Intangible Assets Subject to Amortization (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Gross cost	$ 23,602	$ 23,602
Accumulated amortization	(16,542)	(10,018)
Net	7,060	13,584
Content
Finite-Lived Intangible Assets [Line Items]
Gross cost	10,634	10,634
Accumulated amortization	(10,634)	(7,089)
Net		3,545
Trade Name
Finite-Lived Intangible Assets [Line Items]
Gross cost	5,758	5,758
Accumulated amortization	(2,303)	(1,152)
Net	3,455	4,606
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross cost	7,210	7,210
Accumulated amortization	(3,605)	(1,777)
Net	$ 3,605	$ 5,433