United States and Foreign Components of Consolidated Loss before Income Taxes (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
Schedule Of Income Loss From Continuing Operations [Line Items]
U.S.									$ (16,360)	$ (17,461)	$ (17,256)
Foreign									685	622	439
Loss before income taxes	$ (1,605)	$ (3,405)	$ (1,866)	$ (8,799)	$ (7,686)	$ 2,304	$ (6,382)	$ (5,075)	$ (15,675)	$ (16,839)	$ (16,817)