DEBT, Existing Credit Agreement (Details) $ in Millions, ¥ in Billions	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 JPY (¥)	Dec. 31, 2017 USD ($)	[1]	Dec. 31, 2017 JPY (¥)	[1]	Oct. 09, 2014 USD ($)	Oct. 09, 2014 JPY (¥)
Existing Credit Agreement [Member] | Maximum [Member]
Debt [Abstract]
Consolidated leverage ratio	2.25
Existing Credit Agreement [Member] | Minimum [Member]
Debt [Abstract]
Consolidated interest coverage ratio	3.00
Term Loan Facility [Member]
Debt [Abstract]
Original principal amount	$ 127.5						$ 127.5
Term of facility	5 years
Outstanding balance	$ 0.0		$ 94.8
Japanese Yen Term Loan Facility [Member]
Debt [Abstract]
Original principal amount | ¥		¥ 6.6						¥ 6.6
Term of facility	5 years
Outstanding balance	$ 0.0	¥ 0.0	43.5		¥ 4.9
Revolving Credit Facility [Member]
Debt [Abstract]
Borrowing capacity							$ 187.5
Term of facility	5 years
Outstanding balance	$ 0.0		$ 47.5

[1] The carrying value of the debt reflects the amounts stated in the above table less debt issuance costs of $4.2 million as of September 30, 2018 related to the credit agreement; and a debt discount of $9.1 million and debt issuance costs of $4.0 million (consisting of $11.1 million related to the Convertible Note and $2.0 million related to the credit agreement) as of December 31, 2017, which is not reflected in this table.