Associated Banc-Corp (ASB) 10-K 19 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Trading Symbol	ASB
Entity Registrant Name	ASSOCIATED BANC-CORP
Entity Central Index Key	7,789
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
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 Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Public Float			$ 4,630,394,000
Entity Common Stock, Shares Outstanding		164,338,835

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and due from banks		$ 507,187	$ 483,666
Interest-bearing deposits in other financial institutions		221,226	199,702
Federal funds sold and securities purchased under agreements to resell		148,285	32,650
Investment securities held to maturity, at amortized cost		2,740,511	2,282,853
Investment securities available for sale, at fair value		3,948,510	4,043,446
Federal Home Loan Bank and Federal Reserve Bank stocks, at cost		250,534	165,331
Residential loans held for sale		64,321	85,544
Commercial loans held for sale		14,943	0
Loans		22,940,429	20,784,991
Allowance for loan losses		(238,023)	(265,880)
Loans, net		22,702,406	20,519,111
Bank and corporate owned life insurance		663,203	591,057
Investment in unconsolidated subsidiaries		161,181	170,473
Trading assets		88,943	69,675
Premises and equipment, net		363,225	330,963
Goodwill		1,169,023	976,239
Mortgage servicing rights, net		68,193	58,384
Other intangible assets, net		75,836	15,580
Other assets		460,331	458,920
Total assets		33,647,859	30,483,594
Liabilities and stockholders' equity
Noninterest-bearing demand deposits		5,698,530	5,478,416
Interest-bearing deposits		19,198,863	17,307,546
Total deposits		24,897,393	22,785,962
Federal funds purchased and securities sold under agreements to repurchase		111,651	324,815
Commercial Paper		45,423	67,467
FHLB Advances		3,574,371	3,184,168
Other long-term funding		795,611	497,282
Trading liabilities		87,668	67,660
Accrued expenses and other liabilities		354,855	318,797
Total liabilities		29,866,971	27,246,151
Stockholders’ equity (1)
Preferred equity		256,716	159,929
Common stock		1,752	1,618
Surplus		1,712,615	1,338,722
Retained earnings		2,181,414	1,934,696
Accumulated other comprehensive income (loss)		(124,972)	(62,758)
Treasury stock, at cost		(246,638)	(134,764)
Total common equity		3,524,171	3,077,514
Total stockholders’ equity		3,780,888	3,237,443
Total liabilities and stockholders’ equity		$ 33,647,859	$ 30,483,594
Preferred shares issued		264,458,000	165,000,000
Preferred shares authorized (par value $1.00 per share)		750,000,000	750,000,000
Common shares issued		175,216,409,000	161,751,975,000
Common shares authorized (par value $0.01 per share)		250,000,000,000	250,000,000,000
Treasury shares of common stock		10,775,938,000	8,908,448,000
Net Adjustment, Stock-based Compensation Plans, warrants, options, RSU/A (1)	[1]		$ 115,000
[1]	An adjustment of $115 million

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Stockholders’ equity (1)
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		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest income
Interest and fees on loans		$ 976,990	$ 749,000	$ 659,538
Interest and dividends on investment securities
Taxable		119,741	96,909	95,152
Tax-exempt		44,782	32,977	32,049
Other interest		12,623	7,719	4,829
Total interest income		1,154,137	886,605	791,568
Interest expense
Interest on deposits		176,118	94,025	50,335
Interest on Federal funds purchased and securities sold under agreements to repurchase		2,006	2,527	1,314
Interest on other short-term funding		186	293	248
Interest on FHLB advances		73,668	30,364	10,741
Interest on long-term funding		22,579	18,176	21,657
Total interest expense		274,557	145,385	84,295
Net interest income		879,580	741,220	707,273
Provision for credit losses		0	26,000	70,000
Net interest income after provision for credit losses		879,580	715,220	637,273
Noninterest income
Noninterest Income In Scope of Topic 606		290,084	262,175	252,651
Capital markets, net		20,120	19,642	22,059
Mortgage banking, net		19,911	19,360	38,121
Bank and corporate owned life insurance		13,951	16,250	14,371
Asset gains (losses), net (a)		(1,103)	(1,244)	(86)
Investment securities gains (losses), net		(1,985)	434	9,316
Other		9,051	9,523	8,519
Total noninterest income		355,568	332,680	352,883
Noninterest expense
Personnel		482,676	428,976	424,676
Technology		72,674	63,004	57,300
Occupancy		59,121	53,842	56,069
Business development and advertising		30,923	28,946	26,351
Equipment		23,243	21,201	21,489
Legal and professional		23,061	22,509	19,869
Card issuance and loan costs		12,386	11,760	13,641
Foreclosure / OREO expense, net		3,603	4,878	4,844
FDIC assessment		30,000	31,300	34,750
Other intangible amortization		8,159	1,959	2,093
Other		46,951	40,758	41,478
Total noninterest expense		821,799	709,133	702,560
Income before income taxes		413,349	338,767	287,596
Income tax expense		79,786	109,503	87,322
Net income		333,562	229,264	200,274
Preferred stock dividends		10,784	9,347	8,903
Net income available to common equity		$ 322,779	$ 219,917	$ 191,371
Earnings per common share
Basic		$ 1.92	$ 1.45	$ 1.27
Diluted		$ 1.89	$ 1.42	$ 1.26
Average common shares outstanding
Basic		167,345	150,877	148,769
Diluted		169,732	153,647	149,961
Tax planning in response to TCJA		(3.60%)	0.00%	0.00%
Insurance Commissions and Fees [Member]
Noninterest income
Noninterest Income In Scope of Topic 606		$ 89,511	$ 81,474	$ 80,795
Service charges and deposit account fees
Noninterest income
Noninterest Income In Scope of Topic 606		66,075	64,427	66,609
Card-Based and Loan Fees [Member]
Noninterest income
Service charges on deposit account fees		57,474	52,688	50,077
Trust and asset management fees
Noninterest income
Noninterest Income In Scope of Topic 606		54,316	50,191	46,867
Brokerage and advisory fees
Noninterest income
Noninterest Income In Scope of Topic 606		28,246	19,935	16,235
Operating Segments [Member] | Risk Management and Shared Serivies [Member]
Noninterest income
Asset gains (losses), net (a)	[1]	2,000
Noninterest expense
Acquisition related costs (b)		$ 29,002	$ 0	$ 0
[1]	The year ended December 31, 2018 includes approximately $2 million

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 333,562	$ 229,264	$ 200,274
Investment securities available for sale
Net unrealized gains (losses)	(39,891)	(12,302)	(17,900)
Net unrealized gain (loss) on available for sale securities transferred to held to maturity securities	0	(14,738)	0
Amortization of net unrealized gain (loss) on available for sale securities transferred to held to maturity securities	(572)	(2,665)	(5,887)
Reclassification adjustment for net losses (gains) realized in net income (a)	1,985	0	(9,316)
Reclassification from OCI due to change in accounting principle	(84)	0	0
Reclassification of certain tax effects from OCI	(8,419)	0	0
Income tax (expense) benefit	9,791	11,331	12,565
Other comprehensive income (loss) on investment securities available for sale	(37,189)	(18,374)	(20,538)
Defined benefit pension and postretirement obligations
Amortization of prior service cost	(148)	(148)	(73)
Plan amendments	0	0	1,759
Net actuarial (loss) gain	(28,612)	14,273	(6,141)
Amortization of actuarial loss (gain)	2,203	2,282	2,115
Reclassification of certain tax effects from OCI	(5,235)	0	0
Income tax (expense) benefit	6,767	(6,112)	815
Other comprehensive income (loss) on pension and postretirement obligations	(25,025)	10,295	(1,525)
Total other comprehensive income (loss)	(62,214)	(8,079)	(22,063)
Comprehensive income	$ 271,348	$ 221,185	$ 178,211

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total	Preferred Equity	Common Stock	Surplus	Retained Earnings	AOCI Allocated to Parent [Member]	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2015		$ 2,937,246	$ 121,379	$ 1,642	$ 1,382,446	$ 1,669,315		$ (32,616)	$ (204,920)
Preferred stock shares outstanding, beginning balance (in shares) at Dec. 31, 2015			125
Common stock shares outstanding, beginning balance (in shares) at Dec. 31, 2015				164,200
Comprehensive income:
Net income		200,274	$ 0	$ 0	0	200,274		0	0
Other comprehensive loss		(22,063)	0	0	0	0		(22,063)	0
Comprehensive income		178,211
Common stock issued:
Stock-based compensation plans, net	[1]	21,748	$ 0	$ 0	(17,416)	0		0	39,164
Purchase of common stock returned to authorized but unissued			0	(1,170)
Purchase of common stock returned to authorized but unissued		(20,007)	$ 0	$ (12)	(19,995)	0		0	0
Purchase of treasury stock		(5,074)	0	0	0	0		0	(5,074)
Cash dividends
Common stock dividends		(67,855)	0	0	0	(67,855)		0	0
Preferred stock dividends		(8,903)	$ 0	$ 0	0	(8,903)		0	0
Issuance of preferred stock			100	0
Issuance of preferred stock		97,066	$ 97,066	$ 0	0	0		0	0
Redemption of preferred stock			(60)	0
Redemption of preferred stock		(58,903)	$ (57,338)	$ 0	0	(1,565)		0	0
Purchase of preferred stock			0	0
Purchase of preferred stock		(1,248)	$ (1,178)	$ 0	0	(70)		0	0
Stock-based compensation expense, net		21,971	0	0	21,971	0		0	0
Tax impact of stock-based compensation		(2,940)	0	0	(2,940)	0		0	0
Ending balance at Dec. 31, 2016		3,091,312	$ 159,929	$ 1,630	1,364,066	1,791,196		(54,679)	(170,830)
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2016			165
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2016				163,030
Net Adjustment, Stock-based Compensation Plans, warrants, options, RSU/A						76,000
Comprehensive income:
Net income		229,264	$ 0	$ 0	0	229,264		0	0
Other comprehensive loss		(8,079)	0	0	0	0		(8,079)	0
Comprehensive income		221,185
Common stock issued:
Stock-based compensation plans, net	[1]	27,619	$ 0	$ 0	(17,737)	0		0	45,356
Stock Issued During Period, Shares, Acquisitions			0	291
Stock Issued During Period, Value, Acquisitions		7,151	$ 0	$ 3	7,148	0		0	0
Purchase of common stock returned to authorized but unissued			0	(1,569)
Purchase of common stock returned to authorized but unissued		(37,031)	$ 0	$ (15)	(37,016)	0		0	0
Purchase of treasury stock		(9,290)	0	0	0	0		0	(9,290)
Cash dividends
Common stock dividends		(76,417)	0	0	0	(76,417)		0	0
Preferred stock dividends		(9,347)	0	0	0	(9,347)		0	0
Stock-based compensation expense, net		21,227	0	0	21,227	0		0	0
Tax impact of stock-based compensation		1,034	0	0	1,034	0		0	0
Ending balance at Dec. 31, 2017		3,237,443	$ 159,929	$ 1,618	1,338,722	1,934,696		(62,758)	(134,764)
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2017			165
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2017				161,752
Net Adjustment, Stock-based Compensation Plans, warrants, options, RSU/A	[2]	115,000
Comprehensive income:
Net income		333,562	$ 0	$ 0	0	333,562		0	0
Other comprehensive loss		(62,214)						(62,214)
Other Comprehensive Income, Other, Net of Tax		(48,476)	0	0	0	0		(48,476)	0
Adoption of new accounting standards		(13,738)	0	0	0	0		(13,738)	0
Comprehensive income		271,348
Common stock issued:
Stock-based compensation plans, net	[1]	18,408	$ 0	$ 0	(7,116)	15,096		0	10,428
Stock Issued During Period, Shares, Acquisitions			0	13,705
Stock Issued During Period, Value, Acquisitions		488,408	$ 0	$ 137	396,975	0		0	91,296
Purchase of common stock returned to authorized but unissued			0	(1,357)
Purchase of common stock returned to authorized but unissued		(33,075)	$ 0	$ (14)	(33,061)	0		0	0
Purchase of treasury stock		(213,598)	0	0	0	0		0	(213,598)
Cash dividends
Common stock dividends		(105,519)	0	0	0	(105,519)		0	0
Preferred stock dividends		(10,784)	$ 0	$ 0	0	(10,784)		0	0
Issuance of preferred stock			100	0
Issuance of preferred stock		97,315	$ 97,315	$ 0	0	0		0	0
Purchase of preferred stock			(1)	0
Purchase of preferred stock		(537)	$ (528)	$ 0	0	(8)		0	0
Shares from Warrant Exercises			0	1,116
Proceeds from Warrant Exercises		(1)	$ 0	$ 11	(12)	0		0	0
Stock-based compensation expense, net		17,107	0	0	17,107	0		0	0
Tax Act Reclassification		13,654	0	0	0	13,654		0	0
Change in Equity Securities(2016-01)		84	$ 0	$ 0	0	84	$ 0	(84)	0
Other			0	0
Other		632	$ 0	$ 0	0	632		0	0
Ending balance at Dec. 31, 2018		$ 3,780,888	$ 256,716	$ 1,752	$ 1,712,615	$ 2,181,414		$ (124,972)	$ (246,638)
Preferred stock shares outstanding, ending balance (in shares) at Dec. 31, 2018			264
Common stock shares outstanding, ending balance (in shares) at Dec. 31, 2018				175,216
[1]	bers may not sum due to rounding. (a) An adjustment of $76 million
[2]	An adjustment of $115 million

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock
Cash dividends
Common Stock, per share	$ 0.62	$ 0.50	$ 0.45

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities
Net income	$ 333,562	$ 229,264	$ 200,274
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	0	26,000	70,000
Depreciation and amortization	48,253	46,967	45,434
Addition to (recovery of) valuation allowance on mortgage servicing rights, net	(545)	175	(200)
Amortization of mortgage servicing rights	9,594	10,084	12,327
Amortization of other intangible assets	8,159	1,959	2,093
Amortization and accretion on earning assets, funding, and other, net	11,624	37,476	46,615
Net amortization of tax credit investments	19,425	19,834	5,272
Deferred income taxes	46,947	21,402	10,656
Losses (gains) on sales of investment securities, net	1,985	(434)	(9,316)
Asset (gains) losses, net	1,103	1,244	86
(Gain) loss on mortgage banking activities, net	(22,497)	(3,516)	(27,060)
Mortgage loans originated and acquired for sale	(1,092,318)	(715,357)	(1,271,124)
Proceeds from sales of mortgage loans held for sale	1,131,652	819,950	1,542,660
Pension contributions	(41,877)	(6,242)	0
(Increase) decrease in interest receivable	(7,417)	(9,476)	(7,836)
Increase (decrease) in interest payable	10,407	6,535	(4,642)
Increase (Decrease) Cash Collateral from Counterparties	41,274	(5,578)	0
Net change in other assets and other liabilities	(2,763)	(21,919)	26,144
Net cash provided by operating activities	496,567	458,368	641,383
Cash Flows from Investing Activities
Net increase in loans	(326,464)	(861,934)	(1,682,579)
Purchases of
Available for sale securities	(737,580)	(1,137,191)	(1,304,921)
Held to maturity securities	(682,622)	(234,379)	(195,442)
Federal Home Loan Bank and Federal Reserve Bank stocks	(347,323)	(262,986)	(92,761)
Premises, equipment, and software, net of disposals	(65,854)	(47,369)	(103,881)
Proceeds from
Sales of available for sale securities	601,130	18,467	549,555
Sale of Federal Home Loan Bank and Federal Reserve Bank stocks	282,145	237,656	100,000
Prepayments, calls, and maturities of available for sale investment securities	633,859	713,486	997,701
Prepayments, calls, and maturities of held to maturity investment securities	217,836	210,753	75,796
Sales, prepayments, calls and maturities of other assets	41,856	20,070	27,692
Net change in tax credit and alternative investments	(57,327)	(53,770)	(23,498)
Net cash (paid) received in acquisition	59,472	339	(685)
Net cash used in investing activities	(380,872)	(1,396,858)	(1,653,023)
Cash Flows from Financing Activities
Net increase (decrease) in deposits	270,481	897,514	880,783
Net increase (decrease) in short-term funding	(581,371)	(217,753)	110,619
Net increase (decrease) in short-term FHLB advances	616,000	(198,000)	147,000
Repayment of long-term FHLB advances	(2,150,016)	(115,020)	(38)
Proceeds from long-term FHLB advances	1,837,680	750,000	515,000
Repayment of long-term funding	0	0	(430,000)
Proceeds from issuance of long-term funding	300,000	0	0
Proceeds from issuance of preferred shares	97,315	0	97,066
Proceeds from issuance of common stock for stock-based compensation plans	18,408	27,619	21,748
Redemption of preferred shares	0	0	(58,903)
Redemption of warrants	(1)	0	0
Purchase of preferred shares	(537)	0	(1,248)
Purchase of common stock returned to authorized but unissued	(33,075)	(37,031)	(20,007)
Purchase of treasury stock	(213,598)	(9,290)	(5,074)
Cash dividends on common stock	(105,519)	(76,417)	(67,855)
Cash dividends on preferred stock	(10,784)	(9,347)	(8,903)
Net cash provided by (used in) financing activities	44,983	1,012,275	1,180,188
Net increase (decrease) in cash, cash equivalents, and restricted cash	160,678	73,785	168,548
Cash, cash equivalents, and restricted cash at beginning of period	716,018	642,233	473,685
Cash, cash equivalents, and restricted cash at end of period	876,698	716,018	642,233
Supplemental disclosures of cash flow information
Cash paid for interest	261,724	138,174	88,269
Cash paid for income and franchise taxes	18,335	81,450	75,558
Loans and bank premises transferred to other real estate owned	26,517	11,505	9,752
Capitalized mortgage servicing rights	10,722	7,167	12,262
Loans transferred into held for sale from portfolio, net	33,010	71,954	256,194
Acquisition
Fair value of assets acquired, including cash and cash equivalents	2,567,488	647	522
Fair value ascribed to goodwill and intangible assets	261,243	6,450	4,119
Fair value of liabilities assumed	2,340,323	54	1,423
Common stock issued in acquisition	488,408	7,151	0
Cash and cash equivalents	782,784	643,042	527,135
Restricted Cash	$ 93,914	$ 72,976	$ 115,098

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [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. The following is a description of the more significant of those policies. Business Associated Banc-Corp (individually referred to herein as the "Parent" and together with all of its subsidiaries and affiliates, collectively referred to herein as the "Corporation") is a bank holding company headquartered in Wisconsin. The Corporation provides a full range of banking and related financial services to consumer and commercial customers through its network of bank and nonbank subsidiaries. The Corporation is subject to competition from other financial and non-financial institutions that offer similar or competing products and services. The Corporation is regulated by federal and state agencies and is subject to periodic examinations by those agencies. Basis of Financial Statement Presentation The consolidated financial statements include the accounts of the Parent Company and its wholly-owned subsidiaries. Investments in unconsolidated entities (none of which are considered to be variable interest entities in which the Corporation is the primary beneficiary) are accounted for using the cost method of accounting when the Corporation has determined that the cost method is appropriate. Investments not meeting the criteria for cost method accounting are accounted for using the equity method of accounting. Investments in unconsolidated entities are included in investment in unconsolidated subsidiaries on the consolidated balance sheets, and the Corporation’s share of income or loss is recorded in other noninterest income, while distributions in excess of the investment are asset gains (losses), net. All significant intercompany balances and transactions have been eliminated in consolidation. 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. 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 when there is a reasonable expectation about the amount and timing of such cash flows. If a reasonable expectation on the amount or timing of such cash flows can't be determined, accretion of the fair value discount for nonperforming loans will be recognized using the cost recovery method of accounting. For PCI loans, 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. See Note 2 for additional information on the Corporation's acquisitions. 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. See Note 22 for additional information on revenue recognition. Investment Securities Securities are classified as held to maturity or available for sale at the time of purchase. Investment securities classified as held to maturity, which management has the positive intent and ability to hold to maturity, are reported at amortized cost. Investment securities classified as available for sale, which management has the intent and ability to hold for an indefinite period of time, but not necessarily to maturity, are carried at fair value, with unrealized gains and losses, net of related deferred income taxes, included in stockholders’ equity as a separate component of other comprehensive income. Any decision to sell investment securities available for sale would be based on various factors, including, but not limited to, asset / liability management strategies, changes in interest rates or prepayment risks, liquidity needs, or regulatory capital considerations. Realized gains or losses on investment security sales (using specific identification method) are included in investment securities gains (losses), net, in the consolidated statements of income. Premiums and discounts are amortized or accreted into interest income over the estimated life (earlier of call date, maturity, or estimated life) of the related security, using a prospective method that approximates level yield. In certain situations, management may elect to transfer certain investment securities from the available for sale classification to the held to maturity classification. In such cases, the investment securities are reclassified at fair value at the time of transfer. Any unrealized gain or loss included in accumulated other comprehensive income (loss) at the time of transfer is retained therein and amortized over the remaining life of the investment security as an adjustment to yield. Declines in the fair value of investment securities (with certain exceptions for debt securities noted below) that are deemed to be other-than-temporary are charged to earnings as a realized loss, and a new cost basis for the investment security is established. In evaluating other-than-temporary impairment, management considers the length of time and extent to which the security has been in an unrealized loss position, changes in security ratings, the financial condition and near-term prospects of the issuer, as well as security and industry specific economic conditions. In addition, the Corporation considers the intent and ability to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in fair value in the near term. Declines in the fair value of debt securities below amortized cost are deemed to be other-than-temporary in circumstances where: (1) the Corporation has the intent to sell a security; (2) it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis; or (3) the Corporation does not expect to recover the entire amortized cost basis of the security. If the Corporation intends to sell a security or if it is more likely than not that the Corporation will be required to sell the security before recovery, an other-than-temporary impairment write-down is recognized in earnings equal to the difference between the security’s amortized cost basis and its fair value. If an entity does not intend to sell the security or it is more likely than not that it will not be required to sell the security before recovery, the other-than-temporary impairment write-down is separated into an amount representing credit loss, which is recognized in earnings, and an amount related to all other factors, which is recognized in other comprehensive income. Declines in value determined to be other-than-temporary are included in investment securities gains (losses), net, in the consolidated statements of income. See Note 3 for additional information on investment securities. 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. See Note 3 for additional information on the FHLB and Federal Reserve Bank Stocks. Loans Held for Sale 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. Effective January 1, 2017, management 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. The estimated fair value is based on what secondary markets are currently offering for portfolios with similar characteristics, which the Corporation classifies as a Level 2 fair value measurement. 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. Loans Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off are reported at their outstanding principal balances, net of any deferred fees and costs on originated loans. Origination fee income received on loans and amounts representing the estimated direct costs of origination are deferred and amortized to interest income over the life of the loan using the effective interest method. An allowance for loan losses is established for estimated credit losses in the loan portfolio. See Allowance for Loan Losses below for further policy discussion. See also Note 4 for additional information on loans. Nonaccrual Loans: 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. This determination is based on management's review of current information and other events regarding the borrowers’ ability to repay their obligations. 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. Interest income on loans is based on the principal balance outstanding computed using the effective interest method. The accrual of interest income for commercial loans is discontinued when there is a clear indication that the borrower’s cash flow may not be sufficient to meet payments as they become due, while the accrual of interest income for consumer loans is discontinued when loans reach specific delinquency levels. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. Loans are generally placed on nonaccrual status when contractually past due 90 days or more as to interest or principal payments, unless the loan is well secured and in the process of collection. Additionally, whenever management becomes aware of facts or circumstances that may adversely impact the collectability of principal or interest on loans, it is management’s practice to place such loans on a nonaccrual status immediately, rather than delaying such action until the loans become 90 days past due. When a loan is placed on nonaccrual status, previously accrued and uncollected interest is reversed, amortization of related deferred loan fees or costs is suspended, and income is recorded only to the extent that interest payments are subsequently received in cash and a determination has been made that the principal and interest of the loan is collectible. If collectability of the principal and interest is in doubt, payments received are applied to loan principal. While a loan is in nonaccrual status, some or all of the cash interest payments received may be treated as interest income on a cash basis as long as the remaining recorded investment in the loan (i.e., after charge off of identified losses, if any) is deemed to be fully collectible. The determination as to the ultimate collectability of the loan's remaining recorded investment must be supported by a current, well documented credit evaluation of the borrower’s financial condition and prospects for repayment, including consideration of the borrower’s sustained historical repayment performance and other relevant factors. A nonaccrual loan is returned to accrual status when all delinquent principal and interest payments become current in accordance with the terms of the loan agreement, the borrower has demonstrated a period of sustained repayment performance, and the ultimate collectability of the total contractual principal and interest is no longer in doubt. A sustained period of repayment performance generally would be a minimum of six months. See Note 4 for additional information on loans. Troubled Debt Restructurings (“Restructured Loans”): Loans are considered restructured loans if concessions have been granted to borrowers that are experiencing financial difficulty. The concessions granted generally involve the modification of terms of the loan, such as changes in payment schedule or interest rate, which generally would not otherwise be considered. Restructured loans can involve loans remaining on nonaccrual, moving to nonaccrual, or continuing on accrual status, depending on the individual facts and circumstances of the borrower. Nonaccrual restructured loans are included and treated with all other nonaccrual loans. In addition, all accruing restructured loans are reported as troubled debt restructurings, which are considered and accounted for as impaired loans. Generally, restructured loans remain on nonaccrual until the customer has attained a sustained period of repayment performance under the modified loan terms (generally a minimum of six months). However, performance prior to the restructuring, or significant events that coincide with the restructuring, are considered in assessing whether the borrower can meet the new terms and whether the loan should be returned to or maintained on accrual status. If the borrower’s ability to meet the revised payment schedule is not reasonably assured, the loan remains on nonaccrual status. See Note 4 for additional information on restructured loans. Allowance for Loan Losses: The allowance for loan losses is a reserve for estimated credit losses on individually evaluated loans determined to be impaired as well as estimated credit losses inherent in the loan portfolio, and is based on quarterly evaluations of the collectability and historical loss experience of loans. Actual credit losses, net of recoveries, are deducted from the allowance for loan losses. A provision for loan losses, which is a charge against earnings, is recorded to bring the allowance for loan losses to a level that, in management’s judgment, is appropriate to absorb probable losses in the loan portfolio. The methodology applied by the Corporation, designed to assess the appropriateness of the allowance for loan losses, is based upon management’s ongoing review and grading of the loan portfolio into criticized loan categories (defined as specific loans warranting either specific allocation, or a criticized status of special mention, substandard, doubtful, or loss). The methodology also focuses on evaluation of several factors, including but not limited to: evaluation of facts and issues related to specific loans, management’s ongoing review and grading of the loan portfolio, consideration of historical loan loss and delinquency experience on each portfolio category, trends in past due and nonaccrual loans, the level of potential problem loans, the risk characteristics of the various classifications of loans, changes in the size and character of the loan portfolio, concentrations of loans to specific borrowers or industries, existing economic conditions, the fair value of underlying collateral, and other qualitative and quantitative factors which could affect potential credit losses. Because each of the criteria used is subject to change, the analysis of the allowance for loan losses is not necessarily indicative of the trend of future loan losses in any particular loan category. The total allowance for loan losses is available to absorb losses from any segment of the loan portfolio. When an individual loan is determined to be impaired, the allowance for loan losses attributable to the loan is allocated based on management’s estimate of the borrower’s ability to repay the loan given the availability of collateral, other sources of cash flows, as well as evaluation of legal options available to the Corporation. The amount of impairment is measured based upon the present value of expected future cash flows discounted at the loan’s effective interest rate, the fair value of the underlying collateral less applicable selling costs, or the observable market price of the loan. If foreclosure is probable or the loan is collateral dependent, impairment is measured using the fair value of the loan’s collateral, less costs to sell. Large groups of homogeneous loans, such as residential mortgage, home equity, and other consumer, are collectively evaluated for impairment. Management believes that the level of the allowance for loan losses is appropriate. While management uses currently available information to recognize losses on loans, future adjustments to the allowance for loan losses may be necessary based on newly received appraisals, updated commercial customer financial statements, rapidly deteriorating cash flow, and changes in economic conditions that affect our customers. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Corporation’s allowance for loan losses. Such agencies may require additions to the allowance for loan losses or may require that certain loan balances be charged off or downgraded into criticized loan categories when their credit evaluations differ from those of management based on their judgments about information available to them at the time of their examinations. See Loans and Troubled Debt Restructurings above for further policy discussion and see Note 4 for additional information on the allowance for loan losses. Other Real Estate Owned Other real estate owned is included in other assets in the consolidated balance sheets and is comprised of property acquired through a foreclosure proceeding or acceptance of a deed-in-lieu of foreclosure, and loans classified as in-substance foreclosure. Other real estate owned is recorded at the fair value of the underlying property collateral, less estimated selling costs. This fair value becomes the new cost basis for the foreclosed asset. The initial write-down, if any, will be recorded as a charge off against the allowance for loan losses. Any subsequent write-downs to reflect current fair value, as well as gains and losses on disposition and revenues and expenses incurred in maintaining such properties, are expensed as incurred. Other real estate owned also includes bank premises formerly but no longer used for banking as well as property originally acquired for future expansion but no longer intended to be used for that purpose. Banking premises are transferred at the lower of carrying value or fair value, less estimated selling costs and any write-down is expensed as incurred. Allowance for Unfunded Commitments 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 in the consolidated balance sheets. The determination of the appropriate level of the allowance for unfunded commitments is based upon an evaluation of the unfunded credit facilities, including an assessment of historical commitment utilization experience and credit risk grading of the loan. Net adjustments to the allowance for unfunded commitments are included in the provision for credit losses in the consolidated statements of income. See Note 4 and Note 15 for additional information on the allowance for unfunded commitments. Premises and Equipment and Software Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are computed on the straight-line method over the estimated useful lives of the related assets or the lease term. Maintenance and repairs are charged to expense as incurred, while additions or major improvements are capitalized and depreciated over the estimated useful lives. Leasehold improvements are amortized on a straight-line basis over the lesser of the lease terms or the estimated useful lives of the improvements. Software, included in other assets in the consolidated balance sheets, is amortized on a straight-line basis over the lesser of the contract terms or the estimated useful life of the software. See Note 6 for additional information on premises and equipment. Goodwill and Intangible Assets Goodwill and Other Intangible Assets: The excess of the cost of an acquisition over the fair value of the net assets acquired consists primarily of goodwill, core deposit intangibles, and other identifiable intangibles (primarily related to customer relationships acquired). Core deposit intangibles have estimated finite lives and are amortized on a straight-line basis to expense over a 10 -year period. The other intangibles have estimated finite lives and are amortized on a straight-line basis over their expected useful life. The Corporation reviews long-lived assets and certain identifiable intangibles for impairment at least annually, or whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, in which case an impairment charge would be recorded. 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 impairment testing process is conducted by assigning net assets and goodwill to each reporting unit. An initial qualitative evaluation is made to assess the likelihood of impairment and determine whether further quantitative testing to calculate the fair value is necessary. When the qualitative evaluation indicates that impairment is more likely than not, quantitative testing is required whereby the fair value of each reporting unit is calculated and compared to the recorded book value, “step one.” If the calculated fair value of the reporting unit exceeds its carrying value, goodwill is not considered impaired and “step two” is not considered necessary. If the carrying value of a reporting unit exceeds its calculated fair value, the impairment test continues (“step two”) by comparing the carrying value of the reporting unit’s goodwill to the implied fair value of goodwill. The implied fair value is computed by adjusting all assets and liabilities of the reporting unit to current fair value with the offset adjustment to goodwill. The adjusted goodwill balance is the implied fair value of the goodwill. An impairment charge is recognized if the carrying value of goodwill exceeds the implied fair value of goodwill. See Note 5 for additional information on goodwill and other intangible assets. Mortgage Servicing Rights: The Corporation sells residential mortgage loans in the secondary market and typically retains the right to service the loans sold. Upon sale, a mortgage servicing rights asset is capitalized, which represents the then current fair value of future net cash flows expected to be realized for performing servicing activities. Mortgage servicing rights, when purchased, are initially recorded at fair value. As the Corporation has not elected to subsequently measure any class of servicing assets under the fair value measurement method, the Corporation follows the amortization method. 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. Mortgage servicing rights are carried at the lower of the initial capitalized amount, net of accumulated amortization, or estimated fair value, in the consolidated balance sheets. The Corporation periodically evaluates its mortgage servicing rights asset for impairment. 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 5 for additional information on mortgage servicing rights. Income Taxes Amounts provided for income tax expense are based on income reported for financial statement purposes and do not necessarily represent amounts currently payable under tax laws. Deferred income taxes, which arise principally from temporary differences between the amounts reported in the financial statements and the tax bases of assets and liabilities, are included in the amounts provided for income taxes. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income and tax planning strategies which will create taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, the amount of taxes paid in available carryback years, projected future taxable income, and, if necessary, tax planning strategies in making this assessment. The Corporation files a consolidated federal income tax return and separate or combined state income tax returns. Accordingly, amounts equal to tax benefits of those subsidiaries having taxable federal or state losses or credits are offset by other subsidiaries that incur federal or state tax liabilities. It is the Corporation’s policy to provide for uncertainty in income taxes as a part of income tax expense based upon management’s assessment of whether a tax benefit is more likely than not to be sustained upon examination by tax authorities. At December 31, 2018 and 2017 , the Corporation believes it has appropriately accounted for any unrecognized tax benefits. To the extent the Corporation prevails in matters for which a liability for an unrecognized tax benefit was established or is required to pay amounts in excess of the liability established, the Corporation’s effective tax rate in a given financial statement period may be impacted. See Note 12 for additional information on income taxes. Derivative and Hedging Activities Derivative instruments, including derivative instruments embedded in other contracts, are carried at fair value on the consolidated balance sheets with changes in the fair value recorded to earnings or accumulated other comprehensive income, as appropriate. On the date the derivative contract is entered into, the Corporation designates the derivative as a fair value hedge (i.e., a hedge of the fair value of a recognized asset or liability), a cash flow hedge (i.e., a hedge of the variability of cash flows to be received or paid related to a recognized asset or liability), or a free-standing derivative instrument. For a derivative designated as a fair value hedge, the changes in the fair value of the derivative instrument and the changes in the fair value of the hedged asset or liability are recognized in current period earnings as an increase or decrease to the carrying value of the hedged item on the balance sheet and in the related income statement account. Amounts within accumulated other comprehensive income are reclassified into earnings in the period the hedged item affects earnings. For a derivative designated as a free-standing derivative instrument, changes in fair value are reported in current period earnings. The free-standing derivative instruments included: interest rate risk management, commodity hedging, and foreign currency exchange solutions. In addition, the Corpo

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Acquisition	Acquisitions Completed 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 Agreement and Plan of Merger dated July 20, 2017 (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 common stock of the Corporation on January 31, 2018. The Corporation completed the conversion of Bank Mutual in the second quarter of 2018. The banking subsidiary of Bank Mutual merged with and into Associated Bank, N.A. on June 24, 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 will be material. Goodwill related to the Bank Mutual acquisition increased $6 million during the second quarter of 2018 and an additional $2 million during the third quarter of 2018 to $175 million . Upon review of information relating to events and circumstances existing at the acquisition date, and in accordance with applicable accounting guidance, the Corporation remeasured select previously reported fair value amounts. Based on updated appraisal information, the fair value of premises and equipment decreased by $6 million and $2 million during the second and third quarters of 2018, respectively. Additionally, during the second quarter of 2018, the fair value of loans was increased by less than $1 million due to an updated appraisal and other adjustments. Goodwill created by the acquisition of Bank Mutual is not tax deductible. See Note 5 for additional information on goodwill, as well as the carrying amount and amortization of core deposit and other intangible assets related to the Bank Mutual acquisition. The following table presents the estimated fair values of the assets acquired and liabilities assumed as of the acquisition date related to Bank Mutual: Purchase Accounting Adjustments February 1, 2018 ($ 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 (48,043 ) 1,875,877 Premises and equipment, net 2,930 42,689 Bank owned life insurance (24 ) 65,390 Goodwill 175,499 Core deposit intangibles (included in other intangible assets, net on the face of the Consolidated Balance Sheets) 58,100 58,100 Other real estate owned (included in other assets on the face of the Consolidated Balance Sheets) 199 4,848 Others assets $ 7,054 $ 47,158 Total assets $ 2,820,506 Liabilities Deposits $ 2,498 $ 1,840,950 Other borrowings 1,875 431,886 Other liabilities $ 4,487 $ 65,982 Total liabilities $ 2,338,818 Total consideration paid $ 481,688 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. For loans acquired, the contractual amounts due, expected cash flows to be collected, interest component, and fair value as of the respective acquisition dates were as follows: February 1, 2018 Acquired Performing Loans Acquired Impaired Loans Total ($ in Thousands) Contractual required principal and interest at acquisition $ 1,899,932 $ 23,988 $ 1,923,920 Contractual cash flows not expected to be collected (nonaccretable discount) — (1,866 ) (1,866 ) Expected cash flows at acquisition 1,899,932 22,122 1,922,054 Interest component of expected cash flows (accretable discount) (41,324 ) (4,853 ) (46,177 ) Fair value of acquired loans $ 1,858,608 $ 17,269 $ 1,875,877 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. 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 17 for additional information on fair value measurements. Other Acquisitions During the second quarter of 2018, the Corporation completed the acquisition of Anderson, an independent insurance agency based in Minneapolis, Minnesota. Anderson adds a range of complementary services and significant expertise in workers' compensation and executive risk management services. The transaction was valued at approximately $10 million . As a result of the acquisition, the Corporation recorded goodwill of approximately $7 million and added approximately $3 million of other intangibles related to customer relationships associated with the Anderson acquisition. The other intangibles related to the acquisition are being amortized on a straight-line basis over 7 years . See Note 5 for more information on goodwill and other intangible assets. During the first quarter of 2018, the Corporation completed the acquisition of Diversified. The acquisition improved Associated Benefits and Risk Consulting's 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 5 for more information on goodwill and other intangible assets. Pending Branch Acquisition: During the fourth quarter of 2018, the Corporation announced that Associated had reached an agreement to acquire the Wisconsin branch banking operations of The Huntington National Bank, a subsidiary of Huntington Bancshares Incorporated. Under the terms of the transaction, Associated Bank will acquire approximately $850 million in deposits and $134 million in loans. The Huntington National Bank branch acquisition will add a net 14

Investment Securities

Investment Securities	12 Months Ended
	Dec. 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. See Note 1 for the Corporation’s accounting policy for investment securities. The majority of the Corporation's investment securities are mortgage-related securities issued by GNMA or GSEs such as FNMA and FHLMC. Obligations of state and political subdivisions (municipal securities) and asset backed securities backed by student loans made under FFELP are other security holdings within the Corporation's investment portfolio. The amortized cost and fair values of securities available for sale and held to maturity were as follows: December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U.S. Treasury securities $ 1,000 $ — $ (1 ) $ 999 Residential mortgage-related securities FNMA / FHLMC 296,296 2,466 (3,510 ) 295,252 GNMA 2,169,943 473 (41,885 ) 2,128,531 Private-label 1,007 — (4 ) 1,003 GNMA commercial mortgage-related securities 1,273,309 — (52,512 ) 1,220,797 FFELP asset backed securities 297,347 711 (698 ) 297,360 Other debt securities 3,000 — — 3,000 Other equity securities 1,568 — — 1,568 Total investment securities available for sale $ 4,043,470 $ 3,649 $ (98,610 ) $ 3,948,510 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,790,683 $ 8,255 $ (15,279 ) $ 1,783,659 Residential mortgage-related securities FNMA / FHLMC 92,788 169 (1,795 ) 91,162 GNMA 351,606 1,611 (8,181 ) 345,035 GNMA commercial mortgage-related securities 505,434 7,559 (22,579 ) 490,414 Total investment securities held to maturity $ 2,740,511 $ 17,593 $ (47,835 ) $ 2,710,271 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 December 31, 2018 , are shown below. Expected maturities will 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 $ 2,000 $ 1,999 $ 48,865 $ 49,128 Due after one year through five years 2,000 2,000 187,828 186,797 Due after five years through ten years — — 409,682 406,702 Due after ten years — — 1,144,309 1,141,032 Total debt securities 4,000 3,999 1,790,683 1,783,659 Residential mortgage-related securities FNMA / FHLMC 296,296 295,252 92,788 91,162 GNMA 2,169,943 2,128,531 351,606 345,035 Private-label 1,007 1,003 — — GNMA commercial mortgage-related securities 1,273,309 1,220,797 505,434 490,414 FFELP asset backed securities 297,347 297,360 — — Equity securities 1,568 1,568 — — Total investment securities $ 4,043,470 $ 3,948,510 $ 2,740,511 $ 2,710,271 Ratio of Fair Value to Amortized Cost 97.7 % 98.9 % The proceeds from the sale of investment securities for each of the three years ended December 31 were as follows. There were no other-than-temporary impairment write-downs on investment securities for 2018 , 2017 , or 2016 . 2018 2017 2016 ($ in Thousands) Gross gains on available for sale securities $ 1,954 $ — $ 9,485 Gross gains on held to maturity securities — 439 33 Total gains 1,954 439 9,518 Gross losses on available for sale securities (3,938 ) — (202 ) Gross losses on held to maturity securities — (5 ) — Total losses (3,938 ) (5 ) (202 ) Investment securities gains (losses), net $ (1,985 ) $ 434 $ 9,316 Proceeds from sales of investment securities $ 601,130 $ 18,467 $ 549,555 During 2018, the Corporation executed a strategy to improve the yield on securities and increase interest income during the current and future calendar years. During the third quarter of 2018, the Corporation sold mortgage-related securities totaling approximately $108 million at a slight gain with all proceeds reinvested into higher yielding securities. The taxable equivalent yield of the securities sold was 3.08% while the reinvestment was at 3.51% . During the second quarter of 2018, the Corporation also sold $40 million of lower yielding GNMA commercial mortgage-related securities. In addition, on the acquisition date, the Corporation sold Bank Mutual's entire $453 million securities portfolio. The Corporation originally reinvested the proceeds from the Bank Mutual portfolio into GNMA residential mortgage-related securities with the goal of reinvesting future cash flows into municipal securities. This strategy was completed during August 2018. During 2017, the Corporation sold approximately $18 million of municipal securities classified as held to maturity due to significant credit concerns and negative actions taken by credit rating agencies, primarily as a result of budgetary pressures in the State of Illinois and State of Connecticut. These sales resulted in a net gain of approximately $434,000 . During 2016, as part of an ongoing restructuring of its investment securities portfolio initiated during the prior year, the Corporation sold approximately $550 million of FNMA and FHLMC mortgage-related securities for a net gain on sale of $9 million , with the proceeds reinvested into GNMA mortgage-related securities. The sales of FNMA and FHLMC mortgage- related securities and the subsequent purchase of GNMA mortgage-related securities lowered risk weighted assets and related capital requirements. Investment securities with a carrying value of approximately $3.0 billion and $3.1 billion at December 31, 2018 , and December 31, 2017 , respectively, were pledged to secure certain deposits or for other purposes as required or permitted by law. The following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time individual securities have been in a continuous unrealized loss position, at December 31, 2018 : Less than 12 months 12 months or more Total December 31, 2018 Number of Securities Unrealized Losses Fair Value Number of Securities Unrealized Losses Fair Value Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U.S. Treasury securities — $ — $ — 1 $ (1 ) $ 999 $ (1 ) $ 999 Residential mortgage-related securities FNMA / FHLMC 15 (31 ) 17,993 17 (3,479 ) 189,405 (3,510 ) 207,398 GNMA 12 (4,529 ) 452,183 79 (37,355 ) 1,598,159 (41,885 ) 2,050,342 Private-label 1 (4 ) 1,003 — — — (4 ) 1,003 GNMA commercial mortgage-related securities — — — 93 (52,512 ) 1,220,854 (52,512 ) 1,220,854 FFELP asset backed securities 13 (698 ) 142,432 — — — (698 ) 142,432 Total 41 $ (5,262 ) $ 613,612 190 $ (93,347 ) $ 3,009,417 $ (98,610 ) $ 3,623,028 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) 272 $ (2,860 ) $ 313,212 752 $ (12,419 ) $ 509,374 $ (15,279 ) $ 822,586 Residential mortgage-related securities FNMA / FHLMC 13 (780 ) 57,896 22 (1,015 ) 28,888 (1,795 ) 86,784 GNMA 13 (414 ) 19,822 66 (7,767 ) 320,387 (8,181 ) 340,209 GNMA commercial mortgage-related securities — — — 25 (22,579 ) 490,414 (22,579 ) 490,414 Total 298 $ (4,053 ) $ 390,929 865 $ (43,780 ) $ 1,349,063 $ (47,835 ) $ 1,739,992 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 December 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 December 31, 2018 for mortgage-related securities are due to the increase in overall interest rates. The U.S. Treasury 3 year and 5 year rates increased by 48 bp and 31 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 in an unrealized loss position before recovery of their amortized cost basis. 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 December 31, 2018 , and 2017 , the Corporation had FHLB stock of $173 million and $89 million , respectively. The Corporation had Federal Reserve Bank stock of $77 million and $76 million at December 31, 2018 and 2017

Loans

Loans	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Loans	Loans Loans at December 31 are summarized below: 2018 (a) 2017 ($ in Thousands) Commercial and industrial $ 7,398,044 $ 6,399,693 Commercial real estate - owner occupied 920,443 802,209 Commercial and business lending 8,318,487 7,201,902 Commercial real estate - investor 3,751,554 3,315,254 Real estate construction 1,335,031 1,451,684 Commercial real estate lending 5,086,585 4,766,938 Total commercial 13,405,072 11,968,840 Residential mortgage 8,277,712 7,546,534 Home equity 894,473 883,804 Other consumer 363,171 385,813 Total consumer 9,535,357 8,816,151 Total loans $ 22,940,429 $ 20,784,991 (a) Includes $5 million of purchased credit-impaired loans The Corporation has granted loans to its directors, executive officers, or their related interests. These loans were made on substantially the same terms, including rates and collateral, as those prevailing at the time for comparable transactions with other unrelated customers, and do not involve more than a normal risk of collection. These loans to related parties are summarized below: 2018 2017 ($ in Thousands) Balance at beginning of year $ 20,260 $ 27,589 New loans 3,076 5,329 Repayments (5,017 ) (7,632 ) Change due to status of executive officers and directors (489 ) (5,026 ) Balance at end of year $ 17,831 $ 20,260 The following table presents commercial and consumer loans by credit quality indicator at December 31, 2018 : Pass Special Mention Potential Problem Nonaccrual Total ($ in Thousands) Commercial and industrial $ 7,162,370 $ 78,075 $ 116,578 $ 41,021 $ 7,398,044 Commercial real estate - owner occupied 854,265 6,257 55,964 3,957 920,443 Commercial and business lending 8,016,635 84,332 172,542 44,978 8,318,487 Commercial real estate - investor 3,653,642 28,479 67,481 1,952 3,751,554 Real estate construction 1,321,447 8,771 3,834 979 1,335,031 Commercial real estate lending 4,975,089 37,249 71,315 2,931 5,086,585 Total commercial 12,991,724 121,582 243,856 47,909 13,405,072 Residential mortgage 8,203,729 434 5,975 67,574 8,277,712 Home equity 880,808 1,223 103 12,339 894,473 Other consumer 362,343 749 — 79 363,171 Total consumer 9,446,881 2,406 6,078 79,992 9,535,357 Total loans $ 22,438,605 $ 123,988 $ 249,935 $ 127,901 $ 22,940,429 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 loans $ 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, an appropriate allowance for loan losses, allowance for unfunded commitments, nonaccrual, and charge off policies. See Note 1 for the Corporation's accounting policy for loans. 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 loans are reviewed at a minimum on a quarterly basis, while pass 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 December 31, 2018 : Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due and Still Accruing Nonaccrual (a) Total ($ in Thousands) Commercial and industrial $ 7,356,187 $ 187 $ 338 $ 311 $ 41,021 $ 7,398,044 Commercial real estate - owner occupied 913,787 2,580 119 — 3,957 920,443 Commercial and business lending 8,269,974 2,767 457 311 44,978 8,318,487 Commercial real estate - investor 3,745,835 2,954 813 — 1,952 3,751,554 Real estate construction 1,333,722 330 — — 979 1,335,031 Commercial real estate lending 5,079,557 3,284 813 — 2,931 5,086,585 Total commercial 13,349,531 6,051 1,270 311 47,909 13,405,072 Residential mortgage 8,200,432 9,272 434 — 67,574 8,277,712 Home equity 876,085 4,826 1,223 — 12,339 894,473 Other consumer 358,970 1,401 868 1,853 79 363,171 Total consumer 9,435,487 15,499 2,525 1,853 79,992 9,535,357 Total loans $ 22,785,019 $ 21,550 $ 3,795 $ 2,165 $ 127,901 $ 22,940,429 (a) Of the total nonaccrual loans, $74 million , or 58% , were current with respect to payment at December 31, 2018 . The following table presents loans by past due status at December 31, 2017 : Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Nonaccrual (a) Total ($ 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 loans $ 20,555,250 $ 16,861 $ 2,467 $ 1,867 $ 208,546 $ 20,784,991 (a) 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 $5 million of purchased credit-impaired loans, at December 31, 2018 : Recorded Unpaid Related Average Interest ($ in Thousands) Loans with a related allowance Commercial and industrial $ 40,747 $ 42,131 $ 5,721 $ 52,461 $ 1,167 Commercial real estate - owner occupied 2,080 2,087 24 2,179 104 Commercial and business lending 42,827 44,218 5,745 54,640 1,271 Commercial real estate - investor 799 805 28 827 38 Real estate construction 510 589 75 533 32 Commercial real estate lending 1,309 1,394 103 1,360 70 Total commercial 44,136 45,612 5,848 56,000 1,341 Residential mortgage 41,691 45,149 6,023 42,687 1,789 Home equity 9,601 10,539 3,312 10,209 566 Other consumer 1,181 1,183 121 1,184 3 Total consumer 52,473 56,871 9,456 54,080 2,358 Total loans $ 96,609 $ 102,483 $ 15,304 $ 110,079 $ 3,699 Loans with no related allowance Commercial and industrial $ 22,406 $ 45,024 $ — $ 21,352 $ (344 ) Commercial real estate - owner occupied 3,772 4,823 — 3,975 — Commercial and business lending 26,178 49,847 — 25,327 (344 ) Commercial real estate - investor 1,585 2,820 — 980 68 Real estate construction — — — — — Commercial real estate lending 1,585 2,820 — 980 68 Total commercial 27,763 52,667 — 26,307 (276 ) Residential mortgage 8,795 9,074 — 8,790 203 Home equity 523 542 — 530 — Other consumer — — — — — Total consumer 9,318 9,616 — 9,320 203 Total loans $ 37,081 $ 62,283 $ — $ 35,627 $ (73 ) Total Commercial and industrial $ 63,153 $ 87,155 $ 5,721 $ 73,813 $ 823 Commercial real estate - owner occupied 5,852 6,910 24 6,154 104 Commercial and business lending 69,005 94,065 5,745 79,967 927 Commercial real estate - investor 2,384 3,625 28 1,807 106 Real estate construction 510 589 75 533 32 Commercial real estate lending 2,894 4,214 103 2,340 138 Total commercial 71,899 98,279 5,848 82,307 1,065 Residential mortgage 50,486 54,223 6,023 51,477 1,992 Home equity 10,124 11,081 3,312 10,739 566 Other consumer 1,181 1,183 121 1,184 3 Total consumer 61,791 66,487 9,456 63,400 2,561 Total loans (a) $ 133,690 $ 164,766 $ 15,304 $ 145,707 $ 3,626 (a) The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 72% of the unpaid principal balance at December 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 $ 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 $ 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. See Note 1 for the Corporation's accounting policy for troubled debt restructurings. The Corporation had a recorded investment of approximately $11 million in loans modified in troubled debt restructurings for the year ended December 31, 2018 , of which approximately $3 million were in accrual status and $8 million were in nonaccrual pending a sustained period of repayment. As of December 31, 2018 there was approximately $6 million of commitments to lend additional funds to borrowers with restructured loans. The following table presents nonaccrual and performing restructured loans by loan portfolio: December 31, 2018 December 31, 2017 December 31, 2016 Performing Restructured Loans Nonaccrual Restructured Loans (a) Performing Restructured Loans Nonaccrual Restructured Loans (a) Performing Restructured Loans Nonaccrual Restructured Loans (a) ($ in Thousands) Commercial and industrial $ 25,478 $ 249 $ 30,047 $ 1,776 $ 31,884 $ 1,276 Commercial real estate - owner occupied 2,080 — 3,989 — 5,490 2,220 Commercial real estate - investor 799 933 14,389 — 15,289 924 Real estate construction 311 198 310 157 359 150 Residential mortgage 16,036 22,279 17,068 18,991 18,100 21,906 Home equity 7,385 2,627 7,705 2,537 7,756 2,877 Other consumer 1,174 6 1,110 25 979 32 Total restructured loans $ 53,263 $ 26,292 $ 74,618 $ 23,486 $ 79,857 $ 29,385 (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 years ended December 31, 2018 , 2017 , and 2016 , respectively, and the recorded investment and unpaid principal balance as of December 31, 2018 , 2017 , and 2016 , respectively: Years Ended December 31, 2018 2017 2016 Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) Number Recorded (a) Unpaid (b) ($ in Thousands) Commercial and industrial 5 $ 1,315 $ 1,330 8 $ 3,991 $ 6,339 8 $ 1,509 $ 1,526 Commercial real estate - owner occupied — — — 2 690 690 1 116 122 Commercial real estate - investor 2 1,393 1,472 — — — — — — Real estate construction 1 78 80 — — — 1 65 91 Residential mortgage 41 6,977 7,210 45 4,238 4,364 63 5,535 5,792 Home equity 34 1,649 1,681 22 507 507 57 2,030 2,084 Other consumer 3 17 19 — — — 1 15 16 Total 86 $ 11,429 $ 11,792 77 $ 9,426 $ 11,900 131 $ 9,270 $ 9,631 (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. For the year ended December 31, 2018 , restructured loan modifications of commercial and industrial, commercial real estate, and real estate construction loans primarily included maturity date extensions, interest rate concessions, payment schedule modifications, or a combination of these concessions. 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. The following table provides the number of loans modified in a troubled debt restructuring during the previous twelve months which subsequently defaulted during the year ended December 31, 2018 , 2017 , and 2016 , respectively, as well as the recorded investment in these restructured loans as of December 31, 2018 , 2017 , and 2016 , respectively: Years Ended December 31, 2018 2017 2016 Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Recorded ($ in Thousands) Commercial and industrial 3 $ — 2 $ — — $ — Residential mortgage 20 3,553 36 3,137 44 4,102 Home equity 32 1,688 27 735 23 457 Other consumer — — 1 7 1 15 Total 55 $ 5,241 66 $ 3,879 68 $ 4,574 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. See Note 1 for the Corporation's accounting policy on the allowance for loan losses. 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 15 for additional information on the allowance for unfunded commitments. A summary of the changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2018 , is as follows: Commercial and industrial Commercial real estate - owner occupied Commercial real estate - investor Real estate construction Residential mortgage Home equity Other consumer Total ($ in Thousands) December 31, 2017 $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Charge offs (30,837 ) (1,363 ) (7,914 ) (298 ) (1,627 ) (3,236 ) (5,261 ) (50,536 ) Recoveries 13,714 639 668 446 1,271 2,628 812 20,179 Net charge offs (17,123 ) (724 ) (7,246 ) 149 (355 ) (608 ) (4,448 ) (30,358 ) Provision for loan losses 2,890 (373 ) 7,031 (6,279 ) (3,657 ) (2,252 ) 5,138 2,500 December 31, 2018 $ 108,835 $ 9,255 $ 40,844 $ 28,240 $ 25,595 $ 19,266 $ 5,988 $ 238,023 Allowance for loan losses Individually evaluated for impairment $ 5,721 $ 24 $ 28 $ 75 $ 6,023 $ 3,312 $ 121 $ 15,304 Collectively evaluated for impairment 103,114 9,231 40,816 28,165 19,572 15,954 5,867 222,719 Acquired and accounted for under ASC 310-30 (a) — — — — — — — — Total allowance for loan losses $ 108,835 $ 9,255 $ 40,844 $ 28,240 $ 25,595 $ 19,266 $ 5,988 $ 238,023 Loans Individually evaluated for impairment $ 63,153 $ 5,852 $ 2,384 $ 510 $ 50,486 $ 10,124 $ 1,181 $ 133,690 Collectively evaluated for impairment 7,331,898 913,708 3,748,883 1,334,500 8,226,642 884,266 361,990 22,801,887 Acquired and accounted for under ASC 310-30 (a) 2,994 883 287 21 584 83 — 4,853 Total loans $ 7,398,044 $ 920,443 $ 3,751,554 $ 1,335,031 $ 8,277,712 $ 894,473 $ 363,171 $ 22,940,429 (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 , is as follows: Commercial and industrial Commercial real estate - owner occupied Commercial real estate - investor Real estate construction Residential mortgage Home equity Other consumer Total ($ in Thousands) 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 $12 million at December 31, 2018 and represented 1.62% of total oil and gas loans. Year Ended December 31, 2018 Year Ended December 31, 2017 ($ in Millions) Balance at beginning of period $ 27 $ 38 Charge offs (24 ) (25 ) Recoveries 6 — Net Charge offs (17 ) (25 ) Provision for loan losses 2 14 Balance at end of period $ 12 $ 27 Allowance for loan losses Individually evaluated for impairment $ — $ 5 Collectively evaluated for impairment 12 22 Total allowance for loan losses $ 12 $ 27 Loans Individually evaluated for impairment $ 22 $ 77 Collectively evaluated for impairment 725 523 Total loans $ 747 $ 600 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 15 for additional information on the allowance for unfunded commitments and see Note 1 for the Corporation's accounting policy for allowance for unfunded commitments. A summary of the changes in the allowance for unfunded commitments was as follows: Years Ended December 31, 2018 2017 2016 ($ in Thousands) Allowance for Unfunded Commitments Balance at beginning of period $ 24,400 $ 25,400 $ 24,400 Provision for unfunded commitments (2,500 ) (1,000 ) 1,000 Amount recorded at acquisition 2,436 — — Balance at end of period $ 24,336 $ 24,400 $ 25,400 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. If a reasonable expectation on the amount or timing of such cash flows cannot be determined, accretion of the fair value discount for nonperforming loans will be recognized using the cost recovery method of accounting. Changes in the accretable yield for loans acquired and accounted for under ASC Topic 310-30 were as follows for the years ended December 31, 2018 , and 2017 respectively: Year Ended December 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Changes in Accretable Yield Balance at beginning of period $ — $ — Purchases 4,853 — Accretion (4,954 ) — Net reclassification from non-accretable yield 1,605 — Other (a) (22 ) — Balance at end of period $ 1,482 $ — (a) Primarily includes charge offs which are accounted for under ASC Subtopic 310-30 "Receivables — Loans and Debt Securities Acquired with Deteriorated Credit Quality." 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. At December 31, 2018 , the Corporation had a total of approximately $20 million in net unaccreted purchase discount, of which approximately $18 million was related to performing loans and approximately $2 million

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Other Intangible Assets Goodwill Goodwill is not amortized but is instead 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. See Note 1 for the Corporation’s accounting policy for goodwill and other intangible assets. The Corporation conducted its most recent annual impairment testing in May 2018 , 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 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 were no events since the May 2018 impairment testing that have changed the Corporation's impairment assessment conclusion. There were no impairment charges recorded in 2018 , 2017 , or 2016 . At December 31, 2018 , the Corporation had goodwill of $1.2 billion , compared to $976 million at December 31, 2017 . Goodwill increased $175 million related to the Bank Mutual acquisition, $10 million related to the acquisition of Diversified, and $7 million related to the acquisition of Anderson. 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. During the second quarter of 2018, the Corporation added approximately $3 million of other intangibles related to customer relationships associated with the Anderson acquisition. See Note 2 for additional information on the Corporation's acquisitions. For core deposit intangibles and other intangibles, changes in the gross carrying amount, accumulated amortization, and net book value were as follows: 2018 2017 2016 ($ in Thousands) Core deposit intangibles Gross carrying amount $ 58,100 $ 4,385 $ 4,385 Accumulated amortization (5,326 ) (4,385 ) (4,273 ) Net book value $ 52,774 $ — $ 112 Additions during the period $ 58,100 $ — $ — Amortization during the year $ 5,326 $ 112 $ 281 Other intangibles Gross carrying amount $ 44,931 $ 34,572 $ 32,410 Reductions due to sale (43 ) — — Accumulated amortization (21,825 ) (18,992 ) (17,145 ) Net book value $ 23,062 $ 15,580 $ 15,265 Additions during the period $ 10,359 $ 2,162 $ 1,012 Amortization during the year $ 2,833 $ 1,847 $ 1,812 Mortgage Servicing Rights 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. See Note 1 for the Corporation’s accounting policy for mortgage servicing rights. See Note 15 for a discussion of the recourse provisions on sold residential mortgage loans. See Note 17 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 is as follows: 2018 2017 2016 ($ in Thousands) Mortgage servicing rights Mortgage servicing rights at beginning of year $ 59,168 $ 62,085 $ 62,150 Additions from acquisition 8,136 — — Additions 10,722 7,167 12,262 Amortization (9,594 ) (10,084 ) (12,327 ) Mortgage servicing rights at end of year $ 68,433 $ 59,168 $ 62,085 Valuation allowance at beginning of year (784 ) (609 ) (809 ) (Additions) recoveries, net 545 (175 ) 200 Valuation allowance at end of year (239 ) (784 ) (609 ) Mortgage servicing rights, net $ 68,193 $ 58,384 $ 61,476 Fair value of mortgage servicing rights $ 81,012 $ 64,387 $ 73,149 Portfolio of residential mortgage loans serviced for others (“servicing portfolio”) $ 8,600,983 $ 7,646,846 $ 7,974,742 Mortgage servicing rights, net to servicing portfolio 0.79 % 0.76 % 0.77 % Mortgage servicing rights expense (a) $ 9,049 $ 10,259 $ 12,127 (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 projections of amortization expense are based on existing asset balances, the current interest rate environment, and prepayment speeds as of December 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. The following table shows the estimated future amortization expense for amortizing intangible assets: Estimated Amortization Expense Core Deposit Intangibles Other Intangibles Mortgage Servicing Rights ($ in Thousands) Year ending December 31, 2019 $ 5,810 $ 2,824 $ 9,666 2020 5,810 2,707 10,355 2021 5,810 2,682 8,951 2022 5,810 2,659 7,694 2023 5,810 2,640 6,580 Beyond 2023 23,724 9,551 25,187 Total Estimated Amortization Expense $ 52,774 $ 23,062 $ 68,433

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment See Note 1 for the Corporation’s accounting policy for premises and equipment. A summary of premises and equipment at December 31 is as follows: 2018 2017 ($ in Thousands) Estimated Useful Lives Cost Accumulated Depreciation Net Book Value Net Book Value Land — $ 67,737 $ — $ 67,737 $ 59,257 Land improvements 3 – 15 years 14,730 7,518 7,212 6,313 Buildings and improvements 5 – 39 years 363,000 150,464 212,536 198,431 Computers 3 – 5 years 45,768 33,375 12,392 11,078 Furniture, fixtures and other equipment 3 – 15 years 168,567 118,676 49,891 42,049 Leasehold improvements 3 – 15 years 34,248 20,791 13,457 13,835 Total premises and equipment $ 694,050 $ 330,824 $ 363,225 $ 330,963 Depreciation and amortization of premises and equipment totaled $34 million in 2018 , $32 million in 2017 , and $32 million in 2016 . During 2018, the Corporation acquired properties as a result of the Bank Mutual acquisition. Upon conversion, several Associated Bank and Bank Mutual properties were moved to OREO as a result of branch consolidations. The majority of these properties were sold prior to year-end. The Corporation conducts a portion of its business through certain facilities and equipment under noncancelable operating leases. The Corporation also leases a subdivision of some of its facilities and receives rental income from such lease agreements. The approximate minimum annual rental payments and rental receipts under noncancelable agreements and leases with remaining terms in excess of one year are as follows: ($ in Thousands) Payments Receipts 2019 $ 10,235 $ 2,963 2020 10,107 3,030 2021 9,500 2,860 2022 7,084 1,875 2023 5,183 1,260 Thereafter 22,622 7,806 Total $ 64,732 $ 19,794 Total rental expense under leases, net of lease income, totaled $10 million in 2018 , $6 million in 2017 , and $8 million in 2016 , respectively. The increase of rental expense was primarily driven by lease breakage costs totaling $5 million in 2018

Deposits

Deposits	12 Months Ended
	Dec. 31, 2018
Deposits [Abstract]
Deposits	Deposits The distribution of deposits at December 31 is as follows: 2018 2017 ($ in Thousands) Noninterest-bearing demand $ 5,698,530 $ 5,478,416 Savings 2,012,841 1,524,992 Interest-bearing demand 5,336,952 4,603,157 Money market 9,033,669 8,830,328 Brokered CDs 192,234 18,609 Other time 2,623,167 2,330,460 Total deposits $ 24,897,393 $ 22,785,962 Time deposits of $100,000 or more was $1.4 billion for both December 31, 2018 and 2017 , respectively. Time deposits of $250,000 or more were $924 million and $1.1 billion at December 31, 2018 and 2017 , respectively. Aggregate annual maturities of all time deposits at December 31, 2018 , are as follows: Maturities During Year Ending December 31, ($ in Thousands) 2019 $ 1,952,008 2020 561,758 2021 176,491 2022 67,738 2023 52,576 Thereafter 4,830 Total $ 2,815,401

Short and Long-Term Funding

Short and Long-Term Funding	12 Months Ended
	Dec. 31, 2018
Short-term Debt [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), long-term funding (funding with original contractual maturities greater than one year), and FHLB advances (funding based on original contractual maturities): December 31, 2018 December 31, 2017 ($ in Thousands) Short-Term Funding Federal funds purchased $ 19,710 $ 141,950 Securities sold under agreements to repurchase 91,941 182,865 Federal funds purchased and securities sold under agreements to repurchase 111,651 324,815 Commercial paper 45,423 67,467 Total short-term funding $ 157,074 $ 392,282 Long-Term Funding Senior notes, at par $ 550,000 $ 250,000 Subordinated notes, at par 250,000 250,000 Other long-term funding and capitalized costs (4,389 ) (2,718 ) Total long-term funding 795,611 497,282 Total short and long-term funding, excluding FHLB advances $ 952,685 $ 889,564 FHLB Advances Short-term FHLB advances $ 900,000 $ 284,000 Long-term FHLB advances 2,674,371 2,900,168 Total FHLB advances $ 3,574,371 $ 3,184,168 Total short and long-term funding $ 4,527,056 $ 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 14 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 December 31, 2018 , the Corporation pledged agency mortgage-related securities with a fair value of $194 million as collateral for the repurchase agreements. Securities pledged as collateral under repurchase agreements are maintained with the Corporation's safekeeping agents and are monitored on a daily basis due to the market risk of fair value changes in the underlying securities. The Corporation generally pledges excess securities to ensure there is sufficient collateral to satisfy short-term fluctuations in both the repurchase agreement balances and the fair value of the underlying securities. The remaining contractual maturity of the securities sold under agreements to repurchase in the consolidated balance sheets as of December 31, 2018 and December 31, 2017 are presented in the following table: Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 days 30-90 days Greater than 90 days Total ($ in Thousands) December 31, 2018 Repurchase agreements Agency mortgage-related securities $ 91,941 $ — $ — $ — $ 91,941 Total $ 91,941 $ — $ — $ — $ 91,941 December 31, 2017 Repurchase agreements Agency mortgage-related securities $ 182,865 $ — $ — $ — $ 182,865 Total $ 182,865 $ — $ — $ — $ 182,865 Long-Term Funding Senior Notes In August 2018, Associated Bank, N.A. issued $300 million of senior notes, due August 2021, and callable July 2021. The senior notes have a fixed coupon interest rate of 3.50% and were issued at a discount. 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. FHLB Advances At December 31, 2018 , the Corporation had $3.6 billion of FHLB advances, up $390 million from December 31, 2017 . As of December 31, 2018 , the Corporation had $2.6 billion of long-term putable FHLB advances with a one-time option where the FHLB can call the advance prior to the contractual maturity. The contractual weighted average life to the put date of these advances was 0.9 years, with put dates ranging from 2019 through 2020. The weighted average life to contractual maturity on these advances was 7.6 years, with those dates ranging from 2023 through 2028. As of December 31, 2018 , it is anticipated that all of these advances will be called by the FHLB on their put date. Under agreements with the Federal Home Loan Bank of Chicago, FHLB advances (short-term and long-term) are secured by qualifying mortgages of the subsidiary bank (such as residential mortgage, residential mortgage loans held for sale, home equity, and commercial real estate). At December 31, 2018 , the Corporation had $7.1 billion of total collateral capacity supported by residential mortgage and home equity loans. The original contractual maturity or next put date of the Corporation's FHLB advances as of December 31, 2018 and December 31, 2017 are presented in the following table: December 31, 2018 December 31, 2017 Amount Weighted Average Contractual Coupon Rate Amount Weighted Average Contractual Coupon Rate ($ in Thousands) Maturity or put date 1 year or less $ 2,262,584 2.06 % $ 2,434,000 1.26 % After 1 but within 2 1,285,039 2.39 % 750,013 1.23 % After 2 but within 3 14,393 2.98 % 155 4.91 % After 3 years 12,354 4.55 % — — % FHLB advances and overall rate $ 3,574,371 2.19 % $ 3,184,168 1.26 % The table below summarizes the maturities of the Corporation’s long-term funding, including long-term FHLB advances, at December 31, 2018 : Year ($ in Thousands) 2019 $ 1,612,265 2020 1,285,039 2021 312,047 2022 6,023 2023 2,665 Thereafter 251,943 Total long-term funding $ 3,469,982

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Preferred Equity: In June 2015, the Corporation issued 2.6 million depositary shares, each representing a 1/40th interest in a share of the Corporation’s 6.125% Non-Cumulative Perpetual Preferred Stock, Series C, liquidation preference $1,000 per share (the “Series C Preferred Stock”). Dividends on the Series C Preferred Stock are payable quarterly in arrears only when, as and if declared by the Board of Directors at a rate per annum equal to 6.125% . Shares of the Series C Preferred Stock have priority over the Corporation’s common stock with regard to the payment of dividends and distributions upon liquidation, dissolution or winding up. As such, the Corporation may not pay dividends on or repurchase, redeem, or otherwise acquire for consideration shares of its common stock unless dividends for the Series C Preferred Stock have been declared for that period, and sufficient funds have been set aside to make payment. The Series C Preferred Stock may be redeemed by the Corporation at its option (i) either in whole or in part, from time to time, on any dividend payment date on or after the dividend payment date occurring on June 15, 2020 , or (ii) in whole but not in part, at any time within 90 days following certain regulatory capital treatment events, in each case at a redemption price of $1,000 per share (equivalent to $25 per depositary share), plus any applicable dividends. Except in certain limited circumstances, the Series C Preferred Stock does not have any voting rights. On August 28, 2015 , the Board of Directors authorized the repurchase of up to $10 million of the Corporation's Series C Preferred Stock. As of December 31, 2018 , $10 million remained available under this repurchase authorization. In September 2016, the Corporation issued 4.0 million depositary shares, each representing a 1/40th interest in a share of the Corporation’s 5.375% Non-Cumulative Perpetual Preferred Stock, Series D, liquidation preference $1,000 per share (the “Series D Preferred Stock”). Dividends on the Series D Preferred Stock are payable quarterly in arrears only when, as and if declared by the Board of Directors at a rate per annum equal to 5.375% . Shares of the Series D Preferred Stock have priority over the Corporation’s common stock with regard to the payment of dividends and distributions upon liquidation, dissolution or winding up. As such, the Corporation may not pay dividends on or repurchase, redeem, or otherwise acquire for consideration shares of its common stock unless dividends for the Series D Preferred Stock have been declared for that period, and sufficient funds have been set aside to make payment. The Series D Preferred Stock may be redeemed by the Corporation at its option (i) either in whole or in part, from time to time, on any dividend payment date on or after the dividend payment date occurring on September 15, 2021 , or (ii) in whole but not in part, at any time within 90 days following certain regulatory capital treatment events, in each case at a redemption price of $1,000 per share (equivalent to $25 per depositary share), plus any applicable dividends. Except in certain limited circumstances, the Series D Preferred Stock does not have any voting rights. On July 25, 2017, the Board of Directors authorized the repurchase of up to $15 million of the Corporation's Series D Preferred Stock. During 2018, the Corporation repurchased $537,057 , or approximately 22,000 depositary shares. As of December 31, 2018 , $14 million remained available under this repurchase authorization. In September 2018, the Corporation issued 4.0 million depositary shares, each representing a 1/40th interest in a share of the Corporation’s 5.875% Non-Cumulative Perpetual Preferred Stock, Series E, liquidation preference $1,000 per share (the “Series E Preferred Stock”). Dividends on the Series E Preferred Stock are payable quarterly in arrears only when, as and if declared by the Board of Directors at a rate per annum equal to 5.875% . Shares of the Series E Preferred Stock have priority over the Corporation’s common stock with regard to the payment of dividends and distributions upon liquidation, dissolution or winding up. As such, the Corporation may not pay dividends on or repurchase, redeem, or otherwise acquire for consideration shares of its common stock unless dividends for the Series E Preferred Stock have been declared for that period, and sufficient funds have been set aside to make payment. The Series E Preferred Stock may be redeemed by the Corporation at its option (i) either in whole or in part, from time to time, on any dividend payment date on or after the dividend payment date occurring on December 15, 2023 , or (ii) in whole but not in part, at any time within 90 days following certain regulatory capital treatment events, in each case at a redemption price of $1,000 per share (equivalent to $25 per depositary share), plus any applicable dividends. Except in certain limited circumstances, the Series E Preferred Stock does not have any voting rights. Common Stock Warrants: In November 2008, under the Capital Purchase Program, the Corporation issued to the U.S. Department of the Treasury warrants to purchase approximately 4.0 million shares of common stock. The warrants had a term of 10 years and were exercisable at any time, in whole or in part, at an exercise price of $19.77 per share (subject to certain anti-dilution adjustments). On December 6, 2011 , the U.S. Treasury closed an underwritten secondary public offering of the warrants. The Corporation received no proceeds from the public offering. During 2018, all but 12,507 of the 4.0 million warrants were exercised at an exercise price of $19.77 . The warrants were converted to approximately 1.1 million shares of common stock. The 12,507 unexercised warrants expired on November 21, 2018. Subsidiary Equity: At December 31, 2018 , subsidiary equity equaled $3.8 billion . See Note 18 for additional information on regulatory requirements for the Bank. Common Stock Repurchases: The Board of Directors authorized the repurchase of common stock during 2015. On April 24, 2018, the Board of Directors authorized the repurchase of up to $100 million of the Corporation's common stock. In addition, on September 18, 2018, the Board of Directors authorized the repurchase of up to $200 million of the Corporation's common stock. During 2018, the Corporation repurchased the remaining $51 million under the 2015 Board authorization and all $100 million from the April 2018 Board authorization. During 2018, the Corporation repurchased 9.5 million shares for $240 million (or an average cost per common share of $25.29 ), of which, 8.1 million shares for $206 million went back into treasury stock while the remaining 1.4 million shares for $33 million (or an average cost per common share of $24.38 ) were returned to authorized but unissued shares. During 2017, the Corporation repurchased approximately 1.6 million shares for $37 million (or an average cost per common share of $23.59 ), all of which were returned to authorized but unissued shares. The Corporation also repurchased shares for minimum tax withholding settlements on equity compensation totaling approximately $7 million ( 292,070 shares at an average cost per common share of $24.47 ) during 2018 compared to approximately $9 million ( 370,416 shares at an average cost per common share of $25.08 ) during 2017. As of December 31, 2018 , approximately $111 million remained available to repurchase shares of common stock under previously approved Board of Director authorizations. The repurchase of shares will be based on market and investment opportunities, capital levels, growth prospects, and any necessary regulatory approvals and other 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. Other Comprehensive Income (Loss): See the Consolidated Statements of Comprehensive Income for a summary of activity in other comprehensive income (loss) and see Note 21

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Stock-Based Compensation	Stock-Based Compensation Stock-Based Compensation Plan In February 2017, the Board of Directors, with subsequent approval of the Corporation’s shareholders, approved the adoption of the 2017 Incentive Compensation Plan (“2017 Plan”). All remaining shares available for grant under the 2013 Incentive Compensation Plan were rolled into the 2017 Plan. As of December 31, 2018 , approximately 11.6 million shares remained available for grant under the 2017 Plan. Under the 2017 Plan, options are generally exercisable up to 10 years from the date of grant, have an exercise price that is equal to the closing price of the Corporation’s stock on the grant date, and vest ratably over four years . The Corporation also issues restricted common stock and restricted common stock units to certain key employees (collectively referred to as “restricted stock awards”) under the 2017 Plan. The shares of restricted stock are restricted as to transfer, but are not restricted as to dividend payment or voting rights. Restricted stock units receive dividend equivalents but do not have voting rights. The transfer restrictions lapse over three years or four years , depending upon whether the awards are performance-based or service-based. Performance-based awards are based on earnings per share performance goals, relative total shareholder return, and continued employment or meeting the requirements for retirement and service-based awards are contingent upon continued employment or meeting the requirements for retirement. Performance-based restricted stock awards vest over a performance period of three years and service-based restricted stock awards vest ratably over four years . The 2017 Plan provides that restricted stock awards and stock options will immediately become fully vested upon retirement from the Corporation of those colleagues whose retirement meets the early retirement or normal retirement definitions under the 2017 Plan (“retirement eligible colleagues”). See Note 1 for the Corporation’s accounting policy for stock based compensation. Accounting for 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. Performance awards are based on performance goals of earnings per share and total shareholder return with vesting ranging from a minimum of 25% to a maximum of 150% of the target award. Performance awards are valued utilizing a Monte Carlo simulation model to estimate fair value of the awards at the grant date. 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 that 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 2018 , 2017 , and 2016 : 2018 2017 2016 Dividend yield 2.50 % 2.00 % 2.50 % Risk-free interest rate 2.60 % 2.00 % 2.00 % Weighted average expected volatility 22.00 % 25.00 % 25.00 % Weighted average expected life 5.75 years 5.5 years 5.5 years Weighted average per share fair value of options $4.47 $5.30 $3.36 A summary of the Corporation’s stock option activity for the year ended December 31, 2018 is presented below: Stock Options Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in thousands) 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 (1,031,875 ) 16.45 Forfeited or expired (114,695 ) 23.88 Outstanding at December 31, 2018 5,280,908 $ 19.09 6.18 $ 12,392 Options exercisable at December 31, 2018 3,187,894 $ 16.93 4.92 $ 10,796 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 years ended December 31, 2018 , 2017 , and 2016 the intrinsic value of stock options exercised was $10 million , $13 million , and $9 million , respectively. The total fair value of stock options that vested was $4 million , $4 million , and $3 million , respectively, for the years ended December 31, 2018 , 2017 , and 2016 . For the years ended December 31, 2018 , 2017 , and 2016 , the Corporation recognized compensation expense of $4 million for each of the three years, for the vesting of stock options. Included in compensation expense for 2018 was less than $1 million of expense for the accelerated vesting of stock options granted to retirement eligible colleagues. At December 31, 2018 , the Corporation had $4 million of unrecognized compensation expense related to stock options that is expected to be recognized over the remaining requisite service periods that extend predominantly through the first quarter 2022 . The following table summarizes information about the Corporation’s restricted stock activity for the year ended December 31, 2018 : Restricted Stock Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 2,026,071 $ 19.68 Granted 615,484 24.60 Vested (587,775 ) 18.44 Forfeited (60,948 ) 22.36 Outstanding at December 31, 2018 1,992,832 $ 21.92 The Corporation amortizes the expense related to restricted stock awards as compensation expense over the vesting period specified in the grant. Expense for restricted stock awards of approximately $13 million was recorded for year ended December 31, 2018 and $18 million for both the years ended December 31, 2017 and 2016 , respectively. 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 $18 million of unrecognized compensation costs related to restricted stock awards at December 31, 2018 , that is expected to be recognized over the remaining requisite service periods that extend predominantly 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 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. As described in Note 9

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2018
Defined Benefit Plan [Abstract]
Retirement Plans	Retirement Plan s The Corporation has a noncontributory defined benefit retirement plan ("Retirement Account Plan") 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 Retirement Account Plan after consummation of the business combinations. Any retirement plans of acquired entities are typically merged into the Retirement Account Plan 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 was merged into the Retirement Account Plan on December 31, 2018. Bank Mutual's Postretirement Plan was merged into the Corporation's Postretirement Plan during the first quarter of 2018. The reported figures for both the Retirement Account Plan and Postretirement Plan only include 11 months of Bank Mutual expense due to the timing of the Bank Mutual acquisition. See Note 2 Acquisitions for additional information on the Bank Mutual acquisition. The funded status and amounts recognized in the 2018 and 2017 consolidated balance sheets, as measured on December 31, 2018 and 2017 , respectively, for the Retirement Account Plan and Postretirement Plan were as follows: Retirement Account Plan Bank Mutual Pension Postretirement Plan Retirement Account Plan Postretirement Plan ($ in Thousands) 2018 2018 2018 2017 2017 Change in Fair Value of Plan Assets Fair value of plan assets at beginning of year $ 331,609 N/A $ — $ 295,718 $ — Fair value of Bank Mutual plan assets at February 1, 2018 N/A 59,445 — N/A N/A Actual return on plan assets (14,609 ) (1,665 ) — 41,490 — Employer contributions 4,340 37,537 292 6,242 235 Gross benefits paid (10,582 ) (15,513 ) (292 ) (11,841 ) (235 ) Bank Mutual plan assets transferred at December 31, 2018 79,805 (79,805 ) — N/A N/A Fair value of plan assets at end of year (a) $ 390,564 $ — $ — $ 331,609 $ — Change in Benefit Obligation Net benefit obligation at beginning of year $ 186,423 N/A $ 2,478 $ 176,825 $ 2,403 Net Bank Mutual benefit obligation at February 1, 2018 N/A 66,364 576 N/A N/A Service cost 7,540 — — 6,955 — Interest cost 6,727 2,398 108 7,121 101 Actuarial (gain) loss (8,000 ) (1,701 ) (347 ) 7,363 209 Gross benefits paid (10,582 ) (2,644 ) (292 ) (11,841 ) (235 ) Lump sums paid — (12,868 ) — — — Bank Mutual benefit obligations transferred at December 31, 2018 51,549 (51,549 ) — N/A N/A Net benefit obligation at end of year (a) $ 233,658 $ — $ 2,523 $ 186,423 $ 2,478 Funded (unfunded) status $ 156,906 $ — $ (2,523 ) $ 145,186 $ (2,478 ) Noncurrent assets 156,906 — — 145,186 — Current liabilities — — (219 ) — (233 ) Noncurrent liabilities — — (2,304 ) — (2,245 ) Asset (Liability) Recognized in the Consolidated Balance Sheets $ 156,906 $ — $ (2,523 ) $ 145,186 $ (2,478 ) (a) The fair value of the plan assets represented 167% and 178% of the net benefit obligation of the pension plan at December 31, 2018 and 2017 , respectively. Amounts recognized in accumulated other comprehensive (income) loss, net of tax, as of December 31, 2018 and 2017 follow: Retirement Account Plan Postretirement Plan Retirement Account Plan Postretirement Plan ($ in Thousands) 2018 2018 2017 2017 Prior service cost $ (303 ) $ (588 ) $ (295 ) $ (531 ) Net actuarial loss 50,238 (17 ) 24,926 205 Amount not yet recognized in net periodic benefit cost, but recognized in accumulated other comprehensive (income) loss $ 49,935 $ (605 ) $ 24,631 $ (326 ) Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) (“OCI”), net of tax, in 2018 and 2017 were as follows: Retirement Account Plan Postretirement Retirement Account Plan Postretirement ($ in Thousands) 2018 2018 2017 2017 Net actuarial gain (loss) $ (28,959 ) $ 347 $ 14,482 $ (209 ) Amortization of prior service cost (73 ) (75 ) (73 ) (75 ) Amortization of actuarial loss (gain) 2,195 8 2,278 4 Adjustment for adoption of ASU 2018-02 (5,235 ) — — — Income tax (expense) benefit 6,838 (71 ) (6,219 ) 107 Total Recognized in OCI $ (25,234 ) $ 209 $ 10,468 $ (173 ) The components of net pension cost for the Retirement Account Plan for 2018 , 2017 , and 2016 were as follows: Retirement Account Plan Retirement Account Plan Retirement Account Plan ($ in Thousands) 2018 2017 2016 Service cost $ 7,540 $ 6,955 $ 6,780 Interest cost 9,125 7,121 7,121 Expected return on plan assets (23,195 ) (19,646 ) (20,287 ) Amortization of prior service cost (73 ) (73 ) (73 ) Amortization of actuarial loss (gain) 2,195 2,278 2,115 Recognized settlement loss (gain) 809 — — Total net periodic pension cost $ (3,600 ) $ (3,365 ) $ (4,344 ) The components of net periodic benefit cost for the Postretirement Plan for 2018 , 2017 , and 2016 were as follows: Postretirement Plan Postretirement Plan Postretirement Plan ($ in Thousands) 2018 2017 2016 Interest cost $ 108 $ 101 $ 142 Amortization of prior service cost (75 ) (75 ) — Amortization of actuarial loss (gain) 8 4 — Total net periodic benefit cost $ 41 $ 30 $ 142 The components of net periodic pension cost and 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. As of December 31, 2018 , the estimated actuarial losses and prior service cost that will be amortized during 2019 from accumulated other comprehensive income into net periodic pension cost for the Retirement Account Plan includes expense of approximately $260,000 for actuarial losses and income of approximately $75,000 for the prior service cost. For the Postretirement Plan, the estimated actuarial losses and prior service cost that will be amortized during 2019 from accumulated other comprehensive income into net periodic benefit cost includes income of approximately $75,000 for the prior service cost while the actuarial gain income is estimated to be negligible. Retirement Account Plan Postretirement Plan Retirement Account Plan Postretirement Plan 2018 2018 2017 2017 Weighted average assumptions used to determine benefit obligations Discount rate 4.30 % 4.30 % 3.70 % 3.70 % Rate of increase in compensation levels 3.00 % N/A 3.00 % N/A Weighted average assumptions used to determine net periodic benefit costs Discount rate (a) 3.77 % 3.77 % 4.10 % 4.10 % Rate of increase in compensation levels 3.00 % N/A 4.00 % N/A Expected long-term rate of return on plan assets (b) 5.93 % N/A 6.50 % N/A (a) Weighted average of the 2018 fiscal year discount rate assumption for the Retirement Account Plan was 3.70% and the Bank Mutual Pension Plan was 4.00% (b) Weighted average of the 2018 fiscal year expected return on asset assumption for the Retirement Account Plan was 6.00% and the Bank Mutual Pension Plan was 5.50% The expected long-term (more than 20 years) rate of return was estimated using market benchmarks for equities and bonds applied to the Retirement Account Plan’s anticipated asset allocations. The expected return on equities was computed utilizing a valuation framework, which projected future returns based on current equity valuations rather than historical returns. The actual rate of return for the Retirement Account Plan assets was (3.69)% and 14.60% for 2018 and 2017 , respectively. The Retirement Account Plan’s investments are exposed to various risks, such as interest rate, market, and credit risks. Due to the level of risks associated with certain investments and the level of uncertainty related to changes in the value of the investments, it is at least reasonably possible that changes in risks in the near term could materially affect the amounts reported. The investment objective for the Retirement Account Plan is to maximize total return with a tolerance for average risk. The Retirement Account Plan has a diversified portfolio designed to provide liquidity, current income, and growth of income and principal, with anticipated asset allocation ranges of: equity securities 50 to 70% , fixed-income securities 30 to 50% , other cash equivalents 0 to 10% , and alternative securities 0 to 15% . Based on changes in economic and market conditions, the Corporation could be outside of the allocation ranges for brief periods of time. The asset allocation for the Retirement Account Plan as of the December 31, 2018 and 2017 measurement dates, respectively, by asset category were as follows: Asset Category 2018 2017 Equity securities 49 % 60 % Fixed-income securities 34 % 37 % Group annuity contracts 12 % — % Alternative securities 3 % — % Other 2 % 3 % Total 100 % 100 % The Retirement Account Plan assets include cash equivalents, such as money market accounts, mutual funds, common / collective trust funds (which include investments in equity and bond securities), and a group annuity contract. Money market accounts are stated at cost plus accrued interest, mutual funds are valued at quoted market prices, investments in common / collective trust funds are valued at the amount at which units in the funds can be withdrawn, and the group annuity contract is valued at fair value by discounting the related cash flows based on current yields of similar instruments with comparable durations and considering the credit worthiness of the issuer. The group annuity contract was obtained as part of the Bank Mutual Pension Plan that was acquired on February 1, 2018 and merged into the Retirement Account Plan on December 31, 2018. Based on these inputs, the following table summarizes the fair value of the Retirement Account Plan’s investments as of December 31, 2018 and 2017 : Fair Value Measurements Using ($ in Thousands) December 31, 2018 Level 1 Level 2 Level 3 Retirement Account Plan Investments Money market account $ 7,159 $ 7,159 $ — $ — Common /collective trust funds 138,020 138,020 — — Mutual funds 198,120 198,120 — — Group annuity contracts 47,265 — — 47,265 Total Retirement Account Plan Investments $ 390,564 $ 343,299 $ — $ 47,265 Fair Value Measurements Using ($ in Thousands) December 31, 2017 Level 1 Level 2 Level 3 Retirement Account Plan Investments Money market account $ 9,577 $ 9,577 $ — $ — Common /collective trust funds 133,210 133,210 — — Mutual funds 188,823 188,823 — — Total Retirement Account Plan Investments $ 331,610 $ 331,610 $ — $ — The following presents a summary of the changes in the fair value of the Retirement Account Plan's Level 3 asset during the periods indicated. As noted above, the Corporation's Level 3 asset consists entirely of a group annuity contract issued by a life insurance company. Fair Value Reconciliation of Level 3 Retirement Account Plan Investments 2018 2017 Fair value of group annuity contract at February 1, 2018 (date of Bank Mutual acquisition) $ 49,191 N/A Actual return on plan assets 565 N/A Benefits paid (2,491 ) N/A Fair value of group annuity contract at December 31, 2018 $ 47,265 N/A The Corporation’s funding policy is to pay at least the minimum amount required by federal law and regulations, with consideration given to the maximum funding amounts allowed. The Corporation regularly reviews the funding of its Retirement Account Plan. The Corporation made contributions of $38 million to the Bank Mutual Pension Plan and $4 million to the Retirement Account Plan during 2018 , with the plans merging on December 31, 2018 . The Corporation made contributions of $6 million to the Retirement Account Plan in 2017 . The projected benefit payments were calculated using the same assumptions as those used to calculate the benefit obligations listed above. The projected benefit payments for the Retirement Account and Postretirement Plans at December 31, 2018 , reflecting expected future services, were as follows: ($ in Thousands) Retirement Account Plan Postretirement Plan Estimated future benefit payments 2019 $ 18,774 $ 224 2020 19,265 220 2021 19,161 216 2022 20,210 211 2023 20,086 206 2024-2028 89,992 925 The health care trend rate is an assumption as to how much the Postretirement Plan’s medical costs will change each year in the future. The health care trend rate assumption for pre-65 coverage is an increase of 7% for 2018 , with the rate of increase decreasing 0.25% to 0.50% in each succeeding year, to an ultimate rate of 5% for 2024 and future years. The actual change in 2018 health care premium rates for post-65 coverage was a decrease of 5.1% . The health care trend rate assumption for post-65 coverage is an increase of 6% in 2019 with the rate of increase decreasing 0.25% in each succeeding year, to an ultimate rate of 5% for 2023 and future years. A one percentage point change in the assumed health care cost trend rate would have the following effect: 2018 2017 ($ in Thousands) 100 bp Increase 100 bp Decrease 100 bp Increase 100 bp Decrease Effect on total of service and interest cost $ 7 $ (6 ) $ 7 $ (6 ) Effect on postretirement benefit obligation $ 164 $ (143 ) $ 162 $ (140 ) The Corporation also has a 401(k) and Employee Stock Ownership Plan (the “401(k) plan”). The Corporation’s contribution is determined by the Compensation and Benefits Committee of the Board of Directors. Total expenses related to contributions to the 401(k) plan were $16 million , $14 million , and $14 million in 2018 , 2017 , and 2016

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The current and deferred amounts of income tax expense were as follows: Years Ended December 31, 2018 2017 2016 ($ in Thousands) Current Federal $ 20,246 $ 76,525 $ 73,781 State 12,593 11,576 2,885 Total current 32,839 88,101 76,666 Deferred Federal 34,941 19,755 3,338 State 12,006 1,647 7,318 Total deferred 46,947 21,402 10,656 Total income tax expense $ 79,786 $ 109,503 $ 87,322 Temporary differences between the amounts reported in the financial statements and the tax bases of assets and liabilities resulted in deferred taxes. Deferred tax assets and liabilities at December 31, 2018 and 2017 were as follows: 2018 2017 ($ in Thousands) Deferred tax assets Allowance for loan losses $ 61,143 $ 66,377 Allowance for other losses 8,304 7,095 Accrued liabilities 3,736 3,884 Deferred compensation 24,754 20,015 Benefit of tax loss and credit carryforwards 10,126 8,438 Nonaccrual interest 1,666 1,619 Net unrealized losses on available-for-sale securities 25,731 15,968 Net unrealized losses on pension and postretirement benefits 16,640 9,928 Other 1,916 4,435 Total deferred tax assets 154,015 137,759 Valuation allowance for deferred tax assets (251 ) (269 ) Total deferred tax assets after valuation allowance $ 153,764 $ 137,490 Deferred tax liabilities Prepaid expenses $ 61,250 $ 49,695 Goodwill 20,178 19,144 Mortgage banking activities 17,428 10,949 Deferred loan fee income 11,892 11,467 State deferred taxes 518 2,001 Lease financing 410 535 Bank premises and equipment 18,655 5,063 Purchase accounting 12,414 5,015 Other 684 304 Total deferred tax liabilities $ 143,429 $ 104,173 Net deferred tax assets $ 10,335 $ 33,317 At December 31, 2018 , the valuation allowance for deferred tax assets of approximately $ 251,000 was related to the deferred tax benefit of specific federal tax loss carryforwards of $3 million from the acquisition of Whitnell, while at December 31, 2017 , the valuation allowance for deferred tax assets of approximately $ 269,000 was related to the deferred tax benefit of specific federal tax loss carryforwards of $3 million from the acquisition of Whitnell. The changes in the valuation allowance related to net operating losses for 2018 and 2017 were as follows: 2018 2017 ($ in Thousands) Valuation allowance for deferred tax assets, beginning of year $ (269 ) $ — (Increase) decrease in current year 18 (269 ) Valuation allowance for deferred tax assets, end of year $ (251 ) $ (269 ) At December 31, 2018 , the Corporation had state net operating loss carryforwards of $120 million (of which $56 million was acquired from various acquisitions) that will begin expiring in 2031 . The Corporation acquired Bank Mutual in February 2018, which had federal and state net operating loss carryforwards at the time of acquisition of $5 million and $51 million , respectively. As a result of the change in control, Section 382 of the Internal Revenue Code places an annual limitation on the use of the subsidiary's net operating loss carryforwards. The Corporation does not believe these limitations will limit the usage of the acquired net operating losses. At December 31, 2018 , the Corporation had state net operating loss carryforwards from the Bank Mutual acquisition of $42 million . Those state carryforwards, if unused, expire in calendar years 2031 through 2039 . The acquisition also included AMT credit carryforwards of $1 million . The Corporation expects these credits to be refunded upon the filing of the 2018 federal income tax returns and has therefore included the credit as an income tax receivable at December 31, 2018 . The effective income tax rate differs from the statutory federal tax rate. The major reasons for this difference were as follows: 2018 2017 2016 Federal income tax rate at statutory rate 21.0 % 35.0 % 35.0 % Increases (decreases) resulting from: Tax-exempt interest and dividends (2.6 )% (4.1 )% (4.8 )% State income taxes (net of federal benefit) 3.7 % 2.9 % 2.5 % Bank owned life insurance (0.7 )% (1.7 )% (1.7 )% Tax effect of tax credits and benefits, net of related expenses (0.7 )% (0.7 )% (1.0 )% Tax reserve adjustments / settlements 1.5 % (1.2 )% 0.3 % Net tax benefit from stock-based compensation (0.5 )% (1.3 )% (0.4 )% Tax Act impact on deferred remeasurement — % 3.5 % — % Tax planning in response to the Tax Act (3.6 )% — % — % FDIC premium 0.9 % — % — % Other 0.3 % (0.1 )% 0.5 % Effective income tax rate 19.3 % 32.3 % 30.4 % Included in the Corporation's income tax expense as of December 31, 2018 is a tax benefit totaling $15 million relating to tax planning strategies implemented in response to the Tax Act. Also included in the Corporation's income tax expense as of December 31, 2018 is tax expense from the settlement of the Minnesota Supreme Court Case and open Minnesota Department of Revenue examinations totaling $9 million . Savings banks acquired by the Corporation in 1997 and 2004 qualified under provisions of the Internal Revenue Code that permitted them to deduct from taxable income an allowance for bad debts that differed from the provision for such losses charged to income for financial reporting purposes. Accordingly, no provision for income taxes has been made for $100 million of retained income at December 31, 2018 . If income taxes had been provided, the deferred tax liability would have been approximately $25 million . Management does not expect this amount to become taxable in the future; therefore, no provision for income taxes has been made. The Corporation and its subsidiaries file income tax returns in the U.S. federal jurisdiction and various state jurisdictions. The Corporation’s federal income tax returns are open and subject to examination from the 2015 tax return year and forward. The years open to examination by state and local government authorities varies by jurisdiction. A reconciliation of the beginning and ending amount of unrecognized tax benefits was as follows: 2018 2017 ($ in Millions) Balance at beginning of year $ 4 $ 10 Subtractions for tax positions related to prior years — (5 ) Subtractions for settlements with tax authorities (3 ) (1 ) Additions for tax positions related to current year 1 — Balance at end of year $ 2 $ 4 At December 31, 2018 and 2017 , the total amounts of unrecognized tax benefits that, if recognized, would affect the effective tax rate were $1 million and $3 million , respectively. The Corporation recognizes interest and penalties accrued related to unrecognized tax benefits in the income tax expense line of the consolidated statements of income. Interest and penalty benefits were $1 million at both December 31, 2018 and December 31, 2017 . Accrued interest and penalties were negligible at December 31, 2018 compared to $1 million at December 31, 2017

Derivative and Hedging Activiti

Derivative and Hedging Activities	12 Months Ended
	Dec. 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 Corporation 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. Federal regulations require the Corporation to clear all LIBOR interest rate swaps through a clearing house ("centrally cleared"), if possible. Securities are often pledged as collateral for centrally cleared interest rate swaps and derivatives. The Corporation pledged $36 million of investment securities as collateral at December 31, 2018 , and pledged $24 million of investment securities as collateral at December 31, 2017 . Cash is often pledged as collateral for interest rate swaps and derivatives that are not centrally cleared. At December 31, 2018 , the Corporation posted $1 million cash collateral for the margin compared to $22 million at December 31, 2017 . See Note 17 for fair value information and disclosures and see Note 1 for the Corporation's accounting policy for derivative and hedging activities. 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 markets, net, and typically include interest rate-related instruments (swaps and caps), foreign currency exchange forwards, and commodity contracts. See Note 14 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: December 31, 2018 December 31, 2017 ($ in Thousands) Notional Amount Fair Value Balance Sheet Category Notional Amount Fair Balance Sheet Derivatives not designated as hedging instruments Interest rate-related instruments — customer and mirror $ 2,707,204 $ 52,796 Trading assets $ 2,183,687 $ 28,494 Trading assets Interest rate-related instruments — customer and mirror 2,707,204 (52,653 ) Trading liabilities 2,183,687 (28,035 ) Trading liabilities Foreign currency exchange forwards 117,879 721 Trading assets 124,851 2,495 Trading assets Foreign currency exchange forwards 69,153 (675 ) Trading liabilities 118,094 (2,339 ) Trading liabilities Commodity contracts 331,727 35,426 Trading assets 457,868 38,686 Trading assets Commodity contracts 315,861 (34,340 ) Trading liabilities 457,108 (37,286 ) Trading liabilities Interest rate lock commitments (mortgage) 191,222 2,208 Other assets 222,736 1,538 Other assets Forward commitments (mortgage) 139,984 (2,072 ) Other liabilities 164,567 (313 ) Other liabilities Purchased options (time deposit) 11,185 109 Other assets 31,063 1,175 Other assets Written options (time deposit) 11,185 (109 ) Other liabilities 31,063 (1,175 ) Other liabilities Derivatives designated as hedging instruments Interest rate products 500,000 (40 ) Other liabilities — — — 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) December 31, 2018 Loans and investment securities available for sale (a) $ 499,498 $ (502 ) Total $ 499,498 $ (502 ) (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 December 31, 2018, the amortized cost basis of the closed portfolios used in these hedging relationships was $1.1 billion ; the negative cumulative basis adjustments associated with these hedging relationships was approximately $502,000 ; and the amounts of the designated hedged items were $500 million . The table below identifies the effect of fair value hedge accounting on the Corporation's statement of income during the twelve months ended December 31, 2018 : Location and Amount of Gain or (Loss) Recognized in Income on Fair Value and Cash Flow Hedging Relationships Year Ended December 31, 2018 Year Ended December 31, 2017 ($ 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 (a) $ (1,325 ) $ — $ — $ — 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 (502 ) — — — Derivatives designated as hedging instruments (a) (823 ) — — — (a) Includes net settlements on the derivatives The table below identifies the effect of derivatives not designated as hedging instruments on the Corporation's statement of income during the twelve months ended December 31, 2018 : Income Statement Category of Gain / (Loss) Recognized in Income For the Year Ended December 31, ($ in Thousands) 2018 2017 Derivative Instruments Interest rate-related instruments — customer and mirror, net Capital market fees, net $ (316 ) $ (24 ) Interest rate lock commitments (mortgage) Mortgage banking, net 670 1,332 Forward commitments (mortgage) Mortgage banking, net (1,759 ) (3,221 ) Foreign currency exchange forwards Capital market fees, net (110 ) 97 Commodity contracts Capital market fees, net (314 ) 647

Balance Sheet Offsetting

Balance Sheet Offsetting	12 Months Ended
	Dec. 31, 2018
Offsetting [Abstract]
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 13 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 8 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 of recognized assets Gross amounts not offset in the balance sheet ($ in Thousands) Gross amounts offset in the balance sheet Net amounts presented in the balance sheet Derivative liability available for offset Collateral received Net amount Derivative assets: (a) December 31, 2018 $ 65,596 $ — $ 65,596 $ (22,873 ) $ (41,879 ) $ 843 December 31, 2017 29,503 — 29,503 (16,140 ) (13,234 ) 129 Gross amounts of recognized liabilities Gross amounts not offset in the balance sheet ($ in Thousands) Gross amounts offset in the balance sheet Net amounts presented in the balance sheet Derivative asset available for offset Collateral pledged Net amount Derivative liabilities (b) December 31, 2018 $ 22,951 $ — $ 22,951 $ (22,873 ) $ (63 ) $ 16 December 31, 2017 37,164 — 37,164 (16,140 ) (20,662 ) 362 (a) Includes interest and commodity instrument assets. (b) Includes interest and commodity instrument liabilities.

Commitments, Off-Balance Sheet

Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities	Note 15 Commitments, Off-Balance Sheet Arrangements, and Legal Proceedings 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 13 ). The following is a summary of lending-related commitments: 2018 2017 ($ in Thousands) Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale (a) (b) $ 8,720,293 $ 8,027,187 Commercial letters of credit (a) 7,599 11,886 Standby letters of credit (c) 255,904 235,361 (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 December 31, 2018 and 2017 . (b) Interest rate lock commitments to originate residential mortgage loans held for sale are considered derivative instruments and are disclosed in Note 13 . (c) The Corporation has established a liability of $2 million at both December 31, 2018 and December 31, 2017 , respectively, 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 $24 million at both December 31, 2018 and December 31, 2017 , respectively, and is included in accrued expenses and other liabilities on the consolidated balance sheets. See Note 1 for the Corporation’s accounting policy on the allowance for unfunded commitments. See Note 4 for additional information on the allowance for unfunded commitments. 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 13 . 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 qualified affordable housing projects, federal and state historic projects, and new market projects for the purpose of community reinvestment and obtaining tax credits and other tax benefits. Return on the Corporation's investment in these projects comes in the form of the tax credits and tax losses that pass through to the Corporation. The aggregate carrying value of these investments at December 31, 2018 , was $136 million , compared to $147 million at December 31, 2017 , included in investment in unconsolidated subsidiaries on the consolidated balance sheets. The Corporation utilizes the proportional amortization method to account for investments in qualified affordable housing projects. Under the proportional amortization method, the Corporation amortizes the initial cost of the investment in proportion to the tax credits and other tax benefits. The Corporation recognized additional income tax expense attributable to the amortization of investments in qualified affordable housing projects of $17 million , $8 million , and $3 million during the years ended December 31, 2018 , 2017 , and 2016 , respectively. The Corporation's remaining investment in qualified affordable housing projects accounted for under the proportional amortization method totaled $132 million at December 31, 2018 and $141 million at December 31, 2017 . The Corporation’s unfunded equity contributions relating to investments in qualified affordable housing, federal and state historic projects, and new market projects is recorded in accrued expenses and other liabilities on the consolidated balance sheets. The Corporation’s remaining unfunded equity contributions totaled $51 million and $93 million at December 31, 2018 and 2017 , respectively. During the years ended December 31, 2018 and 2017 , the Corporation did not record any impairment related to qualified affordable housing investments. The Corporation has principal investment commitments to provide capital-based financing to private and public companies through either direct investment in specific companies or through investment funds and partnerships. The timing of future cash requirements to fund such principal investment 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 Corporation also invests in loan pools that support CRA loans. The timing of future cash requirements to fund these pools is dependent upon loan demand, which can vary over time. The aggregate carrying value of these investments at December 31, 2018 , was $25 million , compared to $23 million at December 31, 2017 , included in investment in unconsolidated subsidiaries on the consolidated balance sheets. 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 the Bank. The lawsuit claimed 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 sought 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 appealed the District Court’s summary judgment decision to the Eighth Circuit Court of Appeals. On January 10, 2019, the Eighth Circuit Court of Appeals affirmed the decision of the Circuit Court. As a result, and pursuant to a settlement agreement approved by the District Court on January 23, 2018, this matter was fully and finally resolved without any material impact on the Bank. Regulatory Matters 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 the Corporation's 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 $2 million and $1 million during the years ended December 31, 2018 and 2017 , respectively. The loss reimbursement and settlement claims paid for the years ended December 31, 2018 and 2017 , respectively, were negligible. Make whole requests during 2017 and 2018 generally arose from loans sold during the period of January 1, 2012 to December 31, 2018 , which totaled $11.1 billion at the time of sale, and consisted primarily of loans sold to GSEs. As of December 31, 2018 , approximately $7.3 billion of these sold loans remain outstanding. The balance in the mortgage repurchase reserve at the balance sheet date reflects the estimated amount of potential loss the Corporation could incur from repurchasing a loan, as well as loss reimbursements, indemnifications, and other settlement resolutions. The following summarizes the changes in the mortgage repurchase reserve for the years ended as follows: 2018 2017 ($ in Thousands) Balance at beginning of year $ 987 $ 900 Repurchase provision expense 345 246 Adjustments to provision expense (450 ) — Charge offs, net (218 ) (159 ) Amount recorded at acquisition 88 — Balance at end of year $ 752 $ 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 December 31, 2018 and December 31, 2017 , there were approximately $47 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 December 31, 2018 and December 31, 2017 , there were $57 million and $73 million

Parent Company Only Financial I

Parent Company Only Financial Information	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Parent Company Only Financial Information	Parent Company Only Financial Information Presented below are condensed financial statements for the Parent Company: BALANCE SHEETS December 31, 2018 2017 ($ in Thousands) Assets Cash and due from banks $ 16,245 $ 25,544 Interest-bearing deposits in other financial institutions 38,374 121,333 Investment securities available for sale, at fair value — 11,645 Notes and interest receivable from subsidiaries 453,615 301,378 Investments in and receivable due from subsidiaries 3,787,574 3,320,090 Other assets 47,448 51,466 Total assets $ 4,343,256 $ 3,831,456 Liabilities and Stockholders' Equity Commercial paper $ 45,423 $ 67,467 Senior notes, at par 250,000 250,000 Subordinated notes, at par 250,000 250,000 Long-term funding capitalized costs (2,043 ) (2,718 ) Total long-term funding 497,957 497,282 Accrued expenses and other liabilities 18,988 29,264 Total liabilities 562,368 594,013 Preferred equity 256,716 159,929 Common equity 3,524,171 3,077,514 Total stockholders’ equity 3,780,888 3,237,443 Total liabilities and stockholders’ equity $ 4,343,256 $ 3,831,456 STATEMENTS OF INCOME For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Income Dividends from subsidiaries $ 336,000 $ 213,000 $ 188,000 Interest income on notes receivable from subsidiaries 12,199 4,175 — Other income 994 1,763 4,669 Total income 349,193 218,938 192,669 Expense Interest expense on short and long-term funding 18,355 18,464 21,901 Other expense 11,736 6,927 4,289 Total expense 30,091 25,391 26,190 Income before income tax expense and equity in undistributed net income of subsidiaries 319,102 193,547 166,479 Income tax expense 4,176 4,768 3,468 Income before equity in undistributed net income of subsidiaries 314,926 188,779 163,011 Equity in undistributed net income of subsidiaries 18,636 40,485 37,263 Net income 333,562 229,264 200,274 Preferred stock dividends 10,784 9,347 8,903 Net income available to common equity $ 322,779 $ 219,917 $ 191,371 STATEMENTS OF CASH FLOWS For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Cash Flows from Operating Activities Net income $ 333,562 $ 229,264 $ 200,274 Adjustments to reconcile net income to net cash provided by operating activities: (Increase) decrease in equity in undistributed net income (loss) of subsidiaries (18,636 ) (40,485 ) (37,263 ) (Gain) loss on sales of investment securities, net of impairment write-downs — — (466 ) (Gain) loss on sales of assets, net — (88 ) (793 ) Net change in other assets and other liabilities (92,366 ) (9,589 ) 19,708 Net cash provided by operating activities 222,562 179,102 181,460 Cash Flows from Investing Activities Proceeds from sales of investment securities 827 2,618 47,719 Net increase in notes receivable from subsidiaries (139,317 ) (300,000 ) — Net (increase) decrease in loans 2,210 1,058 2,211 Net cash provided by (used in) investing activities (136,280 ) (296,324 ) 49,930 Cash Flows from Financing Activities Net increase (decrease) in commercial paper (22,044 ) (34,221 ) 33,710 Repayment of long-term funding — — (430,000 ) Proceeds from issuance of common stock for stock-based compensation plans 18,408 27,619 21,748 Proceeds from issuance of preferred stock 97,315 — 97,066 Redemption of preferred stock — — (58,903 ) Purchase of preferred stock (537 ) — (1,248 ) Common stock warrants exercised (1 ) — — Purchase of common stock returned to authorized but unissued (33,075 ) (37,031 ) (20,007 ) Issuance of Treasury Stock for Acquisition 91,296 — — Purchase of treasury stock (213,598 ) (9,290 ) (5,074 ) Cash dividends on common stock (105,519 ) (76,417 ) (67,855 ) Cash dividends on preferred stock (10,784 ) (9,347 ) (8,903 ) Net cash used in financing activities (178,540 ) (138,687 ) (439,466 ) Net increase (decrease) in cash and cash equivalents (92,258 ) (255,909 ) (208,076 ) Cash and cash equivalents at beginning of year 146,877 402,786 610,862 Cash and cash equivalents at end of year $ 54,619 $ 146,877 $ 402,786

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 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). See Note 1 for the Corporation’s accounting policy for fair value measurements. 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 3 for additional disclosure regarding the Corporation’s investment securities. Residential Loans Held For Sale: Residential 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 is 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 related to changes in the underlying interest rate of the hedged item. These hedged interest rate swaps are classified as fair value hedges. See Note 13 for additional disclosure regarding the Corporation's fair value hedges. In addition, the Corporation offers interest rate-related instruments (swaps and caps) to service its 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 13 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 December 31, 2018 and 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 its 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 13 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, which are classified in Level 2 of the fair value hierarchy. See Note 13 for additional disclosures regarding the Corporation’s commodity contracts. 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. 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 December 31, 2018 and 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. The table below presents the Corporation’s financial instruments measured at fair value on a recurring basis as of December 31, 2018 and 2017 , aggregated by the level in the fair value hierarchy within which those measurements fall: Fair Value Hierarchy December 31, 2018 December 31, 2017 ($ in Thousands) Assets Investment securities available for sale U.S. Treasury securities Level 1 $ 999 $ 996 Residential mortgage-related securities FNMA / FHLMC Level 2 295,252 464,768 GNMA Level 2 2,128,531 1,913,350 Private-label Level 2 1,003 1,059 GNMA commercial mortgage-related securities Level 2 1,220,797 1,513,277 FFELP asset backed securities Level 2 297,360 145,176 Other equity securities Level 1 1,568 1,632 Other debt securities Level 2 3,000 3,188 Total investment securities available for sale Level 1 2,567 2,628 Total investment securities available for sale Level 2 3,945,943 4,040,818 Residential loans held for sale Level 2 64,321 85,544 Commercial loans held for sale Level 2 14,943 — Interest rate-related instruments Level 2 52,796 28,494 Foreign currency exchange forwards Level 2 721 2,495 Interest rate lock commitments to originate residential mortgage loans held for sale Level 3 2,208 1,538 Commodity contracts Level 2 35,426 38,686 Purchased options (time deposit) Level 2 109 1,175 Liabilities Interest rate-related instruments Level 2 $ 52,653 $ 28,035 Foreign currency exchange forwards Level 2 675 2,339 Forward commitments to sell residential mortgage loans Level 3 2,072 313 Commodity contracts Level 2 34,340 37,286 Written options (time deposit) Level 2 109 1,175 Interest rate products (designated as hedging instruments) Level 2 40 — The table below presents a rollforward of the balance sheet amounts for the years ended December 31, 2018 and 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) — (1,085 ) Balance December 31, 2018 $ — $ 140 (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 December 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 December 31, 2018 , the closing ratio was 84% . 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 13 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: Commercial 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 December 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 4 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 5 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: ($ in Thousands) Fair Value Hierarchy Fair Value Income Statement Category of Adjustment Recognized in Income December 31, 2018 Assets Impaired loans (a) Level 3 $ 26,191 Provision for credit losses (b) $ (14,521 ) Other real estate owned (c) Level 2 2,200 Foreclosure / OREO expense, net (1,545 ) Mortgage servicing rights Level 3 81,012 Mortgage banking, net 545 December 31, 2017 Assets Impaired loans (a) Level 3 $ 92,534 Provision for credit losses (b) $ (32,159 ) Other real estate owned (c) Level 2 2,604 Foreclosure / OREO expense, net (939 ) Mortgage servicing rights Level 3 64,387 Mortgage banking, net (175 ) (a) Represents individually evaluated impaired loans, net of the related allowance for loan losses. (b) Represents provision for credit losses on individually evaluated impaired loans. (c) If the fair value of the collateral exceeds the carrying amount of the asset, no charge off or adjustment is necessary, the asset is not considered to be carried at fair value, and is therefore not included in the table. 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: December 31, 2018 Valuation Technique Significant Unobservable Input Weighted Average Input Applied Mortgage servicing rights Discounted cash flow Discount rate 11% Mortgage servicing rights Discounted cash flow Constant prepayment rate 11% Impaired loans Appraisals / Discounted cash flow Collateral / Discount factor 40% 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: December 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 $ 507,187 $ 507,187 $ 483,666 $ 483,666 Interest-bearing deposits in other financial institutions Level 1 221,226 221,226 199,702 199,702 Federal funds sold and securities purchased under agreements to resell Level 1 148,285 148,285 32,650 32,650 Investment securities held to maturity Level 2 2,740,511 2,710,271 2,282,853 2,283,574 Investment securities available for sale Level 1 2,567 2,567 2,628 2,628 Investment securities available for sale Level 2 3,945,943 3,945,943 4,040,818 4,040,818 FHLB and Federal Reserve Bank stocks Level 2 250,534 250,534 165,331 165,331 Residential loans held for sale Level 2 64,321 64,321 85,544 85,544 Commercial loans held for sale Level 2 14,943 14,943 — — Loans, net Level 3 22,702,406 22,317,395 20,519,111 20,314,984 Bank and corporate owned life insurance Level 2 663,203 663,203 591,057 591,057 Derivatives (trading and other assets) Level 2 89,052 89,052 70,850 70,850 Derivatives (trading and other assets) Level 3 2,208 2,208 1,538 1,538 Financial liabilities Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts Level 3 $ 22,081,992 $ 22,081,992 $ 20,436,893 $ 20,436,893 Brokered CDs and other time deposits (a) Level 2 2,815,401 2,815,401 2,349,069 2,349,069 Short-term funding (b) Level 2 1,057,074 1,057,074 676,282 676,282 Long-term funding Level 2 3,469,982 3,492,174 3,397,450 3,411,368 Standby letters of credit (c) Level 2 2,482 2,482 2,402 2,402 Derivatives (trading and other liabilities) Level 2 87,817 87,817 68,835 68,835 Derivatives (trading and other liabilities) Level 3 2,072 2,072 313 313 (a) When the estimated fair value is less than the carrying value, the carrying value is reported as the fair value. (b) The carrying amount is a reasonable estimate of fair value for existing short-term funding. (c) The commitment on standby letters of credit was $256 million and $235 million at December 31, 2018 and 2017 , respectively. See Note 15

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2018
Regulatory Capital Requirements [Abstract]
Regulatory Matters	Regulatory Matters Restrictions on Cash and Due From Banks The Corporation’s bank subsidiary is required to maintain certain vault cash and reserve balances with the Federal Reserve Bank to meet specific reserve requirements. These requirements approximated $94 million at December 31, 2018 . Regulatory Capital Requirements The Corporation and its subsidiary bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possible additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Corporation’s financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Corporation must meet specific capital guidelines that involve quantitative measures of the Corporation’s assets, liabilities, and certain off-balance sheet items as calculated under regulatory accounting practices. The Corporation’s capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. Quantitative measures established by regulation to ensure capital adequacy require the Corporation to maintain minimum amounts and ratios (set forth in the table below) of total and Common equity Tier 1 capital (as defined in the regulations) to risk-weighted assets (as defined), and of Tier 1 capital (as defined) to average assets (as defined). Management believes, as of December 31, 2018 and 2017 , that the Corporation meets all capital adequacy requirements to which it is subject. For additional information on the capital requirements applicable for the Corporation and the Bank, please see Part I, Item 1. As of December 31, 2018 and 2017 , the most recent notifications from the Office of the Comptroller of the Currency and the Federal Deposit Insurance Corporation categorized the subsidiary bank as well capitalized under the regulatory framework for prompt corrective action. To be categorized as well capitalized, the subsidiary bank must maintain minimum ratios as set forth in the table. There are no conditions or events since that notification that management believes have changed the institution’s category. The actual capital amounts and ratios of the Corporation and its significant subsidiary are presented below. No deductions from capital were made for interest rate risk in 2018 or 2017 . Actual For Capital Adequacy Purposes To Be Well Capitalized Under Prompt Corrective Action Provisions (b) Amount Ratio (a) Amount Ratio (a) Amount Ratio (a) ($ in Thousands) As of December 31 , 2018 Associated Banc-Corp Total capital $ 3,216,575 13.47 % $ 1,910,022 ≥ 8.00 % Tier 1 capital 2,705,939 11.33 % 1,432,517 ≥ 6.00 % Common equity Tier 1 capital 2,449,721 10.26 % 1,074,388 ≥ 4.50 % Leverage 2,705,939 8.48 % 1,276,624 ≥ 4.00 % Associated Bank, N.A. Total capital $ 2,909,064 12.23 % $ 1,903,155 ≥ 8.00 % $ 2,378,944 ≥ 10.00 % Tier 1 capital 2,646,705 11.13 % 1,427,367 ≥ 6.00 % 1,903,155 ≥ 8.00 % Common equity Tier 1 capital 2,446,782 10.29 % 1,070,525 ≥ 4.50 % 1,546,314 ≥ 6.50 % Leverage 2,646,705 8.31 % 1,274,380 ≥ 4.00 % 1,592,976 ≥ 5.00 % As of December 31 , 2017 Associated Banc-Corp Total capital $ 2,848,851 13.22 % $ 1,723,557 ≥ 8.00 % Tier 1 capital 2,331,245 10.82 % 1,292,668 ≥ 6.00 % Common equity Tier 1 capital 2,171,508 10.08 % 969,501 ≥ 4.50 % Leverage 2,331,245 8.02 % 1,162,929 ≥ 4.00 % Associated Bank, N.A. Total capital $ 2,625,945 12.24 % $ 1,716,910 ≥ 8.00 % $ 2,146,138 ≥ 10.00 % Tier 1 capital 2,357,354 10.98 % 1,287,683 ≥ 6.00 % 1,716,910 ≥ 8.00 % Common equity Tier 1 capital 2,157,354 10.05 % 965,762 ≥ 4.50 % 1,394,989 ≥ 6.50 % Leverage 2,357,354 8.13 % 1,159,959 ≥ 4.00 % 1,449,948 ≥ 5.00 % (a) When fully phased-in on January 1, 2019, the Basel III capital rules include a capital conservation buffer of 2.5% that is added on top of each of the minimum risk-based capital ratios noted above. Implementation began on January 1, 2016 at the 0.625% level and has increased each subsequent January 1, until it reaches 2.5% on January 1, 2019.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share See Note 1 for the Corporation’s accounting policy on earnings per common share. Presented below are the calculations for basic and diluted earnings per common share: For the Years Ended December 31, 2018 2017 2016 ($ in Thousands, Except Per Share Data) Net income $ 333,562 $ 229,264 $ 200,274 Preferred stock dividends (10,784 ) (9,347 ) (8,903 ) Net income available to common equity 322,779 219,917 191,371 Common shareholder dividends (104,981 ) (75,967 ) (67,100 ) Unvested share-based payment awards (537 ) (450 ) (755 ) Undistributed earnings 217,260 143,500 123,516 Undistributed earnings allocated to common shareholders 216,199 142,593 122,205 Undistributed earnings allocated to unvested share-based payment awards 1,060 907 1,311 Undistributed earnings $ 217,260 $ 143,500 $ 123,516 Basic Distributed earnings to common shareholders $ 104,981 $ 75,967 $ 67,100 Undistributed earnings allocated to common shareholders 216,199 142,593 122,205 Total common shareholders earnings, basic $ 321,181 $ 218,560 $ 189,305 Diluted Distributed earnings to common shareholders $ 104,981 $ 75,967 $ 67,100 Undistributed earnings allocated to common shareholders 216,199 142,593 122,205 Total common shareholders earnings, diluted $ 321,181 $ 218,560 $ 189,305 Weighted average common shares outstanding $ 167,345 $ 150,877 $ 148,769 Effect of dilutive common stock awards 1,985 2,038 1,192 Effect of dilutive common stock warrants 402 732 — Diluted weighted average common shares outstanding $ 169,732 $ 153,647 $ 149,961 Basic earnings per common share $ 1.92 $ 1.45 $ 1.27 Diluted earnings per common share $ 1.89 $ 1.42 $ 1.26 Anti-dilutive common stock options of approximately 2 million at the year ended December 31, 2018 and 1 million at the years ended December 31, 2017 and 2016 were excluded from the earnings per common share calculation. Warrants to purchase approximately 4 million

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Reporting	Note 20 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 Note 1 , with certain exceptions. The more significant of these exceptions are described herein. The reportable segment results are presented based on the Corporation's internal management accounting process. 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. Additionally, the information presented is not indicative of how the segments would perform if they operated as independent entities. To determine financial performance of each segment, the Corporation allocates funds transfer pricing ("FTP") assignments, the provision for credit losses, certain noninterest expenses, income tax, and equity to each segment. Allocation methodologies are subject to periodic adjustment as the internal management accounting system is revised, the interest rate environment evolves, and business or product lines within the segments change. Also, because the development and application of these methodologies is a dynamic process, the financial results presented may be periodically reviewed. The Corporation allocates net interest income using an internal FTP methodology that charges users of funds (assets) and credits providers of funds (liabilities, primarily deposits) based on the maturity, prepayment, and / or re-pricing characteristics of the assets and liabilities. The net effect of this allocation is offset in the Risk Management and Shared Services segment to ensure the consolidated total reflects the Corporation's net interest income. The net FTP allocation is reflected as net intersegment interest income (expense) in the accompanying tables. 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 Note 1 to assess the overall appropriateness of the allowance for loan losses and the allowance for unfunded commitments. 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 expenses 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, the net tax residual is recorded in Risk Management and Shared Services. 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). A description of each business segment is presented below. Corporate and Commercial Specialty: The Corporate and Commercial Specialty segment serves a wide range of customers including larger businesses, developers, not-for-profits, municipalities, and financial institutions. In serving this segment we compete based on an in-depth understanding of our customers’ financial needs, the ability to match market competitive solutions to those needs, and the highest standards of relationship and service excellence in the delivery of these services. Delivery of services is provided through our corporate and commercial units, our commercial real estate unit, as well as our specialized industries and commercial financial services units. Within this segment we provide the following products and services: (1) lending solutions, such as commercial loans and lines of credit, commercial real estate financing, construction loans, letters of credit, leasing, asset based lending, and, for our larger clients, loan syndications; (2) deposit and cash management solutions such as commercial checking and interest-bearing deposit products, cash vault and night depository services, liquidity solutions, payables and receivables solutions, and information services, and (3) specialized financial services such as interest rate risk management, foreign exchange solutions, and commodity hedging. Community, Consumer, and Business: The Community, Consumer, and Business segment serves individuals, as well as small and mid-sized businesses. In serving this segment we compete based on providing a broad range of solutions to meet the needs of our customers in their entire financial lifecycle, convenient access to our services through multiple channels such as branches, phone based services, online and mobile banking, and a relationship based business model which assists our customers in navigating any changes and challenges in their financial circumstances. Delivery of services is provided through our various consumer banking, community banking, and private client units. Within this segment we provide the following products and services: (1) lending solutions such as residential mortgages, home equity loans and lines of credit, personal and installment loans, real estate financing, business loans, and business lines of credit; (2) deposit and transactional solutions such as checking, credit, debit and pre-paid cards, online banking and bill pay, and money transfer services; (3) investable funds solutions such as savings, money market deposit accounts, IRA accounts, certificates of deposit, fixed and variable annuities, full-service, discount and on-line investment brokerage; investment advisory services; trust and investment management accounts; (4) insurance and benefits related products and services; and (5) fiduciary services such as administration of pension, profit-sharing and other employee benefit plans, fiduciary and corporate agency services, and institutional asset management. Risk Management and Shared Services: The Risk Management and Shared Services segment includes Corporate Risk Management, Credit Administration, Finance, Treasury, Operations and Technology, which are key shared functions. The segment also includes Parent Company activity, intersegment eliminations and 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). The earning assets within this segment include the Corporation’s investment portfolio, and capital includes both allocated and any remaining unallocated capital. In addition, the segment includes certain unallocated expenses related to Bank Mutual's shared services and operations prior to system conversion in late June 2018. All acquisition costs are included in this segment. Information about the Corporation’s segments is presented below: Corporate and Commercial Specialty For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 457,613 $ 360,789 $ 312,982 Net intersegment interest income (expense) (56,356 ) (3,737 ) 15,621 Segment net interest income 401,258 357,051 328,603 Noninterest income 52,321 52,297 47,776 Total revenue 453,578 409,348 376,379 Credit provision (a) 44,592 42,298 50,397 Noninterest expense 160,399 156,890 148,493 Income (loss) before income taxes 248,587 210,160 177,489 Income tax expense (benefit) 47,850 71,655 59,261 Net income $ 200,737 $ 138,505 $ 118,228 Return on average allocated capital (ROCET1) (b) 16.60 % 12.39 % 11.04 % Average earning assets $ 11,852,662 $ 10,820,998 $ 10,178,813 Average loans 11,841,818 10,811,827 10,169,300 Average deposits 8,112,430 6,938,913 5,904,238 Average allocated capital (CETI) (b) 1,209,558 1,117,761 1,070,598 Allocated goodwill 524,525 428,000 428,000 Community, Consumer, and Business For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 357,245 $ 316,008 $ 306,913 Net intersegment interest income (expense) 87,737 45,353 43,639 Segment net interest income 444,982 361,361 350,551 Noninterest income 295,647 266,250 277,942 Total revenue 740,629 627,611 628,493 Credit provision (a) 20,083 20,400 24,185 Noninterest expense 542,117 490,908 502,285 Income (loss) before income taxes 178,429 116,303 102,023 Income tax expense (benefit) 37,476 40,706 35,708 Net income $ 140,953 $ 75,597 $ 66,315 Return on average allocated capital (ROCET1) (b) 21.57 % 12.89 % 10.53 % Average earning assets $ 10,336,105 $ 9,456,549 $ 9,309,028 Average loans 10,332,665 9,452,253 9,307,723 Average deposits 13,623,852 11,711,407 11,451,759 Average allocated capital (CETI) (b) 653,354 586,417 629,540 Allocated goodwill 644,498 548,238 543,951 Risk Management and Shared Services For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 64,722 $ 64,423 $ 87,378 Net intersegment interest income (expense) (31,382 ) (41,615 ) (59,259 ) Segment net interest income 33,341 22,808 28,119 Noninterest income 7,600 14,133 27,165 Total revenue 40,941 36,941 55,284 Credit provision (a) (64,675 ) (36,698 ) (4,582 ) Noninterest expense (c) 119,283 61,335 51,782 Income (loss) before income taxes (13,668 ) 12,304 8,084 Income tax expense (benefit) (5,540 ) (2,858 ) (7,647 ) Net income $ (8,128 ) $ 15,162 $ 15,731 Return on average allocated capital (ROCET1) (b) (3.19 )% 1.44 % 2.84 % Average earning assets $ 7,861,026 $ 6,722,337 $ 6,538,820 Average loans 543,814 328,303 173,644 Average deposits 2,335,768 3,273,282 3,649,775 Average allocated capital (CETI) (b) 592,006 405,281 240,253 Allocated goodwill — — — Consolidated Total For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 879,580 $ 741,220 $ 707,273 Net intersegment interest income (expense) — — — Segment net interest income 879,580 741,220 707,273 Noninterest income 355,568 332,680 352,883 Total revenue 1,235,148 1,073,900 1,060,156 Credit provision (a) — 26,000 70,000 Noninterest expense 821,799 709,133 702,560 Income (loss) before income taxes 413,349 338,767 287,596 Income tax expense (benefit) 79,786 109,503 87,322 Net income $ 333,562 $ 229,264 $ 200,274 Return on average allocated capital (ROCET1) (b) 13.15 % 10.43 % 9.86 % Average earning assets $ 30,049,793 $ 26,999,884 $ 26,026,661 Average loans 22,718,297 20,592,383 19,650,667 Average deposits 24,072,049 21,923,602 21,005,772 Average allocated capital (CETI) (b) 2,454,919 2,109,459 1,940,391 Allocated goodwill 1,169,023 976,239 971,951 (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. Average allocated capital represents average common equity Tier 1, as defined by the Federal Reserve. For segment reporting purposes, the ROCET1, a non-GAAP financial measure, reflects return on average allocated common equity Tier 1 (“CET1”). 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. (c) For the year ended December 31, 2018 , the Risk Management and Shared Services segment includes approximately $29 million of acquisition related costs within noninterest expense and approximately $2 million

