Leases (Schedule of Lease Income Related to Company's Operating and Finance Leases) (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Leased equipment property tax reimbursements due from customers	$ 4.6	$ 6.1
Revenue related to insurance coverage Commercial Finance leased equipment	$ 6.3	$ 5.4

Lessor, leased equipment property tax reimbursements due from customers.

No definition available.

Name:	cit_LessorLeasedEquipmentPropertyTaxReimbursementsDueFromCustomers
Namespace Prefix:	cit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration