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Shared-Based Payment Accounting In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting. FASB ASC 326 – No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments available-for-sale one-time one-time FASB ASC 740 – No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory FASB ASC 810 No. 2016-17, Consolidation (Topic 810): Interests Held through Related Parties that are under Common Control FASB ASC 805 No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business FASB ASC 350 – No. 2017-04, Intangibles: Goodwill and Other: Simplifying the Test for Goodwill Impairment FASB ASC 610 – No. 2017-05, Other Income – Gains and Losses from the Derecognition of Nonfinancial Assets (Topic 610): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets 610-20 No. 2014-09 2014-09. 610-20 2014-09. FASB ASC 715 – No. 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost FASB ASC 310 – No. 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20):

Acquisition and Divestiture Act

Acquisition and Divestiture Activity	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition and Divestiture Activity	NOTE 2 – ACQUISITION AND DIVESTITURE ACTIVITY Acquisitions Anchor BanCorp Wisconsin Inc. Effective May 1, 2016, Old National completed the acquisition of Madison, Wisconsin-based Anchor (WI) through a stock and cash merger. Anchor (WI) was a savings and loan holding company with AnchorBank (WI) as its wholly-owned subsidiary. AnchorBank (WI) operated 46 banking centers, including 32 banking centers in the Madison, Milwaukee, and Fox Valley triangle. Old National achieved cost savings by integrating the two companies and combining accounting, data processing, retail and lending support, and other administrative functions after the merger, which enabled Old National to achieve economies of scale in these areas. Pursuant to the merger agreement, shareholders of Anchor (WI) could elect to receive either 3.5505 shares of Old National Common Stock or $48.50 in cash for each share of Anchor (WI) they held, subject to a maximum of 40% of the purchase price in cash. The total fair value of consideration paid for Anchor (WI) was $459.8 million, consisting of $186.2 million of cash and the issuance of 20.4 million shares of Old National Common Stock valued at $273.6 million. This acquisition was accounted for under the acquisition method of accounting. Accordingly, Old National recognized amounts for identifiable assets acquired and liabilities assumed at their estimated acquisition date fair values, while $15.9 million of transaction and integration costs were expensed as incurred. As of April 30, 2017, Old National finalized its valuation of all assets acquired and liabilities assumed, resulting in no material change to acquisition accounting adjustments. A summary of the fair values of the acquired assets, liabilities assumed, and resulting goodwill are as follows (in thousands): Cash and cash equivalents $ 123,657 Investment securities 235,240 FHLB stock 4,596 Loans held for sale 9,334 Loans 1,637,806 Premises and equipment 35,721 Accrued interest receivable 7,308 Other real estate owned 17,349 Company-owned life insurance 7,278 Other assets 126,210 Deposits (1,852,713 ) Securities sold under agreements to repurchase (3,132 ) Other borrowings (123 ) Accrued expenses and other liabilities (36,957 ) Net tangible assets acquired 311,574 Definite-lived intangible assets acquired 21,559 Loan servicing rights 15,274 Goodwill 111,347 Total consideration $ 459,754 Goodwill related to this acquisition will not be deductible for tax purposes. The estimated fair value of the core deposit intangible was $21.6 million and is being amortized over an estimated useful life of 7 years. Acquired loan data for Anchor (WI) can be found in the table below: (in thousands) Fair Value Gross Contractual Best Estimate at Acquired receivables subject to ASC 310-30 $ 20,174 $ 29,544 $ 6,153 Acquired receivables not subject to ASC 310-30 $ 1,617,632 $ 2,143,532 $ 274,155 Anchor Bancorp, Inc. Effective November 1, 2017, Old National completed the acquisition of St. Paul, Minnesota-based Anchor (MN) through a stock and cash merger. Anchor (MN) was a bank holding company with Anchor Bank (MN) as its wholly-owned subsidiary. Founded in 1967 and with 17 total branches, Anchor Bank (MN) was one of the largest community banks headquartered in the Twin Cities, and also served Mankato, Minnesota. Anchor Bank (MN) has no affiliation with the former AnchorBank (WI) in Madison, Wisconsin, which Old National acquired in 2016. Old National believes that it will be able to achieve cost savings by integrating the two companies and combining accounting, data processing, retail and lending support, and other administrative functions, which will enable Old National to achieve economies of scale in these areas. Pursuant to the merger agreement, each holder of Anchor (MN) common stock received $2.625 in cash and 1.350 shares of Old National Common Stock per share of Anchor (MN) common stock such holder owned. The total fair value of consideration for Anchor (MN) was $332.8 million, consisting of $31.9 million of cash and the issuance of 16.5 million shares of Old National Common Stock valued at $300.8 million. This acquisition was accounted for under the acquisition method of accounting. Accordingly, Old National recognized amounts for identifiable assets acquired and liabilities assumed at their estimated acquisition date fair values. Through December 31, 2017, transaction and integration costs of $12.3 million associated with this acquisition have been expensed and remaining integration costs will be expensed in future periods as incurred. The following table reflects management’s preliminary valuation of the assets acquired and liabilities assumed (in thousands): Cash and cash equivalents $ 34,501 Investment securities 302,195 FHLB/Federal Reserve Bank stock 6,585 Loans held for sale 1,407 Loans 1,593,991 Premises and equipment 33,556 Accrued interest receivable 5,872 Other real estate owned 1,058 Company-owned life insurance 44,490 Other assets 29,872 Deposits (1,777,449 ) Federal funds purchased and interbank borrowings (45,600 ) Securities sold under agreements to repurchase (22,965 ) Other borrowings (49,257 ) Accrued expenses and other liabilities (25,784 ) Net tangible assets acquired 132,472 Definite-lived intangible assets acquired 27,260 Goodwill 173,033 Total consideration $ 332,765 Prior to the end of the one-year Goodwill related to this acquisition will not be deductible for tax purposes. The estimated fair value of the core deposit intangible was $27.3 million and is being amortized over an estimated useful life of 10 years. Acquired loan data for Anchor (MN) can be found in the table below: (in thousands) Fair Value Gross Contractual Best Estimate at Acquired receivables subject to ASC 310-30 $ 10,555 $ 16,898 $ 4,787 Acquired receivables not subject to ASC 310-30 $ 1,583,436 $ 1,879,449 $ 87,767 Summary of Unaudited Pro-Forma The unaudited pro-forma pro-forma (dollars in thousands) 2017 2016 Revenue (1) $ 700,944 $ 738,280 Income before income taxes $ 213,932 $ 214,737 (1) Net interest income plus noninterest income. Supplemental pro-forma pro-forma Divestitures On August 14, 2015, Old National divested its southern Illinois region (twelve branches) along with four branches in eastern Indiana and one in Ohio. At closing, the purchasers assumed loans of $193.6 million and deposits of $555.8 million. Old National recorded a net pre-tax In addition, Old National consolidated 23 branches throughout the Old National franchise during 2015 based on an ongoing assessment of our service and delivery network and on our goal to continue to move our franchise into stronger growth markets. On May 31, 2016, Old National sold its insurance operations, ONI. Old National received approximately $91.8 million in cash resulting in a pre-tax after-tax 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. Based on an ongoing assessment of our service and delivery network, Old National consolidated 5 branches during 2016 and an additional 29 in 2017.

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investment Securities	NOTE 3 – INVESTMENT SECURITIES The following table summarizes the amortized cost and fair value of the available-for-sale held-to-maturity (dollars in thousands) Amortized Unrealized Unrealized Fair Value December 31, 2017 Available-for-Sale U.S. Treasury $ 5,473 $ 83 $ (5 ) $ 5,551 U.S. government-sponsored entities and agencies 675,643 3 (11,360 ) 664,286 Mortgage-backed securities - Agency 1,704,014 1,600 (37,932 ) 1,667,682 States and political subdivisions 529,835 5,085 (4,727 ) 530,193 Pooled trust preferred securities 16,605 — (8,157 ) 8,448 Other securities 321,016 1,172 (2,141 ) 320,047 Total available-for-sale $ 3,252,586 $ 7,943 $ (64,322 ) $ 3,196,207 Held-to-Maturity Mortgage-backed securities - Agency $ 6,903 153 $ — $ 7,056 States and political subdivisions 677,160 43,495 (8 ) 720,647 Total held-to-maturity $ 684,063 $ 43,648 $ (8 ) $ 727,703 December 31, 2016 Available-for-Sale U.S. Treasury $ 6,963 $ 140 $ — $ 7,103 U.S. government-sponsored entities and agencies 506,234 113 (12,391 ) 493,956 Mortgage-backed securities - Agency 1,551,465 6,923 (33,369 ) 1,525,019 States and political subdivisions 446,003 4,183 (13,502 ) 436,684 Pooled trust preferred securities 17,011 — (8,892 ) 8,119 Other securities 331,001 1,074 (5,782 ) 326,293 Total available-for-sale $ 2,858,677 $ 12,433 $ (73,936 ) $ 2,797,174 Held-to-Maturity U.S. government-sponsored entities and agencies $ 40,131 $ 427 $ — $ 40,558 Mortgage-backed securities - Agency 10,640 300 — 10,940 States and political subdivisions 694,319 38,915 (560 ) 732,674 Total held-to-maturity $ 745,090 $ 39,642 $ (560 ) $ 784,172 Proceeds from sales or calls of available-for-sale Years Ended December 31, (dollars in thousands) 2017 2016 2015 Proceeds from sales of available-for-sale $ 342,233 $ 243,312 $ 343,486 Proceeds from calls of available-for-sale 88,233 635,624 404,277 Total $ 430,466 $ 878,936 $ 747,763 Realized gains on sales of available-for-sale $ 8,710 $ 5,423 $ 5,640 Realized gains on calls of available-for-sale 29 922 605 Realized losses on sales of available-for-sale (263 ) (450 ) (518 ) Realized losses on calls of available-for-sale (8 ) (147 ) (15 ) Other securities gains (losses) (1) 667 100 6 Net securities gains $ 9,135 $ 5,848 $ 5,718 (1) Other securities gains (losses) includes net realized and unrealized gains or losses associated with trading securities and mutual funds. During 2015, Old National sold a municipal bond that was classified as held-to-maturity Investment securities pledged to secure public and other funds had a carrying value of $1.8 billion at December 31, 2017 and $1.4 billion at December 31, 2016. Trading securities, which consist of mutual funds held in trusts associated with deferred compensation plans for former directors and executives, are recorded at fair value and totaled $5.6 million at December 31, 2017 and $5.0 million at December 31, 2016. At December 31, 2017, Old National had a concentration of investment securities issued by certain states and their political subdivisions with the following aggregate market values: $375.1 million by Indiana, which represented 17.4% of shareholders’ equity, and $182.7 million by Texas, which represented 8.5% of shareholders’ equity. Of the Indiana municipal bonds, 98% are rated “A” or better, and the remaining 2% generally represent non-rated As previously disclosed in Note 1, upon the early adoption of ASU No. 2017-12 held-to-maturity available-for-sale available-for-sale held-to-maturity All of the mortgage-backed securities in the investment portfolio are residential mortgage-backed securities. The amortized cost and fair value of the investment securities portfolio are shown by expected maturity. Expected maturities may differ from contractual maturities if borrowers have the right to call or prepay obligations with or without call or prepayment penalties. Weighted average yield is based on amortized cost. At December 31, 2017 (dollars in thousands) Amortized Fair Weighted Maturity Cost Value Yield Available-for-Sale Within one year $ 64,076 $ 64,084 2.13 % One to five years 420,949 417,941 2.02 Five to ten years 337,043 336,999 2.72 Beyond ten years 2,430,518 2,377,183 2.48 Total $ 3,252,586 $ 3,196,207 2.43 % Held-to-Maturity Within one year $ 22,566 $ 22,692 6.23 % One to five years 115,596 120,904 5.08 Five to ten years 159,452 167,547 4.87 Beyond ten years 386,449 416,560 5.75 Total $ 684,063 $ 727,703 5.44 % The following table summarizes the investment securities with unrealized losses at December 31 by aggregated major security type and length of time in a continuous unrealized loss position: Less than 12 months 12 months or longer Total Fair Unrealized Fair Unrealized Fair Unrealized (dollars in thousands) Value Losses Value Losses Value Losses December 31, 2017 Available-for-Sale U.S. Treasury $ 1,480 $ (5 ) $ — $ — $ 1,480 $ (5 ) U.S. government-sponsored entities and agencies 201,773 (1,333 ) 408,493 (10,027 ) 610,266 (11,360 ) Mortgage-backed securities—Agency 789,804 (8,692 ) 774,825 (29,240 ) 1,564,629 (37,932 ) States and political subdivisions 196,024 (1,899 ) 90,637 (2,828 ) 286,661 (4,727 ) Pooled trust preferred securities — — 8,448 (8,157 ) 8,448 (8,157 ) Other securities 61,260 (429 ) 125,517 (1,712 ) 186,777 (2,141 ) Total available-for-sale $ 1,250,341 $ (12,358 ) $ 1,407,920 $ (51,964 ) $ 2,658,261 $ (64,322 ) Held-to-Maturity States and political subdivisions $ 2,309 $ (8 ) $ — $ — $ 2,309 $ (8 ) Total held-to-maturity $ 2,309 $ (8 ) $ — $ — $ 2,309 $ (8 ) December 31, 2016 Available-for-Sale U.S. government-sponsored entities and agencies $ 432,192 $ (12,391 ) $ — $ — $ 432,192 $ (12,391 ) Mortgage-backed securities—Agency 1,177,093 (30,295 ) 57,636 (3,074 ) 1,234,729 (33,369 ) States and political subdivisions 286,351 (13,247 ) 4,919 (255 ) 291,270 (13,502 ) Pooled trust preferred securities — — 8,119 (8,892 ) 8,119 (8,892 ) Other securities 121,498 (2,734 ) 126,539 (3,048 ) 248,037 (5,782 ) Total available-for-sale $ 2,017,134 $ (58,667 ) $ 197,213 $ (15,269 ) $ 2,214,347 $ (73,936 ) Held-to-Maturity States and political subdivisions $ 59,481 $ (560 ) $ — $ — $ 59,481 $ (560 ) Total held-to-maturity $ 59,481 $ (560 ) $ — $ — $ 59,481 $ (560 ) Management evaluates securities for OTTI at least on a quarterly basis, and more frequently when economic or market conditions warrant such an evaluation. The investment securities portfolio is evaluated for OTTI by segregating the portfolio into two general segments and applying the appropriate OTTI model. Investment securities classified as available-for-sale held-to-maturity non-agency 325-10 No. 99-20, Recognition of Interest Income and Impairment on Purchased Beneficial Interests and Beneficial Interests that Continue to be Held by a Transfer in Securitized Financial Assets . In determining OTTI under the FASB ASC 320 model, management considers many factors, including: (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near-term prospects of the issuer, (3) whether the market decline was affected by macroeconomic conditions, and (4) whether the entity has the intent to sell the debt security or more likely than not will be required to sell the debt security before its anticipated recovery. The assessment of whether an other-than-temporary decline exists involves a high degree of subjectivity and judgment and is based on the information available to management at a point in time. The second segment of the portfolio uses the OTTI guidance provided by FASB ASC 325-10 99-20) 325-10 When OTTI occurs under either model, the amount of the OTTI recognized in earnings depends on whether an entity intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss. If an entity intends to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the OTTI shall be recognized in earnings equal to the entire difference between the investment’s amortized cost basis and its fair value at the balance sheet date. Otherwise, the OTTI shall be separated into the amount representing the credit loss and the amount related to all other factors. The amount of the total OTTI related to the credit loss is determined based on the present value of cash flows expected to be collected and is recognized in earnings. The amount of the total OTTI related to other factors shall be recognized in other comprehensive income, net of applicable taxes. The previous amortized cost basis less the OTTI recognized in earnings shall become the new amortized cost basis of the investment. We did not record OTTI in 2017, 2016, or 2015. As of December 31, 2017, Old National’s securities portfolio consisted of 1,789 securities, 737 of which were in an unrealized loss position. The unrealized losses attributable to our U.S. Treasury, U.S. government-sponsored entities and agencies, agency mortgage-backed securities, states and political subdivisions, and other securities are the result of fluctuations in interest rates. Our pooled trust preferred securities are discussed below. At December 31, 2017, we had no intent to sell any securities that were in an unrealized loss position nor is it expected that we would be required to sell any securities. Pooled Trust Preferred Securities At December 31, 2017, our securities portfolio contained three pooled trust preferred securities with a fair value of $8.4 million and unrealized losses of $8.2 million. One of the pooled trust preferred securities in our portfolio falls within the scope of FASB ASC 325-10 99-20) Two of our pooled trust preferred securities with a fair value of $8.1 million and unrealized losses of $5.8 million at December 31, 2017 are not subject to FASB ASC 325-10. The table below summarizes the relevant characteristics of our pooled trust preferred securities as well as our single issuer trust preferred securities that are included in the “other securities” category in this footnote. Each of the pooled trust preferred securities support a more senior tranche of security holders. All three pooled trust preferred securities have experienced credit defaults. However, two of these securities have excess subordination and are not other-than-temporarily impaired as a result of their class hierarchy, which provides more loss protection. Trust preferred securities Actual Expected Excess December 31, 2017 Deferrals Defaults as Subordination (dollars in thousands) # of Issuers and Defaults a % of as a % of Lowest Unrealized Realized Currently as a % of Remaining Current Credit Amortized Fair Gain/ Losses Performing/ Original Performing Performing Class Rating (1) Cost Value (Loss) 2017 Remaining Collateral Collateral Collateral Pooled trust preferred securities: Reg Div Funding 2004 B-2 D $ 2,696 $ 273 $ (2,423 ) $ — 21/36 32.1 % 7.7 % 0.0 % Pretsl XXVII LTD B B 4,414 2,478 (1,936 ) — 34/44 16.7 % 11.8 % 33.1 % Trapeza Ser 13A A2A BBB 9,495 5,697 (3,798 ) — 49/54 4.5 % 8.3 % 53.7 % 16,605 8,448 (8,157 ) — Single Issuer trust preferred securities: Fleet Cap Tr V (BOA) BBB- 3,406 3,290 (116 ) — JP Morgan Chase Cap XIII BBB- 4,778 4,778 — — NB-Global BBB- 803 935 132 — 8,987 9,003 16 — Total $ 25,592 $ 17,451 $ (8,141 ) $ — (1) Lowest rating for the security provided by any nationally recognized credit rating agency.

Loans Held for Sale

Loans Held for Sale	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Loans Held for Sale	NOTE 4 – LOANS HELD FOR SALE Mortgage loans held for immediate sale in the secondary market were $17.9 million at December 31, 2017, compared to $90.7 million at December 31, 2016. Residential loans that Old National has originated with the intent to sell are recorded at fair value in accordance with FASB ASC 825-10, Financial Instruments

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Loans and Allowance for Loan Losses	NOTE 5 – LOANS AND ALLOWANCE FOR LOAN LOSSES Old National’s loans consist primarily of loans made to consumers and commercial clients in various industries including manufacturing, agribusiness, transportation, mining, wholesaling, and retailing. Most of Old National’s lending activity occurs within our principal geographic markets of Indiana, Kentucky, Michigan, Wisconsin, and Minnesota. Old National manages concentrations of credit exposure by industry, product, geography, customer relationship, and loan size, with no concentration of loans exceeding 10% of its portfolio. The composition of loans at December 31 by lending classification was as follows: December 31, (dollars in thousands) 2017 2016 Commercial (1) $ 2,717,269 $ 1,917,099 Commercial real estate: Construction (2) 374,306 357,802 Other (2) 3,980,246 2,773,051 Residential real estate 2,167,053 2,087,530 Consumer credit: Home equity 507,507 476,439 Auto 1,148,672 1,167,737 Other 223,068 230,854 Total loans 11,118,121 9,010,512 Allowance for loan losses (50,381 ) (49,808 ) Net loans $ 11,067,740 $ 8,960,704 (1) Includes direct finance leases of $29.5 million at December 31, 2017 and $10.8 million at December 31, 2016. (2) Certain commercial real estate construction loans were reclassified from commercial real estate - other due to a misclassification at December 31, 2016. The risk characteristics of each loan portfolio segment are as follows: Commercial Commercial loans are primarily based on the identified cash flows of the borrower and secondarily on the underlying collateral provided by the borrower. The cash flows of borrowers, however, may not be as expected and the collateral securing these loans may fluctuate in value. Most commercial loans are secured by the assets being financed or other business assets such as accounts receivable or inventory and may incorporate a personal guarantee; however, some loans may be made on an unsecured basis. In the case of loans secured by accounts receivable, the availability of funds for the repayment of these loans may be substantially dependent on the ability of the borrower to collect amounts due from its customers. Commercial Real Estate These loans are viewed primarily as cash flow loans and secondarily as loans secured by real estate. Commercial real estate lending typically involves higher loan principal amounts, and the repayment of these loans is generally dependent on the successful operation of the property securing the loan or the business conducted on the property securing the loan. Commercial real estate loans may be adversely affected by conditions in the real estate markets or in the general economy. The properties securing Old National’s commercial real estate portfolio are diverse in terms of type and geographic location. Management monitors and evaluates commercial real estate loans based on collateral, geography and risk grade criteria. In addition, management tracks the level of owner-occupied commercial real estate loans versus non-owner Included with commercial real estate are construction loans, which are underwritten utilizing independent appraisal reviews, sensitivity analysis of absorption and lease rates, financial analysis of the developers and property owners, and feasibility studies, if available. Construction loans are generally based on estimates of costs and value associated with the complete project. These estimates may be inaccurate. Construction loans often involve the disbursement of substantial funds with repayment substantially dependent on the success of the ultimate project. Sources of repayment for these types of loans may be pre-committed on-site The acquisition of Anchor (MN) on November 1, 2017 added $864.4 million of commercial real estate loans to our portfolio. At 206%, Old National Bank’s commercial real estate loans as a percentage of its risk-based capital remained well below the regulatory guideline limit of 300% at December 31, 2017. Residential With respect to residential loans that are secured by 1-4 loan-to-value Consumer Home equity loans are typically secured by a subordinate interest in 1-4 Related Party Loans In the ordinary course of business, Old National grants loans to certain executive officers, directors, and significant subsidiaries (collectively referred to as “related parties”). Activity in related party loans during 2017 is presented in the following table: Year Ended (dollars in thousands) December 31, 2017 Balance at beginning of period $ 8,494 New loans 6,041 Repayments (4,885 ) Officer and director changes (169 ) Balance at end of period $ 9,481 Allowance for Loan Losses The allowance for loan losses is maintained at a level believed adequate by management to absorb probable losses incurred in the consolidated loan portfolio. Management’s evaluation of the adequacy of the allowance is an estimate based on reviews of individual loans, pools of homogeneous loans, assessments of the impact of current and anticipated economic conditions on the portfolio, and historical loss experience. The allowance is increased through a provision charged to operating expense. Loans deemed to be uncollectible are charged to the allowance. Recoveries of loans previously charged-off We utilize a PD and LGD model as a tool to determine the adequacy of the allowance for loan losses for performing commercial and commercial real estate loans. The PD is forecast using a transition matrix to determine the likelihood of a customer’s AQR migrating from its current AQR to any other status within the time horizon. Transition rates are measured using Old National’s own historical experience. The model assumes that recent historical transition rates will continue into the future. The LGD is defined as credit loss incurred when an obligor of the bank defaults. The sum of all net charge-offs for a particular portfolio segment are divided by all loans that have defaulted over a given period of time. The expected loss derived from the model considers the PD, LGD, and exposure at default. Additionally, qualitative factors, such as changes in lending policies or procedures, and economic business conditions are also considered. We use historic loss ratios adjusted for economic conditions to determine the appropriate level of allowance for residential real estate and consumer loans. No allowance was brought forward on any of the acquired loans as any credit deterioration evident in the loans was included in the determination of the fair value of the loans at the acquisition date. An allowance for loan losses will be established for any subsequent credit deterioration or adverse changes in expected cash flows. Old National’s activity in the allowance for loan losses for the years ended December 31, 2017, 2016, and 2015 was as follows: Commercial (dollars in thousands) Commercial Real Estate Residential Consumer Total 2017 Allowance for loan losses: Balance at beginning of period $ 21,481 $ 18,173 $ 1,643 $ 8,511 $ 49,808 Charge-offs (1,108 ) (3,700 ) (985 ) (6,924 ) (12,717 ) Recoveries 2,281 3,777 255 3,927 10,240 Provision (3,408 ) 3,186 850 2,422 3,050 Balance at end of period $ 19,246 $ 21,436 $ 1,763 $ 7,936 $ 50,381 2016 Allowance for loan losses: Balance at beginning of period $ 26,347 $ 15,993 $ 2,051 $ 7,842 $ 52,233 Charge-offs (5,047 ) (2,632 ) (800 ) (6,131 ) (14,610 ) Recoveries 3,102 4,763 174 3,186 11,225 Provision (2,921 ) 49 218 3,614 960 Balance at end of period $ 21,481 $ 18,173 $ 1,643 $ 8,511 $ 49,808 2015 Allowance for loan losses: Balance at beginning of period $ 20,670 $ 17,348 $ 2,962 $ 6,869 $ 47,849 Charge-offs (3,513 ) (1,921 ) (1,039 ) (6,404 ) (12,877 ) Recoveries 5,218 4,685 354 4,081 14,338 Provision 3,972 (4,119 ) (226 ) 3,296 2,923 Balance at end of period $ 26,347 $ 15,993 $ 2,051 $ 7,842 $ 52,233 The following table provides Old National’s recorded investment in loans by portfolio segment at December 31, 2017 and 2016 and other information regarding the allowance: Commercial (dollars in thousands) Commercial Real Estate Residential Consumer Total December 31, 2017 Allowance for loan losses: Individually evaluated for impairment $ 3,424 $ 6,654 $ — $ — $ 10,078 Collectively evaluated for impairment 15,790 14,782 1,763 7,802 40,137 Loans acquired with deteriorated credit quality 32 — — 134 166 Total allowance for loan losses $ 19,246 $ 21,436 $ 1,763 $ 7,936 $ 50,381 Loans and leases outstanding: Individually evaluated for impairment $ 26,270 $ 66,061 $ — $ — $ 92,331 Collectively evaluated for impairment 2,685,847 4,266,665 2,155,750 1,874,002 10,982,264 Loans acquired with deteriorated credit quality 5,152 21,826 11,303 5,245 43,526 Total loans and leases outstanding $ 2,717,269 $ 4,354,552 $ 2,167,053 $ 1,879,247 $ 11,118,121 December 31, 2016 Allowance for loan losses: Individually evaluated for impairment $ 4,561 $ 3,437 $ — $ — $ 7,998 Collectively evaluated for impairment 16,838 14,717 1,643 8,334 41,532 Loans acquired with deteriorated credit quality 82 19 — 177 278 Total allowance for loan losses $ 21,481 $ 18,173 $ 1,643 $ 8,511 $ 49,808 Loans and leases outstanding: Individually evaluated for impairment $ 45,960 $ 57,230 $ — $ — $ 103,190 Collectively evaluated for impairment 1,870,289 3,040,849 2,073,950 1,866,815 8,851,903 Loans acquired with deteriorated credit quality 850 32,774 13,580 8,215 55,419 Total loans and leases outstanding $ 1,917,099 $ 3,130,853 $ 2,087,530 $ 1,875,030 $ 9,010,512 Credit Quality Old National’s management monitors the credit quality of its loans in an on-going non-homogeneous Criticized Classified – Substandard Classified – Nonaccrual Classified – Doubtful Pass rated loans are those loans that are other than criticized, classified – substandard, classified – nonaccrual, or classified – doubtful. The risk category of commercial and commercial real estate loans by class of loans at December 31, 2017 and 2016 was as follows: (dollars in thousands) Commercial Commercial Corporate Credit Exposure Real Estate - Real Estate - Credit Risk Profile by Commercial Construction Other Internally Assigned Grade 2017 2016 2017 2016 2017 2016 Grade: Pass $ 2,577,824 $ 1,750,922 $ 357,438 $ 347,325 $ 3,762,896 $ 2,669,890 Criticized 74,876 45,614 14,758 9,258 98,451 40,590 Classified - substandard 37,367 63,978 — 49 58,584 19,715 Classified - nonaccrual 24,798 53,063 2,110 1,170 30,108 33,833 Classified - doubtful 2,404 3,522 — — 30,207 9,023 Total $ 2,717,269 $ 1,917,099 $ 374,306 $ 357,802 $ 3,980,246 $ 2,773,051 Commercial loans as of December 31, 2017 in the table above include loans attributable to the acquisition of Anchor (MN) totaling $26.5 million in the criticized category, $7.3 million in the classified – substandard category, and $7.3 million in the classified – nonaccrual category. Construction commercial real estate loans as of December 31, 2017 in the table above include loans attributable to the acquisition of Anchor (MN) totaling $1.2 million in the classified – nonaccrual category. Other commercial real estate as of December 31, 2017 in the table above includes loans attributable to the acquisition of Anchor (MN) totaling $20.4 million in the criticized category, $3.6 million in the classified – substandard category, and $6.9 million in the classified – nonaccrual category. Old National considers the performance of the loan portfolio and its impact on the allowance for loan losses. For residential and consumer loan classes, Old National also evaluates credit quality based on the aging status of the loan and by payment activity. The following table presents the recorded investment in residential and consumer loans based on payment activity as of December 31, 2017 and 2016: (dollars in thousands) Consumer Home Residential Equity Auto Other December 31, 2017 Performing $ 2,144,882 $ 502,322 $ 1,145,977 $ 217,819 Nonperforming 22,171 5,185 2,695 5,249 Total $ 2,167,053 $ 507,507 $ 1,148,672 $ 223,068 December 31, 2016 Performing $ 2,069,856 $ 472,008 $ 1,166,114 $ 223,786 Nonperforming 17,674 4,431 1,623 7,068 Total $ 2,087,530 $ 476,439 $ 1,167,737 $ 230,854 Impaired Loans Large commercial credits are subject to individual evaluation for impairment. Retail credits and other small balance credits that are part of a homogeneous group are not tested for individual impairment unless they are modified as a TDR. A loan is considered impaired when it is probable that contractual interest and principal payments will not be collected either for the amounts or by the dates as scheduled in the loan agreement. If a loan is impaired, a portion of the allowance is allocated so that the loan is reported net, at the present value of estimated cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Old National’s policy, for all but PCI loans, is to recognize interest income on impaired loans unless the loan is placed on nonaccrual status. The following table shows Old National’s impaired loans as of December 31, 2017 and 2016, respectively. Only purchased loans that have experienced subsequent impairment since the date acquired are included in the table below. Unpaid Recorded Principal Related (dollars in thousands) Investment Balance Allowance December 31, 2017 With no related allowance recorded: Commercial $ 20,557 $ 21,483 $ — Commercial Real Estate—Other 38,678 44,564 — Residential 2,443 2,464 — Consumer 1,685 2,105 — With an allowance recorded: Commercial 5,713 5,713 3,424 Commercial Real Estate—Construction 905 1,371 401 Commercial Real Estate—Other 26,478 26,902 6,253 Residential 870 870 44 Consumer 2,211 2,228 110 Total $ 99,540 $ 107,700 $ 10,232 December 31, 2016 With no related allowance recorded: Commercial $ 29,001 $ 29,634 $ — Commercial Real Estate—Other 30,585 32,413 — Residential 1,610 1,631 — Consumer 827 946 — With an allowance recorded: Commercial 16,959 17,283 4,561 Commercial Real Estate—Construction 467 467 107 Commercial Real Estate—Other 26,178 26,710 3,330 Residential 1,081 1,081 54 Consumer 1,924 1,924 96 Total $ 108,632 $ 112,089 $ 8,148 The average balance of impaired loans for the years ended December 31, 2017 and 2016 are included in the table below. Years Ended December 31, (dollars in thousands) 2017 2016 Average Recorded Investment With no related allowance recorded: Commercial $ 24,780 $ 34,708 Commercial Real Estate—Other 34,632 28,793 Residential 2,415 1,355 Consumer 1,761 855 With an allowance recorded: Commercial 7,002 16,669 Commercial Real Estate—Construction 453 352 Commercial Real Estate—Other 26,562 20,465 Residential 1,012 1,074 Consumer 2,155 2,367 Total $ 100,772 $ 106,638 Old National does not record interest on nonaccrual loans until principal is recovered. Interest income recognized on impaired loans during 2017 and 2016 was immaterial. For all loan classes, a loan is generally placed on nonaccrual status when principal or interest becomes 90 days past due unless it is well secured and in the process of collection, or earlier when concern exists as to the ultimate collectibility of principal or interest. Interest accrued during the current year on such loans is reversed against earnings. Interest accrued in the prior year, if any, is charged to the allowance for loan losses. Cash interest received on these loans is applied to the principal balance until the principal is recovered or until the loan returns to accrual status. Loans may be returned to accrual status when all the principal and interest amounts contractually due are brought current, remain current for a prescribed period, and future payments are reasonably assured. Loans accounted for under FASB ASC Topic 310-30 re-estimation Old National’s past due loans as of December 31 were as follows: Recorded Investment > 30-59 Days 60-89 Days 90 Days and Total (dollars in thousands) Past Due Past Due Accruing Nonaccrual Past Due Current December 31, 2017 Commercial $ 986 $ 360 $ 144 $ 27,202 $ 28,692 $ 2,688,577 Commercial Real Estate: Construction — — — 2,110 2,110 372,196 Other 2,247 89 — 60,315 62,651 3,917,595 Residential 18,948 3,416 — 22,171 44,535 2,122,518 Consumer: Home equity 1,467 230 68 5,185 6,950 500,557 Auto 6,487 1,402 532 2,695 11,116 1,137,556 Other 3,967 1,514 150 5,249 10,880 212,188 Total $ 34,102 $ 7,011 $ 894 $ 124,927 $ 166,934 $ 10,951,187 December 31, 2016 Commercial $ 847 $ 279 $ 23 $ 56,585 $ 57,734 $ 1,859,365 Commercial Real Estate: Construction — — — 1,170 1,170 356,632 Other 1,652 150 — 42,856 44,658 2,728,393 Residential 17,786 3,770 2 17,674 39,232 2,048,298 Consumer: Home equity 1,511 423 — 4,431 6,365 470,074 Auto 5,903 1,037 242 1,623 8,805 1,158,932 Other 3,561 1,919 61 7,068 12,609 218,245 Total $ 31,260 $ 7,578 $ 328 $ 131,407 $ 170,573 $ 8,839,939 Loan Participations Old National has loan participations, which qualify as participating interests, with other financial institutions. At December 31, 2017, these loans totaled $581.0 million, of which $290.4 million had been sold to other financial institutions and $290.6 million was retained by Old National. The loan participations convey proportionate ownership rights with equal priority to each participating interest holder; involve no recourse (other than ordinary representations and warranties) to, or subordination by, any participating interest holder; all cash flows are divided among the participating interest holders in proportion to each holder’s share of ownership; and no holder has the right to pledge the entire financial asset unless all participating interest holders agree. Troubled Debt Restructurings Old National may choose to restructure the contractual terms of certain loans. The decision to restructure a loan, versus aggressively enforcing the collection of the loan, may benefit Old National by increasing the ultimate probability of collection. Any loans that are modified are reviewed by Old National to identify if a TDR has occurred, which is when for economic or legal reasons related to a borrower’s financial difficulties, Old National Bank grants a concession to the borrower that it would not otherwise consider. Terms may be modified to fit the ability of the borrower to repay in line with its current financial status. The modification of the terms of such loans include one or a combination of the following: a reduction of the stated interest rate of the loan, an extension of the maturity date at a stated rate of interest lower than the current market rate of new debt with similar risk, or a permanent reduction of the recorded investment of the loan. Loans modified in a TDR are typically placed on nonaccrual status until we determine the future collection of principal and interest is reasonably assured, which generally requires that the borrower demonstrate a period of performance according to the restructured terms for six months. If we are unable to resolve a nonperforming loan issue, the credit will be charged off when it is apparent there will be a loss. For large commercial type loans, each relationship is individually analyzed for evidence of apparent loss based on quantitative benchmarks or subjectively based upon certain events or particular circumstances. Generally, Old National charges off small commercial loans scored through our small business credit center with contractual balances under $250,000 that are 90 days or more delinquent and do not have adequate collateral support. For residential and consumer loans, a charge off is recorded at the time foreclosure is initiated or when the loan becomes 120 to 180 days past due, whichever is earlier. For commercial TDRs, an allocated reserve is established within the allowance for loan losses for the difference between the carrying value of the loan and its computed value. To determine the value of the loan, one of the following methods is selected: (1) the present value of expected cash flows discounted at the loan’s original effective interest rate, (2) the loan’s observable market price, or (3) the fair value of the collateral value, if the loan is collateral dependent. The allocated reserve is established as the difference between the carrying value of the loan and the collectable value. If there are significant changes in the amount or timing of the loan’s expected future cash flows, impairment is recalculated and the valuation allowance is adjusted accordingly. When a residential or consumer loan is identified as a TDR, the loan is typically written down to its collateral value less selling costs. The following table presents activity in TDRs for the years ended December 31, 2017, 2016, and 2015: (dollars in thousands) Commercial Commercial Residential Consumer Total 2017 Balance at beginning of period $ 16,802 $ 18,327 $ 2,985 $ 2,602 $ 40,716 (Charge-offs)/recoveries 417 381 — (294 ) 504 Payments (22,340 ) (12,183 ) (623 ) (1,038 ) (36,184 ) Additions 13,388 27,749 938 2,568 44,643 Interest collected on nonaccrual loans 3,821 431 15 57 4,324 Balance at end of period $ 12,088 $ 34,705 $ 3,315 $ 3,895 $ 54,003 2016 Balance at beginning of period $ 23,354 $ 14,602 $ 2,693 $ 3,602 $ 44,251 (Charge-offs)/recoveries (1,982 ) 953 42 (6 ) (993 ) Payments (21,956 ) (10,157 ) (513 ) (1,381 ) (34,007 ) Additions 14,996 11,130 761 385 27,272 Interest collected on nonaccrual loans 2,390 1,799 2 2 4,193 Balance at end of period $ 16,802 $ 18,327 $ 2,985 $ 2,602 $ 40,716 2015 Balance at beginning of period $ 15,205 $ 15,226 $ 2,063 $ 2,459 $ 34,953 (Charge-offs)/recoveries 872 1,064 (64 ) 3 1,875 Payments (29,913 ) (6,273 ) (658 ) (1,168 ) (38,012 ) Additions 37,190 4,585 1,352 2,308 45,435 Balance at end of period $ 23,354 $ 14,602 $ 2,693 $ 3,602 $ 44,251 Approximately $34.0 million of the TDRs at December 31, 2017 were included with nonaccrual loans, compared to $26.3 million at December 31, 2016. Old National has allocated specific reserves to customers whose loan terms have been modified in TDRs totaling $5.7 million at December 31, 2017 and $4.0 million at December 31, 2016. As of December 31, 2017, Old National had committed to lend an additional $4.1 million to customers with outstanding loans that are classified as TDRs. The pre-modification (dollars in thousands) Number Pre-modification Post-modification 2017 Troubled Debt Restructuring: Commercial 11 $ 13,388 $ 13,388 Commercial Real Estate—Other 12 27,749 27,749 Residential 6 938 938 Consumer 7 2,568 2,568 Total 36 $ 44,643 $ 44,643 2016 Troubled Debt Restructuring: Commercial 20 $ 14,996 $ 14,996 Commercial Real Estate—Other 10 11,130 11,130 Residential 6 761 761 Consumer 8 385 385 Total 44 $ 27,272 $ 27,272 2015 Troubled Debt Restructuring: Commercial 42 $ 37,190 $ 37,190 Commercial Real Estate—Construction 5 1,162 1,162 Commercial Real Estate—Other 27 3,423 3,423 Residential 13 1,352 1,352 Consumer 32 2,308 2,308 Total 119 $ 45,435 $ 45,435 The TDRs that occurred during 2017 increased the allowance for loan losses by $2.7 million and resulted in $0.2 million of charge-offs during 2017. The TDRs that occurred during 2016 decreased the allowance for loan losses by $2.3 million due to a change in collateral position on a large commercial loan and resulted in $0.8 million of charge-offs during 2016. The TDRs that occurred during 2015 decreased the allowance for loan losses by $0.8 million and resulted in charge-offs of $0.2 million during 2015. A loan is considered to be in payment default once it is 90 days contractually past due under the modified terms. TDRs for which there was a payment default within twelve months following the modification during the year were insignificant in 2017, 2016, and 2015. The terms of certain other loans were modified during 2017 that did not meet the definition of a TDR. It is our process to review all classified and criticized loans that, during the period, have been renewed, have entered into a forbearance agreement, have gone from principal and interest to interest only, or have extended the maturity date. In order to determine whether a borrower is experiencing financial difficulty, an evaluation is performed of the probability that the borrower will be in payment default on its debt in the foreseeable future without the modification. The evaluation is performed under our internal underwriting policy. We also evaluate whether a concession has been granted or if we were adequately compensated through a market interest rate, additional collateral or a bona fide guarantee. We also consider whether the modification was insignificant relative to the other terms of the agreement or the delay in a payment. PCI loans are not considered impaired until after the point at which there has been a degradation of cash flows below our expected cash flows at acquisition. If a PCI loan is subsequently modified, and meets the definition of a TDR, it will be removed from PCI accounting and accounted for as a TDR only if the PCI loan was being accounted for individually. If the PCI loan is being accounted for as part of a pool, it will not be removed from the pool. As of December 31, 2017, it has not been necessary to remove any loans from PCI accounting. In general, once a modified loan is considered a TDR, the loan will always be considered a TDR, and therefore impaired, until it is paid in full, otherwise settled, sold or charged off. However, guidance also permits for loans to be removed from TDR status when subsequently restructured under these circumstances: (1) at the time of the subsequent restructuring, the borrower is not experiencing financial difficulties, and this is documented by a current credit evaluation at the time of the restructuring, (2) under the terms of the subsequent restructuring agreement, the institution has granted no concession to the borrower; and (3) the subsequent restructuring agreement includes market terms that are no less favorable than those that would be offered for a comparable new loan. For loans subsequently restructured that have cumulative principal forgiveness, the loan should continue to be measured in accordance with ASC 310-10, Receivables – Overall 310-40-50-2, Troubled Debt Restructurings by Creditors, Creditor Disclosure of Troubled Debt Restructurings Purchased Credit Impaired Loans Purchased loans acquired in a business combination are recorded at estimated fair value on their purchase date with no carryover of the related allowance for loan and lease losses. In determining the estimated fair value of purchased loans, management considers a number of factors including, among others, the remaining life of the acquired loans, estimated prepayments, estimated loss ratios, estimated value of the underlying collateral, and net present value of cash flows expected to be received. Purchased loans are accounted for in accordance with guidance for certain loans acquired in a transfer (ASC 310-30), non-accretable Old National has purchased loans for which there was, at acquisition, evidence of deterioration of credit quality since origination and it was probable, at acquisition, that all contractually required payments would not be collected. For these loans that meet the criteria of ASC 310-30 December 31, (dollars in thousands) 2017 2016 Commercial $ 5,152 $ 850 Commercial real estate 21,826 32,774 Residential 11,303 13,580 Consumer 5,245 8,215 Carrying amount 43,526 55,419 Allowance for loan losses (166 ) (278 ) Carrying amount, net of allowance $ 43,360 $ 55,141 The outstanding balance of loans accounted for under ASC 310-30, The accretable difference on PCI loans is the difference between the expected cash flows and the net present value of expected cash flows with such difference accreted into earnings using the effective yield method over the term of the loans. Accretion recorded as loan interest income totaled $15.2 million during 2017 and $23.4 million during 2016. Improvement in cash flow expectations has resulted in a reclassification from nonaccretable difference to accretable yield as shown in the table below. Accretable yield of PCI loans, or income expected to be collected, was as follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Balance at beginning of period $ 33,603 $ 45,310 $ 62,533 New loans purchased 1,556 3,217 1,812 Accretion of income (15,217 ) (23,447 ) (35,526 ) Reclassifications from (to) nonaccretable difference 7,614 10,589 14,189 Disposals/other adjustments 279 (2,066 ) 2,302 Balance at end of period $ 27,835 $ 33,603 $ 45,310 Included in Old National’s allowance for loan losses is $0.2 million related to the purchased loans disclosed above at December 31, 2017, compared to $0.3 million at December 31, 2016. PCI loans purchased during 2017 and 2016 for which it was probable at acquisition that all contractually required payments would not be collected were as follows: (dollars in thousands) Anchor (MN) (1) Anchor (WI) (2) Contractually required payments $ 16,898 $ 29,544 Nonaccretable difference (4,787 ) (6,153 ) Cash flows expected to be collected at acquisition 12,111 23,391 Accretable yield (1,556 ) (3,217 ) Fair value of acquired loans at acquisition $ 10,555 $ 20,174 (1) Old National acquired Anchor (MN) effective November 1, 2017. (2) Old National acquired Anchor (WI) effective May 1, 2016. Income would not be recognized on certain purchased loans if Old National could not reasonably estimate cash flows to be collected. Old National had no purchased loans for which it could not reasonably estimate cash flows to be collected.

