EQUITY METHOD INVESTMENTS - Narrative (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended								12 Months Ended			36 Months Ended	48 Months Ended
	Mar. 11, 2019	Mar. 31, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2022	Dec. 31, 2023	Jul. 01, 2023	Mar. 31, 2020	Feb. 28, 2019
Schedule of Equity Method Investments [Line Items]
Revenue			$ 470,351	$ 499,076	$ 533,997	$ 564,764	$ 547,861	$ 580,185	$ 617,944	$ 607,533	$ 2,068,188	$ 2,353,523	$ 2,480,962
Accounts receivable			8,900								8,900
Manufacturing / Wholesale
Schedule of Equity Method Investments [Line Items]
Revenue											13,200
China Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Schedule of Equity Method Investments [Line Items]
Deconsolidation, gain (loss)						5,800
Nutra Manufacturing Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Schedule of Equity Method Investments [Line Items]
Deconsolidation, gain (loss)						(27,100)
JV Framework Agreement
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage																		35.00%
Payment for investment in newly formed joint venture						$ 2,400
Finished goods purchased											156,000
Accounts payable			$ 11,700								$ 11,700
Manufacturing JV capital contribution
Schedule of Equity Method Investments [Line Items]
Payments to acquire interest in joint venture		$ 10,700
IVC Joint Venture
Schedule of Equity Method Investments [Line Items]
Proceeds for investment in newly formed joint venture	$ 101,000	$ 99,200			101,000
IVC Joint Venture | Forecast | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage														100.00%		100.00%
Proceeds for investment in newly formed joint venture														$ 75,000	$ 75,000	$ 75,000
GNC Hong Kong Limited | JV Framework Agreement
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		35.00%				35.00%												35.00%
IVC Joint Venture | International Vitamin Corporation
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		43.00%				43.00%
Purchase price adjustment					$ 1,800
Minimum | IVC Joint Venture | Forecast | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Equity investment on purchase price																	$ 16,000
Maximum | IVC Joint Venture | Forecast | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Equity investment on purchase price																	$ 17,000