TCF Financial 10-Q 8 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 02, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	CHEMICAL FINANCIAL CORP
Entity Central Index Key	19,612
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		71,445,427

Consolidated Statements of Fina

Consolidated Statements of Financial Position - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Cash and cash equivalents:
Cash and cash due from banks	$ 285,605	$ 226,003
Interest-bearing deposits with the Federal Reserve Bank and other banks	379,158	229,988
Total cash and cash equivalents	664,763	455,991
Investment securities:
Carried at fair value	2,736,880	1,963,546
Held-to-maturity, at amortized cost (fair value of $598,197 and $662,906, respectively)	608,367	677,093
Total investment securities	3,345,247	2,640,639
Loans held-for-sale, at fair value	93,736	52,133
Loans	14,796,252	14,155,267
Allowance for loan losses	(104,041)	(91,887)
Net loans	14,692,211	14,063,380
Premises and equipment	123,305	126,896
Loan servicing rights, at fair value	72,707	63,841
Goodwill	1,134,568	1,134,568
Other intangible assets	29,981	34,271
Interest receivable and other assets	748,971	709,154
Total assets	20,905,489	19,280,873
Deposits:
Noninterest-bearing	4,015,323	3,725,779
Interest-bearing	11,429,529	9,917,024
Total deposits	15,444,852	13,642,803
Collateralized customer deposits	377,471	415,236
Short-term borrowings	1,670,000	2,000,000
Long-term borrowings	430,971	372,882
Interest payable and other liabilities	193,271	181,203
Total liabilities	18,116,565	16,612,124
Shareholders’ equity
Preferred stock, none issued	0	0
Common stock issued	71,438	71,207
Additional paid-in capital	2,207,631	2,203,637
Retained earnings	567,510	419,403
Accumulated other comprehensive loss	(57,655)	(25,498)
Total shareholders’ equity	2,788,924	2,668,749
Total liabilities and shareholders’ equity	$ 20,905,489	$ 19,280,873

Consolidated Statements of Fi_2

Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Held-to-maturity, fair value	$ 598,197	$ 662,906
Loan servicing rights, at fair value	$ 72,707	$ 63,841
Preferred stock, no par value (dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	2,000,000	2,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	135,000,000	135,000,000
Common stock, shares issued (in shares)	71,437,826	71,207,114
Common stock, shares outstanding (in shares)	71,437,826	71,207,114

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income
Interest and fees on loans	$ 172,686	$ 148,771	$ 494,892	$ 422,570
Interest on investment securities:
Taxable	16,360	9,326	43,485	21,207
Tax-exempt	6,178	4,577	17,732	13,238
Dividends on nonmarketable equity securities	1,368	1,039	5,458	2,906
Interest on deposits with the Federal Reserve Bank, other banks and Federal funds sold	1,785	1,231	4,326	3,052
Total interest income	198,377	164,944	565,893	462,973
Interest expense
Interest on deposits	27,250	12,926	62,874	32,424
Interest on collateralized customer deposits	721	462	1,886	808
Interest on short-term borrowings	9,510	6,129	28,084	12,100
Interest on long-term borrowings	1,415	1,799	4,168	5,968
Total interest expense	38,896	21,316	97,012	51,300
Net interest income	159,481	143,628	468,881	411,673
Provision for loan losses	6,028	5,499	21,856	15,778
Net interest income after provision for loan losses	153,453	138,129	447,025	395,895
Noninterest income
Net gain on sale of loans and other mortgage banking revenue	9,837	5,241	31,216	24,280
Net gain on sale of investment securities	0	1	3	168
Other	7,372	4,921	22,357	17,102
Total noninterest income	37,917	32,122	116,489	111,700
Operating expenses
Salaries, wages and employee benefits	56,894	52,590	168,599	164,731
Occupancy	8,620	6,871	24,310	23,008
Equipment and software	8,185	7,582	24,120	24,248
Outside processing and service fees	12,660	9,626	33,689	26,061
Merger expenses	0	2,379	0	7,011
Restructuring expenses	0	18,824	0	18,824
Other	23,302	21,667	65,114	58,089
Total operating expenses	109,661	119,539	315,832	321,972
Income before income taxes	81,709	50,712	247,682	185,623
Income tax expense	11,312	10,253	36,701	45,546
Net income	$ 70,397	$ 40,459	$ 210,981	$ 140,077
Earnings per common share:
Basic earnings per common share (dollars per share)	$ 0.99	$ 0.57	$ 2.96	$ 1.98
Diluted earnings per common share (dollars per share)	0.98	0.56	2.93	1.95
Cash dividends declared per common share (dollars per share)	$ 0.34	$ 0.28	$ 0.9	$ 0.82
Service charges and fees on deposit accounts
Noninterest income
Noninterest income	$ 8,187	$ 9,147	$ 25,265	$ 25,928
Wealth management revenue
Noninterest income
Noninterest income	6,040	6,188	19,539	18,973
Other charges and fees for customer services
Noninterest income
Noninterest income	$ 6,481	$ 6,624	$ 18,109	$ 25,249

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 70,397	$ 40,459	$ 210,981	$ 140,077
Other comprehensive income, net of tax:
Unrealized holding gains (losses) on securities available-for-sale arising during the period	(16,634)	1,376	(55,863)	9,643
Reclassification adjustment for gains on realized income	0	(1)	(3)	(168)
Tax effect	3,493	(481)	11,732	(3,316)
Net unrealized gains (losses) on securities available-for-sale, net of tax	(13,141)	894	(44,134)	6,159
Unrealized gains on interest rate swaps designated as cash flow hedges	4,111	550	16,176	84
Reclassification adjustment for (gains) losses included in net income	(662)	575	(1,009)	984
Tax effect	(724)	(374)	(3,185)	(374)
Net unrealized gains on interest rate swaps designated as cash flow hedges, net of tax	2,725	751	11,982	694
Plan remeasurement	0	11,238	0	11,238
Adjustment for pension and other postretirement benefits	142	537	426	1,613
Tax effect	(30)	(4,121)	(90)	(4,498)
Net adjustment for pension and other postretirement benefits	112	7,654	336	8,353
Other comprehensive income (loss), net of tax	(10,304)	9,299	(31,816)	15,206
Total comprehensive income, net of tax	$ 60,093	$ 49,758	$ 179,165	$ 155,283

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands		Total	Stock options	Common stock	Common stockStock options	Additional paid-in capital	Additional paid-in capitalStock options	Retained earnings	Accumulated other comprehensive income (loss)
Changes in Stockholders' Equity
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]	$ 3,659						$ 3,659
Beginning balance at Dec. 31, 2016		2,581,526		$ 70,599		$ 2,210,762		340,201	$ (40,036)
Changes in Stockholders' Equity
Comprehensive income		155,283						140,077	15,206
Cash dividends		(58,504)						(58,504)
Net shares issued under share-based compensation plans			$ (23,448)		$ 553		$ (24,001)
Share-based compensation expense		14,573		0		14,573
Ending balance at Sep. 30, 2017		2,673,089		71,152		2,201,334		425,433	(24,830)
Beginning balance at Jun. 30, 2017		2,639,442		71,131		2,197,501		404,939	(34,129)
Changes in Stockholders' Equity
Comprehensive income		49,758						40,459	9,299
Cash dividends		(19,965)						(19,965)
Net shares issued under share-based compensation plans			(3,792)		21		(3,813)
Share-based compensation expense		7,646		0		7,646
Ending balance at Sep. 30, 2017		2,673,089		71,152		2,201,334		425,433	(24,830)
Changes in Stockholders' Equity
Cumulative effect adjustment of change in accounting policy, net of tax impact	[2]	1,339						1,680	(341)
Beginning balance at Dec. 31, 2017		2,668,749		71,207		2,203,637		419,403	(25,498)
Changes in Stockholders' Equity
Comprehensive income		179,165						210,981	(31,816)
Cash dividends		(64,554)						(64,554)
Net shares issued under share-based compensation plans			(1,766)		231		(1,997)
Share-based compensation expense		5,991		0		5,991
Ending balance at Sep. 30, 2018		2,788,924		71,438		2,207,631		567,510	(57,655)
Beginning balance at Jun. 30, 2018		2,750,999		71,418		2,205,402		521,530	(47,351)
Changes in Stockholders' Equity
Comprehensive income		60,093						70,397	(10,304)
Cash dividends		(24,417)						(24,417)
Net shares issued under share-based compensation plans			$ 336		$ 20		$ 316
Share-based compensation expense		1,913		0		1,913
Ending balance at Sep. 30, 2018		$ 2,788,924		$ 71,438		$ 2,207,631		$ 567,510	$ (57,655)
[1]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies and Note 7, Loan Servicing Rights for further details on the changes in accounting policy.
[2]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies, Note 3, Investment Securities, Note 5, Other Real Estate Owned and Repossessed Assets and Note 9, Derivative Instruments and Balance Sheet Offsetting, for further details on the changes in accounting policy.

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Stockholders' Equity [Abstract]
Cash dividends declared per common share (dollars per share)	$ 0.34	$ 0.28	$ 0.9	$ 0.82

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net income	$ 210,981	$ 140,077
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	21,856	15,778
Gains on sales of loans	(9,772)	(26,537)
Proceeds from sales of loans	569,768	601,694
Loans originated for sale	(599,671)	(577,874)
Net gains on sale of investment securities	(3)	(168)
Net losses (gains) from sales/writedowns of other real estate and repossessed assets	473	(597)
Depreciation of premises and equipment	12,735	13,444
Amortization of intangible assets	4,290	4,564
Additions to loan servicing rights	(6,337)	(6,461)
Valuation change in loan servicing rights	(2,529)	8,242
Net amortization of premiums and discounts on investment securities	14,174	13,933
Share-based compensation expense	5,991	14,573
Deferred income tax expense	18,134	36,508
Change in deferred tax valuation allowance	(456)	60
Net increase in interest receivable and other assets	(34,702)	(148,180)
Net increase in interest payable and other liabilities	12,583	40,181
Net cash provided by operating activities	217,515	129,237
Debt securities – available-for-sale:
Proceeds from maturities, calls and principal reductions	223,049	227,854
Proceeds from sales and redemptions	4,215	17,085
Purchases	(1,069,703)	(1,041,744)
Investment securities – held-to-maturity:
Proceeds from maturities, calls and principal reductions	91,317	73,762
Purchases	(23,523)	(109,704)
Net increase in loans	(661,400)	(862,498)
Proceeds from sales of other real estate and repossessed assets	10,156	15,569
Purchases of premises and equipment, net of disposals	(9,144)	(11,616)
Proceeds from returns of investment in equity method investments	326	143
Net cash used in investing activities	(1,434,707)	(1,691,149)
Cash flows from financing activities
Net increase in interest- and noninterest-bearing demand deposits and savings accounts	1,153,767	828,517
Net increase in time deposits	648,282	103,606
Net (decrease) increase in collateralized customer deposits and other short-term borrowings	(367,765)	1,146,550
Proceeds from issuance of long-term borrowings	200,000	0
Repayment of long-term borrowings	(142,000)	(200,000)
Cash dividends paid	(64,554)	(58,504)
Proceeds from directors’ stock plans and exercise of stock options, net of shares withheld	3,016	3,353
Cash paid for payroll taxes upon conversion of share-based awards	(4,782)	(26,801)
Net cash provided by financing activities	1,425,964	1,796,721
Net increase in cash and cash equivalents	208,772	234,809
Cash and cash equivalents at beginning of period	455,991	474,402
Cash and cash equivalents at end of period	664,763	709,211
Supplemental disclosures of cash flow information:
Interest paid	93,150	51,505
Net income tax payments	4,599	9,922
Non-cash activities:
Loans transferred to other real estate and repossessed assets	8,785	8,972
Net transfer of loans held-for-sale to loans held- for-investment	(1,928)	(2,651)
Closed branch offices transferred to other assets	0	1,634
Business combinations:
Fair value of tangible assets acquired (noncash)	0	420
Goodwill, loans servicing rights and other identifiable intangible assets acquired	0	1,034
Liabilities assumed	$ 0	$ 1,454

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Nature of Operations Chemical Financial Corporation ("Corporation" or "Chemical") operates in a single operating segment — commercial banking. The Corporation is a financial holding company, headquartered in Detroit, Michigan, that operates through one commercial bank, Chemical Bank. Chemical Bank operates within Michigan, Northeast Ohio and Northern Indiana as a Michigan state-chartered commercial bank. Chemical Bank operates through an internal organizational structure of six regional banking units and offers a full range of traditional banking and fiduciary products and services to the residents and business customers in the Corporation’s geographical market areas. The products and services offered by the regional banking units, through branch banking offices, are generally consistent throughout the Corporation, as is the pricing of those products and services. The marketing of products and services throughout the Corporation’s regional banking units is generally uniform, as many of the markets served by the regional banking units overlap. The distribution of products and services is generally uniform throughout the Corporation’s regional banking units and is achieved primarily through retail branch banking offices, automated teller machines and electronically accessed banking products. The Corporation’s primary sources of revenue are interest from its loan products and investment securities, service charges and fees from customer deposit accounts, wealth management revenue and net gain on sale of loans and other mortgage banking revenue. Basis of Presentation and Principles of Consolidation The accompanying unaudited Consolidated Financial Statements of the Corporation and its subsidiaries have been prepared in accordance with United States ("U.S.") generally accepted accounting principles ("GAAP") for interim financial information and with instructions to Form 10-Q, Securities and Exchange Commission ("SEC") rules and interpretive releases and prevailing practices within the banking industry and Rule 10-01 of Regulation S-X. Accordingly, the interim Consolidated Financial Statements do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Corporation’s Consolidated Financial Statements and footnotes thereto included in the Corporation’s Annual Report on Form 10-K for the year ended December 31, 2017 . In the opinion of management, the accompanying unaudited interim Consolidated Financial Statements contain all adjustments believed necessary to present fairly the financial condition and results of operations of the Corporation for the periods presented. All significant income and expenses are recorded on the accrual basis. Intercompany accounts and transactions have been eliminated in preparing the Consolidated Financial Statements. Operating results for the nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . Use of Estimates Management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and accompanying footnotes. Estimates that are particularly susceptible to significant change include the determination of the allowance for loan losses, expected cash flows from acquired loans, income taxes and the valuation of loan servicing rights. Actual results could differ from these estimates. Reclassifications Certain amounts appearing in the Consolidated Financial Statements and notes thereto for prior periods have been reclassified to conform to the current presentation. The reclassifications had no effect on net income or shareholders’ equity as previously reported, except in case of the cumulative effect adjustment of change in accounting policy as noted. Recently Adopted Accounting Policy Effective January 1, 2017, the Corporation elected to account for all loan servicing rights ("LSRs") previously accounted for under the lower of cost or fair value method under the fair value method. The guidance in Accounting Standards Codification Subtopic 860-50, "Transfers and Servicing-Servicing Assets and Liabilities" provides that an entity may make an irrevocable decision to subsequently measure a class of servicing assets and servicing liabilities at fair value at the beginning of any fiscal year. The guidance allows for the Corporation to apply this election prospectively to all new and existing servicing assets and servicing liabilities. Management believes this election will provide more comparable results to peers as many of those within our industry group account for loan servicing rights under the fair value method. The change in accounting policy in the first quarter of 2017 resulted in a cumulative adjustment to increase retained earnings in the amount of $3.7 million , net of taxes. Recently Adopted Accounting Principles Standard Description Adoption Date Effect on the financial statements ASU No. 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities ("ASU 2017-08") ASU 2017-08 reduces the amortization period for certain callable debt securities that are held at a premium to the earliest call date. Debt securities held at a discount will continue to be amortized as a yield adjustment over the life of the instrument. April 1, 2017 The early adoption in the second quarter of 2017 did not have a material impact on the Consolidated Financial Statements. ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income ("ASU 2018-02") ASU 2018-02 required deferred tax liabilities and assets to be adjusted for the effect of a change in tax laws or rate with the effect included in income from continuing operations in the reporting period that includes the enactment date. Fourth quarter of 2017 The early adoption in the fourth quarter of 2017 resulted in a $4.5 million reclassification from accumulated other comprehensive income to retained earnings related to the income tax effects of the Tax Cuts and Jobs Act. ASU No. 2014-09 - Revenue from Contracts with Customers (Topic 606) ASU No. 2016-08 - Principal versus Agent Considerations ASU No. 2016-10 - Identifying Performance Obligations and Licensing ASU No. 2016-12, Narrow-scope Improvements and Practical Expedients ("Updates to Topic 606") The core principle of the Updates to Topic 606 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. The standard is intended to clarify and converge the revenue recognition principles under GAAP and International Financial Reporting Standards and to streamline revenue recognition requirements in addition to expanding required revenue recognition disclosures. January 1, 2018 under the modified retrospective method A large majority of the Corporation's revenue is derived from net interest income, which is excluded from the scope of the guidance. Following detailed review of the Corporation's revenue streams not derived from net interest income on financial assets and liabilities, management identified the recognition of gains from other real estate sales financed by the Corporation to be in the scope of this amended guidance. Effective January 1, 2018, revenue for new seller financed other real estate owned sales will be determined according to the Updates to Topic 606. If all qualifications are met, gains associated with the sales will be recognized into income at the time of closing and therefore not deferred. The cumulative effect of the Updates to Topic 606 increased retained earnings by $1.2 million upon adoption. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Additional required disclosures have been included in Note 13, Revenue from Contracts with Customers. The adoption is not expected to have a material impact on the Corporation's net income on an ongoing basis. Refer to Note 5, Other Real Estate Owned and Repossessed Assets, for further detail. Standard Description Adoption Date Effect on the financial statements ASU No. 2016-01 - Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01") ASU 2016-01 amended current guidance by: (i) requiring equity investments with readily determinable fair values to be measured at fair value with changes in fair value recognized in net income, (ii) allowing an entity to measure equity investments that do not have readily determinable fair values at either fair value or cost minus impairment, changes in measurement is recognized in net income, (iii) simplifying impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment, (iv) eliminating the requirement to disclose the methods and assumptions used to estimate the fair value of financial instruments measured at amortized cost; (v) requiring the use of exit price notion when measuring the fair value of financial instruments; (vi) requiring recognition of changes in the fair value related to instrument-specific credit risk in other comprehensive income if financial liabilities are measured at fair value, (vii) requiring separate presentation in financial statements by measurement category, and (viii) clarifying that an entity should evaluate the need for valuation allowance on deferred tax assets related to available-for-sale securities in combination with the entity’s other deferred tax assets. January 1, 2018 using a modified retrospective approach with the exception of disclosure requirements which are adopted on a prospective basis The Corporation identified available-for-sale investment securities qualifying as equity investments in the securities portfolio at January 1, 2018. The adoption resulted in recognizing the unrealized fair value related to the identified equity investments as a cumulative effect to retained earnings of $0.3 million. In addition, the Corporation has updated disclosures related to the fair value of financial instruments to the use of the exit price notion. Refer to Note 2, Fair Value Measurements and Note 3, Investment Securities, for further detail. ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts as Cash Payments ("ASU 2016-15") 2016-15 was issued to reduce diversity in practice and prevent financial statement restatements. Cash flow issues include: debt prepayment or debt extinguishment costs, settlement of insurance claims, proceeds from the settlement of corporate-owned and bank-owned life insurance policies, distribution received from equity method investees, beneficial interests in securitization transactions and separately identifiable cash flows and application of the predominance principle. January 1, 2018 using retrospective application The adoption did not have a material effect on the presentation of our Consolidated Statements of Cash Flows, as current policies are either already in-line with the clarifications in the updated guidance, or the related cash flows are not material. ASU No. 2017-07 - Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost ("ASU 2017-07") ASU 2017-07 improves the income statement presentation of net periodic benefit cost for an entity's pension and postretirement plans. The standard requires employers to disaggregate current service costs from other components of net benefit cost and present it with other compensation cost. Additionally net benefit cost becomes eligible for capitalization. January 1, 2018 using the retrospective transition method The adoption resulted in a reclassification of $31 thousand and $0.7 million of net periodic income from salaries, wages and employee benefits expense to other expenses on the Consolidated Statements of Income during the three and nine months ended September 30, 2017, respectively. ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvement to Account for Hedging Activities ("ASU 2017-12") ASU 2017-12 eliminates the separate measurement of hedge ineffectiveness as well as the benchmark interest rate concept when applying hedge risk to variable-rate instruments. It also allows a company to elect to perform subsequent effectiveness assessments qualitatively if the initial quantitative hedge effectiveness assessment is found to be highly effective. January 1, 2018 The early adoption resulted in a cumulative adjustment from opening retained earnings to accumulated other comprehensive income of $3 thousand, which represented all previously recognized hedge ineffectiveness. ASU No. 2018-15 - Intangible-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract ("ASU 2018-15") ASU 2018-15 clarifies the accounting treatment for implementation costs for hosting arrangements that are service contracts. The amendments in this update align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal use software in accordance with subtopic 350-40. Under this guidance costs for implementation activities during the development stage shall be capitalized. The said capitalized-costs shall be expensed over the term of the hosting arrangement. Third quarter of 2018 applied retrospectively The early adoption in the third quarter did not have a material effect on the Consolidated Financial Statements. Effective during the nine months ended 2018 , the Corporation also adopted the following standards, none of which had a material impact to the Corporation's financial statements or financial statement disclosures: Standard Effective Date 2016-04 Liabilities—Extinguishments of Liabilities (Subtopic 405-20): Recognition of Breakage for Certain Prepaid Stored-Value Products January 1, 2018 2016-16 Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory January 1, 2018 2016-18 Statement of Cash Flows (Topic 230): Restricted Cash January 1, 2018 2017-01 Business Combinations (Topic 805): Clarifying the Definition of a Business January 1, 2018 2017-05 Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets January 1, 2018 2017-09 Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting January 1, 2018

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value, as defined by GAAP, is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. A fair value measurement assumes that the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability. The price in the principal (or most advantageous) market used to measure the fair value of the asset or liability is not adjusted for transaction costs. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for market activities that are usual and customary for transactions involving such assets and liabilities; it is not a forced transaction. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact and (iv) willing to transact. The Corporation utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. Investment securities — carried at fair value, loans held-for-sale, loan servicing rights and derivatives are recorded at fair value on a recurring basis. Additionally, the Corporation may be required to record other assets, such as impaired loans, goodwill, other intangible assets, other real estate and repossessed assets, at fair value on a nonrecurring basis. These nonrecurring fair value adjustments typically involve the application of lower of cost or market accounting or write-downs of individual assets. The Corporation determines the fair value of its financial instruments based on a three-level hierarchy established by GAAP. The classification and disclosure of assets and liabilities within the hierarchy is based on whether the inputs to the valuation methodology used for measurement are observable or unobservable. Observable inputs reflect market-derived or market-based information obtained from independent sources, while unobservable inputs reflect management’s estimates about market data. The three levels of inputs that may be used to measure fair value within the GAAP hierarchy are as follows: Level 1 Valuation is based upon quoted prices for identical instruments traded in active markets. Level 2 Valuation is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market. Level 2 valuations for the Corporation include government and government-sponsored agency securities, including securities issued by the Federal Home Loan Bank ("FHLB"), Federal Home Loan Mortgage Corporation, Federal National Mortgage Association, Federal Farm Credit Bank, Student Loan Marketing Corporation and the Small Business Administration, securities issued by certain state and political subdivisions, residential mortgage-backed securities, collateralized mortgage obligations, corporate bonds, preferred stock and available-for-sale trust preferred securities. Valuations are obtained from a third-party pricing service for these investment securities. Additionally included in Level 2 valuations are loans held for sale and derivative assets and liabilities. Level 3 Valuation is generated from model-based techniques that use at least one significant assumption not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in pricing the asset or liability. Valuation techniques include use of option pricing models, discounted cash flow models, yield curves and similar techniques. The determination of fair value requires management judgment or estimation and generally is corroborated by external data, which includes third-party pricing services. Level 3 valuations for the Corporation include impaired loans, goodwill, core deposit intangible assets, non-compete intangible assets, LSRs and other real estate and repossessed assets. A description of the valuation methodologies used for instruments measured at fair value, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. These valuation methodologies were applied to all of the Corporation’s financial assets and financial liabilities carried at fair value and all financial instruments disclosed at fair value. Transfers of assets or liabilities between levels of the fair value hierarchy are recognized at the beginning of the reporting period, when applicable. In general, fair value is based upon quoted market prices, where available. If quoted market prices are not available, fair value is based upon third-party pricing services when available. Fair value may also be based on internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be required to record financial instruments at fair value. Any such valuation adjustments are applied consistently over time. The Corporation's valuation methodologies may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. While management believes the Corporation’s valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Furthermore, the fair value amounts may change significantly after the date of the statement of financial position from the amounts reported in the Consolidated Financial Statements and related notes. Assets and Liabilities Recorded at Fair Value on a Recurring Basis Investment securities: Investment securities are recorded at fair value on a recurring basis with the exception of those classified as held-to-maturity. Fair value measurement is based upon quoted prices, if available. If quoted prices are not available, fair values are generally measured using independent pricing models or other model-based valuation techniques that include market inputs, such as benchmark yields, reported trades, broker dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, reference data and industry and economic events. Loans held-for-sale: The Corporation has elected the fair value option for all loans held-for-sale. Accordingly, loans held-for-sale are recorded at fair value on a recurring basis. The fair values of loans held-for-sale are based on the market price for similar loans sold in the secondary market, and therefore, are classified as Level 2 valuations. Loan servicing rights: The Corporation has elected to account for all LSRs under the fair value measurement method. A third party valuation model is used to determine the fair value at the end of each reporting period utilizing a discounted cash flow analysis using interest rates and prepayment speed assumptions currently quoted for comparable instruments and a discount rate determined by management. Because of the nature of the valuation inputs, the Corporation classifies loan servicing rights as Level 3. Refer to Note 7 , "Loan Servicing Rights," for the assumptions included in the valuation of loan servicing rights. Derivatives: The Corporation enters into interest rate lock commitments with prospective borrowers to be sold into the secondary market and forward commitments for the future delivery of mortgage loans to third party investors, which are carried at fair value on a recurring basis. The fair value of these commitments is based on the fair value of related mortgage loans determined using observable market data. Interest rate lock commitments are adjusted for expectations of exercise and funding. This adjustment is not considered to be a material input. The Corporation classifies interest rate lock commitments and forward contracts related to mortgage loans to be delivered for sale as recurring Level 2. Derivative instruments held or issued for risk management or customer-initiated activities are traded in over-the counter markets where quoted market prices are not readily available. Fair value for over-the-counter derivative instruments is measured on a recurring basis using third party models that use primarily market observable inputs, such as yield curves and option volatilities. The fair value for these derivatives may include a credit valuation adjustment that is determined by applying a credit spread for the counterparty or the Corporation, as appropriate, to the total expected exposure of the derivative after considering collateral and other master netting arrangements. These adjustments, which are considered Level 3 inputs, are based on estimates of current credit spreads to evaluate the likelihood of default. The Corporation assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions at both September 30, 2018 and December 31, 2017 and it was determined that the credit valuation adjustments were not significant to the overall valuation of its derivatives. As a result, the Corporation classifies its risk management interest rate swaps designated as cash flow hedges and customer-initiated derivatives valuations in Level 2 of the fair value hierarchy. Foreign exchange forward and option contracts are entered into primarily to accommodate the needs of the customer. These derivatives are not designated as hedging. Fair value of foreign exchange forward and option contracts are measured on a recurring basis using third party models that use primarily market observable inputs, such as yield curves and option volatilities. The Corporation classifies its foreign exchange forward and option contracts in Level 2 of the fair value hierarchy. Written and purchased option derivatives consist of instruments to facilitate an equity-linked time deposit product (the "Power Equity CD"). The Power Equity CD is a time deposit that provides the purchaser a guaranteed return of principal at maturity plus a potential equity return, while the Corporation receives a known stream of funds based on equity returns. The written and purchased options are mirror derivative instruments which are carried at fair value on the Consolidated Statements of Financial Position. Fair value measurements for the Power Equity CD are determined using quoted prices of underlying stocks, along with other terms and features of the derivative instrument. As a result, the Power Equity CD derivatives are classified as Level 2 valuations. Disclosure of Recurring Basis Fair Value Measurements For assets and liabilities measured at fair value on a recurring basis, quantitative disclosures about the fair value measurements for each major category of assets and liabilities follow: (Dollars in thousands) Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total September 30, 2018 Investment securities – carried at fair value: Government and government-sponsored agencies $ — $ 254,453 $ — $ 254,453 State and political subdivisions — 491,909 — 491,909 Residential mortgage-backed securities — 177,021 — 177,021 Collateralized mortgage obligations — 1,477,818 — 1,477,818 Corporate bonds — 287,405 — 287,405 Trust preferred securities — 48,274 — 48,274 Total investment securities – carried at fair value — 2,736,880 — 2,736,880 Loans held-for-sale — 93,736 — 93,736 Loan servicing rights — — 72,707 72,707 Derivative assets: Customer-initiated derivatives — 21,390 — 21,390 Foreign exchange forwards — 3 — 3 Forward contracts related to mortgage loans to be delivered for sale — 760 — 760 Interest rate lock commitments — 1,081 — 1,081 Power Equity CD — 1,260 — 1,260 Risk management derivatives — 21,067 — 21,067 Total derivatives — 45,561 — 45,561 Total assets at fair value $ — $ 2,876,177 $ 72,707 $ 2,948,884 Derivative liabilities: Customer-initiated derivatives $ — $ 21,703 $ — $ 21,703 Foreign exchange forwards — 3 — 3 Power Equity CD — 1,260 — 1,260 Total derivatives — 22,966 — 22,966 Total liabilities at fair value $ — $ 22,966 $ — $ 22,966 December 31, 2017 Investment securities – available-for-sale: Government and government-sponsored agencies $ — $ 202,916 $ — $ 202,916 State and political subdivisions — 345,970 — 345,970 Residential mortgage-backed securities — 150,131 — 150,131 Collateralized mortgage obligations — 1,033,845 — 1,033,845 Corporate bonds — 192,794 — 192,794 Trust preferred securities — 36,066 — 36,066 Preferred stock — 1,824 — 1,824 Total investment securities – available-for-sale — 1,963,546 — 1,963,546 Loans held-for-sale — 52,133 — 52,133 Loan servicing rights — — 63,841 63,841 Derivative assets: Customer-initiated derivatives — 9,376 — 9,376 Interest rate lock commitments — 1,222 — 1,222 Power Equity CD — 2,184 — 2,184 Risk management derivatives — 5,899 — 5,899 Total derivatives — 18,681 — 18,681 Total assets at fair value $ — $ 2,034,360 $ 63,841 $ 2,098,201 Derivative liabilities: Customer-initiated derivatives $ — $ 10,139 $ — $ 10,139 Forward contracts related to mortgage loans to be delivered for sale — 34 — 34 Power Equity CD — 2,184 — 2,184 Total derivatives — 12,357 — 12,357 Total liabilities at fair value $ — $ 12,357 $ — $ 12,357 There were no transfers between levels within the fair value hierarchy during the nine months ended September 30, 2018 and 2017 . The following table summarizes the changes in Level 3 assets measured at fair value on a recurring basis. Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (Dollars in thousands) Loan servicing rights Balance, beginning of period $ 70,364 $ 64,522 $ 63,841 $ 48,085 Transfer in based on new accounting policy election (1) — — — 15,891 Gains (losses): Recorded in earnings (realized): Recorded in "Net gain on sale of loans and other mortgage banking revenue" 257 (4,651 ) 2,529 (8,242 ) New originations 2,086 2,324 6,337 6,461 Balance, end of period $ 72,707 $ 62,195 $ 72,707 $ 62,195 (1) Refer to Note 1, Basis of Presentation and Significant Accounting Policies, for further details. The Corporation has elected the fair value option for loans held-for-sale. These loans are intended for sale and the Corporation believes that the fair value is the best indicator of the resolution of these loans. Interest income is recorded based on the contractual terms of the loans in accordance with the Corporation's policy on loans held for investment in "Interest and fees on loans" in the Consolidated Statements of Income. There were no loans held-for-sale on nonaccrual status or 90 days past due and on accrual status as of September 30, 2018 and December 31, 2017 . The aggregate fair value, contractual balance (including accrued interest), and gain or loss for loans held-for-sale carried at fair value option was as follows: (Dollars in thousands) September 30, 2018 December 31, 2017 Aggregate fair value $ 93,736 $ 52,133 Contractual balance 91,839 50,597 Unrealized gain (loss) 1,897 1,536 The total amount of gains (losses) from loans held-for-sale included in the Consolidated Statements of Income were as follows: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Interest income (1) $ 849 $ 810 $ 1,670 $ 1,824 Change in fair value (2) 577 614 361 2,002 Net gain on sales of loans (2) 4,241 6,512 9,772 26,537 Total included in earnings $ 5,667 $ 7,936 $ 11,803 $ 30,363 (1) Included in "Interest and fees on loans" in the Consolidated Statements of Income. (2) Included in "Net gain on sale of loans and other mortgage banking revenue" in the Consolidated Statements of Income. Assets and Liabilities Recorded at Fair Value on a Nonrecurring Basis Investment securities: Investment securities classified as held-to-maturity are recorded at fair value if the value is below amortized cost and the Corporation has determined that such unrealized loss is an other-than-temporary impairment. Fair value measurement is based upon quoted prices, if available. If quoted prices are not available, fair values are generally measured using independent pricing models or other model-based valuation techniques that include market inputs, such as benchmark yields, reported trades, broker dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, reference data and industry and economic events. Impaired Loans: The Corporation does not record loans held for investment at fair value on a recurring basis. However, from time to time, a loan is considered impaired and an allocation of the allowance (valuation allowance) may be established or a portion of the loan is charged off. Loans for which it is probable that payment of interest and principal will not be made in accordance with the contractual terms of the loan agreement are considered impaired. The fair value of impaired loans is estimated using one of several methods, including the loan’s observable market price, the fair value of the collateral or the present value of the expected future cash flows discounted at the loan’s effective interest rate. Those impaired loans not requiring a valuation allowance represent loans for which the fair value of the expected repayments or collateral exceed the remaining carrying amount of such loans. Impaired loans where a valuation allowance is established or a portion of the loan is charged off based on the fair value of collateral are subject to nonrecurring fair value measurement and require classification in the fair value hierarchy. The Corporation records impaired loans as Level 3 valuations as there is generally no observable market price or management determines the fair value of the collateral is further impaired below the independent appraised value. When management determines the fair value of the collateral is further impaired below appraised value, discounts ranging between 20% and 30% of the appraised value are used depending on the nature of the collateral and the age of the most recent appraisal. Goodwill: Goodwill is subject to impairment testing on an annual basis. The assessment of goodwill for impairment requires a significant degree of judgment. In the event the assessment indicates that it is more-likely-than-not that the fair value is less than the carrying value, the asset is considered impaired and recorded at fair value. Goodwill that is impaired and subject to nonrecurring fair value measurements is a Level 3 valuation. At September 30, 2018 and December 31, 2017 , no goodwill was impaired. Other intangible assets: Other intangible assets consist of core deposit intangible assets and non-compete intangible assets. These items are recorded at fair value when initially recorded. Subsequently, core deposit intangible assets and non-compete intangible assets are amortized primarily on an accelerated basis over periods ranging from ten to fifteen years for core deposit intangible assets and one year for non-compete intangible assets and are subject to impairment testing whenever events or changes in circumstances indicate that the carrying amount exceeds the fair value of the asset. If core deposit intangible asset or non-compete intangible asset impairment is identified, the Corporation classifies impaired core deposit intangible assets and impaired non-compete intangible assets subject to nonrecurring fair value measurements as Level 3 valuations. At September 30, 2018 and December 31, 2017 , there was no impairment identified for core deposit intangible assets or non-compete intangible assets. Other real estate owned and repossessed assets : The carrying amounts for other real estate and repossessed assets are reported in the Consolidated Statements of Financial Position under "Interest receivable and other assets." Other real estate and repossessed assets include real estate and other types of assets repossessed by the Corporation. Other real estate and repossessed assets are recorded at the lower of cost or fair value upon the transfer of a loan to other real estate and repossessed assets and, subsequently, continue to be measured and carried at the lower of cost or fair value. Fair value is based upon independent market prices, appraised values of the property or management’s estimation of the value of the property. The Corporation records other real estate and repossessed assets as Level 3 valuations as management generally determines that the fair value of the property is impaired below the appraised value. When management determines the fair value of the property is further impaired below appraised value, discounts ranging between 20% and 30% of the appraised value are used depending on the nature of the property and the age of the most recent appraisal. Disclosure of Nonrecurring Basis Fair Value Measurements Certain assets may be required to be measured at fair value on a nonrecurring basis. The carrying value of these assets represent end of period values, which approximate the fair value measurements that occurred on the various measurement dates during the period. For assets measured at fair value on a nonrecurring basis, quantitative disclosures about fair value measurements for each major category of assets follows: (Dollars in thousands) Significant Unobservable Inputs (Level 3) September 30, 2018 Impaired loans $ 73,137 Other real estate and repossessed assets 1,843 Total $ 74,980 December 31, 2017 Impaired loans $ 70,619 Other real estate and repossessed assets 2,899 Total $ 73,518 There were no liabilities recorded at fair value on a nonrecurring basis at either September 30, 2018 or December 31, 2017 . The following table presents additional information about the significant unobservable inputs used in the fair value measurement of financial assets measured on a nonrecurring basis that were categorized within the Level 3 of the fair value hierarchy: (Dollars in thousands) Fair Value at Valuation Technique Significant Unobservable Inputs Range Impaired loans $ 73,137 Appraisal of collateral Discount for type of collateral and age of appraisal 20%-30% Other real estate and repossessed assets 1,843 Appraisal of property Discount for type of property and age of appraisal 20%-30% Disclosures about Fair Value of Financial Instruments GAAP requires disclosures about the estimated fair value of the Corporation's financial instruments, including those financial assets and liabilities that are not measured and reported at fair value on a recurring or nonrecurring basis. The Corporation utilized the fair value hierarchy in computing the fair values of its financial instruments. In cases where quoted market prices were not available, the Corporation employed the exit-price notion following the adoption of ASU 2016-01 on January 1, 2018 and used the present value method prior to the adoption of ASU 2016-01, using unobservable inputs requiring management's judgment to estimate the fair values of its financial instruments, which are considered Level 3 valuations. These Level 3 valuations are affected by the assumptions made and, accordingly, are not necessarily indicative of amounts that would be realized in a current market exchange. It is also the Corporation's general practice and intent to hold the majority of its financial instruments until maturity and, therefore, the Corporation does not expect to realize the estimated amounts disclosed. A summary of carrying amounts and estimated fair values of the Corporation’s financial instruments not recorded at fair value in their entirety on a recurring basis on the Consolidated Statements of Financial Position are disclosed in the table below. Level in Fair Value Measurement Hierarchy September 30, 2018 December 31, 2017 (Dollars in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial assets: Investment securities: Held-to-maturity Level 2 $ 607,867 $ 597,747 $ 676,593 $ 662,516 Held-to-maturity Level 3 500 450 500 390 Net loans (1) Level 3 14,692,211 14,301,208 14,063,380 14,114,545 Financial liabilities: Time deposits Level 2 $ 3,865,489 $ 3,827,695 $ 3,217,207 $ 3,225,847 Collateralized customer deposits Level 2 377,471 376,969 415,236 415,236 Short-term borrowings Level 2 1,670,000 1,669,662 2,000,000 1,999,137 Long-term borrowings Level 2 430,971 426,105 372,882 367,984 (1) Included $73.1 million and $70.6 million of impaired loans recorded at fair value on a nonrecurring basis at September 30, 2018 and December 31, 2017 , respectively. The short-term nature of certain assets and liabilities result in their carrying value approximating fair value. These include cash and cash equivalents, nonmarketable equity securities, interest receivable, bank owned life insurance, deposits without defined maturities and interest payable.

