Stockholders' Equity , Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 31, 2016
Share Repurchase Program [Line Items]
Stock repurchased in the period, value	$ 146,100,000	$ 34,700,000	$ 1,046,000,000.0	$ 90,900,000
Repurchase Program [Member]
Share Repurchase Program [Line Items]
Stock repurchase program, authorized amount					$ 2,500,000,000
Stock repurchased in the period, shares	1.4		11.4
Stock repurchased, average price (in dollars per share)	$ 99.69		$ 91.55
Stock repurchased in the period, value	$ 146,100,000		$ 1,000,000,000.0
Stock repurchase program, unused balance	$ 546,800,000		$ 546,800,000