SHARE CAPITAL - PREFERRED SHARES (Details) $ / shares in Units, shares in Millions, $ in Millions												12 Months Ended
	Dec. 01, 2019 $ / shares	Nov. 30, 2019 $ / 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	Mar. 01, 2019 $ / shares	Feb. 28, 2019 $ / shares	Feb. 28, 2019 $ / shares	Dec. 31, 2019 CAD ($) $ / shares shares	Dec. 31, 2019 CAD ($) $ / shares $ / shares shares	Dec. 31, 2018 CAD ($) shares	Dec. 31, 2017 CAD ($) shares	Dec. 31, 2019 $ / shares
Preference shares
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
Quarterly floating rate cumulative dividends per share calculation, period of calendar year												365 days
Quarterly floating rate cumulative dividends per share calculation, maturity period of Government of Canada treasury bill												90 days
Preference Shares, Series A | Preference shares
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
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)	$ 0.25305	$ 0.25243	$ 0.25243	$ 0.25647	$ 0.25647	$ 0.25395		$ 0.25395		$ 0.25459
Preference Shares, Series C | Preference shares
Share Capital
Preferred stock, shares outstanding (in shares) | shares												2	2	2	2
Preferred stock, value, outstanding | $												$ 43	$ 43	$ 43	$ 43
Initial Yield (as a percent)												2.40%
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
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
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
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
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
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
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)								0.27369		0.25000
Preference Shares, Series P | Preference shares
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)					$ 0.25456	$ 0.25000
Preference Shares, Series R | Preference shares
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
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)			$ 0.23356	$ 0.25000
Preference Shares, Series 3 | Preference shares
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
Share Capital
Yearly dividend per share (in dollars per share)									$ 0.33625		$ 0.27500
Preference Shares, Series 5 | Preference shares
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
Share Capital
Yearly dividend per share (in dollars per share)								$ 0.27806		$ 0.27500
Preference Shares, Series 7 | Preference shares
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
Share Capital
Yearly dividend per share (in dollars per share)	$ 0.25606	$ 0.27500
Preference Shares, Series 9 | Preference shares
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
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)												4.40%
Yearly dividend per share (in dollars per share)												$ 1.10000
Per Share Base Redemption Value (in dollars per shares)												$ 25	$ 25
Preference Shares, Series 13 | Preference shares
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)												4.40%
Yearly dividend per share (in dollars per share)												$ 1.10000
Per Share Base Redemption Value (in dollars per shares)												$ 25	$ 25
Preference Shares, Series 15 | Preference shares
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)												4.40%
Yearly dividend per share (in dollars per share)												$ 1.10000
Per Share Base Redemption Value (in dollars per shares)												$ 25	$ 25
Preference Shares, Series 17 | Preference shares
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
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
Share Capital
Reset term of fixed dividend rate												5 years
Preference Shares, Series E | Preference shares
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
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
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
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
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
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
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
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
Share Capital
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
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
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
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
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
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
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
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
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
Share Capital
Quarterly floating rate cumulative dividends per share calculation, spread on Government of US treasury bill rate (as a percent)												2.80%