Employee Benefit Plans (Fair Values of the Company's Pension Plan Assets by Asset Category) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	$ 2,965	$ 2,618
Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	2,252	1,961
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	324	252
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	1,093	914
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	835	795	$ 1,002
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	713	657
Defined Benefit Plan, Equity Securities, US, Large Cap | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	138	137
Defined Benefit Plan, Equity Securities, US, Large Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	58	43
Defined Benefit Plan, Equity Securities, US, Large Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	80	94
Defined Benefit Plan, Equity Securities, US, Large Cap | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Defined Benefit Plan, Equity Securities, US, Small Cap | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	41	23
Defined Benefit Plan, Equity Securities, US, Small Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	41	23
Defined Benefit Plan, Equity Securities, US, Small Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Defined Benefit Plan, Equity Securities, US, Small Cap | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Defined Benefit Plan, Equity Securities, Non-US | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	227	218
Defined Benefit Plan, Equity Securities, Non-US | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	143	115
Defined Benefit Plan, Equity Securities, Non-US | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	84	103
Defined Benefit Plan, Equity Securities, Non-US | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Defined Benefit Plan, Cash and Cash Equivalents | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	26	22
Defined Benefit Plan, Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	10	3
Defined Benefit Plan, Cash and Cash Equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	16	19
Defined Benefit Plan, Cash and Cash Equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Debt Security, Corporate, US | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	414	297
Debt Security, Corporate, US | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Debt Security, Corporate, US | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	337	220
Debt Security, Corporate, US | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	77	77
Debt Security, Developed Markets And Emerging Economies | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	2	4
Debt Security, Developed Markets And Emerging Economies | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Debt Security, Developed Markets And Emerging Economies | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	2	4
Debt Security, Developed Markets And Emerging Economies | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Debt Security, Diverse Portfolio | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	237	142
Debt Security, Diverse Portfolio | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Debt Security, Diverse Portfolio | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	237	142
Debt Security, Diverse Portfolio | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
US Government Agencies Debt Securities | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	81	76
US Government Agencies Debt Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	72	68
US Government Agencies Debt Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	9	8
US Government Agencies Debt Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Developed Markets, Government Agencies Debt Securities | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	7	6
Developed Markets, Government Agencies Debt Securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Developed Markets, Government Agencies Debt Securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	7	6
Developed Markets, Government Agencies Debt Securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Other | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	395	373
Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	18	14
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	377	359
Defined Benefit Plan, Real Estate, Hedge Funds, And Other [Member] | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	684	663
Defined Benefit Plan, Real Estate, Hedge Funds, And Other [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	0	0
Defined Benefit Plan, Real Estate, Hedge Funds, And Other [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	303	304
Defined Benefit Plan, Real Estate, Hedge Funds, And Other [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	$ 381	$ 359