Synovus Financial (SNV) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 26, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	SYNOVUS FINANCIAL CORP
Entity Central Index Key	18,349
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		118,681,256
Trading Symbol	snv
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 5,018,777,602

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 397,848	$ 395,175
Interest bearing funds with Federal Reserve Bank	460,928	527,090
Interest earning deposits with banks	26,311	18,720
Federal funds sold and securities purchased under resale agreements	47,846	58,060
Trading account assets, at fair value	3,820	9,314
Mortgage loans held for sale, at fair value	48,024	51,545
Other loans held for sale	11,356	0
Investment securities available for sale, at fair value	3,987,069	3,718,195
Loans, net of deferred fees and costs	24,787,464	23,856,391
Allowance for loan losses	(249,268)	(251,758)
Loans, net	24,538,196	23,604,633
Premises and equipment, net	426,813	417,485
Goodwill	57,315	59,678
Other intangible assets	11,254	13,223
Other real estate	3,758	22,308
Deferred tax asset, net	165,788	395,356
Other assets	1,035,511	813,220
Total assets	31,221,837	30,104,002
Liabilities
Non-interest bearing deposits	7,686,339	7,085,804
Interest bearing deposits, excluding brokered deposits	16,500,436	16,183,273
Brokered deposits	1,961,125	1,378,983
Total deposits	26,147,900	24,648,060
Federal funds purchased and securities sold under repurchase agreements	161,190	159,699
Long-term debt	1,706,138	2,160,881
Other liabilities	245,043	207,438
Total liabilities	28,260,271	27,176,078
Shareholders' Equity
Series C Preferred Stock – no par value. 5,200,000 shares outstanding at December 31, 2017 and December 31, 2016	125,980	125,980
Common stock - $1.00 par value. Authorized 342,857,143 shares at December 31, 2017 and December 31, 2016; issued 142,677,449 at December 31, 2017 and 142,025,720 at December 31, 2016; outstanding 118,897,295 at December 31, 2017 and 122,266,106 at December 31, 2016	142,678	142,026
Additional paid-in capital	3,043,129	3,028,405
Treasury stock, at cost – 23,780,154 shares at December 31, 2017 and 19,759,614 shares at December 31, 2016	(839,674)	(664,595)
Accumulated other comprehensive loss, net	(54,754)	(55,659)
Retained earnings	544,207	351,767
Total shareholders’ equity	2,961,566	2,927,924
Total liabilities and shareholders' equity	$ 31,221,837	$ 30,104,002

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, shares outstanding	5,200,000	5,200,000
Common stock, par value (per share)	$ 1	$ 1
Common stock, shares authorized	342,857,143	342,857,143
Common stock, shares issued (in shares)	142,677,449	142,025,720
Common stock, shares outstanding	118,897,295	122,266,106
Treasury stock, shares at cost	23,780,154	19,759,614

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Loans, including fees	$ 1,064,276	$ 944,233	$ 877,384
Investment securities available for sale	82,699	67,467	59,154
Trading account assets	141	91	303
Mortgage loans held for sale	1,926	2,646	2,546
Federal Reserve Bank balances	6,470	4,356	3,144
Other earning assets	6,985	4,010	3,431
Total interest income	1,162,497	1,022,803	945,962
Interest expense:
Deposits	81,325	64,206	65,534
Federal funds purchased and securities sold under repurchase agreements	198	200	168
Long-term debt	57,665	59,217	52,942
Total interest expense	139,188	123,623	118,644
Net interest income	1,023,309	899,180	827,318
Provision for loan losses	67,185	28,000	19,010
Net interest income after provision for loan losses	956,124	871,180	808,308
Non-interest income:
Service charges on deposit accounts	79,801	81,425	80,142
Fiduciary and asset management fees	50,485	46,594	45,928
Brokerage revenue	29,705	27,028	27,855
Mortgage banking income	22,798	24,259	24,096
Bankcard fees	32,232	33,318	33,172
Cabela's Transaction Fee	75,000	0	0
Investment securities (losses) gains, net	(289)	6,011	2,769
Decrease in fair value of private equity investments, net	(3,093)	(1,026)	(219)
Other fee income	20,168	20,220	21,170
Other non-interest income	38,520	35,365	33,007
Total non-interest income	345,327	273,194	267,920
Non-interest expense:
Salaries and other personnel expense	433,321	402,026	380,918
Net occupancy and equipment expense	119,964	109,347	107,466
Third-party processing expense	54,708	46,320	42,851
FDIC insurance and other regulatory fees	27,011	26,714	27,091
Professional fees	26,232	26,698	26,646
Advertising expense	22,948	20,264	15,477
Foreclosed real estate expense, net	12,540	12,838	22,803
Loss on early extinguishment of debt, net	23,160	4,735	1,533
Earnout liability adjustments	5,466	0	0
Fair value adjustment to Visa derivative		5,795	1,464
Restructuring charges, net	7,014	8,267	36
Other operating expenses	88,949	92,919	91,370
Total non-interest expense	821,313	755,923	717,655
Income before income taxes	480,138	388,451	358,573
Income tax expense	204,664	141,667	132,491
Net income	275,474	246,784	226,082
Dividends on preferred stock	10,238	10,238	10,238
Net income available to common shareholders	$ 265,236	$ 236,546	$ 215,844
Net income per common share, basic (in dollars per share)	$ 2.19	$ 1.90	$ 1.63
Net income per common share, diluted (in dollars per share)	$ 2.17	$ 1.89	$ 1.62
Weighted average common shares outstanding, basic	121,162	124,389	132,423
Weighted average common shares outstanding, diluted	122,012	125,078	133,201

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income, Before-tax Amount	$ 480,138	$ 388,451	$ 358,573
Net income, Tax (Expense) Benefit	(204,664)	(141,667)	(132,491)
Net income	275,474	246,784	226,082
Net change related to cash flow hedges: Before-tax Amount
Reclassification adjustment for losses realized in net income, Before-tax Amount	130	467	521
Net change related to cash flow hedges: Tax (Expense) Benefit
Reclassification adjustment for losses realized in net income, Tax (Expense) Benefit	(50)	(180)	(201)
Net change related to cash flow hedges: Net of Tax Amount
Reclassification adjustment for losses realized in net income, Net of Tax Amount	80	287	320
Net unrealized gains (losses) on investment securities available for sale: Before-tax Amount
Reclassification adjustment for net losses (gains) realized in net income, Before-tax Amount	289	(6,011)	(2,769)
Net unrealized gains (losses) arising during the period, Before-tax Amount	1,038	(36,432)	(25,707)
Net unrealized gains (losses), Before-tax Amount	1,327	(42,443)	(28,476)
Net unrealized gains (losses) on investment securities available for sale: Tax (Expense) Benefit
Reclassification adjustment for net losses (gains) realized in net income, Tax (Expense) Benefit	(111)	2,314	1,066
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit	(362)	14,027	9,901
Net unrealized gains (losses), Tax (Expense) Benefit	(473)	16,341	10,967
Net unrealized gains (losses) on investment securities available for sale: Net of Tax Amount
Reclassification adjustment for net losses (gains) realized in net income, Net of Tax Amount	178	(3,697)	(1,703)
Net unrealized gains (losses) arising during the period, Net of Tax Amount	676	(22,405)	(15,806)
Net unrealized gains (losses), Net of Tax Amount	854	(26,102)	(17,509)
Post-retirement unfunded health benefit: Before-tax Amount
Reclassification adjustment for gains realized in net income, Before-tax Amount	(110)	(144)	(272)
Actuarial gains arising during the period, Before-tax Amount	61	102	236
Net unrealized (losses) gains, Before-tax Amount	(49)	(42)	(36)
Post-retirement unfunded health benefit: Tax (Expense) Benefit
Reclassification adjustment for gains realized in net income, Tax (Expense) Benefit	43	56	104
Actuarial gains arising during the period, Tax (Expense) Benefit	(23)	(39)	(93)
Net unrealized (losses) gains, Tax (Expense) Benefit	20	17	11
Post-retirement unfunded health benefit: Net of Tax Amount
Reclassification adjustment for gains realized in net income, Net of Tax Amount	(67)	(88)	(168)
Actuarial gains arising during the period, Net of Tax Amount	38	63	143
Net unrealized (losses) gains, Net of Tax Amount	(29)	(25)	(25)
Other comprehensive income (loss), Before-tax Amount	1,408	(42,018)	(27,991)
Other comprehensive income (loss), Tax (Expense) Benefit	(503)	16,178	10,777
Net current period other comprehensive income (loss)	905	(25,840)	(17,214)
Comprehensive income, Net of Tax Amount	$ 276,379	$ 220,944	$ 208,868

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Series C Preferred Stock	Preferred StockSeries C Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained EarningsSeries C Preferred Stock
Balance at Dec. 31, 2014	$ 3,041,270		$ 125,980	$ 139,950	$ 2,960,825	$ (187,774)	$ (12,605)	$ 14,894
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	226,082							226,082
Net current period other comprehensive income (loss)	(17,214)						(17,214)
Cash dividends declared on common stock	(55,354)							(55,354)
Cash dividends paid on Series C Preferred Stock		$ (10,238)							$ (10,238)
Repurchases of common stock	(199,221)				14,516	(213,737)
Restricted share unit activity	(4,984)			304	(4,877)			(411)
Stock options exercised	5,643			338	5,305
Share-based compensation tax benefit (deficiency)	1,656				1,656
Share-based compensation expense	12,556				12,556
Balance at Dec. 31, 2015	3,000,196		125,980	140,592	2,989,981	(401,511)	(29,819)	174,973
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	246,784							246,784
Net current period other comprehensive income (loss)	(25,840)						(25,840)
Cash dividends declared on common stock	(59,425)							(59,425)
Cash dividends paid on Series C Preferred Stock		(10,238)							(10,238)
Repurchases of common stock	(263,084)					(263,084)
Issuance of common stock	26,592			821	25,771
Restricted share unit activity	(5,041)			316	(5,030)			(327)
Stock options exercised	5,155			297	4,858
Share-based compensation tax benefit (deficiency)	(790)				(790)
Share-based compensation expense	13,615				13,615
Balance at Dec. 31, 2016	2,927,924		125,980	142,026	3,028,405	(664,595)	(55,659)	351,767
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	275,474							275,474
Net current period other comprehensive income (loss)	905						905
Cash dividends declared on common stock	(72,506)							(72,506)
Cash dividends paid on Series C Preferred Stock		$ (10,238)							$ (10,238)
Repurchases of common stock	(175,079)					(175,079)
Issuance of common stock	5,460			118	5,342
Restricted share unit activity	(7,993)			336	(8,039)			(290)
Stock options exercised	3,440			198	3,242
Share-based compensation tax benefit (deficiency)	5,000
Share-based compensation expense	14,179				14,179
Balance at Dec. 31, 2017	$ 2,961,566		$ 125,980	$ 142,678	$ 3,043,129	$ (839,674)	$ (54,754)	$ 544,207

Consolidated Statements of Cha7

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Cash dividends declared on common stock, per share	$ 0.60	$ 0.48	$ 0.42

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)		Dec. 31, 2015USD ($)
Operating Activities
Net income	$ 275,474		$ 246,784		$ 226,082
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	67,185		28,000		19,010
Depreciation, amortization, and accretion, net	59,121		58,228		56,741
Deferred income tax expense	231,056		128,837		121,904
Decrease (increase) in trading account assets	5,494		(2,327)		8,766
Originations of mortgage loans held for sale	(622,564)		(705,394)		(790,625)
Proceeds from sales of mortgage loans held for sale	642,193		724,712		807,906
Gain on sales of mortgage loans held for sale, net	(13,450)		(13,780)		(14,966)
(Increase) decrease in other assets	(80,544)	[1]	(21,697)	[1]	6,135	[1]
Increase (decrease) in other liabilities	28,651		(4,239)		(24,906)
Investment securities losses (gains), net	289		(6,011)		(2,769)
Losses and write-downs on other real estate, net	11,382		10,174		17,619
Loss on early extinguishment of debt, net	23,160		4,735		1,533
Share-based compensation expense	14,179		13,615		12,556
Net cash provided by operating activities	641,626		461,637		444,986
Investing Activities
Net cash received in acquisition	0		6,146		0
Net increase in interest earning deposits with banks	(7,591)		(1,335)		(5,577)
Net decrease in federal funds sold and securities purchased under resale agreements	10,214		11,759		3,291
Net decrease (increase) in interest bearing funds with Federal Reserve Bank	66,162		302,797		(108,525)
Proceeds from maturities and principal collections of investment securities available for sale	632,875		894,123		693,608
Proceeds from sales of investment securities available for sale	812,293		968,606		347,954
Purchases of investment securities available for sale	(1,729,902)		(2,051,283)		(1,634,531)
Proceeds from sales of loans	42,726		15,046		28,762
Proceeds from sale of other real estate	14,322		30,762		47,137
Net increase in loans	(1,060,582)		(1,129,422)		(1,411,050)
Purchase of Federal Reserve Bank capital stock	0		(97,293)		0
Purchases of bank-owned life insurance policies, net of settlements	(148,110)	[1]	(28,126)	[1]	(42,444)	[1]
Net increase in premises and equipment	(51,106)		(34,317)		(28,381)
Proceeds from sale of other assets held for sale	3,158		13,072		3,039
Net cash used in investing activities	(1,415,541)		(1,099,465)		(2,106,717)
Financing Activities
Net increase in demand and savings deposits	932,561		1,512,451		2,274,949
Net increase (decrease) in certificates of deposit	566,524		(107,893)		(565,315)
Net increase (decrease) in federal funds purchased and securities sold under repurchase agreements	1,491		(17,326)		50,109
Repayments and redemption of long-term debt	(2,250,422)		(2,263,688)		(823,899)
Proceeds from issuance of long-term debt	1,771,866		1,875,000		871,644
Dividends paid to common shareholders	(54,670)		(59,425)		(55,354)
Dividends paid to preferred shareholders	(10,238)		(10,238)		(10,238)
Stock options exercised	3,440		5,155		5,643
Earnout payment	(892)		0		0
Repurchase of common stock	(175,079)		(263,084)		(199,221)
Taxes paid related to net share settlement of equity awards	(7,993)		(5,041)		(4,984)
Net cash provided by financing activities	776,588		665,911		1,543,334
Increase (decrease) in cash and cash equivalents	2,673		28,083		(118,397)
Cash and cash equivalents at beginning of year	395,175		367,092		485,489
Cash and cash equivalents at end of year	397,848		395,175		367,092
Supplemental Cash Flow Information
Income tax payments, net	18,040		9,340		10,514
Interest paid	143,237		123,560		115,795
Non-cash Activities:
Loans foreclosed and transferred to other real estate	7,154		16,214		26,313
Premises and equipment transferred to other properties held for sale	3,283		25,231		2,340
Other assets held for sale transferred to premises and equipment	4,450		0		0
Investment securities available for sale transferred to trading account assets at fair value	0		1,890		0
Loans transferred to other loans held for sale at fair value	52,829		14,621		26,213
Dividends declared on common stock during the period but paid after period-end	17,835		0		0
Settlement of earnout payment with shares of common stock	5,460		0		0
Mortgage loans held for sale transferred to loans at fair value	0		313		659
Acquisition:
Fair value of non-cash assets acquired	0		408,054		0
Fair value of liabilities assumed	0		387,608		0
Fair value of common stock issued	$ 0		$ 26,592		$ 0
[1]	Related to Synovus' early adoption of ASU 2016-15, certain prior period amounts have been reclassified between operating activities and investing activities. See "Part II - Item 8. Financial Statements and Supplementary Data - Note 1 - Summary of Significant Accounting Policies" of this Report for additional information.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 1 - Summary of Significant Accounting Policies Business Operations The consolidated financial statements of Synovus include the accounts of the Parent Company and its consolidated subsidiaries. Synovus provides integrated financial services, including commercial and retail banking, financial management, insurance, and mortgage services to its customers through its wholly-owned subsidiary bank, Synovus Bank, in offices located throughout Georgia, Alabama, South Carolina, Florida, and Tennessee. In addition to our banking operations, we also provide various other financial services to our customers through direct and indirect wholly-owned non-bank subsidiaries, including: Synovus Securities, headquartered in Columbus, Georgia, which specializes in professional portfolio management for fixed-income securities, investment banking, the execution of securities transactions as a broker/dealer, and the provision of individual investment advice on equity and other securities; Synovus Trust, headquartered in Columbus, Georgia, which provides trust, asset management, and financial planning services; and Synovus Mortgage, headquartered in Birmingham, Alabama, which offers mortgage services. Basis of Presentation The accounting and financial reporting policies of Synovus are in accordance with U.S. GAAP and conform to the accounting and reporting guidelines prescribed by bank regulatory authorities. All significant intercompany accounts and transactions have been eliminated in consolidation. In preparing the consolidated financial statements in accordance with U.S. 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. In connection with the determination of the allowance for loan losses and the valuation of certain impaired loans, management obtains independent appraisals for significant properties and properties collateralizing impaired loans. In making this determination, management also considers other factors or recent developments, such as changes in absorption rates or market conditions at the time of valuation and anticipated sales values based on management’s plans for disposition. The following is a description of the Company's significant accounting policies. Cash and Cash Equivalents Cash and cash equivalents consist of cash and due from banks. At December 31, 2016 , $533 thousand of the due from banks balance was restricted as to withdrawal. No cash was restricted as to withdrawal at December 31, 2017. Short-term Investments 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. At December 31, 2017 and 2016 , interest bearing funds with the Federal Reserve Bank included $8.6 million and $130 million , respectively, on deposit to meet Federal Reserve Bank reserve requirements. Interest earning deposits with banks include $5.9 million at December 31, 2017 and $5.6 million at December 31, 2016 , which is pledged as collateral in connection with certain letters of credit. Federal funds sold include $43.8 million at December 31, 2017 and $56.1 million at December 31, 2016 , which are pledged to collateralize certain derivative instruments. Federal funds sold and securities purchased under resale agreements, and federal funds purchased and securities sold under repurchase agreements generally mature in one day. Trading Account Assets Trading account assets, which are primarily held on a short-term basis for the purpose of selling at a profit, consist of debt and equity securities and are reported at fair value. Fair value adjustments and fees from trading account activities are included as a component of other fee income on the consolidated statements of income. Gains and losses realized from the sale of trading account assets are determined by specific identification and are included as a component of other fee income on the trade date. Interest income on trading assets is reported as a component of interest income on the consolidated statements of income. Mortgage Loans Held for Sale and Mortgage Banking Income Mortgage Loans Held for Sale Mortgage loans held for sale are recorded at fair value. Fair value is derived from a hypothetical bulk sale model used to estimate the exit price of the loan in a loan sale. The bid pricing convention is used for loan pricing for similar assets. The valuation model is based upon forward settlements of a pool of loans of similar coupon, maturity, product, and credit attributes. The inputs to the model are continuously updated with available market and historical data. Until the loans are committed to be sold in the secondary market, the valuation model produces an estimate of fair value that represents the highest and best use of the loans in Synovus' principal market. Mortgage Banking Income Mortgage banking income consists primarily of origination and ancillary fees on loans originated for sale, and gains and losses from the sale of mortgage loans. Mortgage loans are generally sold servicing released, without recourse or continuing involvement, and meet ASC 860-10-65 criteria for sale accounting. Other Loans Held for Sale Loans are transferred to other loans held for sale at fair value when Synovus makes the determination to sell specifically identified loans. The fair value of the loans is primarily determined by analyzing the underlying collateral of the loan and the anticipated market prices of similar assets less estimated costs to sell. At the time of transfer, if the estimated fair value is less than the carrying amount, the difference is recorded as a charge-off against the allowance for loan losses. Decreases in the fair value subsequent to the transfer, as well as gains/losses realized from the sale of these assets, are recorded as gains/losses on other loans held for sale, net, as a component of non-interest expense on the consolidated statements of income. Investment Securities Available for Sale Investment securities available for sale are carried at fair value with unrealized gains and losses, net of the related tax effect, excluded from earnings and reported as a separate component of shareholders' equity within accumulated other comprehensive income (loss) until realized. Synovus performs a quarterly assessment of its investment securities available for sale to determine if the decline in fair value of a security below its amortized cost is deemed to be other-than-temporary. Factors included in the assessment include the length of time the security has been in a loss position, the extent that the fair value is below amortized cost, and the credit standing of the issuer. Other-than-temporary impairment losses are recognized on securities when: (1) the holder has an intention to sell the security; (2) it is more likely than not that the security will be required to be sold prior to recovery; or (3) the holder does not expect to recover the entire amortized cost basis of the security. Other-than-temporary impairment losses are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of the impairment related to other factors is recognized in other comprehensive income (loss). Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the effective interest method and prepayment assumptions. Actual prepayment experience is reviewed periodically and the timing of the accretion and amortization is adjusted accordingly. Interest income on securities available for sale is recorded on the accrual basis. Realized gains and losses for securities are included in investment securities gains (losses), net, on the consolidated statements of income and are derived using the specific identification method, on a trade date basis. Loans and Interest Income on Loans Loans are reported at principal amounts outstanding less amounts charged off, net of deferred fees and expenses. Interest income and deferred fees, net of expenses on loans, are recognized on a level yield basis. Non-accrual Loans Loans on which the accrual of interest has been discontinued are designated as non-accrual loans. Accrual of interest is discontinued on loans when reasonable doubt exists as to the full collection of interest or principal, or when loans become contractually past due for 90 days or more as to either interest or principal, in accordance with the terms of the loan agreement, unless they are both well-secured and in the process of collection. When a loan is placed on non-accrual status, previously accrued and uncollected interest is generally reversed as an adjustment to interest income on loans. Interest payments received on non-accrual loans are generally recorded as a reduction of principal. As payments are received on non-accruing loans, interest income can be recognized on a cash basis; however, there must be an expectation of full repayment of the remaining recorded principal balance. The remaining portion of this payment is recorded as a reduction to principal. Loans are generally returned to accruing status when they are brought fully current with respect to interest and principal and when, in the judgment of management, the loans are estimated to be fully collectible as to both principal and interest, and the borrower has sustained repayment performance under the terms of the loan agreement for a reasonable period of time (generally six months). Impaired Loans Impaired loans are loans for which it is probable that Synovus will not be able to collect all amounts due according to the contractual terms of the loan agreements and all loans modified in a troubled debt restructuring (TDR). Other than TDRs, impaired loans do not include smaller-balance homogeneous loans that are collectively evaluated for impairment, which consist of most retail loans and commercial loan relationships lower than $1.0 million . Impairment is measured on a discounted cash flow method based upon the loan's contractual effective interest rate, or at the loan's observable market price, or at the fair value of the collateral, less costs to sell if the loan is collateral-dependent. Interest income on non-accrual impaired loans is recognized as described above under "non-accrual loans." Impaired accruing loans generally consist of those TDRs for which management has concluded that the collectability of the loan is not in doubt. At December 31, 2017 and 2016, substantially all non-accrual impaired loans were collateral-dependent and secured by real estate. For impairment measured using the estimated fair value of collateral less costs to sell, fair value is estimated using appraisals performed by a certified or licensed appraiser. Management also considers other factors or recent developments, such as selling costs and anticipated sales values, taking into account management's plans for disposition, which could result in adjustments to the fair value estimates indicated in the appraisals. The assumptions used in determining the amount of the impairment are subject to significant judgment. Use of different assumptions, for example, changes in the fair value of the collateral or management's plans for disposition could have a significant impact on the amount of impairment. Under the discounted cash flow method, impairment is recorded as a specific reserve with a charge-off for any portion of the impairment considered a confirmed loss. The reserve is reassessed each quarter and adjusted as appropriate based on changes in estimated cash flows. Where guarantors are determined to be a source of repayment, an assessment of the guarantee is required. This guarantee assessment would include, but not be limited to, factors such as type and feature of the guarantee, consideration for the guarantor's financial strength and capacity to service the loan in combination with the guarantor's other financial obligations as well as the guarantor's willingness to assist in servicing the loan. Troubled Debt Restructurings When borrowers are experiencing financial difficulties, Synovus may, in order to assist the borrowers in repaying the principal and interest owed to Synovus, make certain modifications to the borrower's loan. All loan modifications, renewals, and refinances are evaluated for TDR classification. All TDRs are considered to be impaired loans, and the amount of impairment, if any, is determined in accordance with ASC 310-10-35 . Concessions provided by Synovus in a TDR are generally made in order to assist borrowers so that debt service is not interrupted and to mitigate the potential for loan losses. A number of factors are reviewed when a loan is renewed, refinanced, or modified, including cash flows, collateral values, guarantees, and loan structures. Concessions are primarily in the form of providing a below market interest rate given the borrower's credit risk to assist the borrower in managing cash flows, an extension of the maturity of the loan generally for less than one year, or a period of time generally less than one year with a reduction of required principal and/or interest payments (e.g., interest only for a period of time). Insignificant periods of reduction of principal and/or interest payments, or one time deferrals of three months or less, are generally not considered to be financial concessions. Further, it is generally Synovus' practice not to defer principal and/or interest for more than twelve months. Non-accruing TDRs may generally be returned to accrual status if there has been a period of performance, usually at least a six month sustained period of repayment performance in accordance with the agreement. Consistent with regulatory guidance, a TDR will generally no longer be reported as a TDR after a period of performance and after the loan was reported as a TDR at a year-end reporting date, and if at the time of the modification, the interest rate was at market, considering the credit risk associated with the borrower, and no principal was forgiven. Allowance for Loan Losses The allowance for loan losses represents management's estimate of probable losses inherent in the funded loan portfolio. Changes to the allowance are recorded through a provision for loan losses and reduced by loans charged-off, net of recoveries. Impaired loans are generally evaluated on a loan by loan basis with specific reserves, if any, recorded as appropriate. Specific reserves are determined based on ASC 310-10-35, which provides for measurement of a loan's impairment based on one of three methods. If the loan is collateral-dependent, then the fair value of the loan's collateral, less estimated selling costs, is compared to the loan's carrying amount to determine impairment. Other methods of measuring a loan's impairment include the present value of the expected future cash flows of the loan, or if available, the observable market price of the loan. Synovus considers the pertinent facts and circumstances for each impaired loan when selecting the appropriate method to measure impairment, and quarterly evaluates each selection to ensure its continued appropriateness and evaluates the reasonableness of specific reserves, if any. For loans that are not considered impaired, the allocated allowance for loan losses is determined based upon Expected Loss (EL) factors, which are applied to groupings of specific loan types by loan risk ratings. The EL is determined based upon a probability of default (PD), which is the probability that a borrower, segregated by loan type and loan risk grade, will default, and loss given default (LGD), which is the estimate of the amount of net loss in the event of default. The groupings of the loans into loan categories are determined based upon the nature of the loan types and the level of inherent risk associated with the various loan categories. The loan groupings are further segregated based upon the individual loan risk ratings, as described below. The EL factors applied in the methodology are periodically re-evaluated and adjusted to reflect changes in historical loss levels or other risks. Allocated EL factors may also be adjusted, as necessary, for certain qualitative factors that in management's judgment are necessary to reflect losses incurred in the portfolio. Qualitative factors that management considers in the analysis include: • changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off, and recovery practices not considered elsewhere in estimating credit losses • changes in the volume and severity of past due loans, the volume of non-accrual loans, and the volume and severity of adversely classified or grade loans • loan growth • effects of changes in credit concentrations • experience, ability, and depth of lending management, loan review personnel, and other relevant staff • changes in the quality of the loan review function • national and local economic trends and conditions • value of underlying collateral for collateral-dependent loans • other external factors such as the effects for the current competitive, legal, and regulatory environment The adjusted EL factors by portfolio are then adjusted by a loss emergence period for each loan type. A loss emergence period represents the amount of time between when a loss event first occurs to when it is charged off. The loss emergence period was determined for each loan type based on the Company's historical experience and is validated at least annually. Commercial Loans - Risk Ratings Synovus utilizes two primary methods for risk assessment of the commercial loan portfolio: Single Risk Rating Assessment and Dual Risk Rating (DRR) Assessment. The single and dual risk ratings are based on the borrowers' credit risk profile, considering factors such as debt service history, current and estimated prospective cash flow information, collateral supporting the credit, source of repayment as well as other variables, as appropriate. Each loan is assigned a risk rating during its initial approval process. For single risk rated loans, this process begins with a loan rating recommendation from the loan officer responsible for originating the loan. Commercial single risk rated loans are graded on a 9-point scale. Single risk ratings six through nine are defined consistent with the bank regulatory classifications of special mention, substandard, doubtful, and loss, respectively. The primary determinants of the risk ratings for commercial single risk rated loans are the reliability of the primary source of repayment and the borrower's expected performance (i.e., the likelihood that the borrower will be able to service its obligations in accordance with the terms). Expected performance will be based upon full analysis of the borrower's historical financial results, current financial strength and future prospects, which includes any external drivers. For dual risk rated loans, this process begins with scoring the loan for a rating during its initial approval process. The dual risk rating methodology is used for certain components of the C&I loan portfolio as well as certain income-producing real estate loans. At December 31, 2017 and 2016, approximately $7.6 billion was rated using the DRR methodology. The DRR includes sixteen PD categories and nine categories for estimating losses given an event of default. The result is an EL rate established for each borrower. The loan rating is subject to approvals from other members of management, regional credit and/or loan committees depending on the size of the loan and loan's credit attributes. Loan ratings are regularly re-evaluated based upon annual scheduled credit reviews or on a more frequent basis if determined prudent by management. Additionally, an independent loan review function evaluates Synovus' risk rating processes on a continuous basis. Retail Loans – Risk Ratings Retail loans are generally assigned a risk rating on a 6-point scale at the time of origination based on credit bureau scores, with a loan grade of 1 assigned as the lowest level of risk and a loan grade of 6 as the highest level of risk. At 90-119 days past due, a loan grade of 7-substandard non-accrual rating is applied and at 120 days past due, the loan is generally downgraded to grade 9-loss and is generally charged-off. The credit bureau-based ratings are updated at least semi-annually and the ratings based on the past due status are updated monthly. Premises and Equipment Premises and equipment, including bank owned branch locations and leasehold improvements, are reported at cost, less accumulated depreciation and amortization, which are computed using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are depreciated over the shorter of the estimated useful life or the remainder of the lease term. Synovus reviews long-lived assets, such as premises and equipment, for impairment whenever events and circumstances indicate that the carrying amount of an asset may not be recoverable. Goodwill and Other Intangible Assets Goodwill represents the excess purchase price over the fair value of identifiable net assets of acquired businesses. Goodwill is tested for impairment at the reporting unit level on an annual basis and as events occur or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. Synovus reviews goodwill for impairment as of June 30 th and at interim periods if indicators of impairment exist. Synovus applies judgment when assessing goodwill for impairment. ASC 350-20-35-3A, Goodwill Subsequent Measurement - Qualitative Assessment, provides the option to perform a qualitative assessment to determine whether the two-step goodwill impairment test is necessary. Beginning in 2017, Synovus applies the qualitative assessment guidance in ASC 350-20-35-3A to determine if the following factors indicate that goodwill is more likely than not impaired: macroeconomic conditions, industry and market considerations, cost factors, overall financial performance, other relevant entity-specific events, events affecting the reporting unit, and common stock share price. Management applies judgment when weighing the factors most likely to impact a reporting unit's fair value. Other intangible assets relate primarily to borrower relationships, trade name, and a distribution network resulting from a business acquisition. These intangible assets are amortized using straight line methods based on the remaining lives of the assets. Amortization periods range from eight to ten years. Amortization periods for intangible assets are monitored to determine if events and circumstances require such periods to be reduced. Intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of the intangible assets is measured by a comparison of the carrying amount of the asset to future undiscounted cash flows expected to be generated by the asset. If such assets are considered impaired, the amount of the impairment to be recognized is measured by the amount by which the carrying value of the assets exceeds the fair value of the assets based on the discounted expected future cash flows to be generated by the assets. Other Real Estate Other Real Estate (ORE) consists of properties obtained through a foreclosure proceeding or through an in-substance foreclosure in satisfaction of loans. A loan is classified as an in-substance foreclosure when Synovus has taken possession of the collateral regardless of whether formal foreclosure proceedings have taken place. At foreclosure, ORE is recorded at the lower of cost or fair value less estimated selling costs, which establishes a new cost basis. Subsequent to foreclosure, ORE is evaluated quarterly and reported at fair value less estimated selling costs, not to exceed the new cost basis, determined by review of current appraisals, as well as the review of comparable sales and other estimates of fair value obtained principally from independent sources, adjusted for estimated selling costs. Management also considers other factors or recent developments such as changes in absorption rates or market conditions from the time of the latest appraisal received or previous re-evaluation performed, and anticipated sales values considering management's plans for disposition, which could result in an adjustment to lower the fair value estimates indicated in the appraisals. At the time of foreclosure or initial possession of collateral, any excess of the loan balance over the fair value of the real estate held as collateral, less costs to sell, is recorded as a charge against the allowance for loan losses. Revenue and expenses from ORE operations as well as gains or losses on sales are recorded as foreclosed real estate expense, net, a component of non-interest expense on the consolidated statements of income. Subsequent declines in fair value are recorded on a property-by-property basis through use of a valuation allowance within ORE on the consolidated balance sheets and valuation adjustment account in foreclosed real estate expense, net, a component of non-interest expense on the consolidated statements of income. Synovus' objective is to dispose of ORE properties in a timely manner and to maximize net sale proceeds. Synovus has a centralized managed assets division, with the specialized skill set to facilitate this objective. While there is not a defined timeline for their sale, ORE properties are actively marketed through unaffiliated third parties. Other Assets Other assets include accrued interest receivable and other significant balances as described below. More detail of other asset balances can be found in "Part II - Item 8. Financial Statements and Supplementary Data - Note 9 - Other Assets" of this Report. Cash Surrender Value of Bank-Owned Life Insurance Investments in bank-owned life insurance policies on certain current and former officers of Synovus are recorded at the net realizable value of the policies. Net realizable value is the cash surrender value of the policies less any applicable surrender charges and any policy loans. Synovus has not borrowed against the cash surrender value of these policies. Changes in the cash surrender value of the policies are recognized as a component of other non-interest income in the consolidated statements of income. Investments in Federal Reserve Bank and Federal Reserve Home Loan Bank Stock On November 17, 2016, Synovus Bank made an investment of $97.3 million in Federal Reserve Bank capital stock and became a member of the Federal Reserve System. Synovus held stock in the Federal Reserve Bank totaling $95.6 million at December 31, 2017 and $98.6 million at December 31, 2016 . Synovus also held stock in the FHLB of Atlanta totaling $63.9 million at December 31, 2017 and $71.3 million at December 31, 2016 . The Federal Reserve Bank and FHLB stocks are recorded at amortized cost. The investment in FHLB stock is required for membership in the FHLB system and in relation to the level of FHLB outstanding borrowings. Investments in Affordable Housing Tax Credit Partnerships Synovus applies the proportional amortization method of accounting for its qualified affordable housing investments. The proportional amortization method recognizes the amortized cost of the investment as a component of income tax expense. For affordable housing investments which do not qualify for application of the proportional amortization method of accounting, Synovus applies the equity method of accounting. The equity method recognizes income or loss from affordable housing investments as a component of other non-interest income. GGL/SBA Loans Servicing Asset Synovus has retained servicing responsibilities on sold GGL/SBA loans and receives a servicing fee. The servicing asset is established at fair value at the time of the sale based on an analysis of future cash flows that incorporates estimates for discount rates, prepayment speeds, and delinquency rates. The servicing asset is measured at fair value with changes in fair value included with the associated servicing fee in other non-interest income. Prior to 2017, Synovus accounted for the GGL/SBA loans servicing asset using the amortization method. Private Equity Investments Private equity investments are recorded at fair value on the consolidated balance sheets with realized and unrealized gains and losses recorded on the consolidated statements of income (as a component of other non-interest income). The private equity investments in which Synovus holds a limited partner interest consist of funds that invest in privately held companies. For privately held companies in the fund, the general partner estimates the fair value of the company. The estimated fair value of the company is the estimated fair value as an exit price the fund would receive if it were to sell the company in the marketplace. The fair value of the fund's underlying investments is estimated through the use of valuation models, such as option pricing or a discounted cash flow model. Valuation factors, such as a company's financial performance against budget or milestones, last price paid by investors, with consideration given on whether financing is provided by insiders or unrelated new investors, public market comparables, liquidity of the market, industry and economic trends, and changes in management or key personnel, are used in the determination of estimated fair value. Other Assets Held for Sale Other assets held for sale consist of certain premises and equipment held for sale, including those related to the efficiency initiatives discussed in "Note 3 - Restructuring Charges" of this Report. These assets are classified as held for sale and recorded at the lower of their amortized cost or fair value, less costs to sell, consistent with ASC 360-10. The fair value of these assets is determined primarily on the basis of appraisals or BOV, as circumstances warrant, adjusted for estimated selling costs. Both techniques engage licensed or certified professionals that use inputs such as absorption rates, capitalization rates, and market comparables. Derivative Instruments Synovus’ risk management policies emphasize the management of interest rate risk within acceptable guidelines. Synovus’ objective in maintaining these policies is to limit volatility in net interest income arising from changes in interest rates. Risks to be managed include both fair value and cash flow risks. Utilization of derivative financial instruments provides a valuable tool to assist in the management of these risks. All derivative instruments are recorded on the consolidated balance sheets at their respective fair values, as components of other assets and other liabilities. The accounting for changes in fair value (i.e., unrealized gains or losses) of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, on the reason for holding it. If certain conditions are met, entities may elect to designate a derivative instrument as a hedge of exposures to changes in fair values, cash flows, or foreign currencies. If the hedged exposure is a fair value exposure, the unrealized gain or loss on the derivative instrument is recognized in earnings in the period of change, together with the offsetting unrealized loss or gain on the hedged item attributable to the risk being hedged as a component of other non-interest income on the consolidated statements of income. If the hedged exposure is a cash flow exposure, the effective portion of the gain or loss on the derivative instrument is reported initially as a component of accumulated other comprehensive income (loss), net of the tax impact, and subsequently reclassified into earnings when the hedged transaction affects earnings. Any amounts excluded from the assessment of hedge effectiveness, as well as th

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition	Note 2 - Acquisitions Cabela's Transaction On September 25, 2017, Synovus' wholly owned subsidiary, Synovus Bank, completed the acquisition of certain assets and assumption of certain liabilities of World's Foremost Bank, or WFB. Immediately following the closing of this transaction, Synovus Bank sold WFB’s credit card assets and related liabilities to Capital One Bank (USA), National Association, a bank subsidiary of Capital One Financial Corporation. Synovus retained WFB’s $1.10 billion brokered time deposits portfolio, which had a weighted average remaining maturity of approximately 2.53 years and a weighted average rate of 1.83% as of September 25, 2017. The transaction was accounted for as an assumption of a liability (accounted for under the asset acquisition model). In accordance with ASC 820, Fair Value Measurements and Disclosures, the brokered time deposit portfolio was recorded at $1.10 billion , which was the amount of cash received for the deposits and represented the estimated fair value of the deposits at the transaction date. Additionally, Synovus received a $75.0 million transaction fee from Cabela’s Incorporated and Capital One, which was recognized into earnings upon closing of the transaction, based on having achieved the recognition criteria outlined in SEC SAB Topic 13.A, Revenue Recognition . Acquisition of Global One On October 1, 2016, Synovus completed its acquisition of all of the outstanding stock of Global One. Prior to its acquisition, Global One was an Atlanta-based private specialty financial services company that provided financing primarily to commercial entities, with all loans fully collateralized by cash value life insurance policies and/or annuities issued by investment grade life insurance companies. Under the terms of the merger agreement, Synovus acquired Global One for an up-front payment of $30 million , consisting of the issuance of 821 thousand shares of Synovus common stock valued at $26.6 million and $3.4 million in cash, with additional payments to Global One's former shareholders over the next three to five years based on earnings from the Global One business as further discussed below. The acquisition of Global One constituted a business combination. Accordingly, the assets acquired and liabilities assumed were recorded at their estimated fair values as shown in the following table. The determination of fair value required management to make estimates about discount rates, future expected earnings and cash flows, market conditions, future loan growth, and other future events that are highly subjective in nature and subject to change. During the three months ended September 30, 2017, Synovus completed the determination of the final allocation of the purchase price with respect to the assets acquired and liabilities assumed; thus, these fair value estimates reflect measurement period adjustments to the amounts reported as of December 31, 2016, the most significant of which consisted of a reduction in goodwill of $2.4 million and a decrease in the estimated fair value of the earnout liability of $1.8 million (the income statement impact of such adjustments was insignificant). Global One Acquisition Date (in thousands) Fair Value Assets acquired: Cash and due from banks $ 9,554 Commercial and industrial loans (1) 357,307 Goodwill (2) 32,884 Other intangible assets 12,500 Other assets 3,681 Total assets acquired $ 415,926 Liabilities assumed: Notes payable (3) $ 358,560 Earnout liability 12,234 Deferred tax liability, net 3,229 Other liabilities 11,903 Total liabilities assumed $ 385,926 Consideration paid $ 30,000 Cash paid $ 3,408 Fair value of common stock issued 26,592 (1) The unpaid principal balance of the loans was $356.7 million . (2) The goodwill is not expected to be deductible for tax purposes. (3) The unpaid principal balance of the notes payable was $357.0 million . Under the terms of the merger agreement, the purchase price includes additional annual payments ("Earnout Payments") to Global One's former shareholders over the next three to five years, with amounts based on a percentage of "Global One Earnings," as defined in the merger agreement. The Earnout Payments will consist of shares of Synovus common stock as well as a smaller cash consideration component. The first annual Earnout Payment of stock and cash valued at $6.4 million was made during November 2017. The balance of the earnout liability at December 31, 2017 was $11.3 million based on the estimated fair value of the remaining Earnout Payments. Other intangible assets consist of existing borrower relationships ( 11 years useful life), trade name ( 10 years useful life), and distribution network ( 8 years useful life) with December 31, 2017 net carrying values of $9.6 million , $962 thousand , and $506 thousand , respectively. The following is a description of the methods used to determine the fair values of significant assets and liabilities: Commercial and industrial loans : The fair value of loans was determined based on a discounted cash flow approach. The most significant assumptions used in the valuation of the loan portfolio consisted of the prepayment rate, the probability of extension at maturity, the interest rates on extended loans, and the discount rates. All loans are fully collateralized by cash value life insurance policies and/or annuities issued by investment grade insurance companies. Based on a history of no principal losses on the loan portfolio since inception as well as the collateral position, no losses were estimated in the event of default. Notes payable : The notes payable were extinguished immediately after the closing of the acquisition. Accordingly, the fair value of notes payable was determined based on the amounts paid to extinguish such notes, inclusive of applicable prepayment penalties, which is consistent with the perspective of a market participant. Earnout liability : The fair value of the earnout liability, which represents the fair value of the above referenced Earnout Payments, was determined based on option pricing methods and a Monte Carlo simulation. The most significant assumptions used in the valuation of the earnout liability were the expected cash flows, volatility, and discount rates. Subsequent changes in the fair value of the earnout liability are recognized in earnings until the earnout liability arrangement is settled.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2017
Restructuring Charges [Abstract]
Restructuring Charges	Note 3 - Restructuring Charges For the years ended December 31, 2017 , 2016 , and 2015 total restructuring charges consist of the following components: Years Ended December 31, (in thousands) 2017 2016 2015 Severance charges $ 6,128 $ — $ — Asset impairment charges 715 8,107 229 Gain on sale of assets held for sale, net (4 ) — (401 ) Other charges 175 160 208 Total restructuring charges $ 7,014 $ 8,267 $ 36 Restructuring charges of $7.0 million were recorded for the year ended December 31, 2017, consisting primarily of severance charges of $6.1 million . Severance charges included $6.1 million for termination benefits incurred in conjunction with a voluntary early retirement program offered during the first quarter of 2017. This program was part of Synovus' ongoing efficiency initiatives. The accrual balance for severance charges associated with the voluntary early retirement program was $336 thousand at December 31, 2017. Additionally, during 2017, Synovus recorded restructuring charges of $715 thousand due to additional asset impairment charges on properties previously identified for disposition. For the year ended December 31, 2016, restructuring charges totaled $8.3 million with $5.3 million related to corporate real estate optimization activities and $2.8 million associated with branch closures. For the year ended December 31, 2015, Synovus recorded net gains of $401 thousand on the sale of certain branch locations and recorded additional expense of $437 thousand associated primarily with branches closed during 2014. The following table presents aggregate activity associated with accruals that resulted from the restructuring charges recorded during the years ended December 31, 2017 , 2016 , and 2015 : (in thousands) Severance Charges Lease Termination Charges Total Balance at December 31, 2014 $ 3,291 $ 5,539 $ 8,830 Accruals for lease terminations — (3 ) (3 ) Payments (1,361 ) (849 ) (2,210 ) Balance at December 31, 2015 1,930 4,687 6,617 Accruals for lease terminations — 6 6 Payments (1,849 ) (725 ) (2,574 ) Balance at December 31, 2016 81 3,968 4,049 Accruals for voluntary and involuntary termination benefits 6,128 — 6,128 Payments (5,873 ) (692 ) (6,565 ) Balance at December 31, 2017 $ 336 $ 3,276 $ 3,612 Other charges were paid in the years that they were incurred. No other restructuring charges resulted in payment accruals.

Investment Securities Available

Investment Securities Available for Sale	12 Months Ended
	Dec. 31, 2017
Investments [Abstract]
Investment Securities Available for Sale	Note 4 - Investment Securities Available for Sale The amortized cost, gross unrealized gains and losses, and estimated fair values of investment securities available for sale at December 31, 2017 and 2016 are summarized below. December 31, 2017 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 83,608 $ — $ (934 ) $ 82,674 U.S. Government agency securities 10,771 91 — 10,862 Mortgage-backed securities issued by U.S. Government agencies 121,283 519 (1,362 ) 120,440 Mortgage-backed securities issued by U.S. Government sponsored enterprises 2,666,818 5,059 (31,354 ) 2,640,523 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 1,135,259 144 (23,404 ) 1,111,999 State and municipal securities 180 — — 180 Corporate debt and other securities 20,320 294 (223 ) 20,391 Total investment securities available for sale $ 4,038,239 $ 6,107 $ (57,277 ) $ 3,987,069 December 31, 2016 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 108,221 $ 225 $ (644 ) $ 107,802 U.S. Government agency securities 12,727 266 — 12,993 Mortgage-backed securities issued by U.S. Government agencies 174,440 1,116 (1,354 ) 174,202 Mortgage-backed securities issued by U.S. Government sponsored enterprises 2,543,495 5,416 (42,571 ) 2,506,340 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 905,789 1,214 (16,561 ) 890,442 State and municipal securities 2,780 14 — 2,794 Equity securities 919 2,863 — 3,782 Corporate debt and other securities 20,247 — (407 ) 19,840 Total investment securities available for sale $ 3,768,618 $ 11,114 $ (61,537 ) $ 3,718,195 At December 31, 2017 and 2016 , investment securities with a carrying value of $2.00 billion and $2.04 billion , respectively, were pledged to secure certain deposits and securities sold under repurchase agreements as required by law and contractual agreements. Synovus has reviewed investment securities that are in an unrealized loss position as of December 31, 2017 and 2016 for OTTI and does not consider any securities in an unrealized loss position to be other-than-temporarily impaired. If Synovus intended to sell a security in an unrealized loss position, the entire unrealized loss would be reflected in earnings. Synovus does not intend to sell investment securities in an unrealized loss position prior to the recovery of the unrealized loss, which may not be until maturity, and has the ability and intent to hold those securities for that period of time. Additionally, Synovus is not currently aware of any circumstances which will require it to sell any of the securities that are in an unrealized loss position prior to the respective securities' recovery of all such unrealized losses. Declines in the fair value of available for sale securities below their cost that are deemed to have OTTI are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of the impairment related to other factors is recognized in other comprehensive income. Currently, unrealized losses on debt securities are attributable to increases in interest rates on comparable securities from the date of purchase. Synovus regularly evaluates its investment securities portfolio to ensure that there are no conditions that would indicate that unrealized losses represent OTTI. These factors include the length of time the security has been in a loss position, the extent that the fair value is below amortized cost, and the credit standing of the issuer. As of December 31, 2017 , Synovus had 60 investment securities in a loss position for less than twelve months and 54 investment securities in a loss position for twelve months or longer. Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2017 and December 31, 2016 are presented below. December 31, 2017 Less than 12 Months 12 Months or Longer Total (in thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses U.S. Treasury securities $ 34,243 $ 443 $ 29,562 $ 491 $ 63,805 $ 934 Mortgage-backed securities issued by U.S. Government agencies 36,810 357 55,740 1,005 92,550 1,362 Mortgage-backed securities issued by U.S. Government sponsored enterprises 1,271,012 10,263 929,223 21,091 2,200,235 31,354 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 653,781 9,497 426,237 13,907 1,080,018 23,404 Corporate debt and other securities — — 5,097 223 5,097 223 Total $ 1,995,846 $ 20,560 $ 1,445,859 $ 36,717 $ 3,441,705 $ 57,277 December 31, 2016 Less than 12 Months 12 Months or Longer Total (in thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses U.S Treasury securities $ 64,023 $ 644 $ — $ — $ 64,023 $ 644 Mortgage-backed securities issued by U.S. Government agencies 128,121 1,240 3,626 114 131,747 1,354 Mortgage-backed securities issued by U.S. Government sponsored enterprises 2,123,181 42,571 — — 2,123,181 42,571 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 682,492 15,653 24,801 908 707,293 16,561 Corporate debt and other securities 14,952 48 4,888 359 19,840 407 Total $ 3,012,769 $ 60,156 $ 33,315 $ 1,381 $ 3,046,084 $ 61,537 The amortized cost and fair value by contractual maturity of investment securities available for sale at December 31, 2017 are shown below. The expected life of mortgage-backed securities or CMOs may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. For purposes of the maturity table, mortgage-backed securities and CMOs, which are not due at a single maturity date, have been classified based on the final contractual maturity date. Distribution of Maturities at December 31, 2017 (in thousands) Within One Year 1 to 5 Years 5 to 10 Years More Than 10 Years No Stated Maturity Total Amortized Cost U.S. Treasury securities $ 18,870 $ 64,738 $ — $ — $ — $ 83,608 U.S. Government agency securities 2,331 6,437 2,003 — — 10,771 Mortgage-backed securities issued by U.S. Government agencies — — 31,259 90,024 — 121,283 Mortgage-backed securities issued by U.S. Government sponsored enterprises 18 1,838 434,603 2,230,359 — 2,666,818 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — — 19,769 1,115,490 — 1,135,259 State and municipal securities 180 — — — — 180 Corporate debt and other securities — — 15,000 2,000 3,320 20,320 Total amortized cost $ 21,399 $ 73,013 $ 502,634 $ 3,437,873 $ 3,320 $ 4,038,239 Fair Value U.S. Treasury securities $ 18,870 $ 63,804 $ — $ — $ — $ 82,674 U.S. Government agency securities 2,360 6,459 2,043 — — 10,862 Mortgage-backed securities issued by U.S. Government agencies — — 31,193 89,247 — 120,440 Mortgage-backed securities issued by U.S. Government sponsored enterprises 18 1,928 430,140 2,208,437 — 2,640,523 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — — 19,366 1,092,633 — 1,111,999 State and municipal securities 180 — — — — 180 Corporate debt and other securities — — 15,294 1,935 3,162 20,391 Total fair value $ 21,428 $ 72,191 $ 498,036 $ 3,392,252 $ 3,162 $ 3,987,069 Proceeds from sales, gross gains, and gross losses on sales of securities available for sale for the years ended December 31, 2017 , 2016 and 2015 are presented below. The specific identification method is used to reclassify gains and losses out of other comprehensive income at the time of sale. (in thousands) 2017 2016 2015 Proceeds from sales of investment securities available for sale $ 812,293 $ 968,606 $ 347,954 Gross realized gains on sales (1) $ 7,942 $ 9,586 $ 4,356 Gross realized losses on sales (8,231 ) (3,575 ) (1,587 ) Investment securities (losses) gains, net $ (289 ) $ 6,011 $ 2,769 (1) Includes $1.4 million in gains in 2016 from the transfer of $1.9 million of investment securities available for sale to trading account assets.

