TCF Financial 10-K 26 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Jan. 31, 2016	Jun. 30, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	CHEMICAL FINANCIAL CORP
Entity Central Index Key	19,612
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,194,100,000
Entity Common Stock, Shares Outstanding		38,168,801

Consolidated Statements of Fina

Consolidated Statements of Financial Position - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Cash and cash equivalents:
Cash and cash due from banks	$ 194,136	$ 144,892
Interest-bearing deposits with the Federal Reserve Bank and other banks	44,653	38,128
Total cash and cash equivalents	238,789	183,020
Investment securities:
Available-for-sale, at fair value	553,731	748,864
Held-to-maturity, at amortized cost (fair value - $512,705 at December 31, 2015 and $315,740 at December 31, 2014)	509,971	316,413
Total investment securities	1,063,702	1,065,277
Loans held-for-sale, at fair value	10,327	9,128
Loans	7,271,147	5,688,230
Allowance for loan losses	(73,328)	(75,683)
Net loans	7,197,819	5,612,547
Premises and equipment	106,317	97,496
Goodwill	287,393	180,128
Other intangible assets	38,104	33,080
Interest receivable and other assets	246,346	141,467
Total Assets	9,188,797	7,322,143
Deposits:
Noninterest-bearing	1,934,583	1,591,661
Interest-bearing	5,522,184	4,487,310
Total deposits	7,456,767	6,078,971
Interest payable and other liabilities	76,466	56,572
Short-term borrowings	397,199	389,467
Other Borrowings	242,391	0
Total liabilities	8,172,823	6,525,010
Shareholders' equity:
Preferred stock, no par value:	0	0
Issued and outstanding — 38,167,861 shares at December 31, 2015 and 32,774,420 shares at December 31, 2014	38,168	32,774
Additional paid in capital	725,280	565,166
Retained earnings	281,558	231,646
Accumulated other comprehensive loss	(29,032)	(32,453)
Total shareholders' equity	1,015,974	797,133
Total Liabilities and Shareholders' Equity	$ 9,188,797	$ 7,322,143

Consolidated Statements of Fin3

Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Held-to-maturity, fair value	$ 512,705	$ 315,740
Preferred stock, no par value	$ 0	$ 0
Preferred stock, shares authorized	2,000,000	200,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	60,000,000	45,000,000
Common Stock, Shares Issued	38,167,861	32,774,420
Common stock, shares outstanding	38,167,861	32,774,420

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest Income
Interest and fees on loans	$ 271,772	$ 209,429	$ 195,590
Interest on investment securities:
Taxable	8,786	9,147	10,234
Tax-exempt	9,073	7,054	6,394
Dividends on nonmarketable equity securities	1,648	1,224	1,105
Interest on deposits with the Federal Reserve Bank and other banks	510	407	738
Total Interest Income	291,789	227,261	214,061
Interest Expense
Interest on deposits	15,406	14,254	16,883
Interest Expense, Short-term Borrowings	453	414	484
Interest Expense, Borrowings	1,922	42	47
Total Interest Expense	17,781	14,710	17,414
Net Interest Income	274,008	212,551	196,647
Provision for loan losses	6,500	6,100	11,000
Net Interest Income after Provision for Loan Losses	267,508	206,451	185,647
Noninterest Income
Service charges and fees on deposit accounts	25,481	22,414	21,939
Wealth management revenue	20,552	16,015	13,989
Other charges and fees for customer services	25,513	18,928	17,151
Mortgage banking revenue	6,133	5,041	5,336
Gain on sale of investment securities	630	0	1,133
Gain on sale of merchant card services	0	400	0
Other	1,907	697	861
Total Noninterest Income	80,216	63,095	60,409
Operating Expenses
Salaries, wages and employee benefits	127,920	102,557	96,419
Occupancy	18,213	15,842	13,934
Equipment and software	18,569	14,737	13,734
Business Combination, Acquisition Related Costs	7,804	6,388	0
Other	51,388	40,401	40,861
Total Operating Expenses	223,894	179,925	164,948
Income Before Income Taxes	123,830	89,621	81,108
Federal income tax expense	37,000	27,500	24,300
Net Income	$ 86,830	$ 62,121	$ 56,808
Net Income Per Common Share
Basic	$ 2.41	$ 1.98	$ 2.02
Diluted	2.39	1.97	2
Cash Dividends Declared Per Common Share	$ 1	$ 0.94	$ 0.87

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income	$ 86,830	$ 62,121	$ 56,808
Other Comprehensive Income (Loss), Net of Tax:
Change in net unrealized gains (losses) on investment securities available-for-sale, net of tax expense (benefit) of $(683), $1,222, and $(3,325) for the years ended December 31, 2015, 2014, and 2013, respectively	(1,269)	2,270	(6,177)
Reclassification adjustment for realized gain on sale of investment securities available-for-sale included in net income, net of tax expense of $221 for the year ended December 31, 2015 and $311 for the year ended December 31, 2013	(409)	0	(577)
Change in adjustment for pension and other postretirement benefits, net of tax benefit (expense) of $(2,746), $7,648, and $(9,344) for the years ended December 31, 2015, 2014, and 2013, respectively	5,099	(14,203)	17,353
Total other comprehensive income (loss), net of tax	3,421	(11,933)	10,599
Comprehensive Income	$ 90,251	$ 50,188	$ 67,407

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	$ (683)	$ 1,222	$ (3,325)
Tax expense (benefit) on net unrealized gains (losses) on investment securities available-for-sale	221	0	311
Tax expense on adjustment for pension and other postretirement benefits	$ (2,746)	$ 7,648	$ (9,344)

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2012	$ 596,341	$ 27,499	$ 433,195	$ 166,766	$ (31,119)
Changes in Stockholders' Equity [Roll Forward]
Comprehensive income	67,407			56,808	10,599
Cash dividends declared per share: $0.87 per share in 2013, $0.94 per share in 2014 and $1.00 per share in 2015	(24,521)			(24,521)
Stock Issued During Period, Value, New Issues	53,925	2,214	51,711
Stock issued - stock options	568	41	527
Shares issued - directors' stock plans	305	13	292
Shares issued — restricted stock performance units	(379)	23	(402)
Share-based compensation	2,854		2,854
Ending Balance at Dec. 31, 2013	696,500	29,790	488,177	199,053	(20,520)
Changes in Stockholders' Equity [Roll Forward]
Comprehensive income	50,188			62,121	(11,933)
Cash dividends declared per share: $0.87 per share in 2013, $0.94 per share in 2014 and $1.00 per share in 2015	(29,528)			(29,528)
Stock Issued During Period, Value, New Issues	76,175	2,875	73,300
Stock issued - stock options	931	44	887
Shares issued - directors' stock plans	438	18	420
Shares issued — restricted stock performance units	(502)	37	(539)
Share-based compensation	2,931	10	2,921
Ending Balance at Dec. 31, 2014	797,133	32,774	565,166	231,646	(32,453)
Changes in Stockholders' Equity [Roll Forward]
Comprehensive income	90,251			86,830	3,421
Cash dividends declared per share: $0.87 per share in 2013, $0.94 per share in 2014 and $1.00 per share in 2015	(36,918)			(36,918)
Stock Issued During Period, Value, Acquisitions	159,904	5,183	154,721
Stock issued - stock options	2,157	135	2,022
Shares issued - directors' stock plans	316	11	305
Shares issued — restricted stock performance units	(347)	54	(401)
Share-based compensation	3,478	11	3,467
Ending Balance at Dec. 31, 2015	$ 1,015,974	$ 38,168	$ 725,280	$ 281,558	$ (29,032)

Consolidated Statements of Cha8

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash dividends declared per share	$ 0.26	$ 0.26	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.23	$ 0.23	$ 1	$ 0.94	$ 0.87

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities:
Net Income	$ 86,830	$ 62,121	$ 56,808
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	6,500	6,100	11,000
Gains on sales of loans	(6,354)	(4,451)	(7,108)
Proceeds from sales of loans	228,995	153,743	218,237
Loans originated for sale	(220,765)	(150,795)	(198,683)
Gain on sale of investment securities	(630)	0	(1,133)
Net gains from sales/writedowns of other real estate and repossessed assets	(2,681)	(1,886)	(2,943)
Depreciation of premises and equipment	11,028	8,980	8,713
Amortization and impairment of intangible assets	8,244	3,545	3,492
Net amortization of premiums and discounts on investment securities	6,007	4,497	4,196
Share-based compensation expense	3,478	2,931	2,854
Deferred income tax	5,700	(1,700)	635
Contributions to defined benefit pension plan	0	0	(15,000)
Net (increase) decrease in interest receivable and other assets	(20,570)	953	6,197
Net increase (decrease) in interest payable and other liabilities	(2,800)	5,893	2,414
Net Cash Provided by Operating Activities	102,982	89,931	89,679
Investment securities — available-for-sale:
Proceeds from maturities, calls and principal reductions	239,179	165,749	154,959
Proceeds from sales and redemptions	13,173	0	38,028
Purchases	0	0	(304,264)
Investment securities — held-to-maturity:
Proceeds from maturities, calls and principal reductions	87,189	83,989	65,790
Purchases	(279,226)	(127,187)	(109,655)
Net increase in loans	(493,776)	(586,121)	(502,687)
Proceeds from sales of other real estate and repossessed assets	16,720	12,486	18,018
Purchases of premises and equipment, net	(8,527)	(13,411)	(8,664)
Payments to Acquire Businesses, Net of Cash Acquired	16,551	(14,260)	0
Net Cash Used in Investing Activities	(408,717)	(478,755)	(648,475)
Financing Activities
Net increase in interest- and noninterest-bearing demand deposits and savings accounts	479,386	277,781	341,568
Net decrease in time deposits	(170,598)	(115,642)	(140,626)
Net increase (decrease) in short-term borrowings	(31,268)	62,039	16,965
Proceeds from (Repayments of) Other Debt	125,000	0	0
Repayments of Other Debt	6,000	10,310	34,289
Cash dividends paid	(36,918)	(29,528)	(24,521)
Proceeds from issuance of common stock, net of issuance costs	0	76,175	53,925
Proceeds from directors' stock purchase plan and exercise of stock options	2,473	1,242	806
Cash paid for payroll taxes upon conversion of restricted stock units	(571)	(701)	(379)
Net Cash Provided by Financing Activities	361,504	261,056	213,449
Net Increase (Decrease) in Cash and Cash Equivalents	55,769	(127,768)	(345,347)
Cash and Cash Equivalents at Beginning of Year	183,020	310,788	656,135
Cash and Cash Equivalents at End of Year	238,789	183,020	310,788
Supplemental Disclosure of Cash Flow Information:
Interest paid	16,958	14,823	18,047
Federal income taxes paid	41,450	25,900	19,150
Loans transferred to other real estate and repossessed assets	9,329	11,308	6,382
Closed branch offices transferred to other real estate	2,692	841	382
Business combinations:
Fair value of tangible assets acquired (noncash)	1,282,420	747,181	0
Goodwill and identifiable intangible assets acquired	118,744	82,090	0
Liabilities assumed	1,258,051	815,011	0
Shares and Stock Options Issued in Acquisition	$ 159,904	$ 0	$ 0

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations Chemical Financial Corporation (Corporation) 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. The Bank of Holland and The Bank of Northern Michigan were acquired in the acquisition of Lake Michigan Financial Corporation (Lake Michigan) on May 31, 2015 and were consolidated with and into Chemical Bank during the fourth quarter of 2015. Monarch Community Bank was acquired in the acquisition of Monarch Community Bancorp, Inc. (Monarch) on April 1, 2015 and was consolidated with and into Chemical Bank during the second quarter of 2015. Chemical Bank operates within the State of Michigan as a state-chartered commercial bank. Chemical Bank operates through an internal organizational structure of four regional banking units and offers a full range of traditional banking and fiduciary products and services to the residents and business customers in the bank'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 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 from its loan products and investment securities, service charges and fees from customer deposit accounts and wealth management revenue. Accounting Standards Codification The Financial Accounting Standards Board's (FASB) Accounting Standards Codification (ASC) became effective on July 1, 2009. At that date, the ASC became FASB's officially recognized source of authoritative U.S. generally accepted accounting principles (GAAP) applicable to all public and non-public non-governmental entities, superseding existing FASB, American Institute of Certified Public Accountants (AICPA), Emerging Issues Task Force (EITF) and related literature. Rules and interpretive releases of the Securities and Exchange Commission (SEC) under the authority of federal securities laws are also sources of authoritative GAAP for SEC registrants. All other accounting literature is considered non-authoritative. Basis of Presentation and Principles of Consolidation The accounting and reporting policies of the Corporation and its subsidiaries conform to GAAP, SEC rules and interpretive releases and prevailing practices within the banking industry. The consolidated financial statements of the Corporation include the accounts of the Corporation and its wholly owned subsidiaries. All significant income and expenses are recorded on the accrual basis. Intercompany accounts and transactions have been eliminated in preparing the consolidated financial statements. 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, fair value amounts related to business combinations, pension expense, income taxes, goodwill impairment and those assets that require fair value measurement. Actual results could differ from these estimates. Business Combinations Pursuant to the guidance of ASC Topic 805, Business Combinations (ASC 805), the Corporation recognizes assets acquired, including identified intangible assets, and the liabilities assumed in acquisitions at their fair values as of the acquisition date, with the acquisition-related transaction and restructuring costs expensed in the period incurred. On May 31, 2015, the Corporation acquired all of the outstanding stock of Lake Michigan for total consideration of $187.4 million , which included stock consideration of $132.9 million and cash consideration of $54.5 million . The Corporation recorded $102 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair value of identifiable net assets acquired. Additionally, the Corporation recorded $8.6 million of core deposit and other intangible assets in conjunction with the acquisition. On April 1, 2015, the Corporation acquired all of the outstanding stock of Monarch in an all-stock transaction valued at $27.2 million . The Corporation recorded $5.3 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair value of identifiable net assets acquired. Additionally, the Corporation recorded $1.9 million of core deposit intangible assets in conjunction with the acquisition. On October 31, 2014, the Corporation acquired all of the outstanding stock of Northwestern Bancorp, Inc. (Northwestern) for total cash consideration of $121.0 million . The Corporation recorded $60.3 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair value of the identifiable net assets acquired. Additionally, the Corporation recorded $12.9 million of core deposit intangible assets in conjunction with the acquisition. On December 7, 2012, Chemical Bank acquired 21 branches from Independent Bank, a subsidiary of Independent Bank Corporation (branch acquisition transaction). In connection with the branch acquisition transaction, the Corporation recorded $6.8 million of goodwill, which represented the purchase price over the fair value of identifiable net assets acquired, and $5.6 million of core deposit intangible assets. On April 30, 2010, the Corporation acquired all of the outstanding stock of O.A.K. Financial Corporation (OAK) for total consideration of $83.7 million . The Corporation recorded $43.5 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair values of the identifiable net assets acquired. Additionally, the Corporation recorded $9.8 million of other intangible assets as a result of the OAK acquisition attributable to core deposits, mortgage servicing rights and non-compete agreements acquired. See Note 2 for further information regarding the Corporation's mergers and acquisitions, including its pending merger with Talmer Bancorp, Inc. (Talmer). ASC 805 affords a measurement period beyond the acquisition date that allows the Corporation the opportunity to finalize the acquisition accounting in the event that new information is identified that existed as of the acquisition date but was not known by the Corporation at that time. The Corporation anticipates that measurement period adjustments may arise from adjustments to the fair values of assets and liabilities recognized at the acquisition date for Lake Michigan and Monarch as additional information is obtained, such as appraisals of collateral securing loans and other borrower information. In the event that a measurement period adjustment is identified, the Corporation will recognize the adjustment as part of its acquisition accounting, which may result in an adjustment to goodwill being recorded in the period the adjustment was identified. Cash and Cash Equivalents For purposes of reporting cash flows, cash and cash equivalents include cash on hand and interest-bearing deposits held at the Federal Reserve Bank (FRB). Investment Securities Investment securities include investments in debt, trust preferred and preferred stock securities. Investment securities are accounted for in accordance with ASC Topic 320, Investments — Debt and Equity Securities (ASC 320), which requires investments to be classified within one of three categories (trading, held-to-maturity or available-for-sale). The Corporation held no trading investment securities at December 31, 2015 or 2014 . Designation as an investment security held-to-maturity is based on the Corporation's intent and ability to hold the security to maturity. Investment securities held-to-maturity are stated at cost, adjusted for purchase price premiums and discounts. Investment securities that are not held-to-maturity are accounted for as securities available-for-sale, and are stated at estimated fair value, with the aggregate unrealized gains and losses, not deemed other-than-temporary, classified as a component of accumulated other comprehensive income (loss), net of income taxes. Realized gains and losses on the sale of investment securities and other-than-temporary impairment (OTTI) charges are determined using the specific identification method and are included within noninterest income in the consolidated statements of income. Premiums and discounts on investment securities are amortized over the estimated lives of the related investment securities based on the effective interest yield method and are included in interest income in the consolidated statements of income. The Corporation assesses equity and debt securities that have fair values below amortized cost basis to determine whether declines (impairment) are other-than-temporary. If the Corporation intends to sell an impaired security or it is more-likely-than-not that the Corporation will be required to sell an impaired security prior to the recovery of its amortized cost, an OTTI write-down is recognized in earnings equal to the entire difference between the security's amortized cost basis and its fair value. If the Corporation does not intend to sell an impaired security and it is not more-likely-than-not that the Corporation would be required to sell an impaired security before the recovery of its amortized cost basis, then the recognition of the impairment is bifurcated if a credit loss is deemed to have occurred. For a security where the impairment is bifurcated, the impairment is separated into an amount representing the credit loss, which is recognized in earnings, and an amount related to all other factors, which is recognized in other comprehensive income. In assessing whether OTTI exists, management considers, among other things, (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near-term prospects of the issuer, (iii) the potential for impairments in an entire industry or sub-sector and (iv) the potential for impairments in certain economically depressed geographical locations. Nonmarketable Equity Securities The Corporation is required to hold non-marketable equity securities, comprised of Federal Home Loan Bank of Indianapolis (FHLB) and FRB stock, as a condition of membership. These securities are accounted for at cost, which equals par or redemption value. These securities do not have a readily determinable fair value as their ownership is restricted and there is no market for these securities. These securities can only be redeemed or sold at their par value and only to the respective issuing government supported institution or to another member institution. FHLB stock can only be redeemed upon giving five -years written notice and FRB stock can only be redeemed upon giving six months written notice, with no more than 25% eligible for redemption in any calendar year. The Corporation records these non-marketable equity securities as a component of other assets and they are periodically evaluated for impairment. Management considers these non-marketable equity securities to be long-term investments. Accordingly, when evaluating these securities for impairment, management considers the ultimate recoverability of the par value rather than recognizing temporary declines in value, if applicable. The Corporation's ownership of FHLB stock totaled $23.9 million at December 31, 2015 and $19.0 million at December 31, 2014 . The Corporation's ownership of FRB stock totaled $13.0 million at December 31, 2015 and $8.4 million at December 31, 2014 . Originated Loans Originated loans include all of the Corporation's portfolio loans, excluding loans acquired on May 31, 2015 in the acquisition of Lake Michigan, on April 1, 2015 in the acquisition of Monarch, on October 31, 2014 in the acquisition of Northwestern and on April 30, 2010 in the acquisition of OAK. Originated loans also include loans acquired as part of the branch acquisition transaction on December 7, 2012, as these loans were performing and were considered high-quality loans in accordance with the Corporation's credit underwriting standards at that date. Originated loans are held for investment purposes and are stated at their principal amount outstanding, net of unearned income, charge-offs and unamortized deferred fees and costs. Loan interest income is recognized on the accrual basis. Deferred loan fees and costs are amortized over the loan term based on the level-yield method. Net loan commitment fees are deferred and amortized into fee income on a straight-line basis over the commitment period. The past due status of a loan is based on the loan's contractual terms. A loan is placed in nonaccrual status (accrual of interest is discontinued) when principal or interest is past due 90 days or more (except for a loan that is secured by residential real estate, which is transferred to nonaccrual status at 120 days past due), unless the loan is both well-secured and in the process of collection, or earlier when, in the opinion of management, there is sufficient reason to doubt the collectibility of principal or interest. Interest previously accrued, but not collected, is reversed and charged against interest income at the time the loan is placed in nonaccrual status. Subsequent receipts of interest while a loan is in nonaccrual status are recorded as a reduction of principal. Loans are returned to accrual status when principal and interest payments are brought current, payments have been received consistently for a period of time (generally six months) and collectibility is no longer in doubt. Loans Acquired in a Business Combination Loans acquired in a business combination (acquired loans) consist of loans acquired on May 31, 2015 in the acquisition of Lake Michigan, on April 1, 2015 in the acquisition of Monarch, on October 31, 2014 in the acquisition of Northwestern and on April 30, 2010 in the acquisition of OAK. Acquired loans were recorded at fair value at the date of acquisition, without a carryover of the associated allowance for loan losses related to these loans, through a fair value discount that was, in part, attributable to deterioration in credit quality. The estimate of expected credit losses was determined based on due diligence performed by executive and senior officers of the Corporation, with assistance from third-party consultants. The fair value discount was recorded as a reduction of the acquired loans' outstanding principal balances in the consolidated statement of financial position at the acquisition date. The Corporation accounts for acquired loans, which are recorded at fair value at acquisition, in accordance with ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality (ASC 310-30). Under the provisions of ASC 310-30, the Corporation aggregated acquired loans with an outstanding principal balance at the acquisition date of $63 million for the Lake Michigan transaction, $9 million for the Monarch transaction, $46 million for the Northwestern transaction and $105 million for the OAK transaction that were determined to be loans with deteriorated credit quality and, therefore, met the scope criteria set forth in ASC 310-30. Further, the Corporation understands, as outlined in the AICPA's open letter to the Office of the Chief Accountant of the SEC dated December 18, 2009 and pending further standard setting, that for acquired loans that do not meet the scope criteria of ASC 310-30, a company may elect to account for such acquired loans pursuant to the provisions of either ASC Topic 310-20, Nonrefundable Fees and Other Costs, or ASC 310-30. The Corporation elected to apply ASC 310-30, by analogy, to acquired loans that were determined not to have deteriorated credit quality with an outstanding principal balance at the acquisition date of $947 million for the Lake Michigan transaction, $120 million for the Monarch transaction, $461 million for the Northwestern transaction and $578 million for the OAK transaction and thus follows the accounting and disclosure guidance of ASC 310-30 for these loans. Accordingly, the Corporation applied ASC 310-30 to the entire loan portfolio acquired with a total outstanding principal balance at the acquisition date of $1.01 billion for the Lake Michigan transaction, $129 million for the Monarch transaction, $507 million for the Northwestern transaction and $683 million for the OAK transaction. None of the acquired loans were classified as debt securities. ASC 310-30 allows investors to aggregate acquired loans into loan pools that have common risk characteristics and thereby use a composite interest rate and expectation of cash flows expected to be collected for the loan pools. Under the provisions of ASC 310-30, the Corporation aggregated acquired loans into 2 pools in the acquisition of Lake Michigan, 2 pools in the acquisition of Monarch, 4 pools in the acquisition of Northwestern and 14 pools in the acquisition of OAK based upon common risk characteristics, including types of loans, commercial type loans with similar risk grades and whether loans were performing or nonperforming. A pool is considered a single unit of accounting for the purposes of applying the guidance prescribed in ASC 310-30. A loan will be removed from a pool of acquired loans only if the loan is sold, foreclosed, paid off or written off, and will be removed from the pool at the carrying value. If an individual loan is removed from a pool of loans, the difference between its relative carrying amount and the cash, fair value of the collateral, or other assets received would not affect the effective yield used to recognize the accretable difference on the remaining pool. The Corporation estimated the cash flows expected to be collected over the life of the pools of loans at acquisition and estimates expected cash flows quarterly thereafter, based on a set of assumptions including expectations as to default rates, prepayment rates and loss severities. The Corporation must make numerous assumptions, interpretations and judgments using internal and third-party credit quality information to determine whether it is probable that the Corporation will be able to collect all contractually required payments. This is a point in time assessment and inherently subjective due to the nature of the available information and judgment involved. The calculation of the fair value of the acquired loan pools entails estimating the amount and timing of cash flows attributable to both principal and interest expected to be collected on such loan pools and then discounting those cash flows at market interest rates. The excess of a loan pool's expected cash flows at the acquisition date over its estimated fair value is referred to as the "accretable yield," which is recognized into interest income over the remaining life of the loan on a level-yield basis. The difference between a loan pool's contractually required principal and interest payments at the acquisition date and the cash flows expected to be collected at the acquisition date is referred to as the "nonaccretable difference," which includes an estimate of future credit losses expected to be incurred over the estimated life of the loan pool and interest payments that are not expected to be collected. Decreases to the expected cash flows in each loan pool in subsequent periods will require the Corporation to record a provision for loan losses. Improvements in expected cash flows in each loan pool in subsequent periods will result in reversing a portion of the nonaccretable difference, which is then classified as part of the accretable yield and subsequently recognized into interest income over the estimated remaining life of the loan pool. Loans Modified Under Troubled Debt Restructurings Loans modified under troubled debt restructurings (TDRs) involve granting a concession to a borrower who is experiencing financial difficulty. Concessions generally include modifications to original loan terms, including changes to a loan's payment schedule or interest rate, which generally would not otherwise be considered. The Corporation's TDRs include performing and nonperforming TDRs, which consist of originated loans that continue to accrue interest at the loan's original interest rate as the Corporation expects to collect the remaining principal and interest on the loan, and nonaccrual TDRs, which include originated loans that are in a nonaccrual status and are no longer accruing interest, as the Corporation does not expect to collect the full amount of principal and interest owed from the borrower on these loans. At the time of modification (except for loans on nonaccrual status), a TDR is classified as a nonperforming TDR until a six -month payment history of principal and interest payments, in accordance with the terms of the loan modification, is sustained, at which time the Corporation moves the loan to a performing status (performing TDR). If the Corporation does not expect to collect all principal and interest on the loan, the modified loan is classified as a nonaccrual TDR. All TDRs are accounted for as impaired loans and are included in the Corporation's analysis of the allowance for loan losses. A TDR that has been renewed for a borrower who is no longer experiencing financial difficulty and which yields a market rate of interest at the time of a renewal is no longer considered to be a TDR. Loans in the Corporation's commercial loan portfolio (comprised of commercial, commercial real estate, real estate construction and land development loans) that meet the definition of a TDR generally consist of loans where the Corporation has allowed borrowers to defer scheduled principal payments and make interest-only payments for a specified period of time at the stated interest rate of the original loan agreement or reduced payments due to a moderate extension of the loan's contractual term. If the Corporation does not expect to collect all principal and interest on the loan, the modified loan is classified as a nonaccrual TDR. If the Corporation does not expect to incur a loss on the loan based on its assessment of the borrowers' expected cash flows, as the pre- and post-modification effective yields are approximately the same, the loan is classified as a nonperforming TDR until a six-month payment history is sustained, at which time the loan is classified as a performing TDR. Since no loss is expected to be incurred on these loans, no additional provision for loan losses has been recognized related to these loans, and these loans accrue interest at their contractual interest rate. These loans are individually evaluated for impairment and transferred to nonaccrual status if they become 90 days past due as to principal or interest payments or if it is probable that any remaining principal and interest payments due on the loan will not be collected in accordance with the modified terms of the loan. Loans in the Corporation's consumer loan portfolio (comprised of residential mortgage, consumer installment and home equity loans) that meet the definition of a performing or nonperforming TDR generally consist of residential mortgage loans that include a concession that reduces a borrower's monthly payments by decreasing the interest rate charged on the loan for a specified period of time (generally 24 months) under a formal modification agreement. The Corporation recognizes an additional provision for loan losses related to impairment on these loans on an individual basis based on the present value of expected future cash flows discounted at the loan's original effective interest rate. These loans continue to accrue interest at their effective interest rate, which consists of contractual interest under the terms of the modification agreement in addition to an adjustment for the accretion of computed impairment. These loans are moved to nonaccrual status if they become 90 days past due as to principal or interest payments, or sooner if conditions warrant. Impaired Loans A loan is defined to be impaired when it is probable that payment of principal and interest will not be paid in accordance with the original contractual terms of the loan agreement. Impaired loans include nonaccrual loans (including nonaccrual TDRs), performing and nonperforming TDRs and acquired loans that were not performing in accordance with original contractual terms. Impaired loans are accounted for at the lower of the present value of expected cash flows discounted at the loan's original effective interest rate or the estimated fair value of the collateral, if the loan is collateral dependent. When the present value of expected cash flows or the fair value of collateral of an impaired loan in the originated loan portfolio is less than the amount of unpaid principal outstanding on the loan, the principal balance of the loan is reduced to its carrying value through either an allocation of the allowance for loan losses or a partial charge-off of the loan balance. Nonperforming Loans Nonperforming loans are comprised of loans for which the accrual of interest has been discontinued (nonaccrual loans, including nonaccrual TDRs), accruing originated loans contractually past due 90 days or more as to interest or principal payments and nonperforming TDRs. Acquired loans that were classified as nonperforming loans prior to being acquired and acquired loans that are not performing in accordance with contractual terms subsequent to acquisition are not classified as nonperforming loans subsequent to acquisition because the loans are recorded in pools at net realizable value based on the principal and interest the Corporation expects to collect on such loans. Allowance for Loan Losses The allowance for loan losses (allowance) is presented as a reserve against loans. The allowance represents management's assessment of probable loan losses inherent in the Corporation's loan portfolio. Management's evaluation of the adequacy of the allowance is based on a continuing review of the loan portfolio, actual loan loss experience, the underlying value of the collateral, risk characteristics of the loan portfolio, the level and composition of nonperforming loans, the financial condition of the borrowers, the balance of the loan portfolio, loan growth, economic conditions, employment levels in the Corporation's local markets and special factors affecting specific business sectors. The Corporation maintains formal policies and procedures to monitor and control credit risk. Management evaluates the allowance on a quarterly basis in an effort to ensure the level is appropriate to absorb probable losses inherent in the loan portfolio. The allowance provides for probable losses that have been identified with specific customer relationships and for probable losses believed to be incurred in the remainder of the originated loan portfolio, but that have not been specifically identified. The Corporation utilizes its own loss experience to estimate inherent losses on loans. Internal risk ratings are assigned to each loan in the commercial loan portfolio (commercial, commercial real estate, real estate construction and land development loans) at the time of origination and are subject to subsequent periodic reviews by senior management. The Corporation performs a detailed credit quality review quarterly on all loans greater than $0.25 million that have deteriorated below certain levels of credit risk, and may allocate a specific portion of the allowance to such loans based upon this review. A portion of the allowance is allocated to the remaining loans by applying projected loss ratios, based on numerous factors. Projected loss ratios incorporate factors such as recent charge-off experience, trends with respect to adversely risk-rated loans in the commercial loan portfolio, trends with respect to past due and nonaccrual loans, changes in economic conditions and trends, changes in the value of underlying collateral and other credit risk factors. This evaluation involves a high degree of uncertainty. In determining the allowance and the related provision for loan losses, the Corporation considers four principal elements: (i) valuation allowances based upon probable losses identified during the review of impaired loans in the commercial loan portfolio, (ii) reserves established for adversely-rated loans in the commercial loan portfolio and nonaccrual residential mortgage, consumer installment and home equity loans based on loan loss experience of other adversely-rated loans, (iii) reserves, by loan classes, on all other loans based principally on a five -year historical loan loss experience, loan loss trends and giving consideration to estimated loss emergence periods and (iv) a reserve for qualitative factors that take into consideration risks inherent in the originated loan portfolio that differ from historical loan loss experience. The first element reflects the Corporation's estimate of probable losses based upon the systematic review of individually impaired loans in the originated commercial loan portfolio. These estimates are based upon a number of objective factors, such as payment history, financial condition of the borrower and discounted collateral exposure. The Corporation measures the investment in an impaired loan based on one of three methods: the loan's observable market price; the fair value of the collateral; or the present value of expected future cash flows discounted at the loan's effective interest rate. Loans in the commercial loan portfolio that were in nonaccrual status (including nonaccrual TDRs) were valued based on the fair value of the collateral securing the loan, while performing and nonperforming TDRs in the commercial loan portfolio were valued based on the present value of expected future cash flows discounted at the loan's effective interest rate. It is the Corporation's general policy to obtain new appraisals at least annually on nonaccrual loans in the commercial loan portfolio and at least every other year on nonperforming TDRs in the commercial loan portfolio that are primarily secured by real estate and have a loan balance of greater than $0.25 million . When the Corporation determines that the fair value of the collateral is less than the carrying value of an impaired loan on nonaccrual status and a portion is deemed not collectible, the portion of the impairment that is deemed not collectible is charged off (confirmed loss) and deducted from the allowance. The remaining carrying value of the impaired loan is classified as a nonperforming loan. When the Corporation determines that the fair value of the collateral is less than the carrying value of an impaired loan but believes it is probable it will recover this impairment, the Corporation establishes a valuation allowance for such impairment. The second element reflects the application of the Corporation's loan grade risk rating system. This risk rating system is similar to those employed by state and federal banking regulators. Loans in the commercial loan portfolio that are risk rated below a certain predetermined risk grade and nonaccrual residential mortgage, consumer installment and home equity loans are assigned a loss allocation factor that is based upon a historical analysis of actual loan losses incurred and a valuation of the type of collateral securing the loans. The third element is determined by assigning allocations based principally upon a weighted five -year average of loss experience for each class of loan with higher weighting placed on the most recent years. Average losses may be adjusted based on current loan loss experience, delinquency trends, estimated loss emergence periods and other environmental factors. This component considers the lagging impact of historical charge-off ratios in periods where future loan charge-offs are expected to increase or decrease, trends in delinquencies and nonaccrual loans, the changing portfolio mix in terms of collateral, average loan balance, loan gr

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions	MERGERS AND ACQUISITIONS Pending Merger with Talmer Bancorp, Inc. On January 25, 2016, the Corporation entered into an Agreement and Plan of Merger with Talmer Bancorp, Inc. (Talmer). Under the terms of the merger agreement, each Talmer shareholder will receive $1.61 in cash and 0.4725 shares of the Corporation's common stock for each share of Talmer common stock, subject to adjustment in limited circumstances. Based on the 30-day volume weighted price per share of the Corporation's common stock as of January 25, 2016, the merger had a transaction value of approximately $1.1 billion . Following the completion of the merger, the Corporation intends to consolidate Talmer's wholly-owned subsidiary bank, Talmer Bank and Trust, with and into Chemical Bank. At December 31, 2015, Talmer had total assets of $6.6 billion , total loans of $4.8 billion and total deposits of $5.0 billion , including brokered deposits of $229 million . Talmer Bank and Trust is a full service community bank offering a full suite of commercial banking, retail banking, mortgage banking, wealth management and trust services to small and medium-sized businesses and individuals through 81 full service banking offices located primarily within southeast Michigan and northeast Ohio, as well as in west Michigan, northeast Michigan, Chicago, Illinois, northern Indiana, and Las Vegas, Nevada. Completion of the merger is subject to regulatory approval and the approval of the Corporation's and Talmer's shareholders, in addition to satisfaction of other customary closing conditions. Acquisition of Lake Michigan Financial Corporation On May 31, 2015, the Corporation acquired all of the outstanding stock of Lake Michigan Financial Corporation (Lake Michigan) for total consideration of $187.4 million , which included stock consideration of $132.9 million and cash consideration of $54.5 million . As a result of the acquisition, the Corporation issued approximately 4.3 million shares of its common stock, based on an exchange ratio of 1.326 shares of its common stock, and paid $16.64 in cash, for each share of Lake Michigan common stock outstanding. Lake Michigan, a bank holding company which owned The Bank of Holland and The Bank of Northern Michigan, provided traditional banking services and products with five banking offices in Holland, Grand Haven, Grand Rapids, Petoskey and Traverse City, Michigan. As of the May 31, 2015 acquisition date, Lake Michigan added total assets of $1.24 billion , including total loans of $986 million , and total deposits of $925 million to the Corporation. The Bank of Holland and The Bank of Northern Michigan were consolidated with and into Chemical Bank on November 13, 2015. The Corporation recorded $102 million of goodwill, which was primarily attributable to the synergies and economies of scale expected from combining the operations of the Corporation and Lake Michigan. In addition, the Corporation recorded $8.6 million of core deposit and other intangible assets in conjunction with the acquisition. The results of the merged Lake Michigan operations are presented in the Corporation's consolidated financial statements from the date of acquisition. The disclosure of Lake Michigan's post-acquisition revenue and net income is not practical due to the combining of Lake Michigan's operations with and into Chemical Bank during the fourth quarter of 2015. Acquisition-related expenses associated with the Lake Michigan transaction totaled $5.5 million during 2015. The summary computation of the purchase price, including adjustments to reflect Lake Michigan's assets acquired and liabilities assumed at fair value and the allocation of the purchase price to the net assets of Lake Michigan, is presented below. The acquisition accounting presented below may be further adjusted during a measurement period of up to one year beyond the acquisition date that provides the Corporation with the opportunity to finalize the acquisition accounting in the event that new information is identified that existed as of the acquisition date but was not known by the Corporation at that time. In accordance with ASU 2015-16, no amounts were recorded in the consolidated statements of income for the current reporting period for adjustments that would have been recorded in a previous reporting period had these adjustments been recognized as of the acquisition date. A summary of the purchase price and the excess of the purchase price over the fair value of adjusted net assets acquired (goodwill) follows (in thousands): Fair value of the Corporation's common shares issued on May 31, 2015 (4,322,101 shares at a market price of $30.29 per share) $ 130,916 Fair value of Lake Michigan options converted to the Corporation's options 2,000 Cash paid to acquire outstanding stock 54,478 Total purchase price 187,394 Net assets acquired (1) : Lake Michigan shareholders' equity $ 89,280 Adjustments to reflect fair value of net assets acquired: Loans (22,600 ) Allowance for loan losses 15,888 Premises and equipment (5,031 ) (2) Core deposit intangibles 8,003 Deferred tax assets, net 3,572 (2) Deposits and borrowings, net (3,182 ) (2) Other assets and other liabilities (157 ) Fair value of adjusted net assets acquired 85,773 Goodwill recognized as a result of the Lake Michigan transaction $ 101,621 (1) All amounts were previously reported in the Corporation's Quarterly Report on Form 10-Q for the three- and nine-month periods ended September 30, 2015, with the exception of premises and equipment, other liabilities and deferred tax assets, net. (2) Includes adjustments to the fair value as a result of additional valuation information obtained during the fourth quarter of 2015, including the corresponding tax effects. A summary of these adjustments is included in the section "Allocation of Purchase Price" within this footnote. Allocation of Purchase Price The following schedule summarizes the revised acquisition date estimated fair values, including the adjustments to the fair values identified and recorded from the acquisition date through December 31, 2015, of assets acquired and liabilities assumed from Lake Michigan (in thousands): Assets Cash and cash equivalents $ 39,301 Investment securities 66,699 Loans 985,542 Premises and equipment 10,975 Deferred tax asset, net 16,191 Goodwill 101,621 Core deposit intangible asset 8,003 Bank-owned life insurance 23,844 Other assets 37,659 Assets acquired, at fair value 1,289,835 Liabilities Deposits 924,697 Short-term borrowings 30,000 Other borrowings 124,857 Other liabilities 22,887 Total liabilities acquired, at fair value 1,102,441 Total purchase price $ 187,394 During the three months ended December 31, 2015, additional valuation information was obtained related to the fair value of premises and equipment and other borrowings, which resulted in an adjustment to goodwill acquired in the Lake Michigan transaction. All amounts were previously reported in the Corporation's Quarterly Report on Form 10-Q for the three- and nine-month periods ended September 30, 2015, with the exception of goodwill, premises and equipment, other borrowings and deferred tax assets, net. The adjustments recorded during the fourth quarter of 2015, which resulted in a $0.7 million increase to the preliminary amount of goodwill recorded for the Lake Michigan transaction, included a $1.0 million write-down to premises and equipment related to updated information obtained regarding the fair market value of certain vacant land and non-branch locations, a $0.1 million increase in the fair value assigned to other borrowings based on updated assumptions utilized as part of the valuation, and a $0.4 million increase in the amount of recognizable deferred tax assets based on the tax impact of these adjustments. Upon acquisition, the Lake Michigan loan portfolio had contractually required principal and interest payments receivable of $1.01 billion and $190.2 million , respectively, expected principal and interest cash flows of $986.1 million and $189.6 million , respectively, and a fair value of $985.5 million . The difference between the contractually required payments receivable and the expected cash flows represents the nonaccretable difference, which totaled $22.6 million at the acquisition date, with $22.0 million attributable to expected credit losses. The difference between the expected cash flows and fair value represents the accretable yield, which totaled $190.2 million at the date of acquisition. At December 31, 2015, the outstanding contractual principal balance and the carrying amount of the Lake Michigan acquired loan portfolio were $ 864 million and $ 842 million , respectively, and there was no related allowance for loan losses at that date. Acquisition of Monarch Community Bancorp, Inc. On April 1, 2015, the Corporation acquired all of the outstanding stock of Monarch Community Bancorp, Inc. (Monarch) in an all-stock transaction valued at $27.2 million . As a result of the acquisition, the Corporation issued 860,575 shares of its common stock based on an exchange ratio of 0.0982 shares of its common stock for each share of Monarch common stock outstanding. Monarch, a bank holding company, owned Monarch Community Bank, which operated five full service branch offices in Coldwater, Marshall, Hillsdale and Union City, Michigan. As of the April 1, 2015 acquisition date, Monarch added total assets of $183 million , including total loans of $122 million , and total deposits of $144 million to the Corporation's consolidated statement of financial position. Monarch Community Bank was consolidated with and into Chemical Bank on May 8, 2015. In connection with the acquisition of Monarch, the Corporation recorded $5.3 million of goodwill, which was primarily attributable to the synergies and economies of scale expected from combining the operations of the Corporation and Monarch. In addition, the Corporation recorded $1.9 million of core deposit intangible assets in conjunction with the acquisition. The results of the merged Monarch operations are presented in the Corporation's consolidated financial statements from the date of acquisition. The disclosure of Monarch's post-acquisition revenue and net income is not practical due to the combining of Monarch's operations with and into Chemical Bank during the second quarter of 2015. Acquisition-related expenses associated with the Monarch transaction totaled $2.3 million during 2015. The summary computation of the purchase price, including adjustments to reflect Monarch's assets acquired and liabilities assumed at fair value and the allocation of the purchase price to the net assets of Monarch is presented below. The acquisition accounting presented below may be further adjusted during a measurement period of up to one year beyond the acquisition date that provides the Corporation with the opportunity to finalize the acquisition accounting in the event that new information is identified that existed as of the acquisition date but was not known by the Corporation at that time. In accordance with ASU 2015-16, no amounts were recorded in the consolidated statements of income for the current reporting period for adjustments that would have been recorded in a previous reporting period had these adjustments been recognized as of the acquisition date. A summary of the purchase price and the excess of the purchase price over the fair value of adjusted net assets acquired (goodwill) follows (in thousands): Fair value of the Corporation's common shares issued on April 1, 2015 (860,575 shares at a market price of $31.36 per share) $ 26,988 Cash paid 203 Total purchase price $ 27,191 Net assets acquired (1) : Monarch shareholders' equity $ 15,270 Adjustments to reflect fair value of net assets acquired: Loans (7,150 ) Allowance for loan losses 2,128 Deferred tax assets, net: Net operating loss carryforward 7,900 Other 1,826 (2) Premises and equipment (395 ) (2) Core deposit intangibles 1,930 Mortgage servicing rights 315 Other assets and other liabilities 37 Fair value of adjusted net assets acquired 21,861 Goodwill recognized as a result of the Monarch transaction $ 5,330 (1) All amounts were previously reported in the Corporation's Quarterly Report on Form 10-Q for the three- and nine-month periods ended September 30, 2015, with the exception of premises and equipment and deferred tax assets, net. (2) Includes immaterial adjustments to the fair value as a result of additional valuation information obtained during the fourth quarter of 2015, including the corresponding tax effects. Allocation of Purchase Price The following schedule summarizes the the revised acquisition date estimated fair values, including the adjustments to the fair values identified and recorded from the acquisition date through December 31, 2015, of assets acquired and liabilities assumed from Monarch. Assets Cash and cash equivalents $ 32,171 Loans 121,783 Premises and equipment 3,039 Deferred tax assets, net Net operating loss carryforward 7,900 Other 2,392 Interest receivable and other assets 6,972 Goodwill 5,330 Core deposit intangibles 1,930 Mortgage servicing rights 1,284 Assets acquired, at fair value 182,801 Liabilities Deposits 144,311 FHLB advances 8,000 Interest payable and other liabilities 3,299 Total liabilities acquired, at fair value 155,610 Total purchase price $ 27,191 During the three months ended December 31, 2015, additional valuation information was obtained related to the fair value of premises and equipment, which resulted in an immaterial adjustment to goodwill acquired in the Monarch transaction. All amounts were previously reported in the Corporation's Quarterly Report on Form 10-Q for the three- and nine-month periods ended September 30, 2015, with the exception of goodwill, premises and equipment and deferred tax assets, net. Upon acquisition, the Monarch loan portfolio had contractually required principal and interest payments receivable of $128.9 million and $37.8 million , respectively, expected principal and interest cash flows of $122.6 million and $37.1 million , respectively, and a fair value of $121.8 million . The difference between the contractually required payments receivable and the expected cash flows represents the nonaccretable difference, which totaled $7.1 million at the acquisition date, with $6.3 million attributable to expected credit losses. The difference between the expected cash flows and fair value represents the accretable yield, which totaled $37.9 million at the date of acquisition. At December 31, 2015, the outstanding contractual principal balance and the carrying amount of the Monarch acquired loan portfolio were $ 115 million and $ 108 million , respectively, and there was no related allowance for loan losses at that date. Acquisition of Northwestern Bancorp, Inc. On October 31, 2014, the Corporation acquired all of the outstanding stock of Northwestern Bancorp, Inc. (Northwestern) for total cash consideration of $121 million . Northwestern, a bank holding company which owned Northwestern Bank, provided traditional banking services and products through 25 banking offices serving communities in the northwestern lower peninsula of Michigan. As of the October 31, 2014 acquisition date, Northwestern added total assets of $815 million , including total loans of $475 million , and total deposits of $794 million to the Corporation. Northwestern Bank was consolidated with and into Chemical Bank as of the acquisition date. In connection with the acquisition of Northwestern, the Corporation recorded $60.3 million of goodwill, which was primarily attributable to the synergies and economies of scale expected from combining the operations of the Corporation and Northwestern. In addition, the Corporation recorded $12.9 million of core deposit intangible assets in conjunction with the acquisition. During the fourth quarter of 2015 and prior to the end of the one year measurement period for finalizing the purchase price allocation, the Corporation obtained additional valuation information regarding the fair value of vacant land and closed branch locations, which resulted in a decrease to premises and equipment of $0.3 million , an increase to deferred tax assets of $0.1 million , and an increase to goodwill recognized in the transaction of $0.2 million . In accordance with ASU 2015-16, no amounts were recorded in the consolidated statements of income during 2015 for these adjustments that would have been recorded in a previous reporting period had these adjustments been recognized as of the acquisition date. The results of the merged Northwestern operations are presented within the Corporation’s consolidated financial statements from the acquisition date. The disclosure of Northwestern's post-acquisition revenue and net income is not practical due to the combining of Northwestern Bank’s operations with and into Chemical Bank as of the October 31, 2014 acquisition date. Acquisition-related expenses associated with the Northwestern acquisition totaled $5.8 million during 2014. Upon acquisition, the Northwestern loan portfolio had contractually required principal and interest payments receivable of $507 million and $112 million , respectively, expected principal and interest cash flows of $481 million and $104 million , respectively, and a fair value of $475 million . The difference between the contractually required payments receivable and the expected cash flows represents the nonaccretable difference, which totaled $34 million at the acquisition date, with $26 million attributable to expected credit losses. The difference between the expected cash flows and fair value represents the accretable yield, which totaled $110 million at the acquisition date. The outstanding contractual principal balance and the carrying amount of the Northwestern acquired loan portfolio were $361 million and $330 million , respectively, at December 31, 2015, compared to $485 million and $452 million , respectively, at December 31, 2014. Unaudited Pro Forma Combined Results of Operations The following unaudited pro forma combined results of operations of Chemical, Lake Michigan, Monarch and Northwestern presents results as if the acquisitions had been completed as of the beginning of each period indicated. The unaudited pro forma combined results of operations are presented solely for information purposes and are not intended to represent or be indicative of the consolidated results of operations that Chemical would have reported had these transactions been completed as of the dates and for the periods presented, nor are they necessarily indicative of future results. In particular, no adjustments have been made to eliminate the amount of Lake Michigan's, Monarch's, or Northwestern's provision for loan losses incurred prior to the acquisition date that would not have been necessary had the acquired loans been recorded at fair value as of the beginning of each period indicated. In accordance with Article 11 of SEC Regulation S-X, transaction costs directly attributable to the acquisitions have been excluded. Year ended December 31, 2015 2014 (In thousands, except per share data) Interest income $ 313,851 $ 301,838 Interest expense 21,750 26,386 Net interest income 292,101 275,452 Provision for loan losses 6,500 7,484 Net interest income after provision for loan losses 285,601 267,968 Noninterest income 83,447 86,243 Operating expenses 237,146 243,618 Income before income taxes 131,902 110,593 Federal income tax expense 30,680 31,138 Net income $ 101,222 $ 79,455 Net income per common share: Basic $ 2.66 $ 2.17 Diluted 2.64 2.16 Weighted average shares outstanding: Basic 38,097 36,550 Diluted 38,369 36,770 Acquisition of 21 Branches On December 7, 2012, Chemical Bank acquired 21 branches from Independent Bank, a subsidiary of Independent Bank Corporation. In addition to the branch offices, which are located in the northeast and Battle Creek regions of Michigan, the acquisition included $404 million in deposits and $44 million in loans. The purchase price of the branch offices, including equipment, was $8.1 million and the Corporation paid a premium on deposits of $11.5 million , or approximately 2.85% of total deposits. The loans were purchased at a discount of 1.75% . In connection with the acquisition of the branches, the Corporation recorded $6.8 million of goodwill and $5.6 million of core deposit intangible assets. Acquisition of O.A.K. Financial Corporation On April 30, 2010, the Corporation acquired O.A.K. Financial Corporation (OAK) for total consideration of $83.7 million . As a result of the acquisition, the Corporation issued 3.5 million shares of its common stock. OAK, a bank holding company that owned Byron Bank, provided traditional commercial banking services and products through 14 banking offices serving communities in Ottawa, Allegan and Kent counties in west Michigan. At the acquisition date, OAK added total assets of $820 million , including total loans of $627 million , and total deposits of $693 million , including brokered deposits of $193 million , to the Corporation. The outstanding contractual principal balance and the carrying amount of the acquired OAK loan portfolio were $204 million and $183 million , respectively, at December 31, 2015 , compared to $268 million and $246 million , respectively, at December 31, 2014 . 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: Lake Michigan Monarch North-western OAK Total Year Ended December 31, 2015 Balance at beginning of period $ — $ — $ 104,675 $ 33,286 $ 137,961 Addition attributable to acquisitions 190,246 37,914 — — 228,160 Additions, net of reductions* (12,991 ) 1,336 (3,396 ) 6,601 (8,450 ) Accretion recognized in interest income (24,256 ) (4,692 ) (18,656 ) (11,810 ) (59,414 ) Reclassification from nonaccretable difference — — — — — Balance at end of period $ 152,999 $ 34,558 $ 82,623 $ 28,077 $ 298,257 Year Ended December 31, 2014 Balance at beginning of period $ — $ 32,610 $ 32,610 Addition attributable to acquisitions 110,003 — 110,003 Additions, net of reductions* (1,605 ) 5,411 3,806 Accretion recognized in interest income (3,723 ) (14,735 ) (18,458 ) Reclassification from nonaccretable difference — 10,000 10,000 Balance at end of period $ 104,675 $ 33,286 $ 137,961 * Represents additions in estimated contractual interest expected to be collected from acquired loans being renewed or extended, less reductions in contractual interest resulting from the early payoff of acquired loans. As part of its ongoing assessment of the acquired loan portfolio, management determined during 2014 that the overall credit quality of the OAK acquired loan portfolio has improved, which had resulted in an improvement in expected cash flows of loan pools in the OAK acquired commercial loan portfolio. Accordingly, management reclassified $10.0 million during 2014 from the nonaccretable difference to the accretable yield for these acquired commercial loan pools, which will increase amounts recognized into interest income over the estimated remaining lives of these loan pools.

