Fixed Assets (Detail) (USD $) In Thousands, unless otherwise specified					12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Equipment, Furniture and Fixtures, and Computer Hardware and Software	Dec. 31, 2011 Equipment, Furniture and Fixtures, and Computer Hardware and Software	Dec. 31, 2012 Equipment, Furniture and Fixtures, and Computer Hardware and Software Minimum	Dec. 31, 2012 Equipment, Furniture and Fixtures, and Computer Hardware and Software Maximum	Dec. 31, 2012 Leasehold Improvements	Dec. 31, 2011 Leasehold Improvements	Dec. 31, 2012 Leasehold Improvements Minimum	Dec. 31, 2012 Leasehold Improvements Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life					3 years	7 years			3 years	6 years
Property, plant and equipment, gross	$ 29,479	$ 18,829	$ 27,535	$ 17,617			$ 1,944	$ 1,212
Less: accumulated depreciation and amortization	(15,693)	(13,147)
Fixed assets, net	$ 13,786	$ 5,682