TCF Financial 10-Q 30 Apr 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 18, 2014
Entity Information [Line Items]	'	'
Entity Registrant Name	'CHEMICAL FINANCIAL CORP	'
Entity Central Index Key	'0000019612	'
Document Type	'10-Q	'
Document Period End Date	31-Mar-14	'
Amendment Flag	'false	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	29,865,861

Consolidated_Statements_of_Fin

Consolidated Statements of Financial Position (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Cash and cash equivalents:	'	'	'
Cash and cash due from banks	$122,288	$130,811	$101,501
Interest-bearing deposits with the Federal Reserve Bank	260,097	179,977	477,225
Total cash and cash equivalents	382,385	310,788	578,726
Investment securities:	'	'	'
Available-for-sale, at fair value	657,818	684,570	703,622
Held-to-maturity (fair value - $272,407 at March 31, 2014, $268,271 at December 31, 2013 and $261,405 at March 31, 2013)	278,099	273,905	257,749
Total investment securities	935,917	958,475	961,371
Loans held-for-sale, at fair value	3,814	5,219	14,850
Loans	4,753,289	4,647,621	4,185,261
Allowance for loan losses	-78,473	-79,072	-82,834
Net loans	4,674,816	4,568,549	4,102,427
Premises and equipment (net of accumulated depreciation of $102,163 at March 31, 2014, $100,261 at December 31, 2013 and $94,068 at March 31, 2013)	74,779	75,308	73,501
Goodwill	120,164	120,164	120,164
Other intangible assets	12,872	13,424	14,902
Interest receivable and other assets	133,581	132,781	124,587
Total Assets	6,338,328	6,184,708	5,990,528
Deposits:	'	'	'
Noninterest-bearing	1,219,081	1,227,768	1,086,986
Interest-bearing	4,012,212	3,894,617	3,920,372
Total deposits	5,231,293	5,122,385	5,007,358
Interest payable and other liabilities	40,209	38,395	30,931
Short-term borrowings	361,231	327,428	347,484
Total liabilities	5,632,733	5,488,208	5,385,773
Shareholders’ equity:	'	'	'
Preferred stock, no par value: Authorized - 200,000 shares, none issued	0	0	0
Issued and outstanding — 29,865,841 shares at March 31, 2014, 29,789,825 shares at December 31, 2013 and 27,532,377 shares at March 31, 2013	29,866	29,790	27,532
Additional paid-in capital	489,045	488,177	433,648
Retained earnings	205,985	199,053	174,209
Accumulated other comprehensive loss	-19,301	-20,520	-30,634
Total shareholders’ equity	705,595	696,500	604,755
Total Liabilities and Shareholders’ Equity	$6,338,328	$6,184,708	$5,990,528

Consolidated_Statements_of_Fin1

Consolidated Statements of Financial Position (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, except Share data, unless otherwise specified
Held-to-maturity, fair value	$272,407	$268,271	$261,405
Accumulated depreciation of premises and equipment	$102,163	$100,261	$94,068
Preferred stock, no par value	'	'	'
Preferred stock, shares authorized	200,000	200,000	200,000
Preferred stock, shares issued	0	0	0
Common stock, par value	$1	$1	$1
Common stock, shares authorized	45,000,000	45,000,000	45,000,000
Common stock, shares issued	29,865,841	29,789,825	27,532,377
Common stock, shares outstanding	29,865,841	29,789,825	27,532,377

Consolidated_Statements_of_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Interest Income	'	'
Interest and fees on loans	$49,195	$47,905
Interest on investment securities:	'	'
Taxable	2,383	2,438
Tax-exempt	1,704	1,564
Dividends on nonmarketable equity securities	238	151
Interest on deposits with the Federal Reserve Bank	125	321
Total interest income	53,645	52,379
Interest Expense	'	'
Interest on deposits	3,745	4,566
Interest on short-term borrowings	121	114
Interest on Federal Home Loan Bank (FHLB) advances	0	47
Total interest expense	3,866	4,727
Net Interest Income	49,779	47,652
Provision for loan losses	1,600	3,000
Net interest income after provision for loan losses	48,179	44,652
Noninterest Income	'	'
Service charges and fees on deposit accounts	4,930	5,195
Wealth management revenue	3,631	3,445
Other charges and fees for customer services	4,194	4,651
Mortgage banking revenue	794	2,012
Gain on sale of investment securities	0	847
Other	167	89
Total noninterest income	13,716	16,239
Operating Expenses	'	'
Salaries, wages and employee benefits	24,184	23,369
Occupancy	4,374	3,663
Equipment and software	3,461	3,450
Other	10,163	11,475
Total operating expenses	42,182	41,957
Income before income taxes	19,713	18,934
Federal income tax expense	5,900	5,700
Net Income	$13,813	$13,234
Net Income Per Common Share:	'	'
Basic (in dollars per share)	$0.46	$0.48
Diluted (in dollars per share)	$0.46	$0.48
Cash Dividends Declared Per Common Share (dollars per share)	$0.23	$0.21

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Net income	$13,813	$13,234
Other comprehensive income, net of tax:	'	'
Net unrealized gains on investment securities available-for-sale, net of tax expense of $857 and $227 for the three months ended March 31, 2014 and 2013, respectively	1,593	420
Reclassification adjustment for realized gain on sale of investment securities available-for-sale included in net income, net of tax expense of $296 for the three months ended March 31, 2013	0	-551
Adjustment for pension and other postretirement benefits, net of tax expense (benefit) of $(201) and $332 for the three months ended March 31, 2014 and 2013, respectively	-374	616
Total other comprehensive income, net of tax	1,219	485
Comprehensive income	$15,032	$13,719

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Tax expense (benefit) on net unrealized gains (losses) on investment securities available-for-sale	$857	$227
Tax expense (benefit) on reclassification adjustment for realized gains on sale of investment securities available-for-sale	0	296
Tax expense (benefit) on adjustment for pension and other postretirement benefits	($201)	$332

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (USD $)	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
In Thousands, unless otherwise specified
Beginning Balance at Dec. 31, 2012	$596,341	$27,499	$433,195	$166,766	($31,119)
Changes in Stockholders' Equity [Roll Forward]	'	'	'	'	'
Comprehensive income	13,719	'	'	13,234	485
Cash dividends declared per share: $0.21 and $0.23 per share for the three months ended March 31, 2013 and March 31, 2014, respectively	-5,791	'	'	-5,791	'
Stock issued - stock options	-10	'	-10	'	'
Shares issued – directors’ stock plans	239	11	228	'	'
Shares issued – restricted stock units	-372	22	-394	'	'
Share-based compensation	629	'	629	'	'
Ending Balance at Mar. 31, 2013	604,755	27,532	433,648	174,209	-30,634
Beginning Balance at Dec. 31, 2013	696,500	29,790	488,177	199,053	-20,520
Changes in Stockholders' Equity [Roll Forward]	'	'	'	'	'
Comprehensive income	15,032	'	'	13,813	1,219
Cash dividends declared per share: $0.21 and $0.23 per share for the three months ended March 31, 2013 and March 31, 2014, respectively	-6,881	'	'	-6,881	'
Stock issued - stock options	557	27	530	'	'
Shares issued – directors’ stock plans	310	12	298	'	'
Shares issued – restricted stock units	-477	36	-513	'	'
Share-based compensation	554	1	553	'	'
Ending Balance at Mar. 31, 2014	$705,595	$29,866	$489,045	$205,985	($19,301)

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash dividends declared per share	$0.23	$0.21

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Operating Activities	'	'
Net income	$13,813	$13,234
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Provision for loan losses	1,600	3,000
Gains on sales of loans	-647	-2,394
Proceeds from sales of loans	22,080	71,205
Loans originated for sale	-20,028	-65,996
Net gains on sales of other real estate and repossessed assets	-379	-235
Depreciation of premises and equipment	2,119	2,177
Amortization of intangible assets	695	1,001
Gain on sale of investment securities	0	-847
Net amortization of premiums and discounts on investment securities	1,093	863
Share-based compensation expense	554	629
Contributions to defined benefit pension plan	0	-15,000
Net (increase) decrease in interest receivable and other assets	-1,319	7,154
Net increase (decrease) in interest payable and other liabilities	1,239	-7,837
Net cash provided by operating activities	20,820	6,954
Investment securities – available-for-sale:	'	'
Proceeds from sales	0	33,028
Proceeds from maturities, calls and principal reductions	28,426	41,165
Purchases	0	-191,165
Investment securities – held-to-maturity:	'	'
Proceeds from maturities, calls and principal reductions	31,798	7,111
Purchases	-36,309	-34,940
Net increase in loans	-109,965	-24,374
Proceeds from sales of other real estate and repossessed assets	2,197	2,701
Purchases of premises and equipment and branch bank property, net of disposals	-1,590	-602
Net cash used in investing activities	-85,443	-167,076
Financing Activities	'	'
Net increase in interest- and noninterest-bearing demand deposits and savings accounts	78,246	125,946
Net increase (decrease) in time deposits	30,662	-40,031
Net increase in short-term borrowings	33,803	37,021
Repayment of FHLB advances	0	-34,289
Cash dividends paid	-6,881	-5,791
Proceeds from directors’ stock plans and exercise of stock options, net of shares withheld	867	229
Cash paid for payroll taxes upon conversion of restricted stock units	-477	-372
Net cash provided by financing activities	136,220	82,713
Net increase (decrease) in cash and cash equivalents	71,597	-77,409
Cash and cash equivalents at beginning of period	310,788	656,135
Cash and cash equivalents at end of period	382,385	578,726
Supplemental Disclosure of Cash Flow Information:	'	'
Interest paid	3,858	4,890
Loans transferred to other real estate and repossessed assets	2,098	2,191
Closed branch offices transferred to other real estate	0	382
Federal income taxes paid (refunded)	$0	($3,500)

Significant_Accounting_Policie

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Significant Accounting Policies	'
	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. 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 interest from its loan products and investment securities, service charges and fees from customer deposit accounts and wealth management revenue.
	Basis of Presentation
	The accompanying unaudited consolidated financial statements of the Corporation and its subsidiaries have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, the interim consolidated financial statements do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Corporation’s consolidated financial statements and footnotes thereto included in the Corporation’s Annual Report on Form 10-K for the year ended December 31, 2013. In the opinion of management, the accompanying unaudited interim consolidated financial statements contain all adjustments believed necessary to present fairly the financial condition and results of operations of the Corporation for the periods presented. Operating results for the three months ended March 31, 2014 are not necessarily indicative of the results that may be expected for the year ending December 31, 2014.
	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.
	Originated Loans
	Originated loans include all of the Corporation's portfolio loans, excluding loans acquired on April 30, 2010 in the acquisition of O.A.K. Financial Corporation (OAK). Originated loans also include loans acquired as part of the Corporation's branch acquisition 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 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 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 Accounting Standards Codification (ASC) Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality (ASC 310-30). ASC 310-30 allows investors to aggregate loans acquired 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 14 pools 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 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 estimated remaining life of the loan pool 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 reported 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 refinanced by 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 reported as 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 loans.
	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 the loan's 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 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, with higher weighting placed on the most recent years, and loan loss trends and (iv) an unallocated allowance based on the imprecision in the overall allowance methodology for loans collectively evaluated for impairment.
	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 process, 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.
	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 March 31, 2014, December 31, 2013 and March 31, 2013, 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.
	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. 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.
	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.
	On a quarterly basis, management assesses the reasonableness of its estimated annual effective federal tax rate based upon its current best 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 March 31, 2014, December 31, 2013 or March 31, 2013. The tax periods open to examination by the Internal Revenue Service include the calendar years ended December 31, 2013, 2012, 2011 and 2010.
	Shareholders’ 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, the Corporation’s dividend reinvestment plan, 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 March 31, 2014, there were 500,000 remaining shares available for repurchase under the Corporation’s stock repurchase programs.
	Underwritten Public Offering of Common Stock
	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, after deducting the underwriting discount and issuance-related expenses, totaled $53.9 million. The Corporation intends to use the net proceeds to fund a portion of the purchase price in connection with its pending acquisition of Northwestern Bancorp, Inc.
	Shelf Registration
	The Corporation filed a universal shelf registration statement with the Securities and Exchange Commission (SEC) on May 23, 2013, which became effective on June 7, 2013, to register up to $100 million in securities. The shelf registration statement provides the Corporation with the ability to raise capital, subject to SEC rules and limitations, if the Corporation's board of directors decides to do so. As previously discussed, on September 18, 2013, the Corporation completed a $57.6 million public stock offering, which does not take into account the underwriting discount and issuance-related expenses. As a result of the public stock offering, the Corporation has $42.4 million in securities still available under the shelf registration statement.
	Preferred Stock
	On April 20, 2009, the shareholders of the Corporation authorized the board of directors of the Corporation to issue up to 200,000 shares of preferred stock in connection with either an acquisition by the Corporation of an entity that has shares of preferred stock issued and outstanding pursuant to any program established by the United States government or participation by the Corporation in any program established by the United States government. At March 31, 2014, no shares of preferred stock were issued and outstanding.
	Legal Matters
	The Corporation and Chemical Bank are subject to certain legal actions arising in the ordinary course of business. In the opinion of management, after consultation with legal counsel, the ultimate disposition of these matters is not expected to have a material adverse effect on the consolidated financial condition or results of operations of the Corporation.
	Adopted Accounting Pronouncements
	Joint and Several Liability Arrangements
	In February 2013, the Financial Accounting Standards Board (FASB) issued ASU 2013-04, Liabilities (Topic 405): Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date (ASU 2013-04). ASU 2013-04 provides guidance in relation to the recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. ASU 2013-04 is effective for interim and annual periods beginning after December 15, 2013 and should be applied retrospectively for all periods presented for those obligations resulting from joint and several liability arrangements that exist at the beginning of the fiscal year of adoption. The adoption of ASU 2013-04 as of January 1, 2014 did not have a material impact on the Corporation's consolidated financial condition or results of operations.
	Accounting for Investments in Qualified Affordable Housing Projects
	In January 2014, the FASB issued ASU 2014-01, Investments—Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Qualified Affordable Housing Projects, a consensus of the FASB Emerging Issues Task Force (ASU 2014-01). ASU 2014-01 allows limited liability investors in qualified affordable housing projects to amortize the cost of their investment in proportion to tax credits and other tax benefits received (referred to as the "proportional amortization method"), and present the amortization as a component of income tax expense. The proportional amortization method replaces the equity method, which requires the investment performance to be included in pre-tax income. The following conditions must be met in order for an investor to use the proportional amortization method: (i) it is probable that the tax credits allocable to the investor will be available, (ii) the investor does not have the ability to exercise significant influence over the operating and financial policies of the limited liability entity, (iii) substantially all of the projected benefits are from tax credits and other tax benefits, (iv) the investor's projected yield based solely on the cash flows from the tax credits and other tax benefits is positive, and (v) the investor is a limited liability investor in the limited liability entity for both legal and tax purposes, and the investor's liability is limited to its capital investment. The decision to apply the proportional amortization method is an accounting policy method that, if elected, must be applied consistently to all investments that meet the above conditions. An investor that does not qualify for the proportional amortization method or elects not to apply it will account for its investment under the cost or equity method in accordance with current guidance. ASU 2014-01 also introduces disclosure requirements for all investments in qualified affordable housing projects, regardless of the accounting method used for those investments. An investor must disclose (i) the nature of investments in qualified affordable housing projects and (ii) the effect of the measurement of those investments and the related tax credits on its financial statements. ASU 2014-01 is effective for public companies for interim and annual periods beginning after December 15, 2014, with early adoption permitted. Once adopted, the guidance must be applied retrospectively to all periods presented.
	The Corporation elected to early-adopt ASU 2014-01 as of January 1, 2014. The Corporation previously accounted for its investments in qualified affordable housing projects under the equity method; however, the Corporation determined that its investments in its qualified affordable housing projects meet the conditions set forth in ASU 2014-01 to account for these investments under the proportional amortization method. The Corporation invests in qualified affordable housing projects solely for the purpose of obtaining tax credits and other tax benefits. Accordingly, the Corporation believes that amortizing its investments in qualified affordable housing projects as a component of income tax expense rather than as a component of operating expenses better reflects the nature and intent of these investments. As a result of adopting ASU 2014-01, the Corporation recognized additional income tax expense attributable to the amortization of investments in qualified affordable housing projects of $0.1 million during the three months ended March 31, 2014. While the adoption of ASU 2014-01 requires retrospective application to all periods presented, the Corporation did not restate income tax expense for the three months ended March 31, 2013 as the amount of additional income tax expense attributable to the amortization of investments in qualified affordable housing projects was not considered material. The Corporation's remaining investment in qualified affordable housing projects totaled $3.2 million at both March 31, 2014 and December 31, 2013 and $3.5 million at March 31, 2013.
	Pending Accounting Pronouncements
	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 adoption of ASU 2014-04 is not expected to have a material impact on the Corporation's consolidated financial condition or results of operations.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2014
Business Combinations [Abstract]	'
Acquisitions	'
	Acquisitions
	Pending Acquisition of Northwestern Bancorp, Inc.
	On March 10, 2014, the Corporation and Northwestern Bancorp, Inc. (Northwestern), the parent company of Northwestern Bank, a community bank based in Traverse City, Michigan, entered into a definitive agreement whereby the Corporation will acquire Northwestern in an all cash transaction valued at $120 million, subject to adjustment under limited circumstances. The Corporation anticipates the transaction, with cost savings fully phased in and excluding the impact of acquisition-related transaction costs, to be immediately accretive to earnings. Closing of the merger, which is expected to occur in the third quarter of 2014, is subject to certain conditions, including approval by the shareholders of Northwestern and regulatory approval. The Corporation recognized $0.3 million of pre-tax acquisition-related costs during the three months ended March 31, 2014.
	Acquisition of 21 Branches
	On December 7, 2012, Chemical Bank acquired 21 branches located in the Northeast and Battle Creek regions of Michigan, including $404 million in deposits and $44 million in loans (branch acquisition transaction). 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 branch acquisition transaction, the Corporation recorded goodwill of $6.8 million and other intangible assets attributable to customer core deposits of $5.6 million.
	Acquisition of O.A.K. Financial Corporation (OAK)
	On April 30, 2010, the Corporation acquired OAK and OAK's wholly-owned bank subsidiary, Byron Bank, for total consideration of $83.7 million. Byron Bank, which was subsequently consolidated with and into Chemical Bank, provided traditional banking services and products through 14 banking offices serving communities in Ottawa, Allegan and Kent counties in west Michigan. At the acquisition date, OAK had total assets of $820 million, including total loans of $627 million, and total deposits of $693 million, including brokered deposits of $193 million.
	Upon acquisition, the OAK loan portfolio had contractually required principal payments receivable of $683 million and a fair value of $627 million.The outstanding contractual principal balance and the carrying amount of the acquired loan portfolio were $313 million and $289 million, respectively, at March 31, 2014, compared to $320 million and $295 million, respectively, at December 31, 2013 and $400 million and $374 million, respectively, at March 31, 2013.
	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:
			Three Months Ended
			March 31,
			2014			2013
			(In thousands)
	Balance at beginning of period		$	32,610		$	49,390
	Additions (reductions)*		821			(491		)
	Accretion recognized in interest income		(3,843		)	(4,940		)
	Reclassification from nonaccretable difference		10,000			125
	Balance at end of period		$	39,588		$	44,084
	*	Represents additions of 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 has determined that the overall credit quality of the acquired loan portfolio has improved, which has resulted in an improvement in expected cash flows of loan pools in the acquired commercial loan portfolio. Accordingly, management reclassified $10.0 million during the three months ended March 31, 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	3 Months Ended
	Mar. 31, 2014
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 March 31, 2014, December 31, 2013 and March 31, 2013:
		Investment Securities Available-for-Sale
		Amortized		Unrealized		Unrealized		Fair
		Cost		Gains		Losses		Value
		(In thousands)
	31-Mar-14
	Government sponsored agencies	$	91,613	$	295	$	298	$	91,610
	State and political subdivisions	42,369		1,408		—		43,777
	Residential mortgage-backed securities	291,187		1,023		3,472		288,738
	Collateralized mortgage obligations	167,622		393		1,296		166,719
	Corporate bonds	65,003		505		93		65,415
	Preferred stock	1,389		170		—		1,559
	Total	$	659,183	$	3,794	$	5,159	$	657,818
	31-Dec-13
	Government sponsored agencies	$	93,895	$	250	$	382	$	93,763
	State and political subdivisions	42,450		1,355		7		43,798
	Residential mortgage-backed securities	303,495		968		5,097		299,366
	Collateralized mortgage obligations	182,128		452		1,639		180,941
	Corporate bonds	65,028		499		252		65,275
	Preferred stock	1,389		63		25		1,427
	Total	$	688,385	$	3,587	$	7,402	$	684,570
	31-Mar-13
	Government sponsored agencies	$	94,939	$	608	$	168	$	95,379
	State and political subdivisions	47,043		2,206		—		49,249
	Residential mortgage-backed securities	237,256		1,984		48		239,192
	Collateralized mortgage obligations	246,751		1,087		170		247,668
	Corporate bonds	65,114		783		349		65,548
	Preferred stock	6,144		442		—		6,586
	Total	$	697,247	$	7,110	$	735	$	703,622
		Investment Securities Held-to-Maturity
		Amortized		Unrealized		Unrealized		Fair
		Cost		Gains		Losses		Value
		(In thousands)
	31-Mar-14
	State and political subdivisions	$	267,599	$	5,331	$	6,983	$	265,947
	Trust preferred securities	10,500		—		4,040		6,460
	Total	$	278,099	$	5,331	$	11,023	$	272,407
	31-Dec-13
	State and political subdivisions	$	263,405	$	5,462	$	6,846	$	262,021
	Trust preferred securities	10,500		—		4,250		6,250
	Total	$	273,905	$	5,462	$	11,096	$	268,271
	31-Mar-13
	State and political subdivisions	$	247,249	$	10,002	$	1,886	$	255,365
	Trust preferred securities	10,500		—		4,460		6,040
	Total	$	257,749	$	10,002	$	6,346	$	261,405
	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 March 31, 2014, the Corporation held $10.5 million of trust preferred investment securities that were recorded as held-to-maturity, with $10.0 million of these securities representing a 100% interest in a trust preferred investment security of a small non-public bank holding company in Michigan that has been assessed by the Corporation as financially strong. The remaining $0.5 million represents a 10% interest in another trust preferred investment security of a small non-public bank holding company located in Michigan that was categorized as well-capitalized under regulatory guidelines at March 31, 2014.
	At March 31, 2014, it was the Corporation’s opinion that the market for trust preferred investment securities was not active, and thus, in accordance with GAAP, when there is a significant decrease in the volume and activity for an asset or liability in relation to normal market activity, adjustments to transaction or quoted prices may be necessary or a change in valuation technique or multiple valuation techniques may be appropriate. The Corporation obtained pricing information for its trust preferred investment securities from an independent third-party pricing source. The pricing information was based on both observable inputs and unobservable inputs, including appropriate risk adjustments that market participants would make for possible nonperformance, illiquidity and issuer specifics such as size, leverage position and location. The observable inputs were based on the existing market and insight into appropriate rate of return adjustments that market participants would require for the additional risk associated with a single issue investment security of this nature. Based on the information obtained from the independent third-party pricing source, the Corporation calculated a fair value at March 31, 2014 of $6.2 million on its $10.0 million trust preferred investment security and $0.3 million on its $0.5 million trust preferred investment security, resulting in a combined unrealized loss of $4.0 million at that date.
	The following is a summary of the amortized cost and fair value of investment securities at March 31, 2014, 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.
		31-Mar-14
		Amortized		Fair Value
		Cost
		(In thousands)
	Investment Securities Available-for-Sale:
	Due in one year or less	$	160,093	$	159,861
	Due after one year through five years	403,039		402,251
	Due after five years through ten years	90,096		89,721
	Due after ten years	4,566		4,426
	Preferred stock	1,389		1,559
	Total	$	659,183	$	657,818
	Investment Securities Held-to-Maturity:
	Due in one year or less	$	38,060	$	38,096
Due after one year through five years	104,588		105,892
Due after five years through ten years	79,077		79,653
Due after ten years	56,374		48,766
Total	$	278,099	$	272,407
The following schedule summarizes information for both available-for-sale and held-to-maturity investment securities with gross unrealized losses at March 31, 2014, December 31, 2013 and March 31, 2013, 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		Gross		Fair		Gross		Fair		Gross
	Value		Unrealized		Value		Unrealized		Value		Unrealized
			Losses				Losses				Losses
	(In thousands)
31-Mar-14
Government sponsored agencies	$	45,396	$	110	$	15,204	$	188	$	60,600	$	298
State and political subdivisions	79,787		4,942		56,180		2,041		135,967		6,983
Residential mortgage-backed securities	247,397		3,472		—		—		247,397		3,472
Collateralized mortgage obligations	76,900		885		12,833		411		89,733		1,296
Corporate bonds	—		—		14,907		93		14,907		93
Trust preferred securities	—		—		6,460		4,040		6,460		4,040
Total	$	449,480	$	9,409	$	105,584	$	6,773	$	555,064	$	16,182
31-Dec-13
Government sponsored agencies	$	47,352	$	205	$	14,031	$	177	$	61,383	$	382
State and political subdivisions	126,345		6,475		19,074		378		145,419		6,853
Residential mortgage-backed securities	274,076		5,097		—		—		274,076		5,097
Collateralized mortgage obligations	84,995		1,127		14,684		512		99,679		1,639
Corporate bonds	14,931		78		19,826		174		34,757		252
Trust preferred securities	—		—		6,250		4,250		6,250		4,250
Preferred stock	1,024		25		—		—		1,024		25
Total	$	548,723	$	13,007	$	73,865	$	5,491	$	622,588	$	18,498
31-Mar-13
Government sponsored agencies	$	17,281	$	168	$	—	$	—	$	17,281	$	168
State and political subdivisions	73,880		1,667		10,685		219		84,565		1,886
Residential mortgage-backed securities	86,179		45		374		3		86,553		48
Collateralized mortgage obligations	27,802		133		8,560		37		36,362		170
Corporate bonds	—		—		19,651		349		19,651		349
Trust preferred securities	—		—		6,040		4,460		6,040		4,460
Total	$	205,142	$	2,013	$	45,310	$	5,068	$	250,452	$	7,081
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 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, as of March 31, 2014, represented an other-than-temporary impairment (OTTI). Management believed that the unrealized losses on investment securities at March 31, 2014 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. Unrealized losses of $4.0 million in the trust preferred securities portfolio, related to trust preferred securities of two well-capitalized bank holding companies in Michigan, were attributable to illiquidity in financial markets for these types of investments. The Corporation performed an analysis of the creditworthiness of these issuers and concluded that, at March 31, 2014, the Corporation expected to recover the entire amortized cost basis of these investment securities.
At March 31, 2014, 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 March 31, 2014, 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.

