Associated Banc-Corp (ASB) 10-Q 30 Apr 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 27, 2018
Document And Entity Information [Abstract]
Trading Symbol	ASB
Entity Registrant Name	ASSOCIATED BANC-CORP
Entity Central Index Key	7,789
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		170,794,622

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 328,260	$ 483,666
Interest-bearing deposits in other financial institutions	94,918	199,702
Federal funds sold and securities purchased under agreements to resell	10,000	32,650
Investment securities held to maturity, at amortized cost	2,443,203	2,282,853
Investment securities available for sale, at fair value	4,485,875	4,043,446
Federal Home Loan Bank and Federal Reserve Bank stocks, at cost	233,216	165,331
Residential loans held for sale	103,953	85,544
Commercial loans held for sale	6,091	0
Loans	22,810,491	20,784,991
Allowance for loan losses	(257,058)	(265,880)
Loans, net	22,553,433	20,519,111
Bank and corporate owned life insurance	657,841	591,057
Tax credit and other investments	142,368	147,099
Trading assets	102,890	69,675
Premises and equipment, net	381,327	330,963
Goodwill	1,153,156	976,239
Mortgage servicing rights, net	66,407	58,384
Other intangible assets, net	79,714	15,580
Other assets	523,855	482,294
Total assets	33,366,505	30,483,594
Liabilities and Stockholders’ Equity
Noninterest-bearing demand deposits	5,458,473	5,478,416
Interest-bearing deposits	18,367,129	17,307,546
Total deposits	23,825,602	22,785,962
Federal funds purchased and securities sold under agreements to repurchase	283,954	324,815
Other short-term funding	1,862,420	351,467
Long-term funding	3,233,338	3,397,450
Trading liabilities	100,247	67,660
Accrued expenses and other liabilities	348,246	318,797
Total liabilities	29,653,806	27,246,151
Stockholders’ Equity
Preferred equity	159,853	159,929
Common stock	1,741	1,618
Surplus	1,823,800	1,454,188
Retained earnings	1,859,068	1,819,230
Accumulated other comprehensive income (loss)	(107,673)	(62,758)
Treasury stock, at cost	(24,089)	(134,764)
Total common equity	3,552,847	3,077,514
Total stockholders’ equity	3,712,699	3,237,443
Total liabilities and stockholders’ equity	$ 33,366,505	$ 30,483,594
Preferred shares issued	165,000	165,000
Preferred shares authorized (par value $1.00 per share)	750,000	750,000
Common shares issued	174,107,786	161,751,975
Common shares authorized (par value $0.01 per share)	250,000,000	250,000,000
Treasury shares of common stock	1,925,673	8,908,448

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred shares, par value	$ 1	$ 1
Common shares, par value	$ 0.01	$ 0.01

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest Income
Interest and fees on loans	$ 220,034	$ 173,649
Interest and dividends on investment securities:
Taxable	30,104	23,475
Tax-exempt	9,217	8,129
Other interest	2,177	1,536
Total interest income	261,532	206,789
Interest Expense
Interest on deposits	33,412	16,924
Interest on Federal funds purchased and securities sold under agreements to repurchase	522	515
Interest on other short-term funding	3,005	1,080
Interest on long-term funding	14,722	7,996
Total interest expense	51,661	26,515
Net Interest Income	209,871	180,274
Provision for credit losses	0	9,000
Net interest income after provision for credit losses	209,871	171,274
Noninterest Income
Insurance commissions and fees	22,648	21,620
Service charges on deposit account fees	16,420	16,356
Card-based and loan fees	13,422	12,465
Trust and asset management fees	13,369	11,935
Brokerage commission and fees	7,273	4,333
Mortgage banking, net	6,370	4,579
Capital markets, net	5,306	3,883
Bank and corporate owned life insurance	3,187	2,615
Asset gains (losses), net	(107)	(234)
Other	2,492	2,279
Total noninterest income	90,380	79,831
Noninterest Expense
Personnel (1)	117,685	106,782
Occupancy	15,357	15,219
Technology	17,715	14,420
Equipment	5,556	5,485
Business development and advertising	6,693	5,835
Legal and professional	5,413	4,166
Card issuance and loan costs	3,304	2,620
Foreclosure / OREO expense, net	723	1,505
FDIC assessment	8,250	8,000
Other intangible amortization	1,525	513
Acquisition related costs(2)	20,605	0
Other1	10,140	9,146
Total noninterest expense	212,965	173,691
Income before income taxes	87,285	77,414
Income tax expense	17,829	21,144
Net income	69,456	56,270
Preferred stock dividends	2,339	2,330
Net income available to common equity	$ 67,117	$ 53,940
Earnings per common share:
Basic	$ 0.41	$ 0.36
Diluted	$ 0.40	$ 0.35
Average common shares outstanding:
Basic	163,520	150,815
Diluted	166,432	153,869

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 69,456	$ 56,270
Investment securities available for sale
Net unrealized gains (losses)	(41,834)	3,152
Net unrealized gain (loss) on available for sale securities transferred to held to maturity securities	0	(5,264)
Amortization of net unrealized gain (loss) on available for sale securities transferred to held to maturity securities	(297)	(1,027)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax	(84)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI Reclass Tax Effect, before Tax, Total	(8,419)	0
Income tax (expense) benefit	10,635	1,195
Other comprehensive income (loss) on investment securities available for sale	(40,000)	(1,944)
Defined benefit pension and postretirement obligations
Amortization of prior service cost	(38)	(38)
Amortization of actuarial loss (gains)	465	488
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Defined Benefits Tax Effect BeforeTax	(5,235)	0
Income tax (expense) benefit	(107)	(171)
Other comprehensive income (loss) on pension and postretirement obligations	(4,915)	279
Total other comprehensive income (loss)	(44,915)	(1,665)
Comprehensive income	$ 24,541	$ 54,605

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Preferred Equity	Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2016	$ 3,091,312	$ 159,929	$ 1,630	$ 1,459,498	$ 1,695,764	$ (54,679)	$ (170,830)
Comprehensive income:
Net income	56,270	0	0	0	56,270	0	0
Other comprehensive income	(1,665)	0	0	0	0	1,665	0
Comprehensive income	54,605
Common stock issued:
Stock-based compensation plans, net	17,940	0	0	868	(21,822)	0	38,894
Purchase of treasury stock	(7,743)	0	0	0	0	0	(7,743)
Cash dividends:
Common stock dividends ($0.12 per share in 2016 and $0.15 per share in 2017)	(18,368)	0	0	0	(18,368)	0	0
Preferred stock dividends	(2,330)	0	0	0	(2,330)	0	0
Stock-based compensation expense, net	8,344	0	0	8,344	0	0	0
Other	1,034	0	0	1,034	0	0	0
Ending balance at Mar. 31, 2017	3,144,794	159,929	1,630	1,469,744	1,709,514	(56,344)	(139,679)
Beginning balance at Dec. 31, 2017	3,237,443	159,929	1,618	1,454,188	1,819,230	(62,758)	(134,764)
Comprehensive income:
Net income	69,456	0	0	0	69,456	0	0
Other comprehensive income	(44,915)	0	0	0	0		0
AOCI Loss Net of ASU Adoption and Tax	(31,177)					(31,177)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(13,738)	0	0	0	0	(13,738)	0
Comprehensive income	24,541
Common stock issued:
Stock-based compensation plans, net	10,691	0	0	2,148	(16,076)	0	24,619
Stock Issued for Bank Mutual Acquisitions	481,688	0	134	390,258	0	0	91,296
Purchase of common stock returned to authorized but unissued	(26,480)		(11)	(26,469)	0	0	0
Purchase of treasury stock	(5,240)	0	0	0	0	0	(5,240)
Cash dividends:
Common stock dividends ($0.12 per share in 2016 and $0.15 per share in 2017)	(25,710)	0	0	0	(25,710)	0	0
Preferred stock dividends	(2,339)	0	0	0	(2,339)	0	0
Preferred Stock Redemption Premium	(78)	(76)	0	0	(2)	0	0
Stock-based compensation expense, net	3,675	0	0	3,675	0	0	0
Tax Act Reclassification (2018-2)	13,654	0	0	0	13,654		0
Change in Equity Securities(2016-01)	84	0	0	0	84		0
Other	771	0	0	0	771	0	0
Ending balance at Mar. 31, 2018	$ 3,712,699	$ 159,853	$ 1,741	$ 1,823,800	$ 1,859,068	$ (107,673)	$ (24,089)

Consolidated Statements of Cha7

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Common Stock
Cash dividends:
Common stock dividends (usd per share)	$ 0.50	$ 0.33

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 69,456	$ 56,270
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	0	9,000
Depreciation and amortization	12,208	11,505
Addition to (recovery of) valuation allowance on mortgage servicing rights, net	(474)	217
Amortization of mortgage servicing rights	2,324	2,477
Amortization of other intangible assets	1,525	513
Amortization and accretion on earning assets, funding, and other, net	2,188	8,215
Other Depreciation and Amortization	4,881	1,713
Asset (gains) losses, net	107	234
(Gain) loss on mortgage banking activities, net	624	5,171
Mortgage loans originated and acquired for sale	(197,603)	(101,280)
Proceeds from sales of mortgage loans held for sale	187,624	196,578
(Increase) decrease in interest receivable	(12,859)	(761)
Increase (decrease) in interest payable	1,206	(185)
Other, net	(28,114)	(27,968)
Net cash provided by operating activities	43,093	161,699
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in loans	(160,921)	(113,051)
Purchases of:
Available for sale securities	(646,444)	(163,442)
Held to maturity securities	(208,517)	(2,655)
Federal Home Loan Bank and Federal Reserve Bank stocks	(144,515)	(58,362)
Premises, equipment, and software, net of disposals	(9,892)	(13,586)
Proceeds from:
Sales of available for sale securities	452,866	0
Proceeds from Sale of Federal Home Loan Bank Stock	96,656	59,090
Prepayments, calls, and maturities of available for sale investment securities	158,724	231,019
Prepayments, calls, and maturities of held to maturity investment securities	58,160	22,916
Sales, prepayments, calls, and maturities of other assets	1,182	3,293
Net Change in Tax Credit Investments [Line Items]	(7,240)	2,621
Net cash (paid) received in acquisition	59,605	(217)
Net cash used in investing activities	(350,336)	(32,374)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in deposits	(801,310)	(60,413)
Proceeds from (Repayments of) Short-term Debt	1,124,869	(11,168)
Repayments of Long-term Debt	250,000	8
Proceeds from issuance of common stock for stock-based compensation plans	10,691	17,940
Payments for Repurchase of Redeemable Preferred Stock	(78)	0
Purchase of common stock returned to authorized but unissued	(26,480)	0
Purchase of treasury stock for tax withholding	(5,240)	(7,743)
Cash dividends on common stock	(25,710)	(18,368)
Cash dividends on preferred stock	(2,339)	(2,330)
Net cash provided by financing activities	24,403	(82,090)
Net increase (decrease) in cash and cash equivalents	(282,840)	47,235
Cash and cash equivalents at beginning of period	716,018	642,233	$ 642,233
Cash and cash equivalents at end of period	433,178	689,468	$ 716,018
Supplemental disclosures of cash flow information:
Cash paid for interest	50,286	26,531
Cash paid for income taxes	926	1,052
Loans and bank premises transferred to other real estate owned	2,129	921
Capitalized mortgage servicing rights	9,873	1,920
Loans transferred into held for sale from portfolio, net	3,012	13,905
Unsettled Trades To Purchase Securities	12,095	0
Fair value of assets acquired, including cash and cash equivalents	2,567,123	0
Fair value ascribed to goodwill and intangible assets	242,576	217
Fair value of liabilities assumed	2,809,565	0
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	134	0
Restricted Cash	82,341	70,565
Cash Equivalents, at Carrying Value	$ 350,837	$ 618,903

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments necessary to present fairly the financial position, results of operations and comprehensive income, changes in stockholders’ equity, and cash flows of Associated Banc-Corp (individually referred to herein as the “Parent Company,” and together with all of its subsidiaries and affiliates, collectively referred to herein as the “Corporation”) for the periods presented, and all such adjustments are of a normal recurring nature. The consolidated financial statements include the accounts of all subsidiaries. All significant intercompany transactions and balances have been eliminated in consolidation. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the full year. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and revenues and expenses for the period. Actual results could differ significantly from those estimates. Estimates that are particularly susceptible to significant change include the determination of the allowance for loan losses, goodwill impairment assessment, mortgage servicing rights valuation, and income taxes. Management has evaluated subsequent events for potential recognition or disclosure. Within the tables presented, certain columns and rows may not sum due to the use of rounded numbers for disclosure purposes.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Acquisitions	Acquisitions Bank Mutual Acquisition On February 1, 2018, the Corporation completed its acquisition of Bank Mutual Corporation ("Bank Mutual") in a stock transaction valued at approximately $482 million . Bank Mutual was a diversified financial services company headquartered in Milwaukee, Wisconsin. The merger resulted in a combined company with a larger market presence in markets the Corporation currently operates in, as well as expansion into nearly a dozen new markets. The merger is also expected to provide significant efficiency opportunities and economies of scale associated with a larger financial institution. Under the terms of the Merger Agreement, Bank Mutual’s shareholders received 0.422 shares of the Corporation's common stock for each share of Bank Mutual common stock. The Corporation issued approximately 19.5 million shares for a total deal value of approximately $482 million based on the closing sale price of a share of Associated common stock on January 31, 2018. The acquisition of Bank Mutual constituted a business combination. The merger has been accounted for using the acquisition method of accounting and, accordingly, assets acquired, liabilities assumed, and consideration exchanged were recorded at estimated fair value on the acquisition date. The determination of estimated fair values required management to make certain estimates that are subjective in nature and may require adjustments upon the availability of new information regarding facts and circumstances which existed at the date of acquisition (i.e. appraisals) for up to a year following the acquisition. The Corporation continues to review information relating to events or circumstances existing at the acquisition date. Management anticipates that this review could result in adjustments to the acquisition date valuation amounts presented herein but does not anticipate that these adjustments would be material. The following table presents the estimated fair values of the assets acquired and liabilities assumed as of the acquisition date related to Bank Mutual. Purchase Accounting Adjustments February 1, 2018 ($ in Thousands) Assets Cash and cash equivalents $ — $ 78,052 Investment securities (6,238 ) 452,867 Federal Home Loan Bank stock, at cost — 20,026 Loans (48,533 ) 1,875,386 Premises and equipment, net 11,172 50,930 Bank owned life insurance (24 ) 65,390 Goodwill 166,870 Core deposit intangibles (included in other intangible assets, net on the face of the Consolidated Balance Sheet) 58,100 58,100 Other real estate owned (246 ) 4,403 Others assets $ 5,098 $ 37,151 Total assets $ 2,809,175 Liabilities Deposits $ 2,498 $ 1,840,950 Other borrowings 935 430,946 Other liabilities $ 2,148 $ 55,591 Total liabilities $ 2,327,487 Total consideration paid $ 481,688 The Corporation recorded approximately $167 million of goodwill, which is not tax deductible, related to the Bank Mutual acquisition. See Note 8 for additional information on goodwill, as well as the carrying amount and amortization of core deposit and other intangible assets related to the Bank Mutual acquisition. The following is a description of the methods used to determine the fair value of significant assets and liabilities presented on the balance sheet above. Loans: Fair values for loans were based on a discounted cash flow methodology that considered factors including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan, amortization status and current discount rates. Loans were grouped together according to similar characteristics when applying various valuation techniques. Core deposit intangible ("CDI"): This intangible asset represents the value of the relationships with deposit customers. The fair value was estimated based on a discounted cash flow methodology that gave appropriate consideration to expected customer attrition rates, net maintenance cost of the deposit base, alternative cost of funds, and the interest costs associated with customer deposits. The CDI is being amortized on a straight-line basis over 10 years . Time deposits: The fair values for time deposits are estimated using a discounted cash flow calculation that applies interest rates currently being offered to the contractual interest rates on such time deposits. Federal Home Loan Bank ("FHLB") borrowings: The fair values of FHLB advances are estimated based on quoted market prices for the instrument if available, or for similar instruments if not available, or by using discounted cash flow analyses, based on current incremental borrowing rates for similar types of instruments. See Note 13 for additional information on fair value measurements. Other Acquisitions During the first quarter of 2018, the Corporation completed the acquisition of Diversified Insurance Solutions ("Diversified"). The acquisition improved Associated Benefits and Risk Consulting's ("ABRC") ability to achieve greater scale in the Metro Milwaukee market and to further expand its Wisconsin employee benefits and property and casualty market position and capabilities. The transaction was valued at approximately $19 million . As a result of the acquisition, the Corporation recorded goodwill of approximately $10 million and other intangibles of approximately $8 million . The other intangibles related to the acquisition are being amortized on a straight-line basis over 10 years . See Note 8 for more information on goodwill and other intangible assets.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The accounting and reporting policies of the Corporation conform to U.S. generally accepted accounting principles and to general practice within the financial services industry. A discussion of these policies can be found in Note 1 Summary of Significant Accounting Policies section included in the Corporation’s 2017 Annual Report on Form 10-K. There have been two changes to the Corporation's significant accounting policies since December 31, 2017 . Business combinations The Corporation accounts for its acquisitions using the purchase accounting method. Purchase accounting requires the total purchase price to be allocated to the estimated fair values of assets acquired and liabilities assumed, including certain intangible assets that must be recognized. Typically, this allocation results in the purchase price exceeding the fair value of net assets acquired, which is recorded as goodwill. Core deposit intangibles are a measure of the value of checking, money market and savings deposits acquired in business combinations accounted for under the purchase method. Core deposit intangibles and other identified intangibles with finite useful lives are amortized using the straight line method over their estimated useful lives of up to ten years. Loans that the Corporation acquires in connection with acquisitions are recorded at fair value with no carryover of the related allowance for credit losses. Fair value of the loans involves estimating the amount and timing of principal and interest cash flows expected to be collected on the loans and discounting those cash flows at a market rate of interest. The excess of cash flows expected at acquisition over the estimated fair value is referred to as the accretable discount and is recognized into interest income over the remaining life of the loan. The difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition is referred to as the non-accretable discount. The non-accretable discount includes estimated future credit losses expected to be incurred over the life of the loan. Subsequent decreases to the expected cash flows will require the Corporation to evaluate the need for an additional allowance for credit losses. Subsequent improvement in expected cash flows will result in the reversal of a corresponding amount of the non-accretable discount which the Corporation will then reclassify as accretable discount that will be recognized into interest income over the remaining life of the loan. The Corporation accounts for performing loans acquired in business combinations using the contractual cash flows method of recognizing discount accretion based on the acquired loans’ contractual cash flows. Purchased performing loans are recorded at fair value, including credit, interest, and liquidity discounts. The fair value discount is accreted as an adjustment to yield over the estimated lives of the loans. There is no allowance for loan losses established at the acquisition date for purchased performing loans. A provision for loan losses is recorded for any further deterioration in these loans subsequent to the acquisition. Revenue Recognition The Corporation recognizes revenue in accordance with ASC 606, "Revenue from Contracts with Customers". ASC 606 requires the Corporation to follow a five step process: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation. Revenue recognition under ASC 606 depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for the goods or services. New Accounting Pronouncements Adopted Standard Description Date of adoption Effect on financial statements ASU 2018-02 Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income The FASB issued the amendment to allow a reclassification from accumulated other comprehensive income to retained earnings, the stranded tax effects resulting from the Tax Cuts and Jobs Act. The amendments in this update are effective for all entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption of the update is permitted and should be applied in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate related to the Act is recognized. 1st Quarter 2018 The Corporation has elected to early adopt this Update. During the quarter, the Corporation reclassified approximately $14 million from accumulated other comprehensive income to retained earnings as a result of the Tax Cuts and Jobs Act. No material impact to its results of operations, financial position, and liquidity. See Consolidated Statements of Comprehensive Income and the Statement of Changes in Stockholders' Equity. Standard Description Date of adoption Effect on financial statements ASU 2017-12 Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities The FASB issued the amendment to better align a company’s financial reporting for hedging activities with the economic objectives of those activities for both financial (e.g., interest rate) and commodity risks. The provisions create more transparency around how economic results are presented, both on the face of the financial statements and in the footnotes. It also contains targeted improvements to simplify the application of hedge accounting guidance. This amendment is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Entities should apply the amendment on a modified retrospective transition method in which the cumulative effect of the change will be recognized within equity in the consolidated balance sheet as of the date of adoption. Early adoption is permitted, including in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes the interim period. 1st Quarter 2018 The Corporation has elected to early adopt this Update. No material impact to its results of operations, financial position, and liquidity. See Note 10 for expanded disclosures. ASU 2017-07 Compensation — Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The FASB issued the update to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost, including a requirement that employers disaggregate the service cost component from the other components of net benefit cost. In addition, the amendments provide explicit guidance on how to present the service cost component and the other components of net benefit cost in the income statement and allow only the service cost component of net benefit cost to be eligible for capitalization. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment retrospectively to each period presented and prospectively only for the capitalization component. Early adoption is permitted, but should be within the first interim period if interim financial statements are issued. 1st Quarter 2018 No impact to its results of operations, financial position, and liquidity. The Update required retrospective restatement. For the full year 2017, the Corporation reclassified approximately $9 million from personnel expense to other noninterest expense for the non-service cost components of net periodic pension cost and net periodic postretirement benefit cost. See Note 14 for expanded disclosure. ASU 2017-01 Business Combinations (Topic 805): Clarifying the Definition of a Business The FASB issued amendments to clarify the definition of a business in order to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets versus businesses. The new standard narrows the definition of a business by adding three principal clarifications if: (1) substantially all the fair value of the gross assets in the asset group is concentrated in either a single identifiable asset or group of similar identifiable assets the transaction does not involve a business (2) the asset group does not include a minimum of an input and a substantive process, it does not represent a business, and (3) the integrated set of activities (including its inputs and processes) does not create, or have the ability to create, goods or services to customers, investment income (e,g. dividends or interest) or other revenues, it is not a business. The overall intention is to provide consistency in applying the guidance, reduce the costs of application, and make the definition of a business more operable. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. ASU 2016-18 Statement of Cash Flows (Topic 230): Restricted Cash The FASB issued an amendment to improve GAAP by providing guidance on the presentation of restricted cash or restricted cash equivalents in the statement of cash flows, in order to reduce diversity in practice. The amendment requires that a statement of cash flow explain the change during the period in the total cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included in cash and cash equivalents when reconciling the beginning and end of period total amounts shown on the statement of cash flow. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment retrospectively to each period presented. Early adoption is permitted, including in an interim period. 1st Quarter 2018 No impact to its results of operations, financial position, and liquidity. See Consolidated Statements of Cash Flows. ASU 2016-16 Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory The FASB issued an amendment requiring an entity to recognize income tax consequences on an intra-entity transfer of an asset other than inventory at the time the transaction occurs. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment by means of a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. Early adoption is permitted for all entities in the first interim period if an entity issues interim financial statements. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. ASU 2016-15 Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments The FASB issued an amendment to provide clarification on where to classify cash flows involving certain cash receipts and cash payments. Under the new guidance, cash payments for debt prepayment or debt extinguishment costs should be classified as cash outflows for financing activities. The new guidance also details the specific classification of contingent consideration cash payments made after a business combination depending on the timing of payments. Lastly, cash proceeds received from corporate owned life insurance policies (including BOLI) should be classified as cash inflows from investing, while the cash payments for the premiums may be classified as cash outflows for investing, operating, or a combination of both. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment retrospectively to each period presented. Early adoption is permitted, including in an interim period; however, all of the amendments must be adopted in the same period. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. Standard Description Date of adoption Effect on financial statements ASU 2016-01 Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities The FASB issued an amendment to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. This amendment supersedes the guidance to classify equity securities with readily determinable fair values into different categories, requires equity securities to be measured at fair value with changes in the fair value recognized through net income, and simplifies the impairment assessment of equity investments without readily determinable fair values. The amendment requires public business entities that are required to disclose the fair value of financial instruments measured at amortized cost on the balance sheet to measure that fair value using the exit price notion. The amendment requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option. The amendment requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or in the accompanying notes to the financial statements. The amendment reduces diversity in current practice by clarifying that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available for sale securities in combination with the entity’s other deferred tax assets. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities are required to apply the amendment by means of a cumulative-effect adjustment as of the beginning of the fiscal year of adoption, with the exception of the amendment related to equity securities without readily determinable fair values, which should be applied prospectively to equity investments that exist as of the date of adoption. ASC 2018-04 supersedes previous SEC guidance in the Codification in SAB Topic 5 M. Other-Than-Temporary Impairment of certain investments in equity securities and special balance sheet requirements in Reg S-X rule 3A-05 for public utility Holding companies. 1st Quarter 2018 The Corporation has adopted with Update using the cumulative-effect adjustment as of the beginning of the fiscal year of adoption. Immaterial impact to the result of operations, financial position and liquidity. In 2008, the Corporation received Visa Class B restricted shares as part of Visa’s initial public offering. Based on the existing transfer restriction and the uncertainty of the covered litigation, the approximately 119 thousand Class B shares remaining that the Corporation owned as of March 31, 2018 are carried at a zero cost basis. See Consolidated Statements of Comprehensive Income and Note 13 Fair Value Measurements. ASU 2014-09 Revenue from Contracts with Customers (Topic 606) The FASB issued an amendment to clarify the principles for recognizing revenue and to develop a common revenue standard. The standard outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that “an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.” In applying the revenue model to contracts within its scope, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation. The standard applies to all contracts with customers except those that are within the scope of other topics in the FASB Codification. The standard also requires significantly expanded disclosures about revenue recognition. The FASB continues to release new accounting guidance related to the adoption of this standard, which could impact the Corporation's preliminary materiality analysis and may change the conclusions reached as to the application of this new guidance. The amendment was originally to be effective for annual reporting periods beginning after December 15, 2016 (including interim reporting periods within those periods); however, in July 2015, the FASB approved a one year deferral of the effective date to December 31, 2017. 1st Quarter 2018 The Corporation chose to adopt this Update using the modified retrospective approach with no material impact on the Corporation's results of operations, financial position, or liquidity. See Note 17 for expanded disclosure requirements.

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share Earnings per common share are calculated utilizing the two-class method. Basic earnings per common share are calculated by dividing the sum of distributed earnings to common shareholders and undistributed earnings allocated to common shareholders by the weighted average number of common shares outstanding. Diluted earnings per common share are calculated by dividing the sum of distributed earnings to common shareholders and undistributed earnings allocated to common shareholders by the weighted average number of common shares outstanding adjusted for the dilutive effect of common stock awards (outstanding stock options and unvested restricted stock awards) and common stock warrants. Presented below are the calculations for basic and diluted earnings per common share. For the Three Months Ended March 31, 2018 2017 (In Thousands, except per share data) Net income $ 69,456 $ 56,270 Preferred stock dividends (2,339 ) (2,330 ) Net income available to common equity $ 67,117 $ 53,940 Common shareholder dividends (25,572 ) (18,251 ) Unvested share-based payment awards (138 ) (117 ) Undistributed earnings $ 41,407 $ 35,572 Undistributed earnings allocated to common shareholders 41,225 35,294 Undistributed earnings allocated to unvested share-based payment awards 182 278 Undistributed earnings $ 41,407 $ 35,572 Basic Distributed earnings to common shareholders $ 25,572 $ 18,251 Undistributed earnings allocated to common shareholders 41,225 35,294 Total common shareholders earnings, basic $ 66,797 $ 53,545 Diluted Distributed earnings to common shareholders $ 25,572 $ 18,251 Undistributed earnings allocated to common shareholders 41,225 35,294 Total common shareholders earnings, diluted $ 66,797 $ 53,545 Weighted average common shares outstanding 163,520 150,815 Effect of dilutive common stock awards 2,038 2,216 Effect of dilutive common stock warrants 874 838 Diluted weighted average common shares outstanding 166,432 153,869 Basic earnings per common share $ 0.41 $ 0.36 Diluted earnings per common share $ 0.40 $ 0.35 Non-dilutive common stock options of approximately 1 million and 500,000 for the three months ended March 31, 2018 and 2017 , respectively, were excluded from the earnings per common share calculation

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Stock-Based Compensation	Stock-Based Compensation The fair value of stock options granted is estimated on the date of grant using a Black-Scholes option pricing model, while the fair value of restricted stock awards is their fair market value on the date of grant. The fair values of stock options and restricted stock awards are amortized as compensation expense on a straight-line basis over the vesting period of the grants. For retirement eligible colleagues, expenses related to stock options and restricted stock awards are fully recognized on the date the colleague meets the definition of normal or early retirement. Compensation expense recognized is included in personnel expense in the consolidated statements of income. Assumptions are used in estimating the fair value of stock options granted. The weighted average expected life of the stock option represents the period of time stock options are expected to be outstanding and is estimated using historical data of stock option exercises and forfeitures. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. The expected volatility is based on the implied volatility of the Corporation’s stock. The following assumptions were used in estimating the fair value for options granted in the first three months of 2018 and full year 2017 . 2018 2017 Dividend yield 2.50 % 2.00 % Risk-free interest rate 2.60 % 2.00 % Weighted average expected volatility 22.00 % 25.00 % Weighted average expected life 5.75 years 5.5 years Weighted average per share fair value of options $4.47 $5.30 A summary of the Corporation’s stock option activity for the three months ended March 31, 2018 is presented below. Stock Options Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (a) Outstanding at December 31, 2017 5,118,687 $ 18.02 6.48 $ 38,028 Granted 938,740 24.50 Assumed from Bank Mutual acquisition 370,051 14.35 Exercised (529,869 ) 17.37 Forfeited or expired (24,130 ) 23.35 Outstanding at March 31, 2018 5,873,479 $ 18.86 6.80 $ 35,879 Options Exercisable at March 31, 2018 3,659,277 $ 16.72 5.55 $ 30,009 (a) $ in Thousands Intrinsic value represents the amount by which the fair market value of the underlying stock exceeds the exercise price of the stock option. For the three months ended March 31, 2018 , the intrinsic value of stock options exercised was approximately $5 million . For the three months ended March 31, 2017 , the intrinsic value of the stock options exercised was $10 million . The total fair value of stock options vested was $3 million for the three months ended March 31, 2018 and March 31, 2017 . The Corporation recognized compensation expense for the vesting of stock options of $1 million for both the three months ended March 31, 2018 and March 31, 2017 . Included in compensation expense for 2018 was approximately $450,000 of expense for the accelerated vesting of stock options granted to retirement eligible colleagues. At March 31, 2018 , the Corporation had approximately $8 million of unrecognized compensation expense related to stock options that is expected to be recognized over the remaining requisite service periods that extend through first quarter 2022 . The following table summarizes information about the Corporation’s restricted stock activity for the three months ended March 31, 2018 . Restricted Stock Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 2,026,071 $ 19.68 Granted 570,341 24.63 Vested (498,988 ) 17.97 Forfeited (5,799 ) 20.16 Outstanding at March 31, 2018 2,091,625 $ 21.86 The Corporation amortizes the expense related to restricted stock awards as compensation expense over the vesting period specified in the grant's award agreement. Performance-based restricted stock awards granted during 2017 and 2018 will vest ratably over a three year period, while service-based restricted stock awards granted during 2017 and 2018 will vest ratably over a four year period. Expense for restricted stock awards of approximately $3 million was recorded the three months ended March 31, 2018 and $7 million was recorded for the three months ended March 31, 2017 . Included in compensation expense for 2018 was approximately $1 million of expense for the accelerated vesting of restricted stock awards granted to retirement eligible colleagues. The Corporation had $29 million of unrecognized compensation costs related to restricted stock awards at March 31, 2018 , that is expected to be recognized over the remaining requisite service periods that extend through first quarter 2022 . The Corporation has the ability to issue shares from treasury or new shares upon the exercise of stock options or the granting of restricted stock awards. The Board of Directors has authorized management to repurchase shares of the Corporation’s common stock in the market, to be made available for issuance in connection with the Corporation’s employee incentive plans and for other corporate purposes. The repurchase of shares will be based on market and investment opportunities, capital levels, growth prospects, and regulatory constraints. Such repurchases may occur from time to time in open market purchases, block transactions, private transactions, accelerated share repurchase programs, or similar facilities.

Investment Securities

Investment Securities	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	Investment Securities Investment securities are generally classified as available for sale or held to maturity at the time of purchase. The majority of the Corporation's investment securities are mortgage-related securities issued by the Government National Mortgage Association (“GNMA”) or government-sponsored enterprises ("GSE") such as the Federal National Mortgage Association (“FNMA”) and the Federal Home Loan Mortgage Corporation (“FHLMC”). A portion of the portfolio is also comprised of asset-backed securities backed by student loans made under the Federal Family Education Loan Program ("FFELP"). The amortized cost and fair values of securities available for sale and held to maturity were as follows. March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U. S. Treasury securities $ 1,002 $ — $ (7 ) $ 995 Residential mortgage-related securities FNMA / FHLMC 427,480 7,331 (4,738 ) 430,073 GNMA 2,364,339 21 (54,054 ) 2,310,306 Private-label 1,051 — (7 ) 1,044 GNMA commercial mortgage-related securities 1,497,573 — (49,204 ) 1,448,369 FFELP asset backed securities 288,519 1,835 (54 ) 290,300 Other debt securities 3,200 — (12 ) 3,188 Other equity securities 1,599 — — 1,599 Total investment securities available for sale $ 4,584,763 $ 9,186 $ (108,076 ) $ 4,485,875 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,424,925 $ 4,110 $ (16,579 ) $ 1,412,456 Residential mortgage-related securities FNMA / FHLMC 76,069 227 (1,665 ) 74,631 GNMA 410,275 2,210 (11,624 ) 400,861 GNMA commercial mortgage-related securities 531,934 9,008 (21,694 ) 519,248 Total investment securities held to maturity $ 2,443,203 $ 15,555 $ (51,561 ) $ 2,407,197 December 31, 2017 Amortized Gross Gross Fair Value ($ in Thousands) Investment securities available for sale U. S. Treasury securities $ 1,003 $ — $ (7 ) $ 996 Residential mortgage-related securities FNMA / FHLMC 457,680 9,722 (2,634 ) 464,768 GNMA 1,944,453 275 (31,378 ) 1,913,350 Private-label 1,067 — (8 ) 1,059 GNMA commercial mortgage-related securities 1,547,173 5 (33,901 ) 1,513,277 FFELP asset backed securities 144,322 867 (13 ) 145,176 Other debt securities 3,200 — (12 ) 3,188 Other equity securities 1,519 127 (14 ) 1,632 Total investment securities available for sale $ 4,100,417 $ 10,996 $ (67,967 ) $ 4,043,446 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,281,320 $ 13,899 $ (3,177 ) $ 1,292,042 Residential mortgage-related securities FNMA / FHLMC 40,995 398 (489 ) 40,904 GNMA 414,440 2,700 (6,400 ) 410,740 GNMA commercial mortgage-related securities 546,098 9,546 (15,756 ) 539,888 Total investment securities held to maturity $ 2,282,853 $ 26,543 $ (25,822 ) $ 2,283,574 The expected maturities of investment securities available for sale and held to maturity at March 31, 2018 , are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Available for Sale Held to Maturity Amortized Cost Fair Value Amortized Cost Fair Value ($ in Thousands) Due in one year or less $ 2,002 $ 1,995 $ 44,019 $ 44,261 Due after one year through five years 2,200 2,188 221,411 219,411 Due after five years through ten years — — 346,521 341,147 Due after ten years — — 812,974 807,638 Total debt securities 4,202 4,183 1,424,925 1,412,456 Residential mortgage-related securities FNMA / FHLMC 427,480 430,073 76,069 74,631 GNMA 2,364,339 2,310,306 410,275 400,861 Private-label 1,051 1,044 — — GNMA commercial mortgage-related securities 1,497,573 1,448,369 531,934 519,248 FFELP asset backed securities 288,519 290,300 — — Equity securities 1,599 1,599 — — Total investment securities $ 4,584,763 $ 4,485,875 $ 2,443,203 $ 2,407,197 Ratio of Fair Value to Amortized Cost 97.8 % 98.5 % Investment securities with a carrying value of approximately $3.0 billion and $3.1 billion at March 31, 2018 , and December 31, 2017 , respectively, were pledged to secure certain deposits or for other purposes as required or permitted by law. On the acquisition date, the Corporation sold Bank Mutual's entire securities portfolio. The following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time individual securities have been in a continuous unrealized loss position, at March 31, 2018 . Less than 12 months 12 months or more Total March 31, 2018 Number of Securities Unrealized Losses Fair Value Number of Securities Unrealized Losses Fair Value Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U.S. Treasury securities 1 $ (7 ) $ 995 — $ — $ — $ (7 ) $ 995 Residential mortgage-related securities FNMA / FHLMC 12 (1,389 ) 94,231 9 (3,349 ) 135,316 (4,738 ) 229,547 GNMA 65 (25,956 ) 1,590,545 26 (28,098 ) 718,971 (54,054 ) 2,309,516 Private-label — — — 1 (7 ) 1,044 (7 ) 1,044 GNMA commercial mortgage-related securities 28 (9,895 ) 385,319 76 (39,309 ) 1,063,082 (49,204 ) 1,448,401 FFELP asset backed securities 6 (54 ) 86,988 — — — (54 ) 86,988 Other debt securities 1 (12 ) 188 — — — (12 ) 188 Total 113 $ (37,313 ) $ 2,158,266 112 $ (70,763 ) $ 1,918,413 $ (108,076 ) $ 4,076,679 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) 821 $ (9,876 ) $ 523,716 132 $ (6,703 ) $ 122,632 $ (16,579 ) $ 646,348 Residential mortgage-related securities FNMA / FHLMC 19 (939 ) 54,122 10 (725 ) 15,230 (1,665 ) 69,352 GNMA 58 (7,239 ) 279,707 18 (4,385 ) 113,561 (11,624 ) 393,268 GNMA commercial mortgage-related securities 2 (837 ) 49,711 23 (20,857 ) 469,538 (21,694 ) 519,249 Total 900 $ (18,891 ) $ 907,256 183 $ (32,670 ) $ 720,961 $ (51,561 ) $ 1,628,217 For comparative purposes, the following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2017 . Less than 12 months 12 months or more Total December 31, 2017 Number Unrealized Fair Number Unrealized Fair Unrealized Fair ($ in Thousands) Investment securities available for sale U.S. Treasury securities 1 $ (7 ) $ 996 — $ — $ — $ (7 ) $ 996 Residential mortgage-related securities FNMA / FHLMC 9 (572 ) 69,939 9 (2,062 ) 142,093 (2,634 ) 212,032 GNMA 44 (8,927 ) 1,028,221 25 (22,451 ) 737,198 (31,378 ) 1,765,419 Private-label — — — 1 (8 ) 1,059 (8 ) 1,059 GNMA commercial mortgage-related securities 33 (5,554 ) 480,514 70 (28,347 ) 1,026,642 (33,901 ) 1,507,156 FFELP asset backed securities 1 (13 ) 12,158 — — — — (13 ) 12,158 Other debt securities 1 (12 ) 188 — — — (12 ) 188 Other equity securities 3 (14 ) 1,487 — — — (14 ) 1,487 Total 92 $ (15,099 ) $ 1,593,503 105 $ (52,868 ) $ 1,906,992 $ (67,967 ) $ 3,500,495 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) 157 $ (746 ) $ 122,761 132 $ (2,431 ) $ 127,043 $ (3,177 ) $ 249,804 Residential mortgage-related securities FNMA / FHLMC 8 (73 ) 13,143 10 (417 ) 16,262 (490 ) 29,405 GNMA 35 (3,373 ) 268,388 18 (3,026 ) 120,892 (6,399 ) 389,280 GNMA commercial mortgage-related securities 2 (299 ) 52,997 23 (15,457 ) 486,891 (15,756 ) 539,888 Total 202 $ (4,491 ) $ 457,289 183 $ (21,331 ) $ 751,088 $ (25,822 ) $ 1,208,377 The Corporation reviews the investment securities portfolio on a quarterly basis to monitor its exposure to other-than-temporary impairment. A determination as to whether a security’s decline in fair value is other-than-temporary takes into consideration numerous factors and the relative significance of any single factor can vary by security. Some factors the Corporation may consider in the other-than-temporary impairment analysis include the length of time and extent to which the security has been in an unrealized loss position, changes in security ratings, financial condition and near-term prospects of the issuer, as well as security and industry specific economic conditions. Based on the Corporation’s evaluation, management does not believe any unrealized loss at March 31, 2018 represents an other-than-temporary impairment as these unrealized losses are primarily attributable to changes in interest rates and the current market conditions, and not credit deterioration. The unrealized losses reported for municipal securities relate to various state and local political subdivisions and school districts. The unrealized losses at March 31, 2018 for mortgage-related securities is due to the increase in overall interest rates. The U.S. Treasury 3 year and 5 year rates increased by 41 bp and 36 bp, respectively, from December 31, 2017 . The Corporation does not intend to sell nor does it believe that it will be required to sell the securities contained in the above unrealized losses table before recovery of their amortized cost basis. Federal Home Loan Bank (“FHLB”) and Federal Reserve Bank stocks: The Corporation is required to maintain Federal Reserve stock and FHLB stock as a member of both the Federal Reserve System and the FHLB, and in amounts as required by these institutions. These equity securities are “restricted” in that they can only be sold back to the respective institutions or another member institution at par. Therefore, they are less liquid than other marketable equity securities and their fair value is equal to amortized cost. At March 31, 2018 , and December 31, 2017 , the Corporation had FHLB stock of $157 million and $89 million , respectively. The Corporation had Federal Reserve Bank stock of $76 million at both March 31, 2018 and December 31, 2017 .

Loans

Loans	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Loans	Loans The period end loan composition was as follows. March 31, 2018 (a) December 31, ($ in Thousands) Commercial and industrial $ 6,756,983 $ 6,399,693 Commercial real estate — owner occupied 900,913 802,209 Commercial and business lending 7,657,896 7,201,902 Commercial real estate — investor 4,077,671 3,315,254 Real estate construction 1,579,778 1,451,684 Commercial real estate lending 5,657,449 4,766,938 Total commercial 13,315,345 11,968,840 Residential mortgage 8,197,223 7,546,534 Home equity 923,470 883,804 Other consumer 374,453 385,813 Total consumer 9,495,146 8,816,151 Total loans $ 22,810,491 $ 20,784,991 (a) Includes $15 million of purchased credit-impaired loans The following table presents commercial and consumer loans by credit quality indicator at March 31, 2018 . Pass Special Mention Potential Problem Nonaccrual Total ($ in Thousands) Commercial and industrial $ 6,325,258 $ 132,292 $ 196,766 $ 102,667 $ 6,756,983 Commercial real estate - owner occupied 830,489 15,378 34,410 20,636 900,913 Commercial and business lending 7,155,747 147,670 231,176 123,303 7,657,896 Commercial real estate - investor 3,960,155 54,972 46,970 15,574 4,077,671 Real estate construction 1,547,443 29,421 1,695 1,219 1,579,778 Commercial real estate lending 5,507,598 84,393 48,665 16,793 5,657,449 Total commercial 12,663,345 232,063 279,841 140,096 13,315,345 Residential mortgage 8,134,387 5,580 2,155 55,100 8,197,223 Home equity 908,682 1,383 188 13,218 923,470 Other consumer 373,714 600 — 139 374,453 Total consumer 9,416,783 7,563 2,343 68,456 9,495,146 Total $ 22,080,128 $ 239,626 $ 282,184 $ 208,553 $ 22,810,491 The following table presents commercial and consumer loans by credit quality indicator at December 31, 2017 . Pass Special Mention Potential Problem Nonaccrual Total ($ in Thousands) Commercial and industrial $ 6,015,884 $ 157,245 $ 113,778 $ 112,786 $ 6,399,693 Commercial real estate - owner occupied 723,291 14,181 41,997 22,740 802,209 Commercial and business lending 6,739,175 171,426 155,775 135,526 7,201,902 Commercial real estate - investor 3,266,389 24,845 19,291 4,729 3,315,254 Real estate construction 1,421,504 29,206 — 974 1,451,684 Commercial real estate lending 4,687,893 54,051 19,291 5,703 4,766,938 Total commercial 11,427,068 225,477 175,066 141,229 11,968,840 Residential mortgage 7,490,860 426 1,616 53,632 7,546,534 Home equity 868,958 1,137 195 13,514 883,804 Other consumer 384,990 652 — 171 385,813 Total consumer 8,744,808 2,215 1,811 67,317 8,816,151 Total $ 20,171,876 $ 227,692 $ 176,877 $ 208,546 $ 20,784,991 Factors that are important to managing overall credit quality are sound loan underwriting and administration, systematic monitoring of existing loans and commitments, effective loan review on an ongoing basis, early identification of potential problems, and appropriate allowance for loan losses, allowance for unfunded commitments, nonaccrual, and charge off policies. For commercial loans, management has determined the pass credit quality indicator to include credits that exhibit acceptable financial statements, cash flow, and leverage. If any risk exists, it is mitigated by the loan structure, collateral, monitoring, or control. For consumer loans, performing loans include credits that are performing in accordance with the original contractual terms. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. Special mention credits have potential weaknesses that deserve management’s attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the credit. Potential problem loans are considered inadequately protected by the current net worth and paying capacity of the obligor or the collateral pledged. These loans generally have a well-defined weakness, or weaknesses, that may jeopardize liquidation of the debt and are characterized by the distinct possibility that the Corporation will sustain some loss if the deficiencies are not corrected. Lastly, management considers a loan to be impaired when it is probable that the Corporation will be unable to collect all amounts due according to the original contractual terms of the note agreement, including both principal and interest. Management has determined that commercial and consumer loan relationships that have nonaccrual status or have had their terms restructured in a troubled debt restructuring meet this impaired loan definition. Commercial loans classified as special mention, potential problem, and nonaccrual are reviewed at a minimum on a quarterly basis, while pass and performing rated credits are reviewed on an annual basis or more frequently if the loan renewal is less than one year or if otherwise warranted. The following table presents loans by past due status at March 31, 2018 . Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due (a) Nonaccrual (b) Total ($ in Thousands) Commercial and industrial $ 6,653,188 $ 793 $ 87 $ 248 $ 102,667 $ 6,756,983 Commercial real estate - owner occupied 879,766 511 — — 20,636 900,913 Commercial and business lending 7,532,954 1,304 87 248 123,303 7,657,896 Commercial real estate - investor 4,061,600 240 — 257 15,574 4,077,671 Real estate construction 1,578,069 220 270 — 1,219 1,579,778 Commercial real estate lending 5,639,669 460 270 257 16,793 5,657,449 Total commercial 13,172,623 1,764 357 505 140,096 13,315,345 Residential mortgage 8,125,707 9,876 5,257 1,283 55,100 8,197,223 Home equity 904,305 4,485 1,383 79 13,218 923,470 Other consumer 370,977 1,058 753 1,526 139 374,453 Total consumer 9,400,989 15,419 7,393 2,888 68,456 9,495,146 Total $ 22,573,612 $ 17,184 $ 7,750 $ 3,393 $ 208,553 $ 22,810,491 (a) The recorded investment in loans past due 90 days or more and still accruing totaled $3 million at March 31, 2018 (the same as the reported balances for the accruing loans noted above). (b) Of the total nonaccrual loans, $159 million or 76% were current with respect to payment at March 31, 2018 . The following table presents loans by past due status at December 31, 2017 . Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due (a) Nonaccrual (b) Total ($ in Thousands) Commercial and industrial $ 6,286,369 $ 170 $ 101 $ 267 $ 112,786 $ 6,399,693 Commercial real estate - owner occupied 779,421 48 — — 22,740 802,209 Commercial and business lending 7,065,790 218 101 267 135,526 7,201,902 Commercial real estate - investor 3,310,000 374 — 151 4,729 3,315,254 Real estate construction 1,450,459 168 83 — 974 1,451,684 Commercial real estate lending 4,760,459 542 83 151 5,703 4,766,938 Total commercial 11,826,249 760 184 418 141,229 11,968,840 Residential mortgage 7,483,350 9,186 366 — 53,632 7,546,534 Home equity 863,465 5,688 1,137 — 13,514 883,804 Other consumer 382,186 1,227 780 1,449 171 385,813 Total consumer 8,729,001 16,101 2,283 1,449 67,317 8,816,151 Total $ 20,555,250 $ 16,861 $ 2,467 $ 1,867 $ 208,546 $ 20,784,991 (a) The recorded investment in loans past due 90 days or more and still accruing totaled $2 million at December 31, 2017 (the same as the reported balances for the accruing loans noted above). (b) Of the total nonaccrual loans, $135 million or 65% were current with respect to payment at December 31, 2017 . The following table presents impaired loans individually evaluated under ASC Topic 310, excluding purchased credit-impaired loans, at March 31, 2018 . Recorded Unpaid Related Average Interest ($ in Thousands) Loans with a related allowance Commercial and industrial $ 76,452 $ 81,091 $ 18,778 $ 77,130 $ 312 Commercial real estate — owner occupied 16,264 16,617 2,043 22,978 47 Commercial and business lending 92,716 97,708 20,821 100,108 359 Commercial real estate — investor 18,582 18,619 2,721 16,559 464 Real estate construction 458 532 82 461 7 Commercial real estate lending 19,040 19,151 2,803 17,020 471 Total commercial 111,756 116,859 23,624 117,128 830 Residential mortgage 38,438 40,851 6,635 40,475 431 Home equity 10,762 11,383 3,719 10,238 136 Other consumer 1,066 1,069 116 1,067 1 Total consumer 50,266 53,303 10,470 51,780 568 Total loans (a) $ 162,022 $ 170,162 $ 34,094 $ 168,908 $ 1,398 Loans with no related allowance Commercial and industrial $ 52,389 $ 76,720 $ — $ 55,897 $ (348 ) Commercial real estate — owner occupied 6,225 7,276 — 2,403 — Commercial and business lending 58,614 83,996 — 58,300 (348 ) Commercial real estate — investor 1,805 1,853 — — — Real estate construction — — — — — Commercial real estate lending 1,805 1,853 — — — Total commercial 60,419 85,849 — 58,300 (348 ) Residential mortgage 10,425 10,871 — 6,317 39 Home equity 212 212 — 639 1 Other consumer — — — — — Total consumer 10,637 11,083 — 6,956 40 Total loans (a) $ 71,056 $ 96,932 $ — $ 65,256 $ (308 ) Total Commercial and industrial $ 128,841 $ 157,811 $ 18,778 $ 133,027 $ (36 ) Commercial real estate — owner occupied 22,489 23,893 2,043 25,381 47 Commercial and business lending 151,330 181,704 20,821 158,408 11 Commercial real estate — investor 20,387 20,472 2,721 16,559 464 Real estate construction 458 532 82 461 7 Commercial real estate lending 20,845 21,004 2,803 17,020 471 Total commercial 172,175 202,708 23,624 175,428 482 Residential mortgage 48,863 51,722 6,635 46,792 470 Home equity 10,974 11,595 3,719 10,877 137 Other consumer 1,066 1,069 116 1,067 1 Total consumer 60,903 64,386 10,470 58,736 608 Total loans (a) $ 233,078 $ 267,094 $ 34,094 $ 234,164 $ 1,090 (a) The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 74% of the unpaid principal balance at March 31, 2018 . The following table presents impaired loans individually evaluated under ASC Topic 310 at December 31, 2017 . Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized ($ in Thousands) Loans with a related allowance Commercial and industrial $ 81,649 $ 83,579 $ 10,838 $ 58,494 $ 2,629 Commercial real estate — owner occupied 23,796 23,937 2,973 12,124 736 Commercial and business lending 105,445 107,516 13,811 70,618 3,365 Commercial real estate — investor 17,823 17,862 1,597 16,924 1,694 Real estate construction 467 578 86 484 29 Commercial real estate lending 18,290 18,440 1,683 17,408 1,723 Total commercial 123,735 125,956 15,494 88,026 5,088 Residential mortgage 40,561 42,922 6,512 40,411 1,614 Home equity 10,250 10,986 3,718 10,521 549 Other consumer 1,135 1,138 122 1,140 3 Total consumer 51,946 55,046 10,352 52,072 2,166 Total loans (a) $ 175,681 $ 181,002 $ 25,846 $ 140,098 $ 7,254 Loans with no related allowance Commercial and industrial $ 60,595 $ 82,839 $ — $ 89,275 $ 492 Commercial real estate — owner occupied 2,438 2,829 — 1,948 36 Commercial and business lending 63,033 85,668 — 91,223 528 Commercial real estate — investor 1,295 1,295 — — 45 Real estate construction — — — — — Commercial real estate lending 1,295 1,295 — — 45 Total commercial 64,328 86,963 — 91,223 573 Residential mortgage 6,925 7,204 — 4,999 217 Home equity 641 645 — 540 7 Other consumer — — — — — Total consumer 7,566 7,849 — 5,539 224 Total loans (a) $ 71,894 $ 94,812 $ — $ 96,762 $ 797 Total Commercial and industrial $ 142,244 $ 166,418 $ 10,838 $ 147,769 $ 3,121 Commercial real estate — owner occupied 26,234 26,766 2,973 14,072 772 Commercial and business lending 168,478 193,184 13,811 161,841 3,893 Commercial real estate — investor 19,118 19,157 1,597 16,924 1,739 Real estate construction 467 578 86 484 29 Commercial real estate lending 19,585 19,735 1,683 17,408 1,768 Total commercial 188,063 212,919 15,494 179,249 5,661 Residential mortgage 47,486 50,126 6,512 45,410 1,831 Home equity 10,891 11,631 3,718 11,061 556 Other consumer 1,135 1,138 122 1,140 3 Total consumer 59,512 62,895 10,352 57,611 2,390 Total loans (a) $ 247,575 $ 275,814 $ 25,846 $ 236,860 $ 8,051 (a) The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 80% of the unpaid principal balance at December 31, 2017 . Troubled Debt Restructurings (“Restructured Loans”) Loans are considered restructured loans if concessions have been granted to borrowers that are experiencing financial difficulty. The Corporation had a recorded investment of approximately $4 million in loans modified in troubled debt restructurings for the three months ended March 31, 2018 , of which approximately $1 million were in accrual status and $3 million were in nonaccrual pending a sustained period of repayment. The following table presents nonaccrual and performing restructured loans by loan portfolio. March 31, 2018 December 31, 2017 Performing Restructured Loans Nonaccrual Restructured Loans (a) Performing Restructured Loans Nonaccrual Restructured Loans (a) ($ in Thousands) Commercial and industrial $ 29,580 $ 886 $ 30,047 $ 1,776 Commercial real estate — owner occupied 3,892 — 3,989 — Commercial real estate — investor 13,683 1,007 14,389 — Real estate construction 305 152 310 157 Residential mortgage 19,902 18,640 17,068 18,991 Home equity 8,098 3,117 7,705 2,537 Other consumer 1,041 25 1,110 25 Total $ 76,501 $ 23,827 $ 74,618 $ 23,486 (a) Nonaccrual restructured loans have been included within nonaccrual loans. The following table provides the number of loans modified in a troubled debt restructuring by loan portfolio during the three months ended March 31, 2018 and 2017 , respectively, and the recorded investment and unpaid principal balance as of March 31, 2018 and 2017 , respectively. Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) ($ in Thousands) Commercial and industrial 2 $ 92 $ 92 20 $ 52,326 $ 60,546 Commercial real estate — owner occupied — — — 1 204 204 Commercial real estate — investor 1 1,007 1,037 1 733 744 Residential mortgage 11 1,807 1,807 16 1,301 1,322 Home equity 17 1,044 1,060 15 347 347 Other consumer 2 8 11 — — — Total 33 $ 3,958 $ 4,007 53 $ 54,911 $ 63,163 (a) Represents post-modification outstanding recorded investment. (b) Represents pre-modification outstanding recorded investment. Restructured loan modifications may include payment schedule modifications, interest rate concessions, maturity date extensions, modification of note structure (A/B Note), non-reaffirmed Chapter 7 bankruptcies, principal reduction, or some combination of these concessions. During the three months ended March 31, 2018 , restructured loan modifications of commercial and industrial, commercial real estate, and real estate construction loans primarily included maturity date extensions and payment schedule modifications. Restructured loan modifications of home equity and residential mortgage loans primarily included maturity date extensions, interest rate concessions, non-reaffirmed Chapter 7 bankruptcies, or a combination of these concessions for the three months ended March 31, 2018 . The following table provides the number of loans modified in a troubled debt restructuring during the previous twelve months which subsequently defaulted during the three months ended March 31, 2018 and 2017 , respectively, as well as the recorded investment in these restructured loans as of March 31, 2018 and 2017 , respectively. Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Number of Loans Recorded Investment Number of Loans Recorded Investment ($ in Thousands) Residential mortgage 4 467 6 383 Home equity 12 954 2 26 Total 16 $ 1,421 8 $ 409 All loans modified in a troubled debt restructuring are evaluated for impairment. The nature and extent of the impairment of restructured loans, including those which have experienced a subsequent payment default, is considered in the determination of an appropriate level of the allowance for loan losses. Allowance for Credit Losses The allowance for credit losses is comprised of the allowance for loan losses and the allowance for unfunded commitments. The level of the allowance for loan losses represents management’s estimate of an amount appropriate to provide for probable credit losses in the loan portfolio at the balance sheet date. The allowance for unfunded commitments is maintained at a level believed by management to be sufficient to absorb estimated probable losses related to unfunded credit facilities (including unfunded loan commitments and letters of credit) and is included in accrued expenses and other liabilities on the consolidated balance sheets. See Note 12 for additional information on the allowance for unfunded commitments. The following table presents a summary of the changes in the allowance for loan losses by portfolio segment for the three months ended March 31, 2018 . ($ in Thousands) Commercial and Commercial real estate Commercial real estate - Real estate Residential Home Other Total December 31, 2017 $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Charge offs (8,067 ) (1,042 ) — (47 ) (493 ) (1,250 ) (1,256 ) (12,155 ) Recoveries 1,468 17 8 236 362 573 168 2,832 Net Charge offs (6,599 ) (1,025 ) 8 189 (131 ) (677 ) (1,088 ) (9,323 ) Provision for loan losses 1,377 2,520 1,215 (6,125 ) 536 241 736 500 March 31, 2018 $ 117,847 $ 11,847 $ 42,282 $ 28,434 $ 30,012 $ 21,690 $ 4,946 $ 257,058 Allowance for loan losses Individually evaluated for impairment $ 18,778 $ 2,043 $ 2,721 $ 82 $ 6,635 $ 3,719 $ 116 $ 34,094 Collectively evaluated for impairment 99,069 9,804 39,561 28,352 23,377 17,971 4,830 222,964 Acquired and accounted for under ASC 310-30 (a) — — — — — — — — Total allowance for loan losses $ 117,847 $ 11,847 $ 42,282 $ 28,434 $ 30,012 $ 21,690 $ 4,946 $ 257,058 Loans Individually evaluated for impairment $ 128,841 $ 22,489 $ 20,387 $ 458 $ 48,863 $ 10,974 $ 1,066 $ 233,078 Collectively evaluated for impairment 6,625,314 876,631 4,048,532 1,579,065 8,147,224 912,421 373,388 22,562,575 Acquired and accounted for under ASC 310-30 (a) 2,828 1,793 8,752 255 1,136 74 — 14,838 Total loans $ 6,756,983 $ 900,913 $ 4,077,671 $ 1,579,778 $ 8,197,223 $ 923,470 $ 374,453 $ 22,810,491 (a) Loans acquired in business combinations and accounted for under ASC Subtopic 310-30 "Receivables — Loans and Debt Securities Acquired with Deteriorated Credit Quality." For comparison purposes, a summary of the changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2017 , was as follows. ($ in Thousands) Commercial and Commercial real estate Commercial real estate - Real estate Residential Home Other Total December 31, 2016 $ 140,126 $ 14,034 $ 45,285 $ 26,932 $ 27,046 $ 20,364 $ 4,548 $ 278,335 Charge offs (44,533 ) (344 ) (991 ) (604 ) (2,611 ) (2,724 ) (4,439 ) (56,246 ) Recoveries 11,465 173 242 74 927 3,194 716 16,791 Net Charge offs (33,068 ) (171 ) (749 ) (530 ) (1,684 ) 470 (3,723 ) (39,455 ) Provision for loan losses 16,010 (3,511 ) (3,477 ) 7,968 4,245 1,292 4,473 27,000 December 31, 2017 $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Allowance for loan losses Individually evaluated for impairment $ 10,838 $ 2,973 $ 1,597 $ 86 $ 6,512 $ 3,718 $ 122 $ 25,846 Collectively evaluated for impairment 112,230 7,379 39,462 34,284 23,095 18,408 5,176 240,034 Total allowance for loan losses $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Loans Individually evaluated for impairment $ 142,244 $ 26,234 $ 19,118 $ 467 $ 47,486 $ 10,891 $ 1,135 $ 247,575 Collectively evaluated for impairment 6,257,449 775,975 3,296,136 1,451,217 7,499,048 872,913 384,678 20,537,416 Total loans $ 6,399,693 $ 802,209 $ 3,315,254 $ 1,451,684 $ 7,546,534 $ 883,804 $ 385,813 $ 20,784,991 The allowance related to the oil and gas portfolio was $19 million at March 31, 2018 and represented 3% of total oil and gas loans. ($ in Millions) Three Months Ended March 31, 2018 Year Ended December 31, 2017 Balance at beginning of period $ 27 $ 38 Charge offs (4 ) (25 ) Recoveries — — Net Charge offs (4 ) (25 ) Provision for loan losses (4 ) 14 Balance at end of period $ 19 $ 27 Allowance for loan losses Individually evaluated for impairment $ 10 $ 5 Collectively evaluated for impairment 9 22 Total allowance for loan losses $ 19 $ 27 Loans Individually evaluated for impairment $ 69 $ 77 Collectively evaluated for impairment 588 523 Total loans $ 657 $ 600 The following table presents a summary of the changes in the allowance for unfunded commitments. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Allowance for Unfunded Commitments Balance at beginning of period $ 24,400 $ 25,400 Provision for unfunded commitments (500 ) (1,000 ) Amount recorded at acquisition 2,436 — Balance at end of period $ 26,336 $ 24,400 Loans Acquired in Acquisition Loans acquired in a business combination are recorded at estimated fair value on their purchase date without a carryover of the related allowance for loan and lease losses. Acquired loans are segregated into two types: • Performing loans are accounted for in accordance with ASC Topic 310-20 "Nonrefundable Fees and Other Costs" as these loans do not have evidence of credit deterioration since origination. • Nonperforming loans are accounted for in accordance with ASC Topic 310-30 as they display significant credit deterioration since origination. For performing loans the difference between the estimated fair value of the loans and the principal outstanding is accreted over the remaining life of the loans. In accordance with ASC 310-30, purchased credit-impaired loans are pooled by loan type and the difference between contractually required payments at acquisition and the cash flows expected to be collected is referred to as the non-accretable difference. Further, any excess of cash flows expected at acquisition over the estimated fair value is referred to as the accretable yield and is recognized into interest income over the remaining life of the loan pools when there is a reasonable expectation about the amount and timing of such cash flows. Changes in the accretable yield for loans acquired and accounted for under ASC Topic 310-30 were as follows for the three months ended March 31, 2018 and for the year ended December 31, 2017 Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Changes in Accretable Yield Balance at beginning of period $ — $ — Purchases 4,244 — Accretion — — Other (a) — — Balance at end of period $ 4,244 $ — (a) Represents the accretable difference that is relieved when a loan exits the PCI population due to full payoff, full charge-off, or transfer to repossessed assets, etc. For loans acquired, the fair value of purchased credit-impaired loans, on the acquisition date, was determined based on assigned risk ratings, expected cash flows and the fair value of loan collateral. The fair value of loans that were non-impaired was determined based on estimates of losses on defaults and other market factors.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Other Intangible Assets Goodwill Goodwill is not amortized but, instead, is subject to impairment tests on at least an annual basis, and more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. The Corporation conducted its most recent annual impairment testing in May 2017, utilizing a qualitative assessment. Factors that management considered in this assessment included macroeconomic conditions, industry and market considerations, overall financial performance of the Corporation and each reporting unit (both current and projected), changes in management strategy, and changes in the composition or carrying amount of net assets. In addition, management considered the changes in both the Corporation’s common stock price and in the overall bank common stock index (based on the S&P 400 Regional Bank Sub-Industry Index), as well as the Corporation’s earnings per common share trend over the past year. Based on these assessments, management concluded that the 2017 annual qualitative impairment assessment indicated that it is more likely than not that the estimated fair value exceeded the carrying value (including goodwill) for each reporting unit. Therefore, a step one quantitative analysis was not required. There have been no events since the May 2017 impairment testing that have changed the Corporation's impairment assessment conclusion. There were no impairment charges recorded in 2017 or the first three months of 2018 . At March 31, 2018 , the Corporation had goodwill of $1.2 billion , compared to $976 million at December 31, 2017. Goodwill increased $167 million related to the Bank Mutual acquisition and $10 million related to the acquisition of Diversified Insurance Solutions. See Note 2 for additional information on the Corporation's acquisitions. Other Intangible Assets The Corporation has other intangible assets that are amortized, consisting of core deposit intangibles, other intangibles (primarily related to customer relationships acquired in connection with the Corporation’s insurance agency acquisitions), and mortgage servicing rights. During the first quarter of 2018, the Corporation added approximately $58 million of core deposit intangibles as a result of the Bank Mutual acquisition. In addition, the Corporation added approximately $8 million of other intangibles relating to customer relationships associated with the Diversified acquisition. See Note 2 for additional information on the Corporation's acquisitions. For core deposit intangibles and other intangibles, changes in the gross carrying amount, accumulated amortization, and net book value were as follows. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Core deposit intangibles Gross carrying amount $ 58,100 $ 4,385 Accumulated amortization (968 ) (4,385 ) Net book value $ 57,132 $ — Additions during the periods $ 58,100 $ — Amortization during the year $ 968 $ 112 Other intangibles Gross carrying amount $ 42,131 $ 34,572 Accumulated amortization (19,549 ) (18,992 ) Net book value $ 22,582 $ 15,580 Additions during the period $ 7,559 $ 2,162 Amortization during the year $ 557 $ 1,847 The Corporation sells residential mortgage loans in the secondary market and typically retains the right to service the loans sold. Mortgage servicing rights are amortized in proportion to and over the period of estimated net servicing income and assessed for impairment at each reporting date. The Corporation evaluates its mortgage servicing rights asset for impairment at minimum on a quarterly basis. Impairment is assessed based on fair value at each reporting date using estimated prepayment speeds of the underlying mortgage loans serviced and stratifications based on the risk characteristics of the underlying loans (predominantly loan type and note interest rate). As mortgage interest rates fall, prepayment speeds are usually faster and the value of the mortgage servicing rights asset generally decreases, requiring additional valuation reserve. Conversely, as mortgage interest rates rise, prepayment speeds are usually slower and the value of the mortgage servicing rights asset generally increases, requiring less valuation reserve. A valuation allowance is established, through a charge to earnings, to the extent the amortized cost of the mortgage servicing rights exceeds the estimated fair value by stratification. If it is later determined that all or a portion of the temporary impairment no longer exists for a stratification, the valuation is reduced through a recovery to earnings. An other-than-temporary impairment (i.e., recoverability is considered remote when considering interest rates and loan pay off activity) is recognized as a write-down of the mortgage servicing rights asset and the related valuation allowance (to the extent a valuation allowance is available) and then against earnings. A direct write-down permanently reduces the carrying value of the mortgage servicing rights asset and valuation allowance, precluding subsequent recoveries. See Note 12 for a discussion of the recourse provisions on sold residential mortgage loans. See Note 13 which further discusses fair value measurement relative to the mortgage servicing rights asset. A summary of changes in the balance of the mortgage servicing rights asset and the mortgage servicing rights valuation allowance was as follows. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Mortgage servicing rights Mortgage servicing rights at beginning of period $ 59,168 $ 62,085 Additions from acquisition 8,136 — Additions 1,737 7,167 Amortization (2,324 ) (10,084 ) Mortgage servicing rights at end of period $ 66,717 $ 59,168 Valuation allowance at beginning of period (784 ) (609 ) (Additions) recoveries, net 474 (175 ) Valuation allowance at end of period (310 ) (784 ) Mortgage servicing rights, net $ 66,407 $ 58,384 Fair value of mortgage servicing rights $ 81,810 $ 64,387 Portfolio of residential mortgage loans serviced for others (“servicing portfolio”) $ 8,507,294 $ 7,646,846 Mortgage servicing rights, net to servicing portfolio 0.78 % 0.76 % Mortgage servicing rights expense (a) $ 1,849 $ 10,259 (a) Includes the amortization of mortgage servicing rights and additions / recoveries to the valuation allowance of mortgage servicing rights, and is a component of mortgage banking, net in the consolidated statements of income. The following table shows the estimated future amortization expense for amortizing intangible assets. The projections of amortization expense are based on existing asset balances, the current interest rate environment, and prepayment speeds as of March 31, 2018 . The actual amortization expense the Corporation recognizes in any given period may be significantly different depending upon acquisition or sale activities, changes in interest rates, prepayment speeds, market conditions, regulatory requirements, and events or circumstances that indicate the carrying amount of an asset may not be recoverable. Estimated Amortization Expense Core Deposit Intangibles Other Intangibles Mortgage Servicing Rights ($ in Thousands) Nine Months Ended December 31, 2018 $ 4,358 $ 2,045 $ 7,115 2019 5,810 2,428 9,324 2020 5,810 2,311 8,078 2021 5,810 2,287 6,977 2022 5,810 2,263 6,035 2023 5,810 2,244 5,234 Beyond 2023 23,724 9,004 23,954 Total Estimated Amortization Expense $ 57,132 $ 22,582 $ 66,717

Short and Long-Term Funding

Short and Long-Term Funding	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Short and Long-Term Funding	Short and Long-Term Funding The following table presents the components of short-term funding (funding with original contractual maturities of one year or less) and long-term funding (funding with original contractual maturities greater than one year). March 31, 2018 December 31, 2017 ($ in Thousands) Short-Term Funding Federal funds purchased $ 69,085 $ 141,950 Securities sold under agreements to repurchase 214,869 182,865 Federal funds purchased and securities sold under agreements to repurchase 283,954 324,815 FHLB advances 1,780,000 284,000 Commercial paper 82,420 67,467 Other short-term funding 1,862,420 351,467 Total short-term funding $ 2,146,374 $ 676,282 Long-Term Funding FHLB advances $ 2,735,887 $ 2,900,168 Senior notes, at par 250,000 250,000 Subordinated notes, at par 250,000 250,000 Other long-term funding and capitalized costs (2,549 ) (2,718 ) Total long-term funding 3,233,338 3,397,450 Total short and long-term funding $ 5,379,712 $ 4,073,732 Securities Sold Under Agreements to Repurchase ("Repurchase Agreements") The Corporation enters into agreements under which it sells securities subject to an obligation to repurchase the same or similar securities. Under these arrangements, the Corporation may transfer legal control over the assets but still retain effective control through an agreement that both entitles and obligates the Corporation to repurchase the assets. The obligation to repurchase the securities is reflected as a liability on the Corporation’s consolidated balance sheets, while the securities underlying the repurchase agreements remain in the respective investment securities asset accounts (i.e., there is no offsetting or netting of the investment securities assets with the repurchase agreement liabilities). See Note 11 for additional disclosures on balance sheet offsetting. The Corporation utilizes securities sold under agreements to repurchase to facilitate the needs of its customers. As of March 31, 2018 , the Corporation pledged agency mortgage-related securities with a fair value of $288 million as collateral for the repurchase agreements. Securities pledged as collateral under repurchase agreements are maintained with the Corporation's safekeeping agents and are monitored on a daily basis due to the market risk of fair value changes in the underlying securities. The Corporation generally pledges excess securities to ensure there is sufficient collateral to satisfy short-term fluctuations in both the repurchase agreement balances and the fair value of the underlying securities. The remaining contractual maturity of the securities sold under agreements to repurchase in the consolidated balance sheets as of March 31, 2018 and December 31, 2017 are presented in the following table. Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 days 30-90 days Greater than 90 days Total March 31, 2018 ($ in Thousands) Repurchase agreements Agency mortgage-related securities $ 214,869 $ — $ — $ — $ 214,869 Total $ 214,869 $ — $ — $ — $ 214,869 December 31, 2017 Repurchase agreements Agency mortgage-related securities $ 182,865 $ — $ — $ — $ 182,865 Total $ 182,865 $ — $ — $ — $ 182,865 Long-Term Funding FHLB advances: At March 31, 2018 , the long-term FHLB advances had maturity or call dates primarily ranging from 2018 through 2019, and had a weighted average interest rate of 1.50% , compared to 1.26% at December 31, 2017 . The majority of FHLB advances are indexed to the FHLB discount note and re-price at varying intervals. The advances offer flexible, low cost, long-term funding that improves the Corporation’s liquidity profile. Senior notes: In November 2014, the Corporation issued $250 million of senior notes, due November 2019, and callable October 2019. The senior notes have a fixed coupon interest rate of 2.75% and were issued at a discount. Subordinated notes: In November 2014, the Corporation issued $250 million of 10 -year subordinated notes, due January 2025, and callable October 2024. The subordinated notes have a fixed coupon interest rate of 4.25% and were issued at a discount.