Other Real Estate Owned

Other Real Estate Owned	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Other Real Estate Owned	NOTE 6 – OTHER REAL ESTATE OWNED The following table presents activity in other real estate owned for the years ended December 31, 2017 and 2016: Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 18,546 $ 12,498 Additions (1) 4,016 24,998 Sales (11,160 ) (15,092 ) Impairment (2,592 ) (3,858 ) Balance at end of period (2) $ 8,810 $ 18,546 (1) Additions in 2017 include other real estate owned of $1.1 million acquired from Anchor (MN) in November 2017. Additions in 2016 include other real estate owned of $17.3 million acquired from Anchor (WI) in May 2016. (2) Includes repossessed personal property of $0.3 million at December 31, 2017 and $0.3 million at December 31, 2016. At December 31, 2017, foreclosed residential real estate property included in the table above totaled $1.6 million. At December 31, 2017, consumer mortgage loans collateralized by residential real property that were in the process of foreclosure totaled $5.2 million.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Premises and Equipment	NOTE 7 – PREMISES AND EQUIPMENT The composition of premises and equipment was as follows at December 31: December 31, (dollars in thousands) 2017 2016 Land $ 73,046 $ 71,769 Buildings 343,833 322,165 Furniture, fixtures, and equipment 94,254 102,631 Leasehold improvements 38,918 28,555 Total 550,051 525,120 Accumulated depreciation (91,977 ) (95,498 ) Premises and equipment, net $ 458,074 $ 429,622 The increase in premises and equipment at December 31, 2017 was primarily due to $33.6 million of assets attributable to the Anchor (MN) acquisition. Depreciation expense was $22.2 million in 2017, $16.6 million in 2016, and $14.1 million in 2015. Operating Leases Old National rents certain premises and equipment under operating leases, which expire at various dates. Many of these leases require the payment of property taxes, insurance premiums, maintenance, and other costs. In some cases, rentals are subject to increase in relation to a cost-of-living sub-lease Rent expense was $15.8 million in 2017, $25.4 million in 2016, and $29.1 million in 2015. The following is a summary of future minimum lease commitments as of December 31, 2017: (dollars in thousands) 2018 $ 18,919 2019 17,463 2020 16,865 2021 15,960 2022 13,759 Thereafter 63,828 Total $ 146,794 Old National purchased 23 properties during 2016 that it had previously leased, 20 of which had deferred gains that were accelerated when the associated leases were terminated. These gains were partially offset by the recognition of deferred rent expense, cease-use Old National purchased 14 properties during 2015 that it had previously leased, all of which had deferred gains that were accelerated when the associated leases were terminated. These gains were partially offset by the recognition of deferred rent expense and other expense, resulting in a net gain of $10.8 million. Old National had deferred gains remaining associated with prior sale leaseback transactions totaling $8.2 million at December 31, 2017 and $10.3 million at December 31, 2016. The gains will be recognized over the remaining term of the leases. The leases had original terms ranging from five to twenty-four years. Capital Leases Old National leases two branch buildings and certain equipment under capital leases. See Note 14 to the consolidated financial statements for detail regarding these leases.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	NOTE 8 – GOODWILL AND OTHER INTANGIBLE ASSETS The following table shows the changes in the carrying amount of goodwill for the years ended December 31, 2017 and 2016: Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 655,018 $ 584,634 Acquisitions 173,033 111,347 Divestitures — (40,963 ) Balance at end of period $ 828,051 $ 655,018 Goodwill is reviewed annually for impairment. No events or circumstances since the August 31, 2017 annual impairment test were noted that would indicate it was more likely than not a goodwill impairment exists. During 2017, Old National recorded $173.0 million of goodwill associated with the acquisition of Anchor (MN). See Note 2 to the consolidated financial statements for detail regarding changes in goodwill recorded in 2016 associated with acquisitions and divestitures. The gross carrying amounts and accumulated amortization of other intangible assets at December 31, 2017 and 2016 was as follows: (dollars in thousands) Gross Accumulated Net December 31, 2017 Core deposit $ 108,923 $ (62,874 ) $ 46,049 Customer trust relationships 16,547 (9,533 ) 7,014 Customer loan relationships 4,413 (4,380 ) 33 Total intangible assets $ 129,883 $ (76,787 ) $ 53,096 December 31, 2016 Core deposit $ 81,663 $ (53,214 ) $ 28,449 Customer trust relationships 16,547 (7,753 ) 8,794 Customer loan relationships 4,413 (3,979 ) 434 Total intangible assets $ 102,623 $ (64,946 ) $ 37,677 Other intangible assets consist of core deposit intangibles and customer relationship intangibles and are being amortized primarily on an accelerated basis over their estimated useful lives, generally over a period of 5 to 15 years. During 2017, Old National increased core deposit intangibles by $27.3 million related to the Anchor (MN) acquisition. Old National reviews other intangible assets for possible impairment whenever events or changes in circumstances indicate that carrying amounts may not be recoverable. No impairment charges were recorded in 2017, 2016, or 2015. Total amortization expense associated with intangible assets was $11.8 million in 2017, $12.5 million in 2016, and $11.7 million in 2015. Estimated amortization expense for future years is as follows: (dollars in thousands) 2018 $ 13,561 2019 11,115 2020 8,765 2021 6,498 2022 4,665 Thereafter 8,492 Total $ 53,096

Loan Servicing Rights

Loan Servicing Rights	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Loan Servicing Rights	NOTE 9 – LOAN SERVICING RIGHTS At December 31, 2017, loan servicing rights derived from loans sold with servicing retained totaled $24.7 million, compared to $25.6 million at December 31, 2016. Loans serviced for others are not reported as assets. The principal balance of loans serviced for others was $3.321 billion at December 31, 2017, compared to $3.385 billion at December 31, 2016. Approximately 99.5% of the loans serviced for others at December 31, 2017 were residential mortgage loans. Custodial escrow balances maintained in connection with serviced loans were $8.9 million at December 31, 2017 and $5.3 million at December 31, 2016. The following table summarizes the activity related to loan servicing rights and the related valuation allowance in 2017 and 2016: Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 25,629 $ 10,502 Additions (1) 4,206 20,280 Amortization (5,145 ) (5,153 ) Balance before valuation allowance at end of period 24,690 25,629 Valuation allowance: Balance at beginning of period (68 ) (34 ) (Additions)/recoveries 39 (34 ) Balance at end of period (29 ) (68 ) Loan servicing rights, net $ 24,661 $ 25,561 (1) Additions in 2016 include loan servicing rights of $15.3 million acquired from Anchor (WI) in May 2016. At December 31, 2017, the fair value of servicing rights was $25.8 million, which was determined using a discount rate of 13% and a weighted average prepayment speed of 140% PSA. At December 31, 2016, the fair value of servicing rights was $26.8 million, which was determined using a discount rate of 13% and a weighted average prepayment speed of 136% PSA.

Qualified Affordable Housing Pr

Qualified Affordable Housing Projects and Other Tax Credit Investments	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Qualified Affordable Housing Projects and Other Tax Credit Investments	NOTE 10 – QUALIFIED AFFORDABLE HOUSING PROJECTS AND OTHER TAX CREDIT INVESTMENTS Old National is a limited partner in several tax-advantaged The following table summarizes Old National’s investments in qualified affordable housing projects and other tax credit investments at December 31, 2017 and 2016: (dollars in thousands) December 31, 2017 December 31, 2016 Investment Accounting Method Investment Unfunded Investment Unfunded LIHTC Proportional amortization $ 31,183 $ 15,553 $ 29,110 $ 16,210 FHTC Equity 10,645 12,040 4,434 3,104 CReED Equity 704 1,502 1,504 1,502 Renewable Energy Equity 22,364 19,771 — — Total $ 64,896 $ 48,866 $ 35,048 $ 20,816 (1) All commitments will be paid by Old National by 2027. The following table summarizes the amortization expense and tax benefit recognized for Old National’s qualified affordable housing projects and other tax credit investments during 2017, 2016, and 2015: (dollars in thousands) Amortization Tax Benefit Year ended December 31, 2017 LIHTC $ 1,922 $ (2,666 ) FHTC 10,441 (11,348 ) CReED (3) 800 (1,074 ) Renewable Energy 492 (613 ) Total $ 13,655 $ (15,701 ) Year ended December 31, 2016 LIHTC $ 804 $ (1,125 ) FHTC — — CReED (3) — — Total $ 804 $ (1,125 ) Year ended December 31, 2015 LIHTC $ 804 $ (1,125 ) FHTC — — CReED (3) — — NMTC 143 (233 ) Total $ 947 $ (1,358 ) (1) The amortization expense for the LIHTC investments are included in our income tax expense. The amortization expense for the FHTC, CReED, and Renewable Energy tax credits are included in noninterest expense. (2) All of the tax benefits recognized are included in our income tax expense. The tax benefit recognized for the FHTC, CReED, and Renewable Energy investments primarily reflects the tax credits generated from the investments, and excludes the net tax expense/benefit of the investments’ income/loss. (3) The CReED tax credit investment qualifies for an Indiana state tax credit.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Deposits	NOTE 11 – DEPOSITS The aggregate amount of time deposits in denominations of $250,000 or more was $422.3 million at December 31, 2017 and $313.8 million at December 31, 2016. At December 31, 2017, the scheduled maturities of total time deposits were as follows: (dollars in thousands) Due in 2018 $ 1,111,266 Due in 2019 229,944 Due in 2020 139,689 Due in 2021 62,777 Due in 2022 45,802 Thereafter 44,958 Total $ 1,634,436

Securities Sold Under Agreement

Securities Sold Under Agreements to Repurchase	12 Months Ended
	Dec. 31, 2017
Transfers and Servicing [Abstract]
Securities Sold Under Agreements to Repurchase	NOTE 12 – SECURITES SOLD UNDER AGREEMENTS TO REPURCHASE Securities sold under agreements to repurchase are secured borrowings. Old National pledges investment securities to secure these borrowings. The following table presents securities sold under agreements to repurchase and related weighted-average interest rates for each of the years ended December 31: At or For the (dollars in thousands) 2017 2016 Outstanding at year-end $ 384,810 $ 367,052 Average amount outstanding 336,539 368,757 Maximum amount outstanding at any month-end 402,543 396,695 Weighted average interest rate: During year 0.38 % 0.41 % End of year 0.49 0.47 The following table presents the contractual maturity of our secured borrowings and class of collateral pledged: At December 31, 2017 Remaining Contractual Maturity of the Agreements (dollars in thousands) Overnight and Up to 30 Days 30-90 Days Greater Than Total Repurchase Agreements: U.S. Treasury and agency securities $ 359,810 $ 25,000 $ — $ — $ 384,810 Total $ 359,810 $ 25,000 $ — $ — $ 384,810 The fair value of securities pledged to secure repurchase agreements may decline. Old National has pledged securities valued at 114% of the gross outstanding balance of repurchase agreements at December 31, 2017 to manage this risk.

Federal Home Loan Bank Advances

Federal Home Loan Bank Advances	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Federal Home Loan Bank Advances	NOTE 13 – FEDERAL HOME LOAN BANK ADVANCES The following table summarizes Old National Bank’s FHLB advances at December 31: December 31, (dollars in thousands) 2017 2016 FHLB advances (fixed rates 1.01% to 6.08% and variable rates 1.35% to 1.57%) maturing January 2018 to August 2027 $ 1,610,531 $ 1,353,225 ASC 815 fair value hedge and other basis adjustments (952 ) (133 ) Total other borrowings $ 1,609,579 $ 1,353,092 FHLB advances had weighted-average rates of 1.55% at December 31, 2017 and 0.94% at December 31, 2016. These borrowings are collateralized by investment securities and residential real estate loans up to 143% of outstanding debt. Contractual maturities of FHLB advances at December 31, 2017 were as follows: (dollars in thousands) Due in 2018 $ 999,896 Due in 2019 201,962 Due in 2020 50,000 Due in 2021 — Due in 2022 58,500 Thereafter 300,173 ASC 815 fair value hedge and other basis adjustments (952 ) Total $ 1,609,579

Other Borrowings

Other Borrowings	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Other Borrowings	NOTE 14 – OTHER BORROWINGS The following table summarizes Old National’s other borrowings at December 31: December 31, (dollars in thousands) 2017 2016 Old National Bancorp: Senior unsecured bank notes (fixed rate 4.125%) maturing August 2024 $ 175,000 $ 175,000 Unamortized debt issuance costs related to Senior unsecured bank notes (1,026 ) (1,182 ) Junior subordinated debentures (variable rates of 2.89% to 5.06%) maturing April 2032 to September 2037 60,310 45,000 Other basis adjustments (3,585 ) (3,971 ) Old National Bank: Capital lease obligations 5,389 4,092 Subordinated debentures (fixed rate 5.75%) 12,000 — Premium on subordinated debentures 694 — Total other borrowings $ 248,782 $ 218,939 Contractual maturities of other borrowings at December 31, 2017 were as follows: (dollars in thousands) Due in 2018 $ 127 Due in 2019 137 Due in 2020 147 Due in 2021 160 Due in 2022 172 Thereafter 251,956 Unamortized debt issuance costs and other basis adjustments (3,917 ) Total $ 248,782 Senior Notes In August 2014, Old National issued $175.0 million of senior unsecured notes with a 4.125% interest rate. These notes pay interest on February 15 and August 15. The notes mature on August 15, 2024. Junior Subordinated Debentures Junior subordinated debentures related to trust preferred securities are classified in “other borrowings.” With the addition of Anchor (MN) assets, these securities now qualify as Tier 2 capital for regulatory purposes, subject to certain limitations. Prior to the fourth quarter of 2017, these securities qualified as Tier 1 capital for regulatory purposes. Through various acquisitions, Old National assumed junior subordinated debenture obligations related to various trusts that issued trust preferred securities. Old National guarantees the payment of distributions on the trust preferred securities issued by the trusts. Proceeds from the issuance of each of these securities were used to purchase junior subordinated debentures with the same financial terms as the securities issued by the trusts. Old National, at any time, may redeem the junior subordinated debentures at par and, thereby cause a redemption of the trust preferred securities in whole or in part. On November 1, 2017, Old National assumed junior subordinated debenture obligations in the amount of $25.0 million related to the acquisition of Anchor (MN). The debentures were related to six separate statutory trusts: Anchor Capital Trust II, Anchor Capital Trust III, Anchor Capital Trust IV, VFSC Capital Trust I, VFSC Capital Trust II, and VFSC Capital Trust III. Anchor Capital Trust II had an 8.25% fixed rate of interest. Anchor Capital Trust IV had an 8.00% fixed rate of interest. Subsequent to the acquisition, Old National redeemed these two fixed-rate issuances at par value of $9.7 million, thereby causing a redemption of the related trusts. The remaining four issuances have variable rates of interest and are outstanding as of December 31, 2017. The following table summarizes the terms of our outstanding junior subordinated debentures as of December 31, 2017: (dollars in thousands) Rate at Issuance December 31, Name of Trust Issuance Date Amount Rate 2017 Maturity Date VFSC Capital Trust I April 2002 $ 3,093 3-month 5.06 % April 22, 2032 VFSC Capital Trust II October 2002 4,124 3-month LIBOR plus 3.45% 4.84 % November 7, 2032 VFSC Capital Trust III April 2004 3,093 3-month 4.12 % September 8, 2034 St. Joseph Capital Trust II March 2005 5,000 3-month 3.35 % March 20, 2035 Anchor Capital Trust III August 2005 5,000 3-month 2.89 % August 23, 2035 Tower Capital Trust 2 December 2005 8,000 3-month 3.03 % December 4, 2035 Home Federal Statutory Trust I September 2006 15,000 3-month 3.24 % September 15, 2036 Monroe Bancorp Capital Trust I July 2006 3,000 3-month 2.95 % October 7, 2036 Monroe Bancorp Statutory Trust II March 2007 5,000 3-month 3.19 % June 15, 2037 Tower Capital Trust 3 December 2006 9,000 3-month 3.17 % September 15, 2037 Total $ 60,310 Subordinated Debentures On November 1, 2017, Old National assumed $12.0 million of subordinated fixed-to-floating Capital Lease Obligations On January 1, 2004, Old National entered into a long-term capital lease obligation for a branch office building in Owensboro, Kentucky, which extends for 25 years with one renewal option for 10 years. The economic substance of this lease is that Old National is financing the acquisition of the building through the lease and accordingly, the building is recorded as an asset and the lease is recorded as a liability. The fair value of the capital lease obligation was estimated using a discounted cash flow analysis based on Old National’s current incremental borrowing rate for similar types of borrowing arrangements. On May 1, 2016, Old National acquired Anchor (WI), assuming a five year capital lease obligation for equipment. On November 1, 2017, Old National assumed a capital lease obligation for a banking center in Arden Hills, Minnesota related to the acquisition of Anchor (MN). The remaining base term of the lease is five years with one renewal option of ten years. For purposes of measuring the lease obligation, we determined that we would be “reasonably assured” to exercise the renewal option. The fair value of the capital lease obligation was estimated using a discounted cash flow analysis based on a market rate for similar types of borrowing arrangements. Based on the above assumptions, Old National measured the capital lease obligation at $1.5 million as of the date of acquisition. At December 31, 2017, the future minimum lease payments under the capital lease arrangements were as follows: (dollars in thousands) 2018 $ 568 2019 589 2020 589 2021 589 2022 590 Thereafter 9,274 Total minimum lease payments 12,199 Less amounts representing interest (6,810 ) Present value of net minimum lease payments $ 5,389

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	NOTE 15 – ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following table summarizes the changes within each classification of AOCI, net of tax, for the years ended December 31, 2017, 2016, and 2015: (dollars in thousands) Unrealized Gains Available-for-Sale Unrealized Gains Held-to-Maturity Gains and Defined Total 2017 Balance at beginning of period $ (39,012 ) $ (13,310 ) $ (6,715 ) $ (335 ) $ (59,372 ) Other comprehensive income (loss) before reclassifications 9,615 — 575 — 10,190 Amounts reclassified from AOCI (1) (6,160 ) 1,203 3,803 64 (1,090 ) Net other comprehensive income (loss) 3,455 1,203 4,378 64 9,100 Balance at end of period $ (35,557 ) $ (12,107 ) $ (2,337 ) $ (271 ) $ (50,272 ) 2016 Balance at beginning of period $ (3,806 ) $ (14,480 ) $ (9,276 ) $ (7,235 ) $ (34,797 ) Other comprehensive income (loss) before reclassifications (31,513 ) — (1,440 ) — (32,953 ) Amounts reclassified from AOCI (1) (3,693 ) 1,170 4,001 6,900 8,378 Net other comprehensive income (loss) (35,206 ) 1,170 2,561 6,900 (24,575 ) Balance at end of period $ (39,012 ) $ (13,310 ) $ (6,715 ) $ (335 ) $ (59,372 ) 2015 Balance at beginning of period $ (748 ) $ (15,776 ) $ (5,935 ) $ (9,096 ) $ (31,555 ) Other comprehensive income (loss) before reclassifications 554 — (5,027 ) — (4,473 ) Amounts reclassified from AOCI (1) (3,612 ) 1,296 1,686 1,861 1,231 Net other comprehensive income (loss) (3,058 ) 1,296 (3,341 ) 1,861 (3,242 ) Balance at end of period $ (3,806 ) $ (14,480 ) $ (9,276 ) $ (7,235 ) $ (34,797 ) (1) See table below for details about reclassifications. The following tables summarize the significant amounts reclassified out of each component of AOCI for the years ended December 31, 2017, 2016, and 2015: Details about AOCI Components Amount Reclassified from AOCI Affected Line Item in the Statement of Income Years Ended December 31, (dollars in thousands) 2017 2016 2015 Unrealized gains and losses on available-for-sale $ 9,135 $ 5,848 $ 5,718 Net securities gains (2,975 ) (2,155 ) (2,106 ) Income tax (expense) benefit $ 6,160 $ 3,693 $ 3,612 Net income Unrealized gains and losses on held-to-maturity $ (1,830 ) $ (1,776 ) $ (1,692 ) Interest income (expense) 627 606 396 Income tax (expense) benefit $ (1,203 ) $ (1,170 ) $ (1,296 ) Net income Gains and losses on cash flow hedges Interest rate contracts $ (6,135 ) $ (6,453 ) $ (2,719 ) Interest income (expense) 2,332 2,452 1,033 Income tax (expense) benefit $ (3,803 ) $ (4,001 ) $ (1,686 ) Net income Amortization of defined benefit pension items Actuarial gains (losses) and settlement cost $ (159 ) $ (11,203 ) $ (3,002 ) Salaries and employee benefits 95 4,303 1,141 Income tax (expense) benefit $ (64 ) $ (6,900 ) $ (1,861 ) Net income Total reclassifications for the period $ 1,090 $ (8,378 ) $ (1,231 ) Net income

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 16 – INCOME TAXES Following is a summary of the major items comprising the differences in taxes from continuing operations computed at the federal statutory rate and as recorded in the consolidated statement of income: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Provision at statutory rate of 35% $ 59,032 $ 70,149 $ 57,013 Tax-exempt Tax-exempt (15,026 ) (14,356 ) (13,111 ) Section 291/265 interest disallowance 289 191 142 Company-owned life insurance income (3,029 ) (2,968 ) (3,011 ) Tax-exempt (17,766 ) (17,133 ) (15,980 ) Reserve for unrecognized tax benefits — (1 ) (5 ) State income taxes 998 3,461 4,173 Tax credit investments—federal (8,500 ) (321 ) (411 ) Estimated revaluation of deferred tax assets 39,300 — — ONB Insurance Group, Inc. nondeductible goodwill — 8,328 — Effect of Illinois branch sale — — 1,835 Other, net (125 ) 1,679 (448 ) Income tax expense $ 72,939 $ 66,162 $ 46,177 Effective tax rate 43.3 % 33.0 % 28.3 % The higher effective tax rate in 2017 when compared to 2016 is the result of $39.3 million of additional tax expense to estimate the revaluation of deferred tax assets due to the lowering of the federal corporate tax rate to 21%, partially offset by an increase in federal tax credits available. On December 22, 2017, the Tax Cuts and Jobs Act (“H.R. 1”) was enacted into legislation. Under ASC 740, the effects of changes in tax rates and laws are recognized in the period in which the new legislation is enacted. Accordingly, Old National has recorded an estimated $39.3 million for the revaluation of Old National’s deferred tax assets. Shortly after the enactment date, the SEC issued Staff Accounting Bulletin (“SAB”) 118, which addresses the situations where the accounting for changes in tax laws is complete, incomplete but can be reasonably estimated, and incomplete and cannot be reasonably estimated. SAB 118 also permits a measurement period of up to one year from the date of enactment to refine the provisional accounting. Old National continues to analyze H.R. 1, including the impact on alternative minimum tax credits disclosed further below, as well as the acquisition accounting of Anchor (MN), and expects any refinements to the provisional accounting to be complete in 2018. The higher effective tax rate in 2016 when compared to 2015 is primarily the result of the sale of ONI in May 2016 and the associated tax expense of $8.3 million to record a deferred tax liability relating to ONI’s nondeductible goodwill. The provision for income taxes consisted of the following components for the years ended December 31: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Income taxes currently payable: Federal $ — $ 23,735 $ 17,385 State — 2,242 769 Deferred income taxes related to: Federal 31,915 35,955 24,664 Estimated revaluation of deferred tax assets 39,300 — — State 1,724 4,230 3,359 Deferred income tax expense 72,939 40,185 28,023 Income tax expense $ 72,939 $ 66,162 $ 46,177 Net Deferred Tax Assets Significant components of net deferred tax assets (liabilities) were as follows at December 31: (dollars in thousands) 2017 2016 Deferred Tax Assets Allowance for loan losses, net of recapture $ 12,958 $ 19,773 Benefit plan accruals 11,080 23,846 Alternative minimum tax credit 25,084 19,523 Unrealized losses on benefit plans 108 205 Net operating loss carryforwards 39,631 66,917 Federal tax credits 5,516 35 Other-than-temporary impairment 1,424 3,606 Acquired loans 29,669 40,522 Lease exit obligation 1,337 2,060 Unrealized losses on available-for-sale 14,011 23,365 Unrealized losses on held-to-maturity 3,630 7,118 Unrealized losses on hedges 923 4,116 Other real estate owned 369 3,310 Other, net 829 2,675 Total deferred tax assets 146,569 217,071 Deferred Tax Liabilities Accretion on investment securities (493 ) (700 ) Purchase accounting (16,718 ) (17,552 ) Loan servicing rights (6,058 ) (9,627 ) Premises and equipment (10,052 ) (4,800 ) Prepaid expenses (1,277 ) — Tax credit investments (168 ) — Other, net (946 ) (2,529 ) Total deferred tax liabilities (35,712 ) (35,208 ) Net deferred tax assets $ 110,857 $ 181,863 Through the acquisition of Anchor (WI) in the second quarter of 2016 and Lafayette Savings Bank in the fourth quarter of 2014, both former thrifts, Old National Bank’s retained earnings at December 31, 2017 include base-year bad debt reserves, created for tax purposes prior to 1988, totaling $52.8 million. Of this total, $50.9 million was acquired from Anchor (WI), and $1.9 million was acquired from Lafayette Savings Bank. Base-year reserves are subject to recapture in the unlikely event that Old National Bank (1) makes distributions in excess of current and accumulated earnings and profits, as calculated for federal income tax purposes, (2) redeems its stock, or (3) liquidates. Old National Bank has no intention of making such a nondividend distribution. Accordingly, under current accounting principles, a related deferred income tax liability of $13.0 million has not been recognized. No valuation allowance was recorded at December 31, 2017 or 2016 because, based on current expectations, Old National believes it will generate sufficient income in future years to realize deferred tax assets. Old National has federal net operating loss carryforwards totaling $130.7 million at December 31, 2017 and $162.9 million at December 31, 2016. This federal net operating loss was acquired from the acquisition of Anchor (WI) in 2016. If not used, the federal net operating loss carryforwards will expire from 2028 to 2033. Old National has alternative minimum tax credit carryforwards totaling $25.1 million at December 31, 2017 and $19.5 million at December 31, 2016. The enactment of H.R.1 eliminates the parallel tax system known as the alternative minimum tax and allows any existing alternative minimum tax credits to be used to reduce regular tax or be refunded from 2018 to 2021. ASC 740 may allow for the reclassification of the alternative minimum tax credit from a deferred tax asset to a current tax asset. Old National has not completed its analysis of its alternative minimum tax credit classification, and accordingly is maintaining its alternative minimum tax credit in the deferred asset classification at December 31, 2017. Old National has federal tax credit carryforwards of $5.5 million at December 31, 2017 and $35 thousand at December 31, 2016. The federal tax credits consist mainly of federal historic credits, low income housing credits, and research and development credits that, if not used, will expire from 2027 to 2037. Old National has recorded state net operating loss carryforwards totaling $203.6 million at December 31, 2017 and $206.3 million at December 31, 2016. If not used, the state net operating loss carryforwards will expire from 2024 to 2037. Old National has state tax credits totaling $1.3 million at December 31, 2017. The state tax credits will not expire. The federal and recorded state net operating loss carryforwards are subject to an annual limitation under Internal Revenue Code section 382. Old National believes that all of the recorded net operating loss carryforwards will be used prior to expiration. Unrecognized Tax Benefits Unrecognized state income tax benefits are reported net of their related deferred federal income tax benefit. A reconciliation of the beginning and ending amount of unrecognized tax benefits was as follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Balance at beginning of period $ 777 $ 124 $ 77 Additions based on tax positions related to the current year 162 118 51 Additions based on tax positions related to prior years — 537 — Reductions due to statute of limitations expiring (173 ) (2 ) (4 ) Revaluation due to Tax Reform 108 — — Balance at end of period $ 874 $ 777 $ 124 If recognized, approximately $0.9 million of unrecognized tax benefits, net of interest, would favorably affect the effective income tax rate in future periods. Old National expects the total amount of unrecognized tax benefits to decrease by approximately $0.2 million in the next twelve months. It is our policy to recognize interest and penalties accrued relative to unrecognized tax benefits in their respective federal or state income tax accounts. We recorded interest and penalties in the income statement of $10 thousand in 2017, $0.1 million in 2016, and $0.4 thousand in 2015. The amount accrued for interest and penalties in the balance sheet was $0.1 million at December 31, 2017 and 2016. Old National and its subsidiaries file a consolidated U.S. federal income tax return, as well as filing various state returns. The 2014 through 2017 tax years are open and subject to examination. Old National reversed $0.2 million in 2017 related to uncertain tax positions accounted for under FASB ASC 740-10 Accounting for Uncertainty in Income Taxes 740-10”).