Loans

Loans	3 Months Ended
	Mar. 31, 2014
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 March 31, 2014, December 31, 2013 and March 31, 2013 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. These loans consist of relatively small amounts that are spread across many individual borrowers.
	Home equity — Loans and lines of credit whereby consumers utilize equity in their personal residence, generally through a second mortgage, as collateral to secure the loan.
	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 loans follows:
		March 31,				December 31,				March 31,
		2014				2013				2013
		(In thousands)
	Commercial loan portfolio:
	Commercial	$	1,208,641			$	1,176,307			$	1,038,115
	Commercial real estate	1,279,167				1,232,658				1,162,383
	Real estate construction	85,084				89,795				65,367
	Land development	13,761				20,066				32,640
	Subtotal	2,586,653				2,518,826				2,298,505
	Consumer loan portfolio:
	Residential mortgage	962,009				960,423				872,454
	Consumer installment	675,412				644,769				540,216
	Home equity	529,215				523,603				474,086
	Subtotal	2,166,636				2,128,795				1,886,756
	Total loans	$	4,753,289			$	4,647,621			$	4,185,261
	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 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 four executive and senior officers who have varying limits exceeding $1.5 million and up to $3.5 million. With respect to the group loan authorities, the Corporation 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 $5.0 million, depending on risk rating and credit action required. A directors’ loan committee, consisting of nine members of the board of directors, including the chief executive officer and senior credit officer, meets bi-weekly to consider loans in amounts over $5.0 million, and certain loans under $5.0 million depending on a loan’s risk rating and credit action required. Loans over $10.0 million require majority approval of the board of directors.
	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, which 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 March 31, 2014, December 31, 2013 and March 31, 2013:
		Commercial				Commercial Real Estate				Real Estate			Land			Total
										Construction			Development
		(In thousands)
	31-Mar-14
	Originated Portfolio:
	Risk Grades 1-5	$	1,060,743			$	1,034,517			$	70,750		$	3,831		$	2,169,841
	Risk Grade 6	18,359				33,962				680			968			53,969
	Risk Grade 7	33,768				32,671				815			700			67,954
	Risk Grade 8	17,301				27,552				160			2,267			47,280
	Risk Grade 9	950				16				—			—			966
	Subtotal	1,131,121				1,128,718				72,405			7,766			2,340,010
	Acquired Portfolio:
	Risk Grades 1-5	67,326				139,130				12,679			3,906			223,041
	Risk Grade 6	2,423				2,627				—			—			5,050
	Risk Grade 7	3,635				7,753				—			—			11,388
	Risk Grade 8	4,136				939				—			2,089			7,164
	Risk Grade 9	—				—				—			—			—
	Subtotal	77,520				150,449				12,679			5,995			246,643
	Total	$	1,208,641			$	1,279,167			$	85,084		$	13,761		$	2,586,653
	31-Dec-13
	Originated Portfolio:
	Risk Grades 1-5	$	1,024,461			$	991,964			$	75,696		$	6,874		$	2,098,995
Risk Grade 6	20,082				34,248				654			969			55,953
Risk Grade 7	29,776				30,377				738			3,128			64,019
Risk Grade 8	17,414				28,580				371			2,309			48,674
Risk Grade 9	960				18				—			—			978
Subtotal	1,092,693				1,085,187				77,459			13,280			2,268,619
Acquired Portfolio:
Risk Grades 1-5	73,763				133,653				12,336			4,667			224,419
Risk Grade 6	5,472				5,022				—			—			10,494
Risk Grade 7	852				7,792				—			—			8,644
Risk Grade 8	3,527				1,004				—			2,119			6,650
Risk Grade 9	—				—				—			—			—
Subtotal	83,614				147,471				12,336			6,786			250,207
Total	$	1,176,307			$	1,232,658			$	89,795		$	20,066		$	2,518,826
31-Mar-13
Originated Portfolio:
Risk Grades 1-5	$	868,683			$	858,484			$	50,601		$	11,720		$	1,789,488
Risk Grade 6	28,037				44,603				59			434			73,133
Risk Grade 7	26,040				29,359				1,020			5,754			62,173
Risk Grade 8	10,471				34,170				168			4,105			48,914
Risk Grade 9	1,715				1,679				—			—			3,394
Subtotal	934,946				968,295				51,848			22,013			1,977,102
Acquired Portfolio:
Risk Grades 1-5	93,560				176,523				13,519			7,783			291,385
Risk Grade 6	6,870				5,035				—			242			12,147
Risk Grade 7	874				11,146				—			—			12,020
Risk Grade 8	1,865				1,384				—			2,602			5,851
Risk Grade 9	—				—				—			—			—
Subtotal	103,169				194,088				13,519			10,627			321,403
Total	$	1,038,115			$	1,162,383			$	65,367		$	32,640		$	2,298,505
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 in a nonperforming status until they meet the Corporation’s definition of a performing TDR, at which time they are considered 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 March 31, 2014, December 31, 2013 and March 31, 2013:
	Residential Mortgage				Consumer				Home Equity			Total
					Installment							Consumer
	(In thousands)
31-Mar-14
Originated Loans:
Performing	$	937,968			$	672,984			$	497,196		$	2,108,148
Nonperforming	12,833				806				2,668			16,307
Subtotal	950,801				673,790				499,864			2,124,455
Acquired Loans:
Performing	11,150				1,622				29,020			41,792
Nonperforming	58				—				331			389
Subtotal	11,208				1,622				29,351			42,181
Total	$	962,009			$	675,412			$	529,215		$	2,166,636
31-Dec-13
Originated Loans:
Performing	$	934,747			$	642,370			$	488,996		$	2,066,113
Nonperforming	14,134				676				3,382			18,192
Subtotal	948,881				643,046				492,378			2,084,305
Acquired Loans:
Performing	11,481				1,723				31,182			44,386
Nonperforming	61				—				43			104
Subtotal	11,542				1,723				31,225			44,490
Total	$	960,423			$	644,769			$	523,603		$	2,128,795
31-Mar-13
Originated Loans:
Performing	$	844,240			$	537,817			$	432,489		$	1,814,546
Nonperforming	14,931				699				3,711			19,341
Subtotal	859,171				538,516				436,200			1,833,887
Acquired Loans:
Performing	13,283				1,700				37,724			52,707
Nonperforming	—				—				162			162
Subtotal	13,283				1,700				37,886			52,869
Total	$	872,454			$	540,216			$	474,086		$	1,886,756
Nonperforming Loans
A summary of nonperforming loans follows:
	March 31,				December 31,				March 31,
	2014				2013				2013
	(In thousands)
Nonaccrual loans:
Commercial	$	18,251			$	18,374			$	12,186
Commercial real estate	27,568				28,598				35,849
Real estate construction	160				371				168
Land development	2,267				2,309				4,105
Residential mortgage	6,589				8,921				10,407
Consumer installment	806				676				699
Home equity	2,046				2,648				2,837
Total nonaccrual loans	57,687				61,897				66,251
Accruing loans contractually past due 90 days or more as to interest or principal payments:
Commercial	43				536				4
Commercial real estate	730				190				177
Real estate construction	—				—				—
Land development	—				—				—
Residential mortgage	—				537				196
Consumer installment	—				—				—
Home equity	622				734				874
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,395				1,997				1,251
Nonperforming TDRs:
Commercial loan portfolio	11,218				13,414				14,587
Consumer loan portfolio	6,244				4,676				4,328
Total nonperforming TDRs	17,462				18,090				18,915
Total nonperforming loans	$	76,544			$	81,984			$	86,417
The Corporation’s nonaccrual loans at March 31, 2014, December 31, 2013 and March 31, 2013 included $44.4 million, $37.3 million and $47.0 million, respectively, of nonaccrual TDRs.
Impaired Loans
The following schedule presents impaired loans by classes of loans at March 31, 2014, December 31, 2013 and March 31, 2013:
	Recorded				Unpaid				Related
	Investment				Principal				Valuation
					Balance				Allowance
	(In thousands)
31-Mar-14
Impaired loans with a valuation allowance:
Commercial	$	3,534			$	3,704			$	1,250
Commercial real estate	3,720				3,878				371
Real estate construction	—				—				—
Land development	—				—				—
Residential mortgage	19,944				19,944				444
Subtotal	27,198				27,526				2,065
Impaired loans with no related valuation allowance:
Commercial	38,150				42,914				—
Commercial real estate	49,074				62,207				—
Real estate construction	160				366				—
Land development	4,472				7,773				—
Residential mortgage	6,589				6,589				—
Consumer installment	806				806				—
Home equity	2,046				2,046				—
Subtotal	101,297				122,701				—
Total impaired loans:
Commercial	41,684				46,618				1,250
Commercial real estate	52,794				66,085				371
Real estate construction	160				366				—
Land development	4,472				7,773				—
Residential mortgage	26,533				26,533				444
Consumer installment	806				806				—
Home equity	2,046				2,046				—
Total	$	128,495			$	150,227			$	2,065
31-Dec-13
Impaired loans with a valuation allowance:
Commercial	$	2,517			$	2,656			$	728
Commercial real estate	2,576				2,965				353
Real estate construction	—				—				—
Land development	—				—				—
Residential mortgage	17,408				17,408				510
Subtotal	22,501				23,029				1,591
Impaired loans with no related valuation allowance:
Commercial	38,838				44,377				—
Commercial real estate	48,220				61,444				—
Real estate construction	371				478				—
Land development	7,170				11,817				—
Residential mortgage	8,921				8,921				—
Consumer installment	676				676				—
Home equity	2,648				2,648				—
Subtotal	106,844				130,361				—
Total impaired loans:
Commercial	41,355				47,033				728
Commercial real estate	50,796				64,409				353
Real estate construction	371				478				—
Land development	7,170				11,817				—
Residential mortgage	26,329				26,329				510
Consumer installment	676				676				—
Home equity	2,648				2,648				—
Total	$	129,345			$	153,390			$	1,591
	Recorded				Unpaid				Related
	Investment				Principal				Valuation
					Balance				Allowance
	(In thousands)
31-Mar-13
Impaired loans with a valuation allowance:
Commercial	$	4,347			$	4,931			$	1,629
Commercial real estate	12,876				13,045				3,893
Real estate construction	—				—				—
Land development	—				—				—
Residential mortgage	17,296				17,296				662
Subtotal	34,519				35,272				6,184
Impaired loans with no related valuation allowance:
Commercial	21,565				26,737				—
Commercial real estate	42,852				56,259				—
Real estate construction	372				442				—
Land development	11,247				15,510				—
Residential mortgage	10,407				10,407				—
Consumer installment	699				699				—
Home equity	2,837				2,837				—
Subtotal	89,979				112,891				—
Total impaired loans:
Commercial	25,912				31,668				1,629
Commercial real estate	55,728				69,304				3,893
Real estate construction	372				442				—
Land development	11,247				15,510				—
Residential mortgage	27,703				27,703				662
Consumer installment	699				699				—
Home equity	2,837				2,837				—
Total	$	124,498			$	148,163			$	6,184
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 $21.7 million, $24.0 million and $23.7 million at March 31, 2014, December 31, 2013 and March 31, 2013, respectively, includes confirmed losses (partial charge-offs) of $17.8 million, $20.2 million and $19.9 million, respectively, and fair value discount adjustments of $3.9 million, $3.8 million and $3.8 million, respectively.
Impaired loans included $11.5 million, $9.8 million and $8.6 million at March 31, 2014, December 31, 2013 and March 31, 2013, 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 $41.8 million, $39.6 million and $30.7 million at March 31, 2014, December 31, 2013 and March 31, 2013, respectively, of performing TDRs.
The following schedule presents information related to impaired loans for the three months ended March 31, 2014 and 2013:
	Three Months Ended March 31, 2014
	Average				Interest Income
	Recorded				Recognized
	Investment				While on
					Impaired Status
	(In thousands)
Commercial	$	41,607			$	333
Commercial real estate	53,320				361
Real estate construction	167				—
Land development	4,643				37
Residential mortgage	26,781				303
Consumer installment	773				—
Home equity	2,168				—
Total	$	129,459			$	1,034
	Three Months Ended March 31, 2013
	Average				Interest Income
	Recorded				Recognized
	Investment				While on
					Impaired Status
	(In thousands)
Commercial	$	26,953			$	193
Commercial real estate	56,745				288
Real estate construction	363				2
Land development	10,914				91
Residential mortgage	28,920				295
Consumer installment	719				—
Home equity	2,962				—
Total	$	127,576			$	869
The following schedule presents the aging status of the recorded investment in loans by classes of loans at March 31, 2014, December 31, 2013 and March 31, 2013:
	31-60				61-89				Accruing			Non-accrual			Total		Current		Total
	Days				Days				Loans			Loans			Past Due				Loans
	Past Due				Past Due				Past Due
									90 Days
									or More
	(In thousands)
31-Mar-14
Originated Portfolio:
Commercial	$	6,003			$	1,832			$	43		$	18,251		$	26,129	$	1,104,992	$	1,131,121
Commercial real estate	4,094				1,098				730			27,568			33,490		1,095,228		1,128,718
Real estate construction	18				—				—			160			178		72,227		72,405
Land development	—				—				—			2,267			2,267		5,499		7,766
Residential mortgage	1,259				1,138				—			6,589			8,986		941,815		950,801
Consumer installment	1,950				313				—			806			3,069		670,721		673,790
Home equity	1,500				256				622			2,046			4,424		495,440		499,864
Total	$	14,824			$	4,637			$	1,395		$	57,687		$	78,543	$	4,385,922	$	4,464,465
Acquired Portfolio:
Commercial	$	—			$	—			$	6,496		$	—		$	6,496	$	71,024	$	77,520
Commercial real estate	—				—				2,549			—			2,549		147,900		150,449
Real estate construction	—				—				—			—			—		12,679		12,679
Land development	—				—				2,089			—			2,089		3,906		5,995
Residential mortgage	—				—				58			—			58		11,150		11,208
Consumer installment	49				—				—			—			49		1,573		1,622
Home equity	49				—				331			—			380		28,971		29,351
Total	$	98			$	—			$	11,523		$	—		$	11,621	$	277,203	$	288,824
	31-60				61-89				Accruing			Non-accrual			Total		Current		Total
	Days				Days				Loans			Loans			Past Due				Loans
	Past Due				Past Due				Past Due
									90 Days
									or More
	(In thousands)
31-Dec-13
Originated Portfolio:
Commercial	$	4,748			$	865			$	536		$	18,374		$	24,523	$	1,068,170	$	1,092,693
Commercial real estate	8,560				1,604				190			28,598			38,952		1,046,235		1,085,187
Real estate construction	—				4,107				—			371			4,478		72,981		77,459
Land development	—				—				—			2,309			2,309		10,971		13,280
Residential mortgage	2,191				103				537			8,921			11,752		937,129		948,881
Consumer installment	2,630				359				—			676			3,665		639,381		643,046
Home equity	1,452				278				734			2,648			5,112		487,266		492,378
Total	$	19,581			$	7,316			$	1,997		$	61,897		$	90,791	$	4,262,133	$	4,352,924
Acquired Portfolio:
Commercial	$	—			$	—			$	5,656		$	—		$	5,656	$	77,958	$	83,614
Commercial real estate	—				133				1,695			—			1,828		145,643		147,471
Real estate construction	—				—				—			—			—		12,336		12,336
Land development	—				—				2,332			—			2,332		4,454		6,786
Residential mortgage	—				—				61			—			61		11,481		11,542
Consumer installment	3				51				—			—			54		1,669		1,723
Home equity	394				—				43			—			437		30,788		31,225
Total	$	397			$	184			$	9,787		$	—		$	10,368	$	284,329	$	294,697
31-Mar-13
Originated Portfolio:
Commercial	$	7,948			$	1,664			$	4		$	12,186		$	21,802	$	913,144	$	934,946
Commercial real estate	9,195				2,541				177			35,849			47,762		920,533		968,295
Real estate construction	—				—				—			168			168		51,680		51,848
Land development	927				—				—			4,105			5,032		16,981		22,013
Residential mortgage	2,605				831				196			10,407			14,039		845,132		859,171
Consumer installment	2,038				524				—			699			3,261		535,255		538,516
Home equity	1,374				235				874			2,837			5,320		430,880		436,200
Total	$	24,087			$	5,795			$	1,251		$	66,251		$	97,384	$	3,713,605	$	3,810,989
Acquired Portfolio:
Commercial	$	191			$	—			$	2,504		$	—		$	2,695	$	100,474	$	103,169
Commercial real estate	479				157				3,341			—			3,977		190,111		194,088
Real estate construction	—				—				—			—			—		13,519		13,519
Land development	—				—				2,602			—			2,602		8,025		10,627
Residential mortgage	405				—				—			—			405		12,878		13,283
Consumer installment	34				33				—			—			67		1,633		1,700
Home equity	154				—				162			—			316		37,570		37,886
Total	$	1,263			$	190			$	8,609		$	—		$	10,062	$	364,210	$	374,272
Loans Modified Under Troubled Debt Restructurings (TDRs)
The following schedule presents the Corporation’s loans reported as TDRs at March 31, 2014, December 31, 2013 and March 31, 2013:
	Performing TDRs				Non-Performing TDRs				Nonaccrual TDRs			Total
	(In thousands)
31-Mar-14
Commercial loan portfolio	$	28,123			$	11,218			$	40,511		$	79,852
Consumer loan portfolio	13,700				6,244				3,875			23,819
Total	$	41,823			$	17,462			$	44,386		$	103,671
31-Dec-13
Commercial loan portfolio	$	26,839			$	13,414			$	31,961		$	72,214
Consumer loan portfolio	12,732				4,676				5,321			22,729
Total	$	39,571			$	18,090			$	37,282		$	94,943
31-Mar-13
Commercial loan portfolio	$	17,755			$	14,587			$	42,097		$	74,439
Consumer loan portfolio	12,968				4,328				4,916			22,212
Total	$	30,723			$	18,915			$	47,013		$	96,651
The following schedule provides information on the Corporation's TDRs that were modified during the three months ended March 31, 2014 and 2013:
	Number			Pre-				Post-
	of Loans			Modification				Modification
				Recorded				Recorded
				Investment				Investment
	(Dollars in thousands)
Three Months Ended March 31, 2014
Commercial loan portfolio:
Commercial	12			$	8,356			$	8,356
Commercial real estate	9			2,790				2,790
Land development	1			72				72
Subtotal – commercial loan portfolio	22			11,218				11,218
Consumer loan portfolio (residential mortgage)	30			987				978
Total	52			$	12,205			$	12,196
Three Months Ended March 31, 2013 (as revised)
Commercial loan portfolio:
Commercial	11			$	1,606			$	1,606
Commercial real estate	14			3,644				3,644
Real estate construction	2			364				364
Land development	2			432				432
Subtotal – commercial loan portfolio	29			6,046				6,046
Consumer loan portfolio (residential mortgage)	18			1,391				1,355
Total	47			$	7,437			$	7,401
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 three months ended March 31, 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:
	Number of			Principal Balance at End of Period
	Loans
	(Dollars in thousands)
Three Months Ended March 31, 2014
Commercial loan portfolio:
Commercial	1			$	104
Commercial real estate	2			1,670
Subtotal – commercial loan portfolio	3			1,774
Consumer loan portfolio (residential mortgage)	—			—
Total	3			$	1,774
Three Months Ended March 31, 2013 (as revised)
Commercial loan portfolio:
Commercial	17			$	1,053
Commercial real estate	1			126
Real estate construction	1			160
Subtotal – commercial loan portfolio	19			1,339
Consumer loan portfolio (residential mortgage)	5			484
Total	24			$	1,823
During the three months ended March 31, 2013, the Corporation had excluded nonaccrual TDRs from the schedule of TDRs that were modified during the three months ended March 31, 2013 and the schedule of TDRs for which there was a payment default during the three months ended March 31, 2013. The Corporation has revised the amounts reported for the three months ended March 31, 2013 in these schedules to include activity related to all TDRs, including nonaccrual TDRs.
Allowance for Loan Losses
The following schedule presents, by loan portfolio segment, the changes in the allowance for the three months ended March 31, 2014 and details regarding the balance in the allowance and the recorded investment in loans at March 31, 2014 by impairment evaluation method.
	Commercial				Consumer				Unallocated			Total
	Loan				Loan
	Portfolio				Portfolio
	(In thousands)
Changes in allowance for loan losses for the three months ended March 31, 2014:
Beginning balance	$	44,482			$	30,145			$	4,445		$	79,072
Provision for loan losses	960				855				(215		)	1,600
Charge-offs	(1,209		)		(2,263		)		—			(3,472		)
Recoveries	777				496				—			1,273
Ending balance	$	45,010			$	29,233			$	4,230		$	78,473
Allowance for loan losses balance at March 31, 2014 attributable to:
Loans individually evaluated for impairment	$	1,621			$	444			$	—		$	2,065
Loans collectively evaluated for impairment	43,389				28,289				4,230			75,908
Loans acquired with deteriorated credit quality	—				500				—			500
Total	$	45,010			$	29,233			$	4,230		$	78,473
Recorded investment (loan balance) at March 31, 2014:
Loans individually evaluated for impairment	$	87,587			$	19,944			$	—		$	107,531
Loans collectively evaluated for impairment	2,252,423				2,104,511				—			4,356,934
Loans acquired with deteriorated credit quality	246,643				42,181				—			288,824
Total	$	2,586,653			$	2,166,636			$	—		$	4,753,289
The following schedule presents, by loan portfolio segment, details regarding the balance in the allowance and the recorded investment in loans at December 31, 2013 by impairment evaluation method.
	Commercial				Consumer				Unallocated			Total
	Loan				Loan
	Portfolio				Portfolio
	(In thousands)
Allowance for loan losses balance at December 31, 2013 attributable to:
Loans individually evaluated for impairment	$	1,081			$	510			$	—		$	1,591
Loans collectively evaluated for impairment	43,401				29,135				4,445			76,981
Loans acquired with deteriorated credit quality	—				500				—			500
Total	$	44,482			$	30,145			$	4,445		$	79,072
Recorded investment (loan balance) at December 31, 2013:
Loans individually evaluated for impairment	$	89,905			$	17,408			$	—		$	107,313
Loans collectively evaluated for impairment	2,178,714				2,066,897				—			4,245,611
Loans acquired with deteriorated credit quality	250,207				44,490				—			294,697
Total	$	2,518,826			$	2,128,795			$	—		$	4,647,621
The following schedule presents, by loan portfolio segment, the changes in the allowance for the three months ended March 31, 2013 and details regarding the balance in the allowance and the recorded investment in loans at March 31, 2013 by impairment evaluation method.
	Commercial				Consumer				Unallocated			Total
	Loan				Loan
	Portfolio				Portfolio
	(In thousands)
Changes in allowance for loan losses for the three months ended March 31, 2013:
Beginning balance	$	49,975			$	29,333			$	5,183		$	84,491
Provision for loan losses	2,437				871				(308		)	3,000
Charge-offs	(3,516		)		(1,958		)		—			(5,474		)
Recoveries	211				606				—			817
Ending balance	$	49,107			$	28,852			$	4,875		$	82,834
Allowance for loan losses balance at March 31, 2013 attributable to:
Loans individually evaluated for impairment	$	5,522			$	662			$	—		$	6,184
Loans collectively evaluated for impairment	43,585				27,690				4,875			76,150
Loans acquired with deteriorated credit quality	—				500				—			500
Total	$	49,107			$	28,852			$	4,875		$	82,834
Recorded investment (loan balance) at March 31, 2013:
Loans individually evaluated for impairment	$	84,650			$	17,296			$	—		$	101,946
Loans collectively evaluated for impairment	1,892,452				1,816,591				—			3,709,043
Loans acquired with deteriorated credit quality	321,403				52,869				—			374,272
Total	$	2,298,505			$	1,886,756			$	—		$	4,185,261
The allowance attributable to acquired loans of $0.5 million at March 31, 2014, December 31, 2013 and March 31, 2013 was primarily attributable to two consumer loan pools in the acquired loan portfolio that had a decline in expected cash flows. Management determined that the overall credit quality of the acquired loan portfolio had improved at March 31, 2014, which has resulted in an improvement in expected cash flows of loan pools in the acquired commercial loan portfolio. Accordingly, management reclassified $10.0 million during the three months ended March 31, 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. There were no material changes in expected cash flows for the remaining acquired loan pools at December 31, 2013 or March 31, 2013.

