COMMITMENTS AND CONTINGENCIES - COMMITMENTS (Details) $ in Millions	Dec. 31, 2019 CAD ($)
Annual debt maturities
Total	$ 63,585
Less than 1 year	4,394
2 years	6,856
3 years	4,054
4 years	2,585
5 years	7,712
Thereafter	37,984
Interest obligations
Total	29,498
Less than 1 year	2,416
2 years	2,296
3 years	2,216
4 years	2,076
5 years	1,915
Thereafter	18,579
Purchase of services, pipe and other materials, including transportation
Total	9,448
Less than 1 year	2,891
2 years	1,507
3 years	1,217
4 years	564
5 years	570
Thereafter	2,699
Maintenance agreements
Total	435
Less than 1 year	56
2 years	55
3 years	53
4 years	25
5 years	20
Thereafter	226
Land lease commitments
Total	1,190
Less than 1 year	30
2 years	35
3 years	35
4 years	35
5 years	36
Thereafter	1,019
Total
Total	104,156
Less than 1 year	9,787
2 years	10,749
3 years	7,575
4 years	5,285
5 years	10,253
Thereafter	$ 60,507