Goodwill and Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 segment	Sep. 30, 2012
Finite-Lived Intangible Assets [Line Items]
Number of reporting units			3
Amortization of intangibles	$ 1,351	$ 1,362	$ 4,089	$ 3,029
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets useful life			4 years
Content
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets useful life			4 years
Software
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets useful life			3 years
Minimum | Trade Name
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets useful life			2 years
Maximum | Trade Name
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets useful life			5 years