Intangible_Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Intangible Assets	'
	Intangible Assets
	The Corporation has the following types of intangible assets: goodwill, core deposit intangible assets and mortgage servicing rights (MSRs). Goodwill and core deposit intangible assets arose as the result of business combinations or other acquisitions. MSRs arose as a result of selling residential mortgage loans in the secondary market while retaining the right to service these loans and receive servicing income over the life of the loan. Amortization is recorded on the core deposit intangible assets and MSRs. Goodwill is not amortized but is evaluated at least annually for impairment. The Corporation’s most recent annual goodwill impairment test performed as of October 31, 2013 did not indicate that an impairment of goodwill existed. The Corporation also determined that no triggering events have occurred that indicated impairment from the most recent valuation date through March 31, 2014 and that the Corporation's goodwill was not impaired at March 31, 2014.
	The following table shows the net carrying value of the Corporation’s intangible assets:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Goodwill	$	120,164		$	120,164		$	120,164
	Other intangible assets:
	Core deposit intangible assets	$	9,556		$	10,001		$	11,417
	Mortgage servicing rights	3,316			3,423			3,485
	Total other intangible assets	$	12,872		$	13,424		$	14,902
	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:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Gross original amount	$	18,659		$	18,659		$	18,659
	Accumulated amortization	9,103			8,658			7,242
	Carrying amount	$	9,556		$	10,001		$	11,417
	Amortization expense for the three months ended March 31	$	445					$	493
	The estimated future amortization expense on core deposit intangible assets for periods ending after March 31, 2014 is as follows: 2014 — $1.3 million; 2015 — $1.7 million; 2016 — $1.5 million; 2017 — $1.2 million; 2018 — $1.2 million; 2019 and thereafter — $2.7 million.
	The following shows the net carrying value and fair value of MSRs and the total loans that the Corporation is servicing for others:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Net carrying value of MSRs	$	3,316		$	3,423		$	3,485
	Fair value of MSRs	$	6,706		$	6,878		$	5,326
	Loans serviced for others that have servicing rights capitalized	$	877,530		$	886,730		$	907,823
	The following table shows the activity for capitalized MSRs:
		Three Months Ended March 31,
		2014			2013
		(In thousands)
	Balance at beginning of period	$	3,423		$	3,478
	Additions	143			515
	Amortization	(250		)	(508		)
	Balance at end of period	$	3,316		$	3,485
	There was no impairment valuation allowance recorded on MSRs as of March 31, 2014, December 31, 2013 or March 31, 2013.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2014
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:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Net unrealized gains (losses) on investment securities – available-for-sale, net of related tax expense (benefit) of $(478) at March 31, 2014, $(1,335) at December 31, 2013 and $2,232 at March 31, 2013	$	(887	)	$	(2,480	)	$	4,143
	Pension and other postretirement benefits adjustment, net of related tax benefit of $9,915 at March 31, 2014, $9,714 at December 31, 2013 and $18,726 at March 31, 2013	(18,414		)	(18,040		)	(34,777		)
	Accumulated other comprehensive loss	$	(19,301	)	$	(20,520	)	$	(30,634	)

Regulatory_Capital

Regulatory Capital	3 Months Ended
	Mar. 31, 2014
Banking and Thrift [Abstract]	'
Regulatory Capital	'
	Regulatory Capital
	Federal and state banking regulations place certain restrictions on the transfer of assets, in the form of dividends, loans, or advances, from Chemical Bank to the Corporation. As of March 31, 2014, 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. At March 31, 2014, 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 of the Corporation totaled $4.76 billion, $4.64 billion and $4.22 billion at March 31, 2014, December 31, 2013 and March 31, 2013, respectively.
	At March 31, 2014, December 31, 2013 and March 31, 2013, Chemical Bank’s capital ratios exceeded the quantitative capital ratios required for an institution to be considered “well-capitalized.” Significant factors that may affect capital adequacy include, but are not limited to, a disproportionate growth in assets versus capital and a change in mix or credit quality of assets.
	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:
		Actual				Minimum Required for Capital Adequacy Purposes				Required to be Well Capitalized Under Prompt Corrective Action Regulations
		Capital		Ratio		Capital		Ratio		Capital		Ratio
		Amount				Amount				Amount
		(Dollars in thousands)
	31-Mar-14
	Total Capital to Risk-Weighted Assets:
	Corporation	$	659,644	13.8	%	$	381,146	8	%	N/A		N/A
	Chemical Bank	589,254		12.4		380,542		8		$	475,678	10	%
	Tier 1 Capital to Risk-Weighted Assets:
	Corporation	599,856		12.6		190,573		4		N/A		N/A
	Chemical Bank	529,560		11.1		190,271		4		285,407		6
	Leverage Ratio:
	Corporation	599,856		9.9		243,070		4		N/A		N/A
	Chemical Bank	529,560		8.7		242,939		4		303,673		5
	31-Dec-13
	Total Capital to Risk-Weighted Assets:
	Corporation	$	649,836	14	%	$	371,465	8	%	N/A		N/A
	Chemical Bank	579,494		12.5		370,881		8		$	463,601	10	%
	Tier 1 Capital to Risk-Weighted Assets:
	Corporation	591,535		12.7		185,732		4		N/A		N/A
	Chemical Bank	521,283		11.2		185,440		4		278,160		6
	Leverage Ratio:
	Corporation	591,535		9.9		239,010		4		N/A		N/A
	Chemical Bank	521,283		8.7		238,884		4		298,605		5
	31-Mar-13
	Total Capital to Risk-Weighted Assets:
	Corporation	$	561,092	13.3	%	$	337,508	8	%	N/A		N/A
	Chemical Bank	545,361		13		336,576		8		$	420,720	10	%
	Tier 1 Capital to Risk-Weighted Assets:
	Corporation	507,985		12		168,754		4		N/A		N/A
	Chemical Bank	492,398		11.7		168,288		4		252,432		6
	Leverage Ratio:
	Corporation	507,985		8.8		230,992		4		N/A		N/A
	Chemical Bank	492,398		8.5		230,544		4		288,179		5

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2014
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 these investment securities.
	Level 2	Valuation is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market. Level 2 valuations for the Corporation include government sponsored agency securities, including securities issued by the Federal Home Loan Bank, Federal Home Loan Mortgage Corporation, Federal National Mortgage Association, Federal Farm Credit Bank, Student Loan Marketing Corporation and the Small Business Administration, securities issued by certain state and political subdivisions, residential mortgage-backed securities, collateralized mortgage obligations, corporate bonds and preferred stock. 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, trust preferred investment securities, impaired loans, goodwill, core deposit 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 were as follows:
			Fair Value Measurements – Recurring Basis
			Quoted Prices				Significant				Significant				Total
			In Active				Other				Unobservable
			Markets for				Observable				Inputs
			Identical				Inputs				(Level 3)
			Assets				(Level 2)
			(Level 1)
			(In thousands)
	31-Mar-14
	Investment securities – available-for-sale:
	Government sponsored agencies		$	—			$	91,610			$	—			$	91,610
	State and political subdivisions		—				43,777				—				43,777
	Residential mortgage-backed securities		—				288,738				—				288,738
	Collateralized mortgage obligations		—				166,719				—				166,719
	Corporate bonds		—				65,415				—				65,415
	Preferred stock		—				1,559				—				1,559
	Total investment securities – available-for-sale		—				657,818				—				657,818
	Loans held-for-sale		—				3,814				—				3,814
	Total assets measured at fair value on a recurring basis		$	—			$	661,632			$	—			$	661,632
	31-Dec-13
	Investment securities – available-for-sale:
	Government sponsored agencies		$	—			$	93,763			$	—			$	93,763
	State and political subdivisions		—				43,798				—				43,798
	Residential mortgage-backed securities		—				299,366				—				299,366
	Collateralized mortgage obligations		—				180,941				—				180,941
	Corporate bonds		—				65,275				—				65,275
	Preferred stock		—				1,427				—				1,427
	Total investment securities – available-for-sale		—				684,570				—				684,570
	Loans held-for-sale		—				5,219				—				5,219
	Total assets measured at fair value on a recurring basis		$	—			$	689,789			$	—			$	689,789
	31-Mar-13
	Investment securities – available-for-sale:
	Government sponsored agencies		$	—			$	95,379			$	—			$	95,379
	State and political subdivisions		—				49,249				—				49,249
	Residential mortgage-backed securities		—				239,192				—				239,192
	Collateralized mortgage obligations		—				247,668				—				247,668
	Corporate bonds		—				65,548				—				65,548
	Preferred stock		—				1,831				—				1,831
	Total investment securities – available-for-sale		—				698,867				—				698,867
	Loans held-for-sale		—				14,850				—				14,850
	Total assets measured at fair value on a recurring basis		$	—			$	713,717			$	—			$	713,717
	There were no liabilities recorded at fair value on a recurring basis at March 31, 2014, December 31, 2013 or March 31, 2013.
	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 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 March 31, 2014, December 31, 2013 and March 31, 2013, 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 and MSRs. These items are both recorded at fair value when initially recorded. Subsequently, core deposit 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 impairment is identified, the Corporation classifies impaired core deposit intangible assets subject to nonrecurring fair value measurements as Level 3 valuations. The fair value of MSRs is initially 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 March 31, 2014, December 31, 2013 and March 31, 2013, there was no impairment identified for core deposit intangible assets or 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 were as follows:
		Fair Value Measurements – Nonrecurring Basis
		Quoted Prices				Significant				Significant				Total
		In Active				Other				Unobservable
		Markets for				Observable				Inputs
		Identical				Inputs				(Level 3)
		Assets				(Level 2)
		(Level 1)
		(In thousands)
31-Mar-14
Impaired originated loans		$	—			$	—			$	29,461			$	29,461
Other real estate/repossessed assets		—				—				10,056				10,056
Total		$	—			$	—			$	39,517			$	39,517
31-Dec-13
Impaired originated loans		$	—			$	—			$	28,852			$	28,852
Other real estate/repossessed assets		—				—				9,776				9,776
Total		$	—			$	—			$	38,628			$	38,628
31-Mar-13
Impaired originated loans		$	—			$	—			$	47,073			$	47,073
Other real estate/repossessed assets		—				—				18,194				18,194
Total		$	—			$	—			$	65,267			$	65,267
There were no liabilities recorded at fair value on a nonrecurring basis at March 31, 2014, December 31, 2013 and March 31, 2013.
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 March 31, 2014, December 31, 2013 and March 31, 2013, 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 — available-for-sale that are not measured at fair value on a recurring basis, which previously consisted of fixed-rate cumulative preferred stock issued by a bank holding company under the U.S. Government’s Troubled Asset Relief Program (TARP) with no maturity date, was based on cost. This preferred stock was not traded on a public exchange and did not have a readily determinable fair value. Accordingly, the Corporation had recorded this preferred stock as a cost-method asset as prescribed by ASC Topic 325-20, Cost Method Investments. The issuer redeemed this preferred stock during the second quarter of 2013. Because no impairment indicators were present at March 31, 2013, the Corporation was not required to estimate the fair value of this preferred stock.
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. After reviewing the assumptions used to measure the fair value for its trust preferred investment securities, the Corporation transferred its trust preferred investment securities from nonrecurring Level 2 assets to nonrecurring Level 3 assets during the second quarter of 2013.
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 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.
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. 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. The fair values for variable-interest rate time deposits with defined maturities approximate their carrying amounts.
Short-term borrowings consist of securities sold under agreements to repurchase. 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.
Fair value measurements for FHLB advances are estimated 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.
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 was as follows:
		Level in Fair Value Measurement		31-Mar-14								31-Dec-13						31-Mar-13
		Hierarchy		Carrying				Fair				Carrying				Fair		Carrying		Fair
				Amount				Value				Amount				Value		Amount		Value
				(In thousands)
Assets:
Cash and cash equivalents		Level 1		$	382,385			$	382,385			$	310,788			$	310,788	$	578,726	$	578,726
Investment securities:
Available-for-sale		Level 2		657,818				657,818				684,570				684,570		698,867		698,867
Available-for-sale		NA		—				—				—				—		4,755		4,755
Held-to-maturity		Level 2		267,599				265,947				263,405				262,021		257,749		261,405
Held-to-maturity		Level 3		10,500				6,460				10,500				6,250		—		—
Nonmarketable equity securities		NA		25,572				25,572				25,572				25,572		25,572		25,572
Loans held-for-sale		Level 2		3,814				3,814				5,219				5,219		14,850		14,850
Net loans		Level 3		4,674,816				4,688,814				4,568,549				4,575,532		4,102,427		4,123,585
Interest receivable		Level 2		16,945				16,945				15,748				15,748		16,960		16,960
Liabilities:
Deposits without defined maturities		Level 2		$	3,868,700			$	3,868,700			$	3,790,454			$	3,790,454	$	3,574,832	$	3,574,832
Time deposits		Level 3		1,362,593				1,371,312				1,331,931				1,340,746		1,432,526		1,448,634
Interest payable		Level 2		876				876				868				868		1,338		1,338
Short-term borrowings		Level 2		361,231				361,231				327,428				327,428		347,484		347,484

Earnings_Per_Common_Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2014
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 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 loss per common share and thus are 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:
		Three Months Ended March 31,
		2014		2013
		(In thousands, except per share data)
	Numerator for both basic and diluted earnings per common share, net income	$	13,813	$	13,234
	Denominator for basic earnings per common share, weighted average common shares outstanding	29,825		27,519
	Weighted average common stock equivalents	212		122
	Denominator for diluted earnings per common share	30,037		27,641
	Basic earnings per common share	$	0.46	$	0.48
	Diluted earnings per common share	0.46		0.48
	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 259,288 and 457,689 for the three months ended March 31, 2014 and 2013, respectively.

ShareBased_Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2014
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. Share-based compensation expense related to stock options and restricted stock units totaled $0.6 million during each of the three-month periods ended March 31, 2014 and 2013.
	During the three-month period ended March 31, 2014, the Corporation granted options to purchase 190,011 shares of common stock and 67,896 restricted stock units to certain officers. At March 31, 2014, there were 420,975 shares of common stock available for future grants under the 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. Beginning in 2013, stock options granted vest ratably over a five-year period. Stock options granted prior to 2013 generally vest ratably over a three-year period.
	A summary of activity for the Corporation’s stock options as of and for the three months ended March 31, 2014 is presented below:
			Non-Vested						Stock Options Outstanding
			Stock Options Outstanding
			Number of		Weighted-		Weighted-		Number of		Weighted-
			Options		Average		Average		Options		Average
					Exercise		Grant Date				Exercise
					Price		Fair Value				Price
					Per Share						Per Share
	Outstanding at January 1, 2014		414,080		$	24.29	$	7.19	1,073,990		$	26.84
	Granted		190,011		29.45		9.64		190,011		29.45
	Exercised		—		—		—		(50,917	)	25.4
	Vested		(117,799	)	24.32		7.21		—		—
	Forfeited/expired		(6,900	)	24.57		7.26		(8,287	)	26.56
	Outstanding at March 31, 2014		479,392		$	26.32	$	8.16	1,204,797		$	27.32
	Exercisable/vested at March 31, 2014								725,405		$	27.98
	The weighted-average remaining contractual terms were 6.2 years for all outstanding stock options and 4.3 years for exercisable stock options at March 31, 2014. The intrinsic value of all outstanding in-the-money stock options and exercisable in-the-money stock options was $7.1 million and $4.2 million, respectively, at March 31, 2014. The aggregate intrinsic values of outstanding and exercisable options at March 31, 2014 were calculated based on the closing market price of the Corporation’s common stock on March 31, 2014 of $32.45 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 March 31, 2014, unrecognized compensation expense related to stock options totaled $3.6 million and is expected to be recognized over a remaining weighted average period of 4.0 years.
	The fair value of the stock options granted during the three months ended March 31, 2014 was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions.
	Expected dividend yield	3		%
	Risk-free interest rate	2.16		%
	Expected stock price volatility	42.2		%
	Expected life of options – in years	7
	Weighted average fair value of options granted	$	9.64
	Restricted Stock Units
	In addition to stock options, the Corporation 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. The restricted stock performance units are eligible to vest from 0.25x to 1.5x the number of units originally granted depending on which, if any, of the performance target levels are met. However, if the minimum performance target level is 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 as of and for the three months ended March 31, 2014 is presented below:
			Number of		Weighted-
			Units		Average
					Grant Date
					Fair Value
					Per Unit
	Outstanding at January 1, 2014		188,532		$	21.49
	Granted		67,896		27.48
	Converted into shares of common stock		(50,267	)	19.13
	Forfeited/expired		(1,278	)	23.76
	Outstanding at March 31, 2014		204,883		$	24.04
	At March 31, 2014, unrecognized compensation expense related to restricted stock unit awards totaled $3.5 million and is expected to be recognized over a remaining weighted average period of 2.9 years.

