Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Cash and Cash Equivalents, at Carrying Value	$ 1,338	$ 2,806	$ 2,771	$ 1,758
Restricted Cash and Cash Equivalents	168	185
Advertising Expense	$ 192	270	$ 208
Number of Reportable Segments | segment	3
Variable Interest Entity, Primary Beneficiary [Member]
Cash and Cash Equivalents, at Carrying Value	$ 1,060	$ 944