Stock Repurchases (Details) - USD ($) shares in Millions		2 Months Ended	3 Months Ended	6 Months Ended
	Feb. 04, 2021	Apr. 16, 2021	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jul. 09, 2021	Dec. 31, 2020	Dec. 13, 2019
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						$ 1,000,000,000.0	$ 3,000,000,000.0	$ 500,000,000
Stock repurchase program, remaining authorized amount			$ 46,000,000	$ 46,000,000
Stock Repurchased During Period, Shares		0.7	0.6
Stock Repurchased During Period, Value	$ 200,000,000.0
Shares repurchased from employees who surrendered shares to satisfy minimum tax withholding obligations, value				$ 10,200,000	$ 5,600,000