Pensions and Other Employee Benefits, Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plans [Member]
Equity securities [Abstract]
Fair value of company's plan assets		$ 2,721	$ 2,552	$ 2,570
U.S. Pension Plans' Assets [Member]
Equity securities [Abstract]
Liabilities for unsettled trades, net		(23)	(30)
Fair value of company's plan assets		$ 2,421	$ 2,269
Percentage of mutual fund in total investment in fixed income - investment grade securities		62.00%	59.00%
Percentage of pooled bond funds in total investment in fixed income - investment grade securities		38.00%	41.00%
U.S. Pension Plans' Assets [Member] | U.S. Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	$ 1,331	$ 1,200
U.S. Pension Plans' Assets [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	1,331	1,200
U.S. Pension Plans' Assets [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. Pension Plans' Assets [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. Pension Plans' Assets [Member] | International Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	85	79
U.S. Pension Plans' Assets [Member] | International Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	85	79
U.S. Pension Plans' Assets [Member] | International Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. Pension Plans' Assets [Member] | International Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	414	400
U.S. Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	255	237
U.S. Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	159	163
U.S. Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	0	0
U.S. Pension Plans' Assets [Member] | Fixed Income - High Yield [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	136	114
U.S. Pension Plans' Assets [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
U.S. Pension Plans' Assets [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	136	114
U.S. Pension Plans' Assets [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
U.S. Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	193	170
U.S. Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	193	170
U.S. Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
U.S. Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
U.S. Pension Plans' Assets [Member] | Other [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	114	166
U.S. Pension Plans' Assets [Member] | Other [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
U.S. Pension Plans' Assets [Member] | Other [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	114	166
U.S. Pension Plans' Assets [Member] | Other [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
U.S. Pension Plans' Assets [Member] | Total Assets at Fair Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets		2,273	2,129
U.S. Pension Plans' Assets [Member] | Total Assets at Fair Value [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		1,864	1,686
U.S. Pension Plans' Assets [Member] | Total Assets at Fair Value [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		409	443
U.S. Pension Plans' Assets [Member] | Total Assets at Fair Value [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		0	0
U.S. Pension Plans' Assets [Member] | Other Investments Measured at Net Asset Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6],[7]	171	170
Canadian Pension Plans' Assets [Member]
Equity securities [Abstract]
Liabilities for unsettled trades, net		0	0
Fair value of company's plan assets		300	283
Canadian Pension Plans' Assets [Member] | U.S. Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	79	73
Canadian Pension Plans' Assets [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	79	73
Canadian Pension Plans' Assets [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canadian Pension Plans' Assets [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canadian Pension Plans' Assets [Member] | International Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	104	91
Canadian Pension Plans' Assets [Member] | International Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	104	91
Canadian Pension Plans' Assets [Member] | International Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canadian Pension Plans' Assets [Member] | International Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - High Yield [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
Canadian Pension Plans' Assets [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
Canadian Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canadian Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canadian Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canadian Pension Plans' Assets [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canadian Pension Plans' Assets [Member] | Other [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	32	27
Canadian Pension Plans' Assets [Member] | Other [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	5	6
Canadian Pension Plans' Assets [Member] | Other [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	27	21
Canadian Pension Plans' Assets [Member] | Other [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
Canadian Pension Plans' Assets [Member] | Total Assets at Fair Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets		215	191
Canadian Pension Plans' Assets [Member] | Total Assets at Fair Value [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		188	170
Canadian Pension Plans' Assets [Member] | Total Assets at Fair Value [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		27	21
Canadian Pension Plans' Assets [Member] | Total Assets at Fair Value [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		0	0
Canadian Pension Plans' Assets [Member] | Other Investments Measured at Net Asset Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6],[7]	$ 85	$ 92
Percentage of mutual fund investment in equity trust funds		55.00%	52.00%
Percentage of pooled bond fund investment in equity trust funds		45.00%	48.00%
Postretirement Benefit Plans [Member]
Equity securities [Abstract]
Fair value of company's plan assets		$ 60	$ 57	$ 60
Percentage of mutual fund in total investment in fixed income - investment grade securities		73.00%	73.00%
Percentage of pooled bond funds in total investment in fixed income - investment grade securities		27.00%	27.00%
Postretirement Benefit Plans [Member] | U.S. Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	$ 37	$ 35
Postretirement Benefit Plans [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	37	35
Postretirement Benefit Plans [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	0	0
Postretirement Benefit Plans [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	0	0
Postretirement Benefit Plans [Member] | International Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	1	1
Postretirement Benefit Plans [Member] | International Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	1	1
Postretirement Benefit Plans [Member] | International Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	0	0
Postretirement Benefit Plans [Member] | International Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[8]	0	0
Postretirement Benefit Plans [Member] | Fixed Income - Investment Grade [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[9]	11	11
Postretirement Benefit Plans [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[9]	8	8
Postretirement Benefit Plans [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[9]	3	3
Postretirement Benefit Plans [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[9]	0	0
Postretirement Benefit Plans [Member] | Fixed Income - High Yield [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	2	2
Postretirement Benefit Plans [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
Postretirement Benefit Plans [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	2	2
Postretirement Benefit Plans [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0	0
Postretirement Benefit Plans [Member] | Real Estate Investment Trusts [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[10]	3	3
Postretirement Benefit Plans [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[10]	3	3
Postretirement Benefit Plans [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[10]	0	0
Postretirement Benefit Plans [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[10]	0	0
Postretirement Benefit Plans [Member] | Other [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[11]	3	2
Postretirement Benefit Plans [Member] | Other [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[11]	0	0
Postretirement Benefit Plans [Member] | Other [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[11]	3	2
Postretirement Benefit Plans [Member] | Other [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[11]	0	0
Postretirement Benefit Plans [Member] | Total Assets at Fair Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets		57	54
Postretirement Benefit Plans [Member] | Total Assets at Fair Value [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		49	47
Postretirement Benefit Plans [Member] | Total Assets at Fair Value [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		8	7
Postretirement Benefit Plans [Member] | Total Assets at Fair Value [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		0	0
Postretirement Benefit Plans [Member] | Other Investments Measured at Net Asset Value [Member]
Equity securities [Abstract]
Liabilities for unsettled trades, net	[12],[13]	$ 3	$ 3

