Parent Company Financial Statements - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	$ 83,811	$ 85,888	$ 81,825
Adjustments to Reconcile Net Income to Net Cash from Operations
Net Amortization on Securities	2,161	5,566	6,452
Change in Other Assets	1,748	3,725	(1,094)
Change in Other Liabilities	(1,354)	(3,173)	1,626
Equity Based Compensation	2,947	2,332	2,330
Net Cash from Operating Activities	95,764	107,234	110,036
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from Maturities, Calls and Redemptions of Securities Available-for-Sale	356,471	287,084	143,418
Net Cash from Investing Activities	(82,400)	27,255	(24,181)
CASH FLOWS FROM FINANCING ACTIVITIES
Dividends Paid	(31,845)	(29,433)	(27,022)
Net Cash from Financing Activities	60,098	(136,540)	(363,666)
Net Change in Cash and Cash Equivalents	73,462	(2,051)	(277,811)
Cash and Cash Equivalents at Beginning of Year	115,330	117,381	395,192
Cash and Cash Equivalents at End of Year	188,792	115,330	117,381
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	83,811	85,888	81,825
Adjustments to Reconcile Net Income to Net Cash from Operations
Net Amortization on Securities	8	0	0
Change in Other Assets	(989)	3,929	3,861
Change in Other Liabilities	1,065	(3,113)	1,200
Equity Based Compensation	2,947	2,332	2,330
Equity in Excess Undistributed Income of Subsidiaries	(25,880)	(41,287)	(52,400)
Net Cash from Operating Activities	60,962	47,749	36,816
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from Maturities, Calls and Redemptions of Securities Available-for-Sale	329	0	0
Cash Used for Business Acquisitions	0	0	(49,644)
Net Equity in Dissolution of Subsidiary	0	1,978	0
Net Cash from Investing Activities	329	1,978	(49,644)
CASH FLOWS FROM FINANCING ACTIVITIES
Dividends Paid	(31,845)	(29,433)	(27,022)
Net Cash from Financing Activities	(31,845)	(29,433)	(27,022)
Net Change in Cash and Cash Equivalents	29,446	20,294	(39,850)
Cash and Cash Equivalents at Beginning of Year	66,835	46,541	86,391
Cash and Cash Equivalents at End of Year	$ 96,281	$ 66,835	$ 46,541

Equity in Excess Distributed (Undistributed) Income of Subsidiaries.

No definition available.

Name:	gabc_EquityInExcessDistributedUndistributedIncomeOfSubsidiaries
Namespace Prefix:	gabc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.