Regulatory Capital Requirements - Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Compliance with Regulatory Capital Requirements under Banking Regulations
Number of prior calendar years considered for payment of dividends in excess of net retained profit	2 years
Tier 1 leverage ratio
Capital conservation buffer excluded from minimum capital requirement	2.50%	1.875%
TCF
Regulatory Capital:
Common Equity Tier 1 Capital	$ 4,050,826	$ 2,224,183
Tier 1 capital	4,236,648	2,408,393
Total capital	$ 4,681,630	$ 2,750,581
Common equity Tier 1 capital ratio
Actual, Ratio	10.99%	10.82%
Tier 1 risk-based capital ratio
Actual, Ratio	11.49%	11.72%
Total risk-based capital ratio
Actual, Ratio	12.70%	13.38%
Tier 1 leverage ratio
Actual, Ratio	9.49%	10.44%
TCF Bank
Compliance with Regulatory Capital Requirements under Banking Regulations
Net profits for the current year combined with retained net profits for preceding two calendar years	$ 340,800
Regulatory Capital:
Common Equity Tier 1 Capital	4,039,191	$ 2,282,013
Tier 1 capital	4,059,417	2,300,472
Total capital	$ 4,524,051	$ 2,675,347
Common equity Tier 1 capital ratio
Actual, Ratio	10.97%	11.10%
Well-Capitalized Capital Requirement, Ratio	6.50%
Minimum Capital Requirement, Ratio	4.50%
Tier 1 risk-based capital ratio
Actual, Ratio	11.03%	11.19%
Well-Capitalized Capital Requirement, Ratio	8.00%
Minimum Capital Requirement, Ratio	6.00%
Total risk-based capital ratio
Actual, Ratio	12.29%	13.01%
Well-Capitalized Capital Requirement, Ratio	10.00%
Minimum Capital Requirement, Ratio	8.00%
Tier 1 leverage ratio
Actual, Ratio	9.10%	9.97%
Well-Capitalized Capital Requirement, Ratio	5.00%
Minimum Capital Requirement, Ratio	4.00%
Maximum
Compliance with Regulatory Capital Requirements under Banking Regulations
Percentage of net retained profits for the current year combined with retained net profits for the preceding two calendar years that can be declared as dividend	100.00%