TCF Financial 10-Q 9 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 07, 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	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		71,354,530

Consolidated Statements of Fina

Consolidated Statements of Financial Position - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Cash and cash equivalents:
Cash and cash due from banks	$ 174,173	$ 226,003
Interest-bearing deposits with the Federal Reserve Bank and other banks	379,320	229,988
Total cash and cash equivalents	553,493	455,991
Investment securities:
Carried at fair value	2,297,123	1,963,546
Held-to-maturity, at amortized cost (fair value of $663,621 and $662,906, respectively)	676,847	677,093
Total investment securities	2,973,970	2,640,639
Loans held-for-sale, at fair value	31,636	52,133
Loans	14,218,747	14,155,267
Allowance for loan losses	(94,762)	(91,887)
Net loans	14,123,985	14,063,380
Premises and equipment	126,251	126,896
Loan servicing rights, at fair value	68,837	63,841
Goodwill	1,134,568	1,134,568
Other intangible assets	32,833	34,271
Interest receivable and other assets	710,511	709,154
Total assets	19,756,084	19,280,873
Deposits:
Noninterest-bearing	3,801,125	3,725,779
Interest-bearing	10,166,692	9,917,024
Total deposits	13,967,817	13,642,803
Collateralized customer deposits	490,107	415,236
Short-term borrowings	2,050,000	2,000,000
Long-term borrowings	372,908	372,882
Interest payable and other liabilities	171,975	181,203
Total liabilities	17,052,807	16,612,124
Shareholders’ equity
Preferred stock, no par value: Authorized – 2,000,000 shares at 6/30/2017 and 12/31/2016, none issued	0	0
Common stock, $1.00 par value per share: Authorized — 135,000,000 shares at 6/30/2017 and 100,000,000 shares at 12/31/2016, Issued and outstanding — XX,XXX,XXX shares at 6/30/2017 and 70,599,133 shares at 12/31/2016	71,350	71,207
Additional paid-in capital	2,201,803	2,203,637
Retained earnings	471,178	419,403
Accumulated other comprehensive loss	(41,054)	(25,498)
Total shareholders’ equity	2,703,277	2,668,749
Total liabilities and shareholders’ equity	$ 19,756,084	$ 19,280,873

Consolidated Statements of Fin3

Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Held-to-maturity, fair value	$ 663,621	$ 662,906
Loan servicing rights, at fair value	$ 68,837	$ 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
Servicing Asset at Fair Value, Amount	$ 68,837	$ 63,841
Common stock, shares authorized (in shares)	135,000,000	135,000,000
Common stock, shares issued (in shares)	71,350,127	71,207,114
Common stock, shares outstanding (in shares)	71,350,127	71,207,114

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest income
Interest and fees on loans	$ 156,818	$ 132,485
Interest on investment securities:
Taxable	12,419	4,756
Tax-exempt	5,556	4,235
Dividends on nonmarketable equity securities	1,901	621
Interest on deposits with the Federal Reserve Bank, other banks and Federal funds sold	1,240	799
Total interest income	177,934	142,896
Interest expense
Interest on deposits	15,917	8,916
Interest on collateralized customer deposits	524	150
Interest on short-term borrowings	8,166	1,508
Interest on long-term borrowings	1,464	2,225
Total interest expense	26,071	12,799
Net interest income	151,863	130,097
Provision for loan losses	6,256	4,050
Net interest income after provision for loan losses	145,607	126,047
Noninterest income
Service charges and fees on deposit accounts	8,463	8,004
Wealth management revenue	6,311	5,827
Other charges and fees for customer services	5,754	8,891
Net gain on sale of loans and other mortgage banking revenue	12,535	9,160
Net gain on sale of investment securities	0	90
Other	7,491	6,038
Total noninterest income	40,554	38,010
Operating expenses
Salaries, wages and employee benefits	56,105	59,894
Occupancy	8,011	7,392
Equipment and software	7,659	8,517
Outside processing and service fees	11,332	7,511
Merger expenses	0	4,167
Other	20,251	16,715
Total operating expenses	103,358	104,196
Income before income taxes	82,803	59,861
Income tax expense	12,633	12,257
Net income	$ 70,170	$ 47,604
Earnings per common share:
Basic earnings per common share (dollars per share)	$ 0.99	$ 0.67
Diluted earnings per common share (dollars per share)	0.97	0.67
Cash dividends declared per common share (dollars per share)	$ 0.28	$ 0.27

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 70,170	$ 47,604
Other comprehensive income, net of tax:
Unrealized holding gains (losses) on securities available-for-sale arising during the period	(27,606)	2,739
Reclassification adjustment for gains and losses on realized income	0	(90)
Tax effect	5,797	(927)
Net unrealized gains (losses) on securities available-for-sale, net of tax	(21,809)	1,722
Unrealized gains on interest rate swaps designated as cash flow hedges	7,963	0
Reclassification adjustment for losses included in net income	242	0
Tax effect	(1,723)	0
Net unrealized gains on interest rate swaps designated as cash flow hedges, net of tax	6,482	0
Adjustment for pension and other postretirement benefits	142	537
Tax effect	(30)	(188)
Net adjustment for pension and other postretirement benefits	112	349
Other comprehensive income, net of tax	(15,215)	2,071
Total comprehensive income, net of tax	$ 54,955	$ 49,675

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		49,675						47,604	2,071
Cash dividends declared and paid, $0.82 and $0.79 per share at September 30, 2017 and 2016, respectively		(19,271)						(19,271)
Net shares issued under share-based compensation plans			$ (19,272)		$ 518		$ (19,790)
Share-based compensation expense		3,734		1		3,733
Ending balance at Mar. 31, 2017		2,600,051		71,118		2,194,705		372,193	(37,965)
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		54,955						70,170	(15,215)
Cash dividends declared and paid, $0.82 and $0.79 per share at September 30, 2017 and 2016, respectively		(20,075)						(20,075)
Net shares issued under share-based compensation plans			$ (3,343)		$ 143		$ (3,486)
Share-based compensation expense		1,652		0		1,652
Ending balance at Mar. 31, 2018		$ 2,703,277		$ 71,350		$ 2,201,803		$ 471,178	$ (41,054)
[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 Cha7

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Stockholders' Equity [Abstract]
Cash dividends declared per common share (dollars per share)	$ 0.28	$ 0.27

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 70,170	$ 47,604
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	6,256	4,050
Gains on sales of loans	(1,508)	(6,120)
Proceeds from sales of loans	190,435	191,531
Loans originated for sale	(165,823)	(142,704)
Net gains on sale of investment securities	0	(90)
Net gains from sales/writedowns of other real estate and repossessed assets	(71)	(700)
Depreciation of premises and equipment	4,129	4,521
Amortization of intangible assets	1,438	1,513
Additions to loan servicing rights	(1,967)	(1,753)
Valuation change in loan servicing rights	(3,029)	1,125
Net amortization of premiums and discounts on investment securities	4,298	4,129
Share-based compensation expense	1,652	3,734
Deferred income tax (benefit) expense	(1,638)	17,948
Change in deferred tax valuation allowance	(49)	0
Net decrease (increase) in interest receivable and other assets	12,856	(29,773)
Net decrease in interest payable and other liabilities	(9,060)	(19,282)
Net cash provided by operating activities	108,089	75,733
Debt securities – available-for-sale:
Proceeds from maturities, calls and principal reductions	66,526	60,885
Purchases	(431,670)	(102,702)
Investment securities – held-to-maturity:
Proceeds from maturities, calls and principal reductions	8,744	9,408
Purchases	(8,835)	(33,628)
Net increase in loans	(71,952)	(290,438)
Proceeds from sales of other real estate and repossessed assets	3,351	5,734
Purchases of premises and equipment, net of disposals	(3,484)	(2,272)
Proceeds from returns of investment in equity method investments	266	113
Net cash used in investing activities	(437,054)	(352,900)
Cash flows from financing activities
Net increase in interest- and noninterest-bearing demand deposits and savings accounts	182,108	350,763
Net increase (decrease) in time deposits	142,906	(91,538)
Net increase in collateralized customer deposits and other short-term borrowings	124,871	130,863
Repayment of long-term borrowings	0	(107,000)
Cash dividends paid	(20,075)	(19,271)
Proceeds from directors’ stock plans and exercise of stock options, net of shares withheld	952	1,578
Cash paid for payroll taxes upon conversion of share-based awards	(4,295)	(20,850)
Net cash provided by financing activities	426,467	244,545
Net increase (decrease) in cash and cash equivalents	97,502	(32,622)
Cash and cash equivalents at beginning of period	455,991	474,402
Cash and cash equivalents at end of period	553,493	441,780
Supplemental disclosures of cash flow information:
Interest paid	25,038	12,989
Income tax refunds, net of income taxes paid	(441)	(24,397)
Non-cash activities:
Loans transferred to other real estate and repossessed assets	2,484	4,281
Net transfer of loans held-for-sale to loans held- for-investment	$ (2,607)	$ 0

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	3 Months Ended
	Mar. 31, 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 Midland, 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 seven 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 three months ended March 31, 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 Approximately 79% 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, 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 steadily 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. 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 certain net benefit cost components from salaries, wages and employee benefits expense to other expenses on the Consolidated Statements of Income, which was immaterial. Refer to Note 14, Pension and Other Postretirement Benefit Plans, for further detail. 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. Effective January 1, 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 2018-03 Technical Corrections and Improvements to Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities January 1, 2018