Pension_and_Other_Postretireme

Pension and Other Postretirement Benefit Plans	3 Months Ended
	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]	'
Pension and Other Postretirement Benefit Plans	'
	Pension and Other Postretirement Benefit Plans
	The components of net periodic benefit cost for the Corporation’s qualified and nonqualified pension plans and nonqualified postretirement benefit plan are as follows:
		Three Months Ended March 31,
		2014			2013
		(In thousands)
	Defined Benefit Pension Plans
	Service cost	$	250		$	325
	Interest cost	1,312			1,167
	Expected return on plan assets	(2,078		)	(1,948		)
	Amortization of unrecognized net loss	569			946
	Net periodic benefit cost	$	53		$	490
	Postretirement Benefit Plan
	Service cost	$	5		$	—
	Interest cost	35			75
	Amortization of prior service cost	32			—
	Amortization of unrecognized net gain	(26		)	—
	Net periodic benefit cost	$	46		$	75
	The Corporation’s pension plan does not have a contribution requirement in 2014. The Corporation made a $15.0 million contribution to the pension plan during the three months ended March 31, 2013. The discount rate used to compute the Corporation's pension plan expense for 2014 is 5.00%.
	401(k) Savings Plan expense for the Corporation’s match of participants’ base compensation contributions and a 4% of eligible pay contribution to certain employees who are not grandfathered under the pension plan was $0.8 million and $0.9 million for the three months ended March 31, 2014 and 2013, respectively.

Financial_Guarantees

Financial Guarantees	3 Months Ended
	Mar. 31, 2014
Guarantees [Abstract]	'
Financial Guarantees	'
	Financial Guarantees
	In the normal course of business, the Corporation is a party to financial instruments containing credit risk that are not required to be reflected in the consolidated statements of financial position. For the Corporation, these financial instruments are financial and performance standby letters of credit. The Corporation has risk management policies to identify, monitor and limit exposure to credit risk. To mitigate credit risk for these financial guarantees, the Corporation generally determines the need for specific covenant, guarantee and collateral requirements on a case-by-case basis, depending on the nature of the financial instrument and the customer’s creditworthiness. At March 31, 2014, December 31, 2013 and March 31, 2013, the Corporation had $45 million, $47 million and $47 million, respectively, of outstanding financial and performance standby letters of credit that expire in five years or less. The majority of these standby letters of credit are collateralized. The Corporation determined that there were no potential losses from standby letters of credit at March 31, 2014, December 31, 2013 and March 31, 2013.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
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. 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 interest from its loan products and investment securities, service charges and fees from customer deposit accounts and wealth management revenue.
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited consolidated financial statements of the Corporation and its subsidiaries have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, the interim consolidated financial statements do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Corporation’s consolidated financial statements and footnotes thereto included in the Corporation’s Annual Report on Form 10-K for the year ended December 31, 2013. In the opinion of management, the accompanying unaudited interim consolidated financial statements contain all adjustments believed necessary to present fairly the financial condition and results of operations of the Corporation for the periods presented. Operating results for the three months ended March 31, 2014 are not necessarily indicative of the results that may be expected for the year ending December 31, 2014.
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.
Originated Loans	'
	Originated Loans
	Originated loans include all of the Corporation's portfolio loans, excluding loans acquired on April 30, 2010 in the acquisition of O.A.K. Financial Corporation (OAK). Originated loans also include loans acquired as part of the Corporation's branch acquisition 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 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 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 Accounting Standards Codification (ASC) Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality (ASC 310-30). ASC 310-30 allows investors to aggregate loans acquired 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 14 pools 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 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 estimated remaining life of the loan pool 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 reported 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 refinanced by 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 reported as 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 loans.
	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 the loan's 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 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, with higher weighting placed on the most recent years, and loan loss trends and (iv) an unallocated allowance based on the imprecision in the overall allowance methodology for loans collectively evaluated for impairment.
	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 process, 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.
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 March 31, 2014, December 31, 2013 and March 31, 2013, 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.
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. 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.
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.
	On a quarterly basis, management assesses the reasonableness of its estimated annual effective federal tax rate based upon its current best 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 March 31, 2014, December 31, 2013 or March 31, 2013. The tax periods open to examination by the Internal Revenue Service include the calendar years ended December 31, 2013, 2012, 2011 and 2010.
Shareholders' Equity	'
	Shareholders’ 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, the Corporation’s dividend reinvestment plan, 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 March 31, 2014, there were 500,000 remaining shares available for repurchase under the Corporation’s stock repurchase programs.
	Underwritten Public Offering of Common Stock
	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, after deducting the underwriting discount and issuance-related expenses, totaled $53.9 million. The Corporation intends to use the net proceeds to fund a portion of the purchase price in connection with its pending acquisition of Northwestern Bancorp, Inc.
	Shelf Registration
	The Corporation filed a universal shelf registration statement with the Securities and Exchange Commission (SEC) on May 23, 2013, which became effective on June 7, 2013, to register up to $100 million in securities. The shelf registration statement provides the Corporation with the ability to raise capital, subject to SEC rules and limitations, if the Corporation's board of directors decides to do so. As previously discussed, on September 18, 2013, the Corporation completed a $57.6 million public stock offering, which does not take into account the underwriting discount and issuance-related expenses. As a result of the public stock offering, the Corporation has $42.4 million in securities still available under the shelf registration statement.
	Preferred Stock
	On April 20, 2009, the shareholders of the Corporation authorized the board of directors of the Corporation to issue up to 200,000 shares of preferred stock in connection with either an acquisition by the Corporation of an entity that has shares of preferred stock issued and outstanding pursuant to any program established by the United States government or participation by the Corporation in any program established by the United States government. At March 31, 2014, no shares of preferred stock were issued and outstanding.
Legal Matters	'
	Legal Matters
	The Corporation and Chemical Bank are subject to certain legal actions arising in the ordinary course of business. In the opinion of management, after consultation with legal counsel, the ultimate disposition of these matters is not expected to have a material adverse effect on the consolidated financial condition or results of operations of the Corporation.
Adopted Accounting Pronouncements	'
	Adopted Accounting Pronouncements
	Joint and Several Liability Arrangements
	In February 2013, the Financial Accounting Standards Board (FASB) issued ASU 2013-04, Liabilities (Topic 405): Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date (ASU 2013-04). ASU 2013-04 provides guidance in relation to the recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. ASU 2013-04 is effective for interim and annual periods beginning after December 15, 2013 and should be applied retrospectively for all periods presented for those obligations resulting from joint and several liability arrangements that exist at the beginning of the fiscal year of adoption. The adoption of ASU 2013-04 as of January 1, 2014 did not have a material impact on the Corporation's consolidated financial condition or results of operations.
	Accounting for Investments in Qualified Affordable Housing Projects
	In January 2014, the FASB issued ASU 2014-01, Investments—Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Qualified Affordable Housing Projects, a consensus of the FASB Emerging Issues Task Force (ASU 2014-01). ASU 2014-01 allows limited liability investors in qualified affordable housing projects to amortize the cost of their investment in proportion to tax credits and other tax benefits received (referred to as the "proportional amortization method"), and present the amortization as a component of income tax expense. The proportional amortization method replaces the equity method, which requires the investment performance to be included in pre-tax income. The following conditions must be met in order for an investor to use the proportional amortization method: (i) it is probable that the tax credits allocable to the investor will be available, (ii) the investor does not have the ability to exercise significant influence over the operating and financial policies of the limited liability entity, (iii) substantially all of the projected benefits are from tax credits and other tax benefits, (iv) the investor's projected yield based solely on the cash flows from the tax credits and other tax benefits is positive, and (v) the investor is a limited liability investor in the limited liability entity for both legal and tax purposes, and the investor's liability is limited to its capital investment. The decision to apply the proportional amortization method is an accounting policy method that, if elected, must be applied consistently to all investments that meet the above conditions. An investor that does not qualify for the proportional amortization method or elects not to apply it will account for its investment under the cost or equity method in accordance with current guidance. ASU 2014-01 also introduces disclosure requirements for all investments in qualified affordable housing projects, regardless of the accounting method used for those investments. An investor must disclose (i) the nature of investments in qualified affordable housing projects and (ii) the effect of the measurement of those investments and the related tax credits on its financial statements. ASU 2014-01 is effective for public companies for interim and annual periods beginning after December 15, 2014, with early adoption permitted. Once adopted, the guidance must be applied retrospectively to all periods presented.
	The Corporation elected to early-adopt ASU 2014-01 as of January 1, 2014. The Corporation previously accounted for its investments in qualified affordable housing projects under the equity method; however, the Corporation determined that its investments in its qualified affordable housing projects meet the conditions set forth in ASU 2014-01 to account for these investments under the proportional amortization method. The Corporation invests in qualified affordable housing projects solely for the purpose of obtaining tax credits and other tax benefits. Accordingly, the Corporation believes that amortizing its investments in qualified affordable housing projects as a component of income tax expense rather than as a component of operating expenses better reflects the nature and intent of these investments. As a result of adopting ASU 2014-01, the Corporation recognized additional income tax expense attributable to the amortization of investments in qualified affordable housing projects of $0.1 million during the three months ended March 31, 2014. While the adoption of ASU 2014-01 requires retrospective application to all periods presented, the Corporation did not restate income tax expense for the three months ended March 31, 2013 as the amount of additional income tax expense attributable to the amortization of investments in qualified affordable housing projects was not considered material. The Corporation's remaining investment in qualified affordable housing projects totaled $3.2 million at both March 31, 2014 and December 31, 2013 and $3.5 million at March 31, 2013.
Pending Accounting Pronouncements	'
	Pending Accounting Pronouncements
	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 adoption of ASU 2014-04 is not expected to have a material impact on the Corporation's consolidated financial condition or results of operations.

Acquisitions_Tables

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2014
Business Combinations [Abstract]	'
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:
			Three Months Ended
			March 31,
			2014			2013
			(In thousands)
	Balance at beginning of period		$	32,610		$	49,390
	Additions (reductions)*		821			(491		)
	Accretion recognized in interest income		(3,843		)	(4,940		)
	Reclassification from nonaccretable difference		10,000			125
	Balance at end of period		$	39,588		$	44,084
	*	Represents additions of 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 has determined that the overall credit quality of the acquired loan portfolio has improved, which has resulted in an improvement in expected cash flows of loan pools in the acquired commercial loan portfolio. Accordingly, management reclassified $10.0 million during the three months ended March 31, 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_Tables

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2014
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 March 31, 2014, December 31, 2013 and March 31, 2013:
		Investment Securities Available-for-Sale
		Amortized		Unrealized		Unrealized		Fair
		Cost		Gains		Losses		Value
		(In thousands)
	31-Mar-14
	Government sponsored agencies	$	91,613	$	295	$	298	$	91,610
	State and political subdivisions	42,369		1,408		—		43,777
	Residential mortgage-backed securities	291,187		1,023		3,472		288,738
	Collateralized mortgage obligations	167,622		393		1,296		166,719
	Corporate bonds	65,003		505		93		65,415
	Preferred stock	1,389		170		—		1,559
	Total	$	659,183	$	3,794	$	5,159	$	657,818
	31-Dec-13
	Government sponsored agencies	$	93,895	$	250	$	382	$	93,763
	State and political subdivisions	42,450		1,355		7		43,798
	Residential mortgage-backed securities	303,495		968		5,097		299,366
	Collateralized mortgage obligations	182,128		452		1,639		180,941
	Corporate bonds	65,028		499		252		65,275
	Preferred stock	1,389		63		25		1,427
	Total	$	688,385	$	3,587	$	7,402	$	684,570
	31-Mar-13
	Government sponsored agencies	$	94,939	$	608	$	168	$	95,379
	State and political subdivisions	47,043		2,206		—		49,249
	Residential mortgage-backed securities	237,256		1,984		48		239,192
	Collateralized mortgage obligations	246,751		1,087		170		247,668
	Corporate bonds	65,114		783		349		65,548
	Preferred stock	6,144		442		—		6,586
	Total	$	697,247	$	7,110	$	735	$	703,622
Held-to-maturity Securities	'
		Investment Securities Held-to-Maturity
		Amortized		Unrealized		Unrealized		Fair
		Cost		Gains		Losses		Value
		(In thousands)
	31-Mar-14
	State and political subdivisions	$	267,599	$	5,331	$	6,983	$	265,947
	Trust preferred securities	10,500		—		4,040		6,460
	Total	$	278,099	$	5,331	$	11,023	$	272,407
	31-Dec-13
	State and political subdivisions	$	263,405	$	5,462	$	6,846	$	262,021
	Trust preferred securities	10,500		—		4,250		6,250
	Total	$	273,905	$	5,462	$	11,096	$	268,271
	31-Mar-13
	State and political subdivisions	$	247,249	$	10,002	$	1,886	$	255,365
	Trust preferred securities	10,500		—		4,460		6,040
	Total	$	257,749	$	10,002	$	6,346	$	261,405
Amortized cost and fair value of debt securities by contractual maturity	'
	The following is a summary of the amortized cost and fair value of investment securities at March 31, 2014, 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.
		31-Mar-14
		Amortized		Fair Value
		Cost
		(In thousands)
	Investment Securities Available-for-Sale:
	Due in one year or less	$	160,093	$	159,861
	Due after one year through five years	403,039		402,251
	Due after five years through ten years	90,096		89,721
	Due after ten years	4,566		4,426
	Preferred stock	1,389		1,559
	Total	$	659,183	$	657,818
	Investment Securities Held-to-Maturity:
	Due in one year or less	$	38,060	$	38,096
	Due after one year through five years	104,588		105,892
	Due after five years through ten years	79,077		79,653
	Due after ten years	56,374		48,766
	Total	$	278,099	$	272,407
Summary of continuous unrealized loss position of securities	'
	The following schedule summarizes information for both available-for-sale and held-to-maturity investment securities with gross unrealized losses at March 31, 2014, December 31, 2013 and March 31, 2013, 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		Gross		Fair		Gross		Fair		Gross
		Value		Unrealized		Value		Unrealized		Value		Unrealized
				Losses				Losses				Losses
		(In thousands)
	31-Mar-14
	Government sponsored agencies	$	45,396	$	110	$	15,204	$	188	$	60,600	$	298
	State and political subdivisions	79,787		4,942		56,180		2,041		135,967		6,983
	Residential mortgage-backed securities	247,397		3,472		—		—		247,397		3,472
	Collateralized mortgage obligations	76,900		885		12,833		411		89,733		1,296
	Corporate bonds	—		—		14,907		93		14,907		93
	Trust preferred securities	—		—		6,460		4,040		6,460		4,040
	Total	$	449,480	$	9,409	$	105,584	$	6,773	$	555,064	$	16,182
	31-Dec-13
	Government sponsored agencies	$	47,352	$	205	$	14,031	$	177	$	61,383	$	382
	State and political subdivisions	126,345		6,475		19,074		378		145,419		6,853
	Residential mortgage-backed securities	274,076		5,097		—		—		274,076		5,097
	Collateralized mortgage obligations	84,995		1,127		14,684		512		99,679		1,639
	Corporate bonds	14,931		78		19,826		174		34,757		252
	Trust preferred securities	—		—		6,250		4,250		6,250		4,250
	Preferred stock	1,024		25		—		—		1,024		25
	Total	$	548,723	$	13,007	$	73,865	$	5,491	$	622,588	$	18,498
	31-Mar-13
	Government sponsored agencies	$	17,281	$	168	$	—	$	—	$	17,281	$	168
	State and political subdivisions	73,880		1,667		10,685		219		84,565		1,886
	Residential mortgage-backed securities	86,179		45		374		3		86,553		48
	Collateralized mortgage obligations	27,802		133		8,560		37		36,362		170
	Corporate bonds	—		—		19,651		349		19,651		349
	Trust preferred securities	—		—		6,040		4,460		6,040		4,460
	Total	$	205,142	$	2,013	$	45,310	$	5,068	$	250,452	$	7,081

