Allowance for Credit Losses - Schedule of Allowance for Credit Losses on Unfunded Commitments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	$ 178	$ 225	$ 225
Provision (benefit) for credit losses - unfunded commitments	645	(37)	58
Allowance for credit losses, ending balance	922	178	225
Adoption of ASC 326
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance			(38)
Balance after adoption of ASC 326
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance			187
Financing assets (excluding leases)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	12	13	1
Provision (benefit) for credit losses - unfunded commitments	94	(1)	3
Allowance for credit losses, ending balance	106	12	13
Financing assets (excluding leases) | CIT Group Inc.
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	59
Allowance for credit losses, ending balance		59
Financing assets (excluding leases) | Adoption of ASC 326
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	0	0	9
Allowance for credit losses, ending balance		0	0
Financing assets (excluding leases) | Balance after adoption of ASC 326
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	$ 12	13	10
Allowance for credit losses, ending balance		$ 12	$ 13