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) The following table summarizes the components of accumulated other comprehensive income (loss) at December 31, 2018 , 2017 , and 2016 respectively, including changes during the years then ended as well as any reclassifications out of accumulated other comprehensive income (loss): Investments Securities Available For Sale Defined Benefit Pension and Postretirement Obligations Accumulated Other Comprehensive Income (Loss) ($ in Thousands) Balance, December 31, 2015 $ 459 $ (33,075 ) $ (32,616 ) Other comprehensive income (loss) before reclassifications (17,900 ) (6,141 ) (24,041 ) Amounts reclassified from accumulated other comprehensive income (loss) Investment securities losses (gains), net (9,316 ) — (9,316 ) Personnel expense — (73 ) (73 ) Other expense — 3,874 3,874 Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (5,887 ) — (5,887 ) Income tax (expense) benefit 12,565 815 13,380 Net other comprehensive income (loss) during period (20,538 ) (1,525 ) (22,063 ) Balance, December 31, 2016 $ (20,079 ) $ (34,600 ) $ (54,679 ) Other comprehensive income (loss) before reclassifications (27,040 ) 14,273 (12,767 ) Amounts reclassified from accumulated other comprehensive income (loss) Personnel expense — (148 ) (148 ) Other expense — 2,282 2,282 Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (2,665 ) — (2,665 ) Income tax (expense) benefit 11,331 (6,112 ) 5,219 Net other comprehensive income (loss) during period (18,374 ) 10,295 (8,079 ) Balance, December 31, 2017 $ (38,453 ) $ (24,305 ) $ (62,758 ) Other comprehensive income (loss) before reclassifications (39,891 ) (28,612 ) (68,503 ) Amounts reclassified from accumulated other comprehensive income (loss) Investment securities losses (gains), net 1,985 — 1,985 Personnel expense — (148 ) (148 ) Other expense — 2,203 2,203 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) (572 ) — (572 ) Income tax (expense) benefit 9,791 6,767 16,558 Net other comprehensive income (loss) during period (37,189 ) (25,025 ) (62,214 ) Balance, December 31, 2018 $ (75,643 ) $ (49,330 ) $ (124,972 )

Revenues (Notes)

Revenues (Notes)	12 Months Ended
	Dec. 31, 2018
Revenue Recognition [Abstract]
Revenue from Contract with Customer [Text Block]	Note 22 Revenue Recognition On January 1, 2018, the Corporation adopted Topic 606 using the modified retrospective method. As stated in Note 1 , 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 the Corporation's 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 the Corporation's revenue by major source for the years ended December 31, 2018 , 2017 , and 2016 : Corporate and Commercial Specialty For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ — $ — $ — Service charges and deposit account fees 14,981 16,006 15,378 Card-based and loan fees (a) 1,343 1,163 740 Trust and asset management fees — — — Brokerage and advisory fees — — — Other revenue 685 772 (1,096 ) Noninterest Income (in-scope of Topic 606) $ 17,009 $ 17,941 $ 15,022 Noninterest Income (out-of-scope of Topic 606) 35,311 34,355 32,754 Total Noninterest Income $ 52,321 $ 52,297 $ 47,776 Community, Consumer, and Business For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ 89,472 $ 81,468 $ 80,795 Service charges and deposit account fees 51,025 48,344 51,047 Card-based and loan fees (a) 39,883 34,695 33,765 Trust and asset management fees 54,316 50,191 46,866 Brokerage and advisory fees 28,024 19,935 16,235 Other revenue 9,643 9,249 8,556 Noninterest Income (in-scope of Topic 606) $ 272,363 $ 243,883 $ 237,265 Noninterest Income (out-of-scope of Topic 606) 23,284 22,367 40,677 Total Noninterest Income $ 295,647 $ 266,250 $ 277,942 Risk Management and Share Services For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ 39 $ 6 $ — Service charges and deposit account fees 69 77 184 Card-based and loan fees (a) 98 23 22 Trust and asset management fees — — — Brokerage and advisory fees 222 — — Other revenue 283 245 158 Noninterest Income (in-scope of Topic 606) $ 712 $ 351 $ 364 Noninterest Income (out-of-scope of Topic 606) 6,889 13,783 26,801 Total Noninterest Income $ 7,600 $ 14,133 $ 27,165 Consolidated Total For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ 89,511 $ 81,474 $ 80,795 Service charges and deposit account fees 66,075 64,427 66,609 Card-based and loan fees (a) 41,325 35,881 34,527 Trust and asset management fees 54,316 50,191 46,867 Brokerage and advisory fees 28,246 19,935 16,235 Other revenue 10,611 10,267 7,617 Noninterest Income (in-scope of Topic 606) $ 290,084 $ 262,175 $ 252,651 Noninterest Income (out-of-scope of Topic 606) 65,483 70,505 100,232 Total Noninterest Income $ 355,568 $ 332,680 $ 352,883 (a) Loan fees are out-of-scope of Topic 606. During the first quarter of 2018, the Corporation acquired Bank Mutual which resulted in increased service charges and deposit account fees and card-based and loan fees. In addition, the Corporation acquired Whitnell & Co. during the fourth quarter of 2017 and Diversified and Anderson during 2018 which resulted in increased insurance commissions and fees, trust and asset management fees, and brokerage and advisory fees. Below is a listing of performance obligations for the Corporation's 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 (a) Card-based 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 the 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 and advisory fees Brokerage and advisory 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. (a) Loan fees are out-of-scope of Topic 606. Arrangements with Multiple Performance Obligations The Corporation's 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.

Recent Developments Recent Deve

Recent Developments Recent Developments Details (Notes)	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
Recent Developments	Note 23 Recent Developments On February 5, 2019, the Corporation's Board of Directors declared a regular quarterly cash dividend of $0.17 per common share, payable on March 15, 2019 to shareholders of record at the close of business on March 1, 2019. The Board of Directors also declared a regular quarterly cash dividend of $0.3828125 per depositary share on Associated Banc-Corp's 6.125% Series C Perpetual Preferred Stock, payable on March 15, 2019 to shareholders of record at the close of business on March 1, 2019. The Board of Directors also declared a regular quarterly cash dividend of $0.3359375 per depositary share on Associated's 5.375% Series D Perpetual Preferred Stock, payable on March 15, 2019 to shareholders of record at the close of business on March 1, 2019. The Board of Directors also declared a regular quarterly cash dividend of $0.3671875 per depositary share on Associated's 5.875% Series E Perpetual Preferred Stock, payable on March 15, 2019 to shareholders of record at the close of business on March 1, 2019. On February 5, 2019, the Board of Directors also authorized the repurchase of up to $100 million of Associated’s common stock. This repurchase authorization is in addition to the previously authorized repurchases. There remains approximately $111 million under the previous authorizations, such that there is now approximately $211 million authorized in the aggregate. Repurchases under such authorizations are subject to any necessary regulatory approvals and other limitations and may occur from time to time in open market purchases, block transactions, private transactions, accelerated share repurchases, or similar facilities.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Business and Basis of Financial Statement Presentation	Business Associated Banc-Corp (individually referred to herein as the "Parent" and together with all of its subsidiaries and affiliates, collectively referred to herein as the "Corporation") is a bank holding company headquartered in Wisconsin. The Corporation provides a full range of banking and related financial services to consumer and commercial customers through its network of bank and nonbank subsidiaries. The Corporation is subject to competition from other financial and non-financial institutions that offer similar or competing products and services. The Corporation is regulated by federal and state agencies and is subject to periodic examinations by those agencies. Basis of Financial Statement Presentation The consolidated financial statements include the accounts of the Parent Company and its wholly-owned subsidiaries. Investments in unconsolidated entities (none of which are considered to be variable interest entities in which the Corporation is the primary beneficiary) are accounted for using the cost method of accounting when the Corporation has determined that the cost method is appropriate. Investments not meeting the criteria for cost method accounting are accounted for using the equity method of accounting. Investments in unconsolidated entities are included in investment in unconsolidated subsidiaries on the consolidated balance sheets, and the Corporation’s share of income or loss is recorded in other noninterest income, while distributions in excess of the investment are asset gains (losses), net. All significant intercompany balances and transactions have been eliminated in consolidation.
Business Combinations	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 when there is a reasonable expectation about the amount and timing of such cash flows. If a reasonable expectation on the amount or timing of such cash flows can't be determined, accretion of the fair value discount for nonperforming loans will be recognized using the cost recovery method of accounting. For PCI loans, 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.
Revenue Recognition	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.
Investment Securities	Investment Securities Securities are classified as held to maturity or available for sale at the time of purchase. Investment securities classified as held to maturity, which management has the positive intent and ability to hold to maturity, are reported at amortized cost. Investment securities classified as available for sale, which management has the intent and ability to hold for an indefinite period of time, but not necessarily to maturity, are carried at fair value, with unrealized gains and losses, net of related deferred income taxes, included in stockholders’ equity as a separate component of other comprehensive income. Any decision to sell investment securities available for sale would be based on various factors, including, but not limited to, asset / liability management strategies, changes in interest rates or prepayment risks, liquidity needs, or regulatory capital considerations. Realized gains or losses on investment security sales (using specific identification method) are included in investment securities gains (losses), net, in the consolidated statements of income. Premiums and discounts are amortized or accreted into interest income over the estimated life (earlier of call date, maturity, or estimated life) of the related security, using a prospective method that approximates level yield. In certain situations, management may elect to transfer certain investment securities from the available for sale classification to the held to maturity classification. In such cases, the investment securities are reclassified at fair value at the time of transfer. Any unrealized gain or loss included in accumulated other comprehensive income (loss) at the time of transfer is retained therein and amortized over the remaining life of the investment security as an adjustment to yield. Declines in the fair value of investment securities (with certain exceptions for debt securities noted below) that are deemed to be other-than-temporary are charged to earnings as a realized loss, and a new cost basis for the investment security is established. In evaluating other-than-temporary impairment, management considers the length of time and extent to which the security has been in an unrealized loss position, changes in security ratings, the financial condition and near-term prospects of the issuer, as well as security and industry specific economic conditions. In addition, the Corporation considers the intent and ability to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in fair value in the near term. Declines in the fair value of debt securities below amortized cost are deemed to be other-than-temporary in circumstances where: (1) the Corporation has the intent to sell a security; (2) it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis; or (3) the Corporation does not expect to recover the entire amortized cost basis of the security. If the Corporation intends to sell a security or if it is more likely than not that the Corporation will be required to sell the security before recovery, an other-than-temporary impairment write-down is recognized in earnings equal to the difference between the security’s amortized cost basis and its fair value. If an entity does not intend to sell the security or it is more likely than not that it will not be required to sell the security before recovery, the other-than-temporary impairment write-down is separated into an amount representing credit loss, which is recognized in earnings, and an amount related to all other factors, which is recognized in other comprehensive income. Declines in value determined to be other-than-temporary are included in investment securities gains (losses), net, in the consolidated statements of income. See Note 3
Federal Home Loan Bank (FHLB) and Federal Reserve Bank Stocks	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. See Note 3
Loans Held for Sale	Loans Held for Sale 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. Effective January 1, 2017, management 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. The estimated fair value is based on what secondary markets are currently offering for portfolios with similar characteristics, which the Corporation classifies as a Level 2 fair value measurement. Commercial Loans Held for Sale:
Loans	Loans Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off are reported at their outstanding principal balances, net of any deferred fees and costs on originated loans. Origination fee income received on loans and amounts representing the estimated direct costs of origination are deferred and amortized to interest income over the life of the loan using the effective interest method. An allowance for loan losses is established for estimated credit losses in the loan portfolio. See Allowance for Loan Losses below for further policy discussion. See also Note 4 for additional information on loans. Nonaccrual Loans: 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. This determination is based on management's review of current information and other events regarding the borrowers’ ability to repay their obligations. 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. Interest income on loans is based on the principal balance outstanding computed using the effective interest method. The accrual of interest income for commercial loans is discontinued when there is a clear indication that the borrower’s cash flow may not be sufficient to meet payments as they become due, while the accrual of interest income for consumer loans is discontinued when loans reach specific delinquency levels. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. Loans are generally placed on nonaccrual status when contractually past due 90 days or more as to interest or principal payments, unless the loan is well secured and in the process of collection. Additionally, whenever management becomes aware of facts or circumstances that may adversely impact the collectability of principal or interest on loans, it is management’s practice to place such loans on a nonaccrual status immediately, rather than delaying such action until the loans become 90 days past due. When a loan is placed on nonaccrual status, previously accrued and uncollected interest is reversed, amortization of related deferred loan fees or costs is suspended, and income is recorded only to the extent that interest payments are subsequently received in cash and a determination has been made that the principal and interest of the loan is collectible. If collectability of the principal and interest is in doubt, payments received are applied to loan principal. While a loan is in nonaccrual status, some or all of the cash interest payments received may be treated as interest income on a cash basis as long as the remaining recorded investment in the loan (i.e., after charge off of identified losses, if any) is deemed to be fully collectible. The determination as to the ultimate collectability of the loan's remaining recorded investment must be supported by a current, well documented credit evaluation of the borrower’s financial condition and prospects for repayment, including consideration of the borrower’s sustained historical repayment performance and other relevant factors. A nonaccrual loan is returned to accrual status when all delinquent principal and interest payments become current in accordance with the terms of the loan agreement, the borrower has demonstrated a period of sustained repayment performance, and the ultimate collectability of the total contractual principal and interest is no longer in doubt. A sustained period of repayment performance generally would be a minimum of six months. See Note 4
Troubled Debt Restructurings (Restructured Loans)	Troubled Debt Restructurings (“Restructured Loans”): Loans are considered restructured loans if concessions have been granted to borrowers that are experiencing financial difficulty. The concessions granted generally involve the modification of terms of the loan, such as changes in payment schedule or interest rate, which generally would not otherwise be considered. Restructured loans can involve loans remaining on nonaccrual, moving to nonaccrual, or continuing on accrual status, depending on the individual facts and circumstances of the borrower. Nonaccrual restructured loans are included and treated with all other nonaccrual loans. In addition, all accruing restructured loans are reported as troubled debt restructurings, which are considered and accounted for as impaired loans. Generally, restructured loans remain on nonaccrual until the customer has attained a sustained period of repayment performance under the modified loan terms (generally a minimum of six months). However, performance prior to the restructuring, or significant events that coincide with the restructuring, are considered in assessing whether the borrower can meet the new terms and whether the loan should be returned to or maintained on accrual status. If the borrower’s ability to meet the revised payment schedule is not reasonably assured, the loan remains on nonaccrual status. See Note 4
Allowance for Loan Losses	Allowance for Loan Losses: The allowance for loan losses is a reserve for estimated credit losses on individually evaluated loans determined to be impaired as well as estimated credit losses inherent in the loan portfolio, and is based on quarterly evaluations of the collectability and historical loss experience of loans. Actual credit losses, net of recoveries, are deducted from the allowance for loan losses. A provision for loan losses, which is a charge against earnings, is recorded to bring the allowance for loan losses to a level that, in management’s judgment, is appropriate to absorb probable losses in the loan portfolio. The methodology applied by the Corporation, designed to assess the appropriateness of the allowance for loan losses, is based upon management’s ongoing review and grading of the loan portfolio into criticized loan categories (defined as specific loans warranting either specific allocation, or a criticized status of special mention, substandard, doubtful, or loss). The methodology also focuses on evaluation of several factors, including but not limited to: evaluation of facts and issues related to specific loans, management’s ongoing review and grading of the loan portfolio, consideration of historical loan loss and delinquency experience on each portfolio category, trends in past due and nonaccrual loans, the level of potential problem loans, the risk characteristics of the various classifications of loans, changes in the size and character of the loan portfolio, concentrations of loans to specific borrowers or industries, existing economic conditions, the fair value of underlying collateral, and other qualitative and quantitative factors which could affect potential credit losses. Because each of the criteria used is subject to change, the analysis of the allowance for loan losses is not necessarily indicative of the trend of future loan losses in any particular loan category. The total allowance for loan losses is available to absorb losses from any segment of the loan portfolio. When an individual loan is determined to be impaired, the allowance for loan losses attributable to the loan is allocated based on management’s estimate of the borrower’s ability to repay the loan given the availability of collateral, other sources of cash flows, as well as evaluation of legal options available to the Corporation. The amount of impairment is measured based upon the present value of expected future cash flows discounted at the loan’s effective interest rate, the fair value of the underlying collateral less applicable selling costs, or the observable market price of the loan. If foreclosure is probable or the loan is collateral dependent, impairment is measured using the fair value of the loan’s collateral, less costs to sell. Large groups of homogeneous loans, such as residential mortgage, home equity, and other consumer, are collectively evaluated for impairment. Management believes that the level of the allowance for loan losses is appropriate. While management uses currently available information to recognize losses on loans, future adjustments to the allowance for loan losses may be necessary based on newly received appraisals, updated commercial customer financial statements, rapidly deteriorating cash flow, and changes in economic conditions that affect our customers. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Corporation’s allowance for loan losses. Such agencies may require additions to the allowance for loan losses or may require that certain loan balances be charged off or downgraded into criticized loan categories when their credit evaluations differ from those of management based on their judgments about information available to them at the time of their examinations. See Loans and Troubled Debt Restructurings above for further policy discussion and see Note 4
Other Real Estate Owned	Other Real Estate OwnedOther real estate owned is included in other assets in the consolidated balance sheets and is comprised of property acquired through a foreclosure proceeding or acceptance of a deed-in-lieu of foreclosure, and loans classified as in-substance foreclosure. Other real estate owned is recorded at the fair value of the underlying property collateral, less estimated selling costs. This fair value becomes the new cost basis for the foreclosed asset. The initial write-down, if any, will be recorded as a charge off against the allowance for loan losses. Any subsequent write-downs to reflect current fair value, as well as gains and losses on disposition and revenues and expenses incurred in maintaining such properties, are expensed as incurred. Other real estate owned also includes bank premises formerly but no longer used for banking as well as property originally acquired for future expansion but no longer intended to be used for that purpose. Banking premises are transferred at the lower of carrying value or fair value, less estimated selling costs and any write-down is expensed as incurred.
Reserve for Unfunded Commitments	Allowance for Unfunded Commitments 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 in the consolidated balance sheets. The determination of the appropriate level of the allowance for unfunded commitments is based upon an evaluation of the unfunded credit facilities, including an assessment of historical commitment utilization experience and credit risk grading of the loan. Net adjustments to the allowance for unfunded commitments are included in the provision for credit losses in the consolidated statements of income. See Note 4 and Note 15
Premises and Equipment and Software	Premises and Equipment and Software Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are computed on the straight-line method over the estimated useful lives of the related assets or the lease term. Maintenance and repairs are charged to expense as incurred, while additions or major improvements are capitalized and depreciated over the estimated useful lives. Leasehold improvements are amortized on a straight-line basis over the lesser of the lease terms or the estimated useful lives of the improvements. Software, included in other assets in the consolidated balance sheets, is amortized on a straight-line basis over the lesser of the contract terms or the estimated useful life of the software. See Note 6
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill and Other Intangible Assets: The excess of the cost of an acquisition over the fair value of the net assets acquired consists primarily of goodwill, core deposit intangibles, and other identifiable intangibles (primarily related to customer relationships acquired). Core deposit intangibles have estimated finite lives and are amortized on a straight-line basis to expense over a 10 -year period. The other intangibles have estimated finite lives and are amortized on a straight-line basis over their expected useful life. The Corporation reviews long-lived assets and certain identifiable intangibles for impairment at least annually, or whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, in which case an impairment charge would be recorded. 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 impairment testing process is conducted by assigning net assets and goodwill to each reporting unit. An initial qualitative evaluation is made to assess the likelihood of impairment and determine whether further quantitative testing to calculate the fair value is necessary. When the qualitative evaluation indicates that impairment is more likely than not, quantitative testing is required whereby the fair value of each reporting unit is calculated and compared to the recorded book value, “step one.” If the calculated fair value of the reporting unit exceeds its carrying value, goodwill is not considered impaired and “step two” is not considered necessary. If the carrying value of a reporting unit exceeds its calculated fair value, the impairment test continues (“step two”) by comparing the carrying value of the reporting unit’s goodwill to the implied fair value of goodwill. The implied fair value is computed by adjusting all assets and liabilities of the reporting unit to current fair value with the offset adjustment to goodwill. The adjusted goodwill balance is the implied fair value of the goodwill. An impairment charge is recognized if the carrying value of goodwill exceeds the implied fair value of goodwill. See Note 5
Mortgage Servicing Rights	Mortgage Servicing Rights: The Corporation sells residential mortgage loans in the secondary market and typically retains the right to service the loans sold. Upon sale, a mortgage servicing rights asset is capitalized, which represents the then current fair value of future net cash flows expected to be realized for performing servicing activities. Mortgage servicing rights, when purchased, are initially recorded at fair value. As the Corporation has not elected to subsequently measure any class of servicing assets under the fair value measurement method, the Corporation follows the amortization method. 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. Mortgage servicing rights are carried at the lower of the initial capitalized amount, net of accumulated amortization, or estimated fair value, in the consolidated balance sheets. The Corporation periodically evaluates its mortgage servicing rights asset for impairment. 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 5
Income Taxes	Income Taxes Amounts provided for income tax expense are based on income reported for financial statement purposes and do not necessarily represent amounts currently payable under tax laws. Deferred income taxes, which arise principally from temporary differences between the amounts reported in the financial statements and the tax bases of assets and liabilities, are included in the amounts provided for income taxes. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income and tax planning strategies which will create taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, the amount of taxes paid in available carryback years, projected future taxable income, and, if necessary, tax planning strategies in making this assessment. The Corporation files a consolidated federal income tax return and separate or combined state income tax returns. Accordingly, amounts equal to tax benefits of those subsidiaries having taxable federal or state losses or credits are offset by other subsidiaries that incur federal or state tax liabilities. It is the Corporation’s policy to provide for uncertainty in income taxes as a part of income tax expense based upon management’s assessment of whether a tax benefit is more likely than not to be sustained upon examination by tax authorities. At December 31, 2018 and 2017 , the Corporation believes it has appropriately accounted for any unrecognized tax benefits. To the extent the Corporation prevails in matters for which a liability for an unrecognized tax benefit was established or is required to pay amounts in excess of the liability established, the Corporation’s effective tax rate in a given financial statement period may be impacted. See Note 12
Derivative and Hedging Activities	Derivative and Hedging Activities Derivative instruments, including derivative instruments embedded in other contracts, are carried at fair value on the consolidated balance sheets with changes in the fair value recorded to earnings or accumulated other comprehensive income, as appropriate. On the date the derivative contract is entered into, the Corporation designates the derivative as a fair value hedge (i.e., a hedge of the fair value of a recognized asset or liability), a cash flow hedge (i.e., a hedge of the variability of cash flows to be received or paid related to a recognized asset or liability), or a free-standing derivative instrument. For a derivative designated as a fair value hedge, the changes in the fair value of the derivative instrument and the changes in the fair value of the hedged asset or liability are recognized in current period earnings as an increase or decrease to the carrying value of the hedged item on the balance sheet and in the related income statement account. Amounts within accumulated other comprehensive income are reclassified into earnings in the period the hedged item affects earnings. For a derivative designated as a free-standing derivative instrument, changes in fair value are reported in current period earnings. The free-standing derivative instruments included: interest rate risk management, commodity hedging, and foreign currency exchange solutions. In addition, the Corporation is exposed to changes in the fair value of certain 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. See Note 13 for additional information on derivative and hedging activities.
Securities Sold Under Agreement to Repurchase	Securities Sold Under Agreement to Repurchase 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. These repurchase agreements are accounted for as collateralized financing arrangements (i.e., secured borrowings 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)) 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 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. See Notes 8 and 14
Retirement Plan	Retirement Plans The funded status of the retirement plans is recognized as an asset or liability in the consolidated balance sheets and changes in that funded status are recognized in the year in which the changes occur through other comprehensive income. Plan assets and benefit obligations are measured as of fiscal year end. The measurement of the projected benefit obligation and pension expense involve actuarial valuation methods and the use of various actuarial and economic assumptions. The Corporation monitors the assumptions and updates them periodically. Due to the long-term nature of the pension plan obligation, actual results may differ significantly from estimations. Such differences are adjusted over time as the assumptions are replaced by facts and values are recalculated. See Note 11
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 common stock awards is their fair market value on the date of grant. Performance awards are based on performance goals of earnings per share and total shareholder return with vesting ranging from a minimum of 25% to a maximum of 150% of the target award. Performance awards are valued utilizing a Monte Carlo simulation model to estimate fair value of the awards at the grant date. 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. 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. See Note 10
Comprehensive Income	Comprehensive Income Comprehensive income includes all changes in stockholders’ equity during a period, except those resulting from transactions with stockholders. In addition to net income, other components of the Corporation’s comprehensive income include the after tax effect of changes in net unrealized gain / loss on securities available for sale and changes in net actuarial gain / loss on defined benefit postretirement plans. Comprehensive income is reported in the accompanying consolidated statements of changes in stockholder’s equity and consolidated statements of comprehensive income. See Note 21
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). As there is no active market for many of the Corporation’s financial instruments, estimates are made using discounted cash flow or other valuation techniques. Inputs into the valuation methods are subjective in nature, involve uncertainties, and require significant judgment and therefore cannot be determined with precision. Accordingly, the derived fair value estimates presented herein are not necessarily indicative of the amounts the Corporation could realize in a current market exchange. Assets and liabilities are categorized into three levels based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy in which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. The Corporation’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability. See Note 17 for additional information on fair value measurements. Below is a brief description of each fair value level. Level 1 — Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Corporation has the ability to access. Level 2 — Level 2 inputs are inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals.
Cash and Cash Equivalents	Cash, Cash Equivalents, and Restricted CashFor purposes of the consolidated statements of cash flows, cash, cash equivalents, and restricted cash are considered to include cash and due from banks, interest-bearing deposits in other financial institutions, federal funds sold and securities purchased under agreements to resell.
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. See Note 19
New Accounting Pronouncements Adopted	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 an amendment to allow a reclassification from accumulated other comprehensive income to retained earnings for the stranded tax effects resulting from the Tax Cuts and Jobs Act of 2017. 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 was 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 Tax Cuts and Jobs Act of 2017 is recognized. 1st Quarter 2018 The Corporation elected to early adopt this amendment. During the first quarter of 2018, the Corporation reclassified approximately $14 million from accumulated other comprehensive income to retained earnings as a result of the Tax Act. No material impact on results of operations, financial position, or liquidity. See Consolidated Statements of Comprehensive Income and the Statement of Changes in Stockholders' Equity. ASU 2017-12 Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities The FASB issued an 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 sheets as of the date of adoption. Early adoption was 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. ASU 2018-16 permits the OIS (Overnight Index Swap) rate based on SOFR (Secured Overnight Financing Rate) as a U.S. benchmark interest rate for hedge accounting purposes. 1st Quarter 2018 The Corporation elected to early adopt this amendment. No material impact on results of operations, financial position, or liquidity. See Note 13 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 an amendment 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 was 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. 1st Quarter 2018 No impact on results of operations, financial position, or 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 11 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, then 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. This amendment was effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Entities should apply the amendment prospectively on or after the effective date. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. Standard Description Date of adoption Effect on financial statements ASU 2016-18 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 was 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. 1st Quarter 2018 No impact on results of operations, financial position, or 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 was 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. 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 from 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 bank owned life insurance) should be classified as cash inflows from investing, while the cash payments for the premiums may be classified as cash outflows from investing, operating, or a combination of both. This amendment was 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. 1st Quarter 2018 No material impact on results of operations, financial position, or liquidity. 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 was 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. 1st Quarter 2018 The Corporation has adopted this amendment using the cumulative-effect adjustment as of the beginning of the fiscal year of adoption. No material impact on the result of operations, financial position or liquidity. See Consolidated Statements of Comprehensive Income and Note 17 Fair Value Measurements. 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 December 31, 2018 are carried at a zero cost basis. 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 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 adopted this amendment using the modified retrospective approach with no material impact on the Corporation's results of operations, financial position, or liquidity. See Note 22 for expanded disclosure requirements.

Acquisition Acquisitions (Table

Acquisition Acquisitions (Tables)	12 Months Ended
	Dec. 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 (48,043 ) 1,875,877 Premises and equipment, net 2,930 42,689 Bank owned life insurance (24 ) 65,390 Goodwill 175,499 Core deposit intangibles (included in other intangible assets, net on the face of the Consolidated Balance Sheets) 58,100 58,100 Other real estate owned (included in other assets on the face of the Consolidated Balance Sheets) 199 4,848 Others assets $ 7,054 $ 47,158 Total assets $ 2,820,506 Liabilities Deposits $ 2,498 $ 1,840,950 Other borrowings 1,875 431,886 Other liabilities $ 4,487 $ 65,982 Total liabilities $ 2,338,818 Total consideration paid $ 481,688
Acquired loans fair value calculation	For loans acquired, the contractual amounts due, expected cash flows to be collected, interest component, and fair value as of the respective acquisition dates were as follows: February 1, 2018 Acquired Performing Loans Acquired Impaired Loans Total ($ in Thousands) Contractual required principal and interest at acquisition $ 1,899,932 $ 23,988 $ 1,923,920 Contractual cash flows not expected to be collected (nonaccretable discount) — (1,866 ) (1,866 ) Expected cash flows at acquisition 1,899,932 22,122 1,922,054 Interest component of expected cash flows (accretable discount) (41,324 ) (4,853 ) (46,177 ) Fair value of acquired loans $ 1,858,608 $ 17,269 $ 1,875,877

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investment securities available for sale	December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U.S. Treasury securities $ 1,000 $ — $ (1 ) $ 999 Residential mortgage-related securities FNMA / FHLMC 296,296 2,466 (3,510 ) 295,252 GNMA 2,169,943 473 (41,885 ) 2,128,531 Private-label 1,007 — (4 ) 1,003 GNMA commercial mortgage-related securities 1,273,309 — (52,512 ) 1,220,797 FFELP asset backed securities 297,347 711 (698 ) 297,360 Other debt securities 3,000 — — 3,000 Other equity securities 1,568 — — 1,568 Total investment securities available for sale $ 4,043,470 $ 3,649 $ (98,610 ) $ 3,948,510 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,790,683 $ 8,255 $ (15,279 ) $ 1,783,659 Residential mortgage-related securities FNMA / FHLMC 92,788 169 (1,795 ) 91,162 GNMA 351,606 1,611 (8,181 ) 345,035 GNMA commercial mortgage-related securities 505,434 7,559 (22,579 ) 490,414 Total investment securities held to maturity $ 2,740,511 $ 17,593 $ (47,835 ) $ 2,710,271 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	December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value ($ in Thousands) Investment securities available for sale U.S. Treasury securities $ 1,000 $ — $ (1 ) $ 999 Residential mortgage-related securities FNMA / FHLMC 296,296 2,466 (3,510 ) 295,252 GNMA 2,169,943 473 (41,885 ) 2,128,531 Private-label 1,007 — (4 ) 1,003 GNMA commercial mortgage-related securities 1,273,309 — (52,512 ) 1,220,797 FFELP asset backed securities 297,347 711 (698 ) 297,360 Other debt securities 3,000 — — 3,000 Other equity securities 1,568 — — 1,568 Total investment securities available for sale $ 4,043,470 $ 3,649 $ (98,610 ) $ 3,948,510 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) $ 1,790,683 $ 8,255 $ (15,279 ) $ 1,783,659 Residential mortgage-related securities FNMA / FHLMC 92,788 169 (1,795 ) 91,162 GNMA 351,606 1,611 (8,181 ) 345,035 GNMA commercial mortgage-related securities 505,434 7,559 (22,579 ) 490,414 Total investment securities held to maturity $ 2,740,511 $ 17,593 $ (47,835 ) $ 2,710,271 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 available for sale by contractual maturity	The expected maturities of investment securities available for sale and held to maturity at December 31, 2018 , are shown below. Expected maturities will 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 $ 2,000 $ 1,999 $ 48,865 $ 49,128 Due after one year through five years 2,000 2,000 187,828 186,797 Due after five years through ten years — — 409,682 406,702 Due after ten years — — 1,144,309 1,141,032 Total debt securities 4,000 3,999 1,790,683 1,783,659 Residential mortgage-related securities FNMA / FHLMC 296,296 295,252 92,788 91,162 GNMA 2,169,943 2,128,531 351,606 345,035 Private-label 1,007 1,003 — — GNMA commercial mortgage-related securities 1,273,309 1,220,797 505,434 490,414 FFELP asset backed securities 297,347 297,360 — — Equity securities 1,568 1,568 — — Total investment securities $ 4,043,470 $ 3,948,510 $ 2,740,511 $ 2,710,271 Ratio of Fair Value to Amortized Cost 97.7 % 98.9 %
Realized gains and losses and proceeds from sale	from the sale of investment securities for each of the three years ended December 31 were as follows. There were no other-than-temporary impairment write-downs on investment securities for 2018 , 2017 , or 2016 . 2018 2017 2016 ($ in Thousands) Gross gains on available for sale securities $ 1,954 $ — $ 9,485 Gross gains on held to maturity securities — 439 33 Total gains 1,954 439 9,518 Gross losses on available for sale securities (3,938 ) — (202 ) Gross losses on held to maturity securities — (5 ) — Total losses (3,938 ) (5 ) (202 ) Investment securities gains (losses), net $ (1,985 ) $ 434 $ 9,316 Proceeds from sales of investment securities $ 601,130 $ 18,467 $ 549,555
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 December 31, 2018 : Less than 12 months 12 months or more Total December 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 $ (1 ) $ 999 $ (1 ) $ 999 Residential mortgage-related securities FNMA / FHLMC 15 (31 ) 17,993 17 (3,479 ) 189,405 (3,510 ) 207,398 GNMA 12 (4,529 ) 452,183 79 (37,355 ) 1,598,159 (41,885 ) 2,050,342 Private-label 1 (4 ) 1,003 — — — (4 ) 1,003 GNMA commercial mortgage-related securities — — — 93 (52,512 ) 1,220,854 (52,512 ) 1,220,854 FFELP asset backed securities 13 (698 ) 142,432 — — — (698 ) 142,432 Total 41 $ (5,262 ) $ 613,612 190 $ (93,347 ) $ 3,009,417 $ (98,610 ) $ 3,623,028 Investment securities held to maturity Obligations of state and political subdivisions (municipal securities) 272 $ (2,860 ) $ 313,212 752 $ (12,419 ) $ 509,374 $ (15,279 ) $ 822,586 Residential mortgage-related securities FNMA / FHLMC 13 (780 ) 57,896 22 (1,015 ) 28,888 (1,795 ) 86,784 GNMA 13 (414 ) 19,822 66 (7,767 ) 320,387 (8,181 ) 340,209 GNMA commercial mortgage-related securities — — — 25 (22,579 ) 490,414 (22,579 ) 490,414 Total 298 $ (4,053 ) $ 390,929 865 $ (43,780 ) $ 1,349,063 $ (47,835 ) $ 1,739,992 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)	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Loan composition	Loans at December 31 are summarized below: 2018 (a) 2017 ($ in Thousands) Commercial and industrial $ 7,398,044 $ 6,399,693 Commercial real estate - owner occupied 920,443 802,209 Commercial and business lending 8,318,487 7,201,902 Commercial real estate - investor 3,751,554 3,315,254 Real estate construction 1,335,031 1,451,684 Commercial real estate lending 5,086,585 4,766,938 Total commercial 13,405,072 11,968,840 Residential mortgage 8,277,712 7,546,534 Home equity 894,473 883,804 Other consumer 363,171 385,813 Total consumer 9,535,357 8,816,151 Total loans $ 22,940,429 $ 20,784,991 (a) Includes $5 million
Loans to Related Parties	The Corporation has granted loans to its directors, executive officers, or their related interests. These loans were made on substantially the same terms, including rates and collateral, as those prevailing at the time for comparable transactions with other unrelated customers, and do not involve more than a normal risk of collection. These loans to related parties are summarized below: 2018 2017 ($ in Thousands) Balance at beginning of year $ 20,260 $ 27,589 New loans 3,076 5,329 Repayments (5,017 ) (7,632 ) Change due to status of executive officers and directors (489 ) (5,026 ) Balance at end of year $ 17,831 $ 20,260
Commercial and consumer loans by credit quality indicator	The following table presents commercial and consumer loans by credit quality indicator at December 31, 2018 : Pass Special Mention Potential Problem Nonaccrual Total ($ in Thousands) Commercial and industrial $ 7,162,370 $ 78,075 $ 116,578 $ 41,021 $ 7,398,044 Commercial real estate - owner occupied 854,265 6,257 55,964 3,957 920,443 Commercial and business lending 8,016,635 84,332 172,542 44,978 8,318,487 Commercial real estate - investor 3,653,642 28,479 67,481 1,952 3,751,554 Real estate construction 1,321,447 8,771 3,834 979 1,335,031 Commercial real estate lending 4,975,089 37,249 71,315 2,931 5,086,585 Total commercial 12,991,724 121,582 243,856 47,909 13,405,072 Residential mortgage 8,203,729 434 5,975 67,574 8,277,712 Home equity 880,808 1,223 103 12,339 894,473 Other consumer 362,343 749 — 79 363,171 Total consumer 9,446,881 2,406 6,078 79,992 9,535,357 Total loans $ 22,438,605 $ 123,988 $ 249,935 $ 127,901 $ 22,940,429 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 loans $ 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 December 31, 2018 : Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Past Due and Still Accruing Nonaccrual (a) Total ($ in Thousands) Commercial and industrial $ 7,356,187 $ 187 $ 338 $ 311 $ 41,021 $ 7,398,044 Commercial real estate - owner occupied 913,787 2,580 119 — 3,957 920,443 Commercial and business lending 8,269,974 2,767 457 311 44,978 8,318,487 Commercial real estate - investor 3,745,835 2,954 813 — 1,952 3,751,554 Real estate construction 1,333,722 330 — — 979 1,335,031 Commercial real estate lending 5,079,557 3,284 813 — 2,931 5,086,585 Total commercial 13,349,531 6,051 1,270 311 47,909 13,405,072 Residential mortgage 8,200,432 9,272 434 — 67,574 8,277,712 Home equity 876,085 4,826 1,223 — 12,339 894,473 Other consumer 358,970 1,401 868 1,853 79 363,171 Total consumer 9,435,487 15,499 2,525 1,853 79,992 9,535,357 Total loans $ 22,785,019 $ 21,550 $ 3,795 $ 2,165 $ 127,901 $ 22,940,429 (a) Of the total nonaccrual loans, $74 million , or 58% , were current with respect to payment at December 31, 2018 . The following table presents loans by past due status at December 31, 2017 : Current 30-59 Days Past Due 60-89 Days Past Due 90 Days or More Nonaccrual (a) Total ($ 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 loans $ 20,555,250 $ 16,861 $ 2,467 $ 1,867 $ 208,546 $ 20,784,991 (a) 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 $5 million of purchased credit-impaired loans, at December 31, 2018 : Recorded Unpaid Related Average Interest ($ in Thousands) Loans with a related allowance Commercial and industrial $ 40,747 $ 42,131 $ 5,721 $ 52,461 $ 1,167 Commercial real estate - owner occupied 2,080 2,087 24 2,179 104 Commercial and business lending 42,827 44,218 5,745 54,640 1,271 Commercial real estate - investor 799 805 28 827 38 Real estate construction 510 589 75 533 32 Commercial real estate lending 1,309 1,394 103 1,360 70 Total commercial 44,136 45,612 5,848 56,000 1,341 Residential mortgage 41,691 45,149 6,023 42,687 1,789 Home equity 9,601 10,539 3,312 10,209 566 Other consumer 1,181 1,183 121 1,184 3 Total consumer 52,473 56,871 9,456 54,080 2,358 Total loans $ 96,609 $ 102,483 $ 15,304 $ 110,079 $ 3,699 Loans with no related allowance Commercial and industrial $ 22,406 $ 45,024 $ — $ 21,352 $ (344 ) Commercial real estate - owner occupied 3,772 4,823 — 3,975 — Commercial and business lending 26,178 49,847 — 25,327 (344 ) Commercial real estate - investor 1,585 2,820 — 980 68 Real estate construction — — — — — Commercial real estate lending 1,585 2,820 — 980 68 Total commercial 27,763 52,667 — 26,307 (276 ) Residential mortgage 8,795 9,074 — 8,790 203 Home equity 523 542 — 530 — Other consumer — — — — — Total consumer 9,318 9,616 — 9,320 203 Total loans $ 37,081 $ 62,283 $ — $ 35,627 $ (73 ) Total Commercial and industrial $ 63,153 $ 87,155 $ 5,721 $ 73,813 $ 823 Commercial real estate - owner occupied 5,852 6,910 24 6,154 104 Commercial and business lending 69,005 94,065 5,745 79,967 927 Commercial real estate - investor 2,384 3,625 28 1,807 106 Real estate construction 510 589 75 533 32 Commercial real estate lending 2,894 4,214 103 2,340 138 Total commercial 71,899 98,279 5,848 82,307 1,065 Residential mortgage 50,486 54,223 6,023 51,477 1,992 Home equity 10,124 11,081 3,312 10,739 566 Other consumer 1,181 1,183 121 1,184 3 Total consumer 61,791 66,487 9,456 63,400 2,561 Total loans (a) $ 133,690 $ 164,766 $ 15,304 $ 145,707 $ 3,626 (a) The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 72% of the unpaid principal balance at December 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 $ 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 $ 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	December 31, 2018 December 31, 2017 December 31, 2016 Performing Restructured Loans Nonaccrual Restructured Loans (a) Performing Restructured Loans Nonaccrual Restructured Loans (a) Performing Restructured Loans Nonaccrual Restructured Loans (a) ($ in Thousands) Commercial and industrial $ 25,478 $ 249 $ 30,047 $ 1,776 $ 31,884 $ 1,276 Commercial real estate - owner occupied 2,080 — 3,989 — 5,490 2,220 Commercial real estate - investor 799 933 14,389 — 15,289 924 Real estate construction 311 198 310 157 359 150 Residential mortgage 16,036 22,279 17,068 18,991 18,100 21,906 Home equity 7,385 2,627 7,705 2,537 7,756 2,877 Other consumer 1,174 6 1,110 25 979 32 Total restructured loans $ 53,263 $ 26,292 $ 74,618 $ 23,486 $ 79,857 $ 29,385 (a)
Summary of restructured loans	The following table provides the number of loans modified in a troubled debt restructuring by loan portfolio during the years ended December 31, 2018 , 2017 , and 2016 , respectively, and the recorded investment and unpaid principal balance as of December 31, 2018 , 2017 , and 2016 , respectively: Years Ended December 31, 2018 2017 2016 Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) Number of Loans Recorded Investment (a) Unpaid Principal Balance (b) Number Recorded (a) Unpaid (b) ($ in Thousands) Commercial and industrial 5 $ 1,315 $ 1,330 8 $ 3,991 $ 6,339 8 $ 1,509 $ 1,526 Commercial real estate - owner occupied — — — 2 690 690 1 116 122 Commercial real estate - investor 2 1,393 1,472 — — — — — — Real estate construction 1 78 80 — — — 1 65 91 Residential mortgage 41 6,977 7,210 45 4,238 4,364 63 5,535 5,792 Home equity 34 1,649 1,681 22 507 507 57 2,030 2,084 Other consumer 3 17 19 — — — 1 15 16 Total 86 $ 11,429 $ 11,792 77 $ 9,426 $ 11,900 131 $ 9,270 $ 9,631 (a) Represents post-modification outstanding recorded investment. (b)
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 year ended December 31, 2018 , 2017 , and 2016 , respectively, as well as the recorded investment in these restructured loans as of December 31, 2018 , 2017 , and 2016 , respectively: Years Ended December 31, 2018 2017 2016 Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Recorded ($ in Thousands) Commercial and industrial 3 $ — 2 $ — — $ — Residential mortgage 20 3,553 36 3,137 44 4,102 Home equity 32 1,688 27 735 23 457 Other consumer — — 1 7 1 15 Total 55 $ 5,241 66 $ 3,879 68 $ 4,574
Changes in the allowance for loan losses by portfolio segment	A summary of the changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2018 , is as follows: Commercial and industrial Commercial real estate - owner occupied Commercial real estate - investor Real estate construction Residential mortgage Home equity Other consumer Total ($ in Thousands) December 31, 2017 $ 123,068 $ 10,352 $ 41,059 $ 34,370 $ 29,607 $ 22,126 $ 5,298 $ 265,880 Charge offs (30,837 ) (1,363 ) (7,914 ) (298 ) (1,627 ) (3,236 ) (5,261 ) (50,536 ) Recoveries 13,714 639 668 446 1,271 2,628 812 20,179 Net charge offs (17,123 ) (724 ) (7,246 ) 149 (355 ) (608 ) (4,448 ) (30,358 ) Provision for loan losses 2,890 (373 ) 7,031 (6,279 ) (3,657 ) (2,252 ) 5,138 2,500 December 31, 2018 $ 108,835 $ 9,255 $ 40,844 $ 28,240 $ 25,595 $ 19,266 $ 5,988 $ 238,023 Allowance for loan losses Individually evaluated for impairment $ 5,721 $ 24 $ 28 $ 75 $ 6,023 $ 3,312 $ 121 $ 15,304 Collectively evaluated for impairment 103,114 9,231 40,816 28,165 19,572 15,954 5,867 222,719 Acquired and accounted for under ASC 310-30 (a) — — — — — — — — Total allowance for loan losses $ 108,835 $ 9,255 $ 40,844 $ 28,240 $ 25,595 $ 19,266 $ 5,988 $ 238,023 Loans Individually evaluated for impairment $ 63,153 $ 5,852 $ 2,384 $ 510 $ 50,486 $ 10,124 $ 1,181 $ 133,690 Collectively evaluated for impairment 7,331,898 913,708 3,748,883 1,334,500 8,226,642 884,266 361,990 22,801,887 Acquired and accounted for under ASC 310-30 (a) 2,994 883 287 21 584 83 — 4,853 Total loans $ 7,398,044 $ 920,443 $ 3,751,554 $ 1,335,031 $ 8,277,712 $ 894,473 $ 363,171 $ 22,940,429 (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 , is as follows: Commercial and industrial Commercial real estate - owner occupied Commercial real estate - investor Real estate construction Residential mortgage Home equity Other consumer Total ($ in Thousands) 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 loan losses by oil and gas segment	The allowance related to the oil and gas portfolio was $12 million at December 31, 2018 and represented 1.62% of total oil and gas loans. Year Ended December 31, 2018 Year Ended December 31, 2017 ($ in Millions) Balance at beginning of period $ 27 $ 38 Charge offs (24 ) (25 ) Recoveries 6 — Net Charge offs (17 ) (25 ) Provision for loan losses 2 14 Balance at end of period $ 12 $ 27 Allowance for loan losses Individually evaluated for impairment $ — $ 5 Collectively evaluated for impairment 12 22 Total allowance for loan losses $ 12 $ 27 Loans Individually evaluated for impairment $ 22 $ 77 Collectively evaluated for impairment 725 523 Total loans $ 747 $ 600
Changes in the allowance for unfunded commitments	A summary of the changes in the allowance for unfunded commitments was as follows: Years Ended December 31, 2018 2017 2016 ($ in Thousands) Allowance for Unfunded Commitments Balance at beginning of period $ 24,400 $ 25,400 $ 24,400 Provision for unfunded commitments (2,500 ) (1,000 ) 1,000 Amount recorded at acquisition 2,436 — — Balance at end of period $ 24,336 $ 24,400 $ 25,400
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 years ended December 31, 2018 , and 2017 respectively: Year Ended December 31, 2018 Year Ended December 31, 2017 ($ in Thousands) Changes in Accretable Yield Balance at beginning of period $ — $ — Purchases 4,853 — Accretion (4,954 ) — Net reclassification from non-accretable yield 1,605 — Other (a) (22 ) — Balance at end of period $ 1,482 $ — (a) Primarily includes charge offs which are accounted for under ASC Subtopic 310-30 "Receivables — Loans and Debt Securities Acquired with Deteriorated Credit Quality."