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 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 — available-for-sale, 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 1 valuation for the Corporation includes U.S. Treasury securities that are traded by dealers or brokers in active over-the-counter markets. Valuations are obtained from a third-party pricing service for these investment securities. 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 sponsored agency securities, including securities issued by the Federal Home Loan Bank, 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 securities issued by certain state and political subdivisions, held-to-maturity trust preferred investment securities, 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 classified as available-for-sale are recorded at fair value on a recurring basis. 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 March 31, 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. 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 March 31, 2018 Investment securities – available-for-sale: Government sponsored agencies $ — $ 193,018 $ — $ 193,018 State and political subdivisions — 410,401 — 410,401 Residential mortgage-backed securities — 142,734 — 142,734 Collateralized mortgage obligations — 1,277,976 — 1,277,976 Corporate bonds — 234,916 — 234,916 Trust preferred securities — 36,271 — 36,271 Preferred stock — 1,807 — 1,807 Total investment securities – available-for-sale — 2,297,123 — 2,297,123 Loans held-for-sale — 31,636 — 31,636 Loan servicing rights — — 68,837 68,837 Derivative assets: Customer-initiated derivatives — 11,619 — 11,619 Interest rate lock commitments — 1,774 — 1,774 Power Equity CD — 1,501 — 1,501 Risk management derivatives — 14,104 — 14,104 Total derivatives — 28,998 — 28,998 Total assets at fair value $ — $ 2,357,757 $ 68,837 $ 2,426,594 Derivative liabilities: Customer-initiated derivatives $ — $ 12,055 $ — $ 12,055 Forward contracts related to mortgage loans to be delivered for sale — 404 — 404 Power Equity CD — 1,501 — 1,501 Total derivatives — 13,960 — 13,960 Total liabilities at fair value $ — $ 13,960 $ — $ 13,960 December 31, 2017 Investment securities – available-for-sale: 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 three months ended March 31, 2018 . The following table summarizes the changes in Level 3 assets measured at fair value on a recurring basis. Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 (Dollars in thousands) Loan servicing rights Balance, beginning of period $ 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" 3,029 (1,125 ) New originations 1,967 1,753 Balance, end of period $ 68,837 $ 64,604 (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 March 31, 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) March 31, 2018 December 31, 2017 Aggregate fair value $ 31,636 $ 52,133 Contractual balance 30,800 50,597 Unrealized gain (loss) 836 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 March 31, (Dollars in thousands) 2018 2017 Interest income (1) $ 376 $ 551 Change in fair value (2) (700 ) 601 Net gain on sales of loans (2) 1,508 6,120 Total included in earnings $ 1,184 $ 7,272 (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 a 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 March 31, 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 March 31, 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 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) Total March 31, 2018 Impaired loans $ 54,060 $ 54,060 Other real estate and repossessed assets 2,769 2,769 Total $ 56,829 $ 56,829 December 31, 2017 Impaired loans $ 70,619 $ 70,619 Other real estate and repossessed assets 2,899 2,899 Total $ 73,518 $ 73,518 There were no liabilities recorded at fair value on a nonrecurring basis at both March 31, 2018 and 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 $ 54,060 Appraisal of collateral Discount for type of collateral and age of appraisal 20%-30% Other real estate and repossessed assets 2,769 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. However, the method of estimating fair value for certain financial instruments, such as loans, that are not required to be measured on a recurring or nonrecurring basis, as prescribed by FASB ASC Topic 820, "Fair Value Measurement", does not incorporate the exit-price concept of fair value. 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 present value methods 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, do not necessarily indicate amounts that could 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 March 31, 2018 December 31, 2017 (Dollars in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial assets: Investment securities: Held-to-maturity Level 2 $ 676,347 $ 663,196 $ 676,593 $ 662,516 Held-to-maturity Level 3 500 425 500 390 Net loans (1) Level 3 14,123,985 13,755,579 14,063,380 14,114,545 Financial liabilities: Time deposits Level 2 $ 3,360,113 $ 3,327,989 $ 3,217,207 $ 3,225,847 Collateralized customer deposits Level 2 490,107 488,683 415,236 415,236 Short-term borrowings Level 2 2,050,000 2,049,162 2,000,000 1,999,137 Long-term borrowings Level 2 372,908 368,915 372,882 367,984 (1) Included $54.1 million and $70.6 million of impaired loans recorded at fair value on a nonrecurring basis at March 31, 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	3 Months Ended
	Mar. 31, 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 March 31, 2018 and December 31, 2017 : Investment Securities Carried at Fair Value (Dollars in thousands) Amortized Cost Unrealized Gains (1) Unrealized Losses (1) Fair Value March 31, 2018 Debt securities Government sponsored agencies $ 194,256 $ 436 $ 1,674 $ 193,018 State and political subdivisions 421,564 183 11,346 410,401 Residential mortgage-backed securities 146,736 5 4,007 142,734 Collateralized mortgage obligations 1,300,250 156 22,430 1,277,976 Corporate bonds 238,717 777 4,578 234,916 Trust preferred securities 34,934 1,369 32 36,271 Total debt securities available-for-sale 2,336,457 2,926 44,067 2,295,316 Equity securities Preferred stock 1,389 418 — 1,807 Total equity securities 1,389 418 — 1,807 Total $ 2,337,846 $ 3,344 $ 44,067 $ 2,297,123 December 31, 2017 Debt securities 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 (1) The unrealized gain/loss for equity investment securities formerly in the available-for-sale category was recorded into other comprehensive income prior to January 1, 2018. Following the adoption of ASU No. 2016-01 as of January 1, 2018, the unrealized gain/loss for equity investment securities carried at fair value is recorded to net income and the unrealized gain/loss for available-for-sale debt securities continues to be recorded into other comprehensive income. Investment Securities Held-to-Maturity (Dollars in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value March 31, 2018 State and political subdivisions $ 676,347 $ 2,183 $ 15,334 $ 663,196 Trust preferred securities 500 — 75 425 Total $ 676,847 $ 2,183 $ 15,409 $ 663,621 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 measured 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 carried 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 will be recognized in net income, rather than in accumulated other comprehensive income. As a result, there may be greater volatility in earnings each reporting period related to fair value changes. 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 securities and the associated gains and losses recorded in earnings are listed below: Three Months Ended March 31, (Dollars in thousands) 2018 2017 Proceeds $ — $ — Gross gains — 90 Gross losses — — The following is a summary of the amortized cost and fair value of investment securities at March 31, 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. March 31, 2018 (Dollars in thousands) Amortized Cost Fair Value Investment Securities Carried at Fair Value: Due in one year or less $ 21,498 $ 21,471 Due after one year through five years 131,011 129,135 Due after five years through ten years 397,319 388,757 Due after ten years 1,786,629 1,755,953 Preferred stock 1,389 1,807 Total $ 2,337,846 $ 2,297,123 Investment Securities Held-to-Maturity: Due in one year or less $ 81,162 $ 81,076 Due after one year through five years 241,937 238,254 Due after five years through ten years 162,648 157,828 Due after ten years 191,100 186,463 Total $ 676,847 $ 663,621 Securities with a carrying value of $1.06 billion and $937.2 million were pledged at March 31, 2018 and December 31, 2017 , respectively, to secure borrowings and deposits. At March 31, 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 March 31, 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 March 31, 2018 , the Corporation’s securities portfolio consisted of 2,234 securities, 1,600 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 March 31, 2018 Government sponsored agencies $ 114,568 $ 910 $ 14,236 $ 764 $ 128,804 $ 1,674 State and political subdivisions 577,711 15,991 347,810 10,689 925,521 26,680 Residential mortgage-backed securities 89,157 1,767 53,532 2,240 142,689 4,007 Collateralized mortgage obligations 1,098,199 20,529 88,873 1,901 1,187,072 22,430 Corporate bonds 125,675 3,551 48,557 1,027 174,232 4,578 Trust preferred securities — — 4,274 107 4,274 107 Total $ 2,005,310 $ 42,748 $ 557,282 $ 16,728 $ 2,562,592 $ 59,476 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 March 31, 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 March 31, 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 March 31, 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 March 31, 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	3 Months Ended
	Mar. 31, 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 March 31, 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 personal watercraft and comprised primarily of indirect loans purchased from dealers. These loans 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 $31.6 million at March 31, 2018 and $52.1 million at December 31, 2017 . The Corporation sold loans totaling $190.4 million and $191.5 million during the three months ended March 31, 2018 and 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 March 31, 2018 Commercial loan portfolio: Commercial $ 2,486,533 $ 940,752 $ 3,427,285 Commercial real estate: Owner-occupied 1,185,797 647,027 1,832,824 Non-owner occupied 1,689,022 991,779 2,680,801 Vacant land 43,984 30,767 74,751 Total commercial real estate 2,918,803 1,669,573 4,588,376 Real estate construction and land development 485,474 74,306 559,780 Subtotal 5,890,810 2,684,631 8,575,441 Consumer loan portfolio: Residential mortgage 2,039,349 1,225,271 3,264,620 Consumer installment 1,478,673 93,567 1,572,240 Home equity 603,684 202,762 806,446 Subtotal 4,121,706 1,521,600 5,643,306 Total loans (2) $ 10,012,516 $ 4,206,231 $ 14,218,747 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 $23.9 million and $26.1 million at March 31, 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 March 31, 2018 Balance at beginning of period $ 731,353 $ 95,124 $ 22,496 $ 60,814 $ 17,110 $ 926,897 Accretion recognized in interest income (42,640 ) (6,758 ) (1,156 ) (4,904 ) (3,103 ) (58,561 ) Net reclassification (to) from nonaccretable difference (1) (2,883 ) 1,790 (186 ) (510 ) 2,151 362 Balance at end of period $ 685,830 $ 90,156 $ 21,154 $ 55,400 $ 16,158 $ 868,698 Three Months Ended March 31, 2017 Balance at beginning of period $ 798,210 $ 121,416 $ 27,182 $ 69,847 $ 23,316 $ 1,039,971 Accretion recognized in interest income (44,571 ) (7,266 ) (1,181 ) (3,892 ) (3,277 ) (60,187 ) Net reclassification (to) from nonaccretable difference (1) 21,139 (939 ) 54 (1,058 ) 1,428 20,624 Balance at end of period $ 774,778 $ 113,211 $ 26,055 $ 64,897 $ 21,467 $ 1,000,408 (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 March 31, 2018 and December 31, 2017 : (Dollars in thousands) Pass Special Mention Substandard Doubtful Total March 31, 2018 Originated Portfolio: Commercial $ 2,401,859 $ 37,084 $ 47,590 $ — $ 2,486,533 Commercial real estate: Owner-occupied 1,123,847 16,850 44,789 311 1,185,797 Non-owner occupied 1,652,313 33,895 2,813 1 1,689,022 Vacant land 37,179 53 6,752 — 43,984 Total commercial real estate 2,813,339 50,798 54,354 312 2,918,803 Real estate construction and land development 472,340 9,724 3,410 — 485,474 Subtotal 5,687,538 97,606 105,354 312 5,890,810 Acquired Portfolio: Commercial 830,615 66,480 43,471 186 940,752 Commercial real estate: Owner-occupied 583,937 26,683 36,022 385 647,027 Non-owner occupied 913,327 45,146 33,306 — 991,779 Vacant land 25,632 312 4,823 — 30,767 Total commercial real estate 1,522,896 72,141 74,151 385 1,669,573 Real estate construction and land development 71,736 1,611 959 — 74,306 Subtotal 2,425,247 140,232 118,581 571 2,684,631 Total $ 8,112,785 $ 237,838 $ 223,935 $ 883 $ 8,575,441 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 March 31, 2018 and December 31, 2017 : (Dollars in thousands) Residential Mortgage Consumer Installment Home Equity Total Consumer March 31, 2018 Originated Loans: Performing $ 2,031,728 $ 1,477,751 $ 600,645 $ 4,110,124 Nonperforming 7,621 922 3,039 11,582 Subtotal 2,039,349 1,478,673 603,684 4,121,706 Acquired Loans 1,225,271 93,567 202,762 1,521,600 Total $ 3,264,620 $ 1,572,240 $ 806,446 $ 5,643,306 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) March 31, December 31, Nonperforming assets Nonaccrual loans: Commercial $ 20,000 $ 19,691 Commercial real estate: Owner-occupied 19,855 19,070 Non-owner occupied 5,489 5,270 Vacant land 4,829 5,205 Total commercial real estate 30,173 29,545 Real estate construction and land development 77 77 Residential mortgage 7,621 8,635 Consumer installment 922 842 Home equity 3,039 4,305 Total nonaccrual loans 61,832 63,095 Other real estate owned and repossessed assets 7,719 8,807 Total nonperforming assets $ 69,551 $ 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 $ 322 $ — Commercial real estate: Non-owner occupied — 13 Total commercial real estate — 13 Home equity 913 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 $ 1,235 $ 1,377 The Corporation’s nonaccrual loans at March 31, 2018 and December 31, 2017 included $26.2 million and $29.1 million , respectively, of nonaccrual TDRs. The Corporation had $3.2 million of residential mortgage loans that were in the process of foreclosure at March 31, 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 March 31, 2018 Originated Portfolio: Commercial $ 8,689 $ 6,079 $ 12,122 $ 26,890 $ 2,459,643 $ 2,486,533 $ 322 Commercial real estate: Owner-occupied 10,829 3,368 8,394 22,591 1,163,206 1,185,797 — Non-owner occupied 3,749 897 928 5,574 1,683,448 1,689,022 — Vacant land 675 — 180 855 43,129 43,984 — Total commercial real estate 15,253 4,265 9,502 29,020 2,889,783 2,918,803 — Real estate construction and land development 100 — — 100 485,374 485,474 — Residential mortgage 3,020 246 2,276 5,542 2,033,807 2,039,349 — Consumer installment 2,817 570 257 3,644 1,475,029 1,478,673 — Home equity 3,631 1,360 2,049 7,040 596,644 603,684 913 Total $ 33,510 $ 12,520 $ 26,206 $ 72,236 $ 9,940,280 $ 10,012,516 $ 1,235 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 March 31, 2018 and December 31, 2017 : (Dollars in thousands) Recorded Investment Unpaid Principal Balance Related Valuation Allowance March 31, 2018 Impaired loans with a valuation allowance: Commercial $ 23,500 $ 25,998 $ 1,987 Commercial real estate: Owner-occupied 15,177 19,266 2,510 Non-owner occupied 2,952 5,545 201 Vacant land 1,317 1,520 356 Total commercial real estate 19,446 26,331 3,067 Real estate construction and land development 164 164 26 Residential mortgage 13,434 13,434 1,422 Consumer installment 1,101 1,101 206 Home equity 3,409 3,409 286 Subtotal 61,054 70,437 6,994 Impaired loans with no related valuation allowance: Commercial 14,771 15,637 — Commercial real estate: Owner-occupied 15,435 16,291 — Non-owner occupied 8,122 9,135 — Vacant land 3,854 4,652 — Total commercial real estate 27,411 30,078 — Real estate construction and land development 174 241 — Residential mortgage 5,928 5,928 — Consumer installment — — — Home equity 1,780 1,780 — Subtotal 50,064 53,664 — Total impaired loans: Commercial 38,271 41,635 1,987 Commercial real estate: Owner-occupied 30,612 35,557 2,510 Non-owner occupied 11,074 14,680 201 Vacant land 5,171 6,172 356 Total commercial real estate 46,857 56,409 3,067 Real estate construction and land development 338 405 26 Residential mortgage 19,362 19,362 1,422 Consumer installment 1,101 1,101 206 Home equity 5,189 5,189 286 Total $ 111,118 $ 124,101 $ 6,994 (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 months ended March 31, 2018 and 2017 , and the respective interest income amounts recognized: Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 (Dollars in thousands) Average recorded investment Interest income recognized while on impaired status Average recorded investment Interest income recognized while on impaired status Impaired loans with a valuation allowance: Commercial $ 20,402 $ 165 $ 25,712 $ 224 Commercial real estate: Owner-occupied 14,072 82 14,659 154 Non-owner occupied 3,870 11 3,388 24 Vacant land 3,695 15 1,988 25 Total commercial real estate 21,637 108 20,035 203 Real estate construction and land development 225 2 161 2 Residential mortgage 13,604 117 17,398 155 Consumer installment 906 1 780 1 Home equity 3,694 17 4,071 21 Subtotal $ 60,468 $ 410 $ 68,157 $ 606 Impaired loans with no related valuation allowance: Commercial $ 18,126 $ 95 $ 9,297 $ 30 Commercial real estate: Owner-occupied 15,369 56 9,866 6 Non-owner occupied 7,158 65 9,131 85 Vacant land 1,769 — 4,476 12 Total commercial real estate 24,296 121 23,473 103 Real estate construction and land development 107 1 81 — Residential mortgage 6,138 23 3,808 8 Consumer installment 140 — 215 — Home equity 2,046 7 880 1 Subtotal $ 50,853 $ 247 $ 37,754 $ 142 Total impaired loans: Commercial $ 38,528 $ 260 $ 35,009 $ 254 Commercial real estate: Owner-occupied 29,441 138 24,525 160 Non-owner occupied 11,028 76 12,519 109 Vacant land 5,464 15 6,464 37 Total commercial real estate 45,933 229 43,508 306 Real estate construction and land development 332 3 242 2 Residential mortgage 19,742 140 21,206 163 Consumer installment 1,046 1 995 1 Home equity 5,740 24 4,951 22 Total $ 111,321 $ 657 $ 105,911 $ 748 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 $49.3 million and $48.8 million at March 31, 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 months ended March 31, 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 March 31, 2018 Commercial loan portfolio: Commercial $ 903 $ — $ 1,065 $ 261 18 $ 2,235 $ 2,229 Commercial real estate: Owner-occupied — — 726 482 2 1,208 1,208 Non-owner occupied 68 — — — 1 74 68 Total commercial real estate 68 — 726 482 3 1,282 1,276 Total Commercial 971 — 1,791 743 21 3,517 3,505 Consumer loan portfolio: Residential mortgage 138 — — — 4 142 138 Consumer installment 71 23 28 — 16 128 122 Home equity 185 — 28 — 5 253 213 Total Consumer 394 23 56 — 25 523 473 Total loans $ 1,365 $ 23 $ 1,847 $ 743 46 $ 4,040 $ 3,978 Concession type (Dollars in thousands) Principal Interest Forbearance Total Pre-modification recorded investment Post-modification recorded investment For the three months ended March 31, 2017 Commercial loan portfolio: Commercial $ 50 $ 1,101 $ 579 5 $ 1,739 $ 1,730 Commercial real estate: Owner-occupied 447 75 — 3 522 522 Total commercial real estate 447 75 — 3 522 522 Total Commercial 497 1,176 579 8 2,261 2,252 Consumer loan portfolio: Residential mortgage 98 — — 1 98 98 Consumer installment 10 — — 2 11 10 Home equity 111 — — 1 165 111 Total Consumer 219 — — 4 274 219 Total loans $ 716 $ 1,176 $ 579 12 $ 2,535 $ 2,471 The pre-modification and post-modification recorded investment represents amounts as of the date of loan modification. The difference between the pre-modification and post-modification recorded investment of residential mortgage TDRs represents impairment recognized by the Corporation through the provision for loan losses computed based on a loan's post-modification present value of expected future cash flows discounted at the loan's original effective interest rate. The following schedule presents the Corporation's TDRs at March 31, 2018 and December 31, 2017 : (Dollars in thousands) Accruing TDRs Nonaccrual TDRs Total March 31, 2018 Commercial loan portfolio $ 35,216 $ 21,914 $ 57,130 Consumer loan portfolio 14,070 4,265 18,335 Total $ 49,286 $ 26,179 $ 75,465 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 The following schedule includes TDRs for which there was a payment default during the three months ended March 31, 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 March 31, 2018 (Dollars in thousands) Number of loans Principal balance Commercial loan portfolio (commercial) 1 $ 82 Consumer loan portfolio (residential mortgage) 1 3 Total 2 $ 85 For The Three Months Ended March 31, 2017 (Dollars in thousands) Number of loans Principal balance Commercial loan portfolio (commercial) 3 $ 620 Consumer loan portfolio (residential mortgage) 2 105 Total 5 $ 725 Commitments to lend additional funds to borrowers whose terms have been modified in TDRs totaled $1.6 million and $2 thousand at March 31, 2018 and December 31, 2017 , respectively. Allowance for Loan Losses The following schedule presents, by loan portfolio segment, the changes in the allowance for the originated loan portfolio for the three months ended March 31, 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 March 31, 2018: Beginning balance $ 66,133 $ 25,754 $ 91,887 Provision for loan losses 3,400 2,856 6,256 Charge-offs (2,594 ) (2,230 ) (4,824 ) Recoveries 805 638 1,443 Ending balance $ 67,744 $ 27,018 $ 94,762 Changes in allowance for loan losses for the three months ended March 31, 2017: Beginning balance $ 51,201 $ 27,067 $ 78,268 Provision for loan losses 4,392 (342 ) 4,050 Charge-offs (2,691 ) (2,883 ) (5,574 ) Recoveries 1,413 617 2,030 Ending balance $ 54,315 $ 24,459 $ 78,774 The following schedule presents by loan portfolio segment, details regarding the balance in the allowance and the recorded investment in loans at March 31, 2018 and December 31, 2017 by impairment evaluation method. (Dollars in thousands) Commercial Consumer Total Allowance for loan losses balance at March 31, 2018 attributable to: Loans individually evaluated for impairment $ 5,080 $ 1,914 $ 6,994 Loans collectively evaluated for impairment 62,664 25,104 87,768 Loans acquired with deteriorated credit quality

Other Real Estate Owned and Rep

Other Real Estate Owned and Repossessed Assets	3 Months Ended
	Mar. 31, 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) 1,638 846 Net payments received (103 ) — Disposals (1,678 ) (951 ) Write-downs (651 ) — Balance at March 31, 2018 $ 7,199 $ 520 Balance at January 1, 2017 $ 16,812 $ 375 Additions (1) 3,119 1,162 Net payments received (39 ) — Disposals (3,728 ) (1,037 ) Write-downs (269 ) — Balance at March 31, 2017 $ 15,895 $ 500 (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 March 31, 2018 , the Corporation had $0.6 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 $3.2 million of consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process as of March 31, 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 March 31, 2018 Net gain (loss) on sale $ 756 $ (34 ) Write-downs (651 ) — Net operating expenses (397 ) (1 ) Total $ (292 ) $ (35 ) For the three months ended March 31, 2017 Net gain (loss) on sale $ 1,047 $ (78 ) Write-downs (269 ) — Net operating expenses (508 ) (3 ) Total $ 270 $ (81 )

Goodwill

Goodwill	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Goodwill was $1.13 billion at both March 31, 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 March 31, 2018 and that the Corporation's goodwill was no t impaired at March 31, 2018 .

Loan Servicing Rights

Loan Servicing Rights	3 Months Ended
	Mar. 31, 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 March 31, 2018 Fair value, beginning of period $ 427 $ 63,414 $ 63,841 Additions from loans sold with servicing retained 43 1,924 1,967 Changes in fair value due to: Reductions from pay-offs, pay downs and run-off (29 ) (694 ) (723 ) Changes in estimates of fair value (1) — 3,752 3,752 Fair value, end of period $ 441 $ 68,396 $ 68,837 Principal balance of loans serviced $ 42,032 $ 7,018,307 $ 7,060,339 For the three months ended March 31, 2017 0 0 0 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 — 1,753 1,753 Changes in fair value due to: 0 Reductions from pay-offs, pay downs and run-off (24 ) (582 ) (606 ) Changes in estimates of fair value (1) — (519 ) (519 ) Fair value, end of period $ 320 $ 64,284 $ 64,604 Principal balance of loans serviced $ 50,942 $ 7,253,396 $ 7,304,338 (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 March 31, 2018 and December 31, 2017 . Mortgage As of March 31, 2018 Prepayment speed 0.0 - 36.6% Weighted average ("WA") discount rate 10.1 % WA cost to service/per year $ 66 WA ancillary income/per year $ 31 WA float range 1.9 % 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 $4.6 million and $4.5 million for the three months ended March 31, 2018 and 2017 , respectively.

Other Intangible Assets

Other Intangible Assets	3 Months Ended
	Mar. 31, 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) March 31, December 31, Core deposit intangible assets $ 32,833 $ 34,259 Non-compete intangible assets — 12 Total other intangible assets $ 32,833 $ 34,271 Core Deposit Intangible Assets The Corporation recorded core deposit intangible assets associated with each of its acquisitions. 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 7.3 years as of March 31, 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) March 31, December 31, Gross original amount $ 56,456 $ 59,143 Accumulated amortization 23,623 24,884 Net carrying amount $ 32,833 $ 34,259 Amortization expense recognized on core deposit intangible assets was $1.4 million and $1.5 million for the three months ended March 31, 2018 and 2017 , respectively. The estimated future amortization expense on core deposit intangible assets for periods ending after March 31, 2018 is as follows: 2018 — $4.3 million ; 2019 — $5.4 million ; 2020 — $4.9 million ; 2021 — $4.5 million ; 2022 — $4.2 million ; 2023 and thereafter — $9.5 million .

