Description of Business and Basis of Presentation - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of reportable segments | segment	2
Shareholders' equity	$ 1,763	$ 831	$ 656	$ (115)
COVID-19
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in long-term debt	700
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' equity		(2)	0
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' equity	$ 11,011	9,656	8,594	$ 7,465
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' equity		$ (2)	$ 20