Equity - Stock Repurchase Activities (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended				6 Months Ended	9 Months Ended
	Oct. 31, 2019	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Jan. 31, 2018
Accelerated Share Repurchases [Line Items]
Payment pursuant to ASR							$ 305,700,000	$ 354,900,000
Common stock received, aggregate price		$ 100,400,000			$ 111,100,000		$ 345,700,000	$ 354,900,000
Stock Repurchase Program 2018
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount	$ 3,000,000,000.0								$ 2,000,000,000.0
Stock repurchase program, increase to authorized amount	1,000,000,000.0
Stock repurchased and retired (in shares)		4.2			5.1		14.5	13.7
Common stock received, aggregate price		$ 100,000,000.0			$ 50,000,000.0		$ 300,000,000.0	$ 350,000,000.0
Stock repurchased (in shares)							14.5
Common stock repurchased, average cost per share (in dollars per share)							$ 23.86
Stock repurchase program, remaining authorized repurchase amount		$ 1,400,000,000					$ 1,400,000,000
Accelerated Share Repurchase Program
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount	$ 200,000,000.0
Payment pursuant to ASR				$ 200,000,000.0
Stock repurchased and retired (in shares)			1.8	6.4		8.2
Common stock received, aggregate price				$ 160,000,000.0
Common stock repurchased under stock repurchase program market price (in usd per share)				$ 25.15
Weighted average repurchase price, stock repurchased and retired during period (in usd per share)			$ 24.44