DEBT - 2017 Credit Facility (Details)		3 Months Ended
	Apr. 04, 2017 USD ($)	Mar. 31, 2018 USD ($) d	Mar. 31, 2017 USD ($)	Jul. 21, 2014
Line of Credit Facility [Line Items]
Interest expense, net		$ 4,828,000	$ 2,609,000
Term Loan Facility 2017 [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity, revolving credit facility	$ 135,000,000
Proceeds from lines of credit	135,000,000
Line of credit outstanding		129,900,000
Revolving Loan Facility 2017 [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity, revolving credit facility	50,000,000
Proceeds from lines of credit	$ 10,000,000
Line of credit outstanding		4,000,000
Available borrowing capacity		$ 46,000,000
Credit Facility 2017 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Debt instrument, term	5 years
Debt instrument term, alternative to anniversary of closing date, period prior to maturity of another debt instrument	91 days
Interest rate per annum		6.20%
Minimum interest coverage ratio of consolidated EBITDA to consolidated interest expense	300.00%
Debt issuance costs	$ 4,700,000
Interest expense, net		$ 2,100,000
Amortization of debt issuance costs		200,000
Federal Funds Effective Swap Rate [Member] | Credit Agreement 2017, Base Rate Loans [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Eurodollar [Member] | Credit Agreement 2017, Eurodollar Loans [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	3.75%
Eurodollar [Member] | Credit Agreement 2017, Base Rate Loans [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.00%
Basis spread on variable rate, additional margin	2.75%
Convertible Debt [Member] | Convertible Senior 2019 Notes [Member]
Line of Credit Facility [Line Items]
Long-term Debt		$ 140,700,000
Debt Instrument, Convertible, Threshold Consecutive Trading Days | d		30
Interest rate per annum				2.50%
Amortization of debt issuance costs		$ 200,000	$ 200,000
Line of Credit, Payment Period One [Member] | Credit Facility 2017 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, quarterly payment percent	1.25%
Line of Credit, Payment Period Two [Member] | Credit Facility 2017 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, quarterly payment percent	1.875%
Line of Credit, Payment Period Three [Member] | Credit Facility 2017 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, quarterly payment percent	2.50%
Line of Credit Facility, Covenant Period One [Member] | Credit Facility 2017 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Required maximum leverage ratio of consolidated total indebtedness to consolidated EBITDA	550.00%
Line of Credit Facility, Covenant Period Two [Member] | Credit Facility 2017 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Required maximum leverage ratio of consolidated total indebtedness to consolidated EBITDA	500.00%
Line of Credit Facility, Covenant Period Three [Member] | Credit Facility 2017 [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Required maximum leverage ratio of consolidated total indebtedness to consolidated EBITDA	450.00%