Loans And Allowance For Loan Lo

Loans And Allowance For Loan Losses	12 Months Ended
	Dec. 31, 2017
Loans and Allowance for Loan Losses [Abstract]
Loans And Allowance For Loan Losses	Note 5 - Loans and Allowance for Loan Losses Loans outstanding, by classification, at December 31, 2017 and 2016 are summarized below. December 31, (in thousands) 2017 2016 Investment properties $ 5,670,065 $ 5,869,261 1-4 family properties 781,619 888,553 Land and development 483,604 616,298 Total commercial real estate 6,935,288 7,374,112 Commercial, financial and agricultural 7,179,487 6,909,036 Owner-occupied 4,844,163 4,634,770 Total commercial and industrial 12,023,650 11,543,806 Home equity lines 1,514,227 1,617,265 Consumer mortgages 2,633,503 2,296,604 Credit cards 232,676 232,413 Other consumer loans 1,473,451 818,182 Total consumer 5,853,857 4,964,464 Total loans 24,812,795 23,882,382 Deferred fees and costs, net (25,331 ) (25,991 ) Total loans, net of deferred fees and costs $ 24,787,464 $ 23,856,391 A substantial portion of the loan portfolio is secured by real estate in markets located throughout Georgia, Alabama, South Carolina, Florida, and Tennessee. Accordingly, the ultimate collectability of a substantial portion of the loan portfolio is susceptible to changes in market conditions in these areas. The following is a summary of current, accruing past due, and non-accrual loans by class as of December 31, 2017 and 2016 . Current, Accruing Past Due, and Non-accrual Loans December 31, 2017 ( in thousands) Current Accruing 30-89 Days Past Due Accruing 90 Days or Greater Past Due Total Accruing Past Due Non-accrual Total Investment properties $ 5,663,665 $ 2,506 $ 90 $ 2,596 $ 3,804 $ 5,670,065 1-4 family properties 775,023 3,545 202 3,747 2,849 781,619 Land and development 476,131 1,609 67 1,676 5,797 483,604 Total commercial real estate 6,914,819 7,660 359 8,019 12,450 6,935,288 Commercial, financial and agricultural 7,097,127 11,214 1,016 12,230 70,130 7,179,487 Owner-occupied 4,830,150 6,880 479 7,359 6,654 4,844,163 Total commercial and industrial 11,927,277 18,094 1,495 19,589 76,784 12,023,650 Home equity lines 1,490,808 5,629 335 5,964 17,455 1,514,227 Consumer mortgages 2,622,061 3,971 268 4,239 7,203 2,633,503 Credit cards 229,015 1,930 1,731 3,661 — 232,676 Other consumer loans 1,461,223 10,333 226 10,559 1,669 1,473,451 Total consumer 5,803,107 21,863 2,560 24,423 26,327 5,853,857 Total loans $ 24,645,203 $ 47,617 $ 4,414 $ 52,031 $ 115,561 $ 24,812,795 (1) December 31, 2016 ( in thousands) Current Accruing 30-89 Days Past Due Accruing 90 Days or Greater Past Due Total Accruing Past Due Non-accrual Total Investment properties $ 5,861,198 $ 2,795 $ — $ 2,795 $ 5,268 $ 5,869,261 1-4 family properties 874,477 4,801 161 4,962 9,114 888,553 Land and development 598,624 1,441 — 1,441 16,233 616,298 Total commercial real estate 7,334,299 9,037 161 9,198 30,615 7,374,112 Commercial, financial and agricultural 6,839,700 9,542 720 10,262 59,074 6,909,036 Owner-occupied 4,600,110 17,913 244 18,157 16,503 4,634,770 Total commercial and industrial 11,439,810 27,455 964 28,419 75,577 11,543,806 Home equity lines 1,585,228 10,013 473 10,486 21,551 1,617,265 Consumer mortgages 2,265,966 7,876 81 7,957 22,681 2,296,604 Credit cards 229,177 1,819 1,417 3,236 — 232,413 Other consumer loans 809,418 5,771 39 5,810 2,954 818,182 Total consumer 4,889,789 25,479 2,010 27,489 47,186 4,964,464 Total loans $ 23,663,898 $ 61,971 $ 3,135 $ 65,106 $ 153,378 $ 23,882,382 (2) (1) Total before net deferred fees and costs of $25.3 million . (2) Total before net deferred fees and costs of $26.0 million . Interest income on non-accrual loans outstanding at December 31, 2017 and 2016 that would have been recorded if the loans had been current and performed in accordance with their original terms was $9.1 million and $8.9 million , respectively. Interest income recorded on these loans for the years ended December 31, 2017 and 2016 was $2.7 million and $3.5 million , respectively. The credit quality of the loan portfolio is summarized no less frequently than quarterly using the standard asset classification system utilized by the federal banking agencies. These classifications are divided into three groups – Not Classified (Pass), Special Mention, and Classified or Adverse rating (Substandard, Doubtful, and Loss) and are defined as follows: Pass - loans which are well protected by the current net worth and paying capacity of the obligor (or guarantors, if any) or by the fair value, less cost to acquire and sell in a timely manner, of any underlying collateral. Special Mention - loans which have potential weaknesses that deserve management's close attention. These loans are not adversely classified and do not expose an institution to sufficient risk to warrant an adverse classification. Substandard - loans which are inadequately protected by the current net worth and paying capacity of the obligor or by the collateral pledged, if any. Loans with this classification are characterized by the distinct possibility that the institution will sustain some loss if the deficiencies are not corrected. Doubtful - loans which have all the weaknesses inherent in loans classified as substandard with the added characteristic that the weaknesses make collection or liquidation in full highly questionable and improbable on the basis of currently known facts, conditions, and values. Loss - loans which are considered by management to be uncollectible and of such little value that their continuance on the institution's books as an asset, without establishment of a specific valuation allowance or charge-off, is not warranted. In the following tables, consumer loans are generally assigned a risk grade similar to the classifications described above; however, upon reaching 90 days and 120 days past due, they are generally downgraded to Substandard and Loss, respectively, in accordance with the FFIEC Uniform Retail Credit Classification and Account Management Policy. Additionally, in accordance with the Interagency Supervisory Guidance on Allowance for Loan and Lease Losses Estimation Practices for Loans and Lines of Credit Secured by Junior Liens on 1-4 Family Residential Properties, the risk grade classifications of consumer loans (home equity lines and consumer mortgages) secured by junior liens on 1-4 family residential properties also consider available information on the payment status of the associated senior lien with other financial institutions. Loan Portfolio Credit Exposure by Risk Grade December 31, 2017 (in thousands) Pass Special Mention Substandard (1) Doubtful (2) Loss Total Investment properties $ 5,586,792 $ 64,628 $ 18,645 $ — $ — $ 5,670,065 1-4 family properties 745,299 19,419 16,901 — — 781,619 Land and development 431,759 33,766 14,950 3,129 — 483,604 Total commercial real estate 6,763,850 117,813 50,496 3,129 — 6,935,288 Commercial, financial and agricultural 6,929,506 115,912 132,818 1,251 — 7,179,487 Owner-occupied 4,713,877 50,140 80,073 73 — 4,844,163 Total commercial and industrial 11,643,383 166,052 212,891 1,324 — 12,023,650 Home equity lines 1,491,105 — 21,079 285 1,758 (3) 1,514,227 Consumer mortgages 2,622,499 — 10,607 291 106 (3) 2,633,503 Credit cards 230,945 — 399 — 1,332 (4) 232,676 Other consumer loans 1,470,944 — 2,168 329 10 (3) 1,473,451 Total consumer 5,815,493 — 34,253 905 3,206 5,853,857 Total loans $ 24,222,726 $ 283,865 $ 297,640 $ 5,358 $ 3,206 $ 24,812,795 (5) December 31, 2016 (in thousands) Pass Special Mention Substandard (1) Doubtful (2) Loss Total Investment properties $ 5,794,626 $ 43,336 $ 31,299 $ — $ — $ 5,869,261 1-4 family properties 827,557 33,928 26,790 278 — 888,553 Land and development 521,745 60,205 27,361 6,987 — 616,298 Total commercial real estate 7,143,928 137,469 85,450 7,265 — 7,374,112 Commercial, financial and agricultural 6,635,757 126,268 140,425 6,445 141 (3) 6,909,036 Owner-occupied 4,461,174 60,856 111,330 1,410 — (3) 4,634,770 Total commercial and industrial 11,096,931 187,124 251,755 7,855 141 11,543,806 Home equity lines 1,589,199 — 22,774 2,892 2,400 (3) 1,617,265 Consumer mortgages 2,271,916 — 23,268 1,283 137 (3) 2,296,604 Credit cards 230,997 — 637 — 779 (4) 232,413 Other consumer loans 814,843 — 3,233 42 64 (3) 818,182 Total consumer 4,906,955 — 49,912 4,217 3,380 4,964,464 Total loans $ 23,147,814 $ 324,593 $ 387,117 $ 19,337 $ 3,521 $ 23,882,382 (6) (1) Includes $190.6 million and $256.6 million of Substandard accruing loans at December 31, 2017 and December 31, 2016 , respectively. (2) The loans within this risk grade are on non-accrual status and generally have an allowance for loan losses equal to 50% of the loan amount. (3) The loans within this risk grade are on non-accrual status and have an allowance for loan losses equal to the full loan amount. (4) Represent amounts that were 120 days past due. These credits are downgraded to the Loss category with an allowance for loan losses equal to the full loan amount and are generally charged off upon reaching 181 days past due in accordance with the FFIEC Uniform Retail Credit Classification and Account Management Policy. (5) Total before net deferred fees and costs of $25.3 million . (6) Total before net deferred fees and costs of $26.0 million . The following table details the change in the allowance for loan losses by loan segment for the years ended December 31, 2017 , 2016 and 2015 . As Of and For The Year Ended December 31, 2017 (in thousands) Commercial Real Estate Commercial & Industrial Consumer Total Allowance for loan losses Beginning balance $ 81,816 $ 125,778 $ 44,164 $ 251,758 Charge-offs (12,193 ) (49,244 ) (28,982 ) (90,419 ) Recoveries 8,026 6,685 6,033 20,744 Provision for loan losses (2,651 ) 43,584 26,252 67,185 Ending balance (4) $ 74,998 $ 126,803 $ 47,467 $ 249,268 Ending balance: individually evaluated for impairment $ 4,240 $ 9,515 $ 1,153 $ 14,908 Ending balance: collectively evaluated for impairment $ 70,758 $ 117,288 $ 46,314 $ 234,360 Loans Ending balance: total loans (1) (4) $ 6,935,288 $ 12,023,650 $ 5,853,857 $ 24,812,795 Ending balance: individually evaluated for impairment $ 56,896 $ 111,334 $ 32,056 $ 200,286 Ending balance: collectively evaluated for impairment $ 6,878,392 $ 11,912,316 $ 5,821,801 $ 24,612,509 As Of and For The Year Ended December 31, 2016 (in thousands) Commercial Real Estate Commercial & Industrial Consumer Total Allowance for loan losses Beginning balance $ 87,133 $ 122,989 $ 42,374 $ 252,496 Charge-offs (18,216 ) (25,039 ) (14,705 ) (57,960 ) Recoveries 15,226 9,071 4,925 29,222 Provision for loan losses (2,327 ) 18,757 11,570 28,000 Ending balance (4) $ 81,816 $ 125,778 $ 44,164 $ 251,758 Ending balance: individually evaluated for impairment $ 7,916 $ 8,384 $ 1,811 $ 18,111 Ending balance: collectively evaluated for impairment $ 73,900 $ 117,394 $ 42,353 $ 233,647 Loans Ending balance: total loans (2) (4) $ 7,374,112 $ 11,543,806 $ 4,964,464 $ 23,882,382 Ending balance: individually evaluated for impairment $ 91,410 $ 120,560 $ 37,526 $ 249,496 Ending balance: collectively evaluated for impairment $ 7,282,702 $ 11,423,246 $ 4,926,938 $ 23,632,886 As Of and For The Year Ended December 31, 2015 (in thousands) Commercial Real Estate Commercial & Industrial Consumer Total Allowance for loan losses Beginning balance $ 101,471 $ 118,110 $ 41,736 $ 261,317 Allowance for loan losses of sold Memphis loans — — — — Charge-offs (13,998 ) (22,583 ) (20,758 ) (57,339 ) Recoveries 13,644 8,611 7,253 29,508 Provision for loan losses (13,984 ) 18,851 14,143 19,010 Ending balance (4) $ 87,133 $ 122,989 $ 42,374 $ 252,496 Ending balance: individually evaluated for impairment $ 18,969 $ 10,477 $ 989 $ 30,435 Ending balance: collectively evaluated for impairment $ 68,164 $ 112,512 $ 41,385 $ 222,061 Loans Ending balance: total loans (3) (4) $ 7,394,768 $ 10,772,130 $ 4,292,766 $ 22,459,664 Ending balance: individually evaluated for impairment $ 157,958 $ 105,599 $ 38,243 $ 301,800 Ending balance: collectively evaluated for impairment $ 7,236,810 $ 10,666,531 $ 4,254,523 $ 22,157,864 (1) Total before net deferred fees and costs of $25.3 million . (2) Total before net deferred fees and costs of $26.0 million . (3) Total before net deferred fees and costs of $30.1 million . (4) As of and for the years ended December 31, 2017, 2016, and 2015, there were no purchased credit-impaired loans and no allowance for loan losses for purchased credit-impaired loans. Below is a detailed summary of impaired loans (including accruing TDRs) by class as of and for the years ended December 31, 2017 and 2016 . Impaired Loans (including accruing TDRs) December 31, 2017 (in thousands) Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized With no related allowance recorded Investment properties $ — $ — $ — $ 123 $ — 1-4 family properties — — — 323 — Land and development 56 1,740 — 1,816 — Total commercial real estate 56 1,740 — 2,262 — Commercial, financial and agricultural 8,220 9,576 — 21,686 — Owner-occupied — — — 6,665 — Total commercial and industrial 8,220 9,576 — 28,351 — Home equity lines 2,746 2,943 — 1,205 — Consumer mortgages — — — 496 — Credit cards — — — — — Other consumer loans — — — — — Total consumer 2,746 2,943 — 1,701 — Total 11,022 14,259 — 32,314 — With allowance recorded Investment properties 23,364 23,364 1,100 28,749 1,144 1-4 family properties 15,056 15,056 504 16,257 925 Land and development 18,420 18,476 2,636 23,338 404 Total commercial real estate 56,840 56,896 4,240 68,344 2,473 Commercial, financial and agricultural 65,715 65,851 7,406 50,468 1,610 Owner-occupied 37,399 37,441 2,109 40,498 1,382 Total commercial and industrial 103,114 103,292 9,515 90,966 2,992 Home equity lines 5,096 5,096 114 7,476 334 Consumer mortgages 18,668 18,668 569 19,144 896 Credit cards — — — — — Other consumer loans 5,546 5,546 470 4,765 266 Total consumer 29,310 29,310 1,153 31,385 1,496 Total 189,264 189,498 14,908 190,695 6,961 Total Investment properties 23,364 23,364 1,100 28,872 1,144 1-4 family properties 15,056 15,056 504 16,580 925 Land and development 18,476 20,216 2,636 25,154 404 Total commercial real estate 56,896 58,636 4,240 70,606 2,473 Commercial, financial and agricultural 73,935 75,427 7,406 72,154 1,610 Owner-occupied 37,399 37,441 2,109 47,163 1,382 Total commercial and industrial 111,334 112,868 9,515 119,317 2,992 Home equity lines 7,842 8,039 114 8,681 334 Consumer mortgages 18,668 18,668 569 19,640 896 Credit cards — — — — — Other consumer loans 5,546 5,546 470 4,765 266 Total consumer 32,056 32,253 1,153 33,086 1,496 Total impaired loans $ 200,286 $ 203,757 $ 14,908 $ 223,009 $ 6,961 December 31, 2016 (in thousands) Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized With no related allowance recorded Investment properties $ 748 $ 793 $ — $ 2,013 $ — 1-4 family properties 643 2,939 — 1,021 — Land and development 2,099 7,243 — 6,769 — Total commercial real estate 3,490 10,975 — 9,803 — Commercial, financial and agricultural 17,958 20,577 — 6,321 — Owner-occupied 5,508 7,377 — 8,394 — Total commercial and industrial 23,466 27,954 — 14,715 — Home equity lines 1,051 1,051 — 1,045 — Consumer mortgages 744 814 — 870 — Credit cards — — — — — Other consumer loans — — — — — Total consumer 1,795 1,865 — 1,915 — Total 28,751 40,794 — 26,433 — With allowance recorded Investment properties 31,489 31,489 2,044 42,659 1,436 1-4 family properties 23,642 23,649 769 39,864 855 Land and development 32,789 32,788 5,103 25,568 995 Total commercial real estate 87,920 87,926 7,916 108,091 3,286 Commercial, financial and agricultural 43,386 45,913 5,687 51,968 1,215 Owner-occupied 53,708 53,942 2,697 52,300 1,946 Total commercial and industrial 97,094 99,855 8,384 104,268 3,161 Home equity lines 9,638 9,638 971 9,668 432 Consumer mortgages 20,953 20,953 673 20,993 1,014 Credit cards — — — — — Other consumer loans 5,140 5,140 167 5,062 303 Total consumer 35,731 35,731 1,811 35,723 1,749 Total 220,745 223,512 18,111 248,082 8,196 Total Investment properties 32,237 32,282 2,044 44,672 1,436 1-4 family properties 24,285 26,588 769 40,885 855 Land and development 34,888 40,031 5,103 32,337 995 Total commercial real estate 91,410 98,901 7,916 117,894 3,286 Commercial, financial and agricultural 61,344 66,490 5,687 58,289 1,215 Owner-occupied 59,216 61,319 2,697 60,694 1,946 Total commercial and industrial 120,560 127,809 8,384 118,983 3,161 Home equity lines 10,689 10,689 971 10,713 432 Consumer mortgages 21,697 21,767 673 21,863 1,014 Credit cards — — — — — Other consumer loans 5,140 5,140 167 5,062 303 Total consumer 37,526 37,596 1,811 37,638 1,749 Total impaired loans $ 249,496 $ 264,306 $ 18,111 $ 274,515 $ 8,196 The average recorded investment in impaired loans was $358.3 million for the year ended December 31, 2015 . Excluding accruing TDRs, there was no interest income recognized for the investment in impaired loans for the years ended December 31, 2017 , 2016 , and 2015 . Interest income recognized for accruing TDRs was $9.5 million for the year ended December 31, 2015 . At December 31, 2017 , 2016 , and 2015 , impaired loans of $49.0 million , $53.7 million , and $77.9 million , respectively, were on non-accrual status. Concessions provided in a TDR are primarily in the form of providing a below market interest rate given the borrower's credit risk, a period of time generally less than one year with a reduction of required principal and/or interest payments (e.g., interest only for a period of time), or extension of the maturity of the loan generally for less than one year. Insignificant periods of reduction of principal and/or interest payments, or one time deferrals of three months or less, are generally not considered to be financial concessions. The following tables represent, by concession type, the post-modification balance for loans modified or renewed during the years ended December 31, 2017 , 2016 , and 2015 that were reported as accruing or non-accruing TDRs. TDRs by Concession Type Year Ended December 31, 2017 (in thousands, except contract data) Number of Contracts Principal Forgiveness Below Market Interest Rate Term Extensions and/or Other Concessions Total Investment properties 1 $ — $ — $ 121 $ 121 1-4 family properties 35 — 2,786 2,040 4,826 Land and development 6 — 157 1,614 1,771 Total commercial real estate 42 — 2,943 3,775 6,718 Commercial, financial and agricultural 56 — 9,434 12,145 21,579 Owner-occupied 4 — 35 1,705 1,740 Total commercial and industrial 60 — 9,469 13,850 23,319 Home equity lines — — — — — Consumer mortgages 11 — 2,539 1,190 3,729 Credit cards — — — — — Other consumer loans 38 — 1,624 1,333 2,957 Total consumer 49 — 4,163 2,523 6,686 Total loans 151 $ — $ 16,575 $ 20,148 $ 36,723 (1) (1) No charge-offs were recorded during 2017 upon restructuring of these loans. TDRs by Concession Type Year Ended December 31, 2016 (in thousands, except contract data) Number of Contracts Principal Forgiveness Below Market Interest Rate Term Extensions and/or Other Concessions Total Investment properties 4 $ — $ 1,825 $ 3,518 $ 5,343 1-4 family properties 39 — 5,499 1,488 6,987 Land and development 14 — — 4,099 4,099 Total commercial real estate 57 — 7,324 9,105 16,429 Commercial, financial and agricultural 63 — 17,509 7,160 24,669 Owner-occupied 9 — 7,884 550 8,434 Total commercial and industrial 72 — 25,393 7,710 33,103 Home equity lines 5 — 225 123 348 Consumer mortgages 7 — 413 51 464 Credit cards — — — — — Other consumer loans 28 — 394 2,256 2,650 Total consumer 40 — 1,032 2,430 3,462 Total loans 169 $ — $ 33,749 $ 19,245 $ 52,994 (1) (1) No charge-offs were recorded during 2016 upon restructuring of these loans. TDRs by Concession Type Year Ended December 31, 2015 (in thousands, except contract data) Number of Contracts Principal Forgiveness Below Market Interest Rate Term Extensions and/or Other Concessions Total Investment properties 11 $ — $ 25,052 $ 6,973 $ 32,025 1-4 family properties 43 14,823 4,667 2,763 22,253 Land and development 12 — 614 1,532 2,146 Total commercial real estate 66 14,823 30,333 11,268 56,424 Commercial, financial and agricultural 91 29 3,191 6,477 9,697 Owner-occupied 10 — 3,417 2,064 5,481 Total commercial and industrial 101 29 6,608 8,541 15,178 Home equity lines 53 — 2,826 2,905 5,731 Consumer mortgages 15 — 1,011 895 1,906 Credit cards — — — — — Other consumer loans 27 — 444 703 1,147 Total consumer 95 — 4,281 4,503 8,784 Total loans 262 $ 14,852 $ 41,222 $ 24,312 $ 80,386 (1) (1) Charge-offs of $4.0 million were recorded during 2015 upon restructuring of these loans. For the years ended December 31, 2017, 2016 and 2015, there were eight defaults with a recorded investment of $4.0 million , two defaults with a recorded investment of $181 thousand , and seven defaults with a recorded investment of $12.5 million , respectively, on accruing TDRs restructured during the previous twelve months (defaults are defined as the earlier of the TDR being placed on non-accrual status or reaching 90 days past due with respect to principal and/or interest payments). If at the time that a loan was designated as a TDR the loan was not already impaired, the measurement of impairment resulting from the TDR designation changes from a general pool-level reserve to a specific loan measurement of impairment in accordance with ASC 310-10-35. Generally, the change in the allowance for loan losses resulting from such a TDR is not significant. At December 31, 2017 , the allowance for loan losses allocated to accruing TDRs totaling $151.3 million was $8.7 million compared to accruing TDRs of $195.8 million with an allocated allowance for loan losses of $9.8 million at December 31, 2016 . Non-accrual non-homogeneous loans (commercial-type impaired loan relationships greater than $1 million ) that are designated as TDRs are individually measured for the amount of impairment, if any, both before and after the TDR designation.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Other Comprehensive Income (Loss)	Note 6 - Other Comprehensive Income (Loss) The following table illustrates activity within the balances in accumulated other comprehensive income (loss) by component, and is shown for the years ended December 31, 2017 , 2016 , and 2015 . Changes in Accumulated Other Comprehensive Income (Loss) by Component (Net of Income Taxes) (in thousands) Net Unrealized Gains (Losses) on Cash Flow Hedges Net Unrealized Gains (Losses) on Investment Securities Available for Sale Post-Retirement Unfunded Health Benefit Total Balance at December 31, 2014 $ (12,824 ) $ (713 ) $ 932 $ (12,605 ) Other comprehensive income (loss) before reclassifications — (15,806 ) 143 (15,663 ) Amounts reclassified from accumulated other comprehensive income (loss) 320 (1,703 ) (168 ) (1,551 ) Net current period other comprehensive income (loss) 320 (17,509 ) (25 ) (17,214 ) Balance at December 31, 2015 $ (12,504 ) $ (18,222 ) $ 907 $ (29,819 ) Other comprehensive income (loss) before reclassifications — (22,405 ) 63 (22,342 ) Amounts reclassified from accumulated other comprehensive income (loss) 287 (3,697 ) (88 ) (3,498 ) Net current period other comprehensive income (loss) 287 (26,102 ) (25 ) (25,840 ) Balance at December 31, 2016 $ (12,217 ) $ (44,324 ) $ 882 $ (55,659 ) Other comprehensive income (loss) before reclassifications — 676 38 714 Amounts reclassified from accumulated other comprehensive income (loss) 80 178 (67 ) 191 Net current period other comprehensive income (loss) 80 854 (29 ) 905 Balance at December 31, 2017 $ (12,137 ) $ (43,470 ) $ 853 $ (54,754 ) In accordance with ASC 740-20-45-11(b), a deferred tax asset valuation allowance associated with unrealized gains and losses not recognized in income is charged directly to other comprehensive income (loss). During the years 2010 and 2011, Synovus recorded a deferred tax asset valuation allowance associated with net unrealized losses not recognized in income directly to other comprehensive income (loss) by applying the portfolio approach for allocation of the valuation allowance. Synovus has consistently applied the portfolio approach which treats derivative instruments and available for sale securities as a single portfolio. As of December 31, 2017, the ending balance in net unrealized gains (losses) on cash flow hedges and net unrealized gains (losses) on investment securities available for sale includes unrealized losses of $12.1 million and $13.3 million , respectively, related to the residual tax effects remaining in OCI due to the previously established deferred tax asset valuation allowance. Under the portfolio approach, these unrealized losses are realized at the time the entire portfolio is sold or disposed. The following table illustrates activity within the reclassifications out of accumulated other comprehensive income (loss), for the years ended December 31, 2017 , 2016 , and 2015 . Reclassifications Out of Accumulated Other Comprehensive Income (Loss) Details About Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified From Accumulated Other Comprehensive Income (Loss) Income Statement Line Item Where This is Presented For the Years Ended December 31, (in thousands) 2017 2016 2015 Net unrealized gains (losses) on cash flow hedges: Amortization of deferred losses $ (130 ) $ (270 ) $ (448 ) Interest expense Amortization of deferred losses — (197 ) (73 ) Loss on early extinguishment of debt, net 50 180 201 Income tax (expense) benefit $ (80 ) $ (287 ) $ (320 ) Reclassifications, net of income taxes Net unrealized gains (losses) on investment securities available for sale: Realized (losses) gains, net, on sales of securities (1) $ (289 ) $ 6,011 $ 2,769 Investment securities gains, net 111 (2,314 ) (1,066 ) Income tax (expense) benefit $ (178 ) $ 3,697 $ 1,703 Reclassifications, net of income taxes Post-retirement unfunded health benefit: Amortization of actuarial gains $ 110 $ 144 $ 272 Salaries and other personnel expense (43 ) (56 ) (104 ) Income tax (expense) benefit $ 67 $ 88 $ 168 Reclassifications, net of income taxes (1) Includes $1.4 million in gains in 2016 from the transfer of $1.9 million of investment securities available for sale to trading account assets.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Premises and Equipment	Note 7 - Premises and Equipment Premises and equipment at December 31, 2017 and 2016 consist of the following: (in thousands) Useful Life (in years) 2017 2016 Land Indefinite $ 96,759 $ 97,080 Buildings and improvements 10 - 40 388,254 377,754 Leasehold improvements 10 - 40 38,970 41,355 Furniture and equipment 3 - 10 413,876 370,458 Construction in progress 15,956 29,104 Total premises and equipment 953,815 915,751 Less: Accumulated depreciation and amortization (527,002 ) (498,266 ) Premises and equipment, net $ 426,813 $ 417,485 Net premises and equipment included $1.5 million and $1.6 million related to net capital leases at December 31, 2017 and 2016, respectively. Aggregate rent expense (principally for offices) net of sublease income, totaled $22.0 million , $21.4 million , and $23.1 million for the years ended December 31, 2017, 2016, and 2015, respectively. Depreciation and amortization expense for the years ended December 31, 2017, 2016, and 2015 totaled $42.2 million , $37.1 million , and $35.3 million , respectively. During the years ended December 31, 2017 and 2016, Synovus transferred premises and equipment with a net book value of $3.3 million and $25.2 million , respectively, to other properties held for sale, a component of other assets. Lease Commitments Synovus and its subsidiaries have entered into long-term operating leases for various facilities and equipment. Management expects that as these leases expire they will be renewed or replaced by similar leases based on need. At December 31, 2017 , minimum rental commitments under all such non-cancelable leases for the next five years and thereafter are presented below. (in thousands) 2018 $ 28,187 2019 27,722 2020 26,483 2021 23,876 2022 23,332 Thereafter 98,797 Total $ 228,397

Goodwill And Other Intangible A

Goodwill And Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Note 8 - Goodwill and Other Intangible Assets At December 31, 2017 and 2016 , the net carrying value of goodwill was $57.3 million and $59.7 million , respectively, consisting of goodwill associated with two reporting units. At December 31, 2017, $24.4 million of the goodwill was attributable to the trust services reporting unit, and the remaining $32.9 million was attributable to the Synovus Bank reporting unit and is a result of the Global One business combination completed during 2016. In connection with the Global One acquisition, Synovus also acquired other intangible assets with an aggregate estimated fair value of $12.5 million consisting of existing borrower relationships, trade name, and distribution network. The weighted average amortization period for Global One acquired intangibles was 10.8 years. Aggregate other intangible assets amortization expense for the years ended December 31, 2017, 2016, 2015 was $1.1 million , $521 thousand , and $503 thousand, respectively. Estimated amortization expense over each of the next five years is $1.2 million . At June 30, 2017, Synovus completed its annual goodwill impairment evaluation applying ASC 350-20-35-3A Goodwill Subsequent Measurement - Qualitative Assessment Approach and concluded that goodwill was not impaired. The following table shows the changes in the carrying amount of goodwill for the year ended December 31, 2017 : (in thousands) Trust Services Reporting Unit Synovus Bank Reporting Unit Total Balance as of December 31, 2016 Goodwill $ 24,431 $ 35,247 $ 59,678 Accumulated impairment losses — — — Measurement period adjustments — (2,363 ) (2,363 ) Goodwill, net, as of December 31, 2017 $ 24,431 $ 32,884 $ 57,315 The following table shows the carrying amount of other intangibles as of December 31, 2017 and 2016 : (in thousands) 2017 2016 Other intangibles $ 13,140 $ 14,040 Accumulated amortization (1,886 ) (817 ) Other intangibles, net $ 11,254 $ 13,223

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2017
Other Assets [Abstract]
Other Assets	Note 9 - Other Assets Significant balances included in other assets at December 31, 2017 and 2016 are presented below. (in thousands) 2017 2016 Cash surrender value of bank-owned life insurance $ 540,958 $ 378,830 Federal Reserve Bank and FHLB stock 159,443 169,864 Accrued interest receivable 80,036 70,393 Investments in low income housing tax credit partnerships 60,068 26,495 Taxes receivable (1) 46,330 2,611 Accounts receivable 43,878 29,821 Prepaid expenses 33,298 35,542 Private equity investments 15,771 25,493 Derivative asset positions 11,722 20,623 Other properties held for sale 7,825 14,830 SBA/GGL servicing assets, net 4,101 4,451 Miscellaneous other assets 32,081 34,267 Total other assets $ 1,035,511 $ 813,220 (1) Effective December 31, 2017, alternative minimum tax credits of $42.1 million were reclassified from deferred tax assets to taxes receivable. Synovus’ investment in bank-owned life insurance programs at both December 31, 2017 and December 31, 2016 included approximately $15 million of separate account life insurance policies covered by stable value agreements. At December 31, 2017 , the fair value of the investments underlying the separate account policies was approximately $14 million , which was within the coverage provided by the stable value agreements.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Interest-bearing Deposit Liabilities [Abstract]
Deposits	Note 10 - Deposits A summary of interest bearing deposits at December 31, 2017 and 2016 is presented below. ( in thousands) 2017 2016 Interest bearing demand deposits $ 5,157,175 $ 4,768,313 Money market accounts, excluding brokered deposits 7,435,941 7,251,093 Savings accounts 798,935 929,402 Time deposits, excluding brokered deposits 3,108,385 3,234,465 Brokered deposits 1,961,125 1,378,983 Total interest bearing deposits $ 18,461,561 $ 17,562,256 The aggregate amount of time deposits of $250,000 or more was $921.8 million at December 31, 2017 and $829.5 million at December 31, 2016 . The following table presents contractual maturities of all time deposits at December 31, 2017 . (in thousands) Maturing within one year $ 2,544,033 Between 1 — 2 years 851,665 2 — 3 years 567,279 3 — 4 years 248,473 4 — 5 years 65,521 Thereafter 242,909 $ 4,519,880

Long-term Debt and Short-term B

Long-term Debt and Short-term Borrowings	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-term Debt and Short-term Borrowings	Note 11 - Long-term Debt and Short-term Borrowings Long-term debt at December 31, 2017 and 2016 is presented in the following table. (in thousands) 2017 2016 Parent Company: 3.125% senior notes, due November 1, 2022, $300 million par value at December 31, 2017 with semi-annual interest payments and principal to be paid at maturity $ 296,971 $ — 5.75% fixed to adjustable rate subordinated notes issued December 7, 2015, due December 15, 2025, $250 million par value with semi-annual interest payments at 5.75% for the first five years and quarterly payments thereafter at an adjustable rate equal to the then-current three month LIBOR rate + 418.2 basis points and principal to be paid at maturity 247,618 247,136 LIBOR + 1.80% debentures, due April 19, 2035, $10 million par value with quarterly interest payments and principal to be paid at maturity (rate of 3.39% at December 31, 2017 and 2.76% at December 31, 2016) 10,000 10,000 5.125% subordinated notes, matured June 15, 2017, $278.6 million par value at December 31, 2016 — 278,480 7.875% senior notes, due February 15, 2019, $300 million par value — 297,763 Hedge-related basis adjustment (1) — 873 Total long-term debt — Parent Company 554,589 834,252 Synovus Bank: FHLB advances with interest and principal payments due at various maturity dates through 2022 and interest rates ranging from 1.42% to 1.43% at December 31, 2017 (weighted average interest rate of 1.43% and 0.64% at December 31, 2017 and 2016, respectively) 1,150,000 1,325,000 Capital lease with interest and principal payments due at various dates through 2031 (rate of 1.59% at both December 31, 2017 and 2016) 1,549 1,629 Total long-term debt — Synovus Bank 1,151,549 1,326,629 Total long-term debt $ 1,706,138 $ 2,160,881 (1) Unamortized balance of terminated interest rate swaps reflected in debt for financial reporting purposes. On November 1, 2017, Synovus issued $300.0 million aggregate principal amount of 3.125% senior notes maturing in 2022 in a public offering with aggregate proceeds of $296.9 million , net of discount and debt issuance costs. On November 9, 2017, Synovus redeemed all of the $300.0 million aggregate principal amount of its 7.875% senior notes due 2019 at a "make whole" premium. 2017 results include a loss of $23.2 million related to early extinguishment of these notes. During 2017, Synovus paid off the remaining balance of $278.6 million of its subordinated notes at their maturity date of June 15, 2017. During 2016 and 2015, Synovus repurchased $124.7 million and $46.7 million , respectively, of its subordinated notes maturing in 2017. Results for the years ended December 31, 2016 and 2015 included losses of $4.7 million and $1.5 million , respectively, relating to repurchases of these notes. The provisions of the indentures governing Synovus’ long-term debt contain certain restrictions within specified limits on mergers, sales of all or substantially all of Synovus' assets and limitations on sales and issuances of voting stock of subsidiaries and Synovus’ ability to pay dividends on its capital stock if there is an event of default under the applicable indenture. As of December 31, 2017 and 2016 , Synovus and its subsidiaries were in compliance with the covenants in these agreements. The FHLB advances are secured by certain loans receivable with a recorded balance of $3.40 billion at December 31, 2017 and $3.25 billion at December 31, 2016 . Contractual annual principal payments on long-term debt for the next five years and thereafter are shown on the following table. (in thousands) Parent Company Synovus Bank Total 2018 $ — $ 100,089 $ 100,089 2019 — 90 90 2020 — 350,092 350,092 2021 — 450,096 450,096 2022 300,000 250,107 550,107 Thereafter 260,000 1,075 261,075 Total $ 560,000 $ 1,151,549 $ 1,711,549 The following table sets forth certain information regarding federal funds purchased and other securities sold under repurchase agreements. (dollars in thousands) 2017 2016 2015 Total balance at December 31, $ 161,190 $ 159,699 $ 177,025 Weighted average interest rate at December 31, 0.18 % 0.08 % 0.08 % Maximum month end balance during the year $ 225,475 $ 286,175 $ 250,453 Average amount outstanding during the year 184,093 216,593 205,305 Weighted average interest rate during the year 0.11 % 0.09 % 0.08 %

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Note 12 - Shareholders' Equity The following table shows the changes in shares of preferred and common stock issued and common stock held as treasury shares for the three years ended December 31, 2017 . (shares in thousands) Series C Preferred Stock Issued Common Stock Issued Treasury Stock Held Common Stock Outstanding Balance at December 31, 2014 5,200 139,950 3,827 136,123 Restricted share unit activity — 304 — 304 Stock options exercised — 338 — 338 Repurchase of common stock — — 7,218 (7,218 ) Balance at December 31, 2015 5,200 140,592 11,045 129,547 Issuance of common stock for acquisition — 821 — 821 Restricted share unit activity — 316 — 316 Stock options exercised — 297 — 297 Repurchase of common stock — — 8,715 (8,715 ) Balance at December 31, 2016 5,200 142,026 19,760 122,266 Issuance of common stock for earnout payment — 118 — 118 Restricted share unit activity — 336 — 336 Stock options exercised — 198 — 198 Repurchase of common stock — — 4,021 (4,021 ) Balance at December 31, 2017 5,200 142,678 23,781 118,897 Issuance of Common Stock for Acquisition and Earnout Payment On October 1, 2016, Synovus completed its acquisition of Global One. Under the terms of the merger agreement, Synovus acquired Global One for an up-front payment of $30 million , consisting of the issuance of 821 thousand shares of Synovus common stock valued at $26.6 million and $3.4 million in cash, with additional annual payments to the former shareholders of Global One for three to five years based on a percentage of Global One's earnings as defined in the merger agreement. The first annual Earnout Payment was made during November 2017, consisting of the issuance of 118 thousand shares of Synovus common stock valued at $5.5 million and $892 thousand in cash. Please refer to Note 2 - "Acquisitions" of this Report for more information on the acquisition of Global One. Repurchases of Common Stock During 2017, Synovus repurchased $175.1 million , or 4.0 million shares, of common stock through open market transactions under the $200 million share repurchase program authorized during the fourth quarter of 2016 for execution during 2017. During 2016, Synovus completed its $300 million share repurchase program with repurchases of $262.9 million , or 8.7 million shares, of common stock. This program was authorized during the third quarter of 2015 and was executed over a 15 month period through a combination of open market transactions and an ASR. Share repurchases of common stock during 2016 executed through open market transactions totaled $212.9 million , or 7.3 million shares, and $50.0 million , or 1.4 million shares, were executed through an ASR. During the fourth quarter of 2015, Synovus repurchased $37.1 million , or 1.2 million shares, under the $300 million share repurchase program through open market transactions. During 2015, Synovus completed its $250 million share repurchase program. This program was announced on October 21, 2014 and expired on October 23, 2015. Under this program, Synovus repurchased 9.1 million shares of common stock through a combination of open market transactions and an ASR. From October 2014 through September 30, 2015, Synovus repurchased $175.0 million , or 6.2 million shares, of common stock through open market transactions, including $161.9 million , or 5.7 million shares, of common stock repurchased during 2015. Synovus also entered into a $75.0 million ASR in October 2014. During 2014, Synovus repurchased 2.5 million shares of common stock under this ASR, and during January 2015, Synovus repurchased 392 thousand shares upon completion of this ASR. Series C Preferred Stock In July 2013, Synovus issued 5.2 million shares of Fixed-to Floating Rate Non-Cumulative Perpetual Preferred Stock, Series C, $25.00 per share liquidation preference. Dividends on the shares are non-cumulative and, if declared, will accrue and be payable, in arrears, quarterly at a rate per annum equal to 7.875% for each dividend period from the original issue date to, but excluding August 1, 2018. From and including August 1, 2018, the dividend rate will change to a floating rate equal to the three-month LIBOR plus a spread of 6.39% per annum. The Series C Preferred Stock is perpetual and does not have any maturity date. The Series C Preferred Stock is redeemable at Synovus' option at a redemption price equal to $25.00 per share, plus any declared and unpaid dividends, without accumulation of any undeclared dividends. The Series C Preferred Stock has no preemptive or conversion rights. Except in certain limited circumstances, the Series C Preferred Stock does not have any voting rights. Warrant At December 31, 2017, 2016, and 2015, Synovus had warrants outstanding issued to Treasury to purchase up to 2.2 million shares of Synovus common stock at a per share exercise price of $65.52 expiring on December 19, 2018. The warrants were issued by Synovus to Treasury in 2008 in connection with the Capital Purchase Program, promulgated under the Emergency Economic Stabilization Act of 2008.

Regulatory Capital

Regulatory Capital	12 Months Ended
	Dec. 31, 2017
Regulatory Capital Disclosure [Abstract]
Regulatory Capital	Note 13 - Regulatory Capital Synovus is subject to regulatory capital requirements administered by the federal and state banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory, and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the consolidated financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, Synovus must meet specific capital levels that involve quantitative measures of both on- and off-balance sheet items as calculated under regulatory capital guidelines. Capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. The Basel III capital rules became effective January 1, 2015, for Synovus and Synovus Bank, subject to a transition period for several aspects, including the capital conservation buffer and certain regulatory capital adjustments and deductions, as described below. Under the Basel III capital rules, the minimum capital requirements for Synovus and Synovus Bank include a common equity Tier 1 (CET1) ratio of 4.5% ; Tier 1 capital ratio of 6% ; total capital ratio of 8% ; and leverage ratio of 4% . When fully phased-in on January 1, 2019, the Basel III capital rules include a capital conservation buffer of 2.5% that is added on top of each of the minimum risk-based capital ratios. The implementation of the capital conservation buffer began on January 1, 2016 at the 0.625% level and will be phased-in over a three -year period (increasing by that amount on each subsequent January 1, until it reaches 2.5% on January 1, 2019). As a financial holding company, Synovus and its subsidiary bank, Synovus Bank, are required to maintain capital levels required for a well-capitalized institution as defined by federal banking regulations. Under the Basel III capital rules, Synovus and Synovus Bank are well-capitalized if each has a CET1 ratio of 6.5% or greater, a Tier 1 risk-based capital ratio of 8% or greater, a total risk-based capital ratio of 10% or greater, a leverage ratio of 5% or greater, and are not subject to any written agreement, order, capital directive, or prompt corrective action directive from a federal and/or state banking regulatory agency to meet and maintain a specific capital level for any capital measure. Management currently believes, based on internal capital analysis and earnings projections, that Synovus' capital position is adequate to meet current and future regulatory minimum capital requirements. The following table summarizes regulatory capital information at December 31, 2017 and 2016 on a consolidated basis and for Synovus’ significant subsidiary, defined as any direct subsidiary with assets or net income levels exceeding 10% of the consolidated totals. Actual For Capital Adequacy Purposes To Be Well Capitalized Under Prompt Corrective Action Provisions (1) (dollars in thousands) 2017 2016 2017 2016 2017 2016 Synovus Financial Corp. Common equity tier 1 capital $ 2,763,168 $ 2,654,287 $ 1,250,488 $ 1,199,794 N/A N/A Tier 1 capital 2,872,001 2,685,880 1,660,074 1,599,725 N/A N/A Total risk-based capital 3,383,081 3,201,268 2,213,432 2,132,966 N/A N/A Common equity tier 1 capital ratio 9.99 % 9.96 % 4.50 % 4.50 % N/A N/A Tier 1 capital ratio 10.38 10.07 6.00 6.00 N/A N/A Total risk-based capital ratio 12.23 12.01 8.00 8.00 N/A N/A Leverage ratio 9.19 8.99 4.00 4.00 N/A N/A Synovus Bank Common equity tier 1 capital $ 3,155,163 $ 3,187,583 $ 1,247,462 $ 1,197,976 $ 1,795,004 $ 1,730,410 Tier 1 capital 3,155,163 3,187,583 1,656,927 1,597,302 2,209,236 2,129,736 Total risk-based capital 3,406,243 3,441,563 2,209,236 2,129,736 2,761,545 2,662,169 Common equity tier 1 capital ratio 11.43 % 11.97 % 4.50 % 4.50 % 6.50 % 6.50 % Tier 1 capital ratio 11.43 11.97 6.00 6.00 8.00 8.00 Total risk-based capital ratio 12.33 12.93 8.00 8.00 10.00 10.00 Leverage ratio 10.12 10.68 4.00 4.00 5.00 5.00 (1) The prompt corrective action provisions are applicable at the bank level only.

Net Income Per Common Share

Net Income Per Common Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Per Common Share	Note 14 - Net Income Per Common Share The following table displays a reconciliation of the information used in calculating basic and diluted net income per common share for the years ended December 31, 2017 , 2016 , and 2015 . Years Ended December 31, (in thousands, except per share data) 2017 2016 2015 Net income $ 275,474 $ 246,784 $ 226,082 Dividends on preferred stock 10,238 10,238 10,238 Net income available to common shareholders $ 265,236 $ 236,546 $ 215,844 Weighted average common shares outstanding 121,162 124,389 132,423 Potentially dilutive shares from outstanding equity-based awards and Earnout Payments 850 689 778 Weighted average diluted common shares 122,012 125,078 133,201 Net income per common share, basic $ 2.19 $ 1.90 $ 1.63 Net income per common share, diluted $ 2.17 $ 1.89 $ 1.62 For the years ended December 31, 2017 , 2016 , and 2015 , there were 2.2 million , 2.2 million , and 2.8 million potentially dilutive shares, respectively, related to Warrants and stock options to purchase shares of common stock that were outstanding during 2017 , 2016 , and 2015 , respectively, but were not included in the computation of diluted net income per common share because the effect would have been anti-dilutive.

