Summary of Cash, Cash Equivalents, Short-Term investments, and Restricted Cash and Investments (Details 3) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Fair Value Disclosures [Abstract]
Less than 1 year	$ 66,916		$ 66,916		$ 6,597
Due in 1 to 2 years	3,338		3,338
Due after 5 years					1,700
Total	70,254		70,254		$ 8,297
Impairment losses on its marketable securities	$ 0	$ 0	$ 0	$ 0
Investments in marketable securities in unrealized loss postion in excess of 12 months | item	0		0