MARKETABLE SECURITIES - Contractual Maturity (Details) $ in Millions	Dec. 31, 2016 USD ($)
Amortized Cost
Less than one year	$ 60.5
One to five years	45.4
Six to ten years	59.7
Greater than ten years	130.6
Total Debt Securities	296.2
Fair Value
Less than one year	60.3
One to five years	45.8
Six to ten years	58.3
Greater than ten years	130.8
Total Debt Securities	$ 295.2