Derivative and Hedging Activiti

Derivative and Hedging Activities	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative and Hedging Activities	Derivative and Hedging Activities The Corporation is exposed to certain risk arising from both its business operations and economic conditions. The Corporation principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources, and duration of its assets and liabilities and the use of derivative financial instruments. Specifically, the Corporation enters into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Corporation's derivative financial instruments are used to manage differences in the amount, timing, and duration of the Corporation's known or expected cash receipts and its known or expected cash payments principally related to the Corporation's assets. The contract or notional amount of a derivative is used to determine, along with the other terms of the derivative, the amounts to be exchanged between the counterparties. The Corporation is exposed to credit risk in the event of nonperformance by counterparties to financial instruments. To mitigate the counterparty risk, interest rate and commodity-related instruments generally contain language outlining collateral pledging requirements for each counterparty. Collateral must be posted when the market value exceeds certain mutually agreed upon threshold limits. The Corporation pledged $28 million of investment securities as collateral at March 31, 2018 , and pledged $24 million of investment securities as collateral at December 31, 2017 . Federal regulations require the Corporation to clear all LIBOR interest rate swaps through a clearing house if it can be cleared. As such, the Corporation is required to pledge cash collateral for the margin. At March 31, 2018 the Corporation posted $29 million of cash collateral for the margin compared to $22 million at December 31, 2017 . Fair Value Hedges of Interest Rate Risk The Corporation is exposed to changes in the fair value of certain of its pools of prepayable fixed-rate assets due to changes in benchmark interest rates. The Corporation uses interest rate swaps to manage its exposure to changes in fair value on these instruments attributable to changes in the designated benchmark interest rate. Interest rate swaps designated as fair value hedges involve the payment of fixed-rate amounts to a counterparty in exchange for the Corporation receiving variable-rate payments over the life of the agreements without the exchange of the underlying notional amount. For derivatives designated and that qualify as fair value hedges, the gain or loss on the derivative as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in interest income. Derivatives to Accommodate Customer Needs The Corporation also facilitates customer borrowing activity by entering into various derivative contracts which are designated as free standing derivative contracts. Free standing derivative products are entered into primarily for the benefit of commercial customers seeking to manage their exposures to interest rate risk, foreign currency, and commodity prices. These derivative contracts are not designated against specific assets and liabilities on the balance sheet or forecasted transactions and, therefore, do not qualify for hedge accounting treatment. Such derivative contracts are carried at fair value on the consolidated balance sheets with changes in the fair value recorded as a component of Capital market fees, net, and typically include interest rate-related instruments (swaps and caps), foreign currency exchange forwards, and commodity contracts. See Note 11 for additional information and disclosures on balance sheet offsetting. Interest rate-related instruments: The Corporation provides interest rate risk management services to commercial customers, primarily forward interest rate swaps and caps. The Corporation’s market risk from unfavorable movements in interest rates related to these derivative contracts is generally economically hedged by concurrently entering into offsetting derivative contracts. The offsetting derivative contracts have identical notional values, terms and indices. Foreign currency exchange forwards: The Corporation provides foreign currency exchange services to customers, primarily forward contracts. Our customers enter into a foreign currency exchange forward with the Corporation as a means for them to mitigate exchange rate risk. The Corporation mitigates its risk by then entering into an offsetting foreign currency exchange derivative contract. Commodity contracts: Commodity contracts are entered into primarily for the benefit of commercial customers seeking to manage their exposure to fluctuating commodity prices. The Corporation mitigates its risk by then entering into an offsetting commodity derivative contract. Mortgage Derivatives Interest rate lock commitments to originate residential mortgage loans held for sale and forward commitments to sell residential mortgage loans are considered derivative instruments, and the fair value of these commitments is recorded on the consolidated balance sheets with the changes in fair value recorded as a component of mortgage banking, net. Written and Purchased Options (Time Deposit) Historically, the Corporation had entered into written and purchased option derivative instruments to facilitate an equity linked time deposit product (the “Power CD”), which the Corporation ceased offering in September 2013. The Power CD was a time deposit that provided the purchaser a guaranteed return of principal at maturity plus a potential equity return (a written option), while the Corporation received a known stream of funds based on the equity return (a purchased option). The written and purchased options are mirror derivative instruments, which are carried at fair value on the consolidated balance sheets. The table below identifies the balance sheet category and fair values of the Corporation’s derivative instruments. March 31, 2018 December 31, 2017 ($ in Thousands) Notional Amount Fair Balance Sheet Notional Amount Fair Balance Sheet Derivatives not designated as hedging instruments Interest rate-related instruments — customer and mirror $ 2,626,982 $ 53,189 Trading assets $ 2,183,687 $ 28,494 Trading assets Interest rate-related instruments — customer and mirror 2,626,982 (52,238 ) Trading liabilities 2,183,687 (28,035 ) Trading liabilities Foreign currency exchange forwards 140,554 2,612 Trading assets 124,851 2,495 Trading assets Foreign currency exchange forwards 137,073 (2,484 ) Trading liabilities 118,094 (2,339 ) Trading liabilities Commodity contracts 467,979 47,089 Trading assets 457,868 38,686 Trading assets Commodity contracts 467,957 (45,525 ) Trading liabilities 457,108 (37,286 ) Trading liabilities Interest rate lock commitments (mortgage) 312,567 3,032 Other assets 222,736 1,538 Other assets Forward commitments (mortgage) 245,000 (303 ) Other liabilities 164,567 (313 ) Other liabilities Purchased options (time deposit) 26,389 951 Other assets 31,063 1,175 Other assets Written options (time deposit) 26,389 (951 ) Other liabilities 31,063 (1,175 ) Other liabilities Derivatives designated as hedging instruments Interest Rate Products 250,000 258 Other assets — — Other assets The following table presents amounts that were recorded on the balance sheet related to cumulative basis adjustment for fair value hedges. Line Item in the Statement of Financial Position in Which the Hedged Item is Included Carrying Amount of the Hedged Assets/(Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities) ($ in Thousands) March 31, 2018 Loans and investment securities receivables (a) 249,724 276 Total $ 249,724 $ 276 (a) These amounts include the amortized cost basis of closed portfolios used to designated hedging relationships in which the hedged item is the last layer expected to be remaining at the end of the hedging relationship. At March 31, 2018, the amortized cost basis of the closed portfolios used in these hedging relationships was $523 million ; the cumulative basis adjustments associated with these hedging relationships was $275,767 ; and the amounts of the designated hedged items were $250 million . The table below identifies the effect of fair value hedge accounting on the Corporation's statement of performance during the three months ended March 31, 2018 . Location and Amount of Gain or (Loss) Recognized in Income on Fair Value and Cash Flow Hedging Relationships Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Interest Income Other Income (Expense) Interest Income Other Income (Expense) Total amounts of income and expense line items presented in the statement of financial performance in which the effects of fair value or cash flow hedges are recorded 18 — — — The effects of fair value and cash flow hedging: Gain or (loss) on fair value hedging relationships in Subtopic 815-20 Interest contracts Hedged items 276 — — — Derivatives designated as hedging instruments (258 ) — — — The table below identifies the effect of derivatives not designated as hedging instruments on the Corporation's statement of performance during the three months ended March 31, 2018 . Income Statement Category of Gain / (Loss) Recognized in Income For the Three Months Ended March 31, ($ in Thousands) 2018 2017 Derivative Instruments Interest rate-related instruments — customer and mirror, net Capital market fees, net $ 492 $ 245 Interest rate lock commitments (mortgage) Mortgage banking, net 1,494 1,597 Forward commitments (mortgage) Mortgage banking, net 10 (3,281 ) Foreign currency exchange forwards Capital market fees, net (28 ) (21 ) Commodity contracts Capital market fees, net 164 226

Balance Sheet Offsetting

Balance Sheet Offsetting	3 Months Ended
	Mar. 31, 2018
Offsetting [Abstract]
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition The Corporation recognizes revenue in accordance with ASC 606, "Revenue from Contracts with Customers". ASC 606 requires the Corporation to follow a five step process: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation. Revenue recognition under ASC 606 depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for the goods or services.
Balance Sheet Offsetting	Balance Sheet Offsetting Interest Rate-Related Instruments and Commodity Contracts (“Interest and Commodity Agreements”) The Corporation enters into interest rate-related instruments to facilitate the interest rate risk management strategies of commercial customers. The Corporation also enters into commodity contracts to manage commercial customers' exposure to fluctuating commodity prices. The Corporation mitigates these risks by entering into equal and offsetting interest and commodity agreements with highly rated third party financial institutions. The Corporation is party to master netting arrangements with its financial institution counterparties that creates a single net settlement of all legal claims or obligations to pay or receive the net amount of settlement of the individual interest and commodity agreements. Collateral, usually in the form of investment securities and cash, is posted by the counterparty with net liability positions in accordance with contract thresholds. The Corporation does not offset assets and liabilities under these arrangements for financial statement presentation purposes. See Note 10 for additional information on the Corporation’s derivative and hedging activities. Securities Sold Under Agreements to Repurchase (“Repurchase Agreements”) The Corporation enters into agreements under which it sells securities subject to an obligation to repurchase the same or similar securities. These repurchase agreements are accounted for as collateralized financing arrangements (i.e., secured borrowings) and not as a sale and subsequent repurchase of securities (i.e., there is no offsetting or netting of the investment securities assets with the repurchase agreement liabilities). The right of set-off for a repurchase agreement resembles a secured borrowing, whereby the collateral would be used to settle the fair value of the repurchase agreement should the Corporation be in default (e.g., fails to make an interest payment to the counterparty). In addition, the Corporation does not enter into reverse repurchase agreements; therefore, there is no such offsetting to be done with the repurchase agreements. See Note 9 for additional disclosures on repurchase agreements. The following table presents the assets and liabilities subject to an enforceable master netting arrangement. The interest and commodity agreements we have with our commercial customers are not subject to an enforceable master netting arrangement, and therefore, are excluded from this table. Gross amounts recognized Gross amounts not offset in the balance sheet Gross amounts offset in the balance sheet Net amounts presented in the balance sheet Financial instruments Collateral Net amount ($ in Thousands) March 31, 2018 Derivative assets Interest and commodity agreements $ 47,528 $ — $ 47,528 $ (43,105 ) $ (1,337 ) $ 3,086 Derivative liabilities Interest and commodity agreements $ 43,105 $ — $ 43,105 $ (43,105 ) $ — $ — December 31, 2017 Derivative assets Interest and commodity agreements $ 29,503 $ — $ 29,503 $ (29,503 ) $ — $ — Derivative liabilities Interest and commodity agreements $ 37,164 $ — $ 37,164 $ (29,503 ) $ (7,661 ) $ —

Commitments, Off-Balance Sheet

Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments, Off-Balance Sheet Arrangements, and Legal Proceedings	Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters The Corporation utilizes a variety of financial instruments in the normal course of business to meet the financial needs of its customers and to manage its own exposure to fluctuations in interest rates. These financial instruments include lending-related and other commitments (see below) as well as derivative instruments (see Note 10 ). The following is a summary of lending-related commitments. March 31, 2018 December 31, 2017 ($ in Thousands) Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale (a) (b) $ 8,481,563 $ 8,027,187 Commercial letters of credit (a) 12,456 11,886 Standby letters of credit (c) 253,857 235,361 (a) These off-balance sheet financial instruments are exercisable at the market rate prevailing at the date the underlying transaction will be completed and, thus, are deemed to have no current fair value, or the fair value is based on fees currently charged to enter into similar agreements and is not material at March 31, 2018 or December 31, 2017 . (b) Interest rate lock commitments to originate residential mortgage loans held for sale are considered derivative instruments and are disclosed in Note 10 . (c) The Corporation has established a liability of $2 million at March 31, 2018 and December 31, 2017 , as an estimate of the fair value of these financial instruments. Lending-related Commitments As a financial services provider, the Corporation routinely enters into commitments to extend credit. Such commitments are subject to the same credit policies and approval process accorded to loans made by the Corporation, with each customer’s creditworthiness evaluated on a case-by-case basis. The commitments generally have fixed expiration dates or other termination clauses and may require the payment of a fee. The Corporation’s exposure to credit loss in the event of nonperformance by the other party to these financial instruments is represented by the contractual amount of those instruments. The amount of collateral obtained, if deemed necessary by the Corporation upon extension of credit, is based on management’s credit evaluation of the customer. Since a significant portion of commitments to extend credit are subject to specific restrictive loan covenants or may expire without being drawn upon, the total commitment amounts do not necessarily represent future cash flow requirements. An allowance for unfunded commitments is maintained at a level believed by management to be sufficient to absorb estimated probable losses related to unfunded commitments (including unfunded loan commitments and letters of credit). The allowance for unfunded commitments totaled $26 million at March 31, 2018 and $24 million at December 31, 2017 , and is included in accrued expenses and other liabilities on the consolidated balance sheets. Lending-related commitments include commitments to extend credit, commitments to originate residential mortgage loans held for sale, commercial letters of credit, and standby letters of credit. Commitments to extend credit are legally binding agreements to lend to customers at predetermined interest rates, as long as there is no violation of any condition established in the contracts. Interest rate lock commitments to originate residential mortgage loans held for sale and forward commitments to sell residential mortgage loans are considered derivative instruments, and the fair value of these commitments is recorded on the consolidated balance sheets. The Corporation’s derivative and hedging activity is further described in Note 10 . Commercial and standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. Commercial letters of credit are issued specifically to facilitate commerce and typically result in the commitment being drawn on when the underlying transaction is consummated between the customer and the third party, while standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of the underlying contract with the third party. Other Commitments The Corporation invests in unconsolidated projects including low-income housing, new market tax credit projects, and historic tax credit projects to promote the revitalization of primarily low-to-moderate-income neighborhoods throughout the local communities of its bank subsidiary. As a limited partner in these unconsolidated projects, the Corporation is allocated tax credits and deductions associated with the underlying projects. The aggregate carrying value of these investments at March 31, 2018 was $142 million , compared to $147 million at December 31, 2017 . The Corporation has principal investment commitments to provide capital-based financing to private and public companies through either direct investments in specific companies or through investment funds and partnerships. The timing of future cash requirements to fund such commitments is generally dependent on the investment cycle, whereby privately held companies are funded by private equity investors and ultimately sold, merged, or taken public through an initial offering, which can vary based on overall market conditions, as well as the nature and type of industry in which the companies operate. The aggregate carrying value of these investments at March 31, 2018 was $24 million , compared to $23 million at December 31, 2017 , included in other assets on the consolidated balance sheets. Related to these investments, the Corporation had remaining commitments to fund $111 million at March 31, 2018 , and $119 million at December 31, 2017 . Legal Proceedings The Corporation is party to various pending and threatened claims and legal proceedings arising in the normal course of business activities, some of which involve claims for substantial amounts. Although there can be no assurance as to the ultimate outcomes, the Corporation believes it has meritorious defenses to the claims asserted against it in its currently outstanding matters, including the matters described below, and with respect to such legal proceedings, intends to continue to defend itself vigorously. The Corporation will consider settlement of cases when, in management’s judgment, it is in the best interests of both the Corporation and its shareholders. On at least a quarterly basis, the Corporation assesses its liabilities and contingencies in connection with all pending or threatened claims and litigation, utilizing the most recent information available. On a matter by matter basis, an accrual for loss is established for those matters which the Corporation believes it is probable that a loss may be incurred and that the amount of such loss can be reasonably estimated. Once established, each accrual is adjusted as appropriate to reflect any subsequent developments. Accordingly, management’s estimate will change from time to time, and actual losses may be more or less than the current estimate. For matters where a loss is not probable, or the amount of the loss cannot be estimated, no accrual is established. Resolution of legal claims is inherently unpredictable, and in many legal proceedings various factors exacerbate this inherent unpredictability, including where the damages sought are unsubstantiated or indeterminate, it is unclear whether a case brought as a class action will be allowed to proceed on that basis, discovery is not complete, the proceeding is not yet in its final stages, the matters present legal uncertainties, there are significant facts in dispute, there are a large number of parties (including where it is uncertain how liability, if any, will be shared among multiple defendants), or there is a wide range of potential results. A lawsuit, R.J. ZAYED v. Associated Bank, N.A., was filed in the United States District Court for the District of Minnesota on January 29, 2013. The lawsuit relates to a Ponzi scheme perpetrated by Oxford Global Partners and related entities (“Oxford”) and individuals and was brought by the receiver for Oxford. Oxford was a depository customer of Associated Bank (the "Bank"). The lawsuit claims that the Bank is liable for failing to uncover the Oxford Ponzi scheme, and specifically alleges the Bank aided and abetted (1) the fraudulent scheme; (2) a breach of fiduciary duty; (3) conversion; and (4) false representations and omissions. The lawsuit seeks unspecified consequential and punitive damages. The District Court granted the Bank’s motion to dismiss the complaint on September 30, 2013. On March 2, 2015, the U.S. Court of Appeals for the Eighth Circuit reversed the District Court and remanded the case back to the District Court for further proceedings. On January 31, 2017, the District Court granted the Bank’s motion for summary judgment. The receiver has appealed the District Court’s summary judgment decision to the Eighth Circuit Court of Appeals. On January 23, 2018, the District Court approved a settlement agreement between the parties. Based on the terms of the settlement agreement, the Bank expects that the litigation will not have a material adverse impact on the Bank regardless of the outcome of the appeal to the Eighth Circuit Court of Appeals. A lawsuit by investors in the same Ponzi scheme, Herman Grad, et al v. Associated Bank, N.A., brought in Brown County, Wisconsin in October 2009 was dismissed by the circuit court, and the dismissal was affirmed by the Wisconsin Court of Appeals in June 2011 in an unpublished opinion. Two complaints were filed against the Bank on January 11, 2016 in the United States Bankruptcy Court for the Northern District of Illinois, Eastern Division in connection with the In re: World Marketing Chicago, LLC, et al Chapter 11 bankruptcy proceeding. In the first complaint, The Official Committee of Unsecured Creditors of World Marketing Chicago, LLC, et al v. Associated Bank, N.A., the plaintiff seeks to avoid guarantees and pledges of collateral given by the debtors to secure a revolving financing commitment of $6 million to the debtors’ parent company from the Bank. The plaintiff alleges a variety of legal theories under federal and state law, including fraudulent conveyance, preferential transfer and conversion, in support of its position. The plaintiff seeks return of approximately $4 million paid to the Bank and the avoidance of the security interest in the collateral securing the remaining indebtedness to the Bank. In the second complaint, American Funds Service Company v. Associated Bank, N.A., the plaintiff alleges that approximately $600,000 of funds it had advanced to the World Marketing entities to apply towards future postage fees was swept by the Bank from World Marketing’s bank accounts. Plaintiff seeks the return of such funds from the Bank under several theories, including Sec. 541(d) of the Bankruptcy Code, the creation of a resulting trust, and unjust enrichment. On February 7, 2018, both cases were settled, and the Bank received approximately $540,000 from the proceeds of the liquidation of its collateral. Both cases were dismissed on February 16, 2018. Subsequent to the announcement on July 20, 2017, of the Merger Agreement between the Corporation and Bank Mutual, several lawsuits were filed in connection with the proposed merger. On July 28, 2017, two substantially identical purported class action complaints, each by various individual plaintiffs, were filed with the Wisconsin Circuit Court for Milwaukee County on behalf of the respective named plaintiffs and other Bank Mutual shareholders against Bank Mutual, the members of the Bank Mutual board, and the Corporation. The lawsuits are captioned Schumel et al v. Bank Mutual Corporation et al. and Paquin et al. v. Bank Mutual Corporation et al. Both complaints allege state law breach of fiduciary duty claims against the Bank Mutual board for, among other things, seeking to sell Bank Mutual through an allegedly defective process, for an allegedly unfair price and on allegedly unfair terms. On August 30, 2017, a third purported class action complaint, captioned Wollenburg et al. v. Bank Mutual Corporation et al., was filed in the Wisconsin Circuit Court for Milwaukee County, on behalf of the same class of shareholders and against the same defendants as the prior two complaints. The Wollenburg complaint asserts similar allegations as the prior two complaints, and further alleges that the preliminary proxy statement/prospectus filed with the SEC contains various alleged misstatements or omissions under federal securities law. The Paquin, Schumel and Wollenburg complaints allege that the Corporation aided and abetted Bank Mutual's directors' alleged breaches of fiduciary duty. The parties have entered into a stipulation seeking to consolidate the three actions. On September 13, 2017, the Corporation filed a notice of removal of the Paquin, Schumel and Wollenburg actions to the United States District Court for the Eastern District of Wisconsin. On September 15, 2017, the plaintiffs in the Paquin, Schumel and Wollenburg actions filed identical motions to remand the three cases back to state court, and on September 27, 2017, the defendants filed oppositions to the motions to remand. On October 3, 2017, the defendants filed motions to dismiss the three actions. On September 6, 2017, a fourth purported class action complaint, captioned Parshall et al., v. Bank Mutual Corporation et al., was filed in the U.S. District Court for the Eastern District of Wisconsin, on behalf of the same class of shareholders and against the same defendants as the prior complaints. The Parshall complaint criticizes the adequacy of the merger consideration and alleges that Bank Mutual, the members of the Bank Mutual board and the Corporation allegedly omitted and/or misrepresented certain information in the registration statement on Form S-4 filed in connection with the proposed merger in violation of the federal securities laws. The lawsuits seek, among other things, to enjoin the consummation of the transaction and damages. The Corporation believes the allegations are without merit. On October 13, 2017, Bank Mutual and the Corporation reached agreement with the plaintiffs in each of the four cases whereby Bank Mutual issued certain additional disclosures in a Form 8-K, and each of the plaintiffs have agreed to dismiss their actions with prejudice as to the named plaintiffs and without prejudice as to the rest of the purported class members. Regulatory Matters On May 22, 2015, the Bank entered into a Conciliation Agreement ("Conciliation Agreement") with the U.S. Department of Housing and Urban Development ("HUD") which resolved the HUD investigation into the Bank's lending practices during the years 2008-2010. The Bank's commitments under the Conciliation Agreement are spread over 3 years and include commitments to do the following in minority communities: make mortgage loans of approximately $196 million ; open one branch and four loan production offices; establish special financing programs; make affordable home repair grants; engage in affirmative marketing outreach; provide financial education programs; and make grants to support community reinvestment training and education. The cost of these commitments will be spread over four calendar years and is not expected to have a material impact on the Corporation's financial condition or results of operation. A variety of consumer products, including mortgage and deposit products, and certain fees and charges related to such products, have come under increased regulatory scrutiny. It is possible that regulatory authorities could bring enforcement actions, including civil money penalties, or take other actions against the Corporation and the Bank in regard to these consumer products. The Bank could also determine of its own accord, or be required by regulators, to refund or otherwise make remediation payments to customers in connection with these products. It is not possible at this time for management to assess the probability of a material adverse outcome or reasonably estimate the amount of any potential loss related to such matters. Mortgage Repurchase Reserve The Corporation sells residential mortgage loans to investors in the normal course of business. Residential mortgage loans sold to others are predominantly conventional residential first lien mortgages originated under our usual underwriting procedures, and are most often sold on a nonrecourse basis, primarily to the GSEs. The Corporation’s agreements to sell residential mortgage loans in the normal course of business usually require certain representations and warranties on the underlying loans sold, related to credit information, loan documentation, collateral, and insurability. Subsequent to being sold, if a material underwriting deficiency or documentation defect is discovered, the Corporation may be obligated to repurchase the loan or reimburse the GSEs for losses incurred (collectively, “make whole requests”). The make whole requests and any related risk of loss under the representations and warranties are largely driven by borrower performance. As a result of make whole requests, the Corporation has repurchased loans with principal balances of approximately $394 thousand and $1 million during the three months ended March 31, 2018 and the year ended December 31, 2017 , respectively. The loss reimbursement and settlement claims paid for the three months ended March 31, 2018 were zero and negligible for the year ended December 31, 2017 . Make whole requests during 2017 and the first three months of 2018 generally arose from loans sold during the period of January 1, 2012 to December 31, 2017 , which totaled $10.0 billion at the time of sale, and consisted primarily of loans sold to GSEs. As of March 31, 2018 , approximately $6.0 billion of these sold loans remain outstanding. The balance in the mortgage repurchase reserve at the balance sheet date reflects the estimated amount of potential loss the Corporation could incur from repurchasing a loan, as well as loss reimbursements, indemnifications, and other settlement resolutions. The following summarizes the changes in the mortgage repurchase reserve. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Balance at beginning of period $ 987 $ 900 Repurchase provision expense 56 246 Charge offs, net (48 ) (159 ) Amount recorded at acquisition 88 — Balance at end of period $ 1,083 $ 987 The Corporation may also sell residential mortgage loans with limited recourse (limited in that the recourse period ends prior to the loan’s maturity, usually after certain time and / or loan paydown criteria have been met), whereby repurchase could be required if the loan had defined delinquency issues during the limited recourse periods. At March 31, 2018 , and December 31, 2017 , there were approximately $36 million and $44 million , respectively, of residential mortgage loans sold with such recourse risk. There have been limited instances and immaterial historical losses on repurchases for recourse under the limited recourse criteria. The Corporation has a subordinate position to the FHLB in the credit risk on residential mortgage loans it sold to the FHLB in exchange for a monthly credit enhancement fee. The Corporation has not sold loans to the FHLB with such credit risk retention since February 2005. At March 31, 2018 and December 31, 2017 , there were $69 million and $73 million , respectively, of such residential mortgage loans with credit risk recourse, upon which there have been negligible historical losses to the Corporation.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value represents the estimated price at which an orderly transaction to sell an asset or to transfer a liability would take place between market participants at the measurement date under current market conditions (i.e., an exit price concept). Following is a description of the valuation methodologies used for the Corporation’s more significant instruments measured on a recurring basis at fair value, including the general classification of such instruments pursuant to the valuation hierarchy. Assets and Liabilities Measured at Fair Value on a Recurring Basis Investment Securities Available for Sale: Where quoted prices are available in an active market, investment securities are classified in Level 1 of the fair value hierarchy. If quoted market prices are not available for the specific security, then fair values are estimated by using pricing models, quoted prices of securities with similar characteristics or discounted cash flows, with consideration given to the nature of the quote and the relationship of recently evidenced market activity to the fair value estimate, and are classified in Level 2 of the fair value hierarchy. Lastly, in certain cases where there is limited activity or less transparency around inputs to the estimated fair value, securities are classified within Level 3 of the fair value hierarchy. To validate the fair value estimates, assumptions, and controls, the Corporation looks to transactions for similar instruments and utilizes independent pricing provided by third party vendors or brokers and relevant market indices. While none of these sources are solely indicative of fair value, they serve as directional indicators for the appropriateness of the Corporation’s fair value estimates. The Corporation has determined that the fair value measures of its investment securities are classified predominantly within Level 1 or 2 of the fair value hierarchy. See Note 6 for additional disclosure regarding the Corporation’s investment securities. Residential Loans Held for Sale: Loans held for sale, which consist generally of current production of certain fixed-rate, first-lien residential mortgage loans, are carried at estimated fair value. Management has elected the fair value option to account for all newly originated mortgage loans held for sale which results in the financial impact of changing market conditions being reflected currently in earnings as opposed to being dependent upon the timing of sales. Therefore, the continually adjusted values better reflect the price the Corporation expects to receive from the sale of such loans. The estimated fair value was based on what secondary markets are currently offering for portfolios with similar characteristics, which the Corporation classifies as a Level 2 fair value measurement. Derivative Financial Instruments (Interest Rate-Related Instruments): The Corporation utilizes interest rate swaps to hedge exposure to interest rate risk and variability of fair value associated to changes in the underlying interest rate of the hedged item. These hedged interest rate swaps are classified as fair value hedges. See Note 10 for additional disclosure regarding the Corporation’s fair value hedges. In addition, the Corporation offers interest rate-related instruments (swaps and caps) to service our customers’ needs, for which the Corporation simultaneously enters into offsetting derivative financial instruments (i.e., mirror interest rate-related instruments) with third parties to manage its interest rate risk associated with these financial instruments. The valuation of the Corporation’s derivative financial instruments is determined using discounted cash flow analysis on the expected cash flows of each derivative and also includes a nonperformance / credit risk component (credit valuation adjustment). See Note 10 for additional disclosure regarding the Corporation’s interest rate-related instruments. The discounted cash flow analysis component in the fair value measurement reflects the contractual terms of the derivative financial instruments, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. More specifically, the fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) with the variable cash payments (or receipts) based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. Likewise, the fair values of interest rate options (i.e., interest rate caps) are determined using the market standard methodology of discounting the future expected cash receipts that would occur if variable interest rates fall below (or rise above) the strike rate of the floors (or caps), with the variable interest rates used in the calculation of projected receipts on the floor (or cap) based on an expectation of future interest rates derived from observable market interest rate curves and volatilities. The Corporation also incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative financial instruments for the effect of nonperformance risk, the Corporation has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. While the Corporation has determined that the majority of the inputs used to value its derivative financial instruments fall within Level 2 of the fair value hierarchy, the credit valuation adjustments utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. The Corporation has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions as of March 31, 2018 , and December 31, 2017 , and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivative financial instruments. Therefore, the Corporation has determined that the fair value measures of its derivative financial instruments in their entirety are classified within Level 2 of the fair value hierarchy. Derivative Financial Instruments (Foreign Currency Exchange Forwards): The Corporation provides foreign currency exchange services to customers. In addition, the Corporation may enter into a foreign currency exchange forward to mitigate the exchange rate risk attached to the cash flows of a loan or as an offsetting contract to a forward entered into as a service to our customer. The valuation of the Corporation’s foreign currency exchange forwards is determined using quoted prices of foreign currency exchange forwards with similar characteristics, with consideration given to the nature of the quote and the relationship of recently evidenced market activity to the fair value estimate, and are classified in Level 2 of the fair value hierarchy. See Note 10 for additional disclosures regarding the Corporation’s foreign currency exchange forwards. Derivative Financial Instruments (Commodity Contracts): The Corporation enters into commodity contracts to manage commercial customers' exposure to fluctuating commodity prices, for which the Corporation simultaneously enters into offsetting derivative financial instruments (i.e., mirror commodity contracts) with third parties to manage its risk associated with these financial instruments. The valuation of the Corporation’s commodity contracts is determined using quoted prices of the underlying instruments, and are classified in Level 2 of the fair value hierarchy. See Note 10 for additional disclosures regarding the Corporation’s commodity contracts. The table below presents the Corporation’s financial instruments measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 , aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Hierarchy March 31, 2018 December 31, 2017 ($ in Thousands) Assets Investment securities available for sale U.S. Treasury securities Level 1 $ 995 $ 996 Residential mortgage-related securities FNMA / FHLMC Level 2 430,073 464,768 GNMA Level 2 2,310,306 1,913,350 Private-label Level 2 1,044 1,059 GNMA commercial mortgage-related securities Level 2 1,448,369 1,513,277 FFELP asset backed securities Level 2 290,300 145,176 Other equity securities Level 1 1,599 1,632 Other debt securities Level 2 3,188 3,188 Total investment securities available for sale Level 1 2,594 2,628 Total investment securities available for sale Level 2 4,483,281 4,040,818 Residential loans held for sale Level 2 103,953 85,544 Commercial loans held for sale Level 2 6,091 — Interest rate-related instruments Level 2 53,189 28,494 Foreign currency exchange forwards Level 2 2,612 2,495 Interest rate products (designated as hedging instruments) Level 2 258 — Interest rate lock commitments to originate residential mortgage loans held for sale Level 3 3,032 1,538 Commodity contracts Level 2 47,089 38,686 Purchased options (time deposit) Level 2 951 1,175 Liabilities Interest rate-related instruments Level 2 $ 52,238 $ 28,035 Foreign currency exchange forwards Level 2 2,484 2,339 Forward commitments to sell residential mortgage loans Level 3 303 313 Commodity contracts Level 2 45,525 37,286 Written options (time deposit) Level 2 951 1,175 The table below presents a rollforward of the balance sheet amounts for the three months ended March 31, 2018 and the year ended December 31, 2017 , for financial instruments measured on a recurring basis and classified within Level 3 of the fair value hierarchy. Investment Securities Available for Sale Derivative Financial Instruments ($ in Thousands) Balance December 31, 2016 $ 200 $ 3,114 Total net gains (losses) included in income Mortgage derivative gain (loss) — (1,889 ) Transfer out of level 3 securities (a) (200 ) — Balance December 31, 2017 $ — $ 1,225 Total net gains (losses) included in income Mortgage derivative gain (loss) — 1,501 Balance March 31, 2018 $ — $ 2,726 (a) During the first quarter of 2017, the $200,000 level 3 investment security was transferred to level 2 based upon new pricing information. For Level 3 assets and liabilities measured at fair value on a recurring basis as of March 31, 2018 , the Corporation utilized the following valuation techniques and significant unobservable inputs. Derivative Financial Instruments (Mortgage Derivative — Interest Rate Lock Commitments to Originate Residential Mortgage Loans Held for Sale): The fair value is determined by the change in value from each loan’s rate lock date to the expected rate lock expiration date based on the underlying loan attributes, estimated closing ratios, and investor price matrix determined to be reasonably applicable to each loan commitment. The closing ratio calculation takes into consideration historical experience and loan-level attributes, particularly the change in the current interest rates from the time of initial rate lock. The closing ratio is periodically reviewed for reasonableness and reported to the Associated Mortgage Risk Management Committee. At March 31, 2018 , the closing ratio was 85% . Derivative Financial Instruments (Mortgage Derivative—Forward Commitments to Sell Mortgage Loans): Mortgage derivatives include forward commitments to deliver closed end residential mortgage loans into conforming Agency Mortgage Backed Securities (To be Announced, "TBA") or conforming Cash Forward sales. The fair value of such instruments is determined by the difference of current market prices for such traded instruments or available from forward cash delivery commitments and the original traded price for such commitments. The Corporation also relies on an internal valuation model to estimate the fair value of its forward commitments to sell residential mortgage loans (i.e., an estimate of what the Corporation would receive or pay to terminate the forward delivery contract based on market prices for similar financial instruments), which includes matching specific terms and maturities of the forward commitments against applicable investor pricing available. While there are Level 2 and 3 inputs used in the valuation models, the Corporation has determined that the majority of the inputs significant in the valuation of both of the mortgage derivatives fall within Level 3 of the fair value hierarchy. See Note 10 for additional disclosure regarding the Corporation’s mortgage derivatives. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Following is a description of the valuation methodologies used for the Corporation’s more significant instruments measured on a nonrecurring basis at the lower of amortized cost or estimated fair value, including the general classification of such instruments pursuant to the valuation hierarchy. Commercial Loans Held for Sale: Loans held for sale are carried at the lower of cost or estimated fair value. The estimated fair value is based on a discounted cash flow analysis, which the Corporation classifies as a Level 2 nonrecurring fair value measurement. Other Real Estate Owned: Certain other real estate owned, upon initial recognition, was re-measured and reported at fair value through a charge off to the allowance for loan losses based upon the estimated fair value of the other real estate owned, less estimated selling costs. The fair value of other real estate owned, upon initial recognition or subsequent impairment, was estimated using appraised values, which the Corporation classifies as a Level 2 nonrecurring fair value measurement. For Level 3 assets and liabilities measured at fair value on a nonrecurring basis as of March 31, 2018 , the Corporation utilized the following valuation techniques and significant unobservable inputs. Impaired Loans: The Corporation considers a loan impaired when it is probable that the Corporation will be unable to collect all amounts due according to the original contractual terms of the note agreement, including both principal and interest. Management has determined that commercial and consumer loan relationships that have nonaccrual status or have had their terms restructured in a troubled debt restructuring meet this impaired loan definition. For individually evaluated impaired loans, the amount of impairment is based upon the present value of expected future cash flows discounted at the loan’s effective interest rate, the estimated fair value of the underlying collateral for collateral-dependent loans, or the estimated liquidity of the note. See Note 7 for additional information regarding the Corporation’s impaired loans. Mortgage Servicing Rights: Mortgage servicing rights do not trade in an active, open market with readily observable prices. While sales of mortgage servicing rights do occur, the precise terms and conditions typically are not readily available to allow for a “quoted price for similar assets” comparison. Accordingly, the Corporation utilizes an independent valuation from a third party which uses a discounted cash flow model to estimate the fair value of its mortgage servicing rights. The valuation model incorporates prepayment assumptions to project mortgage servicing rights cash flows based on the current interest rate scenario, which is then discounted to estimate an expected fair value of the mortgage servicing rights. The valuation model considers portfolio characteristics of the underlying mortgages, contractually specified servicing fees, prepayment assumptions, discount rate assumptions, delinquency rates, late charges, other ancillary revenue, costs to service, and other economic factors. The Corporation periodically reviews and assesses the underlying inputs and assumptions used in the model. In addition, the Corporation compares its fair value estimates and assumptions to observable market data for mortgage servicing rights, where available, and to recent market activity and actual portfolio experience. Due to the nature of the valuation inputs, mortgage servicing rights are classified within Level 3 of the fair value hierarchy. The Corporation uses the amortization method (i.e., lower of amortized cost or estimated fair value measured on a nonrecurring basis), not fair value measurement accounting, for its mortgage servicing rights assets. The discounted cash flow analyses that generate expected market prices utilize the observable characteristics of the mortgage servicing rights portfolio, as well as certain unobservable valuation parameters. The significant unobservable inputs used in the fair value measurement of the Corporation’s mortgage servicing rights are the weighted average constant prepayment rate and weighted average discount rate. Significant increases (decreases) in any of those inputs in isolation could result in a significantly lower (higher) fair value measurement. These parameter assumptions fall within a range that the Corporation, in consultation with an independent third party, believes purchasers of servicing would apply to such portfolios sold into the current secondary servicing market. Discussions are held with members from Treasury and the Community, Consumer, and Business segment to reconcile the fair value estimates and the key assumptions used by the respective parties in arriving at those estimates. The Associated Mortgage Risk Management Committee is responsible for providing control over the valuation methodology and key assumptions. To assess the reasonableness of the fair value measurement, the Corporation also compares the fair value and constant prepayment rate to a value calculated by an independent third party on an annual basis. See Note 8 for additional disclosure regarding the Corporation’s mortgage servicing rights. The table below presents the Corporation’s assets measured at fair value on a nonrecurring basis, aggregated by the level in the fair value hierarchy within which those measurements fall. Income Statement Category of Adjustment Recognized in Income ($ in Thousands) Fair Value Hierarchy Fair Value March 31, 2018 Assets Commercial loans held for sale (a) Level 2 $ 6,091 Provision for credit losses $ — Impaired loans (b) Level 3 74,038 Provision for credit losses (c) (14,518 ) Other real estate owned Level 2 2,088 Foreclosure / OREO expense, net (553 ) Mortgage servicing rights Level 3 81,810 Mortgage banking, net 474 December 31, 2017 Assets Impaired loans (b) Level 3 $ 92,534 Provision for credit losses (c) $ (32,159 ) Other real estate owned Level 2 2,604 Foreclosure / OREO expense, net (939 ) Mortgage servicing rights Level 3 64,387 Mortgage banking, net (175 ) (a) Commercial loans held for sale are carried at the lower of cost or estimated fair value. When the cost is less than or equal to the estimated fair value, no adjustment is recognized in income. (b) Represents individually evaluated impaired loans, net of the related allowance for loan losses. (c) Represents provision for credit losses on individually evaluated impaired loans. Certain nonfinancial assets and nonfinancial liabilities measured at fair value on a nonrecurring basis include the fair value analysis in the second step of a goodwill impairment test, and intangible assets and other nonfinancial long-lived assets measured at fair value for impairment assessment. The Corporation's significant Level 3 measurements which employ unobservable inputs that are readily quantifiable pertain to mortgage servicing rights and impaired loans. The table below presents information about these inputs and further discussion is found above. Valuation Technique Significant Unobservable Input Weighted Average Input Applied March 31, 2018 Mortgage servicing rights Discounted cash flow Discount rate 11% Mortgage servicing rights Discounted cash flow Constant prepayment rate 9% Impaired Loans Appraisals / Discounted cash flow Collateral / Discount factor 28% Fair Value of Financial Instruments The Corporation is required to disclose estimated fair values for its financial instruments. Fair value estimates are set forth below for the Corporation’s financial instruments. March 31, 2018 December 31, 2017 Fair Value Hierarchy Level Carrying Amount Fair Value Carrying Amount Fair Value ($ in Thousands) Financial assets Cash and due from banks Level 1 $ 328,260 $ 328,260 $ 483,666 $ 483,666 Interest-bearing deposits in other financial institutions Level 1 94,918 94,918 199,702 199,702 Federal funds sold and securities purchased under agreements to resell Level 1 10,000 10,000 32,650 32,650 Investment securities held to maturity Level 2 2,443,203 2,407,197 2,282,853 2,283,574 Investment securities available for sale Level 1 2,594 2,594 2,628 2,628 Investment securities available for sale Level 2 4,483,281 4,483,281 4,040,818 4,040,818 FHLB and Federal Reserve Bank stocks Level 2 233,216 233,216 165,331 165,331 Residential loans held for sale Level 2 103,953 103,953 85,544 85,544 Commercial loans held for sale Level 2 6,091 6,091 — — Loans, net Level 3 22,553,433 22,195,415 20,519,111 20,314,984 Bank and corporate owned life insurance Level 2 657,841 657,841 591,057 591,057 Derivatives (trading and other assets) Level 2 104,099 104,099 70,850 70,850 Derivatives (trading and other assets) Level 3 3,032 3,032 1,538 1,538 Financial liabilities Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts Level 3 $ 21,148,230 $ 21,148,230 $ 20,436,893 $ 20,436,893 Brokered CDs and other time deposits Level 2 2,677,372 2,677,372 2,349,069 2,349,069 Short-term funding Level 2 2,146,374 2,146,374 676,282 676,282 Long-term funding Level 2 3,233,338 3,242,517 3,397,450 3,411,368 Standby letters of credit (a) Level 2 2,468 2,468 2,402 2,402 Derivatives (trading and other liabilities) Level 2 101,198 101,198 68,835 68,835 Derivatives (trading and other liabilities) Level 3 303 303 313 313 (a) The commitment on standby letters of credit was $254 million and $235 million at March 31, 2018 and December 31, 2017 , respectively. See Note 12 for additional information on the standby letters of credit and for information on the fair value of lending-related commitments.

