Fair Value (Carrying and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and interest bearing deposits	[1]	$ 4,739.0	$ 5,608.5
Credit balances of factoring clients		(1,405.3)	(1,292.0)	$ (1,215.2)
Available-for-sale debt securities		4,765.0
Debt securities carried at fair value with changes recorded in net income		255.6	283.5
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and interest bearing deposits		5,337.9	6,430.6
Assets held for sale (excluding leases)		170.8	428.4
Loans (excluding leases)		26,211.1	26,683.0
Investment securities		5,530.0	4,491.1
Indemnification assets		179.5	233.4
Other assets subject to fair value disclosure and unsecured counterparty receivables		597.2	712.2
Deposits		(30,942.9)	(32,323.2)
Borrowings		(8,700.5)	(15,097.8)
Credit balances of factoring clients		(1,405.3)	(1,292.0)
Other liabilities subject to fair value disclosure		(682.5)	(1,003.6)
Carrying Value [Member] | Non-Qualifying Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets at fair value		79.4	94.7
Derivative liabilities at fair value		(72.2)	(68.8)
Carrying Value [Member] | Qualifying Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets at fair value			16.9
Derivative liabilities at fair value		(42.8)
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and interest bearing deposits		5,337.9	6,430.6
Assets held for sale (excluding leases)		171.2	439.6
Loans (excluding leases)		26,649.2	26,846.7
Investment securities		5,535.0	4,494.2
Indemnification assets		136.0	201.0
Other assets subject to fair value disclosure and unsecured counterparty receivables		597.2	712.2
Deposits		(31,072.7)	(32,490.9)
Borrowings		(9,037.3)	(15,562.7)
Credit balances of factoring clients		(1,405.3)	(1,292.0)
Other liabilities subject to fair value disclosure		(682.5)	(1,003.6)
Agency claimed indemnification assets		28.9	108.0
Estimated Fair Value [Member] | Non-Qualifying Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets at fair value		79.4	94.7
Derivative liabilities at fair value		(72.2)	(68.8)
Estimated Fair Value [Member] | Qualifying Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets at fair value			16.9
Derivative liabilities at fair value		(42.8)
Level 1 [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and interest bearing deposits		5,337.9	6,430.6
Investment securities		349.5	200.4
Level 2 [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets held for sale (excluding leases)		7.4	175.0
Loans (excluding leases)		392.2	390.3
Investment securities		4,145.9	3,199.6
Borrowings		(7,982.0)	(14,457.8)
Level 2 [Member] | Estimated Fair Value [Member] | Non-Qualifying Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets at fair value		79.3	94.7
Derivative liabilities at fair value		(59.5)	(57.3)
Level 2 [Member] | Estimated Fair Value [Member] | Qualifying Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets at fair value			16.9
Derivative liabilities at fair value		(42.8)
Level 3 [Member] | Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets held for sale (excluding leases)		163.8	264.6
Loans (excluding leases)		26,257.0	26,456.4
Investment securities		1,039.6	1,094.2
Indemnification assets		136.0	201.0
Other assets subject to fair value disclosure and unsecured counterparty receivables		597.2	712.2
Deposits		(31,072.7)	(32,490.9)
Borrowings		(1,055.3)	(1,104.9)
Credit balances of factoring clients		(1,405.3)	(1,292.0)
Other liabilities subject to fair value disclosure		(682.5)	(1,003.6)
Available-for-sale debt securities		456.8	485.5
Debt securities carried at fair value with changes recorded in net income		255.6	283.5
Non-marketable securities		256.0	256.4
Held-to-maturity securities		71.0	68.8
Level 3 [Member] | Estimated Fair Value [Member] | Non-Qualifying Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets at fair value		0.1
Derivative liabilities at fair value		$ (12.7)	$ (11.5)

[1] The following table presents information on assets and liabilities related to Variable Interest Entities (VIEs) that are consolidated by the Company. The difference between VIE total assets and total liabilities represents the Company’s interests in those entities, which were eliminated in consolidation. The assets of the consolidated VIEs will be used to settle the liabilities of those entities and, except for the Company’s interest in the VIEs, are not available to the creditors of CIT or any affiliates of CIT.Assets Cash and interest bearing deposits, restricted$93.2 $99.9Total loans, net of allowance for loan losses181.4 300.5Operating lease equipment, net764.4 775.8Assets of discontinued operations— 2,321.7Total Assets$1,039.0 $3,497.9Liabilities Beneficial interests issued by consolidated VIEs (classified as long-term borrowings)$647.4 $770.0Liabilities of discontinued operations— 1,204.6Total Liabilities$647.4 $1,974.6