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 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: 2018 2017 2016 ($ in Thousands) Core deposit intangibles Gross carrying amount $ 58,100 $ 4,385 $ 4,385 Accumulated amortization (5,326 ) (4,385 ) (4,273 ) Net book value $ 52,774 $ — $ 112 Additions during the period $ 58,100 $ — $ — Amortization during the year $ 5,326 $ 112 $ 281 Other intangibles Gross carrying amount $ 44,931 $ 34,572 $ 32,410 Reductions due to sale (43 ) — — Accumulated amortization (21,825 ) (18,992 ) (17,145 ) Net book value $ 23,062 $ 15,580 $ 15,265 Additions during the period $ 10,359 $ 2,162 $ 1,012 Amortization during the year $ 2,833 $ 1,847 $ 1,812
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 is as follows: 2018 2017 2016 ($ in Thousands) Mortgage servicing rights Mortgage servicing rights at beginning of year $ 59,168 $ 62,085 $ 62,150 Additions from acquisition 8,136 — — Additions 10,722 7,167 12,262 Amortization (9,594 ) (10,084 ) (12,327 ) Mortgage servicing rights at end of year $ 68,433 $ 59,168 $ 62,085 Valuation allowance at beginning of year (784 ) (609 ) (809 ) (Additions) recoveries, net 545 (175 ) 200 Valuation allowance at end of year (239 ) (784 ) (609 ) Mortgage servicing rights, net $ 68,193 $ 58,384 $ 61,476 Fair value of mortgage servicing rights $ 81,012 $ 64,387 $ 73,149 Portfolio of residential mortgage loans serviced for others (“servicing portfolio”) $ 8,600,983 $ 7,646,846 $ 7,974,742 Mortgage servicing rights, net to servicing portfolio 0.79 % 0.76 % 0.77 % Mortgage servicing rights expense (a) $ 9,049 $ 10,259 $ 12,127 (a)
Summary of estimated future amortization expense	The projections of amortization expense are based on existing asset balances, the current interest rate environment, and prepayment speeds as of December 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. The following table shows the estimated future amortization expense for amortizing intangible assets: Estimated Amortization Expense Core Deposit Intangibles Other Intangibles Mortgage Servicing Rights ($ in Thousands) Year ending December 31, 2019 $ 5,810 $ 2,824 $ 9,666 2020 5,810 2,707 10,355 2021 5,810 2,682 8,951 2022 5,810 2,659 7,694 2023 5,810 2,640 6,580 Beyond 2023 23,724 9,551 25,187 Total Estimated Amortization Expense $ 52,774 $ 23,062 $ 68,433

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Summary of Premises and Equipment	A summary of premises and equipment at December 31 is as follows: 2018 2017 ($ in Thousands) Estimated Useful Lives Cost Accumulated Depreciation Net Book Value Net Book Value Land — $ 67,737 $ — $ 67,737 $ 59,257 Land improvements 3 – 15 years 14,730 7,518 7,212 6,313 Buildings and improvements 5 – 39 years 363,000 150,464 212,536 198,431 Computers 3 – 5 years 45,768 33,375 12,392 11,078 Furniture, fixtures and other equipment 3 – 15 years 168,567 118,676 49,891 42,049 Leasehold improvements 3 – 15 years 34,248 20,791 13,457 13,835 Total premises and equipment $ 694,050 $ 330,824 $ 363,225 $ 330,963
Minimum annual rentals and commitments under noncancelable operating leases	The approximate minimum annual rental payments and rental receipts under noncancelable agreements and leases with remaining terms in excess of one year are as follows: ($ in Thousands) Payments Receipts 2019 $ 10,235 $ 2,963 2020 10,107 3,030 2021 9,500 2,860 2022 7,084 1,875 2023 5,183 1,260 Thereafter 22,622 7,806 Total $ 64,732 $ 19,794

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2018
Deposits [Abstract]
Deposits by type	The distribution of deposits at December 31 is as follows: 2018 2017 ($ in Thousands) Noninterest-bearing demand $ 5,698,530 $ 5,478,416 Savings 2,012,841 1,524,992 Interest-bearing demand 5,336,952 4,603,157 Money market 9,033,669 8,830,328 Brokered CDs 192,234 18,609 Other time 2,623,167 2,330,460 Total deposits $ 24,897,393 $ 22,785,962
Time deposits by maturity	Aggregate annual maturities of all time deposits at December 31, 2018 , are as follows: Maturities During Year Ending December 31, ($ in Thousands) 2019 $ 1,952,008 2020 561,758 2021 176,491 2022 67,738 2023 52,576 Thereafter 4,830 Total $ 2,815,401

Short and Long-term Funding (Ta

Short and Long-term Funding (Tables)	12 Months Ended
	Dec. 31, 2018
Short-term Debt [Abstract]
Short and Long-term funding	December 31, 2018 December 31, 2017 ($ in Thousands) Short-Term Funding Federal funds purchased $ 19,710 $ 141,950 Securities sold under agreements to repurchase 91,941 182,865 Federal funds purchased and securities sold under agreements to repurchase 111,651 324,815 Commercial paper 45,423 67,467 Total short-term funding $ 157,074 $ 392,282 Long-Term Funding Senior notes, at par $ 550,000 $ 250,000 Subordinated notes, at par 250,000 250,000 Other long-term funding and capitalized costs (4,389 ) (2,718 ) Total long-term funding 795,611 497,282 Total short and long-term funding, excluding FHLB advances $ 952,685 $ 889,564 FHLB Advances Short-term FHLB advances $ 900,000 $ 284,000 Long-term FHLB advances 2,674,371 2,900,168 Total FHLB advances $ 3,574,371 $ 3,184,168 Total short and long-term funding $ 4,527,056 $ 4,073,732
Schedule of Repurchase Agreements	The remaining contractual maturity of the securities sold under agreements to repurchase in the consolidated balance sheets as of December 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 ($ in Thousands) December 31, 2018 Repurchase agreements Agency mortgage-related securities $ 91,941 $ — $ — $ — $ 91,941 Total $ 91,941 $ — $ — $ — $ 91,941 December 31, 2017 Repurchase agreements Agency mortgage-related securities $ 182,865 $ — $ — $ — $ 182,865 Total $ 182,865 $ — $ — $ — $ 182,865
FHLB_Maturity_ [Table Text Block]	The original contractual maturity or next put date of the Corporation's FHLB advances as of December 31, 2018 and December 31, 2017 are presented in the following table: December 31, 2018 December 31, 2017 Amount Weighted Average Contractual Coupon Rate Amount Weighted Average Contractual Coupon Rate ($ in Thousands) Maturity or put date 1 year or less $ 2,262,584 2.06 % $ 2,434,000 1.26 % After 1 but within 2 1,285,039 2.39 % 750,013 1.23 % After 2 but within 3 14,393 2.98 % 155 4.91 % After 3 years 12,354 4.55 % — — % FHLB advances and overall rate $ 3,574,371 2.19 % $ 3,184,168 1.26 %
Schedule of Maturities of Long-term Debt [Table Text Block]	The table below summarizes the maturities of the Corporation’s long-term funding, including long-term FHLB advances, at December 31, 2018 : Year ($ in Thousands) 2019 $ 1,612,265 2020 1,285,039 2021 312,047 2022 6,023 2023 2,665 Thereafter 251,943 Total long-term funding $ 3,469,982

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 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 2018 , 2017 , and 2016 : 2018 2017 2016 Dividend yield 2.50 % 2.00 % 2.50 % Risk-free interest rate 2.60 % 2.00 % 2.00 % Weighted average expected volatility 22.00 % 25.00 % 25.00 % Weighted average expected life 5.75 years 5.5 years 5.5 years Weighted average per share fair value of options $4.47 $5.30 $3.36
Summary of Company's Stock Option Activities	A summary of the Corporation’s stock option activity for the year ended December 31, 2018 is presented below: Stock Options Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in thousands) 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 (1,031,875 ) 16.45 Forfeited or expired (114,695 ) 23.88 Outstanding at December 31, 2018 5,280,908 $ 19.09 6.18 $ 12,392 Options exercisable at December 31, 2018 3,187,894 $ 16.93 4.92 $ 10,796
Summary of Restricted Stock Awards Activity (Excluding Salary Shares)	The following table summarizes information about the Corporation’s restricted stock activity for the year ended December 31, 2018 : Restricted Stock Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 2,026,071 $ 19.68 Granted 615,484 24.60 Vested (587,775 ) 18.44 Forfeited (60,948 ) 22.36 Outstanding at December 31, 2018 1,992,832 $ 21.92

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Defined Benefit Plan [Abstract]
Change in Benefit Obligation	The funded status and amounts recognized in the 2018 and 2017 consolidated balance sheets, as measured on December 31, 2018 and 2017 , respectively, for the Retirement Account Plan and Postretirement Plan were as follows: Retirement Account Plan Bank Mutual Pension Postretirement Plan Retirement Account Plan Postretirement Plan ($ in Thousands) 2018 2018 2018 2017 2017 Change in Fair Value of Plan Assets Fair value of plan assets at beginning of year $ 331,609 N/A $ — $ 295,718 $ — Fair value of Bank Mutual plan assets at February 1, 2018 N/A 59,445 — N/A N/A Actual return on plan assets (14,609 ) (1,665 ) — 41,490 — Employer contributions 4,340 37,537 292 6,242 235 Gross benefits paid (10,582 ) (15,513 ) (292 ) (11,841 ) (235 ) Bank Mutual plan assets transferred at December 31, 2018 79,805 (79,805 ) — N/A N/A Fair value of plan assets at end of year (a) $ 390,564 $ — $ — $ 331,609 $ — Change in Benefit Obligation Net benefit obligation at beginning of year $ 186,423 N/A $ 2,478 $ 176,825 $ 2,403 Net Bank Mutual benefit obligation at February 1, 2018 N/A 66,364 576 N/A N/A Service cost 7,540 — — 6,955 — Interest cost 6,727 2,398 108 7,121 101 Actuarial (gain) loss (8,000 ) (1,701 ) (347 ) 7,363 209 Gross benefits paid (10,582 ) (2,644 ) (292 ) (11,841 ) (235 ) Lump sums paid — (12,868 ) — — — Bank Mutual benefit obligations transferred at December 31, 2018 51,549 (51,549 ) — N/A N/A Net benefit obligation at end of year (a) $ 233,658 $ — $ 2,523 $ 186,423 $ 2,478 Funded (unfunded) status $ 156,906 $ — $ (2,523 ) $ 145,186 $ (2,478 ) Noncurrent assets 156,906 — — 145,186 — Current liabilities — — (219 ) — (233 ) Noncurrent liabilities — — (2,304 ) — (2,245 ) Asset (Liability) Recognized in the Consolidated Balance Sheets $ 156,906 $ — $ (2,523 ) $ 145,186 $ (2,478 ) (a) The fair value of the plan assets represented 167% and 178% of the net benefit obligation of the pension plan at December 31, 2018 and 2017
AOCI Components	Amounts recognized in accumulated other comprehensive (income) loss, net of tax, as of December 31, 2018 and 2017 follow: Retirement Account Plan Postretirement Plan Retirement Account Plan Postretirement Plan ($ in Thousands) 2018 2018 2017 2017 Prior service cost $ (303 ) $ (588 ) $ (295 ) $ (531 ) Net actuarial loss 50,238 (17 ) 24,926 205 Amount not yet recognized in net periodic benefit cost, but recognized in accumulated other comprehensive (income) loss $ 49,935 $ (605 ) $ 24,631 $ (326 )
Changes in OCI	Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) (“OCI”), net of tax, in 2018 and 2017 were as follows: Retirement Account Plan Postretirement Retirement Account Plan Postretirement ($ in Thousands) 2018 2018 2017 2017 Net actuarial gain (loss) $ (28,959 ) $ 347 $ 14,482 $ (209 ) Amortization of prior service cost (73 ) (75 ) (73 ) (75 ) Amortization of actuarial loss (gain) 2,195 8 2,278 4 Adjustment for adoption of ASU 2018-02 (5,235 ) — — — Income tax (expense) benefit 6,838 (71 ) (6,219 ) 107 Total Recognized in OCI $ (25,234 ) $ 209 $ 10,468 $ (173 )
Net period benefit cost for the pension plans	The components of net pension cost for the Retirement Account Plan for 2018 , 2017 , and 2016 were as follows: Retirement Account Plan Retirement Account Plan Retirement Account Plan ($ in Thousands) 2018 2017 2016 Service cost $ 7,540 $ 6,955 $ 6,780 Interest cost 9,125 7,121 7,121 Expected return on plan assets (23,195 ) (19,646 ) (20,287 ) Amortization of prior service cost (73 ) (73 ) (73 ) Amortization of actuarial loss (gain) 2,195 2,278 2,115 Recognized settlement loss (gain) 809 — — Total net periodic pension cost $ (3,600 ) $ (3,365 ) $ (4,344 )
Net period benefit cost for postretirement plan	The components of net periodic benefit cost for the Postretirement Plan for 2018 , 2017 , and 2016 were as follows: Postretirement Plan Postretirement Plan Postretirement Plan ($ in Thousands) 2018 2017 2016 Interest cost $ 108 $ 101 $ 142 Amortization of prior service cost (75 ) (75 ) — Amortization of actuarial loss (gain) 8 4 — Total net periodic benefit cost $ 41 $ 30 $ 142
Weighted Average Benefit Assumptions	Retirement Account Plan Postretirement Plan Retirement Account Plan Postretirement Plan 2018 2018 2017 2017 Weighted average assumptions used to determine benefit obligations Discount rate 4.30 % 4.30 % 3.70 % 3.70 % Rate of increase in compensation levels 3.00 % N/A 3.00 % N/A Weighted average assumptions used to determine net periodic benefit costs Discount rate (a) 3.77 % 3.77 % 4.10 % 4.10 % Rate of increase in compensation levels 3.00 % N/A 4.00 % N/A Expected long-term rate of return on plan assets (b) 5.93 % N/A 6.50 % N/A (a) Weighted average of the 2018 fiscal year discount rate assumption for the Retirement Account Plan was 3.70% and the Bank Mutual Pension Plan was 4.00% (b) Weighted average of the 2018 fiscal year expected return on asset assumption for the Retirement Account Plan was 6.00% and the Bank Mutual Pension Plan was 5.50%
Plan Asset Allocation Percentages	The asset allocation for the Retirement Account Plan as of the December 31, 2018 and 2017 measurement dates, respectively, by asset category were as follows: Asset Category 2018 2017 Equity securities 49 % 60 % Fixed-income securities 34 % 37 % Group annuity contracts 12 % — % Alternative securities 3 % — % Other 2 % 3 % Total 100 % 100 %
Pension Plan Investments	Based on these inputs, the following table summarizes the fair value of the Retirement Account Plan’s investments as of December 31, 2018 and 2017 : Fair Value Measurements Using ($ in Thousands) December 31, 2018 Level 1 Level 2 Level 3 Retirement Account Plan Investments Money market account $ 7,159 $ 7,159 $ — $ — Common /collective trust funds 138,020 138,020 — — Mutual funds 198,120 198,120 — — Group annuity contracts 47,265 — — 47,265 Total Retirement Account Plan Investments $ 390,564 $ 343,299 $ — $ 47,265 Fair Value Measurements Using ($ in Thousands) December 31, 2017 Level 1 Level 2 Level 3 Retirement Account Plan Investments Money market account $ 9,577 $ 9,577 $ — $ — Common /collective trust funds 133,210 133,210 — — Mutual funds 188,823 188,823 — — Total Retirement Account Plan Investments $ 331,610 $ 331,610 $ — $ —
Schedule of Changes in Fair Value of Plan Assets	The following presents a summary of the changes in the fair value of the Retirement Account Plan's Level 3 asset during the periods indicated. As noted above, the Corporation's Level 3 asset consists entirely of a group annuity contract issued by a life insurance company. Fair Value Reconciliation of Level 3 Retirement Account Plan Investments 2018 2017 Fair value of group annuity contract at February 1, 2018 (date of Bank Mutual acquisition) $ 49,191 N/A Actual return on plan assets 565 N/A Benefits paid (2,491 ) N/A Fair value of group annuity contract at December 31, 2018 $ 47,265 N/A
Expected Benefit Payments	The projected benefit payments were calculated using the same assumptions as those used to calculate the benefit obligations listed above. The projected benefit payments for the Retirement Account and Postretirement Plans at December 31, 2018 , reflecting expected future services, were as follows: ($ in Thousands) Retirement Account Plan Postretirement Plan Estimated future benefit payments 2019 $ 18,774 $ 224 2020 19,265 220 2021 19,161 216 2022 20,210 211 2023 20,086 206 2024-2028 89,992 925
One Percentage Point Change in Assumed Health Care Cost	A one percentage point change in the assumed health care cost trend rate would have the following effect: 2018 2017 ($ in Thousands) 100 bp Increase 100 bp Decrease 100 bp Increase 100 bp Decrease Effect on total of service and interest cost $ 7 $ (6 ) $ 7 $ (6 ) Effect on postretirement benefit obligation $ 164 $ (143 ) $ 162 $ (140 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Current and Deferred Income Tax Expense (Benefit)	The current and deferred amounts of income tax expense were as follows: Years Ended December 31, 2018 2017 2016 ($ in Thousands) Current Federal $ 20,246 $ 76,525 $ 73,781 State 12,593 11,576 2,885 Total current 32,839 88,101 76,666 Deferred Federal 34,941 19,755 3,338 State 12,006 1,647 7,318 Total deferred 46,947 21,402 10,656 Total income tax expense $ 79,786 $ 109,503 $ 87,322
Schedule of Deferred Tax Assets and Liabilities	Temporary differences between the amounts reported in the financial statements and the tax bases of assets and liabilities resulted in deferred taxes. Deferred tax assets and liabilities at December 31, 2018 and 2017 were as follows: 2018 2017 ($ in Thousands) Deferred tax assets Allowance for loan losses $ 61,143 $ 66,377 Allowance for other losses 8,304 7,095 Accrued liabilities 3,736 3,884 Deferred compensation 24,754 20,015 Benefit of tax loss and credit carryforwards 10,126 8,438 Nonaccrual interest 1,666 1,619 Net unrealized losses on available-for-sale securities 25,731 15,968 Net unrealized losses on pension and postretirement benefits 16,640 9,928 Other 1,916 4,435 Total deferred tax assets 154,015 137,759 Valuation allowance for deferred tax assets (251 ) (269 ) Total deferred tax assets after valuation allowance $ 153,764 $ 137,490 Deferred tax liabilities Prepaid expenses $ 61,250 $ 49,695 Goodwill 20,178 19,144 Mortgage banking activities 17,428 10,949 Deferred loan fee income 11,892 11,467 State deferred taxes 518 2,001 Lease financing 410 535 Bank premises and equipment 18,655 5,063 Purchase accounting 12,414 5,015 Other 684 304 Total deferred tax liabilities $ 143,429 $ 104,173 Net deferred tax assets $ 10,335 $ 33,317
Summary of Valuation Allowance [Table Text Block]	The changes in the valuation allowance related to net operating losses for 2018 and 2017 were as follows: 2018 2017 ($ in Thousands) Valuation allowance for deferred tax assets, beginning of year $ (269 ) $ — (Increase) decrease in current year 18 (269 ) Valuation allowance for deferred tax assets, end of year $ (251 ) $ (269 )
Schedule of Effective Income Tax Rate Reconciliation	The effective income tax rate differs from the statutory federal tax rate. The major reasons for this difference were as follows: 2018 2017 2016 Federal income tax rate at statutory rate 21.0 % 35.0 % 35.0 % Increases (decreases) resulting from: Tax-exempt interest and dividends (2.6 )% (4.1 )% (4.8 )% State income taxes (net of federal benefit) 3.7 % 2.9 % 2.5 % Bank owned life insurance (0.7 )% (1.7 )% (1.7 )% Tax effect of tax credits and benefits, net of related expenses (0.7 )% (0.7 )% (1.0 )% Tax reserve adjustments / settlements 1.5 % (1.2 )% 0.3 % Net tax benefit from stock-based compensation (0.5 )% (1.3 )% (0.4 )% Tax Act impact on deferred remeasurement — % 3.5 % — % Tax planning in response to the Tax Act (3.6 )% — % — % FDIC premium 0.9 % — % — % Other 0.3 % (0.1 )% 0.5 % Effective income tax rate 19.3 % 32.3 % 30.4 %
Summary Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits was as follows: 2018 2017 ($ in Millions) Balance at beginning of year $ 4 $ 10 Subtractions for tax positions related to prior years — (5 ) Subtractions for settlements with tax authorities (3 ) (1 ) Additions for tax positions related to current year 1 — Balance at end of year $ 2 $ 4

Derivative and Hedging Activi_2

Derivative and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Balance sheet category and fair values of derivative instruments not designated as hedging instruments	The table below identifies the balance sheet category and fair values of the Corporation’s derivative instruments: December 31, 2018 December 31, 2017 ($ in Thousands) Notional Amount Fair Value Balance Sheet Category Notional Amount Fair Balance Sheet Derivatives not designated as hedging instruments Interest rate-related instruments — customer and mirror $ 2,707,204 $ 52,796 Trading assets $ 2,183,687 $ 28,494 Trading assets Interest rate-related instruments — customer and mirror 2,707,204 (52,653 ) Trading liabilities 2,183,687 (28,035 ) Trading liabilities Foreign currency exchange forwards 117,879 721 Trading assets 124,851 2,495 Trading assets Foreign currency exchange forwards 69,153 (675 ) Trading liabilities 118,094 (2,339 ) Trading liabilities Commodity contracts 331,727 35,426 Trading assets 457,868 38,686 Trading assets Commodity contracts 315,861 (34,340 ) Trading liabilities 457,108 (37,286 ) Trading liabilities Interest rate lock commitments (mortgage) 191,222 2,208 Other assets 222,736 1,538 Other assets Forward commitments (mortgage) 139,984 (2,072 ) Other liabilities 164,567 (313 ) Other liabilities Purchased options (time deposit) 11,185 109 Other assets 31,063 1,175 Other assets Written options (time deposit) 11,185 (109 ) Other liabilities 31,063 (1,175 ) Other liabilities Derivatives designated as hedging instruments Interest rate products 500,000 (40 ) Other liabilities — — —
Balance Sheet Recording of Fair Value Hedge [Table Text Block]	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) December 31, 2018 Loans and investment securities available for sale (a) $ 499,498 $ (502 ) Total $ 499,498 $ (502 ) (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 December 31, 2018, the amortized cost basis of the closed portfolios used in these hedging relationships was $1.1 billion ; the negative cumulative basis adjustments associated with these hedging relationships was approximately $502,000 ; and the amounts of the designated hedged items were $500 million
Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block]	The table below identifies the effect of fair value hedge accounting on the Corporation's statement of income during the twelve months ended December 31, 2018 : Location and Amount of Gain or (Loss) Recognized in Income on Fair Value and Cash Flow Hedging Relationships Year Ended December 31, 2018 Year Ended December 31, 2017 ($ 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 (a) $ (1,325 ) $ — $ — $ — 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 (502 ) — — — Derivatives designated as hedging instruments (a) (823 ) — — — (a) Includes net settlements on the derivatives
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 income during the twelve months ended December 31, 2018 : Income Statement Category of Gain / (Loss) Recognized in Income For the Year Ended December 31, ($ in Thousands) 2018 2017 Derivative Instruments Interest rate-related instruments — customer and mirror, net Capital market fees, net $ (316 ) $ (24 ) Interest rate lock commitments (mortgage) Mortgage banking, net 670 1,332 Forward commitments (mortgage) Mortgage banking, net (1,759 ) (3,221 ) Foreign currency exchange forwards Capital market fees, net (110 ) 97 Commodity contracts Capital market fees, net (314 ) 647

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	12 Months Ended
	Dec. 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 of recognized assets Gross amounts not offset in the balance sheet ($ in Thousands) Gross amounts offset in the balance sheet Net amounts presented in the balance sheet Derivative liability available for offset Collateral received Net amount Derivative assets: (a) December 31, 2018 $ 65,596 $ — $ 65,596 $ (22,873 ) $ (41,879 ) $ 843 December 31, 2017 29,503 — 29,503 (16,140 ) (13,234 ) 129 Gross amounts of recognized liabilities Gross amounts not offset in the balance sheet ($ in Thousands) Gross amounts offset in the balance sheet Net amounts presented in the balance sheet Derivative asset available for offset Collateral pledged Net amount Derivative liabilities (b) December 31, 2018 $ 22,951 $ — $ 22,951 $ (22,873 ) $ (63 ) $ 16 December 31, 2017 37,164 — 37,164 (16,140 ) (20,662 ) 362 (a) Includes interest and commodity instrument assets. (b) Includes interest and commodity instrument liabilities.

Commitments, Off-Balance Shee_2

Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of lending-related and other commitments	The following is a summary of lending-related commitments: 2018 2017 ($ in Thousands) Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale (a) (b) $ 8,720,293 $ 8,027,187 Commercial letters of credit (a) 7,599 11,886 Standby letters of credit (c) 255,904 235,361 (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 December 31, 2018 and 2017 . (b) Interest rate lock commitments to originate residential mortgage loans held for sale are considered derivative instruments and are disclosed in Note 13 . (c) The Corporation has established a liability of $2 million at both December 31, 2018 and December 31, 2017
Summary of changes in the residential mortgage repurchase reserve	The following summarizes the changes in the mortgage repurchase reserve for the years ended as follows: 2018 2017 ($ in Thousands) Balance at beginning of year $ 987 $ 900 Repurchase provision expense 345 246 Adjustments to provision expense (450 ) — Charge offs, net (218 ) (159 ) Amount recorded at acquisition 88 — Balance at end of year $ 752 $ 987

Parent Company Only Financial_2

Parent Company Only Financial Information (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Parent Company Balance Sheet	BALANCE SHEETS December 31, 2018 2017 ($ in Thousands) Assets Cash and due from banks $ 16,245 $ 25,544 Interest-bearing deposits in other financial institutions 38,374 121,333 Investment securities available for sale, at fair value — 11,645 Notes and interest receivable from subsidiaries 453,615 301,378 Investments in and receivable due from subsidiaries 3,787,574 3,320,090 Other assets 47,448 51,466 Total assets $ 4,343,256 $ 3,831,456 Liabilities and Stockholders' Equity Commercial paper $ 45,423 $ 67,467 Senior notes, at par 250,000 250,000 Subordinated notes, at par 250,000 250,000 Long-term funding capitalized costs (2,043 ) (2,718 ) Total long-term funding 497,957 497,282 Accrued expenses and other liabilities 18,988 29,264 Total liabilities 562,368 594,013 Preferred equity 256,716 159,929 Common equity 3,524,171 3,077,514 Total stockholders’ equity 3,780,888 3,237,443 Total liabilities and stockholders’ equity $ 4,343,256 $ 3,831,456
Parent Company Income Statement	STATEMENTS OF INCOME For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Income Dividends from subsidiaries $ 336,000 $ 213,000 $ 188,000 Interest income on notes receivable from subsidiaries 12,199 4,175 — Other income 994 1,763 4,669 Total income 349,193 218,938 192,669 Expense Interest expense on short and long-term funding 18,355 18,464 21,901 Other expense 11,736 6,927 4,289 Total expense 30,091 25,391 26,190 Income before income tax expense and equity in undistributed net income of subsidiaries 319,102 193,547 166,479 Income tax expense 4,176 4,768 3,468 Income before equity in undistributed net income of subsidiaries 314,926 188,779 163,011 Equity in undistributed net income of subsidiaries 18,636 40,485 37,263 Net income 333,562 229,264 200,274 Preferred stock dividends 10,784 9,347 8,903 Net income available to common equity $ 322,779 $ 219,917 $ 191,371
Parent Company Statement of Cash Flows	STATEMENTS OF CASH FLOWS For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Cash Flows from Operating Activities Net income $ 333,562 $ 229,264 $ 200,274 Adjustments to reconcile net income to net cash provided by operating activities: (Increase) decrease in equity in undistributed net income (loss) of subsidiaries (18,636 ) (40,485 ) (37,263 ) (Gain) loss on sales of investment securities, net of impairment write-downs — — (466 ) (Gain) loss on sales of assets, net — (88 ) (793 ) Net change in other assets and other liabilities (92,366 ) (9,589 ) 19,708 Net cash provided by operating activities 222,562 179,102 181,460 Cash Flows from Investing Activities Proceeds from sales of investment securities 827 2,618 47,719 Net increase in notes receivable from subsidiaries (139,317 ) (300,000 ) — Net (increase) decrease in loans 2,210 1,058 2,211 Net cash provided by (used in) investing activities (136,280 ) (296,324 ) 49,930 Cash Flows from Financing Activities Net increase (decrease) in commercial paper (22,044 ) (34,221 ) 33,710 Repayment of long-term funding — — (430,000 ) Proceeds from issuance of common stock for stock-based compensation plans 18,408 27,619 21,748 Proceeds from issuance of preferred stock 97,315 — 97,066 Redemption of preferred stock — — (58,903 ) Purchase of preferred stock (537 ) — (1,248 ) Common stock warrants exercised (1 ) — — Purchase of common stock returned to authorized but unissued (33,075 ) (37,031 ) (20,007 ) Issuance of Treasury Stock for Acquisition 91,296 — — Purchase of treasury stock (213,598 ) (9,290 ) (5,074 ) Cash dividends on common stock (105,519 ) (76,417 ) (67,855 ) Cash dividends on preferred stock (10,784 ) (9,347 ) (8,903 ) Net cash used in financing activities (178,540 ) (138,687 ) (439,466 ) Net increase (decrease) in cash and cash equivalents (92,258 ) (255,909 ) (208,076 ) Cash and cash equivalents at beginning of year 146,877 402,786 610,862 Cash and cash equivalents at end of year $ 54,619 $ 146,877 $ 402,786

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 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 December 31, 2018 and 2017 , aggregated by the level in the fair value hierarchy within which those measurements fall: Fair Value Hierarchy December 31, 2018 December 31, 2017 ($ in Thousands) Assets Investment securities available for sale U.S. Treasury securities Level 1 $ 999 $ 996 Residential mortgage-related securities FNMA / FHLMC Level 2 295,252 464,768 GNMA Level 2 2,128,531 1,913,350 Private-label Level 2 1,003 1,059 GNMA commercial mortgage-related securities Level 2 1,220,797 1,513,277 FFELP asset backed securities Level 2 297,360 145,176 Other equity securities Level 1 1,568 1,632 Other debt securities Level 2 3,000 3,188 Total investment securities available for sale Level 1 2,567 2,628 Total investment securities available for sale Level 2 3,945,943 4,040,818 Residential loans held for sale Level 2 64,321 85,544 Commercial loans held for sale Level 2 14,943 — Interest rate-related instruments Level 2 52,796 28,494 Foreign currency exchange forwards Level 2 721 2,495 Interest rate lock commitments to originate residential mortgage loans held for sale Level 3 2,208 1,538 Commodity contracts Level 2 35,426 38,686 Purchased options (time deposit) Level 2 109 1,175 Liabilities Interest rate-related instruments Level 2 $ 52,653 $ 28,035 Foreign currency exchange forwards Level 2 675 2,339 Forward commitments to sell residential mortgage loans Level 3 2,072 313 Commodity contracts Level 2 34,340 37,286 Written options (time deposit) Level 2 109 1,175 Interest rate products (designated as hedging instruments) Level 2 40 —
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 years ended December 31, 2018 and 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) — (1,085 ) Balance December 31, 2018 $ — $ 140 (a) During the first quarter of 2017, the $200,000
Assets and liabilities measured on nonrecurring basis at fair value	The table below presents the Corporation’s assets measured at fair value on a nonrecurring basis, aggregated by the level in the fair value hierarchy within which those measurements fall: ($ in Thousands) Fair Value Hierarchy Fair Value Income Statement Category of Adjustment Recognized in Income December 31, 2018 Assets Impaired loans (a) Level 3 $ 26,191 Provision for credit losses (b) $ (14,521 ) Other real estate owned (c) Level 2 2,200 Foreclosure / OREO expense, net (1,545 ) Mortgage servicing rights Level 3 81,012 Mortgage banking, net 545 December 31, 2017 Assets Impaired loans (a) Level 3 $ 92,534 Provision for credit losses (b) $ (32,159 ) Other real estate owned (c) Level 2 2,604 Foreclosure / OREO expense, net (939 ) Mortgage servicing rights Level 3 64,387 Mortgage banking, net (175 ) (a) Represents individually evaluated impaired loans, net of the related allowance for loan losses. (b) Represents provision for credit losses on individually evaluated impaired loans. (c)
Schedule of assumptions for fair value as of balance sheet date of assets or liabilities that relate to transferor's continuing involvement	The table below presents information about these inputs and further discussion is found above: December 31, 2018 Valuation Technique Significant Unobservable Input Weighted Average Input Applied Mortgage servicing rights Discounted cash flow Discount rate 11% Mortgage servicing rights Discounted cash flow Constant prepayment rate 11% Impaired loans Appraisals / Discounted cash flow Collateral / Discount factor 40%
Estimated fair values of financial instruments	Fair value estimates are set forth below for the Corporation’s financial instruments: December 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 $ 507,187 $ 507,187 $ 483,666 $ 483,666 Interest-bearing deposits in other financial institutions Level 1 221,226 221,226 199,702 199,702 Federal funds sold and securities purchased under agreements to resell Level 1 148,285 148,285 32,650 32,650 Investment securities held to maturity Level 2 2,740,511 2,710,271 2,282,853 2,283,574 Investment securities available for sale Level 1 2,567 2,567 2,628 2,628 Investment securities available for sale Level 2 3,945,943 3,945,943 4,040,818 4,040,818 FHLB and Federal Reserve Bank stocks Level 2 250,534 250,534 165,331 165,331 Residential loans held for sale Level 2 64,321 64,321 85,544 85,544 Commercial loans held for sale Level 2 14,943 14,943 — — Loans, net Level 3 22,702,406 22,317,395 20,519,111 20,314,984 Bank and corporate owned life insurance Level 2 663,203 663,203 591,057 591,057 Derivatives (trading and other assets) Level 2 89,052 89,052 70,850 70,850 Derivatives (trading and other assets) Level 3 2,208 2,208 1,538 1,538 Financial liabilities Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts Level 3 $ 22,081,992 $ 22,081,992 $ 20,436,893 $ 20,436,893 Brokered CDs and other time deposits (a) Level 2 2,815,401 2,815,401 2,349,069 2,349,069 Short-term funding (b) Level 2 1,057,074 1,057,074 676,282 676,282 Long-term funding Level 2 3,469,982 3,492,174 3,397,450 3,411,368 Standby letters of credit (c) Level 2 2,482 2,482 2,402 2,402 Derivatives (trading and other liabilities) Level 2 87,817 87,817 68,835 68,835 Derivatives (trading and other liabilities) Level 3 2,072 2,072 313 313 (a) When the estimated fair value is less than the carrying value, the carrying value is reported as the fair value. (b) The carrying amount is a reasonable estimate of fair value for existing short-term funding. (c) The commitment on standby letters of credit was $256 million and $235 million at December 31, 2018 and 2017 , respectively. See Note 15

