Parent Company Financial Statements (Condensed Parent Company Only Balance Sheet) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Cash and deposits	[1]	$ 278.6	$ 822.1
Securities purchased under agreement to resell		150.0	0.0
Total investment securities		6,469.9	4,491.1
Goodwill		369.9	685.4
Other assets		1,595.5	2,117.0
Total Assets		49,278.7	64,170.2	$ 67,391.9
Liabilities and Equity:
Borrowings		8,974.4	14,935.5
Other liabilities		1,437.1	1,897.6
Total Liabilities		41,958.7	54,167.1
Total Liabilities and Equity		49,278.7	64,170.2
CIT Group Inc.
Assets:
Cash and deposits		311.0	1,172.8
Cash held at bank subsidiary		465.8	15.4
Securities purchased under agreement to resell		150.0	0.0
Total investment securities		0.0	400.3
Receivables from nonbank subsidiaries		2,340.3	9,172.9
Receivables from nonbank subsidiaries		449.4	34.7
Investment in nonbank subsidiaries		2,943.3	3,597.4
Investment in bank subsidiaries		5,121.5	5,187.9
Goodwill		46.9	261.4
Other assets		723.6	2,217.7
Total Assets		12,551.8	22,060.5
Liabilities and Equity:
Borrowings		3,737.5	10,599.0
Liabilities to nonbank subsidiaries		1,148.0	907.9
Liabilities to bank subsidiaries		0.0	4.6
Other liabilities		346.3	546.3
Total Liabilities		5,231.8	12,057.8
Total Stockholders' Equity		7,320.0	10,002.7
Total Liabilities and Equity		$ 12,551.8	$ 22,060.5

[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.