Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Feb. 19, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	000-08185
Entity Registrant Name	TCF Financial Corporation
Entity Incorporation, State or Country Code	MI
Entity Tax Identification Number	38-2022454
Entity Address, Address Line One	333 W. Fort Street, Suite 1800
Entity Address, City or Town	Detroit
Entity Address, State or Province	MI
Entity Address, Postal Zip Code	48226
City Area Code	(866)
Local Phone Number	258-1807
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Central Index Key	0000019612
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		152,604,938
Entity Public Float			$ 4.3
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
TCF Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock (par value $1 per share)
Trading Symbol	TCF
Security Exchange Name	NASDAQ
Depositary Shares
Entity Information [Line Items]
Title of 12(b) Security	Depositary shares, each representing a 1/1000th interest in a share of the 5.70% Series C Non-Cumulative Perpetual Preferred Stock
Trading Symbol	TCFCP
Security Exchange Name	NASDAQ