Investment Securities

Investment Securities	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	Investment Securities The following is a summary of the amortized cost and fair value of investment securities carried at fair value and investment securities held-to-maturity at September 30, 2018 and December 31, 2017 : Investment Securities Carried at Fair Value (Dollars in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2018 Debt securities Government and government-sponsored agencies $ 258,643 $ 14 $ 4,204 $ 254,453 State and political subdivisions 506,277 187 14,555 491,909 Residential mortgage-backed securities 182,983 6 5,968 177,021 Collateralized mortgage obligations 1,517,172 — 39,354 1,477,818 Corporate bonds 293,828 485 6,908 287,405 Trust preferred securities 47,378 1,004 108 48,274 Total $ 2,806,281 $ 1,696 $ 71,097 $ 2,736,880 December 31, 2017 Debt securities Government and government-sponsored agencies $ 203,099 $ 765 $ 948 $ 202,916 State and political subdivisions 350,088 310 4,428 345,970 Residential mortgage-backed securities 151,752 5 1,626 150,131 Collateralized mortgage obligations 1,042,240 89 8,484 1,033,845 Corporate bonds 193,230 1,156 1,592 192,794 Trust preferred securities 34,848 1,280 62 36,066 Total debt securities available-for-sale 1,975,257 3,605 17,140 1,961,722 Equity securities Preferred stock 1,389 435 — 1,824 Total equity securities 1,389 435 — 1,824 Total $ 1,976,646 $ 4,040 $ 17,140 $ 1,963,546 Investment Securities Held-to-Maturity (Dollars in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2018 State and political subdivisions $ 607,867 $ 1,917 $ 12,037 $ 597,747 Trust preferred securities 500 — 50 450 Total $ 608,367 $ 1,917 $ 12,087 $ 598,197 December 31, 2017 State and political subdivisions $ 676,593 $ 3,856 $ 17,933 $ 662,516 Trust preferred securities 500 — 110 390 Total $ 677,093 $ 3,856 $ 18,043 $ 662,906 Investment securities are classified at the time they are acquired as either available-for-sale, held-to-maturity or carried at fair value based upon various factors, including asset/liability management strategies, liquidity and profitability objectives and regulatory requirements. Debt securities classified as available-for-sale and equity securities are recorded at fair value. Investment securities carried at fair value may be sold prior to maturity based upon asset/liability management decisions. Unrealized gains or losses on available-for-sale debt securities are recorded as part of accumulated other comprehensive income in stockholders’ equity. Unrealized gains or losses on equity securities were recorded as part of accumulated other comprehensive income in stockholders' equity through December 31, 2017. Effective January 1, 2018, the amendments within ASU 2016-01, require that equity investments be measured at fair value with changes in fair value recognized in net income. At January 1, 2018, the Corporation's equity securities consisted of $1.8 million in preferred stocks. The Corporation recognized a cumulative effect adjustment in the amount of $344 thousand as of January 1, 2018 to reclassify the fair value position into retained earnings. Beginning January 1, 2018, the fair value changes on equity securities are recognized in net income, rather than in accumulated other comprehensive income. The Corporation sold its remaining position in equity securities during the second quarter of 2018. Held-to-maturity securities are carried at amortized cost, adjusted for amortization of premiums or accretion of discounts. The majority of the Corporation’s residential mortgage-backed securities and collateralized mortgage obligations are backed by a U.S. government agency (Government National Mortgage Association) or a government sponsored enterprise (Federal Home Loan Mortgage Corporation or Federal National Mortgage Association). Proceeds from sales of investment securities carried at fair value and the associated gains and losses recorded in earnings are listed below: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Proceeds $ — $ 7,035 $ 4,215 $ 17,085 Gross gains — 1 42 168 Gross losses — — (39 ) — The following is a summary of the amortized cost and fair value of investment securities at September 30, 2018 , by maturity, for both carried at fair value and held-to-maturity. The maturities of residential mortgage-backed securities and collateralized mortgage obligations are based on scheduled principal payments. The maturities of all other debt securities are based on final contractual maturity. September 30, 2018 (Dollars in thousands) Amortized Cost Fair Value Investment Securities Carried at Fair Value: Due in one year or less $ 32,586 $ 32,424 Due after one year through five years 121,421 119,478 Due after five years through ten years 455,582 443,027 Due after ten years 2,196,692 2,141,951 Total $ 2,806,281 $ 2,736,880 Investment Securities Held-to-Maturity: Due in one year or less $ 57,403 $ 57,248 Due after one year through five years 221,335 218,555 Due after five years through ten years 157,517 153,997 Due after ten years 172,112 168,397 Total $ 608,367 $ 598,197 Securities with a carrying value of $1.02 billion and $937.2 million were pledged at September 30, 2018 and December 31, 2017 , respectively, to secure borrowings and deposits. At September 30, 2018 and December 31, 2017 , there were no holdings of securities of any one issuer, other than the U.S. government and its agencies, in an amount greater than 10% of shareholders' equity. The following schedule summarizes information for debt securities both available-for-sale and held-to-maturity with gross unrealized losses at September 30, 2018 and December 31, 2017 , aggregated by category and length of time that individual securities have been in a continuous unrealized loss position. As of September 30, 2018 , the Corporation’s securities portfolio consisted of 2,074 securities, 1,525 of which were in an unrealized loss position. Less Than 12 Months 12 Months or More Total (Dollars in thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses September 30, 2018 Government sponsored agencies $ 204,095 $ 2,564 $ 39,573 $ 1,640 $ 243,668 $ 4,204 State and political subdivisions 563,202 14,773 414,480 11,819 977,682 26,592 Residential mortgage-backed securities 119,911 2,907 55,068 3,061 174,979 5,968 Collateralized mortgage obligations 990,167 19,414 456,347 19,940 1,446,514 39,354 Corporate bonds 141,365 3,773 76,955 3,135 218,320 6,908 Trust preferred securities 13,716 60 2,789 98 16,505 158 Total $ 2,032,456 $ 43,491 $ 1,045,212 $ 39,693 $ 3,077,668 $ 83,184 December 31, 2017 Government sponsored agencies $ 63,818 $ 510 $ 24,621 $ 438 $ 88,439 $ 948 State and political subdivisions 437,407 12,268 349,242 10,093 786,649 22,361 Residential mortgage-backed securities 93,508 383 56,576 1,243 150,084 1,626 Collateralized mortgage obligations 713,525 7,235 73,707 1,249 787,232 8,484 Corporate bonds 71,447 1,138 47,878 454 119,325 1,592 Trust preferred securities — — 11,164 172 11,164 172 Total $ 1,379,705 $ 21,534 $ 563,188 $ 13,649 $ 1,942,893 $ 35,183 An assessment is performed quarterly by the Corporation to determine whether unrealized losses in its debt securities portfolio are temporary or other-than-temporary by carefully considering all reasonably available information. The Corporation reviews factors such as financial statements, credit ratings, news releases and other pertinent information of the underlying issuer or company to make its determination. Management did not believe any individual unrealized loss on any debt security, as of September 30, 2018 , represented other-than-temporary impairment ("OTTI") as the unrealized losses for these securities resulted primarily from changes in benchmark U.S. Treasury interest rates and not credit issues. Management believed that the unrealized losses on debt securities at September 30, 2018 were temporary in nature and due primarily to changes in interest rates and reduced market liquidity and not as a result of credit-related issues. At September 30, 2018 , the Corporation did not have the intent to sell any of its impaired debt securities and believed that it was more-likely-than-not that the Corporation will not have to sell any such debt securities before a full recovery of amortized cost. Accordingly, at September 30, 2018 , the Corporation believed the impairments in its debt securities portfolio were temporary in nature. However, there is no assurance that OTTI may not occur in the future.

Loans

Loans	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Loans	Loans Loan portfolio segments are defined as the level at which an entity develops and documents a systematic methodology to determine its allowance. The Corporation has two loan portfolio segments (commercial loans and consumer loans) that it uses in determining the allowance. Both quantitative and qualitative factors are used by management at the loan portfolio segment level in determining the adequacy of the allowance for the Corporation. Classes of loans are a disaggregation of an entity’s loan portfolio segments. Classes of loans are defined as a group of loans which share similar initial measurement attributes, risk characteristics, and methods for monitoring and assessing credit risk. The Corporation has six classes of loans, which are set forth below. Commercial — Loans and lines of credit to varying types of businesses, including municipalities, school districts and nonprofit organizations, for the purpose of supporting working capital, operational needs and term financing of equipment. Repayment of such loans is generally provided through operating cash flows of the business. Commercial loans are predominately secured by equipment, inventory, accounts receivable, personal guarantees of the owner and other sources of repayment, although the Corporation may also secure commercial loans with real estate. Commercial real estate — Loans secured by real estate occupied by the borrower for ongoing operations (owner-occupied), non-owner occupied real estate leased to one or more tenants (non-owner occupied) and vacant land that has been acquired for investment or future land development (vacant land). Real estate construction and land development — Real estate construction loans represent secured loans for the construction of business properties. Real estate construction loans often convert to a commercial real estate loan at the completion of the construction period. Land development loans represent secured development loans made to borrowers for the purpose of infrastructure improvements to vacant land to create finished marketable residential and commercial lots/land. Most land development loans are originated with the intention that the loans will be paid through the sale of developed lots/land by the developers within twelve months of the completion date. Land development loans at September 30, 2018 and December 31, 2017 were primarily comprised of loans to develop residential properties. Residential mortgage — Loans secured by one - to four -family residential properties, generally with fixed interest rates for periods of fifteen years or less. The loan-to-value ratio at the time of origination is generally 80% or less. Residential mortgage loans with a loan-to-value ratio of more than 80% generally require private mortgage insurance. Consumer installment — Loans to consumers primarily for the purpose of acquiring automobiles, recreational vehicles and watercraft and comprised primarily of indirect loans purchased from dealers. These loans generally consist of relatively small amounts that are spread across many individual borrowers. Home equity — Loans and lines of credit whereby consumers utilize equity in their personal residence, generally through a second mortgage, as collateral to secure the loan. Loans held-for-sale, comprised of fixed-rate residential mortgage loans, were $93.7 million at September 30, 2018 and $52.1 million at December 31, 2017 . The Corporation sold loans totaling $177.2 million and $569.8 million during the three and nine months ended September 30, 2018 , respectively and $210.2 million and $601.7 million during the three and nine months ended September 30, 2017 , respectively. Commercial, commercial real estate, and real estate construction and land development loans are referred to as the Corporation’s commercial loan portfolio, while residential mortgage, consumer installment and home equity loans are referred to as the Corporation’s consumer loan portfolio. A summary of the Corporation's loans follows: (Dollars in thousands) Originated Acquired (1) Total Loans September 30, 2018 Commercial loan portfolio: Commercial $ 2,951,453 $ 768,469 $ 3,719,922 Commercial real estate: Owner-occupied 1,334,588 563,346 1,897,934 Non-owner occupied 1,875,155 864,545 2,739,700 Vacant land 46,463 27,524 73,987 Total commercial real estate 3,256,206 1,455,415 4,711,621 Real estate construction and land development 554,701 67,446 622,147 Subtotal 6,762,360 2,291,330 9,053,690 Consumer loan portfolio: Residential mortgage 2,285,611 1,106,376 3,391,987 Consumer installment 1,483,540 76,725 1,560,265 Home equity 613,931 176,379 790,310 Subtotal 4,383,082 1,359,480 5,742,562 Total loans (2) $ 11,145,442 $ 3,650,810 $ 14,796,252 December 31, 2017 Commercial loan portfolio: Commercial $ 2,407,606 $ 978,036 $ 3,385,642 Commercial real estate: Owner-occupied 1,185,614 627,948 1,813,562 Non-owner occupied 1,518,787 1,087,974 2,606,761 Vacant land 47,024 33,323 80,347 Total commercial real estate 2,751,425 1,749,245 4,500,670 Real estate construction and land development 498,155 76,060 574,215 Subtotal 5,657,186 2,803,341 8,460,527 Consumer loan portfolio: Residential mortgage 1,967,857 1,284,630 3,252,487 Consumer installment 1,510,540 102,468 1,613,008 Home equity 611,846 217,399 829,245 Subtotal 4,090,243 1,604,497 5,694,740 Total loans (2) $ 9,747,429 $ 4,407,838 $ 14,155,267 (1) Acquired loans are accounted for under ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality (ASC 310-30). (2) Reported net of deferred costs totaling $19.0 million and $26.1 million at September 30, 2018 and December 31, 2017 , respectively. The Corporation acquired loans at fair value as of the acquisition date, which includes loans acquired in the acquisitions of Talmer Bancorp, Inc. ("Talmer"), Lake Michigan Financial Corporation ("Lake Michigan"), Monarch Community Bancorp, Inc. ("Monarch"), Northwestern Bancorp, Inc. ("Northwestern") and O.A.K. Financial Corporation ("OAK"). Acquired loans are accounted for under ASC 310-30 which recognizes the expected shortfall of expected future cash flows, as compared to the contractual amount due, as nonaccretable discount. Any excess of the net present value of expected future cash flows over the acquisition date fair value is recognized as the accretable discount, or accretable yield. The accretable discount is recognized over the expected remaining life of the acquired loans on a pool basis. In the event an acquired loan is renewed or extended, the loan continues to be accounted for as an acquired loan on a pool basis in accordance with ASC 310-30. Activity for the accretable yield, which includes contractually due interest for acquired loans that have been renewed or extended since the date of acquisition and continue to be accounted for in loan pools in accordance with ASC 310-30, follows: (Dollars in thousands) Talmer Lake Michigan Monarch North-western OAK Total Three Months Ended September 30, 2018 Balance at beginning of period $ 616,168 $ 80,442 $ 20,131 $ 49,731 $ 14,292 $ 780,764 Accretion recognized in interest income (40,695 ) (5,980 ) (919 ) (4,341 ) (2,338 ) (54,273 ) Net reclassification (to) from nonaccretable difference (1) 20,250 3,108 (376 ) (765 ) (1,149 ) 21,068 Balance at end of period $ 595,723 $ 77,570 $ 18,836 $ 44,625 $ 10,805 $ 747,559 Three Months Ended September 30, 2017 Balance at beginning of period $ 801,369 $ 121,572 $ 24,270 $ 71,212 $ 19,796 $ 1,038,219 Accretion recognized in interest income (43,816 ) (7,201 ) (1,119 ) (5,263 ) (3,004 ) (60,403 ) Net reclassification (to) from nonaccretable difference (1) 11,861 (14,482 ) 168 (1,358 ) 1,999 (1,812 ) Balance at end of period $ 769,414 $ 99,889 $ 23,319 $ 64,591 $ 18,791 $ 976,004 Nine Months Ended September 30, 2018 Balance at beginning of period $ 731,353 $ 95,124 $ 22,496 $ 60,814 $ 17,110 $ 926,897 Accretion recognized in interest income (125,471 ) (19,040 ) (3,037 ) (13,863 ) (8,323 ) (169,734 ) Net reclassification (to) from nonaccretable difference (1) (10,159 ) 1,486 (623 ) (2,326 ) 2,018 (9,604 ) Balance at end of period $ 595,723 $ 77,570 $ 18,836 $ 44,625 $ 10,805 $ 747,559 Nine Months Ended September 30, 2017 Balance at beginning of period $ 798,210 $ 121,416 $ 27,182 $ 69,847 $ 23,316 $ 1,039,971 Accretion recognized in interest income (133,478 ) (22,050 ) (3,459 ) (15,222 ) (9,595 ) (183,804 ) Net reclassification (to) from nonaccretable difference (1) 104,682 523 (404 ) 9,966 5,070 119,837 Balance at end of period $ 769,414 $ 99,889 $ 23,319 $ 64,591 $ 18,791 $ 976,004 (1) The net reclassification results from changes in expected cash flows of the acquired loans which may include increases in the amount of contractual principal and interest expected to be collected due to improvement in credit quality, increases in balances outstanding from advances, renewals, extensions and interest rates; as well as reductions in contractual principal and interest expected to be collected due to credit deterioration, payoffs, and decreases in interest rates. Credit Quality Monitoring The Corporation maintains loan policies and credit underwriting standards as part of the process of managing credit risk. These standards include making loans generally only within the Corporation’s market areas. The Corporation’s lending markets generally consist of communities throughout Michigan and additional communities located within Northeast Ohio and Northern Indiana. The Corporation, through Chemical Bank, has a commercial loan portfolio approval process involving underwriting and individual and group loan approval authorities to consider credit quality and loss exposure at loan origination. The loans in the Corporation’s commercial loan portfolio are risk rated at origination based on the grading system set forth below. The approval authority of relationship managers is established based on experience levels, with credit decisions greater than $1.25 million requiring credit officer approval and credit decisions greater than $3.0 million requiring group loan authority approval, except for six executive and senior officers who have varying loan limits up to $8.0 million . With respect to the group loan authorities, Chemical Bank has various regional loan committees that meet weekly to consider loans ranging in amounts of $3.0 million to $7.0 million , and a senior loan committee, consisting of certain executive and senior officers, that meets weekly to consider loans ranging in amounts from $7.0 million up to Chemical Bank's internal lending limit, depending on risk rating and credit action required. Credit actions exceeding Chemical Bank's internal lending limit require the approval of the board of directors of Chemical Bank. The majority of the Corporation’s consumer loan portfolio is comprised of secured loans that are relatively small. The Corporation’s consumer loan portfolio has a centralized approval process which utilizes standardized underwriting criteria. The ongoing measurement of credit quality of the consumer loan portfolio is largely done on an exception basis. If payments are made on schedule, as agreed, then no further monitoring is performed. However, if delinquency occurs, the delinquent loans are turned over to the Corporation’s collection department for resolution, resulting in repossession or foreclosure if payments are not brought current. Credit quality for the entire consumer loan portfolio is measured by the periodic delinquency rate, nonaccrual amounts and actual losses incurred. Loans in the commercial loan portfolio tend to be larger and more complex than those in the consumer loan portfolio, and therefore, are subject to more intensive monitoring. All loans in the commercial loan portfolio have an assigned relationship manager, and most borrowers provide periodic financial and operating information that allows the relationship managers to stay abreast of credit quality during the life of the loans. The risk ratings of loans in the commercial loan portfolio are reassessed at least annually, with loans below an acceptable risk rating reassessed more frequently and reviewed by various loan committees within the Corporation at least quarterly. The Corporation maintains a centralized independent loan review function that monitors the approval process and ongoing asset quality of the loan portfolio, including the accuracy of loan grades. The Corporation also maintains an independent appraisal review function that participates in the review of all appraisals obtained by the Corporation for loans in the commercial loan portfolio. Credit Quality Indicators Commercial Loan Portfolio Risk categories for the Corporation's commercial loan portfolio establish the credit quality of a borrower by measuring liquidity, debt capacity, coverage and payment behavior as shown in the borrower's financial statements. The risk categories also measure the quality of the borrower's management and the repayment support offered by any guarantors. Risk categories for the Corporation's commercial loan portfolio are described as follows: Pass: Includes all loans without weaknesses or potential weaknesses identified in the categories of special mention, substandard or doubtful. Special Mention: Loans with potential credit weakness or credit deficiency, which, if not corrected, pose an unwarranted financial risk that could weaken the loan by adversely impacting the future repayment ability of the borrower. Substandard: Loans with a well-defined weakness, or weaknesses, such as loans to borrowers who may be experiencing losses from operations or inadequate liquidity of a degree and duration that jeopardizes the orderly repayment of the loan. Substandard loans also are distinguished by the distinct possibility of loss in the future if these weaknesses are not corrected. Doubtful: Loans with all the characteristics of a loan classified as Substandard, with the added characteristic that credit weaknesses make collection in full highly questionable and improbable. The primary source of repayment is nonexistent and there is doubt as to the value of the secondary source of repayments. A doubtful asset has a high probability of total or substantial loss, but because of pending events that may strengthen the asset, its classification as loss is deferred. Loss: An asset classified as loss is considered uncollectible and of such little value that the continuance as a bankable asset is not warranted. This classification does not mean that an asset has absolutely no recovery or salvage value, but rather that it is not practical or desirable to defer writing off this basically worthless asset even through partial recovery may occur in the future. The following schedule presents the recorded investment of loans in the commercial loan portfolio by credit risk categories at September 30, 2018 and December 31, 2017 : (Dollars in thousands) Pass Special Mention Substandard Doubtful Total September 30, 2018 Originated Portfolio: Commercial $ 2,840,100 $ 54,258 $ 57,095 $ — $ 2,951,453 Commercial real estate: Owner-occupied 1,265,111 33,290 36,168 19 1,334,588 Non-owner occupied 1,854,887 12,542 7,726 — 1,875,155 Vacant land 40,904 480 5,076 3 46,463 Total commercial real estate 3,160,902 46,312 48,970 22 3,256,206 Real estate construction and land development 517,561 5,100 32,040 — 554,701 Subtotal 6,518,563 105,670 138,105 22 6,762,360 Acquired Portfolio: Commercial 707,054 36,227 25,188 — 768,469 Commercial real estate: Owner-occupied 505,246 29,840 28,249 11 563,346 Non-owner occupied 805,466 31,647 27,432 — 864,545 Vacant land 27,311 213 — — 27,524 Total commercial real estate 1,338,023 61,700 55,681 11 1,455,415 Real estate construction and land development 66,294 138 1,014 — 67,446 Subtotal 2,111,371 98,065 81,883 11 2,291,330 Total $ 8,629,934 $ 203,735 $ 219,988 $ 33 $ 9,053,690 December 31, 2017 Originated Portfolio: Commercial $ 2,316,464 $ 41,059 $ 50,083 $ — $ 2,407,606 Commercial real estate: Owner-occupied 1,133,609 19,438 32,567 — 1,185,614 Non-owner occupied 1,504,195 4,728 9,864 — 1,518,787 Vacant land 39,775 38 7,211 — 47,024 Total commercial real estate 2,677,579 24,204 49,642 — 2,751,425 Real estate construction and land development 494,528 837 2,790 — 498,155 Subtotal 5,488,571 66,100 102,515 — 5,657,186 Acquired Portfolio: Commercial 873,861 68,418 35,539 218 978,036 Commercial real estate: Owner-occupied 580,127 23,998 23,036 787 627,948 Non-owner occupied 995,709 43,645 48,620 — 1,087,974 Vacant land 27,849 327 5,147 — 33,323 Total commercial real estate 1,603,685 67,970 76,803 787 1,749,245 Real estate construction and land development 72,346 2,218 1,496 — 76,060 Subtotal 2,549,892 138,606 113,838 1,005 2,803,341 Total $ 8,038,463 $ 204,706 $ 216,353 $ 1,005 $ 8,460,527 Consumer Loan Portfolio The Corporation evaluates the credit quality of loans in the consumer loan portfolio based on the performing or nonperforming status of the loan. Loans in the consumer loan portfolio that are performing in accordance with original contractual terms and are less than 90 days past due and accruing interest are considered to be in a performing status, while those that are in nonaccrual status, contractually past due 90 days or more as to interest or principal payments, are considered to be in a nonperforming status. Loans accounted for under ASC 310-30, "Acquired loans", that are not performing in accordance with contractual terms are not reported as nonperforming because these loans are recorded in pools at their net realizable value based on the principal and interest the Corporation expects to collect on these loans. The following schedule presents the recorded investment of loans in the consumer loan portfolio based on loans in a performing status and loans in a nonperforming status at September 30, 2018 and December 31, 2017 : (Dollars in thousands) Residential Mortgage Consumer Installment Home Equity Total Consumer September 30, 2018 Originated Loans: Performing $ 2,276,000 $ 1,482,190 $ 610,662 $ 4,368,852 Nonperforming 9,611 1,350 3,269 14,230 Subtotal 2,285,611 1,483,540 613,931 4,383,082 Acquired Loans 1,106,376 76,725 176,379 1,359,480 Total $ 3,391,987 $ 1,560,265 $ 790,310 $ 5,742,562 December 31, 2017 Originated Loans: Performing $ 1,959,222 $ 1,509,698 $ 607,541 $ 4,076,461 Nonperforming 8,635 842 4,305 13,782 Subtotal 1,967,857 1,510,540 611,846 4,090,243 Acquired Loans 1,284,630 102,468 217,399 1,604,497 Total $ 3,252,487 $ 1,613,008 $ 829,245 $ 5,694,740 Nonperforming Assets and Past Due Loans Nonperforming assets consist of loans for which the accrual of interest has been discounted, other real estate owned acquired through acquisitions, other real estate owned obtained through foreclosure and other repossessed assets. Loans are considered past due or delinquent when the contractual principal or interest due in accordance with the terms of the loan agreement or any portion thereof remains unpaid after the due date of the scheduled payments. Loans outside of those accounted for under ASC 310-30 are classified as nonaccrual when, in the opinion of management, collection of principal or interest is doubtful. The accrual of interest is discontinued when a loan is placed in nonaccrual status and any payments received reduce the carrying value of the loan. A loan may be placed back on accrual status if all contractual payments have been received and collection of future principal and interest payments are no longer doubtful. Acquired loans that are not performing in accordance with contractual terms are not reported as nonperforming because these loans are recorded in pools at their net realizable value based on the principal and interest the Corporation expects to collect on these loans. A summary of nonperforming loans follows: (Dollars in thousands) September 30, December 31, Nonperforming assets Nonaccrual loans: Commercial $ 25,328 $ 19,691 Commercial real estate: Owner-occupied 14,936 19,070 Non-owner occupied 8,991 5,270 Vacant land 4,711 5,205 Total commercial real estate 28,638 29,545 Real estate construction and land development 28,477 77 Residential mortgage 9,611 8,635 Consumer installment 1,350 842 Home equity 3,269 4,305 Total nonaccrual loans 96,673 63,095 Other real estate owned and repossessed assets 6,584 8,807 Total nonperforming assets $ 103,257 $ 71,902 Accruing loans contractually past due 90 days or more as to interest or principal payments, excluding acquired loans accounted for under ASC 310-30 Commercial $ 632 $ — Commercial real estate: Owner-occupied 47 — Non-owner occupied — 13 Total commercial real estate 47 13 Real estate construction and land development 38 — Home equity 475 1,364 Total accruing loans contractually past due 90 days or more as to interest or principal payments, excluding acquired loans accounted for under ASC 310-30 $ 1,192 $ 1,377 The Corporation’s nonaccrual loans at September 30, 2018 and December 31, 2017 included $28.1 million and $29.1 million , respectively, of nonaccrual TDRs. The Corporation had $5.4 million of residential mortgage loans that were in the process of foreclosure at September 30, 2018 , compared to $4.2 million at December 31, 2017 . Loan delinquency, excluding acquired loans accounted for under ASC 310-30, was as follows: (Dollars in thousands) 30-59 days past due 60-89 days past due 90 days or more past due Total past due Current Total loans 90 days or more past due and still accruing September 30, 2018 Originated Portfolio: Commercial $ 9,280 $ 8,770 $ 12,855 $ 30,905 $ 2,920,548 $ 2,951,453 $ 632 Commercial real estate: Owner-occupied 8,052 2,440 8,458 18,950 1,315,638 1,334,588 47 Non-owner occupied 1,993 762 2,054 4,809 1,870,346 1,875,155 — Vacant land 277 1,399 2,460 4,136 42,327 46,463 — Total commercial real estate 10,322 4,601 12,972 27,895 3,228,311 3,256,206 47 Real estate construction and land development 1,244 13,238 15,277 29,759 524,942 554,701 38 Residential mortgage 3,889 1,576 4,752 10,217 2,275,394 2,285,611 — Consumer installment 3,555 657 617 4,829 1,478,711 1,483,540 — Home equity 5,185 1,123 1,704 8,012 605,919 613,931 475 Total $ 33,475 $ 29,965 $ 48,177 $ 111,617 $ 11,033,825 $ 11,145,442 $ 1,192 December 31, 2017 Originated Portfolio: Commercial $ 13,906 $ 3,766 $ 9,494 $ 27,166 $ 2,380,440 $ 2,407,606 $ — Commercial real estate: Owner-occupied 7,644 1,306 5,027 13,977 1,171,637 1,185,614 — Non-owner occupied 1,653 228 693 2,574 1,516,213 1,518,787 13 Vacant land 83 28 153 264 46,760 47,024 — Total commercial real estate 9,380 1,562 5,873 16,815 2,734,610 2,751,425 13 Real estate construction and land development — — — — 498,155 498,155 — Residential mortgage 2,795 1,415 858 5,068 1,962,789 1,967,857 — Consumer installment 3,324 442 226 3,992 1,506,548 1,510,540 — Home equity 2,319 1,301 2,196 5,816 606,030 611,846 1,364 Total $ 31,724 $ 8,486 $ 18,647 $ 58,857 $ 9,688,572 $ 9,747,429 $ 1,377 Impaired Loans A loan is impaired when, based on current information and events, it is probable that the Corporation will be unable to collect all amounts due according to the contractual terms of the loan agreement. Impaired loans include nonperforming loans and all TDRs. Impaired loans are accounted for at the lower of the present value of expected cash flows or the estimated fair value of the collateral. When the present value of expected cash flows or the fair value of the collateral of an impaired loan not accounted for under ASC 310-30 is less than the amount of unpaid principal outstanding on the loan, the recorded principal balance of the loan is reduced to its carrying value through either a specific allowance for loan loss or a partial charge-off of the loan balance. The following schedules present impaired loans by classes of loans at September 30, 2018 and December 31, 2017 : (Dollars in thousands) Recorded Investment Unpaid Principal Balance Related Valuation Allowance September 30, 2018 Impaired loans with a valuation allowance: Commercial $ 13,394 $ 16,109 $ 1,110 Commercial real estate: Owner-occupied 13,278 15,607 1,281 Non-owner occupied 3,187 4,595 142 Vacant land 2,130 2,130 373 Total commercial real estate 18,595 22,332 1,796 Real estate construction and land development 28,575 28,575 650 Residential mortgage 12,879 12,879 1,146 Consumer installment 1,071 1,071 117 Home equity 3,697 3,697 255 Subtotal 78,211 84,663 5,074 Impaired loans with no related valuation allowance: Commercial 25,021 26,427 — Commercial real estate: Owner-occupied 10,852 11,490 — Non-owner occupied 12,161 13,099 — Vacant land 2,859 3,945 — Total commercial real estate 25,872 28,534 — Real estate construction and land development 140 207 — Residential mortgage 7,988 7,988 — Consumer installment 475 475 — Home equity 1,743 1,743 — Subtotal 61,239 65,374 — Total impaired loans: Commercial 38,415 42,536 1,110 Commercial real estate: Owner-occupied 24,130 27,097 1,281 Non-owner occupied 15,348 17,694 142 Vacant land 4,989 6,075 373 Total commercial real estate 44,467 50,866 1,796 Real estate construction and land development 28,715 28,782 650 Residential mortgage 20,867 20,867 1,146 Consumer installment 1,546 1,546 117 Home equity 5,440 5,440 255 Total $ 139,450 $ 150,037 $ 5,074 (Dollars in thousands) Recorded Investment Unpaid Principal Balance Related Valuation Allowance December 31, 2017 Impaired loans with a valuation allowance: Commercial $ 28,897 $ 31,655 $ 2,296 Commercial real estate: Owner-occupied 17,774 21,588 2,317 Non-owner occupied 5,307 7,870 316 Vacant land 4,922 5,122 594 Total commercial real estate 28,003 34,580 3,227 Real estate construction and land development 313 313 14 Residential mortgage 15,872 15,872 1,487 Consumer installment 966 966 120 Home equity 4,570 4,570 858 Subtotal 78,621 87,956 8,002 Impaired loans with no related valuation allowance: Commercial 8,504 9,291 — Commercial real estate: Owner-occupied 11,351 12,631 — Non-owner occupied 5,977 6,438 — Vacant land 752 792 — Total commercial real estate 18,080 19,861 — Residential mortgage 4,902 4,902 — Home equity 1,770 1,770 — Subtotal 33,256 35,824 — Total impaired loans: Commercial 37,401 40,946 2,296 Commercial real estate: Owner-occupied 29,125 34,219 2,317 Non-owner occupied 11,284 14,308 316 Vacant land 5,674 5,914 594 Total commercial real estate 46,083 54,441 3,227 Real estate construction and land development 313 313 14 Residential mortgage 20,774 20,774 1,487 Consumer installment 966 966 120 Home equity 6,340 6,340 858 Total $ 111,877 $ 123,780 $ 8,002 The following schedule presents additional information regarding impaired loans by classes of loans segregated by those requiring a valuation allowance and those not requiring a valuation allowance for the three and nine months ended September 30, 2018 and 2017 , and the respective interest income amounts recognized: Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 (Dollars in thousands) Average recorded investment Interest income recognized while on impaired status Average recorded investment Interest income recognized while on impaired status Average Interest income Average Interest income Impaired loans with a valuation allowance: Commercial $ 13,945 $ 67 $ 25,628 $ 222 $ 17,495 $ 343 $ 25,278 $ 647 Commercial real estate: Owner-occupied 11,977 94 13,401 155 12,999 257 14,083 459 Non-owner occupied 3,697 13 2,457 17 3,271 34 2,939 68 Vacant land 1,589 7 2,442 25 2,198 39 2,098 75 Total commercial real estate 17,263 114 18,300 197 18,468 330 19,120 602 Real estate construction and land development 9,647 2 175 3 3,372 6 159 8 Residential mortgage 11,620 117 15,945 144 12,662 349 16,529 446 Consumer installment 911 3 748 1 961 6 737 3 Home equity 3,022 20 4,369 21 3,176 58 4,154 58 Subtotal $ 56,408 $ 323 $ 65,165 $ 588 $ 56,134 $ 1,092 $ 65,977 $ 1,764 Impaired loans with no related valuation allowance: Commercial $ 24,114 $ 123 $ 10,120 $ 14 $ 20,773 $ 365 $ 10,142 $ 92 Commercial real estate: Owner-occupied 13,831 68 13,009 1 14,588 205 10,862 13 Non-owner occupied 12,776 81 8,942 88 9,825 184 9,487 255 Vacant land 2,874 — 3,484 12 2,694 — 4,348 36 Total commercial real estate 29,481 149 25,435 101 27,107 389 24,697 304 Real estate construction and land development 3,857 2 71 — 1,986 5 86 — Residential mortgage 8,605 31 5,144 8 7,272 79 4,511 25 Consumer installment 537 — 244 — 240 — 201 — Home equity 2,191 8 1,639 — 2,241 17 1,227 6 Subtotal $ 68,785 $ 313 $ 42,653 $ 123 $ 59,619 $ 855 $ 40,864 $ 427 Total impaired loans: Commercial $ 38,059 $ 190 $ 35,748 $ 236 $ 38,268 $ 708 $ 35,420 $ 739 Commercial real estate: Owner-occupied 25,808 162 26,410 156 27,587 462 24,945 472 Non-owner occupied 16,473 94 11,399 105 13,096 218 12,426 323 Vacant land 4,463 7 5,926 37 4,892 39 6,446 111 Total commercial real estate 46,744 263 43,735 298 45,575 719 43,817 906 Real estate construction and land development 13,504 4 246 3 5,358 11 245 8 Residential mortgage 20,225 148 21,089 152 19,934 428 21,040 471 Consumer installment 1,448 3 992 1 1,201 6 938 3 Home equity 5,213 28 6,008 21 5,417 75 5,381 64 Total $ 125,193 $ 636 $ 107,818 $ 711 $ 115,753 $ 1,947 $ 106,841 $ 2,191 The difference between an impaired loan’s recorded investment and the unpaid principal balance for originated loans represents a partial charge-off resulting from a confirmed loss due to the value of the collateral securing the loan being below the loan balance and management’s assessment that full collection of the loan balance is not likely. Impaired loans included $43.0 million and $48.8 million at September 30, 2018 and December 31, 2017 , respectively, of accruing TDRs. Loans Modified Under Troubled Debt Restructurings (TDRs) The following tables present the recorded investment of loans modified into TDRs during the three and nine months ended September 30, 2018 and 2017 by type of concession granted. In cases where more than one type of concession was granted, the loans were categorized based on the most significant concession. Concession type (Dollars in thousands) Principal Principal Interest Forbearance Total Pre-modification recorded investment Post-modification recorded investment For the three months ended September 30, 2018 Commercial loan portfolio: Commercial $ 2,104 $ — $ 165 $ 1 13 $ 2,277 $ 2,270 Commercial real estate: Owner-occupied 438 — — — 2 438 438 Non-owner occupied — 66 — — 1 69 66 Total commercial real estate 438 66 — — 3 507 504 Total Commercial 2,542 66 165 1 16 2,784 2,774 Consumer loan portfolio: Residential mortgage — 111 108 — 2 220 219 Consumer installment 48 74 44 — 11 172 166 Home equity 91 73 64 — 4 228 228 Total Consumer 139 258 216 — 17 620 613 Total loans $ 2,681 $ 324 $ 381 $ 1 33 $ 3,404 $ 3,387 For the nine months ended September 30, 2018 Commercial loan portfolio: Commercial $ 3,747 $ — $ 1,448 $ 262 44 $ 5,481 $ 5,457 Commercial real estate: Owner-occupied 808 — 888 513 10 2,221 2,209 Non-owner occupied 68 66 — — 2 143 134 Total commercial real estate 876 66 888 513 12 2,364 2,343 Total Commercial 4,623 66 2,336 775 56 7,845 7,800 Consumer loan portfolio: Residential mortgage 269 151 147 — 9 577 567 Consumer installment 134 141 82 — 36 372 357 Home equity 357 73 179 — 13 652 609 Total Consumer 760 365 408 — 58 1,601 1,533 Total loans $ 5,383 $ 431 $ 2,744 $ 775 114 $ 9,446 $ 9,333 Concession type (Dollars in thousands) Principal Interest Forbearance Total Pre-modification recorded investment Post-modification recorded investment For the three months ended September 30, 2017 Commercial loan portfolio: Commercial $ 506 $ 281 $ 1,332 14 $ 2,173 $ 2,119 Commercial real estate: Owner-occupied — 42 335 3 390 377 Non-owner occupied — 27 — 1 28 27 Total commercial real estate — 69 335 4 418 404 Real estate construction and land development 35 — — 1 36 35 Total Commercial 541 350 1,667 19 2,627 2,558 Consumer loan portfolio: Residential mortgage 76 122 — 3 262 198 Consumer installment 47 7 — 11 58 54 Home equity 116 — — 5 124 116 Total Consumer 239 129 — 19 444 368 Total loans $ 780 $ 479 $ 1,667 38 $ 3,071 $ 2,926 For the nine months ended September 30, 2017 Commercial loan portfolio: Commercial $ 841 $ 1,648 $ 1,911 26 $ 4,476 $ 4,400 Commercial real estate: Owner-occupied 447 182 457 9 1,106 1,086 Non-owner occupied — 27 — 1 28 27 Total commercial real estate 447 209 457 10 1,134 1,113 Real estate construction and land development 35 — — 1 36 35 Total Commercial 1,323 1,857 2,368 37 5,646 5,548 Consumer loan portfolio: Residential mortgage 211 383 — 9 676 594 Consumer installment 79 7 — 17 93 86 Home equity 380 — — 10 449 380 Total Consumer 670 390 — 36 1,218 1,060 Total loans $ 1,9

