COMMITMENTS AND CONTINGENCIES Narrative (Details) € in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020 EUR (€)	Mar. 31, 2020 USD ($) facility	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Line of Credit Facility [Line Items]
Number of credit facilities | facility		1
Amount of letters of credit issued		$ 138.4		$ 204.5
Total equity securities, restricted cash, and cash and cash equivalents fair value pledged as security against the letters of credit		138.8		213.4
Collateral held in trust		597.2		528.7
Short term lease cost		$ 0.1	$ 0.1
Term of contract		5 years
Operating lease, ROU asset		$ 0.2		0.2
Operating lease expense		0.0	$ 0.0
Operating lease, liability		$ 0.2		$ 0.2
GRIL
Line of Credit Facility [Line Items]
Short term lease cost | €	€ 0.1