Equity - Treasury stock (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended				6 Months Ended
	Feb. 06, 2019	Nov. 05, 2018	Jun. 30, 2020	Mar. 31, 2019	Feb. 06, 2019	Feb. 05, 2019	Jun. 30, 2020	Jun. 30, 2019	Oct. 22, 2018
Treasury stock:
Purchase/acquisition of treasury stock (in shares)			0				0
Additional Paid-in Capital
Treasury stock:
Repurchases of common stock, net				$ 32				$ 32
Treasury Stock
Treasury stock:
Repurchases of common stock, net				$ 31				$ 31
ASR agreement
Treasury stock:
Payment made for repurchase of shares		$ 455
Purchase/acquisition of treasury stock (in shares)		4,000,000				4,000,000
Repurchases of common stock, net		$ (423)			$ (392)
VWAP (in dollars per share)						$ 98.04
Amount of cash returned from upfront payment in repurchase of stock	$ 63
2018 Stock Repurchase Program
Treasury stock:
Shares authorized to be repurchased (in shares)									8,000,000