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2015
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 available-for-sale and investment securities held-to-maturity at December 31, 2015 and 2014 : Investment Securities Available-for-Sale Amortized Cost Unrealized Gains Unrealized Losses Fair Value (In thousands) December 31, 2015 U.S. Treasury securities $ 5,773 $ — $ 8 $ 5,765 Government sponsored agencies 195,711 78 800 194,989 State and political subdivisions 14,731 395 6 15,120 Residential mortgage-backed securities 189,452 538 2,222 187,768 Collateralized mortgage obligations 133,256 111 1,137 132,230 Corporate bonds 14,825 2 200 14,627 Preferred stock and trust preferred securities 2,888 344 — 3,232 Total $ 556,636 $ 1,468 $ 4,373 $ 553,731 December 31, 2014 U.S. Treasury securities $ 8,272 $ — $ 13 $ 8,259 Government sponsored agencies 263,658 356 511 263,503 State and political subdivisions 45,157 1,087 17 46,227 Residential mortgage-backed securities 240,465 885 1,543 239,807 Collateralized mortgage obligations 145,316 261 1,194 144,383 Corporate bonds 44,930 213 48 45,095 Preferred stock 1,389 201 — 1,590 Total $ 749,187 $ 3,003 $ 3,326 $ 748,864 Investment Securities Held-to-Maturity Amortized Cost Unrealized Gains Unrealized Losses Fair Value (In thousands) December 31, 2015 State and political subdivisions $ 509,471 $ 7,446 $ 4,512 $ 512,405 Trust preferred securities 500 — 200 300 Total $ 509,971 $ 7,446 $ 4,712 $ 512,705 December 31, 2014 State and political subdivisions $ 305,913 $ 7,294 $ 4,557 $ 308,650 Trust preferred securities 10,500 — 3,410 7,090 Total $ 316,413 $ 7,294 $ 7,967 $ 315,740 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). At December 31, 2014, the Corporation held a $10.5 million trust preferred investment security that had been issued by Lake Michigan. With the acquisition of Lake Michigan, this investment was settled as of the acquisition date at par. The following is a summary of the amortized cost and fair value of investment securities at December 31, 2015 , by maturity, for both available-for-sale and held-to-maturity investment securities. 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. December 31, 2015 Amortized Cost Fair Value (In thousands) Investment Securities Available-for-Sale: Due in one year or less $ 170,838 $ 170,098 Due after one year through five years 326,018 324,187 Due after five years through ten years 53,317 52,649 Due after ten years 5,074 5,064 Preferred stock 1,389 1,733 Total $ 556,636 $ 553,731 Investment Securities Held-to-Maturity: Due in one year or less $ 59,834 $ 59,938 Due after one year through five years 236,141 236,491 Due after five years through ten years 136,383 137,188 Due after ten years 77,613 79,088 Total $ 509,971 $ 512,705 The following schedule summarizes information for both available-for-sale and held-to-maturity investment securities with gross unrealized losses at December 31, 2015 and 2014 , aggregated by category and length of time that individual securities have been in a continuous unrealized loss position. Less Than 12 Months 12 Months or More Total Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses December 31, 2015 U.S. Treasury securities $ 5,765 $ 8 $ — $ — $ 5,765 $ 8 Government sponsored agencies 114,640 292 21,681 508 136,321 800 State and political subdivisions 195,285 2,891 68,361 1,627 263,646 4,518 Residential mortgage-backed securities 169,226 2,146 3,435 76 172,661 2,222 Collateralized mortgage obligations 60,459 408 39,382 729 99,841 1,137 Corporate bonds 9,532 200 — — 9,532 200 Trust preferred securities — — 300 200 300 200 Total $ 554,907 $ 5,945 $ 133,159 $ 3,140 $ 688,066 $ 9,085 December 31, 2014 U.S. Treasury securities $ 8,259 $ 13 $ — $ — $ 8,259 $ 13 Government sponsored agencies 166,963 406 31,927 105 198,890 511 State and political subdivisions 62,310 3,348 36,847 1,226 99,157 4,574 Residential mortgage-backed securities 17,276 52 180,194 1,491 197,470 1,543 Collateralized mortgage obligations 63,077 179 31,620 1,015 94,697 1,194 Corporate bonds — — 14,952 48 14,952 48 Trust preferred securities — — 7,090 3,410 7,090 3,410 Total $ 317,885 $ 3,998 $ 302,630 $ 7,295 $ 620,515 $ 11,293 An assessment is performed quarterly by the Corporation to determine whether unrealized losses in its investment 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 investment security at December 31, 2015 , represented an other-than-temporary impairment (OTTI). Management believed that the unrealized losses on investment securities at December 31, 2015 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 December 31, 2015 , the Corporation did not have the intent to sell any of its impaired investment securities and believed that it was more-likely-than-not that the Corporation will not have to sell any such investment securities before a full recovery of amortized cost. Accordingly, at December 31, 2015 , the Corporation believed the impairments in its investment securities portfolio were temporary in nature. However, there is no assurance that OTTI may not occur in the future. Investment securities with an amortized cost of $516 million and $493 million at December 31, 2015 and 2014 , respectively, were pledged to secure public fund deposits, short-term borrowings and for other purposes as required by law.

Loans

Loans	12 Months Ended
	Dec. 31, 2015
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 seven 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, non-owner occupied real estate leased to one or more tenants and vacant land that has been acquired for investment or future land development. Real estate construction — 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 — 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 December 31, 2015 and 2014 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, through a first or second lien mortgage, as collateral to secure the loan. Commercial, commercial real estate, 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: December 31, 2015 2014 (In thousands) Commercial loan portfolio: Commercial $ 1,905,879 $ 1,354,881 Commercial real estate 2,112,162 1,557,648 Real estate construction 210,231 152,745 Land development 21,845 18,750 Subtotal 4,250,117 3,084,024 Consumer loan portfolio: Residential mortgage 1,429,636 1,110,390 Consumer installment 877,457 829,570 Home equity 713,937 664,246 Subtotal 3,021,030 2,604,206 Total loans $ 7,271,147 $ 5,688,230 Chemical Bank has extended loans to its directors, executive officers and their affiliates. These loans were made in the ordinary course of business upon normal terms, including collateralization and interest rates prevailing at the time, and did not involve more than the normal risk of repayment by the borrower. The aggregate loans outstanding to the directors, executive officers and their affiliates totaled $21.7 million at December 31, 2015 and $31.2 million at December 31, 2014 . During 2015 and 2014 , there were $33.3 million and $39.3 million , respectively, of new loans and other additions, while repayments and other reductions totaled $42.8 million and $34.9 million , respectively. Loans held-for-sale, comprised of fixed-rate residential mortgage loans, were $10.3 million at December 31, 2015 and $9.1 million at December 31, 2014 . The Corporation sold residential mortgage loans totaling $223 million in 2015 and $149 million in 2014 . 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 across the lower peninsula of Michigan, except for the southeastern portion of Michigan. The Corporation has no foreign loans. 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 $1.0 million requiring group loan authority approval, except for six executive and senior officers who have varying loan limits exceeding $1.5 million and up to $3.5 million . With respect to the group loan authorities, Chemical Bank has a loan committee, consisting of certain executive and senior officers, that meets weekly to consider loans ranging in amounts from $1.0 million to $10.0 million , depending on risk rating and credit action required. A directors' loan committee of Chemical Bank, consisting of eight independent members of the board of directors of Chemical Bank, the chief executive officer of Chemical Bank and the senior credit officer of Chemical Bank, meets bi-weekly to consider loans in amounts over $10.0 million , and certain loans under $10.0 million depending on a loan's risk rating and credit action required. Loans over $15.0 million 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 The Corporation uses a nine grade risk rating system to monitor the ongoing credit quality of its commercial loan portfolio. These loan grades rank the credit quality of a borrower by measuring liquidity, debt capacity, coverage and payment behavior as shown in the borrower's financial statements. The loan grades also measure the quality of the borrower's management and the repayment support offered by any guarantors. A summary of the Corporation's loan grades (or, characteristics of the loans within each grade) follows: Risk Grades 1-5 (Acceptable Credit Quality) — All loans in risk grades 1 through 5 are considered to be acceptable credit risks by the Corporation and are grouped for purposes of allowance for loan loss considerations and financial reporting. The five grades essentially represent a ranking of loans that are all viewed to be of acceptable credit quality, taking into consideration the various factors mentioned above, but with varying degrees of financial strength, debt coverage, management and factors that could impact credit quality. Business credits within risk grades 1 through 5 range from Risk Grade 1: Prime Quality (factors include: excellent business credit; excellent debt capacity and coverage; outstanding management; strong guarantors; superior liquidity and net worth; favorable loan-to-value ratios; debt secured by cash or equivalents, or backed by the full faith and credit of the U.S. Government) to Risk Grade 5: Acceptable Quality With Care (factors include: acceptable business credit, but with added risk due to specific industry or internal situations). Risk Grade 6 (Watch) — A business credit that is not acceptable within the Corporation's loan origination criteria; cash flow may not be adequate or is continually inconsistent to service current debt; financial condition has deteriorated as company trends/management have become inconsistent; the company is slow in furnishing quality financial information; working capital needs of the company are reliant on short-term borrowings; personal guarantees are weak and/or with little or no liquidity; the net worth of the company has deteriorated after recent or continued losses; the loan requires constant monitoring and attention from the Corporation; payment delinquencies becoming more serious; if left uncorrected, these potential weaknesses may, at some future date, result in deterioration of repayment prospects. Risk Grade 7 (Substandard — Accrual) — A business credit that is inadequately protected by the current financial net worth and paying capacity of the obligor or of the collateral pledged, if any; management has deteriorated or has become non-existent; quality financial information is not available; a high level of maintenance is required by the Corporation; cash flow can no longer support debt requirements; loan payments are continually and/or severely delinquent; negative net worth; personal guaranty has become insignificant; a credit that has a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. The Corporation still expects a full recovery of all contractual principal and interest payments; however, a possibility exists that the Corporation will sustain some loss if deficiencies are not corrected. Risk Grade 8 (Substandard — Nonaccrual ) — A business credit accounted for on a nonaccrual basis that has all the weaknesses inherent in a loan classified as risk grade 7 with the added characteristic that the weaknesses are so pronounced that, on the basis of current financial information, conditions and values, collection in full is highly questionable; a partial loss is possible and interest is no longer being accrued. This loan meets the definition of an impaired loan. The risk of loss requires analysis to determine whether a valuation allowance needs to be established. Risk Grade 9 (Substandard — Doubtful) — A business credit that has all the weaknesses inherent in a loan classified as risk grade 8 and interest is no longer being accrued, but additional deficiencies make it highly probable that liquidation will not satisfy the majority of the obligation; the primary source of repayment is nonexistent and there is doubt as to the value of the secondary source of repayment; the possibility of loss is likely, but current pending factors could strengthen the credit. This loan meets the definition of an impaired loan. A loan charge-off is recorded when management deems an amount uncollectible; however, the Corporation will establish a valuation allowance for probable losses, if required. The Corporation considers all loans graded 1 through 5 as acceptable credit risks and structures and manages such relationships accordingly. Periodic financial and operating data combined with regular loan officer interactions are deemed adequate to monitor borrower performance. Loans graded 6 and 7 are considered higher-risk credits than loans graded 1 through 5 and the frequency of loan officer contact and receipt of financial data is increased to stay abreast of borrower performance. Loans graded 8 and 9 are considered problematic and require special care. Further, loans graded 6 through 9 are managed and monitored regularly through a number of processes, procedures and committees, including oversight by a loan administration committee comprised of executive and senior management of the Corporation, and include highly structured reporting of financial and operating data, intensive loan officer intervention and strategies to exit, as well as potential management by the Corporation's special assets group. The following schedule presents the recorded investment of loans in the commercial loan portfolio by risk rating categories at December 31, 2015 and 2014 : Commercial Commercial Real Estate Real Estate Construction Land Development Total (In thousands) December 31, 2015 Originated Portfolio: Risk Grades 1-5 $ 1,418,301 $ 1,341,202 $ 173,828 $ 9,495 $ 2,942,826 Risk Grade 6 34,727 31,036 180 — 65,943 Risk Grade 7 39,933 26,658 291 832 67,714 Risk Grade 8 26,459 25,163 247 274 52,143 Risk Grade 9 2,095 — — — 2,095 Subtotal 1,521,515 1,424,059 174,546 10,601 3,130,721 Acquired Portfolio: Risk Grades 1-5 340,782 629,430 35,685 5,998 1,011,895 Risk Grade 6 28,321 23,926 — 2,556 54,803 Risk Grade 7 11,607 29,975 — 1,537 43,119 Risk Grade 8 3,654 4,772 — 1,153 9,579 Risk Grade 9 — — — — — Subtotal 384,364 688,103 35,685 11,244 1,119,396 Total $ 1,905,879 $ 2,112,162 $ 210,231 $ 21,845 $ 4,250,117 December 31, 2014 Originated Portfolio: Risk Grades 1-5 $ 1,171,817 $ 1,114,529 $ 134,668 $ 2,952 $ 2,423,966 Risk Grade 6 37,800 34,996 1,408 738 74,942 Risk Grade 7 29,863 29,935 2,502 613 62,913 Risk Grade 8 16,417 24,958 162 225 41,762 Risk Grade 9 1 8 — — 9 Subtotal 1,255,898 1,204,426 138,740 4,528 2,603,592 Acquired Portfolio: Risk Grades 1-5 76,780 321,018 14,005 11,789 423,592 Risk Grade 6 12,687 8,698 — 583 21,968 Risk Grade 7 4,089 12,478 — 197 16,764 Risk Grade 8 5,427 11,028 — 1,653 18,108 Risk Grade 9 — — — — — Subtotal 98,983 353,222 14,005 14,222 480,432 Total $ 1,354,881 $ 1,557,648 $ 152,745 $ 18,750 $ 3,084,024 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 or classified as a nonperforming TDR are considered to be in a nonperforming status. Nonaccrual TDRs in the consumer loan portfolio are included with nonaccrual loans, while other TDRs in the consumer loan portfolio are considered to be in a nonperforming status until they meet the Corporation's definition of a performing TDR, at which time they are considered to be in a performing 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 December 31, 2015 and 2014 : Residential Mortgage Consumer Installment Home Equity Total (In thousands) December 31, 2015 Originated Portfolio: Performing $ 1,207,945 $ 868,975 $ 587,566 $ 2,664,486 Nonperforming 9,030 451 3,246 12,727 Subtotal 1,216,975 869,426 590,812 2,677,213 Acquired Portfolio: Performing 210,580 7,984 122,118 340,682 Nonperforming 2,081 47 1,007 3,135 Subtotal 212,661 8,031 123,125 343,817 Total $ 1,429,636 $ 877,457 $ 713,937 $ 3,021,030 December 31, 2014 Originated Portfolio: Performing $ 987,542 $ 818,878 $ 566,083 $ 2,372,503 Nonperforming 10,459 500 3,013 13,972 Subtotal 998,001 819,378 569,096 2,386,475 Acquired Portfolio: Performing 111,101 10,174 94,696 215,971 Nonperforming 1,288 18 454 1,760 Subtotal 112,389 10,192 95,150 217,731 Total $ 1,110,390 $ 829,570 $ 664,246 $ 2,604,206 Nonperforming Loans A summary of nonperforming loans follows: December 31, 2015 2014 (In thousands) Nonaccrual loans: Commercial $ 28,554 $ 16,418 Commercial real estate 25,163 24,966 Real estate construction 247 162 Land development 274 225 Residential mortgage 5,557 6,706 Consumer installment 451 500 Home equity 1,979 1,667 Total nonaccrual loans 62,225 50,644 Accruing loans contractually past due 90 days or more as to interest or principal payments: Commercial 364 170 Commercial real estate 254 — Residential mortgage 402 557 Home equity 1,267 1,346 Total accruing loans contractually past due 90 days or more as to interest or principal payments 2,287 2,073 Nonperforming TDRs: Commercial loan portfolio 16,297 15,271 Consumer loan portfolio 3,071 3,196 Total nonperforming TDRs 19,368 18,467 Total nonperforming loans $ 83,880 $ 71,184 The Corporation's nonaccrual loans at December 31, 2015 and 2014 included $35.9 million and $37.2 million , respectively, of nonaccrual TDRs. There was no interest income recognized on nonaccrual loans during 2015 , 2014 and 2013 while the loans were in nonaccrual status. During 2015 , 2014 and 2013 , the Corporation recognized $0.9 million , $0.5 million and $0.9 million , respectively, of interest income on these loans while they were in an accruing status. Additional interest income that would have been recorded on nonaccrual loans had they been current in accordance with their original terms was $3.2 million in 2015 , $3.3 million in 2014 and $3.5 million in 2013 . During 2015 , 2014 and 2013 , the Corporation recognized interest income of $3.9 million , $3.6 million and $3.2 million , respectively, on performing and nonperforming TDRs. The Corporation had $2.9 million of residential mortgage loans that were in the process of foreclosure at December 31, 2015, compared to $2.3 million at December 31, 2014. Impaired Loans The following schedule presents impaired loans by classes of loans at December 31, 2015 : Recorded Investment Unpaid Principal Balance Related Valuation Allowance Average Annual Recorded Investment Interest Income Recognized While on Impaired Status (In thousands) Impaired loans with a valuation allowance: Commercial $ 18,898 $ 19,426 $ 5,700 $ 9,511 $ — Commercial real estate 4,448 4,688 497 2,918 — Residential mortgage 21,037 21,037 192 20,661 1,312 Subtotal 44,383 45,151 6,389 33,090 1,312 Impaired loans with no related valuation allowance: Commercial 31,039 37,703 — 32,172 1,303 Commercial real estate 53,518 69,130 — 56,562 1,985 Real estate construction 400 480 — 457 11 Land development 1,736 2,628 — 1,768 104 Residential mortgage 7,638 8,644 — 8,465 165 Consumer installment 498 512 — 480 2 Home equity 2,986 3,270 — 2,736 58 Subtotal 97,815 122,367 — 102,640 3,628 Total impaired loans: Commercial 49,937 57,129 5,700 41,683 1,303 Commercial real estate 57,966 73,818 497 59,480 1,985 Real estate construction 400 480 — 457 11 Land development 1,736 2,628 — 1,768 104 Residential mortgage 28,675 29,681 192 29,126 1,477 Consumer installment 498 512 — 480 2 Home equity 2,986 3,270 — 2,736 58 Total $ 142,198 $ 167,518 $ 6,389 $ 135,730 $ 4,940 The following schedule presents impaired loans by classes of loans at December 31, 2014 : Recorded Investment Unpaid Principal Balance Related Valuation Allowance Average Annual Recorded Investment Interest Income Recognized While on Impaired Status (In thousands) Impaired loans with a valuation allowance: Commercial $ 966 $ 1,040 $ 293 $ 2,117 $ — Commercial real estate 2,587 2,927 710 3,699 — Residential mortgage 19,681 19,681 335 19,740 1,252 Subtotal 23,234 23,648 1,338 25,556 1,252 Impaired loans with no related valuation allowance: Commercial 38,094 44,557 — 39,020 1,375 Commercial real estate 60,616 82,693 — 49,676 1,567 Real estate construction 162 255 — 164 — Land development 1,928 3,484 — 3,551 131 Residential mortgage 7,994 7,994 — 7,005 15 Consumer installment 518 518 — 602 1 Home equity 2,121 2,121 — 2,302 12 Subtotal 111,433 141,622 — 102,320 3,101 Total impaired loans: Commercial 39,060 45,597 293 41,137 1,375 Commercial real estate 63,203 85,620 710 53,375 1,567 Real estate construction 162 255 — 164 — Land development 1,928 3,484 — 3,551 131 Residential mortgage 27,675 27,675 335 26,745 1,267 Consumer installment 518 518 — 602 1 Home equity 2,121 2,121 — 2,302 12 Total $ 134,667 $ 165,270 $ 1,338 $ 127,876 $ 4,353 The average annual recorded investment of impaired loans during 2013 was $121.0 million and was comprised of the following classes of loans: commercial - $29.6 million ; commercial real estate - $50.8 million ; real estate construction - $0.4 million ; land development - $9.8 million ; residential mortgage - $26.8 million ; consumer installment - $0.7 million ; and home equity - $2.9 million . Interest income recognized during 2013 while these loans were in impaired status was $3.8 million , including $1.0 million on commercial loans, $1.3 million on commercial real estate loans, $0.3 million on land development loans and $1.1 million on residential mortgage loans. 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, and for acquired loans that meet the definition of an impaired loan represents fair value adjustments recognized at the acquisition date attributable to expected credit losses and the discounting of expected cash flows at market interest rates. The difference between the recorded investment and the unpaid principal balance of $25.3 million and $30.6 million at December 31, 2015 and December 31, 2014 , respectively, includes confirmed losses (partial charge-offs) of $17.1 million and $15.4 million , respectively, and fair value discount adjustments of $8.2 million and $15.2 million , respectively. Impaired loans included $12.8 million and $19.9 million at December 31, 2015 and December 31, 2014 , respectively, of acquired loans that were not performing in accordance with original contractual terms. Acquired loans that are not performing in accordance with contractual terms are not reported as nonperforming loans 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. Impaired loans also included $47.8 million and $45.7 million at December 31, 2015 and December 31, 2014 , respectively, of performing TDRs. The following schedule presents the aging status of the recorded investment in loans by classes of loans at December 31, 2015 and 2014 : 31-60 Days Past Due 61-89 Days Past Due Accruing Loans Past Due 90 Days or More Non-accrual Loans Total Past Due Current Total Loans (In thousands) December 31, 2015 Originated Portfolio: Commercial $ 3,685 $ 1,230 $ 364 $ 28,554 $ 33,833 $ 1,487,682 $ 1,521,515 Commercial real estate 4,168 1,603 254 25,163 31,188 1,392,871 1,424,059 Real estate construction — — — 247 247 174,299 174,546 Land development — — — 274 274 10,327 10,601 Residential mortgage 1,737 — 402 5,557 7,696 1,209,279 1,216,975 Consumer installment 3,145 644 — 451 4,240 865,186 869,426 Home equity 1,767 788 1,267 1,979 5,801 585,011 590,812 Total $ 14,502 $ 4,265 $ 2,287 $ 62,225 $ 83,279 $ 5,724,655 $ 5,807,934 Acquired Portfolio: Commercial $ 490 $ 532 $ 3,735 $ — $ 4,757 $ 379,607 $ 384,364 Commercial real estate 3,557 691 4,771 — 9,019 679,084 688,103 Real estate construction — — — — — 35,685 35,685 Land development — — 1,154 — 1,154 10,090 11,244 Residential mortgage 1,370 — 2,081 — 3,451 209,210 212,661 Consumer installment 55 — 47 — 102 7,929 8,031 Home equity 847 78 1,007 — 1,932 121,193 123,125 Total $ 6,319 $ 1,301 $ 12,795 $ — $ 20,415 $ 1,442,798 $ 1,463,213 December 31, 2014 Originated Portfolio: Commercial $ 4,033 $ 743 $ 170 $ 16,418 $ 21,364 $ 1,234,534 $ 1,255,898 Commercial real estate 7,515 1,383 — 24,966 33,864 1,170,562 1,204,426 Real estate construction 262 — — 162 424 138,316 138,740 Land development — — — 225 225 4,303 4,528 Residential mortgage 2,126 54 557 6,706 9,443 988,558 998,001 Consumer installment 3,620 512 — 500 4,632 814,746 819,378 Home equity 3,039 660 1,346 1,667 6,712 562,384 569,096 Total $ 20,595 $ 3,352 $ 2,073 $ 50,644 $ 76,664 $ 4,913,403 $ 4,990,067 Acquired Portfolio: Commercial $ 133 $ — $ 5,427 $ — $ 5,560 $ 93,423 $ 98,983 Commercial real estate 2,014 352 11,052 — 13,418 339,804 353,222 Real estate construction — — — — — 14,005 14,005 Land development — — 1,653 — 1,653 12,569 14,222 Residential mortgage 156 — 18 — 174 112,215 112,389 Consumer installment 55 3 454 — 512 9,680 10,192 Home equity 636 106 1,288 — 2,030 93,120 95,150 Total $ 2,994 $ 461 $ 19,892 $ — $ 23,347 $ 674,816 $ 698,163 Loans Modified Under Troubled Debt Restructurings (TDRs) The following schedule presents the Corporation's TDRs at December 31, 2015 and 2014 : Performing TDRs Non-Performing TDRs Nonaccrual TDRs Total (In thousands) December 31, 2015 Commercial loan portfolio $ 29,844 $ 16,297 $ 32,682 $ 78,823 Consumer loan portfolio 17,966 3,071 3,251 24,288 Total $ 47,810 $ 19,368 $ 35,933 $ 103,111 December 31, 2014 Commercial loan portfolio $ 29,179 $ 15,271 $ 32,597 $ 77,047 Consumer loan portfolio 16,485 3,196 4,594 24,275 Total $ 45,664 $ 18,467 $ 37,191 $ 101,322 The following schedule provides information on the Corporation's TDRs that were modified during the years ended December 31, 2015 , 2014 and 2013 : Number of Loans Pre- Modification Recorded Investment Post- Modification Recorded Investment (Dollars in thousands) Year ended December 31, 2015 Commercial loan portfolio: Commercial 53 $ 11,446 $ 11,446 Commercial real estate 21 7,196 7,196 Real estate construction 2 400 400 Land development 1 305 305 Subtotal — commercial loan portfolio 77 19,347 19,347 Consumer loan portfolio (residential mortgage) 65 3,249 3,247 Total 142 $ 22,596 $ 22,594 Year ended December 31, 2014 Commercial loan portfolio: Commercial 53 $ 13,781 $ 13,781 Commercial real estate 46 12,075 12,075 Real estate construction — — — Land development 1 72 72 Subtotal — commercial loan portfolio 100 25,928 25,928 Consumer loan portfolio (residential mortgage) 119 4,184 4,158 Total 219 $ 30,112 $ 30,086 Year ended December 31, 2013 Commercial loan portfolio: Commercial 57 $ 12,123 $ 12,123 Commercial real estate 49 16,222 16,222 Real estate construction 4 575 575 Land development 4 1,958 1,958 Subtotal — commercial loan portfolio 114 30,878 30,878 Consumer loan portfolio (residential mortgage) 85 4,943 4,840 Total 199 $ 35,821 $ 35,718 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 includes TDRs for which there was a payment default during the years ended December 31, 2015 , 2014 and 2013 , 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: Years Ended December 31, 2015 2014 2013 Number of Loans Principal Balance at Year End Number of Loans Principal Balance at Year End Number of Loans Principal Balance at Year End (Dollars in thousands) Commercial loan portfolio: Commercial 1 $ 1,206 7 $ 885 23 $ 2,745 Commercial real estate 5 1,016 6 2,352 8 4,278 Real estate construction — — — — 3 371 Land development — — — — 2 1,526 Subtotal — commercial loan portfolio 6 2,222 13 3,237 36 8,920 Consumer loan portfolio (residential mortgage) 3 65 12 259 22 1,826 Total 9 $ 2,287 25 $ 3,496 58 $ 10,746 Allowance for Loan Losses The following schedule presents, by loan portfolio segment, the changes in the allowance for the year ended December 31, 2015 and details regarding the balance in the allowance and the recorded investment in loans at December 31, 2015 by impairment evaluation method. Commercial Loan Portfolio Consumer Loan Portfolio Unallocated Total (In thousands) Changes in allowance for loan losses for the year ended December 31, 2015: Beginning balance $ 44,156 $ 28,803 $ 2,724 $ 75,683 Provision for loan losses 7,275 1,949 (2,724 ) 6,500 Charge-offs (6,385 ) (7,116 ) — (13,501 ) Recoveries 2,188 2,458 — 4,646 Ending balance $ 47,234 $ 26,094 $ — $ 73,328 Allowance for loan losses balance at December 31, 2015 attributable to: Loans individually evaluated for impairment $ 6,197 $ 192 $ — $ 6,389 Loans collectively evaluated for impairment 41,037 25,902 — 66,939 Loans acquired with deteriorated credit quality — — — — Total $ 47,234 $ 26,094 $ — $ 73,328 Recorded investment (loan balance) at December 31, 2015: Loans individually evaluated for impairment $ 100,379 $ 21,037 $ — $ 121,416 Loans collectively evaluated for impairment 3,030,342 2,656,176 — 5,686,518 Loans acquired with deteriorated credit quality 1,119,396 343,817 — 1,463,213 Total $ 4,250,117 $ 3,021,030 $ — $ 7,271,147 The following presents, by loan portfolio segment, the changes in the allowance for the year ended December 31, 2014 and details regarding the balance in the allowance and the recorded investment in loans at December 31, 2014 by impairment evaluation method. Commercial Loan Portfolio Consumer Loan Portfolio Unallocated Total (In thousands) Changes in allowance for loan losses for the year ended December 31, 2014: Beginning balance $ 44,482 $ 30,145 $ 4,445 $ 79,072 Provision for loan losses 3,464 4,357 (1,721 ) 6,100 Charge-offs (6,399 ) (7,830 ) — (14,229 ) Recoveries 2,609 2,131 — 4,740 Ending balance $ 44,156 $ 28,803 $ 2,724 $ 75,683 Allowance for loan losses balance at December 31, 2014 attributable to: Loans individually evaluated for impairment $ 1,003 $ 335 $ — $ 1,338 Loans collectively evaluated for impairment 43,153 27,968 2,724 73,845 Loans acquired with deteriorated credit quality — 500 — 500 Total $ 44,156 $ 28,803 $ 2,724 $ 75,683 Recorded investment (loan balance) at December 31, 2014: Loans individually evaluated for impairment $ 86,221 $ 19,681 $ — $ 105,902 Loans collectively evaluated for impairment 2,517,371 2,366,794 — 4,884,165 Loans acquired with deteriorated credit quality 480,432 217,731 — 698,163 Total $ 3,084,024 $ 2,604,206 $ — $ 5,688,230 The allowance attributable to acquired loans of $0.5 million at December 31, 2014 was primarily attributable to two consumer loan pools in the acquired loan portfolio that had a decline in expected cash flows. There were no material changes in expected cash flows for the acquired loan pools at December 31, 2015 .

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Premises and Equipment	PREMISES AND EQUIPMENT A summary of premises and equipment follows: December 31, 2015 2014 (In thousands) Cost: Land and land improvements $ 28,447 $ 27,402 Buildings 120,370 110,380 Equipment 77,882 68,540 Total cost 226,699 206,322 Accumulated depreciation (120,382 ) (108,826 ) Total premises and equipment $ 106,317 $ 97,496

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	GOODWILL Goodwill was $287.4 million at December 31, 2015 and $180.1 million at December 31, 2014 . During 2015, the Corporation acquired Lake Michigan and Monarch, which resulted in the recognition of goodwill for each transaction of $101.6 million and $5.3 million , respectively. During 2014, the Corporation acquired Northwestern, which resulted in the recognition of $60.0 million of goodwill. The Corporation also recorded additional goodwill in 2015 of $0.3 million related to the acquisition of Northwestern resulting from adjustments to the original acquisition date valuation of acquired assets and liabilities. Goodwill recognized in the Lake Michigan, Monarch and Northwestern transactions was primarily attributable to the synergies and economies of scale expected from combining their operations with the Corporation. None of the goodwill recorded in conjunction with the Lake Michigan, Monarch and Northwestern acquisitions is deductible for tax purposes. Goodwill is subject to impairment testing annually and on an interim basis if events or changes in circumstances indicate assets might be impaired. The Corporation's most recent annual goodwill impairment assessment, which was performed as of October 31, 2015 , did not indicate that an impairment of goodwill existed. The Corporation also determined that no triggering events occurred that indicated impairment from the most recent assessment date through December 31, 2015 and that the Corporation's goodwill was not impaired at December 31, 2015 .

Other Intangible Assets

Other Intangible Assets	12 Months Ended
	Dec. 31, 2015
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: December 31, 2015 2014 (In thousands) Other intangible assets: Core deposit intangible assets $ 26,654 $ 20,863 Non-compete intangible assets 328 — Mortgage servicing rights (MSRs) 11,122 12,217 Total other intangible assets $ 38,104 $ 33,080 Core Deposit Intangible Assets The following table sets forth the carrying amount, accumulated amortization and amortization expense of core deposit intangible assets that are amortizable and arose from business combinations or other acquisitions: December 31, 2015 2014 (In thousands) Gross original amount $ 40,055 $ 31,550 Accumulated amortization 13,401 10,687 Carrying amount $ 26,654 $ 20,863 Amortization expense for the year ended December 31 $ 4,142 $ 2,029 In conjunction with the acquisitions of Lake Michigan on May 31, 2015 and Monarch on April 1, 2015, the Corporation recorded $8.0 million and $1.9 million , respectively, in core deposit intangible assets. In conjunction with the acquisition of Northwestern on October 31, 2014 , the Corporation recorded $12.9 million in core deposit intangible assets. The estimated future amortization expense on core deposit intangible assets for the years ending after December 31, 2015 is as follows: 2016 - $4.4 million ; 2017 - $3.8 million ; 2018 - $3.6 million ; 2019 - $3.4 million ; 2020 - $2.9 million ; 2021 and thereafter - $8.6 million . Non-compete Intangible Assets In conjunction with the acquisition of Lake Michigan on May 31, 2015, the Corporation recorded $0.6 million in non-compete intangible assets with an amortization period of one year. There were no additions of non-compete intangible assets in 2014. Mortgage Servicing Rights (MSRs) The following shows the net carrying value and fair value of MSRs and the total loans that the Corporation is servicing for others: December 31, 2015 2014 (In thousands) Net carrying value of MSRs $ 11,122 $ 12,217 Fair value of MSRs $ 15,542 $ 14,979 Loans serviced for others that have servicing rights capitalized $ 2,082,899 $ 2,093,140 The fair value of MSRs was estimated by calculating the present value of estimated future net servicing cash flows, taking into consideration expected prepayment rates, discount rates, servicing costs and other economic factors that are based on current market conditions. The prepayment rates and the discount rate are the most significant factors affecting valuation of the MSRs. Increases in mortgage loan prepayments reduce estimated future net servicing cash flows because the life of the underlying loan is reduced. Expected loan prepayment rates are validated by a third-party model. At December 31, 2015 , the weighted average coupon rate, discount rate and constant prepayment rate (CPR) of the Corporation's $888 million originated servicing portfolio was 4.20% , 8.5% and 11.7% , respectively, while the weighted average coupon rate, discount rate and CPR of the Corporation's $1.20 billion acquired servicing portfolio was 4.07% , 10.1% and 10.41% , respectively. At December 31, 2014 , the weighted average coupon rate, discount rate and CPR of the Corporation's $881 million originated servicing portfolio was 4.28% , 8.5% and 13.6% , respectively, while the weighted average coupon rate, discount rate and CPR of the Corporation's $1.21 billion acquired servicing portfolio was 4.08% , 10.1% and 11.7% , respectively. The following shows activity for capitalized MSRs for the last three years: Years Ended December 31, 2015 2014 2013 (In thousands) Balance at beginning of year $ 12,217 $ 3,423 $ 3,478 Acquired through acquisitions 1,284 9,235 — Additions 1,476 1,075 1,528 Amortization (4,055 ) (1,316 ) (1,583 ) Change in valuation allowance 200 (200 ) — Balance at end of year $ 11,122 $ 12,217 $ 3,423 Valuation allowance at December 31 $ — $ 200 $ — The Corporation acquired MSRs of $1.3 million in the acquisition of Monarch on April 1, 2015 and $9.2 million in the acquisition of Northwestern on October 31, 2014. MSRs are stratified into servicing assets originated by the Corporation and those acquired in acquisitions of other institutions and further stratified into relatively homogeneous pools based on products with similar characteristics. The MSR impairment valuation allowance recorded at December 31, 2014 related to impairment within certain pools attributable to the Corporation's servicing portfolio that was acquired in the Northwestern transaction.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2015
Deposits [Abstract]
Deposit Liabilities Disclosures	DEPOSITS A summary of deposits follows: December 31, 2015 2014 (In thousands) Noninterest-bearing demand $ 1,934,583 $ 1,591,661 Interest-bearing demand 1,870,197 1,428,941 Savings 2,004,575 1,720,422 Time deposits over $100,000 701,830 557,476 Other time deposits 945,582 780,471 Total deposits $ 7,456,767 $ 6,078,971 Excluded from total deposits are demand deposit account overdrafts (overdrafts) which have been classified as loans. At December 31, 2015 and 2014 , overdrafts totaled $3.0 million and $4.3 million , respectively. Time deposits of $250,000 or more were $364 million at December 31, 2015 and $249 million at December 31, 2014 . At December 31, 2015 , time deposits with remaining maturities of less than one year were $904 million and time deposits with remaining maturities of one year or more were $743 million . The scheduled maturities of time deposits outstanding at December 31, 2015 were as follows: 2016 - $904 million ; 2017 - $395 million ; 2018 - $139 million ; 2019 - $88 million ; 2020 - $118 million ; and 2021 and thereafter - $3 million .

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2015
Short-term Debt [Abstract]
Short - Term Borrowings	SHORT-TERM BORROWINGS A summary of short-term borrowings, which consisted of securities sold under agreements to repurchase, FHLB advances and federal funds purchased, follows: Ending Balance at Year-End Weighted Average Interest Rate at Year-End Average Amount Outstanding During Year Weighted Average Interest Rate During Year Maximum Outstanding at Any Month-End (Dollars in thousands) 2015 Securities sold under agreements to repurchase $ 297,199 0.06 % $ 327,559 0.07 % $ 372,236 FHLB advances 100,000 0.34 89,208 0.23 280,000 Federal funds purchased — — 3,762 0.37 22,000 2014 Securities sold under agreements to repurchase $ 304,467 0.11 % $ 326,056 0.12 % $ 361,231 FHLB advances 60,000 0.25 6,726 0.27 60,000 Federal funds purchased 25,000 0.40 2,003 0.40 25,000 2013 Securities sold under agreements to repurchase $ 327,428 0.15 % $ 337,649 0.14 % $ 357,976

Other Borrowings Other Borrowin

Other Borrowings Other Borrowings (Notes)	12 Months Ended
	Dec. 31, 2015
Other Borrowings [Abstract]
Borrowings [Text Block]	OTHER BORROWINGS A summary of the Corporation's other borrowings follows: December 31, 2015 Ending Balance Weighted Average Interest Rate At Year-End (Dollars in thousands) Long-term FHLB advances $ 181,394 1.41 % Non-revolving line-of-credit 25,000 2.27 Securities sold under agreements to repurchase 17,453 0.27 Subordinated debentures 18,544 3.99 Total other borrowings $ 242,391 During the third quarter of 2015, the Corporation borrowed $100 million of long-term FHLB advances, which consist of three- and five-year term fixed-rate advances with a weighted-average interest rate of 1.48% . In conjunction with the Lake Michigan and Monarch acquisitions, the Corporation acquired long-term FHLB advances totaling $81.5 million . These advances have a weighted average interest rate of 1.33% at December 31, 2015 . The Corporation's FHLB advances, including both short-term and long-term, require monthly interest payments. The scheduled reductions of long-term FHLB advances as of December 31, 2015 were as follows: 2016 - $7.1 million ; 2017 - $47.1 million ; 2018 - $67.1 million ; 2019; - $0.1 million ; and 2020 - $60.0 million . FHLB advances are collateralized by a blanket lien on qualified one- to four-family residential mortgage loans. At December 31, 2015 , the carrying value of these qualified loans was $1.34 billion . 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 $250 million at December 31, 2015 . Prepayments of fixed-rate advances are subject to prepayment fees under the provisions and conditions of the credit policy of the FHLB. On January 22, 2013, the Corporation paid off early all of its FHLB advances outstanding at that time of $34.3 million , resulting in a prepayment fee of $0.8 million . The Corporation did not incur any prepayment fees in 2015 or 2014 . The Corporation entered into a $25 million secured non-revolving line-of-credit in May 2015 with an unaffiliated third-party financial institution. The Corporation drew on the entire amount of the line-of-credit in order to partially fund the cash portion of the purchase price consideration for the Lake Michigan transaction. The line-of-credit bears a variable rate of interest which is based on the one-, two- or three-month LIBOR, as periodically selected by the Corporation, plus a fixed stated rate (effective interest rate of 2.27% at December 31, 2015 ), and matures in May 2016. The line-of-credit agreement contains certain restrictive covenants. The Corporation was in compliance with all of the covenants at December 31, 2015 . The line-of-credit is secured by all of the issued and outstanding stock of Chemical Bank. In conjunction with the Lake Michigan acquisition, the Company acquired securities sold under agreements to repurchase with an unaffiliated financial institution of $23.7 million as of the acquisition date. These agreements are secured by available for-sale-securities. As of December 31, 2015 , these agreements had scheduled maturities of $8.3 million in 2016 and $9.1 million in 2017. In conjunction with the acquisition of Lake Michigan on May 31, 2015, the Corporation acquired Lake Michigan Financial Capital Trust I (LMFCTI), Lake Michigan Financial Capital Trust II (LMFCTII), and Lake Michigan Financial Capital Trust III (LMFCTIII). LMFCTIII, which held the $10.0 million trust preferred security due to the Corporation, was repaid and settled as of the Lake Michigan acquisition date, and the entity was subsequently dissolved. All of the common securities of the remaining two special purpose trusts are owned by the Corporation. The trusts exist solely to issue capital securities in the form of cumulative preferred securities (trust preferred securities) with a par value of $1,000 per security. The proceeds from the sale of the trust preferred securities were used by each trust to purchase an equivalent amount of subordinated debentures from Lake Michigan. Lake Michigan guaranteed the payment of distributions on the trust preferred securities issued by LMFCTI and LMFCTII. At the acquisition date, the Corporation assumed responsibility of the guarantees. LMFCTI issued $10.3 million in preferred securities in October 2002. This trust preferred subordinated debt, with a stated maturity date of October 2032, pays interest based on a floating rate tied to the three-month LIBOR plus 3.45% (effective interest rate based on par of 3.99% as of December 31, 2015 ). LMFCTII issued $8.2 million in preferred securities in May 2004. This trust preferred subordinated debt, with a stated maturity date of May 2034, pays interest based on a floating rate tied to the three-month LIBOR plus 2.7% (effective interest rate based on par of 3.24% as of December 31, 2015 ). Including the impact of recording these subordinated debentures at fair value at the acquisition date, the weighted-average cost of these obligations was 3.99% as of December 31, 2015 . The Corporation may, at any time, redeem the LMFCTI or LMFCTII subordinated debentures at par. The Corporation has notified the respective trust's trustee of its intent to pay off these debt obligations during the first quarter of 2016.

