Basis of Presentation (Policies)	12 Months Ended
Basis of Presentation (Policies)	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Use of estimates	Use of estimates: We must make estimates and assumptions that affect the reported amounts and disclosures in preparing our financial statements in conformity with accounting principles generally accepted in the United States of America. Actual results could differ from those estimates.
Principles of consolidation	Principles of consolidation: The accompanying consolidated financial statements include the accounts of Summit and its subsidiaries. All significant accounts and transactions among these entities have been eliminated.
Variable interest entities	Variable interest entities: In accordance with ASC Topic 810, Consolidation, business enterprises that represent the primary beneficiary of another entity by retaining a controlling interest in that entity's assets, liabilities and results of operations must consolidate that entity in its financial statements. Prior to the issuance of ASC Topic 810, consolidation generally occurred when an enterprise controlled another entity through voting interests. If applicable, transition rules allow the restatement of financial statements or prospective application with a cumulative effect adjustment. We have determined that the provisions of ASC Topic 810 do not require consolidation of subsidiary trusts which issue guaranteed preferred beneficial interests in subordinated debentures (Trust Preferred Securities). The Trust Preferred Securities continue to qualify as Tier 1 capital for regulatory purposes. The banking regulatory agencies have not issued any guidance which would change the regulatory capital treatment for the Trust Preferred Securities based on the adoption of ASC Topic 810. The adoption of the provisions of ASC Topic 810 has had no material impact on our results of operations, financial condition, or liquidity. See Note 11 of our Notes to Consolidated Financial Statements for a discussion of our subordinated debentures owed to unconsolidated subsidiary trusts.
Cash and cash equivalents	Cash and cash equivalents: Cash and cash equivalents includes cash on hand, amounts due from banks (including cash items in process of clearing), and federal funds sold.
Presentation of cash flows	Presentation of cash flows: For purposes of reporting cash flows, cash flows from demand deposits, NOW accounts, savings accounts and short-term borrowings are reported on a net basis, since their original maturities are less than three months. Cash flows from loans and certificates of deposit and other time deposits are reported net.
Advertising	Advertising: Advertising costs are expensed as incurred.
Trust services	Trust services: Assets held in an agency or fiduciary capacity are not our assets and are not included in the accompanying consolidated balance sheets. Trust services income is recognized on the cash basis in accordance with customary banking practice. Reporting such income on a cash basis rather than the accrual basis does not have a material effect on net income.
Reclassifications	Reclassifications: Certain accounts in the consolidated financial statements for 2013 and 2012, as previously presented, have been reclassified to conform to current year classifications.

Disclosure of accounting policy for cash and cash equivalents, including the policy for determining which items are treated as cash equivalents. Other information that may be disclosed includes (1) the nature of any restrictions on the entity's use of its cash and cash equivalents, (2) whether the entity's cash and cash equivalents are insured or expose the entity to credit risk, (3) the classification of any negative balance accounts (overdrafts), and (4) the carrying basis of cash equivalents (for example, at cost) and whether the carrying amount of cash equivalents approximates fair value.

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- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

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- Definition

Disclosure of accounting policy for consolidation to describe the significant judgments and assumptions made in determining whether a variable interest held by the entity requires the variable interest entity to be consolidated and (or) disclose information about its involvement with the variable interest entity; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; and the significant factors considered and judgments made in determining that the power to direct the activities that significantly impact the economic performance of the variable interest entity are shared (as defined).

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