Pensions and Other Post-Retirement Benefits - Assets at Fair Value (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	$ 627	$ 1,184
Total assets at fair value	901	1,396	$ 1,559
Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	281	260
Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	324	750
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	22	174
Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	11	30
Cash and equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	11	30
Equity securities - U.S.
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	79	63
Equity securities - U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	75	53
Equity securities - U.S. | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	4	10
Equity securities - U.S. | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	30	23
Equity securities - Global
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	151	243
Equity securities - Global | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	36	37
Equity securities - Global | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	115	206
Equity securities - Global | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	40	29
Equity securities – non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	89	77
Equity securities – non-U.S. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	9	9
Equity securities – non-U.S. | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	80	68
Real estate
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	22	42
Real estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	22	42
Real estate | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	5	6
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	192	370
Corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	112	100
Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	80	270
Debt issued by national, state or local government
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	77	225
Debt issued by national, state or local government | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	38	31
Debt issued by national, state or local government | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	39	194
Debt issued by national, state or local government | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	10	10
Other
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	6	134
Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient	6	2
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value excluding NAV per share practical expedient		132
Investments | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	627	1,184
Cash | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	6	4
Liability Driven Investments | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	76	59
Private Equity And Hedge Funds | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	73	60
Insurance And Other | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	$ 34	$ 21