Property and Equipment - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation	$ 69,000,000	$ 69,000,000
Net capital lease assets included in property and equipment			$ 20,000,000
Accumulated depreciation of capital lease assets included in property and equipment			10,000,000
Hurricanes Irma and Maria [Member]
Property, Plant and Equipment [Line Items]
Expenses on property and equipment from hurricane damage	7,000,000		20,000,000
Loss on property and equipment from hurricane damage	22,000,000		$ 54,000,000
Additional insurance receivable recognized for property and equipment damaged from hurricanes	29,000,000
Insurance proceeds received on hurricanes damage	18,000,000
Business interruption insurance recognized	0
Hurricanes Irma and Maria [Member] | Other Assets [Member]
Property, Plant and Equipment [Line Items]
Insurance settlements receivable on hurricanes damage	$ 67,000,000