Equity

Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Equity	EQUITY Common Stock Repurchase Programs From time to time, the board of directors of the Corporation approves common stock repurchase programs allowing management to repurchase shares of the Corporation's common stock in the open market. The repurchased shares are available for later reissuance in connection with potential future stock dividends, employee benefit plans and other general corporate purposes. Under these programs, the timing and actual number of shares subject to repurchase are at the discretion of management and are contingent on a number of factors, including the projected parent company cash flow requirements and the Corporation's market price per share. In January 2008, the board of directors of the Corporation authorized the repurchase of up to 500,000 shares of the Corporation's common stock under a stock repurchase program. In November 2011, the board of directors of the Corporation reaffirmed the stock buy-back authorization with the qualification that the shares may only be repurchased if the share price is below the tangible book value per share of the Corporation's common stock at the time of the repurchase. Since the January 2008 authorization, no shares have been repurchased. At December 31, 2015 , there were 500,000 remaining shares available for repurchase under the Corporation's stock repurchase programs. Underwritten Public Offerings of Common Stock On June 24, 2014, the Corporation issued and sold 2,500,000 shares of common stock at a public offering price of $28.00 per share. An additional 375,000 shares were issued and sold on June 30, 2014 upon the exercise in full of the underwriters' over-allotment option. The net proceeds from the issuance and sale of the common stock of this $80.5 million offering, after deducting the underwriting discount and issuance-related expenses, totaled $76.2 million . On September 18, 2013, the Corporation issued and sold 2,213,750 shares of common stock, including 288,750 shares of common stock that were issued and sold upon the exercise in full of the underwriters' over-allotment option, at a public offering price of $26.00 per share. The net proceeds from the issuance and sale of the common stock of this $57.6 million offering, after deducting the underwriting discount and issuance-related expenses, totaled $53.9 million . Shelf Registration On June 12, 2014, the Corporation filed an automatic shelf registration statement on Form S-3 with the Securities and Exchange Commission (SEC) for an indeterminate amount of securities, which became immediately effective. The shelf registration statement provides the Corporation with the ability to raise capital, subject to SEC rules and limitations, if the board of directors of the Corporation decides to do so. Preferred Stock On April 20, 2015, the shareholders of the Corporation approved an amendment to the restated articles of incorporation which eliminated and replaced the previous class of 200,000 shares of preferred stock, that had been approved by shareholders on April 20, 2009, with a new class of 2,000,000 shares of preferred stock. As of December 31, 2015 , no shares of preferred stock were issued and outstanding. Common Stock On April 20, 2015, the shareholders of the Corporation approved an amendment to the restated articles of incorporation to increase the number of authorized shares of common stock from 45,000,000 to 60,000,000 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Loss	ACCUMULATED OTHER COMPREHENSIVE LOSS The components of accumulated other comprehensive loss, net of related tax benefit/expense, were as follows: December 31, 2015 2014 2013 (In thousands) Net unrealized gains (losses) on investment securities — available-for-sale, net of related tax expense (benefit) of $(1,017) at December 31, 2015, $(113) at December 31, 2014 and ($1,335) at December 31, 2013 $ (1,888 ) $ (210 ) $ (2,480 ) Pension and other postretirement benefits adjustment, net of related tax benefit of $14,616 at December 31, 2015, $17,362 at December 31, 2014 and $9,714 at December 31, 2013 (27,144 ) (32,243 ) (18,040 ) Accumulated other comprehensive loss $ (29,032 ) $ (32,453 ) $ (20,520 )

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
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 to determine fair value disclosures. Investment securities — available-for-sale and loans held-for-sale 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 valuations for the Corporation would include 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 Level 1 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. 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, MSRs 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. 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 — 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. The Corporation elected the fair value option for all residential mortgage loans held-for-sale originated on or after July 1, 2012. 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. Disclosure of Recurring Basis Fair Value Measurements For assets measured at fair value on a recurring basis, quantitative disclosures about the fair value measurements for each major category of assets follow: Fair Value Measurements — Recurring Basis Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (In thousands) December 31, 2015 Investment securities — available-for-sale: U.S. Treasury securities $ 5,765 $ — $ — $ 5,765 Government sponsored agencies — 194,989 — 194,989 State and political subdivisions — 15,120 — 15,120 Residential mortgage-backed securities — 187,768 — 187,768 Collateralized mortgage obligations — 132,230 — 132,230 Corporate bonds — 14,627 — 14,627 Preferred stock and trust preferred securities — 3,232 — 3,232 Total investment securities — available-for-sale 5,765 547,966 — 553,731 Loans held-for-sale — 10,327 — 10,327 Total assets measured at fair value on a recurring basis $ 5,765 $ 558,293 $ — $ 564,058 December 31, 2014 Investment securities — available-for-sale: U.S. Treasury securities $ 8,259 $ — $ — $ 8,259 Government sponsored agencies — 263,503 — 263,503 State and political subdivisions — 46,227 — 46,227 Residential mortgage-backed securities — 239,807 — 239,807 Collateralized mortgage obligations — 144,383 — 144,383 Corporate bonds — 45,095 — 45,095 Preferred stock — 1,590 — 1,590 Total investment securities — available-for-sale 8,259 740,605 — 748,864 Loans held-for-sale — 9,128 — 9,128 Total assets measured at fair value on a recurring basis $ 8,259 $ 749,733 $ — $ 757,992 There were no liabilities recorded at fair value on a recurring basis at December 31, 2015 or 2014 . Assets and Liabilities Recorded at Fair Value on a Nonrecurring Basis 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 independent appraised value, or management determines the fair value of the collateral is further impaired below the appraised value. When management determines the fair value of the collateral is further impaired below the appraised value, discount factors ranging between 70% and 80% of the appraised value are used depending on the nature of the collateral and the age of the most recent appraisal. 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 December 31, 2015 and 2014 , no goodwill was impaired and, therefore, goodwill was not recorded at fair value on a nonrecurring basis. Other intangible assets consist of core deposit intangible assets, non-compete intangible assets and MSRs. 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 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 subject to nonrecurring fair value measurements as Level 3 valuations. At December 31, 2015 and 2014 , there was no impairment identified for core deposit intangible assets or non-compete intangible assets. The fair value of MSRs is estimated using a model that calculates the net present value of estimated future cash flows using various assumptions, including prepayment speeds, the discount rate and servicing costs. If the valuation model reflects a value less than the carrying value, MSRs are adjusted to fair value, as determined by the model, through a valuation allowance. The Corporation classifies MSRs subject to nonrecurring fair value measurements as Level 3 valuations. At December 31, 2014 ,the Corporation recognized a $0.2 million valuation allowance related to impairment within certain pools attributable to the Corporation's servicing portfolio that was acquired in the Northwestern transaction. As a result, the MSRs related to this servicing portfolio were considered to be recorded at fair value on a nonrecurring basis. At December 31, 2015 , there was no impairment identified for MSRs and, therefore, no other intangible assets were recorded at fair value on a nonrecurring basis. The carrying amounts for other real estate (ORE) and repossessed assets (RA) are reported in the consolidated statements of financial position under "Interest receivable and other assets." ORE and RA include real estate and other types of assets repossessed by the Corporation. ORE and RA are recorded at the lower of cost or fair value upon the transfer of a loan to ORE or RA and, subsequently, ORE and RA 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 ORE and RA 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, discount factors ranging between 70% and 75% 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 follow: Fair Value Measurements — Nonrecurring Basis Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (In thousands) December 31, 2015 Impaired originated loans $ — $ — $ 42,065 $ 42,065 Other real estate/repossessed assets — — 9,935 9,935 Total $ — $ — $ 52,000 $ 52,000 December 31, 2014 Impaired originated loans $ — $ — $ 21,323 $ 21,323 Other real estate/repossessed assets — — 14,205 14,205 Mortgage servicing rights — — 8,691 8,691 Total $ — $ — $ 44,219 $ 44,219 There were no liabilities recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 . 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 ASC 820, Fair Value Measurements and Disclosures, 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. The methodologies for estimating the fair value of financial assets and financial liabilities on a recurring or nonrecurring basis are discussed above. At December 31, 2015 and 2014 , the estimated fair values of cash and cash equivalents, interest receivable and interest payable approximated their carrying values at those dates. The methodologies for other financial assets and financial liabilities follow. Fair value measurement for investment securities — held-to-maturity is based upon quoted prices, if available. If quoted prices are not available, fair values are 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. Fair value measurements using Level 2 valuations of investment securities — held-to-maturity include the majority of the Corporation's investment securities issued by state and political subdivisions. Level 3 valuations include certain securities issued by state and political subdivisions and trust preferred investment securities. Fair value measurements of nonmarketable equity securities, which consisted of Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB) stock, are based on their redeemable value, which is cost. The market for these securities is restricted to the issuer of the stock and subject to impairment evaluation. It is not practicable to determine the fair value of these securities within the fair value hierarchy due to the restrictions placed on their transferability. Loans held-for-sale are carried at fair value, as the Corporation elected the fair value option on these loans. The fair value 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. The fair value of variable interest rate loans that reprice regularly with changes in market interest rates are based on carrying values. The fair values for fixed interest rate loans are estimated using discounted cash flow analyses, using the Corporation's interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. The resulting fair value amounts are adjusted to estimate the impact of changes in the credit quality of borrowers after the loans were originated. The fair value measurements for loans are Level 3 valuations. The fair values of deposit accounts without defined maturities, such as interest- and noninterest-bearing checking, savings and money market accounts, are equal to the amounts payable on demand. The fair values for variable-interest rate time deposits with defined maturities approximate their carrying amounts. Fair value measurements for fixed-interest rate time deposits with defined maturities are based on the discounted value of contractual cash flows, using the Corporation's interest rates currently being offered for deposits of similar maturities and are Level 3 valuations. However, if the estimated fair value is less than the carrying value, the carrying value is reported as the fair value. Short-term borrowings consist of securities sold under agreements to repurchase with customers, short-term FHLB advances and federal funds purchased. Fair value measurements for short-term borrowings are based on the present value of future estimated cash flows using current interest rates offered to the Corporation for debt with similar terms and are Level 2 valuations. Other borrowings consist of long-term FHLB advances, securities sold under agreements to repurchase with an unaffiliated financial institution, a non-revolving line-of-credit and subordinated debentures. Fair value measurements for other borrowings are based on the present value of future estimated cash flows using current interest rates offered to the Corporation for debt with similar terms. Long-term FHLB advances and the non-revolving line-of-credit included in other borrowings are Level 2 valuations, while securities sold under agreements to repurchase with an unaffiliated financial institution and subordinated debentures are Level 3 valuations. The Corporation's unused commitments to extend credit, standby letters of credit and loan commitments have no carrying amount and have been estimated to have no realizable fair value. Historically, a majority of the unused commitments to extend credit have not been drawn upon and, generally, the Corporation does not receive fees in connection with these commitments other than standby letter of credit fees, which are not significant. Fair value measurements have not been made for items that are not defined by GAAP as financial instruments, including such items as the value of the Corporation's Wealth Management department and the value of the Corporation's core deposit base. The Corporation believes it is impractical to estimate a representative fair value for these types of assets, even though management believes they add significant value to the Corporation. A summary of carrying amounts and estimated fair values of the Corporation's financial instruments included in the consolidated statements of financial position follows: Level in Fair Value Measurement Hierarchy December 31, 2015 December 31, 2014 Carrying Amount Fair Value Carrying Amount Fair Value (In thousands) Assets: Cash and cash equivalents Level 1 $ 238,789 $ 238,789 $ 183,020 $ 183,020 Investment securities: Available-for-sale Level 1 5,765 5,765 8,259 8,259 Available-for-sale Level 2 547,966 547,966 740,605 740,605 Held-to-maturity Level 2 509,471 512,405 305,913 308,650 Held-to-maturity Level 3 500 300 10,500 7,090 Nonmarketable equity securities NA 36,907 36,907 27,369 27,369 Loans held-for-sale Level 2 10,327 10,327 9,128 9,128 Net loans Level 3 7,197,819 7,201,994 5,612,547 5,623,454 Interest receivable Level 2 21,953 21,953 17,492 17,492 Liabilities: Deposits without defined maturities Level 2 $ 5,809,355 $ 5,809,355 $ 4,741,024 $ 4,741,024 Time deposits Level 3 1,647,412 1,647,412 1,337,947 1,340,015 Interest payable Level 2 1,578 1,578 755 755 Short-term borrowings Level 2 397,199 397,199 389,467 389,467 Other borrowings Level 2 206,394 206,394 — — Other borrowings Level 3 35,997 35,997 — —

Noninterest Income

Noninterest Income	12 Months Ended
	Dec. 31, 2015
Noninterest Income [Abstract]
Noninterest Income	NONINTEREST INCOME The following schedule includes the major components of noninterest income during the past three years: Years Ended December 31, 2015 2014 2013 (In thousands) Service charges and fees on deposit accounts $ 25,481 $ 22,414 $ 21,939 Wealth management revenue 20,552 16,015 13,989 Electronic banking fees 19,119 13,480 12,213 Mortgage banking revenue 6,133 5,041 5,336 Other fees for customer services 4,428 3,539 3,288 Insurance commissions 1,966 1,559 1,650 Gain on sale of investment securities 630 — 1,133 Bank owned life insurance 646 281 197 Rental income 466 145 97 Gain on sale of closed branch offices and other assets 266 — 478 Gain on sale of merchant card servicing business — 400 — Other 529 221 89 Total noninterest income $ 80,216 $ 63,095 $ 60,409

Operating Expenses

Operating Expenses	12 Months Ended
	Dec. 31, 2015
Operating Expenses [Abstract]
Operating Expenses	OPERATING EXPENSES The following schedule includes the major categories of operating expenses during the past three years: Years Ended December 31, 2015 2014 2013 (In thousands) Salaries and wages $ 104,490 $ 83,229 $ 78,014 Employee benefits 23,430 19,328 18,405 Occupancy 18,213 15,842 13,934 Equipment and software 18,569 14,737 13,734 Outside processing and service fees 15,207 11,586 11,134 FDIC insurance premiums 5,485 4,307 4,362 Professional fees 4,842 3,570 3,771 Intangible asset amortization 4,389 2,029 1,909 Postage and express mail 3,313 3,418 3,051 Advertising and marketing 3,288 3,051 2,971 Training, travel and other employee expenses 3,224 2,480 2,512 Telephone 2,608 1,966 1,940 Supplies 2,216 1,897 1,670 Donations 1,375 1,155 2,829 Credit-related expenses 632 996 707 Acquisition-related expenses 7,804 6,388 — Other 4,809 3,946 4,005 Total operating expenses $ 223,894 $ 179,925 $ 164,948

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Retirement Plans	RETIREMENT PLANS Defined Benefit Pension Plan The Corporation has a noncontributory defined benefit pension plan (Pension Plan) covering certain salaried employees. Benefits under the Pension Plan were frozen for approximately two-thirds of the Corporation's salaried employees effective June 30, 2006. Pension benefits continued unchanged for the remaining salaried employees. Normal retirement benefits under the Pension Plan are based on years of vested service, 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 retirement, except for employees whose benefits were frozen. Benefits, for employees with less than 15 years of service or whose age plus years of service were less than 65 at June 30, 2006, will be 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. At December 31, 2015 , the Corporation had 161 employees who were continuing to earn benefits under the Pension Plan. Pension Plan contributions are intended to provide not only for benefits attributed to service-to-date, but also for those benefits expected to be earned in the future for employees whose benefits were not frozen at June 30, 2006. Employees hired after June 30, 2006 and employees affected by the partial freeze of the Pension Plan began receiving 4% of their eligible pay as a contribution to their 401(k) Savings Plan accounts on July 1, 2006. Pension Plan expense was $1.6 million in 2015 , zero in 2014 and $1.7 million in 2013 . Supplemental Plan The Corporation has a supplemental defined benefit pension plan, the Chemical Financial Corporation Supplemental Pension Plan (Supplemental Plan). The Corporation established the Supplemental Plan to provide payments to certain executive officers of the Corporation, as determined by the Compensation and Pension Committee. At December 31, 2015 and 2014 , the only executive officer eligible for benefits under the Supplemental Plan was the Corporation's chief executive officer. 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 Supplemental Plan is designed to provide benefits to which executive officers of the Corporation 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 Supplemental Plan is an unfunded plan and, therefore, has no assets. The Supplemental Plan's projected benefit obligation was $2.2 million and $2.1 million at December 31, 2015 and 2014 , respectively. The Supplemental Plan's accumulated benefit obligation was $1.8 million and $2.0 million at December 31, 2015 and 2014 , respectively. Supplemental Plan expense totaled $0.4 million in 2015 , $0.3 million in 2014 and $0.2 million in 2013 . Postretirement Plan The Corporation has a 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 Corporation's 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. 401(k) Savings Plan The Corporation's 401(k) Savings Plan provides an employer match, in addition to a 4% contribution for employees who are not grandfathered under the Pension Plan discussed above. The 401(k) Savings Plan is available to all regular employees and provides employees with tax deferred salary deductions and alternative investment options. The Corporation matches 50% of the participants' elective deferrals on the first 4% of the participants' base compensation up to the maximum amount allowed under the Internal Revenue Code. The 401(k) Savings Plan provides employees with the option to invest in the Corporation's common stock. The Corporation's match under the 401(k) Savings Plan was $1.6 million in 2015 , $1.0 million in 2014 and $1.1 million in 2013 . Employer contributions to the 401(k) Savings Plan for the 4% benefit for employees who are not grandfathered under the Pension Plan totaled $3.1 million in 2015 , $2.3 million in 2014 and $2.3 million in 2013 . The combined amount of the employer match and 4% contribution to the 401(k) Savings Plan totaled $4.7 million in 2015 , $3.3 million in 2014 and $3.4 million in 2013 . Multi-Employer Defined Benefit Plan In conjunction with the April 1, 2015 acquisition of Monarch, the Corporation acquired a participation in the Pentegra Defined Benefit Plan for Financial Institutions (Pentegra DB plan), a qualified defined benefit plan. Employee benefits for Monarch employees under the Plan were frozen effective April 1, 2004. The Pentegra DB Plan operates as a multi-employer plan for accounting purposes and as a multiple employer plan under the Employee Retirement Income Security Act of 1974 and the Internal Revenue Code (IRC). The Pentegra DB Plan is a single plan under IRC Section 413(c) and, as a result, all the plan's assets stand behind all of the plan's liabilities. Accordingly, contributions made by a participating employer may be used to provide benefits to participants of other participating employers. Contributions made by the Corporation to the Pentegra DB Plan during 2015 totaled less than $0.1 million . The Pentegra DB Plan's Employer Identification Number is 13-5645888 and the Plan Number is 333. Financial information for the Pentegra DB Plan, which maintains a June 30 year end, is made available through the public Form 5500 which is available by April 15th of the year following the plan year end. The Pentegra DB Plan was at least 80% funded as of its most recent year end. The Corporation's allocation of assets and liabilities in the Pentegra DB Plan totaled $3.7 million and $2.6 million , respectively, as of the plan's most recent year end, and the Corporation's allocation of assets comprised less than 5% of the plan's total assets at that date. Benefit Obligations and Plan Expenses The following schedule sets forth the changes in the projected benefit obligation and plan assets of the Corporation's Pension and Postretirement Plans: Pension Plan Postretirement Plan 2015 2014 2015 2014 (In thousands) Projected benefit obligation: Benefit obligation at beginning of year $ 129,160 $ 105,914 $ 3,702 $ 3,477 Service cost 1,021 944 16 18 Interest cost 5,242 5,167 133 142 Net actuarial (gain) loss (10,837 ) 21,314 (363 ) 312 Benefits paid (4,713 ) (4,179 ) (241 ) (247 ) Benefit obligation at end of year 119,873 129,160 3,247 3,702 Fair value of plan assets: Fair value of plan assets at beginning of year 130,775 128,829 — — Actual return on plan assets 868 6,125 — — Employer contributions — — 241 247 Benefits paid (4,713 ) (4,179 ) (241 ) (247 ) Fair value of plan assets at end of year 126,930 130,775 — — Funded (unfunded) status at December 31 $ 7,057 $ 1,615 $ (3,247 ) $ (3,702 ) Accumulated benefit obligation $ 109,583 $ 121,826 $ 3,247 $ 3,702 The decreases in the projected and accumulated benefit obligations of the Pension Plan during 2015 were primarily attributable to an increase in the discount rate used to value these benefit obligations and an increase in the retirement age assumptions. The Corporation did not make a contribution to the Pension Plan in either 2015 or 2014. The Corporation contributed $15.0 million to the Pension Plan in 2013. The Corporation is not required to make a contribution to the Pension Plan in 2016 . Weighted-average rate assumptions of the Pension and Postretirement Plans follow: Pension Plan Postretirement Plan 2015 2014 2013 2015 2014 2013 Discount rate used in determining benefit obligation — December 31 4.55 % 4.15 % 5.00 % 4.23 % 3.75 % 4.27 % Discount rate used in determining expense 4.15 5.00 4.08 3.75 4.27 4.08 Expected long-term return on Pension Plan assets 6.75 7.00 7.00 — — — Rate of compensation increase used in determining benefit obligation — December 31 3.50 3.50 3.50 — — — Rate of compensation increase used in determining pension expense 3.50 3.50 3.50 — — — Year 1 increase in cost of postretirement benefits — — — 7.5 8.0 8.5 The weighted-average rate assumptions of the Supplemental Plan were the same as the Pension Plan for 2015 , 2014 and 2013 , except for the discount rate used in determining the benefit obligation for the Supplemental Plan, which was 4.51% , 4.07% and 4.87% at December 31, 2015 , 2014 and 2013 , respectively. Net periodic pension cost (income) of the Pension and Postretirement Plans was as follows for the years ended December 31: Pension Plan Postretirement Plan 2015 2014 2013 2015 2014 2013 (In thousands) Service cost $ 1,021 $ 944 $ 1,247 $ 16 $ 18 $ 18 Interest cost 5,242 5,167 4,603 133 142 143 Expected return on plan assets (8,645 ) (8,314 ) (7,794 ) — — — Amortization of prior service credit (5 ) (1 ) (1 ) 130 130 343 Amortization of net actuarial loss (gain) 3,962 2,159 3,670 (1 ) (104 ) (73 ) Net cost (income) $ 1,575 $ (45 ) $ 1,725 $ 278 $ 186 $ 431 The following schedule presents estimated future benefit payments under the Pension and Postretirement Plans for retirees already receiving benefits and future retirees, assuming they retire and begin receiving unreduced benefits as soon as they are eligible: Pension Plan Postretirement Plan (In thousands) 2016 $ 5,223 $ 272 2017 5,400 272 2018 5,730 268 2019 6,094 270 2020 6,272 268 2021 - 2025 35,771 1,254 Total $ 64,490 $ 2,604 For measurement purposes for the Postretirement Plan, the annual rates of increase in the per capita cost of covered health care benefits and dental benefits for 2016 were each assumed at 7.5% . These rates were assumed to decrease gradually to 5.0% in 2020 and remain at that level thereafter. The assumed health care and dental cost trend rates could have a significant effect on the amounts reported for the Postretirement Plan. A one percentage-point change in these rates would have the following effects: One Percentage-Point Increase Decrease (In thousands) Effect on total of service and interest cost components in 2015 $ 13 $ (12 ) Effect on postretirement benefit obligation as of December 31, 2015 308 (269 ) Pension Plan Assets The assets of the Pension Plan are invested by the Wealth Management department of Chemical Bank. The investment policy and allocation of the assets of the pension trust were approved by the Compensation and Pension Committee of the board of directors of the Corporation. The Pension Plan's primary investment objective is long-term growth coupled with income. In consideration of the Pension Plan's fiduciary responsibilities, emphasis is placed on quality investments with sufficient liquidity to meet benefit payments and plan expenses, as well as providing the flexibility to manage the investments to accommodate current economic and financial market conditions. To meet the Pension Plan's long-term objective within the constraints of prudent management, target ranges have been set for the three primary asset classes: an equity securities range from 40% to 70% , a debt securities range from 20% to 60% , and a cash and cash equivalents and other range from 0% to 10% . Modest asset positions outside of these targeted ranges may occur due to the repositioning of assets within industries or other activity in the financial markets. Equity securities are primarily comprised of both individual securities and equity-based mutual funds, invested in either domestic or international markets. The stocks are diversified among the major economic sectors of the market and are selected based on balance sheet strength, expected earnings growth, the management team and position within their industries, among other characteristics. Debt securities are comprised of U.S. dollar denominated bonds issued by the U.S. Treasury, U.S. government agencies and investment grade bonds issued by corporations. The notes and bonds purchased are primarily rated A or better by the major bond rating companies from diverse industries. The Pension Plan's asset allocation by asset category was as follows: December 31, Asset Category 2015 2014 Equity securities 68 % 68 % Debt securities 31 30 Other 1 2 Total 100 % 100 % The following schedule sets forth the fair value of the Pension Plan's assets and the level of the valuation inputs used to value those assets at December 31, 2015 and 2014 : Asset Category Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (In thousands) December 31, 2015 Cash $ 354 $ — $ — $ 354 Equity securities: U.S. large- and mid-cap stocks (a) 55,709 — — 55,709 U.S. small-cap mutual funds 4,749 — — 4,749 International large-cap mutual funds 14,124 — — 14,124 Emerging markets mutual funds 4,886 — — 4,886 Chemical Financial Corporation common stock 7,219 — — 7,219 Debt securities: U.S. Treasury and government sponsored agency bonds and notes — 2,815 — 2,815 Corporate bonds (b) — 3,554 — 3,554 Mutual funds (c) 33,424 — — 33,424 Other 96 — — 96 Total $ 120,561 $ 6,369 $ — $ 126,930 December 31, 2014 Cash $ 2,594 $ — $ — $ 2,594 Equity securities: U.S. large- and mid-cap stocks (a) 56,718 — — 56,718 U.S. small-cap mutual funds 5,409 — — 5,409 International large-cap mutual funds 14,805 — — 14,805 Emerging markets mutual funds 6,004 — — 6,004 Chemical Financial Corporation common stock 6,455 — — 6,455 Debt securities: U.S. Treasury and government sponsored agency bonds and notes 998 2,043 — 3,041 Corporate bonds (b) — 6,814 — 6,814 Mutual funds (c) 28,795 — — 28,795 Other 140 — — 140 Total $ 121,918 $ 8,857 $ — $ 130,775 (a) Comprised of common stocks and mutual funds traded on U.S. Exchanges whose issuers had market capitalizations exceeding $3 billion . (b) Comprised of investment grade bonds of U.S. issuers from diverse industries. (c) Comprised primarily of fixed-income bonds issued by the U.S. Treasury and government sponsored agencies and bonds of U.S. and foreign issuers from diverse industries. At both December 31, 2015 and 2014 , equity securities included 210,663 shares of the Corporation's common stock. During each of 2015 and 2014 , cash dividends of $0.2 million were paid on the Corporation's common stock held by the Pension Plan. The fair value of the Corporation's common stock held in the Pension Plan was $7.2 million at December 31, 2015 and $6.5 million at December 31, 2014 , which represented 5.7% and 4.9% of Pension Plan assets at December 31, 2015 and 2014 , respectively. Accumulated Other Comprehensive Loss The following sets forth the changes in accumulated other comprehensive income (loss), net of tax, related to the Corporation's Pension, Postretirement and Supplemental Plans during 2015 : Pension Plan Postretirement Plan Supplemental Plan Total (In thousands) Accumulated other comprehensive income (loss) at beginning of year $ (31,853 ) $ 83 $ (473 ) $ (32,243 ) Comprehensive income (loss) adjustment: Prior service costs (credits) (3 ) 84 — 81 Net actuarial loss 4,565 235 218 5,018 Comprehensive income (loss) adjustment 4,562 319 218 5,099 Accumulated other comprehensive income (loss) at end of year $ (27,291 ) $ 402 $ (255 ) $ (27,144 ) The estimated income (loss) that will be amortized from accumulated other comprehensive income (loss) into net periodic cost, net of tax, in 2016 is as follows: Pension Plan Postretirement Plan Supplemental Plan Total (In thousands) Prior service (costs) credits $ — $ (76 ) $ — $ (76 ) Net gain (loss) (1,468 ) 65 (20 ) (1,423 ) Total $ (1,468 ) $ (11 ) $ (20 ) $ (1,499 )

Share-Based Compensation Plan

Share-Based Compensation Plan	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION The Corporation maintains a share-based compensation plan, 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 years ended December 31, 2015 , 2014 and 2013 , share-based compensation expense related to stock options, restricted stock units and other share-based awards totaled $3.7 million , $2.9 million and $2.9 million , respectively. During the year ended December 31, 2015 , the Corporation granted options to purchase 244,165 shares of common stock, 85,645 restricted stock units and 12,059 shares of common stock to certain officers of the Corporation. On April 20, 2015, the shareholders of the Corporation approved the Stock Incentive Plan of 2015, which provides for 1,300,000 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 December 31, 2015 , there were 1,274,477 shares of common stock available for future grants under the Corporation's share-based compensation plan. Stock Options The Corporation issues stock options to certain officers. Stock options are issued at the current market price of the Corporation's common stock on the date of grant and 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. The following summarizes information about stock options outstanding at December 31, 2015 : Options Outstanding Options Exercisable Range of Exercise Prices Per Share Number Outstanding Weighted Average Exercise Price Per Share Weighted Average Contractual Term (In Years) Number Exercisable Weighted Average Exercise Price Per Share Weighted Average Contractual Term (In Years) $10.56 - 15.84 84,775 $ 13.31 4.73 84,775 $ 13.31 4.73 19.97 - 21.10 74,189 20.47 4.40 74,189 20.47 4.40 23.78 - 25.14 502,845 24.63 5.08 384,912 24.47 4.44 29.45 - 30.18 392,930 29.88 8.76 31,108 29.45 8.17 $10.56 - 30.18 1,054,739 $ 25.38 6.38 574,984 $ 22.58 4.68 The intrinsic value of all outstanding in-the-money stock options and exercisable in-the-money stock options was $7.6 million and $4.9 million , respectively, at December 31, 2015 . The aggregate intrinsic values of outstanding and exercisable options at December 31, 2015 were calculated based on the closing market price of the Corporation's common stock on December 31, 2015 of $34.27 per share less the exercise price. Options with intrinsic values less than zero, or "out-of-the-money" options, were not included in the aggregate intrinsic value reported. At December 31, 2015 , unrecognized compensation cost related to stock options totaled $3.3 million . This cost is expected to be recognized over a remaining weighted average period of approximately 3.5 years . A summary of activity for the Corporation's stock options as of and during the three years ended December 31, 2015 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, 2012 314,765 $ 23.03 $ 6.92 997,222 $ 27.24 Activity during 2013: Granted 244,719 25.14 7.40 244,719 25.14 Exercised — — — (100,145 ) 22.87 Vested (127,443 ) 22.94 6.92 — — Expired or forfeited (17,961 ) 23.34 6.98 (67,806 ) 32.27 Outstanding at December 31, 2013 414,080 24.29 7.19 1,073,990 26.84 Activity during 2014: Granted 190,011 29.45 9.64 190,011 29.45 Exercised — — — (72,936 ) 24.67 Vested (148,016 ) 23.43 6.98 — — Expired or forfeited (23,876 ) 25.67 7.79 (153,754 ) 37.50 Outstanding at December 31, 2014 432,199 26.75 8.30 1,037,311 25.90 Activity during 2015: Granted 244,165 30.18 8.40 244,165 30.18 Lake Michigan converted options — — — 132,883 12.93 Exercised — — — (310,985 ) 25.10 Vested (150,224 ) 25.57 7.80 — — Expired or forfeited (46,385 ) 27.99 8.50 (48,635 ) 28.18 Outstanding at December 31, 2015 479,755 $ 28.75 $ 8.49 1,054,739 $ 25.38 Exercisable/vested at December 31, 2015 574,984 $ 22.58 The fair value of the stock options granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions. 2015 2014 2013 Expected dividend yield 3.50 % 3.00 % 3.50 % Risk-free interest rate 1.78 % 2.16 % 1.34 % Expected stock price volatility 39.1 % 42.2 % 42.1 % Expected life of options — in years 7.0 7.0 7.0 Weighted average fair value per share $8.40 $9.64 $7.40 The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant and the expected life of the options granted. Expected stock volatility was based on historical volatility of the Corporation's common stock over a seven -year period. The expected life of options represents the period of time that options granted are expected to be outstanding and is based primarily upon historical experience, including option exercise behavior. Because of the unpredictability of the assumptions required, the Black-Scholes (or any other valuation) model is incapable of accurately predicting the Corporation's common stock price or of placing an accurate present value on options to purchase its stock. In addition, the Black-Scholes model was designed to approximate value for types of options that are very different from those issued by the Corporation. In spite of any theoretical value that may be placed on a stock option grant, no value is possible under options issued by the Corporation without an increase in the market price per share of the Corporation's common stock over the market price per share of the Corporation's common stock at the date of grant. Restricted Stock Units In addition to stock options, the Corporation also grants restricted stock performance units and restricted stock service-based units (collectively referred to as restricted stock units) to certain officers. The restricted stock performance units vest based on the Corporation achieving certain performance target levels and the grantee completing the requisite service period. The restricted stock performance units are eligible to vest from 0.25 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 restricted stock performance units. The restricted stock service-based units vest upon satisfaction of a service condition. Upon achievement of the performance target level and/or satisfaction of a service condition, if applicable, the restricted stock units are converted into shares of the Corporation's common stock on a one-to-one basis. Compensation expense related to restricted stock units is recognized over the expected requisite performance or service period, as applicable. A summary of the activity for restricted stock units during the three years ended December 31, 2015 is presented below: Number of Units Weighted Average Grant Date Fair Value Per Unit Outstanding at December 31, 2012 156,510 $ 20.83 Activity during 2013: Granted 71,768 23.42 Converted into shares of common stock (36,416 ) 22.44 Forfeited/expired (3,330 ) 21.67 Outstanding at December 31, 2013 188,532 21.49 Activity during 2014: Granted 73,468 27.49 Converted into shares of common stock (52,008 ) 19.23 Forfeited/expired (5,673 ) 24.31 Outstanding at December 31, 2014 204,319 24.14 Activity during 2015: Granted 85,645 28.52 Converted into shares of common stock (70,166 ) 22.51 Forfeited/expired (11,809 ) 25.61 Outstanding at December 31, 2015 207,989 $ 26.41 At December 31, 2015 , unrecognized compensation cost related to restricted stock unit awards totaled $3.2 million and is expected to be recognized over approximately 2.4 years .

Federal Income Taxes

Federal Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal Income Taxes	FEDERAL INCOME TAXES The provision for federal income taxes was less than that computed by applying the federal statutory income tax rate of 35% to pre-tax income, primarily due to tax-exempt interest income on investment securities and loans and income tax credits during 2015 , 2014 and 2013 . The differences between the provision for federal income taxes computed at the federal statutory income tax rate and the amounts recorded in the consolidated financial statements were as follows: Years Ended December 31, 2015 2014 2013 (Dollars in thousands) Tax at statutory rate $ 43,341 $ 31,367 $ 28,388 Changes resulting from: Tax-exempt interest income (3,918 ) (3,118 ) (2,746 ) Income tax credits, net (2,557 ) (1,624 ) (1,615 ) Other, net 134 875 273 Provision for federal income taxes $ 37,000 $ 27,500 $ 24,300 Effective federal income tax rate 29.9 % 30.7 % 30.0 % The provision for federal income taxes consisted of the following: Years Ended December 31, 2015 2014 2013 (In thousands) Current expense $ 31,300 $ 29,200 $ 23,665 Deferred expense (benefit) 5,700 (1,700 ) 635 Total federal income tax expense $ 37,000 $ 27,500 $ 24,300 Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant temporary differences that comprise the deferred tax assets and liabilities of the Corporation were as follows: December 31, 2015 2014 (In thousands) Deferred tax assets: Allowance for loan losses $ 24,863 $ 26,489 Acquisition-related fair value adjustments 29,280 19,457 Accrued expenses not currently deductible 9,331 7,819 Net operating loss carryforward 7,130 — Premises and equipment 4,333 3,311 Nonaccrual loan interest 4,994 4,682 Other 15,296 9,418 Total deferred tax assets 95,227 71,176 Deferred tax liabilities: Core deposit intangible assets 7,379 5,072 Goodwill 5,808 5,205 Mortgage servicing rights 3,893 4,276 Other 7,957 3,884 Total deferred tax liabilities 25,037 18,437 Net deferred tax assets $ 70,190 $ 52,739 Management expects to realize the full benefits of the deferred tax assets recorded at December 31, 2015 . The Corporation had no reserve for contingent income tax liabilities recorded at December 31, 2015 and 2014 . The tax periods open to examination by the Internal Revenue Service include the years ended December 31, 2015 , 2014 , 2013 and 2012 . Upon the Corporation's acquisition of Monarch, there was an ownership change within the meaning of Internal Revenue Code Section 382. At April 1, 2015, Monarch had $22.6 million in gross federal net operating loss carryforwards that expire between 2028-2034, which the Corporation expects to utilize. The Corporation expects to utilize these net operating losses, in part, as Monarch was in a net unrealized built-in gain position as of the acquisition date. The Corporation had remaining gross federal net operating loss carryforwards of $20.4 million at December 31, 2015 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES In the normal course of business, the Corporation enters into various transactions with its customers, which are not included in its consolidated statements of financial condition. These transactions include unused commitments to extend credit, standby letters of credit and approved but undisbursed loans (undisbursed loan commitments). Unused commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the loan contract. Unused commitments to extend credit generally have fixed expiration dates or other termination clauses. Historically, the majority of the unused commitments to extend credit of Chemical Bank have not been drawn upon and, therefore, may not represent future cash requirements. Standby letters of credit are conditional commitments issued by Chemical Bank to generally guarantee the performance of a customer to a third party. Both arrangements have credit risk essentially the same as that involved in making loans to customers and are subject to the Corporation's normal credit policies, including underwriting standards and ongoing review and monitoring. Collateral obtained upon exercise of commitments is determined using management's credit evaluation of the borrowers and may include real estate, business assets, deposits and other items. 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 three -month period. At December 31, 2015 , total unused commitments to extend credit, standby letters of credit and undisbursed loan commitments were $1.59 billion , $39 million and $294 million , respectively. At December 31, 2014 , total unused commitments to extend credit, standby letters of credit and undisbursed loan commitments were $1.08 billion , $41 million and $251 million , respectively. A significant portion of the unused commitments to extend credit and standby letters of credit outstanding as of December 31, 2015 expire one year from their contract date; however, $144 million of unused commitments to extend credit extend for more than five years . The Corporation's unused commitments to extend credit and standby letters of credit have been estimated to have an immaterial realizable fair value, as historically the majority of these commitments have not been drawn upon and generally Chemical Bank does not receive fees in connection with these agreements. At both December 31, 2015 and December 31, 2014 , the Corporation determined that there were no potential losses from standby letters of credit, and therefore, no reserve was needed at those dates. Undisbursed loan commitments of $294 million at December 31, 2015 included $23 million of residential mortgage loans that were expected to be sold in the secondary market. The Corporation locked the interest rate to the customer (mortgage loan commitment) on the $23 million of loans that were expected to be sold in the secondary market and entered into best efforts forward contracts with the secondary market on these mortgage loan commitments at December 31, 2015 . Best efforts forward contracts offset the interest rate risk of market interest rates changing between the date the interest rate is locked with the customer and the date the loan is sold in the secondary market. At December 31, 2014 , the Corporation had mortgage loan commitments of $24 million included in loan commitments, with best efforts forward contracts on these loans at that date. The Corporation has operating leases and other noncancelable contractual obligations on buildings, equipment, computer software and other expenses that will require annual payments through 2034, including renewal option periods for those building leases that the Corporation expects to renew. Minimum payments due in each of the next five years and thereafter are as follows: 2016 - $14.8 million ; 2017 - $12.2 million ; 2018 - $6.4 million ; 2019 - $3.9 million ; 2020 - $2.4 million ; 2021 and thereafter - $9.2 million . Minimum payments include estimates, where applicable, of estimated usage and annual Consumer Price Index increases of approximately 3% . Total expense recorded under operating leases and other noncancelable contractual obligations was $15.6 million in 2015 , compared to $12.4 million in 2014 and $11.6 million in 2013 . The Corporation and Chemical Bank are subject to certain legal actions arising in the ordinary course of business. In the opinion of management, after consulting with legal counsel, the ultimate disposition of these matters is not expected to have a material adverse effect on the financial position or results of operations of the Corporation.

Regulatory Capital and Reserve

Regulatory Capital and Reserve Requirements	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Regulatory Capital and Reserve Requirements	REGULATORY CAPITAL AND RESERVE REQUIREMENTS Banking regulations require that banks maintain cash reserve balances in vault cash, with the FRB, or with certain other qualifying banks. The aggregate average amount of the regulatory balances required to be maintained by Chemical Bank was $65.3 million during 2015 and $46.3 million during 2014 . During 2015 , Chemical Bank satisfied its regulatory reserve requirements by maintaining a combination of vault cash balances and cash held with the FRB in excess of regulatory reserve requirements. Chemical Bank was not required to maintain compensating balances with correspondent banks during 2015 or 2014 . 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. At December 31, 2015 , substantially all of the assets of Chemical Bank were restricted from transfer to the Corporation in the form of loans or advances. Dividends from Chemical Bank are the principal source of funds for the Corporation. During 2015 , 2014 and 2013 , Chemical Bank paid dividends to the Corporation totaling $56.9 million , $64.5 million and $24.5 million , respectively. At December 31, 2015 , Chemical Bank was "well-capitalized" as defined by federal banking regulations. In addition to the statutory limits, the Corporation considers the overall financial and capital position of Chemical Bank prior to making any cash dividend decisions. The Corporation and Chemical Bank are subject to various regulatory capital requirements administered by federal banking agencies. Under these capital requirements, Chemical Bank must meet specific capital guidelines that involve quantitative measures of assets and certain off-balance sheet items as calculated under regulatory accounting practices. In addition, capital amounts and classifications are subject to qualitative judgments by regulators. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Corporation's consolidated financial statements. Quantitative measures established by regulation to ensure capital adequacy require minimum ratios of Tier 1 capital to average assets (Leverage Ratio) and 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 $7.14 billion and $7.13 billion , respectively, at December 31, 2015 , compared to $5.70 billion for both the Corporation and Chemical Bank at December 31, 2014 . In July 2013, the Federal Reserve Board and Federal Deposit Insurance Corporation (FDIC) approved final rules implementing the Basel Committee on Banking Supervision's (BCBS) capital guidelines for U.S. banks (commonly referred to as Basel III). Beginning January 1, 2015, the Basel III capital rules include a new minimum common equity Tier 1 capital to risk-weighted assets (CET) ratio of 4.5%, in addition to raising the minimum ratio of Tier 1 capital to risk-weighted assets from 4.0% to 6.0% and requiring a minimum leverage ratio of 4.0%. The Basel III capital rules also establish 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. At December 31, 2015 and 2014 , 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 the mix or credit quality of assets. The summary below compares the Corporation's and Chemical Bank's actual capital amounts and ratios with the quantitative measures established by regulation to ensure capital adequacy. Amounts as of December 31, 2015 were based on the Basel III capital rules, which became effective January 1, 2015. Amounts as of December 31, 2014 were based on the regulatory capital rules in effect as of that date. Actual Minimum Required for Capital Adequacy Purposes Required to be Well Capitalized Under Prompt Corrective Action Regulations Capital Amount Ratio Capital Amount Ratio Capital Amount Ratio (Dollars in thousands) December 31, 2015 Total Capital to Risk-Weighted Assets: Corporation $ 841,257 11.8 % $ 571,509 8.0 % N/A N/A Chemical Bank 830,294 11.7 570,073 8.0 $ 712,591 10.0 % Tier 1 Capital to Risk-Weighted Assets: Corporation 767,929 10.7 428,631 6.0 N/A N/A Chemical Bank 756,966 10.6 427,555 6.0 570,073 8.0 Common Equity Tier 1 Capital to Risk-Weighted Assets: Corporation 753,815 10.6 321,474 4.5 N/A N/A Chemical Bank 756,966 10.6 320,666 4.5 463,184 6.5 % Leverage Ratio: Corporation 767,929 8.6 356,396 4.0 N/A N/A Chemical Bank 756,966 8.5 355,911 4.0 444,888 5.0 December 31, 2014 Total Capital to Risk-Weighted Assets: Corporation $ 705,130 12.4 % $ 456,302 8.0 % N/A N/A Chemical Bank 654,031 11.5 455,633 8.0 $ 569,541 10.0 % Tier 1 Capital to Risk-Weighted Assets: Corporation 633,779 11.1 228,151 4.0 N/A N/A Chemical Bank 582,783 10.2 227,816 4.0 341,725 6.0 Leverage Ratio: Corporation 633,779 9.3 273,226 4.0 N/A N/A Chemical Bank 582,783 8.5 273,048 4.0 341,310 5.0

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Common Share	EARNINGS PER COMMON SHARE Basic earnings per common share for the Corporation is computed by dividing net income by the weighted average number of common shares outstanding during the period. Basic earnings per common share excludes any dilutive effect of common stock equivalents. Diluted earnings per common share for the Corporation is computed by dividing net income by the sum of the weighted average number of common shares outstanding and the dilutive effect of common stock equivalents using the treasury stock method. 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, stock to be issued under the deferred stock compensation plan for non-employee directors and stock to be issued under the stock purchase plan for non-employee community advisory directors. For any period in which a net loss is recorded, the assumed exercise of stock options, restricted stock units that may be converted to stock and stock to be issued under the deferred stock compensation plan and the stock purchase plan would have an anti-dilutive impact on the net income per common share and thus would be excluded in the diluted earnings per common share calculation. The following summarizes the numerator and denominator of the basic and diluted earnings per common share computations: Years Ended December 31, 2015 2014 2013 (In thousands, except per share data) Numerator for both basic and diluted earnings per common share, net income $ 86,830 $ 62,121 $ 56,808 Denominator for basic earnings per common share, weighted average common shares outstanding 36,081 31,367 28,183 Weighted average common stock equivalents 272 221 169 Denominator for diluted earnings per common share 36,353 31,588 28,352 Net income per common share: Basic $ 2.41 $ 1.98 $ 2.02 Diluted 2.39 1.97 2.00 The average number of exercisable employee stock option awards 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 54,771 for the year ended December 31, 2015 , 240,165 for the year ended December 31, 2014 and 356,328 for the year ended December 31, 2013 .

