Goodwill and Other Intangible Assets - Summary of Goodwill Activity (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Goodwill [Line Items]
Goodwill as of December 31, 2013	$ 348,957
Addition	15,097
Goodwill as of September 30, 2014	364,054
Search and Content
Goodwill [Line Items]
Goodwill as of December 31, 2013	44,815
Addition	15,097
Goodwill as of September 30, 2014	59,912
Tax Preparation
Goodwill [Line Items]
Goodwill as of December 31, 2013	188,541
Addition	0
Goodwill as of September 30, 2014	188,541
E-Commerce
Goodwill [Line Items]
Goodwill as of December 31, 2013	115,601
Addition	0
Goodwill as of September 30, 2014	$ 115,601