Loans_Tables

Loans (Tables)	3 Months Ended
	Mar. 31, 2014
Receivables [Abstract]	'
Summary of loans under portfolio	'
	A summary of loans follows:
		March 31,				December 31,				March 31,
		2014				2013				2013
		(In thousands)
	Commercial loan portfolio:
	Commercial	$	1,208,641			$	1,176,307			$	1,038,115
	Commercial real estate	1,279,167				1,232,658				1,162,383
	Real estate construction	85,084				89,795				65,367
	Land development	13,761				20,066				32,640
	Subtotal	2,586,653				2,518,826				2,298,505
	Consumer loan portfolio:
	Residential mortgage	962,009				960,423				872,454
	Consumer installment	675,412				644,769				540,216
	Home equity	529,215				523,603				474,086
	Subtotal	2,166,636				2,128,795				1,886,756
	Total loans	$	4,753,289			$	4,647,621			$	4,185,261
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 March 31, 2014, December 31, 2013 and March 31, 2013:
		Commercial				Commercial Real Estate				Real Estate			Land			Total
										Construction			Development
		(In thousands)
	31-Mar-14
	Originated Portfolio:
	Risk Grades 1-5	$	1,060,743			$	1,034,517			$	70,750		$	3,831		$	2,169,841
	Risk Grade 6	18,359				33,962				680			968			53,969
	Risk Grade 7	33,768				32,671				815			700			67,954
	Risk Grade 8	17,301				27,552				160			2,267			47,280
	Risk Grade 9	950				16				—			—			966
	Subtotal	1,131,121				1,128,718				72,405			7,766			2,340,010
	Acquired Portfolio:
	Risk Grades 1-5	67,326				139,130				12,679			3,906			223,041
	Risk Grade 6	2,423				2,627				—			—			5,050
	Risk Grade 7	3,635				7,753				—			—			11,388
	Risk Grade 8	4,136				939				—			2,089			7,164
	Risk Grade 9	—				—				—			—			—
	Subtotal	77,520				150,449				12,679			5,995			246,643
	Total	$	1,208,641			$	1,279,167			$	85,084		$	13,761		$	2,586,653
	31-Dec-13
	Originated Portfolio:
	Risk Grades 1-5	$	1,024,461			$	991,964			$	75,696		$	6,874		$	2,098,995
	Risk Grade 6	20,082				34,248				654			969			55,953
	Risk Grade 7	29,776				30,377				738			3,128			64,019
	Risk Grade 8	17,414				28,580				371			2,309			48,674
	Risk Grade 9	960				18				—			—			978
	Subtotal	1,092,693				1,085,187				77,459			13,280			2,268,619
	Acquired Portfolio:
	Risk Grades 1-5	73,763				133,653				12,336			4,667			224,419
	Risk Grade 6	5,472				5,022				—			—			10,494
	Risk Grade 7	852				7,792				—			—			8,644
	Risk Grade 8	3,527				1,004				—			2,119			6,650
	Risk Grade 9	—				—				—			—			—
	Subtotal	83,614				147,471				12,336			6,786			250,207
	Total	$	1,176,307			$	1,232,658			$	89,795		$	20,066		$	2,518,826
	31-Mar-13
	Originated Portfolio:
	Risk Grades 1-5	$	868,683			$	858,484			$	50,601		$	11,720		$	1,789,488
	Risk Grade 6	28,037				44,603				59			434			73,133
	Risk Grade 7	26,040				29,359				1,020			5,754			62,173
	Risk Grade 8	10,471				34,170				168			4,105			48,914
	Risk Grade 9	1,715				1,679				—			—			3,394
	Subtotal	934,946				968,295				51,848			22,013			1,977,102
	Acquired Portfolio:
	Risk Grades 1-5	93,560				176,523				13,519			7,783			291,385
	Risk Grade 6	6,870				5,035				—			242			12,147
	Risk Grade 7	874				11,146				—			—			12,020
	Risk Grade 8	1,865				1,384				—			2,602			5,851
	Risk Grade 9	—				—				—			—			—
	Subtotal	103,169				194,088				13,519			10,627			321,403
	Total	$	1,038,115			$	1,162,383			$	65,367		$	32,640		$	2,298,505
Recorded investment of loans in the consumer loan portfolio based on the credit risk profile of loans in a performing and nonperforming status	'
	The following schedule presents the recorded investment of loans in the consumer loan portfolio based on loans in a performing status and loans in a nonperforming status at March 31, 2014, December 31, 2013 and March 31, 2013:
		Residential Mortgage				Consumer				Home Equity			Total
						Installment							Consumer
		(In thousands)
	31-Mar-14
	Originated Loans:
	Performing	$	937,968			$	672,984			$	497,196		$	2,108,148
	Nonperforming	12,833				806				2,668			16,307
	Subtotal	950,801				673,790				499,864			2,124,455
	Acquired Loans:
	Performing	11,150				1,622				29,020			41,792
	Nonperforming	58				—				331			389
	Subtotal	11,208				1,622				29,351			42,181
	Total	$	962,009			$	675,412			$	529,215		$	2,166,636
	31-Dec-13
	Originated Loans:
	Performing	$	934,747			$	642,370			$	488,996		$	2,066,113
	Nonperforming	14,134				676				3,382			18,192
	Subtotal	948,881				643,046				492,378			2,084,305
	Acquired Loans:
	Performing	11,481				1,723				31,182			44,386
	Nonperforming	61				—				43			104
	Subtotal	11,542				1,723				31,225			44,490
	Total	$	960,423			$	644,769			$	523,603		$	2,128,795
	31-Mar-13
	Originated Loans:
	Performing	$	844,240			$	537,817			$	432,489		$	1,814,546
	Nonperforming	14,931				699				3,711			19,341
	Subtotal	859,171				538,516				436,200			1,833,887
	Acquired Loans:
	Performing	13,283				1,700				37,724			52,707
	Nonperforming	—				—				162			162
	Subtotal	13,283				1,700				37,886			52,869
	Total	$	872,454			$	540,216			$	474,086		$	1,886,756
Summary of nonperforming loans	'
	A summary of nonperforming loans follows:
		March 31,				December 31,				March 31,
		2014				2013				2013
		(In thousands)
	Nonaccrual loans:
	Commercial	$	18,251			$	18,374			$	12,186
	Commercial real estate	27,568				28,598				35,849
	Real estate construction	160				371				168
	Land development	2,267				2,309				4,105
	Residential mortgage	6,589				8,921				10,407
	Consumer installment	806				676				699
	Home equity	2,046				2,648				2,837
	Total nonaccrual loans	57,687				61,897				66,251
	Accruing loans contractually past due 90 days or more as to interest or principal payments:
	Commercial	43				536				4
	Commercial real estate	730				190				177
	Real estate construction	—				—				—
	Land development	—				—				—
	Residential mortgage	—				537				196
	Consumer installment	—				—				—
	Home equity	622				734				874
	Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,395				1,997				1,251
	Nonperforming TDRs:
	Commercial loan portfolio	11,218				13,414				14,587
	Consumer loan portfolio	6,244				4,676				4,328
	Total nonperforming TDRs	17,462				18,090				18,915
	Total nonperforming loans	$	76,544			$	81,984			$	86,417
Schedule of Impaired loans by classes	'
	The following schedule presents impaired loans by classes of loans at March 31, 2014, December 31, 2013 and March 31, 2013:
		Recorded				Unpaid				Related
		Investment				Principal				Valuation
						Balance				Allowance
		(In thousands)
	31-Mar-14
	Impaired loans with a valuation allowance:
	Commercial	$	3,534			$	3,704			$	1,250
	Commercial real estate	3,720				3,878				371
	Real estate construction	—				—				—
	Land development	—				—				—
	Residential mortgage	19,944				19,944				444
	Subtotal	27,198				27,526				2,065
	Impaired loans with no related valuation allowance:
	Commercial	38,150				42,914				—
	Commercial real estate	49,074				62,207				—
	Real estate construction	160				366				—
	Land development	4,472				7,773				—
	Residential mortgage	6,589				6,589				—
	Consumer installment	806				806				—
	Home equity	2,046				2,046				—
	Subtotal	101,297				122,701				—
	Total impaired loans:
	Commercial	41,684				46,618				1,250
	Commercial real estate	52,794				66,085				371
	Real estate construction	160				366				—
	Land development	4,472				7,773				—
	Residential mortgage	26,533				26,533				444
	Consumer installment	806				806				—
	Home equity	2,046				2,046				—
	Total	$	128,495			$	150,227			$	2,065
	31-Dec-13
	Impaired loans with a valuation allowance:
	Commercial	$	2,517			$	2,656			$	728
	Commercial real estate	2,576				2,965				353
	Real estate construction	—				—				—
	Land development	—				—				—
	Residential mortgage	17,408				17,408				510
	Subtotal	22,501				23,029				1,591
	Impaired loans with no related valuation allowance:
	Commercial	38,838				44,377				—
	Commercial real estate	48,220				61,444				—
	Real estate construction	371				478				—
	Land development	7,170				11,817				—
	Residential mortgage	8,921				8,921				—
	Consumer installment	676				676				—
	Home equity	2,648				2,648				—
	Subtotal	106,844				130,361				—
	Total impaired loans:
	Commercial	41,355				47,033				728
	Commercial real estate	50,796				64,409				353
	Real estate construction	371				478				—
	Land development	7,170				11,817				—
	Residential mortgage	26,329				26,329				510
	Consumer installment	676				676				—
	Home equity	2,648				2,648				—
	Total	$	129,345			$	153,390			$	1,591
		Recorded				Unpaid				Related
		Investment				Principal				Valuation
						Balance				Allowance
		(In thousands)
	31-Mar-13
	Impaired loans with a valuation allowance:
Commercial	$	4,347			$	4,931			$	1,629
Commercial real estate	12,876				13,045				3,893
Real estate construction	—				—				—
Land development	—				—				—
Residential mortgage	17,296				17,296				662
Subtotal	34,519				35,272				6,184
Impaired loans with no related valuation allowance:
Commercial	21,565				26,737				—
Commercial real estate	42,852				56,259				—
Real estate construction	372				442				—
Land development	11,247				15,510				—
Residential mortgage	10,407				10,407				—
Consumer installment	699				699				—
Home equity	2,837				2,837				—
Subtotal	89,979				112,891				—
Total impaired loans:
Commercial	25,912				31,668				1,629
Commercial real estate	55,728				69,304				3,893
Real estate construction	372				442				—
Land development	11,247				15,510				—
Residential mortgage	27,703				27,703				662
Consumer installment	699				699				—
Home equity	2,837				2,837				—
Total	$	124,498			$	148,163			$	6,184
Schedule presents information related to impaired loans	'
	The following schedule presents information related to impaired loans for the three months ended March 31, 2014 and 2013:
		Three Months Ended March 31, 2014
		Average				Interest Income
		Recorded				Recognized
		Investment				While on
						Impaired Status
		(In thousands)
	Commercial	$	41,607			$	333
	Commercial real estate	53,320				361
	Real estate construction	167				—
	Land development	4,643				37
	Residential mortgage	26,781				303
	Consumer installment	773				—
	Home equity	2,168				—
	Total	$	129,459			$	1,034
		Three Months Ended March 31, 2013
		Average				Interest Income
		Recorded				Recognized
		Investment				While on
						Impaired Status
		(In thousands)
	Commercial	$	26,953			$	193
	Commercial real estate	56,745				288
	Real estate construction	363				2
	Land development	10,914				91
	Residential mortgage	28,920				295
	Consumer installment	719				—
	Home equity	2,962				—
	Total	$	127,576			$	869
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 March 31, 2014, December 31, 2013 and March 31, 2013:
		31-60				61-89				Accruing			Non-accrual			Total		Current		Total
		Days				Days				Loans			Loans			Past Due				Loans
		Past Due				Past Due				Past Due
										90 Days
										or More
		(In thousands)
	31-Mar-14
	Originated Portfolio:
	Commercial	$	6,003			$	1,832			$	43		$	18,251		$	26,129	$	1,104,992	$	1,131,121
	Commercial real estate	4,094				1,098				730			27,568			33,490		1,095,228		1,128,718
	Real estate construction	18				—				—			160			178		72,227		72,405
	Land development	—				—				—			2,267			2,267		5,499		7,766
	Residential mortgage	1,259				1,138				—			6,589			8,986		941,815		950,801
	Consumer installment	1,950				313				—			806			3,069		670,721		673,790
	Home equity	1,500				256				622			2,046			4,424		495,440		499,864
	Total	$	14,824			$	4,637			$	1,395		$	57,687		$	78,543	$	4,385,922	$	4,464,465
	Acquired Portfolio:
	Commercial	$	—			$	—			$	6,496		$	—		$	6,496	$	71,024	$	77,520
	Commercial real estate	—				—				2,549			—			2,549		147,900		150,449
	Real estate construction	—				—				—			—			—		12,679		12,679
	Land development	—				—				2,089			—			2,089		3,906		5,995
	Residential mortgage	—				—				58			—			58		11,150		11,208
	Consumer installment	49				—				—			—			49		1,573		1,622
	Home equity	49				—				331			—			380		28,971		29,351
	Total	$	98			$	—			$	11,523		$	—		$	11,621	$	277,203	$	288,824
		31-60				61-89				Accruing			Non-accrual			Total		Current		Total
		Days				Days				Loans			Loans			Past Due				Loans
		Past Due				Past Due				Past Due
										90 Days
										or More
		(In thousands)
	31-Dec-13
	Originated Portfolio:
	Commercial	$	4,748			$	865			$	536		$	18,374		$	24,523	$	1,068,170	$	1,092,693
	Commercial real estate	8,560				1,604				190			28,598			38,952		1,046,235		1,085,187
	Real estate construction	—				4,107				—			371			4,478		72,981		77,459
	Land development	—				—				—			2,309			2,309		10,971		13,280
	Residential mortgage	2,191				103				537			8,921			11,752		937,129		948,881
	Consumer installment	2,630				359				—			676			3,665		639,381		643,046
	Home equity	1,452				278				734			2,648			5,112		487,266		492,378
	Total	$	19,581			$	7,316			$	1,997		$	61,897		$	90,791	$	4,262,133	$	4,352,924
	Acquired Portfolio:
	Commercial	$	—			$	—			$	5,656		$	—		$	5,656	$	77,958	$	83,614
	Commercial real estate	—				133				1,695			—			1,828		145,643		147,471
	Real estate construction	—				—				—			—			—		12,336		12,336
	Land development	—				—				2,332			—			2,332		4,454		6,786
	Residential mortgage	—				—				61			—			61		11,481		11,542
	Consumer installment	3				51				—			—			54		1,669		1,723
	Home equity	394				—				43			—			437		30,788		31,225
	Total	$	397			$	184			$	9,787		$	—		$	10,368	$	284,329	$	294,697
	31-Mar-13
	Originated Portfolio:
	Commercial	$	7,948			$	1,664			$	4		$	12,186		$	21,802	$	913,144	$	934,946
	Commercial real estate	9,195				2,541				177			35,849			47,762		920,533		968,295
	Real estate construction	—				—				—			168			168		51,680		51,848
	Land development	927				—				—			4,105			5,032		16,981		22,013
	Residential mortgage	2,605				831				196			10,407			14,039		845,132		859,171
	Consumer installment	2,038				524				—			699			3,261		535,255		538,516
	Home equity	1,374				235				874			2,837			5,320		430,880		436,200
	Total	$	24,087			$	5,795			$	1,251		$	66,251		$	97,384	$	3,713,605	$	3,810,989
	Acquired Portfolio:
	Commercial	$	191			$	—			$	2,504		$	—		$	2,695	$	100,474	$	103,169
Commercial real estate	479				157				3,341			—			3,977		190,111		194,088
Real estate construction	—				—				—			—			—		13,519		13,519
Land development	—				—				2,602			—			2,602		8,025		10,627
Residential mortgage	405				—				—			—			405		12,878		13,283
Consumer installment	34				33				—			—			67		1,633		1,700
Home equity	154				—				162			—			316		37,570		37,886
Total	$	1,263			$	190			$	8,609		$	—		$	10,062	$	364,210	$	374,272
Schedule of Corporation's TDRs	'
	The following schedule presents the Corporation’s loans reported as TDRs at March 31, 2014, December 31, 2013 and March 31, 2013:
		Performing TDRs				Non-Performing TDRs				Nonaccrual TDRs			Total
		(In thousands)
	31-Mar-14
	Commercial loan portfolio	$	28,123			$	11,218			$	40,511		$	79,852
	Consumer loan portfolio	13,700				6,244				3,875			23,819
	Total	$	41,823			$	17,462			$	44,386		$	103,671
	31-Dec-13
	Commercial loan portfolio	$	26,839			$	13,414			$	31,961		$	72,214
	Consumer loan portfolio	12,732				4,676				5,321			22,729
	Total	$	39,571			$	18,090			$	37,282		$	94,943
	31-Mar-13
	Commercial loan portfolio	$	17,755			$	14,587			$	42,097		$	74,439
	Consumer loan portfolio	12,968				4,328				4,916			22,212
	Total	$	30,723			$	18,915			$	47,013		$	96,651
Schedule providing information on performing and nonperforming TDRs	'
	The following schedule provides information on the Corporation's TDRs that were modified during the three months ended March 31, 2014 and 2013:
		Number			Pre-				Post-
		of Loans			Modification				Modification
					Recorded				Recorded
					Investment				Investment
		(Dollars in thousands)
	Three Months Ended March 31, 2014
	Commercial loan portfolio:
	Commercial	12			$	8,356			$	8,356
	Commercial real estate	9			2,790				2,790
	Land development	1			72				72
	Subtotal – commercial loan portfolio	22			11,218				11,218
	Consumer loan portfolio (residential mortgage)	30			987				978
	Total	52			$	12,205			$	12,196
	Three Months Ended March 31, 2013 (as revised)
	Commercial loan portfolio:
	Commercial	11			$	1,606			$	1,606
	Commercial real estate	14			3,644				3,644
	Real estate construction	2			364				364
	Land development	2			432				432
	Subtotal – commercial loan portfolio	29			6,046				6,046
	Consumer loan portfolio (residential mortgage)	18			1,391				1,355
	Total	47			$	7,437			$	7,401
Troubled debt restructurings on financing receivables with defaults payment	'
	The following schedule includes TDRs for which there was a payment default during the three months ended March 31, 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:
		Number of			Principal Balance at End of Period
		Loans
		(Dollars in thousands)
	Three Months Ended March 31, 2014
	Commercial loan portfolio:
	Commercial	1			$	104
	Commercial real estate	2			1,670
	Subtotal – commercial loan portfolio	3			1,774
	Consumer loan portfolio (residential mortgage)	—			—
	Total	3			$	1,774
	Three Months Ended March 31, 2013 (as revised)
	Commercial loan portfolio:
	Commercial	17			$	1,053
	Commercial real estate	1			126
	Real estate construction	1			160
	Subtotal – commercial loan portfolio	19			1,339
	Consumer loan portfolio (residential mortgage)	5			484
	Total	24			$	1,823
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 three months ended March 31, 2014 and details regarding the balance in the allowance and the recorded investment in loans at March 31, 2014 by impairment evaluation method.
		Commercial				Consumer				Unallocated			Total
		Loan				Loan
		Portfolio				Portfolio
		(In thousands)
	Changes in allowance for loan losses for the three months ended March 31, 2014:
	Beginning balance	$	44,482			$	30,145			$	4,445		$	79,072
	Provision for loan losses	960				855				(215		)	1,600
	Charge-offs	(1,209		)		(2,263		)		—			(3,472		)
	Recoveries	777				496				—			1,273
	Ending balance	$	45,010			$	29,233			$	4,230		$	78,473
	Allowance for loan losses balance at March 31, 2014 attributable to:
	Loans individually evaluated for impairment	$	1,621			$	444			$	—		$	2,065
	Loans collectively evaluated for impairment	43,389				28,289				4,230			75,908
	Loans acquired with deteriorated credit quality	—				500				—			500
	Total	$	45,010			$	29,233			$	4,230		$	78,473
	Recorded investment (loan balance) at March 31, 2014:
	Loans individually evaluated for impairment	$	87,587			$	19,944			$	—		$	107,531
	Loans collectively evaluated for impairment	2,252,423				2,104,511				—			4,356,934
	Loans acquired with deteriorated credit quality	246,643				42,181				—			288,824
	Total	$	2,586,653			$	2,166,636			$	—		$	4,753,289
	The following schedule presents, by loan portfolio segment, details regarding the balance in the allowance and the recorded investment in loans at December 31, 2013 by impairment evaluation method.
		Commercial				Consumer				Unallocated			Total
		Loan				Loan
		Portfolio				Portfolio
		(In thousands)
	Allowance for loan losses balance at December 31, 2013 attributable to:
	Loans individually evaluated for impairment	$	1,081			$	510			$	—		$	1,591
	Loans collectively evaluated for impairment	43,401				29,135				4,445			76,981
	Loans acquired with deteriorated credit quality	—				500				—			500
	Total	$	44,482			$	30,145			$	4,445		$	79,072
	Recorded investment (loan balance) at December 31, 2013:
	Loans individually evaluated for impairment	$	89,905			$	17,408			$	—		$	107,313
	Loans collectively evaluated for impairment	2,178,714				2,066,897				—			4,245,611
	Loans acquired with deteriorated credit quality	250,207				44,490				—			294,697
	Total	$	2,518,826			$	2,128,795			$	—		$	4,647,621
	The following schedule presents, by loan portfolio segment, the changes in the allowance for the three months ended March 31, 2013 and details regarding the balance in the allowance and the recorded investment in loans at March 31, 2013 by impairment evaluation method.
		Commercial				Consumer				Unallocated			Total
		Loan				Loan
		Portfolio				Portfolio
		(In thousands)
	Changes in allowance for loan losses for the three months ended March 31, 2013:
	Beginning balance	$	49,975			$	29,333			$	5,183		$	84,491
	Provision for loan losses	2,437				871				(308		)	3,000
	Charge-offs	(3,516		)		(1,958		)		—			(5,474		)
	Recoveries	211				606				—			817
	Ending balance	$	49,107			$	28,852			$	4,875		$	82,834
	Allowance for loan losses balance at March 31, 2013 attributable to:
	Loans individually evaluated for impairment	$	5,522			$	662			$	—		$	6,184
	Loans collectively evaluated for impairment	43,585				27,690				4,875			76,150
	Loans acquired with deteriorated credit quality	—				500				—			500
	Total	$	49,107			$	28,852			$	4,875		$	82,834
	Recorded investment (loan balance) at March 31, 2013:
	Loans individually evaluated for impairment	$	84,650			$	17,296			$	—		$	101,946
	Loans collectively evaluated for impairment	1,892,452				1,816,591				—			3,709,043
	Loans acquired with deteriorated credit quality	321,403				52,869				—			374,272
	Total	$	2,298,505			$	1,886,756			$	—		$	4,185,261

Intangible_Assets_Tables

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Net carrying value of intangible assets	'
	The following table shows the net carrying value of the Corporation’s intangible assets:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Goodwill	$	120,164		$	120,164		$	120,164
	Other intangible assets:
	Core deposit intangible assets	$	9,556		$	10,001		$	11,417
	Mortgage servicing rights	3,316			3,423			3,485
	Total other intangible assets	$	12,872		$	13,424		$	14,902
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:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Gross original amount	$	18,659		$	18,659		$	18,659
	Accumulated amortization	9,103			8,658			7,242
	Carrying amount	$	9,556		$	10,001		$	11,417
	Amortization expense for the three months ended March 31	$	445					$	493
Net carrying value, fair value of MSRs and loans Corporation 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:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Net carrying value of MSRs	$	3,316		$	3,423		$	3,485
	Fair value of MSRs	$	6,706		$	6,878		$	5,326
	Loans serviced for others that have servicing rights capitalized	$	877,530		$	886,730		$	907,823
Activity for capitalized MSRs	'
	The following table shows the activity for capitalized MSRs:
		Three Months Ended March 31,
		2014			2013
		(In thousands)
	Balance at beginning of period	$	3,423		$	3,478
	Additions	143			515
	Amortization	(250		)	(508		)
	Balance at end of period	$	3,316		$	3,485

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2014
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:
		March 31,			December 31,			March 31,
		2014			2013			2013
		(In thousands)
	Net unrealized gains (losses) on investment securities – available-for-sale, net of related tax expense (benefit) of $(478) at March 31, 2014, $(1,335) at December 31, 2013 and $2,232 at March 31, 2013	$	(887	)	$	(2,480	)	$	4,143
	Pension and other postretirement benefits adjustment, net of related tax benefit of $9,915 at March 31, 2014, $9,714 at December 31, 2013 and $18,726 at March 31, 2013	(18,414		)	(18,040		)	(34,777		)
	Accumulated other comprehensive loss	$	(19,301	)	$	(20,520	)	$	(30,634	)

Regulatory_Capital_Tables

Regulatory Capital (Tables)	3 Months Ended
	Mar. 31, 2014
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:
		Actual				Minimum Required for Capital Adequacy Purposes				Required to be Well Capitalized Under Prompt Corrective Action Regulations
		Capital		Ratio		Capital		Ratio		Capital		Ratio
		Amount				Amount				Amount
		(Dollars in thousands)
	31-Mar-14
	Total Capital to Risk-Weighted Assets:
	Corporation	$	659,644	13.8	%	$	381,146	8	%	N/A		N/A
	Chemical Bank	589,254		12.4		380,542		8		$	475,678	10	%
	Tier 1 Capital to Risk-Weighted Assets:
	Corporation	599,856		12.6		190,573		4		N/A		N/A
	Chemical Bank	529,560		11.1		190,271		4		285,407		6
	Leverage Ratio:
	Corporation	599,856		9.9		243,070		4		N/A		N/A
	Chemical Bank	529,560		8.7		242,939		4		303,673		5
	31-Dec-13
	Total Capital to Risk-Weighted Assets:
	Corporation	$	649,836	14	%	$	371,465	8	%	N/A		N/A
	Chemical Bank	579,494		12.5		370,881		8		$	463,601	10	%
	Tier 1 Capital to Risk-Weighted Assets:
	Corporation	591,535		12.7		185,732		4		N/A		N/A
	Chemical Bank	521,283		11.2		185,440		4		278,160		6
	Leverage Ratio:
	Corporation	591,535		9.9		239,010		4		N/A		N/A
	Chemical Bank	521,283		8.7		238,884		4		298,605		5
	31-Mar-13
	Total Capital to Risk-Weighted Assets:
	Corporation	$	561,092	13.3	%	$	337,508	8	%	N/A		N/A
	Chemical Bank	545,361		13		336,576		8		$	420,720	10	%
	Tier 1 Capital to Risk-Weighted Assets:
	Corporation	507,985		12		168,754		4		N/A		N/A
	Chemical Bank	492,398		11.7		168,288		4		252,432		6
	Leverage Ratio:
	Corporation	507,985		8.8		230,992		4		N/A		N/A
	Chemical Bank	492,398		8.5		230,544		4		288,179		5