Retirement Plans

Retirement Plans	3 Months Ended
	Mar. 31, 2018
Defined Benefit Plan [Abstract]
Retirement Plans	Retirement Plans The Corporation has a noncontributory defined benefit retirement plan (the Retirement Account Plan (“RAP”)) covering substantially all employees who meet participation requirements. The benefits are based primarily on years of service and the employee’s compensation paid. Employees of acquired entities generally participate in the RAP after consummation of the business combinations. Any retirement plans of acquired entities are typically merged into the RAP after completion of the mergers, and credit is usually given to employees for years of service at the acquired institution for vesting and eligibility purposes. The Corporation also provides legacy healthcare access to a limited group of retired employees from a previous acquisition in the Postretirement Plan. There are no other active retiree healthcare plans. Bank Mutual was acquired on February 1, 2018. The Bank Mutual Pension Plan has not yet been merged into the Corporation's Retirement Account Plan. However, Bank Mutual's Postretirement Plan was merged into the Corporation's Postretirement Plan during the first quarter of 2018. The components of net periodic benefit cost for the RAP, Bank Mutual Pension Plan, and \Postretirement Plan for three months ended March 31, 2018 and 2017 were as follows. Three Months Ended March 31, 2018 2017 ($ in Thousands) Components of Net Periodic Benefit Cost RAP Service cost $ 1,893 $ 1,781 Interest cost 1,660 1,756 Expected return on plan assets (4,755 ) (4,881 ) Amortization of prior service cost (19 ) (19 ) Amortization of actuarial loss 463 488 Total net pension cost $ (759 ) $ (875 ) Bank Mutual Pension Plan (a) Interest cost $ 433 N/A Expected return on plan assets (532 ) N/A Total net pension cost $ (99 ) N/A Postretirement Plan (b) Interest cost $ 26 $ 24 Amortization of prior service cost (19 ) (19 ) Amortization of actuarial loss 2 — Total net periodic benefit cost $ 9 $ 5 (a) The reported figures for first quarter 2018 only include two months of expense due to the timing of the Bank Mutual acquisition. See Note 2 for additional information on the Bank Mutual acquisition. (b) The portion of the Postretirement Plan attributed to Bank Mutual's Postretirement Plan only includes two months of expense due to the timing of the Bank Mutual acquisition. See Note 2 for additional information on the Bank Mutual acquisition. The components of net periodic benefit cost other than the service cost component are included in the line item "other" of noninterest expense in the Consolidated Statements of Income.

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Corporation utilizes a risk-based internal profitability measurement system to provide strategic business unit reporting. The profitability measurement system is based on internal management methodologies designed to produce consistent results and reflect the underlying economics of the units. Certain strategic business units have been combined for segment information reporting purposes where the nature of the products and services, the type of customer and the distribution of those products and services are similar. The three reportable segments are Corporate and Commercial Specialty; Community, Consumer, and Business; and Risk Management and Shared Services. The financial information of the Corporation’s segments has been compiled utilizing the accounting policies described in the Corporation’s 2017 Annual Report on Form 10-K, with certain exceptions. The more significant of these exceptions are described herein. The Corporation allocates net interest income using an internal funds transfer pricing ("FTP") methodology that charges users of funds (assets) and credits providers of funds (liabilities, primarily deposits) based on the maturity, prepayment and / or repricing characteristics of the assets and liabilities. The net effect of this allocation is recorded in the Risk Management and Shared Services segment. A credit provision is allocated to segments based on the expected long-term annual net charge off rates attributable to the credit risk of loans managed by the segment during the period. In contrast, the level of the consolidated provision for credit losses is determined based on an incurred loss model using the methodologies described in the Corporation’s 2017 Annual Report on Form 10-K to assess the overall appropriateness of the allowance for loan losses. The net effect of the credit provision is recorded in Risk Management and Shared Services. Indirect expenses incurred by certain centralized support areas are allocated to segments based on actual usage (for example, volume measurements) and other criteria. Certain types of administrative expense and bank-wide expense accruals (including amortization of core deposit and other intangible assets associated with acquisitions) are generally not allocated to segments. Income taxes are allocated to segments based on the Corporation’s estimated effective tax rate, with certain segments adjusted for any tax-exempt income or non-deductible expenses. Equity is allocated to the segments based on regulatory capital requirements and in proportion to an assessment of the inherent risks associated with the business of the segment (including interest, credit and operating risk). The management accounting policies and processes utilized in compiling segment financial information are highly subjective and, unlike financial accounting, are not based on authoritative guidance similar to U.S. generally accepted accounting principles. As a result, reported segments and the financial information of the reported segments are not necessarily comparable with similar information reported by other financial institutions. Furthermore, changes in management structure or allocation methodologies and procedures may result in changes in previously reported segment financial data. A brief description of each business segment is presented below. A more in-depth discussion of these segments can be found in the Segment Reporting footnote in the Corporation’s 2017 Annual Report on Form 10-K. The Corporate and Commercial Specialty segment serves a wide range of customers including larger businesses, developers, not-for-profits, municipalities, and financial institutions. The Community, Consumer, and Business segment serves individuals, as well as small and mid-sized businesses. The Risk Management and Shared Services segment includes key shared operational functions and also includes residual revenue and expenses, representing the difference between actual amounts incurred and the amounts allocated to operating segments, including interest rate risk residuals (FTP mismatches) and credit risk and provision residuals (long-term credit charge mismatches). In addition, the Risk Management and Shared Services segment includes certain unallocated expenses related to Bank Mutual's shared services and operations prior to system conversion in late June 2018. Information about the Corporation’s segments is presented below. Segment Income Statement Data ($ in Thousands) Corporate and Commercial Specialty Community, Consumer, and Business Risk Management and Shared Services Consolidated Total Three Months Ended March 31, 2018 Net interest income $ 95,958 $ 103,543 $ 10,370 $ 209,871 Noninterest income 12,683 74,036 3,661 90,380 Total revenue 108,641 177,579 14,031 300,251 Credit provision (a) 10,598 4,966 (15,563 ) — Noninterest expense 39,250 127,144 46,571 212,965 Income (loss) before income taxes 58,793 45,469 (16,977 ) 87,285 Income tax expense (benefit) 11,426 9,549 (3,146 ) 17,829 Net income (loss) $ 47,367 $ 35,920 $ (13,831 ) $ 69,456 Return on average allocated capital (ROCET1) (b) 16.4 % 23.0 % (11.2 )% 11.4 % Three Months Ended March 31, 2017 Net interest income $ 89,388 $ 88,928 $ 1,958 $ 180,274 Noninterest income 11,993 64,870 2,968 79,831 Total revenue 101,381 153,798 4,926 260,105 Credit provision (a) 11,580 4,507 (7,087 ) 9,000 Noninterest expense 37,479 116,097 20,115 173,691 Income (loss) before income taxes 52,322 33,194 (8,102 ) 77,414 Income tax expense (benefit) 17,649 11,618 (8,123 ) 21,144 Net income $ 34,673 $ 21,576 $ 21 $ 56,270 Return on average allocated capital (ROCET1) (b) 12.6 % 15.2 % (2.5 )% 10.6 % Segment Balance Sheet Data ($ in Thousands) Corporate and Commercial Specialty Community, Consumer, and Business Risk Management and Shared Services Consolidated Total Three Months Ended March 31, 2018 Average earning assets $ 11,389,211 $ 10,137,899 $ 7,755,022 $ 29,282,132 Average loans 11,378,390 10,133,202 566,936 22,078,529 Average deposits 8,057,246 13,096,782 2,496,870 23,650,898 Average allocated capital (CET1) (b) $ 1,171,038 $ 632,723 $ 586,172 $ 2,389,933 Three Months Ended March 31, 2017 Average earning assets $ 10,759,811 $ 9,130,457 $ 6,449,046 $ 26,339,314 Average loans 10,753,314 9,128,656 190,755 20,072,725 Average deposits 6,420,401 11,337,064 3,708,257 21,465,722 Average allocated capital (CET1) (b) $ 1,114,610 $ 576,464 $ 370,675 $ 2,061,749 (a) The consolidated credit provision is equal to the actual reported provision for credit losses. (b) The Federal Reserve establishes capital adequacy requirements for the Corporation, including common equity Tier 1. For segment reporting purposes, the ROCET1 reflects return on average allocated common equity Tier 1. The ROCET1 for the Risk Management and Shared Services segment and the Consolidated Total is inclusive of the annualized effect of the preferred stock dividends.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) The following tables summarize the components of accumulated other comprehensive income (loss) at March 31, 2018 and 2017 , changes during the three month periods then ended, and reclassifications out of accumulated other comprehensive income (loss) during the three month periods ended March 31, 2018 and 2017 , respectively. ($ in Thousands) Investment Securities Available For Sale Defined Benefit Pension and Post Retirement Obligations Accumulated Other Comprehensive Income (Loss) Balance January 1, 2018 $ (38,453 ) $ (24,305 ) $ (62,758 ) Other comprehensive income (loss) before reclassifications (41,834 ) — (41,834 ) Amounts reclassified from accumulated other comprehensive income (loss) Personnel expense — (38 ) (38 ) Other expense — 465 465 Adjustment for adoption of ASU 2016-01 (84 ) — (84 ) Adjustment for adoption of ASU 2018-02 (8,419 ) (5,235 ) (13,654 ) Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (297 ) — (297 ) Income tax (expense) benefit 10,635 (107 ) 10,528 Net other comprehensive income (loss) during period (40,000 ) (4,915 ) (44,915 ) Balance March 31, 2018 $ (78,453 ) $ (29,220 ) $ (107,673 ) Balance January 1, 2017 $ (20,079 ) $ (34,600 ) $ (54,679 ) Other comprehensive income (loss) before reclassifications (2,112 ) — (2,112 ) Amounts reclassified from accumulated other comprehensive income (loss) Investment securities gain (loss), net — — — Personnel expense — (38 ) (38 ) Other expense — 488 488 Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (1,027 ) — (1,027 ) Income tax (expense) benefit 1,195 (171 ) 1,024 Net other comprehensive income (loss) during period (1,944 ) 279 (1,665 ) Balance March 31, 2017 $ (22,023 ) $ (34,321 ) $ (56,344 )

Revenues

Revenues	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Revenue Recognition 606 [Text Block]	Below is a listing of performance obligations for our main revenue streams. Revenue Stream Noninterest income in-scope of Topic 606 Insurance commissions and fees The Corporation's insurance revenue has two distinct performance obligations. The first performance obligation is the selling of the policy as an agent for the carrier. This performance obligation is satisfied upon binding of the policy. The second performance obligation is the ongoing servicing of the policy which is satisfied over the life of the policy. For employee benefits, the payment is typically received monthly. For property and casualty, payments can vary, but are typically received at, or in advance, of the policy period. Service charges and deposit account fees Service charges on deposit accounts consist of monthly service fees (i.e. business analysis fees and consumer service charges) and other deposit account related fees. The Corporation's performance obligation for monthly service fees is generally satisfied, and the related revenue recognized, over the period in which the service is provided. Other deposit account related fees are largely transactional based, and therefore, the Corporation's performance obligation is satisfied, and related revenue recognized, at a point in time. Payment for service charges on deposit accounts is primarily received immediately or in the following month through a direct charge to customers’ accounts. Card-based and loan fees (1) Card-based and loan fees are primarily comprised of debit and credit card income, ATM fees, and merchant services income. Debit and credit card income is primarily comprised of interchange fees earned whenever the Corporation's debit and credit cards are processed through card payment networks. ATM and merchant fees are largely transactional based, and therefore, the Corporation's performance obligation is satisfied, and related revenue recognized, at a point in time. Payment is typically received immediately or in the following month. Trust and asset management fees Trust and asset management income is primarily comprised of fees earned from the management and administration of trusts and other customer assets. The Corporation's performance obligation is generally satisfied over time and the resulting fees are recognized monthly, based upon the month-end market value of the assets under management and the applicable fee rate. Payment is generally received a few days after month end through a direct charge to customers’ accounts. The Corporation's performance obligation for these transactional-based services is generally satisfied, and related revenue recognized, at a point in time (i.e., as incurred). Payment is received shortly after services are rendered. Brokerage commissions and fees Brokerage commissions and fees primarily consists of investment advisory, brokerage, retirement services, and annuities. The Corporation's performance obligation for investment advisory services and retirement services is generally satisfied, and the related revenue recognized, over the period in which the services are provided. The performance obligation for annuities is satisfied upon sale of the annuity, and therefore, the related revenue is primarily recognized at the time of sale. Payment for these services are typically received immediately or in advance of the service. (1) Loan fees are out-of-scope of Topic 606. Arrangements with Multiple Performance Obligations Our contracts with customers may include multiple performance obligations. For such arrangements, we allocate revenue to each performance obligation based on its relative standalone selling price. We generally determine standalone selling prices based on the expected cost plus margin. Practical Expedients We do not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less. Using the practical expedient, for contracts with a term of one year or less, the Corporation recognizes incremental costs of obtaining those contracts as an expense when incurred.
Revenues	Revenues On January 1, 2018, the Corporation adopted Topic 606 using the modified retrospective method. As stated in Note 3 , the implementation of the new standard had an immaterial impact to the Corporation. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606. Revenue is recognized when obligations under the terms of a contract with our customer are satisfied. Revenue is measured as the amount of consideration we expect to receive in exchange for transferring goods or providing services. We do not have any material significant payment terms as payment is received at or shortly after the satisfaction of the performance obligation. The following table disaggregates our revenue by major source for the three months ended March 31, 2018 and March 31, 2017. Three Months Ended March 31, 2018 ($ in Thousands) Corporate and Commercial Specialty Community, Consumer, and Business Risk Management and Shared Services Consolidated Total Insurance commissions and fees $ — $ 22,624 $ 24 $ 22,648 Service charges and deposit account fees 4,225 12,183 12 16,420 Card-based and loan fees (1) 315 9,529 25 9,869 Trust and asset management fees — 13,369 — 13,369 Brokerage commissions and fees — 7,032 241 7,273 Other revenue 655 2,461 30 3,146 Noninterest Income (in-scope of Topic 606) $ 5,195 $ 67,198 $ 332 $ 72,725 Noninterest Income (out-of-scope of Topic 606) 7,488 6,838 3,329 17,655 Total Noninterest Income $ 12,683 $ 74,036 $ 3,661 $ 90,380 (1) Loan fees are out-of-scope of Topic 606. Three Months Ended March 31, 2017 ($ in Thousands) Corporate and Community, Risk Management Consolidated Insurance commissions and fees $ — $ 21,620 $ — $ 21,620 Service charges and deposit account fees 4,441 11,889 26 16,356 Card-based and loan fees (1) 272 8,144 5 8,421 Trust and asset management fees — 11,935 — 11,935 Brokerage commissions and fees — 4,333 — 4,333 Other revenue 44 2,119 53 2,216 Noninterest Income (in-scope of Topic 606) $ 4,757 $ 60,040 $ 84 $ 64,881 Noninterest Income (out-of-scope of Topic 606) 7,236 4,830 2,884 14,950 Total Noninterest Income $ 11,993 $ 64,870 $ 2,968 $ 79,831 (1) Loan fees are out-of-scope of Topic 606. During the first quarter of 2018, the Corporation acquired Bank Mutual. This acquisition resulted in increased service charges and deposit account fees and card-based and loan fees. In addition, the Corporation acquired Diversified Investment Solutions and Whitnell & Co. since the first quarter of 2017, which resulted in increased trust and asset management fees and brokerage commissions and fees. Below is a listing of performance obligations for our main revenue streams. Revenue Stream Noninterest income in-scope of Topic 606 Insurance commissions and fees The Corporation's insurance revenue has two distinct performance obligations. The first performance obligation is the selling of the policy as an agent for the carrier. This performance obligation is satisfied upon binding of the policy. The second performance obligation is the ongoing servicing of the policy which is satisfied over the life of the policy. For employee benefits, the payment is typically received monthly. For property and casualty, payments can vary, but are typically received at, or in advance, of the policy period. Service charges and deposit account fees Service charges on deposit accounts consist of monthly service fees (i.e. business analysis fees and consumer service charges) and other deposit account related fees. The Corporation's performance obligation for monthly service fees is generally satisfied, and the related revenue recognized, over the period in which the service is provided. Other deposit account related fees are largely transactional based, and therefore, the Corporation's performance obligation is satisfied, and related revenue recognized, at a point in time. Payment for service charges on deposit accounts is primarily received immediately or in the following month through a direct charge to customers’ accounts. Card-based and loan fees (1) Card-based and loan fees are primarily comprised of debit and credit card income, ATM fees, and merchant services income. Debit and credit card income is primarily comprised of interchange fees earned whenever the Corporation's debit and credit cards are processed through card payment networks. ATM and merchant fees are largely transactional based, and therefore, the Corporation's performance obligation is satisfied, and related revenue recognized, at a point in time. Payment is typically received immediately or in the following month. Trust and asset management fees Trust and asset management income is primarily comprised of fees earned from the management and administration of trusts and other customer assets. The Corporation's performance obligation is generally satisfied over time and the resulting fees are recognized monthly, based upon the month-end market value of the assets under management and the applicable fee rate. Payment is generally received a few days after month end through a direct charge to customers’ accounts. The Corporation's performance obligation for these transactional-based services is generally satisfied, and related revenue recognized, at a point in time (i.e., as incurred). Payment is received shortly after services are rendered. Brokerage commissions and fees Brokerage commissions and fees primarily consists of investment advisory, brokerage, retirement services, and annuities. The Corporation's performance obligation for investment advisory services and retirement services is generally satisfied, and the related revenue recognized, over the period in which the services are provided. The performance obligation for annuities is satisfied upon sale of the annuity, and therefore, the related revenue is primarily recognized at the time of sale. Payment for these services are typically received immediately or in advance of the service. (1) Loan fees are out-of-scope of Topic 606. Arrangements with Multiple Performance Obligations Our contracts with customers may include multiple performance obligations. For such arrangements, we allocate revenue to each performance obligation based on its relative standalone selling price. We generally determine standalone selling prices based on the expected cost plus margin. Practical Expedients We do not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less. Using the practical expedient, for contracts with a term of one year or less, the Corporation recognizes incremental costs of obtaining those contracts as an expense when incurred.

