Debt - Schedule of Interest Expense (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Disclosure [Abstract]
Contractual interest coupon		$ 1	$ 19	$ 11	$ 58
Amortization of debt issuance costs		1	2	4	5
Amortization of debt discounts	[1]		50		138
Total		$ 2	$ 71	$ 15	$ 201

[1] Under the modified retrospective method of adoption of ASU 2020-06, there was neither amortization of debt discounts, nor losses on extinguishment of debt recognized for the three and nine months ended September 30, 2021. Refer to discussion above for further details.