Regulatory Matters (Details) $ in Thousands		Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Regulatory Matters [Abstract]
Undivided profits		$ 68,300
Tier 1 capital to average assets [Abstract]
Capital conservation buffer		0.0250		0.0250
Components of regulatory capital [Abstract]
Total shareholders' equity		$ 373,092	$ 355,123	$ 350,169	$ 340,245	$ 330,846	$ 338,994
Add (deduct) [Abstract]
Accumulated other comprehensive income for regulatory purposes		6,146		(3,786)
Subordinated debt		39,261		0
Consolidated [Member]
Total capital to risk-weighted assets [Abstract]
Total risk-based capital	[1]	$ 441,969		$ 380,454
Actual, Ratio	[1]	0.1562		0.1374
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 226,378		$ 221,562
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0800		0.0800
Tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 366,571		$ 352,764
Actual, Ratio	[1]	0.1295		0.1274
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 169,783		$ 166,171
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0600		0.0600
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 328,288		$ 314,532
Actual, Ratio	[1]	0.1160		0.1136
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 127,338		$ 124,628
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0450		0.0450
Tier 1 capital to average assets [Abstract]
Tier 1 capital	[1]	$ 366,571		$ 352,764
Actual, Ratio	[1]	0.0905		0.1011
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 162,103		$ 139,632
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0400		0.0400
Components of regulatory capital [Abstract]
Total shareholders' equity		$ 373,092		$ 350,169
Add (deduct) [Abstract]
Accumulated other comprehensive income for regulatory purposes		(11,943)		(2,011)
Goodwill and other intangibles		(32,861)		(33,626)
Common equity tier 1 capital	[1]	328,288		314,532
Qualifying trust preferred securities		38,283		38,232
Tier 1 capital	[1]	366,571		352,764
Subordinated debt		40,000		0
Allowance for loan losses and allowance for unfunded lending commitments limited to 1.25% of total risk-weighted assets		35,398		27,690
Total risk-based capital	[1]	441,969		380,454
Independent Bank [Member]
Total capital to risk-weighted assets [Abstract]
Total risk-based capital	[1]	$ 391,033		$ 358,914
Actual, Ratio	[1]	0.1382		0.1296
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 226,310		$ 221,482
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0800		0.0800
Minimum for Well-Capitalized Institutions, Amount	[1]	$ 282,888		$ 276,852
Minimum for Well-Capitalized Institutions, Ratio	[1]	0.1000		0.1000
Tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 355,645		$ 331,224
Actual, Ratio	[1]	0.1257		0.1196
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 169,733		$ 166,111
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0600		0.0600
Minimum for Well-Capitalized Institutions, Amount	[1]	$ 226,310		$ 221,482
Minimum for Well-Capitalized Institutions, Ratio	[1]	0.0800		0.0800
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 355,645		$ 331,224
Actual, Ratio	[1]	0.1257		0.1196
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 127,299		$ 124,583
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0450		0.0450
Minimum for Well-Capitalized Institutions, Amount	[1]	$ 183,877		$ 179,954
Minimum for Well-Capitalized Institutions, Ratio	[1]	0.0650		0.0650
Tier 1 capital to average assets [Abstract]
Tier 1 capital	[1]	$ 355,645		$ 331,224
Actual, Ratio	[1]	0.0878		0.0949
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 162,020		$ 139,615
Minimum for Adequately Capitalized Institutions, Ratio	[1]	0.0400		0.0400
Minimum for Well-Capitalized Institutions, Amount	[1]	$ 202,525		$ 174,519
Minimum for Well-Capitalized Institutions, Ratio	[1]	0.0500		0.0500
Components of regulatory capital [Abstract]
Total shareholders' equity		$ 400,449		$ 366,861
Add (deduct) [Abstract]
Accumulated other comprehensive income for regulatory purposes		(11,943)		(2,011)
Goodwill and other intangibles		(32,861)		(33,626)
Common equity tier 1 capital	[1]	355,645		331,224
Qualifying trust preferred securities		0		0
Tier 1 capital	[1]	355,645		331,224
Subordinated debt		0		0
Allowance for loan losses and allowance for unfunded lending commitments limited to 1.25% of total risk-weighted assets		35,388		27,690
Total risk-based capital	[1]	$ 391,033		$ 358,914

[1] These ratios do not reflect a capital conservation buffer of 2.50% at September 30, 2020 and December 31, 2019.