INCOME TAXES - Unrecognized tax benefits (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] | |||
| Beginning balance | $ 38.4 | $ 22.0 | $ 20.9 |
| Additions for the current year tax positions | 10.2 | 11.6 | 3.9 |
| Additions for prior year tax positions | 5.5 | 9.6 | 2.7 |
| Reductions for prior year tax positions | (1.0) | (4.8) | (1.9) |
| Reductions for settlements with tax authorities | (3.4) | ||
| Reductions for expirations of statute of limitations | (0.5) | (0.2) | |
| Ending balance | 52.6 | 38.4 | 22.0 |
| Unrecognized Tax Benefits that Would Impact Effective Tax Rate | 40.4 | ||
| Uncertain Tax Benefits, Indemnification Receivable | 15.0 | ||
| Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued | $ 7.1 | $ 6.2 | $ 6.1 |