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2018
Regulatory Capital Requirements [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	Actual For Capital Adequacy Purposes To Be Well Capitalized Under Prompt Corrective Action Provisions (b) Amount Ratio (a) Amount Ratio (a) Amount Ratio (a) ($ in Thousands) As of December 31 , 2018 Associated Banc-Corp Total capital $ 3,216,575 13.47 % $ 1,910,022 ≥ 8.00 % Tier 1 capital 2,705,939 11.33 % 1,432,517 ≥ 6.00 % Common equity Tier 1 capital 2,449,721 10.26 % 1,074,388 ≥ 4.50 % Leverage 2,705,939 8.48 % 1,276,624 ≥ 4.00 % Associated Bank, N.A. Total capital $ 2,909,064 12.23 % $ 1,903,155 ≥ 8.00 % $ 2,378,944 ≥ 10.00 % Tier 1 capital 2,646,705 11.13 % 1,427,367 ≥ 6.00 % 1,903,155 ≥ 8.00 % Common equity Tier 1 capital 2,446,782 10.29 % 1,070,525 ≥ 4.50 % 1,546,314 ≥ 6.50 % Leverage 2,646,705 8.31 % 1,274,380 ≥ 4.00 % 1,592,976 ≥ 5.00 % As of December 31 , 2017 Associated Banc-Corp Total capital $ 2,848,851 13.22 % $ 1,723,557 ≥ 8.00 % Tier 1 capital 2,331,245 10.82 % 1,292,668 ≥ 6.00 % Common equity Tier 1 capital 2,171,508 10.08 % 969,501 ≥ 4.50 % Leverage 2,331,245 8.02 % 1,162,929 ≥ 4.00 % Associated Bank, N.A. Total capital $ 2,625,945 12.24 % $ 1,716,910 ≥ 8.00 % $ 2,146,138 ≥ 10.00 % Tier 1 capital 2,357,354 10.98 % 1,287,683 ≥ 6.00 % 1,716,910 ≥ 8.00 % Common equity Tier 1 capital 2,157,354 10.05 % 965,762 ≥ 4.50 % 1,394,989 ≥ 6.50 % Leverage 2,357,354 8.13 % 1,159,959 ≥ 4.00 % 1,449,948 ≥ 5.00 % (a) When fully phased-in on January 1, 2019, the Basel III capital rules include a capital conservation buffer of 2.5% that is added on top of each of the minimum risk-based capital ratios noted above. Implementation began on January 1, 2016 at the 0.625% level and has increased each subsequent January 1, until it reaches 2.5% on January 1, 2019.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 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 Years Ended December 31, 2018 2017 2016 ($ in Thousands, Except Per Share Data) Net income $ 333,562 $ 229,264 $ 200,274 Preferred stock dividends (10,784 ) (9,347 ) (8,903 ) Net income available to common equity 322,779 219,917 191,371 Common shareholder dividends (104,981 ) (75,967 ) (67,100 ) Unvested share-based payment awards (537 ) (450 ) (755 ) Undistributed earnings 217,260 143,500 123,516 Undistributed earnings allocated to common shareholders 216,199 142,593 122,205 Undistributed earnings allocated to unvested share-based payment awards 1,060 907 1,311 Undistributed earnings $ 217,260 $ 143,500 $ 123,516 Basic Distributed earnings to common shareholders $ 104,981 $ 75,967 $ 67,100 Undistributed earnings allocated to common shareholders 216,199 142,593 122,205 Total common shareholders earnings, basic $ 321,181 $ 218,560 $ 189,305 Diluted Distributed earnings to common shareholders $ 104,981 $ 75,967 $ 67,100 Undistributed earnings allocated to common shareholders 216,199 142,593 122,205 Total common shareholders earnings, diluted $ 321,181 $ 218,560 $ 189,305 Weighted average common shares outstanding $ 167,345 $ 150,877 $ 148,769 Effect of dilutive common stock awards 1,985 2,038 1,192 Effect of dilutive common stock warrants 402 732 — Diluted weighted average common shares outstanding $ 169,732 $ 153,647 $ 149,961 Basic earnings per common share $ 1.92 $ 1.45 $ 1.27 Diluted earnings per common share $ 1.89 $ 1.42 $ 1.26

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Selected segment information	Information about the Corporation’s segments is presented below: Corporate and Commercial Specialty For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 457,613 $ 360,789 $ 312,982 Net intersegment interest income (expense) (56,356 ) (3,737 ) 15,621 Segment net interest income 401,258 357,051 328,603 Noninterest income 52,321 52,297 47,776 Total revenue 453,578 409,348 376,379 Credit provision (a) 44,592 42,298 50,397 Noninterest expense 160,399 156,890 148,493 Income (loss) before income taxes 248,587 210,160 177,489 Income tax expense (benefit) 47,850 71,655 59,261 Net income $ 200,737 $ 138,505 $ 118,228 Return on average allocated capital (ROCET1) (b) 16.60 % 12.39 % 11.04 % Average earning assets $ 11,852,662 $ 10,820,998 $ 10,178,813 Average loans 11,841,818 10,811,827 10,169,300 Average deposits 8,112,430 6,938,913 5,904,238 Average allocated capital (CETI) (b) 1,209,558 1,117,761 1,070,598 Allocated goodwill 524,525 428,000 428,000 Community, Consumer, and Business For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 357,245 $ 316,008 $ 306,913 Net intersegment interest income (expense) 87,737 45,353 43,639 Segment net interest income 444,982 361,361 350,551 Noninterest income 295,647 266,250 277,942 Total revenue 740,629 627,611 628,493 Credit provision (a) 20,083 20,400 24,185 Noninterest expense 542,117 490,908 502,285 Income (loss) before income taxes 178,429 116,303 102,023 Income tax expense (benefit) 37,476 40,706 35,708 Net income $ 140,953 $ 75,597 $ 66,315 Return on average allocated capital (ROCET1) (b) 21.57 % 12.89 % 10.53 % Average earning assets $ 10,336,105 $ 9,456,549 $ 9,309,028 Average loans 10,332,665 9,452,253 9,307,723 Average deposits 13,623,852 11,711,407 11,451,759 Average allocated capital (CETI) (b) 653,354 586,417 629,540 Allocated goodwill 644,498 548,238 543,951 Risk Management and Shared Services For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 64,722 $ 64,423 $ 87,378 Net intersegment interest income (expense) (31,382 ) (41,615 ) (59,259 ) Segment net interest income 33,341 22,808 28,119 Noninterest income 7,600 14,133 27,165 Total revenue 40,941 36,941 55,284 Credit provision (a) (64,675 ) (36,698 ) (4,582 ) Noninterest expense (c) 119,283 61,335 51,782 Income (loss) before income taxes (13,668 ) 12,304 8,084 Income tax expense (benefit) (5,540 ) (2,858 ) (7,647 ) Net income $ (8,128 ) $ 15,162 $ 15,731 Return on average allocated capital (ROCET1) (b) (3.19 )% 1.44 % 2.84 % Average earning assets $ 7,861,026 $ 6,722,337 $ 6,538,820 Average loans 543,814 328,303 173,644 Average deposits 2,335,768 3,273,282 3,649,775 Average allocated capital (CETI) (b) 592,006 405,281 240,253 Allocated goodwill — — — Consolidated Total For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Net interest income $ 879,580 $ 741,220 $ 707,273 Net intersegment interest income (expense) — — — Segment net interest income 879,580 741,220 707,273 Noninterest income 355,568 332,680 352,883 Total revenue 1,235,148 1,073,900 1,060,156 Credit provision (a) — 26,000 70,000 Noninterest expense 821,799 709,133 702,560 Income (loss) before income taxes 413,349 338,767 287,596 Income tax expense (benefit) 79,786 109,503 87,322 Net income $ 333,562 $ 229,264 $ 200,274 Return on average allocated capital (ROCET1) (b) 13.15 % 10.43 % 9.86 % Average earning assets $ 30,049,793 $ 26,999,884 $ 26,026,661 Average loans 22,718,297 20,592,383 19,650,667 Average deposits 24,072,049 21,923,602 21,005,772 Average allocated capital (CETI) (b) 2,454,919 2,109,459 1,940,391 Allocated goodwill 1,169,023 976,239 971,951 (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. Average allocated capital represents average common equity Tier 1, as defined by the Federal Reserve. For segment reporting purposes, the ROCET1, a non-GAAP financial measure, reflects return on average allocated common equity Tier 1 (“CET1”). 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. (c) For the year ended December 31, 2018 , the Risk Management and Shared Services segment includes approximately $29 million of acquisition related costs within noninterest expense and approximately $2 million

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Summary of activity in accumulated other comprehensive income (loss)	The following table summarizes the components of accumulated other comprehensive income (loss) at December 31, 2018 , 2017 , and 2016 respectively, including changes during the years then ended as well as any reclassifications out of accumulated other comprehensive income (loss): Investments Securities Available For Sale Defined Benefit Pension and Postretirement Obligations Accumulated Other Comprehensive Income (Loss) ($ in Thousands) Balance, December 31, 2015 $ 459 $ (33,075 ) $ (32,616 ) Other comprehensive income (loss) before reclassifications (17,900 ) (6,141 ) (24,041 ) Amounts reclassified from accumulated other comprehensive income (loss) Investment securities losses (gains), net (9,316 ) — (9,316 ) Personnel expense — (73 ) (73 ) Other expense — 3,874 3,874 Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (5,887 ) — (5,887 ) Income tax (expense) benefit 12,565 815 13,380 Net other comprehensive income (loss) during period (20,538 ) (1,525 ) (22,063 ) Balance, December 31, 2016 $ (20,079 ) $ (34,600 ) $ (54,679 ) Other comprehensive income (loss) before reclassifications (27,040 ) 14,273 (12,767 ) Amounts reclassified from accumulated other comprehensive income (loss) Personnel expense — (148 ) (148 ) Other expense — 2,282 2,282 Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities) (2,665 ) — (2,665 ) Income tax (expense) benefit 11,331 (6,112 ) 5,219 Net other comprehensive income (loss) during period (18,374 ) 10,295 (8,079 ) Balance, December 31, 2017 $ (38,453 ) $ (24,305 ) $ (62,758 ) Other comprehensive income (loss) before reclassifications (39,891 ) (28,612 ) (68,503 ) Amounts reclassified from accumulated other comprehensive income (loss) Investment securities losses (gains), net 1,985 — 1,985 Personnel expense — (148 ) (148 ) Other expense — 2,203 2,203 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) (572 ) — (572 ) Income tax (expense) benefit 9,791 6,767 16,558 Net other comprehensive income (loss) during period (37,189 ) (25,025 ) (62,214 ) Balance, December 31, 2018 $ (75,643 ) $ (49,330 ) $ (124,972 )

Revenues (Tables)

Revenues (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue Recognition [Abstract]
Disaggregation of Revenue [Table Text Block]	The following table disaggregates the Corporation's revenue by major source for the years ended December 31, 2018 , 2017 , and 2016 : Corporate and Commercial Specialty For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ — $ — $ — Service charges and deposit account fees 14,981 16,006 15,378 Card-based and loan fees (a) 1,343 1,163 740 Trust and asset management fees — — — Brokerage and advisory fees — — — Other revenue 685 772 (1,096 ) Noninterest Income (in-scope of Topic 606) $ 17,009 $ 17,941 $ 15,022 Noninterest Income (out-of-scope of Topic 606) 35,311 34,355 32,754 Total Noninterest Income $ 52,321 $ 52,297 $ 47,776 Community, Consumer, and Business For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ 89,472 $ 81,468 $ 80,795 Service charges and deposit account fees 51,025 48,344 51,047 Card-based and loan fees (a) 39,883 34,695 33,765 Trust and asset management fees 54,316 50,191 46,866 Brokerage and advisory fees 28,024 19,935 16,235 Other revenue 9,643 9,249 8,556 Noninterest Income (in-scope of Topic 606) $ 272,363 $ 243,883 $ 237,265 Noninterest Income (out-of-scope of Topic 606) 23,284 22,367 40,677 Total Noninterest Income $ 295,647 $ 266,250 $ 277,942 Risk Management and Share Services For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ 39 $ 6 $ — Service charges and deposit account fees 69 77 184 Card-based and loan fees (a) 98 23 22 Trust and asset management fees — — — Brokerage and advisory fees 222 — — Other revenue 283 245 158 Noninterest Income (in-scope of Topic 606) $ 712 $ 351 $ 364 Noninterest Income (out-of-scope of Topic 606) 6,889 13,783 26,801 Total Noninterest Income $ 7,600 $ 14,133 $ 27,165 Consolidated Total For the Years Ended December 31, 2018 2017 2016 ($ in Thousands) Insurance commissions and fees $ 89,511 $ 81,474 $ 80,795 Service charges and deposit account fees 66,075 64,427 66,609 Card-based and loan fees (a) 41,325 35,881 34,527 Trust and asset management fees 54,316 50,191 46,867 Brokerage and advisory fees 28,246 19,935 16,235 Other revenue 10,611 10,267 7,617 Noninterest Income (in-scope of Topic 606) $ 290,084 $ 262,175 $ 252,651 Noninterest Income (out-of-scope of Topic 606) 65,483 70,505 100,232 Total Noninterest Income $ 355,568 $ 332,680 $ 352,883
Revenue Recognition 606 [Text Block]	Below is a listing of performance obligations for the Corporation's 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 (a) Card-based 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 the 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 and advisory fees Brokerage and advisory 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.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Core Deposit Intangibles
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Other Intangibles
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	11 years	12 years
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	25.00%
Maximum
Finite-Lived Intangible Assets [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	150.00%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies New Accounting Pronouncements Adopted (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expense Reclass (asu 2017-07)		$ 9,000
Visa Restricted Shares Owned	119
AOCI Attributable to Parent [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reporting Comprehensive Income(2018-02)	$ 13,654

Acquisition Bank Mutual Acquisi

Acquisition Bank Mutual Acquisition (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Feb. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Goodwill	$ 1,169,023		$ 976,239
Total liabilities	$ 2,340,323		$ 54	$ 1,423
BKMU Assets Acquired Liabilities Assumed Adjustments [Member]
Financing Receivable, Impaired [Line Items]
Cash and cash equivalents		$ 0
Investment securities		(6,238)
Federal Home Loan Bank stock, at cost		0
Loans		(48,043)
Premises and equipment, net		2,930
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 (included in other assets on the face of the Consolidated Balance Sheet)		199
Other assets		7,054
Deposits		2,498
Other borrowings		1,875
Other liabilities		4,487
BKMU Assets Acquired Liabilities Assumed [Member]
Financing Receivable, Impaired [Line Items]
Cash and cash equivalents		78,052
Investment securities		452,867
Federal Home Loan Bank stock, at cost		20,026
Loans		1,875,877
Premises and equipment, net		42,689
Bank owned life insurance		65,390
Goodwill		175,499
Core deposit intangibles (included in other intangible assets, net on the face of the Consolidated Balance Sheet)		58,100
Other real estate owned (included in other assets on the face of the Consolidated Balance Sheet)		4,848
Other assets		47,158
Total assets		2,820,506
Deposits		1,840,950
Other borrowings		431,886
Other liabilities		65,982
Total liabilities		2,338,818
Total consideration paid		$ 481,688

Acquisition Acquired Impaired L

Acquisition Acquired Impaired Loans (Details) - USD ($) $ in Thousands	Feb. 01, 2018	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable
Interest component of expected cash flows (accretable discount)		$ (4,954)	$ 0
BKMU Assets Acquired Liabilities Assumed [Member]
Financing Receivable
Contractual required principal and interest at acquisition	$ 1,923,920
Contractual cash flows not expected to be collected (nonaccretable discount)	(1,866)
Expected cash flows at acquisition	1,922,054
Interest component of expected cash flows (accretable discount)	(46,177)
Fair value of acquired loans	1,875,877
Acquired Performing Loans | BKMU Assets Acquired Liabilities Assumed [Member]
Financing Receivable
Contractual required principal and interest at acquisition	1,899,932
Contractual cash flows not expected to be collected (nonaccretable discount)	0
Expected cash flows at acquisition	1,899,932
Interest component of expected cash flows (accretable discount)	(41,324)
Fair value of acquired loans	1,858,608
Acquired Impaired Loans | BKMU Assets Acquired Liabilities Assumed [Member]
Financing Receivable
Contractual required principal and interest at acquisition	23,988
Contractual cash flows not expected to be collected (nonaccretable discount)	(1,866)
Expected cash flows at acquisition	22,122
Interest component of expected cash flows (accretable discount)	(4,853)
Fair value of acquired loans	$ 17,269

Acquisition Narrative (Details)

Acquisition Narrative (Details)	Feb. 01, 2018USD ($)shares	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 11, 2018USD ($)branch
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable					$ 488,408,000	$ 7,151,000	$ 0
Bank Mutual [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	$ 482,000,000
Consideration shares transferred | shares	0.422
Stock Issued During Period, Shares, Acquisitions | shares	19,500,000
Goodwill acquired during period	$ 175,000,000
Additions to finite-lived intangible assets	$ 58,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	10 years
BKMU Goodwill Acquired Adjustments [Member]
Business Acquisition [Line Items]
Goodwill acquired during period		$ 2,000,000	$ 6,000,000
BKMU Assets Acquired Liabilities Assumed IncreaseDecrease [Member]
Business Acquisition [Line Items]
Premises and equipment, net		$ 2,000,000	6,000,000
Business Combination, Acquired Receivables, IncreaseDecrease	less than $1 million
Anderson Insurance Investment Agency [Domain]
Business Acquisition [Line Items]
Goodwill acquired during period			7,000,000
Business Combination, Consideration Transferred			10,000,000
Additions to finite-lived intangible assets			$ 3,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			7 years
Diversified Insurance [Member]
Business Acquisition [Line Items]
Goodwill acquired during period				$ 10,000,000
Business Combination, Consideration Transferred				19,000,000
Additions to finite-lived intangible assets				$ 8,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life				10 years
Huntington National Bank [Domain]
Business Acquisition [Line Items]
Estimate Acquired Deposits								$ 850,000,000
Estimate Acquired Loans								$ 134,000,000
Estimate Acquired Net Branches | branch								14

Investment Securities, AFS and

Investment Securities, AFS and HTM Securities Amortized Costs and Fair Values (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investment securities available for sale
Amortized Cost	$ 4,043,470	$ 4,100,417
Gross Unrealized Gains	3,649	10,996
Gross Unrealized Losses	(98,610)	(67,967)
Fair Value	3,948,510	4,043,446
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	2,740,511	2,282,853
Gross Unrealized Gains	17,593	26,543
Held-to-maturity, Gross Unrealized Loss	(47,835)	(25,822)
Fair Value	2,710,271	2,283,574
U.S. Treasury securities
Investment securities available for sale
Amortized Cost	1,000	1,003
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(7)
Fair Value	999	996
Obligations of state and political subdivisions (municipal securities)
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	1,790,683	1,281,320
Gross Unrealized Gains	8,255	13,899
Held-to-maturity, Gross Unrealized Loss	(15,279)	(3,177)
Fair Value	1,783,659	1,292,042
Residential Related Securities | FNMA / FHLMC
Investment securities available for sale
Amortized Cost	296,296	457,680
Gross Unrealized Gains	2,466	9,722
Gross Unrealized Losses	(3,510)	(2,634)
Fair Value	295,252	464,768
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	92,788	40,995
Gross Unrealized Gains	169	398
Held-to-maturity, Gross Unrealized Loss	(1,795)	(489)
Fair Value	91,162	40,904
Residential Related Securities | GNMA
Investment securities available for sale
Amortized Cost	2,169,943	1,944,453
Gross Unrealized Gains	473	275
Gross Unrealized Losses	(41,885)	(31,378)
Fair Value	2,128,531	1,913,350
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	351,606	414,440
Gross Unrealized Gains	1,611	2,700
Held-to-maturity, Gross Unrealized Loss	(8,181)	(6,400)
Fair Value	345,035	410,740
Private-label
Investment securities available for sale
Amortized Cost	1,007	1,067
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4)	(8)
Fair Value	1,003	1,059
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	0
Fair Value	0
GNMA commercial mortgage-related securities
Investment securities available for sale
Amortized Cost	1,273,309	1,547,173
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(52,512)	(33,901)
Fair Value	1,220,797	1,513,277
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	505,434	546,098
Gross Unrealized Gains	7,559	9,546
Held-to-maturity, Gross Unrealized Loss	(22,579)	(15,756)
Fair Value	490,414	539,888
FFELP asset backed securities
Investment securities available for sale
Amortized Cost	297,347	144,322
Gross Unrealized Gains	711	867
Gross Unrealized Losses	(698)	(13)
Fair Value	297,360	145,176
Fixed income securities
Investment securities available for sale
Amortized Cost	3,000	3,200
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(12)
Fair Value	3,000	3,188
Equity securities
Investment securities available for sale
Amortized Cost	1,568	1,519
Gross Unrealized Gains	0	127
Gross Unrealized Losses	0	(14)
Fair Value	1,568	$ 1,632
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	0
Fair Value	$ 0

Investment Securities, AFS an_2

Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less	$ 2,000
Due after one year through five years	2,000
Due after five years through ten years	0
Due after ten years	0
Total debt securities	4,000
Fair Value
Due in one year or less	1,999
Due after one year through five years	2,000
Due after five years through ten years	0
Due after ten years	0
Total debt securities	3,999
Investment securities available for sale, amortized cost	4,043,470	$ 4,100,417
Investment securities available for sale, at fair value	$ 3,948,510	4,043,446
Ratio of Fair Value to Amortized Cost	97.70%
Amortized Cost
Due in one year or less	$ 48,865
Due after one year through five years	187,828
Due after five years through ten years	409,682
Due after ten years	1,144,309
Total debt securities	1,790,683
Amortized Cost	2,740,511	2,282,853
Fair Value
Due in one year or less	49,128
Due after one year through five years	186,797
Due after five years through ten years	406,702
Due after ten years	1,141,032
Total debt securities	1,783,659
Total debt securities	$ 2,710,271	2,283,574
Ratio of Fair Value to Amortized Cost	98.90%
Private-label
Fair Value
Investment securities available for sale, amortized cost	$ 1,007	1,067
Investment securities available for sale, at fair value	1,003	1,059
Amortized Cost
Amortized Cost	0
Fair Value
Total debt securities	0
GNMA commercial mortgage-related securities
Fair Value
Investment securities available for sale, amortized cost	1,273,309	1,547,173
Investment securities available for sale, at fair value	1,220,797	1,513,277
Amortized Cost
Amortized Cost	505,434	546,098
Fair Value
Total debt securities	490,414	539,888
FFELP asset backed securities
Fair Value
Investment securities available for sale, amortized cost	297,347
Investment securities available for sale, at fair value	297,360
Amortized Cost
Amortized Cost	0
Fair Value
Total debt securities	0
Equity securities
Fair Value
Investment securities available for sale, amortized cost	1,568	1,519
Investment securities available for sale, at fair value	1,568	1,632
Amortized Cost
Amortized Cost	0
Fair Value
Total debt securities	0
FNMA / FHLMC | Residential Related Securities
Fair Value
Investment securities available for sale, amortized cost	296,296	457,680
Investment securities available for sale, at fair value	295,252	464,768
Amortized Cost
Amortized Cost	92,788	40,995
Fair Value
Total debt securities	91,162	40,904
GNMA | Residential Related Securities
Fair Value
Investment securities available for sale, amortized cost	2,169,943	1,944,453
Investment securities available for sale, at fair value	2,128,531	1,913,350
Amortized Cost
Amortized Cost	351,606	414,440
Fair Value
Total debt securities	$ 345,035	$ 410,740

Investment Securities, Gains, L

Investment Securities, Gains, Losses, and Proceeds (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Gross gains on available for sale securities	$ 1,954	$ 0	$ 9,485
Gross gains on held to maturity securities	0	439	33
Total gains	1,954	439	9,518
Gross losses on available for sale securities	(3,938)	0	(202)
Gross losses on held to maturity securities	0	(5)	0
Total losses	(3,938)	(5)	(202)
Investment securities gains, net	(1,985)	434	9,316
Proceeds from sales of investment securities	$ 601,130	$ 18,467	$ 549,555

Investment Securities, AFS an_3

Investment Securities, AFS and HTM Securities Gross Unrealized Losses (Details) $ in Thousands	Dec. 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	$ (5,262)	$ (15,099)
Unrealized losses on available for sale securities, 12 months or more	(93,347)	(52,868)
Total unrealized losses on available for sale securities	(98,610)	(67,967)
Fair value of unrealized losses on available for sale securities, less than 12 months	613,612	1,593,503
Fair value of unrealized losses on available for sale securities, 12 months or more	3,009,417	1,906,992
Total fair value of unrealized losses on available for sale securities	$ 3,623,028	$ 3,500,495
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	41	92
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	190	105
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (4,053)	$ (4,491)
Held-to-maturity, Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions, less than 12 Months | security	298	202
Unrealized losses on held to maturity securities, 12 months or more	$ (43,780)	$ (21,331)
Total unrealized losses on held to maturity securities	(47,835)	(25,822)
Fair value of unrealized losses on held to maturity securities, less than 12 months	$ 390,929	$ 457,289
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, 12 Months or Longer | security	865	183
Fair value of unrealized losses on held to maturity securities, 12 months or more	$ 1,349,063	$ 751,088
Total fair value of unrealized losses on held to maturity securities	1,739,992	1,208,377
U.S. 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	0	(7)
Unrealized losses on available for sale securities, 12 months or more	(1)	0
Total unrealized losses on available for sale securities	(1)	(7)
Fair value of unrealized losses on available for sale securities, less than 12 months	0	996
Fair value of unrealized losses on available for sale securities, 12 months or more	999	0
Total fair value of unrealized losses on available for sale securities	$ 999	$ 996
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	0	1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	1	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	$ (2,860)	$ (746)
Unrealized losses on held to maturity securities, 12 months or more	(12,419)	(2,431)
Total unrealized losses on held to maturity securities	(15,279)	(3,177)
Fair value of unrealized losses on held to maturity securities, less than 12 months	313,212	122,761
Fair value of unrealized losses on held to maturity securities, 12 months or more	509,374	127,043
Total fair value of unrealized losses on held to maturity securities	$ 822,586	$ 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	272	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	752	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	$ (4)	$ 0
Unrealized losses on available for sale securities, 12 months or more	0	(8)
Total unrealized losses on available for sale securities	(4)	(8)
Fair value of unrealized losses on available for sale securities, less than 12 months	1,003	0
Fair value of unrealized losses on available for sale securities, 12 months or more	0	1,059
Total fair value of unrealized losses on available for sale securities	$ 1,003	$ 1,059
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	1	0
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	0	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	$ 0	$ (5,554)
Unrealized losses on available for sale securities, 12 months or more	(52,512)	(28,347)
Total unrealized losses on available for sale securities	(52,512)	(33,901)
Fair value of unrealized losses on available for sale securities, less than 12 months	0	480,514
Fair value of unrealized losses on available for sale securities, 12 months or more	1,220,854	1,026,642
Total fair value of unrealized losses on available for sale securities	$ 1,220,854	$ 1,507,156
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	0	33
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	93	70
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ 0	$ (299)
Unrealized losses on held to maturity securities, 12 months or more	(22,579)	(15,457)
Total unrealized losses on held to maturity securities	(22,579)	(15,756)
Fair value of unrealized losses on held to maturity securities, less than 12 months	0	52,997
Fair value of unrealized losses on held to maturity securities, 12 months or more	490,414	486,891
Total fair value of unrealized losses on held to maturity securities	$ 490,414	$ 539,888
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	0	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	25	23
FFELP 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	$ (698)	$ (13)
Unrealized losses on available for sale securities, 12 months or more	0	0
Total unrealized losses on available for sale securities	(698)	(13)
Fair value of unrealized losses on available for sale securities, less than 12 months	142,432	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	$ 142,432	$ 12,158
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	13	1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	0	0
Debt 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		$ (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
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 / 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	$ (31)	$ (572)
Unrealized losses on available for sale securities, 12 months or more	(3,479)	(2,062)
Total unrealized losses on available for sale securities	(3,510)	(2,634)
Fair value of unrealized losses on available for sale securities, less than 12 months	17,993	69,939
Fair value of unrealized losses on available for sale securities, 12 months or more	189,405	142,093
Total fair value of unrealized losses on available for sale securities	$ 207,398	$ 212,032
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	15	9
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	17	9
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (780)	$ (73)
Unrealized losses on held to maturity securities, 12 months or more	(1,015)	(417)
Total unrealized losses on held to maturity securities	(1,795)	(490)
Fair value of unrealized losses on held to maturity securities, less than 12 months	57,896	13,143
Fair value of unrealized losses on held to maturity securities, 12 months or more	28,888	16,262
Total fair value of unrealized losses on held to maturity securities	$ 86,784	$ 29,405
FNMA / 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	13	8
FNMA / 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	22	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	$ (4,529)	$ (8,927)
Unrealized losses on available for sale securities, 12 months or more	(37,355)	(22,451)
Total unrealized losses on available for sale securities	(41,885)	(31,378)
Fair value of unrealized losses on available for sale securities, less than 12 months	452,183	1,028,221
Fair value of unrealized losses on available for sale securities, 12 months or more	1,598,159	737,198
Total fair value of unrealized losses on available for sale securities	$ 2,050,342	$ 1,765,419
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security	12	44
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security	79	25
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract]
Unrealized losses on held to maturity securities, less than 12 months	$ (414)	$ (3,373)
Unrealized losses on held to maturity securities, 12 months or more	(7,767)	(3,026)
Total unrealized losses on held to maturity securities	(8,181)	(6,399)
Fair value of unrealized losses on held to maturity securities, less than 12 months	19,822	268,388
Fair value of unrealized losses on held to maturity securities, 12 months or more	320,387	120,892
Total fair value of unrealized losses on held to maturity securities	$ 340,209	$ 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	13	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	66	18

Investment Securities (Details)

Investment Securities (Details) - USD ($)	Feb. 01, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment Securities (Textuals) [Abstract]
Proceeds from Sale of Available-for-sale Securities		$ 108,000,000		$ 601,130,000	$ 18,467,000	$ 549,555,000
Debt Securities, Held-to-maturity, Sold, Amount					18,000,000
Debt Securities, Held-to-maturity, Sold, Realized Gain (Loss)					434,000
Proceeds from Sale of Securities						550,000,000
Marketable Securities, Gain (Loss)				(1,985,000)	434,000	$ 9,316,000
Federal Home Loan Bank Stock				173,000,000	89,000,000
Federal Reserve Bank Stock				77,000,000	76,000,000
Bank Mutual [Member]
Investment Securities
Debt Securities, Available-for-sale, Sold at Par Value	$ 453,000,000
Investment Securities Class [Domain]
Investment Securities
Securities Received as Collateral				$ 3,000,000,000	$ 3,100,000,000
Securities Sold [Member]
Investment Securities
Taxable Equivalent Yield		3.08%
Reinvestment [Member]
Investment Securities
Taxable Equivalent Yield		3.51%
GNMA commercial mortgage-related securities
Investment Securities
Debt Securities, Available-for-sale, Sold at Par Value			$ 40,000,000

Loans, Loan Composition (Detail

Loans, Loan Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 22,940,429	$ 20,784,991
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	7,398,044	6,399,693
Commercial real estate - owner occupied
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	920,443	802,209
Commercial and business lending
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	8,318,487	7,201,902
Commercial real estate — investor
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,751,554	3,315,254
Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,335,031	1,451,684
Commercial real estate lending
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,086,585	4,766,938
Total commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	13,405,072	11,968,840
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	8,277,712	7,546,534
Home equity
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	894,473	883,804
Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	363,171	385,813
Total consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Net of Deferred Income	9,535,357	$ 8,816,151
Bank Mutual [Member]
Loans and Leases Receivable Disclosure [Line Items]
Purchased credit-impaired loans	$ 5,000

Loans, Related Party Loan Rollf

Loans, Related Party Loan Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable, Related Parties [Roll Forward]
Balance at beginning of year	$ 20,260	$ 27,589
New loans	3,076	5,329
Repayments	(5,017)	(7,632)
Changes due to status of executive officers and directors	(489)	(5,026)
Balance at end of year	$ 17,831	$ 20,260

Loans, Loans by Credit Quality

Loans, Loans by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 22,940,429	$ 20,784,991
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	22,438,605	20,171,876
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	123,988	227,692
Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	249,935	176,877
Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	127,901	208,546
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	7,398,044	6,399,693
Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	7,162,370	6,015,884
Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	78,075	157,245
Commercial and industrial | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	116,578	113,778
Commercial and industrial | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	41,021	112,786
Commercial real estate — owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	920,443	802,209
Commercial real estate — owner occupied | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	854,265	723,291
Commercial real estate — owner occupied | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,257	14,181
Commercial real estate — owner occupied | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	55,964	41,997
Commercial real estate — owner occupied | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,957	22,740
Commercial and business lending
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	8,318,487	7,201,902
Commercial and business lending | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	8,016,635	6,739,175
Commercial and business lending | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	84,332	171,426
Commercial and business lending | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	172,542	155,775
Commercial and business lending | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	44,978	135,526
Commercial real estate — investor
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,751,554	3,315,254
Commercial real estate — investor | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,653,642	3,266,389
Commercial real estate — investor | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	28,479	24,845
Commercial real estate — investor | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	67,481	19,291
Commercial real estate — investor | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,952	4,729
Real estate construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,335,031	1,451,684
Real estate construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,321,447	1,421,504
Real estate construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	8,771	29,206
Real estate construction | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,834	0
Real estate construction | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	979	974
Commercial real estate lending
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,086,585	4,766,938
Commercial real estate lending | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	4,975,089	4,687,893
Commercial real estate lending | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	37,249	54,051
Commercial real estate lending | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	71,315	19,291
Commercial real estate lending | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,931	5,703
Total commercial
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	13,405,072	11,968,840
Total commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	12,991,724	11,427,068
Total commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	121,582	225,477
Total commercial | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	243,856	175,066
Total commercial | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	47,909	141,229
Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	8,277,712	7,546,534
Residential mortgage | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	8,203,729	7,490,860
Residential mortgage | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	434	426
Residential mortgage | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	5,975	1,616
Residential mortgage | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	67,574	53,632
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	894,473	883,804
Home equity | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	880,808	868,958
Home equity | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,223	1,137
Home equity | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	103	195
Home equity | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	12,339	13,514
Other consumer
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	363,171	385,813
Other consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	362,343	384,990
Other consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	749	652
Other consumer | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0	0
Other consumer | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	79	171
Total consumer
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	9,535,357	8,816,151
Total consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	9,446,881	8,744,808
Total consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,406	2,215
Total consumer | Potential Problem
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,078	1,811
Total consumer | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 79,992	$ 67,317

Loans, Loans by Past Due Status

Loans, Loans by Past Due Status (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Summarized details of Loans
Current	$ 22,785,019	$ 20,555,250
Financing Receivable, Recorded Investment, Nonaccrual Status	127,901	208,546
Loans and Leases Receivable, Net of Deferred Income	22,940,429	20,784,991
Nonaccrual Loans, Current Portion	$ 74,000	$ 135,000
Percent of current nonaccrual loans	58.00%	65.00%
30-59 Days Past Due
Summarized details of Loans
Total Past Due	$ 21,550	$ 16,861
60-89 Days Past Due
Summarized details of Loans
Total Past Due	3,795	2,467
90 Days or More Past Due
Summarized details of Loans
Total Past Due	2,165	1,867
Commercial and industrial
Summarized details of Loans
Current	7,356,187	6,286,369
Financing Receivable, Recorded Investment, Nonaccrual Status	41,021	112,786
Loans and Leases Receivable, Net of Deferred Income	7,398,044	6,399,693
Commercial and industrial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	187	170
Commercial and industrial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	338	101
Commercial and industrial | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	311	267
Commercial real estate — owner occupied
Summarized details of Loans
Current	913,787	779,421
Financing Receivable, Recorded Investment, Nonaccrual Status	3,957	22,740
Loans and Leases Receivable, Net of Deferred Income	920,443	802,209
Commercial real estate — owner occupied | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,580	48
Commercial real estate — owner occupied | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	119	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	8,269,974	7,065,790
Financing Receivable, Recorded Investment, Nonaccrual Status	44,978	135,526
Loans and Leases Receivable, Net of Deferred Income	8,318,487	7,201,902
Commercial and business lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,767	218
Commercial and business lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	457	101
Commercial and business lending | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	311	267
Commercial real estate — investor
Summarized details of Loans
Current	3,745,835	3,310,000
Financing Receivable, Recorded Investment, Nonaccrual Status	1,952	4,729
Loans and Leases Receivable, Net of Deferred Income	3,751,554	3,315,254
Commercial real estate — investor | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,954	374
Commercial real estate — investor | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	813	0
Commercial real estate — investor | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	151
Real estate construction
Summarized details of Loans
Current	1,333,722	1,450,459
Financing Receivable, Recorded Investment, Nonaccrual Status	979	974
Loans and Leases Receivable, Net of Deferred Income	1,335,031	1,451,684
Real estate construction | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	330	168
Real estate construction | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	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	5,079,557	4,760,459
Financing Receivable, Recorded Investment, Nonaccrual Status	2,931	5,703
Loans and Leases Receivable, Net of Deferred Income	5,086,585	4,766,938
Commercial real estate lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	3,284	542
Commercial real estate lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	813	83
Commercial real estate lending | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	151
Total commercial
Summarized details of Loans
Current	13,349,531	11,826,249
Financing Receivable, Recorded Investment, Nonaccrual Status	47,909	141,229
Loans and Leases Receivable, Net of Deferred Income	13,405,072	11,968,840
Total commercial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	6,051	760
Total commercial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	1,270	184
Total commercial | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	311	418
Residential mortgage
Summarized details of Loans
Current	8,200,432	7,483,350
Financing Receivable, Recorded Investment, Nonaccrual Status	67,574	53,632
Loans and Leases Receivable, Net of Deferred Income	8,277,712	7,546,534
Residential mortgage | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	9,272	9,186
Residential mortgage | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	434	366
Residential mortgage | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Home equity
Summarized details of Loans
Current	876,085	863,465
Financing Receivable, Recorded Investment, Nonaccrual Status	12,339	13,514
Loans and Leases Receivable, Net of Deferred Income	894,473	883,804
Home equity | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	4,826	5,688
Home equity | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	1,223	1,137
Home equity | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	0	0
Other consumer
Summarized details of Loans
Current	358,970	382,186
Financing Receivable, Recorded Investment, Nonaccrual Status	79	171
Loans and Leases Receivable, Net of Deferred Income	363,171	385,813
Other consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	1,401	1,227
Other consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	868	780
Other consumer | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	1,853	1,449
Total consumer
Summarized details of Loans
Current	9,435,487	8,729,001
Financing Receivable, Recorded Investment, Nonaccrual Status	79,992	67,317
Loans and Leases Receivable, Net of Deferred Income	9,535,357	8,816,151
Total consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	15,499	16,101
Total consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	2,525	2,283
Total consumer | 90 Days or More Past Due
Summarized details of Loans
Total Past Due	$ 1,853	$ 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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	$ 133,690	$ 247,575
Unpaid Principal Balance	164,766	275,814
Related Allowance	15,304	25,846
Average Recorded Investment	145,707	236,860
Interest Income Recognized	$ 3,626	$ 8,051
Net Recorded Investment of the Impaired Loans	72.00%	80.00%
Loans with a related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	$ 96,609	$ 175,681
Unpaid Principal Balance	102,483	181,002
Related Allowance	15,304	25,846
Average Recorded Investment	110,079	140,098
Interest Income Recognized	3,699	7,254
Loans with no related allowance
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	37,081	71,894
Unpaid Principal Balance	62,283	94,812
Related Allowance	0	0
Average Recorded Investment	35,627	96,762
Interest Income Recognized	73	797
Commercial and industrial
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	63,153	142,244
Unpaid Principal Balance	87,155	166,418
Related Allowance	5,721	10,838
Average Recorded Investment	73,813	147,769
Interest Income Recognized	823	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	40,747	81,649
Unpaid Principal Balance	42,131	83,579
Related Allowance	5,721	10,838
Average Recorded Investment	52,461	58,494
Interest Income Recognized	1,167	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	22,406	60,595
Unpaid Principal Balance	45,024	82,839
Related Allowance	0	0
Average Recorded Investment	21,352	89,275
Interest Income Recognized	344	492
Commercial real estate — owner occupied
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	5,852	26,234
Unpaid Principal Balance	6,910	26,766
Related Allowance	24	2,973
Average Recorded Investment	6,154	14,072
Interest Income Recognized	104	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	2,080	23,796
Unpaid Principal Balance	2,087	23,937
Related Allowance	24	2,973
Average Recorded Investment	2,179	12,124
Interest Income Recognized	104	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	3,772	2,438
Unpaid Principal Balance	4,823	2,829
Related Allowance	0	0
Average Recorded Investment	3,975	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	69,005	168,478
Unpaid Principal Balance	94,065	193,184
Related Allowance	5,745	13,811
Average Recorded Investment	79,967	161,841
Interest Income Recognized	927	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	42,827	105,445
Unpaid Principal Balance	44,218	107,516
Related Allowance	5,745	13,811
Average Recorded Investment	54,640	70,618
Interest Income Recognized	1,271	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	26,178	63,033
Unpaid Principal Balance	49,847	85,668
Related Allowance	0	0
Average Recorded Investment	25,327	91,223
Interest Income Recognized	344	528
Commercial real estate — investor
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	2,384	19,118
Unpaid Principal Balance	3,625	19,157
Related Allowance	28	1,597
Average Recorded Investment	1,807	16,924
Interest Income Recognized	106	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	799	17,823
Unpaid Principal Balance	805	17,862
Related Allowance	28	1,597
Average Recorded Investment	827	16,924
Interest Income Recognized	38	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	1,585	1,295
Unpaid Principal Balance	2,820	1,295
Related Allowance	0	0
Average Recorded Investment	980	0
Interest Income Recognized	68	45
Real estate construction
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	510	467
Unpaid Principal Balance	589	578
Related Allowance	75	86
Average Recorded Investment	533	484
Interest Income Recognized	32	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	510	467
Unpaid Principal Balance	589	578
Related Allowance	75	86
Average Recorded Investment	533	484
Interest Income Recognized	32	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	2,894	19,585
Unpaid Principal Balance	4,214	19,735
Related Allowance	103	1,683
Average Recorded Investment	2,340	17,408
Interest Income Recognized	138	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	1,309	18,290
Unpaid Principal Balance	1,394	18,440
Related Allowance	103	1,683
Average Recorded Investment	1,360	17,408
Interest Income Recognized	70	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	1,585	1,295
Unpaid Principal Balance	2,820	1,295
Related Allowance	0	0
Average Recorded Investment	980	0
Interest Income Recognized	68	45
Total commercial
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	71,899	188,063
Unpaid Principal Balance	98,279	212,919
Related Allowance	5,848	15,494
Average Recorded Investment	82,307	179,249
Interest Income Recognized	1,065	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	44,136	123,735
Unpaid Principal Balance	45,612	125,956
Related Allowance	5,848	15,494
Average Recorded Investment	56,000	88,026
Interest Income Recognized	1,341	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	27,763	64,328
Unpaid Principal Balance	52,667	86,963
Related Allowance	0	0
Average Recorded Investment	26,307	91,223
Interest Income Recognized	276	573
Residential mortgage
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	50,486	47,486
Unpaid Principal Balance	54,223	50,126
Related Allowance	6,023	6,512
Average Recorded Investment	51,477	45,410
Interest Income Recognized	1,992	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	41,691	40,561
Unpaid Principal Balance	45,149	42,922
Related Allowance	6,023	6,512
Average Recorded Investment	42,687	40,411
Interest Income Recognized	1,789	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	8,795	6,925
Unpaid Principal Balance	9,074	7,204
Related Allowance	0	0
Average Recorded Investment	8,790	4,999
Interest Income Recognized	203	217
Home equity
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	10,124	10,891
Unpaid Principal Balance	11,081	11,631
Related Allowance	3,312	3,718
Average Recorded Investment	10,739	11,061
Interest Income Recognized	566	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	9,601	10,250
Unpaid Principal Balance	10,539	10,986
Related Allowance	3,312	3,718
Average Recorded Investment	10,209	10,521
Interest Income Recognized	566	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	523	641
Unpaid Principal Balance	542	645
Related Allowance	0	0
Average Recorded Investment	530	540
Interest Income Recognized	0	7
Other consumer
Summarize of nonaccrual loans, accruing loans past due 90 days or more, and restructured loans
Recorded Investment	1,181	1,135
Unpaid Principal Balance	1,183	1,138
Related Allowance	121	122
Average Recorded Investment	1,184	1,140
Interest Income Recognized	3	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	1,181	1,135
Unpaid Principal Balance	1,183	1,138
Related Allowance	121	122
Average Recorded Investment	1,184	1,140
Interest Income Recognized	3	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	61,791	59,512
Unpaid Principal Balance	66,487	62,895
Related Allowance	9,456	10,352
Average Recorded Investment	63,400	57,611
Interest Income Recognized	2,561	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	52,473	51,946
Unpaid Principal Balance	56,871	55,046
Related Allowance	9,456	10,352
Average Recorded Investment	54,080	52,072
Interest Income Recognized	2,358	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	9,318	7,566
Unpaid Principal Balance	9,616	7,849
Related Allowance	0	0
Average Recorded Investment	9,320	5,539
Interest Income Recognized	$ 203	$ 224