Fair Value Accounting

Fair Value Accounting	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Accounting	Note 15 - Fair Value Accounting Synovus carries various assets and liabilities at fair value based on the fair value accounting guidance under ASC 820, Fair Value Measurements, and ASC 825, Financial Instruments . Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an “exit price”) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Synovus has implemented controls and processes for the determination of the fair value of financial instruments. The ultimate responsibility for the determination of fair value rests with Synovus. Synovus has established a process that has been designed to ensure there is an independent review and validation of fair values by a function independent of those entering into the transaction. This includes specific controls to ensure consistent pricing policies and procedures that incorporate verification for both market and derivative transactions. For all financial instruments where fair values are determined by reference to externally quoted prices or observable pricing inputs to models, independent price determination or validation is utilized. Where the market for a financial instrument is not active, fair value is determined using a valuation technique or pricing model. These valuation techniques and models involve a degree of estimation, the extent of which depends on each instrument's complexity and the availability of market-based data. The most frequently applied pricing model and valuation technique utilized by Synovus is the discounted cash flow model. Discounted cash flows determine the value by estimating the expected future cash flows from assets or liabilities discounted to their present value. Synovus may also use a relative value model to determine the fair value of a financial instrument based on the market prices of similar assets or liabilities or an option pricing model such as binomial pricing that includes probability-based techniques. Assumptions and inputs used in valuation techniques and models include benchmark interest rates, credit spreads and other inputs used in estimating discount rates, bond and equity prices, price volatilities and correlations, prepayment rates, probability of default, and loss severity upon default. Synovus refines and modifies its valuation techniques as markets develop and as pricing for individual financial instruments become more or less readily available. While Synovus believes its valuation techniques are appropriate and consistent with other market participants, the use of different methodologies or assumptions could result in different estimates of fair value at the balance sheet date. In order to determine the fair value, where appropriate, management applies valuation adjustments to the pricing information. These adjustments reflect management's assessment of factors that market participants would consider in setting a price, to the extent that these factors have not already been included in the pricing information. Furthermore, on an ongoing basis, management assesses the appropriateness of any model used. To the extent that the price provided by internal models does not represent the fair value of the financial instrument, management makes adjustments to the model valuation to calibrate it to other available pricing sources. Where unobservable inputs are used, management may determine a range of possible valuations based upon differing stress scenarios to determine the sensitivity associated with the valuation. As a final step, management considers the need for further adjustments to the modeled price to reflect how market participants would price the financial instrument. Fair Value Hierarchy Synovus determines the fair value of its financial instruments based on the fair value hierarchy established under ASC 820-10, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the financial instrument's fair value measurement in its entirety. There are three levels of inputs that may be used to measure fair value. The three levels of inputs of the valuation hierarchy are defined below: Level 1 Quoted prices (unadjusted) in active markets for identical assets and liabilities for the instrument or security to be valued. Level 1 assets include marketable equity securities, Treasury securities, and mutual funds. Level 2 Observable inputs other than Level 1 quoted prices, such as quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active or model-based valuation techniques for which all significant assumptions are derived principally from or corroborated by observable market data. Level 2 assets and liabilities include debt securities with quoted prices that are traded less frequently than exchange-traded instruments and derivative contracts whose value is determined by using a pricing model with inputs that are observable in the market or can be derived principally from or corroborated by observable market data. U.S. Government sponsored agency securities, mortgage-backed securities issued by GSEs and agencies, obligations of states and municipalities, collateralized mortgage obligations issued by GSEs, and mortgage loans held for sale are generally included in this category. Level 3 Unobservable inputs that are supported by little, if any, market activity for the asset or liability. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow models and similar techniques, and may also include the use of market prices of assets or liabilities that are not directly comparable to the subject asset or liability. These methods of valuation may result in a significant portion of the fair value being derived from unobservable assumptions that reflect Synovus' own estimates for assumptions that market participants would use in pricing the asset or liability. This category primarily includes collateral-dependent impaired loans, other loans held for sale, other real estate, certain corporate securities, private equity investments, GGL/SBA loan servicing assets, and the earnout liability. Fair Value Option Synovus has elected the fair value option for mortgage loans held for sale primarily to ease the operational burdens required to maintain hedge accounting for these loans. Synovus is still able to achieve effective economic hedges on mortgage loans held for sale without the time and expense needed to manage a hedge accounting program. Valuation Methodology by Product Following is a description of the valuation methodologies used for the major categories of financial assets and liabilities measured at fair value. Trading Account Assets/Liabilities and Investment Securities Available for Sale The fair values of trading securities and investment securities available for sale are primarily based on actively traded markets where prices are based on either quoted market prices or observed transactions. Management employs independent third-party pricing services to provide fair value estimates for Synovus' investment securities available for sale and trading securities. Fair values for fixed income investment securities are typically determined based upon quoted market prices, and/or inputs that are observable in the market, either directly or indirectly, for substantially similar securities. Level 1 securities are typically exchange quoted prices and include financial instruments such as U.S. Treasury securities, marketable equity securities, and mutual fund investments. Level 2 securities are typically matrix priced by the third-party pricing service to calculate the fair value. Such fair value measurements consider observable data such as market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayments speeds, credit information, and the respective terms and conditions for debt instruments. The types of securities classified as Level 2 within the valuation hierarchy primarily consist of collateralized mortgage obligations, mortgage-backed securities, debt securities of GSEs and agencies, corporate debt, and state and municipal securities. When there is limited activity or less transparency around inputs to valuation, Synovus develops valuations based on assumptions that are not readily observable in the marketplace; these securities are classified as Level 3 within the valuation hierarchy. The majority of the balance of Level 3 investment securities available for sale consists primarily of trust preferred securities issued by financial institutions. To determine the fair value of the trust preferred securities, management uses a measurement technique to reflect one that utilizes credit spreads and/or credit indices available from a third-party pricing service. In addition, for each trust preferred security, management projects non-credit adjusted cash flows, and discounts those cash flows to net present value incorporating a relevant credit spread in the discount rate. Other inputs to calculating fair value include potential discounts for lack of marketability. Management uses various validation procedures to confirm the prices received from pricing services are reasonable. Such validation procedures include reference to market quotes and a review of valuations and trade activity of comparable securities. Consideration is given to the nature of the quotes (e.g., indicative or firm) and the relationship of recently evidenced market activity to the prices provided by the third-party pricing service. Further, management also employs the services of an additional independent pricing firm as a means to verify and confirm the fair values of the primary independent pricing firms. Mortgage Loans Held for Sale Synovus elected to apply the fair value option for mortgage loans originated with the intent to sell to investors. When loans are not committed to an investor at a set price, fair value is derived from a hypothetical bulk sale model used to estimate the exit price of the loans in a loan sale. The bid pricing convention is used for loan pricing for similar assets. The valuation model is based upon forward settlements of a pool of loans of similar coupon, maturity, product, and credit attributes. The inputs to the model are continuously updated with available market and historical data. As the loans are sold in the secondary market and primarily used as collateral for securitizations, the valuation model represents the highest and best use of the loans in Synovus’ principal market. Mortgage loans held for sale are classified within Level 2 of the valuation hierarchy. Private Equity Investments Private equity investments consist primarily of equity method investments in venture capital funds, which are classified as Level 3 within the valuation hierarchy. The valuation of these investments requires significant judgment due to the absence of quoted market prices, inherent lack of liquidity, and the long-term nature of such investments. Based on these factors, the ultimate realizable value of these investments could differ significantly from the value reflected in the accompanying audited consolidated financial statements. The valuation of marketable securities that have trading restrictions is discounted until the securities can be freely traded. The private equity investments in which Synovus holds a limited partnership interest consist of funds that invest in privately held companies. For privately held companies in the funds, the general partner estimates the fair value of the company in accordance with GAAP, as clarified by ASC 820, and guidance specific to investment companies. The estimated fair value of the company is the estimated fair value as an exit price the fund would receive if it were to sell the company in the marketplace. The fair value of the fund's underlying investments is estimated through the use of valuation models such as option pricing or a discounted cash flow model. Valuation factors, such as a company's operational performance against budget or milestones, last price paid by investors, with consideration given on whether financing is provided by insiders or unrelated new investors, public market comparables, liquidity of the market, industry and economic trends, and changes in management or key personnel, are used in the determination of fair value. Mutual Funds Held in Rabbi Trusts Mutual funds held in rabbi trusts primarily invest in equity and fixed income securities. Shares of mutual funds are valued based on quoted market prices, and are therefore classified within Level 1 of the fair value hierarchy. GGL/SBA Loans Servicing Asset Synovus has retained servicing responsibilities on sold GGL/SBA loans and receives a servicing fee. The servicing asset is established at fair value at the time of the sale based on an analysis of future cash flows that incorporates estimates for discount rates, prepayment speeds, and delinquency rates. The servicing asset is measured at fair value on a quarterly basis with changes in fair value included with the associated servicing fee in other non-interest income. Prior to 2017, Synovus accounted for the GGL/SBA loans servicing asset using the amortization method. The GGL/SBA loan servicing asset is classified as Level 3. Earnout Liability The earnout liability is a contingent consideration obligation related to the Global One acquisition and is measured at fair value on a recurring basis. The earnout liability will be adjusted to fair value until settled. Since the assumptions used to measure fair value are based on internal metrics that are not market observable, the earnout liability is classified as Level 3. Derivative Assets and Liabilities As part of its overall interest rate risk management activities, Synovus utilizes derivative instruments to manage its exposure to various types of interest rate risk. With the exception of one derivative contract discussed herein, Synovus' derivative financial instruments are all Level 2 financial instruments. The majority of derivatives entered into by Synovus are executed over-the-counter and consist of interest rate swaps. The fair values of these derivative instruments are determined based on an internally developed model that uses readily observable market data, as quoted market prices are not available for these instruments. The valuation models and inputs depend on the type of derivative and the nature of the underlying instrument, and include interest rates, prices and indices to generate continuous yield or pricing curves, volatility factors, and customer credit related adjustments. The principal techniques used to model the value of these instruments are an income approach, discounted cash flows, and Black-Scholes or binomial pricing models. The sale of TBA mortgage-backed securities for current month delivery or in the future and the purchase of option contracts of similar duration are derivatives utilized by Synovus, and are valued by obtaining prices directly from dealers in the form of quotes for identical securities or options using a bid pricing convention with a spread between bid and offer quotations. Interest rate swaps, floors, caps and collars, and TBA mortgage-backed securities are classified as Level 2 within the valuation hierarchy. Synovus enters into interest rate lock commitments related to expected funding of residential mortgage loans at specified times in the future. Interest rate lock commitments that relate to the origination of mortgage loans that will be held-for-sale are considered derivative instruments under applicable accounting guidance. As such, Synovus records its interest rate lock commitments and forward loan sales commitments at fair value, determined as the amount that would be required to settle each of these derivative financial instruments at the balance sheet date. In the normal course of business, Synovus enters into contractual interest rate lock commitments to extend credit at a fixed interest rate and with fixed expiration dates. The commitments become effective when the borrowers "lock-in" a specified interest rate within the established time frames. Market risk arises if interest rates move adversely between the time of the interest rate lock by the borrower and the sale date of the loan to an investor. To mitigate the effect of the interest rate risk inherent in providing interest rate lock commitments to borrowers, Synovus enters into best efforts forward sales contracts with third-party investors. The forward sales contracts lock in a price for the sale of loans similar to those with the specific interest rate lock commitments. Both the interest rate lock commitments to the borrowers and the forward sales contracts to the investors are derivatives, and accordingly, are marked to fair value through earnings. In estimating the fair value of an interest rate lock commitment, Synovus assigns a probability to the interest rate lock commitment based on an expectation that it will be exercised and the loan will be funded. The fair value of the interest rate lock commitment is derived from the fair value of related mortgage loans, which is based on observable market data and includes the expected net future cash flows related to servicing of the loans. The fair value of the interest rate lock commitment is also derived from inputs that include guarantee fees negotiated with the agencies and private investors, buy-up and buy-down values provided by the agencies and private investors, and interest rate spreads for the difference between retail and wholesale mortgage rates. Management also applies fall-out ratio assumptions to the interest rate lock commitments in anticipation of certain mortgage loans which will not close. The fall-out ratio assumptions are based on Synovus' historical experience, conversion ratios for similar loan commitments, and market conditions. While fall-out tendencies are not exact predictions of which loans will or will not close, historical performance review of loan-level data provides the basis for determining the appropriate hedge ratios. In addition, on a periodic basis, Synovus performs analyses of actual rate lock fall-out experience to determine the sensitivity of the mortgage pipeline to interest rate changes from the date of the commitment through loan origination. The expected fall-out ratios (or conversely the "pull-through" percentages) are applied to the determined fair value of the mortgage pipeline. Changes to the fair value of interest rate lock commitments are recognized based on interest rate changes, changes in the probability that the commitment will be exercised, and the passage of time. The fair value of the forward sales contracts to investors considers the market price movement of the same type of security between the trade date and the balance sheet date. These instruments are classified as Level 2 within the valuation hierarchy. In November 2009, Synovus sold certain Visa Class B shares to another Visa USA member financial institution. The sales price was based on the Visa stock conversion ratio in effect at the time for conversion of Visa Class B shares to Visa Class A unrestricted shares at a future date. In conjunction with the sale, Synovus entered into a derivative contract with the purchaser (the Visa derivative), which provides for settlements between the parties based upon a change in the ratio for conversion of Visa Class B shares to Visa Class A shares. The fair value of the Visa derivative is determined based on management's estimate of the timing and amount of the Covered Litigation settlement and the resulting payments due to the counterparty under the terms of the contract. Since this estimation process requires application of judgment in developing significant unobservable inputs used to determine the fair value of the Visa derivative, this derivative has been classified as Level 3 within the valuation hierarchy. See "Part II - Item 8. Financial Statements and Supplementary Data - Note 18 - Visa Shares and Related Agreements" of this Report for additional discussion on the Visa derivative and related litigation. Assets and Liabilities Measured at Fair Value on a Recurring Basis The following table presents all financial instruments measured at fair value on a recurring basis as of December 31, 2017 and 2016 , according to the valuation hierarchy included in ASC 820-10. For equity and debt securities, class was determined based on the nature and risks of the investments. Synovus did not have any transfers between levels for the years ended December 31, 2017 and 2016 . December 31, 2017 (in thousands) Level 1 Level 2 Level 3 Total Assets and Liabilities at Fair Value Assets Trading securities: U.S. Government agency securities $ — $ 3,002 $ — $ 3,002 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — 296 — 296 Other investments 522 — — 522 Total trading securities 522 3,298 — 3,820 Mortgage loans held for sale — 48,024 — 48,024 Investment securities available for sale: U.S. Treasury securities 82,674 — — 82,674 U.S. Government agency securities — 10,862 — 10,862 Mortgage-backed securities issued by U.S. Government agencies — 120,440 — 120,440 Mortgage-backed securities issued by U.S. Government sponsored enterprises — 2,640,523 — 2,640,523 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — 1,111,999 — 1,111,999 State and municipal securities — 180 — 180 Corporate debt and other securities (1) 3,162 15,294 1,935 20,391 Total investment securities available for sale 85,836 3,899,298 1,935 3,987,069 Private equity investments — — 15,771 15,771 Mutual funds held in rabbi trusts 14,140 — — 14,140 GGL/SBA loans servicing asset — — 4,101 4,101 Derivative assets: Interest rate contracts — 10,786 — 10,786 Mortgage derivatives (2) — 936 — 936 Total derivative assets — 11,722 — 11,722 Liabilities Trading account liabilities — 1,000 — 1,000 Earnout liability (3) — — 11,348 11,348 Derivative liabilities: Interest rate contracts — 12,638 — 12,638 Mortgage derivatives (2) — 129 — 129 Visa derivative — — 4,330 4,330 Total derivative liabilities — 12,767 4,330 17,097 December 31, 2016 (in thousands) Level 1 Level 2 Level 3 Total Assets and Liabilities at Fair Value Assets Trading securities: Mortgage-backed securities issued by U.S. Government agencies $ — $ 3,460 $ — $ 3,460 Collateralized mortgage obligations issued by U.S. Government sponsored enterprises — 3,438 — 3,438 State and municipal securities — 426 — 426 Other investments 1,890 100 — 1,990 Total trading securities 1,890 7,424 — 9,314 Mortgage loans held for sale — 51,545 — 51,545 Investment securities available for sale: U.S. Treasury securities 107,802 — — 107,802 U.S. Government agency securities — 12,993 — 12,993 Mortgage-backed securities issued by U.S. Government agencies — 174,202 — 174,202 Mortgage-backed securities issued by U.S. Government sponsored enterprises — 2,506,340 — 2,506,340 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — 890,442 — 890,442 State and municipal securities — 2,794 — 2,794 Equity securities 3,782 — — 3,782 Corporate debt and other securities (1) 3,092 14,952 1,796 19,840 Total investment securities available for sale 114,676 3,601,723 1,796 3,718,195 Private equity investments — — 25,493 25,493 Mutual funds held in rabbi trusts 11,479 — — 11,479 Derivative assets: Interest rate contracts — 17,157 — 17,157 Mortgage derivatives (2) — 3,466 — 3,466 Total derivative assets — 20,623 — 20,623 Liabilities Earnout liability (3) — — 14,000 14,000 Derivative liabilities: Interest rate contracts — 17,531 — 17,531 Visa derivative — — 5,768 5,768 Total derivative liabilities — 17,531 5,768 23,299 (1 ) Based on an analysis of the nature and risks of these investments, Synovus has determined that presenting these investments as a single asset class is appropriate. (2 ) Mortgage derivatives consist of customer interest rate lock commitments that relate to the potential origination of mortgage loans, which would be classified as held for sale and forward loan sales commitments with third-party investors. (3 ) Earnout liability consists of contingent consideration obligation related to Global One acquisition. Fair Value Option The following table summarizes the difference between the fair value and the unpaid principal balance of mortgage loans held for sale at fair value and the changes in fair value of these loans. Mortgage loans held for sale are initially measured at fair value with subsequent changes in fair value recognized in earnings. Changes in fair value were recorded as a component of mortgage banking income in the consolidated statements of income. An immaterial portion of these changes in fair value was attributable to changes in instrument-specific credit risk. Twelve Months Ended December 31, (in thousands) 2017 2016 2015 Changes in fair value included in net income: Mortgage loans held for sale $ 754 $ (667 ) $ (742 ) Mortgage loans held for sale: Fair value 48,024 51,545 59,275 Unpaid principal balance 46,839 51,114 58,177 Fair value less aggregate unpaid principal balance $ 1,185 $ 431 $ 1,098 Changes in Level 3 Fair Value Measurements and Quantitative Information about Level 3 Fair Value Measurements As noted above, Synovus uses significant unobservable inputs (Level 3) in determining the fair value of assets and liabilities classified as Level 3 in the fair value hierarchy. The table below includes a roll-forward of the amounts on the consolidated balance sheet for the year ended December 31, 2017 and 2016 (including the change in fair value), for financial instruments of a material nature that are classified by Synovus within Level 3 of the fair value hierarchy and are measured at fair value on a recurring basis. Transfers between fair value levels are recognized at the end of the reporting period in which the associated changes in inputs occur. During 2017 and 2016, Synovus did not have any transfers between levels in the fair value hierarchy. 2017 (in thousands) Investment Securities Available for Sale Private Equity Investments Visa Derivative Earnout Liability (1) GGL/SBA Loans Servicing Asset (2) Beginning balance, January 1, $ 1,796 $ 25,493 $ (5,768 ) $ (14,000 ) $ — Total (losses) gains realized/unrealized: Included in earnings — (3,093 ) — (5,466 ) (1,681 ) Unrealized gains included in other comprehensive income 139 — — — — Additions — — — — 1,330 Sales — (6,629 ) — — — Settlements — — 1,438 6,352 — Transfer from amortization method to fair value — — — — 4,452 Measurement period adjustments related to Global One acquisition — — — 1,766 — Ending balance, December 31, $ 1,935 $ 15,771 $ (4,330 ) $ (11,348 ) $ 4,101 Total net (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31, $ — $ (3,093 ) $ — $ (5,466 ) $ (1,681 ) 2016 (in thousands) Investment Securities Available for Sale Private Equity Investments Visa Derivative Earnout Liability (1) Beginning balance, January 1, $ 1,745 $ 27,148 $ (1,415 ) $ — Total gains (losses) realized/unrealized: Included in earnings — (1,026 ) (5,795 ) — Unrealized gains included in other comprehensive income 51 — — — Additions — — — (14,000 ) Settlements — (629 ) 1,442 — Ending balance, December 31, $ 1,796 $ 25,493 $ (5,768 ) $ (14,000 ) Total net gains (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31, $ — $ (1,026 ) $ (5,795 ) $ — (1) Earnout liability consists of contingent consideration obligation related to the Global One acquisition. (2) Effective January 1, 2017, Synovus elected the fair value option for determining the value of the GGL/SBA loans servicing asset. Prior to 2017, Synovus accounted for the GGL/SBA loans servicing asset using the amortization method. The table below provides an overview of the valuation techniques and significant unobservable inputs used in those techniques to measure financial instruments that are classified within Level 3 of the valuation hierarchy and are measured at fair value on a recurring basis. The range of sensitivities that management utilized in its fair value calculations is deemed acceptable in the industry with respect to the identified financial instruments. December 31, 2017 December 31, 2016 (dollars in thousands) Valuation Technique Significant Unobservable Input Level 3 Fair Value Range / Weighted Average Level 3 Fair Value Range / Weighted Average Assets measured at fair value on a recurring basis Investment Securities Available for Sale - Other investments: Trust preferred securities Discounted cash flow analysis Credit spread embedded in discount rate $ 1,935 398 bps $1,796 442 bps Private equity investments Individual analysis of each investee company Multiple factors, including but not limited to, current operations, financial condition, cash flows, evaluation of business management and financial plans, and recently executed financing transactions related to the investee companies 15,771 N/A 25,493 N/A Discount for lack of liquidity (1) N/A 15% GGL/SBA loans servicing asset Discounted cash flow analysis Discount rate Prepayment speeds 4,101 13.16% 7.50% N/A N/A Earnout liability Option pricing methods and Monte Carlo simulation Financial projections of Global One 11,348 N/A 14,000 N/A Visa derivative liability Discounted cash flow analysis Estimated timing of resolution of covered litigation, future cumulative deposits to the litigation escrow for settlement of the Covered Litigation, and estimated future monthly fees payable to the derivative counterparty 4,330 1-4 years 5,768 1 - 5 years (1) Represents management's estimate of discount that market participants would require based on the instrument's lack of liquidity. Assets Measured at Fair Value on a Non-recurring Basis Certain assets are recorded at fair value on a non-recurring basis. These non-recurring fair value adjustments typically are a result of the application of lower of cost or fair value accounting or a write-down occurring during the period. For example, if the fair value of an asset in these categories falls below its cost basis, it is considered to be at fair value at the end of the period of the adjustment. The following tables present assets measured at fair value on a non-recurring basis as of the dates indicated for which there was a fair value adjustment during the period. As of December 31, 2017 Fair Value Adjustments for the Year Ended December 31, 2017 (in thousands) Level 1 Level 2 Level 3 Impaired loans* $ — $ — $ 3,603 $ 991 Other loans held for sale — — 10,197 13,004 Other real estate — — 3,363 2,413 Other assets held for sale — — 5,334 2,491 As of December 31, 2016 Fair Value Adjustments for the Year Ended December 31, 2016 Level 1 Level 2 Level 3 Impaired loans* $ — $ — $ 21,742 $ 6,613 Other real estate — — 19,305 1,223 Other assets held for sale — — 12,083 5,715 *Collateral-dependent impaired loans that are written down to fair value during the period. The table below provides an overview of the valuation techniques and significant unobservable inputs used in those techniques to measure financial instruments that are classified within Level 3 of the valuation hierarchy and are measured at fair value on a non-recurring basis. December 31, 2017 December 31, 2016 Valuation Technique Significant Unobservable Input Range (Weighted Average) (1) Range (Weighted Average) (1) Assets measured at fair value on a non-recurring basis Collateral-dependent impaired loans Third-party appraised value of collateral less estimated selling costs Discount to appraised value (2) Estimated selling costs 0%-50% (15%) 0%-10% (7%) 0%-52% (25%) 0%-10% (7%) Other loans held for sale Third-party appraised value of collateral less estimated selling costs Discount to appraised value (2) Estimated selling costs 5%-99% (54%) 0%-10% (2%) N/A Other real estate Third-party appraised value of real estate less estimated selling costs Discount to appraised value (2) Estimated selling costs 0%-85% (35%) 0%-10% (7%) 0%-10% (5%) 0%-10% (7%) Other assets held for sale Third-party appraised value less estimated selling costs or BOV Discoun

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2017
Summary of Derivative Instruments [Abstract]
Derivative Instruments	Note 16 - Derivative Instruments As part of its overall interest rate risk management activities, Synovus utilizes derivative instruments to manage its exposure to various types of interest rate risk. These derivative instruments generally consist of interest rate swaps, interest rate lock commitments made to prospective mortgage loan customers, and commitments to sell fixed-rate mortgage loans. Interest rate lock commitments represent derivative instruments since it is intended that such loans will be sold. Synovus may also utilize interest rate swaps to manage interest rate risks primarily arising from its core banking activities. These interest rate swap transactions generally involve the exchange of fixed and floating interest rate payment obligations without the exchange of underlying principal amounts. Swaps may be designated as either cash flow hedges or fair value hedges, as discussed below. As of December 31, 2017 and 2016 , Synovus had no outstanding interest rate swap contracts utilized to manage interest rate risk related to core banking activities. Synovus is party to master netting arrangements with its dealer counterparties; however, Synovus does not offset assets and liabilities under these arrangements for financial statement presentation purposes. Counterparty Credit Risk and Collateral Entering into derivative contracts potentially exposes Synovus to the risk of counterparties’ failure to fulfill their legal obligations, including, but not limited to, potential amounts due or payable under each derivative contract. Notional principal amounts are often used to express the volume of these transactions, but the amounts potentially subject to credit risk are much smaller. Synovus assesses the credit risk of its dealer counterparties by regularly monitoring publicly available credit rating information, evaluating other market indicators, and periodically reviewing detailed financials. Dealer collateral requirements are determined via risk-based policies and procedures and in accordance with existing agreements. Synovus seeks to minimize dealer credit risk by dealing with highly rated counterparties and by obtaining collateral for exposures above certain predetermined limits. Management closely monitors credit conditions within the customer swap portfolio, which management deems to be of higher risk than dealer counterparties. Collateral is secured at origination and credit related fair value adjustments are recorded against the asset value of the derivative as deemed necessary based upon an analysis, which includes consideration of the current asset value of the swap, customer credit rating, collateral value, and customer standing with regards to its swap contractual obligations and other related matters. Such asset values fluctuate based upon changes in interest rates regardless of changes in notional amounts and changes in customer specific risk. Cash Flow Hedges As of December 31, 2017 and December 31, 2016, there were no cash flow hedges outstanding. The unamortized deferred net loss balance from previously terminated cash flow hedges at December 31, 2016 of $(130) thousand was recognized during 2017. Fair Value Hedges As of December 31, 2017 and December 31, 2016, there were no fair value hedges outstanding. The unamortized deferred gain balance on all previously terminated fair value hedges at December 31, 2016 of $873 thousand was recognized during 2017. Customer Related Derivative Positions Synovus enters into interest rate swap agreements to facilitate the risk management strategies of a small number of commercial banking customers. Synovus mitigates this risk by entering into equal and offsetting interest rate swap agreements with highly rated counterparties. The interest rate swap agreements are free-standing derivatives and are recorded at fair value on Synovus' consolidated balance sheet. Fair value changes are recorded as a component of non-interest income. As of December 31, 2017 , the notional amount of customer related interest rate derivative financial instruments, including both the customer position and the offsetting position, was $1.47 billion , an increase of $141.4 million compared to December 31, 2016 . Visa Derivative In conjunction with the sale of Class B shares of common stock issued by Visa to Synovus as a Visa USA member, Synovus entered into a derivative contract with the purchaser, which provides for settlements between the parties based upon a change in the ratio for conversion of Visa Class B shares to Visa Class A shares. The conversion ratio changes when Visa deposits funds to a litigation escrow established by Visa to pay settlements for certain litigation, for which Visa is indemnified by Visa USA members. The litigation escrow is funded by proceeds from Visa’s conversion of Class B shares. The fair value of the derivative contract was $4.3 million and $5.8 million at December 31, 2017 and 2016 , respectively. The fair value of the derivative contract is determined based on management's estimate of the timing and amount of the Covered Litigation settlement, and the resulting payments due to the counterparty under the terms of the contract. Management believes that the estimate of Synovus' exposure to the Visa indemnification and fees associated with the Visa derivative is adequate based on current information, including Visa's recent announcements and disclosures. However, future developments in the litigation could require potentially significant changes to Synovus' estimate. See "Part II - Item 8. Financial Statements and Supplementary Data - Note 18 - Visa Shares and Related Agreements" of this Report for further information. Mortgage Derivatives Synovus originates first lien residential mortgage loans for sale into the secondary market. Mortgage loans are sold by Synovus for conversion to securities and the servicing of these loans is generally sold to a third-party servicing aggregator, or Synovus sells the mortgage loans as whole loans to investors either individually or in bulk on a servicing released basis. Synovus enters into interest rate lock commitments for residential mortgage loans which commits it to lend funds to a potential borrower at a specific interest rate and within a specified period of time. Interest rate lock commitments that relate to the origination of mortgage loans that, if originated, will be held for sale, are considered derivative financial instruments under applicable accounting guidance. Outstanding interest rate lock commitments expose Synovus to the risk that the price of the mortgage loans underlying the commitments may decline due to increases in mortgage interest rates from inception of the rate lock to the funding of the loan. At December 31, 2017 and 2016 , Synovus had commitments to fund at a locked interest rate, primarily fixed-rate mortgage loans to customers in the amount of $49.3 million and $ 88.2 million , respectively. Fair value adjustments related to these commitments resulted in a loss of ($634) thousand and a gain of $ 182 thousand for the years ended December 31, 2017 and 2016 , respectively, which were recorded as a component of mortgage banking income in the consolidated statements of income. At December 31, 2017 and 2016 , outstanding commitments to sell primarily fixed-rate mortgage loans amounted to $72.5 million and $ 126.5 million , respectively. Such commitments are entered into to reduce the exposure to market risk arising from potential changes in interest rates, which could affect the fair value of mortgage loans held for sale and outstanding rate lock commitments, which guarantee a certain interest rate if the loan is ultimately funded or granted by Synovus as a mortgage loan held for sale. The commitments to sell mortgage loans are at fixed prices and are scheduled to settle at specified dates that generally do not exceed 90 days. Fair value adjustments related to these outstanding commitments to sell mortgage loans resulted in loss of ($2.0) million and a gain of $1.7 million for the years ended December 31, 2017 and 2016, respectively, which were recorded as a component of mortgage banking income in the consolidated statements of income. Collateral Requirements Pursuant to the Dodd-Frank Act, certain derivative transactions have collateral requirements, both at the inception of the trade, and as the value of each derivative position changes. As of December 31, 2017 , collateral totaling $43.8 million of federal funds sold was pledged to the derivative counterparties to comply with collateral requirements. Effective January 3, 2017, the CME amended its rulebook to legally characterize variation margin cash payments for cleared OTC derivatives as settlement rather than as collateral. As a result, in 2017, Synovus began reducing the corresponding derivative asset and liability balances for CME-cleared OTC derivatives to reflect the settlement of those positions via the exchange of variation margin. At December 31, 2017, Synovus had a variation margin of $1.5 million reducing the derivative asset. The impact of derivative instruments on the consolidated balance sheets at December 31, 2017 and 2016 is presented below. Fair Value of Derivative Assets Fair Value of Derivative Liabilities December 31, December 31, (in thousands) Location on Consolidated Balance Sheet 2017 2016 Location on Consolidated Balance Sheet 2017 2016 Derivatives not designated as hedging instruments: Interest rate contracts Other assets $ 10,786 $ 17,157 Other liabilities $ 12,638 $ 17,531 Mortgage derivatives Other assets 936 3,466 Other liabilities 129 — Visa derivative — — Other liabilities 4,330 5,768 Total derivatives not designated as hedging instruments $ 11,722 $ 20,623 $ 17,097 $ 23,299 The pre-tax effect of fair value hedges on the consolidated statements of income for the years ended December 31, 2017 , 2016 and 2015 is presented below. Derivative Gain (Loss) Recognized in Income Years Ended December 31, (in thousands) Location of Gain (Loss) Recognized in Income 2017 2016 2015 Derivatives not designated as hedging instruments Interest rate contracts (1) Other Non- Interest Income $ 20 $ 76 $ 44 Mortgage derivatives (2) Mortgage Banking Income (2,659 ) 1,907 1,099 Total $ (2,639 ) $ 1,983 $ 1,143 (1) Gain (loss) represents net fair value adjustments (including credit related adjustments) for customer swaps and offsetting positions. (2) Gain (loss) represents net fair value adjustments recorded for interest rate lock commitments and commitments to sell mortgage loans to third-party investors. During the years ended December 31, 2017 , 2016 , and 2015 , Synovus reclassified $873 thousand , $1.8 million , and $3.1 million , respectively, from hedge-related basis adjustment, a component of long-term debt, as a reduction to interest expense. Additionally, during 2016 and 2015, Synovus reclassified $1.3 million and $495 thousand , respectively, from hedge-related basis adjustment as a reduction to loss on early extinguishment of debt, net. As of December 31, 2017, all deferred gains related to hedging relationships that had been previously terminated had been recognized into earnings.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2017
Variable Interest Entities [Abstract]
Variable Interest Entities	Note 17 - Variable Interest Entities Synovus has a contractual ownership or other interests in certain VIEs for which the fair value of the VIE's net assets may change exclusive of the variable interests. Under ASC 810, Consolidation , Synovus is deemed to be the primary beneficiary and required to consolidate a VIE if it has a variable interest in the VIE that provides it with a controlling financial interest. For such purposes, the determination of whether a controlling financial interest exists is based on whether a single party has both the power to direct the activities of the VIE that most significantly impact the VIE's economic performance and the obligation to absorb the losses of the VIE or the right to receive benefits from the VIE that could potentially be significant to the VIE. ASC 810-10-65, as amended, requires continual reconsideration of conclusions reached regarding which interest holder is a VIE's primary beneficiary. Synovus’ involvement with VIEs is discussed below. Synovus consolidates VIEs for which it is deemed the primary beneficiary. Consolidated Variable Interest Entities Rabbi Trusts – Synovus has established certain rabbi trusts related to deferred compensation plans offered to its participants (employees and directors). Synovus contributes the participant's cash compensation deferrals to the trusts and directs the underlying investments made by the trusts. The assets of these trusts are available to Synovus creditors only in the event that Synovus becomes insolvent. These trusts are considered VIEs because either there is no equity at risk in the trusts or because Synovus provided the equity interest to their participants in exchange for services rendered. While the participants have the ability to direct their funds within the trusts, Synovus is considered the primary beneficiary of the rabbi trusts as it has the ability to direct the underlying investments made by the trusts as well as make funding decisions related to the trusts, the activities that most significantly impact the economic performance of the rabbi trusts. Synovus includes the assets of the rabbi trusts as a component of other assets and a corresponding liability for the associated benefit obligation in other liabilities in its consolidated balance sheets. At December 31, 2017 and 2016 , the aggregate amount of rabbi trust assets and benefit obligations was $14.1 million and $ 11.5 million , respectively. Non-consolidated Variable Interest Entities Low Income Housing Tax Credit Partnerships – Synovus and its subsidiary bank, Synovus Bank, make equity investments as a limited partner in various partnerships which are engaged in the development and operation of affordable multi-family housing utilizing the LIHTC pursuant to Section 42 of the Code. The purpose of these investments is to earn a return on the investment and to support community reinvestment initiatives of Synovus Bank. The activities of these LIHTC partnerships are limited to development and operation of multi-family housing that is leased to qualifying residential tenants. These partnerships are generally located in southeastern communities where Synovus has a banking presence and are considered VIEs because Synovus, as the holder of an equity investment at risk, does not have voting or similar rights and does not participate in the management or direct the operations of the partnerships (activities which affect the economic performance of the partnerships). Synovus provides construction lending for certain of the LIHTC partnerships in which it also has an equity investment. Synovus is at risk for the amount of its equity investment plus the outstanding amount of any construction loans in excess of the fair value of the collateral for the loan but has no obligation to fund the operations or working capital of the partnerships. The general partners of these partnerships are considered the primary beneficiaries because they are charged with management responsibility which give them the power to direct the activities that most significantly impact the economic performance of the partnerships, and they are exposed to losses beyond Synovus’ equity investment. Synovus records its investment in LIHTC partnerships as a component of other assets in its consolidated balance sheet. The following tables provide a summary of the investments in low income housing tax credit partnerships at December 31, 2017 and 2016 and income (loss) related to these investments for the years ended December 2017, 2016, and 2015. 2017 2016 (in thousands) Proportional amortization method investments included in other assets $ 58,343 $ — Equity method investments included in other assets 1,725 26,495 Cumulative equity investments in LIHTC partnerships 46,659 34,065 Unfunded commitments included in other liabilities 39,994 17,420 Short-term construction loans and letter of credit commitments 7,180 — Funded portion of short-term loans and letters of credit — — Years Ended December 31, 2017 2016 2015 (in thousands) Proportional amortization expense recognized as a component of income tax expense $ 1,820 $ — $ — Income (loss) from equity method investments recognized as a component of non-interest income (1,648 ) 389 553 Real Estate Partnerships – Synovus and its subsidiary bank, Synovus Bank, make equity investments as a limited partner in various partnerships which are engaged in the development and operation of real estate. For certain of these investments, Synovus is both an equity investor and a tenant where they occupy leasehold space in the real estate. The purpose of these investments is to earn a return on the investment and to provide for occupancy needs and banking presence location. The activities of these real estate partnerships are limited to development and operation of commercial real estate that is leased to qualifying commercial tenants. These partnerships are located in southeastern communities where Synovus has a banking presence and are considered VIEs because Synovus, as the holder of an equity investment at risk, does not participate in the management or direct the operations of the partnerships (activities which affect the economic performance of the partnerships), and allocation of distributions, operating results, and net exit proceeds for each investment is variable. Synovus is at risk for the amount of its equity investment and in certain circumstances may have an obligation to fund the operations or working capital of the partnerships. Synovus does have voting or similar rights for these real estate partnerships, however, the general partners of these partnerships are considered the primary beneficiaries because they are charged with management responsibilities which give them the power to direct the activities that most significantly impact the economic performance of the partnerships. Additionally, Synovus has an investment in two former LIHTC partnerships for which the tax credit compliance period is complete and these investments are no longer held for tax credits or other tax benefits. These investments were reclassified from LIHTC investments to real estate investments during 2017. Like the LIHTC partnerships discussed above, the purpose of these investments is to earn a return on the investment and to support community reinvestment initiatives of Synovus Bank. The activities of these former LIHTC partnerships are limited to development and operation of multi-family housing that is leased to qualifying residential tenants. These partnerships are generally located in southeastern communities where Synovus has a banking presence and are considered VIEs because Synovus, as the holder of an equity investment at risk, does not have voting or similar rights and does not participate in the management or direct the operations of the partnerships (activities which affect the economic performance of the partnerships). Synovus is at risk for the amount of its equity investment and has no obligation to fund the operations or working capital of the partnerships. The general partners of these partnerships are considered the primary beneficiaries because they are charged with management responsibility which give them the power to direct the activities that most significantly impact the economic performance of the partnerships, and they are exposed to losses beyond Synovus’ equity investment. Synovus classifies these investments as real estate partnerships because they are no longer held for tax credits or other tax benefits. Synovus records its investments in real estate partnerships as a component of other assets in its consolidated balance sheet. Synovus records equity method income (loss) from real estate partnerships as a component of non interest income in its consolidated income statement. The following tables provide a summary of the investments in real estate partnerships at December 31, 2017 and 2016 and income related to these investments for the years ended December 2017, 2016, and 2015. 2017 2016 (in thousands) Equity method investments included in other assets $ 6,468 $ 6,822 Unfunded commitments included in other liabilities — — Years Ended December 31, 2017 2016 2015 (in thousands) Income from equity method investments recognized as a component of non-interest income $ 1,584 $ 1,040 $ 1,212 Certain Commercial Loans – For certain troubled commercial loans, Synovus restructures the terms of the borrower’s debt in an effort to increase the probability of receipt of amounts contractually due. A TDR generally requires consideration of whether the borrowing entity is a VIE as economic events may have proven that the entity’s equity is not sufficient to permit it to finance its activities without additional subordinated financial support or a restructuring of the terms of its financing. As Synovus does not have the power to direct the activities that most significantly impact such troubled commercial borrowers’ operations, it is not considered the primary beneficiary, even in situations where, based on the size of the financing provided, Synovus is exposed to potentially significant benefits and losses of the borrowing entity. Synovus has no contractual requirements to provide financial support to the borrowing entities beyond certain funding commitments established upon restructuring of the terms of the debt that allow for preparation of the underlying collateral for sale.

Visa Shares and Related Agreeme

Visa Shares and Related Agreements	12 Months Ended
	Dec. 31, 2017
Visa Shares and Litigation Expense [Abstract]
Visa Shares and Related Agreements	Note 18 - Visa Shares and Related Agreements Synovus is a member of the Visa USA network and received shares of Visa Class B common stock in exchange for its membership interest in Visa USA in conjunction with the Visa IPO in 2008. Visa members have indemnification obligations with respect to the Covered Litigation. Visa Class B shares are subject to certain restrictions until settlement of the Covered Litigation. As of December 31, 2017 , all of the Covered Litigation had not been settled. Visa has established a litigation escrow to fund settlement of the Covered Litigation. The litigation escrow is funded by proceeds from Visa's conversion of Class B shares to Class A shares. In November 2009, Synovus sold its remaining Visa Class B shares to another Visa USA member financial institution. In conjunction with the sale, Synovus entered into a derivative contract with the purchaser which provides for settlements between the parties based upon a change in the ratio for conversion of Visa Class B shares to Visa Class A shares. As of December 31, 2017 and 2016 , the fair value of the derivative contract was $4.3 million and $5.8 million , respectively. The fair value of the derivative contract is determined based on management's estimate of the timing and amount of the Covered Litigation settlement, and the resulting payments due to the counterparty under the terms of the contract. For the years ended December 31, 2016 and 2015 , Synovus recognized fair value adjustments to the Visa derivative of $5.8 million and $1.5 million , respectively. No fair value adjustments were recognized during the year ended December 31, 2017. Management believes that the estimate of Synovus' exposure to the Visa indemnification and fees associated with the Visa derivative is adequate based on current information, including Visa's recent announcements and disclosures. However, future developments in the litigation could require potentially significant changes to Synovus' estimate.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 19 - Commitments and Contingencies In the normal course of business, Synovus enters into commitments to extend credit such as loan commitments and letters of credit to meet the financing needs of its customers. Synovus uses the same credit policies in making commitments and conditional obligations as it does for on-balance sheet instruments. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The contractual amount of these financial instruments represents Synovus' maximum credit risk should the counterparty draw upon the commitment, and should the counterparty subsequently fail to perform according to the terms of the contract. Since many of the commitments are expected to expire without being drawn upon, total commitment amounts do not necessarily represent future cash requirements. Additionally, certain commitments (primarily consumer) can generally be canceled by providing notice to the borrower. The allowance for credit losses associated with unfunded commitments and letters of credit is a component of the unfunded commitments reserve recorded within other liabilities on the Consolidated Balance Sheets. Additionally, unearned fees relating to letters of credit are recorded within other liabilities on the Consolidated Balance Sheets. These amounts are not material to Synovus' Consolidated Balance Sheets. Unfunded letters of credit and lending commitments at December 31, 2017 are presented below. (in thousands) Letters of credit* $ 153,372 Commitments to fund commercial and industrial loans 5,090,827 Commitments to fund commercial real estate, construction, and land development loans 1,567,583 Commitments under home equity lines of credit 1,137,714 Unused credit card lines 779,254 Other loan commitments 351,358 Total letters of credit and unfunded lending commitments $ 9,080,108 * Represent the contractual amount net of risk participations of $77 million .

Legal Proceedings

Legal Proceedings	12 Months Ended
	Dec. 31, 2017
Legal Proceedings Disclosure [Abstract]
Legal Proceedings	Note 20 - Legal Proceedings Synovus and its subsidiaries are subject to various legal proceedings and claims that arise in the ordinary course of its business. Additionally, in the ordinary course of business, Synovus and its subsidiaries are subject to regulatory examinations, information gathering requests, inquiries and investigations. Synovus, like many other financial institutions, has been the target of numerous legal actions and other proceedings asserting claims for damages and related relief for losses. These actions include claims and counterclaims asserted by individual borrowers related to their loans and allegations of violations of state and federal laws and regulations relating to banking practices, including putative class action matters. In addition to actual damages if Synovus does not prevail in asserted legal actions, credit-related litigation could result in additional write-downs or charge-offs of loans, which could adversely affect Synovus' results of operations during the period in which the write-down or charge-off were to occur. Synovus carefully examines and considers each legal matter, and, in those situations where Synovus determines that a particular legal matter presents loss contingencies that are both probable and reasonably estimable, Synovus establishes an appropriate accrual. An event is considered to be probable if the future event is likely to occur. While the final outcome of any legal proceeding is inherently uncertain, based on the information currently available, advice of counsel and available insurance coverage, management believes that the amounts accrued with respect to legal matters as of December 31, 2017 are adequate. The actual costs of resolving legal claims may be higher or lower than the amounts accrued. In addition, where Synovus determines that there is a reasonable possibility of a loss in respect of legal matters, Synovus considers whether it is able to estimate the total reasonably possible loss or range of loss. An event is “reasonably possible” if “the chance of the future event or events occurring is more than remote but less than likely.” An event is “remote” if “the chance of the future event or events occurring is more than slight but less than reasonably possible." In many situations, Synovus may be unable to estimate reasonably possible losses due to the preliminary nature of the legal matters, as well as a variety of other factors and uncertainties. For those legal matters where Synovus is able to estimate a range of reasonably possible losses, management currently estimates the aggregate range from our outstanding litigation is from zero to $8 million in excess of the amounts accrued, if any, related to those matters. This estimated aggregate range is based upon information currently available to Synovus, and the actual losses could prove to be higher. As there are further developments in these legal matters, Synovus will reassess these matters, and the estimated range of reasonably possible losses may change as a result of this assessment. Based on Synovus' current knowledge and advice of counsel, management presently does not believe that the liabilities arising from these legal matters will have a material adverse effect on Synovus' consolidated financial condition, results of operations or cash flows. However, it is possible that the ultimate resolution of these legal matters could have a material adverse effect on Synovus' results of operations for any particular period. Synovus intends to vigorously pursue all available defenses to these legal matters, but will also consider other alternatives, including settlement, in situations where there is an opportunity to resolve such legal matters on terms that Synovus considers to be favorable, including in light of the continued expense and distraction of defending such legal matters. Synovus maintains insurance coverage, which may be available to cover legal fees, or potential losses that might be incurred in connection with such legal matters. The above-noted estimated range of reasonably possible losses does not take into consideration insurance coverage which may or may not be available for the respective legal matters.

Employment Expenses and Benefit

Employment Expenses and Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employment Expenses and Benefit Plans	Note 21 - Employment Expenses and Benefit Plans For the years ended December 31, 2017 , 2016, and 2015, Synovus provided a 100% matching contribution on the first 4% of eligible employee 401(k) contributions for a total annual contribution of $11.5 million , $10.8 million , and $9.9 million , respectively. Effective December 29, 2017, Synovus' non-contributory profit sharing plan was merged into the 401(k) plan. For the years ended December 31, 2017 , 2016, and 2015, Synovus sponsored a stock purchase plan for directors and employees whereby Synovus made contributions equal to 15% of employee and director voluntary contributions, subject to certain maximum contribution limitations. The funds are used to purchase outstanding shares of Synovus common stock. Synovus recorded as expense $860 thousand , $826 thousand , and $835 thousand for contributions to these plans in 2017 , 2016 , and 2015 , respectively.

