Summary of Cash, Cash Equivalents, Short-Term investments, and Restricted Cash and Investments (Details 2) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 70,253	$ 8,291
Gross Unrealized Gains	3	6
Gross Unrealized Losses	(2)
Fair Value	70,254	8,297
Money Market Accounts [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	46,952
Fair Value	46,952
Money Market Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	13,442	4,587
Fair Value	13,442	4,587
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	5,840	2,004
Gross Unrealized Gains	1	6
Gross Unrealized Losses	(2)
Fair Value	5,839	2,010
Foreign bonds and note
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,018
Gross Unrealized Gains	1
Fair Value	2,019
U.S. government securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,002
Gross Unrealized Gains	1
Fair Value	1,003
Commercial Papers
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	999
Fair Value	999
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	46,952
Fair Value	46,952
Short Term Investments and Restricted Investments [Member] \| Variable Rate Demand Notes [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		1,700
Fair Value		1,700
Short-Term Investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	23,301
Gross Unrealized Gains	3
Gross Unrealized Losses	(2)
Fair Value	$ 23,302
Restricted cash and investments, non-current [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		8,291
Gross Unrealized Gains		6
Fair Value		$ 8,297

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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