Other Real Estate Owned and Rep

Other Real Estate Owned and Repossessed Assets	9 Months Ended
	Sep. 30, 2018
Other Real Estate [Abstract]
Other Real Estate Owned and Repossessed Assets	Other Real Estate Owned and Repossessed Assets Changes in other real estate owned and repossessed assets, included in interest receivable and other assets on the Consolidated Statements of Financial Position, were as follows: (Dollars in thousands) Other real estate Repossessed Balance at January 1, 2018 $ 8,182 $ 625 Transfers based on adoption of ASU 2014-09 (1) (189 ) — Additions (2) 5,281 3,504 Net payments received (190 ) — Disposals (5,859 ) (3,563 ) Write-downs (1,207 ) — Balance at September 30, 2018 $ 6,018 $ 566 Balance at January 1, 2017 $ 16,812 $ 375 Additions (2) 5,339 3,633 Net payments received (582 ) — Disposals (10,180 ) (3,469 ) Write-downs (1,323 ) — Balance at September 30, 2017 $ 10,066 $ 539 (1) In accordance with the updates to Topic 606 adopted by the Corporation effective January 1, 2018, $1.1 million of other real estate owned sold with seller financing were reclassified on the Consolidated Statements of Financial Position to loans and the related $0.9 million of deferred gains were recognized in income as an adjustment to opening retained earnings. Refer to Note 1, Basis of Presentation and Significant Accounting Policies for further information. (2) Includes loans transferred to other real estate owned and other repossessed assets. At September 30, 2018 , the Corporation had $1.5 million of other real estate owned and repossessed assets as a result of obtaining physical possession in accordance with ASU No. 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans Upon Foreclosure. In addition, there were $5.4 million of consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process as of September 30, 2018 . Income and expenses related to other real estate owned and repossessed assets, recorded as a component of "Other" operating expenses in the Consolidated Statements of Income, were as follows: (Dollars in thousands) Other real estate owned Repossessed assets For the three months ended September 30, 2018 Net gain (loss) on sale $ 224 $ (175 ) Write-downs (424 ) — Net operating expenses (93 ) (2 ) Total $ (293 ) $ (177 ) For the nine months ended September 30, 2018 Net gain (loss) on sale $ 1,003 $ (269 ) Write-downs (1,207 ) — Net operating expenses (808 ) (5 ) Total $ (1,012 ) $ (274 ) For the three months ended September 30, 2017 Net gain (loss) on sale $ 388 $ (112 ) Write-downs (550 ) — Net operating expenses (509 ) (1 ) Total $ (671 ) $ (113 ) For the nine months ended September 30, 2017 Net gain (loss) on sale $ 2,203 $ (283 ) Write-downs (1,323 ) — Net operating expenses (1,727 ) (8 ) Total $ (847 ) $ (291 )

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Goodwill was $1.13 billion at both September 30, 2018 and December 31, 2017 . Goodwill recorded is primarily attributable to the synergies and economies of scale expected from combining the operations of the Corporation and acquired and merged organizations. Goodwill is not amortized but is evaluated at least annually for impairment. The Corporation’s most recent annual goodwill impairment review performed as of October 31, 2017 did not indicate that an impairment of goodwill existed. The Corporation also determined that no triggering events have occurred that indicated impairment from the most recent valuation date through September 30, 2018 and that the Corporation's goodwill was no t impaired at September 30, 2018 .

Loan Servicing Rights

Loan Servicing Rights	9 Months Ended
	Sep. 30, 2018
Transfers and Servicing [Abstract]
Loan Servicing Rights	Loan Servicing Rights Loan servicing rights ("LSRs") are created as a result of selling residential mortgage and commercial real estate loans in the secondary market while retaining the right to service these loans and receive servicing income over the life of the loan, and from acquisitions of other banks that had LSRs. Loans serviced for others are not reported as assets in the Consolidated Statements of Financial Position. The Corporation has elected to account for LSRs under the fair value measurement method. LSRs are established and recorded at the estimated fair value by calculating the present value of estimated future net servicing cash flows, taking into consideration actual and expected mortgage loan prepayment rates, discount rates, servicing costs, and other economic factors, which are determined based on current market conditions. The following table represents the activity for LSRs and the related fair value changes: (Dollars in thousands) Commercial Real Estate Mortgage Total For the three months ended September 30, 2018 Fair value, beginning of period $ 457 $ 69,907 $ 70,364 Additions from loans sold with servicing retained 51 2,035 2,086 Changes in fair value due to: Reductions from pay-offs, pay downs and run-off (28 ) (647 ) (675 ) Changes in estimates of fair value (1) — 932 932 Fair value, end of period $ 480 $ 72,227 $ 72,707 For the nine months ended September 30, 2018 Fair value, beginning of period $ 427 $ 63,414 $ 63,841 Additions from loans sold with servicing retained 139 6,198 6,337 Changes in fair value due to: 0 0 Reductions from pay-offs, pay downs and run-off (86 ) (2,039 ) (2,125 ) Changes in estimates of fair value (1) — 4,654 4,654 Fair value, end of period $ 480 $ 72,227 $ 72,707 Principal balance of loans serviced $ 42,070 $ 6,869,131 $ 6,911,201 For the three months ended September 30, 2017 Fair value, beginning of period $ 486 $ 64,036 $ 64,522 Additions from loans sold with servicing retained — 2,324 2,324 Changes in fair value due to: 0 Reductions from pay-offs, pay downs and run-off (31 ) (579 ) (610 ) Changes in estimates of fair value (1) — (4,041 ) (4,041 ) Fair value, end of period $ 455 $ 61,740 $ 62,195 For the nine months ended September 30, 2017 Fair value, beginning of period $ 344 $ 47,741 $ 48,085 Transfers in based on new accounting policy election (2) — 15,891 15,891 Additions from loans sold with servicing retained 188 6,273 6,461 Changes in fair value due to: Reductions from pay-offs, pay downs and run-off (77 ) (1,803 ) (1,880 ) Change in estimates of fair value (1) — (6,362 ) (6,362 ) Fair value, end of period $ 455 $ 61,740 $ 62,195 Principal balance of loans serviced $ 41,798 $ 7,102,485 $ 7,144,283 (1) Represents estimated LSR value change resulting primarily from market-driven changes in interest rates and prepayments. Included in "Net gain on sale of loans and other mortgage banking revenue" in the Consolidated Statements of Income. (2) The Corporation elected as of January 1, 2017 to account for all loan servicing rights previously accounted for at the lower of cost or fair value under the fair value measurement method. For further information on this election, refer to Note 1, Basis of Presentation and Significant Accounting Policies. Expected and actual loan prepayment speeds are the most significant factors driving the fair value of loan servicing rights. The following table presents assumptions utilized in determining the fair value of loan servicing rights as of September 30, 2018 and December 31, 2017 . Mortgage As of September 30, 2018 Prepayment speed 0.0 - 25.74% Weighted average ("WA") discount rate 10.1 % WA cost to service/per year $ 66 WA ancillary income/per year $ 31 WA float range 2.3 % As of December 31, 2017 Prepayment speed 0.0 - 38.8% WA discount rate 10.1 % WA cost to service/per year $ 66 WA ancillary income/per year $ 31 WA float range 1.6 % The Corporation realized total loan servicing fee income, included in "Net gain on sale of loans and other mortgage banking revenue" in the Consolidated Statements of Income, of $4.3 million and $4.5 million for the three months ended September 30, 2018 and 2017 , respectively and $13.2 million and $13.6 million for the nine months ended September 30, 2018 and 2017 , respectively.

Other Intangible Assets

Other Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangible Assets	Other Intangible Assets The following table shows the net carrying value of the Corporation’s other intangible assets. (Dollars in thousands) September 30, December 31, Core deposit intangible assets $ 29,981 $ 34,259 Non-compete intangible assets — 12 Total other intangible assets $ 29,981 $ 34,271 Core Deposit Intangible Assets The Corporation recorded core deposit intangible assets associated with each of its acquisitions and its merger with Talmer. Core deposit intangible assets are amortized on an accelerated basis over their estimated useful lives and have an estimated remaining weighted-average useful life of 6.8 years as of September 30, 2018 . The following table sets forth the carrying amount and accumulated amortization of core deposit intangible assets that are amortizable and arose from business combinations or other acquisitions: (Dollars in thousands) September 30, December 31, Gross original amount $ 56,456 $ 59,143 Accumulated amortization 26,475 24,884 Net carrying amount $ 29,981 $ 34,259 Amortization expense recognized on core deposit intangible assets was $1.4 million and $1.5 million for the three months ended September 30, 2018 and 2017 , respectively, and $4.3 million and $4.5 million for the nine months ended September 30, 2018 and 2017 , respectively. The estimated future amortization expense on core deposit intangible assets for periods ending after September 30, 2018 is as follows: 2018 — $1.4 million ; 2019 — $5.4 million ; 2020 — $4.9 million ; 2021 — $4.5 million ; 2022 — $4.2 million ; 2023 and thereafter — $9.6 million .

Derivative Instruments and Bala

Derivative Instruments and Balance Sheet Offsetting	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Balance Sheet Offsetting	Derivative Instruments and Balance Sheet Offsetting In the normal course of business, the Corporation enters into various transactions involving derivative instruments to manage exposure to fluctuations in interest rates and to meet the financing needs of customers (customer-initiated derivatives). These financial instruments involve, to varying degrees, elements of market and credit risk. Market and credit risk are included in the determination of fair value. Commitments to fund mortgage loans (interest rate locks) to be sold into the secondary market and forward commitments for the future delivery of mortgage loans to third party investors are considered derivatives. It is the Corporation’s practice to enter into forward commitments for the future delivery of mortgage loans when interest rate lock commitments are entered into in order to economically hedge the effect of changes in interest rates resulting from its commitments to fund the loans. The Corporation enters into interest rate derivatives to provide a service to certain qualifying customers to help facilitate their respective risk management strategies. These customer-initiated derivatives are not used for interest rate risk management purposes and primarily consist of interest rate swaps, interest rate caps and floors and foreign exchange contracts. The Corporation generally takes offsetting positions with dealer counterparts to mitigate the inherent risk. Income primarily results from the spread between the customer derivative and the offsetting dealer positions. Gains and losses on customer-related derivatives are included in other noninterest income. The Corporation utilizes interest rate swaps designated as cash flow hedges for risk management purposes to manage exposure that arises 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. These interest rate swaps designated as cash flow hedges 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 certain variable rate borrowings. The Corporation assesses the effectiveness of each hedging relationship by comparing the changes in cash flows of the derivative instruments with the changes in cash flows of the designated hedged transactions. The changes in fair value of derivatives designated and that qualify as cash flow hedges are recorded in accumulated other comprehensive income (loss) and are subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. For the Corporation's derivative instruments that are designated and qualify as a cash flow hedge, the gain or loss on the derivative instrument, as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in current earnings in the same line item as the offsetting loss or gain on the related interest rate swap. The Corporation expects the hedges to remain highly effective during the remaining terms of the swaps. The Corporation additionally has written and purchased option derivatives consisting of instruments to facilitate an equity-linked time deposit product (the "Power Equity CD"). The Power Equity CD is a time deposit that provides the purchaser a guaranteed return of principal at maturity plus a potential equity return (a written option), while the Corporation receives 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 Statements of Financial Position. The following table presents the notional amount and fair value of the Corporation’s derivative instruments held or issued in connection with customer-initiated and mortgage banking activities. September 30, 2018 December 31, 2017 Fair Value Fair Value (Dollars in thousands) Notional Amount (1) Gross Derivative Assets (2) Gross Derivative Liabilities (2) Notional Amount (1) Gross Derivative Assets (2) Gross Derivative Liabilities (2) Risk management purposes: Derivatives designated as hedging instruments: Interest rate swaps $ 820,000 $ 21,067 $ — $ 620,000 $ 5,899 $ — Total risk management purposes 820,000 21,067 — 620,000 5,899 — Customer-initiated and mortgage banking derivatives: Customer-initiated derivatives 1,960,013 21,390 21,703 1,365,119 9,376 10,139 Foreign exchange forwards 934 3 3 — — — Forward contracts related to mortgage loans to be delivered for sale 169,554 760 — 115,996 — 34 Interest rate lock commitments 98,516 1,081 — 71,003 1,222 — Power Equity CD 37,501 1,260 1,260 38,807 2,184 2,184 Total customer-initiated and mortgage banking derivatives 2,266,518 24,494 22,966 1,590,925 12,782 12,357 Total gross derivatives $ 3,086,518 $ 45,561 $ 22,966 $ 2,210,925 $ 18,681 $ 12,357 (1) Notional or contract amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the Consolidated Statements of Financial Position. (2) Derivative assets are included within "Interest receivable and other assets" and derivative liabilities are included within "Interest payable and other liabilities" on the Consolidated Statements of Financial Position. Included in the fair value of the derivative assets are credit valuation adjustments for counterparty credit risk totaling $272 thousand at September 30, 2018 and $809 thousand at December 31, 2017 . In the normal course of business, the Corporation may decide to settle a forward contract rather than fulfill the contract. Cash received or paid in this settlement manner is included in "Net gain on sale of loans and other mortgage banking revenue" in the Consolidated Statements of Income and is considered a cost of executing a forward contract. The following table presents the net gains (losses) related to derivative instruments reflecting the changes in fair value. Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) Location of Gain (Loss) 2018 2017 2018 2017 Forward contracts related to mortgage loans to be delivered for sale Net gain on sale of loans and other mortgage banking revenue $ 1,185 $ 43 $ 794 $ 25 Interest rate lock commitments Net gain on sale of loans and other mortgage banking revenue (904 ) (198 ) (141 ) 843 Foreign exchange forwards Other noninterest income — 5 — 5 Customer-initiated derivatives Other noninterest income 84 (39 ) 450 (820 ) Total gain (loss) recognized in income $ 365 $ (189 ) $ 1,103 $ 53 The following table presents the net gains (losses) recorded in accumulated other comprehensive income and the Consolidated Statements of Income relating to interest rate swaps designated as cash flow hedges for the three and nine months ended September 30, 2018 and 2017. (Dollars in thousands) Amount of gain (loss) recognized in other comprehensive income Amount of gain (loss) reclassified from other comprehensive income to interest income or expense Three Months Ended September 30, 2018 Interest rate swaps designated as cash flow hedges $ 4,111 $ 662 Three Months Ended September 30, 2017 Interest rate swaps designated as cash flow hedges 751 (575 ) Nine Months Ended September 30, 2018 Interest rate swaps designated as cash flow hedges $ 16,176 $ 1,009 Nine months ended September 30, 2017 Interest rate swaps designated as cash flow hedges 694 (984 ) At September 30, 2018 , the Corporation expected $5.1 million of unrealized gains to be reclassified as an increase to interest expense during the following twelve months. Methods and assumptions used by the Corporation in estimating the fair value of its forward contracts, interest rate lock commitments and customer-initiated derivatives are discussed in Note 2 : Fair Value Measurements. Balance Sheet Offsetting Certain financial instruments, including customer-initiated derivatives and interest rate swaps, may be eligible for offset in the Consolidated Statements of Financial Position and/or subject to master netting arrangements or similar agreements. The Corporation is party to master netting arrangements with its financial institution counterparties; however, the Corporation does not offset assets and liabilities under these arrangements for financial statement presentation purposes based on an accounting policy election. The tables below present information about the Corporation’s financial instruments that are eligible for offset. Gross amounts not offset in the (Dollars in thousands) Gross Gross amounts Net amounts Financial Collateral Net September 30, 2018 Offsetting derivative assets Derivative assets (1) $ 21,376 $ — $ 21,376 $ — $ (26,520 ) $ (5,144 ) Offsetting derivative liabilities Derivative liabilities (1) 21,648 — 21,648 — 5,150 16,498 December 31, 2017 Offsetting derivative assets Derivative assets (1) $ 15,228 $ — $ 15,228 $ — $ — $ 15,228 Offsetting derivative liabilities Derivative liabilities 10,139 — 10,139 — 1,081 9,058 (1) Amount does not include participated interest rate swaps, forward contracts, interest rate lock commitments and power equity CDs as these instruments are not subject to master netting or similar arrangements.

Investments in Qualified Afford

Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits	Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits The Corporation invests in qualified affordable housing projects, federal historic projects, and new market projects for the purpose of community reinvestment and obtaining tax credits. 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 carrying value of the investments is reflected in "Interest receivable and other assets" on the Consolidated Statements of Financial Position. The Corporation utilizes the proportional amortization method to account for investments in qualified affordable housing projects and the equity method to account for investments in other tax credit 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 income tax expense attributable to the amortization of investments in qualified affordable housing projects of $1.0 million and $0.8 million during the three months ended September 30, 2018 and 2017 , respectively, and $3.1 million and $2.3 million during the nine months ended September 30, 2018 and 2017 , respectively. The Corporation's remaining investment in qualified affordable housing projects accounted for under the proportional amortization method totaled $52.2 million at September 30, 2018 and $51.4 million at December 31, 2017 . Under the equity method, the Corporation's share of the earnings or losses is included in "Other operating expenses" on the Consolidated Statements of Income. The Corporation's remaining investment in new market projects accounted for under the equity method totaled $11.0 million and $17.3 million at September 30, 2018 and December 31, 2017 , respectively. The Corporation's unfunded equity contributions relating to investments in qualified affordable housing projects, federal historic tax projects and new market projects is recorded in "Interest payable and other liabilities" on the Consolidated Statements of Financial Position. The Corporation's remaining unfunded equity contributions totaled $42.3 million and $48.1 million at September 30, 2018 and December 31, 2017 , respectively. Management analyzes these investments for potential impairment when events or changes in circumstances indicate that it is more-likely-than-not that the carrying amount of the investment will not be realized. An impairment loss is measured as the amount by which the carrying amount of an investment exceeds its fair value. During the three months ended September 30, 2018 federal historic tax credits resulted in an income tax benefit of $3.2 million , partially offset by impairment expense of $3.2 million , representing $2.5 million net of tax, recorded in "other noninterest expense." During the nine months ended September 30, 2018 federal historic tax credits resulted in an income tax benefit of $6.6 million , partially offset by impairment expense of $6.5 million , representing $5.1 million net of tax, recorded in "other noninterest expense." During both the three and nine months ended September 30, 2017 , an income tax benefit of $2.3 million , partially offset by impairment expense of $3.1 million , representing $2.0 million net of tax, recorded in "other noninterest expense" was recognized as a result of a federal historic tax credit placed into service. The Corporation consolidates variable interest entities ("VIEs") in which it is the primary beneficiary. In general, a VIE is an entity that either (i) has an insufficient amount of equity to carry out its principal activities without additional subordinated financial support, (ii) has a group of equity owners that are unable to make significant decisions about its activities or (iii) has a group of equity owners that do not have the obligation to absorb losses or the right to receive returns as generated by its operations. If any of these characteristics are present, the entity is subject to a variable interest consolidation model, and consolidation is based on variable interests, not on ownership of the entity's outstanding voting stock. Variable interests are defined as contractual, ownership, or other monetary interests in an entity that change with fluctuations in the entity's net asset value. The primary beneficiary consolidates the VIE. The primary beneficiary is defined as the enterprise that has the power to direct the activities and absorb losses or the right to receive benefits. The Corporation is a significant limited partner in the qualified affo rdable housing, federal historic and new market projects it has invested in . These projects meet the definition of VIEs. However, the Corporation is not the primary beneficiary of any of the VIEs in which it holds a limited partnership interest; therefore, the VIEs are not consolidated in the Corporation's Consolidated Financial Statements.

Commitments, Contingencies and

Commitments, Contingencies and Guarantees	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Guarantees	Commitments, Contingencies and Guarantees Commitments In the normal course of business, the Corporation offers a variety of financial instruments containing credit risk that are not required to be reflected in the Consolidated Statements of Financial Position. These financial instruments include outstanding commitments to extend credit, approved but undisbursed loans (undisbursed loan commitments), credit lines, commercial letters of credit and standby letters of credit. The Corporation has risk management policies to identify, monitor and limit exposure to credit risk. To mitigate credit risk for these financial guarantees, the Corporation generally determines the need for specific covenant, guarantee and collateral requirements on a case-by-case basis, depending on the nature of the financial instrument and the customer’s creditworthiness. At September 30, 2018 and December 31, 2017 , the Corporation had $126.1 million and $187.6 million , respectively, of outstanding financial and performance standby letters of credit. The majority of these standby letters of credit are collateralized. The Corporation determined that there were no potential losses from standby letters of credit at September 30, 2018 and December 31, 2017 . Commitments to extend credit are agreements to lend to a customer provided there is no violation of any condition established in the commitment. Commitments generally have fixed expiration dates or other termination clauses and may not require payment of a fee. Since many commitments expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Corporation evaluates each customer's creditworthiness on an individual basis. The amount of collateral obtained, if deemed necessary by the Corporation upon extension of credit, is based on management's credit evaluation of the counterparty. The collateral held varies, but may include securities, real estate, accounts receivable, inventory, plant or equipment. Unfunded commitments under commercial lines of credit, revolving credit lines and overdraft protection agreements are included in commitments to extend credit. These lines of credit are generally not collateralized, usually do not contain a specified maturity date and may be drawn upon only to the total extent to which the Corporation is committed. At September 30, 2018 and December 31, 2017 , the Corporation had $3.10 billion and $3.03 billion , respectively, of commitments to extend credit. The Corporation had undisbursed loan commitments of $600.7 million and $571.0 million at September 30, 2018 and December 31, 2017 , respectively. Undisbursed loan commitments are not included in loans on the Consolidated Statements of Financial Position. The majority of undisbursed loan commitments will be funded and convert to a portfolio loan within a one year period. The allowance for credit losses on lending-related commitments included $1.7 million and $1.2 million at September 30, 2018 and December 31, 2017 , respectively, for probable credit losses inherent in the Corporation's unused commitments and was recorded in "Interest payable and other liabilities" in the Consolidated Statements of Financial Position. Contingencies and Guarantees The Corporation has originated and sold certain loans, and additionally acquired the potential liability for those historical originated and sold loans by merged or acquired entities, for which the buyer has limited recourse to us in the event the loans do not perform as specified in the agreements. These loans had an outstanding balance of $14.4 million and $13.3 million at September 30, 2018 and December 31, 2017 , respectively. The maximum potential amount of undiscounted future payments that the Corporation could be required to make in the event of nonperformance by the borrower totaled $14.2 million and $12.8 million at September 30, 2018 and December 31, 2017 , respectively. In the event of nonperformance, the Corporation has rights to the underlying collateral securing the loans. At September 30, 2018 and December 31, 2017 , the Corporation had recorded a liability of $0.1 million and $0.2 million , respectively, in connection with the recourse agreements, recorded in "Interest payable and other liabilities" in the Consolidated Statements of Financial Position. Representations and Warranties In connection with the Corporation's mortgage banking loan sales, and the historical sales of merged or acquired entities, the Corporation makes certain representations and warranties that the loans meet certain criteria, such as collateral type and underwriting standards. The Corporation may be required to repurchase individual loans and/or indemnify the purchaser against losses if the loan fails to meet established criteria. At September 30, 2018 and December 31, 2017 , the liability recorded in connection with these representations and warranties totaled $4.3 million and $5.3 million , respectively. A summary of the reserve for representations and warranties of the Corporation is as follows: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Reserve balance at beginning of period $ 4,860 $ 5,469 $ 5,349 $ 6,459 Reserve reduction (580 ) (71 ) (1,067 ) (1,061 ) Charge-offs (7 ) (9 ) (9 ) (9 ) Ending reserve balance $ 4,273 $ 5,389 $ 4,273 $ 5,389 (Dollars in thousands) September 30, 2018 December 31, 2017 Reserve balance Liability for specific claims $ 403 $ 531 General allowance 3,870 4,818 Total reserve balance $ 4,273 $ 5,349

Borrowings and Other Short-Term

Borrowings and Other Short-Term Liabilities	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Borrowings and Other Short-Term Liabilities	Borrowings and Other Short-Term Liabilities A summary of the Corporation's short- and long-term borrowings, and other short-term liabilities follows: September 30, 2018 December 31, 2017 (Dollars in thousands) Amount Weighted Average Rate (1) Amount Weighted Average Rate (1) Short-term borrowings: FHLB advances: 2.14% - 2.27% fixed-rate notes $ 1,670,000 2.21 % $ 2,000,000 1.39 % Long-term borrowings: FHLB advances: 1.00% - 2.72% fixed-rate notes due 2018 to 2025 (2) 415,118 2.00 337,204 1.26 Line-of-credit: floating-rate based on one-month LIBOR plus 1.75% — — 19,963 3.10 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 (3) 11,535 4.55 11,425 3.69 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 3.25% due in 2032 (4) 4,318 5.59 4,290 4.59 Total long-term borrowings 430,971 2.10 372,882 1.47 Total borrowings $ 2,100,971 2.19 % $ 2,372,882 1.40 % Other short-term liabilities: Collateralized customer deposits $ 377,471 0.71 % $ 415,236 0.44 % (1) Weighted average rate presented is the contractual rate which excludes premiums and discounts related to purchase accounting. (2) The September 30, 2018 balances include advances payable of $415.0 million and purchase accounting premiums of $0.1 million . The December 31, 2017 balance includes advances payable of $337.0 million and purchase accounting premiums of $0.2 million . (3) The September 30, 2018 balance includes advances payable of $15.0 million and purchase accounting discounts of $3.5 million . The December 31, 2017 balance includes advances payable of $15.0 million and purchase accounting discounts of $3.6 million . (4) The September 30, 2018 balance includes advances payable of $5.0 million and purchase accounting discounts of $0.7 million . The December 31, 2017 balance includes advances payable of $5.0 million and purchase accounting discounts of $0.7 million . Chemical Bank is a member of the FHLB, which provides short- and long-term funding collateralized by mortgage related assets to its members. Each advance is payable at its maturity date, with a prepayment penalty for fixed-rate advances. The Corporation's FHLB advances, including both short-term and long-term, require monthly interest payments and are collateralized by commercial and residential mortgage loans totaling $7.62 billion as of September 30, 2018 . The Corporation's additional borrowing availability through the FHLB, subject to the FHLB's credit requirements and policies and based on the amount of FHLB stock owned by the Corporation, was $547.9 million at September 30, 2018 . Effective January 1, 2018, the Corporation adopted ASU 2016-01. As a result, the Corporation will continue to report FHLB and Federal Reserve Bank ("FRB") stock at cost.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers The Corporation earns a variety of revenue including interest and fees from customers as well as revenues from non-customers. Certain sources of revenue are recognized within interest income and are outside of the scope of ASC Topic 606, Revenue from Contracts with Customers ("ASC 606"). Other sources of revenue fall within the scope of ASC 606 and are mostly recognized within "Noninterest Income" in the Consolidated Statements of Income. The Corporation recognizes revenue when the performance obligations related to the transfer of goods or services under the terms of a contract are satisfied. Some obligations are satisfied at a point in time while others are satisfied over a period of time. Revenue is recognized as the amount of consideration expected to be received in exchange for transferring goods or services to a customer and is segregated based on the nature of product and services offered as part of contractual arrangements. Revenue within the scope of ASC 606 are discussed below. • Service charges and fees on deposit accounts include fees and other charges the Corporation receives to provide various services, including but not limited to, maintaining an account with a customer, providing overdraft services, wire transfers, transferring funds, and accepting and executing stop-payment orders. The consideration includes both fixed (e.g., account maintenance fees) and transaction fees (i.e., wire-transfer fee). Fixed fees are recognized over the period of time the service is provided while transaction fees are recognized when a specific service is rendered to the customer. • Wealth management revenue includes fee income generated from personal and institutional customers. The Corporation also provides investment management services. Services are rendered over a period of time, over which revenue is recognized. Wealth management revenue also includes commissions that are earned for placing a brokerage transaction for execution, such as stocks or other investments. Revenue is recognized once the transaction is completed and the Corporation is entitled to receive consideration. • Other charges and fees for customer services includes service charges on deposit accounts and other fees including account analysis fees, monthly service fees, check orders, ATM fees and other service charges. The Corporation's performance obligation for account analysis fees and monthly service fees is generally satisfied, and therefore, revenue is recognized over the period in which the service is provided. Check orders and other deposit account related fees are largely transactional based, and therefore, the performance obligation is satisfied and related revenue recognized, at a point in time. • Other noninterest expense includes net gain or loss on sales of other real estate and repossessed assets. Revenue is recognized at the time the sale is complete and the Corporation is entitle to receive consideration, including sales that are seller financed as receipt of all payment is expected. The following table presents total noninterest income segregated between contracts with customers within the scope of ASC 606 and those within the scope of other GAAP Topics. The following additionally presents revenues from customers and non-customers that are included within noninterest income and expense. Three Months Ended Nine Months Ended (Dollars in thousands) September 30, 2018 September 30, 2018 Noninterest income Service charges and fees on deposit accounts $ 4,820 $ 13,744 Wealth management revenue 811 3,868 Other charges and fees for customer services 2,522 7,392 Noninterest income from contracts with customers within the scope of ASC 606 8,153 25,004 Noninterest income within the scope of other GAAP topics 29,764 91,485 Total noninterest income $ 37,917 $ 116,489 Noninterest expense Other $ (50 ) $ (734 ) Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration (resulting in a contract receivable) or before payment is due (resulting in a contract asset). A contract liability balance is an entity's obligation to transfer a service to a customer for which the entity has already received payment (or payment is due) from the customer. The Corporation's noninterest income streams are largely based on transactional activity, or standard month-end revenue accruals such as asset management fees based on month-end market values. Consideration is most often received immediately or shortly after the Corporation satisfies its performance obligation and revenue is recognized. The Corporation does not typically enter into long-term revenue contracts with customers, and therefore, does not experience significant contract balances. As of September 30, 2018 and December 31, 2017 , the Corporation did not have a material amount of contract balances.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation The Corporation maintains share-based compensation plans under which it periodically grants share-based awards for a fixed number of shares to certain officers of the Corporation. The fair value of share-based awards is recognized as compensation expense over the requisite service or performance period. During the three months ended September 30, 2018 and 2017 , share-based compensation expense related to share-based awards totaled $1.9 million and $7.6 million , respectively. During the nine months ended September 30, 2018 and 2017 , share-based compensation expense related to share-based awards totaled $6.0 million and $14.6 million , respectively. The excess tax benefit realized from share-based compensation transactions during the three months ended September 30, 2018 and 2017 was a benefit of $98 thousand and an expense of $332 thousand , respectively, and during the nine months ended September 30, 2018 and 2017 was a benefit of $1.9 million and $6.1 million , respectively. During the nine months ended September 30, 2018 , the Corporation granted 315,072 restricted stock units to certain officers of the Corporation. On April 26, 2017, the shareholders of the Corporation approved the Stock Incentive Plan of 2017, which provides for 1,750,000 shares of the Corporation's common stock to be made available for future equity-based awards and canceled the amount of shares available for future grant under prior share-based compensation plans. At September 30, 2018 , there were 1,307,256 shares of common stock available for future grants under the Stock Incentive Plan of 2017. Stock Options The Corporation issues stock options to certain officers from time to time. The exercise price on stock options equals the current market price of the Corporation's common stock on the date of grant and stock options expire ten years from the date of grant. Stock options granted after 2012 vest ratably over a five -year period. Stock options granted prior to 2013 generally vest ratably over a three -year period. Stock options granted prior to August 31, 2016 fully vested upon the merger with Talmer. Stock options assumed by the Corporation in the merger with Talmer on August 31, 2016 were fully vested prior to assumption. A summary of activity for the Corporation’s stock options as of and for the nine months ended September 30, 2018 is presented below: Non-Vested Stock Options Outstanding Stock Options Outstanding Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Grant Date Fair Value Per Share Number of Options Weighted- Average Exercise Price Per Share Outstanding at December 31, 2017 330,870 $ 37.97 $ 7.09 1,110,918 $ 29.56 Exercised — — — (295,419 ) 23.97 Vested (78,533 ) 37.16 6.94 — — Forfeited/expired (14,926 ) 37.51 7.03 (14,928 ) 37.51 Outstanding at September 30, 2018 237,411 $ 38.27 $ 7.14 800,571 $ 38.27 Exercisable/vested at September 30, 2018 563,160 $ 28.61 The weighted-average remaining contractual terms were 6.1 years for all outstanding stock options and 5.4 years for exercisable stock options at September 30, 2018 . The intrinsic value of all outstanding in-the-money stock options and exercisable in-the-money stock options was $17.6 million and $14.0 million , respectively, at September 30, 2018 . The aggregate intrinsic values of outstanding and exercisable options at September 30, 2018 were calculated based on the closing market price of the Corporation’s common stock on September 30, 2018 of $53.40 per share less the exercise price. Options with intrinsic values less than zero, or "out-of-the-money" options, are not included in the aggregate intrinsic value reported. The total intrinsic value of stock options as of September 30, 2017 was $27.7 million . Total cash received from options exercises during both the nine months ended September 30, 2018 and 2017 was $2.6 million , respectively. At September 30, 2018 , unrecognized compensation expense related to stock options totaled $1.4 million and is expected to be recognized over a remaining weighted average period of 2.8 years . Restricted Stock Units The Corporation grants Performance-Based Restricted Stock Units ("PRSUs") and Time-Based Restricted Stock Units ("TRSUs") (collectively referred to as "RSUs") to certain officers from time to time. The PRSUs vest based on the Corporation achieving certain performance target levels and the grantee completing the requisite service period. The PRSUs are eligible to vest from 0.5 x to 1.5 x the number of units originally granted depending on which, if any, of the performance target levels are met. However, if the minimum performance target levels are not achieved, no shares will become vested or be issued for that respective year’s PRSUs. The TRSUs vest upon satisfaction of a service condition. Upon achievement of the performance target level and/or satisfaction of a service condition, as applicable, the RSUs are converted into shares of the Corporation’s common stock on a one-to-one basis. Compensation expense related to RSUs is recognized over the expected requisite performance or service period, as applicable. A summary of the activity for RSUs as of and for the nine months ended September 30, 2018 is presented below: Number of Units Weighted-average grant date fair value per unit Outstanding at December 31, 2017 380,940 $ 41.29 Granted 315,072 54.41 Converted into shares of common stock (70,459 ) 28.96 Forfeited/expired (15,390 ) 47.43 Outstanding at September 30, 2018 610,163 $ 49.33 At September 30, 2018 , unrecognized compensation expense related to RSUs totaled $18.5 million and is expected to be recognized over a remaining weighted average period of 3.2 years . Restricted Stock Awards The Corporation assumed restricted stock awards in the merger with Talmer that vest upon completion of future service requirements. The fair value of these awards is equal to the market price of the Corporation's common stock at the date the awards were assumed with the portion of the fair value related to post-combination service. The Corporation recognizes stock-based compensation expense over the vesting period, using the straight-lined method, based upon the number of shares of restricted stock ultimately expected to vest. If an individual awarded a restricted stock award terminates employment prior to the end of the vesting period, the unvested portion of the stock is forfeited, with certain exceptions. The following table provides information regarding nonvested restricted stock awards: Nonvested restricted stock awards Number of Awards Weighted-average acquisition-date Nonvested at January 1, 2018 83,228 $ 46.23 Vested (41,784 ) 46.23 Forfeited (592 ) 46.23 Nonvested at September 30, 2018 40,852 $ 46.23 At September 30, 2018 , unrecognized compensation expense related to nonvested restricted stock awards totaled $0.8 million and is expected to be recognized over a remaining weighted average period of 0.4 years.

