SHARE CAPITAL - PREFERRED SHARES (Details) $ / shares in Units, shares in Millions, $ in Millions																12 Months Ended
	Dec. 01, 2020 $ / shares	Nov. 30, 2020 $ / shares	Sep. 01, 2020 $ / shares	Aug. 31, 2020 $ / shares	Jun. 01, 2020 $ / shares	May 31, 2020 $ / shares	Mar. 01, 2020 $ / shares	Feb. 29, 2020 $ / shares	Sep. 01, 2019 $ / shares	Aug. 31, 2019 $ / shares	Jun. 01, 2019 $ / shares	May 31, 2019 $ / shares	Mar. 20, 2019 $ / shares	Mar. 01, 2019 $ / shares	Feb. 28, 2019 $ / shares	Dec. 31, 2020 CAD ($) $ / shares shares	Dec. 31, 2020 CAD ($) $ / shares $ / shares shares	Dec. 31, 2019 CAD ($) shares	Dec. 31, 2018 CAD ($) shares	Dec. 31, 2020 $ / shares	Dec. 16, 2020 $ / shares
Preference shares (Note 21)
Share Capital
Preferred stock, value, outstanding | $																$ 7,747	$ 7,747	$ 7,747	$ 7,747
Issuance costs | $																$ (155)		$ (155)	$ (155)
Recurring anniversary period following the redemption option date, at which the entity may redeem preferred shares																5 years
Stock split conversion ratio																1
Quarterly floating rate cumulative dividends per share calculation, base multiplier (in dollars per share) | (per share)																$ 25	$ 25
Preference Shares, Series A | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																5	5	5	5
Preferred stock, value, outstanding | $																$ 125	$ 125	$ 125	$ 125
Initial Yield (as a percent)																5.50%
Yearly dividend per share (in dollars per share)																$ 1.37500
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series B | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																18	18	18	18
Preferred stock, value, outstanding | $																$ 457	$ 457	$ 457	$ 457
Initial Yield (as a percent)																3.42%
Yearly dividend per share (in dollars per share)																$ 0.85360
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series C
Share Capital
Yearly dividend per share (in dollars per share)	$ 0.15349	$ 0.15975	$ 0.15975	$ 0.16779	$ 0.16779	$ 0.25458	$ 0.25458	$ 0.25305
Preference Shares, Series C | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																2	2	2	2
Preferred stock, value, outstanding | $																$ 43	$ 43	$ 43	$ 43
Yearly dividend per share (in dollars per share)																$ 0
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.40%
Preference Shares, Series D | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																18	18	18	18
Preferred stock, value, outstanding | $																$ 450	$ 450	$ 450	$ 450
Initial Yield (as a percent)																4.46%
Yearly dividend per share (in dollars per share)																$ 1.11500
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series F | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																20	20	20	20
Preferred stock, value, outstanding | $																$ 500	$ 500	$ 500	$ 500
Initial Yield (as a percent)																4.69%
Yearly dividend per share (in dollars per share)																$ 1.17224
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series H | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																14	14	14	14
Preferred stock, value, outstanding | $																$ 350	$ 350	$ 350	$ 350
Initial Yield (as a percent)																4.38%
Yearly dividend per share (in dollars per share)																$ 1.09400
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series J | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																8	8	8	8
Preferred stock, value, outstanding | $																$ 199	$ 199	$ 199	$ 199
Initial Yield (as a percent)																4.89%
Yearly dividend per share (in dollars per share)																	$ 1.22160
Per Share Base Redemption Value (in dollars per shares)																				$ 25
Preference Shares, Series L | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																16	16	16	16
Preferred stock, value, outstanding | $																$ 411	$ 411	$ 411	$ 411
Initial Yield (as a percent)																4.96%
Yearly dividend per share (in dollars per share)																	$ 1.23972
Per Share Base Redemption Value (in dollars per shares)																				25
Preference Shares, Series N | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																18	18	18	18
Preferred stock, value, outstanding | $																$ 450	$ 450	$ 450	$ 450
Initial Yield (as a percent)																5.09%
Yearly dividend per share (in dollars per share)																$ 1.27152
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series P
Share Capital
Yearly dividend per share (in dollars per share)														$ 0.24613	$ 0.27500
Preference Shares, Series P | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																16	16	16	16
Preferred stock, value, outstanding | $																$ 400	$ 400	$ 400	$ 400
Initial Yield (as a percent)																4.38%
Yearly dividend per share (in dollars per share)																$ 1.09476
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series R
Share Capital
Yearly dividend per share (in dollars per share)											$ 0.19019	$ 0.27500
Preference Shares, Series R | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																16	16	16	16
Preferred stock, value, outstanding | $																$ 400	$ 400	$ 400	$ 400
Initial Yield (as a percent)																4.07%
Yearly dividend per share (in dollars per share)																$ 1.01825
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series 1 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																16	16	16	16
Preferred stock, value, outstanding | $																$ 411	$ 411	$ 411	$ 411
Initial Yield (as a percent)																5.95%
Yearly dividend per share (in dollars per share)																	$ 1.48728
