FAIR VALUE MEASUREMENTS - Other instruments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Other Financial Instruments
Liabilities representing checks issued but not yet presented for payment	$ 23.1	$ 42.0
Accrued payroll related general and administrative expenses	21.5	44.2
Accrued operating expenses	60.4	67.5
Allowance for Trade Receivables [Member]
Other Financial Instruments
Aggregate allowance for doubtful accounts	$ 1.8	$ 1.5