Search Agreement with Microsoft Corporation - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2013 M	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Search Agreement With Microsoft Corporation [Line Items]
Term of license of core search technology with Microsoft, years			10 years
Term of search agreement with Microsoft, years			10 years
Revenue attributable to Search Agreement			31.00%	25.00%	20.00%
Revenue share rate from Microsoft's services under the Search Agreement, to be received in first five years			88.00%
Revenue share rate from Microsoft's services under the Search Agreement, Affiliate revenue			88.00%
Revenue share rate from Microsoft's services under the Search Agreement, if Microsoft exercises sales exclusivity			93.00%
Revenue share rate from Microsoft's services under the Search Agreement, if the Company exercises its option to retain sales exclusivity			83.00%
Revenue share rate from Microsoft's services under the Search Agreement, no exercise of options regarding sales exclusivity			90.00%
Revenue collected from Search Agreement			$ 21
Uncollected Search Agreement revenue			305	258
Term after transition of paid services for which revenue guaranteed by Microsoft under Search Agreement (in months)		18
Cumulative transition costs exceeded Microsoft's reimbursement cap	150
Reimbursable expenses related to Search Agreement			49	67
Classified as part of prepaid expenses and other current assets			5	5
Search Operating Costs
Search Agreement With Microsoft Corporation [Line Items]
Reimbursements for costs			49	67	212
Transition Costs Incurred In 2011
Search Agreement With Microsoft Corporation [Line Items]
Reimbursements for costs					$ 26