Stockholders' Equity - Changes in Common Shares and Treasury Stock (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
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	501,891,243	501,900,000	501,900,000
Beginning Balance	26,363,022	22,300,000	15,800,000
Stock-based compensation		0	0
Share repurchase program		0	0
Treasury Stock	(1,600,000)	(1,800,000)	(1,700,000)
Ending Balance	501,891,243	501,891,243	501,900,000
Ending Balance	26,573,492	26,363,022	22,300,000
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	$ 1,400,000,000
Shares authorized under repurchase program	$ 2,000,000,000.0
Share Repurchase Program
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock	(1,800,000)	(5,800,000)	(8,200,000)