LONG-TERM INVESTMENTS - Summary of Combined Financial Information (Details) - CAD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income statement information
Revenues	$ 12,470	$ 11,466	$ 10,948	$ 12,187	$ 10,008	$ 9,110	$ 7,956	$ 12,013	$ 47,071	$ 39,087	$ 50,069
Earnings									6,314	3,416	5,827
Earnings/(loss) attributable to controlling interests	1,933	$ 780	$ 1,484	$ 1,992	1,871	$ 1,084	$ 1,741	$ (1,333)	6,189	3,363	5,705
Balance sheet information
Current assets	8,959				7,350				8,959	7,350
Current liabilities	18,229				13,979				18,229	13,979
Noncontrolling interests	2,542				2,996				2,542	2,996
Unconsolidated equity method investments
Income statement information
Revenues									19,891	13,987	15,687
Operating expenses									16,514	12,223	13,153
Earnings									2,952	2,306	3,016
Earnings/(loss) attributable to controlling interests									1,711	1,136	$ 1,503
Balance sheet information
Current assets	3,581				3,136				3,581	3,136
Non-current assets	44,497				45,955				44,497	45,955
Current liabilities	3,678				3,539				3,678	3,539
Non-current liabilities	16,950				19,639				16,950	19,639
Noncontrolling interests	$ 3,786				$ 3,810				$ 3,786	$ 3,810