Tax Matters (Tax Contingencies) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Income Tax Contingency [Line Items]
Net liabilities associated with uncertain tax positions		$ 187		$ 180		$ 182
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, January 1		(182)	[1]	(185)	[1]	(164)
Decreases based on tax positions taken during a prior period	[2],[3]	6		12		6
Increases based on tax positions taken during the current period	[3]	(9)		(8)		(11)
Lapse in statute of limitations		3		2		2
Balance, December 31	[1]	(188)		(182)		(185)
Net interest expense		2		2		1
Gross accrued interest		11		9		8
Gross accrued penalties		3		3		3
Other non-current assets
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, January 1		(3)		(3)
Balance, December 31		(3)		(3)		(3)
Noncurrent Deferred Tax Assets
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, January 1		(2)		(3)
Balance, December 31		(1)		(2)		(3)
Other Taxes Payable
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, January 1		(180)		(182)
Increases based on tax positions taken during a prior period	[3],[4]	(6)		(3)		(24)
Balance, December 31		(187)		(180)		(182)
Belgium
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Settlements	[5]	$ 0		$ 0		$ 6

[1] In 2020, included in Noncurrent deferred tax assets and Other noncurrent assets ($1 million) and Other taxes payable ($187 million). In 2019, included in Noncurrent deferred tax assets and Other noncurrent assets ($2 million) and Other taxes payable ($180 million). In 2018, included in Noncurrent deferred tax assets and Other noncurrent assets ($3 million) and Other taxes payable ($182 million).

[2] In 2020, the decreases are primarily related to effective settlement of certain issues with tax authorities. In 2019, the decreases are primarily related to movements on prior year positions and effective settlement of certain issues with tax authorities, including movements in foreign translation adjustments on prior year positions. In 2018, the decreases are primarily related to movements on prior year positions and closure of audits with tax authorities, including movements in foreign translation adjustments on prior year positions.

[3] Primarily included in Provision for taxes on income.

[4] In 2020 and 2019, the increases are primarily related to movements on prior year positions. In 2018, the increases are primarily related to the impact of the Tax Act and movements on prior year positions.

[5] In 2018, the decreases are due to settlements with tax authorities. See A. Taxes on Income.