Consolidated Statements of Changes in Shareholder's Equity - USD ($) $ in Millions	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income/(loss)	Noncontrolling interests
Balance at Dec. 31, 2017	$ 3,264	$ 745	$ 2	$ 2,969	$ (592)	$ 140
Increase (Decrease) in Shareholder's Equity [Roll Forward]
Profit of consolidated companies	171			162		9
Foreign currency translation, net of tax	(191)				(189)	(2)
Derivative financial instruments, net of tax	(3)				(3)
Balance at Jun. 30, 2018	3,241	745	2	3,131	(784)	147
Balance at Mar. 31, 2018	3,424	745	2	3,060	(533)	150
Increase (Decrease) in Shareholder's Equity [Roll Forward]
Profit of consolidated companies	76			71		5
Foreign currency translation, net of tax	(262)				(254)	(8)
Derivative financial instruments, net of tax	3				3
Balance at Jun. 30, 2018	3,241	745	2	3,131	(784)	147
Balance at Dec. 31, 2018	2,849	745	2	2,874	(925)	153
Increase (Decrease) in Shareholder's Equity [Roll Forward]
Profit of consolidated companies	188			177		11
Foreign currency translation, net of tax	33				33	0
Derivative financial instruments, net of tax	(36)				(36)
Adjustment to adopt new accounting guidance | Accounting Standards Update 2018-02	0			(97)	97
Balance at Jun. 30, 2019	3,034	745	2	2,954	(831)	164
Balance at Mar. 31, 2019	2,954	745	2	2,875	(829)	161
Increase (Decrease) in Shareholder's Equity [Roll Forward]
Profit of consolidated companies	84			79		5
Foreign currency translation, net of tax	18				20	(2)
Derivative financial instruments, net of tax	(22)				(22)
Balance at Jun. 30, 2019	$ 3,034	$ 745	$ 2	$ 2,954	$ (831)	$ 164