Parent Company Only Financial S

Parent Company Only Financial Statements	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Only Financial Statements	PARENT COMPANY ONLY FINANCIAL STATEMENTS Condensed financial statements of Chemical Financial Corporation (parent company) only follow: December 31, Condensed Statements of Financial Position 2015 2014 (In thousands) Assets: Cash at subsidiary bank $ 28,884 $ 45,820 Investment in subsidiaries 1,023,285 745,045 Premises and equipment 3,632 3,601 Goodwill 1,092 1,092 Other assets 13,051 4,654 Total assets $ 1,069,944 $ 800,212 Liabilities and Shareholders' Equity: Other liabilities $ 10,426 $ 3,079 Non-revolving line of credit 25,000 — Subordinated debentures 18,544 — Shareholders' equity 1,015,974 797,133 Total liabilities and shareholders' equity $ 1,069,944 $ 800,212 Years Ended December 31, Condensed Statements of Income 2015 2014 2013 (In thousands) Income: Cash dividends from subsidiaries $ 56,860 $ 64,468 $ 24,488 Other income 144 95 390 Total income 57,004 64,563 24,878 Expenses: Interest expense 761 42 — Operating expenses 7,794 7,200 4,735 Total expenses 8,555 7,242 4,735 Income before income taxes and equity in undistributed net income of subsidiaries 48,449 57,321 20,143 Federal income tax benefit 2,582 2,302 1,556 Equity in undistributed net income of subsidiaries 35,799 2,498 35,109 Net income $ 86,830 $ 62,121 $ 56,808 Years Ended December 31, Condensed Statements of Cash Flows 2015 2014 2013 (In thousands) Operating Activities: Net income $ 86,830 $ 62,121 $ 56,808 Adjustments to reconcile net income to net cash provided by operating activities: Share-based compensation expense 3,478 2,931 2,854 Gain on sale of available-for-sale investment securities — — (245 ) Depreciation of premises and equipment 318 327 416 Equity in undistributed net income of subsidiaries (35,799 ) (2,498 ) (35,109 ) Net (increase) decrease in other assets 2,873 1,101 (711 ) Net increase (decrease) in other liabilities (19,033 ) (2,519 ) 563 Net cash provided by operating activities 38,667 61,463 24,576 Investing Activities: Cash paid, net of cash assumed, in business combinations (45,267 ) (117,853 ) — Proceeds from redemption of available-for-sale investment securities — — 5,000 Purchases of premises and equipment, net (320 ) (26 ) (9 ) Net cash provided by (used in) investing activities (45,587 ) (117,879 ) 4,991 Financing Activities: Cash dividends paid (36,918 ) (29,528 ) (24,521 ) Proceeds from issuance of common stock, net of issuance costs — 76,175 53,925 Repayment of subordinated debt obligations — (10,310 ) — Proceeds from issuance of other borrowings 25,000 — — Proceeds from directors' stock purchase plan and exercise of stock options 2,473 1,242 806 Cash paid for payroll taxes upon conversion of restricted stock units (571 ) (701 ) (379 ) Net cash provided by (used in) financing activities (10,016 ) 36,878 29,831 Net increase (decrease) in cash and cash equivalents (16,936 ) (19,538 ) 59,398 Cash and cash equivalents at beginning of year 45,820 65,358 5,960 Cash and cash equivalents at end of year $ 28,884 $ 45,820 $ 65,358

Summary of Quarterly Statements

Summary of Quarterly Statements of Income (Unaudited)	12 Months Ended
	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Summary of Quarterly Statements of Income (Unaudited)	SUMMARY OF QUARTERLY STATEMENTS OF INCOME (UNAUDITED) The following quarterly information is unaudited. However, in the opinion of management, the information reflects all adjustments that are necessary for the fair presentation of the results of operations for the periods presented. 2015 First Quarter Second Quarter Third Quarter Fourth Quarter Total (In thousands, except per share data) Interest income $ 62,630 $ 69,679 $ 78,851 $ 80,629 $ 291,789 Interest expense 3,450 3,944 5,234 5,153 17,781 Net interest income 59,180 65,735 73,617 75,476 274,008 Provision for loan losses 1,500 1,500 1,500 2,000 6,500 Noninterest income 19,275 20,674 20,215 20,052 80,216 Operating expenses 51,020 56,785 58,265 57,824 223,894 Income before income taxes 25,935 28,124 34,067 35,704 123,830 Federal income tax expense 8,100 9,100 9,600 10,200 37,000 Net income $ 17,835 $ 19,024 $ 24,467 $ 25,504 $ 86,830 Net income per common share: Basic $ 0.54 $ 0.54 $ 0.64 $ 0.67 $ 2.41 Diluted 0.54 0.54 0.64 0.66 2.39 Cash dividends declared per common share 0.24 0.24 0.26 0.26 1.00 2014 First Quarter Second Quarter Third Quarter Fourth Quarter Total (In thousands, except per share data) Interest income $ 53,645 $ 55,180 $ 56,629 $ 61,807 $ 227,261 Interest expense 3,866 3,720 3,561 3,563 14,710 Net interest income 49,779 51,460 53,068 58,244 212,551 Provision for loan losses 1,600 1,500 1,500 1,500 6,100 Noninterest income 13,716 15,801 15,351 18,227 63,095 Operating expenses 42,182 42,425 42,702 52,616 179,925 Income before income taxes 19,713 23,336 24,217 22,355 89,621 Federal income tax expense 5,900 7,100 7,450 7,050 27,500 Net income $ 13,813 $ 16,236 $ 16,767 $ 15,305 $ 62,121 Net income per common share: Basic $ 0.46 $ 0.54 $ 0.51 $ 0.47 $ 1.98 Diluted 0.46 0.54 0.51 0.46 1.97 Cash dividends declared per common share 0.23 0.23 0.24 0.24 0.94

Significant Accounting Polici33

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations Chemical Financial Corporation (Corporation) 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. The Bank of Holland and The Bank of Northern Michigan were acquired in the acquisition of Lake Michigan Financial Corporation (Lake Michigan) on May 31, 2015 and were consolidated with and into Chemical Bank during the fourth quarter of 2015. Monarch Community Bank was acquired in the acquisition of Monarch Community Bancorp, Inc. (Monarch) on April 1, 2015 and was consolidated with and into Chemical Bank during the second quarter of 2015. Chemical Bank operates within the State of Michigan as a state-chartered commercial bank. Chemical Bank operates through an internal organizational structure of four regional banking units and offers a full range of traditional banking and fiduciary products and services to the residents and business customers in the bank'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 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 from its loan products and investment securities, service charges and fees from customer deposit accounts and wealth management revenue.
Basis of Presentation and Principles of Consolidation	Accounting Standards Codification The Financial Accounting Standards Board's (FASB) Accounting Standards Codification (ASC) became effective on July 1, 2009. At that date, the ASC became FASB's officially recognized source of authoritative U.S. generally accepted accounting principles (GAAP) applicable to all public and non-public non-governmental entities, superseding existing FASB, American Institute of Certified Public Accountants (AICPA), Emerging Issues Task Force (EITF) and related literature. Rules and interpretive releases of the Securities and Exchange Commission (SEC) under the authority of federal securities laws are also sources of authoritative GAAP for SEC registrants. All other accounting literature is considered non-authoritative. Basis of Presentation and Principles of Consolidation The accounting and reporting policies of the Corporation and its subsidiaries conform to GAAP, SEC rules and interpretive releases and prevailing practices within the banking industry. The consolidated financial statements of the Corporation include the accounts of the Corporation and its wholly owned subsidiaries. All significant income and expenses are recorded on the accrual basis. Intercompany accounts and transactions have been eliminated in preparing the consolidated financial statements.
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, fair value amounts related to business combinations, pension expense, income taxes, goodwill impairment and those assets that require fair value measurement. Actual results could differ from these estimates.
Business Combinations	Business Combinations Pursuant to the guidance of ASC Topic 805, Business Combinations (ASC 805), the Corporation recognizes assets acquired, including identified intangible assets, and the liabilities assumed in acquisitions at their fair values as of the acquisition date, with the acquisition-related transaction and restructuring costs expensed in the period incurred. On May 31, 2015, the Corporation acquired all of the outstanding stock of Lake Michigan for total consideration of $187.4 million , which included stock consideration of $132.9 million and cash consideration of $54.5 million . The Corporation recorded $102 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair value of identifiable net assets acquired. Additionally, the Corporation recorded $8.6 million of core deposit and other intangible assets in conjunction with the acquisition. On April 1, 2015, the Corporation acquired all of the outstanding stock of Monarch in an all-stock transaction valued at $27.2 million . The Corporation recorded $5.3 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair value of identifiable net assets acquired. Additionally, the Corporation recorded $1.9 million of core deposit intangible assets in conjunction with the acquisition. On October 31, 2014, the Corporation acquired all of the outstanding stock of Northwestern Bancorp, Inc. (Northwestern) for total cash consideration of $121.0 million . The Corporation recorded $60.3 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair value of the identifiable net assets acquired. Additionally, the Corporation recorded $12.9 million of core deposit intangible assets in conjunction with the acquisition. On December 7, 2012, Chemical Bank acquired 21 branches from Independent Bank, a subsidiary of Independent Bank Corporation (branch acquisition transaction). In connection with the branch acquisition transaction, the Corporation recorded $6.8 million of goodwill, which represented the purchase price over the fair value of identifiable net assets acquired, and $5.6 million of core deposit intangible assets. On April 30, 2010, the Corporation acquired all of the outstanding stock of O.A.K. Financial Corporation (OAK) for total consideration of $83.7 million . The Corporation recorded $43.5 million of goodwill in conjunction with the acquisition, which represented the purchase price over the fair values of the identifiable net assets acquired. Additionally, the Corporation recorded $9.8 million of other intangible assets as a result of the OAK acquisition attributable to core deposits, mortgage servicing rights and non-compete agreements acquired. See Note 2 for further information regarding the Corporation's mergers and acquisitions, including its pending merger with Talmer Bancorp, Inc. (Talmer). ASC 805 affords a measurement period beyond the acquisition date that allows the Corporation the opportunity to finalize the acquisition accounting in the event that new information is identified that existed as of the acquisition date but was not known by the Corporation at that time. The Corporation anticipates that measurement period adjustments may arise from adjustments to the fair values of assets and liabilities recognized at the acquisition date for Lake Michigan and Monarch as additional information is obtained, such as appraisals of collateral securing loans and other borrower information. In the event that a measurement period adjustment is identified, the Corporation will recognize the adjustment as part of its acquisition accounting, which may result in an adjustment to goodwill being recorded in the period the adjustment was identified.
Cash and Cash Equivalents	Cash and Cash Equivalents For purposes of reporting cash flows, cash and cash equivalents include cash on hand and interest-bearing deposits held at the Federal Reserve Bank (FRB).
Investment Securities	Investment Securities Investment securities include investments in debt, trust preferred and preferred stock securities. Investment securities are accounted for in accordance with ASC Topic 320, Investments — Debt and Equity Securities (ASC 320), which requires investments to be classified within one of three categories (trading, held-to-maturity or available-for-sale). The Corporation held no trading investment securities at December 31, 2015 or 2014 . Designation as an investment security held-to-maturity is based on the Corporation's intent and ability to hold the security to maturity. Investment securities held-to-maturity are stated at cost, adjusted for purchase price premiums and discounts. Investment securities that are not held-to-maturity are accounted for as securities available-for-sale, and are stated at estimated fair value, with the aggregate unrealized gains and losses, not deemed other-than-temporary, classified as a component of accumulated other comprehensive income (loss), net of income taxes. Realized gains and losses on the sale of investment securities and other-than-temporary impairment (OTTI) charges are determined using the specific identification method and are included within noninterest income in the consolidated statements of income. Premiums and discounts on investment securities are amortized over the estimated lives of the related investment securities based on the effective interest yield method and are included in interest income in the consolidated statements of income. The Corporation assesses equity and debt securities that have fair values below amortized cost basis to determine whether declines (impairment) are other-than-temporary. If the Corporation intends to sell an impaired security or it is more-likely-than-not that the Corporation will be required to sell an impaired security prior to the recovery of its amortized cost, an OTTI write-down is recognized in earnings equal to the entire difference between the security's amortized cost basis and its fair value. If the Corporation does not intend to sell an impaired security and it is not more-likely-than-not that the Corporation would be required to sell an impaired security before the recovery of its amortized cost basis, then the recognition of the impairment is bifurcated if a credit loss is deemed to have occurred. For a security where the impairment is bifurcated, the impairment is separated into an amount representing the credit loss, which is recognized in earnings, and an amount related to all other factors, which is recognized in other comprehensive income. In assessing whether OTTI exists, management considers, among other things, (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near-term prospects of the issuer, (iii) the potential for impairments in an entire industry or sub-sector and (iv) the potential for impairments in certain economically depressed geographical locations.
Nonmarketable Equity Securities	Nonmarketable Equity Securities The Corporation is required to hold non-marketable equity securities, comprised of Federal Home Loan Bank of Indianapolis (FHLB) and FRB stock, as a condition of membership. These securities are accounted for at cost, which equals par or redemption value. These securities do not have a readily determinable fair value as their ownership is restricted and there is no market for these securities. These securities can only be redeemed or sold at their par value and only to the respective issuing government supported institution or to another member institution. FHLB stock can only be redeemed upon giving five -years written notice and FRB stock can only be redeemed upon giving six months written notice, with no more than 25% eligible for redemption in any calendar year. The Corporation records these non-marketable equity securities as a component of other assets and they are periodically evaluated for impairment. Management considers these non-marketable equity securities to be long-term investments. Accordingly, when evaluating these securities for impairment, management considers the ultimate recoverability of the par value rather than recognizing temporary declines in value, if applicable. The Corporation's ownership of FHLB stock totaled $23.9 million at December 31, 2015 and $19.0 million at December 31, 2014 . The Corporation's ownership of FRB stock totaled $13.0 million at December 31, 2015 and $8.4 million at December 31, 2014 .
Originated Loans	Originated Loans Originated loans include all of the Corporation's portfolio loans, excluding loans acquired on May 31, 2015 in the acquisition of Lake Michigan, on April 1, 2015 in the acquisition of Monarch, on October 31, 2014 in the acquisition of Northwestern and on April 30, 2010 in the acquisition of OAK. Originated loans also include loans acquired as part of the branch acquisition transaction on December 7, 2012, as these loans were performing and were considered high-quality loans in accordance with the Corporation's credit underwriting standards at that date. Originated loans are held for investment purposes and are stated at their principal amount outstanding, net of unearned income, charge-offs and unamortized deferred fees and costs. Loan interest income is recognized on the accrual basis. Deferred loan fees and costs are amortized over the loan term based on the level-yield method. Net loan commitment fees are deferred and amortized into fee income on a straight-line basis over the commitment period. The past due status of a loan is based on the loan's contractual terms. A loan is placed in nonaccrual status (accrual of interest is discontinued) when principal or interest is past due 90 days or more (except for a loan that is secured by residential real estate, which is transferred to nonaccrual status at 120 days past due), unless the loan is both well-secured and in the process of collection, or earlier when, in the opinion of management, there is sufficient reason to doubt the collectibility of principal or interest. Interest previously accrued, but not collected, is reversed and charged against interest income at the time the loan is placed in nonaccrual status. Subsequent receipts of interest while a loan is in nonaccrual status are recorded as a reduction of principal. Loans are returned to accrual status when principal and interest payments are brought current, payments have been received consistently for a period of time (generally six months) and collectibility is no longer in doubt.
Loans Acquired in a Business Combination	Loans Acquired in a Business Combination Loans acquired in a business combination (acquired loans) consist of loans acquired on May 31, 2015 in the acquisition of Lake Michigan, on April 1, 2015 in the acquisition of Monarch, on October 31, 2014 in the acquisition of Northwestern and on April 30, 2010 in the acquisition of OAK. Acquired loans were recorded at fair value at the date of acquisition, without a carryover of the associated allowance for loan losses related to these loans, through a fair value discount that was, in part, attributable to deterioration in credit quality. The estimate of expected credit losses was determined based on due diligence performed by executive and senior officers of the Corporation, with assistance from third-party consultants. The fair value discount was recorded as a reduction of the acquired loans' outstanding principal balances in the consolidated statement of financial position at the acquisition date. The Corporation accounts for acquired loans, which are recorded at fair value at acquisition, in accordance with ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality (ASC 310-30). Under the provisions of ASC 310-30, the Corporation aggregated acquired loans with an outstanding principal balance at the acquisition date of $63 million for the Lake Michigan transaction, $9 million for the Monarch transaction, $46 million for the Northwestern transaction and $105 million for the OAK transaction that were determined to be loans with deteriorated credit quality and, therefore, met the scope criteria set forth in ASC 310-30. Further, the Corporation understands, as outlined in the AICPA's open letter to the Office of the Chief Accountant of the SEC dated December 18, 2009 and pending further standard setting, that for acquired loans that do not meet the scope criteria of ASC 310-30, a company may elect to account for such acquired loans pursuant to the provisions of either ASC Topic 310-20, Nonrefundable Fees and Other Costs, or ASC 310-30. The Corporation elected to apply ASC 310-30, by analogy, to acquired loans that were determined not to have deteriorated credit quality with an outstanding principal balance at the acquisition date of $947 million for the Lake Michigan transaction, $120 million for the Monarch transaction, $461 million for the Northwestern transaction and $578 million for the OAK transaction and thus follows the accounting and disclosure guidance of ASC 310-30 for these loans. Accordingly, the Corporation applied ASC 310-30 to the entire loan portfolio acquired with a total outstanding principal balance at the acquisition date of $1.01 billion for the Lake Michigan transaction, $129 million for the Monarch transaction, $507 million for the Northwestern transaction and $683 million for the OAK transaction. None of the acquired loans were classified as debt securities. ASC 310-30 allows investors to aggregate acquired loans into loan pools that have common risk characteristics and thereby use a composite interest rate and expectation of cash flows expected to be collected for the loan pools. Under the provisions of ASC 310-30, the Corporation aggregated acquired loans into 2 pools in the acquisition of Lake Michigan, 2 pools in the acquisition of Monarch, 4 pools in the acquisition of Northwestern and 14 pools in the acquisition of OAK based upon common risk characteristics, including types of loans, commercial type loans with similar risk grades and whether loans were performing or nonperforming. A pool is considered a single unit of accounting for the purposes of applying the guidance prescribed in ASC 310-30. A loan will be removed from a pool of acquired loans only if the loan is sold, foreclosed, paid off or written off, and will be removed from the pool at the carrying value. If an individual loan is removed from a pool of loans, the difference between its relative carrying amount and the cash, fair value of the collateral, or other assets received would not affect the effective yield used to recognize the accretable difference on the remaining pool. The Corporation estimated the cash flows expected to be collected over the life of the pools of loans at acquisition and estimates expected cash flows quarterly thereafter, based on a set of assumptions including expectations as to default rates, prepayment rates and loss severities. The Corporation must make numerous assumptions, interpretations and judgments using internal and third-party credit quality information to determine whether it is probable that the Corporation will be able to collect all contractually required payments. This is a point in time assessment and inherently subjective due to the nature of the available information and judgment involved. The calculation of the fair value of the acquired loan pools entails estimating the amount and timing of cash flows attributable to both principal and interest expected to be collected on such loan pools and then discounting those cash flows at market interest rates. The excess of a loan pool's expected cash flows at the acquisition date over its estimated fair value is referred to as the "accretable yield," which is recognized into interest income over the remaining life of the loan on a level-yield basis. The difference between a loan pool's contractually required principal and interest payments at the acquisition date and the cash flows expected to be collected at the acquisition date is referred to as the "nonaccretable difference," which includes an estimate of future credit losses expected to be incurred over the estimated life of the loan pool and interest payments that are not expected to be collected. Decreases to the expected cash flows in each loan pool in subsequent periods will require the Corporation to record a provision for loan losses. Improvements in expected cash flows in each loan pool in subsequent periods will result in reversing a portion of the nonaccretable difference, which is then classified as part of the accretable yield and subsequently recognized into interest income over the estimated remaining life of the loan pool.
Loans Modified Under Troubled Debt Restructurings	Loans Modified Under Troubled Debt Restructurings Loans modified under troubled debt restructurings (TDRs) involve granting a concession to a borrower who is experiencing financial difficulty. Concessions generally include modifications to original loan terms, including changes to a loan's payment schedule or interest rate, which generally would not otherwise be considered. The Corporation's TDRs include performing and nonperforming TDRs, which consist of originated loans that continue to accrue interest at the loan's original interest rate as the Corporation expects to collect the remaining principal and interest on the loan, and nonaccrual TDRs, which include originated loans that are in a nonaccrual status and are no longer accruing interest, as the Corporation does not expect to collect the full amount of principal and interest owed from the borrower on these loans. At the time of modification (except for loans on nonaccrual status), a TDR is classified as a nonperforming TDR until a six -month payment history of principal and interest payments, in accordance with the terms of the loan modification, is sustained, at which time the Corporation moves the loan to a performing status (performing TDR). If the Corporation does not expect to collect all principal and interest on the loan, the modified loan is classified as a nonaccrual TDR. All TDRs are accounted for as impaired loans and are included in the Corporation's analysis of the allowance for loan losses. A TDR that has been renewed for a borrower who is no longer experiencing financial difficulty and which yields a market rate of interest at the time of a renewal is no longer considered to be a TDR. Loans in the Corporation's commercial loan portfolio (comprised of commercial, commercial real estate, real estate construction and land development loans) that meet the definition of a TDR generally consist of loans where the Corporation has allowed borrowers to defer scheduled principal payments and make interest-only payments for a specified period of time at the stated interest rate of the original loan agreement or reduced payments due to a moderate extension of the loan's contractual term. If the Corporation does not expect to collect all principal and interest on the loan, the modified loan is classified as a nonaccrual TDR. If the Corporation does not expect to incur a loss on the loan based on its assessment of the borrowers' expected cash flows, as the pre- and post-modification effective yields are approximately the same, the loan is classified as a nonperforming TDR until a six-month payment history is sustained, at which time the loan is classified as a performing TDR. Since no loss is expected to be incurred on these loans, no additional provision for loan losses has been recognized related to these loans, and these loans accrue interest at their contractual interest rate. These loans are individually evaluated for impairment and transferred to nonaccrual status if they become 90 days past due as to principal or interest payments or if it is probable that any remaining principal and interest payments due on the loan will not be collected in accordance with the modified terms of the loan. Loans in the Corporation's consumer loan portfolio (comprised of residential mortgage, consumer installment and home equity loans) that meet the definition of a performing or nonperforming TDR generally consist of residential mortgage loans that include a concession that reduces a borrower's monthly payments by decreasing the interest rate charged on the loan for a specified period of time (generally 24 months) under a formal modification agreement. The Corporation recognizes an additional provision for loan losses related to impairment on these loans on an individual basis based on the present value of expected future cash flows discounted at the loan's original effective interest rate. These loans continue to accrue interest at their effective interest rate, which consists of contractual interest under the terms of the modification agreement in addition to an adjustment for the accretion of computed impairment. These loans are moved to nonaccrual status if they become 90 days past due as to principal or interest payments, or sooner if conditions warrant.
Impaired Loans	Impaired Loans A loan is defined to be impaired when it is probable that payment of principal and interest will not be paid in accordance with the original contractual terms of the loan agreement. Impaired loans include nonaccrual loans (including nonaccrual TDRs), performing and nonperforming TDRs and acquired loans that were not performing in accordance with original contractual terms. Impaired loans are accounted for at the lower of the present value of expected cash flows discounted at the loan's original effective interest rate or the estimated fair value of the collateral, if the loan is collateral dependent. When the present value of expected cash flows or the fair value of collateral of an impaired loan in the originated loan portfolio is less than the amount of unpaid principal outstanding on the loan, the principal balance of the loan is reduced to its carrying value through either an allocation of the allowance for loan losses or a partial charge-off of the loan balance.
Nonperforming Loans	Nonperforming Loans Nonperforming loans are comprised of loans for which the accrual of interest has been discontinued (nonaccrual loans, including nonaccrual TDRs), accruing originated loans contractually past due 90 days or more as to interest or principal payments and nonperforming TDRs. Acquired loans that were classified as nonperforming loans prior to being acquired and acquired loans that are not performing in accordance with contractual terms subsequent to acquisition are not classified as nonperforming loans subsequent to acquisition because the loans are recorded in pools at net realizable value based on the principal and interest the Corporation expects to collect on such loans.
Allowance for Loan Losses	Allowance for Loan Losses The allowance for loan losses (allowance) is presented as a reserve against loans. The allowance represents management's assessment of probable loan losses inherent in the Corporation's loan portfolio. Management's evaluation of the adequacy of the allowance is based on a continuing review of the loan portfolio, actual loan loss experience, the underlying value of the collateral, risk characteristics of the loan portfolio, the level and composition of nonperforming loans, the financial condition of the borrowers, the balance of the loan portfolio, loan growth, economic conditions, employment levels in the Corporation's local markets and special factors affecting specific business sectors. The Corporation maintains formal policies and procedures to monitor and control credit risk. Management evaluates the allowance on a quarterly basis in an effort to ensure the level is appropriate to absorb probable losses inherent in the loan portfolio. The allowance provides for probable losses that have been identified with specific customer relationships and for probable losses believed to be incurred in the remainder of the originated loan portfolio, but that have not been specifically identified. The Corporation utilizes its own loss experience to estimate inherent losses on loans. Internal risk ratings are assigned to each loan in the commercial loan portfolio (commercial, commercial real estate, real estate construction and land development loans) at the time of origination and are subject to subsequent periodic reviews by senior management. The Corporation performs a detailed credit quality review quarterly on all loans greater than $0.25 million that have deteriorated below certain levels of credit risk, and may allocate a specific portion of the allowance to such loans based upon this review. A portion of the allowance is allocated to the remaining loans by applying projected loss ratios, based on numerous factors. Projected loss ratios incorporate factors such as recent charge-off experience, trends with respect to adversely risk-rated loans in the commercial loan portfolio, trends with respect to past due and nonaccrual loans, changes in economic conditions and trends, changes in the value of underlying collateral and other credit risk factors. This evaluation involves a high degree of uncertainty. In determining the allowance and the related provision for loan losses, the Corporation considers four principal elements: (i) valuation allowances based upon probable losses identified during the review of impaired loans in the commercial loan portfolio, (ii) reserves established for adversely-rated loans in the commercial loan portfolio and nonaccrual residential mortgage, consumer installment and home equity loans based on loan loss experience of other adversely-rated loans, (iii) reserves, by loan classes, on all other loans based principally on a five -year historical loan loss experience, loan loss trends and giving consideration to estimated loss emergence periods and (iv) a reserve for qualitative factors that take into consideration risks inherent in the originated loan portfolio that differ from historical loan loss experience. The first element reflects the Corporation's estimate of probable losses based upon the systematic review of individually impaired loans in the originated commercial loan portfolio. These estimates are based upon a number of objective factors, such as payment history, financial condition of the borrower and discounted collateral exposure. The Corporation measures the investment in an impaired loan based on one of three methods: the loan's observable market price; the fair value of the collateral; or the present value of expected future cash flows discounted at the loan's effective interest rate. Loans in the commercial loan portfolio that were in nonaccrual status (including nonaccrual TDRs) were valued based on the fair value of the collateral securing the loan, while performing and nonperforming TDRs in the commercial loan portfolio were valued based on the present value of expected future cash flows discounted at the loan's effective interest rate. It is the Corporation's general policy to obtain new appraisals at least annually on nonaccrual loans in the commercial loan portfolio and at least every other year on nonperforming TDRs in the commercial loan portfolio that are primarily secured by real estate and have a loan balance of greater than $0.25 million . When the Corporation determines that the fair value of the collateral is less than the carrying value of an impaired loan on nonaccrual status and a portion is deemed not collectible, the portion of the impairment that is deemed not collectible is charged off (confirmed loss) and deducted from the allowance. The remaining carrying value of the impaired loan is classified as a nonperforming loan. When the Corporation determines that the fair value of the collateral is less than the carrying value of an impaired loan but believes it is probable it will recover this impairment, the Corporation establishes a valuation allowance for such impairment. The second element reflects the application of the Corporation's loan grade risk rating system. This risk rating system is similar to those employed by state and federal banking regulators. Loans in the commercial loan portfolio that are risk rated below a certain predetermined risk grade and nonaccrual residential mortgage, consumer installment and home equity loans are assigned a loss allocation factor that is based upon a historical analysis of actual loan losses incurred and a valuation of the type of collateral securing the loans. The third element is determined by assigning allocations based principally upon a weighted five -year average of loss experience for each class of loan with higher weighting placed on the most recent years. Average losses may be adjusted based on current loan loss experience, delinquency trends, estimated loss emergence periods and other environmental factors. This component considers the lagging impact of historical charge-off ratios in periods where future loan charge-offs are expected to increase or decrease, trends in delinquencies and nonaccrual loans, the changing portfolio mix in terms of collateral, average loan balance, loan growth and the degree of seasoning in the various loan portfolios. Loan loss analyses are performed quarterly and certain inputs and parameters are updated as necessary to reflect the current credit environment. The fourth element is based on qualitative factors that cannot be associated with a specific credit or loan class and reflects an attempt to ensure that the overall allowance appropriately reflects additional losses that are inherent in the Corporation's loan portfolio. Determination of the probable losses inherent in the portfolio, which are not necessarily captured by the allocation methodology discussed above, involves the exercise of judgment. This qualitative portion of the allowance is judgmentally determined and generally serves to compensate for the uncertainty in estimating inherent losses, particularly in times of changing economic conditions, and also considers the inherent judgment associated with risk rating commercial loans. The qualitative portion of the allowance also takes into consideration, among other things, economic conditions within the State of Michigan and nationwide, including unemployment levels, industry-wide and Corporation specific loan delinquency rates, changes in composition of and growth in the Corporation's loan portfolio, changing commercial and residential real estate values and inventory levels of residential lots, condominiums and single family houses held for sale. Although the Corporation allocates portions of the allowance to specific loans and loan types, the entire allowance attributable to originated loans is available for any loan losses that occur in the originated portfolio. Loans that are deemed not collectible are charged off and reduce the allowance. The provision for loan losses and recoveries on loans previously charged off increase the allowance. Collection efforts may continue and recoveries may occur after a loan is charged off. Acquired loans are aggregated into pools based upon common risk characteristics. An allowance may be recorded related to an acquired loan pool if it experiences a decrease in expected cash flows, as compared to those projected at the acquisition date. On a quarterly basis, the expected future cash flow of each pool is estimated based on various factors, including changes in property values of collateral dependent loans, default rates, loss severities and prepayment speeds. Decreases in estimates of expected cash flows within a pool generally result in a charge to the provision for loan losses and a corresponding increase in the allowance allocated to acquired loans for the particular pool. Increases in estimates of expected cash flows within a pool generally result in a reduction in the allowance allocated to acquired loans for the particular pool, if applicable, and then an adjustment to the accretable yield for the pool, which will increase amounts recognized in interest income in subsequent periods. Various regulatory agencies, as an integral part of their examination processes, periodically review the allowance. Such agencies may require additions to the allowance, based on their judgment, reflecting information available to them at the time of their examinations.
Mortgage Banking Operations	Mortgage Banking Operations The origination of residential mortgage loans is an integral component of the business of the Corporation. The Corporation generally sells conforming long-term fixed interest rate mortgage loans it originates in the secondary market. Gains on the sales of these loans are determined using the specific identification method. The Corporation sells residential mortgage loans in the secondary market on either a servicing retained or released basis. The Corporation elected the fair value measurement option, as prescribed by ASC Topic 820, Fair Value Measurements and Disclosures (ASC 820), for all residential mortgage loans held-for-sale originated on or after July 1, 2012. This election allows for a more effective offset of the changes in fair value of residential mortgage loans held-for-sale and the derivative instruments used to economically hedge them without having to apply complex hedge accounting provisions. Residential mortgage loans held-for-sale are carried at fair value, with changes in fair value recorded through earnings. The value of mortgage loans held-for-sale and other residential mortgage loan commitments to customers are hedged by utilizing best efforts forward commitments to sell loans to investors in the secondary market. Such forward commitments are generally entered into at the time customer applications are accepted to protect the value of the mortgage loans from increases in market interest rates during the period held and are generally settled with the investor in the secondary market within 90 days after entering into the forward commitment. Forward loan commitments are accounted for as derivatives and recorded at fair value, with changes in fair value recorded through earnings. The Corporation recognizes revenue associated with the expected future cash flows of servicing loans for loans held-for-sale at the time a forward loan commitment is made to originate a held-for-sale loan, as required under SEC Staff Accounting Bulletin No. 109, Written Loan Commitments Recorded at Fair Value Through Earnings. The Corporation accounts for mortgage servicing rights (MSRs) by separately recognizing servicing assets at the date of sale. An asset is recognized for the rights to service mortgage loans that are created by the origination of mortgage loans that are sold with the servicing retained by the Corporation. The Corporation's MSRs are included in other intangible assets in the statement of financial condition. The Corporation measures its MSRs at the lower of amortized cost or fair value and amortizes MSRs in proportion to and over the period of net servicing income. Unexpected prepayments of mortgage loans result in increased amortization of MSRs, as the remaining book value of the MSRs is expensed at the time of prepayment. The Corporation assesses MSRs for impairment on a quarterly basis based on fair value measurements. For purposes of measuring impairment, MSRs are stratified into relatively homogeneous pools based on characteristics such as period of origination, maturity date and interest rates. MSRs are also stratified between servicing assets originated by the Corporation and those acquired in acquisitions of other institutions. Any temporary impairment of MSRs is recognized as a valuation allowance, resulting in a reduction of mortgage banking revenue. The valuation allowance is recovered when impairment that is believed to be temporary no longer exists. Other-than-temporary impairments are recognized if the recoverability of the carrying value is determined to be remote. When this occurs, the unrecoverable portion of the valuation allowance is recorded as a direct write-down to the carrying value of MSRs. This direct write-down permanently reduces the carrying value of the MSRs, precluding recognition of subsequent recoveries, and results in a reduction of mortgage banking revenue. For purposes of measuring the fair value of MSRs, the Corporation utilizes a third-party modeling software program which is periodically validated by using valuations received from third-party valuation specialists. Servicing income is recognized when earned and is offset by the amortization of MSRs.
Premises and Equipment	Premises and Equipment Land is recorded at cost. Premises and equipment are stated at cost less accumulated depreciation. Premises and equipment are depreciated over the estimated useful lives of the assets. The estimated useful lives are generally 25 to 40 years for buildings and three to ten years for all other depreciable assets. Depreciation is computed on the straight-line method. Maintenance and repairs are charged to expense as incurred.
Other Real Estate	Other Real Estate Other real estate (ORE) is primarily comprised of commercial and residential real estate properties, including vacant land and development properties, obtained in partial or total satisfaction of loan obligations. ORE also includes closed branch offices that are held for sale. ORE is recorded at the lower of cost or the estimated fair value of the property, less anticipated selling costs, based upon the property's appraised value at the date of transfer to ORE and management's estimate of the fair value of the collateral, with any difference between the net realizable value of the property and the carrying value of the loan charged to the allowance for loan losses. Subsequent changes in the fair value of ORE are recognized as adjustments to the carrying amount, not to exceed the initial carrying value of the assets at the time of transfer. Changes in the fair value of ORE, subsequent to the initial transfer to ORE, and costs incurred to maintain ORE are recorded in other operating expenses on the consolidated statements of income. Gains or losses resulting from the sale of ORE are also recognized in other operating expenses on the date of sale. ORE totaling $12.7 million and $14.8 million at December 31, 2015 and 2014 , respectively, was included in the consolidated statements of financial position in interest receivable and other assets. ORE at December 31, 2015 and 2014 included $3.0 million and $0.9 million , respectively, related to closed branch offices.
Goodwill and Other Intangible Assets	Goodwill Goodwill is not amortized, but rather is subject to impairment tests annually, or more frequently if triggering events occur and indicate potential impairment. The Corporation's annual goodwill impairment assessment was performed as of October 31, 2015 . The Corporation elected to utilize the qualitative assessment of goodwill impairment allowed under ASC Topic 350-20, Goodwill (ASC 350-20) that became acceptable as a result of FASB Accounting Standards Update (ASU) 2011-08, Testing Goodwill for Impairment. In accordance with ASC 350-20, the Corporation assessed qualitative factors to determine whether it is more likely than not that the fair value of its reporting units were less than their carrying amounts. In evaluating whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, the Corporation assesses relevant events and circumstances, including macroeconomic conditions, industry and market considerations, overall financial performance, changes in the composition or carrying amount of assets and liabilities, the market price of the Corporation's common stock, and other relevant factors. Based on the qualitative assessment performed, the Corporation determined that no goodwill impairment was evident as of the October 31, 2015 assessment date. The Corporation also determined that no triggering events occurred that indicated impairment from the most recent assessment date through December 31, 2015 and that the Corporation's goodwill was not impaired at December 31, 2015 . Other Intangible Assets Intangible assets consist of core deposit intangible assets, non-compete intangible assets and MSRs. Core deposit intangible assets arose as the result of business combinations or other acquisitions and are amortized over periods ranging from 10 to 15 years , primarily on an accelerated basis, as applicable.
Share-Based Compensation	Share-based Compensation The Corporation grants stock options, stock awards, restricted stock performance units and restricted stock service-based units to certain executive and senior management employees. The Corporation accounts for share-based compensation expense using the modified-prospective transition method. Under that method, compensation expense is recognized for stock options based on the estimated grant date fair value as computed using the Black-Scholes option pricing model and the probability of issuance. The Corporation accounts for stock awards based on the closing stock price of the Corporation's common stock on the date of the award. The fair values of both stock options and stock awards are recognized as compensation expense on a straight-line basis over the requisite service period. Compensation expense is adjusted to reflect actual forfeitures at the time they occur. The Corporation accounts for restricted stock performance units based on the closing stock price of the Corporation's common stock on the date of grant, discounted by the present value of estimated future dividends to be declared over the requisite performance or service period. The fair value of restricted stock performance units is recognized as compensation expense over the expected requisite performance period, or requisite service period for awards with multiple performance and service conditions. The Corporation accounts for restricted stock service-based units based on the closing stock price of the Corporation's common stock on the date of grant, as these awards accrue dividend equivalents equal to the amount of any cash dividends that would have been payable to a shareholder owning the number of shares of the Corporation's common stock represented by the restricted stock service-based units. The fair value of the restricted stock service-based units is recognized as compensation expense over the requisite service period. Cash flows realized from the tax benefits of exercised stock option awards that result from actual tax deductions that are in excess of the recorded tax benefits related to the compensation expense recognized for those options (excess tax benefits) are classified as financing activities on the consolidated statements of cash flows.
Life Insurance, Corporate or Bank Owned	Bank-Owned Life Insurance The Corporation has life insurance policies on certain key officers of its bank subsidiaries. The majority of the bank-owned life insurance policies of the Corporation were obtained through its acquisition of Lake Michigan. Bank-owned life insurance is recorded at the cash surrender value, net of surrender charges, and is included within other assets on the consolidated statements of financial position and changes in the cash surrender values are recorded as other noninterest income on the consolidated statements of income.
Short-term Borrowings	Short-term Borrowings Short-term borrowings are comprised of securities sold under agreements to repurchase with customers, federal funds purchased and short-term FHLB advances with original scheduled maturities of one year or less. Securities sold under agreements to repurchase with customers are collateralized financing transactions and the obligations to repurchase securities sold are reflected as a liability in the accompanying consolidated statements of financial position. The dollar amount of the securities underlying the agreements remain in the Corporation's investment securities portfolio. The Corporation's securities sold under agreements to repurchase with customers are considered a stable source of liquidity, much like its core deposit base, and are generally only provided to customers that have an established banking relationship with Chemical Bank.
Other Borrowings	Other Borrowings Other borrowings are comprised of securities sold under agreements with an unaffiliated third-party financial institution, a secured non-revolving line-of-credit with an unaffiliated third-party financial institution, subordinated debentures and long-term FHLB advances. Securities sold under agreements to repurchase are collateralized financing transactions and the obligations to repurchase securities sold are reflected as a liability in the accompanying consolidated statements of financial position. The dollar amount of the securities underlying the agreements remain in the Corporation's investment securities portfolio. FHLB advances, both short-term and long-term, are borrowings from the FHLB to fund short-term liquidity needs as well as a portion of the loan and investment securities portfolios. These advances are secured, under a blanket security agreement, by first lien residential mortgage loans with an aggregate book value equal to at least 140% of the FHLB advances and the FHLB stock owned by the Corporation. FHLB advances with an original maturity of one year or less are classified as short-term and FHLB advances with an original maturity of more than one year are classified as long-term.
Fair Value Measurements	Fair Value Measurements Fair value for assets and liabilities measured at fair value on a recurring or nonrecurring basis refers to the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants in the market in which the reporting entity transacts such sales or transfers based on the assumptions market participants would use when pricing an asset or liability. Assumptions are developed based on prioritizing information within a fair value hierarchy that gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data, such as the reporting entity's own data. The Corporation may choose to measure eligible items at fair value at specified election dates. Unrealized gains and losses on items for which the fair value measurement option has been elected are reported in earnings at each subsequent reporting date. The fair value option (i) may be applied instrument by instrument, with certain exceptions, allowing the Corporation to record identical financial assets and liabilities at fair value or by another measurement basis permitted under GAAP, (ii) is irrevocable (unless a new election date occurs) and (iii) is applied only to entire instruments and not to portions of instruments. At December 31, 2015 and 2014 , the Corporation had elected the fair value option on all of its residential mortgage loans held-for-sale. The Corporation has not elected the fair value option for any other financial assets or liabilities.
Pension and Postretirement Benefit Plan Actuarial Assumptions	Pension and Postretirement Benefit Plan Actuarial Assumptions The Corporation's defined benefit pension, supplemental pension and postretirement benefit obligations and related costs are calculated using actuarial concepts and measurements. Two critical assumptions, the discount rate and the expected long-term rate of return on plan assets, are important elements of expense and/or benefit obligation measurements. Other assumptions involve employee demographic factors such as retirement patterns, mortality, turnover and the rate of future compensation increases, as well as future health care costs. The Corporation evaluates all assumptions annually. Mortality assumptions at December 31, 2015 were based on the RP-2014 mortality tables, as prescribed by the Pension Protection Act of 2006, using the MP-2015 mortality improvement scale. Mortality assumptions at December 31, 2014 were based on the RP-2014 mortality tables using the MP-2014 mortality improvement scale. The discount rate enables the Corporation to state expected future benefit payments as a present value on the measurement date. The Corporation determined the discount rate at December 31, 2015 and 2014 by utilizing the results from a discount rate model that involves selecting a portfolio of bonds to settle the projected benefit payments of each plan. The selected bond portfolios are derived from a universe of corporate bonds rated at Aa quality. After a bond portfolio is selected, a single rate is determined that equates the market value of the bonds purchased to the discounted value of the plan's benefit payments which represents the discount rate. A lower discount rate increases the present value of benefit obligations and increases pension, supplemental pension and postretirement benefit expenses. To determine the expected long-term rate of return on defined benefit pension plan assets, the Corporation considers the current asset allocation of the defined benefit pension plan, as well as historical and expected returns on each asset class. A lower expected rate of return on defined benefit pension plan assets will increase pension expense. The Corporation recognizes the over- or under-funded status of a plan as an other asset or other liability in the consolidated statements of financial position as measured by the difference between the fair value of the plan assets and the projected benefit obligation. Unrecognized prior service costs and actuarial gains and losses are recognized as a component of accumulated other comprehensive income (loss). The Corporation measures defined benefit plan assets and obligations as of December 31.
Advertising Costs	Advertising Costs Advertising costs are expensed as incurred.
Income and Other Taxes	Income and Other Taxes The Corporation is subject to the income and other tax laws of the United States, the State of Michigan and other states where nexus has been created. These laws are complex and are subject to different interpretations by the taxpayer and the various taxing authorities. In determining the provision for income and other taxes, management must make judgments and estimates about the application of these inherently complex laws, related regulations and case law. In the process of preparing the Corporation's tax returns, management attempts to make reasonable interpretations of enacted tax laws. These interpretations are subject to challenge by the tax authorities upon audit or to reinterpretation based on management's ongoing assessment of facts and evolving case law. The Corporation and its subsidiaries file a consolidated federal income tax return. The provision for federal income taxes is based on income and expenses, as reported in the consolidated financial statements, rather than amounts reported on the Corporation's federal income tax return. The difference between the federal statutory income tax rate and the Corporation's effective federal income tax rate is primarily a function of the proportion of the Corporation's interest income exempt from federal taxation, nondeductible interest expense and other nondeductible expenses relative to pretax income and tax credits. When income and expenses are recognized in different periods for tax purposes than for book purposes, deferred tax assets and liabilities are recognized for the future tax consequences attributable to the temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Differences in the tax and book carrying amounts of assets and liabilities can also be generated when the Corporation acquires other banks or bank branches. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as income or expense in the period that includes the enactment date of the change. On a quarterly basis, management assesses the reasonableness of its effective federal tax rate based upon its estimate of taxable income and the applicable taxes expected for the full year. Deferred tax assets and liabilities are reassessed on a quarterly basis, including the need for a valuation allowance for deferred tax assets. Uncertain income tax positions are evaluated to determine whether it is more-likely-than-not that a tax position will be sustained upon examination based on the technical merits of the tax position. If a tax position is more-likely-than-not to be sustained, a tax benefit is recognized for the amount that is greater than 50% likely to be realized. Reserves for contingent income tax liabilities attributable to unrecognized tax benefits associated with uncertain tax positions are reviewed quarterly for adequacy based upon developments in tax law and the status of audits or examinations. The Corporation had no contingent income tax liabilities recorded at December 31, 2015 and 2014 .
Investments in Tax Credit Projects	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 are reflected in 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 allocated. The Corporation recognized additional income tax expense attributable to the amortization of investments in qualified affordable housing projects of $1.3 million and $0.4 million during 2015 and 2014 , respectively. The Corporation's remaining investment in qualified affordable housing projects accounted for under the proportional amortization method totaled $21.7 million at December 31, 2015 and $4.9 million at December 31, 2014 . The increase in qualified affordable housing project investments at December 31, 2015 , compared to December 31, 2014, was attributable to investments acquired as part of the Lake Michigan transaction. Under the equity method, the Corporation's share of the earnings or losses are included in other operating expenses on the consolidated statements of income. The Corporation's investment in new market projects accounted for under the equity method totaled $1.7 million at December 31, 2015 . There were no investments in such projects accounted for under the equity method as of December 31, 2014. 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 other liabilities on the consolidated statements of financial position. The Corporation's remaining unfunded equity contributions totaled $8.0 million at December 31, 2015 . 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. There were no impairment losses recognized as of December 31, 2015 or 2014 . 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 interests 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 affordable 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.
Comprehensive Income	Comprehensive Income Comprehensive income of the Corporation includes net income and adjustments to shareholders' equity for changes in unrealized gains and losses on investment securities available-for-sale and changes in the net actuarial gain/loss for the Corporation's defined benefit pension and postretirement plans, net of income taxes. The Corporation presents comprehensive income as a component in the consolidated statements of changes in shareholders' equity and the components of other comprehensive income separately in the consolidated statements of comprehensive income.
Reclassifications	Reclassifications Certain amounts appearing in the consolidated financial statements and notes thereto for prior periods have been reclassified to conform with the current presentation. The reclassification had no effect on net income or shareholders’ equity as previously reported.
Adopted and Pending Accounting Pronouncements	Adopted Accounting Pronouncements Business Combinations In September 2015, the FASB issued ASU 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (ASU 2015-16). ASU 2015-16 amends current guidance by requiring companies that make an acquisition to recognize adjustments to provisional amounts identified during the measurement period by calculating the adjustments as if they were known at the acquisition date, but recognizing the adjustments in the reporting period in which they occur, rather than retroactively accounting for provisional adjustments by revising prior-period information as GAAP currently requires. ASU 2015-16 also requires a company to report, either on its income statement or in a footnote disclosure, the portion of the amount that is recorded in its earnings for the current period, by line item, that would have been recorded in previous reporting periods had the adjustment to the provisional amounts been recognized as of the acquisition date. ASU 2015-16 is effective for public companies for interim and annual periods beginning after December 15, 2015, with early adoption permitted. The Corporation elected to adopt the provisions of ASU 2015-16 as of and for its quarter ended September 30, 2015. The Corporation's adoption of ASU 2015-16 in the third quarter of 2015 did not have a material impact on the Corporation's consolidated financial condition or results of operations. During the third quarter of 2015, the Corporation made adjustments to provisional amounts previously recorded related to the acquisitions of Lake Michigan, Monarch and Northwestern. Additional information regarding these adjustments is included in Note 2, Mergers and Acquisitions, to these consolidated financial statements. In-Substance Foreclosures In January 2014, the FASB issued ASU 2014-04, Receivables — Troubled Debt Restructurings by Creditors (Subtopic 310-40): Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure, a consensus of the FASB Emerging Issues Task Force (ASU 2014-04). ASU 2014-04 clarifies that an in-substance foreclosure occurs, and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan, upon either (i) the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or (ii) the borrower conveying all interest in the residential real estate property to the creditor to satisfy the loan through completion of a deed in lieu of foreclosure or similar legal agreement. ASU 2014-04 also requires disclosure of both the amount of foreclosed residential real estate property held by the creditor and the recorded investment in loans collateralized by residential real estate property that are in the process of foreclosure. ASU 2014-04 is effective for public companies for interim and annual periods beginning after December 15, 2014, with early adoption permitted. Once adopted, an entity can elect either (i) a modified retrospective transition method or (ii) a prospective transition method. The modified retrospective transition method is applied by means of a cumulative-effect adjustment to residential mortgage loans and foreclosed residential real estate properties existing as of the beginning of the period for which the amendments of ASU 2014-04 are effective, with real estate reclassified to loans measured at the carrying value of the real estate at the date of adoption and loans reclassified to real estate measured at the lower of net carrying value of the loan or the fair value of the real estate less costs to sell at the date of adoption. The prospective transition method is applied by means of applying the amendments of ASU 2014-04 to all instances of receiving physical possession of residential real estate properties that occur after the date of adoption. The Corporation's adoption of ASU 2014-04 on January 1, 2015 did not have a material impact on the Corporation's consolidated financial condition or results of operations. Share-Based Compensation In June 2014, the FASB issued ASU 2014-12, Compensation — Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period, a consensus of the FASB Emerging Issues Task Force (ASU 2014-12). ASU 2014-12 requires that a performance target that affects vesting of share-based payment awards and that could be achieved after the requisite service period be treated as a performance condition. Compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the periods for which the requisite service has already been rendered. If the performance target becomes probable of being achieved before the end of the requisite service period, the remaining unrecognized compensation cost should be recognized prospectively over the remaining requisite service period. The total amount of compensation cost recognized during and after the requisite service period should reflect the number of awards that are expected to vest and should be adjusted to reflect those awards that ultimately vest. The requisite service period ends when the employee can cease rendering service and still be eligible to vest in the award if the performance target is achieved. ASU 2014-12 is effective for all entities for interim and annual periods beginning after December 15, 2015, with early adoption permitted. An entity may apply the amendments in ASU 2014-12 either (i) prospectively to all awards granted or modified after the effective date or (ii) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. The Corporation's early adoption of ASU 2014-12 on January 1, 2015 did not have a material impact on the Corporation's consolidated financial condition or results of operations. Government-Guaranteed Mortgage Loans In August 2014, the FASB issued ASU 2014-14, Receivables—Troubled Debt Restructurings by Creditors (Subtopic 310-40): Classification of Certain Government Guaranteed Mortgage Loans upon Foreclosure, a consensus of the FASB Emerging Issues Task Force (ASU 2014-14). ASU 2014-14 provides clarifying guidance related to how creditors classify government-guaranteed loans upon foreclosure. Upon foreclosure of a government-guaranteed mortgage loan, the loan should be derecognized and a separate other receivable should be recognized if the following conditions are met: (i) the loan has a government guarantee that is not separable from the loan before foreclosure; (ii) at the time of foreclosure, the creditor has the intent to convey the real estate property to the guarantor and make a claim on the guarantee, and the creditor has the ability to recover under that claim; and (iii) at the time of foreclosure, any amount of the claim that is determined on the basis of the fair value of the real estate is fixed. The separate other receivable should be measured based on the amount of the loan balance (principal and interest) expected to be recovered from the guarantor at the time of foreclosure. ASU 2014-14 is effective for public companies for interim and annual periods beginning after December 15, 2014. An entity should adopt ASU 2014-14 using either the modified retrospective method or the prospective transition method. An entity must apply the same method elected under ASU 2014-04. Early adoption is permitted if the entity has already adopted ASU 2014-04. The Corporation's adoption of ASU 2014-14 on January 1, 2015 did not have a material impact on the Corporation's consolidated financial condition or results of operations. Pending Accounting Pronouncements Recognition and Measurement In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01). ASU 2016-01 amends current guidance by requiring companies to recognize changes in fair value for equity investments that have a readily determinable fair value through net income rather than through other comprehensive income. Under ASU 2016-01, equity investments that do not have a readily determinable fair value will either be accounted for the same as equity investments that have a readily determinable fair value, with changes in fair value recognized through net income, or carried at cost, adjusted for changes in observable prices based on orderly transactions for identical or similar investments issued by the same issuer and further adjusted for impairment, if applicable. ASU 2016-01 also requires a qualitative assessment of impairment indicators each reporting period. If this assessment indicates that impairment exists, companies must adjust the investment to fair value and recognize an impairment loss in net income, even if the impairment is determined to be temporary. ASU 2016-01 is effective for public companies for interim and annual periods beginning after December 15, 2017. The Corporation's adoption of ASU 2016-01 is not expected to have a material impact on the Corporation's consolidated financial condition or results of operations.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information [Table Text Block]	Unaudited Pro Forma Combined Results of Operations The following unaudited pro forma combined results of operations of Chemical, Lake Michigan, Monarch and Northwestern presents results as if the acquisitions had been completed as of the beginning of each period indicated. The unaudited pro forma combined results of operations are presented solely for information purposes and are not intended to represent or be indicative of the consolidated results of operations that Chemical would have reported had these transactions been completed as of the dates and for the periods presented, nor are they necessarily indicative of future results. In particular, no adjustments have been made to eliminate the amount of Lake Michigan's, Monarch's, or Northwestern's provision for loan losses incurred prior to the acquisition date that would not have been necessary had the acquired loans been recorded at fair value as of the beginning of each period indicated. In accordance with Article 11 of SEC Regulation S-X, transaction costs directly attributable to the acquisitions have been excluded. Year ended December 31, 2015 2014 (In thousands, except per share data) Interest income $ 313,851 $ 301,838 Interest expense 21,750 26,386 Net interest income 292,101 275,452 Provision for loan losses 6,500 7,484 Net interest income after provision for loan losses 285,601 267,968 Noninterest income 83,447 86,243 Operating expenses 237,146 243,618 Income before income taxes 131,902 110,593 Federal income tax expense 30,680 31,138 Net income $ 101,222 $ 79,455 Net income per common share: Basic $ 2.66 $ 2.17 Diluted 2.64 2.16 Weighted average shares outstanding: Basic 38,097 36,550 Diluted 38,369 36,770
Activity for accretable yield includes contractually due interest of acquired loans	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: Lake Michigan Monarch North-western OAK Total Year Ended December 31, 2015 Balance at beginning of period $ — $ — $ 104,675 $ 33,286 $ 137,961 Addition attributable to acquisitions 190,246 37,914 — — 228,160 Additions, net of reductions* (12,991 ) 1,336 (3,396 ) 6,601 (8,450 ) Accretion recognized in interest income (24,256 ) (4,692 ) (18,656 ) (11,810 ) (59,414 ) Reclassification from nonaccretable difference — — — — — Balance at end of period $ 152,999 $ 34,558 $ 82,623 $ 28,077 $ 298,257 Year Ended December 31, 2014 Balance at beginning of period $ — $ 32,610 $ 32,610 Addition attributable to acquisitions 110,003 — 110,003 Additions, net of reductions* (1,605 ) 5,411 3,806 Accretion recognized in interest income (3,723 ) (14,735 ) (18,458 ) Reclassification from nonaccretable difference — 10,000 10,000 Balance at end of period $ 104,675 $ 33,286 $ 137,961 * Represents additions in estimated contractual interest expected to be collected from acquired loans being renewed or extended, less reductions in contractual interest resulting from the early payoff of acquired loans.
Lake Michigan Financial Corp [Member]
Business Acquisition [Line Items]
Purchase Accounting Fair Value Adjustments [Table Text Block]	A summary of the purchase price and the excess of the purchase price over the fair value of adjusted net assets acquired (goodwill) follows (in thousands): Fair value of the Corporation's common shares issued on May 31, 2015 (4,322,101 shares at a market price of $30.29 per share) $ 130,916 Fair value of Lake Michigan options converted to the Corporation's options 2,000 Cash paid to acquire outstanding stock 54,478 Total purchase price 187,394 Net assets acquired (1) : Lake Michigan shareholders' equity $ 89,280 Adjustments to reflect fair value of net assets acquired: Loans (22,600 ) Allowance for loan losses 15,888 Premises and equipment (5,031 ) (2) Core deposit intangibles 8,003 Deferred tax assets, net 3,572 (2) Deposits and borrowings, net (3,182 ) (2) Other assets and other liabilities (157 ) Fair value of adjusted net assets acquired 85,773 Goodwill recognized as a result of the Lake Michigan transaction $ 101,621
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following schedule summarizes the revised acquisition date estimated fair values, including the adjustments to the fair values identified and recorded from the acquisition date through December 31, 2015, of assets acquired and liabilities assumed from Lake Michigan (in thousands): Assets Cash and cash equivalents $ 39,301 Investment securities 66,699 Loans 985,542 Premises and equipment 10,975 Deferred tax asset, net 16,191 Goodwill 101,621 Core deposit intangible asset 8,003 Bank-owned life insurance 23,844 Other assets 37,659 Assets acquired, at fair value 1,289,835 Liabilities Deposits 924,697 Short-term borrowings 30,000 Other borrowings 124,857 Other liabilities 22,887 Total liabilities acquired, at fair value 1,102,441 Total purchase price $ 187,394
Monarch Community Bancorp [Member]
Business Acquisition [Line Items]
Purchase Accounting Fair Value Adjustments [Table Text Block]	A summary of the purchase price and the excess of the purchase price over the fair value of adjusted net assets acquired (goodwill) follows (in thousands): Fair value of the Corporation's common shares issued on April 1, 2015 (860,575 shares at a market price of $31.36 per share) $ 26,988 Cash paid 203 Total purchase price $ 27,191 Net assets acquired (1) : Monarch shareholders' equity $ 15,270 Adjustments to reflect fair value of net assets acquired: Loans (7,150 ) Allowance for loan losses 2,128 Deferred tax assets, net: Net operating loss carryforward 7,900 Other 1,826 (2) Premises and equipment (395 ) (2) Core deposit intangibles 1,930 Mortgage servicing rights 315 Other assets and other liabilities 37 Fair value of adjusted net assets acquired 21,861 Goodwill recognized as a result of the Monarch transaction $ 5,330
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following schedule summarizes the the revised acquisition date estimated fair values, including the adjustments to the fair values identified and recorded from the acquisition date through December 31, 2015, of assets acquired and liabilities assumed from Monarch. Assets Cash and cash equivalents $ 32,171 Loans 121,783 Premises and equipment 3,039 Deferred tax assets, net Net operating loss carryforward 7,900 Other 2,392 Interest receivable and other assets 6,972 Goodwill 5,330 Core deposit intangibles 1,930 Mortgage servicing rights 1,284 Assets acquired, at fair value 182,801 Liabilities Deposits 144,311 FHLB advances 8,000 Interest payable and other liabilities 3,299 Total liabilities acquired, at fair value 155,610 Total purchase price $ 27,191
Northwestern Bancorp [Member]
Business Acquisition [Line Items]
Purchase Accounting Fair Value Adjustments [Table Text Block]

