Quarterly Financial Results (unaudited) (Details) (USD $) In Thousands, except Per Share data, 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	Dec. 31, 2009
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 29,222	$ 26,696	$ 25,509	$ 24,519	$ 23,392	$ 22,302	$ 19,175	$ 18,548	$ 105,946	$ 83,417	$ 67,251
Cost of goods sold	7,158	6,444	6,277	5,403	5,394	4,829	4,150	4,373	25,282	18,746	15,030
Operating Expenses	27,761	27,185	24,819	22,790	21,262	22,622	20,202	19,000	102,555	83,087	56,445
Net income (loss)	$ (6,518)	$ (5,857)	$ (6,696)	$ (16,703)	$ (3,665)	$ (6,603)	$ (13,666)	$ (4,795)	$ (35,774)	$ (28,730)	$ 10,653	$ 10,653
Basic income (loss) per share (usd per share)	$ (0.10)	$ (0.10)	$ (0.11)	$ (0.29)	$ (0.06)	$ (0.12)	$ (0.24)	$ (0.09)	$ (0.60)	$ (0.51)	$ 0.22
Diluted income (loss) per share (usd per share)	$ (0.10)	$ (0.10)	$ (0.11)	$ (0.29)	$ (0.06)	$ (0.12)	$ (0.24)	$ (0.09)	$ (0.60)	$ (0.51)	$ 0.21