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition The Corporation recognizes revenue in accordance with ASC 606, "Revenue from Contracts with Customers". ASC 606 requires the Corporation to follow a five step process: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation. Revenue recognition under ASC 606 depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for the goods or services.
Finance, Loan and Lease Receivables, Held-for-sale, Policy	Business combinations The Corporation accounts for its acquisitions using the purchase accounting method. Purchase accounting requires the total purchase price to be allocated to the estimated fair values of assets acquired and liabilities assumed, including certain intangible assets that must be recognized. Typically, this allocation results in the purchase price exceeding the fair value of net assets acquired, which is recorded as goodwill. Core deposit intangibles are a measure of the value of checking, money market and savings deposits acquired in business combinations accounted for under the purchase method. Core deposit intangibles and other identified intangibles with finite useful lives are amortized using the straight line method over their estimated useful lives of up to ten years. Loans that the Corporation acquires in connection with acquisitions are recorded at fair value with no carryover of the related allowance for credit losses. Fair value of the loans involves estimating the amount and timing of principal and interest cash flows expected to be collected on the loans and discounting those cash flows at a market rate of interest. The excess of cash flows expected at acquisition over the estimated fair value is referred to as the accretable discount and is recognized into interest income over the remaining life of the loan. The difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition is referred to as the non-accretable discount. The non-accretable discount includes estimated future credit losses expected to be incurred over the life of the loan. Subsequent decreases to the expected cash flows will require the Corporation to evaluate the need for an additional allowance for credit losses. Subsequent improvement in expected cash flows will result in the reversal of a corresponding amount of the non-accretable discount which the Corporation will then reclassify as accretable discount that will be recognized into interest income over the remaining life of the loan. The Corporation accounts for performing loans acquired in business combinations using the contractual cash flows method of recognizing discount accretion based on the acquired loans’ contractual cash flows. Purchased performing loans are recorded at fair value, including credit, interest, and liquidity discounts. The fair value discount is accreted as an adjustment to yield over the estimated lives of the loans. There is no allowance for loan losses established at the acquisition date for purchased performing loans. A provision for loan losses is recorded for any further deterioration in these loans subsequent to the acquisition.
New Accounting Pronouncements, Policy	New Accounting Pronouncements Adopted Standard Description Date of adoption Effect on financial statements ASU 2018-02 Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income The FASB issued the amendment to allow a reclassification from accumulated other comprehensive income to retained earnings, the stranded tax effects resulting from the Tax Cuts and Jobs Act. The amendments in this update are effective for all entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption of the update is permitted and should be applied in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate related to the Act is recognized. 1st Quarter 2018 The Corporation has elected to early adopt this Update. During the quarter, the Corporation reclassified approximately $14 million from accumulated other comprehensive income to retained earnings as a result of the Tax Cuts and Jobs Act. No material impact to its results of operations, financial position, and liquidity. See Consolidated Statements of Comprehensive Income and the Statement of Changes in Stockholders' Equity. Standard Description Date of adoption Effect on financial statements ASU 2017-12 Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities The FASB issued the amendment to better align a company’s financial reporting for hedging activities with the economic objectives of those activities for both financial (e.g., interest rate) and commodity risks. The provisions create more transparency around how economic results are presented, both on the face of the financial statements and in the footnotes. It also contains targeted improvements to simplify the application of hedge accounting guidance. This amendment is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Entities should apply the amendment on a modified retrospective transition method in which the cumulative effect of the change will be recognized within equity in the consolidated balance sheet as of the date of adoption. Early adoption is permitted, including in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes the interim period. 1st Quarter 2018 The Corporation has elected to early adopt this Update. No material impact to its results of operations, financial position, and liquidity. See Note 10 for expanded disclosures. ASU 2017-07 Compensation — Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The FASB issued the update to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost, including a requirement that employers disaggregate the service cost component from the other components of net benefit cost. In addition, the amendments provide explicit guidance on how to present the service cost component and the other components of net benefit cost in the income statement and allow only the service cost component of net benefit cost to be eligible for capitalization. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment retrospectively to each period presented and prospectively only for the capitalization component. Early adoption is permitted, but should be within the first interim period if interim financial statements are issued. 1st Quarter 2018 No impact to its results of operations, financial position, and liquidity. The Update required retrospective restatement. For the full year 2017, the Corporation reclassified approximately $9 million from personnel expense to other noninterest expense for the non-service cost components of net periodic pension cost and net periodic postretirement benefit cost. See Note 14 for expanded disclosure. ASU 2017-01 Business Combinations (Topic 805): Clarifying the Definition of a Business The FASB issued amendments to clarify the definition of a business in order to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets versus businesses. The new standard narrows the definition of a business by adding three principal clarifications if: (1) substantially all the fair value of the gross assets in the asset group is concentrated in either a single identifiable asset or group of similar identifiable assets the transaction does not involve a business (2) the asset group does not include a minimum of an input and a substantive process, it does not represent a business, and (3) the integrated set of activities (including its inputs and processes) does not create, or have the ability to create, goods or services to customers, investment income (e,g. dividends or interest) or other revenues, it is not a business. The overall intention is to provide consistency in applying the guidance, reduce the costs of application, and make the definition of a business more operable. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. ASU 2016-18 Statement of Cash Flows (Topic 230): Restricted Cash The FASB issued an amendment to improve GAAP by providing guidance on the presentation of restricted cash or restricted cash equivalents in the statement of cash flows, in order to reduce diversity in practice. The amendment requires that a statement of cash flow explain the change during the period in the total cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included in cash and cash equivalents when reconciling the beginning and end of period total amounts shown on the statement of cash flow. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment retrospectively to each period presented. Early adoption is permitted, including in an interim period. 1st Quarter 2018 No impact to its results of operations, financial position, and liquidity. See Consolidated Statements of Cash Flows. ASU 2016-16 Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory The FASB issued an amendment requiring an entity to recognize income tax consequences on an intra-entity transfer of an asset other than inventory at the time the transaction occurs. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment by means of a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. Early adoption is permitted for all entities in the first interim period if an entity issues interim financial statements. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. ASU 2016-15 Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments The FASB issued an amendment to provide clarification on where to classify cash flows involving certain cash receipts and cash payments. Under the new guidance, cash payments for debt prepayment or debt extinguishment costs should be classified as cash outflows for financing activities. The new guidance also details the specific classification of contingent consideration cash payments made after a business combination depending on the timing of payments. Lastly, cash proceeds received from corporate owned life insurance policies (including BOLI) should be classified as cash inflows from investing, while the cash payments for the premiums may be classified as cash outflows for investing, operating, or a combination of both. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment retrospectively to each period presented. Early adoption is permitted, including in an interim period; however, all of the amendments must be adopted in the same period. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. Standard Description Date of adoption Effect on financial statements ASU 2016-01 Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities The FASB issued an amendment to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. This amendment supersedes the guidance to classify equity securities with readily determinable fair values into different categories, requires equity securities to be measured at fair value with changes in the fair value recognized through net income, and simplifies the impairment assessment of equity investments without readily determinable fair values. The amendment requires public business entities that are required to disclose the fair value of financial instruments measured at amortized cost on the balance sheet to measure that fair value using the exit price notion. The amendment requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option. The amendment requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or in the accompanying notes to the financial statements. The amendment reduces diversity in current practice by clarifying that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available for sale securities in combination with the entity’s other deferred tax assets. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities are required to apply the amendment by means of a cumulative-effect adjustment as of the beginning of the fiscal year of adoption, with the exception of the amendment related to equity securities without readily determinable fair values, which should be applied prospectively to equity investments that exist as of the date of adoption. ASC 2018-04 supersedes previous SEC guidance in the Codification in SAB Topic 5 M. Other-Than-Temporary Impairment of certain investments in equity securities and special balance sheet requirements in Reg S-X rule 3A-05 for public utility Holding companies. 1st Quarter 2018 The Corporation has adopted with Update using the cumulative-effect adjustment as of the beginning of the fiscal year of adoption. Immaterial impact to the result of operations, financial position and liquidity. In 2008, the Corporation received Visa Class B restricted shares as part of Visa’s initial public offering. Based on the existing transfer restriction and the uncertainty of the covered litigation, the approximately 119 thousand Class B shares remaining that the Corporation owned as of March 31, 2018 are carried at a zero cost basis. See Consolidated Statements of Comprehensive Income and Note 13 Fair Value Measurements. ASU 2014-09 Revenue from Contracts with Customers (Topic 606) The FASB issued an amendment to clarify the principles for recognizing revenue and to develop a common revenue standard. The standard outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that “an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.” In applying the revenue model to contracts within its scope, an entity should apply the following steps: (1) identify the contract(s) with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation. The standard applies to all contracts with customers except those that are within the scope of other topics in the FASB Codification. The standard also requires significantly expanded disclosures about revenue recognition. The FASB continues to release new accounting guidance related to the adoption of this standard, which could impact the Corporation's preliminary materiality analysis and may change the conclusions reached as to the application of this new guidance. The amendment was originally to be effective for annual reporting periods beginning after December 15, 2016 (including interim reporting periods within those periods); however, in July 2015, the FASB approved a one year deferral of the effective date to December 31, 2017. 1st Quarter 2018 The Corporation chose to adopt this Update using the modified retrospective approach with no material impact on the Corporation's results of operations, financial position, or liquidity. See Note 17 for expanded disclosure requirements.

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Estimated Fair Values of Assets Acquired and Liabilities Assumed	The following table presents the estimated fair values of the assets acquired and liabilities assumed as of the acquisition date related to Bank Mutual. Purchase Accounting Adjustments February 1, 2018 ($ in Thousands) Assets Cash and cash equivalents $ — $ 78,052 Investment securities (6,238 ) 452,867 Federal Home Loan Bank stock, at cost — 20,026 Loans (48,533 ) 1,875,386 Premises and equipment, net 11,172 50,930 Bank owned life insurance (24 ) 65,390 Goodwill 166,870 Core deposit intangibles (included in other intangible assets, net on the face of the Consolidated Balance Sheet) 58,100 58,100 Other real estate owned (246 ) 4,403 Others assets $ 5,098 $ 37,151 Total assets $ 2,809,175 Liabilities Deposits $ 2,498 $ 1,840,950 Other borrowings 935 430,946 Other liabilities $ 2,148 $ 55,591 Total liabilities $ 2,327,487 Total consideration paid $ 481,688

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Calculations for basic and diluted earnings per common share	Presented below are the calculations for basic and diluted earnings per common share. For the Three Months Ended March 31, 2018 2017 (In Thousands, except per share data) Net income $ 69,456 $ 56,270 Preferred stock dividends (2,339 ) (2,330 ) Net income available to common equity $ 67,117 $ 53,940 Common shareholder dividends (25,572 ) (18,251 ) Unvested share-based payment awards (138 ) (117 ) Undistributed earnings $ 41,407 $ 35,572 Undistributed earnings allocated to common shareholders 41,225 35,294 Undistributed earnings allocated to unvested share-based payment awards 182 278 Undistributed earnings $ 41,407 $ 35,572 Basic Distributed earnings to common shareholders $ 25,572 $ 18,251 Undistributed earnings allocated to common shareholders 41,225 35,294 Total common shareholders earnings, basic $ 66,797 $ 53,545 Diluted Distributed earnings to common shareholders $ 25,572 $ 18,251 Undistributed earnings allocated to common shareholders 41,225 35,294 Total common shareholders earnings, diluted $ 66,797 $ 53,545 Weighted average common shares outstanding 163,520 150,815 Effect of dilutive common stock awards 2,038 2,216 Effect of dilutive common stock warrants 874 838 Diluted weighted average common shares outstanding 166,432 153,869 Basic earnings per common share $ 0.41 $ 0.36 Diluted earnings per common share $ 0.40 $ 0.35

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Fair value assumptions of stock options	The following assumptions were used in estimating the fair value for options granted in the first three months of 2018 and full year 2017 . 2018 2017 Dividend yield 2.50 % 2.00 % Risk-free interest rate 2.60 % 2.00 % Weighted average expected volatility 22.00 % 25.00 % Weighted average expected life 5.75 years 5.5 years Weighted average per share fair value of options $4.47 $5.30
Summary of Company's Stock Option Activities	A summary of the Corporation’s stock option activity for the three months ended March 31, 2018 is presented below. Stock Options Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (a) Outstanding at December 31, 2017 5,118,687 $ 18.02 6.48 $ 38,028 Granted 938,740 24.50 Assumed from Bank Mutual acquisition 370,051 14.35 Exercised (529,869 ) 17.37 Forfeited or expired (24,130 ) 23.35 Outstanding at March 31, 2018 5,873,479 $ 18.86 6.80 $ 35,879 Options Exercisable at March 31, 2018 3,659,277 $ 16.72 5.55 $ 30,009
Summary of Restricted Stock Awards Activity (Excluding Salary Shares)	The following table summarizes information about the Corporation’s restricted stock activity for the three months ended March 31, 2018 . Restricted Stock Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 2,026,071 $ 19.68 Granted 570,341 24.63 Vested (498,988 ) 17.97 Forfeited (5,799 ) 20.16 Outstanding at March 31, 2018 2,091,625 $ 21.86

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investment securities available for sale	A portion of the portfolio is also comprised of asset-backed securities backed by student loans made under the Federal Family Education Loan Program ("FFELP"). The amortized cost and fair values of securities available for sale and held to maturity were as follows. March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U. S. Treasury securities $ 1,002 $ — $ (7 ) $ 995 Residential mortgage-related securities FNMA / FHLMC 427,480 7,331 (4,738 ) 430,073 GNMA 2,364,339 21 (54,054 ) 2,310,306 Private-label 1,051 — (7 ) 1,044 GNMA commercial mortgage-related securities 1,497,573 — (49,204 ) 1,448,369 FFELP asset backed securities 288,519 1,835 (54 ) 290,300 Other debt securities 3,200 — (12 ) 3,188 Other equity securities 1,599 — — 1,599 Total investment securities available for sale $ 4,584,763 $ 9,186 $ (108,076 ) $ 4,485,875 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,424,925 $ 4,110 $ (16,579 ) $ 1,412,456 Residential mortgage-related securities FNMA / FHLMC 76,069 227 (1,665 ) 74,631 GNMA 410,275 2,210 (11,624 ) 400,861 GNMA commercial mortgage-related securities 531,934 9,008 (21,694 ) 519,248 Total investment securities held to maturity $ 2,443,203 $ 15,555 $ (51,561 ) $ 2,407,197 December 31, 2017 Amortized Gross Gross Fair Value ($ in Thousands) Investment securities available for sale U. S. Treasury securities $ 1,003 $ — $ (7 ) $ 996 Residential mortgage-related securities FNMA / FHLMC 457,680 9,722 (2,634 ) 464,768 GNMA 1,944,453 275 (31,378 ) 1,913,350 Private-label 1,067 — (8 ) 1,059 GNMA commercial mortgage-related securities 1,547,173 5 (33,901 ) 1,513,277 FFELP asset backed securities 144,322 867 (13 ) 145,176 Other debt securities 3,200 — (12 ) 3,188 Other equity securities 1,519 127 (14 ) 1,632 Total investment securities available for sale $ 4,100,417 $ 10,996 $ (67,967 ) $ 4,043,446 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,281,320 $ 13,899 $ (3,177 ) $ 1,292,042 Residential mortgage-related securities FNMA / FHLMC 40,995 398 (489 ) 40,904 GNMA 414,440 2,700 (6,400 ) 410,740 GNMA commercial mortgage-related securities 546,098 9,546 (15,756 ) 539,888 Total investment securities held to maturity $ 2,282,853 $ 26,543 $ (25,822 ) $ 2,283,574
Investment securities held to maturity	A portion of the portfolio is also comprised of asset-backed securities backed by student loans made under the Federal Family Education Loan Program ("FFELP"). The amortized cost and fair values of securities available for sale and held to maturity were as follows. March 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U. S. Treasury securities $ 1,002 $ — $ (7 ) $ 995 Residential mortgage-related securities FNMA / FHLMC 427,480 7,331 (4,738 ) 430,073 GNMA 2,364,339 21 (54,054 ) 2,310,306 Private-label 1,051 — (7 ) 1,044 GNMA commercial mortgage-related securities 1,497,573 — (49,204 ) 1,448,369 FFELP asset backed securities 288,519 1,835 (54 ) 290,300 Other debt securities 3,200 — (12 ) 3,188 Other equity securities 1,599 — — 1,599 Total investment securities available for sale $ 4,584,763 $ 9,186 $ (108,076 ) $ 4,485,875 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,424,925 $ 4,110 $ (16,579 ) $ 1,412,456 Residential mortgage-related securities FNMA / FHLMC 76,069 227 (1,665 ) 74,631 GNMA 410,275 2,210 (11,624 ) 400,861 GNMA commercial mortgage-related securities 531,934 9,008 (21,694 ) 519,248 Total investment securities held to maturity $ 2,443,203 $ 15,555 $ (51,561 ) $ 2,407,197 December 31, 2017 Amortized Gross Gross Fair Value ($ in Thousands) Investment securities available for sale U. S. Treasury securities $ 1,003 $ — $ (7 ) $ 996 Residential mortgage-related securities FNMA / FHLMC 457,680 9,722 (2,634 ) 464,768 GNMA 1,944,453 275 (31,378 ) 1,913,350 Private-label 1,067 — (8 ) 1,059 GNMA commercial mortgage-related securities 1,547,173 5 (33,901 ) 1,513,277 FFELP asset backed securities 144,322 867 (13 ) 145,176 Other debt securities 3,200 — (12 ) 3,188 Other equity securities 1,519 127 (14 ) 1,632 Total investment securities available for sale $ 4,100,417 $ 10,996 $ (67,967 ) $ 4,043,446 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,281,320 $ 13,899 $ (3,177 ) $ 1,292,042 Residential mortgage-related securities FNMA / FHLMC 40,995 398 (489 ) 40,904 GNMA 414,440 2,700 (6,400 ) 410,740 GNMA commercial mortgage-related securities 546,098 9,546 (15,756 ) 539,888 Total investment securities held to maturity $ 2,282,853 $ 26,543 $ (25,822 ) $ 2,283,574
Amortized cost and fair values of investment securities by contractual maturity	The expected maturities of investment securities available for sale and held to maturity at March 31, 2018 , are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Available for Sale Held to Maturity Amortized Cost Fair Value Amortized Cost Fair Value ($ in Thousands) Due in one year or less $ 2,002 $ 1,995 $ 44,019 $ 44,261 Due after one year through five years 2,200 2,188 221,411 219,411 Due after five years through ten years — — 346,521 341,147 Due after ten years — — 812,974 807,638 Total debt securities 4,202 4,183 1,424,925 1,412,456 Residential mortgage-related securities FNMA / FHLMC 427,480 430,073 76,069 74,631 GNMA 2,364,339 2,310,306 410,275 400,861 Private-label 1,051 1,044 — — GNMA commercial mortgage-related securities 1,497,573 1,448,369 531,934 519,248 FFELP asset backed securities 288,519 290,300 — — Equity securities 1,599 1,599 — — Total investment securities $ 4,584,763 $ 4,485,875 $ 2,443,203 $ 2,407,197 Ratio of Fair Value to Amortized Cost 97.8 % 98.5 %
Realized gains and losses and proceeds from sale	The following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time individual securities have been in a continuous unrealized loss position, at March 31, 2018 . Less than 12 months 12 months or more Total March 31, 2018 Number of Securities Unrealized Losses Fair Value Number of Securities Unrealized Losses Fair Value Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U.S. Treasury securities 1 $ (7 ) $ 995 — $ — $ — $ (7 ) $ 995 Residential mortgage-related securities FNMA / FHLMC 12 (1,389 ) 94,231 9 (3,349 ) 135,316 (4,738 ) 229,547 GNMA 65 (25,956 ) 1,590,545 26 (28,098 ) 718,971 (54,054 ) 2,309,516 Private-label — — — 1 (7 ) 1,044 (7 ) 1,044 GNMA commercial mortgage-related securities 28 (9,895 ) 385,319 76 (39,309 ) 1,063,082 (49,204 ) 1,448,401 FFELP asset backed securities 6 (54 ) 86,988 — — — (54 ) 86,988 Other debt securities 1 (12 ) 188 — — — (12 ) 188 Total 113 $ (37,313 ) $ 2,158,266 112 $ (70,763 ) $ 1,918,413 $ (108,076 ) $ 4,076,679 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) 821 $ (9,876 ) $ 523,716 132 $ (6,703 ) $ 122,632 $ (16,579 ) $ 646,348 Residential mortgage-related securities FNMA / FHLMC 19 (939 ) 54,122 10 (725 ) 15,230 (1,665 ) 69,352 GNMA 58 (7,239 ) 279,707 18 (4,385 ) 113,561 (11,624 ) 393,268 GNMA commercial mortgage-related securities 2 (837 ) 49,711 23 (20,857 ) 469,538 (21,694 ) 519,249 Total 900 $ (18,891 ) $ 907,256 183 $ (32,670 ) $ 720,961 $ (51,561 ) $ 1,628,217
Unrealized losses and fair value of available for sale and held to maturity securities, by investment category and time length	The following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time individual securities have been in a continuous unrealized loss position, at March 31, 2018 . Less than 12 months 12 months or more Total March 31, 2018 Number of Securities Unrealized Losses Fair Value Number of Securities Unrealized Losses Fair Value Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U.S. Treasury securities 1 $ (7 ) $ 995 — $ — $ — $ (7 ) $ 995 Residential mortgage-related securities FNMA / FHLMC 12 (1,389 ) 94,231 9 (3,349 ) 135,316 (4,738 ) 229,547 GNMA 65 (25,956 ) 1,590,545 26 (28,098 ) 718,971 (54,054 ) 2,309,516 Private-label — — — 1 (7 ) 1,044 (7 ) 1,044 GNMA commercial mortgage-related securities 28 (9,895 ) 385,319 76 (39,309 ) 1,063,082 (49,204 ) 1,448,401 FFELP asset backed securities 6 (54 ) 86,988 — — — (54 ) 86,988 Other debt securities 1 (12 ) 188 — — — (12 ) 188 Total 113 $ (37,313 ) $ 2,158,266 112 $ (70,763 ) $ 1,918,413 $ (108,076 ) $ 4,076,679 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) 821 $ (9,876 ) $ 523,716 132 $ (6,703 ) $ 122,632 $ (16,579 ) $ 646,348 Residential mortgage-related securities FNMA / FHLMC 19 (939 ) 54,122 10 (725 ) 15,230 (1,665 ) 69,352 GNMA 58 (7,239 ) 279,707 18 (4,385 ) 113,561 (11,624 ) 393,268 GNMA commercial mortgage-related securities 2 (837 ) 49,711 23 (20,857 ) 469,538 (21,694 ) 519,249 Total 900 $ (18,891 ) $ 907,256 183 $ (32,670 ) $ 720,961 $ (51,561 ) $ 1,628,217 For comparative purposes, the following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2017 . Less than 12 months 12 months or more Total December 31, 2017 Number Unrealized Fair Number Unrealized Fair Unrealized Fair ($ in Thousands) Investment securities available for sale U.S. Treasury securities 1 $ (7 ) $ 996 — $ — $ — $ (7 ) $ 996 Residential mortgage-related securities FNMA / FHLMC 9 (572 ) 69,939 9 (2,062 ) 142,093 (2,634 ) 212,032 GNMA 44 (8,927 ) 1,028,221 25 (22,451 ) 737,198 (31,378 ) 1,765,419 Private-label — — — 1 (8 ) 1,059 (8 ) 1,059 GNMA commercial mortgage-related securities 33 (5,554 ) 480,514 70 (28,347 ) 1,026,642 (33,901 ) 1,507,156 FFELP asset backed securities 1 (13 ) 12,158 — — — — (13 ) 12,158 Other debt securities 1 (12 ) 188 — — — (12 ) 188 Other equity securities 3 (14 ) 1,487 — — — (14 ) 1,487 Total 92 $ (15,099 ) $ 1,593,503 105 $ (52,868 ) $ 1,906,992 $ (67,967 ) $ 3,500,495 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) 157 $ (746 ) $ 122,761 132 $ (2,431 ) $ 127,043 $ (3,177 ) $ 249,804 Residential mortgage-related securities FNMA / FHLMC 8 (73 ) 13,143 10 (417 ) 16,262 (490 ) 29,405 GNMA 35 (3,373 ) 268,388 18 (3,026 ) 120,892 (6,399 ) 389,280 GNMA commercial mortgage-related securities 2 (299 ) 52,997 23 (15,457 ) 486,891 (15,756 ) 539,888 Total 202 $ (4,491 ) $ 457,289 183 $ (21,331 ) $ 751,088 $ (25,822 ) $ 1,208,377

Loans (Tables)

Loans (Tables)	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Loan composition	The period end loan composition was as follows. March 31, 2018 (a) December 31, ($ in Thousands) Commercial and industrial $ 6,756,983 $ 6,399,693 Commercial real estate — owner occupied 900,913 802,209 Commercial and business lending 7,657,896 7,201,902 Commercial real estate — investor 4,077,671 3,315,254 Real estate construction 1,579,778 1,451,684 Commercial real estate lending 5,657,449 4,766,938 Total commercial 13,315,345 11,968,840 Residential mortgage 8,197,223 7,546,534 Home equity 923,470 883,804 Other consumer 374,453 385,813 Total consumer 9,495,146 8,816,151 Total loans $ 22,810,491 $ 20,784,991 (a) Includes $15 million of purchased credit-impaired loans
Commercial and consumer loans by credit quality indicator	The following table presents commercial and consumer loans by credit quality indicator at March 31, 2018 . Pass Special Mention Potential Problem Nonaccrual Total ($ in Thousands) Commercial and industrial $ 6,325,258 $ 132,292 $ 196,766 $ 102,667 $ 6,756,983 Commercial real estate - owner occupied 830,489 15,378 34,410 20,636 900,913 Commercial and business lending 7,155,747 147,670 231,176 123,303 7,657,896 Commercial real estate - investor 3,960,155 54,972 46,970 15,574 4,077,671 Real estate construction 1,547,443 29,421 1,695 1,219 1,579,778 Commercial real estate lending 5,507,598 84,393 48,665 16,793 5,657,449 Total commercial 12,663,345 232,063 279,841 140,096 13,315,345 Residential mortgage 8,134,387 5,580 2,155 55,100 8,197,223 Home equity 908,682 1,383 188 13,218 923,470 Other consumer 373,714 600 — 139 374,453 Total consumer 9,416,783 7,563 2,343 68,456 9,495,146 Total $ 22,080,128 $ 239,626 $ 282,184 $ 208,553 $ 22,810,491 The following table presents commercial and consumer loans by credit quality indicator at December 31, 2017 . Pass Special Mention Potential Problem Nonaccrual Total ($ in Thousands) Commercial and industrial $ 6,015,884 $ 157,245 $ 113,778 $ 112,786 $ 6,399,693 Commercial real estate - owner occupied 723,291 14,181 41,997 22,740 802,209 Commercial and business lending 6,739,175 171,426 155,775 135,526 7,201,902 Commercial real estate - investor 3,266,389 24,845 19,291 4,729 3,315,254 Real estate construction 1,421,504 29,206 — 974 1,451,684 Commercial real estate lending 4,687,893 54,051 19,291 5,703 4,766,938 Total commercial 11,427,068 225,477 175,066 141,229 11,968,840 Residential mortgage 7,490,860 426 1,616 53,632 7,546,534 Home equity 868,958 1,137 195 13,514 883,804 Other consumer 384,990 652 — 171 385,813 Total consumer 8,744,808 2,215 1,811 67,317 8,816,151 Total $ 20,171,876 $ 227,692 $ 176,877 $ 208,546 $ 20,784,991
Summarized details of Loans	The following table presents loans by past due status at March 31, 2018 . Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due (a) Nonaccrual (b) Total ($ in Thousands) Commercial and industrial $ 6,653,188 $ 793 $ 87 $ 248 $ 102,667 $ 6,756,983 Commercial real estate - owner occupied 879,766 511 — — 20,636 900,913 Commercial and business lending 7,532,954 1,304 87 248 123,303 7,657,896 Commercial real estate - investor 4,061,600 240 — 257 15,574 4,077,671 Real estate construction 1,578,069 220 270 — 1,219 1,579,778 Commercial real estate lending 5,639,669 460 270 257 16,793 5,657,449 Total commercial 13,172,623 1,764 357 505 140,096 13,315,345 Residential mortgage 8,125,707 9,876 5,257 1,283 55,100 8,197,223 Home equity 904,305 4,485 1,383 79 13,218 923,470 Other consumer 370,977 1,058 753 1,526 139 374,453 Total consumer 9,400,989 15,419 7,393 2,888 68,456 9,495,146 Total $ 22,573,612 $ 17,184 $ 7,750 $ 3,393 $ 208,553 $ 22,810,491 (a) The recorded investment in loans past due 90 days or more and still accruing totaled $3 million at March 31, 2018 (the same as the reported balances for the accruing loans noted above). (b) Of the total nonaccrual loans, $159 million or 76% were current with respect to payment at March 31, 2018 . The following table presents loans by past due status at December 31, 2017 . Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due (a) Nonaccrual (b) Total ($ in Thousands) Commercial and industrial $ 6,286,369 $ 170 $ 101 $ 267 $ 112,786 $ 6,399,693 Commercial real estate - owner occupied 779,421 48 — — 22,740 802,209 Commercial and business lending 7,065,790 218 101 267 135,526 7,201,902 Commercial real estate - investor 3,310,000 374 — 151 4,729 3,315,254 Real estate construction 1,450,459 168 83 — 974 1,451,684 Commercial real estate lending 4,760,459 542 83 151 5,703 4,766,938 Total commercial 11,826,249 760 184 418 141,229 11,968,840 Residential mortgage 7,483,350 9,186 366 — 53,632 7,546,534 Home equity 863,465 5,688 1,137 — 13,514 883,804 Other consumer 382,186 1,227 780 1,449 171 385,813 Total consumer 8,729,001 16,101 2,283 1,449 67,317 8,816,151 Total $ 20,555,250 $ 16,861 $ 2,467 $ 1,867 $ 208,546 $ 20,784,991 (a) The recorded investment in loans past due 90 days or more and still accruing totaled $2 million at December 31, 2017 (the same as the reported balances for the accruing loans noted above). (b) Of the total nonaccrual loans, $135 million or 65% were current with respect to payment at December 31, 2017 .
Summarized details of impaired Loans	The following table presents impaired loans individually evaluated under ASC Topic 310, excluding purchased credit-impaired loans, at March 31, 2018 . Recorded Unpaid Related Average Interest ($ in Thousands) Loans with a related allowance Commercial and industrial $ 76,452 $ 81,091 $ 18,778 $ 77,130 $ 312 Commercial real estate — owner occupied 16,264 16,617 2,043 22,978 47 Commercial and business lending 92,716 97,708 20,821 100,108 359 Commercial real estate — investor 18,582 18,619 2,721 16,559 464 Real estate construction 458 532 82 461 7 Commercial real estate lending 19,040 19,151 2,803 17,020 471 Total commercial 111,756 116,859 23,624 117,128 830 Residential mortgage 38,438 40,851 6,635 40,475 431 Home equity 10,762 11,383 3,719 10,238 136 Other consumer 1,066 1,069 116 1,067 1 Total consumer 50,266 53,303 10,470 51,780 568 Total loans (a) $ 162,022 $ 170,162 $ 34,094 $ 168,908 $ 1,398 Loans with no related allowance Commercial and industrial $ 52,389 $ 76,720 $ — $ 55,897 $ (348 ) Commercial real estate — owner occupied 6,225 7,276 — 2,403 — Commercial and business lending 58,614 83,996 — 58,300 (348 ) Commercial real estate — investor 1,805 1,853 — — — Real estate construction — — — — — Commercial real estate lending 1,805 1,853 — — — Total commercial 60,419 85,849 — 58,300 (348 ) Residential mortgage 10,425 10,871 — 6,317 39 Home equity 212 212 — 639 1 Other consumer — — — — — Total consumer 10,637 11,083 — 6,956 40 Total loans (a) $ 71,056 $ 96,932 $ — $ 65,256 $ (308 ) Total Commercial and industrial $ 128,841 $ 157,811 $ 18,778 $ 133,027 $ (36 ) Commercial real estate — owner occupied 22,489 23,893 2,043 25,381 47 Commercial and business lending 151,330 181,704 20,821 158,408 11 Commercial real estate — investor 20,387 20,472 2,721 16,559 464 Real estate construction 458 532 82 461 7 Commercial real estate lending 20,845 21,004 2,803 17,020 471 Total commercial 172,175 202,708 23,624 175,428 482 Residential mortgage 48,863 51,722 6,635 46,792 470 Home equity 10,974 11,595 3,719 10,877 137 Other consumer 1,066 1,069 116 1,067 1 Total consumer 60,903 64,386 10,470 58,736 608 Total loans (a) $ 233,078 $ 267,094 $ 34,094 $ 234,164 $ 1,090 (a) The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 74% of the unpaid principal balance at March 31, 2018 . The following table presents impaired loans individually evaluated under ASC Topic 310 at December 31, 2017 . Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized ($ in Thousands) Loans with a related allowance Commercial and industrial $ 81,649 $ 83,579 $ 10,838 $ 58,494 $ 2,629 Commercial real estate — owner occupied 23,796 23,937 2,973 12,124 736 Commercial and business lending 105,445 107,516 13,811 70,618 3,365 Commercial real estate — investor 17,823 17,862 1,597 16,924 1,694 Real estate construction 467 578 86 484 29 Commercial real estate lending 18,290 18,440 1,683 17,408 1,723 Total commercial 123,735 125,956 15,494 88,026 5,088 Residential mortgage 40,561 42,922 6,512 40,411 1,614 Home equity 10,250 10,986 3,718 10,521 549 Other consumer 1,135 1,138 122 1,140 3 Total consumer 51,946 55,046 10,352 52,072 2,166 Total loans (a) $ 175,681 $ 181,002 $ 25,846 $ 140,098 $ 7,254 Loans with no related allowance Commercial and industrial $ 60,595 $ 82,839 $ — $ 89,275 $ 492 Commercial real estate — owner occupied 2,438 2,829 — 1,948 36 Commercial and business lending 63,033 85,668 — 91,223 528 Commercial real estate — investor 1,295 1,295 — — 45 Real estate construction — — — — — Commercial real estate lending 1,295 1,295 — — 45 Total commercial 64,328 86,963 — 91,223 573 Residential mortgage 6,925 7,204 — 4,999 217 Home equity 641 645 — 540 7 Other consumer — — — — — Total consumer 7,566 7,849 — 5,539 224 Total loans (a) $ 71,894 $ 94,812 $ — $ 96,762 $ 797 Total Commercial and industrial $ 142,244 $ 166,418 $ 10,838 $ 147,769 $ 3,121 Commercial real estate — owner occupied 26,234 26,766 2,973 14,072 772 Commercial and business lending 168,478 193,184 13,811 161,841 3,893 Commercial real estate — investor 19,118 19,157 1,597 16,924 1,739 Real estate construction 467 578 86 484 29 Commercial real estate lending 19,585 19,735 1,683 17,408 1,768 Total commercial 188,063 212,919 15,494 179,249 5,661 Residential mortgage 47,486 50,126 6,512 45,410 1,831 Home equity 10,891 11,631 3,718 11,061 556 Other consumer 1,135 1,138 122 1,140 3 Total consumer 59,512 62,895 10,352 57,611 2,390 Total loans (a) $ 247,575 $ 275,814 $ 25,846 $ 236,860 $ 8,051 (a) The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 80% of the unpaid principal balance at December 31, 2017 .
Nonaccrual and performing restructured loans	The following table presents nonaccrual and performing restructured loans by loan portfolio. March 31, 2018 December 31, 2017 Performing Restructured Loans Nonaccrual Restructured Loans (a) Performing Restructured Loans Nonaccrual Restructured Loans (a) ($ in Thousands) Commercial and industrial $ 29,580 $ 886 $ 30,047 $ 1,776 Commercial real estate — owner occupied 3,892 — 3,989 — Commercial real estate — investor 13,683 1,007 14,389 — Real estate construction 305 152 310 157 Residential mortgage 19,902 18,640 17,068 18,991 Home equity 8,098 3,117 7,705 2,537 Other consumer 1,041 25 1,110 25 Total $ 76,501 $ 23,827 $ 74,618 $ 23,486 (a) Nonaccrual restructured loans have been included within nonaccrual loans.
Summary of restructured loans	The following table provides the number of loans modified in a troubled debt restructuring by loan portfolio during the three months ended March 31, 2018 and 2017 , respectively, and the recorded investment and unpaid principal balance as of March 31, 2018 and 2017 , respectively. Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) ($ in Thousands) Commercial and industrial 2 $ 92 $ 92 20 $ 52,326 $ 60,546 Commercial real estate — owner occupied — — — 1 204 204 Commercial real estate — investor 1 1,007 1,037 1 733 744 Residential mortgage 11 1,807 1,807 16 1,301 1,322 Home equity 17 1,044 1,060 15 347 347 Other consumer 2 8 11 — — — Total 33 $ 3,958 $ 4,007 53 $ 54,911 $ 63,163 (a) Represents post-modification outstanding recorded investment. (b) Represents pre-modification outstanding recorded investment.
Troubled debt restructurings subsequent redefault	The following table provides the number of loans modified in a troubled debt restructuring during the previous twelve months which subsequently defaulted during the three months ended March 31, 2018 and 2017 , respectively, as well as the recorded investment in these restructured loans as of March 31, 2018 and 2017 , respectively. Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Number of Loans Recorded Investment Number of Loans Recorded Investment ($ in Thousands) Residential mortgage 4 467 6 383 Home equity 12 954 2 26 Total 16 $ 1,421 8 $ 409
Changes in the allowance for loan losses by portfolio segment	($ in Millions) Three Months Ended March 31, 2018 Year Ended December 31, 2017 Balance at beginning of period $ 27 $ 38 Charge offs (4 ) (25 ) Recoveries — — Net Charge offs (4 ) (25 ) Provision for loan losses (4 ) 14 Balance at end of period $ 19 $ 27 Allowance for loan losses Individually evaluated for impairment $ 10 $ 5 Collectively evaluated for impairment 9 22 Total allowance for loan losses $ 19 $ 27 Loans Individually evaluated for impairment $ 69 $ 77 Collectively evaluated for impairment 588 523 Total loans $ 657 $ 600 The following table presents a summary of the changes in the allowance for loan losses by portfolio segment for the three months ended March 31, 2018 . ($ in Thousands) Commercial and Commercial real estate Commercial real estate - Real estate Residential Home Other Total December 31, 2017 $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Charge offs (8,067 ) (1,042 ) — (47 ) (493 ) (1,250 ) (1,256 ) (12,155 ) Recoveries 1,468 17 8 236 362 573 168 2,832 Net Charge offs (6,599 ) (1,025 ) 8 189 (131 ) (677 ) (1,088 ) (9,323 ) Provision for loan losses 1,377 2,520 1,215 (6,125 ) 536 241 736 500 March 31, 2018 $ 117,847 $ 11,847 $ 42,282 $ 28,434 $ 30,012 $ 21,690 $ 4,946 $ 257,058 Allowance for loan losses Individually evaluated for impairment $ 18,778 $ 2,043 $ 2,721 $ 82 $ 6,635 $ 3,719 $ 116 $ 34,094 Collectively evaluated for impairment 99,069 9,804 39,561 28,352 23,377 17,971 4,830 222,964 Acquired and accounted for under ASC 310-30 (a) — — — — — — — — Total allowance for loan losses $ 117,847 $ 11,847 $ 42,282 $ 28,434 $ 30,012 $ 21,690 $ 4,946 $ 257,058 Loans Individually evaluated for impairment $ 128,841 $ 22,489 $ 20,387 $ 458 $ 48,863 $ 10,974 $ 1,066 $ 233,078 Collectively evaluated for impairment 6,625,314 876,631 4,048,532 1,579,065 8,147,224 912,421 373,388 22,562,575 Acquired and accounted for under ASC 310-30 (a) 2,828 1,793 8,752 255 1,136 74 — 14,838 Total loans $ 6,756,983 $ 900,913 $ 4,077,671 $ 1,579,778 $ 8,197,223 $ 923,470 $ 374,453 $ 22,810,491 (a) Loans acquired in business combinations and accounted for under ASC Subtopic 310-30 "Receivables — Loans and Debt Securities Acquired with Deteriorated Credit Quality." For comparison purposes, a summary of the changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2017 , was as follows. ($ in Thousands) Commercial and Commercial real estate Commercial real estate - Real estate Residential Home Other Total December 31, 2016 $ 140,126 $ 14,034 $ 45,285 $ 26,932 $ 27,046 $ 20,364 $ 4,548 $ 278,335 Charge offs (44,533 ) (344 ) (991 ) (604 ) (2,611 ) (2,724 ) (4,439 ) (56,246 ) Recoveries 11,465 173 242 74 927 3,194 716 16,791 Net Charge offs (33,068 ) (171 ) (749 ) (530 ) (1,684 ) 470 (3,723 ) (39,455 ) Provision for loan losses 16,010 (3,511 ) (3,477 ) 7,968 4,245 1,292 4,473 27,000 December 31, 2017 $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Allowance for loan losses Individually evaluated for impairment $ 10,838 $ 2,973 $ 1,597 $ 86 $ 6,512 $ 3,718 $ 122 $ 25,846 Collectively evaluated for impairment 112,230 7,379 39,462 34,284 23,095 18,408 5,176 240,034 Total allowance for loan losses $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Loans Individually evaluated for impairment $ 142,244 $ 26,234 $ 19,118 $ 467 $ 47,486 $ 10,891 $ 1,135 $ 247,575 Collectively evaluated for impairment 6,257,449 775,975 3,296,136 1,451,217 7,499,048 872,913 384,678 20,537,416 Total loans $ 6,399,693 $ 802,209 $ 3,315,254 $ 1,451,684 $ 7,546,534 $ 883,804 $ 385,813 $ 20,784,991
Changes in the allowance for unfunded commitments	The following table presents a summary of the changes in the allowance for unfunded commitments. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Allowance for Unfunded Commitments Balance at beginning of period $ 24,400 $ 25,400 Provision for unfunded commitments (500 ) (1,000 ) Amount recorded at acquisition 2,436 — Balance at end of period $ 26,336 $ 24,400
Changes In Accretable Yield For Purchased Credit Impaired	Changes in the accretable yield for loans acquired and accounted for under ASC Topic 310-30 were as follows for the three months ended March 31, 2018 and for the year ended December 31, 2017 Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Changes in Accretable Yield Balance at beginning of period $ — $ — Purchases 4,244 — Accretion — — Other (a) — — Balance at end of period $ 4,244 $ — (a) Represents the accretable difference that is relieved when a loan exits the PCI population due to full payoff, full charge-off, or transfer to repossessed assets, etc.

