Regulatory Matters (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Banking Regulation, Tier 1 Leverage Capital [Abstract]
Capital conservation buffer	0.0250		0.0250
Components of regulatory capital [Abstract]
Total shareholders' equity	$ 374,998	$ 375,162	$ 347,596	$ 332,308	$ 331,134	$ 398,484
Add (deduct)
Accumulated other comprehensive (income) loss for regulatory purposes	(92,304)		(92,763)
Subordinated debt	$ 39,491		39,433
Period of transition method for regulatory purposes	3 years
Consolidated
Banking Regulation, Total Capital [Abstract]
Total risk-based capital	$ 564,115		$ 536,549
Actual, ratio	0.1358		0.1362
Banking regulation, total risk-based capital, capital adequacy, minimum	$ 332,292		$ 315,059
Minimum for adequately capitalized institutions, ratio	0.0800		0.0800
Tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 472,126		$ 447,299
Banking regulation, tier 1 risk-based capital ratio, accrual	0.1137		0.1136
Minimum for adequately capitalized institutions, amount	$ 249,219		$ 236,294
Minimum for adequately capitalized institutions, ratio	0.0600		0.0600
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 433,639		$ 408,863
Actual, ratio	0.1044		0.1038
Minimum for adequately capitalized institutions, amount	$ 186,914		$ 177,221
Minimum for adequately capitalized institutions, ratio	0.0450		0.0450
Banking Regulation, Tier 1 Leverage Capital [Abstract]
Tier 1 capital	$ 472,126		$ 447,299
Actual, ratio	0.0894		0.0886
Minimum for adequately capitalized institutions, amount	$ 211,355		$ 201,875
Minimum for adequately capitalized institutions, ratio	0.0400		0.0400
Components of regulatory capital [Abstract]
Total shareholders' equity	$ 374,998		$ 347,596
Add (deduct)
Accumulated other comprehensive (income) loss for regulatory purposes	86,506		86,966
Goodwill and other intangibles	(30,441)		(30,851)
CECL	2,576		5,152
Common equity tier 1 capital	433,639		408,863
Qualifying trust preferred securities	38,487		38,436
Tier 1 capital	472,126		447,299
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	51,989		49,250
Total risk-based capital	564,115		536,549
Independent Bank
Banking Regulation, Total Capital [Abstract]
Total risk-based capital	$ 512,002		$ 480,886
Actual, ratio	0.1234		0.1222
Banking regulation, total risk-based capital, capital adequacy, minimum	$ 331,958		$ 314,733
Minimum for adequately capitalized institutions, ratio	0.0800		0.0800
Minimum for well-capitalized institutions, amount	$ 414,947		$ 393,416
Minimum for well-capitalized institutions, ratio	0.1000		0.1000
Tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 460,064		$ 431,685
Banking regulation, tier 1 risk-based capital ratio, accrual	0.1109		0.1097
Minimum for adequately capitalized institutions, amount	$ 248,968		$ 236,049
Minimum for adequately capitalized institutions, ratio	0.0600		0.0600
Minimum for well-capitalized institutions, amount	$ 331,958		$ 314,733
Minimum for well capitalized institutions, ratio	0.0800		0.0800
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, amount	$ 460,064		$ 431,685
Actual, ratio	0.1109		0.1097
Minimum for adequately capitalized institutions, amount	$ 186,726		$ 177,037
Minimum for adequately capitalized institutions, ratio	0.0450		0.0450
Minimum for well-capitalized institutions, amount	$ 269,716		$ 255,720
Minimum for well-capitalized institutions, ratio	0.0650		0.0650
Banking Regulation, Tier 1 Leverage Capital [Abstract]
Tier 1 capital	$ 460,064		$ 431,685
Actual, ratio	0.0871		0.0856
Minimum for adequately capitalized institutions, amount	$ 211,328		$ 201,820
Minimum for adequately capitalized institutions, ratio	0.0400		0.0400
Banking regulation, tier 1 leverage, capital, well capitalized, minimum	$ 264,160		$ 252,275
Minimum for well capitalized institutions, ratio	0.0500		0.0500
Components of regulatory capital [Abstract]
Total shareholders' equity	$ 401,423		$ 370,418
Add (deduct)
Accumulated other comprehensive (income) loss for regulatory purposes	86,506		86,966
Goodwill and other intangibles	(30,441)		(30,851)
CECL	2,576		5,152
Common equity tier 1 capital	460,064		431,685
Qualifying trust preferred securities	0		0
Tier 1 capital	460,064		431,685
Subordinated debt	0		0
Allowance for credit losses and allowance for unfunded lending commitments limited to 1.25% of total risk-weighted assets	51,938		49,201
Total risk-based capital	$ 512,002		$ 480,886