DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - AOCI (Details) $ in Thousands				3 Months Ended	12 Months Ended
	Dec. 28, 2018 swap	Nov. 29, 2017 swap	Aug. 03, 2017 swap	Mar. 18, 2019 USD ($) swap	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES
Balance, at beginning of period				$ 617,275	$ 626,705	$ 966,589	$ 1,297,347
Balance, at end of period					617,275	626,705	966,589
Number of swaps terminated | swap	1	4	3
Changes related to interest rate swaps designated as cash flow hedges
DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES
Balance, at beginning of period				$ 1,806	1,631	(509)	(2,519)
Other comprehensive income (loss) before reclassifications					1,973	361	(2,227)
Amounts reclassified from accumulated other comprehensive income (loss)					(1,798)	1,779	4,237
Net current period other comprehensive income					175	2,140	2,010
Balance, at end of period					$ 1,806	$ 1,631	$ (509)
Subsequent event
DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES
Number of swaps terminated | swap				2