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	NOTE 17 – EMPLOYEE BENEFIT PLANS Retirement Plan Old National had a funded noncontributory defined benefit plan (the “Retirement Plan”) that had been frozen since December 31, 2005. During the first quarter of 2016, we notified plan participants of our intent to terminate the Retirement Plan effective May 15, 2016. During October 2016, the Retirement Plan settled plan liabilities through either lump sum distributions to plan participants or annuity contracts purchased from a third-party insurance company that provided for the payment of vested benefits to those participants that did not elect the lump sum option. At December 31, 2017, there were no remaining plan assets. Old National made contributions to the Retirement Plan totaling $7.6 million during 2016 and $0.1 million during 2015. As a result of the pension termination, unrecognized losses, which previously were recorded in accumulated other comprehensive loss on the consolidated balance sheets, were recognized as expense and the pension plan settlement loss of $9.8 million was recorded in the consolidated statements of income for the year ended December 31, 2016. Including this settlement charge, the total expense under the Retirement Plan was $11.6 million in 2016. Employee Stock Ownership Plan The Employee Stock Ownership and Savings Plan (the “401(k) Plan”) permits employees to participate the first month following one month of service. Effective as of April 1, 2010, we suspended safe harbor matching contributions to the 401(k) Plan. However, we may make discretionary matching contributions to the 401(k) Plan. For 2017, 2016, and 2015, we matched 50% of employee compensation deferral contributions, up to 6% of compensation. In addition to matching contributions, Old National may contribute to the 401(k) Plan an amount designated as a profit sharing contribution in the form of Old National stock or cash. Our Board of Directors designated no discretionary profit sharing contributions in 2017, 2016, or 2015. All contributions vest immediately and plan participants may elect to redirect funds among any of the investment options provided under the 401(k) Plan. The number of Old National shares in the 401(k) Plan were 0.7 million at December 31, 2017 and 0.8 million at December 31, 2016. All shares owned through the 401(k) Plan are included in the calculation of weighted-average shares outstanding for purposes of calculating diluted and basic earnings per share. Contribution expense under the 401(k) Plan was $4.7 million in 2017, $5.0 million in 2016, and $4.6 million in 2015.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	NOTE 18 – STOCK-BASED COMPENSATION Our Amended and Restated 2008 Incentive Compensation Plan (the “ICP”), which was shareholder-approved, permits the grant of share-based awards to its employees. At December 31, 2017, 4.8 million shares were available for issuance. The granting of awards to key employees is typically in the form of restricted stock awards or units. We believe that such awards better align the interests of our employees with those of our shareholders. Total compensation cost that has been charged against income for the ICPs was $6.3 million in 2017, $7.3 million in 2016, and $4.3 million in 2015. The total income tax benefit was $2.4 million in 2017, $2.8 million in 2016, and $1.6 million in 2015. Restricted Stock Awards Restricted stock awards require certain service requirements and commonly have vesting periods of 3 years. Compensation expense is recognized on a straight-line basis over the vesting period. Shares are subject to certain restrictions and risk of forfeiture by the participants. A summary of changes in our nonvested shares for the year follows: (shares in thousands) Shares Weighted Grant-Date Year Ended December 31, 2017 Nonvested balance at beginning of period 401 $ 13.31 Granted during the year 211 17.61 Vested during the year (194 ) 13.50 Forfeited during the year (11 ) 14.97 Nonvested balance at end of period 407 $ 15.41 As of December 31, 2017, there was $3.9 million of total unrecognized compensation cost related to nonvested shares granted under the ICP. The cost is expected to be recognized over a weighted-average period of 2.0 years. The total fair value of the shares vested was $3.4 million in 2017, $3.8 million in 2016, and $1.6 million in 2015. Restricted Stock Units Restricted stock units require certain performance requirements and have vesting periods of 3 years. Compensation expense is recognized on a straight-line basis over the vesting period. Shares are subject to certain restrictions and risk of forfeiture by the participants. A summary of changes in our nonvested shares for the year follows: (shares in thousands) Shares Weighted Grant-Date Year Ended December 31, 2017 Nonvested balance at beginning of period 821 $ 12.02 Granted during the year 278 16.31 Vested during the year (74 ) 13.47 Forfeited during the year (192 ) 12.09 Dividend equivalents adjustment 16 13.19 Nonvested balance at end of period 849 $ 13.30 As of December 31, 2017, there was $3.7 million of total unrecognized compensation cost related to nonvested shares granted under the ICP. The cost is expected to be recognized over a weighted-average period of 1.8 years. Stock Options Option awards are generally granted with an exercise price equal to the market price of our Common Stock at the date of grant; these option awards have vesting periods ranging from 3 to 5 years and have 10-year Old National has not granted stock options since 2009. However, Old National did acquire stock options through prior year acquisitions. Old National recorded no incremental expense associated with the conversion of these options. A summary of the activity in the stock option plan in 2017 follows: Weighted Weighted Average Aggregate Average Remaining Intrinsic Exercise Contractual Value (shares in thousands) Shares Price Term in Years (in thousands) Year Ended December 31, 2017 Outstanding at beginning of period 694 $ 15.27 Exercised (193 ) 14.01 Forfeited/expired (276 ) 18.89 Outstanding at end of period 225 $ 11.92 1.66 $ 1,436.0 Options exercisable at end of year 225 $ 11.92 1.66 $ 1,436.0 Information related to the stock option plan during each year follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Intrinsic value of options exercised $ 806 $ 660 $ 458 Cash received from option exercises 2,655 2,349 997 Tax benefit realized from option exercises 318 264 159 As of December 31, 2017, all options were fully vested and all compensation costs had been expensed. Stock Appreciation Rights Old National has never granted stock appreciation rights. However, Old National did acquire stock appreciation rights through a prior year acquisition. Old National recorded no incremental expense associated with the conversion of these stock appreciation rights. At December 31, 2017, 0.1 million stock appreciation rights remained outstanding. Outside Director Stock Compensation Program Old National maintains a director stock compensation program covering all outside directors. Compensation shares are earned semi-annually. Beginning in 2017, any shares awarded to directors are anticipated to be issued from the ICP. Approximately 20,000 shares were issued to directors in 2017.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Shareholders' Equity	NOTE 19 – SHAREHOLDERS’ EQUITY Dividend Reinvestment and Stock Purchase Plan Old National has a dividend reinvestment and stock purchase plan under which common shares issued may be either repurchased shares or authorized and previously unissued shares. A new plan became effective on August 13, 2015, with total authorized and unissued common shares reserved for issuance of 3.3 million. At December 31, 2017, 3.3 million authorized and unissued common shares were available for issuance under the plan. Employee Stock Purchase Plan Old National has an employee stock purchase plan under which eligible employees can purchase common shares at a price not less than 95% of the fair market value of the common shares on the purchase date. The amount of common shares purchased cannot exceed ten percent of the employee’s compensation. The maximum number of shares that may be purchased under this plan is 500,000 shares. In 2017, 24,000 shares were issued related to this plan with proceeds of approximately $404,000. In 2016, 32,000 shares were issued related to this plan with proceeds of approximately $388,000.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value	NOTE 20 – FAIR VALUE FASB ASC 820-10 820-10 • Level 1 – Quoted prices (unadjusted) for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date. • Level 2 – Significant other observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data. • Level 3 – Significant unobservable inputs that reflect a company’s own assumptions about the assumptions that market participants would use in pricing an asset or liability. Old National used the following methods and significant assumptions to estimate the fair value of each type of financial instrument: Investment securities Residential loans held for sale Derivative financial instruments Assets and liabilities measured at fair value on a recurring basis, including financial assets and liabilities for which we have elected the fair value option, are summarized below: Fair Value Measurements at December 31, 2017 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Financial Assets Trading securities $ 5,584 $ 5,584 $ — $ — Investment securities available-for-sale: U.S. Treasury 5,551 5,551 — — U.S. government-sponsored entities and agencies 664,286 — 664,286 — Mortgage-backed securities - Agency 1,667,682 — 1,667,682 — States and political subdivisions 530,193 — 530,193 Pooled trust preferred securities 8,448 — — 8,448 Other securities 320,047 30,965 289,082 — Residential loans held for sale 17,930 — 17,930 — Derivative assets 14,118 — 14,118 — Financial Liabilities Derivative liabilities 16,292 — 16,292 — Fair Value Measurements at December 31, 2016 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Financial Assets Trading securities $ 4,982 $ 4,982 $ — $ — Investment securities available-for-sale: U.S. Treasury 7,103 7,103 — — U.S. government-sponsored entities and agencies 493,956 — 493,956 — Mortgage-backed securities - Agency 1,525,019 — 1,525,019 — States and political subdivisions 436,684 — 436,684 Pooled trust preferred securities 8,119 — — 8,119 Other securities 326,293 30,905 295,388 — Residential loans held for sale 90,682 — 90,682 — Derivative assets 17,701 — 17,701 — Financial Liabilities Derivative liabilities 23,574 — 23,574 — The table below presents a reconciliation of all assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3): Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 8,119 $ 7,900 Accretion of discount 17 18 Sales/payments received (424 ) (327 ) Increase in fair value of securities 736 528 Balance at end of period $ 8,448 $ 8,119 The accretion of discounts on securities in the table above is included in interest income. An increase in fair value is reflected in the balance sheet as an increase in the fair value of investment securities available-for-sale, The table below provides quantitative information about significant unobservable inputs used in fair value measurements within Level 3 of the fair value hierarchy: (dollars in thousands) Fair Valuation Techniques Unobservable Input Range (Weighted December 31, 2017 Pooled trust preferred securities $ 8,448 Discounted cash flow Constant prepayment rate (a) 0.00% Additional asset defaults (b) 4.2% - 9.6% (7.5%) Expected asset recoveries (c) 0.0% - 4.1% (0.6%) December 31, 2016 Pooled trust preferred securities $ 8,119 Discounted cash flow Constant prepayment rate (a) 0.00% Additional asset defaults (b) 4.5% - 10.0% (7.9%) Expected asset recoveries (c) 0.0% - 6.1% (0.9%) (a) Assuming no prepayments. (b) Each currently performing pool asset is assigned a default probability based on the banking environment, which is adjusted for specific issuer evaluation, of 0%, 50%, or 100%. (c) Each currently defaulted pool asset is assigned a recovery probability based on specific issuer evaluation of 0%, 25%, or 100%. Significant changes in any of the unobservable inputs used in the fair value measurement in isolation would result in a significant change to the fair value measurement. The pooled trust preferred securities Old National owns are subordinate note classes that rely on an ongoing cash flow stream to support their values. The senior note classes receive the benefit of prepayments to the detriment of subordinate note classes since the ongoing interest cash flow stream is reduced by the early redemption. Generally, a change in prepayment rates or additional pool asset defaults has an impact that is directionally opposite from a change in the expected recovery of a defaulted pool asset. Assets measured at fair value on a non-recurring Fair Value Measurements at December 31, 2017 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Collateral Dependent Impaired Loans: Commercial loans $ 2,217 $ — $ — $ 2,217 Commercial real estate loans 26,319 — — 26,319 Foreclosed Assets: Commercial real estate 1,726 — — 1,726 Residential 55 — — 55 Loan servicing rights 2,964 — 2,964 — Impaired commercial and commercial real estate loans that are deemed collateral dependent are valued based on the fair value of the underlying collateral. These estimates are based on the most recently available appraisals with certain adjustments made based on the type of property, age of appraisal, current status of the property, and other related factors to estimate the current value of the collateral. These impaired commercial and commercial real estate loans had a principal amount of $38.6 million, with a valuation allowance of $10.1 million at December 31, 2017. Old National recorded provision expense associated with these loans totaling $5.2 million in 2017. Other real estate owned and other repossessed property is measured at fair value less costs to sell and had a net carrying amount of $1.8 million at December 31, 2017. The estimates of fair value are based on the most recently available appraisals with certain adjustments made based on the type of property, age of appraisal, current status of the property, and other related factors to estimate the current value of the collateral. There were write-downs of other real estate owned of $2.5 million in 2017. Loan servicing rights are evaluated for impairment based upon the fair value of the rights as compared to the carrying amount. If the carrying amount of an individual tranche exceeds fair value, impairment is recorded on that tranche so that the servicing asset is carried at fair value. Fair value is determined at a tranche level, based on market prices for comparable mortgage servicing contracts when available, or alternatively based on a valuation model that calculates the present value of estimated future net servicing income. The valuation model utilizes a discount rate, weighted average prepayment speed, and other economic factors that market participants would use in estimating future net servicing income and that can be validated against available market data (Level 2). The valuation allowance for loan servicing rights with impairments at December 31, 2017 totaled $29 thousand. Old National recorded recoveries associated with these loan servicing rights totaling $39 thousand in 2017. Assets measured at fair value on a non-recurring Fair Value Measurements at December 31, 2016 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Collateral Dependent Impaired Loans: Commercial loans $ 6,771 $ — $ — $ 6,771 Commercial real estate loans 11,632 — — 11,632 Foreclosed Assets: Commercial real estate 1,352 — — 1,352 Residential 394 — — 394 Loan servicing rights 2,181 — 2,181 — At December 31, 2016, impaired commercial and commercial real estate loans had a principal amount of $26.4 million, with a valuation allowance of $8.0 million. Old National recorded provision recapture associated with these loans totaling $1.1 million in 2016. Other real estate owned and other repossessed property had a net carrying amount of $1.7 million at December 31, 2016. There were write-downs of other real estate owned of $3.0 million in 2016. The valuation allowance for loan servicing rights with impairments at December 31, 2016 totaled $68 thousand. There were impairments associated with these loan servicing rights totaling $34 thousand in 2016. The table below provides quantitative information about significant unobservable inputs used in fair value measurements within Level 3 of the fair value hierarchy: Valuation Unobservable Range (Weighted (dollars in thousands) Fair Value Techniques Input Average) December 31, 2017 Collateral Dependent Impaired Loans Commercial loans $ 2,217 Fair value of collateral Discount for type of property, age of appraisal, and current status 0% - 98% (49%) Commercial real estate loans 26,319 Fair value of collateral Discount for type of property, age of appraisal and current status 10% -78% (32%) Foreclosed Assets Commercial real estate 1,726 Fair value of collateral Discount for type of property, age of appraisal, and current status 7% - 25% (18%) Residential (1) 55 Fair value of collateral Discount for type of property, age of appraisal, and current status 39% (1) There was only one foreclosed residential asset at December 31, 2017, so no range or weighted average rate is reported. December 31, 2016 Collateral Dependent Impaired Loans Commercial loans $ 6,771 Fair value of collateral Discount for type of property, age of appraisal, and current status 0% - 99% (53%) Commercial real estate loans 11,632 Fair value of collateral Discount for type of property, age of appraisal, and current status 10% - 67% (36%) Foreclosed Assets Commercial real estate 1,352 Fair value of collateral Discount for type of property, age of appraisal, and current status 4% - 80% (39%) Residential 394 Fair value of collateral Discount for type of property, age of appraisal, and current status 7% - 60% (30%) Financial instruments recorded using fair value option Under FASB ASC 825-10, instrument-by We have elected the fair value option for residential loans held for sale. For these loans, interest income is recorded in the consolidated statements of income based on the contractual amount of interest income earned on the financial assets (except any that are on nonaccrual status). None of these loans are 90 days or more past due, nor are any on nonaccrual status. Included in the income statement is interest income for loans held for sale totaling $0.2 million in 2017 and $0.1 million in 2016. Residential loans held for sale Old National has elected the fair value option for newly originated conforming fixed-rate and adjustable-rate first mortgage loans held for sale. These loans are intended for sale and are hedged with derivative instruments. Old National has elected the fair value option to mitigate accounting mismatches in cases where hedge accounting is complex and to achieve operational simplification. The fair value option was not elected for loans held for investment. The difference between the aggregate fair value and the aggregate remaining principal balance for loans for which the fair value option has been elected as of December 31, 2017 and 2016 was as follows: Aggregate Contractual (dollars in thousands) Fair Value Difference Principal December 31, 2017 Residential loans held for sale $ 17,930 $ 546 $ 17,384 December 31, 2016 Residential loans held for sale $ 90,682 $ 133 $ 90,549 Accrued interest at period end is included in the fair value of the instruments. The following table presents the amount of gains and losses from fair value changes included in income before income taxes for financial assets carried at fair value for the years ended December 31: Total Changes in Fair Values Other Included in Gains and Interest Interest Current Period (dollars in thousands) (Losses) Income (Expense) Earnings Year Ended December 31, 2017 Residential loans held for sale $ 409 $ 4 $ — $ 413 Year Ended December 31, 2016 Residential loans held for sale $ (103 ) $ — $ — $ (103 ) The carrying amounts and estimated fair values of financial instruments, not previously presented in this note, at December 31, 2017 and 2016 were as follows: Fair Value Measurements at December 31, 2017 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Financial Assets Cash, due from banks, money market, and other interest-earning investments $ 290,432 $ 290,432 $ — $ — Investment securities held-to-maturity: Mortgage-backed securities—Agency 6,903 — 7,056 — State and political subdivisions 677,160 — 720,647 — FHLB/Federal Reserve Bank stock 119,686 N/A N/A N/A Loans, net: Commercial 2,698,023 — — 2,707,385 Commercial real estate 4,333,116 — — 4,347,949 Residential real estate 2,165,290 — — 2,210,951 Consumer credit 1,871,311 — — 1,998,194 Accrued interest receivable 87,102 16 24,001 63,085 Financial Liabilities Deposits: Noninterest-bearing demand deposits $ 3,680,807 $ 3,680,807 $ — $ — NOW, savings, and money market deposits 7,290,521 7,290,521 — — Time deposits 1,634,436 — 1,620,685 — Federal funds purchased and interbank borrowings 335,033 335,033 — — Securities sold under agreements to repurchase 384,810 359,810 25,133 — FHLB advances 1,609,579 — — 1,607,189 Other borrowings 248,782 — 250,443 — Accrued interest payable 7,029 — 7,029 — Standby letters of credit 351 — — 351 Off-Balance Commitments to extend credit $ — $ — $ — $ 2,449 N/A = not applicable Fair Value Measurements at December 31, 2016 Using (dollars in thousands) Carrying Quoted Prices in Significant Significant (Level 3) Financial Assets Cash, due from banks, money market, and other interest-earning investments $ 255,519 $ 255,519 $ — $ — Investment securities held-to-maturity: U.S. government-sponsored entities and agencies 40,131 — 40,558 — Mortgage-backed securities - Agency 10,640 — 10,940 — State and political subdivisions 694,319 — 732,674 — FHLB/Federal Reserve Bank stock 101,716 N/A N/A N/A Loans, net: Commercial 1,895,618 — — 1,971,296 Commercial real estate 3,112,680 — — 3,400,365 Residential real estate 2,085,887 — — 2,228,542 Consumer credit 1,866,519 — — 1,974,180 Accrued interest receivable 81,381 16 22,880 58,485 Financial Liabilities Deposits: Noninterest-bearing demand deposits $ 3,016,093 $ 3,016,093 $ — $ — NOW, savings, and money market deposits 6,259,052 6,259,052 — — Time deposits 1,468,108 — 1,460,778 — Federal funds purchased and interbank borrowings 213,003 213,003 — — Securities sold under agreements to repurchase 367,052 317,052 50,612 — FHLB advances 1,353,092 — — 1,360,599 Other borrowings 218,939 — 217,647 — Accrued interest payable 5,979 — 5,979 — Standby letters of credit 315 — — 315 Off-Balance Commitments to extend credit $ — $ — $ — $ 2,527 N/A = not applicable The following methods and assumptions were used to estimate the fair value of each type of financial instrument. Cash, due from banks, federal funds sold, and money market investments: Investment securities: held-to-maturity FHLB and Federal Reserve Bank stock: Loans Accrued interest receivable and payable: Deposits Federal funds purchased and interbank borrowings Securities sold under agreements to repurchase Federal Home Loan Bank advances Other borrowings Standby letters of credit 460-10 Off-balance off-balance

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	NOTE 21 – DERIVATIVE FINANCIAL INSTRUMENTS As part of our overall interest rate risk management, Old National uses derivative instruments, including interest rate swaps, caps, and floors. The notional amount of these derivative instruments was $708.5 million at December 31, 2017 and $660.0 million at December 31, 2016. These derivative financial instruments at December 31, 2017 consisted of $33.5 million notional amount of receive-fixed, pay-variable pay-fixed, pay-variable pay-fixed, In addition, commitments to fund certain mortgage loans (interest rate lock commitments) and forward commitments for the future delivery of mortgage loans to third party investors are considered derivatives. At December 31, 2017, the notional amount of the interest rate lock commitments was $29.9 million and forward commitments were $41.2 million. At December 31, 2016, the notional amount of the interest rate lock commitments was $40.3 million and forward commitments were $86.1 million. It is our practice to enter into forward commitments for the future delivery of residential mortgage loans to third party investors when interest rate lock commitments are entered into in order to economically hedge the effect of changes in interest rates resulting from our commitment to fund the loans. Old National also enters into derivative instruments for the benefit of its customers. The notional amounts of these customer derivative instruments and the offsetting counterparty derivative instruments were $826.6 million at December 31, 2017. The notional amounts of these customer derivative instruments and the offsetting counterparty derivative instruments were $582.7 million at December 31, 2016. These derivative contracts do not qualify for hedge accounting. These instruments include interest rate swaps, caps, and collars. Commonly, Old National will economically hedge significant exposures related to these derivative contracts entered into for the benefit of customers by entering into offsetting contracts with approved, reputable, independent counterparties with substantially matching terms. Old National enters into derivative financial instruments as part of its foreign currency risk management strategies. These derivative instruments consist of foreign currency forward contracts to accommodate the business needs of its customers. Old National does not designate these foreign currency forward contracts for hedge accounting treatment. The notional amounts of these foreign currency forward contracts and the offsetting counterparty derivative instruments were $0.8 million at December 31, 2017. We did not have any foreign currency forward contracts at December 31, 2016. Credit risk arises from the possible inability of counterparties to meet the terms of their contracts. Old National’s exposure is limited to the replacement value of the contracts rather than the notional, principal, or contract amounts. There are provisions in our agreements with the counterparties that allow for certain unsecured credit exposure up to an agreed threshold. Exposures in excess of the agreed thresholds are collateralized. In addition, we minimize credit risk through credit approvals, limits, and monitoring procedures. Amounts reported in AOCI related to cash flow hedges will be reclassified to interest income or interest expense as interest payments are received or paid on Old National’s derivative instruments. During the next 12 months, we estimate that $0.7 million will be reclassified to interest income and $2.8 million will be reclassified to interest expense. On the balance sheet, asset derivatives are included in other assets, and liability derivatives are included in other liabilities. The following table summarizes the fair value of derivative financial instruments utilized by Old National: December 31, 2017 December 31, 2016 (dollars in thousands) Asset Liability Asset Liability Derivatives designated as hedging instruments Interest rate contracts $ 3,351 $ 5,351 $ 3,056 $ 11,582 Total derivatives designated as hedging instruments $ 3,351 $ 5,351 $ 3,056 $ 11,582 Derivatives not designated as hedging instruments Interest rate contracts $ 10,012 $ 10,933 $ 11,903 $ 11,992 Mortgage contracts 747 — 2,742 — Foreign currency contracts 8 8 — — Total derivatives not designated as hedging instruments $ 10,767 $ 10,941 $ 14,645 $ 11,992 Total $ 14,118 $ 16,292 $ 17,701 $ 23,574 Beginning in 2017, the relevant agreements that allow us to access the central clearing organizations to clear derivative transactions were amended to characterize variation margin payments as settlements of the derivative contract rather than collateral against the exposures. Netting cash collateral exchanged with all central clearing organizations and applying variation margin payments as settlement of derivative transactions resulted in a reduction of net derivative assets on our balance sheet of $3.6 million and a reduction of net derivative liabilities of $2.7 million at December 31, 2017. The effect of derivative instruments on the consolidated statements of income for the years ended December 31 were as follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Derivatives in Fair Value Hedging Relationships Location of Gain or (Loss) Recognized in Amount of Gain or (Loss) Interest rate contracts (1) Interest income / (expense) $ (5,695 ) $ (5,446 ) $ (1,729 ) Interest rate contracts (2) Other income / (expense) 161 126 189 Total $ (5,534 ) $ (5,320 ) $ (1,540 ) Derivatives in Cash Flow Hedging Relationships Location of Gain or (Loss) Recognized in Amount of Gain or (Loss) Interest rate contracts (1) Interest income / (expense) $ 309 $ 329 $ 511 Total $ 309 $ 329 $ 511 Derivatives Not Designated as Hedging Instruments Location of Gain or (Loss) Recognized in Amount of Gain or (Loss) Interest rate contracts (3) Other income / (expense) $ 56 $ 28 $ 18 Mortgage contracts Mortgage banking revenue (1,995 ) 1,390 168 Foreign currency contracts Other income — — — Total $ (1,939 ) $ 1,418 $ 186 (1) Amounts represent the net interest payments as stated in the contractual agreements. (2) Amounts represent ineffectiveness on derivatives designated as fair value hedges. (3) Includes the valuation differences between the customer and offsetting counterparty swaps.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 22 – COMMITMENTS AND CONTINGENCIES Litigation In the normal course of business, Old National Bancorp and its subsidiaries have been named, from time to time, as defendants in various legal actions. Certain of the actual or threatened legal actions may include claims for substantial compensatory and/or punitive damages or claims for indeterminate amounts of damages. Old National contests liability and/or the amount of damages as appropriate in each pending matter. In view of the inherent difficulty of predicting the outcome of such matters, particularly in cases where claimants seek substantial or indeterminate damages or where investigations and proceedings are in the early stages, Old National cannot predict with certainty the loss or range of loss, if any, related to such matters, how or if such matters will be resolved, when they will ultimately be resolved, or what the eventual settlement, or other relief, if any, might be. Subject to the foregoing, Old National believes, based on current knowledge and after consultation with counsel, that the outcome of such pending matters will not have a material adverse effect on the consolidated financial condition of Old National, although the outcome of such matters could be material to Old National’s operating results and cash flows for a particular future period, depending on, among other things, the level of Old National’s revenues or income for such period. Old National will accrue for a loss contingency if (1) it is probable that a future event will occur and confirm the loss and (2) the amount of the loss can be reasonably estimated. Old National is not currently involved in any material litigation. Credit-Related Financial Instruments In the normal course of business, Old National’s banking affiliates have entered into various agreements to extend credit, including loan commitments of $3.144 billion and standby letters of credit of $68.7 million at December 31, 2017. At December 31, 2017, approximately $2.896 billion of the loan commitments had fixed rates and $248.1 million had floating rates, with the floating interest rates ranging from 0% to 18%. At December 31, 2016, loan commitments totaled $2.354 billion and standby letters of credit totaled $51.7 million. These commitments are not reflected in the consolidated financial statements. The allowance for unfunded loan commitments totaled $3.1 million at December 31, 2017 and $3.2 million at December 31, 2016. Old National had credit extensions with various unaffiliated banks related to letter of credit commitments issued on behalf of Old National’s clients totaling $12.4 million at December 31, 2017 and $13.3 million at December 31, 2016. Old National provided collateral to the unaffiliated banks to secure credit extensions totaling $11.5 million at December 31, 2017 and $12.6 million December 31, 2016. Old National did not provide collateral for the remaining credit extensions.

Financial Guarantees

Financial Guarantees	12 Months Ended
	Dec. 31, 2017
Guarantees and Product Warranties [Abstract]
Financial Guarantees	NOTE 23 – FINANCIAL GUARANTEES Old National holds instruments, in the normal course of business with clients, that are considered financial guarantees in accordance with FASB ASC 460-10 Guarantor’s Accounting and Disclosure Requirements for Guarantees, Including Indirect Guarantees of Indebtedness of Others , Old National is a party in three separate risk participation transactions of interest rate swaps, which had total notional amount of $18.0 million at December 31, 2017.

Regulatory Restrictions

Regulatory Restrictions	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Regulatory Restrictions	NOTE 24 – REGULATORY RESTRICTIONS Restrictions on Cash and Due from Banks Old National’s affiliate bank is required to maintain reserve balances on hand and with the Federal Reserve Bank that are interest bearing and unavailable for investment purposes. The reserve balances were $100.9 million at December 31, 2017 and $85.4 million at December 31, 2016. In addition, Old National had cash and due from banks which was held as collateral for collateralized swap positions of $5.7 million at December 31, 2017 and $3.5 million at December 31, 2016. Restrictions on Transfers from Affiliate Bank Regulations limit the amount of dividends an affiliate bank can declare in any year without obtaining prior regulatory approval. Prior regulatory approval is required if dividends to be declared in any year would exceed net earnings of the current year plus retained net profits for the preceding two years. Prior regulatory approval to pay dividends was not required in 2015, 2016, or 2017 and is not currently required. Restrictions on the Payment of Dividends Old National has traditionally paid a quarterly dividend to common stockholders. The payment of dividends is subject to legal and regulatory restrictions. Any payment of dividends in the future will depend, in large part, on Old National’s earnings, capital requirements, financial condition, and other factors considered relevant by our Board of Directors. Capital Adequacy Old National and Old National Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can elicit certain mandatory actions by regulators that, if undertaken, could have a direct material effect on Old National’s financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, Old National and Old National Bank must meet specific capital guidelines that involve quantitative measures of assets, liabilities, and certain off-balance At December 31, 2017, Old National and Old National Bank exceeded the regulatory minimums and Old National Bank met the regulatory definition of well-capitalized based on the most recent regulatory notification. The following table summarizes capital ratios for Old National and Old National Bank as of December 31: Actual Fully Phased-In Well Capitalized (dollars in thousands) Amount Ratio Amount Ratio Amount Ratio 2017 Total capital to risk-weighted assets Old National Bancorp $ 1,424,123 11.40 % $ 1,311,600 10.50 % $ N/A N/A % Old National Bank 1,458,546 11.73 1,305,076 10.50 1,242,929 10.00 Common equity Tier 1 capital to risk-weighted assets Old National Bancorp 1,298,326 10.39 874,400 7.00 N/A N/A Old National Bank 1,393,059 11.21 870,051 7.00 807,904 6.50 Tier 1 capital to risk-weighted assets Old National Bancorp 1,298,326 10.39 1,061,772 8.50 N/A N/A Old National Bank 1,393,059 11.21 1,056,490 8.50 994,344 8.00 Tier 1 capital to average assets Old National Bancorp 1,298,326 8.28 627,258 4.00 N/A N/A Old National Bank 1,393,059 8.93 623,758 4.00 779,697 5.00 2016 Total capital to risk-weighted assets Old National Bancorp $ 1,229,878 12.18 % $ 1,060,662 10.50 % $ N/A N/A % Old National Bank 1,240,180 12.35 1,054,305 10.50 1,004,100 10.00 Common equity Tier 1 capital to risk-weighted assets Old National Bancorp 1,162,817 11.51 707,108 7.00 N/A N/A Old National Bank 1,187,151 11.82 702,870 7.00 652,665 6.50 Tier 1 capital to risk-weighted assets Old National Bancorp 1,176,849 11.65 858,631 8.50 N/A N/A Old National Bank 1,187,151 11.82 853,485 8.50 803,280 8.00 Tier 1 capital to average assets Old National Bancorp 1,176,849 8.43 558,673 4.00 N/A N/A Old National Bank 1,187,151 8.55 555,161 4.00 693,951 5.00 N/A = not applicable (1) When fully phased-in

Parent Company Financial Statem

Parent Company Financial Statements	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Financial Statements	NOTE 25 – PARENT COMPANY FINANCIAL STATEMENTS The following are the condensed parent company only financial statements of Old National: OLD NATIONAL BANCORP (PARENT COMPANY ONLY) CONDENSED BALANCE SHEETS December 31, (dollars in thousands) 2017 2016 Assets Deposits in affiliate bank $ 43,538 $ 91,650 Trading securities - at fair value 5,584 4,982 Investment securities - available-for-sale 1,547 1,535 Investment in affiliates: Banking subsidiaries 2,248,700 1,862,244 Non-banks 5,142 11,388 Other assets 112,353 90,872 Total assets $ 2,416,864 $ 2,062,671 Liabilities and Shareholders’ Equity Other liabilities $ 31,768 $ 33,407 Other borrowings 230,699 214,847 Shareholders’ equity 2,154,397 1,814,417 Total liabilities and shareholders’ equity $ 2,416,864 $ 2,062,671 OLD NATIONAL BANCORP (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF INCOME Years Ended December 31, (dollars in thousands) 2017 2016 2015 Income Dividends from affiliates $ 100,000 $ 160,007 $ 67,717 Net securities gains 667 100 6 Other income 1,966 40,841 1,892 Other income from affiliates 5 6 51 Total income 102,638 200,954 69,666 Expense Interest on borrowings 9,298 9,077 8,684 Other expenses 16,335 18,460 13,957 Total expense 25,633 27,537 22,641 Income before income taxes and equity in undistributed earnings of affiliates 77,005 173,417 47,025 Income tax expense (benefit) (6,240 ) 11,952 (5,473 ) Income before equity in undistributed earnings of affiliates 83,245 161,465 52,498 Equity in undistributed earnings of affiliates 12,480 (27,201 ) 64,218 Net income $ 95,725 $ 134,264 $ 116,716 OLD NATIONAL BANCORP (PARENT COMPANY ONLY) CONDENSED STATEMENT OF CASH FLOWS Years Ended December 31, (dollars in thousands) 2017 2016 2015 Cash Flows From Operating Activities Net income $ 95,725 $ 134,264 $ 116,716 Adjustments to reconcile net income to cash provided by operating activities: Depreciation 36 29 20 Net securities (gains) losses (667 ) (100 ) (6 ) Gain on sale of ONB Insurance Group, Inc. — (41,864 ) — Stock-based compensation expense 6,275 7,318 4,255 (Increase) decrease in other assets (24,004 ) (3,958 ) 6,307 Increase (decrease) in other liabilities 3,968 (225 ) 1,441 Equity in undistributed earnings of affiliates (12,480 ) 27,201 (64,218 ) Total adjustments (26,872 ) (11,599 ) (52,201 ) Net cash flows provided by (used in) operating activities 68,853 122,665 64,515 Cash Flows From Investing Activities Net cash and cash equivalents of acquisitions (24,005 ) (100,220 ) (41,070 ) Proceeds from sale of ONB Insurance Group, Inc. — 91,771 — Purchases of investment securities (62 ) (52 ) (1,053 ) Net advances to affiliates (250 ) (3,500 ) — Purchases of premises and equipment (485 ) (13 ) — Net cash flows provided by (used in) investing activities (24,802 ) (12,014 ) (42,123 ) Cash Flows From Financing Activities Payments for maturities/redemptions of other borrowings (19,856 ) — — Cash dividends paid on common stock (72,604 ) (67,536 ) (55,552 ) Common stock repurchased (2,762 ) (2,202 ) (88,695 ) Proceeds from exercise of stock options 2,655 2,349 997 Common stock issued 404 388 391 Net cash flows provided by (used in) financing activities (92,163 ) (67,001 ) (142,859 ) Net increase (decrease) in cash and cash equivalents (48,112 ) 43,650 (120,467 ) Cash and cash equivalents at beginning of period 91,650 48,000 168,467 Cash and cash equivalents at end of period $ 43,538 $ 91,650 $ 48,000

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	NOTE 26 – SEGMENT INFORMATION During the second quarter of 2016, Old National sold its insurance operations, ONI. During the year ended December 31, 2015, the insurance segment’s net income was $2.1 million and its assets totaled $61.8 million at December 31, 2015. In conjunction with the divestiture, Old National re-evaluated Operating segments are components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and in assessing performance. Old National Bank, Old National’s bank subsidiary, is the only significant subsidiary upon which management makes decisions regarding how to allocate resources and assess performance. Each of the branches of Old National Bank provide a group of similar community banking services, including such products and services as commercial, real estate and consumer loans, time deposits, checking and savings accounts, cash management, brokerage, trust, and investment advisory services. The individual bank branches located throughout our Midwest footprint have similar operating and economic characteristics. While the chief decision maker monitors the revenue streams of the various products, services, and regional locations, operations are managed and financial performance is evaluated on a Company-wide basis. Accordingly, all of the community banking services and branch locations are considered by management to be aggregated into one reportable operating segment, community banking.

Interim Financial Data (Unaudit

Interim Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interim Financial Data (Unaudited)	NOTE 27 – INTERIM FINANCIAL DATA (UNAUDITED) The following table details the quarterly results of operations for the years ended December 31, 2017 and 2016. (unaudited, dollars and shares in thousands, except per share data) Three Months Ended Three Months Ended 12/31/2017 9/30/2017 6/30/2017 3/31/2017 12/31/2016 9/30/2016 6/30/2016 3/31/2016 Interest income $ 135,134 $ 123,525 $ 118,209 $ 118,468 $ 121,849 $ 119,713 $ 110,243 $ 95,329 Interest expense 16,578 15,047 13,876 12,667 11,932 11,910 10,903 9,686 Net interest income 118,556 108,478 104,333 105,801 109,917 107,803 99,340 85,643 Provision for loan losses 1,037 311 1,355 347 (1,756 ) 1,306 1,319 91 Noninterest income 44,825 46,366 49,271 42,920 62,751 47,243 93,385 49,451 Noninterest expense 140,432 103,702 102,811 101,891 126,258 108,062 121,472 98,355 Income before income taxes 21,912 50,831 49,438 46,483 48,166 45,678 69,934 36,648 Income tax expense 40,405 11,459 10,584 10,491 14,710 10,969 30,812 9,671 Net income (loss) $ (18,493 ) $ 39,372 $ 38,854 $ 35,992 $ 33,456 $ 34,709 $ 39,122 $ 26,977 Net income (loss) per share: Basic $ (0.13 ) $ 0.30 $ 0.28 $ 0.27 $ 0.25 $ 0.25 $ 0.31 $ 0.24 Diluted (0.13 ) 0.29 0.28 0.27 0.25 0.25 0.31 0.24 Average shares: Basic 146,073 135,120 135,085 134,912 134,670 134,492 127,508 113,998 Diluted 146,875 135,796 135,697 135,431 135,383 135,011 127,973 114,563 Quarterly results, most notably interest income, noninterest income, and noninterest expense, were impacted by the acquisitions of Anchor (MN) in November 2017 and Anchor (WI) May 2016. In addition, Old National sold its insurance operations, ONI, on May 31, 2016. Income tax expense in the three months ended December 31, 2017 included $39.3 million of additional tax expense to estimate the revaluation of Old National’s deferred tax assets due to the lowering of the federal corporate tax rate to 21%.

