Variable Interest Entities (Narrative) (Details) - Entity	Mar. 31, 2020	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Consolidated VIEs	0	0

Number of consolidated variable interest entities.

No definition available.

Name:	cit_NumberOfConsolidatedVariableInterestEntities
Namespace Prefix:	cit_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant