Shareholders' Equity - Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended							9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2021	Sep. 30, 2020	Jul. 31, 2021	Apr. 30, 2021	Jan. 31, 2021	Jun. 30, 2019
Equity, Class of Treasury Stock [Line Items]
Proceeds from issuance of common stock, net of issuance costs	$ 1,900,000,000								$ 1,900,000,000	$ 0
Amount of common stock authorized for repurchase											$ 3,000,000,000	$ 425,000,000	$ 475,000,000	$ 2,000,000,000
Common Stock
Equity, Class of Treasury Stock [Line Items]
Public offering, new shares (in shares)	21.7
Offering price (in dollars per share)	$ 87.60	$ 87.60							$ 87.60
2019 Program
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased		$ 0	$ 0	$ 0	$ 0	$ 500,000,000	$ 500,000,000	$ 500,000,000	$ 900,000,000	$ 500,000,000