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2015
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 available-for-sale and investment securities held-to-maturity at December 31, 2015 and 2014 : Investment Securities Available-for-Sale Amortized Cost Unrealized Gains Unrealized Losses Fair Value (In thousands) December 31, 2015 U.S. Treasury securities $ 5,773 $ — $ 8 $ 5,765 Government sponsored agencies 195,711 78 800 194,989 State and political subdivisions 14,731 395 6 15,120 Residential mortgage-backed securities 189,452 538 2,222 187,768 Collateralized mortgage obligations 133,256 111 1,137 132,230 Corporate bonds 14,825 2 200 14,627 Preferred stock and trust preferred securities 2,888 344 — 3,232 Total $ 556,636 $ 1,468 $ 4,373 $ 553,731 December 31, 2014 U.S. Treasury securities $ 8,272 $ — $ 13 $ 8,259 Government sponsored agencies 263,658 356 511 263,503 State and political subdivisions 45,157 1,087 17 46,227 Residential mortgage-backed securities 240,465 885 1,543 239,807 Collateralized mortgage obligations 145,316 261 1,194 144,383 Corporate bonds 44,930 213 48 45,095 Preferred stock 1,389 201 — 1,590 Total $ 749,187 $ 3,003 $ 3,326 $ 748,864
Held-to-maturity Securities	Investment Securities Held-to-Maturity Amortized Cost Unrealized Gains Unrealized Losses Fair Value (In thousands) December 31, 2015 State and political subdivisions $ 509,471 $ 7,446 $ 4,512 $ 512,405 Trust preferred securities 500 — 200 300 Total $ 509,971 $ 7,446 $ 4,712 $ 512,705 December 31, 2014 State and political subdivisions $ 305,913 $ 7,294 $ 4,557 $ 308,650 Trust preferred securities 10,500 — 3,410 7,090 Total $ 316,413 $ 7,294 $ 7,967 $ 315,740
Amortized cost and fair value of debt securities by contractual maturity	December 31, 2015 Amortized Cost Fair Value (In thousands) Investment Securities Available-for-Sale: Due in one year or less $ 170,838 $ 170,098 Due after one year through five years 326,018 324,187 Due after five years through ten years 53,317 52,649 Due after ten years 5,074 5,064 Preferred stock 1,389 1,733 Total $ 556,636 $ 553,731 Investment Securities Held-to-Maturity: Due in one year or less $ 59,834 $ 59,938 Due after one year through five years 236,141 236,491 Due after five years through ten years 136,383 137,188 Due after ten years 77,613 79,088 Total $ 509,971 $ 512,705
Summary of continuous unrealized loss position of securities	Less Than 12 Months 12 Months or More Total Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses December 31, 2015 U.S. Treasury securities $ 5,765 $ 8 $ — $ — $ 5,765 $ 8 Government sponsored agencies 114,640 292 21,681 508 136,321 800 State and political subdivisions 195,285 2,891 68,361 1,627 263,646 4,518 Residential mortgage-backed securities 169,226 2,146 3,435 76 172,661 2,222 Collateralized mortgage obligations 60,459 408 39,382 729 99,841 1,137 Corporate bonds 9,532 200 — — 9,532 200 Trust preferred securities — — 300 200 300 200 Total $ 554,907 $ 5,945 $ 133,159 $ 3,140 $ 688,066 $ 9,085 December 31, 2014 U.S. Treasury securities $ 8,259 $ 13 $ — $ — $ 8,259 $ 13 Government sponsored agencies 166,963 406 31,927 105 198,890 511 State and political subdivisions 62,310 3,348 36,847 1,226 99,157 4,574 Residential mortgage-backed securities 17,276 52 180,194 1,491 197,470 1,543 Collateralized mortgage obligations 63,077 179 31,620 1,015 94,697 1,194 Corporate bonds — — 14,952 48 14,952 48 Trust preferred securities — — 7,090 3,410 7,090 3,410 Total $ 317,885 $ 3,998 $ 302,630 $ 7,295 $ 620,515 $ 11,293

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Summary of loans under portfolio	A summary of the Corporation's loans follows: December 31, 2015 2014 (In thousands) Commercial loan portfolio: Commercial $ 1,905,879 $ 1,354,881 Commercial real estate 2,112,162 1,557,648 Real estate construction 210,231 152,745 Land development 21,845 18,750 Subtotal 4,250,117 3,084,024 Consumer loan portfolio: Residential mortgage 1,429,636 1,110,390 Consumer installment 877,457 829,570 Home equity 713,937 664,246 Subtotal 3,021,030 2,604,206 Total loans $ 7,271,147 $ 5,688,230
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 risk rating categories at December 31, 2015 and 2014 : Commercial Commercial Real Estate Real Estate Construction Land Development Total (In thousands) December 31, 2015 Originated Portfolio: Risk Grades 1-5 $ 1,418,301 $ 1,341,202 $ 173,828 $ 9,495 $ 2,942,826 Risk Grade 6 34,727 31,036 180 — 65,943 Risk Grade 7 39,933 26,658 291 832 67,714 Risk Grade 8 26,459 25,163 247 274 52,143 Risk Grade 9 2,095 — — — 2,095 Subtotal 1,521,515 1,424,059 174,546 10,601 3,130,721 Acquired Portfolio: Risk Grades 1-5 340,782 629,430 35,685 5,998 1,011,895 Risk Grade 6 28,321 23,926 — 2,556 54,803 Risk Grade 7 11,607 29,975 — 1,537 43,119 Risk Grade 8 3,654 4,772 — 1,153 9,579 Risk Grade 9 — — — — — Subtotal 384,364 688,103 35,685 11,244 1,119,396 Total $ 1,905,879 $ 2,112,162 $ 210,231 $ 21,845 $ 4,250,117 December 31, 2014 Originated Portfolio: Risk Grades 1-5 $ 1,171,817 $ 1,114,529 $ 134,668 $ 2,952 $ 2,423,966 Risk Grade 6 37,800 34,996 1,408 738 74,942 Risk Grade 7 29,863 29,935 2,502 613 62,913 Risk Grade 8 16,417 24,958 162 225 41,762 Risk Grade 9 1 8 — — 9 Subtotal 1,255,898 1,204,426 138,740 4,528 2,603,592 Acquired Portfolio: Risk Grades 1-5 76,780 321,018 14,005 11,789 423,592 Risk Grade 6 12,687 8,698 — 583 21,968 Risk Grade 7 4,089 12,478 — 197 16,764 Risk Grade 8 5,427 11,028 — 1,653 18,108 Risk Grade 9 — — — — — Subtotal 98,983 353,222 14,005 14,222 480,432 Total $ 1,354,881 $ 1,557,648 $ 152,745 $ 18,750 $ 3,084,024
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 December 31, 2015 and 2014 : Residential Mortgage Consumer Installment Home Equity Total (In thousands) December 31, 2015 Originated Portfolio: Performing $ 1,207,945 $ 868,975 $ 587,566 $ 2,664,486 Nonperforming 9,030 451 3,246 12,727 Subtotal 1,216,975 869,426 590,812 2,677,213 Acquired Portfolio: Performing 210,580 7,984 122,118 340,682 Nonperforming 2,081 47 1,007 3,135 Subtotal 212,661 8,031 123,125 343,817 Total $ 1,429,636 $ 877,457 $ 713,937 $ 3,021,030 December 31, 2014 Originated Portfolio: Performing $ 987,542 $ 818,878 $ 566,083 $ 2,372,503 Nonperforming 10,459 500 3,013 13,972 Subtotal 998,001 819,378 569,096 2,386,475 Acquired Portfolio: Performing 111,101 10,174 94,696 215,971 Nonperforming 1,288 18 454 1,760 Subtotal 112,389 10,192 95,150 217,731 Total $ 1,110,390 $ 829,570 $ 664,246 $ 2,604,206
Summary of nonperforming loans	A summary of nonperforming loans follows: December 31, 2015 2014 (In thousands) Nonaccrual loans: Commercial $ 28,554 $ 16,418 Commercial real estate 25,163 24,966 Real estate construction 247 162 Land development 274 225 Residential mortgage 5,557 6,706 Consumer installment 451 500 Home equity 1,979 1,667 Total nonaccrual loans 62,225 50,644 Accruing loans contractually past due 90 days or more as to interest or principal payments: Commercial 364 170 Commercial real estate 254 — Residential mortgage 402 557 Home equity 1,267 1,346 Total accruing loans contractually past due 90 days or more as to interest or principal payments 2,287 2,073 Nonperforming TDRs: Commercial loan portfolio 16,297 15,271 Consumer loan portfolio 3,071 3,196 Total nonperforming TDRs 19,368 18,467 Total nonperforming loans $ 83,880 $ 71,184
Schedule of Impaired loans by classes	The following schedule presents impaired loans by classes of loans at December 31, 2015 : Recorded Investment Unpaid Principal Balance Related Valuation Allowance Average Annual Recorded Investment Interest Income Recognized While on Impaired Status (In thousands) Impaired loans with a valuation allowance: Commercial $ 18,898 $ 19,426 $ 5,700 $ 9,511 $ — Commercial real estate 4,448 4,688 497 2,918 — Residential mortgage 21,037 21,037 192 20,661 1,312 Subtotal 44,383 45,151 6,389 33,090 1,312 Impaired loans with no related valuation allowance: Commercial 31,039 37,703 — 32,172 1,303 Commercial real estate 53,518 69,130 — 56,562 1,985 Real estate construction 400 480 — 457 11 Land development 1,736 2,628 — 1,768 104 Residential mortgage 7,638 8,644 — 8,465 165 Consumer installment 498 512 — 480 2 Home equity 2,986 3,270 — 2,736 58 Subtotal 97,815 122,367 — 102,640 3,628 Total impaired loans: Commercial 49,937 57,129 5,700 41,683 1,303 Commercial real estate 57,966 73,818 497 59,480 1,985 Real estate construction 400 480 — 457 11 Land development 1,736 2,628 — 1,768 104 Residential mortgage 28,675 29,681 192 29,126 1,477 Consumer installment 498 512 — 480 2 Home equity 2,986 3,270 — 2,736 58 Total $ 142,198 $ 167,518 $ 6,389 $ 135,730 $ 4,940 The following schedule presents impaired loans by classes of loans at December 31, 2014 : Recorded Investment Unpaid Principal Balance Related Valuation Allowance Average Annual Recorded Investment Interest Income Recognized While on Impaired Status (In thousands) Impaired loans with a valuation allowance: Commercial $ 966 $ 1,040 $ 293 $ 2,117 $ — Commercial real estate 2,587 2,927 710 3,699 — Residential mortgage 19,681 19,681 335 19,740 1,252 Subtotal 23,234 23,648 1,338 25,556 1,252 Impaired loans with no related valuation allowance: Commercial 38,094 44,557 — 39,020 1,375 Commercial real estate 60,616 82,693 — 49,676 1,567 Real estate construction 162 255 — 164 — Land development 1,928 3,484 — 3,551 131 Residential mortgage 7,994 7,994 — 7,005 15 Consumer installment 518 518 — 602 1 Home equity 2,121 2,121 — 2,302 12 Subtotal 111,433 141,622 — 102,320 3,101 Total impaired loans: Commercial 39,060 45,597 293 41,137 1,375 Commercial real estate 63,203 85,620 710 53,375 1,567 Real estate construction 162 255 — 164 — Land development 1,928 3,484 — 3,551 131 Residential mortgage 27,675 27,675 335 26,745 1,267 Consumer installment 518 518 — 602 1 Home equity 2,121 2,121 — 2,302 12 Total $ 134,667 $ 165,270 $ 1,338 $ 127,876 $ 4,353 The average annual recorded investment of impaired loans during 2013 was $121.0 million and was comprised of the following classes of loans: commercial - $29.6 million ; commercial real estate - $50.8 million ; real estate construction - $0.4 million ; land development - $9.8 million ; residential mortgage - $26.8 million ; consumer installment - $0.7 million ; and home equity - $2.9 million . Interest income recognized during 2013 while these loans were in impaired status was $3.8 million , including $1.0 million on commercial loans, $1.3 million on commercial real estate loans, $0.3 million on land development loans and $1.1 million on residential mortgage loans.
Schedule representing the aging status of the recorded investment in loans by classes	The following schedule presents the aging status of the recorded investment in loans by classes of loans at December 31, 2015 and 2014 : 31-60 Days Past Due 61-89 Days Past Due Accruing Loans Past Due 90 Days or More Non-accrual Loans Total Past Due Current Total Loans (In thousands) December 31, 2015 Originated Portfolio: Commercial $ 3,685 $ 1,230 $ 364 $ 28,554 $ 33,833 $ 1,487,682 $ 1,521,515 Commercial real estate 4,168 1,603 254 25,163 31,188 1,392,871 1,424,059 Real estate construction — — — 247 247 174,299 174,546 Land development — — — 274 274 10,327 10,601 Residential mortgage 1,737 — 402 5,557 7,696 1,209,279 1,216,975 Consumer installment 3,145 644 — 451 4,240 865,186 869,426 Home equity 1,767 788 1,267 1,979 5,801 585,011 590,812 Total $ 14,502 $ 4,265 $ 2,287 $ 62,225 $ 83,279 $ 5,724,655 $ 5,807,934 Acquired Portfolio: Commercial $ 490 $ 532 $ 3,735 $ — $ 4,757 $ 379,607 $ 384,364 Commercial real estate 3,557 691 4,771 — 9,019 679,084 688,103 Real estate construction — — — — — 35,685 35,685 Land development — — 1,154 — 1,154 10,090 11,244 Residential mortgage 1,370 — 2,081 — 3,451 209,210 212,661 Consumer installment 55 — 47 — 102 7,929 8,031 Home equity 847 78 1,007 — 1,932 121,193 123,125 Total $ 6,319 $ 1,301 $ 12,795 $ — $ 20,415 $ 1,442,798 $ 1,463,213 December 31, 2014 Originated Portfolio: Commercial $ 4,033 $ 743 $ 170 $ 16,418 $ 21,364 $ 1,234,534 $ 1,255,898 Commercial real estate 7,515 1,383 — 24,966 33,864 1,170,562 1,204,426 Real estate construction 262 — — 162 424 138,316 138,740 Land development — — — 225 225 4,303 4,528 Residential mortgage 2,126 54 557 6,706 9,443 988,558 998,001 Consumer installment 3,620 512 — 500 4,632 814,746 819,378 Home equity 3,039 660 1,346 1,667 6,712 562,384 569,096 Total $ 20,595 $ 3,352 $ 2,073 $ 50,644 $ 76,664 $ 4,913,403 $ 4,990,067 Acquired Portfolio: Commercial $ 133 $ — $ 5,427 $ — $ 5,560 $ 93,423 $ 98,983 Commercial real estate 2,014 352 11,052 — 13,418 339,804 353,222 Real estate construction — — — — — 14,005 14,005 Land development — — 1,653 — 1,653 12,569 14,222 Residential mortgage 156 — 18 — 174 112,215 112,389 Consumer installment 55 3 454 — 512 9,680 10,192 Home equity 636 106 1,288 — 2,030 93,120 95,150 Total $ 2,994 $ 461 $ 19,892 $ — $ 23,347 $ 674,816 $ 698,163 Loan
Schedule of Corporation's TDRs	The following schedule presents the Corporation's TDRs at December 31, 2015 and 2014 : Performing TDRs Non-Performing TDRs Nonaccrual TDRs Total (In thousands) December 31, 2015 Commercial loan portfolio $ 29,844 $ 16,297 $ 32,682 $ 78,823 Consumer loan portfolio 17,966 3,071 3,251 24,288 Total $ 47,810 $ 19,368 $ 35,933 $ 103,111 December 31, 2014 Commercial loan portfolio $ 29,179 $ 15,271 $ 32,597 $ 77,047 Consumer loan portfolio 16,485 3,196 4,594 24,275 Total $ 45,664 $ 18,467 $ 37,191 $ 101,322
Schedule providing information on performing and nonperforming TDRs	The following schedule provides information on the Corporation's TDRs that were modified during the years ended December 31, 2015 , 2014 and 2013 : Number of Loans Pre- Modification Recorded Investment Post- Modification Recorded Investment (Dollars in thousands) Year ended December 31, 2015 Commercial loan portfolio: Commercial 53 $ 11,446 $ 11,446 Commercial real estate 21 7,196 7,196 Real estate construction 2 400 400 Land development 1 305 305 Subtotal — commercial loan portfolio 77 19,347 19,347 Consumer loan portfolio (residential mortgage) 65 3,249 3,247 Total 142 $ 22,596 $ 22,594 Year ended December 31, 2014 Commercial loan portfolio: Commercial 53 $ 13,781 $ 13,781 Commercial real estate 46 12,075 12,075 Real estate construction — — — Land development 1 72 72 Subtotal — commercial loan portfolio 100 25,928 25,928 Consumer loan portfolio (residential mortgage) 119 4,184 4,158 Total 219 $ 30,112 $ 30,086 Year ended December 31, 2013 Commercial loan portfolio: Commercial 57 $ 12,123 $ 12,123 Commercial real estate 49 16,222 16,222 Real estate construction 4 575 575 Land development 4 1,958 1,958 Subtotal — commercial loan portfolio 114 30,878 30,878 Consumer loan portfolio (residential mortgage) 85 4,943 4,840 Total 199 $ 35,821 $ 35,718
Troubled debt restructurings on financing receivables with defaults payment	The following schedule includes TDRs for which there was a payment default during the years ended December 31, 2015 , 2014 and 2013 , 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: Years Ended December 31, 2015 2014 2013 Number of Loans Principal Balance at Year End Number of Loans Principal Balance at Year End Number of Loans Principal Balance at Year End (Dollars in thousands) Commercial loan portfolio: Commercial 1 $ 1,206 7 $ 885 23 $ 2,745 Commercial real estate 5 1,016 6 2,352 8 4,278 Real estate construction — — — — 3 371 Land development — — — — 2 1,526 Subtotal — commercial loan portfolio 6 2,222 13 3,237 36 8,920 Consumer loan portfolio (residential mortgage) 3 65 12 259 22 1,826 Total 9 $ 2,287 25 $ 3,496 58 $ 10,746
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 year ended December 31, 2015 and details regarding the balance in the allowance and the recorded investment in loans at December 31, 2015 by impairment evaluation method. Commercial Loan Portfolio Consumer Loan Portfolio Unallocated Total (In thousands) Changes in allowance for loan losses for the year ended December 31, 2015: Beginning balance $ 44,156 $ 28,803 $ 2,724 $ 75,683 Provision for loan losses 7,275 1,949 (2,724 ) 6,500 Charge-offs (6,385 ) (7,116 ) — (13,501 ) Recoveries 2,188 2,458 — 4,646 Ending balance $ 47,234 $ 26,094 $ — $ 73,328 Allowance for loan losses balance at December 31, 2015 attributable to: Loans individually evaluated for impairment $ 6,197 $ 192 $ — $ 6,389 Loans collectively evaluated for impairment 41,037 25,902 — 66,939 Loans acquired with deteriorated credit quality — — — — Total $ 47,234 $ 26,094 $ — $ 73,328 Recorded investment (loan balance) at December 31, 2015: Loans individually evaluated for impairment $ 100,379 $ 21,037 $ — $ 121,416 Loans collectively evaluated for impairment 3,030,342 2,656,176 — 5,686,518 Loans acquired with deteriorated credit quality 1,119,396 343,817 — 1,463,213 Total $ 4,250,117 $ 3,021,030 $ — $ 7,271,147 The following presents, by loan portfolio segment, the changes in the allowance for the year ended December 31, 2014 and details regarding the balance in the allowance and the recorded investment in loans at December 31, 2014 by impairment evaluation method. Commercial Loan Portfolio Consumer Loan Portfolio Unallocated Total (In thousands) Changes in allowance for loan losses for the year ended December 31, 2014: Beginning balance $ 44,482 $ 30,145 $ 4,445 $ 79,072 Provision for loan losses 3,464 4,357 (1,721 ) 6,100 Charge-offs (6,399 ) (7,830 ) — (14,229 ) Recoveries 2,609 2,131 — 4,740 Ending balance $ 44,156 $ 28,803 $ 2,724 $ 75,683 Allowance for loan losses balance at December 31, 2014 attributable to: Loans individually evaluated for impairment $ 1,003 $ 335 $ — $ 1,338 Loans collectively evaluated for impairment 43,153 27,968 2,724 73,845 Loans acquired with deteriorated credit quality — 500 — 500 Total $ 44,156 $ 28,803 $ 2,724 $ 75,683 Recorded investment (loan balance) at December 31, 2014: Loans individually evaluated for impairment $ 86,221 $ 19,681 $ — $ 105,902 Loans collectively evaluated for impairment 2,517,371 2,366,794 — 4,884,165 Loans acquired with deteriorated credit quality 480,432 217,731 — 698,163 Total $ 3,084,024 $ 2,604,206 $ — $ 5,688,230

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Summary of premises and equipment	A summary of premises and equipment follows: December 31, 2015 2014 (In thousands) Cost: Land and land improvements $ 28,447 $ 27,402 Buildings 120,370 110,380 Equipment 77,882 68,540 Total cost 226,699 206,322 Accumulated depreciation (120,382 ) (108,826 ) Total premises and equipment $ 106,317 $ 97,496

Other Intangible Assets (Tables

Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Net carrying value of other intangible assets	The following table shows the net carrying value of the Corporation's other intangible assets: December 31, 2015 2014 (In thousands) Other intangible assets: Core deposit intangible assets $ 26,654 $ 20,863 Non-compete intangible assets 328 — Mortgage servicing rights (MSRs) 11,122 12,217 Total other intangible assets $ 38,104 $ 33,080
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets	The following table sets forth the carrying amount, accumulated amortization and amortization expense of core deposit intangible assets that are amortizable and arose from business combinations or other acquisitions: December 31, 2015 2014 (In thousands) Gross original amount $ 40,055 $ 31,550 Accumulated amortization 13,401 10,687 Carrying amount $ 26,654 $ 20,863 Amortization expense for the year ended December 31 $ 4,142 $ 2,029
Net carrying value and fair value of MSRs and total loans that Corporation is servicing for others	The following shows the net carrying value and fair value of MSRs and the total loans that the Corporation is servicing for others: December 31, 2015 2014 (In thousands) Net carrying value of MSRs $ 11,122 $ 12,217 Fair value of MSRs $ 15,542 $ 14,979 Loans serviced for others that have servicing rights capitalized $ 2,082,899 $ 2,093,140
Activity for capitalized MSRs	The following shows activity for capitalized MSRs for the last three years: Years Ended December 31, 2015 2014 2013 (In thousands) Balance at beginning of year $ 12,217 $ 3,423 $ 3,478 Acquired through acquisitions 1,284 9,235 — Additions 1,476 1,075 1,528 Amortization (4,055 ) (1,316 ) (1,583 ) Change in valuation allowance 200 (200 ) — Balance at end of year $ 11,122 $ 12,217 $ 3,423 Valuation allowance at December 31 $ — $ 200 $ —

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2015
Deposits [Abstract]
Schedule of Deposits	A summary of deposits follows: December 31, 2015 2014 (In thousands) Noninterest-bearing demand $ 1,934,583 $ 1,591,661 Interest-bearing demand 1,870,197 1,428,941 Savings 2,004,575 1,720,422 Time deposits over $100,000 701,830 557,476 Other time deposits 945,582 780,471 Total deposits $ 7,456,767 $ 6,078,971

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2015
Short-term Debt [Abstract]
Summary of short-term borrowings	A summary of short-term borrowings, which consisted of securities sold under agreements to repurchase, FHLB advances and federal funds purchased, follows: Ending Balance at Year-End Weighted Average Interest Rate at Year-End Average Amount Outstanding During Year Weighted Average Interest Rate During Year Maximum Outstanding at Any Month-End (Dollars in thousands) 2015 Securities sold under agreements to repurchase $ 297,199 0.06 % $ 327,559 0.07 % $ 372,236 FHLB advances 100,000 0.34 89,208 0.23 280,000 Federal funds purchased — — 3,762 0.37 22,000 2014 Securities sold under agreements to repurchase $ 304,467 0.11 % $ 326,056 0.12 % $ 361,231 FHLB advances 60,000 0.25 6,726 0.27 60,000 Federal funds purchased 25,000 0.40 2,003 0.40 25,000 2013 Securities sold under agreements to repurchase $ 327,428 0.15 % $ 337,649 0.14 % $ 357,976

Other Borrowings (Tables)

Other Borrowings (Tables)	12 Months Ended
	Dec. 31, 2015
Other Borrowings [Abstract]
Schedule of Other Borrowings [Table Text Block]	December 31, 2015 Ending Balance Weighted Average Interest Rate At Year-End (Dollars in thousands) Long-term FHLB advances $ 181,394 1.41 % Non-revolving line-of-credit 25,000 2.27 Securities sold under agreements to repurchase 17,453 0.27 Subordinated debentures 18,544 3.99 Total other borrowings $ 242,391

Accumulated Other Comprehensi42

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Components of accumulated other comprehensive loss, net of related tax benefit/expense	The components of accumulated other comprehensive loss, net of related tax benefit/expense, were as follows: December 31, 2015 2014 2013 (In thousands) Net unrealized gains (losses) on investment securities — available-for-sale, net of related tax expense (benefit) of $(1,017) at December 31, 2015, $(113) at December 31, 2014 and ($1,335) at December 31, 2013 $ (1,888 ) $ (210 ) $ (2,480 ) Pension and other postretirement benefits adjustment, net of related tax benefit of $14,616 at December 31, 2015, $17,362 at December 31, 2014 and $9,714 at December 31, 2013 (27,144 ) (32,243 ) (18,040 ) Accumulated other comprehensive loss $ (29,032 ) $ (32,453 ) $ (20,520 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Summary of assets measured at fair value on a recurring basis	For assets measured at fair value on a recurring basis, quantitative disclosures about the fair value measurements for each major category of assets follow: Fair Value Measurements — Recurring Basis Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (In thousands) December 31, 2015 Investment securities — available-for-sale: U.S. Treasury securities $ 5,765 $ — $ — $ 5,765 Government sponsored agencies — 194,989 — 194,989 State and political subdivisions — 15,120 — 15,120 Residential mortgage-backed securities — 187,768 — 187,768 Collateralized mortgage obligations — 132,230 — 132,230 Corporate bonds — 14,627 — 14,627 Preferred stock and trust preferred securities — 3,232 — 3,232 Total investment securities — available-for-sale 5,765 547,966 — 553,731 Loans held-for-sale — 10,327 — 10,327 Total assets measured at fair value on a recurring basis $ 5,765 $ 558,293 $ — $ 564,058 December 31, 2014 Investment securities — available-for-sale: U.S. Treasury securities $ 8,259 $ — $ — $ 8,259 Government sponsored agencies — 263,503 — 263,503 State and political subdivisions — 46,227 — 46,227 Residential mortgage-backed securities — 239,807 — 239,807 Collateralized mortgage obligations — 144,383 — 144,383 Corporate bonds — 45,095 — 45,095 Preferred stock — 1,590 — 1,590 Total investment securities — available-for-sale 8,259 740,605 — 748,864 Loans held-for-sale — 9,128 — 9,128 Total assets measured at fair value on a recurring basis $ 8,259 $ 749,733 $ — $ 757,992
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 follow: Fair Value Measurements — Nonrecurring Basis Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (In thousands) December 31, 2015 Impaired originated loans $ — $ — $ 42,065 $ 42,065 Other real estate/repossessed assets — — 9,935 9,935 Total $ — $ — $ 52,000 $ 52,000 December 31, 2014 Impaired originated loans $ — $ — $ 21,323 $ 21,323 Other real estate/repossessed assets — — 14,205 14,205 Mortgage servicing rights — — 8,691 8,691 Total $ — $ — $ 44,219 $ 44,219
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 included in the consolidated statements of financial position follows: Level in Fair Value Measurement Hierarchy December 31, 2015 December 31, 2014 Carrying Amount Fair Value Carrying Amount Fair Value (In thousands) Assets: Cash and cash equivalents Level 1 $ 238,789 $ 238,789 $ 183,020 $ 183,020 Investment securities: Available-for-sale Level 1 5,765 5,765 8,259 8,259 Available-for-sale Level 2 547,966 547,966 740,605 740,605 Held-to-maturity Level 2 509,471 512,405 305,913 308,650 Held-to-maturity Level 3 500 300 10,500 7,090 Nonmarketable equity securities NA 36,907 36,907 27,369 27,369 Loans held-for-sale Level 2 10,327 10,327 9,128 9,128 Net loans Level 3 7,197,819 7,201,994 5,612,547 5,623,454 Interest receivable Level 2 21,953 21,953 17,492 17,492 Liabilities: Deposits without defined maturities Level 2 $ 5,809,355 $ 5,809,355 $ 4,741,024 $ 4,741,024 Time deposits Level 3 1,647,412 1,647,412 1,337,947 1,340,015 Interest payable Level 2 1,578 1,578 755 755 Short-term borrowings Level 2 397,199 397,199 389,467 389,467 Other borrowings Level 2 206,394 206,394 — — Other borrowings Level 3 35,997 35,997 — —

Noninterest Income (Tables)

Noninterest Income (Tables)	12 Months Ended
	Dec. 31, 2015
Noninterest Income [Abstract]
Schedule of major components of noninterest Income	The following schedule includes the major components of noninterest income during the past three years: Years Ended December 31, 2015 2014 2013 (In thousands) Service charges and fees on deposit accounts $ 25,481 $ 22,414 $ 21,939 Wealth management revenue 20,552 16,015 13,989 Electronic banking fees 19,119 13,480 12,213 Mortgage banking revenue 6,133 5,041 5,336 Other fees for customer services 4,428 3,539 3,288 Insurance commissions 1,966 1,559 1,650 Gain on sale of investment securities 630 — 1,133 Bank owned life insurance 646 281 197 Rental income 466 145 97 Gain on sale of closed branch offices and other assets 266 — 478 Gain on sale of merchant card servicing business — 400 — Other 529 221 89 Total noninterest income $ 80,216 $ 63,095 $ 60,409

Operating Expenses (Tables)

Operating Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Operating Expenses [Abstract]
Schedule of major categories of operating expenses	The following schedule includes the major categories of operating expenses during the past three years: Years Ended December 31, 2015 2014 2013 (In thousands) Salaries and wages $ 104,490 $ 83,229 $ 78,014 Employee benefits 23,430 19,328 18,405 Occupancy 18,213 15,842 13,934 Equipment and software 18,569 14,737 13,734 Outside processing and service fees 15,207 11,586 11,134 FDIC insurance premiums 5,485 4,307 4,362 Professional fees 4,842 3,570 3,771 Intangible asset amortization 4,389 2,029 1,909 Postage and express mail 3,313 3,418 3,051 Advertising and marketing 3,288 3,051 2,971 Training, travel and other employee expenses 3,224 2,480 2,512 Telephone 2,608 1,966 1,940 Supplies 2,216 1,897 1,670 Donations 1,375 1,155 2,829 Credit-related expenses 632 996 707 Acquisition-related expenses 7,804 6,388 — Other 4,809 3,946 4,005 Total operating expenses $ 223,894 $ 179,925 $ 164,948