Derivative Instruments and Bala

Derivative Instruments and Balance Sheet Offsetting	3 Months Ended
	Mar. 31, 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, customer-initiated derivatives, and, therefore, are not used for interest rate risk management purposes. These derivatives primarily consist of interest rate swaps and interest rate caps and floors. 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 exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. 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 hedges, 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 swaps. 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. March 31, 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 $ 620,000 $ 14,104 $ — $ 620,000 $ 5,899 $ — Total risk management purposes 620,000 14,104 — 620,000 5,899 — Customer-initiated and mortgage banking derivatives: Customer-initiated derivatives 1,615,445 11,619 12,055 1,365,119 9,376 10,139 Forward contracts related to mortgage loans to be delivered for sale 137,066 — 404 115,996 — 34 Interest rate lock commitments 112,938 1,774 — 71,003 1,222 — Power Equity CD 38,660 1,501 1,501 38,807 2,184 2,184 Total customer-initiated and mortgage banking derivatives 1,904,109 14,894 13,960 1,590,925 12,782 12,357 Total gross derivatives $ 2,524,109 $ 28,998 $ 13,960 $ 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 $416 thousand at March 31, 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 March 31, (Dollars in thousands) Location of Gain (Loss) 2018 2017 Forward contracts related to mortgage loans to be delivered for sale Net gain (loss) on sale of loans and other mortgage banking revenue $ (370 ) $ (977 ) Interest rate lock commitments Net gain (loss) on sale of loans and other mortgage banking revenue 552 1,223 Customer-initiated derivatives Other noninterest income 327 (231 ) Total gain (loss) recognized in income $ 509 $ 15 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 months ended March 31, 2018 . There were no interest rate swaps designated as cash flow hedges outstanding during the three months ended March 31, 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 March 31, 2018 Interest rate swaps designated as cash flow hedges $ 7,963 $ (242 ) At March 31, 2018 , the Corporation expected $3.3 million of unrealized losses 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 March 31, 2018 Offsetting derivative assets Derivative assets (1) $ 25,698 $ — $ 25,698 $ — $ (17,243 ) $ 8,455 Offsetting derivative liabilities Derivative liabilities (1) 12,009 — 12,009 — 230 11,779 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, 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	3 Months Ended
	Mar. 31, 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 additional 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 March 31, 2018 and 2017 , respectively. The Corporation's remaining investment in qualified affordable housing projects accounted for under the proportional amortization method totaled $53.0 million at March 31, 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 $15.6 million and $17.3 million at March 31, 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 $46.8 million and $48.1 million at March 31, 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 March 31, 2018 a federal housing tax credit was placed into service resulting in an income tax benefit of $1.5 million , partially offset by impairment expense of $1.6 million , representing $1.3 million net of tax, recorded in "other noninterest expense." There were no impairment losses recognized during the three months ended March 31, 2017 . 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	3 Months Ended
	Mar. 31, 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 March 31, 2018 and December 31, 2017 , the Corporation had $189.7 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 March 31, 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 both March 31, 2018 and December 31, 2017 , the Corporation had $3.03 billion of commitments to extend credit. The Corporation had undisbursed loan commitments of $492.4 million and $571.0 million at March 31, 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 $1.5 million and $1.2 million at March 31, 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 $12.5 million and $13.3 million at March 31, 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 $12.2 million and $12.8 million at March 31, 2018 and December 31, 2017 , respectively. In the event of nonperformance, the Corporation has rights to the underlying collateral securing the loans. At both March 31, 2018 and December 31, 2017 , the Corporation had recorded a liability of $0.2 million 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 March 31, 2018 and December 31, 2017 , the liability recorded in connection with these representations and warranties totaled $5.1 million and $5.3 million , respectively. A summary of the reserve for representations and warranties of the Corporation is as follows: Three Months Ended March 31, (Dollars in thousands) 2018 2017 Reserve balance at beginning of period $ 5,349 $ 6,459 Reserve reduction (244 ) (770 ) Charge-offs — — Ending reserve balance $ 5,105 $ 5,689 (Dollars in thousands) March 31, 2018 December 31, 2017 Reserve balance Liability for specific claims $ 477 $ 531 General allowance 4,628 4,818 Total reserve balance $ 5,105 $ 5,349

Borrowings and Other Short-Term

Borrowings and Other Short-Term Liabilities	3 Months Ended
	Mar. 31, 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: March 31, 2018 December 31, 2017 (Dollars in thousands) Amount Weighted Average Rate (1) Amount Weighted Average Rate (1) Short-term borrowings: FHLB advances: 1.57% - 1.89% fixed-rate notes $ 2,050,000 1.75 % $ 2,000,000 1.39 % Long-term borrowings: FHLB advances: 0.92% - 2.60% fixed-rate notes due 2018 to 2020 (2) 337,179 1.26 337,204 1.26 Line-of-credit: floating-rate based on one-month LIBOR plus 1.75% 19,968 3.40 19,963 3.10 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 (3) 11,461 4.14 11,425 3.69 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 3.25% due in 2032 (4) 4,300 4.94 4,290 4.59 Total long-term borrowings 372,908 1.51 372,882 1.47 Total borrowings $ 2,422,908 1.71 % $ 2,372,882 1.40 % Other short-term liabilities: Collateralized customer deposits $ 490,107 0.60 % $ 415,236 0.44 % (1) Weighted average rate presented is the contractual rate which excludes premiums and discounts related to purchase accounting. (2) The March 31, 2018 balances include advances payable of $337.0 million and purchase accounting premiums of $0.2 million . The December 31, 2017 balance includes advances payable of $337.0 million and purchase accounting premiums of $0.2 million . (3) The March 31, 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 March 31, 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 $7.36 billion as of March 31, 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 $143.6 million at March 31, 2018 . Effective January 1, 2018, the Corporation adopted ASU 2016-01. As a result, the Corporation will continue to report FHLB and FRB stock at cost. The line-of-credit agreement contains certain restrictive covenants. The Corporation was in compliance with all of the covenants at March 31, 2018 .

Revenue from Contracts with Cus

Revenue from Contracts with Customers	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
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 transfer, 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 March 31, (Dollars in thousands) 2018 Noninterest income Service charges and fees on deposit accounts $ 4,463 Wealth management revenue 784 Other charges and fees for customer services 2,398 Noninterest income from contracts with customers within the scope of ASC 606 7,645 Noninterest income within the scope of other GAAP topics 32,909 Total noninterest income $ 40,554 Noninterest expense Other $ (722 ) 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 March 31, 2018 and December 31, 2017, the Corporation did not have a material amount of contract balances.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 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 March 31, 2018 and 2017 , share-based compensation expense related to share-based awards totaled $1.7 million and $3.8 million , respectively. The excess tax benefit realized from share-based compensation transactions during the three months ended March 31, 2018 and 2017 was $1.4 million and $6.1 million , respectively. During the three months ended March 31, 2018 , the Corporation granted 275,355 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 March 31, 2018 , there were 1,346,965 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 Bancorp, Inc. 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 three months ended March 31, 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 — — — (186,434 ) 20.24 Vested (77,388 ) 37.01 6.93 — — Outstanding at March 31, 2018 253,482 $ 38.26 $ 7.14 924,484 $ 31.44 Exercisable/vested at March 31, 2018 671,002 $ 28.86 The weighted-average remaining contractual terms were 6.5 years for all outstanding stock options and 5.9 years for exercisable stock options at March 31, 2018 . The intrinsic value of all outstanding in-the-money stock options and exercisable in-the-money stock options was $21.5 million and $17.3 million , respectively, at March 31, 2018 . The aggregate intrinsic values of outstanding and exercisable options at March 31, 2018 were calculated based on the closing market price of the Corporation’s common stock on March 31, 2018 of $54.68 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 March 31, 2017 was $29.0 million . Total cash received from options exercises during the three months ended March 31, 2018 and 2017 was $0.9 million and $0.9 million , respectively, resulting in the issuance of 100,885 shares and 496,000 shares, respectively. At March 31, 2018 , unrecognized compensation expense related to stock options totaled $1.8 million and is expected to be recognized over a remaining weighted average period of 3.3 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 three months ended March 31, 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 275,355 54.28 Converted into shares of common stock (61,342 ) 27.87 Outstanding at March 31, 2018 594,953 $ 48.68 At March 31, 2018 , unrecognized compensation expense related to RSUs totaled $21.9 million and is expected to be recognized over a remaining weighted average period of 3.6 years . Restricted Stock Awards The Corporation assumed restricted stock awards in the merger with Talmer Bancorp, Inc. 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 restricted stock awards 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 (41,614 ) 46.23 Nonvested at March 31, 2018 41,614 $ 46.23 At March 31, 2018 , unrecognized compensation expense related to nonvested restricted stock awards totaled $1.7 million and is expected to be recognized over a remaining weighted average period of 0.9 years.

Pension and Other Postretiremen

Pension and Other Postretirement Benefit Plans	3 Months Ended
	Mar. 31, 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 March 31, 2018 . The Pension Plan is fully funded as of March 31, 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 March 31, 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 March 31, (Dollars in thousands) 2018 2017 Defined Benefit Pension Plans Service cost (1) $ — $ 233 Interest cost 1,092 1,302 Expected return on plan assets (2,220 ) (2,217 ) Amortization of unrecognized net loss 178 578 Net periodic benefit cost (income) (2) $ (950 ) $ (104 ) Postretirement Benefit Plan Service cost (1) $ 1 $ 1 Interest cost 20 24 Amortization of unrecognized net gain (36 ) (41 ) Net periodic benefit cost (income) (2) $ (15 ) $ (16 ) (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 $2.8 million and $2.5 million for the three months ended March 31, 2018 and 2017 , respectively. The 401(k) Savings Plan provides employees with the option to invest in the Corporation's common stock.

Regulatory Capital

Regulatory Capital	3 Months Ended
	Mar. 31, 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 March 31, 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 the 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 the 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 March 31, 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 $14.84 billion and $14.80 billion at March 31, 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 March 31, 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 that notification 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 March 31, 2018 Total Capital to Risk-Weighted Assets Corporation $ 1,662,561 11.2 % $ 1,186,869 8.0 % $ 1,465,041 9.9 % N/A N/A Chemical Bank 1,655,547 11.2 1,184,378 8.0 1,461,966 9.9 $ 1,480,472 10.0 % Tier 1 Capital to Risk-Weighted Assets Corporation 1,544,016 10.4 890,152 6.0 1,168,324 7.9 N/A N/A Chemical Bank 1,552,763 10.5 888,283 6.0 1,165,872 7.9 1,184,378 8.0 Common Equity Tier 1 Capital to Risk-Weighted Assets Corporation 1,544,016 10.4 667,614 4.5 945,786 6.4 N/A N/A Chemical Bank 1,552,763 10.5 666,213 4.5 943,801 6.4 962,307 6.5 Leverage Ratio Corporation 1,544,016 8.4 731,240 4.0 731,240 4.0 N/A N/A Chemical Bank 1,552,763 8.5 730,292 4.0 730,292 4.0 912,865 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 4.5 854,509 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 April 24, 2018, a cash dividend on the Corporation's common stock of $0.28 per share was declared. The dividend will be paid on June 15, 2018 to shareholders of record as of June 1, 2018.

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share 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 March 31, (In thousands, except per share data) 2018 2017 Net income $ 70,170 $ 47,604 Net income allocated to participating securities 64 226 Net income allocated to common shareholders (1) $ 70,106 $ 47,378 Weighted average common shares - issued 71,297 70,969 Average unvested restricted share awards (66 ) (341 ) Weighted average common shares outstanding - basic 71,231 70,628 Effect of dilutive securities Weighted average common stock equivalents 675 787 Weighted average common shares outstanding - diluted 71,906 71,415 EPS available to common shareholders Basic earnings per common share $ 0.99 $ 0.67 Diluted earnings per common share $ 0.97 $ 0.67 (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 and warrants 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 $56.23 per share and $51.81 per share for the three months ended March 31, 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 71,046 and zero for the three months ended March 31, 2018 and 2017, respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 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 months ended March 31, 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 March 31, 2018 Beginning balance at December 31, 2017 $ (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 income before reclassifications (21,809 ) — 6,291 (15,518 ) Amounts reclassified from accumulated other comprehensive income — 112 191 303 Net current period other comprehensive income (21,809 ) 112 6,482 (15,215 ) Ending balance $ (32,501 ) $ (19,696 ) $ 11,143 $ (41,054 ) For the three months ended March 31, 2017 Beginning balance $ (14,142 ) $ (25,894 ) $ — $ (40,036 ) Other comprehensive loss before reclassifications 1,780 — — 1,780 Amounts reclassified from accumulated other comprehensive income (58 ) 349 — 291 Net current period other comprehensive income (loss) 1,722 349 — 2,071 Ending balance $ (12,420 ) $ (25,545 ) $ — $ (37,965 ) (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 months ended March 31, 2018 , and 2017 : (Dollars in thousands) Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Income Statement Three Months Ended March 31, 2018 2017 Gains and losses on available-for-sale securities $ — $ 90 Net gain on sale of investment securities (noninterest income) — (32 ) Income tax (expense)/benefit $ — $ 58 Net Income Amortization of defined benefit pension plan items $ 142 $ 537 Salaries, wages and employee benefits (operating expenses) (30 ) (188 ) Income tax (expense)/benefit $ 112 $ 349 Net Income Gains and losses on cash flow hedges $ 242 $ — Interest on short-term borrowings (interest expense) (51 ) — Income tax (expense)/benefit $ 191 $ — Net Income

Basis of Presentation and Sig27

Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 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 Midland, 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 seven 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 three months ended March 31, 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 Principles	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 Approximately 79% 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, 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 steadily 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. 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 certain net benefit cost components from salaries, wages and employee benefits expense to other expenses on the Consolidated Statements of Income, which was immaterial. Refer to Note 14, Pension and Other Postretirement Benefit Plans, for further detail. 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. Effective January 1, 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 2018-03 Technical Corrections and Improvements to Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities January 1, 2018

Basis of Presentation and Sig28

Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 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 Approximately 79% 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, 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 steadily 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. 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 certain net benefit cost components from salaries, wages and employee benefits expense to other expenses on the Consolidated Statements of Income, which was immaterial. Refer to Note 14, Pension and Other Postretirement Benefit Plans, for further detail. 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. Effective January 1, 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 2018-03 Technical Corrections and Improvements to Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities January 1, 2018

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2018 Investment securities – available-for-sale: Government sponsored agencies $ — $ 193,018 $ — $ 193,018 State and political subdivisions — 410,401 — 410,401 Residential mortgage-backed securities — 142,734 — 142,734 Collateralized mortgage obligations — 1,277,976 — 1,277,976 Corporate bonds — 234,916 — 234,916 Trust preferred securities — 36,271 — 36,271 Preferred stock — 1,807 — 1,807 Total investment securities – available-for-sale — 2,297,123 — 2,297,123 Loans held-for-sale — 31,636 — 31,636 Loan servicing rights — — 68,837 68,837 Derivative assets: Customer-initiated derivatives — 11,619 — 11,619 Interest rate lock commitments — 1,774 — 1,774 Power Equity CD — 1,501 — 1,501 Risk management derivatives — 14,104 — 14,104 Total derivatives — 28,998 — 28,998 Total assets at fair value $ — $ 2,357,757 $ 68,837 $ 2,426,594 Derivative liabilities: Customer-initiated derivatives $ — $ 12,055 $ — $ 12,055 Forward contracts related to mortgage loans to be delivered for sale — 404 — 404 Power Equity CD — 1,501 — 1,501 Total derivatives — 13,960 — 13,960 Total liabilities at fair value $ — $ 13,960 $ — $ 13,960 December 31, 2017 Investment securities – available-for-sale: 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 March 31, 2018 Three Months Ended March 31, 2017 (Dollars in thousands) Loan servicing rights Balance, beginning of period $ 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" 3,029 (1,125 ) New originations 1,967 1,753 Balance, end of period $ 68,837 $ 64,604 (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) March 31, 2018 December 31, 2017 Aggregate fair value $ 31,636 $ 52,133 Contractual balance 30,800 50,597 Unrealized gain (loss) 836 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 March 31, (Dollars in thousands) 2018 2017 Interest income (1) $ 376 $ 551 Change in fair value (2) (700 ) 601 Net gain on sales of loans (2) 1,508 6,120 Total included in earnings $ 1,184 $ 7,272 (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) Total March 31, 2018 Impaired loans $ 54,060 $ 54,060 Other real estate and repossessed assets 2,769 2,769 Total $ 56,829 $ 56,829 December 31, 2017 Impaired loans $ 70,619 $ 70,619 Other real estate and repossessed assets 2,899 2,899 Total $ 73,518 $ 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 $ 54,060 Appraisal of collateral Discount for type of collateral and age of appraisal 20%-30% Other real estate and repossessed assets 2,769 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 March 31, 2018 December 31, 2017 (Dollars in thousands) Carrying Amount Fair Value Carrying Amount Fair Value Financial assets: Investment securities: Held-to-maturity Level 2 $ 676,347 $ 663,196 $ 676,593 $ 662,516 Held-to-maturity Level 3 500 425 500 390 Net loans (1) Level 3 14,123,985 13,755,579 14,063,380 14,114,545 Financial liabilities: Time deposits Level 2 $ 3,360,113 $ 3,327,989 $ 3,217,207 $ 3,225,847 Collateralized customer deposits Level 2 490,107 488,683 415,236 415,236 Short-term borrowings Level 2 2,050,000 2,049,162 2,000,000 1,999,137 Long-term borrowings Level 2 372,908 368,915 372,882 367,984 (1) Included $54.1 million and $70.6 million of impaired loans recorded at fair value on a nonrecurring basis at March 31, 2018 and December 31, 2017 , respectively.