Goodwill and Other Intangible32

Goodwill and Other Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of core deposit intangibles and other intangibles	For core deposit intangibles and other intangibles, changes in the gross carrying amount, accumulated amortization, and net book value were as follows. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Core deposit intangibles Gross carrying amount $ 58,100 $ 4,385 Accumulated amortization (968 ) (4,385 ) Net book value $ 57,132 $ — Additions during the periods $ 58,100 $ — Amortization during the year $ 968 $ 112 Other intangibles Gross carrying amount $ 42,131 $ 34,572 Accumulated amortization (19,549 ) (18,992 ) Net book value $ 22,582 $ 15,580 Additions during the period $ 7,559 $ 2,162 Amortization during the year $ 557 $ 1,847
Summary of changes in balance of mortgage servicing rights asset and mortgage servicing rights valuation allowance	A summary of changes in the balance of the mortgage servicing rights asset and the mortgage servicing rights valuation allowance was as follows. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Mortgage servicing rights Mortgage servicing rights at beginning of period $ 59,168 $ 62,085 Additions from acquisition 8,136 — Additions 1,737 7,167 Amortization (2,324 ) (10,084 ) Mortgage servicing rights at end of period $ 66,717 $ 59,168 Valuation allowance at beginning of period (784 ) (609 ) (Additions) recoveries, net 474 (175 ) Valuation allowance at end of period (310 ) (784 ) Mortgage servicing rights, net $ 66,407 $ 58,384 Fair value of mortgage servicing rights $ 81,810 $ 64,387 Portfolio of residential mortgage loans serviced for others (“servicing portfolio”) $ 8,507,294 $ 7,646,846 Mortgage servicing rights, net to servicing portfolio 0.78 % 0.76 % Mortgage servicing rights expense (a) $ 1,849 $ 10,259 (a) Includes the amortization of mortgage servicing rights and additions / recoveries to the valuation allowance of mortgage servicing rights, and is a component of mortgage banking, net in the consolidated statements of income
Summary of estimated future amortization expense	The following table shows the estimated future amortization expense for amortizing intangible assets. The projections of amortization expense are based on existing asset balances, the current interest rate environment, and prepayment speeds as of March 31, 2018 . The actual amortization expense the Corporation recognizes in any given period may be significantly different depending upon acquisition or sale activities, changes in interest rates, prepayment speeds, market conditions, regulatory requirements, and events or circumstances that indicate the carrying amount of an asset may not be recoverable. Estimated Amortization Expense Core Deposit Intangibles Other Intangibles Mortgage Servicing Rights ($ in Thousands) Nine Months Ended December 31, 2018 $ 4,358 $ 2,045 $ 7,115 2019 5,810 2,428 9,324 2020 5,810 2,311 8,078 2021 5,810 2,287 6,977 2022 5,810 2,263 6,035 2023 5,810 2,244 5,234 Beyond 2023 23,724 9,004 23,954 Total Estimated Amortization Expense $ 57,132 $ 22,582 $ 66,717

Short and Long-Term Funding (Ta

Short and Long-Term Funding (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Breakdown of short & long-term debt balances	he components of short-term funding (funding with original contractual maturities of one year or less) and long-term funding (funding with original contractual maturities greater than one year). March 31, 2018 December 31, 2017 ($ in Thousands) Short-Term Funding Federal funds purchased $ 69,085 $ 141,950 Securities sold under agreements to repurchase 214,869 182,865 Federal funds purchased and securities sold under agreements to repurchase 283,954 324,815 FHLB advances 1,780,000 284,000 Commercial paper 82,420 67,467 Other short-term funding 1,862,420 351,467 Total short-term funding $ 2,146,374 $ 676,282 Long-Term Funding FHLB advances $ 2,735,887 $ 2,900,168 Senior notes, at par 250,000 250,000 Subordinated notes, at par 250,000 250,000 Other long-term funding and capitalized costs (2,549 ) (2,718 ) Total long-term funding 3,233,338 3,397,450 Total short and long-term funding $ 5,379,712 $ 4,073,732
Remaining contractual maturity of securities sold under agreements to repurchase	The remaining contractual maturity of the securities sold under agreements to repurchase in the consolidated balance sheets as of March 31, 2018 and December 31, 2017 are presented in the following table. Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 days 30-90 days Greater than 90 days Total March 31, 2018 ($ in Thousands) Repurchase agreements Agency mortgage-related securities $ 214,869 $ — $ — $ — $ 214,869 Total $ 214,869 $ — $ — $ — $ 214,869 December 31, 2017 Repurchase agreements Agency mortgage-related securities $ 182,865 $ — $ — $ — $ 182,865 Total $ 182,865 $ — $ — $ — $ 182,865

Derivative and Hedging Activi34

Derivative and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary Of Other derivative instruments not designated as hedging instruments	The table below identifies the balance sheet category and fair values of the Corporation’s derivative instruments. March 31, 2018 December 31, 2017 ($ in Thousands) Notional Amount Fair Balance Sheet Notional Amount Fair Balance Sheet Derivatives not designated as hedging instruments Interest rate-related instruments — customer and mirror $ 2,626,982 $ 53,189 Trading assets $ 2,183,687 $ 28,494 Trading assets Interest rate-related instruments — customer and mirror 2,626,982 (52,238 ) Trading liabilities 2,183,687 (28,035 ) Trading liabilities Foreign currency exchange forwards 140,554 2,612 Trading assets 124,851 2,495 Trading assets Foreign currency exchange forwards 137,073 (2,484 ) Trading liabilities 118,094 (2,339 ) Trading liabilities Commodity contracts 467,979 47,089 Trading assets 457,868 38,686 Trading assets Commodity contracts 467,957 (45,525 ) Trading liabilities 457,108 (37,286 ) Trading liabilities Interest rate lock commitments (mortgage) 312,567 3,032 Other assets 222,736 1,538 Other assets Forward commitments (mortgage) 245,000 (303 ) Other liabilities 164,567 (313 ) Other liabilities Purchased options (time deposit) 26,389 951 Other assets 31,063 1,175 Other assets Written options (time deposit) 26,389 (951 ) Other liabilities 31,063 (1,175 ) Other liabilities Derivatives designated as hedging instruments Interest Rate Products 250,000 258 Other assets — — Other assets
Cumulative Basis Adjustment for Fair Value Hedges	The following table presents amounts that were recorded on the balance sheet related to cumulative basis adjustment for fair value hedges. Line Item in the Statement of Financial Position in Which the Hedged Item is Included Carrying Amount of the Hedged Assets/(Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities) ($ in Thousands) March 31, 2018 Loans and investment securities receivables (a) 249,724 276 Total $ 249,724 $ 276 (a) These amounts include the amortized cost basis of closed portfolios used to designated hedging relationships in which the hedged item is the last layer expected to be remaining at the end of the hedging relationship. At March 31, 2018, the amortized cost basis of the closed portfolios used in these hedging relationships was $523 million ; the cumulative basis adjustments associated with these hedging relationships was $275,767 ; and the amounts of the designated hedged items were $250 million .
Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block]	The table below identifies the effect of fair value hedge accounting on the Corporation's statement of performance during the three months ended March 31, 2018 . Location and Amount of Gain or (Loss) Recognized in Income on Fair Value and Cash Flow Hedging Relationships Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Interest Income Other Income (Expense) Interest Income Other Income (Expense) Total amounts of income and expense line items presented in the statement of financial performance in which the effects of fair value or cash flow hedges are recorded 18 — — — The effects of fair value and cash flow hedging: Gain or (loss) on fair value hedging relationships in Subtopic 815-20 Interest contracts Hedged items 276 — — — Derivatives designated as hedging instruments (258 ) — — —
Gain (loss) on derivative instruments not designated as hedging instruments	The table below identifies the effect of derivatives not designated as hedging instruments on the Corporation's statement of performance during the three months ended March 31, 2018 . Income Statement Category of Gain / (Loss) Recognized in Income For the Three Months Ended March 31, ($ in Thousands) 2018 2017 Derivative Instruments Interest rate-related instruments — customer and mirror, net Capital market fees, net $ 492 $ 245 Interest rate lock commitments (mortgage) Mortgage banking, net 1,494 1,597 Forward commitments (mortgage) Mortgage banking, net 10 (3,281 ) Foreign currency exchange forwards Capital market fees, net (28 ) (21 ) Commodity contracts Capital market fees, net 164 226

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	3 Months Ended
	Mar. 31, 2018
Offsetting [Abstract]
Balance Sheet Offsetting of Derivative Assets and Liabilities	The following table presents the assets and liabilities subject to an enforceable master netting arrangement. The interest and commodity agreements we have with our commercial customers are not subject to an enforceable master netting arrangement, and therefore, are excluded from this table. Gross amounts recognized Gross amounts not offset in the balance sheet Gross amounts offset in the balance sheet Net amounts presented in the balance sheet Financial instruments Collateral Net amount ($ in Thousands) March 31, 2018 Derivative assets Interest and commodity agreements $ 47,528 $ — $ 47,528 $ (43,105 ) $ (1,337 ) $ 3,086 Derivative liabilities Interest and commodity agreements $ 43,105 $ — $ 43,105 $ (43,105 ) $ — $ — December 31, 2017 Derivative assets Interest and commodity agreements $ 29,503 $ — $ 29,503 $ (29,503 ) $ — $ — Derivative liabilities Interest and commodity agreements $ 37,164 $ — $ 37,164 $ (29,503 ) $ (7,661 ) $ —

Commitments, Off-Balance Shee36

Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of lending-related and other commitments	The following is a summary of lending-related commitments. March 31, 2018 December 31, 2017 ($ in Thousands) Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale (a) (b) $ 8,481,563 $ 8,027,187 Commercial letters of credit (a) 12,456 11,886 Standby letters of credit (c) 253,857 235,361 (a) These off-balance sheet financial instruments are exercisable at the market rate prevailing at the date the underlying transaction will be completed and, thus, are deemed to have no current fair value, or the fair value is based on fees currently charged to enter into similar agreements and is not material at March 31, 2018 or December 31, 2017 . (b) Interest rate lock commitments to originate residential mortgage loans held for sale are considered derivative instruments and are disclosed in Note 10 . (c) The Corporation has established a liability of $2 million at March 31, 2018 and December 31, 2017 , as an estimate of the fair value of these financial instruments.
Summary of changes in the residential mortgage repurchase reserve	The following summarizes the changes in the mortgage repurchase reserve. Three Months Ended March 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Balance at beginning of period $ 987 $ 900 Repurchase provision expense 56 246 Charge offs, net (48 ) (159 ) Amount recorded at acquisition 88 — Balance at end of period $ 1,083 $ 987

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured on Recurring Basis at Fair Value	The table below presents the Corporation’s financial instruments measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 , aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Hierarchy March 31, 2018 December 31, 2017 ($ in Thousands) Assets Investment securities available for sale U.S. Treasury securities Level 1 $ 995 $ 996 Residential mortgage-related securities FNMA / FHLMC Level 2 430,073 464,768 GNMA Level 2 2,310,306 1,913,350 Private-label Level 2 1,044 1,059 GNMA commercial mortgage-related securities Level 2 1,448,369 1,513,277 FFELP asset backed securities Level 2 290,300 145,176 Other equity securities Level 1 1,599 1,632 Other debt securities Level 2 3,188 3,188 Total investment securities available for sale Level 1 2,594 2,628 Total investment securities available for sale Level 2 4,483,281 4,040,818 Residential loans held for sale Level 2 103,953 85,544 Commercial loans held for sale Level 2 6,091 — Interest rate-related instruments Level 2 53,189 28,494 Foreign currency exchange forwards Level 2 2,612 2,495 Interest rate products (designated as hedging instruments) Level 2 258 — Interest rate lock commitments to originate residential mortgage loans held for sale Level 3 3,032 1,538 Commodity contracts Level 2 47,089 38,686 Purchased options (time deposit) Level 2 951 1,175 Liabilities Interest rate-related instruments Level 2 $ 52,238 $ 28,035 Foreign currency exchange forwards Level 2 2,484 2,339 Forward commitments to sell residential mortgage loans Level 3 303 313 Commodity contracts Level 2 45,525 37,286 Written options (time deposit) Level 2 951 1,175
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)	The table below presents a rollforward of the balance sheet amounts for the three months ended March 31, 2018 and the year ended December 31, 2017 , for financial instruments measured on a recurring basis and classified within Level 3 of the fair value hierarchy. Investment Securities Available for Sale Derivative Financial Instruments ($ in Thousands) Balance December 31, 2016 $ 200 $ 3,114 Total net gains (losses) included in income Mortgage derivative gain (loss) — (1,889 ) Transfer out of level 3 securities (a) (200 ) — Balance December 31, 2017 $ — $ 1,225 Total net gains (losses) included in income Mortgage derivative gain (loss) — 1,501 Balance March 31, 2018 $ — $ 2,726 (a) During the first quarter of 2017, the $200,000 level 3 investment security was transferred to level 2 based upon new pricing information.
Assets and Liabilities Measured on Nonrecurring Basis at Fair Value	The table below presents the Corporation’s assets measured at fair value on a nonrecurring basis, aggregated by the level in the fair value hierarchy within which those measurements fall. Income Statement Category of Adjustment Recognized in Income ($ in Thousands) Fair Value Hierarchy Fair Value March 31, 2018 Assets Commercial loans held for sale (a) Level 2 $ 6,091 Provision for credit losses $ — Impaired loans (b) Level 3 74,038 Provision for credit losses (c) (14,518 ) Other real estate owned Level 2 2,088 Foreclosure / OREO expense, net (553 ) Mortgage servicing rights Level 3 81,810 Mortgage banking, net 474 December 31, 2017 Assets Impaired loans (b) Level 3 $ 92,534 Provision for credit losses (c) $ (32,159 ) Other real estate owned Level 2 2,604 Foreclosure / OREO expense, net (939 ) Mortgage servicing rights Level 3 64,387 Mortgage banking, net (175 ) (a) Commercial loans held for sale are carried at the lower of cost or estimated fair value. When the cost is less than or equal to the estimated fair value, no adjustment is recognized in income. (b) Represents individually evaluated impaired loans, net of the related allowance for loan losses. (c) Represents provision for credit losses on individually evaluated impaired loans.
Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Table Text Block]	The table below presents information about these inputs and further discussion is found above. Valuation Technique Significant Unobservable Input Weighted Average Input Applied March 31, 2018 Mortgage servicing rights Discounted cash flow Discount rate 11% Mortgage servicing rights Discounted cash flow Constant prepayment rate 9% Impaired Loans Appraisals / Discounted cash flow Collateral / Discount factor 28%
Estimated fair values of financial instruments	Fair value estimates are set forth below for the Corporation’s financial instruments. March 31, 2018 December 31, 2017 Fair Value Hierarchy Level Carrying Amount Fair Value Carrying Amount Fair Value ($ in Thousands) Financial assets Cash and due from banks Level 1 $ 328,260 $ 328,260 $ 483,666 $ 483,666 Interest-bearing deposits in other financial institutions Level 1 94,918 94,918 199,702 199,702 Federal funds sold and securities purchased under agreements to resell Level 1 10,000 10,000 32,650 32,650 Investment securities held to maturity Level 2 2,443,203 2,407,197 2,282,853 2,283,574 Investment securities available for sale Level 1 2,594 2,594 2,628 2,628 Investment securities available for sale Level 2 4,483,281 4,483,281 4,040,818 4,040,818 FHLB and Federal Reserve Bank stocks Level 2 233,216 233,216 165,331 165,331 Residential loans held for sale Level 2 103,953 103,953 85,544 85,544 Commercial loans held for sale Level 2 6,091 6,091 — — Loans, net Level 3 22,553,433 22,195,415 20,519,111 20,314,984 Bank and corporate owned life insurance Level 2 657,841 657,841 591,057 591,057 Derivatives (trading and other assets) Level 2 104,099 104,099 70,850 70,850 Derivatives (trading and other assets) Level 3 3,032 3,032 1,538 1,538 Financial liabilities Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts Level 3 $ 21,148,230 $ 21,148,230 $ 20,436,893 $ 20,436,893 Brokered CDs and other time deposits Level 2 2,677,372 2,677,372 2,349,069 2,349,069 Short-term funding Level 2 2,146,374 2,146,374 676,282 676,282 Long-term funding Level 2 3,233,338 3,242,517 3,397,450 3,411,368 Standby letters of credit (a) Level 2 2,468 2,468 2,402 2,402 Derivatives (trading and other liabilities) Level 2 101,198 101,198 68,835 68,835 Derivatives (trading and other liabilities) Level 3 303 303 313 313 (a) The commitment on standby letters of credit was $254 million and $235 million at March 31, 2018 and December 31, 2017 , respectively. See Note 12 for additional information on the standby letters of credit and for information on the fair value of lending-related commitments.

Retirement Plans (Tables)

Retirement Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Defined Benefit Plan [Abstract]
Net period benefit cost for the pension and postretirement plans	The components of net periodic benefit cost for the RAP, Bank Mutual Pension Plan, and \Postretirement Plan for three months ended March 31, 2018 and 2017 were as follows. Three Months Ended March 31, 2018 2017 ($ in Thousands) Components of Net Periodic Benefit Cost RAP Service cost $ 1,893 $ 1,781 Interest cost 1,660 1,756 Expected return on plan assets (4,755 ) (4,881 ) Amortization of prior service cost (19 ) (19 ) Amortization of actuarial loss 463 488 Total net pension cost $ (759 ) $ (875 ) Bank Mutual Pension Plan (a) Interest cost $ 433 N/A Expected return on plan assets (532 ) N/A Total net pension cost $ (99 ) N/A Postretirement Plan (b) Interest cost $ 26 $ 24 Amortization of prior service cost (19 ) (19 ) Amortization of actuarial loss 2 — Total net periodic benefit cost $ 9 $ 5

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Selected segment information	Information about the Corporation’s segments is presented below. Segment Income Statement Data ($ in Thousands) Corporate and Commercial Specialty Community, Consumer, and Business Risk Management and Shared Services Consolidated Total Three Months Ended March 31, 2018 Net interest income $ 95,958 $ 103,543 $ 10,370 $ 209,871 Noninterest income 12,683 74,036 3,661 90,380 Total revenue 108,641 177,579 14,031 300,251 Credit provision (a) 10,598 4,966 (15,563 ) — Noninterest expense 39,250 127,144 46,571 212,965 Income (loss) before income taxes 58,793 45,469 (16,977 ) 87,285 Income tax expense (benefit) 11,426 9,549 (3,146 ) 17,829 Net income (loss) $ 47,367 $ 35,920 $ (13,831 ) $ 69,456 Return on average allocated capital (ROCET1) (b) 16.4 % 23.0 % (11.2 )% 11.4 % Three Months Ended March 31, 2017 Net interest income $ 89,388 $ 88,928 $ 1,958 $ 180,274 Noninterest income 11,993 64,870 2,968 79,831 Total revenue 101,381 153,798 4,926 260,105 Credit provision (a) 11,580 4,507 (7,087 ) 9,000 Noninterest expense 37,479 116,097 20,115 173,691 Income (loss) before income taxes 52,322 33,194 (8,102 ) 77,414 Income tax expense (benefit) 17,649 11,618 (8,123 ) 21,144 Net income $ 34,673 $ 21,576 $ 21 $ 56,270 Return on average allocated capital (ROCET1) (b) 12.6 % 15.2 % (2.5 )% 10.6 % Segment Balance Sheet Data ($ in Thousands) Corporate and Commercial Specialty Community, Consumer, and Business Risk Management and Shared Services Consolidated Total Three Months Ended March 31, 2018 Average earning assets $ 11,389,211 $ 10,137,899 $ 7,755,022 $ 29,282,132 Average loans 11,378,390 10,133,202 566,936 22,078,529 Average deposits 8,057,246 13,096,782 2,496,870 23,650,898 Average allocated capital (CET1) (b) $ 1,171,038 $ 632,723 $ 586,172 $ 2,389,933 Three Months Ended March 31, 2017 Average earning assets $ 10,759,811 $ 9,130,457 $ 6,449,046 $ 26,339,314 Average loans 10,753,314 9,128,656 190,755 20,072,725 Average deposits 6,420,401 11,337,064 3,708,257 21,465,722 Average allocated capital (CET1) (b) $ 1,114,610 $ 576,464 $ 370,675 $ 2,061,749 (a) The consolidated credit provision is equal to the actual reported provision for credit losses. (b) The Federal Reserve establishes capital adequacy requirements for the Corporation, including common equity Tier 1. For segment reporting purposes, the ROCET1 reflects return on average allocated common equity Tier 1. The ROCET1 for the Risk Management and Shared Services segment and the Consolidated Total is inclusive of the annualized effect of the preferred stock dividends.

Accumulated Other Comprehensi40

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Summary of activity in accumulated other comprehensive income (loss)	The following tables summarize the components of accumulated other comprehensive income (loss) at March 31, 2018 and 2017 , changes during the three month periods then ended, and reclassifications out of accumulated other comprehensive income (loss) during the three month periods ended March 31, 2018 and 2017 , respectively. ($ in Thousands) Investment Securities Available For Sale Defined Benefit Pension and Post Retirement Obligations Accumulated Other Comprehensive Income (Loss) Balance January 1, 2018 $ (38,453 ) $ (24,305 ) $ (62,758 ) Other comprehensive income (loss) before reclassifications (41,834 ) — (41,834 ) Amounts reclassified from accumulated other comprehensive income (loss) Personnel expense — (38 ) (38 ) Other expense — 465 465 Adjustment for adoption of ASU 2016-01 (84 ) — (84 ) Adjustment for adoption of ASU 2018-02 (8,419 ) (5,235 ) (13,654 ) Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (297 ) — (297 ) Income tax (expense) benefit 10,635 (107 ) 10,528 Net other comprehensive income (loss) during period (40,000 ) (4,915 ) (44,915 ) Balance March 31, 2018 $ (78,453 ) $ (29,220 ) $ (107,673 ) Balance January 1, 2017 $ (20,079 ) $ (34,600 ) $ (54,679 ) Other comprehensive income (loss) before reclassifications (2,112 ) — (2,112 ) Amounts reclassified from accumulated other comprehensive income (loss) Investment securities gain (loss), net — — — Personnel expense — (38 ) (38 ) Other expense — 488 488 Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (1,027 ) — (1,027 ) Income tax (expense) benefit 1,195 (171 ) 1,024 Net other comprehensive income (loss) during period (1,944 ) 279 (1,665 ) Balance March 31, 2017 $ (22,023 ) $ (34,321 ) $ (56,344 )

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Disaggregation of Revenue by Major Source	The following table disaggregates our revenue by major source for the three months ended March 31, 2018 and March 31, 2017. Three Months Ended March 31, 2018 ($ in Thousands) Corporate and Commercial Specialty Community, Consumer, and Business Risk Management and Shared Services Consolidated Total Insurance commissions and fees $ — $ 22,624 $ 24 $ 22,648 Service charges and deposit account fees 4,225 12,183 12 16,420 Card-based and loan fees (1) 315 9,529 25 9,869 Trust and asset management fees — 13,369 — 13,369 Brokerage commissions and fees — 7,032 241 7,273 Other revenue 655 2,461 30 3,146 Noninterest Income (in-scope of Topic 606) $ 5,195 $ 67,198 $ 332 $ 72,725 Noninterest Income (out-of-scope of Topic 606) 7,488 6,838 3,329 17,655 Total Noninterest Income $ 12,683 $ 74,036 $ 3,661 $ 90,380 (1) Loan fees are out-of-scope of Topic 606. Three Months Ended March 31, 2017 ($ in Thousands) Corporate and Community, Risk Management Consolidated Insurance commissions and fees $ — $ 21,620 $ — $ 21,620 Service charges and deposit account fees 4,441 11,889 26 16,356 Card-based and loan fees (1) 272 8,144 5 8,421 Trust and asset management fees — 11,935 — 11,935 Brokerage commissions and fees — 4,333 — 4,333 Other revenue 44 2,119 53 2,216 Noninterest Income (in-scope of Topic 606) $ 4,757 $ 60,040 $ 84 $ 64,881 Noninterest Income (out-of-scope of Topic 606) 7,236 4,830 2,884 14,950 Total Noninterest Income $ 11,993 $ 64,870 $ 2,968 $ 79,831 (1) Loan fees are out-of-scope of Topic 606.

Acquisitions - Bank Mutual Acqu

Acquisitions - Bank Mutual Acquisition (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Feb. 01, 2018	Dec. 31, 2017	Mar. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 1,153,156		$ 976,239
Total liabilities	$ 2,809,565			$ 0
Purchase Accounting Adjustments
Business Acquisition [Line Items]
Cash and cash equivalents		$ 0
Investment securities		(6,238)
Federal Home Loan Bank stock, at cost		0
Loans		(48,533)
Premises and equipment, net		11,172
Bank owned life insurance		(24)
Goodwill
Core deposit intangibles (included in other intangible assets, net on the face of the Consolidated Balance Sheet)		58,100
Other real estate owned		(246)
Others assets		5,098
Deposits		2,498
Other borrowings		935
Other liabilities		2,148
BKMU Assets Acquired, Liabilities Assumed
Business Acquisition [Line Items]
Cash and cash equivalents		78,052
Investment securities		452,867
Federal Home Loan Bank stock, at cost		20,026
Loans		1,875,386
Premises and equipment, net		50,930
Bank owned life insurance		65,390
Goodwill		166,870
Core deposit intangibles (included in other intangible assets, net on the face of the Consolidated Balance Sheet)		58,100
Other real estate owned		4,403
Others assets		37,151
Total assets		2,809,175
Deposits		1,840,950
Other borrowings		430,946
Other liabilities		55,591
Total liabilities		2,327,487
Total consideration paid		$ 481,688

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) - USD ($)	Feb. 01, 2018	Jan. 31, 2018	Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Value of stock transaction			$ 134,000	$ 0
Bank Mutual
Business Acquisition [Line Items]
Value of stock transaction	$ 482,000,000
Number of shares received by shareholders (in shares)	0.422
Number of shares issued		19,500,000
Goodwill acquired	$ 167,000,000
Amortization period	10 years
Additions to finite-lived intangible assets			58,000,000
Diversified Insurance Solutions
Business Acquisition [Line Items]
Goodwill acquired			10,000,000
Value of acquisition			19,000,000
Additions to finite-lived intangible assets			$ 8,000,000

Summary of Significant Accoun44

Summary of Significant Accounting Policies textuals (Details) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)shares
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expense Relcass (asu 2017-07)	$ 9,000
Visa Restricted Stock Owned | shares	119
AOCI Attributable to Parent [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reporting Comprehensive Income(2018-02)	$ 13,654

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Calculations for basic and diluted earnings per common share
Net income	$ 69,456	$ 56,270
Preferred stock dividends	(2,339)	(2,330)
Net income available to common equity	67,117	53,940
Common shareholder dividends	(25,572)	(18,251)
Unvested share-based payment awards	(138)	(117)
Undistributed earnings	41,407	35,572
Undistributed earnings allocated to common shareholders	41,225	35,294
Undistributed earnings allocated to unvested share-based payment awards	182	278
Undistributed earnings	41,407	35,572
Basic
Distributed earnings to common shareholders	25,572	18,251
Undistributed earnings allocated to common shareholders	41,225	35,294
Total common shareholders earnings, basic	66,797	53,545
Diluted
Distributed earnings to common shareholders	25,572	18,251
Undistributed earnings allocated to common shareholders	41,225	35,294
Total common shareholders earnings, diluted	$ 66,797	$ 53,545
Weighted average common shares outstanding (in shares)	163,520	150,815
Effect of dilutive common stock awards (in shares)	2,038	2,216
Effect of dilutive common stock warrants (in shares)	874	838
Diluted weighted average common shares outstanding (in shares)	166,432	153,869
Basic earnings (loss) per common share (in usd per share)	$ 0.41	$ 0.36
Diluted earnings (loss) per common share (in usd per share)	$ 0.40	$ 0.35

Earnings Per Common Share (Text

Earnings Per Common Share (Textual) (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,000	4,000
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		500

Stock-Based Compensation, Stock

Stock-Based Compensation, Stock Option Activity (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair value assumptions of stock options
Dividend yield	2.50%	2.00%
Risk-free interest rate	2.60%	2.00%
Weighted average expected volatility	22.00%	25.00%
Weighted average expected life	5 years 9 months	5 years 6 months
Weighted average per share fair value of stock options (in usd per share)	$ 4.47	$ 5.30
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock Options Shares Outstanding, Beginning balance (in shares)	5,118,687
Granted (in shares)	938,740
Exercised (in shares)	(529,869)
Forfeited or expired (in shares)	(24,130)
Stock Options Shares Outstanding, Ending balance (in shares)	5,873,479		5,118,687
Options exercisable (in shares)	3,659,277
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Stock Options Outstanding, Weighted Average Exercise Price, Beginning balance (in usd per share)	$ 18.02
Granted, Weighted Average Exercise Price (in usd per share)	$ 24.50
Shares used in acquisition	$ 370,051
Exercised, Weighted Average Exercise Price (in usd per share)	$ 17.37
Forfeited or expired, Weighted Average Exercise Price (in usd per share)	23.35
Stock Options Outstanding, Weighted Average Exercise Price, Ending balance (in usd per share)	$ 18.86		$ 18.02
Ex Share Price at Acquisition	$ 14.35
Options Exercisable, Weighted Average Exercise Price (in usd per share)	$ 16.72
Stock Options Outstanding, Weighted Average Remaining Contractual Term	6 years 9 months 17 days		6 years 5 months 24 days
Options exercisable, Weighted Average Remaining Contractual Term	5 years 6 months 18 days
Stock Options Outstanding, Aggregate Intrinsic Value	$ 35,879,000		$ 38,028,000
Options exercisable, Aggregate Intrinsic Value	$ 30,009,000

Stock-Based Compensation, Restr

Stock-Based Compensation, Restricted Stock Activity (Details)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding Shares, Beginning balance (in shares) | shares	2,026,071
Granted (in shares) | shares	570,341
Vested (in shares) | shares	(498,988)
Forfeited (in shares) | shares	(5,799)
Outstanding Shares, Ending balance (in shares) | shares	2,091,625
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding, Weighted Average Grant Date Fair Value, Beginning balance (in usd per share) | $ / shares	$ 19.68
Granted, Weighted Average Grant Date Fair Value (in usd per share) | $ / shares	24.63
Vested, Weighted Average Grant Date Fair Value (in usd per share) | $ / shares	17.97
Forfeited, Weighted Average Grant Date Fair Value (in usd per share) | $ / shares	20.16
Outstanding Weighted Average Grant Date Fair Value, Ending balance (in usd per share) | $ / shares	$ 21.86

