COMMITMENTS, CONTINGENCIES AND REGULATORY MATTERS - Leases (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Right-to-use assets			$ 42.1
Lease obligation liabilities			$ 45.5
Sublease income	$ 0.4	$ 0.5
Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term	6 years