CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Net loss	$ (60,644)	$ (65,478)	$ (84,801)
Unrealized gains (losses) on investments, net of tax	10,253	13,250	(1,719)
Reclassification adjustment for realized gains included in net loss	(1,653)
Comprehensive loss	$ (52,044)	$ (52,228)	$ (86,520)