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2018 and December 31, 2017 : Investment Securities Carried at Fair Value (Dollars in thousands) Amortized Cost Unrealized Gains (1) Unrealized Losses (1) Fair Value March 31, 2018 Debt securities Government sponsored agencies $ 194,256 $ 436 $ 1,674 $ 193,018 State and political subdivisions 421,564 183 11,346 410,401 Residential mortgage-backed securities 146,736 5 4,007 142,734 Collateralized mortgage obligations 1,300,250 156 22,430 1,277,976 Corporate bonds 238,717 777 4,578 234,916 Trust preferred securities 34,934 1,369 32 36,271 Total debt securities available-for-sale 2,336,457 2,926 44,067 2,295,316 Equity securities Preferred stock 1,389 418 — 1,807 Total equity securities 1,389 418 — 1,807 Total $ 2,337,846 $ 3,344 $ 44,067 $ 2,297,123 December 31, 2017 Debt securities 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 March 31, 2018 State and political subdivisions $ 676,347 $ 2,183 $ 15,334 $ 663,196 Trust preferred securities 500 — 75 425 Total $ 676,847 $ 2,183 $ 15,409 $ 663,621 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 securities and the associated gains and losses recorded in earnings are listed below: Three Months Ended March 31, (Dollars in thousands) 2018 2017 Proceeds $ — $ — Gross gains — 90 Gross losses — —
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 March 31, 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. March 31, 2018 (Dollars in thousands) Amortized Cost Fair Value Investment Securities Carried at Fair Value: Due in one year or less $ 21,498 $ 21,471 Due after one year through five years 131,011 129,135 Due after five years through ten years 397,319 388,757 Due after ten years 1,786,629 1,755,953 Preferred stock 1,389 1,807 Total $ 2,337,846 $ 2,297,123 Investment Securities Held-to-Maturity: Due in one year or less $ 81,162 $ 81,076 Due after one year through five years 241,937 238,254 Due after five years through ten years 162,648 157,828 Due after ten years 191,100 186,463 Total $ 676,847 $ 663,621
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 March 31, 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 March 31, 2018 , the Corporation’s securities portfolio consisted of 2,234 securities, 1,600 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 March 31, 2018 Government sponsored agencies $ 114,568 $ 910 $ 14,236 $ 764 $ 128,804 $ 1,674 State and political subdivisions 577,711 15,991 347,810 10,689 925,521 26,680 Residential mortgage-backed securities 89,157 1,767 53,532 2,240 142,689 4,007 Collateralized mortgage obligations 1,098,199 20,529 88,873 1,901 1,187,072 22,430 Corporate bonds 125,675 3,551 48,557 1,027 174,232 4,578 Trust preferred securities — — 4,274 107 4,274 107 Total $ 2,005,310 $ 42,748 $ 557,282 $ 16,728 $ 2,562,592 $ 59,476 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)	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Summary of loans under portfolio	A summary of the Corporation's loans follows: (Dollars in thousands) Originated Acquired (1) Total Loans March 31, 2018 Commercial loan portfolio: Commercial $ 2,486,533 $ 940,752 $ 3,427,285 Commercial real estate: Owner-occupied 1,185,797 647,027 1,832,824 Non-owner occupied 1,689,022 991,779 2,680,801 Vacant land 43,984 30,767 74,751 Total commercial real estate 2,918,803 1,669,573 4,588,376 Real estate construction and land development 485,474 74,306 559,780 Subtotal 5,890,810 2,684,631 8,575,441 Consumer loan portfolio: Residential mortgage 2,039,349 1,225,271 3,264,620 Consumer installment 1,478,673 93,567 1,572,240 Home equity 603,684 202,762 806,446 Subtotal 4,121,706 1,521,600 5,643,306 Total loans (2) $ 10,012,516 $ 4,206,231 $ 14,218,747 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 $23.9 million and $26.1 million at March 31, 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 March 31, 2018 Balance at beginning of period $ 731,353 $ 95,124 $ 22,496 $ 60,814 $ 17,110 $ 926,897 Accretion recognized in interest income (42,640 ) (6,758 ) (1,156 ) (4,904 ) (3,103 ) (58,561 ) Net reclassification (to) from nonaccretable difference (1) (2,883 ) 1,790 (186 ) (510 ) 2,151 362 Balance at end of period $ 685,830 $ 90,156 $ 21,154 $ 55,400 $ 16,158 $ 868,698 Three Months Ended March 31, 2017 Balance at beginning of period $ 798,210 $ 121,416 $ 27,182 $ 69,847 $ 23,316 $ 1,039,971 Accretion recognized in interest income (44,571 ) (7,266 ) (1,181 ) (3,892 ) (3,277 ) (60,187 ) Net reclassification (to) from nonaccretable difference (1) 21,139 (939 ) 54 (1,058 ) 1,428 20,624 Balance at end of period $ 774,778 $ 113,211 $ 26,055 $ 64,897 $ 21,467 $ 1,000,408 (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 March 31, 2018 and December 31, 2017 : (Dollars in thousands) Pass Special Mention Substandard Doubtful Total March 31, 2018 Originated Portfolio: Commercial $ 2,401,859 $ 37,084 $ 47,590 $ — $ 2,486,533 Commercial real estate: Owner-occupied 1,123,847 16,850 44,789 311 1,185,797 Non-owner occupied 1,652,313 33,895 2,813 1 1,689,022 Vacant land 37,179 53 6,752 — 43,984 Total commercial real estate 2,813,339 50,798 54,354 312 2,918,803 Real estate construction and land development 472,340 9,724 3,410 — 485,474 Subtotal 5,687,538 97,606 105,354 312 5,890,810 Acquired Portfolio: Commercial 830,615 66,480 43,471 186 940,752 Commercial real estate: Owner-occupied 583,937 26,683 36,022 385 647,027 Non-owner occupied 913,327 45,146 33,306 — 991,779 Vacant land 25,632 312 4,823 — 30,767 Total commercial real estate 1,522,896 72,141 74,151 385 1,669,573 Real estate construction and land development 71,736 1,611 959 — 74,306 Subtotal 2,425,247 140,232 118,581 571 2,684,631 Total $ 8,112,785 $ 237,838 $ 223,935 $ 883 $ 8,575,441 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 March 31, 2018 and December 31, 2017 : (Dollars in thousands) Residential Mortgage Consumer Installment Home Equity Total Consumer March 31, 2018 Originated Loans: Performing $ 2,031,728 $ 1,477,751 $ 600,645 $ 4,110,124 Nonperforming 7,621 922 3,039 11,582 Subtotal 2,039,349 1,478,673 603,684 4,121,706 Acquired Loans 1,225,271 93,567 202,762 1,521,600 Total $ 3,264,620 $ 1,572,240 $ 806,446 $ 5,643,306 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) March 31, December 31, Nonperforming assets Nonaccrual loans: Commercial $ 20,000 $ 19,691 Commercial real estate: Owner-occupied 19,855 19,070 Non-owner occupied 5,489 5,270 Vacant land 4,829 5,205 Total commercial real estate 30,173 29,545 Real estate construction and land development 77 77 Residential mortgage 7,621 8,635 Consumer installment 922 842 Home equity 3,039 4,305 Total nonaccrual loans 61,832 63,095 Other real estate owned and repossessed assets 7,719 8,807 Total nonperforming assets $ 69,551 $ 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 $ 322 $ — Commercial real estate: Non-owner occupied — 13 Total commercial real estate — 13 Home equity 913 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 $ 1,235 $ 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 March 31, 2018 Originated Portfolio: Commercial $ 8,689 $ 6,079 $ 12,122 $ 26,890 $ 2,459,643 $ 2,486,533 $ 322 Commercial real estate: Owner-occupied 10,829 3,368 8,394 22,591 1,163,206 1,185,797 — Non-owner occupied 3,749 897 928 5,574 1,683,448 1,689,022 — Vacant land 675 — 180 855 43,129 43,984 — Total commercial real estate 15,253 4,265 9,502 29,020 2,889,783 2,918,803 — Real estate construction and land development 100 — — 100 485,374 485,474 — Residential mortgage 3,020 246 2,276 5,542 2,033,807 2,039,349 — Consumer installment 2,817 570 257 3,644 1,475,029 1,478,673 — Home equity 3,631 1,360 2,049 7,040 596,644 603,684 913 Total $ 33,510 $ 12,520 $ 26,206 $ 72,236 $ 9,940,280 $ 10,012,516 $ 1,235 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 March 31, 2018 and December 31, 2017 : (Dollars in thousands) Recorded Investment Unpaid Principal Balance Related Valuation Allowance March 31, 2018 Impaired loans with a valuation allowance: Commercial $ 23,500 $ 25,998 $ 1,987 Commercial real estate: Owner-occupied 15,177 19,266 2,510 Non-owner occupied 2,952 5,545 201 Vacant land 1,317 1,520 356 Total commercial real estate 19,446 26,331 3,067 Real estate construction and land development 164 164 26 Residential mortgage 13,434 13,434 1,422 Consumer installment 1,101 1,101 206 Home equity 3,409 3,409 286 Subtotal 61,054 70,437 6,994 Impaired loans with no related valuation allowance: Commercial 14,771 15,637 — Commercial real estate: Owner-occupied 15,435 16,291 — Non-owner occupied 8,122 9,135 — Vacant land 3,854 4,652 — Total commercial real estate 27,411 30,078 — Real estate construction and land development 174 241 — Residential mortgage 5,928 5,928 — Consumer installment — — — Home equity 1,780 1,780 — Subtotal 50,064 53,664 — Total impaired loans: Commercial 38,271 41,635 1,987 Commercial real estate: Owner-occupied 30,612 35,557 2,510 Non-owner occupied 11,074 14,680 201 Vacant land 5,171 6,172 356 Total commercial real estate 46,857 56,409 3,067 Real estate construction and land development 338 405 26 Residential mortgage 19,362 19,362 1,422 Consumer installment 1,101 1,101 206 Home equity 5,189 5,189 286 Total $ 111,118 $ 124,101 $ 6,994 (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 months ended March 31, 2018 and 2017 , and the respective interest income amounts recognized: Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 (Dollars in thousands) Average recorded investment Interest income recognized while on impaired status Average recorded investment Interest income recognized while on impaired status Impaired loans with a valuation allowance: Commercial $ 20,402 $ 165 $ 25,712 $ 224 Commercial real estate: Owner-occupied 14,072 82 14,659 154 Non-owner occupied 3,870 11 3,388 24 Vacant land 3,695 15 1,988 25 Total commercial real estate 21,637 108 20,035 203 Real estate construction and land development 225 2 161 2 Residential mortgage 13,604 117 17,398 155 Consumer installment 906 1 780 1 Home equity 3,694 17 4,071 21 Subtotal $ 60,468 $ 410 $ 68,157 $ 606 Impaired loans with no related valuation allowance: Commercial $ 18,126 $ 95 $ 9,297 $ 30 Commercial real estate: Owner-occupied 15,369 56 9,866 6 Non-owner occupied 7,158 65 9,131 85 Vacant land 1,769 — 4,476 12 Total commercial real estate 24,296 121 23,473 103 Real estate construction and land development 107 1 81 — Residential mortgage 6,138 23 3,808 8 Consumer installment 140 — 215 — Home equity 2,046 7 880 1 Subtotal $ 50,853 $ 247 $ 37,754 $ 142 Total impaired loans: Commercial $ 38,528 $ 260 $ 35,009 $ 254 Commercial real estate: Owner-occupied 29,441 138 24,525 160 Non-owner occupied 11,028 76 12,519 109 Vacant land 5,464 15 6,464 37 Total commercial real estate 45,933 229 43,508 306 Real estate construction and land development 332 3 242 2 Residential mortgage 19,742 140 21,206 163 Consumer installment 1,046 1 995 1 Home equity 5,740 24 4,951 22 Total $ 111,321 $ 657 $ 105,911 $ 748
Schedule providing information on TDRs	The following schedule presents the Corporation's TDRs at March 31, 2018 and December 31, 2017 : (Dollars in thousands) Accruing TDRs Nonaccrual TDRs Total March 31, 2018 Commercial loan portfolio $ 35,216 $ 21,914 $ 57,130 Consumer loan portfolio 14,070 4,265 18,335 Total $ 49,286 $ 26,179 $ 75,465 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 The following tables present the recorded investment of loans modified into TDRs during the three months ended March 31, 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 March 31, 2018 Commercial loan portfolio: Commercial $ 903 $ — $ 1,065 $ 261 18 $ 2,235 $ 2,229 Commercial real estate: Owner-occupied — — 726 482 2 1,208 1,208 Non-owner occupied 68 — — — 1 74 68 Total commercial real estate 68 — 726 482 3 1,282 1,276 Total Commercial 971 — 1,791 743 21 3,517 3,505 Consumer loan portfolio: Residential mortgage 138 — — — 4 142 138 Consumer installment 71 23 28 — 16 128 122 Home equity 185 — 28 — 5 253 213 Total Consumer 394 23 56 — 25 523 473 Total loans $ 1,365 $ 23 $ 1,847 $ 743 46 $ 4,040 $ 3,978 Concession type (Dollars in thousands) Principal Interest Forbearance Total Pre-modification recorded investment Post-modification recorded investment For the three months ended March 31, 2017 Commercial loan portfolio: Commercial $ 50 $ 1,101 $ 579 5 $ 1,739 $ 1,730 Commercial real estate: Owner-occupied 447 75 — 3 522 522 Total commercial real estate 447 75 — 3 522 522 Total Commercial 497 1,176 579 8 2,261 2,252 Consumer loan portfolio: Residential mortgage 98 — — 1 98 98 Consumer installment 10 — — 2 11 10 Home equity 111 — — 1 165 111 Total Consumer 219 — — 4 274 219 Total loans $ 716 $ 1,176 $ 579 12 $ 2,535 $ 2,471
Troubled debt restructurings on financing receivables with defaults payment	The following schedule includes TDRs for which there was a payment default during the three months ended March 31, 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 March 31, 2018 (Dollars in thousands) Number of loans Principal balance Commercial loan portfolio (commercial) 1 $ 82 Consumer loan portfolio (residential mortgage) 1 3 Total 2 $ 85 For The Three Months Ended March 31, 2017 (Dollars in thousands) Number of loans Principal balance Commercial loan portfolio (commercial) 3 $ 620 Consumer loan portfolio (residential mortgage) 2 105 Total 5 $ 725
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 months ended March 31, 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 March 31, 2018: Beginning balance $ 66,133 $ 25,754 $ 91,887 Provision for loan losses 3,400 2,856 6,256 Charge-offs (2,594 ) (2,230 ) (4,824 ) Recoveries 805 638 1,443 Ending balance $ 67,744 $ 27,018 $ 94,762 Changes in allowance for loan losses for the three months ended March 31, 2017: Beginning balance $ 51,201 $ 27,067 $ 78,268 Provision for loan losses 4,392 (342 ) 4,050 Charge-offs (2,691 ) (2,883 ) (5,574 ) Recoveries 1,413 617 2,030 Ending balance $ 54,315 $ 24,459 $ 78,774 The following schedule presents by loan portfolio segment, details regarding the balance in the allowance and the recorded investment in loans at March 31, 2018 and December 31, 2017 by impairment evaluation method. (Dollars in thousands) Commercial Consumer Total Allowance for loan losses balance at March 31, 2018 attributable to: Loans individually evaluated for impairment $ 5,080 $ 1,914 $ 6,994 Loans collectively evaluated for impairment 62,664 25,104 87,768 Loans acquired with deteriorated credit quality — — — Total $ 67,744 $ 27,018 $ 94,762 Recorded investment (loan balance) at March 31, 2018: Loans individually evaluated for impairment $ 85,466 $ 25,652 $ 111,118 Loans collectively evaluated for impairment 5,805,344 4,096,054 9,901,398 Loans acquired with deteriorated credit quality 2,684,631 1,521,600 4,206,231 Total $ 8,575,441 $ 5,643,306 $ 14,218,747 (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 R32

Other Real Estate Owned and Repossessed Assets (Tables)	3 Months Ended
	Mar. 31, 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) 1,638 846 Net payments received (103 ) — Disposals (1,678 ) (951 ) Write-downs (651 ) — Balance at March 31, 2018 $ 7,199 $ 520 Balance at January 1, 2017 $ 16,812 $ 375 Additions (1) 3,119 1,162 Net payments received (39 ) — Disposals (3,728 ) (1,037 ) Write-downs (269 ) — Balance at March 31, 2017 $ 15,895 $ 500 (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 March 31, 2018 Net gain (loss) on sale $ 756 $ (34 ) Write-downs (651 ) — Net operating expenses (397 ) (1 ) Total $ (292 ) $ (35 ) For the three months ended March 31, 2017 Net gain (loss) on sale $ 1,047 $ (78 ) Write-downs (269 ) — Net operating expenses (508 ) (3 ) Total $ 270 $ (81 )
Adjustments Under New Revenue Recognition Guidance	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 Approximately 79% 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, 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 steadily 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. 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 certain net benefit cost components from salaries, wages and employee benefits expense to other expenses on the Consolidated Statements of Income, which was immaterial. Refer to Note 14, Pension and Other Postretirement Benefit Plans, for further detail. 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. Effective January 1, 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 2018-03 Technical Corrections and Improvements to Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities January 1, 2018

Loan Servicing Rights (Tables)

Loan Servicing Rights (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2018 Fair value, beginning of period $ 427 $ 63,414 $ 63,841 Additions from loans sold with servicing retained 43 1,924 1,967 Changes in fair value due to: Reductions from pay-offs, pay downs and run-off (29 ) (694 ) (723 ) Changes in estimates of fair value (1) — 3,752 3,752 Fair value, end of period $ 441 $ 68,396 $ 68,837 Principal balance of loans serviced $ 42,032 $ 7,018,307 $ 7,060,339 For the three months ended March 31, 2017 0 0 0 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 — 1,753 1,753 Changes in fair value due to: 0 Reductions from pay-offs, pay downs and run-off (24 ) (582 ) (606 ) Changes in estimates of fair value (1) — (519 ) (519 ) Fair value, end of period $ 320 $ 64,284 $ 64,604 Principal balance of loans serviced $ 50,942 $ 7,253,396 $ 7,304,338 (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 March 31, 2018 and December 31, 2017 . Mortgage As of March 31, 2018 Prepayment speed 0.0 - 36.6% Weighted average ("WA") discount rate 10.1 % WA cost to service/per year $ 66 WA ancillary income/per year $ 31 WA float range 1.9 % 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)	3 Months Ended
	Mar. 31, 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) March 31, December 31, Core deposit intangible assets $ 32,833 $ 34,259 Non-compete intangible assets — 12 Total other intangible assets $ 32,833 $ 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) March 31, December 31, Gross original amount $ 56,456 $ 59,143 Accumulated amortization 23,623 24,884 Net carrying amount $ 32,833 $ 34,259

Derivative Instruments and Ba35

Derivative Instruments and Balance Sheet Offsetting (Tables)	3 Months Ended
	Mar. 31, 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. March 31, 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 $ 620,000 $ 14,104 $ — $ 620,000 $ 5,899 $ — Total risk management purposes 620,000 14,104 — 620,000 5,899 — Customer-initiated and mortgage banking derivatives: Customer-initiated derivatives 1,615,445 11,619 12,055 1,365,119 9,376 10,139 Forward contracts related to mortgage loans to be delivered for sale 137,066 — 404 115,996 — 34 Interest rate lock commitments 112,938 1,774 — 71,003 1,222 — Power Equity CD 38,660 1,501 1,501 38,807 2,184 2,184 Total customer-initiated and mortgage banking derivatives 1,904,109 14,894 13,960 1,590,925 12,782 12,357 Total gross derivatives $ 2,524,109 $ 28,998 $ 13,960 $ 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 $416 thousand at March 31, 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 March 31, (Dollars in thousands) Location of Gain (Loss) 2018 2017 Forward contracts related to mortgage loans to be delivered for sale Net gain (loss) on sale of loans and other mortgage banking revenue $ (370 ) $ (977 ) Interest rate lock commitments Net gain (loss) on sale of loans and other mortgage banking revenue 552 1,223 Customer-initiated derivatives Other noninterest income 327 (231 ) Total gain (loss) recognized in income $ 509 $ 15 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 months ended March 31, 2018 . There were no interest rate swaps designated as cash flow hedges outstanding during the three months ended March 31, 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 March 31, 2018 Interest rate swaps designated as cash flow hedges $ 7,963 $ (242 )
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 March 31, 2018 Offsetting derivative assets Derivative assets (1) $ 25,698 $ — $ 25,698 $ — $ (17,243 ) $ 8,455 Offsetting derivative liabilities Derivative liabilities (1) 12,009 — 12,009 — 230 11,779 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, 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 March 31, 2018 Offsetting derivative assets Derivative assets (1) $ 25,698 $ — $ 25,698 $ — $ (17,243 ) $ 8,455 Offsetting derivative liabilities Derivative liabilities (1) 12,009 — 12,009 — 230 11,779 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, forward contracts, interest rate lock commitments and power equity CDs as these instruments are not subject to master netting or similar arrangements.

