Stock Repurchases (Details) - USD ($) shares in Millions		2 Months Ended	3 Months Ended	9 Months Ended
	Feb. 04, 2021	Apr. 16, 2021	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Jul. 09, 2021	Dec. 31, 2020
Stock Repurchased During Period, Shares		0.7	0.6
Percentage Of Accelerated Share Repurchases Of Shares Expected To Be Repurchased	85.00%
Stock repurchase program, authorized amount						$ 1,000,000,000	$ 4,000,000,000
Stock repurchase program, authorized amount						$ 1,000,000,000	$ 4,000,000,000
Stock repurchase program, remaining authorized amount			$ 846,000,000	$ 846,000,000
Stock Repurchased During Period, Shares		0.7	0.6
Stock Repurchased During Period, Value	$ 200,000,000
Shares repurchased from employees who surrendered shares to satisfy minimum tax withholding obligations, value				$ 16,100,000	$ 10,100,000