Share-based Compensation

Share-based Compensation	12 Months Ended
	Dec. 31, 2017
Share-based Compensation [Abstract]
Share-based Compensation	Note 22 - Share-based Compensation General Description of Share-based Plans Synovus has a long-term incentive plan under which the Compensation Committee of the Board of Directors has the authority to grant share-based awards to Synovus employees. The 2013 Omnibus Plan authorizes 8.6 million common share equivalents available for grant, where grants of options count as one share equivalent and grants of full value awards (e.g., restricted share units, market restricted share units, and performance share units) count as two share equivalents. Any restricted share units that are forfeited and options that expire unexercised will again become available for issuance under the Plan. At December 31, 2017 , Synovus had a total of 5.7 million common share equivalents of its authorized but unissued common stock reserved for future grants under the 2013 Omnibus Plan. The Plan permits grants of share-based compensation including stock options, restricted share units, market restricted share units, and performance share units. The grants generally include vesting periods ranging from three to five years and contractual terms of ten years. As further discussed below, market restricted share units and performance share units are granted at a defined target level and are compared annually to required market and performance metrics to determine actual units vested and compensation expense. Synovus has historically issued new shares to satisfy share option exercises and share unit conversions. Dividend equivalents are paid on outstanding restricted share units, market restricted share units, and performance share units in the form of additional restricted share units that vest over the same vesting period or the vesting period left on the original restricted share unit grant. During 2017, Synovus awarded 242,804 restricted share units to employees and non-employee directors and granted 78,174 market restricted share units and 72,825 performance share units to senior management. The weighted average grant date fair value of the awarded restricted share units, market restricted share units, and performance share units was $41.82 , $43.52 , and $41.61 , per share, respectively. During 2016, Synovus awarded 350,458 restricted share units to employees and non-employee directors and granted 93,913 market restricted share units and 83,529 performance share units to senior management. The weighted average grant date fair value of the awarded restricted share units, market restricted share units, and performance share units was $26.43 , $26.93 , and $25.95 , per share, respectively. During 2015, Synovus awarded 321,874 restricted share units to employees and non-employee directors and granted 82,152 market restricted share units and 82,152 performance share units to senior management. The weighted average grant date fair value of the awarded restricted share units, market restricted share units, and performance share units was $28.09 , $29.39 , and $28.06 , per share, respectively. The restricted share units and the market restricted share units granted during 2017 , 2016 , and 2015 contain a service-based vesting period of three years with most awards vesting pro-rata over three years. Share-based Compensation Expense Total share-based compensation expense was $14.2 million , $13.6 million , and $12.6 million for 2017 , 2016 , and 2015 , respectively. The total income tax benefit recognized in the consolidated statements of income related to share-based compensation expense was approximately $5.2 million , $5.0 million , and $4.6 million for 2017 , 2016 , and 2015 , respectively. No share-based compensation costs have been capitalized for the years ended December 31, 2017 , 2016 , and 2015 . As of December 31, 2017 , unrecognized compensation cost related to the unvested portion of share-based compensation arrangements involving shares of Synovus stock was approximately $17.5 million . Stock Options There were no stock option grants in 2017, 2016, or 2015. A summary of stock option activity and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below. Stock Options 2017 2016 2015 Shares Weighted-Average Exercise Price Shares Weighted-Average Exercise Price Shares Weighted-Average Exercise Price Outstanding at beginning of year 973,361 $ 17.76 1,741,975 $ 37.88 2,550,046 $ 45.11 Options exercised (197,631 ) 17.41 (297,225 ) 17.35 (338,808 ) 16.72 Options forfeited — — (1,597 ) 17.64 (12,825 ) 17.17 Options expired/canceled — — (469,792 ) 92.62 (456,438 ) 94.56 Options outstanding at end of year 775,730 $ 17.85 973,361 $ 17.76 1,741,975 $ 37.88 Options exercisable at end of year 775,730 $ 17.85 973,361 $ 17.76 1,504,783 $ 41.08 The aggregate intrinsic value for outstanding and exercisable stock options at December 31, 2017 was $23.8 million and their weighted average remaining contractual life was 4.18 years. The intrinsic value of stock options exercised during the years ended December 31, 2017 , 2016, and 2015 was $5.1 million , $4.7 million , and $4.4 million , respectively. Cash received from option exercises of common stock for the years ended December 31, 2017 , 2016, and 2015 was $3.4 million , $5.2 million , and $5.6 million , respectively. The total grant date fair value of stock options vested during 2016 and 2015 was $7.4 million and $6.5 million , respectively. During 2016, 317,524 stock options with a weighted average exercise price of $93.62 and contractual expiration dates in 2017 and 2018 were canceled without replacement awards. The cancellation resulted in a deferred tax asset write-off totaling $1.7 million , which was recorded as a reduction of additional paid-in capital. Due to the implementation of ASU 2016-09 effective January 1, 2017, if the canceled stock options had remained outstanding through their original contractual expiration dates, the corresponding deferred tax asset write-off totaling $1.7 million would have been recorded as a component of income tax expense during the years ending December 31, 2017 and 2018. Restricted Share Units, Market Restricted Share Units, and Performance Share Units Compensation expense is measured based on the grant date fair value of restricted share units, market restricted share units, and performance share units. The fair value of restricted share units and performance share units is equal to the market price of common stock on the grant date. The fair value of market restricted share units granted was estimated on the date of grant using a Monte Carlo simulation model with the following weighted average assumptions: 2017 2016 2015 Risk-free interest rate 1.48 % 0.81 % 1.05 % Expected stock price volatility 22.9 25.7 26.4 Dividend yield 1.2 1.8 1.4 Simulation period 3.0 years 3.0 years 3.0 years The stock price expected volatility was based on Synovus' historical and implied volatility. The Monte Carlo model estimates fair value based on 100,000 simulations of future share price using a theoretical model of stock price behavior. A summary of restricted share units outstanding and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below (excluding market restricted and performance share units). Restricted Share Units Share Units Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 882,823 $ 19.81 Granted 321,874 28.09 Dividend equivalents granted 9,810 28.09 Vested (428,121 ) 17.48 Forfeited (23,619 ) 24.60 Outstanding at December 31, 2015 762,767 24.57 Granted 350,458 26.43 Dividend equivalents granted 11,105 26.43 Vested (406,496 ) 23.10 Forfeited (12,067 ) 23.96 Outstanding at December 31, 2016 705,767 26.38 Granted 242,804 41.82 Dividend equivalents granted 5,839 41.82 Vested (341,825 ) 26.25 Forfeited (46,637 ) 26.28 Outstanding at December 31, 2017 565,948 $ 33.25 The total fair value of restricted share units vested during 2017 , 2016 , and 2015 was $14.4 million , $11.4 million , and $12.3 million , respectively. As of December 31, 2017 , total unrecognized compensation cost related to the foregoing restricted share units was approximately $9.9 million . This cost is expected to be recognized over a weighted average remaining period of 1.43 years. Synovus granted market restricted share units to senior management during the years ended December 31, 2017 , 2016 , and 2015 . The market restricted share units have a three-year service-based vesting component as well as a total shareholder return multiplier. The number of market restricted share units that will ultimately vest ranges from 75% to 125% of a defined target based on Synovus' total shareholder return (TSR). The total fair value of market restricted share units vested during 2017 , 2016 , and 2015 was $4.8 million , $2.6 million , and $1.4 million , respectively. At December 31, 2017 , total unrecognized compensation cost related to market restricted share units was approximately $3.5 million with a weighted average remaining period of 1.46 years. A summary of market restricted share units outstanding and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below. Market Restricted Share Units Share Units Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 118,186 $ 24.33 Granted 82,152 29.39 Dividend equivalents granted 2,221 29.05 Quantity change by TSR factor 4,838 24.33 Vested (49,149 ) 24.34 Outstanding at December 31, 2015 158,248 27.02 Granted 93,913 26.93 Dividend equivalents granted 3,095 26.93 Quantity change by TSR factor 9,970 26.93 Vested (82,817 ) 26.40 Outstanding at December 31, 2016 182,409 27.25 Granted 78,174 43.52 Dividend equivalents granted 2,811 43.52 Quantity change by TSR factor 22,182 27.25 Vested (114,013 ) 26.78 Outstanding at December 31, 2017 171,563 $ 35.24 Synovus granted performance share units to senior management during the years ended December 31, 2017 , 2016 , and 2015 . These units vest upon meeting certain service and performance conditions. Return on average assets (ROAA) performance is evaluated each year over a three-year performance period, with share distribution determined at the end of the three years. The number of performance share units that will ultimately vest ranges from 0% to 150% of a defined target based on Synovus' three-year weighted average ROAA (as defined). The total fair value of performance share units vested during 2017 was $2.9 million . At December 31, 2017 , total unrecognized compensation cost related to performance share units was approximately $4.1 million with a weighted average remaining period of 1.44 years. A summary of performance share units outstanding and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below. Performance Share Units Share Units Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 67,675 $ 23.47 Granted 82,152 28.06 Dividend equivalents granted 1,740 28.06 Outstanding at December 31, 2015 151,567 26.01 Granted 83,529 25.95 Dividend equivalents granted 3,384 25.95 Outstanding at December 31, 2016 238,480 25.99 Granted 72,825 41.61 Dividend equivalents granted 2,562 41.61 Vested (69,326 ) 23.47 Outstanding at December 31, 2017 244,541 $ 31.54 Other Information Cash paid for taxes due on vesting of employee restricted share units and market restricted share units where restricted share units were withheld to cover taxes was $8.0 million , $5.0 million , and $5.1 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. During 2017 , Synovus recognized $5.0 million of income tax benefits through the income statement from share-based compensation excess tax benefits upon the vesting of restricted share units and exercise of stock options. During 2016, Synovus recognized a share-based compensation net tax deficiency of $790 thousand associated primarily with expired and canceled stock options. The net deficiency was recorded as a reduction of additional paid-in capital within shareholders' equity. During 2015, Synovus recognized a net tax benefit of $1.7 million associated with vesting of restricted share units, exercises of stock options, and expired stock options. The net tax benefit was recorded as an increase of additional paid-in capital. The following table provides aggregate information regarding grants under all Synovus equity compensation plans at December 31, 2017 . Plan Category (a) Number of Securities to be Issued Upon Vesting of Restricted Share Units, Market Restricted Share Units, and Performance Share Units (1) (b) Number of Securities to be Issued Upon Exercise of Outstanding Options (c) Weighted-Average Exercise Price of Outstanding Options in Column (b) (d) Number of Shares Remaining Available for Issuance Excluding Shares Reflected in Columns (a) and (b) Shareholder approved equity compensation plans for shares of Synovus stock 982,052 775,730 $ 17.85 5,671,680 (1) Market restricted and performance share units included at defined target levels. Actual shares issued upon vesting may differ based on actual TSR and ROAA over the measurement period.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 23 - Income Taxes The components of income tax expense (benefit) included in the consolidated statements of income for the years ended December 31, 2017 , 2016 , and 2015 are presented below: (in thousands) 2017 2016 2015 Current Federal $ (32,341 ) $ 7,329 $ 6,163 State 5,949 5,501 4,424 Total current income tax expense (benefit) (26,392 ) 12,830 10,587 Deferred Federal 229,917 117,463 108,877 State 1,139 11,374 13,027 Total deferred income tax expense 231,056 128,837 121,904 Total income tax expense $ 204,664 $ 141,667 $ 132,491 Note: The table above does not reflect a net charge of $790 thousand and a credit of $1.7 million for the years ended December 31, 2016 and 2015, respectively, relating to share-based compensation transactions that were charged or credited directly to shareholders' equity. Income tax expense does not reflect the tax effects of net unrealized gains (losses) on investment securities available for sale and post-retirement unfunded health benefits. These effects are presented in the Consolidated Statements of Comprehensive Income. The 2017 financial results reflect the income tax expense effects from Federal Tax Reform in accordance with ASC Topic 740, Income Taxes . Additionally, Staff Accounting Bulletin No. 118 provides guidance for the application of ASC Topic 740, Income Taxes , in the reporting period in which the Federal Tax Reform was signed into law. Synovus remeasured its deferred tax assets and liabilities based upon the newly enacted U.S. statutory federal rate of 21 percent which is the tax rate at which these deferred tax assets and liabilities are expected to reverse. This resulted in an additional provisional federal income tax expense of $47.2 million in 2017. Based on the information available and our current interpretation of the Federal Tax Reform, Synovus has made reasonable estimates of the impact from the reduction in the corporate tax rate on the remeasurement of applicable deferred tax assets and liabilities. However, certain deferred tax assets and liabilities will continue to be evaluated in the context of Federal Tax Reform through the date of the filing of our 2017 federal income tax return, and may change as a result of evolving management interpretations, elections, and assumptions, as well as new guidance that may be issued by the Internal Revenue Service. Accordingly, the federal income tax expense of $47.2 million relating to the effects from Federal Tax Reform is considered provisional, as defined by SAB 118. Management expects to complete its analysis within the measurement period in accordance with SAB 118. Income tax expense as shown in the consolidated statements of income differed from the amounts computed by applying the U.S. federal income tax rate of 35 percent to income before income taxes. A reconciliation of the differences for the years ended December 31, 2017 , 2016 and 2015 is presented below: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Income tax expense at statutory federal income tax rate $ 168,048 $ 135,957 $ 125,501 Increase (decrease) resulting from: State income tax expense, net of federal income tax benefit 11,961 13,256 12,870 Provisional tax adjustment related to reduction in U.S. federal statutory income tax rate (1)(2) 46,573 — — LIHTC amortization, net of tax benefits 268 — — Tax-exempt income (719 ) (825 ) (835 ) Tax benefit from share-based compensation (4,318 ) — — Bank-owned life insurance (4,702 ) (3,402 ) (2,885 ) Change in valuation allowance (3) (6,227 ) (2,055 ) (589 ) General business tax credits (4) (6,546 ) (1,213 ) (1,173 ) Other, net 326 (51 ) (398 ) Total income tax expense $ 204,664 $ 141,667 $ 132,491 Effective tax rate 42.6 % 36.5 % 36.9 % (1) Does not include a provisional tax expense adjustment of $608 thousand which is included as a component of the change in the valuation allowance. The income tax effect of the provisional federal income tax expense of $47.2 million relating to Federal Tax Reform represents 9.8% of income before taxes. (2) Includes $7.8 million expense from remeasurement of deferred tax assets relating to unrealized losses on available for sale securities which were initially recorded through accumulated other comprehensive income (AOCI). As further described in Note 1, ASU 2018-02, issued in February 2018, provides for the reclassification of the tax effects stranded in AOCI resulting from Federal Tax Reform to retained earnings. As a result, Synovus will elect to apply the ASU 2018-02 guidance during the reporting period ending on March 31, 2018 and reclassify $7.8 million from AOCI to retained earnings. (3) Includes a provisional federal income tax expense of $608 thousand related to Federal Tax Reform. (4) 2017 includes research and development tax credits for the tax years 2013-2017 totaling $4.6 million . Significant portions of the deferred tax assets and liabilities at December 31, 2017 and 2016 are presented below: (in thousands) 2017 2016 Deferred tax assets Allowance for loan losses $ 66,034 $ 100,419 Net operating loss carryforwards 41,059 167,072 Tax credit carryforwards 19,175 67,031 Employee benefits and deferred compensation 18,333 26,183 Net unrealized losses on investment securities available for sale 13,253 19,413 Deferred revenue 12,311 18,639 Non-performing loan interest 10,388 19,137 Other 8,892 14,600 Total gross deferred tax assets 189,445 432,494 Less valuation allowance (3,431 ) (9,658 ) Total deferred tax assets 186,014 422,836 Deferred tax liabilities Other properties held for sale (5,447 ) (8,179 ) Excess tax over financial statement depreciation (6,628 ) (5,343 ) Other (8,151 ) (13,958 ) Total gross deferred tax liabilities (20,226 ) (27,480 ) Net deferred tax asset $ 165,788 $ 395,356 The net decrease in the valuation allowance for the years ended December 31, 2017 and 2016 was $ 6.2 million and $ 2.1 million , respectively, due to the expiration of unused state tax credits, the reversal of valuation allowance on state tax credits that now have been determined to be utilized before they expire, and a provisional tax adjustment of $608 thousand related to the effects from Federal Tax Reform. Management assesses the realizability of deferred tax assets at each reporting period. The determination of whether a valuation allowance for deferred tax assets is appropriate is subject to considerable judgment and requires an evaluation of all the positive and negative evidence. At December 31, 2017 , the Company is not in a three-year cumulative loss position; accordingly, it does not have significant negative evidence to consider when evaluating the realization of its deferred tax assets. Positive evidence supporting the realization of the Company’s deferred tax assets at December 31, 2017 includes generation of taxable income in 2017 , 2016 , and 2015 , continued improvement in credit quality, record of long-term positive earnings prior to the most recent economic downturn, strong capital position, as well as sufficient amounts of projected future taxable income, of the appropriate character, to support the realization of the $165.8 million net deferred tax asset at December 31, 2017 . Synovus expects to realize its net deferred tax asset of $165.8 million through the reversal of existing taxable temporary differences and projected future taxable income. The valuation allowance of $3.4 million at December 31, 2017 relates to specific state income tax credits that will expire in 2018, and before they can be realized. Based on the assessment of all the positive and negative evidence at December 31, 2017 and 2016 , management has concluded that it is more likely than not that the results of future operations will generate sufficient taxable income to realize the deferred tax assets. Synovus expects to realize substantially all of the $165.8 million in net deferred tax assets well in advance of the statutory carryforward period. At December 31, 2017 , $108.9 million of existing deferred tax assets are not related to net operating losses or credits and therefore, have no expiration dates. $41.1 million of the deferred tax assets relate to state net operating losses which will expire in installments annually through the tax year 2035. State tax credits at December 31, 2017 total $19.2 million and have expiration dates through the tax year 2027. State NOL and tax credit carryforwards as of December 31, 2017 are summarized in the following table. Tax Carryforwards As of December 31, 2017 (in thousands) Expiration Dates Deferred Tax Asset Balance (2) Valuation Allowance Net Deferred Tax Asset Balance Pre-Tax Earnings Necessary to Realize (1) Net operating losses - states 2023-2027 $ 1,688 $ — $ 1,688 $ 1,018,310 Net operating losses - states 2028-2032 48,430 — 48,430 1,093,946 Net operating losses - states 2033-2035 360 — 360 7,584 Other credits - states 2018-2022 18,381 (3,431 ) 14,950 N/A Other credits - states 2023-2027 207 — 207 N/A Other credits - states None 587 — 587 N/A (1) N/A indicates credits are not measured on a pre-tax earnings basis. (2) Effective December 31, 2017, alternative minimum tax credits of $42.1 million were reclassified from deferred tax assets to current taxes receivable reflecting their refundability pursuant to Federal Tax Reform. Synovus believes that a portion of its state tax credit carryforwards will not be realized due to the length of certain state carryforward periods. Accordingly, a valuation allowance in the amount of $3.4 million has been established against deferred tax assets at December 31, 2017 compared to a valuation allowance of $9.7 million at December 31, 2016. The decrease of $6.2 million in 2017 reflects the expiration of unused state tax credits, the reversal of a valuation allowance on state tax credits that now have been determined to be utilized before they expire, and a provisional tax adjustment related to the effects from the Federal Tax Reform. A decrease of $2.1 million occurred in 2016. Synovus is subject to income taxation in the United States and various state jurisdictions. Synovus' federal income tax return is filed on a consolidated basis, while state income tax returns are filed on both a consolidated and separate entity basis. Currently, there are no years for which Synovus filed a federal income tax return that are under examination by the IRS. Additionally, Synovus is no longer subject to income tax examinations by the IRS for years before 2013, and excluding certain limited exceptions, Synovus is no longer subject to income tax examinations by state and local income tax authorities for years before 2013. However, amounts reported as net operating losses and tax credit carryovers from closed tax periods remain subject to review by most tax authorities. Although Synovus is unable to determine the ultimate outcome of current and future examinations, Synovus believes that the liability recorded for uncertain tax positions is adequate. A reconciliation of the beginning and ending amount of unrecognized income tax benefits is as follows (unrecognized state income tax benefits are not adjusted for the federal income tax impact). Years Ended December 31, (in thousands) 2017 2016 2015 Balance at January 1, $ 14,745 $ 12,745 $ 13,023 Additions based on income tax positions related to current year 152 — — Additions for income tax positions of prior years * 934 1,811 8 Additions from acquisition — 608 — Reductions for income tax positions of prior years (706 ) — — Statute of limitation expirations (8 ) (419 ) (286 ) Settlements — — — Balance at December 31, $ 15,117 $ 14,745 $ 12,745 *Includes deferred tax benefits that could reduce future tax liabilities. Accrued interest and penalties related to unrecognized income tax benefits are included as a component of income tax expense. Accrued interest and penalties on unrecognized income tax benefits totaled $105 thousand , $38 thousand , and $96 thousand as of December 31, 2017 , 2016 and 2015, respectively. Unrecognized income tax benefits as of December 31, 2017 , 2016 and 2015 that, if recognized, would affect the effective income tax rate totaled $12.3 million , $9.9 million and $8.3 million (net of the federal benefit on state income tax issues). Accrued interest and penalties were approximately $76 thousand and $25 thousand at December 31, 2017 and 2016, respectively. Synovus expects that $17 thousand of uncertain income tax positions will be either settled or resolved during the next twelve months.

Condensed Financial Information

Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only)	Note 24 - Condensed Financial Information of Synovus Financial Corp. (Parent Company only) Condensed Balance Sheets December 31, (in thousands) 2017 2016 Assets Cash due from bank subsidiary $ 191,275 $ 234,339 Funds due from other depository institutions (1) 19,911 19,911 Investment in consolidated bank subsidiary, at equity 3,232,129 3,319,980 Investment in consolidated nonbank subsidiaries, at equity 40,731 71,335 Notes receivable from nonbank subsidiaries — 35,200 Other assets 69,762 101,346 Total assets $ 3,553,808 $ 3,782,111 Liabilities and Shareholders' Equity Liabilities: Long-term debt $ 554,589 $ 834,252 Other liabilities 37,653 19,935 Total liabilities 592,242 854,187 Shareholders’ equity: Series C Preferred Stock 125,980 125,980 Common stock 142,678 142,026 Additional paid-in capital 3,043,129 3,028,405 Treasury stock (839,674 ) (664,595 ) Accumulated other comprehensive loss, net (54,754 ) (55,659 ) Retained earnings 544,207 351,767 Total shareholders’ equity 2,961,566 2,927,924 Total liabilities and shareholders’ equity $ 3,553,808 $ 3,782,111 (1) Restricted as to withdrawal. Condensed Statements of Income Years Ended December 31, (in thousands) 2017 2016 2015 Income Cash dividends received from subsidiaries (1) $ 283,210 $ 325,000 $ 199,904 Cash distributions received from subsidiaries (1) 167,790 — 25,096 Interest income 1,443 2,565 8,865 Other income 345 4,595 (337 ) Total income 452,788 332,160 233,528 Expenses Interest expense 43,922 52,831 46,585 Other expenses 33,955 20,652 10,516 Total expenses 77,877 73,483 57,101 Income before income taxes and equity in undistributed (loss) income of subsidiaries 374,911 258,677 176,427 Allocated income tax benefit (30,421 ) (25,628 ) (18,808 ) Income before equity in undistributed (loss) income of subsidiaries 405,332 284,305 195,235 Equity in undistributed (loss) income of subsidiaries (129,858 ) (37,521 ) 30,847 Net income 275,474 246,784 226,082 Dividends on preferred stock 10,238 10,238 10,238 Net income available to common shareholders $ 265,236 $ 236,546 $ 215,844 (1) Substantially all cash dividends and distributions are from Synovus Bank. Condensed Statements of Comprehensive Income December 31, 2017 December 31, 2016 December 31, 2015 (in thousands) Before-tax Amount Tax (Expense) Benefit Net of Tax Amount Before-tax Amount Tax (Expense) Benefit Net of Tax Amount Before-tax Amount Tax (Expense) Benefit Net of Tax Amount Net income $ 480,138 $ (204,664 ) $ 275,474 $ 388,451 $ (141,667 ) $ 246,784 $ 358,573 $ (132,491 ) $ 226,082 Reclassification adjustment for losses realized in net income on cash flow hedges 130 (50 ) 80 467 (180 ) 287 521 (201 ) 320 Reclassification adjustment for net gains realized in net income on investment securities available for sale (5,506 ) 2,120 (3,386 ) (5,763 ) 2,219 (3,544 ) — — — Net unrealized gains on investment securities available for sale — — — 2,358 (908 ) 1,450 2,908 (1,120 ) 1,788 Other comprehensive gain (loss) of bank subsidiary 6,784 (2,573 ) 4,211 (39,080 ) 15,047 (24,033 ) (31,420 ) 12,098 (19,322 ) Other comprehensive income (loss) $ 1,408 (503 ) 905 (42,018 ) 16,178 (25,840 ) (27,991 ) 10,777 (17,214 ) Comprehensive income $ 276,379 $ 220,944 $ 208,868 Condensed Statements of Cash Flows Years Ended December 31, (in thousands) 2017 2016 2015 Operating Activities Net income $ 275,474 $ 246,784 $ 226,082 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed loss (income) of subsidiaries 129,858 37,521 (30,847 ) Deferred income tax expense (benefit) 60,931 17,989 (2,506 ) Net (decrease) increase in other liabilities (1,095 ) 7,746 (1,709 ) Net (increase) decrease in other assets (8 ) (9,214 ) 1,045 Other, net (3,330 ) (1,648 ) (178 ) Net cash provided by operating activities 461,830 299,178 191,887 Investing Activities Proceeds from sales of investment securities available for sale 4,305 — — Outlays for business combinations — (3,408 ) — Net decrease in short-term notes receivable from non-bank subsidiaries 35,200 31,800 10,000 Net cash provided by investing activities 39,505 28,392 10,000 Financing Activities Dividends paid to common and preferred shareholders (64,908 ) (69,663 ) (65,592 ) Repurchases of common stock (175,079 ) (263,084 ) (199,221 ) Repayments on long-term debt (600,386 ) (130,048 ) (48,553 ) Proceeds from issuance of long-term debt 296,866 — 246,644 Earnout payment (892 ) — — Net cash used in financing activities (544,399 ) (462,795 ) (66,722 ) (Decrease) increase in cash and funds due from banks (43,064 ) (135,225 ) 135,165 Cash and funds due from banks at beginning of year 254,250 389,475 254,310 Cash and funds due from banks at end of year $ 211,186 $ 254,250 $ 389,475 For the years ended December 31, 2017 , 2016, and 2015, the Parent Company paid income taxes of $18.0 million , $9.5 million , and $8.7 million , respectively. For the years ended December 31, 2017 , 2016 , and 2015 , the Parent Company paid interest of $51.0 million , $53.1 million , and $46.9 million , respectively.

Supplemental Financial Data

Supplemental Financial Data	12 Months Ended
	Dec. 31, 2017
Supplemental Income Statement Elements [Abstract]
Supplemental Financial Data	Note 25 - Supplemental Financial Data Components of other non-interest income and other operating expenses in excess of 1% of total interest income and total non-interest income for any of the respective years are as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Insurance and bonds $ 10,314 $ 12,023 $ 12,514

Summary of Quarterly Financial

Summary of Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Summary of Quarterly Financial Data (Unaudited)	Summary of Quarterly Financial Data (Unaudited) Presented below is a summary of the unaudited consolidated quarterly financial data for the years ended December 31, 2017 and 2016 . 2017 (in thousands, except per share data) Fourth Quarter (1) Third Quarter Second Quarter First Quarter Interest income $ 306,934 $ 297,652 $ 285,510 $ 272,401 Net interest income 269,713 262,572 251,097 239,927 Provision for loan losses 8,565 39,686 10,260 8,674 Income before income taxes 103,966 152,675 117,791 105,704 Income tax expense 74,361 54,668 41,788 33,847 Net income 29,605 98,007 76,003 71,857 Net income available to common shareholders 27,046 95,448 73,444 69,298 Net income per common share, basic 0.23 0.79 0.60 0.57 Net income per common share, diluted 0.23 0.78 0.60 0.56 (1) The results for the fourth quarter 2017 include $23.2 million pre-tax loss on early extinguishment of debt, as well as a $47.2 million income tax charge related to the effect of Federal Tax Reform. 2016 Fourth Quarter Third Quarter Second Quarter First Quarter Interest income $ 264,534 $ 256,554 $ 252,393 $ 249,323 Net interest income 233,530 226,007 221,449 218,193 Provision for loan losses 6,259 5,671 6,693 9,377 Income before income taxes 108,068 102,620 94,031 83,730 Income tax expense 39,519 37,375 33,574 31,199 Net income 68,549 65,245 60,457 52,531 Net income available to common shareholders 65,990 62,686 57,898 49,972 Net income per common share, basic 0.54 0.51 0.46 0.39 Net income per common share, diluted 0.54 0.51 0.46 0.39

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
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. At December 31, 2017 and 2016 , interest bearing funds with the Federal Reserve Bank included $8.6 million and $130 million , respectively, on deposit to meet Federal Reserve Bank reserve requirements. Interest earning deposits with banks include $5.9 million at December 31, 2017 and $5.6 million at December 31, 2016 , which is pledged as collateral in connection with certain letters of credit. Federal funds sold include $43.8 million at December 31, 2017 and $56.1 million at December 31, 2016 , which are pledged to collateralize certain derivative instruments. Federal funds sold and securities purchased under resale agreements, and federal funds purchased and securities sold under repurchase agreements generally mature in one day.
Trading Account Assets	Trading account assets, which are primarily held on a short-term basis for the purpose of selling at a profit, consist of debt and equity securities and are reported at fair value. Fair value adjustments and fees from trading account activities are included as a component of other fee income on the consolidated statements of income. Gains and losses realized from the sale of trading account assets are determined by specific identification and are included as a component of other fee income on the trade date. Interest income on trading assets is reported as a component of interest income on the consolidated statements of income.
Mortgage Loans Held for Sale and Mortgage Banking Income	Mortgage Loans Held for Sale Mortgage loans held for sale are recorded at fair value. Fair value is derived from a hypothetical bulk sale model used to estimate the exit price of the loan in a loan sale. The bid pricing convention is used for loan pricing for similar assets. The valuation model is based upon forward settlements of a pool of loans of similar coupon, maturity, product, and credit attributes. The inputs to the model are continuously updated with available market and historical data. Until the loans are committed to be sold in the secondary market, the valuation model produces an estimate of fair value that represents the highest and best use of the loans in Synovus' principal market. Mortgage Banking Income Mortgage banking income consists primarily of origination and ancillary fees on loans originated for sale, and gains and losses from the sale of mortgage loans. Mortgage loans are generally sold servicing released, without recourse or continuing involvement, and meet ASC 860-10-65 criteria for sale accounting.
Other Loans Held for Sale	Loans are transferred to other loans held for sale at fair value when Synovus makes the determination to sell specifically identified loans. The fair value of the loans is primarily determined by analyzing the underlying collateral of the loan and the anticipated market prices of similar assets less estimated costs to sell. At the time of transfer, if the estimated fair value is less than the carrying amount, the difference is recorded as a charge-off against the allowance for loan losses. Decreases in the fair value subsequent to the transfer, as well as gains/losses realized from the sale of these assets, are recorded as gains/losses on other loans held for sale, net, as a component of non-interest expense on the consolidated statements of income.
Investment Securities Available for Sale	Investment securities available for sale are carried at fair value with unrealized gains and losses, net of the related tax effect, excluded from earnings and reported as a separate component of shareholders' equity within accumulated other comprehensive income (loss) until realized. Synovus performs a quarterly assessment of its investment securities available for sale to determine if the decline in fair value of a security below its amortized cost is deemed to be other-than-temporary. Factors included in the assessment include the length of time the security has been in a loss position, the extent that the fair value is below amortized cost, and the credit standing of the issuer. Other-than-temporary impairment losses are recognized on securities when: (1) the holder has an intention to sell the security; (2) it is more likely than not that the security will be required to be sold prior to recovery; or (3) the holder does not expect to recover the entire amortized cost basis of the security. Other-than-temporary impairment losses are reflected in earnings as realized losses to the extent the impairment is related to credit losses. The amount of the impairment related to other factors is recognized in other comprehensive income (loss). Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the effective interest method and prepayment assumptions. Actual prepayment experience is reviewed periodically and the timing of the accretion and amortization is adjusted accordingly. Interest income on securities available for sale is recorded on the accrual basis. Realized gains and losses for securities are included in investment securities gains (losses), net, on the consolidated statements of income and are derived using the specific identification method, on a trade date basis.
Loans and Interest Income on Loans	Loans are reported at principal amounts outstanding less amounts charged off, net of deferred fees and expenses. Interest income and deferred fees, net of expenses on loans, are recognized on a level yield basis. Non-accrual Loans Loans on which the accrual of interest has been discontinued are designated as non-accrual loans. Accrual of interest is discontinued on loans when reasonable doubt exists as to the full collection of interest or principal, or when loans become contractually past due for 90 days or more as to either interest or principal, in accordance with the terms of the loan agreement, unless they are both well-secured and in the process of collection. When a loan is placed on non-accrual status, previously accrued and uncollected interest is generally reversed as an adjustment to interest income on loans. Interest payments received on non-accrual loans are generally recorded as a reduction of principal. As payments are received on non-accruing loans, interest income can be recognized on a cash basis; however, there must be an expectation of full repayment of the remaining recorded principal balance. The remaining portion of this payment is recorded as a reduction to principal. Loans are generally returned to accruing status when they are brought fully current with respect to interest and principal and when, in the judgment of management, the loans are estimated to be fully collectible as to both principal and interest, and the borrower has sustained repayment performance under the terms of the loan agreement for a reasonable period of time (generally six months). Impaired Loans Impaired loans are loans for which it is probable that Synovus will not be able to collect all amounts due according to the contractual terms of the loan agreements and all loans modified in a troubled debt restructuring (TDR). Other than TDRs, impaired loans do not include smaller-balance homogeneous loans that are collectively evaluated for impairment, which consist of most retail loans and commercial loan relationships lower than $1.0 million . Impairment is measured on a discounted cash flow method based upon the loan's contractual effective interest rate, or at the loan's observable market price, or at the fair value of the collateral, less costs to sell if the loan is collateral-dependent. Interest income on non-accrual impaired loans is recognized as described above under "non-accrual loans." Impaired accruing loans generally consist of those TDRs for which management has concluded that the collectability of the loan is not in doubt. At December 31, 2017 and 2016, substantially all non-accrual impaired loans were collateral-dependent and secured by real estate. For impairment measured using the estimated fair value of collateral less costs to sell, fair value is estimated using appraisals performed by a certified or licensed appraiser. Management also considers other factors or recent developments, such as selling costs and anticipated sales values, taking into account management's plans for disposition, which could result in adjustments to the fair value estimates indicated in the appraisals. The assumptions used in determining the amount of the impairment are subject to significant judgment. Use of different assumptions, for example, changes in the fair value of the collateral or management's plans for disposition could have a significant impact on the amount of impairment. Under the discounted cash flow method, impairment is recorded as a specific reserve with a charge-off for any portion of the impairment considered a confirmed loss. The reserve is reassessed each quarter and adjusted as appropriate based on changes in estimated cash flows. Where guarantors are determined to be a source of repayment, an assessment of the guarantee is required. This guarantee assessment would include, but not be limited to, factors such as type and feature of the guarantee, consideration for the guarantor's financial strength and capacity to service the loan in combination with the guarantor's other financial obligations as well as the guarantor's willingness to assist in servicing the loan. Troubled Debt Restructurings When borrowers are experiencing financial difficulties, Synovus may, in order to assist the borrowers in repaying the principal and interest owed to Synovus, make certain modifications to the borrower's loan. All loan modifications, renewals, and refinances are evaluated for TDR classification. All TDRs are considered to be impaired loans, and the amount of impairment, if any, is determined in accordance with ASC 310-10-35 . Concessions provided by Synovus in a TDR are generally made in order to assist borrowers so that debt service is not interrupted and to mitigate the potential for loan losses. A number of factors are reviewed when a loan is renewed, refinanced, or modified, including cash flows, collateral values, guarantees, and loan structures. Concessions are primarily in the form of providing a below market interest rate given the borrower's credit risk to assist the borrower in managing cash flows, an extension of the maturity of the loan generally for less than one year, or a period of time generally less than one year with a reduction of required principal and/or interest payments (e.g., interest only for a period of time). Insignificant periods of reduction of principal and/or interest payments, or one time deferrals of three months or less, are generally not considered to be financial concessions. Further, it is generally Synovus' practice not to defer principal and/or interest for more than twelve months. Non-accruing TDRs may generally be returned to accrual status if there has been a period of performance, usually at least a six month sustained period of repayment performance in accordance with the agreement. Consistent with regulatory guidance, a TDR will generally no longer be reported as a TDR after a period of performance and after the loan was reported as a TDR at a year-end reporting date, and if at the time of the modification, the interest rate was at market, considering the credit risk associated with the borrower, and no principal was forgiven.
Allowance for Loan Losses	The allowance for loan losses represents management's estimate of probable losses inherent in the funded loan portfolio. Changes to the allowance are recorded through a provision for loan losses and reduced by loans charged-off, net of recoveries. Impaired loans are generally evaluated on a loan by loan basis with specific reserves, if any, recorded as appropriate. Specific reserves are determined based on ASC 310-10-35, which provides for measurement of a loan's impairment based on one of three methods. If the loan is collateral-dependent, then the fair value of the loan's collateral, less estimated selling costs, is compared to the loan's carrying amount to determine impairment. Other methods of measuring a loan's impairment include the present value of the expected future cash flows of the loan, or if available, the observable market price of the loan. Synovus considers the pertinent facts and circumstances for each impaired loan when selecting the appropriate method to measure impairment, and quarterly evaluates each selection to ensure its continued appropriateness and evaluates the reasonableness of specific reserves, if any. For loans that are not considered impaired, the allocated allowance for loan losses is determined based upon Expected Loss (EL) factors, which are applied to groupings of specific loan types by loan risk ratings. The EL is determined based upon a probability of default (PD), which is the probability that a borrower, segregated by loan type and loan risk grade, will default, and loss given default (LGD), which is the estimate of the amount of net loss in the event of default. The groupings of the loans into loan categories are determined based upon the nature of the loan types and the level of inherent risk associated with the various loan categories. The loan groupings are further segregated based upon the individual loan risk ratings, as described below. The EL factors applied in the methodology are periodically re-evaluated and adjusted to reflect changes in historical loss levels or other risks. Allocated EL factors may also be adjusted, as necessary, for certain qualitative factors that in management's judgment are necessary to reflect losses incurred in the portfolio. Qualitative factors that management considers in the analysis include: • changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off, and recovery practices not considered elsewhere in estimating credit losses • changes in the volume and severity of past due loans, the volume of non-accrual loans, and the volume and severity of adversely classified or grade loans • loan growth • effects of changes in credit concentrations • experience, ability, and depth of lending management, loan review personnel, and other relevant staff • changes in the quality of the loan review function • national and local economic trends and conditions • value of underlying collateral for collateral-dependent loans • other external factors such as the effects for the current competitive, legal, and regulatory environment The adjusted EL factors by portfolio are then adjusted by a loss emergence period for each loan type. A loss emergence period represents the amount of time between when a loss event first occurs to when it is charged off. The loss emergence period was determined for each loan type based on the Company's historical experience and is validated at least annually. Commercial Loans - Risk Ratings Synovus utilizes two primary methods for risk assessment of the commercial loan portfolio: Single Risk Rating Assessment and Dual Risk Rating (DRR) Assessment. The single and dual risk ratings are based on the borrowers' credit risk profile, considering factors such as debt service history, current and estimated prospective cash flow information, collateral supporting the credit, source of repayment as well as other variables, as appropriate. Each loan is assigned a risk rating during its initial approval process. For single risk rated loans, this process begins with a loan rating recommendation from the loan officer responsible for originating the loan. Commercial single risk rated loans are graded on a 9-point scale. Single risk ratings six through nine are defined consistent with the bank regulatory classifications of special mention, substandard, doubtful, and loss, respectively. The primary determinants of the risk ratings for commercial single risk rated loans are the reliability of the primary source of repayment and the borrower's expected performance (i.e., the likelihood that the borrower will be able to service its obligations in accordance with the terms). Expected performance will be based upon full analysis of the borrower's historical financial results, current financial strength and future prospects, which includes any external drivers. For dual risk rated loans, this process begins with scoring the loan for a rating during its initial approval process. The dual risk rating methodology is used for certain components of the C&I loan portfolio as well as certain income-producing real estate loans. At December 31, 2017 and 2016, approximately $7.6 billion was rated using the DRR methodology. The DRR includes sixteen PD categories and nine categories for estimating losses given an event of default. The result is an EL rate established for each borrower. The loan rating is subject to approvals from other members of management, regional credit and/or loan committees depending on the size of the loan and loan's credit attributes. Loan ratings are regularly re-evaluated based upon annual scheduled credit reviews or on a more frequent basis if determined prudent by management. Additionally, an independent loan review function evaluates Synovus' risk rating processes on a continuous basis. Retail Loans – Risk Ratings Retail loans are generally assigned a risk rating on a 6-point scale at the time of origination based on credit bureau scores, with a loan grade of 1 assigned as the lowest level of risk and a loan grade of 6 as the highest level of risk. At 90-119 days past due, a loan grade of 7-substandard non-accrual rating is applied and at 120 days past due, the loan is generally downgraded to grade 9-loss and is generally charged-off. The credit bureau-based ratings are updated at least semi-annually and the ratings based on the past due status are updated monthly.
Premises and Equipment	Premises and equipment, including bank owned branch locations and leasehold improvements, are reported at cost, less accumulated depreciation and amortization, which are computed using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are depreciated over the shorter of the estimated useful life or the remainder of the lease term. Synovus reviews long-lived assets, such as premises and equipment, for impairment whenever events and circumstances indicate that the carrying amount of an asset may not be recoverable.
Goodwill and Other Intangible Assets	Goodwill represents the excess purchase price over the fair value of identifiable net assets of acquired businesses. Goodwill is tested for impairment at the reporting unit level on an annual basis and as events occur or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. Synovus reviews goodwill for impairment as of June 30 th and at interim periods if indicators of impairment exist. Synovus applies judgment when assessing goodwill for impairment. ASC 350-20-35-3A, Goodwill Subsequent Measurement - Qualitative Assessment, provides the option to perform a qualitative assessment to determine whether the two-step goodwill impairment test is necessary. Beginning in 2017, Synovus applies the qualitative assessment guidance in ASC 350-20-35-3A to determine if the following factors indicate that goodwill is more likely than not impaired: macroeconomic conditions, industry and market considerations, cost factors, overall financial performance, other relevant entity-specific events, events affecting the reporting unit, and common stock share price. Management applies judgment when weighing the factors most likely to impact a reporting unit's fair value. Other intangible assets relate primarily to borrower relationships, trade name, and a distribution network resulting from a business acquisition. These intangible assets are amortized using straight line methods based on the remaining lives of the assets. Amortization periods range from eight to ten years. Amortization periods for intangible assets are monitored to determine if events and circumstances require such periods to be reduced. Intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of the intangible assets is measured by a comparison of the carrying amount of the asset to future undiscounted cash flows expected to be generated by the asset. If such assets are considered impaired, the amount of the impairment to be recognized is measured by the amount by which the carrying value of the assets exceeds the fair value of the assets based on the discounted expected future cash flows to be generated by the assets.
Other Real Estate	Other Real Estate (ORE) consists of properties obtained through a foreclosure proceeding or through an in-substance foreclosure in satisfaction of loans. A loan is classified as an in-substance foreclosure when Synovus has taken possession of the collateral regardless of whether formal foreclosure proceedings have taken place. At foreclosure, ORE is recorded at the lower of cost or fair value less estimated selling costs, which establishes a new cost basis. Subsequent to foreclosure, ORE is evaluated quarterly and reported at fair value less estimated selling costs, not to exceed the new cost basis, determined by review of current appraisals, as well as the review of comparable sales and other estimates of fair value obtained principally from independent sources, adjusted for estimated selling costs. Management also considers other factors or recent developments such as changes in absorption rates or market conditions from the time of the latest appraisal received or previous re-evaluation performed, and anticipated sales values considering management's plans for disposition, which could result in an adjustment to lower the fair value estimates indicated in the appraisals. At the time of foreclosure or initial possession of collateral, any excess of the loan balance over the fair value of the real estate held as collateral, less costs to sell, is recorded as a charge against the allowance for loan losses. Revenue and expenses from ORE operations as well as gains or losses on sales are recorded as foreclosed real estate expense, net, a component of non-interest expense on the consolidated statements of income. Subsequent declines in fair value are recorded on a property-by-property basis through use of a valuation allowance within ORE on the consolidated balance sheets and valuation adjustment account in foreclosed real estate expense, net, a component of non-interest expense on the consolidated statements of income. Synovus' objective is to dispose of ORE properties in a timely manner and to maximize net sale proceeds. Synovus has a centralized managed assets division, with the specialized skill set to facilitate this objective. While there is not a defined timeline for their sale, ORE properties are actively marketed through unaffiliated third parties.
Other Assets	Other assets include accrued interest receivable and other significant balances as described below. More detail of other asset balances can be found in "Part II - Item 8. Financial Statements and Supplementary Data - Note 9 - Other Assets" of this Report. Cash Surrender Value of Bank-Owned Life Insurance Investments in bank-owned life insurance policies on certain current and former officers of Synovus are recorded at the net realizable value of the policies. Net realizable value is the cash surrender value of the policies less any applicable surrender charges and any policy loans. Synovus has not borrowed against the cash surrender value of these policies. Changes in the cash surrender value of the policies are recognized as a component of other non-interest income in the consolidated statements of income. Investments in Federal Reserve Bank and Federal Reserve Home Loan Bank Stock On November 17, 2016, Synovus Bank made an investment of $97.3 million in Federal Reserve Bank capital stock and became a member of the Federal Reserve System. Synovus held stock in the Federal Reserve Bank totaling $95.6 million at December 31, 2017 and $98.6 million at December 31, 2016 . Synovus also held stock in the FHLB of Atlanta totaling $63.9 million at December 31, 2017 and $71.3 million at December 31, 2016 . The Federal Reserve Bank and FHLB stocks are recorded at amortized cost. The investment in FHLB stock is required for membership in the FHLB system and in relation to the level of FHLB outstanding borrowings. Investments in Affordable Housing Tax Credit Partnerships Synovus applies the proportional amortization method of accounting for its qualified affordable housing investments. The proportional amortization method recognizes the amortized cost of the investment as a component of income tax expense. For affordable housing investments which do not qualify for application of the proportional amortization method of accounting, Synovus applies the equity method of accounting. The equity method recognizes income or loss from affordable housing investments as a component of other non-interest income. GGL/SBA Loans Servicing Asset Synovus has retained servicing responsibilities on sold GGL/SBA loans and receives a servicing fee. The servicing asset is established at fair value at the time of the sale based on an analysis of future cash flows that incorporates estimates for discount rates, prepayment speeds, and delinquency rates. The servicing asset is measured at fair value with changes in fair value included with the associated servicing fee in other non-interest income. Prior to 2017, Synovus accounted for the GGL/SBA loans servicing asset using the amortization method. Private Equity Investments Private equity investments are recorded at fair value on the consolidated balance sheets with realized and unrealized gains and losses recorded on the consolidated statements of income (as a component of other non-interest income). The private equity investments in which Synovus holds a limited partner interest consist of funds that invest in privately held companies. For privately held companies in the fund, the general partner estimates the fair value of the company. The estimated fair value of the company is the estimated fair value as an exit price the fund would receive if it were to sell the company in the marketplace. The fair value of the fund's underlying investments is estimated through the use of valuation models, such as option pricing or a discounted cash flow model. Valuation factors, such as a company's financial performance against budget or milestones, last price paid by investors, with consideration given on whether financing is provided by insiders or unrelated new investors, public market comparables, liquidity of the market, industry and economic trends, and changes in management or key personnel, are used in the determination of estimated fair value. Other Assets Held for Sale Other assets held for sale consist of certain premises and equipment held for sale, including those related to the efficiency initiatives discussed in "Note 3 - Restructuring Charges" of this Report. These assets are classified as held for sale and recorded at the lower of their amortized cost or fair value, less costs to sell, consistent with ASC 360-10. The fair value of these assets is determined primarily on the basis of appraisals or BOV, as circumstances warrant, adjusted for estimated selling costs. Both techniques engage licensed or certified professionals that use inputs such as absorption rates, capitalization rates, and market comparables.
Derivative Instruments	Synovus’ risk management policies emphasize the management of interest rate risk within acceptable guidelines. Synovus’ objective in maintaining these policies is to limit volatility in net interest income arising from changes in interest rates. Risks to be managed include both fair value and cash flow risks. Utilization of derivative financial instruments provides a valuable tool to assist in the management of these risks. All derivative instruments are recorded on the consolidated balance sheets at their respective fair values, as components of other assets and other liabilities. The accounting for changes in fair value (i.e., unrealized gains or losses) of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, on the reason for holding it. If certain conditions are met, entities may elect to designate a derivative instrument as a hedge of exposures to changes in fair values, cash flows, or foreign currencies. If the hedged exposure is a fair value exposure, the unrealized gain or loss on the derivative instrument is recognized in earnings in the period of change, together with the offsetting unrealized loss or gain on the hedged item attributable to the risk being hedged as a component of other non-interest income on the consolidated statements of income. If the hedged exposure is a cash flow exposure, the effective portion of the gain or loss on the derivative instrument is reported initially as a component of accumulated other comprehensive income (loss), net of the tax impact, and subsequently reclassified into earnings when the hedged transaction affects earnings. Any amounts excluded from the assessment of hedge effectiveness, as well as the ineffective portion of the gain or loss on the derivative instrument, are reported in earnings immediately as a component of other non-interest income on the consolidated statements of income. If the derivative instrument is not designated as a hedge, the gain or loss on the derivative instrument is recognized in earnings as a component of other non-interest income on the consolidated statements of income in the period of change. Synovus also holds derivative instruments, which consist of interest rate lock agreements related to expected funding of fixed-rate mortgage loans to customers (interest rate lock commitments) and forward commitments to sell mortgage-backed securities and individual fixed-rate mortgage loans. Synovus’ objective in obtaining the forward commitments is to mitigate the interest rate risk associated with the interest rate lock commitments and the mortgage loans that are held for sale. Both the interest rate lock commitments and the forward commitments are reported at fair value, with adjustments recorded in current period earnings in mortgage banking income. Synovus also enters into interest rate swap agreements to facilitate the risk management strategies of certain commercial banking customers. Synovus mitigates this risk by entering into equal and offsetting interest rate swap agreements with highly rated third-party financial institutions. The interest rate swap agreements are free-standing derivatives and are recorded at fair value with any unrealized gain or loss recorded in current period earnings in other non-interest income. These instruments, and their offsetting positions, are recorded in other assets and other liabilities on the consolidated balance sheets.
Non-interest Income	Service Charges on Deposit Accounts Service charges on deposit accounts consist of NSF fees, account analysis fees, and other service charges on deposits which consist primarily of monthly account fees. NSF fees are recognized at the time when the account overdraft occurs in accordance with regulatory guidelines. Account analysis fees consist of fees charged to certain commercial demand deposit accounts based upon account activity (and reduced by a credit which is based upon cash levels in the account). These fees, as well as monthly account fees, are recorded under the accrual method of accounting. Fiduciary and Asset Management Fees Fiduciary and asset management fees are generally determined based upon fair values of assets under management as of a specified date during the period. These fees are recorded under the accrual method of accounting as the services are performed. Brokerage Revenue Brokerage revenue consists primarily of commission income, which represents the spread between buy and sell transactions processed, and net fees charged to customers on a transaction basis for buy and sell transactions processed. Commission income is recorded on a trade-date basis. Brokerage revenue includes portfolio management fees, which represent monthly fees charged on a contractual basis to customers for the management of their investment portfolios and are recorded under the accrual method of accounting. Brokerage revenue also includes investment banking revenue, which includes fees for services arising from securities offerings or placements in which Synovus acts as an agent as well as fees earned from providing advisory services. Revenue is recognized at the time the underwriting is completed and the revenue is reasonably determinable. Bankcard Fees Bankcard fees consist primarily of interchange fees earned, net of fees paid, on debit card and credit card transactions. Net fees are recognized into income as they are collected.
Advertising Expenses	Advertising costs are expensed as incurred and recorded as a component of non-interest expense.
Income Taxes	Synovus is a domestic corporation that files a consolidated federal income tax return with its wholly-owned subsidiaries and files state income tax returns on a consolidated or separate entity basis with the various taxing jurisdictions based on its taxable presence. The current income tax payable or receivable is an estimate of the amounts currently owed to or due from taxing authorities in which Synovus conducts business. It also includes increases and decreases in the amount of taxes payable for uncertain tax positions reported in tax returns for the current and/or prior years. Synovus uses the asset and liability method to account for future income taxes expected to be paid or received (i.e., deferred income taxes). Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement (GAAP) carrying amounts of existing assets and liabilities and their respective tax bases, including operating losses and tax credit carryforwards. The deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in income tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is required for deferred tax assets if, based on available evidence, it is more likely than not that all or some portion of the asset will not be realized. In making this assessment, all sources of taxable income available to realize the deferred tax asset are considered, including taxable income in prior carryback years, future reversals of existing temporary differences, tax planning strategies, and future taxable income exclusive of reversing temporary differences and carryforwards. The predictability that future taxable income, exclusive of reversing temporary differences, will occur is the most subjective of these four sources. Changes in the valuation allowance are recorded through income tax expense. Significant estimates used in accounting for income taxes relate to the valuation allowance for deferred tax assets, estimates of the realizability of income tax credits, utilization of net operating losses, the determination of taxable income, and the determination of temporary differences between book and tax bases. Synovus accrues tax liabilities for uncertain income tax positions based on current assumptions regarding the expected outcome by weighing the facts and circumstances available at the reporting date. If related tax benefits of a transaction are not more likely than not of being sustained upon examination, Synovus will accrue a tax liability or reduce a deferred tax asset for the expected tax impact associated with the transaction. Events and circumstances may alter the estimates and assumptions used in the analysis of its income tax positions and, accordingly, Synovus' effective tax rate may fluctuate in the future. Synovus recognizes accrued interest and penalties related to unrecognized income tax benefits as a component of income tax expense. Synovus applies the proportional amortization method in accounting for its qualified affordable housing tax credit investments. This method recognizes the amortized cost of the investment as a component of income tax expense. On December 22, 2017, H.R.1, formerly known as the Tax Cuts and Jobs Act of 2017 (Federal Tax Reform), was enacted into law. The new legislation included a decrease in the corporate federal income tax rate from 35% to 21% effective January 1, 2018. Under ASC 740, the effects of the changes in tax rates and laws are recognized in the period in which the new legislation is enacted. Therefore, Synovus was required to remeasure its deferred tax assets and liabilities and record the adjustment to income tax expense effective December 22, 2017. In December 2017, the SEC issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), which allows companies to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. Since the Federal Tax Reform was enacted late in 2017, management expects that certain deferred tax assets and liabilities will continue to be evaluated in the context of Federal Tax Reform through the date of the filing of our 2017 federal income tax return, and may change as a result of evolving management interpretations, elections, and assumptions, as well as new guidance that may be issued by the Internal Revenue Service. Accordingly, the federal income tax expense of $47.2 million recorded in 2017 relating to the effects from Federal Tax Reform is considered provisional. Management expects to complete its analysis within the measurement period in accordance with SAB 118.
Share-based Compensation	Synovus has a long-term incentive plan under which the Compensation Committee of the Board of Directors has the authority to grant share-based awards to Synovus employees. Synovus' share-based compensation costs associated with employee grants are recorded as a component of salaries and other personnel expense in the consolidated statements of income. Share-based compensation costs associated with grants made to non-employee directors of Synovus are recorded as a component of other operating expenses. Share-based compensation expense for service-based awards that contain a graded vesting schedule is recognized net of estimated forfeitures for plan participants on a straight-line basis over the requisite service period for the entire award. The non-employee director restricted share units become fully vested and transferable upon the earlier to occur of the completion of three years of service or the date the holder reaches the mandatory retirement age, as set forth in the Company's Corporate Governance Guidelines. Thus, share-based compensation expense for non-employee awards is recognized over the shorter of three years or mandatory retirement.
Earnings Per Share	Basic net income per common share is computed by dividing net income available to common shareholders by the average common shares outstanding for the period. Diluted net income per common share reflects the dilution that could occur if securities or other contracts to issue common stock were exercised or converted. The dilutive effect of outstanding options and restricted share units is reflected in diluted net income per common share, unless the impact is anti-dilutive, by application of the treasury stock method.
Fair Value Measurements and Disclosures	Fair value estimates are made at a specific point in time, based on relevant market information and other information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale, at one time, the entire holdings of a particular financial instrument. Because no market exists for a portion of the financial instruments, fair value estimates are also based on judgments regarding estimated cash flows, current economic conditions, risk characteristics of various financial instruments, and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and, therefore, cannot be determined with precision. Changes in assumptions could significantly affect the estimates. Synovus employs independent third-party pricing services to provide fair value estimates for its investment securities available for sale, trading account assets, and derivative financial instruments. Fair values for fixed income investment securities and certain derivative financial instruments are typically the prices supplied by either the third-party pricing service or an unrelated counterparty, which utilize quoted market prices, broker/dealer quotations for identical or similar securities, and/or inputs that are observable in the market, either directly or indirectly, for substantially similar securities. Level 1 securities are typically exchange quoted prices. Level 2 securities are typically matrix priced by a third-party pricing service to calculate the fair value. Such fair value measurements consider observable data, such as market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayments speeds, credit information, and the respective terms and conditions for debt instruments. Level 3 instruments' value is determined using pricing models, discounted cash flow models and similar techniques, and may also include the use of market prices of assets or liabilities that are not directly comparable to the subject asset or liability. These methods of valuation may result in a significant portion of the fair value being derived from unobservable assumptions that reflect Synovus' own estimates for assumptions that market participants would use in pricing the asset or liability. Management uses various validation procedures to validate the prices received from pricing services and quotations received from dealers are reasonable for each relevant financial instrument, including reference to other market information and a review of valuations and trade activity of comparable securities. Consideration is given to the nature of the quotes (e.g., indicative or firm) and the relationship of recently evidenced market activity to the prices provided by the third-party pricing service. Further, management also employs the services of an additional independent pricing firm as a means to verify and confirm the fair values of its primary independent pricing firm. Understanding the third-party pricing service's valuation methods, assumptions and inputs used by the firm is an important part of the process of determining that reasonable and reliable fair values are being obtained. Management evaluates quantitative and qualitative information provided by the third-party pricing services to assess whether they continue to exhibit the high level of expertise and internal controls that management relies upon. Fair value estimates are based on existing financial instruments on the consolidated balance sheet, without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. Significant assets and liabilities that are not considered financial instruments include deferred income taxes, premises and equipment, equity method investments, goodwill and other intangible assets. In addition, the income tax ramifications related to the realization of the unrealized gains and losses on available for sale investment securities can have a significant effect on fair value estimates and have not been considered in any of the estimates.
Contingent Liabilities and Legal Costs	Synovus estimates its contingent liabilities with respect to outstanding legal matters based on information currently available to management, management’s estimates about the probability of outcomes of each case and the advice of legal counsel. Management accrues an estimated loss from a loss contingency when information available indicates that it is probable that a loss has been incurred and the amount of the loss can be reasonably estimated. In addition, it must be probable that one or more future events will occur confirming the fact of the loss. Significant judgment is required in making these estimates and management must make assumptions about matters that are highly uncertain. Accordingly, the actual loss may be more or less than the current estimate. In many situations, Synovus may be unable to estimate reasonably possible losses due to the preliminary nature of the legal matters, as well as a variety of other factors and uncertainties. As there are further developments, Synovus will reassess these legal matters and the related potential liabilities and will revise, when needed, its estimate of contingent liabilities. Legal costs, including attorney fees, incurred in connection with pending litigation and other loss contingencies are expensed as incurred.
Recently Adopted and Issued Accounting Standards Updates	Recently Adopted Accounting Standards Updates Effective January 1, 2017, Synovus adopted ASU 2016-09, Compensation - Stock Compensation: Improvements to Employee Share-Based Payment Accounting, which simplified 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. Prior to 2017, tax benefits in excess of compensation cost (“windfalls”) and tax deficiencies (“shortfalls”) were recorded in equity. During the year ended December 31, 2017, Synovus recognized $5.0 million of income tax benefits from excess tax benefits that occurred during the year from the vesting of restricted share units and exercise of stock options. As of January 1, 2017, 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. Effective January 1, 2017, Synovus adopted the provisions of ASU 2016-15, Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments . Adoption of the ASU resulted in the classification of the earnout liability payments as cash outflows for financing activities as well as a reclassification of bank owned life insurance cash settlements from cash from operating activities to cash from investing activities. Recently Issued Accounting Standards Updates The following ASUs will be implemented effective January 1, 2018 or later: ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. In February 2018, the FASB issued final guidance on reclassification of tax effects stranded in other comprehensive income due to Federal Tax Reform. The guidance provides entities the option to reclassify the tax effects that are stranded in accumulated other comprehensive income (AOCI) as a result of Federal Tax Reform to retained earnings. The guidance is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. In the period of adoption, an entity can elect to apply the amendments retrospectively to each period in which the effect of the change in the federal income tax rate due to Federal Tax Reform is recognized, or apply the amendments in that reporting period. An entity that elects to record the adjustment in the period of adoption will make an adjustment in the statement of shareholders’ equity as of the beginning of the reporting period. For Synovus, tax effects stranded in AOCI due to Federal Tax Reform totaled $7.8 million at December 31, 2017, and they relate to unrealized losses on the available-for-sale investment securities portfolio. Synovus will elect to apply the guidance during the reporting period ending on March 31, 2018, and record the reclassification adjustment in the period of adoption. The reclassification adjustment will result in an increase to retained earnings as of January 1, 2018 of $7.8 million and a corresponding decrease to accumulated other comprehensive income for the same amount. The reclassification adjustment will increase regulatory capital by $7.8 million , resulting in an approximate 3 b.p.s increase to Tier 1 capital, common equity Tier 1 capital, and total risk based capital ratios, and an approximate 2 b.p.s increase to the leverage ratio. ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities. In January 2016, the FASB issued new accounting guidance related to financial instruments. The guidance requires entities to measure equity investments (except those accounted for under the equity method of accounting or consolidated) at fair value, and record changes in fair value as a component of net income. For financial instruments recorded at amortized cost, the new guidance requires public companies to disclose the fair values using the exit price concept prescribed by ASC 820-10, and eliminates the disclosure requirements related to measurement assumptions. The new guidance also requires separate presentation of financial assets and liabilities based on form and measurement category. The guidance is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Synovus currently accounts for all of its equity investments under the equity method of accounting; therefore, the provisions of the new accounting guidance do not impact Synovus’ accounting for existing equity investments. With respect to the provisions related to financial instruments recorded at amortized cost, Synovus is in the process of evaluating changes needed to the valuation of its loan portfolio to conform to the exit price requirements of the new guidance. Synovus’ current method to estimate the fair value of its loan portfolio does not incorporate the exit price concept of fair value. Management currently expects that the fair value under the exit price concept could result in a lower fair value as compared to the current method. However, management has not yet determined the impact to the fair value estimates as a result of incorporating the exit price concept. Determination of the fair value under the exit price method will require judgment because substantially all of the loans within the loan portfolio do not have observable market prices. The adoption of this guidance will result in the use of the exit price concept for determining the fair value of the loan portfolio for disclosure purposes only. ASU 2016-13, Financial Instruments--Credit Losses (CECL). In June 2016, the FASB issued the new guidance related to credit losses. The new guidance replaces the existing incurred loss impairment guidance with a single expected credit loss methodology. The new guidance will require management’s estimate of credit losses over the full remaining expected life of loans and other financial instruments. For Synovus, the standard will apply to loans, unfunded loan commitments, and debt securities available for sale. The standard is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted on January 1, 2019. Upon adoption, Synovus will record a cumulative effect adjustment to retained earnings as of the beginning of the reporting period of adoption. Synovus has begun its implementation efforts which are led by a cross-functional steering committee. Management expects that the allowance for loan losses will be higher under the new standard; however, management is still in the process of determining the magnitude of the impact on its financial statements and regulatory capital ratios. Additionally, the extent of the expected increase on the allowance for loan losses will depend upon the composition of the loan portfolio upon adoption of the standard, as well as economic conditions and forecasts at that time. ASU 2016-02, Leases. In February 2016, the FASB issued ASU 2016-02, its new standard on lease accounting. ASU 2016-02 introduces a lessee model that brings most leases on the balance sheet. Under the new standard, all lessees will recognize a right-of-use asset and a lease liability, including operating leases, with a lease term greater than 12 months. From a lessor perspective, the accounting model is largely unchanged, though the new standard does include certain targeted improvements to align, where necessary, lessor accounting with the lessee accounting model and the revenue recognition guidance in ASC Topic 606 (those related to evaluating when profit can be recognized). For Synovus, the impact of this ASU will primarily relate to its accounting and reporting of leases as a lessee. The new ASU will be effective for Synovus beginning January 1, 2019. A modified retrospective approach is required at adoption which requires all prior periods presented in the financial statements to be restated with a cumulative effect adjustment to retained earnings as of the beginning of the earliest period presented. The standard also requires additional disclosures regarding leasing arrangements. Synovus is currently evaluating the potential financial statement impact from the implementation of this standard by reviewing its existing lease contracts and other contracts that may include embedded leases. Synovus currently expects to recognize lease liabilities and corresponding right-of-use assets (at their present value) related to substantially all of the $230 million of future minimum lease commitments as disclosed in Note 7. However, the population of contracts requiring balance sheet recognition and their initial measurement continues to be under evaluation. ASU 2014-09, Revenue from Contracts with Customers . In May 2014, the FASB issued new accounting guidance for recognizing revenue from contracts with customers, which is effective on January 1, 2018. ASU 2014-09 and subsequent related updates establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The standard is intended to increase comparability across industries. The core principle of the revenue model is that a company will recognize revenue when it transfers control of goods or services to customers at an amount that reflects the consideration to which it expects to be entitled in exchange for those goods or services. The scope of the guidance explicitly excludes net interest income as well as many other revenues from financial assets. Synovus completed its assessment of revenue contracts as of December 31, 2017. Based on this review, management did not identify material changes to the timing or amount of revenue recognition. Synovus adopted these ASUs on January 1, 2018 using the modified retrospective method of adoption. The adoption resulted in an immaterial cumulative effect adjustment to the opening balance of retained earnings. In connection with the adoption of this standard, Synovus will provide new footnote disclosures beginning in the first quarter of 2018 Form 10-Q, including expanded disaggregated non-interest income disclosures. Additionally, the following ASUs will be implemented effective January 1, 2018 or later but are not expected to have a significant impact on Synovus' consolidated financial statements: • ASU 2016-18, Statement of Cash Flows-Restricted Cash • ASU 2017-12, Derivatives and Hedging • ASU 2017-08, Receivables-Nonrefundable Fees and Other Costs: Premium Amortization on Purchased Callable Debt Securities • ASU 2017-05, Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets, Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets • ASU 2017-04, Intangibles-Goodwill and Other, Simplifying the Test for Goodwill Impairment • ASU 2017-01, Business Combinations-Clarifying the Definition of a Business
Reclassifications	Prior years' consolidated financial statements are reclassified whenever necessary to conform to the current year's presentation.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Business Acquisition	Global One Acquisition Date (in thousands) Fair Value Assets acquired: Cash and due from banks $ 9,554 Commercial and industrial loans (1) 357,307 Goodwill (2) 32,884 Other intangible assets 12,500 Other assets 3,681 Total assets acquired $ 415,926 Liabilities assumed: Notes payable (3) $ 358,560 Earnout liability 12,234 Deferred tax liability, net 3,229 Other liabilities 11,903 Total liabilities assumed $ 385,926 Consideration paid $ 30,000 Cash paid $ 3,408 Fair value of common stock issued 26,592 (1) The unpaid principal balance of the loans was $356.7 million . (2) The goodwill is not expected to be deductible for tax purposes. (3) The unpaid principal balance of the notes payable was $357.0 million .