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2014
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 were as follows:
		Fair Value Measurements – Recurring Basis
		Quoted Prices				Significant				Significant				Total
		In Active				Other				Unobservable
		Markets for				Observable				Inputs
		Identical				Inputs				(Level 3)
		Assets				(Level 2)
		(Level 1)
		(In thousands)
	31-Mar-14
	Investment securities – available-for-sale:
	Government sponsored agencies	$	—			$	91,610			$	—			$	91,610
	State and political subdivisions	—				43,777				—				43,777
	Residential mortgage-backed securities	—				288,738				—				288,738
	Collateralized mortgage obligations	—				166,719				—				166,719
	Corporate bonds	—				65,415				—				65,415
	Preferred stock	—				1,559				—				1,559
	Total investment securities – available-for-sale	—				657,818				—				657,818
	Loans held-for-sale	—				3,814				—				3,814
	Total assets measured at fair value on a recurring basis	$	—			$	661,632			$	—			$	661,632
	31-Dec-13
	Investment securities – available-for-sale:
	Government sponsored agencies	$	—			$	93,763			$	—			$	93,763
	State and political subdivisions	—				43,798				—				43,798
	Residential mortgage-backed securities	—				299,366				—				299,366
	Collateralized mortgage obligations	—				180,941				—				180,941
	Corporate bonds	—				65,275				—				65,275
	Preferred stock	—				1,427				—				1,427
	Total investment securities – available-for-sale	—				684,570				—				684,570
	Loans held-for-sale	—				5,219				—				5,219
	Total assets measured at fair value on a recurring basis	$	—			$	689,789			$	—			$	689,789
	31-Mar-13
	Investment securities – available-for-sale:
	Government sponsored agencies	$	—			$	95,379			$	—			$	95,379
	State and political subdivisions	—				49,249				—				49,249
	Residential mortgage-backed securities	—				239,192				—				239,192
	Collateralized mortgage obligations	—				247,668				—				247,668
	Corporate bonds	—				65,548				—				65,548
	Preferred stock	—				1,831				—				1,831
	Total investment securities – available-for-sale	—				698,867				—				698,867
	Loans held-for-sale	—				14,850				—				14,850
	Total assets measured at fair value on a recurring basis	$	—			$	713,717			$	—			$	713,717
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 were as follows:
		Fair Value Measurements – Nonrecurring Basis
		Quoted Prices				Significant				Significant				Total
		In Active				Other				Unobservable
		Markets for				Observable				Inputs
		Identical				Inputs				(Level 3)
		Assets				(Level 2)
		(Level 1)
		(In thousands)
	31-Mar-14
	Impaired originated loans	$	—			$	—			$	29,461			$	29,461
	Other real estate/repossessed assets	—				—				10,056				10,056
	Total	$	—			$	—			$	39,517			$	39,517
	31-Dec-13
	Impaired originated loans	$	—			$	—			$	28,852			$	28,852
	Other real estate/repossessed assets	—				—				9,776				9,776
	Total	$	—			$	—			$	38,628			$	38,628
	31-Mar-13
	Impaired originated loans	$	—			$	—			$	47,073			$	47,073
	Other real estate/repossessed assets	—				—				18,194				18,194
	Total	$	—			$	—			$	65,267			$	65,267
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 was as follows:
		Level in Fair Value Measurement		31-Mar-14								31-Dec-13						31-Mar-13
		Hierarchy		Carrying				Fair				Carrying				Fair		Carrying		Fair
				Amount				Value				Amount				Value		Amount		Value
				(In thousands)
	Assets:
	Cash and cash equivalents	Level 1		$	382,385			$	382,385			$	310,788			$	310,788	$	578,726	$	578,726
	Investment securities:
	Available-for-sale	Level 2		657,818				657,818				684,570				684,570		698,867		698,867
	Available-for-sale	NA		—				—				—				—		4,755		4,755
	Held-to-maturity	Level 2		267,599				265,947				263,405				262,021		257,749		261,405
	Held-to-maturity	Level 3		10,500				6,460				10,500				6,250		—		—
	Nonmarketable equity securities	NA		25,572				25,572				25,572				25,572		25,572		25,572
	Loans held-for-sale	Level 2		3,814				3,814				5,219				5,219		14,850		14,850
	Net loans	Level 3		4,674,816				4,688,814				4,568,549				4,575,532		4,102,427		4,123,585
	Interest receivable	Level 2		16,945				16,945				15,748				15,748		16,960		16,960
	Liabilities:
	Deposits without defined maturities	Level 2		$	3,868,700			$	3,868,700			$	3,790,454			$	3,790,454	$	3,574,832	$	3,574,832
	Time deposits	Level 3		1,362,593				1,371,312				1,331,931				1,340,746		1,432,526		1,448,634
	Interest payable	Level 2		876				876				868				868		1,338		1,338
	Short-term borrowings	Level 2		361,231				361,231				327,428				327,428		347,484		347,484

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2014
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:
		Three Months Ended March 31,
		2014		2013
		(In thousands, except per share data)
	Numerator for both basic and diluted earnings per common share, net income	$	13,813	$	13,234
	Denominator for basic earnings per common share, weighted average common shares outstanding	29,825		27,519
	Weighted average common stock equivalents	212		122
	Denominator for diluted earnings per common share	30,037		27,641
	Basic earnings per common share	$	0.46	$	0.48
	Diluted earnings per common share	0.46		0.48

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Summary of activity for Corporation's stock options	'
	A summary of activity for the Corporation’s stock options as of and for the three months ended March 31, 2014 is presented below:
			Non-Vested						Stock Options Outstanding
			Stock Options Outstanding
			Number of		Weighted-		Weighted-		Number of		Weighted-
			Options		Average		Average		Options		Average
					Exercise		Grant Date				Exercise
					Price		Fair Value				Price
					Per Share						Per Share
	Outstanding at January 1, 2014		414,080		$	24.29	$	7.19	1,073,990		$	26.84
	Granted		190,011		29.45		9.64		190,011		29.45
	Exercised		—		—		—		(50,917	)	25.4
	Vested		(117,799	)	24.32		7.21		—		—
	Forfeited/expired		(6,900	)	24.57		7.26		(8,287	)	26.56
	Outstanding at March 31, 2014		479,392		$	26.32	$	8.16	1,204,797		$	27.32
	Exercisable/vested at March 31, 2014								725,405		$	27.98
Assumptions of Black-Scholes option pricing model	'
	The fair value of the stock options granted during the three months ended March 31, 2014 was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions.
	Expected dividend yield	3		%
	Risk-free interest rate	2.16		%
	Expected stock price volatility	42.2		%
	Expected life of options – in years	7
	Weighted average fair value of options granted	$	9.64
Summary of activity for restricted stock performance units	'
	A summary of the activity for restricted stock units as of and for the three months ended March 31, 2014 is presented below:
			Number of		Weighted-
			Units		Average
					Grant Date
					Fair Value
					Per Unit
	Outstanding at January 1, 2014		188,532		$	21.49
	Granted		67,896		27.48
	Converted into shares of common stock		(50,267	)	19.13
	Forfeited/expired		(1,278	)	23.76
	Outstanding at March 31, 2014		204,883		$	24.04

Pension_and_Other_Postretireme1

Pension and Other Postretirement Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]	'
Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan	'
	The components of net periodic benefit cost for the Corporation’s qualified and nonqualified pension plans and nonqualified postretirement benefit plan are as follows:
		Three Months Ended March 31,
		2014			2013
		(In thousands)
	Defined Benefit Pension Plans
	Service cost	$	250		$	325
	Interest cost	1,312			1,167
	Expected return on plan assets	(2,078		)	(1,948		)
	Amortization of unrecognized net loss	569			946
	Net periodic benefit cost	$	53		$	490
	Postretirement Benefit Plan
	Service cost	$	5		$	—
	Interest cost	35			75
	Amortization of prior service cost	32			—
	Amortization of unrecognized net gain	(26		)	—
	Net periodic benefit cost	$	46		$	75

Significant_Accounting_Policie2

Significant Accounting Policies (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 18, 2013	23-May-13	Mar. 31, 2013	Apr. 20, 2009	Jan. 31, 2008
	Pools
	Bank
Accounting Policies [Abstract]	'	'	'	'	'	'	'
Number of banks through which company operates	1	'	'	'	'	'	'
Number of regional banking units Chemical Bank operates through	4	'	'	'	'	'	'
Number of minimum days when principal or interest is past due is placed in nonaccrual category	'90 days	'	'	'	'	'	'
Number of minimum days in 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	'	'	'	'	'	'
Number of pools of aggregate acquired loans based upon common risk characteristics	14	'	'	'	'	'	'
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	'	'	'	'	'	'
Minimum number of days past due as to interest or principal payments in accruing loans moves to nonperforming loans	'90 days	'	'	'	'	'	'
Minimum amount of loan reviewed for detailed credit quality	$250,000	'	'	'	'	'	'
Time period for historical loan loss experience	'5 years	'	'	'	'	'	'
Minimum percentage of tax benefit is recognized for the amount likely to be realized	50.00%	'	'	'	'	'	'
Reserve for contingent income tax liabilities recorded	0	0	'	'	0	'	'
Number of shares authorized to be repurchased	'	'	'	'	'	'	500,000
Stock repurchased (shares)	0	'	'	'	'	'	'
Number of remaining shares authorized to be repurchased (shares)	500,000	'	'	'	'	'	'
Common Stock, Shares, Issued	29,865,841	29,789,825	2,213,750	'	27,532,377	'	'
CommonStockIssuedOverAllotment	'	'	288,750	'	'	'	'
Shares Issued, Price Per Share	'	'	$26	'	'	'	'
CommonStock, Value, Issued From Public Offering	'	'	53,900,000	'	'	'	'
Stock Registered Under Universal Shelf Registration	'	'	'	100,000,000	'	'	'
Amount of Common Stock sold in public stock offering	'	'	57,600,000	'	'	'	'
Common Stock Available for Future Stock Offerings, Value	42,400,000	'	'	'	'	'	'
Preferred stock, shares authorized	200,000	200,000	'	'	200,000	200,000	'
Preferred stock, shares issued	0	0	'	'	0	'	'
Preferred stock, shares outstanding	0	'	'	'	'	'	'
Expense related to qualified affordable housing projects	100,000	'	'	'	'	'	'
Remaining investment in qualified affordable housing projects	$3,200,000	$3,200,000	'	'	$3,500,000	'	'

Acquisitions_Activity_for_Acqu

Acquisitions (Activity for Acquired Loans) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Activity for accretable yield includes contractually due interest of acquired loans	'		'
Balance at beginning of period	$32,610		$49,390
Additions (reductions)	821	[1]	-491	[1]
Accretion recognized in interest income	-3,843		-4,940
Reclassification from nonaccretable difference	10,000		125
Balance at end of period	$39,588		$44,084
[1]	Represents additions of 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) (USD $)	3 Months Ended			0 Months Ended		0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 07, 2012	Dec. 07, 2012	Apr. 30, 2010	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
				Independent Bank [Member]	Independent Bank [Member]	OAK [Member]	OAK [Member]	OAK [Member]	OAK [Member]
				Branches	Core Deposits [Member]	Offices
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'
Number of branches acquired (branches)	'	'	'	21	'	'	'	'	'
Deposits acquired	'	'	'	$404,000,000	'	'	'	'	'
Loans acquired	'	'	'	44,000,000	'	627,000,000	'	'	'
Acquisition purchase price	'	'	'	8,100,000	'	83,700,000	'	'	'
Premium paid on deposits purchased	'	'	'	11,500,000	'	'	'	'	'
Premium paid as a percentage of deposits purchased (percent)	'	'	'	2.85%	'	'	'	'	'
Discount on loans purchased (percent)	'	'	'	1.75%	'	'	'	'	'
Goodwill	120,164,000	120,164,000	120,164,000	6,800,000	'	'	'	'	'
Intangibles acquired	'	'	'	'	5,600,000	'	'	'	'
Service provided by acquiree bank through number of branches	'	'	'	'	'	14	'	'	'
Assets of acquiree company	'	'	'	'	'	820,000,000	'	'	'
Deposits of acquiree company	'	'	'	'	'	693,000,000	'	'	'
Brokered deposits of acquiree company	'	'	'	'	'	193,000,000	'	'	'
Contractually required principal payments of loan portfolio, acquisition date	'	'	'	'	'	683,000,000	'	'	'
Acquired loan portfolio acquisition date fair value	'	'	'	'	'	627,000,000	'	'	'
Outstanding contractual principal balance of acquired loan portfolio	'	'	'	'	'	'	313,000,000	320,000,000	400,000,000
Carrying amount of acquired loan portfolio	'	'	'	'	'	'	289,000,000	295,000,000	374,000,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference	$10,000,000	$125,000	'	'	'	'	'	'	'

Investment_Securities_Summary_

Investment Securities (Summary of Amortized Cost and Fair Value of Available-For-Sale Investment Securities) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Available-for-sale Securities	'	'	'
Investment securities available-for-sale, Amortized Cost	$659,183	$688,385	$697,247
Investment securities available-for-sale, Unrealized Gains	3,794	3,587	7,110
Investment securities available-for-sale, Unrealized Losses	5,159	7,402	735
Available-for-sale Securities, Total	657,818	684,570	703,622
Government sponsored agencies [Member]	'	'	'
Available-for-sale Securities	'	'	'
Investment securities available-for-sale, Amortized Cost	91,613	93,895	94,939
Investment securities available-for-sale, Unrealized Gains	295	250	608
Investment securities available-for-sale, Unrealized Losses	298	382	168
Available-for-sale Securities, Total	91,610	93,763	95,379
State and political subdivisions [Member]	'	'	'
Available-for-sale Securities	'	'	'
Investment securities available-for-sale, Amortized Cost	42,369	42,450	47,043
Investment securities available-for-sale, Unrealized Gains	1,408	1,355	2,206
Investment securities available-for-sale, Unrealized Losses	0	7	0
Available-for-sale Securities, Total	43,777	43,798	49,249
Residential mortgage-backed securities [Member]	'	'	'
Available-for-sale Securities	'	'	'
Investment securities available-for-sale, Amortized Cost	291,187	303,495	237,256
Investment securities available-for-sale, Unrealized Gains	1,023	968	1,984
Investment securities available-for-sale, Unrealized Losses	3,472	5,097	48
Available-for-sale Securities, Total	288,738	299,366	239,192
Collateralized Mortgage Obligations [Member]	'	'	'
Available-for-sale Securities	'	'	'
Investment securities available-for-sale, Amortized Cost	167,622	182,128	246,751
Investment securities available-for-sale, Unrealized Gains	393	452	1,087
Investment securities available-for-sale, Unrealized Losses	1,296	1,639	170
Available-for-sale Securities, Total	166,719	180,941	247,668
Corporate bonds [Member]	'	'	'
Available-for-sale Securities	'	'	'
Investment securities available-for-sale, Amortized Cost	65,003	65,028	65,114
Investment securities available-for-sale, Unrealized Gains	505	499	783
Investment securities available-for-sale, Unrealized Losses	93	252	349
Available-for-sale Securities, Total	65,415	65,275	65,548
Preferred stock [Member]	'	'	'
Available-for-sale Securities	'	'	'
Investment securities available-for-sale, Amortized Cost	1,389	1,389	6,144
Investment securities available-for-sale, Unrealized Gains	170	63	442
Investment securities available-for-sale, Unrealized Losses	0	25	0
Available-for-sale Securities, Total	$1,559	$1,427	$6,586

Investment_Securities_Summary_1

Investment Securities (Summary of Amortized Cost and Fair Value of Held-To-Maturity Investment Securities) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Held-to-maturity Securities	'	'	'
Investment securities held-to-maturity, Amortized Cost	$278,099	$273,905	$257,749
Investment securities held-to-maturity, Unrealized Gains	5,331	5,462	10,002
Investment securities held-to-maturity, Unrealized Losses	11,023	11,096	6,346
Total Held-to-maturity securities, Debt maturities, Fair Value	272,407	268,271	261,405
State and political subdivisions [Member]	'	'	'
Held-to-maturity Securities	'	'	'
Investment securities held-to-maturity, Amortized Cost	267,599	263,405	247,249
Investment securities held-to-maturity, Unrealized Gains	5,331	5,462	10,002
Investment securities held-to-maturity, Unrealized Losses	6,983	6,846	1,886
Total Held-to-maturity securities, Debt maturities, Fair Value	265,947	262,021	255,365
Trust Preferred Securities [Member]	'	'	'
Held-to-maturity Securities	'	'	'
Investment securities held-to-maturity, Amortized Cost	10,500	10,500	10,500
Investment securities held-to-maturity, Unrealized Gains	0	0	0
Investment securities held-to-maturity, Unrealized Losses	4,040	4,250	4,460
Total Held-to-maturity securities, Debt maturities, Fair Value	$6,460	$6,250	$6,040

Investment_Securities_Maturiti

Investment Securities (Maturities of Debt Securities) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Investment Securities Available-for-Sale:	'	'	'
Due in one year or less, Amortized Cost	$160,093	'	'
Due after one year through five years, Amortized Cost	403,039	'	'
Due after five years through ten years, Amortized Cost	90,096	'	'
Due after ten years, Amortized Cost	4,566	'	'
Preferred stock, Amortized Cost	1,389	'	'
Total Available-for-sale Securities, Debt Maturities, Amortized Cost	659,183	'	'
Due in one year or less , Fair Value	159,861	'	'
Due after one year through five years, Fair Value	402,251	'	'
Due after five years through ten years, Fair Value	89,721	'	'
Due after ten years, Fair Value	4,426	'	'
Preferred stock, Fair Value	1,559	'	'
Total Available-for-sale securities, Debt maturities, Fair Value	657,818	'	'
Investment Securities Held-to-Maturity:	'	'	'
Due in one year or less, Amortized Cost	38,060	'	'
Due after one year through five years, Amortized Cost	104,588	'	'
Due after five years through ten years, Amortized Cost	79,077	'	'
Due after ten years, Amortized Cost	56,374	'	'
Total Held-to-maturity securities, Debt maturities, Amortized Cost	278,099	273,905	257,749
Due in one year or less , Fair Value	38,096	'	'
Due after one year through five years, Fair Value	105,892	'	'
Due after five years through ten years, Fair Value	79,653	'	'
Due after ten years, Fair Value	48,766	'	'
Total Held-to-maturity securities, Debt maturities, Fair Value	$272,407	$268,271	$261,405

Investment_Securities_Summary_2

Investment Securities (Summary of Investment Securities with Gross Unrealized Losses) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	$449,480	$548,723	$205,142
Less Than 12 Months, Gross Unrealized Losses	9,409	13,007	2,013
12 Months or More, Fair Value	105,584	73,865	45,310
12 Months or More, Gross Unrealized Losses	6,773	5,491	5,068
Total, Fair Value	555,064	622,588	250,452
Total, Gross Unrealized Losses	16,182	18,498	7,081
Government sponsored agencies [Member]	'	'	'
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	45,396	47,352	17,281
Less Than 12 Months, Gross Unrealized Losses	110	205	168
12 Months or More, Fair Value	15,204	14,031	0
12 Months or More, Gross Unrealized Losses	188	177	0
Total, Fair Value	60,600	61,383	17,281
Total, Gross Unrealized Losses	298	382	168
State and political subdivisions [Member]	'	'	'
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	79,787	126,345	73,880
Less Than 12 Months, Gross Unrealized Losses	4,942	6,475	1,667
12 Months or More, Fair Value	56,180	19,074	10,685
12 Months or More, Gross Unrealized Losses	2,041	378	219
Total, Fair Value	135,967	145,419	84,565
Total, Gross Unrealized Losses	6,983	6,853	1,886
Residential mortgage-backed securities [Member]	'	'	'
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	247,397	274,076	86,179
Less Than 12 Months, Gross Unrealized Losses	3,472	5,097	45
12 Months or More, Fair Value	0	0	374
12 Months or More, Gross Unrealized Losses	0	0	3
Total, Fair Value	247,397	274,076	86,553
Total, Gross Unrealized Losses	3,472	5,097	48
Collateralized Mortgage Obligations [Member]	'	'	'
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	76,900	84,995	27,802
Less Than 12 Months, Gross Unrealized Losses	885	1,127	133
12 Months or More, Fair Value	12,833	14,684	8,560
12 Months or More, Gross Unrealized Losses	411	512	37
Total, Fair Value	89,733	99,679	36,362
Total, Gross Unrealized Losses	1,296	1,639	170
Corporate bonds [Member]	'	'	'
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	0	14,931	0
Less Than 12 Months, Gross Unrealized Losses	0	78	0
12 Months or More, Fair Value	14,907	19,826	19,651
12 Months or More, Gross Unrealized Losses	93	174	349
Total, Fair Value	14,907	34,757	19,651
Total, Gross Unrealized Losses	93	252	349
Trust Preferred Securities [Member]	'	'	'
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	0	0	0
Less Than 12 Months, Gross Unrealized Losses	0	0	0
12 Months or More, Fair Value	6,460	6,250	6,040
12 Months or More, Gross Unrealized Losses	4,040	4,250	4,460
Total, Fair Value	6,460	6,250	6,040
Total, Gross Unrealized Losses	4,040	4,250	4,460
Preferred Stock [Member]	'	'	'
Summary of continuous unrealized loss position of securities	'	'	'
Less Than 12 Months, Fair Value	'	1,024	'
Less Than 12 Months, Gross Unrealized Losses	'	25	'
12 Months or More, Fair Value	'	0	'
12 Months or More, Gross Unrealized Losses	'	0	'
Total, Fair Value	'	1,024	'
Total, Gross Unrealized Losses	'	$25	'

Investment_Securities_Textual_

Investment Securities (Textual) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Investments, Debt and Equity Securities [Abstract]	'
Trust preferred investment securities held to maturity	$10.50
Trust preferred investment security of Non Public bank company	10
Interest in Trust preferred investment security	100.00%
Remaining trust preferred investment security of Non Public bank company	0.5
Interest in another trust preferred investment security	10.00%
Carrying value of trust preferred investment security one	10
Carrying value of trust preferred investment security two	0.5
Fair value of trust preferred investment security one	6.2
Fair value of trust preferred investment security two	0.3
Unrealized loss on trust preferred investment securities	4
Unrealized loss on trust preferred securities.	$4

Loans_Summary_of_Loans_Details

Loans (Summary of Loans) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Summary of loans under portfolio	'	'	'
Commercial loan	$2,586,653	$2,518,826	$2,298,505
Consumer loan	2,166,636	2,128,795	1,886,756
Total loans	4,753,289	4,647,621	4,185,261
Commercial [Member]	'	'	'
Summary of loans under portfolio	'	'	'
Commercial loan	1,208,641	1,176,307	1,038,115
Real estate commercial [Member]	'	'	'
Summary of loans under portfolio	'	'	'
Commercial loan	1,279,167	1,232,658	1,162,383
Real estate construction [Member]	'	'	'
Summary of loans under portfolio	'	'	'
Commercial loan	85,084	89,795	65,367
Land development [Member]	'	'	'
Summary of loans under portfolio	'	'	'
Commercial loan	13,761	20,066	32,640
Real estate residential [Member]	'	'	'
Summary of loans under portfolio	'	'	'
Consumer loan	962,009	960,423	872,454
Consumer installment [Member]	'	'	'
Summary of loans under portfolio	'	'	'
Consumer loan	675,412	644,769	540,216
Home equity [Member]	'	'	'
Summary of loans under portfolio	'	'	'
Consumer loan	$529,215	$523,603	$474,086

Loans_Summary_of_Recorded_Inve

Loans (Summary of Recorded Investment of Commercial Loans by Risk Rating Categories) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	$2,586,653	$2,518,826	$2,298,505
Commercial [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	1,208,641	1,176,307	1,038,115
Real estate commercial [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	1,279,167	1,232,658	1,162,383
Real estate construction [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	85,084	89,795	65,367
Land development [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	13,761	20,066	32,640
Originated Portfolio [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	2,340,010	2,268,619	1,977,102
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	2,169,841	2,098,995	1,789,488
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	53,969	55,953	73,133
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	67,954	64,019	62,173
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	47,280	48,674	48,914
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	966	978	3,394
Originated Portfolio [Member] | Commercial [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	1,131,121	1,092,693	934,946
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	1,060,743	1,024,461	868,683
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	18,359	20,082	28,037
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	33,768	29,776	26,040
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	17,301	17,414	10,471
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	950	960	1,715
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	1,128,718	1,085,187	968,295
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	1,034,517	991,964	858,484
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	33,962	34,248	44,603
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	32,671	30,377	29,359
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	27,552	28,580	34,170
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	16	18	1,679
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	72,405	77,459	51,848
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	70,750	75,696	50,601
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	680	654	59
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	815	738	1,020
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	160	371	168
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	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	7,766	13,280	22,013
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	3,831	6,874	11,720
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	968	969	434
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	700	3,128	5,754
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	2,267	2,309	4,105
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	0
Acquired Portfolio [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	246,643	250,207	321,403
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	223,041	224,419	291,385
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	5,050	10,494	12,147
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	11,388	8,644	12,020
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	7,164	6,650	5,851
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	0
Acquired Portfolio [Member] | Commercial [Member]	'	'	'
Recorded investment of loans in commercial loan portfolio by risk rating categories	'	'	'
Recorded investment (loan balance), Commercial, Total	77,520	83,614	103,169
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	67,326	73,763	93,560
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	2,423	5,472	6,870
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	3,635	852	874
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	4,136	3,527	1,865
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	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	150,449	147,471	194,088
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	139,130	133,653	176,523
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	2,627	5,022	5,035
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	7,753	7,792	11,146
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	939	1,004	1,384
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	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	12,679	12,336	13,519
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	12,679	12,336	13,519
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	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	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	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	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	5,995	6,786	10,627
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	3,906	4,667	7,783
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	0	0	242
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	0	0	0
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	2,089	2,119	2,602
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	$0

