DEBT - DESCRIPTION (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Sep. 14, 2016	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
Debt
Total Long-term Debt		$ 786,100	$ 786,100	$ 407,900
Revolving Credit Facility
Debt
Funds available under the revolving credit facility		$ 193,800	193,800
Interest rate during period (as a percent)		1.69%
The Senior Unsecured Notes (The "Series D Notes")
Debt
Debt issued	$ 200,000	$ 200,000	$ 200,000
Interest rate (as a percent)	3.14%	3.14%	3.14%
Debt instrument term	15 years		15 years
Weighted average life	8 years 6 months		8 years 6 months
Frequency of periodic payment			semi-annual
Maximum ratio of debt to consolidated EBITDA	3.25	3.25	3.25
Maximum ratio of consolidated EBITDA to interest expense	3.50	3.50	3.50
Maximum ratio of aggregate principal amount of Priority Debt to Consolidated Tangible Assets	20.00%	20.00%	20.00%
Maximum ratio of aggregate principal amount of Priority Debt to Consolidated Tangible Assets upon certain events	17.50%	17.50%	17.50%
Maximum ratio of aggregate principal amount of priority debt not Title XI Priority Debt to Consolidated Tangible Assets	10.00%	10.00%	10.00%
Maturities of Long-term Debt
Semi-annual principal payments in 2019		$ 6,000	$ 6,000
Semi-annual principal payments in 2020 to 2023		9,200	9,200
Semi-annual principal payments in 2024 to 2031		7,150	7,150
The Senior Unsecured Notes (The "Series B And C Notes")
Debt
Total Long-term Debt		$ 184,300	$ 184,300