PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended			24 Months Ended
	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Feb. 19, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension plans with accumulated benefit obligations greater than plan assets, projected benefit obligations		$ 5,900,000,000	$ 5,700,000,000		$ 5,900,000,000
Pension plans with accumulated benefit obligations greater than plan assets, accumulated benefit obligations		5,900,000,000	5,600,000,000		5,900,000,000
Pension plans with accumulated benefit obligations greater than plan assets, fair value of assets		4,600,000,000		$ 4,500,000,000	4,600,000,000
Accumulated benefit obligation for all defined benefit pension plans		6,700,000,000	6,400,000,000		6,700,000,000
Employer contributions to defined contribution plans		21,000,000	27,000,000	$ 21,000,000
Qualified Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions and benefit payments		$ 0
Defined benefit plan, required contribution		0
Non Qualified Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in control enhanced benefits		$ 1,000,000
Employer contributions and benefit payments		31,000,000
Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 12,000,000	$ 10,000,000		12,000,000
Expected return on plan assets		3.50%	3.50%	3.50%
Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 5,502,000,000	$ 5,341,000,000		$ 5,502,000,000
Expected return on plan assets		8.00%
Retirement Compensation Arrangement | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of assets invested into noninterest-bearing refundable tax account		50.00%			50.00%
U.S. | Non Qualified Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to benefit plans during 2018		$ 19,000,000			$ 19,000,000
U.S. | Pre Medicare [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year		8.90%			8.90%
U.S. | Health Reimbursement Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted health care cost trend rate assumed for next year		4.50%			4.50%
Canada
Defined Benefit Plan Disclosure [Line Items]
Discount rates, net periodic benefit cost		3.70%	4.00%
Weighted health care cost trend rate assumed for next year		4.90%			4.90%
Canada | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions and benefit payments		$ 2,000,000
Expected contribution to benefit plans during 2018		4,000,000			$ 4,000,000
Canada | Registered Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions and benefit payments		25,000,000
Expected contribution to benefit plans during 2018		$ 23,000,000			23,000,000
Investments we are allowed to invest and manage | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets		7.00%
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 557,000,000	$ 455,000,000	$ 546,000,000	$ 557,000,000
Fair value of plan assets, percent		10.10%			10.10%
Fair Value, Inputs, Level 3 | Non Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 0	0		$ 0
Pension
Defined Benefit Plan Disclosure [Line Items]
Change in control enhanced benefits		0	5,000,000
Fair value of plan assets		5,514,000,000	5,351,000,000	$ 5,491,000,000	$ 5,514,000,000
Employer contributions and benefit payments		$ 57,000,000	$ 78,000,000
Pension | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets		8.00%	9.00%	9.00%
Pension | U.S.
Defined Benefit Plan Disclosure [Line Items]
Discount rates, benefit obligation		3.70%	4.30%		3.70%
Discount rates, net periodic benefit cost		4.30%	4.50%	4.10%
Pension | U.S. | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual rate of return on assets over 33 years		13.70%
Annual rate of return on assets over the past 5 years		8.00%
Pension | Canada
Defined Benefit Plan Disclosure [Line Items]
Discount rates, benefit obligation		3.50%	3.70%		3.50%
Discount rates, net periodic benefit cost				3.90%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Change in control enhanced benefits		$ 0	$ 0
Fair value of plan assets		0	0	$ 0	$ 0
Employer contributions and benefit payments		20,000,000	$ 21,000,000
Expected contribution to benefit plans during 2018		$ 19,000,000			$ 19,000,000
Other Postretirement Benefits | U.S.
Defined Benefit Plan Disclosure [Line Items]
Discount rates, benefit obligation		3.50%	3.70%		3.50%
Discount rates, net periodic benefit cost		3.70%	4.00%	3.60%
Other Postretirement Benefits | Canada
Defined Benefit Plan Disclosure [Line Items]
Discount rates, benefit obligation		3.40%	3.60%		3.40%
Discount rates, net periodic benefit cost		3.60%	3.90%	3.80%
Other Postretirement Benefits | Collective Bargaining Arrangement
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to benefit plans during 2018		$ 7,000,000			$ 7,000,000
Plum Creek | Non Qualified Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets assumed						$ 47,000,000
Supplemental pension benefit payments					$ 42,000,000
Change in control enhanced benefits	$ 5,000,000
Plum Creek | Pension
Defined Benefit Plan Disclosure [Line Items]
Change in control enhanced benefits		0	$ 5,000,000	$ 0
Plum Creek | Pension | Qualified and Registered Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets			7.00%
Plum Creek | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Change in control enhanced benefits		$ 0	$ 0	$ 0