Pensions and Other Employee Benefits - Fair Value of the Company's Pension Plans' and Postretirement Benefit Plans' Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Postretirement Benefit Plans Assets [Member]
Equity securities:
Fair value of company's plan assets	$ 60	$ 55
Postretirement Benefit Plans Assets [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	49	47
Postretirement Benefit Plans Assets [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	11	8
Postretirement Benefit Plans Assets [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member]
Equity securities:
Fair value of company's plan assets	36	37
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	36	37
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | International Equity [Member]
Equity securities:
Fair value of company's plan assets	4	3
Postretirement Benefit Plans Assets [Member] | International Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	1	1
Postretirement Benefit Plans Assets [Member] | International Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	3	2
Postretirement Benefit Plans Assets [Member] | International Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member]
Equity securities:
Fair value of company's plan assets	12	9
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	10	7
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Other Asset [Member]
Equity securities:
Fair value of company's plan assets	4	2
Postretirement Benefit Plans Assets [Member] | Other Asset [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Other Asset [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	4	2
Postretirement Benefit Plans Assets [Member] | Other Asset [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member]
Equity securities:
Fair value of company's plan assets	2,267	2,103
U.S. Based Pension Plans [Member] | U.S. Equity [Member]
Equity securities:
Fair value of company's plan assets	1,172	1,144
U.S. Based Pension Plans [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	1,172	1,144
U.S. Based Pension Plans [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | International Equity [Member]
Equity securities:
Fair value of company's plan assets	227	225
U.S. Based Pension Plans [Member] | International Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	87	79
U.S. Based Pension Plans [Member] | International Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	140	146
U.S. Based Pension Plans [Member] | International Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member]
Equity securities:
Fair value of company's plan assets	394	366
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	237	217
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	157	149
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member]
Equity securities:
Fair value of company's plan assets	120	111
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	120	111
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member]
Equity securities:
Fair value of company's plan assets	159	118
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	159	118
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Other Asset [Member]
Equity securities:
Fair value of company's plan assets	208	150
U.S. Based Pension Plans [Member] | Other Asset [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Other Asset [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	208	150
U.S. Based Pension Plans [Member] | Other Asset [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member]
Equity securities:
Fair value of company's plan assets	2,280	2,114
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	1,655	1,558
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	625	556
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Liabilities for Unsettled Trades, Net [Member]
Equity securities:
Fair value of company's plan assets	(13)	(11)
Canadian Based Pension Plans [Member]
Equity securities:
Fair value of company's plan assets	303	300
Canadian Based Pension Plans [Member] | U.S. Equity [Member]
Equity securities:
Fair value of company's plan assets	91	72
Canadian Based Pension Plans [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	58	54
Canadian Based Pension Plans [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	33	18
Canadian Based Pension Plans [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | International Equity [Member]
Equity securities:
Fair value of company's plan assets	120	135
Canadian Based Pension Plans [Member] | International Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	107	117
Canadian Based Pension Plans [Member] | International Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	13	18
Canadian Based Pension Plans [Member] | International Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member]
Equity securities:
Fair value of company's plan assets	62	82
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	62	82
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Other Asset [Member]
Equity securities:
Fair value of company's plan assets	30	11
Canadian Based Pension Plans [Member] | Other Asset [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	4	6
Canadian Based Pension Plans [Member] | Other Asset [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	26	5
Canadian Based Pension Plans [Member] | Other Asset [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member]
Equity securities:
Fair value of company's plan assets	303	300
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	169	177
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	134	123
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Liabilities for Unsettled Trades, Net [Member]
Equity securities:
Fair value of company's plan assets