Patent Assets, Net (Detail) - Patent Assets, Net (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Patent assets	$ 6,298	$ 6,311
Accumulated amortization	(3,840)	(3,085)
Patent assets, net	221,362	199,314
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Patent assets	472,112	403,875
Accumulated amortization	(250,750)	(204,561)
Patent assets, net	221,362	199,314
Additions [Member] | Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Patent assets	68,537
Accumulated amortization	(46,263)
Disposals [Member] | Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Patent assets	(300)
Accumulated amortization	$ 74