Summary of Cash, Cash Equivalents, Short-Term investments, and Restricted Cash and Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Cash and cash equivalents:
Cash	$ 30,298	$ 43,035
Cash equivalents	46,952
Cash and cash equivalents	77,250	43,035	$ 35,269	$ 57,101
Short-term investments	23,302
Restricted cash and investments:
Restricted cash and investments, current	3,062	5,504
Restricted cash and investments, non-current		15,750
Total restricted cash and investments	$ 3,062	$ 21,254