Pension and Other Postretiremen

Pension and Other Postretirement Benefit Plans	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefit Plans	Pension and Other Postretirement Benefit Plans The Corporation's retirement plans include a qualified defined benefit pension plan, a nonqualified pension plan, a nonqualified postretirement benefit plan, a 401(k) savings plan, and a multi-employer defined benefit plan. Qualified Defined Benefit Pension Plan The Chemical Financial Corporation Employees’ Pension Plan (the "Pension Plan") was a qualified defined-benefit, noncontributory pension plan, which provided for postretirement pension benefits for certain salaried employees of the Corporation and its subsidiary, Chemical Bank. Benefits under the Pension Plan were partially frozen effective June 30, 2006. Under the partial freeze of the Pension Plan, benefits for employees with less than 15 years of service or whose combined age plus years of service were less than 65 at June 30, 2006, were based on years of vested service at June 30, 2006 and generally the average of the employee's salary for the five years ended June 30, 2006. In addition, no employee hired after January 1, 2006 was eligible to participate in the Pension Plan. Effective September 30, 2017, the Pension and Compensation Committee approved an amendment to the Pension Plan to cease accruing additional benefits under the existing pension benefit formula after the effective date and all accrued benefits were frozen. Retirement benefits under the Pension Plan were based on years of vested service at September 30, 2017, up to a maximum of thirty years, and the employee's average annual pay for the five highest consecutive years during the ten years preceding September 30, 2017, except for employees whose benefits were previously frozen during 2006. Pension Plan benefits are the present value of estimated future periodic payments that are attributable to services rendered by the employees to the valuation date. Benefits include the benefits expected to be paid to (a) retired or terminated employees or their beneficiaries and (b) present employees or their beneficiaries. A discount rate of 3.68% was utilized for the projected benefit obligation as of September 30, 2018 . The Pension Plan is fully funded as of September 30, 2018 . Nonqualified Pension Plan The Corporation has a supplemental defined benefit nonqualified pension plan, the Chemical Financial Corporation Supplemental Pension Plan ("SERP"). The Corporation established the SERP to provide payments to certain executive officers of the Corporation, as determined by the Compensation and Pension Committee. The Internal Revenue Code limits both the amount of eligible compensation for benefit calculation purposes and the amount of annual benefits that may be paid from a tax qualified retirement plan. The SERP was designed to provide benefits to executive officers of the Corporation that would have been entitled, calculated under the provisions of the Pension Plan, as if the limits imposed by the Internal Revenue Code did not apply. The SERP is an unfunded plan and, therefore, has no assets. Effective September 30, 2017, the Pension and Compensation Committee approved a curtailment to the SERP due to the retirement of the final remaining participant in the SERP. As of September 30, 2018 , a $0.4 million liability was included in other liabilities and recorded in the Consolidated Statements of Financial Position related to the SERP. Nonqualified Postretirement Benefit Plan The Corporation has a nonqualified postretirement benefit plan ("Postretirement Plan") that provides medical and dental benefits, upon retirement, to a limited number of active and retired employees. The majority of the retirees are required to make contributions toward the cost of their benefits based on their years of credited service and age at retirement. Beginning January 1, 2012, the Corporation amended the Postretirement Plan to extend coverage to employees who were at least age 50 as of January 1, 2012. These employees must also retire at age 60 or older, have at least twenty-five years of service with the Corporation and be participating in the active employee group health insurance plan in order to be eligible to participate in the Corporations' Postretirement Plan. Eligible employees may also cover their spouse until age 65 as long as the spouse is not offered health insurance coverage through his or her employer. Employees and their spouses eligible to participate in the Postretirement Plan will be required to make contributions toward the cost of their benefits upon retirement, with the contribution levels designed to cover the projected overall cost of these benefits over the long-term. Retiree contributions are generally adjusted annually. The accounting for these postretirement benefits anticipates changes in future cost-sharing features such as retiree contributions, deductibles, copayments and coinsurance. The Corporation reserves the right to amend, modify or terminate these benefits at any time. The components of net periodic benefit cost for the Corporation’s qualified and nonqualified pension plans and nonqualified postretirement benefit plan are as follows: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Defined Benefit Pension Plans Service cost (1) $ — $ 233 $ — $ 700 Interest cost 1,092 1,302 3,276 3,906 Expected return on plan assets (2,220 ) (2,216 ) (6,659 ) (6,650 ) Amortization of unrecognized net loss 178 578 533 1,734 Settlement — 322 — 322 Net periodic benefit cost (income) (2) $ (950 ) $ 219 $ (2,850 ) $ 12 Postretirement Benefit Plan Service cost (1) $ 1 $ 1 $ 2 $ 4 Interest cost 20 24 61 70 Amortization of unrecognized net gain (36 ) (41 ) (107 ) (121 ) Net periodic benefit cost (income) (2) $ (15 ) $ (16 ) $ (44 ) $ (47 ) (1) Service cost is included in "Salaries, wages and employee benefits expense" on the Consolidated Statements of Income. (2) Net periodic benefit cost (income), excluding service cost is included "Other" operating expenses on the Consolidated Statements of Income. 401(k) Savings Plan The Corporation's 401(k) Savings Plan is available to all employees and provides employees with tax deferred salary deductions and alternative investment options. Effective January 1, 2018, the Corporation provides a safe harbor matching contribution of the participants elective deferrals up to a maximum of 6.0% of eligible compensation up to the maximum amount allowed under the Internal Revenue Code. Prior to the January 1, 2018, the Corporation provided an employer match, in addition to a 4.0% contribution for all employees, with the exception of employees participating in the Pension Plan discussed above, during the time period they were eligible to earn service credits. The Corporation previously matched 50.0% of the participants elective deferrals on the first 4.0% of the participants' base compensation up to the maximum amount allowed under the Internal Revenue Code. The Corporation's match under the 401(k) Savings Plan was $1.5 million and $6.3 million for the three and nine months ended September 30, 2018 , respectively, compared to $2.5 million and $7.5 million for the three and nine months ended September 30, 2017 , respectively. The 401(k) Savings Plan provides employees with the option to invest in the Corporation's common stock.

Regulatory Capital

Regulatory Capital	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Regulatory Capital	Regulatory Capital Federal and state banking regulations place certain restrictions on the transfer of assets, in the form of dividends, loans, or advances, from Chemical Bank to the Corporation. As of September 30, 2018 , substantially all of the assets of Chemical Bank were restricted from transfer to the Corporation in the form of loans or advances. Dividends from Chemical Bank are the principal source of funds for the Corporation. In addition to the statutory limits, the Corporation considers the overall financial and capital position of Chemical Bank prior to making any cash dividend decisions. The Corporation and Chemical Bank are subject to various regulatory capital requirements administered by federal banking agencies. Under these capital requirements, Chemical Bank must meet specific capital guidelines that involve quantitative measures of assets and certain off-balance sheet items as calculated under regulatory accounting practices. In addition, capital amounts and classifications are subject to qualitative judgments by regulators. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Consolidated Financial Statements. Management believes as of September 30, 2018 , the Corporation and Chemical Bank met all capital adequacy requirements to which they are subject. Quantitative measures established by regulation to ensure capital adequacy require minimum ratios of Tier 1 capital to average assets (Leverage Ratio) and Common Equity Tier 1, Tier 1 and Total capital to risk-weighted assets. These capital guidelines assign risk weights to on- and off-balance sheet items in arriving at total risk-weighted assets. Minimum capital levels are based upon the perceived risk of various asset categories and certain off-balance sheet instruments. Risk-weighted assets for the Corporation and Chemical Bank totaled $15.30 billion and $15.26 billion at September 30, 2018 , respectively, compared to $14.74 billion and $14.70 billion at December 31, 2017 , respectively. Effective January 1, 2015, the Corporation adopted the Basel III regulatory capital framework as approved by federal banking agencies, which is subject to a multi-year phase-in period. The adoption of this new framework modified the calculation of the various capital ratios, added a new ratio, common equity tier 1, and revised the adequately and well capitalized thresholds. In addition, Basel III establishes a new capital conservation buffer of 2.5% of risk-weighted assets, which is phased-in over a four-year period beginning January 1, 2016. The capital conservation buffer for 2018 is 1.875% and was 1.25% for 2017 . The Corporation has elected to opt-out of including accumulated other comprehensive income in common equity tier 1 capital. At September 30, 2018 and December 31, 2017 , Chemical Bank's capital ratios exceeded the quantitative capital ratios required for an institution to be considered "well-capitalized." Significant factors that may affect capital adequacy include, but are not limited to, a disproportionate growth in assets versus capital and a change in mix or credit quality of assets. There are no conditions or events since those calculations that management believes have changed the institutions' category. The summary below compares the actual capital amounts and ratios with the quantitative measures established by regulation to ensure capital adequacy: Actual Minimum Required for Capital Adequacy Purposes Minimum Required for Capital Adequacy Purposes Plus Capital Conservation Buffer Required to be Well Capitalized Under Prompt Corrective Action Regulations (Dollars in thousands) Capital Amount Ratio Capital Amount Ratio Capital Amount Ratio Capital Amount Ratio September 30, 2018 Total Capital to Risk-Weighted Assets Corporation $ 1,792,952 11.7 % $ 1,224,203 8.0 % $ 1,511,126 9.9 % N/A N/A Chemical Bank 1,766,477 11.6 1,221,170 8.0 1,507,382 9.9 $ 1,526,463 10.0 % Tier 1 Capital to Risk-Weighted Assets Corporation 1,665,786 10.9 918,153 6.0 1,208,901 7.9 N/A N/A Chemical Bank 1,655,164 10.8 915,878 6.0 1,202,089 7.9 1,221,170 8.0 Common Equity Tier 1 Capital to Risk-Weighted Assets Corporation 1,665,786 10.9 688,614 4.5 975,537 6.4 N/A N/A Chemical Bank 1,655,164 10.8 686,908 4.5 973,120 6.4 992,201 6.5 Leverage Ratio Corporation 1,665,786 8.6 771,041 4.0 771,041 4.0 N/A N/A Chemical Bank 1,655,164 8.6 769,726 4.0 769,726 4.0 962,157 5.0 December 31, 2017 Total Capital to Risk-Weighted Assets Corporation $ 1,614,046 11.0 % $ 1,179,076 8.0 % $ 1,363,307 9.3 % N/A N/A Chemical Bank 1,613,087 11.0 1,176,361 8.0 1,360,167 9.3 $ 1,470,451 10.0 % Tier 1 Capital to Risk-Weighted Assets Corporation 1,498,463 10.2 884,307 6.0 1,068,538 7.3 N/A N/A Chemical Bank 1,513,219 10.3 882,271 6.0 1,066,077 7.3 1,176,361 8.0 Common Equity Tier 1 Capital to Risk-Weighted Asset Corporation 1,498,463 10.2 663,230 4.5 847,461 5.8 N/A N/A Chemical Bank 1,513,219 10.3 661,703 4.5 845,509 5.8 955,793 6.5 Leverage Ratio Corporation 1,498,463 8.3 720,890 4.0 720,890 4.0 N/A N/A Chemical Bank 1,513,219 8.4 720,043 4.0 720,043 4.0 900,053 5.0 On October 23, 2018 , the Corporation declared a cash dividend on its common stock of $0.34 per share. The dividend will be paid on December 21, 2018 to shareholders of record as of December 7, 2018 .

Earnings Per Common Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share The two-class method is used in the calculation of basic and diluted earnings per share. Under the two-class method, earnings available to common shareholders for the period are allocated between common shareholders and participating securities according to dividends declared (or accumulated) and participating rights in undistributed earnings. Average shares of common stock for diluted net income per common share include shares to be issued upon the exercise of stock options granted under the Corporation’s share-based compensation plans, restricted stock units that may be converted to stock, restricted stock awards and stock to be issued under the deferred stock compensation plan for non-employee directors. The factors used in the earnings per share computation follow: Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2018 2017 2018 2017 Net income $ 70,397 $ 40,459 $ 210,981 $ 140,077 Net income allocated to participating securities 40 129 144 566 Net income allocated to common shareholders (1) $ 70,357 $ 40,330 $ 210,837 $ 139,511 Weighted average common shares - issued 71,426 71,139 71,365 71,077 Average unvested restricted share awards (41 ) (228 ) (49 ) (290 ) Weighted average common shares outstanding - basic 71,385 70,911 71,316 70,787 Effect of dilutive securities Weighted average common stock equivalents 702 594 691 667 Weighted average common shares outstanding - diluted 72,087 71,505 72,007 71,454 EPS available to common shareholders Basic earnings per common share $ 0.99 $ 0.57 $ 2.96 $ 1.98 Diluted earnings per common share $ 0.98 $ 0.56 $ 2.93 $ 1.95 (1) Net income allocated to common shareholders for basic and diluted earnings per share may differ under the two-class method as a result of adding common share equivalents for options to dilutive shares outstanding, which alters the ratio used to allocate net income to common shareholders and participating securities for the purposes of calculating diluted earnings per share. For effect of dilutive securities, the average stock valuation is $56.59 per share and $47.68 per share for the three months ended September 30, 2018 and 2017 , respectively and $56.43 and $49.07 for the nine months ended September 30, 2018 and 2017 , respectively. The average number of exercisable employee stock options outstanding that were "out-of-the-money," whereby the option exercise price per share exceeded the market price per share and, therefore, were not included in the computation of diluted earnings per common share because they would have been anti-dilutive totaled 58,882 and 63,014 for the three and nine months ended September 30, 2018 , respectively, and 125,280 and 102,245 for the three and nine months ended September 30, 2017 , respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following table summarizes the changes within each component of accumulated other comprehensive income (loss), net of related tax benefit/expense for the three and nine months ended September 30, 2018 , and 2017 : (Dollars in thousands) Unrealized gains Defined Benefit Pension Plans Unrealized gains (losses) on cash flow hedges, net of tax Total For the three months ended September 30, 2018 Beginning balance $ (41,685 ) $ (19,584 ) $ 13,918 $ (47,351 ) Other comprehensive (loss) income before reclassifications (13,141 ) — 3,248 (9,893 ) Amounts reclassified from accumulated other comprehensive income (loss) — 112 (523 ) (411 ) Net current period other comprehensive (loss) income (13,141 ) 112 2,725 (10,304 ) Ending balance $ (54,826 ) $ (19,472 ) $ 16,643 $ (57,655 ) For the three months ended September 30, 2017 Beginning balance $ (8,877 ) $ (25,195 ) $ (57 ) $ (34,129 ) Other comprehensive income before reclassifications 895 7,305 520 8,720 Amounts reclassified from accumulated other comprehensive (loss) income (1 ) 349 231 579 Net current period other comprehensive income 894 7,654 751 9,299 Ending balance $ (7,983 ) $ (17,541 ) $ 694 $ (24,830 ) For the nine months ended September 30, 2018 Beginning balance $ (10,348 ) $ (19,808 ) $ 4,658 $ (25,498 ) Cumulative effect adjustment of change in accounting policy, net of tax impact (1) (344 ) — 3 (341 ) Beginning balance at January 1, 2018 (10,692 ) (19,808 ) 4,661 (25,839 ) Other comprehensive (loss) income before reclassifications (44,132 ) — 12,779 (31,353 ) Amounts reclassified from accumulated other comprehensive (loss) income (2 ) 336 (797 ) (463 ) Net current period other comprehensive (loss) income (44,134 ) 336 11,982 (31,816 ) Ending balance $ (54,826 ) $ (19,472 ) $ 16,643 $ (57,655 ) For the nine months ended September 30, 2017 Beginning balance $ (14,142 ) $ (25,894 ) $ — $ (40,036 ) Other comprehensive income before reclassifications 6,268 7,305 54 13,627 Amounts reclassified from accumulated other comprehensive (loss) income (109 ) 1,048 640 1,579 Net current period other comprehensive income 6,159 8,353 694 15,206 Ending balance $ (7,983 ) $ (17,541 ) $ 694 $ (24,830 ) (1) Refer to Note 1 , Basis of Presentation and Significant Accounting Policies, Note 3 , Investment Securities, and Note 9 , Derivative Instruments and Balance Sheet Offsetting, for further details on the changes in accounting policy. The following table summarizes the amounts reclassified out of each component of accumulated other comprehensive income (loss) for the three and nine months ended September 30, 2018 , and 2017 : (Dollars in thousands) Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Income Statement Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Gains on available-for-sale securities $ — $ 1 $ 3 $ 168 Net gain on sale of investment securities (noninterest income) — — (1 ) (59 ) Income tax expense $ — $ 1 $ 2 $ 109 Net Income Amortization of defined benefit pension plan items $ 142 $ 537 $ 426 $ 1,613 Salaries, wages and employee benefits (operating expenses) (30 ) (188 ) (90 ) (565 ) Income tax benefit $ 112 $ 349 336 $ 1,048 Net Loss Gains and losses on cash flow hedges $ (662 ) $ 575 $ (1,009 ) $ 984 Interest on short-term borrowings (interest expense) 139 (344 ) 212 (344 ) Income tax expense (benefit) $ (523 ) $ 231 $ (797 ) $ 640 Net (Income)/Loss

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations Chemical Financial Corporation ("Corporation" or "Chemical") operates in a single operating segment — commercial banking. The Corporation is a financial holding company, headquartered in Detroit, Michigan, that operates through one commercial bank, Chemical Bank. Chemical Bank operates within Michigan, Northeast Ohio and Northern Indiana as a Michigan state-chartered commercial bank. Chemical Bank operates through an internal organizational structure of six regional banking units and offers a full range of traditional banking and fiduciary products and services to the residents and business customers in the Corporation’s geographical market areas. The products and services offered by the regional banking units, through branch banking offices, are generally consistent throughout the Corporation, as is the pricing of those products and services. The marketing of products and services throughout the Corporation’s regional banking units is generally uniform, as many of the markets served by the regional banking units overlap. The distribution of products and services is generally uniform throughout the Corporation’s regional banking units and is achieved primarily through retail branch banking offices, automated teller machines and electronically accessed banking products. The Corporation’s primary sources of revenue are interest from its loan products and investment securities, service charges and fees from customer deposit accounts, wealth management revenue and net gain on sale of loans and other mortgage banking revenue.
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying unaudited Consolidated Financial Statements of the Corporation and its subsidiaries have been prepared in accordance with United States ("U.S.") generally accepted accounting principles ("GAAP") for interim financial information and with instructions to Form 10-Q, Securities and Exchange Commission ("SEC") rules and interpretive releases and prevailing practices within the banking industry and Rule 10-01 of Regulation S-X. Accordingly, the interim Consolidated Financial Statements do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Corporation’s Consolidated Financial Statements and footnotes thereto included in the Corporation’s Annual Report on Form 10-K for the year ended December 31, 2017 . In the opinion of management, the accompanying unaudited interim Consolidated Financial Statements contain all adjustments believed necessary to present fairly the financial condition and results of operations of the Corporation for the periods presented. All significant income and expenses are recorded on the accrual basis. Intercompany accounts and transactions have been eliminated in preparing the Consolidated Financial Statements. Operating results for the nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 .
Use of Estimates	Use of Estimates Management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and accompanying footnotes. Estimates that are particularly susceptible to significant change include the determination of the allowance for loan losses, expected cash flows from acquired loans, income taxes and the valuation of loan servicing rights. Actual results could differ from these estimates.
Reclassifications	Reclassifications Certain amounts appearing in the Consolidated Financial Statements and notes thereto for prior periods have been reclassified to conform to the current presentation. The reclassifications had no effect on net income or shareholders’ equity as previously reported, except in case of the cumulative effect adjustment of change in accounting policy as noted.
Recently Adopted Accounting Policy and Principles	Recently Adopted Accounting Policy Effective January 1, 2017, the Corporation elected to account for all loan servicing rights ("LSRs") previously accounted for under the lower of cost or fair value method under the fair value method. The guidance in Accounting Standards Codification Subtopic 860-50, "Transfers and Servicing-Servicing Assets and Liabilities" provides that an entity may make an irrevocable decision to subsequently measure a class of servicing assets and servicing liabilities at fair value at the beginning of any fiscal year. The guidance allows for the Corporation to apply this election prospectively to all new and existing servicing assets and servicing liabilities. Management believes this election will provide more comparable results to peers as many of those within our industry group account for loan servicing rights under the fair value method. The change in accounting policy in the first quarter of 2017 resulted in a cumulative adjustment to increase retained earnings in the amount of $3.7 million , net of taxes. Recently Adopted Accounting Principles Standard Description Adoption Date Effect on the financial statements ASU No. 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities ("ASU 2017-08") ASU 2017-08 reduces the amortization period for certain callable debt securities that are held at a premium to the earliest call date. Debt securities held at a discount will continue to be amortized as a yield adjustment over the life of the instrument. April 1, 2017 The early adoption in the second quarter of 2017 did not have a material impact on the Consolidated Financial Statements. ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income ("ASU 2018-02") ASU 2018-02 required deferred tax liabilities and assets to be adjusted for the effect of a change in tax laws or rate with the effect included in income from continuing operations in the reporting period that includes the enactment date. Fourth quarter of 2017 The early adoption in the fourth quarter of 2017 resulted in a $4.5 million reclassification from accumulated other comprehensive income to retained earnings related to the income tax effects of the Tax Cuts and Jobs Act. ASU No. 2014-09 - Revenue from Contracts with Customers (Topic 606) ASU No. 2016-08 - Principal versus Agent Considerations ASU No. 2016-10 - Identifying Performance Obligations and Licensing ASU No. 2016-12, Narrow-scope Improvements and Practical Expedients ("Updates to Topic 606") The core principle of the Updates to Topic 606 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. The standard is intended to clarify and converge the revenue recognition principles under GAAP and International Financial Reporting Standards and to streamline revenue recognition requirements in addition to expanding required revenue recognition disclosures. January 1, 2018 under the modified retrospective method A large majority of the Corporation's revenue is derived from net interest income, which is excluded from the scope of the guidance. Following detailed review of the Corporation's revenue streams not derived from net interest income on financial assets and liabilities, management identified the recognition of gains from other real estate sales financed by the Corporation to be in the scope of this amended guidance. Effective January 1, 2018, revenue for new seller financed other real estate owned sales will be determined according to the Updates to Topic 606. If all qualifications are met, gains associated with the sales will be recognized into income at the time of closing and therefore not deferred. The cumulative effect of the Updates to Topic 606 increased retained earnings by $1.2 million upon adoption. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Additional required disclosures have been included in Note 13, Revenue from Contracts with Customers. The adoption is not expected to have a material impact on the Corporation's net income on an ongoing basis. Refer to Note 5, Other Real Estate Owned and Repossessed Assets, for further detail. Standard Description Adoption Date Effect on the financial statements ASU No. 2016-01 - Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01") ASU 2016-01 amended current guidance by: (i) requiring equity investments with readily determinable fair values to be measured at fair value with changes in fair value recognized in net income, (ii) allowing an entity to measure equity investments that do not have readily determinable fair values at either fair value or cost minus impairment, changes in measurement is recognized in net income, (iii) simplifying impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment, (iv) eliminating the requirement to disclose the methods and assumptions used to estimate the fair value of financial instruments measured at amortized cost; (v) requiring the use of exit price notion when measuring the fair value of financial instruments; (vi) requiring recognition of changes in the fair value related to instrument-specific credit risk in other comprehensive income if financial liabilities are measured at fair value, (vii) requiring separate presentation in financial statements by measurement category, and (viii) clarifying that an entity should evaluate the need for valuation allowance on deferred tax assets related to available-for-sale securities in combination with the entity’s other deferred tax assets. January 1, 2018 using a modified retrospective approach with the exception of disclosure requirements which are adopted on a prospective basis The Corporation identified available-for-sale investment securities qualifying as equity investments in the securities portfolio at January 1, 2018. The adoption resulted in recognizing the unrealized fair value related to the identified equity investments as a cumulative effect to retained earnings of $0.3 million. In addition, the Corporation has updated disclosures related to the fair value of financial instruments to the use of the exit price notion. Refer to Note 2, Fair Value Measurements and Note 3, Investment Securities, for further detail. ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts as Cash Payments ("ASU 2016-15") 2016-15 was issued to reduce diversity in practice and prevent financial statement restatements. Cash flow issues include: debt prepayment or debt extinguishment costs, settlement of insurance claims, proceeds from the settlement of corporate-owned and bank-owned life insurance policies, distribution received from equity method investees, beneficial interests in securitization transactions and separately identifiable cash flows and application of the predominance principle. January 1, 2018 using retrospective application The adoption did not have a material effect on the presentation of our Consolidated Statements of Cash Flows, as current policies are either already in-line with the clarifications in the updated guidance, or the related cash flows are not material. ASU No. 2017-07 - Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost ("ASU 2017-07") ASU 2017-07 improves the income statement presentation of net periodic benefit cost for an entity's pension and postretirement plans. The standard requires employers to disaggregate current service costs from other components of net benefit cost and present it with other compensation cost. Additionally net benefit cost becomes eligible for capitalization. January 1, 2018 using the retrospective transition method The adoption resulted in a reclassification of $31 thousand and $0.7 million of net periodic income from salaries, wages and employee benefits expense to other expenses on the Consolidated Statements of Income during the three and nine months ended September 30, 2017, respectively. ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvement to Account for Hedging Activities ("ASU 2017-12") ASU 2017-12 eliminates the separate measurement of hedge ineffectiveness as well as the benchmark interest rate concept when applying hedge risk to variable-rate instruments. It also allows a company to elect to perform subsequent effectiveness assessments qualitatively if the initial quantitative hedge effectiveness assessment is found to be highly effective. January 1, 2018 The early adoption resulted in a cumulative adjustment from opening retained earnings to accumulated other comprehensive income of $3 thousand, which represented all previously recognized hedge ineffectiveness. ASU No. 2018-15 - Intangible-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract ("ASU 2018-15") ASU 2018-15 clarifies the accounting treatment for implementation costs for hosting arrangements that are service contracts. The amendments in this update align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal use software in accordance with subtopic 350-40. Under this guidance costs for implementation activities during the development stage shall be capitalized. The said capitalized-costs shall be expensed over the term of the hosting arrangement. Third quarter of 2018 applied retrospectively The early adoption in the third quarter did not have a material effect on the Consolidated Financial Statements. Effective during the nine months ended 2018 , the Corporation also adopted the following standards, none of which had a material impact to the Corporation's financial statements or financial statement disclosures: Standard Effective Date 2016-04 Liabilities—Extinguishments of Liabilities (Subtopic 405-20): Recognition of Breakage for Certain Prepaid Stored-Value Products January 1, 2018 2016-16 Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory January 1, 2018 2016-18 Statement of Cash Flows (Topic 230): Restricted Cash January 1, 2018 2017-01 Business Combinations (Topic 805): Clarifying the Definition of a Business January 1, 2018 2017-05 Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets January 1, 2018 2017-09 Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting January 1, 2018

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Recently Adopted Accounting Principles	Standard Description Adoption Date Effect on the financial statements ASU No. 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities ("ASU 2017-08") ASU 2017-08 reduces the amortization period for certain callable debt securities that are held at a premium to the earliest call date. Debt securities held at a discount will continue to be amortized as a yield adjustment over the life of the instrument. April 1, 2017 The early adoption in the second quarter of 2017 did not have a material impact on the Consolidated Financial Statements. ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income ("ASU 2018-02") ASU 2018-02 required deferred tax liabilities and assets to be adjusted for the effect of a change in tax laws or rate with the effect included in income from continuing operations in the reporting period that includes the enactment date. Fourth quarter of 2017 The early adoption in the fourth quarter of 2017 resulted in a $4.5 million reclassification from accumulated other comprehensive income to retained earnings related to the income tax effects of the Tax Cuts and Jobs Act. ASU No. 2014-09 - Revenue from Contracts with Customers (Topic 606) ASU No. 2016-08 - Principal versus Agent Considerations ASU No. 2016-10 - Identifying Performance Obligations and Licensing ASU No. 2016-12, Narrow-scope Improvements and Practical Expedients ("Updates to Topic 606") The core principle of the Updates to Topic 606 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. The standard is intended to clarify and converge the revenue recognition principles under GAAP and International Financial Reporting Standards and to streamline revenue recognition requirements in addition to expanding required revenue recognition disclosures. January 1, 2018 under the modified retrospective method A large majority of the Corporation's revenue is derived from net interest income, which is excluded from the scope of the guidance. Following detailed review of the Corporation's revenue streams not derived from net interest income on financial assets and liabilities, management identified the recognition of gains from other real estate sales financed by the Corporation to be in the scope of this amended guidance. Effective January 1, 2018, revenue for new seller financed other real estate owned sales will be determined according to the Updates to Topic 606. If all qualifications are met, gains associated with the sales will be recognized into income at the time of closing and therefore not deferred. The cumulative effect of the Updates to Topic 606 increased retained earnings by $1.2 million upon adoption. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Additional required disclosures have been included in Note 13, Revenue from Contracts with Customers. The adoption is not expected to have a material impact on the Corporation's net income on an ongoing basis. Refer to Note 5, Other Real Estate Owned and Repossessed Assets, for further detail. Standard Description Adoption Date Effect on the financial statements ASU No. 2016-01 - Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01") ASU 2016-01 amended current guidance by: (i) requiring equity investments with readily determinable fair values to be measured at fair value with changes in fair value recognized in net income, (ii) allowing an entity to measure equity investments that do not have readily determinable fair values at either fair value or cost minus impairment, changes in measurement is recognized in net income, (iii) simplifying impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment, (iv) eliminating the requirement to disclose the methods and assumptions used to estimate the fair value of financial instruments measured at amortized cost; (v) requiring the use of exit price notion when measuring the fair value of financial instruments; (vi) requiring recognition of changes in the fair value related to instrument-specific credit risk in other comprehensive income if financial liabilities are measured at fair value, (vii) requiring separate presentation in financial statements by measurement category, and (viii) clarifying that an entity should evaluate the need for valuation allowance on deferred tax assets related to available-for-sale securities in combination with the entity’s other deferred tax assets. January 1, 2018 using a modified retrospective approach with the exception of disclosure requirements which are adopted on a prospective basis The Corporation identified available-for-sale investment securities qualifying as equity investments in the securities portfolio at January 1, 2018. The adoption resulted in recognizing the unrealized fair value related to the identified equity investments as a cumulative effect to retained earnings of $0.3 million. In addition, the Corporation has updated disclosures related to the fair value of financial instruments to the use of the exit price notion. Refer to Note 2, Fair Value Measurements and Note 3, Investment Securities, for further detail. ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts as Cash Payments ("ASU 2016-15") 2016-15 was issued to reduce diversity in practice and prevent financial statement restatements. Cash flow issues include: debt prepayment or debt extinguishment costs, settlement of insurance claims, proceeds from the settlement of corporate-owned and bank-owned life insurance policies, distribution received from equity method investees, beneficial interests in securitization transactions and separately identifiable cash flows and application of the predominance principle. January 1, 2018 using retrospective application The adoption did not have a material effect on the presentation of our Consolidated Statements of Cash Flows, as current policies are either already in-line with the clarifications in the updated guidance, or the related cash flows are not material. ASU No. 2017-07 - Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost ("ASU 2017-07") ASU 2017-07 improves the income statement presentation of net periodic benefit cost for an entity's pension and postretirement plans. The standard requires employers to disaggregate current service costs from other components of net benefit cost and present it with other compensation cost. Additionally net benefit cost becomes eligible for capitalization. January 1, 2018 using the retrospective transition method The adoption resulted in a reclassification of $31 thousand and $0.7 million of net periodic income from salaries, wages and employee benefits expense to other expenses on the Consolidated Statements of Income during the three and nine months ended September 30, 2017, respectively. ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvement to Account for Hedging Activities ("ASU 2017-12") ASU 2017-12 eliminates the separate measurement of hedge ineffectiveness as well as the benchmark interest rate concept when applying hedge risk to variable-rate instruments. It also allows a company to elect to perform subsequent effectiveness assessments qualitatively if the initial quantitative hedge effectiveness assessment is found to be highly effective. January 1, 2018 The early adoption resulted in a cumulative adjustment from opening retained earnings to accumulated other comprehensive income of $3 thousand, which represented all previously recognized hedge ineffectiveness. ASU No. 2018-15 - Intangible-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract ("ASU 2018-15") ASU 2018-15 clarifies the accounting treatment for implementation costs for hosting arrangements that are service contracts. The amendments in this update align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal use software in accordance with subtopic 350-40. Under this guidance costs for implementation activities during the development stage shall be capitalized. The said capitalized-costs shall be expensed over the term of the hosting arrangement. Third quarter of 2018 applied retrospectively The early adoption in the third quarter did not have a material effect on the Consolidated Financial Statements. Effective during the nine months ended 2018 , the Corporation also adopted the following standards, none of which had a material impact to the Corporation's financial statements or financial statement disclosures: Standard Effective Date 2016-04 Liabilities—Extinguishments of Liabilities (Subtopic 405-20): Recognition of Breakage for Certain Prepaid Stored-Value Products January 1, 2018 2016-16 Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory January 1, 2018 2016-18 Statement of Cash Flows (Topic 230): Restricted Cash January 1, 2018 2017-01 Business Combinations (Topic 805): Clarifying the Definition of a Business January 1, 2018 2017-05 Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets January 1, 2018 2017-09 Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting January 1, 2018

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Summary of assets measured at fair value on a recurring basis	For assets and liabilities measured at fair value on a recurring basis, quantitative disclosures about the fair value measurements for each major category of assets and liabilities follow: (Dollars in thousands) Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total September 30, 2018 Investment securities – carried at fair value: Government and government-sponsored agencies $ — $ 254,453 $ — $ 254,453 State and political subdivisions — 491,909 — 491,909 Residential mortgage-backed securities — 177,021 — 177,021 Collateralized mortgage obligations — 1,477,818 — 1,477,818 Corporate bonds — 287,405 — 287,405 Trust preferred securities — 48,274 — 48,274 Total investment securities – carried at fair value — 2,736,880 — 2,736,880 Loans held-for-sale — 93,736 — 93,736 Loan servicing rights — — 72,707 72,707 Derivative assets: Customer-initiated derivatives — 21,390 — 21,390 Foreign exchange forwards — 3 — 3 Forward contracts related to mortgage loans to be delivered for sale — 760 — 760 Interest rate lock commitments — 1,081 — 1,081 Power Equity CD — 1,260 — 1,260 Risk management derivatives — 21,067 — 21,067 Total derivatives — 45,561 — 45,561 Total assets at fair value $ — $ 2,876,177 $ 72,707 $ 2,948,884 Derivative liabilities: Customer-initiated derivatives $ — $ 21,703 $ — $ 21,703 Foreign exchange forwards — 3 — 3 Power Equity CD — 1,260 — 1,260 Total derivatives — 22,966 — 22,966 Total liabilities at fair value $ — $ 22,966 $ — $ 22,966 December 31, 2017 Investment securities – available-for-sale: Government and government-sponsored agencies $ — $ 202,916 $ — $ 202,916 State and political subdivisions — 345,970 — 345,970 Residential mortgage-backed securities — 150,131 — 150,131 Collateralized mortgage obligations — 1,033,845 — 1,033,845 Corporate bonds — 192,794 — 192,794 Trust preferred securities — 36,066 — 36,066 Preferred stock — 1,824 — 1,824 Total investment securities – available-for-sale — 1,963,546 — 1,963,546 Loans held-for-sale — 52,133 — 52,133 Loan servicing rights — — 63,841 63,841 Derivative assets: Customer-initiated derivatives — 9,376 — 9,376 Interest rate lock commitments — 1,222 — 1,222 Power Equity CD — 2,184 — 2,184 Risk management derivatives — 5,899 — 5,899 Total derivatives — 18,681 — 18,681 Total assets at fair value $ — $ 2,034,360 $ 63,841 $ 2,098,201 Derivative liabilities: Customer-initiated derivatives $ — $ 10,139 $ — $ 10,139 Forward contracts related to mortgage loans to be delivered for sale — 34 — 34 Power Equity CD — 2,184 — 2,184 Total derivatives — 12,357 — 12,357 Total liabilities at fair value $ — $ 12,357 $ — $ 12,357
Summary of changes in Level 3 assets measured at fair value on a recurring basis	The following table summarizes the changes in Level 3 assets measured at fair value on a recurring basis. Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (Dollars in thousands) Loan servicing rights Balance, beginning of period $ 70,364 $ 64,522 $ 63,841 $ 48,085 Transfer in based on new accounting policy election (1) — — — 15,891 Gains (losses): Recorded in earnings (realized): Recorded in "Net gain on sale of loans and other mortgage banking revenue" 257 (4,651 ) 2,529 (8,242 ) New originations 2,086 2,324 6,337 6,461 Balance, end of period $ 72,707 $ 62,195 $ 72,707 $ 62,195 (1) Refer to Note 1, Basis of Presentation and Significant Accounting Policies, for further details.
Schedule of aggregate fair value contractual balance and gain (loss) for loans held-for-sale	The aggregate fair value, contractual balance (including accrued interest), and gain or loss for loans held-for-sale carried at fair value option was as follows: (Dollars in thousands) September 30, 2018 December 31, 2017 Aggregate fair value $ 93,736 $ 52,133 Contractual balance 91,839 50,597 Unrealized gain (loss) 1,897 1,536
Amount of gains (losses) from loans held for sale included in the Consolidated Statements of Income	The total amount of gains (losses) from loans held-for-sale included in the Consolidated Statements of Income were as follows: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Interest income (1) $ 849 $ 810 $ 1,670 $ 1,824 Change in fair value (2) 577 614 361 2,002 Net gain on sales of loans (2) 4,241 6,512 9,772 26,537 Total included in earnings $ 5,667 $ 7,936 $ 11,803 $ 30,363 (1) Included in "Interest and fees on loans" in the Consolidated Statements of Income. (2) Included in "Net gain on sale of loans and other mortgage banking revenue" in the Consolidated Statements of Income.
Summary of assets measured at fair value on a nonrecurring basis	For assets measured at fair value on a nonrecurring basis, quantitative disclosures about fair value measurements for each major category of assets follows: (Dollars in thousands) Significant Unobservable Inputs (Level 3) September 30, 2018 Impaired loans $ 73,137 Other real estate and repossessed assets 1,843 Total $ 74,980 December 31, 2017 Impaired loans $ 70,619 Other real estate and repossessed assets 2,899 Total $ 73,518
Additional information about significant unobservable inputs used in the fair value measurement of financial assets	The following table presents additional information about the significant unobservable inputs used in the fair value measurement of financial assets measured on a nonrecurring basis that were categorized within the Level 3 of the fair value hierarchy: (Dollars in thousands) Fair Value at Valuation Technique Significant Unobservable Inputs Range Impaired loans $ 73,137 Appraisal of collateral Discount for type of collateral and age of appraisal 20%-30% Other real estate and repossessed assets 1,843 Appraisal of property Discount for type of property and age of appraisal 20%-30%
Summary of carrying amounts and estimated fair values of the financial instruments	A summary of carrying amounts and estimated fair values of the Corporation’s financial instruments not recorded at fair value in their entirety on a recurring basis on the Consolidated Statements of Financial Position are disclosed in the table below. Level in Fair Value Measurement Hierarchy September 30, 2018 December 31, 2017 (Dollars in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial assets: Investment securities: Held-to-maturity Level 2 $ 607,867 $ 597,747 $ 676,593 $ 662,516 Held-to-maturity Level 3 500 450 500 390 Net loans (1) Level 3 14,692,211 14,301,208 14,063,380 14,114,545 Financial liabilities: Time deposits Level 2 $ 3,865,489 $ 3,827,695 $ 3,217,207 $ 3,225,847 Collateralized customer deposits Level 2 377,471 376,969 415,236 415,236 Short-term borrowings Level 2 1,670,000 1,669,662 2,000,000 1,999,137 Long-term borrowings Level 2 430,971 426,105 372,882 367,984 (1) Included $73.1 million and $70.6 million of impaired loans recorded at fair value on a nonrecurring basis at September 30, 2018 and December 31, 2017 , respectively.