Stock-Based Compensation (Detai

Stock-Based Compensation (Details Textuals) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock Based Compensation (Textuals) [Abstract]
Intrinsic value of stock options exercised	$ 5,000,000	$ 10,000,000
Total fair value of vested stock options	$ 3,000,000	$ 3,000,000
Service-based Restricted Stock Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years	4 years
Performance-based Restricted Stock Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years	3 years
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for accelerated vesting of stock options	$ 450,000
Recognized compensation expense for vesting of stock options	1,000,000
Unvested share-based payment awards	$ 8,000,000
Employee Service Share Based Compensation Nonvested Awards Compensation Cost Not Yet Recognized Year For Recognition	first quarter 2022
Restricted Stock Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for accelerated vesting of stock options	$ 1,000,000
Recognized compensation expense for vesting of stock options	3,000,000
Unvested share-based payment awards	$ 29,000,000
Employee Service Share Based Compensation Nonvested Awards Compensation Cost Not Yet Recognized Year For Recognition	first quarter 2022

Investment Securities, AFS and

Investment Securities, AFS and HTM Securities Amortized Costs and Fair Values (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment securities available for sale:
Amortized Cost	$ 4,584,763	$ 4,100,417
Gross Unrealized Gains	9,186	10,996
Gross Unrealized Losses	(108,076)	(67,967)
Fair Value	4,485,875	4,043,446
Investment securities held to maturity:
Amortized Cost	2,443,203	2,282,853
Gross Unrealized Gains	15,555	26,543
Gross Unrealized Losses	(51,561)	(25,822)
Fair Value	2,407,197	2,283,574
US Treasury Securities
Investment securities available for sale:
Amortized Cost	1,002	1,003
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(7)	(7)
Fair Value	995	996
Obligations of state and political subdivisions (municipal securities)
Investment securities held to maturity:
Amortized Cost	1,424,925	1,281,320
Gross Unrealized Gains	4,110	13,899
Gross Unrealized Losses	(16,579)	(3,177)
Fair Value	1,412,456	1,292,042
Private Label
Investment securities available for sale:
Amortized Cost	1,051	1,067
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(7)	(8)
Fair Value	1,044	1,059
Investment securities held to maturity:
Amortized Cost	0
Fair Value	0
GNMA Commercial Mortgage-Related Securities
Investment securities available for sale:
Amortized Cost	1,497,573	1,547,173
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(49,204)	(33,901)
Fair Value	1,448,369	1,513,277
Investment securities held to maturity:
Amortized Cost	531,934
Gross Unrealized Gains	9,008
Gross Unrealized Losses	(21,694)
Fair Value	519,248
Asset backed Securities
Investment securities available for sale:
Amortized Cost	288,519
Gross Unrealized Gains	1,835
Gross Unrealized Losses	(54)
Fair Value	290,300
Investment securities held to maturity:
Amortized Cost	0
Fair Value	0
Other Debt And Other Equity Securities
Investment securities available for sale:
Amortized Cost	3,200	3,200
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(12)	(12)
Fair Value	3,188	3,188
Equity Securities [Member]
Investment securities available for sale:
Amortized Cost	1,599	1,519
Gross Unrealized Gains	0	127
Gross Unrealized Losses	0	(14)
Fair Value	1,599	1,632
Investment securities held to maturity:
Amortized Cost	0
Fair Value	0
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Investment securities available for sale:
Amortized Cost		144,322
Gross Unrealized Gains		867
Gross Unrealized Losses		(13)
Fair Value		145,176
FNMA and FHLMC | Residential Related Securities
Investment securities available for sale:
Amortized Cost	427,480	457,680
Gross Unrealized Gains	7,331	9,722
Gross Unrealized Losses	(4,738)	(2,634)
Fair Value	430,073	464,768
Investment securities held to maturity:
Amortized Cost	76,069	40,995
Gross Unrealized Gains	227	398
Gross Unrealized Losses	(1,665)	(489)
Fair Value	74,631	40,904
GNMA | Residential Related Securities
Investment securities available for sale:
Amortized Cost	2,364,339	1,944,453
Gross Unrealized Gains	21	275
Gross Unrealized Losses	(54,054)	(31,378)
Fair Value	2,310,306	1,913,350
Investment securities held to maturity:
Amortized Cost	410,275	414,440
Gross Unrealized Gains	2,210	2,700
Gross Unrealized Losses	(11,624)	(6,400)
Fair Value	$ 400,861	410,740
GNMA | GNMA Commercial Mortgage-Related Securities
Investment securities held to maturity:
Amortized Cost		546,098
Gross Unrealized Gains		9,546
Gross Unrealized Losses		(15,756)
Fair Value		$ 539,888

Investment Securities, AFS an51

Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortized Cost
Available for Sale, Due in one year or less	$ 2,002
Available for Sale, Due after one year through five years	2,200
Available for Sale, Due after five years through ten years	0
Available for Sale, Due after ten years	0
Available for Sale, Total debt securities	4,202
Investment securities available for sale, amortized cost	4,584,763	$ 4,100,417
Fair Value
Available for Sale, Due in one year or less	1,995
Available for Sale, Due after one year through five years	2,188
Available for Sale, Due after five years through ten years	0
Available for Sale, Due after ten years	0
Available for Sale, Total debt securities	4,183
Investment securities available for sale, at fair value	$ 4,485,875	4,043,446
Ratio of Fair Value to Amortized Cost	97.80%
Amortized Cost
Held to Maturity, Due in one year or less	$ 44,019
Held to Maturity, Due after one year through five years	221,411
Held to Maturity, Due after five years through ten years	346,521
Held to Maturity, Due after ten years	812,974
Held to Maturity, Debt Securities, Amortized Cost Basis	1,424,925
Held to Maturity Amortized Cost	2,443,203	2,282,853
Fair Value
Held to Maturity, Due in one year or less	44,261
Held to Maturity, Due after one year through five years	219,411
Held to Maturity, Due after five years through ten years	341,147
Held to Maturity, Due after ten years	807,638
Held to Maturity, Securities, Debt Securities	1,412,456
Held to Maturity, Total debt securities	$ 2,407,197	2,283,574
Ratio of Fair Value to Amortized Cost	98.50%
Private Label
Amortized Cost
Investment securities available for sale, amortized cost	$ 1,051	1,067
Fair Value
Investment securities available for sale, at fair value	1,044	1,059
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
GNMA Commercial Mortgage-Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	1,497,573	1,547,173
Fair Value
Investment securities available for sale, at fair value	1,448,369	1,513,277
Amortized Cost
Held to Maturity Amortized Cost	531,934
Fair Value
Held to Maturity, Total debt securities	519,248
Asset backed Securities
Amortized Cost
Investment securities available for sale, amortized cost	288,519
Fair Value
Investment securities available for sale, at fair value	290,300
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
Equity Securities [Member]
Amortized Cost
Investment securities available for sale, amortized cost	1,599	1,519
Fair Value
Investment securities available for sale, at fair value	1,599	1,632
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
FNMA and FHLMC | Residential Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	427,480	457,680
Fair Value
Investment securities available for sale, at fair value	430,073	464,768
Amortized Cost
Held to Maturity Amortized Cost	76,069	40,995
Fair Value
Held to Maturity, Total debt securities	74,631	40,904
GNMA | Residential Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	2,364,339	1,944,453
Fair Value
Investment securities available for sale, at fair value	2,310,306	1,913,350
Amortized Cost
Held to Maturity Amortized Cost	410,275	414,440
Fair Value
Held to Maturity, Total debt securities	$ 400,861	410,740
GNMA | GNMA Commercial Mortgage-Related Securities
Amortized Cost
Held to Maturity Amortized Cost		546,098
Fair Value
Held to Maturity, Total debt securities		$ 539,888

Investment Securities, AFS an52

Investment Securities, AFS and HTM Securities Gross Unrealized Losses (Details) $ in Thousands	Mar. 31, 2018USD ($)security	Dec. 31, 2017USD ($)security
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (37,313)	$ (15,099)
Unrealized losses on available for sale securities, 12 months or more	(70,763)	(52,868)
Total unrealized losses on available for sale securities	(108,076)	(67,967)
Fair value of unrealized losses on available for sale securities, less than 12 months	2,158,266	1,593,503
Fair value of unrealized losses on available for sale securities, 12 months or more	1,918,413	1,906,992
Total fair value of unrealized losses on available for sale securities	$ 4,076,679	$ 3,500,495
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	113	92
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	112	105
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (18,891)	$ (4,491)
Unrealized losses on held to maturity securities, 12 months or more	(32,670)	(21,331)
Total unrealized losses on held to maturity securities	$ (51,561)	$ (25,822)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, 12 Months or Longer | security	183	183
Fair value of unrealized losses on held to maturity securities, less than 12 months	$ 907,256	$ 457,289
Fair value of unrealized losses on held to maturity securities, 12 months or more	720,961	751,088
Total fair value of unrealized losses on held to maturity securities	$ 1,628,217	$ 1,208,377
Held-to-maturity, Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions, less than 12 Months | security	900	202
US Treasury Securities
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (7)
Unrealized losses on available for sale securities, 12 months or more	0
Total unrealized losses on available for sale securities	(7)
Fair value of unrealized losses on available for sale securities, less than 12 months	995
Fair value of unrealized losses on available for sale securities, 12 months or more	0
Total fair value of unrealized losses on available for sale securities	$ 995
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	0
Obligations of state and political subdivisions (municipal securities)
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (9,876)	$ (746)
Unrealized losses on held to maturity securities, 12 months or more	(6,703)	(2,431)
Total unrealized losses on held to maturity securities	(16,579)	(3,177)
Fair value of unrealized losses on held to maturity securities, less than 12 months	523,716	122,761
Fair value of unrealized losses on held to maturity securities, 12 months or more	122,632	127,043
Total fair value of unrealized losses on held to maturity securities	$ 646,348	$ 249,804
Obligations of state and political subdivisions (municipal securities) | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	821	157
Obligations of state and political subdivisions (municipal securities) | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	132	132
Private Label
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ 0	$ 0
Unrealized losses on available for sale securities, 12 months or more	(7)	(8)
Total unrealized losses on available for sale securities	(7)	(8)
Fair value of unrealized losses on available for sale securities, less than 12 months	0	0
Fair value of unrealized losses on available for sale securities, 12 months or more	1,044	1,059
Total fair value of unrealized losses on available for sale securities	$ 1,044	$ 1,059
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	0	0
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	1	1
GNMA Commercial Mortgage-Related Securities
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (9,895)	$ (5,554)
Unrealized losses on available for sale securities, 12 months or more	(39,309)	(28,347)
Total unrealized losses on available for sale securities	(49,204)	(33,901)
Fair value of unrealized losses on available for sale securities, less than 12 months	385,319	480,514
Fair value of unrealized losses on available for sale securities, 12 months or more	1,063,082	1,026,642
Total fair value of unrealized losses on available for sale securities	$ 1,448,401	$ 1,507,156
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	28	33
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	76	70
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (837)
Unrealized losses on held to maturity securities, 12 months or more	(20,857)
Total unrealized losses on held to maturity securities	(21,694)
Fair value of unrealized losses on held to maturity securities, less than 12 months	49,711
Fair value of unrealized losses on held to maturity securities, 12 months or more	469,538
Total fair value of unrealized losses on held to maturity securities	$ 519,249
GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	2
GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	23
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (54)	$ (13)
Unrealized losses on available for sale securities, 12 months or more	0	0
Total unrealized losses on available for sale securities	(54)	(13)
Fair value of unrealized losses on available for sale securities, less than 12 months	86,988	12,158
Fair value of unrealized losses on available for sale securities, 12 months or more	0	0
Total fair value of unrealized losses on available for sale securities	$ 86,988	$ 12,158
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	6	1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	0	0
Asset backed Securities
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (12)
Unrealized losses on available for sale securities, 12 months or more	0
Total unrealized losses on available for sale securities	(12)
Fair value of unrealized losses on available for sale securities, less than 12 months	188
Fair value of unrealized losses on available for sale securities, 12 months or more	0
Total fair value of unrealized losses on available for sale securities	$ 188
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	0
Other Debt And Other Equity Securities
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months		$ (12)
Unrealized losses on available for sale securities, 12 months or more		0
Total unrealized losses on available for sale securities		(12)
Fair value of unrealized losses on available for sale securities, less than 12 months		188
Fair value of unrealized losses on available for sale securities, 12 months or more		0
Total fair value of unrealized losses on available for sale securities		$ 188
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security		1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security		0
Equity Securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months		$ (14)
Unrealized losses on available for sale securities, 12 months or more		0
Total unrealized losses on available for sale securities		(14)
Fair value of unrealized losses on available for sale securities, less than 12 months		1,487
Fair value of unrealized losses on available for sale securities, 12 months or more		0
Total fair value of unrealized losses on available for sale securities		$ 1,487
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security		3
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security		0
FNMA and FHLMC | US Treasury Securities
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months		$ (7)
Unrealized losses on available for sale securities, 12 months or more		0
Total unrealized losses on available for sale securities		(7)
Fair value of unrealized losses on available for sale securities, less than 12 months		996
Fair value of unrealized losses on available for sale securities, 12 months or more		0
Total fair value of unrealized losses on available for sale securities		$ 996
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security		1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security		0
FNMA and FHLMC | Residential Related Securities
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (1,389)	$ (572)
Unrealized losses on available for sale securities, 12 months or more	(3,349)	(2,062)
Total unrealized losses on available for sale securities	(4,738)	(2,634)
Fair value of unrealized losses on available for sale securities, less than 12 months	94,231	69,939
Fair value of unrealized losses on available for sale securities, 12 months or more	135,316	142,093
Total fair value of unrealized losses on available for sale securities	$ 229,547	$ 212,032
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	12	9
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	9	9
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (939)	$ (73)
Unrealized losses on held to maturity securities, 12 months or more	(725)	(417)
Total unrealized losses on held to maturity securities	(1,665)	(490)
Fair value of unrealized losses on held to maturity securities, less than 12 months	54,122	13,143
Fair value of unrealized losses on held to maturity securities, 12 months or more	15,230	16,262
Total fair value of unrealized losses on held to maturity securities	$ 69,352	$ 29,405
FNMA and FHLMC | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	19	8
FNMA and FHLMC | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	10	10
GNMA | Residential Related Securities
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (25,956)	$ (8,927)
Unrealized losses on available for sale securities, 12 months or more	(28,098)	(22,451)
Total unrealized losses on available for sale securities	(54,054)	(31,378)
Fair value of unrealized losses on available for sale securities, less than 12 months	1,590,545	1,028,221
Fair value of unrealized losses on available for sale securities, 12 months or more	718,971	737,198
Total fair value of unrealized losses on available for sale securities	$ 2,309,516	$ 1,765,419
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	65	44
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	26	25
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (7,239)	$ (3,373)
Unrealized losses on held to maturity securities, 12 months or more	(4,385)	(3,026)
Total unrealized losses on held to maturity securities	(11,624)	(6,399)
Fair value of unrealized losses on held to maturity securities, less than 12 months	279,707	268,388
Fair value of unrealized losses on held to maturity securities, 12 months or more	113,561	120,892
Total fair value of unrealized losses on held to maturity securities	$ 393,268	$ 389,280
GNMA | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	58	35
GNMA | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security	18	18
GNMA | GNMA Commercial Mortgage-Related Securities
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months		$ (299)
Unrealized losses on held to maturity securities, 12 months or more		(15,457)
Total unrealized losses on held to maturity securities		(15,756)
Fair value of unrealized losses on held to maturity securities, less than 12 months		52,997
Fair value of unrealized losses on held to maturity securities, 12 months or more		486,891
Total fair value of unrealized losses on held to maturity securities		$ 539,888
GNMA | GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security		2
GNMA | GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member]
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Number of held to maturity securities in a continuous unrealized loss position | security		23

Investment Securities (Details

Investment Securities (Details Textual) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Investment Securities (Textuals) [Abstract]
Securities pledged as collateral	$ 3,000	$ 3,100
Federal Home Loan Bank Stock	157	89
Federal Reserve Bank Stock	$ 76	$ 76

Loans - Composition (Details)

Loans - Composition (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Total loans	$ 22,810,491	$ 20,784,991
Purchased credit-impaired loans	233,078	247,575
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Total loans	6,756,983	6,399,693
Purchased credit-impaired loans	128,841	142,244
Commercial real estate — owner occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans	900,913	802,209
Purchased credit-impaired loans	22,489	26,234
Commercial and business lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans	7,657,896	7,201,902
Purchased credit-impaired loans	151,330	168,478
Commercial real estate — investor
Loans and Leases Receivable Disclosure [Line Items]
Total loans	4,077,671	3,315,254
Purchased credit-impaired loans	20,387	19,118
Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Total loans	1,579,778	1,451,684
Purchased credit-impaired loans	458	467
Commercial real estate lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans	5,657,449	4,766,938
Total commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans	13,315,345	11,968,840
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total loans	8,197,223	7,546,534
Purchased credit-impaired loans	48,863	47,486
Home equity
Loans and Leases Receivable Disclosure [Line Items]
Total loans	923,470	883,804
Purchased credit-impaired loans	10,974	10,891
Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans	374,453	385,813
Purchased credit-impaired loans	1,066	1,135
Total consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans	9,495,146	$ 8,816,151
Bank Mutual [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Purchased Credit Impaired Loans And Covered Loans	$ 15,000

Loans - Credit Quality Indicato

Loans - Credit Quality Indicator (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 22,810,491	$ 20,784,991
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	22,080,128	20,171,876
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	239,626	227,692
Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	282,184	176,877
Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	208,553	208,546
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loans	6,756,983	6,399,693
Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	6,325,258	6,015,884
Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	132,292	157,245
Commercial and industrial | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	196,766	113,778
Commercial and industrial | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	102,667	112,786
Commercial real estate — owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans	900,913	802,209
Commercial real estate — owner occupied | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	830,489	723,291
Commercial real estate — owner occupied | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	15,378	14,181
Commercial real estate — owner occupied | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	34,410	41,997
Commercial real estate — owner occupied | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	20,636	22,740
Commercial and business lending
Financing Receivable, Recorded Investment [Line Items]
Loans	7,657,896	7,201,902
Commercial and business lending | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	7,155,747	6,739,175
Commercial and business lending | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	147,670	171,426
Commercial and business lending | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	231,176	155,775
Commercial and business lending | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	123,303	135,526
Commercial real estate — investor
Financing Receivable, Recorded Investment [Line Items]
Loans	4,077,671	3,315,254
Commercial real estate — investor | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	3,960,155	3,266,389
Commercial real estate — investor | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	54,972	24,845
Commercial real estate — investor | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	46,970	19,291
Commercial real estate — investor | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	15,574	4,729
Real estate construction
Financing Receivable, Recorded Investment [Line Items]
Loans	1,579,778	1,451,684
Real estate construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	1,547,443	1,421,504
Real estate construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	29,421	29,206
Real estate construction | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	1,695	0
Real estate construction | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	1,219	974
Commercial real estate lending
Financing Receivable, Recorded Investment [Line Items]
Loans	5,657,449	4,766,938
Commercial real estate lending | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	5,507,598	4,687,893
Commercial real estate lending | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	84,393	54,051
Commercial real estate lending | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	48,665	19,291
Commercial real estate lending | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	16,793	5,703
Total commercial
Financing Receivable, Recorded Investment [Line Items]
Loans	13,315,345	11,968,840
Total commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	12,663,345	11,427,068
Total commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	232,063	225,477
Total commercial | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	279,841	175,066
Total commercial | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	140,096	141,229
Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans	8,197,223	7,546,534
Residential mortgage | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	8,134,387	7,490,860
Residential mortgage | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	5,580	426
Residential mortgage | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	2,155	1,616
Residential mortgage | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	55,100	53,632
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	923,470	883,804
Home equity | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	908,682	868,958
Home equity | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	1,383	1,137
Home equity | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	188	195
Home equity | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	13,218	13,514
Other consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	374,453	385,813
Other consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	373,714	384,990
Other consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	600	652
Other consumer | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0
Other consumer | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	139	171
Total consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	9,495,146	8,816,151
Total consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	9,416,783	8,744,808
Total consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	7,563	2,215
Total consumer | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans	2,343	1,811
Total consumer | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 68,456	$ 67,317

Loans - Past Due Status (Detail

Loans - Past Due Status (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summarized details of Loans
Current	$ 22,573,612	$ 20,555,250
Nonaccrual	208,553	208,546
Total loans	22,810,491	20,784,991
Accruing loans past due 90 days or more	3,000	2,000
Nonaccrual Loans, Current Portion	$ 159,000	$ 135,000
Percent of current nonaccrual loans	76.00%	65.00%
30-59 Days Past Due
Summarized details of Loans
Total Past Due	$ 17,184	$ 16,861
60-89 Days Past Due
Summarized details of Loans
Total Past Due	7,750	2,467
90 Days or More Past Due
Summarized details of Loans
Total Past Due	3,393	1,867
Commercial and industrial
Summarized details of Loans
Current	6,653,188	6,286,369
Nonaccrual	102,667	112,786
Total loans	6,756,983	6,399,693
Commercial and industrial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	793	170
Commercial and industrial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	87	101
Commercial and industrial | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	248	267
Commercial real estate — owner occupied
Summarized details of Loans
Current	879,766	779,421
Nonaccrual	20,636	22,740
Total loans	900,913	802,209
Commercial real estate — owner occupied | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	511	48
Commercial real estate — owner occupied | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial real estate — owner occupied | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial and business lending
Summarized details of Loans
Current	7,532,954	7,065,790
Nonaccrual	123,303	135,526
Total loans	7,657,896	7,201,902
Commercial and business lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	1,304	218
Commercial and business lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	87	101
Commercial and business lending | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	248	267
Commercial real estate — investor
Summarized details of Loans
Current	4,061,600	3,310,000
Nonaccrual	15,574	4,729
Total loans	4,077,671	3,315,254
Commercial real estate — investor | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	240	374
Commercial real estate — investor | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial real estate — investor | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	257	151
Real estate construction
Summarized details of Loans
Current	1,578,069	1,450,459
Nonaccrual	1,219	974
Total loans	1,579,778	1,451,684
Real estate construction | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	220	168
Real estate construction | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	270	83
Real estate construction | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial real estate lending
Summarized details of Loans
Current	5,639,669	4,760,459
Nonaccrual	16,793	5,703
Total loans	5,657,449	4,766,938
Commercial real estate lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	460	542
Commercial real estate lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	270	83
Commercial real estate lending | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	257	151
Total commercial
Summarized details of Loans
Current	13,172,623	11,826,249
Nonaccrual	140,096	141,229
Total loans	13,315,345	11,968,840
Total commercial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	1,764	760
Total commercial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	357	184
Total commercial | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	505	418
Residential mortgage
Summarized details of Loans
Current	8,125,707	7,483,350
Nonaccrual	55,100	53,632
Total loans	8,197,223	7,546,534
Residential mortgage | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	9,876	9,186
Residential mortgage | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	5,257	366
Residential mortgage | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	1,283	0
Home equity
Summarized details of Loans
Current	904,305	863,465
Nonaccrual	13,218	13,514
Total loans	923,470	883,804
Home equity | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	4,485	5,688
Home equity | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	1,383	1,137
Home equity | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	79	0
Other consumer
Summarized details of Loans
Current	370,977	382,186
Nonaccrual	139	171
Total loans	374,453	385,813
Other consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	1,058	1,227
Other consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	753	780
Other consumer | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	1,526	1,449
Total consumer
Summarized details of Loans
Current	9,400,989	8,729,001
Nonaccrual	68,456	67,317
Total loans	9,495,146	8,816,151
Total consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	15,419	16,101
Total consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	7,393	2,283
Total consumer | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	$ 2,888	$ 1,449

Loans, Impaired Loans Recorded

Loans, Impaired Loans Recorded Investment, Unpaid Principal Balance, Related Allowance, Average Recorded Investment, and Interest Income Recognized (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	$ 233,078	$ 247,575
Unpaid Principal Balance	267,094	275,814
Related Allowance	34,094	25,846
Average Recorded Investment	234,164	236,860
Interest Income Recognized	$ 1,090	$ 8,051
Net Recorded Investment of the Impaired Loans	74.00%	80.00%
Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	$ 162,022	$ 175,681
Unpaid Principal Balance	170,162	181,002
Related Allowance	34,094	25,846
Average Recorded Investment	168,908	140,098
Interest Income Recognized	1,398	7,254
Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	71,056	71,894
Unpaid Principal Balance	96,932	94,812
Related Allowance	0	0
Average Recorded Investment	65,256	96,762
Interest Income Recognized	(308)	797
Commercial and industrial
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	128,841	142,244
Unpaid Principal Balance	157,811	166,418
Related Allowance	18,778	10,838
Average Recorded Investment	133,027	147,769
Interest Income Recognized	36	3,121
Commercial and industrial | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	76,452	81,649
Unpaid Principal Balance	81,091	83,579
Related Allowance	18,778	10,838
Average Recorded Investment	77,130	58,494
Interest Income Recognized	312	2,629
Commercial and industrial | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	52,389	60,595
Unpaid Principal Balance	76,720	82,839
Related Allowance	0	0
Average Recorded Investment	55,897	89,275
Interest Income Recognized	(348)	492
Commercial real estate — owner occupied
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	22,489	26,234
Unpaid Principal Balance	23,893	26,766
Related Allowance	2,043	2,973
Average Recorded Investment	25,381	14,072
Interest Income Recognized	47	772
Commercial real estate — owner occupied | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	16,264	23,796
Unpaid Principal Balance	16,617	23,937
Related Allowance	2,043	2,973
Average Recorded Investment	22,978	12,124
Interest Income Recognized	47	736
Commercial real estate — owner occupied | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	6,225	2,438
Unpaid Principal Balance	7,276	2,829
Related Allowance	0	0
Average Recorded Investment	2,403	1,948
Interest Income Recognized	0	36
Commercial and business lending
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	151,330	168,478
Unpaid Principal Balance	181,704	193,184
Related Allowance	20,821	13,811
Average Recorded Investment	158,408	161,841
Interest Income Recognized	11	3,893
Commercial and business lending | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	92,716	105,445
Unpaid Principal Balance	97,708	107,516
Related Allowance	20,821	13,811
Average Recorded Investment	100,108	70,618
Interest Income Recognized	359	3,365
Commercial and business lending | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	58,614	63,033
Unpaid Principal Balance	83,996	85,668
Related Allowance	0	0
Average Recorded Investment	58,300	91,223
Interest Income Recognized	(348)	528
Commercial real estate — investor
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	20,387	19,118
Unpaid Principal Balance	20,472	19,157
Related Allowance	2,721	1,597
Average Recorded Investment	16,559	16,924
Interest Income Recognized	464	1,739
Commercial real estate — investor | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	18,582	17,823
Unpaid Principal Balance	18,619	17,862
Related Allowance	2,721	1,597
Average Recorded Investment	16,559	16,924
Interest Income Recognized	464	1,694
Commercial real estate — investor | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,805	1,295
Unpaid Principal Balance	1,853	1,295
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	45
Real estate construction
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	458	467
Unpaid Principal Balance	532	578
Related Allowance	82	86
Average Recorded Investment	461	484
Interest Income Recognized	7	29
Real estate construction | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	458	467
Unpaid Principal Balance	532	578
Related Allowance	82	86
Average Recorded Investment	461	484
Interest Income Recognized	7	29
Real estate construction | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Commercial real estate lending
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	20,845	19,585
Unpaid Principal Balance	21,004	19,735
Related Allowance	2,803	1,683
Average Recorded Investment	17,020	17,408
Interest Income Recognized	471	1,768
Commercial real estate lending | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	19,040	18,290
Unpaid Principal Balance	19,151	18,440
Related Allowance	2,803	1,683
Average Recorded Investment	17,020	17,408
Interest Income Recognized	471	1,723
Commercial real estate lending | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,805	1,295
Unpaid Principal Balance	1,853	1,295
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	45
Total commercial
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	172,175	188,063
Unpaid Principal Balance	202,708	212,919
Related Allowance	23,624	15,494
Average Recorded Investment	175,428	179,249
Interest Income Recognized	482	5,661
Total commercial | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	111,756	123,735
Unpaid Principal Balance	116,859	125,956
Related Allowance	23,624	15,494
Average Recorded Investment	117,128	88,026
Interest Income Recognized	830	5,088
Total commercial | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	60,419	64,328
Unpaid Principal Balance	85,849	86,963
Related Allowance	0	0
Average Recorded Investment	58,300	91,223
Interest Income Recognized	(348)	573
Residential mortgage
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	48,863	47,486
Unpaid Principal Balance	51,722	50,126
Related Allowance	6,635	6,512
Average Recorded Investment	46,792	45,410
Interest Income Recognized	470	1,831
Residential mortgage | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	38,438	40,561
Unpaid Principal Balance	40,851	42,922
Related Allowance	6,635	6,512
Average Recorded Investment	40,475	40,411
Interest Income Recognized	431	1,614
Residential mortgage | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,425	6,925
Unpaid Principal Balance	10,871	7,204
Related Allowance	0	0
Average Recorded Investment	6,317	4,999
Interest Income Recognized	39	217
Home equity
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,974	10,891
Unpaid Principal Balance	11,595	11,631
Related Allowance	3,719	3,718
Average Recorded Investment	10,877	11,061
Interest Income Recognized	137	556
Home equity | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,762	10,250
Unpaid Principal Balance	11,383	10,986
Related Allowance	3,719	3,718
Average Recorded Investment	10,238	10,521
Interest Income Recognized	136	549
Home equity | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	212	641
Unpaid Principal Balance	212	645
Related Allowance	0	0
Average Recorded Investment	639	540
Interest Income Recognized	1	7
Other consumer
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,066	1,135
Unpaid Principal Balance	1,069	1,138
Related Allowance	116	122
Average Recorded Investment	1,067	1,140
Interest Income Recognized	1	3
Other consumer | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,066	1,135
Unpaid Principal Balance	1,069	1,138
Related Allowance	116	122
Average Recorded Investment	1,067	1,140
Interest Income Recognized	1	3
Other consumer | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Total consumer
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	60,903	59,512
Unpaid Principal Balance	64,386	62,895
Related Allowance	10,470	10,352
Average Recorded Investment	58,736	57,611
Interest Income Recognized	608	2,390
Total consumer | Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	50,266	51,946
Unpaid Principal Balance	53,303	55,046
Related Allowance	10,470	10,352
Average Recorded Investment	51,780	52,072
Interest Income Recognized	568	2,166
Total consumer | Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,637	7,566
Unpaid Principal Balance	11,083	7,849
Related Allowance	0	0
Average Recorded Investment	6,956	5,539
Interest Income Recognized	$ 40	$ 224

Loans, Troubled Debt Restructur

Loans, Troubled Debt Restructurings Performing and Nonaccrual (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	$ 76,501	$ 74,618
Nonaccrual Restructured Loans	23,827	23,486
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	29,580	30,047
Nonaccrual Restructured Loans	886	1,776
Commercial real estate — owner occupied
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	3,892	3,989
Nonaccrual Restructured Loans	0	0
Commercial real estate — investor
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	13,683	14,389
Nonaccrual Restructured Loans	1,007	0
Real estate construction
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	305	310
Nonaccrual Restructured Loans	152	157
Residential mortgage
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	19,902	17,068
Nonaccrual Restructured Loans	18,640	18,991
Home equity
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	8,098	7,705
Nonaccrual Restructured Loans	3,117	2,537
Other consumer
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	1,041	1,110
Nonaccrual Restructured Loans	$ 25	$ 25

Loans, Loans Modified in a Trou

Loans, Loans Modified in a Troubled Debt Restructuring (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)loan	Mar. 31, 2017USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	33	53
Recorded Investment	$ 3,958	$ 54,911
Unpaid Principal Balance	$ 4,007	$ 63,163
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2	20
Recorded Investment	$ 92	$ 52,326
Unpaid Principal Balance	$ 92	$ 60,546
Commercial real estate — owner occupied
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	1
Recorded Investment	$ 0	$ 204
Unpaid Principal Balance	$ 0	$ 204
Commercial real estate — investor
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1	1
Recorded Investment	$ 1,007	$ 733
Unpaid Principal Balance	$ 1,037	$ 744
Residential mortgage
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	11	16
Recorded Investment	$ 1,807	$ 1,301
Unpaid Principal Balance	$ 1,807	$ 1,322
Home equity
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	17	15
Recorded Investment	$ 1,044	$ 347
Unpaid Principal Balance	$ 1,060	$ 347
Other consumer
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2	0
Recorded Investment	$ 8	$ 0
Unpaid Principal Balance	$ 11	$ 0

Loans, Troubled Debt Restruct60

Loans, Troubled Debt Restructurings Subsequent Default (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)loan	Mar. 31, 2017USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	16	8
Recorded Investment | $	$ 1,421	$ 409
Residential mortgage
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	4	6
Recorded Investment | $	$ 467	$ 383
Home equity
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	12	2
Recorded Investment | $	$ 954	$ 26