Basis of Presentation and Sig37

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of Old National Bancorp and its wholly-owned affiliates (hereinafter collectively referred to as “Old National”) and have been prepared in conformity with accounting principles generally accepted in the United States of America and prevailing practices within the banking industry. Such principles require management to make estimates and assumptions that affect the reported amounts of assets, liabilities and the disclosures of contingent assets and liabilities at the date of the financial statements and amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. All significant intercompany transactions and balances have been eliminated. Certain prior year amounts have been reclassified to conform to the 2017 presentation. Such reclassifications had no effect on net income or shareholders’ equity and were insignificant amounts.
Trading Securities	Trading Securities Trading securities consist of mutual funds held in trusts associated with deferred compensation plans for former directors and executives. These mutual funds are recorded as trading securities at fair value. Gains and losses are included in net securities gains.
Investment Securities	Investment Securities Old National classifies investment securities as available-for-sale held-to-maturity available-for-sale held-to-maturity, available-for-sale Other-Than-Temporary Impairment
Federal Home Loan Bank (FHLB) Stock	Federal Home Loan Bank Stock Old National is a member of the FHLB system. Members are required to own a certain amount of stock based on the level of borrowings and other factors and may invest in additional amounts. FHLB stock is carried at cost, classified as a restricted security, and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income.
Loans Held for Sale	Loans Held for Sale Loans that Old National has originated with an intent to sell are classified as loans held for sale and are recorded in accordance with FASB ASC 825-10
Loans	Loans Loans that Old National intends to hold for investment purposes are classified as portfolio loans. Portfolio loans are carried at the principal balance outstanding, net of earned interest, purchase premiums or discounts, deferred loan fees and costs, and an allowance for loan losses. Interest income is accrued on the principal balances of loans outstanding. For all loan classes, a loan is generally placed on nonaccrual status when principal or interest becomes 90 days past due unless it is well secured and in the process of collection, or earlier when concern exists as to the ultimate collectibility of principal or interest. Interest accrued during the current year on such loans is reversed against earnings. Interest accrued in the prior year, if any, is charged to the allowance for loan losses. Cash interest received on these loans is applied to the principal balance until the principal is recovered or until the loan returns to accrual status. Loans may be returned to accrual status when all the principal and interest amounts contractually due are brought current, remain current for a prescribed period, and future payments are reasonably assured. Purchased loans acquired in a business combination are recorded at estimated fair value on their purchase date with no carryover of the related allowance for loan and lease losses. In determining the estimated fair value of purchased loans, management considers a number of factors including, among others, the remaining life of the acquired loans, estimated prepayments, estimated loss ratios, estimated value of the underlying collateral, and net present value of cash flows expected to be received. Purchased loans are accounted for in accordance with guidance for certain loans acquired in a transfer (ASC 310-30), non-accretable
Allowance for Loan Losses	Allowance for Loan Losses The allowance for loan losses is maintained at a level believed adequate by management to absorb probable losses incurred in the consolidated loan portfolio. Management’s evaluation of the adequacy of the allowance is an estimate based on reviews of individual loans, pools of homogeneous loans, assessments of the impact of current and anticipated economic conditions on the portfolio, and historical loss experience. The allowance is increased through a provision charged to operating expense. Loans deemed to be uncollectible are charged to the allowance. Recoveries of loans previously charged-off For all loan classes, a loan is considered impaired when it is probable that contractual interest and principal payments will not be collected either for the amounts or by the dates as scheduled in the loan agreement. If a loan is impaired, a portion of the allowance is allocated so that the loan is reported net, at the present value of estimated cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Old National’s policy, for all but PCI loans, is to recognize interest income on impaired loans unless the loan is placed on nonaccrual status. Acquired loans accounted for under ASC Topic 310-30 re-estimation Old National charges off small commercial loans scored through our small business credit center with contractual balances under $250,000 that are 90 days or more delinquent and do not have adequate collateral support. For all portfolio segments, the general component covers non-impaired Further information regarding Old National’s policies and methodology used to estimate the allowance for loan losses is presented in Note 5.
Premises and Equipment	Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation. Land is stated at cost. Depreciation is charged to operating expense over the useful lives of the assets, principally on the straight-line method. Useful lives for premises and equipment are as follows: buildings and building improvements – 15 to 39 years; and furniture and equipment – 3 to 10 years. Leasehold improvements are depreciated over the lesser of their useful lives or the term of the lease. Maintenance and repairs are expensed as incurred while major additions and improvements are capitalized. Interest costs on construction of qualifying assets are capitalized. Premises and equipment are reviewed for impairment when events indicate their carrying amount may not be recoverable from future undiscounted cash flows. If impaired, the assets are adjusted to fair value. Such impairments are included in other expense.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The excess of the cost of acquired entities over the fair value of identifiable assets acquired less liabilities assumed is recorded as goodwill. In accordance with FASB ASC 350, Intangibles – Goodwill and Other
Company-Owned Life Insurance	Company-Owned Life Insurance Old National has purchased life insurance policies on certain key executives. Old National records company-owned life insurance at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value adjusted for other charges or other amounts due that are probable at settlement.
Loan Servicing Rights	Loan Servicing Rights When loans are sold with servicing retained, servicing rights are initially recorded at fair value with the income statement effect recorded in gain on sales of loans. Fair value is based on market prices for comparable servicing contracts, when available or alternatively, is based on a valuation model that calculates the present value of estimated future net servicing income. All classes of servicing assets are subsequently measured using the amortization method which requires servicing rights to be amortized into noninterest income in proportion to, and over the period of, the estimated future net servicing income of the underlying loans. Loan servicing rights are evaluated for impairment based upon the fair value of the rights as compared to carrying amount. Impairment is determined by stratifying rights into groupings based on predominant risk characteristics, such as interest rate, loan type, term, and investor type. Impairment is recognized through a valuation allowance for an individual grouping, to the extent that fair value is less than the carrying amount. If Old National later determines that all or a portion of the impairment no longer exists for a particular grouping, a reduction of the allowance may be recorded as an increase to income. Changes in valuation allowances are reported with mortgage banking revenue on the income statement. The fair values of servicing rights are subject to significant fluctuations as a result of changes in estimated and actual prepayment speeds and default rates and losses. Servicing fee income, which is reported on the income statement as mortgage banking revenue, is recorded for fees earned for servicing loans. The fees are based on a contractual percentage of the outstanding principal, or a fixed amount per loan and are recorded as income when earned.
Derivative Financial Instruments	Derivative Financial Instruments As part of Old National’s overall interest rate risk management, Old National uses derivative instruments, including TBA forward agreements and interest rate swaps, caps, and floors. All derivative instruments are recognized on the balance sheet at their fair value in accordance with ASC 815, as amended. At the inception of the derivative contract, Old National will designate the derivative as (1) a hedge of the fair value of a recognized asset or liability or of an unrecognized firm commitment (“fair value hedge”), (2) a hedge of a forecasted transaction or of the variability of cash flows to be received or paid related to a recognized asset or liability (“cash flow hedge”), or (3) an instrument with no hedging designation (“stand-alone derivative”). For derivatives that are designated and qualify as a fair value hedge, the change in value of the derivative, as well as the offsetting change in value of the hedged item attributable to the hedged risk, are recognized in current earnings during the period of the change in fair values. For derivatives that are designated and qualify as a cash flow hedge, the effective portion of the change in value on the derivative is reported as a component of other comprehensive income and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. For all hedging relationships, changes in fair value of derivatives that are not effective in hedging the changes in fair value or expected cash flows of the hedged item are recognized immediately in current earnings during the period of the change. Similarly, the changes in the fair value of derivatives that do not qualify for hedge accounting under ASC Topic 815 are also reported currently in earnings, in noninterest income. The accrued net settlements on derivatives that qualify for hedge accounting are recorded in interest income or interest expense, consistent with the item being hedged. Old National formally documents all relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking various hedge transactions. This process includes linking all derivative instruments that are designated as fair-value or cash-flow hedges to specific assets and liabilities on the balance sheet or to specific firm commitments or forecasted transactions. Old National also formally assesses, both at the hedge’s inception and on an ongoing basis, whether the derivative instruments that are used in hedging transactions are highly effective in offsetting changes in fair values or cash flows of hedged items. Old National discontinues hedge accounting prospectively when it is determined that (1) the derivative is no longer effective in offsetting changes in the fair value or cash flows of the hedged item; (2) the derivative expires, is sold, or terminated; (3) the derivative instrument is de-designated When hedge accounting is discontinued, the future changes in fair value of the derivative are recorded as noninterest income. When a fair value hedge is discontinued, the hedged asset or liability is no longer adjusted for changes in fair value and the existing basis adjustment is amortized or accreted over the remaining life of the asset or liability. When a cash flow hedge is discontinued but the hedged cash flows or forecasted transaction is still expected to occur, changes in value that were accumulated in other comprehensive income are amortized or accreted into earnings over the same periods which the hedged transactions will affect earnings. Old National enters into various stand-alone mortgage-banking derivatives in order to hedge the risk associated with the fluctuation of interest rates. Changes in fair value are recorded as mortgage banking revenue. Old National also enters into various stand-alone derivative contracts to provide derivative products to customers which are carried at fair value with changes in fair value recorded as other noninterest income. Old National is exposed to losses if a counterparty fails to make its payments under a contract in which Old National is in the net receiving position. Old National anticipates that the counterparties will be able to fully satisfy their obligations under the agreements. In addition, Old National obtains collateral above certain thresholds of the fair value of its hedges for each counterparty based upon their credit standing. All of the contracts to which Old National is a party settle monthly, quarterly, or semiannually. Further, Old National has netting agreements with the dealers with which it does business.
Credit-Related Financial Instruments	Credit-Related Financial Instruments In the ordinary course of business, Old National’s affiliate bank has entered into credit-related financial instruments consisting of commitments to extend credit, commercial letters of credit, and standby letters of credit. The notional amount of these commitments is not reflected in the consolidated financial statements until they are funded.
Foreclosed Assets	Foreclosed Assets Other assets include real estate properties acquired as a result of foreclosure and repossessed personal property and are initially recorded at the fair value of the property less estimated cost to sell. Any excess recorded investment over the fair value of the property received is charged to the allowance for loan losses. Any subsequent write-downs are charged to expense, as are the costs of operating the properties.
Securities Purchased under Agreements to Resell and Securities Sold under Agreements to Repurchase	Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase We purchase certain securities, generally U.S. government-sponsored entity and agency securities, under agreements to resell. The amounts advanced under these agreements represent short-term secured loans and are reflected as assets in the accompanying consolidated balance sheets. We also sell certain securities under agreements to repurchase. These agreements are treated as collateralized financing transactions. These secured borrowings are reflected as liabilities in the accompanying consolidated balance sheets and are recorded at the amount of cash received in connection with the transaction. Short-term securities sold under agreements to repurchase generally mature within one to four days from the transaction date. Securities, generally U.S. government and federal agency securities, pledged as collateral under these financing arrangements can be repledged by the secured party. Additional collateral may be required based on the fair value of the underlying securities.
Covered Assets, Loss Share Agreements, and Indemnification Asset	Covered Assets, Loss Share Agreements, and Indemnification Asset On July 29, 2011, Old National acquired the banking operations of Integra in an FDIC assisted transaction. As part of the purchase and assumption agreement, Old National and the FDIC entered into loss sharing agreements (each, a “loss sharing agreement” and collectively, the “loss sharing agreements”), whereby the FDIC would cover a substantial portion of any future losses on loans (and related unfunded commitments), OREO and up to 90 days of certain accrued interest on loans. The acquired loans and OREO subject to the loss sharing agreements are referred to collectively as “covered assets.” Old National entered into an agreement with the FDIC on June 22, 2016 to terminate its loss share agreements. As a result of the termination of the loss share agreements, the remaining covered assets that were covered by the loss share arrangements were reclassified to noncovered assets effective June 22, 2016. Prior to the termination of the loss share agreements, the FDIC would have reimbursed us for 80% of expenses and valuation write-downs related to covered assets up to $275.0 million, an amount which we never reached.
Net Income per Share	Net Income per Share Basic net income per share is computed by dividing net income by the weighted-average number of common shares outstanding during each year. Diluted net income per share is computed as above and assumes the conversion of outstanding stock options and restricted stock. The following table reconciles basic and diluted net income per share for the years ended December 31. (dollars and shares in thousands, except per share data) Years Ended December 31, 2017 2016 2015 Basic Earnings Per Share Net income $ 95,725 $ 134,264 $ 116,716 Weighted average common shares outstanding 137,821 127,705 115,726 Basic Net Income Per Share $ 0.69 $ 1.05 $ 1.01 Diluted Earnings Per Share Net income $ 95,725 $ 134,264 $ 116,716 Weighted average common shares outstanding 137,821 127,705 115,726 Effect of dilutive securities: Restricted stock (1) 599 543 440 Stock options (2) 93 53 89 Weighted average shares outstanding 138,513 128,301 116,255 Diluted Earnings Per Share $ 0.69 $ 1.05 $ 1.00 (1) 8 thousand shares and 3 thousand shares of restricted stock at December 31, 2017 and 2016, respectively, were not included in the computation of net income per diluted share because the effect would be antidilutive. There were no shares of restricted stock excluded at December 31, 2015 because the effect would be antidilutive. (2) Options to purchase 0.1 million shares, 0.5 million shares, and 0.7 million shares outstanding at December 31, 2017, 2016, and 2015, respectively, were not included in the computation of net income per diluted share because the exercise price of these options was greater than the average market price of the common shares and, therefore, the effect would be antidilutive.
Stock-Based Compensation	Stock-Based Compensation Compensation cost is recognized for stock options and restricted stock awards and units issued to employees based on the fair value of these awards at the date of grant. A Black-Scholes model is utilized to estimate the fair value of stock options, while the market price of our Common Stock at the date of grant is used for restricted stock awards. A third party provider is used to value certain restricted stock units where the performance measure is based on total shareholder return. Compensation expense is recognized over the requisite service period.
Income Taxes	Income Taxes Income tax expense is the total of the current year income tax due or refundable and the change in deferred tax assets and liabilities. Deferred tax assets and liabilities are the expected future tax amounts for the temporary differences between carrying amounts and tax bases of assets and liabilities, computed using enacted tax rates. A valuation allowance, if needed, reduces deferred tax assets to the amount expected to be realized. We recognize a tax position as a benefit only if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit that is greater than 50% likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded. We recognize interest and/or penalties related to income tax matters in income tax expense. Old National is a limited partner in several tax-advantaged pre-tax
Loss Contingencies	Loss Contingencies Loss contingencies, including claims and legal actions arising in the normal course of business, are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated. See Note 22 to the consolidated financial statements for further disclosure.
Statement of Cash Flows Data	Statement of Cash Flows Data For the purpose of presentation in the accompanying consolidated statement of cash flows, cash and cash equivalents are defined as cash, due from banks, federal funds sold and resell agreements, and money market investments, which have maturities less than 90 days. The following table summarizes the supplemental cash flow information for the years ended December 31: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Cash payments: Interest $ 56,682 $ 43,698 $ 32,712 Income taxes (net of refunds) 4,326 23,636 14,824 Noncash Investing and Financing Activities: Transfer of premises and equipment to assets held for sale 16,617 4,620 9,070
Impact of Accounting Changes	Impact of Accounting Changes FASB ASC 606 – No. 2014-09, Revenue from Contracts with Customers Revenue from Contracts with Customers in-depth In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) No. 2014-09 No. 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing No. 2014-09 No. 2014-09. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients In December 2016, the FASB issued ASU No. 2016-20, Revenue from Contracts with Customers (Topic 606): Technical Corrections and Improvements No. 2014-09 No. 2014-09. No. 2014-09. FASB ASC 825 No. 2016-01, Financial Instruments – Overall (Subtopic 825-10): available-for-sale FASB ASC 842 – No. 2016-02, Leases (Topic 842) right-of-use FASB ASC 815 No. 2016-05, Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships de-designation In March 2016, the FASB issued ASU No. 2016-06, Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments Derivatives and Hedging In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. held-to-maturity available-for-sale FASB ASC 323 No. 2016-07, Investments—Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting step-by-step available-for-sale FASB ASC 718 – No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Shared-Based Payment Accounting In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting. FASB ASC 326 – No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments available-for-sale one-time one-time FASB ASC 740 – No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory FASB ASC 810 No. 2016-17, Consolidation (Topic 810): Interests Held through Related Parties that are under Common Control FASB ASC 805 No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business FASB ASC 350 – No. 2017-04, Intangibles: Goodwill and Other: Simplifying the Test for Goodwill Impairment FASB ASC 610 – No. 2017-05, Other Income – Gains and Losses from the Derecognition of Nonfinancial Assets (Topic 610): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets 610-20 No. 2014-09 2014-09. 610-20 2014-09. FASB ASC 715 – No. 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost FASB ASC 310 – No. 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20):

Basis of Presentation and Sig38

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Table Reconciling Basic and Diluted Net Income Per Share	The following table reconciles basic and diluted net income per share for the years ended December 31. (dollars and shares in thousands, except per share data) Years Ended December 31, 2017 2016 2015 Basic Earnings Per Share Net income $ 95,725 $ 134,264 $ 116,716 Weighted average common shares outstanding 137,821 127,705 115,726 Basic Net Income Per Share $ 0.69 $ 1.05 $ 1.01 Diluted Earnings Per Share Net income $ 95,725 $ 134,264 $ 116,716 Weighted average common shares outstanding 137,821 127,705 115,726 Effect of dilutive securities: Restricted stock (1) 599 543 440 Stock options (2) 93 53 89 Weighted average shares outstanding 138,513 128,301 116,255 Diluted Earnings Per Share $ 0.69 $ 1.05 $ 1.00 (1) 8 thousand shares and 3 thousand shares of restricted stock at December 31, 2017 and 2016, respectively, were not included in the computation of net income per diluted share because the effect would be antidilutive. There were no shares of restricted stock excluded at December 31, 2015 because the effect would be antidilutive. (2) Options to purchase 0.1 million shares, 0.5 million shares, and 0.7 million shares outstanding at December 31, 2017, 2016, and 2015, respectively, were not included in the computation of net income per diluted share because the exercise price of these options was greater than the average market price of the common shares and, therefore, the effect would be antidilutive.
Summary of Supplemental Cash Flow Information	The following table summarizes the supplemental cash flow information for the years ended December 31: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Cash payments: Interest $ 56,682 $ 43,698 $ 32,712 Income taxes (net of refunds) 4,326 23,636 14,824 Noncash Investing and Financing Activities: Transfer of premises and equipment to assets held for sale 16,617 4,620 9,070
Summary of Common Shares Issued and Resultant Value of Total Shareholders' Equity	The following table summarizes the common shares issued and resultant value of total shareholders’ equity associated with acquisitions for the years ended December 31: (dollars and shares in thousands) Shares of Total 2017 Acquisition of Anchor (MN) 16,527 $ 300,828 2016 Acquisition of Anchor (WI) 20,415 $ 273,565 2015 Acquisition of Founders 3,402 $ 50,626

Acquisition and Divestiture A39

Acquisition and Divestiture Activity (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Unaudited Pro-Forma Information	The unaudited pro-forma pro-forma (dollars in thousands) 2017 2016 Revenue (1) $ 700,944 $ 738,280 Income before income taxes $ 213,932 $ 214,737 (1) Net interest income plus noninterest income.
AnchorBank WI [Member]
Summary of Fair Values of Acquired Assets, Liabilities Assumed and Resulting Goodwill	A summary of the fair values of the acquired assets, liabilities assumed, and resulting goodwill are as follows (in thousands): Cash and cash equivalents $ 123,657 Investment securities 235,240 FHLB stock 4,596 Loans held for sale 9,334 Loans 1,637,806 Premises and equipment 35,721 Accrued interest receivable 7,308 Other real estate owned 17,349 Company-owned life insurance 7,278 Other assets 126,210 Deposits (1,852,713 ) Securities sold under agreements to repurchase (3,132 ) Other borrowings (123 ) Accrued expenses and other liabilities (36,957 ) Net tangible assets acquired 311,574 Definite-lived intangible assets acquired 21,559 Loan servicing rights 15,274 Goodwill 111,347 Total consideration $ 459,754
Summary of Acquired Loan Data	Acquired loan data for Anchor (WI) can be found in the table below: (in thousands) Fair Value Gross Contractual Best Estimate at Acquired receivables subject to ASC 310-30 $ 20,174 $ 29,544 $ 6,153 Acquired receivables not subject to ASC 310-30 $ 1,617,632 $ 2,143,532 $ 274,155
Anchor Bank (MN) [Member]
Summary of Fair Values of Acquired Assets, Liabilities Assumed and Resulting Goodwill	The following table reflects management’s preliminary valuation of the assets acquired and liabilities assumed (in thousands): Cash and cash equivalents $ 34,501 Investment securities 302,195 FHLB/Federal Reserve Bank stock 6,585 Loans held for sale 1,407 Loans 1,593,991 Premises and equipment 33,556 Accrued interest receivable 5,872 Other real estate owned 1,058 Company-owned life insurance 44,490 Other assets 29,872 Deposits (1,777,449 ) Federal funds purchased and interbank borrowings (45,600 ) Securities sold under agreements to repurchase (22,965 ) Other borrowings (49,257 ) Accrued expenses and other liabilities (25,784 ) Net tangible assets acquired 132,472 Definite-lived intangible assets acquired 27,260 Goodwill 173,033 Total consideration $ 332,765
Summary of Acquired Loan Data	Acquired loan data for Anchor (MN) can be found in the table below: (in thousands) Fair Value Gross Contractual Best Estimate at Acquired receivables subject to ASC 310-30 $ 10,555 $ 16,898 $ 4,787 Acquired receivables not subject to ASC 310-30 $ 1,583,436 $ 1,879,449 $ 87,767

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Investment Securities Portfolio	The following table summarizes the amortized cost and fair value of the available-for-sale held-to-maturity (dollars in thousands) Amortized Unrealized Unrealized Fair Value December 31, 2017 Available-for-Sale U.S. Treasury $ 5,473 $ 83 $ (5 ) $ 5,551 U.S. government-sponsored entities and agencies 675,643 3 (11,360 ) 664,286 Mortgage-backed securities - Agency 1,704,014 1,600 (37,932 ) 1,667,682 States and political subdivisions 529,835 5,085 (4,727 ) 530,193 Pooled trust preferred securities 16,605 — (8,157 ) 8,448 Other securities 321,016 1,172 (2,141 ) 320,047 Total available-for-sale $ 3,252,586 $ 7,943 $ (64,322 ) $ 3,196,207 Held-to-Maturity Mortgage-backed securities - Agency $ 6,903 153 $ — $ 7,056 States and political subdivisions 677,160 43,495 (8 ) 720,647 Total held-to-maturity $ 684,063 $ 43,648 $ (8 ) $ 727,703 December 31, 2016 Available-for-Sale U.S. Treasury $ 6,963 $ 140 $ — $ 7,103 U.S. government-sponsored entities and agencies 506,234 113 (12,391 ) 493,956 Mortgage-backed securities - Agency 1,551,465 6,923 (33,369 ) 1,525,019 States and political subdivisions 446,003 4,183 (13,502 ) 436,684 Pooled trust preferred securities 17,011 — (8,892 ) 8,119 Other securities 331,001 1,074 (5,782 ) 326,293 Total available-for-sale $ 2,858,677 $ 12,433 $ (73,936 ) $ 2,797,174 Held-to-Maturity U.S. government-sponsored entities and agencies $ 40,131 $ 427 $ — $ 40,558 Mortgage-backed securities - Agency 10,640 300 — 10,940 States and political subdivisions 694,319 38,915 (560 ) 732,674 Total held-to-maturity $ 745,090 $ 39,642 $ (560 ) $ 784,172
Schedule of Proceeds from Sales or Calls and Realized Gain and Losses of Available-for-Sale Investment Securities and Other Securities	Proceeds from sales or calls of available-for-sale Years Ended December 31, (dollars in thousands) 2017 2016 2015 Proceeds from sales of available-for-sale $ 342,233 $ 243,312 $ 343,486 Proceeds from calls of available-for-sale 88,233 635,624 404,277 Total $ 430,466 $ 878,936 $ 747,763 Realized gains on sales of available-for-sale $ 8,710 $ 5,423 $ 5,640 Realized gains on calls of available-for-sale 29 922 605 Realized losses on sales of available-for-sale (263 ) (450 ) (518 ) Realized losses on calls of available-for-sale (8 ) (147 ) (15 ) Other securities gains (losses) (1) 667 100 6 Net securities gains $ 9,135 $ 5,848 $ 5,718 (1) Other securities gains (losses) includes net realized and unrealized gains or losses associated with trading securities and mutual funds.
Expected Maturities of Investment Securities Portfolio	Weighted average yield is based on amortized cost. At December 31, 2017 (dollars in thousands) Amortized Fair Weighted Maturity Cost Value Yield Available-for-Sale Within one year $ 64,076 $ 64,084 2.13 % One to five years 420,949 417,941 2.02 Five to ten years 337,043 336,999 2.72 Beyond ten years 2,430,518 2,377,183 2.48 Total $ 3,252,586 $ 3,196,207 2.43 % Held-to-Maturity Within one year $ 22,566 $ 22,692 6.23 % One to five years 115,596 120,904 5.08 Five to ten years 159,452 167,547 4.87 Beyond ten years 386,449 416,560 5.75 Total $ 684,063 $ 727,703 5.44 %
Investment Securities with Unrealized Losses by Aggregated Major Security Type and Length of Time in Continuous Unrealized Loss Position	The following table summarizes the investment securities with unrealized losses at December 31 by aggregated major security type and length of time in a continuous unrealized loss position: Less than 12 months 12 months or longer Total Fair Unrealized Fair Unrealized Fair Unrealized (dollars in thousands) Value Losses Value Losses Value Losses December 31, 2017 Available-for-Sale U.S. Treasury $ 1,480 $ (5 ) $ — $ — $ 1,480 $ (5 ) U.S. government-sponsored entities and agencies 201,773 (1,333 ) 408,493 (10,027 ) 610,266 (11,360 ) Mortgage-backed securities—Agency 789,804 (8,692 ) 774,825 (29,240 ) 1,564,629 (37,932 ) States and political subdivisions 196,024 (1,899 ) 90,637 (2,828 ) 286,661 (4,727 ) Pooled trust preferred securities — — 8,448 (8,157 ) 8,448 (8,157 ) Other securities 61,260 (429 ) 125,517 (1,712 ) 186,777 (2,141 ) Total available-for-sale $ 1,250,341 $ (12,358 ) $ 1,407,920 $ (51,964 ) $ 2,658,261 $ (64,322 ) Held-to-Maturity States and political subdivisions $ 2,309 $ (8 ) $ — $ — $ 2,309 $ (8 ) Total held-to-maturity $ 2,309 $ (8 ) $ — $ — $ 2,309 $ (8 ) December 31, 2016 Available-for-Sale U.S. government-sponsored entities and agencies $ 432,192 $ (12,391 ) $ — $ — $ 432,192 $ (12,391 ) Mortgage-backed securities—Agency 1,177,093 (30,295 ) 57,636 (3,074 ) 1,234,729 (33,369 ) States and political subdivisions 286,351 (13,247 ) 4,919 (255 ) 291,270 (13,502 ) Pooled trust preferred securities — — 8,119 (8,892 ) 8,119 (8,892 ) Other securities 121,498 (2,734 ) 126,539 (3,048 ) 248,037 (5,782 ) Total available-for-sale $ 2,017,134 $ (58,667 ) $ 197,213 $ (15,269 ) $ 2,214,347 $ (73,936 ) Held-to-Maturity States and political subdivisions $ 59,481 $ (560 ) $ — $ — $ 59,481 $ (560 ) Total held-to-maturity $ 59,481 $ (560 ) $ — $ — $ 59,481 $ (560 )
Trust Preferred Securities	The table below summarizes the relevant characteristics of our pooled trust preferred securities as well as our single issuer trust preferred securities that are included in the “other securities” category in this footnote. Each of the pooled trust preferred securities support a more senior tranche of security holders. All three pooled trust preferred securities have experienced credit defaults. However, two of these securities have excess subordination and are not other-than-temporarily impaired as a result of their class hierarchy, which provides more loss protection. Trust preferred securities Actual Expected Excess December 31, 2017 Deferrals Defaults as Subordination (dollars in thousands) # of Issuers and Defaults a % of as a % of Lowest Unrealized Realized Currently as a % of Remaining Current Credit Amortized Fair Gain/ Losses Performing/ Original Performing Performing Class Rating (1) Cost Value (Loss) 2017 Remaining Collateral Collateral Collateral Pooled trust preferred securities: Reg Div Funding 2004 B-2 D $ 2,696 $ 273 $ (2,423 ) $ — 21/36 32.1 % 7.7 % 0.0 % Pretsl XXVII LTD B B 4,414 2,478 (1,936 ) — 34/44 16.7 % 11.8 % 33.1 % Trapeza Ser 13A A2A BBB 9,495 5,697 (3,798 ) — 49/54 4.5 % 8.3 % 53.7 % 16,605 8,448 (8,157 ) — Single Issuer trust preferred securities: Fleet Cap Tr V (BOA) BBB- 3,406 3,290 (116 ) — JP Morgan Chase Cap XIII BBB- 4,778 4,778 — — NB-Global BBB- 803 935 132 — 8,987 9,003 16 — Total $ 25,592 $ 17,451 $ (8,141 ) $ — (1) Lowest rating for the security provided by any nationally recognized credit rating agency.

Loans and Allowance for Loan 41

Loans and Allowance for Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Schedule of Composition of Loans	The composition of loans at December 31 by lending classification was as follows: December 31, (dollars in thousands) 2017 2016 Commercial (1) $ 2,717,269 $ 1,917,099 Commercial real estate: Construction (2) 374,306 357,802 Other (2) 3,980,246 2,773,051 Residential real estate 2,167,053 2,087,530 Consumer credit: Home equity 507,507 476,439 Auto 1,148,672 1,167,737 Other 223,068 230,854 Total loans 11,118,121 9,010,512 Allowance for loan losses (50,381 ) (49,808 ) Net loans $ 11,067,740 $ 8,960,704 (1) Includes direct finance leases of $29.5 million at December 31, 2017 and $10.8 million at December 31, 2016. (2) Certain commercial real estate construction loans were reclassified from commercial real estate - other due to a misclassification at December 31, 2016.
Schedule of Activity in Related Party Loans	Activity in related party loans during 2017 is presented in the following table: Year Ended (dollars in thousands) December 31, 2017 Balance at beginning of period $ 8,494 New loans 6,041 Repayments (4,885 ) Officer and director changes (169 ) Balance at end of period $ 9,481
Schedule of Activity in Allowance for Loan Losses	Old National’s activity in the allowance for loan losses for the years ended December 31, 2017, 2016, and 2015 was as follows: Commercial (dollars in thousands) Commercial Real Estate Residential Consumer Total 2017 Allowance for loan losses: Balance at beginning of period $ 21,481 $ 18,173 $ 1,643 $ 8,511 $ 49,808 Charge-offs (1,108 ) (3,700 ) (985 ) (6,924 ) (12,717 ) Recoveries 2,281 3,777 255 3,927 10,240 Provision (3,408 ) 3,186 850 2,422 3,050 Balance at end of period $ 19,246 $ 21,436 $ 1,763 $ 7,936 $ 50,381 2016 Allowance for loan losses: Balance at beginning of period $ 26,347 $ 15,993 $ 2,051 $ 7,842 $ 52,233 Charge-offs (5,047 ) (2,632 ) (800 ) (6,131 ) (14,610 ) Recoveries 3,102 4,763 174 3,186 11,225 Provision (2,921 ) 49 218 3,614 960 Balance at end of period $ 21,481 $ 18,173 $ 1,643 $ 8,511 $ 49,808 2015 Allowance for loan losses: Balance at beginning of period $ 20,670 $ 17,348 $ 2,962 $ 6,869 $ 47,849 Charge-offs (3,513 ) (1,921 ) (1,039 ) (6,404 ) (12,877 ) Recoveries 5,218 4,685 354 4,081 14,338 Provision 3,972 (4,119 ) (226 ) 3,296 2,923 Balance at end of period $ 26,347 $ 15,993 $ 2,051 $ 7,842 $ 52,233
Schedule of Recorded Investment in Loans	The following table provides Old National’s recorded investment in loans by portfolio segment at December 31, 2017 and 2016 and other information regarding the allowance: Commercial (dollars in thousands) Commercial Real Estate Residential Consumer Total December 31, 2017 Allowance for loan losses: Individually evaluated for impairment $ 3,424 $ 6,654 $ — $ — $ 10,078 Collectively evaluated for impairment 15,790 14,782 1,763 7,802 40,137 Loans acquired with deteriorated credit quality 32 — — 134 166 Total allowance for loan losses $ 19,246 $ 21,436 $ 1,763 $ 7,936 $ 50,381 Loans and leases outstanding: Individually evaluated for impairment $ 26,270 $ 66,061 $ — $ — $ 92,331 Collectively evaluated for impairment 2,685,847 4,266,665 2,155,750 1,874,002 10,982,264 Loans acquired with deteriorated credit quality 5,152 21,826 11,303 5,245 43,526 Total loans and leases outstanding $ 2,717,269 $ 4,354,552 $ 2,167,053 $ 1,879,247 $ 11,118,121 December 31, 2016 Allowance for loan losses: Individually evaluated for impairment $ 4,561 $ 3,437 $ — $ — $ 7,998 Collectively evaluated for impairment 16,838 14,717 1,643 8,334 41,532 Loans acquired with deteriorated credit quality 82 19 — 177 278 Total allowance for loan losses $ 21,481 $ 18,173 $ 1,643 $ 8,511 $ 49,808 Loans and leases outstanding: Individually evaluated for impairment $ 45,960 $ 57,230 $ — $ — $ 103,190 Collectively evaluated for impairment 1,870,289 3,040,849 2,073,950 1,866,815 8,851,903 Loans acquired with deteriorated credit quality 850 32,774 13,580 8,215 55,419 Total loans and leases outstanding $ 1,917,099 $ 3,130,853 $ 2,087,530 $ 1,875,030 $ 9,010,512
Schedule of Risk Category of Commercial and Commercial Real Estate Loans	The risk category of commercial and commercial real estate loans by class of loans at December 31, 2017 and 2016 was as follows: (dollars in thousands) Commercial Commercial Corporate Credit Exposure Real Estate - Real Estate - Credit Risk Profile by Commercial Construction Other Internally Assigned Grade 2017 2016 2017 2016 2017 2016 Grade: Pass $ 2,577,824 $ 1,750,922 $ 357,438 $ 347,325 $ 3,762,896 $ 2,669,890 Criticized 74,876 45,614 14,758 9,258 98,451 40,590 Classified - substandard 37,367 63,978 — 49 58,584 19,715 Classified - nonaccrual 24,798 53,063 2,110 1,170 30,108 33,833 Classified - doubtful 2,404 3,522 — — 30,207 9,023 Total $ 2,717,269 $ 1,917,099 $ 374,306 $ 357,802 $ 3,980,246 $ 2,773,051
Schedule of Recorded Investment in Residential and Consumer Loans Based on Payment Activity	The following table presents the recorded investment in residential and consumer loans based on payment activity as of December 31, 2017 and 2016: (dollars in thousands) Consumer Home Residential Equity Auto Other December 31, 2017 Performing $ 2,144,882 $ 502,322 $ 1,145,977 $ 217,819 Nonperforming 22,171 5,185 2,695 5,249 Total $ 2,167,053 $ 507,507 $ 1,148,672 $ 223,068 December 31, 2016 Performing $ 2,069,856 $ 472,008 $ 1,166,114 $ 223,786 Nonperforming 17,674 4,431 1,623 7,068 Total $ 2,087,530 $ 476,439 $ 1,167,737 $ 230,854
Schedule of Impaired Loans	The following table shows Old National’s impaired loans as of December 31, 2017 and 2016, respectively. Only purchased loans that have experienced subsequent impairment since the date acquired are included in the table below. Unpaid Recorded Principal Related (dollars in thousands) Investment Balance Allowance December 31, 2017 With no related allowance recorded: Commercial $ 20,557 $ 21,483 $ — Commercial Real Estate—Other 38,678 44,564 — Residential 2,443 2,464 — Consumer 1,685 2,105 — With an allowance recorded: Commercial 5,713 5,713 3,424 Commercial Real Estate—Construction 905 1,371 401 Commercial Real Estate—Other 26,478 26,902 6,253 Residential 870 870 44 Consumer 2,211 2,228 110 Total $ 99,540 $ 107,700 $ 10,232 December 31, 2016 With no related allowance recorded: Commercial $ 29,001 $ 29,634 $ — Commercial Real Estate—Other 30,585 32,413 — Residential 1,610 1,631 — Consumer 827 946 — With an allowance recorded: Commercial 16,959 17,283 4,561 Commercial Real Estate—Construction 467 467 107 Commercial Real Estate—Other 26,178 26,710 3,330 Residential 1,081 1,081 54 Consumer 1,924 1,924 96 Total $ 108,632 $ 112,089 $ 8,148
Schedule of Average Balance of Impaired Loans	The average balance of impaired loans for the years ended December 31, 2017 and 2016 are included in the table below. Years Ended December 31, (dollars in thousands) 2017 2016 Average Recorded Investment With no related allowance recorded: Commercial $ 24,780 $ 34,708 Commercial Real Estate—Other 34,632 28,793 Residential 2,415 1,355 Consumer 1,761 855 With an allowance recorded: Commercial 7,002 16,669 Commercial Real Estate—Construction 453 352 Commercial Real Estate—Other 26,562 20,465 Residential 1,012 1,074 Consumer 2,155 2,367 Total $ 100,772 $ 106,638
Schedule of Past Due Loans	Old National’s past due loans as of December 31 were as follows: Recorded Investment > 30-59 Days 60-89 Days 90 Days and Total (dollars in thousands) Past Due Past Due Accruing Nonaccrual Past Due Current December 31, 2017 Commercial $ 986 $ 360 $ 144 $ 27,202 $ 28,692 $ 2,688,577 Commercial Real Estate: Construction — — — 2,110 2,110 372,196 Other 2,247 89 — 60,315 62,651 3,917,595 Residential 18,948 3,416 — 22,171 44,535 2,122,518 Consumer: Home equity 1,467 230 68 5,185 6,950 500,557 Auto 6,487 1,402 532 2,695 11,116 1,137,556 Other 3,967 1,514 150 5,249 10,880 212,188 Total $ 34,102 $ 7,011 $ 894 $ 124,927 $ 166,934 $ 10,951,187 December 31, 2016 Commercial $ 847 $ 279 $ 23 $ 56,585 $ 57,734 $ 1,859,365 Commercial Real Estate: Construction — — — 1,170 1,170 356,632 Other 1,652 150 — 42,856 44,658 2,728,393 Residential 17,786 3,770 2 17,674 39,232 2,048,298 Consumer: Home equity 1,511 423 — 4,431 6,365 470,074 Auto 5,903 1,037 242 1,623 8,805 1,158,932 Other 3,561 1,919 61 7,068 12,609 218,245 Total $ 31,260 $ 7,578 $ 328 $ 131,407 $ 170,573 $ 8,839,939
Schedule of Activity in Trouble Debt Restructurings	The following table presents activity in TDRs for the years ended December 31, 2017, 2016, and 2015: (dollars in thousands) Commercial Commercial Residential Consumer Total 2017 Balance at beginning of period $ 16,802 $ 18,327 $ 2,985 $ 2,602 $ 40,716 (Charge-offs)/recoveries 417 381 — (294 ) 504 Payments (22,340 ) (12,183 ) (623 ) (1,038 ) (36,184 ) Additions 13,388 27,749 938 2,568 44,643 Interest collected on nonaccrual loans 3,821 431 15 57 4,324 Balance at end of period $ 12,088 $ 34,705 $ 3,315 $ 3,895 $ 54,003 2016 Balance at beginning of period $ 23,354 $ 14,602 $ 2,693 $ 3,602 $ 44,251 (Charge-offs)/recoveries (1,982 ) 953 42 (6 ) (993 ) Payments (21,956 ) (10,157 ) (513 ) (1,381 ) (34,007 ) Additions 14,996 11,130 761 385 27,272 Interest collected on nonaccrual loans 2,390 1,799 2 2 4,193 Balance at end of period $ 16,802 $ 18,327 $ 2,985 $ 2,602 $ 40,716 2015 Balance at beginning of period $ 15,205 $ 15,226 $ 2,063 $ 2,459 $ 34,953 (Charge-offs)/recoveries 872 1,064 (64 ) 3 1,875 Payments (29,913 ) (6,273 ) (658 ) (1,168 ) (38,012 ) Additions 37,190 4,585 1,352 2,308 45,435 Balance at end of period $ 23,354 $ 14,602 $ 2,693 $ 3,602 $ 44,251
Schedule of Loans by Class Modified as Troubled Debt Restructuring	The following table presents loans by class modified as TDRs that occurred during the years ended December 31, 2017, 2016, and 2015: (dollars in thousands) Number Pre-modification Post-modification 2017 Troubled Debt Restructuring: Commercial 11 $ 13,388 $ 13,388 Commercial Real Estate—Other 12 27,749 27,749 Residential 6 938 938 Consumer 7 2,568 2,568 Total 36 $ 44,643 $ 44,643 2016 Troubled Debt Restructuring: Commercial 20 $ 14,996 $ 14,996 Commercial Real Estate—Other 10 11,130 11,130 Residential 6 761 761 Consumer 8 385 385 Total 44 $ 27,272 $ 27,272 2015 Troubled Debt Restructuring: Commercial 42 $ 37,190 $ 37,190 Commercial Real Estate—Construction 5 1,162 1,162 Commercial Real Estate—Other 27 3,423 3,423 Residential 13 1,352 1,352 Consumer 32 2,308 2,308 Total 119 $ 45,435 $ 45,435
Schedule of Activity of Purchased Impaired Loans	For these loans that meet the criteria of ASC 310-30 December 31, (dollars in thousands) 2017 2016 Commercial $ 5,152 $ 850 Commercial real estate 21,826 32,774 Residential 11,303 13,580 Consumer 5,245 8,215 Carrying amount 43,526 55,419 Allowance for loan losses (166 ) (278 ) Carrying amount, net of allowance $ 43,360 $ 55,141
Schedule of Accretable Yield of PCI Loans, or Income Expected to be Collected	Accretable yield of PCI loans, or income expected to be collected, was as follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Balance at beginning of period $ 33,603 $ 45,310 $ 62,533 New loans purchased 1,556 3,217 1,812 Accretion of income (15,217 ) (23,447 ) (35,526 ) Reclassifications from (to) nonaccretable difference 7,614 10,589 14,189 Disposals/other adjustments 279 (2,066 ) 2,302 Balance at end of period $ 27,835 $ 33,603 $ 45,310
Schedule of Receivables for which Contractually Required Payments would not be Collected	PCI loans purchased during 2017 and 2016 for which it was probable at acquisition that all contractually required payments would not be collected were as follows: (dollars in thousands) Anchor (MN) (1) Anchor (WI) (2) Contractually required payments $ 16,898 $ 29,544 Nonaccretable difference (4,787 ) (6,153 ) Cash flows expected to be collected at acquisition 12,111 23,391 Accretable yield (1,556 ) (3,217 ) Fair value of acquired loans at acquisition $ 10,555 $ 20,174 (1) Old National acquired Anchor (MN) effective November 1, 2017. (2) Old National acquired Anchor (WI) effective May 1, 2016.

