Equity - Narrative (Details) - USD ($) $ in Millions		9 Months Ended
	Feb. 28, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common Stock, Voting Rights, Maximum Voting Power for Single Shareholder		9.90%
Common Class A
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount		$ 1,567
Repurchase Authorization 2018 | Common Class A
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 640	$ 150
Stock Repurchase Program, Additional Authorized Amount		0	$ 717
Stock Repurchased During Period, Value		(416)	(544)
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 224	$ 323
Common stock | Common Class M
Class of Stock [Line Items]
Common Stock, Conversion Basis, Percentage Of Share Value Converted	5.00%
Warrant | Common Class M
Class of Stock [Line Items]
Common Stock, Conversion Basis, Percentage Of Share Value Converted	95.00%