Borrowings (Schedule of Long-Term Borrowings) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term borrowings	$ 8,094.3	$ 6,473.4
CIT Group Inc.
Debt Instrument [Line Items]
Long-term borrowings	3,922.9
Subsidiaries
Debt Instrument [Line Items]
Long-term borrowings	4,171.4
Senior unsecured
Debt Instrument [Line Items]
Long-term borrowings	3,975.5	3,967.9
Senior unsecured | CIT Group Inc.
Debt Instrument [Line Items]
Long-term borrowings	3,428.4
Senior unsecured | Subsidiaries
Debt Instrument [Line Items]
Long-term borrowings	547.1
Subordinated debt
Debt Instrument [Line Items]
Long-term borrowings	494.5	494.4
Subordinated debt | CIT Group Inc.
Debt Instrument [Line Items]
Long-term borrowings	494.5
FHLB advances
Debt Instrument [Line Items]
Long-term borrowings	3,050.0	1,650.0
FHLB advances | Subsidiaries
Debt Instrument [Line Items]
Long-term borrowings	3,050.0
Other secured and structured financings
Debt Instrument [Line Items]
Long-term borrowings	561.3	$ 361.1
Other secured and structured financings | Subsidiaries
Debt Instrument [Line Items]
Long-term borrowings	561.3
Securities sold under agreement to repurchase
Debt Instrument [Line Items]
Long-term borrowings	13.0
Securities sold under agreement to repurchase | Subsidiaries
Debt Instrument [Line Items]
Long-term borrowings	$ 13.0