Other Real Estate Owned (Tables

Other Real Estate Owned (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Activity in Other Real Estate Owned	The following table presents activity in other real estate owned for the years ended December 31, 2017 and 2016: Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 18,546 $ 12,498 Additions (1) 4,016 24,998 Sales (11,160 ) (15,092 ) Impairment (2,592 ) (3,858 ) Balance at end of period (2) $ 8,810 $ 18,546 (1) Additions in 2017 include other real estate owned of $1.1 million acquired from Anchor (MN) in November 2017. Additions in 2016 include other real estate owned of $17.3 million acquired from Anchor (WI) in May 2016. (2) Includes repossessed personal property of $0.3 million at December 31, 2017 and $0.3 million at December 31, 2016.

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Summary of Premises and Equipment	The composition of premises and equipment was as follows at December 31: December 31, (dollars in thousands) 2017 2016 Land $ 73,046 $ 71,769 Buildings 343,833 322,165 Furniture, fixtures, and equipment 94,254 102,631 Leasehold improvements 38,918 28,555 Total 550,051 525,120 Accumulated depreciation (91,977 ) (95,498 ) Premises and equipment, net $ 458,074 $ 429,622
Summary of Future Minimum Lease Commitments	The following is a summary of future minimum lease commitments as of December 31, 2017: (dollars in thousands) 2018 $ 18,919 2019 17,463 2020 16,865 2021 15,960 2022 13,759 Thereafter 63,828 Total $ 146,794

Goodwill and Other Intangible44

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Amount of Goodwill	The following table shows the changes in the carrying amount of goodwill for the years ended December 31, 2017 and 2016: Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 655,018 $ 584,634 Acquisitions 173,033 111,347 Divestitures — (40,963 ) Balance at end of period $ 828,051 $ 655,018
Schedule of Gross Carrying Amounts and Accumulated Amortization of Other Intangible Assets	The gross carrying amounts and accumulated amortization of other intangible assets at December 31, 2017 and 2016 was as follows: (dollars in thousands) Gross Accumulated Net December 31, 2017 Core deposit $ 108,923 $ (62,874 ) $ 46,049 Customer trust relationships 16,547 (9,533 ) 7,014 Customer loan relationships 4,413 (4,380 ) 33 Total intangible assets $ 129,883 $ (76,787 ) $ 53,096 December 31, 2016 Core deposit $ 81,663 $ (53,214 ) $ 28,449 Customer trust relationships 16,547 (7,753 ) 8,794 Customer loan relationships 4,413 (3,979 ) 434 Total intangible assets $ 102,623 $ (64,946 ) $ 37,677
Schedule of Estimated Amortization Expense for Future Years	Estimated amortization expense for future years is as follows: (dollars in thousands) 2018 $ 13,561 2019 11,115 2020 8,765 2021 6,498 2022 4,665 Thereafter 8,492 Total $ 53,096

Loan Servicing Rights (Tables)

Loan Servicing Rights (Tables)	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Components of Loan Servicing Rights and Valuation Allowance	The following table summarizes the activity related to loan servicing rights and the related valuation allowance in 2017 and 2016: Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 25,629 $ 10,502 Additions (1) 4,206 20,280 Amortization (5,145 ) (5,153 ) Balance before valuation allowance at end of period 24,690 25,629 Valuation allowance: Balance at beginning of period (68 ) (34 ) (Additions)/recoveries 39 (34 ) Balance at end of period (29 ) (68 ) Loan servicing rights, net $ 24,661 $ 25,561 (1) Additions in 2016 include loan servicing rights of $15.3 million acquired from Anchor (WI) in May 2016.

Qualified Affordable Housing 46

Qualified Affordable Housing Projects and Other Tax Credit Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Schedule of Qualified Affordable Housing Projects and Other Tax Credit Investments	The following table summarizes Old National’s investments in qualified affordable housing projects and other tax credit investments at December 31, 2017 and 2016: (dollars in thousands) December 31, 2017 December 31, 2016 Investment Accounting Method Investment Unfunded Investment Unfunded LIHTC Proportional amortization $ 31,183 $ 15,553 $ 29,110 $ 16,210 FHTC Equity 10,645 12,040 4,434 3,104 CReED Equity 704 1,502 1,504 1,502 Renewable Energy Equity 22,364 19,771 — — Total $ 64,896 $ 48,866 $ 35,048 $ 20,816 (1) All commitments will be paid by Old National by 2027. The following table summarizes the amortization expense and tax benefit recognized for Old National’s qualified affordable housing projects and other tax credit investments during 2017, 2016, and 2015: (dollars in thousands) Amortization Tax Benefit Year ended December 31, 2017 LIHTC $ 1,922 $ (2,666 ) FHTC 10,441 (11,348 ) CReED (3) 800 (1,074 ) Renewable Energy 492 (613 ) Total $ 13,655 $ (15,701 ) Year ended December 31, 2016 LIHTC $ 804 $ (1,125 ) FHTC — — CReED (3) — — Total $ 804 $ (1,125 ) Year ended December 31, 2015 LIHTC $ 804 $ (1,125 ) FHTC — — CReED (3) — — NMTC 143 (233 ) Total $ 947 $ (1,358 ) (1) The amortization expense for the LIHTC investments are included in our income tax expense. The amortization expense for the FHTC, CReED, and Renewable Energy tax credits are included in noninterest expense. (2) All of the tax benefits recognized are included in our income tax expense. The tax benefit recognized for the FHTC, CReED, and Renewable Energy investments primarily reflects the tax credits generated from the investments, and excludes the net tax expense/benefit of the investments’ income/loss. (3) The CReED tax credit investment qualifies for an Indiana state tax credit.

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Schedule of Maturities of Total Time Deposits	At December 31, 2017, the scheduled maturities of total time deposits were as follows: (dollars in thousands) Due in 2018 $ 1,111,266 Due in 2019 229,944 Due in 2020 139,689 Due in 2021 62,777 Due in 2022 45,802 Thereafter 44,958 Total $ 1,634,436

Securities Sold Under Agreeme48

Securities Sold Under Agreements to Repurchase (Tables)	12 Months Ended
	Dec. 31, 2017
Transfers and Servicing [Abstract]
Schedule of Securities Sold under Agreements to Repurchase and Related Weighted-Average Interest Rates	The following table presents securities sold under agreements to repurchase and related weighted-average interest rates for each of the years ended December 31: At or For the (dollars in thousands) 2017 2016 Outstanding at year-end $ 384,810 $ 367,052 Average amount outstanding 336,539 368,757 Maximum amount outstanding at any month-end 402,543 396,695 Weighted average interest rate: During year 0.38 % 0.41 % End of year 0.49 0.47
Schedule of Remaining Contractual Maturity of Secured Borrowings and Class of Collateral Pledged Under Repurchase Agreements	The following table presents the contractual maturity of our secured borrowings and class of collateral pledged: At December 31, 2017 Remaining Contractual Maturity of the Agreements (dollars in thousands) Overnight and Up to 30 Days 30-90 Days Greater Than Total Repurchase Agreements: U.S. Treasury and agency securities $ 359,810 $ 25,000 $ — $ — $ 384,810 Total $ 359,810 $ 25,000 $ — $ — $ 384,810

Federal Home Loan Bank Advanc49

Federal Home Loan Bank Advances (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Summary of FHLB Advances	The following table summarizes Old National Bank’s FHLB advances at December 31: December 31, (dollars in thousands) 2017 2016 FHLB advances (fixed rates 1.01% to 6.08% and variable rates 1.35% to 1.57%) maturing January 2018 to August 2027 $ 1,610,531 $ 1,353,225 ASC 815 fair value hedge and other basis adjustments (952 ) (133 ) Total other borrowings $ 1,609,579 $ 1,353,092
Summary of Contractual Maturities of FHLB Advances	Contractual maturities of FHLB advances at December 31, 2017 were as follows: (dollars in thousands) Due in 2018 $ 999,896 Due in 2019 201,962 Due in 2020 50,000 Due in 2021 — Due in 2022 58,500 Thereafter 300,173 ASC 815 fair value hedge and other basis adjustments (952 ) Total $ 1,609,579

Other Borrowings (Tables)

Other Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Other Borrowings	The following table summarizes Old National’s other borrowings at December 31: December 31, (dollars in thousands) 2017 2016 Old National Bancorp: Senior unsecured bank notes (fixed rate 4.125%) maturing August 2024 $ 175,000 $ 175,000 Unamortized debt issuance costs related to Senior unsecured bank notes (1,026 ) (1,182 ) Junior subordinated debentures (variable rates of 2.89% to 5.06%) maturing April 2032 to September 2037 60,310 45,000 Other basis adjustments (3,585 ) (3,971 ) Old National Bank: Capital lease obligations 5,389 4,092 Subordinated debentures (fixed rate 5.75%) 12,000 — Premium on subordinated debentures 694 — Total other borrowings $ 248,782 $ 218,939
Contractual Maturities of Other Borrowings	Contractual maturities of other borrowings at December 31, 2017 were as follows: (dollars in thousands) Due in 2018 $ 127 Due in 2019 137 Due in 2020 147 Due in 2021 160 Due in 2022 172 Thereafter 251,956 Unamortized debt issuance costs and other basis adjustments (3,917 ) Total $ 248,782
Future Minimum Lease Payments under Capital Lease Arrangements	At December 31, 2017, the future minimum lease payments under the capital lease arrangements were as follows: (dollars in thousands) 2018 $ 568 2019 589 2020 589 2021 589 2022 590 Thereafter 9,274 Total minimum lease payments 12,199 Less amounts representing interest (6,810 ) Present value of net minimum lease payments $ 5,389
Junior Subordinated Debt [Member]
Other Borrowings	The following table summarizes the terms of our outstanding junior subordinated debentures as of December 31, 2017: (dollars in thousands) Rate at Issuance December 31, Name of Trust Issuance Date Amount Rate 2017 Maturity Date VFSC Capital Trust I April 2002 $ 3,093 3-month 5.06 % April 22, 2032 VFSC Capital Trust II October 2002 4,124 3-month LIBOR plus 3.45% 4.84 % November 7, 2032 VFSC Capital Trust III April 2004 3,093 3-month 4.12 % September 8, 2034 St. Joseph Capital Trust II March 2005 5,000 3-month 3.35 % March 20, 2035 Anchor Capital Trust III August 2005 5,000 3-month 2.89 % August 23, 2035 Tower Capital Trust 2 December 2005 8,000 3-month 3.03 % December 4, 2035 Home Federal Statutory Trust I September 2006 15,000 3-month 3.24 % September 15, 2036 Monroe Bancorp Capital Trust I July 2006 3,000 3-month 2.95 % October 7, 2036 Monroe Bancorp Statutory Trust II March 2007 5,000 3-month 3.19 % June 15, 2037 Tower Capital Trust 3 December 2006 9,000 3-month 3.17 % September 15, 2037 Total $ 60,310

Accumulated Other Comprehensi51

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of AOCI	The following table summarizes the changes within each classification of AOCI, net of tax, for the years ended December 31, 2017, 2016, and 2015: (dollars in thousands) Unrealized Gains Available-for-Sale Unrealized Gains Held-to-Maturity Gains and Defined Total 2017 Balance at beginning of period $ (39,012 ) $ (13,310 ) $ (6,715 ) $ (335 ) $ (59,372 ) Other comprehensive income (loss) before reclassifications 9,615 — 575 — 10,190 Amounts reclassified from AOCI (1) (6,160 ) 1,203 3,803 64 (1,090 ) Net other comprehensive income (loss) 3,455 1,203 4,378 64 9,100 Balance at end of period $ (35,557 ) $ (12,107 ) $ (2,337 ) $ (271 ) $ (50,272 ) 2016 Balance at beginning of period $ (3,806 ) $ (14,480 ) $ (9,276 ) $ (7,235 ) $ (34,797 ) Other comprehensive income (loss) before reclassifications (31,513 ) — (1,440 ) — (32,953 ) Amounts reclassified from AOCI (1) (3,693 ) 1,170 4,001 6,900 8,378 Net other comprehensive income (loss) (35,206 ) 1,170 2,561 6,900 (24,575 ) Balance at end of period $ (39,012 ) $ (13,310 ) $ (6,715 ) $ (335 ) $ (59,372 ) 2015 Balance at beginning of period $ (748 ) $ (15,776 ) $ (5,935 ) $ (9,096 ) $ (31,555 ) Other comprehensive income (loss) before reclassifications 554 — (5,027 ) — (4,473 ) Amounts reclassified from AOCI (1) (3,612 ) 1,296 1,686 1,861 1,231 Net other comprehensive income (loss) (3,058 ) 1,296 (3,341 ) 1,861 (3,242 ) Balance at end of period $ (3,806 ) $ (14,480 ) $ (9,276 ) $ (7,235 ) $ (34,797 )
Reclassifications out of Accumulated Other Comprehensive Income (Loss)	The following tables summarize the significant amounts reclassified out of each component of AOCI for the years ended December 31, 2017, 2016, and 2015: Details about AOCI Components Amount Reclassified from AOCI Affected Line Item in the Statement of Income Years Ended December 31, (dollars in thousands) 2017 2016 2015 Unrealized gains and losses on available-for-sale $ 9,135 $ 5,848 $ 5,718 Net securities gains (2,975 ) (2,155 ) (2,106 ) Income tax (expense) benefit $ 6,160 $ 3,693 $ 3,612 Net income Unrealized gains and losses on held-to-maturity $ (1,830 ) $ (1,776 ) $ (1,692 ) Interest income (expense) 627 606 396 Income tax (expense) benefit $ (1,203 ) $ (1,170 ) $ (1,296 ) Net income Gains and losses on cash flow hedges Interest rate contracts $ (6,135 ) $ (6,453 ) $ (2,719 ) Interest income (expense) 2,332 2,452 1,033 Income tax (expense) benefit $ (3,803 ) $ (4,001 ) $ (1,686 ) Net income Amortization of defined benefit pension items Actuarial gains (losses) and settlement cost $ (159 ) $ (11,203 ) $ (3,002 ) Salaries and employee benefits 95 4,303 1,141 Income tax (expense) benefit $ (64 ) $ (6,900 ) $ (1,861 ) Net income Total reclassifications for the period $ 1,090 $ (8,378 ) $ (1,231 ) Net income

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Summary of Differences in Taxes from Continuing Operations Computed at Statutory Rate	Following is a summary of the major items comprising the differences in taxes from continuing operations computed at the federal statutory rate and as recorded in the consolidated statement of income: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Provision at statutory rate of 35% $ 59,032 $ 70,149 $ 57,013 Tax-exempt Tax-exempt (15,026 ) (14,356 ) (13,111 ) Section 291/265 interest disallowance 289 191 142 Company-owned life insurance income (3,029 ) (2,968 ) (3,011 ) Tax-exempt (17,766 ) (17,133 ) (15,980 ) Reserve for unrecognized tax benefits — (1 ) (5 ) State income taxes 998 3,461 4,173 Tax credit investments—federal (8,500 ) (321 ) (411 ) Estimated revaluation of deferred tax assets 39,300 — — ONB Insurance Group, Inc. nondeductible goodwill — 8,328 — Effect of Illinois branch sale — — 1,835 Other, net (125 ) 1,679 (448 ) Income tax expense $ 72,939 $ 66,162 $ 46,177 Effective tax rate 43.3 % 33.0 % 28.3 %
Provision for Income Taxes	The provision for income taxes consisted of the following components for the years ended December 31: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Income taxes currently payable: Federal $ — $ 23,735 $ 17,385 State — 2,242 769 Deferred income taxes related to: Federal 31,915 35,955 24,664 Estimated revaluation of deferred tax assets 39,300 — — State 1,724 4,230 3,359 Deferred income tax expense 72,939 40,185 28,023 Income tax expense $ 72,939 $ 66,162 $ 46,177
Schedule of Significant Components of Net Deferred Tax Assets (Liabilities)	Significant components of net deferred tax assets (liabilities) were as follows at December 31: (dollars in thousands) 2017 2016 Deferred Tax Assets Allowance for loan losses, net of recapture $ 12,958 $ 19,773 Benefit plan accruals 11,080 23,846 Alternative minimum tax credit 25,084 19,523 Unrealized losses on benefit plans 108 205 Net operating loss carryforwards 39,631 66,917 Federal tax credits 5,516 35 Other-than-temporary impairment 1,424 3,606 Acquired loans 29,669 40,522 Lease exit obligation 1,337 2,060 Unrealized losses on available-for-sale 14,011 23,365 Unrealized losses on held-to-maturity 3,630 7,118 Unrealized losses on hedges 923 4,116 Other real estate owned 369 3,310 Other, net 829 2,675 Total deferred tax assets 146,569 217,071 Deferred Tax Liabilities Accretion on investment securities (493 ) (700 ) Purchase accounting (16,718 ) (17,552 ) Loan servicing rights (6,058 ) (9,627 ) Premises and equipment (10,052 ) (4,800 ) Prepaid expenses (1,277 ) — Tax credit investments (168 ) — Other, net (946 ) (2,529 ) Total deferred tax liabilities (35,712 ) (35,208 ) Net deferred tax assets $ 110,857 $ 181,863
Summary of Reconciliation of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits was as follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Balance at beginning of period $ 777 $ 124 $ 77 Additions based on tax positions related to the current year 162 118 51 Additions based on tax positions related to prior years — 537 — Reductions due to statute of limitations expiring (173 ) (2 ) (4 ) Revaluation due to Tax Reform 108 — — Balance at end of period $ 874 $ 777 $ 124

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Changes in Nonvested Restricted Stock Awards	A summary of changes in our nonvested shares for the year follows: (shares in thousands) Shares Weighted Grant-Date Year Ended December 31, 2017 Nonvested balance at beginning of period 401 $ 13.31 Granted during the year 211 17.61 Vested during the year (194 ) 13.50 Forfeited during the year (11 ) 14.97 Nonvested balance at end of period 407 $ 15.41
Summary of Changes in Nonvested Restricted Shares	A summary of changes in our nonvested shares for the year follows: (shares in thousands) Shares Weighted Grant-Date Year Ended December 31, 2017 Nonvested balance at beginning of period 821 $ 12.02 Granted during the year 278 16.31 Vested during the year (74 ) 13.47 Forfeited during the year (192 ) 12.09 Dividend equivalents adjustment 16 13.19 Nonvested balance at end of period 849 $ 13.30
Summary of Activity in Stock Option Plan	A summary of the activity in the stock option plan in 2017 follows: Weighted Weighted Average Aggregate Average Remaining Intrinsic Exercise Contractual Value (shares in thousands) Shares Price Term in Years (in thousands) Year Ended December 31, 2017 Outstanding at beginning of period 694 $ 15.27 Exercised (193 ) 14.01 Forfeited/expired (276 ) 18.89 Outstanding at end of period 225 $ 11.92 1.66 $ 1,436.0 Options exercisable at end of year 225 $ 11.92 1.66 $ 1,436.0
Schedule of Information Related to Stock Option Plan	Information related to the stock option plan during each year follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Intrinsic value of options exercised $ 806 $ 660 $ 458 Cash received from option exercises 2,655 2,349 997 Tax benefit realized from option exercises 318 264 159

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis, including financial assets and liabilities for which we have elected the fair value option, are summarized below: Fair Value Measurements at December 31, 2017 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Financial Assets Trading securities $ 5,584 $ 5,584 $ — $ — Investment securities available-for-sale: U.S. Treasury 5,551 5,551 — — U.S. government-sponsored entities and agencies 664,286 — 664,286 — Mortgage-backed securities - Agency 1,667,682 — 1,667,682 — States and political subdivisions 530,193 — 530,193 Pooled trust preferred securities 8,448 — — 8,448 Other securities 320,047 30,965 289,082 — Residential loans held for sale 17,930 — 17,930 — Derivative assets 14,118 — 14,118 — Financial Liabilities Derivative liabilities 16,292 — 16,292 — Fair Value Measurements at December 31, 2016 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Financial Assets Trading securities $ 4,982 $ 4,982 $ — $ — Investment securities available-for-sale: U.S. Treasury 7,103 7,103 — — U.S. government-sponsored entities and agencies 493,956 — 493,956 — Mortgage-backed securities - Agency 1,525,019 — 1,525,019 — States and political subdivisions 436,684 — 436,684 Pooled trust preferred securities 8,119 — — 8,119 Other securities 326,293 30,905 295,388 — Residential loans held for sale 90,682 — 90,682 — Derivative assets 17,701 — 17,701 — Financial Liabilities Derivative liabilities 23,574 — 23,574 —
Reconciliation of All Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)	The table below presents a reconciliation of all assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3): Years Ended December 31, (dollars in thousands) 2017 2016 Balance at beginning of period $ 8,119 $ 7,900 Accretion of discount 17 18 Sales/payments received (424 ) (327 ) Increase in fair value of securities 736 528 Balance at end of period $ 8,448 $ 8,119
Quantitative Information about Significant Unobservable Inputs Used in Fair Value Measurements	The table below provides quantitative information about significant unobservable inputs used in fair value measurements within Level 3 of the fair value hierarchy: (dollars in thousands) Fair Valuation Techniques Unobservable Input Range (Weighted December 31, 2017 Pooled trust preferred securities $ 8,448 Discounted cash flow Constant prepayment rate (a) 0.00% Additional asset defaults (b) 4.2% - 9.6% (7.5%) Expected asset recoveries (c) 0.0% - 4.1% (0.6%) December 31, 2016 Pooled trust preferred securities $ 8,119 Discounted cash flow Constant prepayment rate (a) 0.00% Additional asset defaults (b) 4.5% - 10.0% (7.9%) Expected asset recoveries (c) 0.0% - 6.1% (0.9%) (a) Assuming no prepayments. (b) Each currently performing pool asset is assigned a default probability based on the banking environment, which is adjusted for specific issuer evaluation, of 0%, 50%, or 100%. (c) Each currently defaulted pool asset is assigned a recovery probability based on specific issuer evaluation of 0%, 25%, or 100%. The table below provides quantitative information about significant unobservable inputs used in fair value measurements within Level 3 of the fair value hierarchy: Valuation Unobservable Range (Weighted (dollars in thousands) Fair Value Techniques Input Average) December 31, 2017 Collateral Dependent Impaired Loans Commercial loans $ 2,217 Fair value of collateral Discount for type of property, age of appraisal, and current status 0% - 98% (49%) Commercial real estate loans 26,319 Fair value of collateral Discount for type of property, age of appraisal and current status 10% -78% (32%) Foreclosed Assets Commercial real estate 1,726 Fair value of collateral Discount for type of property, age of appraisal, and current status 7% - 25% (18%) Residential (1) 55 Fair value of collateral Discount for type of property, age of appraisal, and current status 39% (1) There was only one foreclosed residential asset at December 31, 2017, so no range or weighted average rate is reported. December 31, 2016 Collateral Dependent Impaired Loans Commercial loans $ 6,771 Fair value of collateral Discount for type of property, age of appraisal, and current status 0% - 99% (53%) Commercial real estate loans 11,632 Fair value of collateral Discount for type of property, age of appraisal, and current status 10% - 67% (36%) Foreclosed Assets Commercial real estate 1,352 Fair value of collateral Discount for type of property, age of appraisal, and current status 4% - 80% (39%) Residential 394 Fair value of collateral Discount for type of property, age of appraisal, and current status 7% - 60% (30%)
Assets Measured at Fair Value on a Non-Recurring Basis	Assets measured at fair value on a non-recurring Fair Value Measurements at December 31, 2017 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Collateral Dependent Impaired Loans: Commercial loans $ 2,217 $ — $ — $ 2,217 Commercial real estate loans 26,319 — — 26,319 Foreclosed Assets: Commercial real estate 1,726 — — 1,726 Residential 55 — — 55 Loan servicing rights 2,964 — 2,964 — Assets measured at fair value on a non-recurring Fair Value Measurements at December 31, 2016 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Collateral Dependent Impaired Loans: Commercial loans $ 6,771 $ — $ — $ 6,771 Commercial real estate loans 11,632 — — 11,632 Foreclosed Assets: Commercial real estate 1,352 — — 1,352 Residential 394 — — 394 Loan servicing rights 2,181 — 2,181 —
Schedule of Difference Between the Aggregate Fair Value and the Aggregate Remaining Principal Balance	The difference between the aggregate fair value and the aggregate remaining principal balance for loans for which the fair value option has been elected as of December 31, 2017 and 2016 was as follows: Aggregate Contractual (dollars in thousands) Fair Value Difference Principal December 31, 2017 Residential loans held for sale $ 17,930 $ 546 $ 17,384 December 31, 2016 Residential loans held for sale $ 90,682 $ 133 $ 90,549 The following table presents the amount of gains and losses from fair value changes included in income before income taxes for financial assets carried at fair value for the years ended December 31: Total Changes in Fair Values Other Included in Gains and Interest Interest Current Period (dollars in thousands) (Losses) Income (Expense) Earnings Year Ended December 31, 2017 Residential loans held for sale $ 409 $ 4 $ — $ 413 Year Ended December 31, 2016 Residential loans held for sale $ (103 ) $ — $ — $ (103 )
Carrying Amounts and Estimated Fair Values of Financial Instruments, Not Previously Presented	The carrying amounts and estimated fair values of financial instruments, not previously presented in this note, at December 31, 2017 and 2016 were as follows: Fair Value Measurements at December 31, 2017 Using Significant Quoted Prices in Other Significant Active Markets for Observable Unobservable Carrying Identical Assets Inputs Inputs (dollars in thousands) Value (Level 1) (Level 2) (Level 3) Financial Assets Cash, due from banks, money market, and other interest-earning investments $ 290,432 $ 290,432 $ — $ — Investment securities held-to-maturity: Mortgage-backed securities—Agency 6,903 — 7,056 — State and political subdivisions 677,160 — 720,647 — FHLB/Federal Reserve Bank stock 119,686 N/A N/A N/A Loans, net: Commercial 2,698,023 — — 2,707,385 Commercial real estate 4,333,116 — — 4,347,949 Residential real estate 2,165,290 — — 2,210,951 Consumer credit 1,871,311 — — 1,998,194 Accrued interest receivable 87,102 16 24,001 63,085 Financial Liabilities Deposits: Noninterest-bearing demand deposits $ 3,680,807 $ 3,680,807 $ — $ — NOW, savings, and money market deposits 7,290,521 7,290,521 — — Time deposits 1,634,436 — 1,620,685 — Federal funds purchased and interbank borrowings 335,033 335,033 — — Securities sold under agreements to repurchase 384,810 359,810 25,133 — FHLB advances 1,609,579 — — 1,607,189 Other borrowings 248,782 — 250,443 — Accrued interest payable 7,029 — 7,029 — Standby letters of credit 351 — — 351 Off-Balance Commitments to extend credit $ — $ — $ — $ 2,449 N/A = not applicable Fair Value Measurements at December 31, 2016 Using (dollars in thousands) Carrying Quoted Prices in Significant Significant (Level 3) Financial Assets Cash, due from banks, money market, and other interest-earning investments $ 255,519 $ 255,519 $ — $ — Investment securities held-to-maturity: U.S. government-sponsored entities and agencies 40,131 — 40,558 — Mortgage-backed securities - Agency 10,640 — 10,940 — State and political subdivisions 694,319 — 732,674 — FHLB/Federal Reserve Bank stock 101,716 N/A N/A N/A Loans, net: Commercial 1,895,618 — — 1,971,296 Commercial real estate 3,112,680 — — 3,400,365 Residential real estate 2,085,887 — — 2,228,542 Consumer credit 1,866,519 — — 1,974,180 Accrued interest receivable 81,381 16 22,880 58,485 Financial Liabilities Deposits: Noninterest-bearing demand deposits $ 3,016,093 $ 3,016,093 $ — $ — NOW, savings, and money market deposits 6,259,052 6,259,052 — — Time deposits 1,468,108 — 1,460,778 — Federal funds purchased and interbank borrowings 213,003 213,003 — — Securities sold under agreements to repurchase 367,052 317,052 50,612 — FHLB advances 1,353,092 — — 1,360,599 Other borrowings 218,939 — 217,647 — Accrued interest payable 5,979 — 5,979 — Standby letters of credit 315 — — 315 Off-Balance Commitments to extend credit $ — $ — $ — $ 2,527 N/A = not applicable

Derivative Financial Instrume55

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Fair Value of Derivative Financial Instruments	The following table summarizes the fair value of derivative financial instruments utilized by Old National: December 31, 2017 December 31, 2016 (dollars in thousands) Asset Liability Asset Liability Derivatives designated as hedging instruments Interest rate contracts $ 3,351 $ 5,351 $ 3,056 $ 11,582 Total derivatives designated as hedging instruments $ 3,351 $ 5,351 $ 3,056 $ 11,582 Derivatives not designated as hedging instruments Interest rate contracts $ 10,012 $ 10,933 $ 11,903 $ 11,992 Mortgage contracts 747 — 2,742 — Foreign currency contracts 8 8 — — Total derivatives not designated as hedging instruments $ 10,767 $ 10,941 $ 14,645 $ 11,992 Total $ 14,118 $ 16,292 $ 17,701 $ 23,574
Schedule of Effect of Derivative Instruments on the Consolidated Statements of Income	The effect of derivative instruments on the consolidated statements of income for the years ended December 31 were as follows: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Derivatives in Fair Value Hedging Relationships Location of Gain or (Loss) Recognized in Amount of Gain or (Loss) Interest rate contracts (1) Interest income / (expense) $ (5,695 ) $ (5,446 ) $ (1,729 ) Interest rate contracts (2) Other income / (expense) 161 126 189 Total $ (5,534 ) $ (5,320 ) $ (1,540 ) Derivatives in Cash Flow Hedging Relationships Location of Gain or (Loss) Recognized in Amount of Gain or (Loss) Interest rate contracts (1) Interest income / (expense) $ 309 $ 329 $ 511 Total $ 309 $ 329 $ 511 Derivatives Not Designated as Hedging Instruments Location of Gain or (Loss) Recognized in Amount of Gain or (Loss) Interest rate contracts (3) Other income / (expense) $ 56 $ 28 $ 18 Mortgage contracts Mortgage banking revenue (1,995 ) 1,390 168 Foreign currency contracts Other income — — — Total $ (1,939 ) $ 1,418 $ 186 (1) Amounts represent the net interest payments as stated in the contractual agreements. (2) Amounts represent ineffectiveness on derivatives designated as fair value hedges. (3) Includes the valuation differences between the customer and offsetting counterparty swaps.

Regulatory Restrictions (Tables

Regulatory Restrictions (Tables)	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Schedule of Capital Ratios	The following table summarizes capital ratios for Old National and Old National Bank as of December 31: Actual Fully Phased-In Well Capitalized (dollars in thousands) Amount Ratio Amount Ratio Amount Ratio 2017 Total capital to risk-weighted assets Old National Bancorp $ 1,424,123 11.40 % $ 1,311,600 10.50 % $ N/A N/A % Old National Bank 1,458,546 11.73 1,305,076 10.50 1,242,929 10.00 Common equity Tier 1 capital to risk-weighted assets Old National Bancorp 1,298,326 10.39 874,400 7.00 N/A N/A Old National Bank 1,393,059 11.21 870,051 7.00 807,904 6.50 Tier 1 capital to risk-weighted assets Old National Bancorp 1,298,326 10.39 1,061,772 8.50 N/A N/A Old National Bank 1,393,059 11.21 1,056,490 8.50 994,344 8.00 Tier 1 capital to average assets Old National Bancorp 1,298,326 8.28 627,258 4.00 N/A N/A Old National Bank 1,393,059 8.93 623,758 4.00 779,697 5.00 2016 Total capital to risk-weighted assets Old National Bancorp $ 1,229,878 12.18 % $ 1,060,662 10.50 % $ N/A N/A % Old National Bank 1,240,180 12.35 1,054,305 10.50 1,004,100 10.00 Common equity Tier 1 capital to risk-weighted assets Old National Bancorp 1,162,817 11.51 707,108 7.00 N/A N/A Old National Bank 1,187,151 11.82 702,870 7.00 652,665 6.50 Tier 1 capital to risk-weighted assets Old National Bancorp 1,176,849 11.65 858,631 8.50 N/A N/A Old National Bank 1,187,151 11.82 853,485 8.50 803,280 8.00 Tier 1 capital to average assets Old National Bancorp 1,176,849 8.43 558,673 4.00 N/A N/A Old National Bank 1,187,151 8.55 555,161 4.00 693,951 5.00 N/A = not applicable (1) When fully phased-in

Parent Company Financial Stat57

Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Balance Sheets	OLD NATIONAL BANCORP (PARENT COMPANY ONLY) CONDENSED BALANCE SHEETS December 31, (dollars in thousands) 2017 2016 Assets Deposits in affiliate bank $ 43,538 $ 91,650 Trading securities - at fair value 5,584 4,982 Investment securities - available-for-sale 1,547 1,535 Investment in affiliates: Banking subsidiaries 2,248,700 1,862,244 Non-banks 5,142 11,388 Other assets 112,353 90,872 Total assets $ 2,416,864 $ 2,062,671 Liabilities and Shareholders’ Equity Other liabilities $ 31,768 $ 33,407 Other borrowings 230,699 214,847 Shareholders’ equity 2,154,397 1,814,417 Total liabilities and shareholders’ equity $ 2,416,864 $ 2,062,671
Condensed Statements of Income	OLD NATIONAL BANCORP (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF INCOME Years Ended December 31, (dollars in thousands) 2017 2016 2015 Income Dividends from affiliates $ 100,000 $ 160,007 $ 67,717 Net securities gains 667 100 6 Other income 1,966 40,841 1,892 Other income from affiliates 5 6 51 Total income 102,638 200,954 69,666 Expense Interest on borrowings 9,298 9,077 8,684 Other expenses 16,335 18,460 13,957 Total expense 25,633 27,537 22,641 Income before income taxes and equity in undistributed earnings of affiliates 77,005 173,417 47,025 Income tax expense (benefit) (6,240 ) 11,952 (5,473 ) Income before equity in undistributed earnings of affiliates 83,245 161,465 52,498 Equity in undistributed earnings of affiliates 12,480 (27,201 ) 64,218 Net income $ 95,725 $ 134,264 $ 116,716
Condensed Statement of Cash Flows	OLD NATIONAL BANCORP (PARENT COMPANY ONLY) CONDENSED STATEMENT OF CASH FLOWS Years Ended December 31, (dollars in thousands) 2017 2016 2015 Cash Flows From Operating Activities Net income $ 95,725 $ 134,264 $ 116,716 Adjustments to reconcile net income to cash provided by operating activities: Depreciation 36 29 20 Net securities (gains) losses (667 ) (100 ) (6 ) Gain on sale of ONB Insurance Group, Inc. — (41,864 ) — Stock-based compensation expense 6,275 7,318 4,255 (Increase) decrease in other assets (24,004 ) (3,958 ) 6,307 Increase (decrease) in other liabilities 3,968 (225 ) 1,441 Equity in undistributed earnings of affiliates (12,480 ) 27,201 (64,218 ) Total adjustments (26,872 ) (11,599 ) (52,201 ) Net cash flows provided by (used in) operating activities 68,853 122,665 64,515 Cash Flows From Investing Activities Net cash and cash equivalents of acquisitions (24,005 ) (100,220 ) (41,070 ) Proceeds from sale of ONB Insurance Group, Inc. — 91,771 — Purchases of investment securities (62 ) (52 ) (1,053 ) Net advances to affiliates (250 ) (3,500 ) — Purchases of premises and equipment (485 ) (13 ) — Net cash flows provided by (used in) investing activities (24,802 ) (12,014 ) (42,123 ) Cash Flows From Financing Activities Payments for maturities/redemptions of other borrowings (19,856 ) — — Cash dividends paid on common stock (72,604 ) (67,536 ) (55,552 ) Common stock repurchased (2,762 ) (2,202 ) (88,695 ) Proceeds from exercise of stock options 2,655 2,349 997 Common stock issued 404 388 391 Net cash flows provided by (used in) financing activities (92,163 ) (67,001 ) (142,859 ) Net increase (decrease) in cash and cash equivalents (48,112 ) 43,650 (120,467 ) Cash and cash equivalents at beginning of period 91,650 48,000 168,467 Cash and cash equivalents at end of period $ 43,538 $ 91,650 $ 48,000

Interim Financial Data (Unaud58

Interim Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interim Financial Data	The following table details the quarterly results of operations for the years ended December 31, 2017 and 2016. (unaudited, dollars and shares in thousands, except per share data) Three Months Ended Three Months Ended 12/31/2017 9/30/2017 6/30/2017 3/31/2017 12/31/2016 9/30/2016 6/30/2016 3/31/2016 Interest income $ 135,134 $ 123,525 $ 118,209 $ 118,468 $ 121,849 $ 119,713 $ 110,243 $ 95,329 Interest expense 16,578 15,047 13,876 12,667 11,932 11,910 10,903 9,686 Net interest income 118,556 108,478 104,333 105,801 109,917 107,803 99,340 85,643 Provision for loan losses 1,037 311 1,355 347 (1,756 ) 1,306 1,319 91 Noninterest income 44,825 46,366 49,271 42,920 62,751 47,243 93,385 49,451 Noninterest expense 140,432 103,702 102,811 101,891 126,258 108,062 121,472 98,355 Income before income taxes 21,912 50,831 49,438 46,483 48,166 45,678 69,934 36,648 Income tax expense 40,405 11,459 10,584 10,491 14,710 10,969 30,812 9,671 Net income (loss) $ (18,493 ) $ 39,372 $ 38,854 $ 35,992 $ 33,456 $ 34,709 $ 39,122 $ 26,977 Net income (loss) per share: Basic $ (0.13 ) $ 0.30 $ 0.28 $ 0.27 $ 0.25 $ 0.25 $ 0.31 $ 0.24 Diluted (0.13 ) 0.29 0.28 0.27 0.25 0.25 0.31 0.24 Average shares: Basic 146,073 135,120 135,085 134,912 134,670 134,492 127,508 113,998 Diluted 146,875 135,796 135,697 135,431 135,383 135,011 127,973 114,563

Basis of Presentation and Sig59

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basis Of Presentation And Significant Accounting Policies [Line Items]
Loan placed on nonaccrual when past due, number of days									90 days
Days delinquent required for charge off									90 days
Accrued interest coverage by FDIC, number of days									90 days
Percentage of income tax examination likelihood of tax benefits									50.00%
Tax benefit recorded	$ 40,405,000	$ 11,459,000	$ 10,584,000	$ 10,491,000	$ 14,710,000	$ 10,969,000	$ 30,812,000	$ 9,671,000	$ 72,939,000	$ 66,162,000	$ 46,177,000
Retained earnings	413,130,000				$ 390,292,000				413,130,000	390,292,000
Unrealized holding gains on available-for-sale portfolio									3,455,000	(35,206,000)	(3,058,000)
Stock-based compensation expense									6,275,000	$ 7,318,000	$ 4,255,000
Accounting Standards Update 2016-09 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Stock-based compensation expense									100,000
Accounting Standards Update 2017-12 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Retained earnings	500,000								500,000
Reclassification of securities	324,000,000								324,000,000
Unrealized holding gains on available-for-sale portfolio									26,100,000
Accounting Standards Update 2017-12 [Member] | States and Political Subdivisions [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Reclassification of securities	447,000,000								447,000,000
Maximum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Value of small commercial loans on nonaccrual status or 90 days or more delinquent									$ 250,000
Maturity of short-term securities sold under agreements to repurchase									4 days
Maximum [Member] | Accounting Standards Update 2016-02 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Anticipated increase in assets and liabilities									$ 100,000,000
Maximum [Member] | Other Intangible Assets [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Estimated useful lives of core deposits and customer relationships									15 years
Minimum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Maturity of short-term securities sold under agreements to repurchase									1 day
Minimum [Member] | Accounting Standards Update 2016-02 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Anticipated increase in assets and liabilities									$ 80,000,000
Minimum [Member] | Other Intangible Assets [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Estimated useful lives of core deposits and customer relationships									5 years
Expenses up to $275.0 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Expenses sharing reimbursement threshold									80.00%
Loss amount covered at 80% up to $275 million	$ 275,000,000								$ 275,000,000
Building and Building Improvements [Member] | Maximum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful lives for premises and equipment, years									39 years
Building and Building Improvements [Member] | Minimum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful lives for premises and equipment, years									15 years
Furniture and Equipment [Member] | Maximum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful lives for premises and equipment, years									10 years
Furniture and Equipment [Member] | Minimum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Useful lives for premises and equipment, years									3 years

Basis of Presentation and Sig60

Basis of Presentation and Significant Accounting Policies - Summary of Table Reconciling Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	$ 95,725	$ 134,264	$ 116,716
Basic Earnings Per Share, Weighted average common shares outstanding									137,821	127,705	115,726
Basic Net Income Per Share	$ (0.13)	$ 0.30	$ 0.28	$ 0.27	$ 0.25	$ 0.25	$ 0.31	$ 0.24	$ 0.69	$ 1.05	$ 1.01
Net income	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	$ 95,725	$ 134,264	$ 116,716
Diluted Earnings Per Share, Weighted average common shares outstanding									137,821	127,705	115,726
Effect of dilutive securities: Restricted stock									599	543	440
Effect of dilutive securities: Stock options									93	53	89
Diluted Earnings Per Share, Weighted average shares outstanding	146,875	135,796	135,697	135,431	135,383	135,011	127,973	114,563	138,513	128,301	116,255
Diluted Earnings Per Share	$ (0.13)	$ 0.29	$ 0.28	$ 0.27	$ 0.25	$ 0.25	$ 0.31	$ 0.24	$ 0.69	$ 1.05	$ 1

Basis of Presentation and Sig61

Basis of Presentation and Significant Accounting Policies - Summary of Table Reconciling Basic and Diluted Net Income Per Share (Parenthetical) (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock [Member]
Summary Of Computation Of Basic And Diluted Earnings Per Share [Line Items]
Antidilutive securities not included in the computation of net income per diluted share	8,000	3,000	0
Stock Options [Member]
Summary Of Computation Of Basic And Diluted Earnings Per Share [Line Items]
Antidilutive securities not included in the computation of net income per diluted share	100,000	500,000	700,000

Basis of Presentation and Sig62

Basis of Presentation and Significant Accounting Policies - Summary of Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash payments:
Interest	$ 56,682	$ 43,698	$ 32,712
Income taxes (net of refunds)	4,326	23,636	14,824
Noncash Investing and Financing Activities:
Transfer of premises and equipment to assets held for sale	$ 16,617	$ 4,620	$ 9,070

Basis of Presentation and Sig63

Basis of Presentation and Significant Accounting Policies - Summary of Common Shares Issued and Resultant Value of Total Shareholders' Equity (Detail) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Total Shareholders' Equity	$ 300,828	$ 273,565
Anchor Bank (MN) [Member]
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Total Shareholders' Equity	300,828
AnchorBank WI [Member]
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Total Shareholders' Equity		273,565
Founders Financial Corporation [Member]
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Total Shareholders' Equity			$ 50,626
Common Stock [Member]
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Total Shareholders' Equity	$ 16,527	$ 20,415
Common Stock [Member] | Anchor Bank (MN) [Member]
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Shares of Common Stock	16,527
Common Stock [Member] | AnchorBank WI [Member]
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Shares of Common Stock		20,415
Common Stock [Member] | Founders Financial Corporation [Member]
Common Shares Issued and Value of Shares Holders' Equity [Line Items]
Acquisition, Shares of Common Stock			3,402
Acquisition, Total Shareholders' Equity			$ 3,402

Acquisition and Divestiture A64

Acquisition and Divestiture Activity - Additional Information (Detail) $ / shares in Units, $ in Thousands, shares in Millions	May 01, 2016BankingCenters	Aug. 14, 2015USD ($)Branches	May 31, 2016USD ($)	Dec. 31, 2017USD ($)Branch$ / sharesshares	Dec. 31, 2016USD ($)Branch	Dec. 31, 2015USD ($)Branch	Nov. 01, 2017Branch
Business Acquisition [Line Items]
Purchasers assumed loans		$ 193,600
Other transaction expense related to divestitures		900
Deposits		$ 555,800
Net pre-tax gain						$ 15,627
Goodwill allocation				$ 828,051	$ 655,018	$ 584,634
Number of banking centers consolidated | Branch				5	5	23
Cash received in acquisition					$ 91,771
Goodwill and intangible assets eliminated					$ 40,963
ONB Insurance Group, Inc. [Member]
Business Acquisition [Line Items]
Cash received in acquisition			$ 91,800
Gain on sale of assets before tax			41,900
Gain on sale of assets after tax			17,600
Goodwill and intangible assets eliminated			$ 47,500
Southern Illinois [Member]
Business Acquisition [Line Items]
Number of banking centers | Branches		12
Eastern Indiana [Member]
Business Acquisition [Line Items]
Number of banking centers | Branches		4
Ohio [Member]
Business Acquisition [Line Items]
Number of banking centers | Branches		1
Southern Illinois Franchise [Member]
Business Acquisition [Line Items]
Net pre-tax gain		$ 15,600
Deposit premium		19,300
Goodwill allocation		$ 3,800
AnchorBank WI [Member]
Business Acquisition [Line Items]
Number of banking centers | BankingCenters	46
Portion of share received by merged entity				3.5505
Consideration received in cash by merged entity | $ / shares				$ 48.50
Total fair value of consideration paid				$ 459,800
Purchase price of acquisition, cash				$ 186,200
Issuance of common stock shares for acquisitions of business | shares				20.4
Value of issuance common stock shares				$ 273,600
Acquisition related costs incurred				15,900
Goodwill allocation				$ 111,347
AnchorBank WI [Member] | Maximum [Member]
Business Acquisition [Line Items]
Maximum percentage of purchase price in cash				40.00%
AnchorBank WI [Member] | Core Deposit [Member]
Business Acquisition [Line Items]
Estimated useful life of intangible assets				7 years
Estimated fair value of intangible assets acquired				$ 21,600
AnchorBank WI [Member] | Madison Milwaukee and Fox Valley Triangle [Member]
Business Acquisition [Line Items]
Number of banking centers | BankingCenters	32
Anchor Bank (MN) [Member]
Business Acquisition [Line Items]
Portion of share received by merged entity				1.350
Consideration received in cash by merged entity | $ / shares				$ 2.625
Total fair value of consideration paid				$ 332,800
Purchase price of acquisition, cash				$ 31,900
Issuance of common stock shares for acquisitions of business | shares				300.8
Value of issuance common stock shares				$ 300,800
Acquisition related costs incurred				12,300
Goodwill allocation				$ 173,033
Anchor Bank (MN) [Member] | Core Deposit [Member]
Business Acquisition [Line Items]
Estimated useful life of intangible assets				10 years
Estimated fair value of intangible assets acquired				$ 27,300
Anchor Bank (MN) [Member] | Minnesota [Member]
Business Acquisition [Line Items]
Number of branches | Branch							17

Acquisition and Divestiture A65

Acquisition and Divestiture Activity - Summary of Fair Values of Acquired Assets, Liabilities Assumed and Resulting Goodwill (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 828,051	$ 655,018	$ 584,634
AnchorBank WI [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	123,657
Investment securities	235,240
FHLB stock	4,596
Loans held for sale	9,334
Loans	1,637,806
Premises and equipment	35,721
Accrued interest receivable	7,308
Other real estate owned	17,349
Company-owned life insurance	7,278
Other assets	126,210
Deposits	(1,852,713)
Securities sold under agreements to repurchase	(3,132)
Other borrowings	(123)
Accrued expenses and other liabilities	(36,957)
Net tangible assets acquired	311,574
Definite-lived intangible assets acquired	21,559
Loan servicing rights	15,274
Goodwill	111,347
Total consideration	459,754
Anchor Bank (MN) [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	34,501
Investment securities	302,195
FHLB/Federal Reserve Bank stock	6,585
Loans held for sale	1,407
Loans	1,593,991
Premises and equipment	33,556
Accrued interest receivable	5,872
Other real estate owned	1,058
Company-owned life insurance	44,490
Other assets	29,872
Deposits	(1,777,449)
Federal funds purchased and interbank borrowings	(45,600)
Securities sold under agreements to repurchase	(22,965)
Other borrowings	(49,257)
Accrued expenses and other liabilities	(25,784)
Net tangible assets acquired	132,472
Definite-lived intangible assets acquired	27,260
Goodwill	173,033
Total consideration	$ 332,765

Acquisition and Divestiture A66

Acquisition and Divestiture Activity - Schedule of Acquired Loan Data (Detail) $ in Thousands	Dec. 31, 2017USD ($)
AnchorBank WI [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	$ 1,637,806
AnchorBank WI [Member] | Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	20,174
Gross Contractual Amounts Receivable at Acquisition Date	29,544
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	6,153
AnchorBank WI [Member] | Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	1,617,632
Gross Contractual Amounts Receivable at Acquisition Date	2,143,532
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	274,155
Anchor Bank (MN) [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	1,593,991
Anchor Bank (MN) [Member] | Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	10,555
Gross Contractual Amounts Receivable at Acquisition Date	16,898
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	4,787
Anchor Bank (MN) [Member] | Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	1,583,436
Gross Contractual Amounts Receivable at Acquisition Date	1,879,449
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	$ 87,767

Acquisition and Divestiture A67

Acquisition and Divestiture Activity - Summary of Unaudited Pro-Forma Information (Detail) - Anchor Bank (MN) [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Revenue	$ 700,944	$ 738,280
Income before income taxes	$ 213,932	$ 214,737

Investment Securities - Amortiz

Investment Securities - Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Investment Securities Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Amortized Cost	$ 3,252,586	$ 2,858,677
Available-for-Sale, Unrealized Gains	7,943	12,433
Available-for-Sale, Unrealized Losses	(64,322)	(73,936)
Available-for-Sale securities, Fair Value	3,196,207	2,797,174
Held-to-Maturity, Amortized Cost	684,063	745,090
Held-to-Maturity, Unrealized Gains	43,648	39,642
Held-to-Maturity, Unrealized Losses	(8)	(560)
Held-to-Maturity, Fair Value	727,703	784,172
U.S. Treasury [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Amortized Cost	5,473	6,963
Available-for-Sale, Unrealized Gains	83	140
Available-for-Sale, Unrealized Losses	(5)
Available-for-Sale securities, Fair Value	5,551	7,103
U.S. Government-Sponsored Entities and Agencies [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Amortized Cost	675,643	506,234
Available-for-Sale, Unrealized Gains	3	113
Available-for-Sale, Unrealized Losses	(11,360)	(12,391)
Available-for-Sale securities, Fair Value	664,286	493,956
Held-to-Maturity, Amortized Cost		40,131
Held-to-Maturity, Unrealized Gains		427
Held-to-Maturity, Fair Value		40,558
Mortgage-Backed Securities - Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Amortized Cost	1,704,014	1,551,465
Available-for-Sale, Unrealized Gains	1,600	6,923
Available-for-Sale, Unrealized Losses	(37,932)	(33,369)
Available-for-Sale securities, Fair Value	1,667,682	1,525,019
Held-to-Maturity, Amortized Cost	6,903	10,640
Held-to-Maturity, Unrealized Gains	153	300
Held-to-Maturity, Fair Value	7,056	10,940
States and Political Subdivisions [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Amortized Cost	529,835	446,003
Available-for-Sale, Unrealized Gains	5,085	4,183
Available-for-Sale, Unrealized Losses	(4,727)	(13,502)
Available-for-Sale securities, Fair Value	530,193	436,684
Held-to-Maturity, Amortized Cost	677,160	694,319
Held-to-Maturity, Unrealized Gains	43,495	38,915
Held-to-Maturity, Unrealized Losses	(8)	(560)
Held-to-Maturity, Fair Value	720,647	732,674
Pooled Trust Preferred Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Amortized Cost	16,605	17,011
Available-for-Sale, Unrealized Losses	(8,157)	(8,892)
Available-for-Sale securities, Fair Value	8,448	8,119
Other Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Amortized Cost	321,016	331,001
Available-for-Sale, Unrealized Gains	1,172	1,074
Available-for-Sale, Unrealized Losses	(2,141)	(5,782)
Available-for-Sale securities, Fair Value	$ 320,047	$ 326,293

Investment Securities - Schedul

Investment Securities - Schedule of Proceeds from Sales or Calls and Realized Gain and Losses of Available-for-sale Investment Securities and Other Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales of available-for-sale securities	$ 342,233	$ 243,312	$ 343,486
Proceeds from calls of available-for-sale securities	438,818	1,177,130	764,649
Total	430,466	878,936	747,763
Realized gains on sales of available-for-sale securities	8,710	5,423	5,640
Realized losses on sales of available-for-sale securities	(263)	(450)	(518)
Other securities gains (losses)	667	100	6
Net securities gains	9,135	5,848	5,718
Calls [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from calls of available-for-sale securities	88,233	635,624	404,277
Realized gains on calls of available-for-sale securities	29	922	605
Realized losses on calls of available-for-sale securities	$ (8)	$ (147)	$ (15)

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)SecuritySegment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Investment [Line Items]
Proceeds from sales of investment securities held-to-maturity			$ 855,000
Net securities gains	$ 9,135,000	$ 5,848,000	5,718,000
Securities pledged to secure public and other funds, carrying value	1,800,000,000	1,400,000,000
Trading securities that consist of mutual funds	$ 5,584,000	4,982,000
Number of segments | Segment	2
OTTI losses on securities	$ 0	0	0
Number of securities in security portfolio | Security	1,789
Number of securities in unrealized loss position | Security	737
Unrealized losses	$ 64,322,000	73,936,000
Accounting Standards Update 2017-12 [Member]
Investment [Line Items]
Reclassification of securities	324,000,000
Unrealized holding loss	10,800,000
Municipal Bonds [Member]
Investment [Line Items]
Proceeds from sales of investment securities held-to-maturity			800,000
Net securities gains			$ 52,000
Eastern Indiana [Member]
Investment [Line Items]
Investment securities issued by states and political subdivisions, market value	$ 375,100,000
State and political subdivision investment, equity percentage	17.40%
Percentage of municipal bonds rated A or better	98.00%
Percentage of non rated local interest bonds	2.00%
Texas [Member]
Investment [Line Items]
Investment securities issued by states and political subdivisions, market value	$ 182,700,000
State and political subdivision investment, equity percentage	8.50%
Former Directors and Executives [Member]
Investment [Line Items]
Trading securities that consist of mutual funds	$ 5,600,000	5,000,000
Pooled Trust Preferred Securities, Subject To FASB ASC 325-10 [Member]
Investment [Line Items]
Number of trust preferred securities | Security	1
Securities portfolio at fair value	$ 300,000
Unrealized losses	$ 2,400,000
Pooled Trust Preferred Securities, Not Subject to FASB ASC 325-10 [Member]
Investment [Line Items]
Number of trust preferred securities | Security	2
Securities portfolio at fair value	$ 8,100,000
Unrealized losses	$ 5,800,000
Pooled Trust Preferred Securities [Member]
Investment [Line Items]
Number of trust preferred securities | Security	3
Securities portfolio at fair value	$ 8,400,000
Unrealized losses	8,157,000	8,892,000
OTTI losses	0	0
States and Political Subdivisions [Member]
Investment [Line Items]
Unrealized losses	4,727,000	$ 13,502,000
States and Political Subdivisions [Member] | Accounting Standards Update 2017-12 [Member]
Investment [Line Items]
Reclassification of securities	$ 447,000,000

Investment Securities - Expecte

Investment Securities - Expected Maturities of Investment Securities Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale, Maturity, Within one year, Amortized Cost	$ 64,076
Available-for-Sale, Maturity, One to five years, Amortized Cost	420,949
Available-for-Sale, Maturity, Five to ten years, Amortized Cost	337,043
Available-for-Sale, Maturity, Beyond ten years, Amortized Cost	2,430,518
Available-for-Sale, Amortized Cost	3,252,586	$ 2,858,677
Held-to-Maturity, Maturity, Within one year, Amortized Cost	22,566
Held-to-Maturity, Maturity, One to five years, Amortized Cost	115,596
Held-to-Maturity, Maturity, Five to ten years, Amortized Cost	159,452
Held-to-Maturity, Maturity, Beyond ten years, Amortized Cost	386,449
Held-to-Maturity, Amortized Cost	684,063	745,090
Available-for-Sale, Maturity, Within one year, Fair Value	64,084
Available-for-Sale, Maturity, One to five years, Fair Value	417,941
Available-for-Sale, Maturity, Five to ten years, Fair Value	336,999
Available-for-Sale, Maturity, Beyond ten years, Fair Value	2,377,183
Available-for-Sale securities, Fair Value	3,196,207	2,797,174
Held-to-Maturity, Maturity, Within one year, Fair Value	22,692
Held-to-Maturity, Maturity, One to five years, Fair Value	120,904
Held-to-Maturity, Maturity, Five to ten years, Fair Value	167,547
Held-to-Maturity, Maturity, Beyond ten years, Fair Value	416,560
Held-to-Maturity, Fair Value	$ 727,703	$ 784,172
Available-for-Sale, Maturity, Within one year, Weighted Average Yield	2.13%
Available-for-Sale, Maturity, One to five years, Weighted Average Yield	2.02%
Available-for-Sale, Maturity, Five to ten years, Weighted Average Yield	2.72%
Available-for-Sale, Maturity, Beyond ten years, Weighted Average Yield	2.48%
Available-for-Sale, Weighted Average Yield	2.43%
Held-to-Maturity, Maturity, Within one year, Weighted Average Yield	6.23%
Held-to-Maturity, Maturity, One to five years, Weighted Average Yield	5.08%
Held-to-Maturity, Maturity, Five to ten years, Weighted Average Yield	4.87%
Held-to-Maturity, Maturity, Beyond ten years, Weighted Average Yield	5.75%
Held-to-Maturity, Weighted Average Yield	5.44%

Investment Securities - Investm

Investment Securities - Investment Securities with Unrealized Losses by Aggregated Major Security Type and Length of Time in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	$ 1,250,341	$ 2,017,134
Available-for-Sale, Less than 12 Months, Unrealized Losses	(12,358)	(58,667)
Available-for-Sale, 12 months or longer, Fair Value	1,407,920	197,213
Available-for-Sale, 12 months or longer, Unrealized Losses	(51,964)	(15,269)
Available-for-Sale, Fair Value	2,658,261	2,214,347
Available-for-Sale, Unrealized Losses	(64,322)	(73,936)
Held-to-Maturity, Less than 12 Months, Fair Value	2,309	59,481
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(8)	(560)
Held-to-Maturity, 12 months or longer, Fair Value	0	0
Held-to-Maturity, 12 months or longer, Unrealized Losses	0	0
Held-to-Maturity, Fair Value	2,309	59,481
Held-to-Maturity, Unrealized Losses	(8)	(560)
U.S. Treasury [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	1,480
Available-for-Sale, Less than 12 Months, Unrealized Losses	(5)
Available-for-Sale, Fair Value	1,480
Available-for-Sale, Unrealized Losses	(5)
U.S. Government-Sponsored Entities and Agencies [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	201,773	432,192
Available-for-Sale, Less than 12 Months, Unrealized Losses	(1,333)	(12,391)
Available-for-Sale, 12 months or longer, Fair Value	408,493
Available-for-Sale, 12 months or longer, Unrealized Losses	(10,027)
Available-for-Sale, Fair Value	610,266	432,192
Available-for-Sale, Unrealized Losses	(11,360)	(12,391)
Mortgage-Backed Securities - Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	789,804	1,177,093
Available-for-Sale, Less than 12 Months, Unrealized Losses	(8,692)	(30,295)
Available-for-Sale, 12 months or longer, Fair Value	774,825	57,636
Available-for-Sale, 12 months or longer, Unrealized Losses	(29,240)	(3,074)
Available-for-Sale, Fair Value	1,564,629	1,234,729
Available-for-Sale, Unrealized Losses	(37,932)	(33,369)
States and Political Subdivisions [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	196,024	286,351
Available-for-Sale, Less than 12 Months, Unrealized Losses	(1,899)	(13,247)
Available-for-Sale, 12 months or longer, Fair Value	90,637	4,919
Available-for-Sale, 12 months or longer, Unrealized Losses	(2,828)	(255)
Available-for-Sale, Fair Value	286,661	291,270
Available-for-Sale, Unrealized Losses	(4,727)	(13,502)
Held-to-Maturity, Less than 12 Months, Fair Value	2,309	59,481
Held-to-Maturity, Less than 12 Months, Unrealized Losses	(8)	(560)
Held-to-Maturity, 12 months or longer, Fair Value	0	0
Held-to-Maturity, 12 months or longer, Unrealized Losses	0	0
Held-to-Maturity, Fair Value	2,309	59,481
Held-to-Maturity, Unrealized Losses	(8)	(560)
Pooled Trust Preferred Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, 12 months or longer, Fair Value	8,448	8,119
Available-for-Sale, 12 months or longer, Unrealized Losses	(8,157)	(8,892)
Available-for-Sale, Fair Value	8,448	8,119
Available-for-Sale, Unrealized Losses	(8,157)	(8,892)
Other Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	61,260	121,498
Available-for-Sale, Less than 12 Months, Unrealized Losses	(429)	(2,734)
Available-for-Sale, 12 months or longer, Fair Value	125,517	126,539
Available-for-Sale, 12 months or longer, Unrealized Losses	(1,712)	(3,048)
Available-for-Sale, Fair Value	186,777	248,037
Available-for-Sale, Unrealized Losses	$ (2,141)	$ (5,782)

Investment Securities - Trust P

Investment Securities - Trust Preferred Securities (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Item	Dec. 31, 2016USD ($)
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale securities, Fair Value	$ 3,196,207	$ 2,797,174
Pooled Trust Preferred Securities One [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Amortized Cost	16,605
Available-for-Sale securities, Fair Value	8,448
Available-for-Sale, Unrealized Gain/ (Loss)	(8,157)
Realized Losses 2017	$ 0
Pooled Trust Preferred Securities One [Member] | Reg Div Funding 2004 [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Pooled trust preferred securities, Class	B2
Lowest Credit Rating	D
Amortized Cost	$ 2,696
Available-for-Sale securities, Fair Value	273
Available-for-Sale, Unrealized Gain/ (Loss)	(2,423)
Realized Losses 2017	$ 0
# of Issuers Currently Performing | Item	21
# of Issuers Currently Remaining | Item	36
Actual Deferrals and Defaults as a Percent of Original Collateral	32.10%
Expected Defaults as a % of Remaining Performing Collateral	7.70%
Excess Subordination as a % of Current Performing Collateral	0.00%
Pooled Trust Preferred Securities One [Member] | Pretsl XXVII LTD [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Pooled trust preferred securities, Class	B
Lowest Credit Rating	B
Amortized Cost	$ 4,414
Available-for-Sale securities, Fair Value	2,478
Available-for-Sale, Unrealized Gain/ (Loss)	(1,936)
Realized Losses 2017	$ 0
# of Issuers Currently Performing | Item	34
# of Issuers Currently Remaining | Item	44
Actual Deferrals and Defaults as a Percent of Original Collateral	16.70%
Expected Defaults as a % of Remaining Performing Collateral	11.80%
Excess Subordination as a % of Current Performing Collateral	33.10%
Pooled Trust Preferred Securities One [Member] | Trapeza Ser 13A [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Pooled trust preferred securities, Class	A2A
Lowest Credit Rating	BBB
Amortized Cost	$ 9,495
Available-for-Sale securities, Fair Value	5,697
Available-for-Sale, Unrealized Gain/ (Loss)	(3,798)
Realized Losses 2017	$ 0
# of Issuers Currently Performing | Item	49
# of Issuers Currently Remaining | Item	54
Actual Deferrals and Defaults as a Percent of Original Collateral	4.50%
Expected Defaults as a % of Remaining Performing Collateral	8.30%
Excess Subordination as a % of Current Performing Collateral	53.70%
Single Issuer Trust Preferred Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Amortized Cost	$ 8,987
Available-for-Sale securities, Fair Value	9,003
Available-for-Sale, Unrealized Gain/ (Loss)	16
Realized Losses 2017	$ 0
Single Issuer Trust Preferred Securities [Member] | Fleet Cap Tr V (BOA) [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Lowest Credit Rating	BBB-
Amortized Cost	$ 3,406
Available-for-Sale securities, Fair Value	3,290
Available-for-Sale, Unrealized Gain/ (Loss)	(116)
Realized Losses 2017	$ 0
Single Issuer Trust Preferred Securities [Member] | J P Morgan Chase Cap XIII [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Lowest Credit Rating	BBB-
Amortized Cost	$ 4,778
Available-for-Sale securities, Fair Value	4,778
Realized Losses 2017	$ 0
Single Issuer Trust Preferred Securities [Member] | NB-Global [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Lowest Credit Rating	BBB-
Amortized Cost	$ 803
Available-for-Sale securities, Fair Value	935
Available-for-Sale, Unrealized Gain/ (Loss)	132
Realized Losses 2017	0
Trust Preferred Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Amortized Cost	25,592
Available-for-Sale securities, Fair Value	17,451
Available-for-Sale, Unrealized Gain/ (Loss)	(8,141)
Realized Losses 2017	$ 0

Loans Held for Sale - Additiona

Loans Held for Sale - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Residential Mortgage Loans [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans held for sale	$ 17.9	$ 90.7

Loans and Allowance for Loan 75

Loans and Allowance for Loan Losses - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 01, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 11,118,121,000	$ 9,010,512,000
Loan placed on nonaccrual when past due, number of days	90 days
Loan participations	$ 581,000,000
Loan participations sold	290,400,000
Loan participations retained	$ 290,600,000
Troubled debt restructuring term	6 months
Minimum number of days for loan charge off to be recorded	120 days
Maximum number of days for loan charge off to be recorded	180 days
Nonaccrual period for loans	90 days
Financing receivable TDR's included with non-accrual loans	$ 34,000,000	26,300,000
Financing receivable troubled debt restructurings specific reserves	5,700,000	4,000,000
Unfunded commitments on TDRs	4,100,000
Increase (decrease) in allowance for loan losses	2,700,000	(2,300,000)	$ (800,000)
Allowance for loan losses charge-offs	$ 200,000	800,000	$ 200,000
Number of days for a loan to be considered to be in payment default	90 days
Outstanding loans including principal, interest, fees and penalties	$ 235,900,000	268,000,000
Accretion recorded as loan interest income	15,200,000	23,400,000
Financing receivable allowance for loan losses related to purchased loans	200,000	300,000
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,879,247,000	1,875,030,000
Consumer [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	223,068,000	230,854,000
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,717,269,000	1,917,099,000
Loans	2,717,269,000	1,917,099,000
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,354,552,000	3,130,853,000
Commercial Real Estate [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	374,306,000	357,802,000
Loans	374,306,000	357,802,000
Commercial Real Estate [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,980,246,000	2,773,051,000
Loans	$ 3,980,246,000	2,773,051,000
Credit Concentration Risk [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Concentration Risk Percentage	10.00%
Maximum [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Value of small commercial loans on nonaccrual status or 90 days or more delinquent	$ 250,000
Criticized [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	74,876,000	45,614,000
Criticized [Member] | Commercial Real Estate [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	14,758,000	9,258,000
Criticized [Member] | Commercial Real Estate [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	98,451,000	40,590,000
Classified - Substandard [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	37,367,000	63,978,000
Classified - Substandard [Member] | Commercial Real Estate [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans		49,000
Classified - Substandard [Member] | Commercial Real Estate [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	58,584,000	19,715,000
Classified - Nonaccrual [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	24,798,000	53,063,000
Classified - Nonaccrual [Member] | Commercial Real Estate [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	2,110,000	1,170,000
Classified - Nonaccrual [Member] | Commercial Real Estate [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	30,108,000	33,833,000
AnchorBank WI [Member] | Consumer [Member] | Student Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 68,200,000	$ 77,100,000
AnchorBank WI [Member] | Maximum [Member] | Consumer [Member] | Student Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan guarantee percentage	100.00%
AnchorBank WI [Member] | Minimum [Member] | Consumer [Member] | Student Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan guarantee percentage	97.00%
Anchor Bank (MN) [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Commercial real estate				$ 864,400,000
Anchor Bank (MN) [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Percentage of risk-based capital	206.00%
Regulatory guideline limit	300.00%
Anchor Bank (MN) [Member] | Criticized [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 26,500,000
Anchor Bank (MN) [Member] | Criticized [Member] | Commercial Real Estate [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	20,400,000
Anchor Bank (MN) [Member] | Classified - Substandard [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	7,300,000
Anchor Bank (MN) [Member] | Classified - Substandard [Member] | Commercial Real Estate [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	3,600,000
Anchor Bank (MN) [Member] | Classified - Nonaccrual [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	7,300,000
Anchor Bank (MN) [Member] | Classified - Nonaccrual [Member] | Commercial Real Estate [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	1,200,000
Anchor Bank (MN) [Member] | Classified - Nonaccrual [Member] | Commercial Real Estate [Member] | Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 6,900,000

Loans and Allowance for Loan 76

Loans and Allowance for Loan Losses - Schedule of Composition of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	$ 11,118,121	$ 9,010,512
Allowance for loan losses	(50,381)	(49,808)	$ (52,233)	$ (47,849)
Net loans	11,067,740	8,960,704
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	2,717,269	1,917,099
Allowance for loan losses	(19,246)	(21,481)	$ (26,347)	$ (20,670)
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	2,167,053	2,087,530
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	1,879,247	1,875,030
Consumer [Member] | Consumer Credit - Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	507,507	476,439
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	4,354,552	3,130,853
Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	374,306	357,802
Other [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	223,068	230,854
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	3,980,246	2,773,051
Consumer Credit - Auto [Member] | Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	$ 1,148,672	$ 1,167,737

Loans and Allowance for Loan 77

Loans and Allowance for Loan Losses - Schedule of Composition of Loans (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Direct finance leases	$ 29.5	$ 10.8

Loans and Allowance for Loan 78

Loans and Allowance for Loan Losses - Schedule of Activity in Related Party Loans (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Receivables [Abstract]
Balance at beginning of period	$ 8,494
New loans	6,041
Repayments	(4,885)
Officer and director changes	(169)
Balance at end of period	$ 9,481

Loans and Allowance for Loan 79

Loans and Allowance for Loan Losses - Schedule of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				$ 49,808				$ 52,233	$ 49,808	$ 52,233	$ 47,849
Charge-offs									(12,717)	(14,610)	(12,877)
Recoveries									10,240	11,225	14,338
Provision	$ 1,037	$ 311	$ 1,355	347	$ (1,756)	$ 1,306	$ 1,319	91	3,050	960	2,923
Ending balance	50,381				49,808				50,381	49,808	52,233
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				21,481				26,347	21,481	26,347	20,670
Charge-offs									(1,108)	(5,047)	(3,513)
Recoveries									2,281	3,102	5,218
Provision									(3,408)	(2,921)	3,972
Ending balance	19,246				21,481				19,246	21,481	26,347
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				18,173				15,993	18,173	15,993	17,348
Charge-offs									(3,700)	(2,632)	(1,921)
Recoveries									3,777	4,763	4,685
Provision									3,186	49	(4,119)
Ending balance	21,436				18,173				21,436	18,173	15,993
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				1,643				2,051	1,643	2,051	2,962
Charge-offs									(985)	(800)	(1,039)
Recoveries									255	174	354
Provision									850	218	(226)
Ending balance	1,763				1,643				1,763	1,643	2,051
Consumer Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance				$ 8,511				$ 7,842	8,511	7,842	6,869
Charge-offs									(6,924)	(6,131)	(6,404)
Recoveries									3,927	3,186	4,081
Provision									2,422	3,614	3,296
Ending balance	$ 7,936				$ 8,511				$ 7,936	$ 8,511	$ 7,842