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Schedule of Changes in the Projected Benefit Obligation and Plan Assets of the Corporation’s Pension and Postretirement Plans	The following schedule sets forth the changes in the projected benefit obligation and plan assets of the Corporation's Pension and Postretirement Plans: Pension Plan Postretirement Plan 2015 2014 2015 2014 (In thousands) Projected benefit obligation: Benefit obligation at beginning of year $ 129,160 $ 105,914 $ 3,702 $ 3,477 Service cost 1,021 944 16 18 Interest cost 5,242 5,167 133 142 Net actuarial (gain) loss (10,837 ) 21,314 (363 ) 312 Benefits paid (4,713 ) (4,179 ) (241 ) (247 ) Benefit obligation at end of year 119,873 129,160 3,247 3,702 Fair value of plan assets: Fair value of plan assets at beginning of year 130,775 128,829 — — Actual return on plan assets 868 6,125 — — Employer contributions — — 241 247 Benefits paid (4,713 ) (4,179 ) (241 ) (247 ) Fair value of plan assets at end of year 126,930 130,775 — — Funded (unfunded) status at December 31 $ 7,057 $ 1,615 $ (3,247 ) $ (3,702 ) Accumulated benefit obligation $ 109,583 $ 121,826 $ 3,247 $ 3,702
Schedule of Weighted-average rate assumptions of the Pension and Postretirement Plans	Weighted-average rate assumptions of the Pension and Postretirement Plans follow: Pension Plan Postretirement Plan 2015 2014 2013 2015 2014 2013 Discount rate used in determining benefit obligation — December 31 4.55 % 4.15 % 5.00 % 4.23 % 3.75 % 4.27 % Discount rate used in determining expense 4.15 5.00 4.08 3.75 4.27 4.08 Expected long-term return on Pension Plan assets 6.75 7.00 7.00 — — — Rate of compensation increase used in determining benefit obligation — December 31 3.50 3.50 3.50 — — — Rate of compensation increase used in determining pension expense 3.50 3.50 3.50 — — — Year 1 increase in cost of postretirement benefits — — — 7.5 8.0 8.5
Schedule of Net periodic Pension Cost (Income) of the Pension and Postretirement Plans	Net periodic pension cost (income) of the Pension and Postretirement Plans was as follows for the years ended December 31: Pension Plan Postretirement Plan 2015 2014 2013 2015 2014 2013 (In thousands) Service cost $ 1,021 $ 944 $ 1,247 $ 16 $ 18 $ 18 Interest cost 5,242 5,167 4,603 133 142 143 Expected return on plan assets (8,645 ) (8,314 ) (7,794 ) — — — Amortization of prior service credit (5 ) (1 ) (1 ) 130 130 343 Amortization of net actuarial loss (gain) 3,962 2,159 3,670 (1 ) (104 ) (73 ) Net cost (income) $ 1,575 $ (45 ) $ 1,725 $ 278 $ 186 $ 431
Schedule of Estimated Future Benefit Payments Under the Pension and Postretirement Plans	The following schedule presents estimated future benefit payments under the Pension and Postretirement Plans for retirees already receiving benefits and future retirees, assuming they retire and begin receiving unreduced benefits as soon as they are eligible: Pension Plan Postretirement Plan (In thousands) 2016 $ 5,223 $ 272 2017 5,400 272 2018 5,730 268 2019 6,094 270 2020 6,272 268 2021 - 2025 35,771 1,254 Total $ 64,490 $ 2,604
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates	A one percentage-point change in these rates would have the following effects: One Percentage-Point Increase Decrease (In thousands) Effect on total of service and interest cost components in 2015 $ 13 $ (12 ) Effect on postretirement benefit obligation as of December 31, 2015 308 (269 )
Schedule of Allocation of Plan Assets	The Pension Plan's asset allocation by asset category was as follows: December 31, Asset Category 2015 2014 Equity securities 68 % 68 % Debt securities 31 30 Other 1 2 Total 100 % 100 % The following schedule sets forth the fair value of the Pension Plan's assets and the level of the valuation inputs used to value those assets at December 31, 2015 and 2014 : Asset Category Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total (In thousands) December 31, 2015 Cash $ 354 $ — $ — $ 354 Equity securities: U.S. large- and mid-cap stocks (a) 55,709 — — 55,709 U.S. small-cap mutual funds 4,749 — — 4,749 International large-cap mutual funds 14,124 — — 14,124 Emerging markets mutual funds 4,886 — — 4,886 Chemical Financial Corporation common stock 7,219 — — 7,219 Debt securities: U.S. Treasury and government sponsored agency bonds and notes — 2,815 — 2,815 Corporate bonds (b) — 3,554 — 3,554 Mutual funds (c) 33,424 — — 33,424 Other 96 — — 96 Total $ 120,561 $ 6,369 $ — $ 126,930 December 31, 2014 Cash $ 2,594 $ — $ — $ 2,594 Equity securities: U.S. large- and mid-cap stocks (a) 56,718 — — 56,718 U.S. small-cap mutual funds 5,409 — — 5,409 International large-cap mutual funds 14,805 — — 14,805 Emerging markets mutual funds 6,004 — — 6,004 Chemical Financial Corporation common stock 6,455 — — 6,455 Debt securities: U.S. Treasury and government sponsored agency bonds and notes 998 2,043 — 3,041 Corporate bonds (b) — 6,814 — 6,814 Mutual funds (c) 28,795 — — 28,795 Other 140 — — 140 Total $ 121,918 $ 8,857 $ — $ 130,775 (a) Comprised of common stocks and mutual funds traded on U.S. Exchanges whose issuers had market capitalizations exceeding $3 billion . (b) Comprised of investment grade bonds of U.S. issuers from diverse industries. (c) Comprised primarily of fixed-income bonds issued by the U.S. Treasury and government sponsored agencies and bonds of U.S. and foreign issuers from diverse industries.
Schedule of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax, Related to the Corporation’s Pension, Postretirement and Supplemental Plans	The following sets forth the changes in accumulated other comprehensive income (loss), net of tax, related to the Corporation's Pension, Postretirement and Supplemental Plans during 2015 : Pension Plan Postretirement Plan Supplemental Plan Total (In thousands) Accumulated other comprehensive income (loss) at beginning of year $ (31,853 ) $ 83 $ (473 ) $ (32,243 ) Comprehensive income (loss) adjustment: Prior service costs (credits) (3 ) 84 — 81 Net actuarial loss 4,565 235 218 5,018 Comprehensive income (loss) adjustment 4,562 319 218 5,099 Accumulated other comprehensive income (loss) at end of year $ (27,291 ) $ 402 $ (255 ) $ (27,144 )
Schedule of Estimated Income (Loss) That Will Be Amortized From Accumulated Other Comprehensive Income (Loss) Into Net Periodic Cost	The estimated income (loss) that will be amortized from accumulated other comprehensive income (loss) into net periodic cost, net of tax, in 2016 is as follows: Pension Plan Postretirement Plan Supplemental Plan Total (In thousands) Prior service (costs) credits $ — $ (76 ) $ — $ (76 ) Net gain (loss) (1,468 ) 65 (20 ) (1,423 ) Total $ (1,468 ) $ (11 ) $ (20 ) $ (1,499 )

Share-Based Compensation Plan (

Share-Based Compensation Plan (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of stock options outstanding by exercise price range	The following summarizes information about stock options outstanding at December 31, 2015 : Options Outstanding Options Exercisable Range of Exercise Prices Per Share Number Outstanding Weighted Average Exercise Price Per Share Weighted Average Contractual Term (In Years) Number Exercisable Weighted Average Exercise Price Per Share Weighted Average Contractual Term (In Years) $10.56 - 15.84 84,775 $ 13.31 4.73 84,775 $ 13.31 4.73 19.97 - 21.10 74,189 20.47 4.40 74,189 20.47 4.40 23.78 - 25.14 502,845 24.63 5.08 384,912 24.47 4.44 29.45 - 30.18 392,930 29.88 8.76 31,108 29.45 8.17 $10.56 - 30.18 1,054,739 $ 25.38 6.38 574,984 $ 22.58 4.68
Summary of activity for Corporation's stock options	A summary of activity for the Corporation's stock options as of and during the three years ended December 31, 2015 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, 2012 314,765 $ 23.03 $ 6.92 997,222 $ 27.24 Activity during 2013: Granted 244,719 25.14 7.40 244,719 25.14 Exercised — — — (100,145 ) 22.87 Vested (127,443 ) 22.94 6.92 — — Expired or forfeited (17,961 ) 23.34 6.98 (67,806 ) 32.27 Outstanding at December 31, 2013 414,080 24.29 7.19 1,073,990 26.84 Activity during 2014: Granted 190,011 29.45 9.64 190,011 29.45 Exercised — — — (72,936 ) 24.67 Vested (148,016 ) 23.43 6.98 — — Expired or forfeited (23,876 ) 25.67 7.79 (153,754 ) 37.50 Outstanding at December 31, 2014 432,199 26.75 8.30 1,037,311 25.90 Activity during 2015: Granted 244,165 30.18 8.40 244,165 30.18 Lake Michigan converted options — — — 132,883 12.93 Exercised — — — (310,985 ) 25.10 Vested (150,224 ) 25.57 7.80 — — Expired or forfeited (46,385 ) 27.99 8.50 (48,635 ) 28.18 Outstanding at December 31, 2015 479,755 $ 28.75 $ 8.49 1,054,739 $ 25.38 Exercisable/vested at December 31, 2015 574,984 $ 22.58
Assumptions of Black-Scholes option pricing model	The fair value of the stock options granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions. 2015 2014 2013 Expected dividend yield 3.50 % 3.00 % 3.50 % Risk-free interest rate 1.78 % 2.16 % 1.34 % Expected stock price volatility 39.1 % 42.2 % 42.1 % Expected life of options — in years 7.0 7.0 7.0 Weighted average fair value per share $8.40 $9.64 $7.40
Summary of activity for restricted stock units	A summary of the activity for restricted stock units during the three years ended December 31, 2015 is presented below: Number of Units Weighted Average Grant Date Fair Value Per Unit Outstanding at December 31, 2012 156,510 $ 20.83 Activity during 2013: Granted 71,768 23.42 Converted into shares of common stock (36,416 ) 22.44 Forfeited/expired (3,330 ) 21.67 Outstanding at December 31, 2013 188,532 21.49 Activity during 2014: Granted 73,468 27.49 Converted into shares of common stock (52,008 ) 19.23 Forfeited/expired (5,673 ) 24.31 Outstanding at December 31, 2014 204,319 24.14 Activity during 2015: Granted 85,645 28.52 Converted into shares of common stock (70,166 ) 22.51 Forfeited/expired (11,809 ) 25.61 Outstanding at December 31, 2015 207,989 $ 26.41

Federal Income Taxes (Tables)

Federal Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Federal Effective Income Tax Rate Reconciliation	The differences between the provision for federal income taxes computed at the federal statutory income tax rate and the amounts recorded in the consolidated financial statements were as follows: Years Ended December 31, 2015 2014 2013 (Dollars in thousands) Tax at statutory rate $ 43,341 $ 31,367 $ 28,388 Changes resulting from: Tax-exempt interest income (3,918 ) (3,118 ) (2,746 ) Income tax credits, net (2,557 ) (1,624 ) (1,615 ) Other, net 134 875 273 Provision for federal income taxes $ 37,000 $ 27,500 $ 24,300 Effective federal income tax rate 29.9 % 30.7 % 30.0 %
Provision for Federal Income Taxes Components	The provision for federal income taxes consisted of the following: Years Ended December 31, 2015 2014 2013 (In thousands) Current expense $ 31,300 $ 29,200 $ 23,665 Deferred expense (benefit) 5,700 (1,700 ) 635 Total federal income tax expense $ 37,000 $ 27,500 $ 24,300
Schedule of Deferred Tax Assets and Liabilities	Significant temporary differences that comprise the deferred tax assets and liabilities of the Corporation were as follows: December 31, 2015 2014 (In thousands) Deferred tax assets: Allowance for loan losses $ 24,863 $ 26,489 Acquisition-related fair value adjustments 29,280 19,457 Accrued expenses not currently deductible 9,331 7,819 Net operating loss carryforward 7,130 — Premises and equipment 4,333 3,311 Nonaccrual loan interest 4,994 4,682 Other 15,296 9,418 Total deferred tax assets 95,227 71,176 Deferred tax liabilities: Core deposit intangible assets 7,379 5,072 Goodwill 5,808 5,205 Mortgage servicing rights 3,893 4,276 Other 7,957 3,884 Total deferred tax liabilities 25,037 18,437 Net deferred tax assets $ 70,190 $ 52,739

Regulatory Capital and Reserv49

Regulatory Capital and Reserve Requirements (Tables)	12 Months Ended
	Dec. 31, 2015
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 Corporation's and Chemical Bank's actual capital amounts and ratios with the quantitative measures established by regulation to ensure capital adequacy. Amounts as of December 31, 2015 were based on the Basel III capital rules, which became effective January 1, 2015. Amounts as of December 31, 2014 were based on the regulatory capital rules in effect as of that date. Actual Minimum Required for Capital Adequacy Purposes Required to be Well Capitalized Under Prompt Corrective Action Regulations Capital Amount Ratio Capital Amount Ratio Capital Amount Ratio (Dollars in thousands) December 31, 2015 Total Capital to Risk-Weighted Assets: Corporation $ 841,257 11.8 % $ 571,509 8.0 % N/A N/A Chemical Bank 830,294 11.7 570,073 8.0 $ 712,591 10.0 % Tier 1 Capital to Risk-Weighted Assets: Corporation 767,929 10.7 428,631 6.0 N/A N/A Chemical Bank 756,966 10.6 427,555 6.0 570,073 8.0 Common Equity Tier 1 Capital to Risk-Weighted Assets: Corporation 753,815 10.6 321,474 4.5 N/A N/A Chemical Bank 756,966 10.6 320,666 4.5 463,184 6.5 % Leverage Ratio: Corporation 767,929 8.6 356,396 4.0 N/A N/A Chemical Bank 756,966 8.5 355,911 4.0 444,888 5.0 December 31, 2014 Total Capital to Risk-Weighted Assets: Corporation $ 705,130 12.4 % $ 456,302 8.0 % N/A N/A Chemical Bank 654,031 11.5 455,633 8.0 $ 569,541 10.0 % Tier 1 Capital to Risk-Weighted Assets: Corporation 633,779 11.1 228,151 4.0 N/A N/A Chemical Bank 582,783 10.2 227,816 4.0 341,725 6.0 Leverage Ratio: Corporation 633,779 9.3 273,226 4.0 N/A N/A Chemical Bank 582,783 8.5 273,048 4.0 341,310 5.0

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Numerator and denominator of the basic and diluted earnings per common share computations	The following summarizes the numerator and denominator of the basic and diluted earnings per common share computations: Years Ended December 31, 2015 2014 2013 (In thousands, except per share data) Numerator for both basic and diluted earnings per common share, net income $ 86,830 $ 62,121 $ 56,808 Denominator for basic earnings per common share, weighted average common shares outstanding 36,081 31,367 28,183 Weighted average common stock equivalents 272 221 169 Denominator for diluted earnings per common share 36,353 31,588 28,352 Net income per common share: Basic $ 2.41 $ 1.98 $ 2.02 Diluted 2.39 1.97 2.00

Parent Company Only Financial51

Parent Company Only Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Condensed Statement of Financial Position	Condensed financial statements of Chemical Financial Corporation (parent company) only follow: December 31, Condensed Statements of Financial Position 2015 2014 (In thousands) Assets: Cash at subsidiary bank $ 28,884 $ 45,820 Investment in subsidiaries 1,023,285 745,045 Premises and equipment 3,632 3,601 Goodwill 1,092 1,092 Other assets 13,051 4,654 Total assets $ 1,069,944 $ 800,212 Liabilities and Shareholders' Equity: Other liabilities $ 10,426 $ 3,079 Non-revolving line of credit 25,000 — Subordinated debentures 18,544 — Shareholders' equity 1,015,974 797,133 Total liabilities and shareholders' equity $ 1,069,944 $ 800,212
Parent Company Condensed Statement of Income	Years Ended December 31, Condensed Statements of Income 2015 2014 2013 (In thousands) Income: Cash dividends from subsidiaries $ 56,860 $ 64,468 $ 24,488 Other income 144 95 390 Total income 57,004 64,563 24,878 Expenses: Interest expense 761 42 — Operating expenses 7,794 7,200 4,735 Total expenses 8,555 7,242 4,735 Income before income taxes and equity in undistributed net income of subsidiaries 48,449 57,321 20,143 Federal income tax benefit 2,582 2,302 1,556 Equity in undistributed net income of subsidiaries 35,799 2,498 35,109 Net income $ 86,830 $ 62,121 $ 56,808
Parent Company Condensed Statement of Cash Flows	Years Ended December 31, Condensed Statements of Cash Flows 2015 2014 2013 (In thousands) Operating Activities: Net income $ 86,830 $ 62,121 $ 56,808 Adjustments to reconcile net income to net cash provided by operating activities: Share-based compensation expense 3,478 2,931 2,854 Gain on sale of available-for-sale investment securities — — (245 ) Depreciation of premises and equipment 318 327 416 Equity in undistributed net income of subsidiaries (35,799 ) (2,498 ) (35,109 ) Net (increase) decrease in other assets 2,873 1,101 (711 ) Net increase (decrease) in other liabilities (19,033 ) (2,519 ) 563 Net cash provided by operating activities 38,667 61,463 24,576 Investing Activities: Cash paid, net of cash assumed, in business combinations (45,267 ) (117,853 ) — Proceeds from redemption of available-for-sale investment securities — — 5,000 Purchases of premises and equipment, net (320 ) (26 ) (9 ) Net cash provided by (used in) investing activities (45,587 ) (117,879 ) 4,991 Financing Activities: Cash dividends paid (36,918 ) (29,528 ) (24,521 ) Proceeds from issuance of common stock, net of issuance costs — 76,175 53,925 Repayment of subordinated debt obligations — (10,310 ) — Proceeds from issuance of other borrowings 25,000 — — Proceeds from directors' stock purchase plan and exercise of stock options 2,473 1,242 806 Cash paid for payroll taxes upon conversion of restricted stock units (571 ) (701 ) (379 ) Net cash provided by (used in) financing activities (10,016 ) 36,878 29,831 Net increase (decrease) in cash and cash equivalents (16,936 ) (19,538 ) 59,398 Cash and cash equivalents at beginning of year 45,820 65,358 5,960 Cash and cash equivalents at end of year $ 28,884 $ 45,820 $ 65,358

Summary of Quarterly Statemen52

Summary of Quarterly Statements of Income (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Schedule of Quarterly Financial Information	The following quarterly information is unaudited. However, in the opinion of management, the information reflects all adjustments that are necessary for the fair presentation of the results of operations for the periods presented. 2015 First Quarter Second Quarter Third Quarter Fourth Quarter Total (In thousands, except per share data) Interest income $ 62,630 $ 69,679 $ 78,851 $ 80,629 $ 291,789 Interest expense 3,450 3,944 5,234 5,153 17,781 Net interest income 59,180 65,735 73,617 75,476 274,008 Provision for loan losses 1,500 1,500 1,500 2,000 6,500 Noninterest income 19,275 20,674 20,215 20,052 80,216 Operating expenses 51,020 56,785 58,265 57,824 223,894 Income before income taxes 25,935 28,124 34,067 35,704 123,830 Federal income tax expense 8,100 9,100 9,600 10,200 37,000 Net income $ 17,835 $ 19,024 $ 24,467 $ 25,504 $ 86,830 Net income per common share: Basic $ 0.54 $ 0.54 $ 0.64 $ 0.67 $ 2.41 Diluted 0.54 0.54 0.64 0.66 2.39 Cash dividends declared per common share 0.24 0.24 0.26 0.26 1.00 2014 First Quarter Second Quarter Third Quarter Fourth Quarter Total (In thousands, except per share data) Interest income $ 53,645 $ 55,180 $ 56,629 $ 61,807 $ 227,261 Interest expense 3,866 3,720 3,561 3,563 14,710 Net interest income 49,779 51,460 53,068 58,244 212,551 Provision for loan losses 1,600 1,500 1,500 1,500 6,100 Noninterest income 13,716 15,801 15,351 18,227 63,095 Operating expenses 42,182 42,425 42,702 52,616 179,925 Income before income taxes 19,713 23,336 24,217 22,355 89,621 Federal income tax expense 5,900 7,100 7,450 7,050 27,500 Net income $ 13,813 $ 16,236 $ 16,767 $ 15,305 $ 62,121 Net income per common share: Basic $ 0.46 $ 0.54 $ 0.51 $ 0.47 $ 1.98 Diluted 0.46 0.54 0.51 0.46 1.97 Cash dividends declared per common share 0.23 0.23 0.24 0.24 0.94

Significant Accounting Polici53

Significant Accounting Policies (Nature of Operations and Basis of Presentation) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)Bank
Significant Accounting Policies [Line Items]
Minimum Number of Days Past Due as to Interest or Principal Payments in Accruing Loans Moves to Nonperforming Loans	90 days
Nature of Operations and Basis of Presentation
Number of banks through which company operates	1
Number of regional banking units Chemical Bank operates through	4
Percentage of FHLB advances secured by first lien real estate residential loans	140.00%
Minimum percentage of tax benefit is recognized for the amount likely to be realized	50.00%
Reserve for contingent income tax liabilities recorded | $	$ 0

Significant Accounting Polici54

Significant Accounting Policies (Business Combinations) (Details) - USD ($) $ in Thousands	May. 31, 2015	Apr. 01, 2015	Oct. 31, 2014	Apr. 30, 2010	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill acquired					$ 287,393	$ 180,128
Lake Michigan Financial Corp [Member]
Business Acquisition [Line Items]
Acquisition purchase price	$ 187,394
Goodwill acquired	101,621
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	8,600
Business Combination, Consideration Transferred, Value of Stock and Options Issued	132,900
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock	$ 54,478
Monarch Community Bancorp [Member]
Business Acquisition [Line Items]
Acquisition purchase price		$ 27,191
Goodwill acquired		5,330
Intangibles acquired		1,930
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock		$ 203
Northwestern Bancorp [Member]
Business Acquisition [Line Items]
Acquisition purchase price			$ 121,000
Goodwill acquired			60,000		$ 60,300
Intangibles acquired			$ 12,891
OAK [Member]
Business Acquisition [Line Items]
Acquisition purchase price				$ 83,700
Goodwill acquired				43,500
Intangibles acquired				$ 9,800

Significant Accounting Polici55

Significant Accounting Policies (Nonmarketable Equity Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
FHLB Stock Minimum Redemption Period	5 years
FRB Stock Minimum Redemption Period	6 months
FRB Stock Minimum Annual Amount Redeemable	25.00%
Corporation's ownership in FHLB stock	$ 23.9	$ 19
Corporation's ownership in FRB stock	$ 13	$ 8.4

Significant Accounting Polici56

Significant Accounting Policies (Originated Loans) (Details)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Number of minimum days when principal or interest is past due is placed in nonaccrual category	90 days
Number of minimum days for a real estate residential loan when principal or interest is past due is placed in nonaccrual category	120 days
Time period in which payments receive consistently and loans are returned to accrual status	6 months

Significant Accounting Polici57

Significant Accounting Policies (Loans Acquired in a Business Combination) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)Pools	May. 31, 2015USD ($)	Apr. 01, 2015USD ($)	Dec. 31, 2014USD ($)	Oct. 31, 2014USD ($)	Apr. 30, 2010USD ($)
Receivables Acquired with Deteriorated Credit Quality [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans with deteriorated quality of acquired loan portfolio	$ 1,463,213			$ 698,163
Lake Michigan Financial Corp [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans without deteriorated quality of acquired loan portfolio		$ 947,000
Outstanding contractual principal balance of acquired loan portfolio		1,010,000
Number of pools of aggregate acquired loans based upon common risk characteristics | Pools	2
Lake Michigan Financial Corp [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans with deteriorated quality of acquired loan portfolio		$ 63,000
Monarch Community Bancorp [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans without deteriorated quality of acquired loan portfolio			$ 120,000
Outstanding contractual principal balance of acquired loan portfolio			129,000
Number of pools of aggregate acquired loans based upon common risk characteristics | Pools	2
Monarch Community Bancorp [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans with deteriorated quality of acquired loan portfolio			$ 9,000
OAK [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans without deteriorated quality of acquired loan portfolio						$ 578,000
Outstanding contractual principal balance of acquired loan portfolio						683,000
Number of pools of aggregate acquired loans based upon common risk characteristics | Pools	14
OAK [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans with deteriorated quality of acquired loan portfolio						$ 105,000
Northwestern Bancorp [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans without deteriorated quality of acquired loan portfolio					$ 461,000
Outstanding contractual principal balance of acquired loan portfolio					507,000
Number of pools of aggregate acquired loans based upon common risk characteristics | Pools	4
Northwestern Bancorp [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Business Acquisition [Line Items]
Outstanding contractual principal balance of loans with deteriorated quality of acquired loan portfolio					$ 46,000

Significant Accounting Polici58

Significant Accounting Policies (Loans Modified Under Troubled Debt Restructuring) (Details)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Time period sustained for payment history of principal and interest payments to move them to performing status	6 months
Time period of real estate residential troubled debt restructurings reducing borrower's monthly payments by decreasing the interest rate charged on the loan	24 months
Number of minimum days when principal or interest is past due is placed in nonaccrual category	90 days

Significant Accounting Polici59

Significant Accounting Policies (Allowance for Loan Losses) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Accounting Policies [Abstract]
Minimum amount of loan reviewed for detailed credit quality	$ 250
Time period used for historical loan loss experience	5 years
Minimum amount of impaired loan secured by real estate requiring an updated annual appraisal	$ 250
Period of weighted average losses for the calculation of the allowance for loan losses	5 years

Significant Accounting Polici60

Significant Accounting Policies (Premises and Equipment) (Details)	12 Months Ended
	Dec. 31, 2015
Buildings [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, estimated useful lives	40 years
Buildings [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, estimated useful lives	25 years
Other Depreciable Assets Excluding Buildings [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, estimated useful lives	10 years
Other Depreciable Assets Excluding Buildings [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, estimated useful lives	3 years

Significant Accounting Polici61

Significant Accounting Policies (Other Real Estate) (Details) - Other Assets [Member] - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Real Estate Acquired Through Foreclosure	$ 12.7	$ 14.8
Other real estate - closed branch offices	$ 3	$ 0.9

Significant Accounting Polici62

Significant Accounting Policies (Goodwill and Other Intangible Assets) (Details) - Core deposit intangible assets [Member]	12 Months Ended
	Dec. 31, 2015
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period	10 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization period	15 years

Significant Accounting Polici63

Significant Accounting Policies (Other Borrowings) (Details)	Dec. 31, 2015
Accounting Policies [Abstract]
Percentage of FHLB advances secured by first lien real estate residential loans	140.00%

Significant Accounting Polici64

Significant Accounting Policies (Investment in Tax Credit Projects) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
income tax expense attributable to qualified affordable housing projects	$ 1.3	$ 0.4
Investment in qualified affordable housing projects	21.7	4.9
Equity Method Investments	1.7	$ 0
Variable Interest Entity, Reporting Entity Involvement, Unfunded Obligation, Amount	$ 8

Acquisitions Purchase Accountin

Acquisitions Purchase Accounting Fair Value Adjustments (Details) - USD ($) $ in Thousands		May. 31, 2015	Apr. 01, 2015	Oct. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Purchase Accounting Fair Value Adjustments [Line Items]
Goodwill					$ 287,393	$ 180,128
Lake Michigan Financial Corp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
Business Combination, Consideration Transferred, Value of Stock Issued		$ 130,916
Business Combination, Consideration Transferred, Value of Stock Options		2,000
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock		54,478
Business Combination, Consideration Transferred		187,394
Net Assets Acquired, Acquiree Shareholders Equity		89,280
Purchase Accounting Fair Value Adjustment, Loans		(22,600)
Purchase Accounting Fair Value Adjustment, Allowance for Loan Losses		15,888
Purchase Accounting Fair Value Adjustment, Deferred Tax Asset, Net	[1]	3,572
Purchase Accounting Fair Value Adjustment, Deposits and Other Borrowings	[1]	(3,182)
Purchase Accounting Fair Value Adjustment, Other Assets and Liabilities, Net		(157)
Purchase Accounting Fair Value Adjustment, Premises and Equipment	[1]	(5,031)
Purchase Accounting Fair Value Adjustment, Core Deposit Intangible Asset		8,003
Net Assets Acquired After Purchase Accounting Fair Value Adjustments		85,773
Goodwill		$ 101,621
Monarch Community Bancorp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
Business Combination, Consideration Transferred, Value of Stock Issued			$ 26,988
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock			203
Business Combination, Consideration Transferred			27,191
Net Assets Acquired, Acquiree Shareholders Equity			15,270
Purchase Accounting Fair Value Adjustment, Loans			(7,150)
Purchase Accounting Fair Value Adjustment, Allowance for Loan Losses			2,128
Business Combination, Fair Value Adjustment, Deferred Tax Asset NOL			7,900
Purchase Accounting Fair Value Adjustment, Deferred Tax Asset, Net	[2]		1,826
Purchase Accounting Fair Value Adjustment, Premises and Equipment	[2]		(395)
Purchase Accounting Fair Value Adjustment, Core Deposit Intangible Asset			1,930
Purchase Accounting Fair Value Adjustment, Mortgage Servicing Rights Asset			315
Purchase Accounting, Other assets and other liabilities			37
Net Assets Acquired After Purchase Accounting Fair Value Adjustments			21,861
Goodwill			$ 5,330
Northwestern Bancorp [Member]
Purchase Accounting Fair Value Adjustments [Line Items]
Business Combination, Consideration Transferred				$ 121,000
Goodwill				$ 60,000	$ 60,300
[1]	(2) Includes adjustments to the fair value as a result of additional valuation information obtained during the fourth quarter of 2015, including the corresponding tax effects. A summary of these adjustments is included in the section "Allocation of Purchase Price" within this footnote.
[2]	(2) Includes immaterial adjustments to the fair value as a result of additional valuation information obtained during the fourth quarter of 2015, including the corresponding tax effects.

Acquisitions Schedule of Purcha

Acquisitions Schedule of Purchase Price Allocation (Details) - USD ($) $ in Thousands	May. 31, 2015	Apr. 01, 2015	Dec. 31, 2015	Dec. 31, 2014
Schedule of Purchase Price Allocation [Line Items]
Goodwill			$ 287,393	$ 180,128
Short-term borrowings			397,199	389,467
Other Borrowings			$ 242,391	$ 0
Lake Michigan Financial Corp [Member]
Schedule of Purchase Price Allocation [Line Items]
Business Combination, Acquired Receivables, Fair Value	$ 985,500
Goodwill	101,621
Business Combination Deposits Assumed	925,000
Business Combination, Consideration Transferred	(187,394)
Monarch Community Bancorp [Member]
Schedule of Purchase Price Allocation [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 32,171
Business Combination, Acquired Receivables, Fair Value		121,783
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		3,039
Business Combination, Deferred Tax Asset, Net Operating Loss		7,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent		2,392
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables		6,972
Goodwill		5,330
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		1,930
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Mortgage Servicing Rights Asset		1,284
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		182,801
Business Combination Deposits Assumed		144,311
Other Borrowings		8,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other		3,299
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		155,610
Business Combination, Consideration Transferred		$ (27,191)
Revised Allocation of Purchase Price [Member] [Member] | Lake Michigan Financial Corp [Member]
Schedule of Purchase Price Allocation [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	39,301
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	66,699
Business Combination, Acquired Receivables, Fair Value	985,542
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	10,975
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent	16,191
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	37,659
Goodwill	101,621
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	8,003
Bank Owned Life Insurance	23,844
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	1,289,835
Business Combination Deposits Assumed	924,697
Short-term borrowings	30,000
Other Borrowings	124,857
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	22,887
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	1,102,441
Business Combination, Consideration Transferred	$ (187,394)

Acquisitions Unaudited Pro Form

Acquisitions Unaudited Pro Forma Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Business Acquisition, Pro Forma interest and dividend income	$ 313,851	$ 301,838
Business Acquisition, Pro Forma interest expense	21,750	26,386
Business Acquisition, Pro Forma net interest income	292,101	275,452
Business Acquisition, Pro Forma provision for loan losses	6,500	7,484
Business Acquisition, Pro Forma net interest income after provision for loan losses	285,601	267,968
Business Acquisition, Pro Forma noninterest income	83,447	86,243
Business Acquisition, Pro Forma noninterest expense	237,146	243,618
Business Acquisition, Pro Forma pre-tax net income	131,902	110,593
Business Acquisition, Pro Forma federal income tax expense	30,680	31,138
Business Acquisition, Pro Forma Net Income (Loss)	$ 101,222	$ 79,455
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 2.66	$ 2.17
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 2.64	$ 2.16
Weighted Average Number of Shares Outstanding, Basic			28,183
Weighted Average Number of Shares Outstanding, Diluted	36,353	31,588	28,352

Acquisitions Activity for Acqui

Acquisitions Activity for Acquired Loans (Details) - USD ($) $ in Thousands		May. 31, 2015	Apr. 01, 2015	Dec. 31, 2015	Dec. 31, 2014
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				$ 137,961	$ 32,610
Accretable yield added during the year from acquisitions				228,160	110,003
Accretable Yield Additions, Net of Reductions	[1]			(8,450)	3,806
Accretion recognized into interest income				(59,414)	(18,458)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0	10,000
Balance at end of year				298,257	137,961
Lake Michigan Financial Corp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				0
Accretable yield added during the year from acquisitions		$ 190,200		190,246
Accretable Yield Additions, Net of Reductions	[1]			(12,991)
Accretion recognized into interest income				(24,256)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0
Balance at end of year				152,999	0
Monarch Community Bancorp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				0
Accretable yield added during the year from acquisitions			$ 37,900	37,914
Accretable Yield Additions, Net of Reductions	[1]			1,336
Accretion recognized into interest income				(4,692)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0
Balance at end of year				34,558	0
Northwestern Bancorp [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				104,675	0
Accretable yield added during the year from acquisitions				0	110,003
Accretable Yield Additions, Net of Reductions	[1]			(3,396)	(1,605)
Accretion recognized into interest income				(18,656)	(3,723)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0	0
Balance at end of year				82,623	104,675
OAK [Member]
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of year				33,286	32,610
Accretable yield added during the year from acquisitions				0	0
Accretable Yield Additions, Net of Reductions	[1]			6,601	5,411
Accretion recognized into interest income				(11,810)	(14,735)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference				0	10,000
Balance at end of year				$ 28,077	$ 33,286
[1]	Represents additions in estimated contractual interest expected to be collected from acquired loans being renewed or extended, less reductions in contractual interest resulting from the early payoff of acquired loans.

Acquisitions (Textual) (Details

Acquisitions (Textual) (Details) $ / shares in Units, $ in Thousands	Jan. 25, 2016USD ($)Offices$ / shares	May. 31, 2015USD ($)Offices$ / sharesshares	Apr. 01, 2015USD ($)shares	Oct. 31, 2014USD ($)Offices	Dec. 07, 2012USD ($)Branches	Apr. 30, 2010USD ($)Offices	Dec. 31, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Business Acquisition [Line Items]
Goodwill							$ 287,393	$ 287,393	$ 180,128
Accretable yield								228,160	110,003
Monarch Community Bancorp [Member]
Business Acquisition [Line Items]
Common stock exchange ratio			0.0982
Acquisition purchase price			$ 27,191
Acquisition-related transaction expenses								2,300
Goodwill			5,330
Intangibles acquired			1,930
Assets of acquiree company			183,000
Fair value of loans acquired in acquisition			121,783
Deposits of acquiree company			144,311
Contractually required principal and interest payments of loan portfolio			128,900
Contractually required interest payments of loan portfolio			37,800
Expected principal cash flows of contractually required acquired loan portfolio			122,600
Expected interest cash flows of contractually required acquired loan portfolio			37,100
Nonaccretable difference			7,100
Expected credit losses			6,300
Accretable yield			37,900					37,914
Outstanding contractual principal balance of acquired loan portfolio							115,000	115,000
Carrying amount of acquired loan portfolio							108,000	108,000
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock			$ 203
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares			860,575
Lake Michigan Financial Corp [Member]
Business Acquisition [Line Items]
Common stock exchange ratio		1.326
Acquisition purchase price		$ 187,394
Cash purchase price per share | $ / shares		$ 16.64
Acquisition-related transaction expenses								5,500
Goodwill		$ 101,621
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 8,600
Service provided by acquiree bank through number of branches | Offices		5
Assets of acquiree company		$ 1,240,000
Fair value of loans acquired in acquisition		985,500
Deposits of acquiree company		925,000
Contractually required principal and interest payments of loan portfolio		1,010,000
Contractually required interest payments of loan portfolio		190,200
Expected principal cash flows of contractually required acquired loan portfolio		986,100
Expected interest cash flows of contractually required acquired loan portfolio		189,600
Nonaccretable difference		22,600
Expected credit losses		22,000
Accretable yield		190,200						190,246
Outstanding contractual principal balance of acquired loan portfolio							864,000	864,000
Carrying amount of acquired loan portfolio							842,000	842,000
Business Combination, Consideration Transferred, Value of Stock and Options Issued		132,900
Business Combination, Consideration Transferred, Cash Paid for Outstanding Stock		$ 54,478
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares		4,300,000
Business Combination, Provision Information, Initial Accounting Incomplete, Goodwill							700
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment							1,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles							100
Business Combination, Provisional Information, Initial Accounting Incomplete, Deferred Income Tax Assets							400
Northwestern Bancorp [Member]
Business Acquisition [Line Items]
Acquisition purchase price				$ 121,000
Acquisition-related transaction expenses									5,800
Goodwill				60,000			60,300	60,300
Intangibles acquired				$ 12,891
Service provided by acquiree bank through number of branches | Offices				25
Assets of acquiree company				$ 815,000
Fair value of loans acquired in acquisition				475,000
Deposits of acquiree company				794,000
Contractually required principal and interest payments of loan portfolio				507,000
Contractually required interest payments of loan portfolio				112,000
Expected principal cash flows of contractually required acquired loan portfolio				481,000
Expected interest cash flows of contractually required acquired loan portfolio				104,000
Nonaccretable difference				34,000
Expected credit losses				$ 26,000
Accretable yield								0	110,003
Outstanding contractual principal balance of acquired loan portfolio							361,000	361,000	485,000
Carrying amount of acquired loan portfolio							330,000	330,000	452,000
Business Combination, Provision Information, Initial Accounting Incomplete, Goodwill							200	300
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment							300
Business Combination, Provisional Information, Initial Accounting Incomplete, Deferred Income Tax Assets							100
Independent Bank [Member]
Business Acquisition [Line Items]
Acquisition purchase price					$ 8,100
Number of branches acquired (branches) | Branches					21
Deposits acquired					$ 404,000
Loans acquired					44,000
Premium paid on deposits purchased					$ 11,500
Premium paid as a percent of deposits purchased (percent)					2.85%
Discount on loans purchased (percent)					1.75%
Goodwill					$ 6,800
Intangibles acquired					5,600
OAK [Member]
Business Acquisition [Line Items]
Acquisition purchase price						$ 83,700
Goodwill						43,500
Intangibles acquired						$ 9,800
Service provided by acquiree bank through number of branches | Offices						14
Assets of acquiree company						$ 820,000
Fair value of loans acquired in acquisition						627,000
Deposits of acquiree company						693,000
Brokered deposits of acquiree company						$ 193,000
Accretable yield								0	0
Outstanding contractual principal balance of acquired loan portfolio							204,000	204,000	268,000
Carrying amount of acquired loan portfolio							$ 183,000	$ 183,000	246,000
Reclassification from nonaccretable difference									$ 10,000
Core deposit intangible assets [Member] | Independent Bank [Member]
Business Acquisition [Line Items]
Intangibles acquired					$ 5,600
Talmer Bancorp, Inc. [Member] | Talmer Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Common stock exchange ratio	0.4725
Acquisition purchase price	$ 1,100,000
Cash purchase price per share | $ / shares	$ 1.61
Service provided by acquiree bank through number of branches | Offices	81
Assets of acquiree company	$ 6,600,000
Fair value of loans acquired in acquisition	4,800,000
Deposits of acquiree company	5,000,000
Brokered deposits of acquiree company	$ 229,000

Investment Securities (Summary

Investment Securities (Summary of Amortized Cost and Fair Value of Available-for-Sale Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	$ 556,636	$ 749,187
Investment securities available-for-sale, Unrealized Gains	(1,468)	(3,003)
Investment securities available-for-sale, Unrealized Losses	(4,373)	(3,326)
Available-for-sale, at fair value	553,731	748,864
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	5,773	8,272
Investment securities available-for-sale, Unrealized Gains	0	0
Investment securities available-for-sale, Unrealized Losses	(8)	(13)
Available-for-sale, at fair value	5,765	8,259
Government sponsored agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	195,711	263,658
Investment securities available-for-sale, Unrealized Gains	(78)	(356)
Investment securities available-for-sale, Unrealized Losses	(800)	(511)
Available-for-sale, at fair value	194,989	263,503
State and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	14,731	45,157
Investment securities available-for-sale, Unrealized Gains	(395)	(1,087)
Investment securities available-for-sale, Unrealized Losses	(6)	(17)
Available-for-sale, at fair value	15,120	46,227
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	189,452	240,465
Investment securities available-for-sale, Unrealized Gains	(538)	(885)
Investment securities available-for-sale, Unrealized Losses	(2,222)	(1,543)
Available-for-sale, at fair value	187,768	239,807
Collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	133,256	145,316
Investment securities available-for-sale, Unrealized Gains	(111)	(261)
Investment securities available-for-sale, Unrealized Losses	(1,137)	(1,194)
Available-for-sale, at fair value	132,230	144,383
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	14,825	44,930
Investment securities available-for-sale, Unrealized Gains	(2)	(213)
Investment securities available-for-sale, Unrealized Losses	(200)	(48)
Available-for-sale, at fair value	14,627	45,095
Preferred stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available-for-sale, Amortized Cost	2,888	1,389
Investment securities available-for-sale, Unrealized Gains	(344)	(201)
Investment securities available-for-sale, Unrealized Losses	0	0
Available-for-sale, at fair value	$ 3,232	$ 1,590

Investment Securities (Summar71

Investment Securities (Summary of Amortized Cost and Fair Value of Held-to-Maturity Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Held-to-maturity Securities
Investment securities held-to-maturity, Amortized Cost	$ 509,971	$ 316,413
Investment securities held-to-maturity, Unrealized Gains	(7,446)	(7,294)
Investment securities held-to-maturity, Unrealized Losses	4,712	7,967
Held-to-maturity Securities, Fair Value	512,705	315,740
State and political subdivisions [Member]
Held-to-maturity Securities
Investment securities held-to-maturity, Amortized Cost	509,471	305,913
Investment securities held-to-maturity, Unrealized Gains	(7,446)	(7,294)
Investment securities held-to-maturity, Unrealized Losses	4,512	4,557
Held-to-maturity Securities, Fair Value	512,405	308,650
Trust preferred securities [Member]
Held-to-maturity Securities
Investment securities held-to-maturity, Amortized Cost	500	10,500
Investment securities held-to-maturity, Unrealized Gains	0	0
Investment securities held-to-maturity, Unrealized Losses	200	3,410
Held-to-maturity Securities, Fair Value	$ 300	$ 7,090

Investment Securities (Summar72

Investment Securities (Summary of the Amortized Cost and Fair Value of Investment Securities by Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investment Securities Available-for-Sale:
Due in one year or less, Amortized Cost	$ 170,838
Due after one year through five years, Amortized Cost	326,018
Due after five years through ten years, Amortized Cost	53,317
Due after ten years, Amortized Cost	5,074
Preferred stock, Amortized Cost	1,389
Total Available-for-sale Securities, Amortized Cost	556,636
Due in one year or less , Fair Value	170,098
Due after one year through five years, Fair Value	324,187
Due after five years through ten years, Fair Value	52,649
Due after ten years, Fair Value	5,064
Preferred stock, Fair Value	1,733
Total Available-for-sale securities, Fair Value	553,731
Investment Securities Held-to-Maturity:
Due in one year or less, Amortized Cost	59,834
Due after one year through five years, Amortized Cost	236,141
Due after five years through ten years, Amortized Cost	136,383
Due after ten years, Amortized Cost	77,613
Total Held-to-maturity securities, Amortized Cost	509,971	$ 316,413
Due in one year or less , Fair Value	59,938
Due after one year through five years, Fair Value	236,491
Due after five years through ten years, Fair Value	137,188
Due after ten years, Fair Value	79,088
Total Held-to-maturity securities, Fair Value	$ 512,705	$ 315,740

Investment Securities (Summar73

Investment Securities (Summary of Investment Securities with Gross Unrealized Losses) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 554,907	$ 317,885
Less Than 12 Months, Gross Unrealized Losses	5,945	3,998
12 Months or More, Fair Value	133,159	302,630
12 Months or More, Gross Unrealized Losses	3,140	7,295
Total, Fair Value	688,066	620,515
Total, Gross Unrealized Losses	9,085	11,293
US Treasury Securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	5,765	8,259
Less Than 12 Months, Gross Unrealized Losses	8	13
12 Months or More, Fair Value	0	0
12 Months or More, Gross Unrealized Losses	0	0
Total, Fair Value	5,765	8,259
Total, Gross Unrealized Losses	8	13
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	114,640	166,963
Less Than 12 Months, Gross Unrealized Losses	292	406
12 Months or More, Fair Value	21,681	31,927
12 Months or More, Gross Unrealized Losses	508	105
Total, Fair Value	136,321	198,890
Total, Gross Unrealized Losses	800	511
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	195,285	62,310
Less Than 12 Months, Gross Unrealized Losses	2,891	3,348
12 Months or More, Fair Value	68,361	36,847
12 Months or More, Gross Unrealized Losses	1,627	1,226
Total, Fair Value	263,646	99,157
Total, Gross Unrealized Losses	4,518	4,574
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	169,226	17,276
Less Than 12 Months, Gross Unrealized Losses	2,146	52
12 Months or More, Fair Value	3,435	180,194
12 Months or More, Gross Unrealized Losses	76	1,491
Total, Fair Value	172,661	197,470
Total, Gross Unrealized Losses	2,222	1,543
Collateralized mortgage obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	60,459	63,077
Less Than 12 Months, Gross Unrealized Losses	408	179
12 Months or More, Fair Value	39,382	31,620
12 Months or More, Gross Unrealized Losses	729	1,015
Total, Fair Value	99,841	94,697
Total, Gross Unrealized Losses	1,137	1,194
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	9,532	0
Less Than 12 Months, Gross Unrealized Losses	200	0
12 Months or More, Fair Value	0	14,952
12 Months or More, Gross Unrealized Losses	0	48
Total, Fair Value	9,532	14,952
Total, Gross Unrealized Losses	200	48
Trust preferred securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	0	0
Less Than 12 Months, Gross Unrealized Losses	0	0
12 Months or More, Fair Value	300	7,090
12 Months or More, Gross Unrealized Losses	200	3,410
Total, Fair Value	300	7,090
Total, Gross Unrealized Losses	$ 200	$ 3,410

Investment Securities (Textual)

Investment Securities (Textual) (Details) - USD ($) $ in Millions	Dec. 31, 2015	May. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Trust preferred investment securities held to maturity	$ 10.5
Trust preferred investment security of non public bank company		$ 10
Securities pledged as collateral	$ 516		$ 493

Loans (Summary of Loans) (Detai

Loans (Summary of Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of loans under portfolio
Commercial loan	$ 4,250,117	$ 3,084,024
Consumer loan	3,021,030	2,604,206
Total loans	7,271,147	5,688,230
Commercial [Member]
Summary of loans under portfolio
Commercial loan	1,905,879	1,354,881
Real estate commercial [Member]
Summary of loans under portfolio
Commercial loan	2,112,162	1,557,648
Real estate construction [Member]
Summary of loans under portfolio
Commercial loan	210,231	152,745
Land development [Member]
Summary of loans under portfolio
Commercial loan	21,845	18,750
Real estate residential [Member]
Summary of loans under portfolio
Consumer loan	1,429,636	1,110,390
Consumer installment [Member]
Summary of loans under portfolio
Consumer loan	877,457	829,570
Home equity [Member]
Summary of loans under portfolio
Consumer loan	$ 713,937	$ 664,246

