Stockholders' Equity - Changes in Common Shares and Treasury Stock (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Class of Stock [Line Items]
Common stock, shares authorized	6,000,000,000		6,000,000,000
Preferred stock, authorized (in shares)	1,000,000,000		1,000,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	501,900,000	501,900,000
Beginning Balance	15,800,000	9,000,000.0
Stock-based compensation	0	0
Share repurchase program	0	0
Treasury Stock	(1,700,000)	(1,600,000)
Ending Balance	501,900,000	501,900,000
Ending Balance	22,300,000	15,800,000
December 2016 Share Repurchase Program
Class of Stock [Line Items]
Shares authorized under repurchase program		$ 1,500,000,000
December 2018 Share Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 1,700,000,000
Shares authorized under repurchase program			$ 2,000,000,000.0
Share Repurchase Program
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock	(8,200,000)	(8,300,000)