Restructuring Charges (Tables)

Restructuring Charges (Tables)	12 Months Ended
	Dec. 31, 2017
Restructuring Charges [Abstract]
Schedule of Restructuring and Related Costs	For the years ended December 31, 2017 , 2016 , and 2015 total restructuring charges consist of the following components: Years Ended December 31, (in thousands) 2017 2016 2015 Severance charges $ 6,128 $ — $ — Asset impairment charges 715 8,107 229 Gain on sale of assets held for sale, net (4 ) — (401 ) Other charges 175 160 208 Total restructuring charges $ 7,014 $ 8,267 $ 36 The following table presents aggregate activity associated with accruals that resulted from the restructuring charges recorded during the years ended December 31, 2017 , 2016 , and 2015 : (in thousands) Severance Charges Lease Termination Charges Total Balance at December 31, 2014 $ 3,291 $ 5,539 $ 8,830 Accruals for lease terminations — (3 ) (3 ) Payments (1,361 ) (849 ) (2,210 ) Balance at December 31, 2015 1,930 4,687 6,617 Accruals for lease terminations — 6 6 Payments (1,849 ) (725 ) (2,574 ) Balance at December 31, 2016 81 3,968 4,049 Accruals for voluntary and involuntary termination benefits 6,128 — 6,128 Payments (5,873 ) (692 ) (6,565 ) Balance at December 31, 2017 $ 336 $ 3,276 $ 3,612

Investment Securities Availab38

Investment Securities Available for Sale (Tables)	12 Months Ended
	Dec. 31, 2017
Investments [Abstract]
Summary of Available-for-Sale Investment Securities	The amortized cost, gross unrealized gains and losses, and estimated fair values of investment securities available for sale at December 31, 2017 and 2016 are summarized below. December 31, 2017 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 83,608 $ — $ (934 ) $ 82,674 U.S. Government agency securities 10,771 91 — 10,862 Mortgage-backed securities issued by U.S. Government agencies 121,283 519 (1,362 ) 120,440 Mortgage-backed securities issued by U.S. Government sponsored enterprises 2,666,818 5,059 (31,354 ) 2,640,523 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 1,135,259 144 (23,404 ) 1,111,999 State and municipal securities 180 — — 180 Corporate debt and other securities 20,320 294 (223 ) 20,391 Total investment securities available for sale $ 4,038,239 $ 6,107 $ (57,277 ) $ 3,987,069 December 31, 2016 (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 108,221 $ 225 $ (644 ) $ 107,802 U.S. Government agency securities 12,727 266 — 12,993 Mortgage-backed securities issued by U.S. Government agencies 174,440 1,116 (1,354 ) 174,202 Mortgage-backed securities issued by U.S. Government sponsored enterprises 2,543,495 5,416 (42,571 ) 2,506,340 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 905,789 1,214 (16,561 ) 890,442 State and municipal securities 2,780 14 — 2,794 Equity securities 919 2,863 — 3,782 Corporate debt and other securities 20,247 — (407 ) 19,840 Total investment securities available for sale $ 3,768,618 $ 11,114 $ (61,537 ) $ 3,718,195
Schedule of Unrealized Loss on Investments	Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2017 and December 31, 2016 are presented below. December 31, 2017 Less than 12 Months 12 Months or Longer Total (in thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses U.S. Treasury securities $ 34,243 $ 443 $ 29,562 $ 491 $ 63,805 $ 934 Mortgage-backed securities issued by U.S. Government agencies 36,810 357 55,740 1,005 92,550 1,362 Mortgage-backed securities issued by U.S. Government sponsored enterprises 1,271,012 10,263 929,223 21,091 2,200,235 31,354 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 653,781 9,497 426,237 13,907 1,080,018 23,404 Corporate debt and other securities — — 5,097 223 5,097 223 Total $ 1,995,846 $ 20,560 $ 1,445,859 $ 36,717 $ 3,441,705 $ 57,277 December 31, 2016 Less than 12 Months 12 Months or Longer Total (in thousands) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses U.S Treasury securities $ 64,023 $ 644 $ — $ — $ 64,023 $ 644 Mortgage-backed securities issued by U.S. Government agencies 128,121 1,240 3,626 114 131,747 1,354 Mortgage-backed securities issued by U.S. Government sponsored enterprises 2,123,181 42,571 — — 2,123,181 42,571 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises 682,492 15,653 24,801 908 707,293 16,561 Corporate debt and other securities 14,952 48 4,888 359 19,840 407 Total $ 3,012,769 $ 60,156 $ 33,315 $ 1,381 $ 3,046,084 $ 61,537
Amortized Cost and Estimated Fair Value by Contractual Maturity of Investment Securities Available-for-Sale	For purposes of the maturity table, mortgage-backed securities and CMOs, which are not due at a single maturity date, have been classified based on the final contractual maturity date. Distribution of Maturities at December 31, 2017 (in thousands) Within One Year 1 to 5 Years 5 to 10 Years More Than 10 Years No Stated Maturity Total Amortized Cost U.S. Treasury securities $ 18,870 $ 64,738 $ — $ — $ — $ 83,608 U.S. Government agency securities 2,331 6,437 2,003 — — 10,771 Mortgage-backed securities issued by U.S. Government agencies — — 31,259 90,024 — 121,283 Mortgage-backed securities issued by U.S. Government sponsored enterprises 18 1,838 434,603 2,230,359 — 2,666,818 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — — 19,769 1,115,490 — 1,135,259 State and municipal securities 180 — — — — 180 Corporate debt and other securities — — 15,000 2,000 3,320 20,320 Total amortized cost $ 21,399 $ 73,013 $ 502,634 $ 3,437,873 $ 3,320 $ 4,038,239 Fair Value U.S. Treasury securities $ 18,870 $ 63,804 $ — $ — $ — $ 82,674 U.S. Government agency securities 2,360 6,459 2,043 — — 10,862 Mortgage-backed securities issued by U.S. Government agencies — — 31,193 89,247 — 120,440 Mortgage-backed securities issued by U.S. Government sponsored enterprises 18 1,928 430,140 2,208,437 — 2,640,523 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — — 19,366 1,092,633 — 1,111,999 State and municipal securities 180 — — — — 180 Corporate debt and other securities — — 15,294 1,935 3,162 20,391 Total fair value $ 21,428 $ 72,191 $ 498,036 $ 3,392,252 $ 3,162 $ 3,987,069
Summary of Sales Transactions in the Investment Securities Available-for-Sale Portfolio	The specific identification method is used to reclassify gains and losses out of other comprehensive income at the time of sale. (in thousands) 2017 2016 2015 Proceeds from sales of investment securities available for sale $ 812,293 $ 968,606 $ 347,954 Gross realized gains on sales (1) $ 7,942 $ 9,586 $ 4,356 Gross realized losses on sales (8,231 ) (3,575 ) (1,587 ) Investment securities (losses) gains, net $ (289 ) $ 6,011 $ 2,769 (1) Includes $1.4 million in gains in 2016 from the transfer of $1.9 million of investment securities available for sale to trading account assets.

Loans And Allowance For Loan 39

Loans And Allowance For Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2017
Loans and Allowance for Loan Losses [Abstract]
Loans Outstanding by Classification	Loans outstanding, by classification, at December 31, 2017 and 2016 are summarized below. December 31, (in thousands) 2017 2016 Investment properties $ 5,670,065 $ 5,869,261 1-4 family properties 781,619 888,553 Land and development 483,604 616,298 Total commercial real estate 6,935,288 7,374,112 Commercial, financial and agricultural 7,179,487 6,909,036 Owner-occupied 4,844,163 4,634,770 Total commercial and industrial 12,023,650 11,543,806 Home equity lines 1,514,227 1,617,265 Consumer mortgages 2,633,503 2,296,604 Credit cards 232,676 232,413 Other consumer loans 1,473,451 818,182 Total consumer 5,853,857 4,964,464 Total loans 24,812,795 23,882,382 Deferred fees and costs, net (25,331 ) (25,991 ) Total loans, net of deferred fees and costs $ 24,787,464 $ 23,856,391
Schedule of Current, Accruing Past Due, and Nonaccrual Loans	The following is a summary of current, accruing past due, and non-accrual loans by class as of December 31, 2017 and 2016 . Current, Accruing Past Due, and Non-accrual Loans December 31, 2017 ( in thousands) Current Accruing 30-89 Days Past Due Accruing 90 Days or Greater Past Due Total Accruing Past Due Non-accrual Total Investment properties $ 5,663,665 $ 2,506 $ 90 $ 2,596 $ 3,804 $ 5,670,065 1-4 family properties 775,023 3,545 202 3,747 2,849 781,619 Land and development 476,131 1,609 67 1,676 5,797 483,604 Total commercial real estate 6,914,819 7,660 359 8,019 12,450 6,935,288 Commercial, financial and agricultural 7,097,127 11,214 1,016 12,230 70,130 7,179,487 Owner-occupied 4,830,150 6,880 479 7,359 6,654 4,844,163 Total commercial and industrial 11,927,277 18,094 1,495 19,589 76,784 12,023,650 Home equity lines 1,490,808 5,629 335 5,964 17,455 1,514,227 Consumer mortgages 2,622,061 3,971 268 4,239 7,203 2,633,503 Credit cards 229,015 1,930 1,731 3,661 — 232,676 Other consumer loans 1,461,223 10,333 226 10,559 1,669 1,473,451 Total consumer 5,803,107 21,863 2,560 24,423 26,327 5,853,857 Total loans $ 24,645,203 $ 47,617 $ 4,414 $ 52,031 $ 115,561 $ 24,812,795 (1) December 31, 2016 ( in thousands) Current Accruing 30-89 Days Past Due Accruing 90 Days or Greater Past Due Total Accruing Past Due Non-accrual Total Investment properties $ 5,861,198 $ 2,795 $ — $ 2,795 $ 5,268 $ 5,869,261 1-4 family properties 874,477 4,801 161 4,962 9,114 888,553 Land and development 598,624 1,441 — 1,441 16,233 616,298 Total commercial real estate 7,334,299 9,037 161 9,198 30,615 7,374,112 Commercial, financial and agricultural 6,839,700 9,542 720 10,262 59,074 6,909,036 Owner-occupied 4,600,110 17,913 244 18,157 16,503 4,634,770 Total commercial and industrial 11,439,810 27,455 964 28,419 75,577 11,543,806 Home equity lines 1,585,228 10,013 473 10,486 21,551 1,617,265 Consumer mortgages 2,265,966 7,876 81 7,957 22,681 2,296,604 Credit cards 229,177 1,819 1,417 3,236 — 232,413 Other consumer loans 809,418 5,771 39 5,810 2,954 818,182 Total consumer 4,889,789 25,479 2,010 27,489 47,186 4,964,464 Total loans $ 23,663,898 $ 61,971 $ 3,135 $ 65,106 $ 153,378 $ 23,882,382 (2) (1) Total before net deferred fees and costs of $25.3 million . (2) Total before net deferred fees and costs of $26.0 million .
Loan Portfolio Credit Exposure	In the following tables, consumer loans are generally assigned a risk grade similar to the classifications described above; however, upon reaching 90 days and 120 days past due, they are generally downgraded to Substandard and Loss, respectively, in accordance with the FFIEC Uniform Retail Credit Classification and Account Management Policy. Additionally, in accordance with the Interagency Supervisory Guidance on Allowance for Loan and Lease Losses Estimation Practices for Loans and Lines of Credit Secured by Junior Liens on 1-4 Family Residential Properties, the risk grade classifications of consumer loans (home equity lines and consumer mortgages) secured by junior liens on 1-4 family residential properties also consider available information on the payment status of the associated senior lien with other financial institutions. Loan Portfolio Credit Exposure by Risk Grade December 31, 2017 (in thousands) Pass Special Mention Substandard (1) Doubtful (2) Loss Total Investment properties $ 5,586,792 $ 64,628 $ 18,645 $ — $ — $ 5,670,065 1-4 family properties 745,299 19,419 16,901 — — 781,619 Land and development 431,759 33,766 14,950 3,129 — 483,604 Total commercial real estate 6,763,850 117,813 50,496 3,129 — 6,935,288 Commercial, financial and agricultural 6,929,506 115,912 132,818 1,251 — 7,179,487 Owner-occupied 4,713,877 50,140 80,073 73 — 4,844,163 Total commercial and industrial 11,643,383 166,052 212,891 1,324 — 12,023,650 Home equity lines 1,491,105 — 21,079 285 1,758 (3) 1,514,227 Consumer mortgages 2,622,499 — 10,607 291 106 (3) 2,633,503 Credit cards 230,945 — 399 — 1,332 (4) 232,676 Other consumer loans 1,470,944 — 2,168 329 10 (3) 1,473,451 Total consumer 5,815,493 — 34,253 905 3,206 5,853,857 Total loans $ 24,222,726 $ 283,865 $ 297,640 $ 5,358 $ 3,206 $ 24,812,795 (5) December 31, 2016 (in thousands) Pass Special Mention Substandard (1) Doubtful (2) Loss Total Investment properties $ 5,794,626 $ 43,336 $ 31,299 $ — $ — $ 5,869,261 1-4 family properties 827,557 33,928 26,790 278 — 888,553 Land and development 521,745 60,205 27,361 6,987 — 616,298 Total commercial real estate 7,143,928 137,469 85,450 7,265 — 7,374,112 Commercial, financial and agricultural 6,635,757 126,268 140,425 6,445 141 (3) 6,909,036 Owner-occupied 4,461,174 60,856 111,330 1,410 — (3) 4,634,770 Total commercial and industrial 11,096,931 187,124 251,755 7,855 141 11,543,806 Home equity lines 1,589,199 — 22,774 2,892 2,400 (3) 1,617,265 Consumer mortgages 2,271,916 — 23,268 1,283 137 (3) 2,296,604 Credit cards 230,997 — 637 — 779 (4) 232,413 Other consumer loans 814,843 — 3,233 42 64 (3) 818,182 Total consumer 4,906,955 — 49,912 4,217 3,380 4,964,464 Total loans $ 23,147,814 $ 324,593 $ 387,117 $ 19,337 $ 3,521 $ 23,882,382 (6) (1) Includes $190.6 million and $256.6 million of Substandard accruing loans at December 31, 2017 and December 31, 2016 , respectively. (2) The loans within this risk grade are on non-accrual status and generally have an allowance for loan losses equal to 50% of the loan amount. (3) The loans within this risk grade are on non-accrual status and have an allowance for loan losses equal to the full loan amount. (4) Represent amounts that were 120 days past due. These credits are downgraded to the Loss category with an allowance for loan losses equal to the full loan amount and are generally charged off upon reaching 181 days past due in accordance with the FFIEC Uniform Retail Credit Classification and Account Management Policy. (5) Total before net deferred fees and costs of $25.3 million . (6) Total before net deferred fees and costs of $26.0 million .
Schedule of Allowances for Loan Losses and Recorded Investment in Loans	The following table details the change in the allowance for loan losses by loan segment for the years ended December 31, 2017 , 2016 and 2015 . As Of and For The Year Ended December 31, 2017 (in thousands) Commercial Real Estate Commercial & Industrial Consumer Total Allowance for loan losses Beginning balance $ 81,816 $ 125,778 $ 44,164 $ 251,758 Charge-offs (12,193 ) (49,244 ) (28,982 ) (90,419 ) Recoveries 8,026 6,685 6,033 20,744 Provision for loan losses (2,651 ) 43,584 26,252 67,185 Ending balance (4) $ 74,998 $ 126,803 $ 47,467 $ 249,268 Ending balance: individually evaluated for impairment $ 4,240 $ 9,515 $ 1,153 $ 14,908 Ending balance: collectively evaluated for impairment $ 70,758 $ 117,288 $ 46,314 $ 234,360 Loans Ending balance: total loans (1) (4) $ 6,935,288 $ 12,023,650 $ 5,853,857 $ 24,812,795 Ending balance: individually evaluated for impairment $ 56,896 $ 111,334 $ 32,056 $ 200,286 Ending balance: collectively evaluated for impairment $ 6,878,392 $ 11,912,316 $ 5,821,801 $ 24,612,509 As Of and For The Year Ended December 31, 2016 (in thousands) Commercial Real Estate Commercial & Industrial Consumer Total Allowance for loan losses Beginning balance $ 87,133 $ 122,989 $ 42,374 $ 252,496 Charge-offs (18,216 ) (25,039 ) (14,705 ) (57,960 ) Recoveries 15,226 9,071 4,925 29,222 Provision for loan losses (2,327 ) 18,757 11,570 28,000 Ending balance (4) $ 81,816 $ 125,778 $ 44,164 $ 251,758 Ending balance: individually evaluated for impairment $ 7,916 $ 8,384 $ 1,811 $ 18,111 Ending balance: collectively evaluated for impairment $ 73,900 $ 117,394 $ 42,353 $ 233,647 Loans Ending balance: total loans (2) (4) $ 7,374,112 $ 11,543,806 $ 4,964,464 $ 23,882,382 Ending balance: individually evaluated for impairment $ 91,410 $ 120,560 $ 37,526 $ 249,496 Ending balance: collectively evaluated for impairment $ 7,282,702 $ 11,423,246 $ 4,926,938 $ 23,632,886 As Of and For The Year Ended December 31, 2015 (in thousands) Commercial Real Estate Commercial & Industrial Consumer Total Allowance for loan losses Beginning balance $ 101,471 $ 118,110 $ 41,736 $ 261,317 Allowance for loan losses of sold Memphis loans — — — — Charge-offs (13,998 ) (22,583 ) (20,758 ) (57,339 ) Recoveries 13,644 8,611 7,253 29,508 Provision for loan losses (13,984 ) 18,851 14,143 19,010 Ending balance (4) $ 87,133 $ 122,989 $ 42,374 $ 252,496 Ending balance: individually evaluated for impairment $ 18,969 $ 10,477 $ 989 $ 30,435 Ending balance: collectively evaluated for impairment $ 68,164 $ 112,512 $ 41,385 $ 222,061 Loans Ending balance: total loans (3) (4) $ 7,394,768 $ 10,772,130 $ 4,292,766 $ 22,459,664 Ending balance: individually evaluated for impairment $ 157,958 $ 105,599 $ 38,243 $ 301,800 Ending balance: collectively evaluated for impairment $ 7,236,810 $ 10,666,531 $ 4,254,523 $ 22,157,864 (1) Total before net deferred fees and costs of $25.3 million . (2) Total before net deferred fees and costs of $26.0 million . (3) Total before net deferred fees and costs of $30.1 million . (4) As of and for the years ended December 31, 2017, 2016, and 2015, there were no purchased credit-impaired loans and no allowance for loan losses for purchased credit-impaired loans.
Schedule of Impaired Loans	Below is a detailed summary of impaired loans (including accruing TDRs) by class as of and for the years ended December 31, 2017 and 2016 . Impaired Loans (including accruing TDRs) December 31, 2017 (in thousands) Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized With no related allowance recorded Investment properties $ — $ — $ — $ 123 $ — 1-4 family properties — — — 323 — Land and development 56 1,740 — 1,816 — Total commercial real estate 56 1,740 — 2,262 — Commercial, financial and agricultural 8,220 9,576 — 21,686 — Owner-occupied — — — 6,665 — Total commercial and industrial 8,220 9,576 — 28,351 — Home equity lines 2,746 2,943 — 1,205 — Consumer mortgages — — — 496 — Credit cards — — — — — Other consumer loans — — — — — Total consumer 2,746 2,943 — 1,701 — Total 11,022 14,259 — 32,314 — With allowance recorded Investment properties 23,364 23,364 1,100 28,749 1,144 1-4 family properties 15,056 15,056 504 16,257 925 Land and development 18,420 18,476 2,636 23,338 404 Total commercial real estate 56,840 56,896 4,240 68,344 2,473 Commercial, financial and agricultural 65,715 65,851 7,406 50,468 1,610 Owner-occupied 37,399 37,441 2,109 40,498 1,382 Total commercial and industrial 103,114 103,292 9,515 90,966 2,992 Home equity lines 5,096 5,096 114 7,476 334 Consumer mortgages 18,668 18,668 569 19,144 896 Credit cards — — — — — Other consumer loans 5,546 5,546 470 4,765 266 Total consumer 29,310 29,310 1,153 31,385 1,496 Total 189,264 189,498 14,908 190,695 6,961 Total Investment properties 23,364 23,364 1,100 28,872 1,144 1-4 family properties 15,056 15,056 504 16,580 925 Land and development 18,476 20,216 2,636 25,154 404 Total commercial real estate 56,896 58,636 4,240 70,606 2,473 Commercial, financial and agricultural 73,935 75,427 7,406 72,154 1,610 Owner-occupied 37,399 37,441 2,109 47,163 1,382 Total commercial and industrial 111,334 112,868 9,515 119,317 2,992 Home equity lines 7,842 8,039 114 8,681 334 Consumer mortgages 18,668 18,668 569 19,640 896 Credit cards — — — — — Other consumer loans 5,546 5,546 470 4,765 266 Total consumer 32,056 32,253 1,153 33,086 1,496 Total impaired loans $ 200,286 $ 203,757 $ 14,908 $ 223,009 $ 6,961 December 31, 2016 (in thousands) Recorded Investment Unpaid Principal Balance Related Allowance Average Recorded Investment Interest Income Recognized With no related allowance recorded Investment properties $ 748 $ 793 $ — $ 2,013 $ — 1-4 family properties 643 2,939 — 1,021 — Land and development 2,099 7,243 — 6,769 — Total commercial real estate 3,490 10,975 — 9,803 — Commercial, financial and agricultural 17,958 20,577 — 6,321 — Owner-occupied 5,508 7,377 — 8,394 — Total commercial and industrial 23,466 27,954 — 14,715 — Home equity lines 1,051 1,051 — 1,045 — Consumer mortgages 744 814 — 870 — Credit cards — — — — — Other consumer loans — — — — — Total consumer 1,795 1,865 — 1,915 — Total 28,751 40,794 — 26,433 — With allowance recorded Investment properties 31,489 31,489 2,044 42,659 1,436 1-4 family properties 23,642 23,649 769 39,864 855 Land and development 32,789 32,788 5,103 25,568 995 Total commercial real estate 87,920 87,926 7,916 108,091 3,286 Commercial, financial and agricultural 43,386 45,913 5,687 51,968 1,215 Owner-occupied 53,708 53,942 2,697 52,300 1,946 Total commercial and industrial 97,094 99,855 8,384 104,268 3,161 Home equity lines 9,638 9,638 971 9,668 432 Consumer mortgages 20,953 20,953 673 20,993 1,014 Credit cards — — — — — Other consumer loans 5,140 5,140 167 5,062 303 Total consumer 35,731 35,731 1,811 35,723 1,749 Total 220,745 223,512 18,111 248,082 8,196 Total Investment properties 32,237 32,282 2,044 44,672 1,436 1-4 family properties 24,285 26,588 769 40,885 855 Land and development 34,888 40,031 5,103 32,337 995 Total commercial real estate 91,410 98,901 7,916 117,894 3,286 Commercial, financial and agricultural 61,344 66,490 5,687 58,289 1,215 Owner-occupied 59,216 61,319 2,697 60,694 1,946 Total commercial and industrial 120,560 127,809 8,384 118,983 3,161 Home equity lines 10,689 10,689 971 10,713 432 Consumer mortgages 21,697 21,767 673 21,863 1,014 Credit cards — — — — — Other consumer loans 5,140 5,140 167 5,062 303 Total consumer 37,526 37,596 1,811 37,638 1,749 Total impaired loans $ 249,496 $ 264,306 $ 18,111 $ 274,515 $ 8,196
Troubled Debt Restructurings	The following tables represent, by concession type, the post-modification balance for loans modified or renewed during the years ended December 31, 2017 , 2016 , and 2015 that were reported as accruing or non-accruing TDRs. TDRs by Concession Type Year Ended December 31, 2017 (in thousands, except contract data) Number of Contracts Principal Forgiveness Below Market Interest Rate Term Extensions and/or Other Concessions Total Investment properties 1 $ — $ — $ 121 $ 121 1-4 family properties 35 — 2,786 2,040 4,826 Land and development 6 — 157 1,614 1,771 Total commercial real estate 42 — 2,943 3,775 6,718 Commercial, financial and agricultural 56 — 9,434 12,145 21,579 Owner-occupied 4 — 35 1,705 1,740 Total commercial and industrial 60 — 9,469 13,850 23,319 Home equity lines — — — — — Consumer mortgages 11 — 2,539 1,190 3,729 Credit cards — — — — — Other consumer loans 38 — 1,624 1,333 2,957 Total consumer 49 — 4,163 2,523 6,686 Total loans 151 $ — $ 16,575 $ 20,148 $ 36,723 (1) (1) No charge-offs were recorded during 2017 upon restructuring of these loans. TDRs by Concession Type Year Ended December 31, 2016 (in thousands, except contract data) Number of Contracts Principal Forgiveness Below Market Interest Rate Term Extensions and/or Other Concessions Total Investment properties 4 $ — $ 1,825 $ 3,518 $ 5,343 1-4 family properties 39 — 5,499 1,488 6,987 Land and development 14 — — 4,099 4,099 Total commercial real estate 57 — 7,324 9,105 16,429 Commercial, financial and agricultural 63 — 17,509 7,160 24,669 Owner-occupied 9 — 7,884 550 8,434 Total commercial and industrial 72 — 25,393 7,710 33,103 Home equity lines 5 — 225 123 348 Consumer mortgages 7 — 413 51 464 Credit cards — — — — — Other consumer loans 28 — 394 2,256 2,650 Total consumer 40 — 1,032 2,430 3,462 Total loans 169 $ — $ 33,749 $ 19,245 $ 52,994 (1) (1) No charge-offs were recorded during 2016 upon restructuring of these loans. TDRs by Concession Type Year Ended December 31, 2015 (in thousands, except contract data) Number of Contracts Principal Forgiveness Below Market Interest Rate Term Extensions and/or Other Concessions Total Investment properties 11 $ — $ 25,052 $ 6,973 $ 32,025 1-4 family properties 43 14,823 4,667 2,763 22,253 Land and development 12 — 614 1,532 2,146 Total commercial real estate 66 14,823 30,333 11,268 56,424 Commercial, financial and agricultural 91 29 3,191 6,477 9,697 Owner-occupied 10 — 3,417 2,064 5,481 Total commercial and industrial 101 29 6,608 8,541 15,178 Home equity lines 53 — 2,826 2,905 5,731 Consumer mortgages 15 — 1,011 895 1,906 Credit cards — — — — — Other consumer loans 27 — 444 703 1,147 Total consumer 95 — 4,281 4,503 8,784 Total loans 262 $ 14,852 $ 41,222 $ 24,312 $ 80,386 (1) (1) Charge-offs of $4.0 million were recorded during 2015 upon restructuring of these loans.
Summary of Loans to Executive Officers and Directors, Including Their Associates

Other Comprehensive Income (L40

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Net of Income Taxes)	The following table illustrates activity within the balances in accumulated other comprehensive income (loss) by component, and is shown for the years ended December 31, 2017 , 2016 , and 2015 . Changes in Accumulated Other Comprehensive Income (Loss) by Component (Net of Income Taxes) (in thousands) Net Unrealized Gains (Losses) on Cash Flow Hedges Net Unrealized Gains (Losses) on Investment Securities Available for Sale Post-Retirement Unfunded Health Benefit Total Balance at December 31, 2014 $ (12,824 ) $ (713 ) $ 932 $ (12,605 ) Other comprehensive income (loss) before reclassifications — (15,806 ) 143 (15,663 ) Amounts reclassified from accumulated other comprehensive income (loss) 320 (1,703 ) (168 ) (1,551 ) Net current period other comprehensive income (loss) 320 (17,509 ) (25 ) (17,214 ) Balance at December 31, 2015 $ (12,504 ) $ (18,222 ) $ 907 $ (29,819 ) Other comprehensive income (loss) before reclassifications — (22,405 ) 63 (22,342 ) Amounts reclassified from accumulated other comprehensive income (loss) 287 (3,697 ) (88 ) (3,498 ) Net current period other comprehensive income (loss) 287 (26,102 ) (25 ) (25,840 ) Balance at December 31, 2016 $ (12,217 ) $ (44,324 ) $ 882 $ (55,659 ) Other comprehensive income (loss) before reclassifications — 676 38 714 Amounts reclassified from accumulated other comprehensive income (loss) 80 178 (67 ) 191 Net current period other comprehensive income (loss) 80 854 (29 ) 905 Balance at December 31, 2017 $ (12,137 ) $ (43,470 ) $ 853 $ (54,754 )
Schedule of Reclassifications out of Accumulated Other Comprehensive Income (Loss)	The following table illustrates activity within the reclassifications out of accumulated other comprehensive income (loss), for the years ended December 31, 2017 , 2016 , and 2015 . Reclassifications Out of Accumulated Other Comprehensive Income (Loss) Details About Accumulated Other Comprehensive Income (Loss) Components Amount Reclassified From Accumulated Other Comprehensive Income (Loss) Income Statement Line Item Where This is Presented For the Years Ended December 31, (in thousands) 2017 2016 2015 Net unrealized gains (losses) on cash flow hedges: Amortization of deferred losses $ (130 ) $ (270 ) $ (448 ) Interest expense Amortization of deferred losses — (197 ) (73 ) Loss on early extinguishment of debt, net 50 180 201 Income tax (expense) benefit $ (80 ) $ (287 ) $ (320 ) Reclassifications, net of income taxes Net unrealized gains (losses) on investment securities available for sale: Realized (losses) gains, net, on sales of securities (1) $ (289 ) $ 6,011 $ 2,769 Investment securities gains, net 111 (2,314 ) (1,066 ) Income tax (expense) benefit $ (178 ) $ 3,697 $ 1,703 Reclassifications, net of income taxes Post-retirement unfunded health benefit: Amortization of actuarial gains $ 110 $ 144 $ 272 Salaries and other personnel expense (43 ) (56 ) (104 ) Income tax (expense) benefit $ 67 $ 88 $ 168 Reclassifications, net of income taxes (1) Includes $1.4 million in gains in 2016 from the transfer of $1.9 million of investment securities available for sale to trading account assets.

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Premises and Equipment	Premises and equipment at December 31, 2017 and 2016 consist of the following: (in thousands) Useful Life (in years) 2017 2016 Land Indefinite $ 96,759 $ 97,080 Buildings and improvements 10 - 40 388,254 377,754 Leasehold improvements 10 - 40 38,970 41,355 Furniture and equipment 3 - 10 413,876 370,458 Construction in progress 15,956 29,104 Total premises and equipment 953,815 915,751 Less: Accumulated depreciation and amortization (527,002 ) (498,266 ) Premises and equipment, net $ 426,813 $ 417,485
Schedule of Future Minimum Rental Payments for Operating Leases	At December 31, 2017 , minimum rental commitments under all such non-cancelable leases for the next five years and thereafter are presented below. (in thousands) 2018 $ 28,187 2019 27,722 2020 26,483 2021 23,876 2022 23,332 Thereafter 98,797 Total $ 228,397

Goodwill And Other Intangible42

Goodwill And Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table shows the changes in the carrying amount of goodwill for the year ended December 31, 2017 : (in thousands) Trust Services Reporting Unit Synovus Bank Reporting Unit Total Balance as of December 31, 2016 Goodwill $ 24,431 $ 35,247 $ 59,678 Accumulated impairment losses — — — Measurement period adjustments — (2,363 ) (2,363 ) Goodwill, net, as of December 31, 2017 $ 24,431 $ 32,884 $ 57,315
Schedule of Other Intangible Assets	The following table shows the carrying amount of other intangibles as of December 31, 2017 and 2016 : (in thousands) 2017 2016 Other intangibles $ 13,140 $ 14,040 Accumulated amortization (1,886 ) (817 ) Other intangibles, net $ 11,254 $ 13,223

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Other Assets [Abstract]
Schedule of Other Assets	Significant balances included in other assets at December 31, 2017 and 2016 are presented below. (in thousands) 2017 2016 Cash surrender value of bank-owned life insurance $ 540,958 $ 378,830 Federal Reserve Bank and FHLB stock 159,443 169,864 Accrued interest receivable 80,036 70,393 Investments in low income housing tax credit partnerships 60,068 26,495 Taxes receivable (1) 46,330 2,611 Accounts receivable 43,878 29,821 Prepaid expenses 33,298 35,542 Private equity investments 15,771 25,493 Derivative asset positions 11,722 20,623 Other properties held for sale 7,825 14,830 SBA/GGL servicing assets, net 4,101 4,451 Miscellaneous other assets 32,081 34,267 Total other assets $ 1,035,511 $ 813,220 (1) Effective December 31, 2017, alternative minimum tax credits of $42.1 million were reclassified from deferred tax assets to taxes receivable.

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Interest-bearing Deposit Liabilities [Abstract]
Schedule of Interest Bearing Deposits	A summary of interest bearing deposits at December 31, 2017 and 2016 is presented below. ( in thousands) 2017 2016 Interest bearing demand deposits $ 5,157,175 $ 4,768,313 Money market accounts, excluding brokered deposits 7,435,941 7,251,093 Savings accounts 798,935 929,402 Time deposits, excluding brokered deposits 3,108,385 3,234,465 Brokered deposits 1,961,125 1,378,983 Total interest bearing deposits $ 18,461,561 $ 17,562,256
Schedule of Cash Maturities of Time Deposits	The following table presents contractual maturities of all time deposits at December 31, 2017 . (in thousands) Maturing within one year $ 2,544,033 Between 1 — 2 years 851,665 2 — 3 years 567,279 3 — 4 years 248,473 4 — 5 years 65,521 Thereafter 242,909 $ 4,519,880

Long-term Debt and Short-term45

Long-term Debt and Short-term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	Long-term debt at December 31, 2017 and 2016 is presented in the following table. (in thousands) 2017 2016 Parent Company: 3.125% senior notes, due November 1, 2022, $300 million par value at December 31, 2017 with semi-annual interest payments and principal to be paid at maturity $ 296,971 $ — 5.75% fixed to adjustable rate subordinated notes issued December 7, 2015, due December 15, 2025, $250 million par value with semi-annual interest payments at 5.75% for the first five years and quarterly payments thereafter at an adjustable rate equal to the then-current three month LIBOR rate + 418.2 basis points and principal to be paid at maturity 247,618 247,136 LIBOR + 1.80% debentures, due April 19, 2035, $10 million par value with quarterly interest payments and principal to be paid at maturity (rate of 3.39% at December 31, 2017 and 2.76% at December 31, 2016) 10,000 10,000 5.125% subordinated notes, matured June 15, 2017, $278.6 million par value at December 31, 2016 — 278,480 7.875% senior notes, due February 15, 2019, $300 million par value — 297,763 Hedge-related basis adjustment (1) — 873 Total long-term debt — Parent Company 554,589 834,252 Synovus Bank: FHLB advances with interest and principal payments due at various maturity dates through 2022 and interest rates ranging from 1.42% to 1.43% at December 31, 2017 (weighted average interest rate of 1.43% and 0.64% at December 31, 2017 and 2016, respectively) 1,150,000 1,325,000 Capital lease with interest and principal payments due at various dates through 2031 (rate of 1.59% at both December 31, 2017 and 2016) 1,549 1,629 Total long-term debt — Synovus Bank 1,151,549 1,326,629 Total long-term debt $ 1,706,138 $ 2,160,881 (1) Unamortized balance of terminated interest rate swaps reflected in debt for financial reporting purposes.
Schedule of Principal Payments on Long-term Debt	Contractual annual principal payments on long-term debt for the next five years and thereafter are shown on the following table. (in thousands) Parent Company Synovus Bank Total 2018 $ — $ 100,089 $ 100,089 2019 — 90 90 2020 — 350,092 350,092 2021 — 450,096 450,096 2022 300,000 250,107 550,107 Thereafter 260,000 1,075 261,075 Total $ 560,000 $ 1,151,549 $ 1,711,549
Components of Short-term Borrowings	The following table sets forth certain information regarding federal funds purchased and other securities sold under repurchase agreements. (dollars in thousands) 2017 2016 2015 Total balance at December 31, $ 161,190 $ 159,699 $ 177,025 Weighted average interest rate at December 31, 0.18 % 0.08 % 0.08 % Maximum month end balance during the year $ 225,475 $ 286,175 $ 250,453 Average amount outstanding during the year 184,093 216,593 205,305 Weighted average interest rate during the year 0.11 % 0.09 % 0.08 %

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Schedule of Change in Preferred and Common Shares Issued and Common Shares Held as Treasury Shares	The following table shows the changes in shares of preferred and common stock issued and common stock held as treasury shares for the three years ended December 31, 2017 . (shares in thousands) Series C Preferred Stock Issued Common Stock Issued Treasury Stock Held Common Stock Outstanding Balance at December 31, 2014 5,200 139,950 3,827 136,123 Restricted share unit activity — 304 — 304 Stock options exercised — 338 — 338 Repurchase of common stock — — 7,218 (7,218 ) Balance at December 31, 2015 5,200 140,592 11,045 129,547 Issuance of common stock for acquisition — 821 — 821 Restricted share unit activity — 316 — 316 Stock options exercised — 297 — 297 Repurchase of common stock — — 8,715 (8,715 ) Balance at December 31, 2016 5,200 142,026 19,760 122,266 Issuance of common stock for earnout payment — 118 — 118 Restricted share unit activity — 336 — 336 Stock options exercised — 198 — 198 Repurchase of common stock — — 4,021 (4,021 ) Balance at December 31, 2017 5,200 142,678 23,781 118,897

Regulatory Capital (Tables)

Regulatory Capital (Tables)	12 Months Ended
	Dec. 31, 2017
Regulatory Capital Disclosure [Abstract]
Schedule of Compliance with Regulatory Capital	The following table summarizes regulatory capital information at December 31, 2017 and 2016 on a consolidated basis and for Synovus’ significant subsidiary, defined as any direct subsidiary with assets or net income levels exceeding 10% of the consolidated totals. Actual For Capital Adequacy Purposes To Be Well Capitalized Under Prompt Corrective Action Provisions (1) (dollars in thousands) 2017 2016 2017 2016 2017 2016 Synovus Financial Corp. Common equity tier 1 capital $ 2,763,168 $ 2,654,287 $ 1,250,488 $ 1,199,794 N/A N/A Tier 1 capital 2,872,001 2,685,880 1,660,074 1,599,725 N/A N/A Total risk-based capital 3,383,081 3,201,268 2,213,432 2,132,966 N/A N/A Common equity tier 1 capital ratio 9.99 % 9.96 % 4.50 % 4.50 % N/A N/A Tier 1 capital ratio 10.38 10.07 6.00 6.00 N/A N/A Total risk-based capital ratio 12.23 12.01 8.00 8.00 N/A N/A Leverage ratio 9.19 8.99 4.00 4.00 N/A N/A Synovus Bank Common equity tier 1 capital $ 3,155,163 $ 3,187,583 $ 1,247,462 $ 1,197,976 $ 1,795,004 $ 1,730,410 Tier 1 capital 3,155,163 3,187,583 1,656,927 1,597,302 2,209,236 2,129,736 Total risk-based capital 3,406,243 3,441,563 2,209,236 2,129,736 2,761,545 2,662,169 Common equity tier 1 capital ratio 11.43 % 11.97 % 4.50 % 4.50 % 6.50 % 6.50 % Tier 1 capital ratio 11.43 11.97 6.00 6.00 8.00 8.00 Total risk-based capital ratio 12.33 12.93 8.00 8.00 10.00 10.00 Leverage ratio 10.12 10.68 4.00 4.00 5.00 5.00 (1) The prompt corrective action provisions are applicable at the bank level only.