Loans and Allowance for Loan 80

Loans and Allowance for Loan Losses - Schedule of Recorded Investment in Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	$ 10,078	$ 7,998
Allowance for loan losses, Collectively evaluated for impairment	40,137	41,532
Allowance for loan losses, Loans acquired with deteriorated credit quality	166	278
Total allowance for loan losses	50,381	49,808
Loans and leases outstanding, Individually evaluated for impairment	92,331	103,190
Loans and leases outstanding, Collectively evaluated for impairment	10,982,264	8,851,903
Loans and leases outstanding, Loans acquired with deteriorated credit quality	43,526	55,419
Total loans and leases outstanding	11,118,121	9,010,512
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	3,424	4,561
Allowance for loan losses, Collectively evaluated for impairment	15,790	16,838
Allowance for loan losses, Loans acquired with deteriorated credit quality	32	82
Total allowance for loan losses	19,246	21,481
Loans and leases outstanding, Individually evaluated for impairment	26,270	45,960
Loans and leases outstanding, Collectively evaluated for impairment	2,685,847	1,870,289
Loans and leases outstanding, Loans acquired with deteriorated credit quality	5,152	850
Total loans and leases outstanding	2,717,269	1,917,099
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Individually evaluated for impairment	6,654	3,437
Allowance for loan losses, Collectively evaluated for impairment	14,782	14,717
Allowance for loan losses, Loans acquired with deteriorated credit quality		19
Total allowance for loan losses	21,436	18,173
Loans and leases outstanding, Individually evaluated for impairment	66,061	57,230
Loans and leases outstanding, Collectively evaluated for impairment	4,266,665	3,040,849
Loans and leases outstanding, Loans acquired with deteriorated credit quality	21,826	32,774
Total loans and leases outstanding	4,354,552	3,130,853
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	1,763	1,643
Total allowance for loan losses	1,763	1,643
Loans and leases outstanding, Collectively evaluated for impairment	2,155,750	2,073,950
Loans and leases outstanding, Loans acquired with deteriorated credit quality	11,303	13,580
Total loans and leases outstanding	2,167,053	2,087,530
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	7,802	8,334
Allowance for loan losses, Loans acquired with deteriorated credit quality	134	177
Total allowance for loan losses	7,936	8,511
Loans and leases outstanding, Collectively evaluated for impairment	1,874,002	1,866,815
Loans and leases outstanding, Loans acquired with deteriorated credit quality	5,245	8,215
Total loans and leases outstanding	$ 1,879,247	$ 1,875,030

Loans and Allowance for Loan 81

Loans and Allowance for Loan Losses - Schedule of Risk Category of Commercial and Commercial Real Estate Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commercial [Member]
Risk Category Of Loans [Line Items]
Total	$ 2,717,269	$ 1,917,099
Commercial [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total	2,577,824	1,750,922
Commercial [Member] | Criticized [Member]
Risk Category Of Loans [Line Items]
Total	74,876	45,614
Commercial [Member] | Classified - Substandard [Member]
Risk Category Of Loans [Line Items]
Total	37,367	63,978
Commercial [Member] | Classified - Nonaccrual [Member]
Risk Category Of Loans [Line Items]
Total	24,798	53,063
Commercial [Member] | Classified - Doubtful [Member]
Risk Category Of Loans [Line Items]
Total	2,404	3,522
Commercial Real Estate [Member] | Construction [Member]
Risk Category Of Loans [Line Items]
Total	374,306	357,802
Commercial Real Estate [Member] | Other [Member]
Risk Category Of Loans [Line Items]
Total	3,980,246	2,773,051
Commercial Real Estate [Member] | Pass [Member] | Construction [Member]
Risk Category Of Loans [Line Items]
Total	357,438	347,325
Commercial Real Estate [Member] | Pass [Member] | Other [Member]
Risk Category Of Loans [Line Items]
Total	3,762,896	2,669,890
Commercial Real Estate [Member] | Criticized [Member] | Construction [Member]
Risk Category Of Loans [Line Items]
Total	14,758	9,258
Commercial Real Estate [Member] | Criticized [Member] | Other [Member]
Risk Category Of Loans [Line Items]
Total	98,451	40,590
Commercial Real Estate [Member] | Classified - Substandard [Member] | Construction [Member]
Risk Category Of Loans [Line Items]
Total		49
Commercial Real Estate [Member] | Classified - Substandard [Member] | Other [Member]
Risk Category Of Loans [Line Items]
Total	58,584	19,715
Commercial Real Estate [Member] | Classified - Nonaccrual [Member] | Construction [Member]
Risk Category Of Loans [Line Items]
Total	2,110	1,170
Commercial Real Estate [Member] | Classified - Nonaccrual [Member] | Other [Member]
Risk Category Of Loans [Line Items]
Total	30,108	33,833
Commercial Real Estate [Member] | Classified - Doubtful [Member] | Other [Member]
Risk Category Of Loans [Line Items]
Total	$ 30,207	$ 9,023

Loans and Allowance for Loan 82

Loans and Allowance for Loan Losses - Schedule of Recorded Investment in Residential and Consumer Loans Based on Payment Activity (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Consumer Home Equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment	$ 507,507	$ 476,439
Consumer Home Equity [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Performing	502,322	472,008
Consumer Home Equity [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Nonperforming	5,185	4,431
Consumer Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment	1,148,672	1,167,737
Consumer Auto [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Performing	1,145,977	1,166,114
Consumer Auto [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Nonperforming	2,695	1,623
Consumer - Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment	223,068	230,854
Consumer - Other [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Performing	217,819	223,786
Consumer - Other [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Nonperforming	5,249	7,068
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Residential real estate	2,167,053	2,087,530
Residential [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Performing	2,144,882	2,069,856
Residential [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance receivable recorded investment, Nonperforming	$ 22,171	$ 17,674

Loans and Allowance for Loan 83

Loans and Allowance for Loan Losses - Schedule of Impaired Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Recorded Investment, Total	$ 99,540	$ 108,632
Unpaid Principal Balance, Total	107,700	112,089
Related Allowance	10,232	8,148
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with related allowance	5,713	16,959
Unpaid Principal Balance with related allowance	5,713	17,283
Related Allowance	3,424	4,561
Recorded Investment with no related allowance	20,557	29,001
Unpaid Principal Balance with no related allowance	21,483	29,634
Commercial Real Estate - Other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with related allowance	26,478	26,178
Unpaid Principal Balance with related allowance	26,902	26,710
Related Allowance	6,253	3,330
Recorded Investment with no related allowance	38,678	30,585
Unpaid Principal Balance with no related allowance	44,564	32,413
Residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with related allowance	870	1,081
Unpaid Principal Balance with related allowance	870	1,081
Related Allowance	44	54
Recorded Investment with no related allowance	2,443	1,610
Unpaid Principal Balance with no related allowance	2,464	1,631
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with related allowance	2,211	1,924
Unpaid Principal Balance with related allowance	2,228	1,924
Related Allowance	110	96
Recorded Investment with no related allowance	1,685	827
Unpaid Principal Balance with no related allowance	2,105	946
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with related allowance	905	467
Unpaid Principal Balance with related allowance	1,371	467
Related Allowance	$ 401	$ 107

Loans and Allowance for Loan 84

Loans and Allowance for Loan Losses - Schedule of Average Balance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment, Total	$ 100,772	$ 106,638
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	24,780	34,708
Average Recorded Investment with an allowance recorded	7,002	16,669
Commercial Real Estate - Other [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	34,632	28,793
Average Recorded Investment with an allowance recorded	26,562	20,465
Residential [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	2,415	1,355
Average Recorded Investment with an allowance recorded	1,012	1,074
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	1,761	855
Average Recorded Investment with an allowance recorded	2,155	2,367
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with an allowance recorded	$ 453	$ 352

Loans and Allowance for Credit

Loans and Allowance for Credit Losses - Schedule of Past Due Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	$ 894	$ 328
Nonaccrual	124,927	131,407
Financing Receivables, Past Due	166,934	170,573
Current	10,951,187	8,839,939
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	34,102	31,260
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	7,011	7,578
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	144	23
Nonaccrual	27,202	56,585
Financing Receivables, Past Due	28,692	57,734
Current	2,688,577	1,859,365
Commercial [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	986	847
Commercial [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	360	279
Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	2,110	1,170
Financing Receivables, Past Due	2,110	1,170
Current	372,196	356,632
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	60,315	42,856
Financing Receivables, Past Due	62,651	44,658
Current	3,917,595	2,728,393
Other [Member] | Commercial Real Estate [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	2,247	1,652
Other [Member] | Commercial Real Estate [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	89	150
Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing		2
Nonaccrual	22,171	17,674
Financing Receivables, Past Due	44,535	39,232
Current	2,122,518	2,048,298
Residential [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	18,948	17,786
Residential [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	3,416	3,770
Consumer Home Equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	68
Nonaccrual	5,185	4,431
Financing Receivables, Past Due	6,950	6,365
Current	500,557	470,074
Consumer Home Equity [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	1,467	1,511
Consumer Home Equity [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	230	423
Consumer Auto [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	532	242
Nonaccrual	2,695	1,623
Financing Receivables, Past Due	11,116	8,805
Current	1,137,556	1,158,932
Consumer Auto [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	6,487	5,903
Consumer Auto [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	1,402	1,037
Consumer - Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment > 90 Days and Accruing	150	61
Nonaccrual	5,249	7,068
Financing Receivables, Past Due	10,880	12,609
Current	212,188	218,245
Consumer - Other [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	3,967	3,561
Consumer - Other [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivables, Past Due	$ 1,514	$ 1,919

Loans and Allowance for Credi86

Loans and Allowance for Credit Losses - Schedule of Activity in Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Balance at beginning of period	$ 40,716	$ 44,251	$ 34,953
(Charge-offs)/recoveries	504	(993)	1,875
Payments	(36,184)	(34,007)	(38,012)
Additions	44,643	27,272	45,435
Interest collected on nonaccrual loans	4,324	4,193
Balance at end of period	54,003	40,716	44,251
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Balance at beginning of period	16,802	23,354	15,205
(Charge-offs)/recoveries	417	(1,982)	872
Payments	(22,340)	(21,956)	(29,913)
Additions	13,388	14,996	37,190
Interest collected on nonaccrual loans	3,821	2,390
Balance at end of period	12,088	16,802	23,354
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Balance at beginning of period	18,327	14,602	15,226
(Charge-offs)/recoveries	381	953	1,064
Payments	(12,183)	(10,157)	(6,273)
Additions	27,749	11,130	4,585
Interest collected on nonaccrual loans	431	1,799
Balance at end of period	34,705	18,327	14,602
Residential [Member]
Financing Receivable, Impaired [Line Items]
Balance at beginning of period	2,985	2,693	2,063
(Charge-offs)/recoveries		42	(64)
Payments	(623)	(513)	(658)
Additions	938	761	1,352
Interest collected on nonaccrual loans	15	2
Balance at end of period	3,315	2,985	2,693
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Balance at beginning of period	2,602	3,602	2,459
(Charge-offs)/recoveries	(294)	(6)	3
Payments	(1,038)	(1,381)	(1,168)
Additions	2,568	385	2,308
Interest collected on nonaccrual loans	57	2
Balance at end of period	$ 3,895	$ 2,602	$ 3,602

Loans and Allowance for Loan 87

Loans and Allowance for Loan Losses - Schedule of Loans by Class Modified as Troubled Debt Restructuring (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)SecurityLoan	Dec. 31, 2016USD ($)SecurityLoan	Dec. 31, 2015USD ($)SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	36	44	119
Pre-modification Outstanding Recorded Investment	$ 44,643	$ 27,272	$ 45,435
Post-modification Outstanding Recorded Investment	$ 44,643	$ 27,272	$ 45,435
Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	11	20	42
Pre-modification Outstanding Recorded Investment	$ 13,388	$ 14,996	$ 37,190
Post-modification Outstanding Recorded Investment	$ 13,388	$ 14,996	$ 37,190
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	12	10	27
Pre-modification Outstanding Recorded Investment	$ 27,749	$ 11,130	$ 3,423
Post-modification Outstanding Recorded Investment	$ 27,749	$ 11,130	$ 3,423
Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	6	6	13
Pre-modification Outstanding Recorded Investment	$ 938	$ 761	$ 1,352
Post-modification Outstanding Recorded Investment	$ 938	$ 761	$ 1,352
Consumer - Other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan	7	8	32
Pre-modification Outstanding Recorded Investment	$ 2,568	$ 385	$ 2,308
Post-modification Outstanding Recorded Investment	$ 2,568	$ 385	$ 2,308
Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | SecurityLoan			5
Pre-modification Outstanding Recorded Investment			$ 1,162
Post-modification Outstanding Recorded Investment			$ 1,162

Loans and Allowance for Loan 88

Loans and Allowance for Loan Losses - Schedule of Activity of Purchased Impaired Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	$ 43,526	$ 55,419
Allowance for loan losses	(166)	(278)
Carrying amount, net of allowance	43,360	55,141
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	5,152	850
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	21,826	32,774
Residential [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	11,303	13,580
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	$ 5,245	$ 8,215

Loans and Allowance for Loan 89

Loans and Allowance for Loan Losses - Schedule of Accretable Yield of Noncovered PCI Loans, or Income Expected to be Collected (Detail) - Purchased Credit Impaired Loans [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 33,603	$ 45,310	$ 62,533
New loans purchased	1,556	3,217	1,812
Accretion of income	(15,217)	(23,447)	(35,526)
Reclassifications from (to) nonaccretable difference	7,614	10,589	14,189
Disposals/other adjustments	279	(2,066)	2,302
Balance at end of period	$ 27,835	$ 33,603	$ 45,310

Loans and Allowance for Loan 90

Loans and Allowance for Loan Losses - Schedule of Receivables for which Contractually Required Payments would not be Collected (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Anchor Bank (MN) [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments	$ 16,898
Nonaccretable difference	(4,787)
Cash flows expected to be collected at acquisition	12,111
Accretable yield	(1,556)
Fair value of acquired loans at acquisition	$ 10,555
AnchorBank WI [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments		$ 29,544
Nonaccretable difference		(6,153)
Cash flows expected to be collected at acquisition		23,391
Accretable yield		(3,217)
Fair value of acquired loans at acquisition		$ 20,174

Loans and Allowance for Loan 91

Loans and Allowance for Loan Losses - Schedule of Receivables for which Contractually Required Payments would not be Collected (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
Anchor Bank (MN) [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Effective date of acquisition	Nov. 1, 2017
AnchorBank WI [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Effective date of acquisition	May 1, 2016

Other Real Estate Owned - Activ

Other Real Estate Owned - Activity in Other Real Estate Owned (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Regulatory Assets [Abstract]
Balance at beginning of period	$ 18,546	$ 12,498
Additions	4,016	24,998
Sales	(11,160)	(15,092)
Impairment	(2,592)	(3,858)
Balance at end of period	$ 8,810	$ 18,546

Other Real Estate Owned - Act93

Other Real Estate Owned - Activity in Other Real Estate Owned (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real Estate Properties [Line Items]
Othe real estate	$ 8,810	$ 18,546	$ 12,498
Repossessed personal property	300	300
AnchorBank WI [Member] | Other Real Estate Owned [Member]
Real Estate Properties [Line Items]
Othe real estate		$ 17,300
Anchor Bank (MN) [Member] | Other Real Estate Owned [Member]
Real Estate Properties [Line Items]
Othe real estate	$ 1,100

Other Real Estate Owned - Addit

Other Real Estate Owned - Additional Information (Detail) $ in Millions	Dec. 31, 2017USD ($)
Regulatory Assets [Abstract]
Value of foreclosed residential real estate property	$ 1.6
Value of mortgage loans in process of foreclosure	$ 5.2

Premises and Equipment - Summar

Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total	$ 550,051	$ 525,120
Accumulated depreciation	(91,977)	(95,498)
Premises and equipment, net	458,074	429,622
Land [Member]
Property, Plant and Equipment [Line Items]
Total	73,046	71,769
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total	343,833	322,165
Furniture, Fixtures, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total	94,254	102,631
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total	$ 38,918	$ 28,555

Premises and Equipment - Additi

Premises and Equipment - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)BuildingTerms	Dec. 31, 2016USD ($)Property	Dec. 31, 2015USD ($)Property
Property, Plant and Equipment [Line Items]
Depreciation	$ 22,183	$ 16,558	$ 14,101
Number of additional successive terms extendable at the option | Terms	4
Period of extendable lease term, in years	5 years
Lease term, description	Two years and six months
Rent expense	$ 15,800	25,400	$ 29,100
Sale leaseback transaction, gain recognized over lease term	$ 8,200	$ 10,300
Number of branch buildings under capital leases | Building	2
Anchor Bank (MN) [Member]
Property, Plant and Equipment [Line Items]
Increase in assets due to acquisition	$ 33,556
Minimum [Member]
Property, Plant and Equipment [Line Items]
Lease Term	2 years 6 months
Maximum [Member]
Property, Plant and Equipment [Line Items]
Lease Term	25 years
Prior Sale Leaseback Transactions [Member]
Property, Plant and Equipment [Line Items]
Number of leased properties acquired with deferred gains | Property		20	14
Number of leased properties acquired | Property		23	14
Sale leaseback transaction, gain recognized over lease term		$ 12,000	$ 10,800
Prior Sale Leaseback Transactions [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Lease Term	5 years
Prior Sale Leaseback Transactions [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Lease Term	24 years

Premises and Equipment - Summ97

Premises and Equipment - Summary of Future Minimum Lease Commitments (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Property, Plant and Equipment [Abstract]
2,018	$ 18,919
2,019	17,463
2,020	16,865
2,021	15,960
2,022	13,759
Thereafter	63,828
Total	$ 146,794

Goodwill and Other Intangible98

Goodwill and Other Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Balance at beginning of period	$ 655,018	$ 584,634
Acquisitions	173,033	111,347
Divestitures		(40,963)
Balance at end of period	$ 828,051	$ 655,018

Goodwill and Other Intangible99

Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill acquired during the period	$ 173,033,000	$ 111,347,000
Amortization expense of other intangible assets	11,841,000	12,486,000	$ 11,746,000
Impairment charges	$ 0	$ 0	$ 0
Core Deposits and Other Intangible Assets [Member] | Minimum [Member]
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships	5 years
Core Deposits and Other Intangible Assets [Member] | Maximum [Member]
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships	15 years
Anchor Bank (MN) [Member]
Goodwill [Line Items]
Goodwill acquired during the period	$ 173,000,000
Anchor Bank (MN) [Member] | Core Deposit [Member]
Goodwill [Line Items]
Increase (decrease) in intangible assets	$ 27,300,000

Goodwill and Other Intangibl100

Goodwill and Other Intangible Assets - Schedule of Gross Carrying Amounts and Accumulated Amortization of Other Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 129,883	$ 102,623
Accumulated Amortization and Impairment	(76,787)	(64,946)
Net Carrying Amount	53,096	37,677
Core Deposit [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	108,923	81,663
Accumulated Amortization and Impairment	(62,874)	(53,214)
Net Carrying Amount	46,049	28,449
Customer Trust Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	16,547	16,547
Accumulated Amortization and Impairment	(9,533)	(7,753)
Net Carrying Amount	7,014	8,794
Customer Loan Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,413	4,413
Accumulated Amortization and Impairment	(4,380)	(3,979)
Net Carrying Amount	$ 33	$ 434

Goodwill and Other Intangibl101

Goodwill and Other Intangible Assets - Schedule of Estimated Amortization Expense for Future Years (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 13,561
2,019	11,115
2,020	8,765
2,021	6,498
2,022	4,665
Thereafter	8,492
Net Carrying Amount	$ 53,096	$ 37,677

Loan Servicing Rights - Additio

Loan Servicing Rights - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Transfers and Servicing [Abstract]
Loan servicing rights	$ 24,661	$ 25,561
Principal balance of loans serviced for others	3,321,000	3,385,000
Funds held in escrow	$ 8,900	5,300
Percentage of mortgage loan	99.50%
Fair value of servicing rights	$ 25,800	$ 26,800
Fair value at discount rate	13.00%	13.00%
Fair value inputs weighted average prepayment speed	140.00%	136.00%

Loan Servicing Rights - Compone

Loan Servicing Rights - Components of Loan Servicing Rights and Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Transfers and Servicing [Abstract]
Balance at beginning of period	$ 25,629	$ 10,502
Additions	4,206	20,280
Amortization	(5,145)	(5,153)
Balance before valuation allowance at end of period	24,690	25,629
Valuation allowance:
Balance at beginning of period	(68)	(34)
(Additions)/recoveries	39	(34)
Balance at end of period	(29)	(68)
Loan servicing rights, net	$ 24,661	$ 25,561

Loan Servicing Rights - Comp104

Loan Servicing Rights - Components of Loan Servicing Rights and Valuation Allowance (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	May 31, 2016
Servicing Assets and Liabilities at Fair Value [Line Items]
Loan servicing rights	$ 24,661	$ 25,561
AnchorBank WI [Member]
Servicing Assets and Liabilities at Fair Value [Line Items]
Loan servicing rights			$ 15,300

Qualified Affordable Housing105

Qualified Affordable Housing Projects and Other Tax Credit Investments - Schedule of Qualified Affordable Housing Projects and Other Tax Credit Investments (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Total	$ 64,896,000	$ 35,048,000
Total	48,866,000	20,816,000
Amortization Expense	13,655	804	$ 947
Tax Benefit Recognized	(15,701)	(1,125)	(1,358)
LIHTC [Member]
Investment Holdings [Line Items]
Proportional amortization method of investment	31,183,000	29,110,000
Unfunded commitment, Proportional amortization	15,553,000	16,210,000
Amortization Expense	1,922	804	804
Tax Benefit Recognized	(2,666)	(1,125)	(1,125)
FHTC [Member]
Investment Holdings [Line Items]
Equity method investment	10,645,000	4,434,000
Unfunded commitment, Equity	12,040,000	3,104,000
Amortization Expense	10,441
Tax Benefit Recognized	(11,348)
CReED [Member]
Investment Holdings [Line Items]
Equity method investment	704,000	1,504,000
Unfunded commitment, Equity	1,502,000	$ 1,502,000
Amortization Expense	800
Tax Benefit Recognized	(1,074)
Renewable Energy [Member]
Investment Holdings [Line Items]
Equity method investment	22,364,000
Unfunded commitment, Equity	19,771,000
Amortization Expense	492
Tax Benefit Recognized	$ (613)
NMTC [Member]
Investment Holdings [Line Items]
Amortization Expense			143
Tax Benefit Recognized			$ (233)

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Maturities of Time Deposits [Abstract]
Time deposits, $250,000 or more, total	$ 422.3	$ 313.8

Deposits - Schedule of Maturiti

Deposits - Schedule of Maturities of Total Time Deposits (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Maturities of Time Deposits [Abstract]
Due in 2018	$ 1,111,266
Due in 2019	229,944
Due in 2020	139,689
Due in 2021	62,777
Due in 2022	45,802
Thereafter	44,958
Total	$ 1,634,436	$ 1,468,108

Securities Sold Under Agreem108

Securities Sold Under Agreements to Repurchase - Schedule of Securities Sold under Agreements to Repurchase and Related Weighted-Average Interest Rates (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Securities Sold under Agreements to Repurchase [Abstract]
Outstanding at end of period	$ 384,810,000	$ 367,052,000
Average amount outstanding	336,539,000	368,757,000
Maximum amount outstanding at any month-end	$ 402,543,000	$ 396,695,000
Weighted average interest rate during period	0.38%	0.41%
Weighted average interest rate at end of period	0.49%	0.47%

Securities Sold Under Agreem109

Securities Sold Under Agreements to Repurchase - Schedule of Remaining Contractual Maturity of Secured Borrowings and Class of Collateral Pledged Under Repurchase Agreements (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets Sold under Agreements to Repurchase [Line Items]
Secured borrowings and class of collateral pledged under repurchase agreements	$ 384,810	$ 367,052
U.S. Treasury [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Secured borrowings and class of collateral pledged under repurchase agreements	384,810
Overnight and Continuous [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Secured borrowings and class of collateral pledged under repurchase agreements	359,810
Overnight and Continuous [Member] | U.S. Treasury [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Secured borrowings and class of collateral pledged under repurchase agreements	359,810
Up to 30 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Secured borrowings and class of collateral pledged under repurchase agreements	25,000
Up to 30 Days [Member] | U.S. Treasury [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Secured borrowings and class of collateral pledged under repurchase agreements	$ 25,000

Securities Sold Under Agreem110

Securities Sold Under Agreements to Repurchase - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
Securities Sold under Agreements to Repurchase [Abstract]
Gross outstanding balance of repurchase agreements collateralized by securities percentage	114.00%

Federal Home Loan Bank Advan111

Federal Home Loan Bank Advances - Summary of FHLB Advances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank, Advances [Line Items]
ASC 815 fair value hedge and other basis adjustments	$ (952)
Total other borrowings	1,609,579	$ 1,353,092
Old National Bank [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances (fixed rates 1.01% to 6.08% and variable rates 1.35% to 1.57%) maturing January 2018 to August 2027	1,610,531	1,353,225
ASC 815 fair value hedge and other basis adjustments	$ (952)	$ (133)

Federal Home Loan Bank Advan112

Federal Home Loan Bank Advances - Summary of FHLB Advances (Parenthetical) (Detail) - Old National Bank [Member] - Federal Home Loan Bank Advances [Member]	12 Months Ended
	Dec. 31, 2017
Federal Home Loan Bank, Advances [Line Items]
Maturity, Start date	Jan. 31, 2018
Maturity, End date	Aug. 31, 2027
Minimum [Member]
Federal Home Loan Bank, Advances [Line Items]
Fixed rates	1.01%
Variable rates	1.35%
Maximum [Member]
Federal Home Loan Bank, Advances [Line Items]
Fixed rates	6.08%
Variable rates	1.57%

Federal Home Loan Bank Advan113

Federal Home Loan Bank Advances - Additional Information (Detail)	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank, Advances [Line Items]
Weighted-average rates of FHLB advances	1.55%	0.94%
Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances [Line Items]
Percentage of borrowings collateralized by investment securities and residential real estate loans	143.00%

Federal Home Loan Bank Advan114

Federal Home Loan Bank Advances - Summary of Contractual Maturities of FHLB Advances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Banks [Abstract]
Due in 2018	$ 999,896
Due in 2019	201,962
Due in 2020	50,000
Due in 2021	0
Due in 2022	58,500
Thereafter	300,173
ASC 815 fair value hedge and other basis adjustments	(952)
Total	$ 1,609,579	$ 1,353,092

Other Borrowings - Other Borrow

Other Borrowings - Other Borrowings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Aug. 31, 2014
Debt Instrument [Line Items]
Total other borrowings	$ 248,782	$ 218,939
Old National Bancorp [Member]
Debt Instrument [Line Items]
Other basis adjustments	(3,585)	(3,971)
Total other borrowings	230,699	214,847
Old National Bank [Member]
Debt Instrument [Line Items]
Capital lease obligations	5,389	4,092
Premium on subordinated debentures	694
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Senior unsecured bank notes (fixed rate 4.125%) maturing August 2024			$ 175,000
Senior Unsecured Notes [Member] | Old National Bancorp [Member]
Debt Instrument [Line Items]
Senior unsecured bank notes (fixed rate 4.125%) maturing August 2024	175,000	175,000
Unamortized debt issuance costs related to Senior unsecured bank notes	(1,026)	(1,182)
Junior Subordinated Debt [Member] | Old National Bancorp [Member]
Debt Instrument [Line Items]
Junior subordinated debentures (variable rates of 2.89% to 5.06%) maturing April 2032 to September 2037	60,310	$ 45,000
5.75% Fixed Rate Subordinated Debentures [Member] | Old National Bank [Member]
Debt Instrument [Line Items]
Subordinated debentures (fixed rate 5.75%)	$ 12,000

Other Borrowings - Other Bor116

Other Borrowings - Other Borrowings (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017	Aug. 31, 2014
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Fixed rates		4.125%
Maturity Date	Aug. 15, 2024
Old National Bank [Member] | 5.75% Fixed Rate Subordinated Debentures [Member]
Debt Instrument [Line Items]
Fixed rates	5.75%
Old National Bancorp [Member] | Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Fixed rates	4.125%
Maturity Date	Aug. 15, 2024
Old National Bancorp [Member] | Trust Preferred Securities [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Maturity, Start date	Apr. 30, 2032
Maturity, End date	Sep. 30, 2037
Old National Bancorp [Member] | Trust Preferred Securities [Member] | Junior Subordinated Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Variable rates	2.89%
Old National Bancorp [Member] | Trust Preferred Securities [Member] | Junior Subordinated Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Variable rates	5.06%

Other Borrowings - Contractual

Other Borrowings - Contractual Maturities of Other Borrowings (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
Due in 2018	$ 127
Due in 2019	137
Due in 2020	147
Due in 2021	160
Due in 2022	172
Thereafter	251,956
Unamortized debt issuance costs and other basis adjustments	(3,917)
Total	$ 248,782

Other Borrowings - Additional I

Other Borrowings - Additional Information (Detail) $ in Millions	Nov. 01, 2017USD ($)	May 01, 2016	Jan. 01, 2004Item	Dec. 31, 2017USD ($)Debenture	Aug. 31, 2014USD ($)
Debt Instrument [Line Items]
Long-term capital lease obligation period, in years			25 years
Long-term capital lease obligation renewal period, in years			10 years
Number of renewal option for 10 years period | Item			1
Anchor Bank (MN) [Member]
Debt Instrument [Line Items]
Remaining base term of lease	5 years
Renewal option available for lease in years	10 years
Capital lease obligation	$ 1.5
AnchorBank WI [Member]
Debt Instrument [Line Items]
Capital lease obligation period		5 years
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Number of debentures issued | Debenture				6
Number of debentures redeemed | Debenture				2
Payments for redemption of debentures				$ 9.7
Junior Subordinated Debt [Member] | Anchor Capital Trust II [Member] | Trust Preferred Securities [Member]
Debt Instrument [Line Items]
Fixed rates				8.25%
Junior Subordinated Debt [Member] | Anchor Capital Trust IV [Member] | Trust Preferred Securities [Member]
Debt Instrument [Line Items]
Fixed rates				8.00%
Junior Subordinated Debt [Member] | Anchor Bank (MN) [Member] | Trust Preferred Securities [Member]
Debt Instrument [Line Items]
Junior subordinated debentures	$ 25
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Senior unsecured notes					$ 175
Fixed rates					4.125%
Maturity Date				Aug. 15, 2024
Subordinated Debentures [Member] | Anchor Bank (MN) [Member] | Subordinated Fixed-To-Floating Notes [Member]
Debt Instrument [Line Items]
Fixed rates	5.75%
Maturity Date	Oct. 30, 2025
Value of subordinated fixed-to-floating notes assumed	$ 12
Subordinated debentures, maturity date	Oct. 29, 2020
Description of LIBOR Rate	Three-month LIBOR rate plus 435.6 basis points
LIBOR rate	4.356%
Debt instrument start date	Oct. 30, 2020

Other Borrowings - Summary of T

Other Borrowings - Summary of Terms of Outstanding Junior Subordinated Debentures (Detail) - Trust Preferred Securities [Member] - Junior Subordinated Debt [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Issuance Amount	$ 60,310
VFSC Capital Trust I [Member]
Debt Instrument [Line Items]
Issuance Date	Apr. 30, 2002
Issuance Amount	$ 3,093
Description of LIBOR Rate	3-month LIBOR plus 3.70%
Rate	5.06%
Maturity Date	Apr. 22, 2032
VFSC Capital Trust II [Member]
Debt Instrument [Line Items]
Issuance Date	Oct. 31, 2002
Issuance Amount	$ 4,124
Description of LIBOR Rate	3-month LIBOR plus 3.45%
Rate	4.84%
Maturity Date	Nov. 7, 2032
VFSC Capital Trust III [Member]
Debt Instrument [Line Items]
Issuance Date	Apr. 30, 2004
Issuance Amount	$ 3,093
Description of LIBOR Rate	3-month LIBOR plus 2.80%
Rate	4.12%
Maturity Date	Sep. 8, 2034
St Joseph Capital Trust II [Member]
Debt Instrument [Line Items]
Issuance Date	Mar. 31, 2005
Issuance Amount	$ 5,000
Description of LIBOR Rate	3-month LIBOR plus 1.75%
Rate	3.35%
Maturity Date	Mar. 20, 2035
Anchor Capital Trust III [Member]
Debt Instrument [Line Items]
Issuance Date	Aug. 31, 2005
Issuance Amount	$ 5,000
Description of LIBOR Rate	3-month LIBOR plus 1.55%
Rate	2.89%
Maturity Date	Aug. 23, 2035
Tower Capital Trust 2 [Member]
Debt Instrument [Line Items]
Issuance Date	Dec. 31, 2005
Issuance Amount	$ 8,000
Description of LIBOR Rate	3-month LIBOR plus 1.34%
Rate	3.03%
Maturity Date	Dec. 4, 2035
Home Federal Statutory Trust I [Member]
Debt Instrument [Line Items]
Issuance Date	Sep. 30, 2006
Issuance Amount	$ 15,000
Description of LIBOR Rate	3-month LIBOR plus 1.65%
Rate	3.24%
Maturity Date	Sep. 15, 2036
Monroe Bancorp Capital Trust I [Member]
Debt Instrument [Line Items]
Issuance Date	Jul. 31, 2006
Issuance Amount	$ 3,000
Description of LIBOR Rate	3-month LIBOR plus 1.60%
Rate	2.95%
Maturity Date	Oct. 7, 2036
Monroe Bancorp Statutory Trust II [Member]
Debt Instrument [Line Items]
Issuance Date	Mar. 31, 2007
Issuance Amount	$ 5,000
Description of LIBOR Rate	3-month LIBOR plus 1.60%
Rate	3.19%
Maturity Date	Jun. 15, 2037
Tower Capital Trust 3 [Member]
Debt Instrument [Line Items]
Issuance Date	Dec. 31, 2006
Issuance Amount	$ 9,000
Description of LIBOR Rate	3-month LIBOR plus 1.69%
Rate	3.17%
Maturity Date	Sep. 15, 2037

Other Borrowings - Summary o120

Other Borrowings - Summary of Terms of Outstanding Junior Subordinated Debentures (Parenthetical) (Detail) - Trust Preferred Securities [Member] - Junior Subordinated Debt [Member] - London Interbank Offered Rate (LIBOR) [Member]	12 Months Ended
	Dec. 31, 2017
VFSC Capital Trust I [Member]
Debt Instrument [Line Items]
LIBOR rate	3.70%
VFSC Capital Trust II [Member]
Debt Instrument [Line Items]
LIBOR rate	3.45%
VFSC Capital Trust III [Member]
Debt Instrument [Line Items]
LIBOR rate	2.80%
St Joseph Capital Trust II [Member]
Debt Instrument [Line Items]
LIBOR rate	1.75%
Anchor Capital Trust III [Member]
Debt Instrument [Line Items]
LIBOR rate	1.55%
Tower Capital Trust 2 [Member]
Debt Instrument [Line Items]
LIBOR rate	1.34%
Home Federal Statutory Trust I [Member]
Debt Instrument [Line Items]
LIBOR rate	1.65%
Monroe Bancorp Capital Trust I [Member]
Debt Instrument [Line Items]
LIBOR rate	1.60%
Monroe Bancorp Statutory Trust II [Member]
Debt Instrument [Line Items]
LIBOR rate	1.60%
Tower Capital Trust 3 [Member]
Debt Instrument [Line Items]
LIBOR rate	1.69%

Other Borrowings - Future Minim

Other Borrowings - Future Minimum Lease Payments under Capital Lease Arrangements (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2,018	$ 568
2,019	589
2,020	589
2,021	589
2,022	590
Thereafter	9,274
Total minimum lease payments	12,199
Less amounts representing interest	(6,810)
Present value of net minimum lease payments	$ 5,389

Accumulated Other Comprehens122

Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 1,814,417	$ 1,491,170	$ 1,465,764
Other comprehensive income (loss) before reclassifications	10,190	(32,953)	(4,473)
Amounts reclassified from AOCI	(1,090)	8,378	1,231
Net other comprehensive income (loss)	9,100	(24,575)	(3,242)
Ending Balance	2,154,397	1,814,417	1,491,170
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(39,012)	(3,806)	(748)
Other comprehensive income (loss) before reclassifications	9,615	(31,513)	554
Amounts reclassified from AOCI	(6,160)	(3,693)	(3,612)
Net other comprehensive income (loss)	3,455	(35,206)	(3,058)
Ending Balance	(35,557)	(39,012)	(3,806)
Accumulated Unrealized Gains and Losses on Held-to-Maturity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(13,310)	(14,480)	(15,776)
Amounts reclassified from AOCI	1,203	1,170	1,296
Net other comprehensive income (loss)	1,203	1,170	1,296
Ending Balance	(12,107)	(13,310)	(14,480)
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,715)	(9,276)	(5,935)
Other comprehensive income (loss) before reclassifications	575	(1,440)	(5,027)
Amounts reclassified from AOCI	3,803	4,001	1,686
Net other comprehensive income (loss)	4,378	2,561	(3,341)
Ending Balance	(2,337)	(6,715)	(9,276)
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(335)	(7,235)	(9,096)
Amounts reclassified from AOCI	64	6,900	1,861
Net other comprehensive income (loss)	64	6,900	1,861
Ending Balance	(271)	(335)	(7,235)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(59,372)	(34,797)	(31,555)
Ending Balance	$ (50,272)	$ (59,372)	$ (34,797)

Accumulated Other Comprehens123

Accumulated Other Comprehensive Income (Loss) - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains									$ (9,135)	$ (5,848)	$ (5,718)
Interest income (expense)	$ (118,556)	$ (108,478)	$ (104,333)	$ (105,801)	$ (109,917)	$ (107,803)	$ (99,340)	$ (85,643)	(437,168)	(402,703)	(366,116)
Salaries and employee benefits									(159)	(11,203)	(3,002)
Income tax (expense) benefit	40,405	11,459	10,584	10,491	14,710	10,969	30,812	9,671	72,939	66,162	46,177
Net income	$ 18,493	$ (39,372)	$ (38,854)	$ (35,992)	$ (33,456)	$ (34,709)	$ (39,122)	$ (26,977)	(95,725)	(134,264)	(116,716)
Total reclassifications for Net income the period									1,090	(8,378)	(1,231)
Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for Net income the period									6,160	3,693	3,612
Accumulated Unrealized Gains and Losses on Held-to-Maturity Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for Net income the period									(1,203)	(1,170)	(1,296)
Gains and Losses on Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for Net income the period									(3,803)	(4,001)	(1,686)
Defined Benefit Pension Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for Net income the period									(64)	(6,900)	(1,861)
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains									9,135	5,848	5,718
Income tax (expense) benefit									(2,975)	(2,155)	(2,106)
Net income									6,160	3,693	3,612
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Accumulated Unrealized Gains and Losses on Held-to-Maturity Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income (expense)									(1,830)	(1,776)	(1,692)
Income tax (expense) benefit									627	606	396
Net income									(1,203)	(1,170)	(1,296)
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Gains and Losses on Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit									2,332	2,452	1,033
Net income									(3,803)	(4,001)	(1,686)
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Gains and Losses on Cash Flow Hedges [Member] | Interest Rate Contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income (expense)									(6,135)	(6,453)	(2,719)
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Defined Benefit Pension Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits									(159)	(11,203)	(3,002)
Income tax (expense) benefit									95	4,303	1,141
Net income									$ (64)	$ (6,900)	$ (1,861)