Loans, Changes in the Allowance

Loans, Changes in the Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	$ 265,880	$ 278,335
Charge offs	(12,155)	(56,246)
Recoveries	2,832	16,791
Net Charge offs	(9,323)	(39,455)
Provision for loan losses	500	27,000
Balance at end of period	257,058	265,880
Allowance for loan losses:
Individually evaluated			$ 34,094	$ 25,846
Collectively evaluated			222,964	240,034
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	265,880	278,335	257,058	265,880
Loans:
Individually evaluated			233,078	247,575
Collectively evaluated			22,562,575	20,537,416
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			14,838
Total loans			22,810,491	20,784,991
Commercial and industrial
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	123,068	140,126
Charge offs	(8,067)	(44,533)
Recoveries	1,468	11,465
Net Charge offs	(6,599)	(33,068)
Provision for loan losses	1,377	16,010
Balance at end of period	117,847	123,068
Allowance for loan losses:
Individually evaluated			18,778	10,838
Collectively evaluated			99,069	112,230
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	123,068	140,126	117,847	123,068
Loans:
Individually evaluated			128,841	142,244
Collectively evaluated			6,625,314	6,257,449
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			2,828
Total loans			6,756,983	6,399,693
Commercial real estate — owner occupied
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	10,352	14,034
Charge offs	(1,042)	(344)
Recoveries	17	173
Net Charge offs	(1,025)	(171)
Provision for loan losses	2,520	(3,511)
Balance at end of period	11,847	10,352
Allowance for loan losses:
Individually evaluated			2,043	2,973
Collectively evaluated			9,804	7,379
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	10,352	14,034	11,847	10,352
Loans:
Individually evaluated			22,489	26,234
Collectively evaluated			876,631	775,975
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			1,793
Total loans			900,913	802,209
Commercial real estate — investor
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	41,059	45,285
Charge offs	0	(991)
Recoveries	8	242
Net Charge offs	8	(749)
Provision for loan losses	1,215	(3,477)
Balance at end of period	42,282	41,059
Allowance for loan losses:
Individually evaluated			2,721	1,597
Collectively evaluated			39,561	39,462
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	41,059	45,285	42,282	41,059
Loans:
Individually evaluated			20,387	19,118
Collectively evaluated			4,048,532	3,296,136
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			8,752
Total loans			4,077,671	3,315,254
Real estate construction
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	34,370	26,932
Charge offs	(47)	(604)
Recoveries	236	74
Net Charge offs	189	(530)
Provision for loan losses	(6,125)	7,968
Balance at end of period	28,434	34,370
Allowance for loan losses:
Individually evaluated			82	86
Collectively evaluated			28,352	34,284
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	34,370	26,932	28,434	34,370
Loans:
Individually evaluated			458	467
Collectively evaluated			1,579,065	1,451,217
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			255
Total loans			1,579,778	1,451,684
Residential mortgage
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	29,607	27,046
Charge offs	(493)	(2,611)
Recoveries	362	927
Net Charge offs	(131)	(1,684)
Provision for loan losses	536	4,245
Balance at end of period	30,012	29,607
Allowance for loan losses:
Individually evaluated			6,635	6,512
Collectively evaluated			23,377	23,095
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	29,607	27,046	30,012	29,607
Loans:
Individually evaluated			48,863	47,486
Collectively evaluated			8,147,224	7,499,048
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			1,136
Total loans			8,197,223	7,546,534
Home equity
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	22,126	20,364
Charge offs	(1,250)	(2,724)
Recoveries	573	3,194
Net Charge offs	(677)	470
Provision for loan losses	241	1,292
Balance at end of period	21,690	22,126
Allowance for loan losses:
Individually evaluated			3,719	3,718
Collectively evaluated			17,971	18,408
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	22,126	20,364	21,690	22,126
Loans:
Individually evaluated			10,974	10,891
Collectively evaluated			912,421	872,913
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			74
Total loans			923,470	883,804
Other consumer
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of period	5,298	4,548
Charge offs	(1,256)	(4,439)
Recoveries	168	716
Net Charge offs	(1,088)	(3,723)
Provision for loan losses	736	4,473
Balance at end of period	4,946	5,298
Allowance for loan losses:
Individually evaluated			116	122
Collectively evaluated			4,830	5,176
Allowance Attributable to Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total allowance for loan losses	$ 5,298	$ 4,548	4,946	5,298
Loans:
Individually evaluated			1,066	1,135
Collectively evaluated			373,388	384,678
Financing Receivable Acquired and Accounted under Modification of Impaired Loans			0
Total loans			$ 374,453	$ 385,813

Loans - Changes in the Allowanc

Loans - Changes in the Allowance for Loan Losses by Oil and Gas Segment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 265,880	$ 278,335
Charge offs	(12,155)	(56,246)
Recoveries	2,832	16,791
Net Charge offs	(9,323)	(39,455)
Provision for loan losses	500	27,000
Balance at end of period	257,058	265,880
Allowance for loan losses
Individually evaluated			$ 34,094	$ 25,846
Collectively evaluated			222,964	240,034
Total allowance for loan losses	265,880	278,335	257,058	265,880
Loans
Individually evaluated			233,078	247,575
Collectively evaluated			22,562,575	20,537,416
Total loans			22,810,491	20,784,991
Oil and Gas Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	27,000	38,000
Charge offs	(4,000)	(25,000)
Recoveries	0	0
Net Charge offs	(4,000)	(25,000)
Provision for loan losses	(4,000)	14,000
Balance at end of period	19,000	27,000
Allowance for loan losses
Individually evaluated			10,000	5,000
Collectively evaluated			9,000	22,000
Total allowance for loan losses	$ 27,000	$ 38,000	19,000	27,000
Loans
Individually evaluated			69,000	77,000
Collectively evaluated			588,000	523,000
Total loans			$ 657,000	$ 600,000

Loans, Changes in the Allowan63

Loans, Changes in the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Change in the allowance for unfunded commitments
Balance at beginning of period	$ 24,000
Balance at end of period	26,000	$ 24,000
Allowance for Unfunded Commitments:
Change in the allowance for unfunded commitments
Balance at beginning of period	24,400	25,400
Provision for unfunded commitments	(500)	(1,000)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Provision for Loan Losses	2,436	0
Balance at end of period	$ 26,336	$ 24,400

Loans - Changes to Accretable Y

Loans - Changes to Accretable Yield (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 0	$ 0
Purchases	4,244	0
Accretion	0	0
Other	0	0
Balance at end of period	$ 4,244	$ 0

Loans - Narrative (Details)

Loans - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 3,958	$ 54,911
Restructured Loans Subsequently Accruing	1,000
Ytd Restructured Loans Still On Nonaccrual	3,000
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	257,058		$ 265,880	$ 278,335
Oil and Gas Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	$ 19,000		$ 27,000	$ 38,000
Percent of loans	3.00%

Goodwill and Other Intangible66

Goodwill and Other Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 1,525	$ 513
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	58,100		$ 4,385
Accumulated amortization	(968)		(4,385)
Total Estimated Amortization Expense	57,132		0
Amortization of other intangible assets	968	112
Adjustments to Core Deposits [Member]
Summary of core deposit intangibles and other intangibles
Total Estimated Amortization Expense	58,100		0
Other Intangible Assets
Summary of core deposit intangibles and other intangibles
Gross carrying amount	42,131		34,572
Accumulated amortization	(19,549)		(18,992)
Total Estimated Amortization Expense	22,582		$ 15,580
Additions during the period	7,559	2,162
Amortization of other intangible assets	$ 557	$ 1,847

Goodwill and Other Intangible67

Goodwill and Other Intangible Assets, Mortgage Servicing Rights Roll-Forward (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Business Combination Servicing Asset [Line Items]
MSR Addition from Business Combination		$ 8,136	$ 0
Mortgage servicing rights:
Mortgage servicing rights at beginning of period		59,168	62,085
Additions		1,737	7,167
Amortization		(2,324)	(10,084)
Mortgage servicing rights at end of period		66,717	59,168
Valuation Allowance for Impairment of Recognized Servicing Assets [Roll Forward]
Valuation allowance at beginning of period		(784)	(609)
(Additions) recoveries, net		474	(175)
Valuation allowance at end of period		(310)	(784)
Mortgage servicing rights, net		66,407	58,384
Fair value of mortgage servicing rights		81,810	64,387
Portfolio of residential mortgage loans serviced for others (“servicing portfolio”)		$ 8,507,294	$ 7,646,846
Mortgage servicing rights, net to servicing portfolio		0.78%	0.76%
Mortgage servicing rights expense	[1]	$ 1,849	$ 10,259
[1]	(a) Includes the amortization of mortgage servicing rights and additions / recoveries to the valuation allowance of mortgage servicing rights, and is a component of mortgage banking, net in the consolidated statements of income.

Goodwill and Other Intangible68

Goodwill and Other Intangible Assets, Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other Intangible Assets
Estimated future amortization expense
Nine Months Ended December 31, 2018	$ 2,045
Year ending December 31, 2018	2,428
Year ending December 31, 2019	2,311
Year ending December 31, 2020	2,287
Year ending December 31, 2021	2,263
Year ending December 31, 2022	2,244
Beyond 2,022	9,004
Total Estimated Amortization Expense	22,582	$ 15,580
Mortgage Servicing Rights
Estimated future amortization expense
Nine Months Ended December 31, 2018	7,115
Year ending December 31, 2018	9,324
Year ending December 31, 2019	8,078
Year ending December 31, 2020	6,977
Year ending December 31, 2021	6,035
Year ending December 31, 2022	5,234
Beyond 2,022	23,954
Total Estimated Amortization Expense	66,717
Core Deposit Intangibles
Estimated future amortization expense
Nine Months Ended December 31, 2018	4,358
Year ending December 31, 2018	5,810
Year ending December 31, 2019	5,810
Year ending December 31, 2020	5,810
Year ending December 31, 2021	5,810
Year ending December 31, 2022	5,810
Beyond 2,022	23,724
Total Estimated Amortization Expense	$ 57,132	$ 0

Goodwill and Other Intangible69

Goodwill and Other Intangible Assets (Details Textuals) - USD ($)	Feb. 01, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 1,153,156,000		$ 976,239,000
Goodwill, Impairment Loss		0	$ 0
Bank Mutual
Business Acquisition [Line Items]
Goodwill acquired	$ 167,000,000
Additions to finite-lived intangible assets		58,000,000
Diversified Insurance Solutions
Business Acquisition [Line Items]
Goodwill acquired		10,000,000
Additions to finite-lived intangible assets		$ 8,000,000

Short and Long-Term Funding (Co

Short and Long-Term Funding (Components of Short-term and Long-term Funding) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Short-term Funding [Abstract]
Federal funds purchased	$ 69,085	$ 141,950
Securities sold under agreements to repurchase	214,869	182,865
Federal funds purchased and securities sold under agreements to repurchase	283,954	324,815
FHLB advances	1,780,000	284,000
Commercial paper	82,420	67,467
Other short-term funding	1,862,420	351,467
Total short-term funding	2,146,374	676,282
Long-term Funding
FHLB advances	2,735,887	2,900,168
Senior notes, at par	250,000	250,000
Subordinated notes, at par	250,000	250,000
Other long-term funding and capitalized costs	(2,549)	(2,718)
Total long-term funding	3,233,338	3,397,450
Total short and long-term funding	$ 5,379,712	$ 4,073,732

Short and Long-Term Funding (Re

Short and Long-Term Funding (Remaining Contractual Maturity of the Securities Sold Under Agreements to Repurchase) (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	$ 214,869,000	$ 182,865,000
Overnight and Continuous
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	214,869,000	182,865,000
Up to 30 days
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	0	0
30-90 days
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	0	0
Greater than 90 days
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	0	0
Agency mortgage-related securities
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	214,869,000	182,865,000
Agency mortgage-related securities | Overnight and Continuous
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	214,869,000	182,865,000
Agency mortgage-related securities | Up to 30 days
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	0	0
Agency mortgage-related securities | 30-90 days
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	0	0
Agency mortgage-related securities | Greater than 90 days
RemainingContractualMaturityoftheSecuritiesSoldUnderAgreementtoRepurchase [Line Items]
Repurchase agreements	$ 0	$ 0

Short and Long-Term Funding (Lo

Short and Long-Term Funding (Long-term Funding Narrative) (Details) - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2014	Mar. 31, 2018	Dec. 31, 2017
Subordinated Borrowing [Line Items]
Carrying Value of Securities Purchased under Agreements to Resell and Deposits Paid for Securities Borrowed		$ 288
Federal Home Loan Bank, Advances, Weighted Average Interest Rate		1.50%	1.26%
Two Thousand Fourteen Senior Notes
Subordinated Borrowing [Line Items]
New Senior Debt Issued	$ 250
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Two Thousand Fourteen Subordinated Notes
Subordinated Borrowing [Line Items]
Junior Subordinated Debentures Issued	$ 250
Debt Instrument, Term	10 years
Subordinated Borrowing, Interest Rate	4.25%

Derivative and Hedging Activi73

Derivative and Hedging Activities, Derivative Instruments Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Not Designated as Hedging Instrument | Trading assets | Interest rate-related instruments — customer and mirror
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	$ 2,626,982	$ 2,183,687
Derivative, Fair Value, Net	53,189	28,494
Not Designated as Hedging Instrument | Trading assets | Foreign currency exchange forwards
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	140,554	124,851
Derivative, Fair Value, Net	2,612	2,495
Not Designated as Hedging Instrument | Trading assets | Commodity contracts
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	467,979	457,868
Derivative, Fair Value, Net	47,089	38,686
Not Designated as Hedging Instrument | Trading liabilities | Interest rate-related instruments — customer and mirror
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	2,626,982	2,183,687
Derivative, Fair Value, Net	(52,238)	(28,035)
Not Designated as Hedging Instrument | Trading liabilities | Foreign currency exchange forwards
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	137,073	118,094
Derivative, Fair Value, Net	(2,484)	(2,339)
Not Designated as Hedging Instrument | Trading liabilities | Commodity contracts
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	467,957	457,108
Derivative, Fair Value, Net	(45,525)	(37,286)
Not Designated as Hedging Instrument | Other assets | Interest rate lock commitments (mortgage)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	312,567	222,736
Derivative, Fair Value, Net	3,032	1,538
Not Designated as Hedging Instrument | Other assets | Purchased options (time deposit)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	26,389	31,063
Derivative, Fair Value, Net	951	1,175
Not Designated as Hedging Instrument | Other liabilities | Forward commitments (mortgage)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	245,000	164,567
Derivative, Fair Value, Net	(303)	(313)
Not Designated as Hedging Instrument | Other liabilities | Written options (time deposit)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	26,389	31,063
Derivative, Fair Value, Net	(951)	(1,175)
Designated as Hedging Instrument | Other assets | interest rate product [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	250,000	0
Derivative, Fair Value, Net	$ 258	$ 0

Derivative and Hedging Activi74

Derivative and Hedging Activities - Cumulative Basis Adjustment for Fair Value Hedges (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Balance Sheet Recording of Fair Value Hedge [Line Items]
Carrying Amount of the Hedged Assets/(Liabilities)	$ 102,890	$ 69,675
Designated as Hedging Instrument
Balance Sheet Recording of Fair Value Hedge [Line Items]
Carrying Amount of the Hedged Assets/(Liabilities)	250,000
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities)	276
Amortized cost basis of hedged asset	523,000
adjustment [Member] | Designated as Hedging Instrument
Balance Sheet Recording of Fair Value Hedge [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities)	276
Carrying Value [Member] | Designated as Hedging Instrument
Balance Sheet Recording of Fair Value Hedge [Line Items]
Carrying Amount of the Hedged Assets/(Liabilities)	$ 249,724

Derivative and Hedging Activi75

Derivative and Hedging Activities Income impact of Fair Value and Cash Flow Hedge (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Interest Income [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	$ 18	$ 0
Other Operating Income (Expense) [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Income [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	276	0
Not Designated as Hedging Instrument, Economic Hedge [Member] | Other Operating Income (Expense) [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0
Designated as Hedging Instrument | Interest Income [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(258)	0
Designated as Hedging Instrument | Other Operating Income (Expense) [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	$ 0	$ 0

Derivative and Hedging Activi76

Derivative and Hedging Activities Derivative Impact on Perfomance (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Capital Market Fees [Member] | Interest Rate Related Instruments Customer and Mirror [Member]
Derivative Impact on Performance [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 492	$ 245
Capital Market Fees [Member] | Foreign Exchange Forward [Member]
Derivative Impact on Performance [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(28)	(21)
Capital Market Fees [Member] | Commodity Contract [Member]
Derivative Impact on Performance [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	164	226
Mortgage Banking [Member] | Interest Rate Lock Commitments [Member]
Derivative Impact on Performance [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1,494	1,597
Mortgage Banking [Member] | Forward Contracts [Member]
Derivative Impact on Performance [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 10	$ (3,281)

Derivative and Hedging Activi77

Derivative and Hedging Activities (Details Textuals) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Investment securities and cash equivalents pledged as collateral	$ 28	$ 24
Derivative collateral right to reclaim cash	$ 29	$ 22

Balance Sheet Offsetting (Detai

Balance Sheet Offsetting (Details) - Interest and commodity agreements - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	$ 47,528	$ 29,503
Gross amounts offset in the balance sheet	0	0
Net amounts presented in the balance sheet	47,528	29,503
Financial instruments	(43,105)	(29,503)
Collateral	(1,337)	0
Net amount	3,086	0
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	43,105	37,164
Gross amounts offset in the balance sheet	0	0
Net amounts presented in the balance sheet	43,105	37,164
Financial instruments	(43,105)	(29,503)
Collateral	0	(7,661)
Net amount	$ 0	$ 0

Commitments, Off-Balance Shee79

Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters, Summary of Lending Related and Other Commitments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of lending-related and other commitments [Line Items]
Lending related commitments, fair value	$ 0	$ 0
Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale
Summary of lending-related and other commitments
Lending related commitments	8,481,563	8,027,187
Commercial Letters Of Credit
Summary of lending-related and other commitments
Lending related commitments	12,456	11,886
Standby Letters of Credit
Summary of lending-related and other commitments
Lending related commitments	253,857	235,361
Standby letters of credit, fair value	$ 2,000	$ 2,000

Commitments, Off-Balance Shee80

Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters Residential Mortgage Repurchase Reserve (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Residential mortgage repurchase reserve
Balance at beginning of period	$ 24,000
Balance at end of period	26,000
Mortgage Repurchase Reserve
Residential mortgage repurchase reserve
Balance at beginning of period	987	$ 900
Repurchase provision expense	56	246
Charge offs, net	(48)	(159)
Valuation Allowances and Reserves, Reserves of Businesses Acquired	88	$ 0
Balance at end of period	$ 1,083

Commitments, Off-Balance Shee81

Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters (Details Textuals)	Jan. 11, 2016USD ($)complaint	May 22, 2015USD ($)branchloan_production_office	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 06, 2017complaint	Aug. 30, 2017complaint	Jul. 28, 2017complaint
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Valuation Allowances and Reserves, Balance			$ 26,000,000	$ 24,000,000
Number of complaints filed under legal proceedings | complaint	2
Conciliation Agreement, Commitment Term		3 years
Conciliation Agreement, Mortgage Loan Commitment		$ 196,000,000
Conciliation Agreement, Number of Branch Opening Commitments | branch		1
Conciliation Agreement, Number of Loan Production Offices, Commitment | loan_production_office		4
Loans Repurchased Under Make Whole Requests			0	1,000,000
Loans Sold To Outside Investors Original Amount			10,000,000,000
Loans Sold To Outside Investors Remaining Outstanding Amount			6,000,000,000
Residential Mortgage Loans Sold With Recourse Risk			36,000,000	44,000,000
Residential Mortgage Loans Sold With Credit Recourse Risk			69,000,000	73,000,000
The Official Committee of Unsecured Creditors of World Marketing Chicago LLC v Associated Bank [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Loss Contingency, Damages Sought, Value	$ 6,000,000
Loss Contingency, Damages Sought, Value, Cash	4,000,000
American Funds Service Company v Associated Bank [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Loss Contingency, Damages Sought, Value	600,000
Loss Contingency, Damages Sought, Value, Cash	$ 540,000
Schumel et al v. Bank Mutual Corporation et al, and Paquin et al v. Bank Mutual Corporation et al [Domain]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Number of complaints filed under legal proceedings | complaint							2
Wollenburg et al. v. Bank Mutual Corporation et al. [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Number of complaints filed under legal proceedings | complaint						1
Parshall et al. v. Bank Mutual Corporation et al. [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Number of complaints filed under legal proceedings | complaint					1
UnconsolidatedProjectsLowIncomeHousing [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Other Investments			142,000,000	147,000,000
Commitments Under Unconsolidated Projects			111,000,000	119,000,000
PrincipalInvestmentCommitment [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Other Investments			$ 24,000,000	$ 23,000,000

Fair Value Measurements, Assets

Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment securities available for sale:
Investment securities available for sale	$ 4,485,875	$ 4,043,446
Trading assets	102,890	69,675
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	100,247	67,660
Fair Value, Inputs, Level 1
Investment securities available for sale:
Investment securities available for sale	2,594	2,628
Fair Value, Inputs, Level 2
Investment securities available for sale:
Investment securities available for sale	4,483,281	4,040,818
Trading assets	104,099	70,850
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	101,198	68,835
Fair Value, Inputs, Level 3
Investment securities available for sale:
Trading assets	3,032	1,538
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	303	313
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | US Treasury Securities
Investment securities available for sale:
Investment securities available for sale	995	996
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Other Debt And Other Equity Securities
Investment securities available for sale:
Investment securities available for sale	1,599	1,632
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Total investment securities available for sale
Investment securities available for sale:
Investment securities available for sale	2,594	2,628
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | FNMA / FHLMC
Investment securities available for sale:
Investment securities available for sale	430,073	464,768
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | GNMA
Investment securities available for sale:
Investment securities available for sale	2,310,306	1,913,350
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Private Label
Investment securities available for sale:
Investment securities available for sale	1,044	1,059
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | GNMA Commercial Mortgage-Related Securities
Investment securities available for sale:
Investment securities available for sale	1,448,369	1,513,277
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Investment securities available for sale:
Investment securities available for sale	290,300	145,176
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Other Debt And Other Equity Securities
Investment securities available for sale:
Investment securities available for sale	3,188	3,188
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Total investment securities available for sale
Investment securities available for sale:
Investment securities available for sale	4,483,281	4,040,818
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Residential Loans Held For Sale Member
Investment securities available for sale:
Trading assets	103,953	85,544
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Interest rate-related instruments — customer and mirror
Investment securities available for sale:
Trading assets	53,189	28,494
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	52,238	28,035
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Foreign currency exchange forwards
Investment securities available for sale:
Trading assets	2,612	2,495
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	2,484	2,339
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Commodity contracts
Investment securities available for sale:
Trading assets	47,089	38,686
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	45,525	37,286
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Purchased options (time deposit)
Investment securities available for sale:
Trading assets	951	1,175
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	951	1,175
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Interest rate lock commitments (mortgage)
Investment securities available for sale:
Trading assets	3,032	1,538
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Forward commitments (mortgage)
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	303	313
Total commercial | Fair Value, Inputs, Level 2
Investment securities available for sale:
Loans Held-for-sale, Fair Value Disclosure	6,091	0
Designated as Hedging Instrument
Investment securities available for sale:
Trading assets	250,000
Designated as Hedging Instrument | Fair Value, Inputs, Level 2
Investment securities available for sale:
Interest Rate Fair Value Hedge Derivative at Fair Value, Net	$ 258	$ 0

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments Classified Within Level 3 (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Total investment securities available for sale
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Beginning Balance	$ 0	$ 200
Ending Balance	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Mortgage derivative loss	0	0
Total investment securities available for sale | Fair Value, Measurements, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfer of level 3 to level 2 based on new pricing information		200
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Transfer out of level 3 securities		(200)
Derivative Financial Instruments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning Balance	1,225	3,114
Mortgage derivative loss	1,501	(1,889)
Ending Balance	$ 2,726	1,225
Derivative Financial Instruments | Fair Value, Measurements, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfer of level 3 to level 2 based on new pricing information		0
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Transfer out of level 3 securities		$ 0
Investment security
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfer of level 3 to level 2 based on new pricing information			$ 200
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Transfer out of level 3 securities			$ (200)

Fair Value Measurements, Asse84

Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial Loans Held-for-sale, Fair Value Disclosure	$ 6,091		$ 0
Mortgage servicing rights	66,407		58,384
Mortgage Servicing Rights (MSR) Impairment (Recovery)	(474)	$ 217
Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial Loans Held-for-sale, Fair Value Disclosure	6,091		0
Residential Held-for-sale, Fair Value Disclosure	103,953		85,544
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial Loans Held-for-sale, Fair Value Disclosure	6,091
Provision for Credit Losses, Commercial Loans held-for-sale	0
Other Real Estate Owned Fair Value Disclosure	2,088		2,604
Foreclosure / OREO expense, net	(553)		(939)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	74,038		92,534
Provision for Credit Losses, Impaired Loans	14,518		32,159
Mortgage servicing rights	81,810		64,387
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ 474		$ (175)

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Unobservable Level 3 Measurements (Details) - Fair Value, Inputs, Level 3	3 Months Ended
	Mar. 31, 2018
Discounted Cash Flow | Servicing Contracts
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Discount Rate	11.00%
Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Prepayment Speed	9.00%
Appraisals/Discounted Cash Flow | Impaired Finance Receivable
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Discount Rate	28.00%

Fair Value Measurements, Fair V

Fair Value Measurements, Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financial assets
Cash and due from banks	$ 328,260	$ 483,666
Interest-bearing deposits in other financial institutions	94,918	199,702
Federal funds sold and securities purchased under agreements to resell	10,000	32,650
Investment securities held to maturity	2,443,203	2,282,853
Investment securities held to maturity, fair value	2,407,197	2,283,574
Investment securities available for sale	4,485,875	4,043,446
FHLB and Federal Reserve Bank stocks	233,216	165,331
Commercial Loans Held-for-sale, Fair Value Disclosure	6,091	0
Loans, net	22,553,433	20,519,111
Bank and Corporate Owned Life Insurance	657,841	591,057
Derivatives (trading and other assets)	102,890	69,675
Financial liabilities
Short-term funding	2,146,374	676,282
Long-term funding	3,233,338	3,397,450
Derivatives (trading and other liabilities)	100,247	67,660
Letters of Credit Outstanding, Amount	254,000	235,000
Fair Value, Inputs, Level 1
Financial assets
Cash and due from banks	328,260	483,666
Cash and due from banks, Fair Value	328,260	483,666
Interest-bearing deposits in other financial institutions	94,918	199,702
Interest-bearing deposits in other financial institutions, fair value	94,918	199,702
Federal funds sold and securities purchased under agreements to resell	10,000	32,650
Federal funds sold and securities purchased under agreements to resell, fair value	10,000	32,650
Investment securities available for sale	2,594	2,628
Investment securities available for sale, fair value	2,594	2,628
Fair Value, Inputs, Level 2
Financial assets
Investment securities held to maturity	2,443,203	2,282,853
Investment securities held to maturity, fair value	2,407,197	2,283,574
Investment securities available for sale	4,483,281	4,040,818
Investment securities available for sale, fair value	4,483,281	4,040,818
FHLB and Federal Reserve Bank stocks	233,216	165,331
FHLB and Federal Reserve Bank stocks, fair value	233,216	165,331
Commercial loans held for sale	6,091	0
Commercial Loans Held-for-sale, Fair Value Disclosure	6,091	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage	103,953	85,544
Residential Held-for-sale, Fair Value Disclosure	103,953	85,544
Bank and Corporate Owned Life Insurance	657,841	591,057
Bank owned life insurance, fair value	657,841	591,057
Derivatives (trading and other assets)	104,099	70,850
Derivatives (trading and other assets), fair value	104,099	70,850
Financial liabilities
Brokered CDs and other time deposits	2,677,372	2,349,069
Brokered CDs and other time deposits, fair value	2,677,372	2,349,069
Short-term funding	2,146,374	676,282
Short-term funding, fair value	2,146,374	676,282
Long-term funding	3,233,338	3,397,450
Long-term funding, fair value	3,242,517	3,411,368
Standby letters of credit	2,468	2,402
Standby letters of credit, fair value	2,468	2,402
Derivatives (trading and other liabilities)	101,198	68,835
Derivatives (trading and other liabilities), fair value	101,198	68,835
Fair Value, Inputs, Level 3
Financial assets
Loans, net	22,553,433	20,519,111
Loans, net, fair value	22,195,415	20,314,984
Derivatives (trading and other assets)	3,032	1,538
Derivatives (trading and other assets), fair value	3,032	1,538
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts	21,148,230	20,436,893
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits, fair value	21,148,230	20,436,893
Derivatives (trading and other liabilities)	303	313
Derivatives (trading and other liabilities), fair value	$ 303	$ 313

Fair Value Measurements (Detail

Fair Value Measurements (Details Textuals)	3 Months Ended
	Mar. 31, 2018
Fair Value of Assets and Liabilities [Line Items]
Closing ratio	85.00%

Retirement Plans, Components of

Retirement Plans, Components of Net Periodic Benefit Cost for the Pension and Postretirement Tables (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
RAP
Net period benefit cost for the pension and postretirement plans
Service cost	$ 1,893	$ 1,781
Interest cost	1,660	1,756
Expected return on plan assets	(4,755)	(4,881)
Amortization of prior service cost	(19)	(19)
Amortization of actuarial loss	463	488
Total net pension and periodic benefit cost	(759)	(875)
Other Pension Plan [Member]
Net period benefit cost for the pension and postretirement plans
Interest cost	433
Expected return on plan assets	(532)
Total net pension and periodic benefit cost	(99)
Postretirement Plan (b)
Net period benefit cost for the pension and postretirement plans
Interest cost	26	24
Amortization of prior service cost	(19)	(19)
Amortization of actuarial loss	2	0
Total net pension and periodic benefit cost	$ 9	$ 5

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Income Statement Data Abstract
Net interest income	$ 209,871	$ 180,274
Noninterest income	90,380	79,831
Total revenue	300,251	260,105
Credit provision	0	9,000
Noninterest expense	212,965	173,691
Income (loss) before income taxes	87,285	77,414
Income tax expense (benefit)	17,829	21,144
Net income	$ 69,456	$ 56,270
Return on average allocated capital (ROCET1)	11.40%	10.60%
Segment Balance Sheet Data
Average earning assets	$ 29,282,132	$ 26,339,314
Average loans	22,078,529	20,072,725
Average deposits	23,650,898	21,465,722
Average allocated capital (CET1)	2,389,933	2,061,749
Operating Segments | Corporate and Commercial Specialty
Segment Income Statement Data Abstract
Net interest income	95,958	89,388
Noninterest income	12,683	11,993
Total revenue	108,641	101,381
Credit provision	10,598	11,580
Noninterest expense	39,250	37,479
Income (loss) before income taxes	58,793	52,322
Income tax expense (benefit)	11,426	17,649
Net income	$ 47,367	$ 34,673
Return on average allocated capital (ROCET1)	16.40%	12.60%
Segment Balance Sheet Data
Average earning assets	$ 11,389,211	$ 10,759,811
Average loans	11,378,390	10,753,314
Average deposits	8,057,246	6,420,401
Average allocated capital (CET1)	1,171,038	1,114,610
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income	103,543	88,928
Noninterest income	74,036	64,870
Total revenue	177,579	153,798
Credit provision	4,966	4,507
Noninterest expense	127,144	116,097
Income (loss) before income taxes	45,469	33,194
Income tax expense (benefit)	9,549	11,618
Net income	$ 35,920	$ 21,576
Return on average allocated capital (ROCET1)	23.00%	15.20%
Segment Balance Sheet Data
Average earning assets	$ 10,137,899	$ 9,130,457
Average loans	10,133,202	9,128,656
Average deposits	13,096,782	11,337,064
Average allocated capital (CET1)	632,723	576,464
Operating Segments | Risk Management and Shared Services
Segment Income Statement Data Abstract
Net interest income	10,370	1,958
Noninterest income	3,661	2,968
Total revenue	14,031	4,926
Credit provision	(15,563)	(7,087)
Noninterest expense	46,571	20,115
Income (loss) before income taxes	(16,977)	(8,102)
Income tax expense (benefit)	(3,146)	(8,123)
Net income	$ (13,831)	$ 21
Return on average allocated capital (ROCET1)	(11.20%)	(2.50%)
Segment Balance Sheet Data
Average earning assets	$ 7,755,022	$ 6,449,046
Average loans	566,936	190,755
Average deposits	2,496,870	3,708,257
Average allocated capital (CET1)	$ 586,172	$ 370,675

Accumulated Other Comprehensi90

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (62,758)
Personnel expense	117,685	$ 106,782
Change in Equity Securities(2016-01)	84
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(297)	(1,027)
Total other comprehensive income (loss)	44,915	1,665
Ending Balance	(107,673)
Investment Securities Available For Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(38,453)	(20,079)
Other comprehensive income (loss) before reclassifications	41,834	(2,112)
Investment securities gain, net		0
Personnel expense	0	0
Other Expenses	0	0
Change in Equity Securities(2016-01)	(84)
Reporting Comprehensive Income(2018-02)	(8,419)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(297)	1,027
Income tax (expense) benefit	10,635	(1,195)
Total other comprehensive income (loss)	(40,000)	1,944
Ending Balance	(78,453)	(22,023)
Defined Benefit Pension and Post Retirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(24,305)	(34,600)
Other comprehensive income (loss) before reclassifications	0	0
Investment securities gain, net		0
Personnel expense	(38)	38
Other Expenses	465	(488)
Change in Equity Securities(2016-01)	0
Reporting Comprehensive Income(2018-02)	(5,235)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	0	0
Income tax (expense) benefit	(107)	171
Total other comprehensive income (loss)	(4,915)	(279)
Ending Balance	(29,220)	(34,321)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(62,758)	(54,679)
Other comprehensive income (loss) before reclassifications	41,834	(2,112)
Investment securities gain, net		0
Personnel expense	(38)	38
Other Expenses	465	(488)
Change in Equity Securities(2016-01)	(84)
Reporting Comprehensive Income(2018-02)	(13,654)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(297)	1,027
Income tax (expense) benefit	10,528	(1,024)
Total other comprehensive income (loss)	(44,915)	(1,665)
Ending Balance	$ (107,673)	$ (56,344)

Revenues (Details)

Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	$ 72,725	$ 64,881
Noninterest Income (out-of-scope of Topic 606)	17,655	14,950
Total noninterest income	90,380	79,831
Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	22,648	21,620
Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	16,420	16,356
Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	9,869	8,421
Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	13,369	11,935
Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	7,273	4,333
Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	3,146	2,216
Corporate and Commercial Specialty
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	5,195	4,757
Noninterest Income (out-of-scope of Topic 606)	7,488	7,236
Total noninterest income	12,683	11,993
Corporate and Commercial Specialty | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0
Corporate and Commercial Specialty | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	4,225	4,441
Corporate and Commercial Specialty | Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	315	272
Corporate and Commercial Specialty | Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0
Corporate and Commercial Specialty | Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0
Corporate and Commercial Specialty | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	655	44
Community, Consumer, and Business
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	67,198	60,040
Noninterest Income (out-of-scope of Topic 606)	6,838	4,830
Total noninterest income	74,036	64,870
Community, Consumer, and Business | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	22,624	21,620
Community, Consumer, and Business | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	12,183	11,889
Community, Consumer, and Business | Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	9,529	8,144
Community, Consumer, and Business | Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	13,369	11,935
Community, Consumer, and Business | Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	7,032	4,333
Community, Consumer, and Business | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	2,461	2,119
Risk Management and Shared Services
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	332	84
Noninterest Income (out-of-scope of Topic 606)	3,329	2,884
Total noninterest income	3,661	2,968
Risk Management and Shared Services | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	24	0
Risk Management and Shared Services | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	12	26
Risk Management and Shared Services | Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	25	5
Risk Management and Shared Services | Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0
Risk Management and Shared Services | Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	241	0
Risk Management and Shared Services | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	$ 30	$ 53