Investment Securities (Tables)

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities	The following is a summary of the amortized cost and fair value of investment securities carried at fair value and investment securities held-to-maturity at September 30, 2018 and December 31, 2017 : Investment Securities Carried at Fair Value (Dollars in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2018 Debt securities Government and government-sponsored agencies $ 258,643 $ 14 $ 4,204 $ 254,453 State and political subdivisions 506,277 187 14,555 491,909 Residential mortgage-backed securities 182,983 6 5,968 177,021 Collateralized mortgage obligations 1,517,172 — 39,354 1,477,818 Corporate bonds 293,828 485 6,908 287,405 Trust preferred securities 47,378 1,004 108 48,274 Total $ 2,806,281 $ 1,696 $ 71,097 $ 2,736,880 December 31, 2017 Debt securities Government and government-sponsored agencies $ 203,099 $ 765 $ 948 $ 202,916 State and political subdivisions 350,088 310 4,428 345,970 Residential mortgage-backed securities 151,752 5 1,626 150,131 Collateralized mortgage obligations 1,042,240 89 8,484 1,033,845 Corporate bonds 193,230 1,156 1,592 192,794 Trust preferred securities 34,848 1,280 62 36,066 Total debt securities available-for-sale 1,975,257 3,605 17,140 1,961,722 Equity securities Preferred stock 1,389 435 — 1,824 Total equity securities 1,389 435 — 1,824 Total $ 1,976,646 $ 4,040 $ 17,140 $ 1,963,546
Held-to-maturity Securities	Investment Securities Held-to-Maturity (Dollars in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2018 State and political subdivisions $ 607,867 $ 1,917 $ 12,037 $ 597,747 Trust preferred securities 500 — 50 450 Total $ 608,367 $ 1,917 $ 12,087 $ 598,197 December 31, 2017 State and political subdivisions $ 676,593 $ 3,856 $ 17,933 $ 662,516 Trust preferred securities 500 — 110 390 Total $ 677,093 $ 3,856 $ 18,043 $ 662,906
Proceeds from sales of securities and the associated gains and losses recorded in earnings	Proceeds from sales of investment securities carried at fair value and the associated gains and losses recorded in earnings are listed below: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Proceeds $ — $ 7,035 $ 4,215 $ 17,085 Gross gains — 1 42 168 Gross losses — — (39 ) —
Amortized cost and fair value of debt securities by contractual maturity	The following is a summary of the amortized cost and fair value of investment securities at September 30, 2018 , by maturity, for both carried at fair value and held-to-maturity. The maturities of residential mortgage-backed securities and collateralized mortgage obligations are based on scheduled principal payments. The maturities of all other debt securities are based on final contractual maturity. September 30, 2018 (Dollars in thousands) Amortized Cost Fair Value Investment Securities Carried at Fair Value: Due in one year or less $ 32,586 $ 32,424 Due after one year through five years 121,421 119,478 Due after five years through ten years 455,582 443,027 Due after ten years 2,196,692 2,141,951 Total $ 2,806,281 $ 2,736,880 Investment Securities Held-to-Maturity: Due in one year or less $ 57,403 $ 57,248 Due after one year through five years 221,335 218,555 Due after five years through ten years 157,517 153,997 Due after ten years 172,112 168,397 Total $ 608,367 $ 598,197
Summary of continuous unrealized loss position of securities	The following schedule summarizes information for debt securities both available-for-sale and held-to-maturity with gross unrealized losses at September 30, 2018 and December 31, 2017 , aggregated by category and length of time that individual securities have been in a continuous unrealized loss position. As of September 30, 2018 , the Corporation’s securities portfolio consisted of 2,074 securities, 1,525 of which were in an unrealized loss position. Less Than 12 Months 12 Months or More Total (Dollars in thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses September 30, 2018 Government sponsored agencies $ 204,095 $ 2,564 $ 39,573 $ 1,640 $ 243,668 $ 4,204 State and political subdivisions 563,202 14,773 414,480 11,819 977,682 26,592 Residential mortgage-backed securities 119,911 2,907 55,068 3,061 174,979 5,968 Collateralized mortgage obligations 990,167 19,414 456,347 19,940 1,446,514 39,354 Corporate bonds 141,365 3,773 76,955 3,135 218,320 6,908 Trust preferred securities 13,716 60 2,789 98 16,505 158 Total $ 2,032,456 $ 43,491 $ 1,045,212 $ 39,693 $ 3,077,668 $ 83,184 December 31, 2017 Government sponsored agencies $ 63,818 $ 510 $ 24,621 $ 438 $ 88,439 $ 948 State and political subdivisions 437,407 12,268 349,242 10,093 786,649 22,361 Residential mortgage-backed securities 93,508 383 56,576 1,243 150,084 1,626 Collateralized mortgage obligations 713,525 7,235 73,707 1,249 787,232 8,484 Corporate bonds 71,447 1,138 47,878 454 119,325 1,592 Trust preferred securities — — 11,164 172 11,164 172 Total $ 1,379,705 $ 21,534 $ 563,188 $ 13,649 $ 1,942,893 $ 35,183

Loans (Tables)

Loans (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Summary of loans under portfolio	A summary of the Corporation's loans follows: (Dollars in thousands) Originated Acquired (1) Total Loans September 30, 2018 Commercial loan portfolio: Commercial $ 2,951,453 $ 768,469 $ 3,719,922 Commercial real estate: Owner-occupied 1,334,588 563,346 1,897,934 Non-owner occupied 1,875,155 864,545 2,739,700 Vacant land 46,463 27,524 73,987 Total commercial real estate 3,256,206 1,455,415 4,711,621 Real estate construction and land development 554,701 67,446 622,147 Subtotal 6,762,360 2,291,330 9,053,690 Consumer loan portfolio: Residential mortgage 2,285,611 1,106,376 3,391,987 Consumer installment 1,483,540 76,725 1,560,265 Home equity 613,931 176,379 790,310 Subtotal 4,383,082 1,359,480 5,742,562 Total loans (2) $ 11,145,442 $ 3,650,810 $ 14,796,252 December 31, 2017 Commercial loan portfolio: Commercial $ 2,407,606 $ 978,036 $ 3,385,642 Commercial real estate: Owner-occupied 1,185,614 627,948 1,813,562 Non-owner occupied 1,518,787 1,087,974 2,606,761 Vacant land 47,024 33,323 80,347 Total commercial real estate 2,751,425 1,749,245 4,500,670 Real estate construction and land development 498,155 76,060 574,215 Subtotal 5,657,186 2,803,341 8,460,527 Consumer loan portfolio: Residential mortgage 1,967,857 1,284,630 3,252,487 Consumer installment 1,510,540 102,468 1,613,008 Home equity 611,846 217,399 829,245 Subtotal 4,090,243 1,604,497 5,694,740 Total loans (2) $ 9,747,429 $ 4,407,838 $ 14,155,267 (1) Acquired loans are accounted for under ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality (ASC 310-30). (2) Reported net of deferred costs totaling $19.0 million and $26.1 million at September 30, 2018 and December 31, 2017 , respectively.
Schedule of activity for accretable yield	Activity for the accretable yield, which includes contractually due interest for acquired loans that have been renewed or extended since the date of acquisition and continue to be accounted for in loan pools in accordance with ASC 310-30, follows: (Dollars in thousands) Talmer Lake Michigan Monarch North-western OAK Total Three Months Ended September 30, 2018 Balance at beginning of period $ 616,168 $ 80,442 $ 20,131 $ 49,731 $ 14,292 $ 780,764 Accretion recognized in interest income (40,695 ) (5,980 ) (919 ) (4,341 ) (2,338 ) (54,273 ) Net reclassification (to) from nonaccretable difference (1) 20,250 3,108 (376 ) (765 ) (1,149 ) 21,068 Balance at end of period $ 595,723 $ 77,570 $ 18,836 $ 44,625 $ 10,805 $ 747,559 Three Months Ended September 30, 2017 Balance at beginning of period $ 801,369 $ 121,572 $ 24,270 $ 71,212 $ 19,796 $ 1,038,219 Accretion recognized in interest income (43,816 ) (7,201 ) (1,119 ) (5,263 ) (3,004 ) (60,403 ) Net reclassification (to) from nonaccretable difference (1) 11,861 (14,482 ) 168 (1,358 ) 1,999 (1,812 ) Balance at end of period $ 769,414 $ 99,889 $ 23,319 $ 64,591 $ 18,791 $ 976,004 Nine Months Ended September 30, 2018 Balance at beginning of period $ 731,353 $ 95,124 $ 22,496 $ 60,814 $ 17,110 $ 926,897 Accretion recognized in interest income (125,471 ) (19,040 ) (3,037 ) (13,863 ) (8,323 ) (169,734 ) Net reclassification (to) from nonaccretable difference (1) (10,159 ) 1,486 (623 ) (2,326 ) 2,018 (9,604 ) Balance at end of period $ 595,723 $ 77,570 $ 18,836 $ 44,625 $ 10,805 $ 747,559 Nine Months Ended September 30, 2017 Balance at beginning of period $ 798,210 $ 121,416 $ 27,182 $ 69,847 $ 23,316 $ 1,039,971 Accretion recognized in interest income (133,478 ) (22,050 ) (3,459 ) (15,222 ) (9,595 ) (183,804 ) Net reclassification (to) from nonaccretable difference (1) 104,682 523 (404 ) 9,966 5,070 119,837 Balance at end of period $ 769,414 $ 99,889 $ 23,319 $ 64,591 $ 18,791 $ 976,004 (1) The net reclassification results from changes in expected cash flows of the acquired loans which may include increases in the amount of contractual principal and interest expected to be collected due to improvement in credit quality, increases in balances outstanding from advances, renewals, extensions and interest rates; as well as reductions in contractual principal and interest expected to be collected due to credit deterioration, payoffs, and decreases in interest rates.
Recorded investment of loans in the commercial loan portfolio by risk rating categories	The following schedule presents the recorded investment of loans in the commercial loan portfolio by credit risk categories at September 30, 2018 and December 31, 2017 : (Dollars in thousands) Pass Special Mention Substandard Doubtful Total September 30, 2018 Originated Portfolio: Commercial $ 2,840,100 $ 54,258 $ 57,095 $ — $ 2,951,453 Commercial real estate: Owner-occupied 1,265,111 33,290 36,168 19 1,334,588 Non-owner occupied 1,854,887 12,542 7,726 — 1,875,155 Vacant land 40,904 480 5,076 3 46,463 Total commercial real estate 3,160,902 46,312 48,970 22 3,256,206 Real estate construction and land development 517,561 5,100 32,040 — 554,701 Subtotal 6,518,563 105,670 138,105 22 6,762,360 Acquired Portfolio: Commercial 707,054 36,227 25,188 — 768,469 Commercial real estate: Owner-occupied 505,246 29,840 28,249 11 563,346 Non-owner occupied 805,466 31,647 27,432 — 864,545 Vacant land 27,311 213 — — 27,524 Total commercial real estate 1,338,023 61,700 55,681 11 1,455,415 Real estate construction and land development 66,294 138 1,014 — 67,446 Subtotal 2,111,371 98,065 81,883 11 2,291,330 Total $ 8,629,934 $ 203,735 $ 219,988 $ 33 $ 9,053,690 December 31, 2017 Originated Portfolio: Commercial $ 2,316,464 $ 41,059 $ 50,083 $ — $ 2,407,606 Commercial real estate: Owner-occupied 1,133,609 19,438 32,567 — 1,185,614 Non-owner occupied 1,504,195 4,728 9,864 — 1,518,787 Vacant land 39,775 38 7,211 — 47,024 Total commercial real estate 2,677,579 24,204 49,642 — 2,751,425 Real estate construction and land development 494,528 837 2,790 — 498,155 Subtotal 5,488,571 66,100 102,515 — 5,657,186 Acquired Portfolio: Commercial 873,861 68,418 35,539 218 978,036 Commercial real estate: Owner-occupied 580,127 23,998 23,036 787 627,948 Non-owner occupied 995,709 43,645 48,620 — 1,087,974 Vacant land 27,849 327 5,147 — 33,323 Total commercial real estate 1,603,685 67,970 76,803 787 1,749,245 Real estate construction and land development 72,346 2,218 1,496 — 76,060 Subtotal 2,549,892 138,606 113,838 1,005 2,803,341 Total $ 8,038,463 $ 204,706 $ 216,353 $ 1,005 $ 8,460,527
Recorded investment of loans in the consumer loan portfolio based on the credit risk profile of loans in a performing and nonperforming status	The following schedule presents the recorded investment of loans in the consumer loan portfolio based on loans in a performing status and loans in a nonperforming status at September 30, 2018 and December 31, 2017 : (Dollars in thousands) Residential Mortgage Consumer Installment Home Equity Total Consumer September 30, 2018 Originated Loans: Performing $ 2,276,000 $ 1,482,190 $ 610,662 $ 4,368,852 Nonperforming 9,611 1,350 3,269 14,230 Subtotal 2,285,611 1,483,540 613,931 4,383,082 Acquired Loans 1,106,376 76,725 176,379 1,359,480 Total $ 3,391,987 $ 1,560,265 $ 790,310 $ 5,742,562 December 31, 2017 Originated Loans: Performing $ 1,959,222 $ 1,509,698 $ 607,541 $ 4,076,461 Nonperforming 8,635 842 4,305 13,782 Subtotal 1,967,857 1,510,540 611,846 4,090,243 Acquired Loans 1,284,630 102,468 217,399 1,604,497 Total $ 3,252,487 $ 1,613,008 $ 829,245 $ 5,694,740
Summary of nonperforming loans	A summary of nonperforming loans follows: (Dollars in thousands) September 30, December 31, Nonperforming assets Nonaccrual loans: Commercial $ 25,328 $ 19,691 Commercial real estate: Owner-occupied 14,936 19,070 Non-owner occupied 8,991 5,270 Vacant land 4,711 5,205 Total commercial real estate 28,638 29,545 Real estate construction and land development 28,477 77 Residential mortgage 9,611 8,635 Consumer installment 1,350 842 Home equity 3,269 4,305 Total nonaccrual loans 96,673 63,095 Other real estate owned and repossessed assets 6,584 8,807 Total nonperforming assets $ 103,257 $ 71,902 Accruing loans contractually past due 90 days or more as to interest or principal payments, excluding acquired loans accounted for under ASC 310-30 Commercial $ 632 $ — Commercial real estate: Owner-occupied 47 — Non-owner occupied — 13 Total commercial real estate 47 13 Real estate construction and land development 38 — Home equity 475 1,364 Total accruing loans contractually past due 90 days or more as to interest or principal payments, excluding acquired loans accounted for under ASC 310-30 $ 1,192 $ 1,377
Schedule representing the aging status of the recorded investment in loans by classes	Loan delinquency, excluding acquired loans accounted for under ASC 310-30, was as follows: (Dollars in thousands) 30-59 days past due 60-89 days past due 90 days or more past due Total past due Current Total loans 90 days or more past due and still accruing September 30, 2018 Originated Portfolio: Commercial $ 9,280 $ 8,770 $ 12,855 $ 30,905 $ 2,920,548 $ 2,951,453 $ 632 Commercial real estate: Owner-occupied 8,052 2,440 8,458 18,950 1,315,638 1,334,588 47 Non-owner occupied 1,993 762 2,054 4,809 1,870,346 1,875,155 — Vacant land 277 1,399 2,460 4,136 42,327 46,463 — Total commercial real estate 10,322 4,601 12,972 27,895 3,228,311 3,256,206 47 Real estate construction and land development 1,244 13,238 15,277 29,759 524,942 554,701 38 Residential mortgage 3,889 1,576 4,752 10,217 2,275,394 2,285,611 — Consumer installment 3,555 657 617 4,829 1,478,711 1,483,540 — Home equity 5,185 1,123 1,704 8,012 605,919 613,931 475 Total $ 33,475 $ 29,965 $ 48,177 $ 111,617 $ 11,033,825 $ 11,145,442 $ 1,192 December 31, 2017 Originated Portfolio: Commercial $ 13,906 $ 3,766 $ 9,494 $ 27,166 $ 2,380,440 $ 2,407,606 $ — Commercial real estate: Owner-occupied 7,644 1,306 5,027 13,977 1,171,637 1,185,614 — Non-owner occupied 1,653 228 693 2,574 1,516,213 1,518,787 13 Vacant land 83 28 153 264 46,760 47,024 — Total commercial real estate 9,380 1,562 5,873 16,815 2,734,610 2,751,425 13 Real estate construction and land development — — — — 498,155 498,155 — Residential mortgage 2,795 1,415 858 5,068 1,962,789 1,967,857 — Consumer installment 3,324 442 226 3,992 1,506,548 1,510,540 — Home equity 2,319 1,301 2,196 5,816 606,030 611,846 1,364 Total $ 31,724 $ 8,486 $ 18,647 $ 58,857 $ 9,688,572 $ 9,747,429 $ 1,377
Schedule of Impaired loans by classes	The following schedules present impaired loans by classes of loans at September 30, 2018 and December 31, 2017 : (Dollars in thousands) Recorded Investment Unpaid Principal Balance Related Valuation Allowance September 30, 2018 Impaired loans with a valuation allowance: Commercial $ 13,394 $ 16,109 $ 1,110 Commercial real estate: Owner-occupied 13,278 15,607 1,281 Non-owner occupied 3,187 4,595 142 Vacant land 2,130 2,130 373 Total commercial real estate 18,595 22,332 1,796 Real estate construction and land development 28,575 28,575 650 Residential mortgage 12,879 12,879 1,146 Consumer installment 1,071 1,071 117 Home equity 3,697 3,697 255 Subtotal 78,211 84,663 5,074 Impaired loans with no related valuation allowance: Commercial 25,021 26,427 — Commercial real estate: Owner-occupied 10,852 11,490 — Non-owner occupied 12,161 13,099 — Vacant land 2,859 3,945 — Total commercial real estate 25,872 28,534 — Real estate construction and land development 140 207 — Residential mortgage 7,988 7,988 — Consumer installment 475 475 — Home equity 1,743 1,743 — Subtotal 61,239 65,374 — Total impaired loans: Commercial 38,415 42,536 1,110 Commercial real estate: Owner-occupied 24,130 27,097 1,281 Non-owner occupied 15,348 17,694 142 Vacant land 4,989 6,075 373 Total commercial real estate 44,467 50,866 1,796 Real estate construction and land development 28,715 28,782 650 Residential mortgage 20,867 20,867 1,146 Consumer installment 1,546 1,546 117 Home equity 5,440 5,440 255 Total $ 139,450 $ 150,037 $ 5,074 (Dollars in thousands) Recorded Investment Unpaid Principal Balance Related Valuation Allowance December 31, 2017 Impaired loans with a valuation allowance: Commercial $ 28,897 $ 31,655 $ 2,296 Commercial real estate: Owner-occupied 17,774 21,588 2,317 Non-owner occupied 5,307 7,870 316 Vacant land 4,922 5,122 594 Total commercial real estate 28,003 34,580 3,227 Real estate construction and land development 313 313 14 Residential mortgage 15,872 15,872 1,487 Consumer installment 966 966 120 Home equity 4,570 4,570 858 Subtotal 78,621 87,956 8,002 Impaired loans with no related valuation allowance: Commercial 8,504 9,291 — Commercial real estate: Owner-occupied 11,351 12,631 — Non-owner occupied 5,977 6,438 — Vacant land 752 792 — Total commercial real estate 18,080 19,861 — Residential mortgage 4,902 4,902 — Home equity 1,770 1,770 — Subtotal 33,256 35,824 — Total impaired loans: Commercial 37,401 40,946 2,296 Commercial real estate: Owner-occupied 29,125 34,219 2,317 Non-owner occupied 11,284 14,308 316 Vacant land 5,674 5,914 594 Total commercial real estate 46,083 54,441 3,227 Real estate construction and land development 313 313 14 Residential mortgage 20,774 20,774 1,487 Consumer installment 966 966 120 Home equity 6,340 6,340 858 Total $ 111,877 $ 123,780 $ 8,002
Schedule presents information related to impaired loans	The following schedule presents additional information regarding impaired loans by classes of loans segregated by those requiring a valuation allowance and those not requiring a valuation allowance for the three and nine months ended September 30, 2018 and 2017 , and the respective interest income amounts recognized: Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 (Dollars in thousands) Average recorded investment Interest income recognized while on impaired status Average recorded investment Interest income recognized while on impaired status Average Interest income Average Interest income Impaired loans with a valuation allowance: Commercial $ 13,945 $ 67 $ 25,628 $ 222 $ 17,495 $ 343 $ 25,278 $ 647 Commercial real estate: Owner-occupied 11,977 94 13,401 155 12,999 257 14,083 459 Non-owner occupied 3,697 13 2,457 17 3,271 34 2,939 68 Vacant land 1,589 7 2,442 25 2,198 39 2,098 75 Total commercial real estate 17,263 114 18,300 197 18,468 330 19,120 602 Real estate construction and land development 9,647 2 175 3 3,372 6 159 8 Residential mortgage 11,620 117 15,945 144 12,662 349 16,529 446 Consumer installment 911 3 748 1 961 6 737 3 Home equity 3,022 20 4,369 21 3,176 58 4,154 58 Subtotal $ 56,408 $ 323 $ 65,165 $ 588 $ 56,134 $ 1,092 $ 65,977 $ 1,764 Impaired loans with no related valuation allowance: Commercial $ 24,114 $ 123 $ 10,120 $ 14 $ 20,773 $ 365 $ 10,142 $ 92 Commercial real estate: Owner-occupied 13,831 68 13,009 1 14,588 205 10,862 13 Non-owner occupied 12,776 81 8,942 88 9,825 184 9,487 255 Vacant land 2,874 — 3,484 12 2,694 — 4,348 36 Total commercial real estate 29,481 149 25,435 101 27,107 389 24,697 304 Real estate construction and land development 3,857 2 71 — 1,986 5 86 — Residential mortgage 8,605 31 5,144 8 7,272 79 4,511 25 Consumer installment 537 — 244 — 240 — 201 — Home equity 2,191 8 1,639 — 2,241 17 1,227 6 Subtotal $ 68,785 $ 313 $ 42,653 $ 123 $ 59,619 $ 855 $ 40,864 $ 427 Total impaired loans: Commercial $ 38,059 $ 190 $ 35,748 $ 236 $ 38,268 $ 708 $ 35,420 $ 739 Commercial real estate: Owner-occupied 25,808 162 26,410 156 27,587 462 24,945 472 Non-owner occupied 16,473 94 11,399 105 13,096 218 12,426 323 Vacant land 4,463 7 5,926 37 4,892 39 6,446 111 Total commercial real estate 46,744 263 43,735 298 45,575 719 43,817 906 Real estate construction and land development 13,504 4 246 3 5,358 11 245 8 Residential mortgage 20,225 148 21,089 152 19,934 428 21,040 471 Consumer installment 1,448 3 992 1 1,201 6 938 3 Home equity 5,213 28 6,008 21 5,417 75 5,381 64 Total $ 125,193 $ 636 $ 107,818 $ 711 $ 115,753 $ 1,947 $ 106,841 $ 2,191
Schedule providing information on TDRs	The following tables present the recorded investment of loans modified into TDRs during the three and nine months ended September 30, 2018 and 2017 by type of concession granted. In cases where more than one type of concession was granted, the loans were categorized based on the most significant concession. Concession type (Dollars in thousands) Principal Principal Interest Forbearance Total Pre-modification recorded investment Post-modification recorded investment For the three months ended September 30, 2018 Commercial loan portfolio: Commercial $ 2,104 $ — $ 165 $ 1 13 $ 2,277 $ 2,270 Commercial real estate: Owner-occupied 438 — — — 2 438 438 Non-owner occupied — 66 — — 1 69 66 Total commercial real estate 438 66 — — 3 507 504 Total Commercial 2,542 66 165 1 16 2,784 2,774 Consumer loan portfolio: Residential mortgage — 111 108 — 2 220 219 Consumer installment 48 74 44 — 11 172 166 Home equity 91 73 64 — 4 228 228 Total Consumer 139 258 216 — 17 620 613 Total loans $ 2,681 $ 324 $ 381 $ 1 33 $ 3,404 $ 3,387 For the nine months ended September 30, 2018 Commercial loan portfolio: Commercial $ 3,747 $ — $ 1,448 $ 262 44 $ 5,481 $ 5,457 Commercial real estate: Owner-occupied 808 — 888 513 10 2,221 2,209 Non-owner occupied 68 66 — — 2 143 134 Total commercial real estate 876 66 888 513 12 2,364 2,343 Total Commercial 4,623 66 2,336 775 56 7,845 7,800 Consumer loan portfolio: Residential mortgage 269 151 147 — 9 577 567 Consumer installment 134 141 82 — 36 372 357 Home equity 357 73 179 — 13 652 609 Total Consumer 760 365 408 — 58 1,601 1,533 Total loans $ 5,383 $ 431 $ 2,744 $ 775 114 $ 9,446 $ 9,333 Concession type (Dollars in thousands) Principal Interest Forbearance Total Pre-modification recorded investment Post-modification recorded investment For the three months ended September 30, 2017 Commercial loan portfolio: Commercial $ 506 $ 281 $ 1,332 14 $ 2,173 $ 2,119 Commercial real estate: Owner-occupied — 42 335 3 390 377 Non-owner occupied — 27 — 1 28 27 Total commercial real estate — 69 335 4 418 404 Real estate construction and land development 35 — — 1 36 35 Total Commercial 541 350 1,667 19 2,627 2,558 Consumer loan portfolio: Residential mortgage 76 122 — 3 262 198 Consumer installment 47 7 — 11 58 54 Home equity 116 — — 5 124 116 Total Consumer 239 129 — 19 444 368 Total loans $ 780 $ 479 $ 1,667 38 $ 3,071 $ 2,926 For the nine months ended September 30, 2017 Commercial loan portfolio: Commercial $ 841 $ 1,648 $ 1,911 26 $ 4,476 $ 4,400 Commercial real estate: Owner-occupied 447 182 457 9 1,106 1,086 Non-owner occupied — 27 — 1 28 27 Total commercial real estate 447 209 457 10 1,134 1,113 Real estate construction and land development 35 — — 1 36 35 Total Commercial 1,323 1,857 2,368 37 5,646 5,548 Consumer loan portfolio: Residential mortgage 211 383 — 9 676 594 Consumer installment 79 7 — 17 93 86 Home equity 380 — — 10 449 380 Total Consumer 670 390 — 36 1,218 1,060 Total loans $ 1,993 $ 2,247 $ 2,368 73 $ 6,864 $ 6,608 The following schedule presents the Corporation's TDRs at September 30, 2018 and December 31, 2017 : (Dollars in thousands) Accruing TDRs Nonaccrual TDRs Total September 30, 2018 Commercial loan portfolio $ 29,383 $ 24,091 $ 53,474 Consumer loan portfolio 13,642 3,970 17,612 Total $ 43,025 $ 28,061 $ 71,086 December 31, 2017 Commercial loan portfolio $ 34,484 $ 24,358 $ 58,842 Consumer loan portfolio 14,298 4,748 19,046 Total $ 48,782 $ 29,106 $ 77,888
Troubled debt restructurings on financing receivables with defaults payment	The following schedule includes TDRs for which there was a payment default during the three and nine months ended September 30, 2018 and 2017 , whereby the borrower was past due with respect to principal and/or interest for 90 days or more, and the loan became a TDR during the twelve-month period prior to the default: For The Three Months Ended September 30, 2018 For The Nine Months Ended September 30, 2018 (Dollars in thousands) Number of loans Principal balance Number of loans Principal balance Commercial loan portfolio (commercial) 6 $ 981 9 $ 1,130 Consumer loan portfolio (residential mortgage) 6 241 14 286 Total 12 $ 1,222 23 $ 1,416 For The Three Months Ended September 30, 2017 For The Nine Months Ended September 30, 2017 (Dollars in thousands) Number of loans Principal balance Number of loans Principal balance Commercial loan portfolio (commercial) — $ — 5 $ 1,617 Consumer loan portfolio (residential mortgage) — — 5 163 Total — $ — 10 $ 1,780
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment	The following schedule presents, by loan portfolio segment, the changes in the allowance for the originated loan portfolio for the three and nine months ended September 30, 2018 and 2017 . (Dollars in thousands) Commercial Loan Portfolio Consumer Loan Portfolio Total Originated Loan Portfolio Changes in allowance for loan losses for the three months ended September 30, 2018: Beginning balance $ 72,665 $ 27,350 $ 100,015 Provision for loan losses 2,064 2,994 5,058 Charge-offs (1,048 ) (2,680 ) (3,728 ) Recoveries 1,133 593 1,726 Ending balance $ 74,814 $ 28,257 $ 103,071 Changes in allowance for loan losses for the nine months ended September 30, 2018: Beginning balance $ 66,133 $ 25,754 $ 91,887 Provision for loan losses 13,387 7,499 20,886 Charge-offs (7,532 ) (6,746 ) (14,278 ) Recoveries 2,826 1,750 4,576 Ending balance $ 74,814 $ 28,257 $ 103,071 Changes in allowance for loan losses for the three months ended September 30, 2017: Beginning balance $ 57,955 $ 25,842 $ 83,797 Provision for loan losses 664 4,256 4,920 Charge-offs (3,792 ) (1,650 ) (5,442 ) Recoveries 1,270 636 1,906 Ending balance $ 56,097 $ 29,084 $ 85,181 Changes in allowance for loan losses for the nine months ended September 30, 2017: Beginning balance $ 51,201 $ 27,067 $ 78,268 Provision for loan losses 9,140 6,060 15,200 Charge-offs (7,209 ) (6,112 ) (13,321 ) Recoveries 2,965 2,069 5,034 Ending balance $ 56,097 $ 29,084 $ 85,181 The following schedule presents, by loan portfolio, the changes in the allowance for the acquired loan portfolio. (Dollars in thousands) Commercial Consumer Total Acquired Loan Portfolio Changes in allowance for loan losses for the three months ended September 30, 2018: Beginning balance $ — $ — $ — Provision for loan losses 970 — 970 Charge-offs — — — Recoveries — — — Ending balance $ 970 $ — $ 970 Changes in allowance for loan losses for the nine months ended September 30, 2018: Beginning balance $ — $ — $ — Provision for loan losses 970 — 970 Charge-offs — — — Recoveries — — — Ending balance $ 970 $ — $ 970 Changes in allowance for loan losses for the three months ended September 30, 2017: Beginning balance $ — $ — $ — Provision for loan losses 409 170 579 Charge-offs — — — Recoveries — — — Ending balance $ 409 $ 170 $ 579 Changes in allowance for loan losses for the nine months ended September 30, 2017: Beginning balance $ — $ — $ — Provision for loan losses 409 170 579 Charge-offs — — — Recoveries — — — Ending balance $ 409 $ 170 $ 579 The following schedule presents by loan portfolio segment, details regarding the balance in the allowance and the recorded investment in loans at September 30, 2018 and December 31, 2017 by impairment evaluation method. (Dollars in thousands) Commercial Consumer Total Allowance for loan losses balance at September 30, 2018 attributable to: Loans individually evaluated for impairment $ 3,556 $ 1,518 $ 5,074 Loans collectively evaluated for impairment 71,258 26,739 97,997 Loans acquired with deteriorated credit quality 970 — 970 Total $ 75,784 $ 28,257 $ 104,041 Recorded investment (loan balance) at September 30, 2018: Loans individually evaluated for impairment $ 111,597 $ 27,853 $ 139,450 Loans collectively evaluated for impairment 6,650,763 4,355,229 11,005,992 Loans acquired with deteriorated credit quality 2,291,330 1,359,480 3,650,810 Total $ 9,053,690 $ 5,742,562 $ 14,796,252 (Dollars in thousands) Commercial Loan Portfolio Consumer Loan Portfolio Total Allowance for loan losses balance at December 31, 2017 attributable to: Loans individually evaluated for impairment $ 5,537 $ 2,465 $ 8,002 Loans collectively evaluated for impairment 60,596 23,289 83,885 Loans acquired with deteriorated credit quality — — — Total $ 66,133 $ 25,754 $ 91,887 Recorded investment (loan balance) at December 31, 2017: Loans individually evaluated for impairment $ 83,797 $ 28,080 $ 111,877 Loans collectively evaluated for impairment 5,573,389 4,062,163 9,635,552 Loans acquired with deteriorated credit quality 2,803,341 1,604,497 4,407,838 Total $ 8,460,527 $ 5,694,740 $ 14,155,267

