Debt Instrument, Interest Rate Period

No definition available.

Name:	syn_DebtInstrumentInterestRatePeriod
Namespace Prefix:	syn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Amount of long-term debt classified as other.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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Balance Type:	credit
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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Balance Type:	credit
Period Type:	instant

- Details

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Period Type:

- Details

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- Details

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Balance Type:
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_UsTreasuryUstInterestRateMember
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- Details

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- Details

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Balance Type:
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Name:	us-gaap_VariableRateAxis=syn_SecuredOvernightFinancingRateSOFRMember
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Other Short-term Borrowings and Long-term Debt - Schedule of Long-term Debt Instruments (Details) - USD ($)		12 Months Ended
	Feb. 10, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt		$ 4,109,597,000	$ 1,204,229,000
Repayments of long-term debt, net		700,000,000	0	$ 2,408,939,000
Synovus Bank
Debt Instrument [Line Items]
Long-term debt		3,465,107,000	596,895,000
2.289% Fixed-to-Floating Rate Senior Bank Notes due 2023 \| Synovus Bank
Debt Instrument [Line Items]
Repayments of long-term debt, net	$ 405,300,000
4.00% Subordinated Notes, Due October 29, 2030 \| Synovus Bank
Debt Instrument [Line Items]
Subordinated notes		$ 190,107,000	197,626,000
Stated percentage		4.00%
Debt, face amount		$ 200,000,000.0
Interest rate period		5 years
4.00% Subordinated Notes, Due October 29, 2030 \| Synovus Bank \| US Treasury Rate
Debt Instrument [Line Items]
Basis spread on variable rate		3.625%
Federal Home Loan Bank Advance \| Synovus Bank
Debt Instrument [Line Items]
Other long-term debt		$ 3,275,000,000	0
Weighted average interest rate		4.56%
Senior Notes \| 2.289% Fixed-to-Floating Rate Senior Bank Notes due 2023 \| Synovus Bank
Debt Instrument [Line Items]
Long-term debt, gross		$ 0	399,269,000
Stated percentage		2.289%
Debt, face amount		$ 400,000,000.0
Interest rate period		2 years
Senior Notes \| 2.289% Fixed-to-Floating Rate Senior Bank Notes due 2023 \| Synovus Bank \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate		0.945%
Parent Company
Debt Instrument [Line Items]
Long-term debt		$ 644,490,000	607,334,000
Repayments of long-term debt, net		300,000,000	0	$ 250,000,000
Parent Company \| 5.90% Subordinated Notes, due February 7, 2029
Debt Instrument [Line Items]
Subordinated notes		$ 298,158,000	297,855,000
Stated percentage		5.90%
Debt, face amount		$ 300,000,000.0
Interest rate period		5 years
Parent Company \| 5.90% Subordinated Notes, due February 7, 2029 \| Five-Year Mid Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate		3.379%
Parent Company \| LIBOR 1.80% debentures, due June 15, 2035
Debt Instrument [Line Items]
Unsecured debt		$ 10,000,000	$ 10,000,000
Stated percentage		1.80%
Debt, face amount		$ 10,000,000.0
Interest rate at period end		6.57%	2.00%
Parent Company \| Senior Notes \| 3.125% Senior Notes due November 1, 2022
Debt Instrument [Line Items]
Long-term debt, gross		$ 0	$ 299,479,000
Stated percentage		3.125%
Debt, face amount		$ 300,000,000.0
Parent Company \| Senior Notes \| 5.200% Senior Notes due August 11, 2025
Debt Instrument [Line Items]
Long-term debt, gross		$ 336,332,000	$ 0
Stated percentage		5.20%
Debt, face amount		$ 350,000,000.0