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Basic And Diluted Earnings per Share	The following table displays a reconciliation of the information used in calculating basic and diluted net income per common share for the years ended December 31, 2017 , 2016 , and 2015 . Years Ended December 31, (in thousands, except per share data) 2017 2016 2015 Net income $ 275,474 $ 246,784 $ 226,082 Dividends on preferred stock 10,238 10,238 10,238 Net income available to common shareholders $ 265,236 $ 236,546 $ 215,844 Weighted average common shares outstanding 121,162 124,389 132,423 Potentially dilutive shares from outstanding equity-based awards and Earnout Payments 850 689 778 Weighted average diluted common shares 122,012 125,078 133,201 Net income per common share, basic $ 2.19 $ 1.90 $ 1.63 Net income per common share, diluted $ 2.17 $ 1.89 $ 1.62

Fair Value Accounting (Tables)

Fair Value Accounting (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Financial Instruments Measured at Fair Value on Recurring Basis	The following table presents all financial instruments measured at fair value on a recurring basis as of December 31, 2017 and 2016 , according to the valuation hierarchy included in ASC 820-10. For equity and debt securities, class was determined based on the nature and risks of the investments. Synovus did not have any transfers between levels for the years ended December 31, 2017 and 2016 . December 31, 2017 (in thousands) Level 1 Level 2 Level 3 Total Assets and Liabilities at Fair Value Assets Trading securities: U.S. Government agency securities $ — $ 3,002 $ — $ 3,002 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — 296 — 296 Other investments 522 — — 522 Total trading securities 522 3,298 — 3,820 Mortgage loans held for sale — 48,024 — 48,024 Investment securities available for sale: U.S. Treasury securities 82,674 — — 82,674 U.S. Government agency securities — 10,862 — 10,862 Mortgage-backed securities issued by U.S. Government agencies — 120,440 — 120,440 Mortgage-backed securities issued by U.S. Government sponsored enterprises — 2,640,523 — 2,640,523 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — 1,111,999 — 1,111,999 State and municipal securities — 180 — 180 Corporate debt and other securities (1) 3,162 15,294 1,935 20,391 Total investment securities available for sale 85,836 3,899,298 1,935 3,987,069 Private equity investments — — 15,771 15,771 Mutual funds held in rabbi trusts 14,140 — — 14,140 GGL/SBA loans servicing asset — — 4,101 4,101 Derivative assets: Interest rate contracts — 10,786 — 10,786 Mortgage derivatives (2) — 936 — 936 Total derivative assets — 11,722 — 11,722 Liabilities Trading account liabilities — 1,000 — 1,000 Earnout liability (3) — — 11,348 11,348 Derivative liabilities: Interest rate contracts — 12,638 — 12,638 Mortgage derivatives (2) — 129 — 129 Visa derivative — — 4,330 4,330 Total derivative liabilities — 12,767 4,330 17,097 December 31, 2016 (in thousands) Level 1 Level 2 Level 3 Total Assets and Liabilities at Fair Value Assets Trading securities: Mortgage-backed securities issued by U.S. Government agencies $ — $ 3,460 $ — $ 3,460 Collateralized mortgage obligations issued by U.S. Government sponsored enterprises — 3,438 — 3,438 State and municipal securities — 426 — 426 Other investments 1,890 100 — 1,990 Total trading securities 1,890 7,424 — 9,314 Mortgage loans held for sale — 51,545 — 51,545 Investment securities available for sale: U.S. Treasury securities 107,802 — — 107,802 U.S. Government agency securities — 12,993 — 12,993 Mortgage-backed securities issued by U.S. Government agencies — 174,202 — 174,202 Mortgage-backed securities issued by U.S. Government sponsored enterprises — 2,506,340 — 2,506,340 Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises — 890,442 — 890,442 State and municipal securities — 2,794 — 2,794 Equity securities 3,782 — — 3,782 Corporate debt and other securities (1) 3,092 14,952 1,796 19,840 Total investment securities available for sale 114,676 3,601,723 1,796 3,718,195 Private equity investments — — 25,493 25,493 Mutual funds held in rabbi trusts 11,479 — — 11,479 Derivative assets: Interest rate contracts — 17,157 — 17,157 Mortgage derivatives (2) — 3,466 — 3,466 Total derivative assets — 20,623 — 20,623 Liabilities Earnout liability (3) — — 14,000 14,000 Derivative liabilities: Interest rate contracts — 17,531 — 17,531 Visa derivative — — 5,768 5,768 Total derivative liabilities — 17,531 5,768 23,299 (1 ) Based on an analysis of the nature and risks of these investments, Synovus has determined that presenting these investments as a single asset class is appropriate. (2 ) Mortgage derivatives consist of customer interest rate lock commitments that relate to the potential origination of mortgage loans, which would be classified as held for sale and forward loan sales commitments with third-party investors. (3 ) Earnout liability consists of contingent consideration obligation related to Global One acquisition.
Changes in Fair Value Included in Consolidated Statements of Income	The following table summarizes the difference between the fair value and the unpaid principal balance of mortgage loans held for sale at fair value and the changes in fair value of these loans. Mortgage loans held for sale are initially measured at fair value with subsequent changes in fair value recognized in earnings. Changes in fair value were recorded as a component of mortgage banking income in the consolidated statements of income. An immaterial portion of these changes in fair value was attributable to changes in instrument-specific credit risk. Twelve Months Ended December 31, (in thousands) 2017 2016 2015 Changes in fair value included in net income: Mortgage loans held for sale $ 754 $ (667 ) $ (742 ) Mortgage loans held for sale: Fair value 48,024 51,545 59,275 Unpaid principal balance 46,839 51,114 58,177 Fair value less aggregate unpaid principal balance $ 1,185 $ 431 $ 1,098
Changes in Level 3 Fair Value Measurements	The table below includes a roll-forward of the amounts on the consolidated balance sheet for the year ended December 31, 2017 and 2016 (including the change in fair value), for financial instruments of a material nature that are classified by Synovus within Level 3 of the fair value hierarchy and are measured at fair value on a recurring basis. Transfers between fair value levels are recognized at the end of the reporting period in which the associated changes in inputs occur. During 2017 and 2016, Synovus did not have any transfers between levels in the fair value hierarchy. 2017 (in thousands) Investment Securities Available for Sale Private Equity Investments Visa Derivative Earnout Liability (1) GGL/SBA Loans Servicing Asset (2) Beginning balance, January 1, $ 1,796 $ 25,493 $ (5,768 ) $ (14,000 ) $ — Total (losses) gains realized/unrealized: Included in earnings — (3,093 ) — (5,466 ) (1,681 ) Unrealized gains included in other comprehensive income 139 — — — — Additions — — — — 1,330 Sales — (6,629 ) — — — Settlements — — 1,438 6,352 — Transfer from amortization method to fair value — — — — 4,452 Measurement period adjustments related to Global One acquisition — — — 1,766 — Ending balance, December 31, $ 1,935 $ 15,771 $ (4,330 ) $ (11,348 ) $ 4,101 Total net (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31, $ — $ (3,093 ) $ — $ (5,466 ) $ (1,681 ) 2016 (in thousands) Investment Securities Available for Sale Private Equity Investments Visa Derivative Earnout Liability (1) Beginning balance, January 1, $ 1,745 $ 27,148 $ (1,415 ) $ — Total gains (losses) realized/unrealized: Included in earnings — (1,026 ) (5,795 ) — Unrealized gains included in other comprehensive income 51 — — — Additions — — — (14,000 ) Settlements — (629 ) 1,442 — Ending balance, December 31, $ 1,796 $ 25,493 $ (5,768 ) $ (14,000 ) Total net gains (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31, $ — $ (1,026 ) $ (5,795 ) $ — (1) Earnout liability consists of contingent consideration obligation related to the Global One acquisition. (2) Effective January 1, 2017, Synovus elected the fair value option for determining the value of the GGL/SBA loans servicing asset. Prior to 2017, Synovus accounted for the GGL/SBA loans servicing asset using the amortization method.
Assets and Liabilities Measured at Fair Value on Non-Recurring Basis	The following tables present assets measured at fair value on a non-recurring basis as of the dates indicated for which there was a fair value adjustment during the period. As of December 31, 2017 Fair Value Adjustments for the Year Ended December 31, 2017 (in thousands) Level 1 Level 2 Level 3 Impaired loans* $ — $ — $ 3,603 $ 991 Other loans held for sale — — 10,197 13,004 Other real estate — — 3,363 2,413 Other assets held for sale — — 5,334 2,491 As of December 31, 2016 Fair Value Adjustments for the Year Ended December 31, 2016 Level 1 Level 2 Level 3 Impaired loans* $ — $ — $ 21,742 $ 6,613 Other real estate — — 19,305 1,223 Other assets held for sale — — 12,083 5,715 *Collateral-dependent impaired loans that are written down to fair value during the period.
Fair Value Inputs, Assets, Quantitative Information	The table below provides an overview of the valuation techniques and significant unobservable inputs used in those techniques to measure financial instruments that are classified within Level 3 of the valuation hierarchy and are measured at fair value on a non-recurring basis. December 31, 2017 December 31, 2016 Valuation Technique Significant Unobservable Input Range (Weighted Average) (1) Range (Weighted Average) (1) Assets measured at fair value on a non-recurring basis Collateral-dependent impaired loans Third-party appraised value of collateral less estimated selling costs Discount to appraised value (2) Estimated selling costs 0%-50% (15%) 0%-10% (7%) 0%-52% (25%) 0%-10% (7%) Other loans held for sale Third-party appraised value of collateral less estimated selling costs Discount to appraised value (2) Estimated selling costs 5%-99% (54%) 0%-10% (2%) N/A Other real estate Third-party appraised value of real estate less estimated selling costs Discount to appraised value (2) Estimated selling costs 0%-85% (35%) 0%-10% (7%) 0%-10% (5%) 0%-10% (7%) Other assets held for sale Third-party appraised value less estimated selling costs or BOV Discount to appraised value (2) Estimated selling costs 21%-52%(25%) 0%-10% (7%) 0%-81% (47%) 0%-10% (7%) (1) The weighted average is the measure of central tendencies; it is not the value that management is using for the asset or liability. (2) Synovus also makes adjustments to the values of the assets listed above for various reasons, including age of the appraisal, information known by management about the property, such as occupancy rates, changes to the physical conditions of the property, pending sales, and other factors. The year ended December 31, 2017 included certain balance sheet restructuring actions which resulted in additional discounts to fair value for planned accelerated dispositions of other loans held for sale, other real estate, and other assets held for sale. The table below provides an overview of the valuation techniques and significant unobservable inputs used in those techniques to measure financial instruments that are classified within Level 3 of the valuation hierarchy and are measured at fair value on a recurring basis. The range of sensitivities that management utilized in its fair value calculations is deemed acceptable in the industry with respect to the identified financial instruments. December 31, 2017 December 31, 2016 (dollars in thousands) Valuation Technique Significant Unobservable Input Level 3 Fair Value Range / Weighted Average Level 3 Fair Value Range / Weighted Average Assets measured at fair value on a recurring basis Investment Securities Available for Sale - Other investments: Trust preferred securities Discounted cash flow analysis Credit spread embedded in discount rate $ 1,935 398 bps $1,796 442 bps Private equity investments Individual analysis of each investee company Multiple factors, including but not limited to, current operations, financial condition, cash flows, evaluation of business management and financial plans, and recently executed financing transactions related to the investee companies 15,771 N/A 25,493 N/A Discount for lack of liquidity (1) N/A 15% GGL/SBA loans servicing asset Discounted cash flow analysis Discount rate Prepayment speeds 4,101 13.16% 7.50% N/A N/A Earnout liability Option pricing methods and Monte Carlo simulation Financial projections of Global One 11,348 N/A 14,000 N/A Visa derivative liability Discounted cash flow analysis Estimated timing of resolution of covered litigation, future cumulative deposits to the litigation escrow for settlement of the Covered Litigation, and estimated future monthly fees payable to the derivative counterparty 4,330 1-4 years 5,768 1 - 5 years (1) Represents management's estimate of discount that market participants would require based on the instrument's lack of liquidity.
Carrying and Estimated Fair Values of Financial Instruments Carried on Balance Sheet	The carrying and estimated fair values of financial instruments, as well as the level within the fair value hierarchy, as of December 31, 2017 and 2016 are as follows: December 31, 2017 (in thousands) Carrying Value Fair Value Level 1 Level 2 Level 3 Financial Assets Cash and cash equivalents $ 397,848 $ 397,848 $ 397,848 $ — $ — Interest bearing funds with Federal Reserve Bank 460,928 460,928 460,928 — — Interest earning deposits with banks 26,311 26,311 26,311 — — Federal funds sold and securities purchased under resale agreements 47,846 47,846 47,846 — — Trading account assets 3,820 3,820 522 3,298 — Mortgage loans held for sale 48,024 48,024 — 48,024 — Other loans held for sale 11,356 11,356 — — 11,356 Investment securities available for sale 3,987,069 3,987,069 85,836 3,899,298 1,935 Private equity investments 15,771 15,771 — — 15,771 Mutual funds held in rabbi trusts 14,140 14,140 14,140 — — Loans, net of deferred fees and costs 24,787,464 24,507,141 — — 24,507,141 GGL/SBA loans servicing asset 4,101 4,101 — — 4,101 Derivative assets 11,722 11,722 — 11,722 — Financial Liabilities Trading account liabilities 1,000 1,000 — 1,000 — Non-interest bearing deposits 7,686,339 7,686,339 — 7,686,339 — Interest bearing deposits 18,461,561 18,465,475 — 18,465,475 — Federal funds purchased and securities sold under repurchase agreements 161,190 161,190 161,190 — — Long-term debt 1,706,138 1,721,814 — 1,721,814 — Earnout liability 11,348 11,348 — — 11,348 Derivative liabilities 17,097 17,097 — 12,767 4,330 December 31, 2016 (in thousands) Carrying Value Fair Value Level 1 Level 2 Level 3 Financial assets Cash and cash equivalents $ 395,175 $ 395,175 $ 395,175 $ — $ — Interest bearing funds with Federal Reserve Bank 527,090 527,090 527,090 — — Interest earning deposits with banks 18,720 18,720 18,720 — — Federal funds sold and securities purchased under resale agreements 58,060 58,060 58,060 — — Trading account assets 9,314 9,314 1,890 7,424 — Mortgage loans held for sale 51,545 51,545 — 51,545 — Investment securities available for sale 3,718,195 3,718,195 114,676 3,601,723 1,796 Private equity investments 25,493 25,493 — — 25,493 Mutual funds held in Rabbi Trusts 11,479 11,479 11,479 — — Loans, net of deferred fees and costs 23,856,391 23,709,434 — — 23,709,434 Derivative assets 20,623 20,623 — 20,623 — Financial liabilities Non-interest bearing deposits 7,085,804 7,085,804 — 7,085,804 — Interest bearing deposits 17,562,256 17,560,021 — 17,560,021 — Federal funds purchased and securities sold under repurchase agreements 159,699 159,699 159,699 — — Long-term debt 2,160,881 2,217,544 — 2,217,544 — Earnout liability 14,000 14,000 — — 14,000 Derivative liabilities 23,299 23,299 — 17,531 5,768

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Derivative Instruments [Abstract]
Impact of Derivatives on Balance Sheet	The impact of derivative instruments on the consolidated balance sheets at December 31, 2017 and 2016 is presented below. Fair Value of Derivative Assets Fair Value of Derivative Liabilities December 31, December 31, (in thousands) Location on Consolidated Balance Sheet 2017 2016 Location on Consolidated Balance Sheet 2017 2016 Derivatives not designated as hedging instruments: Interest rate contracts Other assets $ 10,786 $ 17,157 Other liabilities $ 12,638 $ 17,531 Mortgage derivatives Other assets 936 3,466 Other liabilities 129 — Visa derivative — — Other liabilities 4,330 5,768 Total derivatives not designated as hedging instruments $ 11,722 $ 20,623 $ 17,097 $ 23,299
Effect of Fair Value Hedges on Consolidated Statements of Income	The pre-tax effect of fair value hedges on the consolidated statements of income for the years ended December 31, 2017 , 2016 and 2015 is presented below. Derivative Gain (Loss) Recognized in Income Years Ended December 31, (in thousands) Location of Gain (Loss) Recognized in Income 2017 2016 2015 Derivatives not designated as hedging instruments Interest rate contracts (1) Other Non- Interest Income $ 20 $ 76 $ 44 Mortgage derivatives (2) Mortgage Banking Income (2,659 ) 1,907 1,099 Total $ (2,639 ) $ 1,983 $ 1,143 (1) Gain (loss) represents net fair value adjustments (including credit related adjustments) for customer swaps and offsetting positions. (2) Gain (loss) represents net fair value adjustments recorded for interest rate lock commitments and commitments to sell mortgage loans to third-party investors.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Variable Interest Entities [Abstract]
Schedule of Variable Interest Entities	The following tables provide a summary of the investments in low income housing tax credit partnerships at December 31, 2017 and 2016 and income (loss) related to these investments for the years ended December 2017, 2016, and 2015. 2017 2016 (in thousands) Proportional amortization method investments included in other assets $ 58,343 $ — Equity method investments included in other assets 1,725 26,495 Cumulative equity investments in LIHTC partnerships 46,659 34,065 Unfunded commitments included in other liabilities 39,994 17,420 Short-term construction loans and letter of credit commitments 7,180 — Funded portion of short-term loans and letters of credit — — Years Ended December 31, 2017 2016 2015 (in thousands) Proportional amortization expense recognized as a component of income tax expense $ 1,820 $ — $ — Income (loss) from equity method investments recognized as a component of non-interest income (1,648 ) 389 553 The following tables provide a summary of the investments in real estate partnerships at December 31, 2017 and 2016 and income related to these investments for the years ended December 2017, 2016, and 2015. 2017 2016 (in thousands) Equity method investments included in other assets $ 6,468 $ 6,822 Unfunded commitments included in other liabilities — — Years Ended December 31, 2017 2016 2015 (in thousands) Income from equity method investments recognized as a component of non-interest income $ 1,584 $ 1,040 $ 1,212

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Loan Commitments and Letters of Credit	Unfunded letters of credit and lending commitments at December 31, 2017 are presented below. (in thousands) Letters of credit* $ 153,372 Commitments to fund commercial and industrial loans 5,090,827 Commitments to fund commercial real estate, construction, and land development loans 1,567,583 Commitments under home equity lines of credit 1,137,714 Unused credit card lines 779,254 Other loan commitments 351,358 Total letters of credit and unfunded lending commitments $ 9,080,108 * Represent the contractual amount net of risk participations of $77 million .

Share-based Compensation (Table

Share-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Share-based Compensation [Abstract]
Schedule of Stock Options Activity	A summary of stock option activity and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below. Stock Options 2017 2016 2015 Shares Weighted-Average Exercise Price Shares Weighted-Average Exercise Price Shares Weighted-Average Exercise Price Outstanding at beginning of year 973,361 $ 17.76 1,741,975 $ 37.88 2,550,046 $ 45.11 Options exercised (197,631 ) 17.41 (297,225 ) 17.35 (338,808 ) 16.72 Options forfeited — — (1,597 ) 17.64 (12,825 ) 17.17 Options expired/canceled — — (469,792 ) 92.62 (456,438 ) 94.56 Options outstanding at end of year 775,730 $ 17.85 973,361 $ 17.76 1,741,975 $ 37.88 Options exercisable at end of year 775,730 $ 17.85 973,361 $ 17.76 1,504,783 $ 41.08
Fair Value of Option Grants Used in Measuring Compensation Expense	The fair value of market restricted share units granted was estimated on the date of grant using a Monte Carlo simulation model with the following weighted average assumptions: 2017 2016 2015 Risk-free interest rate 1.48 % 0.81 % 1.05 % Expected stock price volatility 22.9 25.7 26.4 Dividend yield 1.2 1.8 1.4 Simulation period 3.0 years 3.0 years 3.0 years
Schedule of Restricted Stock Units Activity	A summary of restricted share units outstanding and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below (excluding market restricted and performance share units). Restricted Share Units Share Units Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 882,823 $ 19.81 Granted 321,874 28.09 Dividend equivalents granted 9,810 28.09 Vested (428,121 ) 17.48 Forfeited (23,619 ) 24.60 Outstanding at December 31, 2015 762,767 24.57 Granted 350,458 26.43 Dividend equivalents granted 11,105 26.43 Vested (406,496 ) 23.10 Forfeited (12,067 ) 23.96 Outstanding at December 31, 2016 705,767 26.38 Granted 242,804 41.82 Dividend equivalents granted 5,839 41.82 Vested (341,825 ) 26.25 Forfeited (46,637 ) 26.28 Outstanding at December 31, 2017 565,948 $ 33.25 A summary of market restricted share units outstanding and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below. Market Restricted Share Units Share Units Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 118,186 $ 24.33 Granted 82,152 29.39 Dividend equivalents granted 2,221 29.05 Quantity change by TSR factor 4,838 24.33 Vested (49,149 ) 24.34 Outstanding at December 31, 2015 158,248 27.02 Granted 93,913 26.93 Dividend equivalents granted 3,095 26.93 Quantity change by TSR factor 9,970 26.93 Vested (82,817 ) 26.40 Outstanding at December 31, 2016 182,409 27.25 Granted 78,174 43.52 Dividend equivalents granted 2,811 43.52 Quantity change by TSR factor 22,182 27.25 Vested (114,013 ) 26.78 Outstanding at December 31, 2017 171,563 $ 35.24 A summary of performance share units outstanding and changes during the years ended December 31, 2017 , 2016 , and 2015 is presented below. Performance Share Units Share Units Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 67,675 $ 23.47 Granted 82,152 28.06 Dividend equivalents granted 1,740 28.06 Outstanding at December 31, 2015 151,567 26.01 Granted 83,529 25.95 Dividend equivalents granted 3,384 25.95 Outstanding at December 31, 2016 238,480 25.99 Granted 72,825 41.61 Dividend equivalents granted 2,562 41.61 Vested (69,326 ) 23.47 Outstanding at December 31, 2017 244,541 $ 31.54
Schedule of Grants Under All Synovus Equity Compensation Plans	The following table provides aggregate information regarding grants under all Synovus equity compensation plans at December 31, 2017 . Plan Category (a) Number of Securities to be Issued Upon Vesting of Restricted Share Units, Market Restricted Share Units, and Performance Share Units (1) (b) Number of Securities to be Issued Upon Exercise of Outstanding Options (c) Weighted-Average Exercise Price of Outstanding Options in Column (b) (d) Number of Shares Remaining Available for Issuance Excluding Shares Reflected in Columns (a) and (b) Shareholder approved equity compensation plans for shares of Synovus stock 982,052 775,730 $ 17.85 5,671,680 (1) Market restricted and performance share units included at defined target levels. Actual shares issued upon vesting may differ based on actual TSR and ROAA over the measurement period.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The components of income tax expense (benefit) included in the consolidated statements of income for the years ended December 31, 2017 , 2016 , and 2015 are presented below: (in thousands) 2017 2016 2015 Current Federal $ (32,341 ) $ 7,329 $ 6,163 State 5,949 5,501 4,424 Total current income tax expense (benefit) (26,392 ) 12,830 10,587 Deferred Federal 229,917 117,463 108,877 State 1,139 11,374 13,027 Total deferred income tax expense 231,056 128,837 121,904 Total income tax expense $ 204,664 $ 141,667 $ 132,491 Note: The table above does not reflect a net charge of $790 thousand and a credit of $1.7 million for the years ended December 31, 2016 and 2015, respectively, relating to share-based compensation transactions that were charged or credited directly to shareholders' equity.
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the differences for the years ended December 31, 2017 , 2016 and 2015 is presented below: Years Ended December 31, (dollars in thousands) 2017 2016 2015 Income tax expense at statutory federal income tax rate $ 168,048 $ 135,957 $ 125,501 Increase (decrease) resulting from: State income tax expense, net of federal income tax benefit 11,961 13,256 12,870 Provisional tax adjustment related to reduction in U.S. federal statutory income tax rate (1)(2) 46,573 — — LIHTC amortization, net of tax benefits 268 — — Tax-exempt income (719 ) (825 ) (835 ) Tax benefit from share-based compensation (4,318 ) — — Bank-owned life insurance (4,702 ) (3,402 ) (2,885 ) Change in valuation allowance (3) (6,227 ) (2,055 ) (589 ) General business tax credits (4) (6,546 ) (1,213 ) (1,173 ) Other, net 326 (51 ) (398 ) Total income tax expense $ 204,664 $ 141,667 $ 132,491 Effective tax rate 42.6 % 36.5 % 36.9 % (1) Does not include a provisional tax expense adjustment of $608 thousand which is included as a component of the change in the valuation allowance. The income tax effect of the provisional federal income tax expense of $47.2 million relating to Federal Tax Reform represents 9.8% of income before taxes. (2) Includes $7.8 million expense from remeasurement of deferred tax assets relating to unrealized losses on available for sale securities which were initially recorded through accumulated other comprehensive income (AOCI). As further described in Note 1, ASU 2018-02, issued in February 2018, provides for the reclassification of the tax effects stranded in AOCI resulting from Federal Tax Reform to retained earnings. As a result, Synovus will elect to apply the ASU 2018-02 guidance during the reporting period ending on March 31, 2018 and reclassify $7.8 million from AOCI to retained earnings. (3) Includes a provisional federal income tax expense of $608 thousand related to Federal Tax Reform. (4) 2017 includes research and development tax credits for the tax years 2013-2017 totaling $4.6 million .
Schedule of Deferred Tax Assets and Liabilities	Significant portions of the deferred tax assets and liabilities at December 31, 2017 and 2016 are presented below: (in thousands) 2017 2016 Deferred tax assets Allowance for loan losses $ 66,034 $ 100,419 Net operating loss carryforwards 41,059 167,072 Tax credit carryforwards 19,175 67,031 Employee benefits and deferred compensation 18,333 26,183 Net unrealized losses on investment securities available for sale 13,253 19,413 Deferred revenue 12,311 18,639 Non-performing loan interest 10,388 19,137 Other 8,892 14,600 Total gross deferred tax assets 189,445 432,494 Less valuation allowance (3,431 ) (9,658 ) Total deferred tax assets 186,014 422,836 Deferred tax liabilities Other properties held for sale (5,447 ) (8,179 ) Excess tax over financial statement depreciation (6,628 ) (5,343 ) Other (8,151 ) (13,958 ) Total gross deferred tax liabilities (20,226 ) (27,480 ) Net deferred tax asset $ 165,788 $ 395,356
Schedule of Net Operating Loss and Tax Credit Carryforward	State NOL and tax credit carryforwards as of December 31, 2017 are summarized in the following table. Tax Carryforwards As of December 31, 2017 (in thousands) Expiration Dates Deferred Tax Asset Balance (2) Valuation Allowance Net Deferred Tax Asset Balance Pre-Tax Earnings Necessary to Realize (1) Net operating losses - states 2023-2027 $ 1,688 $ — $ 1,688 $ 1,018,310 Net operating losses - states 2028-2032 48,430 — 48,430 1,093,946 Net operating losses - states 2033-2035 360 — 360 7,584 Other credits - states 2018-2022 18,381 (3,431 ) 14,950 N/A Other credits - states 2023-2027 207 — 207 N/A Other credits - states None 587 — 587 N/A (1) N/A indicates credits are not measured on a pre-tax earnings basis. (2) Effective December 31, 2017, alternative minimum tax credits of $42.1 million were reclassified from deferred tax assets to current taxes receivable reflecting their refundability pursuant to Federal Tax Reform.
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized income tax benefits is as follows (unrecognized state income tax benefits are not adjusted for the federal income tax impact). Years Ended December 31, (in thousands) 2017 2016 2015 Balance at January 1, $ 14,745 $ 12,745 $ 13,023 Additions based on income tax positions related to current year 152 — — Additions for income tax positions of prior years * 934 1,811 8 Additions from acquisition — 608 — Reductions for income tax positions of prior years (706 ) — — Statute of limitation expirations (8 ) (419 ) (286 ) Settlements — — — Balance at December 31, $ 15,117 $ 14,745 $ 12,745 *Includes deferred tax benefits that could reduce future tax liabilities.

Condensed Financial Informati55

Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule of Condensed Balance Sheets	Condensed Balance Sheets December 31, (in thousands) 2017 2016 Assets Cash due from bank subsidiary $ 191,275 $ 234,339 Funds due from other depository institutions (1) 19,911 19,911 Investment in consolidated bank subsidiary, at equity 3,232,129 3,319,980 Investment in consolidated nonbank subsidiaries, at equity 40,731 71,335 Notes receivable from nonbank subsidiaries — 35,200 Other assets 69,762 101,346 Total assets $ 3,553,808 $ 3,782,111 Liabilities and Shareholders' Equity Liabilities: Long-term debt $ 554,589 $ 834,252 Other liabilities 37,653 19,935 Total liabilities 592,242 854,187 Shareholders’ equity: Series C Preferred Stock 125,980 125,980 Common stock 142,678 142,026 Additional paid-in capital 3,043,129 3,028,405 Treasury stock (839,674 ) (664,595 ) Accumulated other comprehensive loss, net (54,754 ) (55,659 ) Retained earnings 544,207 351,767 Total shareholders’ equity 2,961,566 2,927,924 Total liabilities and shareholders’ equity $ 3,553,808 $ 3,782,111 (1) Restricted as to withdrawal. Condensed Statements of Income Years Ended December 31, (in thousands) 2017 2016 2015 Income Cash dividends received from subsidiaries (1) $ 283,210 $ 325,000 $ 199,904 Cash distributions received from subsidiaries (1) 167,790 — 25,096 Interest income 1,443 2,565 8,865 Other income 345 4,595 (337 ) Total income 452,788 332,160 233,528 Expenses Interest expense 43,922 52,831 46,585 Other expenses 33,955 20,652 10,516 Total expenses 77,877 73,483 57,101 Income before income taxes and equity in undistributed (loss) income of subsidiaries 374,911 258,677 176,427 Allocated income tax benefit (30,421 ) (25,628 ) (18,808 ) Income before equity in undistributed (loss) income of subsidiaries 405,332 284,305 195,235 Equity in undistributed (loss) income of subsidiaries (129,858 ) (37,521 ) 30,847 Net income 275,474 246,784 226,082 Dividends on preferred stock 10,238 10,238 10,238 Net income available to common shareholders $ 265,236 $ 236,546 $ 215,844
Schedule of Condensed Statements of Operations	Condensed Statements of Income Years Ended December 31, (in thousands) 2017 2016 2015 Income Cash dividends received from subsidiaries (1) $ 283,210 $ 325,000 $ 199,904 Cash distributions received from subsidiaries (1) 167,790 — 25,096 Interest income 1,443 2,565 8,865 Other income 345 4,595 (337 ) Total income 452,788 332,160 233,528 Expenses Interest expense 43,922 52,831 46,585 Other expenses 33,955 20,652 10,516 Total expenses 77,877 73,483 57,101 Income before income taxes and equity in undistributed (loss) income of subsidiaries 374,911 258,677 176,427 Allocated income tax benefit (30,421 ) (25,628 ) (18,808 ) Income before equity in undistributed (loss) income of subsidiaries 405,332 284,305 195,235 Equity in undistributed (loss) income of subsidiaries (129,858 ) (37,521 ) 30,847 Net income 275,474 246,784 226,082 Dividends on preferred stock 10,238 10,238 10,238 Net income available to common shareholders $ 265,236 $ 236,546 $ 215,844 (1) Substantially all cash dividends and distributions are from Synovus Bank.
Schedule of Condensed Statements of Comprehensive Income (Loss)	Condensed Statements of Comprehensive Income December 31, 2017 December 31, 2016 December 31, 2015 (in thousands) Before-tax Amount Tax (Expense) Benefit Net of Tax Amount Before-tax Amount Tax (Expense) Benefit Net of Tax Amount Before-tax Amount Tax (Expense) Benefit Net of Tax Amount Net income $ 480,138 $ (204,664 ) $ 275,474 $ 388,451 $ (141,667 ) $ 246,784 $ 358,573 $ (132,491 ) $ 226,082 Reclassification adjustment for losses realized in net income on cash flow hedges 130 (50 ) 80 467 (180 ) 287 521 (201 ) 320 Reclassification adjustment for net gains realized in net income on investment securities available for sale (5,506 ) 2,120 (3,386 ) (5,763 ) 2,219 (3,544 ) — — — Net unrealized gains on investment securities available for sale — — — 2,358 (908 ) 1,450 2,908 (1,120 ) 1,788 Other comprehensive gain (loss) of bank subsidiary 6,784 (2,573 ) 4,211 (39,080 ) 15,047 (24,033 ) (31,420 ) 12,098 (19,322 ) Other comprehensive income (loss) $ 1,408 (503 ) 905 (42,018 ) 16,178 (25,840 ) (27,991 ) 10,777 (17,214 ) Comprehensive income $ 276,379 $ 220,944 $ 208,868 Condensed Statements of Cash Flows Years Ended December 31, (in thousands) 2017 2016 2015 Operating Activities Net income $ 275,474 $ 246,784 $ 226,082 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed loss (income) of subsidiaries 129,858 37,521 (30,847 ) Deferred income tax expense (benefit) 60,931 17,989 (2,506 ) Net (decrease) increase in other liabilities (1,095 ) 7,746 (1,709 ) Net (increase) decrease in other assets (8 ) (9,214 ) 1,045 Other, net (3,330 ) (1,648 ) (178 ) Net cash provided by operating activities 461,830 299,178 191,887 Investing Activities Proceeds from sales of investment securities available for sale 4,305 — — Outlays for business combinations — (3,408 ) — Net decrease in short-term notes receivable from non-bank subsidiaries 35,200 31,800 10,000 Net cash provided by investing activities 39,505 28,392 10,000 Financing Activities Dividends paid to common and preferred shareholders (64,908 ) (69,663 ) (65,592 ) Repurchases of common stock (175,079 ) (263,084 ) (199,221 ) Repayments on long-term debt (600,386 ) (130,048 ) (48,553 ) Proceeds from issuance of long-term debt 296,866 — 246,644 Earnout payment (892 ) — — Net cash used in financing activities (544,399 ) (462,795 ) (66,722 ) (Decrease) increase in cash and funds due from banks (43,064 ) (135,225 ) 135,165 Cash and funds due from banks at beginning of year 254,250 389,475 254,310 Cash and funds due from banks at end of year $ 211,186 $ 254,250 $ 389,475
Schedule of Condensed Statements of Cash Flows	Condensed Statements of Cash Flows Years Ended December 31, (in thousands) 2017 2016 2015 Operating Activities Net income $ 275,474 $ 246,784 $ 226,082 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed loss (income) of subsidiaries 129,858 37,521 (30,847 ) Deferred income tax expense (benefit) 60,931 17,989 (2,506 ) Net (decrease) increase in other liabilities (1,095 ) 7,746 (1,709 ) Net (increase) decrease in other assets (8 ) (9,214 ) 1,045 Other, net (3,330 ) (1,648 ) (178 ) Net cash provided by operating activities 461,830 299,178 191,887 Investing Activities Proceeds from sales of investment securities available for sale 4,305 — — Outlays for business combinations — (3,408 ) — Net decrease in short-term notes receivable from non-bank subsidiaries 35,200 31,800 10,000 Net cash provided by investing activities 39,505 28,392 10,000 Financing Activities Dividends paid to common and preferred shareholders (64,908 ) (69,663 ) (65,592 ) Repurchases of common stock (175,079 ) (263,084 ) (199,221 ) Repayments on long-term debt (600,386 ) (130,048 ) (48,553 ) Proceeds from issuance of long-term debt 296,866 — 246,644 Earnout payment (892 ) — — Net cash used in financing activities (544,399 ) (462,795 ) (66,722 ) (Decrease) increase in cash and funds due from banks (43,064 ) (135,225 ) 135,165 Cash and funds due from banks at beginning of year 254,250 389,475 254,310 Cash and funds due from banks at end of year $ 211,186 $ 254,250 $ 389,475

Supplemental Financial Data (Ta

Supplemental Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Income Statement Elements [Abstract]
Schedule of Income Statement, Supplemental Disclosure	Components of other non-interest income and other operating expenses in excess of 1% of total interest income and total non-interest income for any of the respective years are as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Insurance and bonds $ 10,314 $ 12,023 $ 12,514

Summary of Quarterly Financia57

Summary of Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Schedule of Quarterly Financial Information	Presented below is a summary of the unaudited consolidated quarterly financial data for the years ended December 31, 2017 and 2016 . 2017 (in thousands, except per share data) Fourth Quarter (1) Third Quarter Second Quarter First Quarter Interest income $ 306,934 $ 297,652 $ 285,510 $ 272,401 Net interest income 269,713 262,572 251,097 239,927 Provision for loan losses 8,565 39,686 10,260 8,674 Income before income taxes 103,966 152,675 117,791 105,704 Income tax expense 74,361 54,668 41,788 33,847 Net income 29,605 98,007 76,003 71,857 Net income available to common shareholders 27,046 95,448 73,444 69,298 Net income per common share, basic 0.23 0.79 0.60 0.57 Net income per common share, diluted 0.23 0.78 0.60 0.56 (1) The results for the fourth quarter 2017 include $23.2 million pre-tax loss on early extinguishment of debt, as well as a $47.2 million income tax charge related to the effect of Federal Tax Reform. 2016 Fourth Quarter Third Quarter Second Quarter First Quarter Interest income $ 264,534 $ 256,554 $ 252,393 $ 249,323 Net interest income 233,530 226,007 221,449 218,193 Provision for loan losses 6,259 5,671 6,693 9,377 Income before income taxes 108,068 102,620 94,031 83,730 Income tax expense 39,519 37,375 33,574 31,199 Net income 68,549 65,245 60,457 52,531 Net income available to common shareholders 65,990 62,686 57,898 49,972 Net income per common share, basic 0.54 0.51 0.46 0.39 Net income per common share, diluted 0.54 0.51 0.46 0.39

Summary of Significant Accoun58

Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Dec. 31, 2016	Nov. 17, 2016
Basis Of Presentation [Line Items]
Cash and cash equivalents		$ 8,600,000		$ 130,000,000
Interest earning deposits with banks		5,900,000		5,600,000
Federal funds sold		43,800,000		56,100,000
Loans, net of deferred fees and costs		24,538,196,000		23,604,633,000
Federal Reserve Bank stock held		95,600,000		98,600,000	$ 97,300,000
Federal Home Loan Bank stock held		63,900,000		71,300,000
Tax Cuts and Jobs Act of 2017, income tax expense		47,200,000
Share-based compensation, excess tax benefit, amount		5,000,000
Increase in retained earnings		$ 7,800,000
Forecast
Basis Of Presentation [Line Items]
Increase in retained earnings	$ 7,800,000
Increase in regulatory capital	7,800,000
Accounting Standards Update 2016-02 | Forecast
Basis Of Presentation [Line Items]
Operating lease commitments			$ 230,000,000
Operating lease, right-of-use asset			$ 230,000,000
Accounting Standards Update 2016-09 | Retained Earnings | Forecast
Basis Of Presentation [Line Items]
Cumulative effect of new accounting principle in period of adoption	$ 650,000
Non-employee Director
Basis Of Presentation [Line Items]
Vesting period		3 years
Non-employee
Basis Of Presentation [Line Items]
Vesting period		3 years
DRR Methodology
Basis Of Presentation [Line Items]
Loans, net of deferred fees and costs		$ 7,600,000,000		0
Maximum
Basis Of Presentation [Line Items]
Retail loans and commercial loans, evaluated for impairment		$ 1,000,000
Useful life		10 years
Minimum
Basis Of Presentation [Line Items]
Useful life		8 years
Cash And Cash Equivalents
Basis Of Presentation [Line Items]
Total deposits		$ 0		$ 533,000

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($) $ in Thousands	Sep. 25, 2017	Oct. 01, 2016	Nov. 30, 2017	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Brokered deposits					$ 1,961,125	$ 1,378,983
Common stock, shares issued (in shares)					142,677,449	142,025,720
Common stock					$ 142,678	$ 142,026
Other intangible assets					11,254	$ 13,223
Existing Borrower Relationships
Business Acquisition [Line Items]
Useful life				11 years
Trade Names
Business Acquisition [Line Items]
Useful life				10 years
Distribution Network
Business Acquisition [Line Items]
Useful life				8 years
Global One
Business Acquisition [Line Items]
Consideration transferred		$ 30,000
Common stock, shares issued (in shares)		821,000
Common stock		$ 26,592
Cash paid		$ 3,408
Adjustment in goodwill				$ 2,400
Adjustment in contingent consideration				$ 1,800
Earnout payment of stock and cash			$ 6,400
Earnout liability					11,300
Global One | Existing Borrower Relationships
Business Acquisition [Line Items]
Other intangible assets					9,600
Global One | Trade Names
Business Acquisition [Line Items]
Other intangible assets					962
Global One | Distribution Network
Business Acquisition [Line Items]
Other intangible assets					$ 506
Global One | Minimum
Business Acquisition [Line Items]
Potential additional payments based on earnings, period		3 years
Global One | Maximum
Business Acquisition [Line Items]
Potential additional payments based on earnings, period		5 years
World's Foremost Bank (WFB)
Business Acquisition [Line Items]
Brokered deposits	$ 1,100,000
Deposits portfolio, weighted average maturity, period	2 years 6 months 11 days
Weighted average rate of deposit, brokered	1.83%
Proceeds from fees	$ 75,000

Acquisitions (Assets Acquired a

Acquisitions (Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Oct. 01, 2016	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Brokered deposits			$ 1,961,125	$ 1,378,983
Common stock, shares issued (in shares)			142,677,449	142,025,720
Assets acquired:
Goodwill			$ 57,315	$ 59,678
Liabilities assumed:
Fair value of common stock issued			142,678	142,026
Long-term debt			1,706,138	2,160,881
Other intangible assets			11,254	$ 13,223
Global One
Business Acquisition [Line Items]
Consideration transferred	$ 30,000
Common stock, shares issued (in shares)	821,000
Assets acquired:
Cash and due from banks	$ 9,554
Commercial and industrial loans	357,307
Goodwill	32,884
Other intangible assets	12,500		$ 12,500
Other assets	3,681
Total assets acquired	415,926
Liabilities assumed:
Notes payable	358,560
Earnout liability	12,234
Deferred tax liability, net	3,229
Other liabilities	11,903
Total liabilities assumed	385,926
Consideration paid	30,000
Cash paid	3,408
Adjustment in goodwill		$ 2,400
Fair value of common stock issued	26,592
Loans, unpaid principal balance	356,700
Long-term debt	$ 357,000
Adjustment in contingent consideration		$ 1,800

Restructuring Charges (Narrativ

Restructuring Charges (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net	$ 7,000	$ 7,014	$ 8,267	$ 36
Special and contractual termination benefits		6,100
Severance benefits		336
Asset impairment charges		715	8,107	229
Gain on sale of certain branch locations				401
Other operating expenses		88,949	92,919	91,370
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net		$ 6,100
Continued Corporate Real Estate Optimization Activities
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net			5,300
Facility Closing
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net			$ 2,800
Other operating expenses				$ 437

Restructuring Charges (Restruct

Restructuring Charges (Restructuring and Related Costs) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Charges [Abstract]
Severance charges		$ 6,128	$ 0	$ 0
Asset impairment charges		715	8,107	229
Gain on sale of assets held for sale, net		(4)	0	(401)
Other charges		175	160	208
Total restructuring charges	$ 7,000	$ 7,014	$ 8,267	$ 36

Restructuring Charges (Restru63

Restructuring Charges (Restructuring Reserve) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Reserve [Roll Forward]
Beginning balance	$ 4,049	$ 6,617	$ 8,830
Accruals for lease terminations	6,128	6	(3)
Payments	(6,565)	(2,574)	(2,210)
Ending balance	3,612	4,049	6,617
Employee Severance
Restructuring Reserve [Roll Forward]
Beginning balance	81	1,930	3,291
Accruals for lease terminations	6,128	0	0
Payments	(5,873)	(1,849)	(1,361)
Ending balance	336	81	1,930
Lease Termination Charges
Restructuring Reserve [Roll Forward]
Beginning balance	3,968	4,687	5,539
Accruals for lease terminations	0	6	(3)
Payments	(692)	(725)	(849)
Ending balance	$ 3,276	$ 3,968	$ 4,687

Investment Securities Availab64

Investment Securities Available for Sale (Narrative) (Details) $ in Millions	Dec. 31, 2017USD ($)securities	Dec. 31, 2016USD ($)
Investments [Abstract]
Pledged to secure deposits | $	$ 2,000	$ 2,040
Securities in a loss position for less than twelve months	60
Securities in a loss position for more than twelve months	54

Investment Securities Availab65

Investment Securities Available for Sale (Summary Of Available For Sale Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 4,038,239	$ 3,768,618
Gross Unrealized Gains	6,107	11,114
Gross Unrealized Losses	(57,277)	(61,537)
Fair Value	3,987,069	3,718,195
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	83,608	108,221
Gross Unrealized Gains	0	225
Gross Unrealized Losses	(934)	(644)
Fair Value	82,674	107,802
U.S. Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,771	12,727
Gross Unrealized Gains	91	266
Gross Unrealized Losses	0	0
Fair Value	10,862	12,993
Mortgage-backed securities issued by U.S. Government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	121,283	174,440
Gross Unrealized Gains	519	1,116
Gross Unrealized Losses	(1,362)	(1,354)
Fair Value	120,440	174,202
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,666,818	2,543,495
Gross Unrealized Gains	5,059	5,416
Gross Unrealized Losses	(31,354)	(42,571)
Fair Value	2,640,523	2,506,340
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,135,259	905,789
Gross Unrealized Gains	144	1,214
Gross Unrealized Losses	(23,404)	(16,561)
Fair Value	1,111,999	890,442
State and municipal securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	180	2,780
Gross Unrealized Gains	0	14
Gross Unrealized Losses	0	0
Fair Value	180	2,794
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		919
Gross Unrealized Gains		2,863
Gross Unrealized Losses		0
Fair Value		3,782
Corporate debt and other securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,320	20,247
Gross Unrealized Gains	294	0
Gross Unrealized Losses	(223)	(407)
Fair Value	$ 20,391	$ 19,840

Investment Securities Availab66

Investment Securities Available for Sale (Schedule Of Unrealized Loss On Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 1,995,846	$ 3,012,769
Less than 12 Months, Unrealized Losses	20,560	60,156
12 Months or Longer, Fair Value	1,445,859	33,315
12 Months or Longer, Unrealized Losses	36,717	1,381
Total Fair Value	3,441,705	3,046,084
Total Unrealized Losses	57,277	61,537
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	34,243	64,023
Less than 12 Months, Unrealized Losses	443	644
12 Months or Longer, Fair Value	29,562	0
12 Months or Longer, Unrealized Losses	491	0
Total Fair Value	63,805	64,023
Total Unrealized Losses	934	644
Mortgage-backed securities issued by U.S. Government agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	36,810	128,121
Less than 12 Months, Unrealized Losses	357	1,240
12 Months or Longer, Fair Value	55,740	3,626
12 Months or Longer, Unrealized Losses	1,005	114
Total Fair Value	92,550	131,747
Total Unrealized Losses	1,362	1,354
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	1,271,012	2,123,181
Less than 12 Months, Unrealized Losses	10,263	42,571
12 Months or Longer, Fair Value	929,223	0
12 Months or Longer, Unrealized Losses	21,091	0
Total Fair Value	2,200,235	2,123,181
Total Unrealized Losses	31,354	42,571
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	653,781	682,492
Less than 12 Months, Unrealized Losses	9,497	15,653
12 Months or Longer, Fair Value	426,237	24,801
12 Months or Longer, Unrealized Losses	13,907	908
Total Fair Value	1,080,018	707,293
Total Unrealized Losses	23,404	16,561
Corporate debt and other securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	14,952
Less than 12 Months, Unrealized Losses	0	48
12 Months or Longer, Fair Value	5,097	4,888
12 Months or Longer, Unrealized Losses	223	359
Total Fair Value	5,097	19,840
Total Unrealized Losses	$ 223	$ 407

Investment Securities Availab67

Investment Securities Available for Sale (Amortized Cost And Estimated Fair Value By Contractual Maturity Of Investment Securities Available For Sale) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	$ 21,399
Amortized Cost, 1 to 5 Years	73,013
Amortized Cost, 5 to 10 Years	502,634
Amortized Cost, More Than 10 years	3,437,873
Amortized Cost, Amortized Cost, No Stated Maturity	3,320
Total Amortized Cost	4,038,239
Fair Value, Within One year	21,428
Fair Value, 1 to 5 Years	72,191
Fair Value, 5 to 10 Years	498,036
Fair Value, More Than 10 years	3,392,252
Fair Value, No Stated Maturity	3,162
Total Fair Value	3,987,069
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	18,870
Amortized Cost, 1 to 5 Years	64,738
Amortized Cost, 5 to 10 Years	0
Amortized Cost, More Than 10 years	0
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	83,608
Fair Value, Within One year	18,870
Fair Value, 1 to 5 Years	63,804
Fair Value, 5 to 10 Years	0
Fair Value, More Than 10 years	0
Fair Value, No Stated Maturity	0
Total Fair Value	82,674
U.S. Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	2,331
Amortized Cost, 1 to 5 Years	6,437
Amortized Cost, 5 to 10 Years	2,003
Amortized Cost, More Than 10 years	0
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	10,771
Fair Value, Within One year	2,360
Fair Value, 1 to 5 Years	6,459
Fair Value, 5 to 10 Years	2,043
Fair Value, More Than 10 years	0
Fair Value, No Stated Maturity	0
Total Fair Value	10,862
Mortgage-backed securities issued by U.S. Government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	31,259
Amortized Cost, More Than 10 years	90,024
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	121,283
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	0
Fair Value, 5 to 10 Years	31,193
Fair Value, More Than 10 years	89,247
Fair Value, No Stated Maturity	0
Total Fair Value	120,440
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	18
Amortized Cost, 1 to 5 Years	1,838
Amortized Cost, 5 to 10 Years	434,603
Amortized Cost, More Than 10 years	2,230,359
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	2,666,818
Fair Value, Within One year	18
Fair Value, 1 to 5 Years	1,928
Fair Value, 5 to 10 Years	430,140
Fair Value, More Than 10 years	2,208,437
Fair Value, No Stated Maturity	0
Total Fair Value	2,640,523
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	19,769
Amortized Cost, More Than 10 years	1,115,490
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	1,135,259
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	0
Fair Value, 5 to 10 Years	19,366
Fair Value, More Than 10 years	1,092,633
Fair Value, No Stated Maturity	0
Total Fair Value	1,111,999
State and municipal securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	180
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	0
Amortized Cost, More Than 10 years	0
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	180
Fair Value, Within One year	180
Fair Value, 1 to 5 Years	0
Fair Value, 5 to 10 Years	0
Fair Value, More Than 10 years	0
Fair Value, No Stated Maturity	0
Total Fair Value	180
Corporate debt and other securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	15,000
Amortized Cost, More Than 10 years	2,000
Amortized Cost, Amortized Cost, No Stated Maturity	3,320
Total Amortized Cost	20,320
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	0
Fair Value, 5 to 10 Years	15,294
Fair Value, More Than 10 years	1,935
Fair Value, No Stated Maturity	3,162
Total Fair Value	$ 20,391