Other Real Estate Owned and R_2

Other Real Estate Owned and Repossessed Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Other Real Estate [Abstract]
Tabular disclosure of the changes in non-covered and covered other real estate on properties owned	Changes in other real estate owned and repossessed assets, included in interest receivable and other assets on the Consolidated Statements of Financial Position, were as follows: (Dollars in thousands) Other real estate Repossessed Balance at January 1, 2018 $ 8,182 $ 625 Transfers based on adoption of ASU 2014-09 (1) (189 ) — Additions (2) 5,281 3,504 Net payments received (190 ) — Disposals (5,859 ) (3,563 ) Write-downs (1,207 ) — Balance at September 30, 2018 $ 6,018 $ 566 Balance at January 1, 2017 $ 16,812 $ 375 Additions (2) 5,339 3,633 Net payments received (582 ) — Disposals (10,180 ) (3,469 ) Write-downs (1,323 ) — Balance at September 30, 2017 $ 10,066 $ 539 (1) In accordance with the updates to Topic 606 adopted by the Corporation effective January 1, 2018, $1.1 million of other real estate owned sold with seller financing were reclassified on the Consolidated Statements of Financial Position to loans and the related $0.9 million of deferred gains were recognized in income as an adjustment to opening retained earnings. Refer to Note 1, Basis of Presentation and Significant Accounting Policies for further information. (2) Includes loans transferred to other real estate owned and other repossessed assets.
Schedule of income and expenses related to other real estate owned	Income and expenses related to other real estate owned and repossessed assets, recorded as a component of "Other" operating expenses in the Consolidated Statements of Income, were as follows: (Dollars in thousands) Other real estate owned Repossessed assets For the three months ended September 30, 2018 Net gain (loss) on sale $ 224 $ (175 ) Write-downs (424 ) — Net operating expenses (93 ) (2 ) Total $ (293 ) $ (177 ) For the nine months ended September 30, 2018 Net gain (loss) on sale $ 1,003 $ (269 ) Write-downs (1,207 ) — Net operating expenses (808 ) (5 ) Total $ (1,012 ) $ (274 ) For the three months ended September 30, 2017 Net gain (loss) on sale $ 388 $ (112 ) Write-downs (550 ) — Net operating expenses (509 ) (1 ) Total $ (671 ) $ (113 ) For the nine months ended September 30, 2017 Net gain (loss) on sale $ 2,203 $ (283 ) Write-downs (1,323 ) — Net operating expenses (1,727 ) (8 ) Total $ (847 ) $ (291 )

Loan Servicing Rights (Tables)

Loan Servicing Rights (Tables)	9 Months Ended
	Sep. 30, 2018
Transfers and Servicing [Abstract]
Schedule of activity for loan servicing rights and the related fair value changes	The following table represents the activity for LSRs and the related fair value changes: (Dollars in thousands) Commercial Real Estate Mortgage Total For the three months ended September 30, 2018 Fair value, beginning of period $ 457 $ 69,907 $ 70,364 Additions from loans sold with servicing retained 51 2,035 2,086 Changes in fair value due to: Reductions from pay-offs, pay downs and run-off (28 ) (647 ) (675 ) Changes in estimates of fair value (1) — 932 932 Fair value, end of period $ 480 $ 72,227 $ 72,707 For the nine months ended September 30, 2018 Fair value, beginning of period $ 427 $ 63,414 $ 63,841 Additions from loans sold with servicing retained 139 6,198 6,337 Changes in fair value due to: 0 0 Reductions from pay-offs, pay downs and run-off (86 ) (2,039 ) (2,125 ) Changes in estimates of fair value (1) — 4,654 4,654 Fair value, end of period $ 480 $ 72,227 $ 72,707 Principal balance of loans serviced $ 42,070 $ 6,869,131 $ 6,911,201 For the three months ended September 30, 2017 Fair value, beginning of period $ 486 $ 64,036 $ 64,522 Additions from loans sold with servicing retained — 2,324 2,324 Changes in fair value due to: 0 Reductions from pay-offs, pay downs and run-off (31 ) (579 ) (610 ) Changes in estimates of fair value (1) — (4,041 ) (4,041 ) Fair value, end of period $ 455 $ 61,740 $ 62,195 For the nine months ended September 30, 2017 Fair value, beginning of period $ 344 $ 47,741 $ 48,085 Transfers in based on new accounting policy election (2) — 15,891 15,891 Additions from loans sold with servicing retained 188 6,273 6,461 Changes in fair value due to: Reductions from pay-offs, pay downs and run-off (77 ) (1,803 ) (1,880 ) Change in estimates of fair value (1) — (6,362 ) (6,362 ) Fair value, end of period $ 455 $ 61,740 $ 62,195 Principal balance of loans serviced $ 41,798 $ 7,102,485 $ 7,144,283 (1) Represents estimated LSR value change resulting primarily from market-driven changes in interest rates and prepayments. Included in "Net gain on sale of loans and other mortgage banking revenue" in the Consolidated Statements of Income. (2) The Corporation elected as of January 1, 2017 to account for all loan servicing rights previously accounted for at the lower of cost or fair value under the fair value measurement method. For further information on this election, refer to Note 1, Basis of Presentation and Significant Accounting Policies.
Schedule of assumptions included in loan servicing rights	The following table presents assumptions utilized in determining the fair value of loan servicing rights as of September 30, 2018 and December 31, 2017 . Mortgage As of September 30, 2018 Prepayment speed 0.0 - 25.74% Weighted average ("WA") discount rate 10.1 % WA cost to service/per year $ 66 WA ancillary income/per year $ 31 WA float range 2.3 % As of December 31, 2017 Prepayment speed 0.0 - 38.8% WA discount rate 10.1 % WA cost to service/per year $ 66 WA ancillary income/per year $ 31 WA float range 1.6 %

Other Intangible Assets (Tables

Other Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Net carrying value of intangible assets	The following table shows the net carrying value of the Corporation’s other intangible assets. (Dollars in thousands) September 30, December 31, Core deposit intangible assets $ 29,981 $ 34,259 Non-compete intangible assets — 12 Total other intangible assets $ 29,981 $ 34,271
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets	The following table sets forth the carrying amount and accumulated amortization of core deposit intangible assets that are amortizable and arose from business combinations or other acquisitions: (Dollars in thousands) September 30, December 31, Gross original amount $ 56,456 $ 59,143 Accumulated amortization 26,475 24,884 Net carrying amount $ 29,981 $ 34,259

Derivative Instruments and Ba_2

Derivative Instruments and Balance Sheet Offsetting (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule reflecting the amount and fair value of risk management derivatives and mortgage banking and customer initiated derivatives	The following table presents the notional amount and fair value of the Corporation’s derivative instruments held or issued in connection with customer-initiated and mortgage banking activities. September 30, 2018 December 31, 2017 Fair Value Fair Value (Dollars in thousands) Notional Amount (1) Gross Derivative Assets (2) Gross Derivative Liabilities (2) Notional Amount (1) Gross Derivative Assets (2) Gross Derivative Liabilities (2) Risk management purposes: Derivatives designated as hedging instruments: Interest rate swaps $ 820,000 $ 21,067 $ — $ 620,000 $ 5,899 $ — Total risk management purposes 820,000 21,067 — 620,000 5,899 — Customer-initiated and mortgage banking derivatives: Customer-initiated derivatives 1,960,013 21,390 21,703 1,365,119 9,376 10,139 Foreign exchange forwards 934 3 3 — — — Forward contracts related to mortgage loans to be delivered for sale 169,554 760 — 115,996 — 34 Interest rate lock commitments 98,516 1,081 — 71,003 1,222 — Power Equity CD 37,501 1,260 1,260 38,807 2,184 2,184 Total customer-initiated and mortgage banking derivatives 2,266,518 24,494 22,966 1,590,925 12,782 12,357 Total gross derivatives $ 3,086,518 $ 45,561 $ 22,966 $ 2,210,925 $ 18,681 $ 12,357 (1) Notional or contract amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the Consolidated Statements of Financial Position. (2) Derivative assets are included within "Interest receivable and other assets" and derivative liabilities are included within "Interest payable and other liabilities" on the Consolidated Statements of Financial Position. Included in the fair value of the derivative assets are credit valuation adjustments for counterparty credit risk totaling $272 thousand at September 30, 2018 and $809 thousand at December 31, 2017 .
Schedule reflecting the net gains (losses) relating to derivative instruments related to the changes in fair value	The following table presents the net gains (losses) related to derivative instruments reflecting the changes in fair value. Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) Location of Gain (Loss) 2018 2017 2018 2017 Forward contracts related to mortgage loans to be delivered for sale Net gain on sale of loans and other mortgage banking revenue $ 1,185 $ 43 $ 794 $ 25 Interest rate lock commitments Net gain on sale of loans and other mortgage banking revenue (904 ) (198 ) (141 ) 843 Foreign exchange forwards Other noninterest income — 5 — 5 Customer-initiated derivatives Other noninterest income 84 (39 ) 450 (820 ) Total gain (loss) recognized in income $ 365 $ (189 ) $ 1,103 $ 53 The following table presents the net gains (losses) recorded in accumulated other comprehensive income and the Consolidated Statements of Income relating to interest rate swaps designated as cash flow hedges for the three and nine months ended September 30, 2018 and 2017. (Dollars in thousands) Amount of gain (loss) recognized in other comprehensive income Amount of gain (loss) reclassified from other comprehensive income to interest income or expense Three Months Ended September 30, 2018 Interest rate swaps designated as cash flow hedges $ 4,111 $ 662 Three Months Ended September 30, 2017 Interest rate swaps designated as cash flow hedges 751 (575 ) Nine Months Ended September 30, 2018 Interest rate swaps designated as cash flow hedges $ 16,176 $ 1,009 Nine months ended September 30, 2017 Interest rate swaps designated as cash flow hedges 694 (984 )
Schedule of the Company's financial instruments eligible for offset, offsetting assets	The tables below present information about the Corporation’s financial instruments that are eligible for offset. Gross amounts not offset in the (Dollars in thousands) Gross Gross amounts Net amounts Financial Collateral Net September 30, 2018 Offsetting derivative assets Derivative assets (1) $ 21,376 $ — $ 21,376 $ — $ (26,520 ) $ (5,144 ) Offsetting derivative liabilities Derivative liabilities (1) 21,648 — 21,648 — 5,150 16,498 December 31, 2017 Offsetting derivative assets Derivative assets (1) $ 15,228 $ — $ 15,228 $ — $ — $ 15,228 Offsetting derivative liabilities Derivative liabilities 10,139 — 10,139 — 1,081 9,058 (1) Amount does not include participated interest rate swaps, forward contracts, interest rate lock commitments and power equity CDs as these instruments are not subject to master netting or similar arrangements.
Schedule of the Company's financial instruments eligible for offset, offsetting liabilities	The tables below present information about the Corporation’s financial instruments that are eligible for offset. Gross amounts not offset in the (Dollars in thousands) Gross Gross amounts Net amounts Financial Collateral Net September 30, 2018 Offsetting derivative assets Derivative assets (1) $ 21,376 $ — $ 21,376 $ — $ (26,520 ) $ (5,144 ) Offsetting derivative liabilities Derivative liabilities (1) 21,648 — 21,648 — 5,150 16,498 December 31, 2017 Offsetting derivative assets Derivative assets (1) $ 15,228 $ — $ 15,228 $ — $ — $ 15,228 Offsetting derivative liabilities Derivative liabilities 10,139 — 10,139 — 1,081 9,058 (1) Amount does not include participated interest rate swaps, forward contracts, interest rate lock commitments and power equity CDs as these instruments are not subject to master netting or similar arrangements.

Commitments, Contingencies an_2

Commitments, Contingencies and Guarantees (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of the reserve for unfunded commitments	ed $4.3 million and $5.3 million , respectively. A summary of the reserve for representations and warranties of the Corporation is as follows: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Reserve balance at beginning of period $ 4,860 $ 5,469 $ 5,349 $ 6,459 Reserve reduction (580 ) (71 ) (1,067 ) (1,061 ) Charge-offs (7 ) (9 ) (9 ) (9 ) Ending reserve balance $ 4,273 $ 5,389 $ 4,273 $ 5,389 (Dollars in thousands) September 30, 2018 December 31, 2017 Reserve balance Liability for specific claims $ 403 $ 531 General allowance 3,870 4,818 Total reserve balance $ 4,273 $ 5,349

Borrowings and Other Short-Te_2

Borrowings and Other Short-Term Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Other Borrowings	A summary of the Corporation's short- and long-term borrowings, and other short-term liabilities follows: September 30, 2018 December 31, 2017 (Dollars in thousands) Amount Weighted Average Rate (1) Amount Weighted Average Rate (1) Short-term borrowings: FHLB advances: 2.14% - 2.27% fixed-rate notes $ 1,670,000 2.21 % $ 2,000,000 1.39 % Long-term borrowings: FHLB advances: 1.00% - 2.72% fixed-rate notes due 2018 to 2025 (2) 415,118 2.00 337,204 1.26 Line-of-credit: floating-rate based on one-month LIBOR plus 1.75% — — 19,963 3.10 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 (3) 11,535 4.55 11,425 3.69 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 3.25% due in 2032 (4) 4,318 5.59 4,290 4.59 Total long-term borrowings 430,971 2.10 372,882 1.47 Total borrowings $ 2,100,971 2.19 % $ 2,372,882 1.40 % Other short-term liabilities: Collateralized customer deposits $ 377,471 0.71 % $ 415,236 0.44 % (1) Weighted average rate presented is the contractual rate which excludes premiums and discounts related to purchase accounting. (2) The September 30, 2018 balances include advances payable of $415.0 million and purchase accounting premiums of $0.1 million . The December 31, 2017 balance includes advances payable of $337.0 million and purchase accounting premiums of $0.2 million . (3) The September 30, 2018 balance includes advances payable of $15.0 million and purchase accounting discounts of $3.5 million . The December 31, 2017 balance includes advances payable of $15.0 million and purchase accounting discounts of $3.6 million . (4) The September 30, 2018 balance includes advances payable of $5.0 million and purchase accounting discounts of $0.7 million . The December 31, 2017 balance includes advances payable of $5.0 million and purchase accounting discounts of $0.7 million .

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Segregation of Noninterest Income	The following table presents total noninterest income segregated between contracts with customers within the scope of ASC 606 and those within the scope of other GAAP Topics. The following additionally presents revenues from customers and non-customers that are included within noninterest income and expense. Three Months Ended Nine Months Ended (Dollars in thousands) September 30, 2018 September 30, 2018 Noninterest income Service charges and fees on deposit accounts $ 4,820 $ 13,744 Wealth management revenue 811 3,868 Other charges and fees for customer services 2,522 7,392 Noninterest income from contracts with customers within the scope of ASC 606 8,153 25,004 Noninterest income within the scope of other GAAP topics 29,764 91,485 Total noninterest income $ 37,917 $ 116,489 Noninterest expense Other $ (50 ) $ (734 )

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of activity for Corporation's stock options	A summary of activity for the Corporation’s stock options as of and for the nine months ended September 30, 2018 is presented below: Non-Vested Stock Options Outstanding Stock Options Outstanding Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Grant Date Fair Value Per Share Number of Options Weighted- Average Exercise Price Per Share Outstanding at December 31, 2017 330,870 $ 37.97 $ 7.09 1,110,918 $ 29.56 Exercised — — — (295,419 ) 23.97 Vested (78,533 ) 37.16 6.94 — — Forfeited/expired (14,926 ) 37.51 7.03 (14,928 ) 37.51 Outstanding at September 30, 2018 237,411 $ 38.27 $ 7.14 800,571 $ 38.27 Exercisable/vested at September 30, 2018 563,160 $ 28.61
Summary of activity for restricted stock units and awards	The following table provides information regarding nonvested restricted stock awards: Nonvested restricted stock awards Number of Awards Weighted-average acquisition-date Nonvested at January 1, 2018 83,228 $ 46.23 Vested (41,784 ) 46.23 Forfeited (592 ) 46.23 Nonvested at September 30, 2018 40,852 $ 46.23 A summary of the activity for RSUs as of and for the nine months ended September 30, 2018 is presented below: Number of Units Weighted-average grant date fair value per unit Outstanding at December 31, 2017 380,940 $ 41.29 Granted 315,072 54.41 Converted into shares of common stock (70,459 ) 28.96 Forfeited/expired (15,390 ) 47.43 Outstanding at September 30, 2018 610,163 $ 49.33

Pension and Other Postretirem_2

Pension and Other Postretirement Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan	The components of net periodic benefit cost for the Corporation’s qualified and nonqualified pension plans and nonqualified postretirement benefit plan are as follows: Three Months Ended September 30, Nine Months Ended September 30, (Dollars in thousands) 2018 2017 2018 2017 Defined Benefit Pension Plans Service cost (1) $ — $ 233 $ — $ 700 Interest cost 1,092 1,302 3,276 3,906 Expected return on plan assets (2,220 ) (2,216 ) (6,659 ) (6,650 ) Amortization of unrecognized net loss 178 578 533 1,734 Settlement — 322 — 322 Net periodic benefit cost (income) (2) $ (950 ) $ 219 $ (2,850 ) $ 12 Postretirement Benefit Plan Service cost (1) $ 1 $ 1 $ 2 $ 4 Interest cost 20 24 61 70 Amortization of unrecognized net gain (36 ) (41 ) (107 ) (121 ) Net periodic benefit cost (income) (2) $ (15 ) $ (16 ) $ (44 ) $ (47 ) (1) Service cost is included in "Salaries, wages and employee benefits expense" on the Consolidated Statements of Income. (2) Net periodic benefit cost (income), excluding service cost is included "Other" operating expenses on the Consolidated Statements of Income.

Regulatory Capital (Tables)

Regulatory Capital (Tables)	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Corporation's and Chemical Bank's actual capital amounts and ratios with the quantitative measures established by regulation to ensure capital adequacy	The summary below compares the actual capital amounts and ratios with the quantitative measures established by regulation to ensure capital adequacy: Actual Minimum Required for Capital Adequacy Purposes Minimum Required for Capital Adequacy Purposes Plus Capital Conservation Buffer Required to be Well Capitalized Under Prompt Corrective Action Regulations (Dollars in thousands) Capital Amount Ratio Capital Amount Ratio Capital Amount Ratio Capital Amount Ratio September 30, 2018 Total Capital to Risk-Weighted Assets Corporation $ 1,792,952 11.7 % $ 1,224,203 8.0 % $ 1,511,126 9.9 % N/A N/A Chemical Bank 1,766,477 11.6 1,221,170 8.0 1,507,382 9.9 $ 1,526,463 10.0 % Tier 1 Capital to Risk-Weighted Assets Corporation 1,665,786 10.9 918,153 6.0 1,208,901 7.9 N/A N/A Chemical Bank 1,655,164 10.8 915,878 6.0 1,202,089 7.9 1,221,170 8.0 Common Equity Tier 1 Capital to Risk-Weighted Assets Corporation 1,665,786 10.9 688,614 4.5 975,537 6.4 N/A N/A Chemical Bank 1,655,164 10.8 686,908 4.5 973,120 6.4 992,201 6.5 Leverage Ratio Corporation 1,665,786 8.6 771,041 4.0 771,041 4.0 N/A N/A Chemical Bank 1,655,164 8.6 769,726 4.0 769,726 4.0 962,157 5.0 December 31, 2017 Total Capital to Risk-Weighted Assets Corporation $ 1,614,046 11.0 % $ 1,179,076 8.0 % $ 1,363,307 9.3 % N/A N/A Chemical Bank 1,613,087 11.0 1,176,361 8.0 1,360,167 9.3 $ 1,470,451 10.0 % Tier 1 Capital to Risk-Weighted Assets Corporation 1,498,463 10.2 884,307 6.0 1,068,538 7.3 N/A N/A Chemical Bank 1,513,219 10.3 882,271 6.0 1,066,077 7.3 1,176,361 8.0 Common Equity Tier 1 Capital to Risk-Weighted Asset Corporation 1,498,463 10.2 663,230 4.5 847,461 5.8 N/A N/A Chemical Bank 1,513,219 10.3 661,703 4.5 845,509 5.8 955,793 6.5 Leverage Ratio Corporation 1,498,463 8.3 720,890 4.0 720,890 4.0 N/A N/A Chemical Bank 1,513,219 8.4 720,043 4.0 720,043 4.0 900,053 5.0

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Numerator and denominator of the basic and diluted earnings per common share computations	The factors used in the earnings per share computation follow: Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2018 2017 2018 2017 Net income $ 70,397 $ 40,459 $ 210,981 $ 140,077 Net income allocated to participating securities 40 129 144 566 Net income allocated to common shareholders (1) $ 70,357 $ 40,330 $ 210,837 $ 139,511 Weighted average common shares - issued 71,426 71,139 71,365 71,077 Average unvested restricted share awards (41 ) (228 ) (49 ) (290 ) Weighted average common shares outstanding - basic 71,385 70,911 71,316 70,787 Effect of dilutive securities Weighted average common stock equivalents 702 594 691 667 Weighted average common shares outstanding - diluted 72,087 71,505 72,007 71,454 EPS available to common shareholders Basic earnings per common share $ 0.99 $ 0.57 $ 2.96 $ 1.98 Diluted earnings per common share $ 0.98 $ 0.56 $ 2.93 $ 1.95 (1) Net income allocated to common shareholders for basic and diluted earnings per share may differ under the two-class method as a result of adding common share equivalents for options to dilutive shares outstanding, which alters the ratio used to allocate net income to common shareholders and participating securities for the purposes of calculating diluted earnings per share.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Components of accumulated other comprehensive loss, net of related tax benefit/expense	The following table summarizes the changes within each component of accumulated other comprehensive income (loss), net of related tax benefit/expense for the three and nine months ended September 30, 2018 , and 2017 : (Dollars in thousands) Unrealized gains Defined Benefit Pension Plans Unrealized gains (losses) on cash flow hedges, net of tax Total For the three months ended September 30, 2018 Beginning balance $ (41,685 ) $ (19,584 ) $ 13,918 $ (47,351 ) Other comprehensive (loss) income before reclassifications (13,141 ) — 3,248 (9,893 ) Amounts reclassified from accumulated other comprehensive income (loss) — 112 (523 ) (411 ) Net current period other comprehensive (loss) income (13,141 ) 112 2,725 (10,304 ) Ending balance $ (54,826 ) $ (19,472 ) $ 16,643 $ (57,655 ) For the three months ended September 30, 2017 Beginning balance $ (8,877 ) $ (25,195 ) $ (57 ) $ (34,129 ) Other comprehensive income before reclassifications 895 7,305 520 8,720 Amounts reclassified from accumulated other comprehensive (loss) income (1 ) 349 231 579 Net current period other comprehensive income 894 7,654 751 9,299 Ending balance $ (7,983 ) $ (17,541 ) $ 694 $ (24,830 ) For the nine months ended September 30, 2018 Beginning balance $ (10,348 ) $ (19,808 ) $ 4,658 $ (25,498 ) Cumulative effect adjustment of change in accounting policy, net of tax impact (1) (344 ) — 3 (341 ) Beginning balance at January 1, 2018 (10,692 ) (19,808 ) 4,661 (25,839 ) Other comprehensive (loss) income before reclassifications (44,132 ) — 12,779 (31,353 ) Amounts reclassified from accumulated other comprehensive (loss) income (2 ) 336 (797 ) (463 ) Net current period other comprehensive (loss) income (44,134 ) 336 11,982 (31,816 ) Ending balance $ (54,826 ) $ (19,472 ) $ 16,643 $ (57,655 ) For the nine months ended September 30, 2017 Beginning balance $ (14,142 ) $ (25,894 ) $ — $ (40,036 ) Other comprehensive income before reclassifications 6,268 7,305 54 13,627 Amounts reclassified from accumulated other comprehensive (loss) income (109 ) 1,048 640 1,579 Net current period other comprehensive income 6,159 8,353 694 15,206 Ending balance $ (7,983 ) $ (17,541 ) $ 694 $ (24,830 ) (1) Refer to Note 1 , Basis of Presentation and Significant Accounting Policies, Note 3 , Investment Securities, and Note 9 , Derivative Instruments and Balance Sheet Offsetting, for further details on the changes in accounting policy.
Summary of amounts reclassified out of accumulated other comprehensive income (loss)	The following table summarizes the amounts reclassified out of each component of accumulated other comprehensive income (loss) for the three and nine months ended September 30, 2018 , and 2017 : (Dollars in thousands) Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Income Statement Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Gains on available-for-sale securities $ — $ 1 $ 3 $ 168 Net gain on sale of investment securities (noninterest income) — — (1 ) (59 ) Income tax expense $ — $ 1 $ 2 $ 109 Net Income Amortization of defined benefit pension plan items $ 142 $ 537 $ 426 $ 1,613 Salaries, wages and employee benefits (operating expenses) (30 ) (188 ) (90 ) (565 ) Income tax benefit $ 112 $ 349 336 $ 1,048 Net Loss Gains and losses on cash flow hedges $ (662 ) $ 575 $ (1,009 ) $ 984 Interest on short-term borrowings (interest expense) 139 (344 ) 212 (344 ) Income tax expense (benefit) $ (523 ) $ 231 $ (797 ) $ 640 Net (Income)/Loss

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018Bank	Dec. 31, 2017USD ($)	[1]	Dec. 31, 2016USD ($)	[2]
Accounting Policies [Abstract]
Number of banks through which company operates (in bank) | Bank	1
Number of regional banking units Chemical Bank operates through (in bank) | Bank	6
Business Acquisition
Cumulative effect adjustment of change in accounting policy, net of tax impact | $		$ 1,339		$ 3,659
Retained earnings
Business Acquisition
Cumulative effect adjustment of change in accounting policy, net of tax impact | $		$ 1,680		$ 3,659
[1]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies, Note 3, Investment Securities, Note 5, Other Real Estate Owned and Repossessed Assets and Note 9, Derivative Instruments and Balance Sheet Offsetting, for further details on the changes in accounting policy.
[2]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies and Note 7, Loan Servicing Rights for further details on the changes in accounting policy.

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - ASU Adoptions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification due to TCJA	$ 4,500
Adjustments to retained earnings	419,403			$ 567,510
ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustments to retained earnings	1,200
ASU 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustments to retained earnings	(300)				$ (344)
ASU 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit cost (income)		$ 31	$ 700
Early Adoption | ASU 2017-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustments to retained earnings	$ (3)

Fair Value Measurements - Asset

Fair Value Measurements - Assets on a Recurring Basis (Details) - USD ($)	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0
Summary of assets measured at fair value on a recurring basis
Carried at fair value	2,736,880,000		$ 1,963,546,000
Loan servicing rights	72,707,000	$ 70,364,000	63,841,000	$ 62,195,000	$ 64,522,000	$ 48,085,000
Measured on a Recurring Basis
Summary of assets measured at fair value on a recurring basis
Carried at fair value	2,736,880,000		1,963,546,000
Loans held-for-sale	93,736,000		52,133,000
Loan servicing rights	72,707,000		63,841,000
Total derivatives	45,561,000		18,681,000
Total assets measured at fair value on a recurring basis	2,948,884,000		2,098,201,000
Total derivatives	22,966,000		12,357,000
Total liabilities at fair value	22,966,000		12,357,000
Measured on a Recurring Basis | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Loans held-for-sale	0		0
Loan servicing rights	0		0
Total derivatives	0		0
Total assets measured at fair value on a recurring basis	0		0
Total derivatives	0		0
Total liabilities at fair value	0		0
Measured on a Recurring Basis | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	2,736,880,000		1,963,546,000
Loans held-for-sale	93,736,000		52,133,000
Loan servicing rights	0		0
Total derivatives	45,561,000		18,681,000
Total assets measured at fair value on a recurring basis	2,876,177,000		2,034,360,000
Total derivatives	22,966,000		12,357,000
Total liabilities at fair value	22,966,000		12,357,000
Measured on a Recurring Basis | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Loans held-for-sale	0		0
Loan servicing rights	72,707,000		63,841,000
Total derivatives	0		0
Total assets measured at fair value on a recurring basis	72,707,000		63,841,000
Total derivatives	0		0
Total liabilities at fair value	0		0
Measured on a Recurring Basis | Customer-initiated derivatives
Summary of assets measured at fair value on a recurring basis
Total derivatives	21,390,000		9,376,000
Total derivatives	21,703,000		10,139,000
Measured on a Recurring Basis | Customer-initiated derivatives | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Total derivatives	0		0
Measured on a Recurring Basis | Customer-initiated derivatives | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	21,390,000		9,376,000
Total derivatives	21,703,000		10,139,000
Measured on a Recurring Basis | Customer-initiated derivatives | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Total derivatives	0		0
Measured on a Recurring Basis | Foreign exchange forwards
Summary of assets measured at fair value on a recurring basis
Total derivatives	3,000
Total derivatives	3,000
Measured on a Recurring Basis | Foreign exchange forwards | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0
Total derivatives	0
Measured on a Recurring Basis | Foreign exchange forwards | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	3,000
Total derivatives	3,000
Measured on a Recurring Basis | Foreign exchange forwards | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0
Total derivatives	0
Measured on a Recurring Basis | Forward contracts related to mortgage loans to be delivered for sale
Summary of assets measured at fair value on a recurring basis
Total derivatives	760,000
Total derivatives			34,000
Measured on a Recurring Basis | Forward contracts related to mortgage loans to be delivered for sale | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0
Total derivatives			0
Measured on a Recurring Basis | Forward contracts related to mortgage loans to be delivered for sale | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	760,000
Total derivatives			34,000
Measured on a Recurring Basis | Forward contracts related to mortgage loans to be delivered for sale | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0
Total derivatives			0
Measured on a Recurring Basis | Interest rate lock commitments
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,081,000		1,222,000
Measured on a Recurring Basis | Interest rate lock commitments | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Measured on a Recurring Basis | Interest rate lock commitments | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,081,000		1,222,000
Measured on a Recurring Basis | Interest rate lock commitments | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Measured on a Recurring Basis | Power Equity CD
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,260,000		2,184,000
Total derivatives	1,260,000		2,184,000
Measured on a Recurring Basis | Power Equity CD | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Total derivatives	0		0
Measured on a Recurring Basis | Power Equity CD | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,260,000		2,184,000
Total derivatives	1,260,000		2,184,000
Measured on a Recurring Basis | Power Equity CD | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Total derivatives	0		0
Measured on a Recurring Basis | Risk management derivatives
Summary of assets measured at fair value on a recurring basis
Total derivatives	21,067,000		5,899,000
Measured on a Recurring Basis | Risk management derivatives | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Measured on a Recurring Basis | Risk management derivatives | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	21,067,000		5,899,000
Measured on a Recurring Basis | Risk management derivatives | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0		0
Measured on a Recurring Basis | Government and government-sponsored agencies
Summary of assets measured at fair value on a recurring basis
Carried at fair value	254,453,000		202,916,000
Measured on a Recurring Basis | Government and government-sponsored agencies | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Government and government-sponsored agencies | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	254,453,000		202,916,000
Measured on a Recurring Basis | Government and government-sponsored agencies | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | State and political subdivisions
Summary of assets measured at fair value on a recurring basis
Carried at fair value	491,909,000		345,970,000
Measured on a Recurring Basis | State and political subdivisions | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | State and political subdivisions | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	491,909,000		345,970,000
Measured on a Recurring Basis | State and political subdivisions | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Residential mortgage-backed securities
Summary of assets measured at fair value on a recurring basis
Carried at fair value	177,021,000		150,131,000
Measured on a Recurring Basis | Residential mortgage-backed securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Residential mortgage-backed securities | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	177,021,000		150,131,000
Measured on a Recurring Basis | Residential mortgage-backed securities | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Collateralized mortgage obligations
Summary of assets measured at fair value on a recurring basis
Carried at fair value	1,477,818,000		1,033,845,000
Measured on a Recurring Basis | Collateralized mortgage obligations | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Collateralized mortgage obligations | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	1,477,818,000		1,033,845,000
Measured on a Recurring Basis | Collateralized mortgage obligations | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Corporate bonds
Summary of assets measured at fair value on a recurring basis
Carried at fair value	287,405,000		192,794,000
Measured on a Recurring Basis | Corporate bonds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Corporate bonds | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	287,405,000		192,794,000
Measured on a Recurring Basis | Corporate bonds | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Trust preferred securities
Summary of assets measured at fair value on a recurring basis
Carried at fair value	48,274,000		36,066,000
Measured on a Recurring Basis | Trust preferred securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0		0
Measured on a Recurring Basis | Trust preferred securities | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	48,274,000		36,066,000
Measured on a Recurring Basis | Trust preferred securities | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	$ 0		0
Measured on a Recurring Basis | Preferred stock
Summary of assets measured at fair value on a recurring basis
Carried at fair value			1,824,000
Measured on a Recurring Basis | Preferred stock | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Carried at fair value			0
Measured on a Recurring Basis | Preferred stock | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value			1,824,000
Measured on a Recurring Basis | Preferred stock | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value			$ 0

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis
Balance, beginning of period	$ 70,364	$ 64,522	$ 63,841	$ 48,085
Transfer in based on new accounting policy election	0	0	0	15,891
Gains (losses): Recorded in earnings (realized):
Recorded in Net gain on sale of loans and other mortgage banking revenue	257	(4,651)	2,529	(8,242)
New originations	2,086	2,324	6,337	6,461
Balance, end of period	$ 72,707	$ 62,195	$ 72,707	$ 62,195

Fair Value Measurements - Aggre

Fair Value Measurements - Aggregate Fair Value, Contractual Balance, and Gain or Loss for Loans Held-For-Sale (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Aggregate fair value	$ 93,736	$ 52,133
Contractual balance	91,839	50,597
Unrealized gain (loss)	$ 1,897	$ 1,536

Fair Value Measurements - Gains

Fair Value Measurements - Gains (Losses) from Loans Held-for-Sale (Details) - Loans Held For Sale - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	$ 5,667	$ 7,936	$ 11,803	$ 30,363
Interest income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	849	810	1,670	1,824
Change in fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	577	614	361	2,002
Net gain on sale of loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	$ 4,241	$ 6,512	$ 9,772	$ 26,537

Fair Value Measurements - Textu

Fair Value Measurements - Textual (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value Measurements (Textual) [Abstract]
Impairment of goodwill	$ 0	$ 0
Core deposit intangible assets
Fair Value Measurements (Textual) [Abstract]
Impairment valuation allowance	$ 0	0
Non-compete intangible assets
Fair Value Measurements (Textual) [Abstract]
Expected life of intangible assets	1 year
Minimum | Core deposit intangible assets
Fair Value Measurements (Textual) [Abstract]
Expected life of intangible assets	10 years
Maximum | Core deposit intangible assets
Fair Value Measurements (Textual) [Abstract]
Expected life of intangible assets	15 years
Loans Held For Sale
Fair Value Measurements (Textual) [Abstract]
Loans held for sale that were on nonaccrual status	$ 0	0
Loans held for sale that were 90 days past due and on accrual status	$ 0	0
Total Impaired Loans | Minimum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	20.00%
Total Impaired Loans | Maximum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	30.00%
Other Real Estate and Repossessed Assets | Minimum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	20.00%
Other Real Estate and Repossessed Assets | Maximum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	30.00%
Measured on a Recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 2,948,884,000	2,098,201,000
Fair Value Measurements (Textual) [Abstract]
Liabilities recorded at fair value	22,966,000	12,357,000
Measured on a Nonrecurring Basis
Fair Value Measurements (Textual) [Abstract]
Liabilities recorded at fair value	$ 0	$ 0

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Assets on a Nonrecurring Basis (Details) - Nonrecurring - Significant Unobservable Inputs (Level 3) $ in Thousands	Sep. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 74,980	$ 73,518
Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	73,137	70,619
Other real estate and repossessed assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 1,843	$ 2,899
Discount rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired originated loans, measurement input	0.20
Other real estate assets, measurement input	0.20
Discount rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired originated loans, measurement input	0.30
Other real estate assets, measurement input	0.30

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investment securities:
Held-to-maturity	$ 598,197	$ 662,906
Level 3 | Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	74,980	73,518
Level 3 | Nonrecurring | Impaired loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	73,137	70,619
Carrying Amount | Level 2
Investment securities:
Held-to-maturity	607,867	676,593
Financial liabilities:
Time deposits	3,865,489	3,217,207
Collateralized customer deposits	377,471	415,236
Short-term borrowings	1,670,000	2,000,000
Long-term borrowings	430,971	372,882
Carrying Amount | Level 3
Investment securities:
Held-to-maturity	500	500
Net loans	14,692,211	14,063,380
Fair Value | Level 2
Investment securities:
Held-to-maturity	597,747	662,516
Financial liabilities:
Time deposits	3,827,695	3,225,847
Collateralized customer deposits	376,969	415,236
Short-term borrowings	1,669,662	1,999,137
Long-term borrowings	426,105	367,984
Fair Value | Level 3
Investment securities:
Held-to-maturity	450	390
Net loans	$ 14,301,208	$ 14,114,545