Loans (Summary of Recorded Inve

Loans (Summary of Recorded Investment of Commercial Loans by Risk Rating Categories) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	$ 4,250,117	$ 3,084,024
Commercial [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,905,879	1,354,881
Real estate commercial [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	2,112,162	1,557,648
Real estate construction [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	210,231	152,745
Land development [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	21,845	18,750
Originated Portfolio [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	3,130,721	2,603,592
Originated Portfolio [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	2,942,826	2,423,966
Originated Portfolio [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	65,943	74,942
Originated Portfolio [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	67,714	62,913
Originated Portfolio [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	52,143	41,762
Originated Portfolio [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	2,095	9
Originated Portfolio [Member] | Commercial [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,521,515	1,255,898
Originated Portfolio [Member] | Commercial [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,418,301	1,171,817
Originated Portfolio [Member] | Commercial [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	34,727	37,800
Originated Portfolio [Member] | Commercial [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	39,933	29,863
Originated Portfolio [Member] | Commercial [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	26,459	16,417
Originated Portfolio [Member] | Commercial [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	2,095	1
Originated Portfolio [Member] | Real estate commercial [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,424,059	1,204,426
Originated Portfolio [Member] | Real estate commercial [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,341,202	1,114,529
Originated Portfolio [Member] | Real estate commercial [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	31,036	34,996
Originated Portfolio [Member] | Real estate commercial [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	26,658	29,935
Originated Portfolio [Member] | Real estate commercial [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	25,163	24,958
Originated Portfolio [Member] | Real estate commercial [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	8
Originated Portfolio [Member] | Real estate construction [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	174,546	138,740
Originated Portfolio [Member] | Real estate construction [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	173,828	134,668
Originated Portfolio [Member] | Real estate construction [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	180	1,408
Originated Portfolio [Member] | Real estate construction [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	291	2,502
Originated Portfolio [Member] | Real estate construction [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	247	162
Originated Portfolio [Member] | Real estate construction [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Originated Portfolio [Member] | Land development [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	10,601	4,528
Originated Portfolio [Member] | Land development [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	9,495	2,952
Originated Portfolio [Member] | Land development [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	738
Originated Portfolio [Member] | Land development [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	832	613
Originated Portfolio [Member] | Land development [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	274	225
Originated Portfolio [Member] | Land development [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,119,396	480,432
Acquired Portfolio [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,011,895	423,592
Acquired Portfolio [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	54,803	21,968
Acquired Portfolio [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	43,119	16,764
Acquired Portfolio [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	9,579	18,108
Acquired Portfolio [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member] | Commercial [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	384,364	98,983
Acquired Portfolio [Member] | Commercial [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	340,782	76,780
Acquired Portfolio [Member] | Commercial [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	28,321	12,687
Acquired Portfolio [Member] | Commercial [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	11,607	4,089
Acquired Portfolio [Member] | Commercial [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	3,654	5,427
Acquired Portfolio [Member] | Commercial [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member] | Real estate commercial [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	688,103	353,222
Acquired Portfolio [Member] | Real estate commercial [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	629,430	321,018
Acquired Portfolio [Member] | Real estate commercial [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	23,926	8,698
Acquired Portfolio [Member] | Real estate commercial [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	29,975	12,478
Acquired Portfolio [Member] | Real estate commercial [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	4,772	11,028
Acquired Portfolio [Member] | Real estate commercial [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member] | Real estate construction [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	35,685	14,005
Acquired Portfolio [Member] | Real estate construction [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	35,685	14,005
Acquired Portfolio [Member] | Real estate construction [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member] | Real estate construction [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member] | Real estate construction [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member] | Real estate construction [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	0	0
Acquired Portfolio [Member] | Land development [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	11,244	14,222
Acquired Portfolio [Member] | Land development [Member] | Risk Grades 1-5 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	5,998	11,789
Acquired Portfolio [Member] | Land development [Member] | Risk Grade 6 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	2,556	583
Acquired Portfolio [Member] | Land development [Member] | Risk Grade 7 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,537	197
Acquired Portfolio [Member] | Land development [Member] | Risk Grade 8 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	1,153	1,653
Acquired Portfolio [Member] | Land development [Member] | Risk Grade 9 [Member]
Recorded investment of loans in commercial loan portfolio by risk rating categories
Recorded investment (loan balance), Commercial, Total	$ 0	$ 0

Loans (Summary of Recorded In77

Loans (Summary of Recorded Investment of Consumer Loans by Risk Rating Categories) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	$ 3,021,030	$ 2,604,206
Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	1,429,636	1,110,390
Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	877,457	829,570
Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	713,937	664,246
Originated Portfolio [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	2,677,213	2,386,475
Originated Portfolio [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	1,216,975	998,001
Originated Portfolio [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	869,426	819,378
Originated Portfolio [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	590,812	569,096
Originated Portfolio [Member] | Performing [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	2,664,486	2,372,503
Originated Portfolio [Member] | Performing [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	1,207,945	987,542
Originated Portfolio [Member] | Performing [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	868,975	818,878
Originated Portfolio [Member] | Performing [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	587,566	566,083
Originated Portfolio [Member] | Nonperforming [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	12,727	13,972
Originated Portfolio [Member] | Nonperforming [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	9,030	10,459
Originated Portfolio [Member] | Nonperforming [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	451	500
Originated Portfolio [Member] | Nonperforming [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	3,246	3,013
Acquired Portfolio [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	343,817	217,731
Acquired Portfolio [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	212,661	112,389
Acquired Portfolio [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	8,031	10,192
Acquired Portfolio [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	123,125	95,150
Acquired Portfolio [Member] | Performing [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	340,682	215,971
Acquired Portfolio [Member] | Performing [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	210,580	111,101
Acquired Portfolio [Member] | Performing [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	7,984	10,174
Acquired Portfolio [Member] | Performing [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	122,118	94,696
Acquired Portfolio [Member] | Nonperforming [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	3,135	1,760
Acquired Portfolio [Member] | Nonperforming [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	2,081	1,288
Acquired Portfolio [Member] | Nonperforming [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	47	18
Acquired Portfolio [Member] | Nonperforming [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	$ 1,007	$ 454

(Summary of nonperforming loans

(Summary of nonperforming loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of nonperforming loans
Total nonperforming TDRs	$ 103,111	$ 101,322
Total loans	7,271,147	5,688,230
Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	62,225	50,644
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,287	2,073
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	78,823	77,047
Total loans	4,250,117	3,084,024
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	24,288	24,275
Total loans	3,021,030	2,604,206
Commercial [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	28,554	16,418
Total accruing loans contractually past due 90 days or more as to interest or principal payments	364	170
Real estate commercial [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	25,163	24,966
Total accruing loans contractually past due 90 days or more as to interest or principal payments	254	0
Real Estate Construction Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	247	162
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0
Land Development Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	274	225
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0
Real estate residential [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	5,557	6,706
Total accruing loans contractually past due 90 days or more as to interest or principal payments	402	557
Consumer Installment Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	451	500
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0
Home Equity Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	1,979	1,667
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,267	1,346
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	62,225	50,644
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,287	2,073
Total nonperforming TDRs	19,368	18,467
Total loans	83,880	71,184
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	16,297	15,271
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	3,071	3,196
Nonperforming [Member] | Commercial [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	28,554	16,418
Total accruing loans contractually past due 90 days or more as to interest or principal payments	364	170
Nonperforming [Member] | Real estate commercial [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	25,163	24,966
Total accruing loans contractually past due 90 days or more as to interest or principal payments	254	0
Nonperforming [Member] | Real Estate Construction Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	247	162
Nonperforming [Member] | Land Development Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	274	225
Nonperforming [Member] | Real estate residential [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	5,557	6,706
Total accruing loans contractually past due 90 days or more as to interest or principal payments	402	557
Nonperforming [Member] | Consumer Installment Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	451	500
Nonperforming [Member] | Home Equity Loans [Member] | Originated Portfolio Segment [Member]
Summary of nonperforming loans
Total nonaccrual loans	1,979	1,667
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 1,267	$ 1,346

Loans (Summary of Impaired Loan

Loans (Summary of Impaired Loans by Classes of Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Impaired loans with a valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	$ 44,383	$ 23,234
Unpaid Principal Balance	45,151	23,648
Related Valuation Allowance	6,389	1,338
Average Annual Recorded Investment	33,090	25,556
Interest Income Recognized While on Impaired Status	1,312	1,252
Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	97,815	111,433
Unpaid Principal Balance	122,367	141,622
Related Valuation Allowance	0	0
Average Annual Recorded Investment	102,640	102,320
Interest Income Recognized While on Impaired Status	3,628	3,101
Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	142,198	134,667
Unpaid Principal Balance	167,518	165,270
Related Valuation Allowance	6,389	1,338
Average Annual Recorded Investment	135,730	127,876	$ 121,000
Interest Income Recognized While on Impaired Status	4,940	4,353	3,800
Commercial [Member] | Impaired loans with a valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	18,898	966
Unpaid Principal Balance	19,426	1,040
Related Valuation Allowance	5,700	293
Average Annual Recorded Investment	9,511	2,117
Interest Income Recognized While on Impaired Status	0	0
Commercial [Member] | Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	31,039	38,094
Unpaid Principal Balance	37,703	44,557
Related Valuation Allowance	0	0
Average Annual Recorded Investment	32,172	39,020
Interest Income Recognized While on Impaired Status	1,303	1,375
Commercial [Member] | Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	49,937	39,060
Unpaid Principal Balance	57,129	45,597
Related Valuation Allowance	5,700	293
Average Annual Recorded Investment	41,683	41,137	29,600
Interest Income Recognized While on Impaired Status	1,303	1,375	1,000
Real estate commercial [Member] | Impaired loans with a valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	4,448	2,587
Unpaid Principal Balance	4,688	2,927
Related Valuation Allowance	497	710
Average Annual Recorded Investment	2,918	3,699
Interest Income Recognized While on Impaired Status	0	0
Real estate commercial [Member] | Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	53,518	60,616
Unpaid Principal Balance	69,130	82,693
Related Valuation Allowance	0	0
Average Annual Recorded Investment	56,562	49,676
Interest Income Recognized While on Impaired Status	1,985	1,567
Real estate commercial [Member] | Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	57,966	63,203
Unpaid Principal Balance	73,818	85,620
Related Valuation Allowance	497	710
Average Annual Recorded Investment	59,480	53,375	50,800
Interest Income Recognized While on Impaired Status	1,985	1,567	1,300
Real estate construction [Member] | Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	400	162
Unpaid Principal Balance	480	255
Related Valuation Allowance	0	0
Average Annual Recorded Investment	457	164
Interest Income Recognized While on Impaired Status	11	0
Real estate construction [Member] | Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	400	162
Unpaid Principal Balance	480	255
Related Valuation Allowance	0	0
Average Annual Recorded Investment	457	164	400
Interest Income Recognized While on Impaired Status	11	0
Land development [Member] | Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	1,736	1,928
Unpaid Principal Balance	2,628	3,484
Related Valuation Allowance	0	0
Average Annual Recorded Investment	1,768	3,551
Interest Income Recognized While on Impaired Status	104	131
Land development [Member] | Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	1,736	1,928
Unpaid Principal Balance	2,628	3,484
Related Valuation Allowance	0	0
Average Annual Recorded Investment	1,768	3,551	9,800
Interest Income Recognized While on Impaired Status	104	131	300
Real estate residential [Member] | Impaired loans with a valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	21,037	19,681
Unpaid Principal Balance	21,037	19,681
Related Valuation Allowance	192	335
Average Annual Recorded Investment	20,661	19,740
Interest Income Recognized While on Impaired Status	1,312	1,252
Real estate residential [Member] | Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	7,638	7,994
Unpaid Principal Balance	8,644	7,994
Related Valuation Allowance	0	0
Average Annual Recorded Investment	8,465	7,005
Interest Income Recognized While on Impaired Status	165	15
Real estate residential [Member] | Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	28,675	27,675
Unpaid Principal Balance	29,681	27,675
Related Valuation Allowance	192	335
Average Annual Recorded Investment	29,126	26,745	26,800
Interest Income Recognized While on Impaired Status	1,477	1,267	1,100
Consumer installment [Member] | Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	498	518
Unpaid Principal Balance	512	518
Related Valuation Allowance	0	0
Average Annual Recorded Investment	480	602
Interest Income Recognized While on Impaired Status	2	1
Consumer installment [Member] | Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	498	518
Unpaid Principal Balance	512	518
Related Valuation Allowance	0	0
Average Annual Recorded Investment	480	602	700
Interest Income Recognized While on Impaired Status	2	1
Home equity [Member] | Impaired loans with no valuation allowance [Member]
Schedule of Impaired loans by classes
Recorded Investment	2,986	2,121
Unpaid Principal Balance	3,270	2,121
Related Valuation Allowance	0	0
Average Annual Recorded Investment	2,736	2,302
Interest Income Recognized While on Impaired Status	58	12
Home equity [Member] | Total Impaired Loans [Member]
Schedule of Impaired loans by classes
Recorded Investment	2,986	2,121
Unpaid Principal Balance	3,270	2,121
Related Valuation Allowance	0	0
Average Annual Recorded Investment	2,736	2,302	$ 2,900
Interest Income Recognized While on Impaired Status	$ 58	$ 12

Loans (Summary of the Aging Sta

Loans (Summary of the Aging Status of the Recorded Investment in Loans by Portfolio Segment/Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Originated Portfolio [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	$ 14,502	$ 20,595
Financing receivable, recorded investment 61 to 89 days past due	4,265	3,352
Financing receivable, recorded investment accruing loans past due 90 days or more	2,287	2,073
Financing receivable, recorded investment, Non-accrual loans	62,225	50,644
Financing receivable recorded investment, Total past due	83,279	76,664
Financing receivable, recorded investment, Current	5,724,655	4,913,403
Financing receivable, recorded investment, Total loans	5,807,934	4,990,067
Originated Portfolio [Member] | Commercial [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	3,685	4,033
Financing receivable, recorded investment 61 to 89 days past due	1,230	743
Financing receivable, recorded investment accruing loans past due 90 days or more	364	170
Financing receivable, recorded investment, Non-accrual loans	28,554	16,418
Financing receivable recorded investment, Total past due	33,833	21,364
Financing receivable, recorded investment, Current	1,487,682	1,234,534
Financing receivable, recorded investment, Total loans	1,521,515	1,255,898
Originated Portfolio [Member] | Real estate commercial [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	4,168	7,515
Financing receivable, recorded investment 61 to 89 days past due	1,603	1,383
Financing receivable, recorded investment accruing loans past due 90 days or more	254	0
Financing receivable, recorded investment, Non-accrual loans	25,163	24,966
Financing receivable recorded investment, Total past due	31,188	33,864
Financing receivable, recorded investment, Current	1,392,871	1,170,562
Financing receivable, recorded investment, Total loans	1,424,059	1,204,426
Originated Portfolio [Member] | Real estate construction [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	0	262
Financing receivable, recorded investment 61 to 89 days past due	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0
Financing receivable, recorded investment, Non-accrual loans	247	162
Financing receivable recorded investment, Total past due	247	424
Financing receivable, recorded investment, Current	174,299	138,316
Financing receivable, recorded investment, Total loans	174,546	138,740
Originated Portfolio [Member] | Land development [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	0	0
Financing receivable, recorded investment 61 to 89 days past due	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0
Financing receivable, recorded investment, Non-accrual loans	274	225
Financing receivable recorded investment, Total past due	274	225
Financing receivable, recorded investment, Current	10,327	4,303
Financing receivable, recorded investment, Total loans	10,601	4,528
Originated Portfolio [Member] | Real estate residential [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	1,737	2,126
Financing receivable, recorded investment 61 to 89 days past due	0	54
Financing receivable, recorded investment accruing loans past due 90 days or more	402	557
Financing receivable, recorded investment, Non-accrual loans	5,557	6,706
Financing receivable recorded investment, Total past due	7,696	9,443
Financing receivable, recorded investment, Current	1,209,279	988,558
Financing receivable, recorded investment, Total loans	1,216,975	998,001
Originated Portfolio [Member] | Consumer installment [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	3,145	3,620
Financing receivable, recorded investment 61 to 89 days past due	644	512
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0
Financing receivable, recorded investment, Non-accrual loans	451	500
Financing receivable recorded investment, Total past due	4,240	4,632
Financing receivable, recorded investment, Current	865,186	814,746
Financing receivable, recorded investment, Total loans	869,426	819,378
Originated Portfolio [Member] | Home equity [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	1,767	3,039
Financing receivable, recorded investment 61 to 89 days past due	788	660
Financing receivable, recorded investment accruing loans past due 90 days or more	1,267	1,346
Financing receivable, recorded investment, Non-accrual loans	1,979	1,667
Financing receivable recorded investment, Total past due	5,801	6,712
Financing receivable, recorded investment, Current	585,011	562,384
Financing receivable, recorded investment, Total loans	590,812	569,096
Acquired Portfolio [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	6,319	2,994
Financing receivable, recorded investment 61 to 89 days past due	1,301	461
Financing receivable, recorded investment accruing loans past due 90 days or more	12,795	19,892
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	20,415	23,347
Financing receivable, recorded investment, Current	1,442,798	674,816
Financing receivable, recorded investment, Total loans	1,463,213	698,163
Acquired Portfolio [Member] | Commercial [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	490	133
Financing receivable, recorded investment 61 to 89 days past due	532	0
Financing receivable, recorded investment accruing loans past due 90 days or more	3,735	5,427
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	4,757	5,560
Financing receivable, recorded investment, Current	379,607	93,423
Financing receivable, recorded investment, Total loans	384,364	98,983
Acquired Portfolio [Member] | Real estate commercial [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	3,557	2,014
Financing receivable, recorded investment 61 to 89 days past due	691	352
Financing receivable, recorded investment accruing loans past due 90 days or more	4,771	11,052
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	9,019	13,418
Financing receivable, recorded investment, Current	679,084	339,804
Financing receivable, recorded investment, Total loans	688,103	353,222
Acquired Portfolio [Member] | Real estate construction [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	0	0
Financing receivable, recorded investment 61 to 89 days past due	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	0	0
Financing receivable, recorded investment, Current	35,685	14,005
Financing receivable, recorded investment, Total loans	35,685	14,005
Acquired Portfolio [Member] | Land development [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	0	0
Financing receivable, recorded investment 61 to 89 days past due	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	1,154	1,653
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	1,154	1,653
Financing receivable, recorded investment, Current	10,090	12,569
Financing receivable, recorded investment, Total loans	11,244	14,222
Acquired Portfolio [Member] | Real estate residential [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	1,370	156
Financing receivable, recorded investment 61 to 89 days past due	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	2,081	18
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	3,451	174
Financing receivable, recorded investment, Current	209,210	112,215
Financing receivable, recorded investment, Total loans	212,661	112,389
Acquired Portfolio [Member] | Consumer installment [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	55	55
Financing receivable, recorded investment 61 to 89 days past due	0	3
Financing receivable, recorded investment accruing loans past due 90 days or more	47	454
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	102	512
Financing receivable, recorded investment, Current	7,929	9,680
Financing receivable, recorded investment, Total loans	8,031	10,192
Acquired Portfolio [Member] | Home equity [Member]
Schedule representing the aging status of the recorded investment in loans by classes
Financing receivable, recorded investment 31 to 60 days past due	847	636
Financing receivable, recorded investment 61 to 89 days past due	78	106
Financing receivable, recorded investment accruing loans past due 90 days or more	1,007	1,288
Financing receivable, recorded investment, Non-accrual loans	0	0
Financing receivable recorded investment, Total past due	1,932	2,030
Financing receivable, recorded investment, Current	121,193	93,120
Financing receivable, recorded investment, Total loans	$ 123,125	$ 95,150

Loans (Summary of TDRs) (Detail

Loans (Summary of TDRs) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of corporation's TDRs
Total TDRs	$ 103,111	$ 101,322
Commercial Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	78,823	77,047
Consumer Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	24,288	24,275
Performing [Member]
Schedule of corporation's TDRs
Total TDRs	47,810	45,664
Performing [Member] | Commercial Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	29,844	29,179
Performing [Member] | Consumer Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	17,966	16,485
Nonperforming [Member]
Schedule of corporation's TDRs
Total TDRs	19,368	18,467
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	16,297	15,271
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	3,071	3,196
Substandard Nonaccrual [Member]
Schedule of corporation's TDRs
Total TDRs	35,933	37,191
Substandard Nonaccrual [Member] | Commercial Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	32,682	32,597
Substandard Nonaccrual [Member] | Consumer Loan Portfolio [Member]
Schedule of corporation's TDRs
Total TDRs	$ 3,251	$ 4,594

Loans (Summary of Performing an

Loans (Summary of Performing and Nonperforming TDRs Modified During the Period) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)Loans	Dec. 31, 2014USD ($)Loans	Dec. 31, 2013USD ($)Loans
Commercial Loan Portfolio [Member]
Schedule providing information on performing and nonperforming TDRs
Performing and nonperforming modified TDRs, Number of loans | Loans	142	219	199
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$ 22,596	$ 30,112	$ 35,821
Performing and nonperforming modified TDRs, Post-modification recorded investment	$ 22,594	$ 30,086	$ 35,718
Commercial [Member] | Commercial Loan Portfolio [Member]
Schedule providing information on performing and nonperforming TDRs
Performing and nonperforming modified TDRs, Number of loans | Loans	53	53	57
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$ 11,446	$ 13,781	$ 12,123
Performing and nonperforming modified TDRs, Post-modification recorded investment	$ 11,446	$ 13,781	$ 12,123
Real estate commercial [Member] | Commercial Loan Portfolio [Member]
Schedule providing information on performing and nonperforming TDRs
Performing and nonperforming modified TDRs, Number of loans | Loans	21	46	49
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$ 7,196	$ 12,075	$ 16,222
Performing and nonperforming modified TDRs, Post-modification recorded investment	$ 7,196	$ 12,075	$ 16,222
Real Estate Construction Loans [Member] | Commercial Loan Portfolio [Member]
Schedule providing information on performing and nonperforming TDRs
Performing and nonperforming modified TDRs, Number of loans | Loans	2	0	4
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$ 400	$ 0	$ 575
Performing and nonperforming modified TDRs, Post-modification recorded investment	$ 400	$ 0	$ 575
Land development [Member] | Commercial Loan Portfolio [Member]
Schedule providing information on performing and nonperforming TDRs
Performing and nonperforming modified TDRs, Number of loans | Loans	1	1	4
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$ 305	$ 72	$ 1,958
Performing and nonperforming modified TDRs, Post-modification recorded investment	$ 305	$ 72	$ 1,958
Commercial loan portfolio [Member] | Commercial Loan Portfolio [Member]
Schedule providing information on performing and nonperforming TDRs
Performing and nonperforming modified TDRs, Number of loans | Loans	77	100	114
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$ 19,347	$ 25,928	$ 30,878
Performing and nonperforming modified TDRs, Post-modification recorded investment	$ 19,347	$ 25,928	$ 30,878
Consumer loan portfolio (real estate residential) [Member] | Consumer Portfolio Segment [Member]
Schedule providing information on performing and nonperforming TDRs
Performing and nonperforming modified TDRs, Number of loans | Loans	65	119	85
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$ 3,249	$ 4,184	$ 4,943
Performing and nonperforming modified TDRs, Post-modification recorded investment	$ 3,247	$ 4,158	$ 4,840

Loans (Summary of TDRs with a P

Loans (Summary of TDRs with a Payment Default During the Period) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)Loans	Dec. 31, 2014USD ($)Loans	Dec. 31, 2013USD ($)Loans
Troubled debt restructurings on financing receivables with defaults payment
Financing receivable modifications subsequent default number of loans | Loans	9	25	58
Financing receivable modification subsequent default recorded investment | $	$ 2,287	$ 3,496	$ 10,746
Commercial [Member] | Commercial Loan Portfolio [Member]
Troubled debt restructurings on financing receivables with defaults payment
Financing receivable modifications subsequent default number of loans | Loans	1	7	23
Financing receivable modification subsequent default recorded investment | $	$ 1,206	$ 885	$ 2,745
Real estate commercial [Member] | Commercial Loan Portfolio [Member]
Troubled debt restructurings on financing receivables with defaults payment
Financing receivable modifications subsequent default number of loans | Loans	5	6	8
Financing receivable modification subsequent default recorded investment | $	$ 1,016	$ 2,352	$ 4,278
Real Estate Construction Loans [Member] | Commercial Loan Portfolio [Member]
Troubled debt restructurings on financing receivables with defaults payment
Financing receivable modifications subsequent default number of loans | Loans	0	0	3
Financing receivable modification subsequent default recorded investment | $	$ 0	$ 0	$ 371
Land Development Loans [Member] | Commercial Loan Portfolio [Member]
Troubled debt restructurings on financing receivables with defaults payment
Financing receivable modifications subsequent default number of loans | Loans	0	0	2
Financing receivable modification subsequent default recorded investment | $	$ 0	$ 0	$ 1,526
Commercial loan portfolio [Member] | Commercial Loan Portfolio [Member]
Troubled debt restructurings on financing receivables with defaults payment
Financing receivable modifications subsequent default number of loans | Loans	6	13	36
Financing receivable modification subsequent default recorded investment | $	$ 2,222	$ 3,237	$ 8,920
Consumer loan portfolio (real estate residential) [Member] | Consumer Portfolio Segment [Member]
Troubled debt restructurings on financing receivables with defaults payment
Financing receivable modifications subsequent default number of loans | Loans	3	12	22
Financing receivable modification subsequent default recorded investment | $	$ 65	$ 259	$ 1,826

Loans (Schedule of the Allowanc

Loans (Schedule of the Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	$ 75,683	$ 79,072
Provision for loan losses	(6,500)	(6,100)
Charge-offs	(13,501)	(14,229)
Recoveries	4,646	4,740
Ending balance	73,328	75,683
Allowance for loan losses
Loans individually evaluated for impairment related to allowance for loan losses			$ 6,389	$ 1,338
Loans collectively evaluated for impairment related to allowance for loan losses			66,939	73,845
Total	75,683	79,072	73,328	75,683
Loans individually evaluated for impairment related to recorded investment (loan balance)			121,416	105,902
Loans collectively evaluated for impairment related to recorded investment (loan balance)			5,686,518	4,884,165
Total loans			7,271,147	5,688,230
Commercial Loan Portfolio [Member]
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	44,156	44,482
Provision for loan losses	(7,275)	(3,464)
Charge-offs	(6,385)	(6,399)
Recoveries	2,188	2,609
Ending balance	47,234	44,156
Allowance for loan losses
Loans individually evaluated for impairment related to allowance for loan losses			6,197	1,003
Loans collectively evaluated for impairment related to allowance for loan losses			41,037	43,153
Total	44,156	44,482	47,234	44,156
Loans individually evaluated for impairment related to recorded investment (loan balance)			100,379	86,221
Loans collectively evaluated for impairment related to recorded investment (loan balance)			3,030,342	2,517,371
Total loans			4,250,117	3,084,024
Consumer Loan Portfolio [Member]
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	28,803	30,145
Provision for loan losses	(1,949)	(4,357)
Charge-offs	(7,116)	(7,830)
Recoveries	2,458	2,131
Ending balance	26,094	28,803
Allowance for loan losses
Loans individually evaluated for impairment related to allowance for loan losses			192	335
Loans collectively evaluated for impairment related to allowance for loan losses			25,902	27,968
Total	28,803	30,145	26,094	28,803
Loans individually evaluated for impairment related to recorded investment (loan balance)			21,037	19,681
Loans collectively evaluated for impairment related to recorded investment (loan balance)			2,656,176	2,366,794
Total loans			3,021,030	2,604,206
Unallocated [Member]
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment
Beginning balance	2,724	4,445
Provision for loan losses	2,724	1,721
Charge-offs	0	0
Recoveries	0	0
Ending balance	0	2,724
Allowance for loan losses
Loans individually evaluated for impairment related to allowance for loan losses			0	0
Loans collectively evaluated for impairment related to allowance for loan losses			0	2,724
Total	$ 2,724	$ 4,445	0	2,724
Loans individually evaluated for impairment related to recorded investment (loan balance)			0	0
Loans collectively evaluated for impairment related to recorded investment (loan balance)			0	0
Total loans			0	0
Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loan losses
Allowance for loan losses related to loans acquired with deteriorated credit quality			0	500
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)			1,463,213	698,163
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Loan Portfolio [Member]
Allowance for loan losses
Allowance for loan losses related to loans acquired with deteriorated credit quality			0	0
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)			1,119,396	480,432
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Loan Portfolio [Member]
Allowance for loan losses
Allowance for loan losses related to loans acquired with deteriorated credit quality			0	500
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)			343,817	217,731
Receivables Acquired with Deteriorated Credit Quality [Member] | Unallocated [Member]
Allowance for loan losses
Allowance for loan losses related to loans acquired with deteriorated credit quality			0	0
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)			$ 0	$ 0

Loans (Textual) (Details)

Loans (Textual) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)SegmentLoansBaordOfDirectorsTenantsemployee	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual TDRs Reported in Nonaccrual Loans	$ 35,900	$ 37,200
Number of portfolio segment | Segment	2
Number of classes of loans | Loans	7
Minimum number of tenants leased to for non-owner occupied real estate | Tenants	1
Loans held-for-sale, at fair value	$ 10,327	9,128
Number of bank executives and senior officers with credit decision limits similar to group loan authorities | employee	6
Number of members of the board of directors in loan committee | BaordOfDirectors	8
Minimum due period of loans consider in a nonperforming status	90 days
Interest income recognized on nonaccrual loans while in accruing status	$ 900	500	$ 900
Interest lost on nonaccrual loans	3,200	3,300	3,500
Interest income recognized on TDRs	3,900	3,600	3,200
Difference between recorded investment and unpaid principal balance of loan	25,300	30,600
Confirmed losses (partial charge-offs)	17,100	15,400
Fair value of discount adjustment	8,200	15,200
Financing receivable allowance for acquired loans	500
Residential Mortgage Loans in Process of Foreclosure	2,900	2,300
Management [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to directors, executive officers and affiliates	21,700	31,200
Loans to directors, executive officers and affiliates, current year additions	33,300	39,300
Loans to directors, executive officers and affiliates, current year reductions	42,800	34,900
Commercial Loan Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum value of loan requires executive and senior officer approval	1,500
Minimum value of loan requires group loan authority approval	1,000
Maximum value of loan requires group loan authority approval	$ 10,000
Minimum due period of loans consider in a nonperforming status	90 days
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Original contractual terms	90 days
Minimum due period of loans consider in a nonperforming status	90 days
Acquired Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Loans	$ 12,800	19,900
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum value of loan requires group loan authority approval	1,000
Maximum value of loan requires executive and senior officer approval	$ 3,500
Real Estate Residential Loans [Member]
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%
Loans held-for-sale, recorded investment sold	$ 223,000	149,000
Land Development Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum period for payment of loan	12 months
Maximum [Member] | Commercial Loan Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other loans requiring director loan committee approval depending on risk rating and credit action required	$ 10,000
Maximum [Member] | Real Estate Residential Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Upper limit of number of family residential properties | Tenants	4
Minimum [Member] | Commercial Loan Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum value of loans requiring board of directors approval	$ 15,000
Minimum [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum value of loan requiring director loan committee approval	$ 10,000
Minimum [Member] | Real Estate Residential Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower limit of number of family residential properties | Tenants	1
Fixed-Rate Real Estate Residential Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-sale, at fair value	$ 10,300	9,100
Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Loans	47,800	45,700
Total Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	135,730	127,876	121,000
Impaired Financing Receivable, Interest Income, Accrual Method	4,940	4,353	3,800
Impaired Loans	142,198	134,667
Total Impaired Loans [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	41,683	41,137	29,600
Impaired Financing Receivable, Interest Income, Accrual Method	1,303	1,375	1,000
Impaired Loans	49,937	39,060
Total Impaired Loans [Member] | Real Estate Residential Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	29,126	26,745	26,800
Impaired Financing Receivable, Interest Income, Accrual Method	1,477	1,267	1,100
Impaired Loans	28,675	27,675
Total Impaired Loans [Member] | Land Development Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1,768	3,551	9,800
Impaired Financing Receivable, Interest Income, Accrual Method	104	131	300
Impaired Loans	1,736	1,928
Total Impaired Loans [Member] | Real Estate Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	59,480	53,375	50,800
Impaired Financing Receivable, Interest Income, Accrual Method	1,985	1,567	1,300
Impaired Loans	57,966	63,203
Total Impaired Loans [Member] | Real Estate Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	457	164	400
Impaired Financing Receivable, Interest Income, Accrual Method	11	0
Impaired Loans	400	162
Total Impaired Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	480	602	700
Impaired Financing Receivable, Interest Income, Accrual Method	2	1
Impaired Loans	498	518
Total Impaired Loans [Member] | Home Equity Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	2,736	2,302	$ 2,900
Impaired Financing Receivable, Interest Income, Accrual Method	58	12
Impaired Loans	$ 2,986	$ 2,121

Premises and Equipment (Details

Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total Premises and Equipment, Gross	$ 226,699	$ 206,322
Accumulated depreciation	(120,382)	(108,826)
Total Premises and Equipment, Net	106,317	97,496
Land [Member]
Property, Plant and Equipment [Line Items]
Total Premises and Equipment, Gross	28,447	27,402
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total Premises and Equipment, Gross	120,370	110,380
Equipment [Member]
Property, Plant and Equipment [Line Items]
Total Premises and Equipment, Gross	$ 77,882	$ 68,540

Goodwill (Details)

Goodwill (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2015USD ($)	May. 31, 2015USD ($)	Apr. 01, 2015USD ($)	Dec. 31, 2014USD ($)	Oct. 31, 2014USD ($)	Dec. 07, 2012USD ($)Branches
Goodwill [Line Items]
Goodwill	$ 287,393	$ 287,393			$ 180,128
Lake Michigan Financial Corp [Member]
Goodwill [Line Items]
Goodwill			$ 101,621
Business Combination, Provision Information, Initial Accounting Incomplete, Goodwill	700
Monarch Community Bancorp [Member]
Goodwill [Line Items]
Goodwill				$ 5,330
Northwestern Bancorp [Member]
Goodwill [Line Items]
Goodwill	60,300	60,300				$ 60,000
Business Combination, Provision Information, Initial Accounting Incomplete, Goodwill	$ 200	$ 300
Independent Bank [Member]
Goodwill [Line Items]
Goodwill							$ 6,800
Number of branches acquired (branches) | Branches							21

Other Intangible Assets (Net Ca

Other Intangible Assets (Net Carrying Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other intangible assets:
Total other intangible assets	$ 38,104	$ 33,080
Core deposit intangible assets [Member]
Other intangible assets:
Total other intangible assets	26,654	20,863
Mortgage servicing rights [Member]
Other intangible assets:
Total other intangible assets	$ 11,122	$ 12,217	$ 3,423	$ 3,478

Other Intangible Assets (Amorti

Other Intangible Assets (Amortization Expense of Core Deposit Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Carrying amount	$ 38,104	$ 33,080
Amortization and impairment of intangible assets	8,244	3,545	$ 3,492
Core deposit intangible assets [Member]
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Gross original amount	40,055	31,550
Accumulated amortization	13,401	10,687
Carrying amount	26,654	20,863
Amortization and impairment of intangible assets	$ 4,142	$ 2,029

Other Intangible Assets (Carryi

Other Intangible Assets (Carrying and Fair Value of MSRs) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net carrying value, fair value of MSRs and loans Corporation servicing for others
Total other intangible assets	$ 38,104	$ 33,080
Loans serviced for others that have servicing rights capitalized	2,082,899	2,093,140
Mortgage servicing rights [Member]
Net carrying value, fair value of MSRs and loans Corporation servicing for others
Total other intangible assets	11,122	12,217	$ 3,423	$ 3,478
Fair value of MSRs	15,542	14,979
Originated Portfolio [Member]
Net carrying value, fair value of MSRs and loans Corporation servicing for others
Loans serviced for others that have servicing rights capitalized	$ 888,000	$ 881,000

Other Intangible Assets (Activi

Other Intangible Assets (Activity for Capitalized MSRs) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Intangible Assets [Roll Forward]
Total other intangible assets, Balance at beginning of year		$ 33,080
Amortization		(8,244)	$ (3,545)	$ (3,492)
Total other intangible assets, Balance at end of year		38,104	33,080
Valuation Allowance for Impairment of Recognized Servicing Assets, Balance	[1]	0	200	0
Mortgage servicing rights [Member]
Other Intangible Assets [Roll Forward]
Total other intangible assets, Balance at beginning of year		12,217	3,423	3,478
Acquired through acquisitions		1,284	9,235
Additions		1,476	1,075	1,528
Amortization		(4,055)	(1,316)	(1,583)
Change in valuation allowance attributable to mortage servicing assets		200	(200)	0
Total other intangible assets, Balance at end of year		11,122	12,217	3,423
Mortgage servicing rights [Member] | Monarch Community Bancorp [Member]
Other Intangible Assets [Roll Forward]
Additions		$ 1,300
Mortgage servicing rights [Member] | Northwestern Bancorp [Member]
Other Intangible Assets [Roll Forward]
Additions			$ 9,200
Mortgage servicing rights [Member] | OAK [Member]
Other Intangible Assets [Roll Forward]
Acquired through acquisitions				$ 0
[1]	MSRs are stratified into servicing assets originated by the Corporation and those acquired in acquisitions of other institutions and further stratified into relatively homogeneous pools based on products with similar characteristics. The MSR impairment valuation allowance recorded at December 31, 2014 related to impairment within certain pools attributable to the Corporation's servicing portfolio that was acquired in the Northwestern transaction.

Other Intangible Assets (Textua

Other Intangible Assets (Textual) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 31, 2015	Apr. 01, 2015	Oct. 31, 2014	Dec. 07, 2012
Finite-Lived Intangible Assets [Line Items]
Loans serviced for others that have servicing rights capitalized		$ 2,082,899	$ 2,093,140
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Impairment valuation allowance	[1]	0	200	$ 0
Core deposit intangible assets [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
2,016		4,400
2,017		3,800
2,018		3,600
2,019		3,400
2,020		2,900
Thereafter		8,600
Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Asset Additions		1,476	1,075	$ 1,528
Lake Michigan Financial Corp [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Finite-Lived Noncompete Agreements, Gross					$ 600
Monarch Community Bancorp [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired						$ 1,930
Monarch Community Bancorp [Member] | Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Asset Additions		1,300
Northwestern Bancorp [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired							$ 12,891
Northwestern Bancorp [Member] | Mortgage servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Asset Additions			9,200
Independent Bank [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired								$ 5,600
Independent Bank [Member] | Core deposit intangible assets [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Intangibles acquired								$ 5,600
Originated Portfolio Segment [Member]
Finite-Lived Intangible Assets [Line Items]
Loans serviced for others that have servicing rights capitalized		$ 888,000	$ 881,000
Originated Portfolio Segment [Member] | Weighted Average [Member] | Mortgage servicing rights [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Coupon rate (percent)		4.20%	4.28%
Discount rate (percent)		8.50%	8.50%
Prepayment speed rate (percent)		11.70%	13.60%
Acquired Portfolio Segment [Member]
Finite-Lived Intangible Assets [Line Items]
Loans serviced for others that have servicing rights capitalized		$ 1,200,000	$ 1,210,000
Acquired Portfolio Segment [Member] | Weighted Average [Member] | Mortgage servicing rights [Member]
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]
Coupon rate (percent)		4.07%	4.08%
Discount rate (percent)		10.10%	10.10%
Prepayment speed rate (percent)		10.41%	11.70%
[1]	MSRs are stratified into servicing assets originated by the Corporation and those acquired in acquisitions of other institutions and further stratified into relatively homogeneous pools based on products with similar characteristics. The MSR impairment valuation allowance recorded at December 31, 2014 related to impairment within certain pools attributable to the Corporation's servicing portfolio that was acquired in the Northwestern transaction.

