Stock Repurchases (Details) - USD ($) shares in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 13, 2019
Stock repurchase program, authorized amount				$ 3,000,000,000	$ 500,000,000
Stock repurchase program, remaining authorized amount		$ 446,000,000
Stock Repurchased During Period, Shares	0.4
Stock Repurchased During Period, Value	$ 100,000,000.0
Shares repurchased from employees who surrendered shares to satisfy minimum tax withholding obligations, value		$ 10,100,000	$ 16,900,000