Investment Securities - Availab

Investment Securities - Available-For-Sale Investment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Total debt securities available-for-sale
Amortized Cost	$ 2,806,281		$ 1,975,257
Unrealized Gains	1,696		3,605
Unrealized Losses	71,097		17,140
Fair Value	2,736,880		1,961,722
Total equity securities
Amortized Cost			1,389
Unrealized Gains			435
Unrealized Losses			0
Fair Value			1,824
Total
Amortized Cost	2,806,281		1,976,646
Unrealized Gains			4,040
Unrealized Losses			17,140
Total	2,736,880		1,963,546
Government and government-sponsored agencies
Total debt securities available-for-sale
Amortized Cost	258,643		203,099
Unrealized Gains	14		765
Unrealized Losses	4,204		948
Fair Value	254,453		202,916
State and political subdivisions
Total debt securities available-for-sale
Amortized Cost	506,277		350,088
Unrealized Gains	187		310
Unrealized Losses	14,555		4,428
Fair Value	491,909		345,970
Residential mortgage-backed securities
Total debt securities available-for-sale
Amortized Cost	182,983		151,752
Unrealized Gains	6		5
Unrealized Losses	5,968		1,626
Fair Value	177,021		150,131
Collateralized mortgage obligations
Total debt securities available-for-sale
Amortized Cost	1,517,172		1,042,240
Unrealized Gains	0		89
Unrealized Losses	39,354		8,484
Fair Value	1,477,818		1,033,845
Corporate bonds
Total debt securities available-for-sale
Amortized Cost	293,828		193,230
Unrealized Gains	485		1,156
Unrealized Losses	6,908		1,592
Fair Value	287,405		192,794
Trust preferred securities
Total debt securities available-for-sale
Amortized Cost	47,378		34,848
Unrealized Gains	1,004		1,280
Unrealized Losses	108		62
Fair Value	$ 48,274		36,066
Preferred stock
Total equity securities
Amortized Cost			1,389
Unrealized Gains			435
Unrealized Losses			0
Fair Value		$ 1,800	$ 1,824

Investment Securities - Held-To

Investment Securities - Held-To-Maturity Investment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Held-to-maturity Securities
Amortized Cost	$ 608,367	$ 677,093
Unrealized Gains	1,917	3,856
Unrealized Losses	12,087	18,043
Held-to-maturity, fair value	598,197	662,906
State and political subdivisions
Held-to-maturity Securities
Amortized Cost	607,867	676,593
Unrealized Gains	1,917	3,856
Unrealized Losses	12,037	17,933
Held-to-maturity, fair value	597,747	662,516
Trust preferred securities
Held-to-maturity Securities
Amortized Cost	500	500
Unrealized Gains	0	0
Unrealized Losses	50	110
Held-to-maturity, fair value	$ 450	$ 390

Investment Securities - Gains a

Investment Securities - Gains and (Losses) Recognized in Earnings (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)security	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)security	Sep. 30, 2017USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Investments, Debt and Equity Securities [Abstract]
Securities in unrealized loss positions, qualitative disclosure, number of positions (in security) | security	1,525		1,525
Proceeds	$ 0	$ 7,035	$ 4,215	$ 17,085
Gross gains	0	1	42	168
Gross losses	0	$ 0	(39)	$ 0
Schedule of Investments [Line Items]
Fair Value						$ 1,824
Adjustments to retained earnings	$ 567,510		$ 567,510			419,403
ASU 2016-01
Schedule of Investments [Line Items]
Adjustments to retained earnings					$ (344)	(300)
Preferred stock
Schedule of Investments [Line Items]
Fair Value					$ 1,800	$ 1,824

Investment Securities - Maturit

Investment Securities - Maturities of Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investment Securities Available-for-Sale: Amortized Cost
Due in one year or less	$ 32,586
Due after one year through five years	121,421
Due after five years through ten years	455,582
Due after ten years	2,196,692
Amortized Cost	2,806,281	$ 1,976,646
Investment Securities Available-for-Sale: Fair Value
Due in one year or less	32,424
Due after one year through five years	119,478
Due after five years through ten years	443,027
Due after ten years	2,141,951
Total	2,736,880	1,963,546
Investment Securities Held-to-Maturity: Amortized Cost
Due in one year or less	57,403
Due after one year through five years	221,335
Due after five years through ten years	157,517
Due after ten years	172,112
Amortized Cost	608,367	677,093
Investment Securities Held-to-Maturity: Fair Value
Due in one year or less	57,248
Due after one year through five years	218,555
Due after five years through ten years	153,997
Due after ten years	168,397
Total	598,197	662,906
Collateral Pledged
Investment Securities Held-to-Maturity: Amortized Cost
Amortized Cost	$ 1,020,000	$ 937,200

Investment Securities - Gross U

Investment Securities - Gross Unrealized Losses (Details) $ in Thousands	Sep. 30, 2018USD ($)security	Dec. 31, 2017USD ($)
Schedule of Investments [Line Items]
Total number of securities, available-for-sale and held-to-maturity (in security) | security	2,074
Securities in unrealized loss positions, qualitative disclosure, number of positions (in security) | security	1,525
Fair Value
Less Than 12 Months	$ 2,032,456	$ 1,379,705
12 Months or More	1,045,212	563,188
Total	3,077,668	1,942,893
Gross Unrealized Losses
Less Than 12 Months	43,491	21,534
12 Months or More	39,693	13,649
Total	83,184	35,183
Government and government-sponsored agencies
Fair Value
Less Than 12 Months	204,095	63,818
12 Months or More	39,573	24,621
Total	243,668	88,439
Gross Unrealized Losses
Less Than 12 Months	2,564	510
12 Months or More	1,640	438
Total	4,204	948
State and political subdivisions
Fair Value
Less Than 12 Months	563,202	437,407
12 Months or More	414,480	349,242
Total	977,682	786,649
Gross Unrealized Losses
Less Than 12 Months	14,773	12,268
12 Months or More	11,819	10,093
Total	26,592	22,361
Residential mortgage-backed securities
Fair Value
Less Than 12 Months	119,911	93,508
12 Months or More	55,068	56,576
Total	174,979	150,084
Gross Unrealized Losses
Less Than 12 Months	2,907	383
12 Months or More	3,061	1,243
Total	5,968	1,626
Collateralized mortgage obligations
Fair Value
Less Than 12 Months	990,167	713,525
12 Months or More	456,347	73,707
Total	1,446,514	787,232
Gross Unrealized Losses
Less Than 12 Months	19,414	7,235
12 Months or More	19,940	1,249
Total	39,354	8,484
Corporate bonds
Fair Value
Less Than 12 Months	141,365	71,447
12 Months or More	76,955	47,878
Total	218,320	119,325
Gross Unrealized Losses
Less Than 12 Months	3,773	1,138
12 Months or More	3,135	454
Total	6,908	1,592
Trust preferred securities
Fair Value
Less Than 12 Months	13,716	0
12 Months or More	2,789	11,164
Total	16,505	11,164
Gross Unrealized Losses
Less Than 12 Months	60	0
12 Months or More	98	172
Total	$ 158	$ 172

Loans - Textual (Details)

Loans - Textual (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)executive	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)class_of_loansegmenttenantexecutive	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of portfolio segment (in segment) | segment			2
Number of classes of loans (in class of loan) | class_of_loan			6
Number of minimum tenants under lease of non-owner occupied commercial real estate (in tenant) | tenant			1
Minimum value of loan that requires regional loan committee approval	$ 3,000		$ 3,000
Maximum value of loan that requires regional loan committee approval	7,000		7,000
Total troubled debt restructurings	71,086		71,086		$ 77,888
Residential mortgage loans in process of foreclosure	5,400		5,400		4,200
Commitment to lend additional funds to borrowers whose terms have been modified in TDRs	2,900		2,900		2,000
Loans held-for-sale, at fair value	93,736		93,736		52,133
Proceeds from sales of loans	177,200	$ 210,200	569,768	$ 601,694
Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	28,061		28,061		29,106
Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	43,025		43,025		48,782
Consumer loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	17,612		17,612		19,046
Consumer loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	3,970		3,970		4,748
Consumer loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	13,642		13,642		14,298
Commercial loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	53,474		53,474		58,842
Commercial loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	24,091		24,091		24,358
Commercial loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	29,383		$ 29,383		$ 34,484
Land development loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum period for payment of loan			12 months
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for loan secured under real estate residential security			15 years
Loan-to-value ratio at the time of origination			80.00%
Commercial | Commercial loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum value of loan requires group loan authority approval	1,250		$ 1,250
Maximum value of loan requires senior officer approval	$ 3,000		$ 3,000
Number of bank executives and senior officers with credit decision limits similar to group loan authorities (in executive) | executive	6		6
Maximum value of loan requires executive and senior officer approval	$ 8,000		$ 8,000
Minimum value of loan requires group loan authority approval	$ 7,000		$ 7,000

Loans - Summary of Loans (Detai

Loans - Summary of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Summary of loans under portfolio
Total loans	$ 14,796,252	$ 14,155,267
Deferred income	19,000	26,100
Commercial loan portfolio
Summary of loans under portfolio
Total loans	9,053,690	8,460,527
Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	3,719,922	3,385,642
Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	4,711,621	4,500,670
Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	622,147	574,215
Consumer loan portfolio
Summary of loans under portfolio
Total loans	5,742,562	5,694,740
Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	3,391,987	3,252,487
Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,560,265	1,613,008
Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	790,310	829,245
Originated
Summary of loans under portfolio
Total loans	11,145,442	9,747,429
Originated | Commercial
Summary of loans under portfolio
Total loans	2,951,453	2,407,606
Originated | Total commercial real estate
Summary of loans under portfolio
Total loans	3,256,206	2,751,425
Originated | Real estate construction and land development
Summary of loans under portfolio
Total loans	554,701	498,155
Originated | Residential mortgage
Summary of loans under portfolio
Total loans	2,285,611	1,967,857
Originated | Consumer installment
Summary of loans under portfolio
Total loans	1,483,540	1,510,540
Originated | Home equity
Summary of loans under portfolio
Total loans	613,931	611,846
Originated | Commercial loan portfolio
Summary of loans under portfolio
Total loans	6,762,360	5,657,186
Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,951,453	2,407,606
Originated | Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	3,256,206	2,751,425
Originated | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	554,701	498,155
Originated | Consumer loan portfolio
Summary of loans under portfolio
Total loans	4,383,082	4,090,243
Originated | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	2,285,611	1,967,857
Originated | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,483,540	1,510,540
Originated | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	613,931	611,846
Acquired
Summary of loans under portfolio
Total loans	3,650,810	4,407,838
Acquired | Commercial loan portfolio
Summary of loans under portfolio
Total loans	2,291,330	2,803,341
Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	768,469	978,036
Acquired | Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	1,455,415	1,749,245
Acquired | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	67,446	76,060
Acquired | Consumer loan portfolio
Summary of loans under portfolio
Total loans	1,359,480	1,604,497
Acquired | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	1,106,376	1,284,630
Acquired | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	76,725	102,468
Acquired | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	176,379	217,399
Owner-occupied | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,897,934	1,813,562
Owner-occupied | Originated | Commercial
Summary of loans under portfolio
Total loans	1,334,588	1,185,614
Owner-occupied | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,334,588	1,185,614
Owner-occupied | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	563,346	627,948
Non-owner occupied | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,739,700	2,606,761
Non-owner occupied | Originated | Commercial
Summary of loans under portfolio
Total loans	1,875,155	1,518,787
Non-owner occupied | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,875,155	1,518,787
Non-owner occupied | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	864,545	1,087,974
Vacant land | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	73,987	80,347
Vacant land | Originated | Commercial
Summary of loans under portfolio
Total loans	46,463	47,024
Vacant land | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	46,463	47,024
Vacant land | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	$ 27,524	$ 33,323

Loans - Activity for Accretable

Loans - Activity for Accretable Yield (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Activity for accretable yield
Balance at beginning of period	$ 780,764	$ 1,038,219	$ 926,897	$ 1,039,971
Accretion recognized in interest income	(54,273)	(60,403)	(169,734)	(183,804)
Net reclassification (to) from nonaccretable difference	21,068	(1,812)	(9,604)	119,837
Balance at end of period	747,559	976,004	747,559	976,004
Talmer
Activity for accretable yield
Balance at beginning of period	616,168	801,369	731,353	798,210
Accretion recognized in interest income	(40,695)	(43,816)	(125,471)	(133,478)
Net reclassification (to) from nonaccretable difference	20,250	11,861	(10,159)	104,682
Balance at end of period	595,723	769,414	595,723	769,414
Lake Michigan
Activity for accretable yield
Balance at beginning of period	80,442	121,572	95,124	121,416
Accretion recognized in interest income	(5,980)	(7,201)	(19,040)	(22,050)
Net reclassification (to) from nonaccretable difference	3,108	(14,482)	1,486	523
Balance at end of period	77,570	99,889	77,570	99,889
Monarch
Activity for accretable yield
Balance at beginning of period	20,131	24,270	22,496	27,182
Accretion recognized in interest income	(919)	(1,119)	(3,037)	(3,459)
Net reclassification (to) from nonaccretable difference	(376)	168	(623)	(404)
Balance at end of period	18,836	23,319	18,836	23,319
North-western
Activity for accretable yield
Balance at beginning of period	49,731	71,212	60,814	69,847
Accretion recognized in interest income	(4,341)	(5,263)	(13,863)	(15,222)
Net reclassification (to) from nonaccretable difference	(765)	(1,358)	(2,326)	9,966
Balance at end of period	44,625	64,591	44,625	64,591
OAK
Activity for accretable yield
Balance at beginning of period	14,292	19,796	17,110	23,316
Accretion recognized in interest income	(2,338)	(3,004)	(8,323)	(9,595)
Net reclassification (to) from nonaccretable difference	(1,149)	1,999	2,018	5,070
Balance at end of period	$ 10,805	$ 18,791	$ 10,805	$ 18,791

Loans - Commercial Loans by Ris

Loans - Commercial Loans by Risk Rating Categories (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 14,796,252	$ 14,155,267
Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,145,442	9,747,429
Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,951,453	2,407,606
Originated | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,256,206	2,751,425
Originated | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	554,701	498,155
Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,650,810	4,407,838
Commercial loan portfolio
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,053,690	8,460,527
Commercial loan portfolio | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,629,934	8,038,463
Commercial loan portfolio | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	203,735	204,706
Commercial loan portfolio | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	219,988	216,353
Commercial loan portfolio | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	33	1,005
Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,719,922	3,385,642
Commercial loan portfolio | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,711,621	4,500,670
Commercial loan portfolio | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	622,147	574,215
Commercial loan portfolio | Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,762,360	5,657,186
Commercial loan portfolio | Originated | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,518,563	5,488,571
Commercial loan portfolio | Originated | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	105,670	66,100
Commercial loan portfolio | Originated | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	138,105	102,515
Commercial loan portfolio | Originated | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	22	0
Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,951,453	2,407,606
Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,840,100	2,316,464
Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	54,258	41,059
Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	57,095	50,083
Commercial loan portfolio | Originated | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial loan portfolio | Originated | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,256,206	2,751,425
Commercial loan portfolio | Originated | Total commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,160,902	2,677,579
Commercial loan portfolio | Originated | Total commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	46,312	24,204
Commercial loan portfolio | Originated | Total commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	48,970	49,642
Commercial loan portfolio | Originated | Total commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	22	0
Commercial loan portfolio | Originated | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	554,701	498,155
Commercial loan portfolio | Originated | Real estate construction and land development | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	517,561	494,528
Commercial loan portfolio | Originated | Real estate construction and land development | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,100	837
Commercial loan portfolio | Originated | Real estate construction and land development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	32,040	2,790
Commercial loan portfolio | Originated | Real estate construction and land development | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial loan portfolio | Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,291,330	2,803,341
Commercial loan portfolio | Acquired | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,111,371	2,549,892
Commercial loan portfolio | Acquired | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	98,065	138,606
Commercial loan portfolio | Acquired | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	81,883	113,838
Commercial loan portfolio | Acquired | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	11	1,005
Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	768,469	978,036
Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	707,054	873,861
Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	36,227	68,418
Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	25,188	35,539
Commercial loan portfolio | Acquired | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	218
Commercial loan portfolio | Acquired | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,455,415	1,749,245
Commercial loan portfolio | Acquired | Total commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,338,023	1,603,685
Commercial loan portfolio | Acquired | Total commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	61,700	67,970
Commercial loan portfolio | Acquired | Total commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	55,681	76,803
Commercial loan portfolio | Acquired | Total commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	11	787
Commercial loan portfolio | Acquired | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	67,446	76,060
Commercial loan portfolio | Acquired | Real estate construction and land development | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	66,294	72,346
Commercial loan portfolio | Acquired | Real estate construction and land development | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	138	2,218
Commercial loan portfolio | Acquired | Real estate construction and land development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,014	1,496
Commercial loan portfolio | Acquired | Real estate construction and land development | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Owner-occupied | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,334,588	1,185,614
Owner-occupied | Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,897,934	1,813,562
Owner-occupied | Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,334,588	1,185,614
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,265,111	1,133,609
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	33,290	19,438
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	36,168	32,567
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	19	0
Owner-occupied | Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	563,346	627,948
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	505,246	580,127
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	29,840	23,998
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	28,249	23,036
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	11	787
Non-owner occupied | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,875,155	1,518,787
Non-owner occupied | Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,739,700	2,606,761
Non-owner occupied | Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,875,155	1,518,787
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,854,887	1,504,195
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,542	4,728
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,726	9,864
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	864,545	1,087,974
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	805,466	995,709
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	31,647	43,645
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	27,432	48,620
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Vacant land | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	46,463	47,024
Vacant land | Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	73,987	80,347
Vacant land | Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	46,463	47,024
Vacant land | Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	40,904	39,775
Vacant land | Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	480	38
Vacant land | Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,076	7,211
Vacant land | Commercial loan portfolio | Originated | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	3	0
Vacant land | Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	27,524	33,323
Vacant land | Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	27,311	27,849
Vacant land | Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	213	327
Vacant land | Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	5,147
Vacant land | Commercial loan portfolio | Acquired | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 0	$ 0

Loans - Consumer Loans by Risk

Loans - Consumer Loans by Risk Rating Categories (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 14,796,252	$ 14,155,267
Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,145,442	9,747,429
Originated | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,285,611	1,967,857
Originated | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,483,540	1,510,540
Originated | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	613,931	611,846
Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,650,810	4,407,838
Consumer loan portfolio
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,742,562	5,694,740
Consumer loan portfolio | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,391,987	3,252,487
Consumer loan portfolio | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,560,265	1,613,008
Consumer loan portfolio | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	790,310	829,245
Consumer loan portfolio | Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,383,082	4,090,243
Consumer loan portfolio | Originated | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,285,611	1,967,857
Consumer loan portfolio | Originated | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,483,540	1,510,540
Consumer loan portfolio | Originated | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	613,931	611,846
Consumer loan portfolio | Originated | Performing
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,368,852	4,076,461
Consumer loan portfolio | Originated | Performing | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,276,000	1,959,222
Consumer loan portfolio | Originated | Performing | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,482,190	1,509,698
Consumer loan portfolio | Originated | Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	610,662	607,541
Consumer loan portfolio | Originated | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total loans	14,230	13,782
Consumer loan portfolio | Originated | Nonperforming | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,611	8,635
Consumer loan portfolio | Originated | Nonperforming | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,350	842
Consumer loan portfolio | Originated | Nonperforming | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,269	4,305
Consumer loan portfolio | Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,359,480	1,604,497
Consumer loan portfolio | Acquired | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,106,376	1,284,630
Consumer loan portfolio | Acquired | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	76,725	102,468
Consumer loan portfolio | Acquired | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 176,379	$ 217,399

Loans - Nonperforming Loans (De

Loans - Nonperforming Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 1,192	$ 1,377
Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	632	0
Total commercial real estate
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	47	13
Real estate construction and land development
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	38	0
Home equity
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	475	1,364
Nonperforming
Summary of nonperforming loans
Total nonaccrual loans	96,673	63,095
Other real estate owned and repossessed assets	6,584	8,807
Total nonperforming assets	103,257	71,902
Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	25,328	19,691
Nonperforming | Total commercial real estate
Summary of nonperforming loans
Total nonaccrual loans	28,638	29,545
Nonperforming | Real estate construction and land development
Summary of nonperforming loans
Total nonaccrual loans	28,477	77
Nonperforming | Residential mortgage
Summary of nonperforming loans
Total nonaccrual loans	9,611	8,635
Nonperforming | Consumer installment
Summary of nonperforming loans
Total nonaccrual loans	1,350	842
Nonperforming | Home equity
Summary of nonperforming loans
Total nonaccrual loans	3,269	4,305
Owner-occupied | Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	47	0
Owner-occupied | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	14,936	19,070
Non-owner occupied | Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	13
Non-owner occupied | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	8,991	5,270
Vacant land | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	$ 4,711	$ 5,205

Loans - Aging Status of Loans (

Loans - Aging Status of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule representing the aging status of the recorded investment in loans by classes
Total loans	$ 14,796,252	$ 14,155,267
90 days or more past due and still accruing	1,192	1,377
Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	632	0
Total commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	47	13
Real estate construction and land development
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	38	0
Home equity
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	475	1,364
Originated Portfolio
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	111,617	58,857
Current	11,033,825	9,688,572
Total loans	11,145,442	9,747,429
90 days or more past due and still accruing	1,192	1,377
Originated Portfolio | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	33,475	31,724
Originated Portfolio | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	29,965	8,486
Originated Portfolio | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	48,177	18,647
Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	30,905	27,166
Current	2,920,548	2,380,440
Total loans	2,951,453	2,407,606
90 days or more past due and still accruing	632	0
Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	9,280	13,906
Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	8,770	3,766
Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	12,855	9,494
Originated Portfolio | Total commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	27,895	16,815
Current	3,228,311	2,734,610
Total loans	3,256,206	2,751,425
90 days or more past due and still accruing	47	13
Originated Portfolio | Total commercial real estate | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	10,322	9,380
Originated Portfolio | Total commercial real estate | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	4,601	1,562
Originated Portfolio | Total commercial real estate | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	12,972	5,873
Originated Portfolio | Real estate construction and land development
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	29,759	0
Current	524,942	498,155
Total loans	554,701	498,155
90 days or more past due and still accruing	38	0
Originated Portfolio | Real estate construction and land development | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,244	0
Originated Portfolio | Real estate construction and land development | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	13,238	0
Originated Portfolio | Real estate construction and land development | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	15,277	0
Originated Portfolio | Residential mortgage
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	10,217	5,068
Current	2,275,394	1,962,789
Total loans	2,285,611	1,967,857
90 days or more past due and still accruing	0	0
Originated Portfolio | Residential mortgage | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,889	2,795
Originated Portfolio | Residential mortgage | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,576	1,415
Originated Portfolio | Residential mortgage | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	4,752	858
Originated Portfolio | Consumer installment
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	4,829	3,992
Current	1,478,711	1,506,548
Total loans	1,483,540	1,510,540
90 days or more past due and still accruing	0	0
Originated Portfolio | Consumer installment | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,555	3,324
Originated Portfolio | Consumer installment | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	657	442
Originated Portfolio | Consumer installment | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	617	226
Originated Portfolio | Home equity
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	8,012	5,816
Current	605,919	606,030
Total loans	613,931	611,846
90 days or more past due and still accruing	475	1,364
Originated Portfolio | Home equity | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	5,185	2,319
Originated Portfolio | Home equity | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,123	1,301
Originated Portfolio | Home equity | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,704	2,196
Owner-occupied | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	47	0
Owner-occupied | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	18,950	13,977
Current	1,315,638	1,171,637
Total loans	1,334,588	1,185,614
90 days or more past due and still accruing	47	0
Owner-occupied | Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	8,052	7,644
Owner-occupied | Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,440	1,306
Owner-occupied | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	8,458	5,027
Non-owner occupied | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	0	13
Non-owner occupied | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	4,809	2,574
Current	1,870,346	1,516,213
Total loans	1,875,155	1,518,787
90 days or more past due and still accruing	0	13
Non-owner occupied | Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,993	1,653
Non-owner occupied | Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	762	228
Non-owner occupied | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,054	693
Vacant land | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	4,136	264
Current	42,327	46,760
Total loans	46,463	47,024
90 days or more past due and still accruing	0	0
Vacant land | Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	277	83
Vacant land | Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,399	28
Vacant land | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	$ 2,460	$ 153

Loans - Impaired Loans by Class

Loans - Impaired Loans by Class (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 78,211	$ 78,621
Unpaid Principal Balance	84,663	87,956
Related Valuation Allowance	5,074	8,002
Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	61,239	33,256
Unpaid Principal Balance	65,374	35,824
Related Valuation Allowance	0	0
Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	139,450	111,877
Unpaid Principal Balance	150,037	123,780
Related Valuation Allowance	5,074	8,002
Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,394	28,897
Unpaid Principal Balance	16,109	31,655
Related Valuation Allowance	1,110	2,296
Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	25,021	8,504
Unpaid Principal Balance	26,427	9,291
Related Valuation Allowance	0	0
Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	38,415	37,401
Unpaid Principal Balance	42,536	40,946
Related Valuation Allowance	1,110	2,296
Total commercial real estate | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	18,595	28,003
Unpaid Principal Balance	22,332	34,580
Related Valuation Allowance	1,796	3,227
Total commercial real estate | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	25,872	18,080
Unpaid Principal Balance	28,534	19,861
Related Valuation Allowance	0	0
Total commercial real estate | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	44,467	46,083
Unpaid Principal Balance	50,866	54,441
Related Valuation Allowance	1,796	3,227
Real estate construction and land development | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	28,575	313
Unpaid Principal Balance	28,575	313
Related Valuation Allowance	650	14
Real estate construction and land development | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	140
Unpaid Principal Balance	207
Related Valuation Allowance	0
Real estate construction and land development | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	28,715	313
Unpaid Principal Balance	28,782	313
Related Valuation Allowance	650	14
Residential mortgage | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,879	15,872
Unpaid Principal Balance	12,879	15,872
Related Valuation Allowance	1,146	1,487
Residential mortgage | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,988	4,902
Unpaid Principal Balance	7,988	4,902
Related Valuation Allowance	0	0
Residential mortgage | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	20,867	20,774
Unpaid Principal Balance	20,867	20,774
Related Valuation Allowance	1,146	1,487
Consumer installment | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,071	966
Unpaid Principal Balance	1,071	966
Related Valuation Allowance	117	120
Consumer installment | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	475
Unpaid Principal Balance	475
Related Valuation Allowance	0
Consumer installment | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,546	966
Unpaid Principal Balance	1,546	966
Related Valuation Allowance	117	120
Home equity | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,697	4,570
Unpaid Principal Balance	3,697	4,570
Related Valuation Allowance	255	858
Home equity | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,743	1,770
Unpaid Principal Balance	1,743	1,770
Related Valuation Allowance	0	0
Home equity | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,440	6,340
Unpaid Principal Balance	5,440	6,340
Related Valuation Allowance	255	858
Owner-occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,278	17,774
Unpaid Principal Balance	15,607	21,588
Related Valuation Allowance	1,281	2,317
Owner-occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	10,852	11,351
Unpaid Principal Balance	11,490	12,631
Related Valuation Allowance	0	0
Owner-occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	24,130	29,125
Unpaid Principal Balance	27,097	34,219
Related Valuation Allowance	1,281	2,317
Non-owner occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,187	5,307
Unpaid Principal Balance	4,595	7,870
Related Valuation Allowance	142	316
Non-owner occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,161	5,977
Unpaid Principal Balance	13,099	6,438
Related Valuation Allowance	0	0
Non-owner occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	15,348	11,284
Unpaid Principal Balance	17,694	14,308
Related Valuation Allowance	142	316
Vacant land | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,130	4,922
Unpaid Principal Balance	2,130	5,122
Related Valuation Allowance	373	594
Vacant land | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,859	752
Unpaid Principal Balance	3,945	792
Related Valuation Allowance	0	0
Vacant land | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,989	5,674
Unpaid Principal Balance	6,075	5,914
Related Valuation Allowance	$ 373	$ 594

Loans - Impaired Loans (Details

Loans - Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Average recorded investment
Impaired loans with a valuation allowance	$ 56,408	$ 65,165	$ 56,134	$ 65,977
Impaired loans with no related valuation allowance	68,785	42,653	59,619	40,864
Total impaired loans	125,193	107,818	115,753	106,841
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	323	588	1,092	1,764
Impaired loans with no related valuation allowance	313	123	855	427
Total impaired loans	636	711	1,947	2,191
Commercial
Average recorded investment
Impaired loans with a valuation allowance	13,945	25,628	17,495	25,278
Impaired loans with no related valuation allowance	24,114	10,120	20,773	10,142
Total impaired loans	38,059	35,748	38,268	35,420
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	67	222	343	647
Impaired loans with no related valuation allowance	123	14	365	92
Total impaired loans	190	236	708	739
Total commercial real estate
Average recorded investment
Impaired loans with a valuation allowance	17,263	18,300	18,468	19,120
Impaired loans with no related valuation allowance	29,481	25,435	27,107	24,697
Total impaired loans	46,744	43,735	45,575	43,817
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	114	197	330	602
Impaired loans with no related valuation allowance	149	101	389	304
Total impaired loans	263	298	719	906
Real estate construction and land development
Average recorded investment
Impaired loans with a valuation allowance	9,647	175	3,372	159
Impaired loans with no related valuation allowance	3,857	71	1,986	86
Total impaired loans	13,504	246	5,358	245
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	2	3	6	8
Impaired loans with no related valuation allowance	2	0	5	0
Total impaired loans	4	3	11	8
Residential mortgage
Average recorded investment
Impaired loans with a valuation allowance	11,620	15,945	12,662	16,529
Impaired loans with no related valuation allowance	8,605	5,144	7,272	4,511
Total impaired loans	20,225	21,089	19,934	21,040
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	117	144	349	446
Impaired loans with no related valuation allowance	31	8	79	25
Total impaired loans	148	152	428	471
Consumer installment
Average recorded investment
Impaired loans with a valuation allowance	911	748	961	737
Impaired loans with no related valuation allowance	537	244	240	201
Total impaired loans	1,448	992	1,201	938
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	3	1	6	3
Impaired loans with no related valuation allowance	0	0	0	0
Total impaired loans	3	1	6	3
Home equity
Average recorded investment
Impaired loans with a valuation allowance	3,022	4,369	3,176	4,154
Impaired loans with no related valuation allowance	2,191	1,639	2,241	1,227
Total impaired loans	5,213	6,008	5,417	5,381
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	20	21	58	58
Impaired loans with no related valuation allowance	8	0	17	6
Total impaired loans	28	21	75	64
Owner-occupied | Total commercial real estate
Average recorded investment
Impaired loans with a valuation allowance	11,977	13,401	12,999	14,083
Impaired loans with no related valuation allowance	13,831	13,009	14,588	10,862
Total impaired loans	25,808	26,410	27,587	24,945
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	94	155	257	459
Impaired loans with no related valuation allowance	68	1	205	13
Total impaired loans	162	156	462	472
Non-owner occupied | Total commercial real estate
Average recorded investment
Impaired loans with a valuation allowance	3,697	2,457	3,271	2,939
Impaired loans with no related valuation allowance	12,776	8,942	9,825	9,487
Total impaired loans	16,473	11,399	13,096	12,426
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	13	17	34	68
Impaired loans with no related valuation allowance	81	88	184	255
Total impaired loans	94	105	218	323
Vacant land | Total commercial real estate
Average recorded investment
Impaired loans with a valuation allowance	1,589	2,442	2,198	2,098
Impaired loans with no related valuation allowance	2,874	3,484	2,694	4,348
Total impaired loans	4,463	5,926	4,892	6,446
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	7	25	39	75
Impaired loans with no related valuation allowance	0	12	0	36
Total impaired loans	$ 7	$ 37	$ 39	$ 111

Loans - Loan Modifications by C

Loans - Loan Modifications by Concession Type (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)loan	Sep. 30, 2017USD ($)loan	Sep. 30, 2018USD ($)loan	Sep. 30, 2017USD ($)loan
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 3,387	$ 2,926	$ 9,333	$ 6,608
Total number of loans (in loan) | loan	33	38	114	73
Pre-modification recorded investment	$ 3,404	$ 3,071	$ 9,446	$ 6,864
Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	2,681	780	5,383	1,993
Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	324		431
Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	381	479	2,744	2,247
Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	1	1,667	775	2,368
Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 2,774	$ 2,558	$ 7,800	$ 5,548
Total number of loans (in loan) | loan	16	19	56	37
Pre-modification recorded investment	$ 2,784	$ 2,627	$ 7,845	$ 5,646
Commercial loan portfolio | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	2,542	541	4,623	1,323
Commercial loan portfolio | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	66		66
Commercial loan portfolio | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	165	350	2,336	1,857
Commercial loan portfolio | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	1	1,667	775	2,368
Commercial loan portfolio | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 2,270	$ 2,119	$ 5,457	$ 4,400
Total number of loans (in loan) | loan	13	14	44	26
Pre-modification recorded investment	$ 2,277	$ 2,173	$ 5,481	$ 4,476
Commercial loan portfolio | Commercial | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	2,104	506	3,747	841
Commercial loan portfolio | Commercial | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0		0
Commercial loan portfolio | Commercial | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	165	281	1,448	1,648
Commercial loan portfolio | Commercial | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	1	1,332	262	1,911
Commercial loan portfolio | Total commercial real estate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 504	$ 404	$ 2,343	$ 1,113
Total number of loans (in loan) | loan	3	4	12	10
Pre-modification recorded investment	$ 507	$ 418	$ 2,364	$ 1,134
Commercial loan portfolio | Total commercial real estate | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	438	0	876	447
Commercial loan portfolio | Total commercial real estate | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	66		66
Commercial loan portfolio | Total commercial real estate | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	69	888	209
Commercial loan portfolio | Total commercial real estate | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	335	513	457
Commercial loan portfolio | Real estate construction and land development
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment		$ 35		$ 35
Total number of loans (in loan) | loan		1		1
Pre-modification recorded investment		$ 36		$ 36
Commercial loan portfolio | Real estate construction and land development | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment		35		35
Commercial loan portfolio | Real estate construction and land development | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment		0		0
Commercial loan portfolio | Real estate construction and land development | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment		0		0
Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 613	$ 368	$ 1,533	$ 1,060
Total number of loans (in loan) | loan	17	19	58	36
Pre-modification recorded investment	$ 620	$ 444	$ 1,601	$ 1,218
Consumer loan portfolio | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	139	239	760	670
Consumer loan portfolio | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	258		365
Consumer loan portfolio | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	216	129	408	390
Consumer loan portfolio | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0	0	0
Consumer loan portfolio | Residential mortgage
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 219	$ 198	$ 567	$ 594
Total number of loans (in loan) | loan	2	3	9	9
Pre-modification recorded investment	$ 220	$ 262	$ 577	$ 676
Consumer loan portfolio | Residential mortgage | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	76	269	211
Consumer loan portfolio | Residential mortgage | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	111		151
Consumer loan portfolio | Residential mortgage | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	108	122	147	383
Consumer loan portfolio | Residential mortgage | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0	0	0
Consumer loan portfolio | Consumer installment
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 166	$ 54	$ 357	$ 86
Total number of loans (in loan) | loan	11	11	36	17
Pre-modification recorded investment	$ 172	$ 58	$ 372	$ 93
Consumer loan portfolio | Consumer installment | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	48	47	134	79
Consumer loan portfolio | Consumer installment | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	74		141
Consumer loan portfolio | Consumer installment | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	44	7	82	7
Consumer loan portfolio | Consumer installment | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0	0	0
Consumer loan portfolio | Home equity
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 228	$ 116	$ 609	$ 380
Total number of loans (in loan) | loan	4	5	13	10
Pre-modification recorded investment	$ 228	$ 124	$ 652	$ 449
Consumer loan portfolio | Home equity | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	91	116	357	380
Consumer loan portfolio | Home equity | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	73		73
Consumer loan portfolio | Home equity | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	64	0	179	0
Consumer loan portfolio | Home equity | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0	0	0
Owner-occupied | Commercial loan portfolio | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 438	$ 377	$ 2,209	$ 1,086
Total number of loans (in loan) | loan	2	3	10	9
Pre-modification recorded investment	$ 438	$ 390	$ 2,221	$ 1,106
Owner-occupied | Commercial loan portfolio | Commercial | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	438	0	808	447
Owner-occupied | Commercial loan portfolio | Commercial | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0		0
Owner-occupied | Commercial loan portfolio | Commercial | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	42	888	182
Owner-occupied | Commercial loan portfolio | Commercial | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	335	513	457
Non-owner occupied | Commercial loan portfolio | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 66	$ 27	$ 134	$ 27
Total number of loans (in loan) | loan	1	1	2	1
Pre-modification recorded investment	$ 69	$ 28	$ 143	$ 28
Non-owner occupied | Commercial loan portfolio | Commercial | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0	68	0
Non-owner occupied | Commercial loan portfolio | Commercial | Principal reduction
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	66		66
Non-owner occupied | Commercial loan portfolio | Commercial | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	27	0	27
Non-owner occupied | Commercial loan portfolio | Commercial | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0