Per Share Base Redemption Value (in dollars per shares)																				25
Preference Shares, Series 3
Share Capital
Yearly dividend per share (in dollars per share)									$ 0.18644	$ 0.27500
Preference Shares, Series 3 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																24	24	24	24
Preferred stock, value, outstanding | $																$ 600	$ 600	$ 600	$ 600
Initial Yield (as a percent)																3.74%
Yearly dividend per share (in dollars per share)																$ 0.93425
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series 5 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																8	8	8	8
Preferred stock, value, outstanding | $																$ 206	$ 206	$ 206	$ 206
Initial Yield (as a percent)																5.38%
Yearly dividend per share (in dollars per share)																	$ 1.34383
Per Share Base Redemption Value (in dollars per shares)																				$ 25
Preference Shares, Series 7 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																10	10	10	10
Preferred stock, value, outstanding | $																$ 250	$ 250	$ 250	$ 250
Initial Yield (as a percent)													5.50%			4.45%
Yearly dividend per share (in dollars per share)																$ 1.11224
Per Share Base Redemption Value (in dollars per shares)													$ 25.00			$ 25	$ 25
Preference Shares, Series 9 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																11	11	11	11
Preferred stock, value, outstanding | $																$ 275	$ 275	$ 275	$ 275
Initial Yield (as a percent)																4.10%
Yearly dividend per share (in dollars per share)																$ 1.02424
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series 11 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																20	20	20	20
Preferred stock, value, outstanding | $																$ 500	$ 500	$ 500	$ 500
Initial Yield (as a percent)																3.94%
Yearly dividend per share (in dollars per share)																$ 0.98452
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series 13 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																14	14	14	14
Preferred stock, value, outstanding | $																$ 350	$ 350	$ 350	$ 350
Initial Yield (as a percent)																3.04%
Yearly dividend per share (in dollars per share)																$ 0.76076
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series 15 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																11	11	11	11
Preferred stock, value, outstanding | $																$ 275	$ 275	$ 275	$ 275
Initial Yield (as a percent)																2.98%
Yearly dividend per share (in dollars per share)																$ 0.74576
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Preference Shares, Series 17 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																30	30	30	30
Preferred stock, value, outstanding | $																$ 750	$ 750	$ 750	$ 750
Initial Yield (as a percent)																5.15%
Yearly dividend per share (in dollars per share)																$ 1.28750
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Minimum fixed dividend rate upon reset (as a percent)																5.15%
Preference Shares, Series 19 | Preference shares (Note 21)
Share Capital
Preferred stock, shares outstanding (in shares) | shares																20	20	20	20
Preferred stock, value, outstanding | $																$ 500	$ 500	$ 500	$ 500
Initial Yield (as a percent)																4.90%
Yearly dividend per share (in dollars per share)																$ 1.22500
Per Share Base Redemption Value (in dollars per shares)																$ 25	$ 25
Minimum fixed dividend rate upon reset (as a percent)																4.90%
Preferred Stock Excluding Series | Preference shares (Note 21)
Share Capital
Reset term of fixed dividend rate																5 years
Preference Shares, Series E | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.40%
Series G Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.50%
Series I Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.10%
Series O Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.70%
Series Q Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.50%
Series S Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.50%
Series 4 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.40%
Series 8 Preferred Stock | Preference shares (Note 21)
Share Capital
Initial Yield (as a percent)													5.60%
Per Share Base Redemption Value (in dollars per shares)													$ 25.00
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.60%
Series10 Preferred Stock | Preference shares (Note 21)
Share Capital
Per Share Base Redemption Value (in dollars per shares)																					$ 25.00
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.70%
Series12 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.60%
Series14 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.70%
Series16 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																2.70%
Series18 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																4.10%
Series 20 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of Canada treasury bill rate (as a percent)																3.20%
Series K Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of US treasury bill rate (as a percent)																3.10%
Series M Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of US treasury bill rate (as a percent)																3.20%
Series 2 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of US treasury bill rate (as a percent)																3.10%
Series 6 Preferred Stock | Preference shares (Note 21)
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of US treasury bill rate (as a percent)																2.80%