The Company and Summary of Significant Accounting Principles - Schedule of Concentrations Equal to or Exceeding 10% of Company's Accounts Receivable, Revenue, and Cost of Revenue (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Credit Concentration Risk [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%		10.00%
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Portal and Advertising Customer A [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	14.00%		15.00%
Product Concentration Risk [Member] | Revenue [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%
Product Concentration Risk [Member] | Revenue [Member] | Portal and Advertising Customer A [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	13.00%
Product Concentration Risk [Member] | Revenue [Member] | Google Search [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%	15.00%
Product Concentration Risk [Member] | Revenue [Member] | Google Advertising Affiliate [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		16.00%
Customer Concentration Risk [Member] | Cost of Revenue [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%
Customer Concentration Risk [Member] | Cost of Revenue [Member] | Portal and Advertising Customer B [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	30.00%	20.00%