Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Defined Benefit Plan Disclosure [Line Items]

Fair Value Hierarchy By Assets and Liabilities Measured At Fair Value On A Recurring Basis [Table Text Block]

The fair value hierarchy for assets and liabilities measured at fair value on a recurring basis are as follows:

	December 31, 2018
	Level 1		Level 2		Level 3		NAV		Total
	(Dollars in Millions)
Asset Category:
Retirement plan assets	$	112	$	271	$	14	$	370	$	767
Foreign currency instruments	$	—	$	1	$	—	$	—	$	1
Liability Category:
Foreign currency instruments	$	—	$	16	$	—	$	—	$	16
Interest rate swaps	$	—	$	2	$	—	$	—	$	2

	December 31, 2017
	Level 1		Level 2		Level 3		NAV		Total
	(Dollars in Millions)
Asset Category:
Retirement plan assets	$	139	$	366	$	13	$	349	$	867
Interest rate swaps	$	—	$	1	$	—	$	—	$	1
Liability Category:
Foreign currency instruments	$	—	$	25	$	—	$	—	$	25

Domestic Plan [Member]

Defined Benefit Plan Disclosure [Line Items]

Fair Value of Retirement Plan Assets [Table Text Block]

The fair values of the Company’s U.S. retirement plan assets are as follows:

	December 31, 2018
Asset Category	Level 1		Level 2		NAV		Total
	(Dollars in Millions)
Registered investment companies	$	3	$	—	$	—	$	3
Common and preferred stocks	22		—		—		22
Common trust funds	—		100		127		227
LDI	—		104		—		104
Limited partnerships and hedge funds	—		—		205		205
Cash and cash equivalents	—		6		—		6
Total	$	25	$	210	$	332	$	567

	December 31, 2017
Asset Category	Level 1		Level 2		NAV		Total
	(Dollars in Millions)
Registered investment companies	$	3	$	—	$	—	$	3
Common trust funds	—		185		94		279
LDI	—		103		—		103
Common and preferred stock	27		—		—		27
Limited partnerships and hedge funds	—		—		226		226
Cash and cash equivalents	—		9		—		9
Total	$	30	$	297	$	320	$	647

Significant Unobservable Inputs Used In Fair Value Measurement [Table Text Block]

Foreign Plan [Member]

Defined Benefit Plan Disclosure [Line Items]

Fair Value of Retirement Plan Assets [Table Text Block]

The fair values of the Company’s Non-U.S. retirement plan assets are as follows:

	December 31, 2018
Asset Category	Level 1		Level 2			Level 3		NAV		Total
	(Dollars in Millions)
Registered investment companies	$	29	$	17		$	—	$	—	$	46
Treasury and government securities	50		24			—		—		74
Cash and cash equivalents	6		—			—		—		6
Corporate debt securities	—		3			—		—		3
Common and preferred stock	2		—			—		—		2
Common trust funds	—		22			—		21		43
Limited partnerships	—		—			—		17		17
Insurance contracts	—		—			14		—		14
Derivative instruments	—		(5		)	—		—		(5		)
Total	$	87	$	61		$	14	$	38	$	200

	December 31, 2017
Asset Category	Level 1		Level 2		Level 3		NAV		Total
	(Dollars in Millions)
Registered investment companies	$	52	$	18	$	—	$	—	$	70
Treasury and government securities	45		24		—		—		69
Cash and cash equivalents	7		—		—		—		7
Corporate debt securities	3		4		—		—		7
Common and preferred stock	2		—		—		—		2
Common trust funds	—		20		—		14		34
Limited partnerships	—		—		—		15		15
Insurance contracts	—		—		13		—		13
Derivative instruments	—		3		—		—		3
Total	$	109	$	69	$	13	$	29	$	220

Significant Unobservable Inputs Used In Fair Value Measurement [Table Text Block]

Fair value measurements which used significant unobservable inputs are as follows:

	Insurance Contracts
	(Dollars in Millions)
December 31, 2015	$	10
Purchases, sales and settlements	1
December 31, 2016	$	11
Return on assets held at the reporting date, including currency impacts	1
Purchases	1
December 31, 2017	$	13
Purchases	1
December 31, 2018	$	14