Loans_Summary_of_Recorded_Inve1

Loans (Summary of Recorded Investment of Consumer Loans by Risk Rating Categories) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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	$2,166,636	$2,128,795	$1,886,756
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	962,009	960,423	872,454
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	675,412	644,769	540,216
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	529,215	523,603	474,086
Originated Loans [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	2,124,455	2,084,305	1,833,887
Originated Loans [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	950,801	948,881	859,171
Originated Loans [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	673,790	643,046	538,516
Originated Loans [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	499,864	492,378	436,200
Originated Loans [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	2,108,148	2,066,113	1,814,546
Originated Loans [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	937,968	934,747	844,240
Originated Loans [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	672,984	642,370	537,817
Originated Loans [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	497,196	488,996	432,489
Originated Loans [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	16,307	18,192	19,341
Originated Loans [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	12,833	14,134	14,931
Originated Loans [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	806	676	699
Originated Loans [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	2,668	3,382	3,711
Acquired Loans [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	42,181	44,490	52,869
Acquired Loans [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	11,208	11,542	13,283
Acquired Loans [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	1,622	1,723	1,700
Acquired Loans [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	29,351	31,225	37,886
Acquired Loans [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	41,792	44,386	52,707
Acquired Loans [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	11,150	11,481	13,283
Acquired Loans [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	1,622	1,723	1,700
Acquired Loans [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	29,020	31,182	37,724
Acquired Loans [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	389	104	162
Acquired Loans [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	58	61	0
Acquired Loans [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	0	0	0
Acquired Loans [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	$331	$43	$162

Loans_Summary_of_Nonperforming

Loans (Summary of Nonperforming Loans) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Summary of nonperforming loans	'	'	'
Total nonperforming TDRs	$103,671	$94,943	$96,651
Total loans	4,753,289	4,647,621	4,185,261
Minimum number of days accruing loans past due move to nonaccrual status	'90 days	'	'
Commercial Loan Portfolio [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonperforming TDRs	79,852	72,214	74,439
Total loans	2,586,653	2,518,826	2,298,505
Consumer Loan Portfolio [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonperforming TDRs	23,819	22,729	22,212
Total loans	2,166,636	2,128,795	1,886,756
Nonperforming [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	57,687	61,897	66,251
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,395	1,997	1,251
Total nonperforming TDRs	17,462	18,090	18,915
Total loans	76,544	81,984	86,417
Nonperforming [Member] | Commercial Loan Portfolio [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonperforming TDRs	11,218	13,414	14,587
Nonperforming [Member] | Consumer Loan Portfolio [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonperforming TDRs	6,244	4,676	4,328
Nonperforming [Member] | Commercial [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	18,251	18,374	12,186
Total accruing loans contractually past due 90 days or more as to interest or principal payments	43	536	4
Nonperforming [Member] | Real estate commercial [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	27,568	28,598	35,849
Total accruing loans contractually past due 90 days or more as to interest or principal payments	730	190	177
Nonperforming [Member] | Real Estate Construction Loans [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	160	371	168
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0	0
Nonperforming [Member] | Land Development Loans [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	2,267	2,309	4,105
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0	0
Nonperforming [Member] | Real estate residential [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	6,589	8,921	10,407
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	537	196
Nonperforming [Member] | Consumer Installment Loans [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	806	676	699
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0	0
Nonperforming [Member] | Home Equity Loans [Member]	'	'	'
Summary of nonperforming loans	'	'	'
Total nonaccrual loans	2,046	2,648	2,837
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$622	$734	$874

Loans_Summary_of_Impaired_Loan

Loans (Summary of Impaired Loans by Classes of Loans) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Impaired loans with a valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	$27,198	$22,501	$34,519
Unpaid Principal Balance	27,526	23,029	35,272
Related Valuation Allowance	2,065	1,591	6,184
Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	101,297	106,844	89,979
Unpaid Principal Balance	122,701	130,361	112,891
Related Valuation Allowance	0	0	0
Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	128,495	129,345	124,498
Unpaid Principal Balance	150,227	153,390	148,163
Related Valuation Allowance	2,065	1,591	6,184
Commercial [Member] | Impaired loans with a valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	3,534	2,517	4,347
Unpaid Principal Balance	3,704	2,656	4,931
Related Valuation Allowance	1,250	728	1,629
Commercial [Member] | Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	38,150	38,838	21,565
Unpaid Principal Balance	42,914	44,377	26,737
Related Valuation Allowance	0	0	0
Commercial [Member] | Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	41,684	41,355	25,912
Unpaid Principal Balance	46,618	47,033	31,668
Related Valuation Allowance	1,250	728	1,629
Real estate commercial [Member] | Impaired loans with a valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	3,720	2,576	12,876
Unpaid Principal Balance	3,878	2,965	13,045
Related Valuation Allowance	371	353	3,893
Real estate commercial [Member] | Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	49,074	48,220	42,852
Unpaid Principal Balance	62,207	61,444	56,259
Related Valuation Allowance	0	0	0
Real estate commercial [Member] | Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	52,794	50,796	55,728
Unpaid Principal Balance	66,085	64,409	69,304
Related Valuation Allowance	371	353	3,893
Real estate construction [Member] | Impaired loans with a valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	0	0	0
Unpaid Principal Balance	0	0	0
Related Valuation Allowance	0	0	0
Real estate construction [Member] | Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	160	371	372
Unpaid Principal Balance	366	478	442
Related Valuation Allowance	0	0	0
Real estate construction [Member] | Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	160	371	372
Unpaid Principal Balance	366	478	442
Related Valuation Allowance	0	0	0
Land development [Member] | Impaired loans with a valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	0	0	0
Unpaid Principal Balance	0	0	0
Related Valuation Allowance	0	0	0
Land development [Member] | Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	4,472	7,170	11,247
Unpaid Principal Balance	7,773	11,817	15,510
Related Valuation Allowance	0	0	0
Land development [Member] | Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	4,472	7,170	11,247
Unpaid Principal Balance	7,773	11,817	15,510
Related Valuation Allowance	0	0	0
Real estate residential [Member] | Impaired loans with a valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	19,944	17,408	17,296
Unpaid Principal Balance	19,944	17,408	17,296
Related Valuation Allowance	444	510	662
Real estate residential [Member] | Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	6,589	8,921	10,407
Unpaid Principal Balance	6,589	8,921	10,407
Related Valuation Allowance	0	0	0
Real estate residential [Member] | Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	26,533	26,329	27,703
Unpaid Principal Balance	26,533	26,329	27,703
Related Valuation Allowance	444	510	662
Consumer installment [Member] | Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	806	676	699
Unpaid Principal Balance	806	676	699
Related Valuation Allowance	0	0	0
Consumer installment [Member] | Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	806	676	699
Unpaid Principal Balance	806	676	699
Related Valuation Allowance	0	0	0
Home equity [Member] | Impaired loans with no valuation allowance [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	2,046	2,648	2,837
Unpaid Principal Balance	2,046	2,648	2,837
Related Valuation Allowance	0	0	0
Home equity [Member] | Total Impaired Loans [Member]	'	'	'
Schedule of Impaired loans by classes	'	'	'
Recorded Investment	2,046	2,648	2,837
Unpaid Principal Balance	2,046	2,648	2,837
Related Valuation Allowance	$0	$0	$0

Loans_Summary_of_Information_R

Loans (Summary of Information Related to Impaired Loans) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	$129,459	$127,576
Interest income recognized related to loans with impaired status	1,034	869
Commercial [Member]	'	'
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	41,607	26,953
Interest income recognized related to loans with impaired status	333	193
Real estate commercial [Member]	'	'
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	53,320	56,745
Interest income recognized related to loans with impaired status	361	288
Real estate construction [Member]	'	'
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	167	363
Interest income recognized related to loans with impaired status	0	2
Land development [Member]	'	'
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	4,643	10,914
Interest income recognized related to loans with impaired status	37	91
Real estate residential [Member]	'	'
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	26,781	28,920
Interest income recognized related to loans with impaired status	303	295
Consumer installment [Member]	'	'
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	773	719
Interest income recognized related to loans with impaired status	0	0
Home equity [Member]	'	'
Schedule representing information related to impaired loans	'	'
Average recorded investment related to impaired loans	2,168	2,962
Interest income recognized related to loans with impaired status	$0	$0

Loans_Summary_of_the_Aging_Sta

Loans (Summary of the Aging Status of the Recorded Investment in Loans by Portfolio Segment/Class) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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	$14,824	$19,581	$24,087
Financing receivable, recorded investment 61 to 89 days past due	4,637	7,316	5,795
Financing receivable, recorded investment accruing loans past due 90 days or more	1,395	1,997	1,251
Financing receivable, recorded investment, Nonaccrual loans	57,687	61,897	66,251
Financing receivable recorded investment, Total past due	78,543	90,791	97,384
Financing receivable, recorded investment, current	4,385,922	4,262,133	3,713,605
Financing receivable, recorded investment, Total loans	4,464,465	4,352,924	3,810,989
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	6,003	4,748	7,948
Financing receivable, recorded investment 61 to 89 days past due	1,832	865	1,664
Financing receivable, recorded investment accruing loans past due 90 days or more	43	536	4
Financing receivable, recorded investment, Nonaccrual loans	18,251	18,374	12,186
Financing receivable recorded investment, Total past due	26,129	24,523	21,802
Financing receivable, recorded investment, current	1,104,992	1,068,170	913,144
Financing receivable, recorded investment, Total loans	1,131,121	1,092,693	934,946
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	4,094	8,560	9,195
Financing receivable, recorded investment 61 to 89 days past due	1,098	1,604	2,541
Financing receivable, recorded investment accruing loans past due 90 days or more	730	190	177
Financing receivable, recorded investment, Nonaccrual loans	27,568	28,598	35,849
Financing receivable recorded investment, Total past due	33,490	38,952	47,762
Financing receivable, recorded investment, current	1,095,228	1,046,235	920,533
Financing receivable, recorded investment, Total loans	1,128,718	1,085,187	968,295
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	18	0	0
Financing receivable, recorded investment 61 to 89 days past due	0	4,107	0
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0	0
Financing receivable, recorded investment, Nonaccrual loans	160	371	168
Financing receivable recorded investment, Total past due	178	4,478	168
Financing receivable, recorded investment, current	72,227	72,981	51,680
Financing receivable, recorded investment, Total loans	72,405	77,459	51,848
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	927
Financing receivable, recorded investment 61 to 89 days past due	0	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0	0
Financing receivable, recorded investment, Nonaccrual loans	2,267	2,309	4,105
Financing receivable recorded investment, Total past due	2,267	2,309	5,032
Financing receivable, recorded investment, current	5,499	10,971	16,981
Financing receivable, recorded investment, Total loans	7,766	13,280	22,013
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	1,259	2,191	2,605
Financing receivable, recorded investment 61 to 89 days past due	1,138	103	831
Financing receivable, recorded investment accruing loans past due 90 days or more	0	537	196
Financing receivable, recorded investment, Nonaccrual loans	6,589	8,921	10,407
Financing receivable recorded investment, Total past due	8,986	11,752	14,039
Financing receivable, recorded investment, current	941,815	937,129	845,132
Financing receivable, recorded investment, Total loans	950,801	948,881	859,171
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	1,950	2,630	2,038
Financing receivable, recorded investment 61 to 89 days past due	313	359	524
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0	0
Financing receivable, recorded investment, Nonaccrual loans	806	676	699
Financing receivable recorded investment, Total past due	3,069	3,665	3,261
Financing receivable, recorded investment, current	670,721	639,381	535,255
Financing receivable, recorded investment, Total loans	673,790	643,046	538,516
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	1,500	1,452	1,374
Financing receivable, recorded investment 61 to 89 days past due	256	278	235
Financing receivable, recorded investment accruing loans past due 90 days or more	622	734	874
Financing receivable, recorded investment, Nonaccrual loans	2,046	2,648	2,837
Financing receivable recorded investment, Total past due	4,424	5,112	5,320
Financing receivable, recorded investment, current	495,440	487,266	430,880
Financing receivable, recorded investment, Total loans	499,864	492,378	436,200
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	98	397	1,263
Financing receivable, recorded investment 61 to 89 days past due	0	184	190
Financing receivable, recorded investment accruing loans past due 90 days or more	11,523	9,787	8,609
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	11,621	10,368	10,062
Financing receivable, recorded investment, current	277,203	284,329	364,210
Financing receivable, recorded investment, Total loans	288,824	294,697	374,272
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	0	0	191
Financing receivable, recorded investment 61 to 89 days past due	0	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	6,496	5,656	2,504
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	6,496	5,656	2,695
Financing receivable, recorded investment, current	71,024	77,958	100,474
Financing receivable, recorded investment, Total loans	77,520	83,614	103,169
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	0	0	479
Financing receivable, recorded investment 61 to 89 days past due	0	133	157
Financing receivable, recorded investment accruing loans past due 90 days or more	2,549	1,695	3,341
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	2,549	1,828	3,977
Financing receivable, recorded investment, current	147,900	145,643	190,111
Financing receivable, recorded investment, Total loans	150,449	147,471	194,088
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	0
Financing receivable, recorded investment 61 to 89 days past due	0	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0	0
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	0	0	0
Financing receivable, recorded investment, current	12,679	12,336	13,519
Financing receivable, recorded investment, Total loans	12,679	12,336	13,519
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	0
Financing receivable, recorded investment 61 to 89 days past due	0	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	2,089	2,332	2,602
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	2,089	2,332	2,602
Financing receivable, recorded investment, current	3,906	4,454	8,025
Financing receivable, recorded investment, Total loans	5,995	6,786	10,627
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	0	0	405
Financing receivable, recorded investment 61 to 89 days past due	0	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	58	61	0
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	58	61	405
Financing receivable, recorded investment, current	11,150	11,481	12,878
Financing receivable, recorded investment, Total loans	11,208	11,542	13,283
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	49	3	34
Financing receivable, recorded investment 61 to 89 days past due	0	51	33
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0	0
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	49	54	67
Financing receivable, recorded investment, current	1,573	1,669	1,633
Financing receivable, recorded investment, Total loans	1,622	1,723	1,700
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	49	394	154
Financing receivable, recorded investment 61 to 89 days past due	0	0	0
Financing receivable, recorded investment accruing loans past due 90 days or more	331	43	162
Financing receivable, recorded investment, Nonaccrual loans	0	0	0
Financing receivable recorded investment, Total past due	380	437	316
Financing receivable, recorded investment, current	28,971	30,788	37,570
Financing receivable, recorded investment, Total loans	$29,351	$31,225	$37,886

Loans_Summary_of_TDRs_Details

Loans (Summary of TDRs) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	$103,671	$94,943	$96,651
Commercial Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	79,852	72,214	74,439
Consumer Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	23,819	22,729	22,212
Performing [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	41,823	39,571	30,723
Performing [Member] | Commercial Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	28,123	26,839	17,755
Performing [Member] | Consumer Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	13,700	12,732	12,968
Nonperforming [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	17,462	18,090	18,915
Nonperforming [Member] | Commercial Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	11,218	13,414	14,587
Nonperforming [Member] | Consumer Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	6,244	4,676	4,328
Substandard Nonaccrual [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	44,386	37,282	47,013
Substandard Nonaccrual [Member] | Commercial Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	40,511	31,961	42,097
Substandard Nonaccrual [Member] | Consumer Loan Portfolio [Member]	'	'	'
Schedule of corporation's TDRs	'	'	'
Total nonperforming TDRs	$3,875	$5,321	$4,916

Loans_Summary_of_Performing_an

Loans (Summary of Performing and Nonperforming TDRs Modified During the Period) (Details) (Commercial Loan Portfolio [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
	Loans	Loans
Schedule providing information on performing and nonperforming TDRs	'	'
Performing and nonperforming modified TDRs, Number of loans	52	47
Performing and nonperforming modified TDRs, Pre-modification recorded investment	$12,205	$7,437
Performing and nonperforming modified TDRs, Post-modification recorded investment	12,196	7,401
Subtotal-commercial loan portfolio [Member]	'	'
Schedule providing information on performing and nonperforming TDRs	'	'
Performing and nonperforming modified TDRs, Number of loans	22	29
Performing and nonperforming modified TDRs, Pre-modification recorded investment	11,218	6,046
Performing and nonperforming modified TDRs, Post-modification recorded investment	11,218	6,046
Consumer loan portfolio (real estate residential) [Member]	'	'
Schedule providing information on performing and nonperforming TDRs	'	'
Performing and nonperforming modified TDRs, Number of loans	30	18
Performing and nonperforming modified TDRs, Pre-modification recorded investment	987	1,391
Performing and nonperforming modified TDRs, Post-modification recorded investment	978	1,355
Commercial [Member]	'	'
Schedule providing information on performing and nonperforming TDRs	'	'
Performing and nonperforming modified TDRs, Number of loans	12	11
Performing and nonperforming modified TDRs, Pre-modification recorded investment	8,356	1,606
Performing and nonperforming modified TDRs, Post-modification recorded investment	8,356	1,606
Real estate commercial [Member]	'	'
Schedule providing information on performing and nonperforming TDRs	'	'
Performing and nonperforming modified TDRs, Number of loans	9	14
Performing and nonperforming modified TDRs, Pre-modification recorded investment	2,790	3,644
Performing and nonperforming modified TDRs, Post-modification recorded investment	2,790	3,644
Real Estate Construction Loans [Member]	'	'
Schedule providing information on performing and nonperforming TDRs	'	'
Performing and nonperforming modified TDRs, Number of loans	'	2
Performing and nonperforming modified TDRs, Pre-modification recorded investment	'	364
Performing and nonperforming modified TDRs, Post-modification recorded investment	'	364
Land development [Member]	'	'
Schedule providing information on performing and nonperforming TDRs	'	'
Performing and nonperforming modified TDRs, Number of loans	1	2
Performing and nonperforming modified TDRs, Pre-modification recorded investment	72	432
Performing and nonperforming modified TDRs, Post-modification recorded investment	$72	$432

Loans_Summary_of_TDRs_with_a_P

Loans (Summary of TDRs with a Payment Default During the Period) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
	Loans	Loans
Commercial Loan Portfolio [Member]	'	'
Troubled debt restructurings on financing receivables with defaults payment	'	'
Financing receivable modifications subsequent default number of contract	3	24
Financing receivable modification subsequent default recorded investment	$1,774	$1,823
Commercial [Member] | Commercial Loan Portfolio [Member]	'	'
Troubled debt restructurings on financing receivables with defaults payment	'	'
Financing receivable modifications subsequent default number of contract	1	17
Financing receivable modification subsequent default recorded investment	104	1,053
Real estate commercial [Member] | Commercial Loan Portfolio [Member]	'	'
Troubled debt restructurings on financing receivables with defaults payment	'	'
Financing receivable modifications subsequent default number of contract	2	1
Financing receivable modification subsequent default recorded investment	1,670	126
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 contract	'	1
Financing receivable modification subsequent default recorded investment	'	160
Subtotal-commercial loan portfolio [Member] | Commercial Loan Portfolio [Member]	'	'
Troubled debt restructurings on financing receivables with defaults payment	'	'
Financing receivable modifications subsequent default number of contract	3	19
Financing receivable modification subsequent default recorded investment	1,774	1,339
Consumer loan portfolio (real estate residential) [Member]	'	'
Troubled debt restructurings on financing receivables with defaults payment	'	'
Financing receivable modifications subsequent default number of contract	0	5
Financing receivable modification subsequent default recorded investment	$0	$484

Loans_Schedule_of_the_Allowanc

Loans (Schedule of the Allowance for Loan Losses) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment	'	'	'
Beginning balance	$79,072	$84,491	'
Provision for loan losses	1,600	3,000	'
Charge-offs	-3,472	-5,474	'
Recoveries	1,273	817	'
Ending balance	78,473	82,834	'
Allowance for loan losses	'	'	'
Loans individually evaluated for impairment related to allowance for loan losses	2,065	6,184	1,591
Loans collectively evaluated for impairment related to allowance for loan losses	75,908	76,150	76,981
Loans acquired with deteriorated credit quality related to allowance for loan losses	500	500	500
Total	78,473	82,834	'
Loans individually evaluated for impairment related to recorded investment (loan balance)	107,531	101,946	107,313
Loans collectively evaluated for impairment related to recorded investment (loan balance)	4,356,934	3,709,043	4,245,611
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)	288,824	374,272	294,697
Total loans	4,753,289	4,185,261	4,647,621
Commercial Loan Portfolio [Member]	'	'	'
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment	'	'	'
Beginning balance	44,482	49,975	'
Provision for loan losses	960	2,437	'
Charge-offs	-1,209	-3,516	'
Recoveries	777	211	'
Ending balance	45,010	49,107	'
Allowance for loan losses	'	'	'
Loans individually evaluated for impairment related to allowance for loan losses	1,621	5,522	1,081
Loans collectively evaluated for impairment related to allowance for loan losses	43,389	43,585	43,401
Loans acquired with deteriorated credit quality related to allowance for loan losses	0	0	0
Total	45,010	49,107	'
Loans individually evaluated for impairment related to recorded investment (loan balance)	87,587	84,650	89,905
Loans collectively evaluated for impairment related to recorded investment (loan balance)	2,252,423	1,892,452	2,178,714
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)	246,643	321,403	250,207
Total loans	2,586,653	2,298,505	2,518,826
Consumer Loan Portfolio [Member]	'	'	'
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment	'	'	'
Beginning balance	30,145	29,333	'
Provision for loan losses	855	871	'
Charge-offs	-2,263	-1,958	'
Recoveries	496	606	'
Ending balance	29,233	28,852	'
Allowance for loan losses	'	'	'
Loans individually evaluated for impairment related to allowance for loan losses	444	662	510
Loans collectively evaluated for impairment related to allowance for loan losses	28,289	27,690	29,135
Loans acquired with deteriorated credit quality related to allowance for loan losses	500	500	500
Total	29,233	28,852	'
Loans individually evaluated for impairment related to recorded investment (loan balance)	19,944	17,296	17,408
Loans collectively evaluated for impairment related to recorded investment (loan balance)	2,104,511	1,816,591	2,066,897
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)	42,181	52,869	44,490
Total loans	2,166,636	1,886,756	2,128,795
Unallocated [Member]	'	'	'
Schedule of allowance and recorded investment related to financing receivables segregated by portfolio segment	'	'	'
Beginning balance	4,445	5,183	'
Provision for loan losses	-215	-308	'
Charge-offs	0	0	'
Recoveries	0	0	'
Ending balance	4,230	4,875	'
Allowance for loan losses	'	'	'
Loans individually evaluated for impairment related to allowance for loan losses	0	0	0
Loans collectively evaluated for impairment related to allowance for loan losses	4,230	4,875	4,445
Loans acquired with deteriorated credit quality related to allowance for loan losses	0	0	0
Total	4,230	4,875	'
Loans individually evaluated for impairment related to recorded investment (loan balance)	0	0	0
Loans collectively evaluated for impairment related to recorded investment (loan balance)	0	0	0
Loans acquired with deteriorated credit quality related to recorded investment (loan balance)	0	0	0
Total loans	$0	$0	$0