Commitments, Contingencies an36

Commitments, Contingencies and Guarantees (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Summary of the reserve for unfunded commitments	A summary of the reserve for representations and warranties of the Corporation is as follows: Three Months Ended March 31, (Dollars in thousands) 2018 2017 Reserve balance at beginning of period $ 5,349 $ 6,459 Reserve reduction (244 ) (770 ) Charge-offs — — Ending reserve balance $ 5,105 $ 5,689 (Dollars in thousands) March 31, 2018 December 31, 2017 Reserve balance Liability for specific claims $ 477 $ 531 General allowance 4,628 4,818 Total reserve balance $ 5,105 $ 5,349

Borrowings and Other Short-Te37

Borrowings and Other Short-Term Liabilities (Tables)	3 Months Ended
	Mar. 31, 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: March 31, 2018 December 31, 2017 (Dollars in thousands) Amount Weighted Average Rate (1) Amount Weighted Average Rate (1) Short-term borrowings: FHLB advances: 1.57% - 1.89% fixed-rate notes $ 2,050,000 1.75 % $ 2,000,000 1.39 % Long-term borrowings: FHLB advances: 0.92% - 2.60% fixed-rate notes due 2018 to 2020 (2) 337,179 1.26 337,204 1.26 Line-of-credit: floating-rate based on one-month LIBOR plus 1.75% 19,968 3.40 19,963 3.10 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 (3) 11,461 4.14 11,425 3.69 Subordinated debt obligations: floating-rate based on three-month LIBOR plus 3.25% due in 2032 (4) 4,300 4.94 4,290 4.59 Total long-term borrowings 372,908 1.51 372,882 1.47 Total borrowings $ 2,422,908 1.71 % $ 2,372,882 1.40 % Other short-term liabilities: Collateralized customer deposits $ 490,107 0.60 % $ 415,236 0.44 % (1) Weighted average rate presented is the contractual rate which excludes premiums and discounts related to purchase accounting. (2) The March 31, 2018 balances include advances payable of $337.0 million and purchase accounting premiums of $0.2 million . The December 31, 2017 balance includes advances payable of $337.0 million and purchase accounting premiums of $0.2 million . (3) The March 31, 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 March 31, 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 C38

Revenue from Contracts with Customers (Tables)	3 Months Ended
	Mar. 31, 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 March 31, (Dollars in thousands) 2018 Noninterest income Service charges and fees on deposit accounts $ 4,463 Wealth management revenue 784 Other charges and fees for customer services 2,398 Noninterest income from contracts with customers within the scope of ASC 606 7,645 Noninterest income within the scope of other GAAP topics 32,909 Total noninterest income $ 40,554 Noninterest expense Other $ (722 )

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 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 three months ended March 31, 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 — — — (186,434 ) 20.24 Vested (77,388 ) 37.01 6.93 — — Outstanding at March 31, 2018 253,482 $ 38.26 $ 7.14 924,484 $ 31.44 Exercisable/vested at March 31, 2018 671,002 $ 28.86
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 (41,614 ) 46.23 Nonvested at March 31, 2018 41,614 $ 46.23 A summary of the activity for RSUs as of and for the three months ended March 31, 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 275,355 54.28 Converted into shares of common stock (61,342 ) 27.87 Outstanding at March 31, 2018 594,953 $ 48.68

Pension and Other Postretirem40

Pension and Other Postretirement Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 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 March 31, (Dollars in thousands) 2018 2017 Defined Benefit Pension Plans Service cost (1) $ — $ 233 Interest cost 1,092 1,302 Expected return on plan assets (2,220 ) (2,217 ) Amortization of unrecognized net loss 178 578 Net periodic benefit cost (income) (2) $ (950 ) $ (104 ) Postretirement Benefit Plan Service cost (1) $ 1 $ 1 Interest cost 20 24 Amortization of unrecognized net gain (36 ) (41 ) Net periodic benefit cost (income) (2) $ (15 ) $ (16 ) (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)	3 Months Ended
	Mar. 31, 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 March 31, 2018 Total Capital to Risk-Weighted Assets Corporation $ 1,662,561 11.2 % $ 1,186,869 8.0 % $ 1,465,041 9.9 % N/A N/A Chemical Bank 1,655,547 11.2 1,184,378 8.0 1,461,966 9.9 $ 1,480,472 10.0 % Tier 1 Capital to Risk-Weighted Assets Corporation 1,544,016 10.4 890,152 6.0 1,168,324 7.9 N/A N/A Chemical Bank 1,552,763 10.5 888,283 6.0 1,165,872 7.9 1,184,378 8.0 Common Equity Tier 1 Capital to Risk-Weighted Assets Corporation 1,544,016 10.4 667,614 4.5 945,786 6.4 N/A N/A Chemical Bank 1,552,763 10.5 666,213 4.5 943,801 6.4 962,307 6.5 Leverage Ratio Corporation 1,544,016 8.4 731,240 4.0 731,240 4.0 N/A N/A Chemical Bank 1,552,763 8.5 730,292 4.0 730,292 4.0 912,865 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 4.5 854,509 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)	3 Months Ended
	Mar. 31, 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 March 31, (In thousands, except per share data) 2018 2017 Net income $ 70,170 $ 47,604 Net income allocated to participating securities 64 226 Net income allocated to common shareholders (1) $ 70,106 $ 47,378 Weighted average common shares - issued 71,297 70,969 Average unvested restricted share awards (66 ) (341 ) Weighted average common shares outstanding - basic 71,231 70,628 Effect of dilutive securities Weighted average common stock equivalents 675 787 Weighted average common shares outstanding - diluted 71,906 71,415 EPS available to common shareholders Basic earnings per common share $ 0.99 $ 0.67 Diluted earnings per common share $ 0.97 $ 0.67 (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 and warrants 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 Comprehensi43

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 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 months ended March 31, 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 March 31, 2018 Beginning balance at December 31, 2017 $ (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 income before reclassifications (21,809 ) — 6,291 (15,518 ) Amounts reclassified from accumulated other comprehensive income — 112 191 303 Net current period other comprehensive income (21,809 ) 112 6,482 (15,215 ) Ending balance $ (32,501 ) $ (19,696 ) $ 11,143 $ (41,054 ) For the three months ended March 31, 2017 Beginning balance $ (14,142 ) $ (25,894 ) $ — $ (40,036 ) Other comprehensive loss before reclassifications 1,780 — — 1,780 Amounts reclassified from accumulated other comprehensive income (58 ) 349 — 291 Net current period other comprehensive income (loss) 1,722 349 — 2,071 Ending balance $ (12,420 ) $ (25,545 ) $ — $ (37,965 ) (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 months ended March 31, 2018 , and 2017 : (Dollars in thousands) Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Income Statement Three Months Ended March 31, 2018 2017 Gains and losses on available-for-sale securities $ — $ 90 Net gain on sale of investment securities (noninterest income) — (32 ) Income tax (expense)/benefit $ — $ 58 Net Income Amortization of defined benefit pension plan items $ 142 $ 537 Salaries, wages and employee benefits (operating expenses) (30 ) (188 ) Income tax (expense)/benefit $ 112 $ 349 Net Income Gains and losses on cash flow hedges $ 242 $ — Interest on short-term borrowings (interest expense) (51 ) — Income tax (expense)/benefit $ 191 $ — Net Income

Basis of Presentation and Sig44

Basis of Presentation and Significant Accounting Policies (Details) $ in Thousands	3 Months Ended
	Mar. 31, 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	7
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 Sig45

Basis of Presentation and Significant Accounting Policies - ASU Adoptions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification due to TCJA		$ 4,500
Adjustments to retained earnings	$ 471,178	419,403
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		(344)
Early Adoption | ASU 2017-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustments to retained earnings		$ (3)
Net Interest Income | Revenue | Revenue concentration
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage	79.00%

Fair Value Measurements - Asset

Fair Value Measurements - Assets on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Summary of assets measured at fair value on a recurring basis
Carried at fair value	$ 2,297,123	$ 1,963,546
Loan servicing rights	68,837	63,841	$ 64,604	$ 48,085
Fair Value, Measurements, Recurring [Member]
Summary of assets measured at fair value on a recurring basis
Carried at fair value	2,297,123	1,963,546
Loans held-for-sale	31,636	52,133
Loan servicing rights	68,837	63,841
Total derivatives	28,998	18,681
Total assets measured at fair value on a recurring basis	2,426,594	2,098,201
Total derivatives	13,960	12,357
Total liabilities at fair value	13,960	12,357
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	2,297,123	1,963,546
Loans held-for-sale	31,636	52,133
Loan servicing rights	0	0
Total derivatives	28,998	18,681
Total assets measured at fair value on a recurring basis	2,357,757	2,034,360
Total derivatives	13,960	12,357
Total liabilities at fair value	13,960	12,357
Fair Value, Measurements, Recurring [Member] | 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	68,837	63,841
Total derivatives	0	0
Total assets measured at fair value on a recurring basis	68,837	63,841
Total derivatives	0	0
Total liabilities at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Customer-initiated derivatives
Summary of assets measured at fair value on a recurring basis
Total derivatives	11,619	9,376
Total derivatives	12,055	10,139
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Customer-initiated derivatives | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	11,619	9,376
Total derivatives	12,055	10,139
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Forward contracts related to mortgage loans to be delivered for sale
Summary of assets measured at fair value on a recurring basis
Total derivatives	404	34
Fair Value, Measurements, Recurring [Member] | 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	0
Fair Value, Measurements, Recurring [Member] | 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	404	34
Fair Value, Measurements, Recurring [Member] | 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	0
Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,774	1,222
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,774	1,222
Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0	0
Fair Value, Measurements, Recurring [Member] | Power Equity CD
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,501	2,184
Total derivatives	1,501	2,184
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Power Equity CD | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	1,501	2,184
Total derivatives	1,501	2,184
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Risk management derivatives
Summary of assets measured at fair value on a recurring basis
Total derivatives	14,104	5,899
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Risk management derivatives | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total derivatives	14,104	5,899
Fair Value, Measurements, Recurring [Member] | Risk management derivatives | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total derivatives	0	0
Fair Value, Measurements, Recurring [Member] | Government sponsored agencies
Summary of assets measured at fair value on a recurring basis
Carried at fair value	193,018	202,916
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Government sponsored agencies | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	193,018	202,916
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | State and political subdivisions
Summary of assets measured at fair value on a recurring basis
Carried at fair value	410,401	345,970
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | 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	410,401	345,970
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities
Summary of assets measured at fair value on a recurring basis
Carried at fair value	142,734	150,131
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | 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	142,734	150,131
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Collateralized mortgage obligations
Summary of assets measured at fair value on a recurring basis
Carried at fair value	1,277,976	1,033,845
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Collateralized mortgage obligations | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	1,277,976	1,033,845
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Corporate bonds
Summary of assets measured at fair value on a recurring basis
Carried at fair value	234,916	192,794
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Corporate bonds | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	234,916	192,794
Fair Value, Measurements, Recurring [Member] | Corporate bonds | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Trust preferred securities
Summary of assets measured at fair value on a recurring basis
Carried at fair value	36,271	36,066
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Trust preferred securities | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	36,271	36,066
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Preferred stock
Summary of assets measured at fair value on a recurring basis
Carried at fair value	1,807	1,824
Fair Value, Measurements, Recurring [Member] | 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	0
Fair Value, Measurements, Recurring [Member] | Preferred stock | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	1,807	1,824
Fair Value, Measurements, Recurring [Member] | Preferred stock | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Carried at fair value	$ 0	$ 0

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Assets (Details) - Fair Value, Measurements, Recurring [Member] - Loan servicing rights - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis
Balance, beginning of period	$ 63,841	$ 48,085
Transfer in based on new accounting policy election	0	15,891
Gains (losses): Recorded in earnings (realized):
Recorded in Net gain on sale of loans and other mortgage banking revenue	3,029	(1,125)
New originations	1,967	1,753
Balance, end of period	$ 68,837	$ 64,604

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	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Aggregate fair value	$ 31,636	$ 52,133
Contractual balance	30,800	50,597
Unrealized gain (loss)	$ 836	$ 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
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	$ 1,184	$ 7,272
Interest income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	376	551
Change in fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	(700)	601
Net gain (loss) on sale of loans and other mortgage banking revenue
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	$ 1,508	$ 6,120

Fair Value Measurements - Textu

Fair Value Measurements - Textual (Details) - USD ($)	3 Months Ended
	Mar. 31, 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 Measurements (Textual) [Abstract]
Liabilities recorded at fair value	$ 13,960,000	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 - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	$ 56,829	$ 73,518
Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	56,829	73,518
Impaired loans
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	54,060	70,619
Impaired loans | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	54,060	70,619
Other real estate and repossessed assets
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	2,769	2,899
Other real estate and repossessed assets | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	$ 2,769	$ 2,899

Fair Value Measurements - Level

Fair Value Measurements - Level 3 Assets, Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 56,829	$ 73,518
Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	54,060	70,619
Other real estate and repossessed assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	2,769	2,899
Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	56,829	73,518
Level 3 | Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 54,060	70,619
Level 3 | Impaired loans | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	20.00%
Level 3 | Impaired loans | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	30.00%
Level 3 | Other real estate and repossessed assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 2,769	$ 2,899
Level 3 | Other real estate and repossessed assets | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	20.00%
Level 3 | Other real estate and repossessed assets | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	30.00%

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment securities:
Held-to-maturity	$ 663,621	$ 662,906
Nonrecurring
Financial liabilities:
Impaired loans recorded at fair value on a nonrecurring basis	56,829	73,518
Nonrecurring | Impaired loans
Financial liabilities:
Impaired loans recorded at fair value on a nonrecurring basis	54,060	70,619
Level 3 | Nonrecurring
Financial liabilities:
Impaired loans recorded at fair value on a nonrecurring basis	56,829	73,518
Level 3 | Nonrecurring | Impaired loans
Financial liabilities:
Impaired loans recorded at fair value on a nonrecurring basis	54,060	70,619
Carrying Amount | Level 2
Investment securities:
Held-to-maturity	676,347	676,593
Financial liabilities:
Time deposits	3,360,113	3,217,207
Collateralized customer deposits	490,107	415,236
Short-term borrowings	2,050,000	2,000,000
Long-term borrowings	372,908	372,882
Carrying Amount | Level 3
Investment securities:
Held-to-maturity	500	500
Net loans	14,123,985	14,063,380
Fair Value | Level 2
Investment securities:
Held-to-maturity	663,196	662,516
Financial liabilities:
Time deposits	3,327,989	3,225,847
Collateralized customer deposits	488,683	415,236
Short-term borrowings	2,049,162	1,999,137
Long-term borrowings	368,915	367,984
Fair Value | Level 3
Investment securities:
Held-to-maturity	425	390
Net loans	$ 13,755,579	$ 14,114,545

Investment Securities - Availab

Investment Securities - Available-For-Sale Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Total
Amortized Cost	$ 2,337,846	$ 1,976,646
Unrealized Gains	3,344	4,040
Unrealized Losses	44,067	17,140
Total	2,297,123	1,963,546
Total debt securities available-for-sale
Amortized Cost	2,336,457	1,975,257
Unrealized Gains(1)	2,926	3,605
Unrealized Losses(1)	44,067	17,140
Fair Value	2,295,316	1,961,722
Total equity securities
Amortized Cost	1,389	1,389
Unrealized Gains(1)	418	435
Unrealized Losses(1)	0	0
Fair Value	1,807	1,824
Government sponsored agencies
Total debt securities available-for-sale
Amortized Cost	194,256	203,099
Unrealized Gains(1)	436	765
Unrealized Losses(1)	1,674	948
Fair Value	193,018	202,916
State and political subdivisions
Total debt securities available-for-sale
Amortized Cost	421,564	350,088
Unrealized Gains(1)	183	310
Unrealized Losses(1)	11,346	4,428
Fair Value	410,401	345,970
Residential mortgage-backed securities
Total debt securities available-for-sale
Amortized Cost	146,736	151,752
Unrealized Gains(1)	5	5
Unrealized Losses(1)	4,007	1,626
Fair Value	142,734	150,131
Collateralized mortgage obligations
Total debt securities available-for-sale
Amortized Cost	1,300,250	1,042,240
Unrealized Gains(1)	156	89
Unrealized Losses(1)	22,430	8,484
Fair Value	1,277,976	1,033,845
Corporate bonds
Total debt securities available-for-sale
Amortized Cost	238,717	193,230
Unrealized Gains(1)	777	1,156
Unrealized Losses(1)	4,578	1,592
Fair Value	234,916	192,794
Trust preferred securities
Total debt securities available-for-sale
Amortized Cost	34,934	34,848
Unrealized Gains(1)	1,369	1,280
Unrealized Losses(1)	32	62
Fair Value	36,271	36,066
Preferred stock
Total equity securities
Amortized Cost	1,389	1,389
Unrealized Gains(1)	418	435
Unrealized Losses(1)	0	0
Fair Value	$ 1,807	$ 1,824

Investment Securities - Held-To

Investment Securities - Held-To-Maturity Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Held-to-maturity Securities
Amortized Cost	$ 676,847	$ 677,093
Unrealized Gains	2,183	3,856
Unrealized Losses	15,409	18,043
Held-to-maturity, fair value	663,621	662,906
State and political subdivisions
Held-to-maturity Securities
Amortized Cost	676,347	676,593
Unrealized Gains	2,183	3,856
Unrealized Losses	15,334	17,933
Held-to-maturity, fair value	663,196	662,516
Trust preferred securities
Held-to-maturity Securities
Amortized Cost	500	500
Unrealized Gains	0	0
Unrealized Losses	75	110
Held-to-maturity, fair value	$ 425	$ 390

Investment Securities - Gains a

Investment Securities - Gains and (Losses) Recognized in Earnings (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)security	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Investments, Debt and Equity Securities [Abstract]
Securities in unrealized loss positions, qualitative disclosure, number of positions (in security) | security	1,600
Proceeds	$ 0	$ 0
Gross gains	0	90
Gross losses	0	$ 0
Schedule of Investments [Line Items]
Adjustments to retained earnings	$ 471,178		$ 419,403
ASU 2016-01
Schedule of Investments [Line Items]
Adjustments to retained earnings			$ (344)

