Recently Issued Accounting Standards (Details) - USD ($) $ in Millions		Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity		$ 7,003	$ 8,517		$ 11,531	[1]	$ 11,301	$ 10,320	$ 10,042
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity		$ 4,524	$ 6,365		9,716		$ 9,075	$ 8,050	$ 6,715
Adoption of New Accounting Standard
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	[1]				(17)
Adoption of New Accounting Standard | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	[1]			$ (17)	$ (17)

[1] Transition adjustment due to the adoption of Accounting Standards Update No. 2016-13, Financial Instruments—Credit Losses. See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.