Significant Accounting Policies (Policies)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited interim consolidated financial statements have been prepared in accordance with the instructions to the SEC Form 10-Q and Article 10 of Regulation S-X; therefore, they do not include all information and footnotes necessary for a fair presentation of financial position, results of operations, comprehensive income, and cash flows in conformity with GAAP. All adjustments consisting of normally recurring accruals that, in the opinion of management, are necessary for a fair presentation of the consolidated financial position and results of operations for the periods covered by this Report have been included. The accompanying unaudited interim consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes appearing in Synovus' 2016 Form 10-K. There have been no significant changes to the accounting policies as disclosed in Synovus' 2016 Form 10-K. In preparing the unaudited interim consolidated financial statements in accordance with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the respective consolidated balance sheets and the reported amounts of revenues and expenses for the periods presented. Actual results could differ significantly from those estimates. Material estimates that are particularly susceptible to significant change relate to the determination of the allowance for loan losses, the fair value of investment securities, the fair value of private equity investments, and contingent liabilities related to legal matters.
Cash and Cash Equivalents	Cash and cash equivalents consist of cash and due from banks.
Short-term Investment	Short-term investments consist of interest bearing funds with the Federal Reserve Bank, interest earning deposits with banks, and federal funds sold and securities purchased under resale agreements.
Recently Adopted Accounting Standards Updates	During 2016, the FASB issued ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 simplifies various aspects of the accounting for employee share-based payment transactions for both public and nonpublic entities, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. This accounting standard update includes a requirement to record all tax effects associated with share-based compensation through the income statement. Previously, tax benefits in excess of compensation cost (“windfalls”) and tax deficiencies (“shortfalls”) were recorded in equity. During the first quarter of 2017, Synovus recognized a $4.1 million income tax benefit from excess tax benefits that occurred between January 1, 2017 and March 31, 2017 from the vesting of restricted share units and exercise of stock options. Synovus had no previously unrecognized excess tax benefits. Additionally, beginning January 1, 2017, Synovus modified the denominator in the diluted earnings per common share calculation under the treasury stock method to exclude future excess tax benefits as part of the assumed proceeds. Synovus elected to retain its existing accounting policy election to estimate award forfeitures. During 2015, the FASB issued ASU 2015-17, Income Taxes: Balance Sheet Classification of Deferred Taxes, which became effective January 1, 2017. ASU 2015-17 requires that deferred income tax liabilities and assets be classified as noncurrent in the statement of financial position instead of separating deferred taxes into current and noncurrent amounts. Also, valuation allowances will no longer be classified between current and noncurrent because these allowances will be required to be classified as noncurrent under the new standard. This ASU only impacts classification in the balance sheet, and has no impact on required deferred tax footnote disclosures (i.e., required presentation of “gross” deferred tax assets and “gross” deferred tax liabilities). The current requirement that deferred tax liabilities and assets of a tax-paying component of an entity be offset and presented as a single amount is not affected by this ASU. There is no impact to our balance sheet as a result of this standard because Synovus has not historically distinguished deferred taxes on the balance sheet as current vs. non-current.
Reclassifications	Prior periods' consolidated financial statements are reclassified whenever necessary to conform to the current periods' presentation.

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.

- Definition

Disclosure of accounting policy for investments in financial assets, including marketable securities (debt and equity securities with readily determinable fair values), investments accounted for under the equity method and cost method, securities borrowed and loaned, and repurchase and resale agreements. For marketable securities, the disclosure may include the entity's accounting treatment for transfers between investment categories and how the fair values for such securities are determined. Also, for all investments, an entity may describe its policy for assessing, recognizing and measuring impairment of the investment.

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