Deposits (Details)

Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deposits, by Type [Abstract]
Noninterest-bearing demand	$ 1,934,583	$ 1,591,661
Interest-bearing demand	1,870,197	1,428,941
Savings	2,004,575	1,720,422
Time deposits over $100,000	701,830	557,476
Other time deposits	945,582	780,471
Total deposits	7,456,767	6,078,971
Maturities of Time Deposits [Abstract]
Time deposit maturities, one year or less	904,000
Time deposits maturities, after next twelve months	743,000
Time deposit maturities, 2017	395,000
Time deposit maturities, 2018	139,000
Time deposit maturities, 2019	88,000
Time deposit maturities, 2020	118,000
Time Deposit Maturities, 2021 and beyond	3,000
Demand deposit overdrafts	3,000	4,300
Time Deposits, $250,000 or More	$ 364,000	$ 249,000

Short-Term Borrowings (Details)

Short-Term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Securities Sold under Agreements to Repurchase [Member]
Short-term borrowings [Line Items]
Ending balance	$ 297,199	$ 304,467	$ 327,428
Weighted average interest rate	0.06%	0.11%	0.15%
Average amount outstanding during year	$ 327,559	$ 326,056	$ 337,649
Weighted average interest rate during year	0.07%	0.12%	0.14%
Maximum balance outstanding at any month-end	$ 372,236	$ 361,231	$ 357,976
Federal Home Loan Bank Advances [Member]
Short-term borrowings [Line Items]
Ending balance	$ 100,000	$ 60,000
Weighted average interest rate	0.34%	0.25%
Average amount outstanding during year	$ 89,208	$ 6,726
Weighted average interest rate during year	0.23%	0.27%
Maximum balance outstanding at any month-end	$ 280,000	$ 60,000
Federal Funds Purchased [Member]
Short-term borrowings [Line Items]
Ending balance	$ 0	$ 25,000
Weighted average interest rate	0.00%	0.40%
Average amount outstanding during year	$ 3,762	$ 2,003
Weighted average interest rate during year	0.37%	0.40%
Maximum balance outstanding at any month-end	$ 22,000	$ 25,000

Other Borrowings (Details)

Other Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Other Borrowings [Line Items]
Long-term Federal Home Loan Bank Advances	$ 181,394		$ 34,300
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Weighted Average Interest Rate	1.41%
Nonrevolving line of credit	$ 25,000
Line of Credit Facility, Interest Rate at Period End	2.27%
Securities Sold under Agreements to Repurchase	$ 17,453
Securities sold under agreements to repurchase, interest rate at period end	0.27%
Subordinated Debt	$ 18,544
Weighted-average interest rate, subordinated debt instruments	3.99%
Other Borrowings	$ 242,391	$ 0

Other Borrowings Textuals (Deta

Other Borrowings Textuals (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 31, 2015
Other Borrowings [Line Items]
Proceeds from Federal Home Loan Bank Advances	$ 100,000,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Weighted Average Interest Rate	1.48%
Long-term Federal Home Loan Bank Advances	$ 181,394,000		$ 34,300,000
FHLB Maturities, 2016	7,100,000
FHLB Maturities, 2017	47,100,000
FHLB Maturities, 2018	67,100,000
FHLB Maturities, 2019	100,000
FHLB Maturities, 2020	60,000,000
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	250,000,000
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Prepayment Penalties	0	$ 800,000	$ 0
Nonrevolving line of credit	$ 25,000,000
Line of Credit Facility, Interest Rate at Period End	2.27%
Securities Sold under Agreements to Repurchase	$ 17,453,000
Securities Sold Under Agreements to Repurchase, Maturities in Year One	8,300,000
Securities Sold Under Agreements to Repurchase, Maturities, Due in Year Two	9,100,000
Trust Preferred Investment Security of Non Public Bank Company				$ 10,000,000
subordinated debt par value	1,000
Subordinated Debt	$ 18,544,000
Weighted-average interest rate, subordinated debt instruments	3.99%
Lake Michigan Financial Corp [Member]
Other Borrowings [Line Items]
Long-term Federal Home Loan Bank Advances				81,500,000
Federal Home Loan Bank, Advances, Weighted Average Interest Rate	1.33%
Securities Sold under Agreements to Repurchase				$ 23,700,000
Real Estate Residential Loans [Member]
Other Borrowings [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	$ 1,340,000,000
LMFCTII [Member]
Other Borrowings [Line Items]
Subordinated Debt	$ 8,200,000
Subordinated Borrowing, Interest Rate	2.70%
Debt Instrument, Interest Rate, Effective Percentage	3.24%
LMFCTI [Member]
Other Borrowings [Line Items]
Subordinated Debt	$ 10,300,000
Subordinated Borrowing, Interest Rate	3.45%
Debt Instrument, Interest Rate, Effective Percentage	3.99%

Equity (Details)

Equity (Details) - shares	12 Months Ended
	Dec. 31, 2015	Apr. 20, 2015	Mar. 31, 2015	Dec. 31, 2014	Apr. 20, 2009	Jan. 31, 2008
Class of Stock [Line Items]
Preferred stock, shares authorized	2,000,000	2,000,000		200,000
Preferred stock, shares issued	0			0
Common Stock, Shares Authorized	60,000,000	60,000,000	45,000,000	45,000,000
Common Stock [Member]
Class of Stock [Line Items]
Number of shares authorized to be repurchased						500,000
Stock repurchased during the period, shares	0
Number of remaining shares authorized to be repurchased	500,000
Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized					200,000

Equity Textuals (Details)

Equity Textuals (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Jun. 24, 2014	Sep. 18, 2013
Statement of Stockholders' Equity [Abstract]
Common Stock, Shares, Issued	38,167,861	32,774,420	2,500,000	2,213,750
CommonStockIssuedOverAllotment			375,000	288,750
Shares Issued, Price Per Share			$ 28	$ 26
CommonStock, Value, Issued From Public Offering			$ 76.2	$ 53.9
Amount of Common Stock sold in public stock offering			$ 80.5	$ 57.6

Accumulated Other Comprehensi99

Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of accumulated other comprehensive loss, net of related tax benefit/expense
Net unrealized gains (losses) on investment securities — available-for-sale, net of related tax expense (benefit) of $(1,017) at December 31, 2015, $(113) at December 31, 2014 and ($1,335) at December 31, 2013	$ (1,888)	$ (210)	$ (2,480)
Pension and other postretirement benefits adjustment, net of related tax benefit of $14,616 at December 31, 2015, $17,362 at December 31, 2014 and $9,714 at December 31, 2013	(27,144)	(32,243)	(18,040)
Accumulated other comprehensive loss	$ (29,032)	$ (32,453)	$ (20,520)

Accumulated Other Comprehens100

Accumulated Other Comprehensive Loss (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Loss (Textual) [Abstract]
Net unrealized gains (losses) on investment securities-available-for-sale, tax expense (benefit)	$ (1,017)	$ (113)	$ (1,335)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax Benefit	$ 14,616	$ 17,362	$ 9,714

Fair Value Measurements (Recurr

Fair Value Measurements (Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	$ 553,731	$ 748,864
US Treasury Securities [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	5,765	8,259
Government sponsored agencies [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	194,989	263,503
State and political subdivisions [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	15,120	46,227
Residential mortgage-backed securities [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	187,768	239,807
Collateralized mortgage obligations [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	132,230	144,383
Corporate bonds [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	14,627	45,095
Preferred stock [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	3,232	1,590
Fair Value Measurements Recurring [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	553,731	748,864
Loans held-for-sale	10,327	9,128
Total assets measured at fair value on a recurring basis	564,058	757,992
Fair Value Measurements Recurring [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	5,765	8,259
Loans held-for-sale	0	0
Total assets measured at fair value on a recurring basis	5,765	8,259
Fair Value Measurements Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	547,966	740,605
Loans held-for-sale	10,327	9,128
Total assets measured at fair value on a recurring basis	558,293	749,733
Fair Value Measurements Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Loans held-for-sale	0	0
Total assets measured at fair value on a recurring basis	0	0
Fair Value Measurements Recurring [Member] | US Treasury Securities [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	5,765
Fair Value Measurements Recurring [Member] | US Treasury Securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	5,765
Fair Value Measurements Recurring [Member] | US Treasury Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0
Fair Value Measurements Recurring [Member] | US Treasury Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0
Fair Value Measurements Recurring [Member] | Government sponsored agencies [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	194,989	263,503
Fair Value Measurements Recurring [Member] | Government sponsored agencies [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Government sponsored agencies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	194,989	263,503
Fair Value Measurements Recurring [Member] | Government sponsored agencies [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | State and political subdivisions [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	15,120	46,227
Fair Value Measurements Recurring [Member] | State and political subdivisions [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | State and political subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	15,120	46,227
Fair Value Measurements Recurring [Member] | State and political subdivisions [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Residential mortgage-backed securities [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	187,768	239,807
Fair Value Measurements Recurring [Member] | Residential mortgage-backed securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Residential mortgage-backed securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	187,768	239,807
Fair Value Measurements Recurring [Member] | Residential mortgage-backed securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Collateralized mortgage obligations [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	132,230	144,383
Fair Value Measurements Recurring [Member] | Collateralized mortgage obligations [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Collateralized mortgage obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	132,230	144,383
Fair Value Measurements Recurring [Member] | Collateralized mortgage obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Corporate bonds [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	14,627	45,095
Fair Value Measurements Recurring [Member] | Corporate bonds [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Corporate bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	14,627	45,095
Fair Value Measurements Recurring [Member] | Corporate bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Preferred stock [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	3,232	1,590
Fair Value Measurements Recurring [Member] | Preferred stock [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	0	0
Fair Value Measurements Recurring [Member] | Preferred stock [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	3,232	1,590
Fair Value Measurements Recurring [Member] | Preferred stock [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a recurring basis
Available-for-sale, at fair value	$ 0	$ 0

Fair Value Measurements (Nonrec

Fair Value Measurements (Nonrecurring Basis) (Details) - Fair Value Measurements Nonrecurring [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	$ 52,000	$ 44,219
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	0	0
Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	0	0
Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	52,000	44,219
Impaired originated loans [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	42,065	21,323
Impaired originated loans [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	0	0
Impaired originated loans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	0	0
Impaired originated loans [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	42,065	21,323
Other real estate/repossessed assets [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	9,935	14,205
Other real estate/repossessed assets [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	0	0
Other real estate/repossessed assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	0	0
Other real estate/repossessed assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis	$ 9,935	14,205
Mortgage Servicing Rights [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis		8,691
Mortgage Servicing Rights [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis		0
Mortgage Servicing Rights [Member] | Significant Other Observable Inputs (Level 2) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis		0
Mortgage Servicing Rights [Member] | Significant Unobservable Inputs (Level 3) [Member]
Summary of assets measured at fair value on a nonrecurring basis
Total assets measured at fair value on a nonrecurring basis		$ 8,691

Fair Value Measurements (Carryi

Fair Value Measurements (Carrying Amounts and Estimated Fair Values) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investment securities:
Available-for-sale	$ 553,731	$ 748,864
Held-to-maturity Securities, Fair Value	512,705	315,740
Liabilities:
Short-term borrowings	397,199	389,467
Other Borrowings	242,391	0
Carrying Amount [Member]
Investment securities:
Nonmarketable equity securities	36,907	27,369
Carrying Amount [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	238,789	183,020
Investment securities:
Available-for-sale	5,765	8,259
Carrying Amount [Member] | Level 2 [Member]
Investment securities:
Available-for-sale	547,966	740,605
Held-to-maturity Securities, Fair Value	509,471	305,913
Loans held-for-sale	10,327	9,128
Interest receivable	21,953	17,492
Liabilities:
Deposits without defined maturities	5,809,355	4,741,024
Interest Payable	1,578	755
Short-term borrowings	397,199	389,467
Other Borrowings	206,394	0
Carrying Amount [Member] | Level 3 [Member]
Investment securities:
Held-to-maturity Securities, Fair Value	500	10,500
Net loans	7,197,819	5,612,547
Liabilities:
Time deposits	1,647,412	1,337,947
Other Borrowings	35,997	0
Fair Value [Member]
Investment securities:
Nonmarketable equity securities	36,907	27,369
Fair Value [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	238,789	183,020
Investment securities:
Available-for-sale	5,765	8,259
Fair Value [Member] | Level 2 [Member]
Investment securities:
Available-for-sale	547,966	740,605
Held-to-maturity Securities, Fair Value	512,405	308,650
Loans held-for-sale	10,327	9,128
Interest receivable	21,953	17,492
Liabilities:
Deposits without defined maturities	5,809,355	4,741,024
Interest Payable	1,578	755
Short-term borrowings	397,199	389,467
Other Borrowings	206,394	0
Fair Value [Member] | Level 3 [Member]
Investment securities:
Held-to-maturity Securities, Fair Value	300	7,090
Net loans	7,201,994	5,623,454
Liabilities:
Time deposits	1,647,412	1,340,015
Other Borrowings	$ 35,997	$ 0

Fair Value Measurements (Textua

Fair Value Measurements (Textual) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value Measurements (Textual) [Abstract]
Impairment of goodwill	$ 0	$ 0
Impairment identified for intangible assets	0	0
Valuation Allowance on Mortgage Servicing Rights	0	200
Fair Value Measurements Recurring [Member]
Fair Value Measurements (Textual) [Abstract]
Liabilities recorded at fair value	0	0
Fair Value Measurements Nonrecurring [Member]
Fair Value Measurements (Textual) [Abstract]
Liabilities recorded at fair value	$ 0	$ 0
Minimum [Member]
Fair Value Measurements (Textual) [Abstract]
Discount factors used to determine fair value	70.00%
Minimum [Member] | Other Real Estate and Repossessed Assets [Member]
Fair Value Measurements (Textual) [Abstract]
Discount factors used to determine fair value	70.00%
Maximum [Member]
Fair Value Measurements (Textual) [Abstract]
Discount factors used to determine fair value	80.00%
Maximum [Member] | Other Real Estate and Repossessed Assets [Member]
Fair Value Measurements (Textual) [Abstract]
Discount factors used to determine fair value	75.00%

Noninterest Income (Details)

Noninterest Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Noninterest Income [Abstract]
Service charges and fees on deposit accounts									$ 25,481	$ 22,414	$ 21,939
Wealth management revenue									20,552	16,015	13,989
Electronic banking fees									19,119	13,480	12,213
Mortgage banking revenue									6,133	5,041	5,336
Other fees for customer services									4,428	3,539	3,288
Insurance commissions									1,966	1,559	1,650
Gain on sale of investment securities									630	0	1,133
Bank Owned Life Insurance Income									646	281	197
Rental Income, Nonoperating									466	145	97
Gain (Loss) on Disposition of Other Assets									266	0	478
Gain on sale of merchant card services									0	400	0
Other Noninterest Income									529	221	89
Other									1,907	697	861
Total Noninterest Income	$ 20,052	$ 20,215	$ 20,674	$ 19,275	$ 18,227	$ 15,351	$ 15,801	$ 13,716	$ 80,216	$ 63,095	$ 60,409

Operating Expenses (Details)

Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Expenses [Abstract]
Salaries and wages									$ 104,490	$ 83,229	$ 78,014
Employee benefits									23,430	19,328	18,405
Occupancy									18,213	15,842	13,934
Equipment and software									18,569	14,737	13,734
Outside processing/service fees									15,207	11,586	11,134
FDIC insurance premiums									5,485	4,307	4,362
Professional fees									4,842	3,570	3,771
Postage and express mail									3,313	3,418	3,051
Advertising and marketing									3,288	3,051	2,971
Donations									1,375	1,155	2,829
Training, travel and other employee expenses									3,224	2,480	2,512
Telephone									2,608	1,966	1,940
Intangible asset amortization									4,389	2,029	1,909
Supplies									2,216	1,897	1,670
Credit-related expenses									632	996	707
Business Combination, Acquisition Related Costs									7,804	6,388	0
Other									4,809	3,946	4,005
Total Operating Expenses	$ 57,824	$ 58,265	$ 56,785	$ 51,020	$ 52,616	$ 42,702	$ 42,425	$ 42,182	$ 223,894	$ 179,925	$ 164,948

Retirement Plans (Changes in th

Retirement Plans (Changes in the Projected Benefit Obligation and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 129,160	$ 105,914
Service cost	1,021	944	$ 1,247
Interest cost	5,242	5,167	4,603
Net actuarial (gain) loss	(10,837)	21,314
Benefits paid	(4,713)	(4,179)
Benefit obligation at end of year	119,873	129,160	105,914
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	130,775	128,829
Actual return on plan assets	868	6,125
Employer contributions	0	0	15,000
Benefits paid	(4,713)	(4,179)
Fair value of plan assets at end of year	126,930	130,775	128,829
Funded (unfunded) projected benefit obligation at end of year	7,057	1,615
Accumulated benefit obligation	109,583	121,826
Postretirement Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	3,702	3,477
Service cost	16	18	18
Interest cost	133	142	143
Net actuarial (gain) loss	(363)	312
Benefits paid	(241)	(247)
Benefit obligation at end of year	3,247	3,702	3,477
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	241	247
Benefits paid	(241)	(247)
Fair value of plan assets at end of year	0	0	$ 0
Funded (unfunded) projected benefit obligation at end of year	(3,247)	(3,702)
Accumulated benefit obligation	$ 3,247	$ 3,702

Retirement Plans (Weighted-aver

Retirement Plans (Weighted-average rate assumptions of the Pension and Postretirement Plans) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate used in determining benefit obligation	4.55%	4.15%	5.00%
Discount rate used in determining expense	4.15%	5.00%	4.08%
Expected long-term return on Pension Plan assets	6.75%	7.00%	7.00%
Rate of compensation increase used in determining benefit obligation	3.50%	3.50%	3.50%
Rate of compensation increase used in determining pension expense	3.50%	3.50%	3.50%
Year 1 increase in cost of postretirement benefits	0.00%	0.00%	0.00%
Supplemental Employee Retirement Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate used in determining benefit obligation	4.51%	4.07%	4.87%
Postretirement Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate used in determining benefit obligation	4.23%	3.75%	4.27%
Discount rate used in determining expense	3.75%	4.27%	4.08%
Expected long-term return on Pension Plan assets	0.00%	0.00%	0.00%
Rate of compensation increase used in determining benefit obligation	0.00%	0.00%	0.00%
Rate of compensation increase used in determining pension expense	0.00%	0.00%	0.00%
Year 1 increase in cost of postretirement benefits	7.50%	8.00%	8.50%

Retirement Plans (Net Periodic

Retirement Plans (Net Periodic Pension Cost (Income)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan [Member]
Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan
Service cost	$ 1,021	$ 944	$ 1,247
Interest cost	5,242	5,167	4,603
Expected return on plan assets	(8,645)	(8,314)	(7,794)
Amortization of prior service credit	(5)	(1)	(1)
Amortization of net actuarial loss (gain)	3,962	2,159	3,670
Net cost (income)	1,575	(45)	1,725
Postretirement Plan [Member]
Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan
Service cost	16	18	18
Interest cost	133	142	143
Expected return on plan assets	0	0	0
Amortization of prior service credit	130	130	343
Amortization of net actuarial loss (gain)	(1)	(104)	(73)
Net cost (income)	$ 278	$ 186	$ 431

Retirement Plans (Schedule of E

Retirement Plans (Schedule of Estimated Future Benefit Payments) (Details) $ in Thousands	Dec. 31, 2015USD ($)
Pension Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
Estimated future benefit payments - 2015	$ 5,223
Estimated future benefit payments - 2016	5,400
Estimated future benefit payments - 2017	5,730
Estimated future benefit payments - 2018	6,094
Estimated future benefit payments - 2019	6,272
Estimated future benefit payments - 2020-2024	35,771
Estimated future benefit payments - Total	64,490
Postretirement Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
Estimated future benefit payments - 2015	272
Estimated future benefit payments - 2016	272
Estimated future benefit payments - 2017	268
Estimated future benefit payments - 2018	270
Estimated future benefit payments - 2019	268
Estimated future benefit payments - 2020-2024	1,254
Estimated future benefit payments - Total	$ 2,604

Retirement Plans (Impact of One

Retirement Plans (Impact of One Percentage Point Change in Assumed Health Care and Dental Cost Trend Rates) (Details) - Postretirement Plan [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Effect of one percentage point increase on service and interest cost components	$ 13
Effect of one percentage point decrease on service and interest cost components	(12)
Effect of one percentage point increase on postretirement benefit obligation	308
Effect of one percentage point decrease on postretirement benefit obligation	$ (269)

Retirement Plans (Pension Plan

Retirement Plans (Pension Plan asset Allocations) (Details) - Pension Plan [Member]	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan actual asset allocations	100.00%	100.00%
Equity securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan actual asset allocations	68.00%	68.00%
Debt securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan actual asset allocations	31.00%	30.00%
Other securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan actual asset allocations	1.00%	2.00%

Retirement Plans (Fair Value of

Retirement Plans (Fair Value of Plan Assets by Fair Value Level) (Details) - Pension Plan [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost		$ 1,575		$ (45)	$ 1,725
Fair value of plan assets		126,930		130,775	$ 128,829
Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		126,930		130,775
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		120,561		121,918
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		6,369		8,857
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Cash [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		354		2,594
Cash [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		354		2,594
Cash [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Cash [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
U.S. large- and mid-cap stocks [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		55,709	[1]	56,718
U.S. large- and mid-cap stocks [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	55,709		56,718
U.S. large- and mid-cap stocks [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0		0
U.S. large- and mid-cap stocks [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0		0
U.S. small-cap mutual funds [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,749		5,409
U.S. small-cap mutual funds [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,749		5,409
U.S. small-cap mutual funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
U.S. small-cap mutual funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
International large-cap mutual funds [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		14,124		14,805
International large-cap mutual funds [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		14,124		14,805
International large-cap mutual funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
International large-cap mutual funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Emerging markets mutual funds [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,886		6,004
Emerging markets mutual funds [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,886		6,004
Emerging markets mutual funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Emerging markets mutual funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Common Stock [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7,219		6,455
Common Stock [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7,219		6,455
Common Stock [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Common Stock [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
U.S. Treasury and government sponsored agency bonds and notes [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,815		3,041
U.S. Treasury and government sponsored agency bonds and notes [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		998
U.S. Treasury and government sponsored agency bonds and notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,815		2,043
U.S. Treasury and government sponsored agency bonds and notes [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Corporate bonds [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,554	[2]	6,814
Corporate bonds [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0		0
Corporate bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	3,554		6,814
Corporate bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Mutual funds [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	33,424		28,795
Mutual funds [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	33,424		28,795
Mutual funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0		0
Mutual funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0		0
Other debt securities [Member] | Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		96		140
Other debt securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		96		140
Other debt securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Other debt securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 0		$ 0
[1]	Comprised of common stocks and mutual funds traded on U.S. Exchanges whose issuers had market capitalizations exceeding $3 billion
[2]	Comprised of investment grade bonds of U.S. issuers from diverse industries.
[3]	Comprised primarily of fixed-income bonds issued by the U.S. Treasury and government sponsored agencies and bonds of U.S. and foreign issuers from diverse industries.

Retirement Plans (Changes in Ac

Retirement Plans (Changes in Accumulated Other Comprehensive Income (Loss) Related to Retirement Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	$ (32,243)	$ (18,040)
Prior service credits	81
Net actuarial gain (loss)	5,018
Change in adjustment for pension and other postretirement benefits, net of tax benefit (expense) of $(2,746), $7,648, and $(9,344) for the years ended December 31, 2015, 2014, and 2013, respectively	5,099	(14,203)	$ 17,353
Accumulated other comprehensive income (loss) at end of year	(27,144)	(32,243)	$ (18,040)
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	(31,853)
Prior service credits	(3)
Net actuarial gain (loss)	4,565
Change in adjustment for pension and other postretirement benefits, net of tax benefit (expense) of $(2,746), $7,648, and $(9,344) for the years ended December 31, 2015, 2014, and 2013, respectively	4,562
Accumulated other comprehensive income (loss) at end of year	(27,291)	(31,853)
Postretirement Plan [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	83
Prior service credits	84
Net actuarial gain (loss)	235
Change in adjustment for pension and other postretirement benefits, net of tax benefit (expense) of $(2,746), $7,648, and $(9,344) for the years ended December 31, 2015, 2014, and 2013, respectively	319
Accumulated other comprehensive income (loss) at end of year	402	83
Supplemental Plan [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	(473)
Prior service credits	0
Net actuarial gain (loss)	218
Change in adjustment for pension and other postretirement benefits, net of tax benefit (expense) of $(2,746), $7,648, and $(9,344) for the years ended December 31, 2015, 2014, and 2013, respectively	218
Accumulated other comprehensive income (loss) at end of year	$ (255)	$ (473)

Retirement Plans (Income (Loss)

Retirement Plans (Income (Loss) Estimated to be Amortized from Accumulated Other Comprehensive Income (Loss) into Net Periodic Cost) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amortization of prior service credits, next twelve months	$ (76)
Amortization of net gain (loss), next twelve months	(1,423)
Total amortization of accumulated other comprehensive income (loss), next twelve months	(1,499)
Pension Plan [Member]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amortization of prior service credits, next twelve months	0
Amortization of net gain (loss), next twelve months	(1,468)
Total amortization of accumulated other comprehensive income (loss), next twelve months	(1,468)
Postretirement Plan [Member]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amortization of prior service credits, next twelve months	(76)
Amortization of net gain (loss), next twelve months	65
Total amortization of accumulated other comprehensive income (loss), next twelve months	(11)
Supplemental Plan [Member]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amortization of prior service credits, next twelve months	0
Amortization of net gain (loss), next twelve months	(20)
Total amortization of accumulated other comprehensive income (loss), next twelve months	$ (20)

Retirement Plans (401(k) Saving

Retirement Plans (401(k) Savings Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Employer discretionary contribution percent	4.00%
Maximum annual contribution per employee percent	50.00%
Employer matching contribution percent	4.00%
Employer matching contribution amount	$ 1.6	$ 1	$ 1.1
Contribution to 401(k) savings plan	3.1	2.3	2.3
Employer total contribution amount	$ 4.7	$ 3.3	$ 3.4

Retirement Plans (Textual) (Det

Retirement Plans (Textual) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)employeeshares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)	Jun. 30, 2015	Jun. 24, 2014shares	Sep. 18, 2013shares
Defined Benefit Plan Disclosure [Line Items]
Percentage of eligible pay contribution to certain employees	4.00%
Common Stock, Shares Held by Plan | shares	(38,167,861)	(32,774,420)			(2,500,000)	(2,213,750)
Dividends paid	$ 36,918	$ 29,528	$ 24,521
Multiemployer Plan, Period Contributions	100
Multiemployer Plan Minimum Funding Status				80.00%
Multiemployer Plan, Participating Company, Allocation of Plan Assets	3,700
Multiemployer Plan, Participating Company, Allocation of Plan Liabilities	$ 2,600
Multiemployer Plan, Company's Asset Participation Level				5.00%
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum years of vested service for calculation of retirement benefits	30 years
Years of employees highest average salary for calculation of retirement benefits	5 years
Defined Benefit Plan, Number of Employees Covered | employee	161
Number of years preceding retirement for calculation of retirement benefits	10 years
Maximum years of service for which pension benefits calculation is based upon vested service and average five years of salary	15 years
Maximum total years of age and years of service for which pension benefits calculation is based upon vested service and average five years of salary	65 years
Pension Plan expense	$ 1,575	(45)	1,725
Employer contributions	$ 0	$ 0	$ 15,000
Discount rate used in determining benefit obligation	4.55%	4.15%	5.00%
Pension plan actual asset allocations	100.00%	100.00%
Projected benefit obligation	$ 119,873	$ 129,160	$ 105,914
Accumulated benefit obligation	$ 109,583	$ 121,826
Pension Plan [Member] | Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range - minimum	40.00%
Target plan asset allocations range - maximum	70.00%
Pension plan actual asset allocations	68.00%	68.00%
Pension Plan [Member] | Debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range - minimum	20.00%
Target plan asset allocations range - maximum	60.00%
Pension plan actual asset allocations	31.00%	30.00%
Pension Plan [Member] | Other securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range - minimum	0.00%
Target plan asset allocations range - maximum	10.00%
Pension plan actual asset allocations	1.00%	2.00%
Pension Plan [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Common Stock, Shares Held by Plan | shares	(210,663)
Fair value of common stock	$ 7,200	$ 6,500
Pension plan actual asset allocations	5.70%	4.90%
Supplemental Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of employees covered by the pension plan | employee	1
Discount rate used in determining benefit obligation	4.51%	4.07%	4.87%
Projected benefit obligation	$ 2,200	$ 2,100
Accumulated benefit obligation	1,800	2,000
Supplemental Plan expense	400	300	$ 200
Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Plan expense	278	186	$ 431
Employer contributions	$ 241	$ 247
Discount rate used in determining benefit obligation	4.23%	3.75%	4.27%
Expected health care cost trend rate assumed for 2014	7.50%
Expected ultimate health care cost trend rate in 2020	5.00%
Projected benefit obligation	$ 3,247	$ 3,702	$ 3,477
Accumulated benefit obligation	$ 3,247	3,702
Minimum retirement age (years)	50 years
Maximum benefit age of spouse (years)	65 years
Minimum retirement age with twenty-five years of service to be eligible for postretirement benefits (years)	60 years
Minimum years of service for retirees at age sixty to be eligible for postretirement benefits (years)	25 years
Chemical Financial Corporation [Member] | Pension Plan [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Dividends paid	$ 200	$ 180

Share-Based Compensation Pla118

Share-Based Compensation Plan (Stock Options Outstanding Per Range of Exercise Prices) (Details) - Stock Options [Member]	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding | shares	1,054,739
Options Outstanding, Weighted Average Exercise Price Per Share	$ 25.38
Options Outstanding, Weighted Average Contractual Term	6 years 4 months 16 days
Options Exercisable, Weighted Average Exercise Price Per Share	$ 22.58
Options Exercisable, Weighted Average Contractual Term	4 years 8 months 5 days
Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, lower price range limit	$ 10.56
Maximum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, upper price range limit	$ 30.18
Range of Exercise Prices Per Share, $19.43 - 21.10 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding | shares	84,775
Options Outstanding, Weighted Average Exercise Price Per Share	$ 13.31
Options Outstanding, Weighted Average Contractual Term	4 years 8 months 24 days
Options Exercisable, Number Exercisable | shares	84,775
Options Exercisable, Weighted Average Exercise Price Per Share	$ 13.31
Options Exercisable, Weighted Average Contractual Term	4 years 8 months 24 days
Range of Exercise Prices Per Share, $19.43 - 21.10 [Member] | Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, lower price range limit	$ 10.56
Range of Exercise Prices Per Share, $19.43 - 21.10 [Member] | Maximum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, upper price range limit	$ 15.84
Range of Exercise Prices Per Share, $23.78 - 25.14 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding | shares	74,189
Options Outstanding, Weighted Average Exercise Price Per Share	$ 20.47
Options Outstanding, Weighted Average Contractual Term	4 years 4 months 24 days
Options Exercisable, Number Exercisable | shares	74,189
Options Exercisable, Weighted Average Exercise Price Per Share	$ 20.47
Options Exercisable, Weighted Average Contractual Term	4 years 4 months 24 days
Range of Exercise Prices Per Share, $23.78 - 25.14 [Member] | Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, lower price range limit	$ 19.97
Range of Exercise Prices Per Share, $23.78 - 25.14 [Member] | Maximum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, upper price range limit	$ 21.10
Range of Exercise Prices Per Share, $29.45 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding | shares	502,845
Options Outstanding, Weighted Average Exercise Price Per Share	$ 24.63
Options Outstanding, Weighted Average Contractual Term	5 years 30 days
Options Exercisable, Number Exercisable | shares	384,912
Options Exercisable, Weighted Average Exercise Price Per Share	$ 24.47
Options Exercisable, Weighted Average Contractual Term	4 years 5 months 8 days
Range of Exercise Prices Per Share, $29.45 [Member] | Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, upper price range limit	$ 23.78
Range of Exercise Prices Per Share, $29.45 [Member] | Maximum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, upper price range limit	$ 25.14
Range of Exercise Prices Per Share, $32.28 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding | shares	392,930
Options Outstanding, Weighted Average Exercise Price Per Share	$ 29.88
Options Outstanding, Weighted Average Contractual Term	8 years 9 months 4 days
Options Exercisable, Number Exercisable | shares	31,108
Options Exercisable, Weighted Average Exercise Price Per Share	$ 29.45
Options Exercisable, Weighted Average Contractual Term	8 years 2 months 1 day
Range of Exercise Prices Per Share, $32.28 [Member] | Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, upper price range limit	$ 29.45
Range of Exercise Prices Per Share, $32.28 [Member] | Maximum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price per share, upper price range limit	$ 30.18

Share-Based Compensation Pla119

Share-Based Compensation Plan (Stock Option Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]
Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	$ 8.40	$ 9.64	$ 7.40
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted, Number of Options	244,165
Stock Options [Member] | Non-Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance, Number of Options	432,199	414,080	314,765
Granted, Number of Options	244,165	190,011	244,719
Exercised, , Number of Options	0	0	0
Vested, Number of Options	(150,224)	(148,016)	(127,443)
Forfeited/expired, Number of Options	(46,385)	(23,876)	(17,961)
Ending balance, Number of Options	479,755	432,199	414,080
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Beginning balance, Weighted Average Exercise Price Per Share (USD per share)	$ 26.75	$ 24.29	$ 23.03
Granted, Weighted Average Exercise Price Per Share (USD per share)	30.18	29.45	25.14
Exercised, Weighted Average Exercise Price Per Share (USD per share)	0	0	0
Vested, Weighted Average Exercise Price Per Share (USD per share)	25.57	23.43	22.94
Forfeited/expired, Weighted Average Exercise Price Per Share (USD per share)	27.99	25.67	23.34
Ending balance, Weighted Average Exercise Price Per Share (USD per share)	$ 28.75	26.75	24.29
Converted, Number of Options from Acquisitions	0
Converted options from acquisitions, Weighted Average Exercise Price	$ 0
Converted options from acquisitions, Wtd Avg Grant Date Fair Value	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]
Beginning balance, Weighted Average Grant Date Fair Value Per Share (USD per share)	8.30	7.19	6.92
Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	8.40	9.64	7.40
Exercised, Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	0	0	0
Vested, Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	7.80	6.98	6.92
Forfeited/expired, Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	8.50	7.79	6.98
Ending balance, Weighted Average Grant Date Fair Value Per Share (USD per share)	$ 8.49	$ 8.30	$ 7.19
Stock Options [Member] | Vested & Nonvested [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Converted, Number of Options from Acquisitions	132,883
Converted options from acquisitions, Weighted Average Exercise Price	$ 12.93
Stock Options [Member] | Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance, Number of Options	1,037,311	1,073,990	997,222
Granted, Number of Options	244,165	190,011	244,719
Exercised, , Number of Options	(310,985)	(72,936)	(100,145)
Vested, Number of Options	0	0	0
Forfeited/expired, Number of Options	(48,635)	(153,754)	(67,806)
Ending balance, Number of Options	1,054,739	1,037,311	1,073,990
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Beginning balance, Weighted Average Exercise Price Per Share (USD per share)	$ 25.90	$ 26.84	$ 27.24
Granted, Weighted Average Exercise Price Per Share (USD per share)	30.18	29.45	25.14
Exercised, Weighted Average Exercise Price Per Share (USD per share)	25.10	24.67	22.87
Vested, Weighted Average Exercise Price Per Share (USD per share)	0	0	0
Forfeited/expired, Weighted Average Exercise Price Per Share (USD per share)	28.18	37.50	32.27
Ending balance, Weighted Average Exercise Price Per Share (USD per share)	$ 25.38	$ 25.90	$ 26.84
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]
Options Exercisable, Number Exercisable	574,984
Exercisable/vested, Weighted Average Exercise Price Per Share (USD per share)	$ 22.58

(Black-Scholes Pricing Model As

(Black-Scholes Pricing Model Assumptions) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assumptions of Black-Scholes option pricing model
Expected dividend yield	3.50%	3.00%	3.50%
Risk-free interest rate	1.78%	2.16%	1.34%
Expected stock price volatility	39.10%	42.20%	42.10%
Expected life of options - in years	7 years	7 years	7 years
Weighted average fair value per share	$ 8.40	$ 9.64	$ 7.40

Share-Based Compensation Pla121

Share-Based Compensation Plan (Restricted Stock Unit Activity) (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Number of Shares [Roll Forward]
Beginning balance, Number of Units	204,319	188,532	156,510
Granted, Number of Units	85,645	73,468	71,768
Converted into shares of common stock, Number of Units	(70,166)	(52,008)	(36,416)
Forfeited/expired, Number of Units	(11,809)	(5,673)	(3,330)
Ending balance, Number of Units	207,989	204,319	188,532
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract]
Beginning balance, Weighted Average Grant Date Fair Value Per Share (USD per share)	$ 24.14	$ 21.49	$ 20.83
Granted, Weighted Average Grant Date Fair Value Per Unit (USD per Unit)	28.52	27.49	23.42
Converted into shares of common stock, Weighted Average Grant Date Fair Value Per Unit (USD per Unit)	22.51	19.23	22.44
Forfeited/expired, Weighted Average Grant Date Fair Value Per Unit (USD per Unit)	25.61	24.31	21.67
Ending balance, Weighted Average Grant Date Fair Value Per Share (USD per share)	$ 26.41	$ 24.14	$ 21.49

Share-Based Compensation Pla122

Share-Based Compensation Plan (Textual) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)shares	Apr. 20, 2015shares
Share-Based Compensation Plans (Textual) [Abstract]
Share-based compensation expense	$ 3,478	$ 2,931	$ 2,854
Corporation granted shares of common stock | shares	12,059
Common stock available for future grants under share-based compensation plans | shares	1,274,477			1,300,000
Stock option vesting period, post 2012 grants	5 years
Stock option vesting period pre 2013 grants	3 years
Stock Options and Restricted Stock Performance Units [Member]
Share-Based Compensation Plans (Textual) [Abstract]
Share-based compensation expense	$ 3,700	$ 2,900	$ 2,900
Stock Options [Member]
Share-Based Compensation Plans (Textual) [Abstract]
Corporation granted options to purchase common stock | shares	244,165
Stock option expiration period	10 years
Intrinsic value of outstanding in-the-money stock options	$ 7,600
Intrinsic value of exercisable in-the-money stock options	$ 4,900
Closing price of common stock | $ / shares	$ 34.27
Unrecognized compensation expense related to share-based compensation	$ 3,300
Period of common stock historical volatility	7 years
Equity Option [Member]
Share-Based Compensation Plans (Textual) [Abstract]
Unrecognized Compensation, Stock Options, Total Compensation Cost Not yet Recognized, Period for Recognition	3 years 6 months
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Plans (Textual) [Abstract]
Corporation granted options to purchase restricted stock performance units | shares	85,645	73,468	71,768
Unrecognized compensation expense related to share-based compensation	$ 3,200
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 5 months
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-Based Compensation Plans (Textual) [Abstract]
Restricted stock performance units eligible to vest as a multiple of number of units granted	1.5
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Share-Based Compensation Plans (Textual) [Abstract]
Restricted stock performance units eligible to vest as a multiple of number of units granted	0.25

Federal Income Taxes (Effective

Federal Income Taxes (Effective Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Income Tax Rate, Tax Rate Reconciliation [Abstract]
Tax at statutory rate									$ 43,341	$ 31,367	$ 28,388
Tax-exempt interest income									(3,918)	(3,118)	(2,746)
Income tax credits, net									(2,557)	(1,624)	(1,615)
Other, net									134	875	273
Provision for federal income taxes	$ 10,200	$ 9,600	$ 9,100	$ 8,100	$ 7,050	$ 7,450	$ 7,100	$ 5,900	$ 37,000	$ 27,500	$ 24,300
Effective federal income tax rate									29.90%	30.70%	30.00%

Federal Income Taxes (Provision

Federal Income Taxes (Provision for Federal Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current expense									$ 31,300	$ 29,200	$ 23,665
Deferred expense (benefit)									5,700	(1,700)	635
Total federal income tax expense	$ 10,200	$ 9,600	$ 9,100	$ 8,100	$ 7,050	$ 7,450	$ 7,100	$ 5,900	$ 37,000	$ 27,500	$ 24,300

Federal Income Taxes (Deferred

Federal Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets, Gross [Abstract]
Allowance for loan losses	$ 24,863	$ 26,489
Acquisition-related fair value adjustments	29,280	19,457
Accrued expenses not currently deductible	9,331	7,819
Net operating loss carryover	7,130	0
Premises and equipment	4,333	3,311
Nonaccrual loan interest	4,994	4,682
Other	15,296	9,418
Total deferred tax assets	95,227	71,176
Deferred Tax Liabilities, Gross [Abstract]
Core deposit intangible assets	7,379	5,072
Goodwill	5,808	5,205
Mortgage servicing rights	3,893	4,276
Other	7,957	3,884
Total deferred tax liabilities	25,037	18,437
Net deferred tax assets	$ 70,190	$ 52,739

Federal Income Taxes (Textuals)

Federal Income Taxes (Textuals) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Apr. 01, 2015
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 20.4
Monarch Community Bancorp [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		$ 22.6

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Number of months in which the majority of loan commitments are expected to fund loans	3 months
Loss Contingency, Estimate of Possible Loss	$ 0
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases, future minimum payments due - 2015	14,800,000
Operating leases, future minimum payments due - 2016	12,200,000
Operating leases, future minimum payments due - 2017	6,400,000
Operating leases, future minimum payments due - 2018	3,900,000
Operating leases, future minimum payments due - 2019	2,400,000
Operating leases, future minimum payments due - 2020 and thereafter	$ 9,200,000
Consumer Price Index increase	3.00%
Operating lease rent expense	$ 15,600,000	$ 12,400,000	$ 11,600,000
Commitments to Extend Credit [Member]
Loss Contingencies [Line Items]
Face amount of off-balance sheet liability	$ 1,590,000,000	1,080,000,000
Expiration period of commitments to extend credit	1 year
Face amount of off-balance sheet liability with expiration greater than five years	$ 144,000,000
Commitments to Extend Credit [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Expiration period of commitments to extend credit	5 years
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Face amount of off-balance sheet liability	$ 39,000,000	41,000,000
Loan Origination Commitments [Member]
Loss Contingencies [Line Items]
Face amount of off-balance sheet liability	294,000,000	251,000,000
Loan Origination Commitments [Member] | Real Estate Residential Loans [Member]
Loss Contingencies [Line Items]
Face amount of off-balance sheet liability	$ 23,000,000	$ 24,000,000

Regulatory Capital and Reser128

Regulatory Capital and Reserve Requirements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum average regulatory cash reserve balance	$ 65,300	$ 46,300
Chemical Financial Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid to parent company	(56,860)	(64,468)	$ (24,488)
Risk weighted assets	7,140,000	5,700,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	841,257	705,130
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 571,509	$ 456,302
Actual, Ratio	11.80%	12.40%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 767,929	$ 633,779
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 428,631	$ 228,151
Actual, Ratio	10.70%	11.10%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	4.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets [Abstract]
Actual, Capital Amount	$ 753,815
Minimum Required for Capital Adequacy Purposes, Capital Amount	10.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 321,474
Actual, Ratio	4.50%
Leverage Ratio:
Actual, Capital Amount	$ 767,929	$ 633,779
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 356,396	$ 273,226
Actual, Ratio	8.60%	9.30%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Chemical Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid to parent company	$ 56,900	$ 64,500	$ 24,500
Risk weighted assets	7,130,000	5,700,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	830,294	654,031
Minimum Required for Capital Adequacy Purposes, Capital Amount	570,073	455,633
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 712,591	$ 569,541
Actual, Ratio	11.70%	11.50%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 756,966	$ 582,783
Minimum Required for Capital Adequacy Purposes, Capital Amount	427,555	227,816
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 570,073	$ 341,725
Actual, Ratio	10.60%	10.20%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	8.00%	6.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets [Abstract]
Actual, Capital Amount	$ 756,966
Minimum Required for Capital Adequacy Purposes, Capital Amount	10.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 320,666
Actual, Ratio	4.50%
Minimum Required for Capital Adequacy Purposes, Ratio	$ 463,184
Required to be Well Capital Under Prompt Corrective Action Regulations, Ratio	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 756,966	$ 582,783
Minimum Required for Capital Adequacy Purposes, Capital Amount	355,911	273,048
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 444,888	$ 341,310
Actual, Ratio	8.50%	8.50%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%	5.00%

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator and denominator of the basic and diluted earnings per common share computations
Net Income (Loss) Attributable to Parent	$ 25,504	$ 24,467	$ 19,024	$ 17,835	$ 15,305	$ 16,767	$ 16,236	$ 13,813	$ 86,830	$ 62,121	$ 56,808
Denominator for basic earnings per common share, weighted average common shares outstanding											28,183,000
Weighted average common stock equivalents									272,000	221,000	169,000
Denominator for diluted earnings per common share									36,353,000	31,588,000	28,352,000
Basic earnings per common share	$ 0.67	$ 0.64	$ 0.54	$ 0.54	$ 0.47	$ 0.51	$ 0.54	$ 0.46	$ 2.41	$ 1.98	$ 2.02
Diluted earnings per common share	$ 0.66	$ 0.64	$ 0.54	$ 0.54	$ 0.46	$ 0.51	$ 0.54	$ 0.46	$ 2.39	$ 1.97	$ 2
Stock Option [Member]
Earnings Per Common Share (Textual) [Abstract]
Average number of exercisable employee stock option awards that were not included in the computation of diluted earnings per common share									54,771	240,165	356,328

Parent Company Only Financia130

Parent Company Only Financial Statements Financial Position (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets [Abstract]
Investment securities available-for-sale	$ 553,731	$ 748,864
Premises and equipment	106,317	97,496
Goodwill	287,393	180,128
Other assets	246,346	141,467
Total Assets	9,188,797	7,322,143
Liabilities and Equity [Abstract]
Other liabilities	76,466	56,572
Nonrevolving line of credit	25,000
Subordinated Debt	18,544
Shareholders' equity	1,015,974	797,133	$ 696,500	$ 596,341
Total Liabilities and Shareholders' Equity	9,188,797	7,322,143
Chemical Financial Corporation [Member]
Assets [Abstract]
Cash at subsidiary bank	28,884	45,820
Investment in subsidiary bank	1,023,285	745,045
Premises and equipment	3,632	3,601
Goodwill	1,092	1,092
Other assets	13,051	4,654
Total Assets	1,069,944	800,212
Liabilities and Equity [Abstract]
Other liabilities	10,426	3,079
Nonrevolving line of credit	25,000	0
Subordinated Debt	18,544	0
Shareholders' equity	1,015,974	797,133
Total Liabilities and Shareholders' Equity	$ 1,069,944	$ 800,212

Parent Company Only Financia131

Parent Company Only Financial Statements Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Other income									$ 1,907	$ 697	$ 861
Interest Expense	$ 5,153	$ 5,234	$ 3,944	$ 3,450	$ 3,563	$ 3,561	$ 3,720	$ 3,866	17,781	14,710	17,414
Operating expenses	57,824	58,265	56,785	51,020	52,616	42,702	42,425	42,182	223,894	179,925	164,948
Federal income tax benefit	(10,200)	(9,600)	(9,100)	(8,100)	(7,050)	(7,450)	(7,100)	(5,900)	(37,000)	(27,500)	(24,300)
Net Income	$ 25,504	$ 24,467	$ 19,024	$ 17,835	$ 15,305	$ 16,767	$ 16,236	$ 13,813	86,830	62,121	56,808
Chemical Financial Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Cash dividends from subsidiary bank									56,860	64,468	24,488
Other income									144	95	390
Total income									57,004	64,563	24,878
Interest Expense									761	42	0
Operating expenses									7,794	7,200	4,735
Total Expenses									8,555	7,242	4,735
Income (loss) before income taxes and equity in undistributed net income of subsidiary bank									48,449	57,321	20,143
Federal income tax benefit									2,582	2,302	1,556
Equity in undistributed net income of subsidiary bank									35,799	2,498	35,109
Net Income									$ 86,830	$ 62,121	$ 56,808

Parent Company Only Financia132

Parent Company Only Financial Statements Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net Income	$ 25,504	$ 24,467	$ 19,024	$ 17,835	$ 15,305	$ 16,767	$ 16,236	$ 13,813	$ 86,830	$ 62,121	$ 56,808
Net Cash Provided by (Used in) Operating Activities [Abstract]
Share-based compensation expense									3,478	2,931	2,854
Depreciation of premises and equipment									11,028	8,980	8,713
Net Cash Provided by Operating Activities									102,982	89,931	89,679
Net Cash Provided by (Used in) Investing Activities [Abstract]
Payments to Acquire Businesses, Net of Cash Acquired									16,551	(14,260)	0
Purchase of investment securities available-for-sale									0	0	(304,264)
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities									239,179	165,749	154,959
Purchases of premises and equipment, net									(8,527)	(13,411)	(8,664)
Net Cash Used in Investing Activities									(408,717)	(478,755)	(648,475)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payments of Ordinary Dividends, Common Stock									(36,918)	(29,528)	(24,521)
Proceeds from issuance of common stock, net of issuance costs									0	76,175	53,925
Proceeds from (Repayments of) Other Debt									125,000	0	0
Proceeds from directors' stock purchase plan and exercise of stock options									2,473	1,242	806
Restricted Stock, Value, Shares Issued Net of Tax Withholdings									(571)	(701)	(379)
Net Cash Provided by Financing Activities									361,504	261,056	213,449
Net Increase (Decrease) in Cash and Cash Equivalents									55,769	(127,768)	(345,347)
Cash and Cash Equivalents at Beginning of Year				183,020				310,788	183,020	310,788	656,135
Cash and Cash Equivalents at End of Year	238,789				183,020				238,789	183,020	310,788
Chemical Financial Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net Income									86,830	62,121	56,808
Net Cash Provided by (Used in) Operating Activities [Abstract]
Share-based compensation expense									3,478	2,931	2,854
Gain on sale of available-for-sale investment securities									0	0	(245)
Depreciation of premises and equipment									318	327	416
Equity in undistributed net income of subsidiary bank									(35,799)	(2,498)	(35,109)
Net increase in other assets									2,873	1,101	(711)
Net increase (decrease) in other liabilities									(19,033)	(2,519)	563
Net Cash Provided by Operating Activities									38,667	61,463	24,576
Net Cash Provided by (Used in) Investing Activities [Abstract]
Payments to Acquire Businesses, Net of Cash Acquired									(45,267)	(117,853)	0
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities									0	0	5,000
Purchases of premises and equipment, net									(320)	(26)	(9)
Net Cash Used in Investing Activities									(45,587)	(117,879)	4,991
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payments of Ordinary Dividends, Common Stock									(36,918)	(29,528)	(24,521)
Proceeds from issuance of common stock, net of issuance costs									0	76,175	53,925
Repayments of Subordinated Debt									0	10,310	0
Proceeds from (Repayments of) Other Debt									25,000	0	0
Proceeds from directors' stock purchase plan and exercise of stock options									2,473	1,242	806
Restricted Stock, Value, Shares Issued Net of Tax Withholdings									(571)	(701)	(379)
Net Cash Provided by Financing Activities									(10,016)	36,878	29,831
Net Increase (Decrease) in Cash and Cash Equivalents									(16,936)	(19,538)	59,398
Cash and Cash Equivalents at Beginning of Year				$ 45,820				$ 65,358	45,820	65,358	5,960
Cash and Cash Equivalents at End of Year	$ 28,884				$ 45,820				$ 28,884	$ 45,820	$ 65,358

Summary of Quarterly Stateme133

Summary of Quarterly Statements of Income (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data [Abstract]
Interest income	$ 80,629	$ 78,851	$ 69,679	$ 62,630	$ 61,807	$ 56,629	$ 55,180	$ 53,645	$ 291,789	$ 227,261	$ 214,061
Interest Expense	5,153	5,234	3,944	3,450	3,563	3,561	3,720	3,866	17,781	14,710	17,414
Net Interest Income	75,476	73,617	65,735	59,180	58,244	53,068	51,460	49,779	274,008	212,551	196,647
Provision for loan losses	2,000	1,500	1,500	1,500	1,500	1,500	1,500	1,600	6,500	6,100	11,000
Noninterest Income	20,052	20,215	20,674	19,275	18,227	15,351	15,801	13,716	80,216	63,095	60,409
Operating expenses	57,824	58,265	56,785	51,020	52,616	42,702	42,425	42,182	223,894	179,925	164,948
Income before income taxes	35,704	34,067	28,124	25,935	22,355	24,217	23,336	19,713	123,830	89,621	81,108
Federal income tax expense	10,200	9,600	9,100	8,100	7,050	7,450	7,100	5,900	37,000	27,500	24,300
Net Income	$ 25,504	$ 24,467	$ 19,024	$ 17,835	$ 15,305	$ 16,767	$ 16,236	$ 13,813	$ 86,830	$ 62,121	$ 56,808
Basic earnings per common share	$ 0.67	$ 0.64	$ 0.54	$ 0.54	$ 0.47	$ 0.51	$ 0.54	$ 0.46	$ 2.41	$ 1.98	$ 2.02
Diluted earnings per common share	0.66	0.64	0.54	0.54	0.46	0.51	0.54	0.46	2.39	1.97	2
Cash dividends declared per share	$ 0.26	$ 0.26	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.23	$ 0.23	$ 1	$ 0.94	$ 0.87