Retirement Plans and Profit Sharing Arrangements (Assets Measured at Fair Value) (Details 6) - Pension Plans [Member] - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 748	$ 628	$ 608
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		291	241
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		412	344
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		189	149
U.S. large cap stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		95	73
U.S. large cap stocks [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		94	76
U.S. small cap stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		80	73
U.S. small cap stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		76	69
U.S. small cap stocks [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4	4
Non-U.S. large cap stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		71	56
Non-U.S. large cap stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		28	22
Non-U.S. large cap stocks [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		43	34
Non-U.S. small cap stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		28	21
Non-U.S. small cap stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		28	21
Emerging markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		51	37
Emerging markets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		19	14
Emerging markets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		32	23
U.S. investment grade bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		38	36
U.S. investment grade bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		27	26
U.S. investment grade bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		11	10
U.S. high yield bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		26	24
U.S. high yield bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		26	24
Non-U.S. investment grade bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		16	14
Non-U.S. investment grade bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		16	14
Real estate investment trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	18	17
Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	27	26
Pooled pension funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		166	142
Pooled pension funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		166	142
AVC assets (pooled pension funds) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		20	17
AVC assets (pooled pension funds) [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		20	17
Cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		18	16
Cash equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 18	$ 16

[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. See Note 2 for further information.