Loans, Troubled Debt Restructur

Loans, Troubled Debt Restructurings Performing and Nonaccrual (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	$ 53,263	$ 74,618	$ 79,857
Nonaccrual Restructured Loans	26,292	23,486	29,385
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	25,478	30,047	31,884
Nonaccrual Restructured Loans	249	1,776	1,276
Commercial real estate — owner occupied
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	2,080	3,989	5,490
Nonaccrual Restructured Loans	0	0	2,220
Commercial real estate — investor
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	799	14,389	15,289
Nonaccrual Restructured Loans	933	0	924
Real estate construction
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	311	310	359
Nonaccrual Restructured Loans	198	157	150
Residential mortgage
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	16,036	17,068	18,100
Nonaccrual Restructured Loans	22,279	18,991	21,906
Home equity
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	7,385	7,705	7,756
Nonaccrual Restructured Loans	2,627	2,537	2,877
Other consumer
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	1,174	1,110	979
Nonaccrual Restructured Loans	$ 6	$ 25	$ 32

Loans, Loans Modified in a Trou

Loans, Loans Modified in a Troubled Debt Restructuring (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)loan	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	86	77	131
Recorded Investment	$ 11,429	$ 9,426	$ 9,270
Unpaid Principal Balance	$ 11,792	$ 11,900	$ 9,631
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	5	8	8
Recorded Investment	$ 1,315	$ 3,991	$ 1,509
Unpaid Principal Balance	$ 1,330	$ 6,339	$ 1,526
Commercial real estate — owner occupied
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	2	1
Recorded Investment	$ 0	$ 690	$ 116
Unpaid Principal Balance	$ 0	$ 690	$ 122
Commercial real estate — investor
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2	0	0
Recorded Investment	$ 1,393	$ 0	$ 0
Unpaid Principal Balance	$ 1,472	$ 0	$ 0
Real estate construction
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1	0	1
Recorded Investment	$ 78	$ 0	$ 65
Unpaid Principal Balance	$ 80	$ 0	$ 91
Residential mortgage
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	41	45	63
Recorded Investment	$ 6,977	$ 4,238	$ 5,535
Unpaid Principal Balance	$ 7,210	$ 4,364	$ 5,792
Home equity
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	34	22	57
Recorded Investment	$ 1,649	$ 507	$ 2,030
Unpaid Principal Balance	$ 1,681	$ 507	$ 2,084
Other consumer
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	0	1
Recorded Investment	$ 17	$ 0	$ 15
Unpaid Principal Balance	$ 19	$ 0	$ 16

Loans, Troubled Debt Restruct_2

Loans, Troubled Debt Restructurings Subsequent Default (Details)	12 Months Ended
	Dec. 31, 2018USD ($)loan	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	55	66	68
Recorded Investment | $	$ 5,241	$ 3,879	$ 4,574
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	2	0
Recorded Investment | $	$ 0	$ 0	$ 0
Residential mortgage
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	20	36	44
Recorded Investment | $	$ 3,553	$ 3,137	$ 4,102
Home equity
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	32	27	23
Recorded Investment | $	$ 1,688	$ 735	$ 457
Other consumer
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	1	1
Recorded Investment | $	$ 0	$ 7	$ 15

Loans, Changes in the Allowance

Loans, Changes in the Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	$ 265,880	$ 278,335
Charge offs	(50,536)	(56,246)
Recoveries	20,179	16,791
Net charge offs	(30,358)	(39,455)
Provision for loan losses	2,500	27,000
Balance at end of period	238,023	265,880
Allowance for loan losses:
Individually evaluated for impairment	15,304	25,846
Collectively evaluated for impairment	222,719	240,034
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	238,023	265,880
Loans:
Individually evaluated for impairment	133,690	247,575
Collectively evaluated for impairment	22,801,887	20,537,416
Acquired and accounted for under ASC 310-30(a)	4,853
Loans and Leases Receivable, Net of Deferred Income	22,940,429	20,784,991
Commercial and industrial
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	123,068	140,126
Charge offs	(30,837)	(44,533)
Recoveries	13,714	11,465
Net charge offs	(17,123)	(33,068)
Provision for loan losses	2,890	16,010
Balance at end of period	108,835	123,068
Allowance for loan losses:
Individually evaluated for impairment	5,721	10,838
Collectively evaluated for impairment	103,114	112,230
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	108,835	123,068
Loans:
Individually evaluated for impairment	63,153	142,244
Collectively evaluated for impairment	7,331,898	6,257,449
Acquired and accounted for under ASC 310-30(a)	2,994
Loans and Leases Receivable, Net of Deferred Income	7,398,044	6,399,693
Commercial real estate — owner occupied
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	10,352	14,034
Charge offs	(1,363)	(344)
Recoveries	639	173
Net charge offs	(724)	(171)
Provision for loan losses	(373)	(3,511)
Balance at end of period	9,255	10,352
Allowance for loan losses:
Individually evaluated for impairment	24	2,973
Collectively evaluated for impairment	9,231	7,379
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	9,255	10,352
Loans:
Individually evaluated for impairment	5,852	26,234
Collectively evaluated for impairment	913,708	775,975
Acquired and accounted for under ASC 310-30(a)	883
Loans and Leases Receivable, Net of Deferred Income	920,443	802,209
Commercial real estate — investor
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	41,059	45,285
Charge offs	(7,914)	(991)
Recoveries	668	242
Net charge offs	(7,246)	(749)
Provision for loan losses	7,031	(3,477)
Balance at end of period	40,844	41,059
Allowance for loan losses:
Individually evaluated for impairment	28	1,597
Collectively evaluated for impairment	40,816	39,462
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	40,844	41,059
Loans:
Individually evaluated for impairment	2,384	19,118
Collectively evaluated for impairment	3,748,883	3,296,136
Acquired and accounted for under ASC 310-30(a)	287
Loans and Leases Receivable, Net of Deferred Income	3,751,554	3,315,254
Real estate construction
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	34,370	26,932
Charge offs	(298)	(604)
Recoveries	446	74
Net charge offs	149	(530)
Provision for loan losses	(6,279)	7,968
Balance at end of period	28,240	34,370
Allowance for loan losses:
Individually evaluated for impairment	75	86
Collectively evaluated for impairment	28,165	34,284
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	28,240	34,370
Loans:
Individually evaluated for impairment	510	467
Collectively evaluated for impairment	1,334,500	1,451,217
Acquired and accounted for under ASC 310-30(a)	21
Loans and Leases Receivable, Net of Deferred Income	1,335,031	1,451,684
Residential mortgage
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	29,607	27,046
Charge offs	(1,627)	(2,611)
Recoveries	1,271	927
Net charge offs	(355)	(1,684)
Provision for loan losses	(3,657)	4,245
Balance at end of period	25,595	29,607
Allowance for loan losses:
Individually evaluated for impairment	6,023	6,512
Collectively evaluated for impairment	19,572	23,095
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	25,595	29,607
Loans:
Individually evaluated for impairment	50,486	47,486
Collectively evaluated for impairment	8,226,642	7,499,048
Acquired and accounted for under ASC 310-30(a)	584
Loans and Leases Receivable, Net of Deferred Income	8,277,712	7,546,534
Home equity
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	22,126	20,364
Charge offs	(3,236)	(2,724)
Recoveries	2,628	3,194
Net charge offs	(608)	470
Provision for loan losses	(2,252)	1,292
Balance at end of period	19,266	22,126
Allowance for loan losses:
Individually evaluated for impairment	3,312	3,718
Collectively evaluated for impairment	15,954	18,408
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	19,266	22,126
Loans:
Individually evaluated for impairment	10,124	10,891
Collectively evaluated for impairment	884,266	872,913
Acquired and accounted for under ASC 310-30(a)	83
Loans and Leases Receivable, Net of Deferred Income	894,473	883,804
Other consumer
Changes in the allowance for loan losses by portfolio segment
Balance at beginning of year	5,298	4,548
Charge offs	(5,261)	(4,439)
Recoveries	812	716
Net charge offs	(4,448)	(3,723)
Provision for loan losses	5,138	4,473
Balance at end of period	5,988	5,298
Allowance for loan losses:
Individually evaluated for impairment	121	122
Collectively evaluated for impairment	5,867	5,176
Acquired and accounted for under ASC 310-30(a)	0
Balance at end of period	5,988	5,298
Loans:
Individually evaluated for impairment	1,181	1,135
Collectively evaluated for impairment	361,990	384,678
Acquired and accounted for under ASC 310-30(a)	0
Loans and Leases Receivable, Net of Deferred Income	$ 363,171	$ 385,813

Loans, Changes in the Allowan_2

Loans, Changes in the Allowance for Loan Losses by Oil and Gas Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year	$ 265,880	$ 278,335
Charge offs	(50,536)	(56,246)
Recoveries	20,179	16,791
Net charge offs	(30,358)	(39,455)
Provision for Loan Losses	2,500	27,000
Balance at end of period	238,023	265,880
Allowance for loan losses
Individually evaluated	15,304	25,846
Collectively evaluated	222,719	240,034
Balance at end of period	238,023	265,880
Loans
Individually evaluated	133,690	247,575
Collectively evaluated	22,801,887	20,537,416
Loans and Leases Receivable, Net of Deferred Income	22,940,429	20,784,991
Oil and Gas Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year	27,000	38,000
Charge offs	(24,000)	(25,000)
Recoveries	6,000	0
Net charge offs	(17,000)	(25,000)
Provision for Loan Losses	2,000	14,000
Balance at end of period	12,000	27,000
Allowance for loan losses
Individually evaluated	0	5,000
Collectively evaluated	12,000	22,000
Balance at end of period	12,000	27,000
Loans
Individually evaluated	22,000	77,000
Collectively evaluated	725,000	523,000
Loans and Leases Receivable, Net of Deferred Income	$ 747,000	$ 600,000

Loans, Changes in the Allowan_3

Loans, Changes in the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in the Allowance for Unfunded Commitments
Balance at beginning of period	$ 24,000
Balance at end of period	24,000	$ 24,000
Allowance for Unfunded Commitments
Change in the Allowance for Unfunded Commitments
Balance at beginning of period	24,400	25,400	$ 24,400
Provision for unfunded commitments	(2,500)	(1,000)	1,000
Amount recorded at acquisition	2,436	0	0
Balance at end of period	$ 24,336	$ 24,400	$ 25,400

Loans Changes in Accretable Yie

Loans Changes in Accretable Yield (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Balance at beginning of period	$ 0	$ 0
Purchases	4,853	0
Accretion	(4,954)	0
Net reclassification from non-accretable yield	1,605	0
Other(a)	(22)	0
End Balance	$ 1,482	$ 0

Loans (Details)

Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	$ 238,023	$ 265,880	$ 278,335
Financing Receivable, Modifications, Post-Modification Recorded Investment	11,429	9,426	9,270
Restructured Loans Subsequently Accruing	3,000
Ytd Restructured Loans Still On Nonaccrual	8,000
Loans and Leases Receivable, Impaired, Commitment to Lend	6,000
UnaccretedPurchaseDiscount	20,000
UnaccretedPurchaseDiscount_PerformingLoans	18,000
UnaccretedPurchaseDiscount_NonPerformingLoans	2,000
Oil and Gas Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	$ 12,000	$ 27,000	$ 38,000
Percent of Loans	1.62%
Bank Mutual [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Purchased Credit Impaired Loans And Covered Loans	$ 5,000

Goodwill and Intangible Assets,

Goodwill and Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 8,159	$ 1,959	$ 2,093
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	58,100	4,385	4,385
Accumulated amortization	(5,326)	(4,385)	(4,273)
Net book value	52,774	0	112
Amortization of other intangible assets	5,326	112	281
Adjustments to Core Deposits [Member]
Summary of core deposit intangibles and other intangibles
Additions during the period	58,100	0	0
Other Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	44,931	34,572	32,410
Reductions due to sale	(43)	0	0
Accumulated amortization	(21,825)	(18,992)	(17,145)
Net book value	23,062	15,580	15,265
Additions during the period	10,359	2,162	1,012
Amortization of other intangible assets	$ 2,833	$ 1,847	$ 1,812

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets, Mortgage Servicing Rights Roll-Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Mortgage servicing rights:
Mortgage servicing rights at beginning of year	$ 59,168	$ 62,085	$ 62,150
Additions from acquisition	8,136	0	0
Additions	10,722	7,167	12,262
Amortization	(9,594)	(10,084)	(12,327)
Mortgage servicing rights at end of year	68,433	59,168	62,085
Valuation Allowance for Impairment of Recognized Servicing Assets [Roll Forward]
Valuation allowance at beginning of year	(784)	(609)	(809)
(Additions) recoveries, net	545	(175)	200
Valuation allowance at end of year	(239)	(784)	(609)
Mortgage servicing rights, net	68,193	58,384	61,476
Fair value of mortgage servicing rights	81,012	64,387	73,149
Portfolio of residential mortgage loans serviced for others (“servicing portfolio”)	$ 8,600,983	$ 7,646,846	$ 7,974,742
Mortgage servicing rights, net to servicing portfolio	0.79%	0.76%	0.77%
Mortgage servicing rights expense (a)	$ 9,049	$ 10,259	$ 12,127

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets, Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Core Deposit Intangibles
Estimated future amortization expense
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
Year ending December 31, 2023	5,810
Beyond 2,023	23,724
Net book value	52,774	$ 0	$ 112
Other Intangibles
Estimated future amortization expense
Year ending December 31, 2019	2,824
Year ending December 31, 2020	2,707
Year ending December 31, 2021	2,682
Year ending December 31, 2022	2,659
Year ending December 31, 2023	2,640
Beyond 2,023	9,551
Net book value	23,062	$ 15,580	$ 15,265
Mortgage Servicing Rights
Estimated future amortization expense
Year ending December 31, 2019	9,666
Year ending December 31, 2020	10,355
Year ending December 31, 2021	8,951
Year ending December 31, 2022	7,694
Year ending December 31, 2023	6,580
Beyond 2,023	25,187
Net book value	$ 68,433

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets (Details) - USD ($)	Feb. 01, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill, Impairment Loss				$ 0	$ 0	$ 0
Goodwill				$ 1,169,023,000	$ 976,239,000
Bank Mutual [Member]
Business Acquisition [Line Items]
Goodwill acquired during period	$ 175,000,000
Additions to finite-lived intangible assets	$ 58,000,000
Diversified Insurance [Member]
Business Acquisition [Line Items]
Goodwill acquired during period			$ 10,000,000
Additions to finite-lived intangible assets			$ 8,000,000
Anderson Insurance Investment Agency [Domain]
Business Acquisition [Line Items]
Goodwill acquired during period		$ 7,000,000
Additions to finite-lived intangible assets		$ 3,000,000

Premises and Equipment, Summary

Premises and Equipment, Summary Composition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 694,050
Accumulated Depreciation	330,824
Net Book Value	363,225	$ 330,963
Land
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	67,737
Accumulated Depreciation	0
Net Book Value	67,737	59,257
Land improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	14,730
Accumulated Depreciation	7,518
Net Book Value	$ 7,212	6,313
Land improvements | Maximum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	15 years
Land improvements | Minimum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	3 years
Buildings and improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 363,000
Accumulated Depreciation	150,464
Net Book Value	$ 212,536	198,431
Buildings and improvements | Maximum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	39 years
Buildings and improvements | Minimum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	5 years
Computers
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 45,768
Accumulated Depreciation	33,375
Net Book Value	$ 12,392	11,078
Computers | Maximum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	5 years
Computers | Minimum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	3 years
Furniture, fixtures and other equipment
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 168,567
Accumulated Depreciation	118,676
Net Book Value	$ 49,891	42,049
Furniture, fixtures and other equipment | Maximum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	15 years
Furniture, fixtures and other equipment | Minimum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	3 years
Leasehold improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 34,248
Accumulated Depreciation	20,791
Net Book Value	$ 13,457	$ 13,835
Leasehold improvements | Maximum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	15 years
Leasehold improvements | Minimum
Property, Plant and Equipment, Net, by Type [Abstract]
Estimated Useful Lives	3 years

Premises and Equipment, Minimum

Premises and Equipment, Minimum Annual Rent Under Operating Lease Agreements (Details) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Payments, 2019	$ 10,235
Payments, 2020	10,107
Payments, 2021	9,500
Payments, 2022	7,084
Payments, 2023	5,183
Thereafter	22,622
Total	64,732
Operating Leases, Future Minimum Payments Receivable [Abstract]
Receipts, 2019	2,963
Receipts, 2020	3,030
Receipts, 2021	2,860
Receipts, 2022	1,875
Receipts, 2023	1,260
Thereafter	7,806
Total	$ 19,794

Premises and Equipment (Details

Premises and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 34	$ 32	$ 32
Rental expense under leases	10	$ 6	$ 8
Lease Breakage Cost [Member]
Property, Plant and Equipment [Line Items]
Variable Lease, Cost	$ 5

Deposits, Composition (Details)

Deposits, Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deposits, by Type [Abstract]
Noninterest-bearing demand deposits	$ 5,698,530	$ 5,478,416
Savings	2,012,841	1,524,992
Interest-bearing demand	5,336,952	4,603,157
Money market	9,033,669	8,830,328
Brokered CDs	192,234	18,609
Other time	2,623,167	2,330,460
Total deposits	$ 24,897,393	$ 22,785,962

Deposits, Time Deposit Maturiti

Deposits, Time Deposit Maturities (Details)	Dec. 31, 2018USD ($)
Time Deposits, Fiscal Year Maturity [Abstract]
2,019	$ 1,952,008
2,020	561,758
2,021	176,491
2,022	67,738
2,023	52,576
Thereafter	4,830
Total	$ 2,815,401

Deposits (Details)

Deposits (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deposits [Abstract]
Time Deposits, $100,000 or More	$ 1,400	$ 1,400
Time Deposits, $250,000 Or More	$ 924	$ 1,100

Short and Long-term Funding, Co

Short and Long-term Funding, Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Short-term Debt [Abstract]
Federal funds purchased	$ 19,710	$ 141,950
Securities sold under agreements to repurchase	91,941	182,865
Federal funds purchased and securities sold under agreements to repurchase	111,651	324,815
Commercial paper	45,423	67,467
Total short-term funding	157,074	392,282
Senior notes, at par	550,000	250,000
Subordinated notes, at par	250,000	250,000
Other long-term funding and capitalized costs	(4,389)	(2,718)
Other Long-term Debt	795,611	497,282
Total short and long-term funding, excluding FHLB advances	952,685	889,564
Short-term FHLB advances	900,000	284,000
Long-term FHLB advances	2,674,371	2,900,168
Total FHLB advances	3,574,371	3,184,168
Total short and long-term funding	$ 4,527,056	$ 4,073,732

Short and Long-term Funding Rem

Short and Long-term Funding Remaining Contractual Maturity of Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Remaining Contractual Maturity of the Agreements
Repurchase agreements	$ 91,941	$ 182,865
Agency mortgage-related securities
Remaining Contractual Maturity of the Agreements
Repurchase agreements	91,941	182,865
Overnight and Continuous
Remaining Contractual Maturity of the Agreements
Repurchase agreements	91,941	182,865
Overnight and Continuous | Agency mortgage-related securities
Remaining Contractual Maturity of the Agreements
Repurchase agreements	91,941	182,865
Up to 30 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
Up to 30 days | Agency mortgage-related securities
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
30-90 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
30-90 days | Agency mortgage-related securities
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
Greater than 90 days
Remaining Contractual Maturity of the Agreements
Repurchase agreements	0	0
Greater than 90 days | Agency mortgage-related securities
Remaining Contractual Maturity of the Agreements
Repurchase agreements	$ 0	$ 0

Short and Long-term Funding FHL

Short and Long-term Funding FHLB Maturity Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	$ 3,574,371	$ 3,184,168
Weighted Average Coupon Rate	2.19%	1.26%
Maturity or put date 1 year or less
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	$ 2,262,584	$ 2,434,000
Weighted Average Coupon Rate	2.06%	1.26%
After 1 but within 2
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	$ 1,285,039	$ 750,013
Weighted Average Coupon Rate	2.39%	1.23%
After 2 but within 3
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	$ 14,393	$ 155
Weighted Average Coupon Rate	2.98%	4.91%
After 3 years
FHLB_Maturity_ [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	$ 12,354	$ 0
Weighted Average Coupon Rate	4.55%	0.00%

Short and Long-term Funding Lon

Short and Long-term Funding Long-term Funding, Maturities (Details) $ in Thousands	Dec. 31, 2018USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
2,019	$ 1,612,265
2,020	1,285,039
2,021	312,047
2,022	6,023
2,023	2,665
Thereafter	251,943
Total long-term funding	$ 3,469,982

Short and Long-term Funding Sho

Short and Long-term Funding Short and Long-term Funding (Details) - USD ($) $ in Thousands	1 Months Ended
	Nov. 30, 2014	Dec. 31, 2018	Aug. 31, 2018	Dec. 31, 2017
Subordinated Borrowing [Line Items]
Collateral for repurchase agreements		$ 194,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances		3,574,371		$ 3,184,168
FHLB, Increase in Advances [Domain]
Subordinated Borrowing [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances		390,000
FLHB Advances, Putable [Domain]
Subordinated Borrowing [Line Items]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances		2,600,000
Two Thousand Eighteen Senior Notes [Member] [Domain]
Subordinated Borrowing [Line Items]
New Senior Debt Issued			$ 300,000
Debt Instrument, Interest Rate, Stated Percentage			3.50%
Two Thousand Fourteen Senior Notes [Member]
Subordinated Borrowing [Line Items]
New Senior Debt Issued	$ 250,000
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Two Thousand Fourteen Subordinated Notes [Member]
Subordinated Borrowing [Line Items]
Junior Subordinated Debentures Issued	$ 250,000
Debt Instrument, Term	10 years
Subordinated Borrowing, Interest Rate	4.25%
Maximum
Subordinated Borrowing [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged		$ 7,100,000

Stockholders' Equity (Details)

Stockholders' Equity (Details)	Sep. 19, 2018$ / sharesshares	Sep. 15, 2016$ / sharesshares	Jun. 15, 2015$ / sharesshares	Nov. 30, 2008USD ($)$ / shares	Dec. 31, 2018USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)shares	Feb. 05, 2019USD ($)	Nov. 21, 2018shares	Sep. 18, 2018USD ($)	Apr. 24, 2018USD ($)	Jul. 25, 2017USD ($)	Aug. 28, 2015USD ($)
Stockholders' Equity Note [Abstract]
Subsidiary equity balance					$ 3,800,000,000	$ 3,800,000,000
Class of Stock [Line Items]
Purchase of stock, value						$ 537,000		$ 1,248,000
Series C Preferred Stock
Class of Stock [Line Items]
Depositary shares issued (in shares) | shares			2,600,000
Preferred Stock, Dividend Rate, Percentage			6.125%			6.125%
Liquidation preference on depositary shares (in usd per share) | $ / shares			$ 1,000
Preferred Stock, Redemption Terms			Jun. 15, 2020
Redemption Price On Depositary Shares | $ / shares			$ 1,000
Depositary share value (in usd per share) | $ / shares			$ 25
Stock repurchase program authorized amount														$ 10,000,000
Remaining authorized repurchase amount					10,000,000	$ 10,000,000
Depository share ratio			0.025
Series D Preferred Stock
Class of Stock [Line Items]
Depositary shares issued (in shares) | shares		4,000,000
Preferred Stock, Dividend Rate, Percentage		5.375%				5.375%
Liquidation preference on depositary shares (in usd per share) | $ / shares		$ 1,000
Preferred Stock, Redemption Terms		Sep. 15, 2021
Redemption Price On Depositary Shares | $ / shares		$ 1,000
Depositary share value (in usd per share) | $ / shares		$ 25
Stock repurchase program authorized amount													$ 15,000,000
Purchase of stock, value						$ 537,057
Stock Repurchased During Period, Shares | shares						22,000
Remaining authorized repurchase amount					14,000,000	$ 14,000,000
Depository share ratio		0.025
Series E Preferred Stock
Class of Stock [Line Items]
Depositary shares issued (in shares) | shares	4,000,000
Preferred Stock, Dividend Rate, Percentage	5.875%					5.875%
Liquidation preference on depositary shares (in usd per share) | $ / shares	$ 1,000
Preferred Stock, Redemption Terms	Dec. 15, 2023
Redemption Price On Depositary Shares | $ / shares	$ 1,000
Depositary share value (in usd per share) | $ / shares	$ 25
Depository share ratio	0.025
Common Stock
Class of Stock [Line Items]
Stock repurchase program authorized amount											$ 200,000,000	$ 100,000,000
Purchase of stock, value					100,000,000	$ 51,000,000
Remaining authorized repurchase amount					111,000,000	$ 111,000,000
Warrants to purchase shares of common stock (in shares)				$ 4,000,000
Term of warrants				10 years
Exercise price of warrants (in usd per share) | $ / shares				$ 19.77
Class of Warrant or Right, Outstanding | shares										12,507
Unexercised Warrants, Expired Shares | shares										12,507
Treasury stock shares acquired (in shares) | shares						9,500,000	1,600,000
Treasury stock carrying basis					240,000,000	$ 240,000,000	$ 37,000,000
Treasury stock acquired average cost per share (in usd per share) | $ / shares						$ 25.29	$ 23.59
Repurchased amount for minimum tax withholding settlement						$ 7,000,000	$ 9,000,000
Repurchased shares for minimum tax withholding settlements (in shares) | shares						292,070	370,416
Minimum tax withholding settlement average cost per share (in usd per share) | $ / shares						$ 24.47	$ 25.08
Treasury Stock
Class of Stock [Line Items]
Treasury stock shares acquired (in shares) | shares						1,400,000
Treasury stock carrying basis					$ 33,000,000	$ 33,000,000
Treasury stock acquired average cost per share (in usd per share) | $ / shares						$ 24.38
Treasury Stock, Shares, Retired | shares						8,100,000
Treasury Stock, Retired, Cost Method, Amount						$ 206,000,000
Subsequent Event | Common Stock
Class of Stock [Line Items]
Stock repurchase program authorized amount									$ 100,000,000
Remaining authorized repurchase amount									$ 211,000,000
Common Stock
Class of Stock [Line Items]
Purchase of stock, value						$ 0		$ 0
Stock Repurchased During Period, Shares | shares						0		0
Shares from Warrant Exercises | shares						1,116,000

Stock-Based Compensation Assump

Stock-Based Compensation Assumptions used in Estimating the Fair Value for Options Granted (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Dividend yield	2.50%	2.00%	2.50%
Risk-free interest rate	2.60%	2.00%	2.00%
Weighted average expected volatility	22.00%	25.00%	25.00%
Weighted average expected life	5 years 9 months	5 years 6 months	5 years 6 months
Weighted average per share fair value of options	$ 4.47	$ 5.30	$ 3.36

Stock-Based Compensation, Stock

Stock-Based Compensation, Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
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
Shares used in acquisition	$ 370,051
Exercised (in shares)	(1,031,875)
Forfeited or expired (in shares)	(114,695)
Stock Options Shares Outstanding, Ending balance (in shares)	5,280,908	5,118,687
Options exercisable (in shares)	3,187,894
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
Ex Share Price at Acquisition	$ 14.35
Exercised, Weighted Average Exercise Price (in usd per share)	$ 16.45
Forfeited or expired, Weighted Average Exercise Price (in usd per share)	23.88
Stock Options Outstanding, Weighted Average Exercise Price, Ending balance (in usd per share)	19.09	$ 18.02
Options Exercisable, Weighted Average Exercise Price (in usd per share)	$ 16.93
Stock Options Outstanding, Weighted Average Remaining Contractual Term	6 years 2 months 4 days	6 years 5 months 23 days
Options exercisable, Weighted Average Remaining Contractual Term	4 years 11 months 1 day
Stock Options Outstanding, Aggregate Intrinsic Value	$ 12,392,000	$ 38,028,000
Options exercisable, Aggregate Intrinsic Value	$ 10,796,000

Stock-Based Compensation, Restr

Stock-Based Compensation, Restricted Stock Activity (Details)	12 Months Ended
	Dec. 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	615,484
Vested (in shares) | shares	(587,775)
Forfeited (in shares) | shares	(60,948)
Outstanding Shares, Ending balance (in shares) | shares	1,992,832
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	24.60
Vested, Weighted Average Grant Date Fair Value (in usd per share) | $ / shares	18.44
Forfeited, Weighted Average Grant Date Fair Value (in usd per share) | $ / shares	22.36
Outstanding Weighted Average Grant Date Fair Value, Ending balance (in usd per share) | $ / shares	$ 21.92

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Based Compensation (Textuals) [Abstract]
Intrinsic value of stock options exercised	$ 10	$ 13	$ 9
Total fair value of vested stock options	$ 4	4	3
2017 Incentive Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	4 years
Expiration term of awards	10 years
Shares remaining available for grant (in shares)	11.6
Performance-based Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	3 years
Term of transfer restrictions	3 years
Service-based Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	4 years
Term of transfer restrictions	4 years
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for vesting of stock options	$ 4	4	4
String_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost	less than $1 million
Unvested share-based payment awards	$ 4
Employee Service Share Based Compensation Nonvested Awards Compensation Cost Not Yet Recognized Year For Recognition	first quarter 2022
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense for accelerated vesting of stock options	$ 1
Recognized compensation expense for vesting of stock options	13	$ 18	$ 18
Unvested share-based payment awards	$ 18
Employee Service Share Based Compensation Nonvested Awards Compensation Cost Not Yet Recognized Year For Recognition	first quarter 2022
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	150.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	25.00%

Retirement Plans, Pension and P

Retirement Plans, Pension and Postretirement Plans Table (Details) - USD ($) $ in Thousands	Feb. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets As A Percentage Of Net Benefit Obligation		167.00%	178.00%
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year		$ 331,610
Fair value of plan assets at end of year (a)		390,564	$ 331,610
Retirement Account Plan
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year		331,609	295,718
Actual return on plan assets			41,490
Employer contributions			6,242
Gross benefits paid			(11,841)
Bank Mutual plan assets transferred at December 31, 2018		79,805
Fair value of plan assets at end of year (a)		390,564	331,609	$ 295,718
Change in Benefit Obligation
Net benefit obligation at beginning of year		186,423	176,825
Service cost		7,540	6,955	6,780
Interest cost		9,125	7,121	7,121
Actuarial (gain) loss			7,363
Gross benefits paid			(11,841)
Lump sums paid			0
Bank Mutual benefit obligations transferred at December 31, 2018		51,549
Net benefit obligation at end of year (a)		233,658	186,423	176,825
Funded (unfunded) status		156,906	145,186
Noncurrent assets		156,906	145,186
Current liabilities		0	0
Noncurrent liabilities		0	0
Asset (Liability) Recognized in the Consolidated Balance Sheets		156,906	145,186
Other Pension Plan [Member]
Change in Fair Value of Plan Assets
Fair value of Bank Mutual plan assets at February 1, 2018	$ 59,445
Actual return on plan assets		(1,665)
Employer contributions		37,537
Gross benefits paid		(15,513)
Bank Mutual plan assets transferred at December 31, 2018		(79,805)
Fair value of plan assets at end of year (a)		0
Change in Benefit Obligation
Net Bank Mutual benefit obligation at February 1, 2018	66,364
Service cost		0
Interest cost		2,398
Actuarial (gain) loss		(1,701)
Gross benefits paid		(2,644)
Lump sums paid		(12,868)
Bank Mutual benefit obligations transferred at December 31, 2018		(51,549)
Net benefit obligation at end of year (a)		0
Funded (unfunded) status		0
Noncurrent assets		0
Current liabilities		0
Noncurrent liabilities		0
Asset (Liability) Recognized in the Consolidated Balance Sheets		0
Postretirement Plan
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year		0	0
Fair value of Bank Mutual plan assets at February 1, 2018	0
Actual return on plan assets		0	0
Employer contributions		292	235
Gross benefits paid		(292)	(235)
Bank Mutual plan assets transferred at December 31, 2018		0
Fair value of plan assets at end of year (a)		0	0	0
Change in Benefit Obligation
Net benefit obligation at beginning of year		2,478	2,403
Net Bank Mutual benefit obligation at February 1, 2018	$ 576
Service cost		0	0
Interest cost		108	101	142
Actuarial (gain) loss		(347)	209
Gross benefits paid		(292)	(235)
Lump sums paid		0	0
Bank Mutual benefit obligations transferred at December 31, 2018		0
Net benefit obligation at end of year (a)		2,523	2,478	$ 2,403
Funded (unfunded) status		(2,523)	(2,478)
Noncurrent assets		0	0
Current liabilities		(219)	(233)
Noncurrent liabilities		(2,304)	(2,245)
Asset (Liability) Recognized in the Consolidated Balance Sheets		(2,523)	(2,478)
Retirement Account Plan Prior to Merger [Member]
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year		331,609
Actual return on plan assets		(14,609)
Employer contributions		4,340
Gross benefits paid		(10,582)
Fair value of plan assets at end of year (a)			331,609
Change in Benefit Obligation
Net benefit obligation at beginning of year		186,423
Service cost		7,540
Interest cost		6,727
Actuarial (gain) loss		(8,000)
Gross benefits paid		(10,582)
Lump sums paid		$ 0
Net benefit obligation at end of year (a)			$ 186,423

Retirement Plans, Amounts Recog

Retirement Plans, Amounts Recognized in Accumulated Other Comprehensive Income Table (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Retirement Account Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	$ (303)	$ (295)
Net actuarial loss	50,238	24,926
Amount not yet recognized in net periodic benefit cost, but recognized in accumulated other comprehensive (income) loss	49,935	24,631
Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	(588)	(531)
Net actuarial loss	(17)	205
Amount not yet recognized in net periodic benefit cost, but recognized in accumulated other comprehensive (income) loss	$ (605)	$ (326)

Retirement Plans, Other Changes

Retirement Plans, Other Changes in Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	$ (148)	$ (148)	$ (73)
Amortization of actuarial loss (gain)	(28,612)	14,273	(6,141)
Plan amendments	0	0	1,759
Income tax (expense) benefit	6,767	(6,112)	815
Other comprehensive income (loss) on pension and postretirement obligations	(25,025)	10,295	$ (1,525)
Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	347	(209)
Amortization of prior service cost	(75)	(75)
Amortization of actuarial loss (gain)	8	4
ASU Adjustment RAP (2018-02)	0	0
Income tax (expense) benefit	(71)	107
Other comprehensive income (loss) on pension and postretirement obligations	209	(173)
Retirement Account Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	(28,959)	14,482
Amortization of prior service cost	(73)	(73)
Amortization of actuarial loss (gain)	2,195	2,278
ASU Adjustment RAP (2018-02)	(5,235)	0
Income tax (expense) benefit	6,838	(6,219)
Other comprehensive income (loss) on pension and postretirement obligations	$ (25,234)	$ 10,468

Retirement Plans, Components of

Retirement Plans, Components of Net Pension Cost for the Retirement Account Plan Tables (Details) - Retirement Account Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net period benefit cost for the pension and postretirement plans
Service cost	$ 7,540	$ 6,955	$ 6,780
Interest cost	9,125	7,121	7,121
Expected return on plan assets	(23,195)	(19,646)	(20,287)
Amortization of prior service cost	(73)	(73)	(73)
Amortization of actuarial loss (gain)	2,195	2,278	2,115
Recognized settlement loss (gain)	809	0	0
Total net periodic pension cost	$ (3,600)	$ (3,365)	$ (4,344)

Retirement Plans Retirement Pla

Retirement Plans Retirement Plans, Components of Net Pension Cost for the Post Retirement Plan Table (Details) - Postretirement Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost	$ 108	$ 101	$ 142
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(75)	(75)	0
Defined Benefit Plan, Amortization of Gain (Loss)	8	4	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 41	$ 30	$ 142

Retirement Plans, Weighted Aver

Retirement Plans, Weighted Average Assumptions used to Determine Benefit and Net Periodic Benefit Costs (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Expected long-term rate of return on plan assets	5.93%	6.50%
Retirement Account Plan
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.30%	3.70%
Rate of increase in compensation levels	3.00%	3.00%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.77%	4.10%
Rate of increase in compensation levels	3.00%	4.00%
Expected long-term rate of return on plan assets	5.93%	6.50%
Postretirement Plan
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.30%	3.70%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.77%	4.10%
Retirement Account Plan Prior to Merger [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.70%
Expected long-term rate of return on plan assets	6.00%
Other Pension Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.00%
Expected long-term rate of return on plan assets	5.50%

Retirement Plans, Asset Allocat

Retirement Plans, Asset Allocation for Pension Plan Table (Details)	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total	49.00%	60.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total	34.00%	37.00%
Group Annuity Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	12.00%	0.00%
Alternative Securities
Defined Benefit Plan Disclosure [Line Items]
Total	3.00%	0.00%
Other
Defined Benefit Plan Disclosure [Line Items]
Total	2.00%	3.00%

Retirement Plans, Fair Value of

Retirement Plans, Fair Value of Pension Plan Investments Table (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Pension Plan Investments
Money market account	$ 7,159	$ 9,577
Common /collective trust funds	138,020	133,210
Mutual funds	198,120	188,823
Group annuity contracts	47,265
Total Retirement Account Plan Investments	390,564	331,610
Fair Value, Inputs, Level 1
Pension Plan Investments
Money market account	7,159	9,577
Common /collective trust funds	138,020	133,210
Mutual funds	198,120	188,823
Group annuity contracts	0
Total Retirement Account Plan Investments	343,299	331,610
Fair Value, Inputs, Level 2
Pension Plan Investments
Money market account	0	0
Common /collective trust funds	0	0
Mutual funds	0	0
Group annuity contracts	0
Total Retirement Account Plan Investments	0	0
Fair Value, Inputs, Level 3
Pension Plan Investments
Money market account	0	0
Common /collective trust funds	0	0
Mutual funds	0	0
Group annuity contracts	47,265
Total Retirement Account Plan Investments	$ 47,265	$ 0

Retirement Plans Retirement P_2

Retirement Plans Retirement Plans, Fair Value Reconciliation of Level 3 Retirement Account Plan Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Feb. 01, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of group annuity contract at February 1, 2018 (date of Bank Mutual acquisition)	$ 47,265
Fair value of group annuity contract at December 31, 2018	390,564		$ 331,610
Fair Value, Inputs, Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of group annuity contract at February 1, 2018 (date of Bank Mutual acquisition)	47,265
Fair value of group annuity contract at December 31, 2018	47,265		$ 0
Group Annuity Contracts [Member] | Fair Value, Inputs, Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of group annuity contract at February 1, 2018 (date of Bank Mutual acquisition)		$ 49,191
Actual return on plan assets	565
Transfers from money market funds and equity securities	0
Benefits paid	(2,491)
Fair value of group annuity contract at December 31, 2018	$ 47,265

Retirement Plans, Estimated Fut

Retirement Plans, Estimated Future Benefit Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Retirement Account Plan
Defined Benefit Plan Disclosure [Line Items]
2,019	$ 18,774
2,020	19,265
2,021	19,161
2,022	20,210
2,023	20,086
2024 - 2028	89,992
Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
2,019	224
2,020	220
2,021	216
2,022	211
2,023	206
2024 - 2028	$ 925

Retirement Plans, Effect of 1%

Retirement Plans, Effect of 1% Change in the Assumed Health Care Cost Trend Rate Intro (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Change in assumed health care cost
Effect on total of service and interest cost	$ 7	$ 7
Effect on total of service and interest cost	(6)	(6)
Effect on postretirement benefit obligation (increase)	164	162
Effect on postretirement benefit obligation (decrease)	$ (143)	$ (140)

Retirement Plans (Details)

