Property and Equipment - Depreciation Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 401	$ 636	$ 701
Property, Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 306	$ 574	$ 572