Basis of Presentation - Additional Information (Detail) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020 segment shares	Mar. 31, 2019 shares	Jan. 01, 2020 USD ($)	Jan. 01, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of reportable segments | segment	2
Restricted stock units outstanding to purchase shares included in diluted earnings per common share (in shares) | shares	2	2
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of applying new accounting standards			$ 200	$ (410)
Retained Earnings | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of applying new accounting standards, pre-tax			265
Cumulative effect of applying new accounting standards			$ 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