Retirement Plans and Profit Sharing Arrangements (Assets Measured at Fair Value) (Details 6) - Pension Plans [Member] - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 905	$ 838	$ 728
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		300	307
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		21	24
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
U.S. large cap stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		119	119
U.S. large cap stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		119	119
U.S. small cap stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		80	91
U.S. small cap stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		80	91
Non-U.S. large cap stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		36	32
Non-U.S. large cap stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		36	32
U.S. investment grade bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		68	67
U.S. investment grade bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		47	43
U.S. investment grade bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		21	24
U.S. high yield bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			6
U.S. high yield bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			6
Non-U.S. investment grade bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		18	16
Non-U.S. investment grade bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		18	16
Collective investment funds [Member] [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	289	232
Real estate investment trusts [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	20	20
Hedge funds [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	32	29
Pooled pension funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	218	196
Cash equivalents [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	$ 25	$ 30

[1] Amounts are comprised of certain investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient and have not been classified in the fair value hierarchy.