Regulatory Matters (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2019	Dec. 31, 2018	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Regulatory Matters [Abstract]
Undivided profits		$ 38,300
Tier 1 capital to average assets [Abstract]
Capital conservation buffer		2.50%	1.875%
Components of regulatory capital [Abstract]
Total shareholders' equity		$ 340,245	$ 338,994	$ 330,846	$ 345,204	$ 337,083	$ 264,933
Add (deduct) [Abstract]
Accumulated other comprehensive (income) loss for regulatory purposes		(3,373)	(10,108)
Consolidated [Member]
Total capital to risk-weighted assets [Abstract]
Total risk-based capital	[1]	$ 369,923	$ 371,603
Actual, Ratio	[1]	13.39%	14.25%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 221,065	$ 208,572
Minimum for Adequately Capitalized Institutions, Ratio	[1]	8.00%	8.00%
Tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 342,138	$ 345,419
Actual, Ratio	[1]	12.38%	13.25%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 165,799	$ 156,429
Minimum for Adequately Capitalized Institutions, Ratio	[1]	6.00%	6.00%
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 303,923	$ 307,255
Actual, Ratio	[1]	11.00%	11.79%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 124,349	$ 117,322
Minimum for Adequately Capitalized Institutions, Ratio	[1]	4.50%	4.50%
Tier 1 capital to average assets [Abstract]
Tier 1 capital	[1]	$ 342,138	$ 345,419
Actual, Ratio	[1]	9.93%	10.47%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 137,762	$ 131,930
Minimum for Adequately Capitalized Institutions, Ratio	[1]	4.00%	4.00%
Components of regulatory capital [Abstract]
Total shareholders' equity		$ 340,245	$ 338,994
Add (deduct) [Abstract]
Accumulated other comprehensive (income) loss for regulatory purposes		(2,424)	4,311
Goodwill and other intangibles		(33,898)	(34,715)
Disallowed deferred tax assets		0	(1,335)
Common equity tier 1 capital	[1]	303,923	307,255
Qualifying trust preferred securities		38,215	38,164
Tier 1 capital	[1]	342,138	345,419
Allowance for loan losses and allowance for unfunded lending commitments limited to 1.25% of total risk-weighted assets		27,785	26,184
Total risk-based capital	[1]	369,923	371,603
Independent Bank [Member]
Total capital to risk-weighted assets [Abstract]
Total risk-based capital	[1]	$ 352,432	$ 337,227
Actual, Ratio	[1]	12.76%	12.94%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 220,984	$ 208,456
Minimum for Adequately Capitalized Institutions, Ratio	[1]	8.00%	8.00%
Minimum for Well Capitalized Institutions, Amount	[1]	$ 276,230	$ 260,569
Minimum for Well-Capitalized Institutions, Ratio	[1]	10.00%	10.00%
Tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 324,647	$ 311,043
Actual, Ratio	[1]	11.75%	11.94%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 165,738	$ 156,342
Minimum for Adequately Capitalized Institutions, Ratio	[1]	6.00%	6.00%
Minimum for Well-Capitalized Institutions, Amount	[1]	$ 220,984	$ 208,456
Minimum for Well Capitalized Institutions, Ratio	[1]	8.00%	8.00%
Common equity tier 1 capital to risk-weighted assets [Abstract]
Actual, Amount	[1]	$ 324,647	$ 311,043
Actual, Ratio	[1]	11.75%	11.94%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 124,304	$ 117,256
Minimum for Adequately Capitalized Institutions, Ratio	[1]	4.50%	4.50%
Minimum for Well-Capitalized Institutions, Amount	[1]	$ 179,550	$ 169,370
Minimum for Well Capitalized Institutions, Ratio	[1]	6.50%	6.50%
Tier 1 capital to average assets [Abstract]
Tier 1 capital	[1]	$ 324,647	$ 311,043
Actual, Ratio	[1]	9.43%	9.44%
Minimum for Adequately Capitalized Institutions, Amount	[1]	$ 137,736	$ 131,778
Minimum for Adequately Capitalized Institutions, Ratio	[1]	4.00%	4.00%
Minimum for Well-Capitalized Institutions, Amount	[1]	$ 172,170	$ 164,723
Minimum for Well-Capitalized Institutions, Ratio	[1]	5.00%	5.00%
Components of regulatory capital [Abstract]
Total shareholders' equity		$ 360,969	$ 341,496
Add (deduct) [Abstract]
Accumulated other comprehensive (income) loss for regulatory purposes		(2,424)	4,311
Goodwill and other intangibles		(33,898)	(34,715)
Disallowed deferred tax assets		0	(49)
Common equity tier 1 capital	[1]	324,647	311,043
Qualifying trust preferred securities		0	0
Tier 1 capital	[1]	324,647	311,043
Allowance for loan losses and allowance for unfunded lending commitments limited to 1.25% of total risk-weighted assets		27,785	26,184
Total risk-based capital	[1]	$ 352,432	$ 337,227

[1] These ratios do not reflect a capital conservation buffer of 2.50% and 1.875% at September 30, 2019 and December 31, 2018, respectively.