Retirement Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirements Plans [Line Items]
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year	$ 260,000
Expected long-term rate of return on plan assets	5.93%	6.50%
Actual return on plan assets percentage	(3.69%)	14.60%
Total expense related to 401(k)	$ 16,000,000	$ 14,000,000	$ 14,000,000
Pre-65 Health Care Trend Rate [Member]
Retirements Plans [Line Items]
Health care trend rate assumption	7.00%
Defined Benefit Plan, Health Care Cost Trend, Reduction in Trend Rate Minimum	0.25%
Defined Benefit Plan, Health Care Cost Trend, Reduction in Trend Rate Maximum	0.50%
Ultimate future rate	5.00%
Post-65 Health Care Trend [Member]
Retirements Plans [Line Items]
Health care trend rate assumption	6.00%
Defined Benefit Plan, Health Care Cost Trend, Reduction in Trend Rate Minimum	0.25%
Ultimate future rate	5.00%
Defined Benefit Plan Health Care Cost Rate Change	(5.10%)
Retirement Account Plan
Retirements Plans [Line Items]
Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year	$ 75,000
Expected long-term rate of return on plan assets	5.93%	6.50%
Employer contributions		$ 6,242,000
Retirement Account Plan Prior to Merger [Member]
Retirements Plans [Line Items]
Expected long-term rate of return on plan assets	6.00%
Employer contributions	$ 4,340,000
Postretirement Plan
Retirements Plans [Line Items]
Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year	75,000
Employer contributions	$ 292,000	$ 235,000
Other Pension Plan [Member]
Retirements Plans [Line Items]
Expected long-term rate of return on plan assets	5.50%
Employer contributions	$ 37,537,000
Minimum [Member] | Equity Securities
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	50.00%
Minimum [Member] | Fixed income securities
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	30.00%
Minimum [Member] | Alternative Securities
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Minimum [Member] | Cash and Cash Equivalents
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Maximum [Member] | Equity Securities
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	70.00%
Maximum [Member] | Fixed income securities
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	50.00%
Maximum [Member] | Alternative Securities
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	15.00%
Maximum [Member] | Cash and Cash Equivalents
Retirements Plans [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%

Income Taxes, Current and Defer

Income Taxes, Current and Deferred Amounts of Income Tax Expense Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 20,246	$ 76,525	$ 73,781
State	12,593	11,576	2,885
Total current	32,839	88,101	76,666
Deferred:
Federal	34,941	19,755	3,338
State	12,006	1,647	7,318
Total deferred	46,947	21,402	10,656
Total income tax expense	$ 79,786	$ 109,503	$ 87,322

Income Taxes, Deferred Tax Asse

Income Taxes, Deferred Tax Assets and Liabilities Resulted in Deferred Taxes Table (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gross deferred tax assets:
Allowance for loan losses	$ 61,143	$ 66,377
Allowance for other losses	8,304	7,095
Accrued liabilities	3,736	3,884
Deferred compensation	24,754	20,015
Benefit of tax loss and credit carryforwards	10,126	8,438
Nonaccrual interest	1,666	1,619
Net unrealized losses on available-for-sale securities	25,731	15,968
Net unrealized losses on pension and postretirement benefits	16,640	9,928
Other	1,916	4,435
Total deferred tax assets	154,015	137,759
Valuation allowance for deferred tax assets	(251)	(269)	$ 0
Total deferred tax assets after valuation allowance	153,764	137,490
Gross deferred tax liabilities
Prepaid expenses	61,250	49,695
Goodwill	20,178	19,144
Mortgage banking activities	17,428	10,949
Deferred loan fee income	11,892	11,467
State deferred taxes	518	2,001
Lease financing	410	535
Bank premises and equipment	18,655	5,063
Purchase accounting	12,414	5,015
Other	684	304
Total deferred tax liabilities	143,429	104,173
Net deferred tax assets	$ 10,335	$ 33,317

Income Taxes, Summary of Valuat

Income Taxes, Summary of Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets, Valuation Allowance [Roll Forward]
Valuation allowance for deferred tax assets, beginning of year	$ (269)	$ 0
(Increase) decrease in current year	18	(269)
Valuation allowance for deferred tax assets, end of year	$ (251)	$ (269)

Income Taxes, Major Reasons for

Income Taxes, Major Reasons for the Difference in Effective Income Tax Rate from the Federal Tax Rate (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation
Federal income tax rate at statutory rate	21.00%	35.00%	35.00%
Increases (decreases) resulting from:
Tax-exempt interest and dividends	(2.60%)	(4.10%)	(4.80%)
State income taxes (net of federal benefit)	3.70%	2.90%	2.50%
Bank owned life insurance	(0.70%)	(1.70%)	(1.70%)
Tax effect of tax credits and benefits, net of related expenses	(0.70%)	(0.70%)	(1.00%)
Tax reserve adjustments / settlements	1.50%	(1.20%)	0.30%
Net tax benefit from stock-based compensation	(0.50%)	(1.30%)	(0.40%)
Tax Cuts and Jobs Act impact on deferred remeasurement	0.00%	3.50%	0.00%
Tax planning in response to TCJA	(3.60%)	0.00%	0.00%
FDIC premium	0.90%	0.00%	0.00%
Other	0.30%	(0.10%)	0.50%
Effective income tax rate	19.30%	32.30%	30.40%

Income Taxes, Reconciliation of

Income Taxes, Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 4	$ 10
Subtractions for tax positions related to prior years	0	(5)
Subtractions for settlements with tax authorities	(3)	(1)
Additions for tax positions related to current year	1	0
Balance at end of year	$ 2	$ 4

Income Taxes, Textuals (Details

Income Taxes, Textuals (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Feb. 01, 2018	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Valuation allowance for deferred tax assets	$ (251,000)	$ (269,000)		$ 0
Operating tax loss carryforwards from acquisitions	56,000,000
Deferred Other Tax Expense (Benefit)	15,000,000
Other Tax Expense (Benefit)	9,000,000
Bad debt from acquired savings banks	100,000,000
Deferred tax on bad debt from acquired savings banks	25,000,000
Unrecognized tax benefit impact on effective tax rate	1,000,000	3,000,000
Interest and penalty expense (benefit)	1,000,000	1,000,000
Accrued interest and penalties		1,000,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	120,000,000
Operating tax loss carryforwards from acquisitions	42,000,000		$ 51,000,000
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	3,000,000	$ 3,000,000
Operating tax loss carryforwards from acquisitions			$ 5,000,000
Tax Credit Carryforward, Amount	$ 1,000,000

Derivative and Hedging Activi_3

Derivative and Hedging Activities, Derivative Instruments Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	Dec. 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	$ 2,707,204	$ 2,183,687
Fair Value	52,796	28,494
Not Designated as Hedging Instrument | Trading assets | Foreign currency exchange forwards
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	117,879	124,851
Fair Value	721	2,495
Not Designated as Hedging Instrument | Trading assets | Commodity contracts
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	331,727	457,868
Fair Value	35,426	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	2,707,204	2,183,687
Fair Value	(52,653)	(28,035)
Not Designated as Hedging Instrument | Trading liabilities | Foreign currency exchange forwards
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	69,153	118,094
Fair Value	(675)	(2,339)
Not Designated as Hedging Instrument | Trading liabilities | Commodity contracts
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	315,861	457,108
Fair Value	(34,340)	(37,286)
Not Designated as Hedging Instrument | Other assets | Interest rate lock commitments (mortgage)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	191,222	222,736
Fair Value	2,208	1,538
Not Designated as Hedging Instrument | Other assets | Purchased options (time deposit)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	11,185	31,063
Fair Value	109	1,175
Not Designated as Hedging Instrument | Other liabilities | Forward commitments (mortgage)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	139,984	164,567
Fair Value	(2,072)	(313)
Not Designated as Hedging Instrument | Other liabilities | Written options (time deposit)
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	11,185	31,063
Fair Value	(109)	(1,175)
Designated as Hedging Instrument [Member] | Other assets | interest rate product [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Notional Amount	500,000	0
Derivative, Fair Value, Net	$ (40)	$ 0

Derivative and Hedging Activi_4

Derivative and Hedging Activities Cumulative Basis Adjustment for Fair Value Hedges (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Recording of Fair Value Hedge [Line Items]
Trading assets	$ 88,943	$ 69,675
Designated as Hedging Instrument [Member]
Balance Sheet Recording of Fair Value Hedge [Line Items]
Derivative Asset, Amortized Cost Basis	1,100,000
Trading assets	500,000
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	502
adjustment [Member] | Designated as Hedging Instrument [Member]
Balance Sheet Recording of Fair Value Hedge [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(502)
Carrying Value [Member] | Designated as Hedging Instrument [Member]
Balance Sheet Recording of Fair Value Hedge [Line Items]
Trading assets	$ 499,498

Derivative and Hedging Activi_5

Derivative and Hedging Activities Income Impact of Fair Value and Cash Flow Hedge (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 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	$ (1,325)	$ 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	(502)	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 [Member] | Interest Income [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(823)	0
Designated as Hedging Instrument [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

Derivative and Hedging Activi_6

Derivative and Hedging Activities, Income Statement Category of the Gains and Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Capital market fees, net | Interest rate-related instruments — customer and mirror
Gain (loss) on derivative instruments not designated as hedging instruments
Gain / (Loss) Recognized in Income	$ (316)	$ (24)
Capital market fees, net | Foreign currency exchange forwards
Gain (loss) on derivative instruments not designated as hedging instruments
Gain / (Loss) Recognized in Income	(110)	97
Capital market fees, net | Commodity contracts
Gain (loss) on derivative instruments not designated as hedging instruments
Gain / (Loss) Recognized in Income	(314)	647
Mortgage banking, net | Interest rate lock commitments (mortgage)
Gain (loss) on derivative instruments not designated as hedging instruments
Gain / (Loss) Recognized in Income	670	1,332
Mortgage banking, net | Forward commitments (mortgage)
Gain (loss) on derivative instruments not designated as hedging instruments
Gain / (Loss) Recognized in Income	$ (1,759)	$ (3,221)

Derivative and Hedging Activi_7

Derivative and Hedging Activities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Investment securities and cash equivalents pledged as collateral	$ 36	$ 24
Derivative collateral right to reclaim cash	$ 1	$ 22

Balance Sheet Offsetting (Detai

Balance Sheet Offsetting (Details) - Interest Rate Contract - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	$ 65,596	$ 29,503
Gross amounts offset in the balance sheet	0	0
Net amounts presented in the balance sheet	65,596	29,503
Derivative liability available for offset	(22,873)	(16,140)
Collateral received	(41,879)	(13,234)
Net amount	843	129
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	22,951	37,164
Gross amounts offset in the balance sheet	0	0
Net amounts presented in the balance sheet	22,951	37,164
Derivative asset available for offset	(22,873)	(16,140)
Collateral pledged	(63)	(20,662)
Net amount	$ 16	$ 362

Commitments, Off-Balance Shee_3

Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities, Summary of Lending Related and Other Commitments (Details) - USD ($) $ in Thousands	Dec. 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	8,720,293	8,027,187
Commercial Letters Of Credit
Summary of lending-related and other commitments
Lending related commitments	7,599	11,886
Standby Letters of Credit
Summary of lending-related and other commitments
Lending related commitments	255,904	235,361
Standby letters of credit, fair value	$ 2,000	$ 2,000

Commitments, Off-Balance Shee_4

Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities Residential Mortgage Repurchase Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Residential mortgage repurchase reserve
Balance at beginning of period	$ 24,000
Amount recorded at acquisition	88	$ 0
Balance at end of period	24,000	24,000
Mortgage Repurchase Reserve
Residential mortgage repurchase reserve
Balance at beginning of period	987	900
Repurchase provision expense	345	246
Adjustments to provision expense	(450)	0
Charge offs, net	(218)	(159)
Balance at end of period	$ 752	$ 987

Commitments, Off-Balance Shee_5

Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Unfunded commitments	$ 24	$ 24
Expense Related to Qualified Affordable Housing Projects	17	8	$ 3
Remaining Investment in Qualified Affordable Housing Projects	132	141
Variable Interest Entity Reporting Entity Involvement Unfunded Obligation Amount	51	93
Loans repurchased under make whole requests	2	1
Loans sold to outside investors original amount	11,100
Loans sold to outside investors remaining outstanding amount	7,300
Residential mortgage loans sold with recourse risk	47	44
Residential mortgage loans sold with credit recourse risk	57	73
UnconsolidatedProjectsLowIncomeHousing [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Carrying value of investments	136	147
PrincipalInvestmentCommitment [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Carrying value of investments	$ 25	$ 23

Parent Company Only Financial_3

Parent Company Only Financial Information, Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and due from banks	$ 507,187	$ 483,666
Interest-bearing Deposits in Banks and Other Financial Institutions	221,226	199,702
Investment securities available for sale, at fair value	3,948,510	4,043,446
Other assets	460,331	458,920
Total assets	33,647,859	30,483,594
Liabilities and stockholders' equity
Commercial paper	45,423	67,467
Senior notes, at par	550,000	250,000
Subordinated notes, at par	250,000	250,000
Long-term funding capitalized costs	(4,389)	(2,718)
Total long-term funding	3,469,982
Accrued expenses and other liabilities	354,855	318,797
Total liabilities	29,866,971	27,246,151
Preferred equity	256,716	159,929
Common equity	1,752	1,618
Total stockholders’ equity	3,780,888	3,237,443	$ 3,091,312	$ 2,937,246
Total liabilities and stockholders’ equity	33,647,859	30,483,594
Parent Company Only
Assets
Cash and due from banks	16,245	25,544
Interest-bearing Deposits in Banks and Other Financial Institutions	38,374	121,333
Investment securities available for sale, at fair value	0	11,645
Notes and interest receivable from subsidiaries	453,615	301,378
Investments in and receivable due from subsidiaries	3,787,574	3,320,090
Other assets	47,448	51,466
Total assets	4,343,256	3,831,456
Liabilities and stockholders' equity
Commercial paper	45,423	67,467
Senior notes, at par	250,000	250,000
Subordinated notes, at par	250,000	250,000
Long-term funding capitalized costs	(2,043)	(2,718)
Total long-term funding	497,957	497,282
Accrued expenses and other liabilities	18,988	29,264
Total liabilities	562,368	594,013
Preferred equity	256,716	159,929
Common equity	3,524,171	3,077,514
Total stockholders’ equity	3,780,888	3,237,443
Total liabilities and stockholders’ equity	$ 4,343,256	$ 3,831,456

Parent Company Only Financial_4

Parent Company Only Financial Information, Statement of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
INCOME
Interest income on notes receivable from subsidiaries	$ 976,990	$ 749,000	$ 659,538
Total income	1,235,148	1,073,900	1,060,156
EXPENSE
Income before income tax expense (benefit) and equity in undistributed net income (loss) of subsidiaries	413,349	338,767	287,596
Income tax expense	79,786	109,503	87,322
Net income	333,562	229,264	200,274
Preferred stock dividends	10,784	9,347	8,903
Net income available to common equity	322,779	219,917	191,371
Parent Company Only
INCOME
Dividends from subsidiaries	336,000	213,000	188,000
Interest income on notes receivable from subsidiaries	12,199	4,175	0
Other income	994	1,763	4,669
Total income	349,193	218,938	192,669
EXPENSE
Interest expense on short and long-term funding	18,355	18,464	21,901
Other expense	11,736	6,927	4,289
Total expense	30,091	25,391	26,190
Income before income tax expense (benefit) and equity in undistributed net income (loss) of subsidiaries	319,102	193,547	166,479
Income tax expense	4,176	4,768	3,468
Income before equity in undistributed net income (loss) of subsidiaries	314,926	188,779	163,011
Equity in undistributed net income (loss) of subsidiaries	18,636	40,485	37,263
Net income	333,562	229,264	200,274
Preferred stock dividends	10,784	9,347	8,903
Net income available to common equity	$ 322,779	$ 219,917	$ 191,371

Parent Company Only Financial_5

Parent Company Only Financial Information, Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities
Net income		$ 333,562	$ 229,264	$ 200,274
Adjustments to reconcile net income to net cash provided by operating activities:
Losses (gains) on sales of investment securities, net		1,985	(434)	(9,316)
Asset (gains) losses, net		1,103	1,244	86
Net change in other assets and other liabilities		(2,763)	(21,919)	26,144
Net cash provided by operating activities		496,567	458,368	641,383
Cash Flows from Investing Activities
Proceeds from Sale of Available-for-sale Securities	$ 108,000	601,130	18,467	549,555
Net cash used in investing activities		(380,872)	(1,396,858)	(1,653,023)
Cash Flows from Financing Activities
Net increase (decrease) in short-term funding		(581,371)	(217,753)	110,619
Repayment of long-term funding		0	0	430,000
Proceeds from issuance of common stock for stock-based compensation plans		18,408	27,619	21,748
Proceeds from issuance of preferred stock		97,315	0	97,066
Redemption of preferred stock		0	0	58,903
Purchase of preferred shares		(537)	0	(1,248)
Common stock warrants exercised		(1)
Purchase of common stock returned to authorized but unissued		(33,075)	(37,031)	(20,007)
Issuance of Treasury Stock for Acquisition		488,408	7,151
Purchase of treasury stock		(213,598)	(9,290)	(5,074)
Cash dividends on common stock		(105,519)	(76,417)	(67,855)
Cash dividends on preferred stock		(10,784)	(9,347)	(8,903)
Net cash used in financing activities		44,983	1,012,275	1,180,188
Parent Company Only
Cash Flows from Operating Activities
Net income		333,562	229,264	200,274
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in equity in undistributed net income (loss) of subsidiaries		(18,636)	(40,485)	(37,263)
Losses (gains) on sales of investment securities, net		0	0	(466)
Asset (gains) losses, net		0	(88)	(793)
Net change in other assets and other liabilities		(92,366)	(9,589)	19,708
Net cash provided by operating activities		222,562	179,102	181,460
Cash Flows from Investing Activities
Proceeds from Sale of Available-for-sale Securities		827	2,618	47,719
Net increase in notes receivable from subsidiaries		(139,317)	(300,000)	0
Purchase of other assets, net of disposals		2,210	1,058	2,211
Net cash used in investing activities		(136,280)	(296,324)	49,930
Cash Flows from Financing Activities
Net increase (decrease) in short-term funding		(22,044)	(34,221)	33,710
Repayment of long-term funding		0	0	(430,000)
Proceeds from issuance of common stock for stock-based compensation plans		18,408	27,619	21,748
Proceeds from issuance of preferred stock		97,315	0	97,066
Redemption of preferred stock		0	0	(58,903)
Purchase of preferred shares		(537)	0	(1,248)
Common stock warrants exercised		(1)	0	0
Purchase of common stock returned to authorized but unissued		(33,075)	(37,031)	(20,007)
Issuance of Treasury Stock for Acquisition		91,296	0	0
Purchase of treasury stock		(213,598)	(9,290)	(5,074)
Cash dividends on common stock		(105,519)	(76,417)	(67,855)
Cash dividends on preferred stock		(10,784)	(9,347)	(8,903)
Net cash used in financing activities		(178,540)	(138,687)	(439,466)
Net increase (decrease) in cash, cash equivalents, and restricted cash		(92,258)	(255,909)	(208,076)
Cash, cash equivalents, and restricted cash at beginning of period		146,877	402,786	610,862
Cash, cash equivalents, and restricted cash at end of period		$ 54,619	$ 146,877	$ 402,786

Fair Value Measurements, Assets

Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	$ 3,948,510	$ 4,043,446
Trading Assets	88,943	69,675
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	87,668	67,660
Fair Value, Inputs, Level 1
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	2,567	2,628
Fair Value, Inputs, Level 2
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	3,945,943	4,040,818
Trading Assets	89,052	70,850
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	87,817	68,835
Fair Value, Inputs, Level 3
Assets, Fair Value Disclosure [Abstract]
Trading Assets	2,208	1,538
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	2,072	313
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 | U.S. Treasury securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	999	996
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 | Other securities (debt and equity)
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	1,568	1,632
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 | Total investment securities available for sale
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	2,567	2,628
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | FNMA / FHLMC
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	295,252	464,768
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | GNMA
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	2,128,531	1,913,350
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Private-label
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	1,003	1,059
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | GNMA commercial mortgage-related securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	1,220,797	1,513,277
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Federal Family Education Loan Program (FFELP) Guaranteed Loans
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	297,360	145,176
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Other securities (debt and equity)
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	3,000	3,188
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Total investment securities available for sale
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	3,945,943	4,040,818
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Residential Loans Held For Sale Member [Member]
Assets, Fair Value Disclosure [Abstract]
Trading Assets	64,321	85,544
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Commercial loans held for sale [Domain]
Assets, Fair Value Disclosure [Abstract]
Trading Assets	14,943	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Interest rate-related instruments
Assets, Fair Value Disclosure [Abstract]
Trading Assets	52,796	28,494
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	52,653	28,035
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Foreign currency exchange forwards
Assets, Fair Value Disclosure [Abstract]
Trading Assets	721	2,495
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	675	2,339
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Commodity contracts
Assets, Fair Value Disclosure [Abstract]
Trading Assets	35,426	38,686
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	34,340	37,286
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Purchased options (time deposit)
Assets, Fair Value Disclosure [Abstract]
Trading Assets	109	1,175
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	109	1,175
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 | Interest rate lock commitments to originate residential mortgage loans held for sale
Assets, Fair Value Disclosure [Abstract]
Trading Assets	2,208	1,538
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 | Forward commitments to sell residential mortgage loans
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	2,072	313
Designated as Hedging Instrument [Member]
Assets, Fair Value Disclosure [Abstract]
Trading Assets	500,000
Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2
Liabilities, Fair Value Disclosure [Abstract]
Interest Rate Fair Value Hedge Asset at Fair Value	$ 40	$ 0

Fair Value Measurements, Asse_2

Fair Value Measurements, Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Investment Securities Available for Sale
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Fair Value, Assets, Level 3 to Level 2 Transfers, Amount			$ (200)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Assets, Level 3 to Level 2 Transfers, Amount			$ 200
Derivative Financial Instruments
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Mortgage derivative gain (loss)	$ (1,085)	$ (1,889)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning Balance	1,225	3,114
Mortgage derivative gain (loss)	(1,085)	(1,889)
Ending Balance	140	1,225
Available-for-sale Securities [Member]
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Beginning Balance	0	(200)
Mortgage derivative gain (loss)	0	0
Ending Balance	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Mortgage derivative gain (loss)	$ 0	0
Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Fair Value, Assets, Level 3 to Level 2 Transfers, Amount		0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Assets, Level 3 to Level 2 Transfers, Amount		0
Fair Value, Measurements, Recurring [Member] | Available-for-sale Securities [Member]
Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)
Fair Value, Assets, Level 3 to Level 2 Transfers, Amount		(200)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Assets, Level 3 to Level 2 Transfers, Amount		$ 200

Fair Value Measurements, Asse_3

Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Mortgage servicing rights	$ 68,193	$ 58,384	$ 61,476
Mortgage Servicing Rights (MSR) Impairment (Recovery)	(545)	175	$ (200)
Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial loans held for sale	14,943	0
Mortgage loans held for sale	64,321	85,544
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Other real estate owned (c)	2,200	2,604
Foreclosure / OREO expense, net	(1,545)	(939)
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	26,191	92,534
Provision for Credit Losses, Impaired Loans	(14,521)	(32,159)
Mortgage servicing rights	81,012	64,387
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ 545	$ (175)

Fair Value Measurements, Schedu

Fair Value Measurements, Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities (Details) - Fair Value, Inputs, Level 3	12 Months Ended
	Dec. 31, 2018
Servicing Contracts [Member] | Discounted Cash Flow [Member]
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	11.00%
Impaired Finance Receivable [Member] | Appraisals/Discounted Cash Flow [Member]
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	40.00%

Fair Value Measurements, Fair V

Fair Value Measurements, Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial assets
Cash and due from banks	$ 507,187	$ 483,666
Interest-bearing deposits in other financial institutions	221,226	199,702
Federal funds sold and securities purchased under agreements to resell	148,285	32,650
Investment securities held to maturity	2,740,511	2,282,853
Investment securities held to maturity, fair value	2,710,271	2,283,574
Investment securities available for sale	3,948,510	4,043,446
FHLB and Federal Reserve Bank stocks	250,534	165,331
Commercial loans held for sale	14,943	0
Loans, net	22,702,406	20,519,111
Bank and Corporate Owned Life Insurance	663,203	591,057
Trading Assets	88,943	69,675
Financial liabilities
Short-term funding	157,074	392,282
Other long-term funding	3,469,982
Derivatives (trading and other liabilities)	87,668	67,660
Commitment on standby letters of credit	256,000	235,000
Fair Value, Inputs, Level 1
Financial assets
Cash and due from banks	507,187	483,666
Cash and due from banks, Fair Value	507,187	483,666
Interest-bearing deposits in other financial institutions	221,226	199,702
Interest-bearing deposits in other financial institutions, fair value	221,226	199,702
Federal funds sold and securities purchased under agreements to resell	148,285	32,650
Federal funds sold and securities purchased under agreements to resell, fair value	148,285	32,650
Investment securities available for sale	2,567	2,628
Investment securities available for sale, at fair value	2,567	2,628
Fair Value, Inputs, Level 2
Financial assets
Investment securities held to maturity	2,740,511	2,282,853
Investment securities held to maturity, fair value	2,710,271	2,283,574
Investment securities available for sale	3,945,943	4,040,818
Investment securities available for sale, at fair value	3,945,943	4,040,818
FHLB and Federal Reserve Bank stocks	250,534	165,331
FHLB and Federal Reserve Bank stocks, fair value	250,534	165,331
Mortgage Loans Held-for-sale	64,321	85,544
Mortgages Held-for-sale, Fair Value Disclosure	64,321	85,544
Commercial loans held for sale	14,943	0
Commercial Loans Held-for-sale, Fair Value Disclosure	14,943	0
Bank and Corporate Owned Life Insurance	663,203	591,057
Bank owned life insurance, fair value	663,203	591,057
Trading Assets	89,052	70,850
Derivatives (trading and other assets), fair value	89,052	70,850
Financial liabilities
Brokered CDs and other time deposits	2,815,401	2,349,069
Brokered CDs and other time deposits, fair value	2,815,401	2,349,069
Short-term funding	1,057,074	676,282
Short-term funding, fair value	1,057,074	676,282
Other long-term funding	3,469,982	3,397,450
Long-term funding, fair value	3,492,174	3,411,368
Standby letters of credit	2,482	2,402
Standby letters of credit, fair value	2,482	2,402
Derivatives (trading and other liabilities)	87,817	68,835
Derivatives (trading and other liabilities), fair value	87,817	68,835
Fair Value, Inputs, Level 3
Financial assets
Loans, net	22,702,406	20,519,111
Loans, net, fair value	22,317,395	20,314,984
Trading Assets	2,208	1,538
Derivatives (trading and other assets), fair value	2,208	1,538
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts	22,081,992	20,436,893
Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts, fair value	22,081,992	20,436,893
Derivatives (trading and other liabilities)	2,072	313
Derivatives (trading and other liabilities), fair value	$ 2,072	$ 313

Fair Value Measurements, Textua

Fair Value Measurements, Textuals (Details)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Closing Ratio	84.00%

Regulatory Matters (Details)

Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Associated Banc-Corp
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 3,216,575	$ 2,848,851
Total Capital Actual Ratio	13.47%	13.22%
Total Capital for Capital Adequacy Purposes Amount	$ 1,910,022	$ 1,723,557
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Tier 1 Capital Actual Amount	$ 2,705,939	$ 2,331,245
Tier 1 Capital Actual Ratio	11.33%	10.82%
Tier 1 Capital for Adequacy Purposes Amount	$ 1,432,517	$ 1,292,668
Tier 1 Capital for Adequacy Purposes Ratio	6.00%	6.00%
Common Equity Tier One Capital	$ 2,449,721	$ 2,171,508
Common Equity Tier One Capital to Risk Weighted Assets	10.26%	10.08%
Common Equity Tier One Capital Required for Capital Adequacy	$ 1,074,388	$ 969,501
Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier 1 Leverage Capital Actual Amount	$ 2,705,939	$ 2,331,245
Tier 1 Leverage Capital Actual Ratio	8.48%	8.02%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,276,624	$ 1,162,929
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Associated Bank, N.A.
Regulatory Capital [Abstract]
Total Capital Actual Amount	$ 2,909,064	$ 2,625,945
Total Capital Actual Ratio	12.23%	12.24%
Total Capital for Capital Adequacy Purposes Amount	$ 1,903,155	$ 1,716,910
Total Capital for Adequacy Purposes Ratio	8.00%	8.00%
Total Capital to be Well Capitalized Amount	$ 2,378,944	$ 2,146,138
Total Capital to be Well Capitalized Ratio	10.00%	10.00%
Tier 1 Capital Actual Amount	$ 2,646,705	$ 2,357,354
Tier 1 Capital Actual Ratio	11.13%	10.98%
Tier 1 Capital for Adequacy Purposes Amount	$ 1,427,367	$ 1,287,683
Tier 1 Capital for Adequacy Purposes Ratio	6.00%	6.00%
Tier 1 Capital To Be Well Capitalized Amount	$ 1,903,155	$ 1,716,910
Tier 1 Capital To Be Well Capitalized Ratio	8.00%	8.00%
Common Equity Tier One Capital	$ 2,446,782	$ 2,157,354
Common Equity Tier One Capital to Risk Weighted Assets	10.29%	10.05%
Common Equity Tier One Capital Required for Capital Adequacy	$ 1,070,525	$ 965,762
Common Equity Tier One Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier 1 Equity Capital to be Well Capitalized Amount	$ 1,546,314	$ 1,394,989
Tier 1 Equity Capital to be Well Capitalized Ratio	6.50%	6.50%
Tier 1 Leverage Capital Actual Amount	$ 2,646,705	$ 2,357,354
Tier 1 Leverage Capital Actual Ratio	8.31%	8.13%
Tier 1 Leverage Capital for Adequacy Purposes Amount	$ 1,274,380	$ 1,159,959
Tier 1 Leverage Capital for Adequacy Purposes Ratio	4.00%	4.00%
Tier 1 Leverage Capital To Be Well Capitalized Amount	$ 1,592,976	$ 1,449,948
Tier 1 Leverage Capital To Be Well Capitalized Ratio	5.00%	5.00%

Regulatory Matters (Details Tex

Regulatory Matters (Details Textuals) $ in Millions	Dec. 31, 2018USD ($)
Regulatory Capital Requirements [Abstract]
Required minimum cash and reserve balances	$ 94

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Calculations for basic and diluted earnings per common share
Net income	$ 333,562	$ 229,264	$ 200,274
Preferred stock dividends	(10,784)	(9,347)	(8,903)
Net income available to common equity	322,779	219,917	191,371
Common shareholder dividends	(104,981)	(75,967)	(67,100)
Unvested share-based payment awards	(537)	(450)	(755)
Undistributed earnings	217,260	143,500	123,516
Undistributed earnings allocated to common shareholders	216,199	142,593	122,205
Undistributed earnings allocated to unvested share-based payment awards	1,060	907	1,311
Undistributed earnings	217,260	143,500	123,516
Basic
Distributed earnings to common shareholders	104,981	75,967	67,100
Undistributed earnings allocated to common shareholders	216,199	142,593	122,205
Total common shareholders earnings, basic	321,181	218,560	189,305
Diluted
Distributed earnings to common shareholders	104,981	75,967	67,100
Undistributed earnings allocated to common shareholders	216,199	142,593	122,205
Total common shareholders earnings, diluted	$ 321,181	$ 218,560	$ 189,305
Weighted average common shares outstanding	167,345	150,877	148,769
Effect of dilutive common stock awards	1,985	2,038	1,192
Effect of dilutive common stock warrants	402	732	0
Diluted weighted average common shares outstanding	169,732	153,647	149,961
Basic earnings per common share	$ 1.92	$ 1.45	$ 1.27
Diluted earnings per common share	$ 1.89	$ 1.42	$ 1.26

Earnings Per Common Share Narra

Earnings Per Common Share Narrative (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2	1	1
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			4

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Income Statement Data Abstract
Net interest income	$ 879,580	$ 741,220	$ 707,273
Net intersegment interest income (expense)	0	0	0
Segment net interest income	879,580	741,220	707,273
Noninterest income	355,568	332,680	352,883
Total revenue	1,235,148	1,073,900	1,060,156
Credit provision (a)	0	26,000	70,000
Noninterest expense	821,799	709,133	702,560
Income (loss) before income taxes	413,349	338,767	287,596
Income tax expense (benefit)	79,786	109,503	87,322
Net income	$ 333,562	$ 229,264	$ 200,274
Return on average allocated capital (ROCET1) (b)	13.15%	10.43%	9.86%
Segment Balance Sheet Data
Average earning assets	$ 30,049,793	$ 26,999,884	$ 26,026,661
Average loans	22,718,297	20,592,383	19,650,667
Average deposits	24,072,049	21,923,602	21,005,772
Average allocated capital (CETI)(b)	2,454,919	2,109,459	1,940,391
Allocated goodwill	1,169,023	976,239	971,951
Gain (Loss) on Disposition of Assets for Financial Service Operations	(1,103)	(1,244)	(86)
Operating Segments | Corporate and Commercial Specialty [Member]
Segment Income Statement Data Abstract
Net interest income	457,613	360,789	312,982
Net intersegment interest income (expense)	(56,356)	(3,737)	15,621
Segment net interest income	401,258	357,051	328,603
Noninterest income	52,321	52,297	47,776
Total revenue	453,578	409,348	376,379
Credit provision (a)	44,592	42,298	50,397
Noninterest expense	160,399	156,890	148,493
Income (loss) before income taxes	248,587	210,160	177,489
Income tax expense (benefit)	47,850	71,655	59,261
Net income	$ 200,737	$ 138,505	$ 118,228
Return on average allocated capital (ROCET1) (b)	16.60%	12.39%	11.04%
Segment Balance Sheet Data
Average earning assets	$ 11,852,662	$ 10,820,998	$ 10,178,813
Average loans	11,841,818	10,811,827	10,169,300
Average deposits	8,112,430	6,938,913	5,904,238
Average allocated capital (CETI)(b)	1,209,558	1,117,761	1,070,598
Allocated goodwill	524,525	428,000	428,000
Operating Segments | Community, Consumer and Business [Member]
Segment Income Statement Data Abstract
Net interest income	357,245	316,008	306,913
Net intersegment interest income (expense)	87,737	45,353	43,639
Segment net interest income	444,982	361,361	350,551
Noninterest income	295,647	266,250	277,942
Total revenue	740,629	627,611	628,493
Credit provision (a)	20,083	20,400	24,185
Noninterest expense	542,117	490,908	502,285
Income (loss) before income taxes	178,429	116,303	102,023
Income tax expense (benefit)	37,476	40,706	35,708
Net income	$ 140,953	$ 75,597	$ 66,315
Return on average allocated capital (ROCET1) (b)	21.57%	12.89%	10.53%
Segment Balance Sheet Data
Average earning assets	$ 10,336,105	$ 9,456,549	$ 9,309,028
Average loans	10,332,665	9,452,253	9,307,723
Average deposits	13,623,852	11,711,407	11,451,759
Average allocated capital (CETI)(b)	653,354	586,417	629,540
Allocated goodwill	644,498	548,238	543,951
Operating Segments | Risk Management and Shared Services [Member]
Segment Income Statement Data Abstract
Net interest income	64,722	64,423	87,378
Net intersegment interest income (expense)	(31,382)	(41,615)	(59,259)
Segment net interest income	33,341	22,808	28,119
Noninterest income	7,600	14,133	27,165
Total revenue	40,941	36,941	55,284
Credit provision (a)	(64,675)	(36,698)	(4,582)
Noninterest expense	119,283	61,335	51,782
Income (loss) before income taxes	(13,668)	12,304	8,084
Income tax expense (benefit)	(5,540)	(2,858)	(7,647)
Net income	$ (8,128)	$ 15,162	$ 15,731
Return on average allocated capital (ROCET1) (b)	(3.19%)	1.44%	2.84%
Segment Balance Sheet Data
Average earning assets	$ 7,861,026	$ 6,722,337	$ 6,538,820
Average loans	543,814	328,303	173,644
Average deposits	2,335,768	3,273,282	3,649,775
Average allocated capital (CETI)(b)	592,006	405,281	240,253
Allocated goodwill	$ 0	$ 0	$ 0

Segment Reporting (Details Text

Segment Reporting (Details Textuals)	12 Months Ended
	Dec. 31, 2018segment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of Reportable Segments	3

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (62,758)
Other Comprehensive Income (Loss), Transfers from Available-for-Sale Securities to Held-to-maturity, before Tax	0	$ (14,738)	$ 0
Personnel expense	482,676	428,976	424,676
Adjustment for adoption of ASU 2016-01	84
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(572)	(2,665)	(5,887)
Total other comprehensive income (loss)	(62,214)	(8,079)	(22,063)
Ending Balance	(124,972)	(62,758)
Investments Securities Available For Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(38,453)	(20,079)	459
Other comprehensive income (loss) before reclassifications	(39,891)	(27,040)	(17,900)
Investment securities losses (gains), net	1,985		(9,316)
Personnel expense	0	0	0
Other Expenses	0	0	0
Adjustment for adoption of ASU 2016-01	(84)
Adjustment for adoption of ASU 2018-02	(8,419)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(572)	(2,665)	(5,887)
Income tax (expense) benefit	9,791	11,331	12,565
Total other comprehensive income (loss)	(37,189)	(18,374)	(20,538)
Ending Balance	(75,643)	(38,453)	(20,079)
Defined Benefit Pension and Postretirement Obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(24,305)	(34,600)	(33,075)
Other comprehensive income (loss) before reclassifications	(28,612)	14,273	(6,141)
Investment securities losses (gains), net	0		0
Personnel expense	(148)	(148)	(73)
Other Expenses	2,203	2,282	3,874
Adjustment for adoption of ASU 2016-01	0
Adjustment for adoption of ASU 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	0
Income tax (expense) benefit	6,767	(6,112)	815
Total other comprehensive income (loss)	(25,025)	10,295	(1,525)
Ending Balance	(49,330)	(24,305)	(34,600)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(62,758)	(54,679)	(32,616)
Other comprehensive income (loss) before reclassifications	(68,503)	(12,767)	(24,041)
Investment securities losses (gains), net	1,985		(9,316)
Personnel expense	(148)	(148)	(73)
Other Expenses	2,203	2,282	3,874
Adjustment for adoption of ASU 2016-01	(84)
Adjustment for adoption of ASU 2018-02	(13,654)
Interest income (amortization of net unrealized losses (gains) on available for sale securities transferred to held to maturity securities)	(572)	(2,665)	(5,887)
Income tax (expense) benefit	16,558	5,219	13,380
Total other comprehensive income (loss)	(62,214)	(8,079)	(22,063)
Ending Balance	$ (124,972)	$ (62,758)	$ (54,679)

Revenues Revenue Recognition by

Revenues Revenue Recognition by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	$ 290,084	$ 262,175	$ 252,651
Noninterest Income, Outside of Scope of Topic 606	65,483	70,505	100,232
Total noninterest income	355,568	332,680	352,883
Insurance Commissions and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	89,511	81,474	80,795
Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	66,075	64,427	66,609
Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	41,325	35,881	34,527
Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	54,316	50,191	46,867
Brokerage Commission and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	28,246	19,935	16,235
Other Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	10,611	10,267	7,617
Corporate and Commercial Specialty [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	17,009	17,941	15,022
Noninterest Income, Outside of Scope of Topic 606	35,311	34,355	32,754
Corporate and Commercial Specialty [Member] | Insurance Commissions and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	0	0	0
Corporate and Commercial Specialty [Member] | Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	14,981	16,006	15,378
Corporate and Commercial Specialty [Member] | Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	1,343	1,163	740
Corporate and Commercial Specialty [Member] | Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	0	0	0
Corporate and Commercial Specialty [Member] | Brokerage Commission and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	0	0	0
Corporate and Commercial Specialty [Member] | Other Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	685	772	(1,096)
Community, Consumer and Business [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	272,363	243,883	237,265
Noninterest Income, Outside of Scope of Topic 606	23,284	22,367	40,677
Community, Consumer and Business [Member] | Insurance Commissions and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	89,472	81,468	80,795
Community, Consumer and Business [Member] | Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	51,025	48,344	51,047
Community, Consumer and Business [Member] | Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	39,883	34,695	33,765
Community, Consumer and Business [Member] | Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	54,316	50,191	46,866
Community, Consumer and Business [Member] | Brokerage Commission and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	28,024	19,935	16,235
Community, Consumer and Business [Member] | Other Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	9,643	9,249	8,556
Risk Management and Shared Services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	712	351	364
Noninterest Income, Outside of Scope of Topic 606	6,889	13,783	26,801
Risk Management and Shared Services [Member] | Insurance Commissions and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	39	6	0
Risk Management and Shared Services [Member] | Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	69	77	184
Risk Management and Shared Services [Member] | Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	98	23	22
Risk Management and Shared Services [Member] | Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	0	0	0
Risk Management and Shared Services [Member] | Brokerage Commission and Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	222	0	0
Risk Management and Shared Services [Member] | Other Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	283	245	158
Operating Segments [Member] | Corporate and Commercial Specialty [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total noninterest income	52,321	52,297	47,776
Operating Segments [Member] | Community, Consumer and Business [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total noninterest income	295,647	266,250	277,942
Operating Segments [Member] | Risk Management and Shared Services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total noninterest income	$ 7,600	$ 14,133	$ 27,165

Recent Developments (Details)

Recent Developments (Details) - USD ($)	Feb. 05, 2019	Sep. 19, 2018	Sep. 15, 2016	Jun. 15, 2015	Dec. 31, 2018	Sep. 18, 2018	Apr. 24, 2018	Jul. 25, 2017	Aug. 28, 2015
Series C Preferred Stock
Recent Developments [Line Items]
Preferred Stock, Dividend Rate, Percentage				6.125%	6.125%
Stock repurchase program authorized amount									$ 10,000,000
Remaining authorized repurchase amount					$ 10,000,000
Series D Preferred Stock
Recent Developments [Line Items]
Preferred Stock, Dividend Rate, Percentage			5.375%		5.375%
Stock repurchase program authorized amount								$ 15,000,000
Remaining authorized repurchase amount					$ 14,000,000
Series E Preferred Stock
Recent Developments [Line Items]
Preferred Stock, Dividend Rate, Percentage		5.875%			5.875%
Common Stock
Recent Developments [Line Items]
Stock repurchase program authorized amount						$ 200,000,000	$ 100,000,000
Remaining authorized repurchase amount					$ 111,000,000
Subsequent Event
Recent Developments [Line Items]
Common stock, dividends declared ($ per share)	$ 0.17
Subsequent Event | Series C Preferred Stock
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	0.3828125
Subsequent Event | Series D Preferred Stock
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	0.3359375
Subsequent Event | Series E Preferred Stock
Recent Developments [Line Items]
Preferred stock, dividends declared ($ per share)	$ 0.3671875
Subsequent Event | Common Stock
Recent Developments [Line Items]
Stock repurchase program authorized amount	$ 100,000,000
Remaining authorized repurchase amount	$ 211,000,000