Investment Securities - Maturit

Investment Securities - Maturities of Debt Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investment Securities Available-for-Sale: Amortized Cost
Due in one year or less	$ 21,498
Due after one year through five years	131,011
Due after five years through ten years	397,319
Due after ten years	1,786,629
Amortized Cost	2,337,846	$ 1,976,646
Investment Securities Available-for-Sale: Fair Value
Due in one year or less	21,471
Due after one year through five years	129,135
Due after five years through ten years	388,757
Due after ten years	1,755,953
Total	2,297,123	1,963,546
Investment Securities Held-to-Maturity: Amortized Cost
Due in one year or less	81,162
Due after one year through five years	241,937
Due after five years through ten years	162,648
Due after ten years	191,100
Preferred stock, amortized cost	1,389
Amortized Cost	676,847	677,093
Investment Securities Held-to-Maturity: Fair Value
Due in one year or less	81,076
Due after one year through five years	238,254
Due after five years through ten years	157,828
Due after ten years	186,463
Preferred stock, fair value	1,807
Total	663,621	662,906
Securities with amortized cost pledged to secure borrowings and deposits	$ 1,060,000	$ 937,200

Investment Securities - Gross U

Investment Securities - Gross Unrealized Losses (Details) $ in Thousands	Mar. 31, 2018USD ($)security	Dec. 31, 2017USD ($)
Schedule of Investments [Line Items]
Total number of securities, available-for-sale and held-to-maturity (in security) | security	2,234
Securities in unrealized loss positions, qualitative disclosure, number of positions (in security) | security	1,600
Fair Value
Less Than 12 Months	$ 2,005,310	$ 1,379,705
12 Months or More	557,282	563,188
Total	2,562,592	1,942,893
Gross Unrealized Losses
Less Than 12 Months	(42,748)	(21,534)
12 Months or More	(16,728)	(13,649)
Total	59,476	35,183
Government sponsored agencies
Fair Value
Less Than 12 Months	114,568	63,818
12 Months or More	14,236	24,621
Total	128,804	88,439
Gross Unrealized Losses
Less Than 12 Months	910	510
12 Months or More	764	438
Total	1,674	948
State and political subdivisions
Fair Value
Less Than 12 Months	577,711	437,407
12 Months or More	347,810	349,242
Total	925,521	786,649
Gross Unrealized Losses
Less Than 12 Months	(15,991)	(12,268)
12 Months or More	(10,689)	(10,093)
Total	26,680	22,361
Residential mortgage-backed securities
Fair Value
Less Than 12 Months	89,157	93,508
12 Months or More	53,532	56,576
Total	142,689	150,084
Gross Unrealized Losses
Less Than 12 Months	1,767	383
12 Months or More	2,240	1,243
Total	4,007	1,626
Collateralized mortgage obligations
Fair Value
Less Than 12 Months	1,098,199	713,525
12 Months or More	88,873	73,707
Total	1,187,072	787,232
Gross Unrealized Losses
Less Than 12 Months	20,529	7,235
12 Months or More	1,901	1,249
Total	22,430	8,484
Corporate bonds
Fair Value
Less Than 12 Months	125,675	71,447
12 Months or More	48,557	47,878
Total	174,232	119,325
Gross Unrealized Losses
Less Than 12 Months	3,551	1,138
12 Months or More	1,027	454
Total	4,578	1,592
Trust preferred securities
Fair Value
Less Than 12 Months	0	0
12 Months or More	4,274	11,164
Total	4,274	11,164
Gross Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	(107)	(172)
Total	$ 107	$ 172

Loans - Textual (Details)

Loans - Textual (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)segmenttenantclass_of_loanexecutive	Mar. 31, 2017USD ($)	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
Maximum value of loan that requires regional loan committee approval	7,000
Total troubled debt restructurings	75,465		$ 77,888
Residential mortgage loans in process of foreclosure	3,200		4,200
Commitment to lend additional funds to borrowers whose terms have been modified in TDRs	1,600		2
Loans held-for-sale, at fair value	31,636		52,133
Proceeds from sales of loans	190,435	$ 191,531
Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	26,179		29,106
Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	49,286		48,782
Consumer loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	18,335		19,046
Consumer loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	4,265		4,748
Consumer loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	14,070		14,298
Commercial loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	57,130		58,842
Commercial loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	21,914		24,358
Commercial loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	$ 35,216		$ 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
Maximum value of loan requires senior officer approval	$ 3,000
Number of bank executives and senior officers with credit decision limits similar to group loan authorities (in executive) | executive	6
Maximum value of loan requires executive and senior officer approval	$ 8,000
Minimum value of loan requires group loan authority approval	$ 7,000

Loans - Summary of Loans (Detai

Loans - Summary of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of loans under portfolio
Total loans	$ 14,218,747	$ 14,155,267
Deferred income	23,900	26,100
Commercial loan portfolio
Summary of loans under portfolio
Total loans	8,575,441	8,460,527
Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	3,427,285	3,385,642
Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	4,588,376	4,500,670
Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	559,780	574,215
Consumer loan portfolio
Summary of loans under portfolio
Total loans	5,643,306	5,694,740
Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	3,264,620	3,252,487
Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,572,240	1,613,008
Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	806,446	829,245
Originated
Summary of loans under portfolio
Total loans	10,012,516	9,747,429
Originated | Commercial
Summary of loans under portfolio
Total loans	2,486,533	2,407,606
Originated | Total commercial real estate
Summary of loans under portfolio
Total loans	2,918,803	2,751,425
Originated | Real estate construction and land development
Summary of loans under portfolio
Total loans	485,474	498,155
Originated | Residential mortgage
Summary of loans under portfolio
Total loans	2,039,349	1,967,857
Originated | Consumer installment
Summary of loans under portfolio
Total loans	1,478,673	1,510,540
Originated | Home equity
Summary of loans under portfolio
Total loans	603,684	611,846
Originated | Commercial loan portfolio
Summary of loans under portfolio
Total loans	5,890,810	5,657,186
Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,486,533	2,407,606
Originated | Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	2,918,803	2,751,425
Originated | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	485,474	498,155
Originated | Consumer loan portfolio
Summary of loans under portfolio
Total loans	4,121,706	4,090,243
Originated | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	2,039,349	1,967,857
Originated | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,478,673	1,510,540
Originated | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	603,684	611,846
Acquired
Summary of loans under portfolio
Total loans	4,206,231	4,407,838
Acquired | Commercial loan portfolio
Summary of loans under portfolio
Total loans	2,684,631	2,803,341
Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	940,752	978,036
Acquired | Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	1,669,573	1,749,245
Acquired | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	74,306	76,060
Acquired | Consumer loan portfolio
Summary of loans under portfolio
Total loans	1,521,600	1,604,497
Acquired | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	1,225,271	1,284,630
Acquired | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	93,567	102,468
Acquired | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	202,762	217,399
Owner-occupied | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,832,824	1,813,562
Owner-occupied | Originated | Commercial
Summary of loans under portfolio
Total loans	1,185,797	1,185,614
Owner-occupied | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,185,797	1,185,614
Owner-occupied | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	647,027	627,948
Non-owner occupied | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,680,801	2,606,761
Non-owner occupied | Originated | Commercial
Summary of loans under portfolio
Total loans	1,689,022	1,518,787
Non-owner occupied | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,689,022	1,518,787
Non-owner occupied | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	991,779	1,087,974
Vacant land | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	74,751	80,347
Vacant land | Originated | Commercial
Summary of loans under portfolio
Total loans	43,984	47,024
Vacant land | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	43,984	47,024
Vacant land | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	$ 30,767	$ 33,323

Loans - Activity for Accretable

Loans - Activity for Accretable Yield (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Activity for accretable yield
Balance at beginning of period	$ 926,897	$ 1,039,971
Accretion recognized in interest income	(58,561)	(60,187)
Net reclassification (to) from nonaccretable difference	362	20,624
Balance at end of period	868,698	1,000,408
Talmer
Activity for accretable yield
Balance at beginning of period	731,353	798,210
Accretion recognized in interest income	(42,640)	(44,571)
Net reclassification (to) from nonaccretable difference	(2,883)	21,139
Balance at end of period	685,830	774,778
Lake Michigan
Activity for accretable yield
Balance at beginning of period	95,124	121,416
Accretion recognized in interest income	(6,758)	(7,266)
Net reclassification (to) from nonaccretable difference	1,790	(939)
Balance at end of period	90,156	113,211
Monarch
Activity for accretable yield
Balance at beginning of period	22,496	27,182
Accretion recognized in interest income	(1,156)	(1,181)
Net reclassification (to) from nonaccretable difference	(186)	54
Balance at end of period	21,154	26,055
North-western
Activity for accretable yield
Balance at beginning of period	60,814	69,847
Accretion recognized in interest income	(4,904)	(3,892)
Net reclassification (to) from nonaccretable difference	(510)	(1,058)
Balance at end of period	55,400	64,897
OAK
Activity for accretable yield
Balance at beginning of period	17,110	23,316
Accretion recognized in interest income	(3,103)	(3,277)
Net reclassification (to) from nonaccretable difference	2,151	1,428
Balance at end of period	$ 16,158	$ 21,467

Loans - Commercial Loans by Ris

Loans - Commercial Loans by Risk Rating Categories (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 14,218,747	$ 14,155,267
Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	10,012,516	9,747,429
Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,486,533	2,407,606
Originated | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,918,803	2,751,425
Originated | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	485,474	498,155
Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,206,231	4,407,838
Commercial loan portfolio
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,575,441	8,460,527
Commercial loan portfolio | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,112,785	8,038,463
Commercial loan portfolio | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	237,838	204,706
Commercial loan portfolio | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	223,935	216,353
Commercial loan portfolio | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	883	1,005
Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,427,285	3,385,642
Commercial loan portfolio | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,588,376	4,500,670
Commercial loan portfolio | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	559,780	574,215
Commercial loan portfolio | Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,890,810	5,657,186
Commercial loan portfolio | Originated | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,687,538	5,488,571
Commercial loan portfolio | Originated | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	97,606	66,100
Commercial loan portfolio | Originated | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	105,354	102,515
Commercial loan portfolio | Originated | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	312	0
Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,486,533	2,407,606
Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,401,859	2,316,464
Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	37,084	41,059
Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	47,590	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	2,918,803	2,751,425
Commercial loan portfolio | Originated | Total commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,813,339	2,677,579
Commercial loan portfolio | Originated | Total commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	50,798	24,204
Commercial loan portfolio | Originated | Total commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	54,354	49,642
Commercial loan portfolio | Originated | Total commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	312	0
Commercial loan portfolio | Originated | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	485,474	498,155
Commercial loan portfolio | Originated | Real estate construction and land development | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	472,340	494,528
Commercial loan portfolio | Originated | Real estate construction and land development | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,724	837
Commercial loan portfolio | Originated | Real estate construction and land development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,410	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	2,684,631	2,803,341
Commercial loan portfolio | Acquired | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,425,247	2,549,892
Commercial loan portfolio | Acquired | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	140,232	138,606
Commercial loan portfolio | Acquired | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	118,581	113,838
Commercial loan portfolio | Acquired | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	571	1,005
Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	940,752	978,036
Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	830,615	873,861
Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	66,480	68,418
Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	43,471	35,539
Commercial loan portfolio | Acquired | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	186	218
Commercial loan portfolio | Acquired | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,669,573	1,749,245
Commercial loan portfolio | Acquired | Total commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,522,896	1,603,685
Commercial loan portfolio | Acquired | Total commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	72,141	67,970
Commercial loan portfolio | Acquired | Total commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,151	76,803
Commercial loan portfolio | Acquired | Total commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	385	787
Commercial loan portfolio | Acquired | Real estate construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,306	76,060
Commercial loan portfolio | Acquired | Real estate construction and land development | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	71,736	72,346
Commercial loan portfolio | Acquired | Real estate construction and land development | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,611	2,218
Commercial loan portfolio | Acquired | Real estate construction and land development | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	959	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	1,185,797	1,185,614
Owner-occupied | Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,832,824	1,813,562
Owner-occupied | Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,185,797	1,185,614
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,123,847	1,133,609
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	16,850	19,438
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	44,789	32,567
Owner-occupied | Commercial loan portfolio | Originated | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	311	0
Owner-occupied | Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	647,027	627,948
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	583,937	580,127
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	26,683	23,998
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	36,022	23,036
Owner-occupied | Commercial loan portfolio | Acquired | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	385	787
Non-owner occupied | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,689,022	1,518,787
Non-owner occupied | Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,680,801	2,606,761
Non-owner occupied | Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,689,022	1,518,787
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,652,313	1,504,195
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	33,895	4,728
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,813	9,864
Non-owner occupied | Commercial loan portfolio | Originated | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	1	0
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	991,779	1,087,974
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	913,327	995,709
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	45,146	43,645
Non-owner occupied | Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	33,306	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	43,984	47,024
Vacant land | Commercial loan portfolio | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,751	80,347
Vacant land | Commercial loan portfolio | Originated | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	43,984	47,024
Vacant land | Commercial loan portfolio | Originated | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	37,179	39,775
Vacant land | Commercial loan portfolio | Originated | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	53	38
Vacant land | Commercial loan portfolio | Originated | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,752	7,211
Vacant land | Commercial loan portfolio | Originated | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Vacant land | Commercial loan portfolio | Acquired | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	30,767	33,323
Vacant land | Commercial loan portfolio | Acquired | Commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	25,632	27,849
Vacant land | Commercial loan portfolio | Acquired | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	312	327
Vacant land | Commercial loan portfolio | Acquired | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,823	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	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 14,218,747	$ 14,155,267
Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	10,012,516	9,747,429
Originated | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,039,349	1,967,857
Originated | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,478,673	1,510,540
Originated | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	603,684	611,846
Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,206,231	4,407,838
Consumer loan portfolio
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,643,306	5,694,740
Consumer loan portfolio | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,264,620	3,252,487
Consumer loan portfolio | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,572,240	1,613,008
Consumer loan portfolio | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	806,446	829,245
Consumer loan portfolio | Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,121,706	4,090,243
Consumer loan portfolio | Originated | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,039,349	1,967,857
Consumer loan portfolio | Originated | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,478,673	1,510,540
Consumer loan portfolio | Originated | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	603,684	611,846
Consumer loan portfolio | Originated | Performing
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,110,124	4,076,461
Consumer loan portfolio | Originated | Performing | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,031,728	1,959,222
Consumer loan portfolio | Originated | Performing | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,477,751	1,509,698
Consumer loan portfolio | Originated | Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	600,645	607,541
Consumer loan portfolio | Originated | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,582	13,782
Consumer loan portfolio | Originated | Nonperforming | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,621	8,635
Consumer loan portfolio | Originated | Nonperforming | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	922	842
Consumer loan portfolio | Originated | Nonperforming | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,039	4,305
Consumer loan portfolio | Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,521,600	1,604,497
Consumer loan portfolio | Acquired | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,225,271	1,284,630
Consumer loan portfolio | Acquired | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	93,567	102,468
Consumer loan portfolio | Acquired | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 202,762	$ 217,399

Loans - Nonperforming Loans (De

Loans - Nonperforming Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 1,235	$ 1,377
Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	322	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	0	13
Home equity
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	913	1,364
Nonperforming
Summary of nonperforming loans
Total nonaccrual loans	61,832	63,095
Other real estate owned and repossessed assets	7,719	8,807
Total nonperforming assets	69,551	71,902
Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	20,000	19,691
Nonperforming | Total commercial real estate
Summary of nonperforming loans
Total nonaccrual loans	30,173	29,545
Nonperforming | Real estate construction and land development
Summary of nonperforming loans
Total nonaccrual loans	77	77
Nonperforming | Residential mortgage
Summary of nonperforming loans
Total nonaccrual loans	7,621	8,635
Nonperforming | Consumer installment
Summary of nonperforming loans
Total nonaccrual loans	922	842
Nonperforming | Home equity
Summary of nonperforming loans
Total nonaccrual loans	3,039	4,305
Owner-occupied | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	19,855	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	5,489	5,270
Vacant land | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	$ 4,829	$ 5,205

Loans - Aging Status of Loans (

Loans - Aging Status of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule representing the aging status of the recorded investment in loans by classes
Total loans	$ 14,218,747	$ 14,155,267
90 days or more past due and still accruing	1,235	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	322	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	0	13
Home equity
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	913	1,364
Originated Portfolio
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	72,236	58,857
Current	9,940,280	9,688,572
Total loans	10,012,516	9,747,429
90 days or more past due and still accruing	1,235	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	33,510	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	12,520	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	26,206	18,647
Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	26,890	27,166
Current	2,459,643	2,380,440
Total loans	2,486,533	2,407,606
90 days or more past due and still accruing	322	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	8,689	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	6,079	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	12,122	9,494
Originated Portfolio | Total commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	29,020	16,815
Current	2,889,783	2,734,610
Total loans	2,918,803	2,751,425
90 days or more past due and still accruing	0	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	15,253	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	4,265	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	9,502	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	100	0
Current	485,374	498,155
Total loans	485,474	498,155
90 days or more past due and still accruing	0	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	100	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	0	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	0	0
Originated Portfolio | Residential mortgage
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	5,542	5,068
Current	2,033,807	1,962,789
Total loans	2,039,349	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	3,020	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	246	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	2,276	858
Originated Portfolio | Consumer installment
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,644	3,992
Current	1,475,029	1,506,548
Total loans	1,478,673	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	2,817	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	570	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	257	226
Originated Portfolio | Home equity
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	7,040	5,816
Current	596,644	606,030
Total loans	603,684	611,846
90 days or more past due and still accruing	913	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	3,631	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	1,360	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	2,049	2,196
Owner-occupied | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	22,591	13,977
Current	1,163,206	1,171,637
Total loans	1,185,797	1,185,614
90 days or more past due and still accruing	0	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	10,829	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	3,368	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	8,394	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	5,574	2,574
Current	1,683,448	1,516,213
Total loans	1,689,022	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	3,749	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	897	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	928	693
Vacant land | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	855	264
Current	43,129	46,760
Total loans	43,984	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	675	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	0	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	$ 180	$ 153

