COMMITMENTS, CONTINGENCIES AND REGULATORY MATTERS - Leases (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Right-to-use assets					$ 42.1
Lease obligation liabilities					$ 45.5
Sublease income	$ 0.5	$ 0.4	$ 0.8	$ 0.9
Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year		1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term	6 years		6 years