Investment Securities Availab68

Investment Securities Available for Sale (Summary Of Sales Transactions In The Investment Securities Available For Sale Portfolio) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments [Abstract]
Proceeds from sales of investment securities available for sale	$ 812,293	$ 968,606	$ 347,954
Gross realized gains on sales	7,942	9,586	4,356
Gross realized losses on sales	(8,231)	(3,575)	(1,587)
Investment securities (losses) gains, net	(289)	6,011	2,769
Available-for-sale securities, transfers, gains		1,400
Investment securities available for sale transferred to trading account assets at fair value	$ 0	$ 1,890	$ 0

Loans And Allowance For Loan 69

Loans And Allowance For Loan Losses (Narrative) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)Contract	Dec. 31, 2016USD ($)Contract	Dec. 31, 2015USD ($)Contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, impaired, interest lost on nonaccrual loans									$ 9,100,000	$ 8,900,000
Interest income recognized									6,961,000	8,196,000
Average recorded investment in impaired loans									223,009,000	274,515,000	$ 358,300,000
Accrued interest income recognized											9,500,000
Investments income recognized in impairment loans, excluding TDRs									0	0	0
Impaired financing receivable, recorded investment, nonaccrual status	$ 49,000,000				$ 53,700,000				$ 49,000,000	$ 53,700,000	$ 77,900,000
Subsequent default, number of contracts | Contract									8	2	7
Accruing troubled debt restructuring	151,300,000				195,800,000				$ 151,300,000	$ 195,800,000
Provision for losses on loans	$ 8,565,000	$ 39,686,000	$ 10,260,000	$ 8,674,000	$ 6,259,000	$ 5,671,000	$ 6,693,000	$ 9,377,000	67,185,000	28,000,000	$ 19,010,000
Troubled Debt Restructurings That Subsequently Defaulted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modifications, post-modification recorded investment									4,000,000	181,000	$ 12,500,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial-type impaired loans									1,000,000
Interest Income Recorded
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income recognized									$ 2,700,000	3,500,000
Loss And Charged Off
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan charge-off period (in days)									120 days
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan substandard period (in days)									90 days
Accruing TDRs With Modifications And Renewals Completed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for losses on loans									$ 8,700,000	$ 9,800,000

Loans And Allowance For Loan 70

Loans And Allowance For Loan Losses (Loans Outstanding By Classification) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 24,812,795	$ 23,882,382
Deferred fees and costs, net	(25,331)	(25,991)	$ (30,100)
Total loans, net of deferred fees and costs	24,787,464	23,856,391
Total commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	6,935,288	7,374,112
Total loans	6,935,288	7,374,112
Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	5,670,065	5,869,261
Total loans	5,670,065	5,869,261
Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	781,619	888,553
Total loans	781,619	888,553
Total commercial real estate | Land and development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	483,604	616,298
Total loans	483,604	616,298
Total commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial and industrial	12,023,650	11,543,806
Total loans	12,023,650	11,543,806
Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial and industrial	7,179,487	6,909,036
Total loans	7,179,487	6,909,036
Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial and industrial	4,844,163	4,634,770
Total loans	4,844,163	4,634,770
Total consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	5,853,857	4,964,464
Total loans	5,853,857	4,964,464
Total consumer | Home equity lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	1,514,227	1,617,265
Total loans	1,514,227	1,617,265
Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	2,633,503	2,296,604
Total loans	2,633,503	2,296,604
Total consumer | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	232,676	232,413
Total loans	232,676	232,413
Total consumer | Other consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	1,473,451	818,182
Total loans	$ 1,473,451	$ 818,182

Loans And Allowance For Loan 71

Loans And Allowance For Loan Losses (Schedule Of Current, Accruing Past Due And Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	$ 24,645,203	$ 23,663,898
Accruing 30-89 Days Past Due	47,617	61,971
Accruing 90 Days or Greater Past Due	4,414	3,135
Total Accruing Past Due	52,031	65,106
Non-accrual	115,561	153,378
Total loans	24,812,795	23,882,382
Deferred fees and costs, net	25,331	25,991	$ 30,100
Total commercial real estate
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	6,914,819	7,334,299
Accruing 30-89 Days Past Due	7,660	9,037
Accruing 90 Days or Greater Past Due	359	161
Total Accruing Past Due	8,019	9,198
Non-accrual	12,450	30,615
Total loans	6,935,288	7,374,112
Total commercial real estate | Investment properties
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	5,663,665	5,861,198
Accruing 30-89 Days Past Due	2,506	2,795
Accruing 90 Days or Greater Past Due	90	0
Total Accruing Past Due	2,596	2,795
Non-accrual	3,804	5,268
Total loans	5,670,065	5,869,261
Total commercial real estate | 1-4 family properties
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	775,023	874,477
Accruing 30-89 Days Past Due	3,545	4,801
Accruing 90 Days or Greater Past Due	202	161
Total Accruing Past Due	3,747	4,962
Non-accrual	2,849	9,114
Total loans	781,619	888,553
Total commercial real estate | Land and development
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	476,131	598,624
Accruing 30-89 Days Past Due	1,609	1,441
Accruing 90 Days or Greater Past Due	67	0
Total Accruing Past Due	1,676	1,441
Non-accrual	5,797	16,233
Total loans	483,604	616,298
Total commercial and industrial
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	11,927,277	11,439,810
Accruing 30-89 Days Past Due	18,094	27,455
Accruing 90 Days or Greater Past Due	1,495	964
Total Accruing Past Due	19,589	28,419
Non-accrual	76,784	75,577
Total loans	12,023,650	11,543,806
Total commercial and industrial | Commercial, financial and agricultural
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	7,097,127	6,839,700
Accruing 30-89 Days Past Due	11,214	9,542
Accruing 90 Days or Greater Past Due	1,016	720
Total Accruing Past Due	12,230	10,262
Non-accrual	70,130	59,074
Total loans	7,179,487	6,909,036
Total commercial and industrial | Owner-occupied
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	4,830,150	4,600,110
Accruing 30-89 Days Past Due	6,880	17,913
Accruing 90 Days or Greater Past Due	479	244
Total Accruing Past Due	7,359	18,157
Non-accrual	6,654	16,503
Total loans	4,844,163	4,634,770
Total consumer
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	5,803,107	4,889,789
Accruing 30-89 Days Past Due	21,863	25,479
Accruing 90 Days or Greater Past Due	2,560	2,010
Total Accruing Past Due	24,423	27,489
Non-accrual	26,327	47,186
Total loans	5,853,857	4,964,464
Total consumer | Home equity lines
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	1,490,808	1,585,228
Accruing 30-89 Days Past Due	5,629	10,013
Accruing 90 Days or Greater Past Due	335	473
Total Accruing Past Due	5,964	10,486
Non-accrual	17,455	21,551
Total loans	1,514,227	1,617,265
Total consumer | Consumer mortgages
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	2,622,061	2,265,966
Accruing 30-89 Days Past Due	3,971	7,876
Accruing 90 Days or Greater Past Due	268	81
Total Accruing Past Due	4,239	7,957
Non-accrual	7,203	22,681
Total loans	2,633,503	2,296,604
Total consumer | Credit cards
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	229,015	229,177
Accruing 30-89 Days Past Due	1,930	1,819
Accruing 90 Days or Greater Past Due	1,731	1,417
Total Accruing Past Due	3,661	3,236
Non-accrual	0	0
Total loans	232,676	232,413
Total consumer | Other consumer loans
Valuation and Qualifying Accounts Disclosure [Line Items]
Current	1,461,223	809,418
Accruing 30-89 Days Past Due	10,333	5,771
Accruing 90 Days or Greater Past Due	226	39
Total Accruing Past Due	10,559	5,810
Non-accrual	1,669	2,954
Total loans	$ 1,473,451	$ 818,182

Loans And Allowance For Loan 72

Loans And Allowance For Loan Losses (Loan Portfolio Credit Exposure) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 24,812,795	$ 23,882,382
Performing, accrual of interest	190,600	256,600
Deferred fees and costs, net	25,331	25,991	$ 30,100
Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,935,288	7,374,112
Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,670,065	5,869,261
Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	781,619	888,553
Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	483,604	616,298
Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,023,650	11,543,806
Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,179,487	6,909,036
Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,844,163	4,634,770
Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 5,853,857	4,964,464
Allowance for loan and lease losses, percent of loan amount	50.00%
Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 1,514,227	1,617,265
Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,633,503	2,296,604
Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	232,676	232,413
Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,473,451	818,182
Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	24,222,726	23,147,814
Pass | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,763,850	7,143,928
Pass | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,586,792	5,794,626
Pass | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	745,299	827,557
Pass | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	431,759	521,745
Pass | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,643,383	11,096,931
Pass | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,929,506	6,635,757
Pass | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,713,877	4,461,174
Pass | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,815,493	4,906,955
Pass | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,491,105	1,589,199
Pass | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,622,499	2,271,916
Pass | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	230,945	230,997
Pass | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,470,944	814,843
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	283,865	324,593
Special Mention | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	117,813	137,469
Special Mention | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	64,628	43,336
Special Mention | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	19,419	33,928
Special Mention | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	33,766	60,205
Special Mention | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	166,052	187,124
Special Mention | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	115,912	126,268
Special Mention | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	50,140	60,856
Special Mention | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Special Mention | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	297,640	387,117
Substandard | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	50,496	85,450
Substandard | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	18,645	31,299
Substandard | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	16,901	26,790
Substandard | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	14,950	27,361
Substandard | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	212,891	251,755
Substandard | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	132,818	140,425
Substandard | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	80,073	111,330
Substandard | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	34,253	49,912
Substandard | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	21,079	22,774
Substandard | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	10,607	23,268
Substandard | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	399	637
Substandard | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,168	3,233
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,358	19,337
Doubtful | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,129	7,265
Doubtful | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Doubtful | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	278
Doubtful | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,129	6,987
Doubtful | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,324	7,855
Doubtful | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,251	6,445
Doubtful | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	73	1,410
Doubtful | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	905	4,217
Doubtful | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	285	2,892
Doubtful | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	291	1,283
Doubtful | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Doubtful | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	329	42
Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,206	3,521
Loss | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial real estate | Land and development
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	141
Loss | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	141
Loss | Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,206	3,380
Loss | Total consumer | Home equity lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,758	2,400
Loss | Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment [Line Items]
Total loans	106	137
Loss | Total consumer | Credit cards
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,332	779
Loss | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 10	$ 64

Loans And Allowance For Loan 73

Loans And Allowance For Loan Losses (Schedule Of Allowances For Loan Losses And Recorded Investment In Loans) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 251,758				$ 252,496	$ 251,758	$ 252,496	$ 261,317
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(90,419)	(57,960)	(57,339)
Recoveries									20,744	29,222	29,508
Provision for loan losses	$ 8,565	$ 39,686	$ 10,260	8,674	$ 6,259	$ 5,671	$ 6,693	9,377	67,185	28,000	19,010
Ending balance	249,268				251,758				249,268	251,758	252,496
Ending balance: individually evaluated for impairment	14,908				18,111				14,908	18,111	30,435
Ending balance: collectively evaluated for impairment	234,360				233,647				234,360	233,647	222,061
Ending balance: total loans	24,812,795				23,882,382				24,812,795	23,882,382	22,459,664
Ending balance: individually evaluated for impairment	200,286				249,496				200,286	249,496	301,800
Ending balance: collectively evaluated for impairment	24,612,509				23,632,886				24,612,509	23,632,886	22,157,864
Deferred fees and costs, net	25,331				25,991				25,331	25,991	30,100
Total commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				81,816				87,133	81,816	87,133	101,471
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(12,193)	(18,216)	(13,998)
Recoveries									8,026	15,226	13,644
Provision for loan losses									(2,651)	(2,327)	(13,984)
Ending balance	74,998				81,816				74,998	81,816	87,133
Ending balance: individually evaluated for impairment	4,240				7,916				4,240	7,916	18,969
Ending balance: collectively evaluated for impairment	70,758				73,900				70,758	73,900	68,164
Ending balance: total loans	6,935,288				7,374,112				6,935,288	7,374,112	7,394,768
Ending balance: individually evaluated for impairment	56,896				91,410				56,896	91,410	157,958
Ending balance: collectively evaluated for impairment	6,878,392				7,282,702				6,878,392	7,282,702	7,236,810
Total commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				125,778				122,989	125,778	122,989	118,110
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(49,244)	(25,039)	(22,583)
Recoveries									6,685	9,071	8,611
Provision for loan losses									43,584	18,757	18,851
Ending balance	126,803				125,778				126,803	125,778	122,989
Ending balance: individually evaluated for impairment	9,515				8,384				9,515	8,384	10,477
Ending balance: collectively evaluated for impairment	117,288				117,394				117,288	117,394	112,512
Ending balance: total loans	12,023,650				11,543,806				12,023,650	11,543,806	10,772,130
Ending balance: individually evaluated for impairment	111,334				120,560				111,334	120,560	105,599
Ending balance: collectively evaluated for impairment	11,912,316				11,423,246				11,912,316	11,423,246	10,666,531
Total consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 44,164				$ 42,374	44,164	42,374	41,736
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(28,982)	(14,705)	(20,758)
Recoveries									6,033	4,925	7,253
Provision for loan losses									26,252	11,570	14,143
Ending balance	47,467				44,164				47,467	44,164	42,374
Ending balance: individually evaluated for impairment	1,153				1,811				1,153	1,811	989
Ending balance: collectively evaluated for impairment	46,314				42,353				46,314	42,353	41,385
Ending balance: total loans	5,853,857				4,964,464				5,853,857	4,964,464	4,292,766
Ending balance: individually evaluated for impairment	32,056				37,526				32,056	37,526	38,243
Ending balance: collectively evaluated for impairment	$ 5,821,801				$ 4,926,938				$ 5,821,801	$ 4,926,938	$ 4,254,523

Loans And Allowance For Loan 74

Loans And Allowance For Loan Losses (Schedule Of Impaired Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	$ 11,022	$ 28,751
Unpaid Principal Balance, With no related allowance recorded	14,259	40,794
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	32,314	26,433
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	189,264	220,745
Unpaid Principal Balance, With allowance recorded	189,498	223,512
Related Allowance, With allowance recorded	14,908	18,111
Average Recorded Investment, With allowance recorded	190,695	248,082
Interest Income Recognized, With allowance recorded	6,961	8,196
Recorded Investment	200,286	249,496
Unpaid Principal Balance	203,757	264,306
Related Allowance	14,908	18,111
Average Recorded Investment in Impaired Loans	223,009	274,515	$ 358,300
Interest Income Recognized	6,961	8,196
Total commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	56	3,490
Unpaid Principal Balance, With no related allowance recorded	1,740	10,975
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	2,262	9,803
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	56,840	87,920
Unpaid Principal Balance, With allowance recorded	56,896	87,926
Related Allowance, With allowance recorded	4,240	7,916
Average Recorded Investment, With allowance recorded	68,344	108,091
Interest Income Recognized, With allowance recorded	2,473	3,286
Recorded Investment	56,896	91,410
Unpaid Principal Balance	58,636	98,901
Related Allowance	4,240	7,916
Average Recorded Investment in Impaired Loans	70,606	117,894
Interest Income Recognized	2,473	3,286
Total commercial real estate | Investment properties
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0	748
Unpaid Principal Balance, With no related allowance recorded	0	793
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	123	2,013
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	23,364	31,489
Unpaid Principal Balance, With allowance recorded	23,364	31,489
Related Allowance, With allowance recorded	1,100	2,044
Average Recorded Investment, With allowance recorded	28,749	42,659
Interest Income Recognized, With allowance recorded	1,144	1,436
Recorded Investment	23,364	32,237
Unpaid Principal Balance	23,364	32,282
Related Allowance	1,100	2,044
Average Recorded Investment in Impaired Loans	28,872	44,672
Interest Income Recognized	1,144	1,436
Total commercial real estate | 1-4 family properties
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0	643
Unpaid Principal Balance, With no related allowance recorded	0	2,939
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	323	1,021
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	15,056	23,642
Unpaid Principal Balance, With allowance recorded	15,056	23,649
Related Allowance, With allowance recorded	504	769
Average Recorded Investment, With allowance recorded	16,257	39,864
Interest Income Recognized, With allowance recorded	925	855
Recorded Investment	15,056	24,285
Unpaid Principal Balance	15,056	26,588
Related Allowance	504	769
Average Recorded Investment in Impaired Loans	16,580	40,885
Interest Income Recognized	925	855
Total commercial real estate | Land and development
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	56	2,099
Unpaid Principal Balance, With no related allowance recorded	1,740	7,243
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	1,816	6,769
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	18,420	32,789
Unpaid Principal Balance, With allowance recorded	18,476	32,788
Related Allowance, With allowance recorded	2,636	5,103
Average Recorded Investment, With allowance recorded	23,338	25,568
Interest Income Recognized, With allowance recorded	404	995
Recorded Investment	18,476	34,888
Unpaid Principal Balance	20,216	40,031
Related Allowance	2,636	5,103
Average Recorded Investment in Impaired Loans	25,154	32,337
Interest Income Recognized	404	995
Total commercial and industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	8,220	23,466
Unpaid Principal Balance, With no related allowance recorded	9,576	27,954
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	28,351	14,715
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	103,114	97,094
Unpaid Principal Balance, With allowance recorded	103,292	99,855
Related Allowance, With allowance recorded	9,515	8,384
Average Recorded Investment, With allowance recorded	90,966	104,268
Interest Income Recognized, With allowance recorded	2,992	3,161
Recorded Investment	111,334	120,560
Unpaid Principal Balance	112,868	127,809
Related Allowance	9,515	8,384
Average Recorded Investment in Impaired Loans	119,317	118,983
Interest Income Recognized	2,992	3,161
Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	8,220	17,958
Unpaid Principal Balance, With no related allowance recorded	9,576	20,577
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	21,686	6,321
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	65,715	43,386
Unpaid Principal Balance, With allowance recorded	65,851	45,913
Related Allowance, With allowance recorded	7,406	5,687
Average Recorded Investment, With allowance recorded	50,468	51,968
Interest Income Recognized, With allowance recorded	1,610	1,215
Recorded Investment	73,935	61,344
Unpaid Principal Balance	75,427	66,490
Related Allowance	7,406	5,687
Average Recorded Investment in Impaired Loans	72,154	58,289
Interest Income Recognized	1,610	1,215
Total commercial and industrial | Owner-occupied
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0	5,508
Unpaid Principal Balance, With no related allowance recorded	0	7,377
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	6,665	8,394
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	37,399	53,708
Unpaid Principal Balance, With allowance recorded	37,441	53,942
Related Allowance, With allowance recorded	2,109	2,697
Average Recorded Investment, With allowance recorded	40,498	52,300
Interest Income Recognized, With allowance recorded	1,382	1,946
Recorded Investment	37,399	59,216
Unpaid Principal Balance	37,441	61,319
Related Allowance	2,109	2,697
Average Recorded Investment in Impaired Loans	47,163	60,694
Interest Income Recognized	1,382	1,946
Total consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	2,746	1,795
Unpaid Principal Balance, With no related allowance recorded	2,943	1,865
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	1,701	1,915
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	29,310	35,731
Unpaid Principal Balance, With allowance recorded	29,310	35,731
Related Allowance, With allowance recorded	1,153	1,811
Average Recorded Investment, With allowance recorded	31,385	35,723
Interest Income Recognized, With allowance recorded	1,496	1,749
Recorded Investment	32,056	37,526
Unpaid Principal Balance	32,253	37,596
Related Allowance	1,153	1,811
Average Recorded Investment in Impaired Loans	33,086	37,638
Interest Income Recognized	1,496	1,749
Total consumer | Home equity lines
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	2,746	1,051
Unpaid Principal Balance, With no related allowance recorded	2,943	1,051
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	1,205	1,045
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	5,096	9,638
Unpaid Principal Balance, With allowance recorded	5,096	9,638
Related Allowance, With allowance recorded	114	971
Average Recorded Investment, With allowance recorded	7,476	9,668
Interest Income Recognized, With allowance recorded	334	432
Recorded Investment	7,842	10,689
Unpaid Principal Balance	8,039	10,689
Related Allowance	114	971
Average Recorded Investment in Impaired Loans	8,681	10,713
Interest Income Recognized	334	432
Total consumer | Consumer mortgages
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0	744
Unpaid Principal Balance, With no related allowance recorded	0	814
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	496	870
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	18,668	20,953
Unpaid Principal Balance, With allowance recorded	18,668	20,953
Related Allowance, With allowance recorded	569	673
Average Recorded Investment, With allowance recorded	19,144	20,993
Interest Income Recognized, With allowance recorded	896	1,014
Recorded Investment	18,668	21,697
Unpaid Principal Balance	18,668	21,767
Related Allowance	569	673
Average Recorded Investment in Impaired Loans	19,640	21,863
Interest Income Recognized	896	1,014
Total consumer | Credit cards
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0	0
Unpaid Principal Balance, With no related allowance recorded	0	0
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	0	0
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	0	0
Unpaid Principal Balance, With allowance recorded	0	0
Related Allowance, With allowance recorded	0	0
Average Recorded Investment, With allowance recorded	0	0
Interest Income Recognized, With allowance recorded	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment in Impaired Loans	0	0
Interest Income Recognized	0	0
Total consumer | Other consumer loans
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0	0
Unpaid Principal Balance, With no related allowance recorded	0	0
Related Allowance, With no related allowance recorded	0	0
Average Recorded Investment, With no related allowance recorded	0	0
Interest Income Recognized, With no related allowance recorded	0	0
Recorded Investment, With allowance recorded	5,546	5,140
Unpaid Principal Balance, With allowance recorded	5,546	5,140
Related Allowance, With allowance recorded	470	167
Average Recorded Investment, With allowance recorded	4,765	5,062
Interest Income Recognized, With allowance recorded	266	303
Recorded Investment	5,546	5,140
Unpaid Principal Balance	5,546	5,140
Related Allowance	470	167
Average Recorded Investment in Impaired Loans	4,765	5,062
Interest Income Recognized	$ 266	$ 303

Loans And Allowance For Loan 75

Loans And Allowance For Loan Losses (Troubled Debt Restructurings) (Details)	12 Months Ended
	Dec. 31, 2017USD ($)Contract	Dec. 31, 2016USD ($)Contract	Dec. 31, 2015USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	151	169	262
Post-modification balance for loans modified or renewed	$ 36,723,000	$ 52,994,000	$ 80,386,000
Write-down	$ 0	$ 0	$ 4,000,000
Total commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	42	57	66
Post-modification balance for loans modified or renewed	$ 6,718,000	$ 16,429,000	$ 56,424,000
Total commercial real estate | Investment properties
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	4	11
Post-modification balance for loans modified or renewed	$ 121,000	$ 5,343,000	$ 32,025,000
Total commercial real estate | 1-4 family properties
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	35	39	43
Post-modification balance for loans modified or renewed	$ 4,826,000	$ 6,987,000	$ 22,253,000
Total commercial real estate | Land and development
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	6	14	12
Post-modification balance for loans modified or renewed	$ 1,771,000	$ 4,099,000	$ 2,146,000
Total commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	60	72	101
Post-modification balance for loans modified or renewed	$ 23,319,000	$ 33,103,000	$ 15,178,000
Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	56	63	91
Post-modification balance for loans modified or renewed	$ 21,579,000	$ 24,669,000	$ 9,697,000
Total commercial and industrial | Owner-occupied
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	4	9	10
Post-modification balance for loans modified or renewed	$ 1,740,000	$ 8,434,000	$ 5,481,000
Total consumer
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	49	40	95
Post-modification balance for loans modified or renewed	$ 6,686,000	$ 3,462,000	$ 8,784,000
Total consumer | Home equity lines
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	5	53
Post-modification balance for loans modified or renewed	$ 0	$ 348,000	$ 5,731,000
Total consumer | Consumer mortgages
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	11	7	15
Post-modification balance for loans modified or renewed	$ 3,729,000	$ 464,000	$ 1,906,000
Total consumer | Credit cards
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0	0
Post-modification balance for loans modified or renewed	$ 0	$ 0	$ 0
Total consumer | Other consumer loans
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	38	28	27
Post-modification balance for loans modified or renewed	$ 2,957,000	$ 2,650,000	$ 1,147,000
Principal Forgiveness
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	14,852,000
Principal Forgiveness | Total commercial real estate
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	14,823,000
Principal Forgiveness | Total commercial real estate | Investment properties
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Principal Forgiveness | Total commercial real estate | 1-4 family properties
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	14,823,000
Principal Forgiveness | Total commercial real estate | Land and development
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Principal Forgiveness | Total commercial and industrial
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	29,000
Principal Forgiveness | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	29,000
Principal Forgiveness | Total commercial and industrial | Owner-occupied
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Principal Forgiveness | Total consumer
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Principal Forgiveness | Total consumer | Home equity lines
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Principal Forgiveness | Total consumer | Consumer mortgages
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Principal Forgiveness | Total consumer | Credit cards
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Principal Forgiveness | Total consumer | Other consumer loans
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Below Market Interest Rate
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	16,575,000	33,749,000	41,222,000
Below Market Interest Rate | Total commercial real estate
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	2,943,000	7,324,000	30,333,000
Below Market Interest Rate | Total commercial real estate | Investment properties
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	1,825,000	25,052,000
Below Market Interest Rate | Total commercial real estate | 1-4 family properties
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	2,786,000	5,499,000	4,667,000
Below Market Interest Rate | Total commercial real estate | Land and development
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	157,000	0	614,000
Below Market Interest Rate | Total commercial and industrial
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	9,469,000	25,393,000	6,608,000
Below Market Interest Rate | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	9,434,000	17,509,000	3,191,000
Below Market Interest Rate | Total commercial and industrial | Owner-occupied
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	35,000	7,884,000	3,417,000
Below Market Interest Rate | Total consumer
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	4,163,000	1,032,000	4,281,000
Below Market Interest Rate | Total consumer | Home equity lines
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	225,000	2,826,000
Below Market Interest Rate | Total consumer | Consumer mortgages
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	2,539,000	413,000	1,011,000
Below Market Interest Rate | Total consumer | Credit cards
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Below Market Interest Rate | Total consumer | Other consumer loans
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	1,624,000	394,000	444,000
Term Extensions and/or Other Concessions
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	20,148,000	19,245,000	24,312,000
Term Extensions and/or Other Concessions | Total commercial real estate
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	3,775,000	9,105,000	11,268,000
Term Extensions and/or Other Concessions | Total commercial real estate | Investment properties
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	121,000	3,518,000	6,973,000
Term Extensions and/or Other Concessions | Total commercial real estate | 1-4 family properties
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	2,040,000	1,488,000	2,763,000
Term Extensions and/or Other Concessions | Total commercial real estate | Land and development
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	1,614,000	4,099,000	1,532,000
Term Extensions and/or Other Concessions | Total commercial and industrial
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	13,850,000	7,710,000	8,541,000
Term Extensions and/or Other Concessions | Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	12,145,000	7,160,000	6,477,000
Term Extensions and/or Other Concessions | Total commercial and industrial | Owner-occupied
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	1,705,000	550,000	2,064,000
Term Extensions and/or Other Concessions | Total consumer
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	2,523,000	2,430,000	4,503,000
Term Extensions and/or Other Concessions | Total consumer | Home equity lines
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	123,000	2,905,000
Term Extensions and/or Other Concessions | Total consumer | Consumer mortgages
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	1,190,000	51,000	895,000
Term Extensions and/or Other Concessions | Total consumer | Credit cards
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	0	0	0
Term Extensions and/or Other Concessions | Total consumer | Other consumer loans
Financing Receivable, Modifications [Line Items]
Post-modification balance for loans modified or renewed	$ 1,333,000	$ 2,256,000	$ 703,000

Other Comprehensive Income (L76

Other Comprehensive Income (Loss) (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Accumulated other comprehensive loss	$ 54,754	$ 55,659
Net Unrealized Gains (Losses) on Cash Flow Hedges | Valuation Allowance of Deferred Tax Assets
Class of Stock [Line Items]
Accumulated other comprehensive loss	12,100
Net Unrealized Gains (Losses) on Investment Securities Available for Sale | Valuation Allowance of Deferred Tax Assets
Class of Stock [Line Items]
Accumulated other comprehensive loss	$ 13,300

Other Comprehensive Income (L77

Other Comprehensive Income (Loss) (Changes in Accumulated Other Comprehensive Income (Loss) by Component (Net of Income Taxes)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	$ 2,927,924
Other comprehensive income (loss) before reclassifications	714	$ (22,342)	$ (15,663)
Amounts reclassified from accumulated other comprehensive income (loss)	191	(3,498)	(1,551)
Net current period other comprehensive income (loss)	905	(25,840)	(17,214)
Ending balance	2,961,566	2,927,924
AOCI Attributable to Parent [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(55,659)	(29,819)	(12,605)
Ending balance	(54,754)	(55,659)	(29,819)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(12,217)	(12,504)	(12,824)
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	80	287	320
Net current period other comprehensive income (loss)	80	287	320
Ending balance	(12,137)	(12,217)	(12,504)
Net Unrealized Gains (Losses) on Investment Securities Available for Sale
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(44,324)	(18,222)	(713)
Other comprehensive income (loss) before reclassifications	676	(22,405)	(15,806)
Amounts reclassified from accumulated other comprehensive income (loss)	178	(3,697)	(1,703)
Net current period other comprehensive income (loss)	854	(26,102)	(17,509)
Ending balance	(43,470)	(44,324)	(18,222)
Post-Retirement Unfunded Health Benefit
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	882	907	932
Other comprehensive income (loss) before reclassifications	38	63	143
Amounts reclassified from accumulated other comprehensive income (loss)	(67)	(88)	(168)
Net current period other comprehensive income (loss)	(29)	(25)	(25)
Ending balance	$ 853	$ 882	$ 907

Other Comprehensive Income (L78

Other Comprehensive Income (Loss) (Reclassifications out of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									$ (139,188)	$ (123,623)	$ (118,644)
Loss on early extinguishment of debt, net	$ (23,200)								(23,160)	(4,735)	(1,533)
Investment securities (losses) gains, net									(289)	6,011	2,769
Salaries and other personnel expense									(821,313)	(755,923)	(717,655)
Income tax (expense) benefit	(74,361)	$ (54,668)	$ (41,788)	$ (33,847)	$ (39,519)	$ (37,375)	$ (33,574)	$ (31,199)	(204,664)	(141,667)	(132,491)
Net income available to common shareholders	$ 27,046	$ 95,448	$ 73,444	$ 69,298	$ 65,990	$ 62,686	$ 57,898	$ 49,972	265,236	236,546	215,844
Available-for-sale securities, transfers, gains										1,400
Investment securities available for sale transferred to trading account assets at fair value									0	1,890	0
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									(130)	(270)	(448)
Loss on early extinguishment of debt, net									0	(197)	(73)
Income tax (expense) benefit									50	180	201
Net income available to common shareholders									(80)	(287)	(320)
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) on Investment Securities Available for Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities (losses) gains, net									(289)	6,011	2,769
Income tax (expense) benefit									111	(2,314)	(1,066)
Net income available to common shareholders									(178)	3,697	1,703
Reclassification out of Accumulated Other Comprehensive Income | Post-Retirement Unfunded Health Benefit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and other personnel expense									110	144	272
Income tax (expense) benefit									(43)	(56)	(104)
Net income available to common shareholders									$ 67	$ 88	$ 168

Premises and Equipment (Narrati

Premises and Equipment (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Capital lease obligations	$ 1,500	$ 1,600
Operating leases, rent expense	22,000	21,400	$ 23,100
Depreciation and amortization expense	42,200	37,100	35,300
Premises and equipment transferred to other properties held for sale	$ 3,283	$ 25,231	$ 2,340

Premises and Equipment (Schedul

Premises and Equipment (Schedule of Premises and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total premises and equipment	$ 953,815	$ 915,751
Less: Accumulated depreciation and amortization	(527,002)	(498,266)
Premises and equipment, net	426,813	417,485
Land
Property, Plant and Equipment [Line Items]
Total premises and equipment	96,759	97,080
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment	$ 388,254	377,754
Buildings and improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful Life (in years)	10 years
Buildings and improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful Life (in years)	40 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment	$ 38,970	41,355
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful Life (in years)	10 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful Life (in years)	40 years
Furniture and equipment
Property, Plant and Equipment [Line Items]
Total premises and equipment	$ 413,876	370,458
Furniture and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful Life (in years)	3 years
Furniture and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful Life (in years)	40 years
Construction in progress
Property, Plant and Equipment [Line Items]
Total premises and equipment	$ 15,956	$ 29,104

Premises and Equipment (Operati

Premises and Equipment (Operating Leases) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018	$ 28,187
2,019	27,722
2,020	26,483
2,021	23,876
2,022	23,332
Thereafter	98,797
Total	$ 228,397

Goodwill And Other Intangible82

Goodwill And Other Intangible Assets (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)reporting_unit	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Oct. 01, 2016USD ($)
Goodwill [Line Items]
Goodwill	$ 57,315	$ 59,678
Number of reporting units | reporting_unit	2
Aggregate estimated amortization expense in 2018	$ 1,200
Aggregate estimated amortization expense in 2019	1,200
Aggregate estimated amortization expense in 2020	1,200
Aggregate estimated amortization expense in 2021	1,200
Aggregate estimated amortization expense in 2022	1,200
Global One
Goodwill [Line Items]
Goodwill				$ 32,884
Intangible assets	$ 12,500			$ 12,500
Weighted average amortization period	10 years 9 months 18 days
Accumulated amortization	$ 1,100	521	$ 503
Trust Services Reporting Unit
Goodwill [Line Items]
Goodwill	24,431	24,431
Synovus Bank Reporting Unit
Goodwill [Line Items]
Goodwill	$ 32,884	$ 35,247

Goodwill And Other Intangible83

Goodwill And Other Intangible Assets (Schedule of Goodwill) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Goodwill [Roll Forward]
Goodwill	$ 59,678
Accumulated impairment losses	0
Measurement period adjustments	(2,363)
Goodwill	57,315
Trust Services Reporting Unit
Goodwill [Roll Forward]
Goodwill	24,431
Accumulated impairment losses	0
Measurement period adjustments	0
Goodwill	24,431
Synovus Bank Reporting Unit
Goodwill [Roll Forward]
Goodwill	35,247
Accumulated impairment losses	0
Measurement period adjustments	(2,363)
Goodwill	$ 32,884

Goodwill And Other Intangible84

Goodwill And Other Intangible Assets (Other Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Other intangibles	$ 13,140	$ 14,040
Accumulated amortization	(1,886)	(817)
Other intangibles, net	$ 11,254	$ 13,223

Other Assets (Balances) (Detail

Other Assets (Balances) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Assets [Abstract]
Cash surrender value of bank-owned life insurance	$ 540,958	$ 378,830
Federal Reserve Bank and FHLB stock	159,443	169,864
Accrued interest receivable	80,036	70,393
Investments in low income housing tax credit partnerships	60,068	26,495
Taxes receivable(1)	46,330	2,611
Accounts receivable	43,878	29,821
Prepaid expenses	33,298	35,542
Private equity investments	15,771	25,493
Derivative asset positions	11,722	20,623
Other properties held for sale	7,825	14,830
SBA/GGL servicing assets, net	4,101	4,451
Miscellaneous other assets	32,081	34,267
Total other assets	1,035,511	$ 813,220
Alternative minimum tax credits	$ 42,100

Other Assets (Narrative) (Detai

Other Assets (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Assets [Abstract]
Separate account life insurance	$ 15	$ 15
Investments, fair value	$ 14

Deposits (Details)

Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Interest-bearing Deposit Liabilities [Abstract]
Interest bearing demand deposits	$ 5,157,175	$ 4,768,313
Money market accounts, excluding brokered deposits	7,435,941	7,251,093
Savings accounts	798,935	929,402
Time deposits, excluding brokered deposits	3,108,385	3,234,465
Brokered deposits	1,961,125	1,378,983
Total interest bearing deposits	18,461,561	17,562,256
Aggregate amount of time deposits of $250,000 or more	921,800	$ 829,500
Time Deposits, by Maturity [Abstract]
Maturing within one year	2,544,033
Between 1 — 2 years	851,665
2 — 3 years	567,279
3 — 4 years	248,473
4 — 5 years	65,521
Thereafter	242,909
Time deposits	$ 4,519,880

Long-term Debt and Short Term B

Long-term Debt and Short Term Borrowings (Narrative) (Details) - USD ($)	Nov. 01, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Loss on early extinguishment of debt		$ 23,200,000	$ 23,160,000	$ 4,735,000	$ 1,533,000
Loans Receivable
Debt Instrument [Line Items]
Recorded balance loans receivable		3,400,000,000	3,400,000,000	3,250,000,000
3.125% Senior Notes due November 1, 2022
Debt Instrument [Line Items]
Debt, face amount	$ 300,000,000	$ 300,000,000	$ 300,000,000
Stated percentage	3.125%	3.125%	3.125%
Proceeds from issuance of debt	$ 296,900,000
7.875% Senior Notes due February 15, 2019
Debt Instrument [Line Items]
Debt, face amount				$ 300,000,000
Stated percentage				7.875%
Loss on early extinguishment of debt			$ 23,200,000
5.125% Subordinated Notes due June 15, 2017
Debt Instrument [Line Items]
Extinguishment of debt, amount			$ 278,600,000
Repurchased face amount				$ 124,700,000	46,700,000
Loss on repurchase of debt				$ 4,700,000	$ 1,500,000

Long-term Debt and Short-term89

Long-term Debt and Short-term Borrowings (Schedule of Long-term Debt Instruments) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Nov. 01, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt	$ 1,706,138,000		$ 2,160,881,000
Interest rate at period end	0.18%		0.08%	0.08%
3.125% Senior Notes due November 1, 2022
Debt Instrument [Line Items]
Stated percentage	3.125%	3.125%
Debt, face amount	$ 300,000,000	$ 300,000,000
7.875% Senior Notes due February 15, 2019
Debt Instrument [Line Items]
Stated percentage			7.875%
Debt, face amount			$ 300,000,000
Parent Company
Debt Instrument [Line Items]
Hedge-related basis adjustments	0		873,000
Long-term debt	554,589,000		834,252,000
Parent Company | 3.125% Senior Notes due November 1, 2022 | Senior Notes
Debt Instrument [Line Items]
Long-term debt	296,971,000		0
Parent Company | 5.75% Subordinated Notes, due December 15, 2025
Debt Instrument [Line Items]
Subordinated notes	247,618,000		$ 247,136,000
Stated percentage			5.75%
Debt, face amount	$ 250,000,000
Parent Company | 5.75% Subordinated Notes, due December 15, 2025 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	4.182%
Parent Company | LIBOR 1.80% debentures, due April 19, 2035
Debt Instrument [Line Items]
Unsecured debt	$ 10,000,000		$ 10,000,000
Debt, face amount	$ 10,000,000
Interest rate at period end	3.39%		2.76%
Parent Company | LIBOR 1.80% debentures, due April 19, 2035 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.80%
Parent Company | 5.125% Subordinated Notes due June 15, 2017
Debt Instrument [Line Items]
Subordinated notes	$ 0		$ 278,480,000
Stated percentage			5.125%
Debt, face amount			$ 278,600,000
Parent Company | 7.875% Senior Notes due February 15, 2019 | Senior Notes
Debt Instrument [Line Items]
Long-term debt	0		297,763,000
Synovus Bank Reporting Unit
Debt Instrument [Line Items]
Long-term debt	1,151,549,000		1,326,629,000
Synovus Bank Reporting Unit | FHLB Advances
Debt Instrument [Line Items]
FHLB advances with interest and principal payments due at various maturity dates through 2018	$ 1,150,000,000		$ 1,325,000,000
Weighted average interest rate	1.43%		0.64%
Synovus Bank Reporting Unit | FHLB Advances | Minimum
Debt Instrument [Line Items]
Stated percentage	1.42%
Synovus Bank Reporting Unit | FHLB Advances | Maximum
Debt Instrument [Line Items]
Stated percentage	1.43%
Synovus Bank Reporting Unit | Other Notes Payable and Capital Leases
Debt Instrument [Line Items]
Other notes payable and capital leases with interest and principal payments due at various maturity dates through 2031	$ 1,549,000		$ 1,629,000
Weighted average interest rate	1.59%

Long-term Debt and Short-term90

Long-term Debt and Short-term Borrowings (Principal Payments on Long-term Debt) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
2,018	$ 100,089
2,019	90
2,020	350,092
2,021	450,096
2,022	550,107
Thereafter	261,075
Total long-term debt	1,711,549
Synovus Bank Reporting Unit
Debt Instrument [Line Items]
2,018	100,089
2,019	90
2,020	350,092
2,021	450,096
2,022	250,107
Thereafter	1,075
Total long-term debt	1,151,549
Parent Company
Debt Instrument [Line Items]
2,018	0
2,019	0
2,020	0
2,021	0
2,022	300,000
Thereafter	260,000
Total long-term debt	$ 560,000

Long-term Debt and Short-term91

Long-term Debt and Short-term Borrowings (Components of Short-term Borrowings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Total balance at December 31,	$ 161,190	$ 159,699	$ 177,025
Weighted average interest rate at December 31,	0.18%	0.08%	0.08%
Maximum month end balance during the year	$ 225,475	$ 286,175	$ 250,453
Average amount outstanding during the year	$ 184,093	$ 216,593	$ 205,305
Weighted average interest rate during the year	0.11%	0.09%	0.08%

Shareholders' Equity (Narrativ

Shareholders' Equity (Narrative) (Details) - USD ($)

Nov. 30, 2017

Oct. 01, 2016

Oct. 21, 2014

Jan. 31, 2015

Dec. 31, 2015

Sep. 30, 2015

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Sep. 30, 2015

Dec. 31, 2014

Oct. 31, 2014

Class of Stock [Line Items]

Common stock, shares issued (in shares)

142,677,449

142,025,720

Fair value of common stock issued

$ 142,678,000

$ 142,026,000

Stock repurchase program, authorized amount

200,000,000

Stock Repurchased During Period, Value

$ 175,079,000

263,084,000

$ 199,221,000

Repurchase of common stock

4,000,000

Repurchase of Common Stock 300 Million

Class of Stock [Line Items]

Stock repurchase program, authorized amount

$ 300,000,000

$ 300,000,000

Stock repurchase program, period in force

15 months

Repurchase of Common Stock 300 Million | Common Stock

Class of Stock [Line Items]

Stock Repurchased During Period, Value

$ 262,900,000

Repurchase of common stock

8,700,000

Stock repurchase program, repurchased amount

$ 37,100,000

Stock repurchase program, shares repurchased

1,200,000

Open Market Transactions | Common Stock

Class of Stock [Line Items]

Stock repurchase program, repurchased amount

$ 212,900,000

$ 161,900,000

$ 175,000,000

Stock repurchase program, shares repurchased

7,300,000

5,700,000

6,200,000

Accelerated Share Repurchase Program | Common Stock

Class of Stock [Line Items]

Stock repurchase program, authorized amount

$ 75,000,000

Stock repurchase program, repurchased amount

$ 50,000,000

Stock repurchase program, shares repurchased

392,000

1,400,000

2,500,000

Repurchase of Common Stock 250 Million | Common Stock

Class of Stock [Line Items]

Stock repurchase program, repurchased amount

$ 250,000,000

Stock repurchase program, shares repurchased

9,100,000

Annual Earn-out Payment

Class of Stock [Line Items]

Common stock, shares issued (in shares)

118,000

Fair value of common stock issued

$ 5,500,000

Cash paid

$ 892,000

Global One

Class of Stock [Line Items]

Consideration transferred

$ 30,000,000

Common stock, shares issued (in shares)

821,000

Fair value of common stock issued

$ 26,592,000

Cash paid

$ 3,408,000

Shareholders' Equity (Changes

Shareholders' Equity (Changes in Shares by Class) (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, Common stock, shares outstanding	122,266,106
Stock options exercised	197,631	297,225	338,808
Repurchase of common stock	4,000,000
Balance, Common stock, shares outstanding	118,897,295	122,266,106
Preferred Shares Issued | Series C Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	5,200,000	5,200,000	5,200,000
Issuance of common stock	0	0
Restricted share unit activity	0	0	0
Stock options exercised	0	0	0
Balance	5,200,000	5,200,000	5,200,000
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	142,026,000	140,592,000	139,950,000
Balance, Common stock, shares outstanding	122,266,000	129,547,000	136,123,000
Issuance of common stock	118,000	821,000
Restricted share unit activity	336,000	316,000	304,000
Stock options exercised	198,000	297,000	338,000
Repurchase of common stock	(4,021,000)	(8,715,000)	(7,218,000)
Balance	142,678,000	142,026,000	140,592,000
Balance, Common stock, shares outstanding	118,897,000	122,266,000	129,547,000
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance	19,760,000	11,045,000	3,827,000
Issuance of common stock	0	0
Restricted share unit activity	0	0	0
Stock options exercised	0	0	0
Repurchase of common stock	4,021,000	8,715,000	7,218,000
Balance	23,781,000	19,760,000	11,045,000

Shareholders' Equity (Preferred

Shareholders' Equity (Preferred and Warrant) (Details) - USD ($)	Aug. 01, 2018	Jul. 31, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cumulative Perpetual Preferred Stock
Warrant outstanding (in shares)			2,200,000	2,200,000	2,200,000
Warrant, exercise price (per share)			$ 65.52	$ 65.52	$ 65.52
Series C Preferred Stock
Cumulative Perpetual Preferred Stock
Preferred stock, shares issued		5,200,000
Preferred stock, liquidation value		$ 25
Preferred stock, dividend rate, percentage		7.875%
Preferred stock, redemption price per share			$ 25
Series C Preferred Stock | Forecast | LIBOR
Cumulative Perpetual Preferred Stock
Preferred stock, dividend rate, percentage	6.39%

Regulatory Capital (Details)

Regulatory Capital (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	2.50%
Capital conservation buffer period	3 years
Significant subsidiary, assets or net income as percentage of consolidated total, threshold	10.00%
Common equity tier 1 capital
Common equity tier 1 capital, Actual	$ 2,763,168	$ 2,654,287
Common equity tier 1 capital, For Capital Adequacy Purposes	1,250,488	1,199,794
Tier 1 capital
Tier I capital, Actual	2,872,001	2,685,880
Tier I capital, For Capital Adequacy Purposes	1,660,074	1,599,725
Total risk-based capital
Total risk-based capital, Actual	3,383,081	3,201,268
Total risk-based capital, For Capital Adequacy Purposes	$ 2,213,432	$ 2,132,966
Common equity tier 1 capital ratio
Common equity tier I capital ratio, Actual	9.99%	9.96%
Common equity tier I capital ratio, For Capital Adequacy Purposes	4.50%	4.50%
Tier 1 capital ratio
Tier 1 capital ratio, Actual	10.38%	10.07%
Tier 1 capital ratio, For Capital Adequacy Purposes	6.00%	6.00%
Total risk-based capital ratio
Total risk-based capital ratio, Actual	12.23%	12.01%
Total risk-based capital ratio, For Capital Adequacy Purposes	8.00%	8.00%
Leverage ratio
Leverage ratio, Actual	9.19%	8.99%
Leverage ratio, For Capital Adequacy Purposes	4.00%	4.00%
Minimum
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	0.625%
Well-capitalized status,Tier 1 capital ratio	8.00%
Common equity tier 1 capital ratio
Common equity tier I capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	6.50%
Total risk-based capital ratio
Total risk-based capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	10.00%
Leverage ratio
Leverage ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	5.00%
Synovus Bank Reporting Unit
Common equity tier 1 capital
Common equity tier 1 capital, Actual	$ 3,155,163	$ 3,187,583
Common equity tier 1 capital, For Capital Adequacy Purposes	1,247,462	1,197,976
Common equity tier 1 capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	1,795,004	1,730,410
Tier 1 capital
Tier I capital, Actual	3,155,163	3,187,583
Tier I capital, For Capital Adequacy Purposes	1,656,927	1,597,302
Tier I capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	2,209,236	2,129,736
Total risk-based capital
Total risk-based capital, Actual	3,406,243	3,441,563
Total risk-based capital, For Capital Adequacy Purposes	2,209,236	2,129,736
Total risk-based capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 2,761,545	$ 2,662,169
Common equity tier 1 capital ratio
Common equity tier I capital ratio, Actual	11.43%	11.97%
Common equity tier I capital ratio, For Capital Adequacy Purposes	4.50%	4.50%
Common equity tier I capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	6.50%	6.50%
Tier 1 capital ratio
Tier 1 capital ratio, Actual	11.43%	11.97%
Tier 1 capital ratio, For Capital Adequacy Purposes	6.00%	6.00%
Tier 1 capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	8.00%	8.00%
Total risk-based capital ratio
Total risk-based capital ratio, Actual	12.33%	12.93%
Total risk-based capital ratio, For Capital Adequacy Purposes	8.00%	8.00%
Total risk-based capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	10.00%	10.00%
Leverage ratio
Leverage ratio, Actual	10.12%	10.68%
Leverage ratio, For Capital Adequacy Purposes	4.00%	4.00%
Leverage ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	5.00%	5.00%

Net Income Per Common Share (Na

Net Income Per Common Share (Narrative) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Potentially dilutive shares	2.2	2.2	2.8

Net Income Per Common Share (Sc

Net Income Per Common Share (Schedule Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 29,605	$ 98,007	$ 76,003	$ 71,857	$ 68,549	$ 65,245	$ 60,457	$ 52,531	$ 275,474	$ 246,784	$ 226,082
Dividends on preferred stock									10,238	10,238	10,238
Net income available to common shareholders	$ 27,046	$ 95,448	$ 73,444	$ 69,298	$ 65,990	$ 62,686	$ 57,898	$ 49,972	$ 265,236	$ 236,546	$ 215,844
Weighted average common shares outstanding									121,162	124,389	132,423
Potentially dilutive shares from outstanding equity-based awards and Earnout Payments									850	689	778
Weighted average diluted common shares									122,012	125,078	133,201
Net income per common share, basic (in dollars per share)	$ 0.23	$ 0.79	$ 0.60	$ 0.57	$ 0.54	$ 0.51	$ 0.46	$ 0.39	$ 2.19	$ 1.90	$ 1.63
Net income per common share, diluted (in dollars per share)	$ 0.23	$ 0.78	$ 0.60	$ 0.56	$ 0.54	$ 0.51	$ 0.46	$ 0.39	$ 2.17	$ 1.89	$ 1.62