Loans - Impaired Loans by Class

Loans - Impaired Loans by Class (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 61,054	$ 78,621
Unpaid Principal Balance	70,437	87,956
Related Valuation Allowance	6,994	8,002
Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	50,064	33,256
Unpaid Principal Balance	53,664	35,824
Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	111,118	111,877
Unpaid Principal Balance	124,101	123,780
Related Valuation Allowance	6,994	8,002
Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	23,500	28,897
Unpaid Principal Balance	25,998	31,655
Related Valuation Allowance	1,987	2,296
Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	14,771	8,504
Unpaid Principal Balance	15,637	9,291
Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	38,271	37,401
Unpaid Principal Balance	41,635	40,946
Related Valuation Allowance	1,987	2,296
Total commercial real estate | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	19,446	28,003
Unpaid Principal Balance	26,331	34,580
Related Valuation Allowance	3,067	3,227
Total commercial real estate | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	27,411	18,080
Unpaid Principal Balance	30,078	19,861
Total commercial real estate | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	46,857	46,083
Unpaid Principal Balance	56,409	54,441
Related Valuation Allowance	3,067	3,227
Real estate construction and land development | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	164	313
Unpaid Principal Balance	164	313
Related Valuation Allowance	26	14
Real estate construction and land development | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	174
Unpaid Principal Balance	241
Real estate construction and land development | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	338	313
Unpaid Principal Balance	405	313
Related Valuation Allowance	26	14
Residential mortgage | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,434	15,872
Unpaid Principal Balance	13,434	15,872
Related Valuation Allowance	1,422	1,487
Residential mortgage | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,928	4,902
Unpaid Principal Balance	5,928	4,902
Residential mortgage | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	19,362	20,774
Unpaid Principal Balance	19,362	20,774
Related Valuation Allowance	1,422	1,487
Consumer installment | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,101	966
Unpaid Principal Balance	1,101	966
Related Valuation Allowance	206	120
Consumer installment | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid Principal Balance	0
Consumer installment | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,101	966
Unpaid Principal Balance	1,101	966
Related Valuation Allowance	206	120
Home equity | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,409	4,570
Unpaid Principal Balance	3,409	4,570
Related Valuation Allowance	286	858
Home equity | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,780	1,770
Unpaid Principal Balance	1,780	1,770
Home equity | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,189	6,340
Unpaid Principal Balance	5,189	6,340
Related Valuation Allowance	286	858
Owner-occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	15,177	17,774
Unpaid Principal Balance	19,266	21,588
Related Valuation Allowance	2,510	2,317
Owner-occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	15,435	11,351
Unpaid Principal Balance	16,291	12,631
Owner-occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	30,612	29,125
Unpaid Principal Balance	35,557	34,219
Related Valuation Allowance	2,510	2,317
Non-owner occupied | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,952	5,307
Unpaid Principal Balance	5,545	7,870
Related Valuation Allowance	201	316
Non-owner occupied | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	8,122	5,977
Unpaid Principal Balance	9,135	6,438
Non-owner occupied | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	11,074	11,284
Unpaid Principal Balance	14,680	14,308
Related Valuation Allowance	201	316
Vacant land | Commercial | Impaired loans with a valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,317	4,922
Unpaid Principal Balance	1,520	5,122
Related Valuation Allowance	356	594
Vacant land | Commercial | Impaired loans with no valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,854	752
Unpaid Principal Balance	4,652	792
Vacant land | Commercial | Total Impaired Loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,171	5,674
Unpaid Principal Balance	6,172	5,914
Related Valuation Allowance	$ 356	$ 594

Loans - Impaired Loans (Details

Loans - Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Average recorded investment
Impaired loans with a valuation allowance	$ 60,468	$ 68,157
Impaired loans with no related valuation allowance	50,853	37,754
Total impaired loans	111,321	105,911
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	410	606
Impaired loans with no related valuation allowance	247	142
Total impaired loans	657	748
Commercial
Average recorded investment
Impaired loans with a valuation allowance	20,402	25,712
Impaired loans with no related valuation allowance	18,126	9,297
Total impaired loans	38,528	35,009
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	165	224
Impaired loans with no related valuation allowance	95	30
Total impaired loans	260	254
Total commercial real estate
Average recorded investment
Impaired loans with a valuation allowance	21,637	20,035
Impaired loans with no related valuation allowance	24,296	23,473
Total impaired loans	45,933	43,508
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	108	203
Impaired loans with no related valuation allowance	121	103
Total impaired loans	229	306
Real estate construction and land development
Average recorded investment
Impaired loans with a valuation allowance	225	161
Impaired loans with no related valuation allowance	107	81
Total impaired loans	332	242
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	2	2
Impaired loans with no related valuation allowance	1	0
Total impaired loans	3	2
Residential mortgage
Average recorded investment
Impaired loans with a valuation allowance	13,604	17,398
Impaired loans with no related valuation allowance	6,138	3,808
Total impaired loans	19,742	21,206
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	117	155
Impaired loans with no related valuation allowance	23	8
Total impaired loans	140	163
Consumer installment
Average recorded investment
Impaired loans with a valuation allowance	906	780
Impaired loans with no related valuation allowance	140	215
Total impaired loans	1,046	995
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	1	1
Impaired loans with no related valuation allowance	0	0
Total impaired loans	1	1
Home equity
Average recorded investment
Impaired loans with a valuation allowance	3,694	4,071
Impaired loans with no related valuation allowance	2,046	880
Total impaired loans	5,740	4,951
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	17	21
Impaired loans with no related valuation allowance	7	1
Total impaired loans	24	22
Owner-occupied | Commercial
Average recorded investment
Impaired loans with a valuation allowance	14,072	14,659
Impaired loans with no related valuation allowance	15,369	9,866
Total impaired loans	29,441	24,525
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	82	154
Impaired loans with no related valuation allowance	56	6
Total impaired loans	138	160
Non-owner occupied | Commercial
Average recorded investment
Impaired loans with a valuation allowance	3,870	3,388
Impaired loans with no related valuation allowance	7,158	9,131
Total impaired loans	11,028	12,519
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	11	24
Impaired loans with no related valuation allowance	65	85
Total impaired loans	76	109
Vacant land | Commercial
Average recorded investment
Impaired loans with a valuation allowance	3,695	1,988
Impaired loans with no related valuation allowance	1,769	4,476
Total impaired loans	5,464	6,464
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	15	25
Impaired loans with no related valuation allowance	0	12
Total impaired loans	$ 15	$ 37

Loans - Loan Modifications by C

Loans - Loan Modifications by Concession Type (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)loan	Mar. 31, 2017USD ($)loan
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 3,978	$ 2,471
Total number of loans (in loan) | loan	46	12
Pre-modification recorded investment	$ 4,040	$ 2,535
Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	1,365	716
Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	23
Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	1,847	1,176
Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	743	579
Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 3,505	$ 2,252
Total number of loans (in loan) | loan	21	8
Pre-modification recorded investment	$ 3,517	$ 2,261
Commercial loan portfolio | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	971	497
Commercial loan portfolio | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Commercial loan portfolio | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	1,791	1,176
Commercial loan portfolio | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	743	579
Commercial loan portfolio | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 2,229	$ 1,730
Total number of loans (in loan) | loan	18	5
Pre-modification recorded investment	$ 2,235	$ 1,739
Commercial loan portfolio | Commercial | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	903	50
Commercial loan portfolio | Commercial | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Commercial loan portfolio | Commercial | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	1,065	1,101
Commercial loan portfolio | Commercial | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	261	579
Commercial loan portfolio | Total commercial real estate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 1,276	$ 522
Total number of loans (in loan) | loan	3	3
Pre-modification recorded investment	$ 1,282	$ 522
Commercial loan portfolio | Total commercial real estate | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	68	447
Commercial loan portfolio | Total commercial real estate | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Commercial loan portfolio | Total commercial real estate | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	726	75
Commercial loan portfolio | Total commercial real estate | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	482	0
Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 473	$ 219
Total number of loans (in loan) | loan	25	4
Pre-modification recorded investment	$ 523	$ 274
Consumer loan portfolio | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	394	219
Consumer loan portfolio | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	23
Consumer loan portfolio | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	56	0
Consumer loan portfolio | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0
Consumer loan portfolio | Residential mortgage
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 138	$ 98
Total number of loans (in loan) | loan	4	1
Pre-modification recorded investment	$ 142	$ 98
Consumer loan portfolio | Residential mortgage | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	138	98
Consumer loan portfolio | Residential mortgage | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Consumer loan portfolio | Residential mortgage | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0
Consumer loan portfolio | Residential mortgage | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0
Consumer loan portfolio | Consumer installment
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 122	$ 10
Total number of loans (in loan) | loan	16	2
Pre-modification recorded investment	$ 128	$ 11
Consumer loan portfolio | Consumer installment | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	71	10
Consumer loan portfolio | Consumer installment | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	23
Consumer loan portfolio | Consumer installment | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	28	0
Consumer loan portfolio | Consumer installment | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0
Consumer loan portfolio | Home equity
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 213	$ 111
Total number of loans (in loan) | loan	5	1
Pre-modification recorded investment	$ 253	$ 165
Consumer loan portfolio | Home equity | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	185	111
Consumer loan portfolio | Home equity | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Consumer loan portfolio | Home equity | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	28	0
Consumer loan portfolio | Home equity | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	0
Owner-occupied | Commercial loan portfolio | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 1,208	$ 522
Total number of loans (in loan) | loan	2	3
Pre-modification recorded investment	$ 1,208	$ 522
Owner-occupied | Commercial loan portfolio | Commercial | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0	447
Owner-occupied | Commercial loan portfolio | Commercial | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Owner-occupied | Commercial loan portfolio | Commercial | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	726	75
Owner-occupied | Commercial loan portfolio | Commercial | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	482	$ 0
Non-owner occupied | Commercial loan portfolio | Commercial
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 68
Total number of loans (in loan) | loan	1
Pre-modification recorded investment	$ 74
Non-owner occupied | Commercial loan portfolio | Commercial | Principal deferral
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	68
Non-owner occupied | Commercial loan portfolio | Commercial | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Non-owner occupied | Commercial loan portfolio | Commercial | Interest rate
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	0
Non-owner occupied | Commercial loan portfolio | Commercial | Forbearance agreement
Financing Receivable, Modifications [Line Items]
Post-modification recorded investment	$ 0

Loans - Summary of TDRs (Detail

Loans - Summary of TDRs (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Total TDRs	$ 75,465	$ 77,888
Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	57,130	58,842
Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	18,335	19,046
Accruing TDRs
Financing Receivable, Modifications [Line Items]
Total TDRs	49,286	48,782
Accruing TDRs | Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	35,216	34,484
Accruing TDRs | Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	14,070	14,298
Nonaccrual TDRs
Financing Receivable, Modifications [Line Items]
Total TDRs	26,179	29,106
Nonaccrual TDRs | Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	21,914	24,358
Nonaccrual TDRs | Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Total TDRs	$ 4,265	$ 4,748

Loans - TDRs with a Payment Def

Loans - TDRs with a Payment Default During the Period (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)loan	Mar. 31, 2017USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of loans (in loan) | loan	2	5
Principal balance | $	$ 85	$ 725
Commercial loan portfolio
Financing Receivable, Modifications [Line Items]
Number of loans (in loan) | loan	1	3
Principal balance | $	$ 82	$ 620
Consumer loan portfolio
Financing Receivable, Modifications [Line Items]
Number of loans (in loan) | loan	1	2
Principal balance | $	$ 3	$ 105

Loans - Allowance for Loan Loss

Loans - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	$ 91,887
Ending balance	94,762
Allowance for loan losses
Loans individually evaluated for impairment			$ 6,994	$ 8,002
Loans collectively evaluated for impairment			87,768	83,885
Loans acquired with deteriorated credit quality			0	0
Total allowance for loan losses	91,887		94,762	91,887
Recorded investment (loan balance)
Loans individually evaluated for impairment			111,118	111,877
Loans collectively evaluated for impairment			9,901,398	9,635,552
Loans acquired with deteriorated credit quality			4,206,231	4,407,838
Total loans			14,218,747	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	67,744
Allowance for loan losses
Loans individually evaluated for impairment			5,080	5,537
Loans collectively evaluated for impairment			62,664	60,596
Loans acquired with deteriorated credit quality			0	0
Total allowance for loan losses	66,133		67,744	66,133
Recorded investment (loan balance)
Loans individually evaluated for impairment			85,466	83,797
Loans collectively evaluated for impairment			5,805,344	5,573,389
Loans acquired with deteriorated credit quality			2,684,631	2,803,341
Total loans			8,575,441	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	27,018
Allowance for loan losses
Loans individually evaluated for impairment			1,914	2,465
Loans collectively evaluated for impairment			25,104	23,289
Loans acquired with deteriorated credit quality			0	0
Total allowance for loan losses	25,754		27,018	25,754
Recorded investment (loan balance)
Loans individually evaluated for impairment			25,652	28,080
Loans collectively evaluated for impairment			4,096,054	4,062,163
Loans acquired with deteriorated credit quality			1,521,600	1,604,497
Total loans			5,643,306	5,694,740
Originated Loan Portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	91,887	$ 78,268
Provision for loan losses	6,256	4,050
Charge-offs	(4,824)	(5,574)
Recoveries	1,443	2,030
Ending balance	94,762	78,774
Allowance for loan losses
Total allowance for loan losses	91,887	78,268	94,762	91,887
Originated Loan Portfolio | Commercial loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	66,133	51,201
Provision for loan losses	3,400	4,392
Charge-offs	(2,594)	(2,691)
Recoveries	805	1,413
Ending balance	67,744	54,315
Allowance for loan losses
Total allowance for loan losses	66,133	51,201	67,744	66,133
Originated Loan Portfolio | Consumer loan portfolio
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	25,754	27,067
Provision for loan losses	2,856	(342)
Charge-offs	(2,230)	(2,883)
Recoveries	638	617
Ending balance	27,018	24,459
Allowance for loan losses
Total allowance for loan losses	$ 25,754	$ 27,067	$ 27,018	$ 25,754

Other Real Estate Owned and R72

Other Real Estate Owned and Repossessed Assets - Rollforward Tables (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 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	1,638	3,119
Net payments received	(103)	(39)
Disposals	(1,678)	(3,728)
Write-downs	(651)	(269)
Balance at the end of the period	7,199	15,895
Changes in repossessed assets
Balance at the beginning of the period	625	375
Other additions	846	1,162
Transfers out based on new accounting adoption	0
Net payments received	0	0
Disposals	(951)	(1,037)
Write-downs	0	0
Balance at the end of the period	520	$ 500
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 R73

Other Real Estate Owned and Repossessed Assets - Textual (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Other Real Estate [Abstract]
Other real estate owned and repossessed assets acquired in accordance with ASU 2014-04	$ 0.6
Residential mortgage loans in process of foreclosure	$ 3.2	$ 4.2

Other Real Estate Owned and R74

Other Real Estate Owned and Repossessed Assets - Income and Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income and expenses related to other real estate owned
Net gain (loss) on sale	$ 756	$ 1,047
Write-downs	(651)	(269)
Net operating expenses	(397)	(508)
Total	(292)	270
Income and expenses related to repossessed assets
Net gain (loss) on sale	(34)	(78)
Write-downs	0	0
Net operating expenses	(1)	(3)
Total	$ (35)	$ (81)

Goodwill (Details)

Goodwill (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
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
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	[1]	Dec. 31, 2016	[2]
Loan Servicing Rights
Cumulative effect adjustment of change in accounting policy, net of tax impact			$ 1,339		$ 3,659
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	$ 63,841	$ 48,085
Transfers in based on new accounting policy election(2)		15,891
Additions from loans sold with servicing retained	1,967	1,753
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	723	606
Changes in estimates of fair value	3,752	(519)
Fair value, end of period	68,837	64,604
Principal balance of loans serviced for others that have servicing capitalized	7,060,339	7,304,338
Commercial Real Estate
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	427	344
Transfers in based on new accounting policy election(2)		0
Additions from loans sold with servicing retained	43	0
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	(29)	(24)
Changes in estimates of fair value	0	0
Fair value, end of period	441	320
Principal balance of loans serviced for others that have servicing capitalized	42,032	50,942
Mortgage
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	63,414	47,741
Transfers in based on new accounting policy election(2)		15,891
Additions from loans sold with servicing retained	1,924	1,753
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	(694)	(582)
Changes in estimates of fair value	3,752	(519)
Fair value, end of period	68,396	64,284
Principal balance of loans serviced for others that have servicing capitalized	$ 7,018,307	$ 7,253,396
Retained earnings
Loan Servicing Rights
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.