Loans - Summary of TDRs (Detail

Loans - Summary of TDRs (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Total TDRs	$ 71,086	$ 77,888
Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	53,474	58,842
Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	17,612	19,046
Accruing TDRs
Financing Receivable, Modifications [Line Items]
Total TDRs	43,025	48,782
Accruing TDRs | Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	29,383	34,484
Accruing TDRs | Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	13,642	14,298
Nonaccrual TDRs
Financing Receivable, Modifications [Line Items]
Total TDRs	28,061	29,106
Nonaccrual TDRs | Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	24,091	24,358
Nonaccrual TDRs | Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	$ 3,970	$ 4,748

Loans - TDRs with a Payment Def

Loans - TDRs with a Payment Default During the Period (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)loan	Sep. 30, 2017USD ($)loan	Sep. 30, 2018USD ($)loan	Sep. 30, 2017USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of loans (in loan) | loan	12	0	23	10
Principal balance | $	$ 1,222	$ 0	$ 1,416	$ 1,780
Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Number of loans (in loan) | loan	6	0	9	5
Principal balance | $	$ 981	$ 0	$ 1,130	$ 1,617
Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Number of loans (in loan) | loan	6	0	14	5
Principal balance | $	$ 241	$ 0	$ 286	$ 163

Loans - Allowance for Loan Loss

Loans - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2017
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance			$ 91,887
Ending balance	$ 104,041		104,041
Allowance for loan losses
Loans individually evaluated for impairment					$ 5,074	$ 8,002
Loans collectively evaluated for impairment					97,997	83,885
Loans acquired with deteriorated credit quality					970	0
Total allowance for loan losses	104,041		91,887		104,041	91,887
Recorded investment (loan balance)
Loans individually evaluated for impairment					139,450	111,877
Loans collectively evaluated for impairment					11,005,992	9,635,552
Loans acquired with deteriorated credit quality					3,650,810	4,407,838
Total loans					14,796,252	14,155,267
Commercial loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance			66,133
Ending balance	75,784		75,784
Allowance for loan losses
Loans individually evaluated for impairment					3,556	5,537
Loans collectively evaluated for impairment					71,258	60,596
Loans acquired with deteriorated credit quality					970	0
Total allowance for loan losses	75,784		66,133		75,784	66,133
Recorded investment (loan balance)
Loans individually evaluated for impairment					111,597	83,797
Loans collectively evaluated for impairment					6,650,763	5,573,389
Loans acquired with deteriorated credit quality					2,291,330	2,803,341
Total loans					9,053,690	8,460,527
Consumer loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance			25,754
Ending balance	28,257		28,257
Allowance for loan losses
Loans individually evaluated for impairment					1,518	2,465
Loans collectively evaluated for impairment					26,739	23,289
Loans acquired with deteriorated credit quality					0	0
Total allowance for loan losses	28,257		25,754		28,257	25,754
Recorded investment (loan balance)
Loans individually evaluated for impairment					27,853	28,080
Loans collectively evaluated for impairment					4,355,229	4,062,163
Loans acquired with deteriorated credit quality					1,359,480	1,604,497
Total loans					5,742,562	5,694,740
Acquired Loan Portfolio [Member]
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	0	$ 0	0	$ 0
Provision for loan losses	970	579	970	579
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	970	579	970	579
Allowance for loan losses
Total allowance for loan losses	0	0	0	0	970	0
Acquired Loan Portfolio [Member] | Commercial loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	0	0	0	0
Provision for loan losses	970	409	970	409
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	970	409	970	409
Allowance for loan losses
Total allowance for loan losses	0	0	0	0	970	0
Acquired Loan Portfolio [Member] | Consumer loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	0	0	0	0
Provision for loan losses	0	170	0	170
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	0	170	0	170
Allowance for loan losses
Total allowance for loan losses	0	0	0	0	0	0
Originated Loan Portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	100,015	83,797	91,887	78,268
Provision for loan losses	5,058	4,920	20,886	15,200
Charge-offs	(3,728)	(5,442)	(14,278)	(13,321)
Recoveries	1,726	1,906	4,576	5,034
Ending balance	103,071	85,181	103,071	85,181
Allowance for loan losses
Total allowance for loan losses	100,015	83,797	91,887	78,268	103,071	91,887
Originated Loan Portfolio | Commercial loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	72,665	57,955	66,133	51,201
Provision for loan losses	2,064	664	13,387	9,140
Charge-offs	(1,048)	(3,792)	(7,532)	(7,209)
Recoveries	1,133	1,270	2,826	2,965
Ending balance	74,814	56,097	74,814	56,097
Allowance for loan losses
Total allowance for loan losses	72,665	57,955	66,133	51,201	74,814	66,133
Originated Loan Portfolio | Consumer loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	27,350	25,842	25,754	27,067
Provision for loan losses	2,994	4,256	7,499	6,060
Charge-offs	(2,680)	(1,650)	(6,746)	(6,112)
Recoveries	593	636	1,750	2,069
Ending balance	28,257	29,084	28,257	29,084
Allowance for loan losses
Total allowance for loan losses	$ 27,350	$ 25,842	$ 25,754	$ 27,067	$ 28,257	$ 25,754

Other Real Estate Owned and R_3

Other Real Estate Owned and Repossessed Assets - Rollforward Tables (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017		Dec. 31, 2016	[2]
Repossessed Assets [Line Items]
Cumulative effect adjustment of change in accounting policy, net of tax impact			$ 1,339	[1]	$ 3,659
Changes in other real estate owned
Balance at the beginning of the period	$ 8,182	$ 16,812
Transfers out based on new accounting adoption	(189)
Other additions	5,281	5,339
Net payments received	(190)	(582)
Disposals	(5,859)	(10,180)
Write-downs	(1,207)	(1,323)
Balance at the end of the period	6,018	10,066
Changes in repossessed assets
Balance at the beginning of the period	625	375
Transfers out based on new accounting adoption	0
Other additions	3,504	3,633
Net payments received	0	0
Disposals	(3,563)	(3,469)
Write-downs	0	0
Balance at the end of the period	566	$ 539
Retained earnings
Repossessed Assets [Line Items]
Cumulative effect adjustment of change in accounting policy, net of tax impact			1,680	[1]	$ 3,659
ASU 2014-09
Repossessed Assets [Line Items]
Loans to facilitate reclassified to loans	$ 1,100
ASU 2014-09 | Retained earnings
Repossessed Assets [Line Items]
Cumulative effect adjustment of change in accounting policy, net of tax impact			$ 900
[1]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies, Note 3, Investment Securities, Note 5, Other Real Estate Owned and Repossessed Assets and Note 9, Derivative Instruments and Balance Sheet Offsetting, for further details on the changes in accounting policy.
[2]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies and Note 7, Loan Servicing Rights for further details on the changes in accounting policy.

Other Real Estate Owned and R_4

Other Real Estate Owned and Repossessed Assets - Textual (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Other Real Estate [Abstract]
Other real estate owned and repossessed assets acquired in accordance with ASU 2014-04	$ 1.5
Residential mortgage loans in process of foreclosure	$ 5.4	$ 4.2

Other Real Estate Owned and R_5

Other Real Estate Owned and Repossessed Assets - Income and Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income and expenses related to other real estate owned
Net gain (loss) on sale	$ 224	$ 388	$ 1,003	$ 2,203
Write-downs	(424)	(550)	(1,207)	(1,323)
Net operating expenses	(93)	(509)	(808)	(1,727)
Total	(293)	(671)	(1,012)	(847)
Income and expenses related to repossessed assets
Net gain (loss) on sale	(175)	(112)	(269)	(283)
Write-downs	0	0	0	0
Net operating expenses	(2)	(1)	(5)	(8)
Total	$ (177)	$ (113)	$ (274)	$ (291)

Goodwill (Details)

Goodwill (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 1,134,568,000	$ 1,134,568,000
Goodwill impairment	$ 0

Loan Servicing Rights - LSRs Ac

Loan Servicing Rights - LSRs Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	$ 70,364	$ 64,522	$ 63,841	$ 48,085
Additions from loans sold with servicing retained	2,086	2,324	6,337	6,461
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	(675)	(610)	(2,125)	(1,880)
Changes in estimates of fair value	932	(4,041)	4,654	(6,362)
Transfers in based on new accounting policy election				15,891
Fair value, end of period	72,707	62,195	72,707	62,195
Principal balance of loans serviced	6,911,201	7,144,283	6,911,201	7,144,283
Commercial Real Estate
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	457	486	427	344
Additions from loans sold with servicing retained	51	0	139	188
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	(28)	(31)	(86)	(77)
Changes in estimates of fair value	0	0	0	0
Transfers in based on new accounting policy election				0
Fair value, end of period	480	455	480	455
Principal balance of loans serviced	42,070	41,798	42,070	41,798
Mortgage
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	69,907	64,036	63,414	47,741
Additions from loans sold with servicing retained	2,035	2,324	6,198	6,273
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	(647)	(579)	(2,039)	(1,803)
Changes in estimates of fair value	932	(4,041)	4,654	(6,362)
Transfers in based on new accounting policy election				15,891
Fair value, end of period	72,227	61,740	72,227	61,740
Principal balance of loans serviced	$ 6,869,131	$ 7,102,485	$ 6,869,131	$ 7,102,485

Loan Servicing Rights - Assumpt

Loan Servicing Rights - Assumptions Used in Determining Fair Value (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Loan servicing rights
Loan servicing fee income	$ 4,300,000	$ 4,500,000	$ 13,200,000	$ 13,600,000
Mortgage
Loan servicing rights
WA cost to service/per year			66		$ 66
WA ancillary income/per year			$ 31		$ 31
WA float range			2.30%
Mortgage | Weighted Average
Loan servicing rights
WA float range					1.60%
Prepayment rate | Mortgage | Minimum
Loan servicing rights
Measurement input	0		0		0
Prepayment rate | Mortgage | Maximum
Loan servicing rights
Measurement input	0.2574		0.2574		0.388
Discount rate | Mortgage | Weighted Average
Loan servicing rights
Measurement input	0.101		0.101		0.101

Other Intangible Assets - Intan

Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Total intangible assets	$ 29,981	$ 34,271
Core deposit intangible assets
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Gross original amount	56,456	59,143
Accumulated amortization	26,475	24,884
Total intangible assets	29,981	34,259
Non-compete intangible assets
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Total intangible assets	$ 0	$ 12

Other Intangible Assets - Textu

Other Intangible Assets - Textual (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets			$ (4,290)	$ (4,564)
Core deposit intangible assets
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period			6 years 9 months 18 days
Amortization of intangible assets	$ (1,400)	$ (1,500)	$ (4,300)	$ (4,500)
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2018	1,400		1,400
2,019	5,400		5,400
2,020	4,900		4,900
2,021	4,500		4,500
2,022	4,200		4,200
2023 and thereafter	$ 9,600		$ 9,600

Derivative Instruments and Ba_3

Derivative Instruments and Balance Sheet Offsetting - Notional Amount and Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative instruments
Notional Amount	$ 3,086,518	$ 2,210,925
Gross Derivative Assets	45,561	18,681
Gross Derivative Liabilities	22,966	12,357
Credit valuation adjustments for counterparty credit risk	272	809
Derivatives designated as hedging instruments:
Derivative instruments
Notional Amount	820,000	620,000
Gross Derivative Assets	21,067	5,899
Gross Derivative Liabilities	0	0
Derivatives designated as hedging instruments: | Interest rate swaps
Derivative instruments
Notional Amount	820,000	620,000
Gross Derivative Assets	21,067	5,899
Gross Derivative Liabilities	0	0
Derivatives not designated as hedging | Total customer-initiated and mortgage banking derivatives
Derivative instruments
Notional Amount	2,266,518	1,590,925
Gross Derivative Assets	24,494	12,782
Gross Derivative Liabilities	22,966	12,357
Derivatives not designated as hedging | Customer-initiated derivatives
Derivative instruments
Notional Amount	1,960,013	1,365,119
Gross Derivative Assets	21,390	9,376
Gross Derivative Liabilities	21,703	10,139
Derivatives not designated as hedging | Foreign exchange forwards
Derivative instruments
Notional Amount	934	0
Gross Derivative Assets	3	0
Gross Derivative Liabilities	3	0
Derivatives not designated as hedging | Forward contracts related to mortgage loans to be delivered for sale
Derivative instruments
Notional Amount	169,554	115,996
Gross Derivative Assets	760	0
Gross Derivative Liabilities	0	34
Derivatives not designated as hedging | Interest rate lock commitments
Derivative instruments
Notional Amount	98,516	71,003
Gross Derivative Assets	1,081	1,222
Gross Derivative Liabilities	0	0
Derivatives not designated as hedging | Power Equity CD
Derivative instruments
Notional Amount	37,501	38,807
Gross Derivative Assets	1,260	2,184
Gross Derivative Liabilities	$ 1,260	$ 2,184

Derivative Instruments and Ba_4

Derivative Instruments and Balance Sheet Offsetting - Net Gains (Losses) Related to Changes in Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative instruments
Total gain (loss) recognized in income	$ 365	$ (189)	$ 1,103	$ 53
Forward contracts related to mortgage loans to be delivered for sale | Net gain on sale of loans and other mortgage banking revenue
Derivative instruments
Total gain (loss) recognized in income	1,185	43	794	25
Interest rate lock commitments | Net gain on sale of loans and other mortgage banking revenue
Derivative instruments
Total gain (loss) recognized in income	(904)	(198)	(141)	843
Foreign exchange forwards | Other noninterest income
Derivative instruments
Total gain (loss) recognized in income	0	5	0	5
Customer-initiated derivatives | Other noninterest income
Derivative instruments
Total gain (loss) recognized in income	$ 84	$ (39)	$ 450	$ (820)

Derivative Instruments and Ba_5

Derivative Instruments and Balance Sheet Offsetting - Net Gains (Losses) Recorded in Other Comprehensive Income and the Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative instruments
Unrealized losses on interest rate swaps expected to be reclassified during next twelve months	$ 5,100		$ 5,100
Interest rate swaps | Derivatives designated as hedging instruments:
Derivative instruments
Amount of gain (loss) recognized in other comprehensive income	4,111	$ 751	16,176	$ 694
Amount of gain (loss) reclassified from other comprehensive income to interest income or expense	$ 662	$ (575)	$ 1,009	$ (984)

Derivative Instruments and Ba_6

Derivative Instruments and Balance Sheet Offsetting - Balance Sheet Offsetting (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Offsetting derivative assets
Gross amounts recognized	$ 45,561	$ 18,681
Offsetting derivative liabilities
Gross amounts recognized	22,966	12,357
Interest rate swaps and customer-initiated derivatives
Offsetting derivative assets
Gross amounts recognized	21,376	15,228
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	21,376	15,228
Gross amounts not offset in the statements of financial position
Financial instruments	0	0
Collateral (received)/posted	(26,520)	0
Net Amount	(5,144)	15,228
Offsetting derivative liabilities
Gross amounts recognized	21,648	10,139
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	21,648	10,139
Gross amounts not offset in the statements of financial position
Financial instruments	0	0
Collateral (received)/posted	5,150	1,081
Net Amount	$ 16,498	$ 9,058

Investments in Qualified Affo_2

Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Variable Interest Entity [Line Items]
Expense related to qualified affordable housing projects	$ 1	$ 0.8	$ 3.1	$ 2.3
Remaining investment in qualified affordable housing projects	52.2		52.2		$ 51.4
Equity method investments	11		11		17.3
Remaining unfunded equity contributions	42.3		42.3		$ 48.1
Investment tax credit	3.2	2.3	6.6	2.3
Impairment on tax credit projects	3.2	3.1	6.5	3.1
Other Noninterest Expense [Member]
Variable Interest Entity [Line Items]
Impairment on tax credit projects	$ 2.5	$ 2	$ 5.1	$ 2

Commitments, Contingencies an_3

Commitments, Contingencies and Guarantees - Commitments (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Potential losses from standby letters of credit	$ 0	$ 0
Undisbursed loan commitments	600,700,000	571,000,000
Probable credit losses	1,700,000	1,200,000
Financial and Performance Standby Letters of Credit
Loss Contingencies [Line Items]
Letters of credit outstanding	126,100,000	187,600,000
Commitments to Extend Credit
Loss Contingencies [Line Items]
Loan commitments under financial guarantee	3,100,000,000	3,030,000,000
Performance Guarantee
Loss Contingencies [Line Items]
Recourse liability	$ 100,000	$ 200,000

Commitments, Contingencies an_4

Commitments, Contingencies and Guarantees - Contingencies and Guarantees (Details) - Performance Guarantee - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Recorded liability	$ 14.4	$ 13.3
Maximum potential amount of undiscounted future payments	14.2	12.8
Recourse liability	$ 0.1	$ 0.2

Commitments, Contingencies an_5

Commitments, Contingencies and Guarantees - Warranties (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2017
Changes in the activity related to liability recorded in connection with representations and warranties
Reserve balance at beginning of period	$ 4,860	$ 5,469	$ 5,349	$ 6,459
Reserve reduction	(580)	(71)	(1,067)	(1,061)
Charge-offs	(7)	(9)	(9)	(9)
Ending reserve balance	4,273	5,389	4,273	5,389
Reserve balance
Liability for specific claims					$ 403	$ 531
General allowance					3,870	4,818
Total reserve balance	$ 4,860	$ 5,469	$ 5,349	$ 6,459	$ 4,273	$ 5,349

Borrowings and Other Short-Te_3

Borrowings and Other Short-Term Liabilities - Short/Long-term and Other Short-term Borrowings (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Long-term borrowings:
Amount	$ 430,971	$ 372,882
Weighted Average Rate	2.10%	1.47%
Total borrowings	$ 2,100,971	$ 2,372,882
Total short-term and long-term borrowings, Weighted Average Rate	2.19%	1.40%
FHLB advances: 2.14% - 2.27% fixed-rate notes | Minimum
Long-term borrowings:
Stated interest rate	2.14%
FHLB advances: 2.14% - 2.27% fixed-rate notes | Maximum
Long-term borrowings:
Stated interest rate	2.27%
FHLB Advances | FHLB advances: 0.92% - 7.44% fixed-rate notes due 2017 to 2020
Long-term borrowings:
Amount	$ 415,118	$ 337,204
Weighted Average Rate	2.00%	1.26%
Advances payable from Federal Home Loan Banks	$ 415,000	$ 337,000
Purchase accounting premiums	$ 100	200
FHLB Advances | FHLB advances: 0.92% - 7.44% fixed-rate notes due 2017 to 2020 | Minimum
Long-term borrowings:
Stated interest rate	1.00%
FHLB Advances | FHLB advances: 0.92% - 7.44% fixed-rate notes due 2017 to 2020 | Maximum
Long-term borrowings:
Stated interest rate	2.72%
Line of Credit
Long-term borrowings:
Amount	$ 0	$ 19,963
Weighted Average Rate	0.00%	3.10%
Spread on variable rate	1.75%
Subordinated debt obligations | Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035
Long-term borrowings:
Amount	$ 11,535	$ 11,425
Weighted Average Rate	4.55%	3.69%
Advances payable	$ 15,000	$ 15,000
Purchase accounting discounts	$ 3,500	3,600
Subordinated debt obligations | Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 | Minimum
Long-term borrowings:
Spread on variable rate	1.45%
Subordinated debt obligations | Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 | Maximum
Long-term borrowings:
Spread on variable rate	2.85%
Subordinated debt obligations | Subordinated debt obligations: floating-rate based on three-month LIBOR plus 3.25% due in 2032
Long-term borrowings:
Amount	$ 4,318	$ 4,290
Weighted Average Rate	5.59%	4.59%
Spread on variable rate	3.25%
Advances payable	$ 5,000	$ 5,000
Purchase accounting discounts	700	700
Collateralized customer deposits
Short-term borrowings:
Amount	$ 377,471	$ 415,236
Weighted Average Rate	0.71%	0.44%
FHLB Advances | FHLB advances: 2.14% - 2.27% fixed-rate notes
Short-term borrowings:
Amount	$ 1,670,000	$ 2,000,000
Weighted Average Rate	2.21%	1.39%

Revenue from Contracts with C_3

Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Noninterest income	$ 37,917	$ 32,122	$ 116,489	$ 111,700
Noninterest expense	(109,661)	$ (119,539)	(315,832)	$ (321,972)
Noninterest income from contracts with customers within the scope of ASC 606
Disaggregation of Revenue [Line Items]
Noninterest income	8,153		25,004
Service charges and fees on deposit accounts
Disaggregation of Revenue [Line Items]
Noninterest income	4,820		13,744
Wealth management revenue
Disaggregation of Revenue [Line Items]
Noninterest income	811		3,868
Other charges and fees for customer services
Disaggregation of Revenue [Line Items]
Noninterest income	2,522		7,392
Noninterest income within the scope of other GAAP topics
Disaggregation of Revenue [Line Items]
Noninterest income	29,764		91,485
Other
Disaggregation of Revenue [Line Items]
Noninterest expense	$ (50)		$ (734)

Borrowings and Other Short-Te_4

Borrowings and Other Short-Term Liabilities - Textual (Details) $ in Millions	Sep. 30, 2018USD ($)
Debt Disclosure [Abstract]
FHLB advances	$ 7,620
Additional borrowing available through FHLB	$ 547.9

Share-Based Compensation - Text

Share-Based Compensation - Textual (Details) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2017USD ($)	Apr. 26, 2017shares
Share-based Compensation Plans (Textual)
Share-based compensation expense	$ 1,900	$ 7,600	$ 6,000	$ 14,600
Excess tax benefit from share-based compensation transactions	$ 98	(332)	1,900	6,100
Cash received from option exercises			$ 2,600	2,600
Stock Incentive Plan of 2015
Share-based Compensation Plans (Textual)
Common stock available for future grants under share-based compensation plans (in shares) | shares	1,307,256		1,307,256
Stock Incentive Plan of 2017
Share-based Compensation Plans (Textual)
Number of shares authorized under stock incentive plan (in shares) | shares					1,750,000
Stock Incentive Plans After 2012
Share-based Compensation Plans (Textual)
Vesting period			5 years
Stock Incentive Plans Prior To 2013
Share-based Compensation Plans (Textual)
Vesting period			3 years
Stock options
Share-based Compensation Plans (Textual)
Stock option award vesting period			10 years
Outstanding in-the-money stock options, intrinsic value		$ 27,700		$ 27,700
Restricted stock units
Share-based Compensation Plans (Textual)
Corporation granted options to purchase restricted stock performance units (in shares) | shares			315,072
Stock issued from exercises (in shares) | shares			70,459
Unrecognized compensation expense	$ 18,500		$ 18,500
Unrecognized compensation expense, period for recognition			3 years 2 months
Restricted stock units | Minimum
Share-based Compensation Plans (Textual)
Restricted stock performance units eligible to vest as a multiple of number of units granted			0.5
Restricted stock units | Maximum
Share-based Compensation Plans (Textual)
Restricted stock performance units eligible to vest as a multiple of number of units granted			1.5
Equity Option
Share-based Compensation Plans (Textual)
Weighted-average remaining contractual terms for outstanding stock options			6 years 1 month
Weighted-average remaining contractual terms for exercisable stock options			5 years 5 months
Outstanding in-the-money stock options, intrinsic value	17,600		$ 17,600
Exercisable in-the-money stock options, intrinsic value	$ 14,000		$ 14,000
Closing price of common stock (dollars per share) | $ / shares	$ 53.40		$ 53.40
Unrecognized compensation expense	$ 1,400		$ 1,400
Unrecognized compensation expense, period for recognition			2 years 9 months 10 days
Restricted stock awards
Share-based Compensation Plans (Textual)
Unrecognized compensation expense	$ 800		$ 800
Unrecognized compensation expense, period for recognition			4 months 15 days

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details) - Stock Options	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Non-Vested Stock Options Outstanding, Number of Options
Vested (in shares) | shares	0
Non-Vested Stock Options Outstanding, Weighted- Average Grant Date Fair Value Per Share
Beginning balance (dollars per share)	$ 7.09
Vested (dollars per share)	6.94
Forfeited/expired (dollars per share)	7.03
Ending balance (dollars per share)	$ 7.14
Stock Options Outstanding, Number of Options
Beginning balance (in shares) | shares	1,110,918
Exercised (in shares) | shares	(295,419)
Ending balance (in shares) | shares	800,571
Weighted- Average Exercise Price Per Share
Beginning balance, Weighted Average Exercise Price (dollars per share)	$ 29.56
Exercised, Weighted Average Exercise Price (dollars per share)	23.97
Forfeited/expired, Weighted Average Exercise Price (dollars per share)	37.51
Ending balance, Weighted Average Exercise Price (dollars per share)	$ 38.27
Exercisable/vested, Number of Options (in shares) | shares	563,160
Exercisable/vested, Weighted Average Exercise Price (dollars per share)	$ 28.61
Vested, Weighted Average Exercise Price (dollars per share)	$ 0
Forfeited/expired (in shares) | shares	14,928
Non Vested
Non-Vested Stock Options Outstanding, Number of Options
Beginning balance (in shares) | shares	330,870
Vested (in shares) | shares	(78,533)
Forfeited/expired (in shares) | shares	(14,926)
Ending balance (in shares) | shares	237,411
Stock Options Outstanding, Number of Options
Exercised (in shares) | shares	0
Weighted- Average Exercise Price Per Share
Beginning balance, Weighted Average Exercise Price (dollars per share)	$ 37.97
Exercised, Weighted Average Exercise Price (dollars per share)	0
Forfeited/expired, Weighted Average Exercise Price (dollars per share)	37.51
Vested, Weighted Average Exercise Price (dollars per share)	37.16
Ending balance, Weighted Average Exercise Price (dollars per share)	$ 38.27

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Unit and Award Activity (Details)	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Restricted Stock Units
Number of Units/Awards
Beginning balance (in shares) | shares	380,940
Granted (in shares) | shares	315,072
Converted into shares of common stock (in shares) | shares	(70,459)
Forfeited/expired (in shares) | shares	(15,390)
Ending balance (in shares) | shares	610,163
Weighted-average grant-date fair value
Beginning balance (dollars per share) | $ / shares	$ 41.29
Granted (dollars per share) | $ / shares	54.41
Converted into shares of common stock (dollars per share) | $ / shares	28.96
Forfeited/expired (dollars per share) | $ / shares	47.43
Ending balance (dollars per share) | $ / shares	$ 49.33
Restricted Stock Awards
Number of Units/Awards
Beginning balance (in shares) | shares	83,228
Vested (in shares) | shares	(41,784)
Forfeited/expired (in shares) | shares	(592)
Ending balance (in shares) | shares	40,852
Weighted-average grant-date fair value
Beginning balance (dollars per share) | $ / shares	$ 46.23
Vested (dollars per share) | $ / shares	46.23
Forfeited/expired (dollars per share) | $ / shares	46.23
Ending balance (dollars per share) | $ / shares	$ 46.23

Pension and Other Postretirem_3

Pension and Other Postretirement Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Pension Plans
Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan
Service cost	$ 0	$ 233	$ 0	$ 700
Interest cost	1,092	1,302	3,276	3,906
Expected return on plan assets	(2,220)	(2,216)	(6,659)	(6,650)
Amortization of unrecognized net (gain) loss	178	578	533	1,734
Settlement	0	322	0	322
Net periodic benefit cost (income)	(950)	219	(2,850)	12
Postretirement Benefit Plan
Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan
Service cost	1	1	2	4
Interest cost	20	24	61	70
Amortization of unrecognized net (gain) loss	(36)	(41)	(107)	(121)
Net periodic benefit cost (income)	$ (15)	$ (16)	$ (44)	$ (47)

Pension and Other Postretirem_4

Pension and Other Postretirement Benefit Plans - Textual (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Maximum percent of participants' base compensation matched			6.00%
Percentage of eligible pay contribution to certain employees			4.00%
Corporation match as a percentage of the participants' elective deferrals			50.00%
Employer total contribution amount	$ 1,500,000	$ 2,500,000	$ 6,300,000	$ 7,500,000
Employer contributions to Pentegra DB Plan	0	0	0	0
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Contribution to defined benefit pension plan	0	$ 0	$ 0	$ 0
Defined Benefit Pension Plans | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate for pension plan expense			3.68%
Defined Benefit Pension Plans | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Liability related to SERP plan	$ 400,000		$ 400,000

Regulatory Capital (Details)

Regulatory Capital (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 23, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Leverage Ratio
Cash dividends declared per common share (dollars per share)		$ 0.34	$ 0.28	$ 0.9	$ 0.82
Subsequent Event
Leverage Ratio
Cash dividends declared per common share (dollars per share)	$ 0.34
Chemical Bank
Regulatory Capital
Risk weighted assets		$ 15,260,000		$ 15,260,000		$ 14,700,000
Total Capital to Risk-Weighted Assets
Actual Amount		$ 1,766,477		$ 1,766,477		$ 1,613,087
Actual Ratio		11.60%		11.60%		11.00%
For Capital Adequacy Purposes Amount		$ 1,221,170		$ 1,221,170		$ 1,176,361
For Capital Adequacy Purposes Ratio		8.00%		8.00%		8.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,507,382		$ 1,507,382		$ 1,360,167
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		9.90%		9.90%		9.30%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 1,526,463		$ 1,526,463		$ 1,470,451
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		10.00%		10.00%		10.00%
Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,655,164		$ 1,655,164		$ 1,513,219
Actual Ratio		10.80%		10.80%		10.30%
For Capital Adequacy Purposes Amount		$ 915,878		$ 915,878		$ 882,271
For Capital Adequacy Purposes Ratio		6.00%		6.00%		6.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,202,089		$ 1,202,089		$ 1,066,077
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		7.90%		7.90%		7.30%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 1,221,170		$ 1,221,170		$ 1,176,361
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		8.00%		8.00%		8.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,655,164		$ 1,655,164		$ 1,513,219
Actual Ratio		10.80%		10.80%		10.30%
For Capital Adequacy Purposes Amount		$ 686,908		$ 686,908		$ 661,703
For Capital Adequacy Purposes Ratio		4.50%		4.50%		4.50%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 973,120		$ 973,120		$ 845,509
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		6.40%		6.40%		5.80%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 992,201		$ 992,201		$ 955,793
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		6.50%		6.50%		6.50%
Leverage Ratio
Actual Amount		$ 1,655,164		$ 1,655,164		$ 1,513,219
Actual Ratio		8.60%		8.60%		8.40%
For Capital Adequacy Purposes Amount		$ 769,726		$ 769,726		$ 720,043
For Capital Adequacy Purposes Ratio		4.00%		4.00%		4.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 769,726		$ 769,726		$ 720,043
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		4.00%		4.00%		4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 962,157		$ 962,157		$ 900,053
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		5.00%		5.00%		5.00%
Corporation
Regulatory Capital
Risk weighted assets		$ 15,300,000		$ 15,300,000		$ 14,740,000
Total Capital to Risk-Weighted Assets
Actual Amount		$ 1,792,952		$ 1,792,952		$ 1,614,046
Actual Ratio		11.70%		11.70%		11.00%
For Capital Adequacy Purposes Amount		$ 1,224,203		$ 1,224,203		$ 1,179,076
For Capital Adequacy Purposes Ratio		8.00%		8.00%		8.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,511,126		$ 1,511,126		$ 1,363,307
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		9.90%		9.90%		9.30%
Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,665,786		$ 1,665,786		$ 1,498,463
Actual Ratio		10.90%		10.90%		10.20%
For Capital Adequacy Purposes Amount		$ 918,153		$ 918,153		$ 884,307
For Capital Adequacy Purposes Ratio		6.00%		6.00%		6.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,208,901		$ 1,208,901		$ 1,068,538
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		7.90%		7.90%		7.30%
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,665,786		$ 1,665,786		$ 1,498,463
Actual Ratio		10.90%		10.90%		10.20%
For Capital Adequacy Purposes Amount		$ 688,614		$ 688,614		$ 663,230
For Capital Adequacy Purposes Ratio		4.50%		4.50%		4.50%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 975,537		$ 975,537		$ 847,461
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		6.40%		6.40%		5.80%
Leverage Ratio
Actual Amount		$ 1,665,786		$ 1,665,786		$ 1,498,463
Actual Ratio		8.60%		8.60%		8.30%
For Capital Adequacy Purposes Amount		$ 771,041		$ 771,041		$ 720,890
For Capital Adequacy Purposes Ratio		4.00%		4.00%		4.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 771,041		$ 771,041		$ 720,890
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		4.00%		4.00%		4.00%

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 70,397	$ 40,459	$ 210,981	$ 140,077
Net income allocated to participating securities	40	129	144	566
Net income allocated to common shareholders	$ 70,357	$ 40,330	$ 210,837	$ 139,511
Weighted average common shares - issued (in shares)	71,426,000	71,139,000	71,365,000	71,077,000
Average unvested restricted share awards (in shares)	(41,000)	(228,000)	(49,000)	(290,000)
Weighted average common shares outstanding - basic (in shares)	71,385,000	70,911,000	71,316,000	70,787,000
Effect of dilutive securities
Weighted average common stock equivalents (in shares)	702,000	594,000	691,000	667,000
Weighted average common shares outstanding - diluted (in shares)	72,087,000	71,505,000	72,007,000	71,454,000
EPS available to common shareholders
Basic earnings per common share (dollars per share)	$ 0.99	$ 0.57	$ 2.96	$ 1.98
Diluted earnings per common share (dollars per share)	0.98	0.56	2.93	1.95
Average stock valuation (dollars per share)	$ 56.59	$ 47.68	$ 56.43	$ 49.07
Stock Option
Schedule Of Earnings Per Share By Common Class [Line Items]
Average number of exercisable employee stock option awards that were not included in the computation of diluted earnings per common share (in shares)	58,882	125,280	63,014	102,245

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - Changes in AOCI (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017		Dec. 31, 2016	[2]
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		$ 2,750,999	$ 2,639,442	$ 2,668,749	$ 2,581,526
Cumulative effect adjustment of change in accounting policy, net of tax impact						$ 1,339	[1]	$ 3,659
Other comprehensive (loss) income before reclassifications		(9,893)	8,720	(31,353)	13,627
Amounts reclassified from accumulated other comprehensive income (loss)		(411)	579	(463)	1,579
Other comprehensive income (loss), net of tax		(10,304)	9,299	(31,816)	15,206
Ending balance		2,788,924	2,673,089	2,788,924	2,673,089
Unrealized gains (losses) on securities available-for-sale, net of tax
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		(41,685)	(8,877)	(10,348)	(14,142)
Cumulative effect adjustment of change in accounting policy, net of tax impact						(344)
Beginning balance, adjusted						(10,692)
Other comprehensive (loss) income before reclassifications		(13,141)	895	(44,132)	6,268
Amounts reclassified from accumulated other comprehensive income (loss)		0	(1)	(2)	(109)
Other comprehensive income (loss), net of tax		(13,141)	894	(44,134)	6,159
Ending balance		(54,826)	(7,983)	(54,826)	(7,983)
Defined Benefit Pension Plans
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		(19,584)	(25,195)	(19,808)	(25,894)
Cumulative effect adjustment of change in accounting policy, net of tax impact						0
Beginning balance, adjusted						(19,808)
Other comprehensive (loss) income before reclassifications		0	7,305	0	7,305
Amounts reclassified from accumulated other comprehensive income (loss)		112	349	336	1,048
Other comprehensive income (loss), net of tax		112	7,654	336	8,353
Ending balance		(19,472)	(17,541)	(19,472)	(17,541)
Unrealized gains (losses) on cash flow hedges, net of tax
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		13,918	(57)	4,658	0
Cumulative effect adjustment of change in accounting policy, net of tax impact						3
Beginning balance, adjusted						4,661
Other comprehensive (loss) income before reclassifications		3,248	520	12,779	54
Amounts reclassified from accumulated other comprehensive income (loss)		(523)	231	(797)	640
Other comprehensive income (loss), net of tax		2,725	751	11,982	694
Ending balance		16,643	694	16,643	694
Total
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		(47,351)	(34,129)	(25,498)	(40,036)
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]					(341)
Beginning balance, adjusted						$ (25,839)
Ending balance		$ (57,655)	$ (24,830)	$ (57,655)	$ (24,830)
[1]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies, Note 3, Investment Securities, Note 5, Other Real Estate Owned and Repossessed Assets and Note 9, Derivative Instruments and Balance Sheet Offsetting, for further details on the changes in accounting policy.
[2]	Refer to Note 1, Basis of Presentation and Significant Accounting Policies and Note 7, Loan Servicing Rights for further details on the changes in accounting policy.

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on sale of investment securities	$ 0	$ 1	$ 3	$ 168
Income tax expense	(11,312)	(10,253)	(36,701)	(45,546)
Net income	70,397	40,459	210,981	140,077
Interest on short-term borrowings (interest expense)	159,481	143,628	468,881	411,673
Gains on available-for-sale securities | Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on sale of investment securities	0	1	3	168
Income tax expense	0	0	(1)	(59)
Net income	0	1	2	109
Amortization of defined benefit pension plan items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries, wages and employee benefits (operating expenses)	142	537	426	1,613
Income tax benefit	(30)	(188)	(90)	(565)
Net Loss	112	349	336	1,048
Gains and losses on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax benefit	139	(344)	212	(344)
Gains and losses on cash flow hedges | Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(523)	231	(797)	640
Interest on short-term borrowings (interest expense)	$ (662)	$ 575	$ (1,009)	$ 984