Income Taxes - Summary of Diffe

Income Taxes - Summary of Differences in Taxes from Continuing Operations Computed at Statutory Rate (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Provision at statutory rate of 35%									$ 59,032	$ 70,149	$ 57,013
Tax-exempt interest									(15,026)	(14,356)	(13,111)
Section 291/265 interest disallowance									289	191	142
Company-owned life insurance income									(3,029)	(2,968)	(3,011)
Tax-exempt income									(17,766)	(17,133)	(15,980)
Reserve for unrecognized tax benefits										(1)	(5)
State income taxes									998	3,461	4,173
Tax credit investments - federal									(8,500)	(321)	(411)
Estimated revaluation of deferred tax assets	$ 39,300								39,300
ONB Insurance Group, Inc. nondeductible goodwill										8,328
Effect of Illinois branch sale											1,835
Other, net									(125)	1,679	(448)
Income tax expense	$ 40,405	$ 11,459	$ 10,584	$ 10,491	$ 14,710	$ 10,969	$ 30,812	$ 9,671	$ 72,939	$ 66,162	$ 46,177
Effective tax rate									43.30%	33.00%	28.30%

Income Taxes - Summary of Di125

Income Taxes - Summary of Differences in Taxes from Continuing Operations Computed at Statutory Rate (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory rate	35.00%	35.00%	35.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	May 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Estimated revaluation of deferred tax assets		$ 39,300,000			$ 39,300,000
Statutory rate					35.00%	35.00%	35.00%
Bad debt reserves, created for tax purposes		52,800,000			$ 52,800,000
Unrecognized deferred income tax liability		13,000,000			13,000,000
Valuation allowance recorded		0			0	$ 0
Operating loss carryforwards, federal		130,700,000			130,700,000	162,900,000
AMT carryforwards		25,084,000			25,084,000	19,523,000
Federal tax credits		5,516,000			5,516,000	35,000
Operating loss carryforwards, state		203,600,000			203,600,000	206,300,000
Unrecognized tax benefits, if recognized, would favorably affect the effective tax rate		900,000			900,000
Decrease in unrecognized tax benefits					(200,000)
Interest and penalties					10,000	100,000	$ 400
Interest and penalties, accrued		100,000			100,000	100,000
Uncertain tax position reversal			$ 200,000		173,000	$ 2,000	$ 4,000
State [Member]
Income Taxes [Line Items]
Tax credit		1,300,000			$ 1,300,000
Minimum [Member] | State Net Operating Loss [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration date					2,024
Minimum [Member] | Federal Net Operating Loss [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration date					2,027
Minimum [Member] | Federal Tax Credits [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration date					2,028
Maximum [Member] | State Net Operating Loss [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration date					2,037
Maximum [Member] | Federal Net Operating Loss [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration date					2,037
Maximum [Member] | Federal Tax Credits [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration date					2,033
ONB Insurance Group, Inc. [Member]
Income Taxes [Line Items]
Additional tax expense to record deferred tax liability	$ 8,300,000
Scenario, Forecast [Member]
Income Taxes [Line Items]
Statutory rate				21.00%
AnchorBank WI [Member]
Income Taxes [Line Items]
Bad debt reserves, created for tax purposes		50,900,000			$ 50,900,000
Lafayette Savings Bank [Member]
Income Taxes [Line Items]
Bad debt reserves, created for tax purposes		$ 1,900,000			$ 1,900,000

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal income taxes currently payable									$ 0	$ 23,735	$ 17,385
State income taxes currently payable									0	2,242	769
Federal income taxes deferred									31,915	35,955	24,664
Estimated revaluation of deferred tax assets	$ 39,300								39,300
State income taxes deferred									1,724	4,230	3,359
Deferred income tax expense									72,939	40,185	28,023
Income tax expense	$ 40,405	$ 11,459	$ 10,584	$ 10,491	$ 14,710	$ 10,969	$ 30,812	$ 9,671	$ 72,939	$ 66,162	$ 46,177

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of Net Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets
Allowance for loan losses, net of recapture	$ 12,958	$ 19,773
Benefit plan accruals	11,080	23,846
Alternative minimum tax credit	25,084	19,523
Unrealized losses on benefit plans	108	205
Net operating loss carryforwards	39,631	66,917
Federal tax credits	5,516	35
Other-than-temporary impairment	1,424	3,606
Acquired loans	29,669	40,522
Lease exit obligation	1,337	2,060
Unrealized losses on available-for-sale investment securities	14,011	23,365
Unrealized losses on held-to-maturity investment securities	3,630	7,118
Unrealized losses on hedges	923	4,116
Other real estate owned	369	3,310
Other, net	829	2,675
Total deferred tax assets	146,569	217,071
Deferred Tax Liabilities
Accretion on investment securities	(493)	(700)
Purchase accounting	(16,718)	(17,552)
Loan servicing rights	(6,058)	(9,627)
Premises and equipment	(10,052)	(4,800)
Prepaid expenses	(1,277)
Tax credit investments	(168)
Other, net	(946)	(2,529)
Total deferred tax liabilities	(35,712)	(35,208)
Net deferred tax assets	$ 110,857	$ 181,863

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at beginning of period		$ 777	$ 124	$ 77
Additions based on tax positions related to the current year		162	118	51
Additions based on tax positions related to prior years			537
Reductions due to statute of limitations expiring	$ (200)	(173)	(2)	(4)
Revaluation due to Tax Reform		108
Balance at end of period		$ 874	$ 777	$ 124

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Discretionary profit sharing	$ 0	$ 0	$ 0
Contribution plan, employer matching contribution percentage	50.00%
Defined contribution plans employee contribution percentage of eligible compensation matched by employer	6.00%
Shares allocated to the employee stock ownership plan	0.7	0.8
Contribution expense under employee stock ownership plan	$ 4,700,000	$ 5,000,000	4,600,000
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 0
Discretionary profit sharing		7,600,000	$ 100,000
Settlement loss		9,800,000
Benefit cost, net periodic benefit cost		$ 11,600,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining shares available for issuance	4,800,000
Stock based compensation expense	$ 6,300,000	$ 7,300,000	$ 4,300,000
Total income tax benefit, stock-based compensation cost	$ 2,400,000	$ 2,800,000	1,600,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation awards, vesting period	3 years
Unrecognized compensation expense	$ 3,700,000
Expected weighted-average period for cost recognition (in years)	1 year 9 months 18 days
Stock appreciation rights, Outstanding	849,000	821,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term, in years	10 years
Stock Options [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation awards, vesting period	3 years
Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation awards, vesting period	5 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation awards, vesting period	3 years
Unrecognized compensation expense	$ 3,900,000
Expected weighted-average period for cost recognition (in years)	2 years
Total fair value of shares vested	$ 3,400,000	$ 3,800,000	$ 1,600,000
Stock appreciation rights, Outstanding	407,000	401,000
Stock Appreciation Rights (SARs) [Member] | Old National Bancorp [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock appreciation rights, Outstanding	100,000
Incremental expense associated with conversion of stock appreciation rights	$ 0	$ 0
Outside Director Stock Compensation Program [Member] | Amended and Restated 2008 Incentive Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, issued	20,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Changes in the Nonvested Restricted Shares (Detail) - Restricted Stock [Member] shares in Thousands	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares, Beginning balance | shares	401
Nonvested shares, Granted, Number Outstanding | shares	211
Nonvested shares, Vested, Number Outstanding | shares	(194)
Nonvested shares, Forfeited, Number Outstanding | shares	(11)
Nonvested shares, Ending balance | shares	407
Nonvested shares, Weighted Average Grant-Date Fair Value, Beginning of Period | $ / shares	$ 13.31
Nonvested shares, Granted, Weighted Average Grant-Date Fair Value | $ / shares	17.61
Nonvested shares, Vested, Weighted Average Grant-Date Fair Value | $ / shares	13.50
Nonvested shares, Forfeited, Weighted Average Grant-Date Fair Value | $ / shares	14.97
Nonvested shares, Weighted Average Grant-Date Fair Value, Ending of Period | $ / shares	$ 15.41

Stock-Based Compensation - S133

Stock-Based Compensation - Summary of Changes in the Nonvested Restricted Stock Units (Detail) - Restricted Stock Units [Member] shares in Thousands	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares, Beginning balance | shares	821
Nonvested shares, Granted, Number Outstanding | shares	278
Nonvested shares, Vested, Number Outstanding | shares	(74)
Nonvested shares, Forfeited, Number Outstanding | shares	(192)
Nonvested Shares,dividend equivalents adjustment, Number Outstanding | shares	16
Nonvested shares, Ending balance | shares	849
Nonvested shares, Weighted Average Grant-Date Fair Value, Beginning of Period | $ / shares	$ 12.02
Nonvested shares, Granted, Weighted Average Grant-Date Fair Value | $ / shares	16.31
Nonvested shares, Vested, Weighted Average Grant-Date Fair Value | $ / shares	13.47
Nonvested shares, Forfeited, Weighted Average Grant-Date Fair Value | $ / shares	12.09
Nonvested shares, dividend equivalents adjustment, Weighted Average Grant-Date Fair Value | $ / shares	13.19
Nonvested shares, Weighted Average Grant-Date Fair Value, Ending of Period | $ / shares	$ 13.30

Stock-Based Compensation - S134

Stock-Based Compensation - Summary of the Activity in the Stock Option Plan (Detail) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Stock Based Compensation [Abstract]
Outstanding, Shares, Beginning Balance | shares	694
Exercised, Shares | shares	(193)
Forfeited/expired, Shares | shares	(276)
Outstanding, Shares, Ending Balance | shares	225
Options exercisable at end of year, Shares | shares	225
Weighted Average Exercise Price, Beginning of Period | $ / shares	$ 15.27
Exercised, Weighted Average Exercise Price | $ / shares	14.01
Forfeited/expired, Weighted Average Exercise Price | $ / shares	18.89
Weighted Average Exercise Price, End of Period | $ / shares	11.92
Options exercisable at end of year, Weighted Average Exercise Price | $ / shares	$ 11.92
Weighted Average Remaining Contractual Term in Years, End of Period	1 year 7 months 28 days
Options exercisable at end of year, Weighted Average Remaining Contractual Terms in Years	1 year 7 months 28 days
Aggregate Intrinsic Value, End of Period | $	$ 1,436,000
Options exercisable at end of year, Aggregate Intrinsic Value | $	$ 1,436,000

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Information Related to the Stock Option Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Based Compensation [Abstract]
Intrinsic value of options exercised	$ 806	$ 660	$ 458
Cash received from option exercises	2,655	2,349	997
Tax benefit realized from option exercises	$ 318	$ 264	$ 159

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 13, 2015
Shareholders' Equity [Line Items]
Authorized and unissued common shares available for issuance	300,000,000	300,000,000
Common shares purchase price as percentage of fair market value	95.00%
Maximum value of shares purchased as percentage of employee compensation	10.00%
Common stock issued	$ 404,000	$ 388,000	$ 391,000
Dividend Reinvestment and Stock Purchase Plan [Member]
Shareholders' Equity [Line Items]
Authorized and unissued common shares available for issuance	3,300,000			3,300,000
Employee Stock Purchase Plan [Member]
Shareholders' Equity [Line Items]
Number of shares available for purchase, maximum	500,000
Shares issued related to dividend reinvestment and stock purchase plan	24,000	32,000
Common stock issued	$ 404,000	$ 388,000

Fair Value - Schedule of Fair V

Fair Value - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	$ 5,584	$ 4,982
Investment securities available-for-sale	3,196,207	2,797,174
Derivative assets	14,118	17,701
Derivative liabilities	16,292	23,574
U.S. Treasury [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	5,551	7,103
U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	664,286	493,956
Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	1,667,682	1,525,019
States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	530,193	436,684
Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	8,448	8,119
Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	320,047	326,293
Estimate of Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	5,584	4,982
Estimate of Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Residential loans held for sale	17,930	90,682
Derivative assets	14,118	17,701
Derivative liabilities	16,292	23,574
Estimate of Fair Value Measurement [Member] | U.S. Treasury [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	5,551	7,103
Estimate of Fair Value Measurement [Member] | U.S. Government-Sponsored Entities and Agencies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	664,286	493,956
Estimate of Fair Value Measurement [Member] | Mortgage-Backed Securities - Agency [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	1,667,682	1,525,019
Estimate of Fair Value Measurement [Member] | States and Political Subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	530,193	436,684
Estimate of Fair Value Measurement [Member] | Pooled Trust Preferred Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	8,448	8,119
Estimate of Fair Value Measurement [Member] | Other Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	30,965	30,905
Estimate of Fair Value Measurement [Member] | Other Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	289,082	295,388
Carrying Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	5,584	4,982
Residential loans held for sale	17,930	90,682
Derivative assets	14,118	17,701
Derivative liabilities	16,292	23,574
Carrying Value [Member] | U.S. Treasury [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	5,551	7,103
Carrying Value [Member] | U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	664,286	493,956
Carrying Value [Member] | Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	1,667,682	1,525,019
Carrying Value [Member] | States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	530,193	436,684
Carrying Value [Member] | Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	8,448	8,119
Carrying Value [Member] | Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	$ 320,047	$ 326,293

Fair Value - Reconciliation of

Fair Value - Reconciliation of All Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 8,119	$ 7,900
Accretion of discount	17	18
Sales/payments received	(424)	(327)
Increase in fair value of securities	736	528
Balance at end of period	$ 8,448	$ 8,119

Fair Value - Quantitative Infor

Fair Value - Quantitative Information about Significant Unobservable Inputs Used in Fair Value Measurements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	13.00%	13.00%
Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 2,217	$ 6,771
Valuation Techniques	Fair value of collateral	Fair value of collateral
Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 26,319	$ 11,632
Valuation Techniques	Fair value of collateral	Fair value of collateral
Minimum [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	0.00%	0.00%
Minimum [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	10.00%	10.00%
Maximum [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	98.00%	99.00%
Maximum [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	78.00%	67.00%
Weighted Average [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	49.00%	53.00%
Weighted Average [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	32.00%	36.00%
Pooled Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 8,448	$ 8,119
Valuation Techniques	Discounted cash flow	Discounted cash flow
Pooled Trust Preferred Securities [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional asset defaults	4.20%	4.50%
Expected asset recoveries	0.00%	0.00%
Pooled Trust Preferred Securities [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional asset defaults	9.60%	10.00%
Expected asset recoveries	4.10%	6.10%
Pooled Trust Preferred Securities [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional asset defaults	7.50%	7.90%
Expected asset recoveries	0.60%	0.90%
Commercial Real Estate Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1,726	$ 1,352
Valuation Techniques	Fair value of collateral	Fair value of collateral
Commercial Real Estate Foreclosed Assets [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	7.00%	4.00%
Commercial Real Estate Foreclosed Assets [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	25.00%	80.00%
Commercial Real Estate Foreclosed Assets [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status	18.00%	39.00%
Residential Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 55	$ 394
Valuation Techniques	Fair value of collateral	Fair value of collateral
Discount for type of property, age of appraisal and current status	39.00%
Residential Foreclosed Assets [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status		7.00%
Residential Foreclosed Assets [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status		60.00%
Residential Foreclosed Assets [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for type of property, age of appraisal and current status		30.00%

Fair Value - Quantitative In140

Fair Value - Quantitative Information about Significant Unobservable Inputs Used in Fair Value Measurements (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of adjusted specific issuer evaluation defaults	100.00%	100.00%
Percentage of adjusted specific issuer evaluation recoveries	100.00%	100.00%
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of adjusted specific issuer evaluation defaults	0.00%	0.00%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of adjusted specific issuer evaluation defaults	50.00%	50.00%
Pooled Trust Preferred Securities [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of adjusted specific issuer evaluation recoveries	0.00%	0.00%
Pooled Trust Preferred Securities [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of adjusted specific issuer evaluation recoveries	25.00%	25.00%

Fair Value - Assets Measured at

Fair Value - Assets Measured at Fair Value on a Non-Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 2,217	$ 6,771
Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	26,319	11,632
Commercial Real Estate Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,726	1,352
Residential Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	55	394
Loan Servicing Rights [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,964	2,181
Significant Other Observable Inputs (Level 2) [Member] | Loan Servicing Rights [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,964	2,181
Significant Unobservable Inputs (Level 3) [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,217	6,771
Significant Unobservable Inputs (Level 3) [Member] | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	26,319	11,632
Significant Unobservable Inputs (Level 3) [Member] | Commercial Real Estate Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,726	1,352
Significant Unobservable Inputs (Level 3) [Member] | Residential Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 55	$ 394

Fair Value - Additional Informa

Fair Value - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net carrying amount other real estate owned and other repossessed property	$ 1,800	$ 1,700
Other real estate owned property write-downs	2,500	3,000
Valuation allowance for loan servicing rights with impairments	29	68	$ 34
(Additions)/recoveries on loan servicing rights	$ (39)	34
Past due period of mortgage loans held for sale, days	90 days
Interest income for residential loans held for sale	$ 200	100
Impaired Commercial and Commercial Real Estate Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Principal amount of impaired commercial and commercial real estate loans	38,600	26,400
Valuation allowance	10,100	8,000
Provision for loan losses expensed	$ 5,200
Recapture of provision loan		$ 1,100

Fair Value - Schedule of Differ

Fair Value - Schedule of Difference between the Aggregate Fair Value and the Aggregate Remaining Principal Balance (Detail) - Residential Loans Held for Sale [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Aggregate Fair Value	$ 17,930	$ 90,682
Difference	546	133
Contractual Principal	$ 17,384	$ 90,549

Fair Value - Changes in Fair Va

Fair Value - Changes in Fair Value for Items Measured at Fair Value Pursuant to Election of the Fair Value (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Interest Income	$ 118,556	$ 108,478	$ 104,333	$ 105,801	$ 109,917	$ 107,803	$ 99,340	$ 85,643	$ 437,168	$ 402,703	$ 366,116
Interest (Expense)	$ (16,578)	$ (15,047)	$ (13,876)	$ (12,667)	$ (11,932)	$ (11,910)	$ (10,903)	$ (9,686)	(58,168)	(44,431)	$ (33,073)
Residential Loans Held for Sale [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other Gains and (Losses)									409	(103)
Interest Income									4
Interest (Expense)									0	0
Total Changes in Fair Values Included in Current Period Earnings									$ 413	$ (103)

Fair Value - Carrying Amounts a

Fair Value - Carrying Amounts and Estimated Fair Values of Financial Instruments, Not Previously Presented (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	$ 290,432	$ 255,519	$ 219,818	$ 239,963
Investment securities - held-to-maturity	684,063	745,090
Federal Home Loan Bank/Federal Reserve Bank stock	119,686	101,716
Accrued interest receivable	87,102	81,381
Noninterest-bearing demand deposits	3,680,807	3,016,093
Time deposits	1,634,436	1,468,108
Federal funds purchased and interbank borrowings	335,033	213,003
Securities sold under agreements to repurchase	384,810	367,052
Other borrowings	1,609,579	1,353,092
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	290,432	255,519
Accrued interest receivable	16	16
Noninterest-bearing demand deposits	3,680,807	3,016,093
NOW, savings, and money market deposits	7,290,521	6,259,052
Federal funds purchased and interbank borrowings	335,033	213,003
Securities sold under agreements to repurchase	359,810	317,052
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accrued interest receivable	24,001	22,880
Time deposits	1,620,685	1,460,778
Securities sold under agreements to repurchase	25,133	50,612
Other borrowings	250,443	217,647
Accrued interest payable	7,029	5,979
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	2,707,385	1,971,296
Commercial real estate	4,347,949	3,400,365
Residential real estate	2,210,951	2,228,542
Consumer credit	1,998,194	1,974,180
Accrued interest receivable	63,085	58,485
Federal Home Loan Bank advances	1,607,189	1,360,599
Standby letters of credit	351	315
Commitments to extend credit	2,449	2,527
U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity		40,131
U.S. Government-Sponsored Entities and Agencies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity		40,558
Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity	6,903	10,640
Mortgage-Backed Securities - Agency [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity	7,056	10,940
States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity	677,160	694,319
States and Political Subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity	720,647	732,674
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	290,432	255,519
Federal Home Loan Bank/Federal Reserve Bank stock	119,686	101,716
Commercial	2,698,023	1,895,618
Commercial real estate	4,333,116	3,112,680
Residential real estate	2,165,290	2,085,887
Consumer credit	1,871,311	1,866,519
Accrued interest receivable	87,102	81,381
Noninterest-bearing demand deposits	3,680,807	3,016,093
NOW, savings, and money market deposits	7,290,521	6,259,052
Time deposits	1,634,436	1,468,108
Federal funds purchased and interbank borrowings	335,033	213,003
Securities sold under agreements to repurchase	384,810	367,052
Federal Home Loan Bank advances	1,609,579	1,353,092
Other borrowings	248,782	218,939
Accrued interest payable	7,029	5,979
Standby letters of credit	351	315
Carrying Value [Member] | U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity		40,131
Carrying Value [Member] | Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity	6,903	10,640
Carrying Value [Member] | States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities - held-to-maturity	$ 677,160	$ 694,319

Derivative Financial Instrum146

Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional amount	$ 708,500,000				$ 660,000,000				$ 708,500,000	$ 660,000,000
Reclassified interest income (expense)	118,556,000	$ 108,478,000	$ 104,333,000	$ 105,801,000	109,917,000	$ 107,803,000	$ 99,340,000	$ 85,643,000	437,168,000	402,703,000	$ 366,116,000
Increase (decrease) in derivative assets									3,600,000
Increase (decrease) in derivative liabilities									2,700,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Income [Member]
Derivative [Line Items]
Reclassified interest income (expense)									700,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Expense [Member]
Derivative [Line Items]
Reclassified interest income (expense)									2,800,000
Fixed Interest Swap [Member]
Derivative [Line Items]
Notional amount	33,500,000				35,000,000				33,500,000	35,000,000
Variable Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	675,000,000				625,000,000				675,000,000	625,000,000
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	29,900,000				40,300,000				29,900,000	40,300,000
Forward Commitments [Member]
Derivative [Line Items]
Notional amount	41,200,000				86,100,000				41,200,000	86,100,000
Customer Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	826,600,000				582,700,000				826,600,000	582,700,000
Offsetting Counter Party Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	826,600,000				582,700,000				826,600,000	582,700,000
Offsetting Counter Party Derivative Instrument [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	800,000								800,000
Foreign Currency Forward Contract [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	$ 800,000				$ 0				$ 800,000	$ 0

Derivative Financial Instrum147

Derivative Financial Instruments - Summary of Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Total derivative assets	$ 14,118	$ 17,701
Total derivative liabilities	16,292	23,574
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	3,351	3,056
Total derivative liabilities	5,351	11,582
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Total derivative assets	3,351	3,056
Total derivative liabilities	5,351	11,582
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	10,767	14,645
Total derivative liabilities	10,941	11,992
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Total derivative assets	10,012	11,903
Total derivative liabilities	10,933	11,992
Not Designated as Hedging Instrument [Member] | Mortgage Contracts [Member]
Derivative [Line Items]
Total derivative assets	747	$ 2,742
Not Designated as Hedging Instrument [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Total derivative assets	8
Total derivative liabilities	$ 8

Derivative Financial Instrum148

Derivative Financial Instruments - Schedule of Effect of Derivative Instruments on the Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ (1,939)	$ 1,418	$ 186
Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	(5,534)	(5,320)	(1,540)
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	309	329	511
Interest Rate Contracts [Member] | Interest Income / (Expense) [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	(5,695)	(5,446)	(1,729)
Interest Rate Contracts [Member] | Interest Income / (Expense) [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	309	329	511
Interest Rate Contracts [Member] | Other Income / (Expense) [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	56	28	18
Interest Rate Contracts [Member] | Other Income / (Expense) [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	161	126	189
Mortgage Contracts [Member] | Mortgage Banking Revenue [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ (1,995)	$ 1,390	$ 168

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Loan commitments	$ 3,144	$ 2,354
Fixed rate loan commitment	2,896
Floating rate loan commitment	248.1
Standby letters of credit	$ 68.7	51.7
Loan commitments floating rate, minimum	0.00%
Loan commitments floating rate, maximum	18.00%
Allowance for unfunded loan commitments	$ 3.1	3.2
Extended credit	12.4	13.3
Credit extensions with collateral	$ 11.5	$ 12.6

Financial Guarantees - Addition

Financial Guarantees - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Financial Guarantees [Line Items]
Term of standby letters of credit, years	1 year
Notional amount of standby letters of credit	$ 68,700,000	$ 51,700,000
Carrying value of letters of credit	400,000	300,000
Notional amount	708,500,000	$ 660,000,000
Interest Rate Swap [Member]
Financial Guarantees [Line Items]
Notional amount	$ 18,000,000

Regulatory Restrictions - Addit

Regulatory Restrictions - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Maturities of Time Deposits [Abstract]
Reserve balances	$ 100.9	$ 85.4
Cash and due from banks held as collateral	$ 5.7	$ 3.5
Dividend approval threshold, years	2 years

Regulatory Restrictions - Sched

Regulatory Restrictions - Schedule of Capital Ratios (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Old National Bancorp [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk-weighted assets Actual, Amount	$ 1,424,123	$ 1,229,878
Common equity Tier 1 capital to risk-weighted assets Actual, Amount	1,298,326	1,162,817
Tier 1 capital to risk-weighted assets Actual, Amount	1,298,326	1,176,849
Tier 1 capital to average assets Actual, Amount	$ 1,298,326	$ 1,176,849
Total capital to risk-weighted assets Actual, Ratio	11.40%	12.18%
Common equity Tier 1 capital to risk-weighted assets Actual, Ratio	10.39%	11.51%
Tier 1 capital to risk-weighted assets Actual, Ratio	10.39%	11.65%
Tier 1 capital to average assets Actual, Ratio	8.28%	8.43%
Total capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Amount	$ 1,311,600	$ 1,060,662
Common equity Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Amount	874,400	707,108
Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Amount	1,061,772	858,631
Tier 1 capital to average assets Fully Phased-In Regulatory Guidelines Minimum, Amount	$ 627,258	$ 558,673
Total capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	10.50%	10.50%
Common equity Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	7.00%	7.00%
Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	8.50%	8.50%
Tier 1 capital to average assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	4.00%	4.00%
Old National Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk-weighted assets Actual, Amount	$ 1,458,546	$ 1,240,180
Common equity Tier 1 capital to risk-weighted assets Actual, Amount	1,393,059	1,187,151
Tier 1 capital to risk-weighted assets Actual, Amount	1,393,059	1,187,151
Tier 1 capital to average assets Actual, Amount	$ 1,393,059	$ 1,187,151
Total capital to risk-weighted assets Actual, Ratio	11.73%	12.35%
Common equity Tier 1 capital to risk-weighted assets Actual, Ratio	11.21%	11.82%
Tier 1 capital to risk-weighted assets Actual, Ratio	11.21%	11.82%
Tier 1 capital to average assets Actual, Ratio	8.93%	8.55%
Total capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Amount	$ 1,305,076	$ 1,054,305
Common equity Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Amount	870,051	702,870
Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Amount	1,056,490	853,485
Tier 1 capital to average assets Fully Phased-In Regulatory Guidelines Minimum, Amount	$ 623,758	$ 555,161
Total capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	10.50%	10.50%
Common equity Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	7.00%	7.00%
Tier 1 capital to risk-weighted assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	8.50%	8.50%
Tier 1 capital to average assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	4.00%	4.00%
Total capital to risk-weighted assets Well Capitalized Guidelines, Amount	$ 1,242,929	$ 1,004,100
Common equity Tier 1 capital to risk-weighted assets Well Capitalized Guidelines, Amount	807,904	652,665
Tier 1 capital to risk-weighted assets Well Capitalized Guidelines, Amount	994,344	803,280
Tier 1 capital to average assets Well Capitalized Guidelines, Amount	$ 779,697	$ 693,951
Total capital to risk-weighted assets Well Capitalized Guidelines, Ratio	10.00%	10.00%
Common equity Tier 1 capital to risk-weighted assets Well Capitalized Guidelines, Ratio	6.50%	6.50%
Tier 1 capital to risk-weighted assets Well Capitalized Guidelines, Ratio	8.00%	8.00%
Tier 1 capital to average assets Well Capitalized Guidelines, Ratio	5.00%	5.00%

Regulatory Restrictions - Sc153

Regulatory Restrictions - Schedule of Capital Ratios (Parenthetical) (Detail) - Basel III Capital Rules [Member]	12 Months Ended
	Dec. 31, 2017
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	2.50%
Capital conservation buffer	2.50%
Capital conservation buffer	2.50%
Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk-weighted assets Actual, Ratio	8.00%
Common equity Tier 1 capital to risk-weighted assets Actual, Ratio	4.50%
Tier 1 capital to risk-weighted assets Actual, Ratio	6.00%
Tier 1 capital to average assets Fully Phased-In Regulatory Guidelines Minimum, Ratio	4.00%

Parent Company Financial Sta154

Parent Company Financial Statements - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Trading securities - at fair value	$ 5,584	$ 4,982
Other assets	155,066	115,776
Total assets	17,518,292	14,860,237
Liabilities and Shareholders' Equity
Other borrowings	248,782	218,939
Shareholders' equity	2,154,397	1,814,417	$ 1,491,170	$ 1,465,764
Total liabilities and shareholders' equity	17,518,292	14,860,237
Old National Bancorp [Member]
Assets
Deposits in affiliate bank	43,538	91,650
Trading securities - at fair value	5,584	4,982
Investment securities - available-for-sale	1,547	1,535
Investment in affiliates, Banking subsidiaries	2,248,700	1,862,244
Investment in affiliates, Non-banks	5,142	11,388
Other assets	112,353	90,872
Total assets	2,416,864	2,062,671
Liabilities and Shareholders' Equity
Other liabilities	31,768	33,407
Other borrowings	230,699	214,847
Shareholders' equity	2,154,397	1,814,417
Total liabilities and shareholders' equity	$ 2,416,864	$ 2,062,671

Parent Company Financial Sta155

Parent Company Financial Statements - Condensed Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income
Net securities gains									$ 9,135	$ 5,848	$ 5,718
Expense
Interest on borrowings	$ 16,578	$ 15,047	$ 13,876	$ 12,667	$ 11,932	$ 11,910	$ 10,903	$ 9,686	58,168	44,431	33,073
Other expenses									24,993	28,715	30,974
Income before income taxes	21,912	50,831	49,438	46,483	48,166	45,678	69,934	36,648	168,664	200,426	162,893
Income tax expense (benefit)	40,405	11,459	10,584	10,491	14,710	10,969	30,812	9,671	72,939	66,162	46,177
Net income	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	95,725	134,264	116,716
Old National Bancorp [Member]
Income
Dividends from affiliates									100,000	160,007	67,717
Net securities gains									667	100	6
Other income									1,966	40,841	1,892
Other income from affiliates									5	6	51
Total income									102,638	200,954	69,666
Expense
Interest on borrowings									9,298	9,077	8,684
Other expenses									16,335	18,460	13,957
Total expense									25,633	27,537	22,641
Income before income taxes									77,005	173,417	47,025
Income tax expense (benefit)									(6,240)	11,952	(5,473)
Income before equity in undistributed earnings of affiliates									83,245	161,465	52,498
Equity in undistributed earnings of affiliates									12,480	(27,201)	64,218
Net income									$ 95,725	$ 134,264	$ 116,716

Parent Company Financial Sta156

Parent Company Financial Statements - Condensed Statement of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities
Net income	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	$ 95,725	$ 134,264	$ 116,716
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									22,183	16,558	14,101
Gain on sale of ONB Insurance Group, Inc.										(41,864)
Stock-based compensation expense									6,275	7,318	4,255
(Increase) decrease in other assets									45,008	46,462	16,079
Increase (decrease) in other liabilities									12,141	(24,524)	(26,408)
Total adjustments									194,934	(52,213)	7,040
Net cash flows provided by (used in) operating activities									290,659	82,051	123,756
Cash Flows From Investing Activities
Proceeds from sale of ONB Insurance Group, Inc.										91,771
Purchases of investment securities									(874,555)	(1,625,746)	(832,419)
Purchases of premises and equipment									(37,303)	(224,659)	(85,661)
Net cash flows provided by (used in) investing activities									(576,975)	(698,003)	(500,896)
Cash Flows From Financing Activities
Payments for maturities/redemptions of other borrowings									(20,056)	(67)	(63)
Cash dividends paid on common stock									(72,604)	(67,536)	(55,552)
Common stock repurchased									(2,761)	(2,044)	(88,695)
Proceeds from exercise of stock options									2,655	2,349	997
Common stock issued									404	388	391
Net cash flows provided by (used in) financing activities									321,229	651,653	356,995
Net increase (decrease) in cash and cash equivalents									34,913	35,701	(20,145)
Cash and cash equivalents at beginning of period				255,519				219,818	255,519	219,818	239,963
Cash and cash equivalents at end of period	290,432				255,519				290,432	255,519	219,818
Old National Bancorp [Member]
Cash Flows From Operating Activities
Net income									95,725	134,264	116,716
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									36	29	20
Net securities (gains) losses									(667)	(100)	(6)
Gain on sale of ONB Insurance Group, Inc.										(41,864)
Stock-based compensation expense									6,275	7,318	4,255
(Increase) decrease in other assets									(24,004)	(3,958)	6,307
Increase (decrease) in other liabilities									3,968	(225)	1,441
Equity in undistributed earnings of affiliates									(12,480)	27,201	(64,218)
Total adjustments									(26,872)	(11,599)	(52,201)
Net cash flows provided by (used in) operating activities									68,853	122,665	64,515
Cash Flows From Investing Activities
Net cash and cash equivalents of acquisitions									(24,005)	(100,220)	(41,070)
Proceeds from sale of ONB Insurance Group, Inc.										91,771
Purchases of investment securities									(62)	(52)	(1,053)
Net advances to affiliates									(250)	(3,500)
Purchases of premises and equipment									(485)	(13)
Net cash flows provided by (used in) investing activities									(24,802)	(12,014)	(42,123)
Cash Flows From Financing Activities
Payments for maturities/redemptions of other borrowings									(19,856)
Cash dividends paid on common stock									(72,604)	(67,536)	(55,552)
Common stock repurchased									(2,762)	(2,202)	(88,695)
Proceeds from exercise of stock options									2,655	2,349	997
Common stock issued									404	388	391
Net cash flows provided by (used in) financing activities									(92,163)	(67,001)	(142,859)
Net increase (decrease) in cash and cash equivalents									(48,112)	43,650	(120,467)
Cash and cash equivalents at beginning of period				$ 91,650				$ 48,000	91,650	48,000	168,467
Cash and cash equivalents at end of period	$ 43,538				$ 91,650				$ 43,538	$ 91,650	$ 48,000

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)Segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information [Line Items]
Net income	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	$ 95,725	$ 134,264	$ 116,716
Total assets	$ 17,518,292				$ 14,860,237				$ 17,518,292	$ 14,860,237
Number of reportable operating segment | Segment									2
Community Banking Segment [Member]
Segment Reporting Information [Line Items]
Number of reportable operating segment | Segment									1
Insurance Segments [Member]
Segment Reporting Information [Line Items]
Net income											2,100
Total assets											$ 61,800

Interim Financial Data (Unau158

Interim Financial Data (Unaudited) - Interim Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Interest income	$ 135,134	$ 123,525	$ 118,209	$ 118,468	$ 121,849	$ 119,713	$ 110,243	$ 95,329	$ 495,336	$ 447,134	$ 399,189
Interest expense	16,578	15,047	13,876	12,667	11,932	11,910	10,903	9,686	58,168	44,431	33,073
Net interest income	118,556	108,478	104,333	105,801	109,917	107,803	99,340	85,643	437,168	402,703	366,116
Provision for loan losses	1,037	311	1,355	347	(1,756)	1,306	1,319	91	3,050	960	2,923
Noninterest income	44,825	46,366	49,271	42,920	62,751	47,243	93,385	49,451	183,382	252,830	230,632
Noninterest expense	140,432	103,702	102,811	101,891	126,258	108,062	121,472	98,355	448,836	454,147	430,932
Income before income taxes	21,912	50,831	49,438	46,483	48,166	45,678	69,934	36,648	168,664	200,426	162,893
Income tax expense	40,405	11,459	10,584	10,491	14,710	10,969	30,812	9,671	72,939	66,162	46,177
Net income (loss)	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	$ 95,725	$ 134,264	$ 116,716
Net income per share, Basic	$ (0.13)	$ 0.30	$ 0.28	$ 0.27	$ 0.25	$ 0.25	$ 0.31	$ 0.24	$ 0.69	$ 1.05	$ 1.01
Net income per share, Diluted	$ (0.13)	$ 0.29	$ 0.28	$ 0.27	$ 0.25	$ 0.25	$ 0.31	$ 0.24	$ 0.69	$ 1.05	$ 1
Average shares, Basic	146,073	135,120	135,085	134,912	134,670	134,492	127,508	113,998	137,821	127,705	115,726
Average shares, Diluted	146,875	135,796	135,697	135,431	135,383	135,011	127,973	114,563	138,513	128,301	116,255

Interim Financial Data (Unau159

Interim Financial Data (Unaudited) - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Interim Financial Information [Line Items]
Estimated revaluation of deferred tax assets	$ 39.3		$ 39.3
Statutory rate			35.00%	35.00%	35.00%
Scenario, Forecast [Member]
Selected Interim Financial Information [Line Items]
Statutory rate		21.00%