LONG-TERM DEBT, DERIVATIVES AND LETTERS OF CREDIT - Additional Information (Details) € in Millions	1 Months Ended	6 Months Ended
	Feb. 29, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2016 EUR (€)	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Line of Credit Facility [Line Items]
Borrowing capacity	$ 600,000,000
Commitment fee percentage		0.40%
Maximum ratio of consolidated funded debt to consolidated EBITDA	4.00
Decrease in ratio of consolidated funded debt to consolidated EBITDA	0.25
Maximum ratio of senior secured debt to consolidated EBITDA	3.00
Minimum interest coverage ratio	3.00
Cash on hand		$ 65,440,000		$ 44,825,000	$ 31,877,000	$ 44,426,000
Available borrowing capacity		29,000,000
Unamortized debt issuance costs		2,600,000
Net Investment Hedge
Line of Credit Facility [Line Items]
Borrowing under credit facility		$ 13,700,000	€ 12.3
LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate		2.25%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Borrowing capacity	$ 400,000,000
Debt term	5 years
Term Loan Facility
Line of Credit Facility [Line Items]
Borrowing capacity	$ 200,000,000
Debt term	5 years
Swing Line Facility
Line of Credit Facility [Line Items]
Borrowing capacity	$ 35,000,000.0
Standby Letters of Credit
Line of Credit Facility [Line Items]
Outstanding letter of credit		$ 22,500,000		$ 13,200,000