Segment Reporting - Revenue by Geographic Area (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue by geographic area
Total revenue	$ 21,146	$ 18,412	$ 23,684	$ 17,949	$ 15,782	$ 27,068	$ 17,331	$ 11,299	$ 81,191	$ 71,480	$ 159,039
United States [Member]
Revenue by geographic area
Revenue from Home country									34,591	37,896	29,636
European Countries [Member]
Revenue by geographic area
Revenue from External customers									$ 46,600	$ 33,584	$ 129,403