Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation	$ 62	$ 69
Hurricanes Irma and Maria [Member]
Property, Plant and Equipment [Line Items]
Additional insurance receivable recognized for property and equipment damaged from hurricanes	2	29
Insurance proceeds received on hurricanes damage	1	18
Expenses on property and equipment from hurricane damage		7
Loss on property and equipment from hurricane damage		$ 22
Hurricanes Irma and Maria [Member] | Other Assets [Member]
Property, Plant and Equipment [Line Items]
Insurance settlements receivable on hurricanes damage	$ 23		$ 25