RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Other Financial Instruments (Details) - CAD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Fair Value of Other Financial Instruments
Unrealized gain or losses on the change in fair value of foreign exchange foreign contracts	$ 0	$ 0
Realized gain (loss) recognized in OCI associated with settlement of foreign exchange forward contracts	0	0
FMVA investments	209,000		$ 102,000
Restricted long-term investments	646,000		593,000
Long-term debt, carrying value	79,500,000		79,300,000
Long-term debt	74,900,000		73,500,000
Debt Securities
Fair Value of Other Financial Instruments
Debt securities, available-for-sale, amortized cost	303,000		295,000
Equity Funds And Debt Securities
Fair Value of Other Financial Instruments
Unrealized gain (loss) on lnvestments	15,000	(8,000)
Net investment hedges
Fair Value of Other Financial Instruments
Unrealized foreign exchange gain (loss) on translation of United States dollar denominated debt	59,000	133,000
Realized loss associated with the settlement of foreign exchange forward contracts	44,000	0
Level 1
Fair Value of Other Financial Instruments
Restricted long-term investments	249,000		236,000
Level 1 | Debt Securities
Fair Value of Other Financial Instruments
Fair value of investments	351,000		335,000
Level 2
Fair Value of Other Financial Instruments
Restricted long-term investments	397,000		357,000
Restricted long-term investments, cost basis	451,000		437,000
Level 2 | Debt Securities
Fair Value of Other Financial Instruments
Fair value of investments	309,000		298,000
Fair Value
Fair Value of Other Financial Instruments
Restricted long-term investments	646,000		593,000
Unrealized holding gains (losses)	34,000	$ (60,000)
Fair value note receivable	691,000		752,000
Carrying value
Fair Value of Other Financial Instruments
Non-current notes receivable	$ 691,000		$ 752,000