Regulatory Capital Requirements (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) Rate	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
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%		2.50%
Accounting Standards Update 2016-13
Compliance with Regulatory Capital Requirements under Banking Regulations
Regulatory capital cumulative basis point | Rate	0.00006%
Accounting Standards Update 2016-13 | Estimated incremental effect
Regulatory Capital:
Total capital	$ 211,200
Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment | Estimated incremental effect
Regulatory Capital:
Total capital	159,200	$ 52,000
TCF
Regulatory Capital:
Common equity Tier 1 capital	4,103,007		$ 4,050,826
Tier 1 capital	4,290,793		4,236,648
Total capital	$ 5,026,611		$ 4,681,630
Common equity Tier 1 capital ratio
Actual, Ratio	0.1145		0.1099
Tier 1 risk-based capital ratio
Actual, Ratio	0.1198		0.1149
Total risk-based capital ratio
Actual, Ratio	0.1403		0.1270
Tier 1 leverage ratio
Actual, Ratio	0.0934		0.0949
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	$ 132,100
Regulatory Capital:
Common equity Tier 1 capital	4,093,974		$ 4,039,191
Tier 1 capital	4,112,458		4,059,417
Total capital	$ 4,831,026		$ 4,524,051
Common equity Tier 1 capital ratio
Actual, Ratio	0.1145		0.1097
Well-Capitalized Capital Requirement, Ratio	6.50%
Minimum Capital Requirement, Ratio	4.50%
Tier 1 risk-based capital ratio
Actual, Ratio	0.1150		0.1103
Well-Capitalized Capital Requirement, Ratio	0.0800
Minimum Capital Requirement, Ratio	0.0600
Total risk-based capital ratio
Actual, Ratio	0.1351		0.1229
Well-Capitalized Capital Requirement, Ratio	0.1000
Minimum Capital Requirement, Ratio	0.0800
Tier 1 leverage ratio
Actual, Ratio	0.0897		0.0910
Well-Capitalized Capital Requirement, Ratio	0.0500
Minimum Capital Requirement, Ratio	0.0400
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%