Regulatory Matters (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Banking Regulation, Tier 1 Leverage Capital [Abstract]
Capital conservation buffer	0.0250	0.0250
Components of regulatory capital [Abstract]
Total shareholders' equity	$ 452,369	$ 404,449	$ 430,459	$ 374,998	$ 375,162	$ 347,596
Add (deduct)
Accumulated other comprehensive (income) loss for regulatory purposes	(58,252)	(72,142)
Subordinated debt	$ 39,567	$ 39,510
Period of transition method for regulatory purposes	3 years	3 years
Consolidated
Banking Regulation, Total Capital [Abstract]
Total risk-based capital	$ 606,783	$ 573,972
Actual, ratio	0.1425	0.1371
Banking regulation, total risk-based capital, capital adequacy, minimum	$ 340,539	$ 335,014
Minimum for adequately capitalized institutions, ratio	0.0800	0.0800
Tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 513,461	$ 481,569
Banking regulation, tier 1 risk-based capital ratio, accrual	0.1206	0.1150
Minimum for adequately capitalized institutions, amount	$ 255,404	$ 251,260
Minimum for adequately capitalized institutions, ratio	0.0600	0.0600
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 474,906	$ 443,065
Actual, ratio	0.1116	0.1058
Minimum for adequately capitalized institutions, amount	$ 191,553	$ 188,445
Minimum for adequately capitalized institutions, ratio	0.0450	0.0450
Banking Regulation, Tier 1 Leverage Capital [Abstract]
Tier 1 capital	$ 513,461	$ 481,569
Actual, ratio	0.0962	0.0903
Minimum for adequately capitalized institutions, amount	$ 213,392	$ 213,227
Minimum for adequately capitalized institutions, ratio	0.0400	0.0400
Components of regulatory capital [Abstract]
Total shareholders' equity	$ 452,369	$ 404,449
Add (deduct)
Accumulated other comprehensive (income) loss for regulatory purposes	52,454	66,344
Goodwill and other intangibles	(29,917)	(30,304)
CECL	0	2,576
Common equity tier 1 capital	474,906	443,065
Qualifying trust preferred securities	38,555	38,504
Tier 1 capital	513,461	481,569
Subordinated debt	40,000	40,000
Allowance for credit losses and allowance for unfunded lending commitments limited to 1.25% of total risk-weighted assets	53,322	52,403
Total risk-based capital	606,783	573,972
Independent Bank
Banking Regulation, Total Capital [Abstract]
Total risk-based capital	$ 552,577	$ 521,374
Actual, ratio	0.1300	0.1246
Banking regulation, total risk-based capital, capital adequacy, minimum	$ 340,134	$ 334,673
Minimum for adequately capitalized institutions, ratio	0.0800	0.0800
Minimum for well-capitalized institutions, amount	$ 425,167	$ 418,341
Minimum for well-capitalized institutions, ratio	0.1000	0.1000
Tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 499,317	$ 469,023
Banking regulation, tier 1 risk-based capital ratio, accrual	0.1174	0.1121
Minimum for adequately capitalized institutions, amount	$ 255,100	$ 251,005
Minimum for adequately capitalized institutions, ratio	0.0600	0.0600
Minimum for well-capitalized institutions, amount	$ 340,134	$ 334,673
Minimum for well capitalized institutions, ratio	0.0800	0.0800
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 499,317	$ 469,023
Actual, ratio	0.1174	0.1121
Minimum for adequately capitalized institutions, amount	$ 191,325	$ 188,254
Minimum for adequately capitalized institutions, ratio	0.0450	0.0450
Minimum for well-capitalized institutions, amount	$ 276,359	$ 271,922
Minimum for well-capitalized institutions, ratio	0.0650	0.0650
Banking Regulation, Tier 1 Leverage Capital [Abstract]
Tier 1 capital	$ 499,317	$ 469,023
Actual, ratio	0.0936	0.0880
Minimum for adequately capitalized institutions, amount	$ 213,370	$ 213,180
Minimum for adequately capitalized institutions, ratio	0.0400	0.0400
Banking regulation, tier 1 leverage, capital, well capitalized, minimum	$ 266,712	$ 266,475
Minimum for well capitalized institutions, ratio	0.0500	0.0500
Components of regulatory capital [Abstract]
Total shareholders' equity	$ 476,780	$ 430,407
Add (deduct)
Accumulated other comprehensive (income) loss for regulatory purposes	52,454	66,344
Goodwill and other intangibles	(29,917)	(30,304)
CECL	0	2,576
Common equity tier 1 capital	499,317	469,023
Qualifying trust preferred securities	0	0
Tier 1 capital	499,317	469,023
Subordinated debt	0	0
Allowance for credit losses and allowance for unfunded lending commitments limited to 1.25% of total risk-weighted assets	53,260	52,351
Total risk-based capital	$ 552,577	$ 521,374