Loan Servicing Rights - Assumpt

Loan Servicing Rights - Assumptions Used in Determining Fair Value (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Loan servicing rights
Loan servicing fee income	$ 4,600,000	$ 4,500,000
Mortgage
Loan servicing rights
WA cost to service/per year	66		$ 66
WA ancillary income/per year	$ 31		$ 31
WA float range	1.90%
Mortgage | Weighted Average
Loan servicing rights
Discount rate	10.10%		10.10%
WA float range			1.60%
Mortgage | Minimum
Loan servicing rights
Prepayment speed	0.00%		0.00%
Mortgage | Maximum
Loan servicing rights
Prepayment speed	36.60%		38.80%

Other Intangible Assets - Intan

Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Total intangible assets	$ 32,833	$ 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	23,623	24,884
Total intangible assets	32,833	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
	Mar. 31, 2018	Mar. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ (1,438)	$ (1,513)
Core deposit intangible assets
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	7 years 3 months 19 days
Amortization of intangible assets	$ (1,400)	$ (1,500)
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2018	4,300
2,019	5,400
2,020	4,900
2,021	4,500
2,022	4,200
2023 and thereafter	$ 9,500

Derivative Instruments and Ba80

Derivative Instruments and Balance Sheet Offsetting - Textual (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative instruments
Adjustments to retained earnings	$ 471,178	$ 419,403
Early Adoption | ASU 2017-12
Derivative instruments
Adjustments to retained earnings		$ (3)

Derivative Instruments and Ba81

Derivative Instruments and Balance Sheet Offsetting - Notional Amount and Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative instruments
Notional Amount	$ 2,524,109	$ 2,210,925
Gross Derivative Assets	28,998	18,681
Gross Derivative Liabilities	13,960	12,357
Credit valuation adjustments for counterparty credit risk	416	809
Derivatives designated as hedging instruments:
Derivative instruments
Notional Amount	620,000	620,000
Gross Derivative Assets	14,104	5,899
Gross Derivative Liabilities	0	0
Derivatives designated as hedging instruments: | Interest rate swaps
Derivative instruments
Notional Amount	620,000	620,000
Gross Derivative Assets	14,104	5,899
Gross Derivative Liabilities	0	0
Derivatives not designated as hedging | Total customer-initiated and mortgage banking derivatives
Derivative instruments
Notional Amount	1,904,109	1,590,925
Gross Derivative Assets	14,894	12,782
Gross Derivative Liabilities	13,960	12,357
Derivatives not designated as hedging | Customer-initiated derivatives
Derivative instruments
Notional Amount	1,615,445	1,365,119
Gross Derivative Assets	11,619	9,376
Gross Derivative Liabilities	12,055	10,139
Derivatives not designated as hedging | Forward contracts related to mortgage loans to be delivered for sale
Derivative instruments
Notional Amount	137,066	115,996
Gross Derivative Assets	0	0
Gross Derivative Liabilities	404	34
Derivatives not designated as hedging | Interest rate lock commitments
Derivative instruments
Notional Amount	112,938	71,003
Gross Derivative Assets	1,774	1,222
Gross Derivative Liabilities	0	0
Derivatives not designated as hedging | Power Equity CD
Derivative instruments
Notional Amount	38,660	38,807
Gross Derivative Assets	1,501	2,184
Gross Derivative Liabilities	$ 1,501	$ 2,184

Derivative Instruments and Ba82

Derivative Instruments and Balance Sheet Offsetting - Net Gains (Losses) Related to Changes in Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative instruments
Total gain (loss) recognized in income	$ 509	$ 15
Forward contracts related to mortgage loans to be delivered for sale | Net gain (loss) on sale of loans and other mortgage banking revenue
Derivative instruments
Total gain (loss) recognized in income	(370)	(977)
Interest rate lock commitments | Net gain (loss) on sale of loans and other mortgage banking revenue
Derivative instruments
Total gain (loss) recognized in income	552	1,223
Customer-initiated derivatives | Other noninterest income
Derivative instruments
Total gain (loss) recognized in income	$ 327	$ (231)

Derivative Instruments and Ba83

Derivative Instruments and Balance Sheet Offsetting - Net Gains (Losses) Recorded in Other Comprehensive Income and the Income Statement (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Derivative instruments
Unrealized losses on interest rate swaps expected to be reclassified during next twelve months	$ 3,300
Interest rate swaps | Derivatives designated as hedging instruments:
Derivative instruments
Amount of gain (loss) recognized in other comprehensive income	7,963
Amount of gain (loss) reclassified from other comprehensive income to interest income or expense	$ (242)

Derivative Instruments and Ba84

Derivative Instruments and Balance Sheet Offsetting - Balance Sheet Offsetting (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Offsetting derivative assets
Gross amounts recognized	$ 28,998	$ 18,681
Offsetting derivative liabilities
Gross amounts recognized	13,960	12,357
Interest rate swaps and customer-initiated derivatives
Offsetting derivative assets
Gross amounts recognized	25,698	15,228
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	25,698	15,228
Gross amounts not offset in the statements of financial position
Financial instruments	0	0
Collateral (received)/posted	(17,243)	0
Net Amount	8,455	15,228
Offsetting derivative liabilities
Gross amounts recognized	12,009	10,139
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	12,009	10,139
Gross amounts not offset in the statements of financial position
Financial instruments	0	0
Collateral (received)/posted	230	1,081
Net Amount	$ 11,779	$ 9,058

Investments in Qualified Affo85

Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Variable Interest Entity [Line Items]
Expense related to qualified affordable housing projects	$ 1,000,000	$ 800,000
Remaining investment in qualified affordable housing projects	53,000,000		$ 51,400,000
Equity method investments	15,600,000		17,300,000
Remaining unfunded equity contributions	46,800,000		48,100,000
Investment tax credit	1,500,000
Impairment on tax credit projects	1,600,000		$ 0
Other Noninterest Expense [Member]
Variable Interest Entity [Line Items]
Impairment on tax credit projects	$ 1,300,000

Commitments, Contingencies an86

Commitments, Contingencies and Guarantees - Commitments (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Potential losses from standby letters of credit	$ 0	$ 0
Undisbursed loan commitments	492,400,000	571,000,000
Probable credit losses	1,500,000	1,200,000
Financial and Performance Standby Letters of Credit
Loss Contingencies [Line Items]
Letters of credit outstanding	189,700,000	187,600,000
Commitments to Extend Credit
Loss Contingencies [Line Items]
Loan commitments under financial guarantee	$ 3,030,000,000	$ 3,030,000,000

Commitments, Contingencies an87

Commitments, Contingencies and Guarantees - Contingencies and Guarantees (Details) - Performance Guarantee - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Recorded liability	$ 12.5	$ 13.3
Maximum potential amount of undiscounted future payments	12.2	12.8
Recourse liability	$ 0.2	$ 0.2

Commitments, Contingencies an88

Commitments, Contingencies and Guarantees - Warranties (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Changes in the activity related to liability recorded in connection with representations and warranties
Reserve balance at beginning of period	$ 5,349	$ 6,459
Reserve reduction	(244)	(770)
Charge-offs	0	0
Ending reserve balance	5,105	5,689
Reserve balance
Liability for specific claims			$ 477	$ 531
General allowance			4,628	4,818
Total reserve balance	$ 5,349	$ 6,459	$ 5,105	$ 5,349

Borrowings and Other Short-Te89

Borrowings and Other Short-Term Liabilities - Other Borrowings (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Long-term borrowings:
Amount	$ 372,908	$ 372,882
Weighted Average Rate	1.51%	1.47%
Total borrowings	$ 2,422,908	$ 2,372,882
Total short-term and long-term borrowings, Weighted Average Rate	1.71%	1.40%
FHLB advances: 1.57% - 1.89% fixed-rate notes | Minimum
Long-term borrowings:
Stated interest rate	1.57%
FHLB advances: 1.57% - 1.89% fixed-rate notes | Maximum
Long-term borrowings:
Stated interest rate	1.89%
FHLB Advances | FHLB advances: 0.92% - 7.44% fixed-rate notes due 2017 to 2020
Long-term borrowings:
Amount	$ 337,179	$ 337,204
Weighted Average Rate	1.26%	1.26%
Advances payable from Federal Home Loan Banks	$ 337,000	$ 337,000
Purchase accounting premiums	$ 200	200
FHLB Advances | FHLB advances: 0.92% - 7.44% fixed-rate notes due 2017 to 2020 | Minimum
Long-term borrowings:
Stated interest rate	0.92%
FHLB Advances | FHLB advances: 0.92% - 7.44% fixed-rate notes due 2017 to 2020 | Maximum
Long-term borrowings:
Stated interest rate	2.60%
Line of credit
Long-term borrowings:
Amount	$ 19,968	$ 19,963
Weighted Average Rate	3.40%	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	$ 11,461	$ 11,425
Weighted Average Rate	4.14%	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	$ 4,300	$ 4,290
Weighted Average Rate	4.94%	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	$ 490,107	$ 415,236
Weighted Average Rate	0.60%	0.44%
FHLB Advances | FHLB advances: 1.57% - 1.89% fixed-rate notes
Short-term borrowings:
Amount	$ 2,050,000	$ 2,000,000
Weighted Average Rate	1.75%	1.39%

Revenue from Contracts with C90

Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Noninterest income	$ 40,554	$ 38,010
Noninterest expense	(103,358)	$ (104,196)
Noninterest income from contracts with customers within the scope of ASC 606
Disaggregation of Revenue [Line Items]
Noninterest income	7,645
Service charges and fees on deposit accounts
Disaggregation of Revenue [Line Items]
Noninterest income	4,463
Wealth management revenue
Disaggregation of Revenue [Line Items]
Noninterest income	784
Other charges and fees for customer services
Disaggregation of Revenue [Line Items]
Noninterest income	2,398
Noninterest income within the scope of other GAAP topics
Disaggregation of Revenue [Line Items]
Noninterest income	32,909
Other
Disaggregation of Revenue [Line Items]
Noninterest expense	$ (722)

Borrowings and Other Short-Te91

Borrowings and Other Short-Term Liabilities - Textual (Details) $ in Millions	Mar. 31, 2018USD ($)
Debt Disclosure [Abstract]
FHLB advances	$ 7,360
Additional borrowing available through FHLB	$ 143.6

Share-Based Compensation - Text

Share-Based Compensation - Textual (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares	Mar. 31, 2017USD ($)shares	Apr. 26, 2017shares
Share-based Compensation Plans (Textual)
Share-based compensation expense	$ 1.7	$ 3.8
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	1.4	6.1
Cash received from option exercises	$ 0.9	0.9
Stock Incentive Plan of 2015
Share-based Compensation Plans (Textual)
Common stock available for future grants under share-based compensation plans (in shares) | shares	1,346,965
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		$ 29
Stock issued from exercises (in shares) | shares	100,885	496,000
Restricted stock units
Share-based Compensation Plans (Textual)
Corporation granted options to purchase restricted stock performance units (in shares) | shares	275,355
Stock issued from exercises (in shares) | shares	61,342
Unrecognized compensation expense	$ 21.9
Unrecognized compensation expense, period for recognition	3 years 7 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 6 months
Weighted-average remaining contractual terms for exercisable stock options	5 years 11 months
Outstanding in-the-money stock options, intrinsic value	$ 21.5
Exercisable in-the-money stock options, intrinsic value	$ 17.3
Closing price of common stock (dollars per share) | $ / shares	$ 54.68
Unrecognized compensation expense	$ 1.8
Unrecognized compensation expense, period for recognition	3 years 3 months
Restricted stock awards
Share-based Compensation Plans (Textual)
Unrecognized compensation expense	$ 1.7
Unrecognized compensation expense, period for recognition	10 months 15 days

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details) - Stock Options	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Non-Vested Stock Options Outstanding, Number of Options
Beginning balance (in shares) | shares	330,870
Vested (in shares) | shares	(77,388)
Ending balance (in shares) | shares	253,482
Non-Vested Stock Options Outstanding, Weighted- Average Grant Date Fair Value Per Share
Beginning balance (dollars per share)	$ 7.09
Vested (dollars per share)	6.93
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	(186,434)
Ending balance (in shares) | shares	924,484
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)	20.24
Ending balance, Weighted Average Exercise Price (dollars per share)	$ 31.44
Exercisable/vested, Number of Options (in shares) | shares	671,002
Exercisable/vested, Weighted Average Exercise Price (dollars per share)	$ 28.86
Non Vested
Weighted- Average Exercise Price Per Share
Beginning balance, Weighted Average Exercise Price (dollars per share)	37.97
Vested, Weighted Average Exercise Price (dollars per share)	37.01
Ending balance, Weighted Average Exercise Price (dollars per share)	$ 38.26

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Unit and Award Activity (Details)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Restricted Stock Units
Number of Units/Awards
Beginning balance (in shares) | shares	380,940
Granted (in shares) | shares	275,355
Converted into shares of common stock (in shares) | shares	(61,342)
Ending balance (in shares) | shares	594,953
Weighted-average grant-date fair value
Beginning balance (dollars per share) | $ / shares	$ 41.29
Granted (dollars per share) | $ / shares	54.28
Converted into shares of common stock (dollars per share) | $ / shares	27.87
Ending balance (dollars per share) | $ / shares	$ 48.68
Restricted Stock Awards
Number of Units/Awards
Beginning balance (in shares) | shares	83,228
Vested (in shares) | shares	(41,614)
Ending balance (in shares) | shares	41,614
Weighted-average grant-date fair value
Beginning balance (dollars per share) | $ / shares	$ 46.23
Vested (dollars per share) | $ / shares	46.23
Ending balance (dollars per share) | $ / shares	$ 46.23

Pension and Other Postretirem95

Pension and Other Postretirement Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 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
Interest cost	1,092	1,302
Expected return on plan assets	(2,220)	(2,217)
Amortization of unrecognized net (gain) loss	178	578
Net periodic benefit cost (income)	(950)	(104)
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
Interest cost	20	24
Amortization of unrecognized net (gain) loss	(36)	(41)
Net periodic benefit cost (income)	$ (15)	$ (16)

Pension and Other Postretirem96

Pension and Other Postretirement Benefit Plans - Textual (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Percentage of eligible pay contribution to certain employees	4.00%
Employer total contribution amount	$ 2,800,000	$ 2,500,000
Corporation match as a percentage of the participants' elective deferrals	50.00%
Maximum percent of participants' base compensation matched	6.00%
Employer contributions to Pentegra DB Plan	$ 0	0
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Contribution to defined benefit pension plan	$ 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

Regulatory Capital (Details)

Regulatory Capital (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 24, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Leverage Ratio
Cash dividends declared per common share (dollars per share)		$ 0.28	$ 0.27
Subsequent Event
Leverage Ratio
Cash dividends declared per common share (dollars per share)	$ 0.28
Chemical Bank
Regulatory Capital
Risk weighted assets		$ 14,800,000		$ 14,700,000
Total Capital to Risk-Weighted Assets
Actual Amount		$ 1,655,547		$ 1,613,087
Actual Ratio		11.20%		11.00%
For Capital Adequacy Purposes Amount		$ 1,184,378		$ 1,176,361
For Capital Adequacy Purposes Ratio		8.00%		8.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,461,966		$ 1,360,167
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		9.90%		9.30%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 1,480,472		$ 1,470,451
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		10.00%		10.00%
Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,552,763		$ 1,513,219
Actual Ratio		10.50%		10.30%
For Capital Adequacy Purposes Amount		$ 888,283		$ 882,271
For Capital Adequacy Purposes Ratio		6.00%		6.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,165,872		$ 1,066,077
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		7.90%		7.30%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 1,184,378		$ 1,176,361
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		8.00%		8.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,552,763		$ 1,513,219
Actual Ratio		10.50%		10.30%
For Capital Adequacy Purposes Amount		$ 666,213		$ 661,703
For Capital Adequacy Purposes Ratio		4.50%		4.50%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 943,801		$ 854,509
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		6.40%		5.80%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 962,307		$ 955,793
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		6.50%		6.50%
Leverage Ratio
Actual Amount		$ 1,552,763		$ 1,513,219
Actual Ratio		8.50%		8.40%
For Capital Adequacy Purposes Amount		$ 730,292		$ 720,043
For Capital Adequacy Purposes Ratio		4.00%		4.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 730,292		$ 720,043
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		4.00%		4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		$ 912,865		$ 900,053
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio		5.00%		5.00%
Corporation
Regulatory Capital
Risk weighted assets		$ 14,840,000		$ 14,740,000
Total Capital to Risk-Weighted Assets
Actual Amount		$ 1,662,561		$ 1,614,046
Actual Ratio		11.20%		11.00%
For Capital Adequacy Purposes Amount		$ 1,186,869		$ 1,179,076
For Capital Adequacy Purposes Ratio		8.00%		8.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,465,041		$ 1,363,307
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		9.90%		9.30%
Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,544,016		$ 1,498,463
Actual Ratio		10.40%		10.20%
For Capital Adequacy Purposes Amount		$ 890,152		$ 884,307
For Capital Adequacy Purposes Ratio		6.00%		6.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,168,324		$ 1,068,538
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		7.90%		7.30%
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual Amount		$ 1,544,016		$ 1,498,463
Actual Ratio		10.40%		10.20%
For Capital Adequacy Purposes Amount		$ 667,614		$ 663,230
For Capital Adequacy Purposes Ratio		4.50%		4.50%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 945,786		$ 847,461
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		6.40%		5.80%
Leverage Ratio
Actual Amount		$ 1,544,016		$ 1,498,463
Actual Ratio		8.40%		8.30%
For Capital Adequacy Purposes Amount		$ 731,240		$ 720,890
For Capital Adequacy Purposes Ratio		4.00%		4.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 731,240		$ 720,890
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		4.00%		4.00%

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 70,170	$ 47,604
Net income allocated to participating securities	64	226
Net income allocated to common shareholders	$ 70,106	$ 47,378
Weighted average common shares - issued (in shares)	71,297,000	70,969,000
Average unvested restricted share awards (in shares)	(66,000)	(341,000)
Weighted average common shares outstanding - basic (in shares)	71,231,000	70,628,000
Effect of dilutive securities
Weighted average common stock equivalents (in shares)	675,000	787,000
Weighted average common shares outstanding - diluted (in shares)	71,906,000	71,415,000
EPS available to common shareholders
Basic earnings per common share (dollars per share)	$ 0.99	$ 0.67
Diluted earnings per common share (dollars per share)	0.97	0.67
Average stock valuation (dollars per share)	$ 56.23	$ 51.81
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)	71,046	0

Accumulated Other Comprehensi99

Accumulated Other Comprehensive Loss - Changes in AOCI (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017		Dec. 31, 2016	[2]
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		$ 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 income before reclassifications		(15,518)	1,780
Amounts reclassified from accumulated other comprehensive income		303	291
Other comprehensive income, net of tax		(15,215)	2,071
Ending balance		2,703,277	2,600,051
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		(10,348)	(14,142)
Cumulative effect adjustment of change in accounting policy, net of tax impact				(344)
Beginning balance, adjusted				(10,692)
Other comprehensive income before reclassifications		(21,809)	1,780
Amounts reclassified from accumulated other comprehensive income		0	(58)
Other comprehensive income, net of tax		(21,809)	1,722
Ending balance		(32,501)	(12,420)
Defined Benefit Pension Plans
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		(19,808)	(25,894)
Cumulative effect adjustment of change in accounting policy, net of tax impact				0
Beginning balance, adjusted				(19,808)
Other comprehensive income before reclassifications		0	0
Amounts reclassified from accumulated other comprehensive income		112	349
Other comprehensive income, net of tax		112	349
Ending balance		(19,696)	(25,545)
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		4,658	0
Cumulative effect adjustment of change in accounting policy, net of tax impact				3
Beginning balance, adjusted				4,661
Other comprehensive income before reclassifications		6,291	0
Amounts reclassified from accumulated other comprehensive income		191	0
Other comprehensive income, net of tax		6,482	0
Ending balance		11,143	0
Total
Components of accumulated other comprehensive income (loss), net of related tax benefit/expense
Beginning balance		(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		$ (41,054)	$ (37,965)
[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 Comprehens100

Accumulated Other Comprehensive Loss - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on sale of investment securities	$ 0	$ 90
Income tax (expense)/benefit	(12,633)	(12,257)
Net income	70,170	47,604
Interest on short-term borrowings (interest expense)	8,166	1,508
Gains and losses 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	90
Income tax (expense)/benefit	0	(32)
Net income	0	58
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
Income tax (expense)/benefit	(30)	(188)
Net Income	112	349
Gains and losses on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense)/benefit	(51)	0
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	191	0
Interest on short-term borrowings (interest expense)	$ 242	$ 0