FINANCIAL INSTRUMENTS - Assets and Liabilities Not Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financial assets
Credit card and loan receivables, net	$ 19,126.0	$ 17,472.7
Credit card and loan receivables held for sale	436.2	1,995.5
Total assets measured at fair value	19,562.2	19,468.2
Financial liabilities
Deposits	12,303.6	11,768.7
Non-recourse borrowings of consolidated securitization entities	7,333.6	7,626.9
Long-term and other debt	2,878.8	5,755.3
Total liabilities measured at fair value	22,516.0	25,150.9
Level 2
Financial liabilities
Deposits	12,303.6	11,768.7
Non-recourse borrowings of consolidated securitization entities	7,333.6	7,626.9
Long-term and other debt	2,878.8	5,755.3
Total liabilities measured at fair value	22,516.0	25,150.9
Level 3
Financial assets
Credit card and loan receivables, net	19,126.0	17,472.7
Credit card and loan receivables held for sale	436.2	1,995.5
Total assets measured at fair value	$ 19,562.2	$ 19,468.2