Basis of Presentation - Additional Information (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Dilutive securities (in shares)	2	2	2	2
Pre-tax adjustment	$ 833		$ 833			$ 472
Retained earnings	$ (58,473)		$ (58,473)			$ (53,147)
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201602Member
Adjustments due to Topic 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Pre-tax adjustment					$ 265
Retained earnings					$ 200
Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Maximum threshold period for new customers			210 days
Minimum threshold period for existing customers			210 days
Business
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Maximum threshold period for new customers			12 months
Minimum threshold period for existing customers			12 months