Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,779	$ 1,595
Less: accumulated depreciation and amortization	1,098	880
Property and equipment, net	681	715
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6	6
Building [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 33	33
Estimated useful life-in years	39 years
Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 30	30
Estimated useful life-in years	15 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 593	565
Leasehold Improvements [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life-in years	1 year
Leasehold Improvements [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life-in years	15 years
Equipment and Computer Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 822	$ 672
Estimated useful life-in years	3 years	3 years
Other Transportation Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 179	$ 136
Estimated useful life-in years	10 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 70	70
Estimated useful life-in years	7 years
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 46	$ 83

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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