INCOME TAXES: - TCJA (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2009
Income Taxes
Percentage of ownership by parent	88.90%
U.S. statutory rate (as a percent)	21.00%	21.00%	21.00%	35.00%
Maximum percentage of expenses excluding cost of goods sold	3.00%
Minimum
Income Taxes
BEAT tax rate (as a percent)			5.00%
Minimum | Years 2019 through 2025
Income Taxes
BEAT tax rate (as a percent)	10.00%
Minimum | Years thereafter
Income Taxes
BEAT tax rate (as a percent)	12.50%
AMC | Minimum
Income Taxes
Percentage of ownership by parent					80.00%