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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES - Recently issued accounting updates (Details) - USD ($) $ in Thousands		3 Months Ended
	Oct. 01, 2018	Dec. 31, 2018	Dec. 31, 2017
New accounting pronouncements
Change in prepaid expenses and other		$ (209)	$ (2,672)
Change in accrued liabilities		(2,919)	16,824
Cash provided by operating activities		209,482	79,605
Payment of contingent consideration from acquisition of business			(1,500)
Cash used in financing activities		$ (86,347)	(82,582)
As Reported
New accounting pronouncements
Change in prepaid expenses and other			(8,562)
Change in accrued liabilities			15,324
Cash provided by operating activities			72,215
Cash used in financing activities			(81,082)
ASU 2016-18 \| Adjustments
New accounting pronouncements
Change in prepaid expenses and other			5,890
Cash provided by operating activities			5,890
ASU 2016-15 \| Adjustments
New accounting pronouncements
Change in accrued liabilities			1,500
Cash provided by operating activities			1,500
Payment of contingent consideration from acquisition of business			(1,500)
Cash used in financing activities			$ (1,500)
ASU 2016-01 \| Adjustments
New accounting pronouncements
Reclassification adjustment before tax	$ 44,000
Reclassification adjustment after-tax	29,100
ASU 2016-01 \| Adjustments \| Accumulated Other Comprehensive Income
New accounting pronouncements
Reclassification adjustment after-tax	$ (29,071)