Equity - Statements of Equity with dividends per share (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Balance			$ 2,408				$ 2,408
Net income	$ 102			$ 98			311	$ 357
Balance	2,612						2,612
Common Stock
Balance	1	$ 1	1	1	$ 1	$ 1	1	1
Balance	1	1	1	1	1	1	1	1
Additional Paid-in Capital
Balance	1,138	1,137	1,096	1,128	1,132	1,138	1,096	1,138
Repurchases of common stock, net			32				32
Share-based compensation, net of issuance	(1)	1	9	3		(6)	9	(3)
Other					(4)			(4)
Balance	1,137	1,138	1,137	1,131	1,128	1,132	1,137	1,131
Treasury Stock
Balance	(1,047)	(1,050)	(1,091)	(615)	(476)	(494)	(1,091)	(494)
Repurchases of common stock, net			31	(36)	(141)		31	(177)
Share-based compensation, net of issuance	3	3	10	1	2	18	16	21
Balance	(1,044)	(1,047)	(1,050)	(650)	(615)	(476)	(1,044)	(650)
Accumulated Other Comprehensive Loss
Balance	(1,152)	(1,160)	(1,154)	(1,106)	(972)	(1,013)	(1,154)	(1,013)
Other comprehensive income (loss)	(62)	8	(6)	(18)	(134)	41	(60)	(111)
Other				(7)				(7)
Balance	(1,214)	(1,152)	(1,160)	(1,131)	(1,106)	(972)	(1,214)	(1,131)
Retained Earnings
Balance	3,656	3,594	3,536	3,426	3,355	3,259	3,536	3,259
Net income	99	105	100	95	114	140	304	349
Dividends declared, common stock	(42)	(43)	(42)	(43)	(44)	(44)	(127)	(131)
Other				6	1			7
Balance	3,713	3,656	3,594	3,484	3,426	3,355	3,713	3,484
Non-controlling Interests
Balance	16	22	20	22	24	26	20	26
Net income	3	2	2	3	2	3	7	8
Dividends declared, common stock	(2)	(4)		(3)	(1)	(3)	(6)	(7)
Other comprehensive income (loss)	2	(4)			(2)	(2)	(2)	(4)
Other					(1)			(1)
Balance	$ 19	$ 16	$ 22	$ 22	$ 22	$ 24	$ 19	$ 22