Loans_Textual_Details

Loans (Textual) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
	BaordOfDirectors
	Tenants
	Segment
	Loans
Loans (Textual) [Abstract]	'	'	'
Number of portfolio segment	2	'	'
Number of classes of loans	7	'	'
Number of tenants under lease of real estate	1	'	'
Number of members of the board of directors in loan committee	9	'	'
Minimum due period of loans consider in a nonperforming status	'90 days	'	'
Total nonaccrual TDR loans	$44,400,000	$47,000,000	$37,300,000
Difference between recorded investment and unpaid principal balance of loan	21,700,000	23,700,000	24,000,000
Confirmed losses (partial charge-offs)	17,800,000	19,900,000	20,200,000
Fair value of discount adjustment	3,900,000	3,800,000	3,800,000
Acquired impaired loans	11,500,000	8,600,000	9,800,000
Performing trouble debt restructuring under impaired loans	41,800,000	30,700,000	39,600,000
Financing receivable allowance for acquired loans	500,000	500,000	500,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference	10,000,000	125,000	'
Commercial Loan Portfolio [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Minimum value of loan requires executive and senior officer approval	1,500,000	'	'
Consumer Portfolio Segment [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Maximum due period of loans consider in performing status	'90 days	'	'
Minimum due period of loans consider in a nonperforming status	'90 days	'	'
Commercial [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Minimum value of loan requires group loan authority approval	1,000,000	'	'
Maximum value of loan requires executive and senior officer approval	3,500,000	'	'
Real Estate Residential Loans [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Period for loan secured under real estate residential security	'15 years	'	'
Loan-to-value ratio at the time of origination	80.00%	'	'
Land Development Loans [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Maximum period for payment of loan	'12 months	'	'
Maximum [Member] | Commercial Loan Portfolio [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Maximum value of loan requires group loan authority approval	5,000,000	'	'
Other loans requiring director loan committee approval depending on risk rating and credit action required	5,000,000	'	'
Maximum [Member] | Real Estate Residential Loans [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Upper limit of number of family residential properties	4	'	'
Minimum [Member] | Commercial Loan Portfolio [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Minimum value of loan requires group loan authority approval	1,000,000	'	'
Minimum value of loans depending on risk rating and requires credit action from board of directors	10,000,000	'	'
Minimum [Member] | Commercial [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Minimum value of loans requiring only director loan committee approval	$5,000,000	'	'
Minimum [Member] | Real Estate Residential Loans [Member]	'	'	'
Loans (Textual) [Abstract]	'	'	'
Lower limit of number of family residential properties	1	'	'

Intangible_Assets_Net_Carrying

Intangible Assets (Net Carrying Value) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Net carrying value of intangible assets	'	'	'	'
Goodwill	$120,164	$120,164	$120,164	'
Other intangible assets:	'	'	'	'
Total other intangible assets	12,872	13,424	14,902	'
Core deposit intangible assets [Member]	'	'	'	'
Other intangible assets:	'	'	'	'
Total other intangible assets	9,556	10,001	11,417	'
Mortgage servicing rights [Member]	'	'	'	'
Other intangible assets:	'	'	'	'
Total other intangible assets	$3,316	$3,423	$3,485	$3,478

Intangible_Assets_Amortization

Intangible Assets (Amortization Expense of Core Deposit Intangible Assets) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets	'	'	'
Carrying amount	$12,872	$14,902	$13,424
Amortization of intangible assets	695	1,001	'
Core deposit intangible assets [Member]	'	'	'
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets	'	'	'
Gross original amount	18,659	18,659	18,659
Accumulated amortization	9,103	7,242	8,658
Carrying amount	9,556	11,417	10,001
Amortization of intangible assets	$445	$493	'

Intangible_Assets_Carrying_and

Intangible Assets (Carrying and Fair Value of MSRs) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Net carrying value, fair value of MSRs and loans Corporation servicing for others	'	'	'
Loans serviced for others that have servicing rights capitalized	$877,530	$886,730	$907,823
Mortgage servicing rights [Member]	'	'	'
Net carrying value, fair value of MSRs and loans Corporation servicing for others	'	'	'
Net carrying value of MSRs	3,316	3,423	3,485
Fair value of MSRs	$6,706	$6,878	$5,326

Intangible_Assets_Activity_for

Intangible Assets (Activity for Capitalized MSRs) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Capitalized MSRs [Roll Forward]	'	'
Balance at beginning of period	$13,424	'
Amortization	-695	-1,001
Balance at end of period	12,872	14,902
Mortgage servicing rights [Member]	'	'
Capitalized MSRs [Roll Forward]	'	'
Balance at beginning of period	3,423	3,478
Additions	143	515
Amortization	-250	-508
Balance at end of period	$3,316	$3,485

Intangible_Assets_Textual_Deta

Intangible Assets (Textual) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Core deposit intangible assets [Member]	'	'	'
Estimated Future Amortization Expense, Fiscal Year Maturity [Abstract]	'	'	'
2014	$1,300,000	'	'
2015	1,700,000	'	'
2016	1,500,000	'	'
2017	1,200,000	'	'
2018	1,200,000	'	'
2019 and thereafter	2,700,000	'	'
Mortgage servicing rights [Member]	'	'	'
Intangible Assets (Textual) [Abstract]	'	'	'
Impairment valuation allowance	$0	$0	$0

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
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 $(478) at March 31, 2014, $(1,335) at December 31, 2013 and $2,232 at March 31, 2013	($887)	($2,480)	$4,143
Pension and other postretirement benefits adjustment, net of related tax benefit of $9,915 at March 31, 2014, $9,714 at December 31, 2013 and $18,726 at March 31, 2013	-18,414	-18,040	-34,777
Accumulated other comprehensive loss	($19,301)	($20,520)	($30,634)

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Loss (Textual) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Accumulated Other Comprehensive Loss (Textual) [Abstract]	'	'	'
Net unrealized gains (losses) on investment securities-available-for-sale, tax expense (benefit)	($478)	($1,335)	$2,232
Pension and other postretirement benefits adjustment, tax benefit	$9,915	$9,714	$18,726

Regulatory_Capital_Details

Regulatory Capital (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'	'
Risk weighted assets	$4,760,000,000	$4,640,000,000	$4,220,000,000
Chemical Financial Corporation [Member]	'	'	'
Total Capital to Risk-Weighted Assets:	'	'	'
Actual, Capital Amount	659,644,000	649,836,000	561,092,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	381,146,000	371,465,000	337,508,000
Actual, Ratio	13.80%	14.00%	13.30%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:	'	'	'
Actual, Capital Amount	599,856,000	591,535,000	507,985,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	190,573,000	185,732,000	168,754,000
Actual, Ratio	12.60%	12.70%	12.00%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Leverage Ratio:	'	'	'
Actual, Capital Amount	599,856,000	591,535,000	507,985,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	243,070,000	239,010,000	230,992,000
Actual, Ratio	9.90%	9.90%	8.80%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Chemical Bank [Member]	'	'	'
Total Capital to Risk-Weighted Assets:	'	'	'
Actual, Capital Amount	589,254,000	579,494,000	545,361,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	380,542,000	370,881,000	336,576,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	475,678,000	463,601,000	420,720,000
Actual, Ratio	12.40%	12.50%	13.00%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	10.00%	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets:	'	'	'
Actual, Capital Amount	529,560,000	521,283,000	492,398,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	190,271,000	185,440,000	168,288,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	285,407,000	278,160,000	252,432,000
Actual, Ratio	11.10%	11.20%	11.70%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.00%	6.00%	6.00%
Leverage Ratio:	'	'	'
Actual, Capital Amount	529,560,000	521,283,000	492,398,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	242,939,000	238,884,000	230,544,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$303,673,000	$298,605,000	$288,179,000
Actual, Ratio	8.70%	8.70%	8.50%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%	5.00%	5.00%

Regulatory_Capital_Common_Stoc

Regulatory Capital Common Stock Issued (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Sep. 18, 2013	Mar. 31, 2013
In Millions, except Share data, unless otherwise specified
Shares Issued [Abstract]	'	'	'	'
Common Stock, Shares, Issued	29,865,841	29,789,825	2,213,750	27,532,377
CommonStockIssuedOverAllotment	'	'	288,750	'
Shares Issued, Price Per Share	'	'	$26	'
Issuance of common stock, net of issuance costs	'	'	$53.90	'

Fair_Value_Measurements_Fair_V

Fair Value Measurements (Fair Value of Assets on a Recurring Basis) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	$657,818	$684,570	$703,622
Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	657,818	684,570	698,867
Loans Held-for-sale	3,814	5,219	14,850
Total assets measured at fair value on a recurring basis	661,632	689,789	713,717
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Loans Held-for-sale	0	0	0
Total assets measured at fair value on a recurring basis	0	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	657,818	684,570	698,867
Loans Held-for-sale	3,814	5,219	14,850
Total assets measured at fair value on a recurring basis	661,632	689,789	713,717
Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Loans Held-for-sale	0	0	0
Total assets measured at fair value on a recurring basis	0	0	0
Government sponsored agencies [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	91,610	93,763	95,379
Government sponsored agencies [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	91,610	93,763	95,379
Government sponsored agencies [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Government sponsored agencies [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	91,610	93,763	95,379
Government sponsored agencies [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
State and political subdivisions [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	43,777	43,798	49,249
State and political subdivisions [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	43,777	43,798	49,249
State and political subdivisions [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
State and political subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	43,777	43,798	49,249
State and political subdivisions [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Residential mortgage-backed securities [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	288,738	299,366	239,192
Residential mortgage-backed securities [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	288,738	299,366	239,192
Residential mortgage-backed securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Residential mortgage-backed securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	288,738	299,366	239,192
Residential mortgage-backed securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Collateralized mortgage obligations [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	166,719	180,941	247,668
Collateralized mortgage obligations [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	166,719	180,941	247,668
Collateralized mortgage obligations [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Collateralized mortgage obligations [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	166,719	180,941	247,668
Collateralized mortgage obligations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Corporate bonds [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	65,415	65,275	65,548
Corporate bonds [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	65,415	65,275	65,548
Corporate bonds [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Corporate bonds [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	65,415	65,275	65,548
Corporate bonds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Preferred stock [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	1,559	1,427	6,586
Preferred stock [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	1,559	1,427	1,831
Preferred stock [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	0	0	0
Preferred stock [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	1,559	1,427	1,831
Preferred stock [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]	'	'	'
Summary of assets measured at fair value on a recurring basis	'	'	'
Available-for-sale, at fair value	$0	$0	$0

Fair_Value_Measurements_Fair_V1

Fair Value Measurements (Fair Value of Assets on a Nonrecurring Basis) (Details) (Fair Value Measurements Nonrecurring [Member], USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Summary of assets measured at fair value on a nonrecurring basis	'	'	'
Total assets measured at fair value on a nonrecurring basis	$39,517	$38,628	$65,267
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	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	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	39,517	38,628	65,267
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	29,461	28,852	47,073
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	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	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	29,461	28,852	47,073
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	10,056	9,776	18,194
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	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	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	$10,056	$9,776	$18,194

Fair_Value_Measurements_Schedu

Fair Value Measurements (Schedule of Carrying Amounts and Estimated Fair Value of Financial Instruments) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Thousands, unless otherwise specified
Investment securities:	'	'	'
Available-for-sale	$657,818	$684,570	$703,622
Held-to-maturity	272,407	268,271	261,405
Carrying Amount [Member]	'	'	'
Investment securities:	'	'	'
Available-for-sale	0	0	4,755
Nonmarketable equity securities	25,572	25,572	25,572
Carrying Amount [Member] | Level 1[Member]	'	'	'
Assets:	'	'	'
Cash and cash equivalents	382,385	310,788	578,726
Carrying Amount [Member] | Level 2 [Member]	'	'	'
Investment securities:	'	'	'
Available-for-sale	657,818	684,570	698,867
Held-to-maturity	267,599	263,405	257,749
Loans Held-for-sale	3,814	5,219	14,850
Interest receivable	16,945	15,748	16,960
Liabilities:	'	'	'
Deposits without defined maturities	3,868,700	3,790,454	3,574,832
Interest payable	876	868	1,338
Short-term borrowings	361,231	327,428	347,484
Carrying Amount [Member] | Level 3 [Member]	'	'	'
Investment securities:	'	'	'
Held-to-maturity	10,500	10,500	0
Net loans	4,674,816	4,568,549	4,102,427
Liabilities:	'	'	'
Time deposits	1,362,593	1,331,931	1,432,526
Fair Value [Member]	'	'	'
Investment securities:	'	'	'
Available-for-sale	0	0	4,755
Nonmarketable equity securities	25,572	25,572	25,572
Fair Value [Member] | Level 1[Member]	'	'	'
Assets:	'	'	'
Cash and cash equivalents	382,385	310,788	578,726
Fair Value [Member] | Level 2 [Member]	'	'	'
Investment securities:	'	'	'
Available-for-sale	657,818	684,570	698,867
Held-to-maturity	265,947	262,021	261,405
Loans Held-for-sale	3,814	5,219	14,850
Interest receivable	16,945	15,748	16,960
Liabilities:	'	'	'
Deposits without defined maturities	3,868,700	3,790,454	3,574,832
Interest payable	876	868	1,338
Short-term borrowings	361,231	327,428	347,484
Fair Value [Member] | Level 3 [Member]	'	'	'
Investment securities:	'	'	'
Held-to-maturity	6,460	6,250	0
Net loans	4,688,814	4,575,532	4,123,585
Liabilities:	'	'	'
Time deposits	$1,371,312	$1,340,746	$1,448,634

Fair_Value_Measurements_Textua

Fair Value Measurements (Textual) (Details) (USD $)

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

In Thousands, unless otherwise specified

Core deposit intangible assets [Member]

Core deposit intangible assets [Member]

Core deposit intangible assets [Member]

Maximum [Member]

Minimum [Member]

Total Impaired Loans [Member]

Total Impaired Loans [Member]

Other Real Estate and Repossessed Assets [Member]

Other Real Estate and Repossessed Assets [Member]

Fair Value Measurements Recurring [Member]

Fair Value Measurements Recurring [Member]

Fair Value Measurements Recurring [Member]

Fair Value Measurements Nonrecurring [Member]

Fair Value Measurements Nonrecurring [Member]

Fair Value Measurements Nonrecurring [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Fair Value Measurements (Textual) [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Liabilities recorded at fair value

'

'

'

'

'

'

'

'

'

'

'

'

$0

$0

$0

$0

$0

$0

Expected life of intangible assets

'

'

'

'

'

'

'15 years

'10 years

'

'

'

'

'

'

'

'

'

'

Percentage of discount factors used to determine fair value

'

'

'

'

'

'

'

'

80.00%

70.00%

75.00%

70.00%

'

'

'

'

'

'

Impairment of goodwill

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment identified for intangible assets

'

'

'

$0

$0

$0

'

'

'

'

'

'

'

'

'

'

'

'

Earnings_Per_Common_Share_Deta

Earnings Per Common Share (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Numerator and denominator of the basic and diluted earnings per common share computations	'	'
Numerator for both basic and diluted earnings per common share, net income	$13,813	$13,234
Denominator for basic earnings per common share, weighted average common shares outstanding	29,825,000	27,519,000
Weighted average common stock equivalents	212,000	122,000
Denominator for diluted earnings per common share	30,037,000	27,641,000
Basic earnings per common share (dollars per share)	$0.46	$0.48
Diluted earnings per common share (dollars per share)	$0.46	$0.48
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	259,288	457,689

ShareBased_Compensation_Stock_

Share-Based Compensation (Stock Option Activity) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]	'
Weighted average fair value of options granted	$9.64
Non Vested [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'
Ending balance, Number of Options	479,392
Vested [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'
Ending balance, Number of Options	1,204,797
Stock Options [Member] | Non Vested [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'
Beginning balance, Number of Options	414,080
Exercised, Number of Options	0
Vested, Number of Options	-117,799
Forfeited/expired, Number of Options	-6,900
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]	'
Beginning balance, Weighted Average Exercise Price	$24.29
Granted, Weighted Average Exercise Price	$29.45
Exercised, Weighted Average Exercise Price	$0
Vested, Weighted Average Exercise Price	$24.32
Forfeited/expired, Weighted Average Exercise Price	$24.57
Ending balance, Weighted Average Exercise Price	$26.32
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	$7.19
Weighted average fair value of options granted	$9.64
Exercised, Weighted Average Grant Date Fair Value	$0
Vested, Weighted Average Grant Date Fair Value	$7.21
Forfeited/expired, Weighted Average Grant Date Fair Value	$7.26
Ending balance, Weighted average grant date fair value	$8.16
Stock Options [Member] | Vested [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'
Beginning balance, Number of Options	1,073,990
Granted, Number of Options	190,011
Exercised, Number of Options	-50,917
Vested, Number of Options	0
Forfeited/expired, Number of Options	-8,287
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]	'
Beginning balance, Weighted Average Exercise Price	$26.84
Granted, Weighted Average Exercise Price	$29.45
Exercised, Weighted Average Exercise Price	$25.40
Vested, Weighted Average Exercise Price	$0
Forfeited/expired, Weighted Average Exercise Price	$26.56
Ending balance, Weighted Average Exercise Price	$27.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]	'
Exercisable/vested, Number of Options	725,405
Exercisable/vested, Weighted Average Exercise Price	$27.98

ShareBased_Compensation_BlackS

Share-Based Compensation (Black-Scholes Pricing Model Assumptions) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014
Assumptions of Black-Scholes option pricing model	'
Expected dividend yield	3.00%
Risk-free interest rate	2.16%
Expected stock price volatility	42.20%
Expected life of options - in years	'7 years 0 months 0 days
Weighted average fair value of options granted	$9.64

ShareBased_Compensation_Restri

Share-Based Compensation (Restricted Stock Unit Activity) (Details) (Restricted Stock Units (RSUs) [Member], USD $)	3 Months Ended
	Mar. 31, 2014
Restricted Stock Units (RSUs) [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Number of Shares [Roll Forward]	'
Beginning balance, Number of shares	188,532
Granted, Number of shares	67,896
Converted into shares of common stock, Number of shares	-50,267
Forfeited/expired, Number of shares	-1,278
Ending balance, Number of shares	204,883
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	$21.49
Granted, Weighted Average grant date fair value	$27.48
Converted into shares of common stock, Weighted average grant date fair value	$19.13
Forfeited/expired, Weighted average grant date fair value	$23.76
Ending balance, Weighted average grant date fair value	$24.04

Textual_Details

(Textual) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share-Based Compensation Plans (Textual) [Abstract]	'	'
Share-based compensation expense	$554,000	$629,000
Restricted Stock Units (RSUs) [Member]	'	'
Share-Based Compensation Plans (Textual) [Abstract]	'	'
Corporation granted options to purchase restricted stock performance units	67,896	'
Unrecognized compensation expense	3,500,000	'
Unrecognized compensation expense, period of recognition	'2 years 10 months 28 days	'
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	'
Stock Option [Member]	'	'
Share-Based Compensation Plans (Textual) [Abstract]	'	'
Corporation granted options to purchase common stock	190,011	'
Common stock available for future grants under share-based compensation plans	420,975	'
Weighted-average remaining contractual terms for outstanding stock options	'6 years 2 months 13 days	'
Weighted-average remaining contractual terms for exercisable stock options	'4 years 3 months 19 days	'
Outstanding in-the-money stock options, intrinsic value	7,100,000	'
Exercisable in-the-money stock options, intrinsic value	4,200,000	'
Closing price of common stock	$32.45	'
Unrecognized compensation expense	$3,600,000	'
Unrecognized compensation expense, period of recognition	'4 years 0 months 0 days	'

Pension_and_Other_Postretireme2

Pension and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost (Income)) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Defined Benefit Pension Plans [Member]	'	'
Components of net periodic benefit cost (income) for the Corporation's qualified and nonqualified pension plans and nonqualified postretirement benefits plan	'	'
Service cost	$250	$325
Interest cost	1,312	1,167
Expected return on plan assets	-2,078	-1,948
Amortization of unrecognized net loss (gain)	569	946
Net periodic benefit cost	53	490
Postretirement Benefit 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	5	0
Interest cost	35	75
Amortization of prior service cost	32	0
Amortization of unrecognized net loss (gain)	-26	0
Net periodic benefit cost	$46	$75

Pension_and_Other_Postretireme3

Pension and Other Postretirement Benefit Plans (Textual) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Contribution to corporation's pension plan [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Contribution to defined benefit pension plan	'	$15
Pension Plans, Defined Benefit [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.00%	'
Chemical Financial Corporation [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Percentage of eligible pay contribution to certain employees	4.00%	'
Defined Contribution Plan, Employer Total Contribution Amount	$0.80	$0.90

Financial_Guarantees_Textual_D

Financial Guarantees (Textual) (Details) (Financial Standby Letter of Credit [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Financial Standby Letter of Credit [Member]	'	'	'
Financial Guarantees (Textual) [Abstract]	'	'	'
Letters of credit outstanding	$45	$47	$47
Expiration period for letters of credit, maximum	'5 years	'	'