[1] Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the New York Stock Exchange (NYSE), National Association of Securities Dealers Automated Quotations (NASDAQ), and various international exchanges.

[2] Approximately 62% and 59% at December 31, 2016 and 2015, respectively, of U.S. plan assets that are invested in the Fixed Income - Investment Grade asset category consist of a mutual fund offered by a registered investment company (the Fund) and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy, as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 38% and 41% at December 31, 2016 and 2015, respectively, of U.S. plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2.

[3] Fixed Income - High Yield consists of investments in corporate high-yield bonds from various industries. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs.

[4] Real Estate Investment Trusts (REITs) consist of securities that trade on the major exchanges and invest directly in real estate, either through properties or mortgages.

[5] Other consists primarily of: (1) money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit, and are classified as Level 2, and (2) cash, which is classified as Level 1.

[6] All of the U.S. plans other investments measured using NAV at December 31, 2016 and 2015 and approximately 55% and 52% at December 31, 2016 and 2015, respectively, of the Canadian plans other investments measured using NAV consist of a regulated commingled equity trust fund, for which fair value is based on the NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund's holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV. Approximately 45% and 48% at December 31, 2016 and 2015, respectively, of the Canadian plans other investments measured using NAV are invested in regulated commingled bond funds (the "Bond Funds"). As these Bond Funds do not trade in an active market, the fair value is based on NAVs calculated by fund managers based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs as a practical expedient to estimating fair value and classified as Level 2. Withdrawals are permitted monthly, with notice between 0 and 3 days of the transaction date, based on NAV.

[7] In accordance with ASU 2015-07, certain investments that are measured at fair value using the net asset value (NAV) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position.

[8] Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the NYSE, NASDAQ, and various international exchanges.

[9] Approximately 73% at December 31, 2016 and 2015 of the postretirement benefit plan assets that are invested in the Fixed Income - Investment Grade asset category consist of the Fund and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 27% at December 31, 2016 and 2015 of the postretirement benefit plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2.

[10] REITs consist of securities that trade on the major exchanges and invest directly, either through properties or mortgages.

[11] Other consists primarily of money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit.

[12] All of the postretirement benefit plans other investments measured using NAV at December 31, 2016 and 2015 consist of a regulated commingled equity trust fund, which fair value is based on NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund's holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV.

[13] In accordance with ASU 2015-07, certain investments that are measured at fair value using the NAV per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position.