Fair Value Accounting (Financia

Fair Value Accounting (Financial Instruments Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	$ 3,820	$ 9,314
Investment securities available for sale	3,987,069	3,718,195
Private equity investments	15,771	25,493
Derivative asset positions	11,722	20,623
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	522	1,890
Investment securities available for sale	85,836	114,676
Private equity investments	0	0
GGL/SBA loans servicing asset	0
Derivative asset positions	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	3,298	7,424
Investment securities available for sale	3,899,298	3,601,723
Private equity investments	0	0
GGL/SBA loans servicing asset	0
Derivative asset positions	11,722	20,623
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	1,935	1,796
Private equity investments	15,771	25,493
GGL/SBA loans servicing asset	4,101
Derivative asset positions	0	0
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	3,820	9,314
Mortgage loans held for sale	48,024	51,545
Investment securities available for sale	3,987,069	3,718,195
Private equity investments	15,771	25,493
GGL/SBA loans servicing asset	4,101
Mutual funds held in rabbi trusts	14,140	11,479
Derivative asset positions	11,722	20,623
Derivative liabilities	17,097	23,299
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	522	1,890
Mortgage loans held for sale	0	0
Investment securities available for sale	85,836	114,676
Private equity investments	0	0
GGL/SBA loans servicing asset	0
Mutual funds held in rabbi trusts	14,140	11,479
Derivative asset positions	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	3,298	7,424
Mortgage loans held for sale	48,024	51,545
Investment securities available for sale	3,899,298	3,601,723
Private equity investments	0	0
GGL/SBA loans servicing asset	0
Mutual funds held in rabbi trusts	0	0
Derivative asset positions	11,722	20,623
Derivative liabilities	12,767	17,531
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Mortgage loans held for sale	0	0
Investment securities available for sale	1,935	1,796
Private equity investments	15,771	25,493
GGL/SBA loans servicing asset	4,101
Mutual funds held in rabbi trusts	0	0
Derivative asset positions	0	0
Derivative liabilities	4,330	5,768
Fair Value, Measurements, Recurring | Visa Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities		5,768
Fair Value, Measurements, Recurring | Visa Derivative | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities		0
Fair Value, Measurements, Recurring | Visa Derivative | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities		0
Fair Value, Measurements, Recurring | Visa Derivative | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities		5,768
Fair Value, Measurements, Recurring | Trading account liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities	1,000
Fair Value, Measurements, Recurring | Trading account liabilities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities	0
Fair Value, Measurements, Recurring | Trading account liabilities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities	1,000
Fair Value, Measurements, Recurring | Trading account liabilities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities	0
Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	12,638	17,531
Fair Value, Measurements, Recurring | Interest rate contracts | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Interest rate contracts | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	12,638	17,531
Fair Value, Measurements, Recurring | Interest rate contracts | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Mortgage derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	129
Fair Value, Measurements, Recurring | Mortgage derivatives | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0
Fair Value, Measurements, Recurring | Mortgage derivatives | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	129
Fair Value, Measurements, Recurring | Mortgage derivatives | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0
Fair Value, Measurements, Recurring | Visa derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	4,330
Fair Value, Measurements, Recurring | Visa derivative | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0
Fair Value, Measurements, Recurring | Visa derivative | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0
Fair Value, Measurements, Recurring | Visa derivative | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	4,330
Fair Value, Measurements, Recurring | Earnout Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Earnout liability	11,348	14,000
Fair Value, Measurements, Recurring | Earnout Liabilities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Earnout liability	0	0
Fair Value, Measurements, Recurring | Earnout Liabilities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Earnout liability	0	0
Fair Value, Measurements, Recurring | Earnout Liabilities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Earnout liability	11,348	14,000
Fair Value, Measurements, Recurring | U.S. Government agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	3,002
Investment securities available for sale	10,862	12,993
Fair Value, Measurements, Recurring | U.S. Government agency securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | U.S. Government agency securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	3,002
Investment securities available for sale	10,862	12,993
Fair Value, Measurements, Recurring | U.S. Government agency securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	296	3,438
Investment securities available for sale	1,111,999	890,442
Fair Value, Measurements, Recurring | Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	296	3,438
Investment securities available for sale	1,111,999	890,442
Fair Value, Measurements, Recurring | Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		1,990
Fair Value, Measurements, Recurring | Other investments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		1,890
Fair Value, Measurements, Recurring | Other investments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		100
Fair Value, Measurements, Recurring | Other investments | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		0
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		3,460
Investment securities available for sale	120,440	174,202
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government agencies | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government agencies | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		3,460
Investment securities available for sale	120,440	174,202
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government agencies | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | State and municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		426
Investment securities available for sale	180	2,794
Fair Value, Measurements, Recurring | State and municipal securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | State and municipal securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		426
Investment securities available for sale	180	2,794
Fair Value, Measurements, Recurring | State and municipal securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities		0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Corporate debt and other securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	522
Investment securities available for sale	20,391	19,840
Fair Value, Measurements, Recurring | Corporate debt and other securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	522
Investment securities available for sale	3,162	3,092
Fair Value, Measurements, Recurring | Corporate debt and other securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0
Investment securities available for sale	15,294	14,952
Fair Value, Measurements, Recurring | Corporate debt and other securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0
Investment securities available for sale	1,935	1,796
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	82,674	107,802
Fair Value, Measurements, Recurring | U.S. Treasury securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	82,674	107,802
Fair Value, Measurements, Recurring | U.S. Treasury securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | U.S. Treasury securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government sponsored enterprises
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,640,523	2,506,340
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government sponsored enterprises | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government sponsored enterprises | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,640,523	2,506,340
Fair Value, Measurements, Recurring | Mortgage-backed securities issued by U.S. Government sponsored enterprises | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		3,782
Fair Value, Measurements, Recurring | Equity securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		3,782
Fair Value, Measurements, Recurring | Equity securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		0
Fair Value, Measurements, Recurring | Equity securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		0
Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	10,786	17,157
Fair Value, Measurements, Recurring | Interest rate contracts | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	0	0
Fair Value, Measurements, Recurring | Interest rate contracts | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	10,786	17,157
Fair Value, Measurements, Recurring | Interest rate contracts | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	0	0
Fair Value, Measurements, Recurring | Mortgage derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	936	3,466
Fair Value, Measurements, Recurring | Mortgage derivatives | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	0	0
Fair Value, Measurements, Recurring | Mortgage derivatives | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	936	3,466
Fair Value, Measurements, Recurring | Mortgage derivatives | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset positions	$ 0	$ 0

Fair Value Accounting (Changes

Fair Value Accounting (Changes In Fair Value Included In Consolidated Statements Of Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Mortgage loans held for sale	$ 754	$ (667)	$ (742)
Fair value	48,024	51,545	59,275
Unpaid principal balance	46,839	51,114	58,177
Fair value less aggregate unpaid principal balance	$ 1,185	$ 431	$ 1,098

Fair Value Accounting (Chang100

Fair Value Accounting (Changes In Level 3 Fair Value Measurements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Visa derivative
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance, January 1,	$ (5,768)	$ (1,415)
Included in earnings	0	(5,795)
Unrealized gains included in other comprehensive income	0	0
Additions	0	0
Sales	0
Settlements	1,438	1,442
Transfer from amortization method to fair value	0
Measurement period adjustments related to Global One acquisition	0
Ending balance, December 31,	(4,330)	(5,768)
Total net gains (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31,	0	(5,795)
Earnout Liability
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance, January 1,	(14,000)	0
Included in earnings	(5,466)	0
Unrealized gains included in other comprehensive income	0	0
Additions	0	(14,000)
Sales	0
Settlements	6,352	0
Transfer from amortization method to fair value	0
Measurement period adjustments related to Global One acquisition	1,766
Ending balance, December 31,	(11,348)	(14,000)
Total net gains (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31,	(5,466)	0
GGL/SBA Loans Servicing Asset
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance, January 1,	0
Included in earnings	(1,681)
Unrealized gains included in other comprehensive income	0
Additions	1,330
Sales	0
Settlements	0
Transfer from amortization method to fair value	4,452
Measurement period adjustments related to Global One acquisition	0
Ending balance, December 31,	4,101	0
Total net gains (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31,	(1,681)
Investment Securities Available for Sale
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance, January 1,	1,796	1,745
Included in earnings	0	0
Unrealized gains included in other comprehensive income	139	51
Additions	0	0
Sales	0
Settlements	0	0
Transfer from amortization method to fair value	0
Measurement period adjustments related to Global One acquisition	0
Ending balance, December 31,	1,935	1,796
Total net gains (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31,	0	0
Private Equity Investments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance, January 1,	25,493	27,148
Included in earnings	(3,093)	(1,026)
Unrealized gains included in other comprehensive income	0	0
Additions	0	0
Sales	(6,629)
Settlements	0	(629)
Transfer from amortization method to fair value	0
Measurement period adjustments related to Global One acquisition	0
Ending balance, December 31,	15,771	25,493
Total net gains (losses) for the year included in earnings attributable to the change in unrealized gains (losses) relating to assets and liabilities still held at December 31,	$ (3,093)	$ (1,026)

Fair Value Accounting (Fair Val

Fair Value Accounting (Fair Value Inputs, Quantitative Information) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Measurements, Recurring | Trust Preferred Securities | Discounted cash flow analysis
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Credit spread embedded in discount rate	3.98%		4.42%
Fair Value, Measurements, Recurring | Visa Derivative | Discounted cash flow analysis | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated timing of resolution of covered litigation		1 year	1 year
Fair Value, Measurements, Recurring | Visa Derivative | Discounted cash flow analysis | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated timing of resolution of covered litigation		4 years	5 years
Fair Value, Measurements, Recurring | Private Equity Investments
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount of lack of liquidity		15.00%
Fair Value, Measurements, Recurring | Private Equity Investments | Individual analysis of each investee company
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount of lack of liquidity			15.00%
Fair Value, Measurements, Recurring | Level 3 | Earnout Liabilities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure, Nonrecurring	$ 11,348	$ 11,348	$ 14,000
Fair Value, Measurements, Recurring | Level 3 | Visa Derivative
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure, Nonrecurring	4,330	4,330
Fair Value, Measurements, Recurring | Level 3 | Visa Derivative | Discounted cash flow analysis
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure, Nonrecurring			5,768
Fair Value, Measurements, Recurring | Level 3 | Trust Preferred Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, fair value disclosure	1,935	1,935	1,796
Fair Value, Measurements, Recurring | Level 3 | Private Equity Investments | Individual analysis of each investee company
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, fair value disclosure	15,771	15,771	$ 25,493
Fair Value, Measurements, Recurring | Level 3 | GGL/SBA Loans Servicing Asset
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, fair value disclosure	$ 4,101	$ 4,101
Fair Value, Measurements, Nonrecurring | Collateral Dependent Impaired Loans | Third-party appraised value of collateral less estimated selling costs | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		0.00%	0.00%
Estimated selling costs		0.00%	0.00%
Fair Value, Measurements, Nonrecurring | Collateral Dependent Impaired Loans | Third-party appraised value of collateral less estimated selling costs | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		50.00%	52.00%
Estimated selling costs		10.00%	10.00%
Fair Value, Measurements, Nonrecurring | Collateral Dependent Impaired Loans | Third-party appraised value of collateral less estimated selling costs | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		15.00%	25.00%
Estimated selling costs		7.00%	7.00%
Fair Value, Measurements, Nonrecurring | Other Loans Held for Sale | Third-party appraised value of real estate less estimated selling costs | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		5.00%	0.00%
Estimated selling costs		0.00%	0.00%
Fair Value, Measurements, Nonrecurring | Other Loans Held for Sale | Third-party appraised value of real estate less estimated selling costs | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		99.00%	3.00%
Estimated selling costs		10.00%	10.00%
Fair Value, Measurements, Nonrecurring | Other Loans Held for Sale | Third-party appraised value of real estate less estimated selling costs | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		54.00%	3.00%
Estimated selling costs		2.00%	7.00%
Fair Value, Measurements, Nonrecurring | Other Real Estate | Third-party appraised value of real estate less estimated selling costs | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		0.00%	0.00%
Estimated selling costs		0.00%	0.00%
Fair Value, Measurements, Nonrecurring | Other Real Estate | Third-party appraised value of real estate less estimated selling costs | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		85.00%	10.00%
Estimated selling costs		10.00%	10.00%
Fair Value, Measurements, Nonrecurring | Other Real Estate | Third-party appraised value of real estate less estimated selling costs | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		35.00%	5.00%
Estimated selling costs		7.00%	7.00%
Fair Value, Measurements, Nonrecurring | Other Assets Held for Sale | Third-party appraised value less estimated selling costs or BOV | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		21.00%	0.00%
Estimated selling costs		0.00%	0.00%
Fair Value, Measurements, Nonrecurring | Other Assets Held for Sale | Third-party appraised value less estimated selling costs or BOV | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		52.00%	81.00%
Estimated selling costs		10.00%	10.00%
Fair Value, Measurements, Nonrecurring | Other Assets Held for Sale | Third-party appraised value less estimated selling costs or BOV | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount to appraised value		25.00%	47.00%
Estimated selling costs		7.00%	7.00%

Fair Value Accounting (Assets A

Fair Value Accounting (Assets And Liabilities Measured At Fair Value On A Non-Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 200,286	$ 249,496
Other loans held for sale	11,356	0
Other real estate	3,758	22,308
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other loans held for sale	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other loans held for sale	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other loans held for sale	11,356
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	991	6,613
Other loans held for sale	13,004
Other real estate	2,413	1,223
Other assets held for sale	2,491	5,715
Fair Value, Measurements, Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other loans held for sale	0
Other real estate	0	0
Other assets held for sale	0	0
Fair Value, Measurements, Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other loans held for sale	0
Other real estate	0	0
Other assets held for sale	0	0
Fair Value, Measurements, Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	3,603	21,742
Other loans held for sale	10,197
Other real estate	3,363	19,305
Other assets held for sale	$ 5,334	$ 12,083

Fair Value Accounting (Carrying

Fair Value Accounting (Carrying And Estimated Fair Values Of Financial Instruments Carried On Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financial Assets
Cash and cash equivalents	$ 397,848	$ 395,175
Interest bearing funds with Federal Reserve Bank	460,928	527,090
Interest earning deposits with banks	26,311	18,720
Federal funds sold and securities purchased under resale agreements	47,846	58,060
Trading account assets	3,820	9,314
Mortgage loans held for sale	48,024	51,545
Other loans held for sale	11,356	0
Investment securities available for sale	3,987,069	3,718,195
Private equity investments	15,771	25,493
Loans, net of deferred fees and costs	24,538,196	23,604,633
Derivative assets	11,722	20,623
Financial Liabilities
Non-interest bearing deposits	7,686,339	7,085,804
Interest bearing deposits	18,461,561	17,562,256
Federal funds purchased and securities sold under repurchase agreements	161,190	159,699	$ 177,025
Long-term debt	1,706,138	2,160,881
Level 1
Financial Assets
Cash and cash equivalents	397,848	395,175
Interest bearing funds with Federal Reserve Bank	460,928	527,090
Interest earning deposits with banks	26,311	18,720
Federal funds sold and securities purchased under resale agreements	47,846	58,060
Trading account assets	522	1,890
Mortgage loans held for sale	0	0
Other loans held for sale	0
Investment securities available for sale	85,836	114,676
Private equity investments	0	0
Mutual funds held in rabbi trusts	14,140	11,479
Loans, net of deferred fees and costs	0	0
GGL/SBA loans servicing asset	0
Derivative assets	0	0
Financial Liabilities
Trading account liabilities	0
Non-interest bearing deposits	0	0
Interest bearing deposits	0	0
Federal funds purchased and securities sold under repurchase agreements	161,190	159,699
Long-term debt	0	0
Earnout Liabilities, Fair Value Disclosure	0	0
Derivative liabilities	0	0
Level 2
Financial Assets
Cash and cash equivalents	0	0
Interest bearing funds with Federal Reserve Bank	0	0
Interest earning deposits with banks	0	0
Federal funds sold and securities purchased under resale agreements	0	0
Trading account assets	3,298	7,424
Mortgage loans held for sale	48,024	51,545
Other loans held for sale	0
Investment securities available for sale	3,899,298	3,601,723
Private equity investments	0	0
Mutual funds held in rabbi trusts	0	0
Loans, net of deferred fees and costs	0	0
GGL/SBA loans servicing asset	0
Derivative assets	11,722	20,623
Financial Liabilities
Trading account liabilities	1,000
Non-interest bearing deposits	7,686,339	7,085,804
Interest bearing deposits	18,465,475	17,560,021
Federal funds purchased and securities sold under repurchase agreements	0	0
Long-term debt	1,721,814	2,217,544
Earnout Liabilities, Fair Value Disclosure	0	0
Derivative liabilities	12,767	17,531
Level 3
Financial Assets
Cash and cash equivalents	0	0
Interest bearing funds with Federal Reserve Bank	0	0
Interest earning deposits with banks	0	0
Federal funds sold and securities purchased under resale agreements	0	0
Trading account assets	0	0
Mortgage loans held for sale	0	0
Other loans held for sale	11,356
Investment securities available for sale	1,935	1,796
Private equity investments	15,771	25,493
Mutual funds held in rabbi trusts	0	0
Loans, net of deferred fees and costs	24,507,141	23,709,434
GGL/SBA loans servicing asset	4,101
Derivative assets	0	0
Financial Liabilities
Trading account liabilities	0
Non-interest bearing deposits	0	0
Interest bearing deposits	0	0
Federal funds purchased and securities sold under repurchase agreements	0	0
Long-term debt	0	0
Earnout Liabilities, Fair Value Disclosure	11,348	14,000
Derivative liabilities	4,330	5,768
Carrying Value
Financial Assets
Cash and cash equivalents	397,848	395,175
Interest bearing funds with Federal Reserve Bank	460,928	527,090
Interest earning deposits with banks	26,311	18,720
Federal funds sold and securities purchased under resale agreements	47,846	58,060
Trading account assets	3,820	9,314
Mortgage loans held for sale	48,024	51,545
Other loans held for sale	11,356
Investment securities available for sale	3,987,069	3,718,195
Private equity investments	15,771	25,493
Mutual funds held in rabbi trusts	14,140	11,479
Loans, net of deferred fees and costs	24,787,464	23,856,391
GGL/SBA loans servicing asset	4,101
Derivative assets	11,722	20,623
Financial Liabilities
Trading account liabilities	1,000
Non-interest bearing deposits	7,686,339	7,085,804
Interest bearing deposits	18,461,561	17,562,256
Federal funds purchased and securities sold under repurchase agreements	161,190	159,699
Long-term debt	1,706,138	2,160,881
Earnout Liabilities, Fair Value Disclosure	11,348	14,000
Derivative liabilities	17,097	23,299
Estimated Fair Value
Financial Assets
Cash and cash equivalents	397,848	395,175
Interest bearing funds with Federal Reserve Bank	460,928	527,090
Interest earning deposits with banks	26,311	18,720
Federal funds sold and securities purchased under resale agreements	47,846	58,060
Trading account assets	3,820	9,314
Mortgage loans held for sale	48,024	51,545
Other loans held for sale	11,356
Investment securities available for sale	3,987,069	3,718,195
Private equity investments	15,771	25,493
Mutual funds held in rabbi trusts	14,140	11,479
Loans, net of deferred fees and costs	24,507,141	23,709,434
GGL/SBA loans servicing asset	4,101
Derivative assets	11,722	20,623
Financial Liabilities
Trading account liabilities	1,000
Non-interest bearing deposits	7,686,339	7,085,804
Interest bearing deposits	18,465,475	17,560,021
Federal funds purchased and securities sold under repurchase agreements	161,190	159,699
Long-term debt	1,721,814	2,217,544
Earnout Liabilities, Fair Value Disclosure	11,348	14,000
Derivative liabilities	$ 17,097	$ 23,299

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative, fair value	$ 4,300,000	$ 5,800,000
Unamortized deferred net loss balance from previously terminated cash flow hedges		(130,000)
Remaining deferred (gain) loss balance on all previously terminated fair value hedges		873,000
Gain (loss) on fair value commitments to sell mortgage loans	(2,000,000)	1,700,000
Derivative, Collateral, Right to Reclaim Cash	43,800,000
Variation margin, amount reducing derivative asset	1,500,000
Deferred gains of hedges reclassified into earnings	873,000	1,800,000	$ 3,100,000
Deferred gains of hedges reclassified into loss on extinguishment of debt	1,300,000	495,000
Fixed Rate Residential Mortgage
Derivative [Line Items]
Commitments to fund fixed-rate mortgage loans	49,300,000	88,200,000
Unrealized gain on fair value of fixed-rate mortgage loans to customers	(634,000)	182,000
Sale of outstanding commitments	72,500,000	126,500,000
Interest Rate Swap
Derivative [Line Items]
Notional amount of interest rate swap contracts	1,470,000,000
Increase (decrease) derivative, notional amount	141,400,000
Cash Flow Hedging
Derivative [Line Items]
Derivative, fair value	0	0
Fair Value Hedging
Derivative [Line Items]
Derivative, fair value	$ 0	$ 0

Derivative Instruments (Impact

Derivative Instruments (Impact Of Derivatives On Balance Sheet) (Details) - Not Designated As Hedging Instruments - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Assets
Derivative [Line Items]
Fair Value of Derivative Assets	$ 11,722	$ 20,623
Other Assets | Interest rate contracts
Derivative [Line Items]
Fair Value of Derivative Assets	10,786	17,157
Other Assets | Mortgage derivatives
Derivative [Line Items]
Fair Value of Derivative Assets	936	3,466
Other Assets | Visa Derivative
Derivative [Line Items]
Fair Value of Derivative Assets	0	0
Other Liabilities
Derivative [Line Items]
Fair Value of Derivative Liabilities	17,097	23,299
Other Liabilities | Interest rate contracts
Derivative [Line Items]
Fair Value of Derivative Liabilities	12,638	17,531
Other Liabilities | Mortgage derivatives
Derivative [Line Items]
Fair Value of Derivative Liabilities	129	0
Other Liabilities | Visa Derivative
Derivative [Line Items]
Fair Value of Derivative Liabilities	$ 4,330	$ 5,768

Derivative Instruments (Effect

Derivative Instruments (Effect Of Fair Value Hedges On Consolidated Statements Of Income) (Details) - Not Designated As Hedging Instruments - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ (2,639)	$ 1,983	$ 1,143
Interest rate contracts | Other Non- Interest Income
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	20	76	44
Mortgage derivatives | Mortgage Banking Income
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ (2,659)	$ 1,907	$ 1,099

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Rabbi Trusts
Variable Interest Entity [Line Items]
Carrying value of VIE assets and liabilities, net	$ 14.1	$ 11.5

Variable Interest Entities (Sch

Variable Interest Entities (Schedules) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Low Income Housing Tax Credit Partnerships
Variable Interest Entity [Line Items]
Proportional amortization method investments included in other assets	$ 58,343	$ 0
Equity method investments included in other assets	1,725	26,495
Cumulative equity investments in LIHTC partnerships	46,659	34,065
Unfunded commitments included in other liabilities	39,994	17,420
Short-term construction loans and letter of credit commitments	7,180	0
Funded portion of short-term loans and letters of credit	0	0
Proportional amortization expense recognized as a component of income tax expense	1,820	0	$ 0
Income from equity method investments recognized as a component of non-interest income	(1,648)	389	553
Real Estate Partnerships
Variable Interest Entity [Line Items]
Equity method investments included in other assets	6,468	6,822
Unfunded commitments included in other liabilities	0	0
Income from equity method investments recognized as a component of non-interest income	$ 1,584	$ 1,040	$ 1,212

Visa Shares and Related Agre109

Visa Shares and Related Agreements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Indemnification charge to earnings	$ 0	$ 5,800,000	$ 1,500,000
Visa Class B to Visa Class A Shares Conversion Rate
Derivative [Line Items]
Fair value of derivative liability	$ 4,300,000	$ 5,800,000

Commitments and Contingencie110

Commitments and Contingencies (Details) $ in Thousands	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Contractual amount net of risk participations	$ 77,000
Guarantee Obligations [Member]
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	9,080,108
Letters of credit
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	153,372
Commitments to fund commercial and industrial loans
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	5,090,827
Commitments to fund commercial real estate, construction, and land development loans
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	1,567,583
Commitments under home equity lines of credit
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	1,137,714
Unused credit card lines
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	779,254
Other loan commitments
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	$ 351,358

Legal Proceedings (Details)

Legal Proceedings (Details)	Dec. 31, 2017USD ($)
Minimum
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	$ 0
Maximum
Loss Contingencies [Line Items]
Total letters of credit and unfunded lending commitments	$ 8,000,000

Employment Expenses and Bene112

Employment Expenses and Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Employer matching contribution, percent	100.00%	100.00%	100.00%
401(k) percent of match	4.00%	4.00%	4.00%
Annual contribution	$ 11,500	$ 10,800	$ 9,900
Stock purchase plan, percent of match	15.00%
Stock purchase plans compensation expense	$ 860	$ 826	$ 835

Share-based Compensation (Narra

Share-based Compensation (Narrative) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)simulation$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Apr. 25, 2013shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 14,200	$ 13,600	$ 12,600
Tax benefit recognized from compensation expense	5,200	5,000	4,600
Unrecognized compensation cost	17,500
Options outstanding, aggregate intrinsic value	$ 23,800
Options outstanding, weighted average remaining contractual term (years)	4 years 2 months 5 days
Options exercised, intrinsic value	$ 5,100	4,700	4,400
Cash received from option exercises	$ 3,440	5,155	5,643
Total grant date fair value of stock options vested		$ 7,400	$ 6,500
Options expired/canceled (in shares) | shares	0	469,792	456,438
Options expired (in dollars per share) | $ / shares	$ 0	$ 92.62	$ 94.56
Share-based compensation, excess tax expense, amount	$ 1,700
Share-based compensation tax benefit (deficiency)	5,000	$ (790)	$ 1,656
Contractual Expiration Dates in 2017 and 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options expired/canceled (in shares) | shares		317,524
Options expired (in dollars per share) | $ / shares		$ 93.62
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from option exercises	$ 3,400	$ 5,200	$ 5,600
Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Non-option awards granted (in shares) | shares	242,804	350,458	321,874
Non-option awards granted, weighted-average grant-date fair value (in dollars per share) | $ / shares	$ 41.82	$ 26.43	$ 28.09
Unrecognized compensation cost	$ 9,900
Non-option awards vested, total fair value	$ 14,400	$ 11,400	$ 12,300
Unrecognized compensation cost, period of recognition (years)	1 year 5 months 5 days
Taxes paid for vesting of employee share units	$ 8,000	$ 5,000	$ 5,100
Market Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Non-option awards granted (in shares) | shares	78,174	93,913	82,152
Non-option awards granted, weighted-average grant-date fair value (in dollars per share) | $ / shares	$ 43.52	$ 26.93	$ 29.39
Unrecognized compensation cost	$ 3,500
Number of simulations | simulation	100,000
Non-option awards vested, total fair value	$ 4,800	$ 2,600	$ 1,400
Unrecognized compensation cost, period of recognition (years)	1 year 5 months 16 days
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-option awards granted (in shares) | shares	72,825	83,529	82,152
Non-option awards granted, weighted-average grant-date fair value (in dollars per share) | $ / shares	$ 41.61	$ 25.95	$ 28.06
Unrecognized compensation cost	$ 4,100
Non-option awards vested, total fair value	$ 2,900
Unrecognized compensation cost, period of recognition (years)	1 year 5 months 9 days
Minimum | Market Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting range based on return on average assets (ROAA)	75.00%
Minimum | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, vested and expected to vest, range based on return on average assets	0.00%
Maximum | Market Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting range based on return on average assets (ROAA)	125.00%
Maximum | Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, vested and expected to vest, range based on return on average assets	150.00%
2013 Omnibus Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of authorized but unissued common stock reserved for future grants (in shares) | shares	5,700,000			8,600,000
2013 Omnibus Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
2013 Omnibus Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
Contractual terms	10 years

Stock-based Compensation (Stock

Stock-based Compensation (Stock Option) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation [Abstract]
Stock option grants (in shares)	0	0	0
Shares
Outstanding at beginning of year (in shares)	973,361	1,741,975	2,550,046
Options exercised (in shares)	(197,631)	(297,225)	(338,808)
Options forfeited (in shares)	0	(1,597)	(12,825)
Options expired/canceled (in shares)	0	(469,792)	(456,438)
Options outstanding at end of year (in shares)	775,730	973,361	1,741,975
Options exercisable at end of year (in shares)	775,730	973,361	1,504,783
Weighted-Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 17.76	$ 37.88	$ 45.11
Options exercised (in dollars per share)	17.41	17.35	16.72
Options forfeited (in dollars per share)	0	17.64	17.17
Options expired (in dollars per share)	0	92.62	94.56
Options outstanding at end of year (in dollars per share)	17.85	17.76	37.88
Options exercisable at end of year (in dollars per share)	$ 17.85	$ 17.76	$ 41.08

Share-based Compensation (Fair

Share-based Compensation (Fair Value Assumptions) (Details) - Restricted Share Units	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.48%	0.81%	1.05%
Expected stock price volatility	22.90%	25.70%	26.40%
Dividend yield	1.20%	1.80%	1.40%
Simulation period	3 years	3 years	3 years

Share-based Compensation (Restr

Share-based Compensation (Restricted Stock Units Activity) (Details) - Restricted Share Units - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Units
Outstanding, Beginning of Period (in shares)	705,767	762,767	882,823
Granted (in shares)	242,804	350,458	321,874
Dividend equivalents granted (in shares)	5,839	11,105	9,810
Vested (in shares)	(341,825)	(406,496)	(428,121)
Forfeited (in shares)	(46,637)	(12,067)	(23,619)
Outstanding, End of Period (in shares)	565,948	705,767	762,767
Weighted-Average Grant Date Fair Value
Outstanding, Beginning of Period, Weighted-Average Grant-date Fair Value (in dollars per share)	$ 26.38	$ 24.57	$ 19.81
Granted, Weighted-Average Grant-date Fair Value (in dollars per share)	41.82	26.43	28.09
Dividend equivalents granted, Weighted-Average Grant-date Fair Value (in dollars per share)	41.82	26.43	28.09
Vested, Weighted-Average Grant-date Fair Value (in dollars per share)	26.25	23.10	17.48
Forfeited, Weighted-Average Grant-date Fair Value (in dollars per share)	26.28	23.96	24.60
Outstanding, End of Period, Weighted-Average Grant-date Fair Value (in dollars per share)	$ 33.25	$ 26.38	$ 24.57

Share-based Compensation (Marke

Share-based Compensation (Market Restricted Share Units and Performance Share Units) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Market Restricted Share Units
Share Units
Outstanding, Beginning of Period (in shares)	182,409	158,248	118,186
Granted (in shares)	78,174	93,913	82,152
Dividend equivalents granted (in shares)	2,811	3,095	2,221
Quantity change by TSR factor (in shares)	22,182	9,970	4,838
Vested (in shares)	(114,013)	(82,817)	(49,149)
Outstanding, End of Period (in shares)	171,563	182,409	158,248
Weighted-Average Grant Date Fair Value
Outstanding, Beginning of Period, Weighted-Average Grant-date Fair Value (in dollars per share)	$ 27.25	$ 27.02	$ 24.33
Granted, Weighted-Average Grant-date Fair Value (in dollars per share)	43.52	26.93	29.39
Dividend equivalents granted, Weighted-Average Grant-date Fair Value (in dollars per share)	43.52	26.93	29.05
Quantity change by TSR factor, Weighted-Average Grant-date Fair Value (in dollars per share)	27.25	26.93	24.33
Vested, Weighted-Average Grant-date Fair Value (in dollars per share)	26.78	26.40	24.34
Outstanding, End of Period, Weighted-Average Grant-date Fair Value (in dollars per share)	$ 35.24	$ 27.25	$ 27.02
Performance Share Units
Share Units
Outstanding, Beginning of Period (in shares)	238,480	151,567	67,675
Granted (in shares)	72,825	83,529	82,152
Dividend equivalents granted (in shares)	2,562	3,384	1,740
Vested (in shares)	(69,326)
Outstanding, End of Period (in shares)	244,541	238,480	151,567
Weighted-Average Grant Date Fair Value
Outstanding, Beginning of Period, Weighted-Average Grant-date Fair Value (in dollars per share)	$ 25.99	$ 26.01	$ 23.47
Granted, Weighted-Average Grant-date Fair Value (in dollars per share)	41.61	25.95	28.06
Dividend equivalents granted, Weighted-Average Grant-date Fair Value (in dollars per share)	41.61	25.95	28.06
Vested, Weighted-Average Grant-date Fair Value (in dollars per share)	23.47
Outstanding, End of Period, Weighted-Average Grant-date Fair Value (in dollars per share)	$ 31.54	$ 25.99	$ 26.01

Share-based Compensation (Grant

Share-based Compensation (Grants Under All Synovus Equity Compensation Plan) (Details) - Shareholder approved equity compensation plans for shares of Synovus stock	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of securities to be issued upon vesting of restricted share units (in shares)	982,052
Number of securities to be issued upon exercise of outstanding options (in shares)	775,730
Weighted-average exercise price of outstanding options (in dollars per share) | $ / shares	$ 17.85
Number of shares remaining available for issuance excluding shares discussed (in shares)	5,671,680

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act of 2017, income tax expense	$ 47,200
Decrease in valuation allowance	6,200	$ 2,100
Tax Cuts and Jobs Act of 2017, income tax expense	608
Deferred tax assets expected to be realized	165,800
Valuation allowance	3,431	9,658
Deferred tax assets, not subject to expiration	108,900
Tax credit carryforward, amount	6,200	2,100
Unrecognized tax benefits, income tax penalties and interest accrued	105	38	$ 96
Unrecognized tax benefits that would impact effective tax rate	12,300	9,900	$ 8,300
Unrecognized tax benefits, income tax penalties and interest accrued that would impact effective tax rate	76	$ 25
Approximate range of uncertain income tax positions expected to be settled or resolved during the next 12 months, minimum	17
Period through 2018
Income Tax Contingency [Line Items]
Valuation allowance	3,400
Period through 2035
Income Tax Contingency [Line Items]
Deferred tax assets, subject to expiration	41,100
Federal and State | Period through 2027
Income Tax Contingency [Line Items]
Tax credit carryforward, amount	$ 19,200

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal									$ (32,341)	$ 7,329	$ 6,163
State									5,949	5,501	4,424
Total current income tax expense (benefit)									(26,392)	12,830	10,587
Deferred
Federal									229,917	117,463	108,877
State									1,139	11,374	13,027
Total deferred income tax expense									231,056	128,837	121,904
Total income tax expense	$ 74,361	$ 54,668	$ 41,788	$ 33,847	$ 39,519	$ 37,375	$ 33,574	$ 31,199	204,664	141,667	132,491
Share-based compensation tax benefit (deficiency)									$ 5,000	$ (790)	$ 1,656

Income Taxes (Effective Income

Income Taxes (Effective Income Tax Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Expense (Benefit) Reconciliation
Income tax expense at statutory federal income tax rate										$ 168,048	$ 135,957	$ 125,501
State income tax expense, net of federal income tax benefit										11,961	13,256	12,870
Provisional tax adjustment related to reduction in U.S. federal statutory income tax rate										46,573	0	0
LIHTC amortization, net of tax benefits										268	0	0
Tax-exempt income										(719)	(825)	(835)
Tax benefit from share-based compensation										(4,318)	0	0
Bank-owned life insurance										(4,702)	(3,402)	(2,885)
Change in valuation allowance										(6,227)	(2,055)	(589)
General business tax credits(4)										(6,546)	(1,213)	(1,173)
Other, net										326	(51)	(398)
Total income tax expense		$ 74,361	$ 54,668	$ 41,788	$ 33,847	$ 39,519	$ 37,375	$ 33,574	$ 31,199	$ 204,664	$ 141,667	$ 132,491
Effective tax rate										42.60%	36.50%	36.90%
Tax Cuts and Jobs Act of 2017, income tax expense										$ 608
Increase in retained earnings										7,800
Research and development tax credits totaling										4,600
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act of 2017, income tax expense										$ 47,200
Tax Cuts and Jobs Act of 2017, change in effective tax rate										9.80%
Federal
Income Tax Expense (Benefit) Reconciliation
Total income tax expense		$ 47,200
Forecast
Income Tax Expense (Benefit) Reconciliation
Increase in retained earnings	$ 7,800

Income Taxes (Deferred Tax Asse

Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets
Allowance for loan losses	$ 66,034	$ 100,419
Net operating loss carryforwards	41,059	167,072
Tax credit carryforwards	19,175	67,031
Employee benefits and deferred compensation	18,333	26,183
Net unrealized losses on investment securities available for sale	13,253	19,413
Deferred revenue	12,311	18,639
Non-performing loan interest	10,388	19,137
Other	8,892	14,600
Total gross deferred tax assets	189,445	432,494
Less valuation allowance	(3,431)	(9,658)
Total deferred tax assets	186,014	422,836
Deferred tax liabilities
Other properties held for sale	(5,447)	(8,179)
Excess tax over financial statement depreciation	(6,628)	(5,343)
Other	(8,151)	(13,958)
Total gross deferred tax liabilities	(20,226)	(27,480)
Net deferred tax asset	$ 165,788	$ 395,356

Income Taxes (Tax Carryforwards

Income Taxes (Tax Carryforwards) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Gross	$ 189,445	$ 432,494
Deferred Tax Assets, Valuation Allowance	(3,431)	(9,658)
Total deferred tax assets	186,014	$ 422,836
Alternative minimum tax credits	42,100
State | Net Operating Loss | 2023-2027
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Gross	1,688
Deferred Tax Assets, Valuation Allowance	0
Total deferred tax assets	1,688
Pre-Tax Earnings Necessary to Realize(1)	1,018,310
State | Net Operating Loss | 2028-2032
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Gross	48,430
Deferred Tax Assets, Valuation Allowance	0
Total deferred tax assets	48,430
Pre-Tax Earnings Necessary to Realize(1)	1,093,946
State | Net Operating Loss | 2033-2035
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Gross	360
Deferred Tax Assets, Valuation Allowance	0
Total deferred tax assets	360
Pre-Tax Earnings Necessary to Realize(1)	7,584
State | Other Credits
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Gross	587
Deferred Tax Assets, Valuation Allowance	0
Total deferred tax assets	587
State | Other Credits | 2018-2022
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Gross	18,381
Deferred Tax Assets, Valuation Allowance	(3,431)
Total deferred tax assets	14,950
State | Other Credits | 2023-2027
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Gross	207
Deferred Tax Assets, Valuation Allowance	0
Total deferred tax assets	$ 207

Income Taxes (Unrecognized Tax

Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Income Tax Benefits
Balance at January 1,	$ 14,745	$ 12,745	$ 13,023
Additions based on income tax positions related to current year	152	0	0
Additions for income tax positions of prior years	934	1,811	8
Additions from acquisition	0	608	0
Reductions for income tax positions of prior years	(706)	0	0
Statute of limitation expirations	(8)	(419)	(286)
Settlements	0	0	0
Balance at December 31,	$ 15,117	$ 14,745	$ 12,745

Condensed Financial Informat125

Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets [Abstract]
Cash due from bank subsidiary	$ 397,848	$ 395,175
Other assets	1,035,511	813,220
Total assets	31,221,837	30,104,002
Liabilities and Shareholders' Equity
Long-term debt	1,706,138	2,160,881
Other liabilities	245,043	207,438
Total liabilities	28,260,271	27,176,078
Shareholders’ equity:
Series C Preferred Stock	125,980	125,980
Common stock	142,678	142,026
Additional paid-in capital	3,043,129	3,028,405
Treasury stock	(839,674)	(664,595)
Accumulated other comprehensive loss, net	(54,754)	(55,659)
Retained earnings	544,207	351,767
Total shareholders’ equity	2,961,566	2,927,924
Total liabilities and shareholders' equity	31,221,837	30,104,002
Parent Company
Assets [Abstract]
Cash due from bank subsidiary	191,275	234,339
Funds due from other depository institutions	19,911	19,911
Investment in consolidated bank subsidiary, at equity	3,232,129	3,319,980
Investment in consolidated nonbank subsidiaries, at equity	40,731	71,335
Notes receivable from nonbank subsidiaries	0	35,200
Other assets	69,762	101,346
Total assets	3,553,808	3,782,111
Liabilities and Shareholders' Equity
Long-term debt	554,589	834,252
Other liabilities	37,653	19,935
Total liabilities	592,242	854,187
Shareholders’ equity:
Series C Preferred Stock	125,980	125,980
Common stock	142,678	142,026
Additional paid-in capital	3,043,129	3,028,405
Treasury stock	(839,674)	(664,595)
Accumulated other comprehensive loss, net	(54,754)	(55,659)
Retained earnings	544,207	351,767
Total shareholders’ equity	2,961,566	2,927,924
Total liabilities and shareholders' equity	$ 3,553,808	$ 3,782,111

Condensed Financial Informat126

Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Condensed Statements Of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expenses
Interest expense									$ 139,188	$ 123,623	$ 118,644
Other expenses									821,313	755,923	717,655
Income before income taxes	$ 103,966	$ 152,675	$ 117,791	$ 105,704	$ 108,068	$ 102,620	$ 94,031	$ 83,730	480,138	388,451	358,573
Dividends on preferred stock									10,238	10,238	10,238
Net income available to common shareholders	$ 27,046	$ 95,448	$ 73,444	$ 69,298	$ 65,990	$ 62,686	$ 57,898	$ 49,972	265,236	236,546	215,844
Parent Company
Income
Cash dividends received from subsidiaries(1)									283,210	325,000	199,904
Cash distributions received from Synovus Bank									167,790	0	25,096
Interest income									1,443	2,565	8,865
Other income									345	4,595	(337)
Total income									452,788	332,160	233,528
Expenses
Interest expense									43,922	52,831	46,585
Other expenses									33,955	20,652	10,516
Total expenses									77,877	73,483	57,101
Income before income taxes									374,911	258,677	176,427
Allocated income tax benefit									(30,421)	(25,628)	(18,808)
Income before equity in undistributed (loss) income of subsidiaries									405,332	284,305	195,235
Equity in undistributed (loss) income of subsidiaries									(129,858)	(37,521)	30,847
Net income (loss) available to controlling interest									275,474	246,784	226,082
Dividends on preferred stock									10,238	10,238	10,238
Net income available to common shareholders									$ 265,236	$ 236,546	$ 215,844

Condensed Financial Informat127

Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income, Before-tax Amount									$ 480,138	$ 388,451	$ 358,573
Net income, Tax (Expense) Benefit	$ (74,361)	$ (54,668)	$ (41,788)	$ (33,847)	$ (39,519)	$ (37,375)	$ (33,574)	$ (31,199)	(204,664)	(141,667)	(132,491)
Net income	$ 29,605	$ 98,007	$ 76,003	$ 71,857	$ 68,549	$ 65,245	$ 60,457	$ 52,531	275,474	246,784	226,082
Reclassification adjustment for losses realized in net income, Before-tax Amount									130	467	521
Reclassification adjustment for losses realized in net income, Tax (Expense) Benefit									(50)	(180)	(201)
Reclassification adjustment for losses realized in net income, Net of Tax Amount									80	287	320
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount									289	(6,011)	(2,769)
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Tax (Expense) Benefit									(111)	2,314	1,066
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Net of Tax Amount									178	(3,697)	(1,703)
Net unrealized gains (losses) arising during the period, Before-tax Amount									1,038	(36,432)	(25,707)
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit									(362)	14,027	9,901
Net unrealized gains (losses) arising during the period, Net of Tax Amount									676	(22,405)	(15,806)
Other comprehensive income (loss), Before-tax Amount									1,408	(42,018)	(27,991)
Other comprehensive income (loss), Tax (Expense) Benefit									(503)	16,178	10,777
Net current period other comprehensive income (loss)									905	(25,840)	(17,214)
Comprehensive income, Net of Tax Amount									276,379	220,944	208,868
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income, Before-tax Amount									480,138	388,451	358,573
Net income, Tax (Expense) Benefit									(204,664)	(141,667)	(132,491)
Net income									275,474	246,784	226,082
Reclassification adjustment for losses realized in net income, Before-tax Amount									130	467	521
Reclassification adjustment for losses realized in net income, Tax (Expense) Benefit									(50)	(180)	(201)
Reclassification adjustment for losses realized in net income, Net of Tax Amount									80	287	320
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount									(5,506)	(5,763)	0
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Tax (Expense) Benefit									2,120	2,219	0
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Net of Tax Amount									(3,386)	(3,544)	0
Net unrealized gains (losses) arising during the period, Before-tax Amount									0	2,358	2,908
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit									0	(908)	(1,120)
Net unrealized gains (losses) arising during the period, Net of Tax Amount									0	1,450	1,788
Other comprehensive gain (loss) of bank subsidiary, Before-tax Amount									6,784	(39,080)	(31,420)
Other comprehensive gain (loss) of bank subsidiary, Tax (expense) Benefit									(2,573)	15,047	12,098
Other comprehensive gain (loss) of bank subsidiary, Net of Tax Amount									4,211	(24,033)	(19,322)
Other comprehensive income (loss), Before-tax Amount									1,408	(42,018)	(27,991)
Other comprehensive income (loss), Tax (Expense) Benefit									(503)	16,178	10,777
Net current period other comprehensive income (loss)									905	(25,840)	(17,214)
Comprehensive income, Net of Tax Amount									$ 276,379	$ 220,944	$ 208,868

Condensed Financial Informat128

Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Adjustments to reconcile net income to net cash provided by operating activities:
Net cash provided by operating activities	$ 641,626	$ 461,637	$ 444,986
Investing Activities
Proceeds from sales of investment securities available for sale	812,293	968,606	347,954
Net cash used in investing activities	(1,415,541)	(1,099,465)	(2,106,717)
Financing Activities
Repurchases of common stock	(175,079)	(263,084)	(199,221)
Repayments and redemption of long-term debt	(2,250,422)	(2,263,688)	(823,899)
Proceeds from issuance of long-term debt	1,771,866	1,875,000	871,644
Earnout payment	(892)	0	0
Net cash provided by financing activities	776,588	665,911	1,543,334
Increase (decrease) in cash and cash equivalents	2,673	28,083	(118,397)
Cash and cash equivalents at beginning of year	395,175	367,092	485,489
Cash and cash equivalents at end of year	397,848	395,175	367,092
Income tax payments, net	18,040	9,340	10,514
Interest paid	143,237	123,560	115,795
Parent Company
Operating Activities
Net income	275,474	246,784	226,082
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed loss (income) of subsidiaries	129,858	37,521	(30,847)
Deferred income tax expense (benefit)	60,931	17,989	(2,506)
Net (decrease) increase in other liabilities	(1,095)	7,746	(1,709)
Net (increase) decrease in other assets	(8)	(9,214)	1,045
Other, net	(3,330)	(1,648)	(178)
Net cash provided by operating activities	461,830	299,178	191,887
Investing Activities
Proceeds from sales of investment securities available for sale	4,305	0	0
Net cash received (used) in acquisitions/dispositions	0	(3,408)	0
Net decrease in short-term notes receivable from non-bank subsidiaries	35,200	31,800	10,000
Net cash used in investing activities	39,505	28,392	10,000
Financing Activities
Dividends paid to common and preferred shareholders	(64,908)	(69,663)	(65,592)
Repurchases of common stock	(175,079)	(263,084)	(199,221)
Repayments and redemption of long-term debt	(600,386)	(130,048)	(48,553)
Proceeds from issuance of long-term debt	296,866	0	246,644
Earnout payment	(892)	0	0
Net cash provided by financing activities	(544,399)	(462,795)	(66,722)
Increase (decrease) in cash and cash equivalents	(43,064)	(135,225)	135,165
Cash and cash equivalents at beginning of year	254,250	389,475	254,310
Cash and cash equivalents at end of year	211,186	254,250	389,475
Income tax payments, net	18,000	9,500	8,700
Interest paid	$ 51,000	$ 53,100	$ 46,900

Supplemental Financial Data (De

Supplemental Financial Data (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Income Statement Elements [Abstract]
Insurance and bonds	$ 10,314	$ 12,023	$ 12,514

Summary of Quarterly Financi130

Summary of Quarterly Financial Data (Unaudited) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Loss on early extinguishment of debt	$ 23,200								$ 23,160	$ 4,735	$ 1,533
Income Tax Contingency [Line Items]
Income tax expense	74,361	$ 54,668	$ 41,788	$ 33,847	$ 39,519	$ 37,375	$ 33,574	$ 31,199	$ 204,664	$ 141,667	$ 132,491
Federal
Income Tax Contingency [Line Items]
Income tax expense	$ 47,200

Summary of Quarterly Financi131

Summary of Quarterly Financial Data (Unaudited) (Schedule) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Interest income	$ 306,934	$ 297,652	$ 285,510	$ 272,401	$ 264,534	$ 256,554	$ 252,393	$ 249,323	$ 1,162,497	$ 1,022,803	$ 945,962
Net interest income	269,713	262,572	251,097	239,927	233,530	226,007	221,449	218,193	1,023,309	899,180	827,318
Provision for loan losses	8,565	39,686	10,260	8,674	6,259	5,671	6,693	9,377	67,185	28,000	19,010
Income before income taxes	103,966	152,675	117,791	105,704	108,068	102,620	94,031	83,730	480,138	388,451	358,573
Income tax expense	74,361	54,668	41,788	33,847	39,519	37,375	33,574	31,199	204,664	141,667	132,491
Net income	29,605	98,007	76,003	71,857	68,549	65,245	60,457	52,531	275,474	246,784	226,082
Net income available common shareholders	$ 27,046	$ 95,448	$ 73,444	$ 69,298	$ 65,990	$ 62,686	$ 57,898	$ 49,972	$ 265,236	$ 236,546	$ 215,844
Net income per common share, basic (in dollars per share)	$ 0.23	$ 0.79	$ 0.60	$ 0.57	$ 0.54	$ 0.51	$ 0.46	$ 0.39	$ 2.19	$ 1.90	$ 1.63
Net income per common share, diluted (in dollars per share)	$ 0.23	$ 0.78	$ 0.60	$ 0.56	$ 0.54	$ 0.51	